Leak detection methods for pipelines

For the early detection and localization of small leaks in pipelines a nonlinear adaptive state observer and a special correlation technique were developed, based on pressure and flow measurements at the pipeline inlet and outlet. Simulations and experiments show the results for a gas and a liquid pipeline.     

Multi-leak detection and isolation in fluid pipelines

A multi-leak detection system for pipelines is designed and tested. The multi-leak detection problem is solved using only sensors of flow and pressure at the extremes of the duct, and using the analytical redundancy given of these measurements. The leak detection design is based on a distributed pipeline model that is discretized in space and assumes a set of leaks distributed through the duct. Leak location is accomplished by evaluating the residuals of a bank of unknown input observers that are robust against one leak and sensitive to the rest. Simulation and experimental results are reported to demonstrate the effectiveness of the proposed approach when two leaks appear simultaneously.     

Frequency-based leak signature investigation using acoustic sensors in urban water distribution networks

Cities worldwide have been plagued by water pipe leaks for many decades, resulting in financial losses, public health risks, and environmental impacts. Current practice still relies heavily on periodic and localized inspection rather than long-term continuous monitoring, and since water pipelines are buried underground, leaks can often go undetected for prolonged periods. Noninvasive acoustic-based methods for continuous pipeline monitoring have gained increasing popularity the past decade thanks to the recent advances in sensing and communication technology. Previous research indicates that hydrophones, in particular, are capable of effectively detecting leak-induced acoustic waves inside a water pipe. However, most studies to date have been limited to either controlled or field test-bed settings; hence, findings might not generalize well to real-world complex pipe networks. Through rigorous leak tests conducted in a real water distribution network and an extensive analysis of the field-collected acoustic signals, the current study aims to test the applicability of low-cost, non-intrusive hydrophones attached to fire hydrants for continuous pipe monitoring and leak detection. Continuous wavelet transform, power spectrum, and band power analyses were employed to identify the leak signature and distinguish normal from leak acoustic data in various leak scenarios. Results indicate that the acoustic signals generated by the simulated leaks in this field study are characterized by a consistent increase in the power of the frequency band 150–450 Hz primarily, whereas background noise levels and conditions significantly vary depending on the location of the sensor in the network. Realistic conditions in urban water distribution networks, including background noise, complicated topology, and varying pipe size and material, are still posing significant challenges for cost-effective and widespread implementation of acoustic-based sensors to achieve continuous monitoring in water pipe networks for leak detection. Even though further research and development is required to handle the highly variable conditions of real systems, the low-cost hydrophones tested in this work demonstrated potential in detecting low-flow leaks in simple and complex pipe topologies.     

Framework for integrated oil pipeline monitoring and incident mitigation systems

Wireless Sensor Nodes (motes) have witnessed rapid development in the last two decades. Though the design considerations for Wireless Sensor Networks (WSNs) have been widely discussed in the literature, limited investigation has been done for their application in pipeline surveillance. Given the increasing number of pipeline incidents across the globe, there is an urgent need for innovative and effective solutions for deterring the incessant pipeline incidents and attacks. WSN pose as a suitable candidate for such solutions, since they can be used to measure, detect and provide actionable information on pipeline physical characteristics such as temperature, pressure, video, oil and gas motion and environmental parameters. This paper presents specifications of motes for pipeline surveillance based on integrated systems architecture. The proposed architecture utilizes a Multi-Agent System (MAS) for the realization of an Integrated Oil Pipeline Monitoring and Incident Mitigation System (IOPMIMS) that can effectively monitor and provide actionable information for pipelines. The requirements and components of motes, different threats to pipelines and ways of detecting such threats presented in this paper will enable better deployment of pipeline surveillance systems for incident mitigation. It was identified that the shortcomings of the existing wireless sensor nodes as regards their application to pipeline surveillance are not effective for surveillance systems. The resulting specifications provide a framework for designing a cost-effective system, cognizant of the design considerations for wireless sensor motes used in pipeline surveillance.     

乙二醇泄漏监测的实时报警系统

现代乙二醇是通过管道运输,且管道深埋,传统的检测方法不能很好实现,急需一种泄漏检测报警系统,针对该情况,介绍一种系统通过液位传感器获取乙二醇大量泄漏时液位,同时结合温度和湿度传感器监测渗漏,并利用自带A/D功能的STC单片机,采集传感器数据,调用全球移动通信系统(GSM)MODEM实现发送检测值,接收控制指令。测试系统结果表明:该系统能够实时地上传监测数据和实时控制检测设备,操作方便,达到了无线实时监测的要求。     

无线传感网络在管道输送监控系统中的应用研究

在国际上,管道输送是与铁路、公路、水运、航空并列的五大运输方式之一。作为一种特殊承压设备,其在石油、化工、冶金、电力等行业,以及城市燃气和供热系统中的应用越来越广。管道输送的介质容易泄漏,难以检测,如何保证管道输送系统的安全运行成为管道运输不可忽略的问题。结合管道输送的相关检测理论,提出了一种低成本、低功耗的基于无线传感器网络（WSN）技术的实时监测、实时报警的管道输送监控系统。经实验室局域网测试证明,该设计是可行的。     

PI‐PD controller design for time delay systems via the weighted geometrical center method

In this study, a PI‐PD controller tuning method is presented using the weighted geometrical center method, which is based on the calculation of the weighted geometric center of the stability region obtained by the stability boundary locus method. The proposed method for tuning of PI‐PD controller parameters (k_d,k_f,k_p and k_i ) is performed in three steps. In the first step, the (k_d,k_f) parameter region for the inner loop with PD controller is obtained, and then the weighted geometric center of this region is calculated. In the second step, the inner PD loop is reduced to a single block using the numerical values of (k_d,k_f) that are obtained in the first step. Then, the (k_p,k_i) values of the external loop with PI controller are determined by the same procedure. This tuning method has some advantages over other tuning methods in terms of simplicity and robustness. The simulation examples show that a PI‐PD controller designed using the proposed method provides good performance results when compared to other tuning methods presented in the literature.     

采用无线局域网的输油管道泄漏检测系统的设计与实现

泄漏检测是输油管道正常和高效运行的保证,快速检测出管道泄漏的发生并准确确定泄漏点的位置,能够最大限度地减少经济损失和环境污染。本文阐述了无线局域网的基本概念、传输介质、技术标准及拓扑结构。针对输油管道的地理位置特点,尝试把无线局域网与输油管道泄漏检测相结合,旨在将输油管道泄漏检测提升到远程的网络环境,以极大提高泄漏检测的水平和时效性。提出了一个基于无线局域网的输油管道实时检测系统的解决方案,实现了检测点和厂区局域网的互联,并对方案中的数据采集、数据传输、泄漏检测和定位进行了详细讨论。对于输油管道泄漏,综合运用包括小波分析在内的多种信号处理方法,能够及时、准确地检测泄漏并定位泄漏点。现场应用表明,系统报警时间〈2min,定位误差小于被检测管道长度的1．5％。     

Range free localization technique under erroneous estimation in wireless sensor networks

Minkowski timespace has the capability to overcome the limited accuracy of L₂-norm based range-free localization methods. This paper proposes the concept of Minkowski triangulation uncertainty (MTU) in wireless sensor networks (WSNs) for localization of unknown target. To set up a localization framework, triangulation uncertainty parameter is defined using Lemma 3.1. A two-stage estimation algorithm is then presented: countLocalized and countAnchor. countLocalized computes the number of localized sensor nodes by leveraging the uncertainty strategy based upon indeterminate independent measurement. countAnchor designates the anchor nodes to triangulate the unknown target by formulating a convex hull model. The convex hull is the Minkowski sum of the actual and projected positions of the two vector node positions. The proposed MTU technique establishes that the number of triangulations formed by Minkowski method is inclusive of the triangulations formed by conventional L₂-norm range of sensor nodes in a WSN. Measurement strategies such as angle, distance and positioning error are compared in the simulation. The said technique links Minkowski space to localization by ensuring efficiency in large target areas and number of nodes in manifolds. Results confirm that the MTU technique is better than the existing models by at least 12%, 50%, 5.5% and 24% in terms of localization ratio, localization error, neighbour anchor nodes and network connectivity, respectively.

     

管网检测的无线传感网络信息采集同步

无线传感网络的时钟校准决定了各节点信息采集的同步性。在供水管网泄漏检测中,各节点信息采集的时间同步误差将引入漏点的定位误差。在泛洪时间同步协议的基础上,提出拨号时间同步方案,在同步过程中采用定向拨号和线性回归相结合的方法,周期补偿终端节点间因本地时钟源频差而产生的时钟偏移,实现网络时间校准。对单跳网络,每2分钟进行1次校正,测试表明节点间的同步误差每秒在10微秒以内,累积误差不超过1毫秒,这样引起的管网漏点定位误差在1米以内,可以满足供水管网泄漏检测的要求。     

An automated nondestructive testing system for the surface of pressure pipeline welds

Pressure pipelines are widely used in hydropower generation, oil and gas transmission, and other fields. After years of operation, a pressure pipeline needs regular maintenance to ensure its safety. At present, manual detection methods are unable to meet this demand. An automatic pressure pipeline detection technology is urgently needed to achieve improved efficiency and accuracy. On the basis of the above requirements, a wall-climbing robot is designed for automatic pressure pipe inspection and maintenance tasks. Moreover, rapid nondestructive testing of welds on the inner surface of pressure pipelines was performed, and a weld tracking function was developed for wall-climbing robots. We propose an algorithm framework for weld recognition and centerline extraction by combining computer vision technology with traditional image processing technology using visual images. The experimental verification of the wall-climbing robot designed in this paper and the algorithm framework for weld recognition and centerline extraction were performed based on actual pressure pipelines. The results show that the algorithm framework developed based on the wall-climbing robot equipped with an industrial camera for pressure pipeline weld detection can achieve greatly improved efficiency, and the actual weld identification accuracy can exceed 90%, which is very meaningful for practical applications.     

Modelling and solving the intrusion detection problem in computer networks

We introduce a novel anomaly intrusion detection method based on a Within-Class Dissimilarity, WCD. This approach functions by using an appropriate metric WCD to measure the distance between an unknown user and a known user defined respectively by their profile vectors. First of all, each user performs a set of commands (events) on a given system (Unix for example). The events vector of a given user profile is a binary vector, such that an element of this vector is equal to “1” if an event happens, and to “0” otherwise. In addition to this, each user's class k has a typical profile defined by the vector P_k, in order to test if a new user i defined by its profile vector P_i belongs to the same class k or not. The P_k vector is a weighted events vector E_k, such that each weight represents the number of occurrences of an event e_k. If the “distance” d_ki (measured by a dissimilarity parameter) between an unknown profile P_i and a known profile P_k is reasonable according to a given threshold and to some constraints, then there is no intrusion. Else, the user i is suspicious. A simple example illustrates the WCD procedure. A survey of intrusion detection methods is presented.Our proposed method based on clustering users and using simple statistical formulas is very easy for implementation.     

<Emphasis Type="Italic">k</Emphasis>-Nearest-Neighbor Clustering and Percolation Theory

Let P be a realization of a homogeneous Poisson point process in ℝ ^d with density 1. We prove that there exists a constant k _d , 1<k _d <∞, such that the k-nearest neighborhood graph of P has an infinite connected component with probability 1 when k≥k _d . In particular, we prove that k ₂≤213. Our analysis establishes and exploits a close connection between the k-nearest neighborhood graphs of a Poisson point set and classical percolation theory. We give simulation results which suggest k ₂=3. We also obtain similar results for finite random point sets. Part of the work was done while S.-H. Teng was at Xerox Palo Alto Research Center and MIT. The work of F.F. Yao was supported in part by a grant from the Research Grants Council of the Hong Kong Special Administrative Region, China [Project No. CityU 1165/04E].     

一种新型石油管道压力传感器的设计

提出一种新型带有无线数据传输功能的石油管道压力传感器。传感器采用十字梁结构设计,应变计全桥输出信号随管道内压力改变而变化。传感器通过无线传输的方式将监测数据传输到监测中心,对管道压力进行实时监测。通过应变计性能测试和系统标定,表明该传感器具有较好的灵敏度和线性度。     

All stabilizing PID controllers for time delay systems

This paper presents a method to compute the entire set of stabilizing PID controller parameters for an arbitrary (including unstable) linear time delay system. The main contribution is to handle the infinite number of stability boundaries in the (k_d,k_i)-plane for a fixed proportional gain k_p. For retarded open loops, it is shown that the stable region in the (k_d,k_i)-plane consists of convex polygons. Concerning neutral loops, a new phenomenon is introduced. For certain systems and certain k_p, the exact stable region in the (k_d,k_i)-plane can be described by the limit of a sequence of polygons with an infinite number of vertices. This sequence may be well approximated by convex polygons. Moreover, the paper describes a necessary condition for k_p-intervals potentially having a stable region in the (k_d,k_i)-plane. Thus, the set of stabilizing controller parameters can be calculated after gridding k_p in these intervals. A Matlab tool implementing the presented method is available.     

无线传感器网络定位综述

无线传感器网络定位在当前需求的推动下,已经成为热点研究领域。本文分别从定位方式、定位技术以及定位原理3个方面对无线传感器网络定位研究进行了梳理并展开了综述;其次,分别对3种基于无线传感器网络的定位算法进行了描述;然后,阐述了目前无线传感器网络定位的热点问题,其中,针对定位研究中非视距干扰问题,分别从非视距误差的数值特征和统计特征两个方面的研究现状进行了分析,并对基于多传感器融合的无线传感器网络定位方法进行了分析和总结;最后,针对无线传感器网络定位应用的挑战进行了展望。     

PID Stabilization of Retarded‐Type Time‐Delay System

An analytical method is proposed to construct the stabilizing PID region of a retarded‐type time‐delay system, based on Pontryagin's results and a generalization of the Hermite‐Biehler theorem. It is shown that the stable region in the (k_i, k_d)‐plane is made up of some convex polygons for a fixed k_p, and the whole region in the (k_p, k_i, k_d)‐space is comprised of some polyhedrons, each of which is mapped onto a real used string. Additionally, a method for determining the feasible k_p‐intervals is given in this paper. Two examples are employed to illustrate and verify the construction procedure of the stabilizing PID region in detail.     

Diagnosis and Localization of Pipeline Leak Based on Fuzzy Decision-making Method

A leak detection plays a key role in the overall integrity monitoring for a oil pipeline system.A fuzzy decision-making approach to pipeline leak localization is proposed in this paper. The two main methods,pressure gradient localization and negative pressure wave localization,are combined with fuzzy logical decision-making method to form a novel fault diagnosis scheme.The combination scheme can improve the precision of localization.An application example,14km long oil pipeline leak detection and localization,is illustrated.This method is compared with others through practical experiments and its validity is confirmed by the results.     

Blue‐to‐red electroluminescence from organic light‐emitting field‐effect transistor using various organic semiconductor materials

Abstract— We succeeded in observing visible bright electroluminescence from blue to red in an organic field‐effect‐transistor structure. In particular, tetraphenylpyrene (TPPy) demonstrated a high photoluminescence efficiency of φ_PL ～ 70% and a maximum electroluminescence efficiency of η_EL ～ 10^?2%. The electroluminescence efficiency (ηEL) was enhanced by using a short source‐to‐drain channel length (L_SD < 1 μm). In addition, doping the TPPy layer with highly fluorescent rubrene molecules led to an #PL of ～100% and a maximum ηEL of 0.8%.     

Hybrid atmospheric correction algorithms and evaluation on VNIR/SWIR Hyperion satellite data for soil organic carbon prediction

ABSTRACT

Visible near-infrared and shortwave infrared data acquired by spaceborne sensors contain atmospheric noise, along with target reflectance that may affect its end applications, e.g. geological, vegetation, soil surface studies, etc. Several atmospheric correction algorithms have been already developed to remove unwanted atmospheric components of a spectral signature of Earth targets obtained from airborne/spaceborne hyperspectral image. In spite of this, choosing of an appropriate atmospheric correction algorithm is an ongoing research. In this study, two hybrid atmospheric correction (HAC) algorithms incorporating a modified empirical line (EL_m) method were proposed. The first HAC model (named HAC_1) combines (i) a radiative transfer (RT) model based on the concepts of RT equations, which uses real-time in situ atmospheric and climatic data, and (ii) an EL_m technique. The second one (named HAC_2) combines (i) the well-known ATmospheric CORrection (ATCOR) model and (ii) an EL_m technique. Both HAC algorithms and their component single atmospheric correction algorithms (ATCOR, RT, and EL_m) were applied to radiance data acquired by Hyperion satellite sensor over study sites in Australia. The performances of both HAC algorithms were analysed in two ways. First, the Hyperion reflectances obtained by five atmospheric correction algorithms were analysed and compared using spectral metrics. Second, the performance of each atmospheric correction algorithm was analysed for prediction of soil organic carbon (SOC) using Hyperion reflectances obtained from atmospheric correction algorithms. The prediction model of SOC was built using partial least square regression model. The results show that (i) both the hybrid models produce a good spectrum with lower Spectral Angle Mapper and Spectral Information Divergence values and (ii) both hybrid algorithms provided better SOC prediction accuracy, in terms of coefficient of determination (R²), residual prediction deviation (RPD), and ratio of performance to interquartile (RPIQ), with R² ≥ 0.75, RPD ≥ 2, and RPIQ ≥ 2.58 than single algorithms. HAC algorithms, developed using EL_m technique, may be recommended for atmospheric correction of Hyperion radiance data, when archived Hyperion reflectance data have to be used for SOC prediction mapping.