Basic Analytical Study of Pantograph-catenary System Dynamics

For a high speed electrical rail system, good dynamic performance of the pantograph-catenary system is vital for smooth and continuous current collection. It has been known for many years that to achieve this the head of the pantograph should be made as light as possible and the average stiffness of the catenary should be high. These conclusions, however, have been reached by numerical modelling and operational experience. In this paper the pantograph-catenary system is modelled as a time-varying, single degree-of-freedom system to facilitate an analytical investigation of the system dynamics. Although the model is very simple, it allows physical insight into the dynamic behaviour of the system, and because the excitation is parametric it also allows the stability of the system to be investigated. The finite element method is used to determine the catenary characteristics and Floquet theory is used to analyse the behaviour of the coupled system.     

矿料级配基本性能的试验研究

通过自行设计的填充试验和压碎试验,对混合料的密实度和骨架特性进行深入研究。研究结果表明,级配设计中的最大密实度状态与根据填充试验得到的矿料最大密实度状态是不一致的。压碎试验表明,各种粒径的颗粒在压碎时,其破碎颗粒都在4 75mm处出现峰值,说明4 75mm的颗粒是构成骨架的主要部分;同时填充试验也表明4 75mm的粒径尺寸是填充效率的分界点。因此,本文提出应以4 75mm作为粗细集料的分界点。     

改性生物沥青的基本性能研究

对改性生物沥青进行高温稳定性、塑性、稠度等基本性能进行了研究。通过控制改性沥青种类以及改性沥青掺和比例两种方法,分析这两种因素对改性生物沥青基本性能的影响。结果表明:生物沥青具有较好的高温稳定性,但塑性和稠度性能差。掺入改性沥青后的生物沥青塑性和稠度性能有了大幅度的提高,并且仍然具有较好的高温稳定性。改性沥青掺和比例越大,生物沥青塑性的改善越大,SBR改性沥青改善效果最好。     

Railway Vehicles With Generic Bogies Capable of Perfect Steering

The general form of the equations of motion of a symmetric railway vehicle with two unsymmetric two-axle bogies is derived. The equations include a generic elastic stiffness matrix that describes the nature and configuration of the structural connections between the various components of the vehicle. This matrix satisfies the condition for perfect steering (without generating creep forces) on uniform curves and the necessary condition for dynamic stability derived in previous work. The paper shows the application of these basic conditions to a class of generic unsymmetric bogies. The analysis has as its objective the derivation of the simplest rather than the most general configuration that meets the conditions imposed. The results are related to past and current practice. It is shown that perfect steering, with stability at low speeds, can be achieved by means of passive suspension elements not employing linkages, and that it is possible to simplify existing steering arrangements.     

Railway Vehicles With Generic Bogies Capable of Perfect Steering

SUMMARY

The general form of the equations of motion of a symmetric railway vehicle with two unsymmetric two-axle bogies is derived. The equations include a generic elastic stiffness matrix that describes the nature and configuration of the structural connections between the various components of the vehicle. This matrix satisfies the condition for perfect steering (without generating creep forces) on uniform curves and the necessary condition for dynamic stability derived in previous work. The paper shows the application of these basic conditions to a class of generic unsymmetric bogies. The analysis has as its objective the derivation of the simplest rather than the most general configuration that meets the conditions imposed. The results are related to past and current practice. It is shown that perfect steering, with stability at low speeds, can be achieved by means of passive suspension elements not employing linkages, and that it is possible to simplify existing steering arrangements.     

Dynamics of Automated Guideway Transit Vehicle with Single-axle Bogies

Summary The steering type of a mechanical guidance system has been used for Automated Guideway Transit (AGT) system in Japan. Recently, the single-axle bogie system has developed for AGT vehicle and applied to Yurikamome 7200 type vehicle. This paper describes dynamic characteristics of AGT vehicle with single-axle bogies. Introducing a nonlinear, 15 degree-of-freedom dynamic model, a computer simulation study on the lateral motion of the AGT vehicle with single-axle bogies are carried out. In order to show the dynamic characteristics of the single-axle bogie clearly, it is compared to that of the AGT vehicle with conventional steering system. The simulation study with actual vehicle parameters shows that single-axle bogie has suitable characteristics for AGT system. The multi-body dynamics modeler, DADS, is used to build the dynamic model of AGT vehicle with single-axle bogies and this is used to demonstrate the vehicle motion in actual guideway. Obtained results are compared to that of the field test. It is shown that the vehicle dynamic response can be obtained in realistic situation by using multibody dynamics code, that is useful for designing both vehicle and guideway.     

Dynamics of Automated Guideway Transit Vehicle with Single-axle Bogies

Summary The steering type of a mechanical guidance system has been used for Automated Guideway Transit (AGT) system in Japan. Recently, the single-axle bogie system has developed for AGT vehicle and applied to Yurikamome 7200 type vehicle. This paper describes dynamic characteristics of AGT vehicle with single-axle bogies. Introducing a nonlinear, 15 degree-of-freedom dynamic model, a computer simulation study on the lateral motion of the AGT vehicle with single-axle bogies are carried out. In order to show the dynamic characteristics of the single-axle bogie clearly, it is compared to that of the AGT vehicle with conventional steering system. The simulation study with actual vehicle parameters shows that single-axle bogie has suitable characteristics for AGT system. The multi-body dynamics modeler, DADS, is used to build the dynamic model of AGT vehicle with single-axle bogies and this is used to demonstrate the vehicle motion in actual guideway. Obtained results are compared to that of the field test. It is shown that the vehicle dynamic response can be obtained in realistic situation by using multibody dynamics code, that is useful for designing both vehicle and guideway.     

关于城市防洪规划中若干问题的探讨

通过对湖南省城市防洪规划工作的总结 ,就城市防洪标准、城区排水、内、外河水遭遇分析、防洪规划与河道综合治理等规划中遇到的一些问题进行了探讨。并提出相关建议     

城市人行天桥设计上几个问题的探讨

结合上海、杭州、广州等城市一些人行天桥的设计实践 ,着重探讨了城市中心区复杂条件下人行天桥的选位、选型、结构设计、管线处理等问题     

市政工程质量监督中若干问题的探讨

目前我国市政行业正面临着前所未有的快速发展时间,而市政工程质量监督中还存在很多问题亟待解决。为此,从市政工程建设投资管理方式、地域和行业垄断、不严格执行基本建设程序以及质量技术标准滞后四方面论述市政工程质量监督中存在的种种问题和弊端,提出改变这种情况的建议与措施。     

Theoretical Comparison Between Different Configurations of Radial and Conventional Bogies

This article compares the dynamic behaviour of different configurations of radial and conventional two-axle bogies. In general, the design parameters for a better curve negotiation are not compatible with those for good stability. As the main target of this article is to compare the curving performances of different bogies under the same design basis, several bogie configurations with the same level of stability, obtained by choosing proper primary suspension stiffnesses, have been used. The comparison includes a conventional bogie and three radial bogies with differing self-steering and forced-steering principles in three different passenger services: High Speed, Regional and Mass Transit. The analysis has been concentrated on parameters such as stability, lateral wheel-track forces in curve and wheel wear indices. The results show that the radial bogie configurations studied do not make significant contributions in general applications with regard to a conventional bogie. It is only under specific running conditions and types of service that some radial bogie configurations provide advantages with respect to the conventional bogie.     

Theoretical Comparison Between Different Configurations of Radial and Conventional Bogies

This article compares the dynamic behaviour of different configurations of radial and conventional two-axle bogies. In general, the design parameters for a better curve negotiation are not compatible with those for good stability. As the main target of this article is to compare the curving performances of different bogies under the same design basis, several bogie configurations with the same level of stability, obtained by choosing proper primary suspension stiffnesses, have been used. The comparison includes a conventional bogie and three radial bogies with differing self-steering and forced-steering principles in three different passenger services: High Speed, Regional and Mass Transit. The analysis has been concentrated on parameters such as stability, lateral wheel-track forces in curve and wheel wear indices. The results show that the radial bogie configurations studied do not make significant contributions in general applications with regard to a conventional bogie. It is only under specific running conditions and types of service that some radial bogie configurations provide advantages with respect to the conventional bogie.     

纳米陶瓷添加剂在可生物降解基础油中的抗磨性能研究

以生物降解能力强且综合性能好的菜籽油作为基础油,以极压和抗磨性能较好的纳米材料作为添加剂,采用MS-800型四球磨损试验机对试验油极压特性、抗磨性能和摩擦因数进行了研究,分析不同纳米陶瓷添加量对其性能的影响;通过现有润滑油性能的对比,采用均匀设计安排试验,应用SPSS软件对纳米材料与其他添加剂的配伍性进行了回归分析。结果表明：纳米陶瓷添加剂的加入使菜籽油的摩擦性能显著提高,且加入比例得当能满足润滑油的要求;当纳米陶瓷的添加量（质量分数）为1.5%时,相应的最大无卡咬负荷PB值最高达646.8N,磨斑直径最小达0.59mm,摩擦因数最大可降低27%;纳米陶瓷与其他添加剂的复配以及相互作用可提高菜籽油的极压和抗磨性能。     

城市防洪工程建设监理中若干问题的探讨

城市防洪工程不仅具有一般堤防工程的特点 ,而且还是兼有景观、绿化、旅游等多种功能的综合性工程。本文结合具体的城防工程监理实例对城防监理中的质量控制和监理机构自身建设等若干问题进行了探讨。     

南京市老城环境整治若干问题的探讨

结合南京市老城环境整治工程实践,探讨老城改造和新区建设的规划设计理念以及具体实施中若干原则问题,从而建设独具特色的城市生态交通空间,创造和谐、自然的人居环境。     

对汽车召回制度的探讨

目前，在美国，日本，韩国，加拿大，英国等国家都已实行了汽车召回制度，汽车召回制度实质上是对已经造成社会危害的汽车产品的生产企业的惩戒和对尚未造成危害但已经发现问题的汽车产品的挽救，它维护了消费者的权益，规范了汽车市场，在我国实行汽车召回制度需要创造一定的条件和社会基础，需要制定一套权威而稳定的法律。     

混合塑料发泡颗粒轻质土的强度特性评价方法

针对混合塑料发泡颗粒轻质土的特性,利用两相体模型提出了对其强度及变形等工程性质进行评价的方法;并运用该方法,在考虑构成轻质土两种不同材料性质的基础上,对轻质土的强度与变形特性进行了分析。结果表明:该方法可以比较合理地对塑料发泡颗粒轻质土的应力-应变特征及强度特性进行评价;轻质土强度随轻质填充料体积分数的增大而减小,随龄期的增长而提高。