Objectives: This thesis included 6 manuscripts which focused on the analysis of adverse events following immunization (AEFIs), including general health services utilization (emergency room (ER) visits and hospital admissions) and specific diagnoses (e.g. febrile convulsions). The main objectives of this research were: 1) To demonstrate the utility of the self-controlled case series (SCCS) design coupled with health administrative data for studying the safety of vaccines; 2) Introducing an innovative approach using relative incidence ratios (RIRs) within an SCCS analysis to identify risk factors for AEFIs and to overcome the healthy vaccinee bias; and 3) To demonstrate how SCCS and RIR analyses of health services outcomes in health administrative data can provide important insights into underlying physiological and behavioural mechanisms. Data Sources: This work utilized Ontario health administrative data housed at the Institute for Clinical Evaluative Sciences (ICES). The study included all children born in Ontario, Canada between 2002 and 2011 (over 1 million children). Vaccinations were identified using OHIP fee for service billing codes for general vaccination. Admissions and ER visits for any reason were identified in the Discharge Abstract Database (DAD) and National Ambulatory Care Reporting System (NACRS). Primary reasons for admissions and ER visits were investigated using ICD-10-CA codes reported in the DAD and NACRS databases. Statistical Methods: The self-controlled case series design (SCCS) was used to calculate the relative incidence of admissions, ER visits and other AEFIs. To investigate relative incidence for AEFIs across risk groups of interest, as well as addressing the healthy vaccinee effect bias, RIRs were calculated. RIRs are the ratio of incidence ratios in a subgroup of interest relative to a designated reference group. Results and Conclusions: The combined approach of using the SCCS design and RIRs to identify risk factors and overcome the healthy vaccinee bias proved to be a powerful approach to studying vaccine safety. Future work will be important to characterize the performance and validity of the SCCS + RIR approach in the presence of increasing levels of confounding and differing manifestations of the healthy vaccinee bias, as well as to elucidate the biological and behavioural mechanisms underlying our findings.

Theoretical models suggest that ownership structure may be an important determinant of securities' market characteristics. For example, the presence of informed traders leads to greater bid-ask spreads (Copeland and Galai (1983), and Glosten and Milgrom (1985)), and strategic trading of informed and discretionary liquidity traders leads to intertemporal variation in both trading volume and trading costs (Admati and Pfleiderer (1988), and Foster and Viswanathan (1990)). However, the empirical studies on the effect of ownership structure on market characteristics are limited. Prior studies focus on either one type of market characteristics or one type of owners, and usually do not address the potential endogeneity problem between market characteristics and ownership structure. This dissertation extends existing literature with two essays on ownership and market characteristics. The first essay broadly examines the effect of ownership structure (inside ownership, institutional ownership, and individual ownership) on market characteristics such as order flow, price impact of trade, quoted spread and quoted depth. For each market characteristic examined, I establish an empirical model based on existing theories and empirical evidence. My results indicate that stocks with greater inside ownership have lower order flow, greater price impact of trade, greater quoted spread and lower quoted depth, while stocks with greater active institutional ownership and greater individual shareholders have greater order flow, smaller price impact of trade, lower spread and greater depth. These results may have implications for corporate governance. For example, while agency theory suggests managerial ownership may align interests of managers and shareholders, this essay finds that this comes with a liquidity cost. Further, my results suggest there are liquidity benefits of individual and institutional ownership. If as suggested by Amihud and Mendelson (1989), investors require a higher rate of return for illiquid stocks, firms can target their shares to specific types of investors (for example, active institutions and individuals) to improve liquidity, and reduce their cost of capital. The second essay is a specific application of the first essay and examines the effect of institutional ownership on price discovery around earnings announcements. I select earnings announcements as the event for my analysis because there are three well-documented regularities about earnings announcements. First, market participants anticipate the forthcoming earnings announcements. Second, the announcements of earnings news are usually accompanied by abnormal price changes and abnormal volume. Third, there is evidence that stock price continues to move in the direction of earnings surprise after the announcements of earnings news. Since results from the first essay suggest that institutional investors affect market characteristics such as price impact of trade and quoted spread, I expect that institutional participation would also affect the price discovery process around earnings announcements. My results indicate that institutional ownership is associated with greater anticipation of earnings news. Further, stocks with greater institutional ownership have a greater price response to announcements of earnings news. Finally, institutional investors have no significant effect on post-announcement drift. The results of the second essay suggest that institutional investors contribute to the price discovery process. / Ph. D.

A mathematical model of a small fixed-wing aircraft was developed through application of parameter estimation techniques to simulated flight test data. Multiple controllers were devised based on this model for path following, including a self-scheduled linear parameter-varying (LPV) controller with path curvature as a scheduling parameter. The robustness and performance of these controllers were tested in a rigorous MATLAB simulation environment that included steady winds and gusts, measurement noise, delays, and model uncertainties. The linear controllers designed within were found to be robust to the disturbances and uncertainties in the simulation environment, and had similar or better performance in comparison to a nonlinear control law operating in an inner-outer loop structure. Steps are being taken to implement the resulting controllers on the unmanned aerial vehicle (UAV) testbed in the Nonlinear Systems Laboratory at Virginia Tech. / Master of Science

This thesis proposes a modification of trajectory shaping guidance to provide more accurate path convergence in curved paths. The object of this thesis is to apply this simple guidance law to platooning control to ensure all vehicles in the platoon converge to a desired constant radius path at a desired vehicle separation distance. To show the viability of this new guidance law, it is shown mathematically to be exponentially stable. It is also confirmed through simulations and on ground robots.

An important management practice within the 60-80 million acres of Pinyon-Juniper woodlands is to convert these woodlands to open rangelands. The success or failure of seedling adapted grasses in place of trees is contingent upon the revegetation techniques employed and upon fortuitous weather patterns. In order to formulate policy for Pinyon-Juniper control decisions, persons responsible for such policies need to know the risks of introducing range grasses into given areas. This thesis is essentially a hypothesis concerning the magnitude of such risks. Pinyon-Juniper control has been practiced widely in the five state areas of Arizona, Colorado, Nevada, New Mexico, and Utah. Justification for control and conversion of the woodlands to open grazing areas rests on the assumption that the trees have little apparent utility and, therefore they should be replaced by a grass resource which has relatively greater value. In its extreme form the assumption involves the notion that the trees are actually detrimental to the productivity of the land. they become a hindrance to the growth of various forms of plant life considered desirable. Considerable investment, primarily at the expense of society, has been incurred in the transformation process. Until recent years control projects have been limited to the most accessible sites and areas "invaded" by Pinyon-Juniper trees. At present the conversion place has slackened due to the limited number of remaining accessible sites in some areas, but more importantly to the fact that the projects have had a history of mixed success. While certain rules of thumb have been put forth to explain the nature of the factors influencing seedling emergence and increased forage production, these are so volatile that an apprehension of failure exists among land managers. The intensity of investment can only be balanced against risk levels if there is basic understanding of the roles played by the variables influencing seedling establishment and forage increase. Both policy and nonpolicy (not subject to human manipulation) variables must be identified and their influences upon success measured. The analysis that follows begins by setting forth the objectives to be achieved in evaluating the tree conversion process and its associated risk. Next a theory of range grass seedling establishment is presented. The appropriate variables are identified and an "establishment" model is applied to the empirical data. A third section specifically treats weather as a major influence upon seedling emergence and forage production. A model expressed in probabilistic terms, employing the Markov property is applied to available data to evaluate weather index movements. Finally having dealt with emergence, a theory is developed to explain expected forage production in the period following emergence. The parameters of the associated model are obtained from empirical data.

No description available.

Rule-following has been a controversial issue in professional philosophical literature since Wittgenstein's Philosophical Investigations. Many authors have developed accounts of rule-following along different lines, including those that naturalistically reduce rule-following to non-normative phenomena and those that take rule-following to be an irreducible aspect of cognition and agency. Hannah Ginsborg, a prominent contributor to rule-following literature, has developed a partially reductive account of rule-following, combining features of both reductionist and nonreductionist accounts. But naturalizing or internalistic theories of rule-following, or even Ginsborg's partial reduction of rule-following, ignore important facets of what it is to follow a rule, particularly its social aspect. In this thesis I reject Ginsborg's partial reductionism, holding that her hybrid theory does not escape the particular problems of naturalistic reductionism or nonreductionism about rule-following. I argue instead that certain social concepts are necessary for a satisfactory theory of rule-following. The first concept is how an individual is "enculturated" into her various social and cultural networks. The second is one's "normative identity," the accumulated concepts and behaviors one has as part of a social and cultural network. I develop these notions with inspiration from Wittgenstein and other social contributors to rule-following literature.

The state-of-the-art traffic simulation packages model traffic on a microscopic level. This includes the use of several sets of models that dictate how traffic moves within a transportation network. These models include car-following, gap acceptance, lane-changing and route choice models. The aim of this thesis is to improve the treatment of vehicle dynamics in traffic simulation and, as a result, special attention was paid to car-following models. These models were highlighted because they are largely responsible for capturing a vehicle’s motion and its relevant dynamics in traffic simulation. In order to improve the treatment of vehicle dynamics in traffic simulation, a Dynamic-Interactive-Vehicle (DIV) model was developed. This vehicle model is calibrated with the use of essential vehicle performance specifications that are responsible for the movement of a vehicle in a transportation network. After the calibration process the model is able to accept three inputs from a driver – gas pedal, brake pedal and steering wheel positions. The model then outputs the corresponding longitudinal and latitudinal values which represent the movement of a vehicle along a roadway. The vehicle model will also account for most of the dominant external forces that affect an automobile’s performance along a roadway. This thesis will validate the proposed model by comparing its output from a few performance tests with the performance test results of three passenger cars. The DIV model was validated by comparing the acceleration, braking and steering performance test results of three passenger cars with the output from the DIV model upon performing similar tests. It was found that the DIV model was successful at replicating the two-dimensional vehicle motion.

Though comparisons of simulation models have been conducted, few investigations have examined in detail the logical differences between models. If the output measures of effectiveness are to be interpreted correctly, it is important that the analyst understand some of the underlying logic and assumptions upon which the results are based. An understanding of model logic and its inherent effect on the results will aid the transportation analyst in the application and calibration of a simulation model. In this thesis, the car-following behavior of the CORSIM and INTEGRATION simulation models are examined in significant detail, and its impact on output results explained. In addition, the thesis presents a calibration procedure for the CORSIM sub-model, FRESIM. Currently, FRESIM is calibrated by ad hoc trial-and-error, or by utilizing empirically developed cross-referencing tables. The literature reveals that the relationship between the microscopic input parameters of the CORSIM model, and the macroscopic parameters of capacity is not understood. The thesis addresses this concern. Finally, the thesis compares the INTEGRATION and CORSIM models in freeway and urban environments. The comparison is unique in that the simulated networks were configured such that differences in results could be identified, isolated, and explained. Additionally, the simplified nature of the test networks allowed for the formulation of analytical solutions. The thesis begins by relating steady-state car-following behavior to macroscopic traffic stream models. This is done so that a calibration procedure for the FRESIM (Pipes) car-following model could be developed. The proposed calibration procedure offers an avenue to calibrate microscopic car-following behavior using macroscopic field measurements that can be easily obtained from loop detectors. The calibration procedure, while it does not overcome the inherent shortcomings of the Pipes model, does provide an opportunity to better calibrate the network FRESIM car-following sensitivity factor to existing roadway conditions. The thesis then reports an observed inconsistency in the link-specific car-following sensitivity factor of the FRESIM model. Because calibration of a network on a link-specific basis is key to an accurate network representation, a correction factor was developed that should be applied to the analytically calculated link-specific car-following sensitivity factor. The application of the correction factor resulted in observed saturation flow rates that were within 5% of the desired saturation flow rates. The thesis concludes with a comparison of the CORSIM and INTEGRATION models for transient conditions. As a result of the various intricacies and subtleties that are involved in transient behavior, the comparisons were conducted by running the models on simple networks where analytical solutions to the problem could be formulated. In urban environments, it was observed that the models are consistent in estimates of delay and travel time, and inconsistent in estimates of vehicle stops, stopped delay, fuel consumption, and emissions. Specifically, it was observed that the NETSIM model underestimates the number of vehicle stops in comparison with INTEGRATION and the analytical formulation. It was also observed that the NETSIM vehicles speed and acceleration profiles are characterized by abrupt accelerations and decelerations. These abrupt movements significantly impact stopped time delay and vehicle emissions estimates. Inconsistencies in emissions estimates can also be attributed to differences in the embedded rate tables of each model. In freeway environments for under-saturated conditions, INTEGRATION returned higher values of travel time and delay, and lower values of average speed than the FRESIM model. These results are consistent with the analytical solution, and can be attributed to the speed-flow relationship of each model. In saturated conditions, when the capacity of the bottleneck is equal to the demand volume, the emergent vehicle behavior of the FRESIM model was observed to be inconsistent with the analytical solution. The FRESIM vehicles were observed to dramatically decelerate upon entering a lower-capacity link. This deceleration behavior led to higher travel time and delay time estimates in FRESIM than in INTEGRATION. In over-saturated conditions, longer queue lengths were observed in FRESIM than in INTEGRATION, resulting in slightly higher travel and delay estimates in the FRESIM model. The reason for the discrepancy in queue lengths is unclear, as the network jam density in each model was equivalent. / Master of Science

This thesis was motivated to simulate the evacuation traffic of Mississippi Stated University (MSU) main campus using the Path-Following logic of TSIS/CORSIM and to evaluate a set of traffic management plans. Three scenarios of traffic management plans were developed and tested. A NCT of 123 minutes was projected if evacuate without any plan. In comparison, under a pre-planned traffic management plan the NCT would decrease to 39 minutes. Further, if implement contra flow the NCT would reduce to 21 minutes. If even further adjust the signal timing plans at the university exits a NCT of 20 minutes would be achieved. The sensitivity analysis found that the NCT was sensitive to the CORSIM parameters of free flow speed, time to react to sudden deceleration of lead vehicle and the configuration of driver type, while the effects of discharge headway and start up lost time were not found to be significant.