This thesis concerns the computation of bed adjustments of equilibrium in alluvial meandering streams. It is assumed that the channel centerlines follow sine-generated curves, the banks are rigid, and the steady-state flow is turbulent and sub-critical. The flow width is assumed to remain constant in the streamwise direction, and the flow width-to-depth ratio is large (>=15, say). The bed material is cohesionless and homogeneous. The purpose of the thesis is to develop and test a numerical model for the computation of bed development, given the aforementioned idealized conditions. The model comprises: 1- an initial bed topography generator, to generate the bed at time t = 0 of the calculations; 2- the vertically-averaged hydrodynamic model of Zhang (2007) to calculate the flow fields; and 3- a sediment transport model to relate the bed deformation to the flow. Both the initial bed topography generator (expression of the deformed bed surface) and the numerical sediment transport model based on the sediment transport continuity equation are original and developed entirely by the author. The resulting model is computationally very efficient. In contrast to previous works on the theoretical determination of bed deformation, the beds at the beginning of the calculations may represent any stage of the development process, and not necessarily the initial flat bed. The bed deformation was tested for several test cases, devised on the basis of laboratory runs available in the literature. These include Run ME-2 by Hasegawa (1983) in a 30-degree-channel, Run 3 by Binns (2006) in a 70-degree-channel and the run by Termini (1996) in a 110-degree-channel. The erosion/deposition patterns of the computed equilibrium bed topographies were found to be in reasonable agreement with their measured counterparts. However, as evidenced by the difference plots included in this thesis, in detail there are substantial differences between the computed and measured equilibrium beds, especially in the regions near the banks. As a by-product of the present thesis, the functions representing the parameters required by the hydrodynamic model of Zhang (2007) were also evaluated. In particular, the present results suggest that the coefficient Alpha-q appearing in the expression of the local friction factor (used in the flow model of Zhang 2007) depends on the flow width-to-depth ratio and bed roughness to a much larger extent than previously thought. Considering this, a generalization of the expression of Alpha-q due to El-Tahawy (2004) (and adopted by Zhang 2007 in her model) is proposed. Future work should be carried out to address the application of the present model to real river conditions, including generalizations to irregular meandering plan shapes, unsteady-state flows and non-homogenous bed materials. / Thesis (Ph.D, Civil Engineering) -- Queen's University, 2008-12-19 21:32:06.645

The main objective of this thesis work was to gain understanding of the layer properties and polymer structures that were able to aid lubrication in aqueous media. To this end, three types of polyelectrolytes: a diblock copolymer, a train-of-brushes and two brush-with-anchor mucins have been utilized. Their lubrication ability in the boundary lubrication regime has been examined by Atomic Force Microscopy with colloidal probe. The interfacial behavior of the thermoresponsive diblock copolymer, PIPOZ60-b-PAMPTAM17,on silica was studied in the temperature interval 25-50 ˚C. The main finding is that adsorption hysteresis, due to the presence of trapped states, is important when the adsorbed layers are in contact with a dilute polymer solution. The importance of trapped states was also demonstrated in the measured friction forces, where significantly lower friction forces, at a given temperature, were encountered on cooling than on the preceding heating stage, which was attributed to increased adsorbed amount. On the heating stage the friction force decreased with increasing temperature despite the worsening of the solvent condition, and the opposite trend was observed when using pre-adsorbed layers (constant adsorbed amount) as a consequence of increased segment-segment attraction. The second part of the studies was devoted to the interfacial properties of mucins on PMMA. The strong affinity provided by the anchoring group of C-PSLex and C-P55 together with their more extended layer structure contribute to the superior lubrication of PMMA compared to BSM up to pressures of 8-9 MPa. This is a result of minor bridging and lateral motion of molecules along the surface during shearing. We further studied the influence of glycosylation on interfacial properties of mucin by utilizing the highly purified mucins, C-P55 and C-PSLex. Our data suggest that the longer and more branched carbohydrate side chains on C-PSLex provide lower interpenetration and better hydration lubrication at low loads compared to the shorter carbohydrate chains on C-P55. However, the longer carbohydrates appear to counteract disentanglement less efficiently, giving rise to a higher friction force at high loads. / <p>QC 20170407</p>

Efficient algorithms exist for finding optimal strategies in extensive-form games. However human scale problems, such as poker, are typically so large that computation of these strategies remain infeasible with current technology. State space abstraction techniques allow us to derive a smaller abstract game, in which an optimal strategy can be computed and then used in the real game. This thesis introduces state of the art abstraction techniques. Most of these techniques do not deal with public information. We present a new automatic public state space abstraction technique. We examine the quality of this technique in the domain of poker. Our experimental results show that the new technique brings significant performance improvement. Powered by TCPDF (www.tcpdf.org)

Ausgehend von einer kritischen Betrachtung der bekannten Meßverfahren zur Untersuchung von Halbleiteroberflächen wurde der Feldeffekt mit Sperrstrommessungen derart gekoppelt, dass gleichzeitig an dem Teil der Probe, der auf der Rückseite von einem in Sperr-Richtung vorgespannten pn-Übergang bedeckt ist, der Oberflächenleitwert und der Sperrstrom des pn-Übergangs gemessen werden. Der Sinn dieser Kopplung ist es, die Termanalyse gegenüber den bekannten Methoden zu verbessern. Die vorgenommene Erweiterung der Feldeffektuntersuchungen auf den stationären Nichtgleichgewichtzustand ermöglicht die direkte Messung der Aufspaltung des Ferminiveaus und damit die Bestimmung der Oberflächenrekombinationsgeschwindigkeit allein durch Oberflächenleitwertmessungen. Auch mit der Erweiterung der Sperrstromuntersuchungen, durch Messung der Sperrstromänderung bei Belichtung, ist es möglich, die Oberflächenrekombinationsgeschwindigkeit zu messen. Mit der entwickelten Apparatur wurde durch gleichzeitige Messung der Sperrstromänderungen und des Oberflächenleitwertes eine Verbreiterung der Sperrstromkurven verbunden mit einer Verschiebung des Sperrstrommaximums gegen das Leitwertminimum an CP-4-geätzten Germanium-Oberflächen beobachtet. Die Deutung dieser Erscheinung ermöglicht eine eindeutige Bestimmung des Energieniveaus des Rekombinationsterms und weist darauf hin, dass die Übergangswahrscheinlichkeiten des Rekombinationsterms keine Daten der Terme allein, sondern Daten der Terme und des Zustands der Oberfläche sind. Für die untersuchten, in CP-4-geätzten Oberflächen wurde die bei den Channeluntersuchungen gemachte Voraussetzung bestätigt, dass für die Terme in der oberen Hälfte der verbotenen Zone Cp/Cn > e2(Et – Ei)/kT gilt. Mit der entwickelten Methode zur Messung des Oberflächenleitwertes mit einem hochfrequenten Wechselstrom werden Verwehungseffekte der Ladungsträger vermieden. Durch die Parallelschaltung des ohmschen und des kapazitiven Leitwertes zwischen Inversionsschicht und Volumen werden weiterhin die Schwierigkeiten der Kontaktierung der Inversionsschicht umgangen. Einen solchen Kontakt herzustellen, ist besonders schwierig bei Halbleitern mit niedriger Intrinsic-Konzentration. Bei Silizium wurde diese Methode mit Erfolg angewendet. / Starting with a critical consideration of the well-established measurement procedures for the investigation of semiconductor surfaces, the field effect and the measurement of the reverse current have were linked in such a manner that the surface conductance and the reverse current could be measured simultaneously at that part of the specimen which was covered on the back side by a biased pn-junction. The use of this link-up is the improvement of the analysis of surface terms in comparison with the known methods. The implemented extension of the field effect measurements to the stationary non-equilibrium state allows the direct measurement of the split up of the Fermi level and in this way the determination of the surface recombination velocity by measurements of the surface conductance solely. Also with an extension of the measurements of the reverse current, by measuring the change in reverse current due to illumination, it is possible to determine the surface recombination velocity. By a simultaneous measurement of the changes in reverse current and the surface conductance with the developed apparatus it could be observed a broadening of the reverse current curve in conjunction with a shift of the reverse current maximum versus the conductance minimum on germanium surfaces etched with CP-4.The interpretation of this effect allows an unique determination of the energy level of the recombination term and points to the fact that the transient probabilities of the recombination term are not data of the term itself but data of the term and the state of the surface. By the investigations of the surfaces etched in CP-4, the requirements have been confirmed which were made in channel investigations that for the terms in the upper half of the forbidden zone it is Cp/Cn >e2(Et – Ei)/kT. With the developed method for the measurement of the surface conductance using a high frequency alternating current sweep out effects of the charge carriers can be avoided. Furthermore, by the shunt circuit of the ohmic and the capacitive conductance between the inversion layer and the bulk the difficulties in contacting the inversion layer will be avoided. The production of such a contact is especially difficult for semiconductors with a low intrinsic concentration. This method has been successfully applied to silicon.

This thesis has the dual purpose of raising awareness of the importance of the mixing protocol on the end products of polyelectrolyte-oppositely charged surfactant systems, and to contribute to a better understanding of the properties of bottle-brush polyelectrolytes when adsorbed onto interfaces. In the first part of this thesis work, the effects of the mixing protocol and the mixing procedure on formed polyelectrolyte-oppositely charged surfactant aggregates were investigated. It was shown that the initial properties of the aggregates were highly dependent on the mixing parameters, and that the difference between the resulting aggregates persisted for long periods of time. The second part of the studies was devoted to the surface properties of a series of bottle-brush polyelectrolytes made of charged segments and segments bearing poly(ethylene oxide) side chains; particular attention was paid to the effect of side chain to charge density ratio of the polyelectrolytes. It was shown that the adsorbed mass of the polyelectrolytes, and the corresponding number of poly(ethylene oxide) bearing segments at the interface, went through a maximum as the charge density of the polyelectrolyte was increased. Also, it was found that bottle-brush polyelectrolyte layers were desorbed quite easily when subjected to salt solutions. This observation was rationalized by the unfavourable excluded volume interactions between the side chains and the entropic penalty of confining them at an interface, which weaken the strength of the binding of the polyelectrolytes to the interface. However, it was shown that the same side chains effectively protect the adsorbed layer against desorption when the layer is exposed to solutions containing an oppositely charged surfactant. Investigation of the lubrication properties of the bottle-brush polyelectrolytes in an asymmetric (mica-silica) system also related the observed favourable frictional properties to the protective nature of the side chains. The decisive factor for achieving very low coefficients of friction was found to be the concentration of the side chains in the gap between the surfaces. Interestingly, it was shown that a brush-like conformation of the bottle-brush polyelectrolyte at the interface has little effect on achieving favourable lubrication properties. However, a brush-like conformation is vital for the resilience of the adsorbed layer against the competitive adsorption of species with a higher surface affinity. / QC 20100830

Die Vorhersage und Identifizierung von stabilen und metastabilen Stoffen ist ein wichtiges Instrument zur Bildung neuer Werkstoffe. Vor diesem Hintergrund gewinnen Konzepte einer rationalen Synthese zunehmend an Bedeutung: Die Berechnung der elektrochemischen Spannungsreihe für Festkörper und flüchtiger Phasen ermöglicht eine einfache Vorhersage der Reaktionswege. Unter Verwendung der elektrochemischen Spannungsreihe der Systeme As / P / O und As / P / X (X = F, Cl, Br, I) kann die Bildung von Elementallotropen über die Oxid- und Halogenidverbindungen in thermitischen Reaktionen abgeleitet werden. Die Analyse der Phasenbildung wird mit einer In-situ-Methode zur Überwachung von Gasphasenreaktionen gewonnen. Im Verlauf der Phasenformationen - zur Erreichung des Fest-Gas-Gleichgewichtes - können charakteristische Effekte beobachtet werden. / The prediction and identification of stable and metastable substances is an important tool to achieve new materials. With this objective in mind, concepts of a rational synthesis are gaining increasing importance: calculation of electromotive series of solids allows easy prediction of reaction pathways. Using the electromotive series of systems As/P/O and As/P/X (X = F, Cl, Br, I) the formation of element allotropes via the oxide and halide compounds in thermite type reactions can be deduced. The analysis of phase formation is acquired with an in situ method for monitoring gas-phase reactions. In the course of phase formations - attaining the solid-gas equilibrium state - characteristic effects can be observed.

Die Vorhersage und Identifizierung von stabilen und metastabilen Stoffen ist ein wichtiges Instrument zur Bildung neuer Werkstoffe. Vor diesem Hintergrund gewinnen Konzepte einer rationalen Synthese zunehmend an Bedeutung: Die Berechnung der elektrochemischen Spannungsreihe für Festkörper und flüchtiger Phasen ermöglicht eine einfache Vorhersage der Reaktionswege. Unter Verwendung der elektrochemischen Spannungsreihe der Systeme As / P / O und As / P / X (X = F, Cl, Br, I) kann die Bildung von Elementallotropen über die Oxid- und Halogenidverbindungen in thermitischen Reaktionen abgeleitet werden. Die Analyse der Phasenbildung wird mit einer In-situ-Methode zur Überwachung von Gasphasenreaktionen gewonnen. Im Verlauf der Phasenformationen - zur Erreichung des Fest-Gas-Gleichgewichtes - können charakteristische Effekte beobachtet werden. / The prediction and identification of stable and metastable substances is an important tool to achieve new materials. With this objective in mind, concepts of a rational synthesis are gaining increasing importance: calculation of electromotive series of solids allows easy prediction of reaction pathways. Using the electromotive series of systems As/P/O and As/P/X (X = F, Cl, Br, I) the formation of element allotropes via the oxide and halide compounds in thermite type reactions can be deduced. The analysis of phase formation is acquired with an in situ method for monitoring gas-phase reactions. In the course of phase formations - attaining the solid-gas equilibrium state - characteristic effects can be observed.

The aim of this thesis is to calculate the stiffness and damping coefficients for radial hydrodynamic bearings. Cylindrical and lemon hydrodynamic bearings are considered. The solution to this problem mainly depends on the hydrodynamic pressure in the bearing. The numerical solution of the Reynolds equation is used to calculate the pressure. The effect of variable viscosity and density of the lubricant due to temperature changes is considered. The static equilibrium position of the journal centre is also solved. The stiffness and damping coefficients are determined using small amplitude journal motions about the equilibrium position. Three methods for determining these coefficients are presented. The outcome of this thesis is an algorithm for the calculation of stiffness and damping coefficients for cylindrical and lemon bearings. Results for lemon bearings are presented and comparison with the commercial software DynRot BR is made. The benefit of this thesis is the creation of an algorithm for the calculation of journal centre equilibrium position, a new way of incorporating the temperature changes in the viscosity and the density of the lubricant, and the modification of a method for calculating stiffness and damping coefficients based on experimental analogy.