• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.8
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• pp.523-529
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• 2010

We investigate two-dimensional laminar flow around rectangular cylinders placed in a uniform stream. Numerical simulations are performed, using finite volume method, in the ranges of $50{\leq}Re{\leq}150$ and $0.1{\leq}W/H{\leq}1.0$, where Re and W/H are the Reynolds number and the width-to-height ratio, respectively. The immersed boundary method is used to handle the rectangular cylinder in a rectangular grid system. Comparisons with the previous results show good agreement in Strouhal number, drag and lift coefficient. The present study reports the detailed information of flow structure at different width-to-height ratios in the ranges of $50{\leq}Re{\leq}150$.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2000.12a
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• pp.97-100
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• 2000

본 논문에서는 얼굴의 특징 추출 알고리즘을 제안한다. 입력 영상을 이진 영상으로 처리한 후, 얼굴 요소 후보 블록의 면적, 둘레, 원형도, 종횡비를 이용하여 불변하는 눈, 코, 입의 특징 요소를 추출한다. 사람의 얼굴에 대한 특징 요소를 추출하기 위하여 우선 이진 영상을 생성한다. 하나 하나의 고립된 영역으로 분리하기 위하여 화소 레이블링을 한 후 만들어진 얼굴 요소 후보 블록 단위로 면적을 구하고, 윤곽선 추적 방법에 의하여 둘레를 구한 다음 면적, 둘레, 원형도 및 종횡비의 유사도를 구한다 블록의 종합 유사도, 대칭적 거리, 위치의 유사도를 활용하여 눈, 코, 입을 추출한다. 추출된 각 특징 요소간의 거리와 각도를 이용하여 12개의 특징 인수를 구하는 제안 알고리즘을 수행함으로써 얼굴의 특징 인수들을 추출한다. 각 특징점 사이의 거리와 각 거리간의 기울기를 이용하여 100명으로부터 획득한 297개의 원 영상을 대상으로 12개의 특징 파라미터를 추출한 결과 92.93%의 추출 성공률을 보였다. 이러한 결과는 외부 환경의 영향을 덜 받는 눈, 코, 입의 위치 관계의 블록을 근거로 특징 요소를 추출할 수 있도록 제안 알고리즘을 구성하였던 것으로 판단된다.

• Journal of Power System Engineering
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• v.6 no.1
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• pp.43-49
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• 2002

This paper showed the study on the heat transfer into space by the aspect ratio of solar concentration absorber, and the purpose of this study was to obtain the optimum aspect ratio and tilt angle. The boundary conditions of a numerical model are assumed as follows : (1) The heat source is located at the center of absorber. (2) The bottom wall is opened and adiabatic. (3) The top, right and left walls are cooled wall. The parameters for the study are the tilt angles and the aspect ratio. The velocity vectors and isotherms were dense at wall side and the heat source. The mean Nusselt number had a maximum value at Ar=1:1 and ${\theta}=0^{\circ}$ and showed a low value as the tilt angles were increased.

• Proceedings of the Korea Inteligent Information System Society Conference
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• 2007.11a
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• pp.279-283
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• 2007

움직이는 물체를 분류하는 것은 영상 감시 시스템에서 가장 중요한 분야 중의 하나이다. 사람과 자동차는 영상 감사 시스템에서 인식해야 하는 가장 중요한 물체의 종류이기 때문에 본 연구에서는 인식하는 물체의 종류를 이것들로 제한한다. 사용되는 특성으로는 물체의 움직임에서 추출되는 특성과 형태에서 추출되는 특성이 있다. 이 두 가지 특성들은 정지된 하나의 카메라로부터 입력된 영상에 나타나는 물체를 분류하기 위하여 사용된다. 움직임으로부터 추출되는 특성은 연결 성분 분석을 이용한 물체 추적과 밀접한 관련이 있다. 그리고 형태 기반 특성에 관한 학습은 종횡비(aspect ratio)와 4개의 윤곽선을 가지고 수행된다. 움직임 기반 특성과 종횡비는 물체를 사람과 자동차로 구분하는데 이용되고 각각의 종류를 더욱 세분화하기 위하여 4개의 윤곽선이 사용된다.

• Journal of the Korean Geotechnical Society
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• v.31 no.9
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• pp.69-78
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• 2015

If an active displacement occurs on a wall with finite size, the ground behind the wall forms shapes of 3-dimensional wedges and 3-dimensional active earth pressure are applied on the wall. In the previous studies, shapes of 3-dimensional wedges were measured and the resultant of 3-dimensional active earth pressure has been calculated. In this study, the magnitude and the distribution of 3-dimensional active earth pressure depending on the size of a rectangular wall, which was defined by the aspect ratio (h/w), that is, the ratio between the height and the width of wall, were measured and compared with previous 3-dimensional models. The result shows that, the horizontal displacement (S) of the wall is approx 0.12% of the height of wall (h). The resultant 3-dimensional active earth pressure is similar to that of Karstedt (1982). The distributions of earth pressures on the wall are parabolic shape. The peak earth pressure was measured at the 0.5~0.55 depth from the ground surface. The reduction factor of 3-dimensional active earth pressure against the 2-dimensional earth pressure (${\alpha}$) depending the aspect ratio (h/w) is presented by the diagram.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.10
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• pp.905-911
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• 2011

With the progress of micro actuator technology, studies on the development of micro air flapping wing vehicles are actively undergoing. In the present study, the changes of both lift and thrust characteristics of the wings are investigated using a boundary element method. Lift of the heaving wing is not generated when the wing is beating with smaller frequencies than 1 Hz. Thrust increases with amplitude and frequency. As the wing's taper and aspect ratios increase, both lift and thrust also increase. Results on the pitching oscillation and flapping motion will be included in the future work.

• Proceedings of the Korean Magnestics Society Conference
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• 2013.05a
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• pp.72-73
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• 2013

• Proceedings of the Korean Fiber Society Conference
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• 2000.04a
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• pp.141-144
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• 2000

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.1
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• pp.79-88
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• 2015

This study numerically examined the mixing characteristics of rectangular cavity flows by using the hybrid lattice Boltzmann method (HLBM) applied to the finite difference method (FDM). Multi-relaxation time was used along with a passive scalar method which assumes that two substances have the same mass and that there is no interaction. First, we studied numerical results such as the stream function, position of vortices, and velocity profile for a square cavity and rectangular cavity with an aspect ratio of 2. The data were compared with previous numerical results that have been proven to be reliable. We also studied the mixing characteristics of a rectangular cavity flow such as the concentration profile and average Sherwood number at various Pe numbers and aspect ratios.

• Fire Science and Engineering
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• v.26 no.5
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• pp.67-72
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• 2012

Fire simulation was carried out for an enclosure with three doorways of $20{\times}10{\times}3m^3$ and a cleanroom of $44{\times}48{\times}10m^3$, to suggest appropriate grid size in fire simulations by using of FDS for large scale buildings. The variations of temperature and visibility with time were compared for the x and y direction grid sizes of 0.1~1.0 m (aspect ratios 0.5~5.0), fixing the z direction grid size 0.2 m. The results showed that the grid sizes 0.5 m (aspect ratio 2.5) or smaller are appropriate among the grid sizes tested, whereas 1.0 m is not acceptable. It was confirmed that estimate of the available safe egress time requires a great care due to fluctuations in temperature, visibility, etc., and further investigations on the grid size when selecting a large grid size inevitable, and on the aspect ratios for a larger grid are in need.