Showing papers on "Particle-size distribution published in 1983"

Strength of mineral absorption features in the transmitted component of near‐infrared reflected light: First results from RELAB

Abstract: Bidirectional reflectance measurements are the only type of reflectance data available to the remote observer. For compositional interpretations, data are desired not only for identification of possible mineral components but also for modal abundance. The latter requires detailed information about the strength of absorption features. Using a new laboratory facility, the RELAB, laboratory data in the near infrared are presented that document effects of particle size, mineral mixtures, and viewing geometry for selected materials with well-developed absorption bands. The commonly observed increase in reflectance with decrease in particle size is also observed for absorption bands as well as a related decrease in absorption strength. For small particles in parts of the spectrum of maximum reflectance, however, a minor decrease in reflectance with a decrese in particle size is sometimes observed. Small particles dominate the observed characteristics of particulate surfaces, which contain a range of particle sizes. The mean optical path length (transmission through particles) of reflected radiation measured for a variety of particle sizes has an apparent upper limit of about 2 mm for particles of less than 250 microns. The typical number of particles involved in the optical path is less than 50.

Transport of non-uniform sediments

Abstract: Laboratory experiments lead to a way of modifying two existing transport rate formulae so that transport rates and size distributions of transported material can be predicted knowing the hydraulic conditions and the bed-material grain size distribution. The Ackers and White and the Paintal transport formulae are modified accordingly and used successfully on laboratory data. Difficulties in defining bed-material distributions and the possibility of overpassing in sand/gravel systems are reflected in the results obtained using data from four rivers.

Size estimates of Titan's aerosols based on Voyager high-phase-angle images

Abstract: Limits on the physical properties of the scattering haze near the top of Titan's atmosphere are derived from data obtained from seven high-phase-angle images from Voyager 1 and 2. From the ratio of the intensities observed at two different high phase angles, an estimate can be made of the forward-scattering lobe of the single-scattering phase function. Comparing the forward-scattering estimate with diffraction lobes from particles of different radii, it is concluded that the average radius of the particles found in the upper few tenths of an optical depth exceeds 0.19 micron. Judging from data observed at four different phase angles, the haze particles probably have a refractive index near 1.6 and a mean size of about 0.5 micron, if the widths of their diffraction peaks are close to those for equal-volume spheres. However, the highly polarizing nature of the particles over a broad wavelength-bandpass (Tomasko and Smith, 1982; West et al, 1983) combined with their forward-scattering behavior makes it very unlikely that the particles are spherical. The nonsphericity contributes to the uncertainty about the radii of the particles, but it is thought that the average radius is several tenths of a micron.

A study of the optical characteristics of the suspended particles in the Benthic Nepheloid Layer of the Scotian Rise

Abstract: Light transmission profiles have been used to study the optical properties of the suspended particles which are characteristic of the area of the Scotian Rise in the North Atlantic Ocean. This area is typified by very strong bottom currents and a highly variable bedform morphology. A good correlation (r = 0.96) has been found between the suspended volume and the light beam attenuation coefficient. This correlation is consistent with the fact that the cumulative slope of the hyperbolic particle size distribution is nearly constant throughout the region (slope = 3.1 ± 0.3). Numerical analysis of the optical data in conjunction with particle size analysis yields values of the index of refraction of the suspended particles of 1.20±0.07 relative to water. The conclusion drawn from these results is that the Scotian Rise benthic zone is characterized by suspended particles of high relative index of refraction and size distributions which do not vary much with altitude above bottom or over periods of time of more than a year in spite of the extensive fluctuations in activity of the region.

A 30000 year record of physical and optical properties of microparticles from an East Antarctic ice core and implications for paleoclimate reconstruction models

Abstract: Ice samples from the 905 m deep Dome C core (East Antarctica) were studied in terms of insoluble microparticle contents. Various techniques were used: right angle light scattering, nephelometer (multiangle light scattering), Coulter counter and microscope analyses, in order to make a thorough study of the physical and optical properties of microparticles and their variations over the last 30000 years. Because of the possible effect of atmospheric turbidity on the earth-atmosphere radiation balance, optical parameters of climatic importance were estimated for insoluble microparticles. The detailed profile of total microparticle mass concentrations shows a drastic (factor of 17 ± 13) difference between high Last Glacial Maximum (LGM) and low Holocene concentrations. The optical scattering properties of 18000 BP continental dust do not indicate a significant difference with respect to Holocene dust in terms of particle size distribution and complex refractive index. The number to log radius size distribution of microparticles for the entire 30 000 yr period can be fitted by a log-normal distribution with two parameters (modal radius 0.25 ± 0.08 μm; geometric standard deviation 2.2. ± 0.2). However, for the smallest particles a better adjustment between experimental and theoretical scattering diagrams is obtained by adding to the observed size distribution another log-normal distribution (modal radius = 0.025 μm, σ g = 2). The complex refractive index is 1.53 to 1.56 for the real part and 0.005 ± 0.005 for the imaginary part at the wavelength used (λ= 546 nm). During the LGM stage, over the whole of Antarctica, the change in the total optical depth due to the drastic change in the insoluble aerosol loading is small because insoluble impurities are not the dominant aerosol component. It may have produced a slight warming of the snow surface (≈ 2 K). In the dust source regions, the optical depth would have been a maximum of 2 to 4 times the present value. The possible warming of the atmosphere in these regions is estimated at 3 K per day and should therefore be taken into account in paleoclimate reconstruction models.

Refractive Index and Size Distribution of Aerosols as Estimated from Light Scattering Measurements.

Abstract: Angular distributions of the intensity of light scattered by airborne particles were measured for both parallel and perpendicularly polarized components. A precision polar nephelometer was constructed for use of this study. The data were analyzed using a newly developed inversion library method to give a simultaneous estimate of the complex index of refraction m = mr − mii of aerosols and their size distribution, where mr is the real part and mi the imaginary part of the refractive index. Results of 302 measurements show that the monthly mean values of mr and mi vary within the range 1.47–1.57 and 0.009–0.037, respectively, depending upon the relative humidity. The size distribution of aerosols can be approximated by the log-normal distribution function; the mean radius and the standard deviation are found to be rg = 0.138 μm and σg = 2.56, respectively, as geometrical mean values for the whole data.

Measurements of the aerosol size distributions in the El Chichon cloud

Abstract: Three particle size spectrometers were flown aboard the NASA-U2 on numerous flights before and after the eruption of El Chichon to determine the effects of the eruption. Measurements of aerosol particles between 20° - 50° north latitude over the North American continent show strong orders of magnitude enhancements in number and mass. Our analyses and supporting measurements by others, indicate that the aerosol between 0.1 - 2.0 µm is largely H2SO4 while the aerosol larger than 2 µm is likely ash. Comparisons of measurements using a spectrometer with an aerodynamically sensitive (particle size sorting) inlet with a second one that operated “in situ”, and a third one that operated isokinetically, indicate that the larger ash particles are of low bulk density. Observations of particles as large as 30 µm four months after the eruption are only compatible with very low bulk densities. The H2SO4 droplet populations show decreasing number density with altitude but increasing mass. The distribution is largely bimodal with 0.4 and 1.2 µm modes typically observed. The mass is dominated by the 1.2 µm mode.

Grain growth in samples of aluminum containing alumina particles

Abstract: A study of the two-dimensional and three-dimensional grain size distributions before and after grain growth treatments has been made in samples having a range of oxide contents. In order to collect statistically useful amounts of data, an automatic image analyzer was used and the resulting data were subjected to a series of statistical tests which evaluate the difference between related distributions. Normal grain growth was observed in samples of the lowest oxide content; as the oxide level was increased, a significant narrowing of the grain size distribution was observed. In the latter samples the maximum or limiting grain size measured after prolonged heat treatment is approximately one half that predicted by Zener and is in broad agreement with the values calculated from the models due to Hillert and Gladman. Anomalous grain growth has been observed in samples where normal grain growth is restricted and where the initial grain size distribution is very wide.

Biaxially stretched polyester film

Abstract: PURPOSE: The titled film that is obtained by adding fine particles of a specific inorganic inert mix, thus being suitable for use as magnetic recording media, because of its high flatness, slipperiness, good rolling properties on film forming, resisting to wrinkling, low noise level as an electromagnetic conversion properties, running properties and durability CONSTITUTION: A polyester which is composed of difunctional acid components mainly containing aromatic dicarboxylic acids and of at least one of glycol components is combined with 001W030wt% of large particles (average particle size is 03W15 microns) of calcium carbonate whose particle size distribution ratio is 15W23 according to the equation I and 001W050wt% of small particles (average particle size is 01W05 micron) of anatase titanium dioxide whose particle size distribution ratio is 14W23 The ratio of average particle sizes between both particles is preferably in the range from 16 to 8 The surface roughness [CLL] and the running friction coefficient on the running surface is in such a range satisfying equations IIWV COPYRIGHT: (C)1984,JPO&Japio

Study of pressure drop, void fraction and relative permeabilities of two phase flow through porous media

Abstract: An experimental investigation of two phase flow through porous layers formed of non-heated glass particles (nominal diameter 1 to 6 mm) has been made. Particulate bed depths of 30 cm and 70 cm were used. The effect of particle size, particle size distribution and bed porosity on void fraction and pressure drop through a particulate bed formed in a cylindrical test section has been investigated. The superficial velocity of liquid (water) is varied from 1.83 to 18.3 mm/s while the superficial velocity of gas (air) is varied from 0 to 68.4 mm/s. These superficial velocities were chosen so that pressure drop and void fraction measurement could be made for the porous layer in fixed and fluidized states. A model based on drift flux approach has been developed for the void fraction. Using the two phase friction pressure drop data, the relative permeabilities of the two phases have been concluded with void fraction. The void fraction and two phase friction pressure gradient in beds composed of mixtures of spherical particles as well as sharps of different nominal sizes have also been examined. It is found that the models for single size particles are also applicable to mixtures of particles if amore » mean particle diameter for the mixture is defined.« less

Color photosensitive silver halide material

Abstract: PURPOSE:To improve the gradation of the highlighted part by adding specified phthalic esters to an emulsion layer contg. silver halide particles having a specified particle size distribution. CONSTITUTION:Phthalic esters represented by general formulaI(where each of R1 and R2 is 6-12 C alkyl, and they are identical with or different from each other) are added to an emulsion layer contg. silver halide particles having =95% of all the particles are distributed within + or -40% of the average particle size. The preferred average particle size is 0.2-0.9mum, and >0.9mum average particle size is not effective. When the C numbers of R1 and R2 are =13, the dispersion stability is reduced.

Particle Size Distribution and Its Relation to Sintering—A Case Study for UO2 Powders

Abstract: It is generally recognized that the particle size distribution (PSD) of powders plays a very significant role in powder compaction and sintering. However, particle size distribution data are generally presented in the form of one number (mean diameter). In the case of PSD data obtained by sedimentation, analysis of the whole curve reveals some interesting information. The type of information obtained by such an analysis and its application to an analysis of compaction and sintering is discussed using the case of uranium dioxide powders as an example.

X-ray diffraction analysis of airborne particulates collected by an Andersen sampler. Compound distribution vs. particle size.

Abstract: Commercially available Nuclepore and Fuji microfilters were used as the collection media in an Andersen sampler. After sampling, the filter with the particulates was dissolved in dichloromethane, centrifuged to reduce the amount of the filter material, and formed to a suitably small film for X-ray diffraction analysis. Preparation of the small-film sample, sample mounting on the diffractometer, recovery, reproducibility in the X-ray diffraction intensity, identification of compounds in the particulates, and construction of a compound distribution vs. particle size curve are described. The distribution curves of the compounds are also given for the particulates collected in dry and wet seasons as examples.

Sauce compositions containing agglomerated particles of specified size distribution

Abstract: Vegetable protein particle-containing sauces, such as spaghetti sauces, which are organoleptically superior to the same sauces containing real meat can be prepared by providing protein particles having a specified particle size distribution. This is preferably accomplished by agglomerating finely comminuted protein particles with binder in a heating step.

Measuring device of grain size

Abstract: PURPOSE:To obtain a high-practical device which obtain accurately a grain size distribution as an absolute value even when the number of scattered particles is large by detecting scattered light of laser light in a scattering optical path length area adjusted according to transmittivity due to a particle group to be measured. CONSTITUTION:End surfaces of the specific number of optical fibers 41-4n are arranged at intervals of an extremely fine angle DELTAtheta corresponding to a scatter angle theta on a photodetection system side isolated by glass 12 from the scattering optical path area, and an optical fiber 15 for measuring transmitted light is provided on an optical axis. Then, the transmittivity of laser light in the scattering optical path area of specific length to the particle group 3 to be measured is found through glass plates 11 and 12. Then the scattering optical length L is set and then a computer system 7 calculates a scattered light intensity distribution from the intensity of scattered light found at a position corresponding to the scatter angle theta respectively to calculate the grain size distribution from the scattered light intensity distribution according to the relation shown by a specific equation.

Deposition of Model Crud on Boiling Zircaloy Surfaces at High Temperature

Abstract: The deposition experiments were carried out under high pressure (7 MPa) at 285/sup 0/C using model compounds (..cap alpha..-hematite) to investigate the deposition process of crud on boiling surfaces. The effects of several factors, such as the diameter of the model particles (0.15 to 2.3 ..mu..m), pH (7 to 13), and heat flux of the heated surfaces (5 to 16 W/cm/sup 2/), on the deposition rate during the initial stage were investigated. It was found that the deposition rate of the hematite particle, having a narrow particle size distribution, strongly depends on the particle diameter and pH of the crud suspension. An explanation of these results was based on the assumption that the electrokinetic interaction between the particle and the surface plays an important role in the deposition process of the crud particles. Furthermore, it was found that the deposition rate of the hematite, having a narrow particle size distribution, deviates from the linear proportionality.

Measurements of Atmospheric Aerosols: Experimental Methods and Results of Measurements off the East Coast of the United States.

Abstract: : Accurate measurements of the size distribution of atmospheric aerosols in the size (radius) range from 0.006 to 2.2 micrometers made along the east coast of the United States--both at a shore site (Wallops Island) and from a ship within 300 km of the coast--are presented. Some measurements at Washington, D.C., are included to contrast urban aerosols with aged continental air off the east coast. As air advects from land to sea, there is a rather rapid decay of particles smaller than 0.05 micrometers during the first day or so. After this initial decay of small particles the size distribution was often found to remain remarkably stable for hours. Significant changes in the size distribution were often associated with changes in air masses and meteorological conditions. Some of the changes can be explained qualitatively. Others, such as a pronounced double peak which occurred occasionally in the fine-particle range, are difficult to understand. Measurements of the activation parameter for submicrometer particles were also made and yield values in the range of 0.1 to 0.55. Using the measured size distribution, electromagnetic extinction was calculated for the wavelength range 0.3 to 12 micrometers. The calculations compare favorably to the measured scattering coefficient at 0.55 micrometers in wavelength. Particles in the radius range 0.1 to 0.3 micrometer made the largest contribution to the total extinction at optical wavelengths on nearly all occasions.