• Structural Monitoring and Maintenance
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• v.9 no.3
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• pp.237-258
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• 2022

This paper studies detecting and locating loose bolts using nonlinear guided waves. The 3D Finite Element (FE) simulation is used for the prediction of guided waves' interactions with loose bolted joints. The numerical results are verified by experimentally obtained data. The study considers bolted joints consisting of two bolts. It is shown that the guided waves' interaction with surfaces of a loose bolted joint generates Contact Acoustic Nonlinearity (CAN). The study uses CAN for detecting and locating loose bolts. The processed experimentally obtained data show that the CAN is able to successfully detect and locate loose bolted joints. A 3D FE simulation scheme is developed and validated by experimentally obtained data. It is shown that FE can predict the propagation of guided waves in loose bolts and is also able to detect and locate them. Several numerical case studies with various bolt sizes are created and studied using the validated 3D FE simulation approach. It is shown that the FE simulation modeling approach and the signal processing scheme used in the current study are able to detect and locate the loose bolts in imperfect bolted joints. The outcomes of this research can provide better insights into understanding the interaction of guided waves with loose bolts. The results can also enhance the maintenance and repair of imperfect joints using the nonlinear guided waves technique.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1994.04a
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• pp.506-506
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• 1994

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2012.05a
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• pp.81-82
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• 2012

• Journal of Electrical Engineering and Technology
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• v.1 no.2
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• pp.170-176
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• 2006

This paper proposes a topological locating algorithm to determine the location of the power quality event source. This algorithm makes use of the information on the topology of the monitored network and on the direction of PQ events. As a result, the bus incidence matrix is modified using monitor location and the direction matrix is constructed. With this information, the algorithm determines the suspected locations of the PQ events. To reduce suspicious areas, it utilizes event cause and related equipment. In case of line fault event, it calculates the distance from the monitor to the location of event source. The overall algorithm is applied to the IEEE test feeder and accurately identifies the event source location.

• Molecules and Cells
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• v.20 no.1
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• pp.35-42
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• 2005

A novel combined method for locating box H/ACA small nucleolar RNAs (snoRNAs) is described, together with a software tool. The method adopts both a probabilistic hidden Markov model (HMM) and a minimum free energy (MFE) rule, and filters possible candidate box H/ACA snoRNAs obtained from genomic DNA sequences. With our novel method 12 known box H/ACA snoRNAs, and one strong candidate were identified in 30 nucleolar protein genomic sequences.

• Journal of the Korea Safety Management & Science
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• v.10 no.2
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• pp.217-223
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• 2008

Measurement is used for evaluation of product or process exactly. If it couldn't measured correctly, Quality-cost must be raised and it would be hard to improve product quality. So, this study suggests improvement guide line for the multilateral problems of measuring instrument operation based on the investigation of 157 small and medium-sized enterprises in February, 2008. To use inspection gig correctly, man who treat it must be accustomed with the structure, the performance, the method. The inspection gig is selected properly for the measurement goal. If not, results couldn't be correctly or wasted time, efforts, and costs. When selecting a inspection gig, the locating, the clamping, and the efficiency must be considered.

• Proceedings of the IEEK Conference
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• 2002.07a
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• pp.192-195
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• 2002

About 90% of Thai-style addresses have similar features; e.g. the beginning of each address line is diagonal. In this paper, we propose a method for locating destination address block (DAB) on Thai envelopes based on features of Thai-style addresses. Firstly, we decompose image into smaller blocks and remove all blocks not meeting criteria. Secondly, we search for the DAB candidates. Lastly, heuristic rules and typical features are applied to identify the destination address block. Experimental results using 2,700 envelopes of handwritten and machine printed Thai envelopes show a successful address extraction rate of 91%.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.6
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• pp.703-710
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• 2012

A structural health monitoring technique for locating impact position in a composite plate is presented in this paper. The method employs a single sensor and spatial focusing properties of time reversal(TR) and inverse filtering(IF). We first examine the spatial focusing efficiency of both approaches at the impact position and its surroundings through impact experiments. The imaging results of impact localization show that the impact location can be accurately estimated in any position of the plate. Compared to existing techniques for locating impact or acoustic emission source, the proposed method has the benefits of using a single sensor and not requiring knowledge of anisotropic material properties and geometry of structures. Furthermore, it does not depend on a particular mode of dispersive Lamb waves that is frequently used in other ultrasonic testing of plate-like structures.

• Proceedings of the Acoustical Society of Korea Conference
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• 1992.06a
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• pp.87-90
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• 1992

Detecting acoustic emission (AE) provides an appropriate method to diagonize on-line transformers, since acoustic signal is not influenced by strong electric field. Then AE versus AE signal processing method is investigated. But this processing is difficult that decision of starting point of AE wave with acoustic noise. This problem is sloved by correlation which calculate time interval between two signals eactly. This paper presents a technique locating the eact position of the partial discharge (PD) in a power transformer by the correlation of the AE signals from two ultrasonic sensors. And PD position is displayed on monitor. Laboratory tests confirmed that the proposed method can be used for locating the PD in power transformer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.04c
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• pp.98-102
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• 2008

Methods and analysis of a simple wireless sensor concept for detecting and locating faults as well as for load monitoring are presented. The concept is based on distributed wireless sensors that are attached to the incoming and outgoing power lines of secondary substations. A sensor measures only phase current characteristics of the wire it is attached to, is not synchronized to other sensors and does not need configuration of triggering levels. The main novelty of the concept is in detecting and locating faults by combining power distribution network characteristics on system level with low power sampling methods for individual sensors. This concept enables the sensor design to be simple, energy efficient and thus applicable in new installations and for retrofit purposes in both overhead and underground electrical distribution systems.