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      Optimal configuration of a finite mass reservoir isothermal chemical engine for maximum work output with linear mass transfer law

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          Abstract

          An isothermal endoreversible chemical engine operating between a finite high-chemical- potential reservoir and an infinite low-chemical-potential reservoir in which the mass transfer between the working fluid and the mass reservoirs obeys the linear mass-transfer law [g α Δµ] is put forward in this paper. Optimal control theory is applied to determine the optimal cycle configuration corresponding to the maximum work output for the fixed total cycle time. The optimal cycle configuration is an isothermal endoreversible chemical engine cycle in which the chemical potential (concentration) of the key component in the finite high-chemical- potential mass reservoir and that in the working fluid change nonlinearly with time. The difference in chemical potentials (ratio of the concentrations) between the key component in the finite mass reservoir and the working fluid is a constant, and the chemical potential (concentration) of the key component in the working fluid at the low chemical potential side is also a constant. A numerical example is provided, and the effects of the concentration changes in the key component in the finite high-chemical-potential reservoir on the optimal configuration of the chemical engine are analyzed. The obtained results are compared with those obtained for an endoreversible heat engine operating between a finite heat source and an infinite heat sink with Newton's heat transfer law [q α ΔT]; in the heat transfer processes. The object studied in this paper is general, and the results could provide some guidelines for the optimal design and operation of real chemical engines.

          Translated abstract

          En el presente trabajo se presenta un motor químico endoreversible isotérmico trabajando entre un recipiente finito de alto potencial químico y un recipiente infinito de bajo potencial químico, en el cual, la transferencia de masa entre el fluido de trabajo y la masa contenida obedece a la ley lineal de transferencia de masa [g α Δµ];. Se aplica la teoría del control óptimo para determinar la configuración óptima del ciclo, correspondiente al máximo trabajo de salida para el tiempo total del ciclo. La configuración del ciclo óptimo es el de un motor químico endoreversible isotérmico en el cual, el potencial químico (concentración) de la componente clave en el recipiente finito masivo de alto potencial químico y el del fluido de trabajo cambian de forma no lineal con el tiempo. La diferencia en los potenciales químicos (cociente de las concentraciónes) entre el componente clave del recipiente finito masivo y el fluido de trabajo es una constante, y el potencial químico (concentración) del componente clave en el fluido de trabajo del lado del potencial químico bajo es también una constante. Se proporciona un ejemplo numérico donde se analizan los efectos del cambio en la concentración en la componente clave del recipiente finito con alto potencial químico respecto de la configuración óptima del motor químico. Los resultados obtenidos se comparan con los obtenidos para un motor térmico endoreversible que trabaja entre una fuente de calor finita y un disipador de calor infinito, que obedece a la ley de Newton de transferencia de calor (q α ΔT) en los procesos de tranferencia de calor. El objeto de estudió en el presente trabajo es general y los resultados podrían proporcionar algunas pautas para el diseño óptimo y funcionamiento de motores químicos reales.

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          Lattice simulation method to model diffusion and NMR spectra in porous materials

          A coarse-grained simulation method to predict NMR spectra of ions diffusing in porous carbons is proposed. The coarse-grained model uses input from molecular dynamics simulations such as the free-energy profile for ionic adsorption, and density-functional theory calculations are used to predict the NMR chemical shift of the diffusing ions. The approach is used to compute NMR spectra of ions in slit pores with pore widths ranging from 2 to 10 nm. As diffusion inside pores is fast, the NMR spectrum of an ion trapped in a single mesopore will be a sharp peak with a pore size dependent chemical shift. To account for the experimentally observed NMR line shapes, our simulations must model the relatively slow exchange between different pores. We show that the computed NMR line shapes depend on both the pore size distribution and the spatial arrangement of the pores. The technique presented in this work provides a tool to extract information about the spatial distribution of pore sizes from NMR spectra. Such information is diffcult to obtain from other characterisation techniques.
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            Path Integral Molecular Dynamics within the Grand Canonical-like Adaptive Resolution Technique: Simulation of Liquid Water

            , (2015)
            Quantum effects due to the spatial delocalization of light atoms are treated in molecular simulation via the path integral technique. Among several methods, Path Integral (PI) Molecular Dynamics (MD) is nowadays a powerful tool to investigate properties induced by spatial delocalization of atoms; however computationally this technique is very demanding. The abovementioned limitation implies the restriction of PIMD applications to relatively small systems and short time scales. One possible solution to overcome size and time limitation is to introduce PIMD algorithms into the Adaptive Resolution Simulation Scheme (AdResS). AdResS requires a relatively small region treated at path integral level and embeds it into a large molecular reservoir consisting of generic spherical coarse grained molecules. It was previously shown that the realization of the idea above, at a simple level, produced reasonable results for toy systems or simple/test systems like liquid parahydrogen. Encouraged by previous results, in this paper we show the simulation of liquid water at room conditions where AdResS, in its latest and more accurate Grand-Canonical-like version (GC-AdResS), is merged with two of the most relevant PIMD techniques available in literature. The comparison of our results with those reported in literature and/or with those obtained from full PIMD simulations shows a highly satisfactory agreement.
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              Correlated interaction fluctuations in photosynthetic complexes

              The functioning and efficiency of natural photosynthetic complexes is strongly influenced by their embedding in a noisy protein environment, which can even serve to enhance the transport efficiency. Interactions with the environment induce fluctuations of the transition energies of and interactions between the chlorophyll molecules, and due to the fact that different fluctuations will partially be caused by the same environmental factors, correlations between the various fluctuations will occur. We argue that fluctuations of the interactions should in general not be neglected, as these have a considerable impact on population transfer rates, decoherence rates and the efficiency of photosynthetic complexes. Furthermore, while correlations between transition energy fluctuations have been studied, we provide the first quantitative study of the effect of correlations between interaction fluctuations and transition energy fluctuations, and of correlations between the various interaction fluctuations. It is shown that these additional correlations typically lead to changes in interchromophore transfer rates, population oscillations and can lead to a limited enhancement of the light harvesting efficiency.
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                Author and article information

                Journal
                rmf
                Revista mexicana de física
                Rev. mex. fis.
                Sociedad Mexicana de Física (México, DF, Mexico )
                0035-001X
                October 2009
                : 55
                : 5
                : 399-408
                Affiliations
                [01] Wuhan orgnameNaval University of Engineering orgdiv1Postgraduate School China
                Article
                S0035-001X2009000500011 S0035-001X(09)05500500011
                be25f71e-09c0-43a7-bd69-8c8a951f5e16

                This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

                History
                : 27 July 2009
                : 30 September 2009
                Page count
                Figures: 0, Tables: 0, Equations: 0, References: 60, Pages: 10
                Product

                SciELO Mexico

                Categories
                Research

                generalized thermodynamic optimization,optimal control,maximum work output,isothermal endoreversible chemical engine,Finite high-chemical-potential reservoir,optimización termodinámica generalizada,control óptimo,máximo trabajo de salida,motor químico isotérmico endoreversible,Recipiente finito de alto potencial químico

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