Curvilinear fatigue crack reliability analysis by stochastic boundary element method

In this paper, the stochastic boundary element method, which combines the mixed boundary integral equations method explored in Reference 1 with the first-order reliability method, is developed to study probabilistic fatigue crack growth. Due to the high degree of complexity and non-linearity of the response, direct differentiation coupied with the response-surface method is employed to determine the response gradient. Three random processes, the mode I and mode II. stress intensity factors and the crack direction angle, are included in the expression of the response gradient. The sensitivity of these random processes is determined using a first-order response model. An iteration scheme based on the HL-RF method² is applied to locate the most probable failure point on the limit-state surface. The accuracy and efficiency of the stochastic boundary element method are evaluated by comparing the cumulative distribution function of the fatigue life obtained with Monte Carlo simulation. The reliability index and the corresponding probability of failure are calculated for a fatigue crack growth problem with randomness in the crack geometry, defect geometry, fatigue parameters and external loads. The response sensitivity of each primary random variable at the design point is determined to show its role in the fatigue failure. The variation of each primary random variable at the design point with the change of probability of failure is also presented in numerical examples.     

The geometry effects for stress intensity factor of sandwich specimen for measuring interfacial fracture toughness

The interfacial stress intensity factors for three types of sandwich specimens: the single edge crack tensile specimen, the three point bend specimen and the four point shear specimen were obtained by the finite element analysis and compared with the asymptotic solutions. The results show that the geometric effect for mode II specimen is larger than mode I specimen. The limit curves for geometry factor equal to 1.05 were obtained to indicate the usable range of validity of the asymptotic solution.     

机器人离散滑模变结构—PI控制器

本文采用离散滑模变结构控制方法，针对机器人提出了一种滑模变结构——ＰＩ控制方案，给出了该控制方案滑模存在条件及控制器设计方案。该控制器将离散滑模变结构控制和ＰＩ控制两者的优点有机地结合起来，理论分析和仿真结果表明该控制器能使机器人在各种复杂非线性动力学情况下具有良好的性能指标。这种控制器输出切换小，可以投入应用。     

A Study of the Specific Heats of the Compounds in the Sm_2O_3-BaO-CuO System

By means of X-ray diffraction and adiabatic scanning calorimeter,the specific heatsof five compounds in the Sm_2O_3-BaO--CuO system,such as Sm_2BaO_4,Sm_2CuO_4,BaCuO_4,Sm_2BaCuO_5,SmBa_2Cu_3O_(7-x),from -150℃ to 800℃ have been measured.It is found that the specific heats ofthese compounds increase smoothly with the increase of temperature.     

基因工程干扰素对慢性粒细胞白血病骨髓细胞DNA损伤修复的影响

以姊妹染色体互换为观察指标．观察了干扰素对慢性粒细胞白血病骨髓细胞DNA损伤修复的影响，探讨了干扰素对慢性粒细胞白血病的治疗机理，对指导临床治疗具有重要的意义。     

采用混合物作工质的J—T节流制冷机

报告了国内外采用混合物作工质的Ｊ一Ｔ节流制冷机的实验研究情况。理论计算的两个重要参数（等温节流效应和正常沸点）与这些实验的结果作了对比。另外，给出了工作在不同压力下的一种混合工质及纯氮的焓温图。从理论计算和实验的结果可以看出混合工质Ｊ一Ｔ节流制冷机比单纯工质的Ｊ一Ｔ节流制冷机有更大的制冷量和更高的热效率。     

淀积条件对GDa—SiNx薄膜电学特性的影响

本文讨论了用辉光放电法制备氮化硅薄膜时衬底温度、射频功率和气体流量比对薄膜的电导率、介电常数和击穿强度的影响。通过优化生长条件，制备了优质非晶氮化硅薄膜，其介电常数为７．５、击穿强度为５．５ＭＶ／ｃｍ、电导率为１０－１３（Ωｃｍ）－１。     

直接基于灰度图象的多尺度角点检测方法

在计算机视觉领域中角点特征的提取具有相当重要的地位，因为角点包含了丰富的信息。本文提出了一种新的利用微分几何和小波变换的多尺度角点检测方法，它具有以下特点：一是无须提取边缘图象，而是直接在灰度图象上提取角点。二是由于利用了小波变换技术从多个尺度上进行角点的提取，所以它既较为有效的抑制了由于噪音等原因造成的诸多错误角点位置的出现，又能得到较为精确的有用角点位置。最后通过实验证明了本算法有效性。     

应用多孔阳极氧化电流—时间曲线比较壁垒膜厚

在有壁垒膜存在的表面,多孔膜的生长在氧化初期受到延迟阻碍,这一现象在直流恒压多孔阳极氧化电流一时间曲线上反映出来。电流达到稳态氧化的时间愈长,壁垒膜愈厚。文中应用此法判断了0.5MH_3BO_3介质的pH值、温度对壁垒阳极氧化膜厚的影响,并应用记录同一介质环境壁垒恒流阳极氧化的槽压一时间曲线得到验证。