吊拉组合体系预应力连续加劲梁性能分析

按照６ 种不同分跨的设计方案, 每种方案又按照施工阶段采取几种不同预压荷载的计算比较来研究按照预压合龙施工工艺完成体系转换的预应力连续加劲梁吊拉组合体系桥的主梁结构性能, 并选择体系的最优分跨比．     

隧道三维激光扫描测算一体化技术方案与实践北大核心CSCD

三维激光扫描技术已在隧道工程中得到广泛应用,但其内外业脱节、人工操作过多、实时性不足等问题日益凸显。文章结合工程实践,提出三维激光隧道扫描测算一体化技术方案,通过隧道设计模型录入、坐标里程解算、点云自动过滤、点云降采样与地物分离等,对点云进行特征值提取,得到兼顾规模、精度、效率的点云数据模型;通过点云与设计、点云与点云的对比解算,得到隧道工程质量安全相关成果。该技术方案在某铁路隧道工程中进行实践,可将内外业工作总时间缩短至20 min以内,自动化程度高,成果精度好,具有很好的推广价值。     

China shipbuilding management challenges in the 1980s

Since the economic reforms in the late 1970s, the shipbuilding industry in China has enjoyed rapid growth. Over the past two decades, many new building contracts have been won and successfully completed. However, some shipyards have also suffered great losses. Basing on their experience in Southern China, the authors examine some of the major challenges that Chinese shipbuilders faced during this transitional period, when the industry ventured into the international market. These challenges are broadly categorized into two areas: (i) external factors, such as inflation and infrastructural support that the shipbuilder had no control over, and (ii) shipbuilding management, which the shipbuilder had to master in order to gain competitive advantage. Suggestions on how these problems could be tackled are discussed.     

Solution of an unstable inverse problem: wave source evaluation from observation of velocity distribution

This paper illustrates how to estimate a wave source generating a wave system, including local waves, with the assumption of linear dispersive waves of two dimensions. The estimation of wave source is realized by using an inverse problem. Unfortunately, the inverse problem is ill-posed in the sense of stability, since the wave source information included in local waves diminishes as the distance from the wave source increases. In the area of applied mathematics, there are well-developed methods to tackle ill-posed problems, which are called regularizations. In this paper, three different regularizations which are well known in applied mathematics are introduced and investigated to learn whether they are applicable to the present problem of the estimation of wave source. From the numerical experiments, it is shown that the estimation is realized by the regularizations introduced in this study, so that they can be applied to the determination of a wave source generating a wave system including local waves. Received: June 6, 2000 / Accepted: February 7, 2001     

Analysis of the economic and social parameters of the Three-Wheeler Taxi service in Sri Lanka

Sri Lanka has an extensive Three-Wheeler Taxi service comprised of around 300,000 vehicles. These vehicles, which first made an entry to Sri Lanka’s roads in the early 1980s, account for around 15% of the active motor vehicle fleet at present. Three-Wheelers Taxis also account for around 6% of the passenger kilometres. These vehicles are mostly individually operated with some owned by the operator and others hired on a monthly or daily basis. The industry is unregulated with vehicle registration and driving licenses being the only instruments of regulation. Fares are unregulated. However, most operators belong to associations which are loose collections of operators found in a given locality. These associations impose a degree of self regulation with respect to fares. They also tend to demonstrate oligapolistic behaviour.The paper is based on a survey of 200 operators and 100 passengers from a Divisional Secretariat area in Colombo District. The survey covered a number of details pertaining to ownership, management and fare structures, as well as opinions on the service attributes by users. The survey also covered perceptions of operators to determine the social, economic and transport implications of the services provided. Details were also obtained on the profiles of the operators and their expectations.The paper provides the results of the analysis of this data and draws a number of conclusions on the economics of the industry as well as the social aspects associated with it. It also discusses the characteristics of the users of these three wheelers as well as their typical use. The analysis also investigates complementarily of service provision between three wheelers as an access mode to buses and railways. This analysis has been used to develop an understanding of the manner in which the industry has grown over the last two decades and how it is being operated today. It also identifies areas wherein the industry has become inefficient and assesses the degree of over pricing that exists due to this. The data also helps to determine the relationship between unemployment and provision of self-employed transport services.The paper concludes with a synopsis of the profile of the industry and its role within the wider transport sector and with respect to ownership. It also discusses the positive and negative impacts of the lack of regulation on the industry.     

电力牵引系统用优化的传动机组

原边能源是电动汽车牵引系统中易造成故障的一个组件,力争对应用了成熟技术的发动机组进行优化.     

城市公交票价调节机制设计研究

为优化我国目前较为僵化的城市公交票价体系,构建科学合理的票价调节机制,充分发挥 价格杠杆对城市公交资源配置的导向作用,首先总结出我国城市公交票价体系存在票价水平与定 价成本背离、票价水平长期不变及缺乏科学系统的票价调节机制3 个主要问题。然后,深入研究 了新加坡和香港城市公共交通票价调节机制,并分析了其票价调整公式;在借鉴国际、国内相关 经验的基础上,通过总结我国城市公交运营成本中主要单项成本及各单项成本对总成本的影响规 律,将人员工资、燃料消耗费、轮胎消耗费、运营车辆修理费、其他直接运营费、财务费用等作 为影响城市公交票价的主要成本因素,并确定了各因素的权重系数。在以上研究基础上,设计了 能够合理反映城市公交票价定价成本的城市公共交通票价调节模型以及能够综合考虑企业运营成 本、社会经济发展水平、居民承受能力等因素的动态城市公交票价调节机制和配套措施,包括启 动票价调节的前提条件、调价流程设计等。     

主动控制避免铁道车辆蛇行失稳

为了避免铁道车辆蛇行失稳,提高运行速度,开发了可控机电减振器。通过实验台试验和数值仿真计算,验证了机电减振器的性能。     

巡回出租车市场卫星派遣车队最适规模之研究

出租车乃公共运输系统中最具经营弹性之运输工具,在经济活动频繁之都会地区广为旅行者所欢迎。近年,由于信息与通讯科技的发展,以及日益增高的行车成本,应用卫星派遣俨然已成为出租车市场的趋势与潮流。研究以双层规划数学分析模型描述巡回暨卫星派遣出租车市场之营运绩效,考虑社会福利最大与营运者利润最大的双阶层目标,研析最适车队规模和卫星派遣出租车比例,并针对使用卫星派遣服务之乘客数量,分析出租车市场结构的变化。     

Vibration transmission reduction from a centrifugal turbo blower in a fuel cell electric vehicle

This paper presents a multi-body flexible dynamic analysis of a centrifugal turbo blower for a fuel cell electric vehicle (FCEV) based on the application of computer-aided engineering (CAE) to predict the acceleration at the mount position of the blower. This predicted acceleration is validated by using the measured acceleration data. The numerical simulation for the multi-body flexible dynamics of the blower is used not only to identify the most effective mount among four mounts in an FCEV by controlling the complex stiffness of the isolator, but also to suggest the range of complex stiffness of the isolator at the most effective mount. This numerical simulation technology can be useful for the estimation of the variation of vibration transmission for the structural modification of the turbo blower.