4,274 research outputs found
A neural network system for transformation of regional cuisine style
We propose a novel system which can transform a recipe into any selected
regional style (e.g., Japanese, Mediterranean, or Italian). This system has two
characteristics. First the system can identify the degree of regional cuisine
style mixture of any selected recipe and visualize such regional cuisine style
mixtures using barycentric Newton diagrams. Second, the system can suggest
ingredient substitutions through an extended word2vec model, such that a recipe
becomes more authentic for any selected regional cuisine style. Drawing on a
large number of recipes from Yummly, an example shows how the proposed system
can transform a traditional Japanese recipe, Sukiyaki, into French style
Cosmological Growth History of Supermassive Black Holes and Demographics in the High-z Universe : Do Lyman-Break Galaxies Have Supermassive Black Holes?
We study the demographics of supermassive black holes (SMBHs) in the local
and high-z universe with hard X-ray luminosity functions (HXLFs) of AGNs.
First, we compare the mass accretion history at z>0 with optical luminosity
functions (OLFs) and that with HXLFs. We consider the constraints on parameters
of mass accretion (energy conversion efficiency and Eddington ratio) and
conclude that the constraints based on HXLFs are more adequate rather than that
based on OLFs. The sub-Eddington case is allowed only when we use HXLFs. Next,
we estimate the upper limit of the cumulative mass density of SMBHs at any
redshifts. For an application, we examine if Lyman-Break galaxies (LBGs) at z=3
already have SMBHs in their centers which is suggested by recent observations.
If most of LBGs already has massive SMBHs at z=3, the resultant mass density of
SMBHs at z=0 should exceed the observational estimate because such SMBHs should
further grow by accretion. We show that the special conditions should be met in
order that a large part of LBGs have SMBHs (for example, large energy
conversion efficiency and frequent mergers and/or direct formations at z>3).
The possibility that nearly all LBGs have SMBHs with large mass ratio, such as
M_BH/M_stellar > 0.005, is reliably ruled out.(abridged)Comment: 30 pages including 5 figures, accepted for publication in Ap
What Sets the Initial Rotation Rates of Massive Stars?
The physical mechanisms that set the initial rotation rates in massive stars
are a crucial unknown in current star formation theory. Observations of young,
massive stars provide evidence that they form in a similar fashion to their
low-mass counterparts. The magnetic coupling between a star and its accretion
disk may be sufficient to spin down low-mass pre-main sequence (PMS) stars to
well below breakup at the end stage of their formation when the accretion rate
is low. However, we show that these magnetic torques are insufficient to spin
down massive PMS stars due to their short formation times and high accretion
rates. We develop a model for the angular momentum evolution of stars over a
wide range in mass, considering both magnetic and gravitational torques. We
find that magnetic torques are unable to spin down either low or high mass
stars during the main accretion phase, and that massive stars cannot be spun
down significantly by magnetic torques during the end stage of their formation
either. Spin-down occurs only if massive stars' disk lifetimes are
substantially longer or their magnetic fields are much stronger than current
observations suggest.Comment: 12 pages, 10 figures, Accepted for publication in Ap
The Protostellar Luminosity Function
The protostellar luminosity function (PLF) is the present-day luminosity
function of the protostars in a region of star formation. It is determined
using the protostellar mass function (PMF) in combination with a stellar
evolutionary model that provides the luminosity as a function of instantaneous
and final stellar mass. As in McKee & Offner (2010), we consider three main
accretion models: the Isothermal Sphere model, the Turbulent Core model, and an
approximation of the Competitive Accretion model. We also consider the effect
of an accretion rate that tapers off linearly in time and an accelerating star
formation rate. For each model, we characterize the luminosity distribution
using the mean, median, maximum, ratio of the median to the mean, standard
deviation of the logarithm of the luminosity, and the fraction of very low
luminosity objects. We compare the models with bolometric luminosities observed
in local star forming regions and find that models with an approximately
constant accretion time, such as the Turbulent Core and Competitive Accretion
models, appear to agree better with observation than those with a constant
accretion rate, such as the Isothermal Sphere model. We show that observations
of the mean protostellar luminosity in these nearby regions of low-mass star
formation suggest a mean star formation time of 0.30.1 Myr. Such a
timescale, together with some accretion that occurs non-radiatively and some
that occurs in high-accretion, episodic bursts, resolves the classical
"luminosity problem" in low-mass star formation, in which observed protostellar
luminosities are significantly less than predicted. An accelerating star
formation rate is one possible way of reconciling the observed star formation
time and mean luminosity.Comment: 22 pages, 9 figures, accepted to Ap
Estrutura de custos do manejo do baixo impacto em florestas tropicais - um estudo de caso.
Este estudo teve o objetivo de analisar de forma pontual a estrutura de custos do manejo de baixo impacto em florestas tropicais com dois ciclos de corte. Os dados utilizados foram fornecidos por uma empresa que explora uma floresta situada no município de Marcelândia, Estado do Mato Grosso, e comercializa as toras com as indústrias da região. Os resultados demonstraram elevação dos custos variáveis ao longo do primeiro ciclo em função da implantação dos tratos silviculturais, com o custo fixo permanecendo inalterado. No segundo ciclo, ocorreu redução no custo total em razão do aumento da produtividade para 15m3/ha e da eliminação de operações das atividades pré-exploratória e exploratória. Dos componentes do custo fixo, o custo administrativo é o mais elevado, representando 26,2% do custo total, ou R 22,33/m3, dos quais R$ 12,92/m3 são consumidos pela abertura de estradas e o arraste
The Rossiter-McLaughlin effect and analytic radial velocity curves for transiting extrasolar planetary systems
A transiting extrasolar planet sequentially blocks off the light coming from
the different parts of the disk of the host star in a time dependent manner.
Due to the spin of the star, this produces an asymmetric distortion in the line
profiles of the stellar spectrum, leading to an apparent anomaly of the radial
velocity curves, known as the Rossiter - McLaughlin effect. Here, we derive
approximate but accurate analytic formulae for the anomaly of radial velocity
curves taking account of the stellar limb darkening. The formulae are
particularly useful in extracting information of the projected angle between
the planetary orbit axis and the stellar spin axis, \lambda, and the projected
stellar spin velocity, V sin I_s. We create mock samples for the radial curves
for the transiting extrasolar system HD209458, and demonstrate that constraints
on the spin parameters (V sin I_s, \lambda) may be significantly improved by
combining our analytic template formulae and the precision velocity curves from
high-resolution spectroscopic observations with 8-10 m class telescopes. Thus
future observational exploration of transiting systems using the Rossiter -
McLaughlin effect is one of the most important probes to better understanding
of the origin of extrasolar planetary systems, especially the origin of their
angular momentum.Comment: 39 pages, 16 figures, Accepted to ApJ. To match the published version
(ApJ 623, April 10 issue
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