Software Diversity is one of the fault-tolerance means to achieve dependable systems. In this volume, some experimental systems as well as real-life applications of software diversity are presented. The history, the current state-of-the-art and future perspectives are given. Although this technique is used quite successfully in industrial applications, further research is necessary to solve some open questions. We hope to report on new results and applications in another volume of this series within some years. Acknowledgements The idea of the workshop was put forward by the chairpersons of IFIP WG lOA, J. -c. Laprie, J. F. Meyer and Y. Tohma, in January 1986, and the edi tor of this volume was asked to organize the workshop. This volume was edited with the assistance of the editors of the series, A. AviZienis, H. Kopetz and J. -C. Laprie, who also had the function of reviewers. Karlsruhe, October 1987 U. Voges, Editor Table of Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1. Introduction U. Voges 2. Railway Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 ERICSSON Safety System for Railway Control . . . . . . . . . . . . . . . . . . 11 G. Hagelin 3. Nuclear Applications . . . . . . . . . . . . . . . . . . . . . . 23 Use of Diversity in Experimental Reactor Safety Systems . 29 U. Voges The PODS Diversity Experiment . 51 P. G. Bishop 4. Flight Applications . . . . . . . . . . . . . . . . . . . . . . . . . 85 AIRBUS and ATR System Architecture and Specification. . 95 P. Traverse 5. University Research . . . . . . . . . . . . . . . . . . . 105 Tolerating Software Design Faults in a Command and Control System . . . . . . . . . . . . . . . . . . . . . . 109 T. Anderson, P. A. Barrett, D. N. Halliwell, M. R. Moulding DEDIX 87 - A Supervisory System for Design Diversity Experiments at UCLA . . . . . . . . . . . . . . . . . ."

Robustness analysis addresses the question "Is a control system sufficiently stable under all admissible operating condtions?"

Robust Control (second edition) presents parametric methods and tools for control design catering for several representative operating conditions and design specifications simultaneously, thus reducing the performance effects of parameter uncertainty in both time and frequency domains. The author s graphical parameter space methods guarantee the desired properties for all possible values of plant uncertainty. These methods also help the reader to deal with unstructured disturbances being particularly well-suited for sequences of design steps each having a few uncertain parameters. Kharitonov and edge results and tree-structured decompositions deal with simple structures with many uncertain parameters. Scalar measurement for the distance from an instability and the robustness of sampled-data control are introduced.

In addition to a general large-scale rewriting and editing of existing material, the following specific changes are featured in the second edition:

new results, in particular on frequency-domain specifications for unstructured uncertainties and disturbances, on PID controller design and on singular frequencies;

new chapters dealing with novel applications in car steering (skid and rollover avoidance and automatic steering) and flight control (flutter suppression and engine-out control for unstable aircraft in divers operating conditions);

streamlined more didactic presentation;

author-created downloadable Paradise MATLAB(r) toolbox with detailed commentary in an appendix.

Requiring only an undergraduate background in feedback control, Robust Control (second edition) keeps the mathematics of an important subject simple. The book shows mechanical and electrical engineers who have to design robust mechatronic systems how to adapt its new tools to solve their problems and its solid theoretical development based on historical foundations will be of profit to the control systematician."

This research monograph presents a systematic treatment of the theory of the propagation of transient electromagnetic fields (such as optical pulses) through dielectric media which exhibit both dispersion a.nd absorption. The work divides naturally into two parts. Part I presents a summary of the fundamental theory of the radiation and propagation of rather general electromagnetic waves in causal, linear media which are homogeneous and isotropic but which otherwise have rather general dispersive and absorbing properties. In Part II, we specialize to the propagation of a plane, transient electromagnetic field in a homogeneous dielectric. Although we have made some contributions to the fundamental theory given in Part I, most of the results of our own research appear in Part II. The purpose of the theory presented in Part II is to predict and to explain in explicit detail the dynamics of the field after it has propagated far enough through the medium to be in the mature-dispersion regime. It is the subject of a classic theory, based on the research conducted by A. Sommerfeld and L.

This is the second part of the translation of the original German text Meerestechnische Konstruktionen which was published by Springer-Verlag in 1988. The translated material is a reviewed and updated version of the German text. Wheras the first volume concentrates on general and external factors, this one focuses on factors affecting the design and analysis of offshore structures themselves. In an effort to address a wide audience the topic is presented in a general context. Therefore it introduces students and practising engineers to the field of marine technology and, at the same time, serves as a reference book for experts. Finally it gives specialists in related fields an idea of where their work on individual problems of offshore structures stands in relation to the field as a whole. Offshore Structures, Vol. 2 is based on the authors' lectures and design practice in offshore structures and their components. It assists the reader in developing practical solutions by introducing a large number of examples and reference is made to further specialised literature.

Welcome to Bavaria - Germany - to the THIRD EUROPEAN CARS/TRUCKS SIMULATION SYMPOSIUM. That Schliersee traditional workshop-type meeting is a follow-up to the first and the second symposia which took place in May 1984 and May 1989 respectively. The objective of gathering together is to cover most of the aspects of Automotive Mathematical Modelling and Simulation in theory and practice to promote the exchange of knowledge and experience between different national and international research groups in that field, taking into consideration that every seventh German employee is related to the automotive industry. This effect is also in power at least with the traditional Detroit (U.S.A.) Automotive Industries and the growing up Japanease as well. Futhermore, there is to strenghten the international contact between developers and users of modelling and simulation techniques considering the "new world order" started in 1991 with no borders between West and East affected by the Golf-War and followed up by the "open" European Community borders of 1992. VI The traditional International Conference jointly promoted by ASIMUTH - Applied Simulation Technology and some other members of the Society of Computer Simulaton created an interest to publish new projects including their results. A large number of contributed papers has been strictly examined and selected by the editorial commitee to guarantee a high international technical standard.

Separated flows and jets are closely linked in a variety of applications. They are of great importance in various fields of fluid mechanics including vehicle efficiency, technical branches concerned with gas/liquid flows, atmospheric effects on various constructions, etc. Knowledge of the physics of separated flows and jets and the development of reliable control techniques are prerequisite for future progress in the field. These aspects were in focus during the IUTAM-Symposium which was held in Novosibirsk, 9-13 July, 1990. This volume contains a selection of papers presenting recent results of theoretical and numerical studies as well as experimental work on separated flows and jets. The topics include sub- and supersonic, laminar and turbulent separation as well as organized structures in separated flows and jets. The reader will find here the state of the art and major trends for research in this field of aero-hydrodynamics.

This volume contains eighteen selected papers presented at the Second International Conference on Stochastic Structural Dynamics, which are related to new practical applications in the field. This and a companion volume, related to new theoretical developments, constitute the proceedings of the conference, and reflect the state of the art of the rapidly developing subject. The conference was held in Boca Raton, Florida during May 9-11, 1990 hosted by the Center for Applied Stochastic Research of Florida Atlantic University. A total of 20 technical sessions were organized, and attended by eighty participants from 12 countries. Special emphases of the conference were placed on two areas: applications to earthquake engineering and stochastic stability of nonlinear systems. Two sessions were dedicated to the memory of late Professor Frank Kozin, one of the founders and most active contributors to the stochastic stability theory. We are indebted to the National Center for Earthquake Engineering Research (NCEER) for financial support. Most credit belongs to each of the authors whose contributions were the very basis for the undoubted success of the conference. We are grateful to the reviewers who carefully refereed the contributions for these two volumes. Our special thanks are due to Mrs. Christine Mikulski, who carried out all the necessary secretarial tasks associated with the conference with dedication.

In recent years, increases in the amount and changes in the distribution of air traffic have been very dramatic and are continuing. The need for changes in the current air traffic systems is equally clear. While automation is generally accepted as a method of improving system safety and performance, high levels of automation in complex human-machine systems can have a negative effect on total system performance and have been identified as contributing factors in many accidents and failures. Those responsible for designing the advanced air traffic control systems to be implemented throughout the alliance during the next decade need to be aware of recent progress concerning the most effective application of automation and artificial intelligence in human-computer systems. This volume gives the proceedings of the NATO Advanced Study Institute held in Maratea, Italy, June 18-29, 1990, at which these issues were discussed.

We all know that networks are fundamental prerequisites for prosperity and production. Transportation and communication are indispensible to society, they are the elements which bind all economic systems together. Without networks and communica tion all social and economic life will be reduced to isolated phenomena. Therefore, transportation can't be assessed in the same way as other services. A smoothly functioning system of communications is also a prerequistite for social and economic integration between separate geographical regions. The modernization of the infrastructure is therefore an urgent task and a precondition for carrying out the whole of Europe's ambitious political, economic and social agenda. Since the need for communication and transportation does not know any national borders, the functioning of the networks needs to be adopted to this new economic and political geography. Congestions of cities, highways, railroads, airways and tele communications must be tackled, if precious working, commuting and leisure time is not to be wasted and heavy burdens on the environment avoided. European traffic, is for example, expected to double within the next twenty years. In certain transport modes the growth is expected to be even faster - air passenger transport doubled in 10 years and goods transport on roads doubled in 15 years."

Prices and quantities of both stock and flow variables in an economic system are decisively influenced by their spatial coordinates. Any equilibrium state also mirrors the underlying spatial structure and a tatonnement process also incorporates the spatial ramifications of consumer and producer behaviour. The recognition ofthe spatial element in the formation of a general equilibrium in a complex space-economy already dates back to early work of LOsch, Isard and Samuelson, but it reached a stage of maturity thanks to the new inroads made by T. Takayama. This book is devoted to spatial economic equilibrium (SPE) analysis and is meant to pay homage to the founding father of modern spatial economic thinking, Professor Takayama. This book witnesses his great talents in clear and rigorous economic thinking regarding an area where for decades many economists have been groping in the dark. Everybody who wants to study the phenomenon of spatial economic equilibrium will necessarily come across Takayama's work, but this necessity is at the same time a great pleasure. Studying his work means a personal scientific enrichment in a field which is still not completely explored. The present volume brings together recent contributions to spatial equilibrium analysis, written by friends and colleagues of Takayama. The structure of the book is based on four main uses of spatial equilibrium models: (i) the imbedding of spatial flows in the economic environment, related to e.g.

IUTAM-IAHR Symposium on Ice-Structure Interaction Professor Bez Tabarrok, Chairman of the Canadian National Committee (CNC) of the International Union of Theoretical and Applied Mechanics (IUTAM) invited Professor Derek Muggeridge to organize a symposium on ice structure interaction. Dr. Muggeridge readily agreed and prepared a proposal that was endorsed by the CNC and presented to the General Assembly Meeting of IUTAM for their consideration. This Assembly gave its approval and provided the local organizing committee with the names of individuals who were willing to serve on the Scientific Committee. Dr. Muggeridge became chairman of this committee and Dr. Ian Jordaan became co-chairman of this committee as well as chairman of the local organizing committee. The symposium followed the very successful previous meeting, chaired by Professor P. Tryde in Copenhagen, by ten years. Both symposia uti lized Springer-Verlag to publish their proceedings. The Faculty of En gineering and Applied Science at Memorial University of Newfoundland were particul{lXly pleased to host this prestigious symposium as it marked the twentieth anniversary of its Ocean Engineering Research Centre."

The problems of urban traffic in the industrially developed countries have been at the top of the priority list for a long time. While making a critical contribution to the economic well being of those countries, transportation systems in general and highway traffic in particular, also have detrimental effects which are evident in excessive congestion, high rates of accidents and severe pollution problems. Scientists from different disciplines have played an important role in the development and refinement of the tools needed for the planning, analysis, and control of urban traffic networks. In the past several years, there were particularly rapid advances in two areas that affect urban traffic: 1. Modeling of traffic flows in urban networks and the prediction of the resulting equilibrium conditions; 2. Technology for communication with the driver and the ability to guide him, by providing him with useful, relevant and updated information, to his desired destination.

Rail is potentially a very efficient form of transport, but must be convenient, reliable and cost-effective to compete with road and air transport. Optimal control can be used to find energy-efficient driving strategies for trains. This book describes the train control problem and shows how a solution was found at the University of South Australia. This research was used to develop the Metromiser system, which provides energy-efficient driving advice on suburban trains. Since then, this work has been modified to find practical driving strategies for long-haul trains. The authors describe the history of the problem, reviewing the basic mathematical analysis and relevant techniques of constrained optimisation. They outline the modelling and solution of the problem and finally explain how the fuel consumption can be minimised for a journey, showing the effect of speed limits and track gradients on the optimal driving strategy.

Continuing the tradition of the IUTAM Symposia TRANSSONICA, this review of the numerical simulation and physical modelling of transonic flows presents new developments in the fields of computational and experimental aerodynamics. A major topic of the symposium proceedings is the evaluation of present numerical analysis techniques with respect to transonic aerodynamics. In the field of experimental aerodynamics, the high Reynolds number effect and the interference-free testing in transonic wind tunnels are of special interest.

Since the education of aeronautical engineers at Delft University of Technology started in 1940 under the inspiring leadership of Professor H.J. van der Maas, much emphasis has been placed on the design of aircraft as part of the student's curriculum. Not only is aircraft design an optional subject for thesis work, but every aeronautical student has to carry out a preliminary airplane design in the course of his study. The main purpose of this preliminary design work is to enable the student to synthesize the knowledge ob tained separately in courses on aerodynamics, aircraft performances, stability and con trol, aircraft structures, etc. The student's exercises in preliminary design have been directed through the years by a number of staff members of the Department of Aerospace Engineering in Delft. The author of this book, Mr. E. Torenbeek, has made a large contribution to this part of the study programme for many years. Not only has he acquired vast experience in teaching airplane design at university level, but he has also been deeply involved in design-oriented re search, e.g. developing rational design methods and systematizing design information. I am very pleased that this wealth of experience, methods and data is now presented in this book."

In any rotating machinery system, the bearing has traditionally been a crit ical member of the entire system, since it is the component that permits the relative motion between the stationary and moving parts. Depending on the application, a number of different bearing types have been used, such as oil-lubricated hydrodynamic bearings, gas bearings, magnetic suspensions, rolling element bearings, etc. Hydrodynamic bearings can provide any desired load support, but they are limited in stiffness and the associated power loss may be quite large. Gas bearings are used for high-precision applications where the supported loads are relatively light, bearing power losses are very low, and the rotating speeds generally high. For super precision components where no frictional dissipation or bearing power loss can be tolerated, magnetic suspensions are employed; again, the load support requirements are very low. Rolling element bearings have been widely used for those applications that require greater bearing versatility, due to the requirements for high-load and high-stiffness characteristics, while allowing moderate power loss and permitting variable speeds. A study of the dynamic interaction of rolling elements is, therefore, the subject of this text. Texts covering the analysis and design methodology of rolling elements are very limited. Notable works include Analysis of Stresses and Deflections (Jones, 1946, Vols. I and II), Ball and Roller Bearings, Their Theory, Design and Application (Eschmann, Hasbargen, and Weigand, 1958), Ball and Roller Bearing Engineering (Palmgren, 1959, 3rd ed. ), Advanced Bearing Technology (Bisson and Anderson, 1965), and Rolling Bearing Analysis (Harris, 1966)."

"During the last two decades, research on structural optimization became increasingly concerned with two aspects: the application of general numeri- cal methods of optimization to structural design of complex real structures, and the analytical derivation of necessary and sufficient conditions for the optimality of broad classes of comparatively simple and more or less ideal- ized structures. Both kinds of research are important: the first for obvious reasons; the second, because it furnishes information that is useful in testing the validity, accuracy and convergence of numerical methods and in assess- ing the efficiency of practical designs. " (Prager and Rozvany, 1977a) The unexpected death of William Prager in March 1980 marked, in a sense, the end of an era in structural mechanics, but his legacy of ideas will re- main a source of inspiration for generations of researchers to come. Since his nominal retirement in the early seventies, Professor and Mrs. Prager lived in Savognin, an isolated alpine village and ski resort surrounded by some of Switzerland's highest mountains. It was there that the author's close as- sociation with Prager developed through annual pilgrimages from Australia and lengthy discussions which pivoted on Prager's favourite topic of struc- tural optimization. These exchanges took place in the picturesque setting of Graubunden, on the terrace of an alpine restaurant overlooking snow-capped peaks, on ski-lifts or mountain walks, or during evening meals in the cosy hotels of Savognin, Parsonz and Riom.

The great bulk of the literature on aeroelasticity is devoted to linear models. The oretical work relies heavily on linear mathematical concepts, and experimental results are commonly interpreted by assuming that the physical model behaves in a linear manner. Nevertheless, significant work has been done in nonlinear aero elasticity, and one may expect this trend to accelerate for several reasons: our ability to compute has increased at an astonishing rate; as linear concepts have been assimilated widely, there is a natural increase in interest in the foundations of nonlinear modeling; and, finally, some phenomena long recognized to be of interest, but beyond the effective range of linear models, are now known to be essentially nonlinear in nature. In this volume, an exhaustive review of the literature is not attempted. Rather the emphasis is on fundamental ideas and a representative selection of problems. Despite obvious successes in research on problems of aeroelasticity and the existence of a broad literature, including a number of excellent monographs, up to now little attention has been devoted to a general nonlinear theory of interac tion. For the most part nonlinearity has been considered either solely in the description of the behavior of a shell or in the description of the motion of a gas."

This book is about aerospace sensors, their principles of operation, and their typical advantages, shortcomings, and vulnerabilities. They are described in the framework of the subsystems where they function and in accordance with the flight mission they are designed to serve. The book is intended for students at the advanced undergraduate or graduate level and for research engineers who need to acquire this kind of knowledge. An effort has been made to explain, within a uniform framework of mathematical modeling, the physics upon which a certain sensor concept is based, its construction, its dynamics, and its error sources and their corresponding mathematical models. Equipped with such knowledge and understanding, the student or research engineer should be able to get involved in research and development activities of guidance, control, and navigation systems and to contribute to the initiation of novel ideas in the aerospace sensor field. As a designer and systems engineer, he should be able to correctly interpret the various items in a technical data list and thus to interact intelligently with manufacturers' representatives and other members of an R&D team. Much of the text has evolved from undergraduate and graduate courses given by the author during the past seventeen years at the Department of Aerospace Engineering at the Technion- Israel Institute of Technology and from his earlier research and development experience in flight control, guidance, navigation, and avionics at the Ministry of Defense Central Research Institute.

The Joint Institute for Aeronautics and Acoustics at Stanford University was established in October 1973 to provide an academic environment for long-term cooperative research between Stanford and NASA Ames Research Center. Since its establishment, the In stitute has wnducted theoretical and experimental work in the areas of aerodynamics, acoustics, fluid mechanics, flight dynamics, guid ance and control, and human factors. This research has involved Stanford faculty, research associates, graduate students, and many distinguished visitors in collaborative efforts with the research staff of NASA Ames Research Center. The occasion of the Institute's tenth anniversary was used to reflect back on where that research has brought us, and to consider where our endeavors should be directed next. Thus, an International Symposium was held to review recent advances in the fields relevant to the activities of the Institute and to discuss the areas of research to be undertaken in the future. This anniversary was also chosen a.."1 an opportunity to honor one of the Institute's founders and its di rector, Professor Krishnamurty Karamcheti. It has been his creative inspiration that has provided the ideal research environment at the Joint Institute. The International Symposium on Recent Advances in Aero dynamics and Aconstics was held at Stanford University, Stanford, California, U.S.A., August 22-26, 198: . Thirty-five distinguished scientists were invited to present a comprehensive review on the fol lowing subject areas: unsteady aerodynamics, jets and shear layers, V /STOL aircraft aerodynamics, rotor dynamics and aerodynamics, ."

The author provides new insights into the relationship between transport and the environment, the role of technology and the meaning of the concept of sustainable development for the transport sector. Special attention is given to the relationship between technological progress and policy. The different theoretical approaches are combined to create a strategy for R&D and the implementation of mega-technological innovations. The empirical part deals with two specific cases: Maglev technology and fuel-cell technology for transport purposes. Taking into account the new theoretical insights and the empirical findings, the author presents a synthesis and draws conclusions which are important for researchers and professionals in transportation, environmental sciences and related fields.

This book is an introduction to the elementary technology of automobile suspensions. Inevitably steering geometry must be included in the text, since the dynamic steering behaviour, road-holding and cornering behaviour are all influenced by the suspension design. Steering mechanisms and steering components are not covered in this book. This is not a mathematical treatise, but only a fool or a genius would attempt to design a motor vehicle without mathematics. The mathematics used in this book should present no problem to a first-year university student. SI units have been used in general, but for the benefit of those not familiar with them we have included in brackets, in many cases, the equivalent values in Imperial units. Many engineers regard the Pascal as an impractical unit of pressure. The author has therefore expressed pressures in bars (1 bar = 105Pa). A deviation from SI units is the use of degrees and minutes, instead of radians, to express camber, castor, roll angles, etc. This is still common practice in the motor industry. No attempt has been made to make any stress calculations on suspension components. The automobile engineering student will have access to other textbooks on such subjects as strength of materials and theory of structures.

It is difficult to do justice to fracture mechanics in a textbook, for the subject encompasses so many disciplines. A general survey of the field would serve no purpose other than give a collection of references. The present book by Professor E. E. Gdoutos is refreshing because it does not fall into the esoteric tradition of outlining equations and results. Basic ideas and underlying principles are clearly explained as to how they are used in application. The presentations are concise and each topic can be understood by advanced undergraduates in material science and continuum mechanics. The book is highly recommended not only as a text in fracture mechanics but also as a reference to those interested in the general aspects of failure analysis. In addition to providing an in-depth review of the analytical methods for evaluating the fundamental quantities used in linear elastic fracture mechanics, various criteria are discussed re: O. ecting their limitations and applications. Par ticular emphases are given to predicting crack initiation, subcritical growth and the onset of rapid fracture from a single criterion. Those models in which it is assumed that the crack extends from tip to tip rely on the specific surface energy concept. The differences in the global and energy states before and after crack extension were associated with the energy required to create a unit area of crack surface. Applications were limited by the requirement of self-similar crack growth."

There is a growing social interest in developing vision-based vehicle guidance systems for improving traffic safety and efficiency and the environment. Ex amples of vision-based vehicle guidance systems include collision warning systems, steering control systems for tracking painted lane marks, and speed control systems for preventing rear-end collisions. Like other guidance systems for aircraft and trains, these systems are ex pected to increase traffic safety significantly. For example, safety improve ments of aircraft landing processes after the introduction of automatic guidance systems have been reported to be 100 times better than prior to installment. Although the safety of human lives is beyond price, the cost for automatic guidance could be compensated by decreased insurance costs. It is becoming more important to increase traffic safety by decreasing the human driver's load in our society, especially with an increasing population of senior people who continue to drive. The second potential social benefit is the improvement of traffic efficiency by decreasing the spacing between vehicles without sacrificing safety. It is reported, for example, that four times the efficiency is expected if the spacing between cars is controlled automatically at 90 cm with a speed of 100 kmjh compared to today's typical manual driving. Although there are a lot of tech nical, psychological, and social issues to be solved before realizing the high density jhigh-speed traffic systems described here, highly efficient highways are becoming more important because of increasing traffic congestion."