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   54篇
  免费   0篇
公路运输   9篇
综合类   3篇
水路运输   23篇
综合运输   19篇
  2020年   1篇
  2019年   2篇
  2018年   1篇
  2017年   2篇
  2016年   2篇
  2015年   2篇
  2013年   11篇
  2012年   1篇
  2011年   2篇
  2010年   5篇
  2009年   2篇
  2008年   2篇
  2007年   1篇
  2006年   2篇
  2003年   1篇
  2002年   1篇
  2001年   2篇
  1997年   1篇
  1995年   2篇
  1994年   1篇
  1993年   2篇
  1991年   1篇
  1989年   1篇
  1986年   1篇
  1985年   2篇
  1982年   1篇
  1981年   1篇
  1980年   1篇
排序方式: 共有54条查询结果,搜索用时 15 毫秒
1.
The paper puts the case that historical analysis helps to understand current discussions on user-pays principles and practice. In particular, (a) it is demonstrated that the nature of funding systems is dominated by political considerations, and (b) user-pays systems lead to inadequate funding of infrastructure when politically controlled, but provide funds for expansion when “market-driven” (in pursuit of profit maximisation). The case is illustrated by reference to the experience of interregional transport infrastructure in 19th century in England and 20th century Australia. Revenue deficiencies arising from government-controlled rates can lead to the demise of private transport infrastructure. The problem is considered in the context of the history of interregional roads and railways in England between the 15th and 19th century in England and in Australia in the 19th and 20th century. The current embrace by government of the user-pays system in transport services arises from fiscal deficiencies, as much from economic philosophy. User-pays policies are part of the global re-emergence of economic rationalism since the 1970s. The lesson for other nations from Australia's experience is twofold. First, in a federal system of government, despite the efficiency benefits of user-pays in interregional land transport, fiscal and political objectives will prevail. Second, in sparsely populated and/or developing countries, deregulation of long distance road transport will make funding a national highway system a critical concern.  相似文献   
2.
Green turtles (Chelonia mydas) are among the most high profile species in San Diego Bay, California, and understanding impacts of coastal development and industry is essential to the management and conservation of this local population. Here we describe power plant changing energy production and its impact on turtle habitat use and our ability to research and manage this population. For over 20 years, green sea turtles have been captured, assessed, and tagged near the South Bay Power Plant (SBPP) in the San Diego Bay; from 2002–2011, 104 turtles were captured on 212 occasions. As the 50-year-old SBPP generates less energy, effluent patterns change and water temperatures decrease, presumably to more natural conditions. There has been a concurrent decrease in turtle-capture success, perhaps due to lesser visitation to the effluent site where nets are tended. Seasonal catch-per-unit-effort declined from a high of 4.14 turtles per monitoring day, to a nine-year low of 1.33 during the 2010–2011 season. It is already apparent that management decisions related to energy policy are affecting the habitat and behavior of this stock of endangered turtles. Green turtles are expected to remain in the San Diego Bay after the SBPP becomes inoperative and continuing research will monitor future impacts and distribution shifts resulting from the expected changes in thermal pattern within south San Diego Bay. Research efforts to study this population (i.e., capture methods and locations) will require modification in response to these changes. Lessons learned here are applicable to the immediate coastal development of San Diego, as well as at similar interactions between marine turtles and industrial thermal effluent discharge throughout Southern California, the United States, and beyond.  相似文献   
3.
Dual extended Kalman filter for vehicle state and parameter estimation   总被引:2,自引:0,他引:2  
The article demonstrates the implementation of a model-based vehicle estimator, which can be used for combined estimation of vehicle states and parameters. The estimator is realised using the dual extended Kalman filter (DEKF) technique, which makes use of two Kalman filters running in parallel, thus 'splitting' the state and parameter estimation problems. Note that the two problems cannot be entirely separated due to their inherent interdependencies. This technique provides several advantages, such as the possibility to switch off the parameter estimator, once a sufficiently good set of estimates has been obtained. The estimator is based on a four-wheel vehicle model with four degrees of freedom, which accommodates the dominant modes only, and is designed to make use of several interchangeable tyre models. The paper demonstrates the appropriateness of the DEKF. Results to date indicate that this is an effective approach, which is considered to be of potential benefit to the automotive industry.  相似文献   
4.
Between 1990 and 2000, U.S. transit agencies added service and increased ridership, but the ridership increase failed to keep pace with the service increase. The result was a decline in service effectiveness (or productivity). This marks the continuation of a long-running and often-studied trend. The scholarly literature attributes this phenomenon, at least in part, to transit agency decisions to decentralize their service rather than focus on serving the traditional CBD market. Many scholars argue that a decentralized service orientation is both ineffective and inefficient because it attracts few riders and requires large per-rider subsidies. This research tests whether a non-traditional, decentralized service orientation, called multidestination service, results in reduced service productivity. Contrary to what the literature suggests, we find that MSAs whose transit agencies pursued a multidestination service orientation did not experience lower productivity. These results indicate that policies that have encouraged the growth of decentralized transit services have not necessarily been detrimental to the industry.
Gregory L. ThompsonEmail:
  相似文献   
5.
6.
7.
Crash Prediction Models (CPMs) have been used elsewhere as a useful tool by road Engineers and Planners. There is however no study on the prediction of road traffic crashes on rural highways in Ghana. The main objective of the study was to develop a prediction model for road traffic crashes occurring on the rural sections of the highways in the Ashanti Region of Ghana. The model was developed for all injury crashes occurring on selected rural highways in the Region over the three (3) year period 2005–2007. Data was collected from 76 rural highway sections and each section varied between 0.8 km and 6.7 km. Data collected for each section comprised injury crash data, traffic flow and speed data, and roadway characteristics and road geometry data. The Generalised Linear Model (GLM) with Negative Binomial (NB) error structure was used to estimate the model parameters. Two types of models, the ‘core’ model which included key exposure variables only and the ‘full’ model which included a wider range of variables were developed. The results show that traffic flow, highway segment length, junction density, terrain type and presence of a village settlement within road segments were found to be statistically significant explanatory variables (p < 0.05) for crash involvement. Adding one junction to a 1 km section of road segment was found to increase injury crashes by 32.0% and sections which had a village settlement within them were found to increase injury crashes by 60.3% compared with segments with no settlements. The model explained 61.2% of the systematic variation in the data. Road and Traffic Engineers and Planners can apply the crash prediction model as a tool in safety improvement works and in the design of safer roads. It is recommended that to improve safety, highways should be designed to by-pass village settlements and that the number of junctions on a highway should be limited to carefully designed ones.  相似文献   
8.
为了阐述20世纪除汽车机动性外,交通发展经历的最重要的进程——城市高速公路的出现,考察了过去100年来美国城市交通规划的历史。通过回顾各种研究资料,认为资助州际公路发展所采用的方法使联邦和州公路工程师成为主管,这影响了公路的选线及设计。联邦公路工程师只关注机动车通过效率的最大化,而在很大程度上忽略了城市的其他利害关系。没有先进的规划理念指导、过度建设、稀疏、放射环状的道路网对于加强机动性取得了极大的效益,但通常要为此付出巨大的社会和环境成本。最后指出,在实践中要重新审视具有百年历史的协调交通与土地利用规划的观点,而且,公共财政权宜之计式的政治决策方式将对工程、出行和城市形态产生深远的影响。·  相似文献   
9.
10.
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