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다점 확률분포 모델을 이용한 초임계 압력 액체질소 제트 해석
정기영,김남수,김용모,Jung, Kiyoung,Kim, Namsu,Kim, Yongmo 한국액체미립화학회 2017 한국액체미립화학회지 Vol.22 No.3
This paper describes numerical modeling of transcritical and supercritical fluid flows within a liquid propellant rocket engine. In the present paper, turbulence is modeled by standard $k-{\varepsilon}$ model. A conserved scalar approach in conjunction with multi-environment probability density function model is used to account for the turbulent mixing of real-fluids in the transcritical and supercritical region. The two real-fluid equations of state and dense-fluid correction schemes for mixtures are used to construct thermodynamic data library based on the conserved scalar. In this study, calculations are made on two cryogenic nitrogen jets under different chamber pressures. Sensitivity analysis for two different real-fluid equations of sate is particularly emphasized. Based on numerical results, precise structures of cryogenic nitrogen jets are discussed in detail. Numerical results show that the current real-fluid model can predict the essential features of the cryogenic liquid nitrogen jets.
윤종학(Yoon Jonghak),정기영(Jung Kiyoung),홍성희(Hong Seong-heui) 한국공작기계학회 1999 한국공작기계학회지 Vol.8 No.5
In this paper, hardened SCM440 material and annealed SCM440 material are for cutting experiments by the cutting condition which is chosen respectively, by tool three components of cutting force are recorded using multicorder. Then the surface roughness for various force are measured by Roughness Tester. The results of the experiment are summarized as follow. The hardened material cut by ceramic tool(BX20) gives the highest radial component values among the cutting resistance, radial component is increased higher for the higher cutting speed, even though vertical component and axial component tend to decrease. But when the annealed material was cut, increase in cutting speed results in the increase of three component forces. Since ceramic insert tip used the experiment hardly affect Built-up Edge and heat, the cutting resistance decrease slightly regardless of the increased of cutting speed. The hardened material has higher three component force value than the annealed material because the material of high hardness is increased cutting resistance. The lowest cutting forces for hardened material and annealed material are shown in the cutting speed of 60m/min and 180m/min respectively.
박석윤,정기영,박래현,이낙영,이석훈,이주호,김주한,김홍기,김종우,조한석,정현용,김재문,한상익,전양환,이민선 충남대학교 기초과학연구소 1999 忠南科學硏究誌 Vol.26 No.2
With the correct equipment, microvolt EEG signals can be recorded from the scalp. Their potential use for diagnosis of physiological and psychiatric diseases and for increasing our understanding of cognitive processes is being realized by current research in many fields. Our work focuses on the research for good EEG signal representations and on careful analysis classification results using statistical EEG analysis(SEEG).
박석윤,박래현,이석훈,정현용,한상익,전양환,김재문,정기영 충남대학교 기초과학연구소 1998 忠南科學硏究誌 Vol.25 No.2
This article explores the use of qEEG, began in the 1970s and early 80s as an attempt to extract from brain electrical activity more than what could be ready appreciate by simple, unaided visual inspection of EEG. EEG was able to examine 12 healthy young persons with eye dosed and aged 25-39. We gets 4 sample datasets; each dataset consists of 21 columns corresponding to the 21 channels, the sampling rate is 128 Hz, total time is 2 seconds (i.e. 258 points per channels). And result of qEEG is suggested.