Search

A derivation of the diffusion equation is presented in non-equilibrium statistical mechanics; for this, the continuity equation is used as a cornerstone. The flow velocity form in the equation is obtained by using the principle of maximum caliber for a system that describes a free particle. With this derivation, it is possible to give a statistical description of classical systems with uncertainty, finding a relationship between the mass of a particle and the diffusion coefficient associated with its displacement. [ABSTRACT FROM AUTHOR]

The goal of this paper was to study the viscosity of liquids and gases in nanochannels. The classical molecular dynamics method is used to simulate the viscosity of liquids in nanochannels. However, the transport coefficients are determined by the special fluctuation-dissipation theorems constructed by the authors on the basis of nonequilibrium statistical mechanics. These theorems generalize the well-known Green–Kubo formulas. The dependences of the viscosity coefficient of argon and benzene in channels made of copper and aluminum with square and circular cross-sections on the size of the channel are studied. The fluid viscosity in the channel can be either greater or less than its viscosity in the bulk. It is shown that the effective viscosity of the fluid can be controlled by changing the material of the channel walls. The decisive role in this effect played the depth of the well of the interaction potential of the wall atoms; with its increase, the effective viscosity of the liquid increases. To simulate the transport coefficients of rarefied gases in nanochannels, a method of stochastic molecular modeling has been developed. The walls are assumed to be solid, and the interaction of fluid molecules with them is described by specular, diffuse, or specular-diffuse reflection laws. A strong anisotropy of the viscosity of the gases in nanochannels, even with rather large sizes, has been established. The viscosity coefficients in different directions can differ by more than ten times. In this case the determining role plays the interaction of the gas molecules with the walls of the channel again. [ABSTRACT FROM AUTHOR]

The viscosity of fluids in a nanochannel between flat plates has been investigated by molecular dynamics method. The effective viscosity coefficient was determined using the previously derived from the nonequilibrium statistical theory fluctuation-dissipation theorem. It has been found that the fluid viscosity in a nanochannel depends strongly on the interaction potential between the fluid and channel walls molecules. Increasing the depth of the potential well of this interaction leads to an increase in the effective viscosity coefficient. At the same time, if the depth of the potential well is small, the fluid viscosity in a nanochannel may be lower than its viscosity in a bulk system. Thus, the fluid viscosity in a nanochannel and hence the channel flow resistance can be varied by changing the material of the nanochannel walls. [ABSTRACT FROM AUTHOR]

One of the cornerstones in non-equilibrium statistical mechanics (NESM) is Liouville's theorem, a differential equation for the phase space probability ρ(q; p; t). This is usually derived considering the flow in or out of a given surface for a physical system (composed of atoms), via more or less heuristic arguments. In this work, we derive the Liouville equation as the partial differential equation governing the dynamics of the time-dependent probability ρ(q; p; t) of finding a "particle" with Lagrangian L(q; q; t) in a specific point (q; p) in phase space at time t, with p = ∂L=∂q. This derivation depends only on considerations of inference over a space of continuous paths. Because of its generality, our result is valid not only for "physical" systems but for any model depending on constrained information about position and velocity, such as time series. [ABSTRACT FROM AUTHOR]

Investigation of heat transfer in an annular porous cylinder subjected to segmental heating is carried out. Thermal non-equilibrium condition is applied to porous medium. Finite element method is used to solve the governing partial differential equations. The fluid is assumed to follow Darcy law. The boundary conditions are such that the fluid and solid phase have different temperatures at the hot wall. The current study is an extension of the paper part-A in this conference but elaborating the results for heat transfer behavior in terms of Nusselt number. [ABSTRACT FROM AUTHOR]

We propose a compact reaction rate formula that accounts for a non-equilibrium distribution of residence times of complex molecules, based on a detailed study of the coarse-grained phase space of a reaction coordinate. We take the structural transition dynamics of a six-atom Morse cluster between two isomers as a prototype of multi-dimensional molecular reactions. Residence time distribution of one of the isomers shows an exponential decay, while that of the other isomer deviates largely from the exponential form and has multiple peaks. Our rate formula explains such equilibrium and non-equilibrium distributions of residence times in terms of the rates of diffusions of energy and the phase of the oscillations of the reaction coordinate. Rapid diffusions of energy and the phase generally give rise to the exponential decay of residence time distribution, while slow diffusions give rise to a non-exponential decay with multiple peaks. We finally make a conjecture about a general relationship between the rates of the diffusions and the symmetry of molecular mass distributions. [ABSTRACT FROM AUTHOR]

A nonequilibrium liquid theory for uniformly sheared granular liquids is developed starting from SLLOD equations. We derive a generalized Green-Kubo formula and demonstrate that it yields the nonequilibrium steady-state average which is essentially independent of the choice of the initial condition. It is also shown that the fluctuating hydrodynamics can be derived from Mori-type equations for density and current-density fluctuations if one considers a weak-shear and small-dissipation limit along with the Markovian approximation. [ABSTRACT FROM AUTHOR]

We propose a new thermodynamic inequality which leads to the maximum work that can be extracted from multi-heat baths with the assistance of discrete quantum feedback control by “Maxwell’s demon.” The maximum work is determined by the free-energy difference and a generalized mutual information content between the thermodynamic system and the feedback controller. [ABSTRACT FROM AUTHOR]

Here I discuss an idea called Maximum Caliber, which provides a useful way to frame problems of non-equilibrium statistical mechanics. It may be particularly useful for treating small-numbers situations, such as those that often arise in biology and in nanotech, where the numbers of particles is very small. In analogy with the way the maximization of entropy over microstates leads to the Boltzmann distribution and predictions about equilibria, maximizing a quantity that E.T. Jaynes called “Caliber” over all the possible microtrajectories leads to the dynamical laws such as Fick's law of diffusion and the mass-action laws of chemical kinetics. The Maximum Caliber method yields dynamical distribution functions that characterize the relative probabilities of different microtrajectories, including “bad actors”, i.e., the microtrajectories that contribute net particle motion in the direction opposite to the macroflux predicted by the Second Law. A potential area of application of Maximum Caliber is modern single-particle and few-molecule experiments that can often observe one individual dynamical particle trajectory at a time. [ABSTRACT FROM AUTHOR]

Intense infrasonic emission was observed prior to the birth of a tropical cyclone [1]. It is connected apparently with instability of atmospheric layers in cyclone area. There are different mechanisms of this effect. Stratified compression flow is unstable [2], providing amplification of its potential component. Cooling of air in upward convection flow makes water vapor supersaturated. This is a nonequilibrium state of fluid where effect of instability can be developed [3]. The equation of infrasonic propagation in such a medium is developed and its solutions are obtained. Corresponding analyses makes it possible to clarify some aspects of cyclone infrasonic precursor. [ABSTRACT FROM AUTHOR]

We study the phenomenon of system size stochastic resonance within the nonequilibrium potential’s (NEP) framework. We analyze a simple spatially extended system and show that through the analysis of the NEP we can obtain a clear physical interpretation of this phenomenon in a wide class of extended systems. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

This paper deals with some thermodynamical aspects of a class of models in nonequilibrium quantum statistical mechanics (QSM) which are commonly used to describe the behaviour of infinite quantum systems perturbed by a time-dependent periodic force. We are interested to the thermodynamical properties of the set of non-equilibrium steady states (NESS) of the perturbed system. We extend the construction of the C-Liouvillean originally introduce in [1] to our time-dependent situation to define the C-Liouvillean of Floquet K[sub F]. The NESS are thus described by zero-resonance eigenvectors of K[sub F, sup *]. We also give a time dependent version of the rate of entropy production [2] for the perturbed system based on the relative entropy as defined by Araki [3] in terms of the relative modular operator. [ABSTRACT FROM AUTHOR]

A new hydrodynamic approach based on non-equilibrium statistical mechanics is developed to describe the structure formation in dynamically deformed materials. Self-consistent non-local formulation of the boundary-value problem for a high-strain-rate process is reduced to a nonlinear operator set similar to some resonance problems. The branching of solutions to the problem determines both scales and types of the formed internal structure. The theory is applied to the shock wave propagation in solids. The experimentally observable velocity decay proves to be closely connected with such kinetic characteristics as velocity dispersion and dissipative structure formation. [ABSTRACT FROM AUTHOR]

We studied the cooperative generation of non-equilibrium localized phonons (fractons), which can be observed in experimental studying of the re laxation of groups of excited atoms after the passage of short laser pulse through the glass sample. The increasing of the absorption coefficient in the process of the excitation of glasses by short laser pulse with relatively small power is conditioned by the generation of the non-equilibriurn coherent localized phonons in the process of the relaxation of non-equilibrium excitations, which strongly change the topology of the random potential and, thus, open a new channel of the interband light absorption. [ABSTRACT FROM AUTHOR]

The electric potential is normally positive outside the cell membrane owing to the active transport of ions. It is a typical nonequilibrium phenomena. We propose a Langevin model with a stochastic boundary condition to simulate the menbrane potential. [ABSTRACT FROM AUTHOR]

I summarize progress in describing classical and quantum fields out of equilibrium. Real-time Monte Carlo methods play an important role in assessing various approximation schemes. © 2003 American Institute of Physics [ABSTRACT FROM AUTHOR]

Analyzes two realistic, physically motivated models that share with Toom's voting model a phase diagram with a broad region of phase coexistence. Conclusion from Toom's model that nonequilibrium systems may exhibit generic bistability, in violation of the equilibrium Gibbs phase rule; Resulting conditions for generic bistability in terms of physically relevant parameters that may be controlled experimentally.