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Characterization of MBE-Grown ZnSe Thin Films by Using Photocurrent Spectroscopy
Myunghoon Jung,Jiho Chang,Dongcheol Oh,고항주,Hongseung Kim,Junsuk Song,Kwanghee Kim,Seunghwan Park,Takafumi Yao 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.3
High-quality ZnSe thin films were grown on GaAs substrates by using molecular beam epitaxy (MBE). Low-temperature and temperature-dependent photoluminescence (PL) measurements revealed the high crystal quality of the sample. However, photocurrent spectroscopy showed the existence of defects originating from the interface. Insertion of a buffer layer at a low growth temperature is suggested for improving the crystallinity further.
Ferrous Iron Oxidation by the Immobilized Cells of Acidithiobacillus ferrooxidans
Gyeommin KIM,Myunghoon MOON,Tae Wan KIM 한국생물공학회 2021 한국생물공학회 학술대회 Vol.2021 No.10
This study was aimed to develop the efficient bioprocess for ferrous iron oxidation by immobilized cells of Acidithiobacillus ferrooxidans. First, the medium was statistically optimized to minimize jarosite, a major ferric iron precipitate, based on response surface methodology (RSM). The results of RSM optimization predicted that the jarosite formation would be minimized in a medium at pH 1.8 which contains 2.75g/L of (NH4)2HPO4, 0.3g/L of MgSO4·7H2O, 0.15g/L of KCl, and 45g/L of FeSO4·7H2O. Then, based on the previous report that jarosite formed on the matrix surface helps the adhesion between the cells and the matrix, cell immobilization was performed by incubating flasks containing 9K medium, celite beads and A. ferrooxidans cells, which are favorable conditions for jarosite formation. After recovered, the immobilized cells were cultivated in the optimized medium in a repeated batch mode. It was observed that as the batch culture was repeated 5 times, the ferrous iron oxidation rate increased by 58% from 0.226 to 0.356 g/L/h, which is thought to be due to the increase in the concentration of immobilized cells. This study shows the potential to develop an efficient process for ferrous iron oxidation without loss of ferric iron.
김명훈(MyungHoon Kim),김상하(Sang-Ha Kim),하성규(Sung-Kyu Ha) 한국자동차공학회 1997 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1997 No.11_2
An investigation has been performed to study the response of the front bumper beam of automobiles. In the investigation, a beam theory is used to model the front bumper, and a principle of energy conservation is also used for calculating the deflection and stress distribution of the bumper subjected to the external impact. The primary concern of the investigation is to present a procedure of how to design optimally the cross-sectional shape of the front bumper of automobiles.
제동시 발생하는 리어 드럼브레이크 Creak (scratching) 노이즈 개선
장명훈(Myunghoon Jang),박신(Shin Park),김선호(Sunho Kim),김성환(Sunghwan Kim) 한국소음진동공학회 2013 한국소음진동공학회 학술대회논문집 Vol.2013 No.4
Creak noise is kind of scratching noise which is usually generated in drum brake system on the vehicle. When driver brakes vehicle or applies parking lever, drum brake shoe moves to the drum side to stop the vehicle. And at that time, moving shoe scratches backing plate ledge surface, and that makes scratching noise in special condition. This study presents how we can generate creak noise in the laboratory and how we can reduce it by experimental approach. Through several and various type of tests, we could generate creak noise with damage on ledge area of the backing plate in the lab and we verified tab type shoe design can reduce this scratching noise. As a result of this study, we notified how creak noise happens in the vehicle, and that tab type design shoe has good performance of ledge area damage based on lab test(rig & dynamometer equipment), and that this can reduce potential risk of creak noise in the field.