The overall objective of this thesis is to develop, validate and assess a probabilistic collision damage model to support ongoing work by the Society of Naval Architecture and Marine Engineering (SNAME) Ad Hoc Panel #6 and IMO working groups. It is generally agreed that structural design has a major influence on tanker oil outflow and damaged stability in grounding and collision, but crashworthiness is not considered in present regulations. The proposed methodology provides a practical means of considering structural design in a regulatory framework, and when implemented would improve the safety and environmental performance of ships. This thesis continues the development and applies a Simplified Collision Model (SIMCOL) to calculate damage extent (transverse, vertical and longitudinal) and oil outflow in ship collisions. The primary contribution of this thesis is the development and validation of a theory for the determination of energy absorbed in longitudinal extent of damage, and the implementation of the theory within SIMCOL. SIMCOL is sufficiently fast to be applied to thousands of collision cases as is required for a probabilistic analysis. The following specific tasks were completed using SIMCOL in support of this project: Completed the development of SIMCOL Version 3.0 including: 1) Deformable Bow sub model 2) Implementation and validation of theory for the determination of energy absorbed in longitudinal extent of damage. • Developed the capability to model collision events using LSDYNA. • Validated Virginia Tech LSDYNA ship collision modeling procedure. • Validated SIMCOL using real collision data, and probabilistic collision data for penetrating collisions. / Ph. D.

Adolescence is a transition period during which individuals have increasing autonomy in decision-making for themselves (Casey, Jones, and Hare, 2008), often choosing among options about which they have little knowledge and experience. This process of individuation and independence is reflected as real-world risk taking behaviors (Silveri et al., 2004), including higher motor accidents, unwanted pregnancies, sexually transmitted diseases, drug addictions, and death (Casey et al., 2008). The extent to which adolescents continue to display increased behaviors with negative consequences during this period of life depends critically on their ability to explore and learn potential consequences of actions within novel environments. This learning is not limited to the value of the outcome associated with making choices, but extends to the levels of risk taken in making those choices. While the existing adolescence literature has focused on neural substrates of risk preferences, how adolescents behaviorally and neurally learn about risks remain unknown. Success or failure to learn the potential variability of these consequences, or the risks involved, in ambiguous decisions is hypothesized to be a crucial process to allow the individuals to make decisions based on their risk preferences. The alternative in which adolescents fail to learn about the risks involved in their decisions leaves the adolescent in a state of continued exploration of the ambiguity, reflected as continued risk-taking behavior. This dissertation comprises 2 papers. The first paper is a perspective paper outlining a paradigm that risk taking behavior observed during adolescents may be a product of each adolescent's abilities to learn about risk. The second paper builds on the hypothesis of the perspective paper by first examining neural correlates of risk learning and quantifying individual risk learning abilities and then examining longitudinal risk learning developmental trajectories in relation to real-world risk-trajectories in adolescent individuals. / Doctor of Philosophy / Adolescence is a transition period during which individuals have increasing autonomy in decision-making for themselves, often choosing among options about which they have little knowledge and experience. This process of individuation and independence begins with the adolescent exploring their world and those options they are ignorant of. This is reflected as real-world risk-taking behaviors, including higher motor accidents, unwanted pregnancies, sexually transmitted diseases, drug addictions, and death. We hypothesized and tested the premise that whether adolescents who succeeded or fail to learn about the negative consequences of their actions while exploring will continue to partake in behaviors with negative consequences. This learning is not limited to the value of the outcome associated with making choices, but extends to the range of possible outcomes of the choices or the risks involved. Indeed, the failure to learn the risks involved in decisions with no known information show continued and greater risk-taking behavior, perhaps remaining in a state of continued exploration of the unknown.

Persistently high attrition rates from STEM majors present a stubborn challenge for researchers, administrators, and faculty alike. To approach this problem, my dissertation examined the socialization processes by which students develop a sense of belonging to both their institution and their discipline. Previously identified as an important factor in students' persistence and overall satisfaction with their undergraduate experience, belonging is a critical piece of the retention puzzle. However, not every student experiences or develops belonging in the same way. This dissertation applied the theoretical lens of socialization to deepen the understanding of how social interactions help or hinder students' belonging to their university and chosen major alike. My dissertation work was grounded in the synthesis of two theoretical frameworks: Conrad et al.'s (2006) model of socialization and Strayhorn's (2018e) conceptualization of sense of belonging. The study took the form of an embedded case study of two similar disciplinary contexts within a large public land-grant Research 1 institution, with four students from each context for a total of eight participants. By leveraging four years of interview data from each participant, supported by institutional documentation, I addressed the question: In what ways does a student's socialization experience influence, if at all, their sense of belonging to both their chosen discipline and their university? Data analysis included qualitative coding, trajectory mapping, and thematic analysis. Trajectories were produced for each participant before expanding the analysis to examine patterns across and between the contexts. My findings addressed the mechanisms of socialization at the undergraduate level and how they evolved over time. The primary outcome of my work was a set of three distinct socialization trajectories, named the Anchored, who built strong socializing relationships early and maintained them throughout their undergraduate years; Independents, who neither sought nor wanted such relationships; and Wanderers, whose socializing relationships tended to be short-lived and inconsistent, although desired. Fourteen unique groups of socializing agents were identified, along with five common drivers for intentionally engaging with specific agents: personal and academic support, research and industry aspirations, and finding a path. Pre-college socialization experiences were salient for developing anticipatory belonging, as students who were exposed to their discipline or institution prior to arriving as students had an easier time becoming integrated to their communities. Once students arrived, their socialization trajectories tended to shape their feelings of belonging to the institution, with close ties forming for the Anchored, appreciation for general support among the Independents, and a mix of happiness and frustration for the Wanderers. By contrast, disciplinary belonging was more reliant on the individual participant's goals and interests. Disciplinary differences between the two contexts were identified but were limited in scope and generally linked to the career outcomes students associated with their chosen major rather than their experiences in the major. Finally, my research revealed that a strong sense of belonging in one domain of undergraduate life could be sufficient for a student to persist to degree completion despite weak or absent feelings of belonging in other areas. / Doctor of Philosophy / For decades, students have been leaving STEM majors at alarmingly high rates despite the efforts of researchers, administrators, and faculty. To approach this problem, my dissertation examined how social interactions and relationships can help students feel like they belong in their chosen major and university. Previous research identified such feelings of belonging as an important factor in helping students persist to the completion of their degrees, and my work added onto this body of work by specifically examining the role of students' social connections. My dissertation utilized data from eight total students. Four of the students were chemical engineering students, with the remaining four from chemistry and biochemistry, together called the "chemical sciences." The data for this work included four years of interview data supported by institutional documents. Such documents provided information like curricular requirements, demographic and population information, and course information, which helped provide background for the students' interviews. Leveraging these data, I addressed the aforementioned interaction of students' social interactions and their feelings of belonging on campus and in their major. My data analysis was based around the creation of trajectories that would capture the evolution of a student's experiences over the course of their undergraduate career. Once trajectories were generated for each student, I was then able to look across the trajectories and identify patterns between and within them. The primary finding of my dissertation work was the emergence of three distinct patterns of how students' social interactions evolved over time, labeled the Anchored, who built strong and consistent networks that they maintained over two or more years; the Independents, who neither sought nor wanted such relationships; and the Wanderers, who had relationships and interactions that were often short-lived or inconsistent, but wanted more. Fourteen unique groups with whom students interacted were identified, along with the respective impacts said groups could have on students' feelings of belonging. Additionally, five drivers for seeking out interaction with these groups were identified: personal and academic support, research and industry aspirations, and finding a path. The experiences students had with their university or major prior to enrolling were found to be important for shaping the way students perceived their future, and those with greater exposure to their institution or discipline had an easier time seeing themselves fitting in and finding a place for themselves on campus once they enrolled. Once students arrived, their trajectory of interaction tended to shape how they felt about their institution, with close ties forming for the Anchored, appreciation for general support among the Independents, and a mix of satisfaction and frustration for the Wanderers. By contrast, belonging within the discipline was more reliant on the individual participant's goals and interests. Disciplinary differences between the two contexts were identified but were limited generally linked to the career outcomes students associated with their chosen major rather than their experiences in the major. Finally, my work revealed that when students felt like they belonged in one area of their undergraduate life, those feelings could support lacking feelings in other areas, helping them to persist to graduation.

Ultrahigh-dimensional variable selection is of great importance in the statistical research. And independence screening is a powerful tool to select important variable when there are massive variables. Some commonly used independence screening procedures are based on single replicate data and are not applicable to longitudinal data. This motivates us to propose a new Sure Independence Screening (SIS) procedure to bring the dimension from ultra-high down to a relatively large scale which is similar to or smaller than the sample size. In chapter 2, we provide two types of SIS, and their iterative extensions (iterative SIS) to enhance the finite sample performance. An upper bound on the number of variables to be included is derived and assumptions are given under which sure screening is applicable. The proposed procedures are assessed by simulations and an application of them to a study on systemic lupus erythematosus illustrates the practical use of these procedures. After the variables screening process, we then explore the relationship among the variables. Graphical models are commonly used to explore the association network for a set of variables, which could be genes or other objects under study. However, graphical modes currently used are only designed for single replicate data, rather than longitudinal data. In chapter 3, we propose a penalized likelihood approach to identify the edges in a conditional independence graph for longitudinal data. We used pairwise coordinate descent combined with second order cone programming to optimize the penalized likelihood and estimate the parameters. Furthermore, we extended the nodewise regression method the for longitudinal data case. Simulation and real data analysis exhibit the competitive performance of the penalized likelihood method. / Doctor of Philosophy / Longitudinal data have received a considerable amount of attention in the fields of health science studies. The information from this type of data could be helpful with disease detection and control. Besides, a graph of factors related to the disease can also be built up to represent their relationships between each other. In this dissertation, we develop a framework to find out important factor(s) from thousands of factors in longitudinal data that is/are related to the disease. In addition, we develop a graphical method that can show the relationship among the important factors identified from the previous screening. In practice, combining these two methods together can identify important factors for a disease as well as the relationship among the factors, and thus provide us a deeper understanding about the disease.

Since the days of Booker T. Washington and W. E. B. Du Bois, the argument has flourished relative to the value of vocational education for Black youth. This study, using data from the "High School and Beyond 1980 Sophomore Cohort Third Follow-Up (1986)" survey, investigated three basic areas, namely: (a) the demographic, personological, and educational profile of Black youth enrolled in vocational education, and the manner in which this profile varied in relation to their vocational concentration patterns, (b) the profile of these youth in terms of their employment outcomes, educational expectations, and civic and political participation > practices after completion of their secondary schooling, according to their concentration patterns, and (c) the changes over time among these youth within their vocational concentration patterns, with regard to aptitude, educational and vocational expectations, and employment status. Major findings of this study have been presented for the students by concentration patterns. Some of the major overall findings were: Students with greater concentration in vocational education course work tended to come from urban areas, the southern region of the United States, and the lowest socioeconomic status quartile. Both educational and occupational expectations were unrealistic in terms of Standardized test performance and grades. A large percentage waS not in the labor force and a very small percentage was participating in civic or political activities. Findings for outcome and change over time variables were presented for the three vocational participation patterns, Concentrators, Limited Concentrators, and Samplers. / Ed. D.

Longitudinal data from 113 dual-career couples are used to explore the relationship between perceptions of marital equity and well-being and distress in marital, professional, and parental roles, how perceptions of equity change over time, and to examine efforts to restore equity. Differences in well-being and distress in roles are identified by gender and equity group. study results indicate that for both spouses, perceptions of inequity are associated with lower marital well-being and higher marital distress; however, under benefited wives reported higher professional well-being and under benefited husbands reported higher parental well-being. Couple perceptions of equity decreased between 1986 and 1990; under benefited husbands were more likely to use threats and bargaining to negotiate for relationship changes while wives sought counseling. Results demonstrate the importance of using multiple measures of well-being and distress and including gender and equity type in investigations of marital equity. / Ph. D.

A large body of research has examined if early psychopathology symptoms predict continued social difficulties into adolescence; however, few studies have examined whether early social competence predict which children will develop and maintain psychopathology symptoms across childhood and adolescence. Utilizing the National Institute of Child Health and Human Development Study of Early Child Care and Youth Development dataset, this study included a multi-method assessment of social competence in preschoolers and examined whether these social competency measures predicted internalizing and externalizing psychopathology symptom trajectories throughout childhood and adolescence. Additionally, it examined whether social competency measures predicted narrowband measures of attention-deficit/hyperactivity disorder, oppositional defiant disorder, depression, and psychopathy in 3rd - 9th grade. Exploratory factory analyses could not identify underlying factors among the social competency measures; as such, these were examined individually. Two to four classes were identified using Growth Mixture Modeling for parent- and teacher-reported internalizing and externalizing trajectories. Generally, children who had worse preschool social competence were more likely to be in the various moderate and high psychopathology symptom trajectory classes. Some measures of social competency were predictive of parent and teacher-reported ADHD and ODD and self-reported psychopathy, with differing relations for males and females; no measures were predictive of self-reported depression. This study has important implications with regard to early identification of and intervention for at-risk youth. Identifying these youth during the preschool years can result in improved developmental trajectories and significantly decreased societal costs. / M.S. / A large amount of research has looked to see if early atypical mental or behavioral symptoms (known as psychopathology symptoms) predict continued social difficulties into adolescence; however, only a few studies have looked at whether early social skills and performance (social competence) predict which children will develop and continue to show psychopathology symptoms across childhood and adolescence. Using the National Institute of Child Health and Human Development Study of Early Child Care and Youth Development dataset, this study included multiple ways to assess social competence in preschoolers and wanted to see if these measures predicted psychopathology symptoms over time as the child grows up. Additionally, it looked to see whether social competency measures predicted symptoms of attention-deficit/hyperactivity disorder, oppositional defiant disorder, depression, and psychopathy in 3rd - 9th grade. Generally, after running analyses on the data, children who had worse preschool social competence were more likely to have moderate and high psychopathology symptoms over time. Some measures of social competency were shown to be related to parent and teacher-reported ADHD and ODD and self-reported psychopathy, with different connections for males and females; no measures were connected to self-reported depression. This study has important possibilities when looking at early recognition of and treatment for at-risk youth. Finding these youth during the preschool years can lead to better paths over time.

Team cohesion represents arguably the most studied team construct as it has been consistently shown to be associated with improved performance. However, although cohesion is now understood to be an emergent state—as it develops over a team's life cycle—research has yet to uncover the dynamic nature of cohesion. The current study was designed to particularly test the impact of team personality composition both on the initial status of cohesion, and on changes in cohesion over time. 80 newly formed teams performed a highly interdependent team task, and team cohesion was measured over six time points. Personality was measured prior to the task and calculated at the team level, as both an average and a variability score. After performing longitudinal hierarchical linear modeling, results indicated that team personality impacts cohesion differently at initial status and over time. In particular, higher team agreeableness predicted greater slopes of cohesion, but not initial cohesion levels. Also, higher extraversion predicted greater initial status of cohesion, but not greater slopes. These results present important boundary conditions for understanding the role of team personality composition on team cohesion. / Master of Science

Parenting behaviors and a variety of behavioral problems in children covary. The current study first aimed to examine how and why parenting and child behavioral problems are linked in middle childhood. In particular, a longitudinal design (1364 children assessed from 54 months to 5th grade) was used to examine whether the developmental link between parenting and child behavioral problems were reciprocal. A twin design (131 pairs of monozygotic and 173 pairs of dizygotic twins assessed from 6 to 8 years of age on average) was used to examine the underlying genetic and nongenetic etiology of this link. In addition, using these two samples, the current study also aimed to examine whether parental attributes, including negative affect, executive function, and social cognitive factors, modulate the link between parenting and child behavioral problems. Results across these two studies suggested that parenting and child behavioral problems mutually influenced the development of each other over time, potentially through both evocative and passive gene-environment correlation processes and environmental transmissions. In addition, maternal dispositional anger modulated the effects of child behavioral problems on changes in maternal parenting quality over time. Finally, implications of the current study were also discussed. / Ph. D.

In recent decades, United States public school education has moved toward standards-based curricula. However, performance on standardized tests may not be representative of subject literacy or workforce preparedness. This misalignment may be particularly true in the sciences, where low science literacy and gender-related workforce shortfalls are evident. This study was an exploration of how well standardized test scores and other academic metrics reflected progression to a science major, by gender. This exploratory study used longitudinal data from the Virginia Department of Education, prepared by the Virginia Longitudinal Data System, for students who graduated from Virginia public schools from 2004-2016 (N=1,089,389). Students' standardized assessment scores, science course grades, demographics, and post-secondary major were analyzed using correlation analysis, logistic regression, principal component analysis, and hypothesis testing. Overall, 9% of high school completers enrolled in a post-secondary science major, with approximately half of those students attending 4-year schools. Seventy percent of science majors were female; females were most prevalent in health-related majors and least prevalent in physical sciences. Logistic regression identified the following factors significantly related to enrolling in a post-secondary science major: gender, high school science grades, and the high school's percent of students who majored in science. A student's status as economically disadvantaged or an underrepresented minority was significantly related to enrolling in a 2-year science major. In comparisons among academic metrics, standardized test scores and science grades were uncorrelated, and science grades differed significantly among demographic subgroups. Overall, demographic and school-level factors were more closely related to majoring in science than were academic factors. For both genders and for biological, physical, and health sciences, the percent of students majoring in science doubled from 2005-2015. Standardized test scores and course grades measured different aspects of learning, and higher science grades were related to majoring in science. However, the designation of "science major" is so broad as to be uninformative in a research context; more specificity would be needed to develop academic profiles. From these findings, one can conclude that demographic and cultural factors – rather than academic factors – were more closely related to whether students pursued a science pathway. / Doctor of Philosophy / In recent decades, United States public school education has moved toward standards-based curricula. However, performance on standardized tests may not represent subject knowledge or job preparedness, particularly in the science fields. This study was an exploration of how well standardized test scores and other academic measured were related to majoring in science, for male and female students. This exploratory study used data from the Virginia Department of Education, prepared by the Virginia Longitudinal Data System, for students who graduated from Virginia public schools from 2004-2016. Students' standardized test scores, science course grades, demographics, and college major were analyzed. Overall, 9% of high school completers enrolled in a science major after high school, with approximately half of those students attending 4-year schools. Seventy percent of science majors were female; females were most prevalent in health-related majors and least prevalent in physical sciences. The following factors were significantly related to enrolling in a science major: gender, high school science grades, and the high school's percent of students who majored in science. A student's status as economically disadvantaged or an underrepresented minority was significantly related to enrolling in a 2-year science major. In comparisons among academic measures, standardized test scores and science grades were not related to each other, and science grades differed among demographic groups. Overall, demographic and school-level factors were more closely related to majoring in science than were academic factors. For both genders and for biological, physical, and health sciences, the percent of students majoring in science doubled from 2005-2015. Standardized test scores and course grades measured different aspects of learning, and higher science grades were related to majoring in science. However, the designation of "science major" is so broad as to be uninformative in a research context; more specificity would be needed to develop academic profiles. From these findings, one can conclude that demographic and cultural factors – rather than academic factors – were more closely related to whether students pursued a science pathway.