Hydrothermal synthesis and thermal decomposition mechanism of alkaline earth benzoates

Alkaline earth benzoates were synthesized using hydrothermal reaction. The complexes were characterized by elemental analysis, IR, X-ray powder diffraction. All of them are monoclinic and have layered structure. The mechanism of thermal decomposition of alkaline earth benzoates was studied by using TG, DTA, IR and gas chromatography-mass spectrometry. The thermal decomposition of alkaline earth benzoates in nitrogen proceeded in one or two stages: they decomposed to form MCO₃ (M=Ca, Sr, Ba) or MgO and organic compounds, respectively. The organic compounds obtained from decomposition reaction are mainly benzophenone, triphenylmethane and so on. Supported by the National Natural Science Foundation of China Zhang Keli: born in 1944, Associate professor     

空气环境中水滴和半空间弹性体撞击力学行为的数值模拟

通过将拉格朗日方法与欧拉方法相耦合,分析了在空气环境中直径为1 mm、速度为150 m/s的球形水滴对半空间弹性体的撞击过程.通过对液固撞击过程的数值模拟,给出了撞击过程中水滴内部的压力分布及其随时间的变化、液固接触边缘射流的形成及其破碎的过程、被撞击固体的变形特点和等效应力及其随时间的变化.结果表明:水滴和被撞击固体的可压缩性对整个撞击过程有重要影响;在撞击的初始阶段,水滴中产生水锤压力并使固体表面产生相对很大的变形和应力,水锤压力的理论值和数值计算的结果具有较好的一致性,验证了耦合数值计算方法的可行性和精确度;射流出现的时间比激波脱体的时间晚,高速射流对不再平坦的固体表面的强烈剪切作用使固体进一步变形,并且液固接触边缘的压力高于内部的压力.     

SERVICE LEVEL EVALUATION OF AN ASSEMBLY-TO-ORDER SYSTEM

An assembly-to-order system, which at the end the buffer distinguishes its assembly stages of the system from the downstream systems, is considered in this paper. The system produces semi-finished products for the downstream system and starts from a basic subassembly, and at each stage a component is assembled into the corresponding subassembly. The basic subassembly, components and buffer all follow a periodic-review, order up-to-level inventory policy. The buffer holds the semi-finished products to serve the specific demand from the downstream system. The service level of the system is determined by aggregate effects of the components held at stockpiles before the buffer and the basic subassembly. In order to measure the service level of the system, some notations and assumptions are made, on which the closed form expression of the service level of the system is achieved.     

两个随机变量间线性关系的再讨论

引入了欧线性回归、欧线性相关的定义,研究了它的若干性质,从而使这类问题的研究更具一般性.     

软件无线电发展动态

介绍了软件无线电系统的评价标准,这种评价标准主要是指系统的“软件”程度。还介绍了软件可重用性的实现,即要求软件代码能够应用于不同的软件无线电硬件平台中,这要求为软件无线电定义一套专门的软件标准。给出了在“八六三”项目所采用的一种基于异步传输模式（ Ａ Ｔ Ｍ）交换网络的软件无线电的硬件平台,它具有很好的开放性、可扩展性和可重构性,它能够灵活的配置成为不同功能的软件无线电应用系统。它较之目前国内外讨论较多的总线式结构有明显的优势。最后给出了具体实现上述硬件平台的一种环形结构     

采用球窝控制边界层分离流动的大涡模拟

用具有逆压梯度的平板分离流动模拟低压透平叶片吸力面的分离流动,采用基于动力Sma-gorinsky亚格子应力模型的大涡模拟对逆压梯度条件下布置在平板上单个球窝的流动特性及球窝对边界层分离流动控制的效果进行了研究,详细考察了球窝前沿边界层厚度和球窝深度的比值R分别为0.378、0.994和1.453时球窝的流动特性和控制性能.结果表明:R较小时控制性能最好;球窝内部的马蹄涡对球窝的流动起主导作用;球窝内的马蹄涡周期性脱落并在球窝尾迹区形成发夹涡排,发夹涡涡腿紧贴壁面形成流向涡,流向涡卷吸主流高能流体,由此增强了边界层能量.马蹄涡和发夹涡排对分离流动控制起主要作用.     

微通道中球窝/球凸强化传热特性研究

为了解决微机电系统高热流密度的散热问题,采用数值方法对在宽度为50μm、高度为200μm的矩形截面微通道内布置球窝/球凸结构的传热特性进行了研究,通道的Re为100~900,流向间距为1.5到3.5倍的球窝直径,同时研究了球窝/球凸的叉排和顺排对微通道传热特性及流动规律的影响.结果表明:在微通道内布置球窝/球凸后,Nu与光滑微通道的Nu0比值为1.28~4.77,其数值基本和常规通道范围一致;范宁摩擦系数f同光滑微通道的f0比值范围为1.11~2.04,上限与常规通道的一致,下限较之常规通道的小.随着Re的增加,Nu/Nu0和f/f0近似线性增加;相同Re下,叉排的Nu/Nu0和f/f0大于顺排;相同排列方式下,随着流向间距的减小,Nu/Nu0和f/f0增加.叉排的热性能明显优于顺排;微通道中布置球窝/球凸的节能效果明显优于常规通道中布置球窝/球凸的情况.     

城市旅游产业升级理论与实证研究

以科学发展观为指导,介绍城市旅游产业升级这一命题的提出背景,并通过近年来成都市旅游产业相关统计数据的搜集和整理,回顾近年来成都城市旅游产业的发展态势,探讨了成都城市旅游产业升级的必要性与相关对策.     

Virtualization of Wireless Communication Systems and Its Maximal Ratio Combining Macrodiversity To Extend CDMA Capacity

The developmentof software radio technologyhas led to the concept of virtualization of wirelesscommunications which provides important benefitssuch as fast handoff and easy realization ofmacrodiversity.Macrodiversity can not be easilyrealized in conventional cellular systems. InCDMA soft handoff,macrodiversity is used in thereverse link,but it is based on a selectioncombining algorithm[1,2 ] .In virtualized wirelesscommunication systems,macrodiversity can berealized using different algorithm…