Thesis (Ph.D.)--University of Delaware, 2005. / Principal faculty advisor: Dennis R. Mertz, Dept. of Civil & Environmental Engineering. Includes bibliographical references.

This work embraces two different manufacturing processes: pultrusion androtational moulding. One (pultrusion) is concerned with manufacture with athermosetting composite while the other is concerned with manufacture of anunfilled thermoplastic. The connecting theme is one of energy usage in manufacturewith these processes. While a large number of comprehensive computer models of pultrusion havebeen generated, most are focussed on the prediction of the temperature andconversion distributions within the profile; by contrast, the analysis presented here isdirected towards the prediction of the duty cycle of the mould heaters as a first stepin recognising the significance of the energy consumed in the process. The results ofthe model are compared with experimental measurements of the duty cycle of anindustrial machine. The nature of this particular investigation was predominantlyapplied and in particular directed towards industrial use. For this reason, the modelwas created in MATLAB, a software package which is relatively more accessible tothe reinforced plastics industry than FE packages. The project involved extensivemodelling and experimentation. It is shown that the line speed could be increased significantly by preheatingthe profile before it enters the die. For example, line speed for one particular profilewas increased from 0.4m/min to 0.5 m/min by using a pre-heater set at 80°C. Thiswork also showed that the specific energy consumption of the process was 0.2kWh/kg to 0.3 kWh/kg; under different line speeds and operating conditions. Thiswas achieved by measuring the duty cycle of the heaters on the die. This increase inline speed means a saving of up to 30 % of the specific energy consumption in thepultrusion. The energy theme continues through the work on rotational moulding. It isshown that the specific energy consumption in rotational moulding can be reducedby up to 70% by direct heating of the mould by using electrical resistance heatersinstead of current method of using hot air to heat the mould. The finite elementmodel showed that this alternative heating method is capable of producing asuniform a heat distribution on the surface of the mould as the current heating systemby using cyclic heating.

This study sought to discover the relationship of torque to the academic performance and other variables of children from five to eight years old. Torque was defined as the production of clockwise circles during a writing task. The phenomenon was first reported by Theodore Blau (1977) who proposed that children who torqued past a certain age were predisposed to problems both academic and behavioural. To measure the torquing propensities of children, Blau developed a Torque Test which had children produce six circles around X's (⊗), three with the preferred hand and three with the non-preferred hand. The present study used the preferred writing hand only and two torque tests, the Circling Directionality Test developed by the researcher using an embedded task to detect torquing and a modified form of Blau's Torque Test. Variables of academic achievement, age, sex, point of circle commencement, laterality, neuromuscular motor, control , test comparisons, and circling directionality were analysed. The population for the study consisted of 300 regular classroom children ages five to eight. Seventy-five children per grade were randomly selected by age from grade levels K-3. Significant relationships between torquing and low academic achievement were only found for the eight year old group who also had a higher incidence of left-handedness and crossed hand/foot laterality. Significantly more boys torqued than girls. As well, those who torqued in most instances commenced their circles at the bottom. Predictably significant relationships were found for hand and foot, but only left-handedness was significantly related to torque. No significant relationships could be found for measures of eyedness. Both tests used to measure torque were equally effective. The rapidity of circle construction did not alter the pattern of torquing in the children. There was a significant relationship between age and torquing with over 50% of the five year olds torquing with the preferred hand; by age eight this incidence had been reduced to 8% of the population. Torquing was then seen as a developmental trait found in a large percentage of five and six year olds but by age eight it was indicative of academic school difficulties. Recommendations for further study of the torquing phenomenon were made. / Education, Faculty of / Graduate

Horse riding is a popular global activity involving a wide range of sporting events including dressage, endurance riding, eventing, show jumping, horse racing and rodeo. Unfortunately, horse riding and equestrian sporting events, report a high prevalence of concussion. The most common mechanism for brain injury in equestrian events involve high levels of linear and rotational acceleration during head impacts when falling from a horse. These accelerations create injurious brain tissue strain. While both linear and rotational accelerations occur during head impacts, the rotational components of acceleration are closely linked to brain tissue strain. To reduce brain strain, helmet technologies have been developed with the aim to reduce head rotational accelerations during an impact. The most common rotational managing technology, multi-directional impact protection system (MIPS), employs a low friction layer to reduce the amount of rotational acceleration sustained by the brain during head impacts. MIPS tests equestrian helmets using a monorail drop rig with a 45-degree steel anvil covered in 80 grit sandpaper at 6.2 m/s. The surface experiencing impact in the MIPS test method is a very low compliant surface (steel). It is impacted at a velocity of 6 m/s, and an anvil angle of 45-degrees. In contrast, most impacts in equestrian involve high compliant material such as sand or turf with an average impact velocity is 9 m/s, and the average angle of impact of 27 degrees. The proposed rotational testing method employed by MIPS may not fully represent the most common accidents involving equestrian events. The objective of this research was to evaluate the effectiveness of a helmet with rotational technology to reduce linear and rotational acceleration, rotational velocity, and maximum principal strain (MPS) in equestrian helmets. An equestrian specific test protocol was developed using the common impact conditions for concussive events for equestrian riders. Nine m/s impact velocity, with an angle of 26.5 degrees to the horizontal axis, and an anvil compliance consisting of 66 mm of 602 vinyl nitrile foam with synthetic grass to represent turf impacts was reported as the most common impact characteristics. Using a Rail Guided Launcher, a helmeted Hybrid III headform was launched and impacted a low and high compliance anvil using the defined velocity and angle parameters. Two equestrian helmet types were impacted, a conventional helmet with no rotational technology and the same helmet model with rotational technology. The impact locations tested included front, side, and rear boss, as these were the most common impact locations reported for concussive events in equestrian. Linear and rotational acceleration and rotational velocity were measured using a DTS SLICE sensor installed inside the headform. The linear and rotational acceleration curves were then used as input to the University College Dublin Brain Trauma Model (V2.0) to calculate MPS. Statistical analysis included four t-tests, two 2x2x3 ANOVA's with 8 pairwise Tukey post-hoc test, significance set to α=0.05. The results were not uniform across impact locations and anvil compliances, the rear boss impact location in helmets with rotational technology revealed significantly lower rotational accelerations and rotational velocity. The results revealed helmets with rotational technology should be designed to perform under these high-energy conditions. If the rotational technology was designed with these considerations, it would be possible to investigate the potential of rotational technologies to decrease dynamic head response and the brain tissue strain.

Introduction: Over the recent years, there has been increased interest in the use of transradial (TR) access for percutaneous coronary intervention (PCI), including rotational atherectomy (RA). However, a large proportion of operators seem to be reluctant to use TR access for complex PCI including rotational atherectomy for heavily calcified coronary lesions. Methods: We searched MEDLINE, ClinicalTrials.gov and the Cochrane Library for studies comparing radial versus femoral access in patients undergoing RA. Studies were included if they reported at least one of the following outcomes in each group separately: major adverse cardiac events (MACE), major bleeding, stent thrombosis, myocardial infarction (MI), hospital length of stay, radiation exposure, procedure time, procedure success and all-cause mortality. Odds ratio (OR) or mean difference (MD) with 95% confidence interval (CI) were calculated and a p-value of <0.05 was considered as a level of significance. Results: This meta-analysis included 5 retrospective studies with 3315 patients undergoing RA via radial access and 5838 patients via femoral access. Radial access was associated with lower major access site bleeding (OR: 0.45, 95% CI: 0.31–0.67, p < 0.001), and radiation exposure (MD: −16.1, 95%CI: −25.4–−6.7 Gy cm 2 , p = 0.0007). There were no significant differences observed in all-cause in-hospital mortality (OR: 0.92, 95% CI: 0.69–1.23, p = 0.58); MACE (OR: 0.80, CI: 0.63, 1.02, p = 0.08), stent thrombosis (OR: 0.28, 95%CI: 0.06–1.33 p = 0.11); and MI (OR: 0.43, 95%CI: 0.15–1.24, p = 0.12). There were no significant differences in hospital stay, procedure time or procedure success between the two groups (p > 0.05). Conclusion: This meta-analysis of 9153 patients from observational studies demonstrates similar all-cause mortality, MACE, procedural success and procedural time during RA performed using TR access and TF access. However, TR access was associated with decreased access site bleeding and radiation exposure. Given the observational nature of these findings, a randomized controlled trial is warranted for further evidence.

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Thermotropic liquid crystalline polymers (TLCPs) possess a number of physical and mechanical properties such as: excellent chemical resistance, low permeability, low coefficient of thermal expansion, high tensile strength and modulus, and good impact resistance, which make them desirable for use in the storage of cryogenic fluids. Rotational molding was selected as the processing method for these containers because it is convenient for manufacturing large storage vessels from thermoplastics. Unfortunately, there are no reports of successful TLCP rotational molding in the technical literature. The only related work reported involved the static coalescence of two TLCP powders, where three key results were reported that were expected to present problems that preclude the rotational molding process. The first result was that conventional grinding methods produced powders that were composed of high aspect ratio particles. Secondly, coalescence was observed to be either slow or incomplete and speculated that the observed difficulties with coalescence may be due to large values of the shear viscosity at low deformation rates. Finally, complete densification was not observed for the high aspect ratio particles. However, the nature of these problems were not evaluated to determine if they did, in fact, create processing difficulties for rotational molding or if it was possible to develop solutions to the problems to achieve successful rotational molding. This work is concerned with developing a resin selection method to identify viable TLCP candidates and establish processing conditions for successful rotational molding. This was accomplished by individually investigating each of the phenomenological steps of rotational molding to determine the requirements for acceptable performance in, or successful completion of, each step. The fundamental steps were: the characteristics and behavior of the powder in solids flow, the coalescence behavior of isolated particles, and the coalescence behavior of the bulk powder. The conditions identified in each step were then evaluated in a single-axis, laboratory scale, rotational molding unit. Finally, the rotationally molded product was evaluated by measuring several physical and mechanical properties to establish the effectiveness of the selection method. In addition to the development and verification of the proposed TLCP selection method, several significant results that pertain to the storage of cryogenic fluids were identified as the result of this work. The first, and argueably the most significant, was that the selection method led to the successful extension of the rotational molding process to include TLCPs. Also, the established mechanical properties were found to be similar to rotationally molded flexible chain polymers. The biaxial rotationally molded container was capable of performing to the specified requirements for cryogenic storage: withstand pressures up to 34 psi at both cryogenic and room temperatures, retain nitrogen as a gas and as a cryogenic liquid, the mechanical preform retaining nitrogen, as both a gas and as a cryogenic liquid, and resist the development of micro-cracks during thermal cycling to cryogenic conditions. / Ph. D.

When football originated in the 1800s, players wore no protective equipment. Between 1869 and 1905, there were 18 deaths and 159 serious injuries attributed to the sport. Following this, players began to wear protective equipment. The first use of a football helmet was in 1893, made of leather and designed to reduce the risk of skull fracture. Initially, football helmets were intended to protect a player against the most severe hits they would experience on the field. More recently, it has been shown that mild traumatic brain injuries, such as concussions, can induce long-term neurodegenerative processes. Since their introduction, helmets have transformed into plastic shells with padding designed to mitigate accelerations on the brain. With the growing concern for player safety, regulating bodies, like the National Operating Committee on Standards for Athletic Equipment, have implemented standards for protective equipment, including football helmets. On top of these standards, there have been multiple methods developed to assess helmet performance with different testing apparatuses. Manufacturers are interested in how their helmet performs according to multiple testing methods. This could be costly if they do not have the proper testing equipment that a protocol utilizes. This thesis assesses the interchangeability of different test equipment to reproduce a testing protocol. The desire to perform well in testing standards has driven the improvement of helmet performance and continued design innovation. The second aim of this thesis is to evaluate helmet performance and its relationship with design changes in football helmets manufactured between 1980 and 2018. / Master of Science / When football originated in the 1800s, players wore no protective equipment. Between 1869 and 1905, there were 18 deaths and 159 serious injuries attributed to the sport. Following this, players began to wear protective equipment. The first use of a football helmet was in 1893, made of leather and designed to reduce the risk of skull fracture. Initially, football helmets were intended to protect a player against the most severe hits they would experience on the field. More recently, it has been shown that mild traumatic brain injuries, such as concussions, can induce long-term neurodegenerative processes. Since their introduction, helmets have transformed into plastic shells with padding designed to mitigate accelerations on the brain. With the growing concern for player safety, regulating bodies, like the National Operating Committee on Standards for Athletic Equipment, have implemented standards for protective equipment, including football helmets. On top of these standards, there have been multiple methods developed to assess helmet performance with different testing apparatuses. Manufacturers are interested in how their helmet performs according to multiple testing methods. This could be costly if they do not have the proper testing equipment that a protocol utilizes. This thesis assesses the interchangeability of different test equipment to reproduce a testing protocol. The desire to perform well in testing standards has driven the improvement of helmet performance and continued design innovation. Another aim of this thesis is to evaluate helmet performance and its relationship with design changes in football helmets manufactured between 1980 and 2018.