• Title, Summary, Keyword: numerical methods

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NUMERICAL METHODS FOR FUZZY SYSTEM OF LINEAR EQUATIONS WITH CRISP COEFFICIENTS

  • Jun, Younbae
    • The Pure and Applied Mathematics
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    • v.27 no.1
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    • pp.35-42
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    • 2020
  • In this paper, numerical algorithms for solving a fuzzy system of linear equations with crisp coefficients are presented. We illustrate the efficiency and accuracy of the proposed methods by solving some numerical examples. We also provide a graphical representation of the fuzzy solutions in three-dimension as a visual reference of the solution of the fuzzy system.

Developments of Numerical Methods for Estimations of Viscous Resistances (점선저항 추정을 위한 수치해석 프로그램 개발)

  • Lee, Seung-Hui;Kim, Seon-Yeong
    • 한국기계연구소 소보
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    • pp.167-176
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    • 1987
  • It is well known that, about 70-90% of the total drag of a ship is due to the viscous effects. Large amount of theoretical and/or experimental studies on the topic have already been performed. More studies are needed, however, to develop efficient numerical methods which are useful for practical ship design. The present study deals with the theories and numerical methods essential for understanding of real fluid characteristics. Actual ships are not considered because enough computer capacities were not available at the time. Numerical methods, however, are developed to describe complicated ship geometries, transition processes and turbulent boundary layers. The present study can serve as a good start for estimations of viscous ship resistance if an high speed computer is available.

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NUMERICAL METHODS FOR RECONSTRUCTION OF THE SOURCE TERM OF HEAT EQUATIONS FROM THE FINAL OVERDETERMINATION

  • DENG, YOUJUN;FANG, XIAOPING;LI, JING
    • Bulletin of the Korean Mathematical Society
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    • v.52 no.5
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    • pp.1495-1515
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    • 2015
  • This paper deals with the numerical methods for the reconstruction of the source term in a linear parabolic equation from final overdetermination. We assume that the source term has the form f(x)h(t) and h(t) is given, which guarantees the uniqueness of the inverse problem of determining the source term f(x) from final overdetermination. We present the regularization methods for reconstruction of the source term in the whole real line and with Neumann boundary conditions. Moreover, we show the connection of the solutions between the problem with Neumann boundary conditions and the problem with no boundary conditions (on the whole real line) by using the extension method. Numerical experiments are done for the inverse problem with the boundary conditions.

Investigation on Boundary Conditions of Fractional-Step Methods: Compatibility, Stability and Accuracy (분할단계법의 경계조건에 관한 연구: 적합성, 안정성 및 정확도)

  • Kim, Young-Bae;Lee, Moon-J.;Oh, Byung-Do
    • Proceedings of the KSME Conference
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    • pp.410-415
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    • 2001
  • An analytical and numerical examination of second-order fractional-step methods and boundary condition for the incompressible Navier-Stokes equations is presented. In this study, the compatibility condition for pressure Poisson equation and its boundary conditions, stability, and numerical accuracy of canonical fractional-step methods has been investigated. It has been found that satisfaction of compatibility condition depends on tentative velocity and pressure boundary condition, and that the compatible boundary conditions for type D method and approximately compatible boundary conditions for type P method are proper for divergence-free velocity for type D and approximately divergence-free for type P method. Instability of canonical fractional-step methods is induced by approximation of implicit viscous term with explicit terms, and the stability criteria have been founded with simple model problems and numerical experiments of cavity flow and Taylor vortex flow. The numerical accuracy of canonical fractional-step methods with its consistent boundary conditions shows second-order accuracy except $D_{MM}$ condition, which make approximately first-order accuracy due to weak coupling of boundary conditions.

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MULTI-BLOCK BOUNDARY VALUE METHODS FOR ORDINARY DIFFERENTIAL AND DIFFERENTIAL ALGEBRAIC EQUATIONS

  • OGUNFEYITIMI, S.E.;IKHILE, M.N.O.
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • v.24 no.3
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    • pp.243-291
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    • 2020
  • In this paper, multi-block generalized backward differentiation methods for numerical solutions of ordinary differential and differential algebraic equations are introduced. This class of linear multi-block methods is implemented as multi-block boundary value methods (MB2 VMs). The root distribution of the stability polynomial of the new class of methods are determined using the Wiener-Hopf factorization of a matrix polynomial for the purpose of their correct implementation. Numerical tests, showing the potential of such methods for output of multi-block of solutions of the ordinary differential equations in the new approach are also reported herein. The methods which output multi-block of solutions of the ordinary differential equations on application, are unlike the conventional linear multistep methods which output a solution at a point or the conventional boundary value methods and multi-block methods which output only a block of solutions per step. The MB2 VMs introduced herein is a novel approach at developing very large scale integration methods (VLSIM) in the numerical solution of differential equations.

A Stream Line Method to Remove Cross Numerical Diffusion and Its Application to The Solution of Navier-Stokes Equations (교차수치확산을 제거하는 Stream Line방법과 Wavier-Stokes방정식의 해를 위한 적용)

  • Soon Heung Chang
    • Nuclear Engineering and Technology
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    • v.16 no.1
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    • pp.21-28
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    • 1984
  • The reduction of the truncation error including numerical diffusion, has been one of the most important tasks in the development of numerical methods. The stream line method is used to cancel cross numerical diffusion and some of the non-diffusion type truncation error. The two-step stream line method which is the combination of the stream line method and finite difference methods is developed in this work for the solution of the govern ing equations of incompressible buoyant turbulent flow. This method is compared with the finite difference method. The predictions of both classes of numerical methods are compared with experimental findings. Truncation error analysis also has been performed in order to the compare truncation error of the stream line method with that of finite difference methods.

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NUMERICAL SIMULATIONS OF GALAXY FORMATION

  • Peiran, Sebastien
    • Publications of The Korean Astronomical Society
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    • v.25 no.3
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    • pp.71-76
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    • 2010
  • The current status of numerical simulations of galaxy formation is reviewed. After a description of the main numerical simulation techniques, I will present several applications in order to illustrate how numerical simulations have improved our understanding of the galaxy formation process.

Dynamic analysis of the agglomerated SiO2 nanoparticles-reinforced by concrete blocks with close angled discontinues subjected to blast load

  • Amnieh, Hassan Bakhshandeh;Zamzam, Mohammad Saber
    • Structural Engineering and Mechanics
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    • v.65 no.1
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    • pp.121-128
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    • 2018
  • Three structure-dependent integration methods with no numerical dissipation have been successfully developed for time integration. Although these three integration methods generally have the same numerical properties, such as unconditional stability, second-order accuracy, explicit formulation, no overshoot and no numerical damping, there still exist some different numerical properties. It is found that TLM can only have unconditional stability for linear elastic and stiffness softening systems for zero viscous damping while for nonzero viscous damping it only has unconditional stability for linear elastic systems. Whereas, both CEM and CRM can have unconditional stability for linear elastic and stiffness softening systems for both zero and nonzero viscous damping. However, the most significantly different property among the three integration methods is a weak instability. In fact, both CRM and TLM have a weak instability, which will lead to an adverse overshoot or even a numerical instability in the high frequency responses to nonzero initial conditions. Whereas, CEM possesses no such an adverse weak instability. As a result, the performance of CEM is much better than for CRM and TLM. Notice that a weak instability property of CRM and TLM might severely limit its practical applications.

Sensitivity analysis of numerical schemes in natural cooling flows for low power research reactors

  • Karami, Imaneh;Aghaie, Mahdi
    • Advances in Energy Research
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    • v.5 no.3
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    • pp.255-275
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    • 2017
  • The advantages of using natural circulation (NC) as a cooling system, has prompted the worldwide development to investigate this phenomenon more than before. The interesting application of the NC in low power experimental facilities and research reactors, highlights the obligation of study in these laminar flows. The inherent oscillations of NC between hot source and cold sink in low Grashof numbers necessitates stability analysis of cooling flow with experimental or numerical schemes. For this type of analysis, numerical methods could be implemented to desired mass, momentum and energy equations as an efficient instrument for predicting the behavior of the flow field. In this work, using the explicit, implicit and Crank-Nicolson methods, the fluid flow parameters in a natural circulation experimental test loop are obtained and the sensitivity of solving approaches are discussed. In this way, at first, the steady state and transient results from explicit are obtained and compared with experimental data. The implicit and crank-Nicolson scheme is investigated in next steps and in subsequent this research is focused on the numerical aspects of instability prediction for these schemes. In the following, the assessment of the flow behavior with coarse and fine mesh sizes and time-steps has been reported and the numerical schemes convergence are compared. For more detail research, the natural circulation of fluid was modeled by ANSYS-CFX software and results for the experimental loop are shown. Finally, the stability map for rectangular closed loop was obtained with employing the Nyquist criterion.

A Fourth-Order Accurate Numerical Boundary Scheme for the Planar Dielectric Interface: a 2-D TM Case

  • Hwang, Kyu-Pyung
    • Journal of electromagnetic engineering and science
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    • v.11 no.1
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    • pp.11-15
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    • 2011
  • Preserving high-order accuracy in high-order FDTD solutions across dielectric interfaces is very important for practical time-domain electromagnetic simulations. This paper presents a fourth-order accurate numerical boundary scheme for the planar dielectric interface to be used in the fourth-order FDTD method proposed earlier by the author. The interface scheme for the two-dimensional (2-D) transverse magnetic (TM) polarization case is derived and validated by monitoring the $L_2$ norm errors in the numerical solutions of a partially-filled cavity demonstrating its fourth-order convergence and long-time numerical stability in the presence of the planar dielectric interface.