On the hydroelastic responses of a very large floating structure in waves

New numerical methods are presented for hydroelastic analyses of a very large floating structure (VLFS) of several kilometers length and width. Several methods are presented that accelerate computation without an appreciable loss of accuracy. The accuracy and efficiency of the proposed methods are validated through comparisons with other numerical results as well as with existing experimental results. After confirming the effectiveness of the methods presented, various characteristics of the hydroelastic behavior of VLFSs are examined, using the proposed methods as numerical tools. Received for publication on Dec. 3, 1999; accepted on Dec. 15, 1999     

Variational principle for determining the unknown wetted surface of a planing ship

A variational principle is presented to solve the problem of determining the unknown wetted surface of a planing ship on still water under gravity. The functional associated with the variational principle is expressed by the unknown wetted length distribution, the vortex line function, and the circulation distribution around the longitudinal sections, not by the bottom pressure distribution. In addition, the variational principle is adjoined with pseudoflow, here called reverse flow. The extremal of the functional satisfy the hull boundary integral equation in a similar way to that of lifting-surface theory and the elevated water surface condition along the spray root line. Both are sufficient to determine the wetted surface. A method of high aspect ratio approximation is also investigated. A simple relation is obtained between the wetted surface when moving and at standstill. The calculated shapes of the wetted surface of a planing plate agreed well with experimental results. Received for publication on Nov. 11, 1999; accepted on April 4, 2000     

CFD simulation of 3-dimensional motion of a ship in waves: application to an advancing ship in regular heading waves

A new computational fluid dynamics simulation method has been developed for the unsteady motion of a ship advancing in waves. The objective is to evaluate the added resistance and predict the performance of a ship in waves. In this study, a finite volume method, in the framework of a boundary-fitted grid system, is employed. The motion of the ship is solved with six degrees of freedom by using the hydrodynamic forces and moments obtained from the solution of the simulation method. The marker–density–function method is employed to calculate the nonlinear free surface. This method is applied to the coupled motion problem of heaving and pitching. Received for publication on Nov. 15, 1999; accepted on Nov. 18, 1999     

奥迪无级变速器Multitronic简介

奥迪无级自动变速器Multitronic是目前投放市场的第一种扭矩传递能力达310N.m的无级自动变速器，该变速器按传动比连续变化原理工作，它兼顾了传统有级自动变速器驾乘方便，舒适和手动变速器动力性好，经济好的特点，对Multitronhic的结构特点，主要部件和行驶控制系统进行了简单介绍。     

三效催化转化器在红旗轿车上的应用

为了达到日益严格的排放控制要求,在车辆上采用闭环电控喷射系统配以三效催化转化器是目前比较有效也是最常用的方法之一。本文在红旗轿车上采用闭环多点电控喷射系统并装用三效催化转化器,经试验验证:排放值完全符合排放法规要求,对整车噪声影响不大,功率损失很小且对有害物的转化率也很高,取得了满意的效果。     

轻型汽车自动增力鼓式驻车制动系统常见故障与排除

自动增力鼓式制动器因其结构简单、制动性能优良、维修方便,被广泛应用于轻型汽车的中央驻车制动系统。该制动系统常见的3种故障为制动不良、制动拖滞及制动手柄不易定位。结合实例介绍了该系统的故障现象、原因分析及故障排除。     

汽车空调制冷系统的稳定性

根据研究对象不同，制冷系统稳定性可分为蒸发器完全蒸干点随机振荡现象研究，蒸发和热力膨胀阀控制回路稳定性研究和定容量制冷系统稳定性研究三个阶段，对变排量压缩机汽车空调制冷系统的稳定性问题进行了初步分析，指出该系统中两个流量调节装置存在相互之间的参数耦合和调节协调问题，根据系统使用情况及其非线性的特点，可将变排量压缩机汽车空调制冷系统稳定性划分为小扰动3稳定性和大扰动稳定性。     

模糊神经网络在发动机怠速控制中的应用

讨论了发动机怠速控制方法,对用模糊控制，BP神经网络控制方法进行了深入研究，给出了模糊控制和PID调节在怠速控制上的对比及BP神经网络用于学习模型控制器的输入与输出之间的函数关系，以取代模数控制规则表。在BP网络的训练过程，采用了自调整的学习算子以加速收敛，并给出了仿真结果。     

重型液压组合式半挂车货台升降系统设计

文中介绍的重型液压组合式半挂车由鹅颈部和货台部两部分组成,鹅颈部安装有牵引销、鹅颈转向装置和鹅颈升降装置;货台部采用模块化设计,前后模块备有机械转向装置和液压悬架装置;中间模块视载货需要可以是平板梁或凹心梁。货台可升降是该车型的主要特点之一,而所采用的机械联动转向机构能使车辆完成随动转向和控制转向,极大地提高了运输的可靠性、机动性和经济性。     

67CrVA弹簧钢在斯太尔发动机气门弹簧上的应用试验

针对由67CrVA弹簧钢制造的斯太尔发动机气门弹簧进行了各项性能试验，结果表明，气门弹簧经合适的喷丸强化、热强压工艺处理后，其疲劳寿命、负荷损失率均达到标准要求；松弛试验结果表明，67CrVA弹簧钢是一种具有良好的抗松弛性能和疲劳性能的材料。最后进行了装机试验，经l000h台架试验，67CrVA弹簧钢制造的斯太尔发动机气门弹簧性能指标达到了QZZ1ll8—1994标准的要求。