首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   37篇
  免费   0篇
公路运输   2篇
综合类   2篇
水路运输   20篇
铁路运输   2篇
综合运输   11篇
  2020年   3篇
  2016年   1篇
  2013年   14篇
  2011年   2篇
  2010年   1篇
  2009年   5篇
  2008年   2篇
  2007年   1篇
  2006年   1篇
  2002年   1篇
  1998年   2篇
  1997年   1篇
  1995年   1篇
  1993年   1篇
  1977年   1篇
排序方式: 共有37条查询结果,搜索用时 734 毫秒
1.
Although the success of marine protected areas (MPAs) and associated zoning schemes is largely dependent on stakeholder acceptance and support, there have been relatively few studies examining the response of recreational stakeholders to MPA proposals. This study investigates the response of recreational boaters to a proposed MPA in British Columbia, Canada. Using a structured questionnaire (n = 543) and a focus group (n = 6), the research examines the level of support for the concept of marine zoning and identifies key factors influencing support or opposition. Results indicate that a small majority of recreational boaters support the concept of marine zoning, but that there are areas of concern that ought to be addressed as MPA implementation proceeds. Support for zoning was strongly related to perceived benefits, particularly environmental benefits. Furthermore, perceived benefits overall were found to outweigh concerns as determinants of recreational boater support for zoning. Major dimensions of opposition included perceptions of over-regulation, loss of access for boating, and mistrust of the government. A suggestion is that such concerns may be mitigated through focused communication and meaningful involvement of boaters in the zoning process.  相似文献   
2.
The total annual traffic flow at a road site is probably the single most important item of data needed in transport studies. In this article we describe a method of estimating this flow from a traffic count of less than 24 hours duration. The method is extended to enable an assessment to be made of the merits of repeating a count. The application of the method is discussed in relation to the United Kingdom, but we believe this method to be generally applicable to most countries.

  相似文献   
3.
Fundamental to sustaining the financial support of a coastal ocean observing system is an intimate knowledge of users and their decision-making processes in order to maximize the worth of ocean observations to them. This article explores the evolving mission of GoMOOS (the Gulf of Maine Ocean Observing System), its costs of providing near real-time observations and observing products, possible methods to assess the benefits of an ocean observing system, and a method for indexing the importance—and thus, potentially, the economic value—that users attach to these observations and products.  相似文献   
4.
Philip Laird 《运输评论》2013,33(3):241-256
In 1994/95, the Australian rail freight task was approximately 100 billion tonne kilometres (btkm). This freight task included some 37 btkm for the haulage of iron ore in Western Australia, 28 btkm for coal haulage in Queensland and New South Wales and about 16 btkm for interstate rail freight. This paper mainly concerns how improvements can be made to the efficiency and competitiveness of interstate rail freight services through the upgrading of sections of mainline track that currently have severe speed‐weight restrictions. Recent improvements in rail freight efficiency are discussed, with emphasis on two indicators: average unit revenues (cents per net tonne km), and average energy efficiency (net tonne km per MJ). Rail freight efficiency is high for the Western Australia iron‐ore operations, Queensland coal operations and Adelaide‐Perth general freight operations. However, between Australia's three largest cities of Melbourne, Sydney and Brisbane, some 36% of the mainline track fails to meet basic fast freight train standards with a ruling grade of 1 in 66 and no curve radius less than 800 m. The contraints on efficient rail freight operations imposed by severe terrain, and how the effects of terrain may be reduced by improved track alignment, are discussed. Some economically warranted rail track investment measures are outlined, including those identified for a National Transport Planning Taskforce. These measures have the potential to reduce liquid fuel use by over 250 million litres a year. Factors affecting competitive neutrality between road and rail freight that are outside of the present scope of Australia's National Competition Policy are broadly considered. These factors include the extensive upgrading of the National Highway System with full Federal funding, and low levels of road cost recovery from heavy trucks operating over long distances.  相似文献   
5.
This paper starts with a discussion on typical vehicles. The concepts and the usual practice for rail wagon design, both freight and passengers are presented. A discussion on rail and the environment comes next followed by Truck-Trains. Accident theories, metaphors and investigation methods are widely discussed; Hazard – Barrier – Target Model, Swiss Cheese Model, Bow-Tie Model, Fault Tree Analysis and Event Tree Analysis are explained. This paper concludes with a technical discussion on safety and security of rail vehicles, standards for safety and measures against terrorist attacks.  相似文献   
6.
Abstract

This article presents a comprehensive review of the maritime safety regimes and provides recommendations on how to improve the system. The results show a complex legal framework which generates a high amount of inspections and overlapping of inspection areas where no cross‐recognition is established by the various stakeholders. While the safety system seems to be successful in eliminating substandard vessels and while average insurance claims costs are substantially lower for inspected vessels than non‐inspected vessels, the results indicate that the economic conditions of the shipping market also have an effect on safety quality besides the frequency of inspections. No significant differences can be found between industry inspections and port state control inspections with respect to decreasing the probability of casualty. The system could be made more effective by combining data sources on inspections and using them respectively to improve risk profiling and to decrease the frequency of inspections performed on ship types such as tankers. The results further indicate a lack of proper implementation of the International Safety Management Code (ISM code) and conventions with reference to working and living conditions of crew (ILO 147). A revision of the ISM code and more emphasis on enforcement of ILO 147 could further enhance the level of safety at sea. The authors would like to thank several inspection regimes for their cooperation in providing inspection data and in allowing the observation of surveys and inspections on 26 vessels. In addition, the authors would like to acknowledge the data providers for the casualty data, Clarksons for the economic data as well as two P&I Clubs in making data on insurance claims available.  相似文献   
7.
Various models for competition and ownership of urban rail systems have been used in South East Asia cities since the early 1990s. The paper reviews and classifies the approaches used in Bangkok, Kuala Lumpur, Manila and Singapore. The planning, financing, procurement, implementation and operation of these systems, and the institutional context for them, are examined. All of the systems that have used private sector finance for the development of the initial systems have faced financial problems. Optimism bias in demand forecasts and unrealistic expectations for cost recovery of capital intensive systems have been contributing factors. Lessons to be learned include the importance of clear government leadership and sound institutional arrangements, and the need for improved understanding of the best manner in which the private sector can be used to achieve efficient and effective rail projects.  相似文献   
8.
SCUBA diving can contribute to both coral reef degradation and conservation. Divers’ perceptions of these possible impacts were studied in Phuket, Thailand. The most endorsed impact of diving was a positive one: the educational impact on the divers. Impact perceptions changed after the dive. Perceptions of anchor damage and garbage disposal as negative impacts fell markedly. Following the trip liveaboard divers were more likely than day divers to see the impact of diving as positive. Almost 30% of divers witnessed perceived negative impacts on the reef by their dive group. Divers who saw damage were more likely to feel that diving has a negative impact on the reef than divers who did not see impacts. They were also more likely to take part in a reef conservation project. The results reinforce the potential for diving to be a positive force for reef conservation but indicate the need for greater investment in diver education.  相似文献   
9.
得益于非常安静的背景噪声(风速 140 km/h,声压级小于 58 dBA)和优秀的低频压力脉动(Cp rms < 0.005),中国汽车工程研究院(CAERI)风洞中心的气动声学风洞为汽车空气动力学开发提供良好的声学测试平台。中国汽研风洞中心安装一套由 3 块麦克风阵列(3×168 通道)组成的三维麦克风阵列测试系统,对车外气动噪声源进行定位及分析。采用“声学照相机原理”,即噪声云图通过波束成形的高级算法投射到车身三维表面(3D)上进行定位显示。  相似文献   
10.
Columbia River tidal plume dynamics can be explained in terms of two asymmetries related to plume-front depth and internal wave generation. These asymmetries may be an important factor contributing to the observed greater primary productivity and phytoplankton standing crop on the Washington shelf. The tidal plume (the most recent ebb outflow from the estuary) is initially supercritical with respect to the frontal internal Froude number FR on strong ebbs. It is separated from the rotating plume bulge by a front, whose properties are very different under upwelling vs. downwelling conditions. Under summer upwelling conditions, tidal plume fronts are sharp and narrow (< 20–50 m wide) on their upwind or northern side and mark a transition from supercritical to subcritical flow for up to 12 h after high water. Such sharp fronts are a source of turbulent mixing, despite the strong stratification. Because the tidal plume may overlie newly upwelled waters, these fronts can mix nutrients into the plume. Symmetry would suggest that there should be a sharp front south of the estuary mouth under summer downwelling conditions. Instead, the downwelling tidal plume front is usually diffuse on its upstream side. Mixing is weaker, and the water masses immediately below are low in nutrients. There is also an upwelling–downwelling asymmetry in internal wave generation. During upwelling and weak wind conditions, plume fronts often generate trains of non-linear internal waves as they transition from a supercritical to a subcritical state. Under downwelling conditions, internal wave release is less common and the waves are less energetic. Furthermore, regardless of wind conditions, solition formation almost always begins on the south side of the plume so that the front “unzips” from south to north. This distinction is important, because these internal waves contribute to vertical mixing in the plume bulge and transport low-salinity water across the tidal plume into the plume bulge.FR and plume depth are key parameters in distinguishing the upwelling and downwelling situations, and these two asymmetries can be explained in terms of potential vorticity conservation. The divergence of the tidal outflow after it leaves the estuary embeds relative vorticity in the emerging tidal plume water mass. This vorticity controls the transition of the tidal plume front to a subcritical state and consequently the timing and location of internal wave generation by plume fronts.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号