1,352 research outputs found
1-1.4 Micron Spectral Atlas of Stars
We present a catalog of J-band (1.08 um to 1.35 um) stellar spectra at low
resolution (R ~ 400). The targets consist of 105 stars ranging in spectral type
from O9.5 to M7 and luminosity classes I through V. The relatively featureless
spectra of hot stars, earlier than A4, can be used to remove the atmospheric
features which dominate ground-based J-band spectroscopy. We measure equivalent
widths for three absorption lines and nine blended features which we identify
in the spectra. Using detailed comparison with higher resolution spectra, we
demonstrate that low resolution data can be used for stellar classification,
since several features depend on the effective temperature and gravity. For
example The CN index (1.096 - 1.104 um) decreases with temperature, but the
strength of a blended feature at 1.28 um (consisting of primarily P beta)
increases. The slope of a star's spectrum can also be used to estimate its
effective temperature. The luminosity class of a star correlates with the ratio
of the Mg I (1.1831 um) line to a blend of several species at 1.16 um. Using
these indicators, a star can be classified to within several subclasses.
Fifteen stars with particularly high and low metal abundances are included in
the catalog and some spectral dependence on metal abundance is also found.Comment: 35 pages, 10 figures (3a-e are in gif format. For complete high
resolution figures, go to http://www.astro.ucla.edu/~malkan/newjspec/) ;
Accepted for published in ApJS; For associated spectra files, see
http://www.astro.ucla.edu/~malkan/newjspec
The Domination Number of Grids
In this paper, we conclude the calculation of the domination number of all
grid graphs. Indeed, we prove Chang's conjecture saying that for
every , .Comment: 12 pages, 4 figure
Evolution of CODYRUN from Thermal Simulation to Coupled Thermal and Daylight Simulation Software
AbstractCODYRUN is a multi-zone software integrating thermal building simulation, airflow, and pollutant transfer. Described in numerous publications, this software was originally used for the passive design of buildings, both for research and teaching purposes. In this context, the data treated were mainly concerned with volumes (zones), surfaces and thicknesses (walls and windows), materials, and systems, with the aim to determine temperatures, heat fluxes, energy consumed, air transfers, and so on.The question thus arose as to the integration of indoor lighting conditions into the simulation. Hence, previous data structures had to be amended to incorporate the spatial positioning of entities (walls, windows, and artificial lighting sources) through vertexes. A set of procedures was also developed for polygons as well as calculating natural and artificial lighting.The results of this new daylighting module were then compared with other results of simulation codes and experimental cases both in artificial and natural environments. Excellent agreements were obtained, such as the values for luminous efficiencies in a tropical and humid climate.A simulation exercise was conducted in a classroom located in Reunion Island (French overseas territory in the Indian Ocean), thus confirming the interest for thermal and daylighting designs in low-energy buildings
Heat Transfer in Buildings: Application to Solar Air Collector and Trombe Wall Design
The aim of this paper is to briefly recall heat transfer modes and explain
their integration within a software dedicated to building simulation (CODYRUN).
Detailed elements of the validation of this software are presented and two
applications are finally discussed. One concerns the modeling of a flat plate
air collector and the second focuses on the modeling of Trombe solar walls. In
each case, detailed modeling of heat transfer allows precise understanding of
thermal and energetic behavior of the studied structures. Recent decades have
seen a proliferation of tools for building thermal simulation. These
applications cover a wide spectrum from very simplified steady state models to
dynamic simulation ones, including computational fluid dynamics modules
(Clarke, 2001). These tools are widely available in design offices and
engineering firms. They are often used for the design of HVAC systems and still
subject to detailed research, particularly with respect to the integration of
new fields (specific insulation materials, lighting, pollutants transport,
etc.). Available from:
http://www.intechopen.com/books/evaporation-condensation-and-heat-transfer/heat-transfer-in-buildings-application-to-solar-air-collector-and-trombe-wall-designComment: Available from:
http://www.intechopen.com/books/evaporation-condensation-and-heat-transfer/heat-transfer-in-buildings-application-to-solar-air-collector-and-trombe-wall-desig
Large Scale Cross-Correlations in Internet Traffic
The Internet is a complex network of interconnected routers and the existence
of collective behavior such as congestion suggests that the correlations
between different connections play a crucial role. It is thus critical to
measure and quantify these correlations. We use methods of random matrix theory
(RMT) to analyze the cross-correlation matrix C of information flow changes of
650 connections between 26 routers of the French scientific network `Renater'.
We find that C has the universal properties of the Gaussian orthogonal ensemble
of random matrices: The distribution of eigenvalues--up to a rescaling which
exhibits a typical correlation time of the order 10 minutes--and the spacing
distribution follow the predictions of RMT. There are some deviations for large
eigenvalues which contain network-specific information and which identify
genuine correlations between connections. The study of the most correlated
connections reveals the existence of `active centers' which are exchanging
information with a large number of routers thereby inducing correlations
between the corresponding connections. These strong correlations could be a
reason for the observed self-similarity in the WWW traffic.Comment: 7 pages, 6 figures, final versio
Study of dimuon production in Indium-Indium collisions with the NA60 experiment
The NA60 experiment at the CERN-SPS is devoted to the study of dimuon
production in heavy-ion and proton-nucleus collisions. We present preliminary
results from the analysis of Indium-Indium collisions at 158 GeV per nucleon.
The topics covered are low mass vector meson production, J/psi production and
suppression, and the feasibility of the open charm measurement from the dimuon
continuum in the mass range below the J/psi peak.Comment: Contribution at XXXXth Rencontres de Moriond, "QCD and High Energy
Hadronic Interactions
Superconductor-ferromagnet junction phase qubit
We propose a scheme for a phase qubit in an SIFIS junction, consisting of
bulk superconductors (S), a proximity-induced ferromagnet (F), and insulating
barriers (I). The qubit state is constituted by 0 and phase states of the
junction, in which the charging energy of the junction leads to the
superposition of the two states. The qubit is operated by the gate voltage
applied to the ferromagnet, and insensitive to the decoherence sources existing
in other superconducting qubits. We discuss a scalable scheme for qubit
measurement and tunable two-qubit coupling.Comment: 3 pages, 3 figure
Compensated convexity methods for approximations and interpolations of sampled functions in Euclidean spaces: theoretical foundations
We introduce Lipschitz continuous and C¹,¹ geometric approximation and interpolation methods for sampled bounded uniformly continuous functions over compact sets and over complements of bounded open sets in Rn by using compensated convex transforms. Error estimates are provided for the approximations of bounded uniformly continuous functions, of Lipschitz functions, and of C1,1 functions. We also prove that our approximation methods, which are differentiation and integration free and not sensitive to sample type, are stable with respect to the Hausdorff distance between samples
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