As early as 1994, and with transformation in mind, the African National Congress (ANC) identified the development of the previously disadvantaged communities in South Africa as a national priority. In so doing, sport, among others, was used in this strategy as a medium to improve and change the circumstances of people in disadvantaged communities. Sports development in disadvantaged communities is essential, if taken into consideration that without such further support of the sport talent of some of these children, the needs of these talented children cannot be met and their potential will remain undeveloped. Talent identification (TID), which is based on scientific principles and forms the first step in sports development, still is relatively new in South Africa. Historically, coaches used their own knowledge and experience of the characteristics, which should lead to success in sport as well as participation in competitions in order to do TID. To date, very little research has been done on talent identification and development in sprints and long-jump, especially pertaining to young boy and girl athletes, and in particular concerning athletes from disadvantaged communities. The first and second objectives of this study were to implement sport specific athletics development programmes aimed at improving sprinting and long-jump ability and to determine its effect on the abilities and skills of talented 10 to 15 year-old girls and boys with talent for sprints and long-jump. The third and fourth objectives of this study were to establish which kinanthropometric, physical and motor components will play such a role in 10 to 15 year-olds that it can predict performance ability in sprints and long-jump in girls and boys at this age. The "Australian Talent Search" protocol was used to identify general sport talent in the children (66 girls and 62 boys) who were identified for the study. The talented children (19 girls and 21 boys) from the initial group of were then subjected to a sport specific test battery for sprints and long-jump. The maturation level of the boys was determined by means of a maturity questionnaire, based on the 5 Tanner stages. By using the Statistica and SAS computer programmes, independent t-testing, covariance analyses, correlation coefficients, effect sizes, descriptive statistics as well as a stepwise multiple regression analysis were used to analyze the data with regard to the above-mentioned objectives. A p-value smaller than or equal to 0.05 was accepted as significant. From the results of the study it is evident that the development programmes contributed to the improvement of physical and motor abilities and skills important for performance in both sprints and long-jump in girls (n=19) and boys (n=21) respectively. Among the girls, flexibility, explosive power, muscle endurance, reaction time, speed, speed endurance, acceleration and long-jump showed statistically significant improvement, while abdominal muscle strength and stride length showed no improvement. Secondly, it was established that the development programme contributed statistically significantly to an improvement in flexibility, muscle endurance, 0-40 metres speed and long-jump ability in boys. However, some components did not show improvement, among them explosive power, reaction time, speed endurance, acceleration and stride length. A stepwise multiple regression analysis was used to analyze the third and fourth objectives. It indicated that, in respect to the 100 metres sprint, 7 variables, namely long-jump, push-ups to the point of exhaustion, 7-level abdominal strength, 0-5 metres speed, ankle dorsiflexion, body length and age contributed 84.0% to the total variance in girls. As for long-jump, 7 variables, namely 0-100 metres speed, body length, 7-level abdominal strength, push-ups, ankle dorsiflexion, standing long-jump and body mass proved to be the most important contributors to performance in these items with a total contribution of 79% to the total variance. The fourth objective indicated that average anaerobic power output, acceleration and body mass contributed statistically significantly to performance in the 100 metres sprint in boys with a contribution of 86.5% to the total variance. Horizontal jump, age and acceleration contributed statistically significantly to long-jump performance with a contribution of 81 5% to the total variance. It is evident from this study that sport specific development programmes can successfully be implemented on girls and boys at ages 10-15 in order to improve sprinting and long-jump ability, regardless of poverty-stricken circumstances and poor infrastructure. Furthermore, the study brought to light that specific kinanthropometric, physical and motor abilities exist which can be used to predict performance in sprints and long-jump in girls and boys separately at ages 10 to 15. / Thesis (Ph.D. (Human Movement Science))--North-West University, Potchefstroom Campus, 2007

The contagious nature of the black-tailed prairie dog (Cynomys ludovicianus) jump-yip display may provide information to signalers and receivers regarding the vigilance of neighbours. Videotaping jump-yip bouts and the behaviour of both bout initiators and respondents within those bouts provided evidence that: 1) individuals became vigilant immediately following jump-yip production, but exhibited minimal changes in their immediate post-jump-yip behaviour with changes in the characteristics of the preceding bout, 2) bout initiators spent more time actively foraging and exhibited vigilance behaviours less frequently with greater levels of response in the preceding jump-yip bout, 3) respondents spent more time actively foraging and less time vigilant following bouts with greater response. These results suggest that black-tailed prairie dogs base behavioural decisions at least in part on the characteristics of their jump-yip bouts and thus the jump yip display may provide information about the vigilance of group members.

The main goal of the present study is to investigate the energy dissipation through inclined screens. Recent studies have shown that screens arranged vertically may dissipate more energy than a hydraulic jump does below small hydraulic structures. In the present study a series of laboratory experiments were performed in order to determine the effect of inclination of the screen on the energy dissipated by the screen. The porosity of the screen used in the experiments is 40%. Inclination angle, thickness of the screen, location of the screen, upstream flow depth, and the Froude number of the upstream flow are the major parameters for the laboratory experiments. Froude number of the upstream flow covered a range of 5 to 24. A screen was located up to a distance 100 times the undisturbed upstream flow depth from the gate and the thickness of the screen was changed in correlation with the depth of upstream flow. The results of the experiments show that the inclination parameter has an insignificant effect on the energy dissipated by the screen. Namely, inclination of the screen does not contribute much in reducing the energy of the flowing water further, compared to vertically placed screens.

The objective of this study is to determine the effect of different roughness types and arrangements on hydraulic jump characteristics in a rectangular channel. Three different types of roughness were used along experiments. All of them had rectangular prism shapes and that were placed normal to the flow direction. To avoid cavitation, height of roughness elements were arranged according to level of the channel inlet, so that the crests of roughness elements would not be protruding into the flow. The effects of roughness type and arrangement on hydraulic jump properties, i.e. energy dissipation, length of the jump and tail water depth were investigated. These properties were compared with the available data in literature and with the properties of hydraulic jump occurred on smooth bed.

ABSTRACT EXPERIMENTAL INVESTIGATION OF ENERGY DISSIPATION THROUGH TRIANGULAR SCREENS G&uuml / ng&ouml / r, Endam M.Sc., Department of Civil Engineering Supervisor: Assoc. Prof. Dr. Zafer BozkuS Co-Supervisor: Prof. Dr. Metin Ger May 2005, 82 pages For the present study, a series of experimental works are executed to dissipate energy through triangular screens. Recent studies have shown that the implementation of the screen for energy dissipation is an effective way to extract out the excessive energy of water downstream of small hydraulic structures located in rivers of relatively negligible sediment content. In the present study, double screen arrangement with a porosity of 40% is used. The inclination angle of the screens is opted as 60 degree. The major parameters for the present study are upstream flow depth, location of the screen together with the supercritical upstream flow Froude number for a range covering from 7.5 to 25.5. The gate opening simulating a hydraulic structure is adjusted with various heights of 1 cm, 1.25 cm, 1.6 cm, 1.7 cm, 2 cm, 2.5 cm, 2.7 cm, 3.2 cm and 3.3 cm during the study. The results of the experiments show that the triangular screen configuration with the same pore geometry has no significant additional contribution on the energy dissipation as compared to vertically placed screens. Keywords: Screen, energy dissipation, triangular configuration, porosity, hydraulic jump, supercritical flow.

We utilise several asset pricing models that allow for discontinuities in the returns and volatility time series in order to obtain estimates of Value-at-Risk (VaR). The first class of model that we use mixes a continuous diffusion process with discrete jumps at random points in time (Poisson Jump Diffusion Model). We also apply a purely discontinuous model that does not contain any continuous component at all in the underlying distribution (Variance Gamma Model). These models have been shown to have some success in capturing certain characteristics of return distributions, a few being leptokurtosis and skewness. Calibrating these models onto the returns of an index of Australian stocks (All Ordinaries Index), we then use the resulting parameters to obtain daily estimates of VaR. In order to obtain the VaR estimates for the Poisson Jump Diffusion Model and the Variance Gamma Model, we introduce the use of an innovation from option pricing techniques, which concentrates on the more tractable characteristic functions of the models. Having then obtained a series of VaR estimates, we then apply a variety of criteria to assess how each model performs and also evaluate these models against the traditional approaches to calculating VaR, such as that suggested by J.P. Morgan???s RiskMetrics. Our results show that whilst the Poisson Jump Diffusion model proved the most accurate at the 95% VaR level, neither the Poisson Jump Diffusion or Variance Gamma models were dominant in the other performance criteria examined. Overall, no model was clearly superior according to all the performance criteria analysed, and it seems that the extra computational time required to calibrate the Poisson Jump Diffusion and Variance Gamma models for the purposes of VaR estimation do not provide sufficient reward for the additional effort than that currently employed by Riskmetrics.

Jumping is one of the common methods that flight capable birds use to initiate the take-off phase. Flapping-wing robots that can achieve jumping take-off similar to birds will be significantly valuable since they can reduce the workload of the wing in producing the instantaneous power required for take-off and enables remote operations as well. This thesis progresses the state of the art in leg based jumping systems for flapping-wing robots through a contribution to the fundamental understanding of jumping dynamics and the development of experimentally validated simulation tools. Three reference leg postures are identified from video analysis of a rook take-off: stand, crouch and extended. Birds often use different kinematic patterns for the leg flexion (stand to crouch) and extension (crouch to extended) phases. This is made possible by their multi degree of freedom (Dof) leg structure and complex, multi actuated muscle systems. As an alternative strategy, a conceptual design of a singly actuated jumping leg is proposed where a multi Dof segmented leg is linked to a single actuator. The structure is based on the avian leg and foot anatomy. The study identifies that a dynamically unstable jumping take-off using a tilt and jump approach enables a singly actuated robotic leg to achieve jumping performance similar to birds. A combination of analytical, numerical and physical modelling approaches is used in this study. A generic analytical jumping model is used to establish fundamental understanding of jumping dynamics. The study shows that the take-off dynamics of a jumping system can be idealised as an inelastic collision between the dynamic and static rigid bodies of the system. This provides a simpler way to understand jumping dynamics in general. A physical prismatic jumping model is fabricated principally for validation purposes. A motion capture system is used to quantitatively analyse the jumping kinematics of the model. The take-off velocities predicted through analytical and numerical models agree closely with the experimental data. A multi-segmented numerical simulation model is then developed based on the proposed singly actuated jumping leg design. In the same way an analytical model is developed. It is found that the singly actuated design concept with the assumption of massless segments greatly reduced the complexity of the multi-segmented analytical model. The proposed analytical approach and simulation tool are demonstrated by designing a multi-segmented jumping leg for an example robotic bird. The transparency of the approach enables the designer to understand how design parameters such as take-off weight, actuation properties, leg postures and sizes of the segments affect the take-off velocity. Numerical simulation analysis confirms that jumping performance similar to birds is achieved in the proposed singly actuated jumping legs with the integration of tilt and jump method. For the presented case study, the use of the dynamic tilting method improves the minimum achievable take-off angle from 73° to 12° with respect to the horizontal axis.

Vertedouros em degraus têm se tornado uma boa opção em barragens pela facilidade de construção e, principalmente, por apresentar uma dissipação significativa de energia ao longo de sua calha, o que faz com que a parcela de energia a ser dissipada por ressalto hidráulico a jusante da barragem diminua, ocasionando uma significativa redução nas dimensões da estrutura da bacia de dissipação. A aplicação de soleira terminal em bacias de dissipação provoca uma melhor distribuição das velocidades e um melhor comportamento da flutuação de pressões ao longo da bacia e a jusante, aumentando assim seu desempenho na dissipação de energia. A combinação destas duas formas de dissipação (vertedouro em degraus e bacia de dissipação com soleira terminal) pode ser utilizada como uma solução econômica e segura, entretanto, o dimensionamento dessas estruturas esbarra na falta de critérios e informações, principalmente quanto ao tamanho e posição ideal para o projeto de uma soleira terminal. No presente trabalho foram analisados os dados de pressões médias e flutuações de pressões no interior da bacia e a jusante da soleira terminal, sendo apresentadas metodologias para dimensionamento de tamanho e para posicionamento de uma soleira em função do número de Froude da entrada do ressalto hidráulico. Também está sendo apresentada uma metodologia para análise das pressões médias em bacia do tipo I (sem soleira), além de uma comparação do comportamento dos esforços em bacia com soleira e sem soleira, com vertedouro em degraus e vertedouro de calha lisa. Os dados utilizados foram obtidos em modelo experimental, construído no Laboratório de Obras Hidráulicas (LOH) do Instituto de Pesquisas Hidráulicas (IPH-UFRGS), através de transdutores de pressões fixados junto ao fundo do canal de ensaios para diversas vazões, considerando, além de bacia tipo I, diferentes tamanhos de soleira terminal, situadas em diferentes posições do canal. / Stepped spillways have become a good option in dams for ease of construction and especially to present a significant dissipation of energy throughout the spillway chute, which causes that the parcel of energy to be dissipated by hydraulic jump downstream of dam decreases, causing a significant reduction in the dimensions of the stilling basin structure. The application of end sill in stilling basins causes a better distribution of speeds and better behavior of the fluctuation of pressure along the basin and downstream, thus increasing their performance in energy dissipation. The combination of these two forms of dissipation (stepped spillway and stilling basin with end sill) can be used as an economical and safe solution, however, the sizing of these structures hindered by a lack of criteria and information, especially regarding the ideal size and position for design of an end sill. In this study the data mean pressures and pressure fluctuations within the basin and downstream of the end sill were analyzed, being presented methodologies for design the size and position of a sill as a function of the Froude number of the input of the hydraulic jump. A methodology for analysis of mean pressure in type I basin (without sill) is also being presented, and a comparison of the behavior of efforts in basin with and without end sill, with stepped spillway and flat spillway chute. The data were obtained in an experimental model built at the Laboratory of Hydraulic Works (LOH) at the Institute of Hydraulic Research (IPH-UFRGS), through pressure transducers attached at the bottom of the test channel for various flow rates, considering, in addition of type I basin, different sizes of end sill at different positions of the channel.

In this thesis, we investigate two stock price models, the Black-Scholes (BS) model and the Merton Jump-Diffusion (MJD) model. Comparing the logarithmic return of the BS model and the MJD model with empirical stock price data, we conclude that the Merton Jump-Diffusion Model is substantially more suitable for the stock market. This is concluded visually not only by comparing the density functions but also by analyzing mean, variance, skewness and kurtosis of the log-returns. One technical contribution to the thesis is a suggested decision rule for initial guess of a maximum likelihood estimation of the MJD-modeled parameters.

O dimensionamento seguro e econômico de dissipadores de energia por ressalto hidráulico formado a jusante de vertedouros passa pela compreensão de como se processa a dinâmica do escoamento. Para que isso seja possível é necessário que sejam identificadas as características macroturbulentas do escoamento, tanto no que diz respeito aos valores médios quanto às parcelas flutuantes e extremas dos esforços de pressões atuantes junto ao fundo. Este trabalho, então, propõe a análise dos esforços hidrodinâmicos atuantes na estrutura hidráulica a partir de uma nova abordagem que preconiza que os esforços atuantes junto ao fundo devem ser avaliados como um somatório dos efeitos hidrodinâmicos ocasionados pelas distintas condições do escoamento. Dessa forma, foram avaliados individualmente os efeitos: (i) da curva de concordância vertical entre o perfil vertente e a bacia de dissipação e a sua influência sobre esta, (ii) do escoamento em regime rápido sobre um plano horizontal, (iii) da macroturbulência presente no ressalto hidráulico livre (tipo A) e (iv) do afogamento do ressalto hidráulico. Essa avaliação individualizada proporciona, em última instância, a identificação global dos esforços atuantes junto à estrutura hidráulica, conferindo sensibilidade a esta análise global a partir da identificação da influência de cada um dos efeitos atuantes e das respectivas consequências sobre a bacia de dissipação. O trabalho apresenta, assim, um método analítico de previsão de pressões médias, flutuantes e extremas atuantes ao longo de uma bacia de dissipação por ressalto hidráulico, quer este seja formado integralmente na bacia de dissipação, quer este seja formado parcialmente sobre o perfil vertente, condição predominante na operação de sistemas estruturais de dissipação de energia hidráulica. / To safely and economically design hydraulic jump energy dissipators downstream spillways the comprehension of the flow dynamics is needed. To achieve this it is needed to identify the macroturbulent characteristics of the flow, both the mean pressure values as well as the fluctuating and extreme pressures acting on the floor of the stilling basin. The present work proposes to analyze the hydrodynamic forces acting on the structures by means of a new approach which states that the pressures acting on the basin floor can be evaluates as the sum of hydrodynamic effects caused by the distinct flow conditions. The following effects were individually evaluated (i) transition from the spillway slope to the flat basin slope. (ii) supercrítical flow over a flat slope, (iii) macroturbulence present in a classic hydraulic jump (type A jump) and (iv) jump submergence. This individualized evaluation aims to identify the global forces acting on the spillway structure conferring sensitivity to the global analysis from the identification of each of the acting effects and its consequences. The present work relates an analytical method for predicting of mean, fluctuating and extreme pressures acting on a hydraulic jump stilling basin, be it formed integrally on the structure or partially over the spillway, usual condition in the basin operation.