8,756 research outputs found
Time-Reversal Symmetry Breaking and Decoherence in Chaotic Dirac Billiards
In this work, we perform a statistical study on Dirac Billiards in the
extreme quantum limit (a single open channel on the leads). Our numerical
analysis uses a large ensemble of random matrices and demonstrates the
preponderant role of dephasing mechanisms in such chaotic billiards. Physical
implementations of these billiards range from quantum dots of graphene to
topological insulators structures. We show, in particular, that the role of
finite crossover fields between the universal symmetries quickly leaves the
conductance to the asymptotic limit of unitary ensembles. Furthermore, we show
that the dephasing mechanisms strikingly lead Dirac billiards from the extreme
quantum regime to the semiclassical Gaussian regime
The two-echelon capacitated vehicle routing problem: models and math-based heuristics
Multiechelon distribution systems are quite common in supply-chain and logistics. They are used by public administrations in their transportation and traffic planning strategies, as well as by companies, to model own distribution systems. In the literature, most of the studies address issues relating to the movement of flows throughout the system from their origins to their final destinations. Another recent trend is to focus on the management of the vehicle fleets required to provide transportation among different echelons. The aim of this paper is twofold. First, it introduces the family of two-echelon vehicle routing problems (VRPs), a term that broadly covers such settings, where the delivery from one or more depots to customers is managed by routing and consolidating freight through intermediate depots. Second, it considers in detail the basic version of two-echelon VRPs, the two-echelon capacitated VRP, which is an extension of the classical VRP in which the delivery is compulsorily delivered through intermediate depots, named satellites. A mathematical model for two-echelon capacitated VRP, some valid inequalities, and two math-heuristics based on the model are presented. Computational results of up to 50 customers and four satellites show the effectiveness of the methods developed
Study of the adhesion on overmoulded parts with thermoplastic/LSR combination
Multi-material parts with PBT/LSR combination were produced in two separate steps,
one for the injection of PBT parts, and a second for the LSR overmoulding. The aim of this work is
to study the influence of process-parameters such as mold temperature, curing time, temperature of
the PBT insert before performing the overmoulding with LSR, on the adhesion with LSRâs. The
effect on the adhesion of the amount of glass fiber content on the PBT was also studied. The
adhesion between the materials was measured using a peel-test 90Âș.
The results of the peel-test indicated that the adhesion is influenced by the parameters described.
The adhesion between the two materials increase significantly with the increase of the processparameters
Intense CIII] 1907,1909 emission from a strong Lyman continuum emitting galaxy
We have obtained the first complete ultraviolet (UV) spectrum of a strong
Lyman continuum(LyC) emitter at low redshift -- the compact, low-metallicity,
star-forming galaxy J1154+2443 -- with a Lyman continuum escape fraction of 46%
discovered recently. The Space Telescope Imaging Spectrograph spectrum shows
strong Lya and CIII] 1909 emission, as well as OIII] 1666. Our observations
show that strong LyC emitters can have UV emission lines with a high equivalent
width (e.g. EW(CIII]) rest-frame), although their equivalent
widths should be reduced due to the loss of ionizing photons. The intrinsic
ionizing photon production efficiency of J1154+2443 is high, erg Hz, comparable to that of other recently discovered
LyC emitters. Combining our measurements and earlier
determinations from the literature, we find a trend of increasing with increasing CIII] 1909 equivalent width, which can be understood by
a combination of decreasing stellar population age and metallicity. Simple
ionization and density-bounded photoionization models can explain the main
observational features including the UV spectrum of J1154+2443.Comment: 5 pages, 4 figures. Accepted for publication in A&A Letter
SOPHIE velocimetry of Kepler transit candidates IX. KOI-415 b: a long-period, eccentric transiting brown dwarf to an evolved Sun
We report the discovery of a long-period brown-dwarf transiting companion of
the solar-type star KOI-415. The transits were detected by the Kepler space
telescope. We conducted Doppler measurements using the SOPHIE spectrograph at
the Observatoire de Haute-Provence. The photometric and spectroscopic signals
allow us to characterize a 62.14+-2.69 Mjup, brown-dwarf companion of an
evolved 0.94+-0.06 Msun star in a highly eccentric orbit of P =
166.78805+-0.00022 days and e = 0.698+-0.002. The radius of KOI-415 b is 0.79
(-0.07,+0.12) Rjup, a value that is compatible with theoretical predictions for
a 10 Gyr, low-metallicity and non-irradiated object.Comment: accepted in A&A Letter
SOPHIE velocimetry of Kepler transit candidates XIV. A joint photometric, spectroscopic, and dynamical analysis of the Kepler-117 system
As part of our follow-up campaign of Kepler planets, we observed Kepler-117
with the SOPHIE spectrograph at the Observatoire de Haute-Provence. This
F8-type star hosts two transiting planets in non-resonant orbits. The planets,
Kepler-117 b and c, have orbital periods and days,
and show transit-timing variations (TTVs) of several minutes. We performed a
combined Markov chain Monte Carlo (MCMC) fit on transits, radial velocities,
and stellar parameters to constrain the characteristics of the system. We
included the fit of the TTVs in the MCMC by modeling them with dynamical
simulations. In this way, consistent posterior distributions were drawn for the
system parameters. According to our analysis, planets b and c have notably
different masses ( and M) and low
orbital eccentricities ( and ). The
uncertainties on the derived parameters are strongly reduced if the fit of the
TTVs is included in the combined MCMC. The TTVs allow measuring the mass of
planet b, although its radial velocity amplitude is poorly constrained.
Finally, we checked that the best solution is dynamically stable.Comment: 16 pages, of whom 5 of online material.12 figures, of whom 2 in the
online material. 7 tables, of whom 4 in the online material. Published in A&
SOPHIE velocimetry of Kepler transit candidates. XV. KOI-614b, KOI-206b, and KOI-680b: a massive warm Jupiter orbiting a G0 metallic dwarf and two highly inflated planets with a distant companion around evolved F-type stars
We report the validation and characterization of three new transiting
exoplanets using SOPHIE radial velocities: KOI-614b, KOI-206b, and KOI-680b.
KOI-614b has a mass of and a radius of
, and it orbits a G0, metallic
([Fe/H]=) dwarf in 12.9 days. Its mass and radius are familiar and
compatible with standard planetary evolution models, so it is one of the few
known transiting planets in this mass range to have an orbital period over ten
days. With an equilibrium temperature of K, this places
KOI-614b at the transition between what is usually referred to as "hot" and
"warm" Jupiters. KOI-206b has a mass of and a
radius of , and it orbits a slightly evolved F7-type
star in a 5.3-day orbit. It is a massive inflated hot Jupiter that is
particularly challenging for planetary models because it requires unusually
large amounts of additional dissipated energy in the planet. On the other hand,
KOI-680b has a much lower mass of and requires less
extra-dissipation to explain its uncommonly large radius of . It is one of the biggest transiting planets characterized so far,
and it orbits a subgiant F9-star well on its way to the red giant stage, with
an orbital period of 8.6 days. With host stars of masses of
and , respectively, KOI-206b,
and KOI-680b are interesting objects for theories of formation and survival of
short-period planets around stars more massive than the Sun. For those two
targets, we also find signs of a possible distant additional companion in the
system
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