3,383 research outputs found
Protocolo para criopreservação do sêmen de tambaqui (Colossoma macropomum).
bitstream/item/39781/1/cot-112.pd
Comparisons between synchronizing circuits to control algorithms for single-phase active converters
This paper presents a comparative analysis between synchronizing circuits applied to control algorithms for single-phase active converters. One of these synchronizing circuits corresponds to the single-phase PLL (Phase Locked Loop), implemented in α-β coordinates, whereas the other one corresponds to the E-PLL (Enhanced PLL). These synchronizing circuits are compared in several aspects as processing and settling time and memory space requirements. Moreover, the performance of a single-phase back-to-back converter is also presented, with its control algorithm based on these Synchronizing Circuits. Each one of the control algorithms were implemented in a DSP microprocessor TMS320F2812F from Texas Instruments. Simulation and experimental results, through a back-to-back converter prototype, are presented.Fundação para a Ciência e a Tecnologia (FCT
THE APPLICATION OF THE BOUNDARY ELEMENT METHOD TO SOLVE VISCOUS FLOW PROBLEMS BASED ON PRIMITIVE VARIABLES FORMULATION
The boundary element method is applied to the solution of incompressible
fluid flow problems governed by the continuity and Navier-Stokes
equations. The differential equations are transformed into integral equations.
Indication of the transformation is given in detail. Application to simple flow
cases such as the driven cavity and forward facing step is presented.
Convergence difficulties are indicated, which have limited the applications
to flows of low Reynolds numbers.
Remnant loop quantum black holes
Polymer models inspired by Loop Quantum Gravity (LQG) have been used to
describe non-singular quantum black holes with spherical symmetry, with the
classical singularity replaced by a transition from a black hole to a white
hole. A recent model, with a single polymerisation parameter, leads to a
symmetric transition with same mass for the black and white phases, and to an
asymptotically flat exterior metric. The radius of the transition surface is,
however, not fixed, increasing with the mass. Following similar procedures, in
a previous paper we have fixed that radius by identifying the minimal area on
the transition surface with the area gap of LQG. This allowed to find a
dependence of the polymerisation parameter on the black hole mass, with the
former increasing as the latter decreases. It also permitted to extend the
model to Planck scale black holes, with quantum fluctuations remaining small at
the horizon. In the present paper we extend this analysis to charged black
holes, showing that the Cauchy horizon lies beyond of the transition surface.
We also show the existence of limiting states with zero surface gravity, the
lightest one with and , and the heaviest with . Using our solutions to approximate quasi-steady horizons, we show
that Hawking evaporation leads asymptotically to these extremal states, leaving
remnant black holes of Planck size.Comment: Version to appear in the letter section of Class. Quantum Gra
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