Dissertationen: „Particles size“

1

Xiang, Yanqiao. „Capillary Liquid Chromatography Using Micro Size Particles“. Diss., CLICK HERE for online access, 2004. http://contentdm.lib.byu.edu/ETD/image/etd531.pdf.

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2

Hunt, Eden Meyer. „The formation of nanosized metallic particles in oxide substrates via ion implantation-induced reduction“. Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/19415.

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3

Williams, Melvyn John. „Quantum size effects in colloidal copper“. Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239140.

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4

Lynch, James Andrew. „A study of smoke aging examining changes in smoke particulate size“. Link to electronic thesis, 2004. http://www.wpi.edu/Pubs/ETD/Available/etd-0510104-194400/.

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5

Schaap, Allison Schaap. „Transport and size-separation of airborne particles in a microchannel for continuous particle monitoring“. Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/30230.

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Microfluidics research and development has emerged as a novel and promising tool for the development of sensors and actuators. However, one area in which microfluidics has been only minimally employed is in the handling of airborne particles, or aerosols. The real-time monitoring of aerosols is important for protecting human health and earth’s environment. The small size of microchannels, coupled with the opportunity to integrate sensing technologies, suggests them as a promising tool for the next generation of aerosol sensors. To that end, this thesis presents a microfluidics-based system for the size-separation of aerosols. Specifically, centrifugal force is exerted on each particle as it travels around a curved microchannel, resulting in the particle occupying a size-dependent lateral position in the channel. The behaviours of aerosols in a microchannel are examined, including the effects of flow focusing, the diffusion of airborne particles in a channel, and the centrifugal and viscous forces exerted on particles in a curved microchannel. Mathematical descriptions and computer simulations of these effects are developed to model these effects. Straight and curved microchannels were fabricated and each of these effects was measured experimentally, and compared to the models. Various combinations of airborne particles between 0.2 µm and 3.2 µm were successfully separated by size. A prototype optical particle detector was built and tested for its suitability as a candidate for integration with the microchannel particle separator. This represents the first approach in which aerosols have been separated by centrifugal forces in a microchannel, and one of very few approaches that have been used for any kind of size-based separation of airborne particles in microchannels. The small footprint and potential for integration offered by microsystem fabrication technology make it a desirable avenue of pursuit for the development of small, portable particulate monitors. The results presented here confirm that this approach to size-separation is a feasible option for a future microsystem based size-selective particulate monitor.

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6

Crawford, Russell J., und n/a. „Particle size, hydrophobicity and flotation response“. Swinburne University of Technology, 1986. http://adt.lib.swin.edu.au./public/adt-VSWT20070828.150946.

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Quartz particles of various discrete particle size ranges have been methylated to varying known mounts using trimethylchlorosilane and their flotation behaviour has been assessed in a modification of the Hallimond tube. For each particle size there is a definite degree of. surface coverage below which the particles do not float. A 'flotation domain' is identified which shorvs that both coarse (-100pm) and fine (-10pm) particles require a greater degree of surface coverage to initiate flotation than do intermediate (-40pm) particles. Water contact angles have been measured on quartz plates and powders which have been methylated (under the same conditions) with trimethylchlorosilane. Both advancing and receding water contact angles measured on quartz plates as a function of degree of surface methylationare in good agreement with the angles predicted by the Cassie equation. Advancing water contact angles measured on quartz particles as a function of degree of surface methylation are also in good agreement with angles predicted by the Cassie equation up to surface coverages of'about 70%. The angles measured at higher surface coverages are less than those anticipated by the Cassie equation. The flotation behaviour of the particles has been compared with that predicted by existing flotation theories. It has been shown that coarse particle behaviour is predicted by the kinetic theory of flotation proposed by Schulze. Fine particle behaviour, however, only qualitatively agrees with Scheludko's theory of fine particle behaviour. Calculated induction times, in conjunction with observed flotation behaviour, indicate that the bubble-particle attachment process is most efficient for particles of about 38pm in diameter ander the set experimental conditions used in this study. Flotation rate trials were performed for three particle size ranges and rate constants were evaluated for the various degrees of surface coverage. It was found that the dependence of rate constant on particle size is essentially linear.

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7

Zheng, Feng. „Thermophoretic force measurements of spherical and non-spherical particles /“. Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/9874.

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8

Doychev, Todor [Verfasser]. „The dynamics of finite-size settling particles / Todor Doychev“. Karlsruhe : KIT Scientific Publishing, 2015. http://www.ksp.kit.edu.

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9

Scalon, Joao Domingos. „Spatial and size distributions of particles in composite materials“. Thesis, University of Sheffield, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284351.

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10

Chatterjee, Arpita. „Size-Dependant Separation of Multiple Particles in Spiral Microchannels“. University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1312480517.

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11

Davies, Emlyn John. „Scattering properties of suspended particles“. Thesis, University of Plymouth, 2013. http://hdl.handle.net/10026.1/1577.

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Effective monitoring and modelling of the marine environment is of importance to both the general public and the scientific community, but relies on the ability to obtain accurate measurements of suspended particle characteristics. Many instruments for measuring particles rely on optical and acoustic scattering from the particles and use this information to infer a particle size and concentration. However, assumptions such as spherical particles of a known composition are widely used, both in measurement technology and in numerical modelling. Various imaging techniques have shown great variability in the shape, size and composition of marine particles when measured within their natural environment. Subsequently, there is substantial uncertainty in the response of light scattering instruments to this diverse range of particles. In this study, a holographic camera was modified to simultaneously record in-focus images of marine particles with their forward angle scattering characteristics. This was achieved by combining both laser scattering and transmissometry with digital holography. The results from this system were compared with theoretical models of scattering from spherical particles within the intended size range of both instruments (15-500microns), with particle size information from both techniques agreeing well during these idealised conditions. The combined holographic and light scattering system was then used to investigate the response of the LISST-100 (Sequoia Scientific Inc.) to spherical particles with diameters extending beyond that intended by the instrument 250microns for type-B and 500microns for type-C derivatives), but that have been observed in-situ with imaging methods. This revealed an aliasing of single large particles into multiple smaller particles during the inversion of LISST-100 scattering into a particle size distribution. For spheres greater than the type-C instrument range, the inversion of scattering produces particle volume distributions that peak at varying sizes between 250-400microns. This key finding highlights the need for care to be taken when interpreting particle size distributions from the LISST-100 when there is potential for particles outside of its range limit. Natural particles, extracted from coastal waters, were then recorded by the combined laboratory system. These complex particles produced highly variable scattering properties which were contaminated by asymmetrical features within the azimuthal plane. This observation of strong azimuthal asymmetry is of concern for both measurements and models of optical properties that assume a symmetrical scattering function for natural particle populations. The azimuthal asymmetry in scattering contributed to additional variability in the response of the instrument in comparison to the holographic camera, which was also subjected to apparent particle break-up via segmentation during image processing. A discussion of holographic imaging and laser diffraction for characterising particles in-situ forms the final part of this thesis, which utilises data from a magnified holographic system that covers the same size range of the LISST-100. This final analysis demonstrated the need for future technology to accurately measure size distributions over a much larger range of sizes than is currently possible (e.g. <2microns to 1000microns). In summary, three key factors were identified to cause an increase in the apparent number of small particles reported by the LISST-100: 1) contamination from scattering of particles larger than the intended size range of the instrument; 2) a decrease in refractive index (particle composition); 3) additional scattering from small sub-components of particle geometry. The standard holographic camera systems are capable of accurately obtaining particle size and concentration measurements that are comparable to other techniques such as the LISST-100. However, in situations where background illumination is poor, errors in the image processing routines can cause an apparent particle break-up due to incorrect binarisation. Despite this, the holographic method provides a unique and powerful mechanism that enables images of particles to be analysed within the context of their in-situ environment.

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Thornton, Jenna Louise. „Ice particle size and roughness from novel techniques : in situ measurements and validation“. Thesis, University of Hertfordshire, 2016. http://hdl.handle.net/2299/17644.

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The roughness of ice crystals, defined by small-scale surface roughness and large scale complexity, in high-altitude cloud, has been studied due to its important influence on the radiative properties of ice cloud. The Small Ice Detector 3 (SID-3) created at the University of Hertfordshire was used to measure the characteristics of individual ice crystals in situ. These are supplemented by a range of meteorological in situ measurements, including temperature, relative humidity, and wind velocity to investigate the influence of atmospheric conditions on ice crystal roughness/complexity. Since the method of roughness retrieval was novel, for atmospheric ice particles, laboratory experiments were setup to test and improve the characterization techniques. Criteria were set as a result of the laboratory experiments which data was expected to meet for it to be deemed reliable. These criteria and techniques were applied to data collected in situ on research aircraft. A range of degrees of ice crystal roughness were observed over five flights from two campaigns based out of Scotland in 2012 and 2015 (PIKNMIX and CIRCCREX). When all the flights were combined the majority of particles (51%) were categorised as lightly rough; the second most common roughness type was moderately rough (39%). Smooth particles made up 10% of the total particles, and < 0.02% were classed as severely rough. When considering a wave-cloud case separately, a similar range of roughness values were seen, however, smooth particles were only observed at the cloud leading-edge where nucleation was expected to occur during the only straight level run of the aircraft to probe this region. During the same wave-cloud flight smooth particles were more common in supersaturated regions and moderately rough crystals were more common in subsaturated regions, suggesting that crystals are more likely to tend towards rougher values when observed in subsaturated environments (a statistical T-test showed this hypothesis to be statistically significant). It was found that due to limitations associated with instantaneous measurements, it was challenging to observe how ice particle roughness evolved in situ, since the history of the individual crystals was unknown in most cases. Orographic cloud, however, was found to provide a more robust estimation of crystal evolution as a consequence of having sharp-leading edges where nucleation events were expected to occur, and since crystals then follow streamlines, the distance from the sharp-leading edge can act as a proxy for time since nucleation.

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13

Preuss, Frida, Julia Asp, Sofia Larsson und Stephanie Kylington. „Separation of Nanoporous Silica Particles“. Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-277106.

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In this study a sample of particles in a size region of 0.05-10 μm were run through a centrifugation process with the ambition to make it monodisperse. The product requirements were stated as follows, particles within the size range of 2 to 3.8 μm should be isolated and separated from the sample with a D90/D10 < 1.4 where the D90/D50/D10 values should be approximately 3.8 μm/2.5 μm/2 μm. It was found that two layers of sucrose with a 50/50 volume distribution of 45w% sucrose solution and 60w% sucrose solution respectively, was the most efficient density gradient arrangement for separation of this particular sample. The optimal time and RPM combination was found to be 5 min 3000 RPM with a fast acceleration and slower deceleration, ratio 9:6. Two centrifugation rounds on the same sample improved D90/D10 drastically. The effect of centrifugation rounds on D90/D10 was not investigated further than 3 rounds, however this would be a good starting point for further studies. The upscaled test runs indicated a positive result, i.e. the yields with respect to both mass and purity were reproducible. It is worth mentioning that the upscale was only in the volume, sample load volume and surface area factors. The gradient height or particle travel distance remained the same.

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Mei, Nanxuan. „Characterization of Stainless Steel Welding Fume Particles : Influence of Stainless Steel Grade, Welding Parameters and Particle Size“. Thesis, KTH, Materialvetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-189203.

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Welding is a widely used method to join two pieces of stainless steel. Since it produces a large amount of fume during the process, it can cause adverse health effects. The welding fume particles contain many elements. Among them Cr, Mn and Ni are of concern. These three elements can cause diseases if inhaled by humans, especially Cr(VI). In this project, welding fume particles are collected during welding of different stainless steel grades (austenitic AISI 304L and duplex LDX2101). Furthermore, different welding types (manual metal arc welding and metal active gas welding), shielding gas (MISON 2, MISON 18 and CORGON 18) and welding electrodes were varied (solid and flux cored wire). The particles were tested by scanning electron microscopy, energy dispersive X-ray spectroscopy, cyclic voltammetry and atomic absorption spectroscopy. The composition of the particles was measured and the surface chemical speciation estimated. In addition, metal release (Fe, Cr, Mn, and Ni) in phosphate buffered saline solution (pH 7.4, 37℃, 24h) from the particles was tested. Fe, Cr and Mn were found on the surface of the particles and released to different extent in the phosphate buffered saline solution (dominated by Cr).

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15

Gulcu, Besim. „Incipient Motion Of Coarse Solitary Particles“. Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610420/index.pdf.

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In this study the incipient motion of coarse solitary particles having different specific weights and shapes was investigated. A tilting flume of rectangular cross-section having a net working length of 12 m was used through the experiments. The slope of the channel and the discharge in the channel are the two basic variable parameters that determine the initiation of motion. Particles made of cement and mixture of cement and iron dust in certain ratios were used in the experiments with an obstructing element of various heights right behind the particles. Dimensionless hydraulic parameters determined from theoretical analysis were related to each other. Velocity profiles over the flow depths were measured and flow conditions corresponding to critical conditions were evaluated in terms of critical velocities and shear velocities. The findings of this study were compared with the results of similar studies given in the literature.

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Blanco-Mantecon, Mireia. „Interactions, particle size and surface effects in magnetic nanoparticle systems“. Thesis, Bangor University, 2000. https://research.bangor.ac.uk/portal/en/theses/interactions-particle-size-and-surface-effects-in-magnetic-nanoparticle-systems(2f7d3ef7-ef4c-43b0-b3ad-9e5c68f629e5).html.

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This work has involved the study of the magnetic behaviour of small magnetic nanoparticle systems. Due to the reduced size of magnetic nanoparticles they present distinctive properties, such as size and surface effects, that have been analysed in this work, as well as the effect of interactions in such systems. The samples chosen for the study were magnetite particles in the form of a ferrofluid and Co nanoclusters in a nonmagnetic matrix of Cu. Both systems present very narrow particle size distributions, which facilitates the interpretation of the data. The samples have been subjected to basic characterisation, which includes the determination of the distribution of magnetic particle sizes using the magnetisation curves at room temperatures, TEM microscopy and X-ray diffraction, in the case of the ferrofluid samples. For the nanoclusters, a time of flight spectrometer has been used to obtain the number of atoms per cluster. Many of the measurements have been performed at low temperatures, where thermal effects are minimised. For such measurements the samples have been frozen in a zero applied field, so that they have a random distribution of magnetic moments prior to the measurement. The energy barrier distributions have been calculated via the temperature decay of remanence (TDR). From this study, an effective anisotropy constant has been calculated. For the study of the interactions, surface and size effects, magnetisation, susceptibility (ZFC), remanence and delta-M curves, as well as the time dependence of magnetisation have been studied. The attempt frequency of the different particle size systems has been calculated using different techniques. The basic magnetic behaviour can be explained on the basis of the Neel blocking model. It has been found that the systems with the smaller particles have significant surface effects, which are enhanced at lower temperatures. Interactions, which are weak due to the low concentration of magnetic material in the samples (<10%), have been found to be overall demagnetising and the evolution of the magnetic properties with dilution has been explained. As is the case for the surface effects, interaction effects are stronger at low temperatures due the reduction of thermal effects. The experimental results have been compared with calculations from a Montecarlo model for fine particles, which includes the effects of concentration, anisotropy, particle size and temperature.

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17

Vianna, Sérgio Maurício S. M. „The effect of particle size, collector coverage and liberation on the floatability of galena particles in an ore /“. [St. Lucia, Qld.], 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18153.pdf.

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18

Schlipf, Daniel M. „BIOMOLECULE LOCALIZATION AND SURFACE ENGINEERING WITHIN SIZE TUNABLE NANOPOROUS SILICA PARTICLES“. UKnowledge, 2015. http://uknowledge.uky.edu/cme_etds/44.

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Mesoporous silica materials are versatile platforms for biological catalysis, isolation of small molecules for detection and separation applications. The design of mesoporous silica supports for tailored protein and biomolecule interactions has been limited by the techniques to demonstrate biomolecule location and functionality as a function of pore size. This work examines the interaction of proteins and lipid bilayers with engineered porous silica surfaces using spherical silica particles with tunable pore diameters (3 – 12 nm) in the range relevant to biomolecule uptake in the pores, and large particle sizes (5 - 15 µm) amenable to microscopy imaging The differentiation of protein location between the external surface and within the pore, important to applications requiring protein protection or catalytic activity in pores, is demonstrated. A protease / fluorescent protein system is used to investigate protein location and protection as a function of pore size, indicating a narrow pore size range capable of protein protection, slightly larger than the protein of interest and approaching the protease dimensions. Selective functionalization, in this case exterior-only surface functionalization of mesoporous particles with amines, is extended to larger pore silica materials. A reaction time dependent functionalization approach is demonstrated as the first visually confirmed, selective amine functionalization method in protein accessible supports. Mesoporous silica nanoparticles are effective supports for lipid bilayer membranes and membrane associated proteins for separations and therapeutic delivery, although the role of support porosity on membrane fluidity is unknown. Transport properties of bilayers in lipid filled nanoparticles as a function of pore diameter and location in the particle are measured for the first time. Bilayer diffusivity increases with increasing pore size and is independent of bilayer location within the core, mid or cap of the particle, suggesting uniform long range bilayer mobility in lipid filled pores. Application of lipid bilayers on mesoporous silica was examined for membrane associated proteins A unique method to adhere functional proteins in lipid bilayers on mesoporous silica particles is established using vesicles derived from cell plasma membranes and their associated proteins. This method of membrane protein investigation retains proteins within native lipid membranes, stabilizing proteins for investigation on supports.

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19

Li, Bo. „Detection of particles and estimation of size distribution in process fluids /“. Online version of thesis, 1992. http://hdl.handle.net/1850/11258.

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20

Mateos, González Eduardo. „Measurement of stability and size of colloidal particles in aqueous suspension“. Thesis, Uppsala universitet, Materialfysik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-394083.

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This project focused on the study of self-assembling systems that can be inuenced by an external magnetic field, following the PhD research of Hauke Carstensen. My role was to study the behavior of beads and to optimize the tunable parameters so that the main force driving the dynamics of the system is the magnetic dipolar interaction between beads. To make sure that no other force plays an important role, we checked a number of things, the most problematic of which is flocculation in the colloid, which may happen if some beads get stuck to each other; to prevent them from aggregating we have to make sure that they have a large zeta potential, which will result in an electrically repulsive force between beads and will thus increase the stability of the colloid. We also have to make sure that other forces in the sample do not exceed the magnitude of magnetic forces between particles; examples of such forces can be the drag experienced while moving in the viscous ferrofluid, the gravity force or the random thermal movement of the molecules in the fluid. In order to study these efects, I measured the zeta potential of the magnetic and non-magnetic beads and later I added a surfactant compound (SDS) to our sample in order to increase said potential.

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21

Fornari, Walter. „Suspensions of finite-size rigid particles in laminar and turbulent flows“. Doctoral thesis, KTH, Mekanik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-217812.

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Dispersed multiphase flows occur in many biological, engineering and geophysical applications. Understanding the behavior of suspensions is a difficult task. In the present work, we numerically study the behavior of suspensions of finite-size rigid particles in different flows. Firstly, the sedimentation of spherical particles larger than the Taylor microscale in sustained homogeneous isotropic turbulence and quiescent fluid is investigated. The results show that the mean settling velocity is lower in an already turbulent flow than in a quiescent fluid. We also investigate the settling in quiescent fluid of oblate particles. We find that at low volume fractions the mean settling speed of the suspension is substantially larger than the terminal speed of an isolated oblate. Suspensions of finite-size spheres are also studied in turbulent channel flow. First, we change the solid volume and mass fractions, and the solid-to-fluid density ratio in an idealized scenario where gravity is neglected. Then we investigate the effects of polydispersity. It is found that the statistics are substantially altered by changes in volume fraction. We then consider suspensions of solid spheres in turbulent duct flows. We see that particles accumulate mostly at the corners or at the core depending on the volume fraction. Secondary motions are enhanced by increasing the volume fraction, until excluded volume effects are so strong that the turbulence activity is reduced. The inertial migration of spheres in laminar square duct flows is also investigated. We consider semi-dilute suspensions at different bulk Reynolds numbers and duct-to-particle size ratios. The highest particle concentration is found around the focusing points, except at very large volume fractions. Finally we study the rheology of confined dense suspensions of spheres in simple shear flow. We focus on the weakly inertial regime and show that the effective viscosity varies non-monotonically with increasing confinement.

QC 20171117

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Tungapindi, Navina. „Classification of fine particles using a Taylor-Couette device“. Diss., Rolla, Mo. : Missouri University of Science and Technology, 2009. http://scholarsmine.mst.edu/thesis/pdf/Tungapindi_09007dcc80601425.pdf.

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Thesis (M.S.)--Missouri University of Science and Technology, 2009.
Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed February 18, 2009) Includes bibliographical references (p. 54-56).

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Bäckebo, Markus. „The influence of particle size distribution on bio-coal gasification rate as related to packed beds of particles“. Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-79084.

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This thesis is a part of a collaboration between Höganäs AB and Luleå University of Technology, aiming at replacing fossil process coal with bio-coal in their sponge iron process. The difference in gasification reactivity, i.e. reaction rate, between fossil coals and bio-coals is the major challenge in the endeavor to decrease the climate impact of the existing process. The goal of this thesis is to develop a model of reaction rate for bio-coals in relation to particle size distribution. Different particle size distributions were combined and tested to see how that affects the effective reaction rate. Within the scope of this work, gasification reactivities of different materials, including coal, cokes, and bio-coals, were determined. Three bio-coals were selected to study the effect of particle size distribution on reactivity. Kinetic parameters were determined by using thermogravimetric analysis in the temperature range of 770-850 °C while varying CO2 partial pressure between 0.1-0.4 atm. The effect of particle size on the reaction rate was investigated by using particles with diameter between 0.18 and 6.3 mm. The effect of particle size distribution on the reactivity of bio-coal in a packed bed was carried out in a macro thermogravimetric reactor with a constant bed volume of 6.5 cm3 at 980 °C and 40% (vol.) of CO2. The experimental investigation in three different rate-limiting steps was done for one bio-coal sample, i.e. Cortus Bark bio-coal. The activation energy of the bio-coal was 187 kJ mol-1, and the reaction order was 0.365. For the internal diffusion control regime, an increase in particle size resulted in low reaction rate. The effective diffusivity calculated from the Thiele modulus model was 1.41*10-5 m2 s-1. For the external diffusion control regime, an increase in particle size increased the reaction rate up to a certain point where it plateaued at >1 mm. By choosing two discrete particle size distributions, where a smaller average distribution can fit into a larger average distribution the reaction rate was lowered by 30% compared to only using a single narrow particle size distribution. This solution decreased the difference of apparent reaction rate in a packed bed between the bio-coal and anthracite from 6.5 times to 4.5 times. At the moment the model is not generalized for all bio-coals. However, the developed methodology can be routinely applied to assess the different bio-coal samples. One possible error can be that pyrolysis influences the gasification rate for bio-coal that is pyrolyzed below the temperature of the gasification test. There is a clear correlation between particle size distributions, bulk density, and apparent reactivity. By mixing two distributions the reaction rate of Cortus Bark was reduced from 6.5 times the reaction rate of anthracite to 4.5.

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Rydefalk, Staffan. „Particle Measurements Using Fluctuations in the Regular Transmittance of Light Through a Particle Dispersion : Concentration and Particles size - Theory, Measurement Principles and Applications for Pulp and Paper Production“. Doctoral thesis, KTH, Industriell produktion, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10639.

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The regular transmittance of light or similar radiation through a flowing suspension of particles fluctuates because of the random occurrence of particles in the beam.In the work presented here, a theory for this fluctuating behaviour with the emphasison dispersions of mm-length slender cylindrical particles having circular crosssections is given. The particles in question are wood pulp fibres, which as a first approximation are considered to have a cylinder shape. Four possible measurementprinciples are described theoretically and experimentally. The four principles are for the measurement of concentration, length distribution characterized as lengthclasses, mean length, and mean width. The usefulness in industrial process monitoring of two of these principles is exemplified with pulp measurements. In order to estimate model errors, numerical simulations were used. Although other techniques such as image analysis may compete, the technique presented here is attractive because of the simplicity of the measurement device used.
QC 20100806

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Elhimer, Medhi. „The dynamics of neutrally buoyant particles in isotropic turbulence : an experimental study“. Thesis, Toulouse, INPT, 2012. http://www.theses.fr/2012INPT0049/document.

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Le but de cette étude expérimentale est de caractériser la dynamique de particules solides, à flottabilité nulle, incluse dans un écoulement turbulent isotrope en décroissance libre. Les particules utilisées sont de forme sphérique et ont un diamètre de 4 à 5 fois plus grand que l'échelle spatial de Kolmogorov de l'écoulement. De part leur taille, les particules ont également un nombre de Stokes proche de l'unité. On s'attend alors à ce que ces particules aient une dynamique différente de celle du fluide environnant. Dans cette étude, ont se propose de quantifier les différences de vitesses entre les deux phases à l'aide d'une technique de vélocimétrie simultanée
In this experimental study, the focus is made on the characterization of the dynamics of solid neutrally buoyant particles embedded in a freely decaying, nearly isotropic turbulence, with a weak mean flow. The particles are spherical with diameters several times larger than the Kolmogorov scale. The study of this flow configuration is still challenging both theoretically and numerically. Due to large particle sizes, the local flow around particles can not be considered as uniform and due to fluid-particle density ratio of around unity, the history and Basset forces cannot be neglected in comparison with the viscous drag force. Particle equation of motion is then fully non-linear, in contrast to the equation for heavy particles with diameters smaller then the Kolmogorov scale, for which only the Stokes drag is considered. In several experimental and numerical studies, the effect of particle size on velocity and acceleration statistics has been investigated (Homann and Bec 2010 ; Qureshi et al. 2008 ; Ouellette et al. 2008 ; Xu and Bodenschatz 2008). In the case of isotropic turbulence, Homann and Bec (2010) show that while the PDF of the particle velocity normalized by the square root of its variance does not vary with particle size, the variance itself is size dependent. A scaling relation for particle velocity variance has been proposed by using the Faxen correction (Gatignol 1983) which takes into account the non uniformity of the fluid flow at the scale of the particle. The aim of our research is to further study the dependence of particle dynamics on particle size. To that purpose, a turbulence generator has been set-up and the resulting turbulence is characterized. Then the flow was seeded with millimeter sized, neutrally-buoyant particles and the velocity of the two phases have been measured simultaneously. Simultaneous measurements of particle and surrounding fluid velocities show that although the global velocity statistics of the two phases have comparable values, the particles may have different local velocity from the velocity of the neighboring fluid

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Doychev, Todor [Verfasser], und M. [Akademischer Betreuer] Uhlmann. „The dynamics of finite-size settling particles / Todor Doychev. Betreuer: M. Uhlmann“. Karlsruhe : KIT-Bibliothek, 2014. http://d-nb.info/1063027772/34.

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Orellano, Ramiro E. „Grain size control by thermomechanical processing (TMP) : the role of dispersed particles /“. Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion/05Mar%5F.pdf.

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Wang, Xiaoning. „Size and shape specific particles toward biomedical imaging: design, fabrication, and characterization“. Thesis, Boston University, 2014. https://hdl.handle.net/2144/12947.

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Thesis (Ph.D.)--Boston University
The power of a biomedical imaging modality can be augmented and is, in large part, determined by the capabilities of the available contrast agents. For example, quantum dots represent a colorful palette of powerful contrast agents for optical fluorescence imaging and Raman spectroscopy, given their tunable multiplexing capability and long-term stability compared to traditional organic molecule-based fluorescent labels. On the contrary, as the workhorses in both clinical and research imaging, the full potentials of magnetic resonance imaging and computed tomography have yet to be actualized due to several existing fundamental limitations in the currently available contrast agents, including but not limited to, the lack of multiplexing capability, low sensitivity, as well as the lack of functional imaging capacity. Leveraging both traditional top-down micro- and nanoelectromechanical systems fabrication techniques and bottom-up self-assembly approaches, this dissertation explores the possibility of mitigating these limitations by engineering precisely controllable, size and shape (as well as a host of other materials properties) specific micro- and nanoparticles, for use as the next generation contrast agents for magnetic resonance imaging and computed tomography. Herein, the ways by which engineering approaches can impact the design, fabrication and characterization of contrast agents is investigated. Specifically, different configmations of magnetic micro- and nanoparticles, including double-disk and hollow-cylinder structmes, fabricated using a top-down approach were employed as magnetic resonance imaging contrast agents enabled with a multiplexing capability and improved sensitivity. Subsequently, a scalable nanomanufactming platform, utilizing nanoporous anodized aluminum oxide membranes as templates for pattern transfer as well as thermal/ultraviolet nanoimprinting techniques, was developed for the high throughput fabrication of size and shape specific polymeric nanorods. When ladened with X-ray attenuating tantalum oxide nanoparticle payloads, these polymeric nanorods can be used as contrast agents for computed tomography, yielding prolonged vascular circulation times, improved sensitivity, as well as targeted imaging capabilities. Furthermore, by applying various payload materials, this nanomanufacturing platform also has the flexibility to produce contrast agents for other imaging modalities, as well as the potential to realize dual-purpose agents for both diagnostic and therapeutic applications.

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Faletra, Melissa Kathleen. „Segregation of Particles of Variable Size and Density in Falling Suspension Droplets“. ScholarWorks @ UVM, 2014. http://scholarworks.uvm.edu/graddis/265.

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The problem of the falling under gravity suspension droplet was examined for cases where the droplet contains particles with different densities and different sizes. Cases examined include droplets composed of uniform-size particles with two different densities, of uniform-density particles of two different sizes, and of a distribution of particles of different densities. The study was conducted using both simulations based on Oseenlet particle interactions and laboratory experiments. It is observed that when the particles in the suspension droplet have different sizes and densities, an interesting segregation phenomenon occurs in which lighter/smaller particles are transported downward with the droplet and preferentially leave the droplet by entering into the droplet tail, whereas heavier/larger particles remain for longer periods of time in the droplet. When computations are performed with two particle densities or two particle sizes, a point is eventually reached where all of the lighter/smaller particles have been ejected from the droplet, and the droplet continues to fall with only the heavier/larger particles. A simple model explaining three stages of this segregation process is presented.

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Karlsson, Hanna. „Particularly harmful particles? : a study of airborne particles with a focus on genotoxicity and oxidative stress /“. Stockholm, 2006. http://diss.kib.ki.se/2006/91-7140-972-6/.

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Hamilton, Peter. „Investigation of a drying process of needle-shaped particles using particle size analysis techniques and non-invasive Raman spectrometry“. Thesis, University of Strathclyde, 2011. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=18135.

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Brodie, Ian. „Investigation of stormwater particles generated from common urban surfaces“. University of Southern Queensland, Faculty of Engineering and Surveying, 2007. http://eprints.usq.edu.au/archive/00003558/.

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[Abstract]: Pollution due to urban stormwater runoff is a significant environmental issue. Large regional devices including sediment ponds and constructed wetlands are common features in the urban landscape to treat runoff. In keeping with this approach, data requirements to evaluate stormwater impacts have mainly been met by the monitoring of sizeable urban catchments, typically greater than 10ha in area. Urban runoff characteristics have thus been conventionally linked with broadly defined catchment attributes. Land use, as defined by zonings such as Residential, Commercial and Industrial, is an attribute often used to evaluate stormwater runoff from urban catchments.The emergence of Water Sensitive Urban Design (WSUD) in Australia is changing the management focus from the reliance on a small number of large-scale devices to many smaller-scale source controls distributed throughout the catchment. This paradigm shift in stormwater management places greater emphasis on small-scale processes within urban areas. Subsequently there is a need for more knowledge about stormwater generated from specific urban surfaces (roads, roofs, grassed areas etc).The objective of this study was to demonstrate how urban stormwater quality can be managed on the basis of urban surfaces. The study involved the collection of data for typical urban surfaces and the development of predictive models to estimate stormwater quality. A series of case studies is provided to illustrate the use of surface-related data and modelling tools in stormwater management, particularly in the context of WSUD.Non-Coarse Particles (NCP), defined as suspended solids less than 500μm in size, was selected as the stormwater pollutant under consideration. NCP is divided into the following particle size classes; Very Fine Particles (VFP, <8μm), Fine Particles (FP, 8-63μm) and Medium Particles (MP, 63-500μm). Laboratory methods to determine the concentration of these particle classes within stormwater runoff were adapted and refined from current standard methods. Organic content of each stormwater particle class was also determined.An innovative device, the flow splitter, was developed to collect runoff samples from urban surfaces. The flow splitter was designed to obtain a composite flow-proportional sample, necessary to derive the Event Mean Concentration of stormwater particles. Hydraulic and sediment testing of a prototype flow splitter confirmed that the device is an accurate and unbiased sampling method.Flow splitters were installed at five monitoring sites within inner city Toowoomba, Australia. The sites have small catchments (50 to 450m2 area) representative of urban impervious areas (galvanized iron roof, concrete carpark and bitumen road pavement) and pervious areas (grassed and exposed bare soil). Overall, runoff from 40 storms with rainfalls from 2.5mm to 64.3mm was sampled during the period December 2004 to January 2006.A scatter plot analysis identified potential correlations between measured NCP loads and basic rainfall parameters such as rainfall depth and intensity. An exponential-type trend, consistent with many washoff models, is evident between load and average rainfall intensity for all surfaces. A composite index, referred to as the Rainfall Detachment Index (RDI), was found to be better than average rainfall intensity in explaining a relationship between NCP load and storm rainfall characteristics.The insight gained from the RDI led to the development of a particle Mass Balance Model for impervious surfaces. Depending on the surface type, the model was able for provide reasonable estimates (R2 = 0.74 to 0.97) against the measured NCP loads. Simpler analytical methods for particle load estimation were also developed in the study. A total of five methods were produced. An error analysis was conducted to compare the performance of each method to accurately reproduce the measured NCP loads. The analysis also included three methods used in current practice, which performed poorly compared to the new modelling techniques.The analytical methods provide useful tools in urban stormwater planning. The Mass Balance Model and measured surface-specific data were used in a number of case study examples to demonstrate possible applications. The applications included assessments of 1) the relative contribution that different urban surfaces make to the particle load in runoff; 2) how surface-specific data can be directly transferred to represent a large-scale urban catchment located in a different climate; 3) the particle loads generated from Residential and Commercial land uses; 4) the effect of exposed areas of bare soil on the particle loads from a Residential catchment; 5) the effect that widespread adoption of rainwater tanks may have on particle concentration in Residential urban runoff and 6) the particle load reductions by the use of a grass swale to treat road runoff.

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Emerson, Sean Christian. „Synthesis of Nanometer-size Inorganic Materials for the Examination of Particle Size Effects on Heterogeneous Catalysis“. Digital WPI, 2000. https://digitalcommons.wpi.edu/etd-dissertations/253.

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The effect of acoustic and hydrodynamic cavitation on the precipitation of inorganic catalytic materials was investigated. The overall objective was to understand the fundamental factors involved in synthesizing nanometer-size catalytic materials in the 1-10 nm range in a cavitating field. Materials with grain sizes in this range have been associated with enhanced catalytic activity compared to larger grain size materials. A new chemical approach was used to produce titania supported gold by coprecipitation with higher gold yields compared to other synthesis methods. Using this approach, it was determined that acoustic cavitation was unable to influence the gold mean crystallite size compared to non-sonicated catalysts. However, gold concentration on the catalysts was found to be very important for CO oxidation activity. By decreasing the gold concentration from a weight loading of 0.50% down to approximately 0.05%, the rate of reaction per mole of gold was found to increase by a factor of 19. Hydrodynamic cavitation at low pressures (6.9-48 bar) was determined to have no effect on gold crystallite size at a fixed gold content for the same precipitation technique used in the acoustic cavitation studies. By changing the chemistry of the precipitation system, however, it was found that a synergy existed between the dilution of the gold precursor solution, the orifice diameter, and the reducing agent addition rate. Individually, these factors were found to have little effect and only their interaction allowed gold grain size control in the range of 8-80 nm. Further modification of the system chemistry and the use of hydrodynamic cavitation at pressures in excess of 690 bar allowed the systematic control of gold crystallite size in the range of 2-9 nm for catalysts containing (2.27 ± 0.17)% gold. In addition, it was shown that the enhanced mixing due to cavitation led to larger gold yields compared to classical syntheses. The control of gold grain size was gained at the loss of CO activity, which was attributed to the formation of non-removable sodium titanate species. The increased mixing associated with cavitation contributed to the activity loss by partially burying the gold and incorporating more of the sodium titanate species into the catalysts. This work produced the first evidence of hydrodynamic cavitation influencing the gold crystallite size on titania supported gold catalysts and is the only study reporting the control of grain size by simple mechanical adjustment of the experimental parameters. Despite the low activity observed due to sodium titanate, the methodology of adjusting the chemistry of a precipitating system could be used to eliminate such species. The approach of modifying the chemical precipitation kinetics relative to the dynamics of cavitation offers a general scheme for future research on cavitational processing effects.

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Swanepoel, Francois. „Estimation of particle size distributions in mineral process systems using acoustic techniques“. Thesis, Stellenbosch : Stellenbosch University, 2000. http://hdl.handle.net/10019.1/51746.

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Thesis (MEng)--Stellenbosch University, 2000.
ENGLISH ABSTRACT: A desire to increase the efficiency of the comminution process in mineral process systems has led to the need of determining the size distribution of ore particles at various stages in the system. The objective of this research is to investigate the feasibility of the use of an acoustic sensor for measuring particle size distribution. The acoustic signal generated when the particles impact on a cantilever bar is analysed using digital signal processing techniques. As rocks fall onto a metal bar, the bar vibrates. The vibrations contain information th a t is extracted to determine the size of particles tha t impacted on the bar. The bar is modelled as a linear system which is excited by impulses (impact of particles). The response of the bar is deconvolved from the acoustic signal to obtain an impulse whose amplitude is proportional to the energy of the impact. In order to improve size estimates, deconvolution is performed using a statistical model of the impulse sequence (Bernoulli-Gaussian) and then estimated using MAP estimation. Size estimates are not only a function of the mass of particles, but also on the exact position of impact on the bar. Since there is always a variation in the position of impact, size estimates are erroneous. It was found that the position of impact can be determined as to reduce variances dramatically. Due to physical sampling in space, the sensor has a bias towards larger particles. We show how this can be represented mathematically and removed. This project is mainly concerned with rocks in the +8-25mm (+0,7-22 gram) size range.
AFRIKAANSE OPSOMMING: Vergruising van erts in die mineraalbedryf verg groot hoeveelhede energie. Daar is ’n behoefte gei'dentifiseer orn hierdie proses meer effektief te maak. Aangesien die effektiwiteit van ’n meul ’n funksie is van die ertsgroottes wat gemaal word, kan partikel grootte inligting aangewend word om effektiwiteit te bevorder. Die doel van hierdie tesis is om die lewensvatbaarheid van ’n akoestiese sensor vir die doel van partikelgrootte estimasie, te ondersoek. Erts partikels wat val vanaf ’n vervoerband op ’n kantelbalk, veroorsaak dat die balk vibreer. Deur hierdie vibrasies te meet en verwerk, kan inligting aangaande partikel grootte verkry word. Die stelsel word gemodelleer as ’n lineere sisteem met impulse as intree. Die geobserveerde sein is die konvolusie tussen die intree impulse en die impulsweergawe van die sisteem. Deur gebruik te maak van ’n statistiese model en MAP-estimasie, word die effek van die sisteem gedekonvuleer vanaf die geobserveerde sein om ’n benadering van die intree impuls sein te verkry. Die amplitudes van die impulse word gebruik as ’n aanduiding van partikel massa. Partikelgroottes soos benader deur die stelsel, is ’n funksie van die die posisie waar die partikel die balk tref. Deur van patroonherkenning tegnieke gebruik te maak, word die posisie van impak bepaal om sodoende grootte benaderings aan te pas en die variansie van grootte verspreidings te verminder. As gevolg van die feit dat partikels gemonster word deurdat slegs ’n klein persentasie van die hele omvang van partikels ondersoek word, onstaan daar ’n oorhelling ( “bias” ) na groter partikels. Die kans dat groter partikels die balk tref is groter as vir klein partikels. ’n Wiskundige model vir hierdie verskynsel word voorgestel en gewys hoe die die oorhelling geneutraliseer kan word. Hierdie projek het te doen met ertsgroottes +8-25mm (+0,7-22 gram).

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Zhang, Ming. „Optical measurement of ash particle size and velocity in gas-solid flow“. Morgantown, W. Va. : [West Virginia University Libraries], 2004. https://etd.wvu.edu/etd/controller.jsp?moduleName=documentdata&jsp%5FetdId=3462.

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Thesis (M.S.)--West Virginia University, 2004.
Title from document title page. Document formatted into pages; contains x, 98 p. : ill. (some col.) + 1 video file. Includes a video file (29 sec.). Includes abstract. Includes bibliographical references (p. 91-92).

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Greenwald, Roby. „Real-time measurement of the water-insoluble aerosol size distribution instrument development and implementation /“. Diss., Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-07072005-105355/.

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Thesis (Ph. D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2006.
Armistead Russell, Committee Member ; James Mulholland, Committee Member ; Rodney Weber, Committee Member ; Michael H. Bergin, Committee Chair ; Jean-Luc Jaffrezo, Committee Member.

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Leaper, Mark Christopher. „Segregation of particles of wide size distribution below 300 microns in fluidised beds“. Thesis, University of Birmingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398889.

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Annavarapu, V. N. Ravikanth (Venkata Nagandra Ravikanth). „Size based separation of submicron nonmagnetic particles through magnetophoresis in structured obstacle arrays“. Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/59872.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references.
The focus of this work was on developing a novel scalable size based separation technology for nonmagnetic particles in the submicron size range utilizing magnetophoretic forces. When a nonmagnetic particle is immersed in a magnetic fluid and subjected to magnetic field gradients, it behaves like a magnetic hole and experiences magnetic buoyancy forces proportional to its volume. This size dependence of magnetic buoyancy forces can be exploited to selectively focus larger nonmagnetic particles from a mixture and thus we can fractionate nonmagnetic particles on the basis of size. We designed a separation system composed of a regular array of iron obstacle posts which utilized magnetic buoyancy forces to perform size based separations. A Lagrangian particle tracking model was developed which could describe the behavior of a nonmagnetic particle in regions of inhomogeneous magnetic field gradients. Particle trajectories were simulated for a number of obstacle array geometries and over a range of operating conditions in order to understand the nature of the magnetic buoyancy force and aid in separation system design. Based on the results of the trajectory simulations, an experimental set up was conceptualized and built to demonstrate capture and separation of nonmagnetic particles using magnetic buoyancy forces. Capture visualization experiments were performed utilizing fluorescence microscopy which showed visual evidence of focusing and preferential capture of larger nonmagnetic particles. Experiments also yielded results qualitatively consistent with the Lagrangian trajectory model. Pulse chromatography experiments were also performed in order to quantitatively understand the capture and separation behavior. The results obtained showed quantitative evidence of preferential capture of larger particles. Particle capture efficiencies were compared with predictions from simulations and were found to be qualitatively consistent. Finally, the potential of this separation technology was demonstrated by performing proof-of-concept separation experiments with a mixture of 840 nm and 240 nm particles.
by V. N. Ravikanth Annavarapu.
Ph.D.

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Qin, Zhenpeng. „Modeling of Ion Transport for Micro/Nano Size Particles in Coulter Counter Application“. University of Akron / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=akron1240858653.

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Hubbard, Joshua A. „A study of aerodynamic deaggregation mechanisms and the size control of NanoActive™ aerosol particles“. Thesis, Kansas State University, 2006. http://hdl.handle.net/2097/173.

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Master of Science
Department of Mechanical and Nuclear Engineering
Steven J. Eckels
Christopher M. Sorensen
Large specific surface areas and high concentrations of reactive edge and defect sites make NanoActive™ metal oxide powders ideal chemical adsorbents. These powders are dispersed in aerosol form to remediate toxic wastes and neutralize chemical and biological warfare agents. In the destructive adsorption of toxic chemicals, effective application requires particles be as small as possible, thus, maximizing surface area and number of edge and defect sites. Other applications, e.g. smoke clearing, require particles be large so they will settle in a timely manner. Ideally, particle size control could be engineered into powder dispersion devices. The purpose of this study was to explore particle cohesion and aerodynamic deaggregation mechanisms to enhance the design of powder dispersion devices. An aerosol generator and four experimental nozzles were designed to explore the most commonly referenced deaggregation mechanisms: particle acceleration, particles in shear and turbulent flows, and particle impaction. The powders were then dispersed through the nozzles with increasing flow rates. A small angle light scattering device was used to make in situ particle size measurements. The nozzle designed for impaction deaggregated the NanoActive™ MgO particles to a lesser degree than the other three nozzles, which deaggregated the particles to a similar degree. Flows in three of the four nozzles were simulated in a commercial computational fluid dynamics package. Theoretical particle and aggregate stresses from the literature were calculated using simulated data. These calculations suggest particle acceleration causes internal stresses roughly three orders of magnitude larger than shear and turbulent flows. These calculations, coupled with experimental data, lead to the conclusion that acceleration was the most significant cause of particle deaggregation in these experiments. Experimental data also identified the dependence of deaggregation on primary particle size and agglomerate structure. NanoActive™ powders with smaller primary particles exhibited higher resistance to deaggregation. Small primary particle size was thought to increase the magnitude of van der Waals interactions. These interactions were modeled and compared to theoretical deaggregation stresses previously mentioned. In conclusion, deaggregation is possible. However, the ideas of particle size control and a universal dispersion device seem elusive considering the material dependent nature of deaggregation.

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He, Congrong. „Airborne Particles in Indoor Residential Environment: Source Contribution, Characteristics, Concentration, and Time Variability“. Queensland University of Technology, 2005. http://eprints.qut.edu.au/16017/.

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The understanding of human exposure to indoor particles of all sizes is important to enable exposure control and reduction, but especially for smaller particles since the smaller particles have a higher probability of penetration into the deeper parts of the respiratory tract and also contain higher levels of trace elements and toxins. Due to the limited understanding of the relationship between particle size and the health effects they cause, as well as instrument limitations, the available information on submicrometer (d < 1.0 µm) particles indoors, both in terms of mass and number concentrations, is still relatively limited. This PhD project was conducted as part of the South-East Queensland Air Quality program and Queensland Housing Study aimed at providing a better understanding of ambient particle concentrations within the indoor environment with a focus on exposure assessment and control. This PhD project was designed to investigate comprehensively the sources and sinks of indoor aerosol particles and the relationship between indoor and outdoor aerosol particles, particle and gaseous pollutant, as well as the association between indoor air pollutants and house characteristics by using, analysing and interpreting existing experimental data which were collected before this project commenced, as well as data from additional experiments which were designed and conducted for the purpose of this project. The focus of this research was on submicrometer particles with a diameter between 0.007 - 0.808 µm. The main outcome of this project may be summarised as following: * A comprehensive review of particle concentration levels and size distributions characteristics in the residential and non-industrial workplace environments was conducted. This review included only those studies in which more general trends were investigated, or could be concluded based on information provided in the papers. This review included four parts: 1) outdoor particles and their effect on indoor environments; 2) the relationship between indoor and outdoor concentration levels in the absence of indoor sources for naturally ventilated buildings; 3) indoor sources of particles: contribution to indoor concentration levels and the effect on I/O ratios for naturally ventilated buildings; and 4) indoor/outdoor relationship in mechanically ventilated buildings. * The relationship between indoor and outdoor airborne particles was investigated for sixteen residential houses in Brisbane, Australia, in the absence of operating indoor sources. Comparison of the ratios of indoor to outdoor particle concentrations revealed that while temporary values of the ratio vary in a broad range from 0.2 to 2.5 for both lower and higher ventilation conditions, average values of the ratios were very close to one regardless of ventilation conditions and of particle size range. The ratios were in the range from 0.78 to 1.07 for submicrometer particles, from 0.95 to 1.0 for supermicrometer particles and from 1.01 to 1.08 for PM2.5 fraction. Comparison of the time series of indoor to outdoor particle concentrations showed a clear positive relationship existing for many houses under normal ventilation conditions (estimated to be about and above 2 h-1), but not under minimum ventilation conditions (estimated to be about and below 1 h-1). These results suggest that for normal ventilation conditions and in the absence of operating indoor sources, outdoor particle concentrations could be used to predict instantaneous indoor particle concentrations but not for minium ventilation, unless air exchange rate is known, thus allowing for estimation of the "delay constant". * Diurnal variation of indoor submicrometer particle number and particle mass (approximation of PM2.5) concentrations was investigated in fifteen of the houses. The results show that there were clear diurnal variations in both particle number and approximation of PM2.5 concentrations, for all the investigated houses. The pattern of diurnal variations varied from house to house, however, there was always a close relationship between the concentration and human indoor activities. The average number and mass concentrations during indoor activities were (18.2±3.9)×10³ particles cm-³ and (15.5±7.9) µg m-³ respectively, and under non-activity conditions, (12.4±2.7)x10³ particles cm-³ (11.1±2.6) µg m-³, respectively. In general, there was a poor correlation between mass and number concentrations and the correlation coefficients were highly variable from day to day and from house to house. This implies that conclusions cannot be drawn about either one of the number or mass concentration characteristics of indoor particles, based on measurement of the other. The study also showed that it is unlikely that particle concentrations indoors could be represented by measurements conducted at a fixed monitoring station due to the large impact of indoor and local sources. * Emission characteristics of indoor particle sources in fourteen residential houses were quantified. In addition, characterizations of particles resulting from cooking conducted in an identical way in all the houses were measured. All the events of elevated particle concentrations were linked to indoor activities using house occupants diary entries, and catalogued into 21 different types of indoor activities. This enabled quantification of the effect of indoor sources on indoor particle concentrations as well as quantification of emission rates from the sources. For example, the study found that frying, grilling, stove use, toasting, cooking pizza, smoking, candle vaporizing eucalyptus oil and fan heater use, could elevate the indoor submicrometer particle number concentration levels by more than 5 times, while PM2.5 concentrations could be up to 3, 30 and 90 times higher than the background levels during smoking, frying and grilling, respectively. * Indoor particle deposition rates of size classified particles in the size range from 0.015 to 6 µm were quantified. Particle size distribution resulting from cooking, repeated under two different ventilation conditions in 14 houses, as well as changes to particle size distribution as a function of time, were measured using a scanning mobility particle sizer (SMPS), an aerodynamic particle sizer (APS), and a DustTrak. Deposition rates were determined by regression fitting of the measured size-resolved particle number and PM2.5 concentration decay curves, and accounting for air exchange rate. The measured deposition rates were shown to be particle size dependent and they varied from house to house. The lowest deposition rates were found for particles in the size range from 0.2 to 0.3 µm for both minimum (air exchange rate: 0.61±0.45 h-1) and normal (air exchange rate: 3.00±1.23 h-1) ventilation conditions. The results of statistical analysis indicated that ventilation condition (measured in terms of air exchange rate) was an important factor affecting deposition rates for particles in the size range from 0.08 to 1.0 µm, but not for particles smaller than 0.08 µm or larger than 1.0 µm. Particle coagulation was assessed to be negligible compared to the two other processes of removal: ventilation and deposition. This study of particle deposition rates, the largest conducted so far in terms of the number of residential houses investigated, demonstrated trends in deposition rates comparable with studies previously reported, usually for significantly smaller samples of houses (often only one). However, the results compare better with studies which, similarly to this study, investigated cooking as a source of particles (particle sources investigated in other studies included general activity, cleaning, artificial particles, etc). * Residential indoor and outdoor 48 h average levels of nitrogen dioxide (NO2), 48h indoor submicrometer particle number concentration and the approximation of PM2.5 concentrations were measured simultaneously for fourteen houses. Statistical analyses of the correlation between indoor and outdoor pollutants (NO2 and particles) and the association between house characteristics and indoor pollutants were conducted. The average indoor and outdoor NO2 levels were 13.8 ± 6.3 ppb and 16.7 ± 4.2 ppb, respectively. The indoor/outdoor NO2 concentration ratio ranged from 0.4 to 2.3, with a median value of 0.82. Despite statistically significant correlations between outdoor and fixed site NO2 monitoring station concentrations (p = 0.014, p = 0.008), there was no significant correlation between either indoor and outdoor NO2 concentrations (p = 0.428), or between indoor and fixed site NO2 monitoring station concentrations (p = 0.252, p = 0.465,). However, there was a significant correlation between indoor NO2 concentration and indoor submicrometer aerosol particle number concentrations (p = 0.001), as well as between indoor PM2.5 and outdoor NO2 (p = 0.004). These results imply that the outdoor or fixed site monitoring concentration alone is a poor predictor of indoor NO2 concentration. * Analysis of variance indicated that there was no significant association between indoor PM2.5 and any of the house characteristics investigated (p > 0.05). However, associations between indoor submicrometer particle number concentration and some house characteristics (stove type, water heater type, number of cars and condition of paintwork) were significant at the 5% level. Associations between indoor NO2 and some house characteristics (house age, stove type, heating system, water heater type and floor type) were also significant (p < 0.05). The results of these analyses thus strongly suggest that the gas stove, gas heating system and gas water heater system are main indoor sources of indoor submicrometer particle and NO2 concentrations in the studied residential houses. The significant contributions of this PhD project to the knowledge of indoor particle included: 1) improving an understanding of indoor particles behaviour in residential houses, especially for submicrometer particle; 2) improving an understanding of indoor particle source and indoor particle sink characteristics, as well as their effects on indoor particle concentration levels in residential houses; 3) improving an understanding of the relationship between indoor and outdoor particles, the relationship between particle mass and particle number, correlation between indoor NO2 and indoor particles, as well as association between indoor particle, NO2 and house characteristics.

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Vanos, Robilyn. „In Vitro Macrophage Response to Nanometer-size Particles from Materials Used in Hip Implants“. Thèse, Université d'Ottawa / University of Ottawa, 2011. http://hdl.handle.net/10393/20138.

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Wear particle-induced inflammation leading to periprosthetic osteolysis remains a major cause of hip implant failure. As polyethylene particles from conventional metal-on-polyethylene implants have been associated with these failures, an interest in lower wear metal-on-metal (MM) bearings has emerged. However, the biological effects of nanometer-size chromium oxide particles, predominant type of wear particles produced by MM implants, remain mostly unknown. Therefore, this study aimed to determine the cytotoxicity of nanometer-size Cr2O3 particles on macrophages in vitro, by analyzing their effects on cell mortality and cytokine release and comparing them with those of similarly-sized alumina (Al2O3) particles (known to be relatively bioinert). Results showed that at high concentrations, nanometer-size Cr2O3 particles can be cytotoxic to macrophages, inducing significant decreases in total cell numbers and increases in necrosis. Results also showed that, at high concentrations, the cytotoxicity of Cr2O3 particles was overall higher than that of Al2O3 particles, even though Cr2O3 and Al2O3 are both stable forms of ceramic materials. However, it appeared to be lower than that of previously reported conventional polyethylene and CoCrMo particles. Therefore, chromium oxide particles may not be the main culprit in initiating the inflammatory reaction in MM periprosthetic tissues.

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McCall, David Samuel. „Measurement and modelling of light scattering by small to medium size parameter airborne particles“. Thesis, University of Hertfordshire, 2011. http://hdl.handle.net/2299/6374.

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An investigation into the light scattering properties of Saharan dust grains is presented. An electrodynamic trap has been used to levitate single dust particles. By adjusting the trap parameters, partial randomisation of the particle orientation has been introduced. While levitated, the particles were illuminated by a laser, and a rotating half-wave retarder enabled selection of vertically or horizontally polarized incident light. A laser diffractometer and linear photodiode array have been used to measure intensity at scattering angles between 0.5° and 177°. Combining these measurements with Fraunhofer diffraction as calculated for a range of appropriately-sized apertures allows the calculation of the phase function and degree of linear polarization. The phase functions and degree of linear polarisation for four case study particles are presented - the phase functions are found to be featureless across most of the scattering region, with none of the halo features or rainbow peaks associated with regularly shaped particles such as hexagonal columns or spheres. Particle models comprised of large numbers of facets have been constructed to resemble the levitated particles. Utilizing Gaussian random sphere methods, increasing levels of roughness have been added to the surfaces of these models. A Geometric Optics model and a related model, Ray Tracing with Diffraction on Facets, have been modified to calculate scattering on these particle reconstructions. Scattering calculations were performed on each of these reconstructions using a range of refractive indices and two rotation regimes – one where the orientations of the reconstructed particle were limited to match those observed when the particle was levitated, and one where the orientation was not limited. Qualitative comparisons are performed on the phase functions and degree of linear polarization, where it is observed that the addition of roughness to the modelled spheroids causes the computed phase functions to increasingly resemble those from the levitated particles. Limiting the orientation of the particles does not affect the scattering noticeably. The addition of a very small absorption coefficient does not change the comparisons considerably. As the absorption coefficient is increased, however, the quality of the comparisons decreases rapidly in all cases but one. The phase functions are quantitatively compared using RMS errors, and further comparison is performed using the asymmetry parameter.

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Kewes, Eloi. „Silicon grinding and fine particles : generation and behavior of metallurgical-grade silicon fine particles during grinding for the silicones industry“. Thesis, Ecully, Ecole centrale de Lyon, 2015. http://www.theses.fr/2015ECDL0030/document.

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La poudre de silicium métallurgique (MG-Si, pureté 99 %) ont été étudiées, en se focalisant particulièrement sur les particules fines (taille comprise entre 1 et 10 μm) Ce matériau est utilisé dans l’industrie siliconière pour la synthèse directe du diméthyldichlorosilane et est obtenu par broyage de blocs de silicium. Les propriétés de cette poudre sont cruciales pour le procédé industriel, à la fois en termes de surface spécifique, composition chimique et coulabilité. Comprendre l’influence des particules fines, qui dégradent la coulabilité, et leur origine au cours du broyage est donc d’une importance cruciale. Une nouvelle caractérisation, chimique et cristallographique, des poudres de MG-Si montre que les particules fines sont en moyennes moins chargées en éléments d’alliage que les particules plus grosses. La structure cristalline du silicium est inchangée au cours du broyage, sauf pour les particules superfines (taille inférieure à 1 μm). Celles-ci présentent des zones amorphes : cela montre qu’elles sont soumises à des contraintes plus importantes au cours du broyage, comme cette transformation étant obtenue au-delà d’un seuil de pression. Le comportement du MG-Si en broyage a été étudié pour la première fois. A l’échelle de la particule unique, il est confirmé que les fissures suivent une propagation transgranulaire. De plus, des particules fines peuvent être produites au cours d’un unique événement de broyage, en raison de l’activation simultanée de multiples systèmes de fissures qui peuvent brancher entre elles. La taille critique en-deçà de laquelle la déformation plastique est énergétiquement plus favorable que la propagation de fissure a été estimée à environ 1 μm par une méthode basée sur l’indentation. Ces deux résultats sont cohérents avec la répartition des éléments d’alliages en fonction de la taille de particule. A l’échelle multiparticulaire, une étude pilote en broyeur à tambour tournant a été menée. Les résultats de cette étude ne sont pas disponibles dans cette version publique du manuscrit. Veuillez vous reporter au manuscrit complet. Les conséquences sur la coulabilité de la présence de particules fines dans la poudre de MG-Si produite par broyage ont été caractérisées par mesures d’angle de repos, de dynamique de compaction et en fluidisation. En particulier, un nouveau comportement d’élutriation a été identifié et décrit : l’élutriation séquentielle se produit lorsque des particules fines sont initialement présentes dans le lit fluidisé et se caractérise par l’envolement d’abord des inférieures à environ 30 μm puis seulement des particules de taille supérieure. Ce comportement n’est pas observé en l’absence de fines dans le lit initial. L’explication de ce phénomène pourrait se trouver dans la formation de clusters polydisperses, formés seulement en présence de particules fines. En parallèle de l’élutriation séquentielle, des mesures électrostatiques avec un électromètre externe à la colonne ont montré la présence de potentiels très importants (10 kV), dont le signe correspond à la gamme de taille de particules envolées. Ceci suggère que l’adhésion au sein des clusters pourrait être électrostatique
Metallurgical-grade silicon (MG-Si, 99 %) powders were extensively investigated, particularly focusing on the fine particles (whose size is between 1 and 10 μm) comprised in these powders. This material is a reactant widely used in the silicones industry for the Direct Synthesis and is obtained by size reduction of millimetric silicon lumps. Powder properties are major stakes of the industrial process. Smaller sizes favor high specific surfaces and high rates of production, but can decrease the lowability, thus inducing poor heat evacuation resulting in hot spots and a decrease in selectivity. Such lowability issues are particularly associated with fine particles, hence understand the generation of these particles during grinding is of critical importance. New chemical and crystallographic characterization of MG-Si is presented, showing that fine particles contain on average less alloying elements than larger particles, yet their crystallographic structure is preserved through grinding. On the contrary, superfine particles (smaller than 1 μm) exhibit amorphous zones: this transformation is pressure induced, showing that these particles experience larger stresses during the grinding step. The behavior of MG-Si in grinding mills has been studied for the first time. At the single particle level, it has been confirmed that transgranular fracture is preferred in MG-Si. Moreover, fine particles can be produced from a single fracture event, due to multiple crack propagation and branching. The critical size under which plastic deformation preferentially occurs over fracture has been evaluated to be approximately 1 μm. These two facts are consistent with a lower level of impurities in fines, yet remaining crystalline, and with superfines exhibiting amorphous areas. At the multiple particle level, pilot scale batch milling experiments have been performed. The results are not included in this public version of the manuscript, please refer to the full manuscript. The consequences of the presence of fine particles in ground MG-Si powder on lowability has been assessed by means of angle of repose, compaction tests and fluidization experiments. A new elutriation behavior has been observed and characterized: for naturally ground MS-Si powders (including fine particles), particles smaller than 30 μm are entrained first, then only larger particles. This was not the case in absence of fine particles. The explanation may probably lie within the presence of polydisperse clusters, formed only in presence of fine particles. Parallel to this elutriation behavior, electrostatic measurements with an external electrometer showed that high potential with sign correlated with the type of particle elutriated are attained during elutriation. This may suggest that electrostatics is responsible for cluster formation

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Gurram, Siddardha. „The Effects of Size and Coatings on the ER Behavior of Titanium Dioxide Nano-particles“. Thesis, University of Louisiana at Lafayette, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10002414.

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The thesis investigated how the particles size of a nanoparticles suspension will affect the rheological parameters (such as the yield stress) when an electric field is applied to it. The second study was done on how the coatings on core-shell nanoparticles affect the rheological behavior of nanoparticle suspensions when an electric field is applied. In the first study, four different sizes- 30nm, 50nm, 100nm, and 165nm are used to study the size effects on ER behavior. In the second study, four different types of coatings have been employed, which are Si, Si-Al, Si-Al-Stearic acid, and silicone oil with a constant particle size of 30nm. These particles were suspended in silicone oil of 500cst viscosity at a uniform concentration of 10% wt. Before making any measurements, care was taken to ensure that all the particles have been properly dispersed for a uniform suspension. Nano-titania suspensions were subjected to steady flow tests and dynamic mechanical testing (oscillatory tests). The smallest particles showed the highest storage modulus of up to 100kpa at an electric field strength of 4 kV/mm. The first study showed that as the particle size increased the ER effect of the suspensions decreased showing that smaller particles form stronger structures. In the second study, the coatings had a strong effect on the rheological behavior. Based upon the results from the second study we infer that the dielectric constant, conductivity and hydrophobic/hydrophilic nature play a role in determining the electrorheological response.

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Kim, Yong-Rae. „Integrated Uv-Vis Multiangle-Multiwavelength Spectrometer For Characterization Of Micron And Sub-Micron Size Particles“. Scholar Commons, 2004. https://scholarcommons.usf.edu/etd/723.

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Characterization of micron and sub-micron size particles requires the simultaneous measurement of the joint particle property distribution (JPPD). The JPPD is comprised of particle size, shape, orientation, composition, optical properties, and surface properties. Measurement of each of the particle properties independently is a difficult task and it has been only partially successful. To determine as many particle properties as possible using optical methods it is necessary to simultaneously measure all aspects of the interaction of the incident light with the particles of interest. This approach leads to the concept of multidimensional spectroscopy suggested by Prof. Garcia-Rubio. Dr. Bacon proved the proposition by developing and testing a prototype multianglemultiwavelength (MAMW) spectrometer proposed by Prof. Garcia-Rubio. However, the prototype MAMW spectrometer has limitations in the amount of information it can obtain because of strong absorption of deep UV light and detector saturation due to the use of optical fibers and single integration time for the CCD detector. The Integrated UV-VIS MAMW spectrometer has been developed to overcome the limitations of the prototype MAMW spectrometer. Improvements have become possible through the use of UV lenses and integration time multiplexing (ITM). The Integrated UV-VIS MAMW spectrometer has the capabilities to perform low angle scattering measurements starting from 4o with simultaneous detection of multiwavelength light from 200 nm to 820 nm, UV-VIS transmission spectroscopy, and frequency domain fluorescence spectroscopy. Following the development, possible sources of errors were analyzed and data calibration procedures have been established to ensure the validity and reproducibility of the measurement results. The capabilities of the Integrated UV-VIS MAMW spectrometer were tested by measuring UV-VIS MAMW spectra of polystyrene standards. The measured UV-VIS MAMW spectra clearly show differences due to particle size, shape, and compositional changes. Measurements of the UV-VIS MAMW spectra of sickled whole blood samples demonstrate that particle shape and compositional changes can be detected simultaneously. These results confirmed that the Integrated UV-VIS MAMW spectrometer could be a powerful tool for the characterization of micron and sub-micron size particles. Alternate approaches to enhance these capabilities further, i.e., the development of a new multidimensional MAMW spectrometer, are also described.

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Barrett, Terence. „Development and Characterization of Microfabricated Device for Real-Time Measurement of the Size and Number of Airborne Ultrafine Particles“. ScholarWorks @ UVM, 2013. http://scholarworks.uvm.edu/graddis/17.

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Ultrafine particle emissions in motor-vehicle exhaust are associated with cardiopulmonary health impacts and increased mortality. The emission, evolution, and exposure-uptake of these particles, one hundred nanometers and smaller in diameter, are fundamentally quantified by the number concentration as a function of particle size. Ultrafine particle number distributions are widely varying and fast changing as they are strongly influenced by local environmental conditions and variation in vehicle operation and maintenance. Research and regulation to quantify and control such emissions rely on measurement of the number distribution of ultrafine particles in vehicle exhaust and by the roadside. Instruments to make such measurements are commercially available, but they are expensive, non-portable, and have slow response times. A new instrument, the NanoAPA, is being developed for these in-situ applications as an inexpensive, portable, and real-time instrument. The instrument is designed to perform ultrafine particle sizing and counting through electronic control of a microfabricated device that charges sampled airborne particles with a corona ionizer and then incrementally size-separates, collects, and counts the number of particles in the aerosol. The focus of this thesis was the development and characterization of the smallest device known that can perform these sizing and counting functions. The device miniaturizes a classical instrument from the aerosol field, the double-condenser of Whipple (1960) used for the sizing and counting of atmospheric ions, into a microfabricated device designed to utilize voltage-and-flowrate-variable electrophoresis to measure ultrafine particle aerosols. Performance characterization of the microfabricated device required development of an apparatus for the generation and conditioning of aerosols appropriate to this application. This Standard Aerosol apparatus was demonstrated to produce repeatable, temperature and humidity stable, charge-neutral, monodisperse exhaust-analog aerosols of particles 10 to 100 nanometer in diameter. The microfabricated device was characterized with the Standard Aerosol apparatus for the operating conditions of 0.1 to 1.5 liter per minute flow rate and 0 to 3000 volt separator voltage. Results of the characterization demonstrated effective selection and collection of solvent droplets in the diameter range 10-100nm. The selection and collection results for engine-exhaust analog particles were inconclusive, likely due to particle re-entrainment. Repeatable measurements of particle number proved elusive, likely due to electrical field interference, the limited particle concentration obtainable from the Standard Aerosol apparatus, and signal-to-noise and temporal stability issues with the electrometer electronics. Recommendations are made for approaches likely to overcome these issues.

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Lin, Hong-Ying. „Improving the optoelectronic property and photoactivity of nano-structured titanuim dioxide effect of particle size, oxygen vacancy, and nitrogen doping /“. Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 1581 p, 2008. http://proquest.umi.com/pqdweb?did=1609302401&sid=2&Fmt=2&clientId=8331&RQT=309&VName=PQD.

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Thesis (Ph.D.)--University of Delaware, 2008.
Principal faculty advisors: Chin-Pao Huang, Dept. of Civil and Environmental Engineering, and S. Ismat Shah, Dept. of Materials Science Includes bibliographical references.

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Perboni, Acácio. „Sensibilidade de gotejadores à obstrução por partículas de areia“. Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/11/11152/tde-19042016-103353/.

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Os fatores envolvidos na obstrução dos gotejadores são divididos em químicos, físicos e biológicos, os quais, dependem da qualidade da água utilizada na irrigação e dos adubos utilizados em fertirrigação. Dentre os fatores físicos estão as partículas de areia, que são classificadas como sólidas inertes, pois não sofrem agregação com outras partículas já presentes na água e nem dispersão. O objetivo deste trabalho foi avaliar a influência do tamanho e concentração de partículas de areia e da velocidade de escoamento da água nas linhas laterais na obstrução de um único modelo de gotejador do tipo cilíndrico, não regulado, com vazão nominal de 2 L h-1. Foram realizados ensaios de obstrução com areia misturada em água destilada, combinando os seguintes fatores: três faixas granulométricas de partículas de areia (53-105; 105-250 e 250-500 μm), três concentrações de areia na água destilada (100, 250 e 500 mg L-1) e três velocidades de escoamento da água no início das linhas laterais (0,13; 0,25 e 0,94 m s-1). O tempo de ensaio para cada combinação de fatores foi de 48 horas. A vazão de 32 gotejadores foi medida a cada doze minutos por meio de um sistema automatizado desenvolvido durante esta pesquisa, sendo que esse operou adequadamente durante todo o período de ensaios de obstrução. Utilizaram-se oito linhas laterais conectadas em linha de derivação com bifurcações simétricas, cuja finalidade era distribuir uniformemente a água as partículas de areia entre as linhas laterais. Em ensaios com faixa granulométrica de 105 a 250 μm, ocorreu a obstrução nas concentrações de 250 e 500 mg L-1, para as velocidades de escoamento da água no inicío das linhas laterais V2 (0,25 m s-1) e V3 (0,94 m s-1). Já na faixa granulométrica de 250 a 500 μm, ocorreu obstrução nas concentrações de 100, 250 e 500 mg L-1, para V2 e V3. A obstrução de gotejadores ocorreu de forma aleatória nas oito linhas laterais. Após obstruídos os gotejadores não desobstruíram com o passar do tempo de ensaio, portanto fenômenos de autolimpeza não foram observados durante os experimentos.
Clogging of emitters is influenced by chemical, physical and biological agents that are associated with irrigation water quality and fertilizers, in case of adoption of fertigation practices. Among the physical agents, sand particles are one of the most important clogging sources. Sand particles are considered to be inert since it does not aggregate with other particles suspended in water. The purpose of this research was to assess influence of concentration, size of sand particles, and flow velocity within laterals on sensitivity of drippers to clogging. The results are limited to a cylindrical integrated dripper of 2 L h-1 nominal flow rate that is a nonpressure compensating emitter. Experiments were undertaken using distilled water and sand particles. The following levels were evaluated: (a) three ranges of particles sizes (0.053-0.105; 0.105-0.25 and 0.25-0.5 mm); (b) three concentrations of particles (100, 250 and 500 mg L-1); and, (c) three flow velocities at the laterals inlet (0.13, 0.25 and 0.94 m s-1). Each testing level had 48 hours duration. The flow rate of 32 drippers was measured every 12 minutes by an automated system developed and successfully validated during this research. A manifold with symmetrical bifurcations was designed to assure uniform water distribution among eight parallel laterals installed on the testing bench. Within the range of particle sizes from 105 to 250 μm, clogging of emitters was observed under concentration of particles of 250 and 500 mg L-1 and under flow velocities of 0.25 and 0.94 m s-1. Within the range of particles sizes from 250 to 500 μm, clogging was observed under all concentrations and under flow velocities of 0.25 and 0.94 m s-1. Apparently, clogging of emitters of the eight laterals occurred randomly. Once clogged, emitters did not recovered its initial flow rate, therefore self-cleaning phenomena was not observed during the experiments.

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Hubbard, Joshua A. „A study of aerodynamic deaggregation mechanisms and the size control of NanoActive[trade mark] aerosol particles“. Manhattan, Kan. : Kansas State University, 2006. http://hdl.handle.net/2097/173.

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Dissertationen zum Thema „Particles size“

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