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1
Jin, Nanbo. "Particle swarm optimization in engineering electromagnetics." Diss., Restricted to subscribing institutions, 2007. http://proquest.umi.com/pqdweb?did=1481677311&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Chen, Chi. "Engineering of inhalation aerosols combining theophylline and budesonide." Thesis, University of Bradford, 2014. http://hdl.handle.net/10454/14072.
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In asthma therapy, the use of theophylline to prevent bronchial spasm and glucocorticoids to decrease inflammation is widely indicated. Apart from the acute asthma attack oral theophylline is treated for chronic therapy in order to minimize inflammation and to enhance the efficiency of corticosteroids and recover steroids’ anti-inflammatory actions in COPD treatment. The preferred application route for respiratory disease treatment is by inhalation, such as dry powder inhalers (DPI) being the delivery systems of first choice. As shown recently, there is an advantageous effect if the drugs are given simultaneously which is caused by a synergistic effect at the same target cell in the lung epithelia. Therefore, it seems rational to combine both substances in one particle. This type of particle has the advantage over a combination product containing both drugs in a physical mixture which occurs rather randomly deposition leading to API segregation and non-dose-uniformity. Dry powder inhalers (DPIs) is a type of therapeutic pharmaceutical formulations usually present in the solid form. Due to the nature of the solid-state, an understanding of chemical and physical properties must be established for acquiring optimum performance of the active pharmaceutical ingredients (APIs). In recent year, generation of DPIs is a destructive procedure to meet the micron size. Such processes are inefficient and difficult to control. Moreover, according to current researches on combination APIs formulation, this type of DPIs performed a greater variability in does delivery of each active, leading to poor bioavailability and limit clinical efficient. This result suggest that combination formulations require advanced quality and functionality of particles with suitable physicochemical properties. Hence, in order to production of binary and combination DPIs products, the aim of this study was to develop the spray drying and ultrasonic process for engineering of combination drug particles that will be delivered more efficiently and independently of dose variations to the lung. Microparticles were produced by spray drying or/and ultrasonic technique. The processing parameters and addition of excipients (polymers) were optimized using a full factorial design such that microparticles were produced in a narrow size range suitable for inhalation. Employing excipients resulted in high saturation environment leading to minimized sphere particles when compared to conventional solvent. Solid state characterization of microparticles using powder x-ray diffraction and differential scanning calorimetry indicated that the particles contained crystalline but no cocrystal. The combination particles comparable to or better than micronized drug when formulated as a powder blended with lactose. It was concluded that the use of HPMC enhanced crystallinity suitable for inhalation; and combination particles improved uniform distribution on the stage of NGI.
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Devarakonda, SaiPrasanth. "Particle Swarm Optimization." University of Dayton / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1335827032.
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Gamboa-Marrufo, Mauricio. "Wind engineering applications of particle image velocimetry (PIV)." Thesis, University of Oxford, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.403974.
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Cheikh, Al Ghanami Racha. "Novel thermoresponsive particle gels for tissue engineering applications." Thesis, University of Nottingham, 2011. http://eprints.nottingham.ac.uk/12318/.
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Biomaterials play an important role in tissue engineering, where they are used as scaffolds for the 3D culture of cells, to help the generation of neo tissues in-vitro and achieve superior tissue engraftment and regeneration in-vivo. The work presented in this thesis describes how thermoresponsive particle gels, a class of materials not previously investigated for tissue engineering applications, can find important applications in this field. The main gels developed and studied were the aqueous thermoresponsive particle gels prepared from poly(poly(ethylene glycol) methacrylate ethyl ether) (polyPEGMA246-EE) together with polycaprolactone (PCL) microparticles. The thermoresponsive polymer polyPEGMA246-EE, synthesised by free radical polymerisation, was employed as an adsorbing steric stabiliser for polycaprolactone microparticles prepared by the single emulsion solvent evaporation method. The resulting suspensions exhibited reversible temperature induced gelation based on incipient flocculation, where they switched from being free flowing at temperatures below 19°C to form space filling gels at body temperature (37°C) over periods of ~1 minute. On cooling, the suspensions returned to a fluid state. The viscoelastic properties of the particle gels could be controlled by varying the temperature and composition, enabling these gels to be tailored for specific applications. Using NIH3T3 as a model cell line, PCL/polyPEGMA246-EE particle gels exhibited key characteristics advantageous for the 3D culture of cells. These were mainly the ability to assemble around the cells at temperatures, above the LCST of polyPEGMA246-EE, and the provision of a supportive scaffold with appropriate mechanical properties for growth, along with good cytocompatibility enabling cell spreading and proliferation over extended culture times, as well as the rapid return to a flowable state on cooling allowing for suspension transfer, for cell subculture and harvesting, without the need for enzymes. The latter property would also allow for the injectable delivery of the in-vitro conditioned cell-gel constructs for therapeutic applications. Another variant of thermoresponsive particle gels has also been presented in this thesis. Thermoresponsive magnetic-particle gels were developed from the combination of magnetic polystyrene microparticles and the thermoresponsive polymer polyPEGMA246-EE. These exhibited reversible thermogelling behaviour which allowed for cell encapsulation, while their magnetic sensitivity allowed for cell recovery through simple magnetic particle separation. The novel concept of scaffold deconstruction by temperature, and cell recovery through magnetic-particles separation is significant for applications where a scaffold-free outcome would be desired such as the commercial expansion of therapeutic cells. In this thesis, the preparation and application of first generation biocompatible thermoresponsive particle gels is described. The combination of ease of preparation, the potential for scale-up and positive cell response make thermoresponsive particle gels promising as a new class of materials for applications in cell culture, as supports for tissue growth and in cell delivery systems. The materials developed and studied in this thesis are believed to represent a significant contribution to the fields of biomaterials, drug delivery and tissue engineering.
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Cairns, Malcolm. "Titanium particle combustion." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=86572.
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In order to increase the validity of numerical models of the detonation of heterogeneous titanium explosives, experimental results are needed. The combustino of titanium is studied using two experimental techniques. The first technique is the study of the burn time for a single particle over a wide range of initial diameters while altering the oxygen concentration. To accomplish this a new flat flame burner to study particle burn time has been designed. Luminous tracks caused by the light emitted by the combustion of the particles are analyzed and burn time is inferred. Burn time in air and in an oxygen enriched atmosphere were determined. A second experiment involves the study of large scale detonation of heterogeneous charges. The charges are filled with nitromethane and a packed bed of titanium particles. The titanium particles varied in morphology and particles size. A critical charge diameter for charge ignition (CDPI) was found for irregularly shaped particles but was not found for spherical particles.Pour augmenter la validit des modles numriques sur dtonation d'explosifs htrognes contenants du titane , des rsultats exprimentaux sont ncessaires. Le combustino de titane est tudi en utilisant deux techniques exprimentales. La premire technique est l'tude du temps brle pour une particule sur une large gamme de diamtres initiaux en changeant la concentration d'oxygne. Pour l'accomplir un nouveau brleur de flamme plat pour tudier la particule brle le temps a t conu. Les empreintes lumineuses provoques par la lumire mise par la combustion des particules sont analyses et brlent le temps est dduit. Brlez le temps dans l'air et dans l'atmosphre enrichie d'un oxygne ont t dtermins. Une deuxime exprience implique l'tude de grande dtonation d'chelle de charges htrognes. Les charges sont remplies de nitromethane et un lit emball de particules de titane. Les particules de titane variaient dans la grandeur de particules et la morphologie. Un diamtre de charge critique pour l'ignition de charge (CDPI) a t trouv pour les particules irrgulirement en forme de, mais n'a pas t trouv pour pour les particules irrgulirement en forme de mais n'a pas t trouv pour les particules sphriques.
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Pitchayajittipong, Chonladda. "Engineering of particles for inhalation." Thesis, University of Bath, 2008. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.501621.
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Current pharmaceutical engineering for the manufacture of binary and combined dry powder inhaler (DPI) dosage forms relies on destructive strategies such as micronisation to generate respirable drug particles. Such processes are inefficient and difficult to control to produce particles of defined quality and functionality for inhaled drug delivery, which can affect drug product performance throughout the shelf-life of the product. Furthermore, owing to current pharmaceutical manufacturing practises of combined inhalation products, these products are subject to greater variability in dose delivery of each active, which may be perpetuated as a function of product storage conditions and limit clinical efficacy of the drug product. Hence, there is a requirement of processes that may enable production of binary and combination DPI products that will allow actives to be delivered more efficiently and independently of dose variations. The aim, therefore, of this study was to develop the solution atomisation and crystallisation by sonication (SAX) process for engineering of single and combination drug particles with suitable physicochemical properties for delivery to the lungs. The SAX process consists of key stages, which include, solution atomisation to produce aerosol droplets, generation of highly supersaturated droplets by evaporation of carrier solvent from aerosol droplet, collection of droplets in a crystallisation vessel containing appropriate non-solvent and the application of ultrasonic waves to the crystallisation vessel. Atomisation of a 1.5% w/v solution of budesonide in dichloromethane resulted in particles with defined surface geometry, which were formulated in binary dry powder inhaler (DPI) formulations and assessed using the next generation impactor.
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Chen, Rui. "Novel particle sizing techniques." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/13492/.
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Two novel approaches to particle size measurement are investigated; these are designated as Particle Movement Displacement Distribution (PMDD) method and Separated Multiple Image Technique (SMIT). An advantage of these methods compared with the established particle sizing methods of Static Light Scattering (SLS) and Dynamic Light Scattering (DLS) is that PMDD and SMIT do not suffer from the intensity weighting problem that affects SLS and DLS. The performance of the PMDD method is examined through computer simulations and through analysis of pre-existing experimental data. The SMIT method is investigated through computer simulations and through the construction and use of an optical system. The ability of both methods was measured through the assessment of an ‘area error’ measure which gives an estimate of the accuracy of a recovered particle size distribution. This area error measure varies between 0 and 2; with 0 corresponding to a perfectly recovered distribution. Typically a good inversion of DLS data can achieve an area-error value of 0.32 to 0.34 and this figure (along with the recovered mean particle size and standard deviation of the distribution) was used to judge quantitatively the success of the methods. The PMDD method measures the centre of individual particles in each image. A vector histogram is formed based on the connection between the centres in the first image and the centres in the next image. This vector histogram contains information about the particle size distribution. A maximum likelihood data inversion procedure is used to yield a particle size distribution from this data. The SMIT method is similar to the Static Light Scattering (SLS) method, but it combines angular dependent intensity method and individual visualisation method together to recover individual particle sizes without an intensity weighting. A multi-aperture mask and wedge prisms are utilised in this method to capture particle images formed from light scattered into a number of selected directions. A look-up table is then used to recover the individual particle sizes, which are then formed into a histogram. For the PMDD method, computer simulation results established the optimum values for parameters such as the time interval between frames, the exposure time and the particle concentration and also investigated the effects of different noise sources. For mono-modal size distributions, the PMDD method was shown through computer simulation to be capable of recovering a particle size distribution with an area error of around 0.27 which compares well with the typical DLS result. PMDD results were also recovered from mono-modal experimental data with mean particle sizes close to the manufacturers quoted particle mean size. However, recovery of bi-modal distributions was found to be not so successful; for bi-modal distributions, the recovered distributions generally had only a single peak, which, of course gives a very poor area-error figure. This result compares poorly with the particle tracking method ‘Nano Particle Tracking Analysis’ which is able to recover bi-modal distributions. For this reason further research was concentrated on an image intensity method (SMIT). For the SMIT method, computer simulation results established the optimum values for parameters such as the particle concentration and also investigated the effects of different noise sources and of aberrations in the optical system. The SMIT method was shown through computer simulation to be capable of recovering particle size distributions for both mono-modal and bi-modal distributions. The area error values obtained were in the range 0.24 to 0.45, and most of the results are good compared to the DLS value. The major problem with the SMIT method was found to be the presence of a small number of recovered particle radii much larger (or smaller) than the true sizes. These errors were attributed to ambiguities in the look-up table system used to convert the relative intensity data values into particle sizes. Two potential methods to reduce the influence of these ambiguities were investigated. These were, firstly by combining Brownian motion movement data from tracking individual particles over a few frames of data, and secondly by combining an estimate of the total scattered intensity from a particle with the normal SMIT data to constrain the look-up procedure. In computer simulations both approaches gave some improvement but the use of the total scattered intensity method gave the better results. In a computer simulation this method managed to improve the area-error from 0.37 for SMIT alone to 0.25 for SMIT combined with this extra information. Based on the success of these computer simulation results, an experimental SMIT system was constructed and tested. It was found necessary to first calibrate the optical system, to account for the different optical transmission coefficients of the different prisms/optical paths. But using a particle sample with particles of known size to calibrate; other particle sizes were successfully recovered from the experimental data using the original SMIT data processing. A majority of the recovered particle radius were close to the manufacturers quoted particle mean radius. Attempts to implement the total intensity approach to enhance the SMIT were found not be successful due to the difficulty in measuring the small displacements in particle positions required with sufficient accuracy. A possible alternative design to overcome this problem is suggested in the future work section 7.2.
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Radman, Jennifer. "Particle flow visualization in hydrocyclones using the positron emission particle tracking technique." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=123037.
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The technique of Positron Emission Particle Tracking (PEPT), developed at University of Birmingham in the late 1980s has become a powerful tool to track particles flowing in various industrial engineering applications. Hydrocyclones are extensively used in a widespread amount of applications for many industries, but are predominantly used in closed circuit grinding operations as classifiers in mineral processing. Many attempts have been made to capture the key relationships between hydrocyclone operating and geometrical variables in models, but hydrocyclone characterization is still heavily empirical and on a case-by-case basis. Due to their simplistic design, easy operation, low cost and maintenance, hydrocyclones have gained a widespread positive reputation for solid-liquid separations. Despite their wide use and long history in industry, the internal flow field of the hydrocyclone is complex in nature and remains a challenge to visualize under standard operating conditions. The work presented in this thesis project has looked at the feasibility and potential of PEPT to examine the flow in hydrocyclones. This study presents views of the real-time particle motion within small diameter hydrocyclones by PEPT. There is a need to develop a visualization method by which the velocity distributions can be quantified under realistic industrial conditions. Therefore, this thesis project will give an overview on current hydrocyclone flow field theory, and presents the experimental results of particle flow visualization inside two inch standard and stub hydrocyclones using PEPT under water and water-silica conditions.La technique de localisation des particules par l'émission de positons (PEPT), développée à l'université de Birmingham dans les années 1980s, est un outil puissant dans diverses applications de génie industriel. Les hydrocyclones sont largement utilisés dans une quantité répandue des applications pour de nombreuses industries, mais sont principalement utilisés dans les opérations de broyage en circuit fermé de classification dans le traitement des minerais. De nombreuses tentatives ont été faites pour capturer les relations clés entre hydrocyclone des variables géométriques et fonctionnement mais la caractérisation de l'hydrocyclone est encore largement empirique et au cas par cas. En raison de leur conception simpliste, l'opération facile et faible coût de maintenance, les hydrocyclones ont acquis une bonne réputation répandue pour les séparations solide-liquide. Malgré leur large utilisation et longue histoire dans l'industrie, le champ d'écoulement interne de l'hydrocyclone est de nature complexe et demeure un défi de visualiser dans des conditions d'utilisation normales. Les travaux présentés dans ce projet se sont penché sur la faisabilité et le potentiel de PEPT d'examiner le movement fluide des hydrocyclones. Cette étude présente le mouvement des particules en temps réel de petits hydrocyclones par PEPT. Il est nécessaire de développer une méthode de visualisation par lequel les distributions de vitesse peuvent être quantifiées dans des conditions industrielles réelles. Par conséquent, ce projet donnera un aperçu sur la théorie du champ d'écoulement de l'hydrocyclone actuel et présente les résultats expérimentaux de visualisation de movement de particules à l'intérieur de hydrocyclones en utilisant PEPT pour deux conditions : l'eau et la silice en suspension.
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Tabatabaei, Seyed Mahmood. "Electroviscous particle-wall interactions." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=19517.
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A theoretical analysis is presented to determine the forces of interaction between an electrically charged cylindrical or spherical particle and a charged plane boundary wall when the particle translates parallel to the wall and rotates around its axis in a symmetric electrolyte at rest. The electroviscous effects, arising from the coupling between the electrical and hydrodynamic equations, are determined as a solution of three partial differential equations, derived from Cox's general theory, for electroviscous ion concentration, electroviscous potential and electroviscous flow field. It is a priori assumed that the double layer thickness surrounding each charged surfaces is much smaller than the length scale of the problem. Using the matched asymptotic expansion technique, the electroviscous forces experienced by the cylinder and by the sphere are explicitly determined analytically for low and intermediate Peclet numbers, but small particle-wall distances. The solution for the sphere-wall interactions is extended to arbitrary particle-wall distances analytically for the tangential component of the force and numerically for the normal component of the force by the use of a bipolar coordinate system. The tangential and normal components of the electroviscous force experienced by the sphere-wall interactions for both arbitrary particle-wall distances and arbitrary Peclet numbers are also determined numerically by the use of the finite difference approximation in the bipolar coordinate system. It is found that the tangential force usually increases the drag above the purely hydrodynamic drag, although for certain conditions the drag can be reduced. Similarly the normal force is usually repulsive, i.e. it is an electrokinetic lift force, but under certain conditions the normal force can be attractive.
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Mokkapati, Srinivas Praveen. "Simulation of particle agglomeration using dissipative particle dynamics." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1149.
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Narducci, O. "Particle engineering via sonocrystallization : the aqueous adipic acid system." Thesis, University College London (University of London), 2013. http://discovery.ucl.ac.uk/1396015/.
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Many of the companies involved in powder processing are seeking to improve their economic performance via improved control of the physical properties of their products. Pharmaceutical manufacturers, for example, are considering the potential benefits of moving from batch to continuous operations to improve consistency. Furthermore, in recent years interest in the application of ultrasound to crystallization has received a significant impetus with the increased requirement to prepare complex chemical entities to very exacting standards. Literature reports about sonocrystallization indicate several interesting benefits, including superior crystal habit, purer and easily handled product, narrowed crystal size distribution, and prolific nucleation. The sonocrystallization literature, however, mainly focuses on batch crystallization operations, with less information relating to continuous crystallization processes. The present thesis concerns an evaluation of the use of ultrasonic technology during batch and continuous crystallization of adipic acid crystals and compares it with common industrial operations for product particle engineering. Firstly, the effect of a continuous sonication on a continuous crystallization process has been investigated. Cooling crystallization of adipic acid from aqueous solution is the selected case study. Analogous experiments have been carried out both under silent and continuous insonation regimes in order to investigate the effects of sonication on the time required to reach the steady state, particle size distribution (PSD), solids yield, and crystal habit. The results reveal that under continuous ultrasonic irradiation the steady state particle size distribution is achieved after shorter times than in silent continuous crystallization experiments. Continuous crystallization with ultrasonic irradiation results in significantly smaller crystal sizes, reduced agglomeration and an improved habit of crystals with highly reproducible product characteristics. Furthermore, the product yield is increased. The crystallization kinetics, focused on both the nucleation and growth rates, has been determined using the continuous Mixed-Suspension Mixed-Product-Removal (MSMPR) crystallizer model. Kinetics have been extracted sequentially from experimental data relating the particle size distribution, using the Population Balance Equation (PBE) in terms of moments, and evaluating the effect of mean residence time, supersaturation at steady state and ultrasonic power amplitude on the growth and nucleation rates. Application of ultrasound resulted in the most pronounced effects on the nucleation process, with rates increased by one order of magnitude with the results without sonication. The Mydlarz and Jones three parameters (MJ3) model for size dependent growth fits the non-linearity in the insonated experimental population density data for crystal sizes up to 10 μm. For larger sizes, whereas the population density plot is linear, the growth rate is deemed to be independent of crystal size. Further analysis of the kinetics of nucleation and growth at steady state, in continuous crystallization under continuous insonation, has been developed using the commercially available software package PARSIVAL based on the fully adaptive Galerkin h-p method. The population balance has been modeled with secondary nucleation and a growth rate depending on both supersaturation and particle size, according to the MJ3 model. Numerically derived results from the population balance modelled with PARSIVAL are in reasonable agreement with experimental observations, in terms of population density values. The use of ultrasound in the particle engineering of micron scale adipic acid crystals has been implemented by evaluating its size reducing power compared with the product of industrially established milling processes. Specifically, the steady state particles characteristics of a continuous operation under ultrasonic irradiation and the final product characteristics of batch cooling crystallization under continuous ultrasonic have been compared with hammer milling, micronization, and High Shear Wet Milling (HSWM). Ultrasound applied to batch and continuous crystallization produces particle sizes comparable with those from micronization. Continuous insonation during batch crystallization provides spherical particles, with regular surface roughness and highly reproducible results. The use of ultrasound in the crystal product engineering has been addressed to the achievement of large particles by generating seeds crystals in-situ by means of controlled primary nucleation; the results were compared with the product of conventionally seeded crystallization. Seeded batch cooling crystallization of adipic acid from aqueous solution has been investigated to determine the effects of the method used to produce seeds and optimize seeding load, cooling rate, initial concentration, and supersaturation at seeding to achieve large particle sizes and mono-modal crystal size distribution. Finally, the analysis of final particle size distributions and particle surface characteristics has demonstrated that seed crystals generated in-situ by ultrasound offer advantages comparable with conventionally inoculated seeds, eliminating the need of previous preparation and selection of seeds and the drawbacks associated with seed handling and selection of a suitable inoculation time.
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Mortimer, Bruce John Peter. "Particle ejection system : target particle recovery using a transient water jet." Master's thesis, University of Cape Town, 1991. http://hdl.handle.net/11427/9637.
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Includes bibliographical references.Industry often requires the sorting of one material from another. Although the detection of desired (or undesired) elements is well advanced, the mechanical ejection or removal of particles is fairly underdeveloped. Agriculture and mining applications have used air jets and water jets to eject particles ranging in weight from a few grams to several hundred. With the current trends in mechanization leading towards higher processing speeds, these traditional methods have been found to be unsuitable: they have slow turn-on and turn-off response times, leading to a high volume of material being ejected with the target. Higher processing speeds will lead to even greater amounts of waste material being ejected thus producing even lower yield concentrations. Thus the need for a quick response time, repetitive, impulse ejection mechanism in the sorting industry is apparent. A kinematic analysis of the required ejection mechanism blast strength shows that the required force depends on the target mass, the required deflection angle the force application angle and the force duration. Acoustical techniques in air are unsuitable as ejection force mechanisms. A water jet is proposed to meets these requirements. This water jet is caused by an electrical discharge in a liquid cavity. This produces a weak shock wave which is focused by the cavity to a nozzle where a slug of water is emitted. The cavity is an elliptical cavity of height h, with the electrodes mounted end on at the first focus and a reflecting cone and nozzle at the second focus. The propagation of weak shock waves in the elliptical cavity is studied theoretically and numerically - using a finite difference simulation program. The reflected converging wave is shown to depend on the cavity eccentricity and the wall admittance. The resulting converging shock wave has an asymmetrical pressure distribution. This analysis is used in the design of a prototype water jet generator. The electrical discharge circuit used for the production of shock waves in the cavity is analysed and the physical discharge process of electrical to shock energy conversion reviewed. Conditions for the maximisation of this transfer correspond to large water gap resistances, high voltages and low circuit inductances. Experiments on the prototype generator show that the transient water jet slug energy is relatively low. High speed photographic techniques reveal that the jet velocity is of the order of 30 m/s. Published results show much higher jets speeds are possible. The operation of the electrical discharge circuit is found to critically influence the water jet performance - electrical measurements show that the circuit is a sub-optimum, underdamped RLC circuit. The cone / nozzle operation is also shown to have a marked effect on performance. The nozzle in particular requires optimisation. The prototype in its present form is not suitable for use in an ejection system. Although the pulse length, rise time and channel spread of the device are suitable, the blast strength is not sufficient for deflection of the heaviest range of particles. Optimisation of the electrical circuit and increased energies will increase the blast strength.
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Stamm, Matthew T. "Particle Dynamics and Particle-Cell Interaction in Microfluidic Systems." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/308886.
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Particle-laden flow in a microchannel resulting in aggregation of microparticles was investigated to determine the dependence of the cluster growth rate on the following parameters: suspension void fraction, shear strain rate, and channel-height to particle-diameter ratio. The growth rate of an average cluster was found to increase linearly with suspension void fraction, and to obey a power-law relationships with shear strain rate as S^0.9 and channel-height to particle-diameter ratio as (h/d)^-3.5. Ceramic liposomal nanoparticles and silica microparticles were functionalized with antibodies that act as targeting ligands. The bio-functionality and physical integrity of the cerasomes were characterized. Surface functionalization allows cerasomes to deliver drugs with selectivity and specificity that is not possible using standard liposomes. The functionalized particle-target cell binding process was characterized using BT-20 breast cancer cells. Two microfluidic systems were used; one with both species in suspension, the other with cells immobilized inside a microchannel and particle suspension as the mobile phase. Effects of incubation time, particle concentration, and shear strain rate on particle-cell binding were investigated. With both species in suspension, the particle-cell binding process was found to be reasonably well-described by a first-order model. Particle desorption and cellular loss of binding affinity in time were found to be negligible; cell-particle-cell interaction was identified as the limiting mechanism in particle-cell binding. Findings suggest that separation of a bound particle from a cell may be detrimental to cellular binding affinity. Cell-particle-cell interactions were prevented by immobilizing cells inside a microchannel. The initial stage of particle-cell binding was investigated and was again found to be reasonably well-described by a first-order model. For both systems, the time constant was found to be inversely proportional to particle concentration. The second system revealed the time constant to obey a power-law relationship with shear strain rate as τ∝S^.37±.06. Under appropriate scaling, the behavior displayed in both systems is well-described by the same exponential curve. Identification of the appropriate scaling parameters allows for extrapolation and requires only two empirical values. This could provide a major head-start in any dosage optimization studies.
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Breytenbach, Jacobus Nicolaas. "An investigation of particle collection efficiency in different particle-bubble contacting environments in flotation." Master's thesis, University of Cape Town, 1995. http://hdl.handle.net/11427/20457.
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Bibliography: p. 149-160.The collection efficiency of quartz particles in four different particle-bubble contacting environments was investigated during this thesis. Flotation experiments were carried out in a hybrid flotation column that could be modified into three different cell configurations (a quiescent column cell, an agitated column cell and a Jameson-type cell), while the fourth cell environment comprised a laboratory batch subaeration flotation cell. High purity quartz was used as a probe ore in conjunction with a cationic collector and a commercial frother blend. The quartz was initially contaminated with organic material and needed to be cleaned by calcination. The cleaned quartz was divided into four narrow particle size fractions to determine the effect of particle size on particle collection efficiency. The quartz was floated over a wide range of collector dosages and frother dosage was kept constant during experiments. The flotation was conducted using tap water at neutral pH. Froth depth was kept shallow during all experiments in the hybrid column cell configurations to enable the investigation to focus specifically on the collection zone. The effect of contacting environment (cell type) on particle collection efficiency was investigated by considering the effect of particle hydrophobicity, particle size and agitation speed (turbulence) on flotation recovery in the different cell types. The unique particle-bubble contacting environments resulted in different particle collection efficiencies and it was found that increased contacting intensity generally led to increased efficiency of collection. Increased particle hydrophobicity generally resulted in increased particle collection efficiency, although the overdosing of collector led to decreased flotation recovery which was probably caused by combined collector double layer and flocculation effects. The effect of particle size on flotation recovery exhibited classical n-curve behaviour at intermediate collector dosages and the optimum particle size range as reported in the literature was confirmed. Intense contacting between particles and bubbles followed by relatively quiescent disengagement (such as the mechanism employed in the Jameson cell configuration) proved to be beneficial to collection of both fine and coarse particles.
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Beeckler, John Sachs. "FPGA particle graphics hardware." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=98944.
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Particle graphics simulations are well suited for modeling phenomena such as water, cloth, explosions, fire, smoke, and clouds. They are normally realized in software, as part of an interactive graphics application. Their use in such applications is limited by the computational burden and resource competition they create. This thesis presents the design and implementation of a reconfigurable hardware particle graphics system for accelerating real-time particle graphics effects: The Particle Pipe. We explore the design process, implementation issues, limitations, challenges, and new possibilities of using FPGAs for the acceleration of real-time particle graphics. The Particle Pipe has been synthesized to an operating frequency of 130 MHz and has the potential for an increase in performance of two orders of magnitude over software methods and one order of magnitude over GPU methods.
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Wang, Ge 1965. "Particle modeling of dynamic fragmentation." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=102230.
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In this paper, we first theoretically revise the traditional particle modeling (PM) by means of mathematical derivation in that, adopting of Lennard Jones (LJ) format equations, four conservative rules are satisfied in order to determine the four unknown in a LJ equation, such as the mass, the elastic energy, the Young's modulus and the tensile strength conservations in the PM and molecular dynamic (MD) models. This enables the new developed PM to uniquely define a material's properties to be studied and promisingly become a predictive tool in mining industries. A safe time increment scheme is also defined and a new modification to the model to avoid giving a pseudo-dynamic solution.Consequently, we test this new PM by simulating fracture response of an elastic-brittle material---epoxy, with randomly distributed holes, in tension and then comparing the model results with the experiments.
Then, we use this developed PM to many applications, such as (i) simulating dynamic fragmentation of minerals encountered in comminution and blasting processes in the mining industry. In particular, we simulate single as well as multi-phase materials in two dimensions (2-D) and 3-D. We redefine the interactive particle relationship by which material impact-collision problems are realistically simulated and computational time is saved as well; (ii) investigating cracking propagation of a plate with crack-tip under mode-I loading.
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Martel, Joseph Maurice. "Particle Focusing in Microchannels." Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:11206.
Full textAbstract:
The ability to control the motion of particles and cells in microchannels has been a center of fascination since the advent of microfluidics. Entire fields have been created in order to accomplish separation, volume reduction and overall positioning of particles and cells within microfluidic devices in the fastest and most accurate manner possible. While most of these technologies rely on low Reynolds number operation, one technique entitled inertial focusing takes advantage of the inertia of the surrounding fluid and the interaction between a particle and the channel itself which cause the lateral migration of particles across streamlines to equilibrium positions within a flow. The major advantage of inertial microfluidics in biomedical and microfluidic applications is that it is inherently high throughput being dependent on inertia whereas most microfluidic concepts are dependent on low Reynolds number operation.Engineering and Applied Sciences
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Hill, Martyn. "Ultrasonic resonators for particle manipulation." Thesis, University of Southampton, 2004. https://eprints.soton.ac.uk/46529/.
Full textAbstract:
Ultrasonic standing waves can be used to generate radiation forces which act on particles within a fluid. These forces may be useful for manipulation, separation, or fractionation of these particles. This thesis describes the use and modelling of a number of devices which use such acoustic radiation forces. Initially, the design and testing of a large (multiple wavelength) flow-through ultrasonic separation device is described. This device demonstrated for the first time that flow-through ultrasonic filtration could be made to work successfully on this scale without having to rely on acoustically transparent membranes. Three models are used to examine the behaviour of the resonator. The electro-acoustic model is then used to analyse the performance of two smaller resonators and is shown to match experimental values well. The model is used to explain the behaviour of the resonators in the regions where individual layers of the device themselves have thickness resonances at similar frequencies. It also demonstrates the importance of the bonding between layers and shows that the standing wave at a peak of the energy density response differs, in terms of nodal position and boundary impedance, from simple, rigid-rigid boundary models. The remainder of the thesis concentrates on the design and use of micro-scale devices in which the scale of the layers is similar to or smaller than the wavelengths in use. A novel microfabricated filtration device is described which is primarily constructed using silicon and Pyrex. The modelling, design, fabrication and initial testing of the device are discussed. An expanded version of the electro-acoustic model allows prediction of the radiation forces on an example particle within a standing wave field. This is used to examine the force profile on a particle at resonances with pressure nodes at different positions. An analytical method for predicting modal conditions for combinations of frequencies and layer thickness characteristics is presented, which predicts that resonances can exist that will produce a pressure node at arbitrary positions in the fluid layer of such a system. The model also predicts conditions for multiple sub-wavelength resonances within the fluid layer of a single resonator, each resonance having different nodal planes for particle concentration. This forms the basis for the design of a unique microfabricated resonator with several modes that allow particles to be forced to either boundary of the fluid or to the fluid centre, depending on the operating frequency.
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Thati, Jyothi. "Particle Engineering by Spherical Crystallization:Mechanisms and Influence of Process Conditions." Doctoral thesis, KTH, Teknisk strömningslära, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-32519.
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Spherical agglomerates of benzoic acid crystals have been successfully prepared by drowning-out crystallization in three solvent partial miscible mixtures. Benzoic acid is dissolved in ethanol, bridging liquid is added and this mixture is fed to the agitated crystallizer containing water as the anti-solvent. Small crystals are produced by crystallization of the substance, and the crystals are agglomerated through the action of the bridging liquid. Different solvents: chloroform, toluene, heptane, pentane, cyclohexane, ethyl acetate and diethyl ether are chosen as bridging liquids, all being low soluble in water and showing good wettability for benzoic acid crystals. The influence of process conditions such as concentration of solute, agitation rate, feeding rate, amount of bridging liquid and temperature on the properties of benzoic acid spherical agglomerates, are investigated. Different sets of experiments were accomplished to track how the properties of the particles gradually change during the normal spherical crystallization experiment. Other sets of experiments were performed to examine the influence of agitation and process time for agglomeration. The product properties such as particle size distribution, morphology and mechanical strength have been evaluated. The mechanical strength of single agglomerates has been determined by compression in a materials testing machine, using a 10 N load cell. Compression characteristics for single agglomerates are compared with the data on bed compression. The present study shows that the bridging liquid has significant influence on the product properties, using diethyl ether and ethyl acetate no agglomerates are formed. Using any of the other five solvents (chloroform, toluene, heptane, pentane, and cyclohexane) spherical agglomerates are formed, as long as a sufficient amount of the bridging liquid is used. Using cyclohexane as bridging liquid at 5°C and toluene at 20°C the particles are larger compared to particles formed at other conditions. The highest particle fracture stress is obtained by using toluene as the bridging liquid at 5 and 20°C. Particle morphology depends on the bridging liquid used and the particles are completely spherical when toluene and pentane are used as bridging liquids. Different process parameters are found to have a significant influence on the physico-mechanical properties of the product. The range of operation for spherical agglomeration is relatively narrow and only at certain conditions spherical agglomerates are produced. With increasing amount of bridging liquid the particle size and strength increase and the morphology improves. Particle size decreases and the fracture force increases with increasing feeding rate, but the morphology remains unchanged. For all the solvents, the particle size and the fracture stress increase with decreasing temperature. For four of the solvents the morphology improves with decreasing temperature. For cyclohexane the result is the opposite, in that the particles are spherical at 20°C and irregular at 5°C. Spherical agglomerates of benzoic acid, both as single particles as well as in the form of a bed, have a high compressibility and low elastic recovery, properties that are favorable for direct tabletting. As the feed solution is supplied to the crystallizer the amount of benzoic acid that can crystallize actually does crystallize fairly rapidly. Hydrodynamics are responsible for bringing particles together for the agglomeration. Experiments reveal that during the gradual addition of the feed to the agitated aqueous solution, both particle size and particle number increases. It is clear from the experiments that not only further addition of feed solution leads to larger product particles but also continued agitation. Along the course of the process the properties of the particles change gradually but substantially. By continued agitation, the particle porosity decreases, density, strength gradually increases and also the spherical shape develops gradually.QC 20110419
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Hadi, Kuther. "Spray Drying of Cocrystals for Engineering Particle Properties : Diploma Work." Thesis, Uppsala universitet, Institutionen för farmaci, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-265788.
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The goals of this work were to combine crystal and particle engineering in a single step using spray drying and improve particle properties that can potentially minimize the need for coating agents. Specific aim was to prepare and characterize theophylline cocrystal particles intended for inhalation using by spray drying. Theophylline is a bronchodilator used in the treatment of asthma and is used as a model drug in this study. Theophylline cocrystals with citric acid, flufenamic acid and saccharin were chosen as model systems. The solubilities of different components of cocrystals in different solvents were determined to get an idea of the stability landscape of cocrystals. Thereafter, the cocrystals were prepared by slurry crystallization method. The cocrystal particles from similar solutions were prepared using spray drying. The processing variables are carefully chosen for optimal particle engineering. The resulting solids were subjected to different characterizations such as particle size analysis, tap density and bulk density analysis and new generation impactor studies. Theophylline cocrystals were successfully obtained by both slurry crystallization and spray drying methods. Despite rapid drying, spray dried particles were predominantly crystalline with a particle size and other attributes suitable for inhalation. However, the process yields were low due to adhesion to cyclone walls. The impactor results indicated a decent aerosolization performance of the spray dried particles in pure and when blended with lactose. The cocrystal particles with interesting properties suitable for inhalation application can be prepared in one step using spray drying. The mechanisms behind reasons for adhesion of cocrystal particles should be further elucidated. Key words: spray drying, cocrystals, cocrystallization, coformers, particle engineering, design of experiments, inhalation, theophylline, citric acid, flufenamic acid, saccharin.
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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.
Full textAbstract:
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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Tan, Sheng 1976. "Particle displacement measurement using optical diffraction." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/89368.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.Includes bibliographical references (leaves 82-84).
by Sheng Tan.
S.M.
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Schabel, Michael Joseph 1973. "Particle growth in plasmas." Diss., The University of Arizona, 1999. http://hdl.handle.net/10150/289083.
Full textAbstract:
Plasmas are used extensively in the manufacturing of microelectronic devices. In typical fabrication facilities, plasmas may be used for etching, deposition, cleaning of a substrate, and chamber cleaning. One of the major challenges to the effective use of plasmas for microelectronics processing is the formation of particles and films from reaction byproducts, which can contaminate both the substrate and the chamber. However, in other communities, the growth of particles and films in plasmas provides opportunities for the production of novel materials, for studies of astrophysical phenomena, and for macroscopic simulations of condensed matter physics. Extensive studies of particles and films in plasmas have resulted in an understanding of particle dynamics including charging, trapping, transport, and deposition. However, comparatively little is understood about the nucleation and growth behavior of particles and films. In this contribution, particle and film formation mechanisms in low-pressure fluorocarbon plasmas are discussed. It is shown that gas phase molecular growth reactions are responsible for the formation of chemical precursor to particle and film nucleation. A fluorocarbon chemical reaction library has been developed, and when used in conjunction with a plasma chemical kinetics model, gives excellent agreement with experimental observations of molecular growth reactions and particle and film formation.
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Yoon, Joon Sik 1973. "Discrete particle transport in porous media : discrete observations of physical mechanisms influencing particle behavior." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/30194.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2005.Page 362 blank.
Includes bibliographical references.
An understanding of how discrete particles in the micron to submicron range behave in porous media is important to a number of environmental problems. Discrete particle behavior in the interior of a porous medium is complex and influenced by various physical and chemical factors. This work aimed to provide new insight into the physical factors influencing discrete particle movement and attachment in a uniform, saturated porous medium. As part of this aim, a new technique for visualizing discrete particle transport in the interior of a porous medium has been developed. The technique, which includes the construction of a translucent medium and the use of laser induced fluorescence for particle tracking, was used to examine the behavior of a 50 mg/L suspension of negatively charged, micron-size, non-Brownian particles in the interior of a porous medium constructed from water saturated, mono-size 4mm diameter glass beads. Particle behavior as a function of pore fluid velocity and solid surface roughness was imaged at both the macroscopic and microscopic level. Experimental results revealed two interactions between the discrete particles and the solid phase of the medium. One, particle entrapment, resulted in the firm collection of particles at solid-solid contact points and asperities on the solid surfaces. The other, particle hindrance, resulted in non-firm interactions between the particles and the solid's contact points and surfaces. Both entrapment and hindrance were driven by gravity. Hence, the discrete particles were entrapped and hindered at the top surface of the glass beads comprising the medium, and at the upper portion of the contact points.
(cont.) The entrapment mechanism was physical interlocking on surface roughness and physical straining at the contact points. Particle sedimentation and particle re-entrainment as a result of flow field perturbations were the main mechanisms contributing to the hindrance of particles. Changes in the concentrations of particles that were entrapped or hindered were observed with distance from the particle injection point. These changes, which became more significant as the fluid velocity decreased, were attributed to particle size distribution effects. Experiments conducted with an upward pore fluid velocity supported the hypothesis that particle entrapment and hindrance are driven by gravity. The comparison of the experimental results with particle transport models based on macroscopic mass balance equations demonstrated some of the short-comings of these models. Drainage tests performed using the geotechnical centrifuge and the new visualization technique e also provided initial insight into discrete particle behavior in an unsaturated porous medium. The results of these tests show that particles were scavenged by the air-water interface, adsorbed on the air-water interface of the pendular rings, and were retained by film straining. Thus, it is believed that the visualization technique developed during this work can be used to further investigations of discrete particle transport behavior in partially saturated porous media.
by Joon Sik Yoon.
Ph.D.
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Warner, Scott O. "Autocorrelation-Based Estimate of Particle Image Density in Particle Image Velocimetry." DigitalCommons@USU, 2012. https://digitalcommons.usu.edu/etd/1386.
Full textAbstract:
In Particle Image Velocimetry (PIV), the number of particle images per interrogation region, or particle image density, impacts the strength of the correlation and, as a result, the number of valid vectors and the measurement uncertainty. Therefore, any a-priori estimate of the accuracy and uncertainty of PIV requires knowledge of the particle image density. An autocorrelation-based method for estimating the local, instantaneous, particle image density is presented. Synthetic images were used to develop an empirical relationship based on how the autocorrelation peak magnitude varies with particle image density, particle image diameter, illumination intensity, interrogation region size, and background noise.
This relationship was then tested using images from two experimental setups with different seeding densities and flow media. The experimental results were compared to image densities obtained through using a local maximum method as well as manual particle counts and are found to be robust. The effect of varying particle image intensities was also investigated and is found to affect the particle image density.
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Rkiouak, Laylla. "Mechanism of ozone depletion on the particle candidates for the stratospheric particle injection for a climate engineering project." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709438.
Full text
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Liu, Xuan. "Efficient delay-tolerant particle filtering." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=95173.
Full textAbstract:
Tracking is frequently performed using multiple sensor platforms, with measurements being relayed to a fusion centre over a wireless network. This can lead to some measurements being delayed when adverse environmental conditions cause packet losses to occur. These delayed measurements are called out-of-sequence measurements (OOSMs). Simply discarding the delayed OOSMs can waste important information and lead to much poorer tracking performance. This thesis proposes a novel algorithm for delay-tolerant particle filtering that is computationally efficient and has limited memory requirements. The algorithm estimates the informativeness of the OOSMs and immediately discards uninformative measurements. More informative measurements are then processed using the storage efficient particle filter, which is relatively computationally simple. If the measurement induces a dramatic change in the current filtering distribution, the particle filter is re-run to increase the accuracy. From our simulation results, we observe that our novel algorithm only processes a relatively small portion of the OOSMs, but it performs almost as well as much more computationally-complex techniques that have larger storage requirements.Le suivi est souvent effectué à l'aide de plates-formes composées de multiples capteurs où les mesures sont retransmises à un centre de fusion via un réseau sans fil. Lorsque des conditions environnementales défavorables entraînent des pertes de paquets, la transmission de ces mesures peut être retardée. Ces dernières sont appelées mesures déclassées (OOSM). Jeter ces OOSMs peut gaspiller des informations importantes et peut affecter négativement la performance de l'algorithme de suivi. Cette thèse propose un nouvel algorithme de filtrage de particules tolérantes au délai (delay-tolerant) qui n'est pas gourmand ni en temps de calcul, ni en mémoire. L'algorithme estime la quantité d'information des OOSMs et rejette immédiatement les mesures inutiles. Les mesures contenant suffisamment d'information sont ensuite traitées à l'aide au filtre à particules. Si la mesure induit un changement radical dans la distribution de filtrage actuelle, le filtre à particules est ré exécuter pour augmenter la précision. Nos résultats de simulation indiquent que notre nouvel algorithme ne traite qu'une petite fraction des OOSMs, mais il performe presque aussi bien que de nombreuses techniques qui requièrent des calculs plus complexes et qui ont de plus importants besoins de stockage.
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Inizan, Maxime. "Turbulence-particle interactions on surfaces." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/120445.
Full textAbstract:
Thesis: S.M., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2018.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 105-110).
The physics of adhesion and detachment of particles in ventilation ducts is important to understand and control contaminant and pathogen dispersal indoors. This thesis presents an experimental characterization of parameters which affect the resuspension of settled micro-particles and spores in a turbulent airflow channel. We examine, quantify, and analyze the role of relative humidity (RH), air temperature, particle size, and surface properties on particle detachment rate and mode. This is done using a combination of high-speed imaging in a turbulent channel where spores and particles are deposited initially followed by image-processing and particle-tracking. First, we show that ambient moisture hinders particle detachment, however, we also find that this is only true for a relative humidity higher than 60% RH. At lower air saturation, we show that, instead, another effect dominates, leading to a different mode of detachment. Instead of individual particle detachment, it is a collision dynamics leading to cluster formation that dominates the pattern of detachment of particles from surfaces. We find that collisions lead to aggregations of particles on the surface in the form of clusters of self-similar sizes. We find that the larger the cluster (above 5 particles) the more anisotropic its shape, similarly to what was observed in prior literature examining clusters of air-suspended particles in channel flows. We examined and quantified the role of initial particle surface concentration, mean air velocity, and particle surface properties on these results. Our study have implications in the control of pathogen and contaminant dispersal in confined geometries, relevant for a wide range of applications.
by Maxime Inizan.
S.M.
30
Wellman, R. G. "Solid particle erosion of ceramics." Master's thesis, University of Cape Town, 1993. http://hdl.handle.net/11427/18219.
Full textAbstract:
The zeolite ZSM-5 is well-known for its unique intersecting channel system. This channel system has a great bearing on the shape-selective properties and the long life-times of ZSM-5. In this study, ZSM-5 was modified in various ways to eliminate the external acidity of the catalyst to further improve these properties, and the success and effects of these modifications were investigated primarily using temperature programmed desorption techniques. The internal surface of ZSM-5, a medium pore zeolite, plays a major role in the shape selective properties of this catalyst, due to the diffusional restrictions imposed by the channel system on bulky molecules. Even though the number of acid sites on the external surface is small compared to the total number of acid sites, these easily accessible and non-shape selective acid sites may provide a high turnover rate for non-shape selective reactions. Furthermore, the main cause of deactivation of ZSM-5 is thought to be the formation of polyaromatic molecules on the external surface, which block access to the channels of the catalyst.
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Olsen, Tyler J. (Tyler John). "Continuum modeling of particle suspension conductivity." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/101480.
Full textAbstract:
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 91-94).
A suspension of network-forming, electrically conductive particles imparts electrical conductivity to an otherwise insulating medium. This effect can be used to great effect in many industrial applications. The ability to describe these networks and to predict their physical properties is a key step in designing systems that rely on these properties. In addition, many times these networks are suspended in a flowing fluid, which disrupts existing networks and forms new ones. The extra layer of complexity introduced by flow requires more sophisticated tools to model the effect on the network and its properties. In the first chapter, we derive a model for the full, tensorial effective conductivity of a particle particle network as a function of a local tensor description of the particle network, the "fabric tensor." We validate our model against a large number of computer-generated networks and compare its performance against an analogous existing model in the literature. We show that the model accurately predicts the isotropic magnitude, deviatoric magnitude, and deviatoric direction of a particle network. In the second chapter, we set out to model the effects of flow on a particle network. We propose two frame-indifferent constitutive equations for the evolution of the fabric tensor. We perform conductivity measurements of real flowing carbon black suspensions and fit our models to the results by using the conductivity model derived in chapter 1. We find that our models are able to reproduce out-of-sample experimental results with a high degree of accuracy.
by Tyler J. Olsen.
S.M.
32
Zhou, Junjie 1979. "Reduced model for particle laden flow." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/17955.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.Includes bibliographical references (p. 133-138).
The flow of thin liquid films on solid surfaces is a significant phenomenon in nature and in industrial processes where uniformity and completeness of wetting are paramount in importance. It is well known that when a clear viscous fluid flows down an inclined surface under gravity, after some time, the initially straight contact line becomes unstable with respect to transverse perturbations. Clear fluid is easier to use in experiments, but industrial processes usually involve particulates in the form of either suspensions or dry granular flows. In this work, we study the flow of a thin film down an inclined plane. The particle-fluid mixture is modeled as a single fluid with effective density and viscosity, depending on the concentration of the particles. Since the flow is slow and the fluid layer is very thin, inertial effects are ignored and a lubrication approximation is applied to simplify the analysis. It is assumed that there is no variation in the transverse direction before the onset of instability, and the fluid properties and velocity are depth averaged to remove the height-dependence. The settling velocity of the particles is hindered by the presence of neighboring particles; this phenomenon is captured by the hindered velocity function that decreases with increasing concentration. The normal component of the settling velocity is neglected in this work and the resulting model is a system of two equations accounting for the film thickness and particle concentration changes as the mixture flows down the plane. Numerical simulations are performed and it is found that the mixtures with higher concentration flow more slowly. Compared to the clear viscous fluid, particle laden flow results in a bump that is much bigger and the size of the bump
(cont.) bump increases with concentration. We also observe that the front edge of the bump travels faster than the trailing edge and the bump width increases. Numerical simulations reveal that an intermediate plateau structure due to the presence of particles is formed behind the smaller bump due to surface tension. This intermediate state depends on the inclination angle and the initial concentration. When the higher order terms in our derived model are dropped, we discover that the resulting reduced model is still able to capture the bulk characteristics of the flow. The reduced model is a 2X2 system of conservation laws, in which the solutions can be obtained through classical shock theory analysis. It is found that our system involves a 1-shock at the trailing edge connected by an intermediate state to a 2-shock at the leading edge. The intermediate state as well as the shock speeds can be solved by shock theory analysis, and their values are found to agree very well with the simulations.
by Junjie Zhou.
S.M.
33
Smith, Vincent Combemere. "Particle size estimation of hydrocyclone overflow." Master's thesis, University of Cape Town, 2000. http://hdl.handle.net/11427/5396.
Full textAbstract:
Bibliography : leaves 83-86.This dissertation describes the development of a robust hydrocyclone particle size estimation model that will form the basis of an industrial soft-sensor. Aside from increased throughput, efficient product regulation constitutes the primary function of a milling circuit control system. Before the milling circuit product size can be regulated, it should be measured or estimated. The particle size estimation algorithm developed provides a reliable estimate of the product size and will compliment or replace conventional size measurement devices.
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Petrie, James. "Sulphur sorbent particle effects in fluidised combustion." Doctoral thesis, University of Cape Town, 1988. http://hdl.handle.net/11427/9628.
Full textAbstract:
Bibliography: leaves 132-137.An overall process model is presented for the capture of sulphur dioxide by calcareous sorbents in a fluidised bed combustor for a feed of arbitrary size distribution. The description of sorbent sulphation kinetics, particle attrition and elutriation effects incorporated in this model is supported by experimental data for a wide range of South African sorbents. The sulphation of sorbent particles is described by a simple, two-parameter, kinetic model. No loss in physical relevance is incurred when the decrease in reaction rate with time is given by a negative exponential term. Both sulphation rate and capacity are shown to be functions of sorbent type. The sulphation propensity of the 16 South African samples is correlated against their geologic description. Sorbent properties such as porosity, crystallinity and topography, which affect sulphation capacity directly, are functions of geologic age. It is possible to make a first order assessment of sorbent potential simply from this geologic data. Sorbent attrition, caused by the continuous movement of particles within the combustor, is greatest for deep beds of soft friable material. Most of the attrition takes place in the distributor region where jetting action is important. The attrition model reflects an explicit dependence on fluidising velocity, bed depth, particle diameter, topography and structural strength. Measured values of attrition rate decrease with time to a steady state value, which, under normal FBC operating conditions, is attained after a time in the bed of 6 - 10 hours. The elutriation model considers the effect of fines, generated by attrition, on the carry-over of coarse particles from the bed. The overall process model confirms that choice of sulphation kinetics exerts the greatest influence on attainable sulphur capture,. although bed fluid dynamics, sorbent attrition and feed size distribution all play a role. The model is substantiated by extensive data from the performance of three dissimilar sorbents in a 10 MWth FBC. The contribution of sorbent attrition to the solids loading of downstream gas cleaning equipment is highlighted.
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Ismail, Ernesto Bram. "Smoothed particle hydrodynamics for nonlinear solid mechanics." Master's thesis, University of Cape Town, 2009. http://hdl.handle.net/11427/11888.
Full textAbstract:
Includes abstract.Includes bibliographical references (leaves 115-117).
Smooth Particle Hydrodynamics (SPH) is one of the simplest meshless methods currently in use. The method has seen significant development and has been the germination point for many other meshless methods. The development of new meshless methods regularly uses standard SPH as a starting point, while trying to improve on issues related to consistency and stability. Despite these perceived flaws it is favoured by many researchers because of its simple structure and the ease with which it can be implemented.
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Al-Jabari, Maher. "Particle fractionation by elutriation-spouting." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28409.
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Pulp fibers can be spouted in a conical vessel if the inlet Reynolds number is above a critical value which varies linearly with mass of pulp in the vessel. Continuous pulp spouting is also feasible in a wedge-like vessel within certain limits of flow rate and inlet pulp consistency. Spouting hydrodynamics and particle separation behavior in both vessels were investigated for pulp fibers and recycled pulp suspensions.The minimum spouting velocity (MSV), spouting stability and the pressure drop-flow rate relationship were determined for liquid spouting of pulp fibers and of rigid particles. Liquid spouting of rigid particles is similar to gaseous spouting; pulp spouting is different. The liquid flow field in a conical spouted bed of pulp fibers is of a jet expansion type. A model for predicting the MSV for spouting pulp fibers was developed based on visual observation of the transition of the jet flow patterns in the conical vessel.
Small particles including both ink and pulp fines can be elutriated from a spouted bed of a recycled pulp suspension, with little fiber loss, in both semi-batch and continuous modes using conical and wedge-like vessels, respectively. Both processes were studied using on-line measurement of the exit particle concentration.
For the semi-batch process, the first order elutriation coefficient increased with the flow rate, but was about the same for all pulps. Based on the analysis of the flow field around a porous spherical particle in a shear flow, an elutriation model was developed for fine particle removal from a suspension of porous coarse particles. For the continuous operation, the particle separation mechanism and the fractional particle removal were investigated. Separation occurs by excluding fibers from the top stream, while fines are split according to the ratio of top to bottom flow rates.
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Berggren, Jonas. "Engineering of Pharmaceutical Particles : Modulation of Particle Structural Properties, Solid-State Stability and Tabletting Behaviour by the Drying Process." Doctoral thesis, Uppsala University, Department of Pharmacy, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-3353.
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Relationships between stresses during the drying process, particle structural and functional properties, and particle engineering by the drying process were addressed in this thesis. In the first part, the importance of the drying phase and the effect of the drying rate on the intragranular porosity of microcrystalline cellulose pellets were investigated. Differences in porosities of dried pellets could be explained by liquid-related differences in densification during convective drying rather than by differences in densification during wet agglomeration. An increased drying rate gave more porous pellets with a lower compression shear strength, and thereby stronger tablets. The next part dealt with modulation of solid-state stability and tabletting behaviour of amorphous lactose by incorporation of different polymers by spray drying. Increased content and molecular weight of poly(vinylpyrrolidone) (PVP) resulted in an increased resistance to crystallisation provoked by heat and moisture. The stabilising effect was even more evident after long-term storage. However, the glass transition temperature was almost unaffected and may, therefore, be questioned as a stability indicator for these types of materials. The presence of the polymers resulted in somewhat less deformable particles. Incorporation of PVP increased the compactability, whilst a surfactant decreased it, which could be shown to be related to differences in particle-particle adhesivity between the different particles. This thesis contributes to increased mechanistic understanding in the area of particle engineering that may lead to better prediction and optimisation of the functionality of pharmaceutical particles, which is of the utmost importance in the development and production of solid dosage forms.
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Herigstad, Matthew Omon. "Hybrid Particle-Nonwoven Membrane Materials for Bioseparations." NCSU, 2009. http://www.lib.ncsu.edu/theses/available/etd-04042009-120426/.
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Adsorption separations performed in feed streams containing large particulates pose interesting problems, the solution of which would aid in many fields of bioseapartions. Production of biologically derived protein products is one of the most rapidly expanding sectors in the global economy. The capture and purification of these products has, of late, become the bottleneck of the industry and can account for approximately 50-80% of the production costs. The biopharmaceutical industry has begun to focus on improving overall economics by merging two or more separation schemes into one. The majority of the emphasis has been on combining the initial protein capture and host cell clearance steps; however, many of the currently available methods have shown little efficacy at large-scale. Additionally, interest in the clearance of pathogenic activity, most importantly infectious prions, from blood and blood derived products has grown over the past decade with the increased threat of blood-transfusion of variant Creutzfeldt-Jakob disease. This work characterizes the transport and binding properties of a novel hybrid particle-nonwoven membrane medium in which a polymeric chromatographic resin is entrapped between layers of a nonwoven polypropylene membrane (a particle-impregnated membrane or PIM). This membrane-supported resin construct offers the advantage of increased interstitial pore diameter to allow passage of cells and other debris in the feed, while providing sufficiently high surface area for product capture within the resin particles. Columns packed with stacked disks of PIM displayed excellent flow distribution, and had an interstitial porosity of εb = 0.48 ± 0.01, a 25-60% increase over those typically observed in a packed bed. These columns were able to pass over 95% of E. coli cells and human red blood cell concentrate (RBCC) in 30 column volumes, while maintaining a pressure drop significantly lower than that of a packed bed. The dynamic binding capacity of the chromatographic resin entrapped in the PIM packed column for bovine serum albumin (BSA) was essentially the same as that observed with the same volume of resin in a packed bed. Additionally, the binding of prion was characterized to PIM constructs containing an affinity ligand for PrPSc, in saline, RBCC, and human IgG solutions. The General Rate (GR) model of chromatography was used to analyze experiments indicating that the breakthrough and elution behaviors of the PIM column are predictable, and very similar to those of a normal packed bed. These results indicate that PIM constructs can be designed to process viscous mobile phases containing particulates while retaining the desirable binding characteristics of the embedded chromatographic resin. The PIM systems could find uses in adsorption separation processes from complex feed streams such as whole blood, cell culture, and food processing and could offer a process alternative to expanded beds.
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Shehata, Ashraf Hassan. "A NEW METHOD FOR RADIOACTIVE PARTICLE TRACKING." NCSU, 2005. http://www.lib.ncsu.edu/theses/available/etd-12072005-140754/.
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A system based on the concept of three detectors radio active particle tracking, to track a particle non-invasively in the three dimensions is presented. It consists of a set of three well collimated detectors mounted on a platform that can be moved to track the radioactive particle vertically through one collimated detector with a horizontal slot opening. The other two collimated detectors with vertical slot opening can be rotated angularly to track the radioactive particle in the planar domain, and deduce the polar coordinates. A complete description of the actual system developed is outlined including the hardware, the automation and control software, and the data acquisition aspects. A critique of the conventional tomographic radioactive particle tracking was established in comparison to the new three detectors system we developed. A number of obvious and valuable advantages of the new method were pointed out. The result presented here are illustrative through a series of benchmark experiments to test and verify the performance of the system. Results of real trajectories of a single radioactive particle moving in air, and in a bed filled with a mass of granular spherical attenuating medium is also presented. Through testing benchmark experiments that include a variety of real time trajectories the success of the tracking system is demonstrated.
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Riley, James B. (James Barret). "Laser diffraction particle sizing : sampling and inversion." Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/58492.
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Thesis (Ph. D.)--Joint Program in Oceanographic Engineering (Massachusetts Institute of Technology, Dept. of Ocean Engineering; and the Woods Hole Oceanographic Institution), 1987.Bibliography: p. 213-228.
by James B. Riley.
Ph.D.
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Fewell, Sean E. "The particle erosion of steel by magnetite." Master's thesis, University of Cape Town, 2002. http://hdl.handle.net/11427/4965.
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Includes bibliographical references.This work addresses the problem of erosion of steel heat exchanger coils in a petroleum producing plant by magnetite catalyst particles entrained in the flowing gas stream.
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Achaye, Innocent. "Effect of particle properties on froth stability." Doctoral thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/24985.
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The froth flotation process has found substantial usage in the mineral processing industry for over a century and as long as minerals continue to exist in the earth's crust, the demand for upgrading and recovery of these natural yet valuable resources will continue to exist. It relies on the principle that a bubble-particle collision process should be accompanied by the formation of an attachment between the pair. Of particular importance to the flotation process is the stability of froths. This will affect the mass pull, which, in turn, will affect recovery and the grade that is attainable. Froth stability is affected by many factors, viz. machine properties, hydrodynamics within the flotation cell, reagent suites, as well as mineral particle properties. Of particular interest to reagent suites is the frother dosage and its influence on the prevention of coalescence which has been fairly well studied. Regarding froth stability, the frother influences the amount of water that reports to the concentrate as well as the bubble surface viscosity, limiting drainage and subsequent bubble coalescence. Most of the other factors influence the amount of particles that report to the froth, but it is the particle properties that have the overriding influence on the froth stability. It is in the interest of flotation modelling and optimisation to be able to find relationships for the impact of particle properties on froth stability. This project has focussed on the influence of two main particle properties, i.e. size and hydrophobicity, and their interactive effects on froth stability. In order to establish relationships between particle properties and froth stability, two devices were built in the laboratory, i.e. a non-overflowing stability column to measure froth stability and a bench-scale continuous flotation cell to provide metallurgical information, besides being able to measure froth stability using water recovery and froth surface bubble burst rate. In the first part of the investigation, particles of discrete sizes as well as mixtures of particles sizes were utilised at a constant hydrophobicity. Results obtained show a power law relationship between froth stability and particle size, with all particle combinations falling on the same relationship. Froth stability decreased with increasing particle size. A large increase in froth stability occurred for feed particles of average size below 50 μm. This was attributed to particles in the finer range reporting to the froth by both true flotation and entrainment. These fine particles would result in a higher interfilm viscosity resulting in reduced drainage. A useful linear relationship between froth stability and the reciprocal of feed particle size was obtained. The reciprocal of feed particle size was used to represent the specific surface area of the particles. It was found that as the specific surface area of the particles increased, their froth stabilising effect also increased in a linear fashion. In the second part of the investigation, the influence of particle hydrophobicity and the interactive effects of particle size and hydrophobicity on froth stability were explored. In common with other studies, it was found that froth stability increased with increasing particle hydrophobicity up to an optimum value between 66° and 69° and thereafter it decreased. The smallest size particles (28 μm) produced the highest variation in froth stability with increasing hydrophobicity. The response of the coarse particles to froth stability with increasing hydrophobicity was less pronounced. Particle size was found to have a greater influence on froth stability than particle hydrophobicity. Variations in froth stability were about 1.5 times greater for changes in particle size than changes in hydrophobicity over the relatively large ranges of size and hydrophobicity tested. The relationship between froth stability and feed particle specific surface area was investigated at different hydrophobicities and found to be linear for most practical particle sizes. However, a deviation from linearity occurred at very small particles sizes (28 μm) for particles of optimum hydrophobicities. The slopes of the froth stability versus feed specific surface area relationships in the linear region were found to increase with increasing hydrophobicity, up until an optimum contact angle of between 64° and 68°, whereafter they decreased. Thus, this family of curves would allow the prediction of froth stability of varying hydrophobicities on a size-by-size basis. This relationship was shown to hold for two real ores: a platinum-bearing UG2 ore and an Itabirite iron ore. Thus, a simple linear calibration of grind versus froth stability would allow a prediction of froth stability for a particular ore. A Langmuir-type model was developed to relate the froth stability to the concentrate particle surface area. It was found to be a good fit to the experimental data. This shows that it is possible to model froth stability in terms of the particle packing at the air-water interface in much the same way that surfactant molecular packing at the interface is modelled. The increasing particle surface area affects the surface tension of the films and reduces film drainage. In studying the interactive effects of particle size and hydrophobicity, it was found that all data points of all hydrophobicities fell on the same relationship when froth stability was plotted as a function of concentrate surface area. It was therefore, concluded that particle size and hydrophobicity define the amount of particles that will report to the froth phase, but once in the froth, it is the surface area of the particles that will define the froth stability.
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Humes, Zac. "Particle Characterization and Consentration Using Aerodynamic Vectoring." DigitalCommons@USU, 2008. https://digitalcommons.usu.edu/etd/36.
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An experimental demonstration of a new, non-contact particle characterization technique called Aerodynamic Vectoring Particle Sorting (AVPS) is presented. AVPS uses secondary blowing and suction control flows'flows that are a fraction of the jet flow rate'to sharply change the direction of a planar, particle-laden jet. As the jet is vectored, particles present in the flow experience a resultant drag force, dependent upon their size, that balances inertia. Since this balance determines the particle's trajectory, vectoring the flow leads to a separation of particles downstream. This simple, low-pressure-drop sorting technique classifies particles with less risk of damage or contamination than currently available sorting devices. AVPS is also shown to be capable of concentrating aerosols. Our measurements indicate that an air sample containing water-like particles can be concentrated by a factor of 10 using AVPS.
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Townsend, Rosemary Jane. "Modelling of a microfluid ultrasonic particle separator." Thesis, University of Southampton, 2006. https://eprints.soton.ac.uk/46695/.
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Particles within an ultrasonic standing wave experience an acoustic force causing the particles to move to certain positions within the acoustic field. This phenomenon can be used to manipulate particles and so provides a means to separate, concentrate or trap particles, cells or spores. The work described is applied to a micro-engineered flow-through device for processing small samples and incorporates a fluid filled chamber of depth typically between 100 and 200μm, and therefore approaches microfluidic dimensions. The successful design and subsequent performance of such devices rely on the predictability of particle trajectories which are influenced predominantly by acoustic and fluid flow fields. Therefore, the majority of this research seeks an understanding of the nature of these fields and, in turn, reliable simulation of particle trajectories. Computational fluid dynamics (CFD) modelling is used to develop a robust 2-dimensional model of the device’s microchannels and is used to predict the presence of eddy regions, associated with the etch fabrication techniques, which are likely to disrupt the separation process. Based on a geometric study, simulations and subsequent test results on a fabricated device have revealed geometric modifications which minimise these eddy flows and promote the existence of laminar flow within the main channel of the device. Finite element analysis (FEA) provides a method to investigate the 2-dimensional characteristics of the acoustic field and reveals variations in acoustic pressure across the width of the device, giving rise to lateral radiation forces frequently reported in similar ultrasonic devices. This work investigates acoustic enclosure modes in 2 or 3-dimensions as a possible cause of these lateral variations, with modelled results matching well with experiment. A particle force model has also been developed which predicts the motion of particles through the device, and by which concentration and separation performance may be calculated. This tool is used to investigate acoustic design, operating conditions and separation performance for both the micro-engineered device and a device based on a quarter-wavelength, providing valuable insight into various trends observed. The novelty in this work is the application of macro-scale numerical techniques to microengineered ultrasonic particle manipulators and the execution of an extensive analysis of the design and operation of such devices. These analyses have demonstrated, and therefore have explained, various phenomena associated with the fluid and acoustic fields, and how they influence particle separation performance. The development of similar devices can be aided by the use of the numerical simulation methods featured throughout this thesis.
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Potts, Ian. "Particle Redistribution in Serpentine Engine Inlets." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595542100917769.
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Yang, Fan. "Study on effect of charge on inertial particle motion in turbulence by using holographic particle tracking velocimetry." Thesis, State University of New York at Buffalo, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1567072.
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Particles in turbulence flows, either natural or artificial, can be charged. According to the previous research, electrical charge on particles has an influence on both rain enhancement and particle clustering in turbulent flow. Due to the Lorenz effect of unipolar or bipolar charged particles, particles tend to attract or repel to each other. Moreover, it is well known that electrical field exists in the atmosphere that has an effect on charged particles, especially droplets. As a result, the dynamic behaviors of charged particles can be rather different from uncharged particles, which, to date, are not systematically studied yet.
In order to systematically investigate the charged particles, we developed a method involving holographic particle tracking velocimetry (HPTV) technique to study the kinetic behavior of charged particles in flow. Theoretical analysis was also carried out to correlate kinetic behavior of particles and charge amount on them. This thesis also validated the feasibility of this method. The results of the validation experiment show that this method is capable to measure the velocity and acceleration of particles. By means of the second-order polynomial regression of particles' motion, the average acceleration, initial position and initial velocity of particles were obtained. With the mathematical model of a product of two normally distributed variables, the error bounds in measurement of particle kinetics can be acquired. Therefore, combining with the electrical field and diameter range of particles, we can quantitatively study the dynamic behavior of charged particles in flow.
In order to verify this, some experiments were designed and performed. We applied this method to quantitatively measure the behavior of particles to acquire the charge amount on particles from an enclosed chamber used in turbulence experiments. The result showed that although the charge amount was very low, most particles were charged with positive charge in the enclosed chamber. This result agreed with the triboelectric effect theory that in the friction with PVC tube, glass bubble particles prefer to lose electron and show positive charge. We also studied the effect of fan speed and material on charge amount on particles. Our results show that, by means of changing the material of tube, particle charge level is reduced, although more theoretical and experimental research should be carried out to confirm this conclusion.
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Tavakoli, Behtash. "Numerical simulation of particle-laden turbulent flows-Environmental applications." Thesis, Clarkson University, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3700373.
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In first part of the thesis a detailed study of the particulate pollutant distribution by wind flow over a building in an urban area was performed. The accuracy of RANS-RSTM and LES turbulence models for predicted airflow over a square cylinder was first evaluated. These models are then applied for simulating wind flows over the scale-model of the Center of Excellence (CoE) Building. Comparing the simulation results with the experimental data of Kehs et al. (2009) showed that the RSTM predicted the pressure distribution on the building consistent with the measurements, but it could not capture the details of the airflow velocity field around the building. The LES simulation, however, showed good agreement with the PIV data. The LES model was then used for analyzing the particulate pollutants transport and deposition analysis.
Particle motion was modeled using a one-way coupling, Lagrangian approach. Particular attentions were given to the effect of the turbulent velocity fluctuations on particles dispersion and deposition. Instantaneous turbulent velocity fluctuations were simulated using the Langevin stochastic differential equation. The particle transport model in turbulent flows was validated by comparing the predicted deposition velocity for vertical and horizontal channel flows with the existing experimental data and numerical simulation results. Finally the particulate pollutant dispersion and deposition around the scaled CoE Building were investigated using the LES and unsteady particle tracking approach.
In addition, the size-concentration distribution of secondary organic aerosols (SOAs), as an indoor air aldehyde pollutant, was numerically modeled. The population balance equation of the SOAs was solved using the method of moments (MOM). To close the model, particle size distribution was assumed to follow a lognormal distribution, which was based on the experimental data of Chen and Hopke (2009). The nucleation of SOAs from the chemical reaction of &agr;-pinene (a common emission from indoor furniture), and ozone in the air, as well as, their Brownian coagulation and the surface growth were considered in the numerical model. The computational model was evaluated by comparison with the experimental data of Chen and Hopke (2009).
The MOM was used for modeling the distribution of the SOAs in an office space. The concentrations of SOAs in the breathing zone of an occupant in the room were evaluated for two mixed-mode ventilation systems. The simulation results showed that the pollution concentration in the ventilation system with the air outlet placed in the ceiling was smaller than the one in which the air outlet was in the floor behind the manikin model.
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Peng, Zhizi. "Modeling of Particle and Biological Cell Transport in Microchannels." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1324660368.
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Qiu, Zhenghui. "Investigation of hydro-mechanical particle flow through horizontal orifices." Master's thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/28112.
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In the modern world, as the global population continues to rise, the need for and recovery of natural resources is becoming ever more relevant. Identifying optimisation solutions for the recovery of granular resources has progressed into one of the most dominant development areas in the mining and processing industries. Two relevant examples from these sectors include the offshore extraction of materials from the ocean floor via hydraulic transport and the processing of mineral particulates through chutes, and hoppers. A common feature of recovery employed in such areas is the rate at which these materials pass through an orifice. The orifice is the interface between the implemented collection or transport system and the targeted material source. Extensive research has been done on the gravitational passing of particles through an orifice, where in contrast, limited knowledge exists on alternative driving factors of flow. The movement of particles induced both mechanically and hydraulically formed the basis of this dissertation in which selected granular materials were experimentally characterised. Specifically, the following were studied: the effect of orifice and particle size, changes in system velocity and the effects of suction. The system encompassed a scaled down model of a real-life application. An experimental and numerical analysis approach was undertaken, where the calibration of the simulated model was dependent on the former. A total of 327 experimental tests were conducted on the flow ability of high sphericity (±95% roundness) glass beads. A numerical model based on the physical parameters was calibrated to further assist in the overall analysis of the system. The model was of a discrete element method (DEM) type. Empirically, it was found that the Beverloo law, an expression used to describe the discharge of particles through a hopper, had many aspects that were dimensionally suited for the study. Through certain boundary assumptions made in the study, the law was in agreement with the stated outputs. The ratio (R) between the orifice (Dₒ) and particle diameter (dₚ) had a significant influence on the entrainment rate, where there existed a region (R > 4) of limiting flow. Changes in the system velocity, were found to have a negligible effect on the overall recovery but a direct relationship with the rate at which the material was collected. The introduction of suction improved the recovery of materials greatly, increasing the mass flow rate by more than 300%. The in-depth analysis on a multitude of orifice configurations, considerably extended the understanding of the behaviour of particles passing through an opening, particularly spherical particles under fluid or mechanical driven flow. Results indicated that there was a lot of potential for improving the optimisation of granular flow. Optimisation in this sense was defined as maximising the recovery (%) or collection rate (kg/s) of the system. Boundary conditions and design guidelines were offered to address this issue. Areas where further research could advance this understanding were highlighted.
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Srinivasan, Ganesh. "Numerical Simulation of Nano-scale to Micro-scale Particle Growth in Condensation Particle Counter." University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1204577130.
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