549 research outputs found
Rational weak mixing in infinite measure spaces
Rational weak mixing is a measure theoretic version of Krickeberg's strong
ratio mixing property for infinite measure preserving transformations. It
requires "{\tt density}" ratio convergence for every pair of measurable sets in
a dense hereditary ring. Rational weak mixing implies weak rational ergodicity
and (spectral) weak mixing. It is enjoyed for example by Markov shifts with
Orey's strong ratio limit property. The power, subsequence version of the
property is generic.Comment: Typos in the definitions of "rational weak mixing" and "weak rational
ergodicity" (p.5) are correcte
Empirical testing of algorithms for variable-sized label placement
We report an empirical comparison of different heuristic techniques for variable-sized point-feature label placement.Engineering and Applied Science
Classification of time series by shapelet transformation
Time-series classification (TSC) problems present a specific challenge for classification algorithms: how to measure similarity between series. A \emph{shapelet} is a time-series subsequence that allows for TSC based on local, phase-independent similarity in shape. Shapelet-based classification uses the similarity between a shapelet and a series as a discriminatory feature. One benefit of the shapelet approach is that shapelets are comprehensible, and can offer insight into the problem domain. The original shapelet-based classifier embeds the shapelet-discovery algorithm in a decision tree, and uses information gain to assess the quality of candidates, finding a new shapelet at each node of the tree through an enumerative search. Subsequent research has focused mainly on techniques to speed up the search. We examine how best to use the shapelet primitive to construct classifiers. We propose a single-scan shapelet algorithm that finds the best shapelets, which are used to produce a transformed dataset, where each of the features represent the distance between a time series and a shapelet. The primary advantages over the embedded approach are that the transformed data can be used in conjunction with any classifier, and that there is no recursive search for shapelets. We demonstrate that the transformed data, in conjunction with more complex classifiers, gives greater accuracy than the embedded shapelet tree. We also evaluate three similarity measures that produce equivalent results to information gain in less time. Finally, we show that by conducting post-transform clustering of shapelets, we can enhance the interpretability of the transformed data. We conduct our experiments on 29 datasets: 17 from the UCR repository, and 12 we provide ourselve
The Grizzly, April 19, 2007
Airband a Success • Omega Chi Blood Drive • Hillel Holocaust Discussion • Letter to the Editor • What Dreams May Come • Ivory-billed Woodpecker Not Extinct! • Fiber Facts • Earth-Shattering Drumming • Opinions: No Child Left Behind? Really?; Gitmo on Strike • Bears Win 11th in a Row; Coach McGowan Earns 200th Victory • Women\u27s Lacrosse Hangs Tough with #4 Gettysburghttps://digitalcommons.ursinus.edu/grizzlynews/1738/thumbnail.jp
A multi-layer extension of the stochastic heat equation
Motivated by recent developments on solvable directed polymer models, we
define a 'multi-layer' extension of the stochastic heat equation involving
non-intersecting Brownian motions.Comment: v4: substantially extended and revised versio
The Grizzly, February 15, 2007
Darfur Fast Week Kickoff • United Men of Color Reception • The Peter Pan Project • CoSA Kickoff a Success • Power of Purple • Preview of The Laramie Project • Nutrition Tips • Inside Look at New Member Education • Opinions: Black History Month; Our Long-Awaited Greek Column • Heartbreak at Hopkins • Guntli Leading Rebounder • Senior Day Basketball Double-Headerhttps://digitalcommons.ursinus.edu/grizzlynews/1731/thumbnail.jp
The Very Short Period M Dwarf Binary SDSS J001641-000925
We present follow-up observations and analysis of the recently discovered
short period low-mass eclipsing binary, SDSS J001641-000925. With an orbital
period of 0.19856 days, this system has one of the shortest known periods for
an M dwarf binary system. Medium-resolution spectroscopy and multi-band
photometry for the system are presented. Markov chain Monte Carlo modeling of
the light curves and radial velocities yields estimated masses for the stars of
M1 = 0.54 +/- 0.07 Msun and M2 = 0.34 +/- 0.04 Msun, and radii of R1 = 0.68 +/-
0.03 Rsun and R2 = 0.58 +/- 0.03 Rsun respectively. This solution places both
components above the critical Roche overfill limit, providing strong evidence
that SDSS J001641-000925 is the first verified M-dwarf contact binary system.
Within the follow-up spectroscopy we find signatures of non-solid body rotation
velocities, which we interpret as evidence for mass transfer or loss within the
system. In addition, our photometry samples the system over 9 years, and we
find strong evidence for period decay at the rate of dP/dt ~8 s/yr. Both of
these signatures raise the intriguing possibility that the system is in
over-contact, and actively losing angular momentum, likely through mass loss.
This places SDSS J001641-000925 as not just the first M-dwarf over-contact
binary, but one of the few systems of any spectral type known to be actively
undergoing coalescence. Further study SDSS J001641-000925 is on-going to verify
the nature of the system, which may prove to be a unique astrophysical
laboratory.Comment: 11 figures, ApJ Accepte
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