Digital Commons Network^™

Variable Selection For Cox Proportional Hazards Models Via Subtle Uprooting, Chalani S. Wijayasinghe

Open Access Theses & Dissertations

Cox proportional hazards model (Cox PH model) is heavily used in survival analysis to assess the importance of various covariates on the survival times of individuals or objects through the hazard function. This study suggests a new variables selection method for Cox PH models, under the title 'Subtle uprooting', that does variable selection and model estimation for Cox proportional hazards (PH) models simultaneously.

There are subset selection methods and shrinkage selection methods suggested in the context of Cox PH model. However the subset selection methods become infeasible in higher dimensions and the available shrinkage methods need tuning of parameters making …

Perspectives On The Nature Of Science From A Group Of Students Attending Predominantly Hispanic West Texas High School, Cameron King Wilson

Open Access Theses & Dissertations

The United States is falling far behind the rest of the world in its ability to fulfill its needs for qualified workers in Science, Technology, Engineering, and Mathematics (STEM) fields. The Hispanic population is now the largest minority in the United States but is proportionally underrepresented in the STEM fields today. It is shown that students who have a good understanding of the Nature of Science (NOS) are far more likely to be interested in science which may lead to an interest in careers in STEM fields. There is very little if any research identifying Hispanic high school students' view …

The Effects Of Cognates On Receptive And Expressive Language Among Typically Developing Preschool Second Language-Learners, Jesica B. Zavala De Guerrero

Open Access Theses & Dissertations

This exploratory study considers the facilitating effects of cognates across language of intervention, seeking to assess potential cross-language generalizations among typically developing preschool bilinguals. Nine bilingual, English-Spanish speakers of preschool age were assigned to one of three experimental groups (an English only group, a Spanish only group, and a bilingual group) or to a control condition. Children in the experimental groups were introduced to a vocabulary intervention that incorporated cognates and non-cognates. Analysis of data suggests the absence of a cognate advantage among preschool age children; furthermore limiting any possible cross-language generalizations. It is plausible to suspect that age may …

Enhanced Finite Element Modeling Of The Thermo-Mechanical Responses Of Jointed Pcc Pavements Under Environmental And Traffic Loads, Mohammad Ali Zokaei Ashtiani

Open Access Theses & Dissertations

Jointed plain concrete pavements (JPCP) are the most commonly used type of rigid pavement systems and the accurate modeling of their thermo-mechanical responses is of primary importance in a mechanistic-empirical pavement design procedure. In JPCP, the temperature gradient and resulting slab shape play a crucial role in the magnitude of stresses and deflections caused by the superimposed traffic loads. Temperature gradients through the slab depth can produce thermal curling in slabs and can also produce slab expansion and contraction, which leads to the generation of frictional tractions between slabs and foundation. The prediction of these frictional tractions is complicated by …

Determination Of In Situ Dissolved Inorganic Carbon Concentration And Alkalinity For Marine Sedimentary Porewater, Justine Sauvage, Arthur J. Spivack, Richard W. Murray, Steven D'Hondt

Graduate School of Oceanography Faculty Publications

Dissolved inorganic carbon (DIC) concentration and total alkalinity in marine sediment vary with biological activity, mineral diagenesis and past bottom ocean water composition. Reliable interpretation of this data is often compromised due to precipitation of calcium carbonate (CaCO₃) during sediment recovery, processing and sample storage.

Here we present and test a method that corrects for this precipitation and consequently allows quantification of in situ carbonate system chemistry. Our method relies on the over-determination of the dissolved carbonate system by (i) measuring DIC, alkalinity and calcium, and (ii) explicitly assuming CaCO₃ saturation in the sediment. We experimentally tested …

Essays On The Digital Divide, Belal Abdelfattah

Open Access Theses & Dissertations

The digital divide is a phenomenon that is globally persistent, despite rapidly decreasing costs in technology. While much of the variance in the adoption and use of information communication technology (ICT) that defines the digital divide can be explained by socioeconomic and demographic variables, there is still significant unaccounted variance that needs to be explained if the world's population is expected to be brought more fully into the digital age. The present research addresses this need with three cross-country studies. Study 1 primarily investigates the time individuals spend with traditional media sources as a likely explanation for their frequency of …

On Moral Supervenience, Ramon Alvarado

Open Access Theses & Dissertations

Conventional accounts of moral supervenience are not fit for the moral realist to use against skeptic objections. In particular, they do not provide a sufficiently robust account of dependence or determination needed to counter the argument from queerness.This is shown in their inadequacy to deal with cases of minimal discernibility and cases of moral gradation. A similarity-base account of supervenient seems to be the one that the moral realist ought to incorporate instead.

Smart Grids: A Paradigm Shift On Energy Generation And Distribution With The Emergence Of A New Energy Management Business Model, Jesus Alvaro Cardenas

Open Access Theses & Dissertations

An energy and environmental crisis will emerge throughout the world if we continue with our current practices of generation and distribution of electricity. A possible solution to this problem is based on the Smart grid concept, which is heavily influenced by Information and Communication Technology (ICT). Although the electricity industry is mostly regulated, there are global models used as roadmaps for Smart Grids' implementation focusing on technologies and the basic generation-distribution-transmission model. This project aims to further enhance a business model for a future global deployment. It takes into consideration the many factors interacting in this energy provision process, based …

A Circuit-Based Algorithm For Two-Phase Flow At The Pore Scale In Porous Media, Todd Dorethy

Open Access Theses & Dissertations

Models of two-phase flow in porous media are of practical interest in many fields of science and engineering such as in oil recovery and hydrology. For this class of problem, an immiscible fluid is injected into a single-phase, porous medium to evict its valuable, native fluid. Because the aim is to amass as much of the indigenous fluid as possible, models attempt to output reliable flow regime patterns depicting how well the invading fluid displaces the native fluid.

Flow regime patterns generally depend upon the geometry of the domain, stimulation at the boundaries, and properties of the invading and native …

A Robust Algorithm For Estimating The Balance Of Autonomic Nervous System With Application To Mental Fatigue Detection Using Photoplethysmographic (Ppg) Signals, Ajay Kumar Verma

Open Access Theses & Dissertations

Spectral- and time-domain analysis of Heart Rate Variability (HRV) signal is widely used as a quantitative marker of the Autonomic Nervous System (ANS) activity. A robust algorithm was developed to derive HRV from photoplethysmographic (PPG) signals, to compute FFT- and AR-based spectra of these HRV signals, and to determine time- and frequency-domain features. This algorithm has detrending, sample-rate reductions, false-peak removal, automatic peak detection, peak-to-peak (P-P) interval detection and correction, time-domain feature extraction, HRV signal generation, and spectral-domain feature extraction from the HRV signal. Adapting to the very low spectral contents of the input PPG signal is very helpful in …

Contested Narratives: Theoretical Foundations For A Predictive Model Of Policy Content, Raul Antonio Medellin

Open Access Theses & Dissertations

This work introduces a model to analyze policy making as an iterative narrative contestation process from which policy content can be forecasted. A theoretical foundation for the validity of introducing the Contested Narratives Forecast Model (CNF) as a new theoretical model for policy analysis is established using Lakatos' Methodology of Scientific Research Programs (MSRP). Next, an argument is made that the theoretical frameworks on which the CNF is based are not only ontologically compatible, but they also complement each other to neutralize some of their greatest weaknesses. Finally, the CNF is described using Lakatos' concepts of a negative heuristic, a …

Alkali Promoted Molybdenum (Iv) Sulfide Based Catalysts, Development And Characterization For Alcohol Synthesis From Carbon Monoxide And Hydrogen, Belinda Delilah Molina

Open Access Theses & Dissertations

For more than a century transition metal sulfides (TMS) have been the anchor of hydro-processing fuels and upgrading bitumen and coal in refineries worldwide. As oil supplies dwindle and environmental laws become more stringent, there is a greater need for cleaner alternative fuels and/or synthetic fuels. The depletion of oil reserves and a rapidly increasing energy demand worldwide, together with the interest to reduce dependence on foreign oil makes alcohol production for fuels and chemicals via the Fischer Tropsch synthesis (FTS) very attractive. The original Fischer-Tropsch (FT) reaction is the heart of all gas-to-liquid technologies; it creates higher alcohols and …

Design And Synthesis Of Porous Organic Frameworks For H2 And Ch4 Storage And For Selective Co2 Adsorption, Venkata Neti

Open Access Theses & Dissertations

Three new boronate-ester based covalent organic frameworks (CoPc-PorDBA, CoPc-BPDA and HHTP-PorDBA), an imine-linked porphyrin porous polymer (CuPor-BPDC) and imine and benzothiazole based porous polymers (IBTP), and a triazole based phthalocyanine "click" polymer (Pc-POP) were synthesized. The CoPc-PorDBA and CoPc-BPDA COFs exhibited high BET surface areas (1087, 1315 m2 g-1, respectively) whereas HHTP-PorDBA showed a low BET surface area of 205 m2 g-1. The H2 storage capacities of CoPc-BPDA and CoPc-PorDBA range between 0.8-1.2wt% at 77K, 1bar and the CH4 storage capacities range between 0.4-0.8wt% at 298K, 1bar. These materials also had good thermal stabilities up to 350° C. The BET …

A Study Of Ti-Doped Wo3 Thin Films Using Comparative Theoretical And Experimental Approach, Aurelio Paez

Open Access Theses & Dissertations

Metal oxides like Tungsten Oxide (WO3) are well documented and characterized in the literature, with uses in darkening windows and mirrors, flat computer displays, solar panel cooling, and sensors (of interest in this study). Ti doping of WO3 is less documented and the focus of this study. Sample thin films of pure WO3 and varyingly Ti doped WO3 were prepared using Radio Frequency magnetron sputtering (RF) (13.56 MHz) to grow thin films on a silicon substrate. This study aims to compare multiple Ti doping percentages in WO3 theoretically and then compare with experimental data taken from thin films of various …

El Paso Parking Meter Demand, Edward Pallarez

Open Access Theses & Dissertations

This manuscript analyzes the demand for parking meter purchases in El Paso, TX. A demand function is estimated using four independent variables.

Multi-Dimensional Emotion Recognition From Geometry And Color Information, Geovany A. Ramirez

Open Access Theses & Dissertations

Emotions play a fundamental role in everyday interactions among humans. Humans are adept at expressing themselves and interpreting others through a multi-modal, subtle and complex process using non-verbal cues including speech prosody, facial expression, eye gaze, body gestures, head motion, posture, and skin color changes. However, recognizing the affective state of humans is a difficult task for computers.

Automatic emotion recognition has focused on analysis of the six discrete basic emotions: happiness, sadness, surprise, fear, anger and disgust. However, humans express more complex and subtle affective states such as confusion, shame, pleasure, anxiety or depression. Therefore, a different representation based …

Exploring The Hydrogeologic Controls On Brackish Water And Its Suitability For Use In Hydraulic Fracturing: The Dockum Aquifer, Midland Basin Texas, Francisco Ruben Reyes

Open Access Theses & Dissertations

Water scarcity in arid regions can limit or impede certain hydrocarbon production activities, such as hydraulic fracturing and well drilling. The Midland Basin, a major oil-producing area in semi-arid far west Texas and the eastern sub-basin of the Permian Basin, is already impacted by limited freshwater availability. A typical tight oil well in the Midland Basin requires ~3.8-11.4 x 103 m3 of water per fracture treatment (Nicot et al., 2012). Despite draught conditions and limited resources, data for 2011 indicate freshwater comprises ~70% of the water used in hydraulic fracturing in the Midland basin. Thus, the Midland Basin represents an …

Synthesis And Characterization Of Fluorophores For The Detection Of Lanthanides And Actinides, Robinson I. Roacho

Open Access Theses & Dissertations

A series of fluorophores based in the boron dipyrromethene (BODIPY) family were synthesized and characterized. These fluorophores have the capacity of being introduced to a carbamoyl methyl phosphine oxide (CMPO) lanthanide/actinide extractant. These blue, green and red emission fluorophores show high thermal/moisture stability and high fluorescence efficiencies. The fluorescence intensity seems to be dependent on the restricted rotation about the C(8)-C bond in 8-Ph-BODIPY. By taking advantage of this feature, a hydroxyl- containing BODIPY with high fluorescence intensity was synthesized to be incorporated to a CMPO carboxylic acid via esterification. Unfortunately, we did not observe an optical response upon the …

Platform-Independent Data Locality Analysis To Predict Cache Performance On Abstract Hardware Platforms, Sonish Shrestha

Open Access Theses & Dissertations

This research is part of a co-design project that has the goal of designing hardware systems to match application requirements and efficiently mapping applications to hardware. This thesis is focused on optimizing the platform cache memory hierarchy configuration. To determine application requirements, we characterize the application using platform- independent locality metrics. Next we use locality data and an analytical model to predict cache an application performance of sequential versions of application codes for various cache configurations. After using an analytical model to select a candidate set of cache memory hierarchy configurations, we used architectural simulation to test the selection for …

Evaluation Of Ozone Trends In Southern Doña Ana County, New Mexico Thru Wind Rose Analysis And Use Of Noaa Hysplit Model, Maria Aurelia Sisneros

Open Access Theses & Dissertations

The objective of this study was to determine whether increasing ozone concentrations in 2012 and 2013 at the Santa Teresa air quality monitor in Doña Ana County, New Mexico were due to a local point source impacting this monitor only or part of a regional phenomenon that affects all the monitors within the Paso del Norte Region. In addition, the study focused on identifying local and regional/long-range source areas contributing transport ozone to the study area (southern Doña Ana County).

The study showed that increasing ozone levels were not unique to the Santa Teresa monitor due to the fact that …

Transatlantic Maritime Transportation Between The Czech Republic And The United States, Petr Toman

Open Access Theses & Dissertations

Maritime transportation is the backbone of today´s world trade and therefore there special attention should be paid to all subjects concerning this mode of transportation. It is also necessary to complement maritime transportation by other modes, such as rail and/or truck (road). This thesis deals with the problems of maritime transportation and provides the summary of recent developments, trends and statistics mainly on Transatlantic maritime routes (Europe to U.S.). Besides maritime transportation, this thesis also reviews the trends and statistics of rail and truck (road) transportation in U.S. and Europe.

The second part of thesis seeks to create a mathematical …

The Nature And Influence Of Relationship On Success In A Virtual Work Environment, Carol Locher Ransone

Antioch University Dissertations & Theses

The evolution of technology in the 21st century has led to a greater understanding of the benefits and the challenges of expanding work relationships across geographical boundaries. This expansion has contributed to the development of a global society with over three million employee teleworkers (Global Workplace Analytics and the Telework Research Network, 2013). In spite of the advances in connecting across the globe technologically, the importance of successfully working together in a virtual work environment is grounded in relationships that foster individual growth and group cohesion. The human elements of connectivity are primary to the success of organizations as well …

Integrating Two-Photon Microscopy And Cryo-Electron Microscopy For Studying The Interaction Of Caféteria Roenbergensis And Crov, Seyedmohammadali Aghvami

Open Access Theses & Dissertations

Cafeteria roenbergensis (Cro) is a marine zooplankton; its voracious appetite plays a significant role in regulating bacteria populations. The giant virus that lives within Cro, known as Cafeteria roenbergensis virus (CroV), has an important effect on the mortality of Cro populations. Although viral infections are extremely abundant in oceans, the complete procedure of the infection is still unknown. We study the infection process of Cro by CroV to find out whether the initial contact is through phagocytosis or CroV penetrating the host cell membrane directly. Cro is a moving at speed in the range of 10-100 um/s, therefore, there are …

Growth And Analysis Of Micro And Nano Cdte Arrays For Solar Cell Applications, Brandon Adrian Aguirre

Open Access Theses & Dissertations

CdTe is an excellent material for infrared detectors and photovoltaic applications. The efficiency of CdTe/CdS solar cells has increased very rapidly in the last 3 years to ~20% but is still below the maximum theoretical value of 30%. Although the short-circuit current density is close to its maximum of 30 mA/cm2, the open circuit voltage has potential to be increased further to over 1 Volt. The main limitation that prevents further increase in the open-circuit voltage and therefore efficiency is the high defect density in the CdTe absorber layer. Reducing the defect density will increase the open-circuit voltage above 1 …

A New Bivariate Distribution With Applications, Sathya Amarasekara

Open Access Theses & Dissertations

We construct a bivariate distribution of (X, Y ) by assuming that the conditional distribution of Y given X is a two-parameter Gamma (s, ν(x)), where the scale parameter depends on X. If X is assumed to be any distribution, then clearly the joint distribution is well defined in all cases. We will study this new distribution by developing all possible properties, moments, shapes and estimation of parameters with a view towards applications of the distribution to data from many random number generation methods.

Electronic Structure And Charge Transfer Excited States Of Endohedral Fullerene Containing Electron Donor-Acceptor Complexes Utilized In Organic Photovoltaics, Fatemeh Amerikheirabadi

Open Access Theses & Dissertations

Organic Donor &ndash Acceptor complexes form the main component of the organic photovoltaic devices (OPVs). The open circuit voltage of OPVs is directly related to the charge transfer excited state energies of these complexes. Currently a large number of different molecular complexes are being tested for their efficiency in photovoltaic devices. In this work, density functional theory as implemented in the NRLMOL code is used to investigate the electronic structure and related properties of these donor &ndash acceptor complexes. The charge transfer excitation energies are calculated using the perturbative delta self &ndash consistent field method recently developed in our group …

Long-Term Deformation In The Southern Rí­O Grande Rift As Inferred From Topographic And Uplifted Terraces, Linda K. Armour

Open Access Theses & Dissertations

This study examines Basin and Range topography relating tectonic processes to topographic features. The observation that the terraces along either side of the Franklin Mountains were deformed and uplifted is a reflection of tectonic uplift. The uplift represents long-term deformation of the range. This led to the question of what shapes the deformation and does it represent differential subsidence into the Río Grande Rift or true uplift. A more regional study of the Sacramento, San Andres, and Guadalupe Mountains follows. Two papers form this Dissertation.

The Rí­o Grande Rift and the Franklin Mountains, in particular, are the subject of the …

From Alarm To Action: Closing The Gap Between Belief And Behavior In Response To Climate Change, Kathryn Laing Doherty

Antioch University Dissertations & Theses

The degree to which the climate continues to change will largely be determined by choices made by individuals and nations regarding greenhouse gas emissions. Many Americans engage in energy conservation actions. But, the political will in the United States to adopt emissions reduction policies is unlikely to exist without public demand. Therefore, public mitigation actions of individuals (e.g., contacting elected officials in support of emissions reduction) are critical to induce legislative response. The majority of individuals who are most concerned about climate change (the “Alarmed” segment) do not engage in public mitigation actions, but some do. The purpose of this …

Analyzing Stress Drops Of Earthquakes Near Wellington, New Zealand, Kyle Eugene Barnes

Open Access Theses & Dissertations

Stress drop studies analyze the change of stress across faults before and after an earthquake. The goal of this study was to determine how stress drop varies throughout the Wellington region of the North Island of New Zealand. To the east of the North Island, the Hikurangi Trough obliquely subducts the Pacific Plate beneath the younger Australian Plate. Toward the southern end of the North Island and into Cook Strait the Pacific plate becomes more buoyant and the plate interface displays strong coupling as subduction diminishes into the strike-slip Marlborough fault system. Subduction of the Pacific plate ceases beneath the …

Numerical Prediction Of Collection Efficiency Of A Personal Sampler Based On Cyclone Principle, Antara Badhan

Open Access Theses & Dissertations

A personal bioaerosol sampler is a self-contained, operation flexible, high-efficient device for indoor air quality (IAQ) and health risk exposure monitoring and measurement. Bio-aerosols such germ-laden viruses, microbial species, airborne microorganisms and volatile organic compounds (VOC) are sucked into the sampler and are deposited on the inner wall surface based on cyclone principal. The major concern with bio-aerosol samplers is the collection efficiency. In this study, we used computational fluid dynamics (CFD) tools to evaluate key design parameters, specifically the inlet tube angle and collection tube inner wall roughness. 3D incompressible turbulent flow was simulated using commercial software ANSYS FLUENT. …