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목형의 엔드 밀링시 절삭조건에 따른 가공 특성에 관한 연구
김성일,김종택,김민호,신형곤,김태영 한국공작기계학회 2006 한국공작기계학회 추계학술대회논문집 Vol.2006 No.-
The cutting tests of wood patterns are carried out using CNC milling machine. The cutting forces and surface characteristics of machined surface are investigated at various cutting conditions such as spindle speed, feed speed, cutting direction of wood pattern and wood material. In the CNC end-milling, the surface roughness increases as feed speed increases and decreases as spindle speed increases. However, the cutting force and surface roughness are different along the cutting direction and material of wood pattern.
김영동,강원찬,김남오,김형곤,김병철 조선대학교 에너지.자원신기술연구소 2004 에너지·자원신기술연구소 논문지 Vol.26 No.1
In this paper, digitally controlled electronic ballast for the HID lamps driven by proposed frequency conversion method is described. This electronic ballast consists of a buck converter, a low frequency square wave full bridge inverter, a high voltage pulse generator for the lamp ignition, an over current protection circuit and an 8-bit microcontroller. The fuzzy logic digital control operation is carried out by the 8-bit microcontroller. In spite of the limited control bandwidth caused by low operation speed of the 8-bit microcontroller, the good control performance for the constant lamp current in the warm-up period is obtained using the proposed frequency conversion driving method. The HID lamp is controlled in a constant current mode during the lighting warm up process and is controlled in a constant power mode during lighting steady state. A controlled variable power mode is used to extend the lamp lifetime.
Ga_(2-x)Sb_(x)Se₃단결정 광전소자 제작에 관한 연구
김형곤,송찬일 조선대학교 에너지.자원신기술연구소 2002 에너지·자원신기술연구소 논문지 Vol.24 No.2
Ga_(2-x)Sb_(x)Se₃solid solution crystals were grown by the Bridgman technique. The grown Ga_(2-x)Sb_(x)Se₃single crystals showed excellent photosensitivity from the visible to the near infrared range. The crystal structures of the Ga_(2-x)Sb_(x)Se₃single crystals were found o be cubic for the composition X=0.0, to be tetragonal for X=0.2 t o X=0.8, to be tetragonal and orthorhombic together for X=l0, and to be orthorhombic for X=1.2 to X=2.0, respectively. The optical energy gaps and the photoconductivity peak energies of the Ga_(2-x)Sb_(x)Se₃single crystals have a constant value in composition range from X=0.2 to X=0.8 with tetragonal structure, and an another constant value in composition range from X= 1.2 to X=2.0 with orthorhombic structure. The photoconductivity spectra of Ga_(2-x)Sb_(x)Se₃single crystals showed the photoconductivity peaks at the range corresponding to the band edge for each of the single crystals.
Zn₄GeSe_(6):Co^(2+) 單結晶에서 不純物 光吸收 特性
金亨坤,金柄哲,宋燦日 조선대학교 에너지.자원신기술연구소 2002 에너지·자원신기술연구소 논문지 Vol.24 No.2
In this work Zn₄GeSe_(6):Co^(2+) single crystals were grown by the C.T.R. (chemical transport reaction) method using high purity (6N) elements and iodine as a transport agent. The structure of the grown Zn₄GeSe_(6):Co^(2+) single crystals were monoclinic structure. The optical energy band gap was direct band gap and the temperature dependence of optical energy gap accorded well with the varshni equation. Optical absorption due to impurity in the Zn₄GeSe_(6):Co^(2+) single crystal was observed and described as originating from the electron transition between energy levels of Co^(2+) ion sited at T_(d) symmetry point.
2차원 해석을 이용한 지하복합구조물 설계의 문제점 : 지하철 정거장을 중심으로
김형곤,조현영,정진환 釜山大學校生産技術硏究所 1997 生産技術硏究所論文集 Vol.52 No.-
본 연구에서는, 3차원 지하구조물이 2차원 뼈대조구조해석에 의해서 설계될 때의 문제점 들, 즉 갑작스런 단면의 변화, 개구부, 길이방향으로의 지반상태의 변화들이 검토 되어진다. 구조물들 3차원 해석에서 실제구조물과 가능한한 가장 근사하게 FEM에 의해 이상화되어진다. 본 연구로부터, 다음과 같은 두가지 결론을 내릴수 있다. 첫째, 개구부가 존재하는 곳에서는 보다 정확한 휨 모멘트분포를 얻기 위해 3차원이나 판이론에 의한 세부적인 해석이 수행되어져야 한다. 둘째, 건조수축, 수화열 그리고 힘의 분배에 대한 길이방향 보강을 결정하기 위해서는 더 세심한 검토가 필요하다. In this study, the problems when 3-D underground structures were designed by using 2-D plane frame structure analyses, such as sudden changes of sections, openings, and the variations of the ground conditions in the longitudinal directions, were investigated. The structures were idealized by FEM as close as possible to the real structures in 3-D. From this study, the authors conclude following two results. First, 3-D or detailed analysis with plate theory where openings exist must be carried out to obtain more accurate bending moment distribution. Second, a more refined investigation is needed to determine the longitudinal reinforcement due to shrinkage, the heat of hydration and the distribution of forces.
메탈핼라이드 램프용 저주파 구형파 구동의 퍼지제어 전자식 안정기
金柄哲,金亨坤,全仁柱,宋燦日 조선대학교 에너지.자원신기술연구소 2002 에너지·자원신기술연구소 논문지 Vol.24 No.2
A low frequency square wave driven electronic ballast for metal halide (MH) lamps is developed. The lamp current/wattage is controlled by fuzzy logic controller based on the low cost 8-bit microcontroller. This electronic ballast consists of a buck converter, a low frequency square wave full bridge inverter, a high voltage burst pulse generator using IGBT for the MH lamp ignition, an over-current protection circuit and an 8-bit microcontroller circuit. The ballast system is operated on the constant current mode during the MH lamp start-up process and the system is operated on the constant power mode during steady state. Experimental results show that the fuzzy logic control operation is carried .out successfully by the 8-bit microcontroller PIC16F877. In this electronic ballast system, in spite of the limited control bandwidth caused by low operating speed of the %bit microcontroller, the good performance in the constant lamp current characteristic is obtained. Acoustic resonance of the MH lamps can be effectively avoided because the instantaneous lamp power is fully constant due to the low frequency square wave drive.
마이크로-매크로 셀룰라 시스템을 위한 계층선정 기법분석
김장섭,이상헌,정우곤,최형진 成均館大學校 科學技術硏究所 1998 論文集 Vol.49 No.1
A control scheme to select the appropriate layer between macro- and microcell hierarchical structure is considered. With the assumption that the each mobile speed is known to the system. the algorithm determines the optimal velocity threshold by which the cell section performed. The optimal criterion is to minimize the Grade of Service(GOS), a service criterion in cellular telephone systems. Mobile station with faster speed relative to the determined optimal speed threshold are assigned to a macrocell, while slower moving terminals are assigned to the smaller cells, i,e.. microcells. For the evaluation purpose for the proposed scheme, two different evaluation perspectives are compared and the algorithm proves to work