Digitized by Kansas Correctional Industries

1 / Amanda Rosemary Pahng

Thesis--Ohio State University. / Includes bibliographical references. Available online via OhioLINK's ETD Center

Colloidal gas aphrons (CGAs) recently used as part of water-based drilling fluids have been found effective in controlling the filtration rate by bridging the pores of the reservoir rock and therefore, reducing the formation damage. This research aims to generate colloidal gas aphrons (CGA) in oil based drilling fluids; to study stability, rheology and the filtration loss characteristics of CGAs and to investigate formation damage properties of CGAs as a drilling fluid. Aphrons were generated in mineral oil using a polymer-surfactant mix. Based on how changing the polymer and surfactant concentration affects the physico-chemical characteristics of the fluid, an optimum formulation for the aphron drilling fluid was suggested. The stability of microbubbles was investigated by looking at the effects of time, temperature and pressure on the aphron yield and bubble size distribution. Effects of temperature and pressure on the density of the oil-based aphron fluids have been investigated. Based on the PVT analysis results, an equation of state was proposed. Finally, the performance of the oil-based aphron fluid in porous media was investigated. The effects of changing the CGA fluid injection rate, the type of saturating fluid and the wettability of the porous media on the pressure drop were examined. An assessment of the formation damage following the oil-based CGA fluid injection was also made. / Petroleum Engineering

This dissertation presents the configuration and capacity management of manufacturing cells using cluster analysis. A heuristic based on cluster analysis is developed to solve cell formation in cellular manufacturing systems (CMS). The clustering heuristic is applied for cell formation considering processing requirement (CFOPR) as well as various manufacturing factors (CFVMF). The proposed clustering heuristic is developed by employing a new solving structure incorporating hierarchical and non-hierarchical clustering methods. A new similarity measure is constructed by modifying the Jarccard similarity and a new assignment algorithm is proposed by employing the new pairwise exchange method. In CFOPR, the clustering heuristic is modified by adding a feedback step and more exact allocation rules. Grouping efficacy is employed as a measure to evaluate solutions obtained from the heuristic. The clustering heuristic for CFOPR was evaluated on 23 test problems taken from the literature in order to compare with other approaches and produced the best solution in 18 out of 23 and the second best in the remaining problems. These solutions were obtained in a considerably short time and even the largest test problem was solved in around one and a half seconds. In CFVMF, the machine capacity was first ensured, and then manufacturing cells were configured to minimize intercellular movements. In order to ensure the machine capacity, the duplication of machines and the split of operations are allowed and operations are assigned into duplicated machines by the largest-first rule. The clustering heuristic for CFVMF proposes a new similarity measure incorporating processing requirement, material flow and machine workload and a new machine-part matrix representing material flow and processing time assigned to multiple identical machines. Also, setup time, which has not been clearly addressed in existing research, is discussed in the solving procedure. The clustering heuristic for CFVMF employs two evaluation measures such as the number of intercellular movements and grouping efficacy. In two test problems taken from the literature, the heuristic for CFVMF produced the same results, but the trade-off problem between the two evaluation measures is proposed to consider the goodness of grouping.

In this thesis, we focus on obtaining and interpreting observational information on (i) the role of multiplicity on the properties of young stars; (ii) the early evolutionary influence of circumstellar disks; and (iii) the nature of accretion in young systems. To facilitate this research, we conducted an extensive multi-epoch high-resolution spectroscopic survey at optical wavelengths (3,200-10,000 A) of ~200 T Tauri stars in the ~2 Myr old Chamaeleon I, and Taurus-Auriga star-forming regions with the Magellan Inamori Kyocera Echelle (MIKE) spectrograph on the Magellan Clay 6.5 m telescope. From the spectroscopic data, we identify eight close binaries and four close triples, of which three and two, respectively, are new discoveries. We find that the multiplicity fraction for Cha I and Tau-Aur are similar to each other, and to the results of field star surveys. The frequency of systems with close companions in our sample is not seen to depend on primary mass or accretion. We probed for evidence of disk braking. We did not see a statistically significant difference between the distribution of rotational velocities with the presence of an inner disk. Also, our findings show that F-K stars in our sample have larger rotational velocities and specific angular momentum than M stars. We also analyzed accretion variability in our sample using the H\alpha 10% width and the CaII-8662 line flux as accretion diagnostics. We find that the maximum extent of accretion variability in our sample was reached on timescale of a few days, indicating that rotation could significantly contribute to the variability.

In this thesis, we focus on obtaining and interpreting observational information on (i) the role of multiplicity on the properties of young stars; (ii) the early evolutionary influence of circumstellar disks; and (iii) the nature of accretion in young systems. To facilitate this research, we conducted an extensive multi-epoch high-resolution spectroscopic survey at optical wavelengths (3,200-10,000 A) of ~200 T Tauri stars in the ~2 Myr old Chamaeleon I, and Taurus-Auriga star-forming regions with the Magellan Inamori Kyocera Echelle (MIKE) spectrograph on the Magellan Clay 6.5 m telescope. From the spectroscopic data, we identify eight close binaries and four close triples, of which three and two, respectively, are new discoveries. We find that the multiplicity fraction for Cha I and Tau-Aur are similar to each other, and to the results of field star surveys. The frequency of systems with close companions in our sample is not seen to depend on primary mass or accretion. We probed for evidence of disk braking. We did not see a statistically significant difference between the distribution of rotational velocities with the presence of an inner disk. Also, our findings show that F-K stars in our sample have larger rotational velocities and specific angular momentum than M stars. We also analyzed accretion variability in our sample using the H\alpha 10% width and the CaII-8662 line flux as accretion diagnostics. We find that the maximum extent of accretion variability in our sample was reached on timescale of a few days, indicating that rotation could significantly contribute to the variability.

Les recherches récentes portant sur les expériences de travail en formation professionnelle démontrent que le contexte de travail a une grande influence sur l'apprentissage en milieu réel. De même, la qualité de l'encadrement offert lors d'un stage en entreprise est un facteur essentiel à la réussite de la formation. Les études récentes font toutefois ressortir des lacunes dans l'encadrement exercé auprès des stagiaires. Il nous semble donc important de comprendre ce qui caractérise un encadrement de qualité. Cette recherche, de nature descriptive, s'appuie sur une approche de type étude de cas. Le cas étudié est un programme de diplôme d'études professionnelles (DEP) de mécanique de machines fixes dispensé en alternance. L'étude vise à décrire les pratiques d'encadrement utilisées par les tuteurs en entreprise qui favorisent l'apprentissage des stagiaires. L'échantillon, de type intentionnel, est constitué de neuf tuteurs et de cinq élèves encadrés par ces mêmes tuteurs. Les tuteurs sont choisis en fonction de leur encadrement identifié comme étant exemplaire, mais n'ont bénéficié d'aucune formation qui les aurait préparés à être tuteur. La collecte des données est réalisée à partir d'une entrevue semi-dirigée effectuée auprès de chacun des sujets. L'analyse des données, réalisée selon une approche qualitative, s'appuie sur trois principaux concepts que sont l'encadrement, les caractéristiques du tuteur et l'apprentissage en milieu de stage, défini dans une perspective expérientielle. Les stagiaires rencontrés nous ont appris que les interventions des tuteurs leur ont permis de réaliser des apprentissages de nature variée tels que: les aspects techniques du métier et le fonctionnement de l'entreprise, le développement personnel, la socialisation et l'orientation professionnelle. Ces apprentissages ont été surtout possibles grâce à trois pratiques d'encadrement utilisées par les tuteurs que les stagiaires ont identifiées comme favorisant leur apprentissage: le questionnement, la démonstration et la réalisation de tâches. Ces trois pratiques, telles que les utilisent les tuteurs, favorisent la réflexion et l'expérimentation et ainsi, soutiennent les stagiaires dans leur processus d'apprentissage. Les résultats démontrent que ces pratiques, qui s'inscrivent dans une approche expérientielle de l'apprentissage en milieu de travail, peuvent effectivement être qualifiées de pratiques exemplaires. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : Pratiques d'encadrement, Tuteur, Apprentissage en milieu de stage, Apprentissage expérientiel, Formation professionnelle au secondaire, Alternance travail-études, Supervision en milieu de stage.

Education has proven to be a powerful tool. Higher education in particular has been and continues to be utilized in various ways around the world and has been instrumental in the rise of societies including Americo-Liberian society in Liberia, West Africa. This study investigates how education has been instrumental in the formation of identity for Americo-Liberians (descendants of historically oppressed groups), demonstrates the relationship that existed between education attainment and social stratification within their system, and uncovers the socialization process that existed within the Americo-Liberian system of education. A critical analysis of social structure and history was undertaken to demonstrate how a mythical norm and cultural capital were key in both the identity formation and destruction of the Americo-Liberian population in Liberia, West Africa. Other theoretical frameworks, in particular "othering" were utilized throughout this dissertation to further demonstrate the rise of Americo-Liberians through their employment of a mythical norm and cultural capital, which ultimately led to their demise. A historical case study method was utilized to uncover the cultural capital of the preferred upper class and political elite, known as Americo-Liberians, which was deeply embedded within their system of education. In all, the system that was set up to ensure their privilege led to their demise and the complete destruction of the country as a whole.

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