96 research outputs found
Dynamic update of a virtual cell for programming and safe monitoring of an industrial robot
A hardware/software architecture for robot motion planning and on-line safe monitoring has been developed with the objective to assure high flexibility in production control, safety for workers and machinery, with user-friendly interface. The architecture, developed using Microsoft Robotics Developers Studio and implemented for a six-dof COMAU NS 12 robot, established a bidirectional communication between the robot controller and a virtual replica of the real robotic cell. The working space of the real robot can then be easily limited for safety reasons by inserting virtual objects (or sensors) in such a virtual environment. This paper investigates the possibility to achieve an automatic, dynamic update of the virtual cell by using a low cost depth sensor (i.e., a commercial Microsoft Kinect) to detect the presence of completely unknown objects, moving inside the real cell. The experimental tests show that the developed architecture is able to recognize variously shaped mobile objects inside the monitored area and let the robot stop before colliding with them, if the objects are not too small
Homogeneous Photometry VI: Variable Stars in the Leo I Dwarf Spheroidal Galaxy
We have characterized the pulsation properties of 164 candidate RR Lyrae
variables (RRLs) and 55 candidate Anomalous and/or short-period Cepheids in Leo
I dwarf spheroidal galaxy. On the basis of its RRLs Leo I is confirmed to be an
Oosterhoff-intermediate type galaxy, like several other dwarfs. We show that in
their pulsation properties, the RRLs representing the oldest stellar population
in the galaxy are not significantly different from those of five other nearby,
isolated dwarf spheroidal galaxies. A similar result is obtained when comparing
them to RR Lyrae stars in recently discovered ultra-faint dwarf galaxies. We
are able to compare the period distributions and period-amplitude relations for
a statistically significant sample of ab type RR Lyrae stars in dwarf galaxies
(~1300stars) with those in the Galactic halo field (~14,000stars) and globular
clusters (~1000stars). Field RRLs show a significant change in their period
distribution when moving from the inner (dG14kpc)
halo regions. This suggests that the halo formed from (at least) two dissimilar
progenitors or types of progenitor. Considered together, the RRLs in classical
dwarf spheroidal and ultra-faint dwarf galaxies-as observed today-do not appear
to follow the well defined pulsation properties shown by those in either the
inner or the outer Galactic halo, nor do they have the same properties as RRLs
in globular clusters. In particular, the samples of fundamental-mode RRLs in
dwarfs seem to lack High Amplitudes and Short Periods ("HASP":AV>1.0mag and P
<0.48d) when compared with those observed in the Galactic halo field and
globular clusters. The observed properties of RRLs do not support the idea that
currently existing classical dwarf spheroidal and ultra-faint dwarf galaxies
are surviving representative examples of the original building blocks of the
Galactic halo.Comment: 49 pages in referee format, 12 figure
Relative Frequencies of Blue Stragglers in Galactic Globular Clusters: Constraints for the Formation Mechanisms
We discuss the main properties of the Galactic globular cluster (GC) blue
straggler stars (BSS), as inferred from our new catalog containing nearly 3000
BSS. The catalog has been extracted from the photometrically homogeneous V vs.
(B-V) color-magnitude diagrams (CMD) of 56 GCs, based on WFPC2 images of their
central cores. In our analysis we used consistent relative distances based on
the same photometry and calibration. The number of BSS has been normalized to
obtain relative frequencies (F_{BSS}) and specific densities (N_S) using
different stellar populations extracted from the CMD. The cluster F_{BSS} is
significantly smaller than the relative frequency of field BSS. We find a
significant anti-correlation between the BSS relative frequency in a cluster
and its total absolute luminosity (mass). There is no statistically significant
trend between the BSS frequency and the expected collision rate. F_{BSS} does
not depend on other cluster parameters, apart from a mild dependence on the
central density. PCC clusters act like normal clusters as far as the BSS
frequency is concerned. We also show that the BSS luminosity function for the
most luminous clusters is significantly different, with a brighter peak and
extending to brighter luminosities than in the less luminous clusters. These
results imply that the efficiency of BSS production mechanisms and their
relative importance vary with the cluster mass.Comment: 12 pages, 3 figures. accepted for publication in ApJ
On the use of asymmetric PSF on NIR images of crowded stellar fields
We present data collected using the camera PISCES coupled with the Firt Light
Adaptive Optics (FLAO) mounted at the Large Binocular Telescope (LBT). The
images were collected using two natural guide stars with an apparent magnitude
of R<13 mag. During these observations the seeing was on average ~0.9". The AO
performed very well: the images display a mean FWHM of 0.05 arcsec and of 0.06
arcsec in the J- and in the Ks-band, respectively. The Strehl ratio on the
quoted images reaches 13-30% (J) and 50-65% (Ks), in the off and in the central
pointings respectively. On the basis of this sample we have reached a J-band
limiting magnitude of ~22.5 mag and the deepest Ks-band limiting magnitude ever
obtained in a crowded stellar field: Ks~23 mag.
J-band images display a complex change in the shape of the PSF when moving at
larger radial distances from the natural guide star. In particular, the stellar
images become more elongated in approaching the corners of the J-band images
whereas the Ks-band images are more uniform. We discuss in detail the strategy
used to perform accurate and deep photometry in these very challenging images.
In particular we will focus our attention on the use of an updated version of
ROMAFOT based on asymmetric and analytical Point Spread Functions.
The quality of the photometry allowed us to properly identify a feature that
clearly shows up in NIR bands: the main sequence knee (MSK). The MSK is
independent of the evolutionary age, therefore the difference in magnitude with
the canonical clock to constrain the cluster age, the main sequence turn off
(MSTO), provides an estimate of the absolute age of the cluster. The key
advantage of this new approach is that the error decreases by a factor of two
when compared with the classical one. Combining ground-based Ks with space
F606W photometry, we estimate the absolute age of M15 to be 13.70+-0.80 Gyr.Comment: 15 pages, 7 figures, presented at the SPIE conference 201
On the potential and limitations of quantum extreme learning machines
Quantum reservoir computers (QRC) and quantum extreme learning machines
(QELM) aim to efficiently post-process the outcome of fixed -- generally
uncalibrated -- quantum devices to solve tasks such as the estimation of the
properties of quantum states. The characterisation of their potential and
limitations, which is currently lacking, will enable the full deployment of
such approaches to problems of system identification, device performance
optimization, and state or process reconstruction. We present a framework to
model QRCs and QELMs, showing that they can be concisely described via single
effective measurements, and provide an explicit characterisation of the
information exactly retrievable with such protocols. We furthermore find a
close analogy between the training process of QELMs and that of reconstructing
the effective measurement characterising the given device. Our analysis paves
the way to a more thorough understanding of the capabilities and limitations of
both QELMs and QRCs, and has the potential to become a powerful measurement
paradigm for quantum state estimation that is more resilient to noise and
imperfections.Comment: 12 pages, 7 figures, comments welcom
Stellar photometry with Multi Conjugate Adaptive Optics
We overview the current status of photometric analyses of images collected
with Multi Conjugate Adaptive Optics (MCAO) at 8-10m class telescopes that
operated, or are operating, on sky. Particular attention will be payed to
resolved stellar population studies. Stars in crowded stellar systems, such as
globular clusters or in nearby galaxies, are ideal test particles to test AO
performance. We will focus the discussion on photometric precision and accuracy
reached nowadays. We briefly describe our project on stellar photometry and
astrometry of Galactic globular clusters using images taken with GeMS at the
Gemini South telescope. We also present the photometry performed with DAOPHOT
suite of programs into the crowded regions of these globulars reaching very
faint limiting magnitudes Ks ~21.5 mag on moderately large fields of view (~1.5
arcmin squared). We highlight the need for new algorithms to improve the
modeling of the complex variation of the Point Spread Function across the field
of view. Finally, we outline the role that large samples of stellar standards
plays in providing a detailed description of the MCAO performance and in
precise and accurate colour{magnitude diagrams.Comment: 17 pages, 12 figures, SPIE 201
The Blue Hook Populations of Massive Globular Clusters
We present new HST ultraviolet color-magnitude diagrams of 5 massive Galactic
globular clusters: NGC 2419, NGC 6273, NGC 6715, NGC 6388, and NGC 6441. These
observations were obtained to investigate the "blue hook" phenomenon previously
observed in UV images of the globular clusters omega Cen and NGC 2808. Blue
hook stars are a class of hot (approximately 35,000 K) subluminous horizontal
branch stars that occupy a region of the HR diagram that is unexplained by
canonical stellar evolution theory. By coupling new stellar evolution models to
appropriate non-LTE synthetic spectra, we investigate various theoretical
explanations for these stars. Specifically, we compare our photometry to
canonical models at standard cluster abundances, canonical models with enhanced
helium (consistent with cluster self-enrichment at early times), and
flash-mixed models formed via a late helium-core flash on the white dwarf
cooling curve. We find that flash-mixed models are required to explain the
faint luminosity of the blue hook stars, although neither the canonical models
nor the flash-mixed models can explain the range of color observed in such
stars, especially those in the most metal-rich clusters. Aside from the
variation in the color range, no clear trends emerge in the morphology of the
blue hook population with respect to metallicity.Comment: Accepted for publication in The Astrophysical Journal. Latex, 14
pages, 1 B&W and 6 color figure
Alpsnmr: an r package for signal processing of fully untargeted nmr-based metabolomics
Nuclear magnetic resonance (NMR)-based metabolomics is widely used to obtain metabolic fingerprints of biological systems. While targeted workflows require previous knowledge of metabolites, prior to statistical analysis, untargeted approaches remain a challenge. Computational tools dealing with fully untargeted NMR-based metabolomics are still scarce or not user-friendly. Therefore, we developed AlpsNMR (Automated spectraL Processing System for NMR), an R package that provides automated and efficient signal processing for untargeted NMR metabolomics. AlpsNMR includes spectra loading, metadata handling, automated outlier detection, spectra alignment and peak-picking, integration and normalization. The resulting output can be used for further statistical analysis. AlpsNMR proved effective in detecting metabolite changes in a test case. The tool allows less experienced users to easily implement this workflow from spectra to a ready-to-use dataset in their routines
Stroemgren - near-infrared photometry of the Baade's Window. I. The bulge globular cluster NGC6528 and the surrounding field
We present Stroemgren-NIR photometry of NGC6528 and its surroundings in the
Baade's Window. uvby images were collected with EFOSC2@NTT, while NIR catalogs
are based on VIRCAM@VISTA and SOFI@NTT data. The matching with HST photometry
allowed us to obtain proper-motion-cleaned samples of cluster and bulge stars.
The huge color sensitivity of Stroemgren-NIR CMDs helped us in disentangling
age and metallicity effects. The RGB of NGC6528 is reproduced by scaled-solar
isochrones with solar abundance or alpha-enhanced isochrones with the same iron
content, and an age of t = 11+/-1 Gyr. These findings support literature age
estimates for NGC6528. We also performed a theoretical metallicity calibration
based on the Stroemgren index m1 and on visual-NIR colors for RGs, by adopting
scaled-solar and alpha-enhanced models. We applied the calibration to estimate
the metallicity of NGC6528, finding [Fe/H] = -0.04+/-0.02, with an intrinsic
dispersion of 0.27 dex (by averaging abundances based on the scaled-solar [m],
y - J and [m], y - K Metallicity-Index-Color relations), and of -0.11+/-0.01
(sig = 0.27 dex), by using the m1, y - J and m1, y - K relations. These
findings support the results of Zoccali et al. (2004) which give [Fe/H] =
-0.10+/-0.2, and a low alpha-enhancement, [alpha/Fe] = 0.1, and of Carretta et
al. (2001), that find [Fe/H] = 0.07+/-0.01, with [alpha/Fe] = 0.2. By applying
the scaled-solar MIC relations to Baade's window RGs, we find a metallicity
distribution extending from [Fe/H] ~ -1.0 to ~ 1 dex, with peaks at [Fe/H] ~
-0.2 and +0.55 ([m], y - J and [m], y - K relations), and [Fe/H] ~ -0.25 and
+0.4 (m1, y - J and m1, y - K relations). These findings are in good agreement
with the spectroscopic studies of Hill et al. (2011) for the Baade's window, of
Uttenthaler et al. (2012) for a region centered at (l,b) = (0, -10), and with
the results of the ARGOS survey (Ness et al. 2013a).Comment: 19 pages, 13 figures, 3 tables, accepted for publication on Astronomy
& Astrophysic
On the dwarf irregular galaxy NGC 6822. I. Young, intermediate and old stellar populations
We present accurate and deep multi-band () photometry of the Local
Group dwarf irregular galaxy NGC 6822. The images were collected with wide
field cameras at 2m/4m- (INT,CTIO,CFHT) and 8m-class telescopes (SUBARU)
covering a 2 square degrees FoV across the center of the galaxy. We performed
PSF photometry of 7,000 CCD images and the final catalog includes more
than 1 million objects. We developed a new approach to identify candidate field
and galaxy stars, and performed a new estimate of the galaxy center by using
old stellar tracers finding that it differs by 1.15 (RA) and 1.53 (DEC) arcmin
from previous estimates. We also found that young (Main Sequence, Red
Supergiants), intermediate (Red Clump, Asymptotic Giant Branch [AGB]) and old
(Red Giant Branch [RGB]) stars display different radial distributions. Old
stellar population is spherically distributed and extends to radial distances
larger than previously estimated (1 degree). The young population shows a
well defined bar and a disk-like distribution, as suggested by radio
measurements, that is off-center compared with old population. We discuss pros
and cons of the different diagnostics adopted to identify AGB stars and develop
new ones based on optical-NIR-MIR color-color diagrams (CCDs) to characterize
Oxygen and Carbon (C) rich stars. We found a mean population ratio between
Carbon and M-type (C/M) stars of 0.670.08 (optical/NIR/MIR) and we used
the observed C/M ratio with empirical C/M-metallicity relations to estimate a
mean iron abundance of [Fe/H]-1.25 (=0.04 dex) that agrees quite
well with literature estimates.Comment: Accepted for publication in ApJ, 34 pages, 22 figures, 6 table
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