Investigation of ship waves in a narrow channel

This paper presents a discussion of the characteristics of ship waves in a narrow channel restricted by vertical walls, based on observed data and the results computed by a 2-D model. In the numerical model, the propagation of waves generated by a moving ship is simulated by solving 2-D depth-integrated Boussinesq equations. To get the boundary conditions at the location of the ship, the slender-ship approximation is employed. A field observation was carried out at a straight length of navigation channel. The ships targeted in the observations are two kinds of waterbuses with lengths of 28 and 24 m. The relative depth Froude number for the river current, an appropriate parameter for assessing the influence of the current on ship wave characteristics in a navigation channel, ranged from 0.47 to 0.76. The observed maximum wave height varied between 0.13 and 1.26 m. The maximum wave height of the wave train is sharply increased when the relative depth Froude number exceeds 0.6. The results computed by the present model agree fairly well with the observed data.     

强电、雷电对客运专线通信影响的防护

介绍了强电对客运专线通信影响的分类、评估及其防护措施;雷电对通信影响的途径及其防护措施,并结合工程实例论述了相应的防护方法。     

Flexural gravity wave generation by initial disturbances in the presence of current

The effect of uniform current on the generation of flexural gravity waves resulting from initial disturbances at a point was analyzed in two dimensions. The problem was formulated as an initial boundary value problem under the assumptions of the linearized theory of water waves. By direct application of the Laplace transform and then the Fourier transform, explicit expressions for the velocity potential and free surface elevation were obtained in integral forms; these were evaluated asymptotically for large distances and times by the application of the method of the stationary phase to obtain the far field behavior of the surface elevations in specific cases. Simple numerical computations were performed to illustrate the effect of uniform current on the surface elevation, wavelength, phase velocity, and group velocity of the flexural gravity waves and on the far field behavior of the progressive waves in two different cases, namely, when there is an initial depression concentrated at the origin and an initial impulse concentrated at the origin.     

汽车蓄电池漏电故障诊断分析

分析汽车蓄电池漏电的原因,绘制蓄电池漏电故障树状图,提出诊断分析流程和预防漏电建议。     

客车行业的市场现状及政策趋势

分析客车行业的市场现状及政策趋势；对客车行业应重点关注节能和安全标准的实施进行阐述。     

三相V／V接线牵引变压器负序电流分析

简述了三相V／V接线牵引变压器的结构特征，应用负序电流的一般表达式推导出V／V接线牵引变压器的负序电流，用曲线形式描述了高压侧电流不平衡度的变化规律，并对负序电流引起的不平衡问题进行分析。     

Scott变压器内部故障暂态仿真模型

结合Scott变压器接线原理与基本方程，建立了由2个单相变压器组成的Scott变压器的内部故障仿真模型，分析了故障发生时单相变压器各端口电压同三相电源之间的关系，仿真计算了其内部故障电流及励磁涌流。     

基于高频PWM整流逆变技术的能量回馈装置研究

结合高频PWM整流逆变电路高功率因数、低谐波特性,提出了一种可实现再生能量回馈利用的装置。文中介绍了该装置的主电路拓扑结构和工作原理,并根据它的等效电路和功率平衡关系建立了数学模型。从实现单位功率因数有源逆变控制出发,设计了双闭环直接电流控制系统,利用Ziegler-Nichols整定算法得到内外环PI调节器的参数。通过Matlab/Simulink仿真表明,方案设计合理,控制系统有良好的动静态性能。     

交直传动相控电力机车过电压保护参数的合理匹配

交直电力机车分别在牵引绕组和整流器元件设置阻容吸收电路以降低操作过电压和换流过电压，探讨了二者在整流器工作过程中的相互作用与影响，当参数选配不当，会造成二极管关断损坏和晶闸管开通损坏，阻容器件也会出现烧损故障；指出当前运用机车普遍存在绕组阻容参数失配情况，以致晶闸管故障率高，阻容器件烧损严重，提出满足各种机车过压保护的优化调整方案。     

高速铁路钢轨电力牵引回流集中监测探讨

通过对当前中国高速铁路电力牵引供电方式的介绍,引申出集中监测和分析高速铁路钢轨电力牵引回流的重要意义,提出了高速铁路钢轨电力牵引回流集中监测的方法,为保障高铁运营安全提供了重要的安全保障手段。