船舶在波浪中航行时的安全操纵

船舶在波浪中航行,纯稳性丧失、参数激振和横甩是造成船舶倾覆的主要原因。针对波长与船长、波高与波长、波与船的波舷角三者对船舶稳性的影响进行讨论,揭示了船舶在波浪中航行时的稳性变化规律,提出了应合理地选择船舶的航行姿态、谨慎用舵等操船建议,保证船舶的航行安全。     

Stochastic capacity expansion models for airport facilities

It is important and also challenging to plan airport facilities to meet future traffic needs in a rapidly changing environment, which is characterized by various uncertainties. One key issue in airport facility development is that facility performance functions (delay levels as functions of capacity utilization rates) are nonlinear, which complicates the solution method design. Potential demand fluctuations in a deregulated aviation market add another dimension to the decision making process. To solve this problem, a deterministic total cost minimization model is proposed and then extended into stochastic programs, by including uncertainties in traffic forecasts. After the exploration of properties of the delay cost function, an Outer-Approximation (OA) technique which is superior to the existing discrete approximation is designed. After model enhancements, an efficient solution framework based on the OA technique is used to solve the model to its global optimality by interactively generating upper and lower bounds to the objective. Computational tests demonstrate the validity of developed models and efficiency of proposed algorithms. The total cost is reduced by 18.8% with the stochastic program in the numerical example.     

Optimization of nonlinear control strategy for anti-lock braking system with improvement of vehicle directional stability on split-μ roads

In a hard braking on a split-μ road, the achievement of shorter stopping distance while maintaining the vehicle in the straight line are of great importance. In this paper, to achieve these conflicting aims, an optimal nonlinear algorithm based on the prediction of vehicle responses is presented to distribute the wheel braking forces properly. The base of this algorithm is reducing the maximum achievable braking forces of one side wheels, as low as possible, so that the minimum stabilizing yaw moment is produced. The optimal property of the proposed control method makes it possible to get a trade-off between the shorter stopping distance and the less deviation of the vehicle heading from the straight line. The special case of this algorithm leads to the conventional anti-lock braking system (ABS) which generates the maximum braking forces for all wheels to attain the minimum stopping distance. However, the ABS cannot control the vehicle directional stability directly. The simulation results carried out using a nonlinear 8-DOF vehicle model demonstrate that the designed control system has a suitable performance to attain the desired purposes compared with the convectional ABS.     

斜向不规则波对斜坡堤堤头作用的试验研究

在物理模型试验的基础上,描述斜向不规则波对斜坡式防波堤堤头的作用形态,分析冲击波流的形成原因,找出不同波向所产生冲击波流的影响范围及对护面块体的影响,为同类工程的设计提供借鉴.     

长周期波作用下斜坡式防波堤稳定性及施工分析

通过对印度尼西亚adipala斜坡式防波堤波浪断面物理模型试验进行研究,结合长周期波、大波高作用下波浪水流对施工期防波堤冲刷袭击所出现的不同破坏特性,分析长周期波浪波高、波向与不同平面位置防波堤断面间的相互作用,探讨印度洋长周期波浪作用下防波堤施工期稳定性,以寻求此环境条件下的防波堤有效施工模式,以作同类工程借鉴。     

Scattering of surface water waves involving semi-infinite floating elastic plates on water of finite depth

Two problems of scattering of surface water waves involving a semi-infinite elastic plate and a pair of semi-infinite elastic plates,separated by a gap of finite width,floating horizontally on water of finite depth,are investigated in the present work for a two-dimensional time-harmonic case.Within the frame of linear water wave theory,the solutions of the two boundary value problems under consideration have been represented in the forms of eigenfunction expansions.Approximate values of the reflection and transmission coefficients are obtained by solving an over-determined system of linear algebraic equations in each problem.In both the problems,the method of least squares as well as the singular value decomposition have been employed and tables of numerical values of the reflection and transmission coefficients are presented for specific choices of the parameters for modelling the elastic plates.Our main aim is to check the energy balance relation in each problem which plays a very important role in the present approach of solutions of mixed boundary value problems involving Laplace equations.The main advantage of the present approach of solutions is that the results for the values of reflection and transmission coefficients obtained by using both the methods are found to satisfy the energy-balance relations associated with the respective scattering problems under consideration.The absolute values of the reflection and transmission coefficients are presented graphically against different values of the wave numbers.     

拼装式海上栈桥码头的浮箱拼接计算

采用三维势流理论计算不规则波中的两浮箱的运动响应,其中考虑了它们之间相互作用的影响。而后计算出两模块上连接器之间的相对运动,最终找到浮箱拼装的最佳状态。并提出了一种有效而又简单的方法预报两浮箱在波浪中的耦合运动,为浮箱的拼装作业提供了依据。     

Dawson方法在不同边界条件下的应用

本文对改进后的Dawson方法作了简单的描述，并且给出了船舶在开阔无限水深的海域、限制航道、凹型海底以及其他水下结构物存在的海域中航行时的计算例子。结果显示了改进后的Dawson方法以及计算程序的有效性，是一种可以用来预报不同工程问题中船舶兴波和船舶水动力的简单而实用的方法。     

预应力高强混凝土箱型连续梁结构行为的非线性分析

高强混凝土、钢纤维混凝土作为新型混凝土材料,以其优异的物理力学性能,越来越受到工程界的关注。高强混凝土、钢纤维混凝土在铁路、公路桥梁中有着广泛的应用前景。本论文的主要工作是应用现代数值分析手段对预应力高强混凝土变截面箱型连续梁非线性结构行为进行数值模拟。主要工作包括:(1)基于微平面理论的混凝土本构模型研究。在已有研究工作基础上,对其中主应力组合对微平面抗剪性能的影响和微平面加卸载准则提出修正意见。在Bazant教授的研究中,采用侧限应力来描述主应力组合对微平面抗剪性能的影响,通过定义主应力向量与向量的夹…     

Numerical analysis on free surface waves and stern viscous flow of a ship model

This paper deals with numerical techniques for computing the viscous flow past a ship hull with and without a free surface using a Reynolds-averaged Navier-Stokes solver with global conservation. In the first technique, a coarse grid is used to find an approximate solution to the free surface problem. Interpolation of a fine grid is subsequently carried out, and a more exact solution, particularly in the boundary layer and wake, is obtained. In the second technique, a modified Baldwin-Lomax model is introduced to compute the viscous flow with and without a free surface. These numerical techniques are applied to simulations of the flow around a Series 60 and an SR196C ship model. The results are compared with measurement data, and the usefulness of the numerical techniques is demonstrated.