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구민예(Min Ye Ku),김정현(Jung Hyun Kim),김쾌만(Que Man Kim),이성기(Sung-Ki Lee),강희용(Hee Yong Kang),이교우(Gyo Woo Lee) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11
In this numerical study, we investigated the performance of heat sink used in the inverter of industrial generator. The heat release performance was evaluated with heat input from the heat source, air flowrate of the fan, and ambient air temperature. We set the standard condition on the basis of regular power consumption of chips in the inverter as a 100% heat input, an actual operating flowrate of the fans, ambient air temperature of 298K, and 6 ㎜ spacing between fins. Heat inputs to the heat sink were varied from 100 to 50 % of standard condition. But the portion of heat release thru the heat sink, 89.8%, remains almost the same for the three cases, 100, 75, 50% heat inputs. The other 10.2% of heat was release to ambient thru the natural convection and radiation transfer. While, we changed the air flowrate to the heat sink as 75, 100, and 125%, and the portions of heat release thru the heat sink were 87.7, 89.8, and 91.2%, respectively. Also, the temperature of air flow into the heat sink was varied. In case of 293K, the heat release portion was almost same as that of the standard case, 298K. But the case of 303K, 5K higher than the standard condition, the portion of heat release thru the heat sink was 4% lower than that of standard condition.
탄소나노튜브로 강화된 에폭시 복합재료의 기계적 물성과 열팽창 계수 측정
구민예(Min Ye Ku),김정현(Jung Hyun Kim),강희용(Hee Yong Kang),이교우(Gyo Woo Lee) 대한기계학회 2013 大韓機械學會論文集A Vol.37 No.5
에폭시 수지에 다중벽 탄소나노튜브를 첨가하여 초음파 처리와 전단혼합 방법으로 분산시켜 다중벽 탄소나노튜브로 강화된 에폭시 복합재료를 제조하였으며, 에폭시 수지 내 다중벽 탄소나노튜브의 분산 적정성을 판단하고 기계적 및 열적 물성을 고찰하였다. 충전재 분산에 대한 평가를 위해 정성적인 방법으로 주사전자현미경(scanning electron microscope, SEM) 이미지를 사용하였고, 정량적인 판단을 위해 인장실험을 실시하였다. 또한, 열적 특성을 평가하기 위해 열팽창계수(coefficient of thermal expansion, CTE)를 측정하였다. 주사전자현미경 사진 및 인장 강도와 영률(Young’s modulus)의 작은 편차를 통해서 다중벽 탄소나노튜브가 에폭시 수지 내에 적절히 분산되었음을 확인하였다. 충전재 함량에 따라 인장 강도와 영률이 증가함을 보였고 열팽창계수 측정에서는 열안정성 개선을 고찰하였다. By using shear mixing and ultrasonication, we fabricated specimens of well-dispersed multi-walled carbon nanotube composites. To confirm the proper dispersion of the filler, we used scanning electron microscopy images for quantitative evaluation and a tensile test for qualitative assessment. Furthermore, the coefficients of thermal expansion of several specimens having different filler contents were calculated from the measured thermal strains and temperatures of the specimens. Based on the microscopy images of the well-dispersed fillers and the small deviations in the measurements of the tensile strength and stiffness, we confirmed the proper dispersion of nanotubes in the epoxy. As the filler contents were increased, the values of tensile strength increased from 58.33 to 68.81 MPa, and those of stiffness increased from 2.93 to 3.27 GPa. At the same time, the coefficients of thermal expansion decreased. This implies better thermal stability of the specimen.
산업용 인버터에 사용되는 압입식 및 압출식 히트싱크의 방열 성능 평가
김정현(Jung Hyun Kim),구민예(Min Ye Ku),김쾌만(Que Man Kim),이성기(Sung-Ki Lee),강희용(Hee Yong Kang),이교우(Gyo Woo Lee) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11
In this experiment, we investigated the performance of two types of heat sink, swaged- and extruded-type, used in the inverter of industrial electricity generator. The swaged-type heat sink has 62 fins, and the extruded-type has 38 fins having the same dimension as those of swaged-type. But the extruded-type heat sink maintains the same heat transfer area thru the waved surface which has 1 ㎜ in radius. As a result, the swaged- and extruded-type heat sinks released 70.7% and 63.8% of the heat incoming to the heat sink, respectively. The other incoming heat were naturally convected and radiated to the ambient. In spite of 40% decrease in number of fins, the heat release performance of the extruded-type heat sink was lowered only 6.9% than that of the swaged-type. We believe that, this shows the increment of effective heat transfer area thru the waved surface of fins and the better heat transfer property of the extruded-type heat sink.
Dynamic Gold Ring at the Tri-phase Junction of Complex Emulsion
Kang Hee Ku(구강희) 한국고분자학회 2021 한국고분자학회 학술대회 연구논문 초록집 Vol.46 No.1
Multiphase microscale emulsions are a material platform that can be tuned and dynamically configured by a variety of chemical and physical phenomena, thus rendering them inexpensive and broadly programmable optical transducers for a wide range of sensing scenarios. Herein, multiphasic triblock copolymer surfactants are developed to manipulate the biphasic emulsion shape and optical behavior. Site-specific conjugation of gold nanoparticles affords the creation of gold rings along the tri-phase junction of the emulsions, which amplifies the amount of light available for total internal reflection interference and isotropize the structural colors. Dynamic behavior of complex emulsions is imparted to the gold rings, affording the visualization of emulsion shape into the specific color reflection.