3,870 research outputs found
Invisible pushdown languages
Context free languages allow one to express data with hierarchical structure,
at the cost of losing some of the useful properties of languages recognized by
finite automata on words. However, it is possible to restore some of these
properties by making the structure of the tree visible, such as is done by
visibly pushdown languages, or finite automata on trees. In this paper, we show
that the structure given by such approaches remains invisible when it is read
by a finite automaton (on word). In particular, we show that separability with
a regular language is undecidable for visibly pushdown languages, just as it is
undecidable for general context free languages
Arithmetic on a Distributed-Memory Quantum Multicomputer
We evaluate the performance of quantum arithmetic algorithms run on a
distributed quantum computer (a quantum multicomputer). We vary the node
capacity and I/O capabilities, and the network topology. The tradeoff of
choosing between gates executed remotely, through ``teleported gates'' on
entangled pairs of qubits (telegate), versus exchanging the relevant qubits via
quantum teleportation, then executing the algorithm using local gates
(teledata), is examined. We show that the teledata approach performs better,
and that carry-ripple adders perform well when the teleportation block is
decomposed so that the key quantum operations can be parallelized. A node size
of only a few logical qubits performs adequately provided that the nodes have
two transceiver qubits. A linear network topology performs acceptably for a
broad range of system sizes and performance parameters. We therefore recommend
pursuing small, high-I/O bandwidth nodes and a simple network. Such a machine
will run Shor's algorithm for factoring large numbers efficiently.Comment: 24 pages, 10 figures, ACM transactions format. Extended version of
Int. Symp. on Comp. Architecture (ISCA) paper; v2, correct one circuit error,
numerous small changes for clarity, add reference
Information coding with frequency of oscillations in Belousov-Zhabotinsky encapsulated disks
Information processing with an excitable chemical medium, like the Belousov-Zhabotinsky (BZ) reaction, is typically based on information coding in the presence or absence of excitation pulses. Here we present a new concept of Boolean coding that can be applied to an oscillatory medium. A medium represents the logical TRUE state if a selected region oscillates with a high frequency. If the frequency fails below a specified value, it represents the logical FALSE state. We consider a medium composed of disks encapsulating an oscillatory mixture of reagents, as related to our recent experiments with lipid-coated BZ droplets. We demonstrate that by using specific geometrical arrangements of disks containing the oscillatory medium one can perform logical operations on variables coded in oscillation frequency. Realizations of a chemical signal diode and of a single-bit memory with oscillatory disks are also discussed
Air quality monitoring for vulnerable groups in residential environments using a multiple hazard gas detector
© 2019 by the authors. Licensee MDPI, Basel, Switzerland. This paper presents a smart “e-nose” device to monitor indoor hazardous air. Indoor hazardous odor is a threat for seniors, infants, children, pregnant women, disabled residents, and patients. To overcome the limitations of using existing non-intelligent, slow-responding, deficient gas sensors, we propose a novel artificial-intelligent-based multiple hazard gas detector (MHGD) system that is mounted on a motor vehicle-based robot which can be remotely controlled. First, we optimized the sensor array for the classification of three hazardous gases, including cigarette smoke, inflammable ethanol, and off-flavor from spoiled food, using an e-nose with a mixing chamber. The mixing chamber can prevent the impact of environmental changes. We compared the classification results of all combinations of sensors, and selected the one with the highest accuracy (98.88%) as the optimal sensor array for the MHGD. The optimal sensor array was then mounted on the MHGD to detect and classify the target gases without a mixing chamber but in a controlled environment. Finally, we tested the MHGD under these conditions, and achieved an acceptable accuracy (70.00%)
Revenue divergence and competitive balance in a divisional sports league
The North American model of resource allocation in professional sports leagues is adapted for English (association) football. The theoretical relationship between revenue and competitive balance is shown to be robust with respect to changes in teams’ objectives and labour market conditions. Empirical revenue functions are reported for 1926-1999. These indicate a shift in the composition of demand favouring big-city teams and an increase in the sensitivity of revenue to performance. An analysis of match results in the FA Cup competition suggests an increase in competitive imbalance between teams at different levels of the league’s divisional hierarchy, as the theory suggests
Discovery of a high state AM CVn binary in the Galactic Bulge Survey
We report on the discovery of a hydrogen-deficient compact binary (CXOGBS
J175107.6-294037) belonging to the AM CVn class in the Galactic Bulge Survey.
Deep archival X-ray observations constrain the X-ray positional uncertainty of
the source to 0.57 arcsec, and allow us to uniquely identify the optical and UV
counterpart. Optical spectroscopic observations reveal the presence of broad,
shallow He i absorption lines while no sign of hydrogen is present, consistent
with a high state system. We present the optical lightcurve from Optical
Gravitational Lensing Experiment monitoring, spanning 15 years. It shows no
evidence for outbursts; variability is present at the 0.2 mag level on
timescales ranging from hours to weeks. A modulation on a timescale of years is
also observed. A Lomb-Scargle analysis of the optical lightcurves shows two
significant periodicities at 22.90 and 23.22 min. Although the physical
interpretation is uncertain, such timescales are in line with expectations for
the orbital and superhump periods. We estimate the distance to the source to be
between 0.5 - 1.1 kpc. Spectroscopic follow-up observations are required to
establish the orbital period, and to determine whether this source can serve as
a verification binary for the eLISA gravitational wave mission.Comment: Accepted for publication in MNRAS Letter
ROTSE All Sky Surveys for Variable Stars I: Test Fields
The ROTSE-I experiment has generated CCD photometry for the entire Northern
sky in two epochs nightly since March 1998. These sky patrol data are a
powerful resource for studies of astrophysical transients. As a demonstration
project, we present first results of a search for periodic variable stars
derived from ROTSE-I observations. Variable identification, period
determination, and type classification are conducted via automatic algorithms.
In a set of nine ROTSE-I sky patrol fields covering about 2000 square degrees
we identify 1781 periodic variable stars with mean magnitudes between m_v=10.0
and m_v=15.5. About 90% of these objects are newly identified as variable.
Examples of many familiar types are presented. All classifications for this
study have been manually confirmed. The selection criteria for this analysis
have been conservatively defined, and are known to be biased against some
variable classes. This preliminary study includes only 5.6% of the total
ROTSE-I sky coverage, suggesting that the full ROTSE-I variable catalog will
include more than 32,000 periodic variable stars.Comment: Accepted for publication in AJ 4/00. LaTeX manuscript. (28 pages, 11
postscript figures and 1 gif
Pallet system
Pallet systems are described that can be formed of corrugated paperboard without the necessity of any attachment materials such adhesives, staples, or the like. Individual stringers of a pallet matrix are interwoven together, with stringer notches interlocking with notches of crossing stringers from both above and below any one stringer. Systems can be easily and quickly assembled and, should the need arise, can be quickly repaired, for instance by replacement of one or more individual runners. Systems can also exhibit extremely high strength, and can withstand greater than about 20,000 pounds of static compression at less than about 3/8 inch deflection
Pionium Production in the Cooler
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Simulational study of anomalous tracer diffusion in hydrogels
In this article, we analyze different factors that affect the diffusion
behavior of small tracer particles (as they are used e.g.in fluorescence
correlation spectroscopy (FCS)) in the polymer network of a hydrogel and
perform simulations of various simplified models. We observe, that under
certain circumstances the attraction of a tracer particle to the polymer
network strands might cause subdiffusive behavior on intermediate time scales.
In theory, this behavior could be employed to examine the network structure and
swelling behavior of weakly crosslinked hydrogels with the help of FCS.Comment: 11 pages, 11 figure
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