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트리핑 와이어를 사용한 평판에서의 열전달 특성에 관한 실험적 연구
조우식(Woo-Sik Jo),조웅선(Woong Sun Cho),유성연(Seong-Yeon Yoo) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
The purpose of this research is to investigate how boundary layer separation by the tripping wire installed in front of the flat plate affects the transition from laminar to turbulent, and consequently heat transfer. Naphthalene sublimation technique is used to measure the average and local heat transfer coefficients on the flat plate, and two boundary conditions of the developed and developing flow are considered to evaluate the effects of flow boundary. The heat transfer data from the flat plate with tripping wire is compared with those of flat plate without tripping wire. The variation trend of local heat transfer coefficients from the plate with and without tripping wire is similar each other in case of the developing flow, but quite different for the developed flow. Average Sherwood number on the flat plate with tripping wire is much higher than those of the flat plate without tripping wire due to boundary layer separation.
트리핑 와이어를 사용한 평판에서의 국소물질전달 특성에 관한 실험적 연구
유성연(Seong-Yeon Yoo),조웅선(Woong-Sun Cho),조우식(Woo-Sik Jo) 대한기계학회 2013 大韓機械學會論文集B Vol.37 No.3
본 연구의 목적은 평판의 선단에 설치된 트리핑 와이어에 의한 경계층 박리가 층류에서 난류로의 천이에 미치는 영향과 그 결과로 발생하는 물질전달에 미치는 영향을 규명하는 것이다. 나프탈렌승화법을 사용하여 평판에서의 국소물질전달계수를 측정하였으며, 유동 경계층의 효과를 평가하기 위해 발달된 유동과 발달하는 유동의 조건에서 트리핑 와이어가 설치된 평판에서의 국소물질전달계수를 설치되지 않은 평판에서의 값과 비교하였다. 발달하는 유동에서 국소물질전달계수가 변화하는 경향은 트리핑 와이어가 설치된 평판과 설치되지 않은 평판이 비슷하지만 발달된 유동에서는 상당히 다르게 나타났다. 평균 Sherwood 수는 경계층 박리로 인하여 트리핑와이어가 설치된 평판이 설치되지 않은 평판에 비해서 훨씬 높았다. The purpose of this research is to investigate how the boundary layer separation caused by a tripping wire installed in front of the flat plate affects the transition from laminar to turbulent flow, and consequently mass transfer. A naphthalene sublimation technique is used to measure the local mass transfer coefficients on the flat plate, and two boundary conditions for the developed and developing flow are considered to evaluate the effects of the flow boundary. The local mass transfer data for a flat plate with a tripping wire are compared with the data for a flat plate without a tripping wire. The variation trends of the local heat transfer coefficients for the plates with and without the tripping wire are similar to each other in the case of the developing flow, but are quite different for the developed flow. The average Sherwood number for the flat plate with a tripping wire is much higher than that without a tripping wire because of the boundary layer separation.
경사진 평판에서의 국소물질전달 특성에 관한 실험적 연구
유성연(Seong Yeon Yoo),조우식(Woo Sik Jo),조웅선(Woong Sun Cho) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.5
본 연구의 목적은 평행 평판과 경사진 평판의 물질전달 특성을 비교하여 경사각에 따른 유동의 박리와 재부착이 물질전달에 미치는 영향을 규명하는 것이다. 나프탈렌승화법을 사용하여 평판에서의 국소물질전달계수를 측정하였으며, 평균물질전달계수는 주어진 측정면에 대하여 국소물질전달계수를 평균하여 구하였다. 평판의 경사각은 10°에서 -10°까지 5°간격으로 변화시켰으며 유동 속도는 2㎧에서 15㎧까지 변화시켰다. 양의 각으로 경사진 평판에서 국소 Sherwood 수는 경계층이 발달하면서 감소하는 경향을 보이고 있는며, 음의 각으로 경사진 평판의 경우는 재순환 와류의 박리점에서 최소값을 나타내고, 박리된 유동의 재부착점에서 최대값을 나타내었다. 평균 Sherwood 수는 음의 각과 양의 각 모두 평행 평판보다 낮았다. The purpose of this research is to investigate how the separated and reattached flow affect the mass transfer by comparing local mass transfer characteristics from the inclined flat plate with that of the parallel flat plate. The local mass transfer coefficients on the flat plate were measured using naphthalene sublimation technique, and the average mass transfer coefficients were calculated by averaging the local mass transfer coefficients on the measurement surface. Inclined angle of the flat plate was varied from -10° to 10° with 5° intervals, and the free-stream velocity was varied from 2㎧ to 15㎧. In case of the positive inclined angle, local Sherwood numbers decrease gradually because boundary layer thickness increases. On the other hand, the minimum value at the separation point of the recirculated flow and the maximum value at the reattachment point are observed for the negative inclined angle. Average Sherwood numbers for both positive and negative angle are lower than those of the parallel plate.
경사진 평판에서의 국소물질전달 특성에 관한 실험적 연구
유성연(Seong Yeon Yoo),조우식(Woo Sik Jo),조웅선(Woong Sun Cho) 대한기계학회 2011 大韓機械學會論文集B Vol.35 No.12
본 연구의 목적은 평행 평판과 경사진 평판의 물질전달 특성을 비교하여 경사각에 따른 유동의 박리와 재부착이 물질전달에 미치는 영향을 규명하는 것이다. 나프탈렌승화법을 사용하여 평판에서의 국소물질전달계수를 측정하였으며, 평판의 경사각은 10°에서 -10°까지 5°간격으로 변화시키고 유동 속도는 2㎧에서 15㎧까지 변화시켰다. 양의 각으로 경사진 평판에서 국소 Sherwood 수는 경계층이 발달하면서 감소하는 경향을 보이고 있는며, 음의 각으로 경사진 평판의 경우는 재순환 와류의 박리점에서 최소값을 나타내고, 박리된 유동의 재부착점에서 최대값을 나타내었다. 평균 Sherwood 수는 음의 각과 양의 각 모두 평행 평판보다 낮았다. The purpose of this research is to investigate how separated and reattached flow affects mass transfer, by comparing the local mass transfer characteristics on an inclined flat plate with those on a parallel flat plate. The local mass transfer coefficients for the flat plate were measured using the naphthalene sublimation technique; the inclined angle of the flat plate was varied from -10° to 10° at 5° intervals, and the free-stream velocity was varied from 2㎧ to 15㎧. At positive inclined angles, the local Sherwood numbers decreased gradually because the boundary-layer thickness increased. On the other hand, for negative inclined angles, the local Sherwood numbers assumed the minimum value at the separation point of the recirculation flow and the maximum value at the reattachment point. The average Sherwood numbers for both positive and negative inclined angles were lower than those in the case of the parallel plate.
하조웅(Jo-Woong Ha),정형진(Hyung-Jin Jung) 대한치과이식임플란트학회 1982 The Korean Academy of Implant Dentistry Vol.3 No.1
The preliminary work on the prepartion of fine hydroxyapatite powder and the synthesis of dence hydroxyapatite ceramic from the powder were investigated for the development of artificial bone and tooth materials for implants. The effects of the process variables, such as compositions of the raw materials, the initial pH of the solutions,and sintering temperature on the physical properties were investigated in order to determine the optimum conditions for the fabrication of tooth implant material. As the initial pH of the solutions was increased in the range of 10-11.6, the initial particle size of precipitates was decreased, thus the sinterability of precipitates was improved. It was found that the composition of calcium rich of 1.75 in Ca/p mole ratio exhibited better sinterability and mechanical strength of the apatite ceramics, for example the highest value of Vicker’s hardness obtained from the compositions of 1.75 in Ca/P mole ratio was 764 ± 30 Kg/mm2,compared to the maximum value of 600 Kg/mm2 obtained from the compositions of 1.67 in Ca/P mole ratio.
조웅(Jo, Woong),김형수(Kim, Hyeong-Soo),노창균(Rho, Chang-Gyeun),박범진(Park, Bum-Jin),김명조(Kim, Myeong-Jo) 한국사회체육학회 2016 한국사회체육학회지 Vol.0 No.64
In this study, we performed motion analysis for ten subjects above 75 in order to analyze lower extremity joint movement patterns during upslope and downslope walking. Spatiotemporal parameters of walking, lower extremity joint movements on sagittal plane and ground reaction force were analyzed and the conclusions are as follows. 1. Cadency, walking velocity and stride length decreased during upslope and downslope walking compared to level walking. They showed significant differences at 10° inclination in upslope walking and at 5° inclination in downslope walking. 2. As for flexion/extension movement of lower extremity joint at HC event during gate cycle, the flexion of knee and hip joint increased during upslope walking and dorsal flexion of ankle was large. Knee joint flexion at TO event decreased as the inclination of upslope walking increased, and it was significantly different compared to level walking. 3. As for anterior/posterior tilt of pelvis, it decreased during downslope walking and increased during upslope walking compared to level walking. 4. At ankle joint, the moments were different depending on the inclination of the ramps. At knee and hip joint, the maximum movements were different depending on the inclination of the ramps. 5. GFR in initial stance phase was higher in downslope walking than in upslope walking, and GFR in late stance phase was higher in upslope walking than in downslope walking.