480 research outputs found
Parallelization of shallow water simulations on current multi-threaded systems
Lobeiras, J., Viñas, M., Amor, M., Fraguela, B.B., Arenaz, M., GarcĂa, J., Castro, M. Parallelization of shallow water simulations on current multi-threaded systems. The International Journal of High Performance Computing Applications 27, 493â512. © 2013 The Author(s), © SAGE Publications. https://doi.org/10.1177/1094342012464800[Abstract]: In this work, several parallel implementations of a numerical model of pollutant transport on a shallow water system are presented. These parallel implementations are developed in two phases. First, the sequential code is rewritten to exploit the stream programming model. And second, the streamed code is targeted for current multi-threaded systems, in particular, multi-core CPUs and modern GPUs. The performance is evaluated on a multi-core CPU using OpenMP, and on a GPU using the streaming-oriented programming language Brook+, as well as the standard language for heterogeneous systems, OpenCL.Funding This work was supported by the Galician Government (Consolidation of Competitive Research Groups, Xunta de Galicia ref. 2010/6, projects INCITE08PXIB105161PR and 08TIC001206PR), the Ministry of Science and Innovation, cofunded by the FEDER funds of the European Union (grant number TIN2010-16735, and project numbers MTM2009-11923 and MTM2010-21135).Xunta de Galicia; INCITE08PXIB105161PRXunta de Galicia; 08TIC001206P
A multi-GPU shallow-water simulation with transport of contaminants
[Abstract] This work presents cost-effective multi-graphics processing unit (GPU) parallel implementations of a finite-volume numerical scheme for solving pollutant transport problems in bidimensional domains. The fluid is modeled by 2D shallow-water equations, whereas the transport of pollutant is modeled by a transport equation. The 2D domain is discretized using a first-order Roe finite-volume scheme. Specifically, this paper presents multi-GPU implementations of both a solution that exploits recomputation on the GPU and an optimized solution that is based on a ghost cell decoupling approach. Our multi-GPU implementations have been optimized using nonblocking communications, overlapping communications and computations and the application of ghost cell expansion to minimize communications. The fastest one reached a speedup of 78âĂâusing four GPUs on an InfiniBand network with respect to a parallel execution on a multicore CPU with six cores and two-way hyperthreading per core. Such performance, measured using a realistic problem, enabled the calculation of solutions not only in real time but also in orders of magnitude faster than the simulated time.Copyright © 2012 John Wiley & Sons, Ltd
On BPS preons, generalized holonomies and D=11 supergravities
We develop the BPS preon conjecture to analyze the supersymmetric solutions
of D=11 supergravity. By relating the notions of Killing spinors and BPS
preons, we develop a moving G-frame method (G=GL(32,R), SL(32,R) or Sp(32,R))
to analyze their associated generalized holonomies. As a first application we
derive here the equations determining the generalized holonomies of k/32
supersymmetric solutions and, in particular, those solving the necessary
conditions for the existence of BPS preonic (31/32) solutions of the standard
D=11 supergravity. We also show that there exist elementary preonic solutions,
i.e. solutions preserving 31 out of 32 supersymmetries in a Chern--Simons type
supergravity. We present as well a family of worldvolume actions describing the
motion of pointlike and extended BPS preons in the background of a D'Auria-Fre
type OSp(1|32)-related supergravity model. We discuss the possible implications
for M-theory.Comment: 11 pages, RevTeX Typos corrected, a short note and references adde
Supersymmetric string model with 30 kappa--symmetries in an extended D=11 superspace and 30/ 32 BPS states
A supersymmetric string model in the D=11 superspace maximally extended by
antisymmetric tensor bosonic coordinates, , is proposed. It
possesses 30 -symmetries and 32 target space supersymmetries. The usual
preserved supersymmetry--symmetry correspondence suggests that it
describes the excitations of a BPS state preserving all but two
supersymmetries. The model can also be formulated in any superspace, n=32 corresponding to D=11. It may also be treated as a
`higher--spin generalization' of the usual Green--Schwarz superstring. Although
the global symmetry of the model is a generalization of the super--Poincar\'e
group, , it may be
formulated in terms of constrained OSp(2n|1) orthosymplectic supertwistors. We
work out this supertwistor realization and its Hamiltonian dynamics.
We also give the supersymmetric p-brane generalization of the model. In
particular, the supersymmetric membrane model describes
excitations of a 30/32 BPS state, as the supersymmetric
string does, while the supersymmetric 3-brane and 5-brane correspond,
respectively, to 28/32 and 24/32 BPS states.Comment: 23 pages, RevTex4. V2: minor corrections in title and terminology,
some references and comments adde
Wnt signalling and cancer stem cells
[Abstract] Intracellular signalling mediated by secreted Wnt proteins is essential for the establishment of cell fates and proper tissue patterning during embryo development and for the regulation of tissue homeostasis and stem cell function in adult tissues. Aberrant activation of Wnt signalling pathways has been directly linked to the genesis of different tumours. Here, the components and molecular mechanisms implicated in the transduction of Wnt signal, along with important results supporting a central role for this signalling pathway in stem cell function regulation and carcinogenesis will be briefly reviewed.Ministerio de Ciencia e InnovaciĂłn; SAF2008-0060
Conselhos Municipais de SaĂșde: A Possibilidade dos UsuĂĄrios Participarem e os Determinantes da Participação
Processos de democracia direta: sim ou nĂŁo? Os argumentos clĂĄssicos Ă luz da teoria e da prĂĄtica
Regularmente surgem controvĂ©rsias sobre os processos de democracia direta, dos quais os mecanismos mais frequentes sĂŁo a iniciativa popular, o plebiscito e o referendo. Por um lado, hĂĄ autores que defendem a posição de que essas instituiçÔes tornam o jogo polĂtico mais lento, caro, confuso e ilegĂtimo; outros defendem a posição contrĂĄria e argumentam que processos de democracia direta sĂŁo fundamentais para os cidadĂŁos e a qualidade da democracia. O presente estudo analisa esse tema em torno de sete questĂ”es, baseadas em consideraçÔes teĂłricas e pesquisas empĂricas: 1. A questĂŁo entre o minimalismo e o maximalismo democrĂĄtico; 2. A concorrĂȘncia entre maioria e minoria; 3. A concorrĂȘncia entre as instituiçÔes representativas e os processos de democracia direta; 4. A questĂŁo da competĂȘncia dos cidadĂŁos; 5. A questĂŁo dos efeitos colaterais dos processos de democracia direta; 6. A questĂŁo do tamanho do eleitorado; 7. A questĂŁo dos custos dos processos de democracia direta. As sete questĂ”es sĂŁo analisadas a partir de uma revisĂŁo bibliogrĂĄfica que considera tanto fontes nacionais como internacionais. O estudo mostra que os processos de democracia direta podem ser um complemento para as instituiçÔes representativas em um sistema democrĂĄtico. O bom desempenho dos plebiscitos, referendos e iniciativas populares depende tanto da regulamentação destes como tambĂ©m do desempenho das outras instituiçÔes polĂticas e da situação socioeconĂŽmica de um paĂs. O estudo permite ampliar e aprofundar o debate sobre processos de democracia direta no Brasil
Juegos tradicionales adaptados al fĂștbol para la mejora del rendimiento del portero
Este artĂculo tiene como objetivo dotar a los profesionales de la educaciĂłn
fĂsica y el fĂștbol de una baterĂa de tareas para poder desarrollar la capacidad fĂsica
y técnico-tåctica de sus porteros. Dicho trabajo presenta una serie de juegos
tradicionales adaptados al fĂștbol que nos servirĂĄn como recursos para nuestras
clases de educaciĂłn fĂsica o entrenamientos de fĂștbol. Cabe destacar, como estos
juegos son una herramienta muy Ăștil para realizar el calentamiento, en el que vamos
a conseguir que nuestros jugadores preparen su organismo para la parte principal,
reduzcan la posibilidad de sufrir lesiones y se diviertan al mismo tiempo. Por Ășltimo,
señalar como la apariciĂłn de las nuevas tecnologĂas estĂĄ dejando de lado la
prĂĄctica de los juegos tradicionales en la calle. Por ello, este trabajo pretende su
conservaciĂłn, para que estos juegos sigan siendo una fuente de valor cultural,
patrimonial, educativo y motriz
Confiança nas instituiçÔes democråticas e vitimização por crime: qual a relação?
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