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정원택(Won Taek Jeong),이승재(Seung Jae Yi),김현동(Hyun Dong Kim),김경천(Kyung Chun Kim) 한국가시화정보학회 2011 한국가시화정보학회지 Vol.9 No.4
Oxygen sensitive functional particles(OSParticle) were fabricated by three different methods for using the particles as oxygen sensors and PlV tracers. The used methods were a physical coating method, an ion-exchange method and a dispersion polymerization method. The physical coating method is dipping Si02 hollow particles into dye solution then drying. This method is very simple, but particles are not uniform in diameter and luminescence. The particles fabricated by the ion-exchange method have very uniform diameter and well doped. However, it can not be used in water since the particles are hydrophobic. In case of the dispersion polymerization method, the diameter of OS Particles is quite uniform. The diameter of OS Particles can be changed by controlling the quantity of AIBN (2,2-azobis isobutyronitrile). For the purpose of dissolved oxygen concentration measurement in micro scale water flows, the dispersion polymerized OS Particles turn out to be the most superior functional particles. The luminescent intensity of OS Particles was tested with the variation of dissolved oxygen concentration in water samples. As a result, the luminescent intensity of OSParticles is monotonically decreased with increasing DO (Dissolved oxygen) concentration of water.
김상문(Sang Moon Kim),정원택(Won Taek Jeong),김경천(Kyung Chun Kim) 한국가시화정보학회 2010 한국가시화정보학회 학술발표대회 논문집 Vol.2010 No.11
A visualization study to evaluate bubble motion in a tab water filled cylindrical tank with a varying flow rate of compressed air is conducted. The flow rate of compressed air varies from 1 to 5[L/min]. Time resolved images are acquired by a high speed camera in 10 bit gray level at 100 [fps] and the measurement volume is irradiated by a 230 [w] halogen lamp. It is observed that there are three different regions; the bubble formation region, the rising bubble region and the free surface region. During the rise of bubble, the shape is changed as if an elastic body. Based on the binarized bubble image, the mean diameters of rising bubbles are estimated at beneath of the free surface. As the gas flow rate increases, the mean diameter is increased and the rising velocity also increases with buoyancy force.
김윤기(Yoon Kee Kim),정원택(Won Taek Jeong),김경천(Kyung Chun Kim) 한국가시화정보학회 2010 한국가시화정보학회 학술발표대회 논문집 Vol.2010 No.11
In this study, the pressure drop and performance prediction of a tank cleaning machine for improvement of jet length has investigated using CFX which is a commercial CFD code. In the tank cleaning machine, the sharp increase of dynamic pressure inside flow passage near the nozzle connection part turns out to be the essential factor of pressure loss. The velocity inside tank cleaning machine becomes over than 10m/s partially on account of narrow flow passage, the modification of tank cleaning machine is necessary for the improvement of the jet length. With the flow field analysis, the pressure drop on the original model and the modified models are numerically predicted and compared with that of experimental results. Finally, the best choice of modified tank cleaning machine is logically determined.
김상문(Sang Moon Kim),정원택(Won Taek Jeong),김경천(Kyung Chun Kim) 한국가시화정보학회 2010 한국가시화정보학회지 Vol.8 No.3
A visualization study to evaluate bubble motion in a tab water filled cylindrical tank with a varying flow rate of compressed air is conducted. The flow rate of compressed air varies from 1 to 5 L/min. Time resolved images are acquired by a high speed camera in 10 bit gray level at 100 fps and the measurement volume is irradiated by a 230 W halogen lamp. It is observed that there are three different regions; the bubble formation region, the rising bubble region and the free surface region. During the rise of bubble, the shape is changed as if an elastic body. Based on the binarized bubble image, the mean diameters of rising bubbles are estimated at beneath of the free surface. As the gas flow rate increases, the mean diameter is increased and the rising velocity also increases with buoyancy force.
김상문(Sang Moon Kim),정원택(Won Taek Jeong),김경천(Kyung Chun Kim) 한국가시화정보학회 2010 한국가시화정보학회 학술발표대회 논문집 Vol.2010 No.11
PIV기법과 PLIF기법을 통하여 순간속도 및 농도장을 동시에 측정하였다. 큰 규모의 난류거동의 동적인 특성은 기포의 Re수에 따라 상당히 구별됨을 확인하였다. 지배적인 난류생성 메커니즘으로 기포에 의해 유도되는 난류, 자유표면 진동, 그리고 재순환 와류 이렇게 3가지가 밝혀졌다. 기포의 Re수가 증가됨에 따라, 주된 난류거동은 진동하는 자유표면에 의해 생성되었다. 진동하는 자유표면의 존재로 인하여 압축공기에서 기포구동 액체유동으로의 에너지 전달은 뚜렷한 비선형적인 거동을 가지는 것을 확인하였다. 기포의 Re수가 증가됨에 따라 Reynolds decomposition으로부터 구한 난류에너지는 크게 증가하였으나, 활발한 자유표면의 주기적 진동은 난류 혼합에 큰 기여를 하지 않음에 따라 난류혼합 시간스케일의 감소가 크게 변화하지 않다는 것을 확인하였다.
마찰교반용접된 7075-T651 알루미늄 판재의 피로균열전파의 불규칙성
김선진(Seon Jin Kim),정의한(Yeui Han Jeong),손혜정(Hye Jeong Sohn),정원택(Won Taek Jung) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10
The process of fatigue crack growth is generally random nature, due to many sources of variability, such as external loading, material properties and geometry conditions. Therefore it is important to investigate the statistical variability of fatigue crack growth in order to develop the methodology for stochastic fatigue crack growth life prediction. This paper is concerned with the statistical investigation of fatigue crack growth process for the FSWed 7075-T651 aluminum alloy. In this study, fatigue crack growth tests were conducted on 5 specimens of the FSWed 7075-T651 aluminum alloy under constant stress intensity factor range control, especially base metal, heat affected zones and weld metal specimens.