Short-term post-earthquake bus transit planning in Managua

In December 1972 an earthquake hit Managua, Nicaragua, killing 5,000 inhabitants, while wounding 20,000 persons and destroying its core area of 13 square kilometers. The earthquake also seriously disrupted the bus transit system. Bus transit patronage fell as a result of the loss of population of 144,000 persons who moved temporarily out of the city, while costs rose appreciably as both round trip bus distances and the proportion of the trips on unpaved roads doubled with respect to pre-earthquake levels. By September 1973, ten of the thirteen bus companies were on the verge of bankruptcy and were demanding from the regulatory body stiff increases in fares.This paper presents analyses and recommendations for improving the short-term efficiency of bus routes in Managua by applying planning techniques suited to the data availability problems of developing countries.In view of the lack of cost data for the bus routes, a cost analysis was conducted; Jan de Weille's cost factors were adapted to Nicaragua to portray the near bankrupt condition of most routes. These cost factors were verified by means of selected interviews with the private transit entrepreneurs.Next, a simple patronage prediction model was developed which related patronage for a route to the population and employment served by the route. This simple patronage model was then applied to redesign the bus routes of Managua. A policy of bus route redesign coupled with the paving of city streets along the bus routes is shown to have sufficed in avoiding fare increases. Finally, the paper reviews the bus transit regulatory setting and develops some recommendations for its improvement.Adjunct Associate Professor of the Catholic University of America. This study was conducted while the author was stationed in Nicaragua as a consultant to Harvard Development Advisory Service.     

ICE 3的线性涡流制动--技术观点和运行经验

线性涡流制动(WB)首次正式用于德国铁路的ICE 3列车中,其优点是工作无磨损且与轮轨间的粘着系数无关.简要介绍线性涡流制动批量使用前的主要开发步骤及与线路的相互作用.     

The vertical disintegration of ship management: choice criteria for third party selection and evaluation

An assessment of the rationale for the vertical disintegration of ship management suggests that there might be compelling economic benefits for the separation of ownership from management. In this context, as a means for developing effective marketing strategies, it is important for ship managers to know the criteria used by current and prospective clients for ship manager selection and evaluation. The aim of this paper is to empirically identify the dimensions for ship manager selection and performance evaluation and their relative importance and to discuss the implications for marketing emanating from such an assessment. The methodology adopted includes the collection of secondary and primary data, both from ship managers and their clients, using interviews and a mail survey. The results indicate the prevailing importance of certain dimensions in selection (e.g. technical ability, reputation, competency) and evaluation (responsiveness, trustworthiness, technical ability), whereas it also found that price alone is not perceived to be as important in ship manager selection. It is concluded that placing emphasis on such dimensions in the formulation of a marketing strategy will contribute towards the attraction and retention of clients, whereas cost-cutting measures to allow price reduction, as well as advertising, will be ineffective over the long term.     

Lateral Vehicle Behaviour: Comparison of Subjective/Objective Assessment Using the Choquet Integral

This paper presents an original method for the aggregation of transverse behaviour indicators obtained first from a subjective assessment then from an objective one of different vehicles tested under normal working conditions. The Choquet integral is used with respect to fuzzy measures. The main advantage of this method is to take account of the existing interactions between the indicators: redundancy, complementarity, inde-pendence. When this tool is used for subjective and objective evaluations, the computation methods of the objective indicators can be validated. Moreover, the influence of the human factor in the judgment of vehicle behaviour is easier to understand.     

Direct Computation of the Performance Index for an Optimally Controlled Active Suspension with Preview Applied to a Half-Car Model

A quadratic integral performance index is defined for a linear active preview-type suspension and a series of matrix expressions derived for its evaluation by means of MATLAB or some similar computer program in the case of a unit step input to the system. The computation, which is both fast and accurate compared to simulation, requires the solution of Lyapunov- and Riccati-type equations. Some examples of numerical computation are given and these show excellent agreement with published results. The conclusion features a useful computer program.     

新能源车--世界第一辆混合动车

东日本铁路公司已经把环境保护列为其"集团远景规划"之一,并正在积极地为保护环境而努力.在这方面,减少列车运行所需能量是一个重大的课题,目前正在致力于实现重大改进.然而,由于再生制动不能配置在内燃动车上,因而其能量效率要比电动车低. 东日本铁路公司研发中心一直致力于开发一种新能源车,其目标是通过革新驱动系统,减少铁路动车运行时对环境的影响.作为第一步,已经建造了世界上第一台有混合动力系统的试验车,一种使用锂离子蓄电池储能的批量生产的混合系统已经装车.自2003年5月以来一直在进行试验.该混合系统就其性能和能量效率来说,几乎达到了预想的运行水平.     

A methodology for vehicle sideslip angle identification: comparison with experimental data

Sideslip angle could provide important information concerning vehicle's stability. Unfortunately direct measurement of sideslip angle requires a complex and expensive experimental set-up, which is not suitable for implementation on ordinary passenger cars; thus, this quantity has to be estimated starting from the measurements of vehicle lateral/longitudinal acceleration, speed, yaw rate and steer angle. According to the proposed methodology, sideslip angle is estimated as a weighted mean of the results provided by a kinematic formulation and those obtained through a state observer based on vehicle single-track model. Kinematical formula is considered reliable for a transient manoeuvre, while the state observer is used in nearly quasi-state condition. The basic idea of the work is to make use of the information provided by the kinematic formulation during a transient manoeuvre to update the single-track model parameters (tires cornering stiffnesses). A fuzzy-logic procedure was implemented to identify steady state or transient conditions.     

Maglev Vehicle/Guideway Vertical Random Response and Ride Quality

Summary The research and development (R & D) of maglev technology had made a great progress in China since the early 1980s. Especially, a 35 km-long Shanghai high-speed maglev railway employing the German Transrapid system began to be constructed on March 1, 2001. Based on the Transrapid system, the paper develops a 10-degree-of-freedom model of maglev vehicle running over three types of guideways with constant speed. Random guideway irregularities are discussed and taken into account for simulation of the vehicle response and for evaluation of the ride comfort. Using the direct time integration method and the discrete fast Fourier transform (DFFT), random responses of the maglev vehicle-guideway systems are obtained and analyzed. Numerical results show that the resonant frequency of car body acceleration response is 0.5-1 Hz, and there is a 2.2 Hz periodic vibration due to the periodic configuration of rigid piers when the maglev vehicle travels over the elevated-beam guideway. The car body acceleration power spectral density (PSD) curves meet well the ride quality criterion of the urban tracked aircushion vehicle (UTACV) and the maximum acceleration of car body is less than 0.05 g. Moreover, the Sperling ride index values are less than 2.5 as long as the operational speed is less than 450 km/h. It is concluded that the maglev vehicle ride quality is quite well.