In recent years there has been increased interest in the development of sensorless switched reluctance machine drives. The proper operation of a switched reluctance machine (SRM) requires knowledge of the position of the rotor of the machine. The inclusion of a physical position sensor compromises the inherent robustness of this type of machine. Thus, there has been a need to develop techniques to estimate the position of the rotor in SRM drives. Switched reluctance machines are able to operate over a large range in speed. A fully loaded SRM is typically designed to saturate the ferromagnetic material that comprises the stator and rotor of the machine whereas a lightly loaded machine does not. Therefore, the model of the machine should be able to handle both a large range in frequency and input excitation levels of the magnetic material in the machine. The development of a new dynamic circuit-based ferromagnetic model is described in this thesis. The investigation of the behaviour of 24 gauge M19 silicon steel led to the conclusion that, for this material, a circuit model that has static parameters is unable to accurately reproduce the behaviour of the actual material over a large range of input frequencies and excitation levels without resorting to retuning the parameters of the model. This thesis provides two new mechanisms that dynamically adjust the resistance values of the flux tubes of the model. Comparisons using a normalized vertical least-squares metric between the newly proposed dynamic model and a model that has static resistance values clearly show the improvement that is gained by using these mechanisms. A practical implementation of the new model is also given. Timing using a general purpose CPU shows that this implementation of the model will most likely be able to be used as part of a multi-phase lumped parameter model for a SRM in realtime. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

No description available.

No description available.

This thesis presents the numerical solution for two-dimensional incompressible viscous flow over a rigid bluff body which is elastically supported or alternately undergoing a specified harmonic oscillations. Solutions for the related associate flow in which the body is at rest in a two-dimensional incompressible time-dependent viscous flow have also been -obtained. This work is an extension of the work by Pattani [19] to include the effect of a steady far field flow on an oscillating body. The numerical model utilizes the finite element method based on a velocity-pressure primitive variable representation of the complete Navier-Stokes equations. Curved isoparametric elements with quadratic interpolation for velocities and bilinear interpolation for pressure are used. Nonlinear boundary conditions on the moving body are represented to the first order in the body amplitude parameter. The method of averaging is used to obtain the resulting periodic motion of the fluid. Three non-dimensional parameters are used to completely characterise the flow problem: the frequency Reynolds number Rω , the Reynolds number of steady flow Rℯ₁ and the Reynolds number for time-dependent flow Rℯ₂. Numerical results are obtained for a circular body, a square body and an equilateral triangular body. A parametric study is conducted for different values of the Reynolds numbers in the viscous flow regime. In all cases, results are obtained for streamlines, streaklines, added mass, added damping, added force and the drag coefficients. The limiting cases of steady flow over a fixed body and an oscillating body in a stationary fluid are checked with known results. Results for the associated flow are also obtained. The transformations derived, between the two associated flows are checked. Good agreement is obtained between the present results and other known results. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

This study was to determine the effects of a six-week program of dynamic weight training upon flexibility.

The aim of this thesis is to present a structural model for a wind turbine and its supporting pylon, to analyze and simulate attendant vibration phenomena and to suggest and simulate an appropriate control procedure. A wind turbine can be described as an elastic system consisting of distributed parameter, beam and rod type, elements coupled to a rotating lumped mass generator/turbine component at one end. We allow for both lateral and torsional movements of the beam. Solution methods for related vibration and control problems are suggested and analyzed. Results of computations for sample problems are presented. Applications of control of structural vibrations in wind energy units using proof mass type actuators as part of the tip mass are also analyzed. / Master of Science

No description available.

No description available.

<P> Breast cancer has affected many women around the world throughout history. In order to recognize and treat the early signs of breast cancer, obtaining high quality images is crucial. A variety of imaging modalities are available for use in breast imaging, including conventional mammography and newer optical imaging techniques. One such optical imaging system is the ComfortScan™, which uses red light to image the breast and was the focus of this study. The objectives include investigating whether performing a large scale clinical trial with the ComfortScan TM would be warranted to further patient care and diagnostics for breast imaging, and determining whether the ComfortScan ™ would achieve better correlation to biopsy than mammography alone. An additional goal was to investigate whether the ComfortScan TM system would be beneficial as a mainstream method for a radiologist to diagnose breast cancer risk. </p> <p> The preliminary study with 19 patients demonstrated that there was no difference in diagnostic information between the near-infrared (NIR) image and mammography (p>O.OS). Anecdotal evidence suggests cases where mammography disagreed with biopsy, whereas ComfortScan TM agreed, though these were not statistically significant. Based on these encouraging results, a large scale clinical trial was launched to investigate the potential of widespread use of the ComfortScan ™. The large scale trial included 126 NIR images and found difference in diagnostic information between NIR and mammography (p<O.OS). Mammography agreed with biopsy in 18/33 and the ComfortScan™ system agreed with biopsy in 25/33 cases. The sensitivity and specificity for the ComfortScan™ system was 83% and 67%, respectively. The sensitivity and specificity of mammography was 94% and 13%, respectively. This study included a variety of women with varying ages and BIRADS scores, and demonstrated the effective clinical use of a portable, non-ionizing, inexpensive imaging modality, indicating that the ComfortScan ™ system could likely be successful as a mainstream adjunct to mammography. </p> <p> The potential of using polyvinyl alcohol cryogel (PVA-C) as a breast tissue mimic was investigated and PV A -C was then used to validate the mode of action of the ComfortScan TM system. Two experimental methods reported the absorption coefficients and reduced scattering coefficients of PV A-C. Using a double integrating sphere, the values were J.la = 0.012 ± 0.002 mm-1 and J.ls' = 1.5 ± 0.2 mm-1 and using steady-state spatially resolved diffuse reflectance, the values were J.la = 0.017 ± 0.005 mm-1 and J.ls' = 1.3 ± 0.2 mm-1 at 640 nm. These values are comparable to typical absorption coefficients for tissue reported by others. </p> <p> The mode of action suggested by DOBI (Dynamic Optical Breast Imaging) Medical for the ComfortScan ™ system is that under compression a malignant tumour will highly attenuate light, due to a partial collapse in the tumourous vasculature, resulting in an increased deoxygenation of blood over time. Using a PV A-C breast mimicking phantom, it was shown that by deoxygenating horse blood in a cavity, there was an increase in the attenuation of 640 nm light as compared with the surrounding phantom material; which suggests that the colour representative of malignancies on the ComfortScan ™ is caused by deoxygenating blood. Further evidence suggests that the ComfortS can TM system is not recognizing a total collapse of the vasculature and subsequent void of blood from the tumour as the trigger for malignant detection. The mode of action suggested by DOBI Medical is supported by our findings. </p> / Thesis / Doctor of Philosophy (PhD)

No description available.