• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2011년도 춘계학술발표대회 논문집
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• pp.116-120
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• 2011

In this paper, we studied the optimization of the screen pringting method for crystalline silicon solar cell fabrication. The 156 * 156 mm2 p-type silicon wafers with $200{\mu}m$ thickness and $0.5-3{\Omega}cm$ resistivity were used after texturing, doping, and passivation. Screen printing method is a common way to make the c-Si solar cell with low-cost and high-efficiency. We studied the optimized condition for screen printing with crystalline silicon solar cell as changing the printing direction (finger line or bus bar), finger width, and mesh angle. As a result, the screen printing with finger line direction showed higher finger height and better conversion efficiency, compared with one with bus bar direction. The experiments with various finger widths and mesh angles were also carried out. The characteristics of solar cells was obtained by measuring light current-voltage, optical microscope and electroluminescence.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제51권5호
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• pp.242-248
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• 2002

It is important to develop new effective technologies to increase the interruption capacity and to reduce the size of a UB(Gas Circuit Breakers). Major design parameters such as nozzle geometries and interrupting chamber dimensions affect the cooling of the arc and the breaking performance. But it is not easy to test real GCB model in practice as in theory. Therefore, a simulation tool based on a computational fluid dynamics(CFD) algorithm has been developed to facilitate an optimization of the interrupter. Special attention has been paid to the supersonic flow phenomena between contacts and the observation of hat-gas flow for estimating the breaking performance. However, there are many difficult problems in calculating the flow characteristics in a GCB such as shock wave and complex geometries, which may be either static or in relative motion. Although a number of mesh generation techniques are now available, the generation of meshes around complicated, multi-component geometries like a GCB is still a tedious and difficult task for the computational fluid dynamics. This paper presents the CFD program using CFB-CAD integration technique based on Cartesian cut-cell method, which could reduce researcher's efforts to generate the mesh and achieve the accurate representation of the geometry designed by a CAD tools.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제52권9호
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• pp.434-441
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• 2003

This paper deals with the temperature characteristics according to the cooling medium and the duct size in model transformers. For the analysis and the temperature-rise tests, two 400kVA model transformers have been manufactured. One has been filled with the alpha oil as the cooling medium and constructed the duct sizes of $3\textrm{mm}$ and $5\textrm{mm}$ in the low-voltage and high-voltage windings respectively. The other has been filled the beta oil and the duct sizes were $4\textrm{mm}$ and $6\textrm{mm}$. The temperature-rise tests have been performed by the back-to-back method and the load factor has been controlled the range of 90%∼130%. The temperature values have been measured by the thermocouple and from the sixteen points in each transformer. A commercial CFD program "FLUENT" has been used for the analysis of temperature distribution. The geometry of transformer has been modeled to 3-dimensional by using the hybrid calculation mesh including the radiator. And also, the natural convection velocity has been measured at the oil top position, and compared with the calculated results.

• Advances in aircraft and spacecraft science
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• 제10권2호
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• pp.179-202
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• 2023

This article presents a numerical analysis to investigate the natural frequencies and harmonic response of a perforated cantilever beam attached to two layers of piezoelectric materials by using the finite element method for the first time. The bimorph piezoelectric is composed of 3 layers; two of them at the outer are piezoelectric, and the inner isotropic material. A higher order 3-D 20-node solid element that exhibits quadratic displacement behavior is exploited to discretize the isotropic layer, and coupled piezoelectric 3D element with twenty nodes is used to mesh the top and bottom layers. CIRCU94 element is added to act as a resistor part of the model. The proposed model is validated with previous works. The numerical parametric studies are presented to illustrate the effects of perforation geometry, the number of rows, the resistance on the natural frequencies, frequency response, and power. It is found that the thickness has a positive relationship with the natural frequency. Perforations help in producing higher voltage, and the best shape is rectangular perforations, and to produce higher voltage, two rows of rectangular perforations should be applied.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.433-433
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• 2016

Carbon nanotubes (CNT) emitter has widely become an attractive mechanism that draws growing interests for cold cathode field emission. CNT yarns have demonstrated its potential as excellent field emitters. It was demonstrated that a small focal spot size was achieved by manipulating some electrical parameters, such as applied bias voltage at the mesh gate, and electrostatic focal lenses, geometrical parameters, such as axial distances of the anode, and the electrostatic focal lens from the cathode assembly, and the dimension of the opening of the electrostatic lens. Electrical-optics software was used to systematically investigate the behavior of the electron beam trajectory when the aforementioned variables were manipulated. The results of the experiment agree with the theoretical simulation results. Each variable has an individual effect on the electron beam focal spot size impinging on the target anode. An optimum condition of the parameters was obtained producing good quality of X-ray images. Also, MWCNT yarn was investigated for field emission characteristics and its contribution in the X-ray generation. The dry spinning method was used to fabricate MWCNT yarn from super MWCNTs, which was fabricated by MW-PECVD. The MWCNT yarn has a significant field emission capability in both diode and the triode X-ray generation structure compared to a MWCNT. The low-voltage-field emission of the MWCNT yarn can be attributed to the field enhancing effect of the yarn due to its shape and the contribution of the high-aspect-ratio nanotubes that protrude from the sides of the yarn. Observations of the use of filters on the development of X-ray images were also demonstrated. The amount of exposure time of the samples to the X-ray was also manipulated. The MWCNT yarn can be a good candidate for use in the low voltage field emission application of X-ray imaging.

• The Korean Journal of Pain
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• 제20권2호
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• pp.92-99
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• 2007

Background: A correlation between a T-type voltage activated calcium channel (VACC) and pain mechanism has not yet been established. The purpose of this study is to find out the effect of ethosuximide and mibefradil, representative selective T-type VACC blockers on postoperative pain using an incisional pain model of rats. Methods: After performing a plantar incision, rats were stabilized on plastic mesh for 2 hours. Then, the rats were injected with ethosuximide or mibefradil, intraperitoneally and intrathecally. The level of withdrawal threshold to the von Frey filament near the incision site was determined and the dose response curves were obtained. Results: After an intraperitoneal ethosuximide or mibefradil injection, the dose-response curve showed a dose-dependent increase of the threshold in a withdrawal reaction. After an intrathecal injection of ethosuximide, the threshold of a withdrawal reaction to mechanical stimulation increased and the increase was dose-dependent. After an intrathecal injection of mibefradil, no change occurred in either the threshold of a withdrawal reaction to mechanical stimulation or a dose-response curve. Conclusions: The T-type VACC blockers in a rat model of postoperative pain showed the antihyperalgesic effect. This effect might be due to blockade of T-type VACC, which was distributed in the peripheral nociceptors or at the supraspinal level. Further studies of the effect of T-type VACC on a pain transmission mechanism at the spinal cord level would be needed.

• 조명전기설비학회논문지
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• 제15권3호
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• pp.25-34
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• 2001

본 논문에서는 방전관을 채용하여 전기적 기체방전의 중침을 이용한 새로운 방전형식의 환경개선용 오존발생 기술을 개발하였다. 방전관형 오존발생기(DLO)는 설치된 3개의 전극중 접지전극인 중심전극으로 방전관을 사용 하였으며, 나머지 2개의 메쉬형 내부전극과 나선형 외부전극에 180[$^{\circ}$]의 위상차를 가진 2개의 교류고전압 전원을 인가함으로써 방전관과 내부전극, 방전관과 외부전극사이의 방전공간에서 각각 발생되는 무성방전의 중침에 의하여 오존이 발생되는 구조이다. 이때, 원료가스의 유량, 방전전력 및 DLO의 사용 개수 변화에 따른 방전특성과 오존생성특성을 연구검토하였으며, DLO로부터 생성된 오존을 대기오염물질인 NO 가스에 접촉시켰을 때 NO 제거특성이 우수하여 방전관형 오존발생기가 대기환경개선 설비로 적용가능함을 확인하였다.

• 공업화학
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• 제22권3호
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• pp.249-254
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• 2011

Ferroelectric의 강유전체 소구들을 충전한 원통형의 비열 방전 플라즈마 반응기를 설계 제작하였으며, 강유전체 층방전 구조를 구성하는 평판(20 mm 간격) 금속망 전극 사이에 직경 2.0 mm인 $SrBiTaO_9$ (SBT) 소구들을 위치시키고 고압의 교류 전원을 인가하였다. SBT 소구는 상온($25^{\circ}C$)에서 150, 큐리온도($335^{\circ}C$)에서 500의 유전상수를 가졌다. 플라즈마 반응기에서 오존 생성속도는 거의 인가전압의 증가에 비례하였으며, SBT 소구들이 충전된 경우, 20 kV 이상의 인가전압에서 오존 생성속도는 급격하게 증가하였다. 부코로나 방전에서 오존 생성속도가 정코로나 방전에서의 경우보다 높았다. 그러나 톨루엔 및 메틸렌클로라이드의 분해율은 생성된 오존 농도에 비례하여 증가하지 않았다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.51-53
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• 2003

본 논문에서는 압전 트랜스듀서의 임피던스 해석을 유한 요소법을 통해 실험적으로 검증하였고 이러한 유한 요소법을 이용하여 압전 변압기의 동작 주파수 및 등가회로 정수를 도출하였다. 또한, 등가 회로법을 이용하여 부하 변동에 따른 압전 변압기의 공진 주파수와 효율 변화를 분석하고 이를 실험적으로 검증하였다. 한편, 유한 요소법과 자동 요소 분할 프로그램(Auto-Mesh Generator), 최적화 알고리즘을 이용하여 일정 부하에서 최대 효율과 승압비를 갖는 압전 변압기의 형상 최적화를 수행하였는데, 최적화 기법으로는 sinc함수의 수렴 결과를 통해 타당성이 입증된 진화 알고리즘(Evolution Strategy)을 적용하였다.

• Environmental Analysis Health and Toxicology
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• 제4권3_4호
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• pp.29-59
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• 1989

For the purpose of electrolytic treatment of wastewater containing various heavy metals, the BPBE Cell of batch and continuous type was considered and experimented. Some results from this study were summarized as follows: 1. When the artificial wastewater containing 500 mg/l of the concentration of various heavy metallic ion was electrolyzed in BPBE Cell of batch type, the removal efficicency was over 95% in cadmiun (II), lead (II), chromium (Ⅵ) and over 85% in copper (II), chromium (III). 2, As granular activated carbon packed in BPBE Cell, coconut shell was superior to lignite and the removal efficiency was the highest when the activated carbon was 4/6 mesh, the voltage was 20V. 3. When the heavy metallic ion in wastewater was electrolyzed in BPBE Cell of continuous type, about 1,000mg of heavy metal per 1kg of coconut sell could be removed. 4. The treatment method of heavy metallic ion in wastewater by BPBE Cell cost less than in the former chemical treatment method and the coconut shell packed in BPBE Cell could be regenerated by chemical method.