The treatment of capital costs of vehicles in evaluating road schemes

There are two ways in which new road schemes may influence capital expenditure on vehicles. Firstly, by improving utilisation of existing vehicles, the size of fleet needed to perform a given volume of work may be reduced. This will clearly reduce the amount of capital tied up in motor vehicles at any point in time, and to the extent that vehicle life is determined by age rather than mileage run, will also yield savings in terms of investment in new vehicles. Secondly, by generating additional road traffic, road schemes may lead to an increase in the stock of vehicles in use.This paper argues that the current treatment of vehicle depreciation and interest charges in U.K. cost data fails to allow correctly for either of these items. Errors of logic occur in the way in which the capital stock of vehicles is valued, and in the fact that certain overheads are ignored even when fleet size changes. Moreover, the empirical evidence supporting the current partitioning of depreciation into overhead and running cost components, and the assumption of constant hours in service after an increase in journey speed seems of doubtful validity.An alternative method of calculating vehicle capital costs, based on the concept of annual capital charge, and making explicit the assumptions with respect to vehicle utilisation, is advocated, and the sensitivity of results to the view taken of the latter is demonstrated by means of specimen calculations.     

Ride Dynamics of Articulated Vehicles-A Literature Survey

This paper presents a review of the available literature describing the methods of modelling the vibrational response of articulated vehicles to the road inputs at the tire contact points. It states and discusses the mathematical techniques that have been put forward for obtaining road input characteristics, for modelling the vehicles in a range of degrees of freedom, and for performing the analysis necessary to obtain the vibrational response. Finally the indices that have been proposed for ride comfort and ride safety are given and the manner in which various researchers relate these to the vibrational characteristics of the vehicles is described.     

Analytical Tire Models for Dynamic Vehicle Simulation

Four basic tire models suitable for dynamic vehicle simulation are formulated. The models are compared through a six-degree-of-freedom nonlinear simulation of a cargo truck crossing rough ground. Guidelines are developed for the selection of an optimum tire model for a given dynamic vehicle simulation.     

Freight transport demand revisited: A microeconomic view of multimodal, multicharacteristic service uncertainty and the demand for freight transport

This paper provides a unifying framework for micro-based models of freight transport demand. An expected utility of profits model is posed that clarifies the conditions under which a system of equations (continuous) regression model should be used as opposed to the conditions that make a quantal choice model appropriate. The model also indicates the nature of subjective data that is necessary for estimating demand. In general, the conditions that give rise to the appropriate use of a quantal choice model imply that the needed subjective information is completely contained in the subjective probability distributions on the service characteristics; the utility function itself is irrelevant.     

The valuation of commuter travel time savings for car drivers: evaluating alternative model specifications

The empirical valuation of travel time savings is a derivative of the ratio of parameter estimates in a discrete choice model. The most common formulation (multinomial logit) imposes strong restrictions on the profile of the unobserved influences on choice as represented by the random component of a preference function. As we progress our ability to relax these restrictions we open up opportunities to benchmark the values derived from simple (albeit relatively restrictive) models. In this paper we contrast the values of travel time savings derived from multinomial logit and alternative specifications of mixed (or random parameter) logit models. The empirical setting is urban car commuting in six locations in New Zealand. The evidence suggests that less restrictive choice model specifications tend to produce higher estimates of values of time savings compared to the multinomial logit model; however the degree of under-estimation of multinomial logit remains quite variable, depending on the context.     

二次扩展复数旋转码及其对偶码

扩展复数旋转的基础上,提出了二次扩展复数旋转码及其对偶码的概念。就它们的特性作了初步的讨论,并给出了它们的生成矩阵的构造方式及主要参数。经过与扩展复数旋转码和其对偶码相比较,可以看出它们也是一类码率高、纠错能力强的差错控制码。     

供应链管理及其结构与网络的应用

供应链作为一种普适的逻辑思想,它的提出是管理学发展过程中具有非常重要意义的里程碑。本在时间维上讨论了供应链管理对过去、现在和未来的挑战,旨在从理论和实物两个方面向企业界介绍这一先进科学的管理方法。章中通过阐述供应链网络结构的特性,提出了在实施供应链管理过程中所遇到的问题以及如何更好地实现供应链管理的方法。     

吴文俊与数学机械化

机器证明的思想可以回溯到17世纪的Descartes与Leibnize,20世纪初Hilbert更明确地提出了公理系统的机械化判定问题,但是,随后的种种努力都未能使机器证明取得本质的进展。近20年来,吴俊继承并发展了中国古代的数学思想,在定理机器证明上开创了以多项式组零点集为基本点的消元方法;吴俊的数学机械化方法已在物理规律的发现,机器人学,计算机视觉以及促进现代数学研究等重大高科技的前沿领域实现了成功的应用。数学机械化研究的兴趣,是中国当代数学发展中一个引人瞩目的具有中国传统特色的新里程碑。