基于客户价值和满意度的城市冷链物流时变路径问题

针对车辆保有量日益增加和拥堵情况日趋严重而造成的城市冷链物流时效性不强、客户价值不高、顾客满意度降低等问题，综合考虑客户价值、客户满意度以及成本等因素，提出一种城市冷链物流时变路径优化方法。考虑到冷链配送过程中不同时段的道路拥堵问题，采用分段函数刻画车辆行驶速度，并同时考虑时间窗和车辆载重量等约束，建立了多目标数学模型。使用线性加权法和主要目标法对多目标进行处理，将其转换成单目标数学模型。结合问题NP难特性，设计了单亲遗传算法对小、中、大规模算例进行了求解，结果表明：与未考虑客户价值模型相比，该模型在平均增加3.28%成本的情况下，提高14.96%的客户价值和14.64%的满意度；与未考虑成本模型相比，该模型在减少1.55%的客户价值的前提下，节约17.32%的成本；对比静态路网模型，模型减少0.92%的成本，提高6.27%的客户满意度和16.06%的客户价值。通过对目标函数中成本权重和客户价值权重进行参数分析，表明成本和客户价值之间存在明显的背反关系。     

基于横向安全距离模型的主动避障算法

现有的安全距离模型是基于纵向相对车速或减速度值建立的,没有考虑移动目标的横向运动特性。本文利用移动目标横穿马路的速度、相对位置,建立横向安全距离模型,并提出一种基于横向安全距离模型的主动避障算法。首先,根据横向移动目标横穿马路的速度、相对位置和自车的制动距离建立横向安全距离模型,设计主动避障算法。接着,为计及路面条件对制动效果的影响,引入当前行驶路面估算的附着系数峰值估算最大制动减速度,约束目标避障减速度,并调整制动强度,以适应不同路况的安全避障行驶。最后,以典型横向移动目标骑行者作为研究对象,通过PreScan/Simulink/CarSim联合仿真验证避障算法的有效性。结果表明:基于横向安全距离模型的主动避障算法能有效避免与骑行者碰撞,提高行车的主动安全性。     

Study on State Parameter Control of Intake Air in Utility Tunnels Based on BB-MOPSO北大核心CSCD

In order to explore the control method of the intake air state in utility tunnels when the outside fresh air humidity is too high, taking the ventilation works of a utility tunnel section in Pingtan comprehensive experimental area as the research background, this paper proposes the control method of intake air state parameters for ventilation and dehumidification in utility tunnels under normal and accident conditions, by means of the effective ventilation and dehumidification duration prediction model, the evolutionary multi-objective algorithm (EMOA), and in combination with the ventilation control requirements. The results show that the intake air state parameter controller can be adjusted freely according to the different requirements of decision makers for ventilation fan working duration and dehumidifier working temperature and moisture content, and the optimized appropriate control objectives can be achieved, which is conducive to the real-time decision-making of the intake air state parameter control for ventilation and dehumidification in utility tunnels. © 2022, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

A Practical SSL Server Performance Improvement Algorithm Based on Batch RSA Decryption

The secure socket layer/ transport layer security（SSL/TLS） handshake protocol uses public key cryptographic algorithms such as RSA for key establishment. Typically, public key cryptographic algorithm is computational intensive due to the modular multiplications. Therefore, SSL/TLS servers often become swamped while performing public key decryptions when the simultaneous requests increase quickly. A batch RSA decryption algorithm was proposed. The novel algorithm provides the reasonable response time and optimizes server performance significantly. The decryption speedup is proportional to the batch size b, for instance, the speedup factor is 4, while in Shacham＇s scheme the acceleration rate is only 2.5 when b = 4.     

滚石运动模拟分析与危险性评价

随着公路在山区的建设和使用,危岩体不断地威胁着公路的安全使用。以茂县渭门乡危岩体为例,运用Rockfall软件对滚石的运动轨迹、冲击动能进行模拟,并通过赫兹碰撞理论、质点弹性理论接触问题两种计算方法,分析和求解滚石对行车的最大冲击力;从而得到滚石下落的落点区域主要集中在公路上、滚石下落到公路区域时的动能以及滚石撞击汽车时最大冲击力,综合判定危岩体对公路安全使用造成的危害,必须采取有效措施加以防治,确保安全。     

几种初至自动拾取算法在地震波法隧道超前探测中的对比分析

在地震勘探中,尤其在浅层地震勘探、层析成像和地震波法超前探测中初至时间拾取精度直接影响勘探区域地质结构的反演结果，初至时间的自动拾取也是隧道超前地质预报地震数据处理的一个关键环节。介绍4种初至自动拾取算法--最大振幅法、能量比法、STA/LTA（长短时窗比）法和AIC（峰度赤池信息量准则）法，利用云南某隧道超前地质预报采集到的1组地震数据，对4种初至自动拾取算法进行对比分析，结果显示SLA/LTA算法拾取的初至时间更为精确，AIC法、能量比法次之。进一步利用其他隧道超前地质预报采集到的几组数据进行对比分析，获得相同结论。     

CRTSⅡ型板式无砟轨道-桥梁耦合模型中的钢轨与底座板频响特性研究

针对高速铁路常用的CRTSⅡ型板式无砟轨道结构,根据其特点,建立二维模型时,可将钢轨与底座板模拟为无限长Euler-Bernoulli梁。根据动力学基本原理,首先建立无限长Euler-Bernoulli梁在简谐荷载作用下的运动微分方程,通过稳态响应求解和积分变换,求出梁体的位移、速度和加速度频率响应函数。利用所推导的频响函数,探讨CHN 60型钢轨的位移、速度和加速度频率响应的频谱特性和频响衰减率。通过分析可知,钢轨的位移和速度频率响应随频率增加而降低,而加速度频率响应随频率增加而增大;位移频响衰减率随频率增加而显著降低,速度频响衰减率在10~100 Hz频段较大,加速度频响衰减率随频率增加而显著增大。     

直喷汽油机最佳点火提前角控制算法的研究

通过试验研究了点火提前角对直喷汽油发动机性能的影响，依据发动机实际运行情况通过理论分析与试验相结合，研究了外界因素对直喷汽油发动机最佳点火提前角的影响，给出了各因素对直喷汽油发动机最佳点火提前角相应的修正补偿，结合目前实际运用中对汽油发动机点火提前角的控制提出了一种对直喷汽油发动机最佳点火提前角的控制算法，该控制算法可更简单，更精确，更有效地实现对汽油直喷发动机的最佳点火提前角的控制。     

Lane assignment problem using a genetic algorithm in the Automated Highway Systems

This paper deals with the lane assignment problem in the Automated Highway Systems (AHS). The purpose of lane assignment strategies is to increase throughput on multi-lane highways with many entry and exit points, based on the itineraries of vehicles using the highway (point of entry, time of entry and exit point) and the effects of maneuvers. Using partitioned lane assignment strategies, the lane assignment problem is formulated as an optimization problem to find the proper positions of partitions. Then the optimal problem is solved using a Genetic Algorithm (GA). The proposed algorithm has been validated by comparing its solution with that of an all-cases algorithm for a simple case. Moreover, a traffic simulator with a realistic car-following model as well as lane change logic has been developed. The simulation results show the efficiency of the proposed genetic algorithm, compared with random assignment algorithms.     

Monte Carlo Simulation of Electron Swarms Parameters in c-C4F8/CF4 Gas Mixtures

The swarm parametes for c-C4F8/CF4 mixtures, including the density-normalized effective ionization coefficient, drift velocity and mean energy were calculated using Monte-Carlo method with the null collision technique. The overall density-reduced electric field strength could be varied between 150 and 500 Td,while the c-C4F8 content in gas mixtures is varied in the range of 0-100%. The value of the density-normalize deffective ionization coefficient shows a strong dependence on the c-C4F8 content, becoming more electronegative as the content of c-C4F8 is increased. The drift velocity of c-C4F4/CF4 mixtures is more affected by CF4. The calculated limiting field strength for c-C4F8/CF4 mixtures is higher than that of SF6/CF4.