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Understanding network travel time reliability with on-demand ride service data

Xiqun (Michael) CHEN, Xiaowei CHEN, Hongyu ZHENG, Chuqiao CHEN

《工程管理前沿（英文）》 2017年第4卷第4期页码 388-398 doi: 10.15302/J-FEM-2017046

摘要： Travel time reliability is of increasing importance for travelers, shippers, and transportation managers because traffic congestion has become worse in major urban areas in recent years. To better evaluate the urban network-wide travel time reliability, five indices based on the emerging on-demand ride service data are proposed: network free flow time rate (NFFTR), network travel time rate (NTTR), network planning time rate (NPTR), network buffer time rate (NBTR), and network buffer time rate index (NBTRI). These indices take into account the probability distribution of the travel time rate (i.e., travel time spent for the unit distance, in min/km) of each origin-destination (OD) pair in the road network. We use real-world data extracted from DiDi-Chuxing, which is the largest on-demand ride service platform in China. For demonstrative purposes, the network-wide travel time reliability of Beijing is analyzed in detail from two dimensions of time and space. The results show that the road network is more unreliable in AM/PM peaks than other time periods, and the most reliable time period is the early morning. Additionally, we can find that the central region is more unreliable than other regions of the city based on the spatial analysis results. The proposed network travel time reliability indices provide insights for the comprehensive evaluation of the road network traffic dynamics and day-to-day travel time variations.

关键词： network travel time reliability on-demand ride services travel time rate OD

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Robust energy-efficient train speed profile optimization in a scenario-based position–time–speed network

《工程管理前沿（英文）》 2021年第8卷第4期页码 595-614 doi: 10.1007/s42524-021-0173-1

摘要： Train speed profile optimization is an efficient approach to reducing energy consumption in urban rail transit systems. Different from most existing studies that assume deterministic parameters as model inputs, this paper proposes a robust energy-efficient train speed profile optimization approach by considering the uncertainty of train modeling parameters. Specifically, we first construct a scenario-based position–time–speed (PTS) network by considering resistance parameters as discrete scenario-based random variables. Then, a percentile reliability model is proposed to generate a robust train speed profile, by which the scenario-based energy consumption is less than the model objective value at

α

confidence level. To solve the model efficiently, we present several algorithms to eliminate the infeasible nodes and arcs in the PTS network and propose a model reformulation strategy to transform the original model into an equivalent linear programming model. Lastly, on the basis of our field test data collected in Beijing metro Yizhuang line, a series of experiments are conducted to verify the effectiveness of the model and analyze the influences of parameter uncertainties on the generated train speed profile.

关键词： robust train speed profile percentile reliability model scenario-based position–time–speed network mixed-integer programming

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Negative weights in network time model

Zoltán A. VATTAI, Levente MÁLYUSZ

《工程管理前沿（英文）》 2022年第9卷第2期页码 268-280 doi: 10.1007/s42524-020-0109-1

摘要： Time does not go backward. A negative duration, such as “time period” at first sight is difficult to interpret. Previous network techniques (CPM/PERT/PDM) did not support negative parameters and/or loops (potentially necessitating recursive calculations) in the model because of the limited computing and data storage capabilities of early computers. Monsieur Roy and John Fondahl implicitly introduced negative weights into network techniques to represent activities with fixed or estimated durations (MPM/PDM). Subsequently, the introduction of negative lead and/or lag times by software developers (IBM) apparently overcome the limitation of not allowing negative time parameters in time model. Referring to general digraph (Event on Node) representation where activities are represented by pairs of nodes and pairwise relative time restrictions are represented by weighted arrows, we can release most restraints in constructing the graph structure (incorporating the dynamic model of the inner logic of time plan), and a surprisingly flexible and handy network model can be developed that provides all the advantages of the abovementioned techniques. This paper aims to review the theoretical possibilities and technical interpretations (and use) of negative weights in network time models and discuss approximately 20 types of time-based restrictions among the activities of construction projects. We focus on pure relative time models, without considering other restrictions (such as calendar data, time-cost trade-off, resource allocation or other constraints).

关键词： graph technique network technique construction management scheduling

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基于可观测节点信息的控制器局域网节点可靠性评估 Article

Lei-ming ZHANG, Long-hao TANG, Yong LEI

《信息与电子工程前沿（英文）》 2017年第18卷第5期页码 615-626 doi: 10.1631/FITEE.1601029

摘要：基于控制器局域网的总线技术广泛应用于网络化制造系统。网络作为系统的信息通道，其可靠性对系统的吞吐量、产品质量以及工作人员的安全至关重要。然而，由于节点内部状态的不可访问性，因此使用节点内置的错误计数器值直接评估控制器局域网节点的可靠性是难以进行的。本文提出一种新颖的控制器局域网节点可靠性评估方法，该方法使用节点脱离总线时间作为可靠性测度。基于网络错误日志和错误计数器值可访问的可观测节点信息，该方法可以估计网络中节点的发送错误计数器值。首先，本文基于分段马尔科夫链建立了估计节点发送错误计数器值的模型，该模型考虑了网络中错误分布的稀疏特性。其次，通过学习可观测节点的模型估计值和实际测量值之间的偏差，建立了贝叶斯网络以表述可观测节点的模型估计值更新机制。然后，将该更新机制应用到网络中发送错误计数器值不可访问的节点，完成其模型估计值的更新。最后，建立了节点可靠性评估方法以预测节点的脱离总线时间。为表明文中方法的有效性，进行了多组实验。实验结果表明由文中方法得到的估计值与实际观测值相一致。

关键词：控制器局域网；发送错误计数器；发送错误计数器值估计；贝叶斯网络；脱离总线时间

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结构时变可靠度计算的全随机过程模型

杜斌,向天宇,赵人达

《中国工程科学》 2010年第12卷第3期页码 108-112

摘要：

为了对既有结构的可靠性进行正确评估，必须考虑时间变化的影响，对目前可靠度分析中采用的只考虑荷载随时间变化的半随机过程模型进行改进。基于结构抗力和作用效应相互独立的基本假设，充分依据作用效应和抗力的时变特性，考虑结构抗力为独立增量过程，并计算了抗力的自相关系数，得到了计算结构失效概率的近似算法，建立了结构时变可靠度计算的全随机过程模型。通过实例验证，该方法简单易行，便于工程应用，为基于时变可靠度理论的既有结构评估和寿命预测提供理论依据。

关键词：既有结构随机过程时变可靠度作用效应抗力衰减

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考虑用户出行需求和信息系统可靠性的电动汽车响应能力评估 Article

刘艳丽, 刘珂, 孙旭

《工程（英文）》 2022年第15卷第8期页码 186-196 doi: 10.1016/j.eng.2021.08.031

摘要：

随着电动汽车（EV）渗透率的提高，电动汽车的需求响应能力对促进电力系统的优化和安全运行具有重要意义。本文提出了一种电动汽车响应能力评估方法，该方法考虑了电动汽车用户的出行需求和集成在电网和交通网中的信息系统的可靠性。首次提出了新的信息-电力-交通耦合系统架构，并提出了信息系统可靠性模型。进一步，提出了考虑交通诱导信息生成和发布可靠性的电动汽车入网状态计算方法。最后，基于所提出的反映用户出行需求的电动汽车充电需求松弛度指标，实现了对电动汽车响应能力的评估。在由RBTS BUS6 和北京交通网络构建的信息-电力-交通系统上进行的大量测试验证了所提方法的有效性，分析了信息可靠性对电动汽车出行和响应能力的影响。

关键词：信息系统需求响应电动汽车

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Appraisal of coastal recreational resources in Qingdao by travel cost method

Jingmei LI , Tieying LIU , Yuanyuan ZHANG , Lei LI ,

《环境科学与工程前沿（英文）》 2009年第3卷第3期页码 341-347 doi: 10.1007/s11783-009-0038-z

摘要： This paper serves to appraise the monetary cost of coastal recreational resources in Qingdao using the travel cost method (TCM), which is typically used in developed countries. The total revenue produced by Qingdao’s coastal recreational resources is about RMB 5.51×10 annually, based on questionnaires given at Qingdao’s major tourist destinations. These questionnaires establish correlation functions that factor in the number of tourists, travel expenses, etc. The data processing software named Eviews was used to determine the tourist demand regression curve and to calculate their residual and actual travel expenses. The results of this study can provide a scientific basis for applicable industries interested in development and management decision-making. Therefore, this study assesses the reasonable usage of coastal recreational resources.

关键词： coastal recreational resources travel cost method (TCM) regression analysis Qingdao China

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Virtual network embedding based on real-time topological attributes

Jian DING,Tao HUANG,Jiang LIU,Yun-jie LIU

《信息与电子工程前沿（英文）》 2015年第16卷第2期页码 109-118 doi: 10.1631/FITEE.1400147

摘要： As a great challenge of network virtualization, virtual network embedding/mapping is increasingly important. It aims to successfully and efficiently assign the nodes and links of a virtual network (VN) onto a shared substrate network. The problem has been proved to be NP-hard and some heuristic algorithms have been proposed. However, most of the algorithms use only the local information of a node, such as CPU capacity and bandwidth, to determine how to map a VN, without considering the topological attributes which may pose significant impact on the performance of the embedding. In this paper, a new embedding algorithm is proposed based on real-time topological attributes. The concept of betweenness centrality in graph theory is borrowed to sort the nodes of VNs, and the nodes of the substrate network are sorted according to the correlation properties between the former selected and unselected nodes. In this way, node mapping and link mapping can be well coupled. A simulator is built to evaluate the performance of the proposed virtual network embedding (VNE) algorithm. The results show that the new algorithm significantly increases the revenue/cost (R/C) ratio and acceptance ratio as well as reduces the runtime.

关键词： Virtual network embedding (VNE) Real-time topological attributes Betweenness centrality Correlation properties Network virtualization

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Real-time tool condition monitoring method based on temperature measurement and artificial neural network

《机械工程前沿（英文）》 doi: 10.1007/s11465-021-0661-3

摘要： Tool failures in machining processes often cause severe damages of workpieces and lead to large quantities of loss, making tool condition monitoring an important, urgent issue. However, problems such as practicability still remain in actual machining. Here, a real-time tool condition monitoring method integrated in an in situ fiber optic temperature measuring apparatus is proposed. A thermal simulation is conducted to investigate how the fluctuating cutting heats affect the measuring temperatures, and an intermittent cutting experiment is carried out, verifying that the apparatus can capture the rapid but slight temperature undulations. Fourier transform is carried out. The spectrum features are then selected and input into the artificial neural network for classification, and a caution is given if the tool is worn. A learning rate adaption algorithm is introduced, greatly reducing the dependence on initial parameters, making training convenient and flexible. The accuracy stays 90% and higher in variable argument processes. Furthermore, an application program with a graphical user interface is constructed to present real-time results, confirming the practicality.

关键词： tool condition monitoring cutting temperature neural network learning rate adaption

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Time-series prediction based on global fuzzy measure in social networks

Li-ming YANG,Wei ZHANG,Yun-fang CHEN

《信息与电子工程前沿（英文）》 2015年第16卷第10期页码 805-816 doi: 10.1631/FITEE.1500025

摘要： Social network analysis (SNA) is among the hottest topics of current research. Most measurements of SNA methods are certainty oriented, while in reality, the uncertainties in relationships are widely spread to be overridden. In this paper, fuzzy concept is introduced to model the uncertainty, and a similarity metric is used to build a fuzzy relation model among individuals in the social network. The traditional social network is transformed into a fuzzy network by replacing the traditional relations with fuzzy relation and calculating the global fuzzy measure such as network density and centralization. Finally, the trend of fuzzy network evolution is analyzed and predicted with a fuzzy Markov chain. Experimental results demonstrate that the fuzzy network has more superiority than the traditional network in describing the network evolution process.

关键词： Time-series network Fuzzy network Fuzzy Markov chain

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Data-driven approach to solve vertical drain under time-dependent loading

《结构与土木工程前沿（英文）》 2021年第15卷第3期页码 696-711 doi: 10.1007/s11709-021-0727-7

摘要： Currently, the vertical drain consolidation problem is solved by numerous analytical solutions, such as time-dependent solutions and linear or parabolic radial drainage in the smear zone, and no artificial intelligence (AI) approach has been applied. Thus, in this study, a new hybrid model based on deep neural networks (DNNs), particle swarm optimization (PSO), and genetic algorithms (GAs) is proposed to solve this problem. The DNN can effectively simulate any sophisticated equation, and the PSO and GA can optimize the selected DNN and improve the performance of the prediction model. In the present study, analytical solutions to vertical drains in the literature are incorporated into the DNN–PSO and DNN–GA prediction models with three different radial drainage patterns in the smear zone under time-dependent loading. The verification performed with analytical solutions and measurements from three full-scale embankment tests revealed promising applications of the proposed approach.

关键词： vertical drain artificial neural network time-dependent loading deep learning network genetic algorithm particle swarm optimization

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Mechatronic design of a novel linear compliant positioning stage with large travel range and high out-of-plane

Hua LIU, Xin XIE, Ruoyu TAN, Lianchao ZHANG, Dapeng FAN

《机械工程前沿（英文）》 2017年第12卷第2期页码 265-278 doi: 10.1007/s11465-017-0453-y

摘要：

Most of the XY positioning stages proposed in previous studies are mainly designed by considering only a single performance indicator of the stage. As a result, the other performance indicators are relatively weak. In this study, a 2-degree-of-freedom linear compliant positioning stage (LCPS) is developed by mechatronic design to balance the interacting performance indicators and realize the desired positioning stage. The key parameters and the coupling of the structure and actuators are completely considered in the design. The LCPS consists of four voice coil motors (VCMs), which are conformally designed for compactness, and six spatial leaf spring parallelograms. These parallelograms are serially connected for a large travel range and a high out-of-plane payload capacity. The mechatronic model is established by matrix structural analysis for structural modeling and by Kirchhoff’s law for the VCMs. The sensitivities of the key parameters are analyzed, and the design parameters are subsequently determined. The analytical model of the stage is confirmed by experiments. The stage has a travel range of 4.4 mm× 7.0 mm and a 0.16% area ratio of workspace to the outer dimension of the stage. The values of these performance indicators are greater than those of any existing stage reported in the literature. The closed-loop bandwidth is 9.5 Hz in both working directions. The stage can track a circular trajectory with a radius of 1.5 mm, with 40 mm error and a resolution of lower than 3 mm. The results of payload tests indicate that the stage has at least 20 kg out-of-plane payload capacity.

关键词： mechatronic design linear compliant positioning stage large travel range high out-of-plane payload capacity spatial parallelogram voice coil motor sensitivity analysis

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城市高架桥爆破拆除起爆网路可靠性研究

吴新霞,赵根,谢先启

《中国工程科学》 2014年第16卷第11期页码 72-77

摘要：

本文针对城市高架桥爆破拆除的长距离、长延时，目前只能采用非电起爆网路进行起爆的现状，研究了多发并联起爆网路的接力点雷管延期特性，提出了并联后的接力点起爆时间期望值的简易计算公式。针对不同规模的非电起爆网路提出了相应的可靠度标准，研发了既可保证高架桥倾倒过程不发生侧翻又能提高接力点起爆可靠度并可无限分段的复式交叉接力起爆网路，并推导了其起爆可靠度计算公式。相关成果为高架桥拆除爆破起爆网路设计提供了科学依据。

关键词：高架桥拆除爆破起爆网路可靠性

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Middle East respiratory syndrome coronavirus: current situation and travel-associated concerns

null

《医学前沿（英文）》 2016年第10卷第2期页码 111-119 doi: 10.1007/s11684-016-0446-y

摘要：

The emergence of Middle East respiratory syndrome coronavirus (MERS-CoV) in 2012 brought back memories of the occurrence of severe acute respiratory syndrome coronavirus (SARS-CoV) in 2002. More than 1500 MERS-CoV cases were recorded in 42 months with a case fatality rate (CFR) of 40%. Meanwhile, 8000 cases of SARS-CoV were confirmed in six months with a CFR of 10%. The clinical presentation of MERS-CoV ranges from mild and non-specific presentation to progressive and severe pneumonia. No predictive signs or symptoms exist to differentiate MERS-CoV from community-acquired pneumonia in hospitalized patients. An apparent heterogeneity was observed in transmission. Most MERS-CoV cases were secondary to large outbreaks in healthcare settings. These cases were secondary to community-acquired cases, which may also cause family outbreaks. Travel-associated MERS infection remains low. However, the virus exhibited a clear tendency to cause large outbreaks outside the Arabian Peninsula as exemplified by the outbreak in the Republic of Korea. In this review, we summarize the current knowledge about MERS-CoV and highlight travel-related issues.

关键词： coronavirus MERS Middle East respiratory syndrome

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城市按需空中交通的综合网络设计与需求预测 Article

吴志强, 张瑜

《工程（英文）》 2021年第7卷第4期页码 473-487 doi: 10.1016/j.eng.2020.11.007

摘要：

城市空中交通（UAM）是近年来提出的使用电动垂直起降飞行器（eVTOL）的新兴概念。UAM通过利用低空空域有望为城市地区的乘客和货物运输提供另一种选择，显著提高机动性。除了其他基本要素外，还需要垂直起降机场等地面基础设施来实现UAM从概念到运行的跨越。本研究探讨了UAM按需服务的网络设计，在考虑垂直起降机场的位置和潜在的UAM需求之间相互作用的同时，重点强调使用整数规划和求解算法来确定垂直起降机场的最佳位置、用户分配以及进出模式的选择。一个基于美国佛罗里达州坦帕湾地区模拟分解交通需求数据的案例研究验证了该模型的有效性。通过分析基于佛罗里达州的激光雷达数据和eVTOL运行的自身约束和监管约束下开发出的3D地理信息系统（GIS）地图，我们获得了备选垂直起降机场的位置。垂直起降机场最佳位置的选择以总成本最小为目标，但同时该模型结构允许每个用户根据广义费用在地面运输和UAM之间选择更好的模式。案例研究的结果显示，虽然从地面模式切换到多式联运的行程比重很小，但选择UAM服务的用户明显节省了时间。此外，本文从供应方面探讨了不同参数设置对UAM服务需求的影响，并测试了不同的定价策略对UAM的需求和利润之间的影响。同时分析了垂直起降机场数量与定价策略的综合效应。研究结果为城市决策者和UAM运营商提供了深入的规划和管理意见。本文的结论部分讨论了该研究的注意事项、作者正在进行的工作以及UAM的未来研究方向。

关键词：先进空中交通楼顶停机坪交通方式的选择低空空域无人驾驶系统