• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1488-1493
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• 2004

The purpose of the present work is to develop a compressed air discharging system to eject a projectile from the underwater. For the flow analysis of compressed air tank, projectile ejection tube, and pipe system, the air is assumed as an ideal gas, undergoing 1-dimensional axisymmetric, compressible flow, the Fanno flow analysis was applied. The commercial Fluent code was used to solve 3-D Navier-Stokes equation of the internal flow within the valve. The dynamics of the projectile within the ejection tube was assumed 1-degree of freedom. The calculations were performed to four cases of valve opening area ratio, i.e., 25%, 50%, 75%, and 100% opening area, at both depths of 10m and 50m. The results were shown as the figures of time variation of pressure of the compressed air tank and projectile ejection tube. The velocity and distance of the projectile were also predicted.

• Journal of Animal Science and Technology
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• 제47권4호
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• pp.691-696
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• 2005

본 연구는 모돈이 서있거나 앉아 있을 때 모돈의 배 밑에 공기를 분사하는 것이 모돈과 포유자돈의 압사 관련 행동에 미치는 영향을 규명하고자 수행되었으며, 공시동물로는 경산돈 16복과 포유자돈 179두가 분만 후 4일까지 이용되었다. 모돈의 행동을 관찰한 결과, 서있는 행동과 앉아있는 행동에 있어서 대조구와 공기분사구간에 차이가 없는 것으로 나타나 공기분사가 모돈의 행동에 영향을 미치지 않는 것으로 분석되었다. 반면에 압사와 밀접하게 관련 있는 4가지 포유자돈의 행동을 관찰한 결과 모돈의 뒤로 지나가는 행동, 모돈의 뒤에 서있는 행동, 모돈의 배 밑으로 지나가는 행동, 모돈의 배 밑에 서있는 행동 모두가 대조구에 비해 공기분사구에서 현저히 낮게 나타났다. 따라서, 모돈이 서있거나 앉아있을 때 모돈의 배 밑에 공기분사를 함으로써 모돈의 행동과 포유자돈의 건강에 영향을 미치지 않고 포유자돈의 압사 관련 행동을 억제하여 포유자돈의 압사를 효과적으로 방지할 수 있을 것으로 예상된다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.658-659
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• 2008

Numerical simulation is performed for a microdroplet deposition on the pre-patterned micro-structure. The liquid-air interface is tracked by level set method improved by incorporating the ghost fluid approach based on a sharp-interface representation. The method is further extended to treat the contact angle condition at an immersed solid surface. The present computation of a patterning process using microdroplet ejection demonstrates that the multiphase characteristics between the liquid-gas-solid phases can be used to overcome the patterning error.

• 자동차안전학회지
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• 제7권4호
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• pp.16-19
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• 2015

FMVSS226 Ejection Mitigation Impact Test is usually performed by real vehicle. But it is necessary to perform the test using by Reinforced B.I.W. with considering vehicle developing timing and roof rail airbag (RRAB) supplier capacity. We sometimes need tendency (quick data) instead of slow accurate data to fix RRAB design as proper timing. Test with Reinforced B.I.W. is helpful saving time and cost. But it should be confirmed how much different between vehicle conditioned test result and Reinforced B.I.W. conditioned test result. There are some points to be improved even in the test with vehicle. Understanding of deviation of Reinforced B.I.W. conditioned test result from vehicle conditioned test result is needed to get benefits with using Reinforced B.I.W. conditioned in the test.

• 설비공학논문집
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• 제17권11호
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• pp.990-997
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• 2005

The stratified effect was investigated with three different types of diffuser shape in a thermal storage tank with variation of diffuser diameter, velocity, Froude number etc. Its effect was estimated by the degree of stratification. No matter of diffuser diameter and shape, the degree of stratification was the best as the Froude number gets closer to 1. In the case of a curved diffuser, when its diameter is a quarter of tank diameter and ejection velocity in a diffuser is approximately 0.2 m/s, the Froude number was almost 1. In the case of a flatted diffuser, when ejection velocity was 0.05 m/s, the Froude number was 1.5. Both cases which Froude number were nearer 1, showed the good degree of stratification.

• 한국항공우주학회지
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• 제47권12호
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• pp.904-912
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• 2019

본 연구는 항공기에 근접하여 폭발하는 고폭형 위협 무기의 파편 발사속도 및 발사각을 수치 해석적으로 추정한 결과이다. 고폭형 위협 무기에 대한 항공기의 취약성을 평가하기 위하여 탄두 구성품의 물리량을 이해하는 것은 매우 중요하다. 일반적으로 고폭형 위협 무기에 대한 구성품의 질량, 길이 및 직경 등 물리적 변수는 알려져 있지 않다. Terrier, Sparrow 등 유사 위협 무기들의 데이터를 이용하여 charge to mass 비율, 길이와 직경 비율 등과 관련된 경험식을 수치 해석적으로 유도하였다. 근접신관에 의하여 외부에 폭발하는 탄두에서 탄두 덮개 구성비는 20% 수준으로 나타났으며, 고폭 화약의 양쪽 끝부분에서 방사되는 파편의 발사속도 구배 현상이 뚜렷이 나타났지만 법선 방향에 대한 발사각은 6° 이내로 나타났다.

• 한국유체기계학회 논문집
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• 제17권5호
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• pp.43-53
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• 2014

This paper presents a the study on air curtain system of top and bottom bi-directional jet air discharge for blocking the spread of smoke in case of tunnel fire. The five kinds different air curtains of A, B, C, D, and E of models for various performance tested after manufactured. A results of the various performance test obtained the best efficiency from E model air curtain. And optimize the injection angle of the air curtain nozzle through the three-dimensional computational fluid dynamics (CFD) analysis and analyzed the effects of external pressure of tunnel. and also single factor design have been applied. At present, our attention is focused on the velocity distribution(flow width and flow position) of 1.5m on the ground in tunnel. Also, analyzed the influence of draft in the tunnel. Detailed effects of discharge angle of air curtain and velocity at nozzle exit are discussed.

• The Korean Journal of Physiology and Pharmacology
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• 제4권3호
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• pp.253-261
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• 2000

Head-out water immersion induces marked increase in the cardiac stroke volume. The present study was undertaken to characterize the stroke volume change by analyzing the aortic blood flow and left ventricular systolic time intervals. Ten men rested on a siting position in the air and in the water at $34.5^{circ}C$ for 30 min each. Their stroke volume, heart rate, ventricular systolic time intervals, and aortic blood flow indices were assessed by impedance cardiography. During immersion, the stroke volume increased 56%, with a slight (4%) decrease in heart rate, thus cardiac output increased ${\sim}50%.$ The slight increase in R-R interval was due to an equivalent increase in the systolic and diastolic time intervals. The ventricular ejection time was 20% increased, and this was mainly due to a decrease in pre-ejection period (28%). The mean arterial pressure increased 5 mmHg, indicating that the cardiac afterload was slightly elevated by immersion. The left ventricular end-diastolic volume index increased 24%, indicating that the cardiac preload was markedly elevated during immersion. The mean velocity and the indices of peak velocity and peak acceleration of aortic blood flow were all increased by ${\sim}30%,$ indicating that the left ventricular contractile force was enhanced by immersion. These results suggest that the increase in stroke volume during immersion is characterized by an increase in ventricular ejection time and aortic blood flow velocity, which may be primarily attributed to the increased cardiac preload and the muscle length-dependent increase in myocardial contractile force.

• 한국전산유체공학회지
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• 제17권3호
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• pp.33-38
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• 2012

The droplet ejection behavior from drop-on-demand printhead are investigated numerically for Newtonian and shear-thinning fluid. The numerical simulation is performed using a volume-of-fluid model. In this study, we compare the printable range in terms of Z number and pinch-off time for Newtonian and shear-thinning fluids. The printability range are found to be 1.08 $$\leq_-$$ Z $$\leq_-$$ 12.9 for Newtonian fluid and 0.8 $$\leq_-$$ Z $$\leq_-$$ 12.9 for shear-thinning fluid. However, air entrainment is observed during merging of primary and satellite droplet within the printability range. The pinch-off time of the shear-thinning fluid is apparently shorter compared to the corresponding Newtonian fluid due to shear-thinning effects and the differences in the pinch-off time is enlarged significantly when the capillary number is larger than 0.5.

• 반도체디스플레이기술학회지
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• 제19권2호
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• pp.37-44
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• 2020

In improving laser cutting of optical plastic films for mass production of optoelectronics display units, it is important to understand particle contamination over optical film surface due to fume particle generation and dispersion. This numerical study investigates the effects of downward and upward air flow motions on fume particle dispersion around laser cut line. The simulations employ random particle sampling of up to one million fume particles by probabilistic distributions of particle size, ejection velocity and angle, and fume particle dispersion and surface landing are predicted using Basset-Boussinesq-Oseen model of low Reynolds number flows. The numerical results show that downward air flow scatters fume particles of a certain size range farther away from laser cut line and aggravate surface contamination. However, upward air flow pushes fume particles of this size range back toward laser cut line or sucks them up with rising air motion, thus significantly alleviating surface contamination.