共查询到20条相似文献,搜索用时 140 毫秒
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本文导出一种计算非晶态物质径向分布函数的最大熵方法,给出非晶态D2O径向分布函数的计算实例,并与传统的傅里叶变换法进行了比较,结果表明,最大熵方法对结构信息的反映更为敏感,因而,在同样实验数据的条件下,最大熵方法可能比传统的傅里叶变换法提供更多的结构信息。
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统计物理方法在离散变量模型中的应用及推广 总被引:1,自引:0,他引:1
提出离散变量模型,并基于此模型由最大熵原理出发,展现了统计物理方法在热力学系统中的具体应用.该方法可以推广应用至由大量"个体"所构成的"总体"非物理系统中,如金融系统,社会生产系统等.文中还指出由最大熵原理得到的概率分布函数同时适用于平衡态和非平衡定态的热力学系统. 相似文献
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从粉末衍射数据直接测定晶体结构介材料和晶体学研究的热门课题之一。文章介绍了粉末衍射结构的最大熵法。最大熵法是基于信息论的最大熵原理和最大似然原理的一种方法。由于其独特的优点,最大熵法是最有前景的粉末衍射结构分析方法之一。 相似文献
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稳定温度场的有限元法 对于边界为f的平面物体G,根据变分原理,可以证明满足拉普拉斯方程和第三类边界条件的温度函数t(x,y)是使如下泛函取极小的函数:文献[1]指出,根据不可逆过程热力学的昂色格理论和定态最小熵产生率原理,U(t)是与该物体系统熵产生率相联系的量,而该泛函取极小即是系统定态最小熵产生率原理。同样可以证明,相应于第二类边界条件的泛函为: 相似文献
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不同目的热优化目标函数:热量传递势容损耗与熵产 总被引:4,自引:0,他引:4
热量传递势容(势容)反映了物体的导热能力,在导热过程中势容有损耗,对应于势容损耗最小的导热过程效率最高,传热速率最大。熵反映了过程的不可逆性,在导热过程中熵有增加(熵产),对应于熵产最小的过程是系统做有用功的能力((?))损失最小的过程。以势容损耗和熵产为目标函数,分别对导热平板和圆形导热管进行了导热优化计算。以势容损耗作为目标函数的优化,要求沿传热方向温度的梯度为常数,结果是系统具有最大的导热能力。以熵产作为目标函数的优化,要求沿传热方向温度的自然对数的梯度为常数,结果是系统具有最小的(?)损耗。 相似文献
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乘代数重建法和最大熵重建法比较研究 总被引:5,自引:0,他引:5
本文从最大熵原理引入拉格朗日因子推导出乘代数重建法(MART)和最大熵重建法(MENT),同时他们是等价的,只是迭代方法不同而已。而且用实例进行模拟计算,计算结果也表明这两种方法收敛情况和重建精度完全一致,从而进一步证明MART和MENT的等价性。 相似文献
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The aim of this paper is to show that the procedure of maximum entropy principle for the closure of the moments equations for rarefied monatomic gases can be extended also to polyatomic gases. The main difference with respect to the usual procedure is the existence of two hierarchies of macroscopic equations for moments of suitable distribution function, in which the internal energy of a molecule is taken into account. The field equations for 14 moments of the distribution function, which include dynamic pressure, are derived. The entropy and the entropy flux are shown to be a generalization of the ones for classical Grad’s distribution. The results are in perfect agreement with the recent macroscopic approach of extended thermodynamics for real gases. 相似文献
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Molecular extended thermodynamics of rarefied polyatomic gases is characterized by two hierarchies of equations for moments of a suitable distribution function in which the internal degrees of freedom of a molecule is taken into account. On the basis of physical relevance the truncation orders of the two hierarchies are proven to be not independent on each other, and the closure procedures based on the maximum entropy principle (MEP) and on the entropy principle (EP) are proven to be equivalent. 相似文献
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Jan Korbel 《Entropy (Basel, Switzerland)》2021,23(1)
The maximum entropy principle consists of two steps: The first step is to find the distribution which maximizes entropy under given constraints. The second step is to calculate the corresponding thermodynamic quantities. The second part is determined by Lagrange multipliers’ relation to the measurable physical quantities as temperature or Helmholtz free energy/free entropy. We show that for a given MaxEnt distribution, the whole class of entropies and constraints leads to the same distribution but generally different thermodynamics. Two simple classes of transformations that preserve the MaxEnt distributions are studied: The first case is a transform of the entropy to an arbitrary increasing function of that entropy. The second case is the transform of the energetic constraint to a combination of the normalization and energetic constraints. We derive group transformations of the Lagrange multipliers corresponding to these transformations and determine their connections to thermodynamic quantities. For each case, we provide a simple example of this transformation. 相似文献
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The maximum entropy principle can be used to assign utility values when only partial information is available about the decision maker’s preferences. In order to obtain such utility values it is necessary to establish an analogy between probability and utility through the notion of a utility density function. In this paper we explore the maximum entropy principle to estimate the utility function of a risk averse decision maker. 相似文献
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Based on the principle of maximum entropy, the q-exponential distribution can be derived from several different nonextensive entropies including the incomplete entropy. It is widely used in nonextensive statistical mechanics. In the present paper, it is shown that the incomplete expectation value and incomplete entropy are stable under small deformation of the probability distribution function of the system. 相似文献
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重力场中的大气处于非平衡态,其温度是空间的函数,不同的等温面之间要产生热流,从而改变熵的空间分布。本文推导出重力场中的熵产生公式,并描绘出熵产生随高度变化的近似曲线。 相似文献
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Entropy generation is often used as a figure of merit in thermodynamic cycle optimizations. In this paper, it is shown that the applicability of the minimum entropy generation method to optimizing output power is conditional. The minimum entropy generation rate and the minimum entropy generation number do not correspond to the maximum output power when the total heat into the system of interest is not prescribed. For the cycles whose working medium is heated or cooled by streams with prescribed inlet temperatures and prescribed heat capacity flow rates, it is theoretically proved that both the minimum entropy generation rate and the minimum entropy generation number correspond to the maximum output power when the virtual entropy generation induced by dumping the used streams into the environment is considered. However, the minimum principle of entropy generation is not tenable in the case that the virtual entropy generation is not included, because the total heat into the system of interest is not fixed. An irreversible Carnot cycle and an irreversible Brayton cycle are analysed. The minimum entropy generation rate and the minimum entropy generation number do not correspond to the maximum output power if the heat into the system of interest is not prescribed. 相似文献