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101.
In a variety of applications of traffic flow, including traffic simulation, real-time estimation and prediction, one requires a probabilistic model of traffic flow. The usual approach to constructing such models involves the addition of random noise terms to deterministic equations, which could lead to negative traffic densities and mean dynamics that are inconsistent with the original deterministic dynamics. This paper offers a new stochastic model of traffic flow that addresses these issues. The source of randomness in the proposed model is the uncertainty inherent in driver gap choice, which is represented by random state dependent vehicle time headways. A wide range of time headway distributions is allowed. From the random time headways, counting processes are defined, which represent cumulative flows across cell boundaries in a discrete space and continuous time conservation framework. We show that our construction implicitly ensures non-negativity of traffic densities and that the fluid limit of the stochastic model is consistent with cell transmission model (CTM) based deterministic dynamics. 相似文献
102.
为进一步分析研究高铁隧道凿岩台车与风钻钻爆的优劣及适用性问题,以郑万高铁小三峡隧道工程为依托,介绍风钻钻爆 的施工应用情况及凿岩台车钻爆在施工应用方面的制约因素,并从施工工效、人员配置、安全性、超欠挖控制、成本投入等方面对比 分析。 主要研究结论如下: 1)采用凿岩台车钻爆,在硬岩条件下钻爆速度较快,Ⅲ、Ⅳ级围岩可通过工法调整来提高凿岩台车的施 工效率,遇软弱围岩时应慎重选用; 2)凿岩台车钻爆与风钻钻爆相比,劳动强度低、节省劳动力、安全风险小等方面具有突出成效; 3)理论分析凿岩台车钻爆较风钻钻爆平均线性超挖小,但实际施工过程中却反之,可通过加强管理来缩小与人工钻爆之间的超挖 差距; 4)凿岩台车对风钻钻爆的优势显而易见,随着隧道施工机械化进程不断地发展,将来一段时间凿岩台车钻爆替代风钻钻爆 施工是未来地下工程开挖的发展方向之一。 相似文献
103.
Railway reforms: do they influence operating efficiency? 总被引:1,自引:0,他引:1
This paper considers railway operations in 23 European countries during 1995–2001, where a series of reform initiatives were
launched by the European Commission, and analyses whether these reform initiatives improved the efficiency of the railway
systems. Efficiency is measured using Multi-directional Efficiency Analysis, which enables investigation of how railway reforms
affect the inefficiencies of specific cost drivers. The main findings are that the reform initiatives generally improve technical
efficiency but potentially differently for different cost drivers. Specifically, the paper provides empirical evidence that
accounting separation is important for improving the efficiency in the use of both material and staff costs, whereas other
reforms only influenced one of these factors.
Mette Asmild is Associate Professor in Operational Research at Warwick Business School (UK). Her main research interests are theoretical developments and practical applications of efficiency and productivity analysis techniques, particularly Data Envelopment Analysis. Torben Holvad is Economic Adviser at the European Railway Agency (France), senior research associate at the Transport Studies Unit (University of Oxford) and external associate professor at the Department of Transport (Danish Technical University). He obtained Economics degrees from Copenhagen University (MSc) and the European University Institute in Florence (PhD). Jens Leth Hougaard is Professor in Applied Microeconomics at Department of Food and Resource Economics, University of Copenhagen. His main research interests are related to applied microeconomics and include Efficiency Analysis and Benchmarking. Currently, he is working with cost sharing methods and allocation in networks. Dorte Kronborg is MSc in mathematical statistics from the University of Aarhus and Associate Professor at Center for Statistics, Department of Finance, Copenhagen Business School. Her primary research interests are applications and development of mathematical statistical methods within business economics. 相似文献
Dorte KronborgEmail: |
Mette Asmild is Associate Professor in Operational Research at Warwick Business School (UK). Her main research interests are theoretical developments and practical applications of efficiency and productivity analysis techniques, particularly Data Envelopment Analysis. Torben Holvad is Economic Adviser at the European Railway Agency (France), senior research associate at the Transport Studies Unit (University of Oxford) and external associate professor at the Department of Transport (Danish Technical University). He obtained Economics degrees from Copenhagen University (MSc) and the European University Institute in Florence (PhD). Jens Leth Hougaard is Professor in Applied Microeconomics at Department of Food and Resource Economics, University of Copenhagen. His main research interests are related to applied microeconomics and include Efficiency Analysis and Benchmarking. Currently, he is working with cost sharing methods and allocation in networks. Dorte Kronborg is MSc in mathematical statistics from the University of Aarhus and Associate Professor at Center for Statistics, Department of Finance, Copenhagen Business School. Her primary research interests are applications and development of mathematical statistical methods within business economics. 相似文献
104.
为分析低频钹式换能器的发射电压响应、辐射声功率、发射效率等性能参数,通过ANSYS有限元软件建立了发射换能器的轴对称模型,设计了不同结构参数的共振频率为2kHz左右发射型钹式换能器,从结构阻尼入手,通过仿真分析计算,得到换能器的带宽、品质因数等,比较了不同结构参数的换能器的各项性能,绘制了不同结构参数的发射电压响应曲线,为分析设计钹式换能器提供了理论依据。 相似文献
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108.
运用层次分析法与模糊综合评价法相结合的方法对长沙市公交线路运行效率进行评价,为交通监管部门的决策提供依据。 相似文献
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