基于声发射技术的管道泄漏检测与定位方法研究

为提高管道无损检测中对小孔径泄漏检测灵敏度、泄漏信号判别准确率以及泄漏点定位精确度,提出一种基于声发射技术并结合信号频域特征提取算法的管道泄漏识别和定位方法。设计管道泄漏检测实验平台进行管道泄漏检测实验,采用经验模态分解方法和小波分解重构相结合的信号处理算法进行降噪并提取信号频域特征,研究不同孔径和不同管道压力下管道泄漏检测和泄漏点定位问题。验证了基于声发射技术并结合信号频域特征提取算法的管道泄漏检测方法的有效性。     

基于瞬态模型法的输气管道泄漏检测现场试验研究

对泄漏检测方法进行了介绍,特别对瞬态模型方法的泄漏检测原理做了详细阐述.在永京输气管线杜庄-通捷管段进行泄漏检测试验,应用实时瞬态模型方法进行泄漏检测和定位,得出了泄漏对管线流动参数的影响规律.实验结果表明:瞬态模型泄漏检测法能够准确、快速检测出泄漏,并能够对泄漏量的大小进行准确地判断,使用压力曲线相交的方法可以对泄漏...     

负压波在管道泄漏检测与定位中的应用

负压波泄漏诊断技术具有响应快、精度高、费用低等优点,被广泛应用于管道检测,其应用分泄漏判定与泄漏定位2个过程.文中对负压波技术检漏原理作了阐述,总结了负压波检漏技术应用过程中的相关方法以及存在的问题.针对其在较小压力泄漏与小泄漏检测方面的缺陷,提出结合流量平衡的泄漏检测原理,结合SCADA系统建立泄漏诊断系统,并仿真验证了其在工程中的实用性.提出未来应该重视研究负压波波形和传播模型及与其他技术的结合,以提高精度.     

输油管道泄漏监测技术及在胜利油田中的应用

对国内外输油管道泄漏检测方法进行了分析,对油田输油管道防盗监测方法进行了探讨。针对油田输油管道防盗监测问题,指出了油田输油管道防盗监测系统的关键技术是管道泄漏检测报警及泄漏点的精确定位,并介绍了胜利油田输油管道泄漏监测系统的应用情况。     

输油管线泄漏监测技术研究

文中对国内外输油管道泄漏检测技术现状进行了简要分析,并对油田输油管道泄漏监测的方法进行了探讨.针对油田输油管道泄漏监测问题,指出了油田输油管道泄漏监测系统的关键技术是管道泄漏检测预警及泄漏点的精确定位.采用流量与负压波相结合监测输油管道泄漏的方法,能较好地达到预期效果.在油田输油管道安装泄漏监测系统可以确保管道安全运行...     

油气管道泄漏检测技术

油气管道运输在国民经济中占有重要的地位,而管道泄漏危害严重。因此,选择合适的安全监测和泄漏诊断方法,在线实时动态跟踪管道运行状况,准确报告管道泄漏位置将是保障油气管道安全运行的重要步骤。文中总结了目前国内外常用的油气管道泄漏检测技术,并对其发展方向进行了说明。     

负压波在管道泄漏检测与定位中的应用

文中基于负压波检测原理,对压力管道泄漏进行实时检测及定位.分别在管线上下游设置压力传感器,泄漏产生的负压波通过管道和介质自泄漏点向管线上下游传播,其压力波信号被压力传感器检测.通过分析压力传感器采集的数据,得到上下游的泄漏负压波传播速度,并结合压力传感器捕捉到的压力波波形和上下游压力传感器接收到压力波信号的时间差对泄漏点进行定位.结果表明:该方法对泄漏的判断与定位精度取决于负压波传播速度的测定精确度.     

基于超声技术的气体泄漏容器爆炸监测系统探讨

针对当前气体泄漏事故处置中面临的问题,从气体泄漏容器发生爆炸的机理上进行了分析,对其内部气体压力、泄漏速度以及射流噪声频率等参数的关联性进行了分析与研讨,确定了通过对气体状态参数变化进行监控,达到对压力容器爆炸推测和报警的可能性。并根据当前超声技术发展与应用状况,提出了一种气体泄漏容器爆炸监测方法的设想。     

自来水管网泄漏检测的两种方法

根据管网泄漏的实际情况设计并进行了管网水泄漏的模拟实验，对泄漏产生的信号进行了测试分析，分别采用互相关分析法和人工神经网络方法对泄漏点 进行检测。实验研究表明水管泄漏互相关泮检测技术是适用可行的，但需要两个以上的传感器，而神经网络模型则只需一个传感器即可实现泄漏点的检测,体现了单传感器实现定位检测的良好前景。     

输气管道试压过程中的泄漏数学模型

天然气管道试压过程中可能发生泄漏,及时、准确地确定管道的漏失位置并进行修复,确保管道按时投产运行,是管道试压阶段的一项十分重要的工作.文中从管输天然气理论出发,结合管道试压过程的工艺特点,给出了描述输气管道泄漏的一个数学模型;应用偏微分方程数值反演方法,给出了确定泄漏位置、漏失函数的数学表达式;并给出了数值模拟的方法和步骤.文中提供的理论方法不仅适用于输气管道试压阶段的泄漏检测,而且可以推广到运行中的输气和输油管道的泄漏检测中去.     

Can induced traffic be measured by surveys?

This paper addresses the feasibility of measuring induced traffic by means of appropriately designed surveys. The problems which confront any attempt to measure induced traffic are described and discussed. They include: inherent variability of traffic data, difficulty in establishing what would have happened in the absence of the scheme, uncertainties in the attribution of cause and difficulty in determining the most appropriate time to conduct surveys. Some of these problems have no solution while others can be reduced with an appropriate programme of surveys and control studies. Calculations are made of the sample sizes required to achieve various levels of target accuracy. It is concluded that, given an appropriate programme of traffic counts including control studies and extensive screenlines, it should be possible at relatively modest cost and with reasonable precision, to measure the increases in traffic associated with a scheme and to identify how much of that increase is due to rerouteing. Any further disaggregation of this extra traffic into that which is due to change of mode, change of destination and increased frequency, is much more problematic. The basic traffic counts would need to be supplemented by a programme of public transport surveys, registration plate marking and/or roadside interviews, which would add very considerably to the cost of the exercise. However, even with considerable expenditure, adequate precision may be difficult to achieve and attribution of cause impossible to make.     

The taxi industry: working conditions and health of drivers,a literature review

The taxi industry plays an important role in urban transportation systems, both in economic and mobility terms. In the case of the former, it provides employment for a large number of people and circulates significant amounts of money. In the case of the latter, it is a flexible means of transportation capable of arriving at any destination. Although the way the taxi industry is organised varies across countries and even within countries, some factors are shared at varying latitudes of the globe. Working conditions, habits, health, and exposure to road crashes have been a subject of interest for researchers from various disciplines, including medicine, psychology, and economics. However, much of this research focuses on a part of the problem and is not mutually referential. A review of the literature may be useful not only to researchers of diverse disciplines but also to industry representatives and those public officials responsible for transportation, road safety and health policy. This article provides a comprehensive review of the working conditions of taxi drivers, their relationship to road risk exposure and their consequences on the health of workers. It also includes information on coping strategies and protective behaviors. The review is based on a Scopus database search. The search covered the period from 1990 to 2015. This initial search was complemented with other database searches, which yielded some additional studies. Our goal was to summarise existing knowledge, identify possible lines of research and suggest some practical recommendations. It would be important (a) to reduce the workload, establish adequate time for breaks, and provide access to healthcare, (b) to implement actions to promote and maintain healthy habits, (c) to diagnose, detect and treat indicators of occupational fatigue and stress, and (d) to develop programs that make it possible to evaluate work concerns and broaden coping strategies to foster positive changes.     

BOG处理工艺在液化天然气接收站中的应用

LNG接收站运行期间会产生蒸发气（BOG）,使储罐压力处于不稳定状态,因此要对BOG进行处理。BOG处理工艺分为直接输出工艺和再冷凝工艺,由于再冷凝工艺能耗小、先进、合理,因此应用广泛。文中介绍了LNG接收站再冷凝工艺的工艺流程,其要点是采用BOG压缩机负荷调节、再冷凝器高压补气和调节气液比的方法来实现再冷凝器的液位控制,并使储罐压力和BOG处理系统都达到稳定状态。     

Why railway passengers are more polluting in the peak than in the off-peak; environmental effects of capacity management by railway companies under conditions of fluctuating demand

Given the difference between peak and off-peak occupancy rates in public transport, the average emission per traveller kilometre is lower in the peak than during the off-peak period. However, in this paper it is argued that it is much more fruitful to analyse environmental effects in marginal than in average terms. The issue appears to depend on capacity management policies of public transport suppliers that are facing increases in demand both during the peak and off-peak period. A detailed analysis of capacity management of the Netherlands Railways reveals that the off-peak capacity supply is mainly dictated by the demand levels during the peak period. Topics that receive attention in the analysis are the effects of frequency increases and size of vehicle increases on environmental effects. Also environmental economies of vehicle size are taken into account in the analysis. The main conclusion is that the marginal environmental burden during the peak is much higher than is usually thought, whereas it is almost zero at the off-peak period. Thus, one arrives at a pattern that is entirely reversed compared with the average environmental burden: peak passengers are more polluting than off-peak passengers. The conclusion is that policies based on average environmental performances would lead to misleading conclusions.     

Documents

Automated short headway urban transportation systems were viewed in the early Seventies as a possible means of effecting radical change in the type of transit service available in cities. However, interest has declined and government‐sponsored efforts in this area have ceased. The decline in interest was accompanied by much debate among the advocates of the various forms of transit. However, it does not appear to reflect the potential merits and limitations of short headway systems as disclosed by analysis.

This paper provides a basis for comparing short headway systems of citywide scale with conventional transit means.

The limitations inherent in rapid rail installations are reviewed and contrasted with the performance of short headway systems. Illustrative, large‐scale guideway configurations for systems operating in the three‐second headway range are defined and levels of service are deduced using simplified heuristic methods. A basis is provided for specification and analysis of systems conforming to realistic spatial and passenger‐movement constraints.

It is concluded that automated transit systems operating in the three‐second headway range remain viable candidates for large‐scale installations.     

Driving by choice or necessity?

From just about all accounts, Americans are driving more than ever, not just to work but to shopping, to school, to soccer practice and band practice, to visit family and friends, and so on. Americans also seem to be complaining more than ever about how much they drive—or, more accurately, how much everyone else drives. However, the available evidence suggests that a notable share of their driving is by choice rather than necessity. Although the distinction between choice and necessity is not always so clear, it is important for policy makers. For necessary trips, planners can explore ways of reducing the need for or length of the trip or ways of enhancing alternatives to driving. For travel by choice, the policy implications are much trickier and touch on basic concepts of freedom of choice. This paper first develops a framework for exploring the boundary between choice and necessity based on a categorization of potential reasons for and sources of “excess driving”, and then uses in-depth one-on-one interviews guided by this framework to characterize patterns of excess driving. This research contributes to a deeper understanding of travel behavior and provides a basis for developing policy proposals directed at reducing the growth in driving.     

现金通行费缴款监管及对账系统设计探讨

针对现行的人工手段监管现金通行费缴款用时长、效率低、差错多、监管弱等缺点,文章利用前置机设计开发出现金通行费缴款监管及对账系统,通过银企数据交互,实现通行费款项的自动监管与对账,为防范各种资金安全隐患提供有力的科技手段,有效管控资金风险。     

轻柴油换热器腐蚀原因分析及防范措施

某厂重油催化裂化装置轻柴油换热器管束使用5年后发生严重腐蚀,管束外壁腐蚀严重,多处腐蚀穿孔。通过调查分析,原因是轻柴油中含有少量H2S、HCl和H2O,形成了HCl-H2S-H2O腐蚀环境,特别是低温部由于有液态水存在,腐蚀严重。通过多个方案对比,提出了采用碳钢管束渗铝技术,即节约制造费用,又提高了管束抗腐蚀性能,延长了设备运行周期。     

Generation and recovery of airborne delays in air transport

The analysis of the causes behind the appearance and propagation of delays is one of the major topics inside Air Transport Management research. Existing research focuses by and large on Air Traffic Flow Management regulations and reactionary delays; less attention has been devoted to the study of the mechanisms governing the generation and absorption of delays while airborne, in spite of their important economical and environmental consequences. Here we present a methodology to detect delay-generating events, based on the comparison of planned and real trajectories; these events are then used to characterise several aspects of the dynamics of the system, e.g. its resilience. We apply this methodology to a historical data set of flights crossing the European airspace during 2011, and observe an overall resilient system, able to absorb as much delays as it generates; yet resilience is not constant, but strongly depends on the phase of the flight, and shows high spatial and temporal heterogeneities. We anticipate the proposed methodology to open new doors for the development of a better systemic performance, by enabling the characterisation and understanding of this fundamental type of delay.     

Travel mental budgeting under road toll: An investigation based on user equilibrium

With the approach of introducing the conceptions of mental account and mental budgeting into the process of travelers’ route choice, we try to identify why the usages of tolled roads are often overestimated. Assuming that every traveler sets a mental account for his/her travel to keep track of their expense and keep out-of-pocket spending under control, it addresses these questions such that “How much money can I spend on the travel?” and “What if I spend too much?”. Route tolls that exceed the budget are much more unacceptable compared to those within budget due to the non-fungibility of money between different accounts. A simple network with two nodes and two routes is analyzed firstly, the analytical solutions are obtained and the optimal road tolls supporting the user equilibrium as a system optimum are also derived. The proposed model is then extended to a generalized network. The multiclass user equilibrium conditions with travel mental budgeting are formulated into an equivalent variational inequality (VI) problem and an equivalent minimization problem. Through analyses with numerical examples, it is found that the main reason that the usages of high tolled roads are often overestimated is due to the fact that travelers with low and moderate out-of-pocket travel budget perceive a much higher travel cost than their actual cost on the high tolled roads.