• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2009년도 한국우주과학회보 제18권2호
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• pp.43.3-43.3
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• 2009

Our previous study showed the intensity of the long LBH (1600 - 1715 ${\AA}$) was enhanced very much compared to that of the short LBH (1400 - 1500 ${\AA}$) when the characteristic energy of the precipitating electrons increased from 1 keV to > 7 keV, in accordance with the theoretical models. In this presentation, we would like to present the results of our study for new modeling results about previous report and even higher energy electrons. We selected the events in which the fluxes both in the low energy (100 eV ~ 20 keV) and in the high energy (170 ~ 360 keV) were enhanced, and examined the auroral spectra for these events observed simultaneously by the imaging spectrograph on the same spacecraft. While the accurate characteristic energy could not be determined because of the gap in the energy range, our result showed the intensity ratio of the long LBH to the short LBH ranged from 1.2 to 2.0 in these events, in contrast to 1.0 or smaller for the events in which the highest enhancement was seen only in the low energy. Our study suggests that intense auroras might be accompanied by high energy electrons above 20 keV.

• 드라이브 ㆍ 컨트롤
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• 제9권4호
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• pp.52-57
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• 2012

In this study, in order to understand contents and ranges of design for the EGR Valve test system for improving quality and performance of EGR Valve, engine performance and exhaust gas characteristic of 3L-class diesel engine was analyzed. Experimental operation of engine performance test was performed with 50% engine load and 20% and 100% opening ratio of EGR Valve. From test of performance and exhaust gas characteristic of engine, torque output of engine and temperature and pressure of inlet and outlet of EGR Valve were measured. As a result, for design of EGR Valve test system, input fluid flow of EGR Valve must be set the same amount with exhaust gas flow that was below of engine speed of 2,500 rpm, and temperature of inlet of EGR Valve must be set under about $510^{\circ}C$. And the difference of temperature between inlet and outlet of EGR Valve must be over than about $200^{\circ}C$. Exhaust gas of inlet and outlet of EGR Valve were under 1 bar that was not considerable, and the difference of pressure between inlet and outlet of EGR Valve were under 1 bar that could not effect on mechanical operation of EGR Valve.

• 한국전산구조공학회논문집
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• 제22권4호
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• pp.371-377
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• 2009

본 연구에서는 회전 및 병진 자유도를 갖는 2자유도 진동계의 동적 특성을 다루었다. 강체의 관성모멘트를 새로운 기계 요소인 이너터로 모델링한 뒤 동강성법을 이용하여 2자유도 진동계의 등가모델을 구하였다. 이때 이너터의 크기에 따라 진동계의 동적특성이 결정되는 것을 보였다. 2자유도 진동계를 진동 흡진기로서 단일 모우드 소거에 적용하였을 경우의 흡진기 설계방법론을 구하였다. 비감쇠 진동흡진기의 경우 해석적인 방법론을 제시하였고, 하나의 감쇠기가 존재하는 경우 고정점법을 적용한 방법론을 소개하였다. 수치 예를 통해서 제시된 방법론을 검증하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 제5회 학술대회 논문집 일렉트렛트 및 응용기술연구회
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• pp.82-85
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• 2003

산업의 고도화 및 환경오염의 문제로 1970년대부터 실리콘고무를 이용한 애자의 사용이 시도되기 시작되었다. 그로 인해 실리콘 고무의 표면열화에 대한 수많은 연구가 현재까지 행해지고 있다. 그러나 고온성 형압즉방식으로 제작하는 유기애자의 경우 제조시 발생할 수 있는 내부보이드에 대한 연구는 미흡한 현실이다. 이에 본 연구에서는 실리콘고무의 내부보이드의 형태변화에 따른 전기적열화특성을 연구하기 위하여 3층으로 적층시킨 실리콘 고무의 중간층에 임의적으로 4가지형태의 내부보이드를 성형하여 전압을 변화시키면서 방전전류 및 방전전력을 측정하였다. 그 결과, 보이드의 존재로 방전전류 및 방전전력의 증가를 볼 수 있었으며, 보이드형상의 내부각이 좁을수록 방전전류 및 방전전력값이 커지는 것을 볼 수 있었다.

• 전력전자학회논문지
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• 제10권3호
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• pp.241-247
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• 2005

본 논문에서는 플라이휠의 저장에너지를 이용한 다이나믹 무정전 전원장치를 제안하고 동작기능을 분석하였다. 배터리를 에너지 저장요소로 사용하고 있는 기존의 무정전 전원장치에 비해 플라이휠 방식의 무정전 전원장치는 수명이 길고, 효율이 높으며, 환경공해가 거의 없으며, 크기도 작고, 특히 유지보수 비용이 현저히 작다는 장점을 갖는다. 무정전 기능뿐 아니라 전압보상 기능도 갖는 시스템에 대한 동작특성을 해석하였으며, 순간정전 후 전압이 복귀되는 시점에서의 위상변동을 신속히 추종하는 특성도 살펴보았다. 시뮬레이션과 실험을 통해서 시스템의 유용성을 검증하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집
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• pp.354-357
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• 2002

Thermally grown gate oxide on 4H-SiC wafer was investigated. The oxide layers were grown at l150$^{\circ}C$ varying the carrier gas and post activation annealing conditions. Capacitance-Voltage(C-V) characteristic curves were obtained and compared using various gate electrode such as Al, Ni and poly-Si. The interface trap density can be reduced by using post oxidation annealing process in Ar atmosphere. All of the samples which were not performed a post oxidation annealing process show negative oxide effective charge. The negative oxide effective charges may come from oxygen radical. After the post oxidation annealing, the oxygen radicals fixed and the effective oxide charge become positive. The effective oxide charge is negative even in the annealed sample when we use poly silicon gate. Poly silicon layer was dope by POCl$_3$ process. The oxide layer may be affected by P ions in poly silicon layer due to the high temperature of the POCl$_3$ doping process.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1998년도 춘계 학술대회논문집
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• pp.168-173
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• 1998

A numerical analysis of axisymetric backward facing step main nozzle flow in air jet loom has been accomplished. To obtain basic design data for an optimum main nozzle for an air-jet loom and to predict the transonic/supersonic flow, a characteristic based upwind flux difference splitting compressible Navier-Stokes method has been used. The wall static pressure of the main nozzle and the flow velocity changes in the nozzle tube were analyzed by changing air tank pressures and acceleration tube lengths. The flow inside the nozzle experiences double choking one at the needle tip and the other at the acceleration tube exit at tank pressures over $4kg_f/cm^2$. The tank pressure $P_t$ leading to the critical condition depends on the acceleration tube length; i.e, $P_t$ is higher for longer acceleration tubes. The $P_t$ value required to bring the acceleration tube exit to the critical condition is nearly constant regardless of acceleration tube length. The round needle tip shape might lead to less total pressure loss when compared with step shape.

• International Journal of Automotive Technology
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• 제3권2호
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• pp.71-78
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• 2002

A new control method far vision-based autonomous vehicle is proposed to determine navigation direction by analyzing lane information from a camera and to navigate a vehicle. In this paper, characteristic featured data points are extracted from lane images using a lane recognition algorithm. Then the vehicle is controlled using new Levenberg-Marquardt neural network algorithm. To verify the usefulness of the algorithm, another algorithm, which utilizes the geometric relation of a camera and vehicle, is introduced. The second one involves transformation from an image coordinate to a vehicle coordinate, then steering is determined from Ackermann angle. The steering scheme using Ackermann angle is heavily depends on the correct geometric data of a vehicle and a camera. Meanwhile, the proposed neural network algorithm does not need geometric relations and it depends on the driving style of human driver. The proposed method is superior than other referenced neural network algorithms such as conjugate gradient method or gradient decent one in autonomous lateral control .

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 C
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• pp.1549-1551
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• 1997

In this study, the $\beta$-Polyvinylidene fluoride($\beta$-PVDF) organic thin films were fabricated by physical vapor deposition method as one of the dry-processing methods and applying electric field during the vapor deposition. When the substrate temperature is $80^{\circ}C$, the PVDF organic thin films exhibit the characteristic absorption band of the $\beta$ forms $510cm^{-1}$, $602cm^{-1}$ and $1273cm^{-1}$, and the fraction of $\beta$ form crystals in the total crystalline content was 95%. The molecular structure of PVDF organic thin films were transformed from $\alpha$ to $\beta$ form with increasing of applied electric field and the control of substrate temperature.

• Nuclear Engineering and Technology
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• 제50권1호
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• pp.182-189
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• 2018

A neutron generation system was developed to induce fissile fission in a lead slowing down spectrometer (LSDS) system. The source neutron is one of the key factors for LSDS system work. The LSDS was developed to quantify the isotopic contents of fissile materials in spent nuclear fuel and recycled fuel. The source neutron is produced at a multilayered target by the (e,${\gamma}$)(${\gamma}$,n) reaction and slowed down at the lead medium. Activation analysis of the target materials is necessary to estimate the lifetime, durability, and safety of the target system. The CINDER90 code was used for the activation analysis, and it can involve three-dimensional geometry, position dependent neutron flux, and multigroup cross-section libraries. Several sensitivity calculations for a metal target with different geometries, materials, and coolants were done to achieve a high neutron generation rate and a low activation characteristic. Based on the results of the activation analysis, tantalum was chosen as a target material due to its better activation characteristics, and helium gas was suggested as a coolant. In addition, activation in a lead medium was performed. After a distance of 55 cm from the lead surface to the neutron incidence, the neutron intensity dramatically decreased; this result indicates very low activation.