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오정석(Jeong Suk Oh),윤성근(Sung Gun Yoon),박한준(Han June Park),황원태(Wontae Hwang) 한국가시화정보학회 2019 한국가시화정보학회지 Vol.17 No.3
The dynamic stability of swarms is crucial in preventing collisions in clustered flights and safely moving along a defined path. Although there have been many simulation studies on dynamic stability, there have not been many experimental studies using real clusters due to the difficulty in implementation. In this study, we constructed a particle-lattice structure simulating bird flocks or drone swarms, and conducted experiments within turbulent flow. We identified a criterion that describes dynamically stable particle-lattice structures. The stability increased as this newly defined spatial index increased.
권원순(Won-Soon Kwon),오정석(Jeong-Suk Oh) 한국통상정보학회 2007 통상정보연구 Vol.9 No.3
E-tade has the potential to accelerate existing trends and introduce new ways of conducting traditional trade. The primary purpose of this research is to investigate performance factor and analyzes influence between performance of e-Trade and implementation of company. This research will be used as a basis for examining the actual results of e-Trade usage and export productivity. In order to facilitate the process, analysis began after a research prototype was created and research thesis established.
김문기(Munki Kim),오정석(Jeong-suk Oh),최영일(Young-il Choi),윤영빈(Youngbin Yoon) 한국연소학회 2006 KOSCOSYMPOSIUM논문집 Vol.- No.-
This paper investigates the effects of acoustic forcing on NOx emissions and mixing process in the near field region of turbulent hydrogen nonpremixed flames. The resonance frequency was selected to force the coaxial air jet acoustically, because the resonance frequency is effective to amplify the forcing amplitude and reduce NOx emissions. When the resonance frequency is acoustically excited, a streamwise vortex is formed in the mixing layer between the coaxial air jet and coflowing air. As the vortex develops downstream, it entrains both ambient air and combustion products into the coaxial air jet to mix well. In addition, the strong vortex pulls the flame surface toward the coaxial air jet, causing intense chemical reaction. Acoustic excitation also causes velocity fluctuations of coaxial air jet as well as fuel jet but, the maximum value of centerline fuel velocity fluctuation occurs at the different phases of Ф=180° for nonreacting case and Ф=0° for reacting case. Since acoustic excitation enhances the mixing rate of fuel and air, the line of the stoichiometric mixture fraction becomes narrow. Finally, acoustic forcing at the resonance frequency reduces the normalized flame length by 15 % and EINOx by 25 %, compared to the flame without acoustic excitation.
고빌리루빈혈증과 담도 침범을 동반한 간세포암에 대한 경동맥화학 리피오돌색전술의 안전성과 예후 인자
양경모 ( Keungmo Yang ),성필수 ( Pil Soo Sung ),오정석 ( Jung Suk Oh ),천호종 ( Ho Jong Chun ),장정원 ( Jeong Won Jang ),배시현 ( Si Hyun Bae ),최종영 ( Jong Young Choi ),윤승규 ( Seung Kew Yoon ) 대한간암학회 2018 대한간암학회지 Vol.18 No.2
Background/Aims: The treatments and outcomes of hepatocellular carcinoma (HCC) with bile duct invasion are not well known. We aimed to confirm the safety of transarterial chemolipiodolization (TACL) and identify prognostic factors for patients with bile duct invasion treated with TACL. Methods: Fifty patients with central bile duct invasion treated with TACL between 2005 and 2017 were enrolled. Patients were divided into three groups: hyperbilirubinemia (total bilirubin ≥2.5 mg/dL) with pre-TACL biliary drainage, hyperbilirubinemia without biliary drainage, and without hyperbilirubinemia. Tumor response to TACL, survival outcomes, length of hospitalization, adverse events using Common Terminology Criteria for Adverse Events (CTCAE), and factors affecting overall survival were compared. Results: TACL-induced changes of mean CTCAE grades for albumin, alanine aminotransferase, creatinine, prothrombin time, and platelet were not significantly different among patients with or without initial hyperbilirubinemia. Serum bilirubin level was not significantly changed after TACL in all the three groups. Overall survival was not significantly different among the three groups (P=0.097). On multivariate analysis, alpha-fetoprotein <400 ng/dL (hazard ratio [HR]=0.477, P=0.048) and highest total bilirubin level of <2.5 mg/dL within one month after TACL (HR=0.335, P=0.004) were significantly associated with longer survival. Conclusions: TACL was a safe treatment for HCC patients with central bile duct invasion, irrespective of the presence of initial hyperbilirubinemia. (J Liver Cancer 2018;18:121-129)
박한준(Han June Park),이성광(Sung-Gwang Lee),오정석(Jeong Suk Oh),Steven Barrett,황원태(Wontae Hwang) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
After the World Health Organization (WHO) proclamation of the Severe Acute Respiratory Syndrome-2 (SARS-Cov-2) as a pandemic in 2020, there have been various efforts on establishing the correlation between temperature and humidity on the spread of COVID-19. However, worldwide consensus has not yet been established. The cause of this is that the indoor environment in which virus transmission occurs is not considered, and there is also a lack of physical understanding of droplet evaporation with temperature and humidity. Therefore, in this study, we examine actual droplet dynamics by first measuring droplet evaporation within a constant temperature and humidity environmental chamber. Based on this experiment, simulations were conducted to estimate the effects of temperature and humidity on droplet dispersion. Our results showed that there was no significant correlation between temperature, but that high humidity greatly helps in suppressing virus transmission via respiratory droplets.