不同衬底上低温生长GaN形貌的AFM观察

　Aim　To study the relationship between the substrate temperature and the morphology and properties of GaN. Methods Applying the hydride chemical vapor deposition method, GaN films were deposited on different kinds of substrates, including sapphire, Si(111),Si(100),GaAs and GaP(111) both on the P face and the Ga face. The growth was performed at low temperatures of below 700℃. XRD, Hall measurement, cathodoluminescence (CL) and atomic force microscopy (AFM) were used to characterise the film properties. Results It was found that the temperature and the nature of substrate materials influence the layer morphology. Conclusion The analysis shows that no apparent relationship exists between the optical properties and layer morphology.     

用于车辆传动的金属材料的疲劳试验及统计方法

　Aim　To improve the efficiency of fatigue material tests and relevant statistical treatment of test data. Methods Least square approach and other special treatments were used. Results and Conclusion The concepts of each phase in fatigue tests and statistical treatment are clarified. The method proposed leads to three important properties. Reduced number of specimens brings to the advantage of lowering test expenditures. The whole test procedure has more flexibility for there is no need to conduct many tests at the same stress level as in traditional cases.     

风险分析的尖点突变模型

　Aim　To assess simultaneously various risk states of a system. Methods Using the catastrophe and fuzzy theory, the energy and uncertainty in a system are set as two control variables and the function of the system is used as the state variable for analysis. Results and Conclusion A risk analysis model named the cusp model is presented. Various states regarding the safety of the system such as the accident state, no-accident state and miss state can be represented at will on the cusp model.     

动态系统的自适应模糊神经网络控制

　Aim　To build an adaptive fuzzy neural controller and simulate it. Methods Fuzzy logic and back propagation(BP) algorithm are combined to utilize their advantages while avoiding the disadvantages. Results and Conclusion Simulation results of the third-order plant with disturbances and dead times show the validity of the presented controller. The presented controller can control cases that preceding controllers were unable to control.     

基于DA算法的二维离散余弦逆变换的ASIC设计

　Aim　To present an ASIC design of DA-based 2-D IDCT. Methods In the design of 1-D IDCT is utilized a Chen-based fast IDCT algorithm, and multiplier accumulators based on distributed algorithm contributes in reducing the hardware amount and in enhancing the speed performance. Results and Conclusion VHDL simulation, synthesis and layout design of system are implemented. This 2-D IDCT ASIC design owns best timing performance when compared with other better designs internationally. Results of design prove to be excellent.     

节理岩体弹塑性动态有限元分析

　Aim　To study the elastic-plastic dynamical constitutive relations about a jointed rock mass under explosion load and its computer simulation. Methods Stress history is taken into account and stresses will follow changes in time during a period of explosion load. According to the principle of static force balance, the corresponding nodal concentrated force is calculated and the nodal displacement is counted. The elastic-plastic dynamic finite element equations are thus obtained. Results A finite element method is given for a jointed rock mass under explosion load. Conclusion The problem of large plastic deformation for jointed rock mass on blasting was efficiently resolved through dynamic finite element analysis and the range of damages by blasting simulated, and this pushes forward the problem to engineering practice.     

燃料空气炸药近区抛散过程的研究

　Aim　To study fuel dispersion in fuel air explosive(FAE) and computational ways of fuel dispersion velocity in the near area. Methods The dispersion process of fuel in FAE was analyzed by the use of results measured with KODAK EKTAPRO EM Motion Analyzer and setting up mechanical models. Results Computational methods for fuel dispersion velocity in the acceleration stage is given and taken as a base for the study of fuel dispersion in the intermediate and the far area. Conclusion When the fuel flow velocity is higher than that of the explosion gas in the center cavity, the fuel divides with the explosion gas and its velocity of flow reaches a maximum. The acceleration stage ends at that time. The fuel dispersion velocity at this time is the initial conditions for numeral analyses of dispersion process in the intermediate and far areas.     

矿井通风网络分析的遗传算法

　Aim　To determine the global optimal solution for a mine ventilation network under given network topology and airway characteristics. Methods The genetic algorithm was used to find the global optimal solution of the network. Results A modified genetic algorithm is presented with its characteristics and principle. Instead of working on the conventional bit by bit operation, both the crossover and mutation operators are handled in real values by the proposed algorithms. To prevent the system from turning into a premature problem, the elitists from two groups of possible solutions are selected to reproduce the new populations. Conclusion The simulation results show that the method outperforms the conventional nonlinear programming approach whether from the viewpoint of the number of iterations required to find the optimum solutions or from the final solutions obtained.     

约束系统特性对乘员碰撞响应影响的仿真研究

　Aim　To study the influence of restraint system performance upon the occupant's response during impact, and provide a scientific base for occupant restraint system design. Methods In the light of basic theory of multibody system dynamics and impact dynamics on the basis of classical theory of impact, R-W method is adopted to construct the vehicle-occupant system model consisting of fourteen rigid bodies, thirty seven DOFs and slip joints for the simulation. A software named SVC3D(3-dimensional simulation of vehicle crash) is developed in the FORTRAN language. Results The results of simulation have a good coincidence with those of tests and the restraint system with low elongation webbing and equipped with pretensioner provides better restraint effect for the occupant. Conclusion The model of vehicle-occupant multibody system and SVC3D are suitable for use. Occupant should be belted with low elongation webbing to a certain degree and occupant restraint system should be equipped with pretensioner.     

热处理对共混物中尼龙6熔融行为的影响

　Aim　To investigate the multiple melting behavior of polyamide-6(PA-6) in polyamide-6/linear low density polyethylene blends crystallized from the crystal-amorphous state. Methods The effects of annealing temperature, annealing time, heating rate, and the step-wise annealing were measured by DSC. Results and Conclusion There exists a critical heating rate affecting the middle temperature melting peak. When annealed at the temperature close to the melting peak, the main melting peak of PA-6 shifted to a higher temperature. Within a short time, annealing time has much effect on neat PA-6 but little effect on PA-6 in the blends. Addition of PE results in a decreasing in the height of melting peak. These phenomenon show that the melting behavior of PA-6 was affected by PE, compatibilizer, as well as thermal treatment.     

采用瞬态上流元法的油纸绝缘瞬态电场研究

作为换流变压器的主要绝缘材料,油纸复合材料的绝缘特性受内部空间电荷的影响. 在极性反转电压下,介质内部积聚电荷产生附加场强,可能使局部电场明显增强,从而更易引起绝缘击穿. 基于瞬态上流有限元数值方法,引入界面势垒模型,计算极性反转条件下单层油浸纸、油浸纸-油双层绝缘结构内部空间电荷的运动特性以及瞬态电场随时间的变化规律,并与试验得到的规律进行对比验证. 仿真结果表明：在直流电压下,介质内部积聚的电荷无法快速消散,将对反转瞬间的电场产生叠加作用,引起电极附近场强最大程度畸变. 双层介质的界面阻碍效应产生的界面积聚电荷,导致在极性反转瞬间油中电场瞬时增大. 研究结果可为换流变压器油纸绝缘特性和击穿场强研究提供参考.     

储层电各向异性模型的瞬变电磁响应

采用数字滤波算法对储层电各向异性模型的瞬变电磁响应进行数值模拟,首先在频率域计算出各向异性模型的电场响应,然后利用正弦变换将计算结果转换到时间域。通过对电偶极子源激发下的层状各向异性模型的瞬变电磁场进行计算,结果表明:对薄互层模型而言,当中间薄层为高阻时,视电阻率曲线在晚期随各向异性系数的增大而抬升,且各向异性的影响大于厚度的影响。当中间薄层为低阻时,各向异性系数对视电阻率曲线无影响。这对指导瞬变电磁对油藏勘探具有重要意义。     

550kV电容式电压互感器的均压设计

为改善550kV电容式电压互感器（CVT）电场均匀度,采用有限元分析方法（FEM）对含多重介质的轴对称无界场域电场进行数值模拟.建立了不同绝缘结构的电场计算模型,通过数值仿真计算得出电场分布,得到全场域绝缘性能的影响因素.通过对不同伞群结构以及有无均压环时全场域的电场对比分析,认为产品设计中设置合理的均压环是改善场均匀度的有效方法,并提供了均压环最佳位置及结构的参考尺寸,为550kV电容式电压互感器绝缘结构设计提供了数值基础.     

复燃和截流过电压作用下真空断路器灭弧室内的电场分析

采用暂态电路模型对真空断路器开断空载变压器时由复燃和截流引起的过电压进行了数值模拟，并对暂态过电压的频率成分进行了离散的傅立叶分析，以此作为真空断路器的边界夺件，采用有限元法进行了计算，给出了灭弧室内的暂态电场分布和电场强度随时间变化的曲线，讨论了暂态电场的一些特征，为真空断路器的绝缘设计提供了参考.     

高压SF6断路器灭弧室电场逆问题求解研究

采用有限元法对高压SF6断路器灭弧室内电场分布进行数值仿真求解,计算分析了灭弧室内部动、静触头在开断过程中不同行程下电场分布情况，得到了全场域最大场强所在位置，以及动、静主触和弧触沿面场强分布，研究了灭弧室内部绝缘的主要影响因素，并将仿真结果进行可视化处理.在此基础上进行电场逆问题求解，实现灭弧室内部结构优化设计.在优化设计中分别采用零阶方法和一阶方法，以动、静触头几何结构为优化设计变量，以灭弧室内部最大场强最小为优化目标函数，循环迭代次数为停止准则，进行灭弧室电场逆问题研究.并将优化结果与产品结构进行对比分析，证明了优化设计的可行性和有效性.     

在极不均匀电场下变压器油中气泡运动过程及回旋现象

长期运行的油浸式电力设备内部会有少量气泡存在于变压器油中,而设备内部复杂的电场环境会使油中气泡运动形态发生改变,这将会引起电场畸变并最终造成绝缘劣化。本文首先设计了气泡自动生成装置,通过该装置以模拟油中气泡产生,在此过程中利用高速相机对其运动轨迹进行捕捉;随后通过有限元仿真软件建立了气液两相流模型,已获取气泡周围电场分布;最终借助仿真模型从力学角度对气泡上升时所伴随发生的回旋现象开展相关讨论。在研究中利用图像处理软件对拍摄结果进行处理,分析了气泡尺寸以及电场强度对于气泡运动轨迹的影响,结果表明,气泡尺寸增大以及电场强度的增加均会改变气泡自身受力情况使运动偏移量增大;同时结合仿真计算分析可知极不均匀电场的存在使得气泡不同区域场强有所差异,对气泡表面区域进行划分并利用仿真结果对该区域受力进行计算,发现气泡不同区域受力方向各异,最终分析可知极不均匀场的存在导致表面受力不均是引发气泡位移、形变最终造成多气泡回旋的主要原因;且这一过程两电极间将会出现多气泡短暂聚集,这将使得电场畸变进一步加强,造成绝缘性能显著下降。通过本研究厘清了气泡位于极不均匀场下的运动特性,明确了气泡回旋产生原因及其对绝缘性能的影响。     

极性反转下换流变压器内部电场分析

采用ANSYS电磁场分析软件,利用含电磁性能参数（电容系数、电导率）的暂态电场有限元分析方法,分析了换流变压器内部暂态电场分布规律．研究了不同激励下端部电场的分布以及极性反转时换流变压器油纸复合绝缘电场的分布．重点分析了换流变压器在直流极性反转电压作用下,绝缘介质电阻率对电场分布的影响．     

500kV变压器段间雷电冲击模型试验

应用二维四节点有限元电场数值分析的方法,通过对５００ｋＶ电力变压器段间绝缘雷电冲击试验模型关心区域内电场分布的比较,提出了一种５００ｋＶ变压器段间绝缘雷电冲击试验模型的简化方案,并对该简化试验模型进行了雷电冲击试验。经过试验模型的电场数值分析,得出了由段间固体绝缘材料与变压器油形成的油楔中会出现段间最大电场强度的结论。通过雷电冲击试验,得５０％击穿电压、最小击穿电压与试验模型的匝绝缘厚度、段间油隙     

SF_6管道电缆在水电站的应用

本文论述水电站出线应用SF_6管道电缆的优越性,分析计算运行时的冲击特性和绝缘配合的参数。此外还计算了单芯电缆的最大场强,提出合理的结构尺寸,可供设计运行部门参考。     

10kV户外真空断路器灭弧室电场数值分析

采用有限元法对10KV真空断路器灭弧室内部电进行计算分析，得出不同外绝缘情况下的电场分布情况，通过对真空灭弧室在不同外绝缘尺寸，厚度等条件下悬浮电位的计算及灭弧室内部电场进行的一系列仿真分析，为户外真空断路器的设计及其外绝缘设计提供了理论根据。