Experimental Study on Benard-Marangoni Convection by PIV and TCL

An experimental investigation of Benard-Marangoni convection has been performed in double immiscible liquid layers of rectangular configuration. The two kinds of liquid are 10cst silicon oil and FC-70 respectively. The velocity fields in the vertical cross-section are obtained by PIV. Flow patterns and/or temperature distributions on the horizontal interface are displayed by using thermal color liquid crystal (TLC), and the velocity distributions on the interface were also obtained with the help of the serial particle image of TCL. The evolution processes of convection are observed in the differential thickness ratio of two liquid layers, and the convection styles are discussed.

流体与流体混合物的临界与超临界特性

本文第一部分介绍单组分流体的临界与超临界特性.主要内容为临界点的经典与标度状态方程;临界点异常特性的实验证据;热力学与输运性质的计算等等.第二部分介绍二元流体混合物的临界与超临界特性.第三部分介绍超临界气体萃取的工业应用.

严格求解夹层圆柱壳在轴压下的轴对称失稳问题

本文在文献[1]的基础上,用严格的方法求解两端简支的夹层圆柱壳在均匀轴压下的轴对称失稳问题.内、外表层很薄弹性模量又大,按薄壳理论处理;夹心较厚弹性模量又相当小,横向剪切变形的影响必须考虑,在研究夹层壳的整体失稳尤其是局部失稳时,横向的拉伸和压缩变形也不可忽略,用数学弹性力学的方法处理.本文导得了可求解轴对称整体失稳和局部失稳临界载荷的超越方程,用数值计算的方法可算得临界载荷的最小值.对于整体失稳的情况,给出算例,与夹层壳理论的解作了比较.

四边简支矩形板稳定问题的精确解

本文从三维弹性力学出发,推导了四边均匀受压简支矩形板的临界载荷公式,并进行了数值计算与经典理论及考虑剪应变薄板理论进行了分析比较。

The plastic instability behaviour of laser-textured steel sheet

As the production of a new technique that can offer both good formability and high image clarity for texturing metal sheet, laser-textured sheet has attracted the attention of many manufacturers and users. Among the many subjects to be studied, plastic instability behaviour of the laser-textured sheet is one of most important to understand its ability in extending material ductility and to appropriately control this technique. Experimental investigations are carried out in this paper to study the macroscopic behaviour and microstructural mechanism of the laser-textured sheet, and comparison is made with the normal sheet taken from the same coil of metal sheet. It is demonstrated that, the difference in the behaviour of plastic instability obviously shows tendency to delay strain localization and the onset of thickness necking. Shear banding and internal void damage are spread to a much wider region in the sheet being laser-textured. The prestrained microcraters enforced on the surface of the textured sheet act as hardening spots, which are likely to share out deformation and inhibit the increasing rate of voiding, and eventually favouring the ductility of the material used.

The influence of microcrack density on the elastic and fracture mechanical properties of stripa granite

Microcracks can have a strong influence on the elastic and fracture mechanical properties of rocks if they are numerous, or if they are orientated in unfavourable directions in anisotropic rocks in particular. This paper presents results from a great number of mechanical tests on Stripa granite containing various amounts of microcracks. Variations in the microcrack density were obtained by shock-heating the rock at different temperatures in the range 100–600°C for 3 h.

永乐大钟及悬挂支撑系统的撞钟过程瞬态分析

采用ANSYS有限元分析软件对永乐大钟及其悬挂支撑系统建立了有限元模型,进行了撞钟过程有限元瞬态分析及动力强度校核。通过有限元计算,获得了大钟各局部考察对象及整体的应力、位移分布情况和各部分的动力响应和对强度的影响,为合理撞钟和加固提供了科学依据与技术指导。

多环环间混杂复合材料飞轮离心应力分析

采用平面应力假设,给出了计算多环环间混杂复合材料飞轮的离心应力和初始极限转速的方法,并采用二维轴对称的有限元分析验证了计算方法的合理性,可作为初步设计多环环间混杂复合材料飞轮的依据.本文的算例分析还表明,无论单一纤维或混杂的复合材料飞轮,空心结构的初始极限转速和储能密度均高于相应的实心结构的结果;且对于空心结构,有利于通过选择合适的混杂方案,实现一定意义上的"等强度"设计.

Spatial and Temporal Variation of LURR and Its Implication for the Tendency of Earthquake Occurrence in Southern California

Based on the theory of LURR and its recent development, spatial and temporal variation of Y/Y-c (value of LURR/critical value of LURR) in the Southern California region during the period from 1980 through March, 2001 was studied. According to the previous study on the fault system and stress field in Southern California, we zoned the Southern California region into 11 parts in each of which the stress field is almost uniform. With the time window of one year, time moving step of three months, space window of a circle region with a radius of 100 km and space moving step of 0.25 degree in latitude and longitude direction, the evolution of Y/Y-c were snapshot. The scanning results show that obvious Y/Y-c anomalies occurred before 5/6 of strong earthquakes considered with a magnitude of 6.5 or greater. The critical regions of Y/Y-c are near the epicenters of the strong earthquakes and the Y/Y-c anomalies occur months to years prior to the earthquakes. The tendency of earthquake occurrence in the California region is briefly discussed on the basis of the examination of Y/Y-c.

Spatio-Temporal Scanning and Statistical Test of the Accelerating Moment Release (AMR) Model Using Australian Earthquake Data

The Accelerating Moment Release (AMR) preceding earthquakes with magnitude above 5 in Australia that occurred during the last 20 years was analyzed to test the Critical Point Hypothesis. Twelve earthquakes in the catalog were chosen based on a criterion for the number of nearby events. Results show that seven sequences with numerous events recorded leading up to the main earthquake exhibited accelerating moment release. Two occurred near in time and space to other earthquakes preceded by AM R. The remaining three sequences had very few events in the catalog so the lack of AMR detected in the analysis may be related to catalog incompleteness. Spatio-temporal scanning of AMR parameters shows that 80% of the areas in which AMR occurred experienced large events. In areas of similar background seismicity with no large events, 10 out of 12 cases exhibit no AMR, and two others are false alarms where AMR was observed but no large event followed. The relationship between AMR and Load-Unload Response Ratio (LURR) was studied. Both methods predict similar critical region sizes, however, the critical point time using AMR is slightly earlier than the time of the critical point LURR anomaly.

Integration property of a wedge-elliptic cone waverider with scramjet engine

The hypersonic waverider forebody is designed in this paper. For the present waverider, the undersurface is carved out as a stream surface of a hypersonic inviscid flow field around wedge-elliptic cone, and the upper surface is assumed to be a freestream surface. A finite-volume code is used to generate the three-dimensional flow field. The leading edge is determined by satisfying the condition that the lip is situated at the intersection line of shocks.

Analytical calculations of Eulerian and Lagrangian time correlations in turbulent shear flows

The Taylor series expansion method is used to analytically calculate the Eulerian and Lagrangian time correlations in turbulent shear flows. The short-time behaviors of those correlation functions can be obtained from the series expansions. Especially, the propagation velocity and sweeping velocity in the elliptic model of space-time correlation are analytically calculated and further simplified using the sweeping hypothesis and straining hypothesis. These two characteristic velocities mainly determine the space-time correlations.

板壳断裂力学

本书阐明了板壳断裂理论的基础。论证了Reissner型板壳断裂理论的科学性、经典板壳断裂理论的缺陷及在一定范围内仍具有的实用价值；介绍了作者所创意的研究Reissner型板壳断裂纹尖端场的方法等。

目录

拼接光栅的偏差对光束空间特性的影响

用拼接小尺寸多层介质膜衍射介质膜衍射光栅的办法制作大口径的高破坏阈值光栅成为解决拍瓦激光系统输出能量的关键技术——光栅拼接技术。拼接的每个光栅都存在五维自由度的偏差，对激光脉冲的空间特性和时间特性产生影响。用夫琅禾费衍射的方法分析了拼接光栅的偏差对光束空间特性的影响，建立了偏差和远场强度分布之间的函数关系并用数值方法进行模拟，得出角度偏差对光束远场分布的影响可以忽略，而位移偏差：光栅间拼缝和前后位移偏差是影响光束远场分布的关键因素。