4,514 research outputs found
Alignment of the central galaxies with the environment
In this work, we combine ellipticity and major axis position angle
measurements from the Sloan Digital Sky Server Data Release 16 (SDSS DR16) with
the group finder algorithm of Rodriguez \& Merch\'an to determine the alignment
of the central galaxies with the surrounding structures and satellite galaxies
lying in their group. We use two independent methods: A modified version of the
two-point cross-correlation function and the angle between the central galaxy
orientation and the satellite galaxies relative position. The first method
allows us to study the inner and outer regions of the cluster, while the second
method provides information within the halos. Our results show that central
galaxies present anysotropy in the correlation function up to , which becomes 10\% stronger for the brightest ones
(). When we split the galaxy sample by colour, we find that
red central galaxies are the main contributors to this anisotropy. We also show
that this behaviour does not depend on the group mass or central galaxy
ellipticity. Finally, our results are in agreement with previous findings,
showing that the two-point cross-correlation function is a best tracer of the
galaxy alignments using all galaxies and not only those of the group to which
it belongs. In addition, this feature allows us to explore the behaviour of the
alignment on larger scales.Comment: 10 pages, 9 figures, sent to MNRA
CMOS-3D smart imager architectures for feature detection
This paper reports a multi-layered smart image sensor architecture for feature extraction based on detection of interest points. The architecture is conceived for 3-D integrated circuit technologies consisting of two layers (tiers) plus memory. The top tier includes sensing and processing circuitry aimed to perform Gaussian filtering and generate Gaussian pyramids in fully concurrent way. The circuitry in this tier operates in mixed-signal domain. It embeds in-pixel correlated double sampling, a switched-capacitor network for Gaussian pyramid generation, analog memories and a comparator for in-pixel analog-to-digital conversion. This tier can be further split into two for improved resolution; one containing the sensors and another containing a capacitor per sensor plus the mixed-signal processing circuitry. Regarding the bottom tier, it embeds digital circuitry entitled for the calculation of Harris, Hessian, and difference-of-Gaussian detectors. The overall system can hence be configured by the user to detect interest points by using the algorithm out of these three better suited to practical applications. The paper describes the different kind of algorithms featured and the circuitry employed at top and bottom tiers. The Gaussian pyramid is implemented with a switched-capacitor network in less than 50 μs, outperforming more conventional solutions.Xunta de Galicia 10PXIB206037PRMinisterio de Ciencia e Innovación TEC2009-12686, IPT-2011-1625-430000Office of Naval Research N00014111031
Examining Retirement Housing Preferences Among International Retiree Migrants
Housing demand models based on individual consumers' utility function reflect preferences about the structure and lot, neighborhood, and location as related to socioeconomic characteristics of the occupants. As a growing proportion of aging residents in many countries are undertaking late life moves, their preferences will have an influence on destination housing markets. We examine the characteristics, attitudes and preferences about retirement housing among immigrant retirees currently living in traditional housing in a retirement destination in Alicante, Spain. Using results from a survey of German and British retirees living in the region, we find through logistic regression that preference for retirement housing is associated with aging and gaining access to in-home support services.Housing preferences; Demographic trends; Seniors housing
Measuring the Terminal Heights of Bolides to Understand the Atmospheric Flight of Large Asteroidal Fragments
The extent of penetration into the Earth's atmosphere of a meteoroid is defined by the point where its kinetic energy is no longer sufficient to produce luminosity. For most of the cases this is the point where the meteoroid disintegrates in the atmosphere due to ablation process and dynamic pressure during flight. However, some of these bodies have particular physical properties (bigger size, higher bulk strength, etc.) or favorable flight conditions (lower entry velocity or/and a convenient trajectory slope, etc.) that allow them to become a meteorite-dropper and reach the ground. In both cases, we define the end of the luminous path of the trajectory as the terminal height or end height. Thus, the end point shows the amount of deceleration till the final braking. We thus assume that the ability of a fireball to produce meteorites is directly related to its terminal height. Previous studies have discussed the likely relationship between fireball atmospheric flight properties and the terminal height. Most of these studies require the knowledge of a set of properties and physical variables which cannot be determined with sufficient accuracy from ground-based observations. The recently validated dimensionless methodology offers a new approach to this problem. All the unknowns can be reduced to only two parameters which are easily derived from observations. Despite the calculation of the analytic solution of the equations of motion is not trivial, some simplifications are admitted. Here, we describe the best performance range and the errors associated with these simplifications. We discuss how terminal heights depend on two or three variables that are easily retrieved from the recordings, provided at least three trajectory (h, v) points. Additionally, we review the importance of terminal heights, and the way they have been estimated in previous studies. Finally we discuss a new approach for calculating terminal heights.Peer reviewe
Anisotropic correlation functions as tracers of central galaxy alignments in simulations
Motivated by observational results, we use IllustrisTNG hydrodynamical
numerical simulations to study the alignment of the central galaxies in groups
with the surrounding structures. This approach allows us to analyse galaxy and
group properties not available in observations. To perform this analysis, we
use a modified version of the two-point cross-correlation function and a
measure of the angle between the semi-major axes of the central galaxies and
the larger structures. Overall, our results reproduce observational ones, as we
find large-scale anisotropy, which is dominated by the red central galaxies. In
addition, the latter is noticeably more aligned with their group than the blue
ones. In contrast to the observations, we find a strong dependence of the
anisotropy on the central galaxy with mass, probably associated with the
inability of observational methods to determine them. This result allows us to
link the alignment to the process of halo assembly and the well-known
dependence of halo anisotropy on mass. When we include the dark matter
distribution in our analysis, we conclude that the galaxy alignment found in
simulations (and observations) can be explained by a combination of physical
processes at different scales: the central galaxy aligns with the dark matter
halo it inhabits, and this, in turn, aligns with the surrounding structures at
large scales.Comment: 9 pages, 11 figures, Accepted by MNRA
Montera: A Framework for Efficient Execution of Monte Carlo Codes on Grid Infrastructures
he objective of this work is to improve the performance of Monte Carlo codes on Grid production infrastructures. To do so, the codes and the grid sites are characterized with simple parameters to model their behaviors. Then, a new performance model for grid infrastructures is proposed, and an algorithm that employs this information is described. This algorithm dynamically calculates the number and size of tasks to execute on each site to maximize the performance and reduce makespan. Finally, a newly developed framework called Montera is presented. Montera deals with the execution of Monte Carlo codes in an unattended way, isolating the complexity of the problem from the final user. By employing two fusion Monte Carlo codes as example cases, along with the described characterizations and scheduling algorithm, a performance improvement up to 650 % over current best results is obtained on a real production infrastructure, together with enhanced stability and robustness
Molecular simulation of methane hydrate growth confined into a silica pore
Financiaciado para publicación en acceso aberto: Universidade de Vigo/CISUGThe growth of a methane hydrate seed within a silica slit pore of fixed width has been studied using All-
Atom Molecular Dynamics (AA-MD). An AA force field has been used to describe the molecules of the
solid silica substrate, with a-quartz crystalline structure. The crystallisation of hydrates in confined
geometries is not well understood yet, and the objective of this work is to study the hydrate growth
inside a silica pore using molecular simulation. Both NVT and NpT ensembles were used in the AA-MD
simulations to analyse the hydrate growth from an initial seed. Results showed that the boundary conditions
imposed by the nanometric slit pore yielded a hydrate with structural defects, filling the accessible
space between the silica walls. The water molecules which were not incorporated to the initial seed
hydrate formed a high density water layer trapped between the silica walls and the crystallised hydrate.
These results provide an interesting insight into the hydrate crystallisation process in confined geometries,
resembling those found in natural hydrate deposits.Ministerio de Ciencia e Innovación | Ref. PID2021-125081NB-I00FEDER | Ref. SOE2/P1/P0823Xunta de Galicia | Ref. FSE-GALICIA 2014–2020Fundação para a Ciência e a Tecnologia | Ref. UIDB/50011/2020Fundação para a Ciência e a Tecnologia | Ref. UIDP/50011/2020Fundação para a Ciência e a Tecnologia | Ref. LA/ P/0006/2020Ministerio de Ciencia e Innovación | Ref. PID2019-105898GA-C22Comunidad de Madrid | Ref. APOYOJOVENES- 01HQ1S-129-B5E4M
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