带有高压储液器的制冷系统建模研究

通过对制冷系统循环特性、变工况特性和参数间耦合特性的分析,遵循热力学基本定律和能量、动量、质量守恒定律,采用稳态和动态建模相结合的方法建立压缩式制冷系统的数学模型。针对换热器建模难点采用分相区和移动边界相结合的方法建立其集总参数动态模型,并且冷凝器与高压储液器相结合,构成冷凝器加储液器的整体部件,文中建立的制冷系统的整体模型,反映了制冷系统工况变化时制冷剂质量的重新分配及其对状态变量的影响,提高了系统建模的精度,最后通过实验对所建模型的准确性进行了验证。     

Electrical transport properties of some liquid metals

In the present article, we report the electrical transport properties viz. the electrical resistivity (ρ), the thermoelectric power and thermal conductivity (σ) of several monovalent, divalent and polyvalent liquid metals of the different groups of the periodic table on the basis of model potential formalism. The well-known empty core model potential of Ashcroft is used for the first time with seven local field correction functions proposed by Hartree, Hubbard–Sham, Vashishta–Singwi, Taylor, Ichimaru–Utsumi, Farid et al. and Sarkar et al. in the present computation and found suitable for such study. In the calculation of these properties we have used the values of the theoretical structure factors due to hard core fluid theory. It is concluded that the comparisons of present and theoretical or experimental findings wherever exists are highly encouraging.     

Fluid phase topology of ethanol+benzene+cyclohexane at 101.3 kPa

In this article, isobaric vapor–liquid equilibria for the ternary mixture of ethanol?+?benzene?+?cyclohexane was experimentally investigated at atmospheric pressure. Vapor–liquid equilibria data for ethanol?+?benzene?+?cyclohexane at 101.3?kPa were obtained with a Othmer-type ebulliometer. Data were tested and considered thermodynamically consistent. The experimental results showed that this ternary mixture is completely miscible and exhibits three binary homogeneous azeotropes and a ternary minimum azeotrope at the studied conditions. Satisfactory results were obtained for correlation of equilibrium compositions with UNIQUAC activity coefficients model and also for prediction with UNIFAC method. In both cases, low root mean square deviations of vapor mole fraction and temperature were calculated. The capability of ethanol as modified distillation agent at atmospheric condition is discussed in terms of the thermodynamic topological analysis. However, owing to the complex topology of the ternary mixture it leads to a distillation scheme with three columns and difficult operation and thus, ethanol is not recommended as a separating agent for benzene?+?cyclohexane azeotrope.     

某型光电探测系统可靠性增长评估

光电探测系统研制阶段的试验数据具有小样本特征,针对传统的可靠性评估结果偏保守的问题,基于单调约束模型,通过综合利用光电探测系统多阶段试验数据进行可靠性评估,以达到精确评估的目的。考虑将研制过程中不同试验阶段数据中包含的可靠性增长信息作为约束条件,推导出可靠度分布函数表达式,并给出一种等效的统计抽样计算方法——Monte Carlo模拟算法,使计算过程更加简便,便于工程应用。最后以某型光电探测系统为例,表明利用可靠性增长信息进行可靠性评估,可有效提高评估的精度。     

山东高速通信数据网络建设方案

本文从山东高速的建设需求入手,介绍了山东高速通信数据网络建设的原则和实施方案。     

Oracle DataGuard在灾备系统中的应用

近年来,企业对数据安全的关注程度大大增强,Oracle Data Guard提供高可靠性的数据保护,并可以实现数据的灾难恢复,Oracle Data Guard能将生产数据切换到灾备数据库中,从而减少了由于数据存储而造成的当机时间.Data Guard也能配合备份和恢复技术、集群技术提供高层次的数据可靠性,本文主要阐述如何利用Oracle DataGuard的原理及构建灾备的方法.     

数据挖掘技术及应用

随着信息技术和数据库技术的快速发展和普及应用,信息化建设取得了长足的发展。信息收集能力得到提高,数据信息量快速增长,然而人们对这种大规模数据的分析、利用、决策能力却比较弱;仅仅依靠传统的数据查询和统计已经不能适应现代社会市场竞争的需要。而数据挖掘技术的出现满足了人们的需求,通过将海量的数据信息转化为有用的数据仓库,为各行各业的发展提供决策性的支持。     

云计算对数据中心市场的影响分析

介绍数据中心的发展现状及与云计算的关系,指出云计算技术推动了数据中心的产业升级,同时推动政府数据中心重新布局,但也给数据中心的市场监管带来挑战,建议电信监管与时俱进,作出相应的调整来适应技术与市场的发展。     

票信通产品在信息管税工作中的应用探讨

票信通产品是中国联通利用网络优势与税务机关联合推出的一个网络发票服务产品。文章分析网络发票在我国的应用现状,提出平台的技术架构,介绍票信通产品的主要业务功能。并阐述推广此业务的意义。