Showing papers on "Particle-size distribution published in 1984"

Size spectra and aggregation of suspended particles in the deep ocean

Abstract: Work of the last 10 years has demonstrated that oceanic particle size distribution by volume tends to be flat at mid-water depths (equivalent to a cumulative particle number distribution with a slope of −3) and is peaked in nepheloid layers with active resuspension and in surface waters with active biological production. The observed loss of fine peaks from the suspensions to yield flat distributions requires aggregation of the material, as the fines settle slowly. Mechanisms leading to particle collision are examined; for interactions between particles of similar size, Brownian motion dominates below 1.5 to 8 μm. However, if large particles (such as ‘marine snow’) are present at realistic concentrations, they become important in the removal of fine particles by shear-controlled coagulation. The coagulation times calculated for shear are too long for steady state to be presumed while the size distributions evolve under the influence of coagulation mechanisms. Therefore suggestions that the flat size distributions are quasi-stationary results of shear-controlled coagulation are rejected, and the notion that there is sub-equal production of particles at different points in the spectrum is favoured. Such production and the subsequent scavenging of small particles by large settling ones confers great importance on components of biological origin in both providing elements of the total size spectrum and determining the distribution and sedimentation of others of lithogenic origin. In surface waters, filtration rates by zooplankton indicate that aggregation rates of particles above submicron sizes are biologically determined.

Basic Properties of Sand and Gravel Filters

Abstract: Laboratory experiments have shown that uniform filters will catch particles with diameter of about 0.11D15 when the particles are carried in suspension in seeping water. Smaller particles will be carried through the filter pores and larger particles will not enter. The main current filter criterion, D15/d85⩽5, is shown to be conservative, but not excessively. Its use should be continued. Filter criteria using the ratios D50/d50 and D15/d15 are not supported by experiments or theory. Filters of angular particles of crushed rock are as satisfactory as those of rounded alluvial particles. It is not necessary for the filter particle size distribution to have a shape generally similar to that of the base particle size distribution.

Log-normally preserving size distribution for Brownian coagulation in the free-molecule regime

Abstract: Coagulation of aerosol particles in the free-molecule regime has been studied theoretically by converting the governing partial integrodifferential equation into a set of two ordinary differential equations. The approach assumes that the size distribution of an aerosol attains or can at least be represented by a time-dependent log-normal distribution function during the coagulation process. The calculations have been performed and the results found to be in good agreement with results for previous theories. In addition, the following asymptotic size distribution function is found as an alternative solution for the self-preserving particle size distribution function for Brownian coagulation of an aerosol in the free-molecule regime: , where n is the particle size distribution function, N ∞ is the total number of particles, r is the particle radius, and rg∞ is the geometric mean particle radius. In terms of the parameters used by the self-preserving size distribution theory, the proposed distribution is wri...

Light scattering by size/shape distributions of soil particles and spheroids.

Abstract: A size/shape distribution of spheroids was chosen to approximate a group of micrometer sized soil particles whose angular light scattering patterns had been measured previously. The scattering properties of the randomly oriented spheroids were calculated using the T-matrix method. The largest soil particles, those accounting for ~30% of the total scattering, were not included in the spheroid distribution because of computer limitations. These calculations were made to (1) investigate how well the measured scattering by soil particles is approximated by a similar distribution of spheroids and (2) use the data for spheroids to estimate some scattering properties that were too difficult to measure when the soil particles were studied previously. The shapes of the measured angular scattering patterns are better approximated by the distribution of spheroids than by a distribution of spheres of equal surface area or of equal volume.

The effect of particle size on the electrical conductivity of CuCl (Al2O3) composites

Abstract: The conductivity of CuCl containing Al2O3 of 0.06, 0.3, 1, 3, 8, and 15 micron sized particles was measured between 25 and 390 C. Conductivity was enhanced for the 0.06 and 0.3 sized Al2O3 particles for temperatures below approximately 250 C. The maximum enhancement occurred at 10 m/o of 0.06 micron Al2O3 at 25 C. Uncertain degrees of agglomeration as well as the grain size of the matrix were found to be significant.

Flow of Suspensions Containing Particles of Two Different Sizes through a Capillary Tube. II. Effect of the Particle Size Ratio

Abstract: Effects of the larger‐to‐smaller particle size ratio α and mixing ratio of the particles on the relative apparent viscosity ητ of the suspensions were studied using a capillary viscometer. The decrease in ητ by the addition of a small amount of the smaller particles was remarkable in the low‐shear regime when α was larger than about 2.4 and the diameter ratio of the larger particle to tube was relatively large.

Particle reagent size distribution measurements for immunoassay

Abstract: A highly sensitive and rapid method for quantitatively assaying analytes in liquid media by directly measuring changes in particle size distribution of reagent particles having analyte insolubilized thereon in a system undergoing antibody-induced aggregation has been developed. The amount of analyte initially present can be determined by measuring the change in the distribution of particle size with time, the concentration of a particular size particle at a given time, the rate of formation of a particular size particle, or the steady-state maximum concentration for a particular size particle.

The Postdispersion Coalescence Phenomenon in Polymer-Polymer Blends

Abstract: Three novel experimental techniques have been developed to study the phase separation dynamics and morphology of polymer-polymer blends. Samples prepared from different materials by different methods appear to follow the same phase transformation behavior. The minor phase, dispersed as discrete particles, may change its phase morphology by aggregation and coalescence. The aggregation process involves the change in either particle location (small particles may translate) or particle geometry (to reduce interfacial area). Once the interparticle contact is effected, the flattened interface will break and allow for sintering of particles. The particle size distribution is more or less random and tends to broaden with time. The volume fraction of the second phase has a substantial effect on its growth rate. It has been demonstrated that a combination of hot-staged optical microscopy, transmission electron microscopy, high-speed cinematography, and the three novel sample preparation techniques facilita...

Method of manufacturing sintered ceramic body

Abstract: A sintered ceramic body is manufactured first by preparing a composition containing a binder and a ceramic powder having a particle size distribution given such that 0 to 1 weight % of ceramic particles with a particle size of less than 0.2 μm, 0 to 2 weight % of ceramic particles with a particle size of 0.2 μm to less than 0.5 μm, 5 to 15 weight % of ceramic particles with a particle size of 0.5 μm to less than 1.0 μm, 5 to 15 weight % of ceramic particles with a particle size of 1.0 μm to less than 1.5 μm, 5 to 15 weight % of ceramic particles with a particle size of 1.5 μm to less than 2.0 μm, and 50 to 80 weight % of ceramic particles with a particle size of not less than 2.0 μm. The prepared composition is then injection-molded into a predetermined shape. The binder is removed from the molded body, and the binder-free molded body is sintered.

Effect of relative humidity on the aerosol backscattering coefficient at 0.694- and 10.6-μm wavelengths

Abstract: The effect of relative humidity on the backscattering of 0.694- and 10.6-μm radiation by aerosol particles in the lower troposphere is modeled. Two models of particle composition are considered: (1) all particles are composed of a uniform mixture of water-soluble material, dustlike material, and soot (uniform internal mixture) and (2) pure soot particles coexist with particles which are mixtures of water-soluble and dustlike materials (external mixture of soot). The amount of soot ranges from 1% to 20% of the volume of the aerosol. Changes in relative humidity have a greater effect on the backscattering coefficient, βπ, at 0.694 μm than at 10.6 μm. If soluble material accounts for 30% of the volume of mixed particles and if an urban type aerosol size distribution is assumed, an increase in relative humidity from 0% to 99% results in an increase in βπ at 0.694 μm ranging from a factor of 5.7 for an external mixture containing 20% soot by volume to a factor of 15.6 in the case of a uniform internal mixture containing 20% soot. At 10.6 μm the increase in βπ ranges from a factor of 2.1 to a factor of 2.8. The backscatter-to-extinction relation for 0.694-μm radiation propagating through a region of varying relative humidity is also investigated.

Preparation of composite particle

Abstract: PURPOSE: To obtain a composite particle having appropriate surface characteristics, by applying compressive force and shearing shearing force to a mixture consisting of a particle I having a specific range of a particle size and particle size distribution and a particle II comprising an org. hihg-molecular substance different from that of the particle I and having a specific range of a particle size and particle size distribution. CONSTITUTION: A particle I, of which the particle size (R 1 ) is 1W500μm and the standard deviation of particle size distribution is equal to or less than ±40% of an average particle size, is mixed with a particle II, which comprises an org. high-molecular substance different from the material of the particle I and of which the particle size (R 2 ) is 0.05W10μm and the standard deviation of particle size distribution is equal to or less than ±40% of an average particle size, under a state substantially generating no pulverization. Subsequently, compressive force and shearing force are applied to the resulting mixture and plural particles II are secured to the surface of the particle I to obtain a composite particle. As the material of the particle I, an inorg. material and an org. high- molecular material are used. COPYRIGHT: (C)1986,JPO&Japio

Particle Size Measurement Using Chromatography

Abstract: I. INTRODUCTION A. Background and Overview Determination of the particle size (PS) and particle size distribution (PSD) is one of the most important aspects of the characterization of particulate systems, whether in a powdered, latex, or suspension form. The importance of particle size analysis to the various fields of particle science and technology rests on the wide range of properties which are directly relatable to the PS and PSD. These vary from fundamentally important phenomena such as the stability, light scattering, and viscosity behavior of particulate suspensions, to practically important properties such as the covering power, gloss, and surface protection characteristics of coatings and paints. The number of techniques available is enormous1, 2 and the particular method best suited to a given application will depend primarily on the size or size range in question and whether one is interested in determining an average size or the complete size distribution. A relatively recent review paper3 giv...

Numerical simulations of collisions in systems of non-identical particles

Abstract: The numerical simulations of 200 mutually colliding, non-identical particles indicate that if elasticity depends on the impact velocity, an equipartition of the random kinetic energy is possible if either the particle masses are close to each other, or the number of small particles significantly exceeds that of large particles. On the other hand, if the large particles dominate, the velocities of the smaller particles are at most a few times greater than those of the large ones. In the case of a constant coefficient of restitution no equipartition is observed.

Filler for heat-sensitive recording paper

Abstract: Particulate material suitable for use as a filler for the heat-sensitive recording layer of heat-sensitive recording paper comprises finely divided amorphous silica having a BET specific surface area of 10 to 100 m2/g and a bulk density of 0.14 to 0.30 g/cc, said finely divided amorphous silica having such a secondary particle size distribution that secondary particles having a size smaller than 4 µm, as measured by the centrifugal precipitation method, constitute at least 90% by weight of the total particles. A composite filler for the heat-sensitive recording layer of heat-sensitive recording paper comprises amorphous silica having the same BET specific surface area and bulk density and such a secondary particle size distribution that secondary particles having size smaller than 4 pm, as measured by the centrifugal precipitation method, constitute at least 70% by weight of the total particles, and fine particles of amino resin obtained by condensing substantially equimolar amounts of a functional amino group-containing component and a formaldehyde component in the presence of a catalyst and which has an oil absorption of 20 to 90 mi/100 g and a specific surface area smaller than 20 m2/g, at a weight ratio of amorphous silica: amino resin particles of from 90:10 to 10:90.

Toner application method and developer composition

Abstract: A method for applying a toner comprising: forming, in a container containing a toner and magnetic particles for application of the toner, a magnetic brush of the magnetic particles; circulating the magnetic particles in the container; and forming a thin layer of the toner electrically charged on the toner carrying member; wherein the magnetic particles have a particle size distribution of 30 wt. % or more in the range of 150 to 200 mesh and 5 wt. % or less of under 250 mesh, and the weight ratio of the toner to the magnetic particles is from 5:95 to 50:50 in the region where the magnetic brush is formed.

Electrode for fuel cell

Abstract: PURPOSE:To obtain an electrode with a wide reaction area, high mechanical strength, excellent electron conductivity, and low contact resistance by constituting a multi-layer structure with a layer formed by sintering a powder-like material and a layer formed by sintering a fiber-like material CONSTITUTION:A molding-organic polymer is added to nickel powder with the cumulative volume percentage of grain size distribution within a range of 10- 90% and a grain size of 10-20mum and thoroughly mixed, this mixed powder is applied on a nickel fiber sintered body, it is roller-molded, then it is burnt in the hydrogen atmosphere to obtain an electrode A with a porous two-layer structure Next, nickel chromium fibers are put in a mold and leveled, then nickel chromium powder with the cumulative volume percentage of grain size distribution of 10-90% and a grain size of 2-8mum is mounted on it with uniform thickness, it is pressure-molded into a plate shape and is burnt in the atmosphere containing hydrogen to obtain an electrode B with a porous two- layer structure The electrodes A, B thus obtained are put on both sides of a plate-like electrolyte layer X obtained by mixing together alkali metal or mixed carbonate powder and holding-ceramic powder, heating, pressurizing, and molding the mixture, then a unit cell is constituted

The influence of a fibrous diesel particulate trap on the size distribution of emitted particles

Abstract: Particle mass concentrations and size distributions have been measured upstream and downstream of a ceramic-coated metal fiber filter. The filter has been used to process the exhaust of a 1.5 liter light-duty indirect injection diesel engine. At light filter loadings, the collection efficiency was typically found to range from 50 to 60%. As the trap was loaded, the efficiency slowly increased to a maximum value between 70-80% and then slowly declined. At the same time, the pressure drop across this filter continously increased. The trap was periodically regenerated to prevent excessive pressure drop. When lightly loaded, the trap was found to reduce the particle concentration without having a significant impact on the size distribution. However, a heavily loaded trap significantly shifted the particle size distribution upward. Under some conditions, the trap actually generated coarse, greater than 1.0 ..mu..m, diameter, particles. The trap thus acts as a particle agglomerator. This behavior is explained in terms of collection, surface agglomeration, and subsequent reentrainment of the agglomerated material.

Penetration of submicron aerosols through high-efficiency air filters.

Abstract: Penetration through high-efficiency air filters was measured using dioctyl phthalate (DOP) particles and ambient particles. The tested filters were a Whatman GF/A filter and a Oshitari SO filter, one of the media used in high-efficiency particulate air (HEPA) filters. The particle concentration measurements were made with an automated diffusion battery (DB)/condensation nucleus counter (CNC) submicron-sizing system and a laser-particle spectrometer. It was found that the most penetrating particle sizes through both the GF/A filter and the SO filter were in a size range from 0.10 to 0.18 micron in diam. The values of penetration through the GF/A filter by two different particle-measuring methods, the combined CNC/DB system and the laser-particle spectrometer, were consistent with each other in the limited size range from 0.12 to 0.42 micron. No significant difference between the penetration curve of DOP particles and that of ambient particles was observed.

On the particle size distribution of hydrolyzed plutonium(IV) polymer

Abstract: Relative particle size distribution of plutonium polymer colloid and its aging effective were determined by using an ultracentrifuge. The distribution is not uniform. In the early stage of polymerization, very fine polymer particles of plutonium are formed. The fraction of the larger particles increases with aging.

Determination of aerosol size distribution from observation of the aureole around a point source. 2: Experimental.

Abstract: A theoretical basis is presented for a new method for determining the aerosol size distribution from aureole measurements around a point source. The method involves the determination of the angular scattering coefficient from radiance measurements at different observation angles between 1° and 10° around a source in the solar blind spectral region. The results are used to determine the aerosol size distribution by applying the Twomey-Chahine inversion algorithm. The derived size distribution has the desirable features of being accurate for large particles up to radii of 10 μm and being insensitive to their complex refractive index.