Theses & Dissertations
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This collection is exclusively made up of theses, dissertations, and project reports submitted as a requirement for completing a graduate degree at UPR-Mayagüez.
If you are a UPRM graduate student and you are looking for information related to the deposit process, please refer to https://libguides.uprm.edu/repositorioUPRM/tesis
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PublicationBiochar and spent mushroom compost on tomato production in Puerto Rico( 2024-12-12)Tomatoes are a globally important vegetable crop with a high nutrient requirement. Vegetable growers in Puerto Rico show interest in alternative nutrient sources to chemical fertilizer use. The aim of this two-year trial is to evaluate the use of two locally produced organic soil amendments: spent mushroom compost (SMC) and pine wood biochar (PWB), on growth and yield of field produced tomatoes and the soil’s chemical composition compared to use of the commercial organic fertilizer BioFlora crumble (BF). Trials took place in the Agricultural Experimental Station of Juana Diaz, in the southern region of Puerto Rico in 2022/23 and 2023/24. The study on both years was arranged as a randomized complete block design (RCBD) with four replicates. Treatments were incorporated into the soil series Jacaguas (Fluventic Haplustolls). SMC and BF were applied based on 150 pounds of N/acre, PWB was applied as 0.5% of soil’s volume. Combined treatments: SMC+BF, PWB+BF, and SMC+PWB were applied as half the weight of each material applied alone. Lower number of flower clusters and plant height were observed in PWB treatment. PWB-treated plants also showed higher disease incidence of Target spot (2022/23) and severity of Orthotospovirus (2023/24). Use of SMC resulted in higher yields compared to: PWB (138%), PWB+BF (127%), SMC+PWB (121%), SMC+BF (115%), and BF (103%). After 5 months, SMC-amended plots had a significantly greater change of soil P (112%), S (1,575%) and Zn (102%). Differences in plant tissue nutrient components were found for B, S, and Ca, but all plants were within or above the normal range. Soil amended with SMC sustained competitive yields and fewer diseases; however, crop rotation or use of other nutrient sources may need to be implemented to avoid nutrient imbalance in the soil.
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PublicationCold gas spraying copper metal on AlN ceramic as an alternative to thick DBC substrates( 2024-12-16)This dissertation investigates the use of Cold Gas Spraying (CGS) to deposit copper onto aluminum nitride (AlN) substrates as a viable alternative to thick Direct Bond Copper (DBC) substrates in power electronics packaging. The research begins by functionalizing the AlN surface through potassium hydroxide (KOH) etching, significantly increasing surface roughness and area, which enhanced the adhesion properties critical for effective CGS copper deposition. Key CGS parameters such as temperature, pressure, nozzle standoff distance, travel speed, substrate roughness, and deposition angle were systematically studied to optimize the copper coating quality. The deposition angle, in particular, emerged as a critical factor, with a 60-degree angle yielding the smoothest coating. A uniform 300 µm thick copper layer, comparable to that of commercial DBC substrates, was successfully achieved. The bonding mechanisms between copper and AlN were found to involve mechanical interlocking, plastic deformation, dynamic recrystallization, and grain refinement driven by temperature increases during particle impact, with the copper particle temperature reaching up to 693 K. These mechanisms contributed to strong interfacial bonding and minimal coating defects. Overall, this study demonstrates that CGS offers a promising alternative to conventional DBC substrates, providing high bond strength, excellent thermal stability, and defect-free coatings. The findings provide valuable insights into metal-ceramic bonding in CGS and establish a foundation for future research to further refine this technique for industrial applications in high-voltage and power electronics
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PublicationModelación numérica del método de cocientes espectrales y aplicación de metodología alternativa( 2024-12-16)Una de las principales causas de los daños producidos por los sismos es la amplificación de ondas sísmicas en depósitos de suelo cercanos a la superficie. Para reducir estos daños, es fundamental que el diseñador conozca la frecuencia fundamental en la cual el depósito amplifica las ondas. Entre los métodos disponibles para determinar este parámetro, destaca el método de Nakamura, que utiliza vibraciones ambientales y el análisis de cocientes espectrales H/V para identificar la frecuencia fundamental. El objetivo de esta investigación es evaluar numéricamente el método de cocientes espectrales H/V para caracterizar las propiedades dinámicas de un depósito de suelo. Para ello, se realizaron análisis continuos, basados en la teoría de propagación de ondas, y discretos mediante un software de elementos finitos. Los resultados obtenidos mostraron concordancia con las hipótesis iniciales, respaldando la validez de las metodologías empleadas. Asimismo, se propone una metodología alternativa al método de Nakamura, que también se basa en cocientes espectrales H/V, pero emplea un impulso superficial como fuente de excitación. Esta metodología fue aplicada en dos sitios de estudio, comparándose los resultados con los obtenidos mediante el método de Nakamura, análisis numéricos y estudios previos. Los resultados fueron altamente satisfactorios, permitiendo identificar la frecuencia fundamental del depósito de suelo con el método propuesto. Las comparaciones realizadas con investigaciones anteriores evidenciaron gran consistencia en los valores obtenidos para la frecuencia fundamental.
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PublicationExploring CPU and GPU strategies for solving some coupled nonlinear Schrödinger systems in Julia( 2024-12-12)We developed the SchrodingerToolkit.jl package in the Julia programming language to solve systems of coupled nonlinear Schrödinger equations in both 2D and 3D. The package builds upon the theories, methods, and strategies presented in [1-3]. It supports parallel computations with GPU acceleration and is designed for extensibility, making it a valuable research tool for exploring parallel techniques for these problems. The package features high-order spatial schemes using finite differences and high-order temporal schemes employing composition methods. It also includes tools for plotting, constructing and modeling abstract grids, tracking runtime statistics for execution and solver analysis, and logging key physical quantities such as mass per component, system energy, and total mass perturbation. GPU parallel implementation is achieved through CUDA.jl, allowing the generation of CUDA kernels directly from Julia code. This approach results in significant speedups of 5x to 10x, depending on the method used, particularly for 3D problems where matrix factorizations are often impractical due to time and memory constraints, even for smaller problems. The main bottlenecks in the implementation are related to solving linear systems, especially due to the use of implicit time-stepping methods, which require global communication or some form of internal state.
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PublicationBreeding for ashy stem blight resistance in common bean (𝘗𝘩𝘢𝘴𝘦𝘰𝘭𝘶𝘴 𝘷𝘶𝘭𝘨𝘢𝘳𝘪𝘴 L.) and assessment of hybrids and pigeonpea [𝘊𝘢𝘫𝘢𝘯𝘶𝘴 𝘤𝘢𝘫𝘢𝘯 (L.) Mill.] breeding lines( 2024-12-17)La habichuela (Phaseolus vulgaris L.) y el gandul [Cajanus cajan (L.) Mill] son leguminosas de importancia económica en Puerto Rico. Los objetivos de esta investigación fueron: (1) evaluar la respuesta de germoplasma de habichuela recientemente desarrollado al hongo Macrophomina phaseolina (Tassi) Goidanich, y (2) comparar el comportamiento agronómico de híbridos versus genotipos de gandul. Los genotipos de semilla blanca UPR-Mp-37 y UPR-Mp-48 tuvieron una respuesta intermedia en el invernadero y el campo a las cepas PRI21, PRI22, y PRI23M de M. phaseolina en ensayos en Isabela y Lajas. Los dos genotipos tuvieron una ganancia genética de resistencia a M. phaseolina de > 25% comparado a ‘Beníquez’ y ‘Verano’que fueron susceptibles a todas las cepas del hongo. Para el gandul, los híbridos 13KLAF1 y LA13KF1 y la línea mejorada UPE-4 superaron los rendimientos de ‘Lázaro’ por más del 102% en Isabela (2,890-3,112 kg ha-1) y Lajas (1,143-1,725 kg ha-1).