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Hyungmin Lee,Dong-seob Jeong,Taehong Mun,Babu Pejjai,Vasudeva Reddy Minnam Reddy,Timothy James Anderson,박진호 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.8
CuInSe2 (CISe) thin films were grown on Mo-coated glass substrates by spray coating technique using nanocrystalline ink. The ink was prepared by dissolving binary CuSe and In2Se3 nanoparticles in iso-butanol. The grown films were subsequently annealed in vacuum and selenium atmosphere, and examined by various characterization techniques. The vacuum-annealed films showed the CuSe binary phase along with the CuInSe2 phase, whereas the selenized films showed a single phase CuInSe2. The elemental analysis of the selenized film exhibited near stoichiometry, and the photoluminescence peak was observed in the region of band-to-band transitions (0.97 eV), which indicated the good structural quality of the selenized films. The developed method opens a new prospect for the finetuning of CISe composition by pre-adjusting the composition of each element in the binary to best fit of CISe in the photovoltaic devices.
Hyungmin Kim,Jeaduk Ryu,Kihyung Lee 대한기계학회 2007 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.21 No.1
Premixed diesel engines have the potential to achieve a more homogeneous, leaner mixture near TDC compared to conventional diesel engines. Early studies have shown that the fuel injection timing and injection angle affect the mixture formation in a HCCI (Homogeneous Charge Compression Ignition) engine. Therefore in this study, we investigated the relationship between combustion and mixture formations accordance with injection conditions in a common rail direct injection type HCCI engine using an early injection strategy. From this results, we found that the fuel injection timing and injection angle affect the mixture formation and in turn affect combustion in the HCCI engine. In addition, this study revealed that the injection angle of 100° is effective to reduce smoke emission without any sacrificing power in the early injection case.
Hyungmin Kang,Yingmei Jin,Hyeokbin Kwon,Kyuhong Kim 한국항공우주학회 2017 International Journal of Aeronautical and Space Sc Vol.18 No.4
The characteristics of aerodynamic drag for Transonic Vehicle in Evacuated Tube was investigated using computational fluid dynamics. At first, parametric study on the system was performed according to the Mach number of the vehicle’s speed (Machv), evacuated pressure of the tube (Pret), and blockage ratio (BR) between the vehicle and tube via axisymmetric flow analysis; the Machv ranged from 0.3 to 1.0. The Pret was 100, 1,000 and 10,000 Pa and the BR was 0.1, 0.2, and 0.4. In the calculations, the aerodynamic drag of the vehicle was larger when the BR and the pressure became larger. Concerning the Machv, the drag coefficient (Cd) became the maximum when the Machv was near the Kantrowitz limit and decreased, which showed the typical transonic flow pattern. Then, three dimensional flow analysis was performed by changing the Machv from 0.3 to 1.0 and setting the BR and the Pret as 0.34 and 100 Pa, respectively by referring the Hyperloop Alpha documentation. From the calculations, the Cd from three dimensional flow simulations were somewhat larger than those of axisymmetric ones because of the eccentricity of the vehicle inside the tube. However, the pattern of Cd according to the Machv was compatible with that of axisymmetric ones.