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NEURAL NETWORKS FOR MULTIUSER DETECTION IN CODE-DIVISION MULTIPLE-ACCESS COMMUNICATIONS

IEEE TRANSACTIONS ON COMMUNICATIONS 1992年第7期40卷 1212-1222页

作者： AAZHANG, B PARIS, BP ORSAK, GC Department of Electrical and Computer Engineering Rice University Houston TX USA Public Communication Networks Siemens AG Munich Germany Department of Electrical and Computer Engineering Rice University USA Department of Electrical and Computer Engineering George Mason University Fairfax VA USA

Artificial neural networks are employed for demodulation of spread-spectrum signals in a multiple-access environment. This paper is motivated in large part by the fact that, in a multiuser system, the conventional (matched filter) receiver suffers sever performance degradation as the relative powers of the interfering signals become large (the "near-far" problem). Furthermore, in many cases the optimum receiver, which alleviates the near-far problem, is too complex to be of practical use. Two simple structures employing multilayer perceptrons are proposed for demodulation of spread-spectrum signals in both synchronous and asynchronous Gaussian channels. The optimum receiver is used to benchmark the performance of the proposed receiver;in particular, it is proven to be instrumental in identifying the decision regions for the neural networks. The neural networks are trained for the demodulation of signals via back-propagation type algorithms. In particular, a modified back-propagation algorithm is introduced for single-user and multiuser detection with near-optimum performance that could have applications in other classification and pattern recognition problems. A comparative performance analysis of the three receivers, optimum, conventional and the one employing neural networks, is carried out via Monte Carlo simulations. An importance sampling technique is employed to reduce the number of simulations necessary to evaluate the performance of these receivers in a multiuser environment. In all examples considered, the proposed neural net receiver significantly outperforms the conventional receiver.

关键词： Neural networks Multiuser detection Demodulation Backpropagation algorithms Multilayer perceptrons Spread spectrum communication Gaussian channels Instruments Pattern recognition Performance analysis

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Ethnic differences in the burden of caregiving

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American Journal of Alzheimer's Disease and Other Dementias 1992年第5期7卷 4-7页

作者： Macera, Caroline A. Cornman, Carol Eaker, Elaine D. Goslar, Pamela W. Deandrade, Susan J. Williamson, Jane S. Jannarone, Robert J. School of Public Health University of South Carolina Columbia South Carolina United States Epidemiology Program Office Centers for Disease Control Atlanta Georgia United States Department of Computer and Electrical Engineering University of South Carolina Columbia South Carolina United States

Family caregivers of dementia patients experience varying levels of burden (or stress) associated with care giving tasks. Although this burden may lead to negative health effects for caregivers, very few studies have focused on ethnic differences in the correlates of perceived burden. In a pilot study, we examined correlates of perceived burden associated with providing care for a family member with dementia among African-American (n=20) and white (n=62) caregivers. In this limited sample, we found that mean burden scores were increased among whites if they were the spouse of the patient, and among African-Americans if annual family income was in excess of $20,000. We found no mean burden score differences for either group by past use of a variety of services. Although these results are preliminary, this ongoing study has the potential to provide needed information on sources and correlates of perceived burden among rural African-American and white caregivers. © 1992, Sage publications. All rights reserved.

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DIRECTIONS FOR QUALITATIVE REASONING

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Computational Intelligence 1992年第2期8卷

作者： Jayant Are. Kalagnanam Herbert A. Simon Department of Engineering and Public Policy Department of Psychology and Computer Science Carnegie Mellon University Pittsburgh PA 15213 U.S.A.

Sacks & Doyle provide an excellent overview of the fundamental limitations of the SPQR representations for reasoning about the qualitative properties of dynamic systems. We take this opportunity to outline some new directions for qualitative reasoning. In this paper, we provide a rigorous mathematical characterization for the term “qualitative property” in the context of static and dynamic systems. Based on these characterizations, we show that interval representations are well suited for reasoning about the qualitative properties of static systems such as qualitative comparative statics and qualitative stability. Moreover, we also show that symbolic computations help in the derivation of useful global properties of dynamic systems which can be used to guide numerical sampling of differential equations. The integration of symbolic and numeric methods provides a powerful approach for automating the qualitative analysis of differential equations.

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The greenhouse effect: Damages, costs and abatement

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Environmental & Resource Economics 1991年第3期1卷 237-270页

作者： Ayres, Robert U. Walter, Jörg Department of Engineering and Public Policy Pittsburgh PA United States Department of Computer Science University of Illinois Champagne-Urbana IL United States

The buildup of so-called "greenhouse gases" in the atmosphere - CO2 in particular-appears to be having an adverse impact on the global climate. This paper briefly reviews current expectations with regard to ... 详细信息

The buildup of so-called "greenhouse gases" in the atmosphere - CO₂ in particular-appears to be having an adverse impact on the global climate. This paper briefly reviews current expectations with regard to physical and biological effects, their potential costs to society, and likely costs of abatement. For a "worst case" scenario it is impossible to assess, in economic terms, the full range of possible non-linear synergistic effects. In the "most favorable" (although not necessarily "likely") case (of slow-paced climate change), however, it seems likely that the impacts are within the "affordable" range, at least in the industrialized countries of the world. In the "third world" the notion of affordability is of doubtful relevance, making the problem of quantitative evaluation almost impossible. We tentatively assess the lower limit of quantifiable climate-induced damages at $30 to $35 per ton of "CO₂ equivalent", worldwide, with the major damages being concentrated in regions most adversely affected by sea-level rise. The non-quantifiable environmental damages are also significant and should by no means be disregarded. The costs and benefits of (1) reducing CFC use and (2) reducing fossil fuel consumption, as a means of abatement, are considered in some detail. This strategy has remarkably high indirect benefits in terms of reduced air pollution damage and even direct cost savings to consumers. The indirect benefits of reduced air pollution and its associated health and environmental effects from fossil-fuel combustion in the industrialized countries range from $20 to $60 per ton of CO₂ eliminated. In addition, there is good evidence that modest (e.g. 25%) reductions in CO₂ emissions may be achievable by the U.S. (and, by implication, for other countries) by a combination of increased energy efficiency and restructuring that would permit simultaneous direct economic benefits (savings) to energy consumers of the order of

关键词： Atmosphere benefits carbon climate conservation damages emissions energy greenhouse policy

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Responses to ‘computationalism‘

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Social Epistemology 1990年第2期4卷 155-199页

作者： Balogh, Imre Beakley, Brian Churchland, Paul Gorman, Michael Harnad, Stevan Mertz, David Pattee, H.H. Ramsey, William Ringen, John Schwarz, Georg Slator, Brian Strudler, Alan Wallis, Charles Computing Research Laboratory New Mexico State University Las Cruces NM 88001 United States Department of Philosophy State University of New York Stony Brook NY 11794 United States Department of Philosophy University of California at San Diego La jolla CA 92093 United States Humanities Division University of Virginia Charlottesville VA 22903 United States Department of Psychology Princeton University Princeton NJ 08544 United States Department of Philosophy University of Massachusetts Amherst MA 01003 United States T. J. Watson School of Engineering State University of New York Binghamton NY 13901 United States Department of Philosophy University of Notre Dame Notre Dame IN 46556 United States Department of Philosophy Indiana University at South Bend South Bend IN 47405 United States Department of Philosophy University of California at San Diego La Jolla CA 92093 United States Department of Computer Science North Dakota State University Fargo ND 58105-5075 United States Center for Philosophy and Public Policy University of Maryland College Park MD 20742 United States Department of Philosophy University of Minnesota Minneapolis MN 55455 United States

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An expert system for implementing communication protocols

An expert system for implementing communication protocols

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IEEE International Conference on Communications (ICC)

作者： S. Ram T.-N. Wang Department of Management Information Systems College of Business and Public Administration University of Arizona Tucson Tucson AZ USA Department of Electrical and Computer Engineering University of Arizona Tucson Tucson AZ USA

The Protocol Machine Expert System (PMES) for implementing communication protocols is described. The objective is to develop and implement a general model for communication protocols based on the principles of finite-state machines. The authors have designed an inference method and knowledge representation method, based on semantic networks, for implementing this model. A semantic net consists of points called nodes connected by links called arcs that describe the relations between the nodes. The authors have added interactive capability and automatic error detection to check for invalid external events and other types of errors in their model. They have illustrated the use of PMES by applying it to the TCP (transmission control protocol) of the US Department of Defense Model for Communication.< >

关键词： Expert systems Transport protocols Automata Communication system control Engines computer network reliability Telecommunication network reliability Formal specifications Management information systems Educational institutions

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Design Considerations for the Structural Optimization of a Single-Mode Fiber

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Journal of Lightwave Technology 1983年第2期1卷 363-369页

作者： Kitayama, Ken-Ichi Kato, Yasuyuki Ohashi, Masaharu Ishida, Yukinori Uchida, Naoya Department of Electrical Engineering and Computer Science and Electronics Research Laboratory University of California Berkeley CA 94720 United States Ibaraki Electrical Communication Laboratory Nippon Telegraph and Telephone Public Corporation Ibaraki 319-11 Japan Ibaraki Electrical Communication Laboratory Nippon Telegraph and Telephone Public Corporation Ibaraki 319-11 Japan

Design considerations are made for the structural optimization of single-mode fibers used in high-bit-rate and long-haul transmission systems in the long-wavelength region. As the basic fiber parameters, a combination of the spot size W0 and the effective cutoff wavelength λce is newly chosen, because the combination is found to suitably describe various actual index profiles which deviate from an ideal step-index profile. A procedure to specify the usable range of W0 and λce is established, whereby the overall transmission-line loss in one repeater section is calculated using simple expressions for fiber intrinsic loss, excess loss in the cabling process, and splice lose, etc. The optimum values for a 400 Mbit/s transmission system operating at 1.3 μm with a repeater spacing of 20 km are obtained as W0 = 5.0 ± 0.5 μm and 1.1 μm ≼ λce ≼ 1.28 μm, taking into consideration the additional requirement for the possible use at λ = 1.55 μm. © 1983 IEEE

关键词： Design optimization Propagation losses Optical fiber cables Optical fiber communication Repeaters Optical fiber losses Laboratories Transmission lines Optical refraction Telegraphy

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Book reviews

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Canadian electrical engineering Journal 1981年第2期6卷 32-36页

作者： S. Pasupathy V. C. Hamacher Jan C. Willems M. P. Bhavaraju M. N. S. Swamy Department of Electrical Engineering University of Toronto Departments of Electrical Engineering and Computer Science University of Toronto Mathematics Institute The Netherlands System Planning Public Service Electric & Gas Company Newark New Jersey Engineering and Computer Science Concordia University

This book presents an extremely readable and comprehensive overview of the general engineering considerations necessary for the design of telecommunciation networks. The author's thirtyfive years of experience in the telecommunication industry clearly shows in the easy, but informative and authoritative, way in which he addresses the various complex issues involved in the design of practical networks; this is especially noticable in the coverage on the interaction of the various disciplines involved, such as transmission and switching, in the planning, engineering and expansion of telecommunication systems. The text is written in a very easy-to-read and free-flowing style, avoiding mathematics and complex details; the result is nearly 500 pages of a vast amount of important material, culled from a large body of engineering texts and papers, served to us in a palatable and easily-digestible form.

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BANQUET ADDRESS - TECHNOLOGY IS FUN, ITS THE OTHER THINGS

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NAVAL ENGINEERS JOURNAL 1981年第3期93卷 57-59页

作者： FROSCH, RA President American Association of Engineering Societies Inc Dr. Robert A. Frosch born in New York City on 22 May 1928 attended Columbia University from which he received his B.A. degree in 1947 his M.A. degree in 1949 and his Ph.D. degree in 1952 all in the field of Theoretical Physics. While completing his studies for his doctorate he joined Columbia's Hudson Laboratories in 1951 and worked on naval research projects as a Research Scientist until 1958 when he became the Director Hudson Laboratories a post he held until 1963. From 1965 to 1966 he was Deputy Director Advanced Research Projects Agency (APRA) Department of Defense (DOD) having first joined ARPA in 1963 as the Director for Nuclear Test Detection the position he held until 1965. Since 1969 he also has served as the DOD member of the Committee for Policy Review National Council of Marine Resources and Engineering Development and in 1967 and 1970 as the Chairman of the U.S. Delegation to the Intergovernmental Oceanographic Commission meetings at UNESCO in Paris. In addition he was the Assistant Secretary of the Navy for Research & Development from 1966 to 1973 Assistant Executive Director of the United Nations Environment Program with the rank of Assistant Secretary General of the United Nations from 1973 to 1975 and Assistant Director for Applied Oceanography at the Woods Hole Oceanographic Institution from 1975 until mid-1977. In June 1977 he became the Administrator of the National Aeronautics and Space Agency (NASA) the position he held prior to joining the American Association of Engineering Societies (AAES) Incorporated. On 20 January 1981 he was elected to his present post as President AAES. Additionally he was the Sea Grant Lecturer for the Massachusetts Institute of Technology in 1974 and currently is a National Lecturer for Sigma Xi. During his distinguished career Dr. Frosch has been the recipient of numerous awards among which are the Arthur S. Flemming Award in 1966 the Navy Distinguished Public Service Award in 1

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SOME CONSIDERATIONS ON FUZZY CONDITIONAL INFERENCE

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FUZZY SETS AND SYSTEMS 1980年第3期4卷 243-273页

作者： FUKAMI, S MIZUMOTO, M TANAKA, K Yokosuka Electrical Communication Laboratory Nippon Telegraph and Telephone Public Corporation Yokosuka Kanagawa 238-03 Japan Department of Management Engineering Faculty of Engineering Osaka Electro-Communication University Neyagawa Osaka 572 Japan Department of Information and Computer Sciences Faculty of Engineering Science Osaka University Toyonaka Osaka 560 Japan

In much of human reasoning, the form of reasoning is approximate rather than exact as in ‘A red apple is ripe and this apple is more or less red. Then this apple is more or less ripe.’ L.A. Zadeh and E.H. Mamdani suggested methods for such a fuzzy reasoning as an application of fuzzy set theory. The method involves an inference rule and a conditional proposition which contains fuzzy concepts. In this paper we point out that the consequence inferred by their methods does not always fit our intuitions and we suggest the improved methods which fit our intuitions under several criteria.

关键词： Compositional rule of inference Fuzzy conditional inference Implication

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