Vietnam Journal of Mathematics

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Coupling of Compressible Euler Equations
Vietnam Journal of Mathematics - Tập 47 - Trang 769-792 - 2019
Michael Herty, Siegfried Müller, Aleksey Sikstel
The Riemann problem for coupled Euler equations is analysed. The coupling conditions at a steady interface impose continuous pressure and temperature while momentum differs. The outtake of the momentum models the influence of a gas-powered generator linked to a high-pressure gas network. We prove the existence and uniqueness of the solution to the coupled Riemann problem in case the drop in the mo...... hiện toàn bộ
A Simple Proof for a More Generalized Form of the AZ-identity
Vietnam Journal of Mathematics - Tập 43 - Trang 771-775 - 2015
Tran Thai-Duong, Tran Dan Thu
This paper gives a simple proof for a generalized form of the AZ-identity of one or two set systems. We also extend the results further and establish some new identities related to the AZ-identity. Our method uses some properties of rational functions.
Exponential Stability of Linear Delay Difference Equations with Continuous Time
Vietnam Journal of Mathematics - Tập 43 - Trang 195-205 - 2014
Pham Huu Anh Ngoc, Nguyen Dinh Huy
Linear time-varying delay difference equations with continuous time are considered. New criteria for exponential stability are given. Furthermore, an explicit stability bound for equations subject to time-varying perturbations is presented. Some examples are given to illustrate the obtained results.
Extragradient Algorithms with Linesearches for Solving Nonmonotone Equilibrium Problems in Banach Spaces
Vietnam Journal of Mathematics - - Trang 1-21 - 2023
Bui Van Dinh, Hy Duc Manh, Tran Thi Huyen Thanh
In this paper, we introduce a new extragradient algorithm with linesearches for solving equilibrium problems in a real Banach space where the bifunction is not required to satisfy any monotone property. Under assumptions on the continuity, convexity of the bifunction, and the nonemptyness of the solution set of the Minty equilibrium problem, we show that the iterative sequences generated by this a...... hiện toàn bộ
Pole-Swapping Algorithms for Alternating and Palindromic Eigenvalue Problems
Vietnam Journal of Mathematics - Tập 48 - Trang 679-701 - 2020
Thomas Mach, Thijs Steel, Raf Vandebril, David S. Watkins
Pole-swapping algorithms are generalizations of bulge-chasing algorithms for the generalized eigenvalue problem. Structure-preserving pole-swapping algorithms for the palindromic and alternating eigenvalue problems, which arise in control theory, are derived. A refinement step that guarantees backward stability of the algorithms is included. This refinement can also be applied to bulge-chasing alg...... hiện toàn bộ
Overdetermined Strata for Degree 5 Hyperbolic Polynomials
Vietnam Journal of Mathematics - Tập 43 Số 1 - Trang 139-150 - 2015
Hayssam, Ezzaldine, Houssam, Khalil, Mouhamad, Sarrage, Mouhamad, Hossein
In the present paper, we consider degree 5 hyperbolic polynomials (HPs) in one variable (i.e., real and with all roots real). We are interested in such HPs whose number of equalities between roots of the polynomial and its derivatives is greater or equal to 4. We give a new method, based on resultants and subresultants, to calculate the overdetermined strata for degree 5 hyperbolic polynomials.
On Risk-Averse Stochastic Semidefinite Programs with Continuous Recourse
Vietnam Journal of Mathematics - Tập 47 - Trang 865-879 - 2019
Matthias Claus, Rüdiger Schultz, Kai Spürkel, Tobias Wollenberg
The vast majority of the literature on stochastic semidefinite programs (stochastic SDPs) with recourse is concerned with risk-neutral models. In this paper, we introduce mean-risk models for stochastic SDPs and study structural properties as convexity and (Lipschitz) continuity. Special emphasis is placed on stability with respect to changes of the underlying probability distribution. Perturbatio...... hiện toàn bộ
Partial Theta Function and Separation in Modulus Property of its Zeros
Vietnam Journal of Mathematics - Tập 48 - Trang 145-157 - 2020
Vladimir Petrov Kostov
We consider the partial theta function $\theta (q,z):={\sum }_{j=0}^{\infty }q^{j(j+1)/2}z^{j}$, where $z\in \mathbb {C}$ is a variable and $q\in \mathbb {C}$, 0 < |q| < 1, is a parameter. Set $D(a):=\{q\in \mathbb {C}, 0<|q|\leq a,$$\arg (q)\in [\pi /2,3\pi /2]\}$. We show that for $k\in \mathbb {N}$ and q ∈ D(0.55), there exists exactly one zero of θ(q,⋅) (which is a simple one) in the open annu...... hiện toàn bộ
On Mathematical and Numerical Modelling of Multiphysics Wave Propagation with Polytopal Discontinuous Galerkin Methods: a Review
Vietnam Journal of Mathematics - Tập 50 - Trang 997-1028 - 2022
Paola F. Antonietti, Michele Botti, Ilario Mazzieri
In this work we review discontinuous Galerkin finite element methods on polytopal grids (PolydG) for the numerical simulation of multiphysics wave propagation phenomena in heterogeneous media. In particular, we address wave phenomena in elastic, poro-elastic, and poro-elasto-acoustic materials. Wave propagation is modeled by using either the elastodynamics equation in the elastic domain, the acous...... hiện toàn bộ
t-Dual Baer Modules and t-Lifting Modules
Vietnam Journal of Mathematics - Tập 42 - Trang 159-169 - 2013
Tayyebeh Amouzegar, Derya Keskin Tütüncü, Yahya Talebi
We introduce the notions of t-lifting modules and t-dual Baer modules, which are generalizations of lifting modules. It is shown that an amply supplemented module M is t-lifting if and only if M is t-dual Baer and a t- $\mathcal{K}$ -module. We also prove that, over a right perfect ring R, every noncosingu...... hiện toàn bộ
Tổng số: 452   
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