Final state interactions in the p-p and p-n systems corresponding to the formation of the singlet states of the di-proton and the deuteron have been observed in the reactions He³(He³,2p)He⁴ and T(He³,np)He⁴, by measuring the energy spectra of two of the final state particles detected in coincidence. These interactions appear as regions of high density of events along the kinematic contours in two dimensional energy space. Both p-p and p-He⁴ coincidences from the reaction He³(He³,2p)He⁴ and p-He⁴ coincidences from the reaction T(He³,np)He⁴ were studied. The dominant mechanism producing the three particle final states was found to be the sequential breakup through the states of Li⁵ and He⁵, in agreement with the results of previous experiments. The interaction between the two nucleons affects the distribution of coincidence events only in the region of two dimensional energy space corresponding to a breakup in which the two nucleons emerge with low relative energy. The relative contributions of the different processes in the reaction He³(He³,2p)He⁴ was determined for incident He³ energies from 1.15 MeV to 5.0 MeV. It was found that the nucleon-nucleon interaction becomes less important as the incident energy increases. The validity of two approximate theories of final state interactions, the Watson theory and the Phillips, Griffy and Biedenharn density of states formalism, was checked by comparing their predictions with the observed energy spectra. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Currently, there is much interest in the field of robotics in researching methods of obtaining inverse kinematics solutions for arbitrary manipulators. Simple closed-form inverse kinematics equations can be obtained for a few joint configurations using geometric methods. However, there exist many manipulators which were not originally designed for kinematic control which do not have simple closed-form inverse kinematics equations. An efficient and stable iterative method is investigated in this thesis which solves the general inverse kinematics problem without detailed analysis of the manipulator's structure. The proposed iterative inverse kinematics algorithm combines a calibration procedure to estimate the manipulator's Denavit-Hartenberg parameters with an iterative method using the Jacobian and damped joint corrections. The kinematics control algorithm parameters are selected with a computer graphics simulation of the manipulator. The proposed inverse kinematics algorithm is tested with a simulation of an industrial manipulator arm which does not have a closed-form solution, RSI Robotic Systems International's Kodiak arm, and exhibits stability in all regions of operation and fast convergence over most regions of operation. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

No description available.

No description available.

While Weimaraner size may assist in the performing of tasks of a sporting dog, it also makes the breed more susceptible to hip dysplasia. However, this breed has a lower rate of dysplasia. This may be due to selected gait velocity and mechanics specific to the breed, but gait analysis of Weimaraners is lacking. Study objectives were to define normal trotting mechanics and to determine the influence of velocity on gait. Dogs were trotted at a slow and fast trot and at both velocities. The trot had a diagonal footfall sequence with a 2-beat rhythm alternating between diagonal bipedal support and suspension. Velocity increase was achieved with significant increases in stride length and head, withers, fore, and hind paw displacements (P < 0.05). Range of motion of the elbow and hip significantly increased with increasing velocity (P < 0.05). These parameters will assist in gait evaluation and detection of lameness.

No description available.

Low back pain is the number one cause of disability in the world. It is a well established problem in industry often caused by excessive repetition, awkward postures, and heavy lifting. Back support exoskeletons have increasingly been studied as a solution to this problem. In addition to evaluating exoskeletons, giving some focus to the various lifting styles themselves can also provide some insight into ameliorating this problem. Research evaluating warehouse workplace postures has found that workers switch between a variety of tasks and many different lifting styles, beyond the standard squat and stoop postures, on a daily basis. This dissertation is primarily a compilation of three papers. The first focuses on the VTLowe's exoskeleton and the kinematic differences found during Stoop, Squat, and Freestyle lifting. These lift styles were evaluated while the study participants lifted boxes weighing 0% or 20% of their body weight both With and Without the exoskeleton. Evaluating the kinematic results showed that wearing the exoskeleton resulted in a 1.5 degree increase in ankle dorsiflexion, a 2.6 degree decrease in knee flexion, and a 2.3 degree decrease in SHK angle. Subjects' shoulder, elbow, and wrist heights were slightly higher while wearing the exoskeleton, and they lifted slightly more slowly while wearing the exoskeleton. Subjects moved more quickly while bending down as compared to standing up, and with the 0% bodyweight box as compared to the 20% bodyweight box. The values for Freestyle lifts generally fell in between Squat and Stoop lift styles or were not significantly different from Squat. EMG data (analyzed in a different study) from the leg muscles had relationships with torso torque while the back and stomach muscles showed no significant relationships. Exoskeleton efficacy research has a strong focus on Stoop, Squat, and Freestyle lifting. However, asymmetric styles such as One Legged lifting and Kneeling were found to be frequently used lifting styles in a warehouse setting. The second paper in this dissertation focuses on variations of asymmetric lifts while lifting light objects including Split Legged, Heel Up, One Legged, Kneeling, Asymmetric Squat, Bent Over (a freestyle task) and Bend Walk (picking up bean bags from the ground while walking forward and maintaining a bent over posture). These lift styles can be found not only in industry, but in any individual's daily life such as when it comes to picking up a dropped pen or sorting toys in a bin on the floor. Evaluating Split Legged, Heel Up, and One Legged found that many of the significant differences in muscle activity are dependent on the lifting stance (whether the front foot is on the same side or opposite side as the hand used to pick up objects). Combining the results that same side lifts have greater muscle imbalance in the iliocostalis and overall back muscle activity is greater in Split Legged than in Heel Up or One Legged suggests that One Legged or Heel Up in an Opposite side stance are the best options in regards to minimizing back muscle activity. Although there is a trade-off with the biceps femoris for these lift styles, back injuries are far more prevalent and supporting the back takes priority over minimizing muscle activity in the legs. The analysis for Asymmetric Squat, Bend Walk, Bent Over, and Kneeling was divided into three portions: bending down, picking bags, and rising up. Relevant differences between the lift styles for these portions were seen in the biceps femoris, longissimus, and rectus abdominis, with Bend Walk generally being the most taxing activity. Overall, there were minimal differences while rising up from any of these postures with most changes seen in the biceps femoris. Rising Up also generally had a higher peak muscle activity compared to bending down or picking bags. The final paper in this dissertation evaluates the effect of a different back exoskeleton with the variety of lift styles studied in the second paper. It is important to see how exoskeleton use aids or harms many of the lift styles commonly used by industry workers. Lift side was once again a factor in the Split Legged, Heel Up, and One Legged tasks. Participants benefited more from the exoskeleton in same side lifts as opposed to opposite side. For Asymmetric Squat, Bend Walk, Bent Over, and Kneeling greater benefits were seen in the back and leg muscles while rising up as opposed to bending down. Focusing on the peak of the lift (taken at the peak of bending down for the more static postures) found that the exoskeleton had more significant differences for Split Legged, Heel Up, and One Legged compared to Asymmetric Squat, Bend Walk, Bent Over, and Kneeling. One highly important aspect in evaluating exoskeletons is determining the subject population that would most benefit from its use. Focusing on body mass, the longissimus saw decreased benefits as the body mass increased, with subjects under 75 kg benefiting the most from the exoskeleton, while the iliocostalis and biceps femoris typically saw the opposite effect when results were significant (i.e., heavier subjects benefited the most). / Doctor of Philosophy / Low back pain is the number one cause of disability in the world. It is a well established problem in industry often caused by excessive repetition, awkward postures, and heavy lifting. Back support exoskeletons have increasingly been studied as a solution to this problem. In addition to evaluating exoskeletons, giving some focus to the various lifting styles themselves can also provide some insight into ameliorating this problem. Research evaluating warehouse workplace postures has found that workers switch between a variety of tasks and many different lifting styles, beyond the standard squat and stoop postures, on a daily basis. This dissertation is primarily a compilation of three papers. The first focuses on the VTLowe's exoskeleton and the differences in how people move while wearing the exoskeleton during Stoop, Squat, and Freestyle lifting. These lift styles were evaluated while the study participants lifted boxes weighing 0% or 20% of their body weight both With and Without the exoskeleton. This resulted in small changes in the ankle, knee, and hip angles. Subjects' shoulder, elbow, and wrist heights were slightly higher while wearing the exoskeleton, and they lifted slightly more slowly while wearing the exoskeleton. Subjects moved more quickly while bending down as compared to standing up, and with the 0% bodyweight box as compared to the 20% bodyweight box. The values for Freestyle lifts generally fell in between Squat and Stoop lift styles or were not significantly different from Squat. Electromyography (muscle activity) data, analyzed in a different study, from the leg muscles had relationships with torso torque while the back and stomach muscles showed no significant relationships. Exoskeleton efficacy research has a strong focus on Stoop, Squat, and Freestyle lifting. However, asymmetric styles (i.e., where one side of the body is doing something different from the other side) such as One Legged lifting and Kneeling were found to be frequently used in a warehouse setting. The second paper in this dissertation focuses on variations of asymmetric lifts while lifting light objects including Split Legged, Heel Up, One Legged, Kneeling, Asymmetric Squat, Bent Over (a freestyle task) and Bend Walk (picking up bean bags from the ground while walking forward and maintaining a bent over posture). These lift styles can be found not only in industry, but in any individual's daily life such as when it comes to picking up a dropped pen or sorting toys in a bin on the floor. Evaluating Split Legged, Heel Up, and One Legged found many of the significant differences in muscle activity are dependent on the lifting stance (whether the front foot is on the same side or opposite side as the hand used to pick up objects). The results found that there were different imbalances between the sides of the body depending on the specific lift style examined. Overall, the muscle activity results suggest that One Legged or Heel Up in an Opposite side stance are the best options in regards to minimizing back muscle activity. While leg muscle activity does increase for these lift styles, back injuries are far more prevalent and supporting the back takes priority over minimizing muscle activity in the legs. The analysis for Asymmetric Squat, Bend Walk, Bent Over, and Kneeling was divided into three portions: bending down, picking bags, and rising up. Overall, Bend Walk was the most taxing of those activities. The final paper in this dissertation evaluates the effect of a second back exoskeleton with the variety of lift styles studied in the second paper. It is important to see how exoskeleton use aids or harms many of the lift styles commonly used by industry workers. Participants benefited more from the exoskeleton in same side lifts as opposed to opposite side. For Asymmetric Squat, Bend Walk, Bent Over, and Kneeling greater benefits were seen in the back and leg muscles while rising up as opposed to bending down. The exoskeleton helped Split Legged, Heel Up, and One Legged more than Asymmetric Squat, Bend Walk, Bent Over, and Kneeling. One highly important aspect in evaluating exoskeletons is determining the subject population that would most benefit from its use. One of the back muscles saw decreased benefits as the body mass increased, with subjects under 75 kg benefiting the most from the exoskeleton, while another back muscle and the legs typically saw the opposite effect.

Terrestrial animals encounter natural surfaces which comprise materials that can yield and flow such as sand, rubble, and debris, yet appear to nimbly walk, run, crawl, or climb across them with great ease. In contrast, man-made devices on wheels and treads suffer large performance loss on these surfaces. Legged locomotion thus provides an excellent source of inspiration for creating devices of increased locomotor capabilities on natural surfaces. While principles of legged locomotion on solid ground have been discovered, the mechanisms by which legged animals move on yielding/flowing surfaces remain poorly understood, largely due to the lack of fundamental understanding of the complex interactions of body/limbs with these substrates on the level of the Navier-Stokes Equations for fluids. Granular media (e.g., sand) provide a promising model substrate for discovering the principles of legged locomotion on yielding/flowing surfaces, because they can display solid- and fluid-like behaviors, are directly relevant for many desert-dwelling animals, can be repeatably and precisely controlled, and the intrusion force laws can be determined empirically. In this dissertation, we created laboratory devices to prepare granular media in well-controlled states, and integrated biological, robotic, and physics studies to discover principles of legged locomotion on granular media. For both animals and bio-inspired robots, legged locomotion on granular surfaces must be achieved by limb intrusion to generate sufficient vertical ground reaction force (lift) to balance body weight and inertial force. When limb intrusion was slow (speed < 0.5 m/s), granular forces were independent of intrusion speed (dominated by grain-grain and grain-intruder friction) and generally increased with intrusion depth (due to granular hydrostatic pressure). Locomotor performance (speed) depended sensitively on limb kinematics, limb morphology, and the strength of the granular media, which together determined vertical force balance (or lack thereof). Based on these findings, we developed a granular resistive force theory in the sagittal plane as a general model for calculating forces during low-speed intrusions relevant to legged locomotion.

Thesis (M.S.)--Mississippi State University. Department of Physics and Astronomy. / Title from title screen. Includes bibliographical references.

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.