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21.
杨祖华 《华东交通大学学报》2007,24(6):145-147
形成性评价是学习测量和评价的重要组成部分.通过对其在本校大学英语教学与测试中的效果进行抽样调查研究,分析其在实践当中出现的问题,提出改进办法,以便更好的发挥其在大学英语教学与测试中的反馈和指导作用. 相似文献
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刘志勇 《湖北汽车工业学院学报》2006,20(4):8-10
对燃烧室紧凑性评价参数面容比A/V值进行了分析,讨论了其局限性。提出了新的内燃机燃烧室紧凑性的衡量方法,即面面比S/A,在等容积条件下,进行了各种燃烧室紧凑性及火焰传播距离的比较。 相似文献
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A rising trend in state and federal transportation finance is to invest capital dollars into projects which reduce greenhouse gas (GHG) emissions. However, a key metric for comparing projects, the cost-effectiveness of GHG emissions reductions, is highly dependent on the cost-benefit methodology employed in the analysis. Our analysis comparing California High-Speed Rail and three urban transportation projects shows how four different accounting framings bring wide variations in cost per metric tonne of GHG emissions reduced. In our analysis, life-cycle GHG emissions are joined with full cost accounting to better understand the benefits of cap-and-trade investments. Considering only public subsidy for capital, none of the projects appear to be a cost-effective means to reduce GHG emissions (i.e., relative to the current price of GHG emissions in California’s cap-and-trade program at $12.21 per tonne). However, after adjusting for the change in private costs users incur when switching from the counterfactual mode (automobile or aircraft) to the mode enabled by the project, all investments appear to reduce GHG emissions at a net savings to the public. Policy and decision-makers who consider only the capital cost of new transportation projects can be expected to incorrectly assess alternatives and indirect benefits (i.e., how travelers adapt to the new mass transit alternative) should be included in decision-making processes. 相似文献
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为了提高营运车辆驾驶人安全管理的精细化水平,合理地评估驾驶人驾驶风险程度,有的放矢地降低高风险驾驶人的事故率,基于卫星定位数据特点及驾驶行为与驾驶风险的相关关系设计26个驾驶行为特征参数。考虑到高速和非高速行驶时相同驾驶行为对驾驶风险的影响区别较大,根据23名营运车辆驾驶人的实测数据有针对性地筛选高速和非高速路段驾驶人风险评估指标,构建营运车辆驾驶人驾驶风险评估指标体系。然后,基于熵权法、独立性权系数法和Spearman相关系数法建立集成赋权法,确定各评估指标的权重。最后,雇佣40名营运车辆驾驶人进行实车试验以验证模型的合理性。结果表明:车辆速度和加速度方面的驾驶行为特征可以用于评估驾驶人的驾驶风险且评估效果较好,驾驶风险评估得分与实际交通冲突次数呈正相关关系,所建立模型可以较为准确地评估营运车辆驾驶人驾驶风险的高低,准确率达到77.50%,该模型在不同地区使用时,准确率存在一定的差异,但在容许范围之内,方法具有较好的鲁棒性。 相似文献
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Samples of PM2.5 and PM10 at four types of roadside location (major road, secondary road, branch road, and expressway) in Tianjin were collected and analyzed in 2015. The average annual roadside PM2.5 and PM10 concentrations were higher than the national ambient air quality standard (NAAQS: GB3095-2012). The chromium (Cr), manganese (Mn), nickel (Ni), zinc (Zn), arsenic (As), and cadmium (Cd) concentrations in both PM2.5 and PM10 over four seasons displayed significant differences (p < 0.05). An enrichment factor (EF) analysis revealed that Cd, copper (Cu), Zn, As, Ni, and Pb in PM2.5 and PM10 mainly originated from anthropogenic sources. A factor analysis (FA) and correlation analysis (CA) revealed that vehicle emissions (exhaust and non-exhaust), soil dust, coal combustion, and industrial emissions were the main sources of roadside PM2.5 and PM10 in Tianjin. Both the total hazard quotients (total HQ) and the total carcinogenic risk (total CR) for selected elements in PM2.5 and PM10 were within acceptable limits. The HQ of Pb was higher than for other metals, and it should therefore be given special attention. The CR for traffic policemen was highest for Cr exposure (1.01 × 10−5 for PM2.5 and 1.52 × 10−5 for PM10), followed by As and Ni. A sensitivity analysis showed that the total contributions of the metal concentrations, exposure time (ET), and exposure frequency (EF) accounted for over 50% of the risk for Cr, As, and Ni, suggesting that these metals had the greatest impact on the uncertainty of health risk assessments. 相似文献
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