The Hybrid III and NOCSAE headforms are two headforms used in impact testing, though their vibrational characteristics are not well understood. They may have different kinematic responses in various impact scenarios if the impact excites any of their natural frequencies; resonance is especially likely to occur in short-duration impacts with a wider frequency spectrum. The same impact on two headforms that perform similarly in blunt impacts can be much different in shorter-duration projectile impacts due to the vibrational responses. The research presented in this thesis had three objectives: to identify the natural frequencies of the Hybrid III and NOCSAE headforms and compare them with published human head values to determine which has a more biofidelic vibrational response; to quantify the frequency response of different baseball catcher's masks and assess their abilities to limit vibrations transferred to the headforms; and to compare kinematic and frequency responses between headforms in different impact scenarios (high-speed, low-mass projectile impacts vs. low-speed, high-mass pendulum impacts) and see how they are affected by various types of head protection. The results show the importance of considering frequency content in impact testing, suggesting that the NOCSAE headform may be more biofidelic in short-duration impacts since its natural frequencies better align with those seen in the human head. The catcher's masks experienced greater vibrational responses than the headforms, but since the NOCSAE's first natural frequency falls within the bandwidth being excited, resonance was seen in this headform's acceleration responses for the projectile baseball impacts. Lastly, while both headforms had higher peak linear accelerations (PLAs) from the short-duration projectile impacts than the pendulum impacts, the projectile impacts caused high frequencies to be excited in the NOCSAE headform, while only exciting low frequencies in the Hybrid III. These results may not be as relevant for long-duration loadings, as indicated by the similar responses between headforms for both the pendulum and helmeted projectile impacts. However, when a wide range of frequencies are being excited with short-duration impacts, these results are important to consider, since natural frequency excitation can influence head injury risk due to higher accelerations. / Master of Science / The Hybrid III and NOCSAE headforms are dummy headforms used in impact testing, but their vibrational characteristics are poorly understood. They may perform differently in certain loading environments due to structural differences; their frequency responses might differ based on impact characteristics. Short-duration impacts excite a wider range of frequencies than longer-duration (padded) impacts. While headforms generally perform similarly during padded impacts where resonant frequencies are avoided, excitation of these frequencies during short-duration impacts can result in different kinematic measurements between headforms. The research presented in this thesis had three objectives: to identify the natural frequencies of the Hybrid III and NOCSAE headforms and compare them with published human values to determine which better represents the head's vibrational response; to quantify the vibrational characteristics of different baseball catcher's masks and assess their abilities to limit vibrations transferred to the headforms; and to compare kinematic and frequency responses between headforms in different impact scenarios (high-speed, low-mass projectile impacts vs. low-speed, high-mass pendulum impacts) and see how they are affected by various helmets. The results show the importance of considering frequency content in impact testing, suggesting that the NOCSAE headform behaves more like the human head in short-duration impacts. Even though the catcher's masks "rang" more than the headforms, the vibrations from the projectile impact were in the appropriate range to excite the NOCSAE's natural frequencies. Thus, there was still an oscillatory response in this headform even when protected with the mask. Lastly, the projectile impacts caused higher accelerations in both headforms than the pendulum impacts. However, high frequencies were only experienced by the NOCSAE headform due to the projectile impacts; for the same impact, the Hybrid III just had low frequencies excited. These results are not as relevant for long-duration impacts, since there were similar responses in both headforms for both the pendulum and helmeted projectile impacts. However, they are very applicable for the short-duration impacts that excite a wide range of frequencies, since natural frequency excitation can increase the risk of head injury due to higher acceleration magnitudes.

The goals of this study were to measure the ability of catcher's masks to attenuate head accelerations upon impact with a baseball, and to compare these head accelerations to established injury thresholds for concussions. Testing involved using a pneumatic cannon to shoot baseballs at an instrumented (3-2-2-2 accelerometer array) Hybrid III headform (a 50th percentile male head and neck) with and without a catcher's mask on the head. The ball speed was controlled from approximately 26.8 – 35.8 m/s (60 – 80 mph) and regulation NCAA baseballs were used. Peak linear resultant acceleration was 140 – 180 g without a mask and 16 – 30 g with a mask over the range of balls speeds investigated. Peak angular resultant acceleration was 19500 – 25700 rad/sec2 without a mask and 2250 – 3230 rad/sec2 with a mask. The Head Injury Criterion was 93 – 181 without a mask and 3 – 13 with a mask and the Severity index was 110 – 210 without a mask and 3 – 15 with a mask. Catcher's masks reduced head acceleration metrics by approximately 85% when baseballs were impacted with just the headform. Head accelerations with a catcher's mask were substantially lower than contemporary injury thresholds, yet evidence indicates that baseball impacts to the mask still result in concussions. / Master of Science

The studies presented in this dissertation investigated biomechanical factors associated with sports-related brain injuries on the field and in the laboratory. In the first study, head impact exposure in youth football was observed using a helmet mounted accelerometer system to measure head kinematics. The results suggest that restriction on contact in practice at the youth level can translate into reduced head impact exposure over the course of a season. A second study investigated the effect of measurement error in the head impact kinematic data collected by the helmet mounted system have on subsequent analyses. The objective of this study was to characterize the propagation of random measurement error through data analyses by quantifying descriptive statistic uncertainties and biases for biomechanical datasets with random measurement error. For distribution analyses, uncertainties tend to decrease as sample sizes grow such that for a typical player, the uncertainties would be around 5% for peak linear acceleration and 10% for peak angular (rotational) acceleration. The third and fourth studies looked at comparisons between two headforms commonly used in athletic helmet testing, the Hybrid III and NOCSAE headforms. One study compared the headform shape, particularly looking at regions that are likely to affect helmet fit. Major differences were found at the nape of the neck and in the check/jaw regions that may contribute to difficulty with fitting a helmet to the Hybrid III headform. For the final study, the impact responses of the two headforms were compared. Both headforms were mounted on a Hybrid III neck and impacted at various magnitudes and locations that are representative of impacts observed on the football field. Some condition-specific differences in kinematic parameters were found between the two headforms though they tended to be small. Both headforms showed reasonable repeatability. / Ph. D.

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.

The purpose of this study was to identify the desired leadership characteristics of heads of schools as identified by school board chairs and heads of schools who are members of the Association of Christian Schools International (ACSI). This study is modeled after a Virginia Tech dissertation study of Virginia public school systems by Dr. Michael Thornton in 2009. Data were gathered from the heads of school and the board chairpersons to determine the similarities and differences between the two groups. Quantitative methodology was used in this study. A national sample of school board chairmen and heads of school from K-12 schools with 500 students or more and who are members of the Association of Christian Schools International (ACSI) were identified. Heads of school and school board chairpersons perceived visionary leader, team builder, effective school board relations and Christian school experience as essential leadership characteristics. Heads of school and school board chairpersons perceived that personal and professional integrity, honesty, and fairness and effective communication with board members, staff, parents, students, and the community is essential in head of school leadership. Heads of school and school board chairpersons believe that head of school-school board relations can have an impact on achieving and sustaining school-wide success. / Doctor of Education / The purpose of this study was to identify the desired leadership characteristics of heads of schools as identified by school board chairs and heads of schools who are members of the Association of Christian Schools International (ACSI). This study is modeled after a Virginia Tech dissertation study of Virginia public school systems by Dr. Michael Thornton in 2009. Data was gathered from the heads of school and the board chairpersons to determine the similarities and differences between the two groups. The head of school position in a Christian school equates to the superintendent position in a public school division. Board chairpersons are in the position as the leader of the school board. Heads of school and school board chairpersons perceived visionary leader, team builder, effective school board relations and Christian school experience as essential leadership characteristics. Heads of school and school board chairpersons perceived that personal and professional integrity, honesty, and fairness and effective communication with board members, staff, parents, students, and the community is essential in head of school leadership. Heads of school and school board chairpersons believe that head of school-school board relations can have an impact on achieving and sustaining school-wide success. This research will be important to those who desire to become a head of school and for school boards to recognize the characteristics needed for the position of head of school. It may be useful for graduate school programs in the training of persons seeking to become a head of school.

More than 19 million children participate in youth baseball and softball annually. Although baseball and softball are not commonly depicted as contact sports in the, according to the U.S. CPSC baseball and softball were responsible for 11.6% of all head injuries treated in emergency rooms in 2009; third most behind only cycling and football. Ball impact has been identified as the leading cause of injury in baseball and softball, with the most frequent injury resulting from a ball impacting the head. Reduced injury factor balls, infield softball masks, batter's helmets, and catcher's masks have all been integrated into baseball and softball as a means for preventing serious head injury from ball impact. The research in this thesis had four objectives: to compare the responses of the Hybrid III and NOCSAE headforms during high velocity projectile impacts, to compare head injury risk across a range of baseball stiffness designed for different age groups, to evaluate the effectiveness of infielder softball masks' ability to attenuate facial fracture risk, and to describe a novel methodology to evaluate the performance of batter's helmets and catcher's masks. Results of these research objectives determined the most suitable ATD headform to evaluate head injury risk for high velocity projectile impacts, provided a framework for determining the optimal age-specific ball stiffness and optimal infield mask design, and disseminated STAR ratings for batter's helmets and catcher's masks to the public. The research presented in this thesis can be used to further improve safety in baseball and softball. / MS

Plant-associated microbes (collectively the microbiome) are important contributors to plant health. They are known to play roles in increasing yield via improving stress tolerance, promoting growth, and suppressing the activity of plant pathogens. We investigated the wheat seed-head microbiome (phytomicrobiome) as a potential source of resistance to Fusarium head blight (FHB), or scab. FHB is a devastating disease in wheat, and other cereal grains, that causes losses in both quantity, through reduced yield, and quality of grain, through the production of toxins such as Deoxynivalenol. Efforts to combat FHB have focused primarily on breeding cultivars with resistance and applying fungicides. However, new resources for combatting FHB may lie in microbiome-plant interactions. To explore host-microbiome-pathogen interactions, we used field trials to characterize the seed head bacterial community (16S rRNA gene amplicons) across planting locations, host resistance genotypes, varieties, and plant development stages. We identified bacterial amplicon sequence variants (ASVs) present in each sample and then examined ASV community composition based on our variables. Characterizing bacterial relative abundance across samples, we identified 9,063 ASVs. These ASVs clustered according to plant developmental stages or maturity plant, location, and host genotype, but not by variety or maturity group. First, comparing plants at the pre-flowering versus mature grain-head stage, we found that both bacterial community richness and evenness changed significantly. In addition to these developmental changes, we found that bacterial community structure changes across locations, even between locations. Finally, we found that, in the presence of the pathogen, ASVs cluster by host resistance genotype, and that there are important taxonomic groups that are differentially abundant in the presence of the pathogen. Overall, we found that the wheat grain-head microbiome is shaped by environment-host-pathogen interactions, and that these interactions lead to differential abundance of particular community members that may be important in the management of FHB. / Master of Science in Life Sciences / Plant associated microbes are important contributors to plant health. They are known to play roles in increasing yield via improved stress tolerance, promoting growth, and suppressing plant disease. We investigated the wheat grain-head microbial communities as a source of disease resistance. The disease is called Fusarium Head Blight (FHB) and is caused by Fusarium graminaerum. FHB is a devastating disease in wheat and other cereals, causing losses, through reduced yield and quality through the production of toxins that prohibit use of the grain. To combat FHB, research has focused on developing plants that have resistance and the application of chemical fungicides. However, new resources for combating FHB may lie in the interactions between plants and microbes. This research is focused on identifying microbes that naturally interact with the plant, and how the pathogen, Fusarium, interacts with these beneficial microbes. In field trials, we characterized the microbial community by DNA sequencing technologies across locations, wheat with varying levels of genetic resistance, and wheat developmental stages. First, between the wheat kernel samples of pre-flowering and maturity, we found significant differences in microbial community. Consistent with other studies we found that the largest changes in microbial community composition across different growing locations. Finally, we found an interaction between the grain head microbiome and host resistance state when plants were exposed to the pathogen. Overall, we find that the wheat grain head microbiome is shaped by growing location and through interactions with the plant host and pathogen.

The work presented in this thesis focuses on the design and testing of a casualty extraction robot intended to stabilize the head and neck of an unresponsive person. The employment of robots in dangerous locales such as combat zones or the site of a natural disaster has the potential to help keep first responders out of harm's way as well as to improve the efficiency of search and rescue teams. After a review of robotic search and rescue platforms the Semi-Autonomous Victim Extraction Robot(SAVER) is introduced. The necessity of a device intended to support the head and cervical spine during transport on a rescue robot is then discussed. The kinematic and dynamic analyses of various candidate differential mechanisms intended for the head stabilization device are described, and the chosen mechanism is demonstrated in a proof-of-concept device. Following testing with a simple PID controller, it was determined an advanced feedback controller with disturbance rejection capabilities was required. Linear Active Disturbance Rejection Control (LADRC) was chosen for its effectiveness in rejecting perturbations and handling modeling uncertainties. The performance the proposed LADRC control scheme was compared with PID in simulation and the results are presented. Finally, a prototype of the device was designed and built to validate the functionality of the subsystem, and the results of the corresponding experimentation are discussed. / M. S. / Robots can help to keep first responders and medics out of dangerous situations by performing the rescue operation themselves or by collaborating with the field medic to make the process quicker and more efficient. The work presented in this thesis begins with a review of state-of-the-art rescue robots followed by the a brief description of the design of a Semi-Autonomous Victim Extraction Robot (SAVER) intended to rescue injured and incapacitated people. After the SAVER system is briefly described, the necessity of a device intended to support the head and cervical spine during transport is discussed. The head stabilization subsystem could also be implemented as a standalone device for use by paramedics to help free up valuable time that would otherwise be spent in manually stabilizing the head and neck of the injured person

Yes / This article discusses the current evidence for the short- and long-term effects of concussion in sport and how occurrences of concussion should be managed. The article also considers the potential role of medical imaging in terms of assessing both acute and chronic head injuries. Greater awareness of when medical imaging could be used will aid the practitioner's understanding of its potential contribution while still maintaining the fundamental importance of clinical judgement.

The research presented herein is an analysis of acceleration measurements of the head during helmet-helmet impacts, where a player's helmet impacts another player's helmet, and with a youth population in football. This research is aimed at advancing current understanding of impact biomechanics for two specialized groups. The first study is an observational analysis focusing on helmet-helmet impacts, and the difference in effective mass and head acceleration measurements between the striking player and the struck player. The study involved working with football players outfitted with a sensor integrated into their helmets containing a 6 accelerometer array, capable of measuring linear accelerations and estimating angular accelerations. To evaluate helmet-helmet impacts, video analysis of past NCAA football competitions between Virginia Tech and University of North Carolina (UNC) were utilized to identify these impacts between instrumented players. A force balance was then carried out for the observed impacts and their respective acceleration measurements to compute the effective mass of the players. It was determined that the total mass recruited by the striking player was 28% to 77% more than that of the struck player. The second study focused on documenting the head impact biomechanics of a youth population. To accomplish this objective, unique accelerometer arrays, capable of measuring linear and angular accelerations, were integrated into existing youth football helmets for 7 players on a local team. Acceleration data were collected for every practice and game during the 2011 season to amass a total of 748 impacts. No instrumented player sustained a concussion during the 2011 season. Results of the study indicated impacts of greater magnitudes were more likely to occur in practices, and can be minimized by augmenting practice activities. / Master of Science