混合交通流条件下区域交通信号控制优化模型

针对传统区域交通控制技术无法应对机非冲突干扰的问题, 结合中国城市道路混合交通流的特点, 研究了交叉口与路段非机动车对机动车的干扰。分析了区域路网机动车交通特征, 确定了混合交通特性相似的区域。基于路段非机动车的阻滞作用, 分析了交叉口通行能力的折减与相邻交叉口相位差的优化。以区域路网机动车总延误为优化目标, 建立了非机动车影响条件下的区域交通信号控制优化模型, 优化了信号周期时长、绿信比和相位差等参数, 并利用遗传算法求解模型。利用VISSIM仿真软件, 以上海市杨浦区五角场环形区域路网为例对优化模型进行验证。验证结果表明: 现状信号控制方案下区域路网7个交叉口机动车的车均延误为24.5~42.9s, 平均为35.99s, 路网总延误为256.39h, 优化后交叉口的车均延误为21.8~36.4s, 平均为30.12s, 路网总延误为214.57h, 7个交叉口车均延误减少了10%~24%, 平均为16.31%。可见, 优化模型能够显著降低区域路网车均延误与总延误, 提高区域路网通行效率。     

城市轨道交通运能瓶颈识别方法研究

城市轨道交通庞大的客流量导致了运能紧张及能力利用不合理的现象,严重影响了系统的整体运行效率。针对运能瓶颈问题进行分析,给出了车站瓶颈静态识别模型;结合能力利用公式和AnyLogic仿真软件,对车站的动态瓶颈进行了研究;对于区间线路瓶颈,提出了基于客流的识别方法;进一步分析了车站内部瓶颈以及车站、线路间瓶颈的动态传播变化规律。最后进行了实例应用,结果表明,复兴门站的车站瓶颈为站台层的换乘楼梯口处,2号线各区间的能力利用率相差不大,线路瓶颈最大值出现在建国门至朝阳门这一区间。该方法考虑了车站和线路不同位置的特性,并提出了相应的瓶颈识别思路,具有良好的实用价值。     

桩靴支护结构对桩端极限承载力的影响

以渤海湾\     

混合设计的高性能钢梁抗弯性能试验

采用两点加载的方式, 对3片混合设计的高性能HPS 485W工字钢梁进行抗弯性能试验, 分析了截面几何参数对试验梁抗弯承载力、弹塑性变形和破坏形态的影响。结合跨中单点加载的试验结果, 对比分析了不同加载方式对试验梁抗弯承载力的影响, 建立了能够准确模拟试验梁抗弯过程的有限元模型, 在非厚实截面范围内对混合设计的高性能钢模型梁进行了关键参数的数值分析。分析结果表明: 对两点加载的试验梁, 抗弯破坏形态为纯弯段区出现受压翼缘与受压区腹板的局部屈曲; 随着翼缘宽厚比的降低, 钢梁的塑性转动能力明显提高; 随着腹板高厚比的增加, 钢梁的抗弯强度和延性均会降低; 对相同几何尺寸的模型梁, 加载方式改变时, 钢梁的抗弯过程相似, 但控制钢梁失效的破坏形态不同; 对混合设计的钢梁, 建议腹板与翼缘材料强度等级差不大于2个强度等级。     

上汽通用五菱供应商注塑机台统计分析

上汽通用五菱汽车股份有限公司(下面简称“上通五”)曾经作为在国内连续十几年的单一车企销量冠军,年产销量在2015年就已突破200万辆大关,打造过多个爆火车型,一度被网友们称作“神车”专业户。上通五连续多年巨大的年产销量,多个爆火车型的快速上量对供应商的生产能力也提出了巨大的挑战。本文将对上通五注塑件供应商的注塑能力做主要分析,全面统计上通五在柳州,青岛,重庆三个基地的供应商注塑机台不同吨位区间的机台数量,产能利用率,自动化普及率及注塑机台的综合评分等信息。掌握现有注塑机台的信息将有助于推进供应商的专业化发展,提前识别潜在的产能风险,面对供应商产能不足的情况能快速制定解决措施,平衡各供应商的业务,提升供应商现有的产能利用率,推进设备技术参数统一便于零件平台化设计,识别优质供应商资源建立战略合作关系。     

A capacity maximization scheme for intersection management with automated vehicles

With the advent of connected and automated vehicle technology, in this paper, we propose an innovative intersection operation scheme named as MCross: Maximum Capacity inteRsection Operation Scheme with Signals. This new scheme maximizes intersection capacity by utilizing all lanes of a road simultaneously. Lane assignment and green durations are dynamically optimized by solving a multi-objective mixed-integer non-linear programming problem. The demand conditions under which full capacity can be achieved in MCross are derived analytically. Numerical examples show that MCross can almost double the intersection capacity (increase by as high as 99.51% in comparison to that in conventional signal operation scheme).     

Roads in transition: Integrated modeling of a manufacturer-traveler-infrastructure system in a mixed autonomous/human driving environment

This paper develops an integrated model to characterize the market penetration of autonomous vehicles (AVs) in urban transportation networks. The model explicitly accounts for the interplay among the AV manufacturer, travelers with heterogeneous values of travel time (VOTT), and road infrastructure capacity. By making in-vehicle time use more leisurely or productive, AVs reduce travelers’ VOTT. In addition, AVs can move closer together than human-driven vehicles because of shorter safe reaction time, which leads to increased road capacity. On the other hand, the use of AV technologies means added manufacturing cost and higher price. Thus, traveler adoption of AVs will trade VOTT savings with additional out-of-pocket cost. The model is structured as a leader (AV manufacturer)-follower (traveler) game. Given the cost of producing AVs, the AV manufacturer sets AV price to maximize profit while anticipating AV market penetration. Given an AV price, the vehicle and routing choice of heterogeneous travelers are modeled by combining a multinomial logit model with multi-modal multi-class user equilibrium (UE). The overall problem is formulated as a mathematical program with complementarity constraints (MPCC), which is challenging to solve. We propose a solution approach based on piecewise linearization of the MPCC as a mixed-integer linear program (MILP) and solving the MILP to global optimality. Non-uniform distribution of breakpoints that delimit piecewise intervals and feasibility-based domain reduction are further employed to reduce the approximation error brought by linearization. The model is implemented in a simplified Singapore network with extensive sensitivity analyses and the Sioux Falls network. Computational results demonstrate the effectiveness and efficiency of the solution approach and yield valuable insights about transportation system performance in a mixed autonomous/human driving environment.     

Airport capacity increase via the use of braking profiles

Many airports are encountering the problem of insufficient capacity, which is particularly severe in periods of increased traffic. A large number of elements influence airport capacity, but one of the most important is runway occupancy time. This time depends on many factors, including how the landing roll procedure is performed. The procedure usually does not include the objective to minimize the runway occupancy time. This paper presents an analysis which shows that the way of braking during landing roll has an essential impact on runway throughput and thus on airport capacity. For this purpose, the landing roll simulator (named ACPENSIM) was created. It uses Petri nets and is a convenient tool for dynamic analysis of aircraft movement on the runway with given input parameters and a predetermined runway exit. Simulation experiments allowed to create a set of nominal braking profiles that have different objective functions: minimizing the runway occupancy time, minimizing noise, minimizing tire wear, maximizing passenger comfort and maximizing airport capacity as a whole. The experiments show that there is great potential to increase airport capacity by optimizing the braking procedure. It has been shown that by using the proposed braking profiles it is possible to reduce the runway occupancy time even by 50%.     

Fully autonomous vehicles: analyzing transportation network performance and operating scenarios in the Greater Toronto Area,Canada

Fully autonomous vehicles (AVs) have the potential to considerably change urban mobility in the future. This study simulates potential AV operating scenarios in the Greater Toronto Area (GTA), Canada, and assesses transportation system performance on a regional level. For each scenario, the base capacities of certain types of road links are modified to simulate the theoretical increase in throughput enabled by AV driving behavior. Another scenario examines driverless parking operations in downtown Toronto. Simulation results indicate that the increased attractiveness of freeways relative to other routes leads to slightly increased average travel distance as vehicles divert to access higher capacity road links. Average travel time is found to decrease by up to one-fifth at the 90% AV market penetration level. Concurrently, localized increases in congestion suggest that proactive transportation planning will be needed to mitigate negative consequences of AV adoption, especially in relation to induced demand for personal automobile travel.     

进港航道通过能力经验公式的比较分析

航道通过能力是评价进港航道是否满足港口发展需要的重要指标。由于我国现行规范中对航道通过能力未给出具体计算公式,因此,在工程实践中出现了许多种不同的方法和公式。通过搜集国内外计算航道通过能力的经验公式．分析讨论各公式的特点及适用性条件。