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  Subjects -> ENERGY (Total: 275 journals)
    - ENERGY (185 journals)
    - ENERGY: GENERAL (8 journals)
    - NUCLEAR ENERGY (23 journals)
    - PETROLEUM AND GAS (49 journals)
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ENERGY (185 journals)                  1 2 | Last

Advances in Building Energy Research     Hybrid Journal   (Followers: 12)
Advances in Energy and Power     Open Access   (Followers: 3)
Advances in High Energy Physics     Open Access   (Followers: 12)
Advances in Natural Sciences: Nanoscience and Nanotechnology     Open Access   (Followers: 14)
American Journal of Energy Research     Open Access   (Followers: 7)
Annals of Nuclear Energy     Hybrid Journal   (Followers: 7)
Annual Reports on NMR Spectroscopy     Full-text available via subscription   (Followers: 1)
Annual Review of Resource Economics     Full-text available via subscription   (Followers: 11)
Applied Nanoscience     Open Access   (Followers: 10)
Applied Solar Energy     Hybrid Journal   (Followers: 12)
Archives of Thermodynamics     Open Access   (Followers: 4)
Artificial Photosynthesis     Open Access  
Atomic Energy     Hybrid Journal   (Followers: 5)
Atoms for Peace: an International Journal     Hybrid Journal   (Followers: 4)
Batteries     Open Access  
Biofuels     Hybrid Journal   (Followers: 9)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 6)
Bulletin de droit nucleaire     Full-text available via subscription   (Followers: 1)
Canadian Journal of Remote Sensing     Full-text available via subscription   (Followers: 13)
Canadian Water Resources Journal     Hybrid Journal   (Followers: 20)
Carbon Management     Hybrid Journal   (Followers: 6)
Catalysis for Sustainable Energy     Open Access   (Followers: 2)
CERN courier. International journal of high energy physics     Free  
Chain Reaction     Full-text available via subscription  
Clefs CEA     Full-text available via subscription   (Followers: 1)
Computational Water, Energy, and Environmental Engineering     Open Access   (Followers: 2)
Continental Journal of Renewable Energy     Open Access   (Followers: 11)
Current Sustainable/Renewable Energy Reports     Hybrid Journal   (Followers: 4)
Dams and Reservoirs     Hybrid Journal   (Followers: 3)
Development of Energy Science     Open Access   (Followers: 3)
Distributed Generation & Alternative Energy Journal     Hybrid Journal   (Followers: 1)
E3S Web of Conferences     Open Access  
Economics and Policy of Energy and the Environment     Full-text available via subscription   (Followers: 3)
Electrical and Power Engineering Frontier     Open Access   (Followers: 9)
Energy     Partially Free   (Followers: 26)
Energy & Fuels     Full-text available via subscription   (Followers: 25)
Energy and Buildings     Hybrid Journal   (Followers: 7)
Energy and Emission Control Technologies     Open Access  
Energy and Environment Focus     Free  
Energy and Environment Research     Open Access   (Followers: 9)
Energy and Environmental Engineering     Open Access  
Energy and Power     Open Access   (Followers: 3)
Energy and Power Engineering     Open Access   (Followers: 10)
Energy Conversion and Management     Hybrid Journal   (Followers: 8)
Energy Efficiency     Hybrid Journal   (Followers: 11)
Energy Harvesting and Systems : Materials, Mechanisms, Circuits and Storage     Hybrid Journal   (Followers: 1)
Energy Journal The     Full-text available via subscription  
Energy Law Journal     Full-text available via subscription   (Followers: 2)
Energy Materials: Materials Science and Engineering for Energy Systems     Hybrid Journal   (Followers: 19)
Energy Policy     Partially Free   (Followers: 47)
Energy Prices and Taxes     Full-text available via subscription   (Followers: 5)
Energy Procedia     Open Access   (Followers: 4)
Energy Research & Social Science     Full-text available via subscription  
Energy Science & Engineering     Open Access   (Followers: 4)
Energy Science and Technology     Open Access   (Followers: 12)
Energy Strategy Reviews     Partially Free   (Followers: 6)
Energy Studies Review     Open Access   (Followers: 4)
Energy Systems     Hybrid Journal   (Followers: 11)
Energy Technology     Partially Free   (Followers: 3)
Energy Technology & Policy     Open Access  
Energy, Sustainability and Society     Open Access   (Followers: 19)
Environmental Progress & Sustainable Energy     Hybrid Journal   (Followers: 5)
EPJ Photovoltaics     Open Access   (Followers: 1)
Facta Universitatis, Series : Electronics and Energetics     Open Access  
Foundations and Trends® in Renewable Energy     Full-text available via subscription   (Followers: 1)
Frontiers in Energy     Hybrid Journal   (Followers: 4)
Frontiers in Energy Research     Open Access   (Followers: 1)
Fuel and Energy Abstracts     Full-text available via subscription   (Followers: 5)
Functional Materials Letters     Hybrid Journal   (Followers: 1)
Gcb Bioenergy     Hybrid Journal   (Followers: 3)
Geothermal Energy     Open Access   (Followers: 1)
GeoWorld     Full-text available via subscription   (Followers: 2)
Green     Full-text available via subscription   (Followers: 2)
IEA Electricity Information     Full-text available via subscription   (Followers: 5)
IEA Natural Gas Information     Full-text available via subscription   (Followers: 4)
IEEE Power and Energy     Full-text available via subscription   (Followers: 12)
IEEE Transactions on Energy Conversion     Hybrid Journal   (Followers: 7)
IEEE Transactions on Nuclear Science     Hybrid Journal   (Followers: 7)
IEEE Transactions on Power Systems     Hybrid Journal   (Followers: 11)
IET Power Electronics     Hybrid Journal   (Followers: 13)
Ingeniería Energética     Open Access  
Innovations : Technology, Governance, Globalization     Hybrid Journal   (Followers: 6)
International Journal of Alternative Propulsion     Hybrid Journal   (Followers: 1)
International Journal of Ambient Energy     Hybrid Journal   (Followers: 2)
International Journal of Applied Power Engineering     Open Access   (Followers: 2)
International Journal of Clean Coal and Energy     Open Access   (Followers: 4)
International Journal of Coal Science & Technology     Open Access  
International Journal of Critical Infrastructure Protection     Hybrid Journal   (Followers: 5)
International Journal of Electric and Hybrid Vehicles     Hybrid Journal   (Followers: 5)
International Journal of Emerging Electric Power Systems     Full-text available via subscription   (Followers: 5)
International Journal of Emerging Multidisciplinary Fluid Sciences     Full-text available via subscription  
International Journal of Energy and Environmental Engineering     Open Access   (Followers: 2)
International Journal of Energy and Power     Open Access   (Followers: 7)
International Journal of Energy and Statistics     Hybrid Journal  
International Journal of Energy Engineering     Open Access   (Followers: 12)
International Journal of Energy Research     Hybrid Journal   (Followers: 10)
International Journal of Energy Science     Open Access   (Followers: 1)
International Journal of Flow Control     Full-text available via subscription   (Followers: 3)
International Journal of Global Energy Issues     Hybrid Journal   (Followers: 6)
International Journal of Green Energy     Hybrid Journal   (Followers: 6)

        1 2 | Last

Journal Cover   Structural Control and Health Monitoring
  [SJR: 1.351]   [H-I: 26]   [7 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1545-2255 - ISSN (Online) 1545-2263
   Published by John Wiley and Sons Homepage  [1607 journals]
  • Robust force tracking control scheme for MR dampers
    • Authors: Felix Weber
      Abstract: This paper describes a novel force tracking control scheme for magnetorheological (MR) dampers. The feed forward, which is derived by a control‐oriented mapping approach to reduce modelling effort of the inverse MR damper behaviour, compensates for the main steady‐state nonlinearity of the MR damper force and thereby linearizes the plant. The resulting force tracking error due to model imperfections and parameter uncertainties is reduced by parallel proportional and integral feedback gains that are formulated based on the absolute values of actual MR damper force and desired control force due to the semi‐active constraint of the MR damper force. The feedback is enriched by an anti‐reset windup to account for MR damper current constraints and the concept of current reversal to accelerate demagnetization. The experimental validations of the force tracking control scheme on a rotational and a long‐stroke MR damper demonstrate its robustness and efficacy. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-04-14T00:58:23.226712-05:
      DOI: 10.1002/stc.1750
       
  • Issue Information
    • Abstract: No abstract is available for this article.
      PubDate: 2015-04-08T00:50:45.417625-05:
      DOI: 10.1002/stc.1695
       
  • An electromagnetic vibration absorber with harvesting and tuning
           capabilities
    • Authors: A. Gonzalez‐Buelga; L. R. Clare, S. A. Neild, S. G. Burrow, D. J. Inman
      Abstract: This paper describes the development of an electromagnetic vibration absorber (EVA) with energy recovery and frequency tuning control capabilities. The essential component of the EVA is an electromagnetic transducer, interfacing between electrical and mechanical domains, connected to an external electrical circuit. So far, the use of electromagnetic devices in vibration‐control applications has been driven by energy‐harvesting applications. In these works, the electromagnetic transducer acts as a damper in the mechanical domain by connecting a resistance across the terminals of the device. By emulating the resistive components, some of the power that would have been dissipated in the resistor can be converted into usable power. The use of electromagnetic devices also opens the door (i) to the synthesis of more complex networks in the electrical domain, most of them impractical or too complicated to be synthesized mechanically and (ii) to the development of frequency tuning networks. We consider the possibility of using an EVA along with a resistance emulator to give a self‐powered adaptive EVA. We explore the switching in of different elements across the terminals of the electromagnetic transducer in order to be able to derive new low‐powered control schemes for better vibration absorption. With the underlying goal to develop high performance, energy‐efficient vibration‐control devices, a small scale EVA device was tested, coupled with a virtual host structure. The results presented here demonstrate the potential for self‐tuning of such a device. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-04-07T04:11:32.246912-05:
      DOI: 10.1002/stc.1748
       
  • Investigation of fatigue performance of welded details in long‐span
           steel bridges using long‐term monitoring strain data
    • Authors: Yang Deng; Yang Liu, Dong‐Ming Feng, Ai‐Qun Li
      Abstract: Monitoring strain data provides possibilities for the fatigue assessment of the critical components in real structures under the operational conditions. This paper presents a case study on the investigation of fatigue performance of welded details. Long‐term monitoring strain data of 4 years between 2006 and 2009 collected by the structural health monitoring system mounted on the Runyang Suspension Bridge and Runyang Cable‐stayed Bridge are utilized. The study focuses on two aspects: (i) the effects of different strain components in the raw strain data on the fatigue damage assessment and (ii) the necessity of long‐term strain measurement for fatigue evaluation. The results indicate that temperature effect on the stress range spectrum is negligible. The enormous low‐level stress cycles caused by random interference would result in erroneous equivalent stress ranges and number of cycles, and thus should be eliminated from the stress range spectrum. Through in‐depth analysis of monitoring strain data in three special months and in 3 years, respectively, it is revealed that short‐term data monitored in a few days and medium‐term data monitored in a few months are not adequate enough to reveal the actual fatigue behaviors of steel bridges and would give inaccurate fatigue life prediction. Finally, the fatigue life predictions of two types of welded details by considering traffic flow growth are carried out. Lessons learned from the long‐term monitoring are expected to enhance our understanding in fatigue performances of steel bridges. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-03-26T23:22:11.036488-05:
      DOI: 10.1002/stc.1747
       
  • Tuned liquid column ball damper for seismic vibration control
    • Authors: Sourav Gur; Koushik Roy, Sudib Kumar Mishra
      Abstract: Tuned liquid column damper (TLCD) is a passive control device for vibration control of structures. Recently, the tuned liquid column ball damper (TLCBD) has been introduced for performance enhancement over the original TLCD. In this paper, the efficiency of the TLCBD is assessed under random earthquake events. The response of a single‐degree‐of‐freedom system with TLCBD is evaluated by stochastic analysis and compared with the TLCD. The study reveals significantly improved performance of TLCBD over TLCD in terms of reducing response of the structure as well as the liquid column. The performance largely hinges on the optimum tuning ratio and the ball‐to‐tube diameter ratio values, which are proposed herein. The parametric studies establish the performance robustness of the TLCBD under loading and parametric variations. Furthermore, the accuracy of the optimal stochastic responses is verified through deterministic response analysis under recorded seismic motions. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-03-26T23:03:53.40662-05:0
      DOI: 10.1002/stc.1740
       
  • Elimination of torsion and pounding of isolated asymmetric structures
           under near‐fault ground motions
    • Authors: Mohammed Ismail
      Abstract: This paper aims at forcing the isolated asymmetric structures to behave as symmetric structures with, theoretically, no absolute torsional responses. In addition, it attempts to provide efficient protection to such structures against severe near‐fault ground motions considering limited seismic gaps with no seismic pounding. To achieve these goals, the recently proposed multi‐feature roll‐in‐cage (RNC) isolator is used. An improved full‐feature sap2000 model (Computers and Structures, Inc., Walnut Creek, CA, USA) is first developed for the RNC isolator then validated using analytical and experimental results. Next, an RNC isolation method that could eliminate the eccentricities between both structural centers of mass and rigidity is employed to theoretically remove structural torsion. It is based on using different isolator sets with unequal elastic stiffness to allow for shifting the center of rigidity at the isolation level, having dominant lateral behavior in case of isolated structures, to coincide with the structural center of mass above that level. After that, the ability of the RNC isolator to provide efficient seismic isolation considering relatively limited seismic gaps is investigated under unidirectional and bidirectional near‐fault earthquakes. This could be attained through the independent source of high hysteretic damping and pre‐yield elastic stiffness of the RNC isolator, in addition to its integrated self‐stopping or buffer mechanism. The obtained results demonstrate the capability of the RNC isolator to, theoretically, eliminate torsional responses of isolated asymmetric structures besides providing relatively efficient seismic isolation, with no seismic pounding, considering insufficient or limited seismic gaps under severe near‐fault unidirectional and simultaneous bidirectional ground motions. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-03-24T00:44:08.518601-05:
      DOI: 10.1002/stc.1746
       
  • Investigation of fiber Bragg grating strain sensor in dynamic tests of
           small‐scale dam model
    • Authors: Shuli Fan; Liang Ren, Jianyun Chen
      Abstract: For the low strength of model material, it is difficult to test the deformation of the small‐scale dam model during shaking table tests. Based on the principle friction, a type of fiber Bragg grating (FBG) strain sensor with enhanced strain sensitivity was developed to measure the strain of low‐strength material. The principle of the small‐scale FBG strain sensor and its characteristics of strain transferring were discussed using a calibration test. Dynamic strain and residual strain of dam model were measured using FBG strain sensors embedded in models and compared with data calculated by numerical analysis. The results demonstrate that this type of FBG strain sensor shows advantages of high sensitivity, ease for installation, and high reliability. FBG sensors adhere to model material completely. The strains measured from FBG sensors are agreed with the results calculated by numerical simulation. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-03-24T00:28:42.47323-05:0
      DOI: 10.1002/stc.1745
       
  • Structural model updating of an in‐service bridge using dynamic data
    • Authors: Antonio J. Garcia‐Palencia; Erin Santini‐Bell, Jesse D. Sipple, Masoud Sanayei
      Abstract: Recent developments in instrumentation, modeling, and data collection have advanced the state of the art in structural health monitoring in many engineering areas. However, the application of these developments in civil engineering infrastructure still presents some challenges. With approximately 11% of the bridges in the USA classified as structural deficient and billions of dollars required for either replacement or rehabilitation, transportation authorities require more efficient methods for condition assessment of existing bridges and funding allocation. In this article, a frequency response function‐based, two‐step model updating technique is applied to the Powder Mill Bridge. The Powder Mill Bridge is a typical overpass bridge constructed in 2009 and located in the town of Barre, Massachusetts. The goal of this research is to obtain a baseline finite element model that captures the bridge's behavior in its healthy condition using experimentally collected data from testing performed in 2010. The proposed two‐step protocol successfully identified stiffness, mass, and damping parameters in simulated scenarios with contamination from measurement errors. Likewise, experimental validation using field collected dynamic data produced parameters that were reflective of the field‐observed structural condition of the tested bridge. If the model updating protocol is repeated using collected data at standard intervals, the baseline could be eventually used to identify changes in structural parameters that are indicative of damage. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-03-19T04:47:53.822413-05:
      DOI: 10.1002/stc.1742
       
  • Data‐based structural health monitoring using small training data
           sets
    • Authors: Luciana Balsamo; Raimondo Betti
      Abstract: One of the most efficient ways to solve the damage detection problem using the statistical pattern recognition approach is that of exploiting the methods of outlier analysis. Cast within the pattern recognition framework, damage detection assesses whether the patterns of the damage‐sensitive features extracted from the response of the system under unknown conditions depart from those drawn by the features extracted from the response of the system in a healthy state. The metric dominantly used to measure the testing feature's departure from the trained model is the Mahalanobis Squared Distance (MSD). Evaluation of the MSD requires the use of the inverse of the training population's covariance matrix. It is known that when the feature dimensions are comparable with the number of observations, the covariance matrix is ill‐conditioned and numerically problematic to invert. When the number of observations is smaller than the feature dimensions, the covariance matrix is not even invertible. In this paper, four alternatives to the canonical damage detection procedure are investigated to address this issue: data compression through discrete cosine transform, use of pseudo‐inverse of the covariance matrix, use of shrinkage estimate of the covariance matrix, and a combination of the three aforementioned techniques. The performance of the four methods is first studied on simulated data and then compared using the experimental data recorded on a four‐story steel frame excited at the base by means of a shaking table available at the Carleton Laboratory at Columbia University. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-03-19T04:41:59.712141-05:
      DOI: 10.1002/stc.1744
       
  • A finite‐element based damage detection technique for nonlinear
           reinforced concrete structures
    • Authors: Ai‐Lun Wu; Jann N. Yang, Chin‐Hsiung Loh
      Abstract: Civil engineering structures, such as reinforced concrete frames, exhibit nonlinear behavior when subject to dynamic loads, such as earthquakes. The ability to detect damages in structures after a major earthquake will ensure their reliability and safety. Innovative analysis techniques for damage detection of structures have been extensively studied recently. However, practical and effective local damage identification techniques remain to be developed for nonlinear structures, in particular hysteretic reinforced concrete (RC) structures. In this paper, a smooth hysteretic model with stiffness and strength degradations and with the pinching effect is used to represent the dynamic characteristics of RC frames. A system identification method capable of detecting damages in nonlinear structures, referred to as the adaptive quadratic sum‐square error with unknown inputs (AQSSE‐UI), will be used to detect damages in hysteretic RC frames. The performance of the AQSSE‐UI technique will be demonstrated by the experimental data. A one‐third‐scale two‐story RC frame has been tested experimentally on the shake table at National Center for Research on Earthquake Engineering, Taiwan. This two‐story RC frame was subject to different levels of ground excitations back to back. The RC frame is firstly considered as a time‐varying linear model with rotational springs at joints, and the tracking of the degradation of the time‐varying stiffness parameters is carried out using the AQSSE‐UI technique. Then the same RC frame is considered as a nonlinear structure consisting of plastic hinges at joints following a smooth hysteretic model. Experimental results show that the AQSSE‐UI technique is quite effective for tracking (i) the stiffness degradation of time‐varying linear structures and (ii) the nonlinear hysteretic parameters with stiffness and strength degradations as well as the pinching effect. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-03-13T01:33:17.511086-05:
      DOI: 10.1002/stc.1736
       
  • Damage detection in structures using a transmissibility‐based
           Mahalanobis distance
    • Authors: Yun‐Lai Zhou; E. Figueiredo, N. Maia, R. Sampaio, R. Perera
      Abstract: In this paper, a damage‐detection approach using the Mahalanobis distance with structural forced dynamic response data, in the form of transmissibility, is proposed. Transmissibility, as a damage‐sensitive feature, varies in accordance with the damage level. Besides, Mahalanobis distance can distinguish the damaged structural state condition from the undamaged one by condensing the baseline data. For comparison reasons, the Mahalanobis distance results using transmissibility are compared with those using frequency response functions. The experiment results reveal quite a significant capacity for damage detection, and the comparison between the use of transmissibility and frequency response functions shows that, in both cases, the different damage scenarios could be well detected. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-02-27T03:51:56.089969-05:
      DOI: 10.1002/stc.1743
       
  • Novelty detection for SHM using raw acceleration measurements
    • Authors: Vinicius Alves; Alexandre Cury, Ney Roitman, Carlos Magluta, Christian Cremona
      Abstract: Structural health monitoring is a problem that can be addressed at many levels. One of the most promising approaches used in damage assessment problems is based on pattern recognition. The idea is to extract features from data that characterize only the normal condition and to use them as a template or reference. During structural monitoring, data are measured, and appropriate features are extracted as well as compared with the reference. Any significant deviations are considered as signal novelty or possible damage. Several studies present in the literature are based on the comparison of measured vibration data such as natural frequencies and vibration modes in undamaged and damaged states of the structure. This methodology has proven to be efficient; however, its application may not be the most adequate in cases where the engineer needs to know with certain imperativeness the condition of a given structure. This paper proposes a novelty detection approach where the concept of symbolic data analysis is used to manipulate raw vibration data (i.e., acceleration measurements). These quantities (transformed into symbolic data) are combined to three unsupervised classification techniques: hierarchy agglomerative, dynamic clouds and soft c‐means clustering. In order to attest the robustness of this approach, experimental tests are performed on a simply supported beam considering different damage scenarios. Moreover, this paper presents a study with tests conducted on a motorway bridge, in France, where thermal variation effects also play a major role. In summary, results obtained confirm the efficiency of the proposed methodology. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-02-27T02:17:29.907637-05:
      DOI: 10.1002/stc.1741
       
  • Free vibrations of a two‐cable network with near‐support
           dampers and a cross‐link
    • Authors: Haijun Zhou; Xia Yang, Limin Sun, Feng Xing
      Abstract: Vibration mitigation of cables is a crucial problem for cable‐supported bridges. A hybrid method for cable vibration mitigation that combines cross‐ties and dampers has been applied in engineering practice; however, the damping and frequency of this kind of system needs to be further assessed. In this paper, a system of two parallel cables with a cross‐link and dampers located near the cable anchorage is proposed and analyzed. Based on displacement continuity and force equilibrium at the damper and spring locations, the characteristic equation of the system is derived by applying the transfer matrix method. The complex characteristic equation is then numerically solved to obtain the modal damping and frequencies. The damping and frequency characteristics are discussed in detail for the case when the two cables are identical. Special attention is given to the case when only one damper is installed, and the approximate damping evaluation formulations are proposed when spring stiffness approaches infinity. Effects of mass–tension ratio, cable length ratio and frequency ratio on damping are also addressed. Finally, a case study of multimode damping optimization for bridge hangers is given. The results of this paper could be useful for vibration mitigation of two parallel cables and further development of design guidelines for cable networks with attached dampers. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-02-18T02:57:15.196647-05:
      DOI: 10.1002/stc.1738
       
  • Spatial H∞ approach to damage‐tolerant active control
    • Authors: Nazih Mechbal; Eurípedes G. O. Nóbrega
      Abstract: Damage‐tolerant active control is a new research area targeting to adapt fault‐tolerant control methods to mechanical structures submitted to damage. Active vibration control is a mature engineering area, using modern control methods to address structural issues that may result from excessive vibration. However, the subject of structural vibration control under damage represents a novel subject in the literature. There are some difficulties to adapt regular controller designs to active control, which may not result in good performance even for healthy structures. Fault detection and diagnosing research has conducted to the development of the fault‐tolerant control area, whose methods are equally hard to translate to damaged structure control. Spatial active vibration control encompasses some techniques that present important features to structure control; however, this is not necessarily true in the general control design area, where spatial constraints are normally not involved. In this paper, we propose an investigation of these spatial techniques, applied to structural damage control. Several new strategies for vibration control are presented and analyzed, aiming to attain specific objectives in damage control of mechanical structures. Finite element models are developed for a case study structure, considering healthy and three different damage conditions, which are used to design controllers, adopting an approach based on an H∞ spatial norm, and according to some of the proposed strategies. Discussion of the achieved results contributes to clarify the main concepts related to this new research area, and controller performance analysis permits to foresee successful real case application of the techniques here described. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-02-17T03:26:32.088281-05:
      DOI: 10.1002/stc.1729
       
  • Guided wave propagation in high‐speed train axle and damage
           detection based on wave mode conversion
    • Authors: Fucai Li; Xuewei Sun, Jianxi Qiu, Limin Zhou, Hongguang Li, Guang Meng
      Abstract: Axle is the main bearing part of the bogie system on a high‐speed train and is therefore requested on a higher reliability level. The high‐speed train axle is thick‐walled hollow cylindrical structure with variable cross section, which complicates ultrasonic guided wave propagation in the structure. Characteristics of the guided wave propagation in the train axle are systematically investigated in this study, so as to explore guided wave‐based structural health monitoring (SHM) method for this kind of structure. Piezoelectric patches are used as actuator to excite waves in the axle. Generated wave signals using single actuator and circumferential, limited number of actuator configurations are compared to optimize the transducer network. The longitudinal wave modes are therefore selected for damage detection of this kind of structure. Based on the analytical and finite element analysis (FEA), when the symmetric longitudinal wave modes meet defect, if have, in the train axle with variable cross section, mode conversion will happen and asymmetric flexural wave modes are therefore generated. Wave mode conversion‐based SHM technique is consequently proposed. The FEA results demonstrate the feasibility of guided wave‐based SHM technique for high‐speed train axle. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-02-17T01:02:21.826163-05:
      DOI: 10.1002/stc.1739
       
  • Data compression of very large‐scale structural seismic and typhoon
           responses by low‐rank representation with matrix reshape
    • Authors: Yongchao Yang; Satish Nagarajaiah, Yi‐Qing Ni
      Abstract: The intrinsic low‐dimensional structure, which is implicit in the large‐scale data sets of structural seismic and typhoon responses, is exploited for efficient data compression. Such a low‐dimensional structure, empirically, stems from few modes that are active in the structural dynamic responses. Originally, limited to the sensor and time‐history dimension, the structural seismic and typhoon response data set generally does not have an explicit low‐rank representation (e.g., by singular value decomposition or principal component analysis), which is critical in multi‐channel data compression. By the proposed matrix reshape scheme, the low‐rank structure of the large‐scale data set stands out, regardless of the original data dimension. Examples demonstrate that the developed method can significantly compress the large‐scale structural seismic and typhoon response data sets, which were recorded by the structural health monitoring system of the super high‐rise Canton Tower. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-02-17T00:25:57.338843-05:
      DOI: 10.1002/stc.1737
       
  • Signal‐based nonlinear modelling for damage assessment under
           variable temperature conditions by means of acousto‐ultrasonics
    • Authors: M.‐A. Torres‐Arredondo; Julian Sierra‐Pérez, D.‐A. Tibaduiza, Malcolm McGugan, José Rodellar, C.‐P. Fritzen
      Abstract: Damage assessment can be considered as the main task within the context of structural health monitoring (SHM) systems. This task is not only confined to the detection of damages in its basic algorithms but also in the generation of early warnings to prevent possible catastrophes in the daily use of the structures ensuring their proper functioning. Changes in environmental and operational conditions (EOC), in particularly temperature, affect the performance of SHM systems that constitutes a great limitation for their implementation in real world applications. This paper describes a health monitoring methodology combining the advantages of guided ultrasonic waves together with the compensation for temperature effects and the extraction of defect‐sensitive features for the purpose of carrying out a nonlinear multivariate diagnosis of damage. Two well‐known methods to compensate the temperature effects, namely optimal baseline selection and optimal signal stretch, are investigated within the proposed methodology where the performance is assessed using receiver operating characteristic curves. The methodology is experimentally tested in a pipeline. Results show that the methodology is a robust practical solution to compensate the temperature effects for the damage detection task. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-02-10T05:23:58.831046-05:
      DOI: 10.1002/stc.1735
       
  • Dynamic behavior of adjacent buildings connected by linear
           viscous/viscoelastic dampers
    • Authors: E. Tubaldi
      Abstract: This paper analyzes the properties of the dynamic behavior of two adjacent buildings of different height connected by viscous/viscoelastic dampers located at the top of the shortest building. The adjacent structures are described through a continuum approach as two interconnected uniform shear beams. This permits to identify the set of characteristic parameters describing the building and damper properties that completely control the dynamic behavior of the system. An analytical solution is derived for solving the eigenvalue problem via complex modal analysis, and a parametric study is carried out to evaluate the influence of these characteristic parameters on the properties of the dynamic system. A reduced‐order model of the system is also developed, and simplified formulas are obtained for estimating the damping ratios of the first two modes of the coupled system. Two case studies consisting of realistic shear‐type adjacent buildings coupled by viscous dampers are finally analyzed. The estimates of the modal properties obtained by using the proposed analytical approach and a finite element formulation are compared with each other. It is shown that the proposed approach provides information useful for the preliminary design of the damper properties ensuring the optimal control against seismic loadings. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-02-10T05:23:44.865978-05:
      DOI: 10.1002/stc.1734
       
  • Numerical simulation and analysis of nonlinear state‐space control
           design for hydraulic actuator control
    • Authors: Hadi Moosavi; Reza Mirza Hessabi, Oya Mercan
      Abstract: In order to investigate the dynamic behavior of complex structural systems experimental testing is indispensable and real‐time pseudodynamic (PSD) and real‐time hybrid simulation (RTHS) are versatile testing methods to address this need. Accurate control of hydraulic actuators is essential for the accuracy and stability of these methods. This paper introduces a nonlinear state‐space controller to control hydraulic actuators under displacement control, specifically for real‐time testing applications. The proposed control design process uses the nonlinear state‐space model of the system, and utilizes state feedback linearization through a transformation of the state variables. As such, it can efficiently handle the nonlinearities associated with the servo‐hydraulic system and the test structure. Comparisons of numerical simulation results for linear state‐space and nonlinear state‐space controllers are provided. The improved tracking performance of the proposed controller will contribute to more accurate real‐time test results, which in turn will enable a more accurate assessment of dynamic characteristics of complex structural systems. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-02-09T04:01:46.897354-05:
      DOI: 10.1002/stc.1731
       
  • Investigations on a particle filter algorithm for crack identification in
           beams from vibration measurements
    • Authors: R. Rangaraj; Bharat Pokale, Anuradha Banerjee, Sayan Gupta
      Abstract: This study focuses on crack identification in beams from vibration measurements using principles of dynamic state estimation. The FEM is used to model the beam with cracked‐beam elements that account for the presence of an edge crack under near‐tip elasto‐plastic conditions. The crack size and its location are treated as the variables that are identified using a particle filter algorithm. A parametric study is first carried out with synthetic measurements to numerically analyze the performance of the algorithm. Subsequently, using measurements acquired from physical experiments involving a cantilever beam subjected to arbitrary excitations, the proposed algorithm is used to identify the size and location of crack‐like defects. The proposed method does not require measurements of the undamaged beam, hence, can be used for crack identification in beams for which no earlier measurements are available. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-02-03T00:36:25.645131-05:
      DOI: 10.1002/stc.1733
       
  • Structural identification with incomplete instrumentation and global
           identifiability requirements under base excitation
    • Authors: Suparno Mukhopadhyay; Hilmi Lus, Raimondo Betti
      Abstract: Estimating the mass and stiffness parameters of a structural system via its vibration response measurements is the primary objective in the field of modal testing and structural health monitoring. The attainment of this objective, however, is hindered by various practical and theoretical issues. One such issue is incomplete instrumentation, leading to spatially incomplete mode shapes and often nonunique identification results. When the excitation is induced by ground motion, the problem is further complicated because of arbitrary normalization of mode shapes. This study attempts to address these issues for shear‐building type structures. Mode shape normalization and expansion approaches are developed that utilize the topology of the structural matrices. Theoretical constraints regarding minimal instrumentation and the necessity for any a priori information are addressed vis‐à‐vis the requirements for global identifiability. Some practical implementation issues are discussed. The performance of the method is evaluated using numerical simulations and shake table experiments. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-02-03T00:29:42.294075-05:
      DOI: 10.1002/stc.1732
       
  • Monitoring horizontal displacements in a vertical profile of a tall
           industrial chimney using Global Positioning System technology for
           detecting dynamic characteristics
    • Authors: Peter Breuer; Tadeusz Chmielewski, Piotr Górski, Eduard Konopka, Lesław Tarczyński
      Abstract: Global Positioning System (GPS) dual‐frequency receivers installed at three various levels were used in two field tests to record the response of the 300‐m tall industrial chimney, located in the power station of Bełchatów (Poland), exposed to the light wind and temperature variations. The fast Fourier transformation and the peak‐picking approach based on the band‐pass filtering technique (a second‐order Type 1 Chebyshev band‐pass) were employed to detect dominant natural frequencies and relevant vibrations of the maximum displacements of the chimney. The damping ratios for both tests were also determined. The estimated first natural frequencies and mode shapes, using GPS measurements, matched well with predicted from a calculation of the finite element model, created for the chimney. The assessment of measurement errors caused by GPS system before and after filtering is also presented. This paper concludes that GPS is a viable tool for detecting the structural dynamic characteristics and that GPS is capable of tracking the vibrations of long‐period structures to a few millimetres—in our tests to 2 mm during short time intervals. These results were obtained by using the GPS 10 Hz filtered data. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-01-23T03:16:02.571235-05:
      DOI: 10.1002/stc.1730
       
  • Adaptive HHT (AHHT) based modal parameter estimation from limited
           measurements of an RC‐framed building under multi‐component
           earthquake excitations
    • Authors: Swarup Mahato; Meda Vinay Teja, Arunasis Chakraborty
      Abstract: Present study aims to develop Hilbert–Huang transformation based signal processing scheme to identify the modal parameters of a reinforced concrete framed building subjected to multi‐component earthquake excitations. An adaptive band‐pass filtering strategy is developed to identify modal parameters (i.e. natural frequencies, damping and mode shapes). The proposed method is unique as it identifies the system parameters from the limited measurements due to arbitrary non‐stationary excitations. The advantage of this technique is its ability to extract a complete set of modal frequencies from each measurement. The mode shapes are identified by updating the finite element model using the estimated modal parameters. In this context, the proposed method is effective as the large number of modal parameters identified from each measurement help to optimize the finite element model. The accuracy of the proposed method is demonstrated using both synthetic and actual measurements during an earthquake. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-01-12T04:02:30.761374-05:
      DOI: 10.1002/stc.1727
       
  • Identification of material properties – efficient modelling approach
           based on guided wave propagation and spatial multiple signal
           classification
    • Authors: L. Ambrozinski; P. Packo, L. Pieczonka, T. Stepinski, T. Uhl, W. J. Staszewski
      Abstract: Modern structures are often designed using new types of lightweight materials of interesting properties. Accurate information on physical properties of these materials is a key element of every stage of lifecycle from design through maintenance to retirement. Although there are numerous experimental methods that can be used for material testing, only a small handful of these methods provide required information on material parameters in a nondestructive and in‐operational manner, assuring high level of accuracy. The paper demonstrates application of a method that can be used to estimate material properties of engineering structures. The method is based on guided wave propagation and dispersion characteristics. The proposed approach combines three recently developed elements, that is, efficient numerical, experimental and image processing analyses: (i) wave propagation modelling is based on two finite difference approaches, that is, the semianalytical finite difference method and the 3‐D local interaction simulation approach implemented with a multigeneral‐purpose computing on graphics processing units platform to avoid numerical discrepancies and to reduce the computational effort; (ii) experimental testing utilises noncontact, scanning laser vibrometry; and (iii) image processing involves spatial multiple signal classification to improve dispersion curve estimation. This unique combination offers a reliable approach for material parameter estimation. The proposed method is fully nondestructive and can be performed online under varying operational conditions. The method is demonstrated using Young's modulus estimation of an aluminium plate. The results are compared using the traditional destructive approach based on a three‐point bending test. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-01-07T01:42:59.292331-05:
      DOI: 10.1002/stc.1728
       
  • Modelling the degradation of vibration characteristics of reinforced
           concrete beams due to flexural damage
    • Authors: W. I. Hamad; J. S. Owen, M. F. M. Hussein
      Abstract: This paper presents an improved crack model incorporating non‐linearity of flexural damage in concrete to reproduce changes in vibration properties of cracked reinforced concrete beams. A reinforced concrete beam model with multiple‐distributed flexural cracks is developed, in which the cracked regions are modelled using the fictitious crack approach and the undamaged parts are treated in a linear‐elastic manner. The model is subject to incremental static four‐point bending, and its dynamic behaviour is examined using different sinusoidal excitations including swept sine and harmonic signals. From the swept sine excitations, the model simulates changes in resonant frequency with increasing damage. The harmonic excitations are utilised to investigate changes in modal stiffness extracted from the restoring force surfaces, and changes in the level of non‐linearity are deduced from the appearance of super‐harmonics in the frequency domain. The simulation results are compared with experimental data of reinforced concrete beams subject to incremental static four‐point bending. The comparisons revealed that the proposed crack model is able to quantitatively predict changes in vibration characteristics of cracked reinforced concrete beams. Changes are sensitive to support stiffness, where the sensitivity increases with stiffer support conditions. Changes in the level of non‐linearity with damage are not suitable for damage detection in reinforced concrete structures because they do not follow a monotonic trend. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-12-04T04:47:09.072598-05:
      DOI: 10.1002/stc.1726
       
  • Optimum design of tuned mass damper floor system integrated into
           bending‐shear type building based on H∞, H2, and stability
           maximization criteria
    • Authors: Ping Xiang; Akira Nishitani
      Abstract: A new vibration control system integrating multiple tuned mass damper (TMD) floors into building structures was recently proposed by the authors, which has been demonstrated to be highly effective in mitigating both interstory drifts and floor accelerations for low‐rise and medium‐rise buildings. Actually, this system is attracting especially for tall buildings, which may not be suitable for base isolation because large tensile forces exert on them. This paper aims to investigate the control effect of the proposed TMD floor system for high‐rise buildings that are represented as bending‐shear type models. An optimum design criterion integrating stability maximization criterion is developed for such a multi‐degree‐of‐freedom TMD floor integrated high‐rise building system. Additionally, a multi‐objective optimization genetic algorithm Nondominated Sorting Genetic Algorithm II is employed to solve the multi‐objective optimization problem with the combination of the stability maximization criterion and H∞ or H2 criterion. Two series of numerical simulations, that is, the cases in which all the floors serve as TMDs and only a limited number of floors serve as TMDs, are conducted. The favorable performance of the proposed TMD floor system for high‐rise buildings is demonstrated by comparisons with a fixed floor building equipped with additional high‐damping devices achieving 10% first modal damping ratio under a various of seismic excitations. The TMD floor system is verified to have satisfying control effect, which can also solve the post‐earthquake long‐duration vibration problem of high‐rise buildings observed in the 2011 great Tohoku earthquake. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-12-01T01:44:17.912463-05:
      DOI: 10.1002/stc.1725
       
  • Application of support vector machine for pattern classification of active
           thermometry‐based pipeline scour monitoring
    • Authors: Xuefeng Zhao; Weijie Li, Lei Zhou, Gangbing Song, Qin Ba, Siu Chun Michael Ho, Jinping Ou
      Abstract: Pipeline scour monitoring is becoming one of the key requirements in oil and gas industry. To implement scour monitoring for offshore pipeline, a monitoring system that based on active thermometry is proposed. Our previous investigations have shown that the system has provided many advantages over traditional scour monitoring methods. In this paper, a novel scour automatic detection scheme based on nonlinear curve fitting and support vector machine (SVM) is proposed to realize automatic diagnosis of pipeline scour. On account of the varied heat transfer patterns of a line heat source in sediment and water scenarios, the experimental temperature profiles are nonlinearly fitted to their theoretical models. Features extracted by nonlinear curve fitting can dramatically reduce the dimensions of the data. Subsequently, the extracted features are inputted into SVM classifier to judge where the pipeline is exposed to water or buried in the sediment. In order to evaluate the performance of SVM, SVM with different kernel functions are compared with the back‐propagation neural networks, which is the most popular neural network for pattern recognition and classification. Results show that the SVM model with radial basis function kernel outperformed other classification models. Finally, aiming to obtain the optimal heating time of the system, the optimal SVM model is employed to recognize datasets with different heating time. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-12-01T01:43:20.867919-05:
      DOI: 10.1002/stc.1724
       
  • Structural damage diagnosis using frequency response functions and
           orthogonal matching pursuit: theoretical development
    • Authors: Ryan J. Link; David C. Zimmerman
      Abstract: A structural damage diagnosis procedure that directly uses the frequency response function is developed. Frequency response data from a possibly damaged system and a finite element model of the healthy system are used to form a damage residual—a mathematical proxy or signature of structural damage. This damage residual can be calculated in the presence of incomplete measurements and at multiple frequencies. A system of equations is then formed, which relates the damage residual to the actual damage on each element represented as a fractional stiffness loss. Therefore, only damage affecting the stiffness properties of the structure is considered here. Classical dynamic model condensation is used in the formation of these equations to overcome the coordinate mismatch created by the incomplete measurement problem. The system of equations created using the damage residual is usually overdetermined and subject to noise, error as a result of the model reduction, and general ill‐conditioning. To overcome these issues, a method known as orthogonal matching pursuit is used to solve the equations for the percent damage. Orthogonal matching pursuit is a method of sparse recovery that solves for the damage in terms of the fewest number of elements. Simulation studies are performed on a truss structure. The damage diagnosis method is shown to accurately identify multiple damage cases. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-12-01T01:39:38.502491-05:
      DOI: 10.1002/stc.1720
       
  • Acoustic emission monitoring of early corrosion in prestressed concrete
           piles
    • Authors: William Vélez; Fabio Matta, Paul Ziehl
      Abstract: Prestressed concrete (PC) piles in marine environments are vulnerable to corrosion damage especially at their tidal zone because of the concurrent exposure of steel reinforcement to moisture, chlorides, and oxygen. Early detection of corrosion in prestressed strands is desirable to enable the effective planning and prioritizing of maintenance operations. This paper reports on experiments aimed at testing the hypothesis that acoustic emission (AE) monitoring is suitable to recognize and classify early corrosion damage in PC piles exposed to saltwater. In fact, AE is sensitive to the formation and growth of microcracks in both steel and concrete, which may develop upon depassivation of reinforcement and buildup of corrosion by‐products. In addition, the influence of AE signals produced through flexural cracks in the concrete is of less concern for PC piles as such cracks are seldom produced under service loads. Five specimens representative of full‐scale portions of PC piles were designed to accelerate corrosion and subjected for 1 year to wet/dry cycles in saltwater simulating tidal action. The specimens were monitored continuously with AE sensors. Benchmark electrochemical measurements were routinely performed to understand when depassivation of the steel strands occurred. Visual evidence of early corrosion was collected from strands removed from two decommissioned specimens. It is shown that AE intensity analysis is more effective than AE signal strength and cumulative signal strength analysis in recognizing corrosion damage. Intensity analysis‐based criteria for the assessment of early corrosion damage are proposed, complementing previously developed criteria for more severe corrosion damage in steel strands. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-11-26T07:06:10.445504-05:
      DOI: 10.1002/stc.1723
       
  • Output‐only observer/Kalman filter identification (O3KID)
    • Authors: Francesco Vicario; Minh Q. Phan, Raimondo Betti, Richard W. Longman
      Abstract: This paper presents output‐only observer/Kalman filter identification (O3KID), an effective method for the identification of the dynamic model of a structure and its underlying modal parameters using only output time histories measured on the field. The method is suitable for structural health monitoring based on modal parameters, in particular, for those civil infrastructures whose excitation is random in nature and in the way that it is applied to the structure (e.g., wind and traffic) and therefore is difficult to measure. O3KID is based on a linear‐time‐invariant state‐space model and is derived from an established and successful approach for input–output system identification, known as observer/Kalman filter identification. The paper rigorously proves the applicability of the approach to the output‐only case, presents the resulting new algorithms, and demonstrates them via examples on both numerical and experimental data. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-11-21T03:17:09.104756-05:
      DOI: 10.1002/stc.1719
       
  • Optimal control for vibration peak reduction via minimizing large
           responses
    • Authors: Zu‐Guang Ying; Yi‐Qing Q. Ni
      Abstract: An optimal control method for peak response reduction and its application to a tall building structure for reducing peak earthquake responses are presented in this paper. A critical value is used for magnifying large responses and performance index. A structural control system is transformed, and the dynamical programming principle is applied to form a dynamical programming equation. For a certain higher‐order power function in the index, a nonlinear optimal control law with the corresponding Riccati equation is obtained for minimizing structural large responses or peak responses. The asymptotic stability of the autonomous controlled system is proved by using the Lyapunov method. Then the proposed control method is applied to a single degree‐of‐freedom system and a 51‐storey building structure with active mass damper on the top floor under earthquake excitation. Numerical results on peak displacements, interstorey drifts, accelerations and controls are given to illustrate the high control effectiveness of the proposed control method for peak response reduction. The proposed control method has a simple and convenient procedure for multi‐degree‐of‐freedom structures. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-11-19T03:11:50.071542-05:
      DOI: 10.1002/stc.1722
       
  • Drive‐by damage detection in bridges using the apparent profile
    • Authors: E. J. OBrien; J. Keenahan
      Abstract: The concept of using sensors on a passing vehicle, rather than on the bridge, is known as 'Drive‐by' damage detection. The newly developed traffic speed deflectometer (TSD) is a device used for pavement deflection measurements and is investigated here in numerical simulations as a means of bridge damage detection. A TSD vehicle model containing two displacement sensors is simulated crossing a simply supported finite element beam containing damage simulated as a loss in stiffness of one of the elements. An adapted Cross Entropy optimisation algorithm procedure is proposed to determine the apparent profile, where the displacements recorded by the sensors are used as the inputs. The time‐shifted difference in the apparent profile is used as the damage indicator. Results show that this can be reliably used as a damage indicator in the presence of noise and changes in the transverse position of the vehicle on the bridge. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-11-14T03:28:26.701078-05:
      DOI: 10.1002/stc.1721
       
  • Experimental study of pipeline leak detection based on hoop strain
           measurement
    • Authors: Zi‐guang Jia; Liang Ren, Hong‐nan Li, Siu‐Chun Ho, Gang‐bing Song
      Abstract: Pipelines are widely used for the transport of a large variety of fluids, such as natural gas, across long distances. While pipelines provide a convenient mode of transportation of fluids, their safe usage is one of the foremost concerns especially if their contents are harmful to the environment or if the hosting area is prone to third‐party intrusions. Thus, rapid detection and localization of pipeline leakage is paramount to the minimization of damage brought to the environment and stakeholders in the event of an unexpected leakage. In this work, a novel hoop strain based negative pressure wave (NPW) approach was used to detect and localize pipeline leakages in a 180 ft PVC pipeline equipped with five manually controllable leakage points. Using the new approach, both the arrival time of the NPW and the energy attenuation profile of the NPW can be used to detect and localize leakages with higher accuracy and in a wider variety of situations. The time of arrival approach allowed accurate (within 7.33% error) and repeatable localization of the leakage points; however, using the energy attenuation of the NPW, leakages with low leakage rates (
      PubDate: 2014-11-14T03:26:01.307815-05:
      DOI: 10.1002/stc.1718
       
 
 
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