共查询到6条相似文献,搜索用时 15 毫秒
1.
Profile line deconvolution following a Rietveld approach is applied to Raman spectra obtained from natural zircon grains from the European Alps. The corrected bandwidths are in perfect agreement with the values obtained from an established correction method (after Irmer) as far as the area of validity of the latter is concerned. For Raman active modes smaller than that, the Rietveld approach also yields accurate values for the true Raman bandwidth. Moreover, changes to instrument parameters are compensated by the correction routine. As for the studied zircon grains, Raman spectroscopy was shown to be a suitable tool for the examination of zoning (i.e. regions which show a variable degree of radiation‐induced damage because of a different amount of incorporated uranium and/or thorium). This is complicated by the fact that the measured Raman signal is not restricted to the depth expected from the axial resolution (several micrometers) but a significant contribution comes from a comparatively large excitation volume (tens of micrometer deep). This sampling volume, however, lies within the same order of magnitude as zoning, which itself is blurred by the range of amorphization‐causing alpha‐particles. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
2.
A novel fitting method implemented recently in vibrational spectroscopy of disordered systems is briefly overviewed. It enables modelling of real line profiles intermediate between Lorentzian and Gaussian by an analytical function which has an analytical counterpart in the time domain. Numerous applications of this theoretical approach are discussed. 相似文献
3.
O. Balima J. Boulanger D. Marceau 《Journal of Quantitative Spectroscopy & Radiative Transfer》2011,112(7):1235-1240
Gradient-based algorithms in optical tomography have shown efficiency and robustness due to their self-regularization effect, as they track the largest errors first, which tends to stabilize the reconstruction scheme. This second part shows the application of the presented developments in the first part for the reconstruction of optical properties in complex geometry while taking into account the collimated source direction with such an algorithm. The reconstruction scheme is based on the limited memory BFGS type associated to an inexact line search in order to avoid numerous evaluations of the objective function. Normalization of the objective function with measurements and independent scaling of its gradient are used to improve the quality of the reconstruction. The results show that the algorithm is efficient compared to other solvers with a better recovering of both the absorption and scattering coefficients. 相似文献
4.
Simulation programs may be useful tools for controlling an environmental noise. The computer simulation program PROP11 that enables predictions of the time-average sound level within an urban system is used here. A roadway as a noise source is represented by a sum of the sound exposures due to individual vehicle pass-bys. Different representations of equivalent point sources for various classes of vehicles are allowed including directivity characteristics other than omnidirectional. Propagation throughout an urban system contains multi-reflections from the walls and single and double diffraction at their edges. In this paper, the PROP11 program is used to predict the sound level between opposing façades of buildings in a canyon street. A multi-lane road is assumed to contain two classes of vehicles (light and heavy) ones. The equivalent source representing vehicles is defined by the source power spectrum, its position above the ground and directivity characteristics. The consequences of introducing equivalent source directivity are analyzed. 相似文献
5.
O. Louisnard 《Ultrasonics sonochemistry》2012,19(1):56-65
The bubbles involved in sonochemistry and other applications of cavitation oscillate inertially. A correct estimation of the wave attenuation in such bubbly media requires a realistic estimation of the power dissipated by the oscillation of each bubble, by thermal diffusion in the gas and viscous friction in the liquid. Both quantities and calculated numerically for a single inertial bubble driven at 20 kHz, and are found to be several orders of magnitude larger than the linear prediction. Viscous dissipation is found to be the predominant cause of energy loss for bubbles small enough. Then, the classical nonlinear Caflish equations describing the propagation of acoustic waves in a bubbly liquid are recast and simplified conveniently. The main harmonic part of the sound field is found to fulfill a nonlinear Helmholtz equation, where the imaginary part of the squared wave number is directly correlated with the energy lost by a single bubble. For low acoustic driving, linear theory is recovered, but for larger drivings, namely above the Blake threshold, the attenuation coefficient is found to be more than 3 orders of magnitude larger then the linear prediction. A huge attenuation of the wave is thus expected in regions where inertial bubbles are present, which is confirmed by numerical simulations of the nonlinear Helmholtz equation in a 1D standing wave configuration. The expected strong attenuation is not only observed but furthermore, the examination of the phase between the pressure field and its gradient clearly demonstrates that a traveling wave appears in the medium. 相似文献
6.
In 2005, Zhang presented a Grubin-like inlet zone analysis to the isothermal line contact elastohydrodynamic lubrication under relatively heavy loads when the hydrodynamic film thickness in the Hertzian zone approaches zero and the EHL fluid is Newtonian [Zhang, Y.B. A justification of the load-carrying capacity of elastohydrodynamic lubrication film based on the Newtonian fluid model. Industrial Lubrication and Tribology, 2005, Vol. 57, pp. 224–232]. His results showed that in this EHL, when the rolling speed is lower than the characteristic rolling speed (Uch =) 0.0372W1.50/G, the Hertzian zone is in physical adsorbed layer boundary lubrication while the inlet zone is in conventional hydrodynamic lubrication. This mode of EHL represents a mode of mixed EHL with mixed contact regimes, where hydrodynamic films with different rheological behaviors occur in different areas of the contact. The present paper presents an analysis to this mode of mixed EHL by using the Grubin type method when the contact adhering layer in the inlet zone is neglected. Pressures, film thicknesses and load partition in the contact are obtained from this analysis. It is also found that the formula for the characteristic rolling speed Uch = 0.0372W1.50/G obtained by Zhang [Zhang, Y.B. A justification of the load-carrying capacity of elastohydrodynamic lubrication film based on the Newtonian fluid model. Industrial Lubrication and Tribology, 2005, Vol. 57, pp. 224–232] may be valid for the dimensionless load W > 1.0E−7, while it may be invalid for the dimensionless load W < 1.0E−8. In part II [Zhang, Y.B. Analytical solution to a mode of mixed elastohydrodynamic lubrication with mixed contact regimes: Part II. Considering the contact adhering layer effect in the inlet zone. Journal of Molecular Liquids, 2006, Vol. 117. (doi:10.1016/j.molliq.2006.04.007)] will be presented an analysis to other two modes of mixed EHL with mixed contact regimes for relatively heavy loads, low rolling speeds and Newtonian fluids, where the conventional hydrodynamic lubrication, physical adsorbed layer boundary lubrication and oxidized chemical layer boundary lubrication can simultaneously occur in the inlet zone while the oxidized chemical layer boundary lubrication or the fresh metal-oxidized chemical boundary layer dry contact occur in the Hertzian zone, considering the contact adhering layer effect in the inlet zone. 相似文献