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.

Since the invention of the atomic force microscope (AFM), this technology has had profound implications in the study of material science and molecular biology. The ability to visualize and perform quantitative analysis of the nanoscale properties of surfaces has provided great insights into these nanoscale landscapes. The present dissertation manuscript exploits this technology for the measurement of charge transport through molecular films and the development of combinatorial force microscopy. Firstly, this work probed, for the first time, charge transport through molecular films derived from diazonium salts grafted to carbon electrodes using conductive atomic force microscopy. We found the charge transport properties of a molecular junction are dependent upon the chemical structure of the molecular film. We also investigated the effect of molecular film compression and deformation has on charge transport. In this, we observed increases in current densities associated with increases in applied load to the molecular film. Furthering these initial findings, PPF/NAB/Cu molecular junctions were fabricated having junction sizes ranging between micro-scale and nanoscale. The charge transport experiments reveal an agreement of electron transport properties between the metal deposited PPF/NAB/Cu junction and a PPF/NAB/Cu AFM tip junction at an applied load of approximately 60nN. This form of molecular layer charge transport control may potentially open new horizons for integration of molecular films into the microelectronics industry. This dissertation manuscript also describes the development of the quantitative interrogation opposing chemical libraries involved in combinatorial inverted atomic force microscopy. Tipless cantilevers were patterned with chemically modified nanorods. These modified nanorods were then used as chemical identifiers during a combinatorial force microscopy experiment and for the first time 16 interactions were monitored within one experiment in a continuous medium. Thus, providing excellent for the validation that combi-AFM is a truly quantitative high-throughput technology.

<p>This research describes the development of a state-of-the-art atomic force microscope (AFM) for improved force spectroscopy. Although the AFM has been used extensively in this field of research, the performance of the instrument has been limited by inefficient operation techniques, incorrect experimental assumptions, and inadequate controller design. This research focuses on overcoming these deficiencies by providing precise control over the instrument for specialized research in a manner that is conducive to the natural science researcher.</p><p>To facilitate this research, a custom, multi-axis AFM system was constructed. The instrument was designed primarily for AFM-based force spectroscopy and as a result a substantial amount of research focused on the development of a wide variety of approach/retraction methods for the instrument. Defining research in this area included the development of methods to minimize potentially damaging compressive forces, form polymer bridges at different tip-sample gap widths, produce clean, deconvoluted force-extension curves, and limit single molecule force spectroscopy pulling geometry errors. In an effort to increase the efficiency of the instrument, the programs developed during this research were fully automated, allowing autonomous operation of the instrument for long periods of time. To compliment the data collection programs, both manual and automated analysis programs with force-volume imaging capabilities were also developed.</p><p>By studying the AFM from a dynamic systems, measurements, and controls approach, the resulting controllers were tailored to meet the process requirements of the intended applications. In doing so, the sensitivity of the instrument was improved for applications of interest. By incorporating control over the environment, contact force, loading rate, and pulling angle, the research has increased the accuracy of the AFM such that molecules and receptor-ligand binding events can be investigated with greater detail. Furthermore, the incorporation of a graphical user interface and automated data collection and analysis tools has made the AFM a more user-friendly, efficient instrument for the natural science researcher.</p> / Dissertation

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Chicken breast samples, (n=90; n=30 normal, n=30 moderate woody breast (WB), n=30 severe WB) were collected from a commercial processing plant on 5 separate occasions. After 5 days of storage at 2-4 ºC, 84% of severe WB fillets dissipated to moderate WB, which was greater (P<0.05) than all other storage times. In comparison, 40-52% of the moderate WB fillets dissipated to slight WB or normal breasts after 3 to 5 days of storage. Shear force was greater (P<0.05) for normal breast meat than moderate and severe WB meat on day 0. After 2, 3, 4, and 5 days of storage the upper position (cranial part) of severe WB had greater shear force than normal fillets (P<0.05). Therefore, the dissipation that occurred in woody breast meat over refrigerated storage was apparent through palpation but did not result in improved texture in the cranial portion of the breast, based on shear force results.

Spot welding is a process that is widely used in industries worldwide. This project aims to research and develop a control system to improve the strengths of the spot welds. Conventional (pneumatic) spot welding systems do not lend themselves towards in-process control specifically controlling the forging force during welding. The importance of the forging force is that it is related to the dynamic resistance and hence to the rate of heating of the weld as has been shown in this work. The use of the forging force to control weld strengths was investigated by converting the electrode actuating system of a pneumatic spot welder to a motor driven servo system. This enabled the electrode forging force to be varied during welding. The control system was used to vary the forging force during welding by means of various preset force profiles in order to vary the heating during welding. The effects of the various force profiles to heat generation and weld growth were studied by using the dynamic resistance curve. The relationship between resistance and force enables the dynamic resistance to be used as an indicator for weld performance. Experiments were carried out to propose the force profile that will give the highest weld strength. Results obtained from this project shows that two changes in the characteristics of the force profile, viz, the delay time before ramping and the rate of ramping, affects the amount of heat supplied to the weld during welding which causes change in the weld strength. Statistically significant differences between average weld strengths due to the changes in these characteristics are presented. Forging force control was also found to produce stronger welds compared to the conventional electrode clamping force (ECF) condition, which was found to be statistically significant. It was also found possible to extend the weld lobe region of the electrode clamping force (ECF) condition by using forging force control, to produce improved weld strengths at the no weld and expulsion regions of the lobe. The profile that starts with a lower force and ends with a higher force with a longer ramping delay and slower ramping rate was the profile that produces the strongest weld strength among all the profiles tested. This profile with a welding current below the expulsion limit was suggested as the strategy to produce stronger welds at a faster rate.

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