Numerical simulation of three-dimensional breaking waves

Three-dimensional (3D) wave breaking around bodies of complex geometry has been numerically investigated by use of two types of Navier-Stokes solvers, namely the finite-difference and the finite-volume methods employing rectangular and curvilinear coordinate systems, respectively. Both methods employ the density-function technique to capture the free surface location and can cope with complicated free surface configurations such as breaking waves. The accuracy of the density-function method is examined through the comparison with experimental results, and it is confirmed to be satisfactory when the grid spacing and the time increment are sufficiently small. New computational methods are applied to several problems including 3D breaking waves around ships and wave diffraction around offshore structures. The computed results show good agreement with experimental results indicating that wave breaking phenomena are successfully simulated. The qualitative accuracy, however, could be improved by including the dissipating effect of breaking waves.     

单相谐振MOSFET逆变电源的研究

给出一种用于中频感应加热装置的ＭＯＳＦＥＴ逆变电源,在ＭＯＳＦＥＴＲ 控制信号方面,提出了一种新的控制方法,即正弦波控制法,它能够自动地产生“死区时间”,对于避免同桥壁上,下管子直通有可靠的作用,中详细叙述了装置主电路和控制电路的并给出试验波形。     

ITC模式下地铁列车单/双线出段能力比较分析

主要以地铁十四号线马泉营车辆段为例,分析比较ITC模式下列车自车辆段停车库内采用单线出段和双线出段两种运行组织方式下的出段能力。     

Free Propagation of Wave in Viscoelastic Cables with Small Curvature

IntroductionDynamicbehaviorsofcablesandcable structureshaveattractedtheattentionofmanyresearchers .Therehavebeenmanyreports[1 5 ] ontheproblemsofnaturalfrequencies ,freevibrations,andstabilitybehaviorsofcablesandcablestructures .Manyavailabletechniques ,s…     

一种改进的模型参考自适应算法

针对一种模型跟随自适应算法（DS-AMFC），利用线性神经网络预测系统输出与模型输出之差为控制信号的计算提供较准确的偏差值，用该估计的偏差量进行控制。同时，把控制的误差引入控制信号，在输入信号频率较高时仍具有跟随模型的能力，鲁棒性大大提高。     

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车辆跟驰模型中的驾驶行为是一个复杂的推理、决策、执行过程，在知识表达和推理机制上存在模糊性和随机性。针对当前车辆跟驰模型研究存在的不足，引入云模型理论，确定了跟驰模型中的决策变量及概念判断子集，设计了模型参数标定的实验方法，在实验数据的基础上，计算了相关参数的隶属云特征值，总结了基于行为规则的车辆跟驰云推理机制，构造了车辆跟驰云模型CFCM(Car Following Cloud Model)。     

车流密度变化条件下的跟驰模型研究

把车流密度的跳跃性变化作为车流波现象,在高峰小时或者异常情况下(如雨、雪、雾等异常天气),快速路的瓶颈地段经常出现堵塞以及由堵塞引起的车流波。车流波不仅影响瓶颈点下游车辆的运行,还会降低瓶颈点上游路段的有效通过能力。通过大量的交通数据采集,构建基于模糊推理的驾驶员感知——预测行为模型和车流波传播条件下驾驶员微观跟驰模型。结果表明,模型可以有效、准确地模拟车流波传播过程中驾驶员行为。     

Weather and road geometry impact on longitudinal driving behavior: Exploratory analysis using an empirically supported acceleration modeling framework

The objective of this paper is to quantify and characterize driver behavior under different roadway geometries and weather conditions. In order to explore how a driver perceives the rapidly changing driving surrounding (i.e. different weather conditions and road geometry configurations) and executes acceleration maneuvers accordingly, this paper extends a Prospect Theory based acceleration modeling framework. A driving simulator is utilized to conduct 76 driving experiments. Foggy weather, icy and wet roadway surfaces, horizontal and vertical curves, and different lane and shoulder widths are simulated while having participants driving behind a yellow cab at speeds/headways of their choice. After studying the driving trends observed in the different driving experiments, the extended Prospect Theory based acceleration model is calibrated using the produced trajectory data. The extended Prospect Theory based model parameters are able to reflect a change in risk-perception and acceleration maneuvering when receiving different parameterized exogenous information. The results indicate that drivers invest more attention and effort to deal with the roadway challenges compared to the effort to deal with the weather conditions. Moreover, the calibrated model is used to simulate a highway segment and observe the produced fundamental diagram. The preliminary results suggest that the model is capable of capturing driver behavior under different roadway and weather conditions leading to changes in capacity and traffic disruptions.     

直立圆柱体内孤立波载荷特性数值模拟

以三类内孤立波理论(KdV、eKdV和MCC)的适用性条件为依据,将内孤立波诱导上下层深度平均水平速度作为入口条件,采用Navier-Stokes方程为流场控制方程,建立了两层流体中内孤立波对直立圆柱体强非线性作用的数值模拟方法.结果表明,数值模拟所得内孤立波波形及其振幅与相应理论和实验结果一致,并且直立圆柱体内孤立波水平力、垂向力及其力矩数值模拟结果与实验结果吻合.直立圆柱体内孤立波载荷由波浪压差力、粘性压差力和摩擦力构成,其中摩擦力很小,可以忽略;对于水平力,其波浪压差力与粘性压差力量级相当,流体粘性的影响显著;对于垂向力,粘性压差力很小,流体粘性影响可以忽略.此外,直立圆柱体对内孤立波的波形及其诱导流场的影响很小,因此采用Morison公式和傅汝德—克雷洛夫力分别计算其内孤立波水平力和垂向力是可行的.     

基于动态执行机构的船舶循迹反步积分控制

文章针对连续曲率路径,用一种简单的几何方法生成连续曲率的路径.基于该几何方法生成的连续路径,文中利用line-of-sight(LOS)引导律解决了循迹控制中横向偏差最小的问题.为了减弱控制输出的振荡和获得平滑的控制输出,一种基于动态执行机构的改进反步积分控制器在过驱动船舶循迹控制中得到了应用.值得注意的是,文中用积分操作来抵抗风浪流环境力.数值分析结果展示了该控制器的有效性.