• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2005년도 춘계 학술대회논문집
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• pp.57-64
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• 2005

Aerodynamic characteristics of three-dimensional wings in ground effect for Aero-levitation Electric Vehicle(AEV) are numerically investigated for various fairing shapes at the junctions of 3D Wings. Numerical results show that a sizeable three-dimensional comer flow separation occurs with formation of an arch vortex at the junction of main and vertical wings, and also that this is predicted the main cause of the high lift-to-drag(L/D) reduction rate of the main wing. To avoid the comer flow separation, the main idea of this study is to reduce the cross section gradient of the comer flow tube near the trailing edge for various fairing shapes. Improvements on L/D ratios of the wings are pursued by breaking the coherence of superimposed adverse pressure gradients at the wing junction when the cross section gradient is changed slowly at the trailing edge.

• Nuclear Engineering and Technology
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• 제41권10호
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• pp.1285-1292
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• 2009

The effects of the narrowed upside gap on nucleate pool boiling heat transfer in a vertical annulus were investigated experimentally. For the study, a stainless steel tube with a diameter of 25.4 mm and saturated water that kept an atmospheric condition were used. The ratio between the gaps measured at the upper and the lower regions of the annulus ranged from 0.18 to 1. Two different lengths of the modified gap also were investigated. The change in heat transfer due to the modified gap became evident as the gap ratio decreased and the length of the gap increased. As the gap ratio became less than 0.51, a significant decrease in heat transfer was observed compared to the plain annulus. The longer gap size resulted in an additional decrease in heat transfer. The major cause for the tendency was attributed to the formation of lumped bubbles around the upper region of the annulus followed by the increased flow friction between the fluid and the surface around the modified gap.

• International Journal of Air-Conditioning and Refrigeration
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• 제9권2호
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• pp.19-27
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• 2001

In the present study, the effects of film Reynolds number (60∼200) and volumetric content of non-absorbable gases (0∼10%) in water vapor on the absorption process of aqueous LiBr solution were investigated experimentally. The formation of solution film on the horizontal tubes of six rows was observed to be complete for Re>100. Transition film Reynolds number was found to exist above which the Nusselt number and Schmidt number diminishes with solution flow rate. As the concentration of non-absorbable gases increased, mass transfer rate decreased more seriously than heat transfer rate did. the degradation effects of non-absorbable gases seemed to be significant especially when small amount of non-absorbable gases was introduced to the pure water vapor.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.388-393
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• 2004

A comprehensive numerical study on the three point bending behavior of Aluminum foam-filled stainless steel tube has been performed. Aluminium alloy foams with various densities were produced and their mechanical properites were evaluated. Finite element(FE) analysis of three point bending test was performed to evaluate bending behavior of foam filled cylindrical structures. Results showed that foam filling offered remarkable increase of bending resistance and enhanced the crashworthiness of the structure. It turned out to prevent the inward fold formation at the compression flange, resulted into the multiple propagating folds and increased the load carrying capacity.

• 설비공학논문집
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• 제12권2호
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• pp.218-225
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• 2000

In the present study, the effects of film Reynolds number (60∼200) and volumetric content of non-absorbable gases (0∼10%) in water vapor on the absorption process of aqueous LiBr solution were investigated experimentally. The formation of solution film on the horizontal tubes of six rows were observed to be complete for Re>100. Transition film Reynolds number were found to exist above which the Nusselt number and Schmidt number diminishes with solution flow rate. As the concentration of non-absorbable gases increased, mass transfer rate decreased more seriously than heat transfer rate did. The degradation effects of non-absorbable gases seemed to be significant especially when small amount of non-absorbable gases were introduced to the pure water vapor.

• 대한기관식도과학회:학술대회논문집
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• 대한기관식도과학회 1983년도 제17차 학술대회연제순서 및 초록
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• pp.14.1-14
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• 1983

기관발거 곤란증은 주로 외상으로 인한 경우가 많으나 의인적인 기관손상, 즉 high tracheostomy, 부적절한 cannula사용, 2 차감염, 육아조직생성 및 기관전벽의 광범위한 절제 등과, 기타 정신적인요소등이 그 원인으로 알려져 있으며 치료로는 steroid사용, stent삽입, 기관공확장술 및 협착부위를 절제한 후 단단봉합하는 등의 방법이 알려져 있다. 최근 저자들은 2세된 남아에서 기관지 이물제거를 위해 기관절개술을 시행한 후 발생한 기관발거 곤란증 환자에서 Silicon T-tube를 사용하여 치유한 예를 문헌고찰과 함께 보고한다.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1993년도 추계학술대회
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• pp.110-113
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• 1993

An in vitro experiment under laminar non-pulsatile blood flow and an acute canine ex vivo femoral A-V series shunt experiment were undertaken to investigate the effectiveness of saline perfusion through pores of porous tubes to prevent formation of mural thrombus. PS/SBR porous tubes were used for the in vitro experiment. Commercially obtained ePTFE porous tubes were etched by sodium naphthalenide, and the etched tubes were used for the ex vivo experiment. According to the results of the in vitro experiment, mural thrombus on the surface of the porous tribe could be prevented by the saline perfusion. Adhered blood cells decreased semi-logarithmically with increased perfusion rate (up to $0.022\;ml/min-cm^2$) of isotonic saline solution. According to results of the ex vivo experiment, mural thrombus decreased with increased perfusion rate (upto $0.060\;ml/min-cm^2$).

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2001년도 제33회 춘계학술대회 개최
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• pp.115-121
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• 2001

The wear test has been performed to evaluate the wear mechanism of steam generator (SG) tube materials against ferritic stainless steel in water environment. The wear rates of SG tube materials depend on the change of mechanical properties between contact surfaces during wear test. From the subsurface hardness test, Inconel 690 is more work-hardened than Inconel 600 even though these materials have similar hardness values before the wear test. Main cause is due to the difference of stacking fault energy with the chromium content. In water environment, wear mechanism is closely related with the continuous formation and fracture of deformation layers at the contact surfaces.

• Nuclear Engineering and Technology
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• 제34권2호
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• pp.132-141
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• 2002

The effects of microstructure on fretting wear were investigated in Inconel 690 tube. The microstructure observation indicated that the solution annealing temperature and time affected the grain size of the Inconel 690 tubes. The carbide morphology, along grain boundaries, was mainly affected by thermal treatment time and temperature. The wear test results showed that specimens with larger grain size and with coarse carbides along grain boundaries had better wear resistance. Cracks were found in specimens with carbides along the grain boundary, while few cracks were found in carbide free specimens. It seemed that the carbides on grain boundary assisted crack formation and propagation in carbide containing specimens. On the other hand, the micro-hardness of specimen did not have a major role in fretting wear. It could be inferred from the SEM images of worn surfaces that the main wear mechanism of carbide containing specimen was delamination, while that of carbide free specimen was abrasion.

• Journal of Korean Neurosurgical Society
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• 제64권3호
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• pp.346-358
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• 2021

Secondary neurulation is a morphological process described since the second half of the 19th century; it accounts for the formation of the caudal spinal cord in mammals including humans. A similar process takes place in birds. This form of neurulation is caused by the growth of the tail bud region, the most caudal axial region of the embryo. Experimental work in different animal species leads to questioning dogmas widely disseminated in the medical literature. Thus, it is clearly established that the tail bud is not a mass of undifferentiated pluripotent cells but is made up of a juxtaposition of territories whose fate is different. The lumens of the two tubes generated by the two modes of neurulation are continuous. There seem to be multiple cavities in the human embryo, but discrepancies exist according to the authors. Finally, the tissues that generate the secondary neural tube are initially located in the most superficial layer of the embryo. These cells must undergo internalization to generate the secondary neurectoderm. A defect in internalization could lead to an open neural tube defect that contradicts the dogma that a secondary neurulation defect is closed by definition.