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Micro-CPL의 형상에 따른 열전달특성 변화에 대한 해석
김병기(Kim Byoung-Gi),장환영(Jang Hwan-Young),서정세(Suh Jeong-Se),문석환(Moon Seok-Hwan),황건(Hwang Gunn) 한국태양에너지학회 2006 한국태양에너지학회 학술대회논문집 Vol.- No.-
An analysis is carried out to investigate heat transfer characteristics and pressure drop of micro-capillary pumped loop(MCPL) with the shape of condenser. In this work, the main model is A type and B type which have grooved wicks and bend tubes in condenser region, respectively. was measured Pressure drop and the heat transfer rate were calculated under various operating condition. The results shows that A type has more heat transfer rate than B type and pressure drop in B type has less than A type.
전시작전통제권 전환과 유엔사의 역할: 유엔사의 법적 지위와 정치적 함의를 중심으로
김병기(Byoung Gi Kim)(金柄基) 신아시아연구소(구 신아세아질서연구회) 2019 신아세아 Vol.26 No.4
한국 전쟁시 한반도 평화 회복을 위해 유엔안보리 결의로 창설된 유엔사는 한국을 공산화 위험에서 구했고, 정전협정 체결 이후에도 한·미동맹의 근간으로서 한국군을 작전 통제하여 한국방위 책임을 이어갔다. 1978년 한미연합사창설 이후에는 정전협정 서명 당사자로서 정전관리 책임과 권한을 유지하고 있다. 한국의 국력이 신장되고 냉전이 종식되면서 한국방어에 한국군의 역할이 확대되어 1994년에 정전시 작전통제권을 이양하였으나, 유엔사는 여전히 배타적인 정전관리임무를 유지하고 있다. 2005년부터 논의된 한·미간 전시작전통제권 전환 계획이 북한의 핵 위협과 심각한 무력도발 등으로 인해 두 차례나 연기된 끝에, 현재는 한국군 대장을 사령관으로 하는 새로운 ‘미래연합사’ 창설을 전제로 ‘조건’에 기초한 전작권 전환이 추진되고 있다. 유엔사에서도 ‘Revitalization Program’에 의거하여 정전관리를 포함한 유엔사 임무의 지속적인 수행방안을 검토하고 있다. 그런데 이를 두고 최근 언론에서는 마치 유엔사가 미래연합사의 상위기구로서 한반도에서 전쟁수행사령부 역할을 하고자 한다는 의혹을 제기하고 있다. 북핵 위협 상황에서 전작권 추진 자체가 바람직스럽지 않으나, 이미 한·미 간 합의에 의거 기정사실화되고 있다. 유엔사 창설시부터 현재까지 유엔의 제 결의와 한·미간 합의문서를 기초로 유엔사의 법적 지위를 분석한 결과, 전작권 전환시 전쟁수행사령부 역할은 수행하지 않더라도 현재의 정전관리 역할을 유지하는 것으로 나타났다. 따라서 유엔사의 재활성화 방안을 검토하면서 전작권 전환 이후 신설될 미래연합사와 유엔사간 업무분장과 협조관계에 관한 치밀한 검토가 병행되어야 할 것이다. The United Nations Command (UNC) was established at the beginning of the Korean War by UN Security Council resolution to restore peace on the Korean Peninsula and to save South Korea from communism. Even after establishment of the ROK-US Combined Forces Command (CFC) in 1978, the UNC was had supervisory responsibility for managing the Armistice Agreement. As South Korea’s national strength enhanced and the Cold War ended, the role of the South Korean military in Korea’s defense expanded and the CFC’s Armistice OPCON was given to the ROK JCS in 1994. UNC kept its exclusive armistice management mission. Talks on the transfer of wartime OPCON from the US to the ROK began in 2005, but the move was postponed twice and the parties switched from a terms-based transfer to a ‘condition-based’ transfer as a result of the North Korean nuclear issue and serious provocations. The UNC continues to carry out the UNC’s original mission, including armistice management through the “Revitalization Program” Reportedly, the UNC wants to continue to serve as the warfighting command on the Korean Peninsula as if it were a high-ranking organization in the ‘Future CFC.’ Even though transfer of wartime OPCON is not appropriate now given the North Korean nuclear threat, it’s a fait accompli by ROK-US agreement. According to resolutions of the UN GA/SC since its inception and agreements between the ROK and the US, the UNC’s legal status and role is not supposed to change for armistice management and it should not become a warfighting command after wartime OPCON transfer. Therefore, it is necessary to review the “Revitalization Program” and develop a detailed separation of functions and cooperative relations between the ‘future CFC’ and the UNC.
히트파이프형 이중진공관 태양열집열기의 배열 방식에 따른 열특성의 실험적 연구
정경택(Chung Kyung-Taek),김병기(Kim Byoung-Gi),장환영(Jang Hwan-Young),서정세(Suh Jeong-Se) 한국태양에너지학회 2006 한국태양에너지학회 학술대회논문집 Vol.- No.-
The thermal performance of solar systems for hot water service usually depends on the solar collectors. Evacuated tube solar collector with heat pipe has been developed to improve the thermal efficiency of solar energy collector. In solar energy system, collector modules should be arranged in series and/or parallel pattern. The experiment is carried out to investigate the thermal performance for the module of solar collector in series and parallel, respectively. The results from this study will be presented as the basic data for the arranging pattern of many solar collectors.
선택적 레이저 용융공정으로 제조된 Al-Si-Mg 합금의 열처리에 따른 미세조직 및 특성평가
이기승,엄영성,김경태,김병기,유지훈,Lee, Gi Seung,Eom, Yeong Seong,Kim, Kyung Tae,Kim, Byoung Kee,Yu, Ji Hun 한국분말야금학회 2019 한국분말재료학회지 (KPMI) Vol.26 No.2
In this study, Al-Si-Mg alloys are additively manufactured using a selective laser melting (SLM) process from AlSi10Mg powders prepared from a gas-atomization process. The processing parameters such as laser scan speed and laser power are investigated for 3D printing of Al-Si-Mg alloys. The laser scan speeds vary from 100 to 2000 mm/s at the laser power of 180 and 270 W, respectively, to achieve optimized densification of the Al-Si-Mg alloy. It is observed that the relative density of the Al-Si-Mg alloy reaches a peak value of 99% at 1600 mm/s for 180 W and at 2000 mm/s for 270W. The surface morphologies of the both Al-Si-Mg alloy samples at these conditions show significantly reduced porosities compared to those of other samples. The increase in hardness of as-built Al-Si-Mg alloy with increasing scan speed and laser power is analyzed due to high relative density. Furthermore, it was found that cooling conditions after the heat-treatment for homogenization results in the change of dispersion status of Si phases in the Al-Si matrix but also affects tensile behaviors of Al-Si-Mg alloys. These results indicate that combination between SLM processing parameters and post-heat treatment should be considered a key factor to achieve optimized Al-Si alloy performance.
선택적 레이저 용융공정을 이용한 316L 스테인리스강 분말 3차원 조형체의 미세조직 및 경도 연구
신기훈,최준필,김경태,김병기,유지훈,Shin, Gi Hun,Choi, Joon Phil,Kim, Kyung Tae,Kim, Byoung Kee,Yu, Ji Hun 한국분말야금학회 2017 한국분말재료학회지 (KPMI) Vol.24 No.3
In this study, STS316L powders prepared by gas atomization are used to manufacture bulk structures with dimensions of $10{\times}10{\times}10mm^3$ using selective laser melting (SLM). The microstructures and hardness of the fabricated 316L stainless steel has been investigated with the laser beam overlap varied from 10% to 70%. The microstructures of the fabricated STS316L samples show a decrease in the balling and satellite of powders introducing defect in the bulk samples and the porosity caused by the gap between the molten metal pools disappearing as the overlap ratio increases, whereas a low overlap ratio results in significant balling and a large amount of isolated powders due to the increased gap between the melt pools. Furthermore, the highest value in Vickers hardness is obtained for the sample fabricated by 30% overlapped laser beams. These results show that the overlap ratio of laser beams in the SLM process should be considered as an important process parameter.