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

This licentiate thesis reports analytical results for the electrostatic response to a test charge moving through dusty plasma. Two particular cases for a slowly moving test charge, namely, grain size distribution and grain charging dynamics are considered. Analytical results for the delayed shielding of a test charge due to dynamical grain charging in dusty plasma are also reported. In the first case, a dusty plasma in thermal equilibrium and with a distribution of grain sizes is considered. A size distribution is assumed which decreases exponentially with the grain mass for large sizes and gives a simple smooth reduction for small sizes. The electrostatic response to a slowly moving test charge, using a second order approximation is found and the effects of collisions are also investigated. It turns out that for this particular size distribution, there is a remarkably simple result that the resulting effective distribution for the electrostatic response is a kappa (generalized Lorentzian) distribution. In the second case, we present an analytical model for the shielding of a slowly moving test charge in a dusty plasma with dynamical grain charging for cases both with and without the collision effects. The response potential is treated as a power series in test charge velocity. Analytical expressions for the response potential are found up to second order in test charge velocity. The first-order dynamical charging term is shown to be the consequence of the delay in the shielding due to the dynamics of the charging process. It is concluded that the dynamical charging of the grains in a dusty plasma enhances the shielding of a test charge. To clarify the physics, a separate study is made where the charging is approximated by using a time delay. The resulting potential shows the delayed shielding effect explicitly. The terms in the potential that depend on the charging dynamics involve a spatial shift given by the test charge velocity and the charging time. This kind of work has relevance both in space and astrophysical plasmas. / QC 20101220

The Sultanate of Oman is a rapidly modernizing country with a significant length of its coastline slated for development. Much of the coastline is still in its natural state and basic studies describing the sedimentary systems need to be conducted in order to plan effectively for their sustainable development and to monitor changes in them with time. For such purposes, sediment samples (surface and sub-surface), elevation data, and serial sediment cores were collected at Sur Lagoon during three field seasons. The research objectives, procedures, results, and analyses for Sur lagoon are presented in three chapters. The first chapter compares textural facies, identified on the basis of particle-size distribution (PSD) of surface sediments from Sur Lagoon and evaluated using multi-variate cluster analysis, for their value in recognizing modem sedimentary environments. Clustering the full PSD size spectrum (0.0375- 1888 μm) shows that facies identification is possible is closely tied to surface elevation, particle-size decreasing with increasing elevation above mean sea level. This analytical technique should be tested under different conditions to assess further its utility. The second chapter discusses the taphonomically distinct and laterally extensive (> 1 km2) bivalve shell bed deposited by a tsunami on November 28th, 1945. Taphonomic characteristics of this unit are compared to those of the shell-rich tsunamite from Caesarea, Israel, and resulted in the identification of three generic, tsunamigenic-specific traits in shell beds: 1) thickly bedded and laterally extensive shell deposit, 2) presence of allochthonous articulated bivalves not in life position, and 3) extensive angular fragmentation. When these three traits are found together, a tsunamigenic origin should be considered for the shell bed. The third chapter analyzes the PSD of the tsunamite in eight sediment cores for digested and undigested samples. Cluster analysis of the PSD extended the upper or lower tsunamite contacts in four cores, but in general, the tsunamite thickness is consistent with the previously identified shell beds (Chapter 3). The tsunamigenic processes that resulted in the deposition of the shell bed were complex, and deposition occurred during run-up, flooding, and backwash stages of the tsunami, incorporating marine, lagoonal, and terrestrial (wadi) sediment into the tsunamite. The results of this study provide baseline sedimentological data for an understudied region of the world. New applications of cluster analysis of PSD and taphonomic analysis have the potential to identify previously unknown tsunamites in the geological record, and lithological facies using textural analysis. / Thesis / Doctor of Philosophy (PhD)

<p> The separation of a mixture of carbon tetrachloride in water was studied in a 2 inch diameter glass hydrocyclone. First, the effect of a mixing valve and of oil/water ratio on the volume/surface diameter of the dispersion in the feed to the hydrocyclone was studied using a statistical experiment design. Secondly, the effect of feed drop size distribution, oil/water ratio, and overflow/underflow split on the separation in the hydrocyclone was determined, again using a statistical experiment design. In both designs, five levels of each variable were studied. Flow rate, design shape, and temperature were kept constant. The range of variables was: </p> <p> 1. Mixing Value Pressure Drop 17.95 to 88.25 mm. Hg </p> <p> 2. Oil/Water Ratio 0.132 to 0.211 </p> <p> 3. Overflow/Underflow Split 4/1 to 8/1 </p> <p> From the first part of the work it was found that oil/water ratio had no significant effect on the volume/surface diameter, and that there was a linear relationship between the volume/surface diameter and mixing valve pressure drop. </p> <p> From the second part of the work it was found that volume split had most significant effect on hydrocyclone separation for the range of variables studied. The oil/water ratio had the next most significant effect on separation, and finally, drop size distribution was also found to be significant, but was the least important of the three variables. The interactions of the variables were no significant. The hydrocyclone separation could be predicted. The prediction of the overflow drop-size distribution agreed very well with the distribution observed photographically. Both predictions required assumptions that short-circuit flow and drop-drop coalescence was negligible. </p> / Thesis / Master of Engineering (ME)

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Inkjet printing has generated considerable interest as a technique for the patterning of functional materials in the liquid phase onto a substrate. Despite its high promise, the phenomena associated with inkjet printing remain incompletely understood. This research project investigates inkjet printing of cellulose nanocrystals (CNCs) as a possible method for the fabrication of cellulose micropatterns. CNCs were prepared from wood pulp by H₂SO₄ hydrolysis and characterized in terms of length, width, and thickness distributions by atomic force microscopy (AFM) and dynamic light scattering. Aqueous CNC suspensions were characterized in terms of shear viscosity with a rheometer. Glass substrates were cleaned with a detergent solution, aqua regia, or a solvent mixture, and characterized in terms of surface chemical composition, surface free energy, polarity, roughness, ζ-potential, and surface charge distribution in air by X-ray photoelectron spectroscopy, contact angle measurements, AFM, streaming potential, and scanning Kelvin probe microscopy (SKPM). Additionally, poly(ethylene glycol)-grafted glass substrates were prepared and characterized in terms of surface free energy, polarity, and roughness. Aqueous CNC suspensions were printed in different patterns onto the different glass substrates with a commercial, piezoelectric drop-on-demand inkjet printer. Inkjet deposited droplet residues and micropatterns were analyzed by AFM, scanning electron microscopy, and polarized-light microscopy. At low CNC concentrations (0.05 wt %), inkjet-deposited droplets formed ring-like residues due to the "coffee drop effect". The "coffee drop effect" could be suppressed by the use of higher CNC concentrations. The resulting dot-like droplet residues exhibited Maltese cross interference patterns between crossed polarizers, indicating a radial orientation of the birefringent, elongated CNCs in these residues. The observed Maltese cross interference patterns represent unprecedented indirect evidence for a center-to-edge radial flow in drying droplets. The degree of definition of the micropatterns depended strongly on the surface properties of the glass substrates. Well-defined micropatterns were obtained on aqua regia-cleaned substrates. In addition to the surface free energy and polarity, other factors seemed to play a role in the formation of the inkjet-printed micropatterns. If these factors can be identified and controlled, inkjet deposition of CNCs could become an attractive method for the fabrication of cellulose micropatterns. / Ph. D.