• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.5
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• pp.426-431
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• 2007

When a high-energy ultrasound propagates through a solid body that contains a crack or a delamination, the two faces of the defect do not ordinarily vibrate in unison, and dissipative phenomena such as friction, rubbing and clapping between the faces will convert some of the vibrational energy to heat. By combining this heating effect with infrared imaging, one can detect a subsurface defect in material in real time. In this paper a realtime detection of the brazing defect of thin Inconel plates using the UIR (ultrasonic infrared imaging) technology is described. A low frequency (23 kHz) ultrasonic transducer was used to infuse the welded Inconel plates with a short pulse of sound for 280 ms. The ultrasonic source has a maximum power of 2 kW. The surface temperature of the area under inspection is imaged by an infrared camera that is coupled to a fast frame grabber in a computer. The hot spots, which are a small area around the bound between the two faces of the Inconel plates near the defective brazing point and heated up highly, are observed. And the weak thermal signal is observed at the defect position of brazed plate also. Using the image processing technology such as background subtraction average and image enhancement using histogram equalization, the position of defective brazing regions in the thin Inconel plates can be located certainly.

• Journal of Acupuncture Research
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• v.24 no.2
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• pp.63-71
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• 2007

목적 : 저주파에 해당하는 2Hz 전침 자극이 척수 N-methyl-D-aspartate receptor (NMDAR)의 NR-2B subunit의 발현 및 인산화에 미치는 영향을 조사하였다. 방법 : Sprague-Dawley계 흰쥐를 Storkson등의 방법에 의해 척수막의 지주막하강에 catheter를 삽입하는 수술을 행한 후 마비등의 척수 손상을 나타내지 않는 개체를 대상으로 하였다. N-methyl-D-aspartate (NMDA) antagonist인 D-2-amino-5- phosphonopentanoic acid (AP-5)를 투여한 후 족삼리와 삼음교에 해당하는 부위에 30분간 전침 자극하였다. 무통각 여부는 hot plate test를 시행하였으며 NMDAR NR-2 subunit 발현과 인산화 여부는 Western blot과 면역조직화학적으로 살펴보았다. 결과 : 전침 무통각은 전침 자극 후 180분 후까지 지속되었으며 NMDA antagonist인 AP-5를 투여하였을 때 전침 무통각이 저하되었으나 유의성은 나타내지 않았다. Western blot 분석으로 보아 NMDAR NR-2B 및 인산화 NR-2B의 발현은 전침자극에 의해 미약한 증가를 보이나 AP-5투여에 의해 현저한 저해를 보였다. 면역조직화학에 의한 척수배각 구역별 발현을 보면 NMDAR NR-2B 및 인산화 NR-2B는 전 배각에 걸쳐 관찰되나 경부(층판 V-VI)에서 약한 반응을 보였다. 전침 자극에 의한 각 군별 NR-2B 발현은 유의한 차이를 보여 주지 않았으나 인산화 NR-2B는 천층(층판I-II) 및 고유핵 층판(III-IV)에서 유의성 있는 증가를 보였다. 전침 자극시 AP-5 투여는 유의성은 보이지 않았으나 인산화 NR-2B 발현을 저해하였다. 결론: 저주파 2Hz 전침에 의한 무통각은 NMDA antagonist인 AP-5 투여에 의해 저해될 뿐 아니라 NMDAR NR-2B subunit의 인산화를 저해하는 것으로 보아 전침 무통각의 과정에 NMDAR 및 NMDAR NR-2B의 인산화가 관여함을 알 수 있다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.1
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• pp.48-57
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• 2015

In a sodium-cooled fast reactor, which is a Generation-IV reactor, refueling is conducted by rotating, but not opening, the reactor head to prevent a reaction between the sodium, water and air. Therefore, an inspection technique that checks for the presence of any obstacles between the reactor core and the upper internal structure, which could disturb the rotation of the reactor head, is essential prior to the refueling of a sodium-cooled fast reactor. To this end, an ultrasound-based inspection technique should be employed because the opacity of the sodium prevents conventional optical inspection techniques from being applied to the monitoring of obstacles. In this study, a ranging inspection technique using a plate-type ultrasonic waveguide sensor was developed to monitor the presence of any obstacles between the reactor core and the upper internal structure in the opaque sodium. Because the waveguide sensor installs an ultrasonic transducer in a relatively cold region and transmits the ultrasonic waves into the hot radioactive liquid sodium through a long waveguide, it offers better reliability and is less susceptible to thermal or radiation damage. A 10 m horizontal beam waveguide sensor capable of radiating an ultrasonic wave horizontally was developed, and beam profile measurements and basic experiments were carried out to investigate the characteristics of the developed sensor. The beam width and propagation distance of the ultrasonic wave radiated from the sensor were assessed based on the experimental results. Finally, a feasibility test using cylindrical targets (corresponding to the shape of possible obstacles) was also conducted to evaluate the applicability of the developed ranging inspection technique to actual applications.