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221.
用有限体积法对与来流夹角为45°以及夹角为0°的方柱绕流进行了数值模拟分析.从对方柱的绕流的数值模拟结果可以得出倾角为45°的方柱对尾涡的影响较之倾角为0°的方柱要大得多.由此可知,特征长度越大对柱体尾部涡影响越大.同时还对方柱的受力进行了计算和分析,并与现有实验数据、文献资料进行了比较,两者互相吻合. 相似文献
222.
Abstract The objective of this research is to develop and test a framework for efficiency assessment of road safety measures and evaluate its use in decision‐making. An exhaustive review of standard methodologies and practices related to cost‐effectiveness and cost–benefit analyses is carried out for that purpose. Moreover, a number of case studies are performed, concerning the efficiency assessment of various road safety measures in different countries, covering different types of road safety measures (user‐, vehicle‐ or infrastructure‐oriented, policy or enforcement, etc.), ranging from national to local levels of implementation and including both ex ante and ex post evaluations. From the results conclusions are drawn on the efficiency of different road safety measures and the related determinants. Furthermore, the case studies reveal a number of methodology and data issues for which further research is required. The procedures and barriers involved in the use of efficiency assessment techniques at different levels of decision‐making are also highlighted by means of feedback received during and after the various case studies. On the basis of these results, a framework for the promotion, implementation and evaluation of efficiency assessment in road safety decision‐making is proposed. A particular set of recommendations is also presented regarding the treatment of barriers (fundamental, institutional or technical) within the efficiency assessment itself and the related decision‐making process. 相似文献
223.
Current literature does not adequately discuss India's quickly changing transportation scenario, especially road traffic crash (RTC) concerns. The objectives of this work were to (a) present the national RTC framework and a case study of Andhra Pradesh (AP); (b) analyze and identify risk types; (c) discuss trends and data deficiencies; and (d) recommend prevention strategies. During the period 1970–2009, the nation's road length increased at a compounded annual growth rate (CAGR) of 3.2%, whereas the number of registered vehicles, RTCs, and fatalities grew at 12%, 3.8%, and 5.7% CAGR respectively. Exposure risk dropped from 103 to 11 fatalities per 10 000 vehicles but increased from 2.7 to 10.8 fatalities per 100 000 people. 相似文献