• Journal of the Optical Society of Korea
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• 제19권5호
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• pp.503-507
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• 2015

Using the reflectivity mode of an optical microscope, we analyzed the optical contrast to identify the layer number of flakes of hexagonal boron nitride on a $SiO_2$/Si substrate. Overall optical contrast in the visible range varies with the thickness of flakes. However, the wavelength of zero contrast exhibits a linear redshift of 0.53 nm per layer, independent of the $SiO_2$ thickness, and increases proportionally with $SiO_2$thickness. Experiments show good agreement with calculations and the results of AFM measurements. These results show that this zero-contrast approach is more accurate and easier than the reflectivity-contrast approach using the overall optical contrast.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 춘계학술대회논문집
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• pp.323-326
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• 2003

This paper presents a new algorithm that can refine hexahedral elements while maintaining the appropriate connectivity. In the algorithm, at first the regions of mesh to be refined are defined and, then, the zero-thickness element layers inserted into the interfaces between the regions. All the meshes in the regions, in which the zero-thickness layers are inserted, are to be regularized in order to improve the shape of the slender elements on the interfaces. This algorithm is applied to the analysis of plastic deformation process. The results show that the refined mesh gives smaller relative errors than the original mesh.

• 비파괴검사학회지
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• 제23권6호
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• pp.577-582
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• 2003

This paper describes a new technique for thickness measurement of a very thin layer less than one-quarter of the wavelength of ultrasonic wave used in the ultrasonic pulse-echo measurements. The technique determines the thickness of a thin layer in a tapered medium from constructive interference of multiple reflection waves. The interference characteristics are derived and investigated in theoretical and experimental approaches. Modified total reflection wave g(t) defined as difference between total and first reflection waves increases in amplitude as the interfacial layer thickness decreases down to zero. A layer thickness less than one-tenth of the ultrasonic wavelength is measured using the maximum amplitude of g(t) with a good accuracy and sensitivity. The method also requires no inversion process to extract the thickness information from the waveforms of reflected waves, so that it makes possible to have the on-line thickness measurement of a thin layer such as a lubricating oil film in thrust bearings and journal bearings during manufacturing process.

• 한국CDE학회논문집
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• 제11권2호
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• pp.107-114
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• 2006

A new quadrilateral mesh generation technique from an existing triangle mesh is proposed in this paper. The proposed method is based on advancing front method and zero-thickness layer. Beginning with an initial triangular mesh, boundary triangular elements are removed and quadrilateral elements with zero thickness are generated. A quality of quadrilateral elements is improved during a mesh smoothing process. Until all initial triangular elements are removed, this procedure is repeated. Sample meshes are constructed to demonstrate the mesh generation capability of proposed algorithm.

• 한국정보전자통신기술학회논문지
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• 제11권6호
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• pp.742-750
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• 2018

본 논문에서는 $0.13{\mu}m$ BCD 공정 기반에서 5V MOS 소자만 사용하여 zero layer FTP 셀이 가능하도록 하기 위해 tunnel oxide 두께를 기존의 $82{\AA}$에서 5V MOS 소자의 gate oxide 두께인 $125{\AA}$을 그대로 사용하였고, 기존의 DNW은 BCD 공정에서 default로 사용하는 HDNW layer를 사용하였다. 그래서 제안된 zero layer FTP 셀은 tunnel oxide와 DNW 마스크의 추가가 필요 없도록 하였다. 그리고 메모리 IP 설계 관점에서는 designer memory 영역과 user memory 영역으로 나누는 dual memory 구조 대신 PMIC 칩의 아날로그 회로의 트리밍에만 사용하는 single memory 구조를 사용하였다. 또한 BGR(Bandgap Reference Voltage) 발생회로의 start-up 회로는 1.8V~5.5V의 전압 영역에서 동작하도록 설계하였다. 한편 64비트 FTP 메모리 IP가 power-on 되면 internal reset 신호에 의해 initial read data를 00H를 유지하도록 설계하였다. $0.13{\mu}m$ Magnachip 반도체 BCD 공정을 이용하여 설계된 64비트 FTP IP의 레이아웃 사이즈는 $485.21{\mu}m{\times}440.665{\mu}m$($=0.214mm^2$)이다.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2001년도 추계학술대회 논문집(Proceeding of the KOSME 2001 Autumn Annual Meeting)
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• pp.36-44
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• 2001

The effects of various tripping structures on turbulent boundary layer subjected to adverse pressure gradient were examined. The profiles are compared to zero pressure gradient and adverse pressure gradient. The increases of tripping structures of height, k are affects almost flow parameter included velocity fluctuation, skin friction coefficient and turbulent boundary thickness.

• Journal of Pharmaceutical Investigation
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• 제25권4호
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• pp.339-345
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• 1995

For the effective treatment of aphthous stomatitis, the matrix type mucoadhesive patches containing triamcinolone acetonide have been formulated. The drug layer was obtained by drying the polymer gel which was prepared with carbomer 934P, ammoniomethacrylate copolymer, titanium dioxide and polyethylene glycol 400. The effects of the content of additives on physical characteristics of the polymer gel and the drug layer were evaluated. The addition of carbomer increased the yield point and the zero-shear viscosity of polymer gel as well as the thickness, the water absorption ratio, the adhesive time and $T_{50%}$ of drug layer. The adhesive time and the water absorption ratio of drug layer were also improved by the addition of ammoniomethacrylate copolymer, but the addition of titanium dioxide had decreased the zero-shear viscosity of polymer gel and the adhesive time of drug layer.

• 한국안광학회지
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• 제16권1호
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• pp.107-116
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• 2011

목적: 콘택트렌즈 피팅 시 렌즈 관련 사양의 변화에 따라 다른 값을 가지는 각막에서 산소부족이 없는 최소 Dk값 및 산소농도를 계산/확인할 수 있는 프로그램을 수립하고자 하였다. 방법: 엑셀 프로그램을 이용하여 콘택트렌즈착용 시 렌즈 아래 형성되는 눈물층의 두께와 Dk값을 계산할 수 있는 방정식을 세우고 수치 계산 모델을 확립하였다. 결과: 렌즈사양을 변화시키면 렌즈 아래 눈물층의 두께가 변하며 이에 따라 산소투과도가 다르게되므로 각막이 요구하는 최소 산소농도 역시 달라짐을 계산으로 확인하였으며, 눈물층의 두께를 위한 계산 프로그램은 눈물층의 형태에 따라 다르게 선택되어야 함을 밝혔다. 즉, flat 피팅 시에는 렌즈가장자리와 각막이 만나서 만들어지는 오목면의 형태에 따라 렌즈 아래 눈물층의 두께가 결정되며, flat하게 피팅 될수록 각막주변부 표면의 산소농도는 감소되어 계산값으로는 (-)가 되며 실제로는 산소농도는 0이 된다. Tight 피팅 시 각막표면의 산소를 계산하면 tight 피팅으로 눈물층의 두께가 렌즈의 두께보다 극단적으로 두꺼워지게 되어 계산값은 역시 (-)가 되며 각막 표면의 산소 농도는 0이 되어 산소결핍을 야기하게 됨을 알 수 있다. 결론: 콘택트렌즈의 변수를 조절하여 피팅 상태를 변경할 때에는 눈물층의 두께와 이에 따른 각막표면의 산소농도를 정확하게 계산하여 산소결핍이 나타나는 일이 없도록 하여야 한다.

• Journal of Magnetics
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• 제6권4호
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• pp.132-141
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• 2001

The switching characteristics and the magnetization-flop behavior in magnetic tunnel junctions exchange biased by synthetic antiferromagnets (SyAFs) are investigated by using a computer simulations based on a single-domain multilayer model. The bias field acting on the free layer is found to be sensitive to the thickness of neighboring layers, and the thickness dependence of the bias field is greater at smaller cell dimensions due to larger magnetostatic interactions. The resistance to magnetization flop increases with decreasing cell size due to increased shape anisotropy. When the cell dimensions are small and the synthetic antiferromagnet is weakly, or not pinned, the magnetization directions of the two layers sandwiching the insulating layer are aligned antiparallel due to a strong magnetostatic interaction, resulting in an abnormal magneto resistance (MR) change from the high-MR state to zero, irrespective of the direction of the free-layer switching. The threshold field for magnetization-flop is found to increase linearly with increasing antiferromagnetic exchange coupling in the synthetic antiferromagnet. Irrespective of the magnetic parameters and cell sizes, magnetization flop does not exist near zero applied field, indicating that magnetization flop is driven by the Zeeman energy.

• Journal of Advanced Marine Engineering and Technology
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• 제28권5호
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• pp.728-734
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• 2004

Environmentally friendly refrigerants with zero ozone layer depletion potential are required to be used in refrigerators and air conditioners due to the difficulties related to ozone layer depletion and global warming. A rigorous study for the system performance with new refrigerants having zero ozone layer depletion potential is inevitable before adopting that as a new fluid. The HFC(Hydrofluorocarbon) potential has been recommended as alternatives. In this paper. system performance in the heat pump facilities were studied using R-290, R-600a. R-1270 as an environment friendly refrigerant. R-22 as a HCFC's refrigerant. The experimental apparatus has been set-up as a conventional vapor compression type heat Pump system. The test section is a horizontal double pipe heat exchanger. A tube diameter of 12.70mm with 1.315mm wall thickness is used for this investigation. The test results showed that the COP of hydrocarbon refrigerants were superior to that of R-22 and the maximum increasing rate of COP was found in R-1270. The refrigeration capacity of hydrocarbon refrigerants were higher than that of R-22. The compressor work was obtained with the maximum value in R-1270 and the minimum one in R-22.