• 설비공학논문집
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• 제3권2호
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• pp.97-102
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• 1991

Finite element method has been developed recently for the solution of the convection-diffusion problems. Finite element method has several advantages over finite difference method, but its requirement of the larger memory size of the computer has prevented from wide application. In the present study, line-by-line technique has been implemented to finite element method to overcome this disadvantage. Two dimensional laminar natural convection in square cavity was chosen as an example in this study. The numerical result shows good agreement with bench mark solution and the size of the coefficient marix has been reduced drastically.

• 대한기계학회논문집A
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• 제22권3호
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• pp.635-643
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• 1998

A spectral element method(SEM) is introduced for the vibration analysis of a rectangular plate subject to dynamic concentrated loads. First, the spectral plate element is derived from the relations between the forces and displacements along the two opposite edges of plate element. The global spectral matrix equation is then formulated by assembling two spectral plate elements so that the dynamic concentrated load is located at the connection nodal line between two plate elements. the concentrated load is then spatially Fourier transformed in the direction of the connection nodal line to transform the two-dimensional plate problem into a simplified equivalent one-dimensional beam-like problem. We may benefit from these procedures in that the spectral results from the present SEM is compared with the exact analytical solutions to prove the remarkable accuracy of the present SEM, while this is not true for conventional finite element solutions, especially at high frequency.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.2212-2213
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• 2008

In this paper, we studied the method for simultaneous quenching of a transformer type superconducting fault current limiter (SFCL) with two superconducting elements connected in series. Only an element between two elements of the transformer type SFCL was quenched like the case of the resistive type SFCL. By this quenching characteristics, the power burden of the superconducting element was increased. In order to solve this problem, we connected the neutral line between two superconducting elements and the center of secondary coils. The two elements were all quenched in the transformer type SFCL with a neutral line. As a result, the power burden of superconducting elements was decreased, so it was efficient for the increase of power capacity of the transformer type SFCL.

• 대한기계학회논문집A
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• 제25권9호
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• pp.1325-1333
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• 2001

Critical defects in pressure vessels and pipes are generally found in the form of a semi-elliptical surface crack, and the analysis of which is consequently an important problem in engineering fracture mechanics. Furthermore, in addition to the traditional single parameter K or J-integral, the second parameter like T-stress should be measured to quantify the constraint effect. In this work, the validity of the line-spring finite element is investigated by comparing line-spring J-T solutions to the reference 3D finite element J-T solutions. A full 3D-mesh generating program for semi-elliptical surface cracks is employed to provide such reference 3D solutions. Then some structural characteristics of the surface-cracked T and L-joints are studied by mixed mode line-spring finite element. Negative T-stresses observed in T and L-joints indicate the necessity of J-T two parameter approach for analyses of surface-cracked T and L-joints.

• 소성∙가공
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• 제5권1호
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• pp.37-46
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• 1996

Superplastic forming/diffusion bonding (SPF/DB) processes were analyzed using a rigid visco-plastic finite element method. The optimum pressure-time relationship for a target strain rate and thickness distributions were predicted by two-node line elements based on the membrane approximation for plane strain. Material behavior during SPF/DB of the integral structures having complicated shapes was investigated. The tying condition is employed for the analysis of inter-sheet contact problems. A movement of rib structure is successfully predicted during the forming.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 추계학술대회 논문집
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• pp.878-883
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• 2005

Sleeper, the ballast, and ballast mat in the high-speed railroad line are modelled using a two-dimensional discrete element method to generate circle and line elements. Stress transfer mechanism from the sleeper to the subgrade via the ballast is analyzed. The behavior of ballast bed of the high-speed railroad line is also accessed with the model.

• 대한토목학회논문집
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• 제13권2호
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• pp.41-49
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• 1993

2차원 곡선보요소를 이용하여 대변형효과 및 탄소성거동을 고려한 유한요소법을 제시한다. Total Lagrangian 방법을 적용하며, 보요소는 평면응력요소로부터 유도된다. 또한, 임의의 단면을 갖는 평면뼈대 구조의 탄소성 해석을 수행하기 위하여 layered approach를 사용한다. 비선형 유한요소해석은 하중증분 또는 변위증분법을 적용한다. 본 연구에서 제안한 보요소의 거동과 정확도를 검증하기 위하여, 다른 문헌의 결과와 본 연구의 결과를 비교 분석한 해석예제를 제시한다.

• Wind and Structures
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• 제34권2호
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• pp.215-230
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• 2022

Majority of transmission line system failures at many locations worldwide have been caused by severe localized wind events in the form of tornadoes and downbursts. This study evaluates the structural response of two different transmission line systems under equivalent F2 tornadoes obtained from real incidents. Two multi-span self-supported transmission line systems are considered in the study. Nonlinear three-dimensional finite element models are developed for both systems. The finite element models simulate six spans and five towers. Computational Fluid Dynamics (CFD) simulations are used to develop the tornado wind fields. Using a proper scaling method for geometry and velocity, full-scale tornado flow fields for the Stockton, KS, 2005 and Goshen County WY, 2009 are developed and considered together with a previously developed tornado wind field. The tornado wind profiles are obtained in terms of tangential, radial, and axial velocities. The simulated tornadoes are then normalized to the maximum velocity value for F2 tornadoes in order to compare the effect of different tornadoes having an equal magnitude. The tornado wind fields are incorporated into a three-dimensional finite element model. By varying the location of the tornado relative to the transmission line systems, base shears of the tower of interest and peak internal forces in the tower members are evaluated. Sensitivity analysis is conducted to assess the variation of the structural behaviour of the studied transmission lines associated with the location of the tornado relative to the tower of interest. The tornado-induced forces in both lines due to the three different normalized tornadoes are compared with corresponding values evaluated using the simplified load case method recently incorporated in the ASCE-74 (2020) guidelines, which was previously developed based on the research conducted at Western University.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 ITC-CSCC -1
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• pp.163-166
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• 2000

The design, numerical simulation, and an experimental implementation of two-element cross-shaped microstrip line-fed printed slot array antenna for IMT-2000 at the 2.0 GHz band is presented in this paper. The proposed antenna with relative permittivity 4.3 and thickness 1.0mm is analyzed by the Finite-Difference Time-Domain (FDTD) method. It was shown that the measured 2.0 VSWR bandwidth of one-element microstrip slot antenna is from 1.42 GHz to 2.69 GHz, which is approximately 61.8% and that of two-element microstrip slot array antenna is from 1.42 GHz to 2.56 GHz, which is approximately 57.3% And it was shown that the measured gain of one-element microstrip slot antenna is 2.75 dBi and that of two-element microstrip slot antenna is 4.75 dEi. The antennas were fabricated and tested. The measured results are in good agreements with the FDTD results.

• Earthquakes and Structures
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• 제17권4호
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• pp.387-398
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• 2019

On the basis that ground motions may arrive at a structure from any horizontal direction and that different directions of seismic incidence would result in different structural dynamic responses, this paper focuses on orienting the crucial seismic incidence of transmission tower-line systems based on the wavelet energy method. A typical transmission tower-line system is chosen as the case study, and two finite element (FE) models are established in ABAQUS, with and without consideration of the interaction between the transmission towers and the transmission lines. The mode combination frequency is defined by considering the influence of the higher-order modes of the structure. Subsequently, wavelet transformation is performed to obtain the total effective energy input and the effective energy input rate corresponding to the mode combination frequency to further judge the critical angle of seismic incidence by comparing these two performance indexes under different seismic incidence angles. To validate this approach, finite element history analysis (FEHA) is imposed on both FE models to generate comparative data, and good agreement is found. The results demonstrate that the wavelet energy method can forecast the critical angle of seismic incidence of a transmission tower-line system with adequate accuracy, avoiding time-consuming and cumbersome computer analysis. The proposed approach can be used in future seismic design of transmission tower-line systems.