Search results for "Graph theory"

Topology, Matter, and Space, I: Topological Notions in 19th-Century Natural Philosophy

1998

L'A. montre l'impact de la topologie dans le developpement de la theorie dynamique des phenomenes physiques ainsi que les speculations de la structure topologique de l'espace

Groups with exactly one irreducible character of degree divisible byp

2014

Let [math] be a prime. We characterize those finite groups which have precisely one irreducible character of degree divisible by [math] .

Solving word problems algebraically in a spreadsheet environment in a primary school

2013

This paper presents some results from an investigation into the teaching of the algebraic solving of word problems in a spreadsheet environment in the sixth grade of primary school in Spain (11-12 year old pupils). The main aim of the study was to investigate whether the spreadsheet could be a mediator to the teaching of algebraic problem solving. Through the analysis of excerpts from a case study, the core of the paper is focused on two different types of the difficulties that students showed when solving problems algebraically in a spreadsheet environment.

Paths Coloring Algorithms in Mesh Networks

2003

In this paper, we will consider the problem of coloring directed paths on a mesh network. A natural application of this graph problem is WDM-routing in all-optical networks. Our main result is a simple 4-approximation algorithm for coloring line-column paths on a mesh. We also present sharper results when there is a restriction on the path lengths. Moreover, we show that these results can be extended to toroidal meshes and to line-column or column-line paths.

Improving the local vertex invariants in alkane graphs through a standard molecular orbital approach

2007

Abstract In this work, novel topological indices are introduced by the application of algorithms based on molecular orbital theory. Actually, the novel indices are obtained by computing new values of the local vertex invariants (LOVIs) in alkane graphs. The most significant result is the dramatic increase in the predictive capability achieved with the topological charge indices weighted according the new LOVIs’ values in the prediction of four key properties in the set of octane isomers, namely heat of atomization, molar refraction, heat of vaporization and boiling point.

GRASP with exterior path-relinking and restricted local search for the multidimensional two-way number partitioning problem

2017

In this work, we tackle multidimensional two-way number partitioning (MDTWNP) problem by combining GRASP with Exterior Path Relinking. In the last few years, the combination of GRASP with path relinking (PR) has emerged as a highly effective tool for finding high-quality solutions for several difficult problems in reasonable computational time. However, in most of the cases, this hybridisation is limited to the variant known as interior PR. Here, we couple GRASP with the "exterior form" of path relinking and perform extensive experimentation to evaluate this variant. In addition, we enhance our GRASP with PR method with a novel local search method specially designed for the MDTWNP problem. …

Linear and cyclic radio k-labelings of trees

2007

International audience; Motivated by problems in radio channel assignments, we consider radio k-labelings of graphs. For a connected graph G and an integer k ≥ 1, a linear radio k-labeling of G is an assignment f of nonnegative integers to the vertices of G such that |f(x)−f(y)| ≥ k+1−dG(x,y), for any two distinct vertices x and y, where dG(x,y) is the distance between x and y in G. A cyclic k-labeling of G is defined analogously by using the cyclic metric on the labels. In both cases, we are interested in minimizing the span of the labeling. The linear (cyclic, respectively) radio k-labeling number of G is the minimum span of a linear (cyclic, respectively) radio k-labeling of G. In this p…

Erratum to “Number of equilibrium states of piecewise monotonic maps of the interval”

1997

The Calderón problem for the fractional Schrödinger equation

2020

We show global uniqueness in an inverse problem for the fractional Schr\"odinger equation: an unknown potential in a bounded domain is uniquely determined by exterior measurements of solutions. We also show global uniqueness in the partial data problem where the measurements are taken in arbitrary open, possibly disjoint, subsets of the exterior. The results apply in any dimension $\geq 2$ and are based on a strong approximation property of the fractional equation that extends earlier work. This special feature of the nonlocal equation renders the analysis of related inverse problems radically different from the traditional Calder\'on problem.

Updating the orbital ephemeris of the dipping source XB 1254-690 and the distance to the source

2017

XB 1254-690 is a dipping low mass X-ray binary system hosting a neutron star and showing type I X-ray bursts. We aim at obtaining more accurate orbital ephemeris and at constraining the orbital period derivative of the system for the first time. In addition, we want to better constrain the distance to the source in order to locate the system in a well defined evolutive scenario. We apply for the first time an orbital timing technique to XB 1254-690, using the arrival times of the dips present in the light curves that have been collected during 26 years of X-ray pointed observations performed from different space missions. We estimate the dip arrival times using a statistical method that wei…