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1
Patel, Ketan Shantilal. "Vibro-spring particle size distribution analyser". Thesis, University College London (University of London), 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252097.
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2
Darley, A. D. "Particle size distribution effects in chocolate processing". Thesis, University of Bradford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.253973.
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3
Ip, Trevor Tsz-Leung. "Influence of particle size distribution on fluidized bed hydrodynamics". Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/27891.
Testo completoAbstract (sommario):
Past literature has shown that the production efficiency of a fluidized bed can be affected by changing the particle size distribution. The hydrodynamics of fine particle fluidization were studied with FCC and glass bead powders which have different surface-volume mean particle diameter (40-110 μM) and particle size distributions (narrow cut, wide cut and bimodal) under ambient conditions. Increasing the mean particle size increases the minimum fluidization velocity, minimum bubbling velocity and dense phase velocity (U[sub d]) while decreasing the voidages at minimum fluidization and minimum bubbling and the dense phase voidage (∈[sub d]) as well as the fractional bubble free bed expansion. Increasing the particle size spread increases U[sub d] and decreases ∈[sub d] for FCC, but no clear conclusion can be made for glass bead powders. Increasing the static bed height decreases U[sub d] and ∈[sub d] of FCC powders though it has no effect on minimum fluidization and bubbling properties. The magnitude of pressure fluctuations increases with increasing superficial gas velocity and as the size spread of the FCC powder becomes more narrow. However, the frequency of fluctuations is independent of each of these factors. Therefore, the quality and production efficiency of the fluidization process should improve with the use of a wide and continuous size distribution powder.Applied Science, Faculty of
Chemical and Biological Engineering, Department of
Graduate
4
Jahanzad, Fatemeh. "Evolution of particle size distribution in suspension polymerisation reactions". Thesis, Loughborough University, 2004. https://dspace.lboro.ac.uk/2134/10300.
Testo completoAbstract (sommario):
Suspension polymerisation processes are commercially important for the production of polymer beads having wide applications. Polymers produced by suspension polymerisation can be directly used for particular applications such as chromatographic separations and ion-exchange resins. Particle Size Distribution (PSD) may appreciably influence the performance of the final product. Therefore, the evolution of PSD is a major concern in the design of a suspension polymerisation process. In this research, methyl methacrylate (MMA) has been used as a model monomer. A comparative study of MMA suspension polymerisation and MMNwater dispersion was carried out, for the first time, to elaborate the evolution of mean particle size and distribution. Polyvinyl alcohol (PVA) and Lauroyl Peroxide (LPO) have been used as stabiliser and initiator, respectively. Polymerisation experiments were carried out using a 1-litre jacketed glass reactor equipped with a turbine impeller and a condenser. The stabiliser, initiator and chain transfer concentrations, inhibitor concentration and type, reaction temperature, impeller speed, and monomer hold up were used as variables. A mathematical model was developed to predict the kinetics of polymerisation as well as the evolution of PSD by population balance modelling. The experimental results were compared with the model predictions. From the comprehensive experimental results, the characteristic intervals of a typical suspension polymerisation were realised as: 1) Transition stage during which PSD narrows dramatically and drop size decreases exponentially due to higher rate of drop break up in comparison with drop coalescence . _ until a steady state is reached. The importance, and even the existence, of the transition stage have been totally ignored in the literature. The results indicate that increasing the impeller speed, and PV A concentration will lead to a shorter transition period. Also increasing the rate of reaction, via increasing initiator concentration, and reaction temperature will shorten this period. ABSTRACT 2) Quasi steady-state stage during which the rate of drop break up and drop coalescence are almost balanced leading to a steady-state drop size and distribution. The occurrence of this stage is conditional. Low impeller speed and PV A concentration may remove the quasi steady-state stage completely and drops may start growing considerably after a sharp decrease in size during the transition stage. 3) Growth stage during which the rate of drop break up considerably falls below the rate of drop coalescence due to the viscosity build up in drops leading to drop enlargement and PSD broadening. Results show that the onset of the growth stage may not be fixed and it depends on the balance of the forces acting on drops. The onset of the growth stage in terms of time was advanced with decreasing stirring speed and PV A concentration and increasing monomer hold up. Under a static steady state, which is formed when a high concentration of PV A is used, there is almost no growth. 4) Identification stage during which a solid-liquid suspension is attained and the PSD and mean particle size remain unchanged afterwards. The onset of this stage appears to be fairly constant for different formulations. The developed model could fairly predict the rate of polymerisation. It was also capable of predicting the evolution of particle size average and distribution qualitatively in the course of polymerisation. The results can be used as a guideline for the control of particle size and distribution in suspension polymerisation reactors. A more quantitative exploitation of the model has been left for a future research.
5
Salimi, Farhad. "Characteristics of spatial variation, size distribution, formation and growth of particles in urban environments". Thesis, Queensland University of Technology, 2014. https://eprints.qut.edu.au/69332/1/Farhad_Salimi_Thesis.pdf.
Testo completoAbstract (sommario):
This thesis is the first comprehensive study of important parameters relating to aerosols' impact on climate and human health, namely spatial variation, particle size distribution and new particle formation. We determined the importance of spatial variation of particle number concentration in microscale environments, developed a method for particle size parameterisation and provided knowledge about the chemistry of new particle formation. This is a significant contribution to our understanding of processes behind the transformation and dynamics of urban aerosols. This PhD project included extensive measurements of air quality parameters using state of the art instrumentation at each of the 25 sites within the Brisbane metropolitan area and advanced statistical analysis.
6
Zhang, Shuo. "Relationship between particle size distribution and porosity in dump leaching". Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/63383.
Testo completoAbstract (sommario):
Fluid flow is a critical process involved in the valuable metals extraction from low grade ore in heap and dump leaching as well as the release of harmful substances from waste rock piles. The mechanisms by which fluids move through the porous media depend on the fluid properties and the intrinsic properties of the porous media, with permeability being one critical factor. Particle size distribution is a key factor that affects permeability by forming pores of different structure and size. The objective of this research was to assess the particle size distribution in heterogeneous packed ore/rock beds and quantify the effect of particle size distribution on porosity. In the studied mine site, the particle size distribution in the dump leach pad was determined by analyzing aerial images of multiple dump faces taken by a drone. Particles spanned a wide range in size from less than 2 cm in diameter to larger than 2 m in diameter, with a P80 to be 2 m. The spatial segregation of fine particles and coarse particles along the dump faces was observed, which may contribute to the formation of preferential flow.
The effect of particle size distribution on porosity was quantified by two methods: the bulk density and CT-imaging techniques. Porosities under three particle sorting conditions were studied: narrow-sized particles, poorly sorted particles and well sorted particles. For narrow-sized particles, the porosity measured by the bulk density method decreased as the particle size was increased up to 0.151 mm after which the porosity remained constant in the range tested. The influence of the particle size on the porosity for the well sorted particles was similar to that of the narrow-sized particles from both of the methods. For poorly sorted particles, in both methods, porosity decreased as the fraction of the fine particles added was increased to a certain value, after which the porosity started to increase as the fraction of fine particles was further increased. The results have important implications for metal extraction from run of mine ores using dump leaching and release of contaminants from waste rock piles by influencing fluid flow properties.Applied Science, Faculty of
Materials Engineering, Department of
Graduate
7
Leng, Tianyang. "Cellulose Nanocrystals: Particle Size Distribution and Dispersion in Polymer Composites". Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/34073.
Testo completoAbstract (sommario):
This thesis describes the characterization of the particle size distribution of cellulose nanocrystals (CNC), the synthesis and characterization of fluorescent CNCs, and the development of a fluorescence microscopy method to probe the distribution of fluorescent CNCs in polymer composites.
In this thesis, several methods are used to characterize the size of CNC particles. Size distribution measurements by single particle counting methods (Transmission electron microscopy, Atomic force microscopy) are compared to an ensemble method, Dynamic lighting scattering (DLS) and differences between the various methods will be discussed. The effect of sonication on the CNC size distributions measured by AFM and DLS is examined. Furthermore, a reliable and reproducible method for re-dispersing dry CNC powder will be explored in this chapter since CNC is often stored in a dry environment due to its stability. Rhodamine B isothiocyanate (RBITC) and 5-(4,6-dichlorotriazinyl) amino fluorescein (DTAF) were selected for labelling CNCs. These dyes have the advantage of being cheap and readily available and compatible with relatively simple synthetic chemistry. The photophysical properties of all dye labeled CNCs were studied in more detail than in previous studies. The focus is on understanding the most appropriate labeling efficiency to maximize the ability to detect individual CNCs while minimizing the amount of dye used to avoid modifying the CNC properties. The characterization methods include ensemble methods such as UV-Vis absorption and scattering measurements, fluorescence spectroscopy and single molecule methods such as Total internal reflection fluorescence microscopy (TIRFM), Atomic force microscopy (AFM) and correlated TIRFM/AFM measurements. All of these methods have their advantages and disadvantages. After characterization, the most suitable dye labeled CNC sample was selected for development of a fluorescence microscopy method to characterize CNC distribution in CNC/polymer composites. The dye labeled CNC has been incorporated into polyvinyl alcohol (PVA) films and studied by fluorescence microscopy. These experiments demonstrated that the level of CNC agglomeration varies significantly for different film preparation methods, indicating that fluorescence microscopy is a useful and easily accessible method for optimizing film preparation. The self-quenching of the dye in the film was also measured and discussed and is an important consideration for choice of the dye loading and CNC content in the films.
8
Hildebrand, Erin N. "The effect of particle size distribution on spectral backscattering coefficient". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0015/MQ57296.pdf.
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9
Gursky, Barry Michael. "Particle size distribution optimization of filler content in shingle asphalt". Thesis, Georgia Institute of Technology, 1986. http://hdl.handle.net/1853/20989.
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10
Rekhibi, Soliman Abograra. "Condition monitoring of mining machinery using debris particle size distribution". Thesis, University of Nottingham, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335821.
Testo completo
11
Cheung, Hing Cho. "Study of new particle formation in subtropical urban environment in Brisbane, Australia". Thesis, Queensland University of Technology, 2012. https://eprints.qut.edu.au/60045/1/Hing_Cho_Cheung_Thesis.pdf.
Testo completoAbstract (sommario):
Atmospheric ultrafine particles play an important role in affecting human health, altering climate and degrading visibility. Numerous studies have been conducted to better understand the formation process of these particles, including field measurements, laboratory chamber studies and mathematical modeling approaches. Field studies on new particle formation found that formation processes were significantly affected by atmospheric conditions, such as the availability of particle precursors and meteorological conditions. However, those studies were mainly carried out in rural areas of the northern hemisphere and information on new particle formation in urban areas, especially those in subtropical regions, is limited. In general, subtropical regions display a higher level of solar radiation, along with stronger photochemical reactivity, than those regions investigated in previous studies. However, based on the results of these studies, the mechanisms involved in the new particle formation process remain unclear, particularly in the Southern Hemisphere. Therefore, in order to fill this gap in knowledge, a new particle formation study was conducted in a subtropical urban area in the Southern Hemisphere during 2009, which measured particle size distribution in different locations in Brisbane, Australia.
Characterisation of nucleation events was conducted at the campus building of the Queensland University of Technology (QUT), located in an urban area of Brisbane. Overall, the annual average number concentrations of ultrafine, Aitken and nucleation mode particles were found to be 9.3 x 103, 3.7 x 103 and 5.6 x 103 cm-3, respectively. This was comparable to levels measured in urban areas of northern Europe, but lower than those from polluted urban areas such as the Yangtze River Delta, China and Huelva and Santa Cruz de Tenerife, Spain. Average particle number concentration (PNC) in the Brisbane region did not show significant seasonal variation, however a relatively large variation was observed during the warmer season. Diurnal variation of Aitken and nucleation mode particles displayed different patterns, which suggested that direct vehicle exhaust emissions were a major contributor of Aitken mode particles, while nucleation mode particles originated from vehicle exhaust emissions in the morning and photochemical production at around noon. A total of 65 nucleation events were observed during 2009, in which 40 events were classified as nucleation growth events and the remainder were nucleation burst events. An interesting observation in this study was that all nucleation growth events were associated with vehicle exhaust emission plumes, while the nucleation burst events were associated with industrial emission plumes from an industrial area. The average particle growth rate for nucleation events was found to be 4.6 nm hr-1 (ranging from 1.79-7.78 nm hr-1), which is comparable to other urban studies conducted in the United States, while monthly particle growth rates were found to be positively related to monthly solar radiation (r = 0.76, p <0.05). The particle growth rate values reported in this work are the first of their kind to be reported for the subtropical urban area of Australia.
Furthermore, the influence of nucleation events on PNC within the urban airshed was also investigated. PNC was simultaneously measured at urban (QUT), roadside (Woolloongabba) and semi-urban (Rocklea) sites in Brisbane during 2009. Total PNC at these sites was found to be significantly affected by regional nucleation events. The relative fractions of PNC to total daily PNC observed at QUT, Woolloongabba and Rocklea were found to be 12%, 9% and 14%, respectively, during regional nucleation events. These values were higher than those observed as a result of vehicle exhaust emissions during weekday mornings, which ranged from 5.1-5.5% at QUT and Woolloongabba. In addition, PNC in the semi-urban area of Rocklea increased by a factor of 15.4 when it was upwind from urban pollution sources under the influence of nucleation burst events.
Finally, we investigated the influence of sulfuric acid on new particle formation in the study region. A H2SO4 proxy was calculated by using [SO2], solar radiation and particle condensation sink data to represent the new particle production strength for the urban, roadside and semi-urban areas of Brisbane during the period June-July of 2009. The temporal variations of the H2SO4 proxies and the nucleation mode particle concentration were found to be in phase during nucleation events in the urban and roadside areas. In contrast, the peak of proxy concentration occurred 1-2 hr prior to the observed peak in nucleation mode particle concentration at the downwind semi-urban area of Brisbane. A moderate to strong linear relationship was found between the proxy and the freshly formed particles, with r2 values of 0.26-0.77 during the nucleation events. In addition, the log[H2SO4 proxy] required to produce new particles was found to be ~1.0 ppb Wm-2 s and below 0.5 ppb Wm-2 s for the urban and semi-urban areas, respectively. The particle growth rates were similar during nucleation events at the three study locations, with an average value of 2.7 ± 0.5 nm hr-1. This result suggested that a similar nucleation mechanism dominated in the study region, which was strongly related to sulphuric acid concentration, however the relationship between the proxy and PNC was poor in the semi-urban area of Rocklea. This can be explained by the fact that the nucleation process was initiated upwind of the site and the resultant particles were transported via the wind to Rocklea. This explanation is also supported by the higher geometric mean diameter value observed for particles during the nucleation event and the time lag relationship between the H2SO4 proxy and PNC observed at Rocklea.
In summary, particle size distribution was continuously measured in a subtropical urban area of southern hemisphere during 2009, the findings from which formed the first particle size distribution dataset in the study region. The characteristics of nucleation events in the Brisbane region were quantified and the properties of the nucleation growth and burst events are discussed in detail using a case studies approach. To further investigate the influence of nucleation events on PNC in the study region, PNC was simultaneously measured at three locations to examine the spatial variation of PNC during the regional nucleation events. In addition, the impact of upwind urban pollution on the downwind semi-urban area was quantified during these nucleation events. Sulphuric acid was found to be an important factor influencing new particle formation in the urban and roadside areas of the study region, however, a direct relationship with nucleation events at the semi-urban site was not observed. This study provided an overview of new particle formation in the Brisbane region, and its influence on PNC in the surrounding area. The findings of this work are the first of their kind for an urban area in the southern hemisphere.
12
Zhang, Yanmin. "A study of suspension polymerisation of Methyl Mathacrylate and Styrene in a batch oscillatory baffled reactor". Thesis, University of Strathclyde, 1998. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=22173.
Testo completoAbstract (sommario):
One of the most important issues in suspension polymerisation process is the control of the final particle size distribution (PSD) as this is an indicator for both quality and financial matters. For polymer manufacturers, a narrow PSD is always welcome. The conventional reactors, e. g. stirred tank reactors, generally produce particles of a rather broad PSD. As a result, to explore a new type of polymerisation devices becomes a challenging task. The objectives of this PhD study are to apply a novel mixing apparatus, the oscillatory baffled reactor (OBR), to batch polymerisation of MMA and Styrene (crosslinked) and to characterise all the major aspects of the OBR involved in the pioneering work, with a view to assessing its potential for industrial applications. In order to carry out such investigations, a 1.2 litre batch jacketed OBR system with temperature control and on-line data acquisition units was designed and built. In addition, an off-line image capture system was set up f or droplet studies. From heat transfer study in the OBR, it was found that the temperature profiles across and along the reactor were uniform and a heat transfer correlation was obtained. The oil-water dispersion in the OBR was then investigated for various baffle designs, dispersed phase fractions and the levels of surfactants, enabling the optimal baffle type and parameters to be identified. In order to understand the droplet behaviour in the OBR, the droplet size distribution (DSD) was examined on dispersion uniformity, oscillation time, operational conditions, baffle thickness and the level of surfactant addition. It was found that the DSDs were very uniform within the reactor and the oscillation frequency and amplitude had the same effect on controlling the DSDs. Finally, a series of PMMA and PS tests were successfully conducted in the OBR, indicating that the polymer PSD can be controlled by adjusting both oscillation conditions and the baffle orifice diameter and that the OBR has the potential to produce uniform polymer particles at high oscillation frequencies. A correlation between droplet sizes with no reaction and final polymer particle sizes was established, which can be used to predict the final polymer sizes.
13
Tileti, Pramod Reddy. "Moldability of MIM feedstocks with varying particle size distribution and shape". Thesis, KTH, Materialvetenskap, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-123691.
Testo completo
14
Ukeje, Michael Anayo. "Effect of particle size distribution on the rheology of dispersed systems". Thesis, Imperial College London, 2000. http://hdl.handle.net/10044/1/7492.
Testo completo
15
VIZCARRA, GINO OMAR CALDERON. "EFFECT OF PARTICLE-SIZE-DISTRIBUTION ON MECHANICAL BEHAVIOR OF RAILWAY BALLAST". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2015. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=29913@1.
Testo completoAbstract (sommario):
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
PROGRAMA DE EXCELENCIA ACADEMICA
O efeito da granulometria no comportamento mecânico do lastro tem sido estudado por vários pesquisadores. A revisão destes estudos indicou que uma granulometria mais uniforme que as atualmente usadas pela indústria ferroviária diminuiria a deformação permanente e a degradação do lastro ferroviário. Neste estudo, foi utilizado o equipamento prismoidal triaxial cíclico, projetado e construído na Universidade de Wollongong - Austrália. O deslocamento lateral do lastro ferroviário no campo não está restrito, devido a insuficiente tensão lateral (tensão confinante); por isso a câmera prismoidal triaxial com lados não restritos é uma instalação ideal para a modelagem física das deformações do lastro. Duas granulometrias de lastro foram testadas, sob tensão vertical cíclica máxima de 450 kPa. Uma delas estava de acordo com a granulometria recomendada por Indraratna et al. (2004), para revisão da Norma Australiana AS 2758.7 (1996) e a outra foi preparada em concordância com a norma Brasileira, NBR 5564. Os resultados mostram que a granulometria tem grande influência na deformação permanente e na quebra de lastro ferroviário. Também se apresenta a modelagem de um ensaio de compressão sobre lastro ferroviário utilizando o método dos elementos discretos. Utilizaram-se propriedades típicas de lastro ferroviário tais como peso específico, granulometria, índice de vazios e espessura das camadas. O ensaio virtual compreende a aplicação de uma carga vertical monotônica mediante uma peça de dimensões similares a um dormente, sobre partículas que simulam o lastro colocado numa caixa de dimensões 600 x 800 x 800 mm. São observadas as tensões e velocidades desenvolvidas nas partículas, características difíceis de serem observadas nos ensaios convencionais reais.
The effect of the particle-size-distribution on mechanical behaviour of ballast has been studied by several researchers in the past. The review of these past studies indicated that more uniform gradation than actually used by the railway industry would decrease permanent deformation and degradation of railroad ballast. In this study, the prismoidal cyclic triaxial apparatus designed and built at the University of Wollongong was used. The lateral displacement of railroad ballast in the field is not restricted in the absence of sufficient lateral stress (confining pressure); hence the prismoidal triaxial chamber with unrestrained sides provides an ideal facility for physical modeling of the deformations of ballast. Two different particle size distributions of ballast were tested under cyclic vertical maximum stress of about 450 kPa. One of them was according to PSD recommended by Indraratna et al. (2004) as an improvement to Australian Standard AS 2758.7 (1996) and the other one was prepared in accordance with Brazilian standard NBR 5564. The results showed that gradation had major influence on the permanent deformation and breakage of railroad ballast. Also, it is presented a compression test modelling on railway ballast using the discrete element method. Typical railways ballast properties, such as specific weight, particle-size-distribution, void ratio, layers thickness were used. The virtual test comprises monotonic vertical loading through a piece with similar dimensions to sleeper on particles that simulates ballast inside a 600 x 800 x 800 mm box. Stresses and velocities developed in particles are observed, which are difficult sighting characteristics in real conventional tests.
16
Vazirizadeh, Ali. "The relationship between hydrodynamic variables and particle size distribution in flotation". Doctoral thesis, Université Laval, 2015. http://hdl.handle.net/20.500.11794/25868.
Testo completoAbstract (sommario):
La flottation industrielle est un procédé continu qui se déroule souvent en plusieurs étapes et dans lequel des particules d'une espèce de minéral donnée (généralement celles d'intérêt), présentes en différentes tailles, rencontrent une grande quantité de bulles de gaz (normalement de l'air) pour produire des agrégats bulles-particules minérales, qui sont extraits du dispositif de flottation (colonne ou cellule) en tant que produit de valeur (concentré). Le contenu en bulles est décrit par les conditions hydrodynamiques régnant dans le réacteur de flottation. Celles-ci sont reconnues pour leur influence sur la performance de la flottation. Ce projet de recherche porte sur deux sujets majeurs. Le premier est l'analyse de l’impact des particules solides sur les variables hydrodynamiques et l’effet de ces variables hydrodynamiques sur la récupération d’eau au concentré. Pour ce faire, l'effet du solide sur la distribution de la taille des bulles et le taux de rétention de l’air, ainsi que la corrélation entre la distribution de taille des bulles et le taux de rétention de l’air dans une colonne de flottation ont été étudiés. L'effet du taux de rétention de l’air, de la dimension des bulles et du taux surfacique de bulles (Sb) sur la quantité d’eau extraite au concentré a ensuite été analysé. Le second sujet traite de l'utilisation des variables hydrodynamiques pour la modélisation de la cinétique du procédé de flottation selon distribution granulométrique des particules introduites. La surface inter-faciale de bulle (Ib) est introduite à cet égard comme une variable hydrodynamique fournissant plus d'informations sur la distribution de taille de bulle que le taux surfacique de bulles qui est plus couramment utilisé. De plus, la corrélation entre la constante cinétique, la taille des particules et certaines variables hydrodynamiques a été analysée en utilisant une projection de structures latentes (PSL). Les résultats indiquent que l'importance relative des variables hydrodynamiques pour la modélisation de la cinétique de flottation dépend de la distribution granulométrique des particules. Finalement, les variables hydrodynamiques suggérées pour chaque classe granulométrique considérée ont été utilisées pour produire des modèles de régression mono-variable de la constante cinétique.Industrial flotation is a continuous and often multistage process, where particles of a given mineral species (usually the targeted one), present in different sizes, encounter a large amount of gas bubbles (normally air) to produce mineral–bubble aggregates, which are removed from the flotation device (cell or column) as a valuable product (concentrate). The bubble content inside the cell is characterized by the prevailing hydrodynamic conditions (known as gas dispersion variables), which in turn are known to influence the flotation performance. This research project deals with two major topics. The first one is identifying the effect of mineral particles on hydrodynamic variables, and the effects of hydrodynamic variables on the final water recovery. For this purpose, the effect of solid particles on the bubble size distribution and gas hold-up, as well as the correlation between bubble size distribution and gas hold-up in column flotation were studied. It is followed by an assessment of the effect of the gas hold-up, bubble size and bubble surface area flux (Sb) on the amount of water reporting to the concentrate. The second topic deals with applying appropriate hydrodynamic variables for flotation modeling based on a given introduced particle size distribution. The interfacial area of bubbles (Ib) is introduced to address this issue as a hydrodynamic variable providing more information about the size distribution of bubbles than the commonly used bubble surface area flux. The correlation between the flotation rate constant and particle size as well as given hydrodynamic variables using a Projection to Latent Structures (PLS) has been analyzed. Results suggest that the relative importance of hydrodynamic variables for flotation rate modeling depends on the particle size distribution. Finally the suggested hydrodynamic variables for each of the various particle size-classes considered were used to produce single variable models for the flotation rate constant.
17
Bianco, Nicola. "Optimal control of particle size distribution in semi-batch emulsion polymerisation". Thesis, Imperial College London, 2009. http://hdl.handle.net/10044/1/7474.
Testo completo
18
Sun, Guanglin. "Influence of particle size distribution on the performance of fluidized bed reactors". Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/32013.
Testo completoAbstract (sommario):
The effect of particle size distribution (PSD) on the performance of a fluidized bed reactor was investigated using the ozone decomposition reaction, combined with the study of hydrodynamics, for fresh and spent fluid cracking catalysts, each having three particle size distributions - wide, narrow and bimodal - all with nearly the same mean diameter (60 µm), the same particle density and the same BET surface area. The superficial gas velocity was varied from 0.1 to 1.8 m/s to include the bubbling, slugging, turbulent and fast fluidization regimes. The catalytic rate constant, based on the volume of the particles, ranged from 2 to10 s⁻¹, while the static bed height was varied from 0.15 m to 1 m. Four different multi-orifice gas distributors with different hole diameters (2.2 to 5.1 mm) and hole numbers (4 and 21) were also tested to evaluate the influence of gas distributor on the performance of fluidized bed reactors.
The particle size distribution was found to play a larger role at higher gas velocities than at lower velocities. At low gas velocities (Uf ≤ 0.2 m/s), the reaction conversion was not greatly affected by the PSD. However, with an increase in gas velocity the PSD effect became larger. The wide size distribution gave the highest reactor efficiency, defined as the ratio of the volume of catalyst required in a plug flow reactor to that required in the fluidized bed reactor to achieve the same conversion, while the narrow blend gave the lowest. The differences are not solely a function of the "fines content".
The influence of particle size distribution on the hydrodynamics of fluidization was evaluated by measuring particle concentrations in voids, bubble sizes, and dense phase expansion. When the superficial gas velocity exceeded 0.1 m/s, the bed with the wide size distribution usually gave the highest particle concentration inside the voids, the smallest
bubble size and the greatest dense phase expansion at the same operating conditions. There is evidence that there is a greater proportion of "fines" present in the voids than in the overall particle size distribution. This has been explained in terms of the throughflow velocity inside bubbles being of the same order as the terminal velocity of typical "fines", causing these particles to spend longer periods of time inside the voids.
The effect of the PSD on the fluidization regime and its transitions was determined by measuring pressure fluctuations along the column. The earliest transition from bubbling or slugging to turbulent fluidization occurred in the bed of wide size distribution, while the latest corresponded to the narrow PSD.
For particles of wide size distribution, higher conversion was achieved for the turbulent and fast fluidization regimes than for the bubbling fluidization regime under otherwise identical conditions, while for particles of narrow size distribution, the dependence of conversion on regime was small. Hence, for reactors of wide PSD, the performance can be improved significantly by operating in the turbulent or fast fluidization regime, while for particles of narrow size distribution, the benefit of operating at high gas velocity is slight at best.
The PSD influence should be considered in modelling fluidized bed reactors. The "Two-Phase Bubbling Bed Model" has been modified to account for PSD effects. For the reactor of wide particle size distribution operated at high gas velocities, a single-phase axial dispersion model with closed inlet and open outlet boundary conditions appears to be suitable to predict the performance.
It was also found that a high pressure drop across the gas distributor was not sufficient to maintain good performance of the distributor. The reactor efficiency in the entry region was higher for a distributor with a greater number of orifices, even though it had a lower pressure drop, than for a distributor plate with fewer larger holes.Applied Science, Faculty of
Chemical and Biological Engineering, Department of
Graduate
19
Jing, Cao. "Spray diagnostics by laser diffraction". Thesis, University of Sheffield, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321852.
Testo completo
20
Elmaci, Bilhan. "The detection and wear in mining machinery by debris particle size distribution". Thesis, University of Nottingham, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.352968.
Testo completo
21
Agarwal, Pawan 1971. "Modeling the pneumatic transport of solids with a bimodal particle size distribution". Thesis, The University of Arizona, 1997. http://hdl.handle.net/10150/278610.
Testo completoAbstract (sommario):
Particle size distribution (PSD) plays a key role in fluidization behavior. The effect of PSD in fluidized, gas-solid mixtures is elucidated by considering two types of bimodal particle mixtures. In the first case, a mixture of "large" particles, which engage in particle-particle collisions, and "small" particles or fines, which follow the fluid streamlines, are considered. In this case, one net effect of the fines is to decrease the pressure drop required to convey a given solids flux in a riser. In the second case, a mixture of two sizes of larger particles in which collisions between like and unlike particles occur are considered. In this case, a reduction in particle phase stress in the bimodal mixture as compared to a monosized particle mixture with the same mean particle diameter is predicted. For dilute flow, this stress reduction is minimal but increases in significance as the suspension becomes more concentrated.
22
Steward, Nigel Ian. "Influence of particle size distribution on the sintering of ceramic powder compacts". Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47674.
Testo completo
23
Oladewa, Adekola. "Effect of Random Particle Size Distribution on the Percolation Threshold of Composites". University of Toledo / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1430413546.
Testo completo
24
Rojas, Néstor Y. "Diesel exhaust system influences on transient particulate emissions and particle size distribution". Thesis, University of Leeds, 2001. http://etheses.whiterose.ac.uk/2292/.
Testo completoAbstract (sommario):
The behaviour of particulate matter emissions from a Ford XLD 4T, passengercar diesel engine through a practical exhaust system in place was investigated during transient conditions, namely cold start and fast acceleration. Particulate emissions were measured at four sampling points through the exhaust system and the changes in particulate total mass concentration, total number concentration, particle size distribution and Carbon/SOF fractions were determined for various engine operating conditions. Each cold start test consisted of a step-change cold-start with fast acceleration, reaching one of the following target operation conditions: Idle, 1500rpm - 15kW, 2250rpm - 15kW, 2250rpm-35kW and 3500rpm - 15kW. Two preconditioning procedures were designed to provide repeatable cold start tests. These consisted of a) Idle operation for 4 hours the day before the test, followed by overnight soak; and b)10 minutes at high engine speed operation. Fast acceleration tests consisted of idle preconditioning followed by a step change to the target operation conditions. The particulate matter changes through the exhaust system were shown to be dependent on the previous operational history of the engine, idle conditions being effective at forming particle deposits. The amount of particulate deposited or blown out from the exhaust system constituted a significant fraction of the total engine exhaust emissions in a significant number of cold start and acceleration tests. The changes in particle concentration did not occur throughout the system in the same fashion. The catalyst produced predominantly particle number and mass reduction and the second silencer was a more efficient particle collector than the first silencer. From the first silencer, particles were resuspended more easily and in many more cases. Regarding the chemical composition, high-load conditions produced lower Solvent Organic Fraction (SOF) than their low load counterpart. However, the SOF did not change significantly through the exhaust system. Part of this work consisted of examining the use of the Electrical Low Pressure Impactor (ELP1) to estimate particulate mass emissions. It was observed that the ELP1 tended to overestimate the number of particles in the large (>0.1 (im) size range. This greatly affected the conversion from total particle number concentration to particle mass concentration. A correction based on comparison between the electrical and gravimetric methods (ELPI vs. Andersen Impactors) in the common size range for both techniques was proposed. Transient and steady-state tailpipe emission factors, expressed as grams of particulate per unit of engine work in kWh, were calculated from the test results and used to estimate the effect of transients on total cycle emissions in cycles with a different design from those followed in this work. The ELPI proved to be useful, yet limited for particle collection on Transmission Electron Microscope (TEM) grids in several size ranges. TEM images of particles were analysed and their fractal dimension determined.
25
Svoboda, Svetozár. "Vyhodnocení kontaminace pracovního prostředí aerosoly řezných kapalin při soustružení kovů". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-318769.
Testo completoAbstract (sommario):
The thesis deals with the contamination of the workspace with a liquid aerosol, which is generated by scattering and evaporation of the cooling fluid. Cooling fluid are primarily intended to lubricate, cool and clean the tool and the workpiece, but the unwanted side effect is the formation of a liquid aerosol that holds in the air of the workspace. In such a contaminated work environment, the operator is exposed to a certain dose of a liquid aerosol that causes dermatological and respiratory problems. The topic of the thesis was to find out the number of particles of liquid aerosol that arises under varying working conditions and its dispersion in space. This amount was determined by image analysis using a high-speed camera.
26
Chowdhury, Raziya Sultana. "Size distribution and source apportionment of airborne particulate matter". Thesis, Queensland University of Technology, 2021. https://eprints.qut.edu.au/226864/1/Raziya%20Sultana_Chowdhury_Thesis.pdf.
Testo completoAbstract (sommario):
The study investigated the viability of employing a receptor modelling technique to characterize the sources of atmospheric aerosols from different air quality datasets. Chemical speciated datasets from two Brisbane sites; particle size distribution and organic mass spectral data from Garden Island, Western Australia have been analysed. The investigation produced quantitative information about the nature of the dominant primary and secondary emission sources of atmospheric aerosols at the study sites. Such information can aid air quality management.
27
Vivaldo-Lima, Eduardo. "Development of an effective model for particle size distribution in suspension copolymerization of styrene/divinylbenzene". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0005/NQ42885.pdf.
Testo completo
28
Wangsa-Wirawan, Norbertus Djajasantosa. "Physicochemical properties of protein inclusion bodies". Title page, contents and introduction only, 1999. http://web4.library.adelaide.edu.au/theses/09PH/09phw2465.pdf.
Testo completoAbstract (sommario):
Bibliography: leaves 182-198. Improvements in the current production system of inclusion bodies and the downstream processing sequence are essential to maintain a competitive advantage in the market place. Optimisation of fermentation is considered to improve production yield; then flotation as a possible inclusion body recovery method.
29
Renzi, Danielle. "Effects of Solids Loadings and Particle Size Distribution on Siphon Ceramic Candle Filters". Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/3307.
Testo completoAbstract (sommario):
In the rural areas of Madagascar only 29% of the population has access to clean water and 10% has access to improved sanitation. It has been estimated that environmental risk factors, such as inadequate access to clean drinking water and proper sanitation, are responsible for 94% of the diarrheal disease burden. This study was focused on testing a point-of-use technology called the Tulip filter, which is a siphon ceramic candle filter impregnated with silver. The purpose is to assess its feasibility for implementation in rural regions of Madagascar through a laboratory study performed at the University of South Florida.
The study tested the Tulip filters for turbidity, total coliform, and E. coli removal for various types of water. Each filter processed synthetic water classified as control (tap water, <1 >NTU), low turbidity (5-7 NTU), medium turbidity (25-35 NTU), or high turbidity (60-80 NTU). Approximately once every 100 L the filters processed pond water to test coliform removal. Furthermore, the pthesis size distribution was measured to analyze the effectiveness of filter to remove various pthesis sizes. Two of the seven Tulip filters tested had some quality control issues with the glue connecting the ceramic candle to the plastic cap and failed at 350 L.
Of the functioning filters, the turbidity removal ranged from 93% to 98% with none of the 779 samples taken from 4 filters above the WHO recommended 5 NTU for drinking water. The log removal of total coliforms was about 3.90 to 4.16 and achieved an average of 1 CFU/100mL of E. coli in the filtered water. WHO guidelines consider water with 1-10 CFU/100 mL a "low risk" and all but one of the working filters had E. coli and total coliform concentrations within, or below, this range for all samples (n=20 for each filter). The filters also showed an average of 96% removal of pthesiss of all size ranging from 0.5 to 10 µm.
This study finds that the Tulip filter is an appropriate of point-of-use technology that enables rural areas access to "low risk" water, at a low cost and with minimal maintenance. This study also reinforces the importance of adding silver or another biocide to ceramic filters because pthesiss of sizes up to 10 µm are able to pass through the filter. This is particularly a problem because pathogens can range from 0.01 µm to 100 µm.
30
Wanogho, S. O. "The forensic analysis of soils with particular reference to particle size distribution analysis". Thesis, University of Strathclyde, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381113.
Testo completo
31
Ngeacharernkul, Pratak. "Particle size distribution (PSD) equivalency using novel statistical comparators and PBPK input models". Diss., University of Iowa, 2017. https://ir.uiowa.edu/etd/5973.
Testo completoAbstract (sommario):
For disperse system drug formulations, meaningful particle size distribution (PSD) comparators are essential in determining pharmaceutical equivalency and predicting biopharmaceutical equivalence in terms of the effect of particle size on the rate and extent of drug input. In formulation development and licensure, particle size characterization has been applied to establish relationships for bioequivalence of generic pharmaceutical drug products. The current approaches recommended by the US-FDA using median and span are not adequate to predict drug product performances or account for multi-modal PSD performance properties. The use of PSD similarity metric and the development and incorporation of drug release predictions based on PSD properties into PBPK models for various drug administration routes may provide a holistic approach for evaluating the effect of PSD differences on in vitro release of disperse systems and the resulting pharmacokinetic impact on drug product performance. The objectives of this study are to provide a rational approach for PSD comparisons by 1) developing similarity computations for PSD comparisons and 2) using PBPK-models to specifically account for PSD effects on drug input rates via a subcutaneous (SQ) administration route.
Two techniques for measuring PSDs of reference (reference-listed drug product) and test (generic) drug products were investigated: OVL and PROB, as well as the current standard measurements of median and span. In addition, release rate profiles of each product pair simulated from modified Bikhazi and Higuchi’s model were used to compute release rate comparators such as similarity factor (f2) and fractional time ratios. A subcutaneous input PBPK model was developed and used to simulate blood concentration-time profiles of reference and test drug products. Pharmacokinetic responses such as AUC, Cmax, and Tmax were compared using standard bioequivalence criteria. PSD comparators, release rate comparators, and bioequivalence metrics were related to determine their relationships and identify the appropriate approach for bioequivalence waiver.
OVL showed better predictions for bioequivalence compared to PROB, median, and span. For release profile comparisons, the f2 method was the best for bioequivalence prediction. The use of both release rate (e.g., f2) and PSD (e.g., OVL) comparison metrics significantly improved bioequivalence prediction to about 90%.
32
Marquet, Richard. "Low-rate trickling filter effluent : characterisation and crossflow filtration". Thesis, Loughborough University, 1999. https://dspace.lboro.ac.uk/2134/27897.
Testo completoAbstract (sommario):
The low-rate trickling filter is the most common biological treatment process used in small and medium sized sewage works in the UK. It produces an inconsistent effluent quality, which has traditionally been related to seasonal changes in solids accumulation, grazing activity and sloughing of microbial film. The final effluent solids and, organic matter content is then too high for discharge or reuse. Given the increasingly stringent effluent standards, both in terms of quality and consistency, tertiary treatment is often required. This study was designed to investigate the key parameters affecting the performance of low-rate trickling filters and the characteristics of their effluents in terms of contaminant size, which might influence the efficiency of crossflow filtration as a tertiary treatment for the trickling filter.
33
Bäckebo, Markus. "The influence of particle size distribution on bio-coal gasification rate as related to packed beds of particles". Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-79084.
Testo completoAbstract (sommario):
This thesis is a part of a collaboration between Höganäs AB and Luleå University of Technology, aiming at replacing fossil process coal with bio-coal in their sponge iron process. The difference in gasification reactivity, i.e. reaction rate, between fossil coals and bio-coals is the major challenge in the endeavor to decrease the climate impact of the existing process. The goal of this thesis is to develop a model of reaction rate for bio-coals in relation to particle size distribution. Different particle size distributions were combined and tested to see how that affects the effective reaction rate. Within the scope of this work, gasification reactivities of different materials, including coal, cokes, and bio-coals, were determined. Three bio-coals were selected to study the effect of particle size distribution on reactivity. Kinetic parameters were determined by using thermogravimetric analysis in the temperature range of 770-850 °C while varying CO2 partial pressure between 0.1-0.4 atm. The effect of particle size on the reaction rate was investigated by using particles with diameter between 0.18 and 6.3 mm. The effect of particle size distribution on the reactivity of bio-coal in a packed bed was carried out in a macro thermogravimetric reactor with a constant bed volume of 6.5 cm3 at 980 °C and 40% (vol.) of CO2. The experimental investigation in three different rate-limiting steps was done for one bio-coal sample, i.e. Cortus Bark bio-coal. The activation energy of the bio-coal was 187 kJ mol-1, and the reaction order was 0.365. For the internal diffusion control regime, an increase in particle size resulted in low reaction rate. The effective diffusivity calculated from the Thiele modulus model was 1.41*10-5 m2 s-1. For the external diffusion control regime, an increase in particle size increased the reaction rate up to a certain point where it plateaued at >1 mm. By choosing two discrete particle size distributions, where a smaller average distribution can fit into a larger average distribution the reaction rate was lowered by 30% compared to only using a single narrow particle size distribution. This solution decreased the difference of apparent reaction rate in a packed bed between the bio-coal and anthracite from 6.5 times to 4.5 times. At the moment the model is not generalized for all bio-coals. However, the developed methodology can be routinely applied to assess the different bio-coal samples. One possible error can be that pyrolysis influences the gasification rate for bio-coal that is pyrolyzed below the temperature of the gasification test. There is a clear correlation between particle size distributions, bulk density, and apparent reactivity. By mixing two distributions the reaction rate of Cortus Bark was reduced from 6.5 times the reaction rate of anthracite to 4.5.
34
Wright, Matthew Darren. "Submicron particle size distribution and charge state in urban areas using mobility particle sizers : measurements and instrumentation considerations". Thesis, University of Bristol, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.544324.
Testo completo
35
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.
Testo completoAbstract (sommario):
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
36
Davis, P. Garland. "The effect of particle size distribution on the rheology of ultrafine coal-water slurries". Thesis, Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/104316.
Testo completo
37
Williams, Diane Keith. "Particle Size Dependence on the Luminescence Spectra of Eu3+:Y2O3 and Eu3+:CaO". Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/29719.
Testo completoAbstract (sommario):
Since the Eu3+ ion can occupy different cation sites in a host material, it can serve as a useful probe of nanocrystalline structures to gain more insight into the structural changes that can occur when the particle size is reduced from the bulk to nanometer regime. The use of laser spectroscopy to probe two nanocrystalline structures, Eu3+:Y2O3 and Eu3+:CaO, was investigated. The nanocrystalline structures were prepared by the laser-vaporization-gas-phase condensation of the bulk oxides. The particle size distribution and dominant particle diameters of the nanocrystals were determined by transmission electron microscopy.
The particle size dependency results of Eu3+:Y2O3 revealed three distinct phases: (1) the sharp lines of the monoclinic Y2O3 were dominant in the larger particles; (2) the C2 site of the cubic phase, which appears in the smaller particles; and (3) the amorphous phase that increases in intensity as the particle size decreases. The observation of distinct spectral lines from the monoclinic phase confirms the presence of a crystalline phase for all of particle sizes studied.
The site-selective results of various concentrations of 13-nm Eu3+:CaO showed that the laser-vaporization-gas-phase condensation method of preparation produced two europium-containing phases at most concentrations: cubic CaO and monoclinic Eu2O3. Results showed that the monoclinic Eu2O3 phase could be reduced by 95% by annealing at 800 0C for 30 minutes without particle growth.
Since the Eu3+ ion and the Y3+ ion are isovalent, the substitution of a Eu3+ ion into Y2O3 is considered a trivial case of extrinsic disorder since the impurity is neutral relative to a perfect crystal1. As a result, it is not necessary to have any other defects present in the crystals to maintain charge neutrality. With Eu3+:CaO, the dopant and host cation charges are different and therefore the dopant distribution can be investigated by site-selective spectroscopy.
Since the experimental dopant distribution results for nanocrystalline Eu3+:CaO were inconclusive, a model to predict the theoretical change in the dopant distribution in Eu3+:CaO as a function of particle size was developed. The model predicts that the defect chemistry is affected when the particle size is approximately 50 nm and smaller.Ph. D.
38
Dalecky, Amanda Lee. "Particle Size Distribution Analysis of a Mining-Impacted Gravel-Bed Stream in Ohio Using a Hybrid Sediment Sampling Technique". Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/35721.
Testo completoAbstract (sommario):
As part of a risk assessment study of the Leading Creek Watershed in Ohio, a prior Virginia Tech researcher collected pavement and subpavement sediment samples at 17 sites using the hybrid areal sampling technique with a clay adhesive. The watershed, which is heavily impacted by mining and agricultural activities, suffers from low pH, high concentrations of metals and sediment in the water column, and excessively silted streambeds. The current work presents the results of the particle size analyses performed on the hybrid samples in the context of evaluating the effectiveness of the technique itself and as a tool in future watershed/ecological studies, as well as examining possible relationships between siltation and indicators of ecological health in Leading Creek. By combining clay grid and adhesive sampling methods, the hybrid technique consistently achieved an effective particle size sampling range of 0.05 mm (1.97 x 10-3 in) to over 300 mm (11.8 in), thereby reducing the common problem of trunction. However, the overlap of the clay adhesive and natural sediment distributions and atypical sediment loading from surrounding abandoned and reclaimed mine lands obscured expected trends such as downstream fining and hindered the analysis of materials finer than 0.125 mm (4.93 x 10-3 in). Volumetric conversion of areal samples using the Modified Cube Model with a traditional exponent of -1 for clay was complicated by the large amount of fines in the Leading Creek samples. Further investigation into a more appropriate conversion technique for the evaluation of fine sediment samples is warranted.Master of Science
39
Bekiswa, Sisanda Ongeziwe. "Characterising South Africa’s major dust sources". Master's thesis, Faculty of Science, 2019. http://hdl.handle.net/11427/31241.
Testo completoAbstract (sommario):
The study investigates the surface controls of major dust emissions and determines the patial distribution of major dust source in South Africa. This study follows a multi-disciplinary approach where primary and secondary data were used. The main objective of the study is to determine the spatial distribution of South Africa's Major Dust Sources. Meteosat Second Generation (MSG) satellite imagery, land use and land cover maps were used to achieve the first and the second objectives of the study. Primary data involved sampling 30 soil samples in the field in order to achieve the third objective of the study. The crust, soil moisture, soil texture and grain size are all controls of dust emission. This investigation is however focused predominantly on grain size characteristics. GIS methods were also used to determine soil type from the African soil map. Soil samples in both provinces were then collected to assess the Particle Size Distribution (PSD) of the soils. The particle size was determined based on a sieve analysis for grain sizes that were greater than 2mm and laser diffractometry, MasterSizer (Malvern) was used to achieve this. The results from the Malvern were later put to R Statistics where they were clustered into eight clusters to determine similarities and difference of the grain size. Because there is no uniqueness in the soil types found in the study area, there were no solid conclusions made based in them. The results show that the soil types are found across South Africa but not the same amount of dust activity was detected in the other parts of the country. Previous studies show that global significant dust sources are natural sources such as lakes, pans and depressions. However, results demonstrate that South African dust sources are anthropogenic sources resulting from commercial agriculture in semi-arid regions. This study has demonstrated that surface sediments suitable for dust production are a mixture of fine material, silt (50µm) and coarse material, sand (2000µm) and it appears that all clusters in this study all contained both mixtures and all have potential to emit dust.
40
Elzey, Sherrie Renee. "Applications and physicochemical characterization of nanomaterials in environmental, health, and safety studies". Diss., University of Iowa, 2010. https://ir.uiowa.edu/etd/494.
Testo completoAbstract (sommario):
As commercially manufactured nanomaterials become more commonplace, they have the potential to enter ecological and biological environments sometime during their lifecycle of production, distribution, use or disposal. Despite rapid advances in the production and application of nanomaterials, little is known about how nanomaterials may interact with the environment or affect human health. This research investigates an environmental application of nanomaterials and characterizes the physicochemical properties of commonly manufactured nanomaterials in environmental health and safety studies.
Characterization of nanomaterials for applications and environmental health and safety studies is essential in order to understand how physicochemical properties correlate with chemical, ecological, or biological response or lack of response. Full characterization includes determining the bulk and surface properties of nanomaterials. Bulk characterization methods examine the shape, size, phase, electronic structure and crystallinity, and surface characterization methods include surface area, arrangement of surface atoms, surface electronic structure, surface composition and functionality.
This work investigates the selective catalytic reduction (SCR) of NO2 to N2 and O2 with ammonia on nanocrystalline NaY, Aldrich NaY and nanocrystalline CuY using in situ Fourier transform infrared (FTIR) spectroscopy. It was determined that the kinetics of SCR were 30% faster on nanocrystalline NaY compared to commercial NaY due to an increase in external surface area and external surface reactivity. Copper-cation exchanged nanocrystalline Y resulted in an additional increase in the rate of SCR as well as distinct NO2 and NH3 adsorption sites associated with the copper cation. These superior materials for reducing NOx could contribute to a cleaner environment.
This work consists of characterization of commonly manufactured or synthesized nanomaterials and studies of nanomaterials in specific environmental conditions. Bulk and surface characterization techniques were used to examine carbon nanotubes, titanium dioxide nanoparticles, bare silver nanoparticles and polymer-coated silver nanoparticles, and copper nanoparticles. Lithium titanate nanomaterial was collected from a manufacturing facility was also characterized to identify occupational health risks. Particle size distribution measurements and chemical composition data showed the lithium titanate nanomaterial forms larger micrometer agglomerates, while the nanoparticles present were due to incidental processes.
A unique approach was applied to study particle size during dissolution of nanoparticles in aqueous and acidic conditions. An electrospray coupled to a scanning mobility particle sizer (ES-SMPS) was used to determine the particle size distribution (PSD) of bare silver nanoparticles in nitric acid and copper nanoparticles in hydrochloric acid. The results show unique, size-dependent dissolution behavior for the nanoparticles relative to their micrometer sized counterparts.
This research shows size-dependent properties of nanomaterials can influence how they will be transported and transformed in specific environments, and the behavior of larger sized materials cannot be used to predict nanomaterial behavior. The type of nanomaterial and the media it enters are important factors for determining the fate of the nanomaterial. These studies will be important when considering measures for exposure control and environmental remediation of nanomaterials.
41
Kornilin, Dmitriy V. "Investigation of size, concentration and particle shapes in hydraulic systems using an in-line CMOS image matrix sensor". Thesis, University of Chester, 2018. http://hdl.handle.net/10034/621947.
Testo completoAbstract (sommario):
The theoretical and experimental investigation of the novel in-line CMOS image sensor was performed. This sensor is aimed to investigate particle size distribution, particle concentration and shape in hydraulic liquid in order to implement the proactive maintenance of hydraulic equipment. The existing instruments such as automatic particle counters and techniques are not sufficiently enough to address this task because of their restricted sensitivity, limit of concentration to be measured and they cannot determine particle shape. Other instruments cannot be used as inline sensors because they are not resistant to the arduous conditions such as high pressure and vibration. The novel mathematical model was proposed as it is not possible to use previously developed techniques based on using optical system and complicated algorithms. This model gives the output signal of the image sensor depending on the particle size, its distance from the light source (LED) and image sensor. Additionally, the model takes into account the limited exposure time and particle track simulation. The results of simulation based on the model are also performed in thesis. On the basis of the mathematical model the image processing algorithms were suggested in order to determine particle size even when this size is lower than pixel size. There are different approaches depending on the relation between the size of the particle and the pixel size. The approach to the volume of liquid sample estimation was suggested in order to address the problem of low accuracy of concentration measurement by the conventional automatic particle counters based on the single photodiode. Proposed technique makes corrections on the basis of particle velocity estimation. Approach to the accuracy estimation of the sensor was proposed and simulation results are shown. Generally, the accuracy of particle size and concentration measurement was considered. Ultimately, the experimental setup was used in order to test suggested techniques. The mathematical model was tested and the results showed sufficient correlation with the experiment. The zinc dust was used as a reference object as there are the particles within the range from 1 to 25 microns which is appropriate to check the sensitivity. The results of experiments using reference instrument showed the improved sensitivity and accuracy of volume measured compared to the reference one.
42
Thorvaldsen, Gary Sven. "The effect of the particle size distribution on non-Newtonian turbulent slurry flow in pipes". Thesis, Cape Technikon, 1996. http://hdl.handle.net/20.500.11838/896.
Testo completoAbstract (sommario):
Thesis (MTech (Chemical Engineering))--Cape Technikon, Cape Town,1996The handling of solid-liquid suspensions is an important concern within the chemical and processing industries and many theoretical models have been proposed to try and explain and predict turbulent flow behaviour. However, the prediction of turbulent flow from only the viscous properties of non-Newtonian suspensions has over the years been questioned by researchers. This thesis considers theoretical models well established in the literature and the Slatter model, which uses both the rheology of the suspension and the particle size distribution of the solids. These models are used to analyze the experimental data and the effect that particle size and the particle size distribution has on turbulent flow behaviour. The literature concerning the rheological fundamentals relevant to fluid flow in pipes has been examined. The Newtonian turbulent flow model as well as the non-Newtonian models of Dodge & Metzner, Torrance, Kemblowski & Kolodziejski, Wilson & Thomas and Slatter have been reviewed. Test work was conducted at the University of Cape Town's Hydrotransport Research Laboratory using a pumped recirculating pipe test rig. The test apparatus has been fully described and calibration and test procedures to enable collecting of accurate pipeline data have been presented. Three slurries were used in test work namely kaolin clay, mixture I (kaolin clay and rock flour) and mixture 2 (kaolin clay, rock flour and sand) with ad,s particle size ranging from 24/Lm to 170/Lm. The yield pseudoplastic model has been used to model and predict the laminar flow of the suspensions that were tested and the meth9J adopted by Neill (1988) has been used to determine the rheological constants. The pipeline test results have been presented as pseudoshear diagrams together with the theoretical model lines providing a visual appraisal of the performance of each model. The Slatter model predicts the test data best with the other theoretical models that were considered tending to under predict the head loss. The reason the Slatter model performs better than the other theoretical models is because this model can account for the wall roughness and particle roughness effect. Evidence to support this statement has been presented. This thesis highlights the fact that the particle size distribution is a vitally important property of the suspension and that it does influence turbulent flow behaviour. It shows that turbulence modelling using the particle roughness effect (eg Slatter, 1994) is valid and can be adopted for non-Newtonian slurries. It is concluded that the particle size distribution must be used to determine the particle roughness effect and this effect must be incorporated in the turbulent flow analysis of non-Newtonian slurries.
43
Praechter, Todd A. "Affect of Emission Controls on the Elemental Concentration and Particle Size of Coal Ash". University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1378196568.
Testo completo
44
Cao, Zihan. "Determination of Particle Size Distribution of Particulate Matter Emitted from a Layer Operation in Southeast U.S". NCSU, 2009. http://www.lib.ncsu.edu/theses/available/etd-07302009-201630/.
Testo completoAbstract (sommario):
This thesis reports a field study on characterizing particle size distribution (PSD) of particulate matter (PM) emitted from a commercial layer operation in the Southeastern U.S. across three seasons from October of 2008 to April of 2009. Six low-volume (1m3/h) total suspended particulate (TSP) samplers were used to collect PM samples in two high-rise layer houses. A laser diffraction particle size analyzer (LS13 320) at North Carolina State University (NCSU), a laser scattering particle size analyzer (LA-300) at University of Illinois at Urbana-Champaign (UIUC) and a Coulter Counter Multisizer 3 (CCM 3) at Texas A&M University (TAMU) or USDA-ARS cotton production & processing unit in Lubbock, TX were used to measure PSD of PM samples collected by the TSP samplers. Particle size distributions measured by these three instruments were compared. Results of the study indicate that TSP concentrations across the three seasons ranged from 888 to 5333 µg/m3. Total suspended particulate concentration was affected by season, animal activity, floor, and equivalent air flow rate factor. It was observed that TSP concentration in winter was higher than in spring; concentration on the second floor was higher than that on the first floor; the more active the animals were, the higher the TSP concentration; and the more the fans were on, the lower the concentration. Compared with PM concentration, PSD (characterized by the mass medium diameter, MMD, and geometric standard deviation, GSD) was affected by season, animal activity, floor and equivalent flow rate factor to a lesser extent. Overall MMDs of PM samples collected in fall, winter and spring, measured by the laser diffraction particle size analyzer were 19.21±1.27 µm, 17.13±0.81µm and 18.44±1.44µm, respectively. Geometric standard deviation (GSD) was relatively constant and not affected by those factors (season, animal activity, floor, and equivalent air flow rate factor). The overall GSD was 2.65±0.08. Significant but constant differences in MMDs and GSDs were detected when comparing PSDs measured by the different instruments. In general, the LA-300 provided the largest MMDs, whereas the CCM 3 gave the smallest MMDs. The LS13 320 provided the largest GSDs, whereas the CCM 3 gave the smallest.
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Brennan, William Dennis. "The effects of nozzle geometry on particle size distribution in a small two dimensional rocket motor". Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/25882.
Testo completo
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Rajabi-Hamane, Mehdi [Verfasser]. "Modeling, Validation and Time Optimal Control of Particle Size Distribution in Emulsion Polymerization / Mehdi Rajabi-Hamane". Aachen : Shaker, 2007. http://d-nb.info/1166511340/34.
Testo completo
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Afoakwa, Ohene Emmanuel. "Dark chocolate : effects of particle size distribution and composition on physical qualities and flavour volatiles release". Thesis, University of Strathclyde, 2008. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=24296.
Testo completoAbstract (sommario):
Rheological, texture and melting properties of dark chocolates were studied varying particle size distribution (PSD) [D₉₀ (90% finer than this size) of 18, 25, 35 and 50 µm], fat (25, 30 and 35%) and lecithin (0.3 and 0.5%) contents. Fat pre-crystallisation systems during tempering and fat bloom development were also investigated, and influences on product microstructure, texture, appearance (colour and gloss) and melting characteristics elucidated. Flavour volatile release from varying product matrices were characterised and quantified. Rheological, textural and melting properties were examined quantitatively using Haake rheometer, texture analyzer and differential scanning calorimetry respectively; surface colour and gloss with a HunterLab Colorimeter and Gloss meter respectively; microstructures by light, stereoscopic binocular and scanning electron microscopy; and flavour volatiles quantified by GC-MS and GC-Olfactometry. Multivariate regression, correlation and principal component analyses were employed to explore interrelationships among the rheological, textural and melting characteristics. The PSD, fat and lecithin contents significantly affected all rheological and textural parameters, with significant interactions among factors. Increasing particle size reduced all rheological and textural parameters with greatest effects noted with 25% fat and 0.3% lecithin, which reduced with increasing fat and lecithin contents. Statistical analyses revealed that fat exerted the greatest effect on variability in rheological, textural, melting properties and appearance followed by PSD and lecithin. Microstructures revealed wide variations in crystalline network structure and inter-particle interaction strengths related to PSD, fat content and temper regimes. Correlation (r = 0.78-0.99) and regression coefficients (R² = 0.59-0.99) suggested rheological, textural and melting index parameters had inter-relationships predictive of character. Effects of temper regime were noted with varied influences on product character, and hypotheses proposed for mechanisms of bloom development in under-tempered products. Finally, flavour-active volatiles were characterised and their release quantified with data suggesting potential effects of matrix structure and lipophilic-flavour interactions.
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Dabak, Turgay. "Formulation of the particle size distribution effects on the rheology and hydraulics of highly-concentrated suspensions". Diss., Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/74729.
Testo completoAbstract (sommario):
A formulation was developed for the rheological characterization of highly concentrated suspensions, accounting for the physical effects of particle size distribution. A number of dimensionless parameters were developed signifying the physical characteristics of the solids and the vehicle fluid, and functionally related to the yield-stress and a flow parameter. Each of these expressions of the formulation contains an empirical dimensionless coefficient accounting for the interparticle and fluid/solid interactions that are not explained by the physical parameters involved. A formulation and a methodology were also developed for predicting the shear viscosity behavior of highly concentrated suspensions at low and high shear-rates through the use of three parameters signifying effects of particle size distribution. A number of applications were made using various non-coal and limited coal-liquid mixture data reported in the literature to demonstrate the general validity of the formulations.
A methodology was proposed for the analysis of the particle size distribution effects on the overall optimum energy efficiency during hydraulic transportation and particle size reduction. The computer model developed for this purpose was employed to evaluate the transportation energy consumption and the energy consumed in the grinding process to prepare the slurry, in pipes of various sizes and lengths for a coal slurry of various specified particle size distributions and concentrations. Correlations obtained indicated the sensitivity of transportation energy efficiency to various parameters including the maximum packing concentration, relative concentration, specific surface area of particles, surface area mean size, pipe size and length, and annual mixture throughput. The results of combined energy calculations have shown that the particle size distribution and related physical parameters can significantly affect the energy efficiency due to both grinding and transportation, and the delivered cost of slurry fuels.Ph. D.
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Kuo, Ching-Jey. "FACTORS AFFECTING PARTICLE GROWTH AND RELATED ORGANIC MATTER REMOVAL DURING ALUM COAGULATION (SIZE DISTRIBUTION, TRIHALOMETHANES, HUMIC)". Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/183866.
Testo completoAbstract (sommario):
Effects of several important source-related and operation-related factors on particle formation and growth as well as potential particle and dissolved organic matter removal by alum coagulation are described. Two representative natural water sources, with low turbidities and high concentrations of dissolved organic matter, and one commercially available crystalline silica, with defined characteristics, were employed to establish initial aquatic particle and dissolved organic matter conditions. Six experimental variables utilized for evaluation include initial pH, initial turbidity, applied pre-ozonation dose, alum dose, flocculation time and sedimentation time. A bench-scale experimental apparatus with capabilities of ozonation, coagulation, sedimentation and membrane filtration was employed to conduct a series of selected experiments. Each factor investigated in this research proves to be able to inpart, individually or collectively, statistically significant effects on particle formation and growth during alum coagulation. While the addition of model particles shows significant enhancement in particle growth, it fails to demonstrate significant improvement in the removal of dissolved organic matter. On the contrary, effects of pH and alum dose on particle formation and growth are accompanied by corresponding effects on the removal of dissolved organic matter. Pre-ozonation of dissolved organic matter renders the dissolved organic matter more hydrophilic by increasing the number of carboxylic acid functional groups. This phenomenon can significantly improve or impede particle growth as well as dissolved organic matter removal during alum coagulation, depending on raw water chemistry and other operational factors. Alum coagulation under all of the conditions investigated in this research is demonstrably more effective in removing aquatic humic susbtances with higher apparent molecular weights and fewer carboxylic acid functional groups, as opposed to those with lower apparent molecular weight and more carboxylic acid functional groups. The predominant removal mechanisms were found to occur at the beginning stage of the coagulation process; that is, the rapid mixing period. The remaining dissolved organic matter and humic substances can form significant amounts of trihalomethanes upon reaction with chlorine.
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Arabgol, Raheleh. "MBBR Produced Solids: Particle Characteristics, Settling Behaviour and Investigation of Influencing Factors". Thesis, Université d'Ottawa / University of Ottawa, 2021. http://hdl.handle.net/10393/41919.
Testo completoAbstract (sommario):
The separation of solids from biological wastewater treatment is an important step in the treatment process, as it has a significant impact on effluent water quality. The moving bed biofilm reactor (MBBR) technology is a proven upgrade or replacement wastewater treatment system for carbon and nitrogen removal. However, a challenge of this technology is the characteristics of the effluent solids that results in their poor settlement; with settling being the common method of solids removal. The main objective of this research is to understand and expand the current knowledge on the settling characteristics of MBBR produced solids and the parameters that influence them. In particular, in this dissertation, the impacts are studied of carrier types, biofilm thickness restraint design of carriers, and varying carbonaceous loading rates on MBBR performance, biofilm morphology, biofilm thickness, biofilm mass, biofilm density, biofilm detachment rate, solids production, particle size distribution (PSD) and particle settling velocity distribution (PSVD).
With this aim, three MBBR reactors housing three different carrier types were operated with varying loading rates. In order to investigate the effect of carrier geometrical properties on the MBBR system, the conventional, cylindrically-shaped, flat AnoxK™ K5 carrier with protected voids was compared to two newly-designed, saddle-shaped Z-carriers with the fully exposed surface area. Moreover, the AnoxK™ Z-200 carrier was compared to the AnoxK™ Z-400 carrier to evaluate the biofilm thickness restraint design of these carriers, where the Z-200 carrier is designed for greater biofilm thickness-restraint. The Z-200 carrier is designed to limit the biofilm thickness to the level of 200 µm as opposed to 400 µm for the Z-400 carrier. Finally, to investigate the effects of varying carbonaceous loading rates on system removal performance, biofilm characteristics and solids characteristics, further analyses were performed at three different loading rates of 1.5 to 2.5 and 6.0 g-sBOD/m2·d in steady-state conditions. The PSD and the PSVD analyses were combined to relate these two properties. A settling velocity distribution analytical method, the ViCAs, was applied in combination with microscopy imaging and micro-flow imaging to investigate the relation of PSD and settling behaviour of MBBR produced particles.
The obtained results have indicated that the carrier type significantly impacted the MBBR performance, biofilm, and particle characteristics. As such, the K5 carrier MBBR system demonstrated a statistically significantly higher carbonaceous removal rate and efficiency (3.8 ± 0.3 g-sBOD/m2·d and 59.9 ± 3.0% sBOD removal), higher biofilm thickness (281.1 ± 8.7 μm), higher biofilm mass per carrier (43.9 ± 1.0 mg), lower biofilm density (65.0 ± 1.5 kg/m3), lower biofilm detachment rate (1.7 ± 0.7 g-TSS/ m2·d) and hence lower solids production (0.7 ± 0.3 g-TSS/d) compared to the two Z-carriers. The Z-carriers' different shape exposes the biofilm to additional shear stress, which could explain why the Z-carriers have thinner and denser biofilm, resulting in higher solids production and lower system performance in comparison with K5. Moreover, the carrier type was also observed to impact the particle characteristics significantly. PSD analysis demonstrated a higher percentage of small particles in the Z-carrier system effluent and hence a significantly lower solids settling efficiency. Therefore, the solids produced in the K5 reactor have shown enhanced settling behaviour, consisting of larger particles with faster settling velocities compared to Z-carriers.
This dissertation also investigated the effects of restraint biofilm thickness on MBBR performance by comparing the Z-200 biofilm thickness-restraint carrier to the Z-400 carrier. No significant difference was observed in removal efficiency, biofilm morphology, biofilm density, biofilm detachment rate, and solids production between the Z-200 to the Z-400 carriers. The PSD and the PSVD analyses did not illustrate any significant difference in the particles’ settling behaviour for these two biofilm thickness restraint carriers, indicating that the biofilm thickness-restraint carrier design was not a controlling factor in the settling potential of MBBR produced solids.
Finally, this research studied the effect of varying loading rates and demonstrated a positive, strong linear correlation between the measured sBOD loading rate and the removal rate, indicating first-order BOD removal kinetics. The biofilm thickness, biofilm density and biofilm mass decreased when the surface area loading rate (SALR) was increased from 2.5 to 6.0 g-sBOD/m2·d. The solids retention time (SRT) was also shown to decrease by increasing the SALR, where the lowest SRT (1.7 ± 0.1 days) was observed at the highest SALR, with the highest cell viability (81.8 ± 1.7%). Significantly higher biofilm detachment rate and yield were observed at SALR 2.5, with the thickest biofilm and a higher percentage of dead cells. Consequently, a higher fraction of larger and rapidly settling particles was observed at SALR of 2.5 g-sBOD/m2·d, which leads to a significantly better settling behaviour of the MBBR effluent solids.
This study expands the current knowledge of MBBR-produced particle characteristics and settling behaviour. A comprehensive understanding of the MBBR system performance and the potential influencing factors on the MBBR produced solids, particle characteristics, and their settleability will lead to optimized MBBR design for future pilot- and full-scale applications of the MBBR.