• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1915-1920
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• 2004

An edge tone is the discrete tone or narrow-band sound produced by an oscillating free shear layer impinging on a rigid surface. In this paper we present a two-dimensional edge tone to predict the frequency characteristics of the discrete oscillations of a jet-edge feedback cycle by the finite difference lattice Boltzmann method. We use a new lattice BGK compressible fluid model that has an additional term and allow larger time increment comparing a conventional FDLB model, and also use a boundary fitted coordinates. The jet is chosen long enough in order to guarantee the parabolic velocity profile of the jet at the outlet, and the edge consists of a wedge with an angle of ${\alpha}=23^{\circ}$ . At a stand-off distance ${\omega}$ , the edge is inserted along the centreline of the jet, and a sinuous instability wave with real frequency f is assumed to be created in the vicinity of the nozzle and to propagate towards the downstream. We have succeeded in capturing very small pressure fluctuations result from periodically oscillation of jet around the edge. That pressure fluctuations propagate with the sound speed. Its interaction with the wedge produces an irrotational feedback field which, near the nozzle exit, is a periodic transverse flow producing the singularities at the nozzle lips.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.155-158
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• 2001

The layup optimization by genetic algorithm (GA) for the strength of laminated composites with free-edge is presented. For the calculation of interlaminar stresses of composite laminates with free edges, extended Kantorovich method is applied. In the formulation of GA, repair strategy is adopted for the satisfaction of given constraints. In order to consider the bounded uncertainty of material properties, convex modeling is used. Results of GA optimization with scattered properties are compared with those of optimization with nominal properties. The GA combined with convex modeling can work as a practical tool for light weight design of laminated composite structures since uncertainties are always encountered in composite materials.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 추계학술대회 논문집 학회본부
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• pp.587-589
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• 1995

The safe navigation of a mobile robot requires the recognition of the environment in terms of vision processing. To be guided in the given path, the robot should acquire the information about where the wall and corridor are located. Also unexpected obstacles should be detected as rapid as possible for the safe obstacle avoidance. In the paper, we assume that the mobile robot should be navigated in the flat surface. In terms of this assumption we simplify the correspondence problem by the free navigation surface and matching features in that coordinate system. Basically, the vision processing system adopts line segment of edge as the feature. The extracted line segments of edge out of both image are matched in the free nevigation surface. According to the matching result, each line segment is labeled by the attributes regarding obstacle and free surface and the 3D shape of obstacle is interpreted. This proposed vision processing method is verified in terms of various simulations and experimentation using real images.

• Structural Engineering and Mechanics
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• 제44권3호
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• pp.267-288
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• 2012

Free vibration analysis of arbitrary quadrilateral thick plates with internal columns and elastic edge supports is presented by using the powerful pb-2 Ritz method and Reddy's third order shear deformation plate theory. The computing domain of arbitrary quadrilateral planform is mapped onto a standard square form by coordinate transformation. The versatile pb-2 Ritz functions defined by the product of a two-dimensional polynomial and a basic function are taken to be the admissible functions. Substituting these displacement functions into the energy functional and minimizing the total energy by differentiation, leads to a typical eigenvalue problem, which is solved by a standard eigenvalue solver. Stiffness and mass matrices are numerically integrated over the plate by using Gaussian quadrature. The accuracy and efficiency of the proposed method are demonstrated through several numerical examples by comparison and convergency studies. A lot of numerical results for reasonable natural frequency parameters of quadrilateral plates with different combinations of elastic boundary conditions and column supports at any locations are presented, which can be used as a benchmark for future studies in this area.

• Structural Engineering and Mechanics
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• 제56권6호
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• pp.1003-1020
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• 2015

In this study, free vibration analysis of an edge cracked multilayered symmetric sandwich beams made of functionally graded materials are investigated. Modelling of the cracked structure is based on the linear elastic fracture mechanics theory. Material properties of the functionally graded beams change in the thickness direction according to the power and exponential laws. To represent functionally graded symmetric sandwich beams more realistic, fifty layered beam is considered. Composition of each layer is different although each layer is isotropic and homogeneous. The considered problem is carried out within the Timoshenko first order shear deformation beam theory by using finite element method. A MATLAB code developed to calculate natural frequencies for clamped and simply supported conditions. The obtained results are compared with published studies and excellent agreement is observed. In the study, the effects of crack location, depth of the crack, power law index and slenderness ratio on the natural frequencies are investigated.

• 대한기계학회논문집
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• 제18권3호
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• pp.645-652
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• 1994

The leading edge of a turbine blade was simulated as a circular cylindrical surface. The effect of free-stream turbulence on the mass transfer upstream of the injectionhole has been investigated experimentally. The effects of injection location, blowing ratio on the Sherwood number distribution were examined as well. The mass transfer coefficients were measured by a naphthalene sublimation technique. The free-stream Reynolds number based on the cylinder diameter is 53,000. Other conditions investigated are: free-stream turbulence intensities of 3.9% and 8.0%, injection locations of $40^{\circ}$, $50^{\circ}$, and $60^{\circ}$ from the front stagnation point of the cylinder, and blowing ratios of 0.5 and 1.0. The role of the horseshoe vortex formed upstream edge of the injected jet is dicussed in detail. When the blowing ratio is unity, and the coolant jet is injected at $40^{\circ}$, the mass transfer upstream of the jet is not affected by the coolant jet at all. On the other hand, when the injection hole is located beyond $50^{\circ}$, the mass transfer upstream edge of the injection hole suddenly increases due to the formation of the horseshoe vortex, but it dereases as the free-stream turbulence intensity increases because the strength of the horseshoe vortex structure becomes weakened. The role of the horseshoe vortex is clearly evidenced by placing a rigid rod at the injection hole instead of issuing the jet. In the case of the rigid rod, the spanwise Sherwood number upstream of the injection hole is much larger due to the intense influence of the horseshoe vortex.

• 한국컴퓨터정보학회논문지
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• 제10권4호
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• pp.133-141
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• 2005

웹 영상에서 에지는 픽셀의 밝기가 급격하게 변화되는 부분으로 에지를 통하여 물체의 위치나 크기, 물체의 텍스처에 대한 정보를 얻을 수 있다. 지금까지 에지 검출은 주로 단순한 영상에 대해 미분 연산자를 이용한 수학적 방법에 의해 이루어져왔고 최근에 잡음이 포함된 복잡한 영상에 대해 통계적 방법을 이용한 에지검출에 대한 연구가 활발히 진행되고 있다. 본 논문에서는 영상실험을 통하여 기존의 Sobel 연산자 등을 이용한 수학적 방법과 Canny 방법, Wavelet 변환방법 그리고 통계적인 T 검정과 Wilcoxon 검정을 이용한 방법들과의 에지검출 성능을 비교분석하고 Java 언어를 사용하여 웹 상에서 구현한다.

• Structural Engineering and Mechanics
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• 제3권1호
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• pp.25-34
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• 1995

General free vibration characteristics of cantilevered circular cylindrical tanks are analyzed using the integral equations technique with the cubic spline functions. For computations, the partial differential equations for thin shallow shells as given by Flugge's have been employed after the addition of the inertia forces. The application of the method is illustrated with a numerical examples of tanks which are free at the top edge and fixed at the bottom. The results obtained by this method have been compared with the available results and a good agreement was found.

• Kyungpook Mathematical Journal
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• 제54권1호
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• pp.23-30
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• 2014

For two positive integers r and s, $\mathcal{G}$(n; r; ${\theta}_s$) denotes to the class of graphs on n vertices containing no r of edge disjoint ${\theta}_s$-graphs and f(n; r; ${\theta}_s$) = max{${\varepsilon}(G)$ : G ${\in}$ $\mathcal{G}$(n; r; ${\theta}_s$)}. In this paper, for integers r, $k{\geq}2$, we determine f(n; r; ${\theta}_{2k+1}$) and characterize the edge maximal members in G(n; r; ${\theta}_{2k+1}$).

• 한국전자통신학회논문지
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• 제7권2호
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• pp.303-308
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• 2012

실린더 형태의 롤러에 감기는 원단들의 가장자리에 있는 선 이나 면들을 감지할 수 있는 1차원 선면감지 센서에 대하여 연구하였다. 선면감지 센서는 광학계의 정렬을 필요로 하지 않는 1안 렌즈를 사용한 1:1 광학계를 사용하였고 2분할 실리콘 수광소자를 사용한 두 개 채널로 부터의 차 및 합 신호를 처리하여 구현하였다. 측정된 결과는 다양한 재질 및 색상을 갖는 피사체에 대해서도 0.1mm 까지 선폭을 감지할 수 있었으며 감기는 원단은 0.2mm 편차 이내로 감기는 것을 보여주었다.