• 제목/요약/키워드: Higher order polynomial

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Prediction and analysis of optimal frequency of layered composite structure using higher-order FEM and soft computing techniques

  • Das, Arijit;Hirwani, Chetan K.;Panda, Subrata K.;Topal, Umut;Dede, Tayfun
    • Steel and Composite Structures
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    • 제29권6호
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    • pp.749-758
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    • 2018
  • This article derived a hybrid coupling technique using the higher-order displacement polynomial and three soft computing techniques (teaching learning-based optimization, particle swarm optimization, and artificial bee colony) to predict the optimal stacking sequence of the layered structure and the corresponding frequency values. The higher-order displacement kinematics is adopted for the mathematical model derivation considering the necessary stress and stain continuity and the elimination of shear correction factor. A nine noded isoparametric Lagrangian element (eighty-one degrees of freedom at each node) is engaged for the discretisation and the desired model equation derived via the classical Hamilton's principle. Subsequently, three soft computing techniques are employed to predict the maximum natural frequency values corresponding to their optimum layer sequences via a suitable home-made computer code. The finite element convergence rate including the optimal solution stability is established through the iterative solutions. Further, the predicted optimal stacking sequence including the accuracy of the frequency values are verified with adequate comparison studies. Lastly, the derived hybrid models are explored further to by solving different numerical examples for the combined structural parameters (length to width ratio, length to thickness ratio and orthotropicity on frequency and layer-sequence) and the implicit behavior discuss in details.

Eigenfrequencies of advanced composite plates using an efficient hybrid quasi-3D shear deformation theory

  • Guerroudj, Hicham Zakaria;Yeghnem, Redha;Kaci, Abdelhakim;Zaoui, Fatima Zohra;Benyoucef, Samir;Tounsi, Abdelouahed
    • 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.

고차이론을 이용한 보 및 아치형 구조물의 유한요소 해석 (Finite Element Analysis of Beam-and Arch-Like Structures using Higher-Order Theory)

  • 조진래
    • 전산구조공학
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    • 제10권1호
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    • pp.185-191
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    • 1997
  • 보 및 아치형 구조물은 2차원 탄성체이지만 두께가 상대적으로 매우 얇다는 특성 때문에 Kirchhoff이나 Reissner-Mindlin이론과 같이 변위장의 두께방향 변위를 선형함수로 근사화시켜왔다. 그 결과 2차원 문제가 물체의 중립면에서 표현되는 1차원 문제로 차원이 감소되어 이론적 해석이 간편해 진다. 그러나 경계에서와 같이 두께방향 변위가 복잡한 영역의 거동을 보다 정확히 해석하기 위해서는 2차원 선형 탄성이론이나 두께방향 다항식의 차수가 상당히 높아야 한다. 본 논문은 두께방향 다항식의 차수변화에 따른 해석정도 경향 및 여러 다른 차수를 한 문제 영역에 혼합하는 모델조합에 대한 내용을 제시한다.

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지진 재해도의 닫힌 근사식 제안에 관한 연구 (A Study to Propose Closed-form Approximations of Seismic Hazard)

  • 곽신영;함대기
    • 한국지진공학회논문집
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    • 제22권4호
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    • pp.245-251
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    • 2018
  • In this paper, we address some issues in existing seismic hazard closed-form equations and present a novel seismic hazard equation form to overcome these issues. The presented equation form is based on higher-order polynomials, which can well describe the seismic hazard information with relatively high non-linearity. The accuracy of the proposed form is illustrated not only in the seismic hazard data itself but also in estimating the annual probability of failure (APF) of the structural systems. For this purpose, the information on seismic hazard is used in representative areas of the United States (West : Los Angeles, Central : Memphis and Kansas, East : Charleston). Examples regarding the APF estimation are the analyses of existing platform structure and nuclear power plant problems. As a result of the numerical example analyses, it is confirmed that the higher-order-polynomial-based hazard form presented in this paper could predict the APF values of the two example structure systems as well as the given seismic hazard data relatively accurately compared with the existing closed-form hazard equations. Therefore, in the future, it is expected that we can derive a new improved APF function by combining the proposed hazard formula with the existing fragility equation.

영역화에 기초를 둔 영상 부호화에서 영역 부호화 방법의 개선에 관한 연구 (A Study on the Improvement of Texture Coding in the Region Growing Based Image Coding)

  • 김주은;김성대;김재균
    • 대한전자공학회논문지
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    • 제26권6호
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    • pp.89-96
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    • 1989
  • 본 논문에서는 영역화에 기초를 둔 영상 부호화의 한 부분인 영역 부호화의 개선에 관한 연구가 수행되었다. 영역화시 texture의 효율적인 표현을 위하여 영상을 stochastic random field로 묘사 될 수 있는 stochastic 영역과 non-stochastic 영역으로 구분한다. 영역 부호화 및 복원시 stochastic 영역에 대해서는 autoregressive model을 이용하고 non-stochastic영역은 2차원 다항식 근사화를 이용한다. 제안 방식은 2차원 다항식 근사화만을 이용한 기존 방식보다 더 좋은 주관적 화질을 가지며, 상대적인 data 감축할 수 있었고 영상의 부호화 및 복원에 필요한 수행시간을 단축시켰다.

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탄성지반 위에 놓여있는 다지지 보의 동적해석 제1보 : 고유진동수 (Dynamic Analysis of the Multi-Span Beam on Elastic Foundation Part one : Natural Frequencies)

  • 김용철;최교준
    • 대한조선학회논문집
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    • 제28권1호
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    • pp.83-91
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    • 1991
  • 본 연구에서는 병진 및 회전 스프링을 포함하는 탄성지반 위에 놓여 있는 다지지보의 동적 해석이 수행되었다. 특히 중간 지지점이 있는 경우에 대한 영향도 조사하였다. 문제의 해석방법으로서 우선 기하학적 및 동적 경계조건을 동시에 만족하는 직교 다항식 함수를 구하였으며, Galerkin 방법을 이용하여 시스템의 고유진동수틀 구하였다. 본 연구에서 제시한 방법으로 구한 고차 직교 다항식 함수를 사용하면 정확한 해를 얻을 수 있다는 것을 여러가지 경우에 대한 수치 계산 결과로부터 알 수 있었다.

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Pressure loading, end- shortening and through- thickness shearing effects on geometrically nonlinear response of composite laminated plates using higher order finite strip method

  • Sherafat, Mohammad H.;Ghannadpour, Seyyed Amir M.;Ovesy, Hamid R.
    • Structural Engineering and Mechanics
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    • 제45권5호
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    • pp.677-691
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    • 2013
  • A semi-analytical finite strip method is developed for analyzing the post-buckling behavior of rectangular composite laminated plates of arbitrary lay-up subjected to progressive end-shortening in their plane and to normal pressure loading. In this method, all the displacements are postulated by the appropriate harmonic shape functions in the longitudinal direction and polynomial interpolation functions in the transverse direction. Thin or thick plates are assumed and correspondingly the Classical Plate Theory (CPT) or Higher Order Plate Theory (HOPT) is applied. The in-plane transverse deflection is allowed at the loaded ends of the plate, whilst the same deflection at the unloaded edges is either allowed to occur or completely restrained. Geometric non-linearity is introduced in the strain-displacement equations in the manner of the von-Karman assumptions. The formulations of the finite strip methods are based on the concept of the principle of the minimum potential energy. The Newton-Raphson method is used to solve the non-linear equilibrium equations. A number of applications involving isotropic plates, symmetric and unsymmetric cross-ply laminates are described to investigate the through-thickness shearing effects as well as the effect of pressure loading, end-shortening and boundary conditions. The study of the results has revealed that the response of the composite laminated plates is particularly influenced by the application of the Higher Order Plate Theory (HOPT) and normal pressure loading. In the relatively thick plates, the HOPT results have more accuracy than CPT.

Fuzzy polynomial neural network model and its application to wastewater treatment system

  • Oh, Sung-Kwun;Choi, Jae-Ho;Ahn, Tae-Chon;Hwang, Hyung-Soo
    • 제어로봇시스템학회:학술대회논문집
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    • 제어로봇시스템학회 1996년도 Proceedings of the Korea Automatic Control Conference, 11th (KACC); Pohang, Korea; 24-26 Oct. 1996
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    • pp.185-188
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    • 1996
  • In this paper, a fuzzy PNN algorithm is proposed to estimate the structure and parameters of fuzzy model, using the PNN based on GMDH algorithm. New algorithm uses PNN algorithm and fuzzy reasoning in order to identify the premise structure and parameter of fuzzy implications rules, and the leastsquare method in order to identify the optimal consequence parameters. Both time series data for gas furnace and data for wastewater treatment process are used for the purpose of evaluating the performance of the fuzzy PNN. The results show that the proposed technique can produce the fuzzy model with higher accuracy than other works achieved previously.

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A Fuzzy Model on the PNN Structure and its Applications

  • Sang, R.S.;Oh, Sungkwun;Ahn, T.C.
    • 한국지능시스템학회:학술대회논문집
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    • 한국퍼지및지능시스템학회 1997년도 추계학술대회 학술발표 논문집
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    • pp.259-262
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    • 1997
  • In this paper, a fuzzy model based on the polynomial Neural Network(PNN) structure is proposed to estimate the emission pattern for air pollutant in power plants. The new algorithm uses PNN algorithm based on Group Method of Data Handling (GMDH) algorithm and fuzzy reasoning in order to identify the premise structure and parameter of fuzzy implications rules, and the least square method in order to identify the optimal consequence parameters. Both time series data for the gas furnace and data for the NOx emission process of gas turbine power plants are used for the purpose of evaluating the performance of the fuzzy model. The simulation results show that the proposed technique can produce the optimal fuzzy model with higher accuracy anhd feasibility than other works achieved previously.

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정규 크리깅보간법을 이용한 응력특이문제의 p-적응적 유한요소해석 (p-Adaptive Finite Element Analysis of Stress Singularity Problems by Ordinary Kriging Interpolation)

  • 우광성;박미영;박진환;한상현
    • 한국전산구조공학회:학술대회논문집
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    • 한국전산구조공학회 2006년도 정기 학술대회 논문집
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    • pp.849-856
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    • 2006
  • This paper is to examine the applicability of ordinary Kriging interpolation(OK) to the p-adaptivity of the finite element analysis that is based on variogram. In the p-refinement, the analytical domain has to be refined automatically to obtain an acceptable level of accuracy by increasing the p-level non-uniformly or selectively. In case of non-uniform p-distribution, the continuity between elements with different polynomial orders is achieved by assigning zero higher-order derivatives associated with the edge in common with the lower-order derivatives. It is demonstrated that the validity of the proposed approach by analyzing results for stress singularity problem.

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