ETD Collection for University of Texas, El Paso Copyright (c) 2016 University of Texas at El Paso All rights reserved. http://digitalcommons.utep.edu/dissertations Recent documents in ETD Collection for University of Texas, El Paso en-us Tue, 03 May 2016 08:00:23 PDT 3600 "I was nothing but a lender of what I was ordered to supply..." Francisco Amangual, trustee of the presidio and las companias volantes in the Spanish borderlands, 1701--1812 http://digitalcommons.utep.edu/dissertations/AAI3724941 http://digitalcommons.utep.edu/dissertations/AAI3724941 Fri, 29 Apr 2016 16:21:05 PDT Francisco Amangual represented an agent for the Spanish colonial empire throughout his career as a presidio paymaster and in his ultimate role as the captain of a specialized unit of the borderlands military, the so-called compañías volantes, or flying squadrons. This study reorients colonial borderlands scholarship by making clear the significance of the empire's lesser known intermediaries charged with documenting the seemingly mundane activities of life in the garrison. Further, assigning a cogent place to the presence of the volantes allows for a more thoroughgoing understanding of their history by disentangling their place from among the various presidial units in the Spanish colonial frontier.^

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Roland Rodriguez Latin American history|History|Hispanic American studies
Recovery of nutrient nitrogen from municipal wastewater residuals by gas membrane separation http://digitalcommons.utep.edu/dissertations/AAI1593365 http://digitalcommons.utep.edu/dissertations/AAI1593365 Fri, 29 Apr 2016 16:20:54 PDT There are relatively high amounts of ammonia returned to the headworks of a municipal wastewater plant that are extracted from the dewatering process. This ammonia load contributes to a significant oxygen demand in the secondary treatment, requiring greater air blower energy costs. This goal of this research was to evaluate the feasibility of the recovery of an ammonium sulfate product from belt press filtrate. The objectives of this research were to: (1) analyze wastewater treatment average monthly data flows and constituents with respect to ammonia nitrification, (2) the evaluate the technical performance of a two sage gas-separation membrane for recovering ammonia separation, and (3) evaluate the economic feasibility of wastewater plants operating ammonium sulfate production. Results showed that, for the years 2012–2013, the Bustamante Wastewater Treatment Plant had a monthly average of 1197 lb/day of ammonia (as N), which required an average energy cost of $60,868per year. The ammonia separation process was observed to operate optimally at a pH of 9.8 in the belt press filtrate influent, which maximizes the ammonia speciation without causing calcium carbonate precipitation. At a filtrate feed flowrate of 2.0 gpm in the pilot system, 68% of the ammonia was removed, producing approximately 11 lb/day of ammonium sulfate. Scale-up to treat the average 0.18 million gallons per day (mgd) of belt press filtrate would have an estimated annual energy cost savings of $23,900 and ammonium sulfate revenue of $15,135 per month for a total net financial benefit of $205,500 per year. With an estimated total capital cost of $1,680,280 the simple payback period was estimated to be 8 years. Future work should evaluate more efficient particle pretreatment to minimize fouling of the gas-separation membranes.^

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Evelyn Rios Civil engineering|Environmental engineering
Reckless anxiety http://digitalcommons.utep.edu/dissertations/AAI10061480 http://digitalcommons.utep.edu/dissertations/AAI10061480 Fri, 29 Apr 2016 16:20:36 PDT Reckless Anxiety will focus on fourteen short stories that have characters who all suffer from some form of mental illness, compulsion or disorder. The title is itself a paradox, because anxiety in its general sense could make someone with it more cautious than normal. I wanted to take it to an extreme level and approach writing with the recklessness of an artist afraid of what could happen should he ever stop moving or stop dancing. ^ PROJECT BACKGROUND: Before I started developing my thesis, as a writer I felt as if I was on a path with only one direction. In the periphery, I could see that there were other Latin@ authors and poets that had been charting out the map and making incredible inroads into the literary world. I felt disconnected to that, as if those paths were meant for someone else. I had, however, made inroads myself into different venues of writing. I had been a journalist in high school and in college and had adapted those lessons into my professional career. But for writing on my spare time, that process started changing when I enrolled at the University of Texas at El Paso’s Online Master of Fine Arts in Creative Writing. Before that, my biggest hangup as a writer was being genre-stricken—that is, sticking to either sci-fi or fantasy. Once I started at UTEP, I started a process that made me appreciate, learn, and breathe literary fiction. ^ Writing short stories is a process that, for me, begins first and foremost with writing poetry. In my poetry, I use both image and line to the best of my ability to describe things around me. As a poet, I find something specific that calls to me, whether it is a building off of Houston’s Southwest Freeway, a particularly strong emotion at the closing of a Waldenbooks in Brownsville, or seeing two complete strangers dance the night away in a country western club. Then I scribble a page or two about that particular moment on a notepad that tends to be on my person most of the time. I then wait a week before transferring the physical notes into digital ink, where it then sits in a designated “crockpot” folder. Here, my ideas stew for one more week while I initiate other projects. Once the week passes, I re-open my project and determine whether or not the poem is ready. I have found that waiting several weeks to truly determine the worth of a poem rather than trying to perfect a poem in one sitting, and to view that poem with new clarity, has allowed me to greatly improve my poetic talents. If it is ready, then it is saved and kept in a folder for submissions. If it is not, then I set the poem aside in another folder and cannibalize the imagery for something else, or perhaps for future edits. Within this graveyard of incomplete poetry I can see if there is a connection or enough substance and enough imagery to go deeper. This makes up the first component of my fiction process. The other component involves having all that occur inside my own mind, everything from the initial draft to determining the worth or potential of a creative project. The union of these two processes is what allowed the birth of Reckless Anxiety as my thesis.^

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Hugo Esteban Rodriguez Castaneda Creative writing
Towards analytical techniques for optimizing knowledge acquisition, processing, propagation, and use in cyberinfrastructure http://digitalcommons.utep.edu/dissertations/AAI10027830 http://digitalcommons.utep.edu/dissertations/AAI10027830 Thu, 07 Apr 2016 16:39:05 PDT For many decades, there has been a continuous progress in science and engineering applications. A large part of this progress comes from the new knowledge that researchers acquire, propagate, and use. This new knowledge has revolutionized many aspects of our life, from driving to communications to shopping.^ Somewhat surprisingly, there is one area of human activity which is the least impacted by the modern technological progress: the very processes of acquiring, processing, and propagating information. When we decide where to place sensors, which algorithm to use for processing the data – we rely mostly on our own intuition and on the opinion of the experts. As a result, knowledge-related methods that we select are often far from optimal. To make effective recommendations, it is necessary to build realistic models of the corresponding processes, and then use these models to find optimal ways of controlling these processes.^ The need for such models is well understood. There are many numerical models of knowledge acquisition, processing, and propagations. Some of these models have been successfully used to enhance the corresponding processes. However, these applications are limited by the fact that most of these models are based on detailed numerical simulation of the corresponding processes, which make the resulting models very time-consuming to use. It is therefore necessary to develop analytical models for the corresponding knowledge-related processes, models that would allow easier optimization and application.^ The main purpose of this dissertation is to develop analytical models for all the knowledge-related processes, from knowledge acquisition to knowledge processing and knowledge propagation.^

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Leonardo Octavio Lerma Mathematics|Statistics|Computer science
Libertad perpetua http://digitalcommons.utep.edu/dissertations/AAI10027827 http://digitalcommons.utep.edu/dissertations/AAI10027827 Thu, 07 Apr 2016 16:38:58 PDT Abstract not available.^

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Jose E. Durango Polo Theater
Numerical study of the supercritical solution of the stationary forced Korteweg-de Vries (sfKdV) equation http://digitalcommons.utep.edu/dissertations/AAI10010973 http://digitalcommons.utep.edu/dissertations/AAI10010973 Thu, 07 Apr 2016 16:38:52 PDT The time independent surface waves on a two dimensional incompressible and inviscid fluid flow passing over a bump on a flat bottom are considered. The stationary forced Korteweg-de Vries (fKdV) equation is defined in an unbounded interval. In this project, this unbounded interval is considered as three parts - on the bump, left hand side of the bump and right hand side of the bump. Exact boundary conditions are applied to the end points of the bump. All the possible combination of boundary conditions are used. A numerical approach is proposed to find the solitary wave solutions of fKdV equation by solving the boundary value problem on the bump. Then the solitary wave solutions are found in an extended interval. Using this new method, some new and exciting results are found.^

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Sumi Dey Mathematics
Faculty and student interactions at the community college: An examination of the interaction order http://digitalcommons.utep.edu/dissertations/AAI10007407 http://digitalcommons.utep.edu/dissertations/AAI10007407 Thu, 07 Apr 2016 16:38:47 PDT Community college students represent 46% of all incoming freshman undergraduate students (American Association of Community Colleges, 2013). Increasingly, research on community colleges is focused on student success and in particular student engagement. One area of student engagement is faculty and student interactions which are an essential part of the collegiate experience.^ The purpose of this study is to examine faculty and student interactions at the community college, in particular, the type of interactions, the nature of the interactions as well as how students interpret their interactions with faculty members. With an ever growing emphasis on accountability via student success outcomes within community colleges, it becomes important to better understand how best to support students.^ This study asked the following research questions: What type of interactions occur? What is the nature of the interactions? and How do students (describe or interpret) the interactions?^ Three primary theories guided this study: Goffman’s (1967, 1969, 1983) interaction order, Stanton-Salazar’s (1997) institutional agents and Rendón’s (1994) validation theory. These three frameworks were used in this qualitative, interpretive approach, which primarily utilized interviews to examine and understand faculty and student interactions.^ There were 28 interviews as well as participant observation that was conducted at two campuses within one community college. There were 19 students and 9 faculty members that were interviewed and nine themes emerged from the analysis.^ Specifically, this research can aid policy and practice within community colleges as they seek ways in which to assist students in their educational endeavors.^

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Amber Archuleta-Lucero Education
A methodology for use of digital image correlation for hot mix asphalt testing http://digitalcommons.utep.edu/dissertations/AAI10003082 http://digitalcommons.utep.edu/dissertations/AAI10003082 Thu, 07 Apr 2016 16:38:40 PDT Digital Image Correlation (DIC) is a relatively new technology which aids in the measurement of material properties without the need for installation of sensors. DIC is a noncontact measuring technique that requires the specimen to be marked with a random speckled pattern and to be photographed during the test. The photographs are then post-processed based on the location of the pattern throughout the test. DIC can aid in calculating properties that would otherwise be too difficult even with other measuring instruments. ^ The objective of this thesis is to discuss the methodology and validate the use of DIC in different hot mix asphalt (HMA) tests, such as, the Overlay Tester (OT) Test, Indirect Tensile (IDT) Test, and the Semicircular Bending (SCB) Test. The DIC system provides displacements and strains in any visible surface. The properly calibrated 2-D or 3-D DIC data can be used to understand the complex stress and strain distributions and the modes of the initiation and propagation of cracks. The use of this observational method will lead to further understanding of the complex boundary conditions of the different test, and therefore, allowing it to be implemented in the analysis of other materials. The use of digital image correlation will bring insight and knowledge onto what is happening during a test.^

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Estefany Ramos Civil engineering|Materials science
Cultural diplomacy strategies for Mexico in the XXI century http://digitalcommons.utep.edu/dissertations/AAI10003079 http://digitalcommons.utep.edu/dissertations/AAI10003079 Thu, 07 Apr 2016 16:38:33 PDT This thesis analyzes cultural diplomacy (CD) and how the utilization of the strategies of inserting Mexico into foreign cultures, using cultural activities based on similarities and differences, and expanding CD into other areas, may have the ability to positively influence Mexico`s political, economic, social and cultural foreign policy objectives.^

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Alejandro Siqueiros International relations|Public administration|Public policy
Ethnic disparities in the reproductive and sexual health screening practices of Ecuadorian women http://digitalcommons.utep.edu/dissertations/AAI10000825 http://digitalcommons.utep.edu/dissertations/AAI10000825 Thu, 07 Apr 2016 16:38:27 PDT Background: Evidence suggests that reproductive and other health disparities disproportionately affect Indigenous and Afro-Hispanic ethnic minority groups throughout the Latin American and Caribbean (LAC) region. Factors associated with reproductive health disparities in LAC countries include low social economic status (SES), poor health care access, racial and gender discrimination, machismo, health beliefs and low perceived risk for breast cancer, cervical cancer, sexual transmitted infections (STIs) and other conditions. Preventive measures such as health education and early screening is vital for disease prevention and detection. However, screening rates for breast cancer, cervical cancer, and STIs are lower in most LAC countries compared to the United States (USA), Canada, and other high-income countries. Likewise, the low prevalence of modern contraceptive use (e.g., condom, intrauterine device (IUD), contraceptive pills, Norplant, etc.) is another important public health challenge facing many LAC countries. Ecuador is a middle-income Andean country that displays high rates of fertility and reproductive cancers as well an increasing population burden of human immunodeficiency virus (HIV) and other STIs. The country also has one of the largest ethnic minority populations in the LAC region. Persons of indigenous and African descent constitute an estimated 7-25% and 3-10% of the population of 14 million inhabitants. Ethnic disparities in poverty-linked indicators and some chronic and infectious health outcomes have been reported for indigenous and Afro-Ecuadorian groups but little is known those related to reproductive health. A better understanding of reproductive health disparities and the factors that influence them including health-seeking is useful for improving programs and policies that serve ethnic minority groups in Ecuador. Aims: This study aimed to compare ethnic differences in reported sexual and reproductive health knowledge and practices including health-seeking of reproductive-aged Ecuadorian women. The main objectives were to describe the prevalence of reproductive and sexual health screening behaviors among reproductive-aged Ecuadorian women with respect to cervical cancer, breast cancer, contraception use and sexually transmitted infections and to identify ethnic differences in knowledge and screening practices prevalence of contraceptive use, breast cancer, cervical cancer, HIV and STIs among the three major Ecuadorian ethnic groups. Methods: The ENDEMAIN 2004 national survey was carried out by the Centro de Estudios de Poblacion y Desarrollo Social (CEPAR) with technical assistance from the U.S. Centers for Disease Control and Prevention (CDC). The nationally-representative survey used a multistage clustering design. One reproductive aged woman (15-49 years) per household selected from 10, 814 Ecuadorian households completed a questionnaire on her sexual and reproductive health. The data was analyzed with IBM-SPSS Version 21 database management and analysis software. Univariate analysis was conducted for continuous variables (mean and standard deviation) and categorical variables (frequencies and percentages). Unadjusted bivariate analysis were conducted using Pearson Chi-Square test for categorical variables and ANOVA for continuous variables for majority Mestizo versus minority Indigenous and Afro-Ecuadorian women. Logistic regression was used to compare the prevalence ratio among the three groups (Mestizo versus Indigenous and Afro-Ecuadorian) while adjusting for other covariates. Results: The results from this study demonstrate the health knowledge disparity between Mestizo, and Indigenous women. Indigenous women reported the lowest knowledge percentage for most of contraceptive methods and were less likely than Mestizo women to use a contraceptive method. No statistically significant difference was found between Afro-Ecuadorian and Mestizo women in regards to any lifetime contraceptive method use. As expected, Indigenous and Afro-Ecuadorian women were less likely than Mestizo women to ever hear about breast and cervical cancer and sexual transmitted infections. Discussion: The study results suggest a high need for tailored interventions for reproductive health to include breast and cervical cancer screening and HIV and STIs screening for the most neglected ethnic groups, Indigenous and Afro-Ecuadorians. Although higher HIV screening rates and knowledge rates are reported for Afro-Ecuadorian women in comparison to Indigenous women still the rates are not as high as the majority Mestizo women. Policy development for Ecuador must focus on making health education available to those groups in rural areas in order to reduce the health disparity existing between Mestizo women and Indigenous and Afro-Ecuadorian women. The study findings have implications for reproductive health promotion and intervention design in rural, low income settings and for minority populations. ^

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Ruth Castillo Womens studies|Public health
El momento en que... http://digitalcommons.utep.edu/dissertations/AAI10000823 http://digitalcommons.utep.edu/dissertations/AAI10000823 Thu, 07 Apr 2016 16:38:20 PDT We’ve all experienced moments that move us in some way, moments that we’ve memorized for the rest of our lives. Some we can’t ever forget, and some we wish we could. Nonetheless, these moments are ingrained in the forever of our minds. My collection, El Momento En Que… is a compilation of snapshots of the life of a fictional character named Graciela, who is fourteen and has experienced the tremendous loss of family, sense of place, and sense of self. It is a collage of moments where she questions her life, her parents’ decisions, her relationships with those around her, and essentially, her sense of place. The snapshots begin three years after Graciela’s abuelita died, and her parents decided to pack up and move to Texas where Graciela Flores feels trapped like a butterfly in a jar, unable to breathe. Everyone and thing she loves has changed, and the traditions that made her feel safe are slowly slipping away. The story that I am going to tell in snapshots is how in America, everything feels wrong to Graciela as she watches her family slowly plant their roots in Texas soil. Her father works his fingers to the bone, her mother works for hours on end for Mrs. Constance, and her big sister, Margarita has merged into American culture seamlessly. Margarita is so in love with American culture that she does not want to be Mexican anymore. And the longer the family stays in America, the more Graciela realizes how much her dark skin, plain hair, and everything that makes her Mexican is tearing her and Margarita apart. The themes that I am exploring in my work are voice, culture, family values, culture shock, illness, and a family’s response to crisis. I investigate how a young girl experiences such a culture change, and how it impacts the family unit as well. I explore character development and how one bends and forms to their new circumstance without letting their true self go.^

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Donna Lynn Munoz Creative writing
A cell formation algorithm for sequential processes with alternative machine selection in the automotive lighting industry http://digitalcommons.utep.edu/dissertations/AAI10000820 http://digitalcommons.utep.edu/dissertations/AAI10000820 Thu, 07 Apr 2016 16:38:13 PDT At the present time, there are more than 12 big companies dedicated to design and produce OEM lighting systems for cars and trucks. The manufacturing processes for headlamps, tail lamps and any other exterior vehicle lighting are very common in the auto industry. Still, every automotive lamp assembly is different from brand to brand and even between the different vehicle models. Indeed, there are car headlamps with less than 30 sub-components and others with up to 300 elements. This implies creating diverse part numbers which share or hold varying manufacturing methods within a specific facility. Management of the plant resources becomes highly challenging when the parts to be created and the machines to be operated are not organized in family groups. A great amount of time and effort has to be invested in production planning related to associating parts to machines. Consequently, the foundation of Group Technology (GT) has to be utilized with the purpose of dividing a relatively large system into smaller and more-manageable manufacturing cells. However, existing GT methods have not shown a practical application in the target scenario. This study pretends to find a better approach to the concept of GT throughout the use of a customized cell formation algorithm for the automotive lighting field or any other area that may be pertained.^

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Victor Manuel Loya Garnica Engineering|Industrial engineering
E-quality design of experiments for structural electronics http://digitalcommons.utep.edu/dissertations/AAI10000819 http://digitalcommons.utep.edu/dissertations/AAI10000819 Thu, 07 Apr 2016 16:38:07 PDT Additive Manufacturing (AM) is a technology utilized for creating complex parts by adding layers of material in order to create a three dimensional functional part. This technology has been pushed to a new level of functionality where mechanical parts are combined with electronic components to create Three-Dimensional Structural Electronics (3DSE) systems. This new technology has been used to replace Printed Circuit Boards (PCB), for 3D SE are light weight and can be created in any desired shape. Computer Aided Design (CAD) software is used to design the part and a Fused Deposition Modeling (FDM) machine is used to 3D print the part with slots for the electronic components to be embedded. Researchers have been working on embedding electronic components for several years, but so far all the embedding of components is done manually. The research presented in this paper provides a new approach for embedding electronics by utilizing a Yamaha SCARA robot in order to automate the pick and place process. Automated placement of electronic components is an ongoing research area, and in this paper a design of experiment (DOE) is conducted to measure accuracy on the Yamaha SCARA robot in order to facilitate accurate placement of electronic components.^

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Oscar Alejandro Murga Torres Engineering|Robotics
Virtual rapport with extraverted agents http://digitalcommons.utep.edu/dissertations/AAI10000818 http://digitalcommons.utep.edu/dissertations/AAI10000818 Thu, 07 Apr 2016 16:38:00 PDT Studies from psychology conclude that “birds of a feather flock together”- or, in other words, people tend to seek companionship with those who have a similar personality to their own. Researchers in the fields of Linguistics and Psychology have found numerous markers that differentiate the dialogue of extroverts from that of introverts. Recent work in Human Computer Interaction has sought to understand the nature of creating and maintaining rapport between humans and Embodied Conversational Agents (ECAs). Seeking an interdisciplinary approach that combines knowledge from HCI, Linguistics, and Psychology, I sought to establish whether introverted users report the highest level of rapport when matched with a similarly introverted agent or with an extraverted agent. This understanding can establish a paradigm for creating the highest level of rapport between humans and ECAs from verbal interaction. Questions that I answered include: (1) Will all subjects establish a level of rapport with the extraverted agent? (2) Will extraverted subjects matched with an introverted agent show the lowest level of rapport? (3) If all subjects establish rapport with the extraverted agent, will subjects report the highest level of rapport when interacting with the agent whose extraversion level matches that of the subject? Two agents representing an extrovert and an introvert were created by manipulating three dialogue features. Using a task-oriented but informal setting, participants interacted with an agent in an immersive environment. Responses from participants to a 16-question survey were reviewed using statistical analysis. New exploratory work using qualitative analysis to four free-response questions in the same survey give new insights into both how humans interpret levels of extraversion, and what this means in terms of human-ECA interactions. I report the results of the study’s observations and propose directions for future work. ^

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Jacqueline Elaine Brixey Linguistics|Psychology|Computer science
Design and analysis of a novel latch system implementing fiber-reinforced composite materials http://digitalcommons.utep.edu/dissertations/AAI10000817 http://digitalcommons.utep.edu/dissertations/AAI10000817 Thu, 07 Apr 2016 16:37:53 PDT The use of fiber-reinforced composite materials have increased in the last four decades in high technology applications due to their exceptional mechanical properties and low weight. In the automotive industry carbon fiber have become popular exclusively in luxury cars because of its high cost. However, Carbon-glass hybrid composites offer an effective alternative to designers to implement fiber-reinforced composites into several conventional applications without a considerable price increase maintaining most of their mechanical properties. A door latch system is a complex mechanism that is under high loading conditions during car accidents such as side impacts and rollovers. Therefore, the Department of Transportation in The United States developed a series of tests that every door latch system comply in order to be installed in a vehicle. The implementation of fiber-reinforced composite materials in a door latch system was studied by analyzing the material behavior during the FMVSS No. 206 transverse test using computational efforts and experimental testing. Firstly, a computational model of the current forkbolt and detent structure was developed. Several efforts were conducted in order to create an effective and time efficient model. Two simplified models were implemented with two different contact interaction approaches. 9 composite materials were studied in forkbolt and 5 in detent including woven carbon fiber, unidirectional carbon fiber, woven carbon-glass fiber hybrid composites and unidirectional carbon-glass fiber hybrid composites. The computational model results showed that woven fiber-reinforced composite materials were stiffer than the unidirectional fiber-reinforced composite materials. For instance, a forkbolt made of woven carbon fibers was 20% stiffer than a forkbolt made of unidirectional fibers symmetrically stacked in 0° and 90° alternating directions. Furthermore, Hybrid composite materials behaved as expected in forkbolt noticing a decline in the load-displacement slopes while the percentage of glass fiber increased. In the other hand, results showed that a detent made of only glass fiber layers was preferable than a carbon-glass fiber hybrid detent due to the high stresses shown in carbon fiber layers. Ultimately, forkbolt and detent were redesigned according to their functionality and test results. It was observed that the new design was stiffer than the original by showing a steeper load-displacement curve. Subsequently, an experimental procedure was performed in order to correlate computational model results. Fiber-reinforced composite forkbolt and detent were waterjet cut from a composite laminate manufactured by Vacuum Assisted Resin Transfer Molding (VART) process. Then, samples were tested according to the computational model. Six testing sample combinations of forkbolt and detent were tested including the top three woven iterations forkbolts from the computational model paired with woven and unidirectional glass fiber detents. Test results showed a stiffness drop of 15% when the carbon fiber percentage decreases from 100% to 75%. Also, it was observed that woven glass fiber detent was superior to the unidirectional glass fiber detent by presenting a forkbolt-detent stiffness 38% higher. Moreover, the new design of forkbolt and detent were tested showing a stiffness increment of 29%. Furthermore, it was observed that fiber-reinforced composite forkbolt and detent did not reach the desired load of 5000 N. However, the redesigned forkbolt made of 100% woven carbon fiber and the redesign detent made of 100% woven glass fiber were close to reach that load. The design review based on test results performed (DRBTR) showed that components did not fail where the computational model concluded to be the areas with the highest maximum principal stress. In contrast to the computational model, all samples failed at the contact area between forkbolt and detent.^

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Francisco Javier Guevara Arreola Automotive engineering|Mechanical engineering|Materials science
A rapid approach for considering nonlinear response of flexible pavements under FWD and estimation of remaining lives of pavements http://digitalcommons.utep.edu/dissertations/AAI10000816 http://digitalcommons.utep.edu/dissertations/AAI10000816 Thu, 07 Apr 2016 16:37:46 PDT Most mechanistic empirical pavement analyses are based on the layered elastic models where the stress sensitivity of geomaterials and their nonlinearity are either ignored or accounted for indirectly. Advanced numerical models, such as finite element models, are required to consider the nonlinear nature of the geomaterials. Existing pavements are often tested with the Falling Weight Deflectometer (FWD) to estimate the input moduli to the layered elastic models in order to estimate remaining life and structural capacity of pavements. It has been more than 30 years that FWD tests are being performed to measure structural adequacy of pavements. Backcalculation is the method of evaluation of pavement surface deflections caused by specific pavement deflection devices in order to determine the moduli of pavement layers. Even though the deflection bowls may be influenced by the load-induced nonlinearity during the FWD testing, the extraction of the layer moduli is carried out using a layered elastic forward model. For being consistent in evaluation of the readings, efforts to conduct backcalculation using the nonlinear algorithms are of great academic interest. Because of time consuming characteristic of nonlinear algorithm, this method is not practical for day-to-day implementation. This thesis puts forward a methodology used to relate deflections obtained from nonlinear analysis to those of linear elastic under FWD loading condition at conventional locations. This thesis has two significant contributions. Firstly, the conversion of linear elastic deflections to nonlinear deflections enables one to take full advantage of fast layered elastic analysis of pavements while the geomaterials’ stress dependency behavior is accounted for. Secondly, it will be shown in the relevant section that backcalculation based on linear elastic deflections at conventional locations results in a more realistic computation of layer moduli rather than simply using nonlinear field deflections. In addition, the estimation of critical pavement responses using structural parameters of pavements and FWD readings is also discussed. The conventional approach to determine remaining lives of pavements consists of the following steps. FWD is applied on the pavement to backcalculate layer moduli. Then the pavement becomes subject to design vehicle to calculate critical pavement strains using linear elastic software programs. Critical responses are then converted to allowable number of load application to reach failure. FWD loading is applied on various pavements while nonlinear material properties are present and deflections at conventional locations are measured using finite element (FE) analysis. FWD nonlinear field representative deflection bowls are simulated in the program. Then, equivalent single axle load (ESAL) dual tire is applied to the same pavement structures under linear elastic assumptions to follow the conventional procedure. Critical pavement responses include tensile strains at the bottom of HMA and compressive strains on the top of subgrade, are determined. ANNs are then developed to estimate these responses based on FWD readings and structural properties of the system. Backcalculation process oftentimes provides nonunique layer moduli. The usage of developed ANN provides the elimination of backcalculation process to estimate remaining life. Hence, by using ANN models one can predict remaining lives of pavements while there will be no need to go through backcalculation. ^

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Shahabaldin Shirazi Civil engineering|Transportation
Alternative fatigue cracking resistance assessment criteria of asphalt mixtures with overlay tester http://digitalcommons.utep.edu/dissertations/AAI10000815 http://digitalcommons.utep.edu/dissertations/AAI10000815 Thu, 07 Apr 2016 16:37:39 PDT The accumulation of damage due to cracking of hot mix asphalt (HMA) layers under repeated loading along with the climatic effects is known as fatigue cracking. The Overlay Tester (OT) has been implemented or considered by several highway agencies as an index to evaluate the cracking susceptibility and resistance to cracking of asphalt mixtures in the laboratory. The performance indicator used to measure the quality of the HMA mixes is the number of cycles that a specimen may resist during the test until the crack appears and fully propagates to the top of the specimen. The repeatability of the number of cycles to failure measured with the OT is expressed as a concern to reliably assess the potential of asphalt mixtures to cracking. The goal of this thesis is to methodically evaluate the performance of the current OT test protocol. By addressing alternative cracking test methods and parameters a surrogate performance indicator may reliably estimate the fatigue cracking properties of HMA mixes. Fundamentally, cracking can be characterized in two stages: a) crack initiation and b) crack propagation. In this study, the focus was to analyze the data from the OT test considering these two stages. An alternative failure criteria to rank and screen the cracking resistance of asphalt mixtures was developed for the current OT test.^

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Alejandro Miramontes Civil engineering|Alternative dispute resolution
Does low-level arsenic exposure predict blood pressure in children? http://digitalcommons.utep.edu/dissertations/AAI10000812 http://digitalcommons.utep.edu/dissertations/AAI10000812 Thu, 07 Apr 2016 16:37:31 PDT Background & Significance: Inorganic arsenic is a heavy metal naturally found in soil and human exposure to this heavy metal causes adverse effects. Exposure risks are particularly high in developing children. Arsenic is mainly found in bedrock. It is also a by-product of smelting, it is used in cement production, and historically is has been found in crop pesticides. Among other ill-effects, arsenic exposure in humans can cause respiratory diseases, peripheral neuropathy and liver fibrosis. In particular arsenic has been shown in many studies to be a contributing factor in the risk for hypertension in adults however no studies have yet examined possible associations between blood arsenic and blood pressure in children. Aims & Objectives: The aim of this study was to investigate possible associations between arsenic and systolic and diastolic blood pressure in children. To examine whether possible effects were specific to arsenic, secondary analyses also tested associations between blood lead levels and blood pressure and blood cadmium levels and blood pressure. Hypothesis: It was hypothesized that blood arsenic predicts systolic and diastolic blood pressure. Because previous studies have not been conducted, no direction of association was predicted. Methods: This was an observational study of 204 children from two far west Texas rural communities. Children were recruited from two elementary schools and were between the ages of 4 and 11. Parents completed informed consent prior to testing and provided child and family demographic and medical information. Anthropometric measurements were taken for each child and blood pressure was automatically recorded using an electronic sphygmomanometer. Finger stick blood samples were collected, analyzed using Inductive-Coupled Plasma Spectrometry (ICP-MS) and tested for arsenic, lead, cadmium, and iron in whole blood. For the primary analysis, a generalized linear model was calculated predicting systolic and diastolic blood pressure (in separate models) controlling for sex and age, with school included as a random effect. Results: Blood arsenic level predicted decreased systolic blood pressure (F=8.19, p=.0047). For every 1 µg/dL of arsenic, child systolic blood pressure decreased by 3.99 mmHg. A positive association was found between blood cadmium level and blood pressure. Cadmium blood level in children predicted an association between cadmium and systolic blood pressure (F=5.45, p=.0205). Conclusion: Low-level arsenic exposure as determined by blood arsenic level linearly predicts a decrease in blood pressure in young children. This might be explained by arsenic-induced over production of nitric oxide in the endothelium and interference of nitric oxide synthase leading to vasodilation. Moreover, low-level cadmium exposure as determined by blood cadmium levels predict hypertension (increased systolic and diastolic blood pressure) in young children. The effects might reflect secondary effects of cadmium on kidney function. These and other explanations for the findings are discussed. The findings provide further evidence that very low-level heavy metal exposure has detrimental effects on early critical physiological functions. Additional studies are needed to replicate and expand these findings. Recommendations: Children must be consistently and frequently monitored for low detectable levels of heavy metal exposure. Although not the focus of this study, is should be noted that relatively high levels of prehypertension and hypertension were observed. Physical activity can improve metabolism which may promote toxin clearance in young children while also promoting normal blood pressure and lower body weight. Several physical activity programs currently in use throughout the country have been proposed and should be incorporated into vulnerable children’s daily school regiments.^

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Tania A Mayorga Environmental health|Health sciences
Predicting recessions using the yield spread: The Mexican northern border case http://digitalcommons.utep.edu/dissertations/AAI10000811 http://digitalcommons.utep.edu/dissertations/AAI10000811 Thu, 07 Apr 2016 16:37:25 PDT Business cycle analysis is a difficult endeavor. Policymakers are justifiably concerned over recessionary prospects for their respective economies. Being able to predict an incoming recession allows implementing measures to ameliorate the effects of downturns. The yield spread has been extensively used to analyze business cycles in high income economies. The probit model, the most widely utilized model for this type of analysis, enables estimation of the probability (between 0 and 1) that a recession will occur. This study evaluates the predictive power of the Mexico yield spread, the United States yield spread and the real exchange index to anticipate the probability of recession for eight of the most important northern border metropolitan economies in Mexico. ^

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Laura Mariel Saenz Rojo Economics|Latin American studies
Processing and property evaluation of tungsten-based mixed oxides for photovoltaics and optoelectronics http://digitalcommons.utep.edu/dissertations/AAI10000810 http://digitalcommons.utep.edu/dissertations/AAI10000810 Thu, 07 Apr 2016 16:37:19 PDT Tungsten Oxide (WO3) films and low-dimensional structures have proven to be promising candidates in the fields of photonics and electronics. WO3 is a well-established n-type semiconductor characterized by unique electrochromic behavior, an ideal optical band gap that permits transparency over a wide spectral range, and high chemical integrity. The plethora of diverse properties endow WO3 to be highly effective in applications related to electrochromism, gas sensing, and deriving economical energy. Compared to the bulk films, a materials system involving WO3 and a related species (elements or metal oxides) offer the opportunity to tailor the electrochromic response, and an overall enhancement of the physio-chemical and optical properties. In the present case, WO3 and TiO2 composite films have been fabricated by reactive magnetron sputtering employing W/Ti alloy targets, and individual W and Ti targets for co-sputtering. Composite WO3-TiO2 films were fabricated with variable chemical composition and the effect of variable bulk chemistry on film structure, surface/interface chemistry and chemical valence state of the W and Ti cations was investigated in detail. The process-property relationships between composition and physical properties for the films deposited by using W/Ti alloy targets of variable Ti content are associated with decreases in the deposition rate of the WO3-TiO2 films due to the lower sputter yield of the strongly bonded TiO2 formed on the target surface. Additionally, for the co-sputtered films using variable tungsten power, the optical properties demonstrate unique optical modulation. The changes associated with the physical color of the films demonstrate the potential to tailor the optical behavior for the design and fabrication of multilayer photovoltaic and catalytic devices. The process-structure-property correlation derived in this work will provide a road-map to optimize and produce W-Ti-O thin films with desired properties for a given technological application.^

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Mirella Vargas Engineering|Energy|Materials science
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