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김제인,문요섭,박일룡,김진욱,김문찬,설한신,안종우 한국전산유체공학회 2022 한국전산유체공학회지 Vol.27 No.4
This paper provides the results of a numerical study conducted to predict the open water performance of a pumpjet propulsor designed by Ahn et al.[10]. Changes in the thrust and torque of each part of the pumpjet propulsor according to advance ratio were analyzed by using the RANS method based on the SST k-ω turbulence model. The present numerical results were validated with the results of the open water test performed in the large cavitation tunnel at KRISO. Compared to the condition without the pre-swirl stator and duct, the thrust and torque of the rotor increased due to the effect of those two parts of the pumpjet propulsor. On the other hand, the pre-swirl stator and duct induced drag rather than thrust at advance ratios higher than 0.4. In addition, the rotational direction of the torque predicted for these two parts was opposite to that of the rotor. The forces and efficiency predicted for each part of the pumpjet showed a good agreement with those of the model test, except for the advance ratios higher than 1.0. The reason that the numerical analysis underestimates the forces and efficiency at advance ratios greater than 1.0 is presumed to be the cause of the stall phenomenon in the numerical simulation occurring earlier than in the model test. Through the local flows, the pressure drop phenomenon that can cause cavitation due to the gap flow between the rotor blade and the duct and the characteristics of the tip vortex development according to advance ratio were discussed.
The Correlation Analysis between Heart Rate Variability and Effect of Acupuncture on Obese Women
김제인,양요찬,김고운,조재흥,김송이,박히준,송미연,Kim, Je-In,Yang, Yo-Chan,Kim, Koh-Woon,Cho, Jae-Heung,Kim, Song-Yi,Park, Hi-Joon,Song, Mi-Yeon The society of Korean Medicine Rehabilitation 2016 한방재활의학과학회지 Vol.7 No.2
Objectives The purpose of this study was to investigate the relationship between the effects of acupuncture treatment and heart rate variability (HRV) in pre-menopausal obese women. Methods Thirty-seven obese women who met the inclusion criteria were recruited. To estimate the effects of acupuncture, obesity indices, such as body weight (BW), waist circumference (WC), hip circumference (HC), and the waist-hip ratio (WHR), were measured before and after the treatment. The HRV test was conducted before treatment and analyzed using the frequency domain method. Results The lnLF/HF ratio (natural logarithm of low frequency power/high frequency power ratio of the HRV value) before treatments was negatively correlated with differences in WC, HC, and WHR during treatment. The correlation coefficients between the lnLF/HF ratio and the differences in WC, HC, and WHR were r=-0.459 (p<0.01), r=-0.327 (p<0.05), and r=-0.339 (p<0.05) respectively. Conclusions As the baseline ratio of sympathetic activity to parasympathetic activity decreases, WC, HC, and WHR reduction significantly increased during treatment. Further study is needed to uncover the relationship between obesity-related variables and the autonomic nervous system to predict the effect of acupuncture.
김제인,박일룡,서성부,김민재,구가람,김태우,김선홍 한국전산유체공학회 2023 한국전산유체공학회지 Vol.28 No.3
This paper presents the numerical prediction of the forward speed and moving distance of an underwater body including the analysis of the unsteady characteristics of cavitation developing around the body according to speed change. The flow was assumed to be two-phase incompressible turbulent flow and solved by using the unsteady Reynolds averaged Navier-Stokes method that includes a cavitation model explaining the phase change between the water and vapour. The temporal change of the speed and moving distance of the underwater body estimated from the 1DoF motion analysis showed a satisfactory agreement with the measured results in the underwater test. In addition, the time variations of the cavity predicted along with the speed change of the body also showed a reasonable agreement with the cavity observation of the underwater test. Through this study, we were able to properly explain the drag and speed changes of the underwater body linked to the development of the cavity.
자율신경 활성도와 비만 여성 침치료 효과의 상관성 연구
김제인 ( Je-in Kim ),양요찬 ( Yo-chan Yang ),김고운 ( Koh-woon Kim ),조재흥 ( Jae-heung Cho ),김송이 ( Song-yi Kim ),박히준 ( Hi-joon Park ),송미연 ( Mi-yeon Song ) 대한한의학회 한방재활의학과학회 2016 한방재활의학과학회지 Vol.26 No.4
Objectives The purpose of this study was to investigate the relationship between the effects of acupuncture treatment and heart rate variability (HRV) in pre-menopausal obese women. Methods Thirty-seven obese women who met the inclusion criteria were recruited. To estimate the effects of acupuncture, obesity indices, such as body weight (BW), waist circumference (WC), hip circumference (HC), and the waist-hip ratio (WHR), were measured before and after the treatment. The HRV test was conducted before treatment and analyzed using the frequency domain method. Results The lnLF/HF ratio (natural logarithm of low frequency power/high frequency power ratio of the HRV value) before treatments was negatively correlated with differences in WC, HC, and WHR during treatment. The correlation coefficients between the lnLF/HF ratio and the differences in WC, HC, and WHR were r=-0.459 (p<0.01), r=-0.327 (p<0.05), and r=-0.339 (p<0.05) respectively. Conclusions As the baseline ratio of sympathetic activity to parasympathetic activity decreases, WC, HC, and WHR reduction significantly increased during treatment. Further study is needed to uncover the relationship between obesity-related variables and the autonomic nervous system to predict the effect of acupuncture. (J Korean Med Rehabil 2016;26(4):85-96)
김제인 ( Jane Kim ),조성민 ( Seong-min Cho ),서승현 ( Seung-hyun Seo ) 한국정보처리학회 2021 한국정보처리학회 학술대회논문집 Vol.28 No.1
최근 IBM, Intel 과 같은 글로벌 ICT 기업들과 여러 스타트업들이 양자 컴퓨터 개발에 성공하였으며 그에 따라 양자 시뮬레이터와 컴파일러에 대한 관심이 높아졌다. 여러 개의 시뮬레이터가 존재하는 만큼 시뮬레이터마다 제공하는 기능과 성능 역시 제각각 다르다. 본 논문에서는 비교적 접근이 쉬운 파이썬과 Q# 기반의 대표적인 양자 시뮬레이터 3 가지(Qiskit, Project Q, Quantum Development Kit)에서 제공하는 기능들을 소개하고 시뮬레이션 실행시간을 비교한다. 10 뎁스의 20 큐비트 회로에서는 QDK 시뮬레이터가 0.227 초로 실행 시간이 가장 짧았고, 10 큐비트의 10 뎁스 회로의 경우 Project Q 가, 1000 뎁스의 경우 Qiskit 이 가장 짧은 실행시간으로 측정됐다.