CKA-C型外锁闭装置动力学特性试验研究

在宁波地铁轨道测试线道岔上,安装了CKA-C型外锁闭装置进行行车试验,采集基本轨、尖轨连接铁、锁闭框、锁钩和锁闭杆的动力学响应数据,通过分析加速度信号的频谱及结构件所承受的应力,评估产品的安全性和可靠性。试验结果表明CKA-C型外锁闭装置能够满足使用需要,且具有较大的安全余量;产品的固有频率也避开了行车的特征频率,不会产生共振。     

Generalized transport costs and index numbers: A geographical analysis of economic and infrastructure fundamentals

We rely on the economic theory approach to index numbers to improve the existing definitions and decompositions of variations in generalized transport costs (GTCs). As a value index, we decompose GTCs into price and quantity indices associated to economic—market—costs and infrastructure variables—distance and time within a network. The methodology allows the accurate identification of the sources of GTCs decline. We illustrate it for the case of road freight transportation in Spain between 1980 and 2007 and at a highly detailed geographical level. Average GTCs weighted by trade flows have decreased by 16.3%, with infrastructure driving that reduction. We find large territorial disparities in GTCs, but also significant geographical clusters where the market and network indices show spatial association.     

An advanced traveler general information system for Fresno,California

This study estimates the effects of an advanced traveler general information system (ATGIS), which includes fuel consumption and health-related emissions cost information on transportation network users’ travel choice behavior for recurrent congestion conditions. The effects are estimated using four different formulations based on four different behavioral assumptions. Incorporating stochastic features in link cost estimation rather than in route choice, we provide a novel modeling approach that enables us to use transportation planning models of major metropolitan areas without a need for major computationally-expensive changes in the existing models. We examined the effects of an ATGIS on the Fresno, CA, road network and found several interesting results. First, the ATGIS impact is closely related to pre-system (prior to the implementation of an ATGIS) perceived fuel and emissions costs. Total travel time in the city can be reduced by 17% (no pre-system perceived costs) to 1% (accurate pre-system perceived costs), and even increased by 1% (higher-than-actual pre-system perceived costs). Second, the addition of emissions costs, although negligible relative to fuel and time costs, can effectively reduce total system-wide travel time by up to 1% and fuel consumption by up to 0.6% during peak hours. Third, the ATGIS can reduce annual social costs by as much as $1053 million (high gas price, no pre-system perception) to $48 million (medium gas price, accurate pre-system perception), which are comparable to social cost savings by a congestion pricing (CP) scheme in the study area.     

Achieving environmental sustainability beyond technological improvements: Potential role of high-speed rail in the United States of America

In order to reduce energy use and cut emissions that contribute to climate change, countries need to radically reinvent their fossil-fuel intensive transportation systems. As a major consumer of energy and contributor to greenhouse gas (GHG) emissions, the U.S. transportation sector faces extraordinary challenges in the twenty-first century. Transportation in the U.S. depends heavily on fossil-fuel dependent cars and planes to the near exclusion of more energy-efficient electric trains. In order to address this concern, some policy makers refer to “technological optimism” which seeks no systemic change but instead focuses on employing technology to reduce the energy demand and environmental impact of the status quo. On the other hand, some researchers suggest a systematic paradigm shift away from cars and planes to intermodal systems that improve the sustainability of the system as a whole. High-speed rail (HSR) is arguably such an investment that can further this shift and help to achieve a more diversified and balanced transportation system. In this respect, by largely examining the role of the U.S. cars and planes “culture” in the economy, this paper elaborates on how building a HSR system may help U.S. advance towards environmental sustainability in transportation, make a break from the status quo, and create a more balanced, multimodal transportation system that will improve the quality and efficiency of travel.     

节段预制体外预应力混凝土桥梁计算方法探讨

文章基于对节段预制体外预应力混凝土桥梁的既有研究,对承载能力极限状态、弹性阶段的计算方法进行分析,提出在目前规范支持不完善的情况下该类桥梁结构的计算分析方法,为工程设计提供参考。     

A Heuristic Algorithm for the Allocation of Airport Runway System Capacity

Abstract

This paper develops a heuristic algorithm for the allocation of airport runway capacity to minimise the cost of arrival and departure aircraft/flight delays. The algorithm is developed as a potential alternative to optimisation models based on linear and integer programming. The algorithm is based on heuristic (‘greedy’) criteria that closely reflect the ‘rules of thumb’ used by air traffic controllers. Using inputs such as arrival and departure demand, airport runway system capacity envelopes and cost of aircraft/flight delays, the main output minimises the cost of arrival and departure delays as well as the corresponding interdependent airport runway system arrival and departure capacity allocation. The algorithm is applied to traffic scenarios at three busy US airports. The results are used to validate the performance of the proposed heuristic algorithm against results from selected benchmarking optimisation models.     

A method of minimum reusability estimation for automated software testing

Through reusing software test components, automated software testing generally costs less than manual software testing. There has been much research on how to develop the reusable test components, but few fall on how to estimate the reusability of test components for automated testing. The purpose of this paper is to present a method of minimum reusability estimation for automated testing based on the return on investment (ROI) model. Minimum reusability is a benchmark for the whole automated testing process. If the reusability in one test execution is less than the minimum reusability, some new strategies must be adopted in the next test execution to increase the reusability. Only by this way, we can reduce unnecessary costs and finally get a return on the investment of automated testing.     

城市轨道交通地下线车站选址与平面线形优化

基于已知的线路起终点和研究区域内人口分布情况,研究城市轨道交通地下线平面设计方案。以轨道交通车站的布设数量、位置及线路平面线形为决策变量,考虑实际地理条件、站间距、换乘预留及线路平面设计等约束,建立城市轨道交通地下线平面优化模型,实现客流吸引量最大,以及包括建设投资、运营支出和环境影响在内的线路综合成本最小。设计基于非支配排序遗传算法(NSGA-II)与A*算法的混合启发式算法求解模型。选取国内某城市地铁线路为研究对象,结果表明,算法可求得模型帕累托前沿,提供不同客流吸引量下线路综合成本最低的解决方案。此外,与实际平面设计方案相比,帕累托最优方案能够在不降低客流吸引量情况下减小约 4.4％的线路综合成本。     

机场地区对外客运交通配套发展研究

针对国内机场地区对外客运交通配套发展相对滞后问题,基于综合运输发展的基本思想,在借鉴国内外先进机场地区做法的基础上,以经济社会发展为主线,定性提出三阶段发展理念,并以沈阳桃仙国际机场为研究对象进行探讨。为今后促进区域经济发展、构建机场综合交通枢纽、提升航空运输服务能力及竞争优势提供了思路。     

煤矿井下水泵和地面通风机交流调速装置的节能分析

目前,煤炭销售形式非常好,但有的煤矿经济效益并不如人们所期望的那样高,究其原因主要在于煤炭的生产成本比较高。而节能降耗是煤矿降低煤矿生产成本提高经济效益的主要途径,尤其是针对煤矿中大型机电设备的节能改造是煤矿降低生产成本的主要方式。因此,煤矿需要比较设备不同的运行方式,分析不同情况下的效率,制订节能的运行方案。