Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references (leaves 136-139). Also available in electronic version. Access restricted to campus users.

Shell geometry is one of the many variables that can influence the way energy is absorbed by the helmet during impact. The purpose of this study was to gain knowledge in how shell geometry affects the performance of the shell relative to liner structural characteristics and impact conditions. Samples, representing a section of a hockey helmet, consisted of a shell with one of nine geometric formations (width and angle), and a liner (Dertex or EPP). Each sample was impacted three times at three different levels of energy using a monorail drop test. Significant differences were observed for all main effects and two-way interactions for both liner types. Overall the 90 degree angle and 16mm width performed the best. It was found that geometry influences the elastic properties of the shell in a very specific way. It was also found that geometry can improve energy absorption by 4-35% depending on the combination of other variables involved.

This study evaluated the mechanical durability of ice hockey helmets for multiple impacts at defined energy levels. A monorail drop testing apparatus was used to conduct controlled impact tests according to the CSA standard (CAN/CSA-Z262.1-M90). Five ice hockey helmet models were tested, for a total sample of 45 helmets. All helmets were impacted up to 50 times at each of in four different locations (i.e. front, right side, back, and crown), at one of 40, 50 or 60 J of kinetic energies. In general, by increasing the impact energy, the impact acceleration attenuation properties of the helmets was decreased significantly (from 4% to 80%). Although all the helmets meet the CSA standards, attenuation properties were found to be substantially reduced beyond three repeated impacts and above 40 J impact energy. In particular, all helmets showed effective multiple impact attenuation properties at the crown, front, and rear sites; however, poor multiple impact attenuation durability was evident at the side.

No description available.

These are stories about absurd societies, wigs, ill-fated journeys, guttering candles, obsessed fathers, direful glances, tornadoes, uniforms, strange logic, arcane hierarchies, captivity, the impossible, spectral animals, fields, and red light. They take place in invented or imagined historical settings.

No description available.

Mild traumatic brain injury in snowsports is a prevalent concern. With as many as 130,000 hospitalized injuries in the U.S. associated with snowsports in 2017, head injury constitutes about 28% and is the main cause of fatality. Studies have found that a combination of rotational and linear velocities is the most mechanistic way to model brain injury, but despite decades of research, the biomechanical mechanisms remain largely unknown. However, evidence suggests a difference in concussion tolerance may exist between athlete populations. To improve the ability to predict and therefore reduce concussions, we need to understand the impact conditions associated with head impacts across various sports. There is limited research on the conditions associated with head impacts in snowsports. These head impacts often occur on an angled slope, creating a normal and tangential linear velocity component. Additionally, the impact surface friction in a snowsport environment is highly variable, but could greatly influence the rotational kinematics of head impact. Currently helmet testing standards don't consider these rotational kinematics, or varying friction conditions that potentially occur in real-world scenarios. The purpose of this study is to investigate the head impact conditions in a snowsport environment to inform laboratory testing and evaluate snow helmet design. We determined head impact conditions through video analysis to determine the impact locations, mechanism of fall, and the kinematics pre-impact. We used these data to develop a test protocol that evaluates snowsport helmets in a realistic manner. Ultimately, the results from this research will provide snowsport participants unbiased impact data to make informed helmet purchases, while concurrently providing a realistic test protocol that allows for design interventions to reduce the risk of injury. / Master of Science / Mild traumatic brain injury in snowsports is a prevalent concern. With as many as 130,000 hospitalized injuries in the U.S. associated with snowsports in 2017, head injury constitutes about 28% and is the main cause of fatality. Studies have found that a combination of rotational and linear velocities is the most mechanistic way to model brain injury, but despite decades of research, the biomechanical mechanisms remain largely unknown. However, evidence suggests a difference in concussion tolerance may exist between athlete populations. To improve the ability to predict and therefore reduce concussions, we need to understand the impact conditions associated with head impacts across various sports. There is limited research on the conditions associated with head impacts in snowsports. These head impacts often occur on an angled slope, creating a normal and tangential linear velocity component. Additionally, the impact surface friction in a snowsport environment is highly variable, but could greatly influence the rotational kinematics of head impact. Currently helmet testing standards don't consider these rotational kinematics, or varying friction conditions that potentially occur in real-world scenarios. The purpose of this study is to investigate the head impact conditions in a snowsport environment to inform laboratory testing and evaluate snow helmet design. We determined head impact conditions through video analysis to determine the impact locations, mechanism of fall, and the kinematics pre-impact. We used these data to develop a test protocol that evaluates snowsport helmets in a realistic manner. Ultimately, the results from this research will provide snowsport participants unbiased impact data to make informed helmet purchases, while concurrently providing a realistic test protocol that allows for design interventions to reduce the risk of injury.

Recent applications of medical imaging, advanced polymers, and composites have led to the development of new equipment for athletes and soldiers. A desire to understand the performance of headgear that resists impacts ongoing since the 1970’s has found more traction in recent years with the usage experimental models that have a greater degree of bio-fidelity. In order to determine which features of helmets from different sports (Soccer, Lacrosse, Football, and Hockey) were tested on a Hybrid III 50th Percentile Male headform with an accelerometer rig at the center of mass.Testing was performed by administering impacts to the headform with an impulse hammer that provides transient force data in order to quantify inputs and outputs of the system to develop a non-dimensional transfer function. Helmet performance is compared by sport worn in order to determine desirable manufacturing features and develop prototype helmets that outperforms current athletic equipment.

Thesis (doctoral)--Ethnikon kai Kapodistriakon Panepistēmion Athēnōn, Philosophikē Scholē. / Summary in English. Includes bibliographical references (p. xx-xxviii) and index.

Thesis (doctoral)--Ethnikon kai Kapodistriakon Panepistēmion Athēnōn, Philosophikē Scholē. / Summary in English. Includes bibliographical references (p. xx-xxviii) and index.