Bedding angle is a fundamental property of a particulate system that describes the resistance to rolling motion of a single grain. Mean trends of the bedding angle of sand have been described in the literature. This research expands upon the work to date by investigating the distribution of bedding angle for sands. Experimental measurements of bedding angle distributions are made for eight sands. Additionally, a theoretical description of the variability of bedding angle as a function of random grain size is developed and implemented numerically. The shape of the bedding angle distribution is found to be simulated well from the numerical simulations; the mean value of bedding angle is best predicted from particle roundness and empirical relationships. Together, these procedures provide a means of predicting the complete distribution of bedding angle for any given sand.

This thesis examines the time resolved heat transfer to drops rolling or sliding along inclined, subcritical heated non-wetting surfaces. Results were experimentally obtained using IR imaging for a smooth hydrophobic surface and post as well as rib structured superhydrophobic surfaces of varying solid fraction (f_s = 0.06 - 0.5). Tests were performed at varying inclination angle (α = 10, 15, 20, and 25°), drop volume (12, 20, 30, and 40 μL), and surface temperature (T_w = 50, 65, and 80 °C). Rib structured superhydrophobic surfaces were explored for drops moving parallel and perpendicular to the rib structures. The findings indicate that transient heat transfer is predominantly influenced by the surface’s solid fraction and the velocity of the drops, with a secondary dependence on drop volume. Surfaces with low solid fraction show a significant reduction in initial heating rate (up to 80% reduction) to the drop, when compared with that of the smooth surface. The drop velocity depends on surface solid fraction and inclination angle, with drop volume exerting smaller influence. Rib structured surfaces impact heat transfer by enhancing heat transfer rate for drops that move along the rib direction compared with drops that move perpendicular to the ribs. The difference is likely due to increased drop velocity that exists for the parallel rib orientation.

No description available.

Rolling resistance is a considerable factor in energy consumption for all rolling vehicles. A proper understanding of the phenomenon is an important aspect in order to design energy efficient vehicles. The literature study focus on three main aspects to describe the phenomenon; tire material and its properties, tire components and their effect on tire behavior concerning rolling resistance, and finally the effect of operating conditions on tire behaviour is considered. 58 resources have been studied and summarised in order to make a comprehensive literature study of the rolling resistance phenomenon.

<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> A review of movie projection principles and techniques as applied to conventional projectors and a description of general features, mechanism and film movement of the Rolling Loop Projector are presented.</p> <p> The characteristics of a film loop under static conditions with coplanar clamping planes are investigated in terms of loop shape, supporting forces and bending moments. An extension of this analysis is applicable to the case when the loop is fixed on a curved surface.</p> <p> The motion of a loop in the projector is simulated as it grows and rolls on a flat surface and a numerical technique is employed to find the point paths and the velocity and acceleration vectors of these points on the loop at various instants in a projection cycle.</p> <p> Some design criteria are derived from an examination of the results, and these are presented.</p> / Thesis / Master of Engineering (MEngr)

Das Thema Klimaschutz und daraus folgend auch beispielsweise eine Einsparung fossiler Brennstoffe ist ein großer Forschungsschwerpunkt, wobei vor allem im Automobil und Transportbereich die Substitution der klassischen Materialien wie Stahl durch Leichtbauwerkstoffe, wie Aluminium- und Magnesiumlegierungen, von Interesse ist. Aufgrund der hexagonalen Kristallstruktur des Magnesiums, bringt die Verarbeitung nahezu einzigartigen Herausforderungen mit sich. Dabei wird durch das Hinzulegieren von Calcium, beispielsweise in ZAX-Legierungen – mit Zink, Aluminium und Calcium – die Umformbarkeit bei Raumtemperatur durch eine schwächer ausprägte Textur mit einem Basalpolsplit verbessert. [2] Um die ersetzten Bauteile in den Fahrzeugen zu verbinden, wird beispielsweise das Schweißen verwendet. Dieses Verfahren profitiert allerdings von einer artgleichen Schweißung, wo Grundwerkstoff und Schweißdraht ähnliche Zusammensetzungen besitzen. Zum Schweißen, und auch für eine drahtbasierte additive Fertigung, sind Drähte mit ca. 1 - 1,6 mm Durchmesser nötig, die ausschließlich über einen Ziehprozess erreicht werden können. Für die Herstellung der Vorprodukte von Drähten für das Ziehen rücken die Verfahren Strangpressen und Kaliberwalzen in den Fokus. Für letzteres fehlen allerdings grundsätzliche Erfahrungswerte und Forschungsergebnisse, die aber für eine Anwendung und Einführung in die Wirtschaft unabdingbar sind.

The topic of climate protection and, for example, the resulting need for a reduction in the use of fossil fuels, is a major focus of research. Particular interest is taken in the substitution of traditional metals such as steel with lightweight materials like aluminium and magnesium alloys in the automotive and generally in the transportation sector. Due to the hexagonal crystal structure of magnesium, the processing of its alloys contains some almost unique challenges. By alloying calcium, for example in ZAX-alloys – containing zinc, aluminium and calcium – the formability at room temperature is improved through a less pronounced texture with a basal pole split. [2] To join the replaced components in the cars, welding can be used. This process profits from procedure where base and weld material are of similar compositions. For welding, and for wire-based additive manufacturing too, wires with a diameter of approximately 1 – 1.6 mm are required, which can only be produced through drawing. The production for the preliminary products can be achieved through either extrusion or groove rolling. For the latter there is a lack of fundamental empirical experience and research results that are required for a successful application and implementation in the industry. The extrusion process is more established but groove rolling has the potential to produce larger quantities in the same time and has the added advantage of a greater grain refinement.

RNA-cleaving DNAzymes (RCDs) are a class of functional nucleic acids that can bind various targets ranging in size from small molecules to large proteins, which results in activation of cleavage activity. The activation of RCDs results in the cleavage of a ribonucleotide site in an otherwise all-DNA substrate, leading to two cleavage fragments. In this work, a previously identified DNAzyme that binds to a protein biomarker endogenous to Helicobacter pylori (J99) crude extracellular matrix was evaluated for coupling to an isothermal amplification method termed rolling circle amplification (RCA) as a way to improve the originally reported detection limit. Three RCD constructs were designed with the goal of generating a cleavage fragment that could act as a primer to initiate RCA. The first method used the original HP DNAzyme, which liberated a short cleavage fragment that could be used as a primer. However, the primer fragment was rapidly digested by the bacterial matrix, preventing RCA. A second method evaluated use of a circularized substrate and separate RCD to generate a primer, however this system was not capable of generating a cleavage fragment. A final method redesigned the original RCD to move the substrate region from the 3’ to the 5’ end of the RCD, causing the longer RCD-containing fragment to be the primer for RCA. In this case, target-triggered cleavage was observed and the resulting primer was sufficiently resistant to digestion to allow its use as a primer for RCA. Preliminary characterization of the rearranged RCD showed that it retained selectivity similar to the original RCD, but that the cleavage rate was slower. In addition, the RCA based reaction, while successful, did not produce improved detection sensitivity relative to unamplified assays. Methods to further improve RCA performance are discussed for future work. / Thesis / Master of Science (MSc)

No description available.