Virtual Reality and Computer Simulation

Introduction

Virtual reality and computer simulation have not received much attention from ethicists. It is argued in this essay that this relative neglect is unjustified, and that there are important ethical questions that can be raised in relation to these technologies. First of all, these technologies raise important ethical questions about the way in which they represent reality and the misrepresentations, biased representations and offensive representations that they may contain. In addition, actions in virtual environments can be harmful to others, and can also be morally problematic from the point of view of deontological and virtue ethics. Although immersive virtual reality systems are not yet used on a large scale, nonimmersive virtual reality is regularly experienced by hundreds of millions of users, in the form of computer games and virtual environments for exploration and social networking. These forms of virtual reality also raise ethical questions regarding their benefits and harms to users and society, and the values and biases contained in them. This paper has the following structure. The next section will describe what virtual reality and computer simulations are and what the current applications of these technologies are. This is followed by a section that analyzes the relation between virtuality and reality, and asks whether virtuality can and should function as a substitute for reality. Three subsequent sections discuss ethical aspects of representation in virtual reality and computer simulations, the ethics of behavior in virtual reality and the ethics of computer games. A concluding section discusses issues of professional ethics in the development and professional use of virtual reality systems and computer simulations. Background: The Technology and Its Applications Virtual reality Virtual reality (VR) technology emerged in the 1980s, with the development and marketing of systems consisting of a head mounted display (HMD) and datasuit or dataglove attached to a computer. These technologies simulated three-dimensional (3-D) environments displayed in surround stereoscopic vision on the head mounted display. The user could navigate and interact with simulated environments through the datasuit and dataglove, items that tracked the positions and motions of body parts and allowed the computer to modify its output depending on the recorded positions. This original technology has helped define what is often meant by “virtual reality”: an immersive, interactive three-dimensional computer-generated environment in which interaction takes place over multiple sensory channels and includes tactile and positioning feedback. According to Sherman and Craig (2003), there are four essential elements in virtual reality: a virtual world, immersion, sensory feedback, and interactivity. A virtual world is a description of a collection of objects in a space and rules and relationships governing these objects. In virtual reality systems, such virtual worlds are generated by a computer. Immersion is the sensation of being present in an environment, rather than just observing an environment from the outside. Sensory feedback is the selective provision of sensory data about the environment based on user input. The actions and position of the user provide a perspective on reality and determines what sensory feedback is given. Interactivity, finally, is the responsiveness of the virtual world to user actions. Interactivity includes the ability to navigate virtual worlds and to interact with objects, characters and places. These four elements can be realized to a greater and lesser degree with a computer, and that is why there are both broad and narrow definitions of virtual reality. A narrow definition would only define fully immersive and fully interactive virtual environments as VR. However, there are many virtual environments that do not meet all these criteria to the fullest extent possible, but that could still be categorized as VR. Computer games played on a desktop with a keyboard and mouse, like Doom and HalfLife, are not fully immersive, and sensory feedback and interactivity in them is more limited than in immersive VR systems that include a head mounted display and datasuit. Yet, they do present virtual worlds that are immersive to an extent, and that are interactive and involve visual and auditory feedback. In Brey (1999) I therefore proposed a broader definition of virtual reality, as a three-dimensional interactive computergenerated environment that incorporates a first-person perspective. This definition includes both immersive and nonimmersive (screen-based) forms of VR. The notion of a virtual world, or virtual environment, as defined by Sherman and Craig, is broader than that of virtual reality. A virtual world can be realized by means of sensory feedback, in which case it yields virtual reality, but it can also be realized without it. Classical text-based adventure games like Zork, for example, play in interactive virtual worlds, but users are informed about the state of this world through text. They provide textual inputs, and the game responds with textual information rather than sensory feedback about changes in the world. A virtual world is hence an interactive computer-generated environment, and virtual reality is a special type of virtual world that involves location- and movement-relative sensory feedback. Next to the term “virtual reality,” there is the term “virtuality” and its derivative adjective “virtual”. This term has a much broader meaning than the term “virtual reality” or even “virtual environment”. As explained more extensively in the next section, the term “virtual” refers to anything that is created or carried by a computer and that mimics a “real”, physically localized entity, as in “virtual memory” and “virtual organization”. In this essay, the focus will be on virtual reality and virtual environments, but occasionally, especially in the next section, the broader phenomenon of virtuality will be discussed as well. Returning to the topic of virtual reality, a distinction can be made between singleuser and multi-user or networked VR. In single-user VR, there is only one user, whereas in networked VR, there are multiple users who share a virtual environment and appear to each others as avatars, which are graphical representations of the characters played by users in VR. A special type of VR is augmented reality, in which aspects of simulated virtual worlds are blended with the real world that is experienced through normal vision or a video link, usually through transparent glasses on which computer graphics or data are overlaid. Related to VR, furthermore, are telepresence and teleoperator systems, systems that extend a person’s sensing and manipulation capability to a remote location by displaying images and transmitting sounds from a real environment that can (optionally) be acted on from a distance through remote handling systems such as robotic arms. Computer simulation A computer simulation is a computer program that contains a model of a particular system (either actual or theoretical) and that can be executed, after which the execution output can be analyzed. Computer simulation is also the name of the discipline in which such models are designed, executed and analyzed. The models in computer simulations are usually abstract and either are or involve mathematical models. Computer simulation has become a useful part of the mathematical modeling of many natural systems in the natural sciences, human systems in the social sciences, and technological systems in the engineering sciences, in order to gain insight into the operations of these systems and to study the effects of alternative conditions and courses of action. It is not usually an aim in computer simulations, as it is in virtual reality, to do realistic visual modeling of the systems that they simulate. Some of these systems are abstract, and even for those systems that are concrete, the choice is often made not to design graphic representations of the system, but to rely solely on abstract models of it. When graphical representations of concrete systems are used, they usually only represent features that are relevant to the aims of the simulation, and do not aspire to the realism and detail aspired to in virtual reality. Another difference with virtual reality is that computer simulations need not be interactive. Usually, simulators will determine a number of parameters at the beginning of a simulation and then “run” the simulation without any interventions. In this standard case, the simulator is not himself defined as part of the simulation, as would happen in virtual reality. An exception is an interactive simulation, which is a special kind of simulation, also referred to as a human-in-the-loop simulation, in which the simulation includes a human operator. An example of such a simulation would be a flight simulator. If a computer simulation is interactive and makes use of three-dimensional graphics and sensory feedback, it also qualifies as a form of virtual reality. Sometimes, also, the term “computer simulation” is used to include any computer program that models a system or environment, even if it is not used to gain insight into the operation of a system. In that broad sense, virtual environments, at least those that aim to do realistic modeling, would also qualify as computer simulations. Applications VR is used to simulate both real and imaginary environments. Traditional VR applications are found in medicine, education, arts and entertainment, and the military (Burdea and Coiffet, 2003). In medicine, VR is used for the simulation of anatomical structures and medical procedures in education and training, for example for performing virtual surgery. Increasingly, VR is also being used for (psycho)therapy, for instance for overcoming anxiety disorders by confronting patients with virtual anxiety-provoking situations (Wiederhold and Wiederhold, 2004). In education, VR is used in explorationbased learning and learning by building virtual worlds. In the arts, VR is used to create new art forms and to make the experience of existing art more dynamic and immersive. In entertainment, mostly nonimmersive, screen-based forms of VR are used in computer and video games and arcades. This is a form of VR that many people experience on a regular basis. In the military, finally, VR is used in a variety of training contexts for army, navy and air force. Emerging applications of VR are found in manufacturing, architecture, and training in a variety of (dangerous) civilian professions. Computer simulations are used in the natural and social sciences to gain insight into the functioning of natural and social systems, and in the engineering sciences for performance optimization, safety engineering, training and education. They are used on a large scale in the natural and engineering sciences, where such fields have sprung up as computational physics, computational neuroscience, computational fluid mechanics, computational meteorology and artificial life. They are also used on a somewhat more modest scale in the social sciences, for example in the computational modeling of cognitive processes in psychology, in the computational modeling of artificial societies and social processes, in computational economic modeling, and in strategic management and organizational studies. Computer simulations are increasingly used in education and training, to familiarize students with the workings of systems and to teach them to interact successfully with such systems. Virtuality and Reality The Distinction between the Virtual and the Real In the computer era, the term “virtual” is often contrasted with “real”. Virtual things, it is often believed, are things that only have a simulated existence on a computer, and are therefore not real, like physical things. Take, for example, rocks and trees in a virtual reality environment. They may look like real rocks and trees, but we know that they have no mass, no weight, and no identifiable location in the physical world, and are just illusions generated through electrical processes in microprocessors and the resulting projection of images on a computer screen. “Virtual” hence means “imaginary”, “makebelieve”, “fake”, and contrasts with “real”, “actual” and “physical”. A virtual reality is therefore always only a make-believe reality, and can as such be used for entertainment or training, but it would be a big mistake, in this view, to call anything in virtual reality real, and to start treating it as such. This popular conception of the contrast between virtuality and reality can, however, be demonstrated to be incorrect. “Virtual” is not the perfect opposite of “real”, and some things can be virtual and real at the same time. To see how this is so, let us start by considering the semantics of “virtual”. The word “virtual” has two traditional, pre-computer meanings. On the first, most salient meaning, it refers to things that have certain qualities in essence or in effect, but not in name. For instance, if only a few buffalo are left, one can say that buffalo are virtually extinguished, extinguished for all practical purposes, even though they are not formally or actually extinguished. Virtual can also mean imaginary, and therefore not real, as in optics, where reference is made to virtual foci and images. Notice that only on the second, least salient meaning, “virtual” contrasts with “real”. On the more salient meaning, it does not mean “unreal” but rather “practically but not formally real”. In the computer era, the word “virtual” came to refer to things simulated by a computer, like virtual memory, which is memory that is not actually built into a processor, but nevertheless functioning as such. Later, the scope of the term “virtual” has expanded to include anything that is created or carried by a computer and that mimics a “real” equivalent, like a virtual library and a virtual group meeting. The computer-based meaning of “virtual” conforms more with the traditional meaning of “virtual” as “practically but not formally real” than with “unreal”. Virtual memory, for example, is not unreal memory, but rather a simulation of physical memory that can effectively function as real memory. Under the above definition of “virtual” as “created or carried by a computer and mimicking a “real” equivalent,” virtual things and processes are imitations of real things, but this need not also preclude them from being real themselves. A virtual game of chess, for example, is also a real game of chess. It is just not played with a physically realized board and pieces. I have argued (Brey, 2003) that a distinction can be made between two types of virtual entities: simulations and ontological reproductions. Simulations are virtual versions of real-world entities that have a perceptual or functional similarity to them, but that do not have the pragmatic worth or effects of the corresponding real-world equivalent. Ontological reproductions are computer imitations of real-world entities that have (nearly) the same value or pragmatic effects as their real world counterparts. They hence have a real-world significance that extends beyond the domain of the virtual environment and that is roughly equal to that of their physical counterpart. To appreciate this contrast, consider the difference between a virtual chess game and a virtual beer. A virtual beer is necessarily a mere simulation of a real beer: it may look much like a real one, and may be lifted and consumed in a virtual sense, but it does not provide the taste and nourishment of a real beer and will never get one drunk. A virtual chess game, in contrast, may lack the physical sensation of moving real chess pieces on a board, but this sensation is considered peripheral to the game, and in relevant other respects, playing virtual chess is equivalent to playing chess with physical pieces. This is not to say that the distinction between simulations and ontological reproductions is unproblematic; it is ultimately a pragmatic distinction, and a virtual entity will be classified as one or the other depending on whether it is judged to share enough of the essential features of its physical counterpart. In Brey (2003), I argued that two classes of physical objects and processes can be ontologically reproduced on computers. A first class consists of physical entities that are defined in terms of visual, auditory or computational properties that can be fully realized on multimedia computers. Such entities include images, movies, musical pieces, stereo systems and calculators, which are all such that a powerful computer can successfully reproduce their essential physical or formal properties. A second class consists of what John Searle (1995) has called institutional entities, which are entities that are defined by a status or function that has been assigned to them within a social institution or practice. Examples of institutional entities are activities like buying, selling, voting, owning, chatting, playing chess, trespassing and joining a club, and requisite objects like contracts, money, letters and chess pieces. Most institutional entities are not dependent on a physical medium, because they are only dependent on the collective assignment of a status or function. For instance, we call certain pieces of paper money not because of their inherent physical nature but because we collectively assign monetary value to them. But we could also decide, and have decided, to assign the same status to certain sequences of bits that float around on the Internet. In general, if an institutional entity exists physically, it can also exist virtually. Therefore, many of our institutions and institutional practices, whether social, cultural, religious or economic, can exist in virtual or electronic form. It can be concluded that many virtual entities can be just as real as their physical counterparts. Virtuality and reality are therefore not each others opposites. Nevertheless, a large part of ordinary reality, that includes most physical objects and processes, cannot be ontologically reproduced in virtual form. In addition, institutional virtual entities can both possess and lack real-world implications. Sometimes virtual money can also be used as real money, whereas at other times, it is only a simulation of real money. People can also disagree on the status of virtual money, with some accepting it as legal tender, and others distrusting it. The ontological distinction between reality and virtuality is for these reasons confusing, and the ontological status of encountered virtual objects will often be not immediately clear. Is the Distinction Disappearing? Some authors have argued that the emergence of computer-generated realities is working to erase the distinction between simulation and reality, and therefore between truth and fiction. Jean Baudrillard (1995), for example, has claimed that information technology, media, and cybernetics have yielded a transition from an era of industrial production to an era of simulation, in which models, signs and codes mediate access to reality and define reality to the extent that it is no longer possible to make any sensible distinction between simulations and reality, so that the distinction between reality and simulation has effectively collapsed. Similarly, Albert Borgmann (1999) has argued that virtual reality and cyberspace have lead many people to confuse them for alternative realities that have the same actuality of the real world, thus leading to a collapse of the distinction between representation and reality, whereas according to him VR and cyberspace are merely forms of information and should be treated as such. Philip Zhai (1998), finally, has argued that there is no principled distinction between actual reality and virtual reality, and that with further technological improvements in VR, including the addition of functional teleoperation, virtual reality could be made totally equivalent to actual reality in its functionality for human life. Effectively, Zhai is arguing that any real-world entity can be ontologically reproduced in VR given the right technology, and that virtual environments are becoming ontologically more like real environments as technology progresses. Are these authors right that the distinction between virtuality and reality, and between simulation and reality, is disappearing? First, it is probably true that there is increasingly less difference between the virtual and the real. This is because, as has already been argued, many things are virtual and real at the same time. Moreover, the number of things that are both virtual and real seem to be increasing. This is because as the possibilities of computers and computer networks increase, more and more physical and institutional entities are reproduced in virtual form. There is a flight to the digital realm, in which many believe it is easier and more fun to buy and sell, listen to music or look at art, or do your banking. For many people, therefore, an increasingly large part of their real lives is also virtual, and an increasingly large part of the virtual is also real. Even if virtuality and reality are not opposite concepts, simulation and reality, and representation and reality, certainly are. Are these two distinctions disappearing as well? Suggesting that they at least become more problematic is the fact that more and more of our knowledge of the real world is mediated by representations and simulations, whether they are models in science, raw footage and enactments in broadcast news, and stories and figures in newspapers or on the Internet. Often, it is not possible, in practice or in principle, to verify the truth or accuracy of these representations through direct inspection of the corresponding state-of-affairs. Therefore, one might argue that these representations become reality for us, for they are all the reality we know. In addition, the distinction between recordings and simulations is becoming more difficult to make. Computer technology has made it easy to manipulate photos, video footage and sound recordings, and to generate realistic imagery, so that it is nowadays often unclear of photographic images or video footage on the Internet or in the mass media whether they are authentic or fabricated or enacted. The trend in mass media towards “edutainment” and the enactment and staging of news events has further problematized the distinction. Yet, all this does not prove that the distinction between simulation/representation and reality has collapsed. People do not get all of their information from media representations. They also move around and observe the world for themselves. People still question and critically investigate whether representations are authentic or correspond to reality. People hence still maintain an ontological distinction, even though it has become more difficult epistemologically to discern whether things and events are real or simulated. Zhai’s suggestion that the distinction could be completely erased through further perfection of virtual reality technology is unlikely to hold because it is unlikely that virtual reality could ever fully emulate actual reality in its functionality for human life. Virtual reality environments cannot, after all, sustain real biological processes, and therefore they can never substitute for the complete physical world. Evaluating the Virtual as a Substitute for the Real Next to the ontological and epistemological questions regarding distinction between the virtual and the real and how we can know this distinction, there is the normative question of how we should evaluate virtuality as a substitute for reality. First of all, are virtual things better or worse, more or less valuable, than their physical counterparts? Some authors have argued that they are in some ways better: they tend to be more beautiful, shiny and clean, and more controllable, predictable, and timeless. They attain, as Michael Heim (1983) has argued, a supervivid hyper-reality, like the ideal forms of platonism, more perfect and permanent than the everyday physical world, answering to our desire to transcend our mortal bodies and reach a state of permanence and perfection. Virtual reality, it may seem, can help us live lives that are more perfect, more stimulating and more in accordance with our fantasies and dreams. Critics of virtuality have argued that the shiny, polished objects of VR are mere surrogates: simplified and inferior substitutes for reality that lack authenticity. Albert Borgmann (1999), for example, has argued that virtuality is an inadequate a substitute for reality, because of its fundamental ambiguity and fragility, and lacks the engagement and splendor of reality. He also argues that virtuality threatens to alter our perspective on reality, causing us to see it as yet another sign or simulation. Hubert Dreyfus (2001) has argued that presence in VR and cyberspace gives a disembodied and therefore false experience of reality and that even immersive VR and telepresence present one with impoverished experiences. Another criticism of the virtual as a substitute for the real is that investments in virtual environments tend to correlate with disinvestments in people and activities in real life (Brey, 1998). Even if this were to be no loss to the person making the disinvestments, it may well be a loss to others affected by it. If a person takes great effort in caring for virtual characters, he or she may have less time left to give similar care and emotional attention to actual persons and animals, or may be less interested in giving it. In this way, investments in VR could lead to a neglect of real life and therefore a more solitary society. On the other hand, virtual environments can also be used to vent aggression, harming only virtual characters and property and possibly preventing similar actions in real life. Representation and Simulation: Ethical Issues VR and computer simulations are representational media: they represent real or fictional objects and events. They do so by means of different types of representations: pictorial images, sounds, words and symbols. In this section, ethical aspects of such representations will be investigated. It will be investigated whether representations are morally neutral and whether their manufacture and use in VR and computer simulations involves ethical choices. Misrepresentations, Biased Representations and Indecent Representations I will argue that representations in VR or computer simulations can become morally problematic for any of three reasons. First, they may cause harm by failing to uphold standards of accuracy. That is, they may misrepresent reality. Such representations will be called misrepresentations. Second, they may fail to uphold standards of fairness, thereby unfairly disadvantaging certain individuals or groups. Such representations will be called biased representations. Third, they may violate standards of decency and public morality. I will call such representations indecent representations. Misrepresentation in VR and computer simulation occurs when it is part of the aim of a simulation to realistically depict aspects of the real world, yet the simulation fails to accurately depict these features (Brey, 1999). Many simulations aim to faithfully depict existing structures, persons, state-of-affairs, processes or events. For example, VR applications have been developed that simulate in great detail the visual features of existing buildings such as the Louvre or Taj Mahal or the behavior of existing automobiles or airplanes. Other simulations do not aim to represent particular existing structures, but nevertheless aim to be realistic in their portrayal of people, things and events. For example, a VR simulation of military combat will often be intended to contain realistic portrayals of people, weaponry and landscapes without intending to represent particular individuals or a particular landscape. When simulations aim to be realistic, they are expected to live up to certain standards of accuracy. These are standards that define the degree of freedom that exist in the depiction of a phenomenon, and that specify what kinds of features must be included in a representation for it to be accurate, what level of detail is required, and what kinds of idealizations are permitted. Standards of accuracy are fixed in part by the aim of a simulation. For example, a simulation of surgery room procedures should be highly accurate if it is used for medical training, somewhat accurate when sold as edutainment, and need not be accurate at all when part of a casual game. Standard of accuracy can also be fixed by promises or claims made by manufacturers. For example, if a game promises that surgery room procedures in it are completely realistic, the standards of accuracy for the simulation of these procedures will be high. People may also disagree about the standards of accuracy that are appropriate for a particular simulation. For example, a VR simulation of military combat that does not represent killings in graphic detail may be discounted as inaccurate and misleading by anti-war activists, but may be judged to be sufficiently realistic for the military for training purposes. Misrepresentations of reality in VR and computer simulations are morally problematic to the extent that they can result in harm. The greater these harms are, and the greater the chance that they occur, the greater the moral responsibility of designers and manufacturers to ensure accuracy of representations. Obviously, inaccuracies in VR simulations of surgical procedures for medical training or computer simulations to test the bearing power of bridges can lead to grave consequences. A misrepresentation of the workings of an engine in educational software causes a lesser or less straightforward harm: it causes students to have false beliefs, some of which could cause harms at a later point in time. Biased representations constitute a second category of morally problematic representations in VR modeling and computer simulation (Brey, 1999). A biased representation is a representation that unfairly disadvantages certain individuals or groups or that unjustifiably promotes certain values or interests over others. A representation can be biased in the way it idealizes or selectively represents phenomena. For example, a simulation of global warming may be accurate overall but unjustifiably ignore the contribution to global warming made by certain types of industries or countries. Representations can also be biased by stereotyping people, things and events. For example, a computer game may contain racial or gender stereotypes in its depiction of people and their behaviors. Representations can moreover be biased by containing implicit assumptions about the user, as in a computer game that plays out male heterosexual fantasies, thereby assuming that players will generally be male and heterosexual. They can also be biased by representing affordances and interactive properties in objects that make them supportive of certain values and uses but not of others. For example, a gun in a game may be designed so that it can used to kill but not to knock someone unconscious. Indecent representations constitute a third and final category of morally problematic representations. Indecent representations are representations that are considered shocking or offensive or that are held to break established rules of good behavior or morality and that are somehow shocking to the senses or moral sensibilities. Decency standards vary widely across different individuals and cultures however, and what is shocking or immoral to some will not be so to others. Some will find any depiction of nudity, violence or physical deformities indecent, whereas others will find any such depiction acceptable. The depiction of particular acts, persons or objects may be considered blasphemous in certain religions but not outside these religions. For this reason, the notion of an indecent representation is a relative notion, and there will usually be disagreement about what representations count as indecent. In addition, the context in which representation take place may also influence whether it is considered decent. For example, the representation of open heart surgery, with some patients surviving the procedure but others dying on the operation table, may be inoffensive in the context of a medical simulator, but offensive in the context of a game that makes light of such a procedure. Virtual Child Pornography Pornographic images and movies are considered indecent by many, but there is a fairly large consensus that people have a right to produce pornography and use it in private. Such a consensus does not consist for certain extreme forms of pornography, including child pornography. Child pornography is considered wrong because it harms the children that are used to produce it. But what about virtual child pornography? Virtual child pornography is the digital creation of images or animated pictures that depict children engaging in sexual activities or that depict them in a sexual way. Nowadays, such images and movies can be made to be highly realistic. No real children are abused in this process, and therefore the major reason for outlawing child pornography does not apply for it. Does this mean that virtual child porn is morally permissible and that its production and consumption should be legal? The permissibility of virtual child porn has been defended on the argument that no actual harm is done to children and that that people have a right to free speech by which they should be permitted to produce and own virtual child pornography, even if others find such images offensive. Indeed, the U.S. Supreme Court struck down a congressional ban on virtual child porn in 2002 with the argument that this ban constituted too great a restriction on free speech. The court also claimed that no proof had been given of a connection between computer-generated child pornography and the exploitation of actual children. An additional argument that is sometimes used in favor of virtual child porn is that its availability to pedophiles may actually decrease the chances that they will harm children. Opponents of virtual child porn have sometimes responded with deontological arguments, claiming that it is degrading to children and undermines human dignity. Such arguments cut little ice, however, in a legal arena that is focused on individual rights and harms. Since virtual child porn does not seem to violate the individual rights, opponents have tried out various arguments to the effect that it does cause harm. One existing argument is that virtual child porn causes indirect harm to children because it encourages child abuse. This argument goes opposite the previously stated argument that virtual child porn should be condoned because it makes child abuse less likely. The problem is that it is very difficult to conduct studies that provide solid empirical evidence for either position. Another argument is that failing to criminalize virtual child porn will harm children because it makes it difficult to enforce laws that prohibit actual child pornography. This argument has been used often by law enforcers to criminalize virtual child porn. As Neil Levy (2002) has argued, this argument is however not plausible, amongst other reasons because experts are usually able to make the distinction between virtual and actual pictures. Levy’s own argument against virtual child porn is not that it will indirectly harm children, but that it may ultimately harm women by eroticizing inequality in sexual relationships. He admits, however, that he lacks the empirical evidence to back up this claim. Per Sandin (2004) has presented an argument with better empirical support, which is that virtual child porn should be outlawed because it causes significant harm to a great many people who are revulsed by it. The problem with this argument, however, is that it gives too much weight to harm caused by offense. If actions should be outlawed whenever they offend a large group of people, then individual rights would be drastically curtailed, and many things, ranging from homosexual behavior to interracial marriage, would still be illegal. It can be concluded that virtual child pornography will remain a morally controversial issue for some time to come, as no decisive arguments for or against it have been provided so far. Depiction of Real Persons Virtual environments and computer simulations increasingly include characters that are modeled after the likeness of real persons, whether living or deceased. Also, films and photographs increasingly include manipulated or computer-generated images of real persons who are placed in fictional scenes or are made to perform behaviors that they have not performed in real life. Such appropriations of likenesses are often made without the person’s consent. Is such consent morally required, or should the depictions of real persons be seen as an expression of artistic freedom or free speech? Against arguments for free speech, three legal and moral arguments have traditionally been given for restrictions on the use of someone’s likeness (Tabach-Bank, 2004). First, the right to privacy has been appealed to. It has been argued that the right to privacy includes a right to live a life free from unwarranted publicity (Prosser, 1960). The public use of someone’s likeness can violate someone’s privacy by intruding upon his seclusion or solitude or into his private affairs, by working to publicly disclose embarrassing private facts about him, or to place him in a false light in the public eye. A second argument for restricting the use of someone’s likeness is that it can be used for defamation. Depicting someone in a certain way, for example as being involved in immoral behavior or in a ridiculous situation, can defame him by harming his public reputation. In some countries, like the U.S., there is also a separate recognized right of publicity. The right to publicity is an individual's right to control and profit from the commercial use of his name, likeness and persona. The right to publicity has emerged as a protection of the commercial value of the identity of public personalities, or celebrities, who frequently use their identity to sell or endorse products or services. It is often agreed that celebrities have less of an expectation of privacy, because they are public personalities, but have a greater expectation of a right to publicity. In the use of the likenesses of real persons in virtual environments or doctored digital images, rights to free speech, freedom of the press and freedom of artistic expression will therefore have to be balanced against the right to privacy, the right of publicity and the right to protection from defamation. Behavior in Virtual Environments: Ethical Issues The preceding section focused on ethical issues in design and embedded values in VR and computer simulations. This section focuses on ethical issues in the use of VR and interactive computer simulations. Specifically, the focus will be on the question whether actions within the worlds generated by these technologies can be unethical. This issue will be analyzed for both single-user and multi-user systems. Before it will be taken up, it will first be considered how actions in virtual environments take place, and what the relation is between users and the characters as which they appear in virtual environments. Avatars, Agency and Identity In virtual environments, users assume control over a graphically realized character called an avatar. Avatars can be built after the likeness of the user, but more often, they are generic persons or fantasy characters. Avatars can be controlled from a first-person perspective, in which the user sees the world through the avatar’s eyes, or from a thirdperson perspective. In multi-user virtual environments, there will be multiple avatars corresponding to different users. Virtual environments also frequently contain bots, which are programmed or scripted characters that behave autonomously and are controlled by no one. The identity that users assume in a virtual environment is a combination of the features of the avatar they choose, the behaviors that they choose to display with it, and the way others respond to the avatar and its behaviors. Avatars can function as a manifestation of the user, who behaves and acts like himself, and to whom others respond as if it is the user himself, or as a character that has no direct relation to the user and that merely plays out a role. The actions performed by avatars can therefore range from authentic expressions of the personality and identity of the user to experimentation with identities that are the opposite of who the user normally is. Whether or not the actions of an avatar correspond with how a user would respond in real life, there is no question that the user is causally and morally responsible for actions performed by his or her avatar. This is because users normally have full control over the behavior of their avatars through one or more input devices. There are occasional exceptions to this rule, because avatars are sometimes taken over by the computer and then behave as bots. The responsibility for the behavior of bots could be assigned to either their programmer or to whomever introduced them into a particular environment, or even to the programmer of the environment for not disallowing harmful actions by bots (Ford, 2001). Behavior in Single-User VR Single-user VR offers much less possibilities for unethical behavior than multi-user VR, because there are no other human beings that could be directly affected by the behavior of a user. The question is if there are any behaviors in single-user VR that could qualify as unethical. In Brey (1999), I considered the possibility that certain actions that are unethical when performed in real life could also be unethical when performed in singleuser VR. My focus was particularly on violent and degrading behavior towards virtual human characters, such as murder, torture and rape. I considered two arguments for this position, the argument from moral development and the argument from psychological harm. According to the argument from moral development, it is wrong to treat virtual humans cruelly because doing so will make it more likely that we will treat real humans cruelly. The reason for this is that the emotions appealed to in the treatment of virtual humans are the same emotions that are appealed to in the treatment of real humans, because these actions resemble each other so closely. This argument has recently gained empirical support (Slater et al., 2006). The argument from psychological harm is that third parties may be harmed by the knowledge or observation that people engage in violent, degrading or offensive behavior in single-user VR and that therefore this behavior is immoral. This argument is similar to the argument attributed to Sandin in my earlier discussion of indecent representations. I claimed in Brey (1999) that although harm may be caused by particular actions in single-user VR because people may be offended by them, it does not necessarily follow that the actions are immoral, but only that they cause indirect harm to some people. One would have to balance such harms against any benefits, such as pleasurable experiences to the user. Matt McCormick (2001) has offered yet another argument according to which violent and degrading behavior in single-user VR can be construed as unethical. He argues that repeated engagement in such behavior erodes one’s character and reinforces virtueless habits. He follows Aristotelian virtue ethics in arguing that this is bad because it makes it difficult for us to lead fulfilling lives, because as Aristotle has argued, a fulfilling life can only be lived by those who are of virtuous character. More generally, the argument can be made that the excessive use of single-user VR keeps one from leading a good life, even if one’s actions in it are virtuous, because one invests into fictional worlds and fictional experiences that seem to fulfill one’s desires but do not actually do so (Brey, forthcoming). Behavior in Multi-User VR Many unethical behaviors between persons in the real world can also occur in multi-user virtual environments. As discussed earlier in the section on reality and virtuality, there are two classes of real-world phenomena that can also exist in virtual form: institutional entities that derive their status from collective agreements, like money, marriage, and conversations, and certain physical and formal entities, like images and musical pieces, that computers are capable of physically realizing. Consequently, unethical behaviors involving such entities can also occur in VR, and it is possible for there to be real thefts, insults, deceptions, invasions of privacy, breaches of contract, or damage to property in virtual environments. Immoral behaviors that cannot really happen in virtual environments are those that are necessarily defined over physically realized entities. For example, there can be real insult in virtual environments, but not real murders, because real murders are defined over persons in the physical world, and the medium of VR does not equip users with the power to kill persons in the physical world. It may, of course, be possible to kill avatars in VR, but these are of course not killings of real persons. It may also be possible to plan a real murder in VR, for example by using VR to meet up with a hitman, but this cannot then be followed up by the execution of a real murder in VR. Even though virtual environments can be the site of real events with real consequences, they are often recognized as fictional worlds in which character merely play out roles. In such cases, even an insult may not be a real insult, in the sense of an insult made by a real person to another real person, because it may only have the status of an insult between two virtual characters. The insult is then only real in the context of the virtual world, but is not real in the real world. Ambiguities arise, however, because it will not always be clear when actions and events in virtual environments should be seen as fictional or real (Turkle, 1995). Users may assign different statuses to objects and events, and some users may identify closely with their avatar, so that anything that happens to their avatar also happens to them, whereas others may see their avatar as an object detached from themselves with which they do not identify closely. For this reason, some users may feel insulted when their avatar is insulted, whereas others will not feel insulted at all. This ambiguity in the status of many actions and events in virtual worlds can lead to moral confusion as to when an act that takes place in VR is genuinely unethical and when it merely resembles a certain unethical act. The most famous case of this is the case of the “rape in cyberspace” reported by Julian Dibbell (1993). Dibbell reported an instance of a “cyberrape” in LambdaMOO, a text-only virtual environment in which users interact with user-programmable avatars. One user used a subprogram that took control of avatars and made them perform sex acts on each other. Users felt their characters were raped, and some felt that they themselves were indirectly raped or violated as well. But is it ever possible for someone to be raped through a rape of her avatar, or does rape require a direct violation of someone’s body? Similar ambiguities exist for many other immoral practices in virtual environments, like adultery and theft. If it would constitute adultery when two persons were to have sex with each other, does it also constitute adultery when their avatars have sex? When a user steals virtual money or property from other users, should he be considered a thief in real life? Virtual Property and Virtual Economies For any object or structure found in a virtual world, one may ask the question: Who owns it? This question is already ambiguous, however, because there may both be virtual and real-life owners of virtual entities. For example, a user may be the owner of an island in a virtual world, but the whole world, including the island, may be owned by the company that has created it and permits users to act out roles in it. Users may also become creators of virtual objects, structures and scripted events, and some put in hundreds of hours of work into their creations. May they therefore also assert intellectual property rights to their creations? Or can the company that owns the world in which the objects are found and the software with which they were created assert ownership? What kind of framework of rights and duties should be applied to virtual property? (Burk, 2005). The question of property rights in virtual worlds is further complicated by the emergence of so-called virtual economies. Virtual economies are economies that exist within the context of a persistent multi-user virtual world. Such economies have emerged in virtual worlds like Second Life and The Sims Online, and in massively multiplayer online role-playing games (MMORPGs) like Entropia Universe, World of Warcraft, Everquest and EVE Online. Many of these worlds have millions of users. Economies can emerge in virtual worlds if there are scarce goods and services in them for which users are willing to spend time, effort or money, if users can also develop specialized skills to produce such goods and services, if users are able to assert property rights on goods and resources, and if they can transfer goods and services between them. Some economies in these worlds are primitive barter economies, whereas other make use of recognized currencies. Second Life, for example, makes use of the Linden Dollar (L$) and Entropia Universe has the Project Entropia Dollar (PED), both of which have an exchange rate against real U.S. dollars. Users of these worlds can hence choose to acquire such virtual money by doing work in the virtual world (e.g., by selling services or opening a virtual shop) or by making money in the real world and exchanging it with virtual money. Virtual objects are now frequently traded for real money outside the virtual worlds that contain them, on online trading and auction sites like eBay. Some worlds also allow for the trade of land. In December 2006, the average price of a square meter of land in Second Life was L$ 9.68 or U.S. $ 0.014 (up from L$ 6.67 in November), and over 36,000,000 square meters were sold1 Users have been known to pay thousands of dollars for cherished virtual objects, and over $ 100,000 for real estate. The emergence of virtual economies in virtual environments raises the stakes for their users, and increases the likelihood that moral controversies ensue. People will naturally be more likely to act immorally if money is to be made or if valuable property is to be had. In one incident which took place in China, a man lent a precious sword to another man in the online game Legend of Mir 3, who then sold it to a third party. When the lender found out about this, he visited the borrower at his home and killed him.2 Cases have also been reported of Chinese sweatshop laborers who work day and night in conditions of practical slavery to collect resources in games like World of Warcraft and Lineage, which are then sold for real money. 1 Source: https://secondlife.com/whatis/economy_stats.php. Accessed 1/3/2007. 2 Online gamer killed for selling cyber sword. ABC NewsOnline, March 30, 2005. http://www.abc.net.au/news/newsitems/200503/s1334618.htm. There have also been reported cases of virtual prostitution, for instance on Second Life, where users are paid to (use their avatar to) perform sex acts or to serve as escorts. There have also been controversies over property rights. On Second Life, for example, controversy ensued when someone introduced a program called CopyBot that could copy any item in the world. This program wreaked havoc on the economy, undermining the livelihood of thousands of business owners in Second Life, and was eventually banned after mass protests.3 Clearly, then, the emergence of virtual economies and serious investments in virtual property generates many new ethical issues in virtual worlds. The more time, money and social capital people invest in virtual worlds, the more such ethical issues will come to the front. The Ethics of Computer Games Contemporary computer and video games often play out in virtual environments or include computer simulations, as defined earlier. Computer games are nowadays mass media. A recent study shows that the average American 8- to 18-year old spends almost six hours per week playing computer games, and that 83% has access to a video game console at home (Rideout, Roberts and Foehr, 2005). Adults are also players, with four in ten playing computer games on a regular basis.4 In 2005, the revenue in the U.S. generated by the computer and game industry generated was over U.S. $ 7 billion, far surpassing the film industry’s annual box office results.5 Computer games have had a vast impact on youth culture, but also significantly influence the lives of adults. For these reasons alone, an evaluation of their social and ethical aspects is needed. Some important issues bearing on the ethics of computer games have already been discussed in previous sections, and therefore will be covered less extensively here. These include, amongst others, ethical issues regarding biased and indecent representations; issues of responsibility and identity in the relation between avatars, users and bots; the ethics of behavior in virtual environments; and moral issues regarding virtual property and virtual economies. These issues, and the conclusions reached regarding them, all fully apply to computer games. The focus in this section will be on three important ethical questions that apply to computer games specifically: Do computer games contribute to individual well-being and the social good? What values should govern the design and use of computer games? And do computer games contribute to gender inequality? The Goods and Ills of Computer Games Are computer games a benefit to society? Many parents do not think so. They worry about the extraordinary amount of time their children spend playing computer games, and 3 Linden bans CopyBot following resident protests. Reuters News, Wednesday November 15, 2006. http://secondlife.reuters.com/stories/2006/11/15/linden-bans-copybot-following-resident-protests/ 4 Poll: 4 in 10 adults play electronic games. MSNBC.com, May 8, 2006. http://www.msnbc.msn.com/id/12686020/ 5 2006 Essential Facts about the Computer and Video Game Industry, Entertainment Software Association, 2006. http://www.theesa.com/archives/files/Essential%20Facts%202006.pdf about the excessive violence that takes place in many games. They worry about negative effects on family life, schoolwork and the social and moral development of their kids. In the media, there has been much negative reporting about computer games. There have been stories about computer game addiction and about players dying from exhaustion and starvation after playing video games for days on end. There have been stories about ultraviolent and otherwise controversial video games, and the ease by which children can gain access to them. The Columbine High School massacre, in 1999, in which two teenage students went out on a shooting rampage, was reported in the media to have been inspired by the video game Doom, and since then, other mass shootings have also been claimed to have been inspired by video games. Considerable doubt has been raised, therefore, as to whether computer games are indeed a benefit to society rather than a social ill. The case against computer games tends to center on three perceived negative consequences: addiction, aggression and maladjustment. The perceived problem of addiction is that many gamers get so caught up in playing that their health, work or study, family life, and social relations suffer. How large this problem really is has not yet been adequately documented (though see Chiu, Lee and Huang, 2004). There clearly is a widespread problem, as there has been a worldwide emergence of clinics for video addicts in recent years. Not all hard-core gamers will be genuine addicts in the psychiatric sense, but many do engage in overconsumption, resulting in the neglect described above. The partners of adults who engage in such overconsumption sometimes called gamer widows, analogous to soccer widows, denoting that they have a relationship with a gamer who pays more attention to the game than to them. Whereas there is no doubt that addiction to video games is a real social phenomenon, there is less certainty that playing video games can be correlated with increased aggression, as some have claimed. The preponderance of the evidence seems to indicate, however, that the playing of violent video games can be correlated with increases in aggression, including increases in aggressive thoughts, aggressive feeling, aggressive behaviors, and a desensitization to real-life violence, and a decrease in helpful behaviors (Carnagey, Anderson and Bushman, forthcoming; Bartholow, 2005). However, some studies have found no such correlations, and present findings remain controversial. Whatever the precise relation between violent video games and aggression turns out to be, it is clear now that there is a huge difference between the way that children are taught to behave towards others by their parents and how they learn to behave in violent video games. This at least raises the question of how their understanding of and attitude towards violence and aggression is influenced by violent video games. A third hypothesized ill of video games is that they cause individuals to be socially and cognitively slighted and maladjusted. This maladjustment is attributed in part to the neglect of studies and social relations due to an overindulgence into video games and to increased aggression levels from playing violent games. But it is also held to be due to the specific skills and understandings that users gain from video games. Children that play video games are exposed to conceptions of human relations and the workings of the world that have been designed into them by game developers. These conceptions have not been designed to be realistic or pedagogical, and often rely on stereotypes and simplistic modes of interaction and solutions to problems. It is therefore conceivable that children develop ideas and behavioral routines while playing computer games that leave much to be desired. The case in favor of computer games begins with the observation that they are a new and powerful medium that brings users pleasure and excitement, and that allow for new forms of creative expression and new ways of acting out fantasies. Games moreover do not just cause social isolation, they can also stimulate social interaction. Playing multiplayer games is a social activity that involves interactions with other players, and that can even help solitary individuals find new friends. Computer games may moreover induce social learning and train social skills. This is especially true for role-playing games and games that involve verbal interactions with other characters. Such games let players experiment with social behavior in different social settings, and role-playing game can also make users intimately familiar with the point of view and experiences of persons other than themselves. Computer games have moreover been claimed to improve perceptual, cognitive and motor skills, for example by improving hand-eye coordination and improving visual recognition skills (Johnson, 2005; Green and Bavelier, 2003). Computer Games and Values It has long been argued in computer ethics that computer systems and software are not value-neutral but are instead value-laden (Nissenbaum, 1998; Brey, 2000). Computer games are no exception. Computer games may suggest, stimulate, promote or reward certain values while shunning or discouraging others. Computer games are value-laden, first of all, in the way they represent the world. As discussed, earlier, such representations may contain a variety of biases. They may, for example, promote racial and gender stereotypes (Chan, 2005; Ray, 2003), and they may contain implicit, biased assumptions about the abilities, interests or gender of the player. Simulation games like SimCity may suggest all kinds of unproven causal relations, for example correlations between poverty and crime, that may help shape attitudes and feed prejudices. Computer games may also be value-laden in the interactions that they make possible. They may, for example, be designed to make violent action the only solution to problems faced by a player. Computer games can also be value-laden in the storylines they suggest for players and in the feedback and rewards that are given. Some first-person shooters awards extra points, for example, for not killing innocent bystanders, whereas others instead award extra points for killing as many as possible. A popular game like The Sims can serve to illustrate how values are embedded in games. The Sims is a game that simulates the everyday lives and social relationships of ordinary persons. The goal of characters in the game is happiness, which is attained through the satisfaction of needs like Hunger, Comfort, Hygiene and Fun. These needs can be satisfied through success in one’s career, and through consumption and social interaction. As Miguel Sicart (2003) has argued, The Sims thus presents an idealized version of a progressive liberal consumer society in which the goal in life is happiness, gained by being a good worker and consumer. The team-based first-person shooter America’s Army presents another example. This game is offered as a free download by the U.S. government, who uses it to stimulate U.S. army recruitment. The game is designed to give a positive impression of the U.S. army. Players play as servicemen who obey orders and work together to combat terrorists. The game claims to be highly realistic, yet it has been criticized for not showing certain realistic aspects of military life, such as collateral damage, harassment, and gore. The question is how influential computer games actually are in influencing the values of players. The amount of psychological research done of this topic is still limited. However, psychological research on the effect of other media, such as television, has shown that it is very influential in affecting the value of media users, especially children. Since many children are avid consumers of computer games, there are reasons to be concerned about the values projected on them by such games. Children are still involved in a process of social, moral and cognitive development, and computer games seem to have an increasingly large role in this developmental process. Concern about the values embedded in video games therefore seems warranted. On the other hand, computer games are games, and therefore should allow for experimentation, fantasy, and going beyond socially accepted boundaries. The question is how games can support such social and moral freedom without also supporting the development of skewed values in younger players. Players do not just develop values on the basis of the structure of the game itself, they also develop them by interacting with other players. Players communicate messages to each other about game rules and acceptable in-game behavior. They can respond positively or negatively to certain behaviors, and may praise or berate other players. In this way, social interactions in games may become part of the socialization of individuals and influence their values and social beliefs. Some of these values and norms may remain limited to the game itself, for example, norms governing the permissibility of cheating (Kimppa and Bissett, 2005). In some games, however, like massively multiplayer online role-playing games (MMORPG’s), socialization processes are so complex as to resemble real life (Warner and Raiter, 2005), and values learned in such games may be applied to real life as well. Computer Games and Gender Games magazine and game advertisement foster the impression that computer games are a medium for boys and men. Most pictured gamers are male, and many recurring elements in images, such as scantily clad, big-breasted women, big guns and fast cars, seem to be geared toward men. The impression that computer games are mainly a medium for men is further supported by usage statistics. Research has consistently shown that fewer girls and women play computer games than boys and men, and those that do spend less time playing than men. According to research performed by Electronic Arts, a game developer, among teenagers only 40% of girls play computer games, compared to 90% of boys. Moreover, when they reach high school, most girls lose interest, whereas most boys keep playing.6 A study by the UK games trade body, the Entertainment and Leisure Publishers Association, found that in Europe, women gamers make up only a quarter of the gaming population. 7 6 Games industry is 'failing women'. BBC News, August 21, 2006. http://news.bbc.co.uk/2/hi/technology/5271852.stm 7 Chicks and Joysticks. An Exploration of Women and Gaming. ELSPA White Paper, September 2004. www.elspa.com/assets/files/c/chicksandjoysticksanexplorationofwomenandgaming_176.pdf The question whether there is a gender bias in computer games is morally significant because it is a question about gender equality. If it is the case that computer games tend to be designed and marketed for men, then women are at an unfair disadvantage, as they consequently have less opportunity to enjoy computer games and their possible benefits. Among such benefits may be greater computer literacy, an important quality in today’s marketplace. But is the gender gap between usage of computer games really the result of gender bias in the gaming industry, or could it be the case that women are simply less interested in computer games than men, regardless of how games are designed and marketed? Most analysts hold that the gaming industry is largely to blame. They point to the fact that almost all game developers are male, and that there have been few efforts to develop games suitable for women. To appeal to women, it has been suggested, computer games should be less aggressive, because women have been socialized to be non-aggressive (Norris, 2004). It has also been suggested that women have a greater interest in multiplayer games, games with complex characters, games that contain puzzles, and games that are about human relationships. Games should also avoid assumptions that the player is male and avoid stereotypical representations of women. Few existing games contain good role models for women. Studies have found that most female characters in games have unrealistic body images and display stereotypical female behaviors, and that a disproportionate number of them are prostitutes and strippers. 8 Virtual Reality, Simulation and Professional Ethics In discussing issues of professional responsibility in relation to virtual reality systems and computer simulations, a distinction can be made between the responsibility of developers of such systems and that of professional users. Professional users can be claimed to have a responsibility to acquaint themselves with the technology and its potential consequences and to use it in a way that is consistent with the ethics of their profession. The responsibility of developers includes giving consideration to ethical aspects in the design process and engaging in adequate communication about the technology and its effects to potential users. In the development of computer simulations, the accuracy of the simulation and its reliability as a foundation for decision-making in the real world are of paramount importance. The major responsibility of simulation professionals is therefore to avoid misrepresentations where they can and to adequately communicating the limitations of simulations to users (McLeod, 1983). These responsibilities are, indeed, a central ingredient in a recent code of ethics for simulationists adopted by a large number of professional organizations for simulationists (Ören et al., 2002). The responsibility for accuracy entails the responsibility to take proper precautions to ensure that modeling mistakes do not occur, especially when the stakes are high, and to inform users if inaccuracies do or may occur. It also entails the responsibility not to participate in intentional deception of users (e.g., embellishment, dramatization, or censorship). 8 Fair Play: Violence, Gender and Race in Video Games. Children Now , December 2001. 36 pp. http://publications.childrennow.org/ In Brey (1999), I have argued that designers of simulations and virtual environments also have a responsibility to incorporate proper values into their creations. It has been argued earlier that representations and interfaces are not value-free but may contain values and biases. Designers have a responsibility to reflect on the values and biases contained in their creations and to ensure that they do not violate important ethical principles. The responsibility to do this follows from the ethical codes that are in use in different branches of engineering and computer science, especially the principle that professional expertise should be used for the enhancement of human welfare. If technology is to promote human welfare, it should not contain biases and should regard the values and interests of stakeholders or society at large. Taking into account such values and avoiding biases in design cannot be done without a proper methodology. Fortunately, a detailed proposal for such a methodology has recently been made by Batya Friedman and her associates, and has been termed value-sensitive design (Friedman, Kahn and Borning, 2006). Special responsibilities apply to different areas of applications for VR and computer simulations. The use of virtual reality in therapy and psychotherapy, for example, requires special consideration to principles of informed consent and the ethics of experimentation with human subjects (Wiederhold and Wiederhold, 2004). The computer and video game industry can be argued to have a special responsibility to consider the social and cultural impact of their products, given that they are used by a mass audience that includes children. Arguably, game developers should consider the messages that their products send to users, especially children, and should work to ensure that they develop and market content that is age-appropriate and that is more inclusive of all genders. Virtual reality and computer simulation will continue to present new challenges for ethics, because new and more advanced applications are still being developed, and their use is more and more widespread. Moreover, as has been argued, virtual environments can mimic many of the properties of real life, and therefore contain many of the ethical dilemmas found in real life. It is for this reason that they will not just continue to present new ethical challenges for professional developers and users, but also for society at large.

Virtual Reality and Computer Simulation

Introduction

Virtual reality and computer simulation have not received much attention from ethicists. It is argued in this essay that this relative neglect is unjustified, and that there are important ethical questions that can be raised in relation to these technologies. First of all, these technologies raise important ethical questions about the way in which they represent reality and the misrepresentations, biased representations and offensive representations that they may contain. In addition, actions in virtual environments can be harmful to others, and can also be morally problematic from the point of view of deontological and virtue ethics. Although immersive virtual reality systems are not yet used on a large scale, nonimmersive virtual reality is regularly experienced by hundreds of millions of users, in the form of computer games and virtual environments for exploration and social networking. These forms of virtual reality also raise ethical questions regarding their benefits and harms to users and society, and the values and biases contained in them. This paper has the following structure. The next section will describe what virtual reality and computer simulations are and what the current applications of these technologies are. This is followed by a section that analyzes the relation between virtuality and reality, and asks whether virtuality can and should function as a substitute for reality. Three subsequent sections discuss ethical aspects of representation in virtual reality and computer simulations, the ethics of behavior in virtual reality and the ethics of computer games. A concluding section discusses issues of professional ethics in the development and professional use of virtual reality systems and computer simulations. Background: The Technology and Its Applications Virtual reality Virtual reality (VR) technology emerged in the 1980s, with the development and marketing of systems consisting of a head mounted display (HMD) and datasuit or dataglove attached to a computer. These technologies simulated three-dimensional (3-D) environments displayed in surround stereoscopic vision on the head mounted display. The user could navigate and interact with simulated environments through the datasuit and dataglove, items that tracked the positions and motions of body parts and allowed the computer to modify its output depending on the recorded positions. This original technology has helped define what is often meant by “virtual reality”: an immersive, interactive three-dimensional computer-generated environment in which interaction takes place over multiple sensory channels and includes tactile and positioning feedback. According to Sherman and Craig (2003), there are four essential elements in virtual reality: a virtual world, immersion, sensory feedback, and interactivity. A virtual world is a description of a collection of objects in a space and rules and relationships governing these objects. In virtual reality systems, such virtual worlds are generated by a computer. Immersion is the sensation of being present in an environment, rather than just observing an environment from the outside. Sensory feedback is the selective provision of sensory data about the environment based on user input. The actions and position of the user provide a perspective on reality and determines what sensory feedback is given. Interactivity, finally, is the responsiveness of the virtual world to user actions. Interactivity includes the ability to navigate virtual worlds and to interact with objects, characters and places. These four elements can be realized to a greater and lesser degree with a computer, and that is why there are both broad and narrow definitions of virtual reality. A narrow definition would only define fully immersive and fully interactive virtual environments as VR. However, there are many virtual environments that do not meet all these criteria to the fullest extent possible, but that could still be categorized as VR. Computer games played on a desktop with a keyboard and mouse, like Doom and HalfLife, are not fully immersive, and sensory feedback and interactivity in them is more limited than in immersive VR systems that include a head mounted display and datasuit. Yet, they do present virtual worlds that are immersive to an extent, and that are interactive and involve visual and auditory feedback. In Brey (1999) I therefore proposed a broader definition of virtual reality, as a three-dimensional interactive computergenerated environment that incorporates a first-person perspective. This definition includes both immersive and nonimmersive (screen-based) forms of VR. The notion of a virtual world, or virtual environment, as defined by Sherman and Craig, is broader than that of virtual reality. A virtual world can be realized by means of sensory feedback, in which case it yields virtual reality, but it can also be realized without it. Classical text-based adventure games like Zork, for example, play in interactive virtual worlds, but users are informed about the state of this world through text. They provide textual inputs, and the game responds with textual information rather than sensory feedback about changes in the world. A virtual world is hence an interactive computer-generated environment, and virtual reality is a special type of virtual world that involves location- and movement-relative sensory feedback. Next to the term “virtual reality,” there is the term “virtuality” and its derivative adjective “virtual”. This term has a much broader meaning than the term “virtual reality” or even “virtual environment”. As explained more extensively in the next section, the term “virtual” refers to anything that is created or carried by a computer and that mimics a “real”, physically localized entity, as in “virtual memory” and “virtual organization”. In this essay, the focus will be on virtual reality and virtual environments, but occasionally, especially in the next section, the broader phenomenon of virtuality will be discussed as well. Returning to the topic of virtual reality, a distinction can be made between singleuser and multi-user or networked VR. In single-user VR, there is only one user, whereas in networked VR, there are multiple users who share a virtual environment and appear to each others as avatars, which are graphical representations of the characters played by users in VR. A special type of VR is augmented reality, in which aspects of simulated virtual worlds are blended with the real world that is experienced through normal vision or a video link, usually through transparent glasses on which computer graphics or data are overlaid. Related to VR, furthermore, are telepresence and teleoperator systems, systems that extend a person’s sensing and manipulation capability to a remote location by displaying images and transmitting sounds from a real environment that can (optionally) be acted on from a distance through remote handling systems such as robotic arms. Computer simulation A computer simulation is a computer program that contains a model of a particular system (either actual or theoretical) and that can be executed, after which the execution output can be analyzed. Computer simulation is also the name of the discipline in which such models are designed, executed and analyzed. The models in computer simulations are usually abstract and either are or involve mathematical models. Computer simulation has become a useful part of the mathematical modeling of many natural systems in the natural sciences, human systems in the social sciences, and technological systems in the engineering sciences, in order to gain insight into the operations of these systems and to study the effects of alternative conditions and courses of action. It is not usually an aim in computer simulations, as it is in virtual reality, to do realistic visual modeling of the systems that they simulate. Some of these systems are abstract, and even for those systems that are concrete, the choice is often made not to design graphic representations of the system, but to rely solely on abstract models of it. When graphical representations of concrete systems are used, they usually only represent features that are relevant to the aims of the simulation, and do not aspire to the realism and detail aspired to in virtual reality. Another difference with virtual reality is that computer simulations need not be interactive. Usually, simulators will determine a number of parameters at the beginning of a simulation and then “run” the simulation without any interventions. In this standard case, the simulator is not himself defined as part of the simulation, as would happen in virtual reality. An exception is an interactive simulation, which is a special kind of simulation, also referred to as a human-in-the-loop simulation, in which the simulation includes a human operator. An example of such a simulation would be a flight simulator. If a computer simulation is interactive and makes use of three-dimensional graphics and sensory feedback, it also qualifies as a form of virtual reality. Sometimes, also, the term “computer simulation” is used to include any computer program that models a system or environment, even if it is not used to gain insight into the operation of a system. In that broad sense, virtual environments, at least those that aim to do realistic modeling, would also qualify as computer simulations. Applications VR is used to simulate both real and imaginary environments. Traditional VR applications are found in medicine, education, arts and entertainment, and the military (Burdea and Coiffet, 2003). In medicine, VR is used for the simulation of anatomical structures and medical procedures in education and training, for example for performing virtual surgery. Increasingly, VR is also being used for (psycho)therapy, for instance for overcoming anxiety disorders by confronting patients with virtual anxiety-provoking situations (Wiederhold and Wiederhold, 2004). In education, VR is used in explorationbased learning and learning by building virtual worlds. In the arts, VR is used to create new art forms and to make the experience of existing art more dynamic and immersive. In entertainment, mostly nonimmersive, screen-based forms of VR are used in computer and video games and arcades. This is a form of VR that many people experience on a regular basis. In the military, finally, VR is used in a variety of training contexts for army, navy and air force. Emerging applications of VR are found in manufacturing, architecture, and training in a variety of (dangerous) civilian professions. Computer simulations are used in the natural and social sciences to gain insight into the functioning of natural and social systems, and in the engineering sciences for performance optimization, safety engineering, training and education. They are used on a large scale in the natural and engineering sciences, where such fields have sprung up as computational physics, computational neuroscience, computational fluid mechanics, computational meteorology and artificial life. They are also used on a somewhat more modest scale in the social sciences, for example in the computational modeling of cognitive processes in psychology, in the computational modeling of artificial societies and social processes, in computational economic modeling, and in strategic management and organizational studies. Computer simulations are increasingly used in education and training, to familiarize students with the workings of systems and to teach them to interact successfully with such systems. Virtuality and Reality The Distinction between the Virtual and the Real In the computer era, the term “virtual” is often contrasted with “real”. Virtual things, it is often believed, are things that only have a simulated existence on a computer, and are therefore not real, like physical things. Take, for example, rocks and trees in a virtual reality environment. They may look like real rocks and trees, but we know that they have no mass, no weight, and no identifiable location in the physical world, and are just illusions generated through electrical processes in microprocessors and the resulting projection of images on a computer screen. “Virtual” hence means “imaginary”, “makebelieve”, “fake”, and contrasts with “real”, “actual” and “physical”. A virtual reality is therefore always only a make-believe reality, and can as such be used for entertainment or training, but it would be a big mistake, in this view, to call anything in virtual reality real, and to start treating it as such. This popular conception of the contrast between virtuality and reality can, however, be demonstrated to be incorrect. “Virtual” is not the perfect opposite of “real”, and some things can be virtual and real at the same time. To see how this is so, let us start by considering the semantics of “virtual”. The word “virtual” has two traditional, pre-computer meanings. On the first, most salient meaning, it refers to things that have certain qualities in essence or in effect, but not in name. For instance, if only a few buffalo are left, one can say that buffalo are virtually extinguished, extinguished for all practical purposes, even though they are not formally or actually extinguished. Virtual can also mean imaginary, and therefore not real, as in optics, where reference is made to virtual foci and images. Notice that only on the second, least salient meaning, “virtual” contrasts with “real”. On the more salient meaning, it does not mean “unreal” but rather “practically but not formally real”. In the computer era, the word “virtual” came to refer to things simulated by a computer, like virtual memory, which is memory that is not actually built into a processor, but nevertheless functioning as such. Later, the scope of the term “virtual” has expanded to include anything that is created or carried by a computer and that mimics a “real” equivalent, like a virtual library and a virtual group meeting. The computer-based meaning of “virtual” conforms more with the traditional meaning of “virtual” as “practically but not formally real” than with “unreal”. Virtual memory, for example, is not unreal memory, but rather a simulation of physical memory that can effectively function as real memory. Under the above definition of “virtual” as “created or carried by a computer and mimicking a “real” equivalent,” virtual things and processes are imitations of real things, but this need not also preclude them from being real themselves. A virtual game of chess, for example, is also a real game of chess. It is just not played with a physically realized board and pieces. I have argued (Brey, 2003) that a distinction can be made between two types of virtual entities: simulations and ontological reproductions. Simulations are virtual versions of real-world entities that have a perceptual or functional similarity to them, but that do not have the pragmatic worth or effects of the corresponding real-world equivalent. Ontological reproductions are computer imitations of real-world entities that have (nearly) the same value or pragmatic effects as their real world counterparts. They hence have a real-world significance that extends beyond the domain of the virtual environment and that is roughly equal to that of their physical counterpart. To appreciate this contrast, consider the difference between a virtual chess game and a virtual beer. A virtual beer is necessarily a mere simulation of a real beer: it may look much like a real one, and may be lifted and consumed in a virtual sense, but it does not provide the taste and nourishment of a real beer and will never get one drunk. A virtual chess game, in contrast, may lack the physical sensation of moving real chess pieces on a board, but this sensation is considered peripheral to the game, and in relevant other respects, playing virtual chess is equivalent to playing chess with physical pieces. This is not to say that the distinction between simulations and ontological reproductions is unproblematic; it is ultimately a pragmatic distinction, and a virtual entity will be classified as one or the other depending on whether it is judged to share enough of the essential features of its physical counterpart. In Brey (2003), I argued that two classes of physical objects and processes can be ontologically reproduced on computers. A first class consists of physical entities that are defined in terms of visual, auditory or computational properties that can be fully realized on multimedia computers. Such entities include images, movies, musical pieces, stereo systems and calculators, which are all such that a powerful computer can successfully reproduce their essential physical or formal properties. A second class consists of what John Searle (1995) has called institutional entities, which are entities that are defined by a status or function that has been assigned to them within a social institution or practice. Examples of institutional entities are activities like buying, selling, voting, owning, chatting, playing chess, trespassing and joining a club, and requisite objects like contracts, money, letters and chess pieces. Most institutional entities are not dependent on a physical medium, because they are only dependent on the collective assignment of a status or function. For instance, we call certain pieces of paper money not because of their inherent physical nature but because we collectively assign monetary value to them. But we could also decide, and have decided, to assign the same status to certain sequences of bits that float around on the Internet. In general, if an institutional entity exists physically, it can also exist virtually. Therefore, many of our institutions and institutional practices, whether social, cultural, religious or economic, can exist in virtual or electronic form. It can be concluded that many virtual entities can be just as real as their physical counterparts. Virtuality and reality are therefore not each others opposites. Nevertheless, a large part of ordinary reality, that includes most physical objects and processes, cannot be ontologically reproduced in virtual form. In addition, institutional virtual entities can both possess and lack real-world implications. Sometimes virtual money can also be used as real money, whereas at other times, it is only a simulation of real money. People can also disagree on the status of virtual money, with some accepting it as legal tender, and others distrusting it. The ontological distinction between reality and virtuality is for these reasons confusing, and the ontological status of encountered virtual objects will often be not immediately clear. Is the Distinction Disappearing? Some authors have argued that the emergence of computer-generated realities is working to erase the distinction between simulation and reality, and therefore between truth and fiction. Jean Baudrillard (1995), for example, has claimed that information technology, media, and cybernetics have yielded a transition from an era of industrial production to an era of simulation, in which models, signs and codes mediate access to reality and define reality to the extent that it is no longer possible to make any sensible distinction between simulations and reality, so that the distinction between reality and simulation has effectively collapsed. Similarly, Albert Borgmann (1999) has argued that virtual reality and cyberspace have lead many people to confuse them for alternative realities that have the same actuality of the real world, thus leading to a collapse of the distinction between representation and reality, whereas according to him VR and cyberspace are merely forms of information and should be treated as such. Philip Zhai (1998), finally, has argued that there is no principled distinction between actual reality and virtual reality, and that with further technological improvements in VR, including the addition of functional teleoperation, virtual reality could be made totally equivalent to actual reality in its functionality for human life. Effectively, Zhai is arguing that any real-world entity can be ontologically reproduced in VR given the right technology, and that virtual environments are becoming ontologically more like real environments as technology progresses. Are these authors right that the distinction between virtuality and reality, and between simulation and reality, is disappearing? First, it is probably true that there is increasingly less difference between the virtual and the real. This is because, as has already been argued, many things are virtual and real at the same time. Moreover, the number of things that are both virtual and real seem to be increasing. This is because as the possibilities of computers and computer networks increase, more and more physical and institutional entities are reproduced in virtual form. There is a flight to the digital realm, in which many believe it is easier and more fun to buy and sell, listen to music or look at art, or do your banking. For many people, therefore, an increasingly large part of their real lives is also virtual, and an increasingly large part of the virtual is also real. Even if virtuality and reality are not opposite concepts, simulation and reality, and representation and reality, certainly are. Are these two distinctions disappearing as well? Suggesting that they at least become more problematic is the fact that more and more of our knowledge of the real world is mediated by representations and simulations, whether they are models in science, raw footage and enactments in broadcast news, and stories and figures in newspapers or on the Internet. Often, it is not possible, in practice or in principle, to verify the truth or accuracy of these representations through direct inspection of the corresponding state-of-affairs. Therefore, one might argue that these representations become reality for us, for they are all the reality we know. In addition, the distinction between recordings and simulations is becoming more difficult to make. Computer technology has made it easy to manipulate photos, video footage and sound recordings, and to generate realistic imagery, so that it is nowadays often unclear of photographic images or video footage on the Internet or in the mass media whether they are authentic or fabricated or enacted. The trend in mass media towards “edutainment” and the enactment and staging of news events has further problematized the distinction. Yet, all this does not prove that the distinction between simulation/representation and reality has collapsed. People do not get all of their information from media representations. They also move around and observe the world for themselves. People still question and critically investigate whether representations are authentic or correspond to reality. People hence still maintain an ontological distinction, even though it has become more difficult epistemologically to discern whether things and events are real or simulated. Zhai’s suggestion that the distinction could be completely erased through further perfection of virtual reality technology is unlikely to hold because it is unlikely that virtual reality could ever fully emulate actual reality in its functionality for human life. Virtual reality environments cannot, after all, sustain real biological processes, and therefore they can never substitute for the complete physical world. Evaluating the Virtual as a Substitute for the Real Next to the ontological and epistemological questions regarding distinction between the virtual and the real and how we can know this distinction, there is the normative question of how we should evaluate virtuality as a substitute for reality. First of all, are virtual things better or worse, more or less valuable, than their physical counterparts? Some authors have argued that they are in some ways better: they tend to be more beautiful, shiny and clean, and more controllable, predictable, and timeless. They attain, as Michael Heim (1983) has argued, a supervivid hyper-reality, like the ideal forms of platonism, more perfect and permanent than the everyday physical world, answering to our desire to transcend our mortal bodies and reach a state of permanence and perfection. Virtual reality, it may seem, can help us live lives that are more perfect, more stimulating and more in accordance with our fantasies and dreams. Critics of virtuality have argued that the shiny, polished objects of VR are mere surrogates: simplified and inferior substitutes for reality that lack authenticity. Albert Borgmann (1999), for example, has argued that virtuality is an inadequate a substitute for reality, because of its fundamental ambiguity and fragility, and lacks the engagement and splendor of reality. He also argues that virtuality threatens to alter our perspective on reality, causing us to see it as yet another sign or simulation. Hubert Dreyfus (2001) has argued that presence in VR and cyberspace gives a disembodied and therefore false experience of reality and that even immersive VR and telepresence present one with impoverished experiences. Another criticism of the virtual as a substitute for the real is that investments in virtual environments tend to correlate with disinvestments in people and activities in real life (Brey, 1998). Even if this were to be no loss to the person making the disinvestments, it may well be a loss to others affected by it. If a person takes great effort in caring for virtual characters, he or she may have less time left to give similar care and emotional attention to actual persons and animals, or may be less interested in giving it. In this way, investments in VR could lead to a neglect of real life and therefore a more solitary society. On the other hand, virtual environments can also be used to vent aggression, harming only virtual characters and property and possibly preventing similar actions in real life. Representation and Simulation: Ethical Issues VR and computer simulations are representational media: they represent real or fictional objects and events. They do so by means of different types of representations: pictorial images, sounds, words and symbols. In this section, ethical aspects of such representations will be investigated. It will be investigated whether representations are morally neutral and whether their manufacture and use in VR and computer simulations involves ethical choices. Misrepresentations, Biased Representations and Indecent Representations I will argue that representations in VR or computer simulations can become morally problematic for any of three reasons. First, they may cause harm by failing to uphold standards of accuracy. That is, they may misrepresent reality. Such representations will be called misrepresentations. Second, they may fail to uphold standards of fairness, thereby unfairly disadvantaging certain individuals or groups. Such representations will be called biased representations. Third, they may violate standards of decency and public morality. I will call such representations indecent representations. Misrepresentation in VR and computer simulation occurs when it is part of the aim of a simulation to realistically depict aspects of the real world, yet the simulation fails to accurately depict these features (Brey, 1999). Many simulations aim to faithfully depict existing structures, persons, state-of-affairs, processes or events. For example, VR applications have been developed that simulate in great detail the visual features of existing buildings such as the Louvre or Taj Mahal or the behavior of existing automobiles or airplanes. Other simulations do not aim to represent particular existing structures, but nevertheless aim to be realistic in their portrayal of people, things and events. For example, a VR simulation of military combat will often be intended to contain realistic portrayals of people, weaponry and landscapes without intending to represent particular individuals or a particular landscape. When simulations aim to be realistic, they are expected to live up to certain standards of accuracy. These are standards that define the degree of freedom that exist in the depiction of a phenomenon, and that specify what kinds of features must be included in a representation for it to be accurate, what level of detail is required, and what kinds of idealizations are permitted. Standards of accuracy are fixed in part by the aim of a simulation. For example, a simulation of surgery room procedures should be highly accurate if it is used for medical training, somewhat accurate when sold as edutainment, and need not be accurate at all when part of a casual game. Standard of accuracy can also be fixed by promises or claims made by manufacturers. For example, if a game promises that surgery room procedures in it are completely realistic, the standards of accuracy for the simulation of these procedures will be high. People may also disagree about the standards of accuracy that are appropriate for a particular simulation. For example, a VR simulation of military combat that does not represent killings in graphic detail may be discounted as inaccurate and misleading by anti-war activists, but may be judged to be sufficiently realistic for the military for training purposes. Misrepresentations of reality in VR and computer simulations are morally problematic to the extent that they can result in harm. The greater these harms are, and the greater the chance that they occur, the greater the moral responsibility of designers and manufacturers to ensure accuracy of representations. Obviously, inaccuracies in VR simulations of surgical procedures for medical training or computer simulations to test the bearing power of bridges can lead to grave consequences. A misrepresentation of the workings of an engine in educational software causes a lesser or less straightforward harm: it causes students to have false beliefs, some of which could cause harms at a later point in time. Biased representations constitute a second category of morally problematic representations in VR modeling and computer simulation (Brey, 1999). A biased representation is a representation that unfairly disadvantages certain individuals or groups or that unjustifiably promotes certain values or interests over others. A representation can be biased in the way it idealizes or selectively represents phenomena. For example, a simulation of global warming may be accurate overall but unjustifiably ignore the contribution to global warming made by certain types of industries or countries. Representations can also be biased by stereotyping people, things and events. For example, a computer game may contain racial or gender stereotypes in its depiction of people and their behaviors. Representations can moreover be biased by containing implicit assumptions about the user, as in a computer game that plays out male heterosexual fantasies, thereby assuming that players will generally be male and heterosexual. They can also be biased by representing affordances and interactive properties in objects that make them supportive of certain values and uses but not of others. For example, a gun in a game may be designed so that it can used to kill but not to knock someone unconscious. Indecent representations constitute a third and final category of morally problematic representations. Indecent representations are representations that are considered shocking or offensive or that are held to break established rules of good behavior or morality and that are somehow shocking to the senses or moral sensibilities. Decency standards vary widely across different individuals and cultures however, and what is shocking or immoral to some will not be so to others. Some will find any depiction of nudity, violence or physical deformities indecent, whereas others will find any such depiction acceptable. The depiction of particular acts, persons or objects may be considered blasphemous in certain religions but not outside these religions. For this reason, the notion of an indecent representation is a relative notion, and there will usually be disagreement about what representations count as indecent. In addition, the context in which representation take place may also influence whether it is considered decent. For example, the representation of open heart surgery, with some patients surviving the procedure but others dying on the operation table, may be inoffensive in the context of a medical simulator, but offensive in the context of a game that makes light of such a procedure. Virtual Child Pornography Pornographic images and movies are considered indecent by many, but there is a fairly large consensus that people have a right to produce pornography and use it in private. Such a consensus does not consist for certain extreme forms of pornography, including child pornography. Child pornography is considered wrong because it harms the children that are used to produce it. But what about virtual child pornography? Virtual child pornography is the digital creation of images or animated pictures that depict children engaging in sexual activities or that depict them in a sexual way. Nowadays, such images and movies can be made to be highly realistic. No real children are abused in this process, and therefore the major reason for outlawing child pornography does not apply for it. Does this mean that virtual child porn is morally permissible and that its production and consumption should be legal? The permissibility of virtual child porn has been defended on the argument that no actual harm is done to children and that that people have a right to free speech by which they should be permitted to produce and own virtual child pornography, even if others find such images offensive. Indeed, the U.S. Supreme Court struck down a congressional ban on virtual child porn in 2002 with the argument that this ban constituted too great a restriction on free speech. The court also claimed that no proof had been given of a connection between computer-generated child pornography and the exploitation of actual children. An additional argument that is sometimes used in favor of virtual child porn is that its availability to pedophiles may actually decrease the chances that they will harm children. Opponents of virtual child porn have sometimes responded with deontological arguments, claiming that it is degrading to children and undermines human dignity. Such arguments cut little ice, however, in a legal arena that is focused on individual rights and harms. Since virtual child porn does not seem to violate the individual rights, opponents have tried out various arguments to the effect that it does cause harm. One existing argument is that virtual child porn causes indirect harm to children because it encourages child abuse. This argument goes opposite the previously stated argument that virtual child porn should be condoned because it makes child abuse less likely. The problem is that it is very difficult to conduct studies that provide solid empirical evidence for either position. Another argument is that failing to criminalize virtual child porn will harm children because it makes it difficult to enforce laws that prohibit actual child pornography. This argument has been used often by law enforcers to criminalize virtual child porn. As Neil Levy (2002) has argued, this argument is however not plausible, amongst other reasons because experts are usually able to make the distinction between virtual and actual pictures. Levy’s own argument against virtual child porn is not that it will indirectly harm children, but that it may ultimately harm women by eroticizing inequality in sexual relationships. He admits, however, that he lacks the empirical evidence to back up this claim. Per Sandin (2004) has presented an argument with better empirical support, which is that virtual child porn should be outlawed because it causes significant harm to a great many people who are revulsed by it. The problem with this argument, however, is that it gives too much weight to harm caused by offense. If actions should be outlawed whenever they offend a large group of people, then individual rights would be drastically curtailed, and many things, ranging from homosexual behavior to interracial marriage, would still be illegal. It can be concluded that virtual child pornography will remain a morally controversial issue for some time to come, as no decisive arguments for or against it have been provided so far. Depiction of Real Persons Virtual environments and computer simulations increasingly include characters that are modeled after the likeness of real persons, whether living or deceased. Also, films and photographs increasingly include manipulated or computer-generated images of real persons who are placed in fictional scenes or are made to perform behaviors that they have not performed in real life. Such appropriations of likenesses are often made without the person’s consent. Is such consent morally required, or should the depictions of real persons be seen as an expression of artistic freedom or free speech? Against arguments for free speech, three legal and moral arguments have traditionally been given for restrictions on the use of someone’s likeness (Tabach-Bank, 2004). First, the right to privacy has been appealed to. It has been argued that the right to privacy includes a right to live a life free from unwarranted publicity (Prosser, 1960). The public use of someone’s likeness can violate someone’s privacy by intruding upon his seclusion or solitude or into his private affairs, by working to publicly disclose embarrassing private facts about him, or to place him in a false light in the public eye. A second argument for restricting the use of someone’s likeness is that it can be used for defamation. Depicting someone in a certain way, for example as being involved in immoral behavior or in a ridiculous situation, can defame him by harming his public reputation. In some countries, like the U.S., there is also a separate recognized right of publicity. The right to publicity is an individual's right to control and profit from the commercial use of his name, likeness and persona. The right to publicity has emerged as a protection of the commercial value of the identity of public personalities, or celebrities, who frequently use their identity to sell or endorse products or services. It is often agreed that celebrities have less of an expectation of privacy, because they are public personalities, but have a greater expectation of a right to publicity. In the use of the likenesses of real persons in virtual environments or doctored digital images, rights to free speech, freedom of the press and freedom of artistic expression will therefore have to be balanced against the right to privacy, the right of publicity and the right to protection from defamation. Behavior in Virtual Environments: Ethical Issues The preceding section focused on ethical issues in design and embedded values in VR and computer simulations. This section focuses on ethical issues in the use of VR and interactive computer simulations. Specifically, the focus will be on the question whether actions within the worlds generated by these technologies can be unethical. This issue will be analyzed for both single-user and multi-user systems. Before it will be taken up, it will first be considered how actions in virtual environments take place, and what the relation is between users and the characters as which they appear in virtual environments. Avatars, Agency and Identity In virtual environments, users assume control over a graphically realized character called an avatar. Avatars can be built after the likeness of the user, but more often, they are generic persons or fantasy characters. Avatars can be controlled from a first-person perspective, in which the user sees the world through the avatar’s eyes, or from a thirdperson perspective. In multi-user virtual environments, there will be multiple avatars corresponding to different users. Virtual environments also frequently contain bots, which are programmed or scripted characters that behave autonomously and are controlled by no one. The identity that users assume in a virtual environment is a combination of the features of the avatar they choose, the behaviors that they choose to display with it, and the way others respond to the avatar and its behaviors. Avatars can function as a manifestation of the user, who behaves and acts like himself, and to whom others respond as if it is the user himself, or as a character that has no direct relation to the user and that merely plays out a role. The actions performed by avatars can therefore range from authentic expressions of the personality and identity of the user to experimentation with identities that are the opposite of who the user normally is. Whether or not the actions of an avatar correspond with how a user would respond in real life, there is no question that the user is causally and morally responsible for actions performed by his or her avatar. This is because users normally have full control over the behavior of their avatars through one or more input devices. There are occasional exceptions to this rule, because avatars are sometimes taken over by the computer and then behave as bots. The responsibility for the behavior of bots could be assigned to either their programmer or to whomever introduced them into a particular environment, or even to the programmer of the environment for not disallowing harmful actions by bots (Ford, 2001). Behavior in Single-User VR Single-user VR offers much less possibilities for unethical behavior than multi-user VR, because there are no other human beings that could be directly affected by the behavior of a user. The question is if there are any behaviors in single-user VR that could qualify as unethical. In Brey (1999), I considered the possibility that certain actions that are unethical when performed in real life could also be unethical when performed in singleuser VR. My focus was particularly on violent and degrading behavior towards virtual human characters, such as murder, torture and rape. I considered two arguments for this position, the argument from moral development and the argument from psychological harm. According to the argument from moral development, it is wrong to treat virtual humans cruelly because doing so will make it more likely that we will treat real humans cruelly. The reason for this is that the emotions appealed to in the treatment of virtual humans are the same emotions that are appealed to in the treatment of real humans, because these actions resemble each other so closely. This argument has recently gained empirical support (Slater et al., 2006). The argument from psychological harm is that third parties may be harmed by the knowledge or observation that people engage in violent, degrading or offensive behavior in single-user VR and that therefore this behavior is immoral. This argument is similar to the argument attributed to Sandin in my earlier discussion of indecent representations. I claimed in Brey (1999) that although harm may be caused by particular actions in single-user VR because people may be offended by them, it does not necessarily follow that the actions are immoral, but only that they cause indirect harm to some people. One would have to balance such harms against any benefits, such as pleasurable experiences to the user. Matt McCormick (2001) has offered yet another argument according to which violent and degrading behavior in single-user VR can be construed as unethical. He argues that repeated engagement in such behavior erodes one’s character and reinforces virtueless habits. He follows Aristotelian virtue ethics in arguing that this is bad because it makes it difficult for us to lead fulfilling lives, because as Aristotle has argued, a fulfilling life can only be lived by those who are of virtuous character. More generally, the argument can be made that the excessive use of single-user VR keeps one from leading a good life, even if one’s actions in it are virtuous, because one invests into fictional worlds and fictional experiences that seem to fulfill one’s desires but do not actually do so (Brey, forthcoming). Behavior in Multi-User VR Many unethical behaviors between persons in the real world can also occur in multi-user virtual environments. As discussed earlier in the section on reality and virtuality, there are two classes of real-world phenomena that can also exist in virtual form: institutional entities that derive their status from collective agreements, like money, marriage, and conversations, and certain physical and formal entities, like images and musical pieces, that computers are capable of physically realizing. Consequently, unethical behaviors involving such entities can also occur in VR, and it is possible for there to be real thefts, insults, deceptions, invasions of privacy, breaches of contract, or damage to property in virtual environments. Immoral behaviors that cannot really happen in virtual environments are those that are necessarily defined over physically realized entities. For example, there can be real insult in virtual environments, but not real murders, because real murders are defined over persons in the physical world, and the medium of VR does not equip users with the power to kill persons in the physical world. It may, of course, be possible to kill avatars in VR, but these are of course not killings of real persons. It may also be possible to plan a real murder in VR, for example by using VR to meet up with a hitman, but this cannot then be followed up by the execution of a real murder in VR. Even though virtual environments can be the site of real events with real consequences, they are often recognized as fictional worlds in which character merely play out roles. In such cases, even an insult may not be a real insult, in the sense of an insult made by a real person to another real person, because it may only have the status of an insult between two virtual characters. The insult is then only real in the context of the virtual world, but is not real in the real world. Ambiguities arise, however, because it will not always be clear when actions and events in virtual environments should be seen as fictional or real (Turkle, 1995). Users may assign different statuses to objects and events, and some users may identify closely with their avatar, so that anything that happens to their avatar also happens to them, whereas others may see their avatar as an object detached from themselves with which they do not identify closely. For this reason, some users may feel insulted when their avatar is insulted, whereas others will not feel insulted at all. This ambiguity in the status of many actions and events in virtual worlds can lead to moral confusion as to when an act that takes place in VR is genuinely unethical and when it merely resembles a certain unethical act. The most famous case of this is the case of the “rape in cyberspace” reported by Julian Dibbell (1993). Dibbell reported an instance of a “cyberrape” in LambdaMOO, a text-only virtual environment in which users interact with user-programmable avatars. One user used a subprogram that took control of avatars and made them perform sex acts on each other. Users felt their characters were raped, and some felt that they themselves were indirectly raped or violated as well. But is it ever possible for someone to be raped through a rape of her avatar, or does rape require a direct violation of someone’s body? Similar ambiguities exist for many other immoral practices in virtual environments, like adultery and theft. If it would constitute adultery when two persons were to have sex with each other, does it also constitute adultery when their avatars have sex? When a user steals virtual money or property from other users, should he be considered a thief in real life? Virtual Property and Virtual Economies For any object or structure found in a virtual world, one may ask the question: Who owns it? This question is already ambiguous, however, because there may both be virtual and real-life owners of virtual entities. For example, a user may be the owner of an island in a virtual world, but the whole world, including the island, may be owned by the company that has created it and permits users to act out roles in it. Users may also become creators of virtual objects, structures and scripted events, and some put in hundreds of hours of work into their creations. May they therefore also assert intellectual property rights to their creations? Or can the company that owns the world in which the objects are found and the software with which they were created assert ownership? What kind of framework of rights and duties should be applied to virtual property? (Burk, 2005). The question of property rights in virtual worlds is further complicated by the emergence of so-called virtual economies. Virtual economies are economies that exist within the context of a persistent multi-user virtual world. Such economies have emerged in virtual worlds like Second Life and The Sims Online, and in massively multiplayer online role-playing games (MMORPGs) like Entropia Universe, World of Warcraft, Everquest and EVE Online. Many of these worlds have millions of users. Economies can emerge in virtual worlds if there are scarce goods and services in them for which users are willing to spend time, effort or money, if users can also develop specialized skills to produce such goods and services, if users are able to assert property rights on goods and resources, and if they can transfer goods and services between them. Some economies in these worlds are primitive barter economies, whereas other make use of recognized currencies. Second Life, for example, makes use of the Linden Dollar (L$) and Entropia Universe has the Project Entropia Dollar (PED), both of which have an exchange rate against real U.S. dollars. Users of these worlds can hence choose to acquire such virtual money by doing work in the virtual world (e.g., by selling services or opening a virtual shop) or by making money in the real world and exchanging it with virtual money. Virtual objects are now frequently traded for real money outside the virtual worlds that contain them, on online trading and auction sites like eBay. Some worlds also allow for the trade of land. In December 2006, the average price of a square meter of land in Second Life was L$ 9.68 or U.S. $ 0.014 (up from L$ 6.67 in November), and over 36,000,000 square meters were sold1 Users have been known to pay thousands of dollars for cherished virtual objects, and over $ 100,000 for real estate. The emergence of virtual economies in virtual environments raises the stakes for their users, and increases the likelihood that moral controversies ensue. People will naturally be more likely to act immorally if money is to be made or if valuable property is to be had. In one incident which took place in China, a man lent a precious sword to another man in the online game Legend of Mir 3, who then sold it to a third party. When the lender found out about this, he visited the borrower at his home and killed him.2 Cases have also been reported of Chinese sweatshop laborers who work day and night in conditions of practical slavery to collect resources in games like World of Warcraft and Lineage, which are then sold for real money. 1 Source: https://secondlife.com/whatis/economy_stats.php. Accessed 1/3/2007. 2 Online gamer killed for selling cyber sword. ABC NewsOnline, March 30, 2005. http://www.abc.net.au/news/newsitems/200503/s1334618.htm. There have also been reported cases of virtual prostitution, for instance on Second Life, where users are paid to (use their avatar to) perform sex acts or to serve as escorts. There have also been controversies over property rights. On Second Life, for example, controversy ensued when someone introduced a program called CopyBot that could copy any item in the world. This program wreaked havoc on the economy, undermining the livelihood of thousands of business owners in Second Life, and was eventually banned after mass protests.3 Clearly, then, the emergence of virtual economies and serious investments in virtual property generates many new ethical issues in virtual worlds. The more time, money and social capital people invest in virtual worlds, the more such ethical issues will come to the front. The Ethics of Computer Games Contemporary computer and video games often play out in virtual environments or include computer simulations, as defined earlier. Computer games are nowadays mass media. A recent study shows that the average American 8- to 18-year old spends almost six hours per week playing computer games, and that 83% has access to a video game console at home (Rideout, Roberts and Foehr, 2005). Adults are also players, with four in ten playing computer games on a regular basis.4 In 2005, the revenue in the U.S. generated by the computer and game industry generated was over U.S. $ 7 billion, far surpassing the film industry’s annual box office results.5 Computer games have had a vast impact on youth culture, but also significantly influence the lives of adults. For these reasons alone, an evaluation of their social and ethical aspects is needed. Some important issues bearing on the ethics of computer games have already been discussed in previous sections, and therefore will be covered less extensively here. These include, amongst others, ethical issues regarding biased and indecent representations; issues of responsibility and identity in the relation between avatars, users and bots; the ethics of behavior in virtual environments; and moral issues regarding virtual property and virtual economies. These issues, and the conclusions reached regarding them, all fully apply to computer games. The focus in this section will be on three important ethical questions that apply to computer games specifically: Do computer games contribute to individual well-being and the social good? What values should govern the design and use of computer games? And do computer games contribute to gender inequality? The Goods and Ills of Computer Games Are computer games a benefit to society? Many parents do not think so. They worry about the extraordinary amount of time their children spend playing computer games, and 3 Linden bans CopyBot following resident protests. Reuters News, Wednesday November 15, 2006. http://secondlife.reuters.com/stories/2006/11/15/linden-bans-copybot-following-resident-protests/ 4 Poll: 4 in 10 adults play electronic games. MSNBC.com, May 8, 2006. http://www.msnbc.msn.com/id/12686020/ 5 2006 Essential Facts about the Computer and Video Game Industry, Entertainment Software Association, 2006. http://www.theesa.com/archives/files/Essential%20Facts%202006.pdf about the excessive violence that takes place in many games. They worry about negative effects on family life, schoolwork and the social and moral development of their kids. In the media, there has been much negative reporting about computer games. There have been stories about computer game addiction and about players dying from exhaustion and starvation after playing video games for days on end. There have been stories about ultraviolent and otherwise controversial video games, and the ease by which children can gain access to them. The Columbine High School massacre, in 1999, in which two teenage students went out on a shooting rampage, was reported in the media to have been inspired by the video game Doom, and since then, other mass shootings have also been claimed to have been inspired by video games. Considerable doubt has been raised, therefore, as to whether computer games are indeed a benefit to society rather than a social ill. The case against computer games tends to center on three perceived negative consequences: addiction, aggression and maladjustment. The perceived problem of addiction is that many gamers get so caught up in playing that their health, work or study, family life, and social relations suffer. How large this problem really is has not yet been adequately documented (though see Chiu, Lee and Huang, 2004). There clearly is a widespread problem, as there has been a worldwide emergence of clinics for video addicts in recent years. Not all hard-core gamers will be genuine addicts in the psychiatric sense, but many do engage in overconsumption, resulting in the neglect described above. The partners of adults who engage in such overconsumption sometimes called gamer widows, analogous to soccer widows, denoting that they have a relationship with a gamer who pays more attention to the game than to them. Whereas there is no doubt that addiction to video games is a real social phenomenon, there is less certainty that playing video games can be correlated with increased aggression, as some have claimed. The preponderance of the evidence seems to indicate, however, that the playing of violent video games can be correlated with increases in aggression, including increases in aggressive thoughts, aggressive feeling, aggressive behaviors, and a desensitization to real-life violence, and a decrease in helpful behaviors (Carnagey, Anderson and Bushman, forthcoming; Bartholow, 2005). However, some studies have found no such correlations, and present findings remain controversial. Whatever the precise relation between violent video games and aggression turns out to be, it is clear now that there is a huge difference between the way that children are taught to behave towards others by their parents and how they learn to behave in violent video games. This at least raises the question of how their understanding of and attitude towards violence and aggression is influenced by violent video games. A third hypothesized ill of video games is that they cause individuals to be socially and cognitively slighted and maladjusted. This maladjustment is attributed in part to the neglect of studies and social relations due to an overindulgence into video games and to increased aggression levels from playing violent games. But it is also held to be due to the specific skills and understandings that users gain from video games. Children that play video games are exposed to conceptions of human relations and the workings of the world that have been designed into them by game developers. These conceptions have not been designed to be realistic or pedagogical, and often rely on stereotypes and simplistic modes of interaction and solutions to problems. It is therefore conceivable that children develop ideas and behavioral routines while playing computer games that leave much to be desired. The case in favor of computer games begins with the observation that they are a new and powerful medium that brings users pleasure and excitement, and that allow for new forms of creative expression and new ways of acting out fantasies. Games moreover do not just cause social isolation, they can also stimulate social interaction. Playing multiplayer games is a social activity that involves interactions with other players, and that can even help solitary individuals find new friends. Computer games may moreover induce social learning and train social skills. This is especially true for role-playing games and games that involve verbal interactions with other characters. Such games let players experiment with social behavior in different social settings, and role-playing game can also make users intimately familiar with the point of view and experiences of persons other than themselves. Computer games have moreover been claimed to improve perceptual, cognitive and motor skills, for example by improving hand-eye coordination and improving visual recognition skills (Johnson, 2005; Green and Bavelier, 2003). Computer Games and Values It has long been argued in computer ethics that computer systems and software are not value-neutral but are instead value-laden (Nissenbaum, 1998; Brey, 2000). Computer games are no exception. Computer games may suggest, stimulate, promote or reward certain values while shunning or discouraging others. Computer games are value-laden, first of all, in the way they represent the world. As discussed, earlier, such representations may contain a variety of biases. They may, for example, promote racial and gender stereotypes (Chan, 2005; Ray, 2003), and they may contain implicit, biased assumptions about the abilities, interests or gender of the player. Simulation games like SimCity may suggest all kinds of unproven causal relations, for example correlations between poverty and crime, that may help shape attitudes and feed prejudices. Computer games may also be value-laden in the interactions that they make possible. They may, for example, be designed to make violent action the only solution to problems faced by a player. Computer games can also be value-laden in the storylines they suggest for players and in the feedback and rewards that are given. Some first-person shooters awards extra points, for example, for not killing innocent bystanders, whereas others instead award extra points for killing as many as possible. A popular game like The Sims can serve to illustrate how values are embedded in games. The Sims is a game that simulates the everyday lives and social relationships of ordinary persons. The goal of characters in the game is happiness, which is attained through the satisfaction of needs like Hunger, Comfort, Hygiene and Fun. These needs can be satisfied through success in one’s career, and through consumption and social interaction. As Miguel Sicart (2003) has argued, The Sims thus presents an idealized version of a progressive liberal consumer society in which the goal in life is happiness, gained by being a good worker and consumer. The team-based first-person shooter America’s Army presents another example. This game is offered as a free download by the U.S. government, who uses it to stimulate U.S. army recruitment. The game is designed to give a positive impression of the U.S. army. Players play as servicemen who obey orders and work together to combat terrorists. The game claims to be highly realistic, yet it has been criticized for not showing certain realistic aspects of military life, such as collateral damage, harassment, and gore. The question is how influential computer games actually are in influencing the values of players. The amount of psychological research done of this topic is still limited. However, psychological research on the effect of other media, such as television, has shown that it is very influential in affecting the value of media users, especially children. Since many children are avid consumers of computer games, there are reasons to be concerned about the values projected on them by such games. Children are still involved in a process of social, moral and cognitive development, and computer games seem to have an increasingly large role in this developmental process. Concern about the values embedded in video games therefore seems warranted. On the other hand, computer games are games, and therefore should allow for experimentation, fantasy, and going beyond socially accepted boundaries. The question is how games can support such social and moral freedom without also supporting the development of skewed values in younger players. Players do not just develop values on the basis of the structure of the game itself, they also develop them by interacting with other players. Players communicate messages to each other about game rules and acceptable in-game behavior. They can respond positively or negatively to certain behaviors, and may praise or berate other players. In this way, social interactions in games may become part of the socialization of individuals and influence their values and social beliefs. Some of these values and norms may remain limited to the game itself, for example, norms governing the permissibility of cheating (Kimppa and Bissett, 2005). In some games, however, like massively multiplayer online role-playing games (MMORPG’s), socialization processes are so complex as to resemble real life (Warner and Raiter, 2005), and values learned in such games may be applied to real life as well. Computer Games and Gender Games magazine and game advertisement foster the impression that computer games are a medium for boys and men. Most pictured gamers are male, and many recurring elements in images, such as scantily clad, big-breasted women, big guns and fast cars, seem to be geared toward men. The impression that computer games are mainly a medium for men is further supported by usage statistics. Research has consistently shown that fewer girls and women play computer games than boys and men, and those that do spend less time playing than men. According to research performed by Electronic Arts, a game developer, among teenagers only 40% of girls play computer games, compared to 90% of boys. Moreover, when they reach high school, most girls lose interest, whereas most boys keep playing.6 A study by the UK games trade body, the Entertainment and Leisure Publishers Association, found that in Europe, women gamers make up only a quarter of the gaming population. 7 6 Games industry is 'failing women'. BBC News, August 21, 2006. http://news.bbc.co.uk/2/hi/technology/5271852.stm 7 Chicks and Joysticks. An Exploration of Women and Gaming. ELSPA White Paper, September 2004. www.elspa.com/assets/files/c/chicksandjoysticksanexplorationofwomenandgaming_176.pdf The question whether there is a gender bias in computer games is morally significant because it is a question about gender equality. If it is the case that computer games tend to be designed and marketed for men, then women are at an unfair disadvantage, as they consequently have less opportunity to enjoy computer games and their possible benefits. Among such benefits may be greater computer literacy, an important quality in today’s marketplace. But is the gender gap between usage of computer games really the result of gender bias in the gaming industry, or could it be the case that women are simply less interested in computer games than men, regardless of how games are designed and marketed? Most analysts hold that the gaming industry is largely to blame. They point to the fact that almost all game developers are male, and that there have been few efforts to develop games suitable for women. To appeal to women, it has been suggested, computer games should be less aggressive, because women have been socialized to be non-aggressive (Norris, 2004). It has also been suggested that women have a greater interest in multiplayer games, games with complex characters, games that contain puzzles, and games that are about human relationships. Games should also avoid assumptions that the player is male and avoid stereotypical representations of women. Few existing games contain good role models for women. Studies have found that most female characters in games have unrealistic body images and display stereotypical female behaviors, and that a disproportionate number of them are prostitutes and strippers. 8 Virtual Reality, Simulation and Professional Ethics In discussing issues of professional responsibility in relation to virtual reality systems and computer simulations, a distinction can be made between the responsibility of developers of such systems and that of professional users. Professional users can be claimed to have a responsibility to acquaint themselves with the technology and its potential consequences and to use it in a way that is consistent with the ethics of their profession. The responsibility of developers includes giving consideration to ethical aspects in the design process and engaging in adequate communication about the technology and its effects to potential users. In the development of computer simulations, the accuracy of the simulation and its reliability as a foundation for decision-making in the real world are of paramount importance. The major responsibility of simulation professionals is therefore to avoid misrepresentations where they can and to adequately communicating the limitations of simulations to users (McLeod, 1983). These responsibilities are, indeed, a central ingredient in a recent code of ethics for simulationists adopted by a large number of professional organizations for simulationists (Ören et al., 2002). The responsibility for accuracy entails the responsibility to take proper precautions to ensure that modeling mistakes do not occur, especially when the stakes are high, and to inform users if inaccuracies do or may occur. It also entails the responsibility not to participate in intentional deception of users (e.g., embellishment, dramatization, or censorship). 8 Fair Play: Violence, Gender and Race in Video Games. Children Now , December 2001. 36 pp. http://publications.childrennow.org/ In Brey (1999), I have argued that designers of simulations and virtual environments also have a responsibility to incorporate proper values into their creations. It has been argued earlier that representations and interfaces are not value-free but may contain values and biases. Designers have a responsibility to reflect on the values and biases contained in their creations and to ensure that they do not violate important ethical principles. The responsibility to do this follows from the ethical codes that are in use in different branches of engineering and computer science, especially the principle that professional expertise should be used for the enhancement of human welfare. If technology is to promote human welfare, it should not contain biases and should regard the values and interests of stakeholders or society at large. Taking into account such values and avoiding biases in design cannot be done without a proper methodology. Fortunately, a detailed proposal for such a methodology has recently been made by Batya Friedman and her associates, and has been termed value-sensitive design (Friedman, Kahn and Borning, 2006). Special responsibilities apply to different areas of applications for VR and computer simulations. The use of virtual reality in therapy and psychotherapy, for example, requires special consideration to principles of informed consent and the ethics of experimentation with human subjects (Wiederhold and Wiederhold, 2004). The computer and video game industry can be argued to have a special responsibility to consider the social and cultural impact of their products, given that they are used by a mass audience that includes children. Arguably, game developers should consider the messages that their products send to users, especially children, and should work to ensure that they develop and market content that is age-appropriate and that is more inclusive of all genders. Virtual reality and computer simulation will continue to present new challenges for ethics, because new and more advanced applications are still being developed, and their use is more and more widespread. Moreover, as has been argued, virtual environments can mimic many of the properties of real life, and therefore contain many of the ethical dilemmas found in real life. It is for this reason that they will not just continue to present new ethical challenges for professional developers and users, but also for society at large.

Abstract: A novel combination of blue LED chips, transparent glass substrates and phosphors with PDMS thin film is demonstrated. The flip-chip bonding technology is applied to facilitate this design. The ZrO2 nanoparticles are also doped into the PDMS film to increase light scattering. The resultant luminous efficiency shows an 11% enhancement when compared to the regular COG device. The variation of correlated color temperature of such devices is also reduced to 132K. In addition to these changes, the surface temperature is reduced from 121°C to 104°C due to good thermal dissipation brought by ZrO2 nanoparticles.

1. Introduction

As the energy resources are dwindling these days, it is important to develop the eco-friendly technologies to promote human being’s living. The white light-emitting diodes (LEDs) have been one of the green technologies to replace the conventional incandescent light bulbs [1–3]. In the past, the vertical contact types of LEDs were the dominant design. However, the poor thermal conductivity and insulating substrate pose difficulties in application [4]. To deal with this issue, flip-chip technology becomes popular in recent years because it can induce high light-extraction efficiency and good heat dissipation [5–7]. In the flip-chip scheme, an increase of output power can be observed due to the reflector at the bottom and direct bonding of the contact pads which can reduce the shadowing effect [8, 9]. Further investigation of thermal resistance and junction temperature of these flip-chip bonded devices revealed that direct metal contact and less sapphire substrate can really help heat dissipation [10].
In order to generate the high efficiency white LED, there were many approaches to optimize the performance of the w- LED. One of the important techniques is the application of the nanoscale structures that could increase the light extraction. Delicate designs, such as the sapphire substrate with the high aspect ratio cone-shape, and nano-patterned air voids between

the GaN nano-pillars or the overgrown GaN layer [11], were fabricated on the pattern sapphire substrate to improve the light extraction. In universal, the conventional LED chips were bonded on the opaque substrate to fabricate the SMD (Surface-Mount-Device) type LED package. This type of package can induce certain amount of photon re-absorption such that the degradation of efficiency can be expected. In order to promote the luminous efficiency, the structure of the chip on glass is the good candidate [12, 13]. The highly transparent glass substrate can open up another chance to collect the back-scattered photons and promote the luminous efficiency of the LED. Many results with similar idea have been reported previously. Chien et al. designed a flip glass substrate package to enhance the color bin yield, and Chang et al. promoted the technology of the flip chip bonding on the ITO [14, 15]. However, to use the glass as the substrate would cause the device operating at higher temperature due to the poor thermal conductivity (σ~1 W/mK), and the low emissivity (the value is about 0.8~0.85) of the glass [16–18]. There were many approaches to resolve this heat dissipation problem such as nanoparticles deployment. In the past, graphene nanoparticles were embedded in the LED package to provide good thermal conduction and extra environment protection [19]. Su et al. also investigated the usage of TiO2-doped silicone layer in the LED package [20]. When it was combined with silicone lens, both light extraction and junction temperature can be improved.

This study generated the high luminous efficiency w-LED by the COG (chip on glass) packaging process. One new material, zirconia nanoparticles, could provide a superior photon scattering ability [21–24]. At the same time, the use of the zirconia particles could promote the heat radiation and reduce the temperature of the device due to the high emissivity (the value is 0.95) [25–27]. In this study, ZrO2 nanoparticles are used with the PDMS film to optimize the performance of the w-LED with the flip chip bonding upon the glass substrate.

2. Experimental methods

This study demonstrates two kinds of host structures by the use of the zirconia particles to yield the white light chip on glass (COG). One is to mix ZrO2 directly with phosphor/PDMS slurry and the other is to mix the ZrO2 with silicone to form a diffusing film and then cover this film on the regular phosphor + LED structure. Figure 1(a) shows the schematic and actual structure photograph of the ZrO2 embedded phosphor PDMS film combining with the COG structure to yield the w-LED. The ZrO2 particles are blended with the silicone to form the transparent PDMS film and then covered on the COG structure as shown in Fig. 1(b). The YAG phosphor film was dispensed on the COG structure and pumped by the blue chips to generate the white light LED as shown in Fig. 1(c).The fabrication procedure is described as below: First, prepare the LED chips with the wavelength 450nm and flip-chip bond them on the sapphire substrate and covered with the 10wt% YAG phosphor film as the reference sample. Second, mix the zirconia nanoparticles in the silicone slurry and the 10wt% YAG phosphor silicone slurry. Then spin-coat the mixture on the glass and dry it later in order to form the zirconia films. Finally, peel the zirconia/phosphor film from the glass and then put the film on the COG structure with the ZrO2 of 1wt%, 5wt% and 9wt% to as the Sample1, Sample2, and Sample3, respectively. In the other hand, Sample4, Sample5, and Sample6 are covered by the transparent 1wt%, 5wt% and 9wt% ZrO2 film on the w-LED device (10wt% phosphor film covered on the COG structure), respectively. Table 1 shows the PDMS films with the different doping concentrations of ZrO2 

Fig. 1. (a) The cross section of the w-LED combines with theZrO2 (wt%) 0 1 5 9 1 5 9

Phosphor (wt%) 10 10 10 10 0 0 0

The finished ZrO2 layer and their mixture with phosphors were inspected by SEM. Figure 2(a) and 2(b) show the SEM cross section images of the ZrO2 PDMS film and the YAG phosphor/ZrO2 film. In these images, the thickness of the transparently ZrO2 PDMS film is about 260.2µm, the YAG phosphor/ZrO2 film is about 290µm. Figure 2(c) shows that the PDMS film used in this experiment with a particle size is average about 300nm.

Fig. 2. The cross section view of the (a) ZrO2 film, (b) the phosphor and ZrO2 conjunction film, and the (c) ZrO2 nano-particles in the silicone.

3. Results and discussion

Figure 3(a) shows the spectrum for the reference sample, and other samples with different concentrations of ZrO2 and phosphors at 80mA of driving current. Furthermore, the CCT and the luminous efficiency are shown in Table 2. In general, the samples with zirconia particles and phosphors perform better than the reference. If only zirconia particles are presented, proper concentration is needed to enhance the luminous efficiency. The phenomena are caused by the high scatting ability of the ZrO2 nanoparticles and the improvement results from the better utilization of the blue photons from the LEDs [24]. In order to receive highest lumen efficiency, the best ratio of the ZrO2 blended phosphor film and the pure ZrO2 layer is about 1wt% and 5wt%, respectively. However, as the ratio of the zirconia nanoparticles increasing above 5wt%, it can cause lower luminous efficiency because high concentration of

the ZrO2 would led the extra light trapping and re-absorption of the emitted photons and reduce the transmittance of the layer [24, 25]. Figure 3(b) shows the COG structure w-LED sample with and without ZrO2 layer after 10 minute driving at 80mA. The lumen efficiency of all the COG w-LED samples would decay after driving the devices after 10 minutes. The phenomenon is caused by the poor thermal conductivity and the low emissivity. Due to this low thermal conductivity of the glass substrate, after 10 minutes of electrical driving, the heat dissipation is poor and the package temperature rises accordingly. The lumen efficiency and the CCT of the reference sample and Sample1 to Sample6 after the 10 minutes driving are listed in Table 3. As shown in Table 3, the 5wt% ZrO2 blended phosphor layer with the excellent performance after the time passes. In addition to the spectral intensity change, the efficiency (lumen/watt) of the w-LEDs can be modified after 10 minutes of 80mA continuous arriving. From Fig. 3(c), all samples show some degradation on efficiency, but the reference ones (without any ZrO2) degrade most, and the amount of degradation drops as the weight percent of ZrO 2 increases. We believe the high emissivity of ZrO2 particles (0.95) plays an important role on this phenomenon because they can effectively reduce the internal temperature of the package.

Table 2. The luminous efficiency and CCT for the reference and zirconia layer combined sample

Ref. Sample1 Sample2 Sample3 Sample4 Sample5 Sample6
CCT(K) 4960.1 4736.6 4912 4737 4883 4911.3 4956
Lumen/watt 176.7 196.8 194.4 189.8 188.9 196.1 174.1

Fig. 3. (a) The emission spectra for the reference sample, ZrO 2 embedded phosphor film covered samples and the reference sample covered by the ZrO2 film at 80mA and (b) the emission spectra after 10 minutes driving. (c) The deviation of the lumen efficiency between the original samples and after 10minutes driving samples.

Table 3. The luminous efficiency and CCT for the reference and zirconia layer combined sample after 10 minutes driving

Ref. Sample1 Sample2 Sample3 Sample4 Sample5 Sample6
CCT(K) 6364.5 5010.1 4859 4807.7 5421.8 5042 6275.1
Lumen/watt 130.4 170.2 181.8 178.3 153.1 165 163

To verify this conjecture, we need to check the actual temperature of these units. Figure 4(a)-4(d) shows the w-LED with ZrO2 nanoparticles in operation the surface temperature mapping illustrations. According to the thermal images, the white area represents the maximum surface temperature plotted in the Fig. 4(e) and 4(f). The surface temperatures shown in the figures were measured after 10 minutes of continuous electrical injection with different configurations, the devices demonstrated various temperatures. The temperature differences between the two groups (Sample 1-3 vs Sample 4-6) rise from the different layout in the COG package. In Sample 1-3, there are two phosphor films with ZrO2 embedded. However, for Sample 4-6, there is one additional ZrO2/silicone layer because the phosphor and ZrO2 layers are separated. This additional layer can increase the total temperature by 5°C

due to poorer heat dissipation in the device. As these results showed, the combination of the ZrO2 nanoparticles embedded layer can reduce the surface temperature of the w-LED and resolve the poor heat dissipation of the sapphire for the COG structure effectively.

To understand the possible explanation on the measured surface temperature results, the correlation between the packaged material and heat transfer needs to be clarified. It is true that the higher concentration of ZrO2 can lead to more photon trapping and thus potentially more re-absorption and more temperature rising. In a general LED scheme, about 20% of input power turns into optical energy and 80% becomes heat [28]. These 20% of photons will have about 30% of them becomes stray photons and possibly get re-absorbed in the package. So if we just consider the source of this trapped or re-absorbed photons in terms of total input power, 6% at most of extra heat (20% × 30%) can be generated due to this re-absorption. Comparing to the original heat directly from LED chip, this is a far smaller portion. On the other hand, the high emissivity of the ZrO2 nanoparticles helps the film to relieve from this extra heat generation. From the general theory of heat transport provided in the previous question, the radiation and convection parts are significant when the film to the environment temperature difference is high. Although the number of trapped photons is high, the presence of ZrO2 can radiate more heat out and thus lower the overall temperature of the package.

Fig. 4. (a)-(d) The surface temperature mapping of the COG structure w-LED combine with the zirconia after the 10 minute driving. The surface temperature diversification of (e) the ZrO2 nanoparticles with different ratio doping in the phosphor film w-LED samples and (f) the ZrO2 layer covered on the top of the w-LED samples after the 10 minute driving.

Figure 5 shows the CIE 1931 coordinates of the initial and after 10 minutes of continuous driving. The effect of this 10-minute driving in the reference samples can be observed clearly as the CIE coordinates change before and after, which is not desirable for solid state lighting. On the other hand, all other samples show very little change in the CIE 1931 coordinates, which is a good sign and also can be viewed as another indicator of improvement brought by ZrO2. 

Fig. 5. The variation of the CIE1931 coordinates between the original samples and after 10minutes driving samples

Table 4 shows that the thermal conductivity of the phosphor films changed with the application of ZrO2 nanoparticles. In this table, the thermal conductivity increases as the concentration of the ZrO2 increases.

Table 4. The thermal conductivity of the PDMS film with the different concentrates

ZrO2 concentration 0wt% 1wt% 5wt% 9wt%
Thermal conductivity(W/ m2K) 0.528 0.735 0.739 0.821

To consider the full thermal effect in the mixed film, we must include different components in heat transport: the radiation, convection and conduction terms. The effect caused by the thermal conductivity of the phosphor films is very weak in the total heat transfer rate of the LED. The thermal properties between the phosphor/ZrO2 films and the w-LED can be described by the Eqs. (1)-(4) are calculated using as below [29]:

Q cond = kA  Ts − Ta  d−1 (1)
Qrad = εσ A  Ts  4 −  Ta 4  (2)
Qconv = HA  Ts − Ta  , H = εσ A  Ts + Ta   Ts  4 +  Ta 4  (3)
Qtotal = Qconv + Qrad + Qcond (4)
= εσ A  Ts + Ta    Ts  4 +  Ta  4  + εσ A   Ts  4 −  Ta  4  + kA  Ts − Ta  d−1
In these formulas, Qcond, Qrad and Qconv are defined as the thermal conduction, radiation and convection heat transfer rate for the exterior surface of w-LED, respectively. The total heat transfer rate formula of the w-LEDs is calculated as shown in Eq. (4). Where k is the thermal conductivity, A is the surface area, d is the thickness, ɛ is the emissivity, σ is Stefan-Boltzmann constant, H is the convection heat transfer coefficient, Ts and Ta is the surface temperature and surround temperature of the device, respectively. By the formula, the main

effect for the total heat transfer rate is the combination of the Qconv and Qrad because the influencing factor of the sum for the value: ɛσA (Ts + Ta) [(Ts)4 + (Ta)4] and ɛσA [(Ts)4 - (Ta)4]

is much larger than the factor of conduction heat transfer rate: kA (Ts - Ta)d−1. As the result, the radiation and convection terms are dominant in heat transfer and the emissivity ( ) is more

important than the thermal conductivity. Figure 1 shows the simulation results of the COG structure covered with the different emissivity materials and refers from the Eqs. (1)-(4) by the Flow simulation software. All the factors of the total thermal properties have been considered, such as the surface area, thermal conductivity, and emissivity.
To verify the assumption of emissivity of ZrO2 on the package temperature, we set up a numerical environment to simulate the outcome. Figure 6 shows the simulation results of the COG structure covered with the different emissivity materials refers from the Eqs. (1)-(4) by the Flow simulation software. The simulation is executed based on the structure in Fig. 6(a), covered with the thin film mixing with the different concentration (0wt%, 49wt%, 99wt%) of ZrO2 particles to produce the silicone thin films with the different emissivity(0.7, 0.85, 0.95), respectively. Figure 6(b)-6(d) shows the thermal image of the COG structure covered by the thin film and the temperature of the chip is about 96.7°C (emissivity 0.7), 94.4°C(emissivity 0.85), and 92.8°C(emissivity 0.9), respectively. From our calculation, the surface temperature reduces significantly when the emissivity of the composite film increases and other parameters are kept the same. 

Fig. 6. The modulation emissivity simulation result of the COG structure w-LEDs.

The color uniformity of the w-LED can be evaluated by the deviation of correlated color temperature ( CCT) which is defined as the difference between the CCT(max) and the CCT(min) [24] Beside the nice heat dissipation ability, the ZrO2 nanoparticles are also known for the excellent scattering capability which can improve the uniformity of the CCT [30]. As shown in Fig. 7, the diagram shows the Sample1 to Sample6 with angular distribution of CCT at the current of 80 mA. The CCT deviations for the reference sample, the phosphor and ZrO2 nanoparticles blended PDMS COG w- LEDs (Sample1 to Sample3) is about 420K, 336K and 162K, and the other w-LED samples with the additional the transparent ZrO2 PDMS layer (Sample4 to Sample6) is about 833K, 721K and 434K, respectively. As these results, the use of ZrO2 nanoparticles embedded PDMS film can improve the color uniformity of the w-LED, and the phosphor films doped by ZrO2 nanoparticles are perform better than the samples with the additional transparent ZrO2 PDMS layer. The reason is that the zirconia particles in the phosphor film have a smoother angular -dependent CCT distribution than the ZrO2 nanoparticles embedded in the PDMS film on the surface of the phosphor layer, because which can provide an effective scattering to the excite the around phosphor particles. The haze intensity image permit the doped phosphor films are with the excellent diffuse ability than the covered of the additional transparent ZrO2 PDMS layers on the phosphor films as

shown in Fig. 7(b) However, that would influence the CCT deviations when the concentrate of the ZrO2 nanoparticles increase more than 9%, the best ratio is about 5%.

Fig. 7. (a) The spectrum of angular-dependent CCT at 80mA and (b) the haze intensity of the reference sample and Sample1 to Sample6.

4. Conclusion

This study demonstrates a highly efficient design of w-LED with COG structure and ZrO2 PDMS films. The w-LED can obtain the least CCT deviations (132K) in the case of the 5wt% ZrO2 blended phosphor film and the use of the ZrO 2 film can improve the color uniformity of the w-LED effectively. The phosphor film blended of the 1wt% zirconia particles can improve the luminous efficiency of the w-LED and achieve a 11% enhancement than the COG w-LED without the ZrO2 film covered. The ZrO2 blended phosphor film and pure ZrO2 film can reduce the surface temperature of the COG w-LEDs from 120°C to the 110°C and the ZrO2 blended phosphor film is more effective than the pure ZrO 2 film in terms of thermal dissipation. The high emissivity of ZrO2 can help on this heat dissipation and this is verified via simulation and experiments. In conclusion, it is very useful to resolve the heat dissipation problem and improve the lumen efficiency by the combination of the ZrO2 PDMS films with the COG structure w-LEDsin this case high power LED.s and SMds works better 

Good luck..s.s

Security for the Third Generation (3G) Mobile System Colin Blanchard Network Systems & Security Technologies BTexaCT. Access and use of service to avoid or reduce a legitimate charge. · Loss of confidentiality or integrity of a user’s or operator’s data · Denial of a specific user’s access to their service or denial of access by all users to a service However, user expectations for instant communication and ease of use, as well as terminals which are easily lost or stolen, present a number of unique challenges in the mobile environment. The original first generation analogue mobile employed a simple electronic serial number to confirm that the terminal should be allowed access to the service. It was not long before the protection afforded to this number was broken. Eventually, devices appeared that could read these electronic serial numbers from the air, and access an unsuspecting user’s account for a short time, before moving on to the next, in the hope that the small charges on each bill would not be noticed. So why was this not predicted at the time? Unfortunately, there always seems to be an assumption, with any new development in communications technology, that complexity alone will protect such services from abuse. Second generation systems such as GSM were designed from the beginning with security in mind. This has stood up to the kind of attacks that were prevalent on the analogue system at the time, thanks mainly to the ability to put responsibility for security in the hands of the Home Environment (HE) operator. The HE operator can control the use of the system by the provision of the Subscriber Identity Module (SIM) which contains a user identity and authentication key. This is specifically arranged so that this long life authentication key is not required by the Serving Network (SN) when roaming, exposed over the air or exposed across the interface between the SIM and the mobile. This keeps to the minimum the level of trust the HE operator needs to place in the User, Serving Network and manufacturer of the Mobile Equipment (ME). In 1996, when the 3rd Generation system known as UMTS was being developed in ETSI (European Telecommunications Standards Institute), the opportunity was taken to review the basis for security in existing mobile systems and to develop a new security architecture specifically to be used in UMTS. This early work was subsequently taken forward into the Third Generation Partnership Project (3GPP) and this will be the basis for the Release 99 deployment of 3G systems.

GPRS and UMTS are evolutions of the global system for mobile communication (GSM) networks. GSM is a digital cellular technology that is used worldwide, predominantly in Europe and Asia. GSM is the world’s leading standard in digital wireless communications. GPRS is a 2.5G mobile communications technology that enables mobile wireless service providers to offer their mobile subscribers packet-based data services over GSM networks. Common applications of GPRS include the following: Internet access, intranet/corporate access, instant messaging, and mutlimedia messaging. GPRS was standardized by the European Telecommunications Standards Institute (ETSI), but today is standardized by the Third Generation Partnership Program (3GPP). UMTS is a 3G mobile communications technology that provides wideband code division multiple access (CDMA) radio technology. The CDMA technology offers higher throughput, real-time services, and end-to-end quality of service (QoS), and delivers pictures, graphics, video communications, and other multimedia information as well as voice and data to mobile wireless subscribers. UMTS is standardized by the 3GPP. The GPRS/UMTS packet core comprises two major network elements: • Gateway GPRS support node (GGSN)—a gateway that provides mobile cell phone users access to a public data network (PDN) or specified private IP networks. The GGSN function is implemented via Cisco IOS software on the Cisco 7200 series router or on the Cisco Multi-Processor WAN Application Module (MWAM) installed in a Catalyst 6500 series switch or Cisco 7600 series Internet router. Cisco IOS GGSN Release 4.0 and later provides both the 2.5G GPRS and 3G UMTS GGSN functions.

Serving GPRS support node (SGSN)—connects the radio access network (RAN) to the GPRS/UMTS core and tunnels user sessions to the GGSN. The SGSN sends data to and receives data from mobile stations, and maintains information about the location of a mobile station (MS). The SGSN communicates directly with the MS and the GGSN. SGSN support is available from Cisco partners or other vendors.

In a 2.5G environment, the RAN is composed of mobile stations that connect to a base transceiver station (BTS) that connects to a base station controller (BSC). In a 3G environment, the RAN is made up of mobile stations that connect to NodeB, which connects to a radio network controller (RNC). The RAN connects to the GPRS/UMTS core through an SGSN, which tunnels user sessions to a GGSN that acts as a gateway to the services networks (for example, the Internet and intranet). The connection between the SGSN and the GGSN is enabled through a tunneling protocol called the GPRS tunneling protocol (GTP): GTP Version 0 (GTP V0) for 2.5G applications, and GTP Version 1 (GTP V1) for 3G applications. GTP is carried over IP. Multiple SGSNs and GGSNs within a network are referred to collectively as GPRS support nodes (GSNs).

To assign mobile sessions an IP address, the GGSN uses the Dynamic Host Configuration Protocol (DHCP), Remote Authentication Dial-In User Service (RADIUS) server, or a local address pool defined specified for an access point configured on the GGSN. The GGSN can use a RADIUS server to authorize and authenticate remote users. DHCP and RADIUS services can be specified either at the global configuration level or for each access point configured on the GGSN. In Cisco IOS Release 12.1(5)T and later, the GGSN on the Cisco 7200 series router (with an Integrated Services Adapter [ISA] card) supports IP Security (IPSec) protocol to provide data confidentiality, data integrity, and data authentication between participating peers. On the Cisco MWAM installed in a Catalyst 6500 series switch / Cisco 7600 series Internet router platform, IPSec encryption is performed on the IPSec Virtual Private Network (VPN) Acceleration Services Module. GPRS Interface Reference Model The 2.5G GPRS and 3G UMTS standards use the term interface to label (or identify) the communication path between different network elements. The GPRS/UMTS standards define the requirements and characteristics of communication between different GPRS/UMTS network elements over these interfaces. These interfaces are commonly referred to in descriptions of GPRS/UMTS networks. Figure 1-3 shows the interfaces that are implemented in the Cisco IOS GGSN feature: • Gn interface—Interface between GSNs within the same public land mobile network (PLMN) in a GPRS/UMTS network. GTP is a protocol defined on the Gn interface between GSNs in a GPRS/UMTS network. • Gi interface—Reference point between a GPRS/UMTS network and an external packet data network. • Ga interface—Interface between a GGSN and charging gateway (CG) in a GPRS/UMTS network.

Virtual Template Interface To facilitate configuration of connections between the GGSN and SGSN, and the GGSN and PDNs, the Cisco IOS GGSN software uses an internal interface called a virtual template interface. A virtual template is a logical interface that is not tied directly to a specific interface, but that can be associated dynamically with a interface. As with a physical interface on a router, you can assign an IP address to the virtual template interface. You can also configure IP routing characteristics on the virtual template interface. You are required to configure certain GPRS/UMTS-specific elements on the virtual template interface, such as GTP encapsulation (which is necessary for communicating with the SGSN) and the access list that the GGSN uses to determine which PDNs are accessible on the network.

Access Points The GPRS/UMTS standards define a network identity called an access point name (APN). An APN identifies the service or network to which a user can connect from a GGSN in a GPRS/UMTS network. To configure APNs, the Cisco IOS GGSN software uses the following configuration elements: • Access point—Defines an APN and its associated access characteristics, including security and method of dynamic addressing. • Access point list—Logical interface that is associated with the virtual template of the GGSN. The access-point list contains one or more access points. • Access group—An additional level of security that is configured at an access point to control access to and from a PDN. When an MS is permitted access to the GGSN as defined by a traditional IP access list, the IP access group further defines whether access is permitted to the PDN (at the access point). The IP access group configuration can also define whether access from a PDN to an MS is permitted. For more detailed information on access-point configuration, refer to the “Configuring Access Points on the GGSN” section on page 1-10. Benefits The 2.5G GPRS technology provides the following benefits: • Enables the use of a packet-based air interface over the existing circuit-switched GSM network, which allows greater efficiency in the radio spectrum because the radio bandwidth is used only when packets are sent or received • Supports minimal upgrades to the existing GSM network infrastructure for network service providers who want to add GPRS services on top of GSM, which is currently widely deployed • Supports enhanced data rates in comparison to the traditional circuit-switched GSM data service • Supports larger message lengths than Short Message Service (SMS) • Supports a wide range of access to data networks and services, including VPN/Internet service provider (ISP) corporate site access and Wireless Application Protocol (WAP). In addition to the above, the 3G UMTS technology includes the following: • Enhanced data rates of approximately – 144 kbps—Satellite and rural outdoor – 384 kbps—Urban outdoor – 2048 kbps—Indoor and low-range outdoor • Supports connection-oriented Radio Access Bearers with specified QoS, enabling end-to-end QoS

GGSN Release 5.0 and later is a fully-compliant 2.5G and 3G GGSN that provides the following features: • Release 99 (R99), Release 98 (R98) and Release 97 (R97) support and compliance • GTPv0 and GTPv1 messaging • IP Packet Data Protocol (PDP) and PPP PDP types • Cisco Express Forwarding (CEF) switching for GTPv0 and GTPv1, and for IP and PPP PDP types • Support of secondary PDP contexts for GTPv1 (up to 11) • Virtual APN • VRF support per APN • Multiple APNs per VRF • VPN support – Generic routing encapsulation (GRE) tunneling – Layer 2 Tunneling Protocol (L2TP) extension for PPP PDP type – PPP Regeneration for IP PDP type – 802.1Q virtual LANs (VLANs) • Security features – Duplicate IP address protection – PLMN range checking – Blocking of Foreign Mobiles – Anti-spoofing – Mobile-to-mobile redirection • Quality of service (QoS) – Support of UMTS classes and interworking with differentiated services (DiffServ) – Delay QoS – Canonical QoS – GPRS QoS (R97/R98) conversion to UMTS QoS (R99) and the reverse – Call Admission Control – Per-PDP policing • Dynamic address allocation – External DHCP server – External RADIUS server – Local pools • Per-APN statistics • Anonymous access • RADIUS authentication and accounting • Accounting – Wait accounting – Per-PDP accounting.– Authentication and accounting using RADIUS server groups mapped to APNs – 3GPP vendor-specific attributes (VSAs) for IP PDP type – Transparent mode accounting – Class attribute – Interim updates – Session idle timer – Packet of Disconnect (PoD) • Dynamic Echo Timer • GGSN interworking between 2.5G and 3G SGSNs with registration authority (RA) update from – 2.5G to 2.5G SGSN – 2.5G to 3G SGSN – 3G to 3G SGSN – 3G to 2.5G SGSN • Charging – Time trigger – Charging profiles – Tertiary charging gateway – Switchback to primary charging gateway • Maintenance mode • Multiple trusted PLMN IDs • GGSN-IOS SLB messaging • Session timeout

و اما تحقیقات شخصی اینجانب (دی کد)در آزمایشگاه مجهز خودم به نتیجه ای دیگر رسیدم که دیدن نتیجه خالی از لطف نیست... 

یک هارد یک ترابایتی پر از دیتا حدود 0.008 میکرو گرم وزن دیتا دارد و با نبمی از ظرفیت که 500GB می باشد 0.003 میکرو گرم وزن دیتای آن میباشد البته در حالت فرگ... در حالات دیگر نیز بررسی کردم که جزو تحقیقات اصلی میباشد و برای دریافت مقاله ی کامل باید آن را خریداری کنید.

با بررسی دقیق این فرایند میتوان راه کار های نوینی برای **** و****و****و... داد که در مقاله ی اصلی به تفصیل به آن پرداخته شده.

در سال ۱۹۵۶ گوردون مور بنیان‌گذار اینتل تحلیلی ارایه کرد که بر طبق آن هر ۱۸ ماه تعداد ترانزیستورهای بکار رفته در ریزپردازهای اینتل دو برابر می شود که نصف شدن ابعاد گیت ترانزیستورها با شرط ثابت بودن اندازه تراشه سیلیکونی در آن می‌تواند نتیجه این قوانین باشد. این قاعده به قانون مور موسوم شد. این نصف شدن در واقع پیام‌آور ابعاد اقتصادی بود یعنی هر چه گیت کوچکتر می‌شد ترانزیستور می‌توانست سریعتر سوئیچ کند و درنتیجه انرژی کمتری مصرف می‌شد بنابراین سایز ترانزیستورها هر 3 سال به طور متوسط 0.7 برابر کوچکتر شده است اما به دلیل قوانین مکانیک کوانتوم محدودیت تکنیک های ساخت ممکن است . از کاهش بیش از این از لحاظ اندازه در ترازیستورهای FET معمولی جلوگیری شود و در یکی دو دهه آینده با روش های متداول ساخت در ابعاد زیر 50 نانومتر متوقف شود به این ترتیب کوچک سازی عناصر مدارها تا به حد نانومتری حتی در اندازه مولکولی محققان را به سمتی سوق می دهد که در جهت افزایش قدرت و کارایی ترانزیستور ها خیلی بیشتر از حالت معمولی فعالیت می کنند دستگاههای نانومتری جدید می توانند در دو حالت سوییچ و آمپلی فایر ایفای نقش می کنند با وجود این بر عکس FET های امروزی که عمل آنها بر اساس جابه جایی اجرام الکترونها در حجم ماده می باشند دستگاههای جدید بر اساس پدیده مکانیکی کوانتومی عمل می کنند و در اندازه نانومتری ظاهر می شوند و تعداد بیشتری ترانزیستور در یک تراشه سیلیکون جای می گیرند . افزایش تعداد ترانزیستورها و بازدهی آنها، هزینه را کاهش می‌دهد بنابراین مقرون به صرفه‌ این بود که هر ترانزیستور تا حد امکان کوچکتر شود، این کوچک‌سازی بالاخره در نقطه‌ای متوقف می‌شد بنابراین برای ادامه رشد صنعت الکترونیک باید به فکر فناوریهای جایگزین بود،فناوری که مشکلات گذشته را حل کرده و توجیه اقتصادی داشته باشد و این بار نانو تکنولوژی بود که توانست به کمک الکترونیک بیاید و فناوری الکترونیک مولکولی یا همان نانو‌الکترونیک بنا نهاده شد.

فن آوری نانوالکترونیک نقطه همگرایی علوم مختلف در آینده است. در این میان یکی از پرکاربردترین شاخه ها نانو الکترونیک می باشد. امروزه افزایش ظرفیت ذخیره داده، افزایش سرعت انتقال آن و کوچک کردن هر چه بیشتر وسائل الکترونیکی و به خصوص ترانزیستورها دارای اهمیت بسیاری است زیرا کوچک تر شدن ابعاد وسائل الکترونیکی علاوه بر افزایش سرعت پردازش، توان مصرفی را نیز کاهش می دهد و نانو الکترونیک می تواند در رسیدن به ابعاد هر چه کوچک تر راهگشا باشد. برای آشنایی بیشتر با این فن آوری و درک عمیق تر پدیده های گوناگونی که در ابعاد نانو متر روی می دهد و در نتیجه تحلیل دقیق نتایج و اصلاح اصولی روش های آزمایش، باید علوم پایه ای نظیر فیزیک کوانتوم و مکانیک کوانتومی و فیزیک حالت جامد مورد مطالعه قرار بگیرند.
 نانو تکنولوژی یک رشته وابسته به ابزار است ابزارهایی که به مرور در حال بهتر شدن است نانو تکنولوژی و شاخه‌های کاربردی آن مانند نانوالکترونیک درواقع تولید کارآمد دستگاهها و سیستم‌ها با کنترل ماده در مقیاس طولی نانو است و بهره‌برداری از خواص و پدیده‌های نوظهوری است که در این مقیاس توسعه یافته است. صنعت الکترونیک امروزی مبتنی بر سیلیکون است سن این صنعت به حدود ۵۰ سال می‌رسد و اکنون به مرحله‌ای رسیده است که از لحاظ تکنولوژیکی، صنعتی و تجاری به بلوغ رسیده است. در مقابل این فناوری، الکترونیک مولکولی قرار دارد که در مراحل کاملاً ابتدایی است و قرار است این فناوری به عنوان آینده و نسل بعدی صنعت الکترونیک سیلیکونی مطرح شود. الکترونیک مولکولی دانشی است که مبتنی بر فناوری نانو بوده و کاربردهای وسیعی در صنعت الکترونیک دارد. با توجه به کاربردهای وسیع الکترونیک در محصولات تجاری بازار می‌توان با سرمایه‌گذاری و تامل بیشتر در فناوری نانو الکترونیک در آینده‌ای نه چندان دور شاهد سود‌دهی کلان محصولاتی بود که جایگزین فناوری الکترونیک سیلیکونی شده‌اند.
اهداف:
در دهه‌های اخیر شاهد پیشرفت‌های زیادی در زمینه افزایش قابلیت ذخیره اطلاعات روی حافظه‌ها و همچنین کاهش اندازه آن‌ها بوده‌ایم که نتیجه آن دو برابر شدن سرعت پردازش در عرض هر 18 ماه بوده است و این، انتظار تحولی عظیم در صنعت میکروالکترونیک را طی 15 سال آینده از نظر بنیادی و اقتصادی نوید می‌دهد. اکنون نیز تحقیقات ادامه داشته و هدف از آن تولید خواص نمونه و شکل ظاهری جدید و در نتیجه خلق نانوالکترونیک جدید است.
کاربرد نانوالکترونیک در صنعت:
با استفاده از این فناوری می‌توان ظرفیت ذخیره‌سازی اطلاعات را در حد ۱۰۰۰ برابر یا بیشتر افزایش داد که این نهایتاً به ساخت ابزارهای ابرمحاسباتی به کوچکی یک ساعت مچی منتهی می‌شود. ظرفیت نهایی ذخیره اطلاعات به حدود یک ترابیت در هر اینچ مربع رسده، و این امر موجب ذخیره‌ سازی ۵۰ عدد DVD یا بیشتر در یک هارد دیسک با ابعاد یک کارت اعتباری می‌شود. ساخت تراشه‌ها در اندازه‌های فوق‌العاده کوچک به‌عنوان مثال در اندازه‌های ۳۲ تا ۹۰ نانومتر، تولید دیسک‌های نوری ۱۰۰ گیگابایتی در اندازه‌های کوچک نیز از دیگر محصولات آن می‌باشد.
نمونه هایی از کاربرد فن آوری نانو در الکترونیک:
۱) نانو لوله های کربنی (carbon nanotubes)
نانو تیوب ها دارای فرم لوله ای با ساختار شش ضلعی هستند. نانو تیوب ها را می توان صفحات گرافیتی فرض کرد که لوله شده اند. بر اساس محور چرخش صفحات نانو تیوب ها می توانند رسانا یا نیمه رسانا نیز باشند. به علت اینکه کربن با سه پیوند همچنان دارای یک اوربیتال خالی p می باشد، حرکت موجی الکترون ها به راحتی در سطح بیرونی این لوله ها صورت می گیرد.

این ساختار کربنی علاوه بر رسانایی بالا دارای استحکام مکانیکی بسیار خوبی نیز می باشد . البته در کنار این مزایا مشکلاتی نیز وجود دارد. اغلب فرآیند های ساخت نانو تیوب ها به گو نه ای می باشند که امکان کنترل و نظارت کامل در طول فرآیند را برای شما امکان پذیر نمی کند . به عنوان مثال تعیین قطر دقیق و یکسان برای لوله های کشت شده در یک محیط، کنترل تولید نانو لوله های تک دیواره و یا چند لایه و یا ساخت نانو لوله های مستقیم و بدون خم شدگی با طول زیاد از مسائلی است که هنوز در فرآیند بهبود کیفیت تولید نیاز به مطالعه و تحقیقات بیشتری دارد. همچنین به علت پدیده تونل زنی الکترون که یک پدیده کوانتومی است امکان افزایش نشتی جریان و در نتیجه افزایش تلفات وجود دارد که بررسی روش های کاهش احتمال تونل زنی از جمله کارهایی است که می توان انجام داد. از کربن نانو تیوب هابه دلیل رسانایی بالا و مقاومت کم در دمای محیط در ساخت کانال هدایت ترانزیستورها، نوک میکروسکوپ های عکسبرداری در ابعاد نانو استفاده می شود.
2 ) نانو ترانزیستورها (nanotransistors)
طبق قانون مور( MOORE Law) تعداد ترانزیستورها در واحد سطح تراشه های الکترونیکی در هر بازه 10 تا 18 ماهه دو برابر می شود. نام فن آوری رایج امروز در ساخت ترانزیستورها، MOSFET می باشد که بر پایه استفاده از سیلیکون است. کوچکتر شدن ابعاد ترانزیستورها در MOSFET دارای مشکلاتی است که از جمله آن نشتی های جریان متفاوتی است که ایجاد می شود. یکی از روش های حل این مشکل ساخت تراتزیستورها با استفاده از نانو سختارها و به خصوص نانو تیوب ها می باشد.
3 ) محاسبه گر ها در مقیاس نانو ( nanocomputers)
امروزه در زمینه های مختلف از جمله فن آوری نانو پیوند میان رشته های مختلف علوم امری انکار ناپذیر به حساب می اید . از جمله نتایج این همکاری طراحی نانو محاسبه‌گرها می باشد. هیدرو کربن های آروماتیک از ریشه بنزن به علت وجود اوربیتال های p و ابر الکترونی در بالا و پایین آنها و همچنین پدیده رزونانس می توانند محیط انتقال خوبی برای الکترون باشند و بر عکس هیدروکربن های زنجیری مانند نارسانا عمل می کنند. از به هم پیوستن این هیدروکربن ها با هم می توان دیود، گیت های منطقی و مدارهای الکترونیکی را تشکیل دهند .
4 ) MRAMها ( Magnetic Random Access Memories )
فن آوری های روز حافظه ( RAM, Flash Memory, …) مشکلات متعددی را برای مصرف کنندگان آنها به وجود آورده است که به عنوان نمونه می توان به سرعت پایین خواندن و نوشتن روی Flash Memories و EEPROM و یا محدودیت اقتصادی افزایش فضای RAM اشاره نمود . MRAM یک فن آوری حافظه پایدار می باشد که علاوه بر سرعت بالا می تواند ظرفیت حافظه بالایی را نیز برای شما  فراهم کند. اساس کار MRAM بر پایه تفاوت مقاومت الکتریکی لایه های نازک مواد بر اثر قطبیده شدن ذرات آنها در راستاهای متفاوت می باشد؛ که به مقاومت مغناطیسی موسوم است. چون سلول های حافظه MRAM بر پایه ترانزیستور عمل نمی کنند پس در ابعاد کوچک مشکلاتی نظیر تونل زنی رخ نخواهد داد و می توان سلول های حافظه MRAM را تا ابعاد نانو کوچک کرد.
5 ) C60
از جمله نانو ساختارها که حتی نسبت به نانو لوله های کربنی دارای مزایای بیشتری نیز می باشد C۶۰ است. C۶۰ از ۱۲ پنج ضلعی و ۲۰ شش ضلعی تشکیل شده که به شکل متقارنی در کنار هم قرار گرفته اند.

مولکول های C۶۰ در محلول های بنزن یافت می شوند که با عمل تبخیر قابل استحصال می باشند. انواع ترکیبات C۶۰ با فلزات، نظیر K۳C۶۰ ، Cs۲RbC۶۰، که در آنها فلز فضای خالی درون C۶۰ را پر می کند دارای خاصیت ابر رسانایی در دماهای نسبتاً مناسب را دارا هستند ؛ البته تحقیقات برای دستیابی به ترکیباتی با خاصیت ابررسانایی در دماهای بالاتر همچنان ادامه دارد. کاربرد دیگر C۶۰ استفاده از آن به عنوان گیت های منطقی است. با لیتوگرافی طلا روی یک سطح سیلیکونی و عبور جریان از سیم های طلا یک صفحه مشبک ایجاد می شودکه فاصله بین اتصالات آن در حدود نانو متر است. محلول رقیق C۶۰ را بین اتصالات قرار می دهند به طوری که در هر فاصله یک C۶۰ قرار گیرد. با برقرار شدن جریان در سیم های طلا C۶۰ به علت یک پدیده کوانتومی شروع به نوسان می کند و به همین علت جریان در زمان های معینی بر قرار می شود از این خاصیت می توان در طراحی گیت های منطقی بهره نمود . 
تفاوت اساسی میان تکنولوژی ULSI و نانوتکنولوژی :
 تفاوت اساسی میان تکنولوژی ULSI و نانوتکنولوژی تفاوت میان روش پیاده سازی “بالا به پایین ” و ” پایین به بالا “برای تولید یک محصول است در روش بالا به پایین مساله اصلی هزینه بسیار زیاد کوچک تر کردن ابعاد ترانزیستورها با روش لیتوگرافی است ، در حالی که هدف اصلی تکنولوژی ULSI کاهش هزینه ها بر بیت در حافظه ها و هزینه بر سوییچ در مدارات منطقی بوده است. از آن سو در روش پایین به بالا انتظار می رود که با استفاده از روش های پیچیده شیمیایی و طراحی مولکولی بتوان بلوک های پایه سیستم را پیاده سازی کرد .اما مساله اصلی یکنواختی و قابلیت اطمینان سیستم در مقیاس وسیع است . اگر بتوان معماری فعلی مدارات مجتمع را بر اساس روش پایین به بالا و با قابلیت اطمینان بالا پیاده کرد ، نانو تکنولوژی اهمیت فوق العاده در توسعه صنعت IC پیدا میکند.
در تکنولوژی ULSI از آنجایی که کارآمدی سیستم مورد نظر است بیشترین درجه آزادی در طراحی سیستم و سپس طراحی مدار وجود دارد ، لذا فرآیند ساخت و ادوات نیمه هادی مثل ترانزیستورها کمترین تنوع را دارند . متقابلا در نانو تکنولوژی بلوکهای پایه متنوعی با کارآمدی بالا وجود دارند در حالی که معماری سیستم وارتباط بین بلوک ها به خوبی در نظر گرفته نشده است .به هر حال دو روش برای توسعه نانو الکترنیک متصور است . روش اول آن که نانو تکنولوژی با تکنولوژی موجود ULSI ترکیب شود . تلفیق رشته هایی مثل بیوتکنولوژی و الکترونیک ترکیب بازار صنعت داروسازی و صنعت نیمه هادی و نهایتا پیاده سازی سیستم های مجتمع که از مواد و اجزا متنوعی تشکیل شده اند از نتایج این روش به شمار 
می ایند. روش دوم آن که نانوتکنولوژی جایگزین تکنولوژی ULSI شود .این در صورتی مقدور خواهد بود که بتوان سیستم های فعلی را با کارکرد بهتر و قیمت پایین تر به روش پایین به بالا پیاده سازی کرد. 
نتیجه: 
آنچه که مسلم است، الکترونیک مولکولی دارای آینده‌ای درخشان است و با آهنگ بسیار سریعی در حال رشد و تکامل است. از این رو توجه خاصی را می‌طلبد . نتایج عملی رشد و توسعه شاخه‌های نانوتکنولوژی مانند نانوالکترونیک سبب ساخت تجهیزاتی خواهد شد که در مقایسه با گذشته اختلاف فاحش داشته و نسل کاملاً جدیدی با قابلیت‌های منحصر به فرد خواهد بود . نانو لوله‌ها و DNA به عنوان دو ابزار کارآمد در تولید محصولات نانوالکترونیک از اهمیت خاصی برخوردارند، ولیکن در این میان DNA به دلیل داشتن خواص محلی و وجود آن در بدن موجودات زنده از اهمیت بیشتری برخوردار است . نانوتکنولوژی و شاخه‌های کاربردی آن در علوم مختلف مانند نانوالکترونیک به عنوان پدیده‌هایی نوظهور هنوز قبل از تجاری سازی محصولاتشان، احتیاج به پیشرفت در هر دو زمینه علمی و تکنولوژیکی را دارد. با توجه به اینکه هم‌اکنون برخی از محصولات این فناوری در بازار وجود دارد پیش‌بینی اینکه کدامیک از محصولات آینده بهتری دارند (از نظر رقابتی) نیاز به بررسی بیشتر شاخصهای این فناروی در بخشهای 
صنعت و زیرمجموعه‌های این فناوری دارد .

کارهایی که باید در راستای پیشرفت این علم انجام شود:

نانو الکترونیک زمینه گسترده‌ای با پتانسیل ایجاد تغییرات بنیادی در علوم مختلف حتی در پزشکی است و انجام کارهای زیر برای پیشبرد آن می‌تواند مفید باشد:

1.  فهم اصول انتقال در مقیاس نانو
2.  گسترش فهم هرچه بهتر روش‌های خودچیدمانی(self assembly) ذرات برای انجام کارها به صورت ارزان‌تر، که این خود مستلزم حل مشکلات ارتباطی و جایگزینی در ترانزیستورهاست

SMD capacitor basics

Surface mount capacitors are basically the same as their leaded predecessors. However instead of having leads they have metallised connections at either end.

This has a number of advantages:

• Size:   SMD capacitors can be made very much smaller than their leaded relations. The fact that no wired leads are required means that different construction techniques can be sued and this allows for much smaller components to be made.
• Ease of use in manufacturing:   As with all other surface mount components, SMD capacitors are very much easier to place using automated assembly equipment.
• Lower spurious inductance:   The fact that no leads are required and components are smaller, means that the levels of spurious inductance are much smaller and these capacitors are much nearer the ideal component that their leaded relations.

Multilayer ceramic SMD capacitors

The multilayer ceramic SMD capacitors form the majority of SMD capacitors that are used and manufactured. They are normally contained in the same type of packages used for resistors.

Construction:   The multilayer ceramic SMD capacitor consists of a rectangular block of ceramic dielectric in which a number of interleaved precious metal electrodes are contained. This multilayer structure gives rise to the name and the MLCC abbreviation, i.e. Multi-Layer Ceramic Capacitor.

This structure gives rise to a high capacitance per unit volume. The inner electrodes are connected to the two terminations, either by silver palladium (AgPd) alloy in the ratio 65 : 35, or silver dipped with a barrier layer of plated nickel and finally covered with a layer of plated tin (NiSn).

Ceramic capacitor manufacture:   The raw materials for the dielectric are finely milled and carefully mixed. Then they are heated to temperatures between 1100 and 1300°C to achieve the required chemical composition. The resultant mass is reground and additional materials added to provide the required electric properties.

The next stage in the process is to mix the finely ground material with a solvent and binding additive. This enables thin sheets to be made by casting or rolling.

For multilayer capacitors electrode material is printed on the sheets and after stacking and pressing of the sheets co-fired with the ceramic compact at temperatures between 1000 and 1400°C. The totally enclosed electrodes of a multilayer capacitor ceramic capacitor, MLCC guarantee good life test behaviour as well.

Tantalum SMD capacitors

Tantalum SMD capacitors are widely used to provide levels of capacitance that are higher than those that can be achieved when using ceramic capacitors. As a result of the different construction and requirements for tantalum SMT capacitors, there are some different packages that are used for them. These conform to EIA specifications.

Tantalum SMD capacitor 

. Note the bar across one end indicating the polarity

Electrolytic SMD capacitors

Electrolytic capacitors are now being used increasingly in SMD designs. Their very high levels of capacitance combined with their low cost make them particularly useful in many areas.

Often SMD electrolytic capacitors are marked with the value and working voltage. There are two basic methods used. One is to include their value in microfarads, µF, and another is to use a code. Using the first method a marking of 33 6V would indicate a 33 µF capacitor with a working voltage of 6 volts. An alternative code system employs a letter followed by three figures. The letter indicates the working voltage as defined in the table below and the three figures indicate the capacitance on pico-farads. As with many other marking systems the first two figures give the significant figures and the third, the multiplier. In this case a marking of G106 would indicate a working voltage of 4 volts and a capacitance 0f 10 times 10^6 pico-farads. This works out to be 10µF 

SMD capacitor codes

Comparatively few SMD capacitors have their values marked on their cases. This means that great care must be taken when handling them to ensure they are not misplaced or mixed. However a few capacitors do have markings. The capacitor values are coded. This means that it is necessary to know the SMD capacitor codes. These are simple and easy to decode.

A three figure SMT capacitor code is normally used as there is usually little space for anything more. In common with other marking codes the first two indicate the significant figures, and the third is a multiplier.

SMD capacitor code

Here the two figures 47 indicate the significant figures and the 2 indicates the multiplier of 2, i.e. 100.

Getting Started

1. Getting Started

To highlight the importance of electrical engineering knowledge retention is necessary to evening the most used form of energy is electricity in different areas. Currently, toatesectoarele activity is used, in various ways, electricity. Deacţionare motors of various tools, machinery and transport equipment converts electrical energy into energiemecanică, electric lamps converts light into energy, electric ovens transforms it into energietermica (heat) to melt, heated or dried. If we consider the use of electricity întelecomunicaţii in automation, home appliances, resulting in the vast field of energy aceastăformă finds its use.

1.1. A classification of electrical quantities

a) After the presence or absence of their energy: active Size: sizes are those associated with energy, some of which can be used for measuring înprocesul. The ratio between the total energy, which has the size and power that folosităpentru measurement should be large so as not to affect the value of assets size măsurate.Exemplu sizes: temperature, voltage, electrical current, passive putereaelectrică.Mărimi : are those quantities which possesses its own energy liberia. For their measurement is necessary to resort to an auxiliary power source. Size Examples passive resistance, capacity, inductance, etcb) After-dimensional appearance space: scalars: completely determined by a single vector număr.Mărimi: characterized by: mode (intensity) and direction sens.c) After how variation over time:

MărimeaelectricăConstantă VariabilăDeterministăAleatoareNe eriodicăPeriodicăSinusoidală (aperiodic AlternativăPulsatorie

Fig.1.1. Classification quantities measured by how timpMărimea variaţieîn constant: it is the size which changes its value over time, with only two parameters, amplitude and deterministic polaritate.Mărimea: is that size whose evolution over time is predictable and can be descrisăprintr a mathematical function and that unpredictability comes in a small random măsură.Mărimea: unpredictable variation, the values ​​they take different time points fiindîntâmplătoare. These sizes can not be characterized only in probabilistic sense using methods statistice.5

Getting Started

The mean (DC component) of random sizes within a certain time t

1

-T

2

is given by (1.2) and the actual value of the relationship (1.3).

x (t)) tt (1 = X

TTM is d

∫

-

21

12

(1.2)

(T) d

21

12

x) tt (1 = X

2tte f

∫

-

(1.3) where t

2

-T

1

is the integration time or measurement time.

x (t) tX

med

Fig.1.2. Regular aleatoareMărimea size: has the property that the values ​​they take at certain times, repeat dupăintervale equal time. Thus for a regular size, value instantaneous (momentary), x (t), satisfies the relation:

() ()

Ttxtx

± =

(1.4) where T is the period and f = 1 / T is frecvenţa.Mărimea periodic in time can be described as a function of amplitude, frequency, period and frequency fază.Analiza in these sizes is done using Fourier series, resulting discret.Valoarea defrecvente spectrum average (DC component) of a regular size is:

x (t) T1 = X

T + TTM e d

0

∫

0

(1.5) Another parameter used to characterize periodic quantities is the actual value:

(T) d

0

XT1 = X

2Ttte f

0

∫

+

(1.6) 6

Getting Started

1.1.Să application determine the average value and the actual value of the periodic signal of Fig.1.3.

Tax (t)

τ

 T

Fig.1.3. Signal dreptungiular alternative size:

is the regular size which averaged over a period is zero. The electrical maiîntâlnite alternative sizes are shown in Fig.1.4.

b) square wave) sine wave c) triangular wave d) sawtooth wave egalearii areas egalearii equal egalearii

Fig.1.4. AlternativeFaţă main waveform and DC voltage, whose values ​​are generally stable over time, tensiuneaalternativă alternate polarity (Fig.1.4) and alternating current alternating in direction (Fig.1.5).

 a) b)

Fig.1.5. DC (a) and AC (b) One way to express the intensity or magnitude of a quantity alternative is to measure

peak

or

peak to peak value

(Fig.1.6).

X

max

X

VV

= 2Xmax

Time

Fig.1.6. Maximum and peak to peak value of a quantity alternativeDin Unfortunately each of these values ​​can mislead us if we compare two different wavelengths. Thus, otensiune rectangular 10V peak value is clearly higher than the value for a voltage of 10V devârf triangular effect of these two voltages that supply the same pregnancy fiinddiferit (Fig.1.7) .7

An SSID is a 32-character alphanumeric key uniquely identifying a wireless LAN. Its purpose is stop other wireless equipment accessing your LAN — whether accidentally or intentionally. To communicate, wireless devices must be configured with the same SSID. Most NETGEAR products have a "site survey" tool that automatically looks for other wireless devices, and displays their SSID.

If you unselect Allow broadcast of SSID in a router or access point, the SSID of that device will not be visible in another device's site survey, and must be entered manually.

The SSID is not a strong security measure, and should be used in conjunction with other security such as WEP or WPA.

The Extended Service Set Identification (ESSID) is one of two types of Service Set Identification (SSID). An Ad-hoc wireless network with no access points uses the Basic Service Set Identification (BSSID). In an infrastructure wireless network that includes an access point, the Extended Service Set Identification (ESSID) is used — although it may still be referred in a loose sense as SSID. Some vendors refer to the SSID as the "network name".

کاربرد دستگاه : دستگاه AV200 Desktop امکان ايجاد شبکه اي منسجم جهت نتقل و انتقال داده ها ، صوت و تصوير اینترنت بر روي شبکه برق ايجاد نمايد . تنها کافي است هر دستگاه را به يک پريز برق متصل نموده و آنها را از طريق Ethernet Port به هر PC يا لپ تاپی که داراي قابليت اتصال به پورت Ethernet را دارا باشد متصل نموده ، سپس اینترنتی پر سرعت بر روي کابل هاي برق داشته باشيد
ويژگی های اجمالی
• امکان ايجاد پهناي باند 2Mbps به صورت Full Duplex بر روی کابل های برق
• پشتيباني از Multicasting & IGMP Snooping
• پشتيباني از نقل و انتقال داده ، صوت و تصوير
• 802.1Q VLAN & Optimized VLANs
• QoS,8 Level of queuing ( 802.1p )
• سيستم کدگذاري 168bit – 3DES
• قابليت ايجاد پوشش و دسترسي در سرار منزل و يا دفتر کار
• داراي قابليت مديريت از راه دور
• Plug & Play

یکتکنیک برنامهنویسی است که از تکامل ژنتیکی به عنوان یکالگوي حل مسئله استفاده میکند. در این مقاله سعی (GA ژنتیک(یا

تدریج و در طی زمان از بین میروند. البته درستتر آنست

بهترینها. گاهی در طبیعت گونههاي متکاملتري به وجود

قبلی هستند. آنچه که ممکن است تا حدي علت این رویداد

را توضیح دهد مفهومیست به نام : تصادف یا جهش. بر

دهیم. لذا در ابتدا ساختار یک تقویت کننده قدرت را بررسی

مدل ، نتایج را بررسی مینماییم لذا این مقاله را به 3 بخش

کلی تقسیم میکنیم :

بخشاول : توضیحی بر ژنتیک الگوریتم

بخش دوم : بررسی یک تقویت کننده قدرت و بدست

بخش سوم : بررسی و تحلیل پارامترهاي مورد نظر توسط

یک تکنیک جستجو در علم GA الگوریتم ژنتیک

است.الگوریتم هاي ژنتیک یکی از انواع الگوریتم هاي

[ گرفته شده .[ 2

مطرح کرد. ایده اساسی این الگوریتم انتقال خصوصیات

موروثی توسط ژنهاست. فرض کنید مجموعه خصوصیات

میشوند. هر ژن در این کروموزومها نماینده یک خصوصیت

است که بصورت همزمان دو اتفاق براي کروموزومها میافتد.

است. موتاسیون به این (Mutation) اتفاق اول موتاسیون

میکنند(البته تعداد این گونه ژنها بسیار کم میباشد).

Crossover کروموزوم دیگر است؛ این مساله با نام

شناخته میشود(البته این اتفاق به تعداد بسیار بیشتري

نسبت به موتاسیون رخ میدهد). این همان چیزیست که

[ شدن تام فرزند به تنها یکی از والدین جلوگیري میکند.[ 1

( هادي آریاکیا( 1) ، مسعود مصدق( 1) ، ابراهیمی راد ( 2

1) دانشگاه آزاد اسلامی واحد تهران مرکز ( 2) دانشگاه تهران دانشکده برق و کامپیوتر )

X1,X2,…,Xn، در ابتدا تعداد مشخصی از ورودي ها

هستند را انتخاب می کنیم و X که متعلق به فضاي نمونه

نمایش X=(x1,x2,…xn) آنها را در یک عدد برداي

Colony کروموزوم گفته می شود و به گروه کروموزوم ها

رشد می کند Colony ، یا جمعیت می گوییم.در هر دوره

تکامل می یابد.

ما یک ارزش تناسب ، Xi براي هر کروموزوم

هم مینامیم.عناصر قویتر f(Xi) داریمکه آن را (Fitness)

Colony یا کروموزوم هایی که ارزش تناسب آنها به بهینه

نزدیکتر است شانس بیشتري براي زنده ماندن در طول دوره

به نابودي اند. به عبارت دیگر الگوریتم ورودي هایی که به

کند.

یکبار اتفاق می افتد. محتویات دو کروموزومی که در فرآیند

تولید شرکت می کنند با هم ترکیب میشوند تا 2 کروموزوم

جدید که ما انها را فرزند می نامیم ایجاد کنند.این

هیوریستیک به ما اجازه می دهد تا 2 تا از بهترین ها را

براي ایجاد یکی بهتر از آنها با هم ترکیب کنیم.مانند آنچه

به علاوه در (evolution) . در شکل 1 مشخص میباشد

. [4](Mutation) یابند

قرار X=(x1,x2,..,xn) در یک عدد برداري x هر ورودي

دارد .براي اجراي الگوریتم ژنتیک مان باید هر ورودي را به

یک کروموزوم تبدیل کنیم.می توانیم این را با داشتن

انجام دهیم Xi بیت براي هر عنصرو تبدیل ارزش log(n)

مثل شکل 2

می توانیم از هر روش کد کردن براي اعداد استفاده

را به صورت X کنیم.در دوره 0، یک دسته از ورودي هاي

ام ما ارزش i تصادفی انتخاب می کنیم. بعد براي هر دوره

را تولید،تغییر وانتخاب را اعمال می Fitness مقدار

کنیم.الگوریتم وقتی پایان می یابد که به معیارمان برسیم.

عموما رًاه حلها به صورت 2 تایی 0و 1 نشان داده می

شوند ولی روشهاي نمایش دیگري هم وجود دارد.تکامل از

و در نسلهاي بعدي تکرار می شود.در هر نسل،مناسبترین ها

و نه بهترین ها انتخاب می شوند.

روش هاي مختلفی براي الگوریتم هاي ژنتیک وجود دارند

که می توان براي انتخاب ژنوم ها از آنها استفاده کرد.اما

روش هاي لیست شده در پایین از معمولترین روش ها

هستند.

مناسبترین عضو هر اجتماع انتخاب می : Elitist انتخاب

شود.

یک روش انتخاب است که در آن : Roulette انتخاب

عنصري که عدد برازش(تناسب)بیشتري داشته باشد،انتخاب

می شود.

به موازات افزایش متوسط عدد برازش : Scaling انتخاب

جامعه،سنگینی انتخاب هم بیشتر می شودوجزئی تر.این

روش وقتی کاربرد دارد که مجموعه داراي عناصري باشد که

عدد برازش بزرگی دارند وفقط تفاوت هاي کوچکی آنها را از

هم تفکیک می کند.

یک زیر مجموعه از صفات یک : Tournament انتخاب

تولید انتخاب می شوند.

Rank Selection, : بعضی از روشهاي دیگر عبارتند از

Generational Selection, Steady-State

Selection .Hierarchical Selection

2 کروموزوم براي معاوضه Crossover در روش

سگمنتهاي کدشان انتخاب می شوند.این فرآیند بر اساس

زنده شبیه سازي شده. اغلب روش هاي معمول

هستند Single-point Crossover شامل Crossover

، که نقطه تعویضدر جایی تصادفی بین ژنوم ها است.بخش

50/ می کند،که هر قسمت برگرفته از یک والد است،که 50

انتخاب شده.

تصویر 3 تاثیر هر یک از عملگر هاي ژنتیک را روي

کروموزوم هاي 8 بیتی نشان می دهد.ردیف بالاتر 2 ژنوم را

نشان می دهد که نقطه تعویض بین 5امین و 6امین مکان

در ژنوم قرار گرفته،ایجاد یک ژنوم جدید از پیوند این 2 والد

بدست می آیند.شکل 2وم ژنومی را نشان می دهد که دچار

جهششده و 0 در آن مکان به 1 تبدیل شده .

بپردازیم، داراي شماي کلی بصورت شکل 4 میباشد. البته

فیدبک استفاده خواهیم کرد.با پیش فرضها زیر کار تحیل و

بدست آورد تابع تبدیل سیستم را شروع میکنیم :

مشخصات تقویت کننده عملیاتی :

A1= بهره حلقه باز : 106

f1=10Hz : فرکانس قطع پایین

f2=1MHz : فرکانس قطع بالا

2.5 V : افت ولتاژ

مشخصات تقویت کنندة ترانزیستوري :

A1= بهره حلقه باز : 10

f2=10KHz : فرکانس قطع بالا

1.5 V : افت ولتاژ

توابع تبدیل حلقه باز و حلقه بسته در تصویر 5 مشخص می

مدل سیمولینک تقویت کننده بصورت شکل 6 میباشد :

T1=1/2Πf1 T2=1/2Πf که در آن 2

T3=1/2Πf3 B1=0.01

مدار حساب مینماییم که در تصویر 7 و 8 رسم شده است.

در ضمیمه ampli1.m فایل مربوطه با نام m برنامه

موجود این مقاله موجود میباشد.

100 و KHz هم افتادگی بهره به ترتیب 1.011 و

99KHz همچنین حاشیه فاز و فرکانس برهم افتادگی فاز

میباشد و سیستم در آستانه ناپایداري است.

کننده ترانزیستوري پایداري را افزایش دهیم. شکل مدار ،

نمودار بلوکی و مدل سیمولینک مدار را در تصویر 9

استفاده شده است که در بخش Ampli2.m بود از فایل

ضمیمه موجود میباشد. نتایج بدست آمده و نمودارهاي بود

و پاسخ پله را میتوانید در تصویر 10 مشاهده نمایید

همانطور که از نمودارتصویر 10 و نتایج بدست آمده از قبل

مشخص میباشد، حاشیه فاز و فرکانس بر هم افتادگی بهره

99.6 به 18.9 درجه و 95.3 KHz از 0.06 درجه و

رسیده است. هر چند که این بهبود مطلوب ما میبود KHz

راه دیگري که معمولا براي افزایش فاز سیستمها مورد

است. اما از آنجا که کنترل کننده پس فاز تاخیري را بر

سیستم تحمیل میکند، پاسخ سیستم را کند مینماید که

میشود.

کننده پیش فاز رفتاري شبیه مشتقگیر دارد بهره و سرعت

پاسخ سیستم را افزایشمیدهد. در شکل 11 مدار با فیدبک

genetic در برنامه amplifire براي پیاده سازي این

در مطلب ابتدا تابع تبدیل کل را محاسبه algorithms

همانجور که در تصویر 12 مشاهده مینمایید براي محاسبه

ابتدا باید تابع تبدیل داخلیترین لوپ را محاسبه کنیم براي

1 G1G از فرمول 2 C محاسبه فیدبک منفی 1

G1

k میباشد و 1 A1=10 , T3=1.59*10- که در آن 5

مقدار گین ماست که مجهول است و میخواهیم از طریق

مقدار بهینه آن را بدست Genetic_Algorithms

آوریم.

را که C و 3 C مطابق تصویر 13 مقدار تابع تبدیلهاي 2

A1=1*106 , T1= 0.0159 , T در آن = 2

1.59 میباشد را محاسبه *10-7 , T=2.2*10-5

میکنیم:

تابع تبدیل کلی است صورت و خرج آن را به صورت C4

تعرف کرده و در den و num ماتریس لاپلاس با نامهاي

استفاده Genetic Algorithm در peacksfcn.m

داریم که K و 2 k میکنیم در این جا ما دو مجهول 1

بهترین Genetic Algorithm میخواهیم از طریق برنامه

را به peachsfcn.m مقدار براي این گینها بدست آوریم

اینشکل تعریف میکنیم :

( ) Σi

out e y i y 2 Fitness _[ ] استفاده میکنیم که همان

مقدار بهینهاي است که ye ، ما میباشد Function

خروجی باید به آن برسد.

تعداد نسلها و جمعیت و ژنها را بهترتیب 100،100 و 32

در بهترین حالت Gnetic Algorithm قرار میدهیم تا

را بدست آورد وهمچنین k و 2 k مقدار بهینه گینهاي 1

Gnetic در var_n= تعداد متغیرهایمان را با مقدار دهی 2

تعیین میکنیم Algorithm

محدوده متغیرهاي خودمان را clab.m وهمچنین در

تعریف میکنیمکه در اینجا ما هردو متغیر را از 0,0001 تا 2

تعریف میکنیم

برنامه را اجرا میکنیم F با زدن کلید 5 clab حال در

را از طریق این برنامه k و 2 k و مقدار بهینه 1 (Run)

بدست میآوریم که نتیجه را در تصویر 14 میتوانید

مشاهده نمایید.

و K1= در نسل صدم مقدار 1.994361

بدستآمد. K2=0.009998

Tools/ControlDesign/LinearAnalysis.. ازمنوي

میبینید خروجی به مقدار بهینه خو یعنی 100 در مدت

1.5 رسیده است پس از طریق *10-4sec

با بدست آوردن مقدار بهینه گین Gnetic_Algorithm

همچنین گین کلی مدار هم برابر 100 گردیده است.

از محاسن ذاتی ژنتیک الگوریتم موازي بودن آن مي باشد .

شود يا مينيمم و بايد چند جنبه در نظر گرفته شود و به

همین خاطر از طریق ژنتیک الگوریتم توانستیم به پاسخ

مطلوب دست پیدا کرده علاوه رسیدن به پاسخ پله مناسب

که نمودار آنرا در تصویر 15 مشاهده مینمایید به گین 100

که مطلوبمان بود دست پیدا نماییم. ناگفته نماند ژنتيك

است که منجر به بهترين راه حل براي مسئله Fitness

شود. مشکل ديگر ،که آن را نارس مي ناميم اين است که

محلي سوق دهد. متاسفانه در اینصورت تمام زمانی که براي

ابتدا شروع گردد.

1 Op-amp) Operational Amplifier تقويت كننده هاي عملياتي

op-Amp بررسي مدار هاي تقويت كننده با استفاده از

op-Amp حل و شبيه سازي معادلات ديفرانسيل با استفاده از

2

ترانزيستوري، كليدي ترين نقش را بازي مي كند. از اين رو وقتي كه تعداد طبقات زياد مي شود

ديدگاه خارجي مدار مجتمع بررسي كنيم، يعني بدون اينكه از داخل مدار مجتمع اطلاعاتي داشته

مي ناميم و به Operational amplifier از اين به بعد اين مدار مجتمع را تقويت كننده عملياتي

مي گوييم. Op-amp اختصار به آن

ها يكي از عناصر مداري هستند كه مي توان با op – amp : از ديدگاه فيزيكي Op- amp

Ri Advi

Ro

Ro

Ri

Vi Vo

همان ولتاژ تقويت شده اي است AVi ضريب تقويت مدار مي باشد و A در شكل بالا مي دانيم كه

براي يك تقويت كننده ايده آل به سمت بي نهايت ميل A . كه در خروجي از مدارمان انتظار داريم

كه ادعا مي كنيم يك تقويت op-amp حال با توجه به شكل بالا مي خواهيم شهودي از درون يك

معمولي را بدانيم كه آن را در شكل زير نمايش مي دهيم: op – amp

op – amp شكل ( ۲) طبقات به كار رفته شده در

را بررسي كنيم پس تنها به توضيحات ساده اي از op – amp در اينجا چون قصد نداريم كه داخل

را مشاهده op – amp هر طبقه مي پردازيم و در ضميمه اين فصل مي توانيد مدار واقعي داخل يك

همانطور كه در شكل ۲ مي بينيم طبقه اول يك تقويت كننده تفاضلي است. اين  حسن انتخاب ما را

استفاده مي كنيم. diff- amp ارمغان بياوريم. بنابراين در طبقه اول از يك

در طبقه دوم نياز به تقويت بسيار زيادي داريم كه بدين منظور از چندين ترانزيستور در آرايش اميتر

در ادامه، طبقه تغيير دهنده سطح را قرار مي دهيم كه در اين طبقه اين طور قرارداد مي كنيم كه هرگاه

شد يا به عبارتي ورودي تقويت كننده صفر شد، در خروجي نيز ولتاژ صفر را مشاهده كنيم. Vi=0

نيز از آن بهره برد. DC باشد

• Acute Care Common Stem (ACCS)

• Anaesthesia

• Basic Neurosciences Training (BNT)

• Chemical Pathology

• General Practice

• Histopathology

• Medical Microbiology

• Medicine in General

• O&G

• Ophthalmology

• Oral & Maxillofacial Surgery (OMFS)

• Paediatrics

• Psychiatry

• Public Health

• Radiology

• Surgery in General

• Otolaryngology (ENT)

website (www.oxforddeanerycdu.org.uk ) You should think widely and flexibly about your career

· Educationally approved posts for SHOs with <3 years exerience

· Only available in ST1 and ST2 posts ( except ST3 in paeds or psych)

· Apply for 1 year only

· Individuals can only apply for up to 2 yrs as a FTSTA altogether

· When the FTSTA is completed you can:

o Apply for ST2/3

o Apply for a career grade

o Consider an alternative training programme

· Doctors in this grade will also be known as StRs ( specialty registrars)

Specialist Registrars (SpRs)

Details of this can be found on the RCGP website – www.rcgp.org.uk.

· familiarise yourself with the main learning requirements of the new programme which

· seek advice if need be from local GP trainers in your medical school, foundation

is Dr. Barbara Thornley and she can be contacted on bthornley@oxford-pgmde.co.uk

تقويت كننده برق - تراگذران برق - تر انسدكتور- دستگاه توان، ولتاژ يا جريان

افزا- تراديسنده

ميتواند توسط يك ولتاژ d.c. يا a.c. پيچ است كه با آن يك جريان يا ولتاژ

يا جريان مستقل، و با بهره گيري از پديده اشباع (سيرايي- سيري پذيري ) در

مدار آهنربايي، تغيير كند.

به انگليسي ) Tranducteur magnetiquc اصطلاح فرانسوي

را به Transducteur نبايد با اصطلاح فرانسوي متداول (Tranductor

اشتباه گرفته شود . كاربرد اصطلاح دومي به جاي (Transducer انگليسي

با شد.

 سازن تقويت كننده (سازن= عنصر= المان)- سازن تراگذر- سازن مبدل القايي -

دستگاه تقويت كننده (تراگذر) را شكل ميدهد.

سيم پيچ تحريك -

سيم پيچ روي سازن (عنصر) تقويت كننده (تراگذر ) است كه توسط آن

دستگاه تحريك ميشود.

سيم پيچ توان (قدرت)

سيم پيچ سازن (عنصر) تقويت كننده دستگاه (تراگذر) است كه جريان بار از

آن ميگذرد.۵ سيم پيچ كنترل سيم پيچ تحريك است كه به وسيله آن توان برونداد (خروجي ) ازيك منبع

بيروني كنترل ميشود.

سيم پيچ تحريك گذرا ننده، جرياني كه براي جا به جاسازي نقطه ميانين

كاركرد در روي مشخصه ايستا (استاتيك)، به كار ميرود.

سيم پيچ خود- تحريك (سازي)- سيم پيچ تحريك سرخود

سيم پيچ تحريكي است كه توسط آن پديده خود تحريك شوندگي پديدار

ميشود.

ابزار يا لامپ يكسو كننده خود - تحريك (ساز)- سوپاپ لامپي يكسو كننده

تحريك سرخود ( شير- سوپاپ- لامپ خلا)

ابزار يا لامپ يكسو كننده اي است كه به طور سري (ريسه بند ) به سيم پيچ

توان يك دستگاه تقويت كننده (تراگذر) وصل ميشود تا آن كه خود تحريك

شوندگي در آن پديدار شود.

- اصطلاحهاي مربوط به كميت هاي فيزيكي -

 ولتاژ برونداد- ولتاژ بار

ولتاژي است كه دريك مدار داراي يك دستگاه تقويت كننده (تراگذر ) به

امپدانس بار واگذار (تحويل) ميشود.

 ولتاژ جذب شده -

ولتاژي است كه توسط يك دستگاه تقويت كنند ه (تراگذر) در يك مدار جذب

ميشود.

 جريان كنترل- جريان فرمان -

جرياني است كه در يك سيم پيچ كنترل يك ابزار تقويت كننده (تراگذر )

جاري ميشود.

ولتاژ كنترل -ولتاژ دو سر پايانه هاي كنترلي يك ابزار تقويت كننده (تراگذر) است.

مشخصه ايستا (استاتيك)

(يك ابزار تقويت كننده)؛

منحني انتقال (واگذاري)

(يك ابزار تقويت كننده)

روند (حالت) ماندگار ميباشد.

نسبت ولتاژ

نسبت يك تغيي ر كوچك ولتاژ برونداد، در شرايط روند -ماندگار، به تغيير

متناظر (همنگر) در ولتاژ كنترل در بار و شرايط بهره برداري معين است.

نسبت جريان -تقويت سازي جريان

نسبت يك تغيير كوچك درجريان برونداد، در شرايط روند - ماندگار، به تغيير

متناظر (همنگر) جريان كنترل دربار و شرايط بهره برداري معين است.

تقويت سازي توان- توان افزايي -

نسبت يك تغيير كوچك در توان برونداد، در شرايط روند - ماندگار، به تغيير

متناظر (همنگر) توان كنترل، در بار و شرايط بهره برداري معين است.

ثابت زماني كل -

ثابت زماني پاسخ يك كميت برونداد يك دستگاه تقويت كننده (تراگذر)به يك

تغيير كوچك ناگهاني ولتاژ كنترل دربار و شرايط بهره برداري معين است.

ثابت زمان پس ماند- ثابت زماني پسماند -

ثابت زماني پاسخ يك كميت برونداد يك دستگاه تقويت كننده (تراگذر ) به

ا س ت.

ثابت زمان درونداد- ثابت زماني ورودي -اختلاف ميان ثابت زماني كل و ثابت زماني پس ماند است.

زمان پاسخ -

اين زمان از لحظه تغيير ناگهاني يك كميت كنترل تا تغيير متنا ظر (همنگر) آن

با شد.

القاي اشباع (اشباعي)- القاي سيرايي- اندوكتانس سيري پذيري (اندوكتانس = مقاومت القايي)

مقاومت القايي يك سيم پيچ است كه متناظر (همنگر) با تغييرات يك شار

كوچك درمحدوده سيرايي (اشباع) منحني آهنربايي است.

راكتانس اشباع (اشباعي)- مقاومت واكنشي سيرايي -

مقاومت واكنشي متناظر (همنگر) با مقاومت القايي اشباع (سيرايي ) در بسامد

(فركانس) جريان متناوب، منبع توان است.

۱۵ عدد مزيت- رقم مزيت -

نسبت تقويت سازي توان (توان افزايي) به زمان پاسخ است.

For many, home movies were originally played on the classic vcr tape. Then, the technology moved onto DVD players, and the look of the movies was sharper and of a much better quality. Now the next evolution has started with blue ray technology.

Finding out about what it is includes learning about the differences between this kind of technology and the current mass marketed DVD systems. This new kind of technology has been developing for years, since the mid 1990's when HDTV's were becoming more common for consumers to buy. A technology was needed that could record and play back the high definition recordings. Blue Ray technology was created to fill that void.

So what is so special with this technology and how is it different from the standard DVD? BR technology can store far more information that the traditional DVD, almost 5 times more storage is available on a blue ray disc. The blue ray discs use a blue ray laser to read the information where other DVD's use a red laser.

With a blue laser the wave length is shorter allowing for more storage to be used. This did cause some problems originally, as the discs were much easier to scratch. The case that held the disc had to be made more durable and was somewhat bulky. Advances in polymer coatings have advanced allowing for a better protective coating to be placed on the disc, alleviating the need for the bigger containers.

There are many companies that have a stake in the development of the next cutting edge technology and these companies are looking into both blue ray technology and a HD DVD. Some of the big companies are fighting over which technology should be used and this has caused a split in which companies support which format. Even companies that produce movies are split over which type of technology to use, which means depending on what movie a consumer wishes to purchase; they may need two different types of players.

Both the blue ray and the hddvd players are continuing to improve. In the end, consumers may discover that they enjoy both types of players and they both may be successful with consumers. Learning about what is this technology exactly can help a consumer get a good idea of basic information in regards to this new technology.

FireWire is integrated into Power Macs, iMacs, eMacs, MacBooks, MacBook Pros, and the iPod. FireWire ports were also integrated into many other computer products dating back to the Power Macintosh G3 "Blue & White" computers. All these machines include FireWire ports that operate at up to 400 megabits per second and the latest machines include FireWire ports that support 1394b and operate at up to 800 megabits per second

FireWire is a cross-platform implementation of the high-speed serial data bus -- defined by the IEEE 1394-1995, IEEE 1394a-2000, and IEEE 1394b standards -- that can move large amounts of data between computers and peripheral devices. It features simplified cabling, hot swapping, and transfer speeds of up to 800 megabits per second (on machines that support 1394b

Major manufacturers of multimedia devices have been adopting the FireWire technology, and for good reason. FireWire speeds up the movement of multimedia data and large files and enables easy connection of digital consumer products -- including digital camcorders, digital video tapes,digital video disks, set-top boxes, and music systems -- directly to a personal computer

This page will focus mainly on SRAM (Static RAM). SRAM retains the values you put in it, unlike DRAM (Dynamic RAM), which needs to be refreshed several times every second. The only real advantage DRAM has over SRAM is that it's much cheaper, so it's necessarily used for the main system RAM on most PCs. (If RAM manufacturers used SRAM for main PC RAM, the RAM in your computer would probably cost more than the CPU!) DRAM sucks, however, because the fact that it needs to be constantly refreshed makes it hugely annoying to work with. So, SRAM it will be!

On the outside, SRAM chips are pretty simple. Aside from address bus and data bus pins and two power pins, there are only three other pins on a typical SRAM chip: Chip Enable (CE), Output Enable (OE), and Write Enable (WE). On the inside, all RAM chips consist mainly of a big grid of RAM cells, tiny devices which are each capable of storing a single bit. (Of course, the RAM cells are organized into bytes. Typically, 8 bits make a byte, although this is not necessarily the case.) So we see that all an SRAM chip really has to do is use the address sent to it to select a single byte-sized line of RAM cells, enable all those cells, and if it's writing to memory, to change what's stored in those cells. A short enough explanation, but each step of the process involves devices which contain many smaller devices.

Let's start with the most fundamental part of an SRAM chip: A RAM cell. In SRAM, the RAM cells are basically D-type flip-flops, so to understand RAM cells, you need to understand D flip-flops. Before we get into D flip-flops, however, you need to understand...

The Set/Reset Latch

The set/reset latch is the most basic latch circuit. A latch is a digital electronic logic circuit which, upon receiving an instruction to change its output, will "latch" the output, so that the output does not change even after the input has been removed. The set/reset (S/R) latch looks like this internally:

The S/R latch has two inputs and two outputs. The two inputs are labeled "Set" and "Reset". Set, when enabled, turns on the latch, and Reset turns it off. The two outputs are labeled Q and /Q. (The Q with the line over it in the diagram means "NOT Q", or the inverse of Q. Since there is no way to create a line over a character in text, usually the convention of preceding a signal with a slash is used to indicate "NOT".) Q is the main output for the latch. When the latch is on, Q will be 1. When the latch is off, Q will be 0. /Q is the opposite of Q, so when Q is 1, /Q will be 0, and vice-versa.

Not that this is an active-high S/R latch, meaning that its inputs trigger when they go high. It's possible to make an active-low S/R latch by replacing the NOR gates with NAND gates, but we won't get into that now.

As you can see, when Set goes high, the output of the NOR gate on the bottom must be 0 (because when either NOR input is high, the output is 0). This sets /Q to 0. This same 0 goes to the lower input on the NOR gate at the top; Since Reset must be low (since Set is high), both inputs to the NOR gate at the top are 0. Therefore, since both inputs are 0, it outputs a 1. This 1 hits the top input of the bottom gate, keeping the gate on (and setting Q to 1), and the latch remains stable in this state until Reset goes high. Similarly, the opposite happens when Reset goes high. The workings of this latch may seem confusing at first, but if you follow the logic paths you should be able to understand it clearly.

The R/S latch is the basis for most digital flip-flop circuits. Once you understand it, you can move on to...

The D flip-flop

The D flip-flop is quite a simple digital device with four pins; Two of these pins are inputs, and two are outputs. The chief input is the D (Data) pin, which, like any other digital signal, can receive either a 1 or a 0. The other input is the E (Enable) pin, sometimes labeled the Clock or Clk pin. The two outputs are Q and /Q (NOT Q, or the inverse of Q). However, within RAM, the /Q output of a D flip-flop is not used, and thus the flip-flop can, for purposes of using it in RAM, be reduced to a three-pin device with two input pins and one output pin. A simple enough device, indeed.

The operation of the D flip-flop is simple: The Q output reflects the D input. When the Enable or Clock pin is activated, the state of D is stored in Q. Once this happens, Q stays the same and does not change, regardless of the state of D, unless the Clock pin is triggered again. The D flip-flop thus acts as a single-bit memory storage unit: When you want to store a bit in it, you set D accordingly and pulse its clock. Once this is done, its Q output will reflect the bit stored in the flip-flop until you change it.

Internally, the D flip-flop is basically an R/S latch with some additional circuitry added to the inputs.

Note that D flip-flops are usually "edge-triggered", meaning that they will change their state only in the moment that the Clock pin is enabled. The D flip-flop diagrammed here is not edge-triggered; The output will follow the input as long as the Clock pin is enabled. There's nothing really wrong with this in terms of using the flip-flop for RAM. We could turn it into an edge-triggered device with some more gates, but that's not necessary now.

The D flip-flop is a great device, but to make it more useful, it should come equipped with an Enable pin. Many D flip-flop chips do have Enable pins, but in keeping with the theme of illustrating the internals of these devices, it's appropriate to show you...

How to use a transistor as an Enable pin

In digital logic design, you can add an Enable signal to just about any digital signal by simply running it through a tri-state logic buffer. A digital logic buffer is just a device that takes whatever digital logic is fed into it, and outputs the exact same signal. (Sort of like a NOT gate, except without the inverting part.) A "tri-state" digital device is one which includes an Enable pin, so that you can enable or disable the output. When the Enable pin is turned off, the output goes into a "high-impedance" state in which it is essentially a dead pin, disconnected from the rest of the device. The digital logic symbol for a tri-state logic buffer looks like this:

At the component level, a tri-state digital logic buffer is really just a single transistor. The base of the transistor acts as the Enable pin, the transistor's Collector is the logic input, and the Emitter is the logic output. Thinking about it in this way, the tri-state logic buffer would look like this:

Now that we know how to make a D flip-flop and put an Enable pin on it, we have...

A complete RAM cell

A typical RAM cell has only four connections: Data in (the D pin on the D flip-flop), data out (the Q pin on the D flip-flop), Write Enable (often abbreviated WE; The C pin on the D flip-flop), and Output Enable (the Enable pin which we added). Now that we have this concept, we can black-box it, which, for simplicity's sake, I will do on this web page from this point henceforth. Our RAM cell, made into a logic block, looks like this:

If you've understood everything thus far, you're almost done with understanding how SRAM works. You already know how one individual memory cell works, so now the trick is to just arrange them in an array so that you can address each one independently. To do this, we need to be able to take memory addresses and use them appropriately, so the next thing we'll learn is...

How an address decoder works

An address decoder is a device which reads in a binary-represented memory address, and based on the address it receives, turns on a single output. If an address decoder has n inputs, then it will have 2^n (2 to the power of n) outputs. At any point in time, only one output line is on, and all the others are off. The decoder must have a separate output for every byte in memory. Since a byte is 8 bits (usually), and every RAM cell is one bit, each output from the memory decoder goes to 8 RAM cells.

For simplicity's sake, we'll illustrate two small-scale memory decoders: The 2-to-4 decoder, and the 3-to-8 decoder. In reality, a modern RAM chip would have much larger decoders than this; An 8 kilobyte RAM chip (which is quite small by today's standards) would have a built-in 13-to-8192 decoder, but trying to draw that and represent it here on this website would probably be overkill.

An address decoder is a form of combinatorial circuit; The idea behind it is that for every possible combination of inputs, there needs to be a separate output that will activate. For example, suppose we have a 2-to-4 decoder; This is a decoder with two inputs and four outputs. The idea is that for every possible combination of 1s and 0s on the two inputs, a different output needs to activate. There are four possible ways to put 1s and 0s on two inputs: 00, 01, 10, and 11. If we call the inputs "in0" and "in1" and the outputs "out0" to "out3", then the 2-to-4's truth table looks something like this:

in0 in1 ³ out0 out1 out2 out3
ؤؤؤؤؤؤؤؤإؤؤؤؤؤؤؤؤؤؤؤؤؤؤؤؤؤؤؤؤ
 0   0  ³  1    0    0    0
        ³
 0   1  ³  0    1    0    0
        ³
 1   0  ³  0    0    1    0
        ³
 1   1  ³  0    0    0    1

The circuit diagram for a decoder might look complicated at first, but actually, it can be pieced together from a pretty simple idea, so just before I show you the diagram for one, let me try to explain the concept: To make a decoder, you attach two wires to each input. One wire simply comes directly from the input, while the other wire passes through a NOT gate (an inverter, which sets a logic 0 to a 1, and vice-versa). Once this is done, you have something that looks like this:

After this, take one wire from each input, and connect the ends of them to an AND gate. The output of the AND gate then becomes one of the address decoder's outputs. Add different AND gates for each possible combination of inputs, and you're done. Each outputting AND gate must have a different combination of input triggers. This way, only one output will ever turn on at a time.

For example, while making our 2-to-4 decoder, suppose you just happen to take the input from in0 that DOESN'T pass through an inverter, and the input from in1 which DOES pass through an inverter. It should be clear that in order for both of these wires to be holding a logic 1, in0 needs to be on, and in1 needs to be off. This corresponds with the third line of the truth table above, so after you connect these two wires to the inputs of an AND gate, the output for that AND gate becomes out2.

Whether or not you understand what was written above, perhaps the diagram below of a 2-to-4 decoder will make things clearer now:

The red lines indicate the wires going to the AND gate at the top. The output of this AND gate will come on only when both inputs to the decoder are on. The green lines are for the second-highest AND gate, which will energize when the lower input is on, but the top input is off. The purple wires signify the AND gate which will activate when the top input is on but the bottom one is off, and finally, the blue lines lead to the AND gate for when both inputs are off. There are four possible combinations of input to this decoder, and each has a corresponding single output. A 3-to-8 decoder works the same way, except it would have eight AND gates at the right, three inputs, a NOT gate for each input, and more wiring.

Now that we know how to make a RAM cell, a tri-state buffer, and an address decoder, we have all the sub-circuits we need to make a complete, working RAM array. It's time to put it all together.

An SRAM array

For this introduction, we'll illustrate a 4x2 SRAM array. RAM arrays are designated as bxw, where b is the number of bytes in the array, and w is the byte width, meaning how many bits are in each byte. Thus, our 4x2 RAM array has 4 bytes, and each byte contains two bits. (Most RAM arrays that you see in electronics parts catalogs will be somethingx8, because it's pretty typical to have 8 bits in a byte, but it's good to be different sometimes, and having only two bits to a byte makes things easier to draw, too.)

In an SRAM array, the RAM cells are arranged and wired up as follows:

Typically, when diagrammed, a row of RAM cells represents one byte, and each column represents one bit in each byte. So in our 4x2 RAM array, we would have 4 rows (because we have 4 bytes total), and each row will have be two columns wide (because each has two bits):

The Enable pins on the RAM cells lead from the outputs on the address decoder. Thus, each output on the address decoder goes to each RAM cell in one row of the RAM array (because you want to enable all of the bits in each byte when that byte is accessed).

The outputs from the address decoder are also ANDed with the Write Enable signal to go to the cells' Write Enable pin. That way, when both a particular address AND the Write Enable signal are on, the data gets put into the cell. (Please note that at this point, I lost my patience with trying to draw all this, and so the picture below is only half-done; The output of the AND gate in each row should be going to the RAM cell on the right as well, but things got a bit too cluttered to provide any easy way for me to add this.)

The only thing remaining is the data pins. They can simply be left as they are, to provide two separate data buses (one for data in, the other for data out), but microprocessors usually expect to use a bidirectional data bus. To achieve this, the data bus is connected to both the Data In pins and the Data Out pins of the RAM cells. This gives you a bidirectional data bus, but there needs to be a bit of additional circuitry added to this so that data only flows into the RAM array of out of it, but not both. And so we come to...

Making the data bus bidirectional

To ensure that data only flows in one direction at a time (either coming out of the RAM array or going into it), two diodes are used right next to each RAM cell, so that data only goes into it or out from it, but not both:

And there you have it. That's pretty much how RAM works. At least SRAM, anyway. And you don't really want to know how DRAM works, because DRAM sucks. Everybody should use SRAM and eliminate DRAM altogether.

High fidelity audio and visual components were at first treated with skepticism. Many people didn’t believe there was much of a difference and thought that hi-fi was a gimmick to sell more costly equipment. Enthusiasts soon learned that hi-fi did indeed offer higher quality reproduction. Hi-fi components became so popular that the term was used to refer to the components themselves as well as to the technology. For example, when referring to a record player or turntable, people might say, “Put a record on the hi-fi.”

Today, the term hi-fi is used to describe any sound system of above average quality. It also refers to other components that make up home theater systems. It may include everything from your television, DVD, and satelitte receiver, to your compact disc player, other stereo components, and sorround speakers.

Much like computer enthusiasts, hi-fi enthusiasts enjoy putting together custom systems. Just as a computer enthusiast will choose separate components from diverse manufacturers in order to take advantage of certain specialties, a hi-fi enthusiast will do the same. Not only is this the best way to create a unique, high quality system, but it also allows the enthusiast to build the system one piece at a time, giving her greater freedom to spend more on each component. Instead of putting out a lot of money at one time to purchase an entire system, one can build a collection of high quality components at his own pace. This is also important when it comes to upgrading hi-fi equipment, as the enthusiast can simply replace one piece at a time.

آشكارساز تناسبي چيست؟

كارت هوشمند چيست وچگونه كار مي‌كند؟

يك كارت هوشمند از نظر اندازه شبيه به كارت‌هاي اعتباري پلاستيكي كه يك تراشه در آن كار گذاشته شده است مي‌باشد. قرار دادن يك تراشه در كارت به جاي نوار مغناطيسي، آن را تبديل به يك كارت هوشمند با قدرت سرويس‌دهي در مصارف گوناگون مي‌نمايد. اين كارت‌ها به دليل دارا بودن تراشه، داراي قابليت كنترل عملكرد بوده و فقط اطلاعات مربوط شخصي و تجاري كاربر واجد شرايط را پردازش مي‌نمايد.

كارت هوشمند قابليت استفاده در انواع معاملات بانكي و پشتيباني مالي را دارد و به دليل راحتي حمل و نقل و امنيت موجب آسايش خيال كاربر وتامين اطلاعات گوناگون مورد نياز وي مي‌گردد. استفاده از امكانات متنوع كارت‌هاي هوشمند به تجار اين امكان را مي‌دهد كه محصولات و كالاهاي خود را در بازارهاي جهاني ارائه وفعاليت‌هاي تجاري خود راگسترش دهند. بانك‌ها، شركت‌هاي نرم‌افزاري وسخت افزاري، خطوط هوايي وهمه اين شانس را خواهند داشت كه به بهره‌مندي از خدمات نوين محصولات كارتي خود در جهت ارتقاء سطح فعاليت‌ها و ارائه محصولاتشان دست يابند.

تركيب امكانات نهفته در كارت‌هاي هوشمند سبب ايجاد ارتباط نزديك‌تر ميان طرفين تجاري وآنهايي مي‌گردد كه در اقصي نقاط دنيا به نحوي با يكديگر داراي روابط تجاري مي‌باشند.

امروزه در دنيا بيش از 4/4 ميليارد كارت اعتباري استفاده مي‌شود. فعاليت‌هاي اقتصادي - مالي مبتني بر كارت‌هاي هوشمند به ميزان 30 درصد در سال رشد دارد. همچنين تحقيقات انجام شده حاكي از آن است كه در سراسر دنيا طي 5 سال آينده صنعت كارت‌هاي هوشمند و وسايل و تجهيزاتي كه امكان استفاده از آن را ميسر مي‌سازند به طور قابل توجهي رشد خواهد داشت وهمچنين افزايش امكانات وقابليت‌هاي دستيابي با امنيت كافي به شبكه‌هاي كامپيوتري وتوسعه رو به رشد استفاده از تجارت الكترونيكي سبب رايج‌تر شدن بكارگيري كارت‌هاي هوشمند مي‌گردد.

با در نظر گرفتن همين ميزان مصرف، انتظار مي‌رود كارت‌هاي هوشمند براي 95درصد خدمات تلفن بي‌سيم وديجيتالي كه در تمام دنيا ارائه مي‌شود مورد بهره‌برداري قرار گيرند. آسيا، آمريكاي لاتين وآمريكاي شمالي مناطقي هستند كه بالاترين پتانسيل را در 3 سال آينده براي گرايش به استفاده از كارت‌هاي هوشمند به‌خود اختصاص خواهند داد. 

اكنون بيشترين زمينه‌هاي كاربري از كارت‌هاي هوشمند در سطح دنيا مربوط به تلفن‌هاي پولي وبي‌سيم، بانكداري، خدمات بهداشتي و پرداخت آبونمان و لوازم خانگي بوده است.

چرا كارت‌هاي هوشمند تا اين اندازه متداول شده‌اند؟

با وجودي كه در حال حاضر ميلياردها كارت هوشمند در دنياي فعلي در دست كاربران قرار دارد، اما ممكن است فردي كارت را از يك كشور خاص تهيه نمايد و بخواهد از آن در ساير كشورها استفاده كند. توليدكنندگان تجهيزات و ارائه‌دهندگان كارت‌هاي هوشمند براي تامين چنين كاربردهايي، تكنولوژي كارت‌هاي چند منظوره را ايجاد كرده ودر تلاش هستند تا نوعي سازگاري ميان تجهيزات وكارت هاي توزيع شده در سراسر دنيا به وجود آورند.براي تحقق بخشيدن به اين مساله بايد اصول تجاري و فني مورد نياز واصول استاندارد و هماهنگ با هر كشور، ميان كارت‌ها و پايانه‌ها و مشخصه‌هاي موجود در تجهيزات وسايل  ايجاد و مورد آزمايش قرار گيرند. كليد اصلي در دستيابي به اين امر جهاني در دست صنعت مربوطه قرار دارد.

استاندارد چه نقشي را در كارآيي كارت‌هاي هوشمند ايفا مي‌كند؟

استانداردها در واقع عواملي هستند كه، هماهنگي وتطابق ميان كارت‌ها و وسايل كارت‌خوان يا پشتيباني كننده را تضمين مي‌نمايند. وجود استانداردهاي جهاني و ثابت در اين امر باعث مي‌شود تا كارهاي توليد و توزيع شده در يك قسمت از دنيا به وسيله دستگاهي در بخش ديگري از دنيا پذيرفته شده و مورد استفاده قرار گيرند.

صنايع، خدمات و فعاليت‌هاي بسياري وجود دارد كه از طريق اعمال استانداردها و ضوابط بين‌المللي مي‌توان عملكرد آنها را تحت پوشش كارت‌هاي هوشمند قرار داد كه دستگاه‌هاي پمپ بنزين، سيستم‌هاي پرداخت بانكي و بسياري موارد ديگر از اين قبيل هستند. به همين دليل سازمان بين‌المللي استاندارد، اصولي را براي كارت‌هاي هوشمند ايجاد و تثبيت كرده است و اين اصول همچنان در حال توسعه و همه‌گير شدن هستند.

همچنين بخشي از صنايع انحصاري موفق شده‌اند اصول و استانداردهاي مشخصي را براي استفاده از كارت‌هاي هوشمند به وجود آورده و هم اكنون  در حال گسترش و تثبيت آنها در سراسر دنيا مي‌باشند. لذا حضور وسيع حضور نمايي مزيت‌هاي فراوان موجود دركارت‌هاي هوشمند صنايع و خدمات مختلف جهاني را بر آن داشته تا با ارائه ضوابط و استانداردهاي مدون و قانوني موفقيت آنها را تضمين نمايند.

* مزاياي عمده‌اي كه كارت‌هاي هوشمند به مصرف كننده ارائه مي‌دهند چگونه ارزيابي مي‌شود؟

البته مزاياي كارت‌هاي هوشمند را بايد با در نظر گرفتن كاربردها و نحوه مديريت و ايجاد زيرساخت‌هاي فرهنگي و تخصصي در هر جامعه بررسي نمود. عموما دستورالعمل‌ها و استاندارد محلي وضع شده و نحوه برخورد و حمايت قانون از كاربردهاي اين كارت‌ها در ارتقاء مزاياي آن مؤثر مي‌باشد. شيوه زندگي و اهميت دستيابي به اطلاعات و چگونگي پردازش آنها و قوانين موجود در تنظيم روابط مالي نيز در تعريف مزاياي كارت‌هاي هوشمند براي هر منطقه از دنيا حائز اهميت است كه نمي‌توان آنها را ناديده گرفت. با اين وجود مزاياي عمده اهداف اصلي ايجاد سيستم‌هاي بكارگيري كارت‌هاي هوشمند مي‌توان در توانايي اداره يا كنترل مؤثر فعاليت‌هاي تجاري كاهش چشمگير كلاهبرداري، كاهش كاغذبازي وحذف فعاليت‌هاي زائد و وقت‌گير خلاصه نمود.

كارت هوشمند چند منظوره چيست؟

كارت هوشمند، براي راحت‌تر شدن و كاهش فعاليت‌هاي زائد در امور تجاري و غيره توليد گرديده، فعاليت‌هايي از قبيل (خريد و فروش، برنامه هاي بهداشتي، خدمات بانكي، خدمات مسافرتي و...). اگر قرار باشد براي انجام هر يك از فعاليت‌هاي فوق يك كارت هوشمند اختصاص يابد، آنگاه تعداد كارت‌ها خود مشكل جديدي مي‌شود كه بر تمايلات كاربران تأثير منفي گذاشته و از كارآيي آن نيز مي‌كاهد.

يك كارت چند منظوره پاسخ مناسبي براي اين موضوع است زيرا كارت چند منظوره مي‌تواند انواع مختلفي از كارت‌ها را پشتيباني نمايد.

به عنوان مثال كارت چند منظوره "ويزا" كارتي مي‌باشد كه تركيبي از اعتبار توسعه يافته ويزا در برگيرنده ستون بدهي و توابع ذخيره مالي و ذخيره‌سازي ميزان اعتبار مالي مي‌تواند در مسافرت‌ها كارآيي فراواني داشته باشد.

كارت‌هاي چند منظوره با تحت پوشش قرار دادن موضوعات متنوعي از عمليات خريدها وخدمات گوناگون مالي موجبات آسايش كاربران را فراهم ساخته است.

كارت اعتباري بدون تماس چيست؟

دو نوع كارت اعتباري بدون تماس وجود دارد. اولي يك كارت بدون تماس از راه نزديك است كه با وارد كردن آن در يك دستگاه جانبي مخصوص خوانده مي‌شود. و دومين كارت بدون تماس از راه دور است كه بدون استفاده از دستگاه جانبي كارت‌خوان قادر است از يك مسافرت معين و به صورت كنترل از راه دور خوانده شود كه در دكه‌هاي دريافت عوارض كاربرد زيادي دارد.

قيمت يك كارت تراشه ‌دار چقدر است؟

در تلاش براي پاسخ دادن به اين سئوال كه بيشتر مانند پرسيدن قيمت ماشين، بدون در نظر گرفتن اينكه يك فولكس واگن دسته دوم و قديمي است و يا يك رولزرويس آخرين مدل، بايد گفت بهاي كارت‌هاي تراشه‌دار 15 الي 80 درصد بستگي به ظرفيت آنها و كميت اعتباري داشته و در اين محدوده متغير است.

چرا بارگذاري (شارژ) مجدد يك كارت هوشمند اهميت دارد؟

كارت‌هاي يكبار مصرف و قابل شارژ مجدد، هر دو از بازارهاي مصرف و كاربري برخوردار هستند. كارت‌هاي يكبار مصرف در مواقعي كه كاربر در مسافرت به سر مي‌برد و يا به منظور پرداخت وروديه‌ها و مصارفي شبيه اينها مورد استفاده قرار مي‌‌گيرند و عمدتا استفاده از آن براي يك زمان مشخص مي‌باشد كه پس از اتمام ذخيره، فاقد ارزش و بهره‌برداري مي‌باشد و دور انداخته مي‌شود.

اگر كارت مورد بحث چند منظوره باشد و مثلا ارزش‌ها و اعتبارات را ذخيره كرده و حساب‌هاي بدهكار و بستانكار كاربر را ثبت نمايد، كاربر آن را دور نخواهد انداخت. صحيح‌تر خواهد بود كه انرژي (اعتبار)  ذخيره شده، قابل شارژ يا بارگذاري مجدد بوده و كاربر مجبور به خريد مكرر كارت‌هاي يكبار مصرف نگردد.

كارت‌هاي اعتباري تا چه اندازه ايمن و مطمئن هستند؟

كارت‌هاي هوشمند عملا امنيت و اطمينان بيشتري نسبت به ساير وسايل ذخيره اطلاعات مالي ارائه مي‌دهند. يك كارت هوشمند مكان امني براي ذخيره اطلاعات گران‌بهايي مثل كليدهاي اختصاصي، شماره حساب‌ها، رمزها يا ساير اطلاعات خصوصي ارزشمند مي‌باشد. كارت‌هاي هوشمند با قدرت انجام محاسبه‌هاي پيچيده قابليت تأمين امنيت بالاتر را دارا هستند و سلامت كاري صاحب كارت را فراهم مي‌سازند.

آيا رهنمودهايي براي مصرف‌كننده در استفاده از كارت‌هاي هوشمند وجود دارد؟

بله، براي اولين بار شركت‌هاي توليدي كارت هوشمند، اطلاعاتي را در رابطه با صنعت و توزيع‌كنندگان كارت هوشمند، روش‌هايي عمومي و قانوني ارائه كردند. درك و شناخت صحيح اين رهنمودها بسيار مهم است، خصوصا اينكه براي اولين بار اين اطلاعات توسعه صنايع چندگانه به طور داوطلبانه پذيرفته شده و در حال تكامل است.

* انتظارات شخصي مصرف‌كنندگان را شناسايي كرده و در نظر بگيريد و رهنمودهاي شخصي ارائه شده را در مورد آنان اجرا نماييد.

* به منظور تأمين خدمات بهتر و ارائه فرصت‌هاي جديد به مصرف‌كننده، استفاده، جمع‌آوري و نگهداري اطلاعات مربوطه به آنها را (تا حدي كه نياز است)تهيه و بايد كامل شود.

* وسيله‌اي را براي مصرف‌كنندگان تهيه و در محل‌هاي مختلف تعبيه كنيد تا اسامي آنان را به بازار و با شركت به طور مستقيم يا پست و يا موارد درخواستي ديگر ارسال نمايد.

* روش‌هاي انجام شده و در دسترس، كارمند را از نظر شخصي محدود مي‌سازد.

رباتيك: علم شناخت و طراحی آدمک های مصنوعی و هوشمند
ربات چيست؟
ربات يك ماشين الکترومکانيكی هوشمند است با خصوصيات زير:
·  می توان آن را مکرراً برنامه ريزی کرد.
·  چند کاره است.
·  کارآمد و مناسب برای محيط است.
اجزای يك روبات:
·  وسايل مکانيكی و الکتريكی:
شاسی، موتورها، منبع تغذيه، ...

·  حسگرها (برای شناسايي محيط):
دورين ها، سنسورهای sonar، سنسورهای ultrasound، ...
·  عملکردها (برای انجام اعمال لازم)
بازوی روبات، چرخها، پاها، ...
·  قسمت تصميم گيري (برنامه ای برای تعيين اعمال لازم):
حرکت در يك جهت خاص، دوری از موانع، برداشتن اجسام، ...
·  قسمت کنترل (برای راه اندازی و بررسی حرکات روبات):
نيروها و گشتاورهای موتورها برای سرعت مورد نظر، جهت مورد نظر، کنترل مسير، ...

تاريخچه روباتيك:
- حدود سال 1250 م: بیشاپ آلبرتوس ماگنوس (Bishop Albertus Magnus) ضیافتی ترتیب داد که       درآن، میزبانان آهنی از مهمانان پذیرایی می کردند. با دیدن این روبات، سنت توماس آکویناس (Thomas Aquinas) برآشفته شد، میزبان آهنی را تکه تکه کرد و بیشاب را ساحر و جادوگر خواند.
- سال 1640 م: دکارت ماشين خودکاری به صورت يك خانم ساخت و آن را Ma fille Francine " می نامید.
این ماشين که دکارت را در يك سفر دریایی همراهی می کرد، توسط کاپیتان کشتی به آب پرتاب شد چرا که وی تصور می کرد این موجود ساخته شیطان است.
- سال 1738 م: ژاک دواکانسن (Jacques de Vaucanson) يك اردک مکانيكی  ساخت که از بیش از 4000 قطعه تشکیل شده بود.
این اردک می توانست از خود صدا تولید کند، شنا کند، آب بنوشد، دانه بخورد و آن را هضم و سپس دفع کند. امروزه در مورد محل نگهداری این اردک اطلاعی در دست نیست.
- سال 1805 م: عروسکی توسط میلاردت (Maillardet) ساخته شد که می توانست به زبان انگلیسی و فرانسوی بنویسد و مناظری را نقاشی کند.
- سال 1923 م: کارل چاپک (Karel Capek) برای اولین بار از کلمه روبات (robot) در نمایشنامه خود به عنوان آدم مصنوعی استفاده کرد. کلمه روبات از کلمه چک robota گرفته شده است که به معنی برده و کارگر مزدور است. موضوع نمایشنامه چاپک، کنترل انسانها توسط روباتها بود، ولی او هرگونه امکان جایگزینی انسان با روبات و یا اینکه روباتها از احساس برخوردار شوند، عاشق شوند، یا تنفر پیدا کنند را رد می کرد.
- سال 1940 م: شرکت وستینگهاوس (Westinghouse Co.) سگی به نام اسپارکو (Sparko) ساخت که هم از قطعات مکانيكی و هم الکتريكی در ساخب آن استفاده شده بود. این اولین باری بود که از قطعات الکتريكی نیز همراه با قطعات مکانيكی استفاده می شد.
- سال 1942 م: کلمه روباتيك (robatics) اولین بار توسط ایزاک آسیموف در يك داستان کوتاه ارائه شد. ایزاک آسیموف (1920-1992) نویسنده کتابهای توصیفی درباره علوم و داستانهای علمی تخیلی است.
- دهه 1950 م: تکنولوژی کامپیوتر پیشرفت کرد و صنعت کنترل متحول شد. سؤلاتی مطرح شدند. مثلاً: آیا

کامپیوتر يك روبات غیر متحرک است؟
- سال 1954 م: عصر روبات ها با ارائه اولین روبات آدم نما توسط جرج دوول (George Devol) شروع شد.
امروزه، 90% روباتها، روباتهای صنعتی هستند، یعنی روباتهایی که در کارخانه ها، آزمایشگاهها، انبارها، نیروگاهها، بیمارستانها، و بخشهای مشابه به کارگرفته می شوند.
در سالهای قبل، اکثر روباتهای صنعتی در کارخانه های خودروسازی به کارگرفته می شدند، ولی امروزه تنها حدود نیمی از روباتهای موجود در دنیا در کارخانه های خودروسازی به کار گرفته می شوند.
مصارف روباتها در همه ابعاد زندگی انسان به سرعت در حال گسترش است تا کارهای سخت و خطرناک را به جای انسان انجام دهند.  

برای مثال امروزه برای بررسی وضعیت داخلی رآکتورها از روبات استفاده می شود تا تشعشعات رادیواکتیو به انسانها صدمه نزند.

- سال 1956 م: پس از توسعه فعالیتهای تکنولوژی یک که بعد از جنگ جهانی دوم، یک ملاقات تاریخی بین جورج سی.دوول(George C.Devol) مخترع و کارآفرین صاحب نام، و ژوزف اف.انگلبرگر (Joseph F.Engelberger) که یک مهندس با سابقه بود، صورت گرفت. در این ملاقات آنها به بحث در مورد داستان آسیموف پرداختند. ایشان سپس به موفقیتهای اساسی در تولید روباتها دست یافتند و با تأسیس شرکتهای تجاری، به تولید روبات مشغول شدند. انگلبرگر شرکت Unimate برگرفته از Universal Automation را برای تولید روبات پایه گذاری کرد. نخستین روباتهای این شرکت در کارخانه جنرال موتورز (General Motors) برای انجام کارهای دشوار در خودروسازی به کار گرفته شد. انگلبرگر را "پدر روباتیک" نامیده اند.
- دهه 1960 م: روباتهای صنعتی زیادی ساخته شدند. انجمن صنایع روباتیک این تعریف را برای روبات صنعتی ارائه کرد:
"روبات صنعتی یک وسیلة چند کاره و با قابلیت برنامه ریزی چند باره است که برای جابجایی قطعات، مواد، ابزارها یا وسایل خاص بوسیلة حرکات برنامه ریزی شده، برای انجام کارهای متنوع استفاده می شود."
- سال 1962 م: شرکت خودروسازی جنرال موتورز نخستین روبات Unimate را در خط مونتاژ خود به کار گرفت.
- سال 1967 م: رالف موزر (Ralph Moser) از شرکت جنرال الکتریک (General Electeric) نخستین روبات چهارپا را اختراع کرد.
- سال 1983 م: شرکت Odetics یک روبات شش پا ارائه کرد که می توانست از موانع عبور کند و بارهای سنگینی را نیز با خود حمل کند.
- سال 1985 م: نخستین روباتی که به تنهایی توانایی راه رفتن داشت در دانشگاه ایالتی اهایو (Ohio State Uneversity) ساخته شد.
 سال 1996 م: شرکت ژاپنی هندا (Honda) نخستین روبات انسان نما را ارائه کرد که با دو دست و دو پا طوری طراحی شده بود که می توانست راه برود، از پله بالا برود، روی صندلی بنشیند و بلند شود و بارهایی به وزن 5 کیلوگرم را حمل کند
روباتها روز به روز هوشمندتر می شوند تا هرچه بیشتر در کارهای سخت و پر خطر به یاری انسانها بیایند.  

                        

                              قانون روباتیک مطرح شده توسط آسیموف:

.1- روبات ها نباید هیچگاه به انسانها صدمه بزنند.
.2- روباتهاباید دستورات انسانها را بدون سرپیجی از قانون اوّل اجرا کنند.
.3- روباتها باید بدون نقض قانون اوّل و دوم از خود محافظت کنند.
مزایای روباتها:
.1-  روباتیک و اتوماسیون در بسیاری از موارد می توانند ایمنی، میزان تولید، بهره و کیفیت محصولات را افزایش دهند.
.2-  روباتها می توانند در موقعیت های خطرناک کار کنند و با این کار جان هزاران انسان را نجات دهند.
.3-  روباتها به راحتی محیط اطراف خود توجه ندارند و نیازهای انسانی برای آنها مفهومی ندارد. روباتها هیچگاه خسته نمی شوند.
.4-  دقت روباتها خیلی بیشتر از انسانها است آنها در حد میلی یا حتی میکرو اینچ دقت دارند.
.5-  روباتها می توانند در یک لحظه چند کار را با هم انجام دهند ولی انسانها در یک لحظه تنها یک کار انجام می دهند.
معایب روباتها:

.1-  روباتها در موقعیتهای اضطراری توانایی پاسخگویی مناسب ندارند که این مطلب می تواند بسیار خطرناک باشد
.2-  روباتها هزینه بر هستند.
.3-  قابلیت های محدود دارند یعنی فقط کاری که برای آن ساخته شده اند را انجام می دهند