FCT: DF - Documentos de conferências internacionais
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- Towards Segmentation and Labelling of Motion Data in Manufacturing ScenariosPublication . Santos, António; Rodrigues, João; Folgado, Duarte; Santos, Sara; Fujão, Carlos; Gamboa, Hugo; DF – Departamento de Física; LIBPhys-UNLThere is a significant interest to evaluate the occupational exposure that manufacturing operators are subjected throughout the working day. The objective evaluation of occupational exposure with direct measurements and the need for automatic annotation of relevant events arose. The current work proposes the use of a self similarity matrix (SSM) as a tool to flag events that may be of importance to be analyzed by ergonomic teams. This way, data directly retrieved from the work environment will be summarized and segmented into sub-sequences of interest over a multi-timescale approach. The process occurs under 3 timescale levels: Active working periods, working cycles, and in-cycle activities. The novelty function was used to segment non-active and active working periods with an F1-score of 95%. while the similarity function was used to correctly segment 98% of working cycle with a duration error of 6.12%. In addition, this method was extended into examples of multi time scale segmentation with the intent of providing a summary of a time series as well as support in data labeling tasks, by means of a query-by-example process to detect all subsequences.
- Towards the Development and Validation of a Smartphone-Based Pupillometer for Neuro-Ophthalmological Diseases ScreeningPublication . Sousa, Ana Isabel; Neves, Carlos Marques; Pinto, Luís Abegão; Vieira, Pedro; DF – Departamento de FísicaPupillometry allows a quantitative measurement of PLR and has been mainly used to assess patient’s consciousness and vision function. The analysis of pupil light reflex (PLR) has been showing a renewed interest since the discovery of intrinsically photosensitive retinal ganglion cells (ipRGCs), that are sensitive to the blue light, as they have an important role in pupil response to a stimulus. Some researches have studied pupillometry, particularly chromatic pupillometry that uses blue and red stimuli, to be a screening tool for neuro-ophthalmological diseases. Automated pupillometers have been widely used, however they are either not portable or expensive, reason why this technique has been mainly used in academic research. A smartphone-based pupillometer could be a promising equipment to overcome these limitations and to be a widespread screening tool, due to its low price, portability and accessibility. This work shows our latest advances towards the development and validation of an Android system for pupillometry measurements. Pupillometric data was collected with the smartphone application in a group of five healthy individuals and used to test our proposed data processing algorithms. These tests showed that the data processing methods that we are proposing, although promising, did not behave as expected, indicating that new approaches, better validations and corrections should be made in the future to get a stable software for pupil detection. Nevertheless, preliminary pupillometric data indicate that this system has the potential to work as an inexpensive, easy-to-use and portable pupillometer.
- The Mindfulness Meditation Effect on Brain Electrical Activity: Stress Assessment, Concentration State and Quality of LifePublication . Morais, Pedro; Quintão, Carla; DF – Departamento de Física; LIBPhys-UNLBeing healthy is much more than not being sick. It is essentially living day-to-day under a physical and mental well-being. In Europe a large part of the population suffers from depression, anxiety or stress. This public health problem needs urgent treatment for which the individual's psychic self-regulation can respond. The proposed alternative for improving quality of life is an approach to Mindfulness meditation. It is hoped that the beneficial effect of this practice in a continuous way, living the present in "mindfulness", contributes to improve the individual mental state releasing from a depressive past effect or from a future wrapped in anxiety. Based on visual stimuli, concentration test and stress-inducing challenges, 30 individuals are evaluated at regular intervals during 8 weeks of Mindfulness Based Stress Reduction (MBSR) course. Physiological signals are recorded longitudinally through EEG, ECG and EDA. At the same time, each individual completes three inquiries assessing quality of life (WHOQOL), profile mood state (POMS) and depression, anxiety and stress scale (DASS). Applying the neurophysiologic processing and classification data, with synchronous sources isolation, it is intended to verify functional changes that occur in the pre-frontal cortex. This results will inferring that it is possible to change the cerebral electrical activity with the thought. At the same time, it is expected a slowed heart/sweating rate and an increase in the ability to concentrate, as well as a significant improvement in the individual emotional control response. The current PhD study in Biomedical Engineering intends to show that the Mindfulness meditation practice, being "here and now", promotes a healthy mental health, featured by attention self-regulation and the decrease of anxiety, depression or stress. It can be used as a promising treatment for clinical disorders affecting a large part of the population.
- Semi-automatic tool to identify heterogeneity zones in lge-cmr and incorporate the result into a 3d model of the left ventriclePublication . Narciso, Maria; Ferreira, António; Vieira, Pedro; DF – Departamento de FísicaFatal scar-related arrhythmias are caused by an abnormal electrical wave propagation around non conductive scarred tissue and through viable channels of reduced conductivity. Late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) is the gold-standard procedure used to differentiate the scarred tissue from the healthy, highlighting the dead cells. The border regions responsible for creating the feeble channels are visible as gray zones. Identifying and monitoring (as they may evolve) these areas may predict the risk of arrhythmias that may lead to cardiac arrest. The main goal of this project is the development of a system able to aid the user in the extraction of geometrical and physiological information from LGE images and the replication of myocardial heterogeneities onto a three-dimensional (3D) structure, built by the methods described by our team in another publication, able to undergo electro-physiologic simulations. The system components were developed in MATLAB R2019b the first is a semi-automatic tool, to identify and segment the myocardial scars and gray zones in every two-dimensional (2D) slice of a LGE CMR dataset. The second component takes these results and assembles different sections while setting different conductivity values for each. At this point, the resulting parts are incorporated into the functional 3D model of the left ventricle, and therefore the chosen values and regions can be validated and redefined until a satisfactory result is obtained. As preliminary results we present the first steps of building one functional Left ventricle (LV) model with scarred zones.
- High-power high-brightness solar laser approach for renewable Mg recovery from MgOPublication . Almeida, Joana; Liang, Dawei; CeFITec – Centro de Física e Investigação Tecnológica; DF – Departamento de FísicaHydrogen and heat energy from the reaction of magnesium with water can be used for engines and fuel cells. However, at least 4000 K is necessary for magnesium oxide reduction. Ultra high brightness solar-pumped lasers become essential to make this renewable process technology efficient and economically competitive. 2.3 mg/kJ solar laser - induced magnesium production efficiency has been achieved by T. Yabe et al., in 2012, by focusing a 53 W solar laser beam on a mixture of MgO with Si as reducing agent. This result is however far from the 12.1 mg/kJ attained with 2 kW/mm2 CO2 laser beam. To improve substantially the solar laser - induced Mg production efficiency, a simple high-power, high brightness Nd:YAG solar laser pumping approach is proposed. The solar radiation is both collected and concentrated by four Fresnel lenses, and redirected towards a Nd:YAG laser head by four plane folding mirrors. A fused-silica secondary concentrator is used to compress the highly concentrated solar radiation to a laser rod. Optimum pumping conditions and laser resonator parameters are found through ZEMAX
- Design of high-brightness TEM00-mode solar-pumped laser for renewable material processingPublication . Liang, Dawei; Almeida, Joana; CeFITec – Centro de Física e Investigação Tecnológica; DF – Departamento de FísicaThe conversion of sunlight into laser light by direct solar pumping is of ever-increasing importance because broadband, temporally constant, sunlight is converted into laser light, which can be a source of narrowband, collimated, rapidly pulsed, radiation with the possibility of obtaining extremely high brightness and intensity. Nonlinear processes, such as harmonic generation, might be used to obtain broad wavelength coverage, including the ultraviolet wavelengths, where the solar flux is very weak. The direct excitation of large lasers by sunlight offers the prospect of a drastic reduction in the cost of coherent optical radiation for high average power materials processing. This renewable laser has a large potential for many applications such as high-temperature materials processing, renewable magnesium-hydrogen energy cycle and so on. We propose here a scalable TEM00 mode solar laser pumping scheme, which is composed of four firststage 1.13 m diameter Fresnel lenses with its respective folding mirrors mounted on a two-axis automatic solar tracker. Concentrated solar power at the four focal spots of these Fresnel lenses are focused individually along a common 3.5 mm diameter, 70 mm length Nd:YAG rod via four pairs of second-stage fused-silica spherical lenses and third-stage 2D-CPCs (Compound Parabolic Concentrator), sitting just above the laser rod which is also double-pass pumped by four V-shaped pumping cavities. Distilled water cools both the rod and the concentrators. 15.4 W TEM00 solar laser power is numerically calculated, corresponding to 6.7 times enhancement in laser beam brightness.
- Side-pumping NdPublication . Tomás, G.; Liang, Dawei; Almeida, Joana; CeFITec – Centro de Física e Investigação Tecnológica; DF – Departamento de FísicaTo obtain a good compromise between collection efficiency and brightness figure of merit of solar-pumped lasers, a new side-pumping scheme is proposed. Firstly the solar radiations are collected and concentrated by six 700 mm diameter Fresnel lenses. The concentrated solar radiations are subsequently reflected by six plane folding mirrors with 95% reflectivity, into a common focal spot. This allows the concentration of 1740 W solar power with about 6.4 W/mm2 peak solar flux. A secondary concentrator is composed of six aspheric fused silica lenses, positioned around a 40 mm radius fused silica sphere, compressing all the concentrated solar radiation from the six Fresnel lenses into an 8 mm diameter by 9 mm length Nd:YAG single-crystal rod. By positioning the spherical concentrator slightly above the aspherical lenses, a more uniform absorption profile is achieved. Mechanical support with a water cooling system ensures an efficient cooling to the laser medium. Optimal laser parameters are found through ZEMAXTM and LASCADTM numerical analysis software. Only 16% of the solar power is absorbed by Nd:YAG medium. Solar laser power of 42.6 W is numerically calculated, reaching a collection efficiency of 18.5 W/m2. For a 400 mm plane-concave resonance cavity with -5m radius of curvature, M2 x = M2 y = 22 beam quality factors are numerically predicted. A near uniform pump absorption profile can be achieved by increasing the number of Fresnel lens and folding mirrors.
- Core-doped NdPublication . Garcia, Dário; Liang, Dawei; Almeida, Joana; CeFITec – Centro de Física e Investigação Tecnológica; DF – Departamento de FísicaA novel solar laser uniformly pumped by six Fresnel lenses is proposed here. The incident solar radiation is firstly collected and concentrated by six 0.8 m diameter Fresnel lenses and then reflected by other six plane mirrors to a central focal zone, where a laser head is mounted. About 2.5 kW solar power with 3.5 W/mm2 peak solar flux can be achieved in the focal zone. The laser head is composed of a fused silica six-sphere type secondary concentrator that further compresses the concentrated solar power from the six Fresnel lenses-plane mirrors to a core-doped YAG Nd3+:YAG ceramic disk. Optimum pumping parameters and solar laser output powers are found through ZEMAX non-sequential ray-tracing and LASCAD laser cavity analysis, respectively. The laser resonant cavity is formed by a PR 1064 nm output coupler and a HR 1064 nm plane reflector. An 8 mm diameter central hole is drilled through the six-sphere type concentrator to allow the extraction of laser power from the disk. Since only 16 % of the useful solar power is absorbed by the Nd:YAG medium, for 950 W/m2 of terrestrial solar irradiation, the effective solar pump power of 456 W is assumed in ray-tracing analysis. 72.2 W of multimode laser power is predicted for an 8 mm diameter gain medium embedded within a conical undoped YAG cladding, reaching the collection efficiency of 24.1 W/m2. M2 = 16.6 is numerically calculated, corresponding to the brightness figure of merit of 0.26 W. A near uniform absorbed pump profile is achieved.
- Comparative study of Cr:Nd:YAG and Nd:YAG solar laser performancesPublication . Liang, Dawei; Almeida, Joana; Garcia, Dário; CeFITec – Centro de Física e Investigação Tecnológica; DF – Departamento de FísicaTo improve the efficiency of Nd3+-doped YAG solar laser, cross-pumped Cr3+ and Nd3+ co-doped YAG ceramic material has attracted more attentions in recent years. The sensitizer Cr3+ ions have broad absorption bands in the visible region. Despite the interests in Cr:Nd:YAG ceramic medium, researchers have achieved significant laser efficiencies with different Nd:YAG single-crystal rods. While it is clear about the effectiveness of Nd:YAG single-crystal rods for solar laser operation, there still exist some concerns about the advantages of Cr:Nd:YAG ceramics in solar-pumped lasers. A 0.9 m diameter Fresnel lens is used as an economical solar collector. A 4 mm diameter, 25 mm length 1.0 at% Nd:YAG single-crystal rod and a 0.1 at% Cr: 1.0 at% Nd:YAG ceramic rod are pumped alternatively within a conical cavity through a secondary concentrator. With the Nd:YAG rod, the maximum laser power is 12.3 W, corresponding to 19.3 W/m2 collection efficiency. With the Cr:Nd:YAG ceramic rod, the maximum laser power is 13.5 W, corresponding to 21.2 W/m2 collection efficiency. This result is, to the best of our knowledge, the highest collection efficiency achieved with Cr:Nd:YAG ceramic medium. There is also a 109% increase in slope efficiency. In summary, we have experimentally observed a moderate, but not significant, advantage of Cr:Nd:YAG ceramics over Nd:YAG single-crystal medium in both solar laser conversion and slope efficiency.
- Gneuropathy: Validation process at clinical environmentPublication . Quaresma, Claudia; Gomes, Madalena; Cardoso, Heitor; Ferreira, Nuno; Vigário, Ricardo; Quintão, Carla; Fonseca, Micaela; LIBPhys-UNL; DF – Departamento de FísicaSpinal cord injuries are one of the most traumatic situations with a major impact on a person's quality of life. This type of injury have a extremely impact in the performance of daily life activities not only due to motor alterations but also due to the appearance of neuropathic pain Throughout the rehabilitation process the evaluation and intervention methodologies are not very systematic and are not personalized. Thus, to bridge this gap, the VR4NeuroPain was developed a technology that associates virtual reality with a glove "GNeuroPathy". The glove "GNeuroPathy" allows the collection of physiological parameters, namely to identify the electrodermic activity (EDA) while the patient carries out activities in an immersive environment. The main objective of this article is to present the validation process of the "GNeuroPathy" in clinical context. "GNeuroPathy" was applied to a group of 17 individuals with incomplete spinal cord injury. The results showed that "GNeuroPathy" is easy to apply and is suitable for comfort and texture. Data were also collected from EDA and it was found that there is a significant difference in signal amplitude in patients with low and high functionality.
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