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One of the most fascinating and intriguing aspects of natural phenomena is that complex systems may undergo symme try-breaking instabilities leading to pattern formation or coherent temporal behavior over macroscopic space and time scales. Therefore the understanding of why order may appear spontananeously in open systems far from equilibrium and which planforms are selected among a large manifold of possi bilities has become a major theme of research both theore- cally and experimentally. These studies, first related to fundamental questions, appear now to be of technological importance, especially for materials science problems. Effectively during the last years, the whole field of materials science experienced a complete renewal. By using techniques able to operate in strong nonequilibrium conditions and hence to escape from the constraints of equilibrium thermodynamics, totally new mate rials structures have been processed. Such techniques inclu de ion implantation, laser beam surface melting as well as electron beam heating. For example, ion implantation proces sing is able to create surfaces with compositions markedly different from the bulk, leading to materials having new electric, magnetic or chemical properties. In laser annea ling, after the tremendously rapid melting and recrystalliza tion of the sample surfaces, microstructures with superior resistance to friction, corrosion, ••• are frozen into place. Rapid solidification of alloys trigger the formation of quasi-crystalline structures. Ion beam mixing can modify the electrical properties of polymers or improve the adhesion of metallic films to ceramics.
Understanding the origin of spatio-temporal order in open systems far from thermal equilibrium and the selection mechanisms of spatial struc tures and their symmetries is a major theme of present day research into the structures of continuous matter. The development of methods for pro ducing spatially ordered microstructures in solids by non-equilibrium methods opens the door to many technological applications. It is also be lieved that the key to laminar/turbulence transitions in fluids lies in the achievement of spatio-temporal order. Let us also emphasize the fact that the idea of self-organization in it self is at the origin of a reconceptualisation of science. Indeed, the appear ance of order which usually has been associated with equilibrium phase transitions appears to be characteristic of systems far from thermal equi librium. This phenomenon which was considered exceptional at first now the rule in driven systems. The chemical oscillations obtained appears to be in the Belousov-Zhabotinskii reaction were initially considered to be ther modynamically impossible and were rejected by a large number of chemists. Now these oscillations and related phenomena (waves, chaos, etc. ) are the subject of intensive research and new classes of chemical oscil lators have been recently discovered. Even living organisms have long been considered as the result of chance rather than necessity. Such points of view are now abandoned under the overwhelming influence of spatio-tem poral organization phenomena in various domains ranging from physics to biology via chemistry, nonlinear optics, and materials science .
There are two subjects in this thesis. In the first part, a qualitative method to classify and predict the structure of defects in reaction-diffusion systems is introduced. This qualitative approach makes it easier to analyze the behavior of defects in complex systems. It also gives us information about the inner structure of the defect, and from that point of view, it makes it possible to approach the concept of defect bifurcation in a novel manner. In the second part, we study the normal form governing the evolution of a spatially extended homogeneous temporal instability, in the presence of a temporal forcing. This is equivalent to studying strong resonances of a field of nonlinear oscillators. A detailed analysis of the phase space of this normal form reveals a rich dynamical structure, which gives rise to a variety of spatial structures. These include excitable pulses, excitable spirals, fronts and spatially periodic structures. These structures are studied and their possible bifurcations are analyzed from a qualitative point of view.
The basic aim of the NATO Advanced Research Workshop on "New Trends in Nonlinear Dynamics and Pattern-Forming Phenomena: The Geometry of Nonequilibrium" was to bring together researchers from various areas of physics to review and explore new ideas regarding the organisation of systems driven far from equilibrium. Such systems are characterized by a close relationship between broken spatial and tempo ral symmetries. The main topics of interest included pattern formation in chemical systems, materials and convection, traveling waves in binary fluids and liquid crystals, defects and their role in the disorganisa tion of structures, spatio-temporal intermittency, instabilities and large-scale vortices in open flows, the mathematics of non-equilibrium systems, turbulence, and last but not least growth phenomena. Written contributions from participants have been grouped into chapters addressing these different areas. For additional clarity, the first chapter on pattern formation has been subdivided into sections. One of the main concerns was to focus on the unifying features between these diverse topics. The various scientific communities repre sented were encouraged to discuss and compare their approach so as to mutually benefit their respective fields. We hope that, to a large degree, these goals have been met and we thank all the participants for their efforts. The workshop was held in Cargese (Corsica, France) at the Institut d'Etudes Scientifiques from August 2nd to August 12th, 1988. We greatly thank Yves Pomeau and Daniel Walgraef who, as members of the organising committee, gave us valuable advice and encouragements.
This comprehensive work explores interfacial instability and pattern formation in dynamic systems away from the equilibrium state in solidification and crystal growth. Further, this significantly expanded 2nd edition introduces and reviews the progress made during the last two decades. In particular, it describes the most prominent pattern formation phenomena commonly observed in material processing and crystal growth in the framework of the previously established interfacial wave theory, including free dendritic growth from undercooled melt, cellular growth and eutectic growth in directional solidification, as well as viscous fingering in Hele-Shaw flow. It elucidates the key problems, systematically derives their mathematical solutions by pursuing a unified, asymptotic approach, and finally carefully examines these results by comparing them with the available experimental results. The asymptotic approach described here will be useful for the investigation of pattern formation phenomena occurring in a much broader class of inhomogeneous dynamical systems. In addition, the results on global stability and selection mechanisms of pattern formation will be of particular interest to researchers working on material processing and crystal growth. The stability mechanisms of a curved front and the pattern formation have been fundamental subjects in the areas of condensed-matter physics, materials science, crystal growth, and fluid mechanics for some time now. This book offers a stimulating and insightful introduction for all physicists, engineers and applied mathematicians working in the fields of soft condensed-matter physics, materials science, mechanical and chemical engineering, fluid dynamics, and nonlinear sciences.
Containing almost 250 technical and review papers, these proceedings form an authoritative, state-of-the-art review of this important multidisciplinary topic. Emphasis is placed on the study of the strength of mechanical properties of materials and their dependence on the microstructure and defect arrangements. Areas covered include: dislocations; dislocation arrangements; plastic deformation; strengthening mechanisms; cyclic deformation and fatigue; plastic deformation at high temperatures; fracture; modern strengthening methods in steels; boundaries and interfaces.
For the last several years, the study of interfacial instability and pattern formation phenomena has preoccupied many researchers in the broad area of nonlinear science. These phenomena occur in a variety of dynamical sys tems far from equilibrium. In many practically very important physical sys tems some fascinating patterns are always displayed at the interface between solid and liquid or between two liquids. Two prototypes of these phenomena are dendrite growth in solidification and viscous fingering in a Hele-Shaw cell. These two phenomena occur in completely different scientific fields, but both are described by similar nonlinear free boundary problems of partial differential-equation systems; the boundary conditions on the interface for both cases contain a curvature operator involving the surface tension, which is nonlinear. Moreover, both cases raise the same challenging theoretical is sues, interfacial instability mechanisms and pattern selection, and it is now found that these issues can be solved by the same analytical approach. Thus, these two phenomena are regarded as special examples of a class of nonlinear pattern formation phenomena in nature, and they are the prominent topics of the new interdisciplinary field of nonlinear science. This research monograph is based on a series of lectures I have given at McGill University, Canada (1993-1994), Northwestern Poly technical In stitute, China (1994), Aachen University, Germany (1994), and the CRM summer school at Banff, Alberta, Canada (1995).
This volume contains the proceedings of a NATO Advanced Study Institute which was held in Alghero, Sardinia, in July 1991. The development of computers in the recent years has lead to the emergence of unconventional ideas aiming at solving old problems. Among these, the possibility of computing directly fluid flows from the trajectories of constituent particles has been much exploited in the last few years: lattice gases cellular automata and more generally Molecular Dynamics have been used to reproduce and study complex flows. Whether or not these methods may someday compete with more traditional approaches is a question which cannot be answered at the present time: it will depend on the new computer architectures as well as on the possibility to develop very simple models to reproduce the most complex phenomena taking place in the approach of fully developed turbulence or plastic flows. In any event, these molecular methods are already used, and sometimes in an applied engineering context, to study strong shock waves, chemistry induced shocks or motion of dislocations in plastic flows, that is in domains where a fully continuum description appears insufficient. The main topic of our Institute was the molecular simulations of fluid flows. The project to hold this Institute was made three years ago, in the summer of 1989 during a NATO workshop in Brussels on the same subject.
Almost all real systems are nonlinear. For a nonlinear system the superposition principle breaks down: The system's response is not proportional to the stimulus it receives; the whole is more than the sum of its parts. The three parts of this book contains the basics of nonlinear science, with applications in physics. Part I contains an overview of fractals, chaos, solitons, pattern formation, cellular automata and complex systems. In Part II, 14 reviews and essays by pioneers, as well as 10 research articles are reprinted. Part III collects 17 students projects, with computer algorithms for simulation models included.The book can be used for self-study, as a textbook for a one-semester course, or as supplement to other courses in linear or nonlinear systems. The reader should have some knowledge in introductory college physics. No mathematics beyond calculus and no computer literacy are assumed.