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안병권,정소원,김지혜,정영래,김선범,Ahn, Byoung-Kwon,Jung, So-Won,Kim, Ji-Hye,Jung, Young-Rae,Kim, Sun-Bum 한국군사과학기술학회 2015 한국군사과학기술학회지 Vol.18 No.3
Recently supercavitating underwater torpedo moving at high speed (over 200 knots) has been interested for their practical advantage of the dramatic drag reduction. Cavitator located in front of the torpedo plays an important role to generate a natural supercavity and control the motion of the object. Supercavity can be created artificially by injection of compressed gas from the rear of the cavitator at a relatively low speed. In this paper, we investigated physical characteristics of artificial supercavities through cavitation tunnel experiments. One of the main focuses of the study was to measure pressure inside the cavity, and examined variation of the gravity effects appearing according to different amount of injected air. It was also found that a stable supercavity could be sustained at injection rates less than that required to form the stable supercavity because of hysteresis effect.
Experimental and numerical studies on super-cavitating flow of axisymmetric cavitators
안병권,이창섭,김형태 대한조선학회 2010 International Journal of Naval Architecture and Oc Vol.2 No.1
Recently underwater systems moving at high speed such as a super-cavitating torpedo have been studied for their practical advantage of the dramatic drag reduction. In this study we are focusing our attention on super-cavitating flows around axisymmetric cavitators. A numerical method based on inviscid flow is developed and the results for several shapes of the cavitator are presented. First using a potential based boundary element method, we find the shape of the cavitator yielding a sufficiently large enough cavity to surround the body. Second, numerical predictions of supercavity are validated by comparing with experimental observations carried out in a high speed cavitation tunnel at Chungnam National University (CNU CT).
안병권,최현숙,고하영,최두복 조선대학교 공학기술연구원 2014 공학기술논문지 Vol.7 No.1
The objective of this research was to study L (+)-lactic acid production byrepeated batch culture of Rhizopus arrhizus RA 128 using broken rice as sole carbonsource. The L (+)-lactic acid production increased with the increase of broken riceconcentration by 60g/L. L (+)-lactic acid production was increased from 10.9 to 25.3g/Lwhen pH was increased from 4.0 to 6.0. However, over 7.0 of pH, it was decreased. TheL (+)-lactic acid productivity and cell concentration increased with the increase intemperature from 29 to 35 ℃. The maximum L (+)-lactic acid production and cellconcentration was found with the 1.5% of CaCO3. Repeated batch culture was successfullyperformed for 4cycles for 12 days. All cycles showed that 234.5g/L of broken rice wasconsumed. 75g/L of total L (+)-lactic acid was obtained after 288hr. These results showthat broken rice can be useful for the effective production of L (+)-lactic acid in therepeated batch culture of R. arrhizus RA 128.
안병권,윤덕균 한국산업경영시스템학회 2011 한국산업경영시스템학회 학술대회 Vol.2011 No.추계
The current number of mobile subscribers reached 50 million people can be seen as a nearly saturated state. To attract new customers means that coming to take away from the competition’s customers, so there are the fierce competition to attract to customers. So if there are signs of churn, it should be quickly analysed to avoid moving to competition. This paper estimated the churn of mobile users by using Competing risks model and Bayes’ theorem, and proposed how to prevent it. Proposed method was verified through the experiment, and it has been shown that the results of using the model is effectively predict the probability of churn of mobile users.
점성 및 비점성 해석법을 이용한 초월공동 유동 수치해석
안병권,김지혜,최정규,김형태,나영인,이도형,Ahn, Byoung-Kwon,Kim, Ji-Hye,Choi, Jung-Kyu,Kim, Hyoung-Tae,Nah, Young-In,Lee, Do-Hyung 한국군사과학기술학회 2014 한국군사과학기술학회지 Vol.17 No.1
Recently supercavitating torpedo has been studied because of its high-speed performance as the next generation of underwater weapon systems. In this study, we present a numerical method based on the potential flow. Characteristic features of the shape of supercavities and drag forces are investigated. In addition, we introduce a viscous-potential method to compensate for the effects of viscosity. The results are compared with viscous calculations using a commercial package, FLUENT V13.