在役桥梁的评估方法和发展趋势

基于当今桥梁的评估技术,从五个方面大体概括了桥梁评估的现有方法,同时对桥梁评估方法的发展趋势发表了自己的一些看法和观点。     

Lateral dynamics of motorcycles towing single-wheeled trailers

A motorcycle towing a single-wheel trailer may provide useful transport for light cargo on narrow tracks and off-road use, particularly in rural areas of developing countries. Four designs of such trailers are described. Linear models are derived for the lateral dynamics of an off-road motorcycle towing this type of trailer straight ahead at constant speed. The trailers were tested behind an instrumented motorcycle. Linear autoregressive models were fitted to the experimental data using system identification techniques. Analytical and experimentally derived models largely agreed on frequency, damping and shape of the weave, wobble and trailer sway normal modes. The trailers made the motorcycle’s steering heavier but the analytical models did not predict this. The location of the articulation axes between the motorcycle and the trailer were found to be critical for stability. The best trailer design handled well with loads up to 200 kg and speeds up to 70 km/h.     

FDI理论发展演变的探析

中国在融入世界经济的进程中,对外开放政策正从主要靠“引进来”为主转向“引进来”和“走出去”并重的新阶段。本文阐述并总结了国外及国内的FDI理论,这些理论可以为我国直接投资提供理论支持。     

Market role and regulation of extensive urban minibus services as large bus service capacity is restored - Case studies from Ghana, Georgia and Kazakhstan

In some cities, the degeneration and collapse of formal bus services has allowed large-scale minibus operations to become established but, over time, city authorities and municipal bus operators regain at least part of their operating capacity and seek to regain their market share. This paper examines and compares three case studies: Accra, Tbilisi, and cities of Kazakhstan. It examines the development of the urban minibus services market as conventional bus services went into decline, the gradual re-emergence of large buses, how the authorities have viewed the minibuses as circumstances change, and market and regulatory strategies followed by city authorities.     

Traffic problems in Southeast Asia featuring the case of Cambodia's traffic accidents involving motorcycles

This article provides the background to the special issue by reviewing the status of traffic problems in South East Asian countries, and in particular, the case of Cambodia. The “Make Roads Safe” report by the Commission for Global Road Safety (2011) confirms traffic accidents as the primary cause of youth mortality worldwide. Thus, the United Nations declared the decade from 2011 to 2020 as the “UN Decade of Action for Road Safety 2011-2020”, promoting road safety and to reduce the number of deaths in road accidents by 2020. Furthermore, the “Sustainable Development Goals” adopted in 2015 highlight the important role of sustainable transport in tackling the exclusion of vulnerable groups. On the other hand, the World Health Organization in 2015 indicate an increase in the death rate due to traffic accidents in low-income countries since 2000. Traffic accidents were already recognized as a social problem before the 2000s in countries such as Thailand and the Philippines. At the same time, other ASEAN member states such as Vietnam and Cambodia which have experienced rapid economic growth since the 2000s are now experiencing the seriousness of traffic problems. It is said that 70% of road accidents in Thailand, Cambodia and Laos involve motorcycles and three-wheelers, but despite this situation, the regulatory framework for motorcycles remains undeveloped. In the case of Cambodia, speeding by young people remains the major cause of road deaths and this can be explained by the fact that people can now travel at a higher speed because of road developments but remaining challenges related to underdeveloped traffic legislation, and limited public awareness and knowledge of road safety are overlooked. In 2010, the Cambodian National Road Safety Action Plan 2010–2020 was drafted, aiming to halve the number of deaths in traffic accidents in 2020. However, in reality, the number of road deaths did not decrease to the level anticipated in the action plan until 2016. In this article, the authors emphasize the importance of implementing the “three Es” namely Engineering, Enforcement and Education in developing countries such as Cambodia. In particular, the authors claim that the role of education to increase people's road safety awareness is neglected compared to the other two dimensions and thus, it is highly important to raise people's road safety awareness through education among the young people.     

青藏铁路修筑后次生不良冻土现象的特征及发展趋势

青藏铁路的修建会形成次生不良冻土现象,次生不良冻土现象会对铁路产生诸多危害。研究青藏铁路修筑以后次生不良冻土现象的特征及发展趋势意义重大。对青藏铁路沿线不同类型的次生不良冻土现象进行调查研究,研究青藏铁路修筑以后次生不良冻土现象产生的机理、发育特征及发展趋势。查明对青藏铁路有直接或潜在威胁的次生不良冻土现象18处,其中与路基有关的次生不良冻土现象较少;与桥梁有关的次生不良冻土现象,主要是桥下形成冰椎、冰幔等;与涵洞有关的次生不良冻土现象,主要有涵洞下沉等。研究表明:未来气温升高导致多年冻土上限附近地下冰大量融化,将会产生诸多次生不良冻土病害,影响铁路的正常运营。     

Line haul interstation spacing for low cost feeder modes

The choice behaviour of low cost travel (LCT) modes is very sensitive to travel distance. A line haul system designed on the basis of current planning practice of locating widely spaced stations to cater auto and bus feeder modes with the primary objective of gaining travel speed is hostile to non‐motorized and low cost feeder modes. With the revival of interest in promoting the use of walk'n ride and bike'n ride modes, there is a need to develop an appropriate tool to examine the effect of their specific characteristics in establishing the number and location of stations.

A generic normative behavioural hybrid model for locating the cost minimizing number and location of stations is developed for an LCT‐fed line haul system. The model considers the system with many to many two dimensional line haul demand density function in which the density varies in both x‐ and y‐directions. The feeder mode choice behaviour is incorporated in the model by integrating probability‐access/egress distance function with the objective function. Explicit functional relationships among the parameters of these feeder modes such as modal share as a function of access/egress distance with the parameters of line haul systems are developed. Dynamic programming is used to minimize the system cost. The generic model is shown to collapse into several simplified models capable of yielding approximate solutions for several well known special cases. It has been shown that location of stations is sensitive to the through load on board as well as users’ cost that defines the choice behaviour at large. Numerical examples are presented to demonstrate the applicability of the model.     

我国可降解塑料快餐餐具的研究现状与发展方向

一次性塑料餐具的大量使用给环境造成越来越大的危害，已引起全社会的关注。本文根据我国国情描述了降解餐具的研究背景、研究现状，并指出降解塑料餐具在技术开发、生产应用等领域的发展方向。     

Cities on the move – Ten years after

The World Bank urban transport strategy review, “Cities on the Move” analyzed urban transport problems in developing and transitional economies and articulated a proposed strategy framework for national and city governments. This paper describes how the urban transport problems of the developing world have changed in the last decade and assesses the extent to which the strategies recommended in 2002 have been successfully implemented. It shows that progress has been widespread in some areas – particularly in mass transit analysis and investment and some environmental policies – and that there have developed some good planning and public transport practices in a smaller number of model cities. But more strategic institutional and policy issues, including the mobilization and regulation of private sector initiative in meeting infrastructure and public transport supply deficiencies, have tended to be poorly developed. Above all, the growth of medium sized cities with weak institutions and finance highlights the need for the international development institutions to put greater emphasis on helping those cities by dissemination of best practice in strategic transport planning and traffic management.