Theses & Dissertations
Permanent URI for this collection
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
1 - 5 of 2904
PublicationDesarrollo de un co-digestor anaeróbico para una porqueriza en Cayey, Puerto Rico( 2023-05-12)In PR, many of the small and medium-scale pig farmers face great challenges daily with the handling and management of the organic waste generated in their operations, which in turn generate great economic challenges. The anaerobic digestion process has been called one of the most suitable organic waste treatments because in addition to treats this waste efficiently, it has the advantage of reducing the generation of greenhouse gases emissions (GHGE), generating methane and high-quality composts for agricultural potential. However, often the energy supplied by the biodigester is not enough to meet the energy demand of the farmer. With the purpose of finding a viable way for pig farmers to manage the waste generated in their farming production in a sustainable and economic way, but at the same time taking full advantage of the available resources to generate the greatest amount of energy per unit of volume, decided to test the anaerobic co-digestion method to determine its feasibility for pig slurry wastewater, in combination with different residual biomasses from the food processing industry and distributors. A feedstock characterization analysis for substrates, along with a biological methane potential (BMP) analysis, was used to determine which of these biomasses, and which particle size of these biomasses, generates the greatest increase in methane yield. Of all the residues used as co-substrates in the anaerobic co-digestion, the plantain peel residues were the most efficient in increasing methane yield. It was determined that adding approximately 44g of plantain peels waste, per liter of slurry wastewater, in a particle size of approximately 0.5cm, can generate increases in methane yield production rates up to 111.94 L. Kg (VS) in comparison with the 7.08 L. Kg (VS) obtained with the anaerobic digestion with only pig slurry wastewater.
PublicationParámetros de calidad de dos suelos altamente meteorizados de la zona central de Puerto Rico( 2023-05-12)El efecto de labranza convencional (LC) y no labranza (NL) sobre parámetros de calidad se evaluó en dos suelos altamente meteorizados: Corozal (Typic Haplohumults) y Dagüey (Inceptic Hapludox). Se realizaron dos muestreos de suelo a dos profundidades (0 - 8 cm y 8 - 20 cm) en un intervalo de 10 meses para evaluar parámetros físicos, químicos y biológicos. El pH de ambos suelos fluctuó de fuerte a moderadamente ácido. No se observaron diferencias significativas en P disponible. El contenido de Ca2+, K+ y Mg2+ intercambiables fue mayor en los predios de no labranza y el Al3+ intercambiable fue menor. La actividad de deshidrogenasa y fosfatasa, y la respiración basal fueron mayores en los predios de no labranza y a la profundidad de 0 - 8 cm. Esto se atribuye al mayor contenido de materia orgánica en los predios NL y en los primeros centímetros del suelo. La densidad aparente y la resistencia a penetración fueron menores en los predios de labranza convencional, especialmente hasta la profundidad de 20 cm. A profundidades mayores de los 20 cm se observó un aumento significativo en resistencia a penetración. La labranza convencional disminuyó la estabilidad de agregados en ambos suelos. Se observaron correlaciones lineales positivas entre la EA, DA, actividad de DHA y FOS, RB y la MO en ambos suelos, lo que resalta la importancia de la materia orgánica como un parámetro de calidad de los suelos. El suelo Dagüey mostró mejores parámetros de calidad que el suelo Corozal con un mayor contenido de materia orgánica, mayor actividad de deshidrogenasa y fosfatasa, mayor respiración basal y un menor contenido de Al3+ intercambiable.
PublicationThe use of companion crops to attract natural enemies for aphid management in organic tropical “calabaza” production( 2023-05-10)To determine the effectiveness of companion crops for aphid management with natural enemies, 10 different companion crops were used as treatments in two organic plantings with tropical calabaza Cucurbita moschata (Duchesne ex Poir.) ‘Taina Dorada’ genotype as the main crop. Companion crops were also analyzed to see if they enhanced calabaza yield outcome. Experiments were carried out during two different planting seasons at the Agricultural Experimental Station of the University of Puerto Rico at Isabela. The first planting was in the fall season from October to December 2021 and the second planting was in the spring season from March to May 2022. Calabaza leaves were sampled for aphids by direct observation and companion crops were sampled for aphid predators with sweep-net and yellow sticky traps. The aphids found were Aphis gossypii (Glover) and Myzus persicae (Sulzer). Natural enemies found were two coccinellids species, Cycloneda sanguinea (L.) and Coelophora inaequalis (F.), and chrysopid species Plesiochrysa brasiliensis (Schneider).
PublicationAnalysis of individual forces in force-balance model for bubble departure diameter prediction( 2023-05-12)Understanding two-phase flow is key to the safety and efficiency analysis of Light Water Nuclear reactors (LWR). Because of inaccuracies, LWRs operate below the maximum point of output power to ensure safety. Computational Fluid Dynamics (CFD) methods use heat partitioning models for a better understanding of flow boiling with a special focus on the critical heat flux. In the heat partitioning models the bubble departure diameter is a term that highly influences the prediction of the heat flux. This work seeks an analysis of individual forces contained in a force-balance approach for bubble departure diameter prediction by using high speed photography. To analyze force expressions individually, two scenarios with different operating conditions are proposed. From the first scenario of a static bubble attached to a surface the contact pressure force F_cp and surface tension force F_s were validated to follow the physics of the problem. Then, the second scenario where a rapid growing bubble is analyzed allowed the computation of an experimental growth force based on the force-balance. A comparison was made between the experimental growth force and the growth force estimated from existing models. Comparing the Rayleigh-Plesset model growth force values with the experimental growth force gave a %difference of 833%. While the Added Mass model gave a %difference of 351%. From the comparison between the experimental growth force and the growth force estimated by the models a correction coefficient was proposed for the Rayleigh-Plesset model C=0.02 which made the average %difference 75% and an added mass coefficient was derived C_AM=0.09 for the Added Mass model which made possible an average %difference of 73%. By contributing to an improvement in the prediction of the bubble departure diameter LWRs can operate safely closer to their maximum operating point, thus allowing an increase in efficiency, lower operating cost or less fuel consumption.
PublicationDesarrollo de bebida estimulante a base de sandía [𝘊𝘪𝘵𝘳𝘶𝘭𝘭𝘶𝘴 𝘭𝘢𝘯𝘢𝘵𝘶𝘴 (Thunb.) Matsum.et Nakai.]( 2023-04-04)There is a high demand for fresh and healthy products that has produced an increase in the consumption of natural products such as fruit juice. The demand for fresh products has moved the industry to create energy drinks using fruit juice. Due to the demand of products with high nutritional value, a thermal treatment was applied to the watermelon juice to extend the shelf life of the energy drink. This study aims to determine the effect of pasteurization and the incorporation of milk-based protein in the product’s shelf life. In addition, other qualities such as the final acceptability, physiochemical parameters (color, pH, total soluble solids (˚brix), vitamin C, acid titration, water activity (aw), and microbiology analysis (yeast, fungi, and aerobics) were performed. The energy drink was created by using different juice percentages (30, 40, 50 and 70) and supplementing the juice with the following ingredients: 9.57% saccharose, 0.5% vitamin C, 0.05% citric acid, 0.05 caffeine, 0.24% theobromine, and 0.20% citrulline. Three different formulations were created and identified as follows: Formulation A (No Pasteurization-Protein), Formulation B (Pasteurized-No Protein), Formulation C (Pasteurized- Protein). From the sensory analysis we can conclude that the formulation with 50% watermelon juice had a final consumer acceptability of 6.7 and was used as base for the energy drink (n=75). The energy drink was processed for 45 seconds at a temperature of 80˚C, bottleled in 7oz plastic containers, and analyzed for a period of 3 to 6 months (4˚C). Formulation A presented product shelf life of 2 weeks, while Formulation B had a product shelf life of 6 months and Formulation C of 2 months and 3 weeks. In Formulations B and C the pasteurization significantly reduced the concentration of vitamin C, there was also a reduction in the color of the drink (saturation and tone) as well as in the acid titration. In addition, pasteurization decreased the microorganism growth in Formulations B and C when compared to Formulation A. The addition of protein showed significant differences in pH, titratable acidity ˚Brix and color in Formulation C. Using thermal treatments such as the pasteurization method allows the product’s shelf life to be increased therefore reducing the number of microorganisms in the juice and maintaining the stability of the product.