凸台对多载荷AUV载荷段阻力的影响

为了研究凸台对多载荷AUV载荷段的阻力影响,基于SST k-ω湍流模型,分别对原始模型和带凸台结构模型进行了流场的数值计算.通过分析凸台截面形状及尺寸对流场的影响,研究了凸台减阻机理.结果表明,尾部凸台的出现能够避免过早的发生流体分离,降低模型尾部形成的尾涡强度和尺度,从而减小模型的压差阻力,达到减阻效果.并且,圆柱形凸台的减阻效果并不是随着尾部凸台的直径和长度增加而单调增加,而是有一个较合适的直径及长度进行匹配,从而达到最佳的减阻效果;半球形凸台对模型减阻效果很好,但在一定范围内减阻效果不随直径的增加而增强;组合型凸台的减阻效果比单纯圆柱形凸台和半球形凸台都要好,减阻量可以达到50％以上.     

桂林市城北水厂取水工程施工方案优化

文章以桂林市城北水厂取水工程施工为例,介绍充分利用施工现场地形、地质、水文等自然条件,优化施工方案,降低施工成本的经验.     

高职大学生会计诚信观调查

我国证券市场的会计造假事件屡禁不止,严重损害了会计人员的职业形象。作为会计人才培养基地的高校,肩负着诚信教育的责任．文章通过对南通航院会计专业学生诚信观的调查,了解在校学生在诚信观方面存在的问题,探讨存在这些问题的原因,并提出相应的对策．     

世界车辆法规协调论坛及其管理协定

主要对联合国欧洲经济委员会(UN/ECE)内陆运输委员会(ITC)框架下世界车辆法规协调论坛及其下属的6个工作组,以及所管理的三项协定:1958年协定(车辆结构法规)、1998年协定(全球技术法规)和1997年协定(定期技术检查)等进行论述。     

公路桥头跳车问题探讨

分析了桥头跳车的原因及跳车病害防治措施并进行了一番探讨.     

提高驾培质量信誉有效途径的探讨

以广东省驾培行业现状为例进行分析,调查驾培质量信誉发展状况,指出提高驾培质量信誉的关键是兼顾地区发展不平衡,引导行业进行经营模式变革,并通过长效机制强化市场监督,建立诚信体系,并提出了如何建立符合广东地方特色的驾培质量信誉考评体系,以评促改,以评促建的构想。     

2007年车用发动机活塞市场分析及2008年预测

2007年我国车用发动机活塞市场实现了同步高速稳定的增长.由于国内活塞行业竞争的进一步加剧,加上原材料涨价和政府政策调整及国外同行业公司加入等不利因素的影响,我国活塞企业的经营环境不容乐观,整体盈利能力呈下降趋势.2008年车用发动机及活塞企业面临的情况是机遇与挑战并存,在发展上整体呈现稳中上升的态势,但增长幅度将明显放缓,增幅为18%左右,我国活塞企业的经营环境在短期内无明显改善.     

A discrete–continuous model of households’ vehicle choice and usage, with an application to the effects of residential density

This paper develops a new method to solve multivariate discrete–continuous problems and applies the model to measure the influence of residential density on households’ vehicle fuel efficiency and usage choices. Traditional discrete–continuous modelling of vehicle holding choice and vehicle usage becomes unwieldy with large numbers of vehicles and vehicle categories. I propose a more flexible method of modelling vehicle holdings in terms of number of vehicles in each category, using a Bayesian multivariate ordinal response system. I also combine the multivariate ordered equations with Tobit equations to jointly estimate vehicle type/usage demand in a reduced form, offering a simpler alternative to the traditional discrete/continuous analysis. Using the 2001 National Household Travel Survey data, I find that increasing residential density reduces households’ truck holdings and utilization in a statistically significant but economically insignificant way. The results are broadly consistent with those from a model derived from random utility maximization. The method developed above can be applied to other discrete–continuous problems.     

A case for measuring individuals’ access to private-vehicle travel as a matter of degrees: lessons from focus groups with Mexican immigrants in California

In auto-oriented communities, access to an automobile is essential for good mobility, but not everyone owns a car or is able to drive. Little is known about how individuals in these circumstances might still use vehicles for transportation. To provide insight on the nature of vehicle use by those with potentially limited vehicle access, we present qualitative findings from focus groups with recent Mexican immigrants living in California, half of whom owned no cars. Our results demonstrate varying degrees of participants’ access to vehicle travel not always corresponding to auto ownership, with extensive sharing of cars, borrowing of cars, and getting rides. We describe the different dimensions of vehicle access that participants experienced and identify specific factors that seemed to influence their access levels. We discuss the implications of our findings for transportation policy and future research.