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Non-equilibrium thermodynamics is a branch of thermodynamics that deals with thermodynamic systems that are not in thermodynamic equilibrium. Most systems found in nature are not in thermodynamic equilibrium; for they are changing or can be triggered to change over time, and are continuously and discontinuously subject to flux of matter and energy to and from other systems and to chemical reactions. Non-equilibrium thermodynamics is concerned with transport processes and with the rates of chemical reactions.〔Fowler, R., Guggenheim, E.A. (1939). ''Statistical Thermodynamics'', Cambridge University Press, Canbridge UK, page vii.〕 Today, many natural systems still remain beyond the scope of currently known macroscopic thermodynamic methods. The thermodynamic study of non-equilibrium systems requires more general concepts than are dealt with by equilibrium thermodynamics. One fundamental difference between equilibrium thermodynamics and non-equilibrium thermodynamics lies in the behaviour of inhomogeneous systems, which require for their study knowledge of rates of reaction which are not considered in equilibrium thermodynamics of homogeneous systems. This is discussed below. Another fundamental difference is the difficulty in defining entropy in macroscopic terms for systems not in thermodynamic equilibrium.〔Grandy, W.T., Jr (2008). ''Entropy and the Time Evolution of Macroscopic Systems''. Oxford University Press. ISBN 978-0-19-954617-6.〕〔Lebon, G., Jou, D., Casas-Vázquez, J. (2008). ''Understanding Non-equilibrium Thermodynamics: Foundations, Applications, Frontiers'', Springer-Verlag, Berlin, e-ISBN 978-3-540-74252-4.〕 ==Overview== Non-equilibrium thermodynamics is a work in progress, not an established edifice. This article will try to sketch some approaches to it and some concepts important for it. Some concepts of particular importance for non-equilibrium thermodynamics include time rate of dissipation of energy (Rayleigh 1873, Onsager 1931, also〔Gyarmati, I. (1970). ''Non-equilibrium Thermodynamics. Field Theory and Variational Principles'', translated by E. Gyarmati and W.F. Heinz, Springer, Berlin.〕〔Lavenda, B.H. (1978). ''Thermodynamics of Irreversible Processes'', Macmillan, London, ISBN 0-333-21616-4.〕), time rate of entropy production (Onsager 1931),〔 thermodynamic fields,〔Gyarmati, I. (1967/1970) ''Non-equilibrium Thermodynamics. Field Theory and Variational Principles'', translated by E. Gyarmati and W.F. Heinz, Springer, New York, pages 4-14.〕〔Ziegler, H., (1983). ''An Introduction to Thermomechanics'', North-Holland, Amsterdam, ISBN 0-444-86503-9.〕〔Balescu, R. (1975). ''Equilibrium and Non-equilibrium Statistical Mechanics'', Wiley-Interscience, New York, ISBN 0-471-04600-0, Section 3.2, pages 64-72.〕 dissipative structure,〔 and non-linear dynamical structure.〔 One problem of interest is the thermodynamic study of non-equilibrium steady states, in which entropy production and some flows are non-zero, but there is no time variation of physical variables. One initial approach to non-equilibrium thermodynamics is sometimes called 'classical irreversible thermodynamics'.〔 There are other approaches to non-equilibrium thermodynamics, for example extended irreversible thermodynamics,〔〔 and generalized thermodynamics,〔Eu, B.C. (2002). ''Generalized Thermodynamics. The Thermodynamics of Irreversible Processes and Generalized Hydrodynamics'', Kluwer Academic Publishers, Dordrecht, ISBN 1-4020-0788-4.〕 but they are hardly touched on in the present article. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「nonequilibrium thermodynamics」の詳細全文を読む スポンサード リンク
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