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。     

基于超声导波的管道结构特性识别

文中分析了基于导波频散检测频率优化选择及限制频率等问题,研究了检测参数选择问题。根据不同换能器荷载施加方式、管道实际情况等对导波激励影响,就管道中存在的轴向连续单损及非连续性损伤,提出一种基于优化波形字典的追踪方法,分解损伤信号,评估损伤类型、大小等。文中研究了管道存在的变形损伤类型,分析了新导波检测可行性,为后续管道检测提供参考。     

长输管道智能球检漏技术应用

为研究长输管道微泄漏检测的方法,对声波检漏智能球检测性能进行了现场检测验证。智能球通过在管道内部运行,连续记录管道内的声学信号、压力信号等,通过分析检测数据中信号异常点,找出管道的泄漏点,实现对管道的微泄漏检测。通过对模拟长输管道以及成品油、原油管道进行试检测,成功检测出成品油管道上的泄漏量为0.19 L/min的漏点。通过试检测,确认了微泄漏智能球对长输管道的微泄漏有很好的识别效果。     

长输天然气管道阀门内漏在线检测技术试验研究

文中通过搭建管道阀门内漏模拟试验台,采用声发射检测方法,获得不同泄漏量下的声信号特征,根据泄漏所产生的声发射信号的特点,表征参数采用声发射率和能量。结果表明,阀门内漏时声发射信号灵敏度最强处位于阀门附近的管道下游处,假设内漏孔径一定,阀门内漏率仅与阀门压差有关。     

基于自适应滤波技术的管道泄漏检测方法

提出了一种基于小波变换和Kalman滤波相结合的自适应滤波方法,采用递推算法逐步修正滤波过程,即根据采样得到的压力信号实时地对滤波参数进行修正,使自适应滤波器能够有效地跟踪信号的变化,形成自适应降噪过程,通过自动寻优,选择最佳尺度,使之能在背景噪声较强或变化的情况下也能对管道压力信号进行有效的滤波处理,为准确检测管道泄漏和定位提供了良好基础.应用结果证明:该方法大大提高了信号处理的效率,在管道泄漏在线监测应用中效果较好.     

管道部件及典型缺陷漏磁内检测图像化显示研究

针对管道漏磁内检测图像化显示研究,采用磁偶极子模型建立漏磁场分布与缺陷特征之间对应关系.建立Φ219管道有限元仿真模型,研究永磁场对不同缺陷及管道部件的漏磁信号分析,提取管道周向360°上径向漏磁信号,并将漏磁内检测信号转化成漏磁内检测图像.结果表明,通过对漏磁数据进行图像化显示更加直观辨别缺陷及管件特征,并对后续图像...     

油气管道周向漏磁检测信号分析

用于检测管道腐蚀缺陷的漏磁检测方法已运用多年,但传统的轴向漏磁检测方法无法检测到狭长的轴向腐蚀缺陷,使用周向漏磁检测则能很好地弥补轴向漏磁检测的不足。周向漏磁检测及其信号分析在国内还处于起步阶段。采用ANSYS仿真软件建立了周向漏磁检测模型,并进行了电磁场模拟;对仿真模型提取的漏磁信号与腐蚀缺陷的尺寸信息进行了定性分析,提出应用BP神经网络定量分析油气管道腐蚀缺陷与漏磁信号的关系。结果表明：漏磁信号能定性地判断腐蚀缺陷,而使用BP神经网络方法可以定量地确定管道腐蚀缺陷尺寸,有助于提高检测的精度,同时也为油气管道安全评价提供了依据。     

基于PCM+的埋地钢制管道不开挖检测技术

文中分析了PCM+检测的基本原理,结合某燃气管网100 km管道检验实例,对PCM+检测结果进行验证分析。结果显示:PCM+可有效检测埋地钢管走向埋深、定位防腐层破损点、评价防腐层质量;管道沿线山林、荒地及公路附近区域是防腐层破损点高发区;检测大破损信号覆盖临近小破损信号,造成小破损点漏检;受检管道附近存在导电性较好的结构体并行时,信号在结构体上流失,造成误检。     

长输油气管道金属损失漏磁内检测技术研究

以管道漏磁内检测器为载体,通过对管体进行在线的漏磁内检测,可以达到量化管道缺陷、避免事故发生的目的。文中介绍了管道金属损失漏磁内检测技术,分析了油气管道漏磁内检测技术原理及漏磁内检测系统组成,利用有限元分析方法研究了管道缺陷尺寸对于漏磁场信号的影响,验证了管道漏磁内检测技术的可靠性。     

多功能管道内检测器测试平台研制

针对管道内检测技术开发方法存在的不足,设计了一种多功能管道内检测器开发测试平台,提高了管道智能检测技术相关的元件开发测试的效率。按照实验思路设计不同的检测单元,可以实现多种管道智能检测技术相关元器件的测试,操作方便、节省时间和成本。实验表明,该平台能较好地完成MBN检测信号的采集。     

An object-oriented approach to transport modelling: Software development to calculate road traffic noise

A framework for developing object-oriented software in transport modelling in proposed and demonstrated with the implementation of the calculation of road traffic noise (CORTN). Major tasks in the life cycle of an object-oriented development process are identified, and illustrated with the implementation of TRANSOOP – a software library containing 33,000 lines of C++ programming code. Software re-use from this library to produce a object-oriented noise program is compared with conventional computer programming shows that almost 90 per cent of the lines of code were drawn from TRANSOOP. Advantages of the object-oriented approach are discussed.     

A Review of Pseudo Panel Data Approach in Estimating Short-run and Long-run Public Transport Demand Elasticities

Abstract

The distinctions between short-run and long-run public transport demand elasticities have been highlighted in the literature, but the identification of long-run travel demand has been constrained by existing research methodology and the unavailability of longitudinal travel survey data. The pseudo panel data approach using repeated cross-sectional data has been suggested as an alternative to conducting a longitudinal travel demand analysis when genuine panel data are not available. This paper comprehensively reviews the background and the current practices of pseudo panel data research, and introduces the challenges in applied research that need further investigation, particularly for public transport. A case study using the Sydney Household Travel Survey data is presented to demonstrate pseudo panel data construction and to identify the short-run and long-run public transport demand elasticities using a pseudo panel data approach. The research findings suggest that the public transport demand elasticity of price in Sydney is ?0.22 in the short run and ?0.29 in the long run.     

Introducing synthetic pseudo panels: application to transport behaviour dynamics

Transportation - In this paper, a method to study travel behaviour dynamics by constructing detailed synthetic pseudo panels from repeated cross-sectional data is presented. The method is based on...     

Hierarchal assessment of noise pollution in urban areas – A case study

Noise pollution in urban areas has many harmful effects on the citizens. There are varieties of noise generation sources of which the traffic noise could be a major source. The point which is perhaps less noticed is that sound level is not the only parameter to indicate the extent and intensity of noise pollution. Situation of urban land uses, distribution of population centers and types of passages can deeply affect the concern on this environmental issue but not with a similar ratio. This article presents an overlaying technique to define noise prone areas using all different factors involved. A case study was carried out in the District 14 of Tehran Metropolitan City where there are busy streets and highways. For this purpose, the share of each criterion in noise pollution intensity was determined using Analytical Hierarchy Process (AHP). Afterwards, the map layers were overlaid based upon the relative importance of the criteria to get the final map on which the noise prone areas are specified. The developed method could be used as a tool for indirect estimation of noise pollution by which instead of direct measurement of the equivalent sound level, it would be possible to predict noise susceptible areas considering the most important influential factors.     

Environmental noise inequity in the city of Barcelona

Environmental noise is a growing concern for urban planners and public health experts. Continuous noise exposure has implications for people’s physical and mental health. Urban planning strategies are also involved in the need for regular noise assessments within urban areas. The objective of this study is to evaluate the exposure to noise of vulnerable population groups in the city of Barcelona, and to determine whether they are affected by an environmental inequity regarding this nuisance. Assessment of noise levels was performed by two methods of analysis—real measures and simulation—in order to build the noise database at block level for the 10 districts of the city. The results obtained by various statistical tests and spatial regression analysis show that children and low-income individuals are not affected by environmental inequity. On the other hand, we found a positive relationship between noise levels and the other groups considered: namely, the unemployed and people over age 65.     

The effect of road traffic noise on the prices of residential property – A case study of the polish city of Olsztyn

The key factors that determine the prices of real estate are location, technical standard of property as well as the local environment. In urban agglomerations, road traffic noise has a considerable impact on the purchasing decisions made by apartment buyers. This is a widespread problem in Central-Eastern Europe. The main objective of this study was to verify the working hypothesis that apartment prices are correlated with traffic noise levels in Olsztyn, the capital city of the Region of Warmia and Mazury in north-eastern Poland.The study was carried out in four principal stages. Firstly, traffic noise intensity was determined for apartments (objects of real estate transactions concluded in 2013), based on an acoustic map for the city of Olsztyn. The map was developed in line with the provisions of Directive 2002/49/EC of the European Parliament and of the Council of 25 June 2002 relating to the assessment and management of environmental noise. Secondly, the values of the Noise Depreciation Sensitivity Index (NDSI) were calculated. NDSI determines the percentage change in property prices per dB increase in noise levels. The distribution of unit prices of apartments was mapped relative to noise levels, and the relationships between the analyzed variables were assessed. Thirdly, linear correlations between the unit prices of apartments and noise levels were analyzed. The strength and direction of relationships between the analyzed parameters were determined based on Pearson’s correlation coefficient. In the last stage, the distribution of the unit prices of apartments was mapped by ordinary kriging, a geostatistical estimation method. The research hypothesis was confirmed by comparing the spatial distribution of traffic noise levels measured in stage 1 with the spatial distribution of apartment prices.     

Urban road traffic noise spatiotemporal distribution mapping using multisource data

Many residents are disturbed by road traffic noise which needs to be controlled and managed. The noise map is a helpful and important tool for noise management and acoustical planning in urban areas. However, the static noise map is not sufficient for evaluating noise annoyance at different temporal periods. It is necessary to develop the dynamic noise map or the noise spatiotemporal distribution. In this study, a method about urban road traffic noise spatiotemporal distribution mapping is proposed to obtain the representative road traffic noise maps of different periods. This method relies on the proposed noise spatiotemporal distribution model with two time-dependent variables - traffic density and traffic speed, and the spatiotemporal characteristics derived from multisource data. There are three steps in the method. First, the urban road traffic noise spatiotemporal distribution model is derived from the law of sound propagation. Then, the temporal characteristics are extracted from traffic flow detecting data and E-map road segment speed data by the outlier detection analysis. Finally, the noise distributions corresponding to different periods are calculated by an efficient algorithm which can save 90% above of the computing time. Moreover, a validation experiment was conducted to evaluate the accuracy of the proposed method. There is only 2.26-dB[A] mean absolute error that is within an acceptable range, which shows that the method is effective.     

Noise prediction for highways in Thailand

A model of highway traffic noise is formulated based on vehicle types. The data were collected from local highways in Thailand with free-flow traffic conditions. First, data on vehicle noise was collected from individual vehicles using sound level meters placed at a reference distance. Simultaneously, measurements were made of vehicles’ spot speeds. Secondly, are data for building the highway traffic noise model. This consists of traffic noise levels, traffic volumes by vehicle classification, average spot speeds by vehicle type, and the geometric dimension of highway sections. The free-flow traffic noise model is generated from this database. A reference energy mean emission level (the basic noise) level for each type of vehicles is developed based on direct measurement of Leq (10 s) from the real running condition of each type of vehicles. Modification of terms and parameters are used to make the model fit highway traffic characteristics and different types of vehicle.     

Air traffic assignment to reduce population noise exposure using activity-based approach

Aircraft noise has been regarded as one of the major environmental issues related to air transport. Many airports have introduced a variety of measures to reduce its impact. Several air traffic assignment strategies have been proposed in order to allocate noise more wisely. Even though each decision regarding the assignment of aircraft to routes should consider population exposure to noise, none of the air traffic assignment strategies has addressed daily migrations of population and number of people exposed to noise. The aim of this research is to develop a mathematical model and a heuristic algorithm that could assign aircraft to departure and arrival routes so that number of people exposed to noise is as low as possible, taking into account temporal and spatial variations in population in an airport’s vicinity. The approach was demonstrated on Belgrade airport to show the benefits of the proposed model. Numerical example showed that population exposure to noise could be reduced significantly by applying the proposed air traffic assignment model. As a consequence of the proposed air traffic assignment, overall fuel consumption increased by less than 1%.     

Tyre/road noise damping characteristics using nomographs and fundamental vibroacoustical relationships

Several studies have successfully developed laboratory and field measurement techniques to estimate tyre/road noise damping characteristics. However, laboratory–field noise correlations of pavement types in the form of nomographs is essential to cognize the pavements’ acoustical properties from a practical perspective. A toolkit that readily provides field tyre/road noise intensity of different pavement materials is needed. Thus, the main objective of this study was to develop nomographs with relationships for tyre/road noise versus pavement materials’ viscoelastic–vibroacoustical properties. Isothermal and isochronal nomographs of phase angle–tyre/road noise as toolkits were developed based upon well-established phase angle and noise intensities typical of mixtures, making the nomograph correlations very authentic, realistic, and novel along with benefit to predict tyre/road noise at any desired temperature and traffic speed (or frequency) combination. This study is envisaged to benefit in the discernment of road materials’ damping capabilities from vibroacoustical and field noise–viscoelastic relation aspects.