Wave responses of a coastal cargo ship consisting of unit modules

This article discusses the dynamic responses of a coastal cargo ship that consists of unit modules with advance forward speed in waves. We introduce a simple way of connecting the modules that has enough capability to link the modular parts of the ship as a unified whole. The flexible connection consists of male and female rubber fenders with additional pretensioned ropes. This kind of connection system is proposed for use in coastal regions with relatively calm waters wherein the modular ship can move at a moderate speed. The modules are assumed to be rigid compared to the connections. Computations were performed to investigate the vertical elastic responses of four modules connected end-to-end with the assumption that in the simple hinge, no gaps occur in the flexible rubber connections between adjacent modules. A simple method, which is an extension of the computational analysis we reported previously, is presented to study the hydroelasticity and rope tension forces of the modular ship with forward speed in waves. Experiments with a three-dimensional model at Froude numbers of 0 and 0.16 in head waves were performed to evaluate the effectiveness of the calculation method. In the experiments, deflections for each part were measured using calibrated potentiometers. Force transducers were used to measure the rope tension force between the modules of the articulated cargo ship. Some slight differences were observed, but generally the calculated results showed the same trends as the experimental values.     

软交换技术在辽宁铁通的应用和推广

软交换技术是未来公众网的重要组成技术，介绍软交换技术在辽宁铁通的应用情况，阐述软交换技术网络的优势、特点，以及软交换的市场应用情况及业务推广策略，对于了解软交换技术和应用有一定的帮助。     

广佛江珠城际铁路西江特大桥主桥方案研究

西江特大桥是广佛江珠城际铁路的重要桥梁,为取得主桥合理的桥式方案,遵循"安全、实用、经济、美观"的设计原则,按照单向通航和双向通航的净空要求,采用钢桁拱桥、钢桁斜拉桥及矮塔斜拉桥,对4种桥型设计方案进行对比分析计算,综合考虑施工难度、景观效果、通航条件及工程造价等因素,最终得出双孔252 m钢桁拱桥为推荐方案。     

双流制列车通过中性段的供电切换方案研究

初步研究了重庆铜梁试验线交直供电系统间设置的中性段供电切换方案。在线路条件允许的情况下,建议双流制列车通过接触网中性段时采用不停车、不降弓的车上切换方式进行供电切换。接触网中性段位置宜选择在地面或高架区段。     

用软交换技术建设城市轨道交通公务电话系统

描述了目前城市轨道交通公务电话系统的现状,分析了在技术、设计、管理等方面存在的问题,并通过对软交换技术应用于城市轨道交通适应性等方面的论述,提出了城市轨道交通公务电话系统建设的思路和建议方案,以提高系统投资的有效性和性价比。     

DeviceNet总线在地铁低压智能配电系统中的应用

通过DeviceNet总线的网络结构、通讯模式等技术特点,同时结合DeviceNet现场总线的实际网络配置需求以及同相关系统的接口通讯,介绍了DeviceNet总线在广州地铁三号线和四号线低压智能配电系统中的应用。该项技术的应用对低压智能系统的自动化程度及信息化管理有较大的提升,并且为设备维护的及时性、方便性和经济性提供了便利。     

Dynamic response analysis of a small-scale model tension leg platform

Experimental tests performed on a hydroelastic small-scale model of a tension leg platform for deep water are reported. Comparison between the processed experimental dynamic signals and theoretical responses obtained with a simplified six degrees of freedom model are made. Moreover, some effects of fluid-structure interaction are briefly discussed in the light of results from both impact and wave loading tests.     

半桥串联谐振逆变器的非线性控制方案

本文介绍了半桥串联谐振逆变器的非线性控制方案的分析与设计,并提出了一个零电流转换非线性控制逆变器的设计.其电路拓扑包括两个功率开关、一个输出滤波器.逆变时,在功率通量回路中只有一个功率开关上有传导损耗.开关的零电流开通是通过扼流圈前级的辅助谐振回路实现的.非线性控制方案可以抑制直流输入扰动,并能对正弦脉宽调制控制进行有效的动态调节.我们使用了空间状态平均值的方法来对系统进行分析.文中以一个功率为500 W的逆变器作为设计示例,并对其性能进行评估,该逆变器在额定功率下,可以获得91%以上的效率.     

中国远洋航运业制冷工质R22替代R12技术研究

在哥本哈根会计后，制冷工质Ｒ１２也提前至１９９６年禁用，对我国远洋航海业影响甚大。至今为止，尽管国际上对ＣＦＣ３替代工质的研究不断深入，但是尚未有可以定论的长期ＣＦＣｓ替代工质。Ｒ２２是目前国际上公认的良好过渡性工质。     

三角胶带传动采用内侧张紧轮时的工作能力计算

本文分析了内侧张轮对三角胶带传动工作能力的影响;根据Miner法则导出了胶带寿命降低卑的计算公式;并给出一种能合理地确定胶带寿命和许用功率的计算方法。