Search results for "Engineering sciences"
showing 10 items of 2347 documents
Experimental Investigation and Finite Element Analysis of Dynamic Behavior and Damage of Glass/Epoxy Tubular Structures
2011
This paper presents finite element analysis (FEA) of static and dynamic tests of thick filament wound glass/epoxy tubes. The first part involves the validation of elastic properties and identification of damage initiation and its development in dynamic tests. The results of FEA of the dynamic tests without damage appeared satisfactory. An impact model, including material property degradation, is used for damage prediction. The simulated damage is compared with that obtained experimentally. The sizes of projected and cumulated surfaces are of the same order of magnitude as in the experimental measurements.
Two-Color Single Hybrid Plasmonic Nanoemitters with Real Time Switchable Dominant Emission Wavelength
2015
International audience; We demonstrate two-color nanoemitters that enable the selection of the dominant emitting wavelength by varying the polarization of excitation light. The nanoemitters were fabricated via surface plasmon-triggered two-photon polymerization. By using two polymerizable solutions with different quantum dots, emitters of different colors can be positioned selectively in different orientations in the close vicinity of the metal nanoparticles. The dominant emission wavelength of the metal/polymer anisotropic hybrid nanoemitter thus can be selected by altering the incident polarization.
Transform-limited spectral compression by self-phase modulation of amplitude-shaped pulses with negative chirp
2011
International audience; Spectral compression by self-phase modulation of amplitude- and phase-shaped pulses is demonstrated as superior compared to pulses that have only been phase shaped. We synthesize linearly negatively chirped parabolic pulses, which we send through a nonlinear photonic crystal fiber, in which self-phase modulation compresses the spectrum of the pulses to within 20% of the Fourier transform limit.
Improving the vertical radiation pattern issued from multiple nano-groove scattering centers acting as an antenna for future integrated optics Fourie…
2019
The stationary wave integrated Fourier transform spectrometer (SWIFTS) is based on the sampling of a stationary wave using nano-scattering centers on the surface of a channel waveguide. Single nano-scale scattering centers above the waveguide surface will radiate the sampled signal with wide angular distribution, which is not compatible with the buried detection area of infrared (IR) detectors, resulting in crosstalk between pixels. An implementation of multiple diffraction nano-grooves (antenna) for each sampling center is proposed as an alternative solution to improve directivity towards the detector pixel by narrowing the scattering angle of the extracted light. Its efficiency is demonst…
Residual strain and stress analysis by speckle interferometry combined with the drill of a groove
2007
A new method for residual stresses determination combining Electronic Speckle Pattern Interferometry (ESPI) with the machining of a groove. The internal stress field is perturbed as the depth of the groove is increased incrementally [1]. The structure finds a new equilibrium state generating displacements which are measured using ESPI. This method was tested on an aluminium alloy plate treated locally by ultrasonic shot-peening. The investigation of the images obtained with the phase shifting technique and fringe patterns makes it possible to analyze, simultaneously, the stress profile along two directions: along the depth of the structure, and along the groove direction.
Prediction of Dissipative Properties of Flax Fibers Reinforced Laminates by Vibration Analysis
2016
This study proposes an experimental-numeric method to identify the viscoelastic properties of flax fibres reinforced composite laminate (flax/epoxide). The used method consists in identifying the evolutions of both loss factor and stiffness when vibrational frequency changes. In this way, several free-free symmetrically guided beams are excited on a dynamic range of 10 to 4000 Hz with sweep sine excitation focused around the 4-first’s modes. Fractional derivative Zener model is used to identify the on-axis ply complex moduli and describe the laminate dissipative linear behavior with the classical laminate theory. Results obtained on a quasi-isotropic laminate show that this model adequately…
Study and design of a controlled oscillator for an embedded system to measure the complex impedance of PEM fuel cell »
2017
We present in this paper the study and the design of a voltage controlled oscillator (VCO) for an embedded system to diagnose the PEM fuel cell. Some problems related to fuel cells used in the electric vehicle field are the management of its efficiency and the lifetime of its membranes. To do this, the diagnosis using measuring the complex impedance is an important phase. It is based on the injection of a perturbation signal at the output of the PEM fuel cell, then we observe its behavior by measuring its impedance. The used measurement method is the electrochemical impedance spectroscopy (EIS) using the load modulation technique, which is implemented in an embedded measurement system based…
Silica-coated superparamagnetic nanoparticles as contrast agent for magnetic resonance imaging: Synthesis and physicological charaterizations
2015
Superparamagnetic iron oxide nanoparticles (SPIONs) have received a growing interest for various biomedical applications due to their interesting magnetic properties. Herein, we report a method for facile synthesis of colloidal silica-coated superparamagnetic iron oxide nanoparticles (Si-SPIONs). The polyvinyl alcohol (PVA)-SPIONs were successfully prepared and then coated with silica by the modified Stober method. The obtained Si-SPIONs are highly monodisperse with uniform morphology. Notably, comparing to uncoated SPIONs, silica coated ones show colloidal stability region at physiological pH which is applicable in biomedical applications and synthesis at the scale of grams was easily obta…
Microfocus X-ray computed tomography analysis of corroded glass objects
2009
Abstract Microfocus X-ray computed tomography (µCT) is a useful tool for non-destructive analysis of corroded archaeological glass objects and for monitoring restoration and conservation processes for these materials. This was demonstrated by µCT analysis of artificially corroded laboratory-produced glasses and corroded archaeological glasses retrieved from soil environments. Corrosion layers with a thickness of 20 µm or more can be detected as areas with lower X-ray attenuation values than the non-corroded glass. Features that are revealed by µCT analyses include the degree and patterns of corrosion and the presence of various internal structures in the corrosion layers. The study of resto…
Two multilayered plate models with transverse shear warping functions issued from three dimensional elasticity equations
2014
Abstract A multilayered plate theory which uses transverse shear warping functions is presented. Two methods to obtain the transverse shear warping functions from three-dimensional elasticity equations are proposed. The warping functions are issued from the variations of transverse shear stresses computed at specific points of a simply supported plate. The first method considers an exact 3D solution of the problem. The second method uses the solution provided by the model itself: the transverse shear stresses are computed integrating equilibrium equations. Hence, an iterative process is applied, the model is updated with the new warping functions, and so on. Once the sets of warping functio…