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The Propagation of Atmospheric Photon Fluxes into Natural Water Bodies
Published in Robert P. Bukata, John H. Jerome, Kirill Ya. Kondratyev, Dimitry V. Pozdnyakov, of Inland and Coastal Waters, 2018
Robert P. Bukata, John H. Jerome, Kirill Ya. Kondratyev, Dimitry V. Pozdnyakov
Selection of the initial conditions for Monte Carlo simulations include the directional distributions of the incident photon fluxes (e.g., direct solar radiation, diffuse skylight, angle of incidence, overcast atmospheric conditions). Other required inputs are the physical descriptions of scattering processes (e.g., the selection of Rayleigh scattering to describe molecular scattering within the aquatic medium and the selection of Mie scattering theory to describe particulate scattering). Suffice to say that Rayleigh or molecular scattering occurs when the wavelength of the impinging radiation is considerably larger than the diameter of the scattering center, and Mie scattering occurs when the wavelength of the impinging radiation is of the same order of magnitude or smaller than the diameter of the scattering center. Details and mathematical treatments of Rayleigh (molecular) and Mie (particulate) scattering phenomena may be found in Chandrasekhar,59 Maul,262 and numerous other optical texts.
The Optics of Deep Optical Imaging in Tissues Using Long Wavelengths
Published in Lingyan Shi, Robert R. Alfano, Deep Imaging in Tissue and Biomedical Materials, 2017
Why would g be lower for λ = 1700 nm than for λ = 800 nm? Tissues present a range of sub-μm structure that scatters light, which can be approximately modeled using Mie scattering by spheres in the size range of 200–1000 nm. The ratio of wavelength/diameter governs the value of g, which falls as the ratio increases. So a lower g in soft tissue is expected for 1700 nm light than for 800 nm light, as indicated in Table 4.2. A more detailed analysis would consider the size distribution and close packing of spheres in developing this approximate model, but Table 4.2 illustrates the concept that g should be lower for 1700 nm light than for 800 nm light, and consequently μs is also lower, which allows better penetration of ballistic and near-ballistic photons.
Particle Size
Published in David M. Scott, Industrial Process Sensors, 2018
Mie scattering theory is a comprehensive and completely general description of light scattering by spherical particles. It is a first-principles theory based on two assumptions: the particles scattering the light are assumed to be spheres, and the possibility of multiple scattering is neglected. This second assumption means that the results are valid for the single-scattering regime only and cannot reliably describe scattering in concentrated suspensions. The theory can be extended to consider scattering from particles with different shapes and aspect ratios. The calculation requires the real and imaginary components of the refractive index of the particle and the real component of the refractive index of the fluid.5
The Effect of Fuel Aerosol Particle Size on Aerosol Release Potential in Energetic Core Disruptive Accident Studies
Published in Nuclear Technology, 2023
Experimental data from source term experiments conducted in the FAST facility at ORNL have been reassessed by modeling the effect that aerosol presence may have had on bubble cooling rates. The modeling contributions include the following: Determination of the radiative transfer properties of the aerosol by means of Mie scattering theory.Explication of details of the radiative heat transfer model of Ozisik et al.[22]Model development that provides a means for determining the time required for a given vapor mass to condense, of central interest in the FAST experiments.
Modeling nanomaterial physical properties: theory and simulation
Published in International Journal of Smart and Nano Materials, 2019
Tanujjal Bora, Adrien Dousse, Kunal Sharma, Kaushik Sarma, Alexander Baev, G. Louis Hornyak, Guatam Dasgupta
We have used EMTs extensively in the past to model extrinsic size effects [24] however this simulation method is limited with regard to accurately quantifying intrinsic (quantum) size effects [7]. Extended effective medium theories try to incorporate size-dependent electromagnetic effects like dynamic depolarization, extinction and retardation effects. Mie scattering theory is best applied to homogeneous spherical particles. Extrinsic size effects are those governed by particle size, shape and orientation with respect to the wavelength of light [24]. In other words, the optical constants n and k (sequestered with the dielectric constant ) input into classical EMT are simply those of the bulk material and are functions of the wavelength of the light, . Regarding intrinsic size effects, applicable to particles less than 10 nm radius, , optical constants are expected to be a function of size as well [24].
Metrology Feasibility Study in Support of the National Direct-Drive Program
Published in Fusion Science and Technology, 2018
H. Huang, K. Engelhorn, K. Sequoia, A. Greenwood, W. Sweet, L. Carlson, F. Elsner, M. Farrell
The two primary classical models for understanding light scattering from isolated particles are Mie scattering and Rayleigh scattering. The regimes of validity for these models are determined by the ratio of the particle size to the wavelength of light (Fig. 1). Mie scattering occurs when the particle size is comparable to or larger than the wavelength, and Rayleigh scattering occurs if the particle size is much smaller than the wavelength. For spherical particles, the boundary between the two regimes is where the ratio of the particle radius to the wavelength is 0.2. The important physical difference between these two regimes is the dependence of scattering cross section on the particle size and light wavelength. In the case of Mie scattering, the cross section scales with the diameter squared and has no dependence on wavelength, whereas in the Rayleigh regime, scattering cross section scales with the diameter to the sixth power and the wavelength to the inverse fourth power. This has important physical consequences for the scattering phenomena. For instance, when light scatters off large water droplets in clouds, Mie scattering dominates, and there is weak dependence on wavelength. This makes the clouds appear white. In contrast, when the water particles are small (e.g., water molecules in the sky), Rayleigh scattering dominates and is strongly dependent on wavelength. This makes the sky appear blue.