2,804 research outputs found
Optimal motion control and vibration suppression of flexible systems with inaccessible outputs
This work addresses the optimal control problem
of dynamical systems with inaccessible outputs. A case in which
dynamical system outputs cannot be measured or inaccessible.
This contradicts with the nature of the optimal controllers which can be considered without any loss of generality as state feedback control laws for systems with linear dynamics. Therefore, this work attempts to estimate dynamical system states through a novel state observer that does not require injecting the dynamical system outputs onto the observer structure during its design. A linear quadratic optimal control law is then realized based on the
estimated states which allows controlling motion along with active vibration suppression of this class of dynamical systems with inaccessible outputs. Validity of the proposed control framework is evaluated experimentally
Fuzzy Integral Based Multi-Sensor Fusion for Arc Detection in the Pantograph-Catenary System
The pantograph-catenary subsystem is a fundamental component of a railway train since it provides the traction electrical power. A bad operating condition or, even worse, a failure can disrupt the railway traffic creating economic damages and, in some cases, serious accidents. Therefore, the correct operation of such subsystems should be ensured in order to have an economically efficient, reliable and safe transportation system. In this study, a new arc detection method was proposed and is based on features from the current and voltage signals collected by the pantograph. A tool named mathematical morphology is applied to voltage and current signals to emphasize the effect of the arc, before applying the fast Fourier transform to obtain the power spectrum. Afterwards, three support vector machine-based classifiers are trained separately to detect the arcs, and a fuzzy integral technique is used to synthesize the results obtained by the individual classifiers, therefore implementing a classifier fusion technique. The experimental results show that the proposed approach is effective for the detection of arcs, and the fusion of classifier has a higher detection accuracy than any individual classifier
Test beam studies of the TRD prototype filled with different gas mixtures based on Xe, Kr, and Ar
Towards the end of LHC Run1, gas leaks were observed in some parts of the
Transition Radiation Tracker (TRT) of ATLAS. Due to these leaks, primary Xenon
based gas mixture was replaced with Argon based mixture in various parts.
Test-beam studies with a dedicated Transition Radiation Detector (TRD)
prototype were carried out in 2015 in order to understand transition radiation
performance with mixtures based on Argon and Krypton. We present and discuss
the results of these test-beam studies with different active gas compositions.Comment: 5 pages,12 figures, The 2nd International Conference on Particle
Physics and Astrophysics (ICPPA-2016); Acknowledgments section correcte
Metallicity and absolute magnitude calibrations for F-G type main-sequence stars in the Gaia era
In this study, photometric metallicity and absolute magnitude calibrations
were derived using F-G spectral type main-sequence stars in the Solar
neighbourhood with precise spectroscopic, photometric and Gaia astrometric data
for UBV photometry. The sample consists of 504 main-sequence stars covering the
temperature, surface gravity and colour index intervals
K, (cgs) and mag, respectively. Stars with
relative trigonometric parallax errors were
preferred from Gaia DR2 data for the estimation of their absolute
magnitudes. In order to obtain calibrations, and colour
indices of stars were preferred and a multi-variable second order equation was
used. Calibrations are valid for main-sequence stars in the metallicity and
absolute magnitude ranges dex and mag,
respectively. The mean value and standard deviation of the differences between
original and estimated values for the metal abundance and absolute magnitude
are dex and mag, respectively. In this work, it has been shown that
more precise iron abundance and absolute magnitude values were obtained with
the new calibrations, compared to previous calibrations in the literature.Comment: 14 pages, 10 figures and 4 tables, accepted for publication in
Astrophysics and Space Scienc
Estimation of nasal cavity and conchae volumes by stereological method
Background: Studies evaluating the mean volumes of nasal cavity and concha
are very rare. Since there is little date on the mentioned topic, we aimed to
carry out the presented study to obtain a volumetric index showing the relation
between the nasal cavity and concha.
Material and methods: The volumes of the nasal cavity and concha were
measured in 30 males and 30 females (18–40 years old) on computed tomography
images using stereological methods.
Results: The mean volumes of nasal cavity, concha nasalis media, and concha
nasalis inferior were 5.95 ± 0.10 cm3, 0.56 ± 0.22 cm3, and 1.45 ± 0.68 cm3;
7.01 ± 0.18 cm3, 0.67 ± 0.31 cm3 and 1.59 ± 0.98 cm3 in females and males,
respectively. There were statistically significant differences in the volume of the
nasal cavity and concha nasalis media (p < 0.05) between males and females,
except for concha nasalis inferior (p > 0.05).
Conclusions: Our results could provide volumetric indexes for the nasal cavity
and concha, which could help the physician to manage surgical procedures
related to the nasal cavity and concha
Some results of test beam studies of Transition Radiation Detector prototypes at CERN
Operating conditions and challenging demands of present and future
accelerator experiments result in new requirements on detector systems. There
are many ongoing activities aimed to develop new technologies and to improve
the properties of detectors based on existing technologies. Our work is
dedicated to development of Transition Radiation Detectors (TRD) suitable for
different applications. In this paper results obtained in beam tests at SPS
accelerator at CERN with the TRD prototype based on straw technology are
presented. TRD performance was studied as a function of thickness of the
transition radiation radiator and working gas mixture pressure
A soft kinetic data structure for lesion border detection
Motivation: The medical imaging and image processing techniques, ranging from microscopic to macroscopic, has become one of the main components of diagnostic procedures to assist dermatologists in their medical decision-making processes. Computer-aided segmentation and border detection on dermoscopic images is one of the core components of diagnostic procedures and therapeutic interventions for skin cancer. Automated assessment tools for dermoscopic images have become an important research field mainly because of inter- and intra-observer variations in human interpretations. In this study, a novel approachâgraph spannerâfor automatic border detection in dermoscopic images is proposed. In this approach, a proximity graph representation of dermoscopic images in order to detect regions and borders in skin lesion is presented
Content-Based Image Retrieval of Skin Lesions by Evolutionary Feature Synthesis
Abstract. This paper gives an example of evolved features that improve image retrieval performance. A content-based image retrieval system for skin lesion images is presented. The aim is to support decision making by retrieving and displaying relevant past cases visually similar to the one under examination. Skin lesions of five common classes, including two non-melanoma cancer types, are used. Colour and texture features are extracted from lesions. Evolutionary algorithms are used to create composite features that optimise a similarity matching function. Experiments on our database of 533 images are performed and results are compared to those obtained using simple features. The use of the evolved composite features improves the precision by about 7%.
Lesion detection in demoscopy images with novel density-based and active contour approaches
<p>Abstract</p> <p>Background</p> <p>Dermoscopy is one of the major imaging modalities used in the diagnosis of melanoma and other pigmented skin lesions. Automated assessment tools for dermoscopy images have become an important field of research mainly because of inter- and intra-observer variations in human interpretation. One of the most important steps in dermoscopy image analysis is the detection of lesion borders, since many other features, such as asymmetry, border irregularity, and abrupt border cutoff, rely on the boundary of the lesion. </p> <p>Results</p> <p>To automate the process of delineating the lesions, we employed Active Contour Model (ACM) and boundary-driven density-based clustering (BD-DBSCAN) algorithms on 50 dermoscopy images, which also have ground truths to be used for quantitative comparison. We have observed that ACM and BD-DBSCAN have the same border error of 6.6% on all images. To address noisy images, BD-DBSCAN can perform better delineation than ACM. However, when used with optimum parameters, ACM outperforms BD-DBSCAN, since ACM has a higher recall ratio.</p> <p>Conclusion</p> <p>We successfully proposed two new frameworks to delineate suspicious lesions with i) an ACM integrated approach with sharpening and ii) a fast boundary-driven density-based clustering technique. ACM shrinks a curve toward the boundary of the lesion. To guide the evolution, the model employs the exact solution <abbrgrp><abbr bid="B27">27</abbr></abbrgrp> of a specific form of the Geometric Heat Partial Differential Equation <abbrgrp><abbr bid="B28">28</abbr></abbrgrp>. To make ACM advance through noisy images, an improvement of the modelâs boundary condition is under consideration. BD-DBSCAN improves regular density-based algorithm to select query points intelligently.</p
- âŠ