7,188 research outputs found

    On the computation of Bernstein–Sato ideals

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    In this paper we compare the approach of Brianc¸onand Maisonobe for computing Bernstein–Sato ideals—based on computations in a Poincar´e–Birkhoff–Witt algebra—with the readily available method of Oaku and Takayama. We show that it can deal with interesting examples that have proved intractable so far.Ministerio de Ciencia y Tecnología BFM-2001-3164Junta de Andalucía FQM-33

    Explicit Comparison Theorems for D -modules

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    We prove in an explicit way a duality formula between two A2-modules Mlog and Mflog associated to a plane curve and we give an application of this duality to the comparison between Mflog and the A2-module of rational functions along the curve. We treat the analytic case as well

    Follow-up observations from observatories based in Spain

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    We present a review of the follow-up observations carried out from observatories located in Spain; Calar-Alto, Izanha and Roque de Los Muchachos. It summarizes the observations carried out by our group for 27 GRBs occurred in the period 1999-2000, spanning from GRB 990123 to GRB 001007.Comment: 3 pages, no figures. To appear in the proceedings of the October 2000 Rome Workshop on ``Gamma-Ray Bursts in the Afterglow Era'

    Reduced heart rate variability predicts fatigue severity in individuals with chronic fatigue syndrome/myalgic encephalomyelitis

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    Heart rate variability (HRV) is an objective, non-invasive tool to assessing autonomic dysfunction in chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME). People with CFS/ME tend to have lower HRV; however, in the literature there are only a few previous studies (most of them inconclusive) on their association with illness-related complaints. To address this issue, we assessed the value of different diurnal HRV parameters as potential biomarker in CFS/ME and also investigated the relationship between these HRV indices and self-reported symptoms in individuals with CFS/ME.Peer ReviewedPostprint (published version

    Hybrid Supervised-Unsupervised Channel Estimation Scheme with Dynamic Transmission of Pilots

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    The final publication is available at Springer via http://dx.doi.org/10.1007/s11063-010-9161-x[Abstract] Multiple-Input Multiple-Output (MIMO) digital communications standards typically include pilot symbols in the definition of the transmit signals with the purpose of acquiring the Channel State Information (CSI) using supervised algorithms at the receiver side. Such pilot symbols convey no information and, therefore, system throughput, spectral efficiency and transmit energy consumption are all penalized. In this article, we propose to acquire the CSI combining supervised and unsupervised algorithms. Our strategy avoids the periodical transmission of unnecessary pilots by using a simple decision criterion to determine the time instants when the performance obtained with an unsupervised algorithm degrades or, equivalently, the time instants when pilots are required. We show the performance of this scheme for MIMO systems with Decision-feedback equalizers at the receiver.Galicia. Consellería de Economía e Industria; 09TIC008105PRMinisterio de Ciencia e Innovación; TEC2007-68020-C04-01Ministerio de Ciencia e Innovación; TIN2009-0573Ministerio de Ciencia e Innovación; CSD2008-0001

    Web apps and imprecise probabilities

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    We propose a model for the behaviour of Web apps in the unreliable WWW. Web apps are described by orchestrations. An orchestration mimics the personal use of the Web by defining the way in which Web services are invoked. The WWW is unreliable as poorly maintained Web sites are prone to fail. We model this source of unreliability trough a probabilistic approach. We assume that each site has a probability to fail. Another source of uncertainty is the traffic congestion. This can be observed as a non-deterministic behaviour induced by the variability in the response times. We model non-determinism by imprecise probabilities. We develop here an ex-ante normal to characterize the behaviour of finite orchestrations in the unreliable Web. We show the existence of a normal form under such semantics for orchestrations using asymmetric parallelism.Peer ReviewedPostprint (author's final draft

    A Fuzzy-set hierarchical classification of family firms

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    Family firms can be thought of as heterogeneous configurations where ownership, governance, management and succession are often intertwined. Previous works have typically used a partial definition of family firm based on one or more of these three aspects. In this empirical work we seek to clarify the definitions and typologies of family firms by using fuzzy sets qualitative comparative analysis (fs/QCA). Based on this methodology, we propose a hierarchical classification of family firms based on necessity and sufficiency conditions, including some possible overlapping among alternative types. We use an international sample of 6,611 companies from different industries and national/legal systems

    La interacción del desarrollo turístico en una reserva natural: el caso de la región de Tremiti (Italia)

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    XII Coloquio de Geografía del Turismo, Ocio y Recreación de la Asociación de Geógrafos Españoles. Colmenarejo (Madrid), del 17 al 19 de junio de 2010.Proyecto con referencia 08TUR006210PR, financiado por la Xunta de Galicia: Innovación, Ciencia e Tecnoloxía-INCITEPublicad

    Performance of MIMO systems in measured indoor channels with transmitter noise

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    This study analyzes the impact of transmitter noise on the performance of multiple-input multiple-output (MIMO) systems with linear and nonlinear receivers and precoders. We show that the performance of MIMO linear and decision-feedback receivers is not significantly influenced by the presence of transmitter noise, which does not hold true in the case of MIMO systems with precoding. Nevertheless, we also show that this degradation can be greatly alleviated when the transmitter noise is considered in the MIMO precoder design. A MIMO testbed developed at the University of A Coruña has been employed for experimentally evaluating how much the transmitter noise impacts the system performance. Both the transmitter noise and the receiver noise covariance matrices have been estimated from a set of 260 indoor MIMO channel realizations. The impact of transmitter noise has been assessed in this realistic scenario.Galicia. Consellería de Economía e Industria; 10TIC003CTGalicia. Consellería de Economía e Industria; 09TIC008105PRMinisterio de Ciencia e Innovación; TEC2010-19545-C04-01Ministerio de Ciencia e Innovación; CSD2008-0001

    Algorithms for determining relative position between spheroids and hyperboloids with one sheet

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    ©2019. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https:// creativecommons.org/licenses/by-nc-nd/4.0/. This version of the article: Castro, P. M., Dapena, A., Souto- Salorio, M. J., & Tarrío-Tobar, A. D. (2019). 'Algorithms for determining relative position between spheroids and hyperboloids with one sheet', has been accepted for publication in Mathematics and Computers in Simulation, 160, 168–179.The Version of Record is available online at https://doi.org/10.1016/j.matcom.2018.12.006.[Abstract]: In this work we present a new method for determining relative positions between one moving object, modelled by a bounding spheroid, and surrounding static objects, modelled by circular hyperboloids of one sheet. The proposed strategy is based on the real-time calculation of the coefficients of degree three polynomial. We propose several algorithms for two real applications of this geometric problem: the first one, oriented to the design of video games, and the second one, devoted to surveillance tasks of a quadcopter in industrial or commercial environments.This work has been funded by the Xunta de Galicia, Spain (ED431C 2016-045, ED341D R2016/012, ED431G/01), the Agencia Estatal de Investigación of Spain (TEC2013-47141-C4-1-R, TEC2015-69648-REDC, TEC2016-75067-C4-1-R) and ERDF funds of the EU (AEI/FEDER, UE). The authors wish to thank José Sanmartín for his helpful work in the graphic design of the pictures included in this paper.Xunta de Galicia; ED431C 2016-045Xunta de Galicia; ED341D R2016/012Xunta de Galicia; ED431G/0
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