• 한국방사선학회논문지
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• 제12권3호
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• pp.305-312
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• 2018

유리 표면에 방사성동위원소 $^{14}C$를 고착시키고 문지름 시험을 통해 시험용지별 전이 인자와 표면 형상을 관찰하여 방사성동위원소 누설 점검을 위한 건식 및 습식 문지름 시험법을 연구하였다. 건식 문지름 시험법은 티슈 용지가 종이 필터를 대체 가능할 정도로 2배 높은 전이 인자를 보였고, 습식 문지름 시험법은 종이 필터 용지가 티슈 용지에 비하여 3배 높은 전이 인자를 보였다. 일반적으로 누설 점검을 위해 종이 필터를 사용하고 있지만 건식 문지름 시험법에서 티슈 용지가 대안이 될 수 있음을 보였다.

• 멤브레인
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• 제9권2호
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• pp.132-139
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• 1999

무기 flour로서 방사능물질과 반응하여 섬광을 일으키는 cerium activated ytrium silicate를 폴리설폰 고분자 구조내에 함침시킨 측정막을 제조하고, 이를 이용하여 방사성핵종인 $^3H$-cortisol 으로 오염된 실험실 바닥의 방사능 오염도를 측정하였다. 제조된 측정막을 이용하여 오염지역을 문지르고, 막에 함침된 flour와 오염지역으로부터 막으로 옮겨진 방사능 물질과의 직접 반응에 의해 나타난 섬광을 측정하여 방사성핵종의 양을 결정하였다. 유기 flour 가 용해되어 있는 섬광보조액(scintillation cocktail)의 도움을 필요로 하는 기존의 방사성핵종 측정방법에 비해, 측정막을 이용할 경우 오염도의 측정 효율을 유지하면서 전체적인 방사능 폐기물의 양산을 제어할 수 있는 효과를 거두었다. 한편, 탐지효과의 증대들 위해 시도된 디메틸포름아마이드를 이용한 측정막의 용매 처리는, 막 표면의 형상변화를 유도할 수있었으나, 방사성핵종에 대한 측정효율의 증대로는 귀결되지 않았다.

• 한국안전학회지
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• 제23권6호
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• pp.62-69
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• 2008

As the concerns of dermal exposure of spray painters to isocyanates in the automobile industry, glove performance was examined like permeation rate and breakthrough time including fatigue test. Methylene chloride was used as the solvent for derivatization of the isocyanates with a 97.5% recovery. Ghost wipe pads were used to wipe the surface of the glove material after chemical penetration through the glove material placed under a disposable test cell. Several solvents were tested, such as thinner(xylene, toluene) and cleaning agent(acetone) by using a standard permeation test cell(AS/NZS standard 2161. part 10.3). Solvents accelerate chemical permeation through the gloves more quickly than pure HDI hardener products. The longest breakthrough times were from Nitrosolve gloves, not detected in 8 hours, compared with others like Latex, Neoprene, TNT and Dermo Plus. Therefore Nitrosolve gloves could be recommended as personal protective equipment in crash repair shops. In addition, revised exposure limit of korean regulation should be suggested for employee to minimize the risk of health symptoms.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.945-950
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• 2001

Vacuum interrupters that is used in various switchgear components such as circuit breakers, distribution switches, contactors, etc. spreads the arc uniformly over the surface of the contacts. The electrode of vacuum interrupters is used sintered Cu-Cr material satisfied with good electrical and mechanical characteristics. Because the closing velocity is 1-3m/s, the deformation of the material of electrodes depends on the strain rate and the dynamic behavior of the sintered Cu-Cr material is a key to investigate the impact characteristics of the electrodes. The dynamic response of the material at the high strain-rate is obtained from the split Hopkinson pressure bar test using cylinder type specimens. Experimental results from both quasi-static and dynamic compressive tests with the split Hopkinson pressure bar apparatus are interpolated to construct the Johnson-Cook equation as the constitutive relation that should be applied to simulation of the dynamic behavior of electrodes. To evaluate impact characteristic of a vacuum interrupter, simulation is carried out with five parameters such as initial velocity, added mass of a movable electrode, wipe spring constant, initial offset of a wipe spring and virtual fixed spring constant.

• 대한기계학회논문집A
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• 제26권5호
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• pp.924-931
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• 2002

Vacuum interrupters in order to be used in various switch-gear components such as circuit breakers, distribution switches, contactors, etc. spread the arc uniformly over the surface of the contacts. The electrodes of vacuum interrupters are made of sinter-forged Cu-Cr materials for good electrical and mechanical characteristics. Since the closing velocity is 1-2m/s and impact deformation of the electrode depends on the strain rate at that velocity, the dynamic behavior of the sinter-forged Cu-Cr is a key to investigate the impact characteristics of the electrodes. The dynamic response of the material at the high strain rate is obtained from the split Hopkinson pressure bar test using disc-type specimens. Experimental results from both quasi-static and dynamic compressive tests are Interpolated to construct the Johnson-Cook model as the constitutive relation that should be applied to simulation of the dynamic behavior of the electrodes. The impact characteristics of a vacuum interrupter are investigated with computer simulations by changing the value of five parameters such as the initial velocity of a movable electrode, the added mass of a movable electrode, the wipe spring constant, initial offset of a wipe spring and the virtual fixed spring constant.

• 대한기계학회논문집A
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• 제26권5호
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• pp.939-951
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• 2002

We propose a new multiscale Galerkin method based on interpolation wavelets for two-dimensional Poisson's and plane elasticity problems. The major contributions of the present work are: 1) full multiresolution numerical analysis is carried out, 2) general boundaries are handled by a fictitious domain method without using a penalty term or the Lagrange multiplier, 3) no special integration rule is necessary unlike in the (bi-)orthogonal wavelet-based methods, and 4) an efficient adaptive scheme is easy to incorporate. Several benchmark-type problems are considered to show the effectiveness and the potentials of the present approach. is 1-2m/s and impact deformation of the electrode depends on the strain rate at that velocity, the dynamic behavior of the sinter-forged Cu-Cr is a key to investigate the impact characteristics of the electrodes. The dynamic response of the material at the high strain rate is obtained from the split Hopkinson pressure bar test using disc-type specimens. Experimental results from both quasi-static and dynamic compressive tests are Interpolated to construct the Johnson-Cook model as the constitutive relation that should be applied to simulation of the dynamic behavior of the electrodes. The impact characteristics of a vacuum interrupter are investigated with computer simulations by changing the value of five parameters such as the initial velocity of a movable electrode, the added mass of a movable electrode, the wipe spring constant, initial offset of a wipe spring and the virtual fixed spring constant.

• 분석과학
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• 제22권6호
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• pp.471-479
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• 2009

본 연구에서는 PCBs 함유 고상폐기물의 효율적 관리를 위해 현행 폐기물 공정시험방법의 용출 시험방법을 고상폐기물 종류별 표면채취법, 부재시험방법, 세정시험방법 등의 함량시험방법과 비교검토하여 PCBs 함유 고상폐기물의 시험방법(안) 및 기준(안)을 마련하였다. 우리나라의 표면채취법에 의한 비함침성 고상폐기물의 규제기준은 미국 및 일본과 같은 수준으로 각 국의 액상폐기물인 절연유 기준과 표면채취법에 의한 처리기준의 수치적 관계를 이용하여 산출하는 것이 타당한 것으로 판단되어진다. 이에 PCBs 함유 고상폐기물 중 규소강판 등 표면채취가 가능한 평면형 비함침성 부재는 표면채취법으로 시료를 채취하여 함량분석법으로 분석하는 경우, 비함침성 고상폐기물의 규제기준(안)을 $0.4 {\mu}g/100cm^2$으로 설정하였다. 또한, 표면채취가 어려운 시료를 일정한 크기로 잘라 부재를 채취한 후 함량분석법으로 분석하는 경우에는 규제기준을 0.04 mg/kg을 제안하였다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2005년도 춘계학술발표대회 개요집
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• pp.370-376
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• 2005

Magnesium alloys are becoming important material for light weight car body, due to their low specific density but high specific strength. However they have a poor weldability, caused high oxidization tendency and low vapor temperature. In this study, the welding performance of magnesium alloys was investigated for automobile application. The materials were rolled magnesium alloy sheet contains Al and Zn such as AZ3l , AZ6l and AZ9l. Three types of welding process were studied, that were GTAW, Laser beam welding and FSW. To evaluate the weldability, we examined the appearance of welding bead. Also we checked bead shape and internal defects such as crack and porosity on cross section of welding bead. The mechanical property was measured for welded specimen by tensile test. For determination of the strength change by welding process, the hardness profile across the welding center was measured. For the results, the tensile properties of welded specimen were decreased obviously on all welding process. For the fusion welding process such as GTAW and laser beam welding, the surface of the welding bead was covered with oxidized magnesium dust but it was removed by simple cleaning work as wipe-out with tissue. Also under cut, that caused vaporization of base metal was occurred. for the friction stir welding, there was no oxidation, under-cut or internal defects. However it had poor weld performance, the reason was cleavage fracture occurred at plastic deformation zone. For welding of magnesium alloy, the laser beam welding process was recommended.

• 수산경영론집
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• 제43권1호
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• pp.75-85
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• 2012

In this paper, we study the extent to which the pecking order theory of capital structure provides a satisfactory account of the financing behavior of Korean fisheries firms using financing deficit. The major results of this study are as follows. Firstly, we find that the financing deficit is a important factor that explains the pecking order theory of fisheries firms'capital structure. However, the financing deficit does not wipe out the effects of conventional variables. The information in the financing deficit appears to be factored in along with many other things that fisheries firms take into account. Such result is consistent with the result of Frank and Goyal(2003). Secondly, we find that profitability is only one factor explaining the capital structure of fisheries firms among conventional variables when we test the regression of leverage with financing deficit during post IMF period. This result is different from the previous researches of Korean fisheries firms. (Kang and Jeong; 1997, Nam, Lee, and Hong; 2011) Finally, we examine the dynamics of capital structure of Korean fisheries firms firstly. It will allow a more detailed analysis for capital structure determinants for Korean fisheries firms.

• 한국컴퓨터정보학회논문지
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• 제4권3호
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• pp.28-34
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• 1999

본 논문에서는 DCT 영역에서 DCT블록내의 DC성분과 매크로블록내의 움직임 벡터성분을 이용하여 동영상 장면전환 자동 검출에 관한 방법을 제안한다. 제안하는 방법은 압축된 MPEG 신호열내의 픽쳐 종류와 상관없이 임의의 신호열에서 장면전환을 검출한다. 이를 위해 MPEG 신호열의 DCT 영역에서 픽쳐구성요소의 특징을 이용하여 새로운 비교잣대를 정의하고 움직임 벡터에 예민한 B-picture 의 특성을 이용하여 정확한 장면전환을 검출한다. 이때. I-picture를 가지고 급격한(cut) 장면전환을 검출하고 P. B picture 를 가지고 점진적인(gradual) 장면 전환을 검출한다. 제안한 방법은 다양한 MPEG 신호열에 대하여 시험결과 그 효율성이 우수함을 보인다.