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波浪作用下粉沙质底沙运动特性的试验研究 总被引:6,自引:6,他引:6
本文利用山东潍坊现场沙(d_(50)≈0.0813mm),通过水槽试验研究了波浪作用下粉沙质底沙的运动特性、床面形态、起动特点及输沙规律等,为分析研究粉沙质海岸的泥沙问题提供了基本数据和研究方法. 相似文献
484.
宝兰客专引入兰州枢纽,在规划中采用兰州西客站接轨方案.从城市格局、当地居民的乘车习惯、城市交通现状等方面,提出宝兰客专引入兰州站方案;并对宝兰客专引入兰州站和兰州西站的方案进行了论证分析. 相似文献
485.
针对当前铁路客运专线牵引供电系统存在的主要问题,从设计、施工、运营管理等环节,探讨有效预防和减少高压电缆故障、雷击故障、电气绝缘故障及增强供电系统灵活性等方面的措施和建议,以提高铁路客运专线牵引供电系统的可靠性。 相似文献
486.
王勇 《内蒙古公路与运输》2013,(4):68-70
公路运输统计是整个社会经济统计的重要组成部分,也是道路运输管理的基础工作。公路运输统计为部门宏观调控、制定政策提供决策和依据。文章从统计指标、统计工作适应性、统计制度、协调运作、手段和技术及人员等方面论述了我国目前公路运输统计工作中存在的问题,并提出建议。 相似文献
487.
First and second generation biofuels are among few low-carbon alternatives for road transport that currently are commercially available or in an early commercialization phase. They are thus potential options for meeting climate targets in the medium term. For the case of Sweden, we investigate cost-efficient use of biofuels in road transport under system-wide CO2 reduction targets to 2050, and the effects of implementation of targets for an almost fossil-free road transport sector to 2030. We apply the bottom-up, optimization MARKAL_Sweden model, which covers the entire Swedish energy system including the transport sector. For CO2 reductions of 80% to 2050 in the Swedish energy system as a whole, the results of the main scenario show an annual growth rate for road transport biofuels of about 6% from 2010 to 2050, with biofuels accounting for 78% of road transport final energy use in 2050. The preferred biofuel choices are methanol and biomethane. When introducing additional fossil fuel phase-out policies in road transport (−80% to 2030), a doubling of the growth rate to 2030 is required and system CO2 abatement costs increases by 6% for the main scenario. Results imply that second generation biofuels, along with energy-efficient vehicle technologies such as plug-in hybrids, can be an important part of optimized system solutions meeting stringent medium-term climate targets. 相似文献
488.
Hub‐and‐spoke networking is a key feature of current aviation markets in which hubs, as connecting points, function to consolidate and redistribute flows. This indicates that observation of traffic on a segment does not necessarily convey information about the origin to destination routing of passenger journeys because of the unavoidable detours in the system. This paper examines the heterogeneity of the flow composition in domestic and international US markets, which in turn allows us to observe the variation of operations across major hubs. A modified Route Flow Estimator for origin–destination synthesis (or origin–destination matrix estimation) is designed to decompose the segment traffic into itinerary‐based passenger trips. Several public and commercial databases, which are easily accessible, are exploited (and reconciled) for the model in order to (i) generate possible trip itineraries using those segment markets, and (ii) link data‐driven operational conditions with the underlying segment flows. The results are validated with US domestic trip observations and empirical knowledge related to the air transportation system. Then, the variability of the hub operations is examined based on sensitivity tests using the model parameters. From the resolution of itinerary‐based estimates, we observe that major airports' hub operations are spatially uneven, particularly with respect to domestic and international connecting passengers. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
489.
This paper investigates the valuation of crowding in public transport trips and its implications in demand estimation and cost-benefit analysis. We use a choice-based stated preference survey where crowding levels are represented by means of specially designed pictures, and use these data to estimate flexible discrete choice models. We assume that the disutility associated with travelling under crowded conditions is proportional to travel time. Our results are consistent with and extend previous findings in the literature: passenger density has a significant effect on the utility of travelling by public transport; in fact, the marginal disutility of travel time in a crowded vehicle (6 standing-passengers/m2) is 2.5 times higher than in a vehicle with available seats. We also compare the effects of different policies for improving bus operations, and the effect of adding crowding valuation in cost-benefit analysis. In doing that, we endogenise the crowding level as the result of the equilibrium between demand and supplied bus capacity. Our results indicate that important benefits may be accrued from policies designed to reduce crowding, and that ignoring crowding effects significantly overestimate the bus travel demand the benefits associated with pure travel time reductions. 相似文献
490.
针对楚雄市城市交通的发展,通过实地调查、问卷调查、跟车调查等方法,在分析楚雄市公交现状概况、居民出行方式结构基本特征、公交线路网基本特征、公交客流基本特征的基础上,分析楚雄市公共交通发展存在的问题,并提出相应的对策. 相似文献