1,486 research outputs found
Identifying Alterability States of a Single Track Railway Line Control System
In the context of automation and deployment of computer based control systems, a specific application on French railway line is proposed on low traffic single track railway lines. The issue of updates requires thorough consideration. In the case of low traffic single track railway lines, handling the removal of a shunting track, which role is to allow trains to circulate in both directions of a same line, the issue of timing the update to the control system is particularly critical. Indeed, a wrongly timed update could lead to a deadlock, while one or more trains are expected to travel while respecting safety constraints on the blocked infrastructure. This paper studies the application of works from the field of dynamic software updating, specifically the works of Panzica La Manna et al. [12]. Using their results on a graph based model of a single track rail line, it identifies alterability states that ensure safety constraints are respected at all times without causing deadlocks. These results are then used to discuss the pertinence of using concepts from dynamic software updating in the context of railway systems
A photonic crystal Josephson traveling wave parametric amplifier
An amplifier combining noise performances as close as possible to the quantum
limit with large bandwidth and high saturation power is highly desirable for
many solid state quantum technologies such as high fidelity qubit readout or
high sensitivity electron spin resonance for example. Here we introduce a new
Traveling Wave Parametric Amplifier based on Superconducting QUantum
Interference Devices. It displays a 3 GHz bandwidth, a -102 dBm 1-dB
compression point and added noise near the quantum limit. Compared to previous
state-of-the-art, it is an order of magnitude more compact, its characteristic
impedance is in-situ tunable and its fabrication process requires only two
lithography steps. The key is the engineering of a gap in the dispersion
relation of the transmission line. This is obtained using a periodic modulation
of the SQUID size, similarly to what is done with photonic crystals. Moreover,
we provide a new theoretical treatment to describe the non-trivial interplay
between non-linearity and such periodicity. Our approach provides a path to
co-integration with other quantum devices such as qubits given the low
footprint and easy fabrication of our amplifier.Comment: 6 pages, 4 figures, Appendixe
Evidence for a large fraction of Compton-thick quasars at high redshift
Using mid-infrared and radio selection criteria, we pre-select a sample of
candidate high-redshift type-2 quasars in the Subaru XMM-Newton Deep Field
(SXDF). To filter out starburst contaminants, we use a bayesian method to fit
the spectral energy distributions (SEDs) between 24-microns and B-band, obtain
photometric redshifts, and identify the best candidates for high-z type-2
quasars. This leaves us with 12 z_phot >= 1.7 type-2 quasar candidates in an
area ~0.8 deg^2, of which only two have secure X-ray detections. The two
detected sources have estimated column densities N_H~2 & 3x10^27 m^-2, i.e.
heavily obscured but Compton-thin quasars. Given the large bolometric
luminosities and redshifts of the undetected objects, the lack of X-ray
detections suggests extreme absorbing columns N_H >= 10^28 m^-2 are typical. We
have found evidence for a population of ``Compton-thick'' high-redshift type-2
quasars, at least comparable to, and probably larger than the type-1 quasar
population, although spectroscopic confirmation of their AGN nature is
important.Comment: 6 pages, 2 colour figures. Accepted by MNRAS. Full resolution version
and supplementary figures can be found at:
http://www.mpia.de/homes/martinez/publications.htm
IVOA Recommendation: The UCD1+ controlled vocabulary Version 1.23
This document describes the list of controlled terms used to build the
Unified Content Descriptors, Version 1+ (UCD1+). The document describing the
UCD1+ can be found at the URL: http://www.ivoa.net/Documents/latest/UCD.html.
This document reviews the structure of the UCD1+ and presents the current
vocabulary
IVOA Recommendation: Vocabularies in the Virtual Observatory Version 1.19
This document specifies a standard format for vocabularies based on the W3C's
Resource Description Framework (RDF) and Simple Knowledge Organization System
(SKOS). By adopting a standard and simple format, the IVOA will permit
different groups to create and maintain their own specialised vocabularies
while letting the rest of the astronomical community access, use, and combine
them. The use of current, open standards ensures that VO applications will be
able to tap into resources of the growing semantic web. The document provides
several examples of useful astronomical vocabularies
Taking Back the Work: A Cooperative Inquiry into Leaders of Color in Movement-Building Organizations
Through the Leadership for a Changing World Research and Documentation program, a group of leaders of color committed to social justice came together to reflect on the specific obstacles leaders of color face as they engage in movement building and to find ways to overcome these barriers. Together they asked: How do we build, strengthen and sustain movement-building organizations led by people of color? In the report, the group has identified four strategies to help community-based leaders of color engage in "taking back the work," with examples of each based on their successful work in communities
The truncation of the disk of NGC 4565: Detected up to z=4 kpc, with star formation, and affected by the warp
Context: The hierarchical model of galaxy formation suggests that galaxies
are continuously growing. However, our position inside the Milky Way prevents
us from studying the disk edge. Truncations are low surface brightness features
located in the disk outskirts of external galaxies. They indicate where the
disk brightness abruptly drops and their location is thought to change
dynamically. In previous analyses of Milky Way-like galaxies, truncations were
detected up to 3 kpc above the mid-plane but whether they remain present beyond
that height remains unclear.
Aims: Our goal is to determine whether truncations can be detected above 3
kpc height in the Milky Way-like galaxy NGC 4565, thus establishing the actual
disk thickness. We also aim to study how the truncation relates to disk
properties such as star formation activity or the warp.
Methods: We perform a vertical study of the disk of NGC 4565 edge in
unprecedented detail. We explore the truncation radius at different heights
above/below the disk mid-plane (0<z<8 kpc) and at different wavelengths. We use
new ultra-deep optical data ( mag arcsec; within arcsec boxes) in the , and broad
bands, along with near- and far-ultraviolet, H, and \ion{H}{i}
observations.
Results: We detect the truncation up to 4 kpc in the , and
ultra-deep bands which is 1 kpc higher than in any previous study for any
galaxy. The radial position of the truncation remains constant up to 3 kpc
while higher up it is located at a smaller radius. This result is independent
of the wavelength but is affected by the presence of the warp.
Conclusions: We propose an inside-out growth scenario for the formation of
the disk of NGC 4565. Our results point towards the truncation feature being
linked to a star-forming threshold and to the onset of the disk warp.Comment: 27 pages, 18 figures (incl. 2 appendix); accepted for publication in
A&A; Fixed labels in Fig.
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