• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.262-265
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• 2006

The purpose of this study is to design 200 kW, 15,000 rpm 3 phase induction motor. This research deals with natural frequency and mode shape of rotating shaft of 3 phase induction motor with bearing stiffness by finite element analysis. We present natural frequency characteristic variation of rotating shaft according to change bearing stiffness. Also we are verified stability of rotating shaft from backward and forward critical speed by campbell diagram.

• 한국분무공학회지
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• 제9권2호
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• pp.18-23
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• 2004

An experimental studies of conventional gasoline fuel pump were carried out to obtain fundamental data fur liquid phase LPG injection(LPLi) system. A regenerative type and a roller-vane type of pumps were investigated in various operational condition. The experiments were performed to obtain flow rate of LPG fuel as a function of pressure differences and temperatures. The regenerative pump had too low flow rate at some experimental conditions to use this pump system for LPLi fuel supply system. On the other hand, the roller-vane type pump can be applied to the system only if its check valve is modified. Cavitation might occur in this system which can result in system noise, flow rate variation, and pump durability problem. To solve these problems the system is needed to increase $NPSH_{re}$(required net positive suction head).

• 소성∙가공
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• 제12권4호
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• pp.284-289
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• 2003

The effects of nitrogen on the deformation behavior of duplex stainless steel have been studied. The variation of strength was correlated with the characteristic microstructures pertaining to nitrogen. Analysis based on Hall-fetch relation confirmed that nitrogen enhances phase-boundary strengthening effect. The evolution of dislocation structure, slip traces and misorientation distribution during deformation were also characterized to elucidate the effect of nitrogen on inelastic deformation mechanism. It has been verified in this study that the higher nitrogen content provides a dual-phase microstructure with smaller strength difference between austenite and ferrite resulting into the earlier transfer of inelastic deformation from austenite to ferrite.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 A
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• pp.227-229
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• 1997

The torque of SRM is developed by phase currents and inductance variation. The inductance of torque generation region is nonlinearly varied according to phase current. By this nonlinear characteristics, torque ripple can be generated on the condition of constant current. Otherwise, phase current should be controlled instantaneously in accordance with inductance to reduce torque ripple. In this paper, the control system with neural network that can reduce torque ripple is suggested. In this control system, instantaneous inductance and optimal current waveform for smallest torque ripple is obtained by neural network. And this required optimal current waveform is regulated by voltage control.

• 한국세라믹학회지
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• 제28권1호
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• pp.29-36
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• 1991

Microporous glasses in the system TiO2-SiO2-Al2O3-B2O3-CaO-Na2O were prepared by the phase-separation technique. Morphology and distribution of pore and specific surface area of glasses heated and leached out at various conditions were investigated by SEM and Porosimeter. Crystallization of glasses heated above transition temperature was also inspected by X-ray diffraction method. When the heating temperature and time increased, the pore size and volume increased, but the specific surface area decreased above the critical temperature. The phase-separation, specific surface area and pore size showed more sensitive change on the variation of heating temperature than of heating time. The specific surface area and micropore volume of porous glasses prepared in this study were about 120-330$m^2$/g and 0.001-0.01cc/g, respectively. Mean pore size of porous glasses were about 20-90$\AA$. Anatase phases was deposited when the parent glass was heat-treated at 75$0^{\circ}C$ for 6hrs.

• Journal of Power Electronics
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• 제16권3호
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• pp.915-924
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• 2016

A digital self-sustained phase shift modulation (DSSPSM) strategy that allows for good soft switching and dynamic response performance in the presence of step variations is presented in this paper. The working principle, soft switching characteristics, and voltage gain formulae of a LLC converter with DSSPSM have been provided separately. Furthermore, the method for realizing DSSPSM is proposed. Specifically, some key components of the proposed DSSPSM are carefully investigated, including a parameter variation analysis, the start-up process, and the zero-crossing capture of the resonant current. The simulation and experiment results verify the feasibility of the proposed control method. It is observed that the zero voltage switching of the switches and the zero current switching of the rectifier diodes can be easily realized in presence of step load variations.

• E2M - 전기 전자와 첨단 소재
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• 제7권4호
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• pp.300-305
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• 1994

We determined the alloy composition of the liquid-phase epitaxy(LPE) grown $Al_{x}$G $a_{1-x}$ As by the photoreflectance(PR), and observed the variation of PR signal by changing the condition of annealing and thickness of epilayer. As the measuring temperature was decreased, the broadening parameter was decreased, and the amplitude of PR signal was increased. When the temperature of annealing was increased, the surface carrier concentration was decreased and then the shape and amplitude of PR signal were affected by the surface electric field. The structure change was observed when the specimen was annealed for long time at a high temperature. We found that the surface electric field increased when the thickness of epilayer was decreased by etching, because the band bending was increased by the decreased of the width of depletion layer....

• 대한전자공학회논문지SD
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• 제41권3호
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• pp.31-38
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• 2004

광섬유격자 센서어레이의 복조에 사용할 목적으로 광섬유레이저의 파장변화 검출방법을 제안하였다. 삼각파로 변조된 광섬유레이저의 출력 파장을 Mach-Zehnder 간섭계와 시간지연샘플링 기법으로 분석하였다. 피크간의 시간차를 측정하는 기존의 방법과 달리 파장변조 메카니즘의 비선형 특성에 무관하게 항상 선형적인 출력을 얻을 수 있었으며 6.5 ㎚의 스캔범위에서 약 20 pm의 파장분해능을 얻을 수 있었고, 이는 응답특성이 뛰어난 위상변조기를 사용할 경우 크게 개선될 수 있음을 보였다.

• 한국광학회지
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• 제10권3호
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• pp.201-207
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• 1999

단일모드 광섬유와 결합기를 이용하여 간결한 구조의 광섬유 공초점 간섭 현미경을 구성하였으며, 위상 변위법을 응용한 표면 검색 방법을 제안하여 통신용의 반도체 레이저와 같이 비교적 긴 파장의 광원과, 낮은 NA의 대물렌즈를 사용하더라도 정밀한 시료 표면 검색이 가능함을 보였다. 이때 시료 표면의 높낮이는 시료로부터 반사된 빛의 위상으로부터 결정되며, 종래의 공초점 현미경에 비하여 주사시간을 크게 단축할 수 있었다. 끝으로 종래의 방법에 비해 제안된 방법은 시료의 반사율 변화에 덜 민감함을 확인할 수 있었다.

• 한국국방경영분석학회지
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• 제27권1호
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• pp.10-27
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• 2001

This paper deals with the application of PRICE model in estimating the proper acquisition cost for weapon budgeting phase. The PRICE(Parametric Review of Information for Costing and Evaluation) Hardware model is a computerized method for deriving cost estimates of electronic and mechanical hardware assemblies and systems. The model can be used in obtaining not only initial cost estimates in conceptual phase, but also detailed cost estimates in budgeting phase depending on available historical and empirical data. We analyzed first step cost estimate parameters and derived cost equations using PRICe output dta. Using weight and complexity, We can find cost variation. Sensitivity analysis shows that cost increases exponentially as complexity increases exponentially as complexity increases. We estimated KAAV\`s (Korea Amphibious Assault Vehicle) production cost using the PRICE model and compare with engineering cost estimates which is based on actual production data submitted by the production company. The result shows that tow estimates are close within $\pm2%$ differences.