A generic object-oriented simulation platform is developed in order to conduct experiments on the performance of assignment schemes. The simulation platform, called Genesis, is generic in the sense that it can model the key parameters that describe a parallel system: the architecture, the program, the assignment scheme and the message routing strategy. Genesis uses as its basis a sound architectural representation scheme developed in the thesis. The thesis reports results from a number of experiments assessing the performance of assignment schemes using Genesis. The comparison results indicate that the new assignment scheme proposed in this thesis is a promising alternative to the work-greedy assignment schemes. The proposed scheme has a time-complexity less than those of the work-greedy schemes and achieves an average performance better than, or comparable to, those of the work-greedy schemes. To generate an assignment, some parameters describing the program model will be required. In many cases, accurate estimation of these parameters is hard. It is thought that inaccuracies in the estimation would lead to poor assignments. The thesis investigates this speculation and presents experimental evidence that shows such inaccuracies do not greatly affect the quality of the assignments.

Previous studies have demonstrated that in some instances certain types of auditory stimulation have facilitated a subject's ability at a visual task while in other instances, the subject's ability has been inhibited. The primary objective of this experiment was to investigate the effect of auditory stimulation upon a subject's performance on a visual discrimination task.

Moving through varied and complex environments every day is something that most people do with ease. However, if the input from the visual system is unavailable (e.g., damage to the optic nerves or smoke in a burning building), navigating and avoiding obstacles becomes much more demanding. It is therefore desirable to develop a navigation aide for use where visual input has become unavailable. There is a small body of research concerning such navigation aides and their efficacy. However, many issues that may have serious human factors repercussions for such a system are unexplored. This study was conducted in order to examine the effect of an attentionally demanding distractor task on wayfinding performance with an audio only navigation aide, in this case the System for Wearable Audio Navigation (SWAN). The distractor task was found to have a significant impact on wayfinding performance, which decreased when both tasks were performed simultaneously. However, performance on the distractor task improved during this time, in some cases reaching performance levels similar to when the distractor task was performed by itself. This result may be due to participants shifting attention to the task they perceive to be more difficult when asked to do both simultaneously, in this case the distractor task.

Task-switching studies are a popular measure of executive control, yet the influence of stimulus repetition in these studies is less well recognized. One theory from the literature states that stimuli associated with a certain response interfere with processing of those same stimuli in another task, contributing to task switching costs (Waszak, Hommel, &Allport, 2003). The current study varied stimulus repetition in younger and older adults and found that the previous task associated with a stimulus does influence overall performance but did not find the expected interaction of switch and repetition conditions. Results of this study extend our information about the role of stimulus repetition in task-switching studies as well as how this repetition relates to age differences in switch costs.

This thesis aimed to investigate the benefit of game-based dual-task recumbent bicycle (DT-RC) training among older adults. In addition, the thesis examined the change in cardiac fitness over an 8-week training program. Eleven healthy older adults (70-80 years old) were recruited and received an 8-week dual-task training program; combines a recumbent bicycle with interactive cognitive video games. Outcome measures were collected pre and post the intervention and included measures to assess COP for core balance, spatial-temporal gait variables, performance in visual tracking and cognitive games, neuropsychological tests and HR to workload ratio. Results showed a significant improvement in COP excursion, head tracking and success rate for cognitive games, trails making test and HR to workload ratio decreased by 44%. No significant effects were found for spatial-temporal gait variables. This study shows that the DT-RC program has beneficial effects on dual-task functions and cardiac fitness among healthy older adults.

Increasingly, highway transportation projects are tending to involve maintenance and rehabilitation work. The age and the condition of the transportation asset, in addition to funding constraints have been the key drivers of this trend. This implies that construction operations take place in the presence of traffic flows, leading to the creation of construction work zones. This has safety implications for the commuters and construction workers alike. In addition, construction operations also hamper mobility through the work zone. Effective management of the work zone is thus very important from the perspective of construction and mobility. The preferred and mandated method to manage the impacts of the work zone is the Transportation Management Plan, which prescribes a set of coordinated strategies for the same. The strategies used in a TMP range from enforcing lane closures to modifying the construction sequencing. As the choice of particular strategies or a combination of those affects the work zone, assessing TMP strategies is important to inform future decisions. This thesis proposes a framework for the qualitative assessment of TMP strategies and TMP processes using cognitive task analysis methods. The application of the proposed method is demonstrated through two case studies of large highway reconstruction projects, involving significant bridge reconstruction. The knowledge elicitation techniques are discussed and the obtained knowledge is represented using different knowledge representation structures. The benefits and the applicability of CTA methods are explored through the case studies of projects using different contracting strategies. Finally, recommendations are made for the design of decision support tools, based on the insights obtained through the analysis. / text

Increasingly, highway transportation projects are tending to involve maintenance and rehabilitation work. The age and the condition of the transportation asset, in addition to funding constraints have been the key drivers of this trend. This implies that construction operations take place in the presence of traffic flows, leading to the creation of construction work zones. This has safety implications for the commuters and construction workers alike. In addition, construction operations also hamper mobility through the work zone. Effective management of the work zone is thus very important from the perspective of construction and mobility. The preferred and mandated method to manage the impacts of the work zone is the Transportation Management Plan, which prescribes a set of coordinated strategies for the same. The strategies used in a TMP range from enforcing lane closures to modifying the construction sequencing. As the choice of particular strategies or a combination of those affects the work zone, assessing TMP strategies is important to inform future decisions. This thesis proposes a framework for the qualitative assessment of TMP strategies and TMP processes using cognitive task analysis methods. The application of the proposed method is demonstrated through two case studies of large highway reconstruction projects, involving significant bridge reconstruction. The knowledge elicitation techniques are discussed and the obtained knowledge is represented using different knowledge representation structures. The benefits and the applicability of CTA methods are explored through the case studies of projects using different contracting strategies. Finally, recommendations are made for the design of decision support tools, based on the insights obtained through the analysis. / text

It is well established that people experience a decline in cognitive functions, such as selective attention (SA), as they get older. SA is the ability to focus on task-relevant information and suppress task-irrelevant information. The Stroop task has been used to assess SA. In the current study, the neural correlates of SA were investigated using functional MRI-Stroop task with cognitively normal older adults (NC), patients with amnestic Mild Cognitive Impairment (aMCI) and patients with mild Alzheimer’s disease (AD). The current study reanalyzed previous master student’s data, due to the disagreement in analyzing the data. In the fMRI data analysis, the contrast of correct responses in the naming incongruent color (SC) condition minus correct responses in the reading incongruent word (RW) condition (SC-RW) in series 2a and 2b was reanalyzed using an event-related analysis. The current Stroop experiment was in a block design with four series: series 0, series 1, series 2a and 2b. In behavioral analysis, the performance of the word-reading task was expected to be significantly better than the color-naming task in series 1, series 2a and 2b because the belief that reading incongruent color word was always an easier task than the color-naming task. The results from behavioral analysis showed that significant more errors were made in reading incongruent color words in series 2a and 2b than in series 1. In the functional MRI data analysis, although brain activation associated with inhibition was expected in the contrast of SC-RW of series 2a & 2b, the results did not show any brain activation. The unexpected results could be due to the RSE that was elicited by the task switching paradigm of series 2a and 2b. The results suggest that the current Stroop task adapted from the Stroop Neuropsychological Screening Test may not yield a Stroop interference effect of sufficient magnitude to be detected with fMRI in the contrast of SC-RW of series 2a and 2b. / Thesis (Master, Neuroscience Studies) -- Queen's University, 2010-09-24 11:33:28.83

The increase in the aging population has become one of the most important problems of our society in last few decades. As people grow older, they are at risk of falling and consequent injuries due to the effects of aging. A fall may be the first indication of an undetected illness related to the effects of aging. This study demonstrates the effects of aging on balance, spatio-temporal gait parameters, gaze stability, and cognitive skills under single task conditions and during dual-tasks conditions. In the present study, we included following three groups: Group 1: 30 young healthy adults (aged 20 ± 3 years); Group 2: 30 adults (aged 61.4 ± 4.4 years); Group 3: 30 older adults (aged 75 ± 4.5 years). A computer game based rehabilitation platform has been developed and was used for the single and dual task performance in standing and during treadmill walking. We observed that there was a significant age effect while dual tasking on standing balance, spatial and temporal gait parameters, gaze performance, and cognitive task performance. To conclude, this study shows a vast decline in walking and standing balance and ability to divide attention during dual tasking between the age groups 55-70 years and 71- 85 years and compares both these age groups with the more normative, healthy, young and athletic, 20-30 years old population.

Thesis (M.S.)--Auburn University, 2007. / Abstract. Includes bibliographic references (ℓ. 46-57)