• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2006년도 하계학술대회
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• pp.189-192
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• 2006

본 논문에서는 안테나와 미국 PCS대역(1.85GHz-1.99GHz) FEM(Front End Module)을 결합하여 하나의 패키지로 구현하는 것을 연구하였다. FEM의 크기를 고려하여 안테나의 크기를 작게 만들고 단말기에 내장하기 위해 PIFA(Planar Inverted F Antenna)형식의 안테나를 선택하였다. 안테나의 지지를 위해 비유전율 2의 캐리어를 사용하였고, 안테나와 FEM간의 상호 간섭을 막기 위해 도체로 차폐시켰다. 유한요소법(Finite Element Method)로 모의 실험을 하여 안테나를 설계하고 실제 제작하여 모의 실험결과와 비교하였다. 제작한 안테나를 FEM과 결합, 기판을 제작하여 FEM의 이득을 측정하였다.

• 한국농공학회논문집
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• 제57권5호
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• pp.43-49
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• 2015

Most of agricultural structures located in seashore could not avoid rapid deterioration of concrete because chloride-ion and $CO_2$ gradually penetrate into concrete. However, since most of models can be able to describe the phenomenon of penetration by using one or two dimensional models based on finite difference method (FDM), those modes can not simulate the real geometry and it takes a lot of computational time to complete even the calculation. To overcome those weaknesses, three dimensional numerical model considering time dependent variables such as surface concentration of chloride and diffusion coefficient of domain based on finite element method (FEM) was suggested. This model also included the neutralization occurred by the penetration of $CO_2$. Because the model used various sizes of tetrahedral mesh instead of equivalent rectangular mesh, it reduced the computational time to compare with FDM. As this model is based on FEM, it will be easily extended to execute multi-physics simulation including water evaporation and temperature change of concrete.

• Journal of Magnetics
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• 제18권2호
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• pp.130-134
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• 2013

Most electrical machines like motor, generator and transformer are symmetric in terms of magnetic field distribution and mechanical structure. In order to analyze these problems effectively, many coupling techniques have been introduced. This paper deals with a coupling scheme for open boundary problem of symmetric and periodic structure. It couples an analytical solution of Fourier series expansion with the standard finite element method. The analytical solution is derived for the magnetic field in the outside of the boundary, and the finite element method is for the magnetic field in the inside with source current and magnetic materials. The main advantage of the proposed method is that it retains sparsity and symmetry of system matrix like the standard FEM and it can also be easily applied to symmetric and periodic problems. Also, unknowns of finite elements at the boundary are coupled with Fourier series coefficients. The boundary conditions are used to derive a coupled system equation expressed in matrix form. The proposed algorithm is validated using a test model of a bush bar for the power supply. And the each result is compared with analytical solution respectively.

• 대한전자공학회논문지TC
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• 제43권1호
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• pp.33-40
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• 2006

Single phase unidirectional transducer (SPUDT), 리플렉터, 웨이퍼 본딩 패키지로 구성된 표면탄성파 (surface acoustic wave, SAW) 기반 압력센서가 개발되어 졌다. Coupling of Mode (COM) 모델링에 의한 소자의 시뮬레이션 및 최적 설계 변수가 얻어졌다. Finite Element Methods (FEM)를 통해 주어진 압력에 따른 다이어프램 벤딩, 스트레인/스트레스 변화 및 SAW 속도변위가 미리 예측되어졌다. 유출된 최적 설계 변수를 이용 440 MHz SAW 기반 압력센서가 41o YX LiNbO3 기판 위에서 제작되어졌다. 고 S/N 비, 임펄스 리프렉션 피크, 작은 에러 피크가 관찰되어졌다. 측정된 S11 결과는 COM 모델링 및 FEM 시뮬레이션 결과와 일치함을 보였다.

• Computers and Concrete
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• 제26권2호
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• pp.107-114
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• 2020

In this study, a two dimensional model of receding contact problem has been analyzed using finite element method (FEM) based software ANSYS and ABAQUS. For this aim finite element modeling of elastic layer and two homogeneous, isotropic and symmetrical elastic quarter planes pressed by means of a rigid circular punch has been presented. Mass forces and friction are neglected in the solution. Since the problem is examined for the plane state, the thickness along the z-axis direction is taken as a unit. In order to check the accuracy of the present models, the obtained results are compared with the available results of the open literature as well as the results of two software are compared using Root Mean Square Error (RMSE) and good agreements are found. Numerical analyses are performed considering different values of the external load, rigid circular radius, quarter planes span length and material properties. The contact lengths and contact stresses of these values are examined, and their results are presented. Consequently, it is concluded that the considered non-dimensional quantities have noteworthy influence on the contact lengths and contact stress distributions, additionally if FEM analysis is used correctly, it can be an efficient alternative method to the analytical solutions that need time.

• Steel and Composite Structures
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• 제32권4호
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• pp.423-441
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• 2019

This study aims to accurately predict the first ply failure loads of laminated composite hypar shell roofs with different boundary conditions. The geometrically nonlinear finite element method (FEM) is used to analyse different symmetric and anti-symmetric, cross and angle ply shells. The first ply failure loads are obtained through different well-established failure criteria including Puck's criterion along with the serviceability criterion of deflection. The close agreement of the published and present results for different validation problems proves the correctness of the finite element model used in the present study. The effects of edge conditions on first ply failure behavior are discussed critically from practical engineering point of view. Factor of safety values and failure zones are also reported to suggest design and non-destructive monitoring guidelines to practicing engineers. Apart from these, the present study indicates the rank wise relative performances of different shell options. The study establishes that the angle ply laminates in general perform better than the cross ply ones. Among the stacking sequences considered here, three layered symmetric angle ply laminates offer the highest first ply failure load. The probable failure zones on the different shell surfaces, identified in this paper, are the areas where non-destructive health monitoring may be restricted to. The contributions made through this paper are expected to serve as important design aids to engineers engaged in composite hypar shell design and construction.

• Steel and Composite Structures
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• 제45권4호
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• pp.501-511
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• 2022

In this study, a two-dimensional model of the contact problem has been examined using the finite element method (FEM) based software ANSYS and based on the multilayer perceptron (MLP), an artificial neural network (ANN). For this purpose, a functionally graded (FG) half-infinite layer (HIL) with a crack pressed by means of two rigid blocks has been solved using FEM. Mass forces and friction are neglected in the solution. Since the problem is analyzed for the plane state, the thickness along the z-axis direction is taken as a unit. To check the accuracy of the contact problem model the results are compared with a study in the literature. In addition, ANSYS and MLP results are compared using Root Mean Square Error (RMSE) and coefficient of determination (R2), and good agreement is found. Numerical solutions are made by considering different values of external load, the width of blocks, crack depth, and material properties. The stresses on the contact surfaces between the blocks and the FG HIL are examined for these values, and the results are presented. Consequently, it is concluded that the considered non-dimensional quantities have a noteworthy influence on the contact stress distributions, and also, FEM and ANN can be efficient alternative methods to time-consuming analytical solutions if used correctly.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.1022-1027
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• 2007

This paper presents a method to analyze the unbalance response of a high speed polygon mirror scanner motor supported by sintered metal bearing and flexible structures by using the finite element method and the mode superposition method considering the asymmetry of the gyroscopic effect and sintered metal bearing. The eigenvalues and eigenvectors are calculated by solving the eigenvalue problem and the adjoint eigenvalue problem by using the restarted Arnoldi iteration method. The decoupled equations of motion can be obtained from global finite element motion equations by using the orthogonal relation between the right eigenvectors and left eigenvectors. The decoupled equations of motion are used to analyze the unbalance response of a high speed polygon mirror scanner motor. The validity of the proposed method is verified by comparing the simulated unbalance response with the experimental results.

• 조명전기설비학회논문지
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• 제19권4호
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• pp.108-116
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• 2005

1계 미분항이 포함되는 미분방정식의 수치해를 구하고자 할 때 중앙차분을 사용한 유한차분법이나 Galerkin법을 사용한 유한요소법은 그 해가 매우 불안하여 요소분할을 세밀하게 하여야만 해를 얻을 수 있다. 이러한 해의 불안 정성이 일어나는 이유는 대류항의 크기가 커질수록 후류에서의 경계조건이 해의 급격한 변화를 요구하는데 수치해가 급격한 변화에 적응하지 못하기 때문이다. 이러한 문제를 해결하기 위해 1970년대부터 upwind법이 개발되어 왔다. 본 논문은 1계 미분항이 표현되는 속도기전력이 발생하는 전자계 문제를 유한요소법을 이용하여 해석할 때 발생하는 해의 진동 문제를 해결하기 위해 Heinrich에 의해 제안된 upwind법을 적용하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.596-601
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• 2007

A simplified finite element analysis method is proposed to calculate elasto-plastic responses of general hardening materials. The method provides an effective tool to calculate structural elasto-plastic responses. Numerical examples have demonstrated that its computational efficiency is very much higher than that of the incremental elasto-plastic finite element analysis, and computational results are accurate enough to meet the need of engineering practice. Compared with the general elasto-plastic incremental finite element analysis, the proposed method can avoid the incremental iteration of nodal displacements and the constitutive equation integration at each Gauss integral point, and computational results are accurate enough to meet the need of engineering practice.