The study reported in this dissertation compares the learning effectiveness of two experimental methods that can be used in the teaching of kinematics to Grade 11 learners in Physical Science. The first method is the conventional ticker-timer experiment, while the second utilises high-technology microcomputer-based equipment. The purpose is to make recommendations for improved teaching of basic kinematics concepts and graphs, which learners have difficulties with (Halloun & Hestenes, 1985; McDermott et al., 1987). A group of 48 Grade 11 learners from Thuto-Boswa Secondary School, Ventersdorp, were used in the empirical research. They were divided into two groups of comparable abilities. Group A used the conventional apparatus and group B the microcomputerbased apparatus. The results of the pre- and post-tests were analysed statistically to compare the learning effectiveness of the two methods in terms of the outcomes reached, the gains obtained as well as d-values. Three months after the experiments were conducted the learners were tested again to determine the long-term effect of the methods. Both groups obtained a gain of approximately 0,2 in the pre- versus post-test analysis. The literature (e.g. Thornton, 1998) reveals larger gains with microcomputer-based experiments. Three possible reasons that could contribute to this discrepancy were investigated, namely the learners' acquaintance with the microcomputer, the educator's experience with the apparatus as well as the learners' cultural background and language. All three these factors were found to have a detrimental effect on the learning effectiveness, especially with the microcomputer-based method. Recommendations are made in connection with the teaching of basic kinematics concepts and graphs to Grade 11 learners in South African secondary schools. In addition, it is emphasised that educators should be adequately computer literate before expensive high-technology equipment is purchased for classroom use. It is also pointed out that the implementation of the computer as teaching aid can be a first step to improve computer literacy of disadvantaged learners in our schools. / Thesis (M.Ed.)--North-West University, Potchefstroom Campus, 2004.

Several studies have previously demonstrated that sediment transported as bed load under a standing wave will be moved from between node and antinode towards the node where it accumulates. The end result is the generation of areas of scour in the bed between node and antinode and areas of sediment accretion around the node. However, these studies have failed to provide an adequate description of the mechanisms which led to this so-called "N-type" response. Consequently it has been the purpose of this study to examine the phenomenon of N-type beach response in some detail. As a first step an experimental programme was conducted in a random wave flume using a model beach and vertical, impermeable wall N-type conditions were produced, observations are made on the mechanisms of sediment transport and flow-field measurements are also reported. The experimental results demonstrate that N-type beach response is the direct result of an asymmetry in the main flow-field caused by the superposition of incident and reflected non-linear waves. A second experimental programme examines the N-type equilibrium profile shape using measurements of profiles generated under a range of wave conditions. An equation defined for a given profile amplitude and profile limits is found to predict the underlying characteristic N-type profile shape very well. Finally, a model of N-type beach response is developed. This model follows a relatively simple "grab-and-dump" concept with coefficients based on the understanding gained of the N-type response processes. It is shown that N-type profiles can be predicted reasonably well for the range of wave conditions used in the experiments here. Outside of this range predictions are less good, suggesting a re-examination of the model coefficients is required.

This thesis addresses modeling and simulation of the human lower extremities in order to track walking motion and estimate walking distance. The lower extremities are modeled as an articulated object, which consists of rigid bars connected to each other by joints. This model is tested by using both synthetic and real data. The synthetic data is created based on the main principles of biomechanics. The real data is obtained from the MARG sensors and is processed by the Factored Quaternion algorithm. Next, it is implemented in a simulation program written in Matlab. The program utilizes a mathematical model that represents the human gait-cycle and is based on the theory of forward kinematics as well as on the theory of manipulator kinematics. The simulation program is able to track the motion of the limbs that represent the lower extremities and estimate the traveled distance. Extensive laboratory tests verified the validity of the configuration.

M.Ing. (Mechanical Engineering) / This dissertation presents and explains methods for the dynamic modeling of robot like mechanisms. These mechanisms can have multiple degree of freedom joints and contain closed-chains. A new kinematic notation is proposed. The algorithms, including those used for the inverse and direct dynamics, are all based on spatial notation and a general joint model, providing a quite general, integrated and complete method for solving the dynamics of simple closed-chain mechanisms.

by Lam Miu-Ling. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 64-67). / Abstracts in English and Chinese. / Chapter Chapter 1. --- Introduction --- p.1 / Chapter Chapter 2. --- Mathematical Preliminaries and Problem Definition --- p.6 / Chapter 2.1 --- Grasp Synthesis in Discrete Domain / Chapter 2.2 --- Assumptions / Chapter 2.3 --- Frictionless Form-Closure Grasp / Chapter 2.4 --- Frictional Form-Closure Grasp / Chapter 2.5 --- Problem Definition / Chapter Chapter 3. --- A Qualitative Test Algorithm and a Local Search Algorithm --- p.18 / Chapter 3.1 --- A Qualitative Test Algorithm / Chapter 3.2 --- A Local Search Algorithm / Chapter 3.3 --- Grasp Planning under Kinematic Constraints / Chapter Chapter 4. --- A Divide-and-Conquer Technique --- p.29 / Chapter 4.1. --- Determining a Separating Hyperplane / Chapter 4.2. --- Divide-and-Conquer in Frictionless Case / Chapter 4.3. --- Divide-and-Conquer in Frictional Case / Chapter Chapter 5. --- Implementation and Examples --- p.40 / Chapter 6.1. --- Examples of Frictionless Grasps / Chapter 6.2. --- Examples of Frictional Grasps / Chapter 6.3. --- Examples of Grasps under Kinematic Constraints / Chapter Chapter 6. --- Conclusions --- p.62 / Bibliography --- p.64

The effective prescription of resistance exercise for strength and power development has been a source of debate amongst practitioners and sport scientist alike. One of the key issues in this area relates to the training load that would best facilitate strength and power adaptation. Heavy loads (>60-70% 1RM) have been traditionally used for maximal strength development by facilitating changes in neural function (strength) and muscle size (hypertrophy). However, many studies have now found lighter load (>45%1RM) training equally effective in improving both strength and hypertrophy. Similarly, many studies have found heavy load training effective in enhancing various measures of power though lighter loads (e.g. 45% 1RM) are thought to maximise the mechanical power output of muscle. Realising that adaptation depends upon some interaction between the mechanical, hormonal and metabolic stimuli, examining these responses would enhance our understanding of the underlying determinants of strength and power, and thereby improve strength and conditioning practice. Therefore, the purpose of this study was to examine the mechanical, hormonal and metabolic responses to equal volume light and heavy loading schemes. Eleven males (mean 26.6 ± 6.7 years; mean 79.0 ± 8.1 kg) with a minimum of 12 months weight training experience each performed two exercises (Smith squat and supine squat) at a light (45% 1RM) and heavy (88% 1RM) intensity. The light scheme consisted of eight sets of six repetitions, with six sets of four repetitions performed in the heavy scheme. Rest periods of three and four minutes respectively were used. Saliva sampling was used to determine the hormonal (cortisol and testosterone) and metabolic (lactate) responses. Samples were collected at rest (pre-), immediately after the first exercise (mid-), at the conclusion of the second exercise (P0) and every 15 minutes thereafter for one hour (P15, P30, P45, P60). Mean values for all variables were analysed with a paired sample T-test. Chances that the true effects were substantial (% and qualitative) were also calculated. No significant (P>0.05) difference in total forces was found between schemes; however, the light scheme produced significantly greater total time under tension (36%), total work (37%) and total power output (115%). Total impulse (38%) was the only variable found to be greater in the heavy scheme. A decrease in testosterone (TST) was observed in the heavy scheme (-4 to -29%) with no significant changes found across the light scheme (1 to 12%). Cortisol decreased in the light (-6 to -30%) and heavy (-14 to -44%) schemes until P45. An increase in the TST/cortisol ratio was observed in both the light (17 to 49%) and heavy (2 to 44%) schemes. Both loading schemes resulted in similar increases in lactate (0.3 to 1.0nmol/l). Equating two schemes by volume resulted in differential responses, many of which favoured the lighter scheme in terms of mechanical, hormonal and metabolic outputs. These findings suggest that load or intensity employed may be not as important as initially proposed and that other factors (e.g. volume, technique) may explain the similar strength and hypertrophy adaptation reported in studies comparing light and heavy schemes.

A method to design foot trajectory in Cartesian coordinates for a six-leg walking machine is presented in this thesis. The walking machine is based on the geometry of the darkling beetle. The walking procedure developed by Y.S. Baek is introduced first to provide step length and leg swing time for foot trajectory planning. This procedure also supplies required parameters to describe the relationship between feet and body during locomotion. The trajectory of a single foot consists of the path and its temporal attributes, that is, velocity and acceleration. Several methods and constraints for path and velocity profile design are discussed. Software developed in Microsoft Quick C is used to generate and animate on the screen a single desired foot trajectory applied to each of the six legs by combining paths and velocity profiles. The generated trajectory is converted to joint coordinates to provide necessary data for leg control. Since a single foot trajectory is applied to three pairs of legs of different design, three sets of joint coordinate sequences are produced. Furthermore, each leg consists of three segments and three joints necessitating nine control sequences altogether. Half-ellipse and trochoidal paths are interpolated with 5th and 6th order polynomials to determine minimum required joint acceleration. All paths and their first and second derivatives are required to be smooth. The effect of body pitch are also examined. / Graduation date: 1995

Two possible sets of planning variables for human arm movement are point angles and hand position. Although one might expect these possibilities to be mutually exclusive, recently an apparently contradictory set of data has appeared that indicated straight-line trajectories in both hand space and joint space at the same time. To assist in distinguishing between these viewpoints applied to the same data, we have theoretically characterized the set of trajectories derivable from a joint based planning strategy and have compared them to experimental measurements. We conclude that the apparent straight-lines in joint space happen to be artifacts of movement kinematics near the workspace boundary.

We have derived a new performance measure, product of minors of the Jacobian matrix, that tells how far kinematically redundant manipulators are from singularity. It was demonstrated that previously used performance measures, namely condition number and manipulability measure allowed to change configurations, caused repeatability problems and discontinuity effects. The new measure, on the other hand, assures that the arm solution remains in the same configuration, thus effectively preventing these problems.

Success in baseball batting is fundamental to the sport, however it remains one of, if not the most, challenging skills in sports to master. Batters utilize the kinetic chain to transfer energy from the lower body to the upper body to the bat, hoping to impart the maximum amount of energy into the ball. Scientists and coaches have researched the swing and developed theories on the keys for successful batting, but most of this research has been inadequate in attempting to fully describe the biomechanics of batting. The purposes of this study were to improve upon the methodology of previous researchers, provide a full biomechanical description of the swing, and compare swings against pitches thrown to different locations and at different speeds. AA-level Minor League Baseball players (n=43) took extended rounds of batting practice in an indoor laboratory against a pitcher throwing a mixture of fastballs and changeups. An eight camera motion analysis system and two force plates recording at 300 Hz captured the biomechanical data. The swing was divided into six phases (stance, stride, coiling, swing initiation, swing acceleration, and follow-through) by five key events (lead foot off, lead foot down, weight shift commitment, maximum front foot vertical ground reaction force, and bat-ball contact). Twenty-eight kinematic measurements and six ground reaction force measurements were computed based on the marker and force plate data, and all were assessed throughout the phases. First, a comprehensive description of a composite of the batters’ swings against fastballs “down the middle” was provided. Second, successful swings against fastballs thrown to one of five pitch locations (HIGH IN, HIGH OUT, LOW IN, LOW OUT, MIDDLE) were compared in terms of selected kinematics at the instant of bat-ball contact, timing and magnitude of peak kinematic velocities, and timing and magnitude of peak ground reaction forces. Third, these variables were once again compared for swings against fastballs and changeups. A large number of biomechanical differences were seen among the swings against various pitch locations. More fully rotated positions, particularly of the pelvis and bat were critical to the batters’ successes on inside pitches while less rotated positions keyed successes against outside pitches. The trail and lead arms worked together as part of a closed chain to drive the hand path. Successful swings had the trail elbow extended more for HIGH IN and flexed more for LOW OUT, though batters often struggled to execute this movement properly. A distinct pattern among successful swings against fastballs, successful swings against changeups, and unsuccessful swings against changeups was witnessed; namely a progressive delay in which the batter prematurely initiated the events of the kinetic chain, especially when unsuccessful in hitting a changeup. It was believed that this study was much more effective in capturing the essence of baseball batting than previous scientific works. Some recommendations to batting coaches would be to get batters to take a consistent approach in the early phases of every swing (particularly for the lower body), identify both pitch type and location as early as possible, use the rotation of the pelvis to propagate the energy transfer of the kinetic chain from the group to the upper body, and use the pelvis, and subsequently, the upper body, to orient the trunk and hands to an optimal position to drive the ball to the desired field. Limitations of the current study and ideas for future work were also presented to better interpret the findings of this research and further connect science and sport.