On nonlinear ship waves and wave resistance calculations

A finite difference method based on the Euler equations is developed for computing ship waves and wave resistances. Time marching is carried out using a time-splitting fractional-step method. The second-order central difference is used to discretize the spatial differentials, while the convection terms are discretized by the QUICK scheme. A body- and free-surface-fitted grid system with a cell-centered stencil is used. A Poisson equation for the pressure increment at each time step is solved to enforce mass conservation. The method is validated by comparing the numerical results with the experimental data for a Wigley parabolic hull. The characteristics of ship waves, such as the wave profile along the hull, the wave pattern on the free surface, the pressure distribution on the hull surface, and the wave-making resistance are reasonably predicted. The calculated results are in good agreement with the experimental data. Received for publication on Oct. 13, 1998; accepted on Jan. 20, 1999     

Learning tracking controllers under unknown disturbances for the installation of rigid and flexible structures

During the installation operations of underwater structures, offshore structures such as semisubmersibles, the steady nonlinear hydrodynamic force due to the ocean current, the tidal current, and the hydrodynamic interaction between structures are regarded as major disturbances. Generally, it is difficult and very expensive to collect information about these disturbances in advance, although such knowledge would be important and necessary for precise installation. Because of this situation, we have proposed a learning tracking controller (LTC) for automated tracking/docking operations of offshore structures. The LTC can be operated without any information about current, and can be applied to the installation problem of flexible structures whose flexibility cannot be ignored. In order to confirm the effectiveness of the LTC, basin tests were carried out using experimental models with an unknown current. Two types of basin experiment were executed using an ultrasound ranging system and thrusters. One was trajectory tracking of a semisubmersible, and the other was the precise mating of flexible underwater structures. In both cases the LTC showed good performance, and in the latter case in particular, two flexible models were successfully made to track the given trajectory and dock to the docking targets with an accuracy of ±5 mm, after the trajectory had been tracked six to seven times for learning purposes. No elastic responses were excited in the flexible model. Received for publication on Dec. 1, 1999; accepted on March 13, 2000     

Application of CFD simulation to the design of sails

A finite-volume method was applied to a simulation of the flow about the sail system of IACC sailing boats. The interface boundary technique was employed to generate a proper grid system for the two-sails system, which is composed of head and main sails. The turbulence model was carefully chosen by numerical test, and the most reliable simulation method was completed and used to design the sails. The suitability of the method is demonstrated by some examples of design applications. Received for publication on March 14, 2000; accepted on March 16, 2000     

Effect of microbubbles on the structure of turbulence in a turbulent boundary layer

The time-averaged velocity and turbulence intensity distributions were measured by a laser Doppler velocimeter in a turbulent boundary layer filled with microbubbles. The void fraction distribution was also measured using a fiber-optic probe. The velocity decreased in the region below 100 wall units with an increase in bubble density. This led to a decrease in the velocity gradient at the wall, which was consistent with a decrease in shearing stress on the wall. The turbulence intensity in the buffer layer increased at a low microbubble density, and then began to decrease with an increasing microbubble density. Based on the present measurements, the mechanism of turbulence reduction by microbubbles is discussed and a model is proposed. Received for publication on Dec. 3, 1999; accepted on April 18, 2000     

乌鲁木齐集装箱中心站平面布置方案研究

乌鲁木齐集装箱中心站是《中长期铁路网规划》规划建设的18个铁路集装箱中心站之一,如何有效节约用地、减少土方工程,是平面布置的关键。根据三坪车站既有概况,结合乌鲁木齐铁路枢纽总图规划,从运营条件及运营管理、远期发展条件、与城市道路衔接条件和工程条件与投资等多方面,对提出的3个方案进行论证,最终推荐横列式布置方案。合理的平面布置形式,旨在为填方量较大的场站提供参考。     

龙厦线龙岩站载频设计方案

龙岩站为龙厦线的接轨站,新设计龙岩站共用5个发车口,分别为赣州方面(XG)小池站、龙川方面(XM)红炭山站、漳平方面(SZ)铁山洋站、厦门方面(S/SF)东南线路所,载频设计较为复杂,通过优化设计,充分考虑各接发车口各种因素,完成龙岩站载频设计。     

高粘着利用机车的系统设计

本文指出，机车的高粘着利用是一个系统工程问题，文中由粘着牵引力的基本概念出发，从机械系统、动力与传动系统、控制系统等不同的方面阐述了高粘着利用机车的设计要求及方法，并从系统工程的角度论证了各部分合理匹配与协调。希望能对提高我国机车的设计水平起到一定作用。     

大跨度钢筋混凝土拱桥钢管混凝土劲性骨架施工阶段稳定性分析

本文用荷载增量法，考虑几何非线性，施工加载历程及构件极限承载力的影响，对大跨度ＲＣ拱桥钢管混凝土劲性骨架施工阶段稳定进行了分析，并研制了相应的微机程序。所得结论有助于大桥性骨的架的设计与施工监控。     

THE DISTRIBUTION OF ATRIONATRIURETIC POLYPEPTIDE （ANP）－LIKE SUBSTANCE IN THE HEART OF THE HUMAN FETUS AND RAT－AN IMMUNOHISTOC

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