829 research outputs found
Advanced architectural descriptors in foams: novel 3D computational methods
This work presents 3D computational strategies aimed at providing foam de-structuration of the basic components of a cellular material (struts and cell walls) offering the possibility of analysing separately the structural elements that play an important role in the physical properties of thee materials. Two different methodologies have been used depending on the topological similarities existing between the struts and cell walls: 3D erosion-dilation procedure (thick struts) and solid classification algorithm (thin struts). In a second step, analysis of cell walls is performed in order to show the advantages of analysing separately the two foams components. Particularly, cell wall thickness distribution reveals differences that could not be found prior to the de-structuration
Detecting series periodicity with horizontal visibility graphs
The horizontal visibility algorithm has been recently introduced as a mapping
between time series and networks. The challenge lies in characterizing the
structure of time series (and the processes that generated those series) using
the powerful tools of graph theory. Recent works have shown that the visibility
graphs inherit several degrees of correlations from their associated series,
and therefore such graph theoretical characterization is in principle possible.
However, both the mathematical grounding of this promising theory and its
applications are on its infancy. Following this line, here we address the
question of detecting hidden periodicity in series polluted with a certain
amount of noise. We first put forward some generic properties of horizontal
visibility graphs which allow us to define a (graph theoretical) noise
reduction filter. Accordingly, we evaluate its performance for the task of
calculating the period of noisy periodic signals, and compare our results with
standard time domain (autocorrelation) methods. Finally, potentials,
limitations and applications are discussed.Comment: To be published in International Journal of Bifurcation and Chao
El lenguaje científico, la divulgación de la ciencia y el riesgo de las pseudociencias
El lenguaje de la ciencia, al igual que los lenguajes técnicos, se caracteriza
por su especificidad. En él palabras de uso común 'englobadas en el grupo comunidad científica del resto de la sociedad. No debe pues sorprendernos que
el lenguaje científico especializado sea, en no pocas ocasiones, utilizado por
algunos científicos 'aquéllos que por el hecho de ser científicos se consideran
parte de una élite intelectual' como una suerte de muralla comunicativa, que
los mantiene a una distancia 'prudencial' de los profanos y los diferencia del
resto de los ciudadanos.
Afortunadamente estos científicos son en la actualidad una minoría, ya que
la mayoría entiende que la ciencia debe, ante todo, establecer una relación fluida
con la sociedad. Y aquí es donde entra en juego la divulgación de la ciencia.
Para que la ciencia pueda llegar a la sociedad en su más amplia extensión, y
para que pueda ser entendible y aceptada, debe apostar por desprenderse, al
menos en parte, de esa incomprensible jerga científica para adoptar un lenguaje
más cercano y cotidiano. Pero todo esto colisiona con una corriente opuesta: la
adopción por parte de las llamadas 'pseudociencias', como la homeopatía, la
osteopatía, o el psicoanálisis de un lenguaje deliberadamente opaco que imita al
científico, precisamente con el fin de revestirse de una pátina de respetabilidad,
al modo de las ciencias básicas, e incluso para 'protegerse', dificultando el
acceso y la comprensión del público general hacia ellas.
del vocabulario denominado general' aparecen con significados concretos,
en muchas ocasiones diferentes de los que se dan en el discurso cotidiano o
general. El discurso científico se caracteriza además por contar con un gran
porcentaje relativo de vocabulario específico y exclusivo de este discurso. Esto
hace que el lenguaje científico pueda reflejar cierta opacidad, particularmente
ante la gente ajena a su uso; lo cual crea una barrera que, en la práctica, aísla a laScientific language is characterized by its specific characteristics. Common
general words appear here with specific meanings, frequently different from
the ones used in the daily language. Scientific discourse is also characterized
by the great relative amount of specific vocabulary, exclusive of this discourse.
This makes scientific language to reflect a certain degree of opacity, particularly
to people alien to its use; this in turn creates a sort of barrier which in practice
isolates the scientific community from the rest of society. It is no surprise
that specialized scientific language is often employed by some scientists
'those who believe themselves to be a part of an intellectual élite' as a sort
of communicative barrier, which keeps them at a 'prudential' distance away
from the laypersons and distinguishes them from the rest of people.
Fortunately these elitist scientists are nowadays a minority, for most of
them understand that science must, above all, establish a fluid relationship
with society. And here comes popularization of science. For science to reach
society in its widest extension, and to be understandable, it must get rid of
this incomprehensible scientific jargon in order to adopt a closer and more
quotidian language. All this collides with an opposite trend: the adoption by
the 'pseudo-sciences', such as homeopathy, osteopathy, or psychoanalysis, of a deliberately opaque language which imitates scientific language with the
sole aim of arm these pseudo-sciences with a patina of respectability, which
serves to protect themselves hence hindering the access to them and the
comprehension of the general public
Incongruencias o descuidos científicos. ¿Un recurso literario en la ciencia ficción o en la literatura fantástica?
Mobile Ubiquity:Understanding the Relationship between Cognitive Absorption, Smartphone Addiction and Social Network Services
Spin-texture topology in curved circuits driven by spin-orbit interactions
Interferometry is a powerful technique used to extract valuable information
about the wave function of a system. In this work, we study the response of
spin carriers to the effective field textures developed in curved
one-dimensional interferometric circuits subject to the joint action of Rashba
and Dresselhaus spin-orbit interactions. By using a quantum network technique,
we establish that the interplay between these two non-Abelian fields and the
circuit's geometry modify the geometrical characteristics of the spinors,
particularly on square circuits, leading to the localisation of the electronic
wave function and the suppression of the quantum conductance. We propose a
topological interpretation by classifying the corresponding spin textures in
terms of winding numbers.Comment: 13 pages, 9 figure
Rapid Decreasing in the Orbital Period of the Detached White Dwarf?main Sequence Binary SDSS J143547.87+373338.5
SDSS J143547.87+373338.5 is a detached eclipsing binary that contains a white dwarf with a mass of 0.5 M⊙ and a fully convective star with a mass of 0.21 M⊙. The eclipsing binary was monitored photometrically from 2009 March 24 to 2015 April 10, by using two 2.4-m telescopes in China and in Thailand. The changes in the orbital period are analyzed based on eight newly determined eclipse times together with those compiled from the literature. It is found that the observed?calculated (O?C) diagram shows a downward parabolic change that reveals a continuous period decrease at a rate of dot{P}=-8.04× {10}-11 s s‑1. According to the standard theory of cataclysmic variables, angular momentum loss (AML) via magnetic braking (MB) is stopped for fully convective stars. However, this period decrease is too large to be caused by AML via gravitational radiation (GR), indicating that there could be some extra source of AML beyond GR, but the predicted mass-loss rates from MB seem unrealistically large. The other possibility is that the O?C diagram may show a cyclic oscillation with a period of 7.72 years and a small amplitude of 0.ͩ000525. The cyclic change can be explained as the light-travel-time effect via the presence of a third body because the required energy for the magnetic activity cycle is much larger than that radiated from the secondary in a whole cycle. The mass of the potential third body is determined to be {M}3{sin}{i}prime =0.0189(+/- 0.0016) M⊙ when a total mass of 0.71 M⊙ for SDSS J143547.87+373338.5 is adopted. For orbital inclinations {i}prime ≥slant 15uildrel{circ}over{.} 9, it would be below the stable hydrogen-burning limit of M3 ∼ 0.072 M⊙, and thus the third body would be a brown dwarf.Fil: Qian, S. B.. Chinese Academy of Sciences; República de ChinaFil: Han, Z. T.. Chinese Academy of Sciences; República de ChinaFil: Soonthornthum, B.. National Astronomical Research Institute of Thailand; TailandiaFil: Zhu, L. Y.. Chinese Academy of Sciences; República de ChinaFil: He, J. J.. Chinese Academy of Sciences; República de ChinaFil: Rattanasoon, S.. National Astronomical Research Institute of Thailand; TailandiaFil: Aukkaravittayapun, S.. National Astronomical Research Institute of Thailand; TailandiaFil: Liao, W. P.. Chinese Academy of Sciences; República de ChinaFil: Zhao, E. G.. Chinese Academy of Sciences; República de ChinaFil: Zhang, J.. Chinese Academy of Sciences; República de ChinaFil: Fernandez Lajus, Eduardo Eusebio. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica la Plata; Argentin
A modified equation analysis for immersed boundary methods based on volume penalization: applications to linear advection-diffusion and high-order discontinuous Galerkin schemes
The Immersed Boundary Method (IBM) is a popular numerical approach to impose
boundary conditions without relying on body-fitted grids, thus reducing the
costly effort of mesh generation. To obtain enhanced accuracy, IBM can be
combined with high-order methods (e.g., discontinuous Galerkin). For this
combination to be effective, an analysis of the numerical errors is essential.
In this work, we apply, for the first time, a modified equation analysis to the
combination of IBM (based on volume penalization) and high-order methods (based
on nodal discontinuous Galerkin methods) to analyze a priori numerical errors
and obtain practical guidelines on the selection of IBM parameters. The
analysis is performed on a linear advection-diffusion equation with Dirichlet
boundary conditions. Three ways to penalize the immerse boundary are
considered, the first penalizes the solution inside the IBM region (classic
approach), whilst the second and third penalize the first and second
derivatives of the solution. We find optimal combinations of the penalization
parameters, including the first and second penalizing derivatives, resulting in
minimum errors. We validate the theoretical analysis with numerical experiments
for one- and two-dimensional advection-diffusion equations
Erigeron cabelloi A. Pujadas, R. García-Salmones & E. López (Asteraceae) a new species from the Pyrennees
Erigeron cabelloi A. Pujadas, R. García-Salmones & E. López (Asteraceae) a new species from the Pyrennees. Palabras clave. Andorra, Compositae, Corología, Erigeron neglectus, Flora Ibérica. Key words. Andorra, Chorology, Compositae, Erigeron neglectus, Iberian Flora
A charge-coupled device photometric study of south hemispheric contact binary AE Phoenicis
The complete charge-coupled device light curves in B, V, R, and I bands of the short-period binary system, AE Phe, are presented. It is found that the light curves of AE Phe belong to typical EW-type light variation. Photometric solutions were derived by using the 2003 version of the Wilson–Devinney code. It showed that AE Phe is a Wsubtype shallow-contact system (f = 14.6%(±0.5%)) with a mass ratio of q = 2.5491(±0.0092). The temperature difference between the two components is 227 K. Analysis of the O − C curve suggests that the period of AE Phe shows a long-term continuous increase at a rate of dP /dt = +6.17(±0.44) × 10−8 days year−1. The longterm period increase, the marginal-contact configuration, and the astrophysical parameters of the binary system, all suggest that it is a shallow-contact binary undergoing a thermal relaxation oscillation evolving into a detached binary.Fil: He, J. J.. Chinese Academy of Sciences; República de ChinaFil: Qian, S. B.. Chinese Academy of Sciences; República de ChinaFil: Fernandez Lajus, Eduardo Eusebio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Fariña, Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentin
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