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稠油热采注汽管道采用的保温材料种类很多,但保温效果均不理想,热损失大,平均热效率只有93.77%。因此,保温材料的选择是提高保温热效率的关键问题之一,本文介绍了新型防水珍珠岩制品在稠油热采注汽管道上的应用,它并指出其管道保温热效率可达95.42%,对稠油热采注汽系统的节能具有一定的推广价值。 相似文献
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文中采用Fluent模拟与理论计算结合比较的方法,研究了不同因素对蒸汽管道散热损失的影响规律,并分析了理论计算模型的相对误差.发现增加注汽管线距地面高度,对其散热损失影响较弱;空气温度升高,注汽管道表面散热损失降低;风速和表面发射率对注汽管线表面热损失影响较大;数值模拟结果与理论计算数据相对误差较大. 相似文献
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汽车排放污染物是发动机混合气燃烧反应的产物,影响汽车排放的因素也比较复杂,本文选用定转速和定负荷两种情形分别计算并分析过量空气系数对汽车排放污染物的影响,并应用灰色理论计算出汽车排放污染物各成分浓度与过量空气系数间的关联度。通过对计算结果作的相应的分析,为综合分析汽车排放污染物各成分间的关系提出了新的方法。 相似文献
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由于油田注汽锅炉的先天缺陷及操作技术等客观因素的影响 ,使炉管内不可避免地产生水垢和腐蚀。导致锅炉系统压力增高 ,压差增大 ,降低了锅炉热效率。严重时还会造成爆管事故。结合除垢施工过程所发现的问题 ,就锅炉结垢的原因及处理方法做进一步的探讨 相似文献
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本研究对空气通过螺旋型进气道在发动机进气门附近所产生空气旋流与进气门流量系数的关系进行了探讨。空气是通过安装于进气道蜂窝状旋流器旋转的,流量系数是由变换旋流器速度和气门升程决定,同时导出了旋回气流通过进气门流量系数的计算公式。研究证明,在气门升程较高时旋回流的强度对流量系数影响较大,而气门升程低时旋回流的影响受到了控制。 相似文献
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Physical inactivity of children and adolescents is a major public health challenge of the modern era but, when adequately promoted and nurtured, active travel offers immediate health benefits and forms future sustainable and healthy travel habits. This study explores jointly the choice and the extent of active travel of young adolescents while considering walking and cycling as distinct travel forms, controlling for objective urban form measures, and taking both a “street-buffer” looking at the immediate home surroundings and a “transport-zone” looking at wider neighborhoods. A Heckman selection model represents the distance covered while cycling (walking) given the mode choice being bicycle (walk) for a representative sample of 10–15 year-olds from the Capital Region of Denmark extracted from the Danish national travel survey. Results illustrate the necessity of different urban environments for walking and cycling, as the former relates to “street-buffer” urban form measures and the latter also to “transport-zone ” ones. Results also show that lessening the amount and the density of car traffic, diminishing the movement of heavy vehicles in local streets, reducing the conflict points with the density of intersections, and intervening on crash frequency and severity, would increase the probability and the amount of active travel by young adolescents. Last, results indicate that zones in rural areas and at a higher percentage of immigrants are likely to have lower probability and amount of active travel by young adolescents. 相似文献
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Peter O'Neill 《Transportation》1990,17(3):313-328
Advances in information technology and telecommunications are opening up the possibility of transforming the capture, application and dissemination of information on transport operations and road traffic, at the same time as growing congestion makes accurate and timely information more valuable than ever to users and managers. Because of open access to road networks, public authorities are bound to intervene in the field of travel information: in the provision of infrastructure, the handling of the information, the licensing of services, and the regulation of users affecting safety or social well-being. The paper discusses these rôles and the levels at which they may be exercised, with particular reference to standardisation issues in Europe and internationally. 相似文献
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在我国交通运输行业节能减排的背景下,本文以交通运输行业能耗特点与统计监测方法为基础,建立涵盖了公路客运、公路货运、城市公交、城市出租、水路运输、港口生产等行业的能耗碳排统计监测系统,分析了省级交通运输能耗与排放特点,明确了能耗数据统计对象与内容,并对能耗数据采集的方法进行了研究,建立了省级交通运输能耗统计监测系统,并以辽宁省交通运输为依托,对全省交通运输行业能耗统计监测系统进行了验证与应用,同时也为交通运输行业的节能减排提供了决策支撑和数据支持。 相似文献
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According to the intra-vehicle interaction, a traffic flow can generally be divided into three homogeneous states (1) that of free driving, (2) that of bunched driving, and (3) that of standing. The parameter describing the state of free driving is the desired speed, for the state of bunching it is the intra-vehicle gaps (time headway) within the convoy and the mean speed of the convoy, and for the state of standing it is the maximum jam density. These are the most essential parameters which do not depend on the actual traffic situation.This paper introduces a new model which considers the Fundamental Diagram (equilibrium speed–flow–density relationship) as a function of the homogeneous states. All traffic situations in reality can be considered as combinations of the homogeneous states and therefore can be described by the essential parameters mentioned above. The non-congested (fluid) traffic is a combination (superposition) of the states of free driving and bunched driving, the congested (jam, stop, and go) traffic is a combination of the states of bunched driving (go) and standing (stop). The contribution of the traffic states within the differently congested traffic situations can then be easily obtained from the queuing and probability theory. As a result, Fundamental Diagram in all equilibrium traffic situations is derived as simple functions of the essential parameters.According to the new model the capacity of freeways and rural highways can be determined by measuring the essential parameters. This is much easier than measuring the capacity directly.Furthermore, the probabilities of the various traffic states can be obtained from the new model. This leads to new possibilities in real-time controlling and telematics.The new model is verified by comprehensive measurements carried out on freeways and rural highways in Germany. 相似文献
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