• 한국광학회지
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• 제5권1호
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• pp.25-30
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• 1994

투명한 비등방성 매질의 편광투과특성을 나타내는 유니타리 존즈행렬과 뽀앙카레공의 표면에서의 회전변환이 일대일 대응되는 것을 보여주는 공식을 끌어내었다. 이 공식들을 쓰면 유니타리 존즈행렬의 세 매개변수로부터 이에 대응되는 회전변환의 회전축 방향과 회전각을 보여주는 벡터표현을 얻을 수 있고, 또 거꾸로 회전변환의 벡터표현으로부터 이에 대응디는 유니타리 존즈행렬의 매개변수를 결정할 수 있다. 빛이 투명한 비등방성 선형매질을 지날 때 편광상태의 변화를 살펴보려면 먼저 매질전체의 편광투과특성을 나타내는 존즈행렬을 계산하고, 이로부터 뽀앙카레공에서의 회전변환을 결정하여 뽀앙 카레공 위의 점들이 어떻게 회전이동하는가 보면 된다.

• Steel and Composite Structures
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• 제39권5호
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• pp.543-564
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• 2021

In this study free vibration analysis of a cracked Goland composite wing is investigated. The wing is modelled as a cantilevered beam based on Euler- Bernoulli equations. Also, composite material is modelled based on lamina fiber-reinforced. Edge crack is modelled by additional boundary conditions and local flexibility matrix in crack location, Castigliano's theorem and energy release rate formulation. Governing differential equations are extracted by Hamilton's principle. Using the separation of variables method, general solution in the normalized form for bending and torsion deflection is achieved then expressions for the cross-sectional rotation, the bending moment, the shear force and the torsional moment for the cantilevered beam are obtained. The cracked beam is modelled by separation of beam into two interconnected intact beams. Free vibration analysis of the beam is performed by applying boundary conditions at the fixed end, the free end, continuity conditions in the crack location of the beam and dynamic stiffness matrix determinant. Also, the effects of various parameters such as length and location of crack and fiber angle on natural frequencies and mode shapes are studied. Modal analysis results illustrate that natural frequencies and mode shapes are affected by depth and location of edge crack and coupling parameter.

• Fisheries and Aquatic Sciences
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• 제4권1호
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• pp.1-9
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• 2001

This paper describes a procedure extracting feature vector of a target cell more precisely in the case of identifying specified cell. The classification of object type is based on feature vector such as area, complexity, centroid, rotation angle, effective diameter, perimeter, width and height of the object So, the feature vector plays very important role in classifying objects. Because the feature vectors is affected by noises and holes, it is necessary to remove noises contaminated in original image to get feature vector extraction exactly. In this paper, we propose the following method to do to get feature vector extraction exactly. First, by Otsu's optimal threshold selection method and morphological filters such as cleaning, filling and opening filters, we separate objects from background an get rid of isolated particles. After the labeling step by 4-adjacent neighborhood, the labeled image is filtered by the area filter. From this area-filtered image, feature vector such as area, complexity, centroid, rotation angle, effective diameter, the perimeter based on chain code and the width and height based on rotation matrix are extracted. To prove the effectiveness, the proposed method is applied for yeast Zygosaccharomyces rouxn. It is also shown that the experimental results from the proposed method is more efficient in measuring feature vectors than from only Otsu's optimal threshold detection method.

• 한국인터넷방송통신학회논문지
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• 제10권5호
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• pp.133-138
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• 2010

본 논문에서는 이미지에 대한 공간 특성(Spatial properties) 및 통계적 특성(Statistical properties)을 포함한 특징이미지를 구성하고, 지역 분산 크기를 이용한 공분산 행렬을 생성하여 텍스쳐 분류에 이용함으로서 조도(illumination) 및 노이즈(Noise) 그리고 회전(Rotation)에 강인한 텍스쳐 분류 방법을 제안한다. 또한 영역 합계의 빠른 연산을 위해 사용된 중간 이미지 표현인 적분 이미지(Integral Image)를 이용함으로서 텍스쳐 검출 프로세스의 수행 시간을 최소화 하는 방법을 제공한다. 제안한 방법의 성능 평가를 위해 브로다츠(Brodatz) 질감 이미지를 이용하여 잡음 추가 및 히스토그램 명세화 그리고 회전 이미지를 생성하여 실험하였으며, 96% 이상의 성능을 얻을 수 있었다.

• 한국기계가공학회지
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• 제18권1호
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• pp.1-8
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• 2019

The optimal design parameters of a dynamic absorber (DA) in a machine body (that is considered as a rigid body) are discussed in this paper. The bounce and rotation motions of the rigid body have been controlled passively by a DA, which consists of a mass and a spring. The rigid body is subjected to a harmonically excited force and supported by linear springs at both ends. To define the motion of a rigid body with a DA, the equation of motion was expressed in the third-order matrix form. To define the optimal design conditions of a DA, the reduction of dynamic characteristics, represented by the amplitudes of bounce and rotation, and the transmitted powers, were evaluated and discussed. The level of reduction was found to be highly dependent on the location and spring stiffness of the DA.

• 소성∙가공
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• 제30권4호
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• pp.195-200
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• 2021

In this study, we investigated the dominant processing variables that would influence the microstructural development of AA6061 deformed by differential speed rolling (DSR) at ambient temperature. For this purpose, we carried out a series of DSR on the samples to investigate the effects of roll speed ratio, sample rotation, and number of operation under specific rotation. Among these, the condition with a height reduction of 75% at a speed ratio of 1:4 through rotation along rolling direction (RR) displayed the pronounced results of more homogenous matrix-structure and superior mechanical properties than the others tested in this study. This was mainly due to the cross shearing of macro-shear pattern in segment where dynamic recrystallization took place with ease throughout the sample. Thus, an average microhardness value of 101 Hv was obtained in the present sample deformed by 4-pass DSR with RR where macro cross-shearing was effectively applied.

• 한국항해항만학회지
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• 제30권9호
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• pp.729-734
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• 2006

The authors aim to establish the theory necessary for developing the free gyroscopic compass and focus on mainly two points. One is to suggest north-finding principle by the angular velocity of the earth's rotation, and the other is to suggest orthogonal coordinate transformations of the motion rate of the spin axis, which transforms the components of motion rate in the free gyro frame into those in the platform frame and that this transformed rate is, in turn, transformed into the NED(north-east-down) navigation frame. Subsequently, ship's heading is obtained by using the fore-aft and athwartship components of the motion rate of the spin axis in the NED frame. In addition it was found how to solve the transformation matrix necessary for transforming each frame.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1995년도 봄 학술발표회 논문집
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• pp.17-27
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• 1995

For the post-buckling and elasto-plastic analysis of shell structures, the total Lagrangian formulation is presented based upon the degenerated shell element. Geometrically correct formulation is developed by updating the direction of normal vectors in the iteration process and evaluating the total Green-Lagrange stain corresponding U total displacements. In the calculation of the stiffness matrix, the element formulation takes into account the effect of finite rotation increments by retaining second order rotation terms in the incremental displacement field. The selective or reduced integration scheme using the heterosis element is applied in order to overcome both shear locking phenomena and the zero energy mode. The load/displacement incremental scheme is adopted for geometric non-linear F .E. analysis. Based on such methodology, the computer program is developed and numerical examples to demonstrate the accuracy and the effectiveness of the proposed shell element are presented and compared with references's results.

• 한국통신학회논문지
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• 제30권5C호
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• pp.364-370
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• 2005

얼굴 인식에서는 입력 영상에서 얼굴을 검출한 후에 데이터베이스의 영상과 위치와 크기를 일치시키는 등록 과정이 필요하다. 본 논문에서는 영상의 등록 과정에서 발생하는 얼굴영상의 이동, 회전, 혹은 크기의 차이를 eigenspace에서 보정하는 알고리즘을 제안하였다. 이를 위하여 얼굴 영상의 수직, 수평 이동, 회전, 크기 변환 등의 등록오차를 선형보간 행렬로 근사하였다. 각 변환행렬을 사용하여 등록오차에 따른 미분계수를 eigenspace에서 구하면 subpixel 단위의 등록 오차를 보정할 수 있다. 제안된 방법은 공간 영역에서 오차를 보정하는 것보다 계산량이 훨씬 더 적다. 오차 보정 후 얼굴 인식률이 크게 향상되는 것을 실험으로 확인하였다.

• Journal of Magnetics
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• 제11권3호
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• pp.139-142
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• 2006

We fabricated new one-dimensional magnetophotonic crystal (1D-MPC) utilizing the second and third photonic band gaps where localized modes existed. Structure of the 1D-MPC was $(Ta_{2}O_{5}/SiO_{2})_{5}/Bi:YIG/(SiO_{2}/Ta_{2}O_{5})_{5}$ with optical thicknesses of 3$\lambda$ /4 for $Ta_{2}O_{5} and $SiO_2$ dielectric layers and $\lambda$ /2 for Bi:YIG defect layer, where $\lambda$ is a wavelength of a localized mode in the second photonic band gap. Faraday rotation at the localized mode in the second photonic band gap was enhanced, which was confirmed by calculation using 4${\times}$4 matrix method.