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ASTM D5470 방법으로 연강과 스테인리스강의 열전도도 측정시 열그리스의 영향
조영욱,한병동,이주호,박성혁,백주환,조영래,Cho, Young-Wook,Hahn, Byung-Dong,Lee, Ju Ho,Park, Sung Hyuk,Baeg, Ju-Hwan,Cho, Young-Rae 한국재료학회 2019 한국재료학회지 Vol.29 No.7
Thermal management is a critical issue for the development of high-performance electronic devices. In this paper, thermal conductivity values of mild steel and stainless steel(STS) are measured by light flash analysis(LFA) and dynamic thermal interface material(DynTIM) Tester. The shapes of samples for thermal property measurement are disc type with a diameter of 12.6 mm. For samples with different thickness, the thermal diffusivity and thermal conductivity are measured by LFA. For identical samples, the thermal resistance($R_{th}$) and thermal conductivity are measured using a DynTIM Tester. The thermal conductivity of samples with different thicknesses, measured by LFA, show similar values in a range of 5 %. However, the thermal conductivity of samples measured by DynTIM Tester show widely scattered values according to the application of thermal grease. When we use the thermal grease to remove air gaps, the thermal conductivity of samples measured by DynTIM Tester is larger than that measured by LFA. But, when we did not use thermal grease, the thermal conductivity of samples measured by DynTIM Tester is smaller than that measured by LFA. For the DynTIM Tester results, we also find that the slope of the graph of thermal resistance vs. thickness is affected by the usage of thermal grease. From this, we are able to conclude that the wide scattering of thermal conductivity for samples measured with the DynTIM Tester is caused by the change of slope in the graph of thermal resistance-thickness.
조영욱,최부병,이성복,Cho, Young-Wook,Choi, Boo-Byung,Lee, Seong-Bok 대한턱관절교합학회 2003 구강회복응용과학지 Vol.18 No.2
The object of this study is to observe the effects of magnetism on the osteoblasts using a neodymium magnet. The osteoblasts was cultured under magnetic fields of varying intensities to evaluate the effect of magnetism on the activity and alkaline phosphatase acitivty of the osteoblasts. Osteoblasts were cultured in the cell density of $10^4$ for the evaluation of cell proliferation and 105/ml for the evaluation of ALP activity under 0. 10, 100, 500, 1000, 2000, 4000 gauss for 24 hour. For evaluation of osteoblast morphologic changes under magnetic, osteoblasts were observed by inverted microscope and TEM. To elucidate if IGF-receptors are increased under the magnetic field, we investigated osteoblasts by immunofluoroscence staining. The results were as follows: In the varying intensities of magnetic fields, the degree of cell proliferation was the highest in the magnetic field of 10 gauss and this gradually decreased up to 1000 gauss. In the magnetic fields stronger than 1000 gauss, the degree of the cell proliferation decreased to an even lower level than that of the control group. The ALP activity and protein synthesis showed a similar increase pattern as the degree of cell proliferation compared to the control group but showed little difference. Under the microscope, morphological change of the cells ( decrease in length and increase in roundness) were observed but no peculiarity of cell distribution could be found according to the magnetic field line. In the proper intensity of magnetic fields (10 gauss), the cultured cells showed increase in number of IGF Receptors compared to that of the control group.
지속성 외래 복막 투석 환자에서 복막 투석액 및 혈청 Cancer Antigen 125 (CA125)농도 변화의 임상적 의의
조영욱 ( Young Wook Cho ),우학 ( Hak Woo ),배우균 ( Woo Kyun Bae ),이윤철 ( Yoon Chul Lee ),이민구 ( Min Goo Lee ),이연경 ( Yun Kyung Lee ),조민석 ( Min Seok Cho ),마성권 ( Seong Kwon Ma ),김수완 ( Soo Wan Kim ),김남호 ( Nam Ho K 대한내과학회 2005 대한내과학회지 Vol.68 No.3
조영욱(Yeong Uk Cho),김영일(Young Il Kim),정광섭(Kwang-Seop Chung) 대한설비공학회 2011 설비공학 논문집 Vol.23 No.7
The objective of this research is to study the variation of optimum slope angles of collectors for seven regions in Korea, which are Seoul, Gangneung, Daejeon, Daegu, Gwangju, Busan and Jeju. The results for 2000~2007 are analyzed to see if adjustment of slope angles is necessary each year to receive maximum solar radiation. For an azimuth fixed solar collector, solar radiation of yearly optimized slope angle during May~Sept.(summer), Nov.~Mar.(winter) and the whole year are greater than the fixed slope angle by 0.03%, 0.02%, and 0.04%, respectively. For an azimuth tracking solar collector, solar radiation of yearly optimized slope angle during May~Sept.(summer), Nov.~Mar.(winter) and the whole year are greater than the fixed slope angle by 0.03%, 0.07%, and 0.04% respectively. It is unnecessary to adjust slope angles each year for both azimuth fixed and tracking collectors, since the gains are insignificant. Solar radiation of the azimuth tracking solar collector during May~Sept., Nov.~Mar. and the whole year are greater by 14.7%, 16.0%, and 19.2% than the azimuth fixed solar collector.
특정상호작용에 의한 폴리프로필렌 / EPDM 블렌드의 상용성 향상
조영욱(Young Wook Cho),고진환(Jin Hwan Go),이원기(Won Ki Lee),이진국(Jin Kook Lee),조원제(Won Jei Cho),하창식(Chang Sik Ha) 한국고무학회 2000 엘라스토머 및 콤포지트 Vol.35 No.1
N/A Miscibility improvement between polypropylene(PP) and ethylene-propylenediene-terpolymer (EPDM) was studied by introducing specific interaction into both polymers. PP was modified by grafting malefic anhydride(MAH) onto backbone, leading to MAH-grafted PP(PP-g-MAH). Sulfonated EPDM ionomer neutralized with bivalent zinc cation(ZnSEPDM) was used as one component. The blends of PP-g-MAH and ZnSEPDM were prepared at 200℃ in Brabender Roller Mixer. Fourier transform-infrared(FT-IR) spectroscopic and dynamic mechanical studies have been performed to investigate the miscibility. FT-IR spectral peak corresponding to carbonyl group in PP-g-MAH and that to sulfanate group in ZnSEPDM were shifted to lower and higher frequency with increasing ZnSEPDM content, respectively, in the blends. Glass transition temperature of ZnSEPDM was increased up to 70wt.% of ZnSEPDM, and again decreased above 70wt.%. It can be concluded from the shift of FT-IR characteristic peaks and the changes of glass transition temperatures that the miscibility between PP and EPDM was improved via introducing specific interaction, i.e., dipole-ion interaction.
공기, 지열 및 복합 열원 열펌프의 중간기 에너지 소비량에 관한 연구
조영욱(Yeong Uk Cho),우태호(Tea ho Woo),정광섭(Kwang-Seop Chung),김영일(Youngil Kim) 한국지열·수열에너지학회 2013 한국지열에너지학회논문집 Vol.9 No.4
This study is to compare energy consumption of air-source, ground-source and dual-source heat pump systems during intermediate season using dynamic simulation. Ground-source heat pump has higher COP than that of air-source but requires additional power consumption of auxiliary equipment such as circulation pump. During intermediate season when the outdoor air temperature is favorable, total COP of air-source heat pump may be greater than that of ground-source when circulation pump power consumption is included. Dual-source heat pump which selects the more favorable heat source is compared with air-source only and ground-source only heat pumps for total power consumption. Results show that power consumption of dual-source heat pump is lower than that of ground-source only by 0.73%.