The Rate-Controlled Constrained-Equilibrium Approach to Far-From-Local-Equilibrium Thermodynamics

The Rate-Controlled Constrained-Equilibrium (RCCE) method for the description of the time-dependent behavior of dynamical systems in non-equilibrium states is a general, effective, physically based method for model order reduction that was originally developed in the framework of thermodynamics and chemical kinetics. A generalized mathematical formulation is presented here that allows including nonlinear constraints in non-local equilibrium systems characterized by the existence of a non-increasing Lyapunov functional under the system’s internal dynamics. The generalized formulation of RCCE enables to clarify the essentials of the method and the built-in general feature of thermodynamic consistency in the chemical kinetics context. In this paper, we work out the details of the method in a generalized mathematical-physics framework, but for definiteness we detail its well-known implementation in the traditional chemical kinetics framework. We detail proofs and spell out explicit functional dependences so as to bring out and clarify each underlying assumption of the method. In the standard context of chemical kinetics of ideal gas mixtures, we discuss the relations between the validity of the detailed balance condition off-equilibrium and the thermodynamic consistency of the method. We also discuss two examples of RCCE gas-phase combustion calculations to emphasize the constraint-dependent performance of the RCCE method.Fondazione Cariplo (grant 2008-2290)United States. Army Research Office (grant number W911NF-08-1-0444

Entropy transport equation in large eddy simulation for exergy analysis of turbulent combustion systems

The transport equation of entropy is introduced in large eddy simulation to perform exergy analysis of turbulent combustion systems. The sources of exergy destruction can be evaluated by analyzing entropy generation terms, which appear in unclosed forms in this equation. The closure is based on the filtered density function (FDF) methodology. The primary advantage of FDF is that chemical reaction and its entropy generation effects appear in closed forms. This methodology involves a stochastic model, which is being developed to account for the subgrid scale transport of entropy

Degree of Disequilibrium analysis for automatic selection of kinetic constraints in the Rate-Controlled Constrained-Equilibrium method

The Rate-Controlled Constrained-Equilibrium (RCCE) model reduction scheme for chemical kinetics provides acceptable accuracies with a number of differential equations much lower than the number of species in the underlying Detailed Kinetic Model (DKM). To yield good approximations, however, the method requires accurate identification of the rate controlling constraints. So far, a drawback of the RCCE scheme has been the absence of a fully automatable and systematic procedure that is capable of identifying the best constraints for a given range of thermodynamic conditions and a required level of approximation. In this paper, we propose a new methodology for such identification based on a simple algebraic analysis of the results of a preliminary simulation of the underlying DKM, which is focused on the behavior of the degrees of disequilibrium (DoD) of the individual chemical reactions. The new methodology is based on computing an Approximate Reduced Row Echelon Form of the Actual Degrees of Disequilibrium (ARREFADD) with respect to a preset tolerance level. An alternative variant is to select an Approximate Singular Value Decomposition of the Actual Degrees of Disequilibrium (ASVDADD). Either procedure identifies a low dimensional subspace in the DoD space, from which the actual DoD traces do not depart beyond a fixed distance related to the preset tolerance (ARREFADD methodology) or to the first neglected singular value of the matrix of DoD traces (ASVDADD methodology). The effectiveness and robustness of the method is demonstrated for the case of a very rapid supersonic nozzle expansion of the products of hydrogen and methane oxycombustion and for the case of methane/oxygen ignition. The results are in excellent agreement with DKM predictions. For both variants of the method, we provide a simple Matlab code implementing the proposed constraint selection algorithm

Microstructural evolution, mechanical properties, and corrosion resistance of a heat-treated Mg alloy for the bio-medical application

During the recent years, some Mg based alloys have extensively been considered as a new generation of degradable and absorbable bio-medical materials. In this work, the Mg–2Zn–1Gd–1Ca (wt%) alloy as a new metallic bio-material was produced by the casting process followed by the heat treatment. The samples of the alloy were solution treated at temperatures of 500, 550, and 600 °C and then quench aged at temperatures of 125, 150, and 175 °C. The results of SEM-EDS examinations indicated that the alloy microstructure consists of α-Mg matrix and the Ca2Mg6Zn3 and Mg3Gd2Zn3 secondary phases. With regard to the results of Vickers hardness test, the temperatures of 500 °C and 150 °C were selected as the optimum solutionizing and aging temperatures, respectively. Moreover, the dissolution of casting precipitates and production of lattice distortion occurring after the solution treatment led to the reduction in ultimate shear strength up to 21%. But, the precipitation hardening and morphological changes taking place during the aging treatment improved the ultimate shear strength up to 32%. Furthermore, the results of electro-chemical and weight-loss measurements in a simulated body fluid indicated that the heat-treated alloy is a promising candidate for the Mg based alloys recently considered for the bio-medical applications. Keywords: Mg alloys, Bio-medical applications, Microstructural evolution, Mechanical properties, Corrosion resistanc

Uses of Complementary and Alternative Medicine in Multiple Sclerosis

Multiple sclerosis (MS) is a chronic, disabling, recurrent demyelination of the central nervous system (CNS). It could affect different regions in the brain and spinal cord, and according to the domain which is affected, it could cause different symptoms such as motor, sensory, or visual impairment; fatigue; bowel, bladder, and sexual dysfunction; cognitive impairment; and depression. MS patients also face reduced quality of life. Drugs that are used in MS are not fully efficient and patients suffer from many symptoms and adverse effects. Today there is an increasing trend of using complementary and alternative medicine (CAM). People are more likely to use this type of treatment. Using appropriate lifestyle and CAM therapy can subside some of the symptoms and could improve the quality of life in these patients. Many people with MS explore CAM therapies for their symptoms. This review is aimed to introduce CAM therapies that could be used in MS patients

Measurement Of Systemic Thinking Among TUMS Senior Managers Using Goldman Strategic Model

Background and Aim: Strategic thinking plays a very important role in guarding organizational survival and increasing development in today's dynamic and changing environment. One of the elements of strategic thinking is systemic thinking, which forms the conceptual framework to solve issues in an organization. This study aims to determine the ability of Tehran University of Medical Sciences (TUMS) senior managers to stick to systemic thinking based on Friedrik Goldman’s model. Materials and Methods: This is a cross-sectional, descriptive- analytic study conducted on a sample of 100 TUMS senior managers in 2010. The data collection instrument was a standard questionnaire on systemic thinking, the response rate of which turned out to be 97%. The reliability and validity of the questionnaire were confirmed prior to its distribution. SPSS software was used for data analysis. To this end, single sample t-test and Friedman statistical methods were also applied. Results: The findings revealed that the ability of systemic thinking was optimal among most TUMS senior managers. Conclusion : Enhancing and strengthening systemic thinking among TUMS senior managers are suggested, especially regarding omniscient and multi-end approach