Sintering temperature dependence of microwave dielectric properties in Mg4(TaNb1−xVx)O9 compounds

The relationship between the sintering temperature and the microwave dielectric properties of Mg₄(TaNb_1−xV_x)O₉ (MTNV) compounds were investigated in this study in order to reduce the sintering temperature of the compound. A small amount of V₂O₅ doping lowered the sintering temperature of the MTNV compounds. The variations in the dielectric constant and the quality factor of the MTNV compounds depended on the amount of V₂O₅ doping and the sintering temperature; a small amount of V₂O₅ doping was effective in allowing low sintering temperatures without a detrimental effect on these dielectric properties. As a result, a dielectric constant of approximately 12 and a quality factor of approximately 200,000 GHz were obtained when the MTNV compounds with x = 0.2 was sintered at 1200 °C. The temperature coefficient of resonant frequency of the MTNV compound with x = 0.025 slightly changed from −63 to −73 ppm/ °C with an increased sintering temperature because of the presence of a secondary phase.     

大跨度钢屋架整体滑移方案有限元分析

针对大跨度钢屋架整体滑移方案,以五棵松体育馆为工程背景,应用ANSYS有限元软件对钢结构屋盖主桁架的整体滑移过程进行了动态模拟跟踪分析,得到滑移过程中不同阶段应力及变形的变化范围,以确定最佳安装方案。分析表明,在保证合理措施的条件下,此滑移方案是可行的。     

吸收系数影响受激布里渊散射的实验研究

选用四氯化碳和环己烷的混台溶液作为散射介质，实验研究了不同混合比介质所产生的SBS脉宽、能量和波形的差异．分析讨论了吸收系数对SBS性能的影响。     

考虑缺水滞后效应的作物-水模型研究

本文依据作物生理学有限缺水理论，考虑作物不同生育阶段缺水对叶面积系数、腾发量变化及产量影响的滞后效应，假设这种滞后影响过程的现在阶段只与将来阶段有关，而将来阶段与过去阶段无关，经单阶段和多阶段缺水的两种田间灌溉试验，求得改进的加法模型即考虑缺水滞后效应的作物水模型（ＬＥＭＣＲＷ），与常见的３种国外ＭＣＲＷ比较具有较广泛的适应性和较好精度，只要正确选用不同的敏感指标，可供单阶段和多阶段缺水对产量影响的非充分灌溉模拟．     

工艺过程对散热器电子束钎焊残余应力影响的数值模拟

利用ANSYS软件,建立二维有限元模型,分析了两种不同钎焊工艺对1Cr18Ni9Ti不锈钢散热器电子束钎焊接头残余应力的影响,旨在筛选出一种合适的工艺及参数.结果表明,对于径向残余应力,采用直接加热钎焊工艺,钎焊面上出现明显的应力集中区域;而采用分阶段加热钎焊工艺,钎焊面上没有应力集中区出现,且应力变化曲线比直接加热钎焊工艺平缓得多;对于周向残余应力,分阶段加热与直接加热钎焊工艺相比,拉应力峰值减小了11.2%.两种钎焊工艺的周向残余拉应力峰值均大于径向残余拉应力,钎焊面的危险部位沿圆周方向,即电子束扫描加热的方向.     

湿法烟气脱硫技术

综述了各种湿法烟气脱硫技术的原理及特点:石灰-石灰石法、钠碱法在脱硫过程中多以一次利用为主,且易造成二次污染及设备腐蚀;氨法脱硫过程关键在于脱硫液中氨性质的稳定;醇胺法及生物脱硫法多考虑到脱硫液的再生,以减少溶液的损失,保证脱硫液的脱硫性能。指出利用微生物强化可再生溶液脱硫方法作为一种新型的脱硫方式是烟气脱硫值得发展的方向。     

预应力锚束张拉锁定损失控制

预应力混凝土闸墩可以简化泄水建筑物结构、节省大量钢筋和方便施工,因此被越来越多地采用。锚束张拉中锁定损失控制是张拉过程中较为棘手的问题,锚束愈短愈难达到设计要求。针对此问题,就理论分析和实际操作控制方面提供了可借鉴的经验。     

Numerical and physical simulation of a twin-roll strip caster

The 1：1 water model of a twin-roll strip caster was set up based on the Froude number and the Reynolds number similarity criteria. A new type metal delivery system was designed for the twin-roll strip caster. The level fluctuation and the fluid flow in the pool of the water model were measured using the level detector and the 3D-LDV （laser Doppler velocimetry） technology. It is shown that a wedged delivery system can produce the desirable level fluctuation and even fluid flow distribution in the pool Numerical simulations for the water model were performed. Comparisons between the numerical and physical simulation results show good agreement near the side dams.     

Oxidative stability of cream cheese stored in thermoformed trays as affected by packaging material,drawing depth and light

The oxidative stability of cream cheese stored in thermoformed trays made of amorphous polyethylene terephtalate (A-PET)/polyethylene (PE), polystyrene (PS)/Ethylene-vinylalcohol copolymer (EVOH)/PE and Polypropylene (PP)/PE with different depth (25, 50 and 70 mm) and colour (black, white and transparent) was studied by sensory evaluation and gas chromatographic analysis of volatile compounds. The polymer combination had an important effect on sensory scores of both sunlight and acidulous flavour in cream cheese stored in the dark for 2, 4 and 6 months. Cream cheese stored in trays made of A-PET/PE had higher acidulous flavour and lower content of hexanal and 2-nonanone. Only small differences were observed between PS/EVOH/PE and PP/PE despite the great diversity of oxygen transmission rates. The drawing depth of the packages had no significant effect on oxidative stability of cream cheese, irrespective of storage in the dark or under illumination. The colour of the examined packaging material had a pronounced effect on photoxidative changes in cream cheese.     

无烟煤冲击产尘粒径分布规律的试验研究

运用分形理论分析了伯方煤矿3号煤层煤样冲击产尘的粒径分布特性，得出：冲击煤尘粒径-质量之间存在明显的分形特性.随着冲击高度和冲击次数的增加，产生微细粉尘的总量也在增多，反映在ln d-ln W曲线上即为直线的斜率变小，分形维数D在不断增大.从而为定量地描述煤尘粒径分布特性规律提供了一种新的方法.