Investigation on the Dynamic Responses of a Truss Spar Platform for Different Mooring Line Groups

The dynamic responses of any floating platform are dependent on the mass, stiffness and damping characteristics of the body as well as mooring system. Therefore, it is very essential to study the effect of individual contributions to the system that can finally help to economise their cost. This paper focuses on the effect of mooring stiffness on the responses of a truss spar platform, obtained by different grouping of lines. The study is part of our present researches on mooring systems which include the effect of line pretension, diameter and azimuth angles. The platform is modelled as a rigid body with three degrees-of-freedom and its motions are analyzed in time-domain using the implicit Newmark Beta technique. The mooring lines restoring force-excursion relationship is evaluated using a quasi-static approach. It is observed that the mooring system with lines arranged in less number of groups exhibits better performance in terms of the restoring forces as well as mean position of platform. However, the dynamic motions of platform remain unaffected for different line groups.     

Mercedes-Benz车用柴油机钢活塞

长期以来,钢活塞一直用于载货车用柴油机。2014年,Daimler公司作为最早的汽车制造商将钢活塞应用于轿车柴油机。现在钢活塞不仅用于Daimler公司OM626和OM607柴油机的传统灰铸铁气缸套曲轴箱,还首次用于OM642-V6柴油机全铝气缸体曲轴箱与"Nanoslide"气缸工作表面涂层的组合。     

跳崖与蹦板

南山猴不堪对其大批桃子来历不明事件的丑闻调查愤而跳崖殒命，引起满山众生的极大关注，同情唏嘘者有之，愤懑怨恨者有之，借题发挥者有之，推搡冲突者有之，一时间纷纷扰扰，难以平息。北山猴连日来真是空虚痛苦寂寞难奈。由于长期不事稼穑，只爱鼓捣些烟花爆竹，这些东西又不能当饭吃，想换粮食又没人搭理。这样下去撑不了多久，自己就会被活活饿死。夜来忽得一梦，梦中虎狮熊象众生匍匐尘埃，跪着哀求自己放弃爆竹营生，说情愿奉献上等的米面和鲜桃，并一致公认自己是新一代的东方霸主。     

消除液压系统中液体噪声

引言近几年来反对噪声对我们生活干扰的呼声正在增长。这是个非常现实的问题。极度的噪声有使听觉永遭损坏的危险。有证据表明,在噪声干扰环境下工作的生产人员的生产率和效率都受到影响。虽然在许多情况下在设备交货之前噪声并不是明显的因素,但是,近年来的     

Finite Element Simulation of Processes Involving Moving Heat Sources. Application to Welding and Surface Treatment

IntroductionAwiderangeofweldingorsurfacetreatmentprocessesinvolvetheuseofaheatsourcemovingataconstantspeedoverthesurfaceofthecomPonent.ThreedimensionalcomPutationofresidualstressesanddistortionsinducedbythiskindofprocesses,usingtheusualfiniteelementmethod,needsveryrefinedmeshesinordertocorrectlydescribethepropertiesandstressgradientsintheheataffCctCdzonealongthepathoftheheatsource.Inthispaper,wediscussthedifferentnumericalaPproaches,imPlementedinSYSWELD@software,whichcanbeusedtodorealisti…     

舰船横摇及其预测和减摇

本文旨在向舰船设计人员叙述一下舰船横摇现象、采用现有理论方法进行的横摇预测和采用现有减横摇系统进行的减摇,并对现有的预测方法进行评论。可以断定,采用现有的方法能良好地预测没有减摇装置的横摇运动,而在预测横摇运动中必须考虑到耦合横摇-横荡运动。本文还讨论了被动式和主动式横摇减摇水舱和主动式减摇鳍的使用,并探讨了各种减摇装置的尺寸、性能和优缺点。本文最后认为,需要进行模型试验来确定预测减横摇装置的性能和进一步研究横摇运动。     

欧洲摆式列车倾摆系统比较

欧洲摆式列车主要采取两种倾摆系统，主动倾摆系统和被动倾摆系统。本文重点介绍了ＡＢＢ公司Ｘ２０００和菲亚特公司Ｐｅｎｄｏｌｉｎｏ摆式列车的主动倾摆系统，以及ＳＩＧ公司和Ｔａｌｇｏ公司的被动倾摆系统设计原理，结构特点与试验运用情况，比较了这两种倾摆系统的性能，并对其安全极限和舒适度进行了评价，认为无论是主运还是被动倾摆系统均能有效地提高曲线通过速度，在既有线路上实现高速运营。     

2D非稳态方柱绕流的数值模拟与分析

用有限体积法对与来流夹角为45°以及夹角为0°的方柱绕流进行了数值模拟分析.从对方柱的绕流的数值模拟结果可以得出倾角为45°的方柱对尾涡的影响较之倾角为0°的方柱要大得多.由此可知,特征长度越大对柱体尾部涡影响越大.同时还对方柱的受力进行了计算和分析,并与现有实验数据、文献资料进行了比较,两者互相吻合.     

活塞顶环下周边倾角对窜气和机油消耗的影响

关于活塞气环下侧面与周边面之间的倒角形状和尺寸对窜气和机油消耗的真实影响，有几种不同的意见。对一台柴油机进行了测功试验，以弄清楚这种倒度对发动机性能有无影响。