Impacts of motor vehicle operation on water quality in the US – Cleanup costs and policies

This paper investigates the costs of controlling some of the environmental impacts of motor vehicle transportation on groundwater and on surface waters. We estimate that annualized costs of cleaning-up leaking underground storage tanks range from $0.8 billion to $2.1 billion per year over 10 years. Annualized costs of controlling highway runoff from principal arterials in the US are much larger: they range from $2.9 billion to $15.6 billion per year over 20 years (1.6–8.3% of annualized highway transportation expenditures). Some causes of non-point source pollution were unintentionally created by regulations or could be addressed by simple design changes of motor vehicles. A review of applicable measures suggests that effective policies should combine economic incentives, information campaigns, and enforcement, coupled with preventive environmental measures. In general, preventing water pollution from motor vehicles would be much cheaper than cleaning it up.     

基于虚拟边界条件一维搜索预报的并行算法

对网格方程组作多重网格区域分裂并行计算,虚拟边界预报提出一维搜索算法,并讨论相应的收敛性,通过ＧＳ迭代的性质,构造区间压缩算法,证明了其收敛性,指出此算法能有效地解决区域分裂并行计算中的远程信息传递和频繁通讯问题。     

Book reviews

Coastal Resources Management: Beyond Market and Bureaucracy by Robert B. Ditton, John L. Seymour, and Gerald C. Swanson. Published by D. C. Heath and Company, Lexington, Massachusetts, 1977, 191 pp., 6 figures.

The Urban Sea: Long Island Sound by Lee E. Koppelman, Peter K. Weyl, M. Grant Gross, and DeWitt S. Davies. Published by Praeger Publishers, 1976. 209 pp., 81 figures, 42 tables.     

New highways and land use change: Results from a quasi-experimental research design

Understanding links from new highway construction or capacity expansion to regional growth patterns is crucial for transportation planners and policy makers. In this paper, we incorporate a lagged adjustment regional growth model into a quasi-experimental research design to examine the association between new highway investments and land use change in three California counties. Our study areas provide a mix of urban, small town, and exurban highway projects in order to explore the different effects across project types and geographic contexts. The central finding of this research is that while improvements in surface transportation infrastructure can have large impacts on growth patterns, the nature of the effect depends on the context of the highway investment.     

A Practical Model for Deformation Prediction of Highway Subgrade Soils

This paper reports a practical constitutive relation for highway subgrade soils. The proposed model is derived based on the laboratory repeated-load testing of four subgrade soils. Statistical parameters generally used in the power model of subgrade permanent strain are expanded into material constants with engineering significance. The constitutional relation reported in this paper can be used in the mechanistic-based pavement design of highway flexible pavements and railroad tracks.     

PC局域网上分布式并行处理的性能评估

对ＰＣ局域网上ＰＶＭ分布式编程环境中网络并行计算的性能进行了详尽分析与评估,指出：在ＰＶＭ编程环境中网络并行计算与ＭＰＰ并行计算的根本 区别在于它们的通信行为不同。网络并行计算中的通信是顺序的,不仅通信和计算是顺序发生的,而且各次通信也是顺序发生的。而在ＭＰＰ并行计算中通信是由专门的通信部件并发完成。文章给出一个统一的公式来描绘这两类主要的并行处理系统的性状,并由此导出,对于网络并行计算其加速比服     

An introduction to airport APM systems

The purpose of this paper is to provide an introduction to the nature and purpose of airport automated people mover (APM) systems. Our objective is to provide a convenient research tool for persons seeking an introduction to the airport APM industry. Included are illustrations of typical system designs; a listing of existing airport APM systems, including a tabular presentation of selected data; an organization and discussion of the history and evolution of the existing systems; and a status report on current developments in the APM industry.