22,917 research outputs found
Selection of third party software in Off-The-Shelf-based software development: an interview study with industrial practitioners
The success of software development using third party components highly depends on the ability to select a suitable component for the intended application. The evidence shows that there is limited knowledge about current industrial OTS selection practices. As a result, there is often a gap between theory and practice, and the proposed methods for supporting selection are rarely adopted in the industrial practice. This paper's goal is to investigate the actual industrial practice of component selection in order to provide an initial empirical basis that allows the reconciliation of research and industrial endeavors. The study consisted of semi-structured interviews with 23 employees from 20 different software-intensive companies that mostly develop web information system applications. It provides qualitative information that help to further understand these practices, and emphasize some aspects that have been overlooked by researchers. For instance, although the literature claims that component repositories are important for locating reusable components; these are hardly used in industrial practice. Instead, other resources that have not received considerable attention are used with this aim. Practices and potential market niches for software-intensive companies have been also identified. The results are valuable from both the research and the industrial perspectives as they provide a basis for formulating well-substantiated hypotheses and more effective improvement strategies.Peer ReviewedPostprint (author's final draft
Exact scaling in the expansion-modification system
This work is devoted to the study of the scaling, and the consequent
power-law behavior, of the correlation function in a mutation-replication model
known as the expansion-modification system. The latter is a biology inspired
random substitution model for the genome evolution, which is defined on a
binary alphabet and depends on a parameter interpreted as a \emph{mutation
probability}. We prove that the time-evolution of this system is such that any
initial measure converges towards a unique stationary one exhibiting decay of
correlations not slower than a power-law. We then prove, for a significant
range of mutation probabilities, that the decay of correlations indeed follows
a power-law with scaling exponent smoothly depending on the mutation
probability. Finally we put forward an argument which allows us to give a
closed expression for the corresponding scaling exponent for all the values of
the mutation probability. Such a scaling exponent turns out to be a piecewise
smooth function of the parameter.Comment: 22 pages, 2 figure
The electrical current density vector in the inner penumbra of a Sunspot
We determine the entire electrical current density vector in a geometrical 3D
volume of the inner penumbra of a sunspot from an inversion of
spectropolarimetric data obtained with Hinode/SP. Significant currents are seen
to wrap around the hotter, more elevated regions with lower and more horizontal
magnetic field that harbor strong upflows and radial outflows (the
intraspines). The horizontal component of the current density vector is 3-4
times larger than the vertical; nearly all previous studies only obtain the
vertical component and thus strongly underestimate the current density. The
current density and the magnetic field vectors form an angle of about 20
degrees. The plasma beta at the 0 km level is larger than 1 in the intraspines
and is one order of magnitude lower in the background component of the penumbra
(spines). At the 200 km level, the plasma beta is below 0.3 nearly everywhere.
The plasma beta surface as well as the surface optical depth unity are very
corrugated. At the borders of intraspines and inside, the magnetic field is not
force-free at deeper layers and nearly force free at the top layers. The
magnetic field of the spines is close to being potential everywhere. The
dissipated ohmic energy is five orders of magnitudes smaller than the solar
energy flux and thus negligible for the energy balance of the penumbra.Comment: 5 pages, 4 figures, ApJL, in pres
Rectification of electronic heat current by a hybrid thermal diode
We report the realization of an ultra-efficient low-temperature hybrid heat
current rectifier, thermal counterpart of the well-known electric diode. Our
design is based on a tunnel junction between two different elements: a normal
metal and a superconducting island. Electronic heat current asymmetry in the
structure arises from large mismatch between the thermal properties of these
two. We demonstrate experimentally temperature differences exceeding mK
between the forward and reverse thermal bias configurations. Our device offers
a remarkably large heat rectification ratio up to and allows its
prompt implementation in true solid-state thermal nanocircuits and
general-purpose electronic applications requiring energy harvesting or thermal
management and isolation at the nanoscale.Comment: 8 pages, 6 color figure
Electronic heat current rectification in hybrid superconducting devices
In this work, we review and expand recent theoretical proposals for the
realization of electronic thermal diodes based on tunnel-junctions of normal
metal and superconducting thin films. Starting from the basic rectifying
properties of a single hybrid tunnel junction, we will show how the
rectification efficiency can be largely increased by combining multiple
junctions in an asymmetric chain of tunnel-coupled islands. We propose three
different designs, analyzing their performance and their potential advantages.
Besides being relevant from a fundamental physics point of view, this kind of
devices might find important technological application as fundamental building
blocks in solid-state thermal nanocircuits and in general-purpose cryogenic
electronic applications requiring energy management.Comment: 9 pages, 5 color figure
Integral transformation solution of free-space cylindrical vector beams and prediction of modified-Bessel-Gaussian vector beams
A unified description of the free-space cylindrical vector beams is
presented, which is an integral transformation solution to the vector Helmholtz
equation and the transversality condition. The amplitude 2-form of the angular
spectrum involved in this solution can be arbitrarily chosen. When one of the
two elements is zero, we arrive at either transverse-electric or
transverse-magnetic beam mode. In the paraxial condition, this solution not
only includes the known Bessel-Gaussian vector beam and the axisymmetric
Laguerre-Gaussian vector beam that were obtained by solving the paraxial wave
equations, but also predicts two new kinds of vector beam, called the
modified-Bessel-Gaussian vector beam.Comment: 8 pages and 1 figur
On the improvement of the low energy neutrino factory
The low energy neutrino factory has been proposed as a very sensitive setup
for future searches for CP violation and matter effects. Here we study how its
performance is affected when the experimental specifications of the setup are
varied. Most notably, we have considered the addition of the 'platinum' nu_{mu}
-> nu_{e} channel. We find that, whilst theoretically the extra channel
provides very useful complementary information and helps to lift degeneracies,
its practical usefulness is lost when considering realistic background levels.
Conversely, an increase in statistics in the 'golden' nu_{e} -> nu_{mu} channel
and, to some extent, an improvement in the energy resolution, lead to an
important increase in the performance of the facility, given the rich energy
dependence of the 'golden' channel at these energies. We show that a low energy
neutrino factory with a baseline of 1300 km, muon energy of 4.5 GeV, and either
a 20 kton totally active scintillating detector or 100 kton liquid argon
detector, can have outstanding sensitivity to the neutrino oscillation
parameters theta13, delta and the mass hierarchy. For our estimated exposure of
2.8 x 10^{23} kton x decays per muon polarity, the low energy neutrino factory
has sensitivity to theta13 and delta for sin^{2}(2theta13) > 10^{-4} and to the
mass hierarchy for sin^{2}(2theta13) > 10^{-3}.Comment: 13 pages, 8 eps figures. Version published in PRD - experimental
section with preliminary results removed, abstract and conclusions re-written
accordingly, title changed, author list amended
Observational Evidence for Coronal Twisted Flux Rope
Multi-instrument data sets of NOAA AR10938 on Jan. 16, 2007, (e.g.,
{\emph{Hinode}}, {\it{STEREO}}, {\it{GOES}}, {\it{MLSO}} and {\it{ISOON}}
H) are utilized to study the fine structure and evolution of a magnetic
loop system exhibiting multiple crossing threads, whose arrangement and
individual shapes are very suggestive of individual field lines in a flux rope.
The footpoints of the magnetic threads are closely rooted into pores and plage
areas. A C-class flare recorded by {\it{GOES}} at approximately 2:35 UT near
one of the footpoints of the multi-thread system (along with a wisp of loop
material shown by EUV data) led to the brightening of the magnetic structure
revealing its fine structure with several threads that indicate a high degree
of linking (suggesting a left-handed helical pattern as shown by the filament
structure formed later-on). EUV observations by {\emph{Hinode}}/EIS of hot
spectral lines at 2:46 UT show a complex structure of coronal loops. The same
features were observed about 20 minutes later in X-ray images from
{\emph{Hinode}}/XRT and about 30 minutes further in EUV images of
{\it{STEREO}}/SECCHI/EUVI with much better resolution. H and 304 {\AA}
images revealed the presence of several filament fibrils in the same area. They
evolved a few hours later into a denser structure seemingly showing helical
structure, which persistently lasted for several days forming a segment of a
larger scale filament. The present observations provide an important indication
for a flux robe as a precursor of a solar filament.Comment: 13 pages, 4 figure
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