Radiative Characteristics of High-Porosity Media Containing Randomly Oriented Fibers in Space

2017 ◽  
Vol 9 (2) ◽  
Author(s):  
Herve Thierry Tagne Kamdem
Keyword(s):  
Diffraction Theory ◽  
Incident Radiation ◽  
Spherical Particles ◽  
High Porosity ◽  
Fibrous Media ◽  
Participating Media ◽  
Hemispherical Reflectance ◽  
Scattering Phase Function ◽  
The One ◽  
Radiative Characteristics

This paper proposed radiative characteristics' expressions for media containing randomly oriented fibers in space. In deriving these simple radiative characteristics' expressions, the fibrous medium effective extinction coefficient is defined to match with the one of large particle obtained by combining geometric optics and Fraunhofer diffraction theory. Fibrous media radiative characteristics are then derived as an average over all incident radiation angles of single fiber radiative characteristics. Theoretical hemispherical reflectance and normal transmittance predictions using the proposed fibrous media radiative characteristics based on the Mie theory agreed well with literature experiments. Therefore, media containing fiber randomly oriented in space can be scaled to a suitable equivalent media such that scattering mechanisms behave similarly to that occurring in a participating media containing spherical particles. Numerical investigations show that a theoretical model which assumes Henyey–Greenstein (HG) scattering phase function can conveniently be used for the estimation of equivalent fibrous media radiative characteristics using hemispherical reflectance measurements. On the other hand, the estimated equivalent fibrous media radiative characteristics from hemispherical measurements and using a two-flux model with isotropic scaling radiative characteristics may be subjected to serious errors in the case of semitransparent media for which the absorption is significant.

Numerical Results of an Integral Formulation of Transient Radiative Transfer

1999 ◽  
Author(s):  
Z.-M. Tan ◽  
P.-F. Hsu
Keyword(s):  
Steady State ◽  
Radiative Transfer ◽  
Incident Radiation ◽  
Integral Formulation ◽  
Time Step ◽  
Incident Intensity ◽  
Participating Media ◽  
Upwind Difference Scheme ◽  
The One ◽  
Reflecting Surface

Abstract Numerical computations are performed for the transient radiative transfer equation within the one-dimensional parallel plate geometry using an integral formulation obtained in a prior work. The medium under consideration is absorbing and isotropically scattering. One boundary is a black emitting surface or a transparent surface subjected to the collimated incident radiation. The incident intensity is applied at the start of the transient. The other boundary is a cold and black or specularly reflecting surface. The spatial and temporal incident radiation and radiative flux distributions are presented for different boundary conditions and for uniform and nonuniform property distribution. The transient results at large time step are compared with steady-state solutions by the finite volume and quadrature methods and show excellent agreement. The solutions of reflecting boundary condition exhibit distinctive behavior from that of the non-reflecting boundary. The integral formulation is extended to handle the transient transfer within the nonhomogeneous participating media. The integral formulation has several advantages over the differential treatment of the hyperbolic wave of the radiative transport; among others: (1) The avoidance of using a high order upwind difference scheme in resolving the wave front; (2) Providing a sound basis for physical interpretation as the radiative transfer is a volumetric process; and (3) Many integral equation numerical methods that have previously been developed for the steady state integral formulation can be re-applied to treat the transient problem.

Grinding Performance of Porous Diamond Wheels on Different Materials

2011 ◽  
Vol 189-193 ◽  
pp. 3191-3197
Author(s):  
Qiu Lian Dai ◽  
Can Bin Luo ◽  
Fang Yi You
Keyword(s):  
Grain Size ◽  
Specific Energy ◽  
Experimental Results ◽  
Grinding Process ◽  
High Porosity ◽  
Grinding Forces ◽  
Abrasive Grain ◽  
Grinding Conditions ◽  
Medium Porosity ◽  
The One

In this paper, metal-bonded diamond wheels of different sized abrasive grain with different porosity were fabricated. Grinding experiments with these wheels on three kinds of materials were carried out under different grinding conditions. Experimental results revealed that wheel with high porosity (38%) had smaller grinding forces and specific energy than the one with a medium porosity (24%) on grinding G603. However, on grinding harder materials like Red granite or ceramics of Al2O3, the wheel with 38% porosity had bigger grinding forces and specific energy than the wheel with 24% porosity. Both wheels exhibited good self-sharpening capability during the grinding process of G603 and Red granite, but on grinding ceramics of Al2O3 the wheel with 38% porosity displayed in dull state during the grinding process . With the same porosity, the grinding forces of the wheel with a grain size of 230/270 US mesh were lower than the one with a grain size of W10 when grinding Red granite and ceramics of Al2O3. However revising results were obtained on grinding G603.

scholarly journals Calibrations and Performance of the Airborne Cloud Extinction Probe

2014 ◽  
Vol 31 (2) ◽  
pp. 326-345 ◽  
Author(s):  
Alexei Korolev ◽  
Alex Shashkov ◽  
Howard Barker
Keyword(s):  
Crystal Surface ◽  
Theoretical Calculations ◽  
Light Attenuation ◽  
Spherical Particles ◽  
Nonspherical Particles ◽  
Cloud Droplets ◽  
Fine Crystal ◽  
A New Technique ◽  
And Performance ◽  
Scattering Phase Function

Abstract A new airborne instrument that measures extinction coefficient β in clouds and precipitation has been designed by Environment Canada. The cloud extinction probe (CEP) utilizes the transmissometric method, which is based on direct measurement of light attenuation between the transmitter and receiver. Transmissometers are known to be susceptible to forward scattering, which becomes increasingly significant as the particle size increases. A new technique for calibrating transmissometers was developed here in order to determine the response function of the probe. Laboratory calibrations show that CEP-derived β may be underestimated by a factor of 2 for circular particles with diameters greater than 100 μm. Results for spherical particles are in good agreement with theoretical predictions. For nonspherical particles, however, estimates of β can deviate significantly from those derived for spheres that have the same projected area. For in situ observations of ice particles, CEP measurements often deviate significantly from theoretical calculations, whereas for small cloud droplets agreement is good. It is hypothesized that CEP-derived estimates of β for ice clouds depend much on variations in the scattering phase function that arise from details in ice crystal surface roughness and fine crystal structure. This would complicate greatly the estimation of β from transmissometers for ice-bearing clouds.

Modeling of Interaction Layers from Conductive Microparticles with TE Electromagnetic Wave

2013 ◽  
Vol 646 ◽  
pp. 245-248
Author(s):  
Anton Anzulevich ◽  
Leonid But’ko ◽  
Sergey Moiseev ◽  
Il’ya Zotov
Keyword(s):  
Electromagnetic Wave ◽  
Electromagnetic Radiation ◽  
Incident Radiation ◽  
Spherical Particles ◽  
Metal Powders ◽  
Micro Particles ◽  
Wave Heating ◽  
Powder Metals ◽  
Size Of Particles

Dependences of distribution, penetration, reflection and absorption of microwaves in the layers of conductive micro-particles on the frequency of the incident radiation and size of particles are obtained and investigated. Layers of conductive spherical particles as the shell, and without it are accepted in our work as the most common model of powder metals. So, this study allows to describe and classify features of electromagnetic wave heating of various metal powders and to predict the performance, in which it will be effective heating of metal powders by electromagnetic radiation.

Parallel Flow Through Ordered Fibers: An Analytical Approach

2010 ◽  
Vol 132 (11) ◽  
Author(s):  
A. Tamayol ◽  
M. Bahrami
Keyword(s):  
Entire Range ◽  
Analytical Approach ◽  
High Porosity ◽  
Fibrous Media ◽  
Fully Developed Flow ◽  
Wide Range ◽  
Hexagonal Arrangement ◽  
Flow Through ◽  
Hexagonal Arrays ◽  
Comparison With Experimental Data

In this study, fully developed flow parallel to ordered fibers is investigated analytically. The considered fibrous media are made up of in-line (square), staggered, and hexagonal arrays of cylinders. Starting from the general solution of Poisson’s equation, compact analytical solutions are proposed for both velocity distribution and permeability of the considered structures. In addition, independent numerical simulations are performed for the considered arrangements over the entire range of porosity and the results are compared with the proposed solutions. The developed solutions are successfully verified through comparison with experimental data, collected by others, and the present numerical results over a wide range of porosity. The results show that for the ordered arrangements with high porosity, the parallel permeability is independent of the microstructure geometrical arrangements; on the other hand, for lower porosities the hexagonal arrangement provides lower pressure drop, as expected.

Possible effects of Mercury surface temperatures on the exosphere

2020 ◽  
Author(s):  
Edoardo Rognini ◽  
Alessandro Mura ◽  
Maria Teresa Capria ◽  
Angelo Zinzi ◽  
Anna Milillo ◽  
...  
Keyword(s):  
Internal Heat ◽  
Thermal Response ◽  
Circulation Model ◽  
Sodium Content ◽  
Heat Propagation ◽  
Conductive Heat ◽  
High Porosity ◽  
Surface Temperatures ◽  
Thermophysical Model ◽  
The One

<div> <p>The BepiColombo mission is the first European mission to Mercury; the spacecraft will reach its destination in December 2025, and will study in detail the surface, the exosphere and the magnetosphere of the planet. </p> </div> <div> <p>We have developed a thermophysical model with the aim to analyze the dependence of the temperature of the surface and of the layers close to it on the assumptions on the thermophysical properties of the soil. The code solves the one-dimensional heat equation, assumes purely conductive heat propagation and no internal heat sources; the surface is assumed to be composed of a regolith layer with high porosity and density increasing with depth. The illumination conditions are calculated by using a Mercury shape model and the SPICE routines [1]. </p> </div> <div> <p>The model will help us to interpret the data that will be provided by the instruments onboard the BepiColombo mission. Preliminary calculations have been carried out to analyze the thermal response of the soil as a function of thermal conductivity. The model is currently also used to study the sodium content in the planet's exosphere, whose origin is under investigation [2]; the MESSENGER mission has measured the exospheric sodium content as a function of time, detecting an increase at the "cold poles" (so called because of their lower than average temperature). We therefore want to study the effect of surface temperatures on the sodium content in the exosphere; for this purpose, the temperature distribution calculated with the code is used together with an atmospheric circulation model that calculates the exospheric sodium content [3]. </p> </div> <div> <p>A simplified version of the thermophysical code is almost ready to be available to the scientific community through MATISSE [4], the software developed at the SSDC in ASI and available at https://tools.ssdc.asi.it/Matisse. </p> </div> <p>[1] Acton, C. H. (1996), Planetary and Space Science, 44, 65-70<br />[2] Cassidy, T., et al. (2016), GRL, 43, 11 121-128<br />[3] Mura, A., et al. (2009), Icarus, 1, 1-11<br />[4] Zinzi, A., et al. (2016), Astronomy & Computing, 15, 16-28</p>

Combined Experimental-Numerical Approach to Determine Radiation Properties of Particle Suspensions

2013 ◽  
Author(s):  
Jan Marti ◽  
Matthew Roesle ◽  
Aldo Steinfeld
Keyword(s):  
Monte Carlo Model ◽  
Numerical Approach ◽  
Particle Suspensions ◽  
Participating Media ◽  
Radiation Properties ◽  
Radiation Distribution ◽  
Scattering Phase ◽  
Scattering Phase Function ◽  
Good Agreement ◽  
Sic Particle

A combination of experimental measurements with a numerical model is used to find the intensive radiation properties — extinction coefficient, scattering albedo and scattering phase function — of SiC particle suspensions with varying particle loadings. The experimentally determined angular radiation distribution of irradiated SiC samples is applied to fit a collision-based Monte Carlo model with a continuous participating media defining the particle suspension. A validation case with glass microspheres and Mie theory is used to verify the modeling procedure. Two types of SiC particles with dissimilar optical characteristics are examined and the respective radiation properties are determined for porosities between 0.70–0.95. The extinction coefficients of both types of SiC particle are in good agreement with the dependent scattering correlation of Kaviany and Singh.

scholarly journals Radiative behavior and canopy light extinction coefficient in a savanna urban area

2020 ◽  
Vol 42 ◽  
pp. e18
Author(s):  
Levi Pires de Andrade ◽  
Jonathan Willian Zangeski Novais ◽  
Marta Cristina de Jesus Albuquerque Nogueira ◽  
Luciana Sanches ◽  
José De Souza Nogueira ◽  
...  
Keyword(s):  
Urban Area ◽  
Extinction Coefficient ◽  
Incident Radiation ◽  
Light Extinction ◽  
Area Index ◽  
Transmitted Radiation ◽  
Light Extinction Coefficient ◽  
Radiation Incidence ◽  
Radiative Characteristics

The knowledge of the radiative characteristics of an area is essential to understanding the flows of matter and energy. The value of the Light Extinction Coefficient (K) is a parameter that describes the efficiency of the interception of light in a given canopy, being required, as input, for several SWAP (Soil-Water-Atmosphere-Plant) models, which allow the characterization of the interactive properties among  soil, plant and atmosphere concerning these exchanges of matter and energy. This study aimed to obtain the light extinction coefficient (K) for a savanna fragment located in the urban area of Cuiabá. The used data correspond to one measurement each month, totaling twelve measurements in 30 points during the period from October 2014 to September 2015. The measured variables  were the LAI (Leaf Area Index), the photosynthetically active incident radiation (PARinc) and the transmitted radiation  (PARtrans), and the calculated ones were the zenith angle (Zh) and the extinction coefficient (K). Was observed an annual variability for the light extinction coefficient between 0.49 and 0.69. There are seasonal changes that interfere with the canopy geometry and the position of the study area in relation to the solar radiation incidence, concluding that the K variability is predominantly temporal.

scholarly journals Highly Effective Covalently Crosslinked Composite Alginate Cryogels for Cationic Dye Removal

Gels ◽  
2021 ◽  
Vol 7 (4) ◽  
pp. 178
Author(s):  
Serap Sezen ◽  
Vijay Kumar Thakur ◽  
Mehmet Murat Ozmen
Keyword(s):  
Adsorption Capacity ◽  
Dye Removal ◽  
Low Cost ◽  
Dye Adsorption ◽  
Maximum Adsorption Capacity ◽  
High Porosity ◽  
Order Model ◽  
Removal Capacity ◽  
Pseudo Second Order ◽  
The One

Currently, macroporous hydrogels have been receiving attention in wastewater treatment due to their unique structures. As a natural polymer, alginate is used to remove cationic dyes due to its sustainable features such as abundance, low cost, processability, and being environmentally friendly. Herein, alginate/montmorillonite composite macroporous hydrogels (cryogels) with high porosity, mechanical elasticity, and high adsorption yield for methylene blue (MB) were generated by the one-step cryogelation technique. These cryogels were synthesized by adding montmorillonite into gel precursor, followed by chemical cross-linking employing carbodiimide chemistry in a frozen state. The as-prepared adsorbents were analyzed by FT-IR, SEM, gel fraction, swelling, uniaxial compression, and MB adsorption tests. The results indicated that alginate/montmorillonite cryogels exhibited high gelation yield (up to 80%), colossal water uptake capacity, elasticity, and effective dye adsorption capacity (93.7%). Maximum adsorption capacity against MB was 559.94 mg g−1 by linear regression of Langmuir model onto experimental data. The Pseudo-Second-Order model was fitted better onto kinetic data compared to the Pseudo-First-Order model. Improved porosity and mechanical elasticity yielding enhanced dye removal capacity make them highly potential alternative adsorbents compared to available alginate/montmorillonite materials for MB removal.

scholarly journals EMI Shielding of the Hydrophobic, Flexible, Lightweight Carbonless Nano-Plate Composites

Nanomaterials ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 2086
Author(s):  
Kanthasamy Raagulan ◽  
Jin Soo Ghim ◽  
Ramanaskanda Braveenth ◽  
Moon Jai Jung ◽  
Sang Bok Lee ◽  
...  
Keyword(s):  
Sheet Resistance ◽  
Photoelectron Spectroscopy ◽  
Cost Effective ◽  
Incident Radiation ◽  
Work Of Adhesion ◽  
Emi Shielding ◽  
Minimum Thickness ◽  
X Ray ◽  
Synthetic Strategy ◽  
The One

The cost-effective spray coated composite was successfully synthesis and characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and X-ray diffraction techniques. The one step synthetic strategy was used for the synthesis of nanoplates that have a crystalline nature. The composites are amorphous and hydrophobic with micron thickness (<400 μm). The maximum contact angle showed by composite is 132.65° and have wetting energy of −49.32 mN m−1, spreading coefficient −122.12 mN m−1, and work of adhesion 23.48 mN m−1. The minimum thickness of synthesized nanoplate is 3 nm while the maximum sheet resistance, resistivity, and electrical conductivity of the composites are 11.890 ohm sq−1, 0.4399 Ω.cm−1, and 8.967 S.cm−1, respectively. The cobalt nanoplate coated non-woven carbon fabric (CoFC) possesses excellent sheet resistance, hydrophobic nature, and EMI shielding efficiency of 99.99964%. The composite can block above 99.9913% of incident radiation (X band). Hence, the composite can be utilized in application areas such as medical clothes, mobile phones, automobiles, aerospace, and military equipment.

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