• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.3
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• pp.181-189
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• 2008

GaAs film growth process from trimethylgallium(TMGa) and tertiary-butylarsine(TBAs) using a horizontal MOCVD reactor was numerically studied to explain the experimental result that the decreasing surface reaction rate as the increasing partial pressure of group III species. Using the non-linear model based on the Langmuir isotherm which considers the adsorption and desorption of molecules, film deposition over the entire reactor scale was predicted by computational fluid dynamics (CFD) with the aid of the parameters obtained from the selective area growth (SAG) technique. CFD Results using the non-linear surface reaction model with the parameters determined from the SAG experiments predicted too high film growth rate compared to the measured values at the downstream region where the temperature was decreased abruptly. The pairs of ($k_s^n$, K) from the numerical simulations was $(2.52{\times}10K^{-6}mol/m^2/s,\;1.6{\times}10^5m^3/mol)$, whereas the experimentally determined was $(3.58{\times}10^{-5}mol/m^2/s,\;6.9{\times}10^5m^3/mol)$.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.4
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• pp.55-69
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• 1999

일반적으로 잉크젯 프린터는 농도에 대해 선형적인 계조재현 특성을 나타낸다. 그러나 인간 시각의 경우 농도에 선형적인 프린터 출력에 대하여 비선형적인 지각반응을 나타낸다. 즉 농도가 큰 패치(patch)에 대해서는 명도나 색차에 대한 변별력이 작으며 농도가 작은 패치에 대해서는 좀 더 예민한 변별력을 갖는다. 따라서 농도에 선형적인 프린터 출력은 시각적인 활성영역을 줄이므로 프린터에서 구별되는 계조의 범위가 좁아진다. 그러므로 본 논문에서는 인간의 시지각 특성과 매우 상관도가 높은 CIELAB 색공간을 이용하여 균등한 명도 변화 및 색차를 나타내도록 하는 프린터 계조재현 알고리즘을 제안한다. 이때 시각적으로 균등한 변화를 나타내는 프린터의 입력값을 찾기 위해 다층 퍼셉트론 신경망(multi-layer perceptron neural network, MLP)을 이용하였다. 신경망의 학습을 위해 계조에 따른 패치를 만들고, 프린터 구동입력신호 및 패치의 측정된 값으로 신경망을 학습하였다. 학습된 신경망으로 선형적인 출력을 내는 프린터 구동신호를 찾고 LUT(look-up table)를 이용하여 프린터 입력 신호를 역으로 보정하였다. 결과, 보정된 프린터의 출력이 선형적인 계조 변화를 보였고 변화가 인지되는 계조의 범위가 늘어났으며 실형상에 대한 실험에 있어서도 우수한 화질을 보였다.

• Proceeding of KASS Symposium
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• 2008.05a
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• pp.80-85
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• 2008

This paper investigate the structure instability properties of the shelled space frame structure. The large structure must have thin thickness for build the large space structure there fore structure instability review is important when we do structural design. The structure instability of the shelled structure accept it sensitively by varied conditions. This come to a nonlinear problem with be concomitant large deformation. In this study, it is compared unstable behavior according to lode and boundary condition of the shelled space frame structure through numerical method which considered geometrical nonlinear and grasped influence for the instability phenomenon and investigated the fundamental collapse mechanism.

• Journal of Korean Association for Spatial Structures
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• v.10 no.2
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• pp.45-60
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• 2010

Nonlinear problems for membrane structures are very sensitive in convergence procedure in nonlinear iterations. Therefore many researchers have suggested a lot of ideas in published papers. In this study, authors are trying to get easier solution for taking membrane shape by initial stresses from substitution of the membrane to line elements. To obtain nonlinear stiffness, the nonlinear finite element method is used for both membrane and cable elements, and only geometric nonlinear terms are taken for shape analysis. By some examined models, we can find that the substituted models show better results to get, initial shape in which the concentrating phenomenon is removed at edge parts.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1067-1068
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• 2007

최근 영구자석 선형 동기 전동기(PMSLM)는 이동 장치로써 많은 분야에 사용되고 있다. 영구자석 선형 동기 전동기는 구조적으로 간단하며 고속화 고추력화 등의 많은 장점을 가지고 있다. 그러나 단 1차형 영구자석 선형 동기 전동기는 매우 큰 디텐트력을 지니고 있어 추력 맥동의 원인이 되며, 이는 소음과 진동을 발생시킨다. 단 1차형 영구자석 선형 동기 전동기의 디텐트력은 전기자 내부의 치와 영구자석 사이에 작용하는 힘과 전기자 양 단부와 영구자석 사이에서 작용하는 힘의 합으로 표현된다. 본 논문에서는 코깅력을 줄이기 위한 방법으로 영구자석의 극 수와 전기자의 슬롯 수의 비를 변경한 새로운 구조의 단1차형 영구자석 선형 동기 전동기(PMLSM)를 제안하였고, 단부력을 줄이기 위하여 전기자 양 단부에 전기자 길이 조정법과 챔퍼링 법을 사용하였고, 반응표면법과 (($1+{\lambda}$) evolution strategy)[14]을 이용하여 최적화를 수행하였다.

• Journal of the Korean Chemical Society
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• v.23 no.2
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• pp.104-110
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• 1979

A new least square method for analysis of the whole time course of enzyme-catalyzed reactions is presented. This method requires only a programmable calculator with small capacity and is applicable to both uninhibited reactions and reactions inhibited by products or added compounds. This method fits the data to the nonlinear plot of substrate concentration vs. time, and, consequently, estimates the kinetic parameters better than the least square method based on linearly transformed equations.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.11
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• pp.195-205
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• 2013

The analysis of electroencephalographic signal associated with the attention is essential for the understanding of human cognition. In this paper, the characteristic differences between the attention and inattention status in the brain were inspected by nonlinear analysis. The recurrence quantification analysis was applied to the relatively small number of samples of evoked potential having time varying characteristics, where the recurrence plot (RP), the color recurrence plot (CRP), and mean and time-sequential trend parameters were extracted. The dimension and the time delay in phase transformation can be determined by the paired set of extracted parameters. It is observed from RP, CRP, and parameters that the brain dynamics in attention is more complex than that in the inattention, as well as the synchronized brain response is stable in the mean sense but locally time varying. It is feasible that the non-linear analysis method can be useful for the analysis of complex brain dynamics associated during visual attentional task.

• Applied Chemistry for Engineering
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• v.9 no.5
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• pp.704-709
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• 1998

Non-linear optical polymer based on poly (${\alpha}$-methylstyrene-co-maleic anhydride) (MSMA) substrate polymer was prepared by polymer reaction method and its thermal and electro-optic properties were examined. In the polymer reaction between MSMA substrate polymer and 2-[4-(4-nitrophenylazo)-N-ethylphenylamino]ethanol (DR1) chromophore, the degree of substitution of DR1 into MSMA was higher with the 4-dimethylaminopyridine (DMAP) as catalyst and 3-dicyclohexyl carbodiimide (DCC) as dehydrating agent (sample, MSMA-DC) than the one with just 4-dimethylaminopyridine as catalyst (sample, MSMA-D). The synthesized NLO polymer (MSMA-DC) exhibited electro-optic coefficient of 18 pm/V (632.8 nm) and glass transition temperature ($T_g$) of about $175^{\circ}C$.

• Journal of Korean Society of Steel Construction
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• v.13 no.5
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• pp.587-597
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• 2001

The structural system that discreterized continuous shells is frequently used to make dome-type structures and these structures show the unstable phenomena by snap-through or bifurcation when a load level reaches certain critical value. The characteristic structural behaviour of a cable dome shows a strong nonlinearity and very sensitive according to the initial imperfection. In this study the shape finding problem by applying initial tension stress is investigated and using this the unstable phenomena of perfectly shaped and initially imperfected shape model by external forces are examined to grasp the unstable behavior of cable dome using the Geiger-type model.

• Journal of Korea Water Resources Association
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• v.50 no.5
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• pp.347-358
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• 2017

This study examined characteristic differences by the rainfall direction on the runoff responses. The directional characteristics of hydrological components in a basin were quantified by von Mises distribution. The runoff hydrograph was derived using the result of convolution integration of each distribution and this hydrograph was compared with GIUH model and observed data. As a result, it was found that runoff response by rainfall direction was more similar the observed rainfall-runoff data than the runoff result using GIUH model. These results implies that runoff modeling could be improved by considering directional components in hydrologic analysis. This study would be helpful to reduce uncertainties of hydrologic analysis considering a non-linearity of rainfall-runoff process by the rainfall direction.