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강경조 ( K J Kang ),윤인상 ( I S Yoon ),이방래 ( B R Lee ),강보선 ( B S Kang ) 한국액체미립화학회 2013 한국액체미립화학회 학술강연회 논문집 Vol.2013 No.-
Nanofluids are that metallic or nonmetallic nanometer-sized particles are dispersed in liquid. They can be used in various fields to increase the heat transfer rate because the thermal conductivity of nanofluids can be increased significantly. Nanofluids may be used as a good alternative of coolants in spray cooling. This study conducted experiments to compare the characteristics of sprays between water and nanofluid sprays. The radial distributions of droplet velocities and diameters of water, 0.2% wt.(weight), and 0.5% wt. Al2O3 nanofluids at the pressure of 0.2 and 0.3 MPa were measured by laser doppler instruments. The radial distributions of droplet diameters and velocities at two axial positions with water and 0.2% wt. nanofluid sprays didn’t show much difference. A big difference, however, was observed between 0.5% wt. nanofluid and water sprays. With the increase of the mass of nano-particles, the average droplet diameters were increased and the average droplet velocities were decreased.
김인곤(I. Kim),강경봉(K. B. Kang),이재근(J. K. Lee),오명현(M. H. Oh) 한국표면공학회 2004 한국표면공학회지 Vol.37 No.1
Copper electroforming process has been applied to duplicate Koryo Tripitaka (Taejang'kyong), wooden printing block. Thin copper replica printing plates of 1mm thickness was successfully manufactured from the printing face (54.5 × 25.5 ㎝) of wooden printing plate. Major processes are (1) silicon rubber replication of the master (2) silvering on silicon rubber (3) copper electroforming (4) separation of copper from the silicon mandrel (5) final coloring by brass plating and trimming. This process has various potential applications in making thin metallic objects such as plaques, statues, bust and hollow metal objects for jewelry.
시간응답특성을 고려한 2 광원 1 센서 방식의 capnograph 시스템용 NDIR 식 CO2 가스 챔버 설계 및 측정 회로의 구현
박일용(I . Y . Park),이인기(I . K . Lee),이성기(S . K . Lee),강경목(K . M . Kang),강신원(S . W . Kang),조진호(J . H . Cho) 한국센서학회 2001 센서학회지 Vol.10 No.5
The capnograph system for determining the partial pressure of carbon dioxide in the blood of a patient was developed based on the NDIR(non-dispersive infrared) absrnption technology. NDIR gas analyzing method requires an optical absorption chamber and signal processing hardware. In this paper, we have designed and implemented NDIR type CO₂ gas chamber in consideration of the time response characteristics and lamp chopping frequency. And we have implemented signal processing hardware using two infrared sources to reduce the thermal background effect. The implemented gas chamber and signal processing hardware were tested in the temperature variation experiment and human expiratory experiment. The results showed that the system could produce a stable output signal and a good CO₂ gas concentration curve like a typical capnogram.
김인곤(I. Kim),이재근(J. Lee),강경봉(K. Kang),권식철(S.C. Kwom),김만(M. Kim),이주열(J.Y. Lee) 한국표면공학회 2005 한국표면공학회지 Vol.38 No.1
Tensile properties and hardness of nickel electroform from chloride-free nickel sulfamate electrolyte at 50℃ and PH 4.5 were investigated. Current density varied from 20 to 60 mA/㎠. The deposit thicknesses were 360, 480 and 980 ㎛. It was found in 480 ㎛ thick electroform that highest tensile and yield strengths and hardness of 83.7 ksi, 53.6 ksi and 216 DPH, respectively were obtained at a current density of 40 mA/㎠ and they were slightly decreased at 20 and 60 mA/㎠. However the ductility was lowest of 7.9% at 40 mA/㎠. Such a high strength and low ductility at 40 mA/㎠ seems to be related to the narrower columnar structure than those of other current densities. All the deposits exhibited pronounced necking behavior. Tensile strength, yield strength and ductility increased as the nickel electroform thickens. Initial strong (200) texture developed on stainless steel mandrel decreased and (111) and (220) textures increased as deposit thickness increased, whereas (200) texture was preferred as the current density increased.
김인곤(I. Kim),강경봉(K. Kang),이재근(J. Lee),권식철(S.C. Kwon),김만(M. Kim),이주열(J.Y. Lee) 한국표면공학회 2005 한국표면공학회지 Vol.38 No.1
The control of internal stress is extremely important in electroforming because of the deliberately low adhesion between the electroform and the mandrel. Excessive tensile or compressive stress can cause distortion, separation problem, curling, peeling or separation of electroform prematurely from the mandrel, buckling and blistering. Nickel sulfamate bath has been widely used in electroforming because of its low internal stress and moderate hardness. In this study, real-time stress sensor has been used for stress control in chloride-free nickel sufamate bath for 400 ㎜ × 300 ㎜ × 500 ㎛ nickel electroform. It was found that compressive stress found at low current density indicated the contamination of electrolyte, which is very useful in procuring buckling and peeling of electroform. No compressive stress is allowed for plate electroform. The real-time stress can also be used for accurate stress control of nickel electroform. The tensile stress was found to be increased slightly with increase in nickel electroform thickness, i.e., from initial 1.47 ksi to 2.02 ksi at 320 ㎛.