2,313 research outputs found
Asiago eclipsing binaries program. III. V570 Per
The orbit and physical parameters of the previously unsolved SB2 EB V570 Per
are derived using high resolution Asiago Echelle spectroscopy and B, V
photo-electric photometry. The metallicity from chi^2 analysis is [M/H]=+0.02
+/- 0.03, and reddening from interstellar NaI and KI absorption lines is E(B-V)
=0.023 +/- 0.007. The two components have masses of 1.449 +/- 0.006 and 1.350
+/- 0.006 Msun and spectral types F3 and F5, respectively. They are both still
within the Main Sequence band (T_1 =6842 +/- 25 K, T_2 =6562 +/- 25 K from
chi^2 analysis, R_1 =1.523 +/- 0.030, R_2 =1.388 +/- 0.019 Rsun) and are
dynamically relaxed to co-rotation with the orbital motion (Vrot sin i_{1,2}
=40 and 36 (+/-1) km/sec). The distance to V570 Per obtained from the orbital
solution is 123 +/- 2 pc, in excellent agreement with the revised Hipparcos
distance of 123 +/- 11 pc. The observed properties of V570 Per components are
compared to BaSTI models computed on purpose for exactly the observed masses
and varied chemical compositions. This system is interesting since both
components have their masses in the range where the efficiency of convective
core overshooting has to decrease with the total mass as a consequence of the
decreasing size of the convective core during the central H-burning stage. Our
numerical simulations show that, a small but not null overshooting is required,
with efficiencies lambda_{OV} =0.14 and 0.11 for the 1.449 and 1.350 Msun
components, respectively. This confirms the finding of Paper II on the similar
system V505 Per. At the approx 0.8 Gyr age of the system, the element diffusion
has reduced the surface metallicity of the models from the initial [M/H]=+0.17
to [M/H]=+0.02, in perfect agreement with the spectroscopically derived
[M/H]=+0.02 +/- 0.03 value.Comment: accepted by A&A. This revised upload to astro-ph correct a formatting
error generated by uncorrect A&A style fil
Parametric Macromodels of Differential Drivers and Receivers
This paper addresses the modeling of differential drivers and receivers for the analog simulation of high-speed interconnection systems. The proposed models are based on mathematical expressions, whose parameters can be estimated from the transient responses of the modeled devices. The advantages of this macromodeling approach are: improved accuracy with respect to models based on simplified equivalent circuits of devices; improved numerical efficiency with respect to detailed transistor-level models of devices; hiding of the internal structure of devices; straightforward circuit interpretation; or implementations in analog mixed-signal simulators. The proposed methodology is demonstrated on example devices and is applied to the prediction of transient waveforms and eye diagrams of a typical low-voltage differential signaling (LVDS) data link
Avaliação de genótipos de mandioca da reserva extrativista Cazumbá-Iracema, Acre.
A mandioca é o principal produto agrícola do Acre, cultivado para geração de renda e segurança alimentar, sendo tipicamente de exploração familiar. Este trabalho teve como objetivo avaliar genótipos de mandioca na Reserva Extrativista do Cazumbá-Iracema, localizada no município de Sena Madureira, AC. Foram instalados três experimentos nas localidades Cazumbá, Cuidado e Alto Caeté, utilizando-se o delineamento inteiramente casualizado com quatro repetições. Foram avaliados; número de raízes por planta, percentagem de amido e massa seca de raízes, produtividade e rendimento de farinha de mandioca. Foi realizada a avaliação de oito genótipos nas localidades de Cazumbá e Cuidado e de seis genótipos em Alto Caeté, analisando conjuntamente os quatro genótipos Panatí, Araçá, Colonial e Pirarucu que foram plantados nas três localidades. Os dados foram submetidos a análise de variância e para os efeitos significativos, aplicou-se o teste de Tukey e Scott-Knott a 5 % de probabilidade. A cultivar Pirarucu, que é a mais plantada na reserva, foi ogenótipo que apresentou melhor desempenho quanto a produtividade e rendimento de farinha
SN 2013df, a double-peaked IIb supernova from a compact progenitor and an extended H envelope
Optical observations of the type IIb SN 2013df from a few days to about 250
days after explosion are presented. These observations are complemented with UV
photometry taken by \textit{SWIFT} up to 60 days post-explosion. The
double-peak optical light curve is similar to those of SNe 1993J and 2011fu
although with different decline and rise rates. From the modelling of the
bolometric light curve, we have estimated that the total mass of synthesised
Ni in the explosion is M, while the ejecta mass is
M and the explosion energy erg. In
addition, we have estimated a lower limit to the progenitor radius ranging from
. The spectral evolution indicates that SN 2013df had a
hydrogen envelope similar to SN 1993J ( M). The line
profiles in nebular spectra suggest that the explosion was asymmetric with the
presence of clumps in the ejecta, while the [O\,{\sc i}]
, luminosities, may indicate that the progenitor
of SN 2013df was a relatively low mass star ( M).Comment: 18 pages, 11 figures, 9 tables, accepted for publication in MNRA
Scattering-based nonlinear macromodels of high-speed differential drivers
This paper introduces a scattering-based nonlinear macromodeling framework for high-speed differential drivers. Using an industrial test case, we show that the proposed scattering formulation enables more accurate and robust model identification with respect to standard voltage-current representations. The combination of proposed driver models with a Waveform Relaxation solver allows accurate and efficient transient channel simulation, including nonlinear and dynamic termination effect
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