Search results for "artificial intelligence"
showing 10 items of 6122 documents
Determination of Synchronization of Electrical Activity in the Heart by Shannon Entropy Measure
2005
In this paper we propose a new index of synchronization for the study of heart’s electrical activity during atrial fibrillation (AF). The index relies on the measure of the time delays between correspondent activations in two atrial electrograms and on the characterization of their dispersion by a measure of Shannon Entropy. The algorithm was validated on simulated signals mimicking different degree of synchronization. Results showed the index was able to discriminate among different levels of organization, provided that it works on series of at least 50 activations (time resolution of almost 10 sec during AF). Moreover, we applied the algorithm to real bipolar electrograms, obtained from a…
Color memory matching: Time effect and other factors
1998
The methods of simultaneous and successive, or memory, color matching have been compared for 10 color reference samples distributed in two groups each performed by 50 observers (25 men and 25 women). Our results, obtained with a total of two hundred Munsell color chips arrayed on ten gray cardboard panels, indicate that: (a) while by simultaneous matching the mean color differences obtained are, in most cases, lower than 1 CIELAB unit, those obtained by memory are generally higher; (b) the worst remembered colors are yellow, light green, blue, and pink, and the best remembered color is orange; (c) the influence of the delay time (15 s, 15 min, and 24 h) is significant for the remembered mea…
Color memory in protanomals and deuteranomals: Matching time effect
2003
In a companion paper Perez-Carpinell et al., Color Res Appl 2001;26:158–170, for a set of seven color references, we compared the methods of simultaneous and memory color matching by 15 protanomals and 21 deuteranomals, looking for differences between them and a group of 25 normal trichromat observers investigated previously Perez-Carpinell et al., Color Res Appl 1998;23:234–247. In our current article, matching times of the same anomalous trichromat groups, and with the same reference tests, to select from among the comparison chips the one that most resembled one of the seven reference tests, have been measured under simultaneous and successive color matching procedures. From comparison b…
<title>Electronic eye occluder with time-counting and reflection control</title>
2008
ABSTRACT In pediatric ophthalmology 2 3 % of all the children are impacted by a visual pathology amblyopia. It develops if a clear image isnt presented to the retina during an early stage of the developmen t of the visual system. A common way of treating this pathology is to cover the better-seeing eye to force the lazy eye to learn seeing. However, children are often reluctant to wear such an occluder because they are as hamed or simply because they find it inconvenient. This fact requires to find a way how to track the regi me of occlusion because results of occlus ion is a hint that the actual regime of occlusion isnt that what the optometrist has recommended. We design an electr…
Global flow impacts time-to-passage judgments based on local motion cues
2011
AbstractWe assessed the effect of the coherence of optic flow on time-to-passage judgments in order to investigate the strategies that observers use when local expansion information is reduced or lacking. In the standard display, we presented a cloud of dots whose image expanded consistent with constant observer motion. The dots themselves, however, did not expand and were thus devoid of object expansion cues. Only the separations between the dots expanded. Subjects had to judge which of two colored target dots, presented at different simulated depths and lateral displacements would pass them first. Image velocities of the target dots were chosen so as to correlate with time-to-passage only…
An Automated Visual Inspection System for the Classification of the Phases of Ti-6Al-4V Titanium Alloy
2013
Metallography is the science of studying the physical properties of metal microstructures, by means of microscopes. While traditional approaches involve the direct observation of the acquired images by human experts, Com-puter Vision techniques may help experts in the analysis of the inspected mate-rials. In this paper we present an automated system to classify the phases of a Titanium alloy, Ti-6Al-4V. Our system has been tested to analyze the final products of a Friction Stir Welding process, to study the states of the micro-structures of the welded material.
Discrete Tomography Reconstruction Through a New Memetic Algorithm
2008
Discrete tomography is a particular case of computerized tomography that deals with the reconstruction of objects made of just one homogeneous material, where it is sometimes possible to reduce the number of projections to no more than four. Most methods for standard computerized tomography cannot be applied in the former case and ad hoc techniques must be developed to handle so few projections.
Blind Radio Tomography
2018
From the attenuation measurements collected by a network of spatially distributed sensors, radio tomography constructs spatial loss fields (SLFs) that quantify absorption of radiofrequency waves at each location. These SLFs can be used for interference prediction in (possibly cognitive) wireless communication networks, for environmental monitoring or intrusion detection in surveillance applications, for through-the-wall imaging, for survivor localization after earthquakes or fires, etc. The cornerstone of radio tomography is to model attenuation as the bidimensional integral of the SLF of interest scaled by a weight function. Unfortunately, existing approaches (i) rely on heuristic assumpti…
Multi-label Classification Using Stacked Hierarchical Dirichlet Processes with Reduced Sampling Complexity
2018
Nonparametric topic models based on hierarchical Dirichlet processes (HDPs) allow for the number of topics to be automatically discovered from the data. The computational complexity of standard Gibbs sampling techniques for model training is linear in the number of topics. Recently, it was reduced to be linear in the number of topics per word using a technique called alias sampling combined with Metropolis Hastings (MH) sampling. We propose a different proposal distribution for the MH step based on the observation that distributions on the upper hierarchy level change slower than the document-specific distributions at the lower level. This reduces the sampling complexity, making it linear i…
A Survey of Multi-Label Topic Models
2019
Every day, an enormous amount of text data is produced. Sources of text data include news, social media, emails, text messages, medical reports, scientific publications and fiction. To keep track of this data, there are categories, key words, tags or labels that are assigned to each text. Automatically predicting such labels is the task of multi-label text classification. Often however, we are interested in more than just the pure classification: rather, we would like to understand which parts of a text belong to the label, which words are important for the label or which labels occur together. Because of this, topic models may be used for multi-label classification as an interpretable mode…