19,986 research outputs found
Local Approximation Schemes for Ad Hoc and Sensor Networks
We present two local approaches that yield polynomial-time approximation schemes (PTAS) for the Maximum Independent Set and Minimum Dominating Set problem in unit disk graphs. The algorithms run locally in each node and compute a (1+ε)-approximation to the problems at hand for any given ε > 0. The time complexity of both algorithms is O(TMIS + log*! n/εO(1)), where TMIS is the time required to compute a maximal independent set in the graph, and n denotes the number of nodes. We then extend these results to a more general class of graphs in which the maximum number of pair-wise independent nodes in every r-neighborhood is at most polynomial in r. Such graphs of polynomially bounded growth are introduced as a more realistic model for wireless networks and they generalize existing models, such as unit disk graphs or coverage area graphs
Explaining Violation Traces with Finite State Natural Language Generation Models
An essential element of any verification technique is that of identifying and
communicating to the user, system behaviour which leads to a deviation from the
expected behaviour. Such behaviours are typically made available as long traces
of system actions which would benefit from a natural language explanation of
the trace and especially in the context of business logic level specifications.
In this paper we present a natural language generation model which can be used
to explain such traces. A key idea is that the explanation language is a CNL
that is, formally speaking, regular language susceptible transformations that
can be expressed with finite state machinery. At the same time it admits
various forms of abstraction and simplification which contribute to the
naturalness of explanations that are communicated to the user
Controlled Natural Language Processing as Answer Set Programming: an Experiment
Most controlled natural languages (CNLs) are processed with the help of a
pipeline architecture that relies on different software components. We
investigate in this paper in an experimental way how well answer set
programming (ASP) is suited as a unifying framework for parsing a CNL, deriving
a formal representation for the resulting syntax trees, and for reasoning with
that representation. We start from a list of input tokens in ASP notation and
show how this input can be transformed into a syntax tree using an ASP grammar
and then into reified ASP rules in form of a set of facts. These facts are then
processed by an ASP meta-interpreter that allows us to infer new knowledge
Mesoscale monitoring of the soil freeze/thaw boundary from orbital microwave radiometry
The fundamental objectives are to test the feasibility of delineating the lateral boundary between frozen and thawed condition in the surface layer of soil from orbital microwave radiometry and secondly to examine the sensitivity of general circulation models to an explicit parameterization of the boundary condition. Physical models were developed to relate emissivity to scene properties and a simulation package was developed to predict brightness temperature as a function of emissivity and physical temperature in order to address issues of heterogeneity, scaling, and scene dynamics. Radiative transfer models were develped for both bare soil surfaces and those obscured by an intervening layer of vegetation or snow. These models relate the emissivity to the physical properties of the soil and to those of the snow or vegetation cover. A SMMR simulation package was developed to evaluate the adequacy of the emission models and the limiting effects of scaling for realistic scenarios incorporating spatially heterogeneous scenes with dynamic moisture and temperature gradients at the pixel scale
Trusty URIs: Verifiable, Immutable, and Permanent Digital Artifacts for Linked Data
To make digital resources on the web verifiable, immutable, and permanent, we
propose a technique to include cryptographic hash values in URIs. We call them
trusty URIs and we show how they can be used for approaches like
nanopublications to make not only specific resources but their entire reference
trees verifiable. Digital artifacts can be identified not only on the byte
level but on more abstract levels such as RDF graphs, which means that
resources keep their hash values even when presented in a different format. Our
approach sticks to the core principles of the web, namely openness and
decentralized architecture, is fully compatible with existing standards and
protocols, and can therefore be used right away. Evaluation of our reference
implementations shows that these desired properties are indeed accomplished by
our approach, and that it remains practical even for very large files.Comment: Small error corrected in the text (table data was correct) on page
13: "All average values are below 0.8s (0.03s for batch mode). Using Java in
batch mode even requires only 1ms per file.
Ordovician conodonts from the Mithaka Formation (Georgina Basin, Australia). Regional and paleobiogeographical implications
The systematic analysis of conodonts from the previously unstudied Mithaka Formation (Georgina Basin) yielded 1366 identifiable elements, representing 25 species and 21 genera. One new species was recovered and identified, Triangulodus mithakensis n. sp. Four other new species are described in open nomenclature as Bergstroemognathus? n. sp. A, ?Periodon n. sp. A, Phragmodus n. sp. A and Taoqupognathus n. sp. A. The Mithaka Fm fauna shows similarity with conodonts from several previous Australian studies and lesser similarity with conodonts from North China and North America. Some species of North American Midcontinent (Laurentian Province) affinity include Erismodus quadridactylus (STAUFFER) and Staufferella divisa SWEET, whereas some species of North Chinese affinity include Aurilobodus leptosomatus AN, Panderodus nogamii (LEE) and ?Serratognathus sp. However, many species are distinctly Australian: Bergstroemognathus? n. sp. A, ?Periodon n. sp. A, Phragmodus n. sp. A, Drucognathus yiranus ZHANG, BARNES and COOPER, Erismodus nicolli ZHANG, BARNES and COOPER, Yaoxianognathus? neonychodonta ZHANG, BARNES and COOPER, Triangulodus mithakensis n. sp. and Taoqupognathus n. sp. A. These Australian species support the placement of the Mithaka Fm fauna within the proposed Australian Province. This new conodont fauna is correlated to the early Late Ordovician upper Drucognathus yiranus Zone of the Amadeus Basin, Central Australia and the late Gisbornian Stage. The conodont fauna indicates a shallow open lagoon depositional environment
Microscopic theory of quantum-transport phenomena in mesoscopic systems: A Monte Carlo approach
A theoretical investigation of quantum-transport phenomena in mesoscopic
systems is presented. In particular, a generalization to ``open systems'' of
the well-known semiconductor Bloch equations is proposed. The presence of
spatial boundary conditions manifest itself through self-energy corrections and
additional source terms in the kinetic equations, whose form is suitable for a
solution via a generalized Monte Carlo simulation. The proposed approach is
applied to the study of quantum-transport phenomena in double-barrier
structures as well as in superlattices, showing a strong interplay between
phase coherence and relaxation.Comment: to appear in Phys. Rev. Let
The new HiVIS spectropolarimeter and spectropolarimetric calibration of the AEOS telescope
We designed, built, and calibrated a new spectropolarimeter for the HiVIS
spectrograph (R 12000-49000) on the AEOS telescope. We also did a polarization
calibration of the telescope and instrument. We will introduce the design and
use of the spectropolarimeter as well as a new data reduction package we have
developed, then discuss the polarization calibration of the spectropolarimeter
and the AEOS telescope. We used observations of unpolarized standard stars at
many pointings to measure the telescope induced polarization and compare it
with a Zemax model. The telescope induces polarization of 1-6% with a strong
variation with wavelength and pointing, consistent with the altitude and
azimuth variation expected. We then used scattered sunlight as a linearly
polarized source to measure the telescopes spectropolarimetric response to
linearly polarized light. We then made an all-sky map of the telescope's
polarization response to calibrate future spectropolarimetry.Comment: PASP 118, June 200
Improving Mechanical Ventilator Clinical Decision Support Systems with A Machine Learning Classifier for Determining Ventilator Mode
Clinical decision support systems (CDSS) will play an in-creasing role in
improving the quality of medical care for critically ill patients. However, due
to limitations in current informatics infrastructure, CDSS do not always have
com-plete information on state of supporting physiologic monitor-ing devices,
which can limit the input data available to CDSS. This is especially true in
the use case of mechanical ventilation (MV), where current CDSS have no
knowledge of critical ventilation settings, such as ventilation mode. To enable
MV CDSS to make accurate recommendations related to ventilator mode, we
developed a highly performant ma-chine learning model that is able to perform
per-breath clas-sification of 5 of the most widely used ventilation modes in
the USA with an average F1-score of 97.52%. We also show how our approach makes
methodologic improvements over previous work and that it is highly robust to
missing data caused by software/sensor error
Radiative Decay of Vector Quarkonium: Constraints on Glueballs and Light Gluinos
Given a resonance of known mass, width, and J^{PC}, we can determine its
gluonic branching fraction, b(R->gg), from data on its production in radiative
vector quarkonium decay, V -> gamma+R. For most resonances b(R->gg) is found to
be O(10%), consistent with being q-qbar states, but we find that both
pseudoscalars observed in the 1440 MeV region have b(R->gg) ~ 1/2 - 1, and
b(f_0^{++}->gg) ~ 1/2. As data improves, b(R->gg) should be a useful
discriminator between q-qbar and gluonic states and may permit quantitative
determination of the extent to which a particular resonance is a mixture of
glueball and q-qbar. We also examine the regime of validity of pQCD for
predicting the rate of V -> gamma+eta_gluino, the ``extra'' pseudoscalar bound
state which would exist if there were light gluinos. From the CUSB limit on
peaks in Upsilon -> gamma X, the mass range 3 GeV < m(eta_gluino) < 7 GeV can
be excluded. An experiment must be significantly more sensitive to exclude an
eta_gluino lighter than this.Comment: 36pp (inc figs),RU-94-04. (Replaces original which didn't latex
correctly and didn't have figures.
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