Historical attempts to measure forces in magnetic bearings have been unsuccessful as a result of relatively high uncertainties. Recent advances in the strain-gauge technology have provided a new method for measuring magnetic bearing forces. Fiber optic strain gauges are roughly 100 times more sensitive than conventional strain gauges and are not affected by electro-magnetic interference. At the Texas A&M Turbomachinery Laboratory, installing the fiber-optic strain gauges in magnetic bearings has produced force measurements with low uncertainties. Dynamic flexibility transfer functions exhibiting noticeable gyroscopic coupling have been identified and compared with results of a finite element model. The comparison has verified the effectiveness of using magnetic bearings as calibrated exciters in rotordynamic testing. Many applications including opportunities for testing unexplained rotordynamic phenomena are now feasible.

Damage to motor areas of the brain, caused by stroke, can produce devastating motor deficits, including aberrant control of force. After stroke, reorganization of the brain’s motor system has been identified as one of the fundamental mechanisms involved in recovery of motor control after stroke. Yet, few studies have investigated how force production and modulation are encoded in the brain after stroke and how this relates to motor outcome. Thus, the purpose of this study was to (1) understand how past neuroimaging literature has contributed to establishing common patterns of brain reorganization during both relative and absolute force production after stroke, (2) examine how brain function is reorganized during force production and modulation in individuals with stroke, and (3) relate this task-related reorganization of brain function to the amount of paretic arm use after stroke. In the second chapter, we systematically reviewed all relevant literature examining brain activation during force production after stroke. The following chapters (chapters 3 and 4) applied functional magnetic resonance imaging (fMRI) to examine the neural correlates of force production and modulation after stroke. Chapter 2 supports differences in task-related brain activation dependent on features of stroke, such as severity and chronicity, as well as influence of rehabilitation. In addition, results suggest that activation of common motor areas of the brain during force production can be identified in relation to functional outcome after stroke. Results from the subsequent two chapters (3 and 4), demonstrate that brain function reorganizes in terms of absolute, and not relative force production after stroke. Specifically, stroke participants exhibit greater activation of motor areas than healthy controls when matched for absolute force production. Moreover, there is a relationship between paretic arm usage and brain activation, where stroke participants having less paretic arm use, as measured using wrist accelerometers, exhibit higher brain activation. Results of this thesis suggest that during absolute force production, brain activation may approach near maximal levels in stroke participants at lower forces than healthy controls. Furthermore, this effect may be amplified even further in subjects with less paretic arm usage, as increased activation in motor areas occurs in participants with less arm use after stroke. Ultimately, the results from this thesis will contribute to research relevant to brain reorganization in individuals with stroke and may lead to the development of new, beneficial therapeutic interventions that optimize brain reorganization and improve functional recovery after stroke.

Atomic force microscopy was used to image the action of cellulolytic enzymes in situ on never-dried native cellulose films. Cellomonas fimi, CenA was used as a model enzyme for proof of concept experiments and for the identification of different enzyme action on different cellulose structures. Inactive and active Trichoderma reesei enzymes EGI and CBHI were studied to disentangle the action of the cellulose binding domain from the catalytic domain. A novel procedure, volume analysis, was developed to quantify changes in cellulose fibers as a result of this action. Volume analysis was used to compare fibers in different experiments (with different structural features and enzymes) regardless of where the change in the fiber occurred. The site-specific nature of cellulose-enzyme interactions is accessible using this analysis technique. Additionally, the reported volume change reflects a change in mass that is of interest for industrial purposes. From inactive CBHI action there was no distinguishable change between enzyme action on defect or crystalline regions of the cellulose fiber. From the active enzyme results a quantifiable degradation event was measured. Digestion was initially quick then after one hour the volume plateaued. The crystalline cellulose region plateaued at -20 ± 1% and the defect region at -31 ± 2%. The inactive EGI enzyme was found to have significant non-hydrolytic action on insoluble cellulose fibers. There was more significant swelling effect on the defect than the crystalline regions of the cellulose fiber. From the active EGI results a quantifiable degradation event was measured followed by swelling events. Degradation was initially quick with the total mass loss occurring within the first hour of the experiment. The volume then increased as the enzyme induced swelling of the fiber structure. The extent of degradation and swelling is structure limited with more disordered regions showing larger decreases in volume and predominantly crystalline regions showing mainly swelling events.

I investigate the self-force acting on static scalar and electric charges in Schwarzschild-de Sitter and Schwarzschild-Anti-de Sitter spacetimes. The self-force occurs when a charged particle's field interacts with the curvature of spacetime so that the particle interacts with its own field. Because the field of a point particle is singular at the location of the particle, it is necessary to decompose the field into a regular part responsible for the self-force and a singular part that does not contribute to the self-force. To do this, I use the mode-sum regularization scheme introduced by Barack and Ori, in which the field is decomposed into a sum over modes, and the singular part is removed from each mode using so-called regularization parameters. I find that the electrostatic self-force in Schwarzschild-de Sitter and Schwarzschild-Anti-de Sitter behaves similarly to Schwarzschild self-force near the black hole, but can deviate strongly at larger distances. This is especially true in Schwarzschild-Anti-de Sitter, where the self-force is seen to increase linearly with distance. I provide an explanation for this behaviour using conformal transformations. A particular feature evident in Schwarzschild-Anti-de Sitter is that the self-force can become negative (attractive) at small distances when the Schwarzschild radius and the cosmological length scale are of a similar order. I find that the scalar self-force in Schwarzschild-de Sitter can not actually be computed, and in Schwarzschild-Anti-de Sitter the asymptotic behaviour is similar to its electrostatic counterpart.

Secondary school pupils' concepts of energy were probed by clinical interviews and a multiple choice survey administered to 84 Alberta students. Preliminary information was gathered from curriculum documents, misconceptions literature and eight preliminary interviews. Both the interviews and the written survey were based on the interview-about-intances approach and used multiple-choice questions with free-response justification of answers. The wide range of alternative conceptions that were expressed paralleled findings of similar studies elsewhere. Most descriptions of energy were framed in substantive or ambiguous terms. Energy was frequently associated with living things, movement, and task performance. It was confused with concepts of heat, force, and pressure. Changes in physical systems were seen variously as consuming energy or as producing it upon demand. Aspects of a scientific conception were more evident among senior physics students, but differences between classes and grade levels did not generally reach statistical significance. Very few responses involved notions of energy as an abstract or conserved quantity. References to energy degradation or dissipation during changes were infrequent in interviews, survey responses, and curriculum documents. Subjects tended to choose similar responses on parallel interview and survey quesitions. Interview subjects showed evidence of preferred conceptual orientations towards a variety of situations, although their survey responses showed no parallel consistency. Conflicting evidence was obtained regarding the spontaneous use of energy-based descriptions of physical situations. Findings were interpreted from a constructivist stance, and implications for the study and teaching of specific topics were drawn. In addition, results suggested the efficacy of appropriate multiple choice instruments as an alternative to clinical interviews in the investigation of alternative conceptions. / xi, 234 leaves : ill. ; 29 cm.

Control of the contact force between a robot manipulator and a workpiece is critical for successful execution of tasks where the robot’s end effector must perform a contact operation along the contour of a workpiece. Representative tasks include polishing, grinding and deburring. Considerable research has been conducted on force control with electric robots. By contrast, little research has been conducted on force control with pneumatic robots. The later has the potential to be considerably cheaper. However, the compressible nature of air as the working fluid and relatively high friction means pneumatic robots are more difficult to control. The subject of this thesis is the design and testing of a controller that regulates the normal contact force and tangential velocity of the end effector of a pneumatic gantry robot while tracking the contour of a planar workpiece. Both experimental and simulation results are presented. A PI Force Velocity (FV) controller for contour tracking was designed and tested experimentally. Three different workpiece edge geometries were studied: straight, inclined and curved. The tracking performance with the PI FV controller was comparable to the performance reported by other researchers with a similar controller implemented with an electric robot. This result confirms the potential of pneumatically actuated robots in force control applications. A system model was developed and validated in order to investigate the parameters that affect performance. A good match between experiment and simulation was achieved when the friction of the z-axis cylinder was modeled with a Displacement Dependent Friction Model (DDFM) instead of a Velocity Dependent Friction Model (VDFM). Subsequently, a DDFM based friction compensator was designed and tested. However, it was found that performance could not be improved even with perfect friction compensation, due to the effects of system lag. Two Neural Network (NN) compensators were designed to compensate for both the lag and friction in the system. Simulation results for straight and curved edges were used to examine the effectiveness of the NN compensators. The performance of the PI FV controller was found to improve significantly when a NN compensator was added. This result confirms the value of NN’s in control compensation for tracking applications with pneumatic actuation. / Thesis (Ph.D, Mechanical and Materials Engineering) -- Queen's University, 2008-09-16 12:29:44.679

The use of force by police has been explored through a range of social science perspectives. However, the majority of those perspectives have failed to account for the impact that situational factors have on the use of coercion by police. While situational perspectives have been utilized, they have primarily focused on solitary features of the situation; thus, ignoring a situation’s various component parts. The general absence of consideration given to situational force is exhibited within the sociological literature more generally. This absence contributes to a diminished appreciation for the circumstances that transpire within the context of the situation. This thesis explores the role that the situation plays in the generation of police use of coercion. In addition, this thesis observes whether contemporary theoretical developments can elaborate the explanatory value of the situation in studying the use of violence by police. Specifically, this thesis utilizes Collins’ (2004) micro-situational theory of violence and his concept of forward panic. To examine the utility of Collins’ theory, eight theoretical propositions are used. This research examines the extent to which the propositions were empirically observable and whether they had a value added impact. The propositions examined were: 1) cross-purpose, 2) tension/fear, 3) the prolonged building of tension/fear, 4) docile lingering, 5) suspect in a position of weakness, 6) suspect outnumbered, 7) overkill and piling on of violence, and 8) rhythm. To observe the propositions a multiple case study analysis was conducted using Internet videos and newspaper articles. It was found that in all nine cases each of the propositions as described by Collins (2004) were present. The findings suggest general support for using Collins’ theory to explain police violence. In addition, his theory was found to have value added capability, as each of the situational components of the theory combined to impact on police violence. / Thesis (Master, Sociology) -- Queen's University, 2010-06-01 12:01:57.453

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