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991.
为了研究水泥用量对泡沫沥青混合料强度与疲劳特性的影响,对不同水泥用量(0%、1%、1.5%、2%、2.5%、3%)的泡沫沥青混合料进行干、湿劈裂强度试验。通过控制应力加载方式,变化应力比进行疲劳试验。试验结果表明:增加水泥用量对干、湿劈裂强度有明显的提高作用。添加多于2%的水泥会降低材料抗疲劳性能,建议水泥用量不超过2%。考虑到泡沫沥青混合料强度要求,需要加入水泥用量至少为1.5%。 相似文献
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994.
This paper seeks to use life cycle assessment to investigate the comparative environmental impacts of two proposed bridge designs for the new Mjøsa Bridge over Lake Mjøsa in Norway. The Norwegian Public Roads Administration has designed one timber and one concrete alternative for the 1650 m 4-lane highway bridge. If the timber bridge design is chosen, it will be the longest timber bridge in the world once constructed.The main motivation for building the timber bridge is to utilize local industry and to reduce environmental impacts in road infrastructure. This study aims to determine the expected emissions from both construction designs by using life cycle assessment. Life cycle assessment studies on smaller timber bridges have been carried out in the past with favorable results towards timber designs, but no bridge of this scale has been built and therefore a more comprehensive study is required to confirm if a timber bridge of this size is a sustainable choice for transport infrastructure.The results of the study show that the timber bridge has significantly lower emissions than the concrete bridge across all impact categories included in the scope of this study. Additional environmental gains can be made from end-of-life treatment of materials. This study shows that large scale timber bridge designs should be considered for future road projects. 相似文献
995.
Introduction of electric vehicles (EVs) or plug-in electric vehicles (PEVs) in the road transportation can significantly reduce the carbon emission. Hence, the demand of EVs is likely to increase in the near future. Large penetration of EVs will also ultimately result into high loads on the existing power grids. The controlled charging of EVs can have a significant impact on the power grid load, voltage, frequency, and power losses. In this paper, we have provided a comprehensive review of various energy optimization approaches used for EVs charging. Energy optimization approaches used for EVs not only enhance the battery life but also contribute in regulating the voltage and frequency. During EVs charging, various objective functions such as supporting the renewable energy sources, minimization of the peak load, energy cost, and maximization of the aggregator profit have also been studied from optimization perspectives. The controlled and an optimized EVs charging enhances the performance of EVs batteries and conserves the energy in the system by minimizing the load and power losses. The different EVs charging approaches such as centralized and distributed suited for different objective functions have also been studied and compared with respect to various optimization approaches. 相似文献
996.
This study aims to quantify the environmental impact of two retail distribution networks and offer consumers a channel that is more beneficial to the environment. The environmental impact of replenishing the packaged beverages sold in convenience stores (CVSs) and hypermarkets is assessed using the streamlined life-cycle assessment (LCA) approach. In this study, the life-cycle impact assessment (LCIA) for packaged beverages up to the point of sale illustrates the distribution-level environmental impacts of truck transportation. The matched-pair t-test shows that the environmental impacts of transporting 1800 cartons of 24-pack/10 oz. beverages to be sold in Carrefour and 7-11 stores is different at a significance level of 0.1. The transport-focused LCA is used to improve the understanding and compare the environmental characteristics of the two distribution and retail systems. This study constitutes a vehicle for communicating to both internal and external stakeholders the environmental profiles of distributing the same product sold through two retail channels. 相似文献
997.
The popular consensus is that urban passenger rail is more environmentally friendly than urban passenger bus. This position is largely associated with the key energy source for each mode, respectively electricity and diesel, where electric vehicle use will typically result in local air quality improvements away from the electricity generation source. Surveys of community perceptions reflect this sentiment; however the relationship between the source of energy and its resultant emissions is not something that citizens fully understand. There is a general lack of awareness of the resource base of much of electricity generation in some countries. Where generation sources are suitably renewable or low-carbon, electricity use will offer greenhouse gas abatement potential. However, in countries which still rely heavily on coal-fired power stations, such as Australia, abatement is not as assured and estimating emission outcomes can require careful assessment. Supporters of alternatives to diesel use can focus on the future supply of fossil-fuels, an argument which has merit; however such arguments are often confounded with environmental qualities related to local air pollution and enhanced greenhouse gas emissions. This paper takes a close look at the greenhouse emissions that are associated with urban rail and bus in Australia. Estimated intensities, when presented in the context of effective service delivery (primarily in terms of emissions per passenger kilometre), raise questions about the distortions that are present in the widespread promotion in Australia (at least) of rail as a more environmentally friendly and hence a sustainable mode of urban passenger transport than bus. 相似文献
998.
As decision-makers increasingly embrace life-cycle assessment (LCA) and target transportation services for regional environmental goals, it becomes imperative that outcomes from changes to transportation infrastructure systems are accurately estimated. Greenhouse gas (GHG) reduction policies have created interest in better understanding how public transit systems reduce emissions. Yet the use of average emission factors (e.g., grams CO2e per distance traveled) persists as the state-of-the-art masking the variations in emissions across time, and confounding the ability to accurately estimate the environmental effects from changes to transit infrastructure and travel behavior. An LCA is developed of the Expo light rail line and a competing car trip (in Los Angeles, California) that includes vehicle, infrastructure, and energy production processes, in addition to propulsion. When results are normalized per passenger kilometer traveled (PKT), life-cycle processes increase energy use and GHG emissions up to 83%, and up to 690% for smog and respiratory impact potentials. However, the use of a time-independent PKT normalization obfuscates a decision-maker’s ability to understand whether the deployment of a transit system reduces emissions below a future year policy target (e.g., 80% of 1990 emissions by 2050). The year-by-year marginal effects of the decision to deploy the Expo line are developed including reductions in automobile travel. The time-based marginal results provide clearer explanations for how environmental effects in a region change and the critical life-cycle processes that should be targeted to achieve policy targets. It shows when environmental impacts payback and how much reduction is achieved by a policy-specified future year. 相似文献
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从内燃机使用过程中的经济性、可靠性、排污量与使用寿命之间的关系入手,简析颗粒磨损对内燃机使用寿命的影响;指出了国产内燃机空气滤清器使用中存在的问题,提出了适合中国国情的空气滤清器的使用、更换及鉴别方法。 相似文献