### Recent Submissions

• #### Graphs, friends and acquaintances ﻿

(Faculty of Mathematics and Natural SciencesInstitut Teknologi Bandung (ITB) IndonesiaIndonesian Combinatorial Society (InaCombS)GTA Research GroupGTA Research Group, 2018)
A graph is a mathematical object modeling the existence of a certain relation between pairs of elements of a given set. Many of the first results concerning graphs made reference to relationships between groups of people. ...
• #### Análisis de las actitudes y conocimientos estadísticos elementales en la formación del profesorado ﻿

Resumimos la tesis doctoral de Dña Assumpta Estrada Roca, dirigida por Carmen Batanero y Josep María Fortuny, y presentada en la Universidad Autónoma de Barcelona en septiembre de 2002, reflexionando sobre las implicaciones ...
• #### The Manhattan Product of Digraphs ﻿

(Indonesian Combinatorial Society (InaCombS); Graph Theory and Applications (GTA) Research Centre; University of Newcastle, Australia; Institut Teknologi Bandung (ITB), Indonesia, 2013)
We study the main properties of a new product of bipartite digraphs which we call Manhattan product. This product allows us to understand the subjacent product in the Manhattan street networks and can be used to built other ...
• #### The (∆,D) and (∆,N) problems in double-step digraphs with unilateral distance ﻿

(Indonesian Combinatorial Society (InaCombS); Graph Theory and Applications (GTA) Research Centre; University of Newcastle, Australia; Institut Teknologi Bandung (ITB), Indonesia, 2014)
We study the (Delta,D) and (Delta,N) problems for double-step digraphs considering the unilateral distance, which is the minimum between the distance in the digraph and the distance in its converse digraph, obtained by ...
• #### On Middle Cube Graphs ﻿

(Indonesian Combinatorial Society (InaCombS); Graph Theory and Applications (GTA) Research Centre; University of Newcastle, Australia; Institut Teknologi Bandung (ITB), Indonesia, 2015)
We study a family of graphs related to the $n$-cube. The middle cube graph of parameter k is the subgraph of $Q_{2k-1}$ induced by the set of vertices whose binary representation has either $k-1$ or $k$ number of ones. The ...
• #### The cubic polynomial differential systems with two circles as algebraic limit cycles ﻿

(Walter de Gruyter GmbH, 2018)
In this paper we characterize all cubic polynomial differential systems in the plane having two circles as invariant algebraic limit cycles.
• #### From Subkautz Digraphs to Cyclic Kautz Digraphs ﻿

(World Scientific Publishing, 2018)
Kautz digraphs K(d, l) are a well-known family of dense digraphs, widely studied as a good model for interconnection networks. Closely related with these, the cyclic Kautz digraphs CK(d, l) were recently introduced by ...
• #### A survey on the missing Moore graph ﻿

(Elsevier, 2019)
This is a survey on some known properties of the possible Moore graph (or graphs) ϒ with degree 57 and diameter 2. Moreover, we give some new results about it, such as the following. When we consider the distance partition ...
• #### A new general family of mixed graphs ﻿

(Elsevier, 2019)
A new general family of mixed graphs is presented, which generalizes both the pancake graphs and the cycle prefix digraphs. The obtained graphs are vertex transitive and, for some values of the parameters, they constitute ...
• #### A blow-up method to prove formal integrability for some planar differential systems ﻿

(Shanghai Normal University & Wilmington Scientific Publisher, 2018)
In this work we provide an effective method to prove the formal integrability of the resonant saddles. The method is based on the use of a blow-up and the resolution of a recurrence differential equation using induction. ...
• #### 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 ...
• #### Iterated line digraphs are asymptotically dense ﻿

(Elsevier, 2017)
We show that the line digraph technique, when iterated, provides dense digraphs, that is, with asymptotically large order for a given diameter (or with small diameter for a given order). This is a well-known result for ...
• #### The spectra of subKautz and cyclic Kautz digraphs ﻿

(Elsevier, 2017)
Kautz digraphs K(d, ) are a well-known family of dense digraphs, widely studied as a good model for interconnection networks. Closely related with these, the cyclic Kautz CK(d, ) and the subKautz sK(d, 2) digraphs were ...
• #### An algebraic approach to lifts of digraphs ﻿

(Elsevier, 2018)
We present some applications of a new matrix approach for studying the properties of the lift of a voltage digraph, which has arcs weighted by the elements of a group. As a main result, when the involved group is Abelian, ...
• #### Integrable zero-Hopf singularities and 3-dimensional centers ﻿

(2018-01-25)
In this paper we show that the well-known Poincaré-Lyapunov nondegenerate analytic center problem in the plane and its higher dimensional version expressed as the 3-dimensional center problem at the zero-Hopf singularity ...
• #### On bipartite-mixed graphs ﻿

(Wiley, 2018-04-04)
Mixed graphs can be seen as digraphs that have both arcs and edges (or digons, that is, two opposite arcs). In this arti- cle, we consider the case where such graphs are bipartite. As main results, we show that in this ...
• #### 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 ...
• #### Cyclicity of polynomial nondegenerate centers on center manifolds ﻿

(Elsevier, 2018-11-09)
We consider polynomial families of ordinary differential equations on $\R^3$, parametrized by the admissible coefficients, for which the origin is an isolated singularity at which the linear part of the system has one ...
• #### Endorsement deduction and ranking in social networks ﻿

(Elsevier, 2016)
Some social networks, such as LinkedIn and ResearchGate, allow user endorsements for specific skills. In this way, for each skill we get a directed graph where the nodes correspond to users’ profiles and the arcs represent ...
• #### A Privacy-Preserving Pay-by-Phone Parking System ﻿

(Institute of Electrical and Electronics Engineers (IEEE), 2017)
Most cities around the world require drivers to pay for the time they occupy a parking spot. In this way, drivers are encouraged to shorten parking time so that other drivers are given a reasonable chance of finding ...