Formation Of Dissipative Structures Research Articles

Phase Separation and Formation of Dissipative Structures in Polystyrene/Polybutadiene Blend Solutions Subjected to a Temperature Gradient.

Time evolution of phase separation in a polymer blend solution under a temperature gradient was studied using polystyrene (PS), polybutadiene (PB), and dioctylphthalate (DOP). This study is aimed at making a highly organized structure by using convection. A blend solution with PS/PB/DOP=2/2/96 by weight was placed into the spacer (thickness 0.1 and 0.3mm) of which top and bottom temperatures were kept at 50 and 60°C, respectively. Phase separating processes were observed with a phase-contrast microscope. For 0.3-mm thickness, a polygonal cellular pattern due to convections was formed and phase-separated droplets were mainly arranged in the boundary region of each polygonal cell. For 0.1-mm thickness, quite different structures and a grow process were observed. At a dynamically steady state, doubly-surrounded island-sea structures were observed, where a larger droplet contains a plenty of tiny droplets which are arranged near the interface.

Filament-like structure formation in vacuum thermally evaporated thin films of polyaniline during oxidation in nitric acid

Oxidation of vacuum thermally evaporated thin films of polyaniline by aqueous nitric acid results in autocatalytic formation of filament-like heterogeneous dissipative structures in the oxidized areas due to non-equlibrium reactions between the reduced form of polyaniline and the oxidant.

Defect formation at internal interfaces and grain boundaries of cold-rolled Fe and Ni during heavy ion irradiation

ABSTRACTInstabilities arise out of dynamic events and can lead to nonequilibrium (self-organization) processes. Ion irradiation is by nature a nonequilibrium process and hence formation of structures, metastable or otherwise is to be expected. Recently, it has been theoretically predicted that metals under ion irradiation can lead to dissipative structure formation arising out of radiation damage and their subsequent annealing. The possibility of direct observation of such structures in metals, under irradiation, is however reduced due to nonavailability of a large concentration of defects (mainly point defects) at any point of time. In this experimental presentation we show that this can be overcome through the involvement of microstructural imperfections which rearrange during irradiation. Employing microstructurally impure specimens of Fe and Ni, it is shown that heavy ions dissipate their electronic energy to modify atomic arrangements at the microstructure. The increased concentration of defects (atomic rearrangements), amenable to statistical decay is shown to produce structures in the 4-probe resistivity measurements which we assign to dissipative structure formation.

Plastic deformation viewed as evolution of an active medium

The process of plastic flow in crystalline solids has been viewed as the evolution of an active medium in an open system far from thermodynamic equilibrium. The formation of lattice defects, the localization of strain and its variation in the different stages of flow are shown to be related to emergence and evolution of active media of definite types, the evolution of plastic flow involving propagation of different types of self-excited waves and formation of dissipative structures. The analogy with processes occurring in solids under deformation and with the emergence of structures in chemical and biological systems is discussed. Possible types of waves and observing conditions have been classified.

Fluid models for kinetic effects on coherent nonlinear Alfvén waves. II. Numerical solutions

The influence of various kinetic effects (e.g., Landau damping, diffusive and collisional dissipation, and finite Larmor radius terms) on the nonlinear evolution of finite amplitude Alfvénic wave trains in a finite-β environment is systematically investigated using a novel, kinetic nonlinear Schrödinger (KNLS) equation. The dynamics of Alfvén waves is sensitive to the sense of polarization as well as the angle of propagation with respect to the ambient magnetic field. Numerical solution for the case with Landau damping reveals the formation of dissipative structures, which are quasi-stationary, S-polarized directional (and rotational) discontinuities which self-organize from parallel propagating, linearly polarized waves. Parallel propagating circularly polarized packets evolve to a few circularly polarized Alfvén harmonics on large scales. Stationary arc-polarized rotational discontinuities form from obliquely propagating waves. Collisional dissipation, even if weak, introduces enhanced wave damping when β is very close to unity. Cyclotron motion effects on resonant particle interactions introduce cyclotron resonance into the nonlinear Alfvén wave dynamics.

Capillaries in alginate gel as an example of dissipative structure formation

Abstract Capillaries of uniform diameter (8–300 μm) are formed in a gel growing during diffusion of Me 2+ metal ions into a sol of Na alginate. The alginate chains are cross-linked by the metal ions. The transition from sol to gel is limited by diffusion and occurs in a propagating front. Our investigations provide evidence that the dissipative process of structure formation in this front is caused by friction between the contracting alginate chains and the surrounding solution, leading to a pattern of hydrodynamic flow similar to Rayleigh-Benard convection. This flow pattern is mapped on the growing gel and leads to a structure of parallel capillaries filled with aqueous solution. We present a reduced mathematical model describing the onset of a spontaneous structure formation. The model includes the hydrodynamics of the system formulated by a Navier-Stokes equation. In this equation the frictional force between the contracting alginate chains and the solution plays the role of an external force. A second basic equation describes the binding of alginate molecules to the gel front. The model shows that pattern formation occurs above a critical value of the contraction velocity. This critical value and the spacing of the resulting pattern depend on a number of parameters such as viscosity, chain density, thickness of the contraction zone, friction coefficient between contracting chains and surrounding solution, diffusion constant of alginate and concentration of the sol.

Cellular Automata Simulation of Dissipative Structure Formation in Heterogeneous Polymer Systems, Formation of Networks of a Dispersed Phase by Flocculation

Dissipative structures are responsible for many non-linear property changes in heterogeneous polymer systems, as has been shown experimentally [1] and theoretically [2]. Using the cellular automata program it was possible for the first time to simulate the formation of the complex network structures formed by a complex flocculation process from dispersed particles or phases. The simulation results lead to some interesting conclusions for the behaviour of the real systems.

DISSIPATIVE STRUCTURES IN A DOUBLE PLASMA ON AN EXCITED SEMICONDUCTOR: NEAR ONE-DIMENSIONAL SYSTEMS

The formation of dissipative structures in a double plasma of electron and holes, generated on a semiconductor sample by submitting it to a continuous laser beam, is investigated. The equations of motion for the quasi-particles are obtained after the nonequilibrium statistical operator method and constitute an infinite system of coupled differential equations. When the kinetics of the system is one-dimensional, the search for the eigen-values of the linear stability analysis matrix, in the [Formula: see text] limit, reduces to an equation of 8th degree. The results show that the doped system is intrinsically unstable with respect to the intensity of the laser and that the bifurcation from the stable state to the dissipative structure is from a stable to an unstable node.

Heat and mass transfer in abnormal metal plasticity

The authors show the decisive role and special features of heat and mass transfer in the mechanism of abnormal plasticity and in formation of thermomechanical dissipative structures under large plastic strains by the examples of computer modeling of stretching of a specimen, high-pressure torsional shear in a Bridgeman chamber, and shearing strain of a material in the form of flow of a quasiviscous liquid in a channel with local heat removal via a stationary wall.

Thermodynamic instabilities in machining processes. II. Numerical investigation of stability

A numerical investigation of methods that intensify machining by additional mechanical and thermal actions is performed. Criteria describing the formation of stagnant dissipative structures with thermodynamic instabilities of the technological system and a calculation procedure for machining regimes that ensures stable parameters of the process are proposed.

Schumpeterian growth, chaos, and the formation of dissipative structures

This paper reformulates several basic ideas introduced by Joseph Schumpeter to examine the correlation between productivity growth and technological change in order to explore why American productivity growth has been sluggish for the past two decades. Convetional growth theory maintains that a primary cause of low productivity growth is inadequate capital formation, which in turn is caused by low private domestic saving. This paper borrows concepts from cybernetics, formal information theory, and chaotic dynamic systems to describe the Schumpeterian process through which innovative “new combinations” of capital goods generate wealth, productivity increases, and income growth, and which in turn cause increased savings. It describes the process through which such fundamental technological changes are diffused by entrepreneurs throughout the economy, and concludes that the fundamental causes of America's relatively weak productivity growth are to be found in policies or practices that inhibit innovation and entrepreneurship.

Scaling property in the formation of dissipative structures in a reaction-diffusion system

The asymptotic structure formation dynamics of a reaction-diffusion system is elucidated in terms of a scaling law of the structure function. This reveals that the system evolves much slower than the Swift-Hohenberg equation. It is found that the peak width of the scattering function decays as t -1 8 in a long time. This slow relaxation is due to the coexistence of roll and triangular structures.

Slowing down metal fatigue damage with a magnetic field

It is suggested that metal fatigue and damage can be slowed down with the use of an alternating magnetic field. Through the study of dissipative structure theory, a new idea has been formed: it is suggested that under some specific conditions and using some specific methods which can promote the formation of dissipative structure a metal system may be changed from a chaotic state to a new state of order. In this way, metal fatigue and damage can be checked and possibly even eliminated.

Dissipative structure formation in colloidal systems

Self‐organization phenomena are observed in most real systems. Is this true also for colloidal or microemulsion systems? It is argued that the current general practice of assuming that polymeric and non‐polymeric colloidal systems are in equilibrium is not valid and that non‐equilibrium thermodynamics should be applied. Photon correlation spectroscopy experiments on polyaniline dispersions are considered to indicate the presence of elongated structures (Figure). magnified image

Nonlinear dynamics of the distributed biochemical systems functioning in the dissipative structure formation mode

Nonlinear dynamical biomolecular systems can evidently be considered as prototypes of information processing devices at molecular level capable to solve problems of high computational complexity. Keeping in mind this goal the dynamics of biochemical system based on enzymatic oxidation of uric acid was considered. The system was studied in the version of distributed biomolecular structure having predetermined geometry of enzyme distribution on a porous planar medium. Being in the regime of stepwise dissipative structure formation this system demonstrated complicated modes of behaviour.

The structural-energetic concept in the theory of friction and wear (synergism and self-organization)

The absence of a fundamental approach to friction and wear does not allow for well-founded solutions to the problems of machine service life and reliability control; interdisciplinary nature of tribology is a typical example of this. To find solutions to tribology problems one needs a synthesis of knowledge of mechanics, thermodynamics, material science, physico-chemistry, technology and operation. The fundamentals of tribology lie in the structural-energetic principle (based on the theoretical physics findings on the nature of self-organization and the formation of new phases, i.e. ordered and stable dissipative structures). Dissipative structures form by kinetic phase transition occurring under the cooperative (synergetic) actions of strain, mass transfer and heating. Tribosystems are considered to be open thermodynamic systems that exchange energy and matter with the environment. In the case of friction, all of the processes result from two fundamental phenomena: activation (an increase in the free energy of materials in the tribosystems) and passivation (a decrease). A comprehensive approach is developed that allows us to use a good store of experimental and technical data (graphs, diagrams and tables) as a vast and ever-replenishing bank of tribotechnical characteristics. Possibilities are opened up for an optimal choice of materials, strengthening methods, coatings, lubricants and additives to fit the loading conditions of tribosystems for machines used for various purposes. A systematized physical methodology is presented that allows us to control friction, lubrication and wear through regulation of the activation and passivation processes in tribomaterials by design, technological and operational means. Integral self-organization indexes of tribosystem materials and invariant criteria for the evaluation of the tribosystem state are proposed.

On the probability of cold nuclear fusion implementation: Synergetic hypothesis

Self-organization of matter in non-equilibrium, deuterium-containing systems with dissipative structure formation and separation of subsystems, including atoms having equal excitation degree within them, leads to distortion of the Boltzmann atom distribution in the energy equation and to an increased probability of obtaining by deuterons a sufficient energy packet for nuclear fusion. Calculated intensity of cold fusion is equal to 1·106 original fusion events per 1 cm3 in a second.

Dissipative modulation instability in a nonlinear dispersive ring cavity

We investigate the modulational instability in a synchronously pumped nonlinear dispersive ring cavity. The infinite-dimensional Ikeda map which describes the evolution of the field in the cavity is reduced to a partial derivative equation which allows for analytical developments. We show that, owing to the dissipative nature of the problem, the physics of modulational instability in the ring is fundamentally different from the usual modulational instability in a nonlinear dispersive fiber. In particular, we predict the formation of stable temporal dissipative structures for both the normal and the anomalous dispersion regime of the fiber.

Formation of a regular dissipative structure: a bifurcation and non-linear analysis

A non-linear reaction diffusion model of a negative feedback epigenetic control system is presented. The model involves synthesis of the mitotic inducing and inhibiting proteins, simultaneously with intercellular self-diffusion and cross-diffusion of the latter only. The importance of negative cross-diffusion for creating a regular dissipative structure is shown. A bifurcation analysis of the non-linear diffusive system has been performed and it is concluded that bifurcation is supercritical. Lastly, using Liapunov's direct method, it is shown that the pattern evolved by the system is globally asymptotically stable.

Dissipative Structures in Demixing Binary Liquid Systems

Abstract The demixing of a horizontal fluid layer of far-critical composition in the presence of a vertical temperature gradient can cause the formation of dissipative structures and thereby lead to a regular distribution of the precipitate. The occurrence of these convective structures is explained with the model of a Rayleigh-Benard instability (RBI) which is driven by parallel gradients of temperature and concentration. The distribution of the precipitate is a synergetic effect of the macroscopic convective pattern and the local action of the Marangoni flow at the surfaces of the drops. If boundary conditions prohibit an RBI, the distribution of the precipitate also becomes inhomogeneous in course of time; however, in this case no regular pattern is observable and the inhomogeneities develop mainly due to the Marangoni convection near the surfaces of the larger drops that have settled at the boundary of the sample volume