Travel time estimation from sparse floating car data with consistent path inference: A fixed point approach

Estimation of urban network link travel times from sparse floating car data (FCD) usually needs pre-processing, mainly map-matching and path inference for finding the most likely vehicle paths that are consistent with reported locations. Path inference requires a priori assumptions about link travel times; using unrealistic initial link travel times can bias the travel time estimation and subsequent identification of shortest paths. Thus, the combination of path inference and travel time estimation is a joint problem. This paper investigates the sensitivity of estimated travel times, and proposes a fixed point formulation of the simultaneous path inference and travel time estimation problem. The methodology is applied in a case study to estimate travel times from taxi FCD in Stockholm, Sweden. The results show that standard fixed point iterations converge quickly to a solution where input and output travel times are consistent. The solution is robust under different initial travel times assumptions and data sizes. Validation against actual path travel time measurements from the Google API and an instrumented vehicle deployed for this purpose shows that the fixed point algorithm improves shortest path finding. The results highlight the importance of the joint solution of the path inference and travel time estimation problem, in particular for accurate path finding and route optimization.     

On the degradation of performance for traffic networks with oblivious users

We consider the problem of characterizing user equilibria and optimal solutions for routing in a given network. We extend the known models by considering users oblivious to congestion in the following sense: While in the typical user equilibrium setting the users follow a strategy that minimizes their individual cost by taking into account the (dynamic) congestion due to the current routing pattern, an oblivious user ignores congestion altogether; instead, he or she decides his routing on the basis of cheapest routes on a network without any flow whatsoever. These cheapest routes can be, for example, the shortest paths in the network without any flow. This model tries to capture the fact that a certain percentage of travelers base their route simply on the distances they observe on a map, without thinking (or knowing, or caring) about the delays experienced on this route due to their fellow travelers. In this work we study the effect of such users using as the measure of network performance its price of anarchy, i.e., the ratio of the total latency experienced by the users (oblivious or not) at equilibrium over the social optimum.     

GSM-R中FAS话务量计算

介绍了GSM-R系统的结构,FAS系统及子系统在整个网络中的位置以及系统话务量的计算方法.分别按不同站型计算各站话务量,以此来确定网络的组网方式.     

提高固定资产投资价格统计数据质量的探讨

文章针对目前建筑安装工程固定资产价格统计工作的现状,分析影响施工企业固定资产投资价格统计数据质量的主要因素,从把握工作重点的原则和解决工作难点等四个方面,提出了提高施工企业固定资产投资价格统计数据质量的对策。     

A capacity restraint transit assignment with elastic line frequency

This paper proposes a new formulation for the capacity restraint transit assignment problem with elastic line frequency, in which the line frequency is related to the passenger flows on transit lines. A stochastic user equilibrium transit assignment model with congestion and elastic line frequency is proposed and the equivalent mathematical programming problem is also formulated. Since the passenger waiting time and the line capacity are dependent on the line frequency, a fixed point problem with respect to the line frequency is devised accordingly. The existence of the fixed point problem has been proved. A solution algorithm for the proposed model is presented. Finally, a numerical example is used to illustrate the application of the proposed model and solution algorithm.     

航海院校水上专业固定滚轮技能教学探析

根据滚轮运动的特点,在水上专业学生固定滚轮教学中,采用循序渐进原则,探讨了开展滚轮运动的意义及应注意的问题,通过正确引导,消除了学生的恐惧心理,同时结合相关模仿练习,使学生对固定滚轮产生兴趣,从而提高了教学效果与训练质量。     

深广中通道东隧西桥方案和全隧方案比选

深广中通道是国务院确定的重大基础设施项目,对南沙、广州、珠三角的未来发展具有重要意义。这样一个重大工程项目,对区域经济和社会发展,对国防、水利、航运等均有深远影响,且耗资巨大,需审慎对待,做好前期的方案比选,选择最优方案,不要使工程建设给国家、社会留下遗憾。对东隧西桥方案和全隧方案,从船舶发展趋势、区域经济发展需求、国防要求、水环境影响、技术等方面进行比选。认为东隧西桥方案,本末倒置,违背了在大江大河上建设通道开展论证的基本要求; 坚持该方案,将造成难以估量的战略损失和不可弥补的历史遗憾。提出3条建议： 1）全隧方案可行,建议采取全隧方案; 2）若有关方面对全隧方案有疑虑,建议参照港珠澳大桥的通航标准,缩短隧道长度,仅广州港主航道段以隧道方式穿越; 3）搁置争议,继续深化论证,待时机成熟时再决定建设。     

非收放式减摇鳍精度安装新技术研究

针对非收放式减摇鳍安装工艺现状,提供一种求解安装所需定位参数的理论方法,给出了一种实现鳍座定位所需的专用工装的设计理念与制作要领,提出了双筒体鳍座设计理念,并给出了其制作、船上安装及加工工艺流程,实现了减摇鳍装置的精度安装。     

腐蚀和裂纹损伤下海洋平台极限强度试验研究

根据墨西哥湾某一典型固定式海洋平台为原型,按照刚度相似性和几何相似性,分别设计并制作了完好模型、腐蚀模型、裂纹模型,并对三个试验模型开展极限强度试验研究,试验结果表明腐蚀、裂纹损伤严重影响试验模型极限承载力,且试验模型失效模式各不相同.同时,采用非线性有限元方法,分别对三个试验模型进行计算,将计算结果与试验结果对比分析,验证了该方法在固定式海洋平台极限强度计算方面的有效性.     

固定移动融合(FMC)及其实现

对固定移动融合从概念、技术标准及业务实现方式等进行了详细分析,并通过介绍国外电信运营商提供的FMC服务,提出了运营商开展FMC的相关建议.