5,987 research outputs found
Substructure Discovery Using Minimum Description Length and Background Knowledge
The ability to identify interesting and repetitive substructures is an
essential component to discovering knowledge in structural data. We describe a
new version of our SUBDUE substructure discovery system based on the minimum
description length principle. The SUBDUE system discovers substructures that
compress the original data and represent structural concepts in the data. By
replacing previously-discovered substructures in the data, multiple passes of
SUBDUE produce a hierarchical description of the structural regularities in the
data. SUBDUE uses a computationally-bounded inexact graph match that identifies
similar, but not identical, instances of a substructure and finds an
approximate measure of closeness of two substructures when under computational
constraints. In addition to the minimum description length principle, other
background knowledge can be used by SUBDUE to guide the search towards more
appropriate substructures. Experiments in a variety of domains demonstrate
SUBDUE's ability to find substructures capable of compressing the original data
and to discover structural concepts important to the domain. Description of
Online Appendix: This is a compressed tar file containing the SUBDUE discovery
system, written in C. The program accepts as input databases represented in
graph form, and will output discovered substructures with their corresponding
value.Comment: See http://www.jair.org/ for an online appendix and other files
accompanying this articl
Conic Blocking Sets in Desarguesian Projective Planes
a conic blocking set to be a set of lines in a Desarguesian projective plane such that all conics meet these lines. Conic blocking sets can be used in determining if a collection of planes in projective three-space forms a flock of a quadratic cone. We discuss trivial conic blocking sets and conic blocking sets in planes of small order. We provide a construction for conic blocking sets in planes of non-prime order, and we make additional comments about the structure of these conic blocking sets in certain planes of even order
Policies to Prevent Alcohol Problems: A Research Agenda for 2010-2015
Summarizes policy research priorities with a focus on alcohol-related problems or high-risk drinking involving those not identified as dependent drinkers, including questions of state and local accountability, availability of alcohol, and retail price
An LED-based Flasher System for VERITAS
We describe a flasher system designed for use in monitoring the gains of the
photomultiplier tubes used in the VERITAS gamma-ray telescopes. This system
uses blue light-emitting diodes (LEDs) so it can be operated at much higher
rates than a traditional laser-based system. Calibration information can be
obtained with better statistical precision with reduced loss of observing time.
The LEDs are also much less expensive than a laser. The design features of the
new system are presented, along with measurements made with a prototype mounted
on one of the VERITAS telescopes.Comment: Accepted for publication in Nuclear Instruments and Methods in
Physics Research
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