Teses em Engenharia de Recursos Naturais da Amazônia (Doutorado) - PRODERNA/ITEC

URI Permanente para esta coleçãohttps://repositorio.ufpa.br/handle/2011/4045

O Doutorado Acadêmico inicou-se em 2006 e pertence ao Programa de Pós-Graduação em Engenharia de Recursos Naturais da Amazônia (PRODERNA) do Instituto de Tecnologia da UFPA (ITEC) da Universidade Federal do Pará (UFPA).

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Acesso aberto (Open Access)
Análise de vibrações mecânicas em estruturas esbeltas e flexíveis, como cordas e vigas, sujeitas à movimentação axial utilizando a técnica da transformada integral generalizada
(Universidade Federal do Pará, 2024-05-28) PORFÍRIO, Rogilson Nazaré da Silva; MACÊDO, Emanuel Negrão; http://lattes.cnpq.br/8718370108324505; QUARESMA, João Nazareno Nonato; http://lattes.cnpq.br/7826389991864785; https://orcid.org/0000-0001-9365-7498
The dynamic analysis of vibrations on flexible structures is of an extreme importance in engineering and its solution represents a significant challenge to be tackled. This study has the objective to investigate thin and flexible structures such as beams and ropes, that oscillate in supports clamped-clamped and clamped-concentrated mass, which determine the boundary conditions of the analysis problem. Using the generalized integral transformation technique (GITT) that converts the partial differential equation (PDE) developed by the Hamiltonian method in an Ordinary Differential Equation (ODE), it optimizes the numerical process andcontrols efficiently the relative error of the calculations. In this study, it was developed and applied an innovative method that treats the boundary conditions without the use of filters to homogenize the equations. The calculations methodology was implemented in Fortran, utilizing a sub-routine DIVPAG of IMSL. As reference, a thorough analysis of convergence and stableness was applied, considering the behavior of four different models of ropes and two models of beams. The validation of methodology was approached comparing functional aspects such as transversal displacement, system velocities, frequencies, and damping, with results obtained by GITT and other studies that applied the same simulation conditions. The results of this study were found to be satisfactory, which highlights the relevancy of application of this vibration analysis method. It was also assessed the application of this method in different vibration configurations in each model, which exemplifies its broad potential in problems involving the structures analyzed. Therefore, this study represents a significant contribution to the advance of knowledge in dynamic modeling of thin and flexible structures and highlights the influence of boundary conditions in vibrational characteristics of these structures.Furthermore, it introduces an innovative methodology for treating boundary conditions without the use of filters, expanding the analysis possibilities in this field of engineering.
Acesso aberto (Open Access)
Análise do escoamento magnetohidrodinâmico micropolar de sangue e da captura magnética de nanopartículas em vasos sanguíneos
(Universidade Federal do Pará, 2025-05-09) PONTES, Fábio de Andrade; MIYAGAWA, Helder Kiyoshi; http://lattes.cnpq.br/5848592858919971; MACÊDO, Emanuel Negrão; http://lattes.cnpq.br/8718370108324505
The aim of this work is to numerically analyze the transient two-dimensional magnetohydrodynamic pulsatile flow of micropolar blood considering the heat, mass and momentum transfers through a blood vessel in the presence of a magnetic field applied in the region of a symmetrical stenosis. The flow is considered laminar and incompressible and the magnetic nanoparticles are injected into the blood vessel and captured by the action of the magnetic field in the stenosis. The Method of Lines (MOL) was applied in the spatial discretization of the radial variable of the original 2D-transient model transforming it into a system of 1D-transient PDEs, which was solved numerically by the NDSolve subroutine of the Mathematica 13.1 software. The results of the converged MOL are verified with the results generated by the NDSolve subroutine applied directly to the original 2D-transient model and both are also compared with an analytical solution obtained for the limiting case, obtaining a good agreement between them. The effects of physical model parameters such as Lewis, Hartmann and Womersley numbers, the nanoparticle death kinetic constant and the mass Biot number are studied. The results show that in stenosis the flow is decelerated due to the magnetic field, as well as the microrotation velocity. The nanoparticle fraction field is also affected by the presence of the magnetic field, with concentration being increased in the stenosis region. The average velocity and microrotation increase in stenosis due to the narrowing of the arterial lumen. The average temperature and volumetric nanoparticles fraction are also elevated in the stenotic region due to the action of the magnetic field.
Acesso aberto (Open Access)
Estudo das ftalocianinas metálicas na adsorção de gases do efeito estufa e poluentes utilizando docagem molecular
(Universidade Federal do Pará, 2025-04-30) SOUSA, José Antonio Ferreira de; OLIVEIRA, Mozaniel Santana de; http://lattes.cnpq.br/0810227136654245; CHAVES NETO, Antonio Maia de Jesus; http://lattes.cnpq.br/3507474637884699
Atmospheric pollution, driven by the emission of toxic gases, represents an environmental and public health challenge. This study investigates the application of phthalocyanines (Pc) and metal phthalocyanines (MPc) of iron (FePc), cobalt (CoPc), copper (CuPc), zinc (ZnPc), and titanium (TiPc) for the capture of gases such as carbon dioxide (CO₂), carbon monoxide (CO), ammonia (NH₃), hydrogen cyanide (HCN), hydrogen sulfide (H₂S), and aromatic compounds like benzene (C₆H₆). AutoDock Vina 1.2.0 and Gaussian 09W were the software employed in the molecular docking technique to investigate these interactions. Gaussian 09W enabled adjustments in atomic positions to minimize the total interaction energy and build the molecular models. AutoDock Vina 1.2.0 facilitated the calculation of the most favorable binding mode between the toxic molecules and the MPc and Pc, providing detailed information on the most stable adsorption positions, orientations, and energies. The analyses indicate that MPc and Pc exhibit the best interactions with C₆H₆, while the weakest coupling occurred with H₂S. Among the evaluated substances, the best binding interactions occurred with MPc, and among them, TiPc proved to be the most efficient, exhibiting the strongest attraction to CO₂. These molecules are highly promising for the capture and elimination of the tested molecules and, consequently, constitute fundamental strategies for protecting the environment, promoting public health, and ensuring sustainable development for future generations.
Acesso aberto (Open Access)
. Caracterização física, aspectos morfológicos, comportamentos térmico e mecânico do pecíolo do miriti como um material potencial para aplicações em pás de turbinas eólicas.
(Universidade Federal do Pará, 2024-10-28) GOMES, Igor dos Santos; VAZ, Jerson Rogério Pinheiro; http://lattes.cnpq.br/1623983294183975; WOOD, David Home
In many small wind turbine blades, the internal space between the laminated shells is filled with a core material. In this context, with the aim of enabling the application in both small and large blades, this thesis presents the petiole of the miriti palm (PMP) as a potential material for such applications. PMP is abundant in the Amazon region, and its harvesting does not harm the palm, as the petiole regrows, making the process fully sustainable. This could play an important role in enhancing the sustainability of wind turbine manufacturing. The physical properties, morphological aspects, and thermal and mechanical behaviors of PMP were determined and compared to balsa wood (BW). Additionally, the advantages of using the easily worked petiole for the core in manufacturing were considered, as demonstrated by the construction of a 0.598 m blade and starting performance tests of the turbine in both computational simulations and wind tunnel experiments. The results showed that PMP is about 50% less dense than BW. Consequently, turbine starting simulations indicated that the low density of the small blade made from PMP reduces starting time by 10% compared to EPS and by 42% compared to BW. While PMP and BW have similar morphological aspects as they are natural materials, BW tends to absorb about 3.6% more moisture and around 9% more water than PMP. The thermal behavior of PMP shows stability up to approximately 200°C, making it suitable for most wind turbine manufacturing processes. Regarding mechanical properties such as tensile, compression, bending, and shear strength, both BW and PMP exhibited elastoplastic behavior. Although BW generally possesses higher mechanical properties than PMP, the specific properties of PMP are greater than those of BW, except in cases where the load application does not align with the vascular bundle direction. For instance, the specific elastic strength and specific elastic modulus in tensile with a load applied at 90° in relation to the vascular bundle and in tensile with a load applied at 0° in relation to the vascular bundle of the PMP are approximately 13.5%, 3%, 30% and 61% higher than those of the BW, respectively. PMP’s specific elastic strength in GS compression is approximately 18.5% higher than BW. In shear strength, the specific elastic strength and specific modulus of elasticity of PMP are 20% and 54.5% higher compared to BW. Fatigue results indicate that PMP has a fatigue life of around 106 cycles. Wind tunnel tests showed that, regardless of wind speed, the best results for power coefficient, torque, and thrust were observed in 6-blade configurations, with values of 0.3083, 0.1224, and 2.2993 for λopt equal to 2.519. In analyzing the experimental results for rotation, thrust, torque, and kinetic energy ratio during turbine starting, the periods through which the turbine transitions between transient and steady states were observed, aligning with literature findings. The results presented in this work show that PMP has potential for application in wind turbine blades, as the combination of sustainable materials with significant specific mechanical properties, such as low density, has the potential to improve turbine design, reduce starting time, and extend the high-efficiency operating range.
Acesso aberto (Open Access)
. Predição das propriedades termodinâmicas do biodiesel e diesel comum, suas blendas e efeitos de aditivos via teoria do funcional da densidade e ensemble canônico.
(Universidade Federal do Pará, 2019-11-08) ROCHA, Adriano Santos da; CHAVES NETO, Antonio Maia de Jesus; http://lattes.cnpq.br/3507474637884699
In this study, we analyzed the thermodynamic properties of soy biodiesel, the most widely used biodiesel source among the world's largest consumers, and rapeseed biodiesel, a source with significant employment in the European Union and biodiesel additives. Also, the study of ordinary diesel was carried out to simulate the situations in which this fuel is in mixtures with different concentrations of biodiesel blends. The objective of this work is to study the thermodynamic properties of the fuels mentioned. Based, where possible, on experimental results to validate the expansion of theoretical results and point out the most appropriate methodology for this type of approach. To this end, computational simulations were carried out with theoretical support in the Density Functional Theory combined with the canonical ensemble model. The functional used in the simulations was type B3LYP with bases 6-31 + (d) and 6-311 + g (d), in addition to the composite method CBS-QB3. The calculated enthalpy values are higher in the biofuels in relation to diesel and the same happened with Entropy. When we analyze the change of Gibbs Free Energy, the largest variations were noted for biofuels. The coefficient of adiabatic expansion revealed lower degrees of freedom until 400 K temperature in both types of biodiesel, from that point all fuels have the same behavior for this property. The lowest relative error was found with the B3LYP/6-311 +g(d) method, with a value of 0.15% for the combustion of ordinary diesel. In relation to biofuels, the same method provided 0.48% relative error in the combustion of rapeseed biodiesel as the best result. Regarding the effects of temperature on these fuels, the results showed that both types of biodiesel are less susceptible to heating than ordinary diesel at all calculated points, always requiring more energy to raise their temperature. The results in the additives showed that the antioxidant pyrogallol that most interferes in the biodiesel properties.
Acesso aberto (Open Access)
Obtenção do óleo e da polpa sem gordura do açaí (euterpe oleracea) por extração supercrítica: caracterização físico-química, estudo da citotoxicidade e vida de prateleira
(Universidade Federal do Pará, 2025-01-06) SIQUEIRA, Letícia Maria Martins; BRASIL, Davi do Socorro Barros; http://lattes.cnpq.br/0931007460545219; https://orcid.org/0000-0002-1461-7306; CARVALHO JÚNIOR, Raul Nunes de; http://lattes.cnpq.br/5544305606838748; https://orcid.org/0000-0002-4433-6580
Açaí is a very important product for the development of the state of Pará, for the bioeconomy and the market has been growing. And currently the majority of the state’s production is just fruit pulp, hence the importance of new products with added value and the need to invest in new sustainable processes for the region’s development. Therefore, the objective of this work was to obtain the oil and pulp without açaí fat by supercritical extraction, determine the main bioactive compounds, evaluate the possible cytotoxicity in MRC-5 and VERO cells in vitro and evaluate the shelf life of the products. The freezedried açaí pulp was subjected to extraction with supercritical CO2, under the conditions 323,15 K at 35 MPa, 333,15 K at 42 MPa and 343,15 K at 49 MPa. The highest yield (51,74 %), carotenoids (277,09 μg/g), DPPH (2,55 μmol TE/g), ABTS (2,60 μmol TE/g) and FRAP (15,25 μm ferrous sulfate/g) from oil and ABTS (644,23 μmol TE/g) from pulp without fat were found at 343,15 K at 49 MPa condition. The highest contents of phenolic compounds (150,20 mg GAE/g d.b.), DPPH (414,99 μmol TE/g d.b.) and FRAP (746,2 μm ferrous sulfate/g) from pulp without fat were found at 323,15 K at 35 MPa condition. The pulp without fat presented high levels of anthocyanins without significant variation. The products did not present cytotoxicity. The half-life of the freeze-dried pulp and the fat-free pulp in the presence of light (Becker) was shorter than that of the packaging materials. The sealed packaging achieved a longer half-life compared to vacuum-sealed packaging for the freeze-dried pulp. However, for the fat-free pulp, the vacuum-sealed packaging showed a longer half-life compared to the sealed one. The results of the stability of açaí oil qualify it as a table oil rather than a frying oil, as it degrades more rapidly at higher temperatures. The results demonstrated that the products have potential applications in the industry.
Acesso aberto (Open Access)
Secagem de açaí branco por liofilização e em leito de jorro: influência da concentração e de diferentes agentes carreadores nas características físicas, químicas, bioativas e colorimétricas do pó obtido
(Universidade Federal do Pará, 2024-04-05) BARROS, Hellen Carvalho; COSTA, Cristiane Maria Leal; http://lattes.cnpq.br/0581730621014796; FARIA, Lênio José Guerreiro de; http://lattes.cnpq.br/7428609361678173; https://orcid.org/0000-0002-9534-9998
The objective of this study was to analyze how the use of four different carrier agents (modified starch, gum arabic, maltodextrin and hydrolyzed collagen) and different concentrations (10, 20 and 30%) influence the white açaí powder produced by lyophilization and in a bed of gush. Yield, moisture, total polyphenols, antioxidant activity, hygroscopicity, solubility, fluidity, color, chemical structure, and morphology were the responses evaluated. In freeze-drying, the yield of the process (≥ 75.40%) and the moisture content of white açaí powder (≤ 4.93 g 100 g- 1) did not differ statistically (p ≤ 0.05), regardless of the agent carrier used. In spouted bed drying, the addition of modified starch or hydrolyzed collagen promoted higher process yield (≥ 42.70%). However, the white açaí produced with hydrolyzed collagen was the only one that had a moisture content ≥ 6.00 g 100 g-1. In both drying processes, powders produced with modified starch were less soluble (≤ 48.96%), despite low hygroscopicity (≤ 13.73 g 100 g-1). Samples produced with maltodextrin or gum arabic showed higher levels of total polyphenols (≥ 8.52 mg EAG g-1) and antioxidant activity (≥ 42.75 μmol ET g-1). In addition, they were more soluble (≥ 94.36%), fluid (11 to 15% according to the carr index), and better preserved the original color of the pulp to the detriment of other formulations. The chemical structure of white açaí powders obtained with different carrier agents was like that of the pulp, indicating efficient encapsulation of bioactive compounds and good preservation of functional groups present in the original raw material, even after drying processes.
Acesso aberto (Open Access)
Descontaminação de máscaras N95 em hospital público de Belém/PA: apresentação e avaliação de protocolo simplificado
(Universidade Federal do Pará, 2024-11-25) MATTOS, Simone Lopes de; DIAS, Carmen Gilda Barroso Tavares; http://lattes.cnpq.br/2113791118142177
he author presents a protocol for decontamination of N95 filter masks by means of short wave ultraviolet irradiation (UV-C), as well as the results of the microbiological validation testing of the UV-C device and qualitative research on the adherence of professionals from the João de Barros Barreto University Hospital, of the University Hospital Complex of the Federal University of Pará (HUJBB) to the aforementioned protocol. The microbiological tests demonstrated the efficacy of the decontamination protocol, as there was no bacterial growth in culture media inoculated with swabs of masks used in the hospital and decontaminated in the UV-C device, which proved the germicidal efficiency of UV-C irradiation. The results of the qualitative research point to the adherence of nursing professionals to the practice of mask decontamination, recognizing the practicality and contribution of the protocol to biosafety and occupational safety. As part of the same protocol, an alternative packaging for storing masks in the intervals of use of N95 masks is presented, considering their safe reuse. The protocol also has the following advantages: low cost and practicality of use, in addition to contributing to the reduction of infectious waste. Descriptors: Decontamination. Ultraviolet Rays. Radiation Dosimeters. Personal Protective Equipment. Respiratory Protection Devices. biosecurity.he author presents a protocol for decontamination of N95 filter masks by means of short wave ultraviolet irradiation (UV-C), as well as the results of the microbiological validation testing of the UV-C device and qualitative research on the adherence of professionals from the João de Barros Barreto University Hospital, of the University Hospital Complex of the Federal University of Pará (HUJBB) to the aforementioned protocol. The microbiological tests demonstrated the efficacy of the decontamination protocol, as there was no bacterial growth in culture media inoculated with swabs of masks used in the hospital and decontaminated in the UV-C device, which proved the germicidal efficiency of UV-C irradiation. The results of the qualitative research point to the adherence of nursing professionals to the practice of mask decontamination, recognizing the practicality and contribution of the protocol to biosafety and occupational safety. As part of the same protocol, an alternative packaging for storing masks in the intervals of use of N95 masks is presented, considering their safe reuse. The protocol also has the following advantages: low cost and practicality of use, in addition to contributing to the reduction of infectious waste. Descriptors: Decontamination. Ultraviolet Rays. Radiation Dosimeters. Personal Protective Equipment. Respiratory Protection Devices. biosecurity.he author presents a protocol for decontamination of N95 filter masks by means of short wave ultraviolet irradiation (UV-C), as well as the results of the microbiological validation testing of the UV-C device and qualitative research on the adherence of professionals from the João de Barros Barreto University Hospital, of the University Hospital Complex of the Federal University of Pará (HUJBB) to the aforementioned protocol. The microbiological tests demonstrated the efficacy of the decontamination protocol, as there was no bacterial growth in culture media inoculated with swabs of masks used in the hospital and decontaminated in the UV-C device, which proved the germicidal efficiency of UV-C irradiation. The results of the qualitative research point to the adherence of nursing professionals to the practice of mask decontamination, recognizing the practicality and contribution of the protocol to biosafety and occupational safety. As part of the same protocol, an alternative packaging for storing masks in the intervals of use of N95 masks is presented, considering their safe reuse. The protocol also has the following advantages: low cost and practicality of use, in addition to contributing to the reduction of infectious waste. Descriptors: Decontamination. Ultraviolet Rays. Radiation Dosimeters. Personal Protective Equipment. Respiratory Protection Devices. biosecurity.he author presents a protocol for decontamination of N95 filter masks by means of short wave ultraviolet irradiation (UV-C), as well as the results of the microbiological validation testing of the UV-C device and qualitative research on the adherence of professionals from the João de Barros Barreto University Hospital, of the University Hospital Complex of the Federal University of Pará (HUJBB) to the aforementioned protocol. The microbiological tests demonstrated the efficacy of the decontamination protocol, as there was no bacterial growth in culture media inoculated with swabs of masks used in the hospital and decontaminated in the UV-C device, which proved the germicidal efficiency of UV-C irradiation. The results of the qualitative research point to the adherence of nursing professionals to the practice of mask decontamination, recognizing the practicality and contribution of the protocol to biosafety and occupational safety. As part of the same protocol, an alternative packaging for storing masks in the intervals of use of N95 masks is presented, considering their safe reuse. The protocol also has the following advantages: low cost and practicality of use, in addition to contributing to the reduction of infectious waste. Descriptors: Decontamination. Ultraviolet Rays. Radiation Dosimeters. Personal Protective Equipment. Respiratory Protection Devices. biosecurity.he author presents a protocol for decontamination of N95 filter masks by means of short wave ultraviolet irradiation (UV-C), as well as the results of the microbiological validation testing of the UV-C device and qualitative research on the adherence of professionals from the João de Barros Barreto University Hospital, of the University Hospital Complex of the Federal University of Pará (HUJBB) to the aforementioned protocol. The microbiological tests demonstrated the efficacy of the decontamination protocol, as there was no bacterial growth in culture media inoculated with swabs of masks used in the hospital and decontaminated in the UV-C device, which proved the germicidal efficiency of UV-C irradiation. The results of the qualitative research point to the adherence of nursing professionals to the practice of mask decontamination, recognizing the practicality and contribution of the protocol to biosafety and occupational safety. As part of the same protocol, an alternative packaging for storing masks in the intervals of use of N95 masks is presented, considering their safe reuse. The protocol also has the following advantages: low cost and practicality of use, in addition to contributing to the reduction of infectious waste.
Acesso aberto (Open Access)
Análise do processo de despolimerização de resíduos de resinas dentárias à base de pmma em diferentes escalas de produção
(Universidade Federal do Pará, 2024-06-26) RIBEIRO, Haroldo Jorge da Silva; MACHADO, Nélio Teixeira; http://lattes.cnpq.br/5698208558551065; BORGES, Luiz Eduardo Pizarro; http://lattes.cnpq.br/8756886156388456; https://orcid.org/0000-0002-2337-4238
In recent years, the increasing use of plastics has brought economic and industrial benefits but has also led to a significant rise in waste, representing a global environmental challenge. In this context, pyrolysis emerges as a promising technology, offering potential solutions to address the growing problem of plastic waste and promote a more sustainable circular economy. This study investigated the thermal decomposition of dental waste based on poly(methyl methacrylate) (PMMA), focusing on the thermodynamic characterization and optimization of pyrolysis processes at different production scales. Thermogravimetric analysis (TG) showed that PMMA waste remains stable up to 200 ºC, with degradation starting as mass loss occurs beyond this temperature. Thermal decomposition was observed to occur in a single stage, with a decomposition peak at 366 ºC, within the range of 327 ºC to 405 ºC, primarily due to radical depolymerization under inert nitrogen and argon atmospheres. Differential Scanning Calorimetry (DSC) analysis revealed an endothermic peak between 370 ºC and 433 ºC, highlighting the complexity of the pyrolysis processes. The energy characterization showed specific values of 423 J/g for total heat, 1748 J/g for gasification heat, and approximately 820 J/g for decomposition heat, indicating discrepancies that require further investigation for a more complete understanding. In studies using semi-batch fixed-bed reactors, a temperature gradient along the bed was observed to have an adverse impact on the liquid yield and MMA concentration, especially in technical and pilot scales, where the gradient was more pronounced due to the thicker bed. Two critical variables were identified: reactor load and power load, both of which decreased as the process scale increased, leading to lower pyrolysis temperatures and negatively affecting MMA production. Additionally, higher temperatures were found at the edges of the fixed bed, which increased gas production and reduced liquid yield. The liquid fraction analysis revealed a predominance of MMA at the beginning of the reaction, with a gradual transition to aromatic hydrocarbons in the final stages, associated with the pyrolysis of residual char, which increased with the scale of production. The results highlight the effectiveness of temperatures below 450 ºC in producing MMA-rich liquid fractions, even under temperature gradient conditions, emphasizing the importance of moderate heating rates for efficient PMMA depolymerization in semi-batch systems. These findings provide valuable insights for reactor design and are essential for the economic evaluation and optimization of PMMA recycling processes through pyrolysis at various production scales.
Acesso aberto (Open Access)
Estudo da resistência à corrosão de soldas de ferro fundido branco alto cromo na presença de NaOH (30% p.p)
(Universidade Federal do Pará, 2024-10-03) SANTOS, Renata Soraia Guimarães dos; BRAGA, Eduardo de Magalhães; http://lattes.cnpq.br/4783553888547500; https://orcid.org/0000-0003-0739-7592
In the mining industry, specifically in bauxite beneficiation, adverse working conditions are encountered, requiring high mechanical and chemical resistance. For these conditions, it is necessary to choose potentially resistant materials, such as high Cr white cast iron (FFBA-Cr). However, currently, there is no effective recovery of equipment manufactured with FFBA-Cr, mainly due to the difficulty of machinability generated in the repair process. An alternative recovery has been developed by the Laboratory of Characterization of Metallic Materials of UFPA - LCAM, through electric arc welding, using two filler metals, the electric wire ER307L and the wire with high Mn value. In this context, this work proposes to investigate the corrosion resistance of the welded joint, obtained with these two filler metals. The base metal (FFBA-Cr) as a reference and the metals generated by the welded joints, ER307L and with high Mn value, were analyzed. The samples underwent optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD) and electrochemical tests of corrosion potential, polarization and impedance. It was observed that the samples presented a similar structure of carbide matrix, but with different organization and volumes. However, the electrochemical behavior of corrosion potential, polarization and impedance were similar, with their resulting values very close, variations: 50 V; 3.53 µA; 0.18 ohm, respectively, which was corroborated by the corrosion rate, 0.4 mmpy, and explained by the calculations of Cr and Ni volume, which present inverse values of concentration magnitude between the samples. Raman analyses performed after polarization of the samples indicated the formation of important oxides on this surface and possibly the formation of a passivating layer, which is corroborated by the mass loss analysis that showed the possibility of passivation of the welded joints, despite corrosion processes in the anodic phase of this exposure process over the exposure time.
Acesso aberto (Open Access)
Adsorção de ciprofloxacino e norfloxacino em solução aquosa por carvão ativado produzido a partir da casca do cupuaçu (theobroma grandiflorum)
(Universidade Federal do Pará, 2024-09-19) NASCIMENTO, Rafael Alves do; COSTA, Cristiane Maria Leal; http://lattes.cnpq.br/0581730621014796; FARIA, Lênio José Guerreiro de; http://lattes.cnpq.br/7428609361678173; https://orcid.org/0000-0002-9534-9998
The extensive use of antibiotics has caused several negative consequences for the environment and human health. Fluoroquinolones (FQs), present in the aquatic environment, are of particular concern. This study investigated the removal of ciprofloxacin (CIP) and norfloxacin (NOR) from aqueous solutions using activated carbon derived from cupuaçu bark (CAC), an unconventional and low-cost adsorbent. The CAC was characterized physicochemically and the adsorption experiments followed the Box-Behnken design, evaluating the effects of contact time, adsorbate concentration and adsorbent dosage on the removal and adsorption capacity of CIP and NOR. The optimal conditions of the adsorption process were determined by the desirability function, and under these conditions the kinetic, isothermal and thermodynamic adsorption experiments were carried out. CAC showed a similar yield (50.22%) to other activated carbons with H3PO4, low humidity (4.81%) and ash (4.27%). Acidic functional groups were identified in CAC in greater quantities (3.982 mg Eq/g) than basic ones (0.092 mg Eq/g), and the pHPcz was found to be 3.85. A high surface area was quantified (1335.66 m²/g), with an average pore volume and diameter of 0.753 cm³/g and 2.206 nm, respectively. Due to the zwitterionic characteristics of CIP and NOR, adsorption was more efficient at pH 5.0. In this condition, the CAC assumes a basic character and as the CIP and NOR molecules are predominantly in their cationic forms, the electrostatic interaction is facilitated. The optimal conditions for CIP adsorption were: time of 266.40 min, concentration of 192 mg/L and dosage of 0.57 g/L; for NOR, 273.60 min, 186 mg/L and 0.55 g/L. The pseudo-second order (PSO) model and the external mass transfer resistance (EMTR) model best fitted the experimental data, indicating that external mass diffusion was the controlling step of adsorption. The Langmuir model indicated that adsorption occurred in a monolayer, with CIP adsorption capacities of 6.02 mg/g and NOR of 5.70 mg/g. Thermodynamic analysis revealed that the adsorption of CIP and NOR on CAC predominantly involves physisorption. The suggested mechanism for the adsorption of CIP and NOR on CAC may involve electrostatic forces, π-π interactions and hydrogen bonds. CAC regeneration was more effective with NaOH, but after two cycles of use, the percentage of CIP and NOR removal decreased to less than 50%. Thus, CAC proved to be an effective and low-cost adsorbent for the removal of CIP and NOR, also contributing to the reuse of cupuaçu biomass.
Acesso aberto (Open Access)
Obtenção de extratos com potencial bioativo a partir da polpa do piquiá (caryocar villosum (aubl.) pers.) utilizando dióxido de carbono no estado supercrítico
(Universidade Federal do Pará, 2024-09-30) CORDEIRO, Renato Macedo; CARVALHO JÚNIOR, Raul Nunes de; http://lattes.cnpq.br/5544305606838748; https://orcid.org/0000-0002-4433-6580
In a context of increasing demand for substances with health-beneficial properties, extracts from certain plant species found in the Amazon are a promising source of bioactive compounds. Caryocar villosum (Aubl.) Pers., a native fruit of the Amazon region commonly known as piquiá, is regarded as a source of bioactive compounds. This study investigated the supercritical extraction process of piquiá pulp to evaluate the process parameters, overall yield, extraction kinetics, fatty acid profile, α-tocopherol content, functional quality, and physicochemical characterization. The influence of extraction temperature, pressure, and solvent density on the extraction yield was considered. The quality of the obtained extracts was assessed in terms of fatty acid profile, functional quality indices, physicochemical characterization, and α-tocopherol content. A kinetic study of the piquiá extraction with supercritical fluid was conducted using experimental data and mathematical models. The extraction yield was found to increase with pressure at each isotherm, with the highest yield reaching 62.74% and the lowest at 44.01%. The kinetic mathematical models of Martinez and Barton demonstrated good performance in correlating the extraction process of piquiá pulp. The primary fatty acids observed in the extracts obtained under all operational conditions were oleic and palmitic acids. The extract obtained at the operational condition of 60 °C and 250 bar exhibited the highest α-tocopherol content compared to the other experimental conditions in this study. The results indicated that the extracts from piquiá pulp obtained through supercritical CO₂ extraction present significant potential for the industry due to their functional quality.
Acesso aberto (Open Access)
Aplicação de destilados provenientes do bio- óleo de pirólise de resíduos de gordura animal no asfalto diluído de petróleo
(Universidade Federal do Pará, 2024-08-12) VALENTE, Alex Lopes; MACHADO, Nélio Teixeira; http://lattes.cnpq.bhttp://lattes.cnpq.br/1500327307736428r/5698208558551065; https://orcid.org/0009-0002-4461-7611; BERNAR, Lucas Pinto
Waste animal fats (WAF) can be converted into distillate fractions similar to petroleum solvents and used as biofuels or in other applications through pyrolysis and fractional distillation. The distillate fractions from the pyrolysis of triglycerides exhibit adequate viscosity and volatility compared to petroleum-derived fuels but show acid values between 60-140 mg KOH/g, preventing their direct use as biofuels without considerable purification of the distilled fractions. Diluted petroleum asphalt (DPA), used for priming soil in the construction of flexible pavement, requires adequate viscosity, volatility, and penetration, and the distillate fractions from WAF pyrolysis oil can be used as partial or full substitutes for the standard solvent (kerosene) in DPA production. The aim of this study was to test the compliance of DPAs prepared by substituting kerosene with bio-oil fractions from WAF according to DPA standards. First, WAF is obtained from meat waste through the rendering process. Then, WAF is subjected to pyrolysis in a semi-batch fixed-bed reactor (2L), and the resulting bio-oil is fractionally distilled into gasoline, kerosene, and diesel fractions. The pyrolysis process is analyzed concerning the type of reactor used, with a focus on the influence of temperature and reaction time, as well as the distillation profile. The distilled fractions are characterized by density, viscosity, and acid value before being used in the preparation of DPAs by partial and/or total (0-40% by weight) substitution of standard kerosene. The mixtures were tested for kinematic and Saybolt-Furol viscosity, flash point, and penetration, according to road pavement standards. The results showed that the kerosene and diesel fractions from WAF can be adequately used in the preparation of DPAs as a total substitute for the petroleum kerosene typically used.
Acesso aberto (Open Access)
Modelos matemáticos de transferência de calor e massa: extração de metais por membranas poliméricas e sinterização de materiais cerâmicos
(Universidade Federal do Pará, 2024-07-16) VILHENA, Mailson Batista de; SOUZA, José Antônio da Silva; http://lattes.cnpq.br/6157348947425968; MACÊDO, Emanuel Negrão; http://lattes.cnpq.br/8718370108324505
The overall objective of this work was to present a mathematical study of multicomponent mass transfer in a metal ion extraction cell through a flat polymeric membrane and to conduct an experimental and kinetic study focused on the production of synthetic aggregate from bauxite residue. In the first part of the work, a mass transfer model for the recovery of metal ions using flat polymeric membranes was developed. Unlike most existing models, which are limited to studying a single component and do not consider the selectivity and effects of multiple components on reaction kinetics, a model capable of simulating the simultaneous extraction of various metals is proposed. This model is based on the mass conservation equation and was solved using the Coupled Integral Equations Approach (CIEA), and validated with experimental measurements and previous simulations. In the second part, an experimental and theoretical study was conducted using a kinetic model for the production of coarse synthetic aggregates from bauxite residue, silica, and clay. The experimental study included the production and characterization of the aggregates in different compositions. To analyze the sintering process of a full-sized pellet, a small electric furnace with an attached balance was built, allowing the monitoring of mass loss measurements as a function of temperature and time. Additionally, a kinetic study was carried out using mathematical models to evaluate the main solid-state reactions and their phase transformations during the sintering process, using experimental data from thermal analysis.
Acesso aberto (Open Access)
Uso de resíduo caulins da amazônia para a produção de precursores geopoliméricos utilizados na indústria da construção civil
(Universidade Federal do Pará, 2024-04-25) BRITO, Woshington da Silva; BRAGA, Eduardo de Magalhães; http://lattes.cnpq.br/4783553888547500; https://orcid.org/0000-0003-0739-7592; SOUZA, Jose Antonio da Silva; http://lattes.cnpq.br/6157348947425968
The region of the Capim River (Northeast of the State of Pará), due to its large reserves of kaolin for covering paper, stands out nationally. The extraction of the ore occurs on average at a depth of 20 meters, covered by clayey-sandy sediments from the barrier formation, and from a level of hard kaolin, also known as flint or semi-flint kaolin(Ferruginous), considered stable depending on the content high iron content, which makes its application for roofing unfeasible. The research aims to address the development of geopolymers synthesized from waste containing aluminum silicate. Geopolymers are amorphous, threedimensional alkalis. Aluminosilicate binder materials synthesized from alkaline activation of clays, calcined clays, calcined kaolin, minerals, industrial waste, fly ash and other aluminosilicates. The fly ash generated in the Bayer process boilers under conditions of 900 °C and 120KPa was also used as a source of aluminosilicate in the geopolymerization reaction. To increase the reactivity of the reaction, the use of soft kaolin and flint and semi-flint(ferruginous) kaolin calcined at different temperatures(450,550,650, 700 and 800 °C) was evaluated. And, also at different calcination times(15,30,60 ,90 and 120 minutes). Sodium hydroxide (NaOH, 5-30 M) and sodium silicate (Na2SiO3, SiO2/Na2O = 3.2) as alkaline reaction medium. The residues were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR), thermogravimetric analysis (TGA) and differential thermal analysis (DTA). And, compressive strength tests were also carried out on the geopolymeric samples to evaluate the degree of polymerization, since the more polymerized the structure is, the greater the resistance. For the geopolymer based on (soft kaolin and fly ash), the best results were obtained for the SiO2/Al2O3 ratio of 2.65 and 3.4. For the geopolymer based on (flint kaolin and fly ash) the best result was for the SiO2/Al2O3 ratio of 2.95 and 3.57. The best results for the geopolymers based on (ferruginous metakaolin and fly ash) were obtained with a SiO2/Al2O3 ratio of 2.88 and 3.54. The geopolymeric ceramic plate obtained showed satisfactory performance in relation to mechanical resistance to compression and was also synthesized with raw material that contaminates the environment, as it is considered kaolin residue due to its high iron content.
Acesso aberto (Open Access)
Manufatura aditiva de biocompósitos a partir de ácido poliláctico reforçado por hidroxiapatita e nanotubos de carbono para regeneração de tecido ósseo
(Universidade Federal do Pará, 2024-01-22) BELO, Francilene da Luz; REIS, Marcos Allan Leite dos; http://lattes.cnpq.br/8252507933374637; CANDIDO, Verônica Scarpini; http://lattes.cnpq.br/8274665115727809
Bone tissue is one of the most important tissues in the human body. Unfortunately, some traumatic events can cause fractures that can lead to temporary or permanent disability. Scaffolds are some of the materials that help in the treatment of these fractures, as they play an important role in the bone repair process and can be manufactured by 3D printing. Polylactic acid (PLA), as it is biodegradable, is one of the materials used in the production of scaffolds. Furthermore, the association of PLA and hydroxyapatite (HA) in its manufacture has shown excellent results, accelerating bone regeneration and reducing healing time. Another promising material for making scaffolds are carbon nanotubes (CNT), which have excellent mechanical properties and also accelerate bone growth. Thus, the main objective of this study was to produce scaffolds by additive manufacturing from polylactic acid (PLA) reinforced with hydroxyapatite (HA) and carbon nanotubes (CNT), to be applied in the regeneration of bone tissue and characterized through mechanical and biological. Hydroxyapatite was synthesized by wet means and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), presenting phases characteristic of HA, characteristic groups and a morphology with a porous surface with varying particle sizes, important characteristics for a biomaterial. The pure PLA, PLA/HA and PLA/NTC scaffolds were produced by additive manufacturing with an opening between the walls of 1 mm and 2 mm and characterized through mechanical tests and biological tests. Furthermore, PLA/NTC scaffold samples were impregnated with HA on the surface by thermal and chemical treatment to evaluate the influence of ceramics on the composite surface. The micrograph of the scaffolds showed that the addition of CNT made the PLA surface rougher compared to the sample containing HA; The TGA curves suggested that temperature may favor the thermal stability of PLA/NTC scaffolds impregnated with HA on the surface; Ramam showed an interaction between hydroxyapatite on the CNT surface and a possible structural transformation of PLA/CNT; In compression tests, PLA/NTC scaffolds with an opening between the walls of 1 mm showed better compression resistance; In cell viability assays, fibroblasts incubated with pure PLA, PLA/HA and PLA/NTC scaffolds showed high viability after evaluation by the MTT assay for the two forms of preparation (heat treatment impregnation and chemical treatment impregnation and for the two openings between the walls. More than 85% of the cells remained viable after 48h of incubation with all scaffolds tested, with the groups that had NTC in their composition showing the best results, both for heat treatment (more than 95% of cell viability) as well as chemical treatment (acetone). Given the results presented, it is concluded that PLA scaffold reinforced with HA and CNT may be promising as a biomaterial used to aid in the regeneration of bone tissue, contributing to the reduction of time hospitalization of patients suffering from bone fractures.
Acesso aberto (Open Access)
O uso de fibra de juta (corchorus capsularis) no desenvolvimento de pás de turbina eólica de pequena escala para ventos de baixa intensidade
(Universidade Federal do Pará, 2023-10-17) CARDOSO, Robson Luis Baleeiro; FUJIYAMA, Roberto Tetsuo; http://lattes.cnpq.br/3165747089941318; https://orcid.org/0000-0002-2738-6666
Natural fibers have growing potential for reinforcing polymer composites, representing a promising competitor to the glass and carbon fibres widely used in the construction of wind turbine blades, whose recyclability/disposability and high energy production costs have already been discussed in the main turbine production centres. On the other hand, the development of wind turbines for areas with winds of between 2 and 6 m/s, considered low speed, using the S1210 aerofoil profile could increase the energy generation potential of regions not originally eligible for the installation of large turbines. This study proposes evaluating the use of jute fiber (Corchorus capsularis) in the blade design of a small-scale wind turbine, considering aerodynamic and structural parameters. This project was developed incorporating Blade Element Momentum Theory (BEM), Classical Laminate Theory (TCL) and Extended Bredt-Batho Shear Flow Theory (EBSFT), in order to survey the elastic properties and enable the use of failure criteria. The composite blades were characterised in accordance with ASTM D 3039, ASTM D 638 and ASTM D 5379. The mechanical properties obtained, together with the elastic parameters of the cross-section, torsional stiffness, axial stiffness and flexural stiffness, of EIy 4.97 x 104 Nm2, EIz 1.45 x 106 Nm2, EI 9.47 x 104 Nm2 and GJ 1873.6 x 106 Nm2, respectively, demonstrated the feasibility of using jute fibre applied to the structural laminate in the construction of the blade, defined in accordance with the maximum stress failure criterion, presenting itself to compete with the glass fibres used today.
Acesso aberto (Open Access)
Eletrodeposição e caracterização de revestimento de cobre/nanotubos de carbono dopados com iodo em fios de alumínio liga 1350
(Universidade Federal do Pará, 2023-09-19) RODRIGUES, Fabrício Augusto dos Santos; LEITE, Marcos Allan Reis; http://lattes.cnpq.br/8252507933374637
Nanocomposites based on copper and carbon nanotubes (Cu/NTC) in metallic matrix have been providing improvements in the electrical and thermal properties of materials, presenting great potential for application in areas such as the electrical sector. Great challenges are encountered in the transmission and distribution of electrical energy, such as technical losses, mainly due to the Joule effect, resulting in low efficiency of conventional aluminum (Al) conductors. In this sense, new nanostructured conductors were developed based on functionalized copper/carbon nanotubes and doped with iodine (Cu/NTC-f), as a coating for Al 1350 aluminum wires, using the electrophoretic deposition process in copper sulfate solution, under electrical currents of 1.2 A, 1.5 A and 1.8 A, were investigated for their electrical and mechanical properties. Al@Cu/NTC-f conductors were characterized by scanning electron microscopy; X-ray diffraction; Raman spectroscopy; tensile test, in addition to electrical measurements, at room temperature and under heating, via Kelvin bridge. The results show an increase of approximately 18% of the IACS with good stability under heating compared to the commercial aluminum conductor Al 1350, due to the intrinsic properties of the NTCs, functionalization, good dispersion and the doping effect of iodine, confirmed by Raman spectroscopy with redshifts in the Gint and Gext subbands. The characteristic morphology of the thin films of Cu/NTC-f, presented pyramidal structures, agglomerates, copper structures involved the NTC, as well as NTC homogeneously electrodeposited in the aluminum substrate with good crystallinity, cultivated in the directions (311) and Cu (220), Cu (200), favoring the formation of thin films with good crystallinity. This method of electrodeposition of Cu/NTC-f on the surface of metallic wires shows promise for the production of nanostructured metallic conductors of high ampacity, thermal stability, low density and high performance, applied in electric power transmission lines.
Acesso aberto (Open Access)
Análise quase-estacionária de pequena turbina eólica com pás curvadas
(Universidade Federal do Pará, 2023-10-20) VELOSO, Mauro José Guerreiro; CHAVES NETO, Antônio Maia de Jesus; http://lattes.cnpq.br/3507474637884699; VAZ, Jerson Rogério Pinheiro; http://lattes.cnpq.br/1623983294183975
The installed power generation capacity in renewable energy has stood out in Brazil lately. The Anuário Estatístico Energético Nacional 2023 reported that wind energy improved by 14.3% from 2021 to 2022. Despite the wind energy potential generation in Brazil, there are still obstacles to overcome, including challenges in research and development. So, researchers have conducted investigations on renewable energy, focusing on studying wind turbines' design and performance evaluation and other efforts to alleviate that task. Hence, research has not been conducted on the dynamic starting behavior of small wind turbines with different blade curvatures in wind power systems. In this sense, the main objective of this work is to analyze the influence of different angles of blade curvature on the dynamic response on starting the coupled turbine-generator set. Newton's second law, the blade element theory, and the extension of the Palmgren method are applied to obtain the wind turbine behavior at the start. The dynamic behavior measurements available in the literature at the start of the straight-blade wind turbine is been applied as a reference baseline to validate the methodology. Numerical simulations demonstrate that during start-up, turbines with straight blades and forward-swept blades start in less time, are approximately 19.9% faster at starting, and require 10.7% less wind speed than turbines with backward-swept blades. Compared to straight-blade turbines, backward-swept blade turbines increase the dissipative torque up to 5.86% and the dynamic efforts by 22%. These results indicate the significance of blade geometry on turbine performance and the existence of a swept angle at which the turbine performs better than other angles of the swept blade.
Acesso aberto (Open Access)
Interações com nanotubos de carbono e pontos quânticos de óxido de grafeno com estruturas externas do Sars-cov-2 via simulações de dinâmica e docagem molecular
(Universidade Federal do Pará, 2023-06-02) LOBATO, Júlio César Mendes; OLIVEIRA, Mozaniel Santana de; http://lattes.cnpq.br/0810227136654245; https://orcid.org/0000-0002-4076-2443; CHAVES NETO, Antonio Maia de Jesus; Lattes: 3507474637884699
The interaction between nanoparticles and SARS-CoV-2 virus proteins was evaluated using ligands such as single-walled carbon nanotubes (NTCPUs) and receptors including envelope protein (E-pro), major protease (M-pro) and Spike glycoprotein (Sgly). Molecular docking modeling and molecular dynamics techniques were applied. Molecular dynamics revealed root mean square shift of atomic positions ranging from 0.5Å to 3.0Å. The results indicated that the zigzag nanotube showed better affinity energy, with binding free energy values of -9.48, -9.98 and -10.08 kcal/mol for E-pro, M-pro and S-gly, respectively. Furthermore, the mean square deviation of the atomic positions remained more stable for this type of nanotube, indicating a high probability of binding to the active sites of the macromolecules. Molecular couplings and binding free energy showed strong interaction between NTCPUs and residues of the S-gly active site, with values of -112.73, -94.38 and -80.49 kcal/mol for zigzag, chiral and armchair ligands, respectively. In a second step, five graphene oxide (GO) quantum dots smaller than 20 nm were used as ligands, interacting only with the spike receptors of three different strains: S-GLY-OMICRON, S-GLY-KAPPA and S-GLY-DELTA. Comparing the two ligands, it was observed that the S-GLY-OMICRON/OG-E interaction showed better affinity with Gibbs free energy of 172.2510 KJ/mol, compared to the better affinity of carbon nanotubes, S-gly/zig-zag, with ΔG of -112.73 KJ/mol. The eight proposed ligands have a high probability of binding to the active sites of the macrostructures. In conclusion, both carbon nanotubes and OG showed promise for application in SARS-CoV-2 inhibitor products, such as the development of materials for the manufacture of personal protective equipment, sprays and waterproofing solutions in general.