• 한국의학물리학회지:의학물리
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• 제15권1호
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• pp.1-8
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• 2004

방사선 치료과정에서 가장 중요한 것은 환자에게 조사된 흡수선량을 검증하는 것이다. IMRT에 사용되는 방사선의 물리적 특성을 결정하고 환자에 조사된 선량분포를 검증할 수 있는 정밀한 선량 측정 장치가 필요하다. 본 연구에서 2차원 광자선의 선량검증을 위해 만들어진 BInS (Beam Intensity Scanner)에 관하여 논의한다. BInS에 있는 Scintillator는 광자선이나 전자선에 조사되면 형광을 발생하는 Gd$_2$O$_2$S:Tb를 주성분으로 한다. Scintillator에서 발생된 형광은 디지털 비디오카메라에 의해 수집되어 디지털 신호로 바뀌고 자체 제작한 소프트웨어에 의해 분석되며 상대적인 선량 분포가 3차원 그림으로 표시된다. BInS가 IMRT에서 사용가능한지를 알아보기 위하여 치료에 관련된 몇 가지 측정을 하였다. IMRT의 주요 작동방식 중의 하나인 SMLC (static multileaf collimator) 방식에서는, leaf들의 동작을 통제하여 만들어지는 여러 개의 정적 조사면적(static portal)을 통하여 IMB (intensity modulated beam)이 만들어진다. 따라서 여러 개의 정적 조사면적이 연달아 맞닿아 있는 경우, 연속된 두 조사면적의 경계면에서 penumbra와 산란된 광자들이 겹쳐지고 따라서 hot spot이 생기게 된다. 이와 같이 SMLC 방식에서 나타나는 inter-step hot spot들의 존재를 BInS를 이용하여 측정하여 가시화하였고 또한 그것들을 제거하는 실험적 방법도 제시하였다. IMRT에서 사용되는 다른 주요한 작동방식인 DMLC (dynamic multileaf collimator)는 광자선이나 전자선을 제어하는 leaf의 작동방식이 다르기 때문에 SMLC 방식과는 다른 특성을 보인다. 따라서 BInS를 이용하여 SMLC와 DMLC 방식에 의해 실제로 target에 투사된 선량을 측정 비교하였다. 비록 같은 선량을 target 부위에 투사하기로 계획했을지라도, 실제로는 산란된 광자와 전자들 때문에 DMLC 방식에 의한 선량이 SMLC 방식에 의한 선량보다 14.8%나 큰 것으로 측정되었다.

• Journal of Mechanical Science and Technology
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• 제20권9호
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• pp.1514-1524
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• 2006

This work presents the three-dimensional analysis of flow and heat transfer performed for a wire-wrapped fuel assembly of liquid metal reactor using Reynolds-averaged Wavier-Stokes analysis in conjunction with 557 model as a turbulence closure. The whole fuel assembly has been analyzed for one period of the wire-spacer using periodic boundary conditions at inlet and outlet of the calculation domain. Three different assemblies, two 7-pin wire-spacer fuel assemblies and one bare rod bundle, apart from the pressure drop calculations for a 19-pin case, have been analyzed. Individual as well as a comparative analysis of the flow field and heat transfer have been discussed. Also, discussed is the position of hot spots observed in the wire-spacer fuel assembly. The flow field in the subchannels of a bare rod bundle and a wire-spacer fuel assembly is found to be different. A directional temperature gradient is found to exist in the subchannels of a wire-spacer fuel assembly Local Nusselt number in the subchannels of wire-spacer fuel assemblies is found to vary according to the wire-wrap position while in case of bare rod bundle, it's found to be constant.

• 제어로봇시스템학회논문지
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• 제13권11호
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• pp.1060-1066
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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 efficiently. In this paper a detection of the welding defect of thin SUS 304 plates using the UIR (ultrasonic infrared imaging) technology is described. A low frequency (20kHz) ultrasonic transducer was used to infuse the welded thin SUS 304 plates with a short pulse of sound for 280ms. The ultrasonic source has a maximum power of 2kW. The surface temperature of the area under inspection is imaged by a thermal infrared camera that is coupled to a fast frame grabber in a computer. The hot spots, which are a small area around the defect tip and heated up highly, are observed. From the sequence of the thermosonic images, the location of defective or inhomogeneous regions in the welded thin SUS 304 plates can be detected easily.

• 한국전기전자재료학회논문지
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• 제14권6호
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• pp.518-524
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• 2001

We report the current limiting properties of superconducting fault current limiters (SFCL). Our SFCL was patterned in a spiral type on a YB $a_2$C $u_3$$O_{7-x}$(YBCO) film deposited using rf sputtering techniques and was coated with a gold shunt layer in order to disperse the heat generated at hot spots in the YBCO film. Current increased up to 13.5 $A_{peak}$ at 60 Hz for the voltage of 13 $V_{peak}$, which is the minimum quench point, and increased up to 17.6 $A_{peak}$ at 60 Hz fo the voltage fo 141.4 $V_{peak}$. The quench completion time was 5 msec at 13 $V_{peak}$ and 4 msec at 141. $V_{peak}$ respectively. we think that this architecture using spiral-type SFCL can be useful for the protection of the power delivery systems from fault currents.s. currents.s.

• 천문학회지
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• 제34권1호
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• pp.9-15
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• 2001

We present the results of optical differential photometry of five blazars [PKS0219+428 (3C66A), PKS 0235+164 (AO 0235+16), H0414+019, PKS 0851+202 (OJ 287) and QSO 1807+698 (3C 371)] that were observed on 7 nights between November 05, 1997 and December 29, 1998, using the B and the V band filters. We have detected microvariations in four blazars (3C66A, AO 0235+16, H04l4+019, and OJ 287). In addition, the light curve of AO 0235+16 has displayed a mini-flare when the brightness of this source was decreasing. Night-to-night variations have also been detected in 3C66A, H04l4+019, and OJ 287. The results of our observations are discussed in the framework of accretion disk phenomena (magnetic flares or hot spots in accretion disks) and jet phenomena (plasma instabilities in jets).

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
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• pp.24-24
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• 2003

Research activity in the III-V nitrides materials system has increased markedly in the past several years ever since high-brightness blue light-emitting diodes (LEDs) became commercially available. Despite of excellent optical properties of the GaN, however, inherently poor thermal property of the sapphire used as a substrate material n these devices may lead to thermal degradation of devices, especially during their high power operation. Therefore, dependable thermal analysis and packaging schemes of GaN-based LEDs are necessary for solid lighting applications under high power operation. In this paper, emphasis will be placed upon thermal design of GaN-based LEDs. Thermal measurements of LEDs on chip and packaging scale were performed using the liquid crystal thermographic technology and micro thermocouples for different bias conditions. By a series of optical arrangement, hot spots with specific transition temperatures were obtained with increasing input power. Thermal design of LEDS was made using the finite element method and analytical unit temperature profile approach with optimal boundary conditions. The experimental results were compared to the simulated data and the results agree well enough for the establishment of dependable prediction of thermal behavior in these devices. The paper will present a more detailed understanding of the thermal analysis of the GaN-based blue and white LEDs for high power applications.

• 펄프종이기술
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• 제42권3호
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• pp.58-66
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• 2010

The Annals of beeswax applied-Joseon Dynasty have some serious damages such as cracks, brown, red or black spots, and discolorations by chemical and biological degradation, but others without any beeswax application have still been keeping good quality during over several hundred years. It would be convinced that the beeswax applied in the Annals resulted in these deteriorations. Therefore, in order to focus on the aging mechanism and conservation techniques for the beeswax-applied Annals of Joseon Dynasty, the beeswax applying and dewaxing techniques of Hanji were tried by auto bar coater with a hot plate, and by heat-pressure sensitive extracting treatments. The ageing behaviors of beeswaxed Hanji and dewaxed Hanji were investigated by measuring the changes of physical, optical, morphological, and chemical properties, through accelerated ageing treatment in dry oven at $150^{\circ}C$ during 48 hours. Consequently, the ageing actions of beeswaxed Hanji were even faster than that of Hanji. The optimum dewaxed amounts from beeswaxed Hanji was also obtained in pressure of $40\;kg_f$ under heating conditions.

• Journal of Microbiology and Biotechnology
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• 제5권5호
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• pp.280-284
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• 1995

Aspergi11us niger F-580, a potent producer of aminopeptidase M inhibitor, was isolated from the brown spots of plant leaves with a pathological trait. The inhibitory activity was found only in the fungal mat formed by surface culture of Aspergi11us niger F-580, but not in the culture supernatant or cell pellet. The inhibitor was purified from the hot water extract of this fungal mat by using chromatographies on Diaion HP-20, DEAE-cellulose, Sephadex G-l0 and YMC-ODS-AQ columns. The purified inhibitor was analyzed by UV, mass, and NMR spectroscopies, and identified as OF494911, which had been isolated as an aminopeptidase B inhibitor from Penicillium rugulosum OF4949

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 1999년도 High Temperature Superconductivity Vol.IX
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• pp.214-217
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• 1999

We investigated the quench characteristics of meander line type resistive superconducting fault current limiters based on YBCO thin films grown on 2" diameter LaAlO$_3$ substrates. A gold layer was deposited onto the 0.4 ${\mu}$ m thick YBCO film to disperse the heat generated at hot spots, prior to patterning into 1 mm wide meander lines by photolithography. The limiters were tested with simulated fault currents of various amplitudes. The quench started at 10 A and was completed within 1 msec at the fault current of 65 A$_{peak}$. The dynamic quench characteristics were explained based on the heat conduction within the film and the heat transfer between the film and the surrounding liquid nitrogen. The heat transfer coefficient per unit area was estimated to be 3.0 W/cm$^2$K.

• 농촌지도와개발
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• 제22권3호
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• pp.333-344
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• 2015

The purpose of this study was to assume suitable cultivation areas by items and expectably suitable cultivation areas through coefficient of specialization and spatial concentration analysis, and suggested regional specialized items discovered by this research and regional specialized business management plans & development directions. This study has monitored changing aspects of spatial distribution of suitable cultivation areas in stockbreeding items from 2000 to 2010 by applying methods of location quotient(LQ), a multiple model, and etc, and predicted changing aspects of suitable cultivation areas from 2015 to 2020. As the result of analysis, I found that there were specialized items which were spatially concentrated and that there were hot-spots which were focused on some areas by items. Additionally, there were suitable cultivation areas which remained stable or changed by them. To discover specialized items and to develop businesses, I have suggested that it is necessary to ensure business project's feasibility including the present conditions, circumstances & potential of specialized items, and etc., and to secure business competitiveness including technology exchange, production cost curtailment, business management based on consumer's needs and building systematic data about achievement and etc.