• 한국식품과학회지
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• 제23권2호
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• pp.217-223
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• 1991

Gel식품의 구조적 특성을 밝히는 일은 특수한 장치나 분석방법이 요구되어 왔으나 본 연구에서는 조작이 간편하고 확산식에 잘 맞는 농도의 해를 구할 수 있는 capillary method를 통해 확산량과 확산계수를 예측하였다. 확산량은 거리, 시간, agar% 농도를 독립변수로 하여 도시하고 추정된 몇 가지 함수식으로부터 SPSS 통계 package 중 regression program을 이용해 단순회귀시켜 R-square가 가장 높은 식을 채택하고 다시 각 독립변수에 대한 함수식을 이용해 다중회귀분석을 실시함으로써 최종 model식을 수립하였다. 기존의 확산계수 예측방법은 Fick의 제 2법칙의 해식으로부터 예측되는 것이 일반적이었으나 그 식이 난해하고 시간이 많이 걸려 본 연구에서는 좀 더 간편한 방법으로 확산계수를 구하고자 수치해석적 방법에 따라 확산계수를 예측하였으며 그 산술평균을 확산계수 D값으로 나타내었다.

• 인터넷정보학회논문지
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• 제7권2호
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• pp.93-102
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• 2006

상호작용적 성격을 갖는 통신서비스의 수요확산패턴은 네트워크 효과에 기인한 임계 가입자 규모에 상당한 의존을 보이고 있으며, 이로 인한 통신서비스의 지연 확산 시기 현상이 발생하고 있다. 그러나 통신망이 회선교환망에서 패킷교환망으로 빠르게 진화하고 또한 다양한 패킷기반 서비스들이 개발, 제공됨에 따라 이러한 통신서비스의 확산 패턴 상의 특성은 변화하고 있다. 내구재를 대상으로 수요 확산 패턴을 분석한 기존 연구들과 국내 6개 회선기반서비스 그리고 역시 6개 패킷기반서비스의 확산 패턴을 비교 분석한 결과, 기존 회선기반서비스들에서 보인 지연 확산 시기 현상은 존재하지 않았으며. 뿐만 아니라 다른 내구재들의 초기 확산보다 더 빠른 확산 속도를 보임으로서 오히려 빠른 확산 시기 현상이 발생하고 있음을 발견하였다. 이러한 결과를 바탕으로 향후 신규 통신서비스 확산 전략은 기존의 통신서비스 보급 및 확산을 위한 초기 단계에서의 촉진전략에서 성장 단계의 확산 유지 및 확대 전략이 보다 유용한 전략임을 제시하였다.

• 천문학회보
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• 제44권2호
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• pp.48.4-48.4
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• 2019

We studied the metal-distribution of isolated Milky-way mass galaxy using various hydrodynamic solvers and investigated the difference of the result between AMR and SPH codes. In particle-based codes, physical quantities like mass or metallicity defined in each particle are conserved unless being injected explicitly by the effect of the supernova, whereas in the Eulerian codes the diffusion is simply accomplished by hydro-equation. Therefore, without including explicit physics of diffusion on the SPH- codes, the metal mixing in the galaxy or CGM only can be accomplished by the direct motion of the particles, however, the standard-SPH codes depress the instability of the turbulent fluid mixing. In this work, we simulated under common initial conditions, common gas-physics like cooling-heating models, and star-formation feedback using ENZO(AMR) GIZMO and GADGET-2 codes. We additionally included a metal-diffusion algorithm on the SPH-codes, which follows the subgrid-turbulent mixing model investigated by Shen et al. (2010) and compared the effect of the metal-outflow on the halo region of the galaxy in different hydro-solvers. We also found that for the implementation of the diffusion scheme in the SPH-codes, the existence of a sufficient number of the gas-particles, which is the carrier of the metals, is necessary. So we tested a new initial condition for proper implementation of the diffusion scheme on the SPH simulations. By comparing the metal-contamination of the circumgalactic medium with different hydrodynamics models, we quantify the diffusion strength of AMR codes using diffusion parameterization of the SPH codes and also suggest the calibration solutions in the different behavior of codes in metal-outflow.

• 한국전기전자재료학회논문지
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• 제33권4호
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• pp.263-270
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• 2020

In this study, the physical mechanism and diffusion effects in aluminium implanted silicon was investigated. For fabricating power semiconductor devices, an aluminum implantation can be used as an emitter and a long drift region in a power diode, transistor, and thyristor. Thermal treatment with O₂ gas exhibited to a remarkably deeper profile than inert gas with N₂ in the depth of junction structure. The redistribution of aluminum implanted through via thermal annealing exhibited oxidation-enhanced diffusion in comparison with inert gas atmosphere. To investigate doping distribution for implantation and diffusion experiments, spreading resistance and secondary ion mass spectrometer tools were used for the measurements. For the deep-junction structure of these experiments, aluminum implantation and diffusion exhibited a junction depth around 20 ㎛ for the fabrication of power silicon devices.

• 한국안광학회지
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• 제16권4호
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• pp.403-408
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• 2011

목적: 확산법칙을 이용하여 착색렌즈에서의 농도분포와 확산깊이에 대한 연구를 하였다. 방법: Fick의 제2확산법칙을 바탕으로 유도된 이론적 맞춤곡선을 측정값에 맞춤한다. 결과: 맞춤곡선은 측정값과 매우 잘 일치하였으며, 그 결과로서 착색렌즈의 내부로 확산되어 들어간 단위면적당 착색용액의 질량과 착색시간 사이의 관계, 착색렌즈 내 착색염료에 대한 농도분포, 확산깊이 등을 평가할 수 있었다. 결론: 착색렌즈의 착색기전은 확산법칙으로 잘 설명될 수 있다.

• 한국화재소방학회논문지
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• 제16권3호
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• pp.1-7
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• 2002

Diffusion and dispersion of injected $CO_2$gas into the $N_2$ gas flow are complex. In the packed column with porous particles the axial dispersion and the extra-particle mass transport as well as the intra-particle mass transport are involved. The pulse spreads by stationary diffusion during the period of arrested flow. Hence, the effect of axial dispersion, and of entrance and exit, as well as that of intraparticle convection should be eliminated during the period. The effective diffusivity was determined experimentally by using the gas chromatography, which is to arrest the gas flow during the period after injecting the pulse. This experiment method hasn't been used often in the field. Effective diffusivities are raised with temperature increasing, and it is quite satisfied com-pared to literature values. In this study, the calculated data of gaseous chemical for extinguish fires could be helpful to appreciate several physical phenomenons. Also, it could be expected that, the calculated data of this study might be very useful for development of excellent gaseous chemical for extinguish fires and improvement of its efficiency.

• 한국공작기계학회논문집
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• 제16권3호
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• pp.133-140
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• 2007

A 2-D model of fluid flow, mass transport and electrochemistry is analysed to examine the effect of current density at the current collector depending on active layer thickness of catlyst in polymer elecrolyte fuel cells. The finite element method is used to solve the continuity, potential and Maxwell-Stefan equations in the flow channel and gas diffusion electrode regions. For the material behavior of electrode reactions in the active catalyst layers, the agglomerate model is implemented to solve the diffusion-reaction problem. The calculated model results are described and compared with the different thickness of active catalyst layers. The significance of the results is discussed in the viewpoint of the current collecting capabilities as well as mass transportation phenomena, which is inferred that the mass transport of reactants dictates the efficiency of the electrode in the present analysis.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.73-78
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• 2003

The InP thin films grown by metalorganic chemical vapor deposition (MOCVD) are widely used to optoelectronic devices such as laser diodes, wave-guides and optical modulators. Effects of various parameters controlling film growth rate such as gas-phase reaction rate constant, surface reaction rate constant and mass diffusivity are numerically investigated. Results show that at the upstream region where film growth rate increases with the flow direction, diffusion including thermal diffusion plays an important role. At the downstream region where the growth rate decreases with flow direction, film deposition mechanism is revealed as a mass-transport limited. Mass transport characteristics are also studied using systematic analyses.

• 대한기계학회논문집
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• 제16권6호
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• pp.1171-1178
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• 1992

본 연구에서는 직접접촉식 열교환기를 이용한 실험을 통하여 열교환기 설계에 가장 중요한 열교환기 단위 체적당 총괄 열전달 계수를 시스템의 작동조건에 따라 구 하여 실제 설계자료로 이용하는 데 그 목적이 있다.

• 설비공학논문집
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• 제26권8호
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• pp.366-374
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• 2014

Experimental mass transfer data, which were obtained for the $CO_2$-water slug flows in vertical tubes with 2, 5, and 8mm diameters, were analyzed in comparison with the penetration theory. It was found that a penetration model with molecular diffusion coefficient cannot predict the experimental data accurately. An effective diffusion coefficient, which considers enhancement effect of interfacial waves, was suggested to improve prediction. Another empirical factor was also suggested to consider the effect of non-uniform interface velocity. A modified penetration model was found to be capable of predicting the experimental data reasonably well.