Augmented reality (AR) systems that use head mounted displays to overlay synthetic imagery on the user's view of the real world require accurate viewpoint tracking for quality applications. However, achieving accurate registration is one of the most significant unsolved problems within AR systems, particularly during dynamic motions in unprepared environments. As a result, registration error is a major issue hindering the more widespread growth of AR applications. The main objective for this thesis was to improve dynamic orientation tracking of the head using low-cost inertial sensors. The approach taken within this thesis was to extend the excellent static orientation sensing abilities of accelerometers to a dynamic case by utilising a model of head motion. Head motion is modelled by an inverted pendulum, initially for one degree of rotational freedom, but later this is extended to a more general two dimensional case by including a translational freedom of the centre of rotation. However, the inverted pendulum model consists of an unstable coupled set of differential equations which cannot be solved by conventional solution approaches. A unique method is developed which consists of a highly accurate approximated analytical solution to the full non linear tangential ODE. The major advantage of the analytical solution is that it allows a separation of the unstable transient part of the solution from the stable solution. The analytical solution is written directly in terms of the unknown initial conditions. Optimal initial conditions are found that remove the unstable transient part completely by utilising the independent radial ODE. Thus, leaving the required orientation. The methods are validated experimentally with data collected using accelerometers and a physical inverted pendulum apparatus. A range of tests were performed demonstrating the stability of the methods and solution over time and the robust performance to increasing signal frequency, over the range expected for head motion. The key advantage of this accelerometer model-based method is that the orientation remains registered to the gravitational vector, providing a drift free solution that outperforms existing, state of the art, gyroscope based methods. This proof of concept, uses low-cost accelerometer sensors to show significant potential to improve head tracking in dynamic AR environments, such as outdoors.

This study surveyed school-based speech language pathologists regarding their expectations for children returning to school after suffering a traumatic brain injury. Limited literature exists discussing the coordination procedures that should occur between hospital and school personnel. The survey was developed based on the existing literature and was sent to school-based speech language pathologists in the state of Indiana. A total of 38% of the surveys were completed and returned. Results of the surveys found that many of the coordination procedures in the literature were not consistently being followed. Participants who reported having experience with this population in the schools seemed more aware of the procedures that should be followed, based on their answers to the survey questions. It can be concluded, based on the results of the surveys, that increased knowledge and experience of school personnel about the effects, implications, and needs of students with traumatic brain injury would benefit children returning to the school environment after sustaining this type of injury. / Department of Speech Pathology & Audiology

The present study attempts to further define the neuropsychological characteristics associated with mild, moderate, and severe closed head injuries (CHI). The Dean-Woodcock Neuropsychological Assessment System (D-WNAS), a new neuropsychological battery, was administered to 119 CHI patients. The scores of the cognitive portion of the D-WNAS were then analyzed via cluster analysis in an attempt to further delineate neuropsychological impairment into more specific classifications occurring within types of brain trauma.Results suggested that the cognitive portion of the D-WNAS was effective in separating 4 subtypes within CHI, which are best interpreted as "profiles" or characteristics associated with "levels" of impairment. These levels of impairment were characterized by distinctly different subtest profiles, and were labeled as mild/high functioning, mild, moderate, and severe. The highest performing group, mild/high functioning, showed no neuropsychological deficits. The most severely impaired group was characterized by many deficits in short-term memory, visual stimuli, new learning, processing speed, visual-spatial abilities, abstract reasoning, attention/concentration, and remote memory tasks. A multivariate analysis showed that educational level was significant in differentiating between the subtypes and suggested that, depending on the severity of injury, educational level might also protect individuals from obtaining a poorer prognosis.From this investigation, the cognitive portion of the D-WNAS appears to offer valuable utility in identifying CHI patients and in further classifying their varied neuropsychological characteristics. Implications for diagnosing and differentiating between different levels or profiles of CHI was discussed. / Department of Educational Psychology

Introduction-Physical activity can reduce the risk of contracting many of the 'diseases of the sedentary', such as coronary heart disease and cancer (Blair et al., 1996). Recognition of this protective effect has led to the development of many programmes designed to promote the benefit of participation in sport and physical exercise (Hillary Commission, 1993; Nicholl et aI., 1995). With participation in sport, especially contact sport, the risk for injuries increases, including injuries to the head and neck (Wilberger, 1993; Wekesa et al., 1996; Pettersen, 2002). Mild traumatic brain injuries (MTBI) or concussion as used interchangeably in the literature (Maroon et al., 2000; Wills & Leathem, 2001) are an important public health concern, due to the high incidence and frequently persisting symptomatology (Evans, 1992). Mild traumatic brain injury is defined as a complex patho-physiological process affecting the brain induced by traumatic biomechanical forces (Aubry et al., 2002; McCrory et al., 2004). A sub-concussive injury or very mild traumatic brain injury (vMTBI) may be defined as an apparent brain insult with insufficient force to cause hallmark symptoms of concussion (Jordan, 2000; Webbe & Bath, 2003). The high incidence of sport related head injuries in South Africa is alarming, although the prevalence thereof is unknown and difficult to assess, as the seemingly trivial injuries frequently remain unreported (Roux et al., 1987). This is especially applicable in sport where a milder form of head injury is common. This is cause for concern as cumulative head injuries traditionally regarded as trivial or 'minor' may result in players running the risk of increasingly negative consequences following repetitive 'minor' head injuries. In contact sport such as rugby, players are at great risk of sustaining repetitive mild traumatic brain injuries. The negative outcome following these repetitive minor head injuries has been demonstrated by numerous studies on boxers and other athletes exposed to repeated MTBI and vMTBI (McLatchie et aI., 1987). The incidence of vMTBI has not yet been researched in school rugby and this study is the first to report the incidence of vMTBI in a secondary school rugby team. Obiectives - The objectives of this study were to determine the incidence, the neuropsychological consequences and the effect on the academic performance of repeated mild (MTBI) and very mild traumatic brain injuries (vMTBI) in a secondary school rugby team during one playing season. Methods - A cohort of 35 secondary school male rugby players divided into a vMTBI (group 1) (n=26) and a MTBI (group 2) (n=9) from a local secondary school's first and second team, was followed for a full competitive season by a trained Biokineticist, who was present at all the games and contact sessions played. All vMTBI and MTBI and the severity of these injuries were documented. A control (group 3) that consisted of 10 secondary school non-rugby players were compared with the vMTBI and MTBI groups. The incidence of repeated MTBI and vMTBI in a secondary school rugby team were gathered by questionnaires and observation next to the field by a trained Biokineticist. Pre-season and post-season neuropsychological tests were conducted on the research groups and the control group. The neuropsychological tests that were conducted on the three groups were the Colour Trial Test 1 and 2 (CTT 1 + 2), the Symbol Digit Modalities Test (SDMT), the Wechsler Memory Scale-Revised (WMS-R) and the Standardised Assessment of Concussion (SAC). After each match played throughout the season the research group also completed a SAC test. The academic results of the final examination (year 1) of the year of the specific rugby season were obtained, as well as the academic results of the final examination of the preceding two years (year 2 and 3). The programme STATISTICA (version 7.0, Stat soft, Tulsa, OK) was used to analyse the data. Descriptive statistics, one-way ANOVA's, two-way repeated measures ANOVA's, Post-hoc Tuckey HSD analysis and Pearson's product moment correlation were used for all the statistical analyses. Results - This study of a secondary school rugby team has shown 726 vMTBI's and 18 MTBI's throughout one rugby season. This relates to 1951 vMTBI's per 1000 player hours and 48 MTBI's per 1000 player hours. Reductions in delayed memory (p=O.O1)from preseason to post-season in a group of players with repetitive vMTBI's during a single rugby season were found. This was the first evidence of possible neurocognitive deficits towards delayed memory in very mild traumatic brain injuries at secondary school level. Statistically significant (p<=0.05)results of the SAC test totals between both the vMTBI and MTBI groups were documented in the different games throughout the rugby season and compared with the baseline test. No statistically significant differences (p<=0.05) between the pre-season and post-season's scores of the SAC test totals were documented. A decrease in academic performance in the subject Afrikaans (year 1 compared with year 2) with a p-value of p=O.O17(group 1) and p=O.O16(group 2) respectively was found. Conclusion - The findings of this study indicate a high incidence of vMTBI in a cohort of secondary school rugby players in one season, a statistically significant reduction (p=O.O1 )in delayed memory of the vMTBI rugby players and a statistically significant decrease in academic performance p=O.O17 (group 1) and p=O.O16 (group 2) in the subject Afrikaans from year 1 to year 2 final examinations. / Thesis (Ph.D. (Human Movement Science))--North-West University, Potchefstroom Campus, 2006.

This thesis investigates head injuries (HIs) occurring in sports and recreation (SR) that presented to emergency departments (EDs) in Edmonton, Alberta, from April 1st, 1997 to March 31st, 2008. There were 4,950 SR HIs identified over the 11 years (5.13 HIs per 1,000 ED injury visits). Individuals less than 18 years old were 3.4 times more likely, and males were 1.25 times more likely to present with a head injury from SR (p < 0.0001). A history of one or two previous SR HIs increased the odds of subsequent HI by 2.62 and 5.94 times, respectively, while children aged 7 13 and 14 17 were more than four times more likely to sustain a HIs from SR (p < 0.001). The effects of multiple HIs occurring in children participating in SR activities needs to be addressed, due to the chronic neurobehavioral effects of HIs. / Epidemiology

Thesis (Ph. D.)--Ohio State University, 2007. / Full text release at OhioLINK's ETD Center delayed at author's request

Thesis (Ph.D.)--Auburn University, 2007. / Abstract. Includes survey instruments. Includes bibliographic references (ℓ. 108-126)

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 4 uppsatser.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2006. / Härtill 4 uppsatser.

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (p. 125-137).