원환유동층에서의 기체혼합특성

유영태,김상돈,강용 한국화학공학회 1981 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.19 No.4

Annular형태의 유동층에서 기체의 축 방향 혼합계수와 측면방향(lateral) 혼합계수를 구하였다. Annular단면에서 기체유속, 입자크기 및 유동화입자의 유동화조건이 다른 입자의 첨가가 기체의 혼합에 미치는 영향을 결정하였다. 측면 방향혼합계수의 산출은 diffusion type motel을 제안하여 적용하였으며 축 방향혼합에서는 Schu¨gerl의 Model를 사용하였다. 측면방향 기체혼합계수와 축 방향혼합계수 모두 기체의 유속이 증가함에 따라 지수함수적으로 증가하였고 입자크기의 증가에 따라 측면방향 혼합은 감소하며 기체유속의 영향은 축 방향혼합계수가 측면방향보다 크게 나타났다. 이들 기체혼합계수는 본 실험의 조건에서 입자크기와 기체유속의 함수로서 잘 표현되었다. Lateral and axial gas phase mixing have been measured in the annular section of an annular fluidized bed which was constructed from two pieces of 7.6㎝-diameter and 2.54㎝-diameter plexiglass cylinder. Effects of gas velocity, particle size and weight percent of added inert particles on gas phase mixing have been determined. For lateral mixing, a diffusion type model was proposed to analyze the present system and Schugerl model H was employed to calculate the axial gas mixing coefficients. Both gas mixing coefficients increased exponentially with gas flow rate. Lateral gas mixing decreased with particle size. The addition of inert particles increased lateral gas mixing however, the reverse trend was observed for axial gas mixing with the addition of inert particles. Axial and lateral gas mixing coefficients were correlated in terms of gas flow rate and particle size in an annular fluidized bed.

정사각 덕트의 출구 영역에서 속도분포에 대한 실험적 연구

유영태,모양우,나기대,임인호 朝鮮大學校 機械技術硏究所 2002 機械技術硏究 Vol.5 No.2

A numerical simulation has been performed with the non-linear turbulence model proposed by Speziale(1987) coupled with the k-ε equations coming from the renormalization group theory(RNG) derived by Yakhot et al(1992). The fully developed turbulent flow through a straight square duct, involing secondary motion is simulated. This paper represent computations of the interaction between measurement and numerical computation of turbulent flow on velocity distribution of outlet region in a square duct. RNG turbulent model was adapted and compared with the experimental data and the result of Standard k-ε turbulent model. The predictions obtained with the RNG k-ε model show improvements when compared with the Standard k-ε model. Mean velocity, turbulence kinetic energy and Reynolds shear stresses are in quantitiative agreement with the experimental data. We feel that the RNG k-ε model suggested in this paper can be a useful turbulence model for practical engineering

고출력 레이저에 의한 이종금속 용접시험평가에 관한 연구

유영태,신호준,송성욱,모양우 朝鮮大學校 機械技術硏究所 2004 機械技術硏究 Vol.7 No.1

Laser welding techniques have been characterised for various materials. In this paper. the laser weldability of STS304 stainless steel and Inconel 600 at dissimilar metal welds using a continuous wave Nd:YAG laser are experimentally investigated. Inconel 600 is being used in a steam generator tubing of pressurized water reactor(PWR) exposed to some corrosion. Stress corrosion cracking can occur on this material. An experimental study was conducted to determine effects of welding parameters, on eliminating or reducing the extent welding zone formation at dissimilar metal welds and to optimize those parameters that have the most influence parameters such as focus length, power, beam speed, shielding gas, and wave length of laser were tested.

오스테나이트계 304 스테인레스강의 Nd:YAG 레이저 초점크기와 용접특성

유영태,오용석,노경보 조선대학교 에너지.자원신기술연구소 2002 에너지·자원신기술연구소 논문지 Vol.24 No.2

Laser beam welding is increasingly being used in welding of structural steels. The laser welding process is one of the most advanced manufacturing technologies owing to its high speed and penetration. The thermal cycles associated with laser welding are generally much faster than those involved in conventional arc welding processes, leading to a rather small weld zone. The experiments are performed for 304 stainless steel plate applying variation of : laser power(1500~2000W), welding speed (3~5m/min), shielding gas flow rate, presence of surface pollution, with fixed or variable gap and misalignment between the similar and dissimilar and plates, etc. The follow conclusions can be drawen that unlikely laser power, welding speed has a pronounced effect on size and shape of the fusion zone. Increase in welding speed resulted inan increase in weld depth/ welding ratio and hence a decrease in the fusion zone size. The penetration depth increased with the increase in laser power.

Poly(ethylene oxide)/Poly(ε-caprolactone) 혼성체로부터 Bioactive Agent의 방출 거동에 관한 연구

유영태,허정림,정채열 건국대학교 1995 學術誌 Vol.39 No.2

Poly(ε-caprolactone)/poly(ε-caprolactone)-b-poly(ethylene oxide) hybrid membranes were used for the zeroth order release of lyophobic drug. Diffusivity of the drug increased with the copolymer content of the blend and the release rate was inversely proportional to the thickness of the membrane. The effective diffusivity of the drug was estimated as 1.07×10-3mm2/hr, 1.27×10-3mm2/hr and 1.83×10-3mm2/hr for the membranes containing 37.5wt% of PCL-PEO-PCL block copolymers with compositions of 20k-20k-20k, 15k-15k-15k and 6k-6k-6k, respectively.

레슬링 그레꼬로만형의 파테르 기술훈련지침 개발

유영태,방대두,이종각 한국스포츠정책과학원(구 한국스포츠개발원) 2000 체육과학연구 Vol.11 No.4

본 연구는 레슬링 그레꼬로만형의 파테르 공격과 수비에 관한 전문지도서가 전무한 실정이며, 특히 훈련 현장에서 사용되는 기술훈련 지도방법도 체계화되어 있지 못한 상태에서 각 지도자마다 자신의 경험을 바탕으로 선수들을 지도하고 있으므로 레슬링 경기력 향상을 위하여 최근의 세계규모대회에 사용되고 있는 공격과 수비기술의 유형들을 분류하고, 이러한 기술들을 효과적으로 지도할 수 있는 기술훈련체계를 개발하는데 목적이 있다. 이러한 목적을 달성하기 위하여 본 연구에서는 최근 6년간 개최된 아시아 및 세계규모 대회의 경기 내용을 분석하고 파테르 공격과 수비기술의 개발 및 기술훈련 체계와 지침을 구안하였다. 본 연구를 통하여 개발된 기술훈련지침은 레슬링 지도자들의 의견과 전문가 합의과정을 거쳐 수정·보완되었으며, 특히 시드니올림픽을 대비한 국가대표팀의 훈련에도 적용되어 기술의 완성도를 높이는데 효과를 보았다. 또한 각 기술동작들을 비디오에 담아 레슬링 협회를 통하여 현장지도자들에게 보급하여 호평을 받은 바 있다.

고출력레이저에 의한 인코넬600의 맞대기용접 시험 평가

유영태,신호준,모양우 조선대학교 에너지.자원신기술연구소 2004 에너지·자원신기술연구소 논문지 Vol.26 No.1

Welding characteristics of Inconel 600 Alloy using a continuous wave Nd:YAG laser are experimentally investigated. The major process parameters studied in the present laser welding experiment were position of focus, laser power, travel speed. The gap and offset maintained as small as possible. Optical microscope were used to investigate the microstructures of the welded zone. This study shows the result of the tension experiments. And then this paper used the Electronic Speckle Pattern Interferometry to present the welding residual stress in welds. The follow conclusions can be drawn the laser power and travel speed have a pronounced effect the fusion zone size and shape.

레이저를 이용한 SM45C와 STS304의 이종금속용접

유영태,신호준 조선대학교 에너지.자원신기술연구소 2004 에너지·자원신기술연구소 논문지 Vol.26 No.2

For many years and primarily for economical reasons, Dissimilar Metal Welds have been used as transition joints in a variety of equipment and applications. But Dissimilar Metal Welds have several fabrication and metallurgical drawbacks that can often lead to in-service failures For example, the most pronounced fabrication faults are hot cracks. Laser welding techniques have been characterised for various materials. In this paper, the laser weldability of STS304 stainless steel and SM45C at dissimilar metal welds using a continuous wave Nd:YAG laser are experimentally investigated. An experimental study was conducted to determine effects of welding parameters, on eliminating or reducing the extent welding zone formation at dissimilar metal welds and to optimize those parameters that have the most influence parameters such as focus length, Power, beam speed, shielding gas, and wave length of laser were tested.

덕트 입구 영역에서 천이 맥동유동의 입구길이에 관한 연구

유영태,박선종,박길문,고영하 대한기계학회 1989 대한기계학회 춘추학술대회 Vol.- No.-

유압관로의 동력손실에서 임피던스 특성

유영태,강성균,정지철 朝鮮大學校 機械技術硏究所 2001 機械技術硏究 Vol.4 No.1

A Viscous wave equation is analyzed for making investigation into frequency-dependent friction in transient laminar liquid flow by the method of characteristics. The procedure consists of determining an approximate expression for frequency-dependent friction. Theoretical results for a test system are compared with the experimental results so show that the approximate expression predicts accurately the surge pressures, pressure wave distortion as well as attenuation of pressure pulses in hydraulic lines. The theoretical method used here makes it possible to experimentally investigate transient flows in a pipe with a circular orifice. The theoretical analysis is investigated under assumption that the characteristics of an orifice placed in a transient wave transmission line are approximated by the steady-state ones, if there is no reverse flow at the orifice. The transient variations of flow rate are measured by a modified impedance tube method which is realized by virtue of the present analytical technique.