• 대한수학회논문집
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• 제12권2호
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• pp.479-490
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• 1997

We consider long nonlinear waves in the two-layer flow of an inviscid and incompressible fluid bounded above by a free surface and below by a rigid boundary. The flow is forced by a bump on the bottom. The derivation of the forced KdV equation fails when the density ratio h and the depth ratio $\rho$ yields a condition $1 + h\rho = (2-h)((1-h)^2 + 4\rho h)^{1/2}$. To overcome this difficulty we derive a forced modified KdV equation by a refined asymptotic method. Numerical solutions are given and hydraulic fall solution of a two layer fluid is expressed analytically in the case that derivation of the forced KdV (FKdV) equation fails.

• Nuclear Engineering and Technology
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• 제49권1호
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• pp.216-223
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• 2017

In this work, linear and mass attenuation coefficients, effective atomic number and electron density, mean free paths, and half value layer and $10^{th}$ value layer values of barium-bismuth-borosilicate glasses were obtained for 662 keV, 1,173 keV, and 1,332 keV gamma ray energies using MCNP-4C code and XCOM program. Then obtained data were compared with available experimental data. The MCNP-4C code and XCOM program results were in good agreement with the experimental data. Barium-bismuth-borosilicate glasses have good gamma ray shielding properties from the shielding point of view.

• 대한수학회보
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• 제36권4호
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• pp.637-647
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• 1999

In this paper, we consider a free boundary problem with Pushchino dynamics satisfying the Dirichlet boundary condition. We shall the stationary solutions ($v^{*}(x),s^{*}$) exist and the Hopf bifurcation occurs at a critical point when s $\in$ (1/3,1).

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1995년도 추계 학술대회논문집
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• pp.126-131
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• 1995

In this paper we study steady capillary-gravity waves in a two-layer fluid bounded above by a free surface and below by a horizontal rigid boundary with a small obstruction, Two critical speeds for the waves are obtained. Near the smaller critical speed, the derivation of the usual forced KdV equation (FKdV) fails when the coefficient of the nonlinear term in the FKdV vanishes. To overcome this difficulty, a new equation called a forced extended KdV equation (FEKdV) governing interfacial wave forms is obtained by a refined asymptotic method. Various solutions and numerical results of this equation are presented.

• 대한기계학회논문집
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• 제7권3호
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• pp.278-285
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• 1983

The momentum transfer in axisymmetric turbulent boundary layer over a rotating cone submerged in a free stream was studied by experiments and numerical analysis. In numerical analysis the velocity profiles were calculated by finite difference method using Prandtl mixing length concept, and the results were compared with experimental results. The agreement was good. By the numerical analysis the wall fircition coefficient was increased as the Reynolds number increased when the rotational speed is large, but the wall friction coefficient was decreased as the rotational speed increased.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.262-262
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• 2010

We introduce a novel and efficient strategy for producing free-standing functional films via photo-crosslinking and electrostatic layer-by-layer (LbL) assembly, which can allow the buildup of hydrophilic multilayers onto hydrophobic surfaces. Hydrophobic multilayers were deposited on ionic substrates by a photo-crosslinking LbL process using photo-crosslinkable polymers. The photo-crosslinked surface was converted to an anionic surface by excess UV light irradiation. This treatment allowed also the stable adhesion between metal electrode or cationic polyelectrolyte and hydrophobic multilayers. After dissolving the ionic substrates in water, the formed free-standing films exhibited unique functionalities of inserted components within hydrophobic and/or hydrophilic multilayers.

• 한국분말재료학회지
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• 제22권2호
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• pp.134-137
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• 2015

The monolayer engineering diamond particles are aligned on the oxygen free Cu plates with electroless Ni plating layer. The mean diamond particle sizes of 15, 23 and $50{\mu}m$ are used as thermal conductivity pathway for fabricating metal/carbon multi-layer composite material systems. Interconnected void structure of irregular shaped diamond particles allow dense electroless Ni plating layer on Cu plate and fixing them with 37-43% Ni thickness of their mean diameter. The thermal conductivity decrease with increasing measurement temperature up to $150^{\circ}C$ in all diamond size conditions. When the diamond particle size is increased from $15{\mu}m$ to $50{\mu}m$ (Max. 304 W/mK at room temperature) tended to increase thermal conductivity, because the volume fraction of diamond is increased inside plating layer.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2008년도 공동학술대회
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• pp.57-62
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• 2008

탄성파 수치 모형 계산에 있어서 널리 사용되는 엇갈린 격자 방법이 아니라 회전된 엇갈린 격자 방법을 사용하여 탄성파 수치 모사를 수행하였다. 표준 엇갈린 격자 방법에서는 자유 경계조건을 적용하여야 하는 단점이 있지만 회전된 격자 방법에서는 자유 경계조건을 적용할 필요 없이 물성을 부여함으로써 해결될 수 있다. 파동전파에 있어서 유한 경계 조건에서 발생하는 인공 반사파를 제거하기 위하여 최근에 뛰어난 성능을 보이는 PML(Perfectly Matched Layer)법이 많이 적용되고 있다. 이 연구에서는 PML보다 성능이 뛰어나기도 하지만 차분에 있어 파동식을 분리할 필요가 없는 CPML(Convolutional Perfectly Matched Layer)법을 회전된 엇갈린 격자법(RSG : Rotatged Staggered Grid)에 적용하고자 하였다. Cerjan법의 감쇠법과 비교한 결과 매우 효과적으로 인공 반사파를 제거할 수 있음을 알 수 있었다.

• International Journal of Aerospace System Engineering
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• 제2권2호
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• pp.6-9
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• 2015

A new cross disciplinary conception of transitional aero-optics is built up during analyzing and measuring the linkage between the hypersonic boundary layer transition on a flat plate and the jittering characteristics of the small-aperture beam through that boundary layer. Based on that conception, the Small-Aperture Beam Technique (SABT) and high-speed Imaging Camera System (ICS) used in aero-optical studies are considered as new techniques for the assessment of the hypersonic transition in the boundary layer on a flat plate. In the FD-20 gun tunnel, for the free stream parameters with Mach number of 8 and unit Reynolds number of $1{\times}10^7$ (1/m), those two optical techniques are used to measure the jitter of the small-aperture beam. At the same free stream parameters, the distribution of the heat transfer along the centerline of the flat plate is also measured by the thin film resistance gauge technique. The results show the similarity of the increase trend between the heat transfer and the jitter of the small-aperture beam in the transitional region. It helps us to surmise that it may be feasible to diagnose the transition in a hypersonic boundary layer on a flat plate by means of those above optical techniques.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.152-153
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• 2006

The new approach to buffer layer design for CIGS solar cells that permitted to reduce the buffer absorption losses in the short wavelength range and to overcome the disadvantages inherent to Cd-free CIGS solar cells was proposed. A chemical bath deposition method has been used to produce a high duality buffer layer that comprises thin film of CdS and Zn-based film. The double layer was grown on either ITO or CIGS substrates and its morphological, structural and optical properties were characterized. The Zn-based film was described as the ternary compound $ZnS_x(OH)_y$. The composition of the $ZnS_x(OH)_y$ layer was not uniform throughout its thickness. $ZnS_x(OH)_y$/CdS/substrate region was a highly intermixed region with gradually changing composition. The short wavelength cut-off of double layer was shifted to shorter wavelength (400nm) compared to that (520 nm) for the standard CdS by optimization of the double buffer design. The results show the way to improve the light energy collection efficiency of the nearly cadmium-free CIGS-based solar cells.