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Technical, Economic, and Life Cycle Assessment of Membrane-Based Air-Cooling Systems
No full textThe escalating demand for space cooling in Qatar, projected to triple by 2050, underscores the urgent need to shift from traditional refrigerant-based systems to more sustainable air-cooling technologies. This transition aims to mitigate the significant contributions to global warming, with a potential increase in global temperatures by 0.44��C by the century's end. Current research in membrane-based air-cooling systems, which combine adiabatic evaporative cooling with isothermal dehumidification, shows promise for enhanced efficiency. However, existing studies often overlook key operational energy requirements, such as the energy for low-temperature condensation, leading to underestimating system costs and efficiency. Moreover, environmental assessments of these systems frequently neglect the construction phase and criteria beyond electricity consumption. Experimentally, the focus has been on developing thin-film composites and nanocomposites on unaltered support membranes, which, despite increasing selectivity, do not significantly improve overall permeance. This limitation increases the need for membrane area, raising costs for membrane-based cooling solutions.
This research employs two primary methodologies to address the challenges of space cooling in Qatar, focusing on enhancing the efficiency and environmental sustainability of membrane dehumidification systems. A comprehensive simulation of various system configurations initially underpins these systems' exhaustive technoeconomic and environmental life-cycle assessment (LCA), benchmarked against conventional cooling technologies. Utilizing the Recipe2016 methodology for both Midpoint and Endpoint analyses, this LCA reveals a significant reduction (50-66%) in human health and ecotoxicity impacts compared to traditional AC systems while highlighting the minimal (<1%) environmental impact of the construction phase. Subsequent technoeconomic analysis identifies membrane cost as a critical factor in the viability of condenser-based membrane air-cooling systems. This underscores the necessity for membranes with a water vapor permeance (WVP) above 20,000 GPU. To address this, novel mixed matrix membranes containing hydrophilic nanomaterials into a polyethersulfone matrix were designed and fabricated using phase inversion to significantly enhance permeance without compromising mechanical stability. Among these MMM, the membrane containing 0.2 wt.% sulfonated graphene oxide with exceptional WVP of ~ 25,000, now protected by a US provisional patent, was coated with a thin active Pebax layer to enhance water vapor air selectivity. Economic assessment based on this SGO-TFN revealed a minimum loss of 15% saving in the total annualized relative to conventional systems, with a 60% increase in equipment manufacturing costs
When Modes of Learning Shift Unexpectedly: How Instructors Choose Online Teaching Strategies
No full textThis study examined how in-person instructors selected online teaching and learning strategies when shifting to a different mode of learning during the COVID-19 pandemic. As many in-person instructors have little to no experience with online learning or instructional design, examining how strategies were selected during this time provides an understanding of what strategies worked, the challenges in shifting to a different mode of learning, and practices that were retained moving back to in-person instruction. The findings revealed that instructors selected strategies during these shifts through adapting existing in-person instructional strategies to address the changing circumstance
Phase Field Fracture Simulations of High Burn-Up Uranium Dioxide Under Accident Transients
No full textUranium dioxide stands as the predominant fuel type in contemporary nuclear reactors. Despite its notable utility, there is a desire to enhance its performance in high burn-up scenarios. Such advancements would not only mitigate operational costs within existing reactor fleets but also ensure the long-term sustainability of global nuclear programs. To this end, significant progress has been made concerning the thermal performance of uranium dioxide. One notable advancement has been the use of computer simulations to test the fuel in ways that are difficult to replicate in traditional experiments.
This research introduces a novel variant of the cohesion phase-field fracture model within the Multiphysics Object-Oriented Simulation Environment (MOOSE) framework. This model was used to simulate high burn-up uranium dioxide under two specific transient scenarios. The first involves a transient representative of reactor start-up, serving to verify the model and establish a performance baseline. The second scenario involves a high-power ramp transient, simulating an unforeseen accident that could potentially occur at any point during operation. The resulting crack patterns from these transients were systematically studied and subsequently compared with existing literature.
The study of these transients has yielded several significant results. During reactor start-up, a limited number of discrete radial cracks would form at the edge and propagate toward the center of the fuel pellet. Characteristics of these cracks, such as their length and quantity, exhibit correlations with start-up power and fuel heat rate. Additional cracking was observed later in the transient when the fuel temperature was increased. These additional cracks would branch off existing cracks and move in the circumferential direction.
The morphological features of the cracks generated in these simulations are consistent with observations from historical and contemporary experiments. Moreover, the model employed in these simulations demonstrates competitiveness with contemporary counterparts, distinguishing itself by offering greater flexibility and fewer artificial restrictions
Improving Access to River Discharge Data Through Satellite Remote Sensing
No full textRivers are a critical engine for the transportation of water, nutrients, and sediments across landscapes, making them an integral natural resource for many ecosystems and civilizations. Historically, river discharge, the volumetric flow of water at a point, has been measured using river gauges. These gauge discharge measurements serve a vital role in water resource management by improving our understanding of river dynamics and informing flood predictions. In this dissertation, I compile the largest collection of publicly available river gauge data and analyze this database for spatial and temporal trends in river gauge availability. I find that global gauge availability has remained stable since 1980 but the gauge network is biased towards the Americas and Europe. In addition, I find that 77% of global gauge records are not available in real-time, limiting our ability to make effective water management decisions. To alleviate the issues associated with the global gauge network, I leverage satellite remote sensing to provide real-time estimates of discharge in both gauged and ungauged reaches. By developing empirical relationships between gauge discharge measurements and satellite river widths, I am able to add nearly 300 thousand daily discharge observations to the global gauge record. Along ungauged North American reaches, I develop an algorithm, RODEO, to estimate river discharge efficiently and accurately from Landsat imagery. RODEO is available as a publicly available Google Earth Engine application and provides a path forward for the accurate quantification of remote sensing of discharge uncertainty. River discharge can directly influence and be influenced by lake dynamics. With the aim of better understanding lakes and rivers as an interconnected system, I develop the LakeFlow algorithm. LakeFlow leverages satellite observations from the recently launched Surface Water and Ocean Topography (SWOT) mission and mass conservation principles to estimate discharge at river-lake boundaries. LakeFlow has been tested using synthetic datasets at three lakes and shows promising accuracy. Ultimately, LakeFlow can be used to provide discharge at approximately 35 thousand river reaches globally
Latinx Individuals in US Sport
No full textThe dissertation central objective is to critically examine the underrepresentation of Latinx individuals in the realm of the United States (US) sport landscape. Commencing with Study 1, a meticulous scoping review of literature was undertaken, revealing a conspicuous research gap spanning four decades, particularly in the context of Latinas in sport. Significantly, 74.1% of the studies surveyed relied on quantitative methodologies, shedding light on the imperative for broader research methods to unravel the intricate dimensions of experiences within this population.
Study 2, grounded in Latin Critical Race Theory (LatCrit), investigated micro and meso-level factors affecting Latinx student-athletes in Predominantly White Institutions (PWI). Despite Diversity, Equity, and Inclusion (DEI) interventions, participants reported encountering racial biases from athletic staff and peers, relying on familial support and campus resources to address these issues. The outcomes underscore the urgent need for initiatives to mitigate disparities faced by Latinx student-athletes.
Subsequently, Study 3 sought to comprehend macro-level experiences of Latinx individuals, undocumented populations, and DACA recipients in the US, with a specific focus on sports participation and community engagement. Grounded in Critical Race Theory (CRT) and Sport for Development and Peace Theory (SFDT), the data collection phase extended over 13 weeks within a Houston, Texas community. Findings illuminated the challenges confronting DACA holders and undocumented individuals in assimilating into new communities, with community-oriented programs identified as pivotal catalysts for positive change.
In conclusion, the dissertation rigorously examines the limitations, theoretical contributions, practical implications, and future trajectories emanating from the tripartite studies. Emphasizing the imperative for diverse research methodologies, it underscores the urgency of addressing racial biases in PWIs and accentuates the pivotal role of community programs in facilitating integration for Latinx individuals, DACA recipients, and undocumented populations within the sporting milieu
Turbulent Spherical Flames in a Constant-Volume Fan-Stirred Vessel
No full textTurbulent flame speed is a measurement of the flame propagation rate in a turbulent flow field, combining chemical kinetics with fluid mechanics. Because turbulence is very influential to the flame propagation rate, it is a challenge to model turbulent combustion. The velocity field and relevant length scales of the test chamber flow must be determined to fully analyze the turbulent combustion. In spherically expanding turbulent flame speed experiments, wrinkles in the flame front form pockets and cause the flame to morph into a non-spherical shape. Because of this random non-spherical propagation, the experimental variability is higher for turbulent flame speed experiments than laminar flame speed experiments. The experiments in this study were conducted inside a fan-stirred flame vessel at Texas A&M University.
In this study, we aimed to verify the new heating system and reestablish the turbulent flame analysis method to prepare for future turbulent experiments. To verify the heating system, we performed laminar flame speed experiments and measured the pre-test temperature distribution with an array of thermocouples. Because of the interest in methane as a rocket propellant, the turbulent experiment matrix used methane as the chosen fuel. Methane-air turbulent flame speed experiments were performed for pressures of 1 and 5 atm; turbulent intensities of 1.4 and 2.8 m/s; and equivalence ratios of 0.8, 1.0, and 1.2. The data confirmed that increased turbulence increases the flame speed due to additional instability at the flame front and increased material transport due to turbulent flow. The experiments at higher turbulence intensity show an increased flame acceleration compared to the lower-turbulence tests. Turbulent flame speed increases with increased pressure due to stronger wrinkles increasing the surface area of the flame front
La Imagen del Recuerdo: Sagrada Memoria y Always from Somewhere Else de Marjorie Agos��n
No full textEl presente trabajo propone un an��lisis comparativo de Sagrada memoria (1994) y Always from somewhere else (1998) de la escritora chilena Marjorie Agos��n. Estas obras presentan los recuerdos de Frida y Mois��s Agos��n, los padres de la autora, pero constituyen un testimonio que va m��s all�� de sus vivencias personales. Estos testimonios trascienden el ��mbito familiar conformando memorias colectivas, siendo el retrato de la realidad heredada por los supervivientes del Holocausto que emigraron a Latinoam��rica. Los recuerdos, marcados por la imaginaci��n y subjetividad, son reflejo de experiencias discriminatorias antisemitas, pero tambi��n raciales y de g��nero. El presente estudio tiene como principal objetivo el an��lisis comparativo de dichas memorias en cuanto a conceptos como testimonio, memoria, postmemoria e imaginaci��n ic��nica, entre otros. Dicho an��lisis nos lleva a encontrar las siguientes tem��ticas comunes: el mandato jud��o de recordar, el trauma heredado, la imposibilidad de narrar el recuerdo, el antisemitismo, el exilio, la identidad del sujeto diasp��rico, la subjetividad, el imaginario o memoria social o colectiva y el reconocimiento. Estas tem��ticas permiten establecer nexos entre estas memorias y la concepci��n art��stica de la artista judeo-chilena Patricia Israel, cuya obra tambi��n conjuga la imagen y la palabra con el fin de abordar la memoria tanto privada como colectiva. La imaginaci��n ic��nica juega un papel importante en la elaboraci��n de im��genes verbales, lo que permite establecer relaciones entre la narraci��n y algunas de las obras del pintor jud��o Marc Chagall que propongo como un intertexto visual, as�� como entender el significado simb��lico que los tatuajes y los trenes adquirieron a partir del Holocausto. Adem��s, el contraste entre las memorias permite realizar una lectura de g��nero que manifiesta los estereotipos codificados en cuanto a la vida y funciones de la madre y del padre
Architecture and Facies of the Sullivan Peak Member Within the Lower Permian Wolfcamp-A Equivalent Skinner Ranch Formation on the Southern Margin of the Delaware Basin, from Outcrop in the Glass Mountains in West Texas
No full textStrata of the Sullivan Peak Member within the Lower Permian Skinner Ranch Formation are well exposed along the Lenox Hills of the Glass Mountains in Brewster County, West Texas. These outcrops provide a unique opportunity to describe equivalent strata of the prolific Wolfcamp-A Formation along the southern margin of the Delaware Basin. The Sullivan Peak Member is exposed along a 1.5 mi wide by 100 ft vertical exposure of carbonate-rich, coarse-grained, and conglomeratic strata interbedded with mudstone. Three coarse-grained facies and one mudstone facies were characterized from an outcrop aerial photogrammetry model, hand samples, and thin section petrography. These include: 1) a Normally-Graded Carbonate-Clast Conglomerate facies (CCC), 2) a Normally-Graded Skeletal Grainstone facies (NmGs), 3) a Massive Skeletal Grainstone-Packstone facies (MaGs), and 4) a Mudstone facies (Mdst). Three Facies Associations (FA-1, FA-2, FA-3) w ere defined and correlated using the facies scheme and the photogrammetry model. Three Lowstand Systems Tracts (LST���s) w ere delineated within the Sullivan Peak Member (LST-1, LST-2, and LST-3)
Salmonella Survival, Growth, and Presence in Onion Bulbs, Extracts, and Production Environment
No full textThe purpose of this research was to investigate the presence, survival, and growth of Salmonella in onions and their environment as a prerequisite to understanding the risk that Salmonella poses to the consumer. Extracts from red and white onions grown under blue light significantly (P < 0.05) inhibited the growth of Salmonella. Extracts from genotype 1104 showed an optical density (OD) that was significantly lower than all other extracts, with total inhibition in extracts from the outer scales. Salmonella Newport was inoculated at various depths using a syringe (wounding) in and on red, white, and yellow onions and stored at room temperature for up to 18 days. At intervals, samples were collected from the top layer (skin) and inner layers of each onion and were tested for Salmonella. In all cases, the outer layer of all onion varieties not only inhibited S. Newport growth, but the populations of this pathogen were reduced by 3.2, 2.4, and 2.5 log cycles on red, white, and yellow onions, respectively within the first 3 days of storage, with no significant further changes in counts over 18 days. In contrast, Salmonella Newport grew by 1.7, 2.3, and 2.5 log cycles over the 18-d storage time in the inner layers of red, white, and yellow onions. In the trials to track the presence of Salmonella in onion-producing environments, a total of 255 samples (101 from fields, and 154 from packing plants) were collected and subjected to qualitative and quantitative Salmonella assay in a BAX system with the SalQuant kit. Salmonella was detected in 3 (13%) of 23 samples of well water collected from one onion field, 3 (4%) of 75 samples of soil collected from 3 fields, and 16 (10%) of 151 surface samples collected from 3 onion packing plants. In field samples that tested positive, the quantitative assay gave mean counts of 0.1 log CFU/50 L in water and 1.2 log CFU/g in soil. For environmental samples from packing plants, the mean counts for positive samples ranged between 1.9 and 3.2 CFU/cm2 , no significant differences between types of surfaces were found in the Salmonella counts
Effect of Select Interpretive Story-Telling Techniques on Narrative Transportation and Engagement Among Youth Educational Travelers
No full textThis study examined the effect of select story-telling strategies interpreters use on engagement and narrative transportation of youth educational travelers. Engagement is the subjective state of motivation that occurs when one���s attention is focused on a story being told. Narrative transportation can also occur during story experiences. The traveler (i.e., reader, listener, spectator) is carried, via imagination, to the destination of the story; a different time, place, and set of circumstances. Heritage interpreters and tour guides for youth educational travel experiences use a variety of techniques to invite narrative transportation and engagement, but the effects of such techniques have not been studied experimentally. Four strategies were evaluated: use of visual aids, verisimilitude, use of music, and self-relevance elicitation. One hundred forty-four experience observations from 18 4-H youth enrolled in an educational travel experience to Spain were analyzed. Youth visited different sites in Barcelona and Madrid. During the daily reflection period, the researcher told a fictional story set in the site or sites visited that day. The four techniques were systematically varied across eight different stories to determine the relative effect of each technique on narrative transportation and engagement. After listening to each story, youth completed an electronic questionnaire measuring narrative transportation, engagement, and down-stream outcomes (perceived value of time spent and proclivity to recommend). Verisimilitude and self-relevance increased engagement and engagement increased narrative transportation. The effects of music and visual aids were not significant. Narrative transportation increased with increases in engagement, and perceived value of time spent listening to the story and proclivity to recommend were positively correlated with narrative transportation