No description available.

Emulsions constitute a wide range of natural as well as processed products. Pharmaceutical applications of emulsions include oral administration, parenteral delivery, ophthalmic medicine, topical and transdermal creams, and fluorocarbon-in-water emulsions for blood oxygenation. In the foods area many of the products like mayonnaise, margarine, ice-creams are emulsions by nature and some products can also be used for delivery of active ingredients (e.g. nutraceuticals) with potential health benefits. Emulsions are also encountered at many stages of petroleum recovery, transportation, and processing. Typically, emulsions are manufactured in a two-step process. First a coarse emulsion called a premix is made which is passed through a high-pressure homogenizer. Intense energy supplied in the high pressure homogenizer causes breakage of the coarse emulsion to a fine one with a tighter distribution. Population balance equation (PBE) models are useful for emulsions since they allow prediction of the evolution of the drop size distribution on specification of the two rate processes i.e., breakage of drops due to the flow field and coalescence of colliding drops. In our work, we developed a PBE model to describe emulsion breakage in a high pressure homogenizer. The focus of the work was breakage and conditions to keep coalescence to minimum were implemented. Two breakage rates representing two mechanisms i.e., turbulent inertial and turbulent viscous breakage were necessary for reproducing the bimodal nature of the distributions. We used mechanistic functions in the PBE model to develop a predictive model which could be extended to changes in formulation variables as well as process variables. Starting with the assumption of binary breakage, the model was refined to include multiple drop breakage. The developed model was found to be extensible to reasonable changes in oil concentration, surfactant concentration, continuous phase viscosity and constant ratio of oil to surfactant. Anomalies in pressure prediction encountered earlier were also corrected for by including some additional features like heating, maximum stable diameter, and number of daughter drops. A preliminary attempt was also made to use the developed model for designing experiments for making target emulsions with pre-specified properties.

<p> The advantages of Thin-Slab Cast Direct-Rolling (TSCDR) process include reduced capital, energy, labour and inventory costs, as well as the ability to roll thinner strip compared to the conventional process of thick slab casting, reheating and hot rolling. There is great interest in utilizing this technology to produce microalloyed steels which can meet American Petroleum Institute (API) standards. However, whereas the conventional approach can produce APIX80, APIXlOO, and even APIX120 steels; the TSCDR process can only produce APIX70 and APIX80. The main obstacles in the way of achieving high API grades are the non-uniform initial as-cast microstructure and the large grains that result from grain growth at high temperature. The production of APIX80 and higher grade steels can only be achieved through a comprehensive research initiative that combines careful control of solidification, homogenization, thermomechanical-processing, cooling and coiling. </p> <p> This contribution examines the solid state microstructure evolution of microalloyed steels under simulated TSCDR conditions. The grain growth kinetics in delta-ferrite and austenite were studied separately using two model alloys. At high temperatures and in the absence of precipitation, the growth kinetics in both delta-ferrite and austenite appeared to follow a simple parabolic growth law. The measured grain growth kinetics was then applied to the problem of grain-size control during the process of TSCDR. Several strategies of controlling and refining the grain size were examined. The kinetics of delta-ferrite to austenite phase transformation was investigated using a quenching dilatometer; the results showed that the austenite phase formed along the original delta grain boundaries, and that the precipitation of austenite at the delta-ferrite grain boundaries effectively pins delta grain growth. The kinetics of the phase transformation was modeled using a local equilibrium model that captures the partitioning of the substitutional elements during the transformation. </p> <p> A novel delta-ferrite/austenite duplex microstructure is proposed to achieve fine and uniform high-temperature microstructure. The grain growth of the matrix phase (delta-ferrite) is controlled by the coarsening mechanism of pinning phase (austenite). The effectiveness of this delta/austenite duplex microstructure was validated experimentally and analyzed in details using a physically-based model. </p> / Thesis / Doctor of Philosophy (PhD)

<p> Preliminary experiments indicated that lysosomes are present in rat liver and onion embryos. A differential centrifugation study was made of the intracellular distribution of acid phosphatase in pea embryo tissue in an attempt to show that this enzyme is enclosed by a membrane forming granules similar to the lysosomes of hepatic tissue. The results reveal that acid phosphatase is soluble under the conditions employed, but it is believed that this may well have resulted from excessive damage to the subcellular bodies during homogenization.</p> / Thesis / Master of Science (MSc)

No description available.

No description available.

In comparison to traditionally fabricated steels that can undergo extensive processing to produce a complex-shaped component, the powder metallurgy (PM) technique can provide a more efficient approach as it is capable of producing intricately-shaped components that require little to no additional processing and machining [1], [2]. A key factor in being able to do so pertains to quenching and utilizing an appropriate quenching agent that can provide dimensional stability to the part being quenched [3], [4]. To ensure that a PM component can perform equally well when being quenched by a quenchant of reduced cooling capability, the PM component should be if not more, then just as hardenable. Steel hardenability can inevitably be improved with the increase of overall alloying content [5], however, if overall alloying content is to be kept at a minimum, the concept of lean PM steel design is one worth investigating; where a lean steel entails that each and every alloying addition is utilized to its maximum potential. This study evaluates the homogenization behaviour of alloying elements in PM steels during sintering as well as the efficiency of wide-spread industrial practices involving the use of various master alloys and ferroalloys, and investigates the realm of liquid phase sintering to understand and optimize the homogenization behaviour of alloying elements and mechanical properties of PM steels. In the context of this work, multi-component master alloys contain at least three of non-ferrous metals as alloying elements and ferroalloys are master alloys containing iron in addition to typically a maximum of two other non-ferrous alloying additions. Part one of this study discusses a combination of thermodynamic software (DICTRA and Thermo-Calc), incremental sintering experiments and scanning electron microscopy (SEM) - wavelength dispersive spectroscopy (WDS) that were used in order to form a deeper understanding of the homogenization behaviour of alloying elements within PM steel during sintering. Electron microscopy analyses on partially and industrially sintered components provide elemental maps to track the evolution of alloying elements as they relax to homogeneity. Electron microscopy analyses for this portion of the study were conducted on an industryproduced automotive component that was sectioned and sintered industrially as well as experimentally at 1280°C for 30 minutes and 13.4 hours. DICTRA simulations carried out for this research provide a 1-D insight into the evolution of concentration profiles and phases throughout various sintering times for systems involving Cr, Mn, C and Fe. DICTRA simulation results of alloying sources were studied alongside alloying element profiles obtained by compiling point quantification from wavelength dispersive spectroscopy maps for the sintered automotive component. Computational results provided conservative, semi-quantitative recommendations on optimal alloy addition forms that lead to an improvement in homogenization. Part two of this study involves the approach of fabricating and testing multi-component master alloy additions. As these materials are widely employed in PM and are typically fabricated by solidification, their states are non-equilibrium and therefore have regions containing phases precipitating in the beginning of freezing which have higher melting temperatures than regions with phases forming later on. During heating, it is hypothesized that Scheil’s solidification path backtracks and as a result, a fraction of liquid in the ferroalloy can be estimated at sintering temperature. If the fraction is significant, the utilization of this ferroalloy implies liquid phase sintering. Through a combination of Thermo-Calc and Fortran softwares, multi-component ferroalloys with promising compositions were discovered in Fe-C-Cr-Mn, Fe-C-Cr-Mn-Ni, FeC-Mn-Mo, Fe-C-Mn-Mo-Ni and Fe-C-Cr-Mn-Mo-Ni systems for low temperature liquid phase sintering. Those of the Fe-C-Cr-Mn-Mo, Fe-C-Cr-Mn-Mo-Ni and Fe-Mn-Mo-Ni system were fabricated and tried in practice. Compositional maps and mechanical properties of PM steels made with variations of this specially tailored multi-component master alloys were compared with those for which traditional alloy additions were used. / Thesis / Master of Applied Science (MASc)

This study is devoted to the development of an integrated numerical modeling enabling one to investigate the static and the dynamic behaviors and failures of 2-D textile composite as well as 3-D orthogonal woven composite structures weakened by cracks and subjected to static-, impact- and ballistic-type loads. As more complicated modeling about textile composite structures is introduced, some of homogenization schemes, geometrical modeling and crack propagations become more difficult problems to solve. To overcome these problems, this study presents effective mesh-generation schemes, homogenization modeling based on a repeating unit cell and sinusoidal functions, and also a cohesive element to study micro-crack shapes. This proposed research has two: 1) studying behavior of textile composites under static loads, 2) studying dynamic responses of these textile composite structures subjected to the transient/ballistic loading. In the first part, efficient homogenization schemes are suggested to show the influence of textile architectures on mechanical characteristics considering the micro modeling of repeating unit cell. Furthermore, the structures of multi-layered or multi-phase composites combined with different laminar such as a sub-laminate, are considered to find the mechanical characteristics. A simple progressive failure mechanism for the textile composites is also presented. In the second part, this study focuses on three main phenomena to solve the dynamic problems: micro-crack shapes, textile architectures and textile effective moduli. To obtain a good solutions of the dynamic problems, this research attempts to use four approaches: I) determination of governing equations via a three-level hierarchy: micro-mechanical unit cell analysis, layer-wise analysis accounting for transverse strains and stresses, and structural analysis based on anisotropic plate layers, II) development of an efficient computational approach enabling one to perform transient response analyses of 2-D plain woven, 2-D braided and 3-D orthogonal woven composite structures featuring matrix cracking and exposed to time-dependent ballistic loads, III) determination of the structural characteristics of the textile-layered composites and their degraded features under smeared and discrete cracks, and assessment of the implications of stiffness degradation on dynamic response to impact loads, and finally, IV) the study of the micro-crack propagation in the textile/ceramic layered plates. A number of numerical models have been carried out to investigate the mechanical behavior of 2-D plain woven, 2-D braided and 3-D orthogonal woven textile composites with several geometrical representations, and also study the dynamic responses of multi-layered or textile layered composite structures subjected to ballistic impact penetrations with a developed in-house code. / Ph. D.

We explore the effect of multiscale structure on weakly interacting diffusions through two main projects. In the first, we consider a collection of weakly interacting diffusion processes moving in a two-scale locally periodic environment. We study the large deviations principle of the empirical distribution of the particles' positions in the combined limit as the number of particles grow to infinity and the time-scale separation parameter goes to zero simultaneously. We make use of weak convergence methods providing a convenient representation for the large deviations rate function, which allow us to characterize the effective controlled mean field dynamics. In addition, we obtain equivalent representations for the large deviations rate function of the form of Dawson-Gartner which hold even in the case where the diffusion matrix depends on the empirical measure and when the particles undergo averaging in addition to the propagation of chaos. In the second, we consider a fully-coupled slow-fast system of McKean-Vlasov SDEs with full dependence on the slow and fast component and on the law of the slow component and derive convergence rates to its homogenized limit. We do not make periodicity assumptions, but we impose conditions on the fast motion to guarantee ergodicity. In the course of the proof we obtain related ergodic theorems and we gain results on the regularity of Poisson type of equations and of the associated Cauchy-Problem on the Wasserstein space that are of independent interest.

Hamilton-Jacobi equations are a class of partial differential equations that arise in many areas of science and engineering. Originating from classical mechanics, they are widely used in various fields such as optimal control theory, quantitative finance, and game theory. Stochastic homogenization is a phenomenon used to study the behavior of solutions to partial differential equations in stationary ergodic media, aiming to understand how these solutions average out or 'homogenize' over large scales. This process results in effective deterministic descriptions, called effective Hamiltonians, which capture the essential behavior of the system. We consider nonconvex Hamilton-Jacobi equations in one space dimension. We provide a fully constructive proof of homogenization, which yields a formula for the effective Hamiltonian. Our proof employs sublinear correctors, functions extensively discussed in the literature. The proof involves strong induction: we first show homogenization for our base cases, then use gluing processes to generalize the solution for the strong induction. Finally, we extend the result to a wide class of functions. We study the properties of the resulting effective Hamiltonian and investigate the occurrence of flat pieces. Additionally, we develop a Python-based computational tool that performs the same homogenization steps in a computing environment, returning the effective Hamiltonian along with its graph and properties. / Mathematics