Articoli di riviste: "Particle size distribution"

1

Lin, Hsin-Yi, Der-Jen Hsu e Jia-Shan Su. "Particle Size Distribution of Aromatic Incense Burning Products". International Journal of Environmental Science and Development 6, n. 11 (2015): 857–60. http://dx.doi.org/10.7763/ijesd.2015.v6.712.

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Vítěz, T., e P. Trávníček. "Particle size distribution of sawdust and wood shavings mixtures". Research in Agricultural Engineering 56, No. 4 (1 dicembre 2010): 154–58. http://dx.doi.org/10.17221/8/2010-rae.

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Particle size distribution of the sample of waste sawdust and wood shavings mixtures were made with two commonly used methods of mathematical models by Rosin-Rammler (RR model) and by Gates-Gaudin-Schuhmann (GGS model).On the basis of network analysis distribution function F (d) (mass fraction) and density function f (d) (number of particles captured between two screens) were obtained. Experimental data were evaluated using the RR model and GGS model, both models were compared. Better results were achieved with GGS model, which leads to a more accurate separation of the different particle sizes in order to obtain a better industrial profit of the material.

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Nauman, E. Bruce, e Timothy J. Cavanaugh. "Method of Calculating True Particle Size Distributions from Observed Sizes in a Thin Section". Microscopy and Microanalysis 4, n. 2 (aprile 1998): 122–27. http://dx.doi.org/10.1017/s1431927698980102.

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Particle size distributions obtained from a thin section are usually a skewed version of the true distribution. A previous method for determining the parent distribution was questionable because negative particle frequencies could be obtained. Here, we describe a method of determining parent distributions of spherical particles using a model with adjustable parameters. Our calculated distributions are somewhat broader than the distributions obtained with previous methods, but the average particle sizes are nearly identical. The newly developed model is applicable to any type of transmission microscopy.

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Pfeifer, Sascha, Thomas Müller, Kay Weinhold, Nadezda Zikova, Sebastiao Martins dos Santos, Angela Marinoni, Oliver F. Bischof et al. "Intercomparison of 15 aerodynamic particle size spectrometers (APS 3321): uncertainties in particle sizing and number size distribution". Atmospheric Measurement Techniques 9, n. 4 (7 aprile 2016): 1545–51. http://dx.doi.org/10.5194/amt-9-1545-2016.

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Abstract. Aerodynamic particle size spectrometers are a well-established method to measure number size distributions of coarse mode particles in the atmosphere. Quality assurance is essential for atmospheric observational aerosol networks to obtain comparable results with known uncertainties. In a laboratory study within the framework of ACTRIS (Aerosols, Clouds, and Trace gases Research Infrastructure Network), 15 aerodynamic particle size spectrometers (APS model 3321, TSI Inc., St. Paul, MN, USA) were compared with a focus on flow rates, particle sizing, and the unit-to-unit variability of the particle number size distribution. Flow rate deviations were relatively small (within a few percent), while the sizing accuracy was found to be within 10 % compared to polystyrene latex (PSL) reference particles. The unit-to-unit variability in terms of the particle number size distribution during this study was within 10 % to 20 % for particles in the range of 0.9 up to 3 µm, which is acceptable for atmospheric measurements. For particles smaller than that, the variability increased up to 60 %, probably caused by differences in the counting efficiencies of individual units. Number size distribution data for particles smaller than 0.9 µm in aerodynamic diameter should only be used with caution. For particles larger than 3 µm, the unit-to-unit variability increased as well. A possible reason is an insufficient sizing accuracy in combination with a steeply sloping particle number size distribution and the increasing uncertainty due to decreasing counting. Particularly this uncertainty of the particle number size distribution must be considered if higher moments of the size distribution such as the particle volume or mass are calculated, which require the conversion of the aerodynamic diameter measured to a volume equivalent diameter. In order to perform a quantitative quality assurance, a traceable reference method for the particle number concentration in the size range 0.5–3 µm is needed.

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Pfeifer, S., T. Müller, K. Weinhold, N. Zikova, S. Santos, A. Marinoni, O. F. Bischof et al. "Intercomparison of 15 aerodynamic particle size spectrometers (APS 3321): uncertainties in particle sizing and number size distribution". Atmospheric Measurement Techniques Discussions 8, n. 11 (3 novembre 2015): 11513–32. http://dx.doi.org/10.5194/amtd-8-11513-2015.

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Abstract. Aerodynamic particle size spectrometers are a well-established method to measure number size distributions of coarse mode particles in the atmosphere. Quality assurance is essential for atmospheric observational aerosol networks to obtain comparable results with known uncertainties. In a laboratory study within the framework of ACTRIS (Aerosols, Clouds, and Trace gases Research Infrastructure Network), 15 aerodynamic particle size spectrometers (APS model 3321, TSI Inc., St. Paul, MN, USA) were compared with a focus on flow rates accuracy, particle sizing, and unit-to-unit variability of the particle number size distribution. Flow rate deviations were relatively small (within a few percent), while the sizing accuracy was found to be within 10 % compared to polystyrene latex (PSL) reference particles. The unit-to-unit variability in terms of the particle number size distribution during this study was within 10–20 % for particles in the range of 0.9 up to 3 μm, which is acceptable for atmospheric measurements. For particles smaller than that, the variability increased up to 60 %, probably caused by differences in the counting efficiencies of individual units. Number size distribution data for particles smaller than 0.9 μm in aerodynamic diameter should be only used with caution. For particles larger than 3 μm, the unit-to-unit variability increased as well. A possible reason is an insufficient sizing accuracy in combination with a steeply sloping particle number size distribution and the increasing uncertainty due to decreasing counting. This uncertainty of the particle number size distribution has especially to be considered if higher moments of the size distribution such as the particle volume or mass are calculated, which require the conversion of the aerodynamic diameter measured to a volume equivalent diameter. In order to perform a quantitative quality assurance, a traceable reference method for the particle number concentration in the size range 0.5–3 μm is needed.

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Ferguson, J. R., e D. E. Stock. "“Heavy” Particle Dispersion Measurements With Mono- and Polydisperse Particle Size Distributions". Journal of Fluids Engineering 115, n. 3 (1 settembre 1993): 523–26. http://dx.doi.org/10.1115/1.2910170.

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A method is presented to estimate the effects of a polydisperse particle size distribution on the measured turbulent dispersion of particles. In addition, the analysis provides a means to estimate the standard deviation of the size distribution for which a class of particles may be considered monodisperse. If monodisperse particles are unavailable because of practical considerations (e.g., the required standard deviation of particle size is too small to obtain a sufficient quantity) then the method provides a means to correct the data of near monodisperse size distributions to reflect the dispersion of monodisperse particles.

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Kontkanen, Jenni, Chenjuan Deng, Yueyun Fu, Lubna Dada, Ying Zhou, Jing Cai, Kaspar R. Daellenbach et al. "Size-resolved particle number emissions in Beijing determined from measured particle size distributions". Atmospheric Chemistry and Physics 20, n. 19 (5 ottobre 2020): 11329–48. http://dx.doi.org/10.5194/acp-20-11329-2020.

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Abstract. The climate and air quality effects of aerosol particles depend on the number and size of the particles. In urban environments, a large fraction of aerosol particles originates from anthropogenic emissions. To evaluate the effects of different pollution sources on air quality, knowledge of size distributions of particle number emissions is needed. Here we introduce a novel method for determining size-resolved particle number emissions, based on measured particle size distributions. We apply our method to data measured in Beijing, China, to determine the number size distribution of emitted particles in a diameter range from 2 to 1000 nm. The observed particle number emissions are dominated by emissions of particles smaller than 30 nm. Our results suggest that traffic is the major source of particle number emissions with the highest emissions observed for particles around 10 nm during rush hours. At sizes below 6 nm, clustering of atmospheric vapors contributes to calculated emissions. The comparison between our calculated emissions and those estimated with an integrated assessment model GAINS (Greenhouse Gas and Air Pollution Interactions and Synergies) shows that our method yields clearly higher particle emissions at sizes below 60 nm, but at sizes above that the two methods agree well. Overall, our method is proven to be a useful tool for gaining new knowledge of the size distributions of particle number emissions in urban environments and for validating emission inventories and models. In the future, the method will be developed by modeling the transport of particles from different sources to obtain more accurate estimates of particle number emissions.

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8

Ensor, David, Robert Donovan e Bruce Locke. "Particle Size Distributions in Clean Rooms". Journal of the IEST 30, n. 6 (1 novembre 1987): 44–49. http://dx.doi.org/10.17764/jiet.1.30.6.m24044316827q326.

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Measurements of particle size distributions smaller than 0.1 μm in Class 100 clean rooms are summarized. The size distributions were measured in operational rooms during periods of time with little activity—the so-called "at rest" conditions. A simple particle number balance model is proposed, illustrating the importance of filter penetration and atmospheric aerosol on the concentration of submicrometer particles. Preliminary calculations are used to explain the absence of < 0.1 μm diameter particles in the clean rooms tested. A ratio of condensation nucleus counter concentration to optical particle counter concentration is suggested as a parameter to provide an indication of changes in clean room particle size distribution.

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Rao, S., e C. R. Houska. "X-ray particle-size broadening". Acta Crystallographica Section A Foundations of Crystallography 42, n. 1 (1 gennaio 1986): 6–13. http://dx.doi.org/10.1107/s0108767386099981.

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X-ray diffraction profiles and Fourier coefficients are given for particles distributed according to experimentally verified size distributions. Calculations are based upon the log normal distribution of sphere diameters and intercept lengths in addition to a normal distribution of column heights. It is found that the diffraction profile is not sensitive to the fine details of the distribution but rather the mean column height and the column-height variation coefficient. Errors in particle-size determinations will result from an improper choice of the variation coefficient. Two simplified models are given that describe the diffraction profiles for a large range of variation coefficients.

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10

Friedman, B., A. Zelenyuk, J. Beránek, G. Kulkarni, M. Pekour, A. G. Hallar, I. B. McCubbin, J. A. Thornton e D. J. Cziczo. "Aerosol measurements at a high elevation site: composition, size, and cloud condensation nuclei activity". Atmospheric Chemistry and Physics Discussions 13, n. 7 (9 luglio 2013): 18277–306. http://dx.doi.org/10.5194/acpd-13-18277-2013.

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Abstract. Measurements of cloud condensation nuclei (CCN) concentrations, single particle composition and size distributions at a high-elevation research site from March 2011 are presented. The temporal evolution of detailed single particle composition is compared with changes in CCN activation on four days, two of which include new particle formation and growth events. Sulfate-containing particles dominated the single particle composition by number; biomass burning particles, sea salt particles, and particles containing organic components also were present. CCN activation largely followed the behavior of the sulfate-containing particle types; biomass burning particle types also likely contained hygroscopic material that impacted CCN activation. Newly formed particles also may contribute to CCN activation at higher supersaturation conditions. Derived aerosol hygroscopicity parameters from the size distribution and CCN concentration measurements are within the range of previous reports of remote continental kappa values.

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Friedman, B., A. Zelenyuk, J. Beranek, G. Kulkarni, M. Pekour, A. Gannet Hallar, I. B. McCubbin, J. A. Thornton e D. J. Cziczo. "Aerosol measurements at a high-elevation site: composition, size, and cloud condensation nuclei activity". Atmospheric Chemistry and Physics 13, n. 23 (9 dicembre 2013): 11839–51. http://dx.doi.org/10.5194/acp-13-11839-2013.

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Abstract. Measurements of cloud condensation nuclei (CCN) concentrations, single particle composition and size distributions at a high-elevation research site from March 2011 are presented. The temporal evolution of detailed single particle composition is compared with changes in CCN activation on four days, two of which include new particle formation and growth events. Sulfate-containing particles dominated the single particle composition by number; biomass burning particles, sea salt particles, and particles containing organic components were also present. CCN activation largely followed the behavior of the sulfate-containing particle types; biomass burning particle types also likely contained hygroscopic material that impacted CCN activation. Newly formed particles also may contribute to CCN activation at higher supersaturation conditions. Derived aerosol hygroscopicity parameters from the size distribution and CCN concentration measurements are within the range of previous reports of remote continental kappa values.

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12

Ringuet, J., E. Leoz-Garziandia, H. Budzinski, E. Villenave e A. Albinet. "Particle size distribution of nitrated and oxygenated polycyclic aromatic hydrocarbons (NPAHs and OPAHs) on traffic and suburban sites of a European megacity: Paris (France)". Atmospheric Chemistry and Physics Discussions 12, n. 6 (6 giugno 2012): 14169–96. http://dx.doi.org/10.5194/acpd-12-14169-2012.

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Abstract. The size distribution of particulate nitrated and oxygenated polycyclic aromatic hydrocarbons (NPAHs and OPAHs) was determined during two field campaigns at a traffic site in summer 2010 and at a suburban site during the MEGAPOLI (Megacities: Emissions, urban, regional and Global Atmospheric POLlution and climate effects, and Integrated tools for assessment and mitigation) experiment in summer 2009. Both, OPAHs and NPAHs were strongly associated (>85%) to fines particles (Dp < 2.5 μm) increasing the interest of their study on a sanitary point of view. Results showed really different NPAH and OPAH particle size distributions between both sites. At traffic site, clearly bimodal (notably for NPAHs) particle size distributions (Dp = 0.14 and 1.4 μm) were observed, while the particle size distributions were more scattered at the suburban site, especially for OPAHs. Bimodal particle size distribution observed at traffic site for the NPAH could be assigned to the vehicle emissions and the particle resuspension. Broadest distribution observed at the suburban site could be attributed to the mass transfer of compounds by volatilization/sorption processes during the transport of particles in the atmosphere. Results also showed that the combination of the study of particle size distributions applied to marker compounds (primary: 1-nitropyrene; secondary: 2-nitrofluoranthene) and to NPAH or OPAH chemical profiles bring some indications on their primary and/or secondary origin. Indeed, 1,4-anthraquinone seemed only primary emitted by vehicles while 7-nitrobenz[a]anthracene, benz[a]antracen7,12-dione and benzo[b]fluorenone seemed secondarily formed in the atmosphere.

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13

Ringuet, J., E. Leoz-Garziandia, H. Budzinski, E. Villenave e A. Albinet. "Particle size distribution of nitrated and oxygenated polycyclic aromatic hydrocarbons (NPAHs and OPAHs) on traffic and suburban sites of a European megacity: Paris (France)". Atmospheric Chemistry and Physics 12, n. 18 (28 settembre 2012): 8877–87. http://dx.doi.org/10.5194/acp-12-8877-2012.

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Abstract. The size distribution of particulate nitrated and oxygenated polycyclic aromatic hydrocarbons (NPAHs and OPAHs) was determined during two field campaigns at a traffic site in summer 2010 and at a suburban site during the MEGAPOLI (Megacities: Emissions, urban, regional and Global Atmospheric POLlution and climate effects, and Integrated tools for assessment and mitigation) experiment in summer 2009. Both, OPAHs and NPAHs were strongly associated (>85%) to fine particles (Dp< 2.5 μm) increasing the interest of their study on a sanitary point of view. Results showed really different NPAH and OPAH particle size distributions between both sites. At traffic site, clearly bimodal (notably for NPAHs) particle size distributions (Dp = 0.14 and 1.4 μm) were observed, while the particle size distributions were more scattered at the suburban site, especially for OPAHs. Bimodal particle size distribution observed at traffic site for the NPAH could be assigned to the vehicle emissions and the particle resuspension. Broadest distribution observed at the suburban site could be attributed to the mass transfer of compounds by volatilization/sorption processes during the transport of particles in the atmosphere. Results also showed that the combination of the study of particle size distributions applied to marker compounds (primary: 1-nitropyrene; secondary: 2-nitrofluoranthene) and to NPAH or OPAH chemical profiles bring some indications on their primary and/or secondary origin. Indeed, 1,4-anthraquinone seemed only primary emitted by vehicles while 7-nitrobenz[a]anthracene, benz[a]antracen7,12-dione and benzo[b]fluorenone seemed secondarily formed in the atmosphere.

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Gkatzelis, G. I., D. K. Papanastasiou, K. Florou, C. Kaltsonoudis, E. Louvaris e S. N. Pandis. "Measurement of nonvolatile particle number size distribution". Atmospheric Measurement Techniques 9, n. 1 (18 gennaio 2016): 103–14. http://dx.doi.org/10.5194/amt-9-103-2016.

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Abstract. An experimental methodology was developed to measure the nonvolatile particle number concentration using a thermodenuder (TD). The TD was coupled with a high-resolution time-of-flight aerosol mass spectrometer, measuring the chemical composition and mass size distribution of the submicrometer aerosol and a scanning mobility particle sizer (SMPS) that provided the number size distribution of the aerosol in the range from 10 to 500 nm. The method was evaluated with a set of smog chamber experiments and achieved almost complete evaporation (> 98 %) of secondary organic as well as freshly nucleated particles, using a TD temperature of 400 °C and a centerline residence time of 15 s. This experimental approach was applied in a winter field campaign in Athens and provided a direct measurement of number concentration and size distribution for particles emitted from major pollution sources. During periods in which the contribution of biomass burning sources was dominant, more than 80 % of particle number concentration remained after passing through the thermodenuder, suggesting that nearly all biomass burning particles had a nonvolatile core. These remaining particles consisted mostly of black carbon (60 % mass contribution) and organic aerosol (OA; 40 %). Organics that had not evaporated through the TD were mostly biomass burning OA (BBOA) and oxygenated OA (OOA) as determined from AMS source apportionment analysis. For periods during which traffic contribution was dominant 50–60 % of the particles had a nonvolatile core while the rest evaporated at 400 °C. The remaining particle mass consisted mostly of black carbon with an 80 % contribution, while OA was responsible for another 15–20 %. Organics were mostly hydrocarbon-like OA (HOA) and OOA. These results suggest that even at 400 °C some fraction of the OA does not evaporate from particles emitted from common combustion processes, such as biomass burning and car engines, indicating that a fraction of this type of OA is of extremely low volatility.

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Kaatz, F. H., G. M. Chow e A. S. Edelstein. "Narrowing sputtered nanoparticle size distributions". Journal of Materials Research 8, n. 5 (maggio 1993): 995–1000. http://dx.doi.org/10.1557/jmr.1993.0995.

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By adjusting the sputtering rate and gas pressure, it is possible to form nanoparticles of different sizes, phases, and materials. We have investigated the spatial distribution of sputtered particle formation using a vertical, linear arrangement of substrates. Collecting the particles soon after they are formed, before they have time to grow and agglomerate, allows one to obtain a narrow size distribution. In the case of molybdenum, a narrow distribution of cubic particles is formed at relatively large distances (8 cm) from the source. These cubic particles collide and self-assemble in the vapor into arrays of larger cubic particles. The particle size histograms are fitted to lognormal distribution functions. How supersaturation occurs is discussed qualitatively as a function of the distance from the substrate, sputtering rate, and the mean free path in the vapor. This method of nanocrystalline particle formation has potential use in magnetic and opto-electronic (quantum dot) applications, where a narrow size distribution is required.

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Hwang, K. J. "Effect of particle size on the performance of batchwise centrifugal filtration". Water Science and Technology 44, n. 10 (1 novembre 2001): 185–89. http://dx.doi.org/10.2166/wst.2001.0615.

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The effect of particle size distribution on the performance of batchwise centrifugal filtration is studied. By analyzing the velocity of particles in a filter, a numerical program is designed for simulating the migration and deposition of particles. The particle size distributions and the average specific filtration resistances of cake are then estimated under various rotating speeds of the centrifuge. A large deviation of particle concentration profiles in the filter chamber will occur if the particle size distribution is not taken into consideration. A more heterogeneous cake will form under a lower rotating speed due to the sedimentation effect of particles. The predicted results of particle size distribution and average specific filtration resistance of cake agree well with the available experimental data.

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17

Uchiyama, Hideki. "Measurement of particle size distribution of suspended particles." Japan journal of water pollution research 9, n. 12 (1986): 763–66. http://dx.doi.org/10.2965/jswe1978.9.763.

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18

Welker, Roger. "Size Distributions of Particles Extracted from Different Materials Compared with the MIL-STD-1246 Particle Size Distribution". Journal of the IEST 43, n. 4 (19 settembre 2000): 25–29. http://dx.doi.org/10.17764/jiet.43.4.b9490831l54t44wt.

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MIL-STD-1246 particle-size distribution is the basis for specifying the particle cleanliness of surfaces for many governmental and industrial applications. MIL-STD-1246 states that naturally occurring particle contamination on surfaces follows a log-normal particle-size distribution, with a geometric mean of 1 μm, following a very precise size specification. However, the naturally occurring particle-size distribution may be a function of the material under examination or the prior cleaning or surface treatment history of the material. This paper explores the relation between the MIL-STD-1246 particle-size distribution and particle-size distributions measured after extraction followed by liquidborne particle-size distribution analysis.

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XU, YONGFU, e YIDONG WANG. "SIZE EFFECT ON SPECIFIC ENERGY DISTRIBUTION IN PARTICLE COMMINUTION". Fractals 25, n. 02 (aprile 2017): 1750016. http://dx.doi.org/10.1142/s0218348x17500165.

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A theoretical study is made to derive an energy distribution equation for the size reduction process from the fractal model for the particle comminution. Fractal model is employed as a valid measure of the self-similar size distribution of comminution daughter products. The tensile strength of particles varies with particle size in the manner of a power function law. The energy consumption for comminuting single particle is found to be proportional to the 5(D−3)/3rd order of the particle size, [Formula: see text] being the fractal dimension of particle comminution daughter. The Weibull statistics is applied to describe the relationship between the breakage probability and specific energy of particle comminution. A simple equation is derived for the breakage probability of particles in view of the dependence of fracture energy on particle size. The calculated exponents and Weibull coefficients are generally in conformity with published data for fracture of particles.

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Surowiak, Agnieszka, e Marian Brożek. "METHODOLOGY OF CALCULATION THE TERMINAL SETTLING VELOCITY DISTRIBUTION OF SPHERICAL PARTICLES FOR HIGH VALUES OF THE REYNOLD’S NUMBER". Archives of Mining Sciences 59, n. 1 (1 marzo 2014): 269–82. http://dx.doi.org/10.2478/amsc-2014-0019.

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Abstract The particle settling velocity is the feature of separation in such processes as flowing classification and jigging. It characterizes material forwarded to the separation process and belongs to the so-called complex features because it is the function of particle density and size. i.e. the function of two simple features. The affiliation to a given subset is determined by the values of two properties and the distribution of such feature in a sample is the function of distributions of particle density and size. The knowledge about distribution of particle settling velocity in jigging process is as much important factor as knowledge about particle size distribution in screening or particle density distribution in dense media beneficiation. The paper will present a method of determining the distribution of settling velocity in the sample of spherical particles for the turbulent particle motion in which the settling velocity is expressed by the Newton formula. Because it depends on density and size of particle which are random variable of certain distributions, the settling velocity is a random variable. Applying theorems of probability, concerning distributions function of random variables, the authors present general formula of probability density function of settling velocity for the turbulent motion and particularly calculate probability density function for Weibull’s forms of frequency functions of particle size and density. Distribution of settling velocity will calculate numerically and perform in graphical form. The paper presents the simulation of calculation of settling velocity distribution on the basis of real distributions of density and projective diameter of particles assuming that particles are spherical.

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Nad, Alona, e Marian Brożek. "Application of Three-Parameter Distribution to Approximate the Particle Size Distribution Function of Comminution Products of Dolomitic Type of Copper Ore". Archives of Mining Sciences 62, n. 2 (27 giugno 2017): 411–22. http://dx.doi.org/10.1515/amsc-2017-0031.

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AbstractThe paper presents the results of analyze the particle size distribution function of comminution products of dolomitic type of copper ore. The breakage tests for single irregular particles were performed with using a hydraulic press device. The authors prepared five particle size fractions of each material, within ranges: 16-18 mm, 18-20 mm, 20-25 mm, 25-31,5 mm and 31-45 mm. The particle size distribution function of single-particle breakage test was calculated separately for each size fraction. In addition, the cumulative particle size distribution function for five particle size fractions was presented. In theoretical part the study of applied functions of particle size distribution for comminution a set of particles and models of crushing single particles was performed. In that paper the curves of the particle size distribution were approximated by the three-parameter function, which parameters depend on the particle strength and material type. For conformity assessment the model distribution function to the empirical distribution function a residual deviation and non-linear correlation coefficient were calculated. The three-parameter function approximating agrees well with the particle size distribution obtained from experimental data. The dependence of the parameters of a particle size distribution function on the dolomite particle strength was presented. The results indicate the identity of single particle grinding mechanism by slow compression of irregular particles of dolomitic type of copper ore, regardless of the initial particle size.

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Ichiji, M., H. Akiba, H. Nagao e I. Hirasawa. "Particle size distribution control of Pt particles used for particle gun". Journal of Crystal Growth 469 (luglio 2017): 180–83. http://dx.doi.org/10.1016/j.jcrysgro.2016.09.003.

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Pfeifer, S., W. Birmili, A. Schladitz, T. Müller, A. Nowak e A. Wiedensohler. "A novel inversion algorithm for mobility particle size spectrometers considering non-sphericity and additional aerodynamic/optical number size distributions". Atmospheric Measurement Techniques Discussions 6, n. 3 (29 maggio 2013): 4735–67. http://dx.doi.org/10.5194/amtd-6-4735-2013.

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Abstract. Multiple charge inversion is an essential procedure to convert the raw mobility distributions recorded by mobility particle size spectrometers, such as the DMPS or SMPS (Differential or Scanning Mobility Particle Sizers) into true particle number size distributions. In this work, we present a new multiple charge inversion algorithm with extended functionality. The algorithm can incorporate size distribution information from sensors that measure beyond the upper sizing limit of the mobility spectrometer, such as an aerodynamic particle sizer (APS), or an optical particle counter (OPC). This feature can considerably improve the multiple charge inversion result in the upper size range of the mobility spectrometer, for example, when substantial numbers of coarse particles are present. The program also yields a continuous size distribution from both sensors as an output. The algorithm is able to calculate the propagation of measurement errors, such as those based on counting statistics, into on the final particle number size distribution. As an additional aspect, the algorithm can perform all inversion steps under the assumption of non-spherical particle shape, including constant or size-dependent shape factor profiles.

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Hostomský, Jiří. "Particle size distribution of agglomerated crystal product from a continuous crystallizer". Collection of Czechoslovak Chemical Communications 52, n. 5 (1987): 1186–97. http://dx.doi.org/10.1135/cccc19871186.

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Relationships have been derived for the particle size distribution in a continuous crystallizer operating in a steady-state regime, where agglomeration of the primarily generated crystalline particles takes place. The derivation was made for a constant kinetic coefficient of agglomeration (independent of the particle size) and for a negligible particle growth rate. The relatioships are used to interpret the particle size distribution of calcium carbonate precipitated from 0.2 mol dm-3 solutions of calcium chloride and sodium carbonate in a laboratory continuous crystallizer. Anomalous shapes of the size distributions of small particles frequently observed in continuous crystallizers are discussed in terms of the agglomeration phenomenon.

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Williamson, Christina, Agnieszka Kupc, James Wilson, David W. Gesler, J. Michael Reeves, Frank Erdesz, Richard McLaughlin e Charles A. Brock. "Fast time response measurements of particle size distributions in the 3–60 nm size range with the nucleation mode aerosol size spectrometer". Atmospheric Measurement Techniques 11, n. 6 (19 giugno 2018): 3491–509. http://dx.doi.org/10.5194/amt-11-3491-2018.

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Abstract. Earth's radiation budget is affected by new particle formation (NPF) and the growth of these nanometre-scale particles to larger sizes where they can directly scatter light or act as cloud condensation nuclei (CCN). Large uncertainties remain in the magnitude and spatiotemporal distribution of nucleation (less than 10 nm diameter) and Aitken (10–60 nm diameter) mode particles. Acquiring size-distribution measurements of these particles over large regions of the free troposphere is most easily accomplished with research aircraft. We report on the design and performance of an airborne instrument, the nucleation mode aerosol size spectrometer (NMASS), which provides size-selected aerosol concentration measurements that can be differenced to identify aerosol properties and processes or inverted to obtain a full size distribution between 3 and 60 nm. By maintaining constant downstream pressure the instrument operates reliably over a large range of ambient pressures and during rapid changes in altitude, making it ideal for aircraft measurements from the boundary layer to the stratosphere. We describe the modifications, operating principles, extensive calibrations, and laboratory and in-flight performance of two NMASS instruments operated in parallel as a 10-channel battery of condensation particle counters (CPCs) in the NASA Atmospheric Tomography Mission (ATom) to investigate NPF and growth to cloud-active sizes in the remote free troposphere. An inversion technique to obtain size distributions from the discrete concentrations of each NMASS channel is described and evaluated. Concentrations measured by the two NMASS instruments flying in parallel are self-consistent and also consistent with measurements made with an optical particle counter. Extensive laboratory calibrations with a range of particle sizes and compositions show repeatability of the response function of the instrument to within 5–8 % and no sensitivity in sizing performance to particle composition. Particle number, surface area, and volume concentrations from the data inversion are determined to better than 20 % for typical particle size distributions. The excellent performance of the NMASS systems provides a strong analytical foundation to explore NPF around the globe in the ATom dataset.

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26

Gómez Bonilla, Juan S., Laura Unger, Jochen Schmidt, Wolfgang Peukert e Andreas Bück. "Particle Lagrangian CFD Simulation and Experimental Characterization of the Rounding of Polymer Particles in a Downer Reactor with Direct Heating". Processes 9, n. 6 (23 maggio 2021): 916. http://dx.doi.org/10.3390/pr9060916.

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Polypropylene (PP) powders are rounded at different conditions in a downer reactor with direct heating. The particles are fed through a single central tube, while the preheated sheath gas is fed coaxially surrounding the central aerosol jet. The influence of the process parameters on the quality of the powder product in terms of particle shape and size is analyzed by correlating the experimental results with the flow pattern, residence time distribution of the particles and temperature distribution predicted by computational fluid dynamics (CFD) simulations. An Eulerian–Lagrangian numerical approach is used to capture the effect of the particle size distribution on the particle dynamics and the degree of rounding. The simulation results reveal that inlet effects lead to inhomogeneous particle radial distributions along the total length of the downer. The configuration of particle/gas injection also leads to fast dispersion of the particles in direction of the wall and to particle segregation by size. Broad particle residence time distributions are obtained due to broad particle size distribution of the powders and the particles dispersion towards the wall. Lower mass flow ratios of aerosol to sheath gas are useful to reduce the particle dispersion and produce more homogenous residence time distributions. The particles’ residence time at temperatures above the polymer’s melting onset is determined from the simulations. This time accounts for the effective treatment (rounding) time of the particles. Clear correlations are observed between the numerically determined effective rounding time distributions and the progress of shape modification on the particles determined experimentally.

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Beaucage, G., H. K. Kammler e S. E. Pratsinis. "Particle size distributions from small-angle scattering using global scattering functions". Journal of Applied Crystallography 37, n. 4 (17 luglio 2004): 523–35. http://dx.doi.org/10.1107/s0021889804008969.

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Control and quantification of particle size distribution is of importance in the application of nanoscale particles. For this reason, polydispersity in particle size has been the focus of many simulations of particle growth, especially for nanoparticles synthesized from aerosols such as fumed silica, titania and alumina. Single-source aerosols typically result in close to a log-normal distribution in size and micrograph evidence generally supports close to spherical particles, making such particles ideal candidates for considerations of polydispersity. Small-angle X-ray scattering (SAXS) is often used to measure particle size in terms of the radius of gyration,Rg, using Guinier's law, as well as particle surface area,S/V, from the Porod constantBand the scattering invariantQ. In this paper, the unified function is used to obtain these parameters and various moments of the particle size distribution are calculated. The particle size obtained from BET analysis of gas adsorption data directly agrees with the moment calculated fromS/V. Scattering results are also compared with TEM particle-counting results. The potential of scattering to distinguish between polydisperse single particles and polydisperse particles in aggregates is presented. A generalized index of polydispersity for symmetric particles, PDI =BRg4/(1.62G), whereGis the Guinier prefactor, is introduced and compared with other approaches to describe particle size distributions in SAXS, specifically the maximum-entropy method.

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28

Hong Qi, Hong Qi, Biao Zhang Biao Zhang, Yatao Ren Yatao Ren, Liming Ruan Liming Ruan e Heping Tan Heping Tan. "Retrieval of spherical particle size distribution using ant colony optimization algorithm". Chinese Optics Letters 11, n. 11 (2013): 112901–5. http://dx.doi.org/10.3788/col201311.112901.

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29

IGUSHI, Tatsuo. "Particle Size Distribution Measurement Methods". Journal of the Japan Society of Colour Material 79, n. 9 (2006): 410–18. http://dx.doi.org/10.4011/shikizai1937.79.410.

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30

Wilson, S. R., P. J. Ridler e B. R. Jennings. "Magnetic birefringence particle size distribution". Journal of Physics D: Applied Physics 29, n. 3 (14 marzo 1996): 885–88. http://dx.doi.org/10.1088/0022-3727/29/3/056.

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31

Hill, Priscilla J., e Ka M. Ng. "Particle size distribution by design". Chemical Engineering Science 57, n. 12 (giugno 2002): 2125–38. http://dx.doi.org/10.1016/s0009-2509(02)00106-9.

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32

Burch, W. M., M. M. Boyd, D. E. Crellin, M. Lemb, T. H. Oei, H. Eifert e B. G�nther. "Technegas: particle size and distribution". European Journal of Nuclear Medicine 21, n. 4 (aprile 1994): 365–67. http://dx.doi.org/10.1007/bf00947975.

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33

Maxim, L. D., A. Klein, M. E. Meyer e C. H. Kuist. "Particle size distribution by turbidimetry". Journal of Polymer Science Part C: Polymer Symposia 27, n. 1 (8 marzo 2007): 195–205. http://dx.doi.org/10.1002/polc.5070270115.

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34

Gkatzelis, G. I., D. K. Papanastasiou, K. Florou, C. Kaltsonoudis, E. Louvaris e S. N. Pandis. "Measurement of non-volatile particle number size distribution". Atmospheric Measurement Techniques Discussions 8, n. 6 (25 giugno 2015): 6355–93. http://dx.doi.org/10.5194/amtd-8-6355-2015.

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Abstract. An experimental methodology was developed to measure the non-volatile particle number concentration using a thermodenuder (TD). The TD was coupled with a high-resolution time-of-flight aerosol mass spectrometer, measuring the chemical composition and mass size distribution of the submicrometer aerosol and a scanning mobility particle sizer (SMPS) that provided the number size distribution of the aerosol in the range from 10 to 500 nm. The method was evaluated with a set of smog chamber experiments and achieved almost complete evaporation (> 98 %) of secondary organic as well as freshly nucleated particles, using a TD temperature of 400 °C and a centerline residence time of 15 s. This experimental approach was applied in a winter field campaign in Athens and provided a direct measurement of number concentration and size distribution for particles emitted from major pollution sources. During periods in which the contribution of biomass burning sources was dominant, more than 80 % of particle number concentration remained after passing through the thermodenuder, suggesting that nearly all biomass burning particles had a non-volatile core. These remaining particles consisted mostly of black carbon (60 % mass contribution) and organic aerosol, OA (40 %). Organics that had not evaporated through the TD were mostly biomass burning OA (BBOA) and oxygenated OA (OOA) as determined from AMS source apportionment analysis. For periods during which traffic contribution was dominant 50–60 % of the particles had a non-volatile core while the rest evaporated at 400 °C. The remaining particle mass consisted mostly of black carbon (BC) with an 80 % contribution, while OA was responsible for another 15–20 %. Organics were mostly hydrocarbon-like OA (HOA) and OOA. These results suggest that even at 400 °C some fraction of the OA does not evaporate from particles emitted from common combustion processes, such as biomass burning and car engines, indicating that a fraction of this type of OA is of extremely low volatility.

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Pandit, Ajinkya V., e Vivek V. Ranade. "Chord length distribution to particle size distribution". AIChE Journal 62, n. 12 (9 giugno 2016): 4215–28. http://dx.doi.org/10.1002/aic.15338.

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36

Antony, S. J., e M. Ghadiri. "Size Effects in a Slowly Sheared Granular Media". Journal of Applied Mechanics 68, n. 5 (8 gennaio 2001): 772–75. http://dx.doi.org/10.1115/1.1387443.

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In this paper, we analyze the nature of stress distribution experienced by large particles in a dense granular media subjected to slow shearing, using the distinct element method. The particles were generated in a three-dimensional cuboidal periodic cell in which a large solid spherical particle was submerged (“submerged particle”) at the center of a bed of monodispersed spherical particles. The granular systems with different size ratio (i.e., the ratio of the diameter of submerged particle to that of the surrounding monodispersed particles) were subjected to quasi-static shearing under constant mean stress condition. The evolution of stress distribution in the submerged particle during shearing was carefully tracked down and presented here. The nature of stress distribution is bifurcated into two components, viz., (i) hydrostatic and (ii) deviatoric components. It has been shown that, for size ratio greater than c.a. 10, the nature of stress distribution in the submerged particle is hydrostatically dominant (increases the ‘fluidity’). For smaller size ratios, the nature of stress distribution in the submerged particle is dominantly deviatoric.

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37

Guo, Hai, Aijun Ding, Lidia Morawska, Congrong He, Godwin Ayoko, Yok-sheung Li e Wing-tat Hung. "Size distribution and new particle formation in subtropical eastern Australia". Environmental Chemistry 5, n. 6 (2008): 382. http://dx.doi.org/10.1071/en08058.

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Environmental context. Atmospheric submicrometre particles have a significant impact on human health, visibility impairment, acid deposition and global climate. This study aims to understand the size distribution of submicrometre particles and new particle formation in eastern Australia and the results indicate that photochemical reactions of airborne pollutants are the main mechanism of new particle formation. The findings will contribute to a better understanding of the effects of aerosols on climate and the reduction of submicrometre particles in the atmosphere. Abstract. An intensive measurement campaign of particle concentrations, nitrogen oxides and meteorological parameters was conducted at a rural site in subtropical eastern Australia during September 2006. The aim of this work was to develop an understanding of the formation and growth processes of atmospheric aerosols, and the size distributions under various meteorological conditions. In order to achieve this, the origins of air arriving at the site were explored using back trajectories cluster analysis and the diurnal patterns of particle number concentration and size distribution for the classified air masses were investigated. The study showed that the photochemical formation of nucleation mode particles and their consequent growth was often observed. Furthermore, the nucleation mode usually dominated the size distribution and concentration of the photochemical event in the first 3–4 h with a geometric mean diameter of 26.9 nm and a geometric standard deviation of 1.28. The average particle growth rate was estimated to be 1.6 nm h–1, which is lower than that observed at urban sites, but comparable to the values reported in clean environments. The potential precursors of the photochemical events are also discussed.

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38

Dado, Miroslav, Jozef Salva, Marián Schwarz, Miroslav Vanek e Lucia Bustin. "Effect of Grit Size on Airborne Particle Concentration and Size Distribution during Oak Wood Sanding". Applied Sciences 12, n. 15 (29 luglio 2022): 7644. http://dx.doi.org/10.3390/app12157644.

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Adverse health effects caused by exposure to airborne particles have been detected in recent years, however there is little knowledge about exposure to ultrafine particles with a diameter <100 nm. In this study, particle number concentration and size distribution in a range of particle diameters from 10 nm to 10 µm were determined during oak wood sanding. A hand-held orbit sander in combination with three types of grit size (P60, 120 and 240) of sandpaper were used. Measurements were obtained using a portable particle size distribution analyzer and an optical particle size spectrometer, carried out at 15-min intervals for each treatment by static sampling in the breathing zone. We also compared the optical particle size spectrometer to the aerosol monitor in order to evaluate the mass concentration of airborne particles in the range of 1 to 10 µm in diameter. Sanding paper with the finest grit, P240, showed a significantly higher number concentration of ultrafine particles, compared with P60 and P120 grits. The differences among particular grit size were statistically significant for microparticles. The size distribution of particles during sanding was not affected by grit size. For each grit size, apparent peak values of ultrafine and microparticle number concentrations were determined at approximately 15 nm, and 0.1 µm, respectively. Optical particle size spectrometer and aerosol monitor showed comparable results of mass concentration for the respirable fraction.

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39

Kim, S., S. H. Cho e H. Park. "Effects of particle size distribution on the cake formation in crossflow microfiltration". Water Supply 2, n. 2 (1 aprile 2002): 305–11. http://dx.doi.org/10.2166/ws.2002.0077.

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In crossflow microfiltration, the tendency of particle deposition of polydisperse suspensions has been established experimentally and compared with that of monodisperse suspensions. The mass transfers of particles are different according to size in polydisperse suspensions. The most particles, which deposit to membrane surface without clogging pore in microfiltration, are much larger than 0.1 μm. Among these particles, smaller particles are easier to deposit than larger particles because of shear-induced diffusion and particle deposition depends on the size distribution of small particles. Effective particle diameter is introduced as a representative particle size which can reflect the diffusivity of each particle according to size and it describes the tendency of particle deposition very well in polydisperse suspensions. The effect of effective particle diameter is larger than that of feed concentration. The most important factor affecting particle deposition of polydisperse suspensions is effective particle diameter. The results of our research suggest that the effective particle diameter can be an important factor which can represent the potential for cake formation.

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40

Rahimi, Abbas, Andy Cordonier e Abhilash J. Chandy. "Particle Distribution Statistics in CFD Modeling of Polymer Processing". Applied Mechanics and Materials 704 (dicembre 2014): 12–16. http://dx.doi.org/10.4028/www.scientific.net/amm.704.12.

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This study presents statistical analysis of particle size distribution from a CFD simulation of polymer devolatilization in contactor, that uses superheated steam to isolate the polymers. This is accomplished by estimating marginal distributions of particle size and temperature using maximum Shannon Entropy theory and capturing their dependence structure by employing Copula thoery. The Copula-based conditional distribution of particles at different temperatures reveals the strong dependence of particle size to heat exchange and corresponding temperature.

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41

Hussein, T., J. Kukkonen, H. Korhonen, M. Pohjola, L. Pirjola, D. Wraith, J. Härkönen et al. "Evaluation and modeling of the size fractionated aerosol particle number concentration measurements nearby a major road in Helsinki – Part II: Aerosol measurements within the SAPPHIRE project". Atmospheric Chemistry and Physics 7, n. 15 (3 agosto 2007): 4081–94. http://dx.doi.org/10.5194/acp-7-4081-2007.

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Abstract. This study presents an evaluation and modeling exercise of the size fractionated aerosol particle number concentrations measured nearby a major road in Helsinki during 23 August–19 September 2003 and 14 January–11 February 2004. The available information also included electronic traffic counts, on-site meteorological measurements, and urban background particle number size distribution measurement. The ultrafine particle (UFP, diameter<100 nm) number concentrations at the roadside site were approximately an order of magnitude higher than those at the urban background site during daytime and downwind conditions. Both the modal structure analysis of the particle number size distributions and the statistical correlation between the traffic density and the UFP number concentrations indicate that the UFP were evidently from traffic related emissions. The modeling exercise included the evolution of the particle number size distribution nearby the road during downwind conditions. The model simulation results revealed that the evaluation of the emission factors of aerosol particles might not be valid for the same site during different time.

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42

Cai, Runlong, Dongsen Yang, Lauri R. Ahonen, Linlin Shi, Frans Korhonen, Yan Ma, Jiming Hao et al. "Data inversion methods to determine sub-3 nm aerosol size distributions using the particle size magnifier". Atmospheric Measurement Techniques 11, n. 7 (26 luglio 2018): 4477–91. http://dx.doi.org/10.5194/amt-11-4477-2018.

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Abstract. Measuring particle size distribution accurately down to approximately 1 nm is needed for studying atmospheric new particle formation. The scanning particle size magnifier (PSM) using diethylene glycol as a working fluid has been used for measuring sub-3 nm atmospheric aerosol. A proper inversion method is required to recover the particle size distribution from PSM raw data. Similarly to other aerosol spectrometers and classifiers, PSM inversion can be deduced from a problem described by the Fredholm integral equation of the first kind. We tested the performance of the stepwise method, the kernel function method (Lehtipalo et al., 2014), the H&A linear inversion method (Hagen and Alofs, 1983), and the expectation–maximization (EM) algorithm. The stepwise method and the kernel function method were used in previous studies on PSM. The H&A method and the expectation–maximization algorithm were used in data inversion for the electrical mobility spectrometers and the diffusion batteries, respectively (Maher and Laird, 1985). In addition, Monte Carlo simulation and laboratory experiments were used to test the accuracy and precision of the particle size distributions recovered using four inversion methods. When all of the detected particles are larger than 3 nm, the stepwise method may report false sub-3 nm particle concentrations because an infinite resolution is assumed while the kernel function method and the H&A method occasionally report false sub-3 nm particles because of the unstable least squares method. The accuracy and precision of the recovered particle size distribution using the EM algorithm are the best among the tested four inversion methods. Compared to the kernel function method, the H&A method reduces the uncertainty while keeping a similar computational expense. The measuring uncertainties in the present scanning mode may contribute to the uncertainties of the recovered particle size distributions. We suggest using the EM algorithm to retrieve the particle size distributions using the particle number concentrations recorded by the PSM. Considering the relatively high computation expenses of the EM algorithm, the H&A method is recommended for preliminary data analysis. We also gave practical suggestions on PSM operation based on the inversion analysis.

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43

Zhu, Yong Jian, Dai Qiang Deng e Ping Wang. "Fractal Features of Cracked Backfill Particle Size Distribution". Advanced Materials Research 588-589 (novembre 2012): 1894–98. http://dx.doi.org/10.4028/www.scientific.net/amr.588-589.1894.

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Based on the taking sample by geological drilling, combined with the fractal principle, analysis on the cracked backfill particle size of its fractal features and strength correlation. Even each backfill sand specimen particle size is difference, but calculation data shows that the particle size of each sand specimen has preferable fractal feature, the sand specimen particle size distribution has remarkable fractal structure by the linear fitted results of the sand specimens. The fractal relationship of strength and particle size distribution shows that with the increased of fractal dimension, the strength of backfill is decreased, that is to say there is negative correlation, the main cause is that the higher parameter D of the fractal dimension, the higher fine-grained content and more non-uniform of the particle size distribution, especially for the thinner full tailings, if properly increasing the content of slightly crude particles, the strength of backfill will be certainly improved to some extent.

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44

Thorvaldsson, T., S.-O. Broman e J. Lindqvist. "Particle size distribution measurement of intermetallic particles in zircaloy". Ultramicroscopy 19, n. 4 (gennaio 1986): 409–10. http://dx.doi.org/10.1016/0304-3991(86)90152-x.

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45

Finder, Christiane, Michael Wohlgemuth e Christian Mayer. "Analysis of Particle Size Distribution by Particle Tracking". Particle & Particle Systems Characterization 21, n. 5 (dicembre 2004): 372–78. http://dx.doi.org/10.1002/ppsc.200400948.

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46

Halter, Wolfgang, Rahel Eisele, Dirk Rothenstein, Joachim Bill e Frank Allgöwer. "Moment Dynamics of Zirconia Particle Formation for Optimizing Particle Size Distribution". Nanomaterials 9, n. 3 (2 marzo 2019): 333. http://dx.doi.org/10.3390/nano9030333.

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We study the particle formation process of Zirconia ( ZrO 2 )-based material. With a model-based description of the particle formation process we aim for identifying the main growth mechanisms for different process parameters. After the introduction of a population balance based mathematical model, we derive the moment dynamics of the particle size distribution and compare the model to experimental data. From the fitted model we conclude that growth by molecular addition of Zr-tetramers or Zr-oligomers to growing particles as well as size-independent particle agglomeration takes place. For the purpose of depositing zirconia-based material (ZrbM) on a substrate, we determine the optimal process parameters such that the mineralization solution contains preferably a large number of nanoscaled particles leading to a fast and effective deposition on the substrate. Besides the deposition of homogeneous films, this also enables mineralization of nanostructured templates in a bioinspired mineralization process. The developed model is also transferable to other mineralization systems where particle growth occurs through addition of small molecular species or particle agglomeration. This offers the possibility for a fast determination of process parameters leading to an efficient film formation without carrying out extensive experimental investigations.

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Kaminski, Iris, Nicolae Vescan e Avner Adin. "Particle size distribution and wastewater filter performance". Water Science and Technology 36, n. 4 (1 agosto 1997): 217–24. http://dx.doi.org/10.2166/wst.1997.0123.

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Particle size distribution (PSD) allows more accurate simulations of filtration models and better understanding of filter performance. PSD in municipal activated sludge effluent filtration is determined, varying filtration rate, grain size, flocculant type and dosage and function parameters are examined in this work. Results show, that removal efficiency varies for different size groups: small particles in the range of 5-10 μm in initialization stage, with no chemical aids, are poorly removed. Higher rate filters were more sensitive to the particle size than lower rate filters. Filtration with chemical aids is more sensitive to filtration conditions than filtration with no chemical additions. Particle size distribution in filtrate generally fits power law function behavior better than in raw effluent. The treatment smoothens the function somewhat. In a similar manner to the effect of settling in tanks or in natural lakes. Degree of correlation to power law function may indicate the mode of filter operation: high - working stage, low - breakthrough stage. β may also reflect on filters performance: high values - initial filtration stages. Decrease in β values - cycle progress towards breakthrough. Low β values, with low PSD correlation to power law function, may indicate low filtration efficiency or breakthrough.

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48

Половченко, S. Polovchenko, Веденин, Evgeniy Vedenin, Чартий, Pavel Chartiy, Шеманин e Valeriy Shemanin. "Particle Size Distribution Functions at Dust Separation Equipment’s Various Operating Modes". Safety in Technosphere 5, n. 1 (25 febbraio 2016): 41–47. http://dx.doi.org/10.12737/19022.

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The size-consist measure is an aerosol particle distribution function (PDF). The suspended particles’ size-consist affects their behavior during the dust separation process, their behavior in the atmosphere, and on the degree of their negative impact on the environment and human health. A numeric parameter allowing recover the particle size distribution function is the mean volumetrically-superficial particle diameter. This diameter changes during the dust separation equipment’s various operating modes. Therefore, the suspended particles’ size-consist control through the mean volumetrically-superficial particle diameter measuring allows determine the most harmful to the environment and human health suspended particle emissions, and more objectively calculate the suspended particle dispersion in the atmosphere.

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49

Krudysz, M., K. Moore, M. Geller, C. Sioutas e J. Froines. "Intra-community spatial variability of particulate matter size distributions in southern California/Los Angeles". Atmospheric Chemistry and Physics Discussions 8, n. 3 (27 maggio 2008): 9641–72. http://dx.doi.org/10.5194/acpd-8-9641-2008.

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Abstract. Ultrafine particle (UFP) number concentrations vary significantly on small spatial and temporal scales due to their short atmospheric lifetimes and multiplicity of sources. To determine UFP exposure gradients within a community, simultaneous particle number concentration measurements at a network of sites are necessary. Concurrent particle size distribution measurements aid in identifying UFP sources, while providing data to investigate local scale effects of both photochemical and physical processes on UFP. From April to December 2007, we monitored particle size distributions at 13 sites within 350 m to 11 km of each other in the vicinity of the Ports of Los Angeles and Long Beach using Scanning Mobility Particle Sizers (SMPS). Typically, three SMPS units were simultaneously deployed and rotated among sites at 1–2 week intervals. Total particle number concentration measurements were conducted continuously at all sites. Seasonal and diurnal size distribution patterns are complex, highly dependent on local meteorology, nearby PM sources, and times of day, and cannot be generalized over the study area nor inferred from one or two sampling locations. Spatial variation in particle number size distributions was assessed by calculating the coefficient of divergence (COD) and correlation coefficients (r) between site pairs. Results show an overall inverse relationship between particle size and CODs, implying that number concentrations of smaller particles (<40 nm) differ from site to site, whereas larger particles tend to have similar concentrations at various sampling locations. In addition, variations in r values as a function of particle size are not necessarily consistent with corresponding COD values, indicating that using results from correlation analysis alone may not accurately assess spatial variability.

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50

Krudysz, M., K. Moore, M. Geller, C. Sioutas e J. Froines. "Intra-community spatial variability of particulate matter size distributions in Southern California/Los Angeles". Atmospheric Chemistry and Physics 9, n. 3 (12 febbraio 2009): 1061–75. http://dx.doi.org/10.5194/acp-9-1061-2009.

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Abstract (sommario):

Abstract. Ultrafine particle (UFP) number concentrations vary significantly on small spatial and temporal scales due to their short atmospheric lifetimes and multiplicity of sources. To determine UFP exposure gradients within a community, simultaneous particle number concentration measurements at a network of sites are necessary. Concurrent particle number size distribution measurements aid in identifying UFP sources, while providing data to investigate local scale effects of both photochemical and physical processes on UFP. From April to December 2007, we monitored particle number size distributions at 13 sites within 350 m–11 km of each other in the vicinity of the Ports of Los Angeles and Long Beach using Scanning Mobility Particle Sizers (SMPS). Typically, three SMPS units were simultaneously deployed and rotated among sites at 1–2 week intervals. Total particle number concentration measurements were conducted continuously at all sites. Seasonal and diurnal number size distribution patterns are complex, highly dependent on local meteorology, nearby PM sources, and times of day, and cannot be generalized over the study area nor inferred from one or two sampling locations. Spatial variation in particle number size distributions was assessed by calculating the coefficient of divergence (COD) and correlation coefficients (r) between site pairs. Results show an overall inverse relationship between particle size and CODs, implying that number concentrations of smaller particles (<40 nm) differ from site to site, whereas larger particles tend to have similar concentrations at various sampling locations. In addition, variations in r values as a function of particle size are not necessarily consistent with corresponding COD values, indicating that using results from correlation analysis alone may not accurately assess spatial variability.

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