Search results for "Engineering and Technology"
showing 10 items of 16184 documents
Review of the PEA Method for Space Charge Measurements on HVDC Cables and Mini-Cables
2019
This review takes into account articles and standards published in recent years concerning the application of the Pulsed Electro Acoustic (PEA) method for space charge measurement on High Voltage Direct Current (HVDC) cables and mini-cables. Since the 80s, the PEA method has been implemented for space charge measurements on flat specimens in order to investigate space charge phenomena and to evaluate the ageing of dielectrics. In recent years, this technique has been adapted to cylindrical geometry. Several studies and experiments have been carried out on the use of the PEA method for full size cables and HVDC cable models. The experiments have been conducted using different arrangements of…
Multiphysical Modeling of Transport Phenomena During Laser Welding of Dissimilar Steels
2016
Abstract The success of new high-strength steels allows attaining equivalent performances with lower thicknesses and significant weight reduction. The welding of new couples of steel grades requires development and control of joining processes. Thanks to high precision and good flexibility, laser welding became one of the most used processes for joining of dissimilar welded blanks. The prediction of the local chemical composition in the weld formed between dissimilar steels in function of the welding parameters is essential because the dilution rate and the distribution of alloying elements in the melted zone determines the final tensile strength of the weld. The goal of the present study i…
Multiple vibrational resonances in the Raman spectra of liquid ethanes
1990
The Raman spectra of liquid ethane, ethane-d3 and ethane-d6 were recorded and analysed. The CH3 and CD3 stretching regions were computer resolved using Cauchy-Gaussian and Voigt functions to account for asymmetric band shapes. Multiple vibrational resonances were investigated using the wavenumbers and observed intensities in these regions. The developed basis functions show strong mixing of the levels in these regions. In general the resonances appear to be less strong in the liquid phase than reported in previous studies of the gaseous state. Some new assignments in the liquid-state spectra of ethanes could be suggested.
Germanium Dicarbide: Evidence for a T-Shaped Ground State Structure
2017
The equilibrium structure of germanium dicarbide GeC2 has been an open question since the late 1950s. Although most high-level quantum calculations predict an L-shaped geometry, a T-shaped or even a linear geometry cannot be ruled out because of the very flat potential energy surface. By recording the rotational spectrum of this dicarbide using sensitive microwave and millimeter techniques, we unambiguously establish that GeC2 adopts a vibrationally averaged T-shaped structure in its ground state. From analysis of 14 isotopologues, a precise r0 structure has been derived, yielding a Ge–C bond length of 1.952(1) A and an apex angle of 38.7(2)°.
pKa at Quartz/Electrolyte Interfaces.
2016
Acidity of silanol sites at the crystalline quartz/aqueous electrolyte (NaCl, NaI, KCl) interfaces are calculated from ab initio molecular dynamics simulations. pKa’s are found to follow a combination of the cationic and anionic Hofmeister series in the order pKa(neat solution) < pKa(NaCl) < pKa(NaI) < pKa(KCl), in agreement with experimental measurements. Rationalization of this ranking is achieved in terms of the microscopic local solvation of the protonated silanols and their conjugated bases, the silanolates SiO–. The change in the pKa is the result of both water destructuring by alkali halides, as well as of the specific cation/SiO– interaction, depending on the electrolyte. M…
Inelastic neutron scattering study of proton dynamics in Ca(OH)2 at 20 K
1995
Abstract Inelastic neutron scattering (INS) spectra of Ca(OH) 2 at 20 K are presented from 30 to 4000 cm −1 for a powder sample, from 30 to 12000 cm −1 for an oriented single-crystal. INS band splitting due to the lattice density-of-states is observed. Polarization effects reveal the orientation of atomic displacements for each mode and a new band assignment scheme is proposed. For the single-crystal, the v OH mode and overtones are observed. This oscillator shows only moderate anharmonicity. Spectrum simulation reveals that INS spectral intensities are not consistent with simple normal coordinates and harmonic force-fields for Ca(OH) 2 entities. A new dynamical model is proposed, including…
Neutron imaging and tomography: Applications in food science
2018
International audience; Neutron imaging and tomography allow observing the structure of large objects (from few to hundred centimeters) at a resolution around 100 μm. This non-destructive method is based on the detection of the transmission of a neutron beam through an object in 2D (imaging) or 3D after rotating the sample (tomography). The components of the object attenuate the neutron beam differently, depending on their composition, and produce accurate pictures of objects which give information about their structure. Neutron imaging has been used for quality control purposes in industries (aircraft, motor engineering...), but also find application from materials sciences (fuel cells, li…
Comparaison expérimentale de techniques de caractérisation en intensité et phase d'impulsions optiques ultracourtes
2006
Nous comparons experimentalement les resultats de la caracterisation en intensite et en phase d'impulsions optiques ultracourtes obtenus par differentes techniques employant un montage auto/inter-correlateur en intensite et un analyseur de spectre. Nous employons pour ces tests une impulsion en limite de Fourier, une impulsion affectee par l'auto-modulation de phase et une impulsion similariton.
A Study of Milk Particles Size Variation with pH Change using Dynamic Light Scattering
2019
A very simple experimental setup for a Dynamic Light Scattering measurement was used to measure the average size of the milk proteins in aqueous suspensions at 20 °C. The PH of the suspensions was adjusted using Calcium lactate, in its most common form of pentahydrate C6H10CaO6•5H2O. The mean size variation of the suspended particles in time has been monitored and reveals a fast increase over a time interval of less than ten of seconds.
Polarization-driven spin precession of mesospheric sodium atoms: publisher's note.
2018
This publisher's note corrects an error in the author listing of Opt. Lett.43, 5825 (2018)OPLEDP0146-959210.1364/OL.43.005825.