• Journal of the Korean Society for Precision Engineering
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• v.18 no.5
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• pp.34-41
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• 2001

More accurate and fast inspection method for mechanical parts and structure is required to guarantee the safety. Conventional methods using compliance method, eddy current method, ultrasonic wave, acoustic emission for non-destructive testing in mechanical parts and structure have been performed as the method of contact with objects to be inspected. With this reason these methods have been taken relatively much time, money, and manpower. In this study, in order to overcome these shortcomings, we used In-plane Electronic Speckle pattern Interferometry(In-plane ESPI) that was full-field measurement and noncontact method. We detected the cracks of the specimen at a real time and measured the length of the crack by using In-place ESPI system. Finally, we compared this results with conventional microscope method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.300-305
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• 2012

The vibration and stress analysis program of comprehensive vibration assessment program (CVAP) is to verify theoretically the structural integrity of reactor vessel internals (RVI) and to provide the basis for selecting the locations monitored in measurement and inspection programs. This paper covers the verification of the vibration and stress analysis methodology of APR1400 RVI CVAP. The analysis methodology was developed to use 3-dimensional hydraulic and structural models with ANSYS and CFX. To validate the methodology, the hydraulic loads and structural reponses of OPR1000 were predicted and compared with the calculated and measured data in the OPR1000 RVI CVAP. Since the results predicted with this methodology were close to the measured values considerably, it was confirmed that the analysis methodology was developed properly.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1960-1962
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• 2000

Polyehtylene[PE] in polymer insulation materials of used power cable have carried out in abundance of experiment and study for electrical conduction. insulation breakdown. dielectric character and so on. When apply to field for power cable to make PE, application of DC withstand test to put in practice for inspection is get to effect accumulated space charge. In this paper, to make use of Pulsed Electro-Acoustic(PEA). It is analysis to take shape space charges under AC and DC voltage, clear up the point at issue for effect of DC withstand test.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.613-616
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• 1999

Polyehtylene[PE] in polymer insulation materials of used power cable have carried out in abundance of experiment and study for electrical conduction, insulation breakdown, dielectric character and so on. when apply to field for power cable to make PE, application of DC withstand test to put in practice for inspection is get to effect accumulated space charge. In this paper, to make use of Pulsed Electro-Acoustic(PEA), It is analysis to take shape space charge under AC and DC, clear up the point at issue for DC withstand test impressing

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.3
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• pp.200-206
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• 2010

In ultrasound-excited thermography, the injected ultrasound to an object is transformed to heat and the appearance of defects can be visualized by thermography camera. The advantage of this technology is selectively sensitive to thermally active defects. Despite the apparent simplicity of the scheme, there are a number of experimental considerations that can complicate the implementation of ultrasound excitation thermography inspection. Factors including acoustic horn location, horn-crack proximity, horn-sample coupling, and effective detection range all significantly affect the detect ability of this technology. As conclusions, the influence of coupling pressures between ultrasound exciter and specimen was analyzed, which was dominant factor in frictional heating model.

• Proceedings of the Korea Information Processing Society Conference
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• 2013.11a
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• pp.486-488
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• 2013

In the earth more than half of the space filled with water. In that water most of the part is in the form of oceans. The ocean atmosphere determines climate on the land. Combining the Underwater Acoustic Sensor Network (UWASN) system with Internet Of Things (IoT) is called Internet of Underwater Things (IoUT). Using IoUT we can find the changes in the ocean environment. Underwater sensor nodes are used in UWASN. Underwater sensor nodes are constructive in offshore investigation, disaster anticipation, data gathering, assisted navigation, pollution checking and strategic inspection. By using IoT components such as Database, Server and Internet, ocean data can be broadcasted. This paper introduces IoUT architecture and and explains fish forming application scenario with this IoUT architecture.

• The Journal of the Acoustical Society of Korea
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• v.39 no.4
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• pp.303-317
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• 2020

Extracorporeal Shock Wave Therapy (ESWT) is an innovative treatment in chronic musculoskeletal pain management and cardiovascular diseases. In this study, we surveyed the acoustic shock wave outputs from the domestically used focal type ESWT devices. The survey data were collected through 30 technical documents registered to the Ministry of Food and Drug Safety (MFDS), Rep. Korea. The results show that the focusing geometry varies largely, 5 mm to 65 mm in the focal length, 3 mm to 30 mm in focal width, and 4 mm to 108 mm in focal depth. The maximum positive pressure (P+) ranges from 7 MPa to 280 MPa, the focal Energy Flux Density (EFD) from 0.0035 mJ/㎟ to 35 mJ/㎟, and the energy per pulse (E) from 0.737 mJ to 80.86 mJ. All domestic PE-type (five) and one EM-type domestic devices included in the analysis of the correlation between P+ and EFD are shown to be far beyond the usual ranges and do not comply with expected correlation so that the reliability of their data was suspected. For the suspected, post-performance tests are required by a recognized testing agency. MFDS guidelines need to be revised so that the pass criteria for the shock wave acoustic outputs can be based on the clinical tests for indications.

• Economic and Environmental Geology
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• v.49 no.2
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• pp.121-134
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• 2016

We characterize the spatial distribution of Cobalt-rich ferromanganese crusts covering the summit and slopes of a seamount in the western Pacific, using acoustic backscatter from multibeam echo sounders (MBES) and seafloor video observation. Based on multibeam bathymetric data, we identify that ~70% of the summit area of this flattopped seamount has slope gradients less than $5^{\circ}$. The histogram of the backscatter intensity data shows a bi-modal distribution, indicating significant variations in seabed hardness. On the one hand, visual inspection of the seafloor using deep-sea camera data exhibits that the steep slope areas with high backscatter are mainly covered by manganese crusts. On the other hand, the visual analyses for the summit reveal that the summit areas with relatively low backscatter are covered by sediments. The other summit areas, however, exhibit high acoustic reflectivity due to coexistence of manganese crusts and sediments. Comparison between seafloor video images and acoustic backscatter intensity suggests that the central summit has relatively flat topography and low backscatter intensity resulting from unconsolidated sediments. In addition, the rim of the summit and the slopes are of high acoustic reflectivity because of manganese crusts and/or bedrock outcrops with little sediments. Therefore, we find a strong correlation between the acoustic backscatter data acquired from sea-surface multibeam survey and the spatial distribution of sediments and manganese crusts. We propose that analyzing acoustic backscatter can be one of practical methods to select optimal minable areas of the ferromanganese crusts from seamounts for future mining.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.2
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• pp.136-141
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• 2004

A torsional guided wave mode was applied to detect a crack in a pipe. An array of electromagnetic acoustic transduce. (EMAT that can generate and receive torsional guided ultrasound with the frequency of 200kHz was designed and fabricated for testing a pipe of 2.5 inch diameter Artificial notches with various depths were fabricated in a bent feeder pipe mock-up and the detectability was examined from the distance of 2m of the specimen. The axial notches with the depth of 5% of wall thickness were successfully detected by a torsional mode (T(0,1)) generated by the EMAT However, it was found that the depth of defects was not related to the signal amplitude.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.419-423
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• 2011

Unlike other non-destructive inspection method, AE Structural defects that are likely to grow in the operation status can be detected, and the advantage of being due to the continuous monitoring of large structures has been widely used to evaluate the stability. AE sensor used to detect sound wave that occurs between 20kHz to 20MHz. and Sound wave result may vary depending on sensor's sensitivity. In this paper, Tensile test conducted on STS 304 and SS400, and tries to detect the crack signal. In tensile test, specimens were conducted using different sensor sensitivity to the same tensile test condition. The crack signal parameters divided into 4 types of communities by conducting cluster analysis. It was demonstrated that crack signal of two sensor is not different by statistical analysis of null hypotheses. Based on the results, waveform of this tension test is crack signal.