Thesis (M.S. in Electrical Engineering) Naval Postgraduate School, June 1997. / Thesis advisor, Robert W. Ashton. "June 1997." Includes bibliographical references (p. 149). Also available online.

A control system is designed and validated for a 3-unit CubeSat science mission. Utilizing three magnetorquers and one reaction wheel the system achieves a 6 rotation per minute spin rate and orbit normal pointing vector of the long axis of a 3-unit CubeSat. The design is validated across an evolution of scenarios, from idealized to flight-like with expected bias and noise terms added in. Estimated mass imbalances and the limitations of the power system driving the magnetorquers force the final system design to use only magnetorquers. Considerations are also taken for the science instrument to limit the interference of magnetorquers. The overall satellite design and software implementation are also briefly discussed. / text

A control system is designed and validated for a 3-unit CubeSat science mission. Utilizing three magnetorquers and one reaction wheel the system achieves a 6 rotation per minute spin rate and orbit normal pointing vector of the long axis of a 3-unit CubeSat. The design is validated across an evolution of scenarios, from idealized to flight-like with expected bias and noise terms added in. Estimated mass imbalances and the limitations of the power system driving the magnetorquers force the final system design to use only magnetorquers. Considerations are also taken for the science instrument to limit the interference of magnetorquers. The overall satellite design and software implementation are also briefly discussed. / text

The ability of nanoparticles to stabilize oil/water emulsions provides many interesting opportunities for the petroleum industry. Emulsions can be used as a displacing fluid for enhanced oil recovery to improve sweep efficiencies. Emulsions can be used to improve conformance control by effectively blocking thief zones in reservoirs with a high degree of heterogeneity. As shown in this thesis emulsions can be used to deliver fluids that contact and mobilize residual oil. It is imperative to understand emulsion behavior in porous media for design purposes in enhanced or improved oil recovery processes involving emulsions. Nanoparticle-stabilized oil-in-water emulsions were continuously generated by co-injecting aqueous nanoparticle dispersion and oil through a beadpack. There exists a critical shear rate below which a stable emulsion will not be generated. The critical shear rate increased with decreasing bead size. Above the critical shear rate, the droplet size of the generated emulsion was a function of shear rate and decreased with increasing shear rate. The stable emulsions were characterized by their droplet size and rheology. The emulsion viscosity was highly dependent upon droplet size and not the bulk oil viscosity in the emulsion. The emulsions were highly shear thinning and emulsions with smaller droplets were more viscous than emulsions with larger droplets. Highly stable emulsions that were generated by co-injection were collected, separated from excess phase(s) and injected into beadpacks. In most experiments the injected emulsion coalesced into the bulk fluids. Whether the bulk fluids generated a new emulsion in the bead pack depended on the shear rate, bead size, and initial saturation of the beadpack. Different beadpack experiments showed the transition from one flow regime to a second flow regime as the slow movement of a coalescence/regeneration front propagated through the beadpack. Coreflood experiments confirmed the mechanisms hypothesized for the beadpack emulsion injection experiments. When a stable emulsion was injected the effluent emulsion rheology and droplet size were altered solely as a result of being forced through sandstone cores, not because of fluids contacted within the core. The shear rate controlled whether the emulsion coalesced and produced no effluent emulsion, regenerated into an emulsion with larger droplets, or regenerated into an emulsion with smaller droplets. Oil recovery experiments showed that nanoparticle-stabilized oil-in-water emulsion increased the recovery of oil compared to a waterflood for cores with immobile and mobile oil. The mechanism is the coalesced oil droplets form a flowing phase that is miscible with oil present in the core and thus achieves a much more efficient displacement. The possible continuous generation and coalescence of droplets may have increased the apparent viscosity, improving the sweep efficiency of the emulsion injection. A novel oil recovery mechanism was shown in imbibition experiments where nanoparticle dispersion was used to displace oil. Large shear rates coupled with the affinity for nanoparticles at the oil water interface enabled residual oil to be mobilized, or for residual oil blobs to spawn smaller droplets that are stabilized by the nanoparticles and thus can be transported with the dispersion through the core. / text

Made available in DSpace on 2014-06-11T19:24:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2004-07Bitstream added on 2014-06-13T18:51:55Z : No. of bitstreams: 1 assis_sc_me_guara.pdf: 1352384 bytes, checksum: 82532e5fd71ac4103ee475d8432b8f1f (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Universidade Estadual Paulista (UNESP) / Um abordagem analítica para a propagação de atitude de satélites estabilizados por rotação em órbita circular é apresentada, incluindo o torque magnético residual (torque devido ao momento magnético ao longo do eixo de rotação do satélite). O modelo de quadripolo é utilizado para descrever o campo geomagnético. O método da média é aplicado para determinar o torque ao longo de um período orbital. Observa-se que Torque Magnético Residual Médio não possui componente ao longo do eixo de rotação, de modo que não afeta o módulo da velocidade de rotação do satélite. Para um período orbital uma solução analítica é apresentada. Esta solução mostra que o torque residual contribui para a deriva e precessão do eixo de rotação. Simulações são realizadas com os dados dos Satélites de Coleta de Dados Brasileiros (SCD1 e SCD2). / An analytical approach for the attitude motion of spin stabilized artificial satellite in circular orbit is presented, including residual torque. The quadripolo model is used to described the geomagnetic field. The averaged residual torque is computed for one orbital period. It is observed that the residual magnetic torque does not have a component along the spin axis. The inclusion of this torque on the rotational motion differential equations of spin stabilized spacecraft's yields the conditions to derive an analytical solution. The solution shows that residual torque does not affect the spin velocity magnitude, contributing only for the precession and the drift of the spin axis of the spacecraft. Applications are shown for the spin stabilized Brazilian satellites SCD1 and SCD2.

<p> Nonaqueous poly(methyl methacrylate) latices were prepared by nonaqueous dispersion polymerization of poly(methyl methacrylate) in heptane in the presence of either trimethylsilyl terminated or vinyl terminated polydimethylsiloxane stabilizer. Poly(methyl methacrylate) particles stabilized by vinyl terminated polydimethylsiloxane showed smaller particle sizes than did those stabilized by trimethylsilyl terminated polydimethylsiloxane. Diameters of the various latex preparations ranged from 1.4 to 0.8 μm and silicone content was around 2 mole percent in each case. Differences between the two types of latex were explained in terms of the nucleation mechanism operating during the preparation of the latices and in terms of the type of attachment of the stabilizer chain to the poly(methyl methacrylate) core.</p> <p> The effect of the silicone concentration present during particle formation was investigated. Vinyl terminated polydimethylsiloxane stabilized latex gave better stabilized particles than did methyl terminated polydimethylsiloxane stabilized latex. The results of varying the concentration and type of initiator were consistent with the conclusions about differences in nucleation and grafting mechanisms.</p> <p> The stability of polydimethylsiloxane stabilized poly(methyl methacrylate) particles was investigated in n-heptane. Acidified montmorillonite clay was determined as the optimum catalyst for this latex system. Flocculation set in at 70% of the original silicone content when the siloxane on the particle surface was degraded with montmorillonite clay in a good solvent. Flocculation was irreversible and occurred abruptly. The point of flocculation was reproducible and the rate of flocculation was identical for two different types of silicone stabilized poly(methyl methacrylate) latex.</p> / Thesis / Master of Science (MSc)

Foamed asphalt stabilized material as a high quality granular base incorporating high percentages of fine fractionated reclaimed asphalt material is investigated. A foamed asphalt mix is designed using a fabricated asphalt foaming device. The final specimens are tested for indirect tensile strength, indirect tensile resilient modulus, triaxial resilient modulus, triaxial repeated load permanent deformation, and unconfined compression. Results are compared to those with the same aggregate blends without stabilization for triaxial resilient modulus and repeated load permanent deformation. Stabilized materials are tested in soaked and unsoaked states to establish moisture susceptibility. Foam stabilization is found to significantly improve triaxial resilient modulus in all materials as well as permanent deformation resistance in materials with high RAP content. Soaking only marginally reduces triaxial resilient modulus and the effects are lesser in materials incorporating high RAP content. / Thesis / Master of Applied Science (MASc)

<div>Fluid interfaces containing surface-active species (e.g., surfactants, polymers, and particles) have rheological properties that are vital to the kinetic stability of emulsions. Many practical applications of emulsions necessitate superb stability during storage, such as in emulsion-based therapeutic delivery systems. While in other cases, stabilized systems are entirely unwanted (e.g., separating oil and aqueous phases in enhanced oil recovery and bilge water applications).</div><div><br></div><div>Techniques for modulating emulsion stability are highly desired and are largely determined by the mechanics of the interfacially-trapped species. However, the utility of these techniques is often limited by difficulties in measuring and interpreting the rheological characteristics of complex fluid interfaces. Lack of control over interface formation during emulsification magnifies this problem, further obscuring relationships between interfacial rheology and bulk emulsion stability. Thus, the objectives of this research were to (1) elucidate these fundamental relationships through emulsion stability and interfacial rheological measurements, and (2) present innovative methodologies for modulating the kinetic stability of model oil-in-water emulsions using physical chemistry principles.</div><div><br></div><div>Objective 1 was addressed by studying correlations between the dilatational rheology of single- and multi-component oil-water interfaces and the susceptibility to coalescence of the bulk systems they comprised. Oscillating pendant drop tensiometry was used to probe interfacial viscoelastic behavior, while dynamic light scattering and optical microscopy were used to characterize coalescence susceptibility in bulk oil-in-water emulsions. The magnitude of the low-frequency dilatational elastic modulus was shown to positively correlate with oil droplet coalescence resistance over time. Objective 2 was addressed by analyzing how physical chemistry principles can be applied to control various emulsion droplet destabilization phenomena and produce desirable bulk behavior. To this aim, two emulsion destabilization studies were performed; one related to the nanoparticle-induced flocculation of oil droplets in a dilute, electrostatically-stabilized emulsion and one related to the convective flows generated by the asymmetric dilatational rheology of coalescing droplets. <br></div><div><br></div><div>The knowledge garnered from this body of work is highly relevant to academic and industrial emulsion formulators who seek inexpensive, yet robust methods for predicting, characterizing and tailoring the kinetic stability of oil-in-water emulsions.</div>

Polymer stabilized cholesteric liquid crystals (PSCLCs) provide many advantages over other electro-optical materials. The unique helical structure of the cholesteric liquid crystal (CLC) creates a natural gradient for light interacting across each CLC domain layer. Not only does the CLC helical structure greatly increase the bandwidth tuning and broadening range, it also allows CLCs to act as a polarizer, notch filter, reflector, and optical rotator all in one material. However, while many novel PSCLC materials have been created, little is understood about how complex initial system interactions affect final electro-optical (e-o) properties.1,2 In this work, the principal variables affecting PSCLC blue shift electro-optical behavior have been determined through structural analysis and measurement of electro-optical properties. Typical PSCLC materials must meet both formulation and photopolymerization processing requirements to display blue shift e-o properties. Threshold photoinitiator concentrations (0.5-1.5 wt%) and morpholine containing group concentrations (0.25-1.0 wt%) were both shown to be primary factors, along with sufficient UV exposure time (10-30 min) and light intensity (500 mW/cm2, 365 nm), for PSCLC blue shift bandwidth tuning/broadening to occur. Morpholine was initially identified as a component of photoinitators Irgacure 369 and 907 and was proven to increase PSCLC ion density altering LC-polymer network interactions with several proposed theories included later in this work. The use of an appropriate morpholine containing LC monomer to directly incorporate morpholine into the LC-polymer network was shown to greatly improve PSCLC sample stability. Through the results of this research we successfully induced blue shift e-o behavior in a previous red shift only PSCLC using only 30% of the UV exposure that a model PSCLC blue shift sample required while extending the blue shift broadening range over threefold (from 75 nm to 250 nm). The fundamental understanding and design of PSCLC systems described herein serves as a starting point for engineering PSCLC materials with specific and desirable electro-optical properties.

Mechanically Stabilize Earth (MSE) is a method in which soil tensile strength and shear resistance is increased by using reinforcement. The traditional forms of reinforcement include bars, galvanized strips, welded wire mats or steel grids, and geosynthetics.When steel is used as reinforcement in MSE walls, it gets corroded or decayed. Certain shapes of reinforcement will have less corrosion because less surface area is exposed. Pullout resistance is the ability to resist a tensile force. This can be affected by the design and shape of the steel. This study simulates different overburden depths or pressures for pullout resistance and evaluates standard corrosion rates.