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Aouni A. Lakis – One of the best experts on this subject based on the ideXlab platform.

  • Application of time–frequency analysis for automatic hidden corrosion detection in a multilayer Aluminum Structure using pulsed eddy current
    NDT & E International, 2012
    Co-Authors: Saleh Hosseini, Aouni A. Lakis

    Abstract:

    Abstract Pulsed eddy current (PEC) is a non-destructive testing method used to detect corrosion and cracks in multilayer Aluminum Structures which are typically found in aircraft applications. Corrosion and metal loss in thin multi-layer Structures are complex and variable phenomena that diminish the reliability of pulsed eddy current measurements. In this article, pulsed eddy current signals are processed to improve the accuracy and reliably of these measurements. PEC’s results (time domain data) are converted by time–frequency analysis (Rihaczek distribution) to represent data in three dimensions. The time–frequency approach generates a large amount of data. Principal component analysis is applied as feature extraction to reduce redundant data to provide new features for classifiers. K -means clustering and expectation–maximization are applied to classify data and automatically determine corrosion distribution in each layer.

Saleh Hosseini – One of the best experts on this subject based on the ideXlab platform.

  • Application of time–frequency analysis for automatic hidden corrosion detection in a multilayer Aluminum Structure using pulsed eddy current
    NDT & E International, 2012
    Co-Authors: Saleh Hosseini, Aouni A. Lakis

    Abstract:

    Abstract Pulsed eddy current (PEC) is a non-destructive testing method used to detect corrosion and cracks in multilayer Aluminum Structures which are typically found in aircraft applications. Corrosion and metal loss in thin multi-layer Structures are complex and variable phenomena that diminish the reliability of pulsed eddy current measurements. In this article, pulsed eddy current signals are processed to improve the accuracy and reliably of these measurements. PEC’s results (time domain data) are converted by time–frequency analysis (Rihaczek distribution) to represent data in three dimensions. The time–frequency approach generates a large amount of data. Principal component analysis is applied as feature extraction to reduce redundant data to provide new features for classifiers. K -means clustering and expectation–maximization are applied to classify data and automatically determine corrosion distribution in each layer.

Lucía Martínez-arcos – One of the best experts on this subject based on the ideXlab platform.

  • Durability of solar reflector materials for secondary concentrators used in CSP systems
    Solar Energy Materials and Solar Cells, 2014
    Co-Authors: Aránzazu Fernández-garcía, Maria Elena Cantos-soto, Marc Röger, Christian Wieckert, Christian Hutter, Lucía Martínez-arcos

    Abstract:

    Abstract Secondary concentrators are used in solar concentrating systems to redirect solar beams reflected by the primary concentrators to the focal point or line. These components allow to increase the concentrated solar flux density and hence to lower thermal radiation losses. Solar reflectors for secondary concentrators are permanently exposed to environmental conditions, high radiation fluxes and elevated temperatures that potentially cause stress and degradation throughout the time. Therefore, analyzing solar reflectors of secondary concentrators by simulating these conditions is crucial. No previous research works about the durability of solar reflector materials for secondary concentrators have been reported. The present work is focused on studying the degradation of the reflector materials by simulating accelerated aging, caused by several ambient parameters and the effect of concentrated radiation. Both cooled and uncooled systems for secondary concentrators are included in this study. According to results obtained, Aluminum reflectors and thin silvered-glass reflectors glued to an Aluminum Structure showed minimum reflectance losses and structural degradation under the operation conditions of cooled 3D secondary concentrators (tower systems). Following critical aspects to avoid reflector degradation were identified: to select a suitable adhesive material to glue the thin silvered-glass reflector to the support Aluminum Structure, to properly protect reflectors edges, to design a suitable cooling system and to avoid the combination of high radiation fluxes with mechanical stress. In addition, laminated silvered-glass reflectors have shown to be suitable for uncooled 2D secondary concentrators (Fresnel collectors). Furthermore, a comparison with naturally aged secondary concentrators using silvered-glass reflectors glued to an Aluminum Structure revealed that the simulated degradation under accelerated conditions performed in this work did reproduce the most frequent degradation patterns suffered in real operating conditions.