Navegando por Data de Publicação, começando com "2018-04-26"

Filtrar resultados por ano ou mês

Agora exibindo 1 - 9 de 9

Procedimentos e resultados de ensaios de caracterização física e mecânica de blocos cerâmicos estruturais e de vedação
(Universidade Federal de São Carlos, 2018-04-26) Baptista, Adriana Cristina Morais; Parsekian, Guilherme Aris; https://lattes.cnpq.br/7798651726059215; https://lattes.cnpq.br/8582765500383125
In Brazil ceramic blocks are widely used in masonry constructions and their quality is guaranteed by the Brazilian standard ABNT NBR 15270. This standard went through a revision process in the year 2017 and this research took advantage of this moment to evaluate some of the current Brazilian standard tests, such as wa-ter absorption index determination, initial absorption index and compressive strength tests, and to perform non-standard tests such as density, durability, adhesion strength and efflorescence tests in order to validade the code review and contribute for its future update. The tests were performed in blocks donated by manufacturers from the states of São Paulo, Minas Gerais, Rio de Janeiro, Rio Grande do Norte and Pará. The research showed that the tests of total absorption indices carried out in hot and cold water present similar results in Brazilian ceramic blocks. The abra-sion resistance test was related to the compressive strength test, where blocks with higher resistance to abrasion presented higher resistance to compression. In the test of adhesion with and without roughcast, the blocks without roughcast had poor ad-hesion levels and the blocks with roughcast showed acceptable adhesion levels. As for the efflorescence tests, the Franco test (2012) and the American standard ASTM C67 were evaluated, where the methodology of the American standard presented procedures was concluded more appropriate. From the density tests with and with-out paraffin, the values indicate that there a difference in each procedure result.
Controle nebuloso ("fuzzy”) aplicado à combustão em caldeiras a bagaço de cana
(Universidade Federal de São Carlos, 2018-04-26) Mello, Fernando Martins de; Sousa Júnior, Ruy de; https://lattes.cnpq.br/1983482879541203; https://lattes.cnpq.br/3019610702811546
In the sugarcane industry, boilers are widely used for cogeneration. This term designates the simultaneous generation of more than one type of energy, namely thermal and electrical, from the same fuel source. This industry uses mainly sugarcane bagasse as the primary fuel source followed by other types of biomass, such as cane straw, woodchips and corn stover. According to the Brazilian Sugarcane Industry Union (UNICA) and the National Electric Energy Agency (ANEEL), the installed capacity for electricity supply from biomass represents 9% of the Brazilian energy matrix. Fuel price has a major impact on the industry’s results, due to the current scenario of the energy market. Therefore, optimizing the combustion is an important lever to reduce this cost. Real-time measurement of oxygen content in the boilers’ flue gas is one of the requirements for this optimization. Due to the capital cost and the requirements for personnel qualification for maintenance and calibration, sugarcane mills rarely apply such analyzers in closed loop. In this work, a fuzzy control was implemented in the combustion air flowrate of a large boiler in the Tereos group, to maintain the oxygen content in the combustion products within the optimum range. A tool was used to identify the process dynamics and to tune the control loop in real time. After downloading the new strategy in the factory’s control system and tuning the controller, the oxygen control loop started operation in automatic mode. After twenty-four hours of continuous operation, regulatory and servo controls were able to, respectively, keep the desired setpoint with low variability (± 1,2% variation in excess air coefficient) and respond to setpoint changes with good response speed (1,5-20 minutes) and overshoot (8-56%). Results reached so far demonstrate the applicability of fuzzy control for combustion in boilers on sugarcane bagasse, with 40% less variability than the PID controller, and 69% less variability compared to operation in manual mode.
Avaliação de Bacias de Detenção na gestão de águas pluviais em Araraquara, SP
(Universidade Federal de São Carlos, 2018-04-26) Peroni, Carolina Sulzbach Lima; Teixeira, Bernardo Arantes do Nascimento; https://lattes.cnpq.br/1166854416745527; https://lattes.cnpq.br/5078829117479037
The quest for the mitigation of the impacts of urbanization on stormwater runoff and infiltration gave rise, in the 1970s, to the compensatory techniques on urban drainage. These techniques, which were widespread in North America and Europe, were strengthened in the 1990s, with emphasis on detention basins, which are unique for the control of peak flows with Great return times. In the past decade, this trend has intensified in medium-sized cities, such as the municipality of Araraquara, São Paulo, which requires the construction of these basins for new subdivisions. In this context, the present research has the objective of evaluating 3 Detention Basin Systems (DBS) and 20 Detention Basins (DB) constructed in the urban environment of the Municipality of Araraquara, SP, regarding urban insertion, maintenance and integration of these units with their environments. In order to reach this goal, the DBS and DB inserted in the municipality were identified, characterized and mapped using satellite images, on-site visits and the QGIS software version 2.14.13-Essen, respectively. Variables were defined for the evaluation of the units that include aspects of direct observation of the units with and without the precipitation event; aspects of design, construction and operation of the units; and aspects of population perception regarding units. It is necessary to use questionnaires to obtain data, particulary those referring to engineering projects and maintenance practices, as well as the perception of the population neighboring the units. This methodology is expected to identify similarities and discrepancies of insertion and the maintenance of the studied units. In a preliminary way, SBD and SB were found to be located in the Ribeirão das Cruzes sub-basin and distributed upstream of the Cruzes Dam (surface catchment point), even though this is a region susceptible to erosive processes and geotechnical risk. It was also observed a tendency to implant these units isolated from their surroundings, without their integration with urban space, and exclusively focused on the hydrological function. In terms of maintenance, the basins prove to be inadequate, largely due to the excess vegetation, as well as the presence of sediments inside them. The depredation of insulation structures (fence and gate) as well as the inadequate disposal of solid waste, especially those from demolition and civil construction, were other aspects commonly identified in the basins, which indicated absence or low frequency of maintenance practices. It was also verified the filling of more than half of the units and its emptying in less than 24 hours, not being observed or reported overflow of the units. Regarding the dimensioning, it was observed the adoption of two methodologies to calculate the volume of detention and the discrepancy between these values. The estimated costs of implementation varied from R$32.16/m² to R$75.13/m² and from R$21.4/m³ to R$25.8/m³. The maintenance cost was R$333.00 per practice. The surrounding population was in favor of the units, as long as they have frequent maintenance and multifunctionality of these spaces, public policies are necessary to encourage its integration with their surroundings, favoring its appropriation by their community.
Contribuição ao estudo do desempenho de biorreatores airlift de circulação interna: análise das condições operacionais e da geometria do equipamento
(Universidade Federal de São Carlos, 2018-04-26) Esperança, Mateus Nordi; Béttega, Rodrigo; https://lattes.cnpq.br/1379682125857376; Badino Júnior, Alberto Colli; https://lattes.cnpq.br/6244428434217018; https://lattes.cnpq.br/7010012819835496
The high oxygen transfer capacity associated with low energy consumption have made the airlift bioreactor an important equipment to be used in bioprocesses, with the performance of these devices being strongly dependent on their geometry. In order to extend the understanding of the relationship between hydrodynamics and mass transfer of these equipment and their construction project, the objective of this thesis was to evaluate the effect of the geometry on the performance of 10 L internal-loop airlift bioreactors of different models (concentric duct and split) and with different cross-sectional shapes (circular and square). By evaluating the volumetric oxygen transfer coefficient (kLa) and the global gas hold-up (εG), a strong influence of the gas-liquid separator geometry was observed, while a small effect of the bottom geometry was verified. On the other hand, the liquid circulation velocity was affected by the geometry of all regions of airlift bioreactors (riser, downcomer, bottom, gas-liquid separator), exhibiting a high effect of the downcomer-to-riser cross-sectional ratio (AD/AR). Four promising geometries of square cross-section airlift bioreactors were selected based on oxygen transfer coefficient (kLa) and riser superficial liquid velocity (ULR) criteria, exhibiting different kLa and ULR levels for the same specific air flow rate (3 vvm), demonstrating the flexibility of airlift bioreactors to attend specific bioprocess requirements. By establishing an analogy between the gas-liquid flow in a concentric duct airlift bioreactor and the liquid flow in a smooth pipe, it has been found that computational fluid dynamics (CFD) can be satisfactorily applied to predict the shear rate. A non-uniform distribution of this parameter was observed in airlift bioreactors, where the maximum shear rate was observed close the sparger holes, showing a direct relationship with the gas injection velocity. In this way, the design of the gas sparger was the key parameter to the definition of maximum shear conditions in pneumatic bioreactors and should be considered in the project of these equipments.
Obtenção e caracterização de uma lacase amarela recombinante de Leucoagaricus gongylophorus
(Universidade Federal de São Carlos, 2018-04-26) Rodrigues, Juliana Gomes; Souza, Dulce Helena Ferreira de; https://lattes.cnpq.br/3428955299526003; https://lattes.cnpq.br/3527738525140248
Laccases are enzymes that have a wide range of applications including their use in bioremediation. These enzymes have been described as multi copper oxidases that reduce oxygen to water while oxidizing compounds. Some laccases not present absorbance at 600 nm and blue color which are common in these enzymes and, for this reason, they have been denominated yellow laccases. An important feature of yellow laccases is the ability to degrade non-phenolic substrates in the absence of chemical mediators. However, the origin and structural factors that differentiate the blue and yellow laccases are not well understood. The objectives of this work were to express, purify and characterize a recombinant yellow laccase (LacRLg) from a cDNA library of Leucoagaricus gongylophorus, the symbiont fungus of leaf cutting ants. From the clone of the fungus cDNA library, the laccase ORF was cloned into the pPICZαA expression vector, resulting in the clone pPICZαA-Lac which was transformed into three strains of the yeast Pichia pastoris, X-33, KM71H and GS115. This system proved to be efficient in expressing the enzyme in soluble and active form, and a colony of the X-33 lineage was more effective in the expression of the enzyme. LacRLg was expressed in the extracellular medium and purified on a molecular exclusion column, followed by an ion exchange column. The recombinant enzyme has an apparent molecular mass of approximately 66 kDa as assessed by SDS-PAGE. LacRLg does not absorb light at 600 nm and therefore does not show blue coloration and can be classified as a yellow laccase. The enzyme presented catalytic activity against syringaldizine, considered a specific substrate for laccases. The enzymatic extract was used in to evaluate the potential of degradation of polycyclic aromatic hydrocarbons (HPA's) in the absence of mediators. HPA's are organic pollutants of persistence and their degradation plays a role in maintaining the environment. The degradability of HPA's by LacRLg was evaluated against the anthracene, phenanthrene and pyrene in a LC system to UV-Vis detector and SPD M10A. LacRLg was able to degrade, in 24 hours, 95% of anthracene, 87% of phenanthrene and 88% of pyrene. These results suggest that this enzyme, due to its ability to degrade HPA's in the absence of chemical mediators, has potential use in bioremediation processes.
“Catalisadores Au/m-ZrO2 aplicados na conversão direta do etanol em acetato de etila: efeito do grau de recobrimento do suporte nas propriedades catalíticas”
(Universidade Federal de São Carlos, 2018-04-26) Ribeiro, Murillo Cardoso; Marques, Clélia Mara de Paula; https://lattes.cnpq.br/0451284088402660; https://lattes.cnpq.br/4768550929014572
In this present work, the direct formation of ethyl acetate from ethanol was studied using monometallic catalysts of Au supported on m-ZrO2. Other supports, such as MgO and SiO2, as well as Cu-based catalysts were prepared for comparison. Au-based catalysts were prepared by deposition-precipitation method with NaOH and investigated by different characterization methods, such as X-ray diffraction (XRD), N2 physisorption, X-ray excited photoelectron spectroscopy (XPS), X-ray spectroscopy Diffuse reflectance in the infrared region with adsorbed CO Fourier transform (DRIFTS-CO), inductively coupled plasma optical emission spectroscopy (ICP-OES), extended X-ray absorption fine structure spectroscopy (EXAFS), and electron microscopy of transmission (TEM). The gold loading was confirmed by ICP-OES and it showed a close correlaction with the synthesis pH, as well as with the chemical composition of the support. For all the analyzed catalysts, no reflection corresponding to Au could be observed by XRD. In addition, Au NPS presented as small crystallites and highly dispersed on the surface of the support. The average size of Au NPS, determined by TEM, was dependent on the chemical composition of the support, the synthesis pH and the activation temperature of the catalysts. Analysis of EXAFS data showed only Au-Au binding distance, indicating that Au0 prevails in reaction condition. The catalytic tests revealed, for the first time, high selectivity to ethyl acetate using Au-based catalysts, whose value (yield higher than 63.0%) for the Au / m-ZrO2 catalyst, with a real Au content of 5,01%, was higher than that achieved by the classical Cu-based catalysts. In addition, the results presented in this thesis have allowed to propose that not only the extension of the metal-support interface, but also the degree of coverage of ZrO2 by Au, as well as the electronic properties of this metal are fundamental factors for the high performance presented by these catalysts in the direct transformation of ethanol into ethyl acetate.
Potencialidades das técnicas com fonte de plasma e da espectrometria de absorção atômica em forno de grafite de alta resolução com fonte contínua para análise de fertilizantes
(Universidade Federal de São Carlos, 2018-04-26) Machado, Raquel Cardoso; Resano, Martín; Nogueira, Ana Rita de Araújo; https://lattes.cnpq.br/7034773971317045; https://lattes.cnpq.br/6744663235898188
Each year, Brazil sets records on agricultural productivity, which significantly increases the use of fertilizers in crops to provide the essential nutrientes. However, fertilizers can also be sources of toxic elements from the raw material and manufacturing processes, which can be absorbed by crops. In this thesis, different strategies were adopted to the development of analytical methods employing tniques with plasma sources, as microwave induced plasma optical emission spectrometry (MIP OES) and inductively coupled plasma mass spectrometry with a tandem mass configuration (ICP-MS/MS), and direct solids analysis using high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GFAAS) for fertilizers analysis, overcoming spectral and non-spectral interferences. The hydride generation coupling to MIP OES (HG-MIP OES) favored the determination of As, Bi, Ge, Sb, and Sn in fertilizer samples, with recovery of 106 % for As obtained from the certified reference material (CRM) NIST 695 and recoveries between 90 and 118 % from addition and recovery experiments. Silicon in fertilizers was determined by MIP OES using air addition into the N2 plasma after microwave-assisted digestion in acid and alkaline médium. The air addition into the N2 plasma render it more robust against the addition of electrons in the plasma due to the presense of Na, which is easily ionizable. The Si results obtained by MIP OES were compared with reference values obtained by X-ray fluorescence (XRF) and inductively coupled plasma optical emission spectrometry (ICP OES). The recoveries between 80 and 89 % without and 97 and 100 % with air addition were obtainde, respectively. In another study, a multi-energy calibration method (MEC) with matrix-matching capability was evaluated for fertilizer analysis by MIP OES. This strategy was effective for determination of As, Cd, Ba, Cr and Pb in mineral fertilizers, whose recoveries ranged from 96 to 101 % in fertilizer reference material (NIST 695) for As, Ba, Cr, and Pb and from 92 to 105 % for Cd in addition and recovery experiments in fertilizer samples. In fertilizers analysis by ICP-MS/MS, free-interference determinations were obtained for Cd and Sn, and for platinum group metals, such as Pd, Pt, and Rh, Rhodium and Pt were determined from the mode MS/MS mass-shift and Cd, Pd, and Sn were determined from the mode MS/MS on mass. To evaluate the accuracy, addition and recovery experiments at three concentration levels were performed and recoveries between 81 and 102 %, and 80 to 113 % were obtained for the MS/MS mass-shift mode and MS/MS on mass, respectively. Direct analysis of fertilizers solids was proposed for the simultaneous determination of Co, Cr, Fe, and Ni by HR-CS GFAAS, using in situ microfusion procedure to matriz elimination. The monitoring of the spectral region around the wavelength 298.560 nm allowed simultaneous determination of analytes, employing aqueous solutions for calibration. Applying the method developed, recoveries ranged from 81 and 120 % were obtained for direct analysis of CRM NIST 695.
Nanocompósito de poli(oxido de etileno) reforçado com nanocristais de celulose extraídos da fibra de tucum
(Universidade Federal de São Carlos, 2018-04-26) Vasques, José Carlos; Lucas, Alessandra de Almeida; https://lattes.cnpq.br/9754332336954137; Menezes, Aparecido Junior de; https://lattes.cnpq.br/0484426340349483; https://lattes.cnpq.br/5192233313952291
The using of a nonrenewable resources in the production of new materials, in particular synthetics plastics, it is a cause for concern and environmental call ones due to its long degradability time. Although a lot of thermoplastics are passing by recycling this it is not a common activity in the world which makes the biodegradable materials researches a viable alternative to minimize environment impacts. Advances in researches on natural fibers and the development of composites and nanocomposites it is one of the challenges for obtaining new materials produced by renewable sources. There are great advantages when using natural fibers rather than synthetic fibers as plastic reinforcement like: abundance due to the enormous variety of plants available in biodiversity, comes from renewable resource, high biodegradability and low density. The natural lignocellulosic fibers of Tucum studied are among the least known and investigated. Few researches show results about its structural characteristics and reinforced polymer nanocomposites with them. The head of this research was prepare and characterize nanocomposites constituted by polyoxyethylene (POE) reinforced with cellulose nanocrystals extracted from Tucum fibers by solvent evaporation. To determine the chemical, thermal and morphological characterization of the fibers, nanocrystals and reinforced polymer was used tensile testing, x-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMTA), scanning electron microscopy (SEM) and field emission scanning electron microscopy (FESEM).
Avaliação da utilização de argilas em poliestireno de alto impacto reciclado de equipamentos eletroeletrônicos (REEE)
(Universidade Federal de São Carlos, 2018-04-26) Consul, Thiago Bueno; Paiva, Jane Maria Faulstich de; https://lattes.cnpq.br/7926832511513537; https://lattes.cnpq.br/1673404474980115
Due an annually increase of polymer production, lots of residues are being generated and recycled by low technology investments and it is used to produce simple material, as bags and containers. However, engineering polymers that have specific properties, and toxic components that could cause harm to humans, require proper sorting and recycling. Waste electrical and electronic equipment (WEEE) residues have these characteristics polymers and is not suitable to discard high value residues because of its economic and environmental inviability. In this context, the recycled high impact polystyrene from this study is important and the second most used polymer in EEE due to its mechanical properties. Two different methods were used, compression molding with heating was used in a hydraulic press with recycled HIPS and different types of bentonite clays (untreated from Tecmas and CloisiteNa and also organophilic clays as Claytone 40 and Cloisite 15A). Also, these composites were also obtained by extrusion with each clay to improve its dispersion and molded by compression with heating in the same hydraulic press. The composites were mechanically evaluated in tensile, flexural and impact strength, as also for thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC).The results of the mechanical tests of the recycled HIPS presented values close to the virgin HIPS of the literature. The tensile strength results from composites with Tecmas and CloisiteNa clays (14.25 ± 2.02 and 11.46 ± 4.06 MPa) were close to the recycled HIPS (12.74 ± 0.51 MPa to 13.28 ± 0.60 MPa). Recycled HIPS tensile modulus and its composites were similar and with values around 1400 MPa. However, the use of organophilic clays reduced the mechanical tensile and flexural properties of the composites. Impact strength from HIPS/Tecmas clay composites (90.8 ± 7.8 J/m) were close to recycled HIPS (88.5 ± 7.0 e 98.9 ± 13.4 J/m), other composites were under 80 J/m. Similar results were obtained with extruded composites of HIPS/Clay in mechanical tests. Thermogravimetric analysis demonstrated variation in graphic curves with higher temperatures related to the elastomer degradation and better clay interaction due its organophilic properties. While in DSC results were not possible to observe any variation in temperatures related to polybutadien and polystyrene. Despite the decrease in some mechanical properties from the composites, using clay is an option for flame retardancy and to smooth polymer reclying and molding of new materials.