• Earthquakes and Structures
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• 제7권2호
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• pp.119-139
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• 2014

A new method is proposed for random vibration anaylsis of hysteretic systems subjected to non-stationary random excitations. With the Bouc-Wen model, motion equations of hysteretic systems are first transformed into quasi-linear equations by applying the concept of equivalent excitations and decoupling of the real and hysteretic displacements, and the derived equation system can be solved by either the precise time integration or the Newmark-${\beta}$ integration method. Combining the numerical solution of the auxiliary differential equation for hysteretic displacements, an explicit iteration algorithm is then developed for the dynamic response analysis of hysteretic systems. Because the computational cost for a large number of deterministic analyses of hysteretic systems can be significantly reduced, Monte-Carlo simulation using the explicit iteration algorithm is now viable, and statistical characteristics of the non-stationary random responses of a hysteretic system can be obtained. Numerical examples are presented to show the accuracy and efficiency of the present approach.

• Structural Engineering and Mechanics
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• 제62권1호
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• pp.85-95
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• 2017

This paper presents an explicit analytical iteration method for form-finding analysis of suspension bridges. By extending the conventional analytical form-finding method predicated on the elastic catenary theory, two nonlinear governing equations are derived for calculating the accurate unstrained lengths of the entire cable systems both the main cable and the hangers. And for the gradient-based iteration method, the derivation of explicit calculation for the Jacobian matrix while solving the nonlinear governing equation enhances the computational efficiency. The results from sensitivity analysis show well performance of the explicit Jacobian matrix compared with the traditional finite difference method. According to two numerical examples of long span suspension bridges studied, the proposed method is also compared with those reported approaches or the fundamental criterions in suspension bridge structural analysis, which eventually confirms the accuracy and efficiency of the proposed approach.

• Journal of applied mathematics & informatics
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• 제27권3_4호
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• pp.715-723
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• 2009

The aim of this paper is to present an explicit iteration method for finding a common fixed point of a finite family of strictly pseudocon-tractive mappings defined on q-uniformly smooth and uniformly convex Banach spaces.

• 한국분말재료학회지
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• 제30권1호
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• pp.29-34
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• 2023

A fixed-point iteration is proposed to integrate the stress and state variables in the incremental analysis of plastic deformation. The Conventional Newton-Raphson method requires a second-order derivative of the yield function to generate a complicated code, and the convergence cannot be guaranteed beforehand. The proposed fixed-point iteration does not require a second-order derivative of the yield function, and convergence is ensured for a given strain increment. The fixed-point iteration is easier to implement, and the computational time is shortened compared with the Newton-Raphson method. The plane-stress condition is considered for the biaxial loading conditions to confirm the convergence of the fixed-point iteration. 3-dimensional tensile specimen is considered to compare the computational times in the ABAQUS/explicit finite element analysis.

• 물과 미래
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• 제29권3호
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• pp.163-176
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• 1996

균일조도관이 경사지어 설치되어 있을 때, 적정량의 유체를 유송하기 위하여 요구되는 펌프의 동력은 양해법으로 바로 산정할 수 있다. 그러나 펌프의 동력이 기지값으로 주어져 있고 관내 유출률이나 관경을 구하고자 할 때 기존 방법은 상당한 반복과정을 거쳐야 된다. 이러한 경우 유동훈(1995b)은 펌프가 작동치 않는 자연경사관이나 수평관에 펌프만 작동할 때의 균일조도관에 대하여 양해법 산정식을 개발한 바 있다. 본 연구는 그의 연구결과에 기초하여 균일조도 경사관에 펌프가 동시에 작동할 때 반복 시산과정을 거치지 않고 관내 유출률이나 관경을 양해법으로 바로 산정하는 수식을 개발하여 제시하였다. 양해법 산정식의 선택에 있어 관로흐름의 수리특성을 다섯가지로 구분하여 각 수리 특성구간의 경계조건식도 양해법으로 도출하였다. 또한 개발된 양해법 근사식을 간단한 설계예에 적용하여 계산의 효율성과 정확성을 확인하였다.

• 한국수자원학회논문집
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• 제30권5호
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• pp.495-501
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• 1997

펌프동력이 기지 값으로 주어져 있을 때, 유량이나 관경을 산정하는 경우 기존의 방법으로는 상당한 반복과정을 거쳐야 된다. 이에 유동훈과 강찬수(1996)는 균일조도 동력경사관인 경우 유량인 관경을 양해법으로 산정하는 식을 개발한 바 있다. 마찰계수 산정을 위한 지수함수식의 이용은 본 양해법 산정식의 개발을 가능하게 하였다. 유동훈(1995a)은 상용관이나 복합면을 가진 관의 마찰계수 산정을 위한 마찰계수 평균법을 제시한 바 있다. 그와 같은 접근방법으로 본고는 마찰계수 평균법을 상용관 마찰계수 산정식에 적용하여 동력경사 상용관의 유량이나 관경을 양해법으로 구할 수 있는 산정식을 개발하였다.

• Nuclear Engineering and Technology
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• 제52권2호
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• pp.258-270
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• 2020

A new task of using the Jacobian-Free-Newton-Krylov (JFNK) method for the PWR core transient simulations involving neutronics, thermal hydraulics and mechanics is conducted. For the transient scenario of PWR, normally the Picard iteration of the coupled coarse-mesh nodal equations and parallel channel TH equations is performed to get the transient solution. In order to solve the coupled equations faster and more stable, the Newton Krylov (NK) method based on the explicit matrix was studied. However, the NK method is hard to be extended to the cases with more physics phenomenon coupled, thus the JFNK based iteration scheme is developed for the nodal method and parallel-channel TH method. The local gap conductance is sensitive to the gap width and will influence the temperature distribution in the fuel rod significantly. To further consider the local gap conductance during the transient scenario, a 1D mechanics model is coupled into the JFNK scheme to account for the fuel thermal expansion effect. To improve the efficiency, the physics-based precondition and scaling technique are developed for the JFNK iteration. Numerical tests show good convergence behavior of the iterations and demonstrate the influence of the fuel thermal expansion effect during the rod ejection problems.

• Kyungpook Mathematical Journal
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• 제52권3호
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• pp.327-346
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• 2012

In this paper, we present a simple explicit type numerical method for discretizations in time for solving one dimensional Burgers' equations. The proposed method does not need an iteration process that may be required in most implicit methods and have good convergence and efficiency in computational sense compared to other known numerical methods. For evidences, several numerical demonstrations are also provided.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제13권4호
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• pp.267-280
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• 2009

In this paper we investigate a simple two-level additive Schwarz preconditioner for the P1 symmetric interior penalty Galerkin method of the Poisson equation on rectangular meshes. The construction is based on the decomposition of the global space of piecewise linear polynomials into the sum of local subspaces, each of which corresponds to an element of the underlying mesh, and the global coarse subspace consisting of piecewise constants. This preconditioner is a direct combination of the block Jacobi iteration and the cell-centered finite difference method, and thus very easy to implement. Explicit upper and lower bounds for the maximum and minimum eigenvalues of the preconditioned matrix system are derived and confirmed by some numerical experiments.

• Korean Journal of Hydrosciences
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• 제7권
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• pp.107-124
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• 1996

Pipe design normally requires pump power, discharge or pipe diameter for each condition given. Due to several investigators the pipe friction factor con now be estimated by explicit way for a wide range of flow condition. In various problems of pipe design, however, the flow condition cannot be pre-determined even for a uniformly rough pipe. In these cases a lot of iterations are often required to have an accurate solution with ordinary approach. This paper presents the direct computation method of discharge and pipe diameter without any iteration process. Introducing the power law of friction factor, various non-dimensional physical numbers are derived such as power-diameter number, power-discharge number, diameter-slope number and discharge-slope number. One of the physical numbers concerned with discharge or pipe diameter can be related to a combination of the other in an explicit way.