Search results for "DISPERSION"

Numerical study of shock formation in the dispersionless Kadomtsev-Petviashvili equation and dispersive regularizations

2013

The formation of singularities in solutions to the dispersionless Kadomtsev-Petviashvili (dKP) equation is studied numerically for different classes of initial data. The asymptotic behavior of the Fourier coefficients is used to quantitatively identify the critical time and location and the type of the singularity. The approach is first tested in detail in 1+1 dimensions for the known case of the Hopf equation, where it is shown that the break-up of the solution can be identified with prescribed accuracy. For dissipative regularizations of this shock formation as the Burgers' equation and for dispersive regularizations as the Korteweg-de Vries equation, the Fourier coefficients indicate as …

Solid phase techniques in the extraction of pesticides and related compounds from foods and soils

1994

The application of SPE technology to the isolation of pesticides and related compounds from food and soils has grown enormously in the last decade. Much of this growth has been due to the relative ease of sample handling and the wide range of solid supports currently available for a variety of applications. The aim of this review is to present the methods for solid phase extraction (SPE) of pesticide residues from soils and foods. There are three main areas according to the type of approach used to handle the sample: solid phase extraction, solid phase clean-up (SPC), and matrix solid phase dispersion (MSPD). This review covers milk products, fatty foods, fruits, vegetables, and soils. Soli…

Determination of mycotoxins in multicereal flour by matrix solid phase dispersion and LC–MS/MS

2010

Lagrangian finite element modelling of dam–fluid interaction: Accurate absorbing boundary conditions

2007

The dynamic dam-fluid interaction is considered via a Lagrangian approach, based on a fluid finite element (FE) model under the assumption of small displacement and inviscid fluid. The fluid domain is discretized by enhanced displacement-based finite elements, which can be considered an evolution of those derived from the pioneering works of Bathe and Hahn [Bathe KJ, Hahn WF. On transient analysis of fluid-structure system. Comp Struct 1979;10:383-93] and of Wilson and Khalvati [Wilson EL, Khalvati M. Finite element for the dynamic analysis of fluid-solid system. Int J Numer Methods Eng 1983;19:1657-68]. The irrotational condition for inviscid fluids is imposed by the penalty method and con…

Superior Fischer-Tropsch performance of uniform cobalt nanoparticles deposited into mesoporous SiC

2020

Electrochemically-derived well-crystalline mesoporous silicon carbide (pSiC) was used as a host for cobalt nanoparticles to demonstrate superior catalytic performance during the CO hydrogenation according to Fischer-Tropsch. Colloidal Co nanoparticles (9 ± 0.4 nm) were prepared independently using colloidal recipes before incorporating them into pSiC and, for comparison purposes, into commercially available silica (Davisil) as well as foam-like MCF-17 supports. The Co/pSiC catalyst demonstrated the highest (per unit mass) catalytic activity of 117 µmol.g(CO)-1.g-1(Co).s-1 at 220 °C which was larger by about one order of magnitude as compared to both silica supported cobalt catalysts. Furthe…

Model of scanning force microscopy on ionic surfaces.

1995

We present a theoretical model of the scanning force microscope using an atomistic simulation technique for the interaction between a crystalline sample and a tip nanoasperity combined with a semi- empirical treatment of the mesoscopic van der Waals attraction between tip and surface, and the macroscopic parameter of cantilever deflection. For the nanoasperity at the end of the tip, we used a neutral and a protonated (MgO${)}_{32}$ cube, which model a hard tip made of oxide material. Static calculations based on total-energy minimization were used to determine the surface and tip geometries and total energy as a function of tip position. Scan lines of the perfect (001) surfaces of NaCl and …

Multi-model ensemble simulations of olive pollen distribution in Europe in 2014

2017

Abstract. A 6-models strong European ensemble of Copernicus Atmospheric Monitoring Service (CAMS) was run through the season of 2014 computing the olive pollen dispersion in Europe. The simulations have been compared with observations in 6 countries, members of the European Aeroallergen Network. Analysis was performed for individual models, the ensemble mean and median, and for a dynamically optimized combination of the ensemble members obtained via fusion of the model predictions with observations. The models, generally reproducing the olive season of 2014, showed noticeable deviations from both observations and each other. In particular, the season start was reported too early, by 8 days …

Suspended core tellurite glass optical fibers for infrared supercontinuum generation

2011

International audience; We report the fabrication and characterization of tellurite TeO(2)-ZnO-Na(2)O (TZN) microstructured suspended core optical fibers (MOFs). These fibers are designed for infrared supercontinuum generation with zero dispersion wavelength (ZDW) at 1.451 mu m. The measured losses at this wavelength are approximately 6 dB/m for a MOF with a 2.2 mu m diameter core. The effective area of a particular fiber is 3.5 mu m(2) and the nonlinear coefficient is calculated to be 437 W(-1)km(-1). By pumping a 20 cm long fiber at 1.56 mu m with a sub-nj femtosecond laser source, we generate a supercontinuum (SC) spanning over 800 nm in the 1-2 mu m wavelength range.

Polarization Modulation Instability in All-Normal Dispersion Microstructured Optical Fibers With Quasi-Continuous Pump

2019

We report the experimental observation of the polarization modulation instability (PMI) effect in all-normal dispersion (ANDi) microstructured optical fibers (MOFs) with quasi-continuous pumping. The small unintentional birefringence (~10-5), that any realistic non-polarization maintaining MOF exhibits, contributes to this nonlinear effect. PMI can produce two sidebands whose polarization state is orthogonal to the polarization of the pump. In this work, only one type of PMI process is observed, i.e., when the pump is polarized along the slow axis of the fiber and sidebands are generated in the fast axis mode. This PMI process was studied experimentally in two ANDi fibers with different dis…

Time dispersion characterization for UWB mobile radio channels between 3.1 and 10.6 GHz

2007

In this paper, a characterization of the UWB mobile radio channel time dispersion is presented. The results provided were obtained from a measurement campaign carried out in a typical indoor office scenario in the band from 3.1 to 10.6 GHz. Time dispersion metrics as delay spread, coherence bandwidth, delay interval and delay window, in both line-of-sight (LOS) and non-line-of-sight (NLOS) conditions are provided.