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.
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PublicationEstudio de kumquat (𝘍𝘰𝘳𝘵𝘶𝘯𝘦𝘭𝘭𝘢 𝘮𝘢𝘳𝘨𝘢𝘳𝘪𝘵𝘢) injertado en cuatro patrones y evaluación de formulaciones de fertilizantes en distintas dosis para su producción como cítrico ornamental( 2023-12-05)The main objective of this project was to evaluate the cultivation of Fortunella margarita (Kumquat) for its production as an ornacitrus. Graft survival was compared in four rootstocks ('Cleopatra', 'Flying Dragon', 'HRS-812', and 'Volkameriana'). The graft survival in 'HRS-812' resulted in the highest success with 53%, ‘Volkameriana’ with 29.2%, ‘Cleopatra’ with 11.9%, and 'Flying Dragon' was the lowest with 5.8%. In addition, its development when grafted on 'HRS-812' and cultivated in pots of 11.34 L inside a structure was studied by applying a high and low dosages of two fertilizers formulations: 13-6-9 (low dosage 27 g and high dosage 42 g) and 5-2-6 (low dosage 30 g and high dosage 44 g). The following parameters were evaluated: rootstock stem diameter, graft height and diameter, flower count, number of fruits, and chlorophyll content. The trees treated with the highest dose of the 13-6-9 fertilizer obtained significantly higher means for rootstock diameter, graft height, and diameter. Applying a low dose of this same fertilizer resulted in a higher number of flowers and quantity of fruits. Leaf tissue analysis showed a sufficient range for the macronutrients Ca, S, P, K, Na, and the micronutrients B, Mn, and Zn. There was a deficiency of N and Mg, an excess of Cu and high value of Fe. Tree development grown in pots in the open field was also studied, considering the same parameters, but applying three fertilizers (13-6-9, 15-3-19, and 15-5-15) in two doses: high 142 g, and low 42 g. Higher means for height and number of flowers were obtained when applying the 13-6-9 fertilizer at the highest dose. The rootstock diameter and canopy width had higher means when applying the 15-3-19 fertilizer at the highest dose. There was no difference in graft diameter or number of fruits. When analyzing the leaf tissue, a sufficient range was obtained for the nutrients Ca, S, P, K, B, Mn, and Fe. Nitrogen and Mg were deficient, Zn was low, and Cu was in excess. The amount of chlorophyll was higher when using 13-6-19 for trees grown in the structure and in the open field than the other fertilizers. The pH and electrical conductivity were measured. Most of the treatments remained within acceptable ranges regardless of the fertilizers applied throughout both experiments. Kumquat production is recommended as an ornamental in Puerto Rico using the rootstock 'HRS-812' and the use of 13-6-9 fertilizer in doses of 142 g for the cultivation of Kumquat in pots and including foliar applications of Ca and Mg.
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PublicationCaracterización química de la leche de cabra producida en diferentes regiones agrícolas de Puerto Rico( 2023-12-08)Goats produce approximately 2.4% of the global milk supply. There is evidence that in Puerto Rico (P.R.) there is consumer interest in goat milk and its derivative products. However, there is no literature on the composition of goat milk produced in P.R. This project sought to analyze and compare the chemical characteristics of goat milk produced in 5 agricultural regions of the island. Between January and June 2022, 6 samples were collected from each region (N=30). For these, the moisture content, total solids, water activity (aw), crude fat, crude protein, lactose, minerals, lactic acid, and pH were evaluated. The results show that there are significant differences for certain characteristics between the regions. It is inferred that these variations are due to differences in feeding and herd management. However, the studied goat milk contains similar values of water (88.04 ± 1.75%), aw (0.9945 ± 0.001), crude fat (3.34 ± 1.07%), crude protein (3.03 ± 0.42), lactose (2.95 ± 0.43%), pH (6.78 ± 0.22), sodium (59 ± 11mg/100g), magnesium (14 ± 4mg/100g) and iron (0.08 ± 0.1mg/100g) when compared with the literature. In addition, it contains higher values of total minerals (0.84 ± 0.08%). Meanwhile, it has lower values of lactic acid (0.11 ± 0.05%) and calcium (105 ± 36mg/100g). This study suggests that the composition of milk produced in P.R. varies in certain characteristics from those produced in other countries, including the United States. Also, its composition may vary between agricultural regions. Therefore, establishing routine analyzes such as these would help to standardize and optimize the goat milk industry in P.R. In addition, knowing the composition of milk allows for the correct labeling and marketing of milk and its derivative products.
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PublicationA wide dynamic range RF-DC rectifier circuit for a 900MHz energy harvesting system using 180nm CMOS technology( 2023-12-07)En los captadores de energía de RF, la eficiencia del rectificador RF-DC viene determinada por la potencia de RF de entrada, que suele fluctuar debido a las pérdidas en el espacio libre y a las interferencias de la señal, entre otras causas. Para maximizar la transferencia de potencia de RF, el rectificador RF-DC debe mantener una eficiencia de conversión de potencia (PCE) cercana al máximo en un amplio rango de entrada, conocido como rango dinámico (DR). Sin embargo, esto presenta retos a bajos niveles de potencia debido a la tensión umbral del transistor y a altos niveles de potencia debido a las corrientes de fuga inversas del transistor. Este trabajo presenta un rectificador diferencial RF-DC de 900 MHz para sistemas de captación de energía optimizado para un amplio rango dinámico. La arquitectura propuesta incorpora un circuito de realimentación adaptativo para maximizar la transferencia de potencia a niveles bajos de potencia de entrada y reducir las corrientes de fuga a niveles medios y altos de potencia de entrada. Se ha diseñado, simulado y fabricado un prototipo del rectificador RF-DC en la tecnología CMOS de 180 nm Mixed-Mode/RF de UMC. Los resultados de la simulación muestran dos eficiencias de conversión de potencia de pico del 84,49% a -11,34 dBm y del 82,71% a -24,16 dBm, una RD teórica de 30 dB, una RD práctica de 16.56 dB y una sensibilidad de -18,99 dBm.
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PublicationCharacterization of automation systems development in the medical device industry: design of a process model( 2023-12-03)This research presents a comprehensive process model for the implementation of Automation Systems (AS) projects in the medical device industry. To build this model, seven Subject Matter Experts (SMEs) were interviewed aiming to capture their know-how, practices, and lessons learned. The study revealed how AS are implemented from different angles thanks to the diversity of companies and roles of the SMEs. An Agile-Stage-Gate model is incorporated as a contribution of this work. This model was validated with four experts who mentioned activities, roles, deliverables missing in the first version of it. After the first round of validation, all experts agreed on the completeness and readiness of the process model. This graphical tool presents, defines, and organized the process in a simplified way. It represents the consensus among SMEs about how to develop AS. This process model defines phases, steps, activities, deliverables, tools, decisions, and critical tasks inside the project.
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PublicationSpatial ecology of the yellow-shouldered blackbird during the post-fledgling period and its implication on population growth( 2023-12-05)In this thesis I showcase the results of a two-year study, conducted in Pitahaya mangrove forest and “Bahía Sucia” in southwestern Puerto Rico, focusing on estimating survival of the Yellow-shouldered Blackbird during the post-fledging period during the 2019 and 2020 breeding seasons. In this study, a total of 51 fledglings were tagged with radio-transmitters. The wing chord (p=0.005) and tarsus (p=0.035) were longer in 2019 than in 2020, but no significant difference was found in mass (p=0.94). Size disparity within nests revealed older siblings larger and more developed than younger ones, with significant mass differences (p=0.01). Older siblings also displayed superior flight capabilities, with 81% reaching the edge of the mangrove forest when fledging, compared to only 18% of younger ones. Survival rates between the two years showed little variation, with six deaths occurring among the tagged fledglings, resulting in survival rates of 0.897 (2019) and 0.870 (2020) – a non-significant difference (p=0.80). Initial post-fledging behavior had fledglings perched low, begging for food. However, by day 20, their plumage resembled that of adults, but they could still be identified by their begging behavior. Parental feeding decreased after 30-40 days but continued up to 62 days post-fledging. Mean, home range size for the 2019 and 2020 groups, using the MCP method, was 65 ha and 265 ha, respectively, and using KDE was 228 ha and 391 ha. However, these differences were not statistically significant. The morphological traits of wing chord length, and tarsus length showed significant relationship with home range size, while weight did not. This study also included the use of a seasonal population matrix model to determine the influence of each life stage on population growth, adjusting for species-specific sex ratios and using clutch sizes from the two years. Using stage transition matrices, the analysis identified adult survival as a critical factor in the species' population growth. Emphasizing the reproductive value of adults due to their ability to survive, this study also highlighted the importance of clutch and nestling survival, implying vulnerability to both density-dependent and non-density-dependent factors. The results indicate that the YSBL population in southwestern Puerto Rico is currently declining at a rate of approximately 42% per year. Furthermore, the multiple factors identified underscore the need for adaptive conservation and suggest a comprehensive approach to understanding the reproductive patterns and survival determinants of the Yellow-shouldered Blackbird.