23,356 research outputs found
Dirichlet's and Thomson's principles for non-selfadjoint elliptic operators with application to non-reversible metastable diffusion processes
We present two variational formulae for the capacity in the context of
non-selfadjoint elliptic operators. The minimizers of these variational
problems are expressed as solutions of boundary-value elliptic equations. We
use these principles to provide a sharp estimate for the transition times
between two different wells for non-reversible diffusion processes. This
estimate permits to describe the metastable behavior of the system
Online Forum Thread Retrieval using Pseudo Cluster Selection and Voting Techniques
Online forums facilitate knowledge seeking and sharing on the Web. However,
the shared knowledge is not fully utilized due to information overload. Thread
retrieval is one method to overcome information overload. In this paper, we
propose a model that combines two existing approaches: the Pseudo Cluster
Selection and the Voting Techniques. In both, a retrieval system first scores a
list of messages and then ranks threads by aggregating their scored messages.
They differ on what and how to aggregate. The pseudo cluster selection focuses
on input, while voting techniques focus on the aggregation method. Our combined
models focus on the input and the aggregation methods. The result shows that
some combined models are statistically superior to baseline methods.Comment: The original publication is available at
http://www.springerlink.com/. arXiv admin note: substantial text overlap with
arXiv:1212.533
Approximate 3-Dimensional Electrical Impedance Imaging
We discuss a new approach to three-dimensional electrical impedance imaging
based on a reduction of the information to be demanded from a reconstruction
algorithm. Images are obtained from a single measurement by suitably
simplifying the geometry of the measuring chamber and by restricting the nature
of the object to be imaged and the information required from the image. In
particular we seek to establish the existence or non-existence of a single
object (or a small number of objects) in a homogeneous background and the
location of the former in the (x,y)-plane defined by the measuring electrodes.
Given in addition the conductivity of the object rough estimates of its
position along the z-axis may be obtained. The approach may have practical
applications.Comment: 12 pages, 4 figures, LaTeX, Appendix added and other minor change
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