• 한국멀티미디어학회논문지
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• 제7권1호
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• pp.80-90
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• 2004

본 논문에서는 패치별 EGI 분포를 이용한 3D 메쉬 모델(mesh model) 워터마킹 알고리즘을 제안하였다. 제안한 알고리즘에서는 기하학적 변형에 견고하기 위하여 3D 메쉬 모델을 6개 패치로 분할한다. 그리고 위상학적 변형에 견실한 특성을 가지는 EGI 분포를 각 패치별로 구한다. 그리고 동일한 워터마크 비트열을 각 패치의 EGI 분포 중에서 길이가 큰 면체에 투영된 메쉬 법선 벡터들에 각각 삽입한다. 그러므로 제안한 알고리즘은 기하학적 및 위상학적 변형에 견고하며, 특히 워터 마크 추출시 복잡한 재표본화 과정 및 원 모델이 필요 없다. 본 논문에서 제안한 워터마킹 알고리즘의 성능 평가를 위한 모의 실험에서 워터마크가 삽입된 모델의 비가시성 및 다양한 공격에 대한 견고성이 우수함을 확인하였다.

• 한국HCI학회:학술대회논문집
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• 한국HCI학회 2008년도 학술대회 1부
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• pp.688-692
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• 2008

3차원 아바타 시스템에서 아이템들은 아비타의 체형마다 맞춰서 제작하여야 한다. 이러한 제작방식은 사업적인 측면에서 불리한점이 클 뿐만 아니라, 서비스하는 아바타의 체형, 종류와 같은 다양성 측면에서도 소비자의 욕구를 만족하기 어렵다. 다양한 체형의 아비타를 서비스하기 위해 제작해야 할 작업량은 기하급수적으로 늘어날 수밖에 없다. 본 연구는 아바타의 제형을 최소한의 데이터 제작으로 표현가능 하도록 메쉬모핑(mesh morphing) 기법을 활용한 3D 아바타 체형변형방법에 관한 것이다. 아바타의 기본제형과 변형될 체형을 토대로 실시간으로 표현할 수 있는 중간체형을 생성하는 방법과 기본체형에 맞게 제작된 의상, 헤어스타일, 신발 등 아바타 아이템 들을 중간체형에 맞도록 자동으로 변형하는 방법을 소개한다. 제시한 방법을 이용하면, 새로운 체형의 아바타를 도입하더라도 기 제작된 아이템들의 추가 제작 없이 새로운 체형에 맞는 아이템을 서비스할 수 있음을 보여준다. 또한 새로운 체형의 표현 방법이 실시간으로 적용할 수 있는 방직임을 보여준다.

• 암석학회지
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• 제22권4호
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• pp.251-261
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• 2013

영남육괴 지리산지구의 남동부에 위치하는 화개지역은 주로 선캠브리아기 지리산 변성암복합체로 구성되어 있으며, 선캠브리아기 구성암류는 남-북 방향의 밀착습곡과 동-서 방향의 개방습곡 형태의 암상분포를 보인다. 이 논문에서는 하동 회장암복합체의 서부에 위치하는 화개지역에서 지리산 변성암복합체의 변형된 암석구조에 대한 운동학적 기하학적 특징과 중첩된 변형구조들의 선후관계로부터 연구지역의 지질구조를 연구하였다. 그 결과, 연구지역의 지질구조는 적어도 세 번의 연성 변형단계를 거쳐 형성되었음을 알게 되었다. (1) $D_1$ 변형과 관련된 구조요소는 대부분 $D_2$ 변형에 의해 전위되어 $S_{0-1-2}$ 복합엽리로 인지된다. (2) $D_2$ 변형은 동-서 방향의 압축 지구조환경 하에서 남-북 방향의 $F_2$ 습곡과 $F_2$ 습곡축면에 (준)평행하게 발달하는 $D_2$ 연성전단대를 형성시켰다. (3) $D_3$ 변형은 남-북 방향의 압축 지구조환경 하에서 발생하여 그 이전 형성된 구조요소들의 방향성을 국부적으로 동북동 내지 서북서 방향으로 재배열시켰다. 이는 선캠브리아기 구성암류의 광역적인 남-북 방향의 밀착습곡과 동-서 방향의 개방습곡 형태의 암상분포는 각각 $D_2$ 변형, $D_3$ 변형과 밀접한 관련이 있음을 의미한다.

• Smart Structures and Systems
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• 제22권1호
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• pp.121-132
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• 2018

This research investigates the free vibration analysis of advanced composite plates such as functionally graded plates (FGPs) resting on a two-parameter elastic foundations using a hybrid quasi-3D (trigonometric as well as polynomial) higher-order shear deformation theory (HSDT). This present theory, which does not require shear correction factor, accounts for shear deformation and thickness stretching effects by a sinusoidal and parabolic variation of all displacements across the thickness. Governing equations of motion for FGM plates are derived from Hamilton's principle. The closed form solutions are obtained by using Navier technique, and natural frequencies are found, for simply supported plates, by solving the results of eigenvalue problems. The accuracy of the present method is verified by comparing the obtained results with First-order shear deformation theory, and other predicted by quasi-3D higher-order shear deformation theories. It can be concluded that the proposed theory is efficient and simple in predicting the natural frequencies of functionally graded plates on elastic foundations.

• 소성∙가공
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• 제26권4호
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• pp.228-233
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• 2017

In flat rolling mills, demands for precise process set-up and control are increasing than ever before. Consequently, it is imperative to establish a novel approach, which would provide valuable information regarding the detailed aspects of deformation behavior of the strip, and rolls during rolling. In this paper, we present a finite element (FE) approach for 3-D coupled analysis of the elastic-plastic deformation of the strip and the elastic deformation of rolls in the roll-stack of a mill stand.

• Geomechanics and Engineering
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• 제12권3호
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• pp.347-360
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• 2017

The problem of cylindrical cavity expansion incorporating deformation dependent of intermediate principal stress in rock or soil mass is investigated in the paper. Assumptions that the initial axial total strain is a non-zero constant and the axial plastic strain is not zero are defined to obtain the numerical solution of strain which incorporates deformation-dependent intermediate principal stress. The numerical solution of plastic strains are achieved by the 3-D plastic potential functions based on the M-C and generalized H-B failure criteria, respectively. The intermediate principal stress is derived with the Hook's law and plastic strains. Solution of limited expansion pressure, stress and strain during cylindrical cavity expanding are given and the corresponding calculation approaches are also presented, which the axial stress and strain are incorporated. Validation of the proposed approach is conducted by the published results.

• International Journal of Aeronautical and Space Sciences
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• 제14권4호
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• pp.310-323
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• 2013

In this paper, the aeroelastic static response of flexible wings with arbitrary cross-section geometry via a coupled CUF-XFLR5 approach is presented. Refined structural one-dimensional (1D) models, with a variable order of expansion for the displacement field, are developed on the basis of the Carrera Unified Formulation (CUF), taking into account cross-sectional deformability. A three-dimensional (3D) Panel Method is employed for the aerodynamic analysis, providing more accuracy with respect to the Vortex Lattice Method (VLM). A straight wing with an airfoil cross-section is modeled as a clamped beam, by means of the finite element method (FEM). Numerical results present the variation of wing aerodynamic parameters, and the equilibrium aeroelastic response is evaluated in terms of displacements and in-plane cross-section deformation. Aeroelastic coupled analyses are based on an iterative procedure, as well as a linear coupling approach for different free stream velocities. A convergent trend of displacements and aerodynamic coefficients is achieved as the structural model accuracy increases. Comparisons with 3D finite element solutions prove that an accurate description of the in-plane cross-section deformation is provided by the proposed 1D CUF model, through a significant reduction in computational cost.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제52권6호
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• pp.247-253
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• 2003

A novel finite element mesh regeneration method is presented for 3D shape optimization of electromagnetic devices. The method has its theoretical basis in the structural deformation of an elastic body. When the shape of the electromagnetic devices changes during the optimization process, a proper 3D finite element mesh can be easily obtained using the method from the initial mesh. For real engineering problems, the method guarantees a smooth shape with proper mesh quality, and maintains the same mesh topology as the initial mesh. Application of the optimum design of an electromagnetic shielding plate shows the effectiveness of the presented method.

• 패션비즈니스
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• 제20권3호
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• pp.17-29
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• 2016

To develop baseball catcher leg guards, 3-dimensional (3D) methodologies, which are 3D human body data, reverse engineering, modeling, and printing, optimized guard design for representative positions. Optimization was based on analysis of 3D body surface data and subjective evaluation using 3D printing products. Reverse engineering was used for analysis and modeling based on data in three postures: standing, $90^{\circ}$ knee flexion, and $120^{\circ}$ knee flexion. During knee flexion, vertical skin length increased, with the thigh and knee larger in anterior area compared to the horizontal dimension. Moreover, $120^{\circ}$ knee flexion posture had a high radius of curvature in knee movement. Therefore, guard designs were based on increasing rates of skin deformation and numerical values of radius of curvature. Guards were designed with 3-part zoning at the thigh, knee, and shin. Guards 1 and 2 had thigh and knee boundaries allowing vertical skin length deformation because the shape of thigh and knee significantly affects to its performance. Guard 2 was designed with a narrower thigh and wider knee area than guard 1. The guards were manufactured as full-scale products on a 3D printer. Both guards fit better in sitting than standing position, and guard 2 received better evaluations than guard 1. Additional modifications were made and an optimized version (guard 3) was tested. Guard 3 showed the best fit. A design approach based on 3D data effectively determines best fitting leg guards, and 3D printing technology can customize guard design through immediate feedback from a customer.

• Steel and Composite Structures
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• 제32권3호
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• pp.389-410
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• 2019

In this article, a simple quasi-3D shear deformation theory is employed for thermo-mechanical bending analysis of functionally graded material (FGM) sandwich plates. The displacement field is defined using only 5 variables as the first order shear deformation theory (FSDT). Unlike the other high order shear deformation theories (HSDTs), the present formulation considers a new kinematic which includes undetermined integral variables. The governing equations are determined based on the principle of virtual work and then they are solved via Navier method. Analytical solutions are proposed to provide the deflections and stresses of simply supported FGM sandwich structures. Comparative examples are presented to demonstrate the accuracy of the present theory. The effects of gradient index, geometrical parameters and thermal load on thermo-mechanical bending response of the FG sandwich plates are examined.