The Experts below are selected from a list of 732 Experts worldwide ranked by ideXlab platform

Klaus Regenauer-lieb - One of the best experts on this subject based on the ideXlab platform.

  • Cross-diffusion waves in hydro-poro-mechanics
    Journal of The Mechanics and Physics of Solids, 2020
    Co-Authors: Christoph Schrank, Klaus Regenauer-lieb
    Abstract:

    We propose a new class of wave-phenomena in multiphase solids (and granular media) triggered by Hydro-Poro-Mechanical coupling and cross-diffusion feedbacks of porous materials. We define cross-diffusion as the phenomenon when a Generalized Thermodynamic Force induces a Generalized Thermodynamic flux of another kind. Addition of cross-diffusion relaxes the adiabatic constraints on the reaction part of the system and corrects the mathematical ill-posedness. We identify the important aspect of cross-diffusion terms and present a linear stability analysis of the governing partial differential equations (PDE’s). Multiple transient wave instabilities are found as solutions of the coupled PDE’s. In the long-wavelength limit (long-time scale) these waves feed into solitary waves that are standing wave patterns frozen into the porous medium at various scales. We revisit earlier work showing that the wavenumber of the standing wave is entirely defined by the ratio of the mechanical over the fluid (self-diffusion) coefficients of the coupled reaction-cross-diffusion equations. Diffusion coefficients are hence identified as material parameters controlling the criterion for nucleation of waves and the signature of both transient cross- and stationary self-diffusion waves. We show examples of self- and cross-diffusion waves in nature and laboratory experiments as stationary and time-lapse diffusional waves. Our approach offers a simple mathematical framework for analysis of coupled hydro-mechanical porous medium, providing a new fundamental perspective for analyses of the initiation of macroscopic instabilities and transient precursors in many disciplines.

Christoph Schrank - One of the best experts on this subject based on the ideXlab platform.

  • Cross-diffusion waves in hydro-poro-mechanics
    Journal of The Mechanics and Physics of Solids, 2020
    Co-Authors: Christoph Schrank, Klaus Regenauer-lieb
    Abstract:

    We propose a new class of wave-phenomena in multiphase solids (and granular media) triggered by Hydro-Poro-Mechanical coupling and cross-diffusion feedbacks of porous materials. We define cross-diffusion as the phenomenon when a Generalized Thermodynamic Force induces a Generalized Thermodynamic flux of another kind. Addition of cross-diffusion relaxes the adiabatic constraints on the reaction part of the system and corrects the mathematical ill-posedness. We identify the important aspect of cross-diffusion terms and present a linear stability analysis of the governing partial differential equations (PDE’s). Multiple transient wave instabilities are found as solutions of the coupled PDE’s. In the long-wavelength limit (long-time scale) these waves feed into solitary waves that are standing wave patterns frozen into the porous medium at various scales. We revisit earlier work showing that the wavenumber of the standing wave is entirely defined by the ratio of the mechanical over the fluid (self-diffusion) coefficients of the coupled reaction-cross-diffusion equations. Diffusion coefficients are hence identified as material parameters controlling the criterion for nucleation of waves and the signature of both transient cross- and stationary self-diffusion waves. We show examples of self- and cross-diffusion waves in nature and laboratory experiments as stationary and time-lapse diffusional waves. Our approach offers a simple mathematical framework for analysis of coupled hydro-mechanical porous medium, providing a new fundamental perspective for analyses of the initiation of macroscopic instabilities and transient precursors in many disciplines.

Klymko Katherine - One of the best experts on this subject based on the ideXlab platform.

  • Statistical Mechanics and Dynamics of Driven and Active Systems
    eScholarship University of California, 2018
    Co-Authors: Klymko Katherine
    Abstract:

    Systems driven out of equilibrium display a rich variety of patterns and surprising response behaviors. There exist different types of non-equilibrium processes, for instance a system that has been prepared in a non-Boltzmann initial state and is relaxing back to equilibrium, or a system that adopts a non-equilibrium steady state distribution when it is driven by an external field. In these different cases, the main characteristic that distinguishes these systems as non-equilibrium is that they are constantly dissipating heat, or likewise producing entropy. This entropy production is often the starting point for developing a systematic theory to describe such non-equilibrium processes.Entropy production can be related to the irreversible processes occurring within a system. Particularly strong statements can be made about non-equilibrium systems when a local equilibrium assumption can be made, that is, when smaller subsets of a large system can be considered to be in equilibrium. This turns out to be justified for a wide variety of systems under different conditions. When this holds, the entropy production can be written as a Generalized Thermodynamic Force (often the gradient of some intensive variable of the system) multiplied by a flux. When the Thermodynamic Force is small, the fluxes can be written as linear combinations of the Thermodynamic Forces, connected by response coefficients–this is known as linear irreversible Thermodynamics. The full extension of equilibrium Thermodynamic concepts to dissipative processes beyond this linear regime, including the development of microscopic principles justifying irreversible Thermodynamic theories (as equilibrium statistical mechanics justifies equilibrium Thermodynamics), is still a work in progress.In this thesis, we work towards advancing the Thermodynamic theory of non-equilibrium phenomena by studying models of driven-diffusive systems, growth processes, and active matter. We use developments from stochastic Thermodynamics, large deviation theory, and irreversible Thermodynamics to characterize the non-equilibrium phases and properties exhibited by these systems. We question to what extent equilibrium approximations are valid for predicting pattern formation in these systems and whether there exist general unifying features describing these non-equilibriums processes. In the process we develop trajectory sampling methods to investigate the statistics of dynamical order parameters distinguishing these phases. We show how the first and second laws of Thermodynamics, including consistent expressions for entropy production, can be extended to active systems, where microscopic reversibility is broken at the level of individual particles. Additionally we derive fluctuation relations, exact analytical results for the fluctuations of entropy production in the form of equalities, for the entropy production in active systems. We also extend the Irving-Kirkwood procedure to active systems, deriving the balance laws of mass, momentum, and energy. Consequently we obtain expressions for the stress and couple stress tensors in the system as functions of the microscopic variables. This provides a foundation to extend the framework of irreversible Thermodynamics to active systems

Salimi S. - One of the best experts on this subject based on the ideXlab platform.

  • Bounds on charging power of open quantum batteries
    2020
    Co-Authors: Zakavati S., Tabesh F. T., Salimi S.
    Abstract:

    In general, quantum systems most likely undergo open system dynamics due to their smallness and sensitivity. Energy storage devices, so-called quantum batteries, are not excepted from this phenomenon. Here, we study fundamental bounds on the power of open quantum batteries from the geometric point of view. By defining an \emph{activity operator}, a tight upper bound on the charging power is derived for the open quantum batteries in terms of the fluctuations of the activity operator and the quantum Fisher information. The variance of the activity operator may be interpreted as a Generalized Thermodynamic Force, while the quantum Fisher information describes the speed of evolution in the state space of the battery. The Thermodynamic interpretation of the upper bound is discussed in detail. As an example, a model for the battery, taking into account the environmental effects, is proposed and the effect of dissipation and decoherence during the charging process on both the stored work and the charging power is investigated. Our results show that the upper bound is saturated in some time intervals. Also, the maximum value of both the stored work and the corresponding power is achieved under the non-Markovian dynamics and underdamped regime.Comment: 9 pages, 6 figure

Zakavati S. - One of the best experts on this subject based on the ideXlab platform.

  • Bounds on charging power of open quantum batteries
    2020
    Co-Authors: Zakavati S., Tabesh F. T., Salimi S.
    Abstract:

    In general, quantum systems most likely undergo open system dynamics due to their smallness and sensitivity. Energy storage devices, so-called quantum batteries, are not excepted from this phenomenon. Here, we study fundamental bounds on the power of open quantum batteries from the geometric point of view. By defining an \emph{activity operator}, a tight upper bound on the charging power is derived for the open quantum batteries in terms of the fluctuations of the activity operator and the quantum Fisher information. The variance of the activity operator may be interpreted as a Generalized Thermodynamic Force, while the quantum Fisher information describes the speed of evolution in the state space of the battery. The Thermodynamic interpretation of the upper bound is discussed in detail. As an example, a model for the battery, taking into account the environmental effects, is proposed and the effect of dissipation and decoherence during the charging process on both the stored work and the charging power is investigated. Our results show that the upper bound is saturated in some time intervals. Also, the maximum value of both the stored work and the corresponding power is achieved under the non-Markovian dynamics and underdamped regime.Comment: 9 pages, 6 figure