水中声波之间非线性作用时能量变化的分析

为研究声波之间的变参数相互作用,以伯格斯方程为基础,用谱分解方法推导了泵波与弱信号波整倍频率相互作用后弱信号波的数学解析式,研究了弱信号波在受到泵波不同频率、幅度和初始相位干扰时的能量变化情况.研究表明:二者频率比为2时,信号能量变化最大,可达9.84 dB;随着幅度比增大,信号能量变化减小;频率比大于3时,可不考虑二者初始相位差对信号波能量变化的影响;间断距离内随着传播距离的增加,弱信号波能量变化增大.     

双馈风力发电机组的动态模型仿真

为满足在电网发生故障时风电机组需保持与电网连接并向系统不间断供电的要求,提出了双馈风力发电机的动态模型、变流器模型、变流器保护及电网模型,以研究双馈风力发电机的暂态特性.以1.5.MW SUT1500双馈风力发电机为原型,由一个无穷大电源等效电网模型,变流器模型采用定子磁链的定向电流矢量控制方法,利用PSCAD软件对双馈电机的暂态特性进行仿真.仿真结果表明,矢量控制能够实现双馈电机的有功、无功解耦,并可改善系统的低压穿越能力.     

基于流固耦合的叶片动力特性分析

在考虑耦合流场与旋转预应力条件下,建立了对应的叶片流固耦合系统的动力特性方程.采用ANSYS与FLUENT对整体叶片的耦合模态进行了计算,并利用实验获得气流压力脉动数据,对叶片振动进行了瞬态分析.结果表明:在旋转预应力与耦合流场压力作用下,叶片模态频率约有9Hz的上升,模态振型的最大位移位置点转移,振动方向改变,前三阶相对振幅分别从29.128,19.400,44.566下降到28.945,19.285,44.562;叶片最大变形和加速度位于前缘的上端,最大应力点集中在叶片根部一侧.     

基于红外原理的微型多气体检测系统的设计

为了解决目前煤矿瓦斯事故以及大量使用天然气的家庭安全、环境污染等问题,设计并开发了一种具有集成化、微型化的红外多气体检测系统,通过实验数据的测试对比和数据分析,这种系统达到了微功耗、微体积、宽量程、高分辨率等技术要求,且能集成多气体检测的微型检测系统.重点介绍了红外检测的光学原理,以及从单气体检测引入到集成多气体检测的设计思想和方法,并介绍了有关CAN总线的数据传输方式和无线数据通信方式在系统中的应用.     

作为统一知识体的美术与设计

设计学和美术学是专业分科不断细化的结果,其实设计学和美术学具有共同的理论基础,是统一的知识体。设计和美术在现代主义思潮中的分离只是实践方向的分离,而它们的行动态度则带有相似的社会批判性质。二战后设计力求摆脱美术理论的影响,转而追求创建属于设计学自身的“准科学”理论。但是设计无法回避形式和价值评判这两大问题。美术史学科常常不拘于设计和美术之间人为的界限,为美术和设计共享的理论基础贡献新的知识。我们应当超越对专业化的执着,追求认知的整体性。     

MATLAB在经编织物几何特性探讨中的应用

本文主要介绍了经编织物的线圈几何结构及其应用性;用MATLAB语言模拟出真实的线圈及组织结构;分析编链组织,建立起相应的模型,实现在模拟出的织物上进行仿真,并与实际结构进行比较。     

Effect of low-frequency rotary electromagnetic-field on solidification structure of continuous casting austenitic stainless steel

To understand the solidification behavior of austenitic stainless steel in rotary electromagnetic-field, the influence of low-frequency rotary electromagnetic-field on solidification structure of austenitic stainless steel in horizontal continuous casting was investigated based on industrial experiments. The results show that the solidification structure of austenitic stainless steel can be remarkably refined, the central porosity and shrinkage cavity can be remarkably decreased, and the equiaxed grains zone are enlarged by means of application of appropriate low-frequency electromagnetic-field parameters. The industrial trials verify that the stirring intensity of austenitic stainless steel should be higher compared with that of plain carbon steel. Electromagnetic stirring affects the macrostructure even if the average magnetic flux density of the electromagnetic stirring reaches 90 mT (amplitude reaches 141 mT) with the frequency of 3–4 Hz. Due to a higher viscosity, rotating speed of molten stainless steel is 20%–30% lower than that of molten carbon steel in the same magnetic flux density. Foundation item: Project(CSTC2007BB4216) supported by the Natural Science Foundation of Chongqing, China     

Damage and deterioration mechanism and curing technique of concrete structure in main coal cleaning plants

Concrete structures in main coal cleaning plants have been rebuilt and reinforced in the coal mines of the Shanghai Da-tun Energy Sources Co. Ltd., the first colliery of the Pingdingshan Coal Co. Ltd. and the Sanhejian mine of the Xuzhou Mining Group Co. Ltd. In these projects, the operating environment and reliability of concrete structures in the main plants of the three companies were investigated and the safety of the structures inspected. Qualitative and quantitative analyses were made on the spe-cial natural, technological and mechanical environments around the structures. On the basis of these analyses, we discuss the long-term, combined actions of the harsh natural (corrosive gases, liquids and solids) and mechanical environments on concrete structures and further investigated the damage and deteriorating mechanisms and curing techniques of concrete structures in the main coal cleaning plants. Our study can provide a theoretical basis for ensuring the reliability of concrete structures in main coal cleaning plants.     

面向校园网格环境的多域监控系统

文章建立了一种分域多层网格监控模型,利用LDAP提供的目录层次服务,动态设置多层虚拟监控域,进行分区域监控,实现全局监控与局部监控的分离.结合移动Agent技术的定制服务,过滤弱相关数据,满足多样化监控需求.文中详细讨论了校园网格监控系统的实现,并在此基础上,针对资源调度应用,给出了一种动态时间间隔算法,可以有效减少网格监控对系统资源的占用.