放宽条件定点集结模式下编组站车辆 集结排队系统分析

集结模式决定了货车集结过程的结束条件，定点集结是一种高效率的集结方式，有利于提高运输质量.针对放宽条件定点集结模式下编组站车辆集结过程，建立离散时间批到达批服务排队模型，利用嵌入式马尔可夫链方法求得离去时刻瞬时系统集结车辆队长分布，并求得任意时刻车辆集结队长分布，在此基础上分别分析了最小编成辆数，车组大小分布，车流到达强度，服务时间间隔分布对车辆平均集结队长，集结延误时间，效率，一昼夜发送车流量等系统指标的影响.分析结果表明，各因素对车辆集结排队系统影响明显.因此，利用本文提出的模型能为编组站的精细化管理和车流组织优化提供决策参考.     

An optimal data-splitting algorithm for aircraft scheduling on a single runway to maximize throughput

In this research, we present a data-splitting algorithm to optimally solve the aircraft sequencing problem (ASP) on a single runway under both segregated and mixed-mode of operation. This problem is formulated as a 0–1 mixed-integer program (MIP), taking into account several realistic constraints, including safety separation standards, wide time-windows, and constrained position shifting, with the objective of maximizing the total throughput. Varied scenarios of large scale realistic instances of this problem, which is NP-hard in general, are computationally difficult to solve with the direct use of commercial solver as well as existing state-of-the-art dynamic programming method. The design of the algorithm is based on a recently introduced data-splitting algorithm which uses the divide-and-conquer paradigm, wherein the given set of flights is divided into several disjoint subsets, each of which is optimized using 0–1 MIP while ensuring the optimality of the entire set. Computational results show that the difficult instances can be solved in real-time and the solution is efficient in comparison to the commercial solver and dynamic programming, using both sequential, as well as parallel, implementation of this pleasingly parallel algorithm.     

市域(郊)铁路信号系统制式比选及建议

基于市域(郊)铁路公交化运营、互联互通运行的功能需求,对现有信号系统制式与市域(郊)铁路的匹配性进行了分析。建议根据市域(郊)铁路运营需求的差异,选择相匹配的市域(郊)铁路信号系统。     

硬岩顶管卡滞原因分析及脱困技术研究

针对长距离岩石地层顶管施工中预制管卡滞工程难题,结合观景口水利工程2#无压洞工程,通过资料查阅、案例调研、专家咨询等方法,对多种处理方案进行对比分析。结合工程实践,提出预制管受困点判别方法,并研究制定出沉渣冲洗清理及预制管拆除方案;结合顶管施工特点就如何预防预制管卡滞提出针对性改进措施。经工程验证,所采取方案与技术措施顺利解决了预制管卡滞难题,并确保了后期工程的顺利进行,既缩短了工期又取得了良好的经济效益.,可为类似工程提供借鉴和参考。     

兰州地铁地温分布特性及其演化规律

以兰州地铁所在地区为研究对象,实测地铁隧道开挖前的地温(简称为初始地温),根据实测数据,提出地铁初始地温预测模型公式。采用非稳态传热的数值模型,分析运营条件下地铁隧道围岩温度的演化规律。结果表明:兰州地铁初始地温随环境气温和埋深的变化而变化;年变温层位于自地表至埋深12m处;年恒温层位于埋深12m及其以下,温度为15℃左右;年变温层中,1年内初始地温变化规律与环境气温变化规律相似,近似呈正弦曲线状分布,但存在相位滞后的现象;1年中初始地温的振幅随埋深的增大呈指数下降趋势。在隧道内空气与围岩之间热交换中,兰州地铁隧道围岩的温度及其梯度、热透厚度(未达到极限时)均与隧道内环境温度、热交换时间成正相关关系,但与距隧道内壁的距离成负相关关系。     

25t轴重荷载作用下隧底脱空区域受力特性分析

为了研究在役铁路隧道在通车之后隧底脱空病害的问题,采用有限元理论,建立隧道脱空区域在围岩压力与25 t轴重列车动载作用下的数值计算模型,主要研究80 cm与40 cm脱空宽度分别距隧道中心线0,80 cm与160 cm时脱空区域的受力特性。结果表明:在围岩压力下,脱空区域中线上壁和外侧顶角混凝土中产生拉应力及内侧顶角中产生压应力,其中压应力对脱空的宽度更为敏感;同时施加列车动载作用时,脱空区域上壁出现了竖向动应力与横向拉应力,得到了脱空区域力学指标的最大响应值及其出现的具体位置,宽度的增加对脱空区上壁横向拉应力更为显著,上壁横向拉应力增幅超过200%,竖向动应力增幅达50%。因此,隧底脱空区周围应力分布复杂,拉应力与压应力在脱空区域同时存在,应力突变严重,对脱空现象应及时组织处理。     

船用电器柜抗冲击设计研究

为增强船内部电器柜的抗冲击性能,采用有限元法对船内不同安装型式的电器柜结构进行了模态和抗冲击性能仿真分析,通过对比分析得出了使用撑杆加固型式安装的电器柜能显著提高船内电器柜的抗冲击性能的结论,并确定了电器柜抗冲击优化设计方案。     

Generalized Maximum Benefit Multiple Chinese Postman Problem

This research is focused on a generalization on the Max Benefit Chinese Postman Problem and the multiple vehicle variant of the Chinese Postman Problem. We call this generalization, the Generalized Maximum Benefit k-Chinese Postman Problem (GB k-CPP). We present a novel Mixed Integer Programming (MIP) formulation for the GB k-CPP. Four different cases of the model are discussed. The first case, performs arc-routing with profits and assumes that the origin and destination for each vehicle is the same for each cycle and is given by the user. The next case relaxes the assumption that the origin and destination for each vehicle should be the same and allows the users to select possible origins/destinations for vehicles. Case three gets the origin for each vehicle as input and produces a solution based on finding the best destination for each vehicle. The last case, that is very general, allows the optimization model to select possibly different locations for vehicle origin and destination, during each cycle. The different cases are applied to a security patrolling case conducted on the network of University of Maryland at College Park campus and the results are compared.     

向量法在不规则隧道边仰坡面积计算中的应用

根据隧道边仰坡三维坐标测量数据,通过计算边仰坡斜面和投影水平面的法向量,进而计算两面之间夹角的方法,反算边仰坡斜面面积,在类似不规则隧道边仰坡等斜面面积计算中具有广泛的应用价值。     

桥梁大体积混凝土施工技术探讨

从原材料选择、合理安排施工进度、养护及施工缝处理等角度分析桥梁大体积混凝土施工技术要点.对同类工程有一定的借鉴意义.