• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2007년도 춘계 학술대회논문집
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• pp.177-181
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• 2007

Present study examines the numerical issues of cell structure simulation for various regimes of detonation phenomena ranging from weakly unstable to highly unstable detonations. Inviscid fluid dynamics equations with $variable-{\gamma}$ formulation and one-step Arrhenius reaction model are solved by a MUSCL-type TVD scheme and 4th order accurate Runge-Kutta time integration scheme. A series of numerical studies are carried out for the different regimes of the detonation phenomena to investigate the computational requirements for the simulation of the detonation wave cell structure by varying the reaction constants and grid resolutions. The computational results are investigated by comparing the solution of steady ZND structure to draw out the minimum grid resolutions and the size of the computational domain for the capturing cell structures of the different regimes of the detonation phenomena.

• Steel and Composite Structures
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• 제26권2호
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• pp.241-253
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• 2018

Mode II fracture toughness, $K_{IIC}$, of single-ply triaxially woven fabric (TWF) composite due to tow waviness and anisotropy effects were numerically and experimentally studied. The numerical wavy beam network model with anisotropic material description denoted as TWF anisotropic was first validated with experimental Mode II fracture toughness test employing the modified compact tensile shear specimen configuration. 2D planar Kagome and TWF isotropic models were additionally constructed for various relative densities, crack lengths, and cell size parameters for examining effects due to tow waviness and anisotropy. $K_{IIC}$ generally increased with relative density, the inverse of cell size, and crack length. It was found that both the waviness and anisotropy of tow inflict a drop in $K_{IIC}$ of TWF. These effects were more adverse due to the waviness of tow compared to anisotropy.

• Journal of Microbiology and Biotechnology
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• 제11권1호
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• pp.97-105
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• 2001

The viability of Bifidobacterium longum KCTC 3128, entrapped in calcium alginate beds in simulated gastroenteric juices (gastric and bile salt solution), was tested to evaluate the influences of several parameters (gel concentration, bead size, and initial cell number). The death rate of B. longum in beads after being sequentially exposed to simulated gastric juices and bile salt solution decreased propertionally with increasing both the alginate gel concentration and bead size. The number of initial cell loading in beads affected the numbers of survivors after being exposed to these solutions, while the death rate of the viable cells were not affected. From the results obtained, the influence of entrapment parameters on the survival of bifidobacteria was quantitatively and systematically evaluated by using a mathematical method.

• Nuclear Engineering and Technology
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• 제16권1호
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• pp.29-35
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• 1984

유리섬유 여과포에 의한 0.1~0.45$\mu\textrm{m}$ 크기의 DOP 부유입자의 제거효율시험을 1~10cm/sec의 유속범위에서 수행하였다. 섬유여과포에 의한 미세입자의 여과는 여과속도에 의하여 결정되는데, 최소제거 효율을 나타내는 DOP 입자의 크기는 여과속도가 증가함에 따라 감소한다. Kuwabara Cell Model과 Von Mises Transformation을 사용하여 유리섬유 여과포내에서 화산에 의한 입자 제거효율을 수치해석적으로 전개하여 구하였으며, 이 계산치는 실험치와 잘 일치하였다. 본 실험의 결과는 여과포의 입자제거효율을 예측하고 최적 운전조건을 추구하는데 기여할 수 있을 것이다.

• 대한전자공학회논문지SD
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• 제41권10호
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• pp.105-113
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• 2004

본 논문은 B-I (delay insensitive) 모델을 사용하는 비동기 프로세서의 메모리 동작 완료 신호 생성 회로를 제안한다. 제안된 설계 방법은 더미셀과 완료 신호 생성 회로를 이용하여 메모리의 읽기 및 쓰기 동작의 완료 신호를 생성한다. 비트라인과 메모리 셀의 지연을 고려하여 메모리를 지수적 블록 크기로 나누어 최소의 완료 신호 회로를 추가하여 D-I 모델로 동작하는 메모리를 설계하였다. 각 구역의 크기가 지수적으로 증가하도록 메모리를 분할하는 제안된 분할 알고리즘은 기존의 동일한 크기를 갖는 구역들로 메모리를 분할하는 방법에 비해 약 40% 정도 동작 지연을 개선하였다.

• 한국전자파학회논문지
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• 제13권2호
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• pp.217-224
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• 2002

FDTD 해석법에서 공간적 셀의 크기는 해석의 정확도를 결정하는 중요한 요소이다. 하지만 정확도를 향상시키기 위하여 진의 크기를 줄이게 되면, 해석시간과 기억용량의 증가를 초래하게 되는데 서브 그리딩을 사용하여 이를 해결할 수 있다. 본 논문에서는 관심영역만 세밀하게 해석할 수 있는 3차원 서브 그리딩법을 기술하고 이를 응용하여 몇 가지의 구조를 해석하였다. 제안한 방범의 타당성을 화인하기 위하여 균일 그리딩과 서브 그리딩을 적용하여 특성을 해석하고 그 격과를 비교하였다. 제안한 방법을 사용하였을 경우 동일한 정확도에서 균일 그리딩에 비하여 6배의 해석시간의 줄었고 기억용량은 2.5배 정도 줄어들었다.

• 대한산업공학회지
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• 제34권2호
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• pp.151-159
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• 2008

An efficient location registration scheme is essential to accommodate continuously increasing mobile subscribers and to offer a variety of multimedia services with good quality. In this study, we consider a distance-based registration scheme where the number of location areas varies on the basis of cell-by-cell, not of ring-by-ring, to analyze the optimal size of the location area. Using our proposed cell-by-cell distance-based registration scheme with random walk mobility model, we analyze a variety of circumstances to obtain the optimal number of cells for location area that minimizes total signaling traffic on radio channels. From our analysis results, we show that the optimal number of cells for location area is between 4 and 6 in most cases, and our cell-by-cell distance-based location registration scheme has less signaling traffic than optimal ring-by-ring distance-based location registration scheme where optimal distance threshold is 2 (thus the optimal number of cells for location area is 7).

• 한국통신학회논문지
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• 제23권9A호
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• pp.2289-2304
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• 1998

For the performance analysis and traffic control of ATM networks carrying video sequences, need an appropriate video traffic model. In this paper, we propose a new traffic model for MPEG compressed videos which are widely used for any type of video applications at th emoment. The proposed modeling scheme uses scene-based traffic characteristics and considers the correlation between frames of consecutiv GOPs. Using a simple scene detection algorithm, scene changes are modeled by state transitions and the number of GOPs of a scene state is modeled by a geometric distirbution. Frames of a scene stte are modeled by mean I, P, and B frame size. For more accurate traffic modeling, quantization errors (residual bits) that the state transition model using mean values has are compensated by autoregressive processes. We show that our model very well captures the traffic chracteristics of the original videos by performance analysis in terms of autocorrelation, histogram of frame bits genrated by the model, and cell loss rate in the ATM multiplexer with limited buffers. Our model is able to perrorm translations between levels (i.e., GOP, frame, and cell levels) and to estimate very accurately the stochastic characteristics of the original videos by each level.

• 청정기술
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• 제12권4호
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• pp.224-231
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• 2006

현탁액중의 부유입자를 제거하는 입상여과공정을 Network 모델을 이용하여 여과효율과 압력손실에 대해 예측하였다. 구형 여재로 구성되어 있는 여재 층을 node와 원통형 bond로 구성된 network로 가정하였으며 여과 공정을 통해 부유입자는 bond 표면에 포집된다. 원통형 bond에서의 여과효율은 bond의 세공부피를 단위 cell의 유체 막 부피로 가정하여 입자의 경로 분석을 이용하여 구하였으며, 포집된 부유입자가 추가적인 여재로서의 역할은 bond 세공이 좁아짐에 따른 효율 증가로 나타내었다. 또한 세공이 좁아짐에 따른 압력손실도 예측하였다. 본 network 모델의 세공 분포를 부여하는 과정의 stochastic한 성질로 인하여 많은 전산모사가 필요하지만, 본 모델을 이용하여 여과효율과 압력손실을 동시에 예측할 수 있었다.

• 반도체디스플레이기술학회지
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• 제13권2호
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• pp.37-44
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• 2014

In this study, the performance of dye-sensitized solar cells with different thickness of the photelectrode film was simulated by using the electron-diffusion differential model. Through this simulation, the relationships between the thickness of the photoelectrode film and the performances (open-circuit voltage, short-circuit current density, and overall photoelectric-conversion efficiency) of cells were understood and the performances with different thickness of the photoelectrede film were also examined. For considering the refractive index in the liquid electrolyte and exploring the scattering effect of titanium dioxide particles with different sizes using the Mie light-scattering theory, the highest scattering effect of each particles was found out and the optimal size of the titanium dioxide particle was determined for light scattering in the photoelectrode film of dye-sensitized solar cell. Through experiment, the mixed titanium dioxide cell was better than the single titanium dioxide cell and generated a higher overall conversion efficiency because the optimal titanium dioxide particles in the phoelectrode film as light scattering.