软土地区地铁环境振动对精密仪器的影响研究

为评估软土地区地铁环境振动对精密仪器的影响,基于环境振动分析预测有限元仿真模型,模拟实际工况下距线路不同距离上的不同楼层内地板的振动响应.模拟计算分析表明,距隧道中心线20 m、50 m、100 m 3种工况中,距隧道中心线20 m、50 m的建筑物内振动超过精密仪器对环境振动的要求限值,距隧道中心线100 m的建筑物...     

机械类大学生创新实践及其效果分析

结合全国大学生机械创新设计大赛这一创新实践活动,阐述了通过加强创新实践,可以在一定程度上提高学生的就业竞争力和教师的实践能力,还可以增加学校的教学科研成果数量.实践表明,加强创新实践离不开学校的政策支持.     

水泥混凝土路面质量风险探讨

从风险管理角度出发,系统地分析水泥混凝土路面质量风险的各种风险源。运用层次分析法(AHP)和模糊数学相结合的定量分析方法,建立水泥混凝土路面质量风险模糊层次分析法评价模型,利用该模型进行实证分析。     

汽车前照灯水汽凝聚现象的瞬态CFD预测

汽车前照灯光品质是衡量汽车照明系统安全性的一项重要指标.通过商用计算流体力学(Computational Fluid Dynamics,CFD)软件Star-CCM+对汽车前照灯内部的流动情况、热力学特性以及起雾/除雾过程进行了模拟.研究表明,雾层厚度与分布主要与湿度、流动条件以及换热条件相关.探索了完整的大灯起雾仿真...     

强夯施工对环境振动的影响分析

利用强夯法加固软弱地基时,其夯击能将以波的形式向外扩散,进而导致周围环境的振动.本文以半无限弹性体理论为基础,考察了瑞利波的径向振动量和竖向振动量沿地基深度的衰减特性,认为竖向振动量是引发环境安全的主要因素;通过现场实测,研究了强夯引起的自由场地地面振动加速度及振动速度随距离的衰减规律,并对隔振沟的隔振效果进行了测试研究.     

形成性评价在大学英语实践中反映的问题

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.     

A trial application of FSA methodology to the hatchway watertight integrity of bulk carriers

Formal safety assessment (FSA) is a formal, structured and systematic methodology, aimed at enhancing maritime safety, including protection of life, property and marine environment, by using risk and cost–benefit assessments. For the application of this methodology to the rule-making process, the International Maritime Organization (IMO) presented the Interim Guidelines, which describe procedures of FSA and inputs/outputs of each procedure in detail. This paper basically deals with an application of FSA methodology according to the IMO's Interim Guidelines to the hatchway watertight integrity of bulk carriers, which was carried out as a cooperative research between Korean Register of Shipping and Seoul National University. As results of this application study, 18 hazards are identified and 32 risk control measures are devised to reduce the associated risks. Potential risks, costs and benefits when some Risk Control Options are introduced are evaluated in monetary unit of US $. Finally, some discussions and recommendations based on experiences are also given for both future work and better application of this FSA methodology to the rule-making process.     

高速公路改扩建工程中的环境保护

通过对高速公路改扩建工程环境保护的研究,文章首先分析改扩建工程中环境保护的必要性,并对高速公路改扩建工程中环境保护的具体内容进行分析,重点探讨高速公路改扩建工程中环境保护的具体应用,对某高速公路改扩建案例的深入分析,提出四大环境保护措施。     

Cost-effectiveness of reductions in greenhouse gas emissions from High-Speed Rail and urban transportation projects in California

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.     

内补口车在钢管内防腐层补口施工中的应用

大口径管道防腐层一般采用人工补口方法施工,存在施工效率低、质量缺陷多及受限空间施工安全风险大等问题.文中主要介绍了在钢管内防腐补口施工中采用内补口车替代人工补口的施工技术.设备调试、定位、通过性及质量控制是施工中的技术难点,施工中通过参数调整、视频定位、使用专有的机械设计、合理施加外力及采用过程中监控等技术方案顺利解决...