32 research outputs found

    Método de pontos interiores barreira logarítmica preditor-corretor especializado para o problema de regressão pela norma Lp

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    The logaritmie barrier and predictor-corretor interior point methods are applied to the Lp norm fitting problem exploiting the matrix structure in order to obtain an efficient implementation.. The fitting problem has numerous applications in various areas. The 2-norin is very popular, among other reasons, for allowing a direct solution. The 1-norin allows the reduction of the effect of outliers while the ∞-norin provides protection against the worst case. The pnorm allows to think these characteristics in different ways adapting the method to the problem to be solved. The interior point method implementation to be developed is compared with existing methods.Os métodos de pontos interiores barreira logarítmica e preditor-corretor são aplicados ao problema de regressão pela norma Lp com algumas particularidades com o objetivo de obter uma implementação eficiente. O problema de regressão tem inúmeras aplicações em diversas áreas. A norma-2 é muito popular, entre outros motivos, por permitir uma solução direta. Por sua vez, a norma-1 permite reduzir o efeito de pontos discrepantes enquanto que a norma-∞ garante proteção contra o pior caso. A norma-p permite pensar estas características de diferentes formas, adaptando o método ao problema a ser resolvido. A implementação do método de pontos interiores desenvolvida é comparada com métodos existentes.21923

    Corrosion resistance and antibacterial properties of copper coating deposited by cold gas spray

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    This work describes the morphology, corrosion resistance, and antibacterial performance of copper coating deposited onto carbon steel by cold gas spray (CGS). Cross-sectional images of the coating showed a dense microstructure, with porosity lower than 1%. XRD analysis revealed no oxides or phases different to pure copper. The results of electrochemical tests demonstrated the efficient barrier properties and the compact microstructure of the coating, which protected the substrate against corrosion in chloride solution for > 1000 h. The copper coating was effective as an antimicrobial agent for inhibiting the growth of Staphylococcus aureus, with bacterial growth being completely inhibited after 10 min of direct contact between the bacteria and the coating surface

    Quenching of chlorophyll fluorescence induced by silver nanoparticles

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    The interaction between chlorophyll (Chl) and silver nanoparticles (AgNPs) was evaluated by analyzing the optical behavior of Chl molecules surrounded by different concentrations of AgNPs (10, 60, and 100 nm of diameter). UV–Vis absorption, steady state and time-resolved fluorescence measurements were performed for Chl in the presence and absence of these nanoparticles. AgNPs strongly suppressed the Chl fluorescence intensity at 678 nm. The Stern-Volmer constant (KSV) showed that fluorescence suppression is driven by the dynamic quenching process. In particular, KSV was nanoparticle size-dependent with an exponential decrease as a function of the nanoparticle diameter. Finally, changes in the Chl fluorescence lifetime in the presence of nanoparticles demonstrated that the fluorescence quenching may be induced by the excited electron transfer from the Chl molecules to the metal nanoparticles

    A New Predictor–corrector Method For Optimal Power Flow

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    A predictor–corrector interior-point method is developed in order to deal with the AC active and reactive optimal power flow problem. Voltage rectangular coordinates are adopted instead of polar ones, since they allow nonlinear corrections for the primal and dual feasibility conditions and not only for the complementary constraints as in the traditional nonlinear programming methods. A new heuristic is proposed to handle voltage magnitude constraints. Computational experiments for IEEE test systems and a real Brazilian system are presented and show the advantages of the proposed approach
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