1,730 research outputs found
Magnetic polarons in Ca_(1-x)Y_xMnO_3
Experimental evidence show that in the magnetoresistive manganite Ca_(1-x)
Y_xMnO_3, ferromagnetic (FM) polarons arises in an antiferromagnetic (AF)
background, as a result of the doping with Yttrium. This hypothesis is
supported in this work by classical Monte Carlo (MC) calculations performed on
a model where FM Double Exchange (DE) and AF Superexhange (SE) compite.Comment: 3 pages, 3 figs, submitted to LAW3M conferenc
Nocturnal activity by the primarily diurnal Central American agouti (Dasyprocta punctata) in relation to environmental conditions, resource abundance and predation risk
An animal's fitness is in part based on its ability to manage the inherent risks (foraging costs, predation, exposure to disease) with the benefits (resource gain, access to mates, social interactions) of activity (Abrams 1991, Altizer et al. 2003, Lima & Bednekoff 1999, Rubenstein & Hohmann 1989, Wikelski et al. 2001). Thus, understanding an animal's pattern of activity is key to understanding behavioural and ecological processes. However, while numerous laboratory methodologies are available to continuously quantify activity over long periods of time, logistical difficulties have greatly hindered activity studies of animals in the field (DeCoursey 1990)
An efficient GPU version of the preconditioned GMRES method
[EN] In a large number of scientific applications, the solution of sparse linear systems is the stage that concentrates most of the computational effort. This situation has motivated the study and development of several iterative solvers, among which preconditioned Krylov subspace methods occupy a place of privilege. In a previous effort, we developed a GPU-aware version of the GMRES method included in ILUPACK, a package of solvers distinguished by its inverse-based multilevel ILU preconditioner. In this work, we study the performance of our previous proposal and integrate several enhancements in order to mitigate its principal bottlenecks. The numerical evaluation shows that our novel proposal can reach important run-time reductions.Aliaga, JI.; Dufrechou, E.; Ezzatti, P.; Quintana-Orti, ES. (2019). An efficient GPU version of the preconditioned GMRES method. The Journal of Supercomputing. 75(3):1455-1469. https://doi.org/10.1007/s11227-018-2658-1S14551469753Aliaga JI, Badia RM, Barreda M, Bollhöfer M, Dufrechou E, Ezzatti P, Quintana-Ortà ES (2016) Exploiting task and data parallelism in ILUPACK’s preconditioned CG solver on NUMA architectures and many-core accelerators. Parallel Comput 54:97–107Aliaga JI, Bollhöfer M, Dufrechou E, Ezzatti P, Quintana-Ortà ES (2016) A data-parallel ILUPACK for sparse general and symmetric indefinite linear systems. In: Lecture Notes in Computer Science, 14th Int. Workshop on Algorithms, Models and Tools for Parallel Computing on Heterogeneous Platforms—HeteroPar’16. SpringerAliaga JI, Bollhöfer M, MartÃn AF, Quintana-Ortà ES (2011) Exploiting thread-level parallelism in the iterative solution of sparse linear systems. Parallel Comput 37(3):183–202Aliaga JI, Bollhöfer M, MartÃn AF, Quintana-Ortà ES (2012) Parallelization of multilevel ILU preconditioners on distributed-memory multiprocessors. Appl Parallel Sci Comput LNCS 7133:162–172Aliaga JI, Dufrechou E, Ezzatti P, Quintana-Ortà ES (2018) Accelerating a preconditioned GMRES method in massively parallel processors. In: CMMSE 2018: Proceedings of the 18th International Conference on Mathematical Methods in Science and Engineering (2018)Bollhöfer M, Grote MJ, Schenk O (2009) Algebraic multilevel preconditioner for the Helmholtz equation in heterogeneous media. SIAM J Sci Comput 31(5):3781–3805Bollhöfer M, Saad Y (2006) Multilevel preconditioners constructed from inverse-based ILUs. SIAM J Sci Comput 27(5):1627–1650Dufrechou E, Ezzatti P (2018) A new GPU algorithm to compute a level set-based analysis for the parallel solution of sparse triangular systems. In: 2018 IEEE International Parallel and Distributed Processing Symposium, IPDPS 2018, Canada, 2018. IEEE Computer SocietyDufrechou E, Ezzatti P (2018) Solving sparse triangular linear systems in modern GPUs: a synchronization-free algorithm. In: 2018 26th Euromicro International Conference on Parallel, Distributed and Network-Based Processing (PDP), pp 196–203. https://doi.org/10.1109/PDP2018.2018.00034Eijkhout V (1992) LAPACK working note 50: distributed sparse data structures for linear algebra operations. Tech. rep., Knoxville, TN, USAGolub GH, Van Loan CF (2013) Matrix computationsHe K, Tan SXD, Zhao H, Liu XX, Wang H, Shi G (2016) Parallel GMRES solver for fast analysis of large linear dynamic systems on GPU platforms. Integration 52:10–22 http://www.sciencedirect.com/science/article/pii/S016792601500084XLiu W, Li A, Hogg JD, Duff IS, Vinter B (2017) Fast synchronization-free algorithms for parallel sparse triangular solves with multiple right-hand sides. Concurr Comput 29(21)Saad Y (2003) Iterative methods for sparse linear systems, 2nd edn. SIAM, PhiladelphiaSchenk O, Wächter A, Weiser M (2008) Inertia revealing preconditioning for large-scale nonconvex constrained optimization. SIAM J Sci Comput 31(2):939–96
Single particle spectrum of the flux phase in the FM Kondo Model
We investigate the 2D ferromagnetic Kondo lattice model for manganites with
classical corespins at Hund's rule coupling J_H=6, with antiferromagnetic
superexchange 0.03 < J' < 0.05. We employ canonical and grand canonical
unbiased Monte Carlo simulations and find paramagnetism, weak ferromagnetism
and the Flux phase, depending on doping and on J'. The observed single particle
spectrum in the flux phase differs from the idealized infinite lattice case,
but agrees well with an idealized finite lattice case with thermal
fluctuations.Comment: contribution to the SCES04 conferenc
The scientific impact of an academic journal: the case of RELIEVE
We review some indicators about scientific impact of an academic journal. Data about quality, academics opinion polls, citation, diffusion audience o attraction showns a high impact of RELIEVE..
Continuous adaptation and improvement in the edition of RELIEVE
The changes in RELIEVE (Electronic Journal of Educational Research, Assessment and Evaluation) during the last year are presented and commented
Internacionalidad de revistas académicas: Un estudio de caso con RELIE-VE
Se revisa elconcepto y los criterios propuestos en la literatura para establecer que unarevista es 'internacional'. Se aplican posteriormente estos criterios alanálisis de las caracterÃsticas de RELIEVE (la Revista ELectrónica de Investigación y EValuación Educativa). Los datos analizados permiten concluir que RELIEVE es plenamente una revista internacional
Cross-link Interference Modeling in 6G Millimeter Wave and Terahertz LEO Satellite Communications
One of the important questions when discussing next-generation near-Earth
mmWave and terahertz (THz) band satellite communications as an integral part of
the 5G-Advanced and 6G landscape is the potential interference-related issues
when deploying such systems. While the space-to-ground and ground-to-space
interference has been explored in multiple works already, the interference at
mmWave and THz cross-links, the links between the satellites themselves, have
not been extensively studied yet. However, severe cross-link interference may
both challenge the reliability of the data exchange within the constellation,
as well as compromise the efficient co-existence of multiple satellite
constellations (i.e., by different providers) covering the same or neighboring
areas. In this paper, both relevant mathematical models and extensive
simulation studies are presented for cross-link mmWave and THz satellite
communications. Our results indicate that the cross-link interference in the
considered setups is a non-negligible factor that must be further explored and
accounted for in the design and deployment of next-general mmWave and THz
satellite communication systems.Comment: 7 pages, 7 figures, accepted to IEEE International Conference on
Communications, 2023. The copyright may be transferred without further notice
after which this version may not be longer availabl
Non-circular rotating beams and CMB experiments
This paper is concerned with small angular scale experiments for the
observation of cosmic microwave background anisotropies. In the absence of
beam, the effects of partial coverage and pixelisation are disentangled and
analyzed (using simulations). Then, appropriate maps involving the CMB signal
plus the synchrotron and dust emissions from the Milky Way are simulated, and
an asymmetric beam --which turns following different strategies-- is used to
smooth the simulated maps. An associated circular beam is defined to estimate
the deviations in the angular power spectrum produced by beam asymmetry without
rotation and, afterwards, the deviations due to beam rotation are calculated.
For a certain large coverage, the deviations due to pure asymmetry and
asymmetry plus rotation appear to be very systematic (very similar in each
simulation). Possible applications of the main results of this paper to data
analysis in large coverage experiments --as PLANCK-- are outlined.Comment: 13 pages, 9 figures, to appear in A&
Modeling Interference from Millimeter Wave and Terahertz Bands Cross-links in Low Earth Orbit Satellite Networks for 6G and Beyond
High-rate satellite communications among hundreds and even thousands of
satellites deployed at low-Earth orbits (LEO) will be an important element of
the forthcoming sixth-generation (6G) of wireless systems beyond 2030. With
millimeter wave communications (mmWave, ~30GHz-100GHz) completely integrated
into 5G terrestrial networks, exploration of its potential, along with
sub-terahertz (sub-THz, 100GHz-300GHz), and even THz (300GHz-3THz) frequencies,
is underway for space-based networks. However, the interference problem between
LEO mmWave/THz satellite cross-links in the same or different constellations is
undeservedly forgotten. This article presents a comprehensive mathematical
framework for modeling directional interference in all key possible scenario
geometries. The framework description is followed by an in-depth numerical
study on the impact of cross-link interference on various performance
indicators, where the delivered analytical results are cross-verified via
computer simulations. The study reveals that, while highly directional mmWave
and, especially, THz beams minimize interference in many cases, there are
numerous practical configurations where the impact of cross-link interference
cannot be neglected and must be accounted for.Comment: 16 pages, 10 Figures, 2 Tables. The work has been accepted for
publication in IEEE Journal on Selected Areas in Communications (JSAC), 2024.
Copyright may be transferred without notice, after which this version may no
longer be accessibl
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