In turbomachinery, extra excitation forces may result from non-idealised operation conditions and may sometime cause excessive vibrations and unsteady rotor motions. The goal of this thesis is to investigate the effects of such excitation forces. The extra excitation forces investigated here are the Thomas/Alford force due to the blade tip clearance change, the steam excitation force caused by the variation of inlet steam speed and state blade trailing wake and the dominant magnetic pull force due to dynamic eccentricity of the rotor. The main research results in this thesis include: (1) The modelling of the Jeffcott rotor and the 600MW steam-turbine generator. The used in-house ??transient?? program can only handle the circular short bearings with the modified short bearing method while the simulated steam-turbine should be supported by tilting pad bearings. The first critical speeds of systems supported by tilting pad bearings are more approaching to the lab data for all four rotor models while that of journal bearing supported systems are normally lower than the real operating critical speed. (2) Applying three sorts of excitation forces into the single-stage rotor-bearing system. The numerical simulation shows that for the model with each single excitation force, all of these three forces need to reach some limit to force the system into the unsteady state. For all the three forces, higher limits are needed if the machine runs at lower running speeds. Furthermore, unbalance loading also can influence the system behaviours. As the unbalance increases, the system will still stay steady while the spectra become noisier, though the amplitude still low comparing to harmonics. (3) Combing three types of excitation forces into the assembled rotor-bearing system. The numerical simulation shows that the assembled system presents similar vibration responses as the single stage rotor-bearing system. Furthermore, these three forces cannot cancel each other and the combination will unstabilise the system. Meanwhile, the influence of the dominant magnetic pull force is less than other two forces.

In turbomachinery, extra excitation forces may result from non-idealised operation conditions and may sometime cause excessive vibrations and unsteady rotor motions. The goal of this thesis is to investigate the effects of such excitation forces. The extra excitation forces investigated here are the Thomas/Alford force due to the blade tip clearance change, the steam excitation force caused by the variation of inlet steam speed and state blade trailing wake and the dominant magnetic pull force due to dynamic eccentricity of the rotor. The main research results in this thesis include: (1) The modelling of the Jeffcott rotor and the 600MW steam-turbine generator. The used in-house ??transient?? program can only handle the circular short bearings with the modified short bearing method while the simulated steam-turbine should be supported by tilting pad bearings. The first critical speeds of systems supported by tilting pad bearings are more approaching to the lab data for all four rotor models while that of journal bearing supported systems are normally lower than the real operating critical speed. (2) Applying three sorts of excitation forces into the single-stage rotor-bearing system. The numerical simulation shows that for the model with each single excitation force, all of these three forces need to reach some limit to force the system into the unsteady state. For all the three forces, higher limits are needed if the machine runs at lower running speeds. Furthermore, unbalance loading also can influence the system behaviours. As the unbalance increases, the system will still stay steady while the spectra become noisier, though the amplitude still low comparing to harmonics. (3) Combing three types of excitation forces into the assembled rotor-bearing system. The numerical simulation shows that the assembled system presents similar vibration responses as the single stage rotor-bearing system. Furthermore, these three forces cannot cancel each other and the combination will unstabilise the system. Meanwhile, the influence of the dominant magnetic pull force is less than other two forces.

The process of coset enumeration has become a significant factor in group theoretical investigations since the advent of modern computing power, but in some respects the process is still not well understood. This thesis investigates some features of coset enumeration, working mainly with the group F(2,7). Chapter 1 describes the characteristics of coset enumeration and algorithms used for it. A worked example of the method is provided. Chapter 2 discusses some features which would be desirable in computer programs for use in investigating the coset enumeration process itself, and reviews the Havas/Alford program which to date best meets the requirements. Chapter 3 deals with the use of coset ammeration in proofs, either in its own right or as a basis for other workings. An example of one attempt to obtain a proof by coset enumeration is given. Chapter 4 reviews techniques designed to reduce the length of coset enumerations and proposes the 'equality list' technique as a way to reduce enumeration length for some groups. Extra insights obtainable using the equality list method are also discussed. Chapter 5 summarises the factors by which the success of different coset enumerations can be compared and proposes an algorithm for making systematic comparisons among enumerations. Chapter 6 reports five coset enumerations, obtained manually by three main methods on the group F(2,7). All these enumerations were shorter than is so far obtainable by machine and one is shorter than other known hand enumerations. The enumerations were compared by applying the process developed in Chapter 5. Chapter 7 presents a shorter proof of the cyclicity of the group F(2,7) than was hitherto available. The proof derives from the workings for one of the coset enumerations described in Chapter 6. There are eight appendices and an annotated bibliography. The appendices contain, inter alia, edited correspondence between well-known coset-enumerators, a guide to the Havas/Alford program, further details on the equality list method and listings of various enumerations.

Indiana University-Purdue University Indianapolis (IUPUI) / Nonprofit organizations that “speak for, act for, and look after the interests of their constituents when they interact with government are, by any definition of political science, interest groups.” Indiana’s recent implementation of the Healthy Indiana Plan 2.0 (HIP 2.0) under the Affordable Care Act (ACA) opened a window of opportunity to closely examine the role of nonprofits in shaping the implementation of health care policy. Existing literature on health and human service nonprofit organizations did not examine in depth the role and influence of nonprofits as interest groups in the implementation of public policy. This study examines a deeper research question that was not given adequate attention under existing studies with a special focus on the health care policy field: whose interest do nonprofit organizations advance when they attempt to influence the implementation of public policy? To answer this question, it is critical to understand why nonprofits engage in the public policy process (motivation and values), the policy actions that nonprofits make during the implementation of the policy (how?), and the method by which nonprofits address or mitigate conflicts and contradictions between organizational interest and constituents’ interest (whose interest do they advance?). The main contribution of this study is that it sheds light on the implementation of the largest extension of domestic social welfare policy since the “War on Poverty” using Robert Alford’s theory of interest groups to examine the role of nonprofit organizations during the implementation of HIP 2.0 in Indiana. Given the complexity of the policy process, this study utilizes a qualitative methods approach to complement existing quantitative findings. Finally, this study provides a deeper examination of the relationships between nonprofits as actors within a policy field, accounts for the complexity of the policy and political environment, analyzes whether or not dominant interest groups truly advance the interest of their constituents, and provides additional insights into how nonprofits mitigate and prioritize competing interests.