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IntroductionA promising way to stimulate physical activity is to promote the choice for active modes of transport (walking and cycling). Over the past years, several interventions and policies have been implemented to stimulate this mode shift. However, information concerning the effectiveness of these interventions and policies is still limited. The aim of the present study was to systematically review the effectiveness of interventions designed to stimulate a shift from car use to cycling or walking and to obtain insight into the intervention tools that have been used to promote and/or implement these interventions.MethodsFive databases were searched and articles published in English, Dutch, German, Danish, Norwegian and Swedish were included. Only studies that focussed on a mode shift from car use towards active transport in a general adult population, which were published in peer reviewed journals and which investigated effectiveness were included. Intervention tools used were categorized by using the model of Hoogerwerf & Herweijer, as either legal, economic (subsidy, reward system, penalty), communicative (written materials, behavioural tools) and physical tools (providing bicycles, providing better bicycle facilities at work, adjustment of the environment).ResultsNineteen studies met our inclusion criteria. Studies included described work-place-based interventions, architectural and urbanistic adjustments, population-wide interventions, and bicycle-renting systems. Nearly all studies (except three) showed positive effects concerning a mode shift. Most of the included studies used more than one intervention tool and the tools used differed between types of interventions. However, information about the statistical significance of these results was often lacking and the study methodologies used were not of high quality.ConclusionNearly all studies showed results in a positive direction. However, the quality of the included studies was mostly low and intervention characteristics were poorly described. 相似文献
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铁路桥梁检定部门主要依据《铁路桥梁检定规范》对铁路桥墩进行状态评估。由于桥墩在列车激励下的振幅随列车的种类、速度、轴重以及轨道不平顺状态的不同而变化,所以利用振幅指标难以定量判断桥墩的损伤。为此,通过理论分析、数值模拟计算、实验室试验和现场试验,对冲击振动试验法进行系统的研究,提出基于自振频率指标的桥墩健全度评估方法。主要研究内容如下。(1)从理论上给出推导冲击振动试验法的基本原理,编制冲击振动试验信号处理的计算机程序。(2)通过实验室试验和悬臂墩、简支梁、单墩桥梁体系、多墩多梁桥梁体系及空间桁梁模型等数… 相似文献
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根据模态曲率的概念,构造结构损伤指标。采用有限元方法,对1座设定主梁不同位置发生损伤的大跨度预应力混凝土斜拉桥进行动力特性分析,利用构造的结构损伤指标对结构损伤进行识别研究。结果表明:结构损伤指标对结构损伤的识别精度与参与计算的模态振型及节点间距有关。应选择在损伤位置振幅较大的模态振型,而避免平衡位置处于损伤位置或附近的模态振型。该方法对结构的早期损伤可进行定性判断,结构损伤指标随结构的早期损伤程度的增大而增大,且增长幅度逐渐变小,当结构损伤达到一定程度后,损伤指标不再增大,而在渐近线附近波动。节点间距在一定范围内增大时,不影响损伤位置的识别,甚至可以确定损伤程度,但可能会反映不出损伤对其临近区域的影响;节点间距过大,可能发生漏判。 相似文献
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以成功应用于京沪线提速工程中的自动闭塞系统为例,介绍了ZPW-2000A的试验流程和模拟试验方法,并针对ZPW-2000A特有的小轨道探讨了模拟方案. 相似文献
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Prediction of fatigue life and estimation of its reliability on the parts of an air suspension system 总被引:1,自引:0,他引:1
K. J. Jun T. W. Park S. H. Lee S. P. Jung J. W. Yoon 《International Journal of Automotive Technology》2008,9(6):741-747
Air suspension systems have been implemented in various commercial vehicles, such as buses and special purpose trucks, because
of the comfortable ride and easy height control. An evaluation of the durability of vehicle parts has been required for service
life and safety starting in the early stages of design. The cyclic load applied to the vehicle can cause fatigue failure of
parts, such as the suspension frame. This paper presents a method to predict the fatigue life of the suspension frame at the
design stage of the air suspension system used in a heavy-duty vehicle. To estimate the fatigue life using the SN method,
the Dynamic Stress Time History (DSTH) is necessary for the part of interest. DSTH can be obtained from the results of the
flexible body dynamic analysis using the Belgian road simulation and the Modal Stress Recovery (MSR) method. Furthermore,
the reliability of the predicted fatigue life can be evaluated by considering the variations in material properties. The probability
and distribution of the expected life cycle can be obtained using experimental design with a minimum number of simulations.
The advantage of using statistical methods to evaluate the life cycle is the ability to predict replacement time and the probability
of failure of mass-produced parts. This paper proposes a rapid and simple method that can be effectively applied to the design
of vehicle parts. 相似文献
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针对某车型怠速工况下转向盘抖动问题,对整车进行了怠速振动试验并对转向盘进行了模态试验,确认转向盘系统与仪表板横梁及横梁与车身连接处的连接刚度不足导致整个转向系统模态下降,从而引起了共振。针对该问题建立了转向系统有限元模型,并根据模态试验结果对模型进行了验证。在该模型基础上对上述连接刚度进行了优化,对优化方案进行试验验证的结果表明该方案有效。 相似文献
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相位连续移频信号的数字化实现 总被引:1,自引:0,他引:1
分析了相位连续与不连续移频信号的频谱并比较了它们的带宽。相位连续的移频信号有较窄的带宽,抗干扰性能强。目前,在移频轨道电路中产生相位连续信号的方法主要有两种:直接调频法,频率转换法。前者相位连续但频率稳定性差;后者频率稳定性高但相位近似连续。为克服上述不足,本文提出了数字化直接调频法,其相位连续、频率可调、频稳性高。 相似文献
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