Analytical determination of the ultimate strength of sandwich beams

An analytical determination of the ultimate strength of a typical GRP/PVC sandwich beam has been performed. These beams represent common building practise in marine applications. Equations describing the behaviour of a sandwich panel under beam loading and various failure modes have been developed. The method has been applied to predict the ultimate load for a simple supported sandwich beam. The critical loads have been compared with those from the experimental investigation of a typical bulkhead-to-hull GRP/PVC sandwich T-joint under pull out forces.     

Special Features of Erosion Wear of Rotor Blades of Cogeneration Steam Turbines

Numerous results of their own studies and published data are used by the authors to conclude that the highest erosion damage is typical for the low-pressure part of steam turbine rotor blades operating in a mode of low steam flow rates and especially at a zero rate. Despite the absence of process moisture in the flow-through part of the low-pressure cylinder under such operating conditions, the toroidal and near-root vortexes are very intense and cause enhanced wear of rotor blades. Design solutions for erosion protection of the blade system are considered and recommended. The refined method for computing the erosion wear of blades under the conditions of slow steam flows through the LPC yields values close to experimental data obtained for a T-250/300-240 turbine.     

Direct modification for non‐conforming elements with drilling DOF

A unified approach to eliminate the undesirable lockings in distorted meshes for both non‐conforming quadrilateral membrane and hexahedral elements with drilling (or rotational) degrees of freedom is presented. The direct modification scheme is utilized in the formulation of non‐conforming modes to improve the general behaviour of isoparametric‐based elements. It is shown that the direct modification is very effective in eliminating the locking and this improvement of element behaviour may be doubled if the selective integration scheme is used simultaneously. To verify the validity of elements formulated by the proposed schemes and to evaluate their effectiveness, several numerical tests are carried out. The combined use of additional non‐conforming modes with the direct modification method and the selective integration technique plays an important role to improve the behaviour of elements, especially for distorted mesh cases. Test results also show that the results for both non‐conforming quadrilateral membrane and hexahedral elements obtained by the proposed schemes are equally satisfactory. Copyright © 2002 John Wiley & Sons, Ltd.     

引黄供水灌溉模式的特点及其应用前景

引黄供水灌溉模式是多种多样的 ,作者就各种供水灌溉模式的工程灌溉特点进行了系统的论述 ,从引黄形式、灌溉方式、泥沙处理和水沙综合利用等对供水灌溉模式的适用性进行了综合比较。指出供水灌溉模式并存、水沙综合利用和环境治理、防洪和节水灌溉兼顾是黄河下游供水灌溉的主要发展方向     

Finite element computation of sloshing modes in containers with elastic baffle plates

A finite element method to approximate the vibration modes of a plate in contact with an incompressible fluid is analysed in this paper. The effect of the fluid is taken into account by means of an added mass formulation, discretized by standard piecewise linear tetrahedral finite elements. Gravity waves on the free surface of the liquid are considered in the model. The plate is modelled by Reissner–Mindlin equations discretized by MITC3 locking‐free elements. Implementation issues are discussed and numerical experiments are presented. In particular, the method is compared with analytical approximations and with an experimental study which has been recently reported. Copyright © 2002 John Wiley & Sons, Ltd.     

WindowsNT环境中雷达实时数据处理软件的数据交换方式

分析了雷达实时数据处理软件的任务需求，介绍了ＷｉｎｄｏｗｓＮＴ操作系统环境中雷达实时数据处理软件多线程间几种行之有效的数据交换方式。     

Oxygen isotope shifts of the Raman modes of YBa2Cu3O7−x

Raman scattering experiments have been carried out on sintered pellets of YBa₂Cu₃ ¹⁶O_7−x and YBa₂Cu₃ ¹⁸O_7−x obtained both by gas exchange and by growth with substituted oxides. The frequencies of the modes at 340, 435 and 502 cm⁻¹, which involve motion of the oxygen atoms and which shift significantly upon oxygen isotope substitution, have been measured for several sets of samples. The measured frequency shifts indicate that the isotope exchange on the O(2) and O(3) sites is more complete than the exchange on the O(4) site. The 502 cm⁻¹ line of the¹⁸O samples is observed to be broadened and this is attributed to¹⁸O-¹⁶O disorder on the O(4) sites. The results are discussed with reference to previous measurements of site activation energies and models for the exchange mechanism.     

研究一类高维系统Hopf分叉解的模态不变流形方法

基于非线性模态不变流形及范式理论，针对一类非线性结构振动系统和机电耦合系统，提出一种分析其简单Ｈｏｐｆ分叉解的模态不变流形方法。此方法不要求进行对角化和求中心流形，而是通过求解非线性模态系数来构造所谓中心模态流形。通过算例与常规方法进行比较，证明了本文方法的正确与有效。     

机器人腕关节伺服系统的变结构控制

基于不连续控制的滑模变结构控制理论,具有控制算法简单,易于实现,系统鲁棒性强等特点。本文针对一类特殊的伺服运动——机器人关节运动,采用变结构理论,做了一些设计工作,仿真结果和实际调试,证实了变结构控制的有效性。