Linear thermodynamic analysis of the reversible Selkov model: An interpretation of the Chatelier‐like principle for local concentration fluctuations near thermodynamic equilibrium

1990 ◽  
Vol 92 (5) ◽  
pp. 3058-3061 ◽  
Author(s):  
Arun K. Dutt
Keyword(s):  
Thermodynamic Analysis ◽  
Thermodynamic Equilibrium ◽  
Concentration Fluctuations ◽  
Local Concentration ◽  
Linear Thermodynamic

Reactive transport in porous media with local mixing limitation: A Lagrangian modeling approach

2020 ◽  
Author(s):  
Guillem Sole-Mari ◽  
Daniel Fernàndez-Garcia ◽  
Xavier Sanchez-Vila ◽  
Diogo Bolster
Keyword(s):  
Porous Media ◽  
Reactive Transport ◽  
Mathematical Formulation ◽  
Random Motion ◽  
Concentration Fluctuations ◽  
Local Concentration ◽  
Flow And Transport ◽  
Transport In Porous Media ◽  
Lagrangian Modeling ◽  
Rate Interaction

<p>Hydrological models are unable to fully resolve subsurface flow and transport down to the microscale. Instead, modelers usually work with upscaled flow and transport properties that represent the behavior of the system at a given coarse scale. While this approach is justified from a practical standpoint, it disregards the local heterogeneity of porous media flows, which tend to produce mixing-limited reactive transport behaviors that cannot be captured by classical modeling approaches. While some innovative methods have been suggested in the past in order to address this problem, none of them has proposed a mathematical formulation which can potentially reproduce the generation, transport and decay of local concentration fluctuations and their impact on chemical reactions, for general initial and boundary conditions. Here, we propose a Lagrangian approach based on the random motion of fluid particles that locally mix following a Multi-Rate Interaction by Exchange with the Mean (MRIEM) formulation. Concentration fluctuations in the proposed model display the typical behavior associated to transport in porous media with mixing-limited conditions. Experimental results of reactive transport are successfully reproduced by the model.</p>

scholarly journals Influence of Concentration Fluctuations on Relaxation Processes in Spin Glasses

2018 ◽  
Vol 2 (4) ◽  
pp. 26 ◽  
Author(s):  
Julia Wagner ◽  
Wolfgang Häußler ◽  
Olaf Holderer ◽  
Andreas Bauer ◽  
Stephen Shapiro ◽  
...  
Keyword(s):  
Phase Transition ◽  
Spin Glass ◽  
Spin Glasses ◽  
Glass Phase ◽  
Concentration Fluctuations ◽  
Neutron Resonance ◽  
Relaxation Processes ◽  
Local Concentration ◽  
Spin Glass Phase ◽  
Resonance Spin

Using the unique combination of atomically resolved atom probe tomography (APT) and volume averaged neutron (resonance) spin echo (NRSE and NSE) experiments, the influence of nano-scaled clusters on the spin relaxation in spin glasses was studied. For this purpose, the phase transition from the paramagnetic phase to the spin glass phase in an Fe-Cr spin glass with a composition of Fe 17 . 8 Cr 82 . 2 was studied in detail by means of NRSE. The microstructure was characterised by APT measurements, which show local concentration fluctuations of Fe and Cr on a length scale of 2 to 5 nm, which lead (i) to the coexistence of ferro- and anti-ferromagnetic clusters and (ii) a change of the magnetic properties of the whole sample, even in the spin glass phase, where spins are supposed to be randomly frozen. We show that a generalized spin glass relaxation function, which was successfully used to describe the phase transition in diluted spin glasses, can also be used for fitting the spin dynamics in spin glasses with significant concentration fluctuations.

scholarly journals Thermodynamic analysis based on the second-order variations of thermodynamic potentials

2008 ◽  
Vol 35 (1-3) ◽  
pp. 215-234 ◽  
Author(s):  
Vlado Lubarda
Keyword(s):  
Thermodynamic Analysis ◽  
Thermodynamic Equilibrium ◽  
Second Order ◽  
Constrained Minimization ◽  
Specific Heats ◽  
Thermodynamic Relationships ◽  
Thermodynamic Potentials ◽  
Convexity Properties ◽  
Classical Derivation

An analysis of the Gibbs conditions of stable thermodynamic equilibrium based on the constrained minimization of the four fundamental thermodynamic potentials, is presented with a particular attention given to the previously unexplored connections between the second-order variations of thermodynamic potentials. These connections are used to establish the convexity properties of all potentials in relation to each other, which systematically deliver thermodynamic relationships between the specific heats, and the isentropic and isothermal bulk moduli and compressibilities. The comparison with the classical derivation is then given.

scholarly journals Iron Catalyst Local Concentration Fluctuations Found in Dissipative Reactions by X-Ray Microanalysis

1981 ◽  
Vol 54 (1) ◽  
pp. 321-322 ◽  
Author(s):  
Csaba P. Keszthelyi ◽  
József Soós ◽  
András G. S. Janossy ◽  
Kristóf Vovács
Keyword(s):  
Iron Catalyst ◽  
Concentration Fluctuations ◽  
Local Concentration ◽  
X Ray

scholarly journals Simulation of V(CN) Precipitation in Steels Allowing for Local Concentration Fluctuations

2006 ◽  
Vol 47 (11) ◽  
pp. 2732-2736 ◽  
Author(s):  
Javier Aldazabal ◽  
Carlos Garcia-Mateo ◽  
Carlos Capdevila
Keyword(s):  
Concentration Fluctuations ◽  
Local Concentration
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