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Bacillus coagulans ATCC 8038 의 β- galactosidase 생산증진에 관한 연구
김현욱,안종건,권일경 한국낙농학회 1981 韓國酪農學會誌 Vol.3 No.2
This study was to stimulate β-galactosidase production of Bacillus coagulans ATCC8038, a thermophilic, sporeforming, and facultatively anaerobic lactose fermenting bacterium. Optimum initial pH for the enzyme production was pH 7.0 in the medium which contained 0.4% of lactose, 0.1% of peptone, 0.2 % of yeast extract, 0.7% Na-acetate. 3 H₂O and 0.03% CaCl₂.2H₂O. Potassium phospate buffer(0.05M, pH 7.0)induced the better production of β- galactosidase, and optimum concentrations of lactose, yemit extract, peptone and Na - acetate. 3H₂O in β-galactosidase production medium were found to be 0.4% , 1%, 0.1% and 0.7% respectively.
양방향 링크를 갖는 개선된 DSR Ad Hoc 라우팅에 관한 연구
김현욱,이광배,김정일,최동근 명지대학교 산업기술연구소 2001 産業技術硏究所論文集 Vol.20 No.-
In this paper, we enhanced the existing DSR routing protocol for ad hoc networks with bidirectional link. In mobile ad hoc network, mobile nodes themselves have router capability. Thus, for communication between two mobile nodes, the routing protocol for route set-up is required. DSR routing protocol, which is one of famous mobile ad hoc routing protocols, has the following problem: when route error occurs, the sending data packets drop as route recovery is delayed. In order to alleviate such problem, we modified route maintenance process of the existing DSR protocol so that the route recovery time from route error was shortened. As the result of performance evaluation, it was found the route recovery time of the proposed routing protocol was about 12 times faster than that of the existing DSR protocol. In addition, the data reception rate was more than 90 % for mobile ad hoc networks with slow mobility.
3차원 유한요소 해석을 통한 압전에너지 도로의 장기 공용성 예측
김현욱,남정희,최지영,Kim, Hyun Wook,Nam, Jeong-Hee,Choi, Ji Young 한국도로학회 2017 한국도로학회논문집 Vol.19 No.5
PURPOSES : The piezoelectric energy road analysis technology using a three-dimensional finite element method was developed to investigate pavement behaviors when piezoelectric energy harvesters and a new polyurethane surface layer were installed in field conditions. The main purpose of this study is to predict the long-term performance of the piezoelectric energy road through the proposed analytical steps. METHODS : To predict the stresses and strains of the piezoelectric energy road, the developed energy harvesters were embedded into the polyurethane surface layer (50 mm from the top surface). The typical type of triaxial dump truck loading was applied to the top of each energy harvester. In this paper, a general purpose finite element analysis program called ABAQUS was used and it was assumed that a harvester is installed in the cross section of a typical asphalt pavement structure. RESULTS : The maximum tensile stress of the polyurethane surface layer in the initial fatigue model occurred up to 0.035 MPa in the transverse direction when the truck tire load was loaded on the top of each harvester. The maximum tensile stresses were 0.025 MPa in the intermediate fatigue model and 0.013 MPa in the final fatigue model, which were 72% and 37% lower than that of the initial stage model, respectively. CONCLUSIONS : The main critical damage locations can be estimated between the base layer and the surface layer. If the crack propagates, bottom-up cracking from the base layer is the main cracking pattern where the tensile stress is higher than in other locations. It is also considered that the possibility of cracking in the top-down direction at the edge of energy harvester is more likely to occur because the material strength of the energy harvester is much higher and plays a role in the supporting points. In terms of long-term performance, all tensile stresses in the energy harvester and polyurethane layer are less than 1% of the maximum tensile strength and the possibility of fatigue damage was very low. Since the harvester is embedded in the surface layer of the polyurethane, which has higher tensile strength and toughness, it can assure a good, long-term performance.
김현욱,Christopher Ulan-Kvitberg,Claude Daley 대한조선학회 2014 International Journal of Naval Architecture and Oc Vol.6 No.3
Understanding of ‘spatial’ pressure distribution is required to determine design loads on local structures, such as plating and framing. However, obtaining a practical ‘spatial’ pressure distribution is a hard task due to the sensitivity of the data acquisition frequency and resolution. High-resolution Pessure-Idicating Flm (PIF) was applied to obtain pressure distribution and pressure magnitude using stepped crushing method. Different types of PIF were stacked at each test to creating a pressure distribution plot at specific time steps. Two different concepts of plotting ‘spatial’ pressure-area curve was introduced and evaluated. Diverse unit pixel size was chosen to investigate the effect of the resolution in data analysis. Activated area was not significantly affected by unit pixel size; however, total force was highly sensitive.