12,209 research outputs found
The Wiener-Filtered COBE DMR Data and Predictions for the Tenerife Experiment
We apply a Wiener filter to the two-year COBE DMR data. The resulting sky map
has significantly reduced noise levels compared to the raw data: the most
prominent hot and cold spots are significant at the 4-sigma level. Furthermore,
the entire covariance matrix of the errors in the filtered sky map is known,
and it is therefore possible to make constrained realizations of the microwave
sky with the correct a posteriori probability distribution. The filtered DMR
sky map is used to make predictions for the Tenerife experiment. Two prominent
features are predicted in a region of the sky not yet analyzed by the Tenerife
group. The presence of these features is a robust prediction of the standard
cosmological paradigm; if these features are not observed, some of our
fundamental assumptions must be incorrect.Comment: 15 pages of uuencoded compressed PostScript. A PostScript file
including figures is available at ftp://pac2.berkeley.edu/pub/bunn/wienerten
Automatic Conflict Detection in Police Body-Worn Audio
Automatic conflict detection has grown in relevance with the advent of
body-worn technology, but existing metrics such as turn-taking and overlap are
poor indicators of conflict in police-public interactions. Moreover, standard
techniques to compute them fall short when applied to such diversified and
noisy contexts. We develop a pipeline catered to this task combining adaptive
noise removal, non-speech filtering and new measures of conflict based on the
repetition and intensity of phrases in speech. We demonstrate the effectiveness
of our approach on body-worn audio data collected by the Los Angeles Police
Department.Comment: 5 pages, 2 figures, 1 tabl
Nonlinear denoising of transient signals with application to event related potentials
We present a new wavelet based method for the denoising of {\it event related
potentials} ERPs), employing techniques recently developed for the paradigm of
deterministic chaotic systems. The denoising scheme has been constructed to be
appropriate for short and transient time sequences using circular state space
embedding. Its effectiveness was successfully tested on simulated signals as
well as on ERPs recorded from within a human brain. The method enables the
study of individual ERPs against strong ongoing brain electrical activity.Comment: 16 pages, Postscript, 6 figures, Physica D in pres
A Detailed Investigation into Low-Level Feature Detection in Spectrogram Images
Being the first stage of analysis within an image, low-level feature detection is a crucial step in the image analysis process and, as such, deserves suitable attention. This paper presents a systematic investigation into low-level feature detection in spectrogram images. The result of which is the identification of frequency tracks. Analysis of the literature identifies different strategies for accomplishing low-level feature detection. Nevertheless, the advantages and disadvantages of each are not explicitly investigated. Three model-based detection strategies are outlined, each extracting an increasing amount of information from the spectrogram, and, through ROC analysis, it is shown that at increasing levels of extraction the detection rates increase. Nevertheless, further investigation suggests that model-based detection has a limitation—it is not computationally feasible to fully evaluate the model of even a simple sinusoidal track. Therefore, alternative approaches, such as dimensionality reduction, are investigated to reduce the complex search space. It is shown that, if carefully selected, these techniques can approach the detection rates of model-based strategies that perform the same level of information extraction. The implementations used to derive the results presented within this paper are available online from http://stdetect.googlecode.com
Doppler imaging of the young late-type star LO Pegasi (BD +22 4409) in September 2003
A Doppler image of the ZAMS late-type rapidly rotating star LO Pegasi, based
on spectra acquired between 12 and 15 September 2003, is presented. The Least
Square Deconvolution technique is applied to enhance the signal-to-noise ratio
of the mean rotational broadened line profiles extracted from the observed
spectra. In the present application, a unbroadened spectrum is used as a
reference, instead of a simple line list, to improve the deconvolution
technique applied to extract the mean profiles. The reconstructed image is
similar to those previously obtained from observations taken in 1993 and 1998,
and shows that LO Peg photospheric activity is dominated by high-latitude spots
with a non-uniform polar cap. The latter seems to be a persistent feature as it
has been observed since 1993 with little modifications. Small spots, observed
between ~ 10 and ~ 60 degrees of latitude, appears to be different with respect
to those present in the 1993 and 1998 maps.Comment: 21 pages, 10 figures, accepted by Monthly Notices of the Royal
Astronomical Societ
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