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Identifiability of Ludwik's law parameters depending on the sample geometry via inverse identification procedure

  • Zaplatic, Andrija;Tomicevic, Zvonimir;Cakmak, Damjan;Hild, Francois
    • Coupled systems mechanics
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    • v.11 no.2
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    • pp.133-149
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    • 2022
  • The accurate prediction of elastoplasticity under prescribed workloads is essential in the optimization of engineering structures. Mechanical experiments are carried out with the goal of obtaining reliable sets of material parameters for a chosen constitutive law via inverse identification. In this work, two sample geometries made of high strength steel plates were evaluated to determine the optimal configuration for the identification of Ludwik's nonlinear isotropic hardening law. Finite element model updating(FEMU) was used to calibrate the material parameters. FEMU computes the parameter changes based on the Hessian matrix, and the sensitivity fields that report changes of computed fields with respect to material parameter changes. A sensitivity analysis was performed to determine the influence of the sample geometry on parameter identifiability. It was concluded that the sample with thinned gauge region with a large curvature radius provided more reliable material parameters.

Application of a deep learning algorithm to Compton imaging of radioactive point sources with a single planar CdTe pixelated detector

  • Daniel, G.;Gutierrez, Y.;Limousin, O.
    • Nuclear Engineering and Technology
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    • v.54 no.5
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    • pp.1747-1753
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    • 2022
  • Compton imaging is the main method for locating radioactive hot spots emitting high-energy gamma-ray photons. In particular, this imaging method is crucial when the photon energy is too high for coded-mask aperture imaging methods to be effective or when a large field of view is required. Reconstruction of the photon source requires advanced Compton event processing algorithms to determine the exact position of the source. In this study, we introduce a novel method based on a Deep Learning algorithm with a Convolutional Neural Network (CNN) to perform Compton imaging. This algorithm is trained on simulated data and tested on real data acquired with Caliste, a single planar CdTe pixelated detector. We show that performance in terms of source location accuracy is equivalent to state-of-the-art algorithms, while computation time is significantly reduced and sensitivity is improved by a factor of ~5 in the Caliste configuration.

Hybrid infrared-visible multiview correlation to study damage in a woven composite complex-shaped specimen

  • Andrija Zaplatic;Zvonimir Tomicevic;Xuyang Chang;Ivica Skozrit;Stephane Roux;Francois Hild
    • Coupled systems mechanics
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    • v.12 no.5
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    • pp.445-459
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    • 2023
  • In this study, a cyclic tensile test on a notched butterfly specimen made of woven glass fiber composite was performed on a modified Arcan fixture. During the mechanical test, the sample was monitored with a hybrid stereoscopic system comprised of two visible lights and one infrared camera. The visible light cameras were employed for kinematic measurements using a finite-element-based multiview correlation technique. A semi-hybrid correlation approach was followed, providing Lagrangian temperature fields of the Region of Interest. Due to the complex composite architecture and specimen shape, localized shearing was observed during the tensile loading. Furthermore, asymmetrical damage developed around the notches as revealed by localized strains and thermal hot spots.

Effectiveness and patient satisfaction of dental emergencies in Pitié Salpêtrière Hospital, Paris, during the COVID 19 pandemic

  • Rodriguez, Isabelle;Zaluski, Daniel;Jodelet, Pierre Alain;Lescaille, Geraldine;Toledo, Rafael;Boucher, Yves
    • Journal of Dental Anesthesia and Pain Medicine
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    • v.22 no.4
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    • pp.255-266
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    • 2022
  • Background: A previous study reported the effectiveness and patient satisfaction in the dental emergency unit (DEU) of the Pitie Salpetrière Hospital in Paris before coronavirus disease 2019 (COVID-19). The same methodology was used during the COVID-19 pandemic to compare pain, anxiety, and patient satisfaction during the two periods. Methods: This prospective study was conducted in 2020 (NCT04354272) on adult patients. Data were collected on day zero (D0) on site and then by phone during the daytime on day one (D1), day three (D3), and day seven (D7). The primary objective was to assess the pain intensity at D1. Secondary objectives were to assess pain intensity at D3 and D7, anxiety intensity at D1, D3, and D7, and patient satisfaction. Patients were evaluated on a 0-10 numeric scale on D1, D3, and D7; mean scores were compared with non-parametric statistics (ANOVA, Dunn's). Results: A total of 445 patients were given the opportunity to participate in the study, and 370 patients consented. Seventy-one were lost during follow-up. Ultimately, 299 patients completed all the questionnaires and were included in the analysis. In the final sample (60% men, 40% women, aged 39 ± 14 years), 94% had health insurance. The mean pain scores were: D0, 6.1 ± 0.14; D1, 3.29 ± 0.16; D3, 2.08 ± 0.16; and D7, 1.07 ± 0.35. This indicates a significant decrease of 46%, 67%, and 82% at D1, D3, and D7, respectively, when compared to D0 (P < 0.0001). The mean anxiety scores were D0, 4.7 ± 0.19; D1, 2.6 ± 0.16; D3, 1.9 ± 0.61; and D7, 1.4 ± 0.15. This decrease was significant between D0 and D7 (ANOVA, P < 0.001). Perception of general health improved between D1 and D7. The overall satisfaction was 9.3 ± 0.06. Conclusion: DEU enabled a significant reduction in pain and anxiety with high overall satisfaction during COVID-19, which was very similar to levels observed pre-COVID-19 pandemic.

Special Issue on computational methods in engineering (CILAMCE 2018 - Paris/Compiegne)

  • Ibrahimbegovic, Adnan;Pimenta, Paulo M.
    • Coupled systems mechanics
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    • v.8 no.2
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    • pp.95-98
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    • 2019
  • This special issue contains selected papers first presented in a short format at the Congress CILAMCE 2018 ($39^{th}$ Ibero-Latin American Congress on Computational Methods in Engineering) held in Paris and in $Compi{\grave{e}}gne$, France, from 11 to 14 November 2018.