32 research outputs found
Optimización de las prestaciones de la plataforma de colaboración P2P: p2people
In this paper, the performance optimization of
the P2People platform is analyzed. For this purpose, the
performance critical-points of P2P applications are
examined firstly. Provided that P2People is based on
P2P-JXTA architecture, the performance increase
between JXTA releases is explored below. P2People
optimization deals with the increase of its architecture
throughput and the individual improvement of the
different P2People modules. So, the performance
increase strategies for these elements are shown and
evaluated. Finally the experimental results probe that
this optimization is well fitted.Ingeniería, Industria y Construcció
Gestión de la reputación en redes P2P: algoritmo de reputación de p2people
In this paper, a new reputation management
system is presented for a peer-to-peer platform called
P2People. Due to peer-to-peer applications providing
anonymity features, malicious peers collectives try to
subvert these systems under self interests. So, additional
mechanisms need to be implemented to increase the
security at each node of the network. Based on human
perception of trustworthiness, the P2People reputation
algorithm tries to get accurate results in order to
minimize the number of downloads and transactions
from/with malicious peers, and at the same time to
isolate them. The simulation results shown that this first
approach gets to reduce hugely the number of corrupted
files and the contact with undesirable peers in the
network.Ingeniería, Industria y Construcció
3D mechanical characterization of artificial muscles with stereoscopic computer vision and active contours
Artificial muscles are formed by attaching a conducting polymeric
film to a non-conducting one. Applying an electrical
current on the muscle. a macroscopic bending movement
appears on it. Study of curvature variations and related parameters,
such as speed of motion or energy of curvature,
is necessary for improving the efficiency of these devices.
In a previous work. a one-cam computer vision system was
developed to estimate motion parameters in 2D with precise
results. In this paper, a two-cam stereo vision system is proposed
to process the image sequence and track the muscle in
3D. Active contours models are employed in motion detection
and mechanical parameters estimation. Results prove
the validity of this approach, allowing automatic testing on
the research into artificial muscles.This work was supported by MCYI' BQLJ2001-047
Estimación de parámetros de músculos artificiales usando contornos activos y visión estereoscópica
Conducting polymers have the ability to transform electrical
energy into mechanical energy through an electrochemical
reaction. Artificial muscles are formed by attaching a
conducting polymeric film to a non-conducting one. Applying
an electrical current on the muscle, a bending movement
appears on it. A one-cam computer vision system has
performed this study of electromechanical properties using
active contour models. This system shows the movement only
in the normal direction of the camera. In this paper we
propose a preliminary two-cam stereovision system to study
these properties in 3D
Validity and Reliability of an Instrumented Treadmill with an Accelerometry System for Assessment of Spatio-Temporal Parameters and Impact Transmission
Running retraining programs focused on concurrent feedback of acceleration impacts have been demonstrated to be a good strategy to reduce running-related injuries (RRI), as well as to improve running economy and reduce acceleration impacts and injury running incidence. Traditionally, impacts have been registered by mean of accelerometers attached directly to the athletes, which is inaccessible to the entire population, because it requires laboratory conditions. This study investigated the validity and reliability of a new device integrated directly into the treadmill, compared to a traditional acceleration impact system. Thirty healthy athletes with no history of RRI were tested on two separate days over the instrumented treadmill (AccTrea) and simultaneously with an acceleration impact system attached to the participant (AccAthl). AccTrea was demonstrated to be a valid and reliable tool for measuring spatio-temporal parameters like step length (validity intraclass correlation coefficient (ICC) = 0.94; reliability ICC = 0.92), step time (validity ICC = 0.95; reliability ICC = 0.96), and step frequency (validity ICC = 0.95; reliability ICC = 0.96) during running. Peak acceleration impact variables showed a high reliability for the left (reliability ICC = 0.88) and right leg (reliability ICC = 0.85), and peak impact asymmetry showed a modest validity (ICC = 0.55). These results indicated that the AccTrea system is a valid and reliable way to assess spatio-temporal variables, and a reliable tool for measuring acceleration impacts during running.This research was funded by Bodytone International Sport, S.L., grant number CFE-BODYTONE-03-18
Modification of Angular Kinematics and Spatiotemporal Parameters during Running after Central and Peripheral Fatigue
Fatigue causes kinematics modifications during running, and it could be related to injuries. The aim was to identify and compare the effects of central and peripheral fatigue on angular kinematics and spatiotemporal parameters during running. Angular kinematics and spatiotemporal parameters were evaluated using an infrared motion capture system and were registered during 2 min treadmill running in pre- and post-fatigue states in eighteen male recreational runners. Central fatigue was induced by a 30 min running fatigue protocol on a treadmill, while peripheral fatigue in quadriceps and hamstrings muscles was induced by an isokinetic dynamometer fatigue protocol. Central fatigue increased the anterior shank oscillation during the initial contact, knee flexion during the maximum absorption, posterior shank oscillation during propulsion, and stance time (p < 0.05). Peripheral fatigue decreased ankle dorsiflexion during initial contact and increased knee flexion and posterior shank oscillation during propulsion (p < 0.05). Moreover, central fatigue increased to a greater extent the hip and knee flexion and ankle dorsiflexion during initial contact and maximum absorption as well as stance time and propulsion time (p < 0.05). These results suggested that central fatigue causes greater increases in the range of movements during the midstance than peripheral fatigue
Automatic Segmentation of the Retinal Nerve Fiber Layer by Means of Mathematical Morphology and Deformable Models in 2D Optical Coherence Tomography Imaging
[EN] Glaucoma is a neurodegenerative disease process that leads to progressive damage of the optic nerve to produce visual impairment and blindness. Spectral-domain OCT technology enables peripapillary circular scans of the retina and the measurement of the thickness of the retinal nerve fiber layer (RNFL) for the assessment of the disease status or progression in glaucoma patients. This paper describes a new approach to segment and measure the retinal nerve fiber layer in peripapillary OCT images. The proposed method consists of two stages. In the first one, morphological operators robustly detect the coarse location of the layer boundaries, despite the speckle noise and diverse artifacts in the OCT image. In the second stage, deformable models are initialized with the results of the previous stage to perform a fine segmentation of the boundaries, providing an accurate measurement of the entire RNFL. The results of the RNFL segmentation were qualitatively assessed by ophthalmologists, and the measurements of the thickness of the RNFL were quantitatively compared with those provided by the OCT inbuilt software as well as the state-of-the-art methods.This work was partially funded by Spanish National projects AES2017-PI17/00771 and AES2017-PI17/00821 (Instituto de Salud Carlos III), PID2019-105142RB-C21 (AI4SKIN) (Spanish Ministry of Economy and Competitiveness), PTA2017-14610-I (State Research Spanish Agency), regional project 20901/PI/18 (Fundacion Seneca) and Polytechnic University of Valencia (PAID-01-20).Berenguer-Vidal, R.; Verdú-Monedero, R.; Morales-Sánchez, J.; Sellés-Navarro, I.; Del Amor, R.; García-Pardo, JG.; Naranjo Ornedo, V. (2021). Automatic Segmentation of the Retinal Nerve Fiber Layer by Means of Mathematical Morphology and Deformable Models in 2D Optical Coherence Tomography Imaging. Sensors. 21(23):1-30. https://doi.org/10.3390/s21238027S130212
Formulación frecuencial de la ecuación de Euler-Lagrange para modelos deformables
Deformable models, i.e., active contours and active
meshes, are useful tools in image processing and computer
vision, because of their ability to take the shape of real 2D/3D
objects. The original formulation of the models is defined on the
spatial domain and it is based on the minimization of an energy
functional through the Euler-Lagrange differential equations.
In this paper, a new formulation is proposed in the frequency
domain, for the adaptation process of the contours and meshes to
the external forces. The presented frequency approach provides
an easier and more computationally efficient implementation,
allowing the use of deformable models to a greater number of
areas.Este trabajo está financiado por el Ministerio de Ciencia y
Tecnología, bajo el proyecto TEC2006-13338/TC
Au-IDA microelectrodes modified with Au-doped graphene oxide for the simultaneous determination of uric acid and ascorbic acid in urine samples
An electrochemical sensor based on graphene oxide decorated with gold nanoparticles has been prepared for the simultaneous quantification of uric acid (UA) and ascorbic acid (AA) in urine samples. The gold interdigitated microelectrodes array (Au-IDA) has been modified using graphene oxide doped with gold nanoparticles (AuNPs-GO/Au-IDA), which was characterized by TEM, FE-SEM, XPS and cyclic voltammetry. Excellent results were obtained for the separate quantification of UA and AA by chronoamperometry. The electrochemical sensor exhibits limits of detection (LODs) of 1.4 μM and 0.62 μM for AA and UA, respectively, limits of quantification (LOQs) of 4.6 μM (AA) and 2.0 μM (UA), and the working ranges obtained were between 4.6 μM and 193 μM for AA and between 2 μM and 1.05 mM for UA. The repeatability was studied at 20 μM providing coefficients of variation of 16% for AA and 13% for UA. Moreover, UA does not interfere in the measurement of AA and viceversa (provided that the concentration of UA is equal to or higher than 450 μM in the latter case). For lower concentrations of UA, an easy and fast strategy to quantify both analytes is presented. The good electrocatalytic activity achieved with this material makes it useful for the quantification of AA and UA in biological fluids. Other analytes like glucose, dopamine and epinephrine have been investigated. The results allow us to conclude that they do not interfere in the quantification of AA and UA in PBS (0.25 M, pH 7.0). Human urine samples have been analyzed using the method proposed, contaning AA and UA concentration levels of (0.588 ± 0.002) mM and (1.43 ± 0.02) mM, respectively, which are in the concentration range of these analytes in urine samples for healthy people.This work is supported by the Generalitat Valenciana (Prometeo2013/038 and PROMETEOII/2014/010) and by the Ministerio de Economia y Competitividad (MAT201676595-R). A. Abellán-Llobregat also thanks the Generalitat Valenciana for her fellowship
Impact of late presentation of HIV infection on short-, mid- and long-term mortality and causes of death in a multicenter national cohort: 2004–2013
SummaryObjectivesTo analyze the impact of late presentation (LP) on overall mortality and causes of death and describe LP trends and risk factors (2004–2013).MethodsCox models and logistic regression were used to analyze data from a nation-wide cohort in Spain. LP is defined as being diagnosed when CD4 < 350 cells/ml or AIDS.ResultsOf 7165 new HIV diagnoses, 46.9% (CI95%:45.7–48.0) were LP, 240 patients died.First-year mortality was the highest (aHRLP.vs.nLP = 10.3[CI95%:5.5–19.3]); between 1 and 4 years post-diagnosis, aHRLP.vs.nLP = 1.9(1.2–3.0); and >4 years, aHRLP.vs.nLP = 1.5(0.7–3.1).First-year's main cause of death was HIV/AIDS (73%); and malignancies among those surviving >4 years (32%). HIV/AIDS-related deaths were more likely in LP (59.2% vs. 25.0%; p < 0.001). LP declined from 55.9% (2004–05) to 39.4% (2012–13), and reduced in 46.1% in men who have sex with men (MSM) and 37.6% in heterosexual men, but increased in 22.6% in heterosexual women.Factors associated with LP: sex (ORMEN.vs.WOMEN = 1.4[1.2–1.7]); age (OR31–40.vs.<30 = 1.6[1.4–1.8], OR41–50.vs.<30 = 2.2[1.8–2.6], OR>50.vs.<30 = 3.6[2.9–4.4]); behavior (ORInjectedDrugUse.vs.MSM = 2.8[2.0–3.8]; ORHeterosexual.vs.MSM = 2.2[1.7–3.0]); education (ORPrimaryEducation.vs.University = 1.5[1.1–2.0], ORLowerSecondary.vs.University = 1.3[1.1–1.5]); and geographical origin (ORSub-Saharan.vs.Spain = 1.6[1.3–2.0], ORLatin-American.vs.Spain = 1.4[1.2–1.8]).ConclusionsLP is associated with higher mortality, especially short-term- and HIV/AIDS-related mortality. Mid-term-, but not long-term mortality, remained also higher in LP than nLP. LP decreased in MSM and heterosexual men, not in heterosexual women. The groups most affected by LP are low educated, non-Spanish and heterosexual women