• 한국통신학회논문지
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• 제19권2호
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• pp.331-337
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• 1994

저항띠의 양끝에서 0( /square)으로 변하는 저항율을 가진 저항띠의 적자구조에 비스듬히 입사하는 E분극 평면파에 의한 전자파 산람눙제를 과수영역에서 모멘트 법을 이용하여 해석하였따. 이때 저항띠에 유도되는 전류일도는 2종 Chebyshev 다항식의 급수로 전개하였다 전개계수들은 과수영역에서 수치계산하였고, 본 논문에서의 변하는 저항율을 갖는 경우와 기존의 균일 저항율을 갖는 경우에 대해 기하광학적 반사계수의 수치계산 결과를 비교하였다. 그리고 기하광학적 반사계수의 크기에서 급변점들이 위치는 입사각과 스트립 주기를 변화시킴으로써 이동시킬 수 있었다. 이러한 급변점들은 전파모드와 감쇠모드 사이서 고차모드가 천이될 때 발생함을 알 수 있었다.

• 한국소음진동공학회논문집
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• 제17권8호
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• pp.693-700
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• 2007

We can predict spatial acoustic pressure distribution on the plane of interest by using acoustic holography. However, the information embedded in the distribution plot is usually much more than what we need: for example, source locations and their overall propagation pattern. One possible candidate to solve the problem is complex envelope analysis. Complex envelope analysis extracts slowly-varying envelope signal from a band signal. We have attempted to extend this method to space domain so that we can have spatial information that we need. We have to modulate two dimensional data for obtaining spatial envelope. Although spatial modulation basically follows the same concept that is used in time domain, the algorithm for the spatial modulation turns out to be different from temporal modulation. We briefly describe temporal complex envelope analysis and extend it to spatial envelope of 2-D acoustic field by introducing geometric transformation. In the end, the results of applying the spatial envelope to the holography are envisaged and verified.

• Structural Engineering and Mechanics
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• 제42권4호
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• pp.589-608
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• 2012

In this study, the effect of in-plane deformations on the dynamic behavior of laminated plates is investigated. For this purpose, the displacement-time and strain-time histories obtained from the large deflection analysis of laminated plates are compared for the cases with and without including in-plane deformations. For the first one, in-plane stiffness and inertia effects are considered when formulating the dynamic response of the laminated composite plate subjected to the blast loading. Then, the problem is solved without considering the in-plane deformations. The geometric nonlinearity effects are taken into account by using the von Karman large deflection theory of thin plates and transverse shear stresses are ignored for both cases. The equations of motion for the plate are derived by the use of the virtual work principle. Approximate solution functions are assumed for the space domain and substituted into the equations of motion. Then, the Galerkin method is used to obtain the nonlinear algebraic differential equations in the time domain. The effects of the magnitude of the blast load, the thickness of the plate and boundary conditions on the in-plane deformations are investigated.

• 한국재료학회지
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• 제22권10호
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• pp.519-525
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• 2012

Enhancement of light trapping in solar cells is becoming increasingly urgent for the development of next generation thin film solar cells. One of the possible candidates for increasing light trapping in thin film solar cells that has emerged recently is the use of scattering from metallic nanostructures. In this study, we have investigated the effects of the geometric parameters of Ag nanorings on the light scattering efficiency by using three dimensional Finite Different Time Domain (FDTD) calculations. We have found that the forward scattering of incident radiation from Ag nanorings strongly depends on the geometric parameters of the nanostructures such as diameter, height, etc. The forward scattering to substrate direction is increased as the outer diameter and height of the nanorings decrease. In particular, for nanorings larger than 200 nm, the inner diameter of Ag nanorings should be optimized to enhance the forward scattering efficiency. Light absorption and scattering efficiency calculations for the various nanoring arrays revealed that the periodicity of nanorings arrays also plays an important role in the absorption and the scattering efficiency enhancement. Light scattering efficiency calculations for nanoring arrays also revealed that enhancement of scattering efficiency could be utilized to enhance the light absorption through the forward scattering mechanism.

• 대한수학회보
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• 제50권1호
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• pp.175-184
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• 2013

In this paper, the reverse Bonnesen style inequalities for convex domain in the Euclidean plane $\mathbb{R}^2$ are investigated. The Minkowski mixed convex set of two convex sets K and L is studied and some new geometric inequalities are obtained. From these inequalities obtained, some isoperimetric deficit upper limits, that is, the reverse Bonnesen style inequalities for convex domain K are obtained. These isoperimetric deficit upper limits obtained are more fundamental than the known results of Bottema ([5]) and Pleijel ([22]).

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 1989년도 수공학논총 제31권
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• pp.123-132
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• 1989

자연하천에서의 흐름특성을 해석하기 위해 Boundary - fitted(BF) coordinate system을 응용하여 유한차분법에 의한 2차원모델을 개발하였다. BF coordinates는 경계면의 형상에 관계없이 적용할 수 있으며 모든 계산은 기본식의 좌표변환을 통해 직각좌표계에서 행해지므로 경계조건의 입력에 용이하다. Physical domain(X - Y 좌표계)에서 하천의 형상을 입력하면 Grid generation에 의해 모든 계산은 Computational domain($\varepsilon$ - n 좌표계)에서 행해진다. Computational domain에서의 유한차분법은 half - time step으로 ADI 방법을 이용했고, 한 방향의 유속과 수위를 Double sweep으로 풀었다. 유속, 수위 및 하상의 격점망은 Staggered grid system을 사용했으며 geometric elements는 각 격점별로 계산하였다. 본 모델을 이용하므로써 불규칙한 수로나 하천의 흐름상태를 해석할 수 있으므로 흐름의 종단, 횡단방향의 유속분포, Superelevation을 구할 수 있고 하천의 계획, 관리, 제방의 호안이나 구조물의 설치등으로 일어나는 수리학적 영향등을 예측할 수 있다.

• 한국정밀공학회지
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• 제9권3호
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• pp.122-131
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• 1992

In this paper an approximate solution method for the large-scale Traveling Salesman Problem (TSP) is presented. The method starts with the subdivision of the problem domain into a number of cluster by considering their geometric characteristic. Each cluster has a limited number of nodes so as to get a local solution. They are linked go give the least pathe which covers the whole domain and become TSPs solution with start-and end-node. The approximate local solution in each cluster are obtained based on geometrical properties of the cluster, and combined to give an overall approximate solution for the larte-scale TSP.

• Structural Engineering and Mechanics
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• 제36권3호
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• pp.279-299
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• 2010

A methodology on application of the discrete singular convolution (DSC) technique to the free vibration analysis of thin plates with curvilinear quadrilateral platforms is developed. In the proposed approach, irregular physical domain is transformed into a rectangular domain by using geometric coordinate transformation. The DSC procedures are then applied to discretization of the transformed set of governing equations and boundary conditions. For demonstration of the accuracy and convergence of the method, some numerical examples are provided on plates with different geometry such as elliptic, trapezoidal having straight and parabolic sides, sectorial, annular sectorial, and plates with four curved edges. The results obtained by the DSC method are compared with those obtained by other numerical and analytical methods. The method is suitable for the problem considered due to its generality, simplicity, and potential for further development.

• International Journal of Aeronautical and Space Sciences
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• 제2권1호
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• pp.78-92
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• 2001

In this paper, several dynamic systems are modeled using the time domain finite element method. Galerkins' Weak Principle is used to model the general second-order mechanical system, and is applied to a simple pendulum dynamics. Problems caused by approximating the final momentum are also investigated. Extending the research, some dynamic analysis methods are suggested for the hybrid coordinate systems that have both slew and flexible modes. The proposed methods are based on both Extended Hamilton's Principle and Galerkin's Weak Principle. The matrix wave equation is propagated in space domain, satisfying the geometric/natural boundary conditions. As a result, the flexible motion can be obtained compatible with the applied control input. Numerical example is shown to demonstrate the effectiveness of the proposed modeling methods for the hybrid coordinate systems.

• 대한전자공학회논문지SP
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• 제43권4호
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• pp.108-115
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• 2006

본 논문에서는 이산 웨이블릿 기반의 진화 알고리듬을 이용한 워터마킹 기법을 제안한다. 제안한 알고리듬은 웨이블릿 변환을 이용한 주파수 영역에서의 워터마크 삽입과 유전자 알고리듬을 이용한 워터마크 추출로 구성된다. 강인한 워터마크의 삽입을 위하여 웨이블릿 도메인의 저주파 영역에서 이루어지며, 워터마크 추출은 유전자 알고리듬을 이용하여 기하학적인 공격에 대하여 효과적인 추출을 수행한다. 본 논문에서 제안한 워터마킹 기법은 JPEG이나 JPEG2000과 같은 영상 압축과 다양한 기하학적인 공격에 대한 실험을 통해서 워터마크의 요구조건인 강인성과 비가시성의 관점에서 기존 기술에 대한 상대적 우수성을 확인하였다.