No description available.

No description available.

No description available.

This thesis is a treatise on optimal assembly methods for double row ball bearings. As with common single row bearings, double row ball bearings, consist of four general components, namely, an inner ring, an outer ring, a complement of balls and a cage or retainer to keep the balls separate. Unlike single row bearings, however, double row ball bearings have two complements of balls in two distinct parallel races. Although this double row configuration is desirable in a number of applications, it makes the bearings more difficult and expensive to assemble. In addition, current manual assembly procedures require a great deal of digital manipulation, leading to concern about carpal tunnel syndrome and other long-term repetitive motion injuries. This thesis attempts to develop an improved assembly process for all types of double row bearings. Although the work is intended to be general, the Torrington 5203 double row ball bearing is adopted as a specific application example. This bearing's assembly difficulties and additional cost are a result of its manual Conrad assembly method and a rubber O-ring and groove used solely for bearing assembly. In the assembly process, the O-ring supports the upper balls temporarily until the two rings can be aligned concentrically, thus snapping the balls into the bearing races. This thesis addresses the replacement of the rubber O-ring and explores opportunities for bearing assembly automation. Design synthesis of a retractable or reusable assembly component to replace the rubber O-ring supporting the upper balls during assembly is presented. A large group of design concepts are developed and evaluated, resulting in a small group of feasible designs. These feasible solutions are then tested, and a design that has the potential immediate implementation in an improved manual assembly process is proposed. In addition, two design concepts are presented as candidates for possible implementation in an automated assembly process. / Master of Science

No description available.

Power electronics is a constantly growing and demanding technical field. Consumer demand and developing technologies have made the improvement of power density a primary emphasis of research for this area. Power semiconductors present some of the major challenges for increasing system level power density due to high loss density and interconnection requirements. Advanced cooling schemes, such as double-sided, forced liquid convection or multi-phase flow, can be implemented with non-wire bond packaging to improve thermal management while maintaining proper electrical performance. Embedded power is one such packaging technology, which provides a compact structure for interface of power semiconductor to fluid flow. The objective of this work was to identify the potential of implementing embedded power packaging with double-sided forced liquid convection. Physics based, electro-thermal models were first used to predict the improvement in heat transfer of double-sided, forced liquid convection with embedded power packaging over single-sided liquid cooled wire bond based packaging. A liquid module test bed was designed and constructed based on the electro-thermal models, which could be interfaced with high power MOSFET based samples implementing various packaging technologies. Experiments were used to verify the model predictions and identify practical limitations of high flow rate, double-sided liquid cooling with embedded power. An improvement of 45% to 60% in total junction to case thermal resistance is shown for embedded power packaging with double-sided liquid cooling for water flow rates between 0.25 and 4.5 gal/min. / Master of Science

The strengthening of steel bridges using CFRP laminates has become a commonly used technique because of its numerous advantages compared to conventional repairs which involve welding or bolting of new steel plates. These structures will experience some sort of irregular cyclic loading during their lifetime and to analyze these complex loading cases, small scale testing is used to evaluate the fatigue performance between the steel substrate, adhesive layer and the CFRP laminate. In this research, double-strap joints (DSJ) were fabricated consisting of two high-modulus CFRP laminates and ASTM A36 steel plates bonded using a two-part epoxy adhesive. Two types of steel surface conditions were considered to evaluate the fatigue behavior under constant force amplitudes. Roughness on the steel substrate was achieved by ½ in (13 mm) diameter pits approximately 1/8 in (3.18 mm) deep to simulate an irregular surface. The results show that the surface condition has marginal influence on the total life of the specimens. To assess the damage accumulation in the DSJ, phenomenological methods like the nonlinear strength wearout Model (NLSW) and stiffness degradation were used. It was found that residual strength and stiffness decreased in a non-linear fashion. A non-linear model was used that agrees well with the experimental results and can be used to predict the residual strength of the specimens under variable amplitude fatigue (VAF). / Master of Science / With an aging and deteriorating infrastructure potentially being subjected to heavier loads than initially designed for, bridge engineers are increasingly looking for innovative, yet cost-effective solutions for repairing and maintaining the existing bridge inventory with sufficient capacity to carry legal loads. One alternative is to enhance the flexural strength of deteriorated steel members using carbon fiber-reinforced polymers (CFRP). This research project will investigate whether the use of CFRP retrofits is feasible for fatigue strengthening. The research will serve as insight to help guide bridge engineers or researchers on when and where the use of CFRP retrofits is suitable for the strengthening of steel bridges.

This study argues that the formation of Americo-Liberian identity overwhelmingly relied on White American middle class cultural values despite the founders' criticisms and rejection of racial oppression and slavery. Americo-Liberians' previous participation in a culture that downgrades African heritage fostered the internalization of Western notions of civilization and African inferiority that led them to establish an oppressive regime similar to the one they had escaped from, and even enslaved the indigenous population, which they considered "uncivilized." The study thus investigates how formerly oppressed and enslaved blacks became oppressors and enslavers of other black people in the name of a "civilizing mission." The relationship that developed between Americo-Liberians and indigenous Liberians provides a case study to explore the impact of White supremacy ideology on enslaved Africans and racial uplift ideology. Building on contributions of social theory and conflict theory my analysis of Americo-Liberians demonstrates how social class and ideology interacted to produce socio-economic developments that led to the Liberian Civil War. This study covers the founding of Liberia as a republic during the 1840's through the League of Nation's intervention in 1928. It is during this time period that Americo-Liberians fostered an exploitative and colonizing relationship with the indigenous Liberian population. Previous scholarship regarding Liberia engages in descriptive analysis this study is the first to employ the theoretical framework of double-consciousness to further illuminate the ambivalent positions of the Americo-Liberians vis-a-vis indigenous Liberians

A brief introduction to the current state of research in the Origins of Life field is given in Part I of this work. Part II covers original research performed by the author and co-workers. Layered Double Hydroxide (LDH) systems are anion-exchanging clays that have the general formula M(II)xM(III)(OH)(2x+2)Y, where M(II) and M(III) are any divalent and trivalent metals, respectively. Y can be nearly any anion, although modern naturally occuring LDH systems incorporate carbonate (CO32-), chloride (Cl-), or sulfate (SO42-) anions. Intercalated cobalticyanide anion shows a small yet observable deviation from local Oh symmetry causing small differences between its oriented and non-oriented infrared spectra. Nitroprusside is shown to intercalate into 2:1 Mg:Al LDH with decomposition to form intercalated ferrocyanide and nitrosyl groups of an unidentified nature. The [Ru(CN)6]4- anion is shown to intercalate into layered double hydroxides in the same manner as other hexacyano anions, such as ferrocyanide and cobalticyanide, with its three-fold rotational axis perpendicular to the hydroxide sheets. The square-planar tetracyano-nickelate(II), -palladate(II), and platinate(II) anions were intercalated into both 2:1 and 3:1 Mg:Al layered double hydroxides (LDH). The basal spacings in the 2:1 hosts are approximately 11 Å, indicating that the anions are inclined approximately 75 degrees relative to the hydroxide layers, while in the 3:1 hosts the square-planar anions have enough space to lie more nearly parallel to the LDH cation layers, giving basal spacings of approximately 8 Å. It has been found that the LDH Mg2Al(OH)6Cl catalyzes the self-addition of cyanide, to give in a one-pot reaction at low concentrations an increased yield of diaminomaleonitrile and in addition, at higher ($0.1M) concentrations, a purple-pink material that adheres to the LDH. We are investigating whether this reaction also occurs with hydrotalcite itself, what is the minimum effective concentration of cyanide, and what can be learned about the products and how they compare with those reported at high HCN concentrations in the absence of catalyst.

SuperNEMO est un projet de détecteur de nouvelle génération pour la recherche de la décroissance double bêta sans émission de neutrinos. La technique expérimental déployée est dans la lignée du son prédécesseur NEMO3, combinant un trajectographe et un calorimètre, afin d’identifier non seulement les électrons des décroissances double bêta, mais également pour mesurer l’ensemble des composantes de bruit de fond du détecteur. Le projet vise ainsi une sensibilité de 10^26 ans sur la période du 82Se, ce qui permettrait de sonder une masse effective du neutrino de 50 meV. Pour atteindre cette sensibilité, le projet prévoit notamment de mettre en place un calorimètre composé d’un millier de compteur à scintillation de basse radioactivité, dont la résolution en énergie serait meilleure que 8 % FWHM pour des électrons de 1 MeV.Ce travail de thèse apporte une contribution importante dans les travaux de Recherche et Développements pour améliorer les performances des scintillateurs et photomultiplicateurs, et pour réduire leur radioactivité, avec notamment la conception d’un nouveau photomultiplicateur en collaboration avec Photonis. / SuperNEMO is a next generation double beta decay experiment which will extend the successful “tracko-calo” technique employed in NEMO 3. The main characteristic of this type of detector is to identify not only double beta decays, but also to mesure its own background components. The projet aims to reach a sensitivity up to 1026 years on the half-life of 82Se. One of the main challenge of the Research and Development is to achieve an unprecedented energy resolution for the electron calorimeter, better than 8 % FWHM at 1 MeV.This thesis contributes to improve scintillators and photomultiplicators performances and reduce their radioactivity, including in particular the development of a new photomultiplier in collaboration with Photonis.