354,998 research outputs found
Dynamic Discovery of Type Classes and Relations in Semantic Web Data
The continuing development of Semantic Web technologies and the increasing
user adoption in the recent years have accelerated the progress incorporating
explicit semantics with data on the Web. With the rapidly growing RDF (Resource
Description Framework) data on the Semantic Web, processing large semantic
graph data have become more challenging. Constructing a summary graph structure
from the raw RDF can help obtain semantic type relations and reduce the
computational complexity for graph processing purposes. In this paper, we
addressed the problem of graph summarization in RDF graphs, and we proposed an
approach for building summary graph structures automatically from RDF graph
data. Moreover, we introduced a measure to help discover optimum class
dissimilarity thresholds and an effective method to discover the type classes
automatically. In future work, we plan to investigate further improvement
options on the scalability of the proposed method
Controlling services in a mobile context-aware infrastructure
Context-aware application behaviors can be described as logic rules following the Event-Control-Action (ECA) pattern. In this pattern, an Event models an occurrence of interest (e.g., a change in context); Control specifies a condition that must hold prior to the execution of the action; and an Action represents the invocation of arbitrary services. We have defined a Controlling service aiming at facilitating the dynamic configuration of ECA rule specifications by means of a mobile rule engine and a mechanism that distributes context reasoning activities to a network of context processing nodes. In this paper we present a novel context modeling approach that provides application developers and users with more appropriate means to define context information and ECA rules. Our approach makes use of ontologies to model context information and has been developed on top of web services technology
Adverse selection costs, trading activity and price discovery in the NYSE: An empirical analysis
This paper studies the role that trading activity plays in the price discovery process of a NYSE-listed stock. We measure the expected information content of each trade by estimating its permanent price impact. It depends on observable trade features and market conditions. We also estimate the time required for quotes to incorporate all the information content of a particular trade. Our results show that price discovery is faster after risky trades and also at the extreme intervals of the session. The quote adjustment to trade-related shocks is progressive and this causes risk persistency and unusual short-term market conditions.Publicad
Discovery of the Spin Frequency of 4U 0614+09 with SWIFT/BAT
We report the discovery of burst oscillations at 414.7 Hz during a
thermonuclear X-ray burst from the low mass X-ray binary (LMXB) 4U 0614+091
with the Burst Alert Telescope (BAT) onboard SWIFT. In a search of the BAT
archive, we found two burst triggers consistent with the position of 4U
0614+091. We searched both bursts for high frequency timing signatures, and
found a significant detection at 414.7 Hz during a 5 s interval in the cooling
tail of the brighter burst. This result establishes the spin frequency of the
neutron star in 4U 0614+091 as 415 Hz. The oscillation had an average amplitude
(rms) of 14%, These results are consistent with those known for burst
oscillations seen in other LMXBs. The inferred ratio of the frequency
difference between the twin kHz QPOs, and the spin frequency in this source is
strongly inconsistent with either 0.5 or 1, and tends to support the recent
suggestions by Yin et al., and Mendez & Belloni, that the kHz QPO frequency
difference may not have a strong connection to the neutron star spin frequency.Comment: 10 pages, 3 figures. AASTeX. Accepted for publication in the
Astrophysical Journal Letter
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