IDES have been realized in modulation doped AIGaAs/GaAs heterostructures by fabricating split-gate configurations and ultrafine etched structures with optimized lithography and etching techniques. With deep-mesa etching technique it is possible to prepare single and multi-layered quantum wire systems. From dc magnetotransport typical confinement energies of 2me V are determined. The FIR response is strongly governed by collective effects which give the resonances the character of local plasmon modes. In multi-layered quantum wire structures a splitting of the plasmon dispersion in longitudinal and acoustical type of layer-coupled local plasmon modes is observed. ACKNOWLEDGEMENT We would like to thank K Ploog for providing us with excellent samples and acknowledge financial support from the Bundesministerium fur Forschung und Tech- nologie, Bonn. REFERENCES 1K-F. Berggren, T. J. Thornton, D. J. Newson, and M. Pepper, Phys. Rev. Lett. 57, 1769 (1986) 2H. van Houten, B. J. van Wees, M. G. J. Heijman, J. P. Andre, D. Andrews, and G. J. Davies, Appl. Phys. Lett. 49, 1781 (1986) 3J. Cibert, P. M. Petroff, G. J. Dolan, S. J. Pearton, A. C. Gossard, and J. H. English, Appl. Phys. Lett. 49, 1275 (1986) 4T. P. Smith, III. , H. Arnot, J. M. Hong, C. M. Knoedler, S. E. Laux, and H. Schmid, Phys. Rev. Lett. 59, 2802 (1987) 5M. L. Roukes, A. Scherer, S. J. Allen, Jr. , H. G. Craighead, R. M. Ruthen, E. D. Beebe, and J. P. Harbison, Phys. Rev. Lett.

During the 1970s there was a rapid increase in interest in metacognition and metalinguistics. The impetus came from linguistics, psychology, and psycho linguistics. But with rather unusual rapidity the work from these scientific dis ciplines was taken over in education. This new direction in these various areas of academic study was taken simultaneously by several different investigators. Although they had varying emphases, their work sometimes appears to be over lapping; despite this, it has been rather difficult to find a consensus. This is reflected in the varying terminology used by these independent investigators "linguistic awareness," "metacognition," "metalinguistic ability," "task aware ness," "lexical awareness," and so on. For educators these developments presented a glittering array of new ideas that promised to throw light on children's thinking processes in learning how to read. Many reading researchers and graduate students have perceived this as a new frontier for the development of theory and research. However, the variety of independent theoretical approaches and their accompanying terminologies has been somewhat confusing."

Mobile computing is one of the biggest issues of computer technology, science and industry today. This book looks at the requirements of developing mobile computing systems and the challenges they pose to computer designers. It examines the requirements of mobile computing hardware, infrastructure and communications services. Information security and the data protection aspects of design are considered, together with telecommunications facilities for linking up to the worldwide computer infrastructure. The book also considers the mobility of computer users versus the portability of the equipment. The text also examines current applications of mobile computing in the public sector and future innovative applications.

Open Distributed Processing contains the selected proceedings of the Third International Conference on Open Distributed Systems, organized by the International Federation for Information Processing and held in Brisbane, Australia, in February 1995. The book deals with the interconnectivity problems that advanced computer networking raises, providing those working in the area with the most recent research, including security and management issues.

This introduction to random variables and signals provides engineering students with the analytical and computational tools for processing random signals using linear systems. It presents the underlying theory as well as examples and applications using computational aids throughout, in particular, computer-based symbolic computation programs are used for performing the analytical manipulations and the numerical calculations. Intended for a one-semester course for advanced undergraduate or beginning graduate students, the book covers such topics as: set theory and probability; random variables, distributions, and processes; deterministic signals, spectral properties, and transformations; and filtering, and detection theory. The large number of worked examples together with the programming aids make the book eminently suited for self study as well as classroom use.

How to produce images with sound has intrigued engineers and scientists for many years. Bats, whales and dolphins can easily get good mental images with acoustical energy, but humans have little natural ability for obtaining such images. The history of engineering and science, however, is an impressive demonstration that technological solutions can compensate, and then some, for deficiencies of nature in humans. Thus with the proper technology, we too can "see" with sound. Many methods involv ing ultrasonic energy can be employed to enable us to do so. Few of these methods are at all reminiscent of the acoustic systems employed by animals. Pulse-echo, phase-amplitude and amplitude-mapping approaches constitute the conceptual bases for three fundamentally different types of acoustic imaging systems and can be used for categorizing the systems. However, by now systems exist that combine the approaches in such sophisticated ways as to make an unambiguous categorization of some of the more complicated systems difficult or impossible. Among the instruments so far pro duced are mechanically-scanning focused instruments, chirped pulse-echo instruments, and instruments involving holography, tomography, parametric excitation, phase conju gation, neural networks, random phase transduction, finite element methods, Doppler frequency shifting, pseudo inversion, Bragg diffraction and reflection, and a host of other principles. The fifty-five chapters in this volume are selected from papers presented at the Eighteenth International Symposium on Acoustical Imaging which was held in Santa Barbara, California on September 18 - 20, 1989.

The need for a general collection of electroacoustical reference and design data in graphical form has been felt by acousticians and engineers for some time. This type of data can otherwise only be found in a collection of handbooks. Therefore, it is the author's intention that this book serve as a single source for many electroacoustical reference and system design requirements. In form, the volume closely resembles Frank Massa's Acoustic Design Charts, a handy book dating from 1942 that has long been out of print. The basic format of Massa's book has been followed here: For each entry, graphical data are presented on the right page, while text, examples, and refer ences appear on the left page. In this manner, the user can solve a given problem without thumbing from one page to the next. All graphs and charts have been scaled for ease in data entry and reading. The book is divided into the following sections: A. General Acoustical Relationships. This section covers the behavior of sound transmis sion in reverberant and free fields, sound absorption and diffraction, and directional characteris tics of basic sound radiators. B. Loudspeakers. Loudspeakers are discussed in terms of basic relationships regarding cone excursion, sensitivity, efficiency, and directivity index, power ratings, and architectural layout. c. Microphones. The topics in this section include microphone sensitivity and noise rating, analysis of directional properties, stereo microphone array characteristics, proximity effects, and boundary conditions. D. Signal Transmission."

This monograph attempts to provide a systematic and consistent survey of the fundamentals of the theory of free, linear, isentropic oscillations in spherically symmetric, gaseous equilibrium stars, whose structure is affected neither by axial rotation, nor by the tidal action of a companion, nor by a magnetic eld. Three parts can be distinguished. The rst part, consisting of Chaps.1-8, covers the basic concepts and equations, the distinction between spheroidal and toroidal normal modes, the solution of Poisson's differential equation for the perturbation of the gravitational potential, and Hamilton's variational principle. The second part, consisting of Chaps.9-13, is devotedto the possible existenceof waves propagating in the radial direction, the origin and classi cation of normal modes, the comple- ness of the normal modes, and the relation between the local stability with respect to convection and the global stability of a star. In the third part, Chaps.14-18 c- tain asymptoticrepresentationsof normalmodes. Chapter 19 deals with slow period changes in rapidly evolving pulsating stars. The theory is developed within the framework of the Newtonian theory of gr- itation and the hydrodynamics of compressible uids. It is described in its present status, with inclusion of open questions. We give preference to the use of the adjective "isentropic" above that of the adjective "adiabatic," since, from a thermodynamic point of view, these stellar - cillations are described as reversible adiabatic processes and thus as processes that take place at constant entropy.

This book is the first in a set of forthcoming books focussed on state-of-the-art development in the VLSI Signal Processing area. It is a response to the tremendous research activities taking place in that field. These activities have been driven by two factors: the dramatic increase in demand for high speed signal processing, especially in consumer elec tronics, and the evolving microelectronic technologies. The available technology has always been one of the main factors in determining al gorithms, architectures, and design strategies to be followed. With every new technology, signal processing systems go through many changes in concepts, design methods, and implementation. The goal of this book is to introduce the reader to the main features of VLSI Signal Processing and the ongoing developments in this area. The focus of this book is on: * Current developments in Digital Signal Processing (DSP) pro cessors and architectures - several examples and case studies of existing DSP chips are discussed in Chapter 1. * Features and requirements of image and video signal processing architectures - both applications specific integrated circuits (ASICs) and programmable image processors are studied in Chapter 2. * New market areas for signal processing - especially in consumer electronics such as multimedia, teleconferencing, and movie on demand. * Impact of arithmetic circuitry on the performance of DSP pro cessors - several topics are discussed in Chapter 3 such as: number representation, arithmetic algorithms and circuits, and implementa tion.

From Coherent Tunneling to Relaxation is an impressive review of ten years of progress in our understanding of interacting tunneling systems. The dielectric and elastic response of (111) off-center impurities in alkalide halides is investigated in detail and the coherent motion of an impurity pair is discussed in view of recently observed rotary echoes. The low-temperature properties of defect crystals with an impurity concentration higher than 100 ppm are reviewed and the dipolar interaction is shown to drive the cross-over to relaxational dynamics. This comprehensive presentation of the theory is illustrated by experimental data for lithium, cyanide, and hydroxyl impurities in various host crystals. This monograph is an ideal reference book for scientists working with defect crystals and glasses

In 1945, Dr. Ernst Weber founded, and was the first Director of, the Microwave Research Institute (MRI) at Polytechnic University (at that time named the Polytechnic Institute of Brooklyn). MRI gained worldwide recognition in the 50s and 60s for its research in electromagnetic theory, antennas and radiation, network theory and microwave networks, microwave components, and devices. It was also known through its series of 24 topical symposia and the widely distributed hardbound MRI Symposium Proceedings. Rededicated as the Weber Research Institute (WRI) in 1986, the institute currently conducts research in such areas as electromagnetic propagation and antennas, ultrabroadband electromagnetics, pulse power, acoustics, gaseous electronics, plasma physics, solid-state materials, quantum electronics, electromagnetic launchers, and networks. Following MRI tradition, WRI has launched its own series of in-depth topical conferences with published proceedings. Previous conferences in this series were: Directions in Electromagnetic Wave Modeling; October 1990 Ultra-Wideband Short-Pulse Electromagnetics; October, 1992 Ultra-Wideband Short-Pulse Electromagnetics, II; October, 1994 The proceedings of these conferences were also published by Plenum Press. This volume constitutes the proceedings of the fourth WRI International Conference dealing with Guided-Wave Optoelectronics: Device Characterization, Analysis and Design. The conference was held October 26-28, 1994, at the Polytechnic University in Brooklyn, New York, in cooperation with the IEEE Lasers and Electro Optics Society, and with the Optical Society of America. Theodor Tamir Giora Griffel Henry L. Bertoni v CONTENTS INTRODUCTORY Scanning the symposium. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . T. Tamir and G. Griffel Photonics in telecommunications. . . . . . . . . . . . . . . . . . . . . . . 3 . . . . . . . . . H."

This volume presents selected papers from the IUTAM Symposium on Reynolds Number Scaling in Turbulent Flow, convened in Princeton, NJ, USA, September I1-13, 2002. The behavior ofturbulence at high Reynolds number is interesting from a fundamental point of view, in that most theories of turbulence make very specific predictions in the limit of infinite Reynolds number. From a more practical point of view, there exist many applications that involve turbulent flow where the Reynolds numbers are extremely large. For example, large vehicles such as submarines and commercial transports operate at Reynolds 9 numbers based on length ofthe order oft0 , and industrial pipe flows cover a 7 very wide range of Reynolds numbers up to 10 * Many very important applications of high Reynolds number flow pertain to atmospheric and other geophysical flows where extremely high Reynolds numbers are the rule rather than the exception, and the understanding of climate changes and the prediction of destructive weather effects hinges to some extent on our appreciation ofhigh-Reynolds number turbulence behavior. The important effects of Reynolds number on turbulence has received a great deal of recent attention. The objective of the Symposium was to bring together many of the world's experts in this area to appraise the new experimental results, discuss new scaling laws and turbulence models, and to enhance our mutual understanding of turbulence.

Digital Signal Processing for Communication Systems examines the plans for the future and the progress that has already been made, in the field of DSP and its applications to communication systems. The book pursues the progression from communication and information theory through to the implementation, evaluation and performance enhancing of practical communication systems using DSP technology. Digital Signal Processing for Communication Systems looks at various types of coding and modulation techniques, describing different applications of Turbo-Codes, BCH codes and general block codes, pulse modulations, and combined modulation and coding in order to improve the overall system performance. The book examines DSP applications in measurements performed for channel characterisation, pursues the use of DSP for design of effective channel simulators, and discusses equalization and detection of various signal formats for different channels. A number of system design issues are presented where digital signal processing is involved, reporting on the successful implementation of the system components using DSP technology, and including the problems involved with implementation of some DSP algorithms. Digital Signal Processing for Communication Systems serves as an excellent resource for professionals and researchers who deal with digital signal processing for communication systems, and may serve as a text for advanced courses on the subject.

Based on a NATO Advanced Study Institute held in 1993, this book addresses recent advances in automatic speech recognition and speech coding. The book contains contributions by many of the most outstanding researchers from the best laboratories worldwide in the field. The contributions have been grouped into five parts: on acoustic modeling; language modeling; speech processing, analysis and synthesis; speech coding; and vector quantization and neural nets. For each of these topics, some of the best-known researchers were invited to give a lecture. In addition to these lectures, the topics were complemented with discussions and presentations of the work of those attending. Altogether, the reader is given a wide perspective on recent advances in the field and will be able to see the trends for future work.

Rapid advances in Direct Numerical Simulation (DNS) and Large Eddy Simulation (LES) of turbulence provide opportunities for improved prediction of incompressible and compressible turbulent flows. The book includes five invited and thirty-eight contributed papers presented at the Second AFOSR International Conference on DNS and LES held at Rutgers - The State University of New Jersey, on June 7-9, 1999. A broad range of topics in DNS and LES are presented, including new developments in LES modeling, numerical algorithms for LES and DNS, DNS and LES of reacting flows, and DNS and LES for supersonic and hypersonic boundary layers. The book provides a extensive view of the state of the art in DNS and LES.

This book contains the lectures delivered at the NATO Advanced Research Workshop on the "Intersubband Transistions in Quantum Wells" held in Cargese, France, between the t 9 h and the 14th of September 1991. The urge for this Workshop was justified by the impressive growth of work dealing with this subject during the last two or three years. Indeed, thanks to recent progresses of epitaxial growth techniques, such as Molecular Beam Epitaxy, it is now possible to realize semiconductor layers ( e.g. GaAs) with thicknesses controlled within one atomic layer, sandwiched between insulating layers (e.g. AlGaAs). When the semiconducting layer is very thin, i.e. less than 15 nm, the energy of the carriers corresponding to their motion perpendicular to these layers is quantized, forming subbands of allowed energies. Because of the low effective masses in these semiconducting materials, the oscillator strengths corresponding to intersubband transitions are extremely large and quantum optical effects become giant in the 5 - 20 ~ range: photoionization, optical nonlinearities, ... Moreover, a great theoretical surprise is that - thanks to the robustness of the effective mass theory - these quantum wells are a real life materialization of our old text book one-dimensional quantum well ideal. Complex physical phenomena may then be investigated on a simple model system.

The symposium on Acoustical Signal Processing in the Central Auditory System which was held in Prague on September 4--7, 1996 was the third in a series organized in Prague, after the Neuronal Mechanisms of Hearing symposium in 1980 and Auditory Pathway - Structure and Function symposium in 1987. Approximately 100 scientists regis tered for the symposium and presented 82 separate papers and posters. The present vol ume contains 53 of these contributions, mostly presented at the symposium as invited review papers. Several essential changes occurred since the previous meeting in 1987. In auditory neuroscience, recently developed methods opened new horizons in the investigation of the structure and function of the central auditory pathway. Methods like c-fos tracing tech niques and monoclonal antibodies for neurotransmitters and their receptors, like the intro duction of electrophysiological recording from brain slices have made possible new insights into the function of individual neurons and their interconnections, particularly in the cochlear nuclei and in the superior olivary complex. Integrative approaches towards understanding the central auditory function started to dominate in the field. It is not easy at the present time to differentiate between purely morphological and neurochemical ap proaches; similarly electrophysiological approaches are accompanied inevitably by behav ioral and psychophysical studies. The understanding of human brain function advanced significantly during the last several years. mainly due to the contribution of magneto encephalography. positron emission tomography and functional nuclear magnetic reso nance imaging.

Inverse problems in wave propagation occur in geophysics, ocean acoustics, civil and environmental engineering, ultrasonic non-destructive testing, biomedical ultrasonics, radar, astrophysics, as well as other areas of science and technology. The papers in this volume cover these scientific and technical topics, together with fundamental mathematical investigations of the relation between waves and scatterers.

This eagerly awaited follow-up to Nonlinear Control Systems incorporates recent advances in the design of feedback laws, for the purpose of globally stabilizing nonlinear systems via state or output feedback. The author is one of the most prominent researchers in the field.

Aimed at readers who have learned the principles of harmonic analysis, this book provides a variety of perspectives on this very important classical subject. The authors have written a truly outstanding book which distinguishes itself by its excellent expository style.

The papers in this Volume were given at a two-day Conference on the subject of Optoelectronics in Medicine. The meeting was held in Florence, and promoted by the Consortium Centro di Eccellenza Optronica (C.E.O.). It represented the first of a series of Meetings on Optoelectronics that C.E.O. is organizing in order to stimulate new developments in this field and more efficient cooperation among local, national, and international research centers, industries, utilizers, etc .. Italian scientists have contributed consistently to the development of laser sources and to their applications to Medicine. A significant role has also been played by research institutes and industries in Florence. However, in this Conference, and in the Proceadings only a few Italian scientists were invited to present a lecture, thus offering the local and national communities as wide an international view as possible. Many more were present, however, as chairmen, and contributed successfully to making the discussions stimulating and fruitful. AB Editor, I had to substitute last-minute missing manuscripts with papers of my own, in order to keep the scheduled index of papers. The contributions presented at the Conference are written as extended, review like papers to provide a broad and representative coverage of the fields of light sources, optoelectronic systems for medical diagnosis, and light and laser applications to Medicine."

This volume contains the formal record of the lectures presented at the 9th Course of the International School of Radiation Damage and Protection held at the "E . Majorana" International Centre for Scientific Culture in Erice (Italy) from May 9 to May 20, 1989. This course was the last of a series of 4 courses, started in 1981, that were dedicated to the assessment of risk hazard from non-ionizing radiation. The proceedings of these courses were all published by Plenum Press with the following headings: 1) M. Grandolfo, S. M. Michaelson and A. Rindi, Eds. : "Biological Effects and Dosimetry of Nonionizing Radiation; Radiofrequency and Microwave Energy", Plenum Press, New York, NATO ASI Series A Life Sciences, Vo1. 49 (1983); 2) M. Grandolfo, S. M. Michaelson and A. Rindi, Eds. : "Biological Effects and Dosimetry of Static and ELF Electromagnetic Fields", Plenum Press, New York, E. Majorana International Science Series, Life Sciences, Vol. 19 (1985) ; 3) M. H. Repacholi, M. Grandolfo and A. Rindi, Eds. : "Ultrasound; medical applications, biological effects and hazard potential", Plenum Press, New York (1987). We hope that all these volumes together may represent a complete textbook and a reference for the students and scientists interested in the physics, biology, measurement and dosimetry, health effects and standard setting, in short, the risk assessment of that wide field of radiation presently classified as non-ionizing radiation. We are indebted to the Associa?ione Italiana Protezione dalle Radiazioni (AIRP), The Internat:l.

To place this book in perspective it is useful for the reader to be aware of the recent history of the topic of underwater sound generation at the ocean surface by natural mechanisms. A meeting in Lerici, Italy in 1987 was convened within the NATO Advanced Research Workshop series, to bring together underwater acousticians and ocean hydrodynamicists to examine various mechanisms which generate sound naturally at the ocean surface. A record of that meeting was published in the NATO scientific publication series in 1988 under the title 'Sea Surface Sound'. That meeting was successful in inspiring and co ordinating both participants and non-attending colleagues to examine some key issues which were raised during the course of presentations and discussions. The understanding among those present was that another meeting should be convened 3 years hence to report and review progress in the subject. Accordingly the second conference was convened in Cambridge in 1990, whose proceedings are presented here. This volume represents a very gratifying increase in only a 3 year interval in our understanding of a number of physical processes which generate sound at the peripheries of oceans. In fact it represents both the acceleration of singular effort as well as the development of interdisciplinary sophistication and co-operation. The enthusiasm, goodwill, and intense scientific curiosity which characterized the Lerici meeting carried through to Cambridge. The collegial atmosphere established by the participants was perfectly timed to foster another major advance in studies of ocean surface sound.

This IMA Volume in Mathematics and its Applications DYNAMICAL ISSUES IN COMBUSTION THEORY is based on the proceedings of a workshop which was an integral part of the 1989-90 IMA program on "Dynamical Systems and their Applications." The aim of this workshop was to cross-fertilize research groups working in topics of current interest in combustion dynamics and mathematical methods applicable thereto. We thank Shui-Nee Chow, Martin Golubitsky, Richard McGehee, George R. Sell, Paul Fife, Amable Liiian and Foreman Williams for organizing the meeting. We especially thank Paul Fife, Amable Liiilin and Foreman Williams for editing the proceedings. We also take this opportunity to thank those agencies whose financial support made the workshop possible: the Army Research Office, the National Science Foundation and the Office of Naval Research. Avner Friedman Willard Miller, Jr. ix PREFACE The world ofcombustion phenomena is rich in problems intriguing to the math ematical scientist. They offer challenges on several fronts: (1) modeling, which involves the elucidation of the essential features of a given phenomenon through physical insight and knowledge of experimental results, (2) devising appropriate asymptotic and computational methods, and (3) developing sound mathematical theories. Papers in the present volume, which are based on talks given at the Workshop on Dynamical Issues in Combustion Theory in November, 1989, describe how all of these challenges have been met for particular examples within a number of common combustion scenarios: reactiveshocks, low Mach number premixed reactive flow, nonpremixed phenomena, and solid propellants."

One of the great twentieth-century achievements in the mechanics of fluids was the full elucidation of the physics of shock waves and the later comprehensive development of understanding of how shock waves propagate (i) through otherwise undisturbed fluid and (ii) in interaction either with solid bodies or with independently generated fluid flows. The interaction problems (ii) were soon found to raise some very special difficulties (beginning with the common formation of "Mach stems" in shock-wave reflection) yet they also turned out to possess enormous scientific interest as well as being highly important in practical applications. For all these reasons the appearance of this book on "Interaction of Shock Waves" by one of the world's major contributors to knowledge in that field is most particularly to be welcomed. It covers all those approaches to the subject which have been found fruitful, and most satisfactorily goes into comprehensive detail about each. At last the important achievements of the leading research workers, experimental as well as theoretical, on shockwave interaction problems are brought together in a single convenient and well written volume. I warmly congratulate the author and the publisher on having performed, for the benefit of everyone interested in the mechanics of fluids, this immensely valuable service.