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991.
长江下游感潮河段造床流量计算研究 总被引:1,自引:0,他引:1
针对长江下游大通至长江口的感潮河段,借助潮流数学模型,计算造床流量,研究其特点及变化规律。研究表明:计算感潮河段造床流量时,流量输沙率法使用方便,计算结果较为合理;对于天生港以上河段,存在两个造床流量,而对于徐六泾以下河段,则存在一个造床流量群;大通至仪征河段的造床流量沿程变化较少,自仪征开始造床流量沿程逐渐提高,主要应与纳潮量沿程增加有关。 相似文献
992.
Birgit Pauksztat 《Maritime Policy and Management》2017,44(7):899-915
Previous research on job demands in seafaring has focused on the effects of workload and circadian disturbance on seafarers’ health and fatigue. Taking a more comprehensive approach, this study identifies job demands of short sea cargo shipping lines and explores their effects on work and life on board. Data came from 54 interviews with officers and crew on five cargo ships. Findings revealed job demands related to characteristics of the schedule, ports, and sea voyages; these were not only associated with workload and circadian disturbance, but also with the difficulty of the work, the ability to plan ahead, and intrusions from third parties. Job demands affected outcomes through two interconnected processes. First, job demands had direct and indirect effects on fatigue and the working climate on board. Second, potential positive effects of job demands (i.e. interesting work and pay) were related to motivation and, together with a good working climate, could reduce turnover. Connecting the two processes, a good working climate was pivotal in counteracting negative emotions and supporting motivation and collaboration. In this way, it functioned as a key resource. External constraints could either buffer or reinforce these effects. 相似文献
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对桥面铺装超薄沥青混凝土混合料的路用性能,进行了室内试验研究。试验结果表明,超薄沥青混凝土各项性能指标均满足技术规范的要求,完全可以用于高速公路的桥面铺装。 相似文献
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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
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Reliable and accurate short-term subway passenger flow prediction is important for passengers, transit operators, and public agencies. Traditional studies focus on regular demand forecasting and have inherent disadvantages in predicting passenger flows under special events scenarios. These special events may have a disruptive impact on public transportation systems, and should thus be given more attention for proactive management and timely information dissemination. This study proposes a novel multiscale radial basis function (MSRBF) network for forecasting the irregular fluctuation of subway passenger flows. This model is simplified using a matching pursuit orthogonal least squares algorithm through the selection of significant model terms to produce a parsimonious MSRBF model. Combined with transit smart card data, this approach not only exhibits superior predictive performance over prevailing computational intelligence methods for non-regular demand forecasting at least 30 min prior, but also leverages network knowledge to enhance prediction capability and pinpoint vulnerable subway stations for crowd control measures. Three empirical studies with special events in Beijing demonstrate that the proposed algorithm can effectively predict the emergence of passenger flow bursts. 相似文献
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为更好地理解螺旋列板对涡激振动(VIV)的影响,采用大涡模拟(LES)的方法,对长径比为10的立管和不同螺距、螺高的螺旋列板进行模拟分析。结果表明:附加螺旋列板加大了顺流向的阻力,并且在螺高一定时,阻力随着螺距的加大而增大;与螺距相比,螺旋列板的高度对立管VIV的影响更大,且随高度增大,抑制效果越好。 相似文献
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