6,094 research outputs found
IEAD: A Novel One-Line Interface to Query Astronomical Science Archives
In this article I present IEAD, a new interface for astronomical science
databases. It is based on a powerful, yet simple, syntax designed to completely
abstract the user from the structure of the underlying database. The
programming language chosen for its implementation, JavaScript, makes it
possible to interact directly with the user and to provide real-time
information on the parsing process, error messages, and the name resolution of
targets; additionally, the same parsing engine is used for context-sensitive
autocompletion. Ultimately, this product should significantly simplify the use
of astronomical archives, inspire more advanced uses of them, and allow the
user to focus on what scientific research to perform, instead of on how to
instruct the computer to do it.Comment: 13 pages, PASP in pres
Dark soliton collisions in superfluid Fermi gases
In this work dark soliton collisions in a one-dimensional superfluid Fermi
gas are studied across the BEC-BCS crossover by means of a recently developed
finite-temperature effective field theory [S. N. Klimin, J. Tempere, G.
Lombardi, J. T. Devreese, Eur. Phys. J. B 88, 122 (2015)] . The evolution of
two counter-propagating solitons is simulated numerically based on the theory's
nonlinear equation of motion for the pair field. The resulting collisions are
observed to introduce a spatial shift into the trajectories of the solitons.
The magnitude of this shift is calculated and studied in different conditions
of temperature and spin-imbalance. When moving away from the BEC-regime, the
collisions are found to become inelastic, emitting the lost energy in the form
of small-amplitude density oscillations. This inelasticity is quantified and
its behavior analyzed and compared to the results of other works. The
dispersion relation of the density oscillations is calculated and is
demonstrated to show a good agreement with the spectrum of collective
excitations of the superfluid
Soliton core filling in superfluid Fermi gases with spin-imbalance
In this paper the properties of dark solitons in superfluid Fermi gases with
spin-imbalance are studied by means of a recently developed effective field
theory [S. N. Klimin, J. Tempere, G. Lombardi, J. T. Devreese, Eur. Phys. J. B
88, 122 (2015)] suitable to describe the BEC-BCS crossover in ultracold gases
in an extended range of temperatures as compared to the usual Ginzburg-Landau
treatments. The spatial profiles for the total density and for the density of
the excess-spin component, and the changes of their properties across the
BEC-BCS crossover are examined in different conditions of temperature and
imbalance. The presence of population imbalance is shown to strongly affect the
structure of the soliton excitation by filling its core with unpaired atoms.
This in turn influences the dynamical properties of the soliton since the
additional particles in the core have to be dragged along thus altering the
effective mass.Comment: 9 pages, 9 figure
Finite temperature effective field theory and two-band superfluidity in Fermi gases
We develop a description of fermionic superfluids in terms of an effective
field theory for the pairing order parameter. Our effective field theory
improves on the existing Ginzburg - Landau theory for superfluid Fermi gases in
that it is not restricted to temperatures close to the critical temperature.
This is achieved by taking into account long-range fluctuations to all orders.
The results of the present effective field theory compare well with the results
obtained in the framework of the Bogoliubov - de Gennes method. The advantage
of an effective field theory over Bogoliubov - de Gennes calculations is that
much less computation time is required. In the second part of the paper, we
extend the effective field theory to the case of a two-band superfluid. The
present theory allows us to reveal the presence of two healing lengths in the
two-band superfluids, to analyze the finite-temperature vortex structure in the
BEC-BCS crossover, and to obtain the ground state parameters and spectra of
collective excitations. For the Leggett mode our treatment provides an
interpretation of the observation of this mode in two-band superconductors.Comment: 17 pages, 11 figures. In the published version [EPJB 88, 122 (2015)],
there is a misprint in expressions (20) and (21). There must be "E_k" instead
of "\xi_k" in the arguments of the functions "f_n" in those two formulae. In
the present version, this misprint is correcte
A BIM-based PSS approach for the management of maintenance operations of building equipment
The service-centered economy has grown considerably in the last few years, shifting from product-based solutions towards service centered offerings, i.e., Product-Service System (PSS) solutions. Such an approach is also emerging in the context of building equipment, where maintenance activities play a fundamental role in facility management. In this field, Building Information Modeling (BIM) based tools are diffusely used to improve the performances of facility management. However, few studies have addressed the above issues while considering a shift from product-based approaches in favor of more advanced servitization models. The study aims at integrating BIM based approaches in a PSS context for the improvement of the management of maintenance operations of building equipment. A general framework for maintenance management has been developed, merging the implementation of the PSS components in a BIM model for the definition of maintenance management. A first application of this methodology to a real case study concerning the elevators of an existing building has shown the efficacy of the proposed approach. The study highlighted the benefits that can be achieved, especially in terms of reduced periods of equipment unavailability, reduced costs and augmented customer satisfaction, while enhancing the information exchange between the PSS actors. Hence, although further research is still needed for its validation, the proposed approach can offer practical insights for the development of promising BIM-based PSS solutions for facility management in the construction industry
El Roque de Los Muchachos Site Characteristics. II. Analysis of Wind, Relative Humidity and Air Pressure
In this paper we present an analysis of wind speed, wind direction, relative
humidity and air pressure taken at TNG, CAMC and NOT at Observatorio del Roque
de Los Muchachos, in the Canary Islands. Data are compared in order to check
local variations and both long term and short term trends of the microclimate.
Furthermore, influence of wind speed on the astronomical seeing is estimated to
the aim to better understand the influence of wide scale parameters on local
meteorological data. The three telescopes show different prevailing wind
direction, wind speed, relative humidity and air pressure confirming
differences in local microclimate. We found that seeing deteriorates when wind
speed is lower than 3.3 m/s. Comparison in terms of wind speed and high
relative humidity (> 90%) shows that TNG seems to have optimal observational
conditions with respect to CAMC and NOT. Air pressure analysis shows that ORM
is dominated by high pressure. Short time variations of pressure anticipate
temperature variations tipically by 2-3 hours, this property vanishes in time
scales higher than some hours and disappear in longer time scales.Comment: 10 pages, 9 figures, accepted for publication in PAS
High Redshift Candidates and the Nature of Small Galaxies in the Hubble Deep Field
We present results on two related topics: 1. A discussion of high redshift
candidates (z>4.5), and 2. A study of very small galaxies at intermediate
redshifts, both sets being detected in the region of the northern Hubble Deep
Field covered by deep NICMOS observations at 1.6 and 1.1 microns. The high
redshift candidates are just those with redshift z>4.5 as given in the recent
catalog of Thompson, Weymann and Storrie-Lombardi, while the ``small galaxy''
sample is defined to be those objects with isophotal area <= 0.2 squ. arcsec
and with photometric redshifts 1<z<4.5. Of the 19 possible high redshift
candidates listed in the Thompson et al. catalog, 11 have (nominal) photometric
redshifts less than 5.0. Of these, however, only 4 are ``robust'' in the sense
of yielding high redshifts when the fluxes are randomly perturbed with errors
comparable to the estimated measuring error in each wave band. For the 8 other
objects with nominal photometric redshifts greater than 5.0, one (WFPC2 4--473)
has a published spectroscopic redshift. Of the remaining 7, 4 are robust in the
sense indicated above. Two of these form a close pair (NIC 586 and NIC 107).
The redshift of the object having formally the highest redshift, at 6.56
(NIC118 = WFPC2 4--601), is problematic, since F606W and F814W flux are clearly
present, and the nature of this object poses a dilemma. (abridged)Comment: 44 pages, 12 figures, to appear in ApJ v591, July 10, 200
Hydrothermal stability of Ru/SiO2-C: A promising catalyst for biomass processing through liquid-phase reactions
In this work, structural and morphological properties of SiO2-C composite material to be used as support for catalysts in the conversion of biomass-derived oxygenated hydrocarbons, such as glycerol, were investigated in liquid water under various temperatures conditions. The results show that this material does not lose surface area, and the hot liquid water does not generate changes in the structure. Neither change in relative concentrations of oxygen functional groups nor in Si/C ratio due to hydrothermal treatment was revealed by X-ray photoelectron spectroscopy (XPS) analysis. Raman analysis showed that the material is made of a disordered graphitic structure in an amorphous silica matrix, which remains stable after hydrothermal treatment. Results of the hydrogenolysis of glycerol using a Ru/SiO2-C catalyst indicate that the support gives more stability to the active phase than a Ru/SiO2 consisting of commercial silica
A new 21-cm absorber identified with an galaxy
We present Giant Metrewave Radio Telescope (GMRT) observations of redshifted
21-cm absorption from the metal line absorption system towards PKS
1243-072. HI absorption is clearly detected; the absorption profile has a
velocity spread of km/s. Detection of 21-cm absorption indicates that
the absorber has an HI column density large enough to be classified as a damped
Lyman- system. Follow up ground based optical imaging and spectroscopy
allow us to identify the absorber with an galaxy at an impact
parameter of kpc from the line of sight to the QSO. The absorbing
galaxy is unusual in that it has bright emission lines. On the basis of the
optical spectrum we are unable to uniquely classify the galaxy since its
emission line ratios lie in the transition region between starburst and Seyfert
II type spectra.Comment: 5 pages, 3 figures. Accepted for publication in Astronomy &
Astrophysic
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