Pyroelectricity and related properties in the fresnoite pseudobinary system Ba2TiGe2O8-Ba2TiSi2O8

Complete solid solubility is found in the pseudobinary system Ba₂TiGe₂O₈-Ba₂TiSi₂O₈ by studies on ceramics and single crystals (Czochralski technique). The spontaneous birefringence perpendicular to the polar axis of the orthorhombic low temperature phase has been measured versus temperature and silicon contents: the temperature of the phase transition of species 4mmFmm2 is of second order and decreases from 1103 K at 0 at % Si to about 400 K at 40 at % Si. The pyroelectric coefficient in the orthorhombic mm2 and the tetragonal 4 mm phase is of the order of 10^–6 C m^–2 K^–1 in the entire system and has a positive temperature coefficient for all compositions studied except for Ba₂TiGe₂O₈, in which the pyroelectric coefficient changes sign at about 308 K. The spacegroup of the orthorhombic phase is proposed to be C _2v ¹¹ -Cmm2.     

Effect of potentially probiotic lactobacilli on faecal enzyme activity in minipigs on a high-fat, high-cholesterol diet-a preliminary in vivo trial

Minipigs were fed a "Western-style", high-cholesterol diet for a baseline period, followed by the diet containing a mixture of three Lactobacillus strains with potential probiotic features, after which a normal pig diet was followed. The faecal enzyme activity for beta-glucuronidase and azoreductase, which are commonly considered as markers for procarcinogenic activity, was significantly reduced during the 5 weeks of "probiotic" supplementation. During the period of Lactobacillus administration, the cell counts for total anaerobes increased, whereas the total number of aerobes showed no change.     

小卫星星务计算机系统总线的研究与实现

目前微小卫星昨璁计算机系统通信总线面临了一系列新的要求,而在这一领域应用的几种串行通信总线都不尽如人意。CAN（Controller Area Network)总线结构灵活,可靠性高,比较适合小卫星,针对小卫星运行环境单粒子效应较多的情况,为TS－1小卫星设计的“基于CAN的双冗余系统总线”采用二模冗余的方法进一步提高了系统总线可靠性,是一种高性能、高可靠、低价位的系统总线设计方案。在CAN的多机通信模拟平台上进行的一系列试验验 证了“基于CAN的双冗余总线技术方案”的可行性。     

2006年我国粉末冶金零件生产进展

本文介绍了2006年我国粉末冶金生产状况和市场变化,分析了当前我国粉末冶金零件产业面临的挑战.     

调度员培训仿真系统中的网络拓扑

提出了一种改进的ＤＴＳ拓扑结构的两级搜索算法，并着眼于局部搜索效率的提高，对厂站拓扑搜索进行了改进，减小了全网搜索的概率，给出了电力系统在初始状态及开关动作两种民政部下的拓扑搜索过程。     

液闪法提高~(32)P计数效率的研究

对 32 P的切仑科夫计数法及液闪测量作了比较 ,同时对于不同样品瓶和闪烁液对 32 P计数效率的影响进行了实验比较 ,指出提高 32 P测量效率的途径     

钢水温度和碳对镁铝尖晶石质耐火材料侵蚀的影响

根据热力学分析和热态实验研究了钢水温度及其碳质量分数对镁铝尖晶石质耐火材料侵蚀的影响，并探讨了耐火材料的侵蚀机理。研究表明，提高温度将加剧钢水对耐火材料的侵蚀，随钢水中碳质量分数的增加，耐火材料的侵蚀指数先增加后减小。侵蚀机理包括：一是钢水中碳与耐火材料组分氧化镁反应化学侵蚀耐火材料；二是钢水向耐火材料内部的渗入以及低熔点物相在耐火材料颗粒界面的析出，降低了耐火材料颗粒间的结合力，加剧了钢水冲刷对耐火材料的损毁程度。     

CALCULATION OF FRICTION FACTORS AND NUSSELT NUMBERS FOR LAMINAR FLOW IN RECTANGULAR DUCTS USING FINITE ELEMENTS

A finite-element technique is described to determine the wall shear stresses and heat fluxes for fully developed laminar flow at the wall of a rectangular duct. It is shown that these values are accurate and that they can in some instances be independent of the grid resolution. These values are then used to obtain the friction factors and Nusselt numbers for Poiseuille-Brinkman flow in various rectangular ducts. The results are found to be in good agreement with the values quoted in a number of well-known textbooks. Some small discrepancies in some of the quoted values are also pointed out.     

Application of power addition as modelling technique for flow processes: Two case studies

In many of the continuum processes typically found in chemical engineering, the functional dependency of the dependent variable is only known for large and small values of the independent variable. Exact solutions in the transitional regime are often obscure for various reasons (e.g. narrow band within which the transition from one regime to the other occurs, inadequate knowledge of the physics in this area, etc.). An established method for the matching of limiting solutions is reviewed and subsequently applied. The method regards the known solutions as asymptotes and proposes addition to a power of such asymptotes. It yields a single, adjustable correlating equation that is applicable over the entire domain. This procedure circumvents the introduction of ad hoc curve fitting measures for the different regions and subsequent, unwanted discontinuities in piece-wise fitted correlative equations for the dependent variables. Experimental data of two diverse processes, namely flow in a straight-through diaphragm valve and the fluidisation of a packed bed, are analysed as case studies. Empirical results are investigated for possible asymptotic bounds whereafter power addition is applied to the functional dependencies. The outcome is compared to those of the empirical models and the results discussed. The procedure is revealed to be highly useful in the summarising and interpretation of experimental data in an elegant and simplistic manner. It may also, in general, aid the setup of experimental apparatus for investigation of continuum processes.