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양기훈(Ki Hoon Yang),김동억(Dong Eok Kim),황경원(Kyung Won Hwang),하영호(Young Ho Ha),김무환(Moo Hwan Kim) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
An experimental study was performed to investigate local condensation heat transfer coefficients (HTCs) of high pressure steam. The test section was a single vertical tube with an inner diameter of 15.8㎜, a length of 1.5m, and composed of SUS 316. Experiments were conducted for mass fluxes from 20.4 to 51.0㎏/㎡s and pressures from 10 to 60bar. HTCs were compared with several correlations. The predictions of those correlations were largely deviated from the experimental HTCs, because the correlations did not directly reflect the local effects of the liquid film and vapor shear stress. However, in Nusselt equation, although the absolute values of prediction had large differences to measured values, in the aspect of tendency, the equation was outstanding compared to other correlations. Thus, for predicting efficiently the condensation heat transfer phenomena, the modification of the Nusselt theory equation based on the effects of liquid film and vapor shear stress would be promising.
저산소와 NO 조건에서 Mycobacterium smegmatis의 adenylyl cyclase 유전자 발현
전한승(Han-Seung Jeon),양기훈(Ki-Hoon Yang),고인정(In-Jeong Ko),오정일(Jeong-Il Oh) 한국생명과학회 2014 생명과학회지 Vol.24 No.12
결핵균인 Mycobacterium tuberculosis H37Rv에서는 16개의 adenylyl cyclase (AC) 유전자가, 비병원성인 M. smegmatis에서는 10개의 AC 유전자가 발견되었다. M. smegmatis에서 발견된 10개의 AC 유전자들 중 MSMEG_0228, MSMEG_3243, MSMEG_3780, MSMEG_4279, MSMEG_4477, MSMEG_6154 유전자들의 발현은 저산소 조건에서 유도되었다. 반면에 M. smegmatis가 nitric oxide (NO)에 노출이 되면 MSMEG_3780과 MSMEG_4279 유전자의 발현이 유도되었다. 유산소 조건에서 키운 M. smegmatis와 비교할 때, 저산소 조건에서 성장한 M. smegmatis 세포내부와 성장 배지 내의 cAMP 양은 각각 450배와 9.8배 증가하였다. M. smegamtis가 NO에 노출이 되면 세포 내의 cAMP 농도는 5.8배 증가하였다. DevSR two-component system은 M. smegmatis가 저산소 조건이나 NO에 노출되었을 때 많은 유전자의 발현을 유도하는 주요 조절계로 알려져 있는데, 저산소 조건에서 발현이 유도된 6개의 AC 유전자의 발현이 M. smegmatis devR mutant에서도 wild type에서와 마찬가지로 저산소 조건에서 유도됨이 관찰되었다. 이 결과는 저산소 조건에서 발현이 유도되는 6개의 AC 유전자들이 DevSR two-component system에 의해 조절되지 않음을 나타내고 있다. 저산소 조건에서 발현이 가장 많이 유도된 MSMEG_3780 유전자의 발현조절에 관련이 있는 조절자를 발굴하기 위해 ligand fishing 분석을 수행하였고, 후보 조절자로서 MSMEG_5136을 발굴하였다. In Mycobacterium tuberculosis H37Rv 16 adenylyl cyclase (AC) genes have been identified, while 10 AC genes have been found in non-pathogenic Mycobacterium smegmatis. Expression of 6 AC genes (MSMEG_0218, MSMEG_3243, MSMEG_3780, MSMEG_4279, MSMEG_4477, and MSMEG_6154) among 10 AC genes in M. smegmatis was increased when M. smegmatis was subjected to hypoxic growth conditions. On the other hand, only MSMEG_3780 and MSMEG_4279 were slightly induced in the presence of NO. The cAMP levels in cells and culture media were 450- and 9.8-fold increased, respectively, when M. smegmatis was grown under hypoxic conditions relative to those grown aerobically. Intracellular levels of cAMP were increased 5.8-fold on the exposure to NO. The DevSR two-component system is known to be involved in the induction of many genes whose expression is induced under hypoxic conditions and in the presence of NO. Expression of 6 hypoxically induced AC genes was observed to be induced in a devR deletion mutant grown under hypoxic conditions, indicating that the induction of the 6 AC genes under hypoxic conditions is independent of the DevSR two-component system. In order to identify a trans-acting regulatory element that is pertinent in the hypoxic induction of MSMEG_3780, ligand-fishing analysis was performed using the upstream DNA of MSMEG_3780 and MSMEG_5136 protein was identified.
해외사례 고찰을 통한 한국형 궤도관리 시스템 개발 방향
우병구(Woo Byoung-Koo),이춘길(Lee Choon-Kil),박현우(Park Hyun-Woo),양기훈(Yang Ki-Hoon),이성욱(Lee Sung -Uk) 한국철도학회 2007 한국철도학회 학술발표대회논문집 Vol.- No.-
At this current, KORAIL track maintenance system has been worked with the method of corrective maintenance which is repaired some location exceeded the track management criteria as a result of track measurement. It brings about a lot of additional expenses that the corrective maintenance might be a way of missing an appropriate maintenance time, after occurring some trouble on the track due to track maintenance characteristic. We sincerely need a track maintenance system including the concept of preventive maintenance that track is corrected with predicting the trend of track irregularity. I would like to present a development direction for Korea track maintenance system having a good application in our track with analyzing TRAMS21 and RAMSYS as overseas railway company has operated a track maintenance system.
확산접합기술을 이용한 H2 Station용 PCHE형 Compact 열교환기 개발
김정길(Jeong Kil Kim),심덕남(Deog Nam Shim),선칠령(Chil Yeong Seon),양기훈(Ki Hoon Yang),박해지(Hae Ji Park),김동진(Dong Jin Kim) 대한용접·접합학회 2017 대한용접·접합학회지 Vol.35 No.5
Diffusion bonding was performed on STS316L plate with micro channels to understand the relationship between bonding conditions and mechanical properties of the joints. Various defects such as spot and line defects developed along the joints bonded at various bonding conditions. As the bonding temperature increased, these defects had a tendency to decrease. With experimental results, it was revealed that bonding temperature was the most critical for formation of defects along the joints. Additionally, the sound joint showed coalescence of grains along the joint by migration of the grain boundaries. Tensile test result showed that the sound joint had better mechanical properties than STS316L base metal, and that crack initiated at spot and line defects followed by fracture. Based on experimental results, PCHE was manufactured and it passed hydraulic test under 1200 bar.