1,523 research outputs found
Surviving opinions in Sznajd models on complex networks
The Sznajd model has been largely applied to simulate many sociophysical
phenomena. In this paper we applied the Sznajd model with more than two
opinions on three different network topologies and observed the evolution of
surviving opinions after many interactions among the nodes. As result, we
obtained a scaling law which depends of the network size and the number of
possible opinions. We also observed that this scaling law is not the same for
all network topologies, being quite similar between scale-free networks and
Sznajd networks but different for random networks.Comment: 9 pages, 3 figure
Energy Resolution Enhancement of Mercuric Iodide Detectors
A pulse processing technique has been developed which improves the gamma-ray energy resolution of mercuric iodide detectors. The technique employs a fast (100 ns) and a slow (6.4 µs) pulse height analysis to correct for signal variations due to variations in charge trapping. The capabilities of the technique for energy resolution enhancement are discussed as well as the utility of the technique for examining the trapping characteristics of individual detectors. We have achieved an energy resolution of 2.6% FWHM at 662 keV with an acceptance efficiency of 100% from a mercuric iodide detector which gives 8.3% FWHM using standard techniques
Is the Cepheus E Outflow driven by a Class 0 Protostar?
New early release observations of the Cepheus E outflow and its embedded
source, obtained with the Spitzer Space Telescope, are presented. We show the
driving source is detected in all 4 IRAC bands, which suggests that traditional
Class 0 classification, although essentially correct, needs to accommodate the
new high sensitivity infrared arrays and their ability to detected deeply
embedded sources. The IRAC, MIPS 24 and 70 microns new photometric points are
consistent with a spectral energy distribution dominated by a cold, dense
envelope surrounding the protostar. The Cep E outflow, unlike its more famous
cousin the HH 46/47 outflow, displays a very similar morphology in the near and
mid-infrared wavelengths, and is detected at 24 microns. The interface between
the dense molecular gas (where Cep E lies) and less dense interstellar medium,
is well traced by the emission at 8 and 24 microns, and is one of the most
exotic features of the new IRAC and MIPS images. IRS observations of the North
lobe of the flow confirm that most of the emission is due to the excitation of
pure H2 rotational transitions arising from a relatively cold (Tex~700 K) and
dense (N{H}~9.6E20 cm-2 molecular gas.Comment: 14 pages (pre-print format), including 6 figures. Published in ApJ
Special Spitzer Issue (2004
A Catalog of Background Stars Reddened by Dust in the Taurus Dark Clouds
Normal field stars located behind dense clouds are a valuable resource in
interstellar astrophysics, as they provide continua in which to study phenomena
such as gas-phase and solid-state absorption features, interstellar extinction
and polarization. This paper reports the results of a search for highly
reddened stars behind the Taurus Dark Cloud complex. We use the Two Micron All
Sky Survey (2MASS) Point Source Catalog to survey a 50 sq deg area of the cloud
to a limiting magnitude of K = 10.0. Photometry in the 1.2-2.2 micron passbands
from 2MASS is combined with photometry at longer infrared wavelengths (3.6-12
micron) from the Spitzer Space Telescope and the Infrared Astronomical
Satellite to provide effective discrimination between reddened field stars and
young stellar objects (YSOs) embedded in the cloud. Our final catalog contains
248 confirmed or probable background field stars, together with estimates of
their total visual extinctions, which span the range 2-29 mag. We also identify
the 2MASS source J04292083+2742074 (IRAS 04262+2735) as a previously
unrecognized candidate YSO, based on the presence of infrared emission greatly
in excess of that predicted for a normal reddened photosphere at wavelengths >5
microns
Spin-orbit hybrid entanglement of photons and quantum contextuality
We demonstrate electromagnetic quantum states of single photons and of
correlated photon pairs exhibiting "hybrid" entanglement between spin and
orbital angular momentum. These states are obtained from entangled photon pairs
emitted by spontaneous parametric down conversion, by employing a -plate for
coupling the spin and orbital degrees of freedom of a photon. Entanglement and
contextual quantum behavior (that is also non-local, in the case of photon
pairs) is demonstrated by the reported violation of the
Clauser-Horne-Shimony-Holt inequality. In addition a classical analog of the
hybrid spin-orbit photonic entanglement is reported and discussed.Comment: 5 pages, 3 figure
Analysis of Neighbourhoods in Multi-layered Dynamic Social Networks
Social networks existing among employees, customers or users of various IT
systems have become one of the research areas of growing importance. A social
network consists of nodes - social entities and edges linking pairs of nodes.
In regular, one-layered social networks, two nodes - i.e. people are connected
with a single edge whereas in the multi-layered social networks, there may be
many links of different types for a pair of nodes. Nowadays data about people
and their interactions, which exists in all social media, provides information
about many different types of relationships within one network. Analysing this
data one can obtain knowledge not only about the structure and characteristics
of the network but also gain understanding about semantic of human relations.
Are they direct or not? Do people tend to sustain single or multiple relations
with a given person? What types of communication is the most important for
them? Answers to these and more questions enable us to draw conclusions about
semantic of human interactions. Unfortunately, most of the methods used for
social network analysis (SNA) may be applied only to one-layered social
networks. Thus, some new structural measures for multi-layered social networks
are proposed in the paper, in particular: cross-layer clustering coefficient,
cross-layer degree centrality and various versions of multi-layered degree
centralities. Authors also investigated the dynamics of multi-layered
neighbourhood for five different layers within the social network. The
evaluation of the presented concepts on the real-world dataset is presented.
The measures proposed in the paper may directly be used to various methods for
collective classification, in which nodes are assigned to labels according to
their structural input features.Comment: 16 pages, International Journal of Computational Intelligence System
The Circumstellar Disk of the Butterfly Star in Taurus
We present a model of the circumstellar environment of the so-called
``Butterfly Star'' in Taurus (IRAS 04302+2247). The appearance of this young
stellar object is dominated by a large circumstellar disk seen edge-on and the
light scattering lobes above the disk. The model is based on multi-wavelength
continuum observations: Millimeter maps and high-resolution near-infrared
images obtained with HST/NICMOS.
It was found that the disk and envelope parameters are comparable with those
of the circumstellar environment of other young stellar objects. A main result
is that the dust properties must be different in the circumstellar disk and in
the envelope: While a grain size distribution with grain radii up to 100 micron
is required to reproduce the millimeter observations of the disk, the envelope
is dominated by smaller grains similar to those of the interstellar medium.
Preprint with high figure quality available at:
http://spider.ipac.caltech.edu/staff/swolf/homepage/public/preprints/i04302.psComment: 32 pages, 9 figure
Reduction algorithms for the multiband imaging photometer for Spitzer: 6 months of flight data
The first six months of flight data from the Multiband Imaging Photometer for Spitzer (MIPS) were used to test MIPS reduction algorithms based on extensive preflight laboratory data and modeling. The underlying approach for the preflight algorithms has been found to be sound, but some modifications have improved the performance. The main changes are scan mirror dependent flat fields at 24 μm, hand processing to remove the time dependent stim flash latents and fast/slow response variations at 70 μm, and the use of asteroids and other sources instead of stars for flux calibration at 160 μm due to a blue "leak." The photometric accuracy of flux measurements is currently 5%, 10%, and 20% at 24, 70, and 160 μm, respectively. These numbers are expected to improve as more flight data are analyzed and data reduction algorithms refined
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