597 research outputs found
Essential Constraints of Edge-Constrained Proximity Graphs
Given a plane forest of points, we find the minimum
set of edges such that the edge-constrained minimum spanning
tree over the set of vertices and the set of constraints contains .
We present an -time algorithm that solves this problem. We
generalize this to other proximity graphs in the constraint setting, such as
the relative neighbourhood graph, Gabriel graph, -skeleton and Delaunay
triangulation. We present an algorithm that identifies the minimum set
of edges of a given plane graph such that for , where is the
constraint -skeleton over the set of vertices and the set of
constraints. The running time of our algorithm is , provided that the
constrained Delaunay triangulation of is given.Comment: 24 pages, 22 figures. A preliminary version of this paper appeared in
the Proceedings of 27th International Workshop, IWOCA 2016, Helsinki,
Finland. It was published by Springer in the Lecture Notes in Computer
Science (LNCS) serie
Conformal Antenna Array for Millimeter-Wave Communications: Performance Evaluation
In this paper, we study the influence of the radius of a cylindrical
supporting structure on radiation properties of a conformal millimeter-wave
antenna array. Bent antenna array structures on cylindrical surfaces may have
important applications in future mobile devices. Small radii may be needed if
the antenna is printed on the edges of mobile devices and in items which human
beings are wearing, such as wrist watches, bracelets and rings. The antenna
under study consists of four linear series-fed arrays of four patch elements
and is operating at 58.8 GHz with linear polarization. The antenna array is
fabricated on polytetrafluoroethylene substrate with thickness of 0.127 mm due
to its good plasticity properties and low losses. Results for both planar and
conformal antenna arrays show rather good agreement between simulation and
measurements. The results show that conformal antenna structures allow
achieving large angular coverage and may allow beam-steering implementations if
switches are used to select between different arrays around a cylindrical
supporting structure.Comment: Keywords: conformal antenna, millimeter-wave communications, patch
antenna array. 11 pages, 10 figures, 1 tabl
Histoire et modélisation des dynamiques socio-environnementales Holocènes des paysages fluviaux de la côte d'Azur
History and modelling of the socio-environmental dynamics of the fluvial landscapes of Côte-d'Azur (France) during the Holocene A research program was initiated in 2006 in order to reconstruct the evolution of the coastal hydrosystems of the rivers Argens (Var), Loup, Cagne and Malvan (Alpes-Maritimes) during the Holocene. The paper presents the archaeological and palaeoenvironmental data and the me thods used to apprehend the effects of the landscapes mobility over settlement patterns, and the impact of human occupation over the ecosystems.Un programme de recherches a été initié en 2006 afin de retracer l'évolution des hydrosystèmes côtiers de l'Argens (Var), du Lou p, de la Cagne et du Malvan (Alpes-Maritimes) au cours de l'Holocène. L'article présente les données archéologiques et paléoenvironnementales mobilisées et les méthodes mises en œuvre pour appréhender les répercussions de la mobilité de ces paysages sur le peuplement et l'impact de l'occupation humaine sur les écosystème
Evaluating Signs of Determinants Using Single-Precision Arithmetic
We propose a method of evaluating signs of 2×2 and 3×3 determinants with b-bit integer entries using only b and (b + 1)-bit arithmetic, respectively. This algorithm has numerous applications in geometric computation and provides a general and practical approach to robustness. The algorithm has been implemented and compared with other exact computation methods
Strain and correlation of self-organized Ge_(1-x)Mn_x nanocolumns embedded in Ge (001)
We report on the structural properties of Ge_(1-x)Mn_x layers grown by
molecular beam epitaxy. In these layers, nanocolumns with a high Mn content are
embedded in an almost-pure Ge matrix. We have used grazing-incidence X-ray
scattering, atomic force and transmission electron microscopy to study the
structural properties of the columns. We demonstrate how the elastic
deformation of the matrix (as calculated using atomistic simulations) around
the columns, as well as the average inter-column distance can account for the
shape of the diffusion around Bragg peaks.Comment: 9 pages, 7 figure
Structural and paramagnetic properties of dilute Ga1-xMnxN
Systematic investigations of the structural and magnetic properties of single
crystal (Ga,Mn)N films grown by metal organic vapor phase epitaxy are
presented. High resolution transmission electron microscopy, synchrotron x-ray
diffraction, and extended x-ray absorption fine structure studies do not reveal
any crystallographic phase separation and indicate that Mn occupies
Ga-substitutional sites in the Mn concentration range up to 1%. The magnetic
properties as a function of temperature, magnetic field and its orientation
with respect to the c-axis of the wurtzite structure can be quantitatively
described by the paramagnetic theory of an ensemble of non-interacting
Mn ions in the relevant crystal field, a conclusion consistent with the
x-ray absorption near edge structure analysis. A negligible contribution of Mn
in the 2+ charge state points to a low concentration of residual donors in the
studied films. Studies on modulation doped p-type (Ga,Mn)N/(Ga,Al)N:Mg
heterostructures do not reproduce the high temperature robust ferromagnetism
reported recently for this system.Comment: 15 pages, 14 figure
Tournaments and Even Graphs are Equinumerous
A graph is called \emph{odd} if there is an orientation of its edges and an
automorphism that reverses the sense of an odd number of its edges, and
\emph{even} otherwise. Pontus von Br\"omssen (n\'e Andersson) showed that the
existence of such an automorphism is independent of the orientation, and
considered the question of counting pairwise non-isomorphic even graphs. Based
on computational evidence, he made the rather surprising conjecture that the
number of pairwise non-isomorphic \emph{even graphs} on vertices is equal
to the number of pairwise non-isomorphic \emph{tournaments} on vertices. We
prove this conjecture using a counting argument with several applications of
the Cauchy-Frobenius Theorem
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