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Personne :
Fleuret, Julien

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Fleuret

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Julien

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Université Laval. Département de génie électrique et de génie informatique

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ncf11735166

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Voici les éléments 1 - 3 sur 3
  • PublicationAccès libre
    Non-destructive investigation of paintings on canvas by continuous wave terahertz imaging and flash thermography
    (Springer, 2017-04-05) Avdelidis, Nicolas P.; Fleuret, Julien; Saluja, Karan; Zhang, Hai; Peeters, Jeroen; Maldague, Xavier; Ibarra Castanedo, Clemente; Duan, Yuxia; Sfarra, Stefano; Fernandes, Henrique
    Terahertz (THz) imaging is increasingly used in the cultural heritage field. In particular, continuous wave (CW) and low frequency THz is attracting more attention. The first application of the THz technique inherent to the cultural heritage field dates back 10 years ago. Since 2006, tangible improvements have been conducted in the refinement of the technique, with the aim to produce clear maps useful for any art restorer. In this paper, a CW THz (0.1 THz) imaging system was used to inspect paintings on canvas both in reflection and in transmission modes. In particular, two paintings were analyzed: in the first one, similar materials and painting execution of the original artwork were used, while in the second one, the canvas layer is slightly different. Flash thermography was used herein together with the THz method in order to observe the differences in results for the textile support materials. A possible application of this method for the detection of artwork forgery requires some parameterization and analysis of various materials or thickness influence which will be addressed in a future study. In this work, advanced image processing techniques including principal component thermography (PCT) and partial least squares thermography (PLST) were used to process the infrared data. Finally, a comparison of CW THz and thermographic results was conducted.
  • PublicationAccès libre
    Automated assessment and tracking of human body thermal variations using unsupervised clustering
    (The Optical Society of America, 2016-11-17) Fleuret, Julien; Zhang, Hai; Maldague, Xavier; Yousefi, Bardia; Watt, Raymond; Klein, Matthieu
    The presented approach addresses a review of the overheating that occurs during radiological examinations, such as magnetic resonance imaging, and a series of thermal experiments to determine a thermally suitable fabric material that should be used for radiological gowns. Moreover, an automatic system for detecting and tracking of the thermal fluctuation is presented. It applies hue-saturated-value-based kernelled k-means clustering, which initializes and controls the points that lie on the region-of-interest (ROI) boundary. Afterward, a particle filter tracks the targeted ROI during the video sequence independently of previous locations of overheating spots. The proposed approach was tested during experiments and under conditions very similar to those used during real radiology exams. Six subjects have voluntarily participated in these experiments. To simulate the hot spots occurring during radiology, a controllable heat source was utilized near the subject’s body. The results indicate promising accuracy for the proposed approach to track hot spots. Some approximations were used regarding the transmittance of the atmosphere, and emissivity of the fabric could be neglected because of the independence of the proposed approach for these parameters. The approach can track the heating spots continuously and correctly, even for moving subjects, and provides considerable robustness against motion artifact, which occurs during most medical radiology procedures.
  • PublicationAccès libre
    Pulsed micro-laser line thermography on submillimeter porosity in carbon fiber reinforced polymer composites : experimental and numerical analyses for the capability of detection
    (Optical Society of America, 2016-08-08) Fleuret, Julien; Zhang, Hai; Maldague, Xavier; Hassler, Ulf; Ibarra Castanedo, Clemente; Robitaille, François; Djupkep Dizeu, Frank Billy; Genest, Marc; Fernandes, Henrique; Joncas, Simon
    In this article, pulsed micro-laser line thermography (pulsed micro-LLT) was used to detect the submillimeter porosities in a 3D preformed carbon fiber reinforced polymer composite specimen. X-ray microcomputed tomography was used to verify the thermographic results. Then, finite element analysis was performed on the corresponding models on the basis of the experimental results. The same infrared image processing techniques were used for the experimental and simulation results for comparative purposes. Finally, a comparison of experimental and simulation postprocessing results was conducted. In addition, an analysis of probability of detection was performed to evaluate the detection capability of pulsed micro-LLT on submillimeter porosity.