Search results for " Multilayer"

Modelling of Pulsed Electro Acoustic Method for Space Charge Detection on Single and Multilayer Dielectrics

Artificial neural network comparison for a SHM procedure applied to composite structures.

2013

In this paper different architectures of Artificial Neural Networks (ANNs) for structural damage detection are studied. The main objective is to create an ANN able to detect and localize damage without any prior knowledge on its characteristics so as to serve as a realtime data processor for SHM systems. Two different architectures are studied: the standard feed-forward Multi Layer Perceptron (MLP) and the Radial Basis Function (RBF) ANNs. The training data are given, in terms of a Damage Index ℑD, properly defined using the piezoelectric sensor signal output to obtain suitable information on the damage position and dimensions. The electromechanical response of the assembled structure has b…

Growth of metal/oxide periodic multilayer : relation between structure and electrical behaviour in systems based on titanium and tungsten

2014

Periodic multilayers have found many applications in the fields of optics, mechanics or electronics. However, few studies focus on the electrical responses of the metal/oxide periodic structures versus temperature. The interest of this work was focused on the characterization of the multilayers and their electrical properties versus temperature. In TiO/Ti/TiO/TiO2 and WO/W/WO/WO3 systems produced by the reactive gas pulsing process, sample structures were established by transmission electron microscopy for sublayers thicknesses between 1.3 and 50.8 nm. Then, this study highlights a modification of conventional electrical behavior versus temperature. An empirical relationship was established…

Reliability of PEA Measurement in Presence of an Air Void Defect

2020

This paper deals with the reliability of the Pulsed Electro-Acoustic (PEA) technique in the case of a specimen containing an air layer. The first approach to this study has been proposed by the authors in previously published works. In these papers, the mathematical description, the PEA cell simulation model, and some experimental tests have been reported. In this work, a more accurate description of the acoustic wave behavior within the PEA cell and specimen with and without an air layer is given. Moreover, the comparison between simulation and experimental tests for both cases (specimen with and without air layer) allowed the validation of the previously developed PEA cell simulation mode…

Low-temperature atomic layer deposition of SiO2/Al2O3 multilayer structures constructed on self-standing films of cellulose nanofibrils

2018

In this paper, we have optimized a low-temperature atomic layer deposition (ALD) of SiO 2 using AP-LTO® 330 and ozone (O 3 ) as precursors, and demonstrated its suitability to surface-modify temperature-sensitive bio-based films of cellulose nanofibrils (CNFs). The lowest temperature for the thermal ALD process was 80°C when the silicon precursor residence time was increased by the stop-flow mode. The SiO 2 film deposition rate was dependent on the temperature varying within 1.5–2.2 Å cycle −1 in the temperature range of 80–350°C, respectively. The low-temperature SiO 2 process that resulted was combined with the conventional trimethyl aluminium + H 2 O process in order to prepare thin mul…

A high-resolution layer-wise discontinuous Galerkin formulation for multilayered composite plates

2020

Abstract In this work, a novel high-resolution formulation for multilayered composite plates is presented. The formulations is referred to as high-resolution since it combines (i) Layer-Wise plate theories, which are based on a per-layer, high-order expansion of the primary variables throughout the plate’s thickness, providing a detailed layer-level description of the sought solution; (ii) The discontinuous Galerkin method, a numerical approach based on a discontinuous representation of the unknown fields over the mesh elements and on the introduction of boundary integral operators enforcing inter-element continuity, which allow the natural treatment of high-order mesh elements and provide …

Astronomical soft x-ray mirrors reflectivity enhancement by multilayer coatings with carbon overcoating

2004

A number of X-ray astronomical missions of near future will make use of hard X-ray optics with broad-band multilayer coatings. However multilayer mirrors can be also useful to enhance the effective area of a given X-ray telescope in the "classical" low energy X-ray band (0.1 – 10 keV), the window where X-ray spectroscopy provides very useful plasma diagnostics) with a consistent gain with respect to usual single-layer reflectors. Multilayers for soft X-rays are based on stacks with constant d-spacing (in order to minimize the loss due to the photoelectric effect). A further gain in reflectivity (however only restricted to the energy range between 0.5 and 4 keV) can be achieved by using a lo…

Etude de la stabilité de films industriels de PLA et de leur modification de surface pour des applications en tant qu'emballage alimentaire biodégrad…

2017

Poly(lactic acid) (PLA) is a biodegradable and renewable polyester, which is considered as the most promising eco-friendly substitute of conventional plastics. It is mainly used for food packaging applications, but some drawbacks still reduce its applications. On the one hand, its low barrier performance to gases (e.g. O2 and CO2) limits its use for applications requiring low gas transfer, such as modified atmosphere packaging (MAP) or for carbonate beverage packaging. On the other hand, its natural water sensitivity, which contributes to its biodegradation, limits its use for high moisture foods with long shelf life.Other biopolymers such as wheat gluten (WG) can be considered as interesti…

A unified formulation for multilayered smart plate advanced models

2017

Magneto-electro-elastic (MEE) composite materials are attracting increasing consideration as they couple mechanical, electrical and magnetic fields and this makes them particularly suitable for smart applications. They are often employed as multilayered configurations that appear to be more effective than bulk MEE composites. Thus, reliable and efficient modelling tools are required for an effective design. The present talk deals with a unified formulation to derive advanced models for multilayered MEE plates. The approach is based on the condensation of the electro-magnetic state into the plate kinematics. This leads to models involving kinematical variables only, which takes the multifiel…

Melt Processed PCL/PEG Scaffold with Discrete Pore Size Gradient for Selective Cellular Infiltration

2016

In order to develop scaffold able to mimic the natural gradient properties of tissues, biphasic and triphasic approaches were adopted. In this work, polycaprolactone/polyethylene glycol (PCL/PEG) scaffolds were prepared by using a combination of melt mixing and selective leaching without harmful solvents. The method permitted to develop three-layer scaffolds with high control of porosity and pore size. The mechanical properties were evaluated under physiological condition in order to simulate the real conditions of work. Co-culture of osteoblastic and fibroblastic mice cells were carried out in order to study the differential cellular permeation through the different pore size layers.