4,485 research outputs found
Revisiting the Hubble sequence in the SDSS DR7 spectroscopic sample: a publicly available bayesian automated classification
We present an automated morphological classification in 4 types
(E,S0,Sab,Scd) of ~700.000 galaxies from the SDSS DR7 spectroscopic sample
based on support vector machines. The main new property of the classification
is that we associate to each galaxy a probability of being in the four
morphological classes instead of assigning a single class. The classification
is therefore better adapted to nature where we expect a continuos transition
between different morphological types. The algorithm is trained with a visual
classification and then compared to several independent visual classifications
including the Galaxy Zoo first release catalog. We find a very good correlation
between the automated classification and classical visual ones. The compiled
catalog is intended for use in different applications and can be downloaded at
http://gepicom04.obspm.fr/sdss_morphology/Morphology_2010.html and soon from
the CasJobs database.Comment: A&A in press, english corrections from language editor adde
Matrix factorizations for quantum complete intersections
We introduce twisted matrix factorizations for quantum complete intersections
of codimension two. For such an algebra, we show that in a given dimension,
almost all the indecomposable modules with bounded minimal projective
resolutions correspond to such matrix factorizations.Comment: 13 page
Optical bandgap engineering in nonlinear silicon nitride waveguides
Silicon nitride is awell-established material for photonic devices and
integrated circuits. It displays a broad transparency window spanning from the
visible to the mid-IR and waveguides can be manufactured with low losses. An
absence of nonlinear multi-photon absorption in the erbium lightwave
communications band has enabled various nonlinear optic applications in the
past decade. Silicon nitride is a dielectric material whose optical and
mechanical properties strongly depend on the deposition conditions. In
particular, the optical bandgap can be modified with the gas flow ratio during
low-pressure chemical vapor deposition (LPCVD). Here we show that this
parameter can be controlled in a highly reproducible manner, providing an
approach to synthesize the nonlinear Kerr coefficient of the material. This
holistic empirical study provides relevant guidelines to optimize the
properties of LPCVD silicon nitride waveguides for nonlinear optics
applications that rely on the Kerr effect
Galaxy size trends as a consequence of cosmology
We show that recently documented trends in galaxy sizes with mass and
redshift can be understood in terms of the influence of underlying cosmic
evolution; a holistic view which is complimentary to interpretations involving
the accumulation of discreet evolutionary processes acting on individual
objects. Using standard cosmology theory, supported with results from the
Millennium simulations, we derive expected size trends for collapsed cosmic
structures, emphasising the important distinction between these trends and the
assembly paths of individual regions. We then argue that the observed variation
in the stellar mass content of these structures can be understood to first
order in terms of natural limitations of cooling and feedback. But whilst these
relative masses vary by orders of magnitude, galaxy and host radii have been
found to correlate linearly. We explain how these two aspects will lead to
galaxy sizes that closely follow observed trends and their evolution, comparing
directly with the COSMOS and SDSS surveys. Thus we conclude that the observed
minimum radius for galaxies, the evolving trend in size as a function of mass
for intermediate systems, and the observed increase in the sizes of massive
galaxies, may all be considered an emergent consequence of the cosmic
expansion.Comment: 14 pages, 13 figures. Accepted by MNRA
Interfacing Quantitative NDE with Computer Algorithms for Automated Statistical Process Control
In the Factory of the Future (FOF), production will be unified under a system of Computer Integrated Manufacturing (CIM). Automatic computer-integrated control of processes, detection of errors, and determination of corrective action will be necessary because of the proposed level of manpower in the FOFL[1,2]. Under these circumstances, a process which might go out of control and remain that way would be highly detrimental. Very rapid Statistical Process Control (SPC) will provide definitive warnings of out-of-control conditions
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