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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.
Experimental investigation of supercavitating flows
안병권,Tae-Kwon Lee,Hyoung-Tae Kim,Chang-Sup Lee 대한조선학회 2012 International Journal of Naval Architecture and Oc Vol.4 No.2
When the object is traveling in the water at tremendously high speeds, the cavity forms and grows up at a fore part of the object called cavitator, and the object is eventually enveloped by vaporized water, supercavitation. As a result, the only part of the object in direct contact with the water is the cavitator, so skin-friction drag is significantly reduced. This is why recently supercavitating objects have been interested in many applicable fields. In this study we are focused out attention on supercavitating flows around various shapes of two and three dimensional cavitators. First,general features of supercavitation are examined by analyzing results obtained by the previously developed numerical method. Second, experimental observations are carried out at a cavitation tunnel at the Chungnam National University (CNU CT), and supercavity dimensions are scrutinized.
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.
직장암에 대한 수술 전 방사선-화학요법 적용시 통상적인 영상진단 검사로 충분한가?
안병권 고신대학교의과대학 2007 고신대학교 의과대학 학술지 Vol.22 No.1
Background : Recently, preoperative chemoradiation has been accepted to control locally advanced rectal cancer according to increasing the anal sphincter preservation, improving the resectability and survival. However, patient selection of preoperative chemoradiation should be done carefully, because distant metastasis or peritoneal seeding of cancer was found in some patients during interval between preoperative chemoradiation and surgery, or in surgery or at immediate postoperative period. Methods : We reviewed a total of 139 patients who were treated by preoperative chemoradiation between January, 1995 and December, 2004, all of them had locally advanced rectal cancer. In work-up study for preoperative chemoradiation, no distant metastasis was proven by chest x-ray, abdominal and pelvic CT. All patients received the full scheduled dose of radiation (range, 4500- 5500 cGy). The radiation was administered in divided tractions over a five-week period. 5flurouracil (450 mg/㎡/day) and leucovorin (20 mg/㎡/day) were administered continuously on day 1-5 and 19-33. Interval between preoperative chemoradiation and surgery was within 48 weeks. Before surgery, all patients underwent chest x-ray, liver ultrasonography and pelvic CT to do restaging. Results : One lung metastasis, 1 inguinal lymph node metastasis, and 1 bone metastasis were identified by restaging period. Three hepatic metastasis, 1 peritoneal seeding, 5 paraaortic lymph node metastasis were identified in operation field. Two bone metastases were identified at immediate postoperative period within 3 months. The 3 patients with bone metastasis complained of shoulder pain or back pain and all of bone metastases were identified by bone scan. As a result, 14 patients(10.1%) were inadequately included to preoperative chemoradiation with conventional imaging study. All of them died within one and a half year. Conclusions : In conclusion, in order to select preoperative chemoradiation adequately in locally advanced rectal cancer, it seems that specific imaging study is necessary to confirm liver metastasis or peritoneal seeding of cancer precisely. In addition, bone scan is mandatory to work-up of preoperative chemoradiation, if patient complained of shoulder or back pain.
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.
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).