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RISS 인기검색어
- 검색키워드
- 저자 : 김근배 ( Keun Bae Kim ) (검색결과 37 건)
- 무료
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김근배,김유,Kim, Keun-Bae,Kim, Yoo 한국군사과학기술학회 2006 한국군사과학기술학회지 Vol.9 No.2
Experimental studies of the cylindrical sintered-copper wick heat pipes were carried out to investigate the capillary heat transfer characteristics. Six models of the sintered-copper wick heat pipes were manufactured and tested to evaluate the heat transport limitations and the thermal characteristics. Also the performance of the heat pipes was analyzed theoretically and compared with the test results. The heat pipe models are divided into two sintered-wick groups and the nominal particle sizes are $180{\mu}m$(wick #1) and $200{\mu}m$(wick #2) respectively The experimental results showed that, the porosity of wick #1 was higher than that of wick #2, and also the wick #1 was generally superior than the wick #2 for the heat transport capability. The maximum heat transport rates were increased as the wick thicknesses and the vapor temperatures were increased.
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인터넷 포탈사이트들의 트래픽 형태와 트래픽 결정요인들간의 관계에 대한 연구
김근배 ( Keun Bae Kim ),임병훈 ( Byung Hoon Lim ),최성아 ( Sung Ah Choi ) 한국소비자학회 2002 소비자학연구 Vol.13 No.3
Currently, more than 20 portal sites are trying to find ways of differentiation to survive fierce competition. In the beginning stage, these firm were able to gain huge number of members with the financial support from venture investors. However only a few firms are making profits now. Revenue from the advertising turned out to be very limited due to the narrow target market. Expected profit from the sale of contents and e-mailing service is also negligible due to the low switching cost from the view of netizens and little differentiation in contents among the sites. In this study, we investigate the level of differentiation by analyzing traffic data for portal sites. Based on the Double Jeopardy phenomena, we find that the level of differentiation is very low as expected. Next we tried to find the effect of individual contents on the level of visit frequency and site stickiness. Results show that current wide portfolio of contents has some effect on visit frequency. However the impact on site stickiness, which is the sign of high loyalty, turns out to be too small for netizens to pay for the service.
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김근배(Kim, Keun-Bae),이보화(Lee, Bo-Hwa),박부민(Park, Poo-Min) 한국항공우주연구원 2016 항공우주산업기술동향 Vol.14 No.1
전기추진시스템은 화석연료로 인한 기후변화에 대응할 수 있는 효과적인 기술로서, 기본적으로 이차전지와 연료전지 그리고 태양전지와 같은 전기동력원을 기반으로 항공기에 사용된다. 현재 리튬-이온 이차전지의 에너지밀도가 한계에 다다르면서 비행시간과 거리를 증대시키기 위해 더 높은 에너지밀도를 갖는 리튬-황 이차전지와 연료전지 개발이 진행되고 있으며, 고고도 장기체공을 위한 태양광 무인기들도 개발되고 있다. 한편 다수의 소형 추진장치를 이용한 분산추진기술이 대두되면서 소음을 줄이고 비행체의 성능과 안전성을 높이고 있다. 최근에 화석연료 엔진과 발전기, 전기모터를 조합한 하이브리드 전기추진시스템이 개발되고 있으며, 향후 연료효율은 더욱 높아지고 배출가스는 더욱 감소될 것으로 기대된다. Electric propulsion system is a effective technology to counteract climate change due to fossil fuel, basically the aircraft uses electric power sources such as battery, fuel cell and solar cell. As the energy density of Li-ion battery is now approaching the limit, Li-S battery and fuel cells having higher energy density are developing to increase flight time and range, and solar UAVs are also developing to stay long time at high altitude. Meanwhile, rising distributed propulsion technology based on many small propulsion devices is decreasing noise and enhancing the aircraft performance and safety. Currently, hybrid electric propulsion systems combining fossil fuel engine, generator and electric motor are developing, which is expected to improve fuel efficiency and to decrease emission.
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김근배(Keun Bae Kim) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
Theoretical analysis and the experiments of the cylindrical sintered-copper wick heat pipes were carried out to investigate the capillary heat transfer characteristics. Six models of the sintered-copper wick heat pipes were manufactured and tested to investigate the heat transport limitations and the thermal characteristics. The heat pipe models divided into two sintered-wick groups using two kinds of copper powders that the nominal particle sizes are 180 ㎛(wick #1) and 200 ㎛(wick #2). The experimental results showed that, the porosity of wick #1 was higher than that of wick #2, and also the wick #1 was generally superior than the wick #2 in terms of heat transport capability based on the wick structure characteristics. The maximum heat transport rates were increased as the wick thicknesses and the vapor temperatures were increased.
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고고도 장기체공(HALE) 무인기 추진시스템 기술 동향
김근배(Kim Keun-Bae),양인영(Yang In-Young),김난영(Kim Nan-Young),장병희(Jang Byung-Hee) 한국항공우주연구원 2011 항공우주산업기술동향 Vol.9 No.2
고고도 장기체공(High Altitude Long Endurance, 이하 HALE) 무인기는 고도 20km 정도의 성층권에서 장기체공하면서 각종 관측 및 통신 중계 등의 다양한 임무를 수행할 수 있다. HALE 무인기가 성층권의 높은 고도에서 안정적으로 장기간 운용되기 위해서는 고효율/고신뢰성/고내구성의 추진시스템이 필수적으로 요구된다. 이와 관련하여 현재 고효율 터보차저를 장착하고 수소연료를 사용하는 왕복엔진 시스템 및 연료전지 또는 태양전지와 배터리를 조합한 몇 가지 형식의 하이브리드 시스템 개발이 진행되고 있다. 향후, 고고도의 극한 환경조건에서 안정적으로 운용될 수 있는 무인기 플랫폼을 토대로 최대의 효율과 내구성을 갖는 추진시스템이 결합된 고고도 장기체공 무인기의 상용화가 곧 도래할 것으로 전망된다. A high altitude long endurance(HALE) UAV will perform many kinds of missions for observation, monitoring and communication relay service etc staying for a long time in the stratosphere almost 20㎞ of height. The propulsion system with high-efficiency, high-reliability and long-endurance is required to operate stably for a long time in the high altitude of stratosphere for HALE UAV. With reference to that, currently, developments of a reciprocating engine system using hydrogen fuel equipped a high-efficiency turbocharger and some kinds of hybrid system combined fuel cell, solar cell and battery are progressing. In the future, a commercial HALE UAV will be showed that combining the propulsion system with the best efficiency and long duration capability based on the UAV platform applicable to the extreme environmental conditions of high altitude.
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김근배(Keun-Bae Kim) 한국항공우주연구원 2009 항공우주산업기술동향 Vol.7 No.2
연료전지는 소음이 낮고 CO2 배출이 없는 친환경적 특성을 기반으로 항공기 추진시스템에 적용되고 있으며, 현재 연료전지를 탑재한 여러 종류의 무인항공기와 소형 유인항공기 개발이 진행되고 있다. 항공기용 연료전지는 대표적으로 PEMFC(Proton Exchange Membrane Fuel Cell)방식과 SOFC(Solid Oxide Fuel Cell) 방식으로 분류되며, 항공기의 임무 및 운용조건에 적합한 연료전지 시스템이 개발되고 있다. 무인항공기의 경우 대부분 PEM 연료전지 기술을 기반으로 군용 또는 상용으로 활용할 수 있는 다양한 형태와 크기의 항공기가 개발되고 있으며, 시스템의 안정성과 운용시간이 더욱 향상될 것이다. 소형 유인항공기에서는 추진시스템을 연료전지로 대체하기 위한 많은 연구가 수행되고 있으며, 또한 대형 상용 항공기의 보조동력장치(APU)에 연료전지를 적용하여 성능을 높이기 위한 개발이 진행되고 있다. 향후, 연료전지항공기는 연료전지의 전력밀도 증가와 더불어 신뢰성과 효율을 더욱 향상시킬 것으로 기대된다. Fuel cells are applied to the propulsion system of aircraft based on environmental-friendly characteristics with low noise and zero emission of CO2, currently many kinds of UAV and small manned aircraft equipped with fuel cells are being developed. Fuel cells for aircraft typically classified into PEMFC(Proton Exchange Membrane Fuel Cell) type and SOFC(Solid Oxide Fuel Cell) type and the system is developed to adapt missions and operational conditions of aircraft. For UAV, various types of aircraft mostly based on PEM fuel cell technology are investigated for military or commercial uses, and the stability and endurance of system will be improved. For small manned aircraft, many researches are carried out to substitute the propulsion system by fuel cell, also some developments for the higher performance of APU of large commercial aircraft to apply fuel cells are in progress. In the future, a fuel cell aircraft will be expected to improve the reliability and efficiency with higher power density.
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