BDTD - Biblioteca Digital de Teses e Dissertações
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Master Thesis Análise da vulnerabilidade à seca na Bacia do Rio Apodi-Mossoró(Universidade Federal do Rio Grande do Norte, 2025-10-31) Macedo, Igor Tauan Santiago Lopes de; Silva, Jonathan Mota da; https://orcid.org/0000-0001-9995-8451; http://lattes.cnpq.br/3379521354576211; https://orcid.org/0009-0006-7639-5506; http://lattes.cnpq.br/9133105797769854; Mutti, Pedro Rodrigues; http://lattes.cnpq.br/5475390537931966; Pessoa, Zoraide Souza; https://orcid.org/0000-0002-9509-5027; http://lattes.cnpq.br/7738736219606737; Reis, Gabriela de Azevedo; http://lattes.cnpq.br/8941140624803701Drought, a natural phenomenon increasingly intensified by climate change, poses a growing threat to arid and semi-arid regions, where its impacts directly affect water security, agricultural production, and the socioeconomic conditions of local populations. This study assessed drought vulnerability in the Apodi-Mossoró River Basin (BHRAM), located in the semi-arid region of Rio Grande do Norte (Brazil), aiming to identify the most susceptible areas to water scarcity and support strategies for living with drought. The research considered multiple dimensions — socioeconomic, climatic, environmental, and water management — analyzed across different spatial scales, from the basin domain to the municipal level, while accounting for local adaptive capacity. The iSECA model, adapted to regional conditions, was applied to integrate indicators from these dimensions and produce a spatially explicit vulnerability index. Results revealed marked structural inequality among the four Delimitated Units (UDs) of the basin. The Upper Course exhibited High to Extreme vulnerability, driven by socioeconomic fragility and strong climatic exposure. The Upper Middle Course presented a heterogeneous pattern, with High to Very High vulnerability, influenced by rainfall irregularity and limited water infrastructure. The Lower Middle Course stood out as the least critical area, showing Low to Moderate vulnerability, acting as a buffer zone due to a better balance between exposure and adaptive capacity. Conversely, the Lower Course emerged as the most vulnerable region, with predominance of Very High and Extreme classes, reflecting high water demand and low surface storage capacity. Additionally, a perception analysis was conducted with public managers, civil defense representatives, and members of the river basin committee to compare the modeled vulnerability with the perceived drought impacts. The responses confirmed strong correspondence between both perspectives, highlighting irrigated agriculture, livestock farming, and domestic water supply as the most affected sectors. The findings demonstrate that drought vulnerability in the BHRAM transcends climatic variability, reflecting a complex interaction of physical, social, and institutional factors. The study provides a comprehensive and integrated understanding of the multiple dimensions of vulnerability, contributing to the development of resilient public policies and evidence-based decisionmaking at different management levels. It emphasizes the need to strengthen participatory water governance, invest in infrastructure adapted to semi-arid conditions, and promote education and community awareness as key pillars for a sustainable and resilient coexistence with droughts.Master Thesis Síntese e estudo do óxido de alta entropia (Fe0,2,Ni0,2Co0,2Al0,2Zn0,2)3O4 pelo método sol-gel assistido por polivinilpirrolidona (PVP) e sua aplicação como eletrocatalisador para a reação de evolução de oxigênio(Universidade Federal do Rio Grande do Norte, 2025-06-02) Vasconcelos, Gabriel dos Santos; Gomes, Uilame Umbelino; Torres, Marco Antonio Morales; http://lattes.cnpq.br/0091292234916055; http://lattes.cnpq.br/9858094266525225; http://lattes.cnpq.br/2806155952751330; Mashhadikarimi, Meysam; https://orcid.org/0000-0003-1449-3654; http://lattes.cnpq.br/9422624675887080; Silva, Ariadne de Souza; https://orcid.org/0009-0002-9675-0748; http://lattes.cnpq.br/5623381698478389; Raimundo, Rafael Alexandre; https://orcid.org/0000-0002-9943-9464; http://lattes.cnpq.br/9772819884310876High-entropy oxides (HEOs) have emerged as a promising class of functional materials due to their tunable electrochemical and magnetic properties, with potential applications in electrocatalysis, energy storage, and electronic devices. In this context, the present study aims to synthesize and thoroughly characterize the high-entropy oxide (Fe₀.₂Ni₀.₂Co₀.₂Al₀.₂Zn₀.₂)₃O₄, referred to as HEO-600, synthesized at 600 °C via the sol-gel method assisted by polyvinylpyrrolidone (PVP). Additional samples were produced at higher temperatures, revealing the formation of distinct crystalline phases, including spinel-type and rock-salt structures. Structural and compositional characterization was carried out using various techniques, including X-ray diffraction (XRD), field-emission scanning electron microscopy (FEG-SEM) with energy-dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). XPS analysis confirmed the equimolar composition of the elements in the HEO-600 sample, whereas the EDS analysis revealed a homogeneous distribution of cations, corroborating the formation of a uniform solid solution. TEM micrographs showed well-dispersed, non-agglomerated particles with an average size of 9.2 nm. The magnetic properties of the HEO-600 sample were investigated using Mössbauer spectroscopy, direct current (DC) magnetometry, and alternating current (AC) magnetometry. The Mössbauer spectrum indicated that iron ions were distributed between tetrahedral (A) and octahedral (B) sites in a 43% and 57% ratio, respectively, confirming a partially inverted spinel structure. Magnetic susceptibility measurements (DC and AC) revealed superparamagnetic behavior at room temperature, as well as the presence of a spin glass-like phase, with a transition temperature at 206 K. This magnetic phase was suppressed under an external field of approximately 4300 Oe, highlighting the complexity of magnetic interactions in the system. In addition to structural characterization, spectroscopic and electrochemical analyses were performed to evaluate the catalytic potential of the HEO-600 sample for the oxygen evolution reaction (OER). Fourier-transform infrared (FTIR) spectroscopy provided additional information on the vibrational configuration of the system, and the chemical bonds present in the oxide. Electrochemical experiments demonstrated that the HEO-600 sample exhibits promising performance for OER, with an overpotential of 358 mV at a current density of 10 mA cm⁻². This value indicates competitive catalytic activity compared to other transition metal-based high-entropy oxides. Thus, this work significantly contributes to the advance in the understanding of the structural, magnetic, and electrochemical properties of high-entropy oxides. The results obtained not only expand the knowledge of the correlation between synthesis, structure, and properties of these materials but also highlight their potential for technological applications in electrochemical catalysis.Master Thesis Desenvolvimento de nanocompósitos cimentícios a base de nanoplacas de grafeno para aplicações em poços CCS(Universidade Federal do Rio Grande do Norte, 2025-12-12) Silva, Dayanne Gabriella da; Martinelli, Antonio Eduardo; https://orcid.org/0000-0003-3885-9104; http://lattes.cnpq.br/0022988322449627; http://lattes.cnpq.br/3415325334445679; Freitas, Júlio Cézar de Oliveira; https://orcid.org/0000-0003-1324-9705; http://lattes.cnpq.br/2357217530716519; Braga, Glauco Soares; http://lattes.cnpq.br/4514550024139119Carbon Capture and Storage (CCS) is a fundamental technology for reducing largescale greenhouse gas emissions. This technique enables the safe confinement of carbon dioxide (CO₂), one of the main contributors to global warming, in deep geological formations, thereby limiting its release into the atmosphere. To implement this technology, it is essential to construct wells that allow the injection of CO₂ captured from industrial sources, ensuring secure storage and preventing its return to the surface. In this context, the cementitious material responsible for zonal isolation and well structural integrity must exhibit high chemical and mechanical resistance, as its degradation by CO₂ can compromise the long-term durability of the system. Thus, the incorporation of nanomaterials such as graphene nanoplatelets (GNPs) into cement pastes emerges as a promising approach, since their two-dimensional lamellar structure and high aspect ratio can enhance the mechanical strength, conductivity, and chemical stability of the cementitious system. Additionally, GNPs offer high scalability and lower cost compared with other graphene-based derivatives. This study aimed to evaluate the effect of different GNP concentrations (0.03%, 0.06%, and 0.09% BWOC) on the mechanical strength, permeability, and chemical resistance of cement pastes. The formulations were subjected to carbonation tests under supercritical CO₂ conditions in an aqueous medium, with evaluations performed after 7, 14, and 28 days of exposure. Complementary analyses, including X-ray Diffraction (XRD), Thermogravimetry (TG), and Scanning Electron Microscopy (SEM), were conducted to identify and quantify hydration and carbonation products formed before and after chemical attack, as well as to assess GNP dispersion within the cement matrix and its influence on product formation. The results showed that GNP-containing pastes exhibited increased compressive strength and reduced permeability, particularly at early curing ages. Carbonation was also slowed by the addition of GNPs, with the 0.06% concentration demonstrating the best performance. Microstructural analysis revealed well-dispersed GNPs in the cement matrix and the presence of carbonation products, while thermal and crystallographic analyses indicated the effect of GNP addition on the formation of compounds before and after CO₂ exposure. Therefore, the results indicate that GNPs present strong potential for the development of cementitious nanocomposites designed for CCS well construction.Master Thesis Modelagem hidrológica do efeito da expansão urbana no regime hidrológico do Rio Pitimbu(Universidade Federal do Rio Grande do Norte, 2025-08-29) Lima, Lucas Luan Maia de; Silva, Jonathan Mota da; https://orcid.org/0000-0001-9995-8451; http://lattes.cnpq.br/3379521354576211; http://lattes.cnpq.br/9430179940138200; Leal, Karinne Reis Deusdará; http://lattes.cnpq.br/7837242989204504; Saad, Sandra Isay; https://orcid.org/0000-0002-4380-3175; http://lattes.cnpq.br/0103102694865890Water security is one of the main challenges for water management and urban supply in Brazil. Ensuring it requires the conservation and restoration of water resources, as well as guaranteeing water availability that meets the needs of multiple uses. Imbalances in the water budget are a key dimension of water insecurity, often leading to the onset of water crises. Among the processes that can cause such imbalance is urban expansion. In this context, the urban watershed of the Pitimbu River—which supplies roughly 30% of the southern portion of Natal—has undergone intense land-use and land-cover changes, particularly the expansion of urban areas. The effects of this expansion have not yet been well investigated regarding its impacts on the hydrological regime of the basin, nor on future water-security risks if urban growth continues.Thus, the objective of this study was to evaluate the effects of urbanization, and its expansion, on the hydrological regime of the Pitimbu River basin for the land-use and land-cover conditions of 1985, 2022, and 2047. To this end, long-term hydrological simulations (over 30 years) were performed using the distributed hydrological model SWAT (Soil and Water Assessment Tool Account Procedure), which requires spatial physical data (topography, vegetation cover, and soil types) and meteorological inputs. The daily hydrological regime was simulated for the years 1986–2019. Spatial analysis of land-cover change revealed that urbanization increased by 20% between 1985 and 2022, with an additional 12% projected by 2047 according to the mapping conducted with the InVEST model, indicating an accelerated occupation process. The simulations showed that this expansion significantly altered the basin’s hydrological behavior, intensifying surface runoff and reducing baseflow and lateral flow. Flow-duration curves and their quantiles, as well as the annual discharge cycle, confirmed an increase in the irregularity of the hydrological regime—characterized by higher flood peaks and lower dry-season flows. This shift reflects changes in the temporal distribution of streamflow, with a tendency toward higher maximum flows and lower minimum flows, compromising the reliability of water supply and posing risks to the region’s water security.Master Thesis Aplicação do modelo SPEEDY para a simulação dos eventos de El Niño baseado nas categorias e ensemble(Universidade Federal do Rio Grande do Norte, 2025-09-30) Ferreira Neto, José Augusto; Mendes, David; https://orcid.org/0000-0003-1418-5109; http://lattes.cnpq.br/4411895644401494; https://orcid.org/0009-0002-5733-1591; http://lattes.cnpq.br/0401494432064481; Oliveira, Cristiano Prestrelo de; https://orcid.org/0000-0003-2871-1595; http://lattes.cnpq.br/2461244145338043; Oliveira Júnior, José Francisco de; Gonçalves, Weber Andrade; http://lattes.cnpq.br/3901367142857642Several factors modulate or influence Earth's climate and its variability, among them atmospheric teleconnections—patterns that, originating in one region of the globe, affect the climate in remote areas. One of the most important modes of climate variability is the El Niño–Southern Oscillation (ENSO), whose positive phase, El Niño, exerts significant impacts in Brazil, such as droughts in the North and Northeast and excessive rainfall in the South. This study assessed the predictive skill of the SPEEDY model in simulating the impacts of El Niño events of varying intensity on the North, Northeast and South regions of Brazil. Monthly ensemble forecast simulations comprising 100 members were used for El Niño events categorized on the basis of the Oceanic Niño Index (ONI, Niño 3.4). The model was evaluated for three variables—large-scale precipitation, convective precipitation, and 2-m air temperature—by comparison with ERA5 reanalysis data. Forecast skill, reliability, and uncertainty were quantified using the following metrics: Brier Score (BS), Continuous Ranked Probability Score (CRPS), and Relative Operating Characteristic (ROC). The results indicate that the SPEEDY model exhibits skill in capturing the large-scale patterns associated with intense El Niño events. However, systematic biases were identified: temperature is overestimated in the Amazon and underestimated in the South. Convective precipitation is overestimated in the South and underestimated in the Northeast and North, with the largest errors occurring principally for extreme values. The ensemble exhibited underdispersion and a weak spread–skill relationship, indicating an underestimation of forecast uncertainty. Spatial coherence of the forecasts was greater for events classified as strong and very strong El Niños, and diminished for events classified as moderate and weak. We conclude that the SPEEDY model displays substantial variability in the reliability of its forecasts across different regions of Brazil and as a function of El Niño event intensity.Doctoral Thesis Evolução do uso e ocupação do solo e seus impactos na vazão da bacia hidrográfica do rio Maxaranguape: uma análise histórica e de modelagem hidrológica(Universidade Federal do Rio Grande do Norte, 2025-08-11) Gomes, Kaline Muriel de Figueiredo; Silva, Jonathan Mota da; https://orcid.org/0000-0001-9995-8451; http://lattes.cnpq.br/3379521354576211; http://lattes.cnpq.br/8065941309451571; Rodrigues, Daniele Tôrres; https://orcid.org/0000-0003-4307-2832; http://lattes.cnpq.br/4682555268827167; Silva, Fabrício Daniel dos Santos; https://orcid.org/0000-0002-3185-6413; http://lattes.cnpq.br/9324908747974694; Tavares, Jean Leite; http://lattes.cnpq.br/5264177368997967; Medeiros, Joana Darc Freire de; http://lattes.cnpq.br/1359759456699671Unplanned agricultural expansion accelerates the transformation of land use and occupation, putting pressure on natural ecosystems and damaging water resources. Although there are extensive deforested areas in Brazil, agricultural expansion still occurs over natural ecosystems, such as the watershed Maxaranguape, where this pressure is pronounced, with the conversion of natural areas into agricultural areas. The objective of this study was to analyze the evolution of land use and occupation and its impacts on the streamflow regime of the watershed Maxaranguape, based on the analysis of trends in Hydroclimatic variables and hydrological modeling. In the latter, two scenarios were considered: an optimistic one (S1), in which agricultural expansion occurs over degraded pasture areas, and the other business-as-usual scenario (S2), in which agricultural expansion occurs over natural vegetation. The trend analysis of the historical series of precipitation and evapotranspiration did not indicate a significant change; on the other hand, the analysis of the average streamflow indicated a significant decrease of 0.07 m³/s per year (2.28% per year of the average annual streamflow). In the analysis of land use and occupation, it was noted that the rate of agricultural expansion grew by 5.8 km²/year in the river basin. This rate was the basis for projecting scenarios S1 and S2 for 15 years, which resulted in an increase of 5% and 9% of the agricultural area, respectively. The impact of this expansion resulted in an increase in surface runoff of 11.8% and 13.2%, while underground flow suffered a decrease of 0.6% and 1.1% in scenarios S1 and S2, respectively. In general, the results showed that, in both scenarios, there was a decrease in minimum streamflows and an increase in maximum streamflows, but with different patterns depending on the river section of the watershed evaluated. For all river sections analyzed, the current trend scenario (S2) reduced the minimum streamflow more, especially the largest minimum streamflows. The decrease in the minimum streamflow weakens water availability, and, considering the frequent occurrence of droughts in northeastern Brazil, the current trend scenario S2 promotes greater water insecurity. On the other hand, agricultural expansion over degraded pasture areas (S1), an acceptable scenario, would bring less hydrological disservice, as it would prevent the advance of agricultural areas over natural vegetation and reduce the impact on water availability.Master Thesis Caracterização geoquímica em solos na Bacia Potiguar (Onshore): subsídios para definição de valores de background(Universidade Federal do Rio Grande do Norte, 2006) Nogueira, Mary Lucia da Silva; Melo Júnior, Germano; https://orcid.org/0009-0007-7295-9324; http://lattes.cnpq.br/4424267212835477; http://lattes.cnpq.br/2546229173660779; Oliveira, Francisco; Carvalho, Maria de Fátima Batista de; http://lattes.cnpq.br/2785866053924926Educacional Product Equações do 1° grau(Universidade Federal do Rio Grande do Norte, 2025-08-29) Ayronn da Silva Santos; Gutierre, Liliane dos Santos; https://orcid.org/0000-0001-5628-9569Doctoral Thesis Assimilação variacional multiescala de profundidade óptica de aerossóis atmosféricos com o sistema EURAD-IM no nordeste brasileiro(Universidade Federal do Rio Grande do Norte, 2025-09-08) Münchow, Gabriel Bonow; Hoelzemann, Judith Johanna; Oliveira, Cristiano Prestrelo de; https://orcid.org/0000-0003-2871-1595; http://lattes.cnpq.br/2461244145338043; http://lattes.cnpq.br/6590472437235971; http://lattes.cnpq.br/8280352824217134; Alves, Rita de Cássia Marques; https://orcid.org/0000-0001-7804-8141; http://lattes.cnpq.br/7123107007429083; Martins, Leila Droprinchinski; https://orcid.org/0000-0003-2176-6534; http://lattes.cnpq.br/8069461151838819; Oliveira, Pablo Eli Soares de; https://orcid.org/0000-0003-1172-6870; http://lattes.cnpq.br/9234882860270063This thesis aims to improve numerical simulations of particulate matter in the Northeast of Brazil (NEB), covering scales from regional to intra-urban, using the threedimensional variational assimilation of aerosol optical depth at 550 nm (AOD550) data with the EURopean Air Pollution Dispersion – Inverse Model (EURAD-IM) atmospheric chemical transport model. The motivation stems from the relevance of atmospheric aerosols in the Earth’s radiative balance, in the modification of the hydrological cycle, and in the degradation of air quality, directly affecting climate and public health. The NEB, although influenced by the intercontinental transport of mineral dust from Africa and by local sources such as biomass burning and vehicular emissions, suffers from a scarcity of observational data, which hinders the diagnosis and monitoring of air pollution. In this context, the integration between numerical modeling and observational data is essential to reduce uncertainties and improve the representation of the atmospheric chemical state. This study uses MODIS AOD550 retrievals products: Deep Blue (DB), Dark Target (DT) at 10 km and 3 km resolutions, and MAIAC at 1 km resolution. These products are evaluated and compared with data from the AERONET network sites at Petrolina-PE and Natal-RN. Their spatial and temporal behavior also is analyzed across the NEB biomes. This stage aims to identify the most accurate product(s) for the region for subsequent assimilation into the EURAD-IM system. The EURAD-IM models are configured with three nested grids, ranging from 20 km resolution over the entire NEB, 5 km over the northeastern sector covering the metropolitan regions of Fortaleza-CE, Recife-PE, and Natal-RN, and a 1 km grid over Natal. The methodology includes experiments assimilating AOD550 data from the MAIAC, DB, and DT products. Validation of these experiments is carried out using independent AERONET AOD observations and particulate matter (PM10) concentration measurements from air quality monitoring stations in the states of Bahia and Pernambuco. When comparing AOD with AERONET data, the DB and MAIAC products show the best results. A strong relationship is observed in the NEB between the temporal pattern of aerosol loading in the atmosphere and local fire hotspots in different biomes. The data assimilation experiments demonstrate increased accuracy in AOD550 simulations when including MODIS data, particularly the MAIAC product. There is a reduction of up to 24% in RMSE, a decrease in biases, and an increase in correlation with AERONET data. However, the analysis of simulated surface PM10 concentrations indicates that the data assimilation experiments reduced model accuracy compared to EURAD-IM simulations without assimilation. These results demonstrate the great potential of assimilating AOD550 data with the EURAD-IM model for the NEB region. However, adjustments in the assimilation system are necessary, especially in the method for vertical profile correction and in the homogeneous correction among the different particle types simulated by the model.Educacional Product Povo Potiguara da Paraíba e a presença da geometria em suas pinturas corporais(Universidade Federal do Rio Grande do Norte, 2025-08-28) Gomes, Leonardo Cinésio; Cury, Fernando Guedes