Now showing items 184-203 of 259

• #### On the Integrability of Liénard systems with a strong saddle ﻿

(Elsevier, 2017)
We study the local analytic integrability for real Li\'{e}nard systems, $\dot x=y-F(x),$ $\dot y= x$, with $F(0)=0$ but $F'(0)\ne0,$ which implies that it has a strong saddle at the origin. First we prove that this problem ...
• #### On the multiple zeros of a real analytic function with applications to the averaging theory of differential equations ﻿

(IOP Publishing, 2018-11-21)
In this work we consider real analytic functions $d(z,\la,\e)$, where $d : \Omega \times \mathbb{R}^p \times I \to \Omega$, $\Omega$ is a bounded open subset of $\R$, $I \subset \mathbb{R}$ is an interval containing the ...
• #### On the origin of the deflection of light ﻿

(Elsevier, 2008)
Action at distance in Newtonian physics is replaced by finite propagation speeds in classical post–Newtonian physics. As a result, the differential equations of motion in Newtonian physics are replaced by functional ...
• #### On the origin of the inertia: the modified Newtonian dynamics theory ﻿

(Elsevier, 2009)
The sameness between the inertial mass and the gravitational mass is an assumption and not a consequence of the equivalent principle is shown. In the context of the Sciama’s inertia theory, the sameness between the inertial ...
• #### On the periodic orbit bifurcating from a Hopf bifurcation in systems with two slow and one fast variables ﻿

(Elsevier, 2014)
The Hopf bifurcation in slow-fast systems with two slow variables and one fast variable has been studied recently, mainly from a numerical point of view. Our goal is to provide an analytic proof of the existence of the ...
• #### On the planar integrable differential systems ﻿

(Springer Verlag, 2011)
Under very general assumptions we prove that the planar differential systems having a first integral are essentially the linear differential systems u˙ = u, ˙v = v. Additionally such systems always have a Lie symmetry. We ...
• #### On the Randić index of graphs ﻿

(Elsevier, 2018-09-11)
For a given graph G = (V, E), the degree mean rate of an edge uv ∈ E is a half of the quotient between the geometric and arithmetic means of its end-vertex degrees d(u) and d(v). In this note, we derive tight bounds for ...
• #### On Vosperian and Superconnected Vertex-Transitive Digraphs ﻿

(Springer, 2013)
We investigate the structure of a digraph having a transitive automorphism group where every cutset of minimal cardinality consists of all successors or all predecessors of some vertex. We give a complete characterization ...
• #### Open problems involving super edge-magic labelings and related topics ﻿

(Institute of Combinatorics and its Applications, 2012)
Graph labelings has experimented a fast development during the last four decades. Two books dedicated to this topic, a very complete survey on the subject and over 1000 papers in the literature constitute a good proof of ...
• #### Optimizing the enzymatic elimination of clogging of a microfiltration membrane by Parellada grape cake ﻿

(Wiley, 2016)
Clogging of the filtration membranes is one of the main problems in the process of obtaining grape must for white wine; therefore, clogging must be reduced to the maximum. The aim of this work was to find the optimal values ...
• #### Perfect (super) Edge-Magic Crowns ﻿

(Springer, 2017)
A graph G is called edge-magic if there is a bijective function f from the set of vertices and edges to the set {1,2, ,|V(G)|+|E(G)|} such that the sum f(x)+f(xy)+f(y) for any xy in E(G) is constant. Such a function is ...
• #### Period annulus of the harmonic oscillator with zero cyclicity under perturbations with a homogeneous polynomial field ﻿

(Bolyai Institute. University of SzegedHungarian Academy of Sciences, 2019-01-14)
In this work we prove, using averaging theory at any order in the small perturbation parameter, that the period annulus of the harmonic oscillator has cyclicity zero (no limit cycles bifurcate) when it is perturbed by any ...
• #### Periodic orbits in Hyperchaotic Chen systems ﻿

(Texas State University, 2015)
In this work, we show a zero-Hopf bifurcation in a Hyperchaotic Chen system. Using averaging theory, we prove the existence of two periodic orbits bifurcating from the zero-Hopf equilibria located at the origin of ...
• #### Periodic solutions for nonlinear differential systems: the second order bifurcation function ﻿

(Nicolaus Copernicus University in Torun, Juliusz Schauder Centre for Nonlinear Studies, 2014)
We are concerned here with the classical problem of Poincaré of persistence of periodic solutions under small perturbations. The main contribution of this work is to give the expression of the second order bifurcation ...
• #### Perturbed rank 2 Poisson systems and periodic orbits on Casimir invariant manifolds ﻿

(Taylor & Francis, 2020-02-05)
A class of n-dimensional Poisson systems reducible to an unperturbed harmonic oscillator shall be considered. In such case, perturbations leaving invariant a given symplectic leaf shall be investigated. Our purpose will ...
• #### Polynomial and rational first integrals for planar homogeneous polynomial differential systems ﻿

(Universitat Autònoma de Barcelona, 2014)
In this paper we find necessary and suficient conditions in order that a planar homogeneous polynomial differential system has a polynomial or rational first integral. We apply these conditions to linear and quadratic ...
• #### Polynomial and rational first integrals for planar quasi-homogeneous polynomial differential systems ﻿

(American Institute of Mathematical Sciences, 2013-10)
In this paper we find necessary and sufficient conditions in order that a planar quasi-homogeneous polynomial differential system has a polynomial or a rational first integral. We also prove that any planar quasi-homogeneous ...
• #### Population Dynamics P system (PDP) models: a standarized protocol for describing and applying novel bio-inspires computing tools ﻿

(Public Library of Science (PLoS), 2013)
Today, the volume of data and knowledge of processes necessitates more complex models that integrate all available information. This handicap has been solved thanks to the technological advances in both software and hardware. ...
• #### Properties of mixed Moore graphs of directed degree one ﻿

(Elsevier, 2015-04-01)
Mixed graphs of order n such that for any pair of vertices there is a unique trail of length at most k between them are known as mixed Moore graphs. These extremal graphs may only exist for diameter k = 2 and certain ...
• #### Rainbow eulerian multidigraphs and the product of cycles ﻿

(DMTCS, 2016)
An arc colored eulerian multidigraph with $l$ colors is rainbow eulerian if there is an eulerian circuit in which a sequence of $l$ colors repeats. The digraph product that refers the title was introduced by Figueroa-Centeno ...