3,433 research outputs found
Bessel Filter Analysis
In this technical report, we prove two fundamental theorems for an edge detection algorithm based on a Bessel filter. These theorems are bases of a scale invariant feature extraction method in which extracted features are independent of scale
Scale Space Smoothing, Image Feature Extraction and Bessel Filters
The Green function of Mumford-Shah functional in the absence of discontinuities is known to be a modified Bessel function of the second kind and zero degree. Such a Bessel function is regularized here and used as a filter for feature extraction. It is demonstrated in this paper that a Bessel filter does not follow the scale space smoothing property of bounded linear filters such as Gaussian filters. The features extracted by the Bessel filter are therefore scale invariant. Edges, blobs, and junctions are features considered here to show that the extracted features remain unchanged by varying the scale of a Bessel filter. The scale invariance property of Bessel filters for edges is analytically proved here. We conjecture that Bessel filters also enjoy this scale invariance property for other kinds of features. The experimental results presente
New photometry and astrometry of the isolated neutron star RX J0720-3125 using recent VLT/FORS observations
Since the first optical detection of RXJ0720.4-3125 various observations have
been performed to determine astrometric and photometric data. We present the
first detection of the isolated neutron star in the V Bessel filter to study
the spectral energy distribution and derive a new astrometric position. At ESO
Paranal we obtained very deep images with FORS 1 (three hours exposure time) of
RXJ0720.4-3125 in V Bessel filter in January 2008. We derive the visual
magnitude by standard star aperture photometry.Using sophisticated resampling
software we correct the images for field distortions. Then we derive an updated
position and proper motion value by comparing its position with FORS 1
observations of December 2000. We calculate a visual magnitude of V = 26.81 +-
0.09mag, which is seven times in excess of what is expected from X-ray data,
but consistent with the extant U, B and R data. Over about a seven year epoch
difference we measured a proper motion of mu = 105.1 +- 7.4mas/yr towards theta
= 296.951 deg +- 0.0063 deg (NW), consistent with previous data.Comment: 7 pages, 9 figure
Scale Space Smoothing, Image Feature Extraction and Bessel Filters
The Green function of Mumford-Shah functional in the absence of discontinuities is known to be a modified Bessel function of the second kind and zero degree. Such a Bessel function is regularized here and used as a filter for feature extraction. It is demonstrated in this paper that a Bessel filter does not follow the scale space smoothing property of bounded linear filters such as Gaussian filters. The features extracted by the Bessel filter are therefore scale invariant. Edges, blobs, and junctions are features considered here to show that the extracted features remain unchanged by varying the scale of a Bessel filter. The scale invariance property of Bessel filters for edges is analytically proved here. We conjecture that Bessel filters also enjoy this scale invariance property for other kinds of features. The experimental results presente
MIA computer simulation test results report
Results of the first noise susceptibility computer simulation tests of the complete MIA receiver analytical model are presented. Computer simulation tests were conducted with both Gaussian and pulse noise inputs. The results of the Gaussian noise tests were compared to results predicted previously and were found to be in substantial agreement. The results of the pulse noise tests will be compared to the results of planned analogous tests in the Data Bus Evaluation Laboratory at a later time. The MIA computer model is considered to be fully operational at this time
A Current Mode Detector Array for Gamma-Ray Asymmetry Measurements
We have built a CsI(Tl) gamma-ray detector array for the NPDGamma experiment
to search for a small parity-violating directional asymmetry in the angular
distribution of 2.2 MeV gamma-rays from the capture of polarized cold neutrons
by protons with a sensitivity of several ppb. The weak pion-nucleon coupling
constant can be determined from this asymmetry. The small size of the asymmetry
requires a high cold neutron flux, control of systematic errors at the ppb
level, and the use of current mode gamma-ray detection with vacuum photo diodes
and low-noise solid-state preamplifiers. The average detector photoelectron
yield was determined to be 1300 photoelectrons per MeV. The RMS width seen in
the measurement is therefore dominated by the fluctuations in the number of
gamma rays absorbed in the detector (counting statistics) rather than the
intrinsic detector noise. The detectors were tested for noise performance,
sensitivity to magnetic fields, pedestal stability and cosmic background. False
asymmetries due to gain changes and electronic pickup in the detector system
were measured to be consistent with zero to an accuracy of in a few
hours. We report on the design, operating criteria, and the results of
measurements performed to test the detector array.Comment: 33 pages, 20 figures, 2 table
Fully-Automatic Multiresolution Idealization for Filtered Ion Channel Recordings: Flickering Event Detection
We propose a new model-free segmentation method, JULES, which combines recent
statistical multiresolution techniques with local deconvolution for
idealization of ion channel recordings. The multiresolution criterion takes
into account scales down to the sampling rate enabling the detection of
flickering events, i.e., events on small temporal scales, even below the filter
frequency. For such small scales the deconvolution step allows for a precise
determination of dwell times and, in particular, of amplitude levels, a task
which is not possible with common thresholding methods. This is confirmed
theoretically and in a comprehensive simulation study. In addition, JULES can
be applied as a preprocessing method for a refined hidden Markov analysis. Our
new methodolodgy allows us to show that gramicidin A flickering events have the
same amplitude as the slow gating events. JULES is available as an R function
jules in the package clampSeg
The Data Acquisition System for the KOTO Experiment
We developed and built a new system of readout and trigger electronics, based
on the waveform digitization and pipeline readout, for the KOTO experiment at
J-PARC, Japan. KOTO aims at observing the rare kaon decay
. A total of 4000 readout channels from
various detector subsystems are digitized by 14-bit 125-MHz ADC modules
equipped with a 10-pole Bessel filter in order to reduce the pile-up effects.
The trigger decision is made every 8-ns using the digitized waveform
information. To avoid dead time, the ADC and trigger modules have pipelines in
their FPGA chips to store data while waiting for the trigger decision. The KOTO
experiment performed the first physics run in May 2013. The data acquisition
system worked stably during the run.Comment: 5 pages,12 figures, Transactions on Nuclear Science, Proceedings of
the 19th Real Time Conference, Preprin
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