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961.
K. Ohtani D. Numata T. Kikuchi M. Sun K. Takayama K. Togami 《International Journal of Impact Engineering》2006,33(1-12):555-565
This paper reports a result of hypervelocity impact experiments on cryogenically cooled aluminum alloys and a composite material. Experiments are carried out on a target palate at 122 K. Aluminum spheres at 1.95 km/s in 50 kPa air were impinged against the target plate at cryogenic temperature and the result was compared with room temperature target plates. Hypervelocity impact (HVI) processes were visualized with shadowgraph arrangement and recorded with high-speed video camera and to ensure the temperature dependence we compared HVI tests with metal target plates with AUTODYN 2D and SPH numerical simulations. We found that cryogenic impacts created slight differences of impact damage from room temperature ones, i.e., the shape and averaged diameters of HVI crater holes were less at cryogenic impacts. 相似文献
962.
We prepared Ti/CoCrPt/Ti pseudo-sandwich granular films by radio-frequency and dc magnetron sputtering onto glass substrates and subsequent in situ annealing. We investigated the microstructure and magnetic properties of the films as a function of Ti overlayer thickness (x). X-ray diffraction profiles show that the CoCrPt magnetic layers are formed as the hexagonal close-packed (HCP) structure. Vibrating sample magnetometer measurements indicate that the out-of-plane coercivity reaches the maximum 1675.5 Oe when x=5 nm. Atomic force microscopy images show the minimum average grain size D=7.2 nm and the average roughness R/sub a/=1.0 nm. Magnetic force microscopy images show that the minimum average magnetic cluster size is about 6.4 nm at x=5 nm. 相似文献
963.
简介了首钢氧气厂新建35000m^3/h空分设备的工艺流程及技术参数,详细分析了常规变负荷和快速变负荷调节时空分设备的运行工况以及快速变负荷调节时的工艺特点。 相似文献
964.
Meshless methods have some advantages over their counterparts such as the finite-element method (FEM). However, existing meshless methods for computational electromagnetic fields are still not as efficient as FEM. In this paper, we compare two meshless methods of discretizing the computational domain of Poisson-like problems; namely, the point collocation and Galerkin methods (which use the strong and weak forms of the governing equation respectively), and their effects on the computational accuracy and efficiency of the magnetic fields. We also discuss methods of handling discontinuities at the material interface. We present several examples, which also provide a means to validate and evaluate both meshless methods. Exact solutions and/or FEM are used as a basis for comparison. In addition, we also verify the results by comparing computed magnetic forces against those measured experimentally. 相似文献
965.
The effect of carbon precursor on the pore size distribution of mesoporous carbon during templating synthesis process 总被引:1,自引:0,他引:1
Wenzhong Shen Xiangping Yang Qingjie Guo Yihong Liu Yanru Song Zhongxiang Han Qinglei Sun Jian Cheng 《Materials Letters》2006,60(29-30):3517-3521
The starch and cyclodextrin were selected as the precursors and the mixture of surfactant and tetraethyl orthosilicate (TEOS) as template to prepare mesoporous carbon. The result showed that a bimodal pore size distribution in mesoporous carbon derived from starch appeared; one was around 3.4 nm and the other ranged from 3.8 to 16.2 nm. However, there existed a concentrated pore size distribution from 3.2 to 4.2 nm in mesoporous carbon derived from cyclodextrin. The different molecular structure of starch and cyclodextrin and their polymerization process in the presence of sulfur acid were responsible for the resulted mesoporous carbon structure; the starch could polymerize by head to head or side by side, but the cycleodextrin was only polymerized by head to head. 相似文献
966.
Xuekun Sun 《Engineering Fracture Mechanics》2006,73(10):1343-1361
Nonlinear finite element analyses are used to examine the effects of friction and geometric nonlinearities on the energy release rate in three- and four-point bend end-notched flexure tests. Energy release rates are first determined by a recently developed direct energy balance approach. It is shown that the finite diameter loading rollers that are typically used in practical test set-ups cause both tests to be inherently nonlinear. The effect of these nonlinearities on the energy release rate is shown to be larger in the four point than the three point test and to increase with increasing roller diameter, increasing coefficient of friction along the crack plane, and decreasing supporting span length. For the four point test, the effect of these nonlinearities is also shown to increase with increasing ratio of inner to outer span length. Next, energy release rates at the onset of crack advance are determined by a simulated compliance calibration technique. This “perceived toughness” is compared with predictions of the “true toughness” given by the direct energy balance approach at the same load. It is shown that perceived toughnesses from this simulated compliance calibration procedure are larger than previously reported results that were obtained in a similar fashion using linear theory. In addition, the perceived toughness is shown to strongly depend upon the range used for fitting the load versus deflection data to obtain compliance. These findings are used to make some general recommendations regarding use of the two test methods and their associated data reduction techniques. 相似文献
967.
968.
969.
用于3D模型检索的扩展距离球面调和表达 总被引:1,自引:0,他引:1
使用光线投射方法对3D模型定义了一个对应的球函数--扩展距离球函数,然后引入了球面调和分析方法,构造了一种对于平移、缩放和旋转变换具有不变性的特征向量,并用于基于形状的3D模型检索中.与基于向径方法结合,提高了检索的效果,扩大了应用范围. 相似文献
970.
GPS车辆调度系统是应用全球定位系统GPS(Global Positioning System),并基于GSM移动通信网络,通过短消息通信的方式对网内车辆进行定位、跟踪和监控的监管系统.目前,在许多行业(如公安、公交和银行等)中,GPS车辆调度系统已经相当普及,GPS车辆调度系统的相关研究也成为业界的一大热门课题.本文LCD中文显示的一种编码方法是笔者在设计GPS车载终端通信系统时使用的方法. 相似文献