1,412 research outputs found

    Modulational instability windows in the nonlinear Schr\"odinger equation involving higher-order Kerr responses

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    We introduce a complete analytical and numerical study of the modulational instability process in a system governed by a canonical nonlinear Schr\"odinger equation involving local, arbitrary nonlinear responses to the applied field. In particular, our theory accounts for the recently proposed higher-order Kerr nonlinearities, providing very simple analytical criteria for the identification of multiple regimes of stability and instability of plane-wave solutions in such systems. Moreover, we discuss a new parametric regime in the higher-order Kerr response which allows for the observation of several, alternating stability-instability windows defining a yet unexplored instability landscape.Comment: 9 pages, 8 figure

    Contributions to the efficient use of general purpose coprocessors: kernel density estimation as case study

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    142 p.The high performance computing landscape is shifting from assemblies of homogeneous nodes towards heterogeneous systems, in which nodes consist of a combination of traditional out-of-order execution cores and accelerator devices. Accelerators provide greater theoretical performance compared to traditional multi-core CPUs, but exploiting their computing power remains as a challenging task.This dissertation discusses the issues that arise when trying to efficiently use general purpose accelerators. As a contribution to aid in this task, we present a thorough survey of performance modeling techniques and tools for general purpose coprocessors. Then we use as case study the statistical technique Kernel Density Estimation (KDE). KDE is a memory bound application that poses several challenges for its adaptation to the accelerator-based model. We present a novel algorithm for the computation of KDE that reduces considerably its computational complexity, called S-KDE. Furthermore, we have carried out two parallel implementations of S-KDE, one for multi and many-core processors, and another one for accelerators. The latter has been implemented in OpenCL in order to make it portable across a wide range of devices. We have evaluated the performance of each implementation of S-KDE in a variety of architectures, trying to highlight the bottlenecks and the limits that the code reaches in each device. Finally, we present an application of our S-KDE algorithm in the field of climatology: a novel methodology for the evaluation of environmental models

    Modulational instability windows in the nonlinear Schrödinger equation involving higher-order Kerr responses.

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    [EN]We introduce a complete analytical and numerical study of the modulational instability process in a system governed by a canonical nonlinear Schrödinger equation involving local, arbitrary nonlinear responses to the applied field. In particular, our theory accounts for the recently proposed higher-order Kerr nonlinearities, providing very simple analytical criteria for the identification of multiple regimes of stability and instability of plane-wave solutions in such systems. Moreover, we discuss a new parametric regime in the higher-order Kerr response, which allows for the observation of several, alternating stability-instability windows defining a yet unexplored instability landscap

    Las alternativas de financiamiento para la pequeña y mediana empresa.

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    El sistema financiero mexicano está constituido por un conjunto de instituciones que captan, administran y canalizan a la inversión, el ahorro tanto de nacionales como de extranjeros; supervisados por: I. CNBV II. CNSF III. CONSAR Bajo el concepto anterior y tomando en cuenta la canalización de la inversión y crédito, para las micro, pequeñas y medianas empresas (MIPYMES) han sido catalogadas como organizaciones con un carácter muy importante para las economías en general y para la sociedad en particular; por su potencial de fomentar empleos, por su capacidad de generar ingresos para las economías débiles entre otras y lo más importante, por ser portadoras del crecimiento y desarrollo económico. Las MIPYMES poseen una ventaja clara frente a la competencia, su tamaño les permite una respuesta rápida a los cambios del entorno y facilita su integración, como eslabón en las cadenas productivas; también como abastecedor de materias primas, insumos y productos terminados

    Endoglin involvement in integrin-mediated cell adhesion as a putative pathogenic mechanism in hereditary hemorrhagic telangiectasia type 1 (HHT1)

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    5 p.-2 fig.Mutations in the endoglin gene (ENG) are responsible for ∼50% of all cases with hereditary hemorrhagic telangiectasia (HHT). Because of the absence of effective treatments for HHT symptoms, studies aimed at identifying novel biological functions of endoglin which could serve as therapeutic targets of the disease are needed. Endoglin is an endothelial membrane protein, whose most studied function has been its role as an auxiliary receptor in the TGF-β receptor complex. However, several lines of evidence suggest the involvement of endoglin in TGF-β-independent functions. Endoglin displays, within its zona pellucida domain, an RGD motif, which is a prototypic sequence involved in integrin-based interactions with other proteins. Indeed, we have recently described a novel role for endothelial endoglin in leukocyte trafficking and extravasation via its interaction with leukocyte integrins. In addition, functional, as well as protein and gene expression analysis have shown that ectopic endoglin represses the synthesis of several members of the integrin family and modulates integrin-mediated cell adhesions. This review focuses on the tight link between endoglin and integrins and how the role of endothelial endoglin in integrin-dependent cell adhesion processes can provide a better understanding of the pathogenic mechanisms leading to vascular lesions in endoglin haploinsufficient HHT1 patients.This study was supported by grants from the Ministerio de Economia y Competitividad of Spain (SAF2010-19222 and SAF2013-43421-R to Carmelo Bernabeu; SAF2010-1588, SAF2013-45784-R, and RD12/0021/0032-REDINREN to José M. Lopez-Novoa).Peer reviewe

    Sistema robótico basado en el comportamiento de las hormigas para la optimización en la búsqueda de rutas más cortas

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    In recent decades, bio-inspired systems or biological systems have become essential elements for the understanding and explanation of the logic and complexity of life.[1] Given a problem or task, it is always possible to find a way to find a solution, but when the tasks to be performed become complex, so do the solutions. Given a problem or task, it is always possible to find a way to find a solution, but when the tasks to be performed become complex, so do the solutions become more complex, so it is more practical to provide solutions from bio-inspired systems that have already provided solutions to many existing problems in our reality through evolution, which leads to the implementation of a bio-inspired algorithm, which takes as a basis the behavior of what nature already provides and uses it in its favor to solve real-life problems more efficiently [2][3].En las últimas décadas, los sistemas bio-inspirados o sistemas biológicos se han convertido en elementos imprescindibles para la comprensión y la explicación de la lógica y la complejidad de la vida.[1]Dado un problema o tarea siempre se puede buscar la manera de dar con una solución, pero cuando las tareas a realizar se vuelven complejas, así mismo se hacen más complejas las soluciones, por lo cual es más práctico dar solución desde los sistemas bio-inspirados que ya han dado solución a muchos problemas existentes en nuestra realidad por medio de la evolución, lo cual lleva a la implementación de un algoritmo bio-inspirado, que toma como base el comportamiento de lo que ya otorga la naturaleza y lo usa en su favor para así resolver de manera más eficiente problemas de la vida real [2][3]

    Incidencia de la cultura tributaria en el pago de arbitrios en la Municipalidad de Comas, 2019

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    En la investigación titulada: “Incidencia de la Cultura Tributaria en el pago de Arbitrios en la Municipalidad de Comas 2019”, el objetivo general de la investigación fue determinar la relación que existe entre la Cultura Tributaría y pago de Arbitrios municipales en el distrito de Comas año 2019. El tipo de investigación es básica, con un nivel de investigación descriptivo correlacional, teniendo como diseño de la investigación no experimental transversal y un enfoque cuantitativo. La muestra estuvo conformada por 68 colaboradores. La técnica que se utilizó es la encuesta y los instrumentos de recolección de datos fueron dos cuestionarios aplicados a los colaboradores de la municipalidad de Comas. Para validar los instrumentos se utilizó el juicio de 03 expertos y para tener confiabilidad de cada instrumento se utilizó el alfa de Cron Bach que salió muy alta en ambas variables: 0,82 que son cultura tributaria y pago de arbitrios. Con referencia al objetivo general: Determinar la relación sobre la Cultura Tributaría y pago de Arbitrios municipales del distrito de Comas, 2019 se concluye que existe relación directa y significativa entre la Cultura Tributaría y pago de Arbitrios municipales del distrito de Comas, 2019. Lo que se demuestra el estadístico de p valor (sig. bilateral = .000 < 0.05; coef. Nagelkerke = 0.596). Significa que la Cultura Tributaría en sus dimensiones interno y externo, se relacionan significativamente y favorecen el pago de Arbitrios municipales del distrito de Comas, 2019 aceptando como válida la hipótesis general de la investigación

    Area-delay Trade-offs of Texture Decompressors for a Graphics Processing Unit

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    Graphics Processing Units have become a booster for the microelectronics industry. However, due to intellectual property issues, there is a serious lack of information on implementation details of the hardware architecture that is behind GPUs. For instance, the way texture is handled and decompressed in a GPU to reduce bandwidth usage has never been dealt with in depth from a hardware point of view. This work addresses a comparative study on the hardware implementation of different texture decompression algorithms for both conventional (PCs and video game consoles) and mobile platforms. Circuit synthesis is performed targeting both a reconfigurable hardware platform and a 90nm standard cell library. Area-delay trade-offs have been extensively analyzed, which allows us to compare the complexity of decompressors and thus determine suitability of algorithms for systems with limited hardware resources

    Scalability of an Eulerian-Lagrangian large-eddy simulation solver with hybrid MPI/OpenMP parallelisation

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    Eulerian-Lagrangian approaches capable of accurately reproducing complex fluid flows are becoming more and more popular due to the increasing availability and capacity of High Performance Computing facilities. However, the parallelisation of the Lagrangian part of such methods is challenging when a large number of Lagrangian markers are employed. In this study, a hybrid MPI/OpenMP parallelisation strategy is presented and implemented in a finite difference based large-eddy simulation code featuring the immersed boundary method which generally employs a large number of Lagrangian markers. A master-scattering-gathering strategy is used to deal with the handling of the Lagrangian markers and OpenMP is employed to distribute their computational load across several CPU threads. A classical domain-decomposition-based MPI approach is used to carry out the Eulerian, fixed-mesh fluid calculations. The results demonstrate that by using an effective combination of MPI and OpenMP the code can outperform a pure MPI parallelisation approach by up to 20%. Outcomes from this paper are of interest to various Eulerian-Lagrangian applications including the immersed boundary method, discrete element method or Lagrangian particle tracking.This research was partially funded by EPSRC under the grant EP/K502819/1. The simulations were carried out in the facilities of the Supercomputing Wales, a project partly funded by the European Regional Development Fund (ERDF) via Welsh Government

    Modulational instability windows in the nonlinear Schrödinger equation involving higher-order Kerr responses

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    We introduce a complete analytical and numerical study of the modulational instability process in a system governed by a canonical nonlinear Schrödinger equation involving local, arbitrary nonlinear responses to the applied field. In particular, our theory accounts for the recently proposed higher-order Kerr nonlinearities, providing very simple analytical criteria for the identification of multiple regimes of stability and instability of plane-wave solutions in such systems. Moreover, we discuss a new parametric regime in the higher-order Kerr response, which allows for the observation of several, alternating stability-instability windows defining a yet unexplored instability landscape.Xunta de Galicia | Ref. EM2013/00
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