published_or_final_version / Physics / Doctoral / Doctor of Philosophy

published_or_final_version / Physics / Doctoral / Doctor of Philosophy

Even since railway vehicles were invented, railway scientists and engineers have been putting a lot of effort in finding the solution to the fundamental conflict between vehicle stability in the lateral plane and vehicle's capability of negotiating curves. Many configurations of railway bogie vehicles have been proposed and applied to minimise the conflict. The purpose of the research project is i) to create new configurations that can decouple the basic conflict, ii) to investigate dynamic behaviour of the new configurations and iii) to conceive a new mechanism that can improve the dynamics of the new configurations. Three configurations of body-steered bogie vehicles have been set up in the research. The sufficient conditions for them to be capable of perfect steering have been derived. They are called perfect steering vehicles when they satisfy these sufficient conditions. Their curving ability, stability and ride performance have been investigated. To overcome the disadvantages of the perfect steering vehicles, the reconfigurable mechanism has been conceived. The improvement in the dynamic behaviour of the perfect steering vehicles with the reconfigurable mechanism has been demonstrated. A computer program has been developed to undertake the simulation. The steering capability of the perfect steering vehicles is much better than that of conventional bogie vehicles. There are two modes of instability in the perfect steering vehicles: low conicity instability and conventional instability in the perfect steering vehicle. The perfect steering vehicles can decouple the conflict between their conventional stability and curving. The improvement of stability and ride performance of the perfect steering vehicles is, however, limited by the low conicity instability. When the reconfigurable mechanism is applied, a body-steered bogie vehicle can become a perfect steering vehicle when on curves and can become a conventional bogie vehicle when in other circumstances. Low conicity instability can be eliminated when the reconfigurable mechanism is used. This class of vehicles possess the advantages of both conventional bogie vehicles and perfect steering vehicles, and thus, provide a very valuable solution for the fundamental conflicts between the stability and steering ability and between ride performance and stability of railway vehicles. The findings in this thesis have great significance in developing perfect steering vehicles.

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<p> This thesis summarizes theoretical results of two projects on the investigation of a novel organometallic polymer, the polyferrocenylsilanes(PFS). The study is carried out in collaboration with the experimental groups of Prof. Manners and Prof. Winnik at the Department of Chemistry of University of Toronto. </p> <p> In the first project, a rotational isomeric state (RIS) model is applied to study the configurational statistics of an ideal polyferrocenyldimethylsilane (PFDMS) chain: Fc[Fe(C5H4)2SiMe2]nH (Fe= Fe(C5H5)(C5H4)). The necessary conformation energies are derived from the molecular mechanics study of oligomeric (n=1,2) models for PFDMS reported by O'Hare et al.(J. Am. Chem. Soc. 1996, 118, 7578). In particular, pseudoatom and pseudobonds are introduced to describe the RIS chain of PFDMS, consistent with the special molecular geometry of the repeating ferrocene and organosilane units. The mean square unperturbed dimensions ((r^2)0, (R^2g)0), the characteristic ratios Cn(C∞) and the temperature coefficients dln (r^2)0/dT of PFDMS are calculated. The results show that an ideal PFDMS chain has a relatively low value of Coo and fast convergence of Cn to C∞ with increasing n, indicating a high static flexibility of this type of transition metal-containing polymer. The previously unknown Kuhn length of PFDMS is obtained based on the calculated C∞ </p> <p> In the second project, by taking PFS-b-PDMS/alkane as a model system, general phase behaviours of the self-assembled micelles in dilute crystalline-coil copolymer solutions (solvents are selective for the coil blocks) are investigated. Three types of aggregates - lamellar, rodlike and tubular micelles are studied based on the existing experimental observations. The computation results reveal three types of phase diagrams, namely, lamella-tube-rod phase diagrams with or without a triple point and lamella-rod phase diagrams. It is shown that lamella-tube-rod morphological transitions can be induced by changing the coil/crystalline block ratio or the temperature. Possible improvement of the theory and the current challenges of studying PFS-b-PDMS self-assembly in alkane solvents for both theories and experiments are discussed. </p> / Thesis / Master of Science (MSc)

This investigation examines a new concept in airliner configurations from an experimental aerodynamics point of view. The concept proposes mounting the fuselages at the tips of a low aspect ratio wing. The motivation for this configuration is to provide an increase in the number of passengers carried with no increase in span over conventional designs. An additional motivation is the change in the wake flow of the wing, due to the fuselages and vertical tails, which may reduce the effect of the trailing vortex on trailing aircraft. During this investigation, two models of different scales were used to measure the aerodynamic forces and moments of the inboard wing configuration. The tests were conducted in the Virginia Tech 6X6 ft. wind tunnel using a six-component strain gauge balance. The Reynolds number based on chord for the small model was 465,000 and for the large model was 1,225,000. For reference, tests were also conducted with a plain wing having the same span as the full configuration. The L/D values found for this non-optimized configuration were modest compared to those for conventional transports. The vertical tails were shown to act as winglets, reducing drag and increasing L/D. These results suggest areas for substantial improvement in aerodynamic performance of the configuration. / Master of Science

The behavior of all cyber-systems in a data center or an enterprise system largely depends on their configuration which describes the resource allocations to achieve the desired goal under certain constraints. Poorly configured systems become a bottleneck for satisfying the desired goal and add to unnecessary overheads such as under-utilization, loss of functionality, poor performance, economic burden, energy consumption, etc. Ill-effects related to system misconfiguration are well documented with quantifiable metrics showing their impact on the economy, security incidents, service recovery time, loss of confidence, social impact, etc. However, configuration modeling and diagnosis of data center systems is challenging because of the complexities of subsystem interactions and the many (known and unknown) parameters that influence the behavior of the system. Further, a configuration is not a static object - but a dynamically evolving entity that requires changes (either automatically or manually) to address the evolving state of the system. We believe that a well-defined approach for configuration modeling is important as it paves a path to keeps the systems functioning properly in spite of the dynamic changes to configurations. Proper configuration of large systems is difficult because interdependencies between various configuration parameters and their impact on performance or other attributes of the system are generally poorly understood. Consequently, properly configuring a system or a subsystem/device within it is largely dependent on expert knowledge developed over time. In this work, we attempt to formalize some approaches to configuration management, particularly in the area of network devices and Cloud/Edge storage solutions. In particular, we address the following aspects in this study: (i) impact of resource allocation on the energy-performance trade-off, with a network topology as an example, (ii) prediction of performance of a complex IT system (such as Cloud Storage Gateway or an Edge Storage Infrastructure) under given conditions, (iii) development of a data-driven method to efficiently configure (allocate resources) to satisfy required QoS levels under constrained conditions, and (iv) a model to express configuration health as a quantifiable metric. With increasing stress on data center networks and correspondingly increasing energy consumption, we propose a method to simultaneously configure routing and energy management related parameters to ensure that the network can both avoid congestion and maximize opportunities for putting network ports in lower power mode. We also study the problem of choosing hardware and resource settings to minimize cost and achieve a given level of performance. Because of the complexity of the problem, we explored machine learning (ML) based techniques. For concreteness, we studied the problem in the context of configuring a cloud storage gateway (CSG) that involves such parameters as speed and number of CPU cores, memory size, and bandwidth, IO size and bandwidth, data and metadata cache size, etc. It turns out that it is very difficult to obtain a reliable ML model for this, and instead our approach is to use a model for the opposite problem (predicting optimal cost or performance for a given configuration) along with meta-heuristic such as genetic algorithm or simulated annealing. We show that an intelligent grouping of configuration parameters based on expected relationships between parameters and relative importance of the groups substantially outperforms the standard meta-heuristic based exploration of the state space. Our work in the configuration space revealed a dominant void, we noticed the absence of common vocabulary or quantifiable metric to clearly and unambiguously express the quality of the configuration. In our diagnosis work, we designed a model to define a simple, reproducible, and verifiable metric that allows users to express the quality of device configuration as a health score. Our configuration diagnosis model expresses the strength (or weakness) of a configuration as a ‘Health Index’, a vector of dimensions like performance, availability, and security. This health index will help users/administrators to identify the weak configuration objects and take remedial actions to rectify the configurations. Our work on Configuration Modeling and Diagnosis addresses an important topic in this vast chaotic space. Using industry-driven problems and empirical data, we bring in some meaning to this complex problem. Though our research and experiments involved specific devices (network topology, Cloud Gateway, Edge Storage, network routers, etc.) - we show that the proposed solution is generic and can be adequately applied to other domains. We hope that this work will encourage other communities to explore new 'configuration' challenges in a rapidly changing IT landscape. / Computer and Information Science

<p>The world of systems engineering methods is changing as rigorous ‘off-the-shelf’ systems engineering methods become more popular. One example of such a systems engineering method is Rational Unified Process. In order to cover all phases in a software development process, and a wide range of project-types, such methods need to be of an impressive size. Thus, the need for configuring such methods in a structured way is increasing accordingly. In this thesis, method configuration is considered as a particular kind of method engineering that focuses on tailoring a standard systems engineering method. We propose a meta-method for method configuration based on two fundamental values: standard systems engineering method’s rationality and reuse. A conceptual framework is designed, introducing the concepts Configuration Package and Configuration Template. A Configuration Package is a pre-made ideal method configuration suitable for a delimited characteristic of a (type of) software artifact, or a (type of) software development project, or a combination thereof. Configuration Templates with different characteristics are built combining a selection of Configuration Packages and used as a base for a situational method. The aim of the proposed meta-method is to ease the burden of configuring the standard systems engineering method in order to reach an appropriate situational method.</p>

Knowledge about the configuration of an environment is used preferentially when navigating through an urban environment (Penn, 2003). However, it the locus of this effect is poorly understood. One possibility is that the local environment, such as the shape of an intersection, is sufficient to determine route choice in the context of the global configuration of an environment (Meilinger, Franz, & Bülthoff, in press; Meilinger, Knauff & Bülthoff, 2008). Two experiments were performed to investigate this hypothesis using two novel virtual environments, one with a simplistic configuration, and one with a more complicated configuration. In Experiment 1, peripheral vision was either available or constrained throughout a wayfinding task. A significant influence of global configuration information with minimal use of local configuration account was found. In Experiment 2, central vision was either limited to the local intersection or unconstrained. Again, a strong effect of configuration was found, with limited evidence for the use of local visual information. The results support a synergistic mechanism of wayfinding where the environmental configuration is used to inform existing knowledge about the environment.

Knowledge about the configuration of an environment is used preferentially when navigating through an urban environment (Penn, 2003). However, it the locus of this effect is poorly understood. One possibility is that the local environment, such as the shape of an intersection, is sufficient to determine route choice in the context of the global configuration of an environment (Meilinger, Franz, & Bülthoff, in press; Meilinger, Knauff & Bülthoff, 2008). Two experiments were performed to investigate this hypothesis using two novel virtual environments, one with a simplistic configuration, and one with a more complicated configuration. In Experiment 1, peripheral vision was either available or constrained throughout a wayfinding task. A significant influence of global configuration information with minimal use of local configuration account was found. In Experiment 2, central vision was either limited to the local intersection or unconstrained. Again, a strong effect of configuration was found, with limited evidence for the use of local visual information. The results support a synergistic mechanism of wayfinding where the environmental configuration is used to inform existing knowledge about the environment.