中国网络购物产业分析

本文根据2006年中国网络购物市场最新发展现状,结合对网络购物市场、购物网站、网络购物用户的分析,讨论了中国网络购物市场的五大发展趋势,中国的网络购物产业将在逐步走向成熟.     

聚合物改性乳化沥青的制备与应用

结合聚合物改性乳化沥青实际工程,总结SBS改性乳化沥青的检验标准、产品制备的过程控制及应用于透层油施工工艺的控制.     

大连发展绿色物流的研究

绿色物流是新世纪物流产业发展的必然趋势。介绍了绿色物流的含义和大连的物流现状,剖析了大连发展绿色物流的必要性,提出了发展绿色物流的主要对策。     

浅析铁路选线中输电线路的影响及对策

从输电线路对铁路选线的影响入手,介绍特高压、超高压输电线路基本知识和规划建设情况,结合在建、拟建项目勘察设计中实际案例,总结铁路选线的相关原则。     

Robust adaptive horizontal vibration isolation of towed seismic streamers

The horizontal vibration of towed seismic streamers is a main reason for efficiency reduction of the seismic survey and tail tangling. A vibration suppression scheme of towed seismic streamers is investigated in this paper. The towed seismic streamer is divided into two spans, a controlled span, i.e., the low tension span, and an uncontrolled span, i.e., the high tension span, by a bird. The system model includes a hyperbolic partial differential equation with variable coefficient describing the towed seismic streamers, and an ordinary differential equation describing the dynamic of bird. Robust based-model knowledge and adaptive controllers, based on the Lyapunov method, are designed to isolate the vibration of towed seismic streamers caused by the course deviations of towing vessel, the variations of towing vessel velocity and the variations of towed seismic streamer density. The robust based-model knowledge and adaptive controllers exponentially and asymptotically drive the span-towed seismic streamer displacement to zero, respectively. A finite difference scheme is used to validate the efficiency of the control law. The proposed controller can isolate effectively the disturbance originated from the towed vessel, and can provide the improved damping but not sacrifice the isolation performance. The adaptive scheme can tolerate the lack of knowledge of some uncertain parameters and can directly execute the online adjustment of the parameters. Meanwhile, the proposed control law is robust and can resist the model uncertainty due to parameter incertitude, model error and unknown disturbance and so on. The control law only includes velocity and slope, while it does not need the displacement which is difficult to measure in the practical operations. Thus it is easy to implement.     

地铁直流牵引供电系统杂散电流分析

从离散模型出发,利用有限元分析法对地铁直流牵引供电系统的接触电压及杂散电流进行了分析.分析结果表明,结构钢电阻率对接触电压和杂散电流影响不大,而钢轨电阻率、过渡电阻、机车电流以及供电区间长度等参数均对接触电压和杂散电流有明显影响.地铁杂散电流防护工程中,关键在于前期对源头的控制,如加强轨道对结构钢的绝缘,合理设计结构钢筋的截面积等.地铁建成后,应重视杂散电流的监测与防护的功能.即"注重维护,加强监测"的防治原则.     

基于遗传算法的操舵仪控制参数在线优化

采用遗传算法对航向保持自动操作仪控制参数进行在线优化,计算机仿真表明,遗传算法可以方便地得到全局最优解,故控制器可以快速稳定地跟踪预定航向,且系统具有较好的鲁棒性。     

检波器在鱼雷引信系统中应用分析

针对鱼雷引信中所采用的同步检波器与包络检波器,本文对检波器在引信系统中的应用进行了分析。在运用数学方法对检波器的原理进行推导的基础上,仿真分析和比较了两种检波器的解调性能以及抗噪声性能,为进一步研究鱼雷引信系统抗干扰能力提供了参考依据。     

寒区桩基负摩阻力计算理论分析

介绍寒区桩基负摩阻力的成因机理、影响因素、研究现状、简化模型分析、理论计算方法、负摩阻力防治、措施及理论分析的发展方向。     

地铁电动客车牵引单耗测量技术的研究

介绍北京地铁在用电管理方面对地铁电动客车牵引单耗测量的情况,对电耗的统计数据进行分析比较,解决了北京地铁电动客车耗电无测量手段的问题．使地铁电平衡工作更加完善;并提出在新生产的电动客车上应加装电能计量装置以便准确计量电耗的建议。