4,827 research outputs found
Experimental Demonstration of Dual Polarization Nonlinear Frequency Division Multiplexed Optical Transmission System
Multi-eigenvalues transmission with information encoded simultaneously in
both orthogonal polarizations is experimentally demonstrated. Performance below
the HD-FEC limit is demonstrated for 8-bits/symbol 1-GBd signals after
transmission up to 207 km of SSMF
Copper and Barium Abundances in the Ursa Major Moving Group
We present Cu and Ba abundances for 7 G-K dwarf stars, members of the
solar-metallicity, 0.3 Gyr old Ursa Major Moving Group. All analyzed member
stars show [Ba/Fe] excesses of +0.3-plus, associated with [Cu/Fe] deficiencies
of up to -0.23 dex. The present results suggest that there is an
anti-correlation between the abundances of Cu and the heavy elements produced
by the main component of the neutron capture s-process. Other possible
anomalies are Na and C deficiencies with respect to normal solar-metallicity
stars. The new data do not confirm the recent claim that the group member
HR6094 is a Ba dwarf star.Comment: 8 pages, 6 figures, accepted to MNRA
Dual polarization nonlinear Fourier transform-based optical communication system
New services and applications are causing an exponential increase in internet
traffic. In a few years, current fiber optic communication system
infrastructure will not be able to meet this demand because fiber nonlinearity
dramatically limits the information transmission rate. Eigenvalue communication
could potentially overcome these limitations. It relies on a mathematical
technique called "nonlinear Fourier transform (NFT)" to exploit the "hidden"
linearity of the nonlinear Schr\"odinger equation as the master model for
signal propagation in an optical fiber. We present here the theoretical tools
describing the NFT for the Manakov system and report on experimental
transmission results for dual polarization in fiber optic eigenvalue
communications. A transmission of up to 373.5 km with bit error rate less than
the hard-decision forward error correction threshold has been achieved. Our
results demonstrate that dual-polarization NFT can work in practice and enable
an increased spectral efficiency in NFT-based communication systems, which are
currently based on single polarization channels
A photometric and spectroscopic survey of solar twin stars within 50 parsecs of the Sun: I. Atmospheric parameters and color similarity to the Sun
Solar twins and analogs are fundamental in the characterization of the Sun's
place in the context of stellar measurements, as they are in understanding how
typical the solar properties are in its neighborhood. They are also important
for representing sunlight observable in the night sky for diverse photometric
and spectroscopic tasks, besides being natural candidates for harboring
planetary systems similar to ours and possibly even life-bearing environments.
We report a photometric and spectroscopic survey of solar twin stars within 50
pc of the Sun. Hipparcos absolute magnitudes and (B-V)_Tycho colors were used
to define a 2 sigma box around the solar values, where 133 stars were
considered. Additional stars resembling the solar UBV colors in a broad sense,
plus stars present in the lists of Hardorp, were also selected. All objects
were ranked by a color-similarity index with respect to the Sun, defined by
uvby and BV photometry. Moderately high-resolution, high-S/N spectra were used
for a subsample of equatorial-southern stars to derive Teff, log g, and [Fe/H]
with average internal errors better than 50 K, 0.20 dex, and 0.08 dex,
respectively. Ages and masses were estimated from theoretical HR diagrams. The
color-similarity index proved very successful. We identify and rank new
excellent solar analogs, which are fit to represent the Sun in the night sky.
Some of them are faint enough to be of interest for moderately large
telescopes. We also identify two stars with near-UV spectra indistinguishable
from the Sun's. We present five new "probable" solar twin stars, besides five
new "possible" twins. Masses and ages for the best solar twin candidates lie
very close to the solar values, but chromospheric activity levels range
somewhat. We propose that the solar twins be emphasized in the ongoing searches
for extra-solar planets and SETI searches.Comment: 25 pages, 15 figures, 14 table
Linear and Nonlinear Impairment Compensation in Coherent Optical Transmission with Digital Signal Processing
Seismic vulnerability assessment of clustered historical centers: fragility curves based on local collapse mechanisms analyses
open5noProtection and preservation of minor historical centres against earthquakes effects are
not trivial tasks, particularly in the cases, quite common, of complex aggregate buildings. The paper
aims at evaluating the seismic vulnerability of historical clustered buildings on a urban scale, through the
analysis of local collapse mechanisms, carried out with a parametric approach. This procedure is applied
to four historical centres of L’Aquila province struck by the 2009 earthquake. The identification of the
significant parameters is related to the definition of representative typologies within the city centres. Each
typology is characterized by recurring features, mainly recognizable with a survey performed outside the
buildings. After the identification of the relevant aspects, local mechanisms of collapse analyses are carried
out, by varying the parameters between defined range of values, in order to take into account possible
uncertainties in the data collection. A set of fragility curves for each identified typology is defined
and the obtained results are compared to the damage data gathered in the post-earthquake phase for the
buildings. This approach allows for possible extensions to buildings that may be included in the typology
categories here defined.openTaffarel, S.; Caliman, M.; Valluzzi, M.R; da Porto, F.; Modena, C.Taffarel, Sabrina; Caliman, M.; Valluzzi, MARIA ROSA; DA PORTO, Francesca; Modena, Claudi
Seismic vulnerability assessment on a territorial scale based on a Bayesian approach
Italian historical centres are mostly characterized by aggregate buildings. As defined by
the Italian codes (Norme Tecniche per le Costruzioni 2008 and Circolare n. 617), the analysis of the most
representative local mechanisms of collapse must be performed in order to assess their vulnerability. In
this article, the out-of-plane local mechanisms of collapse analysis is implemented by applying a new
method of analysis based on a probabilistic approach. Usually information which are necessary for the
implementation of the local mechanisms analyses are affected by uncertainty or are missing, therefore
in lots of cases it is only possible to hypothesize them on the basis of the other buildings information
collected during the on-site survey. In this context, the implementation of a Bayesian approach allows to
deduce buildings lacking information (i.e. wall thickness and interstorey height) starting from certain collected
data (i.e. facades height). The historical centre of Timisoara (Romania) is selected as the case study
for the implementation of this new method of analysis, given the extension of the on-site survey already
carried out in the area (information about more than 200 structural units have been collected) and the
seismic vulnerability assessment on an urban scale already performed by applying a traditional method.
Results obtained by adopting the two approaches are then compared and a validation and a calibration
of the new one is carried out
Indicadores sociais, econômicos e tecnológicos da agropecuária da zona sul e do estado do Rio Grande do Sul.
bitstream/item/31542/1/comunicado59.pd
The application of a Bayesian approach to assess the seismic vulnerability of historical centers
The seismic vulnerability of historical centers at a territorial scale cannot be assessed performing
detailed analysis which are usually adopted at the single building scale. In fact, a traditional complete survey
would be extremely time-consuming and not sustainable for this purpose.
The approach described in this paper is based on the idea that it is possible to infer quantities which cannot be directly
detected from buildings outside inspection starting from parameters that can be measured. In order to
achieve this purpose, a Bayesian approach is applied, updating initial hypotheses when new data become available.
In this context, the procedure herein proposed aims at applying a probabilistic approach instead of a deterministic
one to define facades inter-storey height starting from buildings height knowledge. In order to validate the method,
for out of plane local mechanisms of collapse (walls overturning), horizontal loads multiplier \uf0610 values are calculated
and compared to results obtained by using data collected on-site
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