65,347 research outputs found
Automatic Classification of Text Databases through Query Probing
Many text databases on the web are "hidden" behind search interfaces, and
their documents are only accessible through querying. Search engines typically
ignore the contents of such search-only databases. Recently, Yahoo-like
directories have started to manually organize these databases into categories
that users can browse to find these valuable resources. We propose a novel
strategy to automate the classification of search-only text databases. Our
technique starts by training a rule-based document classifier, and then uses
the classifier's rules to generate probing queries. The queries are sent to the
text databases, which are then classified based on the number of matches that
they produce for each query. We report some initial exploratory experiments
that show that our approach is promising to automatically characterize the
contents of text databases accessible on the web.Comment: 7 pages, 1 figur
Geodynamics Branch research report, 1982
The research program of the Geodynamics Branch is summarized. The research activities cover a broad spectrum of geoscience disciplines including space geodesy, geopotential field modeling, tectonophysics, and dynamic oceanography. The NASA programs which are supported by the work described include the Geodynamics and Ocean Programs, the Crustal Dynamics Project, the proposed Ocean Topography Experiment (TOPEX) and Geopotential Research Mission. The individual papers are grouped into chapters on Crustal Movements, Global Earth Dynamics, Gravity Field Model Development, Sea Surface Topography, and Advanced Studies
Understanding entanglement as resource: locally distinguishing unextendible product bases
It is known that the states in an unextendible product basis (UPB) cannot be
distinguished perfectly when the parties are restricted to local operations and
classical communication (LOCC). Previous discussions of such bases have left
open the following question: What entanglement resources are necessary and/or
sufficient for this task to be possible with LOCC? In this paper, I present
protocols which use entanglement more efficiently than teleportation to
distinguish certain classes of UPB's. The ideas underlying my approach to this
problem offer rather general insight into why entanglement is useful for such
tasks.Comment: Final, published version. Many revisions following very useful
suggestions of the referee have been added. In particular, Appendix A has
been completely rewritte
The WISE InfraRed Excesses around Degenerates (WIRED) Survey
The Wide-field Infrared Survey Explorer (WISE) is a NASA medium class Explorer
mission that performed an all sky survey in four infrared bands. We present an overview of the WISE
InfraRed Excesses around Degenerates (WIRED) Survey, which has the goals of characterizing
white dwarf stars in the WISE bands, confirming objects known to have infrared excess from past
observations, and revealing new examples of white dwarfs with infrared excess that can be attributed
to unresolved companions or debris disks. We obtained preliminary WISE detections (S/N > 2) in
at least one band of 405 white dwarfs from the 9316 unique possible targets in the Sloan Digital
Sky Survey Data Release 4 Catalog of Spectroscopically Identified White Dwarfs (not all potential
targets were available in the sky coverage used here). A companion paper in this volume discusses
specific results from our target detections
Research program of the Geodynamics Branch
This report is the Fourth Annual Summary of the Research Program of the Geodynamics Branch. The branch is located within the Laboratory for Terrestrial Physics of the Space and Earth Sciences Directorate of the Goddard Space Flight Center. The research activities of the branch staff cover a broad spectrum of geoscience disciplines including: tectonophysics, space geodesy, geopotential field modeling, and dynamic oceanography. The NASA programs which are supported by the work described in this document include the Geodynamics and Ocean Programs, the Crustal Dynamics Project and the proposed Ocean Topography Experiment (TOPEX). The reports highlight the investigations conducted by the Geodynamics Branch staff during calendar year 1985. The individual papers are grouped into chapters on Crustal Movements and Solid Earth Dynamics, Gravity Field Modeling and Sensing Techniques, and Sea Surface Topography. Further information on the activities of the branch or the particular research efforts described herein can be obtained through the branch office or from individual staff members
Coherent pumping of a Mott insulator: Fermi golden rule versus Rabi oscillations
Cold atoms provide a unique arena to study many-body systems far from
equilibrium. Furthermore, novel phases in cold atom systems are conveniently
investigated by dynamical probes pushing the system out of equilibrium. Here,
we discuss the pumping of doubly-occupied sites in a fermionic Mott insulator
by a periodic modulation of the hopping amplitude. We show that deep in the
insulating phase the many-body system can be mapped onto an effective two-level
system which performs coherent Rabi oscillations due to the driving. Coupling
the two-level system to the remaining degrees of freedom renders the Rabi
oscillations damped. We compare this scheme to an alternative description where
the particles are incoherently pumped into a broad continuum.Comment: 4 pages, 3 figure
Supersymmetric Baryogenesis from Exotic Quark Decays
In a simple extension of the minimal supersymmetric standard model,
out-of-equilibrium decays of TeV scale exotic vector-like squarks may generate
the baryon asymmetry of the universe. Baryon number and CP violation are
present in the superpotential, so this mechanism does not rely on CP violation
in supersymmetry breaking parameters. We discuss phenomenological constraints
on the model as well as potential signals for the Large Hadron Collider and
electronic dipole moment experiments. A variation on the TeV scale model allows
the exotic squarks to be the messengers of gauge mediated supersymmetry
breaking.Comment: 28 pages, 7 figures, 2 appendices, v2: typos corrected, results
unchange
A novel method for the injection and manipulation of magnetic charge states in nanostructures
Realising the promise of next-generation magnetic nanotechnologies is
contingent on the development of novel methods for controlling magnetic states
at the nanoscale. There is currently demand for simple and flexible techniques
to access exotic magnetisation states without convoluted fabrication and
application processes. 360 degree domain walls (metastable twists in
magnetisation separating two domains with parallel magnetisation) are one such
state, which is currently of great interest in data storage and magnonics.
Here, we demonstrate a straightforward and powerful process whereby a moving
magnetic charge, provided experimentally by a magnetic force microscope tip,
can write and manipulate magnetic charge states in ferromagnetic nanowires. The
method is applicable to a wide range of nanowire architectures with
considerable benefits over existing techniques. We confirm the method's
efficacy via the injection and spatial manipulation of 360 degree domain walls
in Py and Co nanowires. Experimental results are supported by micromagnetic
simulations of the tip-nanowire interaction.Comment: in Scientific Reports (2016
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