准移动闭塞系统针对市域快线的适用性分析

针对国内城市轨道交通中被广泛采用的准移动闭塞系统,对市域快线的运营速度、站间距、牵引供电方式等进行分析,从理论上说明基于数字轨道电路的准移动闭塞信号系统可以满足市域快线的要求。     

Regional climate impact of aerosols emitted by transportation modes and potential effects of policies on demand and emissions

The transportation system is one of the main sectors with significant climate impact. In the U.S. it is the second main emitter of carbon dioxide. Its impact in terms of emission of carbon dioxide is well recognized. But a number of aerosol species have a non-negligible impact. The radiative forcing due to these species needs to be quantified. A radiative transfer code is used. Remote sensing data is retrieved to characterize different regions. The radiative forcing efficiency for black carbon are 396 ± 200 W/m²/AOD for the ground mode and 531 ± 190 W/m²/AOD for the air transportation, under clear sky conditions. The radiative forcing due to contrail is 0.14 ± 0.06 W/m² per percent coverage. Based on the forcing from the different species emitted by each mode of transportation, policies may be envisioned. These policies may affect demand and emissions of different modes of transportation. Demand and fleet models are used to quantify these interdependencies. Depending on the fuel price of each mode, mode shifts and overall demand reduction occur, and more fuel efficient vehicles are introduced in the fleet at a faster rate. With the introduction of more fuel efficient vehicles, the effect of fuel price on demand is attenuated. An increase in fuel price of 50 cents per gallon, scaled based on the radiative forcing of each mode, results in up to 5% reduction in emissions and 6% reduction in radiative forcing. With technologies, significant reduction in climate impact may be achieved.     

A spatial autoregressive panel model to analyze road network spillovers on production

The production function approach is used to introduce the effect of public infrastructure on economic growth focusing on its spillover effects. We improve the existing literature both from a conceptual and methodological perspective. As regressors we incorporate variables related to the new concepts of internal and imported transport infrastructure capital stocks, which are actually used in commercial flows, calculated by network analysis performed in GIS. The internally used capital stock represents own infrastructure that benefits accessing markets within the region itself, while the imported capital stock captures the spillover effect associated to the use of the infrastructure situated in neighboring regions. From a methodological perspective, we introduce spatial interdependence into these models, applying the most recent spatial econometric techniques based on instrumental variables estimation in spatial autoregressive panel models in comparison with Maximum Likelihood estimation methods. We illustrate the methodology with Spanish provincial panel data for the period 1980–2007. Results support the hypothesis that the imported capital has a positive spillover effect on production.     

区域性交通影响评价阈值的确定方法

新改扩建项目交通影响评价协调了交通需求与交通供给之间的关系,但单体建设项目的交通影响评价方法对于协调城市中某一区域的交通往往带来诸多利益主体平衡的困难,导致交通影响评价的效果不理想.为此,在城市快速发展时期,需要建立侧重于较大范围的区域性交通影响评价方法.针对区域性交通影响评价中范围阈值的确定,提出了标准区域类比法,研究了标准区域的确定方法和阈值确定的过程,并结合北京某区域实际,进行了区域确定方法的案例研究.     

Matching biological traits to environmental conditions in marine benthic ecosystems

The effects of variability in environmental conditions on species composition in benthic ecosystems are well established, but relatively little is known about how environmental variability relates to ecosystem functioning. Benthic invertebrate assemblages are heavily involved in the maintenance of ecological processes and investigation of the biological characteristics (traits) expressed in these assemblages can provide information about some aspects of functioning. The aim of this study was to establish and explore relationships between environmental variability and biological traits expressed in megafauna assemblages in two UK regions. Patterns of trait composition were matched to environmental conditions and subsets of variables best describing these patterns determined. The nature of the relationships were subsequently examined at two separate scales, both between and within the regions studied. Over the whole area, some traits related to size, longevity, reproduction, mobility, flexibility, feeding method, sociability and living habit were negatively correlated with salinity, sea surface temperature, annual temperature range and the level of fishing effort, and positively associated with fish taxon richness and shell content of the substratum. Between the two regions, reductions in temperature range and shell content were associated with infrequent relative occurrences of short-lived, moderately mobile, flexible, solitary, opportunistic, permanent-burrow dwelling fauna and those exhibiting reproductive strategies based on benthic development. Relationships between some traits and environmental conditions diverged within the two regions, with increases in fishing effort and shell content of the substratum being associated with low frequencies of occurrence of moderately mobile and moderately to highly flexible fauna within one region, but high frequencies in the other. These changes in trait composition have implications for ecosystem processes, with, for example, reductions in permanent-burrow dwellers within one of the regions potentially compromising the ability of the assemblages to process and store chemicals and waste products. However, the connections between environmental conditions and trait composition are complex and incorporate many factors. Experimental investigations will be necessary to determine the extent and consequences of these important relationships.     

高速铁路对区域经济的影响分析——以京津城际铁路为例

高速铁路凭借其显著的技术优势,对沿线地区的经济发展起到了很大的推动作用。此文在阐述国内外研究成果的基础上,分析高速铁路对沿线区域经济的影响,主要包括提高沿线线路运输能力、提高区域可达性、推动区域经济发展、优化产业结构、促进就业等几个方面。并采用有无高速铁路的对比法,分析和评价京津城际铁路对京津地区社会经济发展带来的影响。不管在生产总值、各产业增加值、就业人数、环境污染治理等方面都做出了贡献。并提出发展高速铁路的建议及促进区域经济发展注意的问题。     

全电子化区域计算机联锁系统技术方案研究

介绍了分散控制模式下全电子化区域计算机联锁系统的实现方案。详细阐述了方案中系统实现的功能、总体结构、设备配置和工作模式,并从软件角度论述了实现可靠通信的措施     

枢纽内区域计算机联锁系统构成方案

简要介绍区域计算机联锁系统在枢纽型大站场应用现状,分析枢纽内区域计算机联锁系统的结构,并对其进行优缺点对照。     

基于增长极理论的区域物流枢纽城市规划方法研究

区域物流发展的不平衡性要求区域物流发展规划体现出层次性和规划的重点,为此本文提出了物流枢纽城市的概念和以其为中心的区域物流规划思路,再应用增长极理论主要研究了物流枢纽城市的作用机理和规划原则,然后结合灰色聚类法提出了物流枢纽城市的规划方法,最后通过实际应用证明该方法的可行性和有效性。     

广佛同城化区域交通一体化规划实践

文章分析了广州、佛山两市同城化区域交通存在的问题,探讨了交通一体化战略目标及发展策略;同时通过结合城市群交通规划特点及实践,提出了城市群交通一体化规划的一般方法,对今后城市群交通一体化规划开展更深入的研究提出了相关建议。