THE RADIATIVE PROPERTIES OF SOOT AGGLOMERATES: THE MODEL OF THE VIRTUAL REFRACTIVE INDEX AND FIRST-ORDER MULTIPLE SCATTERING

1995 ◽  
Author(s):  
Rolf Dittmann
Keyword(s):  
Refractive Index ◽  
Multiple Scattering ◽  
Radiative Properties ◽  
First Order

Influence of Fine-Dispersed Dielectric Particles on Dye Luminescence in a Polymer Matrix

2004 ◽  
Vol 99-100 ◽  
pp. 153-156 ◽  
Author(s):  
E. Tikhonov ◽  
Vasil P. Yashchuk ◽  
O. Prygodjuk ◽  
V. Bezrodny ◽  
Yu. Filatov
Keyword(s):  
Refractive Index ◽  
Multiple Scattering ◽  
Polymer Matrix ◽  
Organic Dye ◽  
Sample Thickness ◽  
Luminescence Spectra ◽  
Scattering Media ◽  
Dielectric Particles ◽  
Multiple Light Scattering ◽  
Luminescence Light

The behaviour of the luminescence spectra of the organic dye R6G in a multiple scattering polymer matrix was studied with reference to the parameters of the scattering media. It was found that some of the luminescent parameters depend on the concentration of scattering particles, the refractive index of the scattering particles and the sample thickness. As it was shown, that the reason for these dependences is the reabsorption of luminescence light enhanced by multiple light scattering. In addition, an increase in the absorption caused by multiple scattering was observed.

Independent Evaluation of the Ability of Spaceborne Radar and Lidar to Retrieve the Microphysical and Radiative Properties of Ice Clouds

2006 ◽  
Vol 23 (2) ◽  
pp. 211-227 ◽  
Author(s):  
Robin J. Hogan ◽  
Malcolm E. Brooks ◽  
Anthony J. Illingworth ◽  
David P. Donovan ◽  
Claire Tinel ◽  
...  
Keyword(s):  
Particle Size ◽  
Water Content ◽  
Multiple Scattering ◽  
Optical Depth ◽  
Radiative Properties ◽  
Molecular Scattering ◽  
Retrieval Algorithms ◽  
Ice Water Content ◽  
Ice Water ◽  
Better Than

Abstract The combination of radar and lidar in space offers the unique potential to retrieve vertical profiles of ice water content and particle size globally, and two algorithms developed recently claim to have overcome the principal difficulty with this approach—that of correcting the lidar signal for extinction. In this paper “blind tests” of these algorithms are carried out, using realistic 94-GHz radar and 355-nm lidar backscatter profiles simulated from aircraft-measured size spectra, and including the effects of molecular scattering, multiple scattering, and instrument noise. Radiation calculations are performed on the true and retrieved microphysical profiles to estimate the accuracy with which radiative flux profiles could be inferred remotely. It is found that the visible extinction profile can be retrieved independent of assumptions on the nature of the size distribution, the habit of the particles, the mean extinction-to-backscatter ratio, or errors in instrument calibration. Local errors in retrieved extinction can occur in proportion to local fluctuations in the extinction-to-backscatter ratio, but down to 400 m above the height of the lowest lidar return, optical depth is typically retrieved to better than 0.2. Retrieval uncertainties are greater at the far end of the profile, and errors in total optical depth can exceed 1, which changes the shortwave radiative effect of the cloud by around 20%. Longwave fluxes are much less sensitive to errors in total optical depth, and may generally be calculated to better than 2 W m−2 throughout the profile. It is important for retrieval algorithms to account for the effects of lidar multiple scattering, because if this is neglected, then optical depth is underestimated by approximately 35%, resulting in cloud radiative effects being underestimated by around 30% in the shortwave and 15% in the longwave. Unlike the extinction coefficient, the inferred ice water content and particle size can vary by 30%, depending on the assumed mass–size relationship (a problem common to all remote retrieval algorithms). However, radiative fluxes are almost completely determined by the extinction profile, and if this is correct, then errors in these other parameters have only a small effect in the shortwave (around 6%, compared to that of clear sky) and a negligible effect in the longwave.

scholarly journals Multiple Scattering Theory for Heterogeneous Elastic Continua with Strong Property Fluctuation: Theoretical Fundamentals and Applications

2019 ◽  
Author(s):  
Huijing He
Keyword(s):  
Nondestructive Evaluation ◽  
Multiple Scattering ◽  
Elastic Waves ◽  
Scattering Theory ◽  
New Model ◽  
First Order ◽  
Weak Property ◽  
Strong Property ◽  
Scattering Of Elastic Waves ◽  
Dispersion And Attenuation

Scattering of elastic waves in heterogeneous media has become one of the most important problems in the field of wave propagation due to its broad applications in seismology, natural resource exploration, ultrasonic nondestructive evaluation and biomedical ultrasound. Nevertheless, it is one of the most challenging problems because of the complicated medium inhomogeneity and the complexity of the elastodynamic equations. A widely accepted model for the propagation and scattering of elastic waves, which properly incorporates the multiple scattering phenomenon and the statistical information of the inhomogeneities is still missing. In this work, the author developed a multiple scattering model for heterogeneous elastic continua with strong property fluctuation and obtained the exact solution to the dispersion equation under the first-order smoothing approximation. The model establishes an accurate quantitative relation between the microstructural properties and the coherent wave propagation parameters and can be used for characterization or inversion of microstructures. Starting from the elastodynamic differential equations, a system of integral equation for the Green functions of the heterogeneous medium was developed by using Green’s functions of a homogeneous reference medium. After properly eliminating the singularity of the Green tensor and introducing a new set of renormalized field variables, the original integral equation is reformulated into a system of renormalized integral equations. Dyson’s equation and its first-order smoothing approximation, describing the ensemble averaged response of the heterogeneous system, are then derived with the aid of Feynman’s diagram technique. The dispersion equations for the longitudinal and transverse coherent waves are then obtained by applying Fourier transform to the Dyson equation. The exact solution to the dispersion equations are obtained numerically. To validate the new model, the results for weak-property-fluctuation materials are compared to the predictions given by an improved weak-fluctuation multiple scattering theory. It is shown that the new model is capable of giving a more robust and accurate prediction of the dispersion behavior of weak-property-fluctuation materials. Numerical results further show that the new model is still able to provide accurate results for strong-property-fluctuation materials while the weak-fluctuation model is completely failed. As applications of the new model, dispersion and attenuation curves for coherent waves in the Earth’s lithosphere, the porous and two-phase alloys, and human cortical bone are calculated. Detailed analysis shows the model can capture the major dispersion and attenuation characteristics, such as the longitudinal and transverse wave Q-factors and their ratios, existence of two propagation modes, anomalous negative dispersion, nonlinear attenuation-frequency relation, and even the disappearance of coherent waves. Additionally, it helps gain new insights into a series of longstanding problems, such as the dominant mechanism of seismic attenuation and the existence of the Mohorovičić discontinuity. This work provides a general and accurate theoretical framework for quantitative characterization of microstructures in a broad spectrum of heterogeneous materials and it is anticipated to have vital applications in seismology, ultrasonic nondestructive evaluation and biomedical ultrasound.

scholarly journals Effect of Aging with Pollution on the Complex Refractive Index of Pure Submicron Clay Particles

2021 ◽  
Vol 8 (1) ◽  
pp. 31
Author(s):  
Sarla Yadav ◽  
Sumit Kumar Mishra
Keyword(s):  
Refractive Index ◽  
Complex Refractive Index ◽  
Chemical Properties ◽  
Radiative Properties ◽  
Submicron Particles ◽  
Visible Range ◽  
Refractive Indices ◽  
Clay Particles ◽  
Physico Chemical ◽  
Refractive Index Data

Modelling the optical and radiative properties of atmospheric particles is governed by one of the key input parameters, i.e., the refractive index of aerosols. Availability of the region-specific refractive index data of aerosols is a major challenge for the atmospheric community. The refractive index of aerosols is a function of their physico-chemical properties. Uncertainty in the computation of the spectral refractive indices of aerosols leads to erroneous assessment of their optical and radiative properties. In the present work, the refractive indices of pure clay (kaolinite, illite) and polluted clay with anthropogenic hematite, AH (0.10 to 1.48%) submicron particles have been computed for the wavelength range of 0.38 to 1.2 µm. Anthropogenic hematite enhanced the overall absorption in the UV and visible range with maximum absorption at lower wavelengths (less than 0.55 µm).

scholarly journals Spectral Radiative Properties of a Liquid n-Octane Droplet in the Midinfrared Region

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Liang Zhao ◽  
Chaoyu Jing ◽  
Yu Jin ◽  
Jiangping Chen ◽  
Ke Yin ◽  
...  
Keyword(s):  
Refractive Index ◽  
Wavelength Range ◽  
Optical Constants ◽  
Absorption Efficiency ◽  
Efficiency Factor ◽  
Radiative Properties ◽  
Droplet Radius ◽  
Scattering Efficiency ◽  
Scattering Coefficients ◽  
Increasing Temperature

The optical constants of a liquid hydrocarbon such as liquid n-octane are basic material properties that may be used to evaluate their thermal radiation transfer capabilities. In this study, the ellipsometry method was used to measure the optical constants of liquid n-octane in the midinfrared wavelength range of 2.0–16.0 μm at temperatures of 20, 50, and 80°C. Experimental analyses indicate the significant effect of temperature on the refractive index, although it has little effect on the absorption index. With increasing temperature, the refractive index shows a linear decrease, and reduced density leads to weaker absorption intensities. The radiative properties of n-octane droplets, including the absorption and scattering efficiency factors of single droplets with droplet radii r = 10, 20, 50, and 100 μm and the absorption and scattering coefficients in a droplets-air system of droplet volume fractions fv = 2%, 3%, and 4%, were calculated using Mie theory. The numerical results indicate that, with increasing temperature, the absorption efficiency factor slightly decreases, and the variation trend of the scattering efficiency factor is more complicated. With increasing droplet radius, the absorption efficiency factor increases within the studied wavelength range, except for certain absorption peaks, but the scattering efficiency factor tends to decrease. While the absorption is greater, the scattering is weaker for a given droplet radius. With an increasing volume fraction of n-octane droplets, the absorption and scattering coefficients increase linearly within the studied wavelength range.

First-order multiple scattering theory for nonspherical particles

1984 ◽  
Vol 23 (22) ◽  
pp. 4132 ◽  
Author(s):  
A. Ishimaru ◽  
C. Yeh ◽  
D. Lesselier
Keyword(s):  
Multiple Scattering ◽  
Scattering Theory ◽  
Nonspherical Particles ◽  
Multiple Scattering Theory ◽  
First Order
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