11,590 research outputs found
Evolving a DSL implementation
Domain Specific Languages (DSLs) are small languages designed for use in a specific domain. DSLs typically evolve quite radically throughout their lifetime, but current DSL implementation approaches are often clumsy in the face of such evolution. In this paper I present a case study of an DSL evolving in its syntax, semantics, and robustness, implemented in the Converge language. This shows how real-world DSL implementations can evolve along with changing requirements
ShapeFit and ShapeKick for Robust, Scalable Structure from Motion
We introduce a new method for location recovery from pair-wise directions
that leverages an efficient convex program that comes with exact recovery
guarantees, even in the presence of adversarial outliers. When pairwise
directions represent scaled relative positions between pairs of views
(estimated for instance with epipolar geometry) our method can be used for
location recovery, that is the determination of relative pose up to a single
unknown scale. For this task, our method yields performance comparable to the
state-of-the-art with an order of magnitude speed-up. Our proposed numerical
framework is flexible in that it accommodates other approaches to location
recovery and can be used to speed up other methods. These properties are
demonstrated by extensively testing against state-of-the-art methods for
location recovery on 13 large, irregular collections of images of real scenes
in addition to simulated data with ground truth
Physical properties of high-mass clumps in different stages of evolution
(Abridged) Aims. To investigate the first stages of the process of high-mass
star formation, we selected a sample of massive clumps previously observed with
the SEST at 1.2 mm and with the ATNF ATCA at 1.3 cm. We want to characterize
the physical conditions in such sources, and test whether their properties
depend on the evolutionary stage of the clump.
Methods. With ATCA we observed the selected sources in the NH3(1,1) and (2,2)
transitions and in the 22 GHz H2O maser line. Ammonia lines are a good
temperature probe that allow us to accurately determine the mass and the
column-, volume-, and surface densities of the clumps. We also collected all
data available to construct the spectral energy distribution of the individual
clumps and to determine if star formation is already occurring, through
observations of its most common signposts, thus putting constraints on the
evolutionary stage of the source. We fitted the spectral energy distribution
between 1.2 mm and 70 microns with a modified black body to derive the dust
temperature and independently determine the mass.
Results. The clumps are cold (T~10-30 K), massive (M~10^2-10^3 Mo), and dense
(n(H2)>~10^5 cm^-3) and they have high column densities (N(H2)~10^23 cm^-2).
All clumps appear to be potentially able to form high-mass stars. The most
massive clumps appear to be gravitationally unstable, if the only sources of
support against collapse are turbulence and thermal pressure, which possibly
indicates that the magnetic field is important in stabilizing them.
Conclusions. After investigating how the average properties depend on the
evolutionary phase of the source, we find that the temperature and central
density progressively increase with time. Sources likely hosting a ZAMS star
show a steeper radial dependence of the volume density and tend to be more
compact than starless clumps.Comment: Published in A&A, Vol. 556, A1
Trigonometric Parallaxes of Massive Star-Forming Regions. IX. The Outer Arm in the First Quadrant
We report a trigonometric parallax measurement with the Very Long Baseline
Array for the water maser in the distant high-mass star-forming region
G75.30+1.32. This source has a heliocentric distance of 9.25+-0.45 kpc, which
places it in the Outer arm in the first Galactic quadrant. It lies 200 pc above
the Galactic plane and is associated with a substantial HI enhancement at the
border of a large molecular cloud. At a Galactocentric radius of 10.7 kpc,
G75.30+1.32 is in a region of the Galaxy where the disk is significantly warped
toward the North Galactic Pole. While the star-forming region has an
instantaneous Galactic orbit that is nearly circular, it displays a significant
motion of 18 km/s toward the Galactic plane. The present results, when combined
with two previous maser studies in the Outer arm, yield a pitch angle of about
12 degrees for a large section of the arm extending from the first quadrant to
the third.Comment: 19 pages, 5 figures, 4 tables, accepted by The Astrophysical Journa
Determinação do poder calorífico de resíduos florestais em função do seu teor de umidade.
Resumo
Briquetagem de biomassa florestal: variáveis do processo e qualidade do produto.
EVINCI. Resumo
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