爆炸冲击波数值计算网格划分方法研究

在爆炸冲击波数值计算过程中,计算精度很大程度上取决于空气和炸药的有限元网格尺寸.现在常用的爆炸冲击波数值计算网格划分方法大多是针对某一当量炸药的,在使用中存在一定的局限性.针对这一问题,本文提出了一种与炸药当量相关的网格划分方法,并应用有限元软件LS-DYNA进行了计算对比,结果表明:该方法适用性很好,而且在计算精度与计算效率上取得了很好的平衡.     

砌体等效断裂韧度的实用解析方法研究

根据砌体准脆性材料的断裂特性,提出了一种基于竖向灰缝模型的求解砌体等效断裂韧度的实用解析方法.首先根据复合材料力学和线弹性断裂力学的基本原理,运用修正的剪滞理论,分区引入变异层,建立了分层剪滞模型;然后根据能量法则,推导出了求解无筋砌体等效断裂韧度的解析计算模式;最后针对相关试验数据,得到了对应数值解的解析解,且与相关试验对应的数值解相比,解析解的均方差和变异系数更小,由此可以看出,本文的解析方法具有很好的鲁棒性.结果还证明了无筋砌体等效断裂韧度是与试件尺寸无关的断裂参数.该方法为砌体结构开裂机理的研究和发展,砌体结构力学性能的研究提供了新的技术路径.     

Development of Zr/ZrO<Subscript>2</Subscript> high temperature and high pressure sensors for <Emphasis Type="Italic">in-situ</Emphasis> measuring chemical parameters of deep-sea water

In order to in situ measure chemical parameters of deep-sea water and hydrothermal fluids at midocean ridge(MOR), it is necessary to use high temperature and high pressure chemical sensors.Developing new sensors is essential to measure in-situ pH and other chemical parameters(dissolved H2, dissolved H2S) of deep-sea water and hydrothermal fluids in a wide temperature range(2℃―400℃) at MOR vents.The YSZ(Yttria Stabilized Zirconia, 9%Y2O3) ceramic-based(HgO/Hg) chemical sensors possess excellent electrochemic...     

Orientation angle workspaces of planar serial three-link manipulators

This paper presents a classification on the workspaces of planar serial three-link manipulators, that is, position workspace and orientation angle workspace. Position workspace indicates the region reached by the reference point on the end-effector. Orientation angle workspace indicates a set of angle ranges by which the end-effector can reach with certain orientation for every point in the reachable position workspace. By introducing a virtual equivalent mechanism, reachable position workspace can be divided into several Grashof intervals and non-Grashof intervals. The calculation equations of orientation angle workspace are deduced in three situations according to the relationships among four link lengths in the virtual four-bar chain. Three examples are given for three kinds of relationship of link lengths. The orientation angle workspace of extended groups, that is, two of the three link lengths equal, and the orientation angle workspace when the reference point on the end-effector moves along a non-radial direction are also discussed. A program is developed to calculate orientation angle workspaces and output variation curves of orientation angle workspace and key data within the position workspace. The approach and program in this paper can be used for fast calculation and identification of the variation rule of the orientation angle workspace of any given planar serial three-link manipulator on the basis of its link parameters, and for the design of a highly dexterous serial manipulator with proposed link relations. Supported by the Natural Science Foundation of Shanxi Province (Grant No. 20041070)     

基于超声波原理的开孔参数标定系统研究

针对传统的人工丈量方法标定开孔方位角和倾斜角存在操作程序繁琐、稳钻时间长、精度低等问题,设计了基于超声波原理的钻孔开孔参数标定系统。该系统采用超声波渡越时间检测法测量参考点之间的距离,并由单片机解算出钻杆的方位角,选用微机械三轴加速度计测量倾斜角,实现了全自动化的实时跟踪测量及智能化的钻机姿态调整语音指导操作;在误差允许范围内,可快速标定所需开孔参数。该系统提高了开孔参数标定精度、标定效率及煤矿管理水平,降低了矿工劳动强度和煤矿管理成本。     

Al2O3陶瓷粉料的喷雾干燥工艺要点

本文阐述了喷雾造粒过程中的相关制备工艺 ,并通过实验总结出一套合理的工艺控制参数     

Bubble size effect on low liquid input drift-flux parameters

We investigated the effect of bubble size on the drift-flux parameters at low liquid flow conditions by measuring the radial profiles of void fraction and phase velocities in a vertical bubbly pipe flow of diameter and height . To study the effect of the bubble size we used two different types of bubble inlets. We measured the local bubble fraction and velocity U_g by using single and four-point-optical fibre probes, and we used Laser Doppler Anemometry to determine the liquid velocity U_l. The distribution parameter C₀ and the weighted mean drift velocity |U_drift| were directly computed from the local measurements at a height on our experimental set-up. Both parameters were influenced by the bubble size. Provided no liquid flow reversal occurred at the near wall region, the distribution parameter reached a below unity minimum plateau value of C₀=0.95 for wall peaking void fraction profiles. At low liquid input conditions both the liquid input and bubble size had an influence on the distribution parameter. Extreme values such as C₀>2 were measured. From these measurements we developed models for the drift-flux parameters to take into account the effect of bubble size and input-flow conditions for our intermediate pipe diameter value. These models were tested and validated with separately collected experimental data.     

差异化运动参数的有效挖掘技术仿真

研究运动参数准确挖掘方法.在运动参数挖掘的过程中,由于图像采集时间间隔比较短,短时间内运动幅度的变化非常小,所以很难对运动参数差异性进行准确的描述,无法实现运动参数准确挖掘.提出利用蚁群聚类算法的运动参数挖掘方法.根据约束模糊聚类相关原理,获取运动参数特征聚类目标函数,对特征差异目标进行最大化处理,完成运动参数特征提取.计算残留信息素对于聚类中心的隶属度,设置合理的蚁群目标搜索调整因子,计算聚类中心和对应的偏差,并对偏差进行有效补偿,完成参数挖掘.实验结果表明,利用改进算法进行运动参数挖掘,能够有效提高挖掘的准确性,提高数据管理的效率.     

Specific features of thermal decomposition of ammonium perchlorate subjected to γ radiation

Results of studying thermal decomposition of ammonium perchlorate (AP) samples in the original form and after irradiation by γ-quanta of ⁶⁰Co by methods of differential scanning calorimetry and dynamic thermogravimetry with heating rates b = 0.1–0.3 K/sec are described. Irradiation is performed in air at a temperature of 298 ± 2 K and a dose rate of ≈0.2 Gy/sec in the range of absorbed doses D = 0–150 kGy. Preliminary irradiation is demonstrated to lead to substantial transformations of the pattern of thermal decomposition of ammonium perchlorate in the dynamic regime of heating: the single-stage process of decomposition of non-irradiated samples proceeding at b = 0.107 K/sec in the temperature range of 625 to 743 K is replaced by a multistage process. At D = 150 kGy, exothermal transformations accompanied by noticeable losses of sample mass are observed starting from 473 K. Within experimental errors, the total thermal effect of AP decomposition is found to be independent of the absorbed dose and amounts to −1150 kJ/kg on the average. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 6, pp. 69–74, November–December, 2007.     

超细六硝基芪的热分解性能

为了解超细六硝基芪（HNS）的热分解性能，通过DSC—TG实验研究HNS—IV的热分解过程，用Kissinger法和Ozawa法计算了HNS-Ⅳ热分解反应动力学参数。结果表明，HNS-Ⅳ的热稳定性与HNS-Ⅱ相当。Kissinger法和Ozawa法得到的HNS-Ⅳ分解表观活化能分别为221．4kJ／mol和220．3kJ／mol，比静态气氛下HNS-Ⅱ热分解反应的表观活化能减小27kJ／mol。