Browsing Articles publicats (Matemàtica) by Title
Now showing items 162-181 of 259
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Magic coverings and the Kronecker product
(2014)In this paper we study a relationship existing among (super) magic coverings and the well known Kronecker product of matrices. We also introduce the concept of Zn-property for digraphs in order to study this relation ... -
Mixed Moore Cayley graphs
(Elsevier, 2014-09-01)Cayley graphs are well known objects with interesting properties, also in the context of Moore graphs and digraphs. In $1978$ Bos\'ak extended Moore's property to the mixed setting (with arcs allowed along with edges), in ... -
Mobile terrestrial laser scanner applications in precision fruticulture/ horticulture and tools to extract information from canopy point clouds
(Springer Science+Business Media, 2017-01-01)LiDAR sensors are widely used in many areas and, in recent years, that includes agricultural tasks. In this work, a self-developed mobile terrestrial laser scanner based on a 2D light detection and ranging (LiDAR) sensor ... -
Modeling tactical planning decisions through a linear optimization model in sow farms
(Elsevier, 2012)This paper deals with tactical planning decisions for breeding farms producing piglets through a linear optimization model. A medium-term planning horizon based on weekly periods is considered. The proposed model maximizes ... -
Modeling the consequences of the demise and potential recovery of a keystone-species: wild rabbits and avian scavengers in Mediterranean landscapes
(Nature Publishing Group, 2015)Restoration of demised keystone-species populations is an overriding concern in conservation biology. However, since no population is independent of its environment, progress is needed in predicting the efficacy of restoration ... -
Modelling the effects of sanitary policies on European vulture conservation
(Nature Publishing Group, 2012)Biodiversity losses are increasing as a consequence of negative anthropogenic effects on ecosystem dynamics. However, the magnitude and complexity of these effects may still be greatly underestimated. Most Old World ... -
New Moore-Like Bounds and Some Optimal Families of Abelian Cayley Mixed Graphs
(2020-06-06)Mixed graphs can be seen as digraphs that have both arcs and edges (or digons, that is, two opposite arcs). In this paper, we consider the case where such graphs are Cayley graphs of abelian groups. Such groups can be ... -
New problems related to the valences of (super) edge-magic labelings
(2013)A graph G of order p and size q is edge-magic if there is a bijective function f : V (G) ∪ E(G) −→ {i} p+q i=1 such that f(x) + f(xy) + f(y) = k , for all xy ∈ E(G) . The function f is an edge-magic labeling of G and the ... -
Nilpotent centres via inverse integrating factors
(Cambridge University Press, 2016-10)In this paper we are interested in the nilpotent center problem of planar analytic monodromic vector fields. It is known that the formal integrability is not enough to characterize such centers. More general objects are ... -
Non existence of almost Moore digraphs of diameter three
(Electronic Journal of Combinatorics, 2008)Almost Moore digraphs appear in the context of the degree/diameter problem as a class of extremal directed graphs, in the sense that their order is one less than the unattainable Moore bound M(d; k) = 1 + d + + dk, where ... -
Non-existence of limit cycles for planar vector fields
(Texas State University. Department of Mathematics, 2014)This article presents sufficient conditions for the non-existence of limit cycles for planar vector fields. Classical methods for the nonexistence of limit cycles are connected with the theory developed here. -
Non-smooth quadratic centers defined in two arbitrary sectors
(Elsevier, 2016-11-25)In this paper we analyze the center-focus problem of some families of piecewise planar quadratic vector fields on two zones of R2. The zones we consider are two unbounded sectors defined by an arbitrary angle α and a fixed ... -
Nondegenerate centers for Abel polynomial differential equations of second kind
(Elsevier, 2017)In this paper we study the center problem for Abel polynomial differential equations of second kind. Computing the focal values and using modular arithmetics and Gröbner bases we find the center conditions for such systems ... -
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 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 ... -
On mixed almost Moore graphs of diameter two
(Electronic Journal of Combinatorics, 2016-04-01)Mixed almost Moore graphs appear in the context of the Degree/Diameter problem as a class of extremal mixed graphs, in the sense that their order is one less than the Moore bound for mixed graphs. The problem of their ... -
On super edge-magic decomposable graphs
(Springer, 2012)Let G be any graph and let {Hi}i∈I be a family of graphs such that E(Hi) ∩ E(Hj ) = ∅ when i 6= j, ∪i∈IE(Hi) = E(G) and E(Hi) 6= ∅ for all i ∈ I. In this paper we introduce the concept of {Hi}i∈I -super edge-magic decomposable ... -
On the ℓ-adic valuation of the cardinality of elliptic curves over finite extensions of Fq
(Springer Verlag, 2015)Let E be an elliptic curve defined over a finite field Fq of odd characteristic. Let l≠2 be a prime number different from the characteristic and dividing #E(Fq). We describe how the l-adic valuation of the number of points ... -
On the beta-number of forests with isomorphic components
(De Gruyter Open, 2018)The beta-number, β (G), of a graph G is defined to be either the smallest positive integer n for which there exists an injective function f : V (G) → {0, 1, . . . , n} such that each uv ∈ E (G) is labeled |f (u) − f (v)| ... -
On the center conditions for analytic monodromic degenerate singularities
(World Scientific Publishing, 2012)In this paper we present two methods for detecting centers of monodromic degenerate singularities of planar analytic vector fields. These methods use auxiliary symmetric vector fields can be applied independently that the ...