Malvern particle size measurements in media with time varying index of refraction gradients

1990 ◽  
Vol 29 (31) ◽  
pp. 4563 ◽  
Author(s):  
B. H. Miles ◽  
Paul E. Sojka ◽  
G. B. King
Keyword(s):  
Particle Size ◽  
Index Of Refraction ◽  
Time Varying

Supercritical CO2 Extraction of Rhizoma Atractylodis macrocephalae

2012 ◽  
Vol 549 ◽  
pp. 60-64
Author(s):  
Zhen Huang ◽  
Xiao Han Shi ◽  
Shao Fang Liu ◽  
Wei Juan Jiang
Keyword(s):  
Particle Size ◽  
Orthogonal Array ◽  
Time Pressure ◽  
Extraction Yield ◽  
Extraction Time ◽  
Time Varying ◽  
Orthogonal Array Design ◽  
Array Design ◽  
Different Sources

An orthogonal array design was employed for optimizing the supercritical CO2 extraction of Rhizoma Atractylodis Macrocephalae. The extraction was performed at temperature from 40 to 60oC, pressure from 15 to 35MPa, extraction time varying from 30 to 90min and particle size spanning from 20 to 80 mesh. The results reflect that the extraction yield is more significantly influenced by the extraction time, pressure and particle size but less by temperature. The experiments show that the extraction yield obviously increases with increasing pressure, different from the literatures. In terms of the sample origin, a comparison shows that outstanding differences exist among the extraction yields from different sources.

A Parametric Numerical Study of Radiative Transfer in Thermotropic Materials

2013 ◽  
Author(s):  
Adam C. Gladen ◽  
Susan C. Mantell ◽  
Jane H. Davidson
Keyword(s):  
Particle Size ◽  
Radiative Transfer ◽  
Optical Thickness ◽  
Parametric Study ◽  
Volume Fraction ◽  
Numerical Study ◽  
Anisotropic Scattering ◽  
Index Of Refraction ◽  
Spherical Particles ◽  
Size Parameter

A thermotropic material is modeled as an absorbing, thin slab containing anisotropic scattering, monodisperse, spherical particles. Monte Carlo ray tracing is used to solve the governing equation of radiative transfer. Predicted results are validated by comparison to the measured normal-hemispherical reflectance and transmittance of samples with various volume fraction and relative index of refraction. A parametric study elucidates the effects of particle size parameter, scattering albedo, and optical thickness on the normal-hemispherical transmittance, reflectance, and absorptance. The results are interpreted for a thermotropic material used for overheat protection of a polymer solar absorber. For the preferred particle size parameter of 2, the optical thickness should be less than 0.3 to ensure high transmittance in the clear state. To significantly reduce the transmittance and increase the reflectance in the translucent state, the optical thickness should be greater than 2.5 and the scattering albedo should be greater than 0.995. For optical thickness greater than 5, the reflectance is asymptotic and any further reduction in transmittance is through increased absorptance. A case study is used to illustrate how the parametric study can be used to guide the design of thermotropic materials. Low molecular weighted polyethylene in poly(methyl methacrylate) is identified as a potential thermotropic material. For this material and a particle radius of 200 nm, it is determined that the volume fraction and thickness should equal 10% and 1 mm, respectively.

A Remediation Scheme to Global Warming: Engineering Biodegradable Aerosols With Maximum Scattering Potential

2006 ◽  
Author(s):  
Daniel Attinger ◽  
Brendan Green
Keyword(s):  
Particle Size ◽  
Global Warming ◽  
Exploratory Study ◽  
Mie Scattering ◽  
Index Of Refraction ◽  
Numerical Code ◽  
Biodegradable Nanoparticles ◽  
Tiny Amount ◽  
Wide Range ◽  
Scattering Potential

This exploratory study evaluates the following moderation scheme against global warming: deploying nanoparticles in the atmosphere in order to scatter a tiny amount of sunlight (1% or 2W/m2) up to space. Such a strategy could be a last-resort method to counteract unbearable effects of global warming. For particles made of a wide range of known materials, the scattering ability is defined to quantify how efficient the particle is at scattering sunlight. This scattering ability is a function of the particle radius and index of refraction, and is calculated by an in-house numerical code solving the Mie scattering equations. The code is validated against scattering calculations for SO2 particles published by Schwartz[1]. Our calculations show that an optimum particle size exists, which would minimize the amounts to be deployed in the atmosphere. Also, we evaluate the deployment of biodegradable nanoparticles, which would counteract global warming and minimize dangers related to their redeposition.

Influence of Index of Refraction and Particle Size Distribution on Radiative Heat Transfer in a Pulverized Coal Combustion Furnace

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Robert Johansson ◽  
Tim Gronarz ◽  
Reinhold Kneer
Keyword(s):  
Heat Transfer ◽  
Particle Size ◽  
Radiative Heat Transfer ◽  
Coal Combustion ◽  
Radiative Heat ◽  
Pulverized Coal ◽  
Index Of Refraction ◽  
Pulverized Coal Combustion ◽  
Complex Index ◽  
Complex Index Of Refraction

In this work, the influence of the radiative properties of coal and ash particles on radiative heat transfer in combustion environments is investigated. Emphasis is placed on the impact on the impact of the complex index of refraction and the particle size on particle absorption and scattering efficiencies. Different data of the complex index of refraction available in the literature are compared, and their influence on predictions of the radiative wall flux and radiative source term in conditions relevant for pulverized coal combustion is investigated. The heat transfer calculations are performed with detailed spectral models. Particle radiative properties are obtained from Mie theory, and a narrow band model is applied for the gas radiation. The results show that, for the calculation of particle efficiencies, particle size is a more important parameter than the complex index of refraction. The influence of reported differences in the complex index of refraction of coal particles on radiative heat transfer is small for particle sizes and conditions of interest for pulverized coal combustion. For ash, the influence of variations in the literature data on the complex index of refraction is larger, here, differences between 10% and 40% are seen in the radiative source term and radiative heat fluxes to the walls. It is also shown that approximating a particle size distribution with a surface area weighted mean diameter, D32, for calculation of the particle efficiencies has a small influence on the radiative heat transfer.

scholarly journals 1.1.17 A Search for Forward Scattering of Sunlight from the Lunar Libration Clouds

1976 ◽  
Vol 31 ◽  
pp. 73-73
Author(s):  
C.L. Ross
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Power Law ◽  
White Light ◽  
Index Of Refraction ◽  
Particle Type ◽  
Upper Limit ◽  
The Mean ◽  
Complex Index Of Refraction

Observations to determine the radiance of forward scattered sunlight from particles in lunar libration regions have been attempted with the white light coronagraph on Skylab. The libration regions could not be distinguished against the solar K + F coronal background; the upper limit to the libration cloud radiance is determined to be 2.5 × 10−11 Bo, where Bo is the radiance of the mean solar disk. Employing models of the particle type and size distribution in the libration clouds, density enhancements have been calculated on the basis of the upper limit of the forward scattered radiance presented herein, and on the basis of earlier observations of the libration region backscattered radiance. The cases where the power law particle size distribution exponent K and complex index of refraction m are 2.5, 1.33-0.051 and 2.5, 1.50-0.051, respectively, are inconsistent with the forward and backscatter observations. Finally, the brightness contrast of remaining possible models of the libration clouds with respect to the K- and F-coronal background is calculated, and is shown to be a maximum in the vicinity of elongation angle ~30°.

Radiation Properties for Polydispersions: Application to Coal

1980 ◽  
Vol 102 (1) ◽  
pp. 99-103 ◽  
Author(s):  
R. O. Buckius ◽  
D. C. Hwang
Keyword(s):  
Particle Size ◽  
Index Of Refraction ◽  
Spherical Particles ◽  
Asymmetry Factor ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Absorption Coefficients ◽  
Spectral Radiation ◽  
Radiation Properties ◽  
Practical Temperature

The extinction and absorption coefficients and the asymmetry factor for polydispersions of absorbing spherical particles are analyzed. The results are based upon Mie’s theory for single spherical particles and particle size distributions found in practical systems. Dimensinnless spectral radiation properties are shown to be independent of the explicit size distribution and functions only of the average radii and the index of refraction. The Planck and Rosseland mean coefficients are also presented and the dependence on temperature is explicitly denoted for a large practical temperature range. The results for coal with optical properties which are wavelength dependent indicate the usefulness of the dimensionless and mean properties.

scholarly journals Sensitivity of Multispectral Imager Liquid Water Cloud Microphysical Retrievals to the Index of Refraction

2020 ◽  
Vol 12 (24) ◽  
pp. 4165 ◽  
Author(s):  
Steven Platnick ◽  
Kerry Meyer ◽  
Nandana Amarasinghe ◽  
Galina Wind ◽  
Paul A. Hubanks ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Particle Size ◽  
Liquid Water ◽  
Infrared Imaging ◽  
Sensitivity Study ◽  
Bulk Water ◽  
Index Of Refraction ◽  
Bulk Liquid ◽  
Cloud Particle ◽  
Laboratory Index

A cloud property retrieved from multispectral imagers having spectral channels in the shortwave infrared (SWIR) and/or midwave infrared (MWIR) is the cloud effective particle radius (CER), a radiatively relevant weighting of the cloud particle size distribution. The physical basis of the CER retrieval is the dependence of SWIR/MWIR cloud reflectance on the cloud particle single scattering albedo, which in turn depends on the complex index of refraction of bulk liquid water (or ice) in addition to the cloud particle size. There is a general consistency in the choice of the liquid water index of refraction by the cloud remote sensing community, largely due to the few available independent datasets and compilations. Here we examine the sensitivity of CER retrievals to the available laboratory index of refraction datasets in the SWIR and MWIR using the retrieval software package that produces NASA’s standard Moderate Resolution Imaging Spectroradiometer (MODIS)/Visible Infrared Imaging Radiometer suite (VIIRS) continuity cloud products. The sensitivity study incorporates two laboratory index of refraction datasets that include measurements at supercooled water temperatures, one in the SWIR and one in the MWIR. Neither has been broadly utilized in the cloud remote sensing community. It is shown that these two new datasets can significantly change CER retrievals (e.g., 1–2 µm) relative to common datasets used by the community. Further, index of refraction data for a 265 K water temperature gives more consistent retrievals between the two spectrally distinct 2.2 µm atmospheric window channels on MODIS and VIIRS. As a result, 265 K values from the SWIR and MWIR index of refraction datasets were adopted for use in the production version of the continuity cloud product. The results indicate the need to better understand temperature-dependent bulk water absorption and uncertainties in these spectral regions.

Microstructural characterization of laser-melted/roller-quenched dicalcium silicate

1988 ◽  
Vol 46 ◽  
pp. 582-583
Author(s):  
C. J. Chan ◽  
K. R. Venkatachari ◽  
W. M. Kriven ◽  
J. F. Young
Keyword(s):  
Particle Size ◽  
Raw Materials ◽  
Shape Change ◽  
Microstructural Characterization ◽  
Particle Size Effect ◽  
Dicalcium Silicate ◽  
Laser Melting ◽  
Uniform Size ◽  
Cell Shape Change ◽  
Wide Range

Dicalcium silicate (Ca2SiO4) is a major component of Portland cement. It has also been investigated as a potential transformation toughener alternative to zirconia. It has five polymorphs: α, α'H, α'L, β and γ. Of interest is the β-to-γ transformation on cooling at about 490°C. This transformation, accompanied by a 12% volume increase and a 4.6° unit cell shape change, is analogous to the tetragonal-to-monoclinic transformation in zirconia. Due to the processing methods used, previous studies into the particle size effect were limited by a wide range of particle size distribution. In an attempt to obtain a more uniform size, a fast quench rate involving a laser-melting/roller-quenching technique was investigated.The laser-melting/roller-quenching experiment used precompacted bars of stoichiometric γ-Ca2SiO4 powder, which were synthesized from AR grade CaCO3 and SiO2xH2O. The raw materials were mixed by conventional ceramic processing techniques, and sintered at 1450°C. The dusted γ-Ca2SiO4 powder was uniaxially pressed into 0.4 cm x 0.4 cm x 4 cm bars under 34 MPa and cold isostatically pressed under 172 MPa. The γ-Ca2SiO4 bars were melted by a 10 KW-CO2 laser.

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