Emerging research has suggested that the nature of cognitive deficits in Amnestic-MCI (a-MCI) may extend beyond memory impairments and can include deficits in attention (Gualtieri & Johnson, 2005; 2007). Recent studies have found significant differences between subjects with a-MCI and cognitively healthy individuals on measures of processing speed (Gorus, De Raedt, Lambert, Lemper, & Mets, 2008; Gualtieri & Johnson, 2005; Levinoff, Saumier, & Chertkow, 2005; Silveri et al., 2007). The current study sought to add to the limited research currently available on processing speed in a-MCI by comparing cognitively healthy individuals (M age = 64.57; SD = 6.61) and an age-matched a-MCI group (M age = 64.19; SD = 5.79) on a measure of processing speed, an index of attention. Second, the study evaluated the utility of the “25 Numbers Test” in differentiating individuals with a-MCI from a cognitively healthy group of participants. As expected, the participants with a-MCI performed more poorly (t(72) = -5.96, p < .01) on the 25 Numbers Test and demonstrated greater intra-individual variability in comparison to the cognitively healthy group (t(72) = -3.009, p < .01). The 25 Numbers Test effectively discriminated cognitively healthy individuals from those with a-MCI (AUC = 0.85, p < .01). Results will add to the limited research on processing speed in a-MCI and provide a basis for the importance of evaluating processing speed as part of routine screening for a-MCI.

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This thesis presents an econometric test of the offsetting behavior hypothesis concerning drivers of light trucks relative to cars. The main objective is to determine whether drivers of light trucks offset perceived safety benefits associated with larger vehicles by driving more aggressively than drivers of cars, subsequently causing more fatal crashes, holding all else constant. An empirical model using data on pedestrian fatalities across the United States over a five-year period is developed and analyzed in order to capture the desired results. Estimates provide substantial evidence in support of the offsetting behavior hypothesis. To strengthen the case for driver offsetting behavior beyond previous studies, the model is estimated again using pedalcyclist fatalities. The results also point to interesting conclusions regarding the effects of increased speed limits on the behavior of drivers.

Diabetes (DM) and hypertension (HTN) are prevalent chronic diseases among older adults. For example, in the U.S., 1 in 4 older adults have DM, 3 in 4 have HTN and 1 in 6 have DM and HTN. Moreover, each year, health care costs attributable to DM and HTN are estimated at $327 billion and $131 billion USD respectively. Both diseases also impose tremendous burden on the health and well-being of older adults. For example, gait speed (GS) is reduced in older adults with DM or HTN compared to older adults without DM or HTN. Gait speed is a powerful indicator of health status among older adults. Reduced GS predicts various adverse health outcomes including falls, frailty, cognitive impairment, reduced quality of life, hospitalization and even death. Moreover, adequate GS is required to safely execute daily activities. For example, GS of 1.14 m/s or faster is required to safely cross the street. Reduced GS in older adults with DM or HTN can partly be explained by multimorbidity (e.g., older adults with DM are at increased risk of developing HTN) as well as complications that are frequently associated with DM and HTN. For example, older adults with DM or HTN are at increased risk of developing peripheral artery disease, which causes reduced lower extremity muscle strength and pain, as well as retinopathy, which causes vision impairment. Additionally, older adults with DM are at increased risk of developing peripheral neuropathy, which causes pain and impaired balance. Although the physiological mechanisms of these complications are largely understood, research is needed to determine the extent to which these complications contribute to GS decline among older adults with DM, HTN or DM and HTN. The overarching objective of this thesis was to examine how multimorbidity patterns (i.e., types/combinations of chronic diseases), and sensory and motor impairments impact GS in older adults with DM, HTN or DM and HTN. This thesis also examined how GS changes over time (i.e., trajectories) in this population. This thesis is comprised of 3 manuscripts and was conducted using data from the National Health and Aging Trends Study (NHATS); a large, nationally representative sample of American older adults. Annual data collection began in 2011 and is ongoing. In 2015, the NHATS was replenished with approximately 50% new participants, to account for death and loss-to-follow-up. Therefore, data was analyzed in two cohorts: cohort A (individuals recruited in 2011) and cohort B (individuals recruited in 2015 and individuals recruited in 2011 who remained in the sample at the time of replenishment). In manuscript 1, latent class analysis was performed to identify multimorbidity patterns in older adults with DM, HTN or DM and HTN. Additionally, analysis of covariance (ANCOVA) was conducted to examine differences in GS among these multimorbidity patterns. This study identified a total of nine multimorbidity patterns in cohort A: two patterns in older adults with DM (low multimorbidity and cardiovascular-joint multimorbidity), three patterns in older adults with HTN (low multimorbidity, psychological multimorbidity and cardiovascular multimorbidity) and four patterns in older adults with DM and HTN (metabolic-cardiovascular-psychological-joint multimorbidity, metabolic-bone-joint multimorbidity, metabolic-cardiovascular-joint multimorbidity and metabolic multimorbidity). Additionally, this study identified a total of ten multimorbidity patterns in cohort B: two patterns in older adults with DM (low multimorbidity and joint multimorbidity), four patterns in older adults with HTN (cardiovascular-joint-respiratory multimorbidity, cardiovascular multimorbidity, psychological-joint multimorbidity and joint multimorbidity) and four patterns in older adults with DM and HTN (metabolic-cardiovascular-joint-respiratory multimorbidity, metabolic-psychological-joint multimorbidity, metabolic-bone-joint multimorbidity and metabolic-joint multimorbidity). Overall, multimorbidity patterns with larger numbers of chronic diseases patterns or patterns that included depression or anxiety were associated with the slowest GS. In manuscript 2, multinomial logistic regression was used to conduct state-based analyses which examined the relationship between impairments (i.e., hearing, and vision impairment, pain, balance, and lower extremity strength impairment) and GS transitions (i.e., fast to, intermediate walker, intermediate to slow walker etc.) in older adults with DM, HTN or DM and HTN. Balance and lower extremity strength impairment were associated with an increased risk of GS decline (i.e., transitioning from an intermediate to slow walker). Moreover, older adults with vision, hearing, balance, or lower extremity strength impairment and those who used pain medication at least 5 days/week were more likely to be slow walkers at baseline and remain slow walkers at follow-up. In manuscript 3, group-based trajectory modeling was used to identify longitudinal trajectories of GS in older adults with DM, HTN or DM and HTN. Multinomial logistic regression was then conducted to examine the correlates of these trajectories. This study identified four GS trajectories in both cohorts: i) fast-stable GS, ii) intermediate GS with slow decline, iii) intermediate GS with moderate decline and iv) slow GS with fast decline. Additionally, one trajectory was unique to cohort A: intermediate-stable GS and two trajectories were unique to cohort B: fast GS with slow decline, and intermediate GS with fast decline. In both cohorts, individuals who were older, Black (non-Hispanic), had a higher number of chronic diseases or higher body mass index (BMI) were more likely to belong to a trajectory group with faster GS decline. Conversely, individuals with higher education, or higher baseline GS were less likely to belong to a trajectory group with faster GS decline. From a population health perspective, findings from this thesis can inform large-scale monitoring and management strategies to mitigate GS decline in older adults with DM, HTN or DM and HTN. For example, individuals who are older, identify as Black non-Hispanic or those with a higher number of chronic diseases or higher BMI may benefit from more frequent monitoring of their GS. Moreover, findings from this thesis can be used to determine how older adults with different multimorbidity patterns, or different types of sensory and motor impairments respond to interventions. Lastly, older adults with DM and/or HTN should be educated about the importance of maintaining their GS as they age to prevent adverse outcomes including falls, hospitalization, and premature death. / Thesis / Doctor of Philosophy (PhD) / Diabetes and hypertension are common chronic diseases among older adults globally. Moreover, these two chronic diseases are frequently found in the same individual due to shared risk factors including physical inactivity, and family history. Additionally, older adults with diabetes and/or hypertension are at risk of developing complications including vision loss, heart disease and stroke. These complications often cause impairments (i.e., changes in body structure or function) which also occur with aging including vision and hearing impairment, pain, and balance impairment which may reduce physical function (e.g., walking speed). There is a need for research to examine which other chronic diseases are linked to diabetes and hypertension and the impact of these diseases and disease-related impairments on walking speed among older adults with diabetes and/or hypertension. Moreover, it is important to examine how walking speed changes over time (i.e., trajectories) in older adults with diabetes and/or hypertension. Results from this thesis show that older adults with diabetes and/or hypertension who used pain medication at least 5 days/week, had vision, balance, or lower extremity strength impairment as well as older adults who are female, Black non-Hispanic, had a higher number of chronic diseases and a higher body mass index were at greatest risk of reduced walking speed. On the other hand, higher education and higher baseline walking speed were linked to lower risk of walking speed decline. Older adults who were identified as “high-risk” may benefit from closer monitoring and management of their walking speed to prevent further decline.

SPEED AND AGILITY TRAINING THE MUSTANG WAY: THE DEVELOPMENT OF AN INSTRUCTIONAL DVD FOR CAL POLY ATHLETES’ SUMMER TRAINING Gary Douglas Heron The purpose of this project was to create an instructional DVD of speed and agility training for Cal Poly student-athletes. The DVD is for athletes’ use when they are away from campus during summer break and contains information about the same drills and information the strength and conditioning coaches provided while athletes were on campus. The project was filmed and edited by the graduate assistant strength and conditioning coach for Cal Poly intercollegiate athletics. The DVD contains 74 drills that encompass speed techniques, acceleration techniques, plyometrics, footwork, and change of direction. Recommendations for further empirical research in the area of speed and agility training are provided.

High-speed planing craft operating in waves are subject to frequent water impact, or slamming, as a portion or whole of the craft exits the water and re-enters at high velocity. The global load induced by slamming can cause fatigue-related damages to structures. The local slamming can cause local damage to structures and its induced acceleration can cause damage to equipment and personnel aboard. Therefore the slamming loads in high-speed craft are critical design loads. Nowadays, due to the increasing use of composite materials in high-speed craft, the interaction between the hydrodynamic loading and structural response, or hydroelasticity, must be considered. In this work, a flexible V-shaped wedge, which vertically enters the calm water with an impact velocity, was examined experimentally and numerically to characterize the slamming of a representative cross-section of high-speed craft. Physical quantities of interest include rigid-body kinematic motions, spray root propagation, hydrodynamic loading, and structural response. In the experimental work, with varied impact velocity and flexural rigidity of the wedge bottom plate, a wide range of hydroelasticity factors were investigated. The intersection between the bottom plate and side plate is called chine. The phases before and after the spray root reached the chine are called chine-unwetted and chine-wetted phase, respectively. It was found that the maximum deflection and strain occur in the chine-unwetted phase while a structural vibration with rapidly decaying magnitude is observed in the chine-wetted phase. Furthermore, the kinematic effect of hydroelasticity changes the spray root propagation and hence the pressure, while the inertial effect elongates the natural period of the plate. Inspired by the experimental work, a computational framework was proposed to focus on the chine-unwetted phase. Several hydroelastic models can be obtained from this framework. The hydroelastic models were validated to show reasonable agreement with experiments. Various parameters were studied through the computational framework. The hydroelasticity factor was modified to account for the mass and boundary conditions. It was found that the nondimensional rigid-body kinematic motions and maximum deflection showed little dependence on the hydroelasticity factor. Hydroelastic effects increased the time it takes for the peak maximum deflection to be reached for small values of the hydroelasticity factor. Hydroelastic effects also have little influence on the magnitude of the maximum deflection. These discoveries further the understanding of hydroelastic slamming and show the potential to guide the structural optimization and design of high-speed craft. / Doctor of Philosophy / High-speed planing craft operating in waves are prone to frequent water impact, or slamming, as a portion or whole of the craft exits the water and re-enters at high velocity. The slamming loads in high-speed craft are critical design loads as the slamming can cause damage to the structures and equipment as well as injure personnel aboard. Nowadays, due to the increasing use of composite materials in high-speed craft, the interaction between the hydrodynamic loading and structural response, or hydroelasticity, must be considered. In this work, a flexible V-shaped wedge entering water is studied experimentally and computationally to characterize the slamming of a representative cross-section of high-speed craft. The contact point between the water surface and the wedge bottom is called the spray root. It was found that the hydrodynamic loading and structural response interact with each other through the spray root. The maximum deflection and strain occur when the wedge bottom is partially submerged while a structural vibration with rapidly decaying magnitude is observed when the wedge bottom is fully submerged. Using the hydroelasticity factor proposed by other researchers, the extent of fluid-structure interaction was quantified. Hydroelastic effects manifest themselves when the hydroelasticity factor is small These discoveries further the understanding of hydroelastic slamming and show the potential to guide the structural optimization and design of high-speed craft.

An experimental investigation was conducted to better understand the aerodynamics of magnetically levitated (MagLev) high speed vehicles operating in ground effect. A high speed moving track system was designed and developed to be used in the Virginia Tech Stability wind tunnel. Flowfield surveys confirmed the system was providing proper flow simulation. Aerodynamic tests were conducted on two vehicle geometries, Mag950 and Magl002. Tests included force and moment measurements, surface pressure measurements, vehicle wake flowfield survey, and flow visualization using tufts. The results showed a higher drag coefficient when the vehicle is operating InGround- Effect (IGE) versus Out-of-Ground-Effect (OGE), with the Magl002 displaying a slightly less drag than the Mag950 vehicle geometry. The experimental values showed higher drag compared with the available computational results by Grumman. The brief chart below shows the summary of force and moment results. Contrary to expectation, higher positive lift was observed with the vehicles operating IOE. The computational results also showed a positive lift at IGE versus OGE. The hot-wire wake data and tuft photos gave results consistent with Grumman's computational calculations. Overall, the Mag 1 002 vehicle geometry seems to be a better candidate for further development. / Master of Science

Electric vehicles with autonomous driving are the future of transportation, as they are sustainable, efficient, environmentally friendly, and can provide collision-free congestion-free driving. However, the sensing and control technology adds new accessory loads which increase the vehicle energy use. Thus, it is critical to minimize energy use where possible, and optimal speed planning is a promising way to achieve this goal and is thus the topic of study for this thesis. First, a low-computation framework for the onboard calculation of energy-optimal cruising speed of battery electric vehicles is proposed. The framework is used to investigate the critical parameters for energy-optimal cruising speed determination, and it includes major internal and external vehicle losses, uses accurate motor-inverter efficiency maps as look-up tables, and does not require knowledge of the future route. This framework is validated using three electric vehicle models in MATLAB/SIMULINK. Secondly, a novel two-level model predictive control (MPC) speed control algorithm for battery electric autonomous vehicles as a successive convex optimization problem is proposed. The proposed successive convex approach produces a highly accurate optimal speed profile while also being solvable in real-time with the vehicle's onboard computing resources. This algorithm is used to perform a variety of simulated test cases, which show an energy savings potential of about 1% to 20% for different driving conditions, compared to a non-energy-optimal driving profile. Lastly, the research is expanded to consider fuel cell hybrid electric vehicles (FCHEVs), which have the added need for an optimal energy management strategy inv addition to optimal speed planning. Novel successive and integrated convex speed planning and energy management algorithms are proposed to solve the minimum hydrogen consumption problem for autonomous FCHEVs. The simulation results show that the proposed integrated method, which considers fuel cell system efficiency in the optimization objective function for speed planning, leads to 0.19% to 2.37% less hydrogen consumption compared to the successive method on short drive cycles with varying accessory loads. On the same test cycles, the integrated method uses 10.12% to 21.62% less hydrogen than an arbitrary constant-speed profile. / Thesis / Doctor of Philosophy (PhD) / Autonomous vehicles are expected to be the future of transportation, however, the high continuous electrical accessory power needed for control and perception is a challenge. Fortunately, there is an inherent property of speed planning for autonomous vehicles that can help deal with this problem. This thesis focuses on optimal speed planning to minimize energy use, proposing convex methods considering detailed internal and external losses for battery electric vehicles (BEVs), and optimal speed planning integrated with optimal energy management for fuel cell hybrid electric vehicles (FCHEVs). The proposed framework in this thesis is accurate while maintaining a low computational effort, which are the desired criteria for real-time algorithms.

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