Problems involving synthesis of mathematical models of various physical systems, making use of these models in practice and verifying them qualitatively has - come an especially important area of research since more and more physical - periments are being replaced by computer simulations. Such simulations should make it possible to carry out a comprehensive analysis of the various properties of the system being modelled. Most importantly its dynamic properties can be - dressed in a situation where this would be difficult or even impossible to achieve through a direct physical experiment. To carry out a simulation of a real, phy- cally existing system it is necessary to have its mathematical description; the s- tem being described mathematically by equations, which include certain variables, their derivatives and integrals. If a single independent variable is sufficient in - der to describe the system, then derivatives and integrals with respect to only that variable will appear in the equations. Differentiation of the equation allows the integrals to be eliminated and produces an equation which includes derivatives with respect to only one independent variable i. e. an ordinary differential equation. In practice, most physical systems can be described with sufficient accuracy by linear differential equations with time invariant coefficients. Chapter 2 is devoted to the description of models by such equations, with time as the independent va- able.

A systematic treatment of current crashworthiness practice in the automotive, railroad and aircraft industries. Structural, exterior and interior design, occupant biomechanics, seat and restraint systems are dealt with, taking account of statistical data, current regulations and state-of-the-art design tool capabilities. Occupant kinematics and biomechanics are reviewed, leading to a basic understanding of human tolerance to impact and of the use of anthropometric test dummies and mathematical modelling techniques. Different types of restraining systems are described in terms of impact biomechanics. The material and structural behaviour of vehicle components is discussed in relation to crash testing. A variety of commonly used techniques for simulating occupants and structures are presented, in particular the use of multibody dynamics, finite element methods and simplified macro-elements, in the context of design tools of increasing complexity, which can be used to model both vehicles and occupants. Audience: An excellent reference for researchers, engineers, students and all other professionals involved in crashworthiness work.

Thisvolumecontainsacollectionofpapersbyinternationalexpertsingeoph- ical ?uid dynamics, based upon presentations at a colloquium held in memory of Pedro Ripa on the ?rst anniversary of his untimely death. They review or present recent developments in hydrodynamic stability theory, Hamiltonian ?uid mechanics, balanceddynamics, waves, vortices, generaloceanographyand the physical oceanography of the Gulf ofCalifornia; all of them subjects in which Professor Ripamadeimportant contributions. His work, but also his friendly spiritandkindnesswerehighly regardedandappreciatedby colleagues and students alike around the world. This book is a tribute to his scienti?c legacy and constitutes a valuable reference for researchers and graduate s- dents interested in geophysical and general ?uid mechanics. Earlyin his career asa physicaloceanographer, Pedro Ripa made two la- mark contributions to geophysical ?uid dynamics. In 1981, he showed that the conservation of the potential vorticity is related to the invariance of the eq- tions of motion under the symmetry transformationsof the labels that identify the ?uid particles. That is, potential vorticity conservation is a consequence, via Noether's theorem, of the particle re-labelling symmetry. Two years later he published a paper entitled "General stability conditions for zonal ?ows in a one-layer model on the beta-plane or the sphere," where he established nec- sary conditions for stability in the shallow water equations, nowadays known as "Ripa's Theorem. " This is one of the very few Arnol'd-like stability con- tions that goes beyond two-dimensional or quasi-geostrophic ?ow, and stands alongside other famous stability criteria in making the foundations of the ?eld.

This book is primarily a research monograph that presents in a unified man ner some recent research on a class of hybrid dynamical systems (HDS). The book is intended both for researchers and advanced postgraduate stu dents working in the areas of control engineering, theoretical computer science, or applied mathematics and with an interest in the emerging field of hybrid dynamical systems. The book assumes competence in the basic mathematical techniques of modern control theory. The material presented in this book derives from a period of fruitful research collaboration between the authors that began in 1994 and is still ongoing. Some of the material contained herein has appeared as isolated results in journal papers and conference proceedings. This work presents this material in an integrated and coherent manner and also presents many new results. Much of the material arose from joint work with students and colleagues, and the authors wish to acknowledge the major contributions made by Ian Petersen, Efstratios Skafidas, Valery Ugrinovskii, David Cook, Iven Mareels, and Bill Moran. There is currently no precise definition of a hybrid dynamical system; however, in broad terms it is a dynamical system that involves a mixture of discrete-valued and continuous-valued variables. Since the early 1990s, a bewildering array of results have appeared under the umbrella of HDS, ranging from the analysis of elementary on-off control systems to sophis ticated mathematical logic-based descriptions of large real-time software systems.

This text is an introduction to the feedback control of lightly damped flexible structures; the emphasis is placed on basic issues such as actuator and sensor selection, placement and dynamics, and actual implementation for solving practical problems. The book consists of 11 chapters; in chapters 2 to 5, the open-loop transfer functions of various active structures are derived from their constitutive equations; the discussion includes a truss and sandwich beams and plates with embedded piezoelectric actuators and sensors. The virtues of collocated actuator-sensor configurations are pointed out and used to develop active damping with guaranteed stability. Chapters 6 to 8 are devoted to the model-based control of SISO systems; optimal control is developed graphically using the symmetric root locus; the gain-phase relationship is discussed and the design tradeoffs are explained in the frequency domain. The issues of robustness with respect to the parametric uncertainty and the spillover instability are examined. After two short chapters on controllability (ch. 9) and stability (ch. 10), the book concludes with a set of applications to active damping and precision positioning of a set of aerospace, mechanical and civil engineering structures. The book is intended for structural engineers who want to acquire some background in vibration control; it can be used as a textbook for a graduate course on vibration control or active structures. The text is supplemented with 98 problems.

Most practical processes such as chemical reactor, industrial furnace, heat exchanger, etc., are nonlinear stochastic systems, which makes their con trol in general a hard problem. Currently, there is no successful design method for this class of systems in the literature. One common alterna tive consists of linearizing the nonlinear dynamical stochastic system in the neighborhood of an operating point and then using the techniques for linear systems to design the controller. The resulting model is in general an approximation of the real behavior of a dynamical system. The inclusion of the uncertainties in the model is therefore necessary and will certainly improve the performance of the dynamical system we want to control. The control of uncertain systems has attracted a lot of researchers from the control community. This topic has in fact dominated the research effort of the control community during the last two decades, and many contributions have been reported in the literature. Some practical dynamical systems have time delay in their dynamics, which makes their control a complicated task even in the deterministic case. Recently, the class ofuncertain dynamical deterministic systems with time delay has attracted some researchers, and some interesting results have been reported in both deterministic and stochastic cases. But wecan't claim that the control problem ofthis class ofsystems is completely solved; more work must be done for this class of systems.

Multibody dynamics started with the ideas of Jacob and Daniel Bernoul li and later on with d'Alembert's principle. In establishing a solution for the problem of the center of oscillation for a two-mass-pendulum Jacob Ber noulli spoke about balancing the profit-and-Ioss account with respect to the motion of the two masses. Daniel Bernoulli extended these ideas to a chain pendulum and called forces not contributing to the motion "lost forces," thus being already very close to d'Alembert's principle. D'Alembert considered a "system of bodies, which are interconnected in some arbitrary way. " He suggested separating the motion into two parts, one moving, the other being at rest. In modern terms, or at least in terms being applied in engineering mechanics, this means that the forces acting on a system of bodies are split into active and passive forces. Active forces generate motion, passive forces do not; they are a result of constraints. This interpretation of d'Alembert's principle is due to Lagrange and up to now has been the basis of multi body dynamics (D' Alembert, Traite de Dynamique, 1743; Lagrange, Mecanique Analytique, 1811). Thus, multibody dynamics started in France. During the nineteenth century there were few activities in the multi body field even though industry offered plenty of possible applications and famous re presentatives of mechanics were aware of the problems related to multibody dynamics. Poisson in his "Traite de Mecanique" (Paris 1833) gave an im pressive description of these problems, including impacts and friction."

Advances in computational mechanics can only be achieved on the basis of fruitful discussion between researchers and practising engineers. This has been achieved in the present publication, which contains all the papers presented at the first International DIANA Conference on Computational Mechanics. Nearly all papers show the results of calculations achieved with the DIANATM Finite Element System. Broadly, the book follows the line of research from the material level, via the element level, to the structural level. But it should be emphasised that much current research passes from one level to the other, and such an interaction is also reflected here. The following domains are treated: (hyper)elasticity, (visco)plasticity and cracking; (enriched) damaging continua models; material experiments vs. computational models; stochastic approaches; fluid--structure interactions; element technology; geometrical nonlinearity and structural instability; nonlinear dynamics; solution procedures.

In this book several connections between probability theory and wave propagation are explored. The connection comes via the probabilistic (or path integral) representation of both the (fixed frequency) Green functions and of the propagators -operators mapping initial into present time data. The formalism includes both waves in continuous space and in discrete structures.
One of the main applications of the formalism developed is to inverse problems in wave propagation. Using the probabilistic formalism, the parameters of the medium and the surfaces determining the region of propagation appear explicitly in the path integral representation of the Green functions and propagators. This fact is what provides a useful starting point for inverse problem formulation.

Audience: The book is suitable for advanced graduate students in the mathematical, physical or in the engineering sciences. The presentation is quite self-contained, and not extremely rigorous.

In this book, regular structures are de ned as periodic structures consisting of repeated elements (translational symmetry) as well as structures with a geom- ric symmetry. Regular structures have for a long time been attracting the attention of scientists by the extraordinary beauty of their forms. They have been studied in many areas of science: chemistry, physics, biology, etc. Systems with geometric symmetry are used widely in many areas of engineering. The various kinds of bases under machines, cyclically repeated forms of stators, reduction gears, rotors with blades mounted on them, etc. represent regular structures. The study of real-life engineering structures faces considerable dif culties because they comprise a great number of working mechanisms that, in turn, consist of many different elastic subsystems and elements. The computational models of such systems represent a hierarchical structure and contain hundreds and thousands of parameters. The main problems in the analysis of such systems are the dim- sion reduction of model and revealing the dominant parameters that determine its dynamics and form its energy nucleus. The two most widely used approaches to the simulation of such systems are as follows: 1. Methods using lumped parameters models, i.e., a discretization of the original system and its representation as a system with lumped parameters [including nite-element method (FEM)]. 2. The use of idealized elements with distributed parameters and known analytical solutions for both the local elements and the subsystems.

During the last decades, applications of dynamical analysis in advanced, often nonlinear, engineering systems have been evolved in a revolutionary way. In this context one can think of applications in aerospace engineering like satellites, in naval engineering like ship motion, in mechanical engineering like rotating machinery, vehicle systems, robots and biomechanics, and in civil engineering like earthquake dynamics and offshore technology. One could continue with this list for a long time. The application of advanced dynamics in the above fields has been possible due to the use of sophisticated computational techniques employing powerful concepts of nonlinear dynamics. These concepts have been and are being developed in mathematics, mechanics and physics. It should be remarked that careful experimental studies are vitally needed to establish the real existence and observability of the predicted dynamical phenomena. The interaction between nonlinear dynamics and nonlinear control in advanced engineering systems is becoming of increasing importance because of several reasons. Firstly, control strategies in nonlinear systems are used to obtain desired dynamic behaviour and improved reliability during operation, Applications include power plant rotating machinery, vehicle systems, robotics, etc. Terms like motion control, optimal control and adaptive control are used in this field of interest. Since mechanical and electronic components are often necessary to realize the desired action in practice, the engineers use the term mechatronics to indicate this field. If the desired dynamic behaviour is achieved by changing design variables (mostly called system parameters), one can think of fields like control of chaos.

"Symposium Transsonicum" was founded by Klaus Oswatitsch four decades ago when there was clearly a need for a systematic treatment of flow problems in the higher speed regime in aeronautics. The first conference in 1962 brought together scientists concerned with fundamental problems involving the sonic flow speed regime. Results of the conference provided an understanding of some basic tran sonic phenomena by proposing mathematical methods that allowed for the de velopment of practical calculations. The "Transonic Controversy" (about shock free flows) was still an open issue after this meeting. In 1975 the second symposium was held, by then there was much understanding in how to avoid shocks in a steady plane flow to be designed, but still very little was known in unsteady phenomena due to a lack of elucidating experiments. A third meeting in 1988 reflected the availability oflarger computers which allowed the numerical analysis of flows with shocks to a reasonable accuracy. Because we are trying to keep Oswatitsch's heritage in science alive especially in Gottingen, we were asked by the aerospace research community to organize another symposium. Much had been achieved already in the knowledge, techno logy and applications in transonics, so IUT AM had to be convinced that a fourth meeting would not just be a reunion of old friends reminiscing some scientific past. The scientific committee greatly supported my efforts to invite scientists ac tively working in transonic problems which still pose substantial difficulties to ae rospace and turbomachinery industry."

... a wise man knows all things in a manner in which this is possible, not, however, knowing them individually. Aristotle. Metaphysics * The problem of consideration of vortex fields' influence on solid body dynamics has a long history. One constantly comes upon it in flight dynamics of airplanes, helicopters, and other flying vehicles (FV) moving in the atmosphere, in dynamics of ships with hydrofoils, and in dynamics of rocket carriers (RC) and spacecrafts (SC) with liquid-propellant rocket engines (LPRE), that are equipped with special damping devices and other structural elements inside fluid tanks. Similar problems occur when solving problems related to attitude control and stabilization of artificial Earth satellites (AES) and spacecrafts with magnetic (electro magnetic) systems, in conducting elements of which eddy currents are induced while control of those vehicles' angular position. It is also true with special test facilities for dynamic testing of space vehicles and their systems, with modern high-speed magnetic suspension transport systems (those based on the phenomenon of 'magnetic levitation'), with generators having rotors carried in 'magnetic bearings', and so on."

The IUT AM / IFToMM Symposium on Synthesis of Nonlinear Dynamical Systems, held in Riga, Latvia, 24-28 August 1998, was one of a series of IUTAM sponsored symposia which focus on the theory and application of methods of nonlinear dynamics in mechanics. The symposium follows eighteen symposia on Analysis and Synthesis of Nonlinear Mechanical Oscillatory Systems held at Riga Technical University from 1971 to 1991 and in 1996 (prof. E. Lavendelis and Prof. M. Zakrzhevsky). Early in the late fifties and sixties Prof. J. G. Panovko organised several successful conferences in Riga on Nonlinear Oscillations. The participants in all these conferences and symposia (except 1996) were only from the ex-Soviet Union. This symposium, organised by the Institute of Mechanics of Riga Technical University, brought together scientists active in different fields of nonlinear dynamics. Selected scientists from 14 countries represented a wide range of expertise in' mechanics, from pure theoreticians to people primarily oriented towards application of nonlinear and chaotic dynamics and nonlinear oscillations. The goal of the symposium was to stimulate development of the theory of strongly nonlinear dynamical systems and its new applications in the fields of applied mechanics, engineering and other branches of science and technology.

This is the second and final issue of the collection of papers that were contributed by friends and colleagues of (Late) Professor P. R. "Pat" Sethna of the University of Minnesota to commemorate his 70th birthday on May 26, 1993. The first set of contributions was published in Nonlinear Dynamics as the last issue (no. 6) of Vol. 4 in 1993. As circumstances would have it, Professor Sethna was diagnosed with cancer in the fall of 1992 and, after an extended battle with the disease, he passed away on November 4, 1993, just a few days before the first set of contributed papers appeared in print. It is gratifying to report that the organizers of these vi Foreword commemorative issues in Nonlinear Dynamics were able to present to Professor Sethna, on the occasion of his 70th birthday, complete details of the planned commemorative issues. This second set of contributions is dedicated, in memoriam, to Professor P. R. Sethna. As many of you are well aware, Professor Sethna was an active researcher in the field of nonlinear vibrations and dynamics for nearly forty years, making many fundamental and significant contributions to both the theoretical and applied aspects of this field. He was also recognized for his outstanding leadership and administrative abilities, amply demonstrated through his position as the Head of the Department of Aerospace Engineering and Mechanics at the University of Minnesota for twenty-six years (1966-1992).

Nonlinearity and stochastic structural dynamics is of common interest to engineers and applied scientists belonging to many disciplines. Recent research in this area has been concentrated on the response and stability of nonlinear mechanical and structural systems subjected to random escitation. Simultaneously the focus of research has also been directed towards understanding intrinsic nonlinear phenomena like bifurcation and chaos in deterministic systems. These problems demand a high degree of sophistication in the analytical and numerical approaches. At the same time they arise from considerations of nonlinear system response to turbulence, earthquacke, wind, wave and guidancy excitations. The topic thus attracts votaries of both analytical rigour and practical applications. This books gives important and latest developments in the field presenting in a coherent fashion the research findings of leading international groups working in the area of nonlinear random vibration and chaos.

Ad ap tive Contro l provid es tec hniques for aut omatic adjustment in real t ime of cont roller parameter s in order to achieve or to maintain a desired level for the performance of cont rol systems when the dyn amic param et ers of t he process are unknown and/or var y in time. These techniques have as a main feature t he abilit y to ext ract significant information from real dat a in ord er to tune the cont roller and they feature a me chanism for adjust ing parameter s (of a plant model or of a cont roller). While the history of Adaptive Control is lon g, significant progr ess in under - standing and applying Adaptive Con trol began in the early sevent ies. The growing availability of digital com puters have also contributed to the devel- opment of the field . The earlier applicat ions in the sevent ies and beginning of the eight ies, provided important feedback for the development of the field . Theoretical developments allowed a number of basic problems to be solved . The aim of this book is to provide a coherent and comprehensive treatment of the field . The presentation takes the read er from the basic problem formu- lation to the analytical solutions who se prac tical significance is illustrated by applications.

The numerous applications of optimal control theory have given an incentive to the development of approximate techniques aimed at the construction of control laws and the optimization of dynamical systems. These constructive approaches rely on small parameter methods (averaging, regular and singular perturbations), which are well-known and have been proven to be efficient in nonlinear mechanics and optimal control theory (maximum principle, variational calculus and dynamic programming). An essential feature of the procedures for solving optimal control problems consists in the necessity for dealing with two-point boundary-value problems for nonlinear and, as a rule, nonsmooth multi-dimensional sets of differential equations. This circumstance complicates direct applications of the above-mentioned perturbation methods which have been developed mostly for investigating initial-value (Cauchy) problems. There is now a need for a systematic presentation of constructive analytical per turbation methods relevant to optimal control problems for nonlinear systems. The purpose of this book is to meet this need in the English language scientific literature and to present consistently small parameter techniques relating to the constructive investigation of some classes of optimal control problems which often arise in prac tice. This book is based on a revised and modified version of the monograph: L. D. Akulenko "Asymptotic methods in optimal control." Moscow: Nauka, 366 p. (in Russian)."

By providing all the basic knowledge needed to assess how useful active noise control will be for a given problem, this book assists in the designing, setting up, and tuning of an active noise-control system. Written for students who have no prior knowledge of acoustics, signal processing, or noise control but who do have a reasonable grasp of basic physics and mathematics, the text is short and descriptive, leaving all mathematical details and proofs concerning vibrations, signal processing and the like to more advanced texts or research monographs. The book can thus be used in independent study, in a classroom with laboratories, or in conjunction with a kit for experiment or demonstration. Topics covered include basic acoustics, human perception and sound, sound intensity and related concepts, fundamentals of passive noise- control strategies, basics of digital systems and adaptive controllers, and active noise control systems.

This book presents the latest research results in the area of applied nonlinear dynamics and chaos theory. Papers by three academic generations address new applications of nonlinear dynamics to mechanics, including fluid-structure interaction, machining and mechanics of solids, and many other applications.

The main objective of the First International Symposium on Lubricated Transport of Viscous Materials was to bring together scientists and engineers from academia and industryto discuss current research work and exchange ideas in this newly emerging field. It is an area offluid dynamics devoted to laying bare the principlesofthe lubricated transport of viscous materials such as crude oil, concentrated oil/water emulsion, slurries and capsules. It encompasses several types of problem. Studies of migration of particulates away from walls, Segre-Silverberg effects, lubrication versus lift and shear-induced migration belong to one category. Some of the technological problems are the fluid dynamics ofcore flows emphasizing studies ofstability, problems of start-up, lift-off and eccentric flow where gravity causes the core flow to stratify. Another category of problems deals with the fouling of pipe walls with oil, with undesirable increases in pressure gradients and even blocking. This study involves subjects like adhesion and dynamic contact angles. The topics ofshear-induced diffusion ofsmall particles and wall slip in slow flow are other appropriate subjects. Computer intensive studiesofflow-induced microstructures and moving interface problems are yet additional research directions. The general consensus was that the Symposium was a tremendous success, although the number of presentations fell below expectations. Scientists from the petroleum industry, and this includes INTEVEP (Venezuela), Schlumberger and Syncrude Canada Ltd., and consultants to oil companies actively participated in the Symposium. The meeting produced new insights which should lead to further interesting research work and established contacts for possiblejoint investigations."

This volume contains selected papers presented at the Symposium on "Recent Developments in Non-linear Oscillations of Mechanical Systems", held in Hanoi, Vietnam, from 2 - 5 March 1999. This Symposium was initiated and sponsored by the International Union of Theoretical and Applied Mechanics (lUI AM) and organised in conjunction with Vietnam National University, Hanoi. Ihe purpose of the Symposium was to bring together scientists active in different fields of oscillations with the aim to review the recent progress in theory of oscillations and engineering applications and to outline the prospects in its further achievements to then co-ordinate and direct research in this field to further co-operation between scientists and various scientific institutions. An International Scientific Committee was appointed by the Bureau of IUI AM with the following members: Nguyen Van Dao (Vietnam, Co-Chairman) E.J. Kreuzer (Germany, Co-Chairman) D.H. van Campen (The Netherlands) F.L. Chernousko (Russia) A.H. Nayfeh (U.S.A) Nguyen Xuan Hung (Vietnam) W.O. Schiehlen (Germany) J.M.T. Thompson (U.K) Y. Veda (Japan). This Committee selected the participants to be invited and the papers to be presented at the Symposium. As a result of this procedure, 52 active scientists from 16 countries responded to the invitation, and 42 papers were presented in lecture and poster discussion sessions.

The aim of this book is to provide an account of the state of the art in Com putational Kinematics. We understand here under this term that branch of kinematics research involving intensive computations not only of the nu merical type, but also of symbolic as well as geometric nature. Research in kinematics over the last decade has been remarkably ori ented towards the computational aspects of kinematics problems. In fact, this work has been prompted by the need to answer fundamental questions such as the number of solutions, whether real or complex, that a given problem can admit as well as computational algorithms to support geo metric analysis. Problems of the first kind occur frequently in the analysis and synthesis of kinematic chains, when fine displacements are considered. The associated models, that are derived from kinematic relations known as closure equations, lead to systems of nonlinear algebraic equations in the variables or parameters sought. The algebraic equations at hand can take the form of multivariate polynomials or may involve trigonometric functions of unknown angles.

This book presents the most recent research advances in the theory, design, control and application of robotic systems, which are intended for a variety of purposes such as manipulation, manufacturing, automation, surgery, locomotion and biomechanics. The issues addressed are fundamentally kinematic in nature, including synthesis, calibration, redundancy, force control, dexterity, inverse and forward kinematics, kinematic singularities, as well as over-constrained systems. Methods used include line geometry, quaternion algebra, screw algebra, and linear algebra. These methods are applied to both parallel and serial multi-degree-of-freedom systems. The results should interest researchers, teachers and students, in fields of engineering and mathematics related to robot theory, design, control and application. All articles in the book were reported at the seventh international symposium on Advances in Robot Kinematics that was organised in June 2000 in the beautiful ancient Mediterranean town of Piran in Slovenia. The preceding symposia of the series took place in Ljubljana (1988), Linz (1990), Ferrara (1992), Ljubljana (1994), and Piran (1996), and Salzburg (1998).

In Fascination of Fluid Dynamics contains a collection of papers by international experts in hydrodynamics, based on oral presentations at a symposium held in honour of Professor Leen van Wijngaarden on his 65th birthday. The book begins with a personal sketch of his life and scientific career. It continues with a mixture of papers that address recent developments in various branches of fluid mechanics. Many of the papers cover different aspects of multiphase flows: bubble dynamics, cavitation, bubbles and particles in turbulent flows, suspension flows, and wave phenomena in fluidised beds. Other topics that are addressed include: dynamics of jets, shock waves, MHD turbulence, selforganisation phenomena in 2D turbulence, vortex rings and the thermodynamics of tropical cyclones. This edited volume will be valuable reading for researchers, engineers and students interested in hydrodynamics, and in particular in multiphase flows.