My work has been focused on compliant mechanisms, origami engineering, and rapid prototyping. Two of the projects that I worked on were focused on compliant mechanisms and origami engineering. The similar goal of both of those projects was to create an origami membrane whose kinematics mimic that of an existing mechanism. The first project created an origami membrane to mimic the kinematics of a planar shape-changing mechanism. This mechanism was a square shaped unit-cell which could shear, compress, and expand in its own plane. In addition to waterproofing the mechanism, the first project also sought to optimize the dimensions of the mechanism in order to reduce internal stresses during actuation. The results of the optimization portion of this project were a reduction of internal stresses by more than 22%. The results of the origami synthesis portion of the project was the creation of a membrane with an origami pattern whose kinematics mimic that of the shape-shifting surface. The origami membrane is capable of being folded into each of the various positions that the shape-shifting surface is able to fold into. The second project sought to create a similar type of origami fold pattern, but for a Shape Morphing Space Frame (SMSF). This project created an origami membrane designed to mimic the kinematics of a mechanism that had been developed in a different previous project. The mechanism consisted of a series of Linear Bistable Elements (LBEs) which were assembled to form a cylinder. When the LBEs were actuated the cylinder would deform to a hyperboloid. This project created an origami membrane whose kinematics mimic that of the shape-morphing space frame and was able to change side length by more than 30%. The origami membrane was able to fold to each of the SMSF’s states. This project also developed a method for synthesizing an origami fold pattern with shape-morphing triangles. Both of the first two projects that comprise this dissertation sought to develop an origami fold pattern whose kinematics mimic that of an existing mechanism. In each of these projects one of the future goals for the project was to create a prototype where the mechanism and the origami are fabricated together as one integrated prototype. Possible methods of accomplishing this goal include rapid prototyping. Thus, the mechanics of rapid prototyping are of concern for future work on these projects. The third project developed a part which could be printed from a Fused Deposition Modeling (FDM) machine to test certain material properties (yield strength and elastic modulus) after it had been processed through the FDM. This would allow the material properties to be tested without the use of expensive test equipment. This project developed eight parts which could be used to bracket certain material properties of rapid prototyped parts after processing. The parts developed in this project were capable of bracketing the material properties of the materials in question, and were able to do so when tested across multiple FDM machines. The results of this work were stress-strain data which indicates the behavior of the part under load, and a method for inexpensively testing the material properties of rapid prototyped parts after processing.

The problem of the study was to determine the better predictors of sprint performance for male and female sprinters from selected leg power and isokinetic strength tests. Ten male and five female sprinters volunteered to be measured for vertical jump performance, anaerobic power and capacity, peak isokinetic torque at the hip, knee, and ankle joint, and sprint performance. A forward stepwise multiple regression analysis was performed to allow selection from all strength and power variables regressed on the dependent variables of 30 meters, 60 meters, and flying 30 meter sprints. This procedure allowed one to examine the contribution of each predictor variable to the regression model. Only the independent variables that elicited a regression equation significant at the .05 level were used in final regression models. The regression models developed for the males were: 30 meters (crouch start) = 6.115 - .083(anaerobic power) - .055(vertical jump) - .044(plantarflex 120"/s) - .022(knee flex 60'/s); 60 meters (crouch start) = 11.111 - .145(vertical jump) - .086 (anaerobic power) - .172(hip flex 300'/s) - .098(knee flex 60'/s); and 30 meters (flying start) = 4.295- .055(anaerobic power) - .312(knee flex 180'/s) - .090(hip flex 300'/s). The regression models for the women were different than the males and were: 30 meters (crouch start) = 9.530 - .346(vertical jump); 60 meters (crouch start) = 18.083- .686(vertical jump); and 30 meters (flying start) = 8.733- .352(vertical jump) . By knowledge of the variance of the better strength and power measures, 83.2% to 98.0% of the variance of the respective sprint tests were explained. The regression models could allow for the identification of potential sprint performers and the development of optimal sprint training program.

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Children with unilateral spastic cerebral palsy (USCP) have impairments affecting upper limb function, particularly in grasping abilities. Specifically, children with USCP may display precision grip impairments, which can lead to activity limitations. The interplay between feedforward and feedback control is essential for successful grasping, requiring somatosensory information to be integrated with the motor output. This integration occurs through the transmission of somatosensory information through the dorsal column medial lemniscus (DCML) pathway, while independent finger movement to grasp an object is controlled by the motor cortex via the corticospinal tract (CST). While previous studies demonstrated the CST relates to anticipatory control of grasping, this may not explain all the variance of grasp impairments in children with USCP. Although studies have highlighted the importance of sensory information in grasping in typically developing (TD) adults, there are no studies examining the relationship between brain structure and function in terms of precision grip impairments in children with USCP. Additionally, sensorimotor integration plays an important role in precision grip. In some children with USCP, the lesion that occurs in the brain can cause the CST to reorganize to the contralesional hemisphere. This results in the sensory and motor tracts in different hemispheres, impacting motor impairments. When this sensory-motor dissociation occurs or when there are successive lifts of an object with each hand, it is thought that the information is transferred through the corpus callosum (CC). However, damage to the CC can restrict somatosensory processing, which can further impair grasping abilities. Previous studies have only looked at precision grip impairments in relation to the CST. Therefore, an integrative approach is necessary to fully understand the mechanisms of precision grip impairments in children with USCP. In this study our aim was to examine the neural basis of precision grip in children with USCP. Twenty-seven children participated in an MRI assessment. This included the acquisition of structural and diffusion-weighted images (DWI) to extract diffusion metrics of the CST, DCML pathway, and CC. Children also participated in clinical sensory measures, including the stereognosis test, grating orientation task, and the two-point discrimination task. Additionally, children performed precision grip lifts using a custom-made object. All children were asked to grasp an object with interchangeable surfaces (i.e., sandpaper and rayon) to measure adaptation of grip force (GF) to object texture. They were also asked to grasp the same object, hold it in the air and slowly release their grip so that the object gradually slips from their fingertips. Twenty-seven children performed these tasks with their less affected hand, and 16 with their more affected hand. Additionally, 17 participants grasped an object with various weights with each lifting sequence consisting of lifting an object in succession with the same hand and then one lift with the contralateral hand. The results demonstrate the greater reduction of integrity (more damage) of the DCML pathway, the poorer the grasp task performance, as indicated through the safety margin (the difference between the minimum amount of force needed to prevent slipping and the applied grip force). Regression analyses and cluster analyses display that CST integrity and organization may also contribute to safety margin. This suggests that diffusion metrics of multiple pathways and CST organization when considered together contribute to grasping impairments in children with USCP. To assess this further, we examined the relative difference in the peak rate of force between objects with various weights during successive lifts with each hand. Children with USCP did demonstrate anticipatory control within hands and a generalization of anticipatory control between hands. However, a loss of the transfer information was shown when first grasping the object with their less affected hand and then their more affected hand, in children with an absent contralateral CST. Therefore, the results suggest precision grip impairments may not exclusively be due to sensory impairments, but instead how the sensory information is integrated with the motor output of the same hand.

This investigation was conducted to explore the between trial variability of the measures of the isometric peak force, time to peak force, area to peak force, area under the curve, slope (20%-80%), and the average slope of subjects assigned to perform a series of four isometric grip strength contractions and to develop a discriminant function equation that would predict group membership. Forty-nine college students were instructed to perform either a series of four maximal voluntary contractions (sincere) or a series of four submaximal (deceptive) contractions. The subjects were retested 24-48 hours after the initial test session. Data from both test sessions were recorded, displayed, and analyzed using segmental curve analysis. The coefficients of variation were computed for each test variable. The grand mean coefficient of variation for the sincere condition was .31 ± .02 compared to the grand mean coefficient of variation for the deceptive condition which was .77 ± .11 (p < .01). Coefficients of variation were used to predict group membership. The prediction equation accurately classified 92% of the sincere condition and 64% of the deceptive condition. / Master of Science

No / Photo-irradiation of poly para-phenylene terephthalamide (PPTA) fibre is normally associated with deterioration of physical properties. Nonwoven fabrics produced from 100% photo-irradiated PPTA fibres might therefore be expected to yield fabrics with poorer mechanical properties compared to those produced from non-irradiated fibres. To test this hypothesis, the bursting strength of hydroentangled fabrics manufactured from photo-irradiated PPTA fibres was explored. Prior to fabric manufacture, virgin PPTA staple fibres were photo-irradiated under controlled lighting conditions (xenon short arc lamp with a luminous flux of 13,000 lm) for 0, 5, 10, 20, 40, 60 and 100 h. The photo-irradiated fibres were then hydroentangled to produce nonwoven fabrics. Photo-irradiation exposure of PPTA fibre up to 30 MJ m 2 was not found to be detrimental to fabric bursting strength and at irradiation energies of 5e10 MJ m 2 a small, but statistically significant increase in fabric bursting strength was observed compared to fabrics manufactured from non-irradiated fibre. This may be linked to a change in the surface and skin properties of the PPTA photo-irradiated fibres identified by atomic force microscopy (AFM) following photoirradiation.

It is often difficult to optimize strength qualities in-season due to the conflicting influences of extensive skill practices combined with frequent game play of the competition schedule. The purpose of this study was to investigate the effects of two interventions on strength qualities and CMJ performance. Thirteen women volleyball players competing in NCAA Division I were tested before and after four weeks of an inseason strength training program with emphasis on heavy squatting (6-IORM), and then before and after three weeks of unloaded jump training. Dynamic squat strength, isometric squat strength, optimal power, CMJ, SJ and approach jump and reach were all tested before and after both cycles. There was a significant increase in both average 1RM squat strength (5%) and vertical jump (1%) following the strength cycle. Following the unloaded training, there was a significant increase in both peak power output (18%) and peak velocity (14%) in the CMJ. SJ performance significantly increased in both peak force (6%) and maximum height (10%). Throughout training, there were no decreases in maximal strength levels or post-test Vertec jump and reach. This study indicates that heavy squatting can improve vertical jump as well as 1RM squat despite a high volume in-season practice and competition schedule. Furthermore, unloaded training can improve the explosive qualities of athletes when used as a peaking cycle late in-season. Athletes maintained dynamic strength and jumping ability from pre-testing scores, while significantly increasing both peak velocity and power in the CMJ. / School of Physical Education

The purpose of this project is to review current literature on the mechanics and physiology of the vertical jump and to provide an understanding of the jump itself. The second purpose is to develop a step by step program to increase vertical jump from grade school through high school.

Seventeen strength and power athletes (n = 11 males, 6 females; height: 177.5 ± 7.0 cm, 165.8 ± 11.4 cm; body mass: 90.0 ± 14.1 kg, 66.4 ± 13.9 kg; age: 30.6 ± 10.4 years, 30.8 ± 8.7 years), who regularly performed weightlifting movements during their resistance training programs, were recruited to examine the effect of altering body posture and barbell position on the between-session reliability of force-time characteristics generated in the isometric mid-thigh pull (IMTP). After participants were familiarised with the testing protocol, they undertook two testing sessions which were separated by seven days. In each session, the participants performed three maximal IMTP trials in each of the four testing positions examined, with the order of testing randomized. In each position, no significant differences were found between sessions for all force-time characteristics (p = >0.05). Peak force (PF), time-specific force (F50, F90, F150, F200, F250) and IMP time-bands (0–50, 0–90, 0–150, 0–200, 0–250 ms) were reliable across each of the four testing positions (ICC ≥ 0.7, CV ≤ 15%). Time to peak force, peak RFD, RFD time-bands (0–50, 0–90, 0–150, 0–200, 0–250 ms) and peak IMP were unreliable regardless of the testing position used (ICC =15%). Overall, the use of body postures and barbell positions during the IMTP that do not correspond to the second pull of the clean have no adverse effect on the reliability of the force-time characteristics generated.

Important aspects of adhesion occur at interfaces, including structures that may be different from those in the bulk materials. However, probing the orientation of molecules in functional adhesives poses a significant challenge because adhesive molecules are always located at a buried interface. The limited penetration depth of surface-specific analysis prohibits the study of buried interfaces using those techniques. The large quantity of bulk molecules relative to the adhesive molecules interacting at the interface results in the bulk signal swamping out adhesive signal in bulk analysis techniques. An interface-specific technique is required to study functional adhesives. One such technique that has shown promise in recent years is Vibrational sum frequency generation (VSFG) spectroscopy. This technique is useful for studying interactions that occur at surfaces and interfaces because it selectively probes regions of broken inversion symmetry. Despite the ability of VSFG to isolate signal from a buried interface, a non-resonant signal that is produced simultaneously with the resonant signal corrupts the vibrational data of interest and greatly impedes reliable analysis of VSFG spectra. Over the last several years, researchers have experimentally removed non-resonant signal by delaying the upconverting pulse with respect to the initial excitation. Obtaining reliable results from VSFG data depends upon complete removal of non-resonant signal. However, complete removal of non-resonant signal presents a challenge because it can be present in spectra even when the indicators of non-resonant signal are absent. By taking advantage of polarization selection rules for VSFG and the differing symmetry of an azimuthally isotropic film and an azimuthally non-isotropic substrate, spectra containing non-resonant signal can be easily identified. These and other advances in VSFG methodology have enabled the study of surface and interfacial systems of interest. In a study of the effects of plasma treatment on polystyrene thin films, plasma exposure was found to affect not only the free surface but also portions of the sub-surface polymer, challenging previous assumptions that plasma effects are constrained to the free surfaces of materials. The next step is to use VSFG to study functional adhesives under known amounts of applied stress. An apparatus is in place to simultaneously collect VSFG spectra during mechanical testing of a functional adhesive, and in preliminary studies, an increase in VSFG non-resonant signal has been observed when a pulling force is applied to the adhesive bond.