一种新型在线长输管道管体检测技术

文中介绍一种以磁应力为原理的检测技术,即磁力断层摄影检测技术.该技术是一种非接触式的被动检测技术,可以检测出长输管道管体各类型缺陷.首先简单阐述了检测原理,其次详细说明了执行一次检测的全流程工作步骤,以及各步骤的工作内容,然后简要介绍了其独特的经验性计算MAOP和剩余寿命的公式,接着以实际试点检测工作为例,说明了该技术的可行性,最后指明了该技术的优缺点.     

Probabilistic multi-aircraft conflict detection approach for trajectory-based operation

Conflict detection (CD) is one of the key functions used to ensure air transport safety and efficiency. In trajectory-based operation (TBO), aircraft are provided with more flexibility in en route trajectory planning and more responsibility for self-separation. The high flexibility in trajectory planning enables random changes in pilot intent, thus increasing the uncertainty in trajectory prediction and CD. This study proposes a novel probabilistic CD approach for TBO in which the uncertainty of pilot intent is taken into account by quantifying the aircraft reachable domain constrained by the flight plan. First, a probabilistic model for aircraft trajectory prediction is developed using the truncated Brownian bridge method. Based on this model, a novel conflict probability estimation method is developed. Finally, the performance of the proposed probabilistic CD approach is demonstrated through an illustrative air traffic scenario.     

Structural Optimization and Strength Analysis of the Lifting Arm of a Wet Shotcrete Spraying Unit北大核心CSCD

Wet shotcrete spraying units are widely used in underground engineering, for railways, highways, water conservancy and hydropower stations, municipal works, mining and military and other industries. Structural analysis and mechanical behavior optimization are conducted regarding the lifting arm of a TKJ series shotcrete spraying unit, and optimization of the hinge point position and working scope of the lifting arm is realized. The optimal layout scheme for the hinge force is given based on the Monte Carlo method, the hinge force of the lifting arm is improved for the mean and maximum values, and the maximum and average hinge force of the lifting cylinder decrease by 23.14% and 7.70%, respectively, compared with that of the original scheme. The static strength is checked using Ansys-Workbench for the optimized scheme, and the results show that the optimized scheme has a larger safety re-serve and that the structural design is more reasonable than the original scheme. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

Assessing the impact of reduced visibility on traffic crash risk using microscopic data and surrogate safety measures

Due to the difficulty of obtaining accurate real-time visibility and vehicle based traffic data at the same time, there are only few research studies that addressed the impact of reduced visibility on traffic crash risk. This research was conducted based on a new visibility detection system by mounting visibility sensor arrays combined with adaptive learning modules to provide more accurate visibility detections. The vehicle-based detector, Wavetronix SmartSensor HD, was installed at the same place to collect traffic data. Reduced visibility due to fog were selected and analyzed by comparing them with clear cases to identify the differences based on several surrogate measures of safety under different visibility classes. Moreover, vehicles were divided into different types and the vehicles in different lanes were compared in order to identify whether the impact of reduced visibility due to fog on traffic crash risk varies depending on vehicle types and lanes. Log-Inverse Gaussian regression modeling was then applied to explore the relationship between time to collision and visibility together with other traffic parameters. Based on the accurate visibility and traffic data collected by the new visibility and traffic detection system, it was concluded that reduced visibility would significantly increase the traffic crash risk especially rear-end crashes and the impact on crash risk was different for different vehicle types and for different lanes. The results would be helpful to understand the change in traffic crash risk and crash contributing factors under fog conditions. We suggest implementing the algorithms in real-time and augmenting it with ITS measures such as VSL and DMS to reduce crash risk.     

改进的锤击法测量原点阻抗

机械阻抗是机械系统特性的集中参数表示, 是解决机械系统耦合问题的一个重要工具。现有的机械阻抗方法有激振器激振传感器,冲击锤敲击实验结构等方法,但都有各自的局限性。本文提出了改进的锤击法测量原点阻抗。通过实验对比,对其可行性进行了研究,证明了此种方法可以快速并较为准确的获得结构的原点阻抗,具有工程实用性。     

轻型井点降水工艺在工程中的应用

在地下水位较高的含水层中进行基坑开挖时,地下水会不断渗入基坑,较易产生流砂、管涌等破坏现象,甚至使边坡或坑壁失稳坍塌。在基坑开挖前,采用轻型井点降水工艺,将基坑内外水位降低,从而达到开挖基坑的目的,是常用且较为有效的施工方法。以恒大海上威尼斯排水涵闸施工工程涵闸基坑开挖为例,从方案设计到具体的施工过程叙述轻型井点降水。     

基于相关性模型的舰船系统测试性建模与分析

本文提出一种基于相关性模型的舰船系统级产品的测试性建模与分析方法.该方法通过建立产品任务模型、相关性图示模型等,利用一阶相关性列矢量法求解产品的相关性数学模型,进而建立产品诊断树和进行测试性预计,并为优化产品诊断策略提供建议.同时,根据舰用燃气轮机滑油系统组成和任务特征,建立其典型任务模型并进行精简,并在此基础上进行测试性建模、诊断树建立、测试性预计以及诊断策略优化等工作,为舰船系统级产品的测试性建模、分析和诊断策略研究提供新思路和手段.     

单侧边载作用下黏土中单桩负摩阻力特性模型试验研究

桩基础边载作用会在桩周产生负摩阻力,进而危及软土地区高桩码头、人工岛、路基等工程的安全。通过开展黏土中单侧堆载作用下单桩室内模型试验,测定桩身应变、桩顶沉降和水平位移,研究边载作用距离和桩型对桩身轴力及弯矩的影响,探讨桩身负摩阻力、桩顶沉降和水平位移在黏土固结过程中的时间效应。结果表明:边载作用距离对桩身最大轴力和最大弯矩有较大影响;翼板桩会增加桩身最大轴力和最大弯矩;负摩阻力和有效应力系数随时间增长且增速趋缓;增加边载作用距离和添加翼板都会提升桩身中性点位置,在这两组试验中均提升了8.33%。     

地质雷达在上三高速公路护面墙检测中的应用

上三高速公路K224+720 ～ K225+020左山体自2008年以来,每逢大雨,该山体第二级坡面的长约20m范围内有局部泥沙从泄水孔带出,在对护面墙及碎落台的跟踪检查中,由于局限于目前管理单位的检测设备,未发现空洞、变形.为确保高速公路的安全畅通,此次采用地质雷达对该山体的护面墙进行检测,可快速了解护面墙的厚度、密实度等质量情况.     

公路黄土隧道洞口段施工技术要点

由于黄土隧道自身稳定性差,在开挖过程中,特别是刚进洞时的洞口（浅埋）段,容易出现不稳定的问题,所以需认清洞口段常见的灾害类型及成因,加强施工中各个环节的控制,以保证施工的正常、安全进行。