轮对诊断试验台

众所周知,列车运行的安全性在很大程度上取决于机车车辆走行部分的状态,这一点对于现代化的高速列车来说更是如此。所以,世界各国的铁路十分重视用于诊断轮对总成(车辆下不推出或推出轮对)的设备以及在工艺检查与维修保养时用于诊断单个车轮的设备的研制与使用。     

Wave scattering by undulating bed topography in a two-layer ocean

The problem of wave scattering by undulating bed topography in a two-layer ocean is investigated on the basis of linear theory. In a two-layer fluid with the upper layer having a free surface, there exist two modes of waves propagating at both the free surface of the upper layer and the interface between the two layers. Due to a wave train of a particular mode incident on an obstacle which is bottom-standing on the lower layer, reflected and transmitted waves of both modes are created by the obstacle. For small undulations on the bottom of the lower layer, a perturbation method is employed to obtain first-order reflection and transmission coefficients of both modes for incident wave trains of again both modes in terms of integrals involving the bed-shape function. For sinusoidal undulations, numerical results are presented graphically to illustrate the energy transfer between the waves of different modes by the undulating bed. U. BASU was born in 1949. She is a professor in the Department Applied Mathematics, Calcutta University, India. Her current research interests include water wave problems, continuum mechanics, etc.     

Oblique Wave-free Potentials for Water Waves in Constant Finite Depth

In this paper, a method to construct oblique wave-free potentials in the linearised theory of water waves for water with uniform finite depth is presented in a systematic manner. The water has either a free surface or an ice-cover modelled as a thin elastic plate. For the case of free surface, the effect of surface tension may be neglected or taken into account. Here, the wave-free potentials are singular solutions of the modified Helmholtz equation, having singularity at a point in the fluid region and they satisfy the conditions at the upper surface and the bottom of water region and decay rapidly away from the point of singularity. These are useful in obtaining solutions to oblique water wave problems involving bodies with circular cross-sections such as long horizontal cylinders submerged or half-immersed in water of uniform finite depth with a free surface or an ice-cover modelled as a floating elastic plate. Finally, the forms of the upper surface related to the wave-free potentials constructed here are depicted graphically in a number of figures to visualize the wave motion. The results for non-oblique wave-free potentials and the upper surface wave-free potentials are obtained. The wave-free potentials constructed here will be useful in the mathematical study of water wave problems involving infinitely long horizontal cylinders, either half-immersed or completely immersed in water.     

带舭龙骨柱体的横摇阻尼的粘性流计算

文章用RANSE求解器计算在自由面上带舭龙骨二维柱体的横摇水动力系数(附加惯量和阻尼).采用有限体积法(VOF)和两相流技术在时间域内求解柱体横摇强迫振荡所扰动的带自由面粘性流场.由柱体所受到的横摇水动力矩的时间历程导出横摇水动力系数.文中所给算例与已公开发表的试验结果吻合令人满意.     

农业循环经济发展评价问题研究

发展农业循环经济的目的在于形成以"资源-产品-废物-再生资源"为主要内容的闭环式系统,是改进与优化我国农业产业结构,更加合理地运用资源,保护当地生态环境,实现我国农业可持续发展的新型经济形态之一。科学规范的农业循环经济发展评价模式对于合理监测与预测农业循环经济的发展具有极为重要的意义,能够为我国未来的农业发展规划提供充足的决策依据。本文阐述了农业循环经济评价指标体系的功能、构建原则和基本框架,并提出了改进农业循环经济评价指标体系的建议。     

通过喷油规律造型改善柴油机燃烧

优化喷油参数是进一步开发柴油机的重点。亚琛工业大学内燃机教授开发了一种喷油规律造型具有极好柔性的喷油器样品。这种喷油器在压力罐中和单缸柴油机上的试验证实了其改善喷油器针阀开启时间可以进一步降低废气排放的潜力。     

用于降低商用车发动机氮氧化物和CO2排放的技术方案

在美国,日益严苛的氮氧化物(NOx)排放法规要求汽车制造商显著降低其车型产品的有害物排放,为此必须使车辆在所有运行条件下都具有最高的NOx转化率。     

全俄内燃机车和养路机械科学研究院简介

全俄内燃机车和养路机械科学院的前身是全苏内燃机车科学研究院。随着前苏联的解体，全苏内燃机车科学研究院归属俄罗斯联邦，成为俄罗斯交通部下属的一个科研机构，改名为全俄内燃机车和养路机械科学研究院。本文简要介绍了该院的发展情况，重点介绍了该院各阶段的主要科研任务。     

Renault柴油机氮氧化物后处理系统的开发

柴油机为达到未来的废气排放标准限值，要求在机内优化的基础上应用排气后处理系统。Renault公司开发的降氮氧化物（NOx）催化器系统使得质量较重的商务车能达到未来的排放标准，并仍保持柴油机二氧化碳排放低的优势，从而降低了Espace dCi 175型轿车的NOx排放，并达到了欧5排放标准，为未来的欧6排放标准作好了准备。