Increase In Scattering Coefficient Research Articles

Influence of Surface Scattering on Auditorium Acoustic Parameters

Surface scattering greatly impacts and improves the acoustic quality of an auditorium, affecting properties such as the reverberation time, early decay time, definition, and sound strength. However, this aspect has not been sufficiently investigated to date. In this study, six completed auditoriums are taken as research samples and computer simulations are performed to analyze the variation patterns in the acoustic-quality parameters as functions of increments in the surface scattering coefficients. The results show that the reverberation time and early decay time change marginally (<5%) when the ceiling scattering coefficient increases from 0.01 to 0.99. When the sidewall scattering coefficient increases, the reverberation time and early decay time shorten, and the variation range expands (5–16.7%). In most cases, the definition and sound strength do not significantly change (<0.05 and 1.0 dB). A balcony on the auditorium sidewall can affect the reverberation time-change curve when the sidewall scattering coefficient changes. Changes in the ceiling and sidewall scattering coefficients affect the reflected sound-energy distribution along the time axis differently. Sidewall scattering has a significantly greater impact on the impulse response than ceiling scattering. The findings of this study provide theoretical guidance for the scattering design of the surface of theater auditoriums.

Polarized laser speckle images produced by calibrated polystyrene microspheres suspensions: comparison between backscattering and transmission experimental configurations

In this paper, we analyze polarized laser speckle images produced by calibrated polystyrene microspheres suspensions and discuss the results obtained while considering two different experimental configurations for light detection: speckle-transmission setup and speckle-backscattering one. The degree of light polarization (DOP) and speckle grain size (dx) were monitored in both cases. Results show that, when backscattered photons are detected, the degree of circular polarization allows a fine monitoring of the variation of scatterers concentration in a sample. A helicity flipping is detected as the scatterers concentration increases, showing that a transition from a simple scattering regime to a multiple scattering one is taking place. When transmitted scattered photons are detected dx is a better parameter than DOP for following changes in scattering regime: dx values initially increase slightly then decrease as the scattering coefficient increases. The observed maximum corresponds to the shift from a simple to a multiple scattering regime.

Heating frequency optimization for artificial field-aligned scattering

In this study, we present a simulation study of artificial field-aligned irregularities (AFAI) to calculate the scattering coefficient considering a Gaussian autocorrelation function for the wave number spectrum of the density fluctuation. By analyzing variations in the scattering coefficient under different ionospheric backgrounds, the optimal range of the heating frequency was found, which is about 0.9–1 times the critical frequency of the F2 layer. This is especially noticeable as when the heating frequency varies from 0.5 times to 0.9 times of the critical frequency, the scattering coefficient increases by 6.8–16.2 dB. These results should be useful for optimizing the heating frequency in the future artificial field-aligned scattering (AFAS) transmission applications at middle and low latitudes.

Local structure of Yb3+ ions and X-ray induced defect in Yb-doped silica glass

The local structure of Yb3+ ions in Yb-doped silica glass was investigated by extended X-ray absorption fine structure, the Rayleigh scattering and optical absorption measurements. It was found that the Yb coordination number increases from 3 to 4.5 with increasing Yb concentration. Simultaneously, the absorption cross-section of Yb3+ ion decreases and the Rayleigh scattering coefficient increases. These results suggest that local structure observed in Yb2O3 or Yb2Si2O7 crystals appears in high-Yb samples. Furthermore, photodarkening by X-ray irradiation was measured, and the correlation to the local structure change was clarified.

Solvent effects on Raman band intensities

The intensities of polarized Raman bands of carbon tetrachloride, tetrachloroethylene, benzene, cyclohexane, carbon disulfide, chloroform, acetone, and acetonitrile have been measured in binary mixtures with a wide variety of solvents, at concentrations ranging from 20 to 80% in volume. The scattering coefficient increases, in most cases linearly, with the refractive index of the mixture; furthermore, its value extrapolated to zero concentration exhibits a close correlation with the refractive index of the pure solvent. The results are in fair agreement with a theoretical formula, derived from Onsager's theory of dielectric polarization.