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문지훈,문용주,최혜자,윤석권 대한피부과학회 2003 대한피부과학회지 Vol.41 No.6
We present an unusual case of molluscum contagiosum occurring in epidermal cyst on back of a 5-year-old girl. Histology showed an intradermal cyst containing lamellated horny materials and typical molluscum cclls. In Korean literature, 5 such case were reported. We report an additional case of molluscum occurring in epidermal cyst. (Korean J Dermatol 3003;41(6) : 790~792)
A Study of the Shock Tube Flow with a Finite Rupture Time of Diaphragm
Yong-Hun Kweon(권용훈),Heuy-Dong Kim(김희동),Toshiaki Setoguchi(??口俊明) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
Shock tubes are devices in which the state of a gas is changed suddenly from one uniform state to another by the passage of shock and expansion waves. In the theory of ideal shock tube flow, it is customarily assumed plane wave. However, such waves are generally not centered, or may not even by plane in practice. In the present research, the numerical and experimental studies were carried out in order to investigate the effect of the diaphragm rupture process on the flow characteristics of expansion and shock waves generated near the diaphragm using dried cellophane.
Effect of Mesh Screen Device on Over-Expanded Supersonic Jet Noise
Yong-Hun Kweon(권용훈),Jae-Hyung Kim(김재형),Chae-Min Lim(임채민),Toshiyuki Aoki(靑木俊之),Heuy-Dong Kim(김희동) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
This paper describes an experimental work to investigate the effect of mesh screen device on the jet structure and acoustic characteristics of over-expanded supersonic jet. The mesh screen device is placed into the supersonic jet stream. In order to perturb mainly the initial jet shear layer, the hole is perforated in the central part of the mesh screen. The diameter of the perforated hole and the location of mesh screen device are varied. A Schlieren optical system is used to visualize the flow fields of supersonic jet without and with the mesh screen device. Pitot pressure measurement is carried out to obtain the pressure distribution in the jet flow. Acoustic measurement also is performed to obtain the OASPL and noise spectra. The results obtained show that the jet structure and the jet noise control effectiveness is strongly dependent upon the diameter of the perforated hole and the location of the mesh screen device in the jet stream. Provided that the mesh screen device is placed at the location to perturb effectively the initial shear layer, the present control method is effective in suppressing the supersonic jet noise.
권영훈(Yong-Hun KWEON),靑木俊之(Toshiyuki AOKI),김희동(Heuy-Dong KIM) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11
Supersonic jet issuing from a nozzle invariably cause high-frequency noises. These consist of three<br/> principal components ; the turbulent mixing noise, the broadband shock-associated noise, and the screech tone.<br/> In present study, it was experimentally investigated to the effect of nozzle lip thickness on the characteristics<br/> of supersonic jet noise. The convergent-divergent nozzle of a design Mach number 2.0 was used in<br/> experiment. With three different nozzle-lip thicknesses, the jet pressure ratio was varied in the range between<br/> 2.0 and 12.0. Acoustic measurements were conducted by microphones in an anechoic room, and the major<br/> structures of the supersonic jets were visualized by a Schlieren optical system to investigate the effect of<br/> nozzle lip thickness. The measured results show that the characteristics of supersonic jet noise, such as overall<br/> sound pressure level (OASPL) and screech frequency, strongly depend upon the thickness of nozzle-lip.
권용훈(Yong-Hun Kweon),장태인(Tae-In Jang),문종현(Jong-Hyun Moon),이성진(Sung-Jin Lee) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12
In the continuous hot-dip galvanizing process, the gas-jet wiping is generally used to control the coating weight of moving steel strip. The high speed gas-jet discharged from the nozzle slot impinges on the strip, and at this moment, wipes the liquid coating layer dragged by a moving strip. The coating weight is influenced on the flow characteristics of wiping gas-jet such as the impinging pressure distribution, pressure gradient and shear stress distribution on the surface of strip. However, the conventional gas-jet wiping method brings about inefficient and environmental problems such as the treatment of zinc dross and severe jet noise over 120dB. In this study, new wiping apparatus (Magnetic Wheel) using electrodynamic force is experimentally investigated to solve these undesirable problems mentioned above. Based upon the results obtained, the characteristics of magnetic wheel are discussed in detail. The experimetal results show that the electrodynamic force (i.e., wiping force) strongly depends on the standoff distance between the magnetic wheel to the Zn-plate and the number of rotation of magnetic wheel.