• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.95-95
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• 2012

스터퍼링 기술이 1852년 Grove에 의해서 최초 발견되어 1979년 Chapin에 의해서 planar magnetron cathode 개발로 진공코팅기술의 새로운 영역을 열게 되어 현재까지 디스플레이, 반도체, 태양전지, 광학산업 및 전자부품 등 나노 산업에 필수적으로 적용되고 있다. 스퍼터링 입자는 운동량 전달에 의한 것으로 운동량을 갖는 나노 스퍼터링 입자는 기판에 대한 박막의 부착력이 우수하고 대면적에 균일하고 재현성 있게 성막되는 특징을 갖고 있다. 마그네트론 스퍼터링 기술이 산업에 응용되면서 주로 4분야에서 많은 연구, 개발이 되어져 왔다. 첫째는 타겟의 고순도 및 고밀도화와 더불어 가격이 고가로 됨에 따라 타겟 사용효율의 향상이다. 플라즈마를 발생시키는 캐소드의 자기회로를 1차원, 2차원 및 회전운동을 통해서 사용효율을 향상시키고 있다. 둘째는 기판에 대해서 박막특성이 균일하도록 코팅하는 것이다. 디스플레이에서는 글래스 기판이 대면적으로 됨에 따라서 핸들링이 어려워져 여러 개의 캐소드 자기회로를 선형적으로 이동시켜 박막두께분포를 최적화하며 반응성 가스를 사용해서 균일한 특성의 박막을 제작하는 경우에는 가스분사관과 배기펌프계의 기하학적 위치 및 가스 유동학적 해석이 필요하다. 셋째는 스퍼터링 입자의 이온화로 의한 박막의 특성향상과 반도체 trench의 높은 aspect ratio hole을 채우는 것이다. 이온화 방법으로는 inductively coupled plasma (ICP), microwave amplified (MA), high power impulse (HIPI), hollow cathode magnetron (HCM), self-sustained sputtering 등이 사용되어져 왔으며 최근에는(neutral beam-assisted sputtering (NBAS)에 의한 박막특성향상 방법이 발표되고 있다. 넷째는 플라즈마 및 박막두께 시뮬레이션에 대해서 많은 발표가 되고 있다. 본 발표에서는 상기의 4 분야를 포함한 향후 개발방향에 대해서 소개할 예정이다.

• Proceedings of the Korea Water Resources Association Conference
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• 1992.07a
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• pp.55-66
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• 1992

The energy and momentum coefficients ${\alpha}$ and ${\beta}$ are measures of homogenerity of velocity distribution in a chanel section. They indicate the effect of energy and momentum transport. However, in most practical applications, they are assumed to be unity due to the difficulty in estimating them. Efforts have been made in this study to estimate these coefficients and to develop equations for practical applications. The Prandtl-von Karman logarithmic equation as being used today has limitations and far-reaching assumptions. Therefore, this paper uses Chiu's velocity distribution equation which seems to be capable of serving as such an alternative, to estimate the velocity distribution and the energy and momentum coefficients, ${\alpha}$ and ${\beta}$ results are compared with those computed by other existing equations. For practical applications, this paper also uses Chiu's equation along with the Mannig's equation to calculate ${\alpha}$, ${\beta}$ without velocity data

• Fire Science and Engineering
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• v.19 no.4 s.60
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• pp.18-25
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• 2005

In this study, numerical analysis of two-dimensional unsteady natural convection of air in a square enclosure heated from below, was performed as a basic research of fire science. SIMPLE algorithm was used to the pressure term of momentum equations in the numerical analysis. The numerical analysis were studied for the two model cases and two heat conditions, respectively, which are different with insulation of enclosures and position of heat applied. Also, the ceiling temperatures of enclosure were measured to compare the accuracy of numerical analysis, and it is found that the temperature predicted by numerical analysis were agreed well with the measurements. Streamline and isotherm of the each model case were acquired for each time step.

• Journal of the Korean Institute of Gas
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• v.12 no.4
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• pp.21-28
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• 2008

A numerical analysis is achieved to elucidate the behavior of lifted flames and characteristics of flow near flame zone according to the exit velocity of triple flame, Poiseuille and uniform distribution. For the cases of Poiseuille and uniform nozzle exit velocity, we reviewed previous results with the present numerical results and investigated characteristics of the flame structure near the flame zone comparing with liftoff height generalized by momentum flux. In addition, a close inquiry into the combustion flow characteristics near flame zone was made with the characteristics of velocity, pressure, temperature and chemical reaction. From nozzle to flame zone, center line velocity profile traced well with the velocity profile of typical cold jet flow, but very near the flame zone, this study examined phenomenon that flow velocity decreases very quickly before the flame zone and then increases very quickly after the flame zone. Because flame zone acts as a barrier at the flow region which is before the flame zone and accelerate the flow velocity when it pass through the flame zone. This phenomenon was not clarified previous cold jet flow.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.8
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• pp.1103-1112
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• 2001

The effect of pressure gradients on the hairpin structures in three different turbulent boundary layers (ZPG : Re(sub)$\theta$=910, FPG : Re(sub)$\theta$=575, APG : Re(sub)$\theta$=1290) has been examined with instantaneous velocity fields obtained in streamwise-wall-normal planes using PIV (particle image velocimetry) method. In the outer layer hairpin vortices occur in streamwise-aligned packets that propagate with small velocity dispersion. The signature pattern of the hairpin consists of a spanwise vortex core located above a region of strong second quadrant fluctuation (u<0 and v>0 : Q2 event) is clearly observed. The formation of packets explains the occurrence of multiple VITA events in turbulent burst. Noticeable differences are found in the average inclination angles of hairpin vortex packets which are 45$^{\circ}$, 35.7$^{\circ}$, and 51.9$^{\circ}$in the case of ZPG, FPG and APG, respectively. It is found that the large, time-varying, irregularly shaped zones with nearly constant streamwise momentum exist throughout the boundary layer. Within the interior of the envelope the spatial coherence between the velocity fields induced by the individual vortices leads to strongly retarded streamwise momentum, explaining the zones of uniform momentum. The formation of the uniform momentum zone is remarkably different with respect to the pressure gradients especially in the logarithmic layer.

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.5
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• pp.51-59
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• 2007

The end-burning combustion field using impinging oxidizer injectors are analyzed with tangential type injectors in order to examine their mixing and combustion characteristics. The impinging type showed further improved mixing effect as well as the combustion efficiency compared to the previously studied tangential injector. A novel injector capable of delivering impinging and swirl effect is introduced in this study where it demonstrated that the grain coning effect can be avoided. It was found that the combined impinging and swirling flow would promote the radial mixing rate increasing the residence time and the turbulent intensity. However, the use of the step combustor which may augment the turbulent intensity did not show any notable difference compared to the basic combustor.