蒸发过程中饱和土壤水稳定同位素运移规律浅析

基于Fick定律和质量守恒定律推导了饱和土壤水在蒸发过程中的稳定同位素微分方程模型,分析了饱和土壤水的边界条件,给出了解析解,为数值模拟蒸发、蒸发过程中土壤水的稳定同位素组成变化提供了确定性的数学基础,对土壤水分运动以及土壤水稳定同位素的研究具有一定的理论意义.     

高液限土和煤系土抗剪强度的水敏感性比较研究

为研究分布在广梧高速公路沿线的高液限土和煤系土的水敏感性,通过常规直接剪切试验测定了不同含水状态高液限土和煤系土试样的抗剪强度,对比分析了含水量对两者抗剪强度的影响,并探讨了实际工程中应对高液限土和煤系土问题的策略.研究结果表明:高液限土和煤系土的抗剪强度均与起始含水量具有明显的相关关系,起始含水量越大抗剪强度越小.随着含水量的增大,高液限土黏聚力的对数与含水量成线性关系减小,其内摩擦角则先小幅减小,后急剧减小.随着含水量的增大,煤系土黏聚力变化具有显著的分段性:先小幅减小,后大幅减小,且其对数与含水量成指数关系.含水量变化对煤系土内摩擦角的影响较小.粒组成分的不同是导致高液限土和煤系土水敏感性不同的主要原因.     

基于Matlab的径向基函数数值计算软件包

为推动基于无网格方法的计算软件的发展,介绍基于Matlab自主开发的径向基函数（Radial Basis Function,RBF）数值计算软件包,阐述软件的理论基础、设计思路以及该软件包的功能和特点,并结合边界节点法（Boundary Knot Method,BKM）的数值实例给出软件的使用过程．该软件包可以根据不同的数学物理模型选择合适的数值算法来求解多种实际物理问题,也可对不同数值算法得到的结果进行比较．最后,总结应用Matlab进行数值计算软件开发的优缺点．     

引入趋近律的功率因数校正滑模控制仿真研究

提出一种引入趋近律的滑模变结构控制(SMVSC)方法来实现有源功率因数校正(APFC),减少电流的谐波成分.SMVSC是一种解决非线性时变系统(如APFC系统)问题的良好办法,但是实际应用中SMVSC的"抖振"现象问题必须要解决好.引入趋近律来削弱APFC系统在滑模控制中的"抖振"现象,并且依此推导出了控制APFC系统中的功率开关的PWM占空比.采用Matlab平台进行仿真验证控制策略控制APFC电路几乎得到单位功率因数,同时超调减小、响应时间缩短.     

钟形箱涵式进水流道泵装置特性模型试验研究

对钟形箱涵流道过流特性及流态进行了试验分析,结合浦东薛家泓泵站模型试验,对钟形箱涵流道立式潜水轴流泵站模型泵装置的能量、气蚀、飞逸特性进行了全面试验研究,得出泵装置综合性能曲线及飞逸特性曲线,同时用示踪线法对进水流道内的流态进行了观察研究,试验分析了不同导流方案对模型泵装置能量特性的影响,提出了改善流态的有效措施,对优化设计高效潜水轴流泵装置提出了几点建议。研究成果不仅对薛家泓泵站设计和施工提供了必要依据,对提高泵站运行维护水平,保证同类泵站安全可靠运行起着重要的指导作用。     

天荒坪抽水蓄能电站水泵水轮机"S"形特性及其对策

天荒坪抽水蓄能电站水泵水轮机为高水头、大容量、高转速、单级单转速双向旋转的混流可逆式机型，其全特性曲线中存在明显的“S”形区域。经现场调试知，当机组在低水头发电空载运行时，极易进入“S”形特性区域，造成机组并网困难、逆功率或甩负荷后不能达到空载稳态。当采用导叶不同步预开装置（MGV装置）后，基本解决了此类问题，增强了机组的运行稳定性。     

基于ARM9平台的嵌入式SIP服务器的设计

SIP服务器由重定向服务器、代理服务器、注册服务器组成，在VoIP系统中起着重要作用。该文基于嵌入式ARM CPU S3C2410，设计了硬件平台，对Linux2.6内核进行了移植，实现了SIP协议栈和服务器软件。该服务器已成功应用于某水利部门的实时语音通信平台中，取得了良好效果。     

Elastic Anisotropic Viscoplastic Modeling of the Strain-Rate-Dependent Stress–Strain Behavior of K0-Consolidated Natural Marine Clays in Triaxial Shear Tests

This paper presents a new three-dimensional (3D) anisotropic elastic viscoplastic (EVP) model for the time-dependent stress–strain behavior of K0-consolidated marine clays. A nonlinear creep function with a limit for the creep volumetric strain under an isotropic or odometer K0-consolidated stressing condition and a nonsymmetrical elliptical loading locus are incorporated in the 3D anisotropic EVP model. An α-line defines the inclination of the nonsymmetrical elliptical loading locus in the p′-q plane and is commonly used for natural soils. All model parameters are determined from the results of one set of consolidated undrained compression tests and an isotropic consolidation/creep test. With the parameters determined, the 3D anisotropic EVP model is used to simulate the behavior of K0-consolidation tests and the strain-rate-dependent stress–strain behaviors of the K0-consolidated triaxial compression and extension tests on natural Hong Kong marine deposit clay specimens. These triaxial K0-consolidated specimens were sheared at step-changed axial strain rates from +2?to?+0.2, +20, ?2 (unloading) and +2%/h (reloading) for compression tests; or from ?2?to??0.2, ?20, +2 (unloading), and ?2%/h (reloading) for extension tests, all in an undrained condition. The simulation results of all these tests are compared with the test results. The validation and limitations of the model are then evaluated and discussed.     

Bond strength prediction for deformed steel rebar embedded in recycled coarse aggregate concrete

This paper summarizes the results of an experimental investigation into the bond behavior between recycled aggregate concrete (RAC) and deformed steel rebars, with the main variables being the recycled coarse aggregate replacement ratio (RCAr) and water-to-cement ratio of the concrete mixture. The investigation into splitting cracking strength indicates that the degradation of the bond splitting tensile stress of the cover concrete was affected by not only the roundness of the coarse aggregate particles but also the weak interfacial transition zone (ITZ) between the cement paste and the RCA that has a more porous structure in the ITZ than normal concrete. In this study, a linear relationship between the bond strength and the density of the RCA was found, but the high compressive strength reduced the effects of the parameters. To predict the bond strength of RAC using the main parameters, a multivariable model was developed using nonlinear regression analysis. It can be inferred from this study that the degradation characteristic of the bond strength of RAC can be predicted well, whereas other empirical equations and code provisions are very conservative.     

基于支持向量机的区域水安全预警模型及应用

基于支持向量机算法建立了区域水安全预警评价模型,根据水安全评价标准及其所属的评价等级值,随机内插生成序列来建立评价分类的样本集,并以松江区为例进行研究。研究结果表明基于SVM方法建立的模型简单,评价结果合理可行,可用于区域水安全预警评价。