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저압 유기 금속 화학 증착법으로 성장시킨 GaN박막의 캐소드루미네슨스에 대한 연구
홍창희 대한전자공학회 1999 電子工學會論文誌, D Vol.d36 No.5
본 논문에서는 저압 유기 금속 화학증착법으로 성장시킨 GaN박막들을 실온 케소드루미네슨스 방법으로 광학적 특성을 측정하여 결정성장 메커니즘과 광학적 특성과의 관계를 규명하였다. 관측된 스펙트럼은 주로 364nm의 강한 band-edge emission 피크와 550nm의 깊은 준위 피크이었다. 빔 전류의 증가에 따라 364nm 스펙트럼의 세기가 깊은 준위 발광 스펙트럼보다 크게 증가시켰다. 이는 성장 초기 GaN박막의 결정 결함이 깊은 준위 발광 스펙트럼과 깊은 관계가 있음을 나타내 주고 있다. 또한 미세 결정 구조와 깊은 준위 발광 스펙프럼과의 관계 분석을 위해 주사형 전자현미경 사진과 캐소드루미네슨스 스펙트럼을 비교 검토하였다. In this paper, the correlation between the growth mechanism and the optical property in GaN films grown by low-pressure metalorganic chemical vapor deposition was characterized using room temperature cathodoluminescence spectroscopy. An intense near band-edge emission, 364nm, and deep-level emission, 550nm, were observed. The intensity of 364nm peak was increased with increasing the beam current. Also the peak position of 364nm emission was red-shifted and the intensity of 550nm peak was increased with increasing the accelerating voltage. It shows that the deep-level emission is strongly associated with crystalline defects in the GaN at early stage. The relationship between the microstructure and the deep level emission observed by scanning electron microscope images and cathodoluminescence spectra was carefully analyzed.
Dither 효과를 이용한 서어보 위치 제어계의 응답특성 개선
홍창희,장기효 동아대학교 공과대학 부설 한국자원개발연구소 1987 硏究報告 Vol.11 No.1
The position control system of DC servomotor using dither effect improves the characteristics of response, but oscillation in setting the desired position control is caused by jerking motion in the steady state. A method for supressing the jerking motion using dither effect is proposed. By this method compensating the characteristics of response in the case of setting the desired position control, we can verify the useful-ness of this method in obtaining the best characteristics of position control response in the position control system.
문태정,강정호,홍창희 東亞大學校 附設 情報通信硏究所 1998 情報通信硏究所論文誌 Vol.6 No.1
Antilock Brake Sysytem(ABS) si the device for getting the braking force and the cornering force of the car. The ABS sensor consists of a permanent magnet and pickup coil. When the rotor and the sensor changes, The air gap between the rotor and the sensor changes. This disturbs the magnetic flux emanating from the permanent magnet and generates ac voltage in the pickup coil. The frequency fo this ac voltage changes with the speed of rotation, and in this way the system is able to measure the rotation speed of the wheel. The purpose of this report is to describe a development method of a new type sensor after analyzing two kinds of typical sensors.
洪昌熹 忠州大學校 1971 한국교통대학교 논문집 Vol.4 No.1
Practical calculation of transient resistance effects in conductors are reported. Induced are the current density distribution in cylindrical and semi-infinite solid conductors for an applied surface step electric field E, and the density in a flat wide conductor. Two analogies used to yield useful result ; thermal diffusion in a cylinder and voltage transient, on a semi-infinite transmission line. Results are applied to the calculation of time constants of a transmission line.
三相凸極同期電動機의 起動 torque에 關한 數理的 考察
金容柱,洪昌憙 충주대학교 1970 한국교통대학교 논문집 Vol.3 No.-
Synchronous motors must usually be started from rest as induction motors with no field excitation, brought up to as near synchronous speed as possible, and then pulled into synchronism by application of field voltage. In order to apply large starting torque, we must install amortisseur windings in the synchronous motor. In such case, it is very difficult to calculate the special quantities of synchronous motor, becaus the mutual or self inductance of the motor is very random. So as to distinguish at a glance, we applied the matrices for analysising the motor characteristics, and instead of 3 phase symmatrical coordinate methode, we introduce Blondel's two-axis methode becaus of the saliency of the synchronous motors. Much more conveniently, we assumed that the innertia of the rotor is so larger that the component of the rotor vibration can be neglected. Thus we may calculate the only average torque. Finaly we compared the theoretical calculating value with the measuring value. The compared results of those are coincided. Consequently we conclude that the introducing theoretical methodes are very fine.