1,398 research outputs found
A study of separability criteria for mixed three-qubit states
We study the noisy GHZ-W mixture. We demonstrate some necessary but not
sufficient criteria for different classes of separability of these states. It
turns out that the partial transposition criterion of Peres and the criteria of
G\"uhne and Seevinck dealing with matrix elements are the strongest ones for
different separability classes of this 2 parameter state. As a new result we
determine a set of entangled states of positive partial transpose.Comment: 18 pages, 10 figures, PRA styl
A Robust Classification of Galaxy Spectra: Dealing with Noisy and Incomplete Data
Over the next few years new spectroscopic surveys (from the optical surveys
of the Sloan Digital Sky Survey and the 2 degree Field survey through to
space-based ultraviolet satellites such as GALEX) will provide the opportunity
and challenge of understanding how galaxies of different spectral type evolve
with redshift. Techniques have been developed to classify galaxies based on
their continuum and line spectra. Some of the most promising of these have used
the Karhunen and Loeve transform (or Principal Component Analysis) to separate
galaxies into distinct classes. Their limitation has been that they assume that
the spectral coverage and quality of the spectra are constant for all galaxies
within a given sample. In this paper we develop a general formalism that
accounts for the missing data within the observed spectra (such as the removal
of sky lines or the effect of sampling different intrinsic rest wavelength
ranges due to the redshift of a galaxy). We demonstrate that by correcting for
these gaps we can recover an almost redshift independent classification scheme.
From this classification we can derive an optimal interpolation that
reconstructs the underlying galaxy spectral energy distributions in the regions
of missing data. This provides a simple and effective mechanism for building
galaxy spectral energy distributions directly from data that may be noisy,
incomplete or drawn from a number of different sources.Comment: 20 pages, 8 figures. Accepted for publication in A
Vortices within vortices: hierarchical nature of vortex tubes in turbulence
The JHU turbulence database [1] can be used with a state of the art
visualisation tool [2] to generate high quality fluid dynamics videos. In this
work we investigate the classical idea that smaller structures in turbulent
flows, while engaged in their own internal dynamics, are advected by the larger
structures. They are not advected undistorted, however. We see instead that the
small scale structures are sheared and twisted by the larger scales. This
illuminates the basic mechanisms of the turbulent cascade.Comment: 2 pages, 1 low quality video, 1 high quality vide
Sensor Drift Compensation Using Fuzzy Interference System and Sparse-Grid Quadrature Filter in Blood Glucose Control
Diabetes mellitus is a serious chronic condition of the human
metabolism. The development of an automated treatment has reached
clinical phase in the last few years. The goal is to keep the blood glucose
concentration within a certain region with minimal interaction required
by the patient or medical personnel. However, there are still several prac-
tical problems to solve. One of these would be that the available sensors
have significant noise and drift. The latter is rather difficult to manage,
because the deviating signal can cause the controller to drive the glu-
cose concentration out of the safe region even in the case of frequent
calibration. In this study a linear-quadratic-Gaussian (LQG) controller
is employed on a widely used diabetes model and enhanced with an ad-
vanced Sparse-grid quadratic filter and a fuzzy interference system-based
calibration supervisor
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