长壁开采覆岩离层产生的条件

研究了长壁采煤上覆岩层运动中层间脱开的条件、存在过程及其与岩层结构和采矿条件的关系．以理论分析、相似模拟和数值仿真为基础，提出了产生离层的覆岩结构类型，离层起始条件、扩展条件和离层量的预测方法．进一步提出了层间注浆的作用机理．这一研究对于大范围岩层控制和地面建筑物的保护具有重要意义     

无线网络中的移动模型

移动ad hoc网络(MANET)是指不依赖于固定设备,而由一组无线节点通过自组织而形成的网络.移动性是MANET最主要的特性之一,对网络的性能产生极大的影响.该文主要介绍了MANET中常见的移动模型,并简要分析了他们的主要特点和适用环境.     

矩形膨胀节的位移特性

推导出了矩形膨胀节在轴向、横向、角向位移下产生的力、力矩、当量轴向位移以及刚度等公式，还对ＥＪＭＡ标准矩形膨胀节的刚度公式及力矩公式作了补充和修正。指出矩形波纹角部的最大应力为位移应力，因此该部位易于破坏。     

不同顶管施工工艺对深层土体移动的影响分析

对杭州市石桥路手掘式、泥水式及土压式顶管施工所引起的深层土体移动进行了分析,得出了一些有意义的结论。     

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双轴自同步平动椭圆振动筛比强迫同步的平动椭圆筛结构简单，噪音小，维护保养方便，且处理量比自同步直线振动筛大。它是继强迫同步的平动椭圆筛和自同步直线振动筛之后的钻井振动筛的又一主流筛型。建立了双轴自同步平动椭圆振动筛的运动方程，从激振轴的转矩方程出发，得到了其自同步条件；利用振动筛的稳定性扰动方程得到了同步稳定运转条件。建立了双轴自同步平动椭圆振动筛的力心理论和利用力心理论设计的方法。结果表明：双电机驱动的椭圆振动筛能够实现自同步稳定运转，且两电机的驱动力矩之差、摩擦力矩之差及参振质量对质心的转动惯量越小，同步性越好；大激振轴回转中心和筛箱质心运动的椭圆长轴方向间的距离与筛箱质心和该激振轴回转中心到质心椭圆长轴方向的垂线间的距离之差越小，振动筛的运动稳定性越好，当激振力的力心与参振质量的质心重合时，就能实现平动椭圆运动。     

A videomicrographic low-frequency movement analyser (VLMA) and perifusion chamber for recording and analysis of the physical behaviour of seminiferous tubules and other contractile tissues in vitro

A method has been developed for the recording and analysis of low frequency movements such as those of the surfaces of live seminiferous tubules. The method involves time-lapse videomicrographic recording of the tubules followed by frame-by-frame measurement of the position of the edge of the tubule image in the video field. These measurements, which describe the movement of the tubule, may be analysed into a series of power spectra relating to sequential time periods through the recording. The group of spectrum plots for each tubule preparation can be plotted as isometric, pseudo three-dimensional figures, with time represented on the s-axis. The shapes of the spectra represent the contractile activity of the seminiferous tubules. Alterations in the level of activity and/or in the position of the frequency peaks, between control and experimentally treated preparations, are readily apparent. We also describe the construction and features of the perifusion chamber used with the VLMA.     

The Role of Misfit Dislocations in Strength Enhancement of Cu/Ni Microlaminates

This paper simulated the nanoindentations of Cu/Ni thin films with 2D Molecular Dynamics Simulations (MDS) and examined the effects of the misfit dislocations on the mechanical properties of the microlaminates. The misfit dislocation network plays an important role in strength enhancement of Cu/Ni microlaminates because of its resistance to glide dislocations. But the strengthening also relies on the wavelength, which is defined as the thickness of adjacent two layers in microlaminates. When the wavelength is less than the critical value λc, the stress concentration caused by the movement of misfit dislocations will make Cu/Ni microlaminates weaken. Also, the critical wavelength should be more than the depth at which the dislocation nucleates in the homogeneous layer.     

A computer model to assess fire hazards in tunnels (FASIT)

A computer model that simulates fire growth movement in tunnels is described, and a brief overview of tunnel systems is presented. The methods for predicting mass flows, velocities, smoke concentrations, and heat transfer are presented, along with a list of hazard output parameters. The validation of the model against experiment, and possible directions for future work are also presented.(previously with AEA Consultancy Services)     

Application of Curved Surface of Ball Movement in Hydraulic Engineering

The curved surface of ball movement is a connecting bent pipe commonly used in hydraulic engineering. The curved surface poses a complicated problem with computation. The mathematic model of the circular curved surface of ball movement in engineering is set up by adopting the concept of envelope curved surface.     

Mesh deformation using the biharmonic operator

The use of the biharmonic operator for deforming a mesh in an arbitrary–Lagrangian–Eulerian simulation is investigated. The biharmonic operator has the advantage that two conditions can be specified on each boundary of the mesh. This allows both the position and the normal mesh spacing along a boundary to be controlled, which is important for two‐fluid interfaces and periodic boundaries. At these boundaries, we can simultaneously fix the position of the boundary and ensure that the normal mesh spacing is continuous across the boundary. In addition, results for deforming surfaces show that greater surface deformation can be tolerated when using biharmonic equations compared to approaches using second‐order partial differential equations. A final advantage is that with the biharmonic operator, the integrity of a grid in a moving boundary layer can be preserved as the boundary moves. The main disadvantage of the approach is its increased computational expense. Copyright © 2003 John Wiley & Sons, Ltd.