The Experts below are selected from a list of 174 Experts worldwide ranked by ideXlab platform
C. Sato - One of the best experts on this subject based on the ideXlab platform.
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Numerical analysis of simultaneous Nonlinear Algebraic Equations
1988. IEEE International Symposium on Circuits and Systems, 1Co-Authors: C. SatoAbstract:J.B. Moore's (J. Assoc. Comp. Math., vol.14, p.311-5, 1976) method of solving a single-variable Algebraic Equation is generalized to a method for multivariable simultaneous Algebraic Equations. The proposed method makes use of an objective function similar to the Lyapunov function, but it has multiple-zero points corresponding to the solution of the original Algebraic Equation. Using the proposed method, all solutions of a simultaneous Nonlinear Algebraic Equation with complex coefficients are obtained for both real and complex roots. >
Suchuan Dong - One of the best experts on this subject based on the ideXlab platform.
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an unconditionally energy stable scheme based on an implicit auxiliary energy variable for incompressible two phase flows with different densities involving only precomputable coefficient matrices
Journal of Computational Physics, 2019Co-Authors: Zhiguo Yang, Suchuan DongAbstract:Abstract We present an energy-stable scheme for numerically approximating the governing Equations for incompressible two-phase flows with different densities and dynamic viscosities for the two fluids. The proposed scheme employs a scalar-valued auxiliary energy variable in its formulation, and it satisfies a discrete energy stability property. More importantly, the scheme is computationally efficient. Within each time step, it computes two copies of the flow variables (velocity, pressure, phase field function) by solving individually a linear Algebraic system involving a constant and time-independent coefficient matrix for each of these field variables. The coefficient matrices involved in these linear systems only need to be computed once and can be pre-computed. Additionally, within each time step the scheme requires the solution of a Nonlinear Algebraic Equation about a scalar-valued number using the Newton's method. The cost for this Nonlinear solver is very low, accounting for only a few percent of the total computation time per time step, because this Nonlinear Equation is about a scalar number, not a field function. Extensive numerical experiments have been presented for several two-phase flow problems involving large density ratios and large viscosity ratios. Comparisons with theory show that the proposed method produces physically accurate results. Simulations with large time step sizes demonstrate the stability of computations and verify the robustness of the proposed method. An implication of this work is that energy-stable schemes for two-phase problems can also become computationally efficient and competitive, eliminating the need for expensive re-computations of coefficient matrices, even at large density ratios and viscosity ratios.
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numerical approximation of incompressible navier stokes Equations based on an auxiliary energy variable
Journal of Computational Physics, 2019Co-Authors: Zhiguo Yang, Lianlei Lin, Suchuan DongAbstract:Abstract We present a numerical scheme for approximating the incompressible Navier-Stokes Equations based on an auxiliary variable associated with the total system energy. By introducing a dynamic Equation for the auxiliary variable and reformulating the Navier-Stokes Equations into an equivalent system, the scheme satisfies a discrete energy stability property in terms of a modified energy and it allows for an efficient solution algorithm and implementation. Within each time step, the algorithm involves the computations of two pressure fields and two velocity fields by solving several de-coupled individual linear Algebraic systems with constant coefficient matrices, together with the solution of a Nonlinear Algebraic Equation about a scalar number involving a negligible cost. A number of numerical experiments are presented to demonstrate the accuracy and the performance of the presented algorithm.
Arpad Nyers - One of the best experts on this subject based on the ideXlab platform.
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Investigation of Heat Pump Condenser Performance in Heating Process of Buildings using a Steady-State Mathematical Model
Energy and Buildings, 2014Co-Authors: Jozsef Nyers, Arpad NyersAbstract:Abstract The general aim of the paper is the wide-range analysis of heat pump plate condenser performance depending on external impacts. The external impacts are the inlet temperature of hot water, the hydraulic resistance of the hot water circuit, the power of circulation pump and the surface of condenser. The additional goal is to find the appropriate power of circulation pump to obtain the near maximum condenser performance as a function of resistance to flow in the hot water circuit and dimension of condenser. The performance of condenser is the quantity of heat exchanged inside the condenser between the refrigerant and the hot water. The analysis of performance and appropriate power is done using the non-linear lumped parameter mathematical model. The mathematical model includes Equations of heat transfer between the hot water and the refrigerant inside the condenser, the power of circulation pump and the hydraulic resistance in hot water circuit. The mathematical model of the condenser is divided into a section of superheated steam cooling and a section of saturation steam condensation of refrigerant. In order to solve the mathematical model, which comprises of Nonlinear Algebraic Equation system, the Newton–Taylor linearization and Gauss elimination methods were applied.
Yugeng Xi - One of the best experts on this subject based on the ideXlab platform.
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A two‐step predictive control design for input saturated Hammerstein systems
International Journal of Robust and Nonlinear Control, 2006Co-Authors: Baocang Ding, Yugeng XiAbstract:The two-step model predictive control is designed for input saturated Hammerstein systems. It first applies the unconstrained linear dynamic subsystem to get the desired intermediate variable, and then obtains the actual control action by solving Nonlinear Algebraic Equation group and desaturation. The stability of the closed-loop system is analysed and its domain of attraction is designed applying semi-global stabilization techniques. The stability conclusions are illustrated with an example. Copyright © 2006 John Wiley & Sons, Ltd.
A. A. Pershin - One of the best experts on this subject based on the ideXlab platform.
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Influence of cosmological expansion on the threshold effects in the annihilation reaction of hard photons with CMB photons
Astronomy Letters, 2005Co-Authors: Yu. S. Grishkan, A. A. PershinAbstract:The redshift ( z ) dependence of the dispersion relations for free particles is analyzed by taking into account the Lorentz invariance violation. A Nonlinear Algebraic Equation is derived for the momenta of the particles involved in the annihilation reaction of a hard photon from a γ -ray source with a soft cosmic microwave background (CMB) photon near the threshold of this reaction. The solutions of this threshold Equation are constructed and analyzed as a function of the redshift. We show that the threshold of the reaction under consideration tends to decrease with increasing z ; the energy spectra of γ -ray sources at energies of ∼10 TeV must be cut off in accordance with the calculated z dependence. We also calculate the time delay of the light signals from γ -ray sources that corresponds to the Lorentz invariance violation for photons. We discuss the possibility of improving the standard constraints on the Lorentz invariance violation parameters for fields of various physical natures.
