Improvement of the Irreversibility Line of the 1212 Compound Tl0.5Pb0.5Sr2CaCu2O7?δ

The superconducting properties and the irreversibility line of the Tl_0.5Pb_0.5Sr₂CaCu₂O_7– were studied by ac susceptibility on both ceramic and powder samples prepared in sealed quartz tube at 960°C. In parallel, carefull investigations by DTA/Tg, X rays diffraction and plasma emission spectroscopy were performed on each sample after each thermal treatment. It is shown that the superconducting properties are strongly dependent on further heat treatments and that the irreversibility line may be optimized. Nevertheless, the results obtained suggest that further improvement of the irreversibility line might be expected.     

链篦机-回转窑铁矿氧化球团焙烧过程的分析

为了降低链-回-环系统球团矿焙烧过程的能耗,对某工业装置进行了平衡测试和分析,得到了流图。分析表明,传热不可逆损和燃烧不可逆损是系统损的主要部分。建立了气体质流量、床层空隙率、床高、球团直径、烟气中氧含量等运行参数与损的关系。结果表明,适当减小气体质流量、床高和球团直径,增大床层空隙率,可以减小损。在其它条件不变的情况下,当烟气中二氧化碳浓度为1.0%～9.0%,将空气消耗系数控制在1.6～2.0,可使损最小。     

论动态规划方法在不确定性投资理论中的应用

不确定性条件下的经济问题非常重要,采取动态规划方法研究不确定性投资理论的应用现实意义重大。本文介绍了动态规划及其基本方程———贝尔曼方程,然后应用贝尔曼方程和处理不确定性问题的基本引理———伊藤引理,阐释了一个著名的不可逆性投资模型及其现实应用,由此抛砖引玉,推进该领域的研究。     

Y0.75Ca0.25MnO3体系的自旋玻璃行为与输运特性研究

研究了Y0.75Ca0.25MnO3体系的结构和电磁特性,结果表明,场冷(FC)和零场冷(ZFC)直流磁化曲线在低温下存在典型的分叉现象,相应的Tcusp=34K;不同频率下交流磁化测量表明了随着频率的增加自旋冻结温度Tf=Tcusp向高温区移动,结合电输运测量,证明Y0.75Ca0.25MnO3体系为一典型的自旋玻璃绝缘(SGI)体系.     

LONG-RANGE DEPENDENCE, NON-LINEARITY AND TIME IRREVERSIBILITY

Abstract. A rather general class of stationary processes with long-range dependence is introduced by mixing independent processes with short-range dependence. The class is used to study the relation between non-linearity and time irreversibility of the long-range dependence process and the corresponding features of the component processes.     

Thermo-environmental performance analysis of irreversible solid oxide fuel cell – Stirling heat engine

A hybrid, irreversible solid oxide fuel cell – Stirling heat engine system is taken into account. Thermoenvironmental criterion approach, which enables to evaluate environmental impact of any thermal cycle, is applied to the considered system for the first time. Power density, exergy density, thermoenvironmental function density, energy and exergy efficiencies are considered. Results are presented and discussed to determine optimum operating conditions. Some important results for the hybrid system are ordered: maximum power density is 7489.92 (A?m^?2), maximum energy and exergy efficiencies are 0.800 and 0.887, respectively, and finally, thermoenvironmental function density is 0.0276 (W?mpts^?1?m^?2).     

热机不可逆过程中不可逆因子研究

通过引入内、外不可逆因子,深入地讨论了热机热力循环中不可逆程度对热机循环过程的影响.论述了不可逆因子不是建立热机热力循环模型所必需的,是为了描述热机热力循环过程的不可逆程度定义的一个参数,是由所建立的热机模型决定的一个函数,从而澄清了对不可逆因子的某些模糊认识.对于不可逆因子的计算提出了一种新的方法,由算例可以看出,不可逆因子的计算,只要建立的热机模型恰当,在一定的条件下都可以找到计算表达式.最后得出结论:不可逆因子不是一个简单的常数,是由热机热力循环模型所决定的复杂的函数.当建立起热机热力循环模型并给定热机有关参数后,不可逆因子可以计算出来,从而定量的研究不可逆程度对循环性能的影响,以及影响热力循环不可逆性的各种因素.     

刘维空间反常朗之万方程为基础的非平衡统计物理

考虑到热力学不可逆性和流体力学方程不能严格统一地从刘维方程推导出，本文提出了刘维空间的反常朗之万方程作为统计物理的基本方程．这个方程反映了粒子在动力学中遵守的可逆的确定性的运动规律到统计热力学系统中变为不可逆的随机性的．由这个基本方程可严格推导出非平衡热力学基本方程、嫡增长原理、最小墒产生定理以及流体力学方程如广义纳维尔－斯托克斯方程、质量漂移－扩散方程等．所有这些都是统一的自洽的．但是难以证明所有非均匀远离平衡的孤立系统中的熵产生密度在各处都满足σ≥０     

非平衡态势力学与动力学

综述了平衡态热力学、线性非平衡热力学和非线性非平衡热力学与动力学,指出了非平均态热力学并未抛弃经典热力学的基本结论,而是给以新的解释和重要的补充,它不仅为弄清物理学和化学中的各种有序现象的起因指明了方向,更有助于人们对宏观过程不可逆性的本质及其作用的认识。     

Thermoeconomic optimization of simple refrigerators

Thermoeconomic optimization of simple refrigerators is formulated and applied to a specific case. Condenser and evaporator areas and compressor efficiency are selected as the independent design variables of the system components. Exergy analysis is carried out to find local and total irreversibilities. Costs assigned for exergy losses are combined with capital and recovery costs, and equations for thermoeconomic optimum of components are derived. Finally, as a case study, the equations are solved to determine the thermoeconomic optimum refrigeration system of a domestic refrigerator whose cooling load and operation temperatures (inner and outer) are specified. Copyright © 1999 John Wiley & Sons, Ltd.