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排序方式: 共有214条查询结果,搜索用时 125 毫秒
91.
This paper analyses the choice between road and rail in Spain where rail market share for freight is still residual. Discrete choice models are estimated with data obtained through a two-phase fieldwork, thus allowing us to carry out a stated preference efficient design for each interviewee. We analyse the existence of attribute cut-offs and the presence of a segment of the population with a zero value of frequency. Our results show that ignoring the existence of cut-offs and segments of the population with polarised valuations can lead to erroneous conclusions in terms of the possibilities of rail for absorbing significant quota.  相似文献   
92.
93.
This paper presents an innovative approach to analyzing road vehicle freight traffic that uses a dynamic panel data specification derived from a gravity model. This dynamic approach, which has recently been employed in international goods trade models in lieu of the traditional static specification, is applied to the case of Spain using data for the countrys 15 NUTS-3 regions between 1999 and 2009. Using the system general method of moments approach, we obtained significant evidence that the flow of vehicles carrying commodities by road has a strong persistence effect when controlling for unobserved heterogeneity. We also found that the quality of road transport infrastructure has a significant impact on vehicle trips. According to our findings, we suggest that this type of specification be employed in distribution models in which fixed effects and lags of the dependent variable are included to account for unobserved heterogeneity and persistence effects, respectively.  相似文献   
94.
There is a large variety of multiple driven axle vehicles. Some of the most common are the 3-axle rigid vehicles and the 4-axle articulated vehicles, which can in some cases have different steering mechanisms, adaptive suspension, etc. This last kind of vehicles usually have very complex transmission configurations. Moreover, the required torques in each of the wheels can be very different, especially when the vehicle is working in rough terrains. The aim of this work is to study and model the driveline of this kind of vehicles, when using a hydrostatic transmission, from the performance and efficiency point of view, by analysing the influence of the operating conditions in the transmission efficiency. A global model is used to quantify the power flow in each of the transmission elements and the overall performance of the entire vehicle driveline, given the operating conditions thereof. A sensitivity analysis has also been done showing the influence of vehicle speed, rolling resistance, terrain slope and hydraulic motors displacement in the overall transmission efficiency. The interest of this work is also to make a contribution to the literature in the field of global modelling of drivelines under variable operating conditions and its application to ATVs. One important aspect is the influence of different actuation requirements that occur in different wheels at the same time. The results show that the overall performance of the transmission is highly dependent on operating conditions, on the selected transmission configuration and on the used components.  相似文献   
95.
This paper describes a new method of real-time train monitoring based on the ZigBee/IEEE 802.15.4 protocol. The system consists of a mobile device embedded in the moving train which transmits parameter signals that are being measured by a base unit with the help of routers. When applied, the technique monitors and controls vehicles operating on permanent routes, making a real-time evaluation of their performance and location, and allowing an effective planning of trains. It consists of a low cost, low power consumption and safe modular technology capable of monitoring many different variables simultaneously.  相似文献   
96.
The objective of the research described in this paper was to develop a model for computation of an ultimate capacity of a single track line and to provide a sensitivity analysis of this capacity to the parameters which influence it. The model is based in a concept of mathematical expectation of capacity and can be applied under saturation conditions i.e. a constant demand for service. It can serve for planning purposes, computation of single track line capacity on the base of which estimations are possible concerning a single track line performance under given conditions, as well as commercial time‐tables planning, decisions about a partial or complete construction of the second parallel track along the line in service, intermediate stations locations planning and the necessary facilities along the line under construction.

In the sensitivity analysis, the model allows a change of parameters upon which the capacity depends. These are: the length of the line segment which is considered to be bottleneck for calculation of capacity, traffic distributions per directions, train mix, train velocities and train spacing rules applied by the dispatching service when regulating the traffic on a line.  相似文献   
97.
Cantillo  Tatiana  Vargas  Andrés  Cantillo  Víctor  Ramos  José 《Transportation》2020,47(5):2267-2286
Transportation - Inadequate infrastructure is recognized as an important barrier to cycling; therefore, improvements in the provision of bicycle facilities, such as bikeways, are frequently...  相似文献   
98.
This article presents a comprehensive analysis of beach management in the Catalan coast (NW Mediterranean) by introducing and integrating results from different partial projects. They analyzed the legal, political, and administrative framework of beach management, the quality tools available, the practices of management, the processes of beach use, and beach waste/litter dynamics. The information obtained served to create a new beach management tool referred to as the Beach Quality Index, which was developed by an interdisciplinary team of academics from the natural/physical sciences and social sciences that worked together during the course of four years. Information obtained from users and key stakeholders served to create the index. The study demonstrated that as a consequence of the shortcomings in the legal and administrative system as well as inadequate practices of beach managers, beach management in the area experiences coordination problems, insufficient information and lack of proactive management, pollution, and in general problems associated with the satisfaction of short-term user demands.  相似文献   
99.
Abstract

Indigenous peoples’ efforts toward environmental conservation are indivisible from their cultural identity and their social and political organizations. Indigenous resurgence, including the reinvigoration and reestablishment of Indigenous ways of living, are linked to the management, restoration, and conservation of marine and coastal ecosystems around the world. However, there remains a significant gap in the recognition and support of Indigenous governance systems in international policy discussions regarding conservation work. As a way to address this gap, we offer an analysis of marine Indigenous community-led conservation initiatives from around the world that were recipients of the UNDP Equator Prize, framed by initial research on Indigenous-led conservation in British Columbia, Canada. We highlight specific Indigenous governance strategies undertaken by such communities that foster both marine resource conservation and stewardship. The strategies we identified included practicing Indigenous traditional resource management, protection of traditional territories, Indigenous-led actions of environmental conservation, and data collection and monitoring. We also identified networking and collaboration with non-Indigenous supporters, as was reinvestment into education and capacity-building within the community. We conclude with concrete policy suggestions drawn from these cases that can help strengthen the leadership and self-determination of Indigenous peoples on local resource and environmental issues, and aid in much broader conservation efforts globally.  相似文献   
100.
Abstract

Port efficiency and port clustering are two aspects that have received different degrees of attention in the existing literature. While the actual estimation of port efficiency has been extensively studied, the existing literature has paid little attention to developing robust methodologies for port classification. In this paper, we review the literature on classification methods for port efficiency, and present an approach that combines stochastic frontier analysis, clustering and self-organized maps (SOM). Cluster methodologies that build on the estimated cost function parameters could group ports into performance metrics’ categories. This helps when setting improvement targets for ports as a function of their specific cluster. The methodology is applied to a database of Spanish port authorities. The dendrogram features three clusters and five outlier Spanish Port Authorities. SOM are employed to track the temporal evolution of Spanish Port Authorities that are of special interest for some reasons (i.e. outliers). Results show that use of a combination of cost frontier and cluster methods to define robust port typology and SOMs, jointly or in isolation, offers useful information to the decision-makers.  相似文献   
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