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The relationship among highway geometrics,traffic-related elements and motor-vehicle accident frequencies 总被引:1,自引:0,他引:1
This research provides a demonstration of a statistical model of accident frequency that can eventually be used as part of a proactive program to allocate safety-related highway improvement funds. Negative binomial regressions of annual accident frequency on sections of principal arterials in Washington State were estimated using data from two years (1992 and 1993). In all, 31306 observations were used in model estimation (annual accident frequencies on specific sections of highway). Our estimation results isolated the effects of various highway geometric and traffic characteristics on annual accident frequency. Subsequent elasticity computations identified the relative importance of the variables included in our specifications. The findings show that the negative binomial regression used in this paper is a powerful predictive tool and one that should be increasingly applied in future accident frequency studies. 相似文献
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多重化电力变换器具有良好的输出特性,其有效开关频率高、波形质量好、动态响应快、冗余度高,在大容量电力变换器中占有优势.文章深入分析了一种变压器耦合串联型三相二重化电压源逆变器及其谐波特性,阐述了其物理意义,揭示了多重化后逆变器输出谐波的相位关系和对消规律.物理意义明确,易于理解.分析方法具有普遍性,可以应用于任意重化逆变器的谐波分析. 相似文献
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The Influences of the Built Environment and Residential Self-Selection on Pedestrian Behavior: Evidence from Austin, TX 总被引:3,自引:0,他引:3
Pedestrian travel offers a wide range of benefits to both individuals and society. Planners and public health officials alike
have been promoting policies that improve the quality of the built environment for pedestrians: mixed land uses, interconnected
street networks, sidewalks and other facilities. Whether such policies will prove effective remains open to debate. Two issues
in particular need further attention. First, the impact of the built environment on pedestrian behavior may depend on the
purpose of the trip, whether for utilitarian or recreational purposes. Second, the connection between the built environment
and pedestrian behavior may be more a matter of residential location choice than of travel choice. This study aims to provide
new evidence on both questions. Using 1368 respondents to a 1995 survey conducted in six neighborhoods in Austin, TX, two
separate negative binomial models were estimated for the frequencies of strolling trips and pedestrian shopping trips within
neighborhoods. We found that although residential self-selection impacts both types of trips, it is the most important factor
explaining walking to a destination (i.e. for shopping). After accounting for self-selection, neighborhood characteristics
(especially perceptions of these characteristics) impact strolling frequency, while characteristics of local commercial areas
are important in facilitating shopping trips. 相似文献
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三相V,v接线和单相I,i接线牵引变压器的组合应用 总被引:1,自引:1,他引:0
对某既有电气化铁路增建四线工程中一个110kV单相牵引变电所的扩能改建方案进行了深入研究,通过对不同牵引变压器接线型式与既有单相I,i接线牵引变压器的组合效果进行静态和动态比较后提出了利用三相V,v接线和单相I,i接线牵引变压器构成组合三相平衡接线来降低电气化铁道牵引负荷对电力系统的负序影响、充分利用供电能力的技术方案。这种组合接线的应用,既能降低对电力系统短路容量的要求,又增大了对不平衡牵引负荷的负载能力。对既有电气化铁路增建新线工程以及铁路枢纽的牵引供电系统设计具有参考价值。 相似文献
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负压对供皮区创面再上皮化速度的影响 总被引:3,自引:0,他引:3
目的观察负压对猪供皮区创面再上皮化速度的影响。方法5头小猪,每头猪的背部各形成面积为5 cm×10 cm断层皮片供皮创面。实验组采用连续120 mmHg(1 mmHg=0.133 kPa)负压治疗,对照组用凡士林纱布换药。结果负压治疗组创面再上皮化速度显著提高,治疗后4-6 d创面即愈合,较对照组提前2-4 d;创面炎症反应明显减轻;毛囊上皮、再生的基底以及腺上皮细胞增殖活跃,S期及G2 M期细胞比例增多(P<0.01);细胞核增殖抗原表达显著增强。结论负压可以显著提高供皮区创面再上皮化速度。 相似文献
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引气剂的使用能够提高混凝土的抗冻性和抗渗性,缓解碱集料反应和化学侵蚀膨胀,改善路面混凝土的耐候性,增强耐久性,有利于提高混凝土的路用品质。重点研究使用引气剂混凝土在负温条件下含气量对混凝土强度的影响。 相似文献