Search results for "Dispersion."
showing 10 items of 1094 documents
Fast relaxation phenomena and slow mode in extended thermodynamics of superfluids
2003
A macroscopic monofluid model of liquid helium II which is based on extended thermodynamics was formulated in previous works, both in the presence and in the absence of dissipative phenomena. In all these studies, the time evolution of the nonequilibrium stress tensor was neglected, putting the relaxation times @t"0 and @t"2 of the nonequilibrium pressure and of the stress deviator equal to zero. In this work, the time evolution of these fields is not neglected and the complete model with 14 fields is studied, in the linear approximation. The propagation of waves is studied and a dispersion relation of degree 14 is obtained. The solutions of this equation are carried out, perturbing the sol…
Resonant Beam Steering and Carpet Cloaking Using an Acoustic Transformational Metascreen
2018
International audience; We invoke the Huygens principle to derive dispersion characteristics of acoustic transformational meta-surfaces that can deflect parallel wavefronts in a desired direction. We also propose a dual-Lorentz resonator whose aperture fields can be tuned by geometrical changes to implement a particular phase with unity reflection coefficient. The proposed metascreen is designed by our arranging slightly detuned Lorentz cavities that generate the necessary interference to compensate for the incident wavefronts. Since a complete 0-2 pi range of the reflection phase is achieved, the metascreen can steer a beam across the full horizon. Moreover, since the proposed dual resonat…
Modeling propagation for high-power cylindrical microwave applicators
2001
In this letter, the dispersion characteristics and energy configurations of a cylindrical partially filled waveguide or lossy multilayered rod shielded by a metallic enclosure are presented for several modes. These parameters are obtained by a numerical simulation based on the residues theory. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 192–195, 2001.
Broadband telecom to mid-infrared supercontinuum generation in a dispersion-engineered silicon germanium waveguide.
2015
We demonstrate broadband supercontinuum generation (SCG) in a dispersion-engineered silicon-germanium waveguide. The 3 cm long waveguide is pumped by femtosecond pulses at 2.4 μm, and the generated supercontinuum extends from 1.45 to 2.79 μm (at the −30 dB point). The broadening is mainly driven by the generation of a dispersive wave in the 1.5–1.8 μm region and soliton fission. The SCG was modeled numerically, and excellent agreement with the experimental results was obtained.
Simple method for measuring bilayer system optical parameters
2012
A simple method for measuring bilayer system refractive indexes and thicknesses in the low absorbing part of spectra is demonstrated. The method is based on application of Savitzky - Golay smoothing filters and interference fringe separation in the reflected or transmitted spectra of the bilayer system. The refractive indexes and thicknesses are extracted from the wavelengths corresponding to extreme points in the spectrum. Due to the fact that wavelength difference of extreme points in the analyzed spectrum is defined by the product of both, the layer thickness and refractive index, one must generate an appropriate initial guess of these parameters. For refractive index approximation two d…
Microstructured Optical Fiber on the Silica Platform for pulse-maintaining 2-octave supercontinuum in short-wavelength infra-red
2016
Numerical design of all normal dispersion fiber for SWIR supercontinuum generation based on standard air-silica microstructure is presented. We increase the spectral width of generated supercontinuum up to 2 octaves while maintaining perfect spectral flatness by tailoring the dispersion profile.
Effect of different dispersing additives on the morphology and the properties of polyethylene-based nanocomposite films
2011
In this work, the use of a polar wax, e.g. amphiphilic Tegomer ® E 525 (TEG) is investigated with the aim of mod- ifying, and possibly improving, the dispersion of an organically modified nanoclay (OMMT), loaded at 5 wt%, in a poly- ethylene matrix (PE) at relatively low loading levels. We have indeed found that the incorporation of low loadings, e.g. 0.5 wt%, of TEG, an amphiphilic block co-polymer, into a PE/OMMT sample results in a substantial improvement of the clay dispersion in the nanocomposite and, consequently, of the mechanical and thermomechanical properties of the films. The achieved results are comparable to those obtained for systems containing traditional dispersing agents su…
Flavor release from salad dressings: sensory and physicochemical approaches in relation with the structure
2000
The effect of process and formulation on sensory perception and flavor release was investigated on salad dressing models. Oil/vinegar emulsions (φ = 0.5, droplet size > 10 μm) with thickeners and a whey protein concentrate were prepared with different fat droplet sizes and different distributions of fat droplet size. The effect of the amount of emulsifier was also tested. Sensory profile analysis was performed by a trained panel and flavor release quantified by dynamic headspace analysis. When the droplet size is increased, the lemon smell and citrus aroma significantly increase, whereas the egg note, mustard, and butter aroma significantly decrease. The concentrations of alcohols and acids…
Overdispersion tests in count-data analysis.
2008
Count data are commonly assumed to have a Poisson distribution, especially when there is no diagnostic procedure for checking this assumption. However, count data rarely fit the restrictive assumptions of the Poisson distribution. The violation of much of such assumptions commonly results in overdispersion, which invalidates the Poisson distribution. Undetected overdispersion may entail important misleading inferences, so its detection is essential. In this study, different overdispersion diagnostic tests are evaluated through two simulation studies. In Exp. 1, the nominal error rate is compared under different sample sizes and Λ conditions. Analysis shows a remarkable performance of the χ…
Peak dispersion in gradient elution: An insight based on the plate model.
2020
Gradient elution in liquid chromatography reduces the analysis time, improves the efficiency and increases the peak capacity. The study of this chromatographic mode has been based mainly on kinetic dispersion models. The plate model has been applied to a lesser extent, despite being the basis for the concepts of plate height and chromatographic efficiency. In this work, a general equation describing peak dispersion in HPLC gradient elution is derived from the plate model. This equation is studied and validated for three types of gradients: (i) a reference gradient without ramp in which the retention factor varies with time identically throughout the column, (ii) a gradient of stationary pha…