熵定律的不可逆本质论

 熵定律,也就是热力学第二定律,是物理化学中的一个重要定律。无论从宏观的观点出发,还是从微观的角度分析,在热力学理论体系中,熵定律“占有至高无上的地位”。它与热力学第一定律一起,构成了复杂热力学系统能量转换、状态演化方向的度量和判据,且被广泛应用于科学和工程技术的许多领域。然而,如何引入熵定律,如何准确理解熵定律的物理内涵,并适度泛化熵定律,却一直是我们探讨的问题。1.熵定律的表述热力学第二定律,始于19世纪40年代人们对如何提高热机效率问题的研究。     

如何让学生深刻理解熵的概念

 熵的概念,是热力学和统计物理学中非常重要而又较难理解的.克劳修斯(ClaUSiUS.R.J.E,1822-1888德国物理学家)于1850年提出热力学第二定律,1865年提出熵的概念,并将热力学第二定律表述为“宇宙的能量是不变的,而它的熵则总在增加.”现在,熵这个概念已经远远超出了热力学、统计物理学范畴,直接扩展到信息论、控制论、概率论、数论、天体物理、宇宙论、科学管理以及生命系统等各个不同领域.因此,如何在教学中让学生深入理解熵的概念,是一个重要的课题.     

论与熵有关的几个问题

自克劳修斯提出熵这个物理概念后,一百多年来,它的应用已经远远超出了热力学、统计物理学范畴,而直接或间接地波及诸如信息论、控制论、概率论、数论、天体物理、宇宙论乃至生命等各个不同领域。因此,如何在热力学、统计物理课程的教学中,让学生较深入和正确地了解熵概念,是一个重要的课题。本文仅从客观上,就热力学第二定律中熵的概念,谈点粗浅的看法。 熵是热力学第二定律的最有力的概括 在一般热力学教材中,对热力学第二定律的阐述通常是采用:先从大量实验事实归纳出克劳修斯说法、开尔文说法、普朗克说法,进而证明卡诺定理,再推广应用到…     

Schwarzchild-de Sitter 黑洞的热力学性质

在考虑黑洞视界与宇宙视界具有关联性的基础上,证明de Sitter时空的热力学熵为黑洞视界热力学熵与宇宙视界热力学熵之和.给出了考虑两视界具有关联性后的de Sitter时空的热力学特性.研究表明,de Sitter时空的能量上限为纯de Sitter时空能量,deSitter时空的热容量是负的,de Sitter时空一般是量子力学不稳定的.     

对"燃料电池物理及化学性能的有限时间热力学分析法”的讨论

近期在本刊发表的"燃料电池物理及化学性能的有限时间热力学分析法”一文[1],将近20多年来新发展的有限时间热力学理论用于化学过程的研究,是很有意义的,特别是在研究中考虑了化学反应不可逆性和传热不可逆性,更值得提倡和重视.但文献[1]的结果是不正确的,主要对系统和有关环境的总熵产生率计算有问题,概念上有错误.     

与介质有热的和机械的相互作用系统中的H定理

对于孤立系,从玻耳兹曼的积分微分方程出发,已经证明了H定理[1,2].H定理指出,处于非平衡态的气体随时间流逝,必将趋于平衡态.这与热力学第二定律即孤立系的熵不会减少,本质上是一致的.但H函数较之热力学熵更具普遍性,因熵只定义于平衡态.进一步的研究表明,玻氏方程并不是“纯”力学处理的结果.事实上,在导出此方程时引进了与力学规律的时间可逆性相矛盾的分子混沌性假设,正是这个假设使玻氏方程给出H定理的结果. 对于非孤立系,热力学第二定律可用克劳修斯不等式表示:dS≥Q/T,其中dS是熵增量;dQ是任一过程中系统从温度为T的热源吸收的热…     

熵与生命科学

 热力学第二定律指出,一切与热现象有关的实际宏观过程都是不可逆的。而直接反映热力学第二定律的是态函数熵,其数学表达式是熵增加原理：ｄｓ≥０。其物理意义是：一个孤立系统的自发过程总是朝着搞增加的方向进行,即从有序走向无序。而生命的发生、演化及成长过程都是从低级到高级、从无序到有序的变化。表面看来,这似乎都与热力学第二定律相矛盾。普里高津的耗散结构理论澄清了这一切。打开了一个从物理科学通向生命科学的窗口。耗散结构理论突破了热力学第二定律只适用于孤立系统的限制,将其适用范围推广到开放系统,并将热力学第二定律的数学表达式改为ｄｓ＝ｄ１ｓ＋ｄｅｓ。     

计入固液界面作用的润滑热力学模型与分析

摩擦与润滑过程是典型的能量耗散过程, 在机理上与非平衡热力学中的熵增、耗散结构等理论颇有相似之处. 通过热力学分析可以对一些典型的摩擦磨损过程做出合理的机理揭示与推测. 本文利用热力学理论对典型的润滑过程进行了建模分析. 采用分离压模型表征和计入了微尺度下的固液界面作用, 揭示分析了润滑热力学模型与润滑状态Stribeck曲线的联系. 从分析计算结果来看, 润滑Stribeck曲线的摩擦系数最低点与系统热力学上的熵增率最低点具有相当好的对应关系, 而润滑状态从弹流润滑向薄膜润滑的转变过程, 可以用耗散结构理论加以机理解释. 文中的热力学模型和方法能够有效地体现出润滑过程中多物理要素跨尺度非线性耦合的作用, 对实际工程与实验有着重要的指导作用.     

热波传递过程中的熵产分析

傅里叶导热定律导出的温度演化方程将得出无限大的热扰动传播速率。为了克服这个问题,一些修正导热模型被提出,可以得到双曲型温度方程,保证有限的热波传播速率。但是,新的传热模型得出的温度演化将使现有的不可逆热力学中熵产不能保持正定。拓展不可逆热力学通过修正熵以及熵产的表达式,使双曲导热也能得到正定的熵产率。热质理论用力学的概...     

熵与绝热去磁制冷的物理原理

本文从熵的观点出发,利用热力学,统计物理与量子力学理论分别从宏观与微观的角度对磁制冷的物理原理进行了初等分析。     

On the Meaning of Lorentz Covariance

In classical mechanics, Galilean covariance and the principle of relativity are completely equivalent and hold for all possible dynamical processes. In contrast, in relativistic physics the situation is much more complex. It will be shown that Lorentz covariance and the principle of relativity are not completely equivalent. The reason is that the principle of relativity actually only holds for the equilibrium quantities that characterize the equilibrium state of dissipative systems. In the light of this fact it will be argued that Lorentz covariance should not be regarded as a fundamental symmetry of the laws of physics.     

Der harmonische Oszillator an der Oszillationsschwelle Untersuchungen unter dem Aspekt der Phasenübergänge

The harmonic oscillator with positive feed-back is a system far away from thermal equilibrium. Nevertheless, it can be treated as a thermodynamical system when replacing the temperature by the degree of feed-back. Thereby a kind of thermodynamical potentials can be calculated. At the oscillatory threshold all characteristics of 2nd or higher order phase transitions appear, stationary ones as well as dynamical ones. This is shown by calculations and experiments.     

A Variational Principle for Thermodynamical Waves

When the dissipative processes are dominant in the system, the assumption of local equilibrium holds good and the space time evolution of irreversible system can be described by the variational principle of GYARMATI. However when imposed changes in the state variables are fast, the system can not be in a state of local equilibrium and to define the nonequilibrium state of the system it is necessary to extend the formalism of classical irreversible thermodynamics. The wave approach of Onsagerian thermodynamics is one such pursuit and is a direct generalization of the original Onsager-Machlup proposition. An important consequence of this theory is that it leads to transport equations with finite propagation velocities, which are referred to as thermodynamical waves. In this note we endeavour to write the appropriate form of GYARMATI'S variational principle for thermodynamical waves.     

Replica-symmetry breaking in dynamical glasses

Systems of globally coupled logistic maps (GCLM) can display complex collective behaviour characterized by the formation of synchronous clusters. In the dynamical clustering regime, such systems possess a large number of coexisting attractors and might be viewed as dynamical glasses. Glass properties of GCLM in the thermodynamical limit of large system sizes N are investigated. Replicas, representing orbits that start from various initial conditions, are introduced and distributions of their overlaps are numerically determined. We show that for fixed-field ensembles of initial conditions all attractors of the system become identical in the thermodynamical limit up to variations of order 1/, and thus replica symmetry is recovered for N→∞. In contrast to this, when fluctuating-field ensembles of initial conditions are chosen, replica symmetry remains broken in the thermodynamical limit. Received 9 July 2001     

中能重离子核反应的碎裂、集体流和其同位旋效应

本文总结了中能重离子核反应的一般特征及热核反应与衰变过程的动力学、热力学和化学（同位旋组分）效应。尤其是，综合了作者在当前中能重离子核物理研究热点，如多重碎裂，“颈”发射，集体流及其同位旋物理等这些方面的系统性工作，作了较为完整深入的介绍，最后我们还对当前中能重离子核物理的发展前景作了扼要的介绍。     

中能重离子核反应的碎裂、集体流和其同位旋效应

本文总结了中能重离子核反应的一般特征及热核反应与衰变过程的动力学、热力学和化学 (同位旋组分 )效应。尤其是 ,综合了作者在当前中能重离子核物理研究热点 ,如多重碎裂、“颈”发射、集体流及其同位旋物理等这些方面的系统性工作 ,作了较为完整深入的介绍 ,最后我们还对当前中能重离子核物理的发展前景作了扼要的介绍。     

Algebraic theory of the chemical potential and the condition of reactive equilibrium

Under the assumption that the time evolution of an infinite system in thermodynamical equilibrium commutes with a closed, connected proper subgroup of the full gauge group (reflecting the particle structure of the system), it is shown that the chemical potentials satisfy conditions of reactive equilibrium. In addition, it arises as a direct consequence of the compactness of the gauge group that the stoichiometric coefficients are integers.     

Static versus dynamic heterogeneities in the D = 3 Edwards-Anderson-Ising spin glass

We numerically study the aging properties of the dynamical heterogeneities in the Ising spin glass. We find that a phase transition takes place during the aging process. Statics-dynamics correspondence implies that systems of finite size in equilibrium have static heterogeneities that obey finite-size scaling, thus signaling an analogous phase transition in the thermodynamical limit. We compute the critical exponents and the transition point in the equilibrium setting, and use them to show that aging in dynamic heterogeneities can be described by a finite-time scaling ansatz, with potential implications for experimental work.     

Vibrational properties of Re2N and Re3N compounds

Using first-principles calculations, we have studied the structural, lattice dynamical and thermodynamical properties of the recently synthesized Re₂N and Re₃N compounds. The generalized gradient approximation is used to model exchange-correlation effects. The phonon dispersion curves are derived using the direct method. The calculated equilibrium lattice parameters are in overall agreement with the available experimental and theoretical results. The present phonon dispersion results show that both compounds are dynamically stable for the structures considered. The temperature-dependent behavior of thermodynamical properties, such as free energy, entropy, heat capacity, and internal energy, is also presented.