Search results for " processing"
showing 10 items of 7549 documents
Totally incoherent optical processing operations with achromatic diffraction-based setups
2000
We report on a novel family of totally incoherent, chromatic-dispersion compensated hybrid (refractive-diffractive) lens setups for implementing, in the Fraunhofer or in the Fresnel diffraction region, different achromatic diffraction-based processing operations.
Observation of optical Smith-Purcell radiation at an electron beam energy of 855 MeV.
2002
Smith-Purcell radiation, generated when a beam of charged particles passes close to the surface of a diffraction grating, has been studied in the visible spectral range at wavelengths of 360 and 546 nm with the low emittance 855 MeV electron beam of the Mainz Microtron MAMI. The beam focused to a spot size of $4 \ensuremath{\mu}\mathrm{m}$ (full width at half maximum) passed over optical diffraction gratings of echelle profiles with blaze angles of $0.8\ifmmode^\circ\else\textdegree\fi{}, 17.27\ifmmode^\circ\else\textdegree\fi{},$ and $41.12\ifmmode^\circ\else\textdegree\fi{}$ and grating periods of 0.833 and $9.09 \ensuremath{\mu}\mathrm{m}.$ Taking advantage of the specific emission chara…
Undergraduate experiment with fractal diffraction gratings
2011
We present a simple diffraction experiment with fractal gratings based on the triadic Cantor set. Diffraction by fractals is proposed as a motivating strategy for students of optics in the potential applications of optical processing. Fraunhofer diffraction patterns are obtained using standard equipment present in most undergraduate physics laboratories and compared with those obtained with conventional periodic gratings. It is shown that fractal gratings produce self-similar diffraction patterns which can be evaluated analytically. Good agreement is obtained between experimental and numerical results. © 2011 IOP Publishing Ltd.
The continuous cooling transformation (CCT) as a flexible tool to investigate polymer crystallization under processing conditions
2009
An experimental route for investigating polymer crystallization over a wide range of cooling rates (from 0.01 to 1000◦C/s) and pressures (from 0.1 to 40 MPa) is illustrated, using a method that recalls the approach adopted in metallurgy for studying structure development in metals. Two types of experimental setup were used, namely an apparatus for fast cooling of thin films (100–200 μm thick) at various cooling rates under atmospheric pressure and a device (based on a on-purpose modified injection molding machine) for quenching massive samples (about 1–2 cm3) under hydrostatic pressure fields. In both cases, ex situ characterization experiments were carried out to probe the resulting struct…
Fast and robust phase-shift estimation in two-dimensional structured illumination microscopy.
2019
A method of determining unknown phase-shifts between elementary images in two-dimensional Structured Illumination Microscopy (2D-SIM) is presented. The proposed method is based on the comparison of the peak intensity of spectral components. These components correspond to the inherent structured illumination spectral content and the residual compo- nent that appears from wrongly estimated phase-shifts. The estimation of the phase-shifts is carried out by finding the absolute maximum of a function defined as the normalized peak intensity difference in the Fourier domain. This task is performed by an optimization method providing a fast estimation of the phase-shift. The algorithm stability an…
Wideband THz time domain spectroscopy based on optical rectification and electro-optic sampling
2013
We present an analytical model describing the full electromagnetic propagation in a THz time-domain spectroscopy (THz-TDS) system, from the THz pulses via Optical Rectification to the detection via Electro Optic-Sampling. While several investigations deal singularly with the many elements that constitute a THz-TDS, in our work we pay particular attention to the modelling of the time-frequency behaviour of all the stages which compose the experimental set-up. Therefore, our model considers the following main aspects: (i) pump beam focusing into the generation crystal; (ii) phase-matching inside both the generation and detection crystals; (iii) chromatic dispersion and absorption inside the c…
Detection of H. pylori induced gastric inflammation by diffuse reflectance analysis
2018
International audience; Spectral acquisitions contain rich information and thus, are promising modalities for early detection of gastric diseases. In this study, we analyze the diffuse reflectance of the gastric inflammatory lesions induced by the bacterium H. pylori in the mouse stomach. A pipeline has been designed to characterize and classify spectra acquired on mice. The pipeline is based on a band clustering algorithm followed by the computation of meaningful division and subtraction features and by classification with a linear SVM classifier. Currently, the pipeline is able to recognize inflamed stomachs spectra with an accuracy of 98%. These results are promising and the same pipelin…
Colossal barocaloric effects in the complex hydride Li$_{2}$B$_{12}$H$_{12}$
2021
Traditional refrigeration technologies based on compression cycles of greenhouse gases pose serious threats to the environment and cannot be downscaled to electronic device dimensions. Solid-state cooling exploits the thermal response of caloric materials to external fields and represents a promising alternative to current refrigeration methods. However, most of the caloric materials known to date present relatively small adiabatic temperature changes ($|\Delta T| \sim 1$ K) and/or limiting irreversibility issues resulting from significant phase-transition hysteresis. Here, we predict the existence of colossal barocaloric effects (isothermal entropy changes of $|\Delta S| \sim 100$ JK$^{-1}…
Traitement d'images avec un système non linéaire
2017
National audience; Cette communication porte sur la présentation d’un outil de traitement d’images s’inspirant des processus de réaction-diffusion.Cet outil s’appuie sur des ́equations différentielles non linéaires et tire plus particulièrement profit des propriétéde multistabilité liées à la non linéarité de ces processus de diffusion. Certaines caractéristiques d’une image peuvent ainsi être extraites.
Are tools all we need? Digital Humanities in the time of its institutionalisation
2011
Three key features of the Digital Humanities today are its quantitative growth, its institutionalisation and its definition as a discipline. In the first part of this article (2. Institutional models) I shall pinpoint some models of institutionalisation that are emerging in the international scenario. Against this background, I shall then discuss (3. Tools) some concepts central to Digital Humanities’ self-definition, such as those of practice, ‘building’, centre, project, product and tools, particularly questioning the opinion that the creation of friendly digital tools is the key issue in the future of the field. I shall finally suggest that ‘instrumentalism’, ‘project fever’ and an exces…