Capitalization of BRT network expansions effects into prices of non-expansion areas

A before and after hedonic model is used to determine the property value impacts on properties already served by the transit system caused by extensions to Bogotá’s bus rapid transit system. Asking prices of residential properties belonging to an intervention area (N = 1407 before, 1570 after) or a control area (N = 267 before, 732 after) and offered for sale between 2001 and 2006 are used to determine capitalization of the enhanced regional access provided by the extension. Properties offered during the year the extension was inaugurated and in subsequent years have asking prices that are between 13% and 14% higher than prices for properties in the control area, after adjusting for structural, neighborhood and regional accessibility characteristics of each property. Furthermore, the appreciation is similar for properties within 500 m and properties between 500 m and 1 km of the BRT.     

可提高能量再生效率的锂离子充电电池

近30多年来,再生制动系统已为电动车组降低能耗做出了极大贡献.然而,这种系统还存在许多问题,如再生能被车轮滑行和拖车电压抵消,在高速范围电制动力降低,供电电路阻抗限定了再生功率.为了利用和循环利用制动能,确保稳定的再生荷载,我们选用锂离子电池来储能,开发出锂离子充电电池(600V系统),作为重要的替换方法之一用于电动车组.阐述了使用锂离子充电电池、能量再利用的无接触导线电车,展示了电车性能和电池特性.并表明,开发中的电池在能量和功率密度、效率、500A充电和放电电流、内部电阻和维护等各方面都有极好的性能.     

加拿大的城市轨道交通技术

加拿大幅员辽阔,但人口稀少(大约3000万人).由于气候地理的原因,90%的加拿大人居住在与美国邻界322 km宽的窄带内.另外,加拿大的大多数人,确切地说是76.6%,居住在城市和城镇,只有23.4%的人居住在乡村.因此,加拿大的城市发展问题十分重要.多伦多、蒙特利尔、卡尔加里、温哥华等城市已发展成为国际大都市,多种经济形式并存,服务业十分发达,还有银行、工程、医药和科学研究等.     

A model of traffic dispersion from a congested road

The study of traffic flow dynamics is developed by defining and clarifying traffic divergence, continuity, congestion and dispersion. Velocity potential is introduced as a gravity function generated by the interaction of two or more motorists occupying neighbouring points in space and describes interference to continuous traffic flow. The relationship between the potential function and carrying capacity is developed and dispersion, when considered as a random walk, satisfies a diffusion equation. A model of traffic dispersion along a maximum congested road in space and time is presented as eigenfunctions of the velocity potential. This suggests that traffic can be dispersed by a series of quantum steps. A probability density function is introduced to define the probability of locating a motorist in a congestion zone.     

旅客信息系统的现状与未来

有轨运输的旅客信息系统广泛使用了信息和通信技术.这种系统既用于地面,例如站台上,又用于移动的列车中.技术的不断发展为显示、计算机和通信开辟了新的功能和应用场合.继续发展的这些技术,给旅客信息系统提供了有利于铁路运营部门和旅客的新功能.德国铁路公司的403/406/411和415/605型车辆使用了最现代化的旅客信息系统,文章以该系统为例介绍这种移动应用的技术现状以及由于技术进步提供的新应用情况.     

异步电机用随机定位空间矢量PWM降低开关噪声

任意脉宽调制(RPWM)是用来将电压、电流谐波扩展到宽频率范围的开关技术.通过任意改变逆变器开关频率,可以将电磁声频噪声的功率频谱扩展到宽带区.与窄带噪声相比,宽带噪声给人们带来的不适和干扰较小.因而,在逆变驱动系统中,RPWM作为一种能降低声频噪声的极好途径,正在引起研究人员的注意.文章提出并实现了一种新型的任意定位空间矢量PWM(RPPWM)技术.在每一个开关周期内,三相脉冲均可以任意定位.采用一个C167微控制器就能够实现PWM脉冲的任意定位和空间矢量调制.仿真和试验结果表明,通过应用一种新的RPPWM技术,可以将电压、电流谐波扩展到宽带区,从而降低开关声频噪声.     

Nonlinear Dynamics of Vehicle Traction

Summary The purpose of this study is to understand the nonlinear dynamics of longitudinal ground vehicle traction. Specifically, single-wheel models of rubber-tired automobiles under straight-ahead braking and acceleration conditions are investigated in detail. Customarily, the forward vehicle speed and the rotational rate of the tire/wheel are taken as dynamic states. This paper motivates an alternative formulation in which wheel slip, a dimensionless measure of the difference between the vehicle speed and the circumferential speed of the tire relative to the wheel center, replaces the angular velocity of the tire/wheel as a dynamic state. This formulation offers new insight into the dynamic behavior of vehicle traction. The unique features of the modeling approach allow one to capture the full range of dynamic responses of the single-wheel traction models in a relatively simple geometric manner. The models developed here may also be useful for developing and implementing anti-lock brake and traction control control schemes.     

General stochastic user equilibrium traffic assignment problem with link capacity constraints

This paper addresses a general stochastic user equilibrium (SUE) traffic assignment problem with link capacity constraints. It first proposes a novel linearly constrained minimization model in terms of path flows and then shows that any of its local minimums satisfies the generalized SUE conditions. As the objective function of the proposed model involves path‐specific delay functions without explicit mathematical expressions, its Lagrangian dual formulation is analyzed. On the basis of the Lagrangian dual model, a convergent Lagrangian dual method with a predetermined step size sequence is developed. This solution method merely invokes a subroutine at each iteration to perform a conventional SUE traffic assignment excluding link capacity constraints. Finally, two numerical examples are used to illustrate the proposed model and solution method.     

Deviated state detection method in driving around curves based on naturalistic driving behavior database for driver assistance systems

The objective of this study is to propose the indices which detect the deviated state of drivers while driving by considering drivers’ judgment process and using road environment and naturalistic driving behavior database. To realize this objective, drivers’ speed choice behavior around curve situations was focused and the speed choice process was formulated. Moreover, a deviated state detection method considering the formulated speed choice process around curve situations was proposed and the validity of the method was examined.