Mechanical engineering, an engineering discipline born of the needs of the industrial revolution, is once again asked to do its substantial share in the call for industrial renewal. The general call is urgent as we face profound is­ sues of productivity and competitiveness that require engineering solutions, among others. The Mechanical Engineering Series features graduate texts and research monographs intended to address the need for information in contemporary areas of mechanical engineering. The series is conceived as a comprehensive one that will cover a broad range of concentrations important to mechanical engineering graduate ed­ ucation and research. We are fortunate to have a distinguished roster of consulting editors, each an expert in one of the areas of concentration.

This book is the third in a series of four devoted to POWER ELECTRONIC CONVERTERS: The first of these concerns AC to DC conversion. The second concerns AC to AC conversion. This volume examines DC to DC conversion. The fourth is devoted to DC to AC conversion. Converters which carry out the DC-DC conversion operate by chopping the input voltage or current: they are called choppers or switch-mode power converters. Their operating frequency is not imposed by either the input or the output, both of which are at zero frequency. A frequency which is much greater than that of the industrial network can be chosen, provided that suitable configurations and semiconductor devices are used. This is the first difference compared to the rectifiers and AC-AC converters, analyzed in the previous volumes and which often operate at the industrial network frequency. The second difference concerns the commutation mode. Choppers operate in forced commutation. The beginning of an operating phase does not auto­ matically turn off the semiconductor devices which were conducting during the previous phase and which have to be brought to the blocking state. This turn-off must be carried out autonomously. These two differences - the higher frequency of commutations and, espe­ cially, the different mode of commutation -justify the first two chapters in this work: - Chapter 1 examines general notions concerning converters, supplies and loads, and more especially, how they can be characterized with regard to commutations.

This is the final volume in a four-volume series concerning POWER ELEC­ TRONIC CONVERTERS. The first volume studies AC/DC conversion, the second studies AC/ AC conversion, and the third DC/DC conversion. This final volume deals with DC/AC conversion, i.e. with inverters. At the output of an inverter fed by a DC voltage supply, this voltage is alternatively found with one polarity and then with the other; in other words, an AC voltage made up of square pulses is obtained. Filtering must be carried out if, as is normally the case, a virtually sinusoidal voltage is required: this problem of filtering underlies the entire study of inverters. In some applications, the load itself provides the filtering. In others, a filter is installed between the inverter and the load; however, as it will be shown in Chap. 2, in cases where the filtered voltage is at industrial network frequency and comprises only a single square-wave pulse per half-cycle, the filter becomes bulky and costly, and the results obtained are poor. Filtering problems explain the considerable development of inverters during the last years: - Firstly there is increasing use of pulse width modulation: each half-cycle is cut up into several pulses of suitable widths; this greatly simplifies filtering. The use of a chopping frequency which is much greater than the frequency of the fundamental components of the inverter output voltage and current has only been made possible by progress in the field of semiconductor devices.

This volume presents an exhaustive treatment of computation and algorithms for finite fields.
Topics covered include polynomial factorization, finding irreducible and primitive polynomials, distribution of these primitive polynomials and of primitive points on elliptic curves, constructing bases of various types, and new applications of finite fields to other araes of mathematics. For completeness, also included are two special chapters on some recent advances and applications of the theory of congruences (optimal coefficients, congruential pseudo-random number generators, modular arithmetic etc.), and computational number theory (primality testing, factoring integers, computing in algebraic number theory, etc.) The problems considered here have many applications in computer science, coding theory, cryptography, number theory and discrete mathematics.
The level of discussion presuppose only a knowledge of the basic facts on finite fields, and the book can be recommended as supplementary graduate text.
For researchers and students interested in computational and algorithmic problems in finite fields.

The majority of the chapters in this volume represent a series of lectures. that were given at a workshop on quantum transport in ultrasmall electron devices, held at San Miniato, Italy, in March 1987. These have, of course, been extended and updated during the period that has elapsed since the workshop was held, and have been supplemented with additional chapters devoted to the tunneling process in semiconductor quantum-well structures. The aim of this work is to review and present the current understanding in nonequilibrium quantum transport appropriate to semiconductors. Gen­ erally, the field of interest can be categorized as that appropriate to inhomogeneous transport in strong applied fields. These fields are most likely to be strongly varying in both space and time. Most of the literature on quantum transport in semiconductors (or in metallic systems, for that matter) is restricted to the equilibrium approach, in which spectral densities are maintained as semiclassical energy­ conserving delta functions, or perhaps incorporating some form of collision broadening through a Lorentzian shape, and the distribution functions are kept in the equilibrium Fermi-Dirac form. The most familiar field of nonequilibrium transport, at least for the semiconductor world, is that of hot carriers in semiconductors.

The NATO Advanced Study on Waveguide Optoelectronics was held at the Kelvin Conference Centre in Glasgow, Scotland, between 30 July and 10 August 1990. In aliSO students and 15 lecturers attended the ASI. The successof the meeting was due not only to the high quality of the presentations but also to the enthusiasm ofall the participants and their willingness to take part in the discussion and poster sessions. 1990 was also the year in which Glasgow was the European City of Culture. This resulted in interesting diversions during the middle weekend of the school and also made the meeting probably the first NATO ASI to share accommodation with the Bolshoi Opera and Ballet who gave memorable performances as partof the City's celebrations. This volume is, however, intended to be more than merely a record of presentations at the NATO meeting. The authors have written their material so as to be approachable by a first­ degree graduate with some background in optoelectronics. The principal materials considered are the III-V semiconductors, lithium niobate and silica. Recent developments towards optoelectronic integration in semiconductors, developments in devices fabricated in doped silica and doped lithium niobate, and developments in all-optical switching networks are highlighted. The role of reduced dimensional structures is examined in some detail.

Solar Energy Technology deals with all aspects of solar energy systems. The fundamentals of predicting avail- ability; economic appraisal strategies; specific collector sub-systems, including a proven analytical procedure for predicting performance; and analyses of solar energy systems from dryers to greenhouses, passive solar buildings to water pumps, are covered in depth. Researchers and technologists need to have an insight into the challenges implementation entails, and this book presents practical constraints, operational considerations, and the latest research results. The book should be of great interest to students as well as professionals undertaking feasibility studies, development and implementation, technical assistance, and training assignments. Political action and pressure groups will also find the text useful for developing energy policies.

This book emerged from lecture notes of a course taught in the second year to students of Computer Science at the Federal Institute of Tech­ nology, Zurich. The topic of hardware design plays a relatively minor role in Compu­ ter Science curricula at many universities. Most courses concentrate on the various aspects of theory, software, and of information sys­ tems. Students therefore obtain few opportunities to deal with con­ crete engineering problems and physical devices. We consider this as rather unfortunate, particularly for technical universities. As a result, we observe a growing gap between interest in and understanding of design issues involving not only software but also hardware and inter­ faces. This is regrettable at a time when new and advanced solutions to many problems are often crucially influenced by recent hardware de­ velopments, at a time when the engineer needs to be competent in both software and hardware issues in order to fmd an optimally inte­ grated, competitive solution. It turns out that the hesitation of many students in Computer Science to take an active interest in hardware - his or her daily tool! - does not only stem from a preference of "clean", abstract concepts with a corre­ sponding distaste for dealing with concrete components, construction techniques, and the "dirty" realities inflicted by nature, but also stems from the lack of a bridge between the two realms.

Neural Networks presents concepts of neural-network models and techniques of parallel distributed processing in a three-step approach: - A brief overview of the neural structure of the brain and the history of neural-network modeling introduces to associative memory, preceptrons, feature-sensitive networks, learning strategies, and practical applications. - The second part covers subjects like statistical physics of spin glasses, the mean-field theory of the Hopfield model, and the "space of interactions" approach to the storage capacity of neural networks. - The final part discusses nine programs with practical demonstrations of neural-network models. The software and source code in C are on a 3 1/2" MS-DOS diskette can be run with Microsoft, Borland, Turbo-C, or compatible compilers.