大型加强板结构焊接顺序的效果研究(英文)

Welding sequence has a significant effect on distortion pattern of large orthogonally stiffened panels normally used in ships and offshore structures. These deformations adversely affect the subsequent fitup and alignment of the adjacent panels. It may also result in loss of structural integrity. These panels primarily suffer from angular and buckling distortions. The extent of distortion depends on several parameters such as welding speed, plate thickness, welding current, voltage, restraints applied to the job while welding, thermal history as well as sequence of welding. Numerical modeling of welding and experimental validation of the FE model has been carried out for estimation of thermal history and resulting distortions. In the present work an FE model has been developed for studying the effect of welding sequence on the distortion pattern and its magnitude in fabrication of orthogonally stiffened plate panels.     

BMW公司新型4缸2.0 L增压直接喷射汽油机

BMW公司开发了一种新型2.0L 4缸涡轮增压直接喷射汽油机,旨在明显降低燃油耗的同时,进一步提高行驶动力性能和驾驶乐趣,使其成为高效动力学经营战略的另一个重要组成部分。将来,该机型计划被配装在BMW公司几乎所有车型上。     

有限水深中垂直下潜弹性薄板的水波散射(英文)

The problem of water wave scattering by a thin vertical elastic plate submerged in uniform finite depth water is investigated here.The boundary condition on the elastic plate is derived from the Bernoulli-Euler equation of motion satisfied by the plate.Using the Green’s function technique,from this boundary condition,the normal velocity of the plate is expressed in terms of the difference between the velocity potentials(unknown)across the plate.The two ends of the plate are either clamped or free.The reflection and transmission coefficients are obtained in terms of the integrals’involving combinations of the unknown velocity potential on the two sides of the plate,which satisfy three simultaneous integral equations and are solved numerically.These coefficients are computed numerically for various values of different parameters and depicted graphically against the wave number in a number of figures.     

两维心回声图的临床应用

<正> 本文评论两维心回声图比M型超声心动图对成人心脏疾患的诊断具有更多的优点。它可以可靠的评价冠心病,左室室壁瘤,室壁运动失常和心室功能障碍。早先的研究证明它对于急性心肌梗塞后局部心脏的扩大及其预后的判断,检测左冠状动脉主干是否狭窄,和室壁瘤患者是否可以手术等方面都是有用的。二尖瓣(以下均简写为瓣)瓣狭窄患者二尖瓣口大小的确定,两维心回声图与手术所见或心导管检查资料对比提示有很好的相关。对于二尖瓣的返流的原因亦可以较可靠地阐明是瓣膜本身病变,还是心肌病理学上的异常所致。此外,左室、右室     

C系列柴油机的设计与发展

<正> C系列柴油机是一种缸径为114mm,冲程为135mm,总排量为8.3升的直列、六缸、直喷式柴油机。此系列柴油机在保持原有构件负荷的基础上,实现了高水平的涡轮增压,并达到了可靠性和耐久性指标。新增加的构件数量不多,成本和复杂性基本保持不变。 本文介绍了此系列发动机的主要零部件以及为达到技术指标而进行的主要设计与开发工作。文中也讨论了一些有关机械和热力分析方面的实例。此外,还论述了燃烧和排放优化及燃烧特性等问题。     

用自激感应发电机和强制换向整流系统作为直流电源

本文介绍了一种用自激三相感应发电机与强制换向整流器相配合而构成的一种新的直流电源系统。对系统的稳态特性基于简单的数学方法进行了分析,并且已被实验所证明。关于平波电抗器大小的影响本文也做了分析,结果表明,如果对负载脉动电流没有限制,可以不用平波电抗器。     

电力装置的自动控制系统

本文论述电力装置自动控制系统的用途及主要职能,确定自动化范围,自动控制系统的结构原则,同步和主电流自动开关的控制,备用柴油发电机的自动接入,发电机的过载自动保护,电站主要参数的检查及柴油发电机的控制。文章给出了电力装置自动遥控系统线路图及同步线路图。