船用直流组网技术比较

全电力推进系统相对于传统推进系统具有明显优势,是目前船舶推进技术的研究热点之一。全电力推进技术正在经历由交流组网技术向直流组网技术过渡的过程。在比较直流组网技术相对于交流组网技术的优势后,详细介绍目前几种流行的已经得到实船验证的直流组网技术路线,并对其异同点进行比较。分析结果表明,直流组网技术明显优于交流组网技术,不同的直流组网技术路线本身也会对系统的性能产生巨大的影响,特别是异步发电机+全控整流器的方案相对于其他的直流组网技术路线具有明显的优势。     

LNG/LPG船耐低温材料的焊接发展综述

液化天然气和液化石油气需要在低温条件下储存和运输,因此液舱(液罐)材料的耐低温性能和焊接性是保证结构安全的关键。文中以殷瓦钢、5083铝合金和304不锈钢为例,介绍了LNG船与LPG船使用的耐低温材料的种类和物理性能,在此基础上分析了这三种材料的焊接性,总结了殷瓦钢、5083铝合金和304不锈钢的焊接研究进展及发展趋势。     

鱼雷斜入水过程非定常运动仿真研究

针对鱼雷反潜时复杂的入水过程,采用FEM/SPH耦合方法,对鱼雷入水过程进行了仿真,研究了鱼雷入水过程中的冲击加速度和入水初始段鱼雷姿态的变化。仿真过程中发现了"忽扑"现象对鱼雷入水后非定常运动的重要影响。通过分析试验数据,完善仿真模型,模拟了"低压力"引起的鱼雷入水后的"忽扑"现象,仿真分析了鱼雷真实的入水非定常运动过程。结果可为鱼雷入水弹道设计和结构承载能力设计提供一定的依据。     

船用空调风机变频调节节能研究

介绍空调风机变速调节节能原理，并根据实船测得的数据，针对不同海区和时刻，对空调动态热负荷的变化进行分析，进而对节能指标进行数值计算，得出了空调风机变频调节节能率高的结论．     

Circulation features in the Japan/East Sea related to statistically obtained wind patterns in the warm season

A response of the circulation in the Japan/East Sea (JES) to different kinds of wind forcing is studied, with the emphasis on the warm season, using a primitive equation oceanic model. Wind forcing is based on typical patterns obtained from complex empirical orthogonal functions of 1°-gridded NCEP/NCAR 6 h winds for 1998–2005. These patterns are distinguished by a prevailing wind direction. Northwestern wind and strong cyclonic (C) curl prevail in winter, while a variety of patterns occur in the warm season, differing in the wind direction and curl. Three model runs are performed to examine the circulation in response to a prevailing C wind stress curl or an alternating C and anticyclonic (AC) curl or a strong C curl in the warm season. The simulated features are consistent with the observational evidence, in particular with thermal fronts and frequent eddy locations derived from multi-year infrared satellite imagery. The simulated C circulation intensifies and the subarctic region extends southward with the strengthening of a summer C wind stress curl over the JES. Variability of Subarctic Front (SF) in the western JES (between 130°E and 133°E) is strongly affected by summer wind stress curl. Forcing by an AC curl tends to shift SF northward, while SF shifts to the south under the forcing by a C curl, reaching the southern Ulleung Basin in the case of the strong C curl. In the northwestern JES (off Peter the Great Bay, Russia, and North Korea), the SF northwestern branch (NWSF) is simulated. It is a known feature in autumn and early winter and can also occur in the warm season. The simulation results suggest an AC wind stress curl as the forcing of the formation of the NWSF in the warm season. The Siberia Seamount and sharply bending coastline near Peter the Great Bay facilitate partial separation of the Primorye (Liman) Current from the coast. The wind stress curl can be an additional forcing of the Tsushima Warm Current (TWC) branching off the Korea Strait to the East Korea Warm Current (EKWC) and the offshore branch (OB). In the warm season, the simulated TWC bifurcation occurs farther north, the EKWC is strong, and the OB is weak under the forcing of the AC wind stress curl. The EKWC is weak and the OB is strong under the forcing of the strong C wind stress curl.     

A review of the effect of a/ W ratio on fracture toughness （Ⅲ） ——theoretical analysis

In part I and II of this series, experimental investigation in both EPFM and LEFM had been discussed. In this part, further theoretical analysis is given. The theoretical development of Two Parameter Fracture Mechanics by Hancock etc, has rationalized our experimental results. This method can be applied to engineering practice, and will allow the advantage of enhanced toughness for specimens with low levels of constraint to be taken into account for defect assessment.     

超大型石化临港工业码头平面布局

中科合资广东炼油化工一体化项目拟在湛江东海岛建设一座超大型临港石化基地及配套码头工程。项目具有规模庞大、码头承担运输的货物种类繁多、物性复杂、流向广泛、工厂毗邻大型钢铁基地及规划的石化园区、影响因素复杂的特点。从论证石化临港工业码头建设规模、大型原料码头选址、码头分区布局、平面布置关键问题等方面进行了分析归纳,合理确定码头工程的平面布局,为调整港区规划提供了依据,研究结论可为类似工程提供参考。     

基于HLA的防空兵群作战仿真系统设计

文章在分析防空兵群作战过程的基础上,结合HLA高层体系结构程序设计技术,设计开发一种基于HLA的防空兵群作战仿真系统,以解决防空兵群作战效能评估实际面l临的困难,辅助指挥员训练。针对仿真系统开发的规律和特点,重点介绍了仿真联邦设计以及FOM／SOM设计与实现。     

Simulations of roughness growth on rails - results from a 2D non-Hertzian, non-steady contact model

A new model for simulating rail roughness growth on tangent track is presented in this paper. The model consists of three relatively independent components: (1) a time-domain vehicle/track interaction model; (2) a 2D non-Hertzian and non-steady wheel/rail contact model; and (3) a wear model. Wheel/rail contact forces for a given initial roughness obtained from the vehicle/track interaction model are used by the contact model to calculate the contact patch size, normal pressure and tangential stresses with material removal assumed to be linearly proportional to the friction work in the contact patch. The roughness profile is updated and fed back into vehicle/track interaction model. The 2D contact model is initially compared with a 3D model for various wavelength of initial sinusoidal roughness. Long term roughness growth is then simulated with the 2D contact model. Simulation shows that all initial sinusoidal roughness of wavelengths between 20-100 mm are levelled out. The wavelength-fixing mechanism, that has previously been used to explain the cause of corrugation, is not found in the present investigations.     

水下隧道工程实践面临的挑战、对策及思考

首先介绍钻爆法、TBM/盾构法以及沉管法3种主要水下隧道建设方法的优点及不足,进而从地质条件、水流速度、水面交通、隧道埋深、通行车道数量、渗漏情况、工程总量、施工工期、施工安全、工程造价等方面对3种修建方法进行对比分析。最后重点分析当前水下隧道工程建设过程中存在的主要挑战与相应对策,主要包括:沉管法施工中河床冲刷、管段局部高出河床、埋深增大的挑战及对策,盾构穿越浅覆土层、刀盘刀具磨损、埋深提高、轴承损坏及盾构通过断层和破碎地层施工中的挑战与对策。