9,207 research outputs found
Representation Learning for Clustering: A Statistical Framework
We address the problem of communicating domain knowledge from a user to the
designer of a clustering algorithm. We propose a protocol in which the user
provides a clustering of a relatively small random sample of a data set. The
algorithm designer then uses that sample to come up with a data representation
under which -means clustering results in a clustering (of the full data set)
that is aligned with the user's clustering. We provide a formal statistical
model for analyzing the sample complexity of learning a clustering
representation with this paradigm. We then introduce a notion of capacity of a
class of possible representations, in the spirit of the VC-dimension, showing
that classes of representations that have finite such dimension can be
successfully learned with sample size error bounds, and end our discussion with
an analysis of that dimension for classes of representations induced by linear
embeddings.Comment: To be published in Proceedings of UAI 201
Computational fluid dynamics research
The focus of research in the computational fluid dynamics (CFD) area is two fold: (1) to develop new approaches for turbulence modeling so that high speed compressible flows can be studied for applications to entry and re-entry flows; and (2) to perform research to improve CFD algorithm accuracy and efficiency for high speed flows. Research activities, faculty and student participation, publications, and financial information are outlined
Plasmon dispersion in semimetallic armchair graphene nanoribbons
The dispersion relations for plasmons in intrinsic and extrinsic semimetallic
armchair graphene nanoribbons (acGNR) are calculated in the random phase
approximation using the orthogonal p_z-orbital tight binding method. Our model
predicts new plasmons for acGNR of odd atomic widths N=5,11,17,... Our model
further predicts plasmons in acGNR of even atomic width N=2,8,14,... related to
those found using a Dirac continuum model, but with different quantitative
dispersion characteristics. We find that the dispersion of all plasmons in
semimetallic acGNR depends strongly on the localization of the p_z electronic
wavefunctions. We also find that overlap integrals for acGNR behave in a more
complex way than predicted by the Dirac continuum model, suggesting that these
plasmons will experience a small damping for all q not equal to 0. Plasmons in
extrinsic semimetallic acGNR with the chemical potential in the lowest
(highest) conduction (valence) band are found to have dispersion
characteristics nearly identical to their intrinsic counterparts, with
negligible differencs in dispersion arising from the slight differences in
overlap integrals for the interband and intraband transitions.Comment: 8 pages, 9 figure
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