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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PublicationShort-term effect of three tillage and two soil conservative practices in the soil health and eggplant production in a Mollisol( 2024-04-09)Intensive agricultural production can lead to soil health depletion, which can be reduced using conservation practices such as minimum tillage and the incorporation of organic matter. Contrary to conventional tillage practices, conservation tillage leaves at least 30% of crop residue on the soil surface, which helps to minimize soil properties disruption. This study aimed to assess the soil health effect of incorporating biochar saturated with effective microorganisms on the Mollisols-Jacaguas treated with three cover cycles using the combination of four cover crops with three soil tillage treatments, Conventional Plow (CP), Spader and Keyline. The results of this study indicated that incorporating the plant residues of four CC cycles with Keyline tillage had a significant effect on the soil health within the short-term. The interactions of biochar incorporation with CC and tillage treatments had no significant effect on soil pH, LOC, PLFA and Saturated hydraulic conductivity because the small amount of biochar applied (<0.3%) was not sufficient to affect the above-mentioned soil properties at the short-term.
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PublicationCalibración del análisis de suelo de fósforo para la forrajera Brachiaria decumbens en un Ultisol, Puerto Rico( 2024-03-05)Phosphorus (P) is one of the most limiting factors for forage production in the Tropics. Contrary to what should be done soil test P is not used as a guide to generate P fertilization recommendations in Puerto Rico. The response of the forage Brachiaria decumbens to five levels of P fertilization was evaluated: (P1) 0, (P2) 60, (P3) 120, (P4) 180, (P5) 240 kg P₂O₅/ha/year, in a Ultisol (Typic Haplustults) in southwest Puerto Rico with soil test P in the Low category. The increase in soil test P per applied fertilizer P ranged from 0.3 to 1.1 mg P/kg per 100 kg of P₂O₅ at the end of the experiment. B. decumbens responded to the application of P, but not at the expected magnitude. Dry matter (DM) yield increased 13% with P fertilization with a maximum yield of 18,613 kg DM/ha/year. Forage DM yield was fit to a modified Mitscherlich model, and a critical fertilizer P application level of 24 kg P₂O₅/ha/year was obtained, which is four times lower than the current P recommendation for pastures. P extraction estimates ranged from 27.5 and 52.2 kg P/ha/year and increased with fertilizer-P applied. P use efficiency and P balance demonstrated that the forage was highly efficient as it extracted at least 50% of the P applied in all treatments. The application of 60 kg P₂O₅/ha/year resulted in higher P use efficiency, improved partial productivity factor and a higher removal efficiency. A linear relationship was found between STP and P balance, suggesting its usefulness as a fertilizer-P management strategy. Discrete economic analysis demonstrates that fertilizer-P applications beyond 60 kg P₂O₅/ha/year have negative net and investment returns and should not be considered profitable P application levels.
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PublicationEvaluation of tropical bamboo species with potential as a renewable source for charcoal( 2008)This research investigated the use of bamboo as a highly renewable primary material for charcoal production. Bamboo (Bambusaea) is an efficient, accessible and economical resource that can meet the demand for fuel and provide added income while mitigating land ecosystem damaged. Bamboo charcoal has been tested and proven to be a viable biomass in many countries for domestic use and commercial applications. The potential to develop bamboo charcoal in Haiti, where over 85% of the population relies on biomass energy for domestic uses was explored. This research sourced samples of 19 tropical bamboo species maintained at USDA-ARS Tropical Agricultural Research Station (TARS) in Mayagüez, Puerto Rico, to measure its calorific value. Three tree wood species, Caoba, (Swietenia Mahogany), Mango, (Mangifera indica), and Ucar (Bucida buceras) were tested to compare its calorific value. For each bamboo and tree species, three replications were prepared in raw form (air dried or oven dried, but not carbonized), and three replications were carbonized to produce charcoal. Carbonization was performed in a metal can, fueled by propane, at a peak temperature of 500oC. Calorific value for each raw and charcoal sample was determined using the IKA Oxygen Bomb Calorimeter. The mean results showed that bamboo charcoal has higher calorific value range than raw bamboo wood (25.92MJ/kg vs 17.97MJ/kg), and also has similar calorific value to tree wood charcoal (25.92MJ/kg vs 26.78MJ/kg). Raw bamboo also has similar calorific value as raw tree wood (17.97MJ/kg vs 17.26MJ/kg). The research also determined that calorific value is not related to wall thickness. These results, which show similar capacities for bamboo and tree wood, has potential to sustainably impact the local environment, because charcoal producers can explore the use of bamboo as a viable alternative to tree wood. Finally, through conversations with local charcoal producers in Haiti, this research reveals a consciousness of the negative environmental impacts of using trees for charcoal, and a willingness to experiment with bamboo as an alternative.
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PublicationEvaluación de propiedades físicas y mecánicas de algunos bambús tropicales cultivados en Mayagüez, Puerto Rico( 2016)La actual crisis ecológica y social que enfrentamos en el mundo exige adoptar enfoques alternativos que valoren la labor humana, la redistribución justa de los recursos y el bienestar con la Naturaleza. Desde el campo de la ingeniería estructural se puede avanzar hacia estos objetivos a través de la bioconstrucción, el cual entre muchos factores considera el uso y manejo responsable de los materiales locales y naturales. Dentro de este contexto, el bambú y su utilización tiene un gran potencial como fuente de tecnología apropiada para Puerto Rico. El bambú leñoso es una grama gigante (familia poaceae) de rápido crecimiento con múltiples beneficios ecológicos y sociales. Dentro del sector de la construcción alternativa su material ha sido identificado por sus buenas capacidades mecánicas, sustentabilidad ambiental, alta renovabilidad en producción y socialmente resiliente, entre otras. Dada su naturaleza, múltiples factores (anatómicos, geográficos, geométricos y otros) afectan directamente su desarrollo creando variaciones en sus propiedades físicas y mecánicas. Por lo tanto, el estudio detallado de estas propiedades se convierte en un componente indispensable para el análisis y diseño estructural adecuado con bambú. Estudios precedentes a las propiedades físicas y mecánicas del bambú en Puerto Rico se limitan a una investigación (Properties of Some Bamboos Cultivated in the Western Hemisphere, 1956). No obstante, las especies estudiadas y los métodos experimentales utilizados no satisfacen los factores de aplicabilidad constructiva con bambú y de comparación con investigaciones más contemporáneas. Por otro lado, esta tesis sigue un protocolo de prueba utilizando los requisitos del ISO-22157 1&2 y una selección de especie tomando en cuenta factores como el cumplimiento con maduración optima, disponibilidad y su potencial de uso para sistemas estructurales. Las seis especies de bambús seleccionadas (Bambusa vulgaris, Bambusa tulda, Bambusa oldhamii, Dendrocalamus asper, Gigantochloa apus y Guadua angustifolia) fueron muestreadas de la colección de bambús tropicales del Tropical Agricultural Research Station (TARS-USDA), Mayagüez, Puerto Rico. Para las mismas se algunas propiedades físicas y mecánicas básicas incluyendo la densidad, contenido de humedad, el módulo de elasticidad, el esfuerzo último a compresión paralelo a la fibra, el esfuerzo último cortante paralelo a la fibra y el momento flector último. Además, se adjunta otros experimentos cortos enfocados en entender las influencias de factores físicos en el comportamiento mecánico del bambú y la evaluación en efectividad para ocho alternativas de soluciones preservantes. El rango de valores promedios obtenidos, dentro de todas las especies, para esfuerzos últimos en muestras húmedas fue de: compresión paralelo a la fibra 4.84 - 8.09 ksi (33.40 - 55.79 MPa), cortante paralelo a la fibra 0.87 - 1.27 ksi (5.93 - 8.77 MPa), flexión 8.62 - 17.17 ksi (59.47 - 117.54 MPa) y módulo de elasticidad 2,361 - 3,644 ksi (16.28 - 25.48 GPa). La comparación directa de estos valores con los recolectados de otras investigaciones presentan patrones de cercanía o similitud. En general, esta tesis permitió el desarrollo de las instalaciones del Laboratorio de Materiales y Estructuras del Departamento de Ingeniería Civil y Agrimensura de la Universidad de Puerto Rico, Recinto de Mayagüez, para ejecutar pruebas mecánicas de bambú, brindado oportunidades a investigaciones futuras. Por otro lado, este trabajo también sirvió como foco de inspiración para el desarrollo de otras actividades como clases, talleres, charlas comunitarias y colaboraciones, entre otras, con la finalidad de promover la investigación y desarrollo sustentable del bambú, particularmente en Puerto Rico.
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PublicationComputational study of foreshocks in the Burridge-Knopoff earthquake model using machine learning( 2023-12-13)The study of mechanical models of earthquake faults is important for understanding the different behaviors observed in real earthquakes. The model considered for this work was introduced by Burridge and Knopoff, consisting of blocks connected by linear springs in contact with a moving rough surface. A numerical simulation of the model was implemented, revealing a variety in event size that follows a power-law distribution. As the next step, a database of artificial earthquakes was created with the purpose of training an artificial neural network (ANN) model capable of estimating the magnitude of the events generated by the simulation. The ANN models show satisfactory results in estimating the magnitude of artificial seismic events; however, there are still significant aspects to be discovered before they can be effectively applied to real seismic events.