• Composites Research
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• v.13 no.4
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• pp.33-41
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• 2000

In this research, the mathematical modeling of the formation of SiC layer on the activated carbon was studied to improve the durability and the oxidation resistance of catalyst supports. SiC layer on the activated carbon was formed by permeating SiC from dichlorodimethylsilane(DDS) into pores and depositing while the porous structure was kept. The best conditions of manufacturing the support were found by studying the characteristics of SiC/C which was modelled under various deposition conditions. Changes of the amount of deposition, the pore diameter, the surface area with time were obtained by simulating convection, diffusion and reaction in an isothermal reactor at a steady state. The uniform deposition in the pores of samples was obtained at a lower concentration of the reactant and a lower pressure. Additionally, it was observed that the pore diameter and the surface area have points of inflection at certain times of deposition, because deposition occurred on the inside surface of the pore at first and then on the outside surface of the particle.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.2
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• pp.39-45
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• 2016

In a coaxial porous injector, a gas propellant is injected through the porous cylinder surface to the liquid jet which is encircled by a porous cylinder. In this study, to observe the differences in disintegration mechanisms between a shear coaxial injector and a coaxial porous injector, cold-flow tests and 2-D axisymmetric numerical analysis have been carried out. The shadowgraph images and Sauter mean diameters were compared in similar experimental conditions, and the effects of velocity distributions at the inner injector region on the disintegration of liquid jet were investigated through the numerical calculations. As a result, in high air mass flow rate condition, the disintegration performance of coaxial porous injector is better than shear coaxial injector, in spite of a lower velocity at the inner injector region.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1770-1772
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• 2003

본 연구는 국내에서 최초로 제안되고 적용가능성이 입증되어 설계, 제작된 Probe-type Pockets sensor(HY-Pockets Sensor)를 GIS등의 고전압 장비들에 응용한 레이저 부분방전 진단 시스템 개발을 목표로 하고 있다. 이러한 목적으로, 170kV 급 실 규모 GIS내부의 전류 도체에 다양한 곡률 반경의 침 전극을 부착시켜 부분 방전에 기인된 불평등 전계를 형성시켜 개발된 센서의 실규모 적용 가능성을 고찰하였다. 본 레이저 계측 시스템은 He-Ne laser, single multi-mode optical fiber, $2{\times}2$ 50/50 laser to single mode fiber coupler, probe-type Pockets sensor, photo detector 등으로 구성하여 레이저의 진행을 유도하고, 신호의 특성을 분석하였다. probe-type Pockets sensor로부터 의 출력 신호는 photo detector를 통해 전기적 신호로 변환되어 digital oscilloscope에 의해 측정되고, 또한 PC를 통해 데이터의 저장과 통계적, 분석적 처리 과정을 수행하게 된다. 본 연구의 결과로서 부분방전원에서 생성된 방전 신호에 대한 거리에 따른 센서 감도 결정, 그에 대한 센서 감도의 보정 향상, 전계의 세기의 변화에 따른 센서의 선형성 등이 도출되었고, 이러한 실험결과를 통해 실 GIS(170kv급) 내부에서 발생하는 부분방전의 검출에 본 레이저 부분방전 진단 시스템의 적용 가능성이 제시 되었다.

• Journal of Conservation Science
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• v.11 no.1 s.14
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• pp.15-27
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• 2002

The Buddhist Triad Cave in Gunwi, which consists of porphyritic biotite granite, has been deteriorated by a few weatherings. Origin of the weatherings is rain that can be leaked into the cave. Therefore the author investigates a few possible joints and bypasses leaking water, and reinforces any protective schemes for the rain influx. The porphyritic granite around the cave regularly develops two NEE and NWW joint sets. The NEE joint set could be divided into 4 joint zones among which $J_m\;and\;J_3$ may directly affect the leaking water into the cave. A extensional joint, in northern wall of the cave, runs through the $J_m$ joint zone. A small rain could rarely gets through the bypass, but a heavy rain has a good circulation through the joints to be leaked into the cave for a long time because of its long way. Many joints and cracks, in the ceiling near the cave entrance, immediately get to the $J_3$ joint zone, and have a good circulation of a small rain 10 mm. It is the desirable protective schemes that forbid rains to influx along the ranges from L -9 m to +10 m in the $J_m$ joint zone and upper half circle with radius 5 m in the $J_3$ joint zone. The joint apertures should be filled with a petro-epoxy and petro-filler to stop the water flow.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.8A
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• pp.962-971
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• 2004

In this paper, we present the numerical analysis method for analyzing scattering characteristics of a rectangular waveguide with the conducting half cylinder using the mode matching method and compute scattering characteristics of a waveguide according to the rotation and changing radius of the half cylinder. Also, in conjunction with the generalized scattering method, the proposed method can be easily applied to a rectangular waveguide with cascade structure of conducting half cylinders. From the simulated result of a two pole filter, resonance frequency could be controlled by the rotation of half cylinders. The simulated result shows good agreement with the HFSS's result. The proposed structure and analysis method are easily applied to the design of waveguide components with conducting half cylinders.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.12
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• pp.1011-1016
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• 2015

In a roll-to-roll continuous system, winding is one of the most important processes since it determines the quality of the final manufactured products such as flexible film and printed electronic devices. Since an adequate winding tension can reduce the incidence of the defects that are derived from the inner stress of the wound roll such as starring and telescoping, it is necessary to determine the optimal taper-tension profile. In this study, an algorithm for the setting of an optimal taper-tension profile in consideration of the residual stress in the wound roll is suggested; furthermore, the algorithm was adjusted for the determination of an optimal taper-tension profile regarding the winding process of $10{\mu}m$ polypropylene (PP) film. As a result of the algorithm-generated, optimal taper-tension profile, the residual stress and radial stress in a PP wound roll were decreased to 27.37 % and 40.05 % (mean value), respectively.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.1
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• pp.9-14
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• 2004

The fluorescent lamp has been successfully modeled by employing the radial variation of particle density and considering driving circuit effects on the characteristics of discharge process. The electron energy distribution is assumed to have a Maxwellian. The electron mobility and the ambipolar diffusion coefficients are considered to vary with an electron energy rather than a simple uniform value. Energy states of mercury atom in the discharge process are regarded as six levels rather than simple 4 or 5 levels. These discharge processes have been accurately solved by numerically employing mixed the FDM and the 2nd Runge-Kutta method. This model was applied to analyzing real circuit. Simulation and experimental results were presented to verify the feasibility of the modeling. Simulation and experimental results were presented to verify the feasibility of the modeling.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.4
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• pp.69-76
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• 2002

The aim of this study is to provide fundamental informations that make it possible to use a cool stream and a hot stream simultaneously. We changed the pressure of compressed air that flows into a tube, the inner diameter of orifice that a cold stream exits, and the mass flow rate ratio. And in each case, we measured the temperature of a cold stream and a hot stream in each exit of a tube. Also we measured the axial and the radial temperature distribution in internal spare of a tube. From the study, fellowing conclusive remarks 7an be made. First, As the number of nozzles increase, separation point move into the hot exit. Second, When we use guide vane type nozzle, the axial temperature distribution constant over the 0.75 of air mass flow rate radio. Third, When we use Spiral type nozzle, axial and radial temperature distribution in the inner space is higher than another nozzle. Fourth, Axial and radial temperature distribution in the inner space vortex-tube is determined by separation point. And separation point is moved by changing of air mass flow rate ratio. At last, A heating apparatus is possible far vortex-tube to use.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.10
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• pp.3251-3261
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• 1996

Flows were measured in an unshrouded centrifugal impeller. By using a single slanted hot-wire probe and a Kiel probe mounted on the impeller hub disk, the 3-D relative velocities and the rotary stagnation pressures were measured in seven circumferential planes between the inlet and outlet of the impeller rotating at 700 rpm, which diameter is 0.39 meter, and the static pressures and the slip factor at the impeller outlet were estimated from the measured values. Measurements were made for three flow rates corresponding to zero incidence and two others with the greater and the smaller one than zero. From the measured data in these flow rates, the followings were investigated in the impeller passage, the variation of the primary and secondary flows, the leakage flows, the wake's position and its size, the static pressure rise and the loss production mechanism. Furthermore the static pressure and the slip factor were compared with the results of inviscid Quasi-3D calculation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.10
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• pp.3262-3271
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• 1996

Flow patterns were measured in a shrouded centrifugal impeller. The flow rate in measurements was fixed at the value corresponding to a nearly zero incidence at the blade inlet. By using a single slanted hot-wire probe and a Kiel probe mounted on the impeller hub disk, the 3-D relative velocities and the rotary stagnation pressures were measured in seven circumferential planes from the inlet to the outlet of impeller rotating at 700 rpm, and the static pressure distribution along flow passage and the slip factor at impeller outlet were calculated from the measured values. From these measured data, the primary and secondary flows, the wake production and the static pressure rise in the impeller passage were investigated. Furthermore, the secondary flow patterns and the wake's location in this impeller passage were compared with those of the unshrouded impeller.