238 research outputs found
Extended two-body problem for rotating rigid bodies
A new technique that utilizes surface integrals to find the force, torque and
potential energy between two non-spherical, rigid bodies is presented. The
method is relatively fast, and allows us to solve the full rigid two-body
problem for pairs of spheroids and ellipsoids with 12 degrees of freedom. We
demonstrate the method with two dimensionless test scenarios, one where
tumbling motion develops, and one where the motion of the bodies resemble
spinning tops. We also test the method on the asteroid binary (66391) 1999 KW4,
where both components are modelled either as spheroids or ellipsoids. The two
different shape models have negligible effects on the eccentricity and
semi-major axis, but have a larger impact on the angular velocity along the
-direction. In all cases, energy and total angular momentum is conserved,
and the simulation accuracy is kept at the machine accuracy level.Comment: 24 pages, 9 figures, accepted for publication in Celestial Mechanics
and Dynamical Astronom
Segmentation techniques in image analysis: A comparative study
[EN] Nowadays, the detection, localization, and quantification of different kinds of features
in an RGB image (segmentation) is extremely helpful for, e.g., process monitoring
or customer product acceptance. In this article, some of the most commonly
used RGB image segmentation approaches are compared in an orange quality control
case study. Analysis of variance and correspondence analysis are combined for
determining their most relevant differences and highlighting their pros and cons.Spanish Ministry of Economy and Competitiveness, Grant/Award Number: DPI2014-55276-C5-1R; Spanish National Institute for Agricultural and Food Research and Technology (INIA), Grant/Award Number: RTA2012-00062-C04-01; European Regional Development Fund (FEDER); Shell Global Solutions International B.V.Vitale, R.; Prats-Montalbán, JM.; López García, F.; Blasco Ivars, J.; Ferrer, A. (2016). Segmentation techniques in image analysis: A comparative study. Journal of Chemometrics. 30(12):749-758. https://doi.org/10.1002/cem.2854S7497583012Prats-Montalbán, J. M., de Juan, A., & Ferrer, A. (2011). Multivariate image analysis: A review with applications. Chemometrics and Intelligent Laboratory Systems, 107(1), 1-23. doi:10.1016/j.chemolab.2011.03.002Bevilacqua, M., Bucci, R., Magrì, A. D., Magrì, A. L., Nescatelli, R., & Marini, F. (2013). Classification and Class-Modelling. Chemometrics in Food Chemistry, 171-233. doi:10.1016/b978-0-444-59528-7.00005-3Manning, C. D., Raghavan, P., & Schutze, H. (2008). Introduction to Information Retrieval. doi:10.1017/cbo9780511809071MacQueen J Some methods for classification and analysis of multivariate observations Proceedings of the Berkeley Symposium on Mathematical Statistics and Probability Berkeley, CA University of California Press 1967 281 297Haralick, R. M. (1979). Statistical and structural approaches to texture. Proceedings of the IEEE, 67(5), 786-804. doi:10.1109/proc.1979.11328Felzenszwalb, P. F., & Huttenlocher, D. P. (2004). Efficient Graph-Based Image Segmentation. International Journal of Computer Vision, 59(2), 167-181. doi:10.1023/b:visi.0000022288.19776.77Barker, M., & Rayens, W. (2003). Partial least squares for discrimination. Journal of Chemometrics, 17(3), 166-173. doi:10.1002/cem.785Postma, G. J., Krooshof, P. W. T., & Buydens, L. M. C. (2011). Opening the kernel of kernel partial least squares and support vector machines. Analytica Chimica Acta, 705(1-2), 123-134. doi:10.1016/j.aca.2011.04.025Vitale, R., de Noord, O. E., & Ferrer, A. (2014). A kernel-based approach for fault diagnosis in batch processes. Journal of Chemometrics, 28(8), S697-S707. doi:10.1002/cem.2629Prats-Montalbán, J. M., & Ferrer, A. (2007). Integration of colour and textural information in multivariate image analysis: defect detection and classification issues. Journal of Chemometrics, 21(1-2), 10-23. doi:10.1002/cem.1026Prats-Montalbán J Control estadístico de procesos mediante análisis multivariante de imágenes Ph.D. Thesis 2005López, F., Prats, J. M., Ferrer, A., & Valiente, J. M. (2006). Defect Detection in Random Colour Textures Using the MIA T2 Defect Maps. Image Analysis and Recognition, 752-763. doi:10.1007/11867661_68Ho, P.-G. (Ed.). (2011). Image Segmentation. doi:10.5772/628Pal, N. R., & Pal, S. K. (1993). A review on image segmentation techniques. Pattern Recognition, 26(9), 1277-1294. doi:10.1016/0031-3203(93)90135-jMATLAB R2012b (8.0.0.783), Natick, USA: The Mathworks IncWold, S., Esbensen, K., & Geladi, P. (1987). Principal component analysis. Chemometrics and Intelligent Laboratory Systems, 2(1-3), 37-52. doi:10.1016/0169-7439(87)80084-9Geladi, P., & Kowalski, B. R. (1986). Partial least-squares regression: a tutorial. Analytica Chimica Acta, 185, 1-17. doi:10.1016/0003-2670(86)80028-9Cao, D.-S., Liang, Y.-Z., Xu, Q.-S., Hu, Q.-N., Zhang, L.-X., & Fu, G.-H. (2011). Exploring nonlinear relationships in chemical data using kernel-based methods. Chemometrics and Intelligent Laboratory Systems, 107(1), 106-115. doi:10.1016/j.chemolab.2011.02.004Vitale, R., de Noord, O. E., & Ferrer, A. (2015). Pseudo-sample based contribution plots: innovative tools for fault diagnosis in kernel-based batch process monitoring. Chemometrics and Intelligent Laboratory Systems, 149, 40-52. doi:10.1016/j.chemolab.2015.09.013Hirschfeld, H. O. (1935). A Connection between Correlation and Contingency. Mathematical Proceedings of the Cambridge Philosophical Society, 31(4), 520-524. doi:10.1017/s030500410001351
A Simplified Model of ADAF with the Jet Driven by the Large-Scale Magnetic Field
We propose a simplified model of outflow/jet driven by the Blandford-Payne
(BP) process from advection dominated accretion flows (ADAF) and derive the
expressions of the BP power and disk luminosity based on the conservation laws
of mass, angular momentum and energy. We fit the 2--10 keV luminosity and
kinetic power of 15 active galactic nucleus (AGNs) of sub-Eddington luminosity.
It is found that there exists an anti-correlation between the accretion rate
and the advection parameter, which could be used to explain the correlation
between Eddington-scaled kinetic power and bolometric luminosity of the 15
samples. In addition, the Ledlow-Owen relation for FR I/II dichotomy is
re-expressed in a parameter space consisting of logarithm of dimensionless
accretion rate versus that of the BH mass. It turns out that the FR I/II
dichotomy is determined mainly by the dimensionless accretion rate, being
insensitive to the BH mass. And the dividing accretion rate is less than the
critical accretion rate for ADAFs, suggesting that FR I sources are all in the
ADAF state.Comment: 16 pages, 5 figures, 1 table. Accepted by New Astronom
The role of black hole mass in quasar radio activity
We use a homogeneous sample of about 300, 0.3 <~ z <~ 3, radio-loud quasars
drawn from the FIRST and 2dF QSO surveys to investigate a possible dependence
of radio activity on black-hole mass. By analyzing composite spectra for the
populations of radio-quiet and radio-loud QSOs -- chosen to have the same
redshift and luminosity distribution -- we find with high statistical
significance that radio-loud quasars are on average associated with black holes
of masses ~10^{8.6} M_sun, about twice as large as those measured for
radio-quiet quasars (~10^{8.3} M_sun). We also find a clear dependence of black
hole mass on optical luminosity of the form log (M_BH/M_sun)_{RL}= 8.57(\pm
0.06) - 0.27(\pm 0.06) (M_B + 24.5) and log (M_BH/M_sun)_{RQ}= 8.43(\pm 0.05)
-0.32(\pm 0.06) (M_B + 24.5), respectively for the case of radio-loud and
radio-quiet quasars. It is intriguing to note that these two trends run roughly
parallel to each other, implying that radio-loud quasars are associated to
black holes more massive than those producing the radio-quiet case at all
sampled luminosities. On the other hand, in the case of radio-loud quasars, we
find evidence for only a weak (if any) dependence of the black hole mass on
radio power. The above findings seem to support the belief that there exists --
at a given optical luminosity -- a threshold black hole mass associated with
the onset of significant radio activity such as that of radio-loud QSOs;
however, once the activity is triggered, there appears to be very little
connection between black hole mass and level of radio output.Comment: 10 pages, 10 figures, minor changes to match the accepted versio
Host galaxies of luminous quasars: population synthesis of optical off-axis spectra
There is increasing evidence of a connection between AGN activity and galaxy
evolution. To obtain further insight into this potentially important
evolutionary phase, we analyse the properties of quasar host galaxies. In this
paper, we present a population synthesis modeling technique for off-axis
spectra, the results of which constrain host colour and the stellar ages of
luminous quasars (M_V(nuc)<-23). Our technique is similar to well established
quiescent-galaxy models, modified to accommodate scattered nuclear light (a
combination of atmospheric, instrumental and host galaxy scattered light)
observed off axis. In our model, subtraction of residual scattered quasar light
is performed, while simultaneously modeling the constituent stellar populations
of the host galaxy. The reliability of this technique is tested via a
Monte-Carlo routine in which the correspondence between synthetic spectra with
known parameters and the model output is determined. Application of this model
to a preliminary sample of 10 objects is presented and compared to previous
studies. Spectroscopic data was obtained via long-slit and integral-field unit
observations on the Keck and WIYN telescopes. We confirm that elliptical quasar
hosts are distinguishable (bluer) from inactive ellipticals in rest frame B-V
colour. Additionally, we note a trend for radio luminous (L_5GHz > 10^40 erg
s^-1) quasars to be located in redder host galaxies in comparison to their less
luminous radio counterparts. While the host colour and age of our radio
luminous sample is in close proximity to the green valley, our radio faint
sample is consistent with quiescent star-forming galaxies. However, further
observations are needed to confirm these results. Finally, we discuss future
applications for our technique on a larger sample of objects being obtained via
SALT and WIYN telescope observing campaigns.Comment: 18 pages, 10 figures, accepted for publication in MNRA
High Grade Hemangioendothelioma of the Temporal Bone in a Child: A Case Report
Hemangioendothelioma is a rare vascular tumor characterized by endothelial tumor cells and variable malignant behavior, and it's not common for this lesion to involve the bone. Although there are a few reports of cranial involvement by hemangioendothelioma, only rare cases arising in temporal bone have been published. We present the radiologic findings of a 7-year-old boy who had a high grade hemangioendothelioma involving the temporal bone with intracranial extension. Evidence of flow voids on MR images suggested a tumor of vascular origin, and the ill-defined margins, cortical destruction and intracranial extension on the CT and MR images were correlated with the tumor's high histologic grade
Clustering of Radio Galaxies and Quasars
We compute the cross-correlation between a sample of 14,000 radio-loud AGN
(RLAGN) with redshifts between 0.4 and 0.8 selected from the Sloan Digital Sky
Survey and a reference sample of 1.2 million luminous red galaxies in the same
redshift range. We quantify how the clustering of radio-loud AGN depends on
host galaxy mass and on radio luminosity. Radio-loud AGN are clustered more
strongly on all scales than control samples of radio-quiet galaxies with the
same stellar masses and redshifts, but the differences are largest on scales
less than 1 Mpc. In addition, the clustering amplitude of the RLAGN varies
significantly with radio luminosity on scales less than 1 Mpc. This proves that
the gaseous environment of a galaxy on the scale of its dark matter halo, plays
a key role in determining not only the probability that a galaxy is radio-loud
AGN, but also the total luminosity of the radio jet. Next, we compare the
clustering of radio galaxies with that of radio-loud quasars in the same
redshift range. Unified models predict that both types of active nuclei should
cluster in the same way. Our data show that most RLAGN are clustered more
strongly than radio-loud QSOs, even when the AGN and QSO samples are matched in
both black hole mass and radio luminosity. Only the most extreme RLAGN and
RLQSOs in our sample, with radio luminosities in excess of 10^26 W/Hz, have
similar clustering properties. The majority of the strongly evolving RLAGN
population at z~0.5 are found in different environments to the quasars, and
hence must be triggered by a different physical mechanism.Comment: 12 pages, 13 Figures, submitted to MNRA
VISIR/VLT mid-infrared imaging of Seyfert nuclei: Nuclear dust emission and the Seyfert-2 dichotomy
Half of the Seyfert-2 galaxies escaped detection of broad lines in their
polarised spectra observed so far. Some authors have suspected that these
non-HBLRs contain real Sy2 nuclei without intrinsic broad line region hidden
behind a dust torus. If this were true, then their nuclear structure would
fundamentally differ from that of Sy2s with polarised broad lines: in
particular, they would not be explained by orientation-based AGN unification.
Further arguments for two physically different Sy2 populations have been
derived from the warm and cool IRAS F25/F60 ratios. These ratios, however,
refer to the entire host galaxies and are unsuitable to conclusively establish
the absence of a nuclear dust torus. Instead, a study of the Seyfert-2
dichotomy should be performed on the basis of nuclear properties only. Here we
present the first comparison between [OIII] 5007A and mid-infrared imaging at
matching spatial resolution. Exploring the Seyfert-2 dichotomy we find that the
distributions of nuclear mid-infrared/[OIII] luminosity ratios are
indistinguishable for Sy1s and Sy2s with and without detected polarised broad
lines and irrespective of having warm or cool IRAS F25/F60 ratios. We find no
evidence for the existence of a population of real Sy2s with a deficit of
nuclear dust emission. Our results suggest 1) that all Seyfert nuclei possess
the same physical structure including the putative dust torus and 2) that the
cool IRAS colours are caused by a low contrast of AGN to host galaxy. Then the
Seyfert-2 dichotomy is explained in part by unification of non-HBLRs with
narrow-line Sy1s and to a larger rate by observational biases caused by a low
AGN/host contrast and/or an unfavourable scattering geometry.Comment: 11 pages, 6 figures, accepted by A&
Precise Identifications of Submillimeter Galaxies: Measuring the History of Massive Star-Forming Galaxies to z>5
We carried out extremely sensitive Submillimeter Array (SMA) 340 GHz (860
micron) continuum imaging of a complete sample of SCUBA 850 micron sources (>4
sigma) with fluxes >3 mJy in the GOODS-N. Using these data and new SCUBA-2
data, we do not detect 4 of the 16 SCUBA sources, and we rule out the original
SCUBA fluxes at the 4 sigma level. Three more resolve into multiple fainter SMA
galaxies, suggesting that our understanding of the most luminous high-redshift
dusty galaxies may not be as reliable as we thought. 10 of the 16 independent
SMA sources have spectroscopic redshifts (optical/infrared or CO) to z=5.18.
Using a new, ultradeep 20 cm image obtained with the Karl G. Jansky Very Large
Array (rms of 2.5 microJy), we find that all 16 of the SMA sources are detected
at >5 sigma. Using Herschel far-infrared (FIR) data, we show that the five
isolated SMA sources with Herschel detections are well described by an Arp 220
spectral energy distribution template in the FIR. They also closely obey the
local FIR-radio correlation, a result that does not suffer from a radio bias.
We compute the contribution from the 16 SMA sources to the universal star
formation rate (SFR) per comoving volume. With individual SFRs in the range
700-5000 solar masses per year, they contribute ~30% of the
extinction-corrected ultraviolet-selected SFR density from z=1 to at least z=5.
Star formation histories determined from extinction-corrected ultraviolet
populations and from submillimeter galaxy populations only partially overlap,
due to the extreme ultraviolet faintness of some submillimeter galaxies.Comment: 26 pages, minor changes to match published versio
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