237 research outputs found
HMM-based Offline Recognition of Handwritten Words Crossed Out with Different Kinds of Strokes
In this work, we investigate the recognition of words that have been crossed-out by the writers and are thus degraded. The degradation consists of one or more ink strokes that span the whole word length and simulate the signs that writers use to cross out the words. The simulated strokes are superimposed to the original clean word images. We considered two types of strokes: wave-trajectory strokes created with splines curves and line-trajectory strokes generated with the delta-lognormal model of rapid line movements. The experiments have been performed using a recognition system based on hidden Markov models and the results show that the performance decrease is moderate for single writer data and light strokes, but severe for multiple writer data
Handwriting Recognition of Historical Documents with few labeled data
Historical documents present many challenges for offline handwriting
recognition systems, among them, the segmentation and labeling steps. Carefully
annotated textlines are needed to train an HTR system. In some scenarios,
transcripts are only available at the paragraph level with no text-line
information. In this work, we demonstrate how to train an HTR system with few
labeled data. Specifically, we train a deep convolutional recurrent neural
network (CRNN) system on only 10% of manually labeled text-line data from a
dataset and propose an incremental training procedure that covers the rest of
the data. Performance is further increased by augmenting the training set with
specially crafted multiscale data. We also propose a model-based normalization
scheme which considers the variability in the writing scale at the recognition
phase. We apply this approach to the publicly available READ dataset. Our
system achieved the second best result during the ICDAR2017 competition
Absolute Single Ion Thermometry
We describe and experimentally implement a single-ion local thermometry
technique with absolute sensitivity adaptable to all laser-cooled atomic ion
species. The technique is based on the velocity-dependent spectral shape of a
quasi-dark resonance tailored in a J J transition such that the
two driving fields can be derived from the same laser source leading to a
negligible relative phase shift. We validated the method and tested its
performances in an experiment on a single 88 Sr + ion cooled in a surface
radio-frequency trap. We first applied the technique to characterise the
heating-rate of the surface trap. We then measured the stationary temperature
of the ion as a function of cooling laser detuning in the Doppler regime. The
results agree with theoretical calculations, with an absolute error smaller
than 100 K at 500 K, in a temperature range between 0.5 and 3 mK and
in the absence of adjustable parameters. This simple-to-implement and reliable
method opens the way to fast absolute measurements of single-ion temperatures
in future experiments dealing with heat transport in ion chains or
thermodynamics at the single-ion level
Text Line Segmentation of Historical Documents: a Survey
There is a huge amount of historical documents in libraries and in various
National Archives that have not been exploited electronically. Although
automatic reading of complete pages remains, in most cases, a long-term
objective, tasks such as word spotting, text/image alignment, authentication
and extraction of specific fields are in use today. For all these tasks, a
major step is document segmentation into text lines. Because of the low quality
and the complexity of these documents (background noise, artifacts due to
aging, interfering lines),automatic text line segmentation remains an open
research field. The objective of this paper is to present a survey of existing
methods, developed during the last decade, and dedicated to documents of
historical interest.Comment: 25 pages, submitted version, To appear in International Journal on
Document Analysis and Recognition, On line version available at
http://www.springerlink.com/content/k2813176280456k3
Strong quantum correlations in four wave mixing in Rb vapor
We study quantum intensity correlations produced using four-wave mixing in a
room-temperature rubidium vapor cell. An extensive study of the effect of the
various parameters allows us to observe very large amounts of non classical
correlations.Comment: 8 pages and 8 figures; work presented at the SPIE Photonics Europe
conference (Brussels, 2010
How major depressive disorder affects the ability to decode multimodal dynamic emotional stimuli
Most studies investigating the processing of emotions in depressed patients reported impairments in the decoding of negative emotions. However, these studies adopted static stimuli (mostly stereotypical facial expressions corresponding to basic emotions) which do not reflect the way people experience emotions in everyday life. For this reason, this work proposes to investigate the decoding of emotional expressions in patients affected by Recurrent Major Depressive Disorder (RMDDs) using dynamic audio/video stimuli. RMDDsâ performance is compared with the performance of patients with Adjustment Disorder with Depressed Mood (ADs) and healthy (HCs) subjects. The experiments involve 27 RMDDs (16 with acute depression - RMDD-A, and 11 in a compensation phase - RMDD-C), 16 ADs and 16 HCs. The ability to decode emotional expressions is assessed through an emotion recognition task based on short audio (without video), video (without audio) and audio/video clips. The results show that AD patients are significantly less accurate than HCs in decoding fear, anger, happiness, surprise and sadness. RMDD-As with acute depression are significantly less accurate than HCs in decoding happiness, sadness and surprise. Finally, no significant differences were found between HCs and RMDD-Cs in a compensation phase. The different communication channels and the types of emotion play a significant role in limiting the decoding accuracy
Large 2D Coulomb crystals in a radio frequency surface ion trap
We designed and operated a surface ion trap, with an ion-substrate distance
of 500\mum, realized with standard printed-circuit-board techniques. The trap
has been loaded with up to a few thousand Sr+ ions in the Coulomb-crystal
regime. An analytical model of the pseudo-potential allowed us to determine the
parameters that drive the trap into anisotropic regimes in which we obtain
large (N>150) purely 2D ion Coulomb crystals. These crystals may open a simple
and reliable way to experiments on quantum simulations of large 2D systems.Comment: 4 pages, 4 figure
Isotope shifts of natural Sr+ measured by laser fluorescence in a sympathetically cooled Coulomb crystal
We measured by laser spectroscopy the isotope shifts between
naturally-occurring even-isotopes of strontium ions for both the
5s\,\,^2S_{1/2}\to 5p\,\,^2P_{1/2} (violet) and the 4d\,\,^2D_{3/2}\to
5p\,\,^2P_{1/2} (infrared) dipole-allowed optical transitions. Fluorescence
spectra were taken by simultaneous measurements on a two-component Coulomb
crystal in a linear Paul trap containing -- laser-cooled Sr
ions. The isotope shifts are extracted from the experimental spectra by fitting
the data with the analytical solution of the optical Bloch equations describing
a three-level atom in interaction with two laser beams. This technique allowed
us to increase the precision with respect to previously reported data obtained
by optogalvanic spectroscopy or fast atomic-beam techniques. The results for
the 5s\,\,^2S_{1/2}\to 5p\,\,^2P_{1/2} transition are
MHz and MHz, in
agreement with previously reported measurements. In the case of the previously
unexplored 4d\,\,^2D_{3/2}\to 5p\,\,^2P_{1/2} transition we find
MHz and MHz. These
results provide more data for stringent tests of theoretical calculations of
the isotope shifts of alkali-metal-like atoms. Moreover, they simplify the
identification and the addressing of Sr isotopes for ion frequency
standards or quantum-information-processing applications in the case of
multi-isotope ion strings.Comment: 19 pages; 5 figures; accepted on Phys. Rev. A (http://pra.aps.org/
Pre-Processing of Degraded Printed Documents by Non-Local Means and Total Variation
We compare in this study two image restoration approaches for the pre-processing of printed documents: namely the Non-local Means filter and a total variation minimization approach. We apply these two ap- proaches to printed document sets from various periods, and we evaluate their effectiveness through character recognition performance using an open source OCR. Our results show that for each document set, one or both pre-processing methods improve character recog- nition accuracy over recognition without preprocessing. Higher accuracies are obtained with Non-local Means when characters have a low level of degradation since they can be restored by similar neighboring parts of non-degraded characters. The Total Variation approach is more effective when characters are highly degraded and can only be restored through modeling instead of using neighboring data
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