创新之桥——计量学在科学与技术中的应用——2010年世界计量日致词

<正>作为计量研究人员的快乐之一就是:计量学让我们走在科学的最前沿。我们总是试图了解,为什么大自然要限制我们去执行某种测量的能力。这种限制究竟是不可逾越的自然法则抑或是借助更睿智的思想便能攀越的藩篱。显然,这种智力挑战就是开拓新领域的动力。     

The economics of railway safety

This paper reviews the statistics and economics of railway safety in Great Britain, the European Union and the United States, together with some results for Finland and Japan. In these countries railway safety has improved over recent decades. That finding applies both to train accidents and to personal accidents such as persons struck by trains. Fatal train collisions and derailments command most attention even though they are infrequent and account for only a small minority of railway fatalities. Great Britain, the EU and the USA formally espouse conventional cost benefit analysis for the appraisal of railway safety measures, using the same valuations for the prevention of casualties as are used in road safety appraisal. However there are often strong institutional, legal and political pressures towards adopting railway safety measures with safety benefit: cost ratios well below 1. The best-documented examples of this are automatic train protection systems, which are discussed in the paper. Apart from trespassers, the largest group of railway fatalities occur at level crossings, which the paper also discusses. Level crossing safety measures would seem to be an appropriate subject for cost benefit analysis, but there are few case-studies in the literature. Over the last few decades, the railways in many countries have been privatised or deregulated with the aim of improving their economic performance. Such changes have the potential to affect safety. The paper reviews evidence of the effects on safety of railway restructuring in Great Britain, Japan and the United State, and finds no evidence that safety deteriorated.     

通过合作伙伴开发的井口控制技术

娜威的6yda油田位于北海南部的UIa和lkofisk之间,于1990年开始投产。该油田是用一个集钻井、膳宿、加工为一体的钢套管架设施开发的。该设施的日产量为将近14000桶原油。     

Getting the best of both worlds: a framework for combining disaggregate travel survey data and aggregate mobile phone data for trip generation modelling

Transportation - Traditional approaches to travel behaviour modelling primarily rely on household travel survey data, which is expensive to collect, resulting in small sample sizes and infrequent...     

Some considerations in the thyristors' reactive effects on the power supply

Silicon Controlled Rectifier (SCR) drives have become a standard technique for transit systems. Their utilization meets the most demanding specifications and results in an effective decrease in power consumption which translates in decreased costs for energy. The regenerative DC power may be inverted to 3-phase AC power and returned to the line as usable power. However, regenerative capability is at a cost penalty.     

Using ordered attitudinal indicators in a latent variable choice model: a study of the impact of security on rail travel behaviour

There is growing interest in the use of models that recognise the role of individuals’ attitudes and perceptions in choice behaviour. Rather than relying on simple linear approaches or a potentially bias-inducing deterministic approach based on incorporating stated attitudinal indicators directly in the choice model, researchers have recently recognised the latent nature of attitudes. The uptake of such latent attitude models in applied work has however been slow, while a number of overly simplistic assumptions are also commonly made. In this article, we present an application of jointly estimated attitudinal and choice models to a real-world transport study, looking at the role of latent attitudes in a rail travel context. Our results show the impact that concern with privacy, liberty and security, and distrust of business, technology and authority have on the desire for rail travel in the face of increased security measures, as well as for universal security checks. Alongside demonstrating the applicability of the model in applied work, we also address a number of theoretical issues. We first show the equivalence of two different normalisations discussed in the literature. Unlike many other latent attitude studies, we explicitly recognise the repeated choice nature of the data. Finally, the main methodological contribution comes in replacing the typically used continuous model for attitudinal response by an ordered logit structure which more correctly accounts for the ordinal nature of the indicators.     

Estimating choice models containing attraction variables

The paper presents a family of disaggregate choice models, which are shown to be equivalent to many of the aggregate models commonly used in planning studies. A brief summary is given of the method that has been developed for estimating the parameters of these models. A generalisation is then introduced in which variables representing the attractiveness in terms of size or quantity of each alternative are allowed to enter the model. It is shown that the form in which these variables enter the model requires a more general estimation algorithm than is commonly used, and such an algorithm is presented. A series of practical tests of the new algorithm is described.     

New routes on old railways: increasing rail’s mode share within the constraints of the existing railway network

This paper describes an integrated methodology for identifying potential ‘quick wins’ for mode shift from road to passenger rail transport. Firstly, a procedure for analysing rail’s relative competitiveness in the market for passenger transport between large urban areas is developed and then applied to a UK case study. The purpose of such analysis is to allow the identification of flows where rail is currently relatively uncompetitive (in terms of journey time in particular) and to assess the reasons for this poor performance, so that the issues which suppress rail use may be addressed. In parallel, a framework, methodology and tool for the assessment of existing and potential capacity (trains, seats, TEUs, etc.) is developed for both passenger and freight traffic, to identify and address network constraints. An illustrative example of the use of these demand and capacity assessment tools is then presented, with the tools used to identify and evaluate flows where rail demand is suppressed by poor service quality and where spare capacity exists which would allow the passenger rail service to be improved without requiring significant investments in infrastructure. The effects of such improvements on demand are predicted, and the cost implications of operating such additional services are discussed. The analysis suggests that there may be significant potential for increasing rail’s mode share by providing additional inter-urban services where rail currently offers an inferior service.     

National policy towards cars: Singapore

Singapore has experienced rapid growth in car ownership, and private transport accounts for just under half of motorized trips in Singapore. Yet only since 1970 have determined efforts been made to curtail this increase. Simultaneously with this growth, Singapore's land‐use planners had called for the diversion of population growth into outlying residential estates while maintaining the central area's importance as an employment centre. The resulting anticipated concentration of commuter movement suggested a need for controls to restrain car ownership, reduce central‐area congestion and divert road users on to public transport. The policies followed are described. Those against ownership have included heavy road taxes and registration fees, with a system of discounts on the latter to discourage new purchasers except when replacing scrapped cars. Policies against car use include fuel taxes and the Area Licensing Scheme in the city centre, while parking space is also closely regulated. The measures adopted imply a goal of efficiency in promoting Singapore's planning objectives rather than environmental, safety or equity considerations, although the first two of these have lately received much more attention than formerly. The policies’ effect has been a temporary reversal in the growth of car ownership, but this growth has since resumed and recent further fee increases suggest a panic reaction rather than a coordinated strategy. Such coordination appears at present to be hampered by the fragmented administration of matters relating to transport. Other measures relating to car ownership and use in Singapore are also described.