Space missions have evolved considerably in the last fifty years in both complexity and ambition. In order to enable this continued improvement in the scientific and commercial return of space missions new control systems are needed that can manage complex combinations of state of the art hardware with a minimum of human interaction. Distributed multi-agent systems are one approach to controlling complex multisatellite space missions. A distributed system is not enough on its own however,the spacecraft must be able to carry out complex tasks such as planning,negotiation and close proximity formation flying autonomously. It is the coupling of distributed control with autonomy that is the focus of this thesis. Three contributions to the state of the art are described herein. They all involve the innovative use of multi-agent systems in space missions. The first is the development of a multi-agent architecture, HASA, specifically for space missions. The second is to use embedded agents to autonomously control an interferometric type space telescope. The third is based on software agents that coordinate multiple Earth observation missions coupled with a global optimisation technique for data extraction. The HASA architecture was developed in reaction to the over generality of most multi-agent architectures in the computer science and robotics literature and the ad-hoc, case-by-case approach, to multi-agent architectures when developed and deployed for space missions. The HASA architecture has a recursive nature which allows for the multi-agent system to be completely described throughout its development process as the design evolves and more sub-systems are implemented. It also inherits a focus on the robust generation of a product and safe operation from architectures in use in the manufacturing industry. A multi-agent system was designed using the HASA architecture for an interferometric space telescope type mission. This type of mission puts high requirements on formation flying and cooperation between agents. The formation flying agents were then implemented using a Java framework and tested on a multi-platform distributed simulation suite developed especially for this thesis. Three different control methods were incorporated into the agents and the multi-agent system was shown to be able to acquire and change formation and avoid collisions autonomously. A second multi-agent system was designed for the GMES mission in collaboration with GMV, the industrial partner in this project. This basic MAS design was transferred to the HASA architecture. A novel image selection algorithm was developed to work alongside the GMES multi-agent system. This algorithm uses global optimisation techniques to suggest image parameters to users based on the output of the multi-agent system.

The brain undergoes structural changes in response to new experiences like learning a new skill. Skilled motor movements depend greatly on the primary motor cortex for their execution. Recent studies describe rat strain differences in motor performance related to differential synaptic efficacy in the motor cortex of rats. Previous studies identified differences in motor performance related to differential dendritic morphology and strain related differences in synaptic function in the motor cortex. Strain differences are one way of investigating anatomical organization and behaviour of the motor system. The object of this research was to examine strain related differences in dendritic morphology in layer II / III pyramidal cells of the forelimb area of the sensory motor cortex in both Long-Evans and Fischer 344 rats after reach training. This research also examined whether changes in reaching behaviour could be attributed to changes in dendritic morphology. Rats were trained once a day for 30 days to reach for a food pellet through a slot in a reaching box. Pyramidal cells in the motor sensory forelimb (MSF) cortex were stained with the Golgi Cox method. Subsequent analysis of Sholl and branch order data of cell drawings determined that there were no significant differences in any measure of dendritic length or dendritic length at branch order 3, 4, 5 of pyramidal cells in layer II/III of the MSF cortex between the Long Evans and Fischer 344 rat strain. The only significant strain related difference was that the Fischer 344 strain exhibited fewer reaches for each food pellet obtained, demonstrating greater reaching proficiency than similarly trained Long-Evans rats. These findings suggest that further research examining strain comparisons is required to understand the neural mechanisms underlying the differences in motor behaviour observed in these rat strains.

The purpose of the investigation was to determine the effect of variations in relative frequency of concurrent visual feedback (CVF) on the acquisition and retention of a serial skill. Subjects (n=24) were college-aged females with no gymnastics experience. Subjects viewed a demonstration tape of a skilled gymnast performing a series of seven gymnastics dance skills consisting of simple and complex movements. Following this, subjects performed the dance sequence in front of a floor to ceiling mirror for concurrent visual feedback on a certain percentage of acquisition trials. The percentage of trials a subject received CVF depended on the group to which a subject was assigned: 100% relative frequency of CVF, 50% CVF (given on alternating trials), 50% faded CVF, or a control group that received no CVF. All subjects participated in three, 12trial acquisition sessions on different days. A two-trialshort-term no-CVF retention test was administered after each acquisition session with one long-term retention test administered 72 hours after the last acquisition session.The results of this study indicated no significant differences in form rating scores between groups. Thus, variations in the relative frequency of CVF during acquisition did not seem to enhance or detract from acquisition or retention performance. In addition, the ability to reproduce the correct sequence was not dependent upon the variation in the frequency of CVF employed throughout acquisition trials.The presence of a significant session effect in both acquisition and retention form rating indicated that learning did occur regardless of the presence or absence of CVF. / School of Physical Education

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The purpose of this study was to determine the effect of priming on performance of a closed motor task (dart throwing). The priming task involved either reading or listening to one of three different sets of instructions explaining the mechanics of dart throwing: positive (emphasizing what to do or focus on), negative (emphasizing what not to do or focus on), and neutral. One hundred-twenty four participants were randomly assigned to 4 experimental groups (n = 21 for each) and 2 control groups (n = 20 for each) based on media (verbal or written) and direction (positive, negative, control) of script. Each participant completed a total of 6 blocks (3 dart-throws per block). In subsequent order, participants completed Blocks 1 and 2 (practice trials), the priming task, and then Blocks 3 through 6 (experimental trials).A 2 x 3 x 6 (Media x Direction x Block) ANOVA with repeated measures on the last factor found only a significant main effect for Block. However, tests of within-subject contrasts indicated a Block x Direction interaction from Block 1 to Block 2 and from Block 2 to Block 3, with the most dramatic change in performance seen in the group receiving the negative instructions. The results indicated that negative instruction can have an immediate negative impact on performance that is not seen with positive instruction. This negative impact can be overcome, however, if the performer is left alone to practice after receiving the negative instruction. This study has provided additional evidence that priming can influence motor responses. / School of Physical Education, Sport, and Exercise Science

Various research sources indicate that effective sensory functioning is critical to the optimal development of a child. However, the influence of problems that are associated with poor socio-economic circumstances, as well as the differences between the genders and groups from different socio-economic backgrounds with regard to sensory functioning and motor development, is not clear. The aim of this study was to determine the possible significant relationship between problems that are associated with poor socio-economic circumstances and the sensory development of five to six year old children from these backgrounds. The study also attempted to compare the sensory development of five to six year old children from poor socio-economic backgrounds on the one side and those from good socio-economic backgrounds on the other. Further aims of this study were to analyse the possible differences between motor and sensory development of five to six year old boys and girls in poor socio-economic circumstances, as well as to determine the possible significant relationship between the general motor and sensory development of five to six year old children in poor socioeconomic circumstances. Fifty families were selected from three hundred families in the Thusano project by making use of a stratified random sampling procedure. All the five to six year old children belonging to these fifty families were selected for the purposes of this study as the QNST test can only be used for analysis on children from the age of five years. The total group that were selected from this poor socio-economic background consisted of twelve girls and eight boys (N= 20). A control group was made up of children from better socio-economic backgrounds and consisted of five girls and six boys between the ages of five and six years (N=11). The children were all evaluated according to the "Peabody Developmental Motor Scales - 2" (PDMS-2) to determine their motor development. The "Sensory Input Systems Screening Test" and the "Quick Neurological Screening Test II" (QNST) were used to evaluate their sensory development. The children with poor socio-economic circumstances were also evaluated by means of a questionnaire to determine aspects related to the birth process, medical history and education of the mother. With regard to aim 1, it is apparent from the results, which were obtained by using 'Statistica', that there are significant differences in the sensory development of children from poor socio-economic circumstances and good socio-economic circumstances when the QNST test was taken into account. The six tests showing the significant differences in the two groups are the two tests for tactile input ('palm shape' and 'hand-cheek'), the tests for auditory input ('sound'), the tests for pro-prioceptive input ('arm-leg extension') and the two tests for vestibular input ('finger-nose' and 'one leg stand'). However, no significant difference was found between the two groups with regard to the Pyfer test. When focussing on aim 2, the results indicated significant relationships between certain problems that are associated with poor socio-economic circumstances and the sensory development of children. With regard to aim 3, it is apparent from the results of t-testing (p≤ 0.05) that the motor skills of girls are better when compared to boys. Significant differences were found in favour of the girls with regard to the gross-motor percentile, the gross-motor grading, the total quotient and the total motor percentile where the girls did better than the boys. With regard to the sensory development, a t-test showed that the girls performed significantly poorer than the boys in the test for visual tracking, while the boys performed significantly poorer than the girls in the tests for spatial orientation ('finger-nose') and bilateral integration ('repetitive hand movements'). With regard to aim 4, correlation analysis indicated that there was a relationship between sensory, general and fine motor development in the group as a whole, while a discriminant analysis showed that visual perception contributed most to the overall motor developmental levels of the group. No relationship was, however, found between the gross-motor and sensory development of the group. These results substantiate that the motor en sensory development of children living in poor socio-economic conditions are hampered by their environment, and that they should receive additional attention to try to prevent deficiencies in this regard. / Thesis (M.A. (Human Movement Science))--North-West University, Potchefstroom Campus, 2005.

South Africa's automotive industry has become an increasingly important contributor to the country's gross domestic product, largely through the strong growth in the motor vehicle and component exporting sector. The South African Motor Industry is ranked 20th in the world in terms of vehicle production. It is responsible for an estimated 80% of Africa's vehicle productivity and makes 0.85% of the world's vehicles. In this study, the automotive industry in South Africa is investigated, how it was influenced during the recession which started at the end of 2008 and went through the 2009 period, what effect it had on the market as well as the influence on sales during that period. In the literature section, the 4P's of the marketing mix are explained and discussed as well as how it influences the automotive industry. The purpose of this study is to see specifically how the Klerksdorp dealerships were influenced by the recession and what decisions they had undertaken to tackle the problems that they encountered. This study also investigates what influences the marketing mix had on the different dealerships in Klerksdorp area. From the empirical study done, the conclusion is that the dealerships in Klerksdorp were struggling through the economic crisis. As far as the product was concerned, the different dealerships concentrated on the best selling lines during the recession period. Very few dealerships adjusted their prices and very few offered extras that were already included in the price. With the promotion, it was actually established that the dealerships did not actually put any extra effort in order to promote their vehicles. Four out of nine dealerships decreased their promotion expenditure, while the other five kept it at the same level. None of the dealerships has increased their promotional spending during the time of recession. Finally, the recommendations to the dealerships, as how to improve the marketing and sales through the correct use of the marketing mix, especially through the use of promotion in the Klerksdorp dealerships were made. / Thesis (M.B.A.)--North-West University, Potchefstroom Campus, 2010.

Individuals employed within the South African workforce are finding themselves operating in an increasingly uneven playing field. The global marketplace is continually amplifying the already stiff competition, forcing employers to reduce the security they are able to offer their workers, in an effort to off-set their profit margins. Examining and consequently addressing these private sector employees' functioning in those spheres that may influence their health and consequent work performance, which in turn affects the performance of the industry - and therefore the economy – is thus essential. The objective of this study was to investigate the relationship between job insecurity, resilience and general health of personnel (N= 207) employed within the motor-trade industry and to examine differences among the job insecurity, resilience and general health levels of different demographic groups. A cross-sectional survey design was implemented. The constructs were measured by means of the Job Insecurity Scale (JIS), the Resilience Scale (RS) and the General Health Questionnaire (GHQ). The research method for the article consists of a concise literature review, followed by an empirical study. Cronbach alpha coefficients inter-item correlation coefficients and confirmatory factor analyses were used to determine the validity and reliability if the measuring instruments. Descriptive statistics were used to analyse the data and Pearson product moment correlation coefficients, as well as regression analyses were used to examine the relationships between the constructs employed in this research. No significant differences were found to exist based on biographical characteristics regarding job insecurity, resilience and general health. Job insecurity and the somatic symptoms, social dysfunction and severe depression subscales of the general health measure were found to be statistically significantly negatively correlated. Statistically significant correlations were displayed between resilience and general health, as well as all of its subscales. Resilience was shown to play a moderating role in the relationship between job insecurity and social dysfunction (and not in any of the other general health dimensions), as results indicated that the social functioning of individuals measuring high on resilience was less affected by job insecurity than those individuals measuring low on resilience. Conclusions are made, limitations of the current research are discussed and recommendations for future research are put forward. / Thesis (M.A. (Industrial Psychology))--North-West University, Vaal Triangle Campus, 2007.

Individuals employed within the South African workforce are finding themselves operating in an increasingly uneven playing field. The global marketplace is continually amplifying the already stiff competition, forcing employers to reduce the security they are able to offer their workers, in an effort to off-set their profit margins. Examining and consequently addressing these private sector employees' functioning in those spheres that may influence their health and consequent work performance, which in turn affects the performance of the industry - and therefore the economy – is thus essential. The objective of this study was to investigate the relationship between job insecurity, resilience and general health of personnel (N= 207) employed within the motor-trade industry and to examine differences among the job insecurity, resilience and general health levels of different demographic groups. A cross-sectional survey design was implemented. The constructs were measured by means of the Job Insecurity Scale (JIS), the Resilience Scale (RS) and the General Health Questionnaire (GHQ). The research method for the article consists of a concise literature review, followed by an empirical study. Cronbach alpha coefficients inter-item correlation coefficients and confirmatory factor analyses were used to determine the validity and reliability if the measuring instruments. Descriptive statistics were used to analyse the data and Pearson product moment correlation coefficients, as well as regression analyses were used to examine the relationships between the constructs employed in this research. No significant differences were found to exist based on biographical characteristics regarding job insecurity, resilience and general health. Job insecurity and the somatic symptoms, social dysfunction and severe depression subscales of the general health measure were found to be statistically significantly negatively correlated. Statistically significant correlations were displayed between resilience and general health, as well as all of its subscales. Resilience was shown to play a moderating role in the relationship between job insecurity and social dysfunction (and not in any of the other general health dimensions), as results indicated that the social functioning of individuals measuring high on resilience was less affected by job insecurity than those individuals measuring low on resilience. Conclusions are made, limitations of the current research are discussed and recommendations for future research are put forward. / Thesis (M.A. (Industrial Psychology))--North-West University, Vaal Triangle Campus, 2007.

Everyday movements, such as reaching for a drink of water or typing on a keyboard highlight the relative ease with which we move and interact with our surroundings. However, the success of these skilled movements depends on the motor system’s ability to consider a variety of factors, such as the goal of the behavioral task, the surrounding environment and the physical properties of the musculoskeletal system. Recent theories of voluntary motor control, namely optimal feedback control, suggest that such skilled motor behavior is achieved through sophisticated feedback control. This thesis investigates one physiological implication of this theory. Specifically, we hypothesize that rapid feedback responses following mechanical perturbations possess many of the functional attributes thought to be reserved for voluntary control because these two systems have contributions from similar neural substrates (eg. motor areas in cortex). Our studies were specifically designed to investigate rapid feedback responses during the long-latency epoch, which occurs between 50-100ms following a mechanical perturbation. Consistent with our hypothesis, we found that the sophistication of the long-latency response rivals that of voluntary control. In our first study (Chapter 2) we examined if rapid feedback responses were sensitive to features of the end target. We found that muscle activity during the long-latency epoch was modulated by the size/shape of the end. In our second study (Chapter 3) we observed flexible responses in muscle activity during the long-latency epoch that reflected rapid ‘decisions’ during online control regarding how to navigate around obstacles in the environment as well as how to select amongst multiple potential goals. In our final study (Chapter 4) we examined if rapid feedback responses in the shortened muscle parallel the sophisticated responses observed in the lengthened muscle. We found that unloading a pre-excited muscle elicited sophisticated inhibitory responses, including knowledge of limb mechanics and rapid target selection, during the long-latency epoch that are comparable to the excitatory responses observed during loading. Taken together, the studies presented in this thesis demonstrate that the responses in the long-latency epoch reflect several functional attributes typically reserved for voluntary control. / Thesis (Ph.D, Neuroscience Studies) -- Queen's University, 2014-04-29 16:54:12.489