Extensive attention has been paid to consolidate nanoparticles into nanocrystalline components that possess better properties than their coarse-grained counterparts. Nanocrystalline monolithic tungsten (W) has been envisaged to possess better properties than coarse-grained tungsten and to improve the performance of many military components. Commercially available nano-W powders were characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and Brunauer, Emmett, and Teller (BET) measurement. While the bulk of nano-W powders consisted of bcc-W as confirmed by XRD and TEM, much of their surface consisted of WO3 with traces of WO2 and WC. Despite the irregular morphology and agglomerates greater than 1 m in size, the diameter of individual nano-W powders ranged from 30 to 100 nm with a surface area of 10.4 m2/g. To obtain green bodies of higher densities and more homogeneous microstructures after consolidation, W nanopowders were de-agglomerated in water and slip cast in plaster molds. De-agglomeration in water was conducted by repeated ultrasonication, washing, centrifuge and pH adjustment. The change in particle size and morphology was examined via SEM. After the initial surface oxide was removed by repeated washing, the reactivity of W nanoparticles to water was somewhat inhibited. Increasing the number of cycles for ultrasonication and washing increased the pH, the degree of de-agglomeration and the stability of W suspension. The zeta potential was more negative with increasing pH and most negative at pH values close to 5. Viscosity also decreased with increasing pH and reached a minimum at a pH 5. To obtain the highest solid loading with the lowest viscosity, the pH value of W suspension was adjusted to 5 using aqueous tetramethylammonium hydroxide solutions. The relative density of the slip cast increased with longer ultrasonic time, increasing slurry pH up to 5, and consequent increase in solids loading. Smaller particles were separated from larger ones by ultrasonication, washing with water and centrifugation. At a 27.8 vol.% solids loading, the size-separated fine W slurry was slip cast into pellets with relative green densities up to 41.3 % and approximate particle sizes of 100 nm. W powders were also ultrasonicated in aqueous poly (ethyleneimine) (PEI) solutions with various concentrations. SEM examinations of particle sizes showed that 1 wt.% PEI led to the optimum dispersion and ultrasonication for longer time with a low power resulted in better dispersion. 0.5 g of W powders were ultrasonicated in 10 ml aqueous poly (allylamine hydrochloride) (PAH) solutions with molar concentrations ranging from 0.01 to 0.05 M. W suspensions with 0.03 M and 0.04 M PAH after two washing cycles showed improved dispersion. Cold isostatic pressing can further increase the green density following slip casting. Sintered slip casts made from de-agglomerated nanoparticle W showed a lower density, more uniform microstructure, smaller grains and smaller pores than the sintered dry pressed pellets.

The automotive manufacturing industry is facing an interesting period of trial when a lot of improvement is expected of them in a short period of time to contribute to a cleaner planet by applying technologies that will reduce fossil fuel consumption. Electrification was good, but this must be accompanied by substantial curb weight reduction, which was provided by alloys such as A365, Aural 5 (AlSi8MnMg), Aural 2 (AlSi10MnMg), and Mercalloy 367 (AlSi9MgMnSr) for making structural parts. The use of these Al alloys is accompanied with extensive heat treatment which on its own involves fossil fuel consumption. In this research, test plates were made utilizing high vacuum high pressure die casting (HVHPDC) and a unique Al-Fe based eutectic alloy with Zn and Mg as precipitation strengtheners. Experimental results demonstrated that they age naturally, with their mechanical properties rising to the industry requirement within three days. DSC experiments carried out at various ages gave further experimental evidence to this natural ageing phenomenon. A portion of the samples was then given an experimental "paint bake" treatment at different ages. This is typical on an assembly line where the coated parts are baked at a temperature range of 120 - 200oC for thirty minutes. It was evidently defensible that samples of various ages respond to the treatment in different ways. The mechanical characteristics of the samples decreased after treatment to same value and progressively increased to match the values of the control samples. During the duration of the experiment, some samples rose quickly while others remained "nearly dead" in the state of low mechanical characteristics or climbed sluggishly to catch up with the natural ageing curve. The poorest results were seen in samples handled at the early stage when the initial clusters are forming indicating that it might not be a good idea to interfere with the NA process at those times. / Thesis / Master of Applied Science (MASc) / Fueled by the desire to produce an Al alloy with good mechanical properties arising from natural ageing, high vacuum high pressure die casting (HVHPDC) was used in making castings of this alloy which contains Fe for improvement on its castability and recyclability, contains Zn and Mg which act as the precipitating strengtheners driving the natural ageing phenomenon. Tests and experiments like uniaxial tensile tests, differential scanning calorimetry and electrical conductivity tests were carried out to ascertain its suitability to be used for structural automotive parts without heat treatment. The results showed that the new Nemalloy HE700 met with the minimum industry requirements for mechanical properties of materials for structural automotive applications within 3 days of natural ageing. The alloy was then subjected to experimental paint bake treatment to observe its reaction to paint bake process and the results were able to show when to do paint bake for best outcome.

A global shift towards reducing carbon (CO2) emissions in the automotive industry while increasing fuel efficiency and range security has triggered the exploration of new processing routes and material alternatives for automotive components. To achieve such goals, manufacturing processes such as high vacuum high pressure die casting (HV-HPDC) have gained attention in recent years to fabricate cast Al alloys for structural automotive components. HV-HPDC allows for increased and more economical production as compared to other manufacturing methods due to the minimal steps involved in the process. Higher degrees of tolerance and precision can be upheld with HV-HPDC, ceasing the need for secondary operations to form the component into desired complex shapes. In this research, the effect of pre-solidified grains (PSG) and heightened metal residence time on the microstructure and mechanical properties were investigated in a new heat-treatable casting alloy, (Al-1.1wt%Fe-4.7wt%Zn-0.95wt%Mg)-0.07wt%Ti, also known as Nemalloy HE700 alloy, manufactured via HV-HPDC. Developed at McMaster University in conjunction with Nemak USA/CAN and CanmetMATERIALS, Nemalloy HE700 alloy is intended for structural automotive applications with its higher strength and increased light weighting capabilities. Nemalloy HE700 serves as a suitable candidate to replace existing Al-Si alloys such as Aural-5 (Al-8wt%Si-Mg-Mn), currently used in the market today. As-cast test plate castings adhering to two geometries: a 3-step plate geometry (nominal plate thicknesses of 3 mm, 2.5 mm, and 2.3 mm) and a singular plate (2.5 mm) with increasing shot delay intervals of 3 additional seconds to a total of 10 seconds from normal operating conditions (i.e., 1, 4, 7, and 10 seconds) were fabricated with the intention of increasing PSG content within the final cast components to study the underlying effects. Experimental efforts through metallography revealed that, much like traditional high pressure die cast (HPDC) components, PSG gravitated toward the centers of the castings in all operating conditions with heightened agglomerations and potential abnormal grain growth in higher delay samples. Moreover, distributions of PSG became more dispersed through the cross-sections as the delay time was increased. Size distributions of PSG adhered to a standard characteristic grain of 100 µm to sizes of 1000+ µm. Larger sizes of PSG grew substantially in equivalent circular diameter (ECD) and extent in higher delay interval samples. Affected area percentage as a result of an increase in PSG content uncovered higher degrees of porosity presenting themselves as shrinkage and gas porosities in the microstructure. A rise in gas porosity size and quantity was realized with higher delay intervals. Uniaxial mechanical testing of tensile specimens from both geometries indicated a directional relationship of PSG where samples were increasingly more brittle and demonstrated adverse mechanical properties when testing was performed parallel to the metal flow direction as opposed to when performed perpendicularly. Moreover, Nemalloy HE700 alloy exhibited a lower propensity of formation of PSG than Aural-5 in higher levels of shot delay times, primarily due to compositional and differing solidification behaviours of the two alloys. The research presented characterizes the nature of PSG formation in HV-HPDC Al alloys with increased metal residence time and the resultant adverse effects on performance. As efforts shift toward manufacturing structural Al components using HV-HPDC, a greater understanding of such effects will aid in alloy development, die mould design, and disseminate information on HV-HPDC to produce components of heightened quality. Additionally, the resultant findings aim to address gaps in current literature as automotive manufacturers transition from non-structural HPDC components to structural HV-HPDC products for commercial use. / Thesis / Master of Applied Science (MASc)

<p dir="ltr"> Most industrial processes are not fully-automated. Although reference tracking can be handled by low-level controllers, initializing and adjusting the reference, or setpoint, values, are commonly tasks assigned to human operators. A major challenge that arises, though, is control policy variation among operators which in turn results in inconsistencies in the final product. In order to guide operators to pursue better and more consistent performance, researchers have explored the optimal control policy through different approaches. Although in different applications, researchers use different approaches, an accurate process model is still crucial to the approaches. However, for a highly transient process (e.g., the startup of a manufacturing process), modeling can be challenging and inaccurate, and approaches highly relying on a process model may not work well. One example is process startup in a twin-roll steel strip casting process and motivates this work. </p><p dir="ltr"><br></p><p dir="ltr"> In this dissertation, I propose three offline reinforcement learning (RL) algorithms which require the RL agent to learn a control policy from a fixed dataset that is pre-collected by human operators during operations of the twin-roll casting process. Compared to existing offline RL algorithms, the proposed algorithms focus on exploiting the best control policy used by human operators rather than exploring new control policies constrained by the existing policies. In addition, in existing offline RL algorithms, there is not enough consideration of the imbalanced dataset problem. In the second and the third proposed algorithms, I leverage the idea of cost sensitive learning to incentivize the RL agent to learn the most valuable control policy, rather than the most common one represented in the dataset. In addition, since the process model is not available, I propose a performance metric that does not require a process model or simulator for agent testing. The third proposed algorithm is compared with benchmark offline RL algorithms and achieves better and more consistent performance.</p>

The AM60 Mg alloy has been used in the automotive industry to help achieve higher fuel efficiency. However, its products, mostly fabricated via high pressure die casting process, are inherently plagued with porosity issues. The presence of porosity impairs mechanical properties, especially fatigue properties, and thus affects the product reliability. We have therefore studied the effect of porosity on the fatigue behavior of samples drawn from a prototype AM60 shock tower by conducting strain-controlled fatigue test along with X-ray computed tomography (XCT). The 3D analysis of porosity by XCT showed discrepancies from 2D metallographic characterization. Fatigue testing results showed the machined surface is the preferential site for crack initiation to occur, on which pores are revealed after specimen extraction. A large scatter in fatigue life was observed as crack initiating at a large pore situated on the surface will result in a significantly shorter fatigue life. SEM fractography showed fracture surfaces are generally flat and full of randomly orientated serration patterns but without fatigue striations. The observations and measurements of porosity and fatigue cracks made by XCT were confirmed by SEM, supporting it as a reliable characterization tool for 3D objects and has value in assisting the failure analysis by SEM. Fatigue life was found to decrease with the increase of fatigue-crack-initiating pore size. The same trend was also found between the fatigue life and the volume fraction of porosity. The pore shape and pore orientation should be taken into account when determining the pore size as they can result in the difference in pore size between 2D and 3D measurement. / Thesis / Master of Applied Science (MASc) / The AM60 Mg alloy has been used in the automotive industry to help achieve higher fuel efficiency. However, its products, mostly fabricated via high pressure die casting process, are inherently plagued with porosity issues. The presence of porosity impairs mechanical properties, especially fatigue properties, and thus affects the product reliability. We have therefore studied the effect of porosity on the fatigue behavior of samples drawn from a prototype AM60 shock tower by conducting strain-controlled fatigue test along with X-ray computed tomography (XCT). The 3D analysis of porosity by XCT showed discrepancies from 2D metallographic characterization. Fatigue testing results showed the machined surface is the preferential site for crack initiation to occur, on which pores are revealed after specimen extraction. A large scatter in fatigue life was observed as crack initiating at a large pore situated on the surface will result in a significantly shorter fatigue life. SEM fractography showed fracture surfaces are generally flat and full of randomly orientated serration patterns but without fatigue striations. The observations and measurements of porosity and fatigue cracks made by XCT were confirmed by SEM, supporting it as a reliable characterization tool for 3D objects and has value in assisting the failure analysis by SEM. Fatigue life was found to decrease with the increase of fatigue-crack-initiating pore size. The same trend was also found between the fatigue life and the volume fraction of porosity. The pore shape and pore orientation should be taken into account when determining the pore size as they can result in the difference in pore size between 2D and 3D measurement.

<p dir="ltr">Antennas are used to transmit communication signals for many applications including for the navigation of aircraft. To protect the antennas from environmental conditions electromagnetic transparent structures called radomes are used. Advancements in technology have led to the development of hypersonic flight vehicles. These aircraft travel at speeds of Mach 5 and greater subjecting them to extreme environmental conditions. These aircraft require precise navigation making it important to have radome materials that can withstand the extreme conditions of high-speed flight while maintaining transparency to the incoming and outgoing signals of the antenna. Silicon nitride is a ceramic material of interest for high temperature radomes due to its mechanical properties, temperature stability, and satisfactory dielectric properties. Incorporating porosity into silicon nitride further enhances the transmission performance making porous silicon nitride a leading candidate material for high temperature radomes. In this dissertation slip casting with pressureless sintering is proposed as a route to fabricate porous silicon nitride ceramics for radomes. Modification of sintering aids and sintering temperatures are explored as a method to control the amount of porosity. Mechanical properties and dielectric properties of these materials are investigated. </p><p dir="ltr">First, an aqueous silicon nitride suspension developed for slip casting was optimized by investigating the rheological properties, zeta potential, and sedimentation behavior. It was determined that a suspension with 30 vol% solids, 0.5 wt% dispersant (PEI), and a pH of 7 was the optimized condition that resulted in uniform cast parts. This optimized suspension was used to fabricate silicon nitride samples with yttria and alumina sintering aids. An average density of 93% with an average strength of 659 MPa at room temperature and a strength of 472 MPa maintained up to 1200°C was achieved. Dielectric constant and loss tangent were measured on samples with 4-17% porosity to be 5.85-7.70 and <0.02, respectively. </p><p dir="ltr">To create samples with higher levels of porosity and therefore lower dielectric constants the yttria and alumina sintering aids were replaced with ytterbium oxide. Ytterbium oxide assists in forming porous silicon nitride due to the high melting temperature and high viscosity of the resulting glassy phase. Slip cast samples with 5% Yb₂O₃ were sintered at temperatures of 1700-1850°C resulting in porosities of 21-32% and strengths of 267-445 MPa. The dielectric constants of these materials were measured to be 4.56-5.80 with average loss tangents <0.006. The amount of ytterbium oxide was also studied to determine the effects on density, microstructure, mechanical properties, and dielectric properties. Slip-cast samples with 5-15% Yb₂O₃ were made having average porosities of 23-36% and strengths of 275-421 MPa. The dielectric constants of these materials were measured to be 4.13-4.65 with average loss tangents of <0.007. </p><p dir="ltr">Lastly, slip casting using the previously developed and evaluated suspensions was done to fabricate various radome shapes as well as layered structures. The processing method presented in this dissertation shows the potential for fabricating porous silicon nitride for high temperature radome applications with controlled porosity and relatively high strengths.</p>

The manufacturing of UHTC materials has significantly advanced over recent years, allowing for the development of new microstructures, architectures, shapes, and geometries to explore new properties and applications for these materials beyond aerospace. One of the UHTCs, titanium diboride (TiB2) exhibits high electrical and thermal conductivity that could satisfy the needs of functional ceramic component applications, like battery cathodes, by tailoring its microstructure and architecture. This thesis represents one of the first detailed studies to understand how the processing-microstructure-properties relationship of TiB2 can be shifted to explore new applications. In order to do that, TiB2 has been manufactured with a processing technique never used before, with significant porosity, exploration of which has been very limited for this material. Additionally, this thesis also explores the synthesis and utilization of novel anisotropic particles to further explore this material relationship. In this work, aqueous tape casting of TiB2 has been investigated. Zeta potential measurements and suspension rheology were used to understand the role of dispersant, binder and plasticizer in the suspension and their interaction with the surface chemistry of the TiB2 particles to develop a stable, homogenous suspension, with minimum additive amounts (0-2 wt%). Homogeneous, flexible and strong TiB2 tapes were prepared using suspensions with 30 vol% solids and characterized to compare different compositions, mixing methods, and thicknesses. The characterization shows the tailoring of the properties as a function of the controlled suspension formulation with minimum amount of additives. Green tapes with 2 wt% dispersant, 1 wt% binder, and 2 wt% plasticizer had similar microstructure to those with half the plasticizer but quintuple the Young's modulus (1.96 GPa). The effect on other relevant properties is also discussed. Tape casting aligns anisotropic particles along the direction of casting, which can be taken advantage of for increasing fracture toughness directionally or producing aligned pore networks using sacrificial fillers. The relationship between alignment, porosity, and the mechanical properties of titanium diboride has not been studied. In this work, we characterize the porous sintered bodies produced through aqueous tape casting of non-spherical TiB2 particles of aspect ratio close to 1, as well as composites with an added high aspect ratio particle (2 wt% PCN-222). Synthesis of uniform, spherical ZrC is difficult and generally not cost-effective, as is the case for most ultra-high temperature ceramics. High aspect ratio particles for reinforcement of ceramic composites are even more difficult to synthesize. Metal organic frameworks (MOF) are crystalline coordination polymers composed of multidentate organic linkers bridging metal nodes to form porous structures. Thermal decomposition of MOFs presents a new and cost-effective route to synthesis of ZrC. In this study, heat treatment at 2000°C of MOF PCN-222 produces zirconium carbide (ZrC) within a highly anisotropic particle. The resulting rod-shaped, glass-like carbon matrix embedded with ZrC crystals is described. These rods have potential as reinforcements for iii high temperature applications and as a synthetic route for ultra-high temperature ceramics with unique morphologies. It is the first time that this type of transformation from a MOF into a UHTC has been reported. We have determined through analysis of SEM images that regardless of tape casting speed, about 57% of the TiB2 particles are aligned with the tape casting direction. The mechanical properties are dominated by the effects of the porosity (38%), but the alignment exhibited here could be further exploited for anisotropic behavior across the sintered tapes. Composites cast with high aspect ratio particles exhibited strong alignment in the casting direction. Further work is required to understand the interplay between alignment and porosity and their effects on material properties. / Doctor of Philosophy / Titanium diboride (TiB2) is an ultra-high temperature ceramic with a melting point of 3225°C. Many applications for this material require fully dense structural ceramics, such as cutting tools,1 armor,2 and high temperature structural supports.2,3 These applications rely mainly on the high mechanical strength of TiB2, which is maintained in extreme thermal and chemical environments. The field of knowledge surrounding TiB2 lacks information about the ways that porosity affects its otherwise well-known properties;4,5 to bridge this gap could open up applications for functional and porous ceramics such as lithium-air batteries,6 electrochemical components,7 semiconductors,8 and more. This work intends to provide a foundation for this endeavor by developing for the first time a colloidal suspension formulation that allows for the tape casting of TiB2 and characterizing the resulting porous ceramics. Among these new potential applications, many require thin ceramics less than 1 mm thick—a result which has been accomplished for other materials via tape casting.4,9 This is a wet route of producing ceramics that provides the ability to tailor the surface chemistry of the particles, giving greater control over the stability of the suspension (TiB2 particles suspended in water) and quality of the end product than is afforded by dry processing routes.10 This also allows for more complex shaping than simple pressing, which ultimately saves costs; by producing the near-net shape in the green body before firing, less machining must be done to the sintered body when it is removed from the high temperature furnace.11 In tape casting, the suspension is spread over a substrate by a doctor blade to the desired thickness. It is known that tape casting tends to align anisotropic particles along the direction of casting due to a nonuniform velocity imparted by the shear force of the doctor blade spreading the suspension, an advantage which can provide directional properties in the final ceramic.9 While this process is well known, it has never been applied to the material TiB2 prior to this work. In this work, a suspension is formulated to allow for the tape casting of TiB2 with minimum organic additive content, which is cost-effective and reduces potential for defects. Porosity and alignment in the tape cast specimens are characterized. For comparison, a highly anisotropic or rod-shaped particle (PCN-222, a metal organic framework material) was included in the TiB2 suspensions for tape casting. This metal organic framework (MOF) has been transformed into a high temperature material after thermal treatment at the sintering temperature of 2000°C, showing that the resulting particle is made of glass-like carbon embedded with zirconium carbide (ZrC) crystallites. This particle could be used as a reinforcement for ultra-high temperature ceramics, and in this work was shown to align strongly in the tape casting direction. At the level of porosity (38%) and alignment (57%) in the TiB2 specimens in this study, porosity dominates the mechanical properties. This relationship is shown to be more complicated than lowering the strength by the same proportion that the density is lowered, and various models for understanding the role of porosity on the elastic modulus are explored.

Seit drei Jahrzehnten eröffnet die elektrische Stimulation des Nervus vagus (N. X) neue Möglichkeiten in der Therapie chronischer Erkrankungen wie Epilepsie oder rheumatoider Arthritis. Hierfür erfolgt die chirurgische Implantation einer Elektrode am cervicalen Anteil des N. X. Therapeutische Nebenwirkungen treten bei zwei von drei Patienten auf (Giordano et al. 2017), während bei einem Viertel der behandelten Patienten kein therapeutischer Nutzen messbar ist (Englot et al. 2011). Ultraschall wird zur Beurteilung der Morphologie und zur Messung der Nervenquerschnittsflächen des N. X eingesetzt. Bis heute ist jedoch unklar, wie präzise der Ultraschall den N. X im Kontext der Stimulationstherapie beschreiben kann. Ziel dieser Arbeit war es daher, die im Ultraschall ermittelte Nervenquerschnittsfläche des N. X kritisch im Hinblick auf ihre Bedeutung für die klinische Stimulationstherapie zu beurteilen. Die Abformung mit Epineurium des N. X mit zeichnungsscharfen dentalen Abformmaterialien ermittelt Messwerte, die der Nervenquerschnittsfläche im klinischen Kontext am ehesten entsprechen (Reid 1990; Spuck et al. 2010; Giordano et al. 2017; González et al. 2019; Patil et al. 2001). Bei 12 nativen Körperspendern wurde deshalb die Nervenquerschnittsfläche des N. X im Ultraschall und in der Histologie dargestellt und mit Messwerten aus einer manuellen Abformung des Nervs verglichen. Die Kombination dreier Methoden zur Ermittlung der Nervenquerschnittsfläche des N. X stellt einen neuen und bisher nicht praktizierten Untersuchungsansatz dar und ist Alleinstellungsmerkmal dieser Arbeit. Die Nervenquerschnittsfläche des N. X im Ultraschall war kleiner als in der Abformung mit Epineurium und in der Histologie (1,5±0,4 vs. 3,1±0,9 vs. 2,3±0,7 mm2). Die Berücksichtigung des Epineuriums ergab signifikante Unterschiede in der gemessenen Nervenquerschnittsfläche. Die Messung der Nervenquerschnittsfläche des N. X im Ultraschall führte zu einer systematischen Unterschätzung, während die Ultraschallmessung mit Epineurium zu einer systematischen Überschätzung der Querschnittsfläche im Vergleich zur Messung in der Abformung mit Epineurium führte. Der Ultraschall ist somit wahrscheinlich keine geeignete Messmethode zur präoperativen Einschätzung der Nervenquerschnittsfläche des N. X. In der klinischen Praxis könnte durch eine zu kleine Elektrode die Gefäßversorgung des N. X unterbrochen und die folgende Hypoxie mit partialer axonaler Degeneration die häufig auftretenden Nebenwirkungen erklären. Stimmbandlähmungen wurden in diesem Kontext bereits als Folge der resultierenden Hypoxie beschrieben (Robinson und Winston 2015; Révész et al. 2016). Eine zu große Elektrode könnte in einer insuffizienten Überleitung elektrischer Impulse von der Elektrode auf den Nerv resultieren und erklären, weshalb die Stimulationstherapie bei einigen Patienten keine messbare Wirkung entfaltet. Die Magnetresonanztomographie (MRT) bildet möglicherweise eine Alternative in der Darstellung der Nervenquerschnittsfläche des N. X zum Ultraschall. Zukünftige Arbeiten könnten die Nervenquerschnittsfläche des N. X in der MRT mit Messergebnissen aus einer mechanischen Abformung mit Epineurium vergleichen, um Aussagen über die Anwendung der MRT zur präoperativen Einschätzung der Nervenquerschnittsfläche des N. X treffen zu können. Die Nervenquerschnittsfläche des N. X ist abhängig von der Körperseite (rechts signifikant größer als links). Ursächlich sind wahrscheinlich die Innervationsgebiete des N. X, die sich ebenfalls in Abhängigkeit der Körperseite unterscheiden und seitenspezifische Effekte in der Stimulationstherapie hervorrufen (Howland 2014). Der Body-Mass-Index korreliert signifikant mit der Nervenquerschnittsfläche des N. X und beeinflusst den Anteil des Epineuriums und den Anteil der Axone an der gesamten Nervenquerschnittsfläche. Die Nervenquerschnittsfläche des N. X steht in enger Verbindung mit dem Alter der Probanden. Ursächlich könnten die axonale Degeneration oder die an Häufigkeit zunehmenden pathologischen Prozesse mit steigendem Alter sein. Limitiert werden die Ergebnisse dieser Arbeit durch die geringe Fallzahl und die spezifische Altersgruppe (ø 88,4±8,5 Jahre) der Körperspender. Während der Ultraschall die Nervenquerschnittsfläche des N. X in corpore bestimmt, misst die Methode Abformung mit Epineurium die Struktur nach Verletzung der nervalen Integrität. Abschließend handelt es sich bei der histologischen Untersuchung um eine in vitro Messung.:Inhaltsverzeichnis 1. Einleitung 1 1.1 Problemstellung 1 1.2 Klinische Bedeutung der Stimulationstherapie 3 1.2.1 Wirkungsweise der Nervenstimulation für ausgewählte Erkrankungen 3 1.2.2 Implantationsmethodik 5 1.3 Embryologie 6 1.3.1 Entwicklung des N. vagus 6 1.3.2 Entwicklung der Vagina carotica 8 1.4 Morphologie 8 1.4.1 Verlauf des N. X innerhalb der Vagina carotica 8 1.4.2 Relative Position des N. X in der Vagina carotica 10 1.4.3 Durchmesser und NQF des N. X 10 1.4.4 Vaskularisation des N. X 14 1.4.5 Qualitäten und Innervationsgebiete des N. vagus 16 2. Material und Methoden 17 2.1 Untersuchungsmaterial 17 2.2 Das Körperspendewesen des Instituts für Anatomie der Universität Leipzig 19 2.3 Übersicht über den Versuchsaufbau 19 2.3.1 Versuchsprotokoll 21 2.4 Ultraschalluntersuchung 22 2.4.1 Vorbereitungen des Schallgerätes 22 2.4.2 Darstellung des N. X 22 2.4.3 Digitale Dokumentation der NQF 26 2.4.4 Messung der NQF mittels der Software ImageJ 26 2.4.5 Bestimmung der morphologischen Zusammensetzung des N. X 30 2.4.6 Bestimmung der Position des N. X 30 2.4.7 Bestimmung der Nervenform 30 2.5 Makroskopische Präparation des N. X 33 2.6 Die Abformung mit Epineurium des N. X 37 2.6.1 Digitalisierung und Messung der NQF mittels der Software ImageJ 39 2.7 Die histologische Untersuchung des N. X 40 2.7.1 Probenentnahme 40 2.7.2 Fixierung mit Paraformaldehyd 40 2.7.3 Einbettung der Gewebeprobe 40 2.7.4 Herstellung der Gewebeschnitte 43 2.7.5 Färbung der histologischen Schnitte 44 2.7.6 Mikroskopische Untersuchung und digitale Analyse 46 2.8 Literaturrecherche 48 2.9 Statistische Auswertung 49 3. Ergebnisse 52 3.1 Ultraschall, Abformung, Histologie – Gibt es Unterschiede in der ermittelten NQF? 52 3.1.1 Unterschiede zwischen der NQF im Ultraschall und in der Abformung 56 3.1.2 Korrekturfaktor 57 3.1.3 Das Epineurium im Ultraschall – eine Messmethode Abseits der Norm 59 3.1.4 Welchen Einfluss hat die Fixierung des N. X mit Paraformaldehyd? 61 3.2 Morphologische Beobachtungen zum N. vagus 62 3.2.1 Ist die Querschnittsfläche des N. X abhängig von der Körperseite? 63 3.2.2 Ist der N. X eine kreisrunde Struktur? 64 3.2.3 Vaskularisation und Nervenfaszikel 67 3.2.4 Die Position des N. X im Halsbereich 68 3.2.5 Welchen Einfluss hat der BMI auf die Morphologie des N. X? 70 3.2.6 Die Veränderung des N. X im Alter 71 3.3 Wie variabel ist die NQF des N. X? 73 3.4 Die Konsistenz der Bestimmung der NQF – Intraklassen-Koeffizient 73 4. Diskussion 76 4.1 Warum treten signifikante Unterschiede zwischen Ultraschall, Abformung mit Epineurium und Histologie auf? 76 4.1.1 Welche Rolle hat das Epineurium in der Bestimmung der NQF? 77 4.1.2 Ist die Fehleinschätzung der NQF des N. X eine mögliche Ursache für Nebenwirkung bei der Stimulationstherapie? 77 4.1.3 Können Ultraschallmessungen zur NQF des N. X korrigiert werden? 79 4.1.4 Die NQF im Ultraschall in Referenz zur Literatur 79 4.1.5 Alternative bildgebende Verfahren zur Darstellung der NQF des N. X 81 4.2 Die NQF des N. X ist auf der rechten Körperseite größer als links 81 4.3 Einfluss des BMI auf die morphologische Zusammensetzung der NQF des N. X 83 4.4 Der Einfluss des Alters auf die NQF des N. X 84 5. Zusammenfassung 86 6. Literaturverzeichnis 88 7. Abbildungsverzeichnis 95 8. Tabellenverzeichnis 98 9. Anlagen 99 9.1 Ausführliche Informationen zu allen untersuchten Körperspendern 99 10. Eigenständigkeitserklärung 100 11. Lebenslauf 101 12. Publikation 102 13. Danksagung 103

I examined how one may establish directorial and choreographic proficiency in the contemporary society of American musical theatre. I did so by completing an examination of five personal observations in my craft. These observations included: (1) Directorship and choreography of Welcome to Vegas, an original jukebox musical; (2) Mentorship on Theatre UCF’s Nine as Assistant Director and Co-Choreographer; (3) Research on the methodologies of various directors and choreographers; (4) Directorship and choreography of Welcome to Broadway, an original jukebox musical; and (5) Assistant to the Program Director of Broadway Theatre Project. I evaluated parallels of my directing and choreography methodologies with those of noted directors and choreographers in the entertainment industry. These industry professionals include famed choreographer Ernest O. Flatt, Ron Field, Hermes Pan, Joe Layton, and Lee Theodore, acclaimed directors Harold Clurman, Dr. Louis E. Catron, and Jon Jory, and prolific director-choreographers Patricia Birch, Donald Saddler, Bob Avian, Bob Fosse, Tommy Tune, and Michael Bennett, as well as Professor Weaver. I have worked for people who believe that experience alone is enough to make one a successful director, choreographer, or director-choreographer. My experience working with and observations of professional directors, choreographers, and director-choreographers, however, has proven that it takes more than experience alone in order to succeed. I predicted the process of establishing my own directorial and choreographic proficiency will stem from a combination of inspiration, mentorship, trial and error, and experience.

Electrochemical conversion devices are a developing technology that prove to be a viable and more efficient alternative to current environmentally friendly generation devices. As such, constant research has been done in the last few decades to increase their applications and reliability. One of these systems, and the focus of this research, is the single cell Solid Oxide Fuel Cell (SOFC). These systems are a developing technology which main caveat is the need of high operating temperatures and costs. As such, most multidisciplinary research has been focused on researching materials and/or processes that help mitigate the costs or lower the operating temperature. The research presented in this paper focused on the manufacturing of a cubic stabilized zirconia (CSZ) electrolyte thin membrane for a single cell SOFC through tape casting. Thus, the process was divided into slurry preparation, tape casting, further processing, and analysis of samples. First the tape was produced reaching optimal viscosity (between 500 to 6000 cP) and minimizing impurities. Then, the slurry was poured into the doctor's blade with a 200 micrometers gap and allowed to dry. Samples were punched from the green tape with a diameter of 28 inches. Afterwards, these samples were pressed and sintered with a force of 218016 N and temperature of 1550 degrees celsius, respectively. These steps are done to maximize density and grain growth and minimize porosity. Lastly, the tape went further analysis and it was stated that further research should be done to determine this tape viability for stationary SOFC application.