• Title/Summary/Keyword: 곡선 경계

Search Result 363, Processing Time 0.025 seconds

Finite Element Analysis for Circulation Phenomena in Sudden Expansion of Open Channel (유한요소법을 이용한 개수로단면급확대부의 순환현상해석)

  • 윤태훈;서승원
    • Water for future
    • /
    • v.21 no.1
    • /
    • pp.67-76
    • /
    • 1988
  • Analyzed was the circulation phenomena in the open channel with sudden expansion, by applying the Galerkin's finite element method to the depth-averaged 2-dimensional continuity and momentum equations. Wave tests were done in the simplified channel in order to review the validity of this newly developed model and the computed results were within 0.5% of $L_2$-norm error, and application of this model to the simulation of simplified dam-break gave very close results compared with the analytical solution, thus, it can be concluded that this model is valid and efficient. The main flow in the expanded channel was defined as a new initial condition with given velocity and the flow in the expanded portion was at rest in simulating the circulation, and besides the Neumann's condition the slip boundary condition for lateral wall was found to be proper condition than the no-slip condition. It can be concluded, from the numerical tests in the sudden expension, that the circulating phenomena depend mainly on the convective inertia and the effect of turbulence due to bottom shear and lateral shear is insignificant.

  • PDF

FE Based Numerical Model to Consider Bond-slip Effect in Composite Beams (합성보의 부착슬립 효과를 고려한 유한요소 기반의 수치해석모델)

  • Kwak, Hyo-Gyoung;Hwang, Jin-Wook
    • Journal of the Computational Structural Engineering Institute of Korea
    • /
    • v.23 no.1
    • /
    • pp.95-110
    • /
    • 2010
  • A numerical model to simulate bond-slip behavior of composite beam bridges is introduced in this paper. Assuming a linear bond stress-slip relation along the interface between the slab and girder, the slip behavior is implemented into a finite element formulation. Adopting the introduced model, the slip behavior can be taken account even in a beam element which is composed of both end nodes only. Governing equation of the slip behavior, based on the linear partial interaction theory, can be determined from the force equilibrium and a constant curvature distribution across the section of a composite beam. Since the governing equation for the slip behavior requires the moment values at both end nodes, the piecewise linear distribution of the constant bending moment in an element is assumed. Analysis results by the model are compared with numerical results and experimental values, and load-displacement relations of composite beams were then evaluated to verify the validity of the proposed model.

Development of Modification Coefficient for Nonlinear Single Degree of Freedom System Considering Plasticity Range for Structures Subjected to Blast Loads (폭발 하중을 받는 구조물의 소성 범위를 고려한 비선형 단자유도 시스템의 수정계수 개발)

  • Tae-Hun Lim;Seung-Hoon Lee;Han-Soo Kim
    • Journal of the Computational Structural Engineering Institute of Korea
    • /
    • v.37 no.3
    • /
    • pp.179-186
    • /
    • 2024
  • In this paper, a modification coefficient for equivalent single degree of freedom (SDOF), considering the plasticity range of the member subjected to shock wave type of blast load, was developed. The modification coefficient for the equivalent SDOF was determined through comparison with the analysis of a multi-degree of freedom (MDOF) system. The parameters influencing the equivalent SDOF system analysis were chosen as the boundary conditions of the member and the ratio of the duration of blast load to the natural period of the member. The modification coefficient was calculated based on the elastic load-mass transformation factor. The modification coefficient curve was derived using an elliptical equation to ensure it exists between the upper and lower parameter bounds. Using the modification coefficient on examples with varying cross sections and boundary conditions reduced the SDOF analysis error rate from 15% to 3%. This study shows that using the modification coefficient significantly improves the accuracy of SDOF analysis. The modification coefficient proposed in this study can be used for blast analysis.

Assessment of Non-permeability of Gd-DTPA for Dynamic Susceptibility Contrast in Human Brain: A Preliminary Study Using Non-linear Curve Fitting (뇌영역의 동적 자화율 대조도 영상에서 Gd-DTPA 조영제의 비투과성 조사: 새로운 비선형 곡선조화 알고리즘 개발의 예비연구)

  • Yoon, Seong-Ik;Jahng, Geon-Ho;Khang, Hyun-Soo;Kim, Young-Joo;Choel, Bo-Young
    • Investigative Magnetic Resonance Imaging
    • /
    • v.11 no.2
    • /
    • pp.103-109
    • /
    • 2007
  • To develop an advanced non-linear curve fitting (NLCF) algorithm for performing dynamic susceptibility contrast study of the brain. The first pass effects give rise to spuriously high estimates of $K^{trans}$ for the voxels that represent the large vascular components. An explicit threshold value was used to reject voxels. The blood perfusion and volume estimation were accurately evaluated in the $T2^*$-weighted dynamic contrast enhanced (DCE)-MR images. From each of the recalculated parameters, a perfusion weighted image was outlined by using the modified non-linear curve fitting algorithm. The present study demonstrated an improvement of an estimation of the kinetic parameters from the DCE $T2^*$-weighted magnetic resonance imaging data with using contrast agents.

  • PDF

In-Plane Extensional Buckling Analysis of Curved Beams under Uniformly Distributed Radial Loads Using DQM (등분포하중 하에서 미분구적법(DQM)을 이용한 곡선 보의 내평면 신장 좌굴해석)

  • Kang, Ki-Jun
    • Journal of the Korea Academia-Industrial cooperation Society
    • /
    • v.19 no.7
    • /
    • pp.265-274
    • /
    • 2018
  • The increasing use of curved beams in buildings, vehicles, ships, and aircraft has prompted studies directed toward the development of an accurate method for analyzing the dynamic behavior of such structures. The stability behavior of elastic curved beams has been the subject of a large number of investigations. Solutions of the relevant differential equations have been obtained traditionally using standard finite difference or finite element methods. These techniques require a great deal of computer time as the number of discrete nodes becomes relatively large under the conditions of complex geometry and loading. One of the efficient procedures for the solution of partial differential equations is the method of differential quadrature. The differential quadrature method (DQM) has been applied to a large number of cases to overcome the difficulties of the complex algorithms of programming for the computer, as well as the excessive use of storage due to the conditions of complex geometry and loading. The in-plane buckling of curved beams considering the extensibility of the arch axis was analyzed under uniformly distributed radial loads using the DQM. The critical loads were calculated for the member with various parameter ratios, boundary conditions, and opening angles. The results were compared with the precise results by other methods for cases, in which they were available. The DQM, using only a limited number of grid points, provided results that agreed very well (less than 0.3%) with the exact ones. New results according to diverse variations were obtained, showing the important roles in the buckling behavior of curved beams, and can be used in comparisons with other numerical solutions or with experimental test data.

Dynamic Characteristics of Nonlinear Beam Shear Deformation (전단변형을 고려한 비선형 보의 동적특성에 관한 연구)

  • Park, Sungjin;Baek, Jooeun
    • Journal of the Society of Disaster Information
    • /
    • v.12 no.1
    • /
    • pp.69-73
    • /
    • 2016
  • In this study, the applicability and validity of collocation method to nonlinear vibration issues in comparison to other solutions are confirmed, and the applicability of collocation method to nonlinear dynamic response issues in comparison to the response curve with F.E.M results is examined. Also, it is also examined how the influence of axial inertia varies according to the size of slenderness ratio.

Boundary element analysis of stress intensity factors for Z-shaped cracks (Z형상 균열의 응력세기계수에 대한 경계요소 해석)

  • 이강용;원동성;최형집
    • Transactions of the Korean Society of Mechanical Engineers
    • /
    • v.11 no.1
    • /
    • pp.36-43
    • /
    • 1987
  • Stress intensity factors are computed by the boundary element method employing the multiregion technique along with the double-point concept. To demonstrate the validity of the current method, the stress intensity factors of the well-known simple models such as a slanted edge crack and an arcular crack are determined, in advanced, which are proved to be in good agreement within 5% with the pre-existing solutions. Z-shaped cracks are analyzed with various branch crack lengths and branching angles.

Chaotic Dynamics of a Forced Perfect Circular Plate (강제진동중인 완전 원판의 혼돈운동)

  • Lee, Won-Kyoung;Park, Hae-Dong
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2005.05a
    • /
    • pp.430-435
    • /
    • 2005
  • 조화가진력이 작용하는 고정경계를 가진 완전원판의 비선형 진동에 대한 응답특성을 연구하였다. 원판의 비대칭모드의 고유진동수 근처에 가진주파수가 작용하는 주공진에서의 응답은 정상파(standing wave)뿐만 아니라 진행파(traveling wave)가 존재한다고 알려져 있다. 주공진 근처의 정상상태 응답곡선에서 최대한 5개의 안정한 응답이 존재하는 것으로 밝혀졌으며, 이들은 1개의 정상파와 4개의 진행파로 나타난다. 이 진행파중 2개는 Hope분기에 의해 안정성을 잃은 후 주기배가운동을 거쳐 혼돈운동에 이르게 된다. Lyaponov 지수를 사용하여 혼돈운동을 정량적으로 평가하였으며, 주평면의 개념을 이용하여 이 혼돈운동의 흡인영역이 Fractal임을 확인하였다.

  • PDF

An Analysis of Stream Bed Variation at the Down Stream Part of Ji-chun (지천 하류부의 하상변동 분석)

  • Choi Ho;Jung Jae Uk;Lim Chang Soo;Yoon Sei Eui
    • Proceedings of the Korea Water Resources Association Conference
    • /
    • 2005.05b
    • /
    • pp.965-969
    • /
    • 2005
  • 본 연구에서는 기존의 하상변동 예측모형 중에서 HEC-6와 GSTARS 모형을 선택하여 지천 하류부의 하상변동을 예측하고 실측치와 비교, 분석하였다. 연구대상구간은 지천하류부의 신지천교부터 상류쪽으로 1320m구간이다. 2003년 11월 7일에 하천측량을 실시하고 2004년 6월 24일과 2004년 9월 24일에 측량을 실시하였다. 하상재료의 구성을 파악하기 위하여 12개 지점에서 시료를 채취하여 채가름 분석에 의해 입도분포 곡선을 작성하였다. 두 모형의 경계조건으로는 수위-유량자료와 유입 유사량 자료가 필요하므로 수위-유량 자료는 대상구간의 신지천교 구룡 수위표에서 얻었고, 유입 유사량은 Toffaleti공식, Meyer-Peter와 Muller공식, Ackers와 White공식 3가지 방법으로 산정하여 모형에 적용하였다. 모형의 적용결과 유입 유사량 산정공식 중에서 지천 하류부의 하상변동을 실측치와 가장 유사하게 예측한 공식은 Toffaleti 공식이었으며 최심부의 종방향 하상변동은 GSTARS 모형이 HEC-6 모형보다 실측치와 일치하는 경향을 나타내고 있다.

  • PDF

Efficient Error Concealment using Genetic Algorithms with Isophote Constraint (Isophote 제약조건을 사용한 유전자 알고리즘 기반의 효율적인 오류 은닉)

  • 문채현;김종배;이경미;김항준
    • Proceedings of the Korean Information Science Society Conference
    • /
    • 2003.04c
    • /
    • pp.202-204
    • /
    • 2003
  • 본 논문은 isophote 제약조건을 사용한 유전자 알고리즘(Genetic Algorithms) 기반의 효율적인 오류 은닉 방법을 제안한다. 제안된 방법은 먼저 오류 블록을 경계선 정합 알고리즘(Boundary Matching Algorithm)을 사용하여 오류 블록의 주변과 가장 유사한 블록을 이전 프레임에서 찾아 교체한 후, isophote를 제약조건으로 가진 유전자 알고리즘을 사용하여 교체된 오류 블록을 재구성하는 것이다. Isophote들은 영상에서 일정한 밝기 값을 가지는 곡선들로, 본 논문에서는 비디오 통신 시 화질을 개선하기 위해, 전송 오류에 의한 끊어진 isophote들을 부드럽게 연결한다. 끊어진 isophote들을 연결하기 위해, isophote를 제약조건으로 가진 적합도 함수를 최소화하는 픽셀 값을 유전자 알고리즘을 사용하여 추정하고, 그 값을 isephote 방향으로 투영한다. 실험 결과, 제안된 방법이 다른 오류 은닉 방법 보다 좀 더 화질을 개선시킬 수 있다.

  • PDF