悬臂式基坑开挖对邻近地下管线的影响分析

通过有限元软件ABAQUS,分别考虑软土地区基坑的不同围护结构和管线的不同下卧层土质等因素,对悬臂式基坑工程中临近的地下管线位移进行了三维有限元模拟分析,结果表明：围护结构刚度和下卧层土质均对临近管线位移有较大影响;距基坑越近,管线变形越大;出现了地表及管线的沉降,但在基坑端角附近有管线上浮现象;基坑端角部以外2/3的基坑开挖深度范围内,管线水平和竖向位移较大,但在1.2倍的基坑开挖深度之外,开挖对管线位移影响较小.     

悬臂梁振型的弯曲变形和剪切变形分解

介绍了铁木辛科梁的理论以及悬臂梁频率和对应振型的求解方法.从振型中分解出了弯曲变形和剪切变形分量,并求出了弯曲变形能和剪切变形能.     

刚构桥基于敏感性原理的参数敏感度分析

针对预应力混凝土连续刚构悬臂施工控制中的参数敏感度问题,基于敏感性分析的基本原理,利用数值仿真模型,分析了材料容重、弹性模量、环境湿度、预应力管道偏差、施工荷载等因素对这类桥梁成桥线形的影响程度。详细探讨了成桥线形对这些影响因素的敏感度。相关结论可为同类桥梁的设计和施工提供参考。     

具有边梁的悬臂矩形板的弯曲问题

本文建议一个求解具有边梁悬臂矩形板弯曲问题的解析解法。该法将有边梁和无边梁悬臂矩形板弯曲问题的解融为一体,在有边梁悬臂矩形板的解中令边梁弯曲刚度为零即得到无边梁悬臂矩形板的解。     

加热炉炉内悬臂辊道设计

介绍了目前国内比较常用的几种悬臂辊结构。     

Microcantilever sensors with embedded piezoresistive transistor read-out: Design and characterization

Microcantilevers are very effective tools in detecting of small amount of bio-species and chemicals. Recent advances in metal-oxide-semiconductor field effect transistor (MOSFET) as a transducer to detect the molecule binding-induced cantilever deflection has gained extensive attention due to its high sensitivity and direct compatibility with micro-electro-mechanical system (MEMS) sensors. In this paper, six different piezoresistive nMOSFET-embedded microcantilevers are designed and characterized to systematically study the impacts of different cantilever and transistor channel geometries on the device sensitivity. It is found that the amount of change in the drain current is the same range as reported in the literature. For point-loading applications, transistors with lower channel width are optimal for relative drain current change even though their absolute current output is less. In particular, the embedded nMOSFET Exhibits 63.6% higher sensitivity by decreasing transistor channel width from 300 to 60 μm. Furthermore, theoretical results are compared with experimental data to optimize cantilever and transistor geometrical factors to achieve higher stress or force sensitivity. The low frequency noise characteristics of the devices show better resolution for higher aspect-ratio transistors, with drain current noise in the nanoampere range. Results reveal useful design guidelines to enhance the MOSFET-embedded microcantilever sensitivity for various applications.     

基于FlexSim 的军队自动化立体仓库货位优化研究

为提高军队自动化立体仓库出货速度和运行稳定性,提出了在堆垛机闲时对货位进行以分类存储L 形分区为导向的再分配优化设计。根据用户需求,程序自动生成分类存储的L 形分类存储货位分区信息,并调用堆垛机对在存货品逐一判断、搬运,让所有货品按照L 形区域排列,完成货位优化。利用FlexSim 软件对具体实例进行了仿真,结果表明,优化后的货位能较大程度地提高仓库的输出效率。     

端部约束悬臂输流管道的动力学特性

根据梁模型横向弯曲振动模态函数一般表达式,由边界约束条件确定其模态函数的一般表达式,采用Galerkin法将运动方程在模态空间内展开,利用动力学分析方法,分析端部受线性弹簧支承和扭转弹簧约束的端部约束悬臂管道从非保守系统逐渐变为保守系统过程中的固有特性和稳定性。数值仿真结果表明,这种特殊边界输流管道具有复杂变化的动力学特性,支承和约束刚度系数的变化对系统固有特性和稳定性产生很大的影响:随着弹簧刚度的增大,系统的固有频率上升,管道失稳方式从颤振变为屈曲,并且影响系统其他参数对管道动力学特性的作用。     

Water-assisted sub-critical crack growth along an interface between polyimide passivation and epoxy underfill

Direct chip attach (DCA) microelectronic packaging technology is gaining prominence due to its numerous advantages. Delamination (debonding) of the underfill epoxy/ polyimide passivation interface of a DCA during hydro-thermal reliability testing has always been one of the salient problems. We have studied the water-assisted sub-critical crack growth along this interface and our measurement offers important clues as to the origins of the poor hydro-thermal testing results for these interfaces. A modified asymmetric double cantilever beam (ADCB) testing technique has been used to measure the sub-critical crack growth velocity v at various relative humidities and temperatures as a function of the crack driving force (strain energy release rate) G ^*. The presence of a significant partial pressure of water p _H2O produces a marked decrease (by up to a factor of 12) in the threshold G ^* for crack growth at measurable velocities. Above the threshold log v rises linearly with but then enters a regime where the crack velocity (v=v ^*) is almost independent of . Finally, at the values of G ^* corresponding to rapid crack propagation in the absence of water, log v increases very rapidly with G ^*. By analogy to the classic work on water-assisted sub-critical crack growth in silica-based glasses, where very similar features are observed, we believe that the sub-critical crack growth along the polyimide-epoxy interface results from stress-assisted hydrolysis of primary covalent bonds, in our case ester bonds across the interface. The regime of just above the threshold corresponds to a physicochemical situation where the water activity (p _{H 2O} ) at the crack tip is the same as that of the gaseous environment. In the regime where v=v ^* constant, the water activity at the crack tip is below that in the environment and the crack growth velocity is limited by the transport of water vapor to the bonds ahead of the crack tip. We develop a model of this crack growth following Wiederhorn 1967 that allows us to predict the sub-critical crack growth as a function of G ^* for arbitrary relative humidity and temperature conditions.     

悬移支架放顶煤技术成功应用浅析

谢一矿采用悬移支架放顶煤采煤方法,实现了高产高效安全生产,取得了较好的效果。对影响悬移支架放顶煤技术成功应用因素进行了系统分析,并总结出了其主要影响因素。