Dissertations, Academic -- Florida Atlantic University

The current studies tested the hypothesis, that early exposure is sufficient for
nativelike proficiency. Study 1 compared the English skill of 116 5 year olds who had
been exposed to English and Spanish from birth with English monolingual and found that
the bilingual children had significantly lower levels of vocabulary skill. Study 2 assessed
65 adult bilinguals, comparing them to 25 English and 25 Spanish monolinguals on a
battery of language measures. The bilinguals had lower scores in Spanish in 7 of the 8
domains of language skill measured. The bilinguals were not different from the English
monolingual speakers in most, but not all, aspects of language proficiency. These
findings provide evidence that the monolingual-bilingual gap observed in childhood is no
longer evident among adult bilinguals, but that despite early exposure and continued use
into adulthood, second generation immigrants are not native-like in their heritage
language skills.

With the issuance of the Notice of Proposed Rule Making (NPRM) for Vehicle
to Vehicle (V2V) communications by the United States National Highway Tra c
Safety Administration (NHTSA), the goal of the widespread deployment of vehicular
networking has taken a signi cant step towards becoming a reality. In order for
consumers to accept the technology, it is expected that reasonable mechanisms will
be in place to protect their privacy. Cooperative Caching has been proposed as an
approach that can be used to improve privacy by distributing data items throughout
the mobile network as they are requested. With this approach, vehicles rst attempt
to retrieve data items from the mobile network, alleviating the need to send all requests
to a centralized location that may be vulnerable to an attack. However, with
this approach, a requesting vehicle may expose itself to many unknown vehicles as
part of the cache discovery process.
In this work we present a Public Key Infrastructure (PKI) based Cooperative
Caching system that utilizes a genetic algorithm to selectively choose members of the
mobile network to query for data items with a focus on improving overall privacy. The
privacy improvement is achieved by avoiding those members that present a greater risk of exposing information related to the request and choosing members that have a
greater potential of having the needed data item. An Agent Based Model is utilized
to baseline the privacy concerns when using a broadcast based approach to cache
discovery. In addition, an epidemiology inspired mathematical model is presented to
illustrate the impact of reducing the number of vehicles queried during cache discovery.
Periodic reports from neighboring vehicles are used by the genetic algorithm to
identify which neighbors should be queried during cache discovery. In order for the
system to be realistic, vehicles must trust the information in these reports. A PKI
based approach used to evaluate the trustworthiness of each vehicle in the system is
also detailed. We have conducted an in-depth performance study of our system that
demonstrates a signi cant reduction in the overall risk of exposure when compared
to broadcasting the request to all neighbors.

In this research, a new reputation-based model is utilized to disincentivize collusion
of defenders and attackers in Software Defined Networks (SDN), and also, to disincentivize
dishonest mining strategies in Blockchain. In the context of SDN, the model uses the
reputation values assigned to each entity to disincentivize collusion with an attacker. Our
analysis shows that not-colluding actions become Nash Equilibrium using the reputationbased
model within a repeated game setting. In the context of Blockchain and mining,
we illustrate that by using the same socio-rational model, miners not only are incentivized
to conduct honest mining but also disincentivized to commit to any malicious activities
against other mining pools. We therefore show that honest mining strategies become Nash
Equilibrium in our setting.
This thesis is laid out in the following manner. In chapter 2 an introduction to
game theory is provided followed by a survey of previous works in game theoretic network
security, in chapter 3 a new reputation-based model is introduced to be used within the
context of a Software Defined Network (SDN), in chapter 4 a reputation-based solution
concept is introduced to force cooperation by each mining entity in Blockchain, and finally,
in chapter 5, the concluding remarks and future works are presented.

The purpose of this qualitative study was to explore the lived experience of
suffering through the 2010 earthquake in Haiti. The experiences of 13 individuals who
lived suffering through the 2010 earthquake in Haiti were elicited. Heideggerian
hermeneutical phenomenology served as both the guiding philosophy and methodology
for this research study, while Eriksson’s (1981) theory of caritative caring provided the
caring science lens. Diekelmann, Allen, and Tanner’s (1989) seven-stage method of
hermeneutical analysis provided the structure for data analysis. The relational themes that
were interpreted were: Experiencing the Unimaginable, Awakening to a Changed Reality,
Agonizing for Others, Compounding Losses, Finding a Way Forward, and Being
Transformed. These six relational themes are illuminated and aesthetically re-presented
in six watercolor paintings. The constitutive pattern Suffering With and For Others
expressed the meaning of suffering for participants through the 2010 earthquake in Haiti
as a lived experience.

This research study employed both quantitative and qualitative
methodology to explore high school students’ perceptions about online math
homework and paper math homework. The purpose of this study was threefold:
to understand how high school students perceive online math homework, to
determine what aspects of online math homework aid and/or hinder student
learning, and to improve the student learning experience with online math
homework. Through quantitative analysis, the researcher noted that although not
all students learned best with online math homework, nearly every student used
the online tools provided when assigned online math homework. Through
qualitative analysis, the researcher noted that the most commonly mentioned aid
for both online math homework and paper math homework was showing your work. The two most commonly mentioned hindrances to learning were guessing
or cheating with online math homework and losing your homework with paper
math homework. Participants stated that they actually have more opportunities to
cheat with online math homework than with paper math homework; these results
diverge from the literature, which states that online math homework helps to
eliminate cheating. The data suggests that while online resources, such as
examples, were a commonly mentioned aid to online math homework, many
students indicated that the online resources also prevented them from truly
having to think, as they could just follow the online examples step by step.
This research study determined that the majority of students did not have
a strong inherent like or dislike toward either online or paper math homework.
Instead, students often stated that they preferred whichever medium allowed
them to earn higher grades or receive more support. Therefore, if students
continue to receive the necessary support, they can continue to learn
mathematical concepts through the use of both online and paper math
homework.

Gopherus polyphemus populations are diminishing throughout their range due
to urbanization, fragmentation, and poor management of habitats. Increased
population densities, poor habitat quality, and lack of fire may influence disease
transmission. Parasite roles within wild tortoise populations are largely unknown,
despite evidence these pathogens may pose health risks. This study provides a
baseline of gopher tortoise endoparasites across South Florida and reports on how
varying environmental and tortoise characteristics may affect endoparasite species
prevalence, approximate loads, and overall distributions. Tortoise fecal samples were
taken from five differing SF habitats. Seven species of intestinal parasites were
discovered from 123 tortoises. Identified parasites include endo-helminths such as
cyathostomes, pinworms, ascarids, flukes, and protozoans including Eimeria,
Cryptosporidium, and Amoeba species. Significant differences in parasite prevalence and loads were seen between sampling years, seasons, size classes, and sites,
however, overall parasite distributions suggest parasitism remains relatively
ubiquitous throughout most host and site characteristics.

As part of the education reforms of the 1990s, charter schools were proposed as a
private alternative to public education, offering parents and their children greater choices.
Publicly financed but privately operated, charter schools have now grown in numbers and
influence. While there are many studies of student outcomes in charter schools
demonstrating mixed results, one negative outcome of charter schools has been less
examined. Since inception, 23% of charter schools nationally have closed and these
closures are disruptive to parents, children, and their school districts. This paper
addresses charter school closures from an organizational perspective. Applying theory
from population ecology and resource dependency theory, the population of nonprofit
charter schools is examined. What are the primary determinants of charter school success
and failure?
Florida, with the third highest number of charter schools nationally and, at the
same time, the highest number of charter school closures in the United States, is a paradox. This study identifies the significant variables that are related to school survival
and failure in the state of Florida over the years 2015-16 through 2015-16.
Variables tested in this study, using Survival Analysis (SA), include age,
management structure, size, school performance, grants, and density. All variables except
density at founding were significant in explaining the unique variance in survival rates
among charters. Charter schools sub-contracted by for-profit educational management
organizations (EMOs) were larger, achieved higher grades, secured more grants and
achieved higher survival rates than their counterpart nonprofit, independent, and charter
management organization (CMO) led schools. These results contribute to our
understanding of charter school survival and failure, thereby informing public policy
options to strengthen the charter school population and the nation’s public education
system overall.

The first essay introduces a portfolio theory motivated approach to measuring
mutual fund family-level diversification and hedging strategies. Diversification of
idiosyncratic risk (systematic risk) is measured by the average cross-fund correlation in
idiosyncratic returns (predicted returns from the multifactor model). Using new
methodology, I find evidence of cross-sectional variation in family-level diversification
and examine several fund families’ characteristics as the determinants of this crosssectional
variation. On average, fund families that offer more objectives are more
diversified in terms of both idiosyncratic and systematic risks; however, in the subsample
of larger fund families, greater number of objectives is associated with increase
(decrease) in idiosyncratic (systematic) risk diversification. Families that concentrate in
the retail sector are more diversified. I also find that less diversification of idiosyncratic
risk on the family level is associated with better risk-adjusted performance, while greater diversification of systematic risk is associated with greater performance during an
economic downturn.
The second essay examines whether new measures of diversification are
additional determinants of fund family flows and flow volatility. I find that fund family
capital flows increase in systematic risk focus, as more of the fund family’s assets are
held by institutional investors. Family flow volatility decreases in diversification of
systematic risk during market downturn, increase in market uncertainty and during
recession. I further find that families with greater concentration in the retail sector
(institutional sector) exhibit less family capital flow volatility as the diversification of
systematic risk (idiosyncratic risk) increases. Fund-level volatility of focused and
concentrated funds within diversified families is greater than in less diversified families,
signaling that diversification on the family level may decrease participation costs for the
investors. Moreover, in support of participation cost hypothesis, I find that the
performance of worst performing funds within fund families increases in the family-level
diversification; thus, family-level diversification affects the convexity in the fund flowperformance
relation documented in the previous studies. On the family-level,
diversification is associated with convexity in flow-performance relation, while family
focus with more direct flow-performance relation.

Gravitational N-body problems are central in classical mathematical physics.
Studying their long time behavior raises subtle questions about the interplay between
regular and irregular motions and the boundary between integrable and chaotic dynamics.
Over the last hundred years, concepts from the qualitative theory of dynamical
systems such as stable/unstable manifolds, homoclinic and heteroclinic tangles,
KAM theory, and whiskered invariant tori, have come to play an increasingly important
role in the discussion. In the last fty years the study of numerical methods for
computing invariant objects has matured into a thriving sub-discipline. This growth
is driven at least in part by the needs of the world's space programs.
Recent work on validated numerical methods has begun to unify the computational
and analytical perspectives, enriching both aspects of the subject. Many
of these results use computer assisted proofs, a tool which has become increasingly
popular in recent years. This thesis presents a proof that the circular restricted four
body problem is non-integrable. The proof of this result is obtained as an application
of more general rigorous numerical methods in nonlinear analysis.

Contemporary educational trends have created a false dichotomy between the arts
and science. The will to make STEM subjects the focus of K-12 education, ignores both a
shared history and the potential for greater learning in a shared future.The intention of
Points of Intersection is to demonstrate that design, science and math intersect in their
concepts, practices and history. In the past, these disciplines were explored and studied
together and benefited from each other. By exploring what design and science have in
common and the points where they intersect, we can see the relevance and importance of
art and design in k-12 education and change STEM to STEAM. The exhibition will
explore point, line, plane and the “Golden Ratio” demonstrating how these concepts can
be understood from the perspectives of physics, math, art and design on a basic level.
These basic principles can be used to introduce these fields of study and bring a better understanding of them to students in K-12. Future designers and scientists with this
educational underpinning will have a better mutual understanding of one another’s field
and the potential for shared research, process and results.