Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 141-147). Also available on the World Wide Web.

Thesis (Ph. D.)--Ohio State University, 2005. / Title from first page of PDF file. Document formatted into pages; contains xxiii, 187 p.; also includes graphics Includes bibliographical references (p. 179-187). Available online via OhioLINK's ETD Center

Thesis--Massachusetts Institute of Technology. / Includes bibliographical references (p. 264-270).

Thesis--University of California, Berkeley, 1958. / "Chemistry-General" -t.p. Includes bibliographical references (p. 141-142).

Thesis (M.S.)--Brigham Young University. Dept. of Chemical Engineering, 2005. / Includes bibliographical references (p. 81-86).

The efficiency of flotation processes may be improved through an understanding of the flotation models. Two mathematical models, particle trajectory and mixing zone models, have been modified and used to describe flotation results obtained from a semi-continuous flotation rig. Two types of clay suspensions, kaolin and Wyoming bentonite, were used as representative raw materials treated with a cationic surfactant, hexadecyltrimethylammonium bromide (HT AB), and/or coagulants i.e. alum, ferric chloride and polyaluminium chloride (PAC). HT AB concentrations were varied in the range of I x 10-6 to 3 x 10-5 mol/L. Alum at a concentration of 40 mg/L, ferric chloride at 40 mg/L and PAC at 10 mg/L were the selected coagulant dosages to be used in flotation tests. For the clay-HT AB-coagulant system, a HT AB concentration of I x 10-s mol/L was used in the flotation tests. Suspension flow rate was chosen at 2 Llmin and recycle ratios were varied in the range of 6-40% at room temperature. Two categories, suspensions with and without flocs, have been considered. The trajectory model gave a good match even taking account of the decreases In flotation efficiency at high recycle ratios where flocs had been broken by shear gradients. This model included hydrodynamic and surface forces i.e. electrostatic, van der Waals and hydrophobic forces and was calculated by a Runge Kutta technique. The effect of the shear force on a size reduction was determined from particle size measurements (Lasentec apparatus) in a mixing tank and the results showed a decrease of floc sizes with increasing agitator speeds. Bubble zeta potentials obtained using a modified rectangular cell in a Rank Brothers' apparatus gave points of zero charge at concentrations of 1.61 x 10-9 mollL for HTAB, 1.69 x 10-8 mol/L for tetradecyltrimethylammonium (TTAB) and 2.37 x 10-7 mol/L for dodecyltrimethylammonium bromide (DTAB) at 2SoC respectively. Van der Waals and hydrophobic or hydration forces were obtained from contact angle measurements on solid surfaces. The hydrophobic forces were increased by increasing HT AB concentrations while the hydration effects occurred upon the addition of coagulants to the suspensions. A flocculation model using the extended-DLVO theory showed a good correlation when compared to experimental results. For the mixing zone model, an attachment efficiency for the aggregation of a particle and a bubble was proposed from a ratio between the energy barrier (E1) and the maximum free energy at equilibrium. When particle size is constant, the attachment efficiency values rise with increasing hydrophobic force levels. On the other hand, when floc sizes are increased, the attachment efficiencies are decreased due to the increase in the repulsive long range van der Waals force.

In underwater wireless optical communications (UWOC), the obstruction of light propagation by air bubbles is one of the main factors which causes light power to fluctuate at the receiver. In this thesis, we construct a statistical model for the received power in the presence of air bubbles. First, we postulate some random variables based on some real experiments, such as the size of a bubble, the generation of each bubble, and the horizontal and vertical movements of a bubble. Second, we mathematically express the amount of obstructed power which the shade of each bubble causes over the beam area and sum them all up to get the total obstructed power. In order to use the method of moments, we find the expectation, the second and/or the third moments of the total obstructed power. Lastly, we use these two or three moments of it to find suitable distributions that match the simulation data, which are the Weibull distribution and Generalized gamma distribution respectively. With these distributions, we construct the statistical model of the received power. Furthermore, we show that those distributions fit well to the simulation data.

京都大学 / 0048 / 新制・課程博士 / 博士(経済学) / 甲第22625号 / 経博第617号 / 新制||経||293(附属図書館) / 京都大学大学院経済学研究科経済学専攻 / (主査)教授 新後閑 禎, 教授 柴田 章久, 准教授 高橋 修平 / 学位規則第4条第1項該当 / Doctor of Economics / Kyoto University / DGAM

Bubbles are commonly found in the world around us, from industrial products to carbonated beverages. This thesis will discuss three processes involving of bubbles, from applications to fundamental phenomena. In the first portion of this thesis, I describe the use of bubbles to prevent the formation of marine biofilms and other colonizing organisms onto built structures, collectively referred to as biofouling. Biofouling detrimentally affects the structures upon which they grow, increasing drag and fuel consumption of moving vessels, reducing performance of acoustic sensors, and enhancing degradation of static structures. With recent international bans placed on common biocidal coatings, there is a demand for environmentally friendly antifouling technologies with strong performance. Bubbles rising along a submerged surface have been shown to inhibit biofouling growth, but little work has been done to determine the primary mechanisms responsible for their antifouling behavior. In this thesis I discuss a combination of field and laboratory experiments as well as a theoretical approach used to gain insight into the dominant mechanisms at play, thus laying a foundation for optimization of this antifouling technique. We find that biofouling is inhibited by shear stresses generated throughout the flow, and the degree of biofouling prevention relates to the distribution of bubbles which locally alters the shear stress. Inspired by the potential for direct interactions between bubbles and biofouling, the second topic of this thesis considers the process by which a bubble dewets, or "sticks to", a solid surface. As a bubble approaches a solid surface, the liquid between the gas and solid begins to drain until it resembles a thin film. Upon rupture of this thin film, the air dewets the surface as a contact line is formed and expands. Previous work regarding this contact line motion assumes viscous effects dominate the spreading dynamics while inertial effects are neglected. Studying the early-time dynamics of dewetting bubbles, we find viscosity to be negligible while inertia and capillarity govern the motion of a newly established contact line, suggesting early stages of dewetting are more rapid than anticipated. In the final portion of this thesis, I discuss the fundamental stability of bubbles in volatile liquids. When a bubble arrives at a free surface, we typically expect the film of the bubble cap to thin over some period of time until it ruptures. Traditionally, the drainage of this film has been considered inevitable with evaporation only hastening the film rupture. Here I show air bubbles at the free surface of liquids which appear to defy traditional drainage rules and can avoid rupture, persisting for hours until dissolution. Using pure, volatile liquids free of any surfactants, we highlight and model a thermocapillary phenomenon in which liquid surrounding the bubble is continuously drawn into the bubble cap, effectively overpowering the drainage effects. / 2020-09-28T00:00:00Z

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