复合笼型转子感应电动机起动性能的数值计算

给出复合笼型转子感应电动机起动时的求解域、边界条件和假设条件.利用电磁场理论和变分法建立了复合笼型转子感应电动机起动时二维电磁场的数学模型,给出了正弦时变场单元分析过程和离散格式以及最终的总体合成方程.在电磁场的数值计算过程中,以定子端电压为约束条件,对定子起动电流进行迭代计算,得到了额定电压下的起动电流和起动转矩,最后把正弦电磁场计算结果与实测结果进行对比,表明复合笼型转子感应电动机起动性能的计算结果满足工程实际的需要.同时,将计算结果与普通感应电动机进行比较,表明了复合笼型转子感应电动机具有良好的起动性能.通过改变复合材料的磁导率和电阻率的大小,进一步研究了复合材料磁性能和电性能的变化对起动性能的影响,对于合理选取复合性材料铜铁合金配方有一定的意义.根据复合笼型转子感应电动机一对极下的非线性时变场的求解结果,计算了10个槽的漏感,计算结果表明,起动时各槽参数并不相同.     

简易垃圾填埋场封场设计介绍

简易生活垃圾填埋场封场工程由垃圾堆体整形、终场覆盖、雨水收集与导排、填埋气的导排与处理、渗滤液收集与处理、安全与环境检测等系统组成。结合具体情况,优化设计,最大限度减少垃圾填埋场污染环境,节省投资。     

超深地下连续墙施工中若干问题探讨

随着地下空间工程的不断发展,超深地下连续墙的应用越来越多,施工的风险也越来越高。结合工程实践,对超深地下连续墙施工方法及施工中存在的若干问题进行探讨、分析,并提出相对应的解决措施。通过采用先进合理的解决措施,超深地下连续墙的施工是完全能达到设计要求的。     

Bhc-cNMPs as either water-soluble or membrane-permeant photoreleasable cyclic nucleotides for both one- and two-photon excitation

Cyclic nucleoside monophosphates (cNMPs) play key roles in many cellular regulatory processes, such as growth, differentiation, motility, and gene expression. Caged derivatives that can be activated by irradiation could be powerful tools for studying such diverse functions of intracellular second messengers, since the spatiotemporal dynamics of these molecules can be controlled by irradiation with appropriately focused light. Here we report the synthesis, photochemistry, and biological testing of 6-bromo-7-hydroxycoumarin-4-ylmethyl esters of cNMP (Bhc-cNMP) and their acetyl derivatives (Bhc-cNMP/Ac) as new caged second messengers. Irradiation of Bhc-cNMPs quantitatively produced the parent cNMPs with one-photon uncaging efficiencies (Phiepsilon) of up to one order of magnitude better than those of 2-nitrophenethyl (NPE) cNMPs. In addition, two-photon induced photochemical release of cNMP from Bhc-cNMPs (7 and 8) can be observed with the two-photon uncaging action cross-sections (delta(u)) of up to 2.28 GM (1 GM=10(-50) cm(4) s photon(-1)), which is the largest value among those of the reported Bhc-caged compounds. The wavelength dependence of the delta(u) values of 7 revealed that the peak wavelength was twice that of the one-photon absorption maximum. Bhc-cNMPs showed practically useful water solubility (nearly 500 microM), whereas 7-acetylated derivatives (Bhc-cNMPs/Ac) were expected to have a certain membrane permeability. Their advantages were demonstrated in two types of biological systems: the opening of cAMP-mediated transduction channels in newt olfactory receptor cells and cAMP-mediated motility responses in epidermal melanophores in scales from medaka fish. Both examples showed that Bhc and Bhc/Ac caged compounds have great potential for use in many cell biological applications.     

交流伺服系统鲁棒控制策略研究

本文针对鼠笼异步电动机间接磁场定向控制系统，提出一种ＰＩ调节器和模型跟踪调节相结合的鲁棒控制方案。理论分析、仿真和实验证明了该方案具有工程应用价值。     

新一代炸药──多硝基笼状化合物的研究综述

综述了美国对多硝基笼状化合物性能参数的理论计算结果和笼状化合物最佳硝基数目的确定以及近年来的合成研制现状和下一步的合成目标．     

钴放射防护井实践爆破

用控制爆破法掘深钻放射防护井,对难以用机械钻孔的钢筋混凝土整体结构的防护井,采用射孔器射孔和切割器切割钢筋的办法,得到了令人满意的结果。     

长螺旋钻孔灌注桩施工技术在工程中的应用

指出长螺旋钻孔灌注桩是近年来日益广泛应用的一种新型灌注桩技术,具有不挤土、无需护壁、单桩承载力高、成桩质量较好的特点。笔者重点介绍了该技术的施工工艺、技术特点及其应用范围,可供类似工程借鉴、参考。     

平衡套筒式减压阀设计

针对高压降下的节流减压易产生气蚀导致减压阀节流件过早损坏问题,设计了平衡套筒式阀瓣结构,使一套阀瓣实现两级节流,减小单级节流压降,避免了气蚀产生。     

基于托架动不干涉条件的停车设备链传动系统的设计

建立了垂直循环式停车设备托架运动不干涉条件，提出了根据托架运动不干涉条件设计停车设备链传动系统的方法。模型试验表明，所给出的托架运动不干涉条件和链传动系统设计方法合理可行，可用于实际停车设备链传动系统设计。