1,167 research outputs found

    Generalized switching function model of modular multilevel converter

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    This paper presents a generalized switching function model of the modular multilevel converter (MMC) that can be used instead of MMC electromagnetic transient simulation model for full-scale simulations of high-voltage dc (HVDC) and flexible ac transmission systems (FACTS). The proposed method is computationally more efficient and numerically stable than its electromagnetic transient simulation counterpart, and it is applicable for wide range of studies, including ac and dc network faults. The proposed switching function model is packaged in a graphical form to suit various simulation platforms such as Simulink and PSCAD. The validity of the presented model is confirmed using simulation and its scalability has been demonstrated on MMC with 301 cells per arm, considering power reversal during normal operation and dc short circuit fault

    Comprehensive meta-analysis of excess mortality in depression in the general community versus patients with specific illnesses

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    Objective: Several hundred studies have shown that depression is associated with an elevated risk of dying at follow-up. It is not clear, however, whether the mechanisms for this association are disease specific, leading to higher mortality in specific patient groups, or generic, resulting in comparable mortality rates in all patient groups as well as in community samples. The authors conducted a comprehensive meta-analysis of prospective studies of community as well as patient samples associating depression at baseline with excess mortality at follow-up

    Multiscale Discriminant Saliency for Visual Attention

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    The bottom-up saliency, an early stage of humans' visual attention, can be considered as a binary classification problem between center and surround classes. Discriminant power of features for the classification is measured as mutual information between features and two classes distribution. The estimated discrepancy of two feature classes very much depends on considered scale levels; then, multi-scale structure and discriminant power are integrated by employing discrete wavelet features and Hidden markov tree (HMT). With wavelet coefficients and Hidden Markov Tree parameters, quad-tree like label structures are constructed and utilized in maximum a posterior probability (MAP) of hidden class variables at corresponding dyadic sub-squares. Then, saliency value for each dyadic square at each scale level is computed with discriminant power principle and the MAP. Finally, across multiple scales is integrated the final saliency map by an information maximization rule. Both standard quantitative tools such as NSS, LCC, AUC and qualitative assessments are used for evaluating the proposed multiscale discriminant saliency method (MDIS) against the well-know information-based saliency method AIM on its Bruce Database wity eye-tracking data. Simulation results are presented and analyzed to verify the validity of MDIS as well as point out its disadvantages for further research direction.Comment: 16 pages, ICCSA 2013 - BIOCA sessio

    Fully differential W' production and decay at next-to-leading order in QCD

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    We present the fully differential production and decay of a W' boson, with arbitrary vector and axial-vector couplings, to any final state at next-to-leading order in QCD. We demonstrate a complete factorization of couplings at next-to-leading order in both the partial width of the W' boson, and in the full two-to-two cross section. We provide numerical predictions for the contribution of a W' boson to single-top-quark production, and separate results based on whether the mass of the right-handed neutrino (nu_R) is light enough for the leptonic decay channel to be open. The single-top-quark analysis will allow for an improved direct W' mass limit of 525-550 GeV using data from run I of the Fermilab Tevatron. We propose a modified tolerance method for estimating parton distribution function uncertainties in cross sections.Comment: 23 pages, revtex3, 13 ps fig
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