Efficient calculation of slamming pressures on ships in irregular seas

An efficient method for calculation of the slamming pressures on ship hulls in irregular waves is presented and validated for a 290-m cruise ship. Nonlinear strip theory was used to calculate the ship–wave relative motions. The relative vertical and roll velocities for a slamming event were input to the slamming calculation program, which used a two-dimensional boundary element method (BEM) based on the generalized 2D Wagner formulation presented by Zhao et al. To improve the calculation efficiency, the method was divided into two separate steps. In the first step, the velocity potentials were calculated for unit relative velocities between the section and the water. In the next step, these precalculated velocity potentials were used together with the real relative velocities experienced in a seaway to calculate the slamming pressure and total slamming force on the section. This saved considerable computer time for slamming calculations in irregular waves, without significant loss of accuracy. The calculated slamming pressures on the bow flare of the cruise ship agreed quite well with the measured values, at least for time windows in which the calculated and experimental ship motions agreed well. A simplified method for calculation of the instantaneous peak pressure on each ship section in irregular waves is also presented. The method was used to identify slamming events to be analyzed with the more refined 2D BEM method, but comparisons with measured values indicate that the method may also be used for a quick quantitative assessment of the maximum slamming pressures.     

Experimental study on the nonlinear pressure acting on a high-speed vessel in regular waves

It is well known that the hydrodynamic responses of a high-speed vessel traveling in regular head waves of even moderate wave height can show significant nonlinear behavior, and so linear statistical techniques become insufficient for predicting the statistics of responses in irregular waves. On the other hand, it has been shown that an approximate third-order Volterra model is applicable to handling the statistics of some nonlinear seakeeping problems, such as motions and vertical hull girder loads. In the present study, the focus is on the nonlinear behavior of the pressure responses of the hull surface, especially on the pressures acting on alternately wet and dry areas near the waterline and on the bow zone with high deadrise angles that may be subject to slight impact and water pile-up effects. To clarify the validity of applying Volterra modeling to this problem, a series of experiments in regular and irregular head waves were carried out, and approximate third-order and fifth-order Volterra models with the proposed algorithm for finding frequency response functions (FRFs) were applied as a means of validation. In the present article, the first part of the validation was performed using experimental data in regular waves. It was confirmed that the third-order Volterra model has adequate accuracy to simulate deterministically the variation of pressure responses in regular waves of different wave steepness up to a wave amplitude to wavelength ratio of 0.01 even for the highly nonlinear pressures acting on the above-mentioned areas of the hull surface.     

国际货运代理人法律地位及其认定标准

国际货运代理人的法律地位不是唯一的,具有作为代理人的法律地位及作为当事人的法律地位,两者所承担的法律责任也大不相同。国际货运代理人的法律地位可以从以下几个方面认定:合同的内容;签发提单;拼箱、拥有自己的运输工具提供服务;公布自己的运价;挣取差价等。     

41 CASES REPORT OF CLINICAL APPLICATION OF MITRAL VALVE RECONSTRUCTION

４１ＣＡＳＥＳＲＥＰＯＲＴＯＦＣＬＩＮＩＣＡＬＡＰＰＬＩＣＡＴＩＯＮＯＦＭＩＴＲＡＬＶＡＬＶＥＲＥＣＯＮＳＴＲＵＣＴＩＯＮ（李兆志）（黄庆恒）（耿希刚）ＬｉＺｈａｏｚｈｉ；ＨｕａｎｇＱｉｎｇｈｅｎｇ；ＧｅｎｇＸｉｇａｎｇ；（ＤｅｐａｒｔｍｅｎｔｏｆＣ...     

某海底服务隧道施工中涌水处理及风险控制措施

详细介绍了某海底隧道施工过程中突发涌水事故的成因、发生过程和处理方案,并提出了相应的防范和控制措施,对后期海底隧道施工潜在的涌水风险进行了分析和评估。     

基于软件易测试性的CBTC区域控制器系统设计

区域控制器系统是CBTC铁路运行系统中重要的一部分，对提高列车运行效率和安全起着重要的作用。首先介绍了区域控制器的工作原理和易测试性的特点，然后将易测试性方法应用于区域控制器系统的设计中。这种设计方法提高了测试效率，降低了测试成本。     

基于因瓦尺的高精度控制测量方法及其应用

在特种工程测量、工业测量、近景摄影测量和三维扫描仪标定中,往往涉及到范围较小(如10m到50m范围内),但绝对精度要求很高(精度要求在±0.5mm以内)的测量问题,电子全站仪或工业测量手段很难达到精度要求。建立了一个基于因瓦尺的物方坐标系,用电子全站仪测出因瓦尺上点的角值,反求出测站的坐标,再用前方交会测定其他待定点的坐标。理论分析、实验验证及应用实例证明,该方法简便易行,且能达到很高的精度。     

世界汽车工业的发展动向

世界汽车工业现状主要表现在两个方面：全球性汽车生产能力过剩和世界汽车工业的全球化。据美国《纽约时报》报道，美国一家大型咨询公司预测，最迟到2002年，世界汽车的供应量将比需求量多2000万辆。北美自由贸易协定的签署取消了贸易壁垒，汽车市场和用户对新技术和新产品永不满足的追求，致使各发达国家企业间在竞争的同时实现企业跨国联合。     

异步多传感器数据融合

在分布式多传感器数据融合系统中，由于每个传感器的采样周期不同以及具有不同的通信延迟，导致送入融合中心的局部航迹往往不是同步的。提出一种多传感器异步数据融合算法，该算法首先利用最小二乘实现时域融合，将航迹同步化，然后利用一种序贯的Kalman滤波方法进行融合。