Poisson's ratio and the fragility of glass-forming liquids

The nature of the transformation by which a supercooled liquid 'freezes' to a glass--the glass transition--is a central issue in condensed matter physics but also affects many other fields, including biology. Substantial progress has been made in understanding this phenomenon over the past two decades, yet many key questions remain. In particular, the factors that control the temperature-dependent relaxation and viscous properties of the liquid phase as the glass transition is approached (that is, whether the glass-forming liquid is 'fragile' or 'strong') remain unclear. Here we show that the fragility of a glass-forming liquid is intimately linked to a very basic property of the corresponding glass phase: the relative strength of shear and bulk moduli, or Poisson's ratio.     

The relationship between fragility, configurational entropy and the potential energy landscape of glass-forming liquids

Glass is a microscopically disordered, solid form of matter that results when a fluid is cooled or compressed in such a manner that it does not crystallize. Almost all types of materials are capable of glass formation, including polymers, metal alloys and molten salts. Given such diversity, general principles by which different glass-forming materials can be systematically classified are invaluable. One such principle is the classification of glass-formers according to their fragility. Fragility measures the rapidity with which a liquid's properties (such as viscosity) change as the glassy state is approached. Although the relationship between the fragility, configurational entropy and features of the energy landscape (the complicated dependence of energy on configuration) of a glass-former have been analysed previously, a detailed understanding of the origins of fragility is lacking. Here I use simulations to analyse the relationship between fragility and quantitative measures of the energy landscape for a model liquid whose fragility depends on its bulk density. The results reveal that fragility depends on changes in the vibrational properties of individual energy minima in addition to their total number and spread in energy. A thermodynamic expression for fragility is derived, which is in quantitative agreement with kinetic fragilities obtained from the liquid's diffusivity.     

低密度玻璃化液体中力学模量与脆性的关联研究

利用低密度玻璃化液体的径向分布函数,导出过冷液体脆性与玻璃化温度、体模量和剪切模量的比值及与柏松比之间简单明确的关系.此结论定性地与实验结果一致.并为各种玻璃化液体的研究,提供有效的途径.     

快速接入无线局域网解决方案

为顺应人们快速接入网络的要求,根据无线网络的工作原理以及用户对网络性能的要求,制定了采用CISCO设备实现快速接入无线局域网的一个解决方案,以此来达到移动的、稳定的、高速的、安全的接入网络.实验表明,此解决方案基本上可以满足当前的办公及家庭娱乐需求.     

用状态方程研究硬球模型液体的声速及其热力学关系

将基于分布函数理论的状态方程应用于硬球模型液体，给出了超声波声速及其热力学关系的表达式，计算结果与实验值符合较好     

喀斯特地区生态环境脆弱性现状区划初探—以贵州省乌江流域为例

本文以贵州乌江流域的42个县(市)为例,论述了喀斯特地区生态环境脆弱性区划的主要原则,探讨了脆弱性区划的指标,并进行了量化。在此基础上,用灰色关联度分析并确定了各影响因子(即区划因子)的权重,经过综合评判,笔者把流域内生态环境脆弱性划分为五种类型。并提出了相应的防治对策。     

城市地貌环境的脆弱性研究

城市地貌环境具有两大地域系统和三类地貌单元。由于城市中人类活动产生的反馈效应日益强化，城市地貌环境具有明显的脆弱性，表现为：环境变异敏感度高，环境的持续利用性降低和环境对灾变的承受弹性较小。     

古代汉语与佛教渊源简论

汉语在发展过程中，大量吸收了外来文化的精髓，这主要表现在词汇上。通过古代汉语词语对佛教的吸收的三个主要途径的论述，指出中国古代汉语言与佛教有着极深的渊源。     

A thermodynamic explanation for black smoker temperatures

There is a remarkable difference between the maximum temperature of black smoker effluent (350 degrees C-400 degrees C) and the temperature of the solidifying magma which heats it (approximately 1,200 degrees C). It has been suspected for some time that the nonlinear thermodynamic properties of water might be responsible for this discrepancy. Here, we translate this hypothesis into a physical model, by examining the internal temperature structure of convection cells in a porous medium. We demonstrate that, at pressures appropriate to seafloor crust, plumes of pure water form naturally at approximately 400 degrees C for any heat source with temperature greater than approximately 500 degrees C. Higher temperatures are confined to a boundary layer at the base of the convection cell, where the flow is horizontal. The phenomenon is explained analytically using the thermodynamic properties of water, and is illustrated by numerical simulations. Our model predicts the existence of the high-temperature 'reaction zone' found in ophiolites and suggests that vent temperatures will remain steady as magma chambers solidify and cool.     

Delphi中数据库的动态连接研究

现在的信息管理系统发展势头非常好，但是经常出现发布后的前台应用程序和后台的数据库连接设为静态，将系统移植到其他的计算机上就比较麻烦。于是我采用动态的方式来连接，即应用程序留出端口供用户设置，这样就比较方便了．主要介绍了用Delphi语言开发信息管理系统中应用程序和数据库的动态连接的理论基础和具体实现过程。     

磷铁掺钴制备磷化二钴的热力学研究

用"物质吉布斯自由能法"对磷铁掺钴制备磷化二钴进行了热力学研究.结果表明:在298～1600 K的范围内,FeP、Fe2 P与Co反应制备Co2 P可行,吉布斯自由能分别由-60.96、-27.55 kJ/mol升高至-33.40、-15.48 kJ/mol.对应反应的标准平衡常数与温度的关系分别为:lg Kθ1=34...     

一种新的连接性指数与卤化物热力学性质的相关性

定义原子特征值f     

溶剂萃取法制备碳酸盐的热力学讨论

向金属氯化物(Ⅰ)的水溶液中通入CO_2气体,以期制备相应的碳酸盐和酸式碳酸盐,在常温常压下,体系的△G>0,反应几乎是不可能的。向反应体系中加入有机溶剂(S),使生成的HCl即被萃取,可促进Ⅰ的继续转化。分析计算表明,S对HCl必须有很强的萃取能力,其K_萃须在10~5以上。研究了加入有机溶剂N_(235)前后,体系的热力学状态、函数及其变化。加入N_(235)后,K_萃值增大了5个数量级。考察了温度、时间和通气次数对系统热力学性质的影响。根据反应的耦合原理和热力学分析,提出萃取剂选择的原则。结合实验数据的估算说明:溶剂萃取法由Ⅰ和CO_2制备碳酸盐的工艺路线是可行的。     

基于ATM网络的虚连接技术

通过对ATM网络的分析，阐述了虚连接的概念，并介绍了在ATM网络中建立虚连接的方法和措施。     

特殊螺纹套管接头连接性能的安全可靠性分析

建立套管接头内、外螺纹牙啮合物理力学模型,依据螺纹啮合对变形协调方程和单个螺纹牙轴向弹性变形分析,推导出套管接头螺纹牙承载分布不均性规律及其法向接触力计算方程组,并利用有限元计算结果验证了螺纹牙受力解析值的可参考性.结合弹性力学理论和API偏梯形螺纹计算准则,根据可靠度理论建立特殊螺纹套管接头三种连接失效形式的极限状态方程,利用Monte Carlo方法对服从正态分布的螺纹各项加工参数进行抽样,统计得出套管接头发生连接失效的概率及其相应可靠度.计算结果表明:特殊螺纹套管接头各连接失效形式的可靠度由大到小排序为螺纹跳扣>管体屈服>螺纹牙剪切>接头抗拉.     

Hadamard幂下不可约M矩阵最小特征值界的研究

利用不可约非负矩阵A的Hadamard幂,矩阵特征值存在域定理,以及非奇异M矩阵B的若干性质,首先给出了不可约非负矩阵AB-1的谱半径的上界;其次,当A的每个元素都为1时,给出了τ(B)的一些新下界.数值例子说明这些新界一定程度上提高了已有文献中的结果.     

对体育专业女生短跑成绩提高因素的灰色关联分析

本文运用灰色系统理论中的关联度分析法,对体育专业女生短跑成绩的提高因素进行了系统的分析研究,探讨其提高短跑成绩与各因素之间的相互关系,旨在提高短跑教学质量。     

再论通用特征函数的性质

根据通用特征函数的集合表示，证明了通用特征函数是态函数．当热力学系统经历某一自发过程达到平衡态时，与过程对应的通用特征函数达到极小值．在通用特征函数独立变量中的所有强度量不变的过程中，系统给外界传递的能量不大于与该过程对应的通用特征函数的减少．从而进一步说明，通用特征函数与传统热力学特征函数理论完全一致．并在任意复杂系统中，克服了传统特征函数方法带来的困难，因而具有更高的概括性和公理化．