150,916 research outputs found
Plasmon-soliton waves in planar slot waveguides: I. Modeling
We present two complementary models to study stationary nonlinear solutions
in one-dimensional plasmonic slot waveguides made of a finite-thickness
nonlinear dielectric core surrounded by metal regions. The considered
nonlinearity is of focusing Kerr type. In the first model, it is assumed that
the nonlinear term depends only on the transverse component of the electric
field and that the nonlinear refractive index change is small compared to the
linear part of the refractive index. This first model allows us to describe
analytically the field profiles in the whole waveguide using Jacobi elliptic
special functions. It also provides a closed analytical formula for the
nonlinear dispersion relation. In the second model, the full dependency of the
Kerr nonlinearity on the electric field components is taken into account and no
assumption is required on the amplitude of the nonlinear term. The disadvantage
of this approach is that the field profiles must be computed numerically.
Nevertheless analytical constraints are obtained to reduce the parameter space
where the solutions of the nonlinear dispersion relations are sought.Comment: 13 pages, 1 figure, see next article part II entitled
"Plasmon-soliton waves in planar slot waveguides: II. Results for stationary
waves and stability analysis", link: http://arxiv.org/abs/1506.0817
Are Smell-Based Metrics Actually Useful in Effort-Aware Structural Change-Proneness Prediction? An Empirical Study
Bad code smells (also named as code smells) are symptoms of poor design choices in implementation. Existing studies empirically confirmed that the presence of code smells increases the likelihood of subsequent changes (i.e., change-proness). However, to the best of our knowledge, no prior studies have leveraged smell-based metrics to predict particular change type (i.e., structural changes). Moreover, when evaluating the effectiveness of smell-based metrics in structural change-proneness prediction, none of existing studies take into account of the effort inspecting those change-prone source code. In this paper, we consider five smell-based metrics for effort-aware structural change-proneness prediction and compare these metrics with a baseline of well-known CK metrics in predicting particular categories of change types. Specifically, we first employ univariate logistic regression to analyze the correlation between each smellbased metric and structural change-proneness. Then, we build multivariate prediction models to examine the effectiveness of smell-based metrics in effort-aware structural change-proneness prediction when used alone and used together with the baseline metrics, respectively. Our experiments are conducted on six Java open-source projects with up to 60 versions and results indicate that: (1) all smell-based metrics are significantly related to structural change-proneness, except metric ANS in hive and SCM in camel after removing confounding effect of file size; (2) in most cases, smell-based metrics outperform the baseline metrics in predicting structural change-proneness; and (3) when used together with the baseline metrics, the smell-based metrics are more effective to predict change-prone files with being aware of inspection effort
4U 0115+63 from RXTE and INTEGRAL Data: Pulse Profile and Cyclotron Line Energy
We analyze the observations of the transient X-ray pulsar 4U 0115+63 with the
RXTE and INTEGRAL observatories in a wide X-ray (3-100 keV) energy band during
its intense outbursts in 1999 and 2004. The energy of the fundamental harmonic
of the cyclotron resonance absorption line near the maximum of the X-ray flux
from the source (luminosity range 5x10^{37} - 2x10^{38} erg/s) is ~11 keV. When
the pulsar luminosity falls below ~5x10^{37} erg/s, the energy of the
fundamental harmonic is displaced sharply toward the high energies, up to ~16
keV. Under the assumption of a dipole magnetic field configuration, this change
in cyclotron harmonic energy corresponds to a decrease in the height of the
emitting region by ~2 km, while other spectral parameters, in particular, the
cutoff energy, remain essentially constant. At a luminosity ~7x10^{37} erg/s,
four almost equidistant cyclotron line harmonics are clearly seen in the
spectrum. This suggests that either the region where the emission originates is
compact or the emergent spectrum from different (in height) segments of the
accretion column is uniform. We have found significant pulse profile variations
with energy, luminosity, and time. In particular, we show that the profile
variations from pulse to pulse are not reduced to a simple modulation of the
accretion rate specified by external conditions.Comment: 30 pages, 13 figures, Astronomy Letters, 33, 368 (2007
Type IIP Supernova SN 2004et: A Multi-Wavelength Study in X-Ray, Optical and Radio
We present X-ray, broad band optical and low frequency radio observations of
the bright type IIP supernova SN 2004et. The \cxo observed the supernova at
three epochs, and the optical coverage spans a period of 470 days since
explosion. The X-ray emission softens with time, and we characterise the X-ray
luminosity evolution as \Lx \propto t^{-0.4}. We use the observed X-ray
luminosity to estimate a mass-loss rate for the progenitor star of \sim
\ee{2}{-6} M_\odot \mathrm{yr}^{-1}. The optical light curve shows a
pronounced plateau lasting for about 110 days. Temporal evolution of
photospheric radius and color temperature during the plateau phase is
determined by making black body fits. We estimate the ejected mass of Ni
to be 0.06 0.03 M. Using the expressions of Litvinova &
Nad\"{e}zhin (1985) we estimate an explosion energy of (0.98 0.25)
erg. We also present a single epoch radio observation of SN
2004et. We compare this with the predictions of the model proposed by Chevalier
et al. (2006). These multi-wavelength studies suggest a main sequence
progenitor mass of 20 M for SN 2004et.Comment: 13 Figures, Accepted for Publication in MNRA
LSQ13ddu: a rapidly evolving stripped-envelope supernova with early circumstellar interaction signatures
This paper describes the rapidly evolving and unusual supernova LSQ13ddu, discovered by the La Silla-QUEST survey. LSQ13ddu displayed a rapid rise of just 4.8 ± 0.9 d to reach a peak brightness of −19.70 ± 0.02 mag in the LSQgr band. Early spectra of LSQ13ddu showed the presence of weak and narrow HeI features arising from interaction with circumstellar material (CSM). These interaction signatures weakened quickly, with broad features consistent with those seen in stripped-envelope SNe becoming dominant around two weeks after maximum. The narrow HeI velocities are consistent with the wind velocities of luminous blue variables but its spectra lack the typically seen hydrogen features. The fast and bright early light curve is inconsistent with radioactive ⁵⁶Ni powering but can be explained through a combination of CSM interaction and an underlying ⁵⁶Ni decay component that dominates the later time behaviour of LSQ13ddu. Based on the strength of the underlying broad features, LSQ13ddu appears deficient in He compared to standard SNe Ib
Is GRB 050904 at z=6.3 absorbed by dust?
Claim of dust extinction for this GRB has been debated in the past. We
suggest that the discrepant results occur primarily because most of previous
studies have not simultaneously investigated the X-ray to near-IR spectral
energy distribution of this GRB. The difficulty with this burst is that the
X-ray afterglow is dominated by strong flares at early times and is poorly
monitored at late times. In addition, the Z band photometry, which is the most
sensitive to dust extinction, has been found to be affected by strong
systematics. In this paper we carefully re-analyze the Swift/XRT afterglow
observations of this GRB, using extensive past studies of X-ray flare
properties when computing the X-ray afterglow flux level and exploiting the
recent reanalysis of the optical (UV rest frame) data of the same GRB. We
extract the X-ray to optical/near-IR afterglow SED for the three epochs where
the best spectral coverage is available: 0.47, 1.25, and 3.4 days after the
trigger. A spectral power-law model has been fitted to the extracted SEDs. We
discuss that no spectral breaks or chromatic temporal breaks are expected in
the epochs of interest. To fit any UV rest-frame dust absorption, we tested the
Small Magellanic Cloud (SMC) extinction curve, the mean extinction curve (MEC)
found for a sample of QSO at and its corresponding attenuation curve, as
well as a starburst attenuation curve, and the extinction curve consistent with
a supernova dust origin (SN-type). The SMC extinction curve and the SN-type one
provide good fit to the data at all epochs, with an average amount of dust
absorption at of mag.
These results indicate that the primeval galaxy at hosting this GRB
has already enriched its ISM with dust.Comment: 8 pages, 3 figures, accepted for publication in Astronomy and
Astrophysics; figure 1 has been degraded, full resolution version at
http://dl.dropbox.com/u/1670579/fig01.p
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