This study investigated the effects of incremented loads greater than maximal acceptable loads on selected locomotor kinematic and psychophysical variables for four different hand-held load-carriage methods. Ten male and ten female subjects, between the ages of 18 and 30, participated in four experimental sessions. Data collection involved obtaining selected anthropometric, strength, maximal load and preferred load, gait kinematic, and psychophysical values. The anthropometric, strength and load capacity variables enabled absolute and morphology normalised sex-based comparisons to be made. The kinematic and psychophysical parameters were used to quantify any changes from two sets of baseline values,"unloaded" and "maximal acceptable load" values, when loads were increased and carrying methods changed. Statistical analysis revealed that males were taller, heavier and stronger than females (p<0.05). Males chose significantly greater maximal acceptable loads and absolute maximal loads than females when expressed in their absolute or relative terms. Preferred walking speeds were not significantly different for unloaded or loaded conditions, although males walked significantly faster in absolute terms (but not in relative terms) than females. Different load carrying methods and incremented loads brought. about significant changes to several of the kinematic parameters investigated. Finally, ratings of perceived exertion, as well as the number of exertion sites, were seen to increase significantly as load increased. These values were not, however, significantly affected by differences in load carriage method.

Planetary nebulae are formed from the ejecta of evolved stars. These ejecta are swept up by the fast low density wind from the hot central star, as it evolves towards a white dwarf. The sweep-up mechanism is called the Interacting Stellar Winds model (Kwok et al. 1978). The history of mass loss is imprinted on the nebular ejecta. The velocity field of the ejecta traces the mass loss event. A continuous mass loss gives a different velocity field from a brief mass loss event. We employed Integral Field Unit spectroscopy to study the velocity fields of three Bulge Planetary Nebulae. The preliminary results show the advantage of continuously sampled IFU spectroscopy over long slit spectroscopy. The kinematic of the nebula NGC 6302 was studied in the plane of the sky by com- parison of two epochs of Hubble Space Telescope images separated by 10 years. A two dimensional velocity field was created from 200 measurements. The nebular lobes are found to follow a Hubble-Flow, and were ejected in a brief event 2250 ± 35 yr ago. The ejection of lobes occurred about 700 yr after the end of AGB mass loss. The distribution of ages revealed that the inner nebula appears to be younger. This effect can be explained with additional acceleration at later stages of nebula evolution. The central star of NGC 6302 is believed to be extremely hot based on observed ionization stages in the spectrum. In this thesis the detection of the NGC 6302 central star is reported. The luminosity of the star was determined to be 4 010 L⊙. Together with age of the nebula age the mass of the star could be considerably narrowed down the mass determination of the star to 0.64 ± 0.01 M⊙.

No description available.

The eggbeater kick is a skill used frequently in water polo and synchronized swimming to elevate the upper body for shooting, passing, blocking or compete with the opponent for position in the water. The hips, knees, and ankles are involved in creating favourable orientations of the feet so that propulsive forces in the vertical direction can be created. Literature reporting the technique of the eggbeater kick is scarce and limited to description of kinematics or muscle activity. The relationship of the kinematics to the demands on specific muscles has not been established. The purpose of this study was to analyze the kinematics and muscle activity of the water polo eggbeater kick in fatigued and unfatigued states to provide foundational knowledge on which training programs can be based. Twelve water polo players were tested executing the eggbeater kick in the vertical position while trying to maintain as high a position as possible for the duration of the test. The test was terminated when the player could not keep the top of the sternum marker above water. Anthropometric data were collected using the ‘eZone’ method. Three dimensional coordinates for the lower limbs and two dimensional coordinates of the above water top of the sternum marker were obtained. Surface electromyography recorded the muscle activity of the Tibialis Anterior, Rectus Femoris and Biceps Femoris muscles on both legs. Differences between fatigued and unfatigued conditions and between dominant and nondominant sides were tested using a two factor ANOVA with repeated measures. Differences within subjects were also investigated on a subject by subject basis with regard to muscle activity. Results indicated differences for kinematic and muscle activity variables between fatigue levels. The amplitude of anatomic angles and speed of the feet decreased with fatigue. Significant differences were found between dominant and non-dominant sides for the ankle motion. The non-dominant ankle was more inverted and adducted than the dominant ankle during the knee flexion phase of the cycle. The Rectus Femoris muscle had consistent patterns across subjects, while Tibialis Anterior and Biceps Femoris muscles were more subject specific in their responses. The Rectus Femoris and the Biceps Femoris have an agonist/antagonist relationship during knee flexion and extension. The Tibialis Anterior was active for long periods in the cycle while dorsiflexing and inverting the foot. As a consequence activity in these muscles decreased with fatigue. These findings point towards the necessity for players and coaches to address specific motions and muscles during the training of the eggbeater technique. Future work should focus on developing eggbeater kick training programs that address specific strength and flexibility.

This dissertation deals with the control, guidance and stabilisation of nonlinear, non¬holonomic systems. It is shown that the kinematics of the system can be separated from the dynamics of the system by using successively two inverse dynamics type of transformations. This leads to a linear decoupled kinematical system, control strategies can then be developed that directly control the motion of the system. The method is applied to a system which is composed of a disk rolling on a plane, a controlled slender rod that is pivoted through its center of mass about the disk's center and two overhead rotors with their axes fixed in the upper part of the rod. Control strategies are designed under which the disk's inclination is stabilised about its vertical position and the disk's motion is able to asymptotically track any given smooth ground trajectory. The control strategy is shown to be stable in the presence parametric uncertainties. It was furthermore shown that the system is path controllable. Finally an extended inverse dynamics control law is introduced which deals directly with underactuated systems. An example of an articulated crane is solved using extended inverse dynamics control. Feasible control is used to ensure that the internal dynamics of the system remains bounded and that the crane reach its desired final position in a given time interval [O, tƒ]. / Dissertation (MSc (Applied SCience))--University of Pretoria, 2007. / Electrical, Electronic and Computer Engineering / unrestricted

A complete solution to the inverse kinematics problem for a large class of practical manipulators, which includes manipulators with no closed form inverse kinematics equations, is presented in this thesis. A complete solution to the inverse kinematics problem of a manipulator is defined as a method for obtaining the required joint variable values to establish the desired endpoint position, endpoint orientation, and manipulator configuration; the only requirement being that the desired solution exists. For all manipulator geometries that satisfy a set of conditions (THEOREM I), an algorithm is presented that is theoretically guaranteed to always converge to the desired solution (if it exists). The algorithm is extensively tested on two complex 6 degree of freedom manipulators which have no known closed form inverse kinematics equations. It is shown that the algorithm can be used in real time manipulator control. Applications of the method to other 6 DOF manipulator geometries and to redundant manipulators are discussed. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

Purpose of study: Examine ASO (soft) and Malleoloc semi-rigid stirrup (SRS) ankle orthosis designs on ankle kinematics during field-sport movements: sprint, one-legged jump, and 45-degree cut. Participants: 13 competitive Ultimate players who regularly wore an ankle orthosis during physical activity. Methods: ASO or Malleoloc orthosis was randomly assigned to each person. Kinematic data were captured while the participants performed several trials for each movement in a motion analysis laboratory. Participants repeated the protocol with the other orthosis. Results: ASO allowed significantly more plantar-flexion during weight acceptance of the planting foot in cutting (p=0.038). In jumping, the Malleoloc allowed significantly more eversion-inversion range during stance (p=0.048) and eversion-inversion angular velocity from midstance to toe-off (p=0.026). Qualitative data also showed a significant preference for ASO. Conclusion: Hypotheses that ankle inversion and eversion would be greater with the ASO; and plantar-flexion and dorsiflexion would be greater with the Malleoloc were refuted.

This study examined the effects of laryngeal activity on articulation by comparing the articulatory kinematics of the /i/ and /u/ vowels produced in different speaking conditions (loud, comfortable, soft and whisper). Participants included 10 males and 10 females with no history of communication disorders. The participants read six stimulus sentences in loud, comfortable, soft and whispered conditions. An electromagnetic articulograph was used to track the articulatory movements. The experimenters selected the sentence We do agree the loud noise is annoying from the other utterances and the words we do agree were segmented from the sentence. We do agree was chosen because of the tongue and lip movements associated with the retracted and rounded vowels. Results reveal the soft condition generally has smaller and slower articulatory movements than the comfortable condition, whereas the whispered condition shows an increase in size and the loud condition shows the greatest increase in both size and speed compared to the comfortable condition. The increase in the size of the movements in whispered speech may be due to unfamiliarity as well as a decrease in auditory feedback that requires the speaker to rely more on tactile feedback. These findings suggest that adjusting laryngeal activity by speaking more loudly or softly influences articulation; this may be useful in treating both voice and articulation impairments.

No description available.

Continuum robots are the biologically inspired robots that mimic the behaviors of mammalian tongues, elephant trunks, and octopus arms. These robots feature a backboneless structure similar to their biological counterparts, such as termed muscular hydrostats. The drawbacks of two existing designs are examined and a new mechanical design that uses a single latex rubber tube as the central member is proposed, providing a design that is both simple and robust. Next, a novel verification procedure is applied to examine the validity of the proposed model in two different domains of applicability. A two-level electrical control scheme enables rapid prototyping and can be used to control the continuum robot remotely with a joystick via a Local Area Network (LAN). Next, a new geometrical approach to solve inverse kinematics for continuum type robot manipulators is introduced. Given the tip of a three-section robot, end-points of section 1 and section 2 are computed, and a complete inverse kinematics solution for a multisection continuum robot is then achieved by applying inverse kinematics to each section continuum trunk. Moreover, the algorithm provides a solution space rather than a single valid solution. Finally, the techniques involved in visualization of AirOctor/OctArm in 3D space in real-time are discussed.The algorithm has been tested with several system topologies.