横向风与列车风联合作用下车桥系统绕流分析

采用3维定常不可压缩雷诺平均N-S方程,结合RNGk-ε湍流模型,利用多重参考系法,对横向风作用下ICE高速列车在日本屋代南桥上运行的绕流进行分析。结果表明:列车风对流场的影响主要表现在对列车表面附近、桥面、挡风墙间的局部流场的影响;列车运行时对头部、尾部附近的空气有排挤、拖曳作用;列车尾部靠迎风侧有一个很强的旋涡;列车风对列车中部附近流场的影响很小,对列车的阻力、横向力、升力、摇头力矩影响较大;列车风的作用使整个列车产生一种向上提升和沿横风向摇头的作用,列车风对列车附近区域桥梁的气动力有明显影响。     

管窥美国密西西比河流域航运发展后的浅见和启示

密西西比河是河流资源综合利用开发的典范,其在平衡各种资源利用、保障河流生命力并使其资源可持续利用等方面做得较好,其中的航运资源得以较高程度的利用,对区域经济发展贡献度较大。我国目前正处在内河航运建设的高潮,密西西比河的成功经验值得借鉴。     

航运企业选择战略联盟伙伴的决策方法

战略联盟作为企业经营的一种新理念 ,自美国DEC公司总裁简·霍普兰德 (J .Hopland)和管理学家罗杰·奈杰尔 (R .Nigle)提出以来 ,在近 2 0多年的时间里 ,越来越多的企业通过战略联盟的方式参与全球竞争 ,并取得了显著的效果。这一组织制度的创新理论 ,迅速成为各大公司获取自身利益最大化的最优选择。我国加入WTO后 ,航运业的竞争也将日趋激烈 ,对如何提高航运企业的竞争优势 ,作出合理的决策 ,关系到企业的生存大计。通过对航运企业实施战略联盟的分析 ,提出了航运企业在选择战略联盟伙伴时 ,可供采取的模糊综合评判决策方法     

PMM tests in a circulating water channel and nonlinear analysis

As a result of frequent marine disasters leading to the loss of human life and pollution of vast areas of the ocean, ship manoeuvrability has become a very important characteristic of ship design. Among several recent experimental techniques to determine ship manoeuvrability, the most popular is captive model testing using a planar motion mechanism (PMM). This article describes some tests, analyses, and results of PMM tests in a circulating water channel (CWC) using a model of a training ship. The hydrodynamic forces and moments acting on a model of the training ship Shioji Maru in pure yawing motion were measured, and hydrodynamic derivatives were obtained using two different methods of analysis: singular value decomposition (a least-squares fit method) and Fourier analysis. Derivatives obtained from the tests were used to simulate the turning trajectory of the actual ship, and these were compared with the results of sea trials. The results indicate that both methods of analysis yield fairly similar derivatives. The simulation results were also found to be a close match with the trial results. Received: February 7, 2002 / Accepted: May 14, 2002 Address correspondence to: K. Shoji (shoji@ipc.tosho-u.ac.jp)     

列车接近防护系统的设计与实现

介绍一种列车接近防护系统的设计，详细介绍系统的结构与组成、系统参数以及软硬件的实现方法。     

Bayesian estimation of multinomial probit models of work trip choice

In this paper, we estimate a multinomial probit model of work trip mode choice in Seoul, Korea, using the Bayesian approach with Gibbs sampling. This method constructs a Markov chain Gibbs sampler that can be used to draw directly from the exact posterior distribution and perform finite sample likelihood inference. We estimate direct and cross-elasticities with respect to travel cost and the value of time. Our results show that travel demands are more sensitive to travel time than travel cost. The cross-elasticity results show that the bus has a greater substitute relation to the subway than the auto (and vice versa) and that an increase in the cost of an auto will increase the demand for bus transport more so than that of the subway.     

长江中游罗湖洲水道航道整治工程设计经验总结

罗湖洲水道是目前长江中游实施了航道整治工程的几个碍航浅水道之一,该水道航道整治工程是顺利开展长江中游航道系统整治的基础。在介绍罗湖洲水道整治工程具体布置的基础上,通过工程建成后几个水文年实际的工程效果分析,总结了该工程在工程设计或施工中取得的经验。     

基于分枝定界法的环肋圆柱壳优化研究

基于分枝定界方法,研究了环肋圆柱壳静水压力作用下,考虑强度和稳定性约束时重量最轻的混合变量优化设计问题,讨论了强度约束和稳定性约束以及材料、几何参数对优化结果的影响.该方法能够有效求解环肋圆柱壳的混合优化问题,计算量小,精度高;环肋圆柱壳经优化后,壳板的重量比例大约是70%,肋骨重量占30%.并且随壳体的长径比(L/R)变化不大.环肋圆柱壳的优化中,肋骨的应力约束是主要约束,肋骨应力已经非常接近许用应力标准,其他应力、局部和总体失稳压力还有一定的储备.     

掏挖法地下连续墙施工工艺的研究

在扩建和改建的地下工程中,经常遇见施工区域内存在大量纵横交错的地下管线,对这些管线的拆除,不仅严重影响工程进度和公用设施的正常运行,而且严重影响了施工工期,更带来巨大的经济浪费。该文阐述一种在不进行管线切改的前提下进行地下连续墙施工的特殊方法,旨在促进地下连续墙的施工工艺得到进一步完善和提高。     

Joint distortion model for progressive image transmission using error correcting arithmetic codes

A novel joint source channel distortion model was proposed, which can essentially estimate the average distortion in progressive image transmission. To improve the precision of the model, the redundancy generated by a forbidden symbol in the arithmetic codes is used to distinguish the quantization distortion and the channel distortion, all the coefficients from the first error one to the end of the sequence are set to be a value within the variance range of the coefficients instead of zero, then the error propagation coming from the entropy coding can be essentially estimated, which is disregarded in the most conventional joint source channel coding （JSCC） systems. The precision of the model in terms of average peak-signal-to-noise has been improved about 0.5 dB compared to classical works. An efficient unequal error protection system based on the model is developed, and can be used in the wireless communication systems.