Thermal Radiation from a Microscopically Roughened Dielectric Surface

1972 ◽  
Vol 94 (1) ◽  
pp. 73-79 ◽  
Author(s):  
R. P. Caren ◽  
C. K. Liu
Keyword(s):  
Refractive Index ◽  
Surface Layer ◽  
Thermal Radiation ◽  
Spatial Variation ◽  
Riccati Equation ◽  
Radiant Energy ◽  
Dielectric Surface ◽  
Inhomogeneous Surface ◽  
Roughened Surface ◽  
Total Emittance

The emission of thermal radiation from a microscopically roughened dielectric surface is treated using a laminar-inhomogeneous layered model for a representation of the effective spatial variation in refractive index associated with a roughened surface layer. The Riccati equation is used to calculate the modification to the spectral angular transmittance of the surface due to the presence of this inhomogeneous surface layer. A consideration of the emission of radiant energy from the bulk dielectric through the surface layer permits the angular emittance to be determined. Total emittance values are obtained using the spectral angular emittance data.

scholarly journals Features of the Surface and Subsurface Waves Application for Ultrasonic Evaluation of Physicomechanical Properties of Solids. Part 2. Strenghtned Inhomogeneous Surface Layer

2019 ◽  
Vol 10 (1) ◽  
pp. 69-79
Author(s):  
A. R. Baev ◽  
A. L Mayorov ◽  
N. V. Levkovich ◽  
M. V. Asadchaya
Keyword(s):  
Experimental Data ◽  
Surface Layer ◽  
Spatial Distribution ◽  
Surface Wave ◽  
High Frequency ◽  
Hardened Layer ◽  
Gray Iron ◽  
Physicomechanical Properties ◽  
Inhomogeneous Surface ◽  
Ultrasonic Evaluation

The propagation of a pulsed signal of a surface wave over an object with a non-uniform surface layer, obtained, for example, as a result of surface hardening, with structural damage, is accompanied by the dispersion of the velocity of the wave carrying important information about the parameters of such a layer. The aim of the work is to study the relationship between the acoustic parameters of a pulsed acoustic signal of a surface and subsurface waves and the surface layer of steel specimens hardened by high-frequency hardening, and gray iron-chill. Features of the surface and subsurface waves application for ultrasonic evaluation of physicomechanical properties of solids. Strenghtned inhomogeneous surface layer.A brief analysis of the known works on determining the depth of hardened surface layers by various methods, including high-frequency hardening, cementation, etc., is carried out. Based on the Oulder integral expression. The dependence connecting the wave velocity, its frequency, the depth of the hardened layer and the spatial distribution of hardness represented as a step with a changing slope of its side surface simulating the transition zone of the hardened layer are calculated.Using the pulse method and low-aperture transducers with a frequency of 1−3.8 MHz, the dependences of the surface wave velocity on the cutting height of a layer hardened by HDTV hardening are obtained. A comparison of experimental data and calculations of the theoretical model showed a good qualitative correspondence between them, demonstrate a high «sensitivity» of the method in relation to the nature of the change in hardness over the depth of the hardened layer. It is shown that the proposed approach is promising for solving the inverse problem of restoring the spatial distribution of hardness based on experimental data.The goniometric method was approbated to determine the dependence between amplitude-angle characteristics and depth of the surface steel layers hardened by high-frequency hardening and depth of hardened gray iron specimens layer – with chill. It is shown that the optimal angle corresponding maximum of excited surface wave amplitude in steel specimens is decreasing up to 24–26'vs. hardened depth layer. But when the tested specimens from cast iron this angle decreasing is nearly of 6°. Recommendations on the use of research results in practice are given.

The spatial variation of the refractive index in biological cells

1996 ◽  
Vol 41 (3) ◽  
pp. 369-382 ◽  
Author(s):  
J Beuthan ◽  
O Minet ◽  
J Helfmann ◽  
M Herrig ◽  
G Müller
Keyword(s):  
Refractive Index ◽  
Spatial Variation ◽  
Biological Cells

Spatial variation of refractive index in a pane of float glass

2003 ◽  
Vol 43 (2) ◽  
pp. 71-76 ◽  
Author(s):  
R.L. Bennett ◽  
N.D. Kim ◽  
J.M. Curran ◽  
S.A. Coulson ◽  
A.W.N. Newton
Keyword(s):  
Refractive Index ◽  
Spatial Variation ◽  
Float Glass

scholarly journals Ellipsometric Diagnostics of a Transient Surface Layer in Optical Glass

2019 ◽  
Vol 64 (5) ◽  
pp. 442 ◽  
Author(s):  
O. V. Makarenko ◽  
L. V. Poperenko ◽  
O. I. Zavalistyi ◽  
A. L. Yampolskiy
Keyword(s):  
Optical Properties ◽  
Surface Layer ◽  
Layer Structure ◽  
Optical Glass ◽  
Target Function ◽  
Morphological Structure ◽  
Thin Layers ◽  
Inhomogeneous Surface ◽  
Interference Phenomenon ◽  
Near Surface

Optical properties of a transient layer with a broken structure that arises at the surface of optical glass at its treatment have been considered. Rather often, the surface of optical elements is considered to be perfect, although the actual inhomogeneous surface structure can have a significant effect for precision physical experiments or novel technological problems. Furthermore, the simulation of the surface layer structure and the corresponding optical characteristics, as well as the study of a possibility to determine those parameters from the results of optical researches, is also of theoretical interest, which is demonstrated in this work. Ellipsometric measurements of optical glass specimens with a broken surface layer are carried out. When modeling the angular dependences of the ellipsometric parameters tan ф and cos б, the near-surface specimen region is considered as a stack of 500 thin layers, and the matrix method of light reflection in this structure with regard for the interference phenomenon is used in calculations. Five models are tested for the optical profile of a nonuniform layer, whose parameters are fitted to achieve the minimum of the target function describing the discrepancy between the calculated and measured data. It is found that the theoretical models describe the optical properties of the specimens more accurately, if they make allowance for the inhomogeneous surface layer. Nevertheless, the solution of the inverse ellipsometric problem turns out ambiguous, so that additional measurements are required for the final choice of a model that would be adequate to the actual morphological structure of the broken layer to be made. However, the key advantage of the applied method consists in that it allows a direct registration of the optical response of the system.

On the Wave Speed of Thermal Radiation Inside and Near the Boundary of an Absorbing Material

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Bair V. Budaev ◽  
David B. Bogy
Keyword(s):  
Refractive Index ◽  
Thermal Radiation ◽  
Thermal Equilibrium ◽  
Wave Speed ◽  
Normal Modes ◽  
Absorbing Medium ◽  
Absorbing Material ◽  
Absorbing Media ◽  
Planck’S Law ◽  
Complex Valued

Abstract Planck's law describes thermal radiation into vacuum from a black body in thermal equilibrium. This law can be easily adapted to describe radiation into a transparent medium with a constant refractive index, and it admits a less trivial extension to radiation into a transparent medium with a nonconstant refractive index. However, this law cannot be straightforwardly generalized to describe thermal radiation into absorbing media and, in particular, to describe thermally exited electromagnetic fields inside the radiating body itself. We first analyze Planck's law and show why it cannot be straightforwardly extended to radiation into an absorbing medium. The derivation of this law relies on the assumption that a radiated field admits decomposition into normal modes, which cannot exist in absorbing media that are characterized by a complex-valued refractive index n=n′+in″, whose imaginary part describes the rate of energy dissipation. Correspondingly, the speed of electromagnetic waves in absorbing media c=c0/n, where c0 is the speed of light in vacuum, is also complex-valued, which suggests that the conventional concept of a complex valued wave speed is not suitable for modeling thermal radiation. We demonstrate that complex-valued wave speeds adequately describe waves that carry signals, such as radio waves and laser beams. Such waves decay because they pass some of their energy to the medium. The energy absorbed by the medium is eventually reradiated, but in studies focused on the transmission of signals, the reradiated fields are ignored as noise. In order to study thermal radiation in an absorbing material, one must treat the material and the radiation together as a closed system. The energy in such a system is conserved, and its distribution between the material and radiation does not change in time. This radiation admits decomposition into normal modes, which makes it possible to extend Planck's law to radiation into absorbing materials. This paper proposes a model of thermal radiation in an absorbing medium as a closed, energy conserving system. The radiation field has normal modes that correspond to an effective speed of wave propagation. Assuming that an absorbing material and the radiation in it are in thermal equilibrium, we show that deep inside the material, the average speed of photons is given by a frequency and temperature-dependent expression c∗=c0/(1+e−ℏω/κT). While this result is independent of the material, we further show that close to the boundary of the medium, the speed of thermal radiation depends in a complex way on the refractive index and the extinction coefficient of the material, as well as the direction of propagation and the distance from the material's surface.

scholarly journals A new method for estimating aerosol mass flux in the urban surface layer using LAS technology

2016 ◽  
Vol 9 (4) ◽  
pp. 1925-1937 ◽  
Author(s):  
Renmin Yuan ◽  
Tao Luo ◽  
Jianning Sun ◽  
Hao Liu ◽  
Yunfei Fu ◽  
...  
Keyword(s):  
Refractive Index ◽  
Surface Layer ◽  
Atmospheric Aerosol ◽  
Mass Concentration ◽  
Light Propagation ◽  
Vertical Transport ◽  
New Method ◽  
Aerosol Mass ◽  
Aerosol Mass Concentration ◽  
Transport Flux

Abstract. Atmospheric aerosol greatly influences human health and the natural environment, as well as the weather and climate system. Therefore, atmospheric aerosol has attracted significant attention from society. Despite consistent research efforts, there are still uncertainties in understanding its effects due to poor knowledge about aerosol vertical transport caused by the limited measurement capabilities of aerosol mass vertical transport flux. In this paper, a new method for measuring atmospheric aerosol vertical transport flux is developed based on the similarity theory of surface layer, the theory of light propagation in a turbulent atmosphere, and the observations and studies of the atmospheric equivalent refractive index (AERI). The results show that aerosol mass flux can be linked to the real and imaginary parts of the atmospheric equivalent refractive index structure parameter (AERISP) and the ratio of aerosol mass concentration to the imaginary part of the AERI. The real and imaginary parts of the AERISP can be measured based on the light-propagation theory. The ratio of the aerosol mass concentration to the imaginary part of the AERI can be measured based on the measurements of aerosol mass concentration and visibility. The observational results show that aerosol vertical transport flux varies diurnally and is related to the aerosol spatial distribution. The maximum aerosol flux during the experimental period in Hefei City was 0.017 mg m−2 s−1, and the mean value was 0.004 mg m−2 s−1. The new method offers an effective way to study aerosol vertical transport in complex environments.

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