595 research outputs found
Tree automata and pigeonhole classes of matroids -- II
Let be a sentence in the counting monadic second-order logic of
matroids. Let F be a finite field. Hlineny's Theorem says there is a
fixed-parameter tractable algorithm for testing whether F-representable
matroids satisfy , with respect to the parameter of branch-width. In a
previous paper we proved there is a similar fixed-parameter tractable algorithm
for any efficiently pigeonhole class. In this sequel we apply results from the
first paper and thereby extend Hlineny's Theorem to the classes of fundamental
transversal matroids, lattice path matroids, bicircular matroids, and
H-gain-graphic matroids, when H is a finite group. As a consequence, we can
obtain a new proof of Courcelle's Theorem.Comment: Extending the main theorem slightly to cover a more expressive logi
Defining bicircular matroids in monadic logic
We conjecture that the class of frame matroids can be characterised by a
sentence in the monadic second-order logic of matroids, and we prove that there
is such a characterisation for the class of bicircular matroids. The proof does
not depend on an excluded-minor characterisation
Tree automata and pigeonhole classes of matroids -- I
Hlineny's Theorem shows that any sentence in the monadic second-order logic
of matroids can be tested in polynomial time, when the input is limited to a
class of F-representable matroids with bounded branch-width (where F is a
finite field). If each matroid in a class can be decomposed by a subcubic tree
in such a way that only a bounded amount of information flows across displayed
separations, then the class has bounded decomposition-width. We introduce the
pigeonhole property for classes of matroids: if every subclass with bounded
branch-width also has bounded decomposition-width, then the class is
pigeonhole. An efficiently pigeonhole class has a stronger property, involving
an efficiently-computable equivalence relation on subsets of the ground set. We
show that Hlineny's Theorem extends to any efficiently pigeonhole class. In a
sequel paper, we use these ideas to extend Hlineny's Theorem to the classes of
fundamental transversal matroids, lattice path matroids, bicircular matroids,
and H-gain-graphic matroids, where H is any finite group. We also give a
characterisation of the families of hypergraphs that can be described via tree
automata: a family is defined by a tree automaton if and only if it has bounded
decomposition-width. Furthermore, we show that if a class of matroids has the
pigeonhole property, and can be defined in monadic second-order logic, then any
subclass with bounded branch-width has a decidable monadic second-order theory.Comment: Slightly extending the main theorem to cover a more expressive logi
On excluded minors for real-representability
AbstractWe show that for any infinite field K and any K-representable matroid N there is an excluded minor for K-representability that has N as a minor
Commissioning ShARCS: the Shane Adaptive optics infraRed Camera-Spectrograph for the Lick Observatory 3-m telescope
We describe the design and first-light early science performance of the Shane
Adaptive optics infraRed Camera-Spectrograph (ShARCS) on Lick Observatory's 3-m
Shane telescope. Designed to work with the new ShaneAO adaptive optics system,
ShARCS is capable of high-efficiency, diffraction-limited imaging and
low-dispersion grism spectroscopy in J, H, and K-bands. ShARCS uses a
HAWAII-2RG infrared detector, giving high quantum efficiency (>80%) and Nyquist
sampling the diffraction limit in all three wavelength bands. The ShARCS
instrument is also equipped for linear polarimetry and is sensitive down to 650
nm to support future visible-light adaptive optics capability. We report on the
early science data taken during commissioning.Comment: 9 pages, 7 figures. Presented at SPIE Astronomical Telescopes +
Instrumentation conference, paper 9148-11
Opto-Mechanical Design of ShaneAO: the Adaptive Optics System for the 3-meter Shane Telescope
A Cassegrain mounted adaptive optics instrument presents unique challenges
for opto-mechanical design. The flexure and temperature tolerances for
stability are tighter than those of seeing limited instruments. This criteria
requires particular attention to material properties and mounting techniques.
This paper addresses the mechanical designs developed to meet the optical
functional requirements. One of the key considerations was to have
gravitational deformations, which vary with telescope orientation, stay within
the optical error budget, or ensure that we can compensate with a steering
mirror by maintaining predictable elastic behavior. Here we look at several
cases where deformation is predicted with finite element analysis and Hertzian
deformation analysis and also tested. Techniques used to address thermal
deformation compensation without the use of low CTE materials will also be
discussed.Comment: 14 pages, 14 figures, 4 tables. Presented at SPIE Astronomical
Telescopes + Instrumentation conference, paper 9148-11
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Understanding packet loss for sound monitoring in a smart stadium IoT testbed
The Smart Stadium for Smarter Living project provides an end-to-end testbed for IoT innovation through a collaboration between Croke Park Stadium in Dublin, Ireland and Dublin City University, Intel and Microsoft. This enables practical evaluations of IoT solutions in a controlled environment that is small enough to conduct trials but large enough to prove and challenge the technologies. An evaluation of sound monitoring capabilities during the 2016 sporting finals was used to test the capture, transfer, storage and analysis of decibel level sound monitoring. The purpose of the evaluation was to use existing sound level microphones to measure crowd response to pre-determined events for display on big screens at half-time and to test the end-to-end performance of the testbed. While this is not the specific original purpose of the sound level microphones, it provided a useful test case and produced engaging content for the project. Analysis of the data streams showed significant packet loss during the events and further investigations were conducted to understand where and how this loss occurred. This paper describes the smart stadium testbed configuration using Intel gateways linking with the Azure cloud platform and analyses the performance of the system during the sound monitoring evaluation
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