1,720,988 research outputs found
A quantitative approach to retrieve delamination extension from thermal images recorded during impact tests
No full textA linearized impact localization algorithm for the health monitoring of aerospace components
No full textLiterature presents a wide range of techniques and algorithms for the localization of impact source in isotropic structures. However, many of these methods involve either solving complex systems of nonlinear equations or a-priori training of the monitored structure. This is not only time consuming, but it requires high levels of computational effort that may often result in a poor estimation of the impact coordinates. This paper presents a novel structural health monitoring system for the impact localization on aluminium components. The proposed methodology, in contrast to current impact localization techniques, relies on an optimal sensor placement, which allows reducing the nonlinear system of equations to a linearized and simplified form. Two different Akaike Information Criterion (AIC) pickers are used to calculate the arrival times of the direct elastic waves originated by the impact source. To validate this methodology, experimental tests were carried out on aerospace components using four surface-bonded piezoelectric sensors. The results showed that this technique allows detecting and localizing the impact source with a high level of accuracy in any point of the structure
Locomotor and Posture Strategies in Patients with Duchenne Muscular Dystrophy (DMD). Part 2: Posture Analysis.
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Locomotor and Posture Strategies in Patients with Duchenne Muscular Dystrophy (DMD). Part 1: Gait Analysis.
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Epidemiologia delle alterazioni muscolo-scheletriche da sovraccarico biomeccanico del rachide nella movimentazione manuale dei pazienti
No full textThe painful lumbosacral symptoms associated with manual lifting by nursing staff constitutes an increasingly important problem in Occupational Health. This category of workers is in fact particularly exposed to risk situations involving the lumbar region of the spine, due especially to the extreme variability of work on the shift, the nature of what is lifted and not always sufficient knowledge and proper performance of the movements. On the basis of a review of a series of studies made on this topic, it was possible to assess the incidence and prevalence of low back pain in selected populations and identify the postural risk to which nursing staff are exposed at work, stressing also the importance of a correct knowledge of manual lifting techniques, frequency and mode of performing them, and the psychological aspects (perception of the intensity of tasks and osteoarticular strain). It was also observed that the data on painful lumbosacral symptoms were underestimated due to the type of epidemiological investigations carried out (mostly cross-sectional) and that comparison of the data proposed was often difficult due to the different criteria of evaluation used to classify the painful symptoms and also to the various epidemiological parameters used (incidence, cumulative incidence, prevalence)
A novel heatsink for thermo-electric power harvesting of structural health monitoring systems
No full textRecent research in energy harvesting is leading to the possibility of developing self-powered structural health monitoring (SHM) systems for aerospace applications. Particularly, temperature gradients originated at different locations of the aircraft can be converted into electric current by using thermoelectric generators (TEGs). TEGs are a suitable option for power harvesting since they (i) can be easily mounted on aircraft components, (ii) are lightweight, (iii) do not contain movable parts and (iv) provide high-energy conversion. TEGs are generally combined with thermal diffusion systems (heatsinks) to dissipate heat from a high temperature surface to the ambient air. The present study investigates the design, manufacturing and testing of a novel air-cooled heatsink used to increase temperature gradients on the surfaces of a commercial TEG element and, in turn, the power generation. In particular, a novel heatsink geometry and hybrid material configuration are analysed to enhance the heat spread in the power harvesting system in order to further improve the TEG performance. Numerical finite element simulations and experimental tests are carried out to assess the characteristics of the novel heatsink in combination with a commercial TEG device. Experimental results reveal that the proposed thermal diffusion system provides higher level of performance in comparison with traditional fin array heatsinks. Moreover, considering 100°C and 25°C as heat source and ambient temperature, respectively, the presented heatsink-TEG arrangement produces enough energy to power an ultrasound SHM system for aerospace applications (output power over 30 mW)
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