Showing papers on "Particle published in 1985"
TL;DR: In this article, the amount of particle crushing in a soil element under stress depends on particle size distribution, particle shape, state of effective stress, effective stress path, void ratio, particle hardness, and the presence or absence of water.
Abstract: In order to understand the physics of the strength and stress‐strain behavior of soils and to devise mathematical models that adequately represent such behavior, it is important to define the degree to which the particles of an element of soil are crushed or broken during loading. The amount of particle crushing in a soil element under stress depends on particle size distribution, particle shape, state of effective stress, effective stress path, void ratio, particle hardness, and the presence or absence of water. Data are analyzed for single mineral soils and rockfill‐like materials and equations are presented that can be used to estimate the total breakage expected for a given soil subjected to a specified loading.
955 citations
386 citations
TL;DR: Sedimentation, wherein particles fall under the action of gravity through a fluid in which they are suspended, is commonly used in the chemical and petroleum industries as a way of separating particles from fluid as discussed by the authors.
Abstract: Sedimentation, wherein particles fall under the action of gravity through a fluid in which they are suspended, is commonly used in the chemical and petroleum industries as a way of separating particles from fluid, as well as a way of separating particles with different settling speeds from each other. Examples of such separations include dewatering of coal slurries, clarifi cation of waste water, and processing of drilling and mining fluids containing rock and mineral particles of various sizes. The separation of different particles by sedimentation is also the basis of some laboratory techniques for determining the distribution of particle sizes in a particulate dispersion. Owing to the significance of the subject, there have been numerous experimental and theoretical investigations of the sedimentation of par ticles in a fluid. One of the earliest of these is Stokes' analysis of the translation of a single rigid sphere through an unbounded quiescent Newtonian fluid at zero Reynolds number, which led to his well-known law (0) _ 2a2(p. p )g u 9J.l ' (1.1)
374 citations
293 citations
TL;DR: In this paper, an analysis of the electrophoretic motion of a charged nonconducting sphere in the proximity of rigid boundaries is presented for three boundary configurations: a single flat wall, two parallel walls, and a long circular tube.
Abstract: An analysis is presented for electrophoretic motion of a charged non-conducting sphere in the proximity of rigid boundaries. An important assumption is that κa → ∞, where a is the particle radius and κ is the Debye screening parameter. Three boundary configurations are considered: single flat wall, two parallel walls (slit), and a long circular tube. The boundary is assumed a perfect electrical insulator except when the applied field is directed perpendicular to a single wall, in which case the wall is assumed to have a uniform potential (perfect conductor). There are three basic effects causing the particle velocity to deviate from the value given by Smoluchowski's classic equation: first, a charge on the boundary causes electro-osmotic flow of the suspending fluid; secondly, the boundary alters the interaction between the particle and applied electric field; and, thirdly, the boundary enhances viscous retardation of the particle as it tries to move in response to the applied field. Using a method of reflections, we determine the particle velocity for a constant applied field in increasing powers of λ up to O(λ6), where λ is the ratio of particle radius to distance from the boundary. Ignoring the O(λ0) electro-osmotic effect, the first effect attributable to proximity of the boundary is O(λ3) for all boundary configurations, and in cases when the applied field is parallel to the boundaries the electrophoretic velocity is proportional to ζp − ζw, the difference in zeta potential between the particle and boundary.
278 citations
TL;DR: A search for axion-like particles was performed at the 400 GeV proton beam-dump experiment at CERN as mentioned in this paper, but no evidence for the existence for such particles was found in this experiment.
275 citations
TL;DR: In this paper, the fraction of atoms at the surface of small metal particles increases as their size diminishes in the range 10 to 2 nm, and it is shown that certain classes of reaction may be designated as "structure-insensitive" in that their rates depend only minimally on particle size.
226 citations
TL;DR: In this article, a computer-aided particle tracking facility was used to measure solids motion in a fluidized bed, where a radioactive tracer particle was mixed with the solids in the bed and the gamma radiation from the tracer was continuously monitored by a large number of scintillation detectors located around the bed.
Abstract: Measurements of solids motion in a fluidized bed have been made in a computer-aided particle tracking facility. A radioactive tracer particle, dynamically identical to the solid particles to be studied, was mixed with the solids in thebed. The gamma radiation from the tracer was continuously monitored by a large number of scintillation detectors located around the bed, providing information on the tracer's instantaneous location. Prudent use was made of the purposely introduced redundant distance data to achieve improved accuracy. The recognition of the existence of secondary emission due to the interaction of the primary radiation and other system materials and the subsequent devising of a scheme to mitigate its effect contribute much to the success. Results for a bed with a uniform air distributor plate show the existence of two counter-rotating toroidal vortices whose relative sizes and strengths vary with the fluidizing velocity. Fluctuating motions at low frequencies ranging from 1.6 to 16 Hz have been observed at various locations in the bed.
212 citations
TL;DR: In this paper, the impactor characteristics of impactors with round or rectangular nozzles have been determined by the numerical solution of the Navier-Stokes equations and of the equation of motion of the particles.
Abstract: The characteristics of impactors with round or rectangular nozzles have been determined by the numerical solution of the Navier-Stokes equations and of the equation of motion of the particles. The sensitivity of this solution to the system of grid lines was investigated by decreasing the spacing between them; these studies yielded sharper curves and higher √St50 for finer grids. The particle trajectory calculation program included an empirical ultra-Stokesian drag coefficient and a facility for handling particle interception. Studies comparing the results of runs made using the ultra-Stokesian drag law with those assuming Stokes law indicated that the latter underpredicts the √St20 by 5 to 10%. The influence of particle interception was found to be small except at very low Reynolds numbers, the characteristics for which demon strated low-efficiency tails. Dimensional analysis of the impactor system required the introduction of a second dimensionless quantity (in addition to the St) to char acterize the pa...
196 citations
TL;DR: The results of the first extended ion probe study of interplanetary dust particles (IDPs) are reported in this article, and the analytic procedures and current limits on the precision and accurary of isotopic measurements of light elements are discussed in considerable detail.
188 citations
TL;DR: In this article, the authors describe the results of tests conducted on a Stairmand high-efficiency cyclone, which was pilot-plant scale with a design air flow of 0.139 m3/s (300 cfm).
Abstract: This paper describes the results of tests conducted on a Stairmand high-efficiency cyclone. The cyclone was pilot-plant scale with a design air flow of 0.139 m3/s (300 cfm). Collection efficiency and pressure drop were measured over a range of air flows at ambient temperature and pressure. An oil mist was used as a test aerosol because it consisted of spherical drops of uniform density unlikely to bounce or reentrain after striking the cyclone wall. At each air flow, a fractional efficiency curve (collection efficiency versus particle diameter) was determined. Experimental curves were compared with fractional efficiency curves generated by several cyclone efficiency theories. Over the range of particle sizes measured (1 to 7 μm), the predictions of a modified version of Barth's theory and the Leith-Licht theory were closest to experimental results.
TL;DR: In this article, an analysis of the forces of adhesion of small particles to surfaces, most specifically as applied to semiconductor surfaces, was carried out and it was shown that the van der Waals forces can increase as a function of time due to particle and/or surface deformation which increases the contact area.
Abstract: This paper constitutes an analysis of the forces of adhesion of small particles to surfaces, most specifically as applied to semiconductor surfaces. The primary forces of adhesion of small, less than 50 μm diam particles on a dry surface are van der Waals forces. These van der Waals forces of adhesion can increase as a function of time due to particle and/or surface deformation which increases the contact area; micron‐size particles can be held to surfaces by forces exceeding 100 dyn, which corresponds to pressures of 109 dyn/cm2 or more. Total forces of adhesion for micron‐size particles exceed the gravitational force on that particle by factors greater than 106. Electrostatic forces only become important and predominate for particles larger than 50 μm diam. Immersion of the adhered particle system can, in some cases, greatly reduce the total adhesion force, first by shielding of the electrostatic and van der Waals attractions, and also by adding double layer repulsion because of dipolar alignment of liquid molecules or dissolved ions at the surfaces. Double layer interactions may, however, also add to the attractive forces if dipoles align properly for attraction. An important consideration is the possibility that if the particles are not removed by the liquid immersion, then a liquid bridge can be formed by capillary action between the particle and surface upon removal from the liquid. This would add a very large capillary force to the total force of adhesion. This capillary force has been shown to remain, in some cases, even when the system is baked at above the liquid boiling point for more than 24h. Removal of these small particles from surfaces is in theory possible but is in practice extremely difficult. It is clear that emphasis should be placed on prevention of particle deposition rather than on counting on achieving subsequent removal.
TL;DR: In this paper, the thickness, length, width, area and perimeter of 575 particles from 16 aqueously dispersed samples of a variety of interstratified clays, smectites and illite have been recorded using TEM techniques.
Abstract: A B S T R A C T : The thickness, length, width, area and perimeter of 575 particles from 16 aqueously dispersed samples of a variety of interstratified clays, smectites and illite have been recorded using TEM techniques. Complete dispersion of the clay material was achieved by saturating the clay with either Na § or Li +, removal of excess ions by dialysis, and isolation of the <0.1 or <0.2/~m fraction by centrifugation. The samples have mean maximum dimensions of 1900 to 90 nm and the dispersed system can be considered as colloidal in nature. The mean thickness of the clays is about 1 nm for smectites, corresponding to that of elementary 2:1 silicate layers, from 1.9 to 4.9 nm for the interstratified clays, and 9 nm for illite. From these data the volume, total surface area and other parameters have been calculated and compared with independent determinations of surface area and CEC. The total surface area by TEM, assuming a density of 2.6 g/cm 3, varies from ~675 m2/g for smectites to 86 mZ/g for illite, and is inversely proportional to the mean particle thickness. The charge density of monovalent cation exchange sites on the surface of the particles as determined for nine of the samples varies from 0.54 to 1.16 nm2/site. The particle-thickness distribution data can be used to calculate interstratified XRD layer sequence probabilities and composition parameters, and agree with XRD data for interstratified clay with <60% illite layers. The thickness data also provide a rationale for the interpretation of TEM lattice-fringe images. Relationships between the particle area, length, thickness and volume are shown to be potentially useful in assessing the mechanism(s) of crystal growth of these extremely small phyllosilicate particles.
TL;DR: In this paper, an AT-cut quartz resonator with metal electrodes as the substrate was used to determine the bonding force between particle and substrate, which was determined by the bonding forces of Au spheres on etched Au electrodes.
Abstract: We use an AT‐cut quartz resonator with metal electrodes as the substrate. The material properties of the quartz are well characterized, and the resonant frequency can be determined accurately (1 part in 108 or better). When a particle was placed on the electrode, the resonant frequency increased, contrary to mass loading theory. If the particle‐resonator system is modeled mechanically as a coupled oscillator system, indeed the resonant frequency should increase. The increase is determined by the bonding force constant between particle and substrate, which we calculate. Experimental data on the autohesion force constants of Au spheres on etched Au electrodes in air is presented.
TL;DR: In this article, the authors evaluated portable air cleaning devices for control of indoor concentrations of respirable particles using in situ chamber decay tests, and found that particle size distribution was log normal with a count median diameter of 0.15 μm and a geometric standard deviation of 2.0.
TL;DR: In this article, the relative importance of various effects on particle motion was assessed in the context of thermal plasma processing of materials, and the results indicated that the correction term required for the viscous drag coefficient due to strongly varying properties is the most important factor; non-continuum effects are important for smaller particles and/or reduced pressures.
Abstract: A particle injected into a thermal plasma will experience a number of effects which are not present in an ordinary gas. In this paper effects exerted on the motion of a particle will be reviewed and analyzed in the context of thermal plasma processing of materials. The primary purpose of this paper is an assessment of the relative importance of various effects on particle motion. Computer experiments are described, simulating motion of a spherical particle in a laminar, confined plasma jet or in a turbulent, free plasma jet. Particle sizes range from 5 to 50 µm, and as sample materials alumina and tungsten are considered. The results indicate that (i) the correction term required for the viscous drag coefficient due to strongly varying properties is the most important factor; (ii) non-continuum effects are important for particle sizes <10 µm at atmospheric pressure and these effects will be enhanced for smaller particles and/or reduced pressures; (iii) the Basset history term is negligible, unless relatively large and light particles are considered over long processing distances; (iv) thermophoresis is not crucial for the injection of particles into thermal plasmas; (v) turbulent dispersion becomes important for particle <10 µm in diameter.
TL;DR: In this article, a theoretical description for plasmon resonances of such particles is developed, which includes the effects of finite particle size and of dipolar interactions between the particles, and the role of particle interactions in shifting and broadening the plasman resonances is discussed.
Abstract: The enhancement of electromagnetic processes on metallic surfaces is discussed in view of applications in surface photochemistry and surface analytics. The strongest enhancements are found on substrates that consist of discrete metal particles. A theoretical description for plasmon resonances of such particles is developed, which includes the effects of finite particle size and of dipolar interactions between the particles. Spheroidal particles with dimensions in the range 10–100 nm are found to produce the strongest enhancements; the role of particle interactions in shifting and broadening the plasmon resonances is discussed. Potential applications of the amplified local fields for chemical processes include photochemistry, chemical vapour deposition, and etching. Storage of excitation energy in the bonds to be transformed is necessary for these reactions. The enhanced excitation rate is competing with radiationless energy transfer to the substrate. This rate must be reduced by a spacer layer between met...
01 Jan 1985
TL;DR: In this article, the rule governing many-body wave functions for particles obeying fractional statistics in two-dimensional space was obtained, which generalizes and continuously interpolates the usual symmetrization and antisymmetric.
Abstract: We obtain the rule governing many-body wave functions for particles obeying fractional statistics in two (space) dimensions. It generalizes and continuously interpolates the usual symmetrization and antisymmetrization. Quantum mechanics of more than two particles is discussed and some new features are found.
TL;DR: In this paper, a gas-particle mixture is initiated by a shock wave, which is decelerated by the inertia and heat capacity of the particles, and the frozen pressure jump is decaying.
Abstract: A shock wave which is incident onto a gas-particle mixture or initiated within such a mixture needs a certain distance to reach a constant velocity. This effect is due to the inertia and the heat capacity of the particles. In general the shock wave is decelerated and the frozen pressure jump is decaying.
TL;DR: The adsorption isotherm of 125I-protein A onto gold particles was studied quantitatively with gold sols buffered at pH 4–7.1 and maximum binding of the complex to immobilized IgG occurred with particles labelled with at least 9 molecules of protein A.
Abstract: Colloidal gold complexes with protein A are extensively used in immunocytochemistry as secondary reagents for the localization of antigens. However detailed information on the process and extent of adsorption of protein A onto gold particles, the optimal condition of preparation and the stability of such complexes are lacking. The adsorption isotherm of 125I-protein A onto gold particles (11.2 nm in diameter) was studied quantitatively with gold sols buffered at pH 4-7. At low coverage of the particles, the isotherm was independent of pH. However in the presence of a large excess of protein A, the highest coverage was obtained with a gold sol buffered at pH 5.1, the isoelectric point of the protein. The association constant was decreased at high coverage of the particles. Maximum binding of the complex to immobilized IgG occurred with particles labelled with at least 9 molecules of protein A. The complex was stable under storage with up to 12 molecules adsorbed per particle. At high coverage (26 molecules per particle), a progressive loss of protein A was observed. The optimum condition for preparing the complex are reported.
Patent•
23 Apr 1985TL;DR: In this article, a self-supporting structure of high compressive strength is described for Whetlerite carbon particles, in which the self support structure substantially eliminates the formation of carbon fines while retaining the adsorption characteristics of the carbon particles.
Abstract: A process for immobilizing reactive Whetlerite carbon particles and forming a self-supporting structure of high compressive strength therefrom is described in which the self-supporting structure substantially eliminates the formation of carbon fines while retaining the adsorption characteristics of the carbon particles. The process for immobilizing the adsorbent carbon particles in the self-supporting structure comprises the steps of: (a) mixing in an environment having a relative humidity of less than about 35 percent, Whetlerite carbon particles, a major portion of which has particle sizes in the range of from about 200 to about 2,000 microns, with a powdered polymeric binding material, preferably a thermoplastic material having a solid-liquid transition stage, in an amount of about 5 to about 20 percent by weight, based on the weight of the total mixture, a major portion of the particles of the polymeric binding material having particle sizes in the range of about 8 to about 30 microns, to form a mixture of the carbon particles partially coated with the polymeric binding material; (b) placing the mixture in a container of a desired shape; and (c) applying a pressure of up to about 400 psi while the mixture is contacted with an inert gas and is at an elevated temperature, this temperature being near the solid-liquid transition stage (when the polymeric binding material is a thermoplastic material), thereby forming the structure and immobilizing the particles.
01 Jan 1985
TL;DR: In this paper, the rate of burning of small concentrations of fine graphite powder has been measured in a flat, laminar weak methane-air flame at sub-atmospheric pressure.
Abstract: The rate of burning of small concentrations of fine graphite powder has been measured in a flat, laminar weak methane-air flame at sub-atmospheric pressure. Measurements were obtained with a laser doppler system, that not only measured particle velocities, but also particle concentrations and size distributions through the flame. Particle temperatures were measured by the two colour method and gas temperatures with thermocouples. An appreciable increase in the oxidation rate was observed in the flame reaction zone, attributable to the reaction zone transient species, O, H, and OH. A computational study of the flame, with comprehensive chemical kinetics and detailed representation of the transport fluxes, yielded the concentrations of all species through the flame. The observed rates of graphite oxidation are kinetically explained in terms of rates of reaction of all species with graphite. The observed elevations of particle above gas temperature in the reaction zone are higher than would be expected if the heating were due only to reactions in which the carbon surface was attacked. Amongst other possible explanations there is that of heating by exothermic radical recombination on the carbon surface.
TL;DR: In this paper, a cooperative climb over groups of particles leads to a resistance to deformation, rather than a threshold stress that is insensitive to the particle size but which depends strongly on applied stress.
TL;DR: In this article, a laboratory and field study was performed to assess the contribution to visibility reduction of both light scattering and absorption by air pollutant particles and gases, focusing on minimizing sampling artifacts for nitrate and sulfate since previous visibility studies were generally subject to substantial errors from these sources.
TL;DR: In this article, the experimental and theoretical light flux-vs-time curves are compared by means of the Mie theory to determine particle size and number concentration in colloidal systems.
TL;DR: Particle size effects on magnetic properties of BaFe12−2xTixCoxO19 fine particles were investigated in this article, where the existence of a nonmagnetic thin layer, several angstroms in thickness, on the surface of the particles was explained.
Abstract: Particle size effects on magnetic properties of BaFe12−2xTixCoxO19 fine particles were investigated. Saturation magnetization of these particles decreased with decreasing particle size. This result can be explained with the existence of a nonmagnetic thin layer, several angstroms in thickness, on the surface of the particles. Particle size dependence of coercivity for these particles, below 1000 A in size, follows the superparamagnetism theory. For the decrease in coercivity above 2000 A, multidomain nucleation is inferred as one of the possible mechanisms. Particle shape dependence of coercivity is well explained with the coherent rotation model, considering shape anisotropy.
Patent•
24 Dec 1985
TL;DR: In this paper, a method of forming a high-strength proppant that resists the deleterious effects of high temperature saline environments characterized by the steps of form a plurality of particles of propping agent; and coating particles with a thin high strength covering in a fluidized bed employing chemical vapor deposition to deposit a coating substantially uniformly over all the exposed surfaces of the particles to increase durability and resistance to hot saline environment.
Abstract: What is disclosed is a method of forming a high-strength proppant that resists the deleterious effects of high temperature saline environments characterized by the steps of forming a plurality of particles of propping agent; and coating particles with a thin high-strength covering in a fluidized bed employing chemical vapor deposition to deposit a coating substantially uniformly over all the exposed surfaces of the particles to increase durability of the particles, as well as their strength and resistance to the deleterious effects of hot saline environment. Preferably, each particle has at least one passageway formed directly therethrough for increased permeability once deposited.
TL;DR: In this paper, an enhanced energy transfer between donor-acceptor pairs within a single aerosol particle was demonstrated for the first time, and the overall energy transfer within a particle 10 μm in diameter was found to exceed conventional dipole-dipole transfer by more than a factor of 10 2.
TL;DR: In this paper, the tensile strength and packing density of powder compacts containing submicron particles were derived using Hamaker's expression for the van der Waals force and the law of corresponding states, which is used to evaluate an energy parameter ϵ o for a given powder on an absolute scale.
TL;DR: In this paper, the authors evaluated the potential of hydrothermal plumes as particle transport agents and mapped their distribution along and across the 80-100m-deep axial valley of the southern Juan de Fuca Ridge in the north-east Pacific Ocean (∼44°30′ N, 130° W).
Abstract: Hydrothermal particles originate in buoyant plumes emanating from seafloor thermal vents1–4 and accumulate as metalliferous sediments found along oceanic spreading centres5–7. Observational evidence of the transport pathway of hydrothermal particles is scarce, however, and the structure, extent and particle concentrations of hydrothermal plumes remain largely conjectural. To evaluate the potential of hydrothermal plumes as particle transport agents, we mapped their distribution along and across the 80–100-m-deep axial valley of the southern Juan de Fuca Ridge in the north-east Pacific Ocean (∼44°30′ N, 130° W), an area of known hydrothermal activity8–11. Continuous light-scattering measurements, reported here, defined numerous particle plumes centred 30–120 m above bottom (m.a.b.); elemental analysis of the plume particles and the theta (potential temperature)–S (salinity) signatures of the plume water verified their hydrothermal origin. Concentrations of hydrothermal particles remained elevated at ridge-crest depths at least 100 km from the ridge, indicating distant off-axis dispersal of hydrothermal emissions.