4,302 research outputs found
State of the art of pricing policy in air transportation: network carriers vs. low-cost airlines
The modern air transport industry is highly competitive. To survive in the market, the implementation of a successful marketing strategy is fundamental. In particular, an effective pricing policy has become crucial for airlines to remain profitable. Correspondingly, the different types of airline in the market have also established very distinct pricing policies. The present study is based on a literature review and presents the state of the art of pricing policy in air transportation. The aim is to compare and discuss the pricing strategies of network carriers and low-cost airlines. Special attention is paid to Revenue Management, which is a very important management tool used by airlines to take advantage of the differences in willingness to pay of passengers. The pricing policy, however, depends on the overall business strategy of the airline. Results show many differences, resulting from the fact that these two types of airline are characterized by very different fundamental business models and, correspondingly, also target groups. Since network carriers and also low-cost airlines have adjusted their pricing strategies lately, these recent developments will be discussed as well. This paper adds to the knowledge of this topic because it presents the most up-to-date and complete study on pricing regarding network carriers vs. low-cost airlines.A moderna indústria do transporte aéreo é altamente competitiva. Para
sobreviver no mercado, a implementação de uma estratégia de marketing
bem-sucedida é fundamental. Em particular, uma política de preços eficaz
tornou-se crucial para as companhias aéreas continuarem lucrativas. Os
diferentes tipos de companhias aéreas no mercado também
estabeleceram políticas de preços muito distintas. O presente estudo
baseia-se numa revisão da literatura e apresenta o estado da arte da
política de preços no transporte aéreo. O objetivo é comparar e discutir
as estratégias de preços de companhias aéreas de linha e companhias
aéreas de baixo custo. Atenção especial é dada à Gestão de Receitas
(Revenue Management), que é uma ferramenta de gestão usada pelas
companhias aéreas para aproveitar as diferenças na disposição de pagar
dos passageiros. A política de preços, no entanto, depende da estratégia
geral de negócios da companhia aérea. Os resultados mostram muitas
diferenças, resultantes do facto de que esses dois tipos de companhias
aéreas são caracterizados por modelos de negócios fundamentais muito
diferentes e, correspondentemente, também grupos-alvo. Como as
operadoras de rede e também as companhias aéreas de baixo custo
ajustaram as suas estratégias de preços ultimamente, esses
desenvolvimentos recentes também serão discutidos. Este documento
contribui para o conhecimento deste tópico, pois apresenta o estudo mais
atualizado e completo sobre preços de companhias aéreas de linha versus
companhias aéreas de baixo custo.info:eu-repo/semantics/publishedVersio
Comment on "Theory and computer simulation for the equation of state of additive hard-disk fluid mixtures"
A flaw in the comparison between two different theoretical equations of state
for a binary mixture of additive hard disks and Monte Carlo results, as
recently reported in C. Barrio and J. R. Solana, Phys. Rev. E 63, 011201
(2001), is pointed out. It is found that both proposals, which require the
equation of state of the single component system as input, lead to comparable
accuracy but the one advocated by us [A. Santos, S. B. Yuste, and M. L\'{o}pez
de Haro, Mol. Phys. 96, 1 (1999)] is simpler and complies with the exact limit
in which the small disks are point particles.Comment: 4 pages, including 1 figur
Are beryllium abundances anomalous in stars with giant planets?
In this paper we present beryllium (Be) abundances in a large sample of 41
extra-solar planet host stars, and for 29 stars without any known
planetary-mass companion, spanning a large range of effective temperatures. The
Be abundances were derived through spectral synthesis done in standard Local
Thermodynamic Equilibrium, using spectra obtained with various instruments. The
results seem to confirm that overall, planet-host stars have ``normal'' Be
abundances, although a small, but not significant, difference might be present.
This result is discussed, and we show that this difference is probably not due
to any stellar ``pollution'' events. In other words, our results support the
idea that the high-metal content of planet-host stars has, overall, a
``primordial'' origin. However, we also find a small subset of planet-host
late-F and early-G dwarfs that might have higher than average Be abundances.
The reason for the offset is not clear, and might be related either to the
engulfment of planetary material, to galactic chemical evolution effects, or to
stellar-mass differences for stars of similar temperature.Comment: 15 pages, 9 figures, accepted for publication in Astronomy &
Astrophysic
Abrupt Changes in the Dynamics of Quantum Disentanglement
Entanglement evolution in high dimensional bipartite systems under
dissipation is studied. Discontinuities for the time derivative of the lower
bound of entanglement of formation is found depending on the initial conditions
for entangled states. This abrupt changes along the evolution appears as
precursors of entanglement sudden death.Comment: 4 pages and 6 figures, submitted for publicatio
Light elements in stars with exoplanets
It is well known that stars orbited by giant planets have higher abundances
of heavy elements when compared with average field dwarfs. A number of studies
have also addressed the possibility that light element abundances are different
in these stars. In this paper we will review the present status of these
studies. The most significant trends will be discussed.Comment: 10 pages, 6 figures. Submitted to the proceedings of IAU symposium
268: Light elements in the universe
Beryllium anomalies in solar-type field stars
We present a study of beryllium (Be) abundances in a large sample of field
solar-type dwarfs and sub-giants spanning a large range of effective
temperatures. The analysis shows that Be is severely depleted for F stars, as
expected by the light-element depletion models. However, we also show that
Beryllium abundances decrease with decreasing temperature for stars cooler than
6000 K, a result that cannot be explained by current theoretical models
including rotational mixing, but that is, at least in part, expected from the
models that take into account internal wave physics. In particular, the light
element abundances of the coolest and youngest stars in our sample suggest that
Be, as well as lithium (Li), has already been burned early during their
evolution. Furthermore, we find strong evidence for the existence of a Be-gap
for solar-temperature stars. The analysis of Li and Be abundances in the
sub-giants of our sample also shows the presence of one case that has still
detectable amounts of Li, while Be is severely depleted. Finally, we compare
the derived Be abundances with Li abundances derived using the same set of
stellar parameters. This gives us the possibility to explore the temperatures
for which the onset of Li and Be depletion occurs.Comment: 16 pages, 13 figures, accepted for publication in Astronomy &
Astrophysic
Nitrogen abundances in Planet-harbouring stars
We present a detailed spectroscopic analysis of nitrogen abundances in 91
solar-type stars, 66 with and 25 without known planetary mass companions. All
comparison sample stars and 28 planet hosts were analysed by spectral synthesis
of the near-UV NH band at 3360 \AA observed at high resolution with the
VLT/UVES,while the near-IR NI 7468 \AA was measured in 31 objects. These two
abundance indicators are in good agreement. We found that nitrogen abundance
scales with that of iron in the metallicity range -0.6 <[Fe/H]< +0.4 with the
slope 1.08 \pm 0.05. Our results show that the bulk of nitrogen production at
high metallicities was coupled with iron. We found that the nitrogen abundance
distribution in stars with exoplanets is the high [Fe/H] extension of the curve
traced by the comparison sample of stars with no known planets. A comparison of
our nitrogen abundances with those available in the literature shows a good
agreement.Comment: 15 pages, 7 figures, Accepted for publication in A&
Beryllium abundances in stars hosting giant planets
We have derived beryllium abundances in a wide sample of stars hosting
planets, with spectral types in the range F7V-K0V, aimed at studying in detail
the effects of the presence of planets on the structure and evolution of the
associated stars. Predictions from current models are compared with the derived
abundances and suggestions are provided to explain the observed
inconsistencies. We show that while still not clear, the results suggest that
theoretical models may have to be revised for stars with Teff<5500K. On the
other hand, a comparison between planet host and non-planet host stars shows no
clear difference between both populations. Although preliminary, this result
favors a ``primordial'' origin for the metallicity ``excess'' observed for the
planetary host stars. Under this assumption, i.e. that there would be no
differences between stars with and without giant planets, the light element
depletion pattern of our sample of stars may also be used to further
investigate and constraint Li and Be depletion mechanisms.Comment: A&A in press -- accepted on the 22/02/2002 (11 pages, 6 figures
included
Isotropy theorem for cosmological vector fields
We consider homogeneous Abelian vector fields in an expanding universe. We find a mechanical analogy in which the system behaves as a particle moving in three dimensions under the action of a central potential. In the case of bounded and rapid evolution compared to the rate of expansion, we show-by making use of the virial theorem-that for an arbitrary potential and polarization pattern, the average energy-momentum tensor is always diagonal and isotropic despite the intrinsic anisotropic evolution of the vector field. For simple power law potentials of the form V = lambda(A(mu)A(mu))(n), the average equation of state is found to be w = (n - 1)/(n + 1). This implies that vector coherent oscillations could act as natural dark matter or dark energy candidates. Finally, we show that under very general conditions, the average energy-momentum tensor of a rapidly evolving bounded vector field in any background geometry is always isotropic and has the perfect fluid form for any locally inertial observer
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