• 한국가스학회지
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• 제7권4호
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• pp.14-19
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• 2003

일반적으로 발생하는 사고중의 가스폭발사고는 일정한 상태로의 혼합과정보다는 불균일하게 이루어진 상태로 폭발이 발생하고 있다. 본 연구에서는 불균일 상태에서의 불균일 농도에 의한 폭발현상을 실제 실내의 축소형으로 폭발통을 제작, 모형화하여 여러현상을 재현함으로서 실제 사고시의 폭발현상을 예측할 수 있었다. 그 결과, 어떤 공간에서 가스가 누출될 경우 내부의 가스의 혼합정도는 누출구의 크기 및 누출속도에 따라 영향을 받으며, 불균일 정도가 클수록 폭발압력 및 압력상승속도는 낮아지고 폭발압력은 감소하지만 화염의 체류시간이 증가하여 폭발화염의 복사열에 의한 폭발 후에는 화재의 위험성이 증가함을 알 수 있었다.

• 한국의류산업학회지
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• 제6권6호
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• pp.707-714
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• 2004

This study was carried out to research the actual condition of narrator models' wearing uniform, targeting on the narrator models who are being currently active and are from 19-year-old to 30-year-old. A poll was performed through visiting internet circles and spots, and the characteristic of objects, the form of uniform, attitude on uniform, dissatisfaction index on wearing uniform and preference index on wearing uniform were researched. It was carried out from August 18, 2003 to August 31, 2003. In order to perform this study, 161 questionnaires were used in all, and frequency analysis was implemented using SPSS 10.0. The objects of study were composed of female. Those who are from 21-year-old to 25-year-old accounted for 74.5%, and those who have career from 2 years to 3 years accounted for 75.5%. In respect to attitude on wearing uniform, affirmative answers, affirmative answers, such as a sense of belonging, a pride in activity and increase of efficiency, accounted for 68.8%. On the other hand, in respect to a harmonization between uniform and work, just the 39.8-percent showed affirmative reaction. Concerning the functionality of uniform, such as retaining warmth and ventilating, dissatisfaction index showed very high value; it is judged that it should be improved henceforth. Working postures were researched, following the order of standing posture and arm-using posture. In inconvenient actions, bending down and moving arms were orderly pointed out. With regard to the dissatisfaction of size, busts, the length of skirt and waist girth were orderly pointed out. Likewise, considering the parts of which room is required, bust, hip girth and waist girth were orderly pointed out. As to the points that should be bettered, design and functionality were orderly pointed out. In respect to materials of uniform, sweat-absorption material, light material and well-ventilated material were orderly suggested.

• 대한기계학회논문집
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• 제16권8호
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• pp.1451-1457
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• 1992

본 연구에서는 작업롤의 온도분포를 정상 상태에서 롤의 길이 방향만을 고려 한 경우에 대하여 구한 다음 Fouries 급수로 전개하여 이 온도분포에 따른 작업롤의 축대칭 3차원 열-탄성문제를 해석함으로서 롤의 크라운 양과 열응력을 구하여 이 결과 를 유한요소법에 의한 결과와 비교 검토 하였다.

• 한국안전학회지
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• 제36권5호
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• pp.27-35
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• 2021

This study investigated the change in stiffness and deflection of a scaffold working plate caused by damage to a cross-beam in the plate. Experiments were conducted considering various load and damage conditions of cross-beams. A cross-beam falling off from the working plate was considered damaged. The load-displacement curves of specimens at the center of the uniform load showed that the working plate stiffness decreased by 14.66%-1.89%, depending on the load interval due to the damage of one cross-beam. A reduction in the stiffness of 33.94%-40.76% resulted from the damage of two cross-beams. Moreover, the displacement increased by an average of 25% when one cross-beam was damaged and an average of 65% when two cross-beams were damaged. Therefore, damage to the cross-beam in the working plate can potentially cause accidents and harm workers. As the load increases, the risk of an accident due to the aforementioned damage also increases because the stiffness remarkably decreases with the load increase. Further, the damage to the cross-beam mainly reduces the stiffness but increases the displacement rather than the strength of the working scaffold plate.

• 대한산업공학회지
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• 제26권2호
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• pp.95-100
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• 2000

Presented in this paper is a scheme for constructing ball rolling blends of a non-uniform B-spline surface(NUBS) patches. Ball rolling blending is a popular technique for blending between parametric surfaces. Along the "common edge" of a pair of "base surfaces" to be blended, a sequence of "ball positions" is sampled. The radius of the ball may vary along the line. At each sampling point, a ball center point and a pair of ball contact points are computed by applying a Jacobian inversion method. Using ball contact points, the constructing scheme of blend NUBS patches consists three steps; 1) determination of intermediate control vertices; 2) determination of boundary vectors; 3) determination of B-spline control vertices. The proposed blending scheme has been tested in a Omega CAM system and found to be working satisfactorily.

• Journal of Mechanical Science and Technology
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• 제15권2호
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• pp.268-276
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• 2001

In order to improve the efficiency of a direct contact heat exchanger for a solar thermal energy system, the working fluid should be dispersed into small and uniform droplets, and stay within a heat exchanger for a long time. Therefore, installation of meshes in a direct contact heat exchanger is suggested in the present study, and the performance of the direct contact heat exchanger with several layers of meshes is experimentally investigated. Diethyl phthalate is used as the working fluid, and the performance of the heat exchanger is tested for several different operating conditions and compared to that of the heat exchanger without meshes. The results of this investigation show that meshes make droplets uniform and small when the flow rate is low. The relationship between the Peclet number and the Nusselt number becomes linear if it is steady. And, the Nusselt number for the direct contact heat exchanger with meshes becomes greater than that without meshes as the Peclet number increases.

• 한국화재소방학회논문지
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• 제19권1호
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• pp.46-50
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• 2005

본 논문에서는 작업복의 연소특성을 실험적으로 연구하였으며, 초기 점화위치는 상의소매 부분, 상의전면 중앙부분 및 하의무릎 부분으로 하였다. 실험결과는 다음과 같다. 미연소 질량비는 점화위치가 하의무릎 부분의 경우가 가장 빨리 감소하며 다음으로 상의소매 부분, 상의전면 중앙부분의 경우 순으로 감소하였다. 최고평균표면온도는 점화위치가 상의소매 부분, 상의전면 중앙부분, 하의무릎 부분의 경우 순으로 높게 나타났다. 연소 중 최고복사열유속은 점화위치가 상의소매 부분$(0.5\;W/cm^2)$, 상의전면 중앙부분 $(0.45\;W/cm^2)$, 하의무릎 부분$(0.44\;W/cm^2)$의 경우 순으로 높게 나타났다.

• Journal of Magnetics
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• 제22권2호
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• pp.326-332
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• 2017

The effects of exposure to an extremely low-frequency magnetic field (25 Hz 20G) on animal cells have been studied. In some reports, stimulation was performed for fixed frequency and variations in magnitude; however, animal-cell experiments have established that both parameters play an important role. The present work undertook the modeling, simulation, and development of a uniform-magnetic-field generation system with variable frequency and stimulation intensity (0-60 Hz, 1-25G) for experimentation with cell cultures in situ. The results showed a coefficient of variation less than 1 % of the magnetic-field dispersion at the working volume, which is consistent with the corresponding simulation results demonstrating a uniform magnetic field. On the other hand, long-term tests during the characterization process indicated that increments of only $0.4^{\circ}C$ in the working volume temperature will not be an interfering factor when experiments are carried out in in situ cell cultures.

• 태양에너지
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• 제20권1호
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• pp.81-89
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• 2000

In the present study, the characteristics of conductive and convective heat transfer occurred in a circular absorber of PTC (parabolic trough concentrator) for medium temperature solar energy utility were numerically investigated. A circular tube was considered as an absorber and the shape of PTC modeled in this study was based on the system that was installed in Korea Institute of Energy Research. Not only convection inside the tube but also conduction through the wall of the tube were analyzed, simultaneously. Circumferentially non-uniform heat flux that was simulated from the non-uniform solar disc model proposed by Jose was applied as thermal boundary condition on the tube surface. And, hydrodynamically fully developed laminar velocity profile was used as the inlet boundary condition and it was assumed that the working fluid was water. And, local heat fluxes at the interface of the tube and the working fluid were calculated for different wall thickness and thermal conductivity of the tube at various Reynolds number. Based on the results, the effects of thermal conduction of the tube on the local heat transfer were investigated.

• 제어로봇시스템학회논문지
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• 제4권6호
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• pp.786-794
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• 1998

This paper proposes an automatic microshaping technology using laser and applies it to implementation of semicutting control system of the panel inside which a car air bag is equipped. Since it is impossible to project laser directly onto the desired working point of a target panel due to fixedness of laser generator, we reflect the generated laser, using reflection mirrors and focusing lenses, to project onto the desired working point. Also, in order to conduct an uniform semicutting control with constant width and depth, we control the end-effector of manipulator, which grasp the laser reflection mirror, to track working path with constant speed and orientation. The validity and effectiveness of the proposed methods are checked through experiments tracking a path formatted with straight lines and arcs.