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동적 모드Ⅲ 하중을 받는 등방성체/직교이방성체 이종재료의 파이버 각도변화가 응력 및 위 성분에 미치는 영향
하재기,유재용 김천과학대학 2001 김천과학대학 논문집 Vol.27 No.-
In interpreting problems of bimaterial fracture mechanics, it is important to understand stress and displacement on the interface of bimaterial. Especially, a crack contained in the interface of the bimaterial has more complicated and dangerous fracture behavior than a crack contained in general material does. Therefore, the fracture problems of an interface crack in the bimaterial has been attracted by many researchers. In this paper, a crack on bond interface gets the load of dynamic modeⅢ and proceeds to the steady state when the mediums, i.e., isotropic/orthotropic material, are combined. In other words, we induce stress field and displacement field near a crack tip, and general stress field and displacement field apart from a crack tip in case that the velocity of a crack and direction are proportion to the change of time. And we then investigate the effect of the fiber direction of isotropic/orthotropic material to the stress and displacement fields of modeⅢ occured in the bi-material interfacial under constant velocity crack.
등방성체 동적 광탄성 하이브리드 법 개발 및 에너지 해방률에 대한 연구
하재기 김천과학대학 2001 김천과학대학 논문집 Vol.27 No.-
In this paper, dynamic photoelastic hybrid method is developed and its validity is certified. And dynamic energy release rate was calculated. The dynamic photoelastlic hybrid method can be used on the obtaining of dynamic stress intensity factors and dynamic stress components. The effect of crack length on the dynamic stress intensity factors is less than those on the static stress intensity factors. When structures are under the dynamic mixed mode load, dynamic stress intensity factor of mode I is almost produced.
하재기 김천과학대학 2005 김천과학대학 논문집 Vol.31 No.-
An experimental study was carried out to obtain fundamental data about liquid state gas fuel supply pump. Two types of pumps were used. One was a regenerative type which was generally used for gasoline engine fuel system. The other was a roller-vane type which was also used for automotive engine fuel system. The experiments were performed to obtain flow rate as a function of pressure differences and temperatures. The regenerative pump had low flow rate at some experimental conditions. Therefore, it is impossible to use this pump system for liquid state gas 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 NPSHre.
모터 및 배터 리 용량에 따른 소형전기자동차 성능 특성 연구
하재기 김천과학대학 2009 김천과학대학 논문집 Vol.35 No.-
Now that Earth Environmental has been more important, Developing & Producing of Eco-Friendly vehicle is more incremented. It has been incremented by needs of small electric vehicle(SEV) that current people's driving pattern changed by more shorter than previous that. In this Paper, we define Small Electric Vehicle through out National Highway Traffic Safety Administration of United States of America's regulation and explain motor and battery of primary constituents of that. We used MATLAB and ADVISOR 2002 programmes for Simulation, and proposed that SEV's Model can be got in 2 passenger. In this Model, the motor was applied for 8kW permanent magnet synchronous motor (PM motor). And the batteries were applied for Lead acid battery(72V, 25~340Ah) and Li-ion battery(72V, 25~340Ah) to compare each other. We compared change of driving range of SEV through out non-changing speed Driving(10km/h, 20km/h, 30 km/h, 40km/h) and Manhattan driving schedule.
가솔린-LP가스燃料가 單機筒 SI機關의 性能에 미치는 影響에 關한 實驗的 硏究
하재기 김천과학대학 1998 김천과학대학 논문집 Vol.24 No.-
This is a study to improve the performance of the SI engine. In this study, a existing gasoline was modified to a LPG-dedicated engine which can be operated with LPG. This modified model was tested with various load change, being compared with a gasoline engine, the results are as follows; 1. LPG-dedicated engine can be operated with better fuel economy (about 20~30%) and better thermal efficiency(about 10%). 2. The discharge density of hydrocarbon is not influenced by engine load, and carbon monoxide the is a lowest in the optimal combustion condition. 3. The attrition rate of lubricant does not change with load change, but gasoline engine is a little higher in lower load category.
일본의 채란양계시설$\cdot$기구 - 현황과 앞으로의 전망 -
하재기 대한양계협회 1984 월간 양계 Vol.16 No.8
양계기구업체의 관점에서만이 아니라 양계가와 긴밀한 협조를 통한 자료의 교환, 실적에 의한 시설기구의 선택이 절실히 요구된다.