新型局域共振橡胶减振垫振动传递特性测试分析

为了研究一种应用于浮置板轨道结构的新型橡胶减振垫的振动传递特性,对比某基于局域共振新型减振垫与普通橡胶减振垫的减振性能,研究预压质量与激振加速度对振动传递特性的影响,对新型橡胶减振垫进行刚度试验与振动传递特性试验,测试其在30~200 Hz频率下的传递特性,试验过程中采用不同的预压质量与激振加速度,振动传递特性测试采用加速度激振的方法,以加速度传递率作为减振垫振动传递特性的评价指标。结果表明:新型减振垫加速度传递率更小,减振效果更好,最大可以减小10 dB左右;减振垫上方预压质量对振动传递特性有较大影响,预压质量越大,加速度传递率越大,减振效果越差;减振垫的刚度对其振动传递特性有一定的影响,激振的加速度幅值对加速度传递率影响较小。     

Non-exhaust particle emissions under various driving conditions: Implications for sustainable mobility

Non-exhaust particle (NEP) emissions from road traffic contribute significantly to Particulate Matter (PM) pollution in urban areas. The primary objective herein is to develop the knowledge required to move toward more sustainable mobility. NEP emissions are studied by means of complementary experiments on chassis dynamometers, on test tracks and at the roadside. Laboratory tests demonstrate that brake wear particles (BWP) emissions can change with braking force and frequency. A brake pad temperature threshold exists, above which the rate of ultrafine particle emissions is quite high. Below this threshold, the BWP emissions are dominant in the accumulation and coarse modes. Test track measurements have demonstrated that tire-road contact particle (TRCP) emissions considerably modify the atmospheric PM background especially for the supermicron fraction. Their number size distribution highlighted an ultrafine and accumulation modes centered at about 40 nm and 200 nm, respectively. The TRCP level increases with vehicle speed and during the acceleration and deceleration phases. Roadside measurements in the urban environment confirm the presence of NEP in significant proportions, in both the accumulation and coarse modes. The chemical composition of NEP differs depending on the size mode: BWP mainly stem from the degradation of brake pad lining materials, while TRCP are a mixture of tire tread wear and re-suspended dust. The presence of Fe-rich particles nevertheless serves as a good indicator of the NEP contribution to PM at the roadside. Lastly, in considering the parameters influencing NEP emissions, a series of recommendations are offered in order to achieve a more sustainable mobility.     

浅谈水泥混凝土面板施工中的质量问题

混凝土路面完工后，经常发生一些断板、起皮、起砂、露骨等，导致质量缺陷和影响行车舒适安全。就其产生的原因进行了分析，并结合实际提出防治措施共同探讨。     

Forecasting demand for high speed rail

It is sometimes argued that standard state-of-practice logit-based models cannot forecast the demand for substantially reduced travel times, for instance due to High Speed Rail (HSR). The present paper investigates this issue by reviewing the literature on travel time elasticities for long distance rail travel and comparing these with elasticities observed when new HSR lines have opened. This paper also validates the Swedish long distance model, Sampers, and its forecast demand for a proposed new HSR, using aggregate data revealing how the air–rail modal split varies with the difference in generalized travel time between rail and air. The Sampers long distance model is also compared to a newly developed model applying Box–Cox transformations. The paper contributes to the empirical literature on long distance travel, long distance elasticities and HSR passenger demand forecasts. Results indicate that the Sampers model is indeed able to predict the demand for HSR reasonably well. The new non-linear model has even better model fit and also slightly higher elasticities.     

预应力管道压浆质量控制分析

预应力管道压浆直接关系预应力构件的稳定性和耐久性,影响着工程交付后的安全。因此,必须高度重视预应力管道压浆的质量控制问题,切实控制好后灰浆的水灰比和配合比,严格遵循操作规范,创新施工方法,提高施工质量。     

Individual freight effects,capacity utilization,and Amtrak service quality

This paper offers a new perspective on the post-deregulation rail industry. We hypothesize that a link exists between individual freight effects and Amtrak service quality. Specifically, we investigate the relationship between freight control of the infrastructure on which Amtrak trains operate and Amtrak train delays. Our sample consists of 1117 directional station-pairs for fiscal years 2002 through 2007 on 28 Amtrak non-Northeast Corridor passenger routes. We found that freight effects have a significant impact on Amtrak train delays after controlling for other important delay determinants such as the capacity utilization rate. The impact is higher on long-distance routes. We also observed significant differences between the effects of different freight railroads. For example, Amtrak operations on infrastructure controlled by several Class I railroads experienced significantly larger delays than baseline operations, while Amtrak train delays on Burlington Northern and Santa Fe’s tracks actually fell below baseline levels.     

新疆农村公路沥青路面的压实质量控制技术探析

结合新疆地区农村公路特点,重点阐述了在施工条件有限的情况下,必须建立系统的管理措施和工艺规范,注重设备与人员的搭配和投入,同时总结实际施工经验,方能做好路面基层的质量控制.     

论灌注桩施工技术在桥梁工程中的应用

灌注桩基础施工对确保桥梁工程安全具有非常重要的意义。对灌注桩施工技术在桥梁工程中的应用及其常见问题和解决措施进行了论述,可为我国桥梁施工提供参考。     

提升高职院校维修电工实训教学质量措施研究

文章在指出了高职院校维修电工实训教学中存在问题的基础上,提出了提高维修电工实训教学质量的具体措施。这些措施有助于提高实训教学质量,从而培养出更多具有专业技能和创新能力的高素质人才。     

论基础工程专业核心能力的培养

针对我国基础工程专业人才需求情况与基础工程专业学生培养现状,在调查分析了社会对基础工程专业学生职业能力与素质要求的基础上,提出了高职院校如何培养基础工程专业学生的建设性建议。