柔性路面车辙预估的粘弹性方法

沥青混合料的粘弹性流动导致沥青路面产生永久变形(车辙)。对于粘弹性体系,永久变形与材料的弹性参数无关,但可通过采用粘性参数的线弹性模型预估出来。为了确定沥青混合料在较大环境变化条件下的粘性,该文引入了一个新的基于常规试验数据的简单理论方法,并将根据此方法得到的车辙预估深度与法国新近的一个足尺试验数据进行对比,结果表明此线性车辙模型的适用性较好。     

Analysis of characteristics of foreign unmanned surface vehicle swarm combat application and proposed countermeasures北大核心CSCD

无人船(USV)集群作为未来海上军事运用的重要组成力量,是各国海上无人装备的重要发展方向。首先,通过梳理总结当前国外无人船集群发展战略规划与运用现状,对无人船集群作战关键技术进行归纳分析,从集群自组网通信、战场态势感知、集群协同任务分配等3个方面剖析无人船集群相关技术的研究进展;然后,对无人船集群在军事上运用的典型样式和主要效益进行分析及研判;最后,总结分析当前应对无人船集群的难点,并对无人船集群应对的技术发展予以展望。     

雾环境下高速公路驾驶人跟驰行为研究

雾环境下驾驶人行车与正常天气相比,在低能见度下视觉参照物较少,驾驶人更倾向于跟驰行驶。为研究雾环境下高速公路驾驶人跟驰行为,以真实雾环境下实车试验方式,选择多条高速公路作为试验路段,以Smart Eye眼动仪获取车辆在雾环境下高速公路驾驶人视觉参数,包含驾驶人注视区域、注视角度、注视持续时间、瞳孔直径、扫视速度以及扫视幅度等,以归一化方法对驾驶人注视重心进行分析,研究不同能见度下驾驶人的跟驰需求,并通过对雾环境下上述视觉参数进行规律总结。对雾环境下驾驶人跟驰特性进行统计及分类,将跟驰行为划分为主动、半主动、半被动以及全被动跟驰;通过分析雾区低能见度下驾驶人跟驰行驶条件,引入多维偏好理论及后悔理论,进行驾驶人跟驰决策模型构建,并基于差分法对模型进行参数标定及验证。研究结果表明：驾驶人在1次跟驰动态过程中,正常车道保持时驾驶人扫视速度较低,而当处于车道调整时,驾驶人扫视速度存在较大波动,且平均扫视速度较高,低能见度下驾驶人注视点转移速度27.0 （°）·s^-1明显低于晴好天气的52.0 （°）·s^-1;驾驶人在跟驰过程中,能见度对驾驶人跟驰时的视觉特征有显著影响,通过跟驰模型构建可为后续雾环境下车辆跟驰前后车距及车速预测提供理论支撑。     

Analysis of the application and development of integrated electric power technology for unmanned ships北大核心CSCD

近年来,随着动力、信息等技术的不断发展,无人船在反水雷、反潜、电子战、海上安全、海上拦截等军用领域凸显出越来越大的优势。为此,首先阐述无人船及其动力技术的发展概况,明确综合电力系统已成为中大型无人船的重要发展趋势,然后介绍综合电力系统在有人/无人平台的应用情况,提出设备尺寸、重量和振动噪声控制等问题是综合电力系统应用于无人平台的研究重点,最后阐明无人平台综合电力技术的发展趋势,指出综合电力系统智能化运行、高性能电机材料、复杂电机系统信息感知、电力电子器件与系统、高性能电能变换和高效储能是无人平台综合电力技术的关键科学问题。     

Do transportation network companies increase or decrease transit ridership? Empirical evidence from San Francisco

Transportation - Transportation network companies (TNCs), such as Uber and Lyft, have been hypothesized to both complement and compete with public transit. Existing research on the topic is limited...     

Do frequent satisfying trips by public transport impact its intended use in later life?

Transportation - Previous studies have indicated that factors such as the built environment, attitudes and past behaviour can influence travel behaviour. However, the possible effect of travel...     

岩溶隧道排水管结晶堵塞试验与数值模拟研究北大核心CSCD

为实现岩溶区隧道排水系统堵塞过程的精准刻画和预警防控,开展了与现场1∶1等比例的排水系统堵管室内试验,探讨了仿真现场水动力、水化学和干湿循环条件下管道结晶沉淀量的变化规律,构建了考虑水动力和碳酸盐岩组分溶解-沉淀化学反应耦合驱动过程的数值模型,结合室内试验数据,对所建立的隧道排水管结晶堵塞模型进行验证。模拟结果表明,随着时间的推移,模拟值与试验观测值之间的误差逐渐减小,至15 d左右,二者拟合决定系数R2为0.67,证明在相对较长时间尺度下,所构建的数值模型在一定程度上能够较好地预测隧道排水管道内的结晶生成过程,模型能为隧道排水系统堵塞问题的防治提供理论指导,进而为岩溶隧道地质灾害的早期识别与安全评价提供保障。     

Study of the Impact of Single-and Double-tube Tunnel Systems on Rockburst in Deep-buried Extra-long Tunnelling北大核心CSCD

Rockburst is one of the main disasters for tunnelling under high ground stress. Taking the rockburst section of Ping'an Tunnel with high ground stress, which is located on Chengdu-Lanzhou Railway, as the study object, this paper adopts combined methods of filed measurement, numerical analysis, and laboratory test, and with respect to rockburst development mechanism, energy density change and rockburst strength it comprehensively analyzes the impact of two construction schemes (single-tube double-track tunnel system and double-tube single-track tunnel system) on the rockburst in deep-buried extra-long tunnels with high ground stress. The study results show that the order relation of maximum energy density at various locations of the tunnel is Uside wall >Uhance >Utunnel face >Uvault, and rockburst easily occurs at the working face of the tunnel section to be excavated and both side walls of excavated and supported section; compared with vault, hance, side wall and other locations, more energy would be released at the tunnel face, and the stress release holes shall be reasonably installed in the process of excavation; the doubletube single-track tunnel system scheme can effectively reduce the rockburst intensity and the rockburst hazards, so as to better avoid the occurrence of rockburst. © 2022, Editorial Office of Modern Tunnelling Technology. All right reserved.     

Comprehensive Evaluation of the Intelligent Degree of the Mining Face Based on Grey Relational Analysis北大核心CSCD

In order to further evaluate the intelligent degree of the coal mining face scientifically and reasonably, this paper constructs a gray relational analysis based comprehensive evaluation model for the intelligent degree of mining face by deeply analyzing the influencing factors on the intelligent degree of mining face, such as surrounding rock detection, mining equipment, production system, supporting production system, organization and management, etc. By quantifying and scoring factors affecting the intelligence degree of mining face, using the hierarchical analysis method to obtain the weights and determine the correlations, the intelligence degrees of mining face are classified into four levels: excellent, good, medium and poor. Using the comprehensive evaluation model to empirically verify the 802 working face of Shaanxi Huangling Mining Co., Ltd., the calculated correlation is 0.765 8, which indicates that the intelligent degree of 802 working face is excellent according to the rating criteria, and it is consistent with the actual situation. Therefore, the comprehensive evaluation model based on gray relational analysis can accurately and objectively evaluate the intelligent degree of the mining face. © 2022, Editorial Office of Modern Tunnelling Technology. All right reserved.     

铁路隧道衬砌施工自动浇筑振捣新技术北大核心CSCD

铁路隧道衬砌质量问题导致的衬砌背后空洞、开裂、掉块等病害会对铁路正常运营造成极大威胁,混凝土的浇筑和振捣是保证隧道衬砌质量的关键。为此,研发了一种隧道衬砌施工自动浇筑振捣新技术,以提升隧道衬砌质量。研究表明,自动旋转布料机逐窗浇筑技术每次换管时间仅为3~4 min,具有结构简单、操作方便、效果优良、安全可靠的特点,既加快了隧道衬砌进度,又保证了隧道衬砌质量;新型插入式振捣技术采用边墙自动提升插入式振捣技术和拱顶自动气动式插入振捣技术,可以有效地提高混凝土振捣效果;拱顶衬砌采用60°斜孔带压反向浇筑,与传统的拱顶浇筑方法相比,堵管次数、浇筑口模板变形次数都明显减少,混凝土浇筑质量得到了显著提升。