Papers by Keyword: Acoustic Monitoring

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Authors: C. Meng, C.J. De Pater
Abstract: Active acoustic monitoring can capture two types of fracture behavior in rock samples, opening and closure of an existing fracture and tip movement of a propagating fracture. The first type is related to wave transmission across the fracture interface. The second one is related to the travel times of waves that diffract at the fracture tip. A series of experiment has been conducted with an acoustic system that has transducers mounted on the loading frames of a tri-axial cell situated in the Rock Mechanics Laboratory, TUDelft, the Netherlands. The existing fractures are formed by cleaving the rock samples into layers and putting them back together. The propagating fractures were created by hydraulic fracturing via bore-hole injection. The tests in this study featured both cleaved and hydraulic fractures, and aimed to characterize the interaction between them. This paper focus on the data processing that is adapted to these special tests and comparison between the monitored and recovered fractures.
833
Authors: Kenneth Burnham, Gareth Pierce
Abstract: The total electrical generation capacity from wind sources in the International Energy Agency (IEA) Wind Member Countries has increased from 4 GW in 1995 to more than 51 GW in 2005 thus underlining the strategic importance of the resource. In the last year alone the UK increased its wind generation by 447 MW, an increase of 85% over that for the previous year. In 2004, wind generation formed just 0.5% of the national electric demand; this contribution is set to rise over the next few years with some predictions that wind energy will rise to 8% of the total UK demand by 2010. The rotor blades of a wind turbine system are a significant structural component of the overall system, and typically account for 30% of lifecycle costs, and contribute 34% to overall system downtime. Despite their importance, there is currently very little monitoring of the structural integrity of rotor components, and what does exist is limited. We perceive that especially with the current political and technological emphasis on offshore installations, there will be an increase in the perceived need for remote structural monitoring, and there is indeed currently great interest in this area from the wind turbine industry. This work focuses on the applications of acoustic techniques to assess the integrity of typical rotor blade structures. Preliminary results discuss the limiting aspects of acoustic based techniques based on the physics of acoustic wave propagation in typical structural components. Comparisons between acoustic emission approaches and conventional active ultrasound will be considered.
639
Authors: Peng Tong, Chun Jing Gen
Abstract: The problem of how to detect and diagnose the tube leakage and blast through the methods of acoustics and information fusion is dealt with in this paper with the purpose of detecting the accident more accurately at its initial phase. Firstly, the acoustic monitoring method is employed since it is contactless, and then the weak leakage is detected, analyzed and diagnosed through such methods as the PCA, neural network and D-S evidence theory. Secondly, the simulation is conducted, which testifies that the diagnosis effect can be improved greatly by this way.
886
Authors: Chun Ting Yang, Yang Liu
Abstract: Recent years, many utilities have experienced catastrophic rupture of critical Prestressing Concrete Cylinder Pipe (PCCP) lines throughout the world. Much attention has been focused on reliably assessing the condition of PCCP mains. However, assessment of embedded prestressing wire is difficult. Continuous acoustic monitoring can provide a means of locating problematic pipe sections. In this paper the application of support vector machine (SVM) in acoustic signal detection is proposed. And the effect of this method is investigated. Some key parameters of SVM and kernel functions are surveyed. SVM methods are more effective, especially for the case of lack of training samples. The experiment shows that the SVM method has good classification ability and robust performances. The techniques can provide the opportunity to identify problematic pipe sections and repair the pipe prior to failure. Therefore it can help to prolong the life of a suspect pipeline while minimizing the potential for catastrophic failure.
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