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When you want to pick up an object, it is usually a simple matter to reach out to its location, and accurately pick it up. Almost every action in such a sequence is guided and checked by vision, with eye movements usually preceding motor actions (Hayhoe & Ballard, 2005; Hayhoe, Shrivastava, Mruczek, & Pelz, 2003). However, most research in this area has been concerned about the sequence of movements in complex “everyday” tasks like making tea or tool use. Less emphasis has been placed on the object itself and where on it the eye and hand movements land, and how gaze behaviour is different when generating a perceptual response to that same object. For those studies that have, very basic geometric shapes have been used such as rectangles, crosses and triangles. In everyday life, however, there are a range of problems that must be computed that go beyond such simple objects. Objects typically have complex contours, different textures or surface properties, and variations in their centre of mass. Accordingly, the primary goals in conducting this research were three fold: (1) To provide a deeper understanding of the function of gaze in perception and action when interacting with simple and complex objects (Experiments 1a, 1b, 1c); (2) To examine how gaze and grasp behaviours are influenced when you dissociate important features of an object such as the COM and the horizontal centre of the block (Experiments 2a, 2c); and (3) To explore whether perceptual biases will influence grasp and gaze behaviours (Experiment 2b). The results from the current series of studies showed the influence of action (i.e., the potential to act) on perception in terms of where we look on an object, and vice versa, the influence of perceptual biases on action output (i.e. grasp locations). In addition, grasp locations were found to be less sensitive to COM changes than previously suggested (for example see Kleinholdermann, Brenner, Franz, & Smeets, 2007), whereas fixation locations were drawn towards the ‘visual’ COM of objects, as shown in other perceptual studies (for example see He & Kowler, 1991; Kowler & Blaser, 1995; McGowan, Kowler, Sharma, & Chubb, 1998; Melcher & Kowler, 1999; Vishwanath & Kowler, 2003, 2004; Vishwanath, Kowler, & Feldman, 2000), even when a motor response was required. The implications of these results in terms of vision for Perception and vision for Action are discussed.

Introduction: The Hawthorne effect, or behaviour change due to awareness of being observed, is believed to inflate directly observed hand hygiene compliance rates, but evidence is limited. Methods: A real-time location system tracked hospital hand hygiene auditors and recorded alcohol-based hand rub and soap dispenses. Rates of hand hygiene events per dispenser per hour within sight of auditors were compared to dispensers not exposed to auditors. Results: The event rate in dispensers visible to auditors (3.75/dispenser/hour) was significantly higher than unexposed dispensers at the same time (1.48) and in prior weeks (1.07). The rate increased significantly when auditors were present compared to five minutes prior to arrival. There were no significant changes inside patient rooms. Conclusions: Hand hygiene event rates increase in hallways when auditors are visible and the increase occurs after the auditors’ arrival, consistent with the existence of a Hawthorne effect localized to areas where auditors are visible.

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No description available.

This thesis centers on the study of the design principles used in creating hand-drawn effects and how they can be applied to computer-generated 3D effects. By studying the rich history of hand-drawn effects animation, artists working on computer-generated films can enhance the emotional impact and visual appeal of their effects without devoting years to creating hand-drawn effects. From reference clips of animated effects and writings by artists, a list of aesthetic guidelines for the production of stylized effects is generated. A series of case study animations is created to demonstrate how these guidelines can be used to create effects in various styles and of various elements.

The aim of this thesis is to create a low-cost sensor equipped glove using commercially available components that can be used to obtain position, velocity and acceleration data for individual fingers of a hand within an optical motion capture environment. Tracking the full degrees of freedoms of the hand and finger motions without any hindrances is a challenging task in optical motion capture measurements. Attaching markers on every finger and hand joint makes motion capture systems troublesome due to practical problems such as blind spots and/or obtaining higher derivative motion constraints, such as velocities and accelerations. To alleviate this, we propose a method to capture the hand and finger kinematics with a reduced set of optical markers. Additionally inertial sensors are attached to the fingertips to obtain linear acceleration measurements. For optimal velocity estimation, a Kinematic Kalman Filter (KKF) is implemented and its result is compared to the time derivative of the Motion Capture System measurement. The higher derivative specifications are related to contact and curvature constraints between the fingers and the grasped object and are later used in formulating the synthesis task for the design of robotic fingers and hands. A preliminary prototype device has been developed to obtain position, velocity and acceleration information of each fingertip by incorporating multiple accelerometers into the basic design of reduced marker set.

Maximum voluntary forces and psychophysically acceptable forces are often used to set force guidelines for exertions as a means to protect against overexertion injuries in the workplace. The focus of this dissertation was the exploration of the roles of whole body balance, shoe-floor friction and joint strength in limiting the capacity of a person to produce maximum voluntary hand forces and psychophysically acceptable hand forces. The underlying goal was to advance knowledge regarding how physical exertion capacity is biomechanically governed, then to use this information to develop models to predict capability based on these governing principles. The hypothesis underscoring this work was that maximum voluntary hand force capability is governed by whole body balance, shoe-floor friction and joint strength; and consequently, psychophysically acceptable forces would be chosen proportionally to this maximum voluntary force capability, where the magnitude of the proportionality was dependent on the limiting factor, or ‘weakest link’. To investigate this hypothesis, both experimental and mathematical modeling paradigms were used. Initially, an experimental study was used to investigate how biomechanical factors governed maximum hand force capability across a range of exertions. It revealed that each governing factor differentially limited maximum force capability. Moreover, this study identified how foot placement, handle height, distance from the handle, friction, and body posture all influence the underlying biomechanical weakest link, and ultimately force producing capability. Data gathered in the experimental study was next used to evaluate a mathematical model that was developed to predict maximum force capability, given information on posture and direction of force application. In addition, the model also predicted population variability in maximum capacity based on the inclusion of a novel approach to probabilistically represent population variability. The evaluation demonstrated that the model underestimated maximum hand force capability compared to measured hand forces by approximately 18, 26, and 41% during medial, pulling and downward exertions respectively. However, it appeared that the ‘weakest link’ principle for predicting maximum force capacity was plausible, as evidenced by significant rank ordered correlations between the measured and predicted hand forces. Further research investigated if psychophysically acceptable forces were selected as a proportion of task specific maximum voluntary force capability, where the proportionality was related to the biomechanical weakest link. Using an experimental design, psychophysically acceptable forces and corresponding maximum forces were measured. Participants chose psychophysically acceptable forces that were 4/5ths of their task specific maximum voluntary force capability when capability was limited by balance. Additionally, they choose psychophysically acceptable forces that were 2/3rds of their maximum voluntary force capability when capability was limited by joint strength. The identification and confirmation of a weakest link proportionality principle represents an important contribution to the field of occupational biomechanics. The weakest link proportionality principle was integrated into the model to allow prediction of: maximum voluntary hand force capability, the limiting factor, and psychophysically acceptable hand force capability. The updated model underestimated empirically measured psychophysically acceptable forces by 24% and 43% during downward and pulling exertions respectively. However, the original model underestimated the maximum hand force capacity by 23% and 34% during the same exertions, without the proportional relationships. This underestimation may be a result of the underlying assumption that joint strength is independent, resulting in an underestimation of maximum joint strength capacity and a corresponding underestimation of maximum hand force capacity. The underestimation may also be due to differences in strength capacities between the participants tested during this thesis compared to those tested in past research used to determine the maximum strength indices reported in the literature. This body of work supported the hypothesis that psychophysically acceptable forces are selected as a proportion of the maximum voluntary hand force, where the proportionality depends on the underlying biomechanical weakest link. The model is a promising first step towards predicting maximum and psychophysically acceptable occupational force threshold limits.

Functional recovery of the upper limb after stroke is influenced by many factors, one being amount of affected arm and hand use following stroke. In the healthy population, amount of hand use is influenced by degree of hand dominance. Depending on side of stroke and previous hand dominance, these preferences may be altered, consequently affecting the amount of upper limb use. Determining hand preference in patients after stroke, when measured, is commonly assessed with questionnaires; however, these reports are subjective and patients may have difficulty recalling from memory which hand they use for the numerous activities on the questionnaire. A preferential reaching task has been shown to correlate with the degree of hand dominance as determined by the Waterloo Handedness Questionnaire, providing an objective performance-based method to assess the continuum of hand dominance in healthy subjects. A modified version of this preferential reaching task, with varying degrees of proximal to distal control, was used to investigate the influence of impairment, pre-stroke dominance and task difficulty on affected arm reach percentage. Results of the study revealed that it is feasible to administer a modified preferential reaching task in the stroke population, as the test could be completed in less than 10 minutes with no adverse effects reported from the patients. Heterogeneity made it difficult to detect statistical effects of task difficulty and pre-stroke dominance on post-stroke preference; however, there were trends observed indicating that patients with their dominant arm affected may have greater preference for the affected arm compared to those with their non-dominant arm affected. This was despite similar impairment levels between these patient groups. Preference for the dominant arm (whether affected or unaffected) was stronger when the task was at midline or in contralateral space, and when tasks required the greatest degree of distal control. In future, the degree of hand preference measured with this tool will have important implications for identifying areas in therapy requiring greater focus as well as identifying individuals who would most benefit from therapies that promote affected arm use, such as constraint induced movement therapy