Enhancing rail infra durability through freight bogie design

The extensive usage of railway infrastructure demands a high level of robustness, which can be achieved partly by considering (and managing) the track and rolling stock as one integral system with due attention to their interface. A growing number of infra managers consider, in this framework, the track-friendliness of vehicles that have access to their tracks as a key control parameter. The aim of this study is to provide further insight into potential contributions to track-friendliness, assessed in relation to track deterioration mechanisms and cost, understanding how potential benefits are best to be utilised. Six proposed freight bogie design measures are evaluated with respect to the improvement in curving behaviour, switch negotiation and related track degradation mechanisms. To this purpose a sensitivity analysis has been carried out by means of track–train simulations in the VAMPIRE® multi body simulation software. Additionally, the impact on track deterioration costs has been calculated for those track-friendly design modifications identified as most promising. Conclusions show that the standard Y25L freight bogie design displays rather a track-friendly behaviour. Tuning the primary yaw stiffness shows a high potential to further improve track-friendliness, significantly reducing track deterioration cost at narrow radius curves and switches (by, respectively, 30% and 60%). When calculating the overall deterioration cost for the travelled route, the calculation model should include a well-balanced representation of switches and narrow radius curves.     

回到1971的未来

战火纷飞的年代,汽车制造商们关心的是汽车的安全性能和楔形主题1971是动荡的一年。北爱尔兰动乱升级,多少无辜的平民被杀害;美国仍深陷越南战争的泥潭。第26届联合国大会以压倒性多数通过第258号决议,决定恢复中华人民共和国在联合国的一切合法权利。那时的苏联仍是西方阵营的头号敌人。     

The impact of fuel availability on demand for alternative-fuel vehicles

We study the impact of fuel availability on demand for alternative-fuel vehicles, using data from a survey of potential car buyers in Germany. The survey was conducted as a computer-assisted personal interview and included a choice experiment involving cars with various fuel types. Applying a standard logit model, we show that alternative fuel availability influences choices positively, but its marginal utility diminishes with supply. Furthermore, we derive consumers’ marginal willingness-to-pay for an expanded service station network. The results suggest that a failure to expand the availability of alternative fuel stations represents a significant barrier to the widespread adoption of alternative-fuel vehicles.     

Modeling bus bunching using massive location and fare collection data

Bus bunching is a well-known phenomenon for operators, users and regulators of high-frequency bus services. Bus operations are usually affected by increasing differences in the time intervals (headways) between consecutive buses. The effect of this variability is that buses tend to group into bunches of two or more, which severely affects the quality of service and the operational efficiency. The aim of this paper is to analyze which factors are associated to the phenomenon, using massive data from high-frequency services available in Santiago (Chile) and common-route services in Gatineau (Canada). The data is obtained from the bus GPS and AFC systems and are processed to obtain headways between buses. Using data from one week, we develop models to explain the variation of the continuous and discrete indicators of bus bunching as a function of variables related to the operation, variables related to the demand structure, and variables related to the infrastructure. Some of the factors that contribute to increase bus bunching are: stops located toward the end of the route, high scheduled frequency, irregular bus dispatch headways, non-homogeneous fleet, high demand, and high variability of demand. The results are useful for the design of quality indexes to measure bunching in bus operations, and for the design and operation of bus routes, taking into consideration the potential bus bunching problems.     

车胎压力监测系统简述及两种实现方案

车胎压力对汽车的安全行驶至关重要,保障车胎压力正常的汽车轮胎压力监测系统(TirePressureMonitoringSystem,TPMS)受到国内外汽车工业界越来越多的重视。本文对目前常用的两种TPMS实现方案:间接监测和直接监测方法做了详细的介绍,并对两种方法的性能指标做了全面的对比。     

Analytical formulae for predicting the surf-riding threshold for a ship in following seas

Making use of Melnikov’s method, a generalized formula for predicting the surf-riding threshold is developed as an extension to the applications of Kan and Spyrou. A new analytical formula for calculating the surf-riding threshold of a ship in following seas is also proposed in light of nonlinear dynamical system theory. By applying a continuous piecewise linear approximation to the wave-induced surge force, a heteroclinic bifurcation point is obtained analytically with an uncoupled surge equation. Results calculated using these formulae are presented, and they show good agreement with those obtained utilizing numerical bifurcation analysis. Further, it was confirmed that the surf-riding threshold obtained using the proposed formulae agrees reasonably well with that obtained experimentally for an unconventional vessel.     

OCS development: A new law and a new beginning

Abstract

This article reviews the conflicts that led to the establishment of a special Congressional Committee on offshore oil and gas exploration, development, and production and the attempted resolution of various issues by that Committee and the Congress in the 1978 Amendments to the Outer Continental Shelf Lands Act of 1953. A short review is provided of the history of Outer Continental Shelf (OCS) development, of the conflict between the federal government and other interested entities and persons, and of the Congressional mechanism to respond to these conflicts. A more detailed analysis is provided of the most significant OCS issues. The article describes the various risks and benefits of offshore activity and the various benefits and risks of proposed changes in the law concerning such development. A review of the Congressional mechanism to assess these risks and benefits and balance them is included in a discussion of the various issues and legislated solutions. Finally, the article notes the need for continuing oversight and review of the benefits and risks and how effective the 1978 Amendments are in balancing them.     

Turning cities inside out: transportation and the resurgence of downtowns in North America

North American urban areas have changed dramatically over the last four decades. While downtowns were thought to be in long-term decline 40 years ago, central business districts are today the most vibrant residential and commercial centers throughout a largely suburban continent. This paper examines the role of transportation technology and policy in the earlier decline and recent revival of American downtowns and examines challenges to the continuation of urban regeneration. Major recent investments in physical improvements in central cities have been complemented by a dramatic shift in the locus of logistical and goods processing activities from city centers to outlying areas. While many tout the energy efficiency and environmental benefits of walkable and denser inner cities, a more complete accounting of their impacts also requires analysis of increasing urban congestion and the steady rise in urban goods movement in support of the new development patterns.