长输天然气与城市燃气管道风险评价指标体系比较分析

长输天然气管道和城市燃气管道都是输气管道系统的重要组成部分,但是由于它们所处的位置和经过的区域大不相同,因此二者的风险有很大的不同。文中以《管道风险管理手册》为基础,结合半定量风险评价法中的管道指数法,通过比较长输天然气与城市燃气管道风险评价的指标体系,分析了它们之间的区别,对城市燃气管道的风险评价有一定的指导意义,为其风险评价提供了依据。     

水下管道探测技术浅议

简要介绍了水下管道电磁法探测系统的主要设备、技术指标及检测方法。并结合探测实例对该种探测技术及设备进行了总体评价。     

瞬变电磁法在燃气管道腐蚀检测中的应用

燃气管道运营过程中,会受很多因素影响,使其失效,发生泄漏、造成事故,其中最常见的问题就是管体自身的腐蚀老化。文中提出用瞬变电磁法(TEM)检测埋地燃气管道,主要介绍了瞬变电磁法检测在役燃气管道的原理,并结合工程实例对燃气管道进行检测,以验证此方法的可行性。结果表明:利用瞬变电磁法检测埋地燃气管道腐蚀具有有效性和实用性,应进一步研究以提高检测精度与效率,为保障燃气管道安全运营提供新的方法。     

隧道施工时探查、预报断层、岩溶、地下水的技术新进展

文章介绍了隧道施工超前预报部分物探技术重点研究开发的陆地声纳法、瞬变电磁法和探地雷达为主的新进展,列举了应用该方法及其组合方法在探查和预报断层、岩溶、地下水等方面所取得的成功例子,为今后推广该方法积累了经验。     

油气管道音波泄漏检测技术

随着国内石油天然气管道的迅速发展，泄漏检测作为保障管道运行安全的重要手段被深入研究。简要概述了油气管道泄漏检测技术，详细阐述了音波泄漏检测与定位的基本原理、系统的硬件设置及特点，说明了系统实现中存在的问题，并提出了建议。     

值得借鉴的加拿大-美国联合输气管道

联合管道是横跨美国和加拿大的长距离高压输气管道，本文从管道的建设历程，低操作成本及低输气费，压缩机附加功率的配置，先进的自控系统，配套设施建设等方面介绍了联合管道的特点。指出在我国天然气工业的发展初期，天然气管道建设应做好相关的技术研发和储备工作，充分考虑市场的落实程度及资源的可靠性，把握好管线建设进度。     

天然气管道的完整性管理

根据天然气管道完整性管理技术的研究现状,概述了天然气管道完整性管理的框架流程。阐述了天然气管道完整性管理的主要内容,分析了影响管道安全的主要因素、天然气管道事故后果,介绍了管道完整性检测方法,提出了天然气管道腐蚀控制措施以及天然气管道完整性管理体系发展建议。     

城市燃气埋地钢质管道泄漏检测定位技术

目前,基于硬件法和软件法的埋地钢质管道泄漏检测技术得到了快速发展,对这些新技术的优缺点进行了比较。这些新技术具有局限性,并不适用于城市燃气老旧钢质管道泄漏检测定位。对人工巡检法进行了改进,与埋地燃气管道定位相结合进行燃气泄漏点检测定位。现场实践证明对于准确定位燃气泄漏点具有很好的效果,同时具有检测时机灵活,检测成本低的优势。     

管道泄漏检测技术研究进展

按照检测位置的不同，管道泄漏检测技术可分为管内检漏法和管外检漏法。后者根据检测对象的不同，又大致可分为直接检漏法和间接检漏法。文中总结了各种检漏技术的原理及优缺点，重点介绍了近年来迅速发展的基于软件的检漏方法，并预测这方面的研究将在很长一段时间内成为管道泄漏检测技术的热点。     

压力管道无损检测技术及应用

无损检测具有不破坏试件、检测灵敏度高等优点,主要应用于压力管道原材料及制造检验和再用检验。文中介绍了压力管道进行无损检测的重要性,重点对辐射、声学、电磁以及其他领域的检测技术进行介绍,简述这些技术的原理及使用特点,为压力管道无损检测方法选择提供参考。     

Model,process, technique,and the good thing

The paper unpacks the planning process into its component parts: model, process, technique, and goals—the “good thing”. The paper advances the concept that planning, policy-making, and organizational restructuring can be analyzed under the same framework. Each of the four components is described and reductionist examples are presented to clarify the intention and to illustrate the technique that the transport analyst teams employ in their work. The examples cover both successes and failures. They point toward the enormous scientific task ahead for planning to become meaningful and relevant to the problems of today. Finally, in the frame of the willingness to pay, the paper puts forward a case for an institutional framework for a financially autonomous road administration. Similarly organized, administered, and managed entities are relevant also for other transport modes.

Walking frequency, cars, dogs, and the built environment

To explain walking propensity or frequency, empirical studies have generally used two sets of explanatory variables, namely, socio-demographic variables and built environment variables. They have generally shown that both socio-demographic characteristics and built environment characteristics are associated with walking propensity. We examine the traditional walkability variables that encompass density, mix of uses, and network connectivity in New Jersey, using a statewide sample including an oversample of Jersey City. We estimate a two-stage least squares model using a conditional mixed process that combines an ordered probit model of walking frequency in the second stage based on a truncated regression of car ownership in the first stage. Our results show that built environment variables have some small effects, mainly from better network connectivity associated with increased walking frequency. One of our key findings is that built environment features also work indirectly via how they influence car ownership. In general, we find sufficient evidence that suggests fewer cars are owned in areas with more walkable built environment features. The other key variable that we control for is whether a household owns a dog. This also proved to be strongly associated with walking suggesting that dog ownership is a necessary control variable to understand the frequency of walking.     

Space,money, life-stage,and the allocation of time

Demographic, socioeconomic, seasonal, and scheduling factors affect the allocation of time to various activities. This paper examines those variables through exploration of the 1990 Nationwide Personal Transportation Survey, which has been inverted to track activity duration. Two key issues are considered. First, how much can activity duration and frequency explain travel duration? The analysis shows activity duration has positive and significant effects on travel duration, supporting recent arguments in favor of activity based models. Second, which recent trend is the main culprit in the rise in travel: suburbanization, rising personal incomes, or female labor force participation? This paper examines the share of time within a 24-hour budget allocated to several primary activities: home, work, shop, and other. The data suggest that income and location have modest effects on time allocation compared with the loss of discretionary time due to working.

     

Governing autonomous vehicles: emerging responses for safety,liability, privacy,cybersecurity, and industry risks

ABSTRACT

The benefits of autonomous vehicles (AVs) are widely acknowledged, but there are concerns about the extent of these benefits and AV risks and unintended consequences. In this article, we first examine AVs and different categories of the technological risks associated with them. We then explore strategies that can be adopted to address these risks, and explore emerging responses by governments for addressing AV risks. Our analyses reveal that, thus far, governments have in most instances avoided stringent measures in order to promote AV developments and the majority of responses are non-binding and focus on creating councils or working groups to better explore AV implications. The US has been active in introducing legislations to address issues related to privacy and cybersecurity. The UK and Germany, in particular, have enacted laws to address liability issues; other countries mostly acknowledge these issues, but have yet to implement specific strategies. To address privacy and cybersecurity risks strategies ranging from introduction or amendment of non-AV specific legislation to creating working groups have been adopted. Much less attention has been paid to issues such as environmental and employment risks, although a few governments have begun programmes to retrain workers who might be negatively affected.     

Poverty,policy, and public transportation

By all appearances, the circumstances surrounding employment and income distribution in the United States have remained notably the same over the past 30–40 years. At the same time, policies for improving the conditions of low-income persons have remained relatively unchanged. Relevant published accounts continue to cite poorly integrated residential and employment location patterns and poor public transportation service as critical obstacles to improving the economic and social conditions of low-income persons. The relationship between poverty and public transportation was researched extensively during the late 1960s and the early 1970s; however, little recognition has been given to these efforts by more recent research efforts. To learn from the past we should review public transportation policies from 1960 to 2000 to highlight federal policies that affected urban areas during this time period, especially in relation to low-income transportation mobility.     

Integrated scheduling of m-truck,m-drone,and m-depot constrained by time-window,drop-pickup,and m-visit using constraint programming

The idea of deploying unmanned aerial vehicles, also known as drones, for final-mile delivery in logistics operations has vitalized this new research stream. One conceivable scenario of using a drone in conjunction with a traditional delivery truck to distribute parcels is discussed in earlier literature and termed the parallel drone scheduling traveling salesman problem (PDSTSP). This study extends the problem by considering two different types of drone tasks: drop and pickup. After a drone completes a drop, the drone can either fly back to depot to deliver the next parcels or fly directly to another customer for pickup. Integrated scheduling of multiple depots hosting a fleet of trucks and a fleet of drones is further studied to achieve an operational excellence. A vehicle that travels near the boundary of the coverage area might be more effective to serve customers that belong to the neighboring depot. This problem is uniquely modeled as an unrelated parallel machine scheduling with sequence dependent setup, precedence-relationship, and reentrant, which gives us a framework to effectively consider those operational challenges. A constraint programming approach is proposed and tested with problem instances of m-truck, m-drone, m-depot, and hundred-customer distributed across an 8-mile square region.     

Adaptive traffic control system: Control strategy,prediction, resolution,and accuracy

Recent advances in traffic control methods have led to flexible control strategies for use in an adaptive traffic control system (ATCS). ATCS aims at controlling the imminent traffic, which is yet to arrive and hence not known perfectly. Therefore, volume prediction is an essential part. Associated with the prediction are two aspects: resolution and accuracy. Recent studies indicate a tradeoff between prediction resolution and accuracy: finer resolutions, larger errors. It is imperative to study the relationship and tradeoff between the control strategy, prediction resolution, and its associated error, which are crucial to the development of ATCS. This study investigates this relationship through an extensive simulation of scenarios in Hong Kong with a recently developed dynamic traffic control model, DISCO. Based on the Hong Kong scenarios conducted with DISCO, the major findings include: (i) the importance of resolution outweighs that of error; (ii) dynamic timing plans generally outperform time‐invariant timing plans; (iii) up to a certain extent, overestimated predictions lead to better results than underestimated predictions.     

Activity sequencing,location, and formation of individual non-mandatory tours: application to the activity-based models for Columbus,Cincinnati, and Cleveland,OH

Most of the earlier activity based models (ABMs) largely relied on a tour-based modeling paradigm which explicitly predicts tour frequency and then adds details including stop frequency, order, and location of stops within each tour. The current study is part of new tour formation design framework for an ABM in which the underlying tour structure and the stop frequency within tours emerge from temporal, sequencing, and locational preferences of activities that the traveler intends to participate during the day. In order to do this, the study developed a modified rank-ordered logit (ROL) framework that is capable of modeling sequence, locations, as well as the underlying tour structure of all activity episodes simultaneously in an integrated manner. Model estimation with the household survey data, provided several important behavioral insights into underlying choices that drive tour formation. Specifically, the study uncovered pairwise ordering preferences among episodes of different activity purposes, clustering tendencies among episodes of same activity purpose, the impact of supply side activity opportunities on the location and sequence choice dimensions, and impedance effects (including distance and mode and time-of-day logsums) on location and tour break dimensions. The developed models are incorporated in the operational ABM structure adopted for three major cities (Columbus, Cleveland, and Cincinnati) in Ohio.     

Tradeoffs among free-flow speed, capacity, cost, and environmental footprint in highway design

This paper investigates differentiated design standards as a source of capacity additions that are more affordable and have smaller aesthetic and environmental impacts than modern expressways. We consider several tradeoffs, including narrow versus wide lanes and shoulders on an expressway of a given total width, and high-speed expressway versus lower-speed arterial. We quantify the situations in which off-peak traffic is sufficiently great to make it worthwhile to spend more on construction, or to give up some capacity, in order to provide very high off-peak speeds even if peak speeds are limited by congestion. We also consider the implications of differing accident rates. The results support expanding the range of highway designs that are considered when adding capacity to ameliorate urban road congestion.