Institute Investigacion En Ingenieria Of Aragon I3A

Molina de Aragón, Spain

Institute Investigacion En Ingenieria Of Aragon I3A

Molina de Aragón, Spain
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Sola I.J.,University of Salamanca | Collados M.V.,Institute Investigacion En Ingenieria Of Aragon I3A | Atencia J.,Institute Investigacion En Ingenieria Of Aragon I3A | Varela O.,University of Salamanca | And 4 more authors.
Applied Physics B: Lasers and Optics | Year: 2012

We have designed and developed a pulse compressor with volume transmission holographic gratings to be implemented in post-compression experiments based on filamentation in gases. Pulse compression down to 13 fs has been demonstrated. The gratings have been recorded in commercial PFG-04 dichromated gelatin emulsions with a recording wavelength of 532 nm, attaining sufficient index modulation to achieve high efficiency when they are illuminated by an 800-nm laser. © Springer-Verlag 2011.

Mosteo A.R.,Institute Investigacion En Ingenieria Of Aragon I3A | Mosteo A.R.,Centro Universitario Of La Defensa Of Zaragoza Cud
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2017

The ReactiveX API, also known as the Reactive Extensions in the .NET world, is a recently popularized reactive programming framework for asynchronous, event-based, multi-threaded programming. Presented by its proponents as a solid tool for applications requiring a simple yet powerful approach to event-driven systems, it has seen favorable adoption in many popular languages. Although Ada has been long-favored by powerful tasking capabilities that reduce the need for additional multithreading support, the reactive approach has properties that are wellsuited to the safety and maintainability culture predominant in the Ada world, such as complexity reduction, race-condition and deadlock avoidance, and enhanced maintainability by means of concise and well-defined information flows. This work presents the design for a ReactiveX Ada implementation that aims to balance desirable library properties such as compile-time checks, reasonable user-required generic instantiations, and a shallow learning curve for both library clients and maintainers. The Ada programmer can henceforth benefit from the abundant documentation existing for the language-agnostic ReactiveX approach without stepping out of the Ada tool chain. © Springer International Publishing AG 2017.

Lopez-Larraz E.,University of Zaragoza | Lopez-Larraz E.,Institute Investigacion En Ingenieria Of Aragon I3A | Trincado-Alonso F.,National Hospital for Spinal Cord Injury | Rajasekaran V.,Polytechnic University of Catalonia | And 8 more authors.
Frontiers in Neuroscience | Year: 2016

The closed-loop control of rehabilitative technologies by neural commands has shown a great potential to improve motor recovery in patients suffering from paralysis. Brain-machine interfaces (BMI) can be used as a natural control method for such technologies. BMI provides a continuous association between the brain activity and peripheral stimulation, with the potential to induce plastic changes in the nervous system. Paraplegic patients, and especially the ones with incomplete injuries, constitute a potential target population to be rehabilitated with brain-controlled robotic systems, as they may improve their gait function after the reinforcement of their spared intact neural pathways. This paper proposes a closed-loop BMI system to control an ambulatory exoskeleton-without any weight or balance support-for gait rehabilitation of incomplete spinal cord injury (SCI) patients. The integrated system was validated with three healthy subjects, and its viability in a clinical scenario was tested with four SCI patients. Using a cue-guided paradigm, the electroencephalographic signals of the subjects were used to decode their gait intention and to trigger the movements of the exoskeleton. We designed a protocol with a special emphasis on safety, as patients with poor balance were required to stand and walk. We continuously monitored their fatigue and exertion level, and conducted usability and user-satisfaction tests after the experiments. The results show that, for the three healthy subjects, 84.44 ± 14.56% of the trials were correctly decoded. Three out of four patients performed at least one successful BMI session, with an average performance of 77.6 1 ± 14.72%. The shared control strategy implemented (i.e., the exoskeleton could only move during specific periods of time) was effective in preventing unexpected movements during periods in which patients were asked to relax. On average, 55.22 ± 16.69% and 40.45 ± 16.98% of the trials (for healthy subjects and patients, respectively) would have suffered from unexpected activations (i.e., false positives) without the proposed control strategy. All the patients showed low exertion and fatigue levels during the performance of the experiments. This paper constitutes a proof-of-concept study to validate the feasibility of a BMI to control an ambulatory exoskeleton by patients with incomplete paraplegia (i.e., patients with good prognosis for gait rehabilitation). © 2016 López-Larraz, Trincado-Alonso, Rajasekaran, Pérez-Nombela, del-Ama, Aranda, Minguez, Gil-Agudo and Montesano.

Banos R.A.,University of Zaragoza | Cruz A.,University of Zaragoza | Fernandez L.A.,University of Zaragoza | Fernandez L.A.,Complutense University of Madrid | And 27 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

We study the sample-to-sample fluctuations of the overlap probability densities from large-scale equilibrium simulations of the three-dimensional Edwards-Anderson spin glass below the critical temperature. Ultrametricity, stochastic stability, and overlap equivalence impose constraints on the moments of the overlap probability densities that can be tested against numerical data. We found small deviations from the Ghirlanda-Guerra predictions, which get smaller as system size increases. We also focus on the shape of the overlap distribution, comparing the numerical data to a mean-field-like prediction in which finite-size effects are taken into account by substituting delta functions with broad peaks. © 2011 American Physical Society.

Aparicio L.C.,University of Zaragoza | Segarra J.,University of Zaragoza | Segarra J.,Institute Investigacion En Ingenieria Of Aragon I3A | Rodriguez C.,University of the Basque Country | And 2 more authors.
Journal of Systems Architecture | Year: 2011

In multitasking real-time systems it is required to compute the WCET of each task and also the effects of interferences between tasks in the worst case. This is very complex with variable latency hardware, such as instruction cache memories, or, to a lesser extent, the line buffers usually found in the fetch path of commercial processors. Some methods disable cache replacement so that it is easier to model the cache behavior. The difficulty in these cache-locking methods lies in obtaining a good selection of the memory lines to be locked into cache. In this paper, we propose an ILP-based method to select the best lines to be loaded and locked into the instruction cache at each context switch (dynamic locking), taking into account both intra-task and inter-task interferences, and we compare it with static locking. Our results show that, without cache, the spatial locality captured by a line buffer doubles the performance of the processor. When adding a lockable instruction cache, dynamic locking systems are schedulable with a cache size between 12.5% and 50% of the cache size required by static locking. Additionally, the computation time of our analysis method is not dependent on the number of possible paths in the task. This allows us to analyze large codes in a relatively short time (100 KB with 1065 paths in less than 3 min). © 2011 Elsevier B.V. All rights reserved.

Jarabo A.,University of Zaragoza | Masia B.,University of Zaragoza | Masia B.,Massachusetts Institute of Technology | Masia B.,Institute Investigacion En Ingenieria Of Aragon I3A | And 5 more authors.
Computer Graphics Forum | Year: 2015

We present a real-time framework which allows interactive visualization of relativistic effects for time-resolved light transport. We leverage data from two different sources: real-world data acquired with an effective exposure time of less than 2 picoseconds, using an ultra-fast imaging technique termed femto-photography, and a transient renderer based on ray-tracing. We explore the effects of time dilation, light aberration, frequency shift and radiance accumulation by modifying existing models of these relativistic effects to take into account the time-resolved nature of light propagation. Unlike previous works, we do not impose limiting constraints in the visualization, allowing the virtual camera to explore freely a reconstructed 3D scene depicting dynamic illumination. Moreover, we consider not only linear motion, but also acceleration and rotation of the camera. We further introduce, for the first time, a pinhole camera model into our relativistic rendering framework, and account for subsequent changes in focal length and field of view as the camera moves through the scene. © 2015 The Eurographics Association and John Wiley & Sons Ltd.

Lopez-Larraz E.,University of Zaragoza | Lopez-Larraz E.,Institute Investigacion En Ingenieria Of Aragon I3A | Montesano L.,University of Zaragoza | Montesano L.,Institute Investigacion En Ingenieria Of Aragon I3A | And 5 more authors.
PLoS ONE | Year: 2015

Spinal cord injury (SCI) does not only produce a lack of sensory and motor function caudal to the level of injury, but it also leads to a progressive brain reorganization. Chronic SCI patients attempting to move their affected limbs present a significant reduction of brain activation in the motor cortex, which has been linked to the deafferentation. The aim of this work is to study the evolution of the motor-related brain activity during the first months after SCI. Eighteen subacute SCI patients were recruited to participate in bi-weekly experimental sessions during at least two months. Their EEG was recorded to analyze the temporal evolution of the event-related desynchronization (ERD) over the motor cortex, both during motor attempt and motor imagery of their paralyzed hands. The results show that the α and β ERD evolution after SCI is negatively correlated with the clinical progression of the patients during the first months after the injury. This work provides the first longitudinal study of the event-related desynchronization during the subacute phase of spinal cord injury. Furthermore, our findings reveal a strong association between the ERD changes and the clinical evolution of the patients. These results help to better understand the brain transformation after SCI, which is important to characterize the neuroplasticity mechanisms involved after this lesion and may lead to new strategies for rehabilitation and motor restoration of these patients. © 2015 López-Larraz et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Iturrate I.,Institute Investigacion En Ingenieria Of Aragon I3A | Iturrate I.,University of Zaragoza | Chavarriaga R.,Ecole Polytechnique Federale de Lausanne | Montesano L.,Institute Investigacion En Ingenieria Of Aragon I3A | And 5 more authors.
Journal of Neural Engineering | Year: 2014

Objective. A fundamental issue in EEG event-related potentials (ERPs) studies is the amount of data required to have an accurate ERP model. This also impacts the time required to train a classifier for a brain-computer interface (BCI). This issue is mainly due to the poor signal-to-noise ratio and the large fluctuations of the EEG caused by several sources of variability. One of these sources is directly related to the experimental protocol or application designed, and may affect the amplitude or latency of ERPs. This usually prevents BCI classifiers from generalizing among different experimental protocols. In this paper, we analyze the effect of the amplitude and the latency variations among different experimental protocols based on the same type of ERP. Approach. We present a method to analyze and compensate for the latency variations in BCI applications. The algorithm has been tested on two widely used ERPs (P300 and observation error potentials), in three experimental protocols in each case. We report the ERP analysis and single-trial classification. Main results. The results obtained show that the designed experimental protocols significantly affect the latency of the recorded potentials but not the amplitudes. Significance. These results show how the use of latency-corrected data can be used to generalize the BCIs, reducing the calibration time when facing a new experimental protocol. © 2014 IOP Publishing Ltd.

Iturrate I.,Institute Investigacion En Ingenieria Of Aragon I3A | Iturrate I.,University of Zaragoza | Montesano L.,Institute Investigacion En Ingenieria Of Aragon I3A | Montesano L.,University of Zaragoza | And 3 more authors.
Journal of Neural Engineering | Year: 2013

Objective. A major difficulty of brain-computer interface (BCI) technology is dealing with the noise of EEG and its signal variations. Previous works studied time-dependent non-stationarities for BCIs in which the user's mental task was independent of the device operation (e.g., the mental task was motor imagery and the operational task was a speller). However, there are some BCIs, such as those based on error-related potentials, where the mental and operational tasks are dependent (e.g., the mental task is to assess the device action and the operational task is the device action itself). The dependence between the mental task and the device operation could introduce a new source of signal variations when the operational task changes, which has not been studied yet. The aim of this study is to analyse task-dependent signal variations and their effect on EEG error-related potentials.Approach. The work analyses the EEG variations on the three design steps of BCIs: an electrophysiology study to characterize the existence of these variations, a feature distribution analysis and a single-trial classification analysis to measure the impact on the final BCI performance.Results and significance. The results demonstrate that a change in the operational task produces variations in the potentials, even when EEG activity exclusively originated in brain areas related to error processing is considered. Consequently, the extracted features from the signals vary, and a classifier trained with one operational task presents a significant loss of performance for other tasks, requiring calibration or adaptation for each new task. In addition, a new calibration for each of the studied tasks rapidly outperforms adaptive techniques designed in the literature to mitigate the EEG time-dependent non-stationarities. © 2013 IOP Publishing Ltd.

Escolano C.,Institute Investigacion En Ingenieria Of Aragon I3A | Navarro-Gil M.,BitandBrain Technologies SL | Garcia-Campayo J.,University of Zaragoza | Minguez J.,Institute Investigacion En Ingenieria Of Aragon I3A
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS | Year: 2013

Conditioning of the upper-alpha rhythm to improve cognitive performance in healthy users by means of neurofeedback (NF) has been evaluated by several studies, however its effectiveness in people with severe cognitive deficits, such as depressive subjects, remains underexplored. This paper reports on a preliminary uncontrolled study to assess the effects of an upper-alpha NF intervention on patients with major depressive disorder (MDD). The NF effects on the EEG and cognitive performance were assessed. The EEG results showed that patients were able to modulate the upper-alpha rhythm in task-related EEG and during training, in both cases across the executions of the NF sessions, and pre and post within each session. The behavioral results showed the effectiveness of this intervention in a variety of cognitive functions such as working memory, attention, and executive functions. © 2013 IEEE.

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