SOME APPROXIMATIONS IN THE NUMERICAL TREATMENT OF RADIATION TRANSPORT THROUGH MEDIA WITH FREQUENCY-DEPENDENT ABSORPTION COEFFICIENTS

1962 ◽  
Author(s):  
B. E. Freeman
Keyword(s):  
Radiation Transport ◽  
Numerical Treatment ◽  
Absorption Coefficients ◽  
Frequency Dependent ◽  
Dependent Absorption

scholarly journals Optimal Band Selection for the Calculation of Planck Mean Absorption Coefficients

2017 ◽  
Vol 4 (1) ◽  
pp. 70-73
Author(s):  
M. Gnybida ◽  
Ch. Rümpler ◽  
V. R. T. Narayanan
Keyword(s):  
Temperature Profile ◽  
Low Voltage ◽  
Optimization Procedure ◽  
Optimal Number ◽  
Discrete Ordinates ◽  
Radiation Balance ◽  
Absorption Coefficients ◽  
Loss Mechanism ◽  
Spectral Solution ◽  
Dependent Absorption

Radiative heat transfer is a major heat loss mechanism in thermal plasmas generated during arc flashes/faults in switchgear applications or during high current interruption in low voltage circuit breakers. A common way to calculate the radiation balance is by means of approximate non-gray radiation models like P1 or discrete ordinates (DOM), where the frequency dependent absorption and emission are described in a number of frequency intervals (bands) using a constant absorption coefficient in each band. Current work is focused on finding the optimal number of bands as well as band interval boundaries that provide a reasonable level of accuracy in comparison to a full spectral solution. An optimization procedure has been applied to different SF<sub>6</sub> and copper vapor gas mixtures for an assumed temperature profile. Radiation model results using optimized band averaged absorption coefficients as well as spectral values are provided and discussed for the exemplary temperature profile.

Optical Response of Mixed Molybdenum Dichalcogenides for Solar Cell Applications Using the Modified Becke–Johnson Potential

2016 ◽  
Vol 71 (3) ◽  
pp. 213-223 ◽  
Author(s):  
Ushma Ahuja ◽  
Ritu Joshi ◽  
D.C. Kothari ◽  
Harpal Tiwari ◽  
K. Venugopalan
Keyword(s):  
Solar Cell ◽  
Dielectric Constants ◽  
Full Potential ◽  
Energy Bands ◽  
Absorption Coefficients ◽  
Augmented Plane Wave ◽  
Wave Technique ◽  
Degree Of Anisotropy ◽  
Dependent Absorption ◽  
First Time

AbstractEnergy bands and density of states (DOS) of mixed molybdenum dichalcogenides like MoS2, MoSeS, MoSe2, MoTe2, MoTeS, and MoTe0.5S1.5 are reported for the first time using the Tran–Blaha modified Becke–Johnson potential within full potential-linearised augmented plane wave technique. From the partial DOS, a strong hybridisation between the Mo-d and chalcogen-p states is observed below the Fermi energy EF. In addition, the dielectric constants, absorption coefficients, and refractivity spectra of these compounds have also been deduced. The integrated absorption coefficients derived from the frequency-dependent absorption spectra within the energy range of 0–4.5 eV show a possibility of using molybdenum dichalcogenides, particularly MoTe0.5S1.5, in solar cell applications. Birefringence and degree of anisotropy are also discussed using the data on refractivity and imaginary components of the dielectric constant.

Acoustic wave propagation in air‐bubble curtains in water—Part II: Field experiment

Geophysics ◽  
1982 ◽  
Vol 47 (3) ◽  
pp. 354-375 ◽  
Author(s):  
S. N. Domenico
Keyword(s):  
Plane Wave ◽  
Field Experiment ◽  
Bubble Radius ◽  
Air Pressure ◽  
Peak Amplitude ◽  
Frequency Dependent ◽  
Air Curtain ◽  
Air Bubble ◽  
Dependent Absorption ◽  
Pulse Peak

A field experiment consisted of hydrophone recordings in a pond, 25 ft deep, of signals transmitted through air‐bubble curtains from a water gun source. The air curtains issued from one to 13 pipes (20 ft long and spaced at 1.67 ft intervals). Air pressures used in the pipes were 15, 25, and 50 psi. Length and complexity of the signals indicate that reverberations occurred to an increasing extent as the number of consecutive air curtains was increased. Analysis of the first pulse in the recorded signals, after approximate removal of hydrophone and recorder response, indicates that the reverberations occur principally in the bubble‐free corridors between air curtains. This pulse broadens and its peak amplitude is delayed linearly as the number of successive air curtains is increased. The peak amplitude is decreased substantially by the first air curtain and thereafter remains between 0.1 and 0.2 of the amplitude without air curtains. The time delay increases measurably, whereas the amplitude appears insensitive to an increase in air pressure. Width of the bubble‐free corridor, velocity in the air curtains, and reflection coefficient at the air curtain/corridor interface were determined for each of the three air pressures from signal onset times and delay time of the first pulse peak amplitude. The corridor width was approximately three times the air curtain width and did not appear to vary with air pressure. Traveltime in the air curtain, however, increased with air pressure and was from three to four times the traveltime in the corridor. Reflection coefficients ranged from about 0.75 at 15 psi to 0.82 at 50 psi. These data were used to predict, successfully, times of multiple reflections between the outer interfaces of the outermost air curtains. Plane‐wave synthetic signals, based on absorptionless models simulating the air curtain configurations and velocities, correspond satisfactorily to recorded signals for the successive‐pipe sequence. As for the recorded signals, peak amplitude of the first pulse is decreased substantially by a single air curtain and not appreciably more by additional air curtains. Recorded‐signal amplitudes, however, exceed synthetic‐signal amplitudes, possibly due to inadequacy of the plane‐wave models and to backscattered signals within the pond. The dominant reverberations prevented meaningful measurements of the frequency‐dependent absorption in the air curtains. Theoretical absorption values were obtained after synthetically eliminating the bubble‐free corridors by expansion of the air curtains. Absorption as a function of air curtain width was determined for each of the three air pressures and for the extremes of possible bubble radii (0.002 to 0.014 ft). Similar to reduction of the first pulse peak amplitude on recorded signals, amplitude of synthetic signals is decreased substantially by the air curtain from a single pipe and at a much lower rate as the air curtain width increases. Frequency‐dependent absorption for the smaller bubble radius (0.002 ft) is substantially greater and increases with air curtain width at a greater rate.

scholarly journals Quantification of frequency-dependent absorption phenomena

2019 ◽  
Author(s):  
Leander Claes ◽  
Sarah Johannesmann ◽  
Elmar Baumhögger ◽  
Bernd Henning
Keyword(s):  
Frequency Dependent ◽  
Dependent Absorption
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