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Radiometry and Photometry
Published in Antoni Rogalski, Zbigniew Bielecki, Detection of Optical Signals, 2022
Antoni Rogalski, Zbigniew Bielecki
The scattering process causes a redirected radiation beam to propagate in various directions away from the original direction [9]. There are three main types of scattering: Rayleigh, Mie and non-selective. The scattering type depends on a relationship between both scattering particles’ size and the wavelength of the propagating light. Rayleigh scattering is caused by particles with a size much smaller than the light wavelength. In this case, the scattering intensity decreases with the wavelength as ~λ-4. When the particle size is comparable or as large as a radiation wavelength, Mie scattering is observed. Non-selective scattering occurs for a particle with a size larger than the beam wavelength. In this case, Mie theory is approximated by the principles of reflection, refraction and diffraction. The scattering coefficient depends on the concentration Nscat and the effective cross section parameters σscat of the particles and can be described byβscat=σscatNscat.
Radiowave Propagation
Published in Indrakshi Dey, Propagation Modeling for Wireless Communications, 2022
Multipath fading is most widely modeled using Rayleigh distribution, when there is no direct LOS path between the transmitter and the receiver. The fading amplitude, α is distributed according to pα(α)=2αΩexp(−α2Ω)α≥0
Geophysical investigation techniques: seismic
Published in Ian Acworth, Investigating Groundwater, 2019
Rayleigh waves are a type of surface wave confined to the near surface of the ground. Rayleigh waves include both longitudinal and transverse motions that decrease exponentially in amplitude as distance from the surface increases. There is also a phase difference between these component motions. The speed of the Rayleigh wave is a little less than the shear wave and can be approximated from Equation 8.16: VRayleigh=0.862+1.14μ1+μ
Preconceptual Design of Multifunctional Gas-Cooled Cartridge Loop for the Versatile Test Reactor: Instrumentation and Measurement—Part II
Published in Nuclear Science and Engineering, 2022
Piyush Sabharwall, Kevan Weaver, N. K. Anand, Chris Ellis, Xiaodong Sun, Hangbok Choi, Di Chen, Rich Christensen, Brian M. Fronk, Joshua Gess, Yassin Hassan, Igor Jovanovic, Annalisa Manera, Victor Petrov, Rodolfo Vaghetto, Silvino Balderrama-Prieto, Adam J. Burak, Milos Burger, Alberto Cardenas-Melgar, Daniel Orea, Reynaldo Chavez, Byunghee Choi, Londrea Garrett, Genevieve L. Gaudin, Noah Sutton, Ken William Ssennyimba, Josh Young
Fiber sensors for measuring distributed strain (and temperature) generally rely on an interferometry technique. Light (from either a tunable laser or broadband source) is sent into the fiber under test. Rayleigh scattering is an elastic scattering of light due to the presence of scattering sites that are much smaller than the wavelength of the light. In an elastic scattering process, the wavelength is conserved, and only direction changes. The scattering amplitude is inversely proportional to the wavelength to the fourth power λ−4. This implies that shorter-wavelength light is scattered more intensely. Scattering sites in fiber-optic cables arise due to microscopic local density differences or other inhomogeneity arising from the fiber manufacturing process. When light is transmitted through the cable, some fraction is scattered in a direction 180 deg to the propagation axis (Rayleigh backscatter) and can be analyzed as it returns to the source. Backscattered light is then detected, and changes in the backscattered characteristics can be used to understand quasi-local strain and, in turn, temperature.
The unique asymmetric nano-cluster formation by the uneven hockey-stick-shaped mesogen based on 1,3,4-oxadiazole in Langmuir–Blodgett thin film
Published in Journal of Dispersion Science and Technology, 2022
Alpana Baidya, Bandana Das, Santanu Majumder, Sandip K. Saha, Ranendu K. Nath, Manoj K. Paul
When a photon interacts with a particle it scatters, that is, reflection, refraction, or diffraction. The elastic collision generates two types of scattering, the Rayleigh scattering, and the Mie scattering, depending on the size of the particles. The Rayleigh scattering happens when the particle size is very minute, below the one-tenth of the wavelength of incident radiation and it remains below 50 nm, like air molecules, because the visible light is between 400 and 700 nm. The amount of light that is scattered in Rayleigh scattering is expressed as the extinction coefficient, Q, which is proportional to the ratio between the radius of the particle and the wavelength. The forward and backscattering are almost equal. But Mie scattering occurs when the particle diameter is one-tenth or the full size of the wavelength of incident radiation. Most of the scattering is in the forward direction and little in the backward direction.[25] In Mie scattering the extinction coefficient, Q depends on
Experimental study of finger behavior due to miscible viscous and gravity contrast in a porous model
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
Seyed Mostafa Hosseinalipoor, Arash Nemati, Behrooz Zare Vamerzani, Hamid Saffari
Displacing a high viscous fluid by a fluid of lower viscosity causes some instability at the interface between two fluids (Lewis 1950; Taylor 1950). The instability, caused by viscosity contrast, propagates through the displaced fluid in the finger-form patterns that is known as Saffman–Taylor instability (Saffman and Taylor 1958) or viscous fingering instability. Rayleigh–Taylor instability (Chandrasekhar 1961) is another type of instability which is encountered when the denser fluid, due to density contrast, moves into the lighter one in the presence of gravitational field. These instabilities usually occur in environmental and technological processes such as filtration, hydrology, enhanced oil recovery, chromatography to name a few. Viscous fingering patterns can also be used for controlled shaping of fluid in various applications including microfluidic mixers, capillary pump, and heat exchangers (Islam and Gandhi 2017). Thus, analyzing fingering instability is a significant tool to predict displacements of fluids in the abovementioned practices.