Digital Commons Network^™

On The Inhibition Of Metal Transfer By Ion Implantation, Luke F. Autry

Doctoral Dissertations

Metal transfer is a phenomena associated with adhesive wear during dry-sliding, boundary lubrication, and elastohydrodynamic lubrication. Coatings, lubricants, and proper wear couple selection are traditionally implemented to reduce metal transfer. Ion implantation is a surface modification technique that has been studied for over 30 years with the goal of improving tribosurfaces. It has the following advantages over traditional techniques: it is a non-equilibrium process in that any element can literally be implanted into a surface, is non-evasive in that bulk material chemistry, structure, dimensionality is unaltered, and coating adhesion is not a factor. The goal of this study was to …

Hiv Care Utilization: A Theory-Based Approach To Retention In Care, Laramie Smith

Doctoral Dissertations

Maintaining HIV care attendance with some degree of regularity (i.e., retention in HIV care) is critical to attain optimal health outcomes for people living with HIV (PLWH) and HIV-affected communities. In the United States, approximately 50% of all PLWH who know their status are inadequately retained in HIV care once care has been initiated. Poor retention in HIV care is associated with deceased odds of viral suppression (resulting in increased risk of transmission to HIV-negative others), more rapid progression to an AIDS diagnosis, and increased odds of death. As such promoting patients’ retention in HIV care is a critical need …

Hydrologic Data Assimilation For Operational Streamflow Forecasting, Feyera Aga Hirpa

Doctoral Dissertations

Data assimilation (DA) is a method that optimally combines imperfect models and uncertain observations to correct model states using new information acquired from the incoming observations. In recent years, DA has been extensively used for improving the uncertainty of hydrologic prediction, largely due to the emergence of advanced remote sensing tools for observations of soil moisture, river discharge and precipitation. Several DA methods have been explored in hydrology; however the choice and the effectiveness of a specific DA method may vary depending on the model and the observation. The goal of this dissertation study was reducing streamflow forecast uncertainty, and …

Borel Complexity Of The Isomorphism Relation For O-Minimal Theories, Davender Singh Sahota '99

Doctoral Dissertations

In 1988, Mayer published a strong form of Vaught's Conjecture for o-minimal theories (1). She showed Vaught's Conjecture holds, and characterized the number of countable models of an o-minimal theory T if T has fewer than 2K ° countable models. Friedman and Stanley have shown in (2) that several elementary classes are Borel complete. This work addresses the class of countable models of an o-minimal theory T when T has 2N ° countable models, including conditions for when this class is Borel complete. The main result is as follows.

Theorem 1. Let T be an o-minimal theory in a countable …

Individual Differences On Multi-Scale Measures Of Executive Function, Jason Anastas

Doctoral Dissertations

Cognitive control is a central issue in developmental psychology. Traditional theories of psychology solve this problem by positing a top-down central executive, which coordinates cognitive resources in pursuit of goals. We propose an alternative explanation: cognitive control arises from physical interactions across many different timescales within the system. We examined whether measures of individual differences of these multi-scale interactions could predict individual differences in executive function development. Preschool-aged participants were asked to complete a series of executive function tasks while we tracked the motion of their dominant hand. We found that multi-scale interactions differed depending on experimental constraints. We also …

Handling Data With Three Types Of Missing Values, Jennifer Boyko

Doctoral Dissertations

Missing values present challenges in the analysis of data across many areas of research. Handling incomplete data incorrectly can lead to bias, over-confident intervals, and inaccurate inferences. One principled method of handling incomplete data is multiple imputation. This dissertation considers incomplete data in which values are missing for three qualitatively different reasons and applies a modified multiple imputation framework in the analysis of that data. The first major contribution of this dissertation is a derivation of the methodology for implementing multiple imputation in three stages. Also included is a discussion of extensions to estimating rates of missing information and ignorability …

Electronic And Mechanical Properties Of Nano-Heterostructures From First Principles, Satyesh K. Yadav

Doctoral Dissertations

Reducing the size of components to the nanoscale (e.g., in nano-heterostructures) gives rise to new possibilities. Nano-heterostructures are material systems involving at least two different materials with at least one of them having dimensions less than 100 nm. Such architectures have demonstrated great potential for diverse functionalities within a single nanostructure, which is nonexistent in the individual component materials. Nevertheless, it has been difficult to utilize their full potential due to a lack of understanding of the complex correlation between structure and properties. In this bifocal thesis, state-of-the-art first principles computations are employed to perform systematic studies of (1) the …

On The Integrated Squared Error Of The Linear Wavelet Density Estimator, Lu Lu

Doctoral Dissertations

Archival abstract submitted

Snake Graph Calculus And Cluster Algebras From Surfaces, Ilke Canakci

Doctoral Dissertations

Snake graphs appear naturally in the theory of cluster algebras. For cluster algebras from surfaces, each cluster variable is given by a formula which is parametrized by the perfect matchings of a snake graph. Furthermore it is known that the product of two cluster variables can be described geometrically in the surface using skein relations. In this thesis work, we identify each cluster variable with its snake graph, and interpret relations among the cluster variables in terms of these graphs. Taking a more general viewpoint, we introduce the notion of abstract snake graphs and develop a graphical calculus for abstract …

The Perception Of Movement Through Musical Sound: Towards A Dynamical Systems Theory Of Music Performance, Alexander P. Demos

Doctoral Dissertations

Performers’ ancillary body movements, which are generally thought to support sound-production, appear to be related to musical structure and musical expression. Uncovering systematic relationships has, however, been difficult. Researchers have used the framework of embodied gestures, adapted from language research, to categorize and analyze performer’s movements. I have taken a different approach, conceptualizing ancillary movements as continuous actions in space-time within a dynamical systems framework. The framework predicts that the movements of the performer will be complexly, but systematically, related to the musical movement and that listeners will be able to hear both the metaphorical motion implied by the musical …

A Mathematical Model And Numerical Method For Thermoelectric Dna Sequencing, Liwei Shi

Doctoral Dissertations

DNA sequencing is the process of determining the precise order of nucleotide bases, adenine, guanine, cytosine, and thymine within a DNA molecule. It includes any method or technology that is used to determine the order of the four bases in a strand of DNA. The advent of rapid DNA sequencing methods has greatly accelerated biological and medical research and discovery. Thermoelectric DNA sequencing is a novel method to sequence DNA by measuring the heat that is released when DNA polymerase inserts a deoxyribonucleoside triphosphate into a growing DNA strand. The thermoelectric device for this project is composed of four parts: …

The Measurement Of The Dielectric Constant Of Concrete Pipes And Clay Pipes, David Mcgraw

Doctoral Dissertations

To optimize the effectiveness of the rehabilitation of underground utilities, taking in consideration limitation of available resources, there is a need for a cost effective and efficient sensing systems capable of providing effective, in real time and in situ, measurement of infrastructural characteristics. To carry out accurate non-destructive condition assessment of buried and above ground infrastructure such as sewers, bridges, pavements and dams, an advanced ultra-wideband (UWB) based radar was developed at Trenchless Technology Centre (TTC) and Centre for Applied Physics Studies (CAPS) at Louisiana Tech University (LTU). One of the major issues in designing the FCC compliant UWB radar …

Position-Adaptive Localization Of An Electro-Magnetic Source Using Static And Mobile Wireless Sensor Networks, Miguel D. Gates

Doctoral Dissertations

We present new results in detection and localization of a hidden emitter using Wireless Sensor Networks (WSNs). While this type of problem has been explored extensively, this research combines multiple dynamics, such as mobility and adaptation, to extend the value beyond the typical search mission. Using Micro-Aerial Vehicles (MAVs), in conjunction with multiple static wireless sensor nodes, we create a hybrid sensor network capable of detection and localization of a hidden electro-magnetic (EM) emitter.

In order to localize the emitter, a Received Signal Strength Indicator (RSSI) is used as an approximation of distance from the transmitter to the revolving receivers. …

Exploration Of Aqueous Interfaces And Their Effect On Ion Behavior, Oneka T. Cummings

Doctoral Dissertations

An in-depth understanding of a wide range of physical, chemical, atmospheric and biological processes can only be achieved after the structure and dynamics of interfaces and the interfacial behavior of aqueous species, such as ions, are thoroughly studied and understood. This dissertation describes computational studies conducted to gain a more comprehensive understanding of such interfaces and the behavior of ions in the bulk and interfacial regions of the (1) air/water interface, and (2) alkane/water interfaces.

At the air/water interface the effect of counterion (sodium cations) charge and the influence of ion pairing on anion (chloride) propensity for the air/water interface …

The Effect Of Mentoring On Beginning Teacher Retention In Bossier Parish (Louisiana) School System, Frederick O. Ogunyemi

Doctoral Dissertations

This study examined the effect of mentoring on beginning teacher retention in the Bossier Parish Schools, a northwest Louisiana parish school system. The sample consisted of complete responses from 161 participants out of a population of 499 Pre-K through 12th grade teachers who had participated in the Louisiana Teacher Assistance and Assessment Program (LaTAAP) between August 1998 and May 2007. Participants completed a 28-item questionnaire that was posted on the internet via SurveyMonkey. The questionnaire was divided into three sections: (a) general information, (b) appraisal of mentoring and professional development activities, and (c) background information.

Statistical analyses were performed according …

Predicting Threat Potential Using Cyber Sensors, Mark Anthony Thompson

Doctoral Dissertations

The proliferation of the Internet has created a culture of a connected society dependent upon technology for communication and information sharing needs. In this dissertation, we hypothesize that attackers are increasingly using electronic resources that are capable of leaving a digital footprint, such as social media services, e-mail, text messages, blogs, and websites for the communication, planning, and coordination of attacks. In its current form, however, traffic analysis is primarily concerned with using communications volume to extract intelligence information, but largely ignores the content of communications transmissions that is needed to meet the security challenges and demands of continually emerging …

Generalized Finite-Difference Time-Domain Schemes For Solving Nonlinear Schrödinger Equations, Frederick Ira Moxley Iii

Doctoral Dissertations

The nonlinear Schrödinger equation (NLSE) is one of the most widely applicable equations in physical science, and characterizes nonlinear dispersive waves, optics, water waves, and the dynamics of molecules. The NLSE satisfies many mathematical conservation laws. Moreover, due to the nonlinearity, the NLSE often requires a numerical solution, which also satisfies the conservation laws. Some of the more popular numerical methods for solving the NLSE include the finite difference, finite element, and spectral methods such as the pseudospectral, split-step with Fourier transform, and integrating factor coupled with a Fourier transform. With regard to the finite difference and finite element methods, …

The Wave Boundary Layer Over The Open Ocean And The Implications To Air-Sea Interaction, Alejandro P. Cifuentes-Lorenzen

Doctoral Dissertations

Wave field and atmospheric observations during the Southern Ocean Gas Exchange experiment 2008 were used to explore air-sea boundary layer dynamics. The closure of a momentum budget at the air-sea interface allows the selection and tuning of a wave growth parameter consistent with the observed conditions. An energy balance between the atmospheric energy input and the observed wind-wave spectral energy is posed based on the turbulent kinetic energy budget. The energy input is defined as the rate of work done by the wave-induced stress over the wind velocity profile. Wave induced perturbations on the airflow are modeled by an exponential …

First Principles Study Of Band Offsets And Band Bending Of Inxga1-Xn/Gan And Zn1-Xbexo/Zno Heterostructures And Quantum Wells, Liang Dong

Doctoral Dissertations

In_xGa_1-xN (InGaN) and Zn_1-xBe_xO (ZnBeO) are compound semiconductor solid solutions that display a wide band gap tuning range and strong spontaneous and piezoelectric polarizations due to the wurtzite crystal structure. They have gained significant importance in electronic and optoelectronic devices where the active layers are often fabricated as InGaN/GaN and ZnBeO/ZnO multiple quantum well (MQW) structures to take the advantage of an enhanced quantum confinement. The performances of devices based on such polarizable MQWs are significantly affected by band offsets and band bending, two critical interlayer interfacial parameters closely related …

Mechanisms Of Nutrient Limitation And Nutrient Acquisition In Managed And Unmanaged Forest Ecosystems, Matthew A. Vadeboncoeur

Doctoral Dissertations

Understanding the interactions between global change, human and natural disturbances, and other factors on biogeochemical processes in forests is necessary to ensure the sustainability of forest management. Here I report the results of several investigations into nutrient acquisition processes in the forests of New Hampshire. I begin with a meta-analysis of fertilization studies showing that phosphorus (P) and calcium (Ca) as well as nitrogen (N) may limit primary production in deciduous forests of the region. Because these limiting nutrients are all removed from the ecosystem when trees are harvested, I compared nutrient budgets under a range of harvesting scenarios with …

Multi-State Memory And Logic Designs Using Multi-Quantum Channel Nano-Fets, Pawan Gogna

Doctoral Dissertations

In this dissertation, implementation of multi value logic using a novel algebra and Spatial Wavefunction Switched Field Effect Transistor (SWSFET) has been explored. The quantum mechanical simulations, characteristics of the fabricated SWS structures are discussed. The novel device and quaternary algebra has been used to implement multi-value logic. The designs of quaternary SRAM cells, basic logic gates and arithmetic cells are presented. In addition, mixed signal architectures using SWSFET are explored. Simulations for the memory, logic and mixed signal designs are presented. BSIM3 equivalent channel models were used for SWSFET. Cadence Spectre Simulator and Advanced Design Simulator were used as …

Replicated Stratified Sampling For Sensitivity Analysis, Milanthi K. Sarukkali

Doctoral Dissertations

Reliance on results from actuarial models for regulatory reporting as well as management decisions is increasing with complexity of financial products, economic volatility and the advancement of computing power. Sensitivity analysis is an important tool in modeling and is used to understand the impact of inputs and assumptions on the final result. However, we are constrained by computing time and resources, so the number of sensitivities that can be performed is limited.

Replicated Stratified Sampling (RSS) is a statistical technique that can be applied to efficiently run sensitivity tests on any actuarial model. We assume that model results with baseline …

Investigating The Academic Vocabulary Development Of Spanish-English Bilingual Students In Middle School, Eileen Mercedes Gonzalez

Doctoral Dissertations

This study examined the vocabulary development of Spanish-English bilingual adolescents (n= 98) from the end of 6^th through the end of 7^th grade in a dual language setting by looking at the patterns of growth in English and Spanish vocabulary post intervention and adding to the body of research on vocabulary development. Data were analyzed using descriptive statistics and Hierarchical Linear Modeling (HLM).

At the first level (TIME), the analysis helped to describe the shape of each person’s individual growth trajectory and to examine within person variability. The analysis at the second level (STUDENTS) considered inter-individual differences in …

Inorganic Carbon And Nitrogen Utilization In Mixotrophic Ciliates, Donald M. Schoener

Doctoral Dissertations

Mixotrophy is a common nutritional strategy that uses both heterotrophy and photosynthesis. Kleptoplastidic mixotrophs do not make their own plastids but acquire them from their algal prey. Before we can add mixotrophs to standard ecological models we need to understand how much each nutritional mode contributes to mixotrophic growth, and how this balance may be influenced by plastid acquisition, retention, and turnover.

In order to examine the role of captured chloroplasts in the metabolism of the oligotrich ciliate Strombidium rassoulzadegani. I evaluated the uptake and retention of chloroplasts, the ability of two different algae to supply functional chloroplasts, and …

How School Counselors From Recognized American School Counselor Association Model Programs (Ramp) Implement Equitable College And Career Readiness: A Delphi Study, Jennifer L. Parzych Dr.

Doctoral Dissertations

The goal of this research is to understand the relationship between a fully implemented American School Counselor Association (ASCA) National Model school counseling program on student career readiness and college attainment. The Delphi technique was employed to gain consensus from a group of experts on indicators of students’ college and career readiness, as well as counseling components necessary for promoting equitable college and career readiness. Eleven school counselors from districts with Recognized ASCA Model Programs (RAMP) at every level (K – 12) agreed to fully participate as experts in this study. Expert participants identified 60 indicators of student college and …

Puerto Rican Students' Perspectives Of Socio-Cultural Characteristics Of Giftedness And Talent Development, Miriam Morales Taylor

Doctoral Dissertations

Puerto Rican Students’ Perspectives of Socio-cultural Characteristics of

Giftedness and Talent Development

Miriam Morales Taylor

University of Connecticut, 2013

This qualitative study was conducted to investigate the social and cultural characteristics of gifted and talented students and their perceptions of the educational factors that have contributed to the development of their gifts and talents. Twelve Puerto Rican English Language Learner (PR-ELL) students who are identified as gifted and attend a full-time academy for gifted and talented students were selected for the study. Both ethnography and comparative case methodology were used as the participants completed a questionnaire with 67 questions and …

Siegel Functions, Modular Curves, And Serre's Uniformity Problem, Harris B. Daniels

Doctoral Dissertations

Serre’s uniformity problem asks whether there exists a bound k such that for any p > k, the Galois representation associated to the p-torsion of an elliptic curve E/Q is surjective independent of the choice of E. Serre showed that if this representation is not surjective, then it has to be contained in either a Borel subgroup, the normalizer of a split Cartan subgroup, the normalizer of a non-split Cartan subgroup, or one of a finite list of “exceptional” subgroups. We will focus on the case when the image is contained in the normalizer of a split Cartan subgroup. In particular, …

Homogeneous Representations Of Khovanov-Lauda-Rouquier Algebras, Gabriel Feinberg

Doctoral Dissertations

The Khovonov-Lauda-Rouquier (KLR) algebra arose out of attempts to categorify quantum groups. Kleshchev and Ram proved a result reducing the representation theory of these algebras to the study of irreducible cuspidal representations. In finite types, these cuspidal representations are part of a larger class of homogeneous representations, which are related to fully commutative elements of Coxeter groups.

For KLR algebras of types A_n and D_n, we classify and enumerate these homogeneous representations.

Multilevel Impacts On Mathematical Learning Using Differentiated Curricula, Jennifer Foreman

Doctoral Dissertations

The research literatures on mathematics education and gifted and talented education share many common conclusions about effective practices for strengthening students’ cognitive engagement and deep conceptual understandings. Enrichment learning and differentiated instruction comprise two broad approaches long advocated by proponents of gifted education. Enrichment learning shares many conceptual parallels with process standards advocated in mathematics education. Yet the effectiveness of applying curricular and pedagogical principles initially developed for gifted education/talent development programs to heterogeneous elementary school mathematics classrooms has received little research attention. Therefore, it is difficult to determine if these principles should be disseminated and implemented more frequently in …

Statistical Methods And Computing For Semiparametric Accelerated Failure Time Model With Induced Smoothing, Sy Han Chiou

Doctoral Dissertations

In survival analysis, semiparametric accelerated failure time (AFT) models directly relate the predicted failure times to covariates and are a useful alternative to relative risk models. Recent developments in rank-based estimation and least squares estimation provide promising tools to make the AFT models more attractive in practice. In this dissertation, we propose fast and accurate inferences for AFT models with applications under various sampling schemes.

The challenge in computing the rank-based estimator comes from solving nonsmooth estimating equations. This difficulty can be overcome with an induced smoothing approach. We generalize the induced smoothing approach to incorporate weights with missing data …