Showing papers on "Particle-size distribution published in 1997"
TL;DR: In this paper, the grain size of soil and sediment samples is determined by the sieve method for the coarse fractions and by the pipette method, based on the Stokes sedimentation rates, for the fine fractions.
Abstract: Classically, the grain size of soil and sediment samples is determined by the sieve method for the coarse fractions and by the pipette method, based on the ‘Stokes’ sedimentation rates, for the fine fractions. Results from the two methods are compared with results from laser diffraction size analysis, which is based on the forward scattering of monochromatic coherent light. From a point of view of laboratory efficiency, the laser sizing technique is far superior. Accuracy and reproducibility are shown by measurements on certified materials. It appears that laser grain size measurements of certified materials correspond very well with the certificated measurements. Tests were also done on a set of randomly selected sediments of fluvial, aeolian and lacustrine origin. Except for the (<2 μm) clay fraction, there is a coarsening of the mean diameter of one to two size classes (0.25 ɛ), caused by the non-sphericity of the particles. The platy form of the clay particles induces considerable differences (eight size classes) between pipette and laser measurements: the <2 μm grain size, defined by the pipette method corresponds with a grain size of 8 μm defined by the Laser Particle Sizer for the studied sediments. Using a higher grain size level for the clay fraction, when laser analysis is applied, enables workers in the geological and environmental field to compare classical pipette analysis with a laser sizing technique.
990 citations
TL;DR: It is proposed that epidemiologic studies using PM10 or TSP may provide more useful information on the acute health effects of fine particles than coarse particles, and that a PM measurement at a central monitor can serve as a better indicator of the community-wide concentration offine particles than of coarse particles.
Abstract: Fine particles and coarse particles are defined in terms of the modal structure of particle size distributions typically observed in the atmosphere. Differences between the various modes are discussed. The fractions of fine and coarse particles collected in specific size ranges, such as total suspended particulate matter (TSP), PM10, PM2.5, and PM(10-2.5), are shown. Correlations of 24-h concentrations of PM2.5, PM10, and PM(10-2.5) at the same site show that, in Philadelphia and St. Louis, PM2.5 is highly correlated with PM10 but poorly correlated with PM (10-2.5). Among sites distributed across these urban areas, the site-to-site correlations of 24-h PM concentrations are high for PM2.5 but not for PM(10-2.5). This indicates that a PM measurement at a central monitor can serve as a better indicator of the community-wide concentration of fine particles than of coarse particles. The fraction of ambient outdoor particles found suspended indoors is greater for fine particles than for coarse particles because of the difference in indoor lifetimes. Consideration of these relationships leads to the hypothesis that the statistical associations found between daily PM indicators and health outcomes may be the result of variations in the fine particle component of the atmospheric aerosol, not of variations in the coarse component. As a result, epidemiologic studies using PM10 or TSP may provide more useful information on the acute health effects of fine particles than coarse particles. Fine and coarse particles are separate classes of pollutants and should be measured separately in research and epidemiologic studies. PM2.5 and PM(10-2.5) are indicators or surrogates, but not measurements, of fine and coarse particles.
577 citations
TL;DR: In this article, the hygroscopic properties of freshly produced carbon and diesel soot particles at subsaturations (i.e. at relative humidity < 100%) were investigated. And the results showed that freshly emitted combustion particles are unlikely to act as cloud condensation nuclei whereas an aging of the particles will enhance their nucleation ability.
493 citations
TL;DR: In this article, the authors measured physical characteristics of solids transported in lateral pavement sheet flow from a heavily traveled urban roadway in Cincinnati and sorted solids according to particle size distributions.
237 citations
TL;DR: In this article, the authors used pyroclasts from remelted volcanic rock (olivine-melilitite) to enhance interpretation of fragmentation mechanisms during explosive volcanism.
Abstract: With the aim to enhance interpretation of fragmentation mechanisms during explosive volcanism from size and shape characteristics of pyroclasts experimental studies have been conducted using remelted volcanic rock (olivine-melilitite). The melt was fragmented and ejected from a crucible by the controlled release of pressurized air volumes (method 1) or by controlled generation of phreatomagmatic explosions (Molten Fuel Coolant Interaction (MFCI); method 2). Both methods were adjusted so that the ejection history of the melt was identical in both cases. The experiments demonstrate that exclusively during MFCI, angular particles in the grain size interval 32 to 130 μm are generated that show surface textures dominated by cracks and pitting. The physical process of their generation is described as a brittle process acting at cooling rates of >106 K/s, at stress rates well above 3 GPa/m2, and during ∼700 μs. In this time period the emission of intense shock waves in the megahertz range was detected, releasing kinetic energy of >1000 J. By both experimental methods, three more types of particles were produced in addition, which could be identified and related to the acceleration and ejection history of the melt: spherical particles, elongated particles, and Pele's hair. Abundance and grain size distribution of these particles were found to be proportional to the rate of acceleration and the speed of ejection but were not influenced by the experimental method used. Pele's hair occurred at ejection speeds of >75 m/s.
209 citations
TL;DR: In this paper, the authors evaluated the applicability of fractal dimensioning techniques to quantification of both physical particle roughness and grain size distribution of granular soil, and the results confirm the importance of differentiating between textural and structural aspects of roughness.
205 citations
TL;DR: In this article, the authors determined the daily mean size distributions of ambient particles in Erfurt, a city in Eastern Germany, for 180 days during the winter 1991/92 daily mean sizes.
143 citations
TL;DR: In this article, size-resolved diesel particle chemistry has been examined by collecting particles directly from a diesel car exhaust with a low-pressure impactor, and the impactor samples have been weighed and analyzed chemically to construct continuous size distributions for selected compounds present in the particulate phase.
Abstract: Diesel vehicles are a major source of fine, atmospheric particulate matter in urban environments. The influences diesel particles exert on solar radiation, on atmospheric chemistry, and on humans depend crucially on the size and chemical character of these particles. In this work, size-resolved diesel particle chemistry has been examined by collecting particles directly from a diesel car exhaust with a low-pressure impactor. The impactor samples have been weighed and analyzed chemically to construct continuous size distributions for selected compounds present in the particulate phase. Submicron diesel-particle mass size distributions displayed three log-normal modes that were centered at 0.09, 0.2, and 0.7−1 μm of particle aerodynamic diameter (EAD) and that had average geometric standard deviations of 1.34, 1.61, and 1.34, respectively. The lowest two modes had approximately the same particulate mass, whereas over 80% of the number of particles were estimated to be found in the mode around 0.1 μm. The th...
131 citations
TL;DR: Matrices designed for fluidized-bed adsorption should have small particle diameter and increased mean particle density to ensure small diffusion path length in the particle and a high interstitial velocity to improve film mass transfer.
Abstract: The influence of matrix properties and operating conditions on the performance in fluidized-bed adsorption has been studied using Streamline diethyl-aminoethyl (DEAE), an ion exchange matrix based on quartz-weighted agarose, and bovine serum albumin (BSA) as a model protein. Three different particle size fractions (120-160 microm, 120-300 microm, and 250-300 microm) were investigated. Dispersion in the liquid phase was reduced when particles with a wide size distribution were fluidized compared to narrow particle size distributions. When the mean particle diameter was reduced, the breakthrough capacities during frontal adsorption were enlarged due to a shorter diffusion path length within the matrix. At small particle diameters the effect of film mass transfer became more relevant to the adsorption performance in comparison to larger particles. Therefore matrices designed for fluidized-bed adsorption should have small particle diameter and increased mean particle density to ensure small diffusion path length in the particle and a high interstitial velocity to improve film mass transfer. Studies on the influence of sedimented matrix height on axial mixing showed an increased Bodenstein number with increasing bed length. Higher breakthrough capacities were also found for longer adsorbent beds due to reduced dispersion and improved fluid and particle side mass transfer. With increasing bed height the influence of flow rate on breakthrough capacity was reduced. For a settled bed height of 50 cm breakthrough capacities of 80% of the equilibrium capacity for flow rates varying from 3 to 9 cm/min could be achieved.
124 citations
TL;DR: In this article, the relationship between emissions of particulates and gaseous compounds was studied; morphology and size distribution of submicron particles were investigated; and the relative coverage of the particle surface with PPAHs was found to increase strongly for operation with reduced combustion air supply.
Abstract: In order to investigate properties of fine particles emitted by wood burners, different methods were applied. The relationship between emissions of particulates and gaseous compounds was studied; morphology and size distribution of submicron particles were investigated. The particles were found to be compact structures with fractal-like dimen sions close to three; they contained low mass fractions of volatile compounds. It was shown that the operating conditions, i.e., the amount of combustion air supply, had a strong impact on the particle size distribution and the emis sion of particle-bound polycyclic aromatic hydrocarbons (PPAHs). Moreover, the relative coverage of the particle surface with PPAHs was found to increase strongly for operation with reduced combustion air supply.
112 citations
TL;DR: In this article, the events occurring in a clear TPA-silicalite-1 precursor solution, hydrothermally treated at 70°C, were monitored in situ by dynamic light scattering using a high-effect laser light source.
Book•
01 Jan 1997
TL;DR: In this article, permeametry and gas diffusion are used to determine pore size distribution by gas adsorption, and surface area determination by mercury porosimetry.
Abstract: Volume 1: Permeametry and gas diffusion. Surface area determination by gas adsorption. Determination of pore size distribution by gas adsorption. Pore size determination by mercury porosimetry. Other methods for determining surface area. Volume 2: Powder sampling. Data presentation and interpretation. Particle size by image analysis. Particle size analysis by sieving. Fluid classification. Interaction between fluids and particles. Sedimentation theory. Sedimentation methods of particle size measurement. Stream scanning methods of particle size measurement. Field scanning methods of particle size measurement. Industrial applications of particle size measurement. Appendix: Manufacturers and suppliers. Author index. Subject index.
TL;DR: In this article, the size distributions and hygroscopic growth spectra of aerosol particles were measured during the GCE cloud experiment at Great Dun Fell in the Pennine Hills in northern England.
TL;DR: In this article, the authors developed and evaluated ambient fine particle concentrators for conducting animal and human exposure studies, which utilized the technology of virtual impactors to concentrate particles in the range 0.15 -2.5 μm.
TL;DR: In this paper, the authors present results from a study showing the first on-line measurement of the size and chemical composition of individual particles emitted in automobile exhaust, and demonstrate the potential of using ATOFMS for analyzing vehicular exhaust in an on-online matter.
Abstract: This paper presents results from a study showing the first on-line measurement of the size and chemical composition of individual particles emitted in automobile exhaust. Particles sampled directly from the exhaust pipes of a number of vehicles upon startup were analyzed using aerosol time-of-flight mass spectrometry (ATOFMS). Both organic and inorganic chemical species including lead, cerium, platinum, molybdenum, calcium, and sodium were observed in individual exhaust particles. In general, a qualitative correlation exists between particle size and composition, typified by the presence of predominately organic species in particles in the fine size mode and inorganic species in particles in the coarse size mode. This study demonstrates the potential of using ATOFMS for analyzing vehicular exhaust in an on-line matter. Ultimately, ATOFMS can be used as a real-time monitor, characterizing particles produced from vehicles under a variety of well-defined operating conditions that will allow for further development of the understanding of particle formation and reaction processes. Furthermore, determination of chemical tracers in individual exhaust particles will allow for more accurate source allocation of atmospheric particles. (A)
TL;DR: In this article, the particle size distribution (PSD) was modelled in two portions, below and above 5 μm, using two types of equation: a power law (Pareto distribution) and an exponential law.
TL;DR: In this paper, an analytical solution to the Brownian coagulation of aerosol particles in the low Knudsen number regime is presented which provides time evolution of the particle size distribution.
TL;DR: In this article, the size distribution of suspended particulate matter in estuaries and coastal waters is determined in-situ using a focused beam reflectance (FBR) system.
TL;DR: In this article, the size distributions of ammonium and sulfate ions measured in this work were compared with those determined about 30 years ago: a decrease in the absolute concentration and an increase in the mass median diameter of both ions have been observed.
TL;DR: In this article, the authors focus on particle size distribution, fluidity, charging characteristics and their effects on the first pass transfer efficiency of powder coating and demonstrate the importance of characterizing physical parameters and control techniques to achieve desirable performance.
Patent•
30 Jul 1997
TL;DR: In this paper, a nonaqueous-electrolyte secondary cell has a negative electrode made of a carbon material which can be doped with lithium and from which dopant lithium can be removed.
Abstract: A nonaqueous-electrolyte secondary cell having a negative electrode made of a carbon material which can be doped with lithium and from which dopant lithium can be removed, a positive electrode, a nonaqueous electrolyte prepared by dissolving an electrolyte in a nonaqueous solvent. The carbon material is a pulverized graphite material having a true density of 2.1 g/cm3 and a bulk density of 0.4 g/cm3. This graphite material is such a powder that the mean value of the shape parameter (x) expressed by the following formula is below 125.x = (L/T) x (W/T) where x is the shape parameter of the powder, T is the thickness of powder at the thinnest part, L is the length of powder in the length direction. W is the length of powder in the direction normal to the length direction. The graphite material has a specific surface area of 9 m2/g and a cumulative 10 % grain size of 3 νm, a cumulative 50 % grain size of 10 νm, and a cumulative 90 % grain size of 70 νm in the particle size distribution found by a laser diffraction method. Such a graphite material powder is prepared by, for example, graphitizing a molded body of a carbon material by heat treatment and grinding the graphitized molded body. The mean fracture strength value of the particles of the graphitic material is greater than 6.0 kgf/mm2.
TL;DR: In this paper, primary and secondary effluents of three waste water treatment works were analyzed for the size distribution of particle mass, chemical oxygen demand (COD), and phosphorus fractionation of suspended solids was done by 01-80μm polycarbonate filters and 32-125μm sieves, respectively.
TL;DR: In this article, a method for the preparation of nanosized zirconium (hydrous) oxide particles of narrow size distribution is described, which yields stable dispersions at low temperatures and short reaction times in the absence of surfactants.
Abstract: A method for the preparation of nanosized zirconium (hydrous) oxide particles of narrow size distribution is described. The procedure yields stable dispersions at low temperatures and short reaction times in the absence of surfactants, using inorganic zirconium salts. Crystal structure, particle size distribution, electrokinetic properties, stability, and thermal behavior of the prepared particles were investigated. Colloidal dispersions were treated with ultrasound to study their effect on the crystal structure of the calcined samples.
TL;DR: In this article, Kranck et al. used a grain size analysis to determine the floc limit of a sediment, which is the amount of material deposited in a flocculated state and the maximum size of the particles composing it.
Abstract: Grain size is the most basic of classification criteria for sediments. The size distribution of a given sediment records the physical transport processes involved in its formation. By using precise grain size analysis and the model of Kranck et al. (1996a, b), it is possible to break down a sediment into the three major components from which it was formed: material deposited as floes, material deposited as single grains from suspension, and material carried under higher energy conditions. With this method, both the amount of material deposited in a flocculated state and the maximum size, or floc limit, of the particles composing the floc can be determined. Changes in floc limit indicate changes in the aggregation dynamics of the system. As most trace metals and many other contaminants associate closely with the fine particle fraction of sediments, it is important to determine both the areal distribution and reworking history of the floc settled portion of a sediment. This paper discusses the application of the method to coastal inlets in Atlantic Canada and examines the relationship between proportion of floc-settled material and trace metal concentrations. Disaggregated inorganic grain size distributions are also used to illustrate changes in the aggregation dynamics in areas of intense aquaculture.
05 Oct 1997
TL;DR: The role of tribocharging in fluidization, flowability, and q/m distribution as functions of particle size distribution (PSD), fluidization time, and transport tubes of different materials was investigated in this paper.
Abstract: In this paper, we investigated the role of tribocharging in fluidization, flowability, and q/m distribution as functions of particle size distribution (PSD), fluidization time, and transport tubes of different materials. A charge separator was used to determine mass fractions of powder that had positive, zero, and negative charges. For the two acrylic powders tested, one (Sample A) had volume median diameter d/sub 50/ 18.73 /spl mu/m while the other (Sample B) had d/sub 50/ 24.17-/spl mu/m diameter. During fluidization for 1 h at a relative humidity of 57%, powder B acquired positive charge with charge-to-mass ratio Q/M=0.3 /spl mu/C/g, and 25% of the powder mass had negative charge with Q/M=-0.36 /spl mu/C/g. About 35% of the powder mass had particles with nearly zero net charge. Tribocharging during fluidization and transport processes was attributed to particle-particle and particle-wall collisions. Of the total charged particles, about 60% were positively charged while 40% were negatively charged. Each particle may have had patches of charges on its surface, some positive and some negative. The sum total of all patches of charges may yield positive, negative, or essentially neutral polarities on a given particle. For a relatively narrow size distribution of powder, the PSD is often assumed to be conserved during fluidization. A shift in PSD toward larger diameter particles was anticipated because of the possible elutriation of the fine fraction of the powder, but the actual shift was only about 1 /spl mu/m after 1 h of fluidization. Under identical operational conditions using a fluidized bed, powder pump, transport hose, and corona gun, powder B had nearly twice the mass flow rate of Powder A. Such differences in flowability of powders influence charging and deposition efficiencies in powder coating applications.
TL;DR: In this article, the particle size distribution of a tomato concentrate was determined by wet sieving and the results showed that the size of many particles was considerably larger (up to two to three times) than the diameter of the pores through which they have passed during the sieving.
Abstract: The particle size distribution of a tomato concentrate was determined by wet sieving. Wet sieve fractions were then investigated by microscopy and a method based on laser diffraction. Both methods showed that the size of many particles was considerably larger (up to two to three times) than the diameter of the pores through which they have passed during wet sieving. This was explained by the deformability of the tomato cell wall. Effects of particle size distribution on rheological properties were studied by standardizing wet sieve fractions (dry matter, pH). Highest values for yield stress and apparent viscosity were found for the 90-125 and 125-180 μm wet sieve fractions.
TL;DR: In this article, the three-dimensional β-Si3N4 grain size distributions were reconstructed by a stereological method using scanning electron microscopy in combination with quantitative microscopy.
Abstract: Si3N4 ceramics with a constant molar fraction of Al2O3 and Y2O3 or Yb2O3 have been microstructurally characterised by scanning electron microscopy in combination with quantitative microscopy, and the three-dimensional β-Si3N4 grain size distributions were subsequently reconstructed by a stereological method. The Si3N4 ceramics were densified by gas pressure sintering at 1900 °C under a pressure of 980 kPa for 1, 3, 5 and 10 h. The microstructural analysis showed that the Y 2 O 3 Al 2 O 3 ratio in the starting powder mixture affects the β-Si3N4 grain shape and size distribution. An increased Y 2 O 3 Al 2 O 3 ratio resulted in a higher mean aspect ratio. A replacement of Y2O3 by Yb2O3 increased the mean aspect ratio further and resulted in a more narrow grain size distribution with an increased mean grain volume. The mean grain size increased with densification time, and a grain growth exponent of n = 3.2 implied that the β-Si3N4 grain growth was rate controlled by diffusion through the liquid phase. The metal oxide composition also determined the formation of secondary crystalline phases. Crack propagation and, hence, fracture toughness was dependent upon β-Si3N4 grain morphology and the intergranular structure.
Book•
01 Jan 1997
TL;DR: In this article, permeametry and gas diffusion are used to determine pore size distribution by gas adsorption, and surface area determination by mercury porosimetry.
Abstract: Volume 1: Permeametry and gas diffusion. Surface area determination by gas adsorption. Determination of pore size distribution by gas adsorption. Pore size determination by mercury porosimetry. Other methods for determining surface area. Volume 2: Powder sampling. Data presentation and interpretation. Particle size by image analysis. Particle size analysis by sieving. Fluid classification. Interaction between fluids and particles. Sedimentation theory. Sedimentation methods of particle size measurement. Stream scanning methods of particle size measurement. Field scanning methods of particle size measurement. Industrial applications of particle size measurement. Appendix: Manufacturers and suppliers. Author index. Subject index.
TL;DR: In this article, the influence of the particle size distribution in binary system on the packing density and the rate of hydration is analyzed. And the relationship between the porosity and the Particle Size Distribution is calculated and discussed.
TL;DR: In this article, the particle size distribution for the fine-grained fraction of eleven soil samples was determined using four commercially available, state-of-the-art automated particle-size distribution analysis instruments.
Abstract: The particle-size distribution for the fine-grained fraction of eleven soil samples was determined using four commercially available, state-of-the-art automated particle-size distribution analysis instruments. Two of the instruments operate on the principle of interaction of laser light with soil particles suspended in water in a highly agitated state, and two operate on the principle of the absorption of an X-ray beam by a suspension of soil particles settling in a quiescent column of water. The results from each instrument for each soil sample were compared to size analysis data determined by the hydrometer technique. The X-ray absorption instruments produced particle-size distributions very close to those of the hydrometer method, with the exception of soils with high mica concentrations. The laser-based instrument data did not agree as well with the hydrometer data, although for soils with significant mica contents the results were closer than the results from the X-ray absorption instruments. Based on these results, however, it appears that the automated X-ray absorption/sedimentation-based instruments show promise as alternatives or as a possible supplement for the manual hydrometer method of size analysis for soils without significant mica particle concentrations.