Navegando por Data de Publicação, começando com "2013-03-19"

Filtrar resultados por ano ou mês

Agora exibindo 1 - 5 de 5

Análise da secagem convectiva de folhas de manjericão (Ocimum basilicum L.)
(Universidade Federal de São Carlos, 2013-03-19) Lima, Renata de Aquino Brito; Ferreira, Maria do Carmo; https://lattes.cnpq.br/7070885875161111; https://lattes.cnpq.br/5050641829811424
Convective drying of leaves involves heat and mass transfer in packed-beds of deformable material, since the leaves shrink significantly when the moisture is removed. Therefore, the packing structure changes over time, and the transfer properties alter as well. An additional drawback is the challenge to obtain reproducible packings, given the random nature of packing for such an irregular type of material. In this work, an experimental investigation was conducted to analyze how basil leaves (Ocimum basilicum L.) behave during drying focusing in the challenging characteristics of this particulate phase. A full characterization of the leaves as a particulate solid was conducted by measuring their dimensions, specific density, initial moisture content and equilibrium moisture content. Loose and compacted bulk densities were measured for beds of leaves under different moisture content. Results indicate that the basil leaves have a low sphericity (=0.160), a high projected area (Aproj=4.55 cm2) and density equal to 0.874 g.cm-3. Bulk density of fresh leaves was 0.089 g.cm-3 in loosely packed-beds, and 0.198 g.cm-3 in compacted packed-beds. Drying experiments were performed in a range of 30 to 60oC under different air-particle contact modes, including fixed and moving beds. Drying cells 10 cm in diameter with heights of either 1 or 12 cm (corresponding to thin-layer and deep-layer beds respectively) were tested with air flowing perpendicular to the samples. In moving beds, a rectangular chamber of dimensions 20 cm x 11 cm was used, also with air flowing perpendicular to the samples. In the conditions tested, problems were observed regarding reproducibility of data of moisture content versus time, bed shrinking, channeling and non-homogeneous drying. It was demonstrated that these problems appear due to the inherent characteristics of the leaves (low density, high ratios of surface area to volume, rough surface, etc.), and also due to their biological variability, which made it difficult to obtain packed-beds with reproducible characteristics in different assays. Homogeneous drying was obtained only for moving beds with vertical vibration, under dimensionless vibration parameter equal to 1.0 and an amplitude of vibration of 0.5 cm. The effect of the cell diameter to mean leaf size ratio (D/dm) on the bulk densities and drying rates was also investigated. For that, the size of leaves was reduced by cutting them in two parts widthways (half-sized particles), and also in four parts, width- and lengthways (quarter-sized particles), resulting in D/dm= 4.2 (whole leaves), 5.3 and 7.8 (half- and quarter-sized leaves respectively). It was observed that loose and compacted bulk densities did not vary significantly for beds of half-sized particles, but increased approximately 20% in beds of quarter-sized leaves. Regarding the drying rates, a tendency of an increase as D/dm was raised to 7.8 was observed, but the variation remained within the range of standard deviation of experimental data. Axial shrinking of the beds throughout drying was measured in deep packed-beds. The initial bed height was reduced by approximately 47% after 100 minutes of drying at 60 oC. The pressure drop through the bed decreased drastically when the leaves were dried, resulting in an increase by 141 times in the bed permeability for drying at a temperature of 60°C. The results obtained show that the packed-bed structure strongly affects the heat and mass transfer during convective drying of leaves.
Aplicação do resíduo de bauxita como fonte de Al2O3 e Fe2O3 na preparação de clínqueres de cimentos portland
(Universidade Federal de São Carlos, 2013-03-19) Lourenço, Rafaela Roberta; Rodrigues, José de Anchieta; https://lattes.cnpq.br/4000441989868775; https://lattes.cnpq.br/9480551360978454
During the past decades, the bauxite residue (BR) generated in the aluminium production was considered unusable waste. However, the difficulties and the costs associated with the residue management and storage have motivated companies to invest in innovative research to find economical and environmentally safe applications for the BRin order to reduce the volume of waste stored. In this context, the building industry offers a promising application for BR. This sort of residue could be used in large quantities in the production of Portland cement, one of the most important materials in this sector. The partnership between the aluminium and cement producers might benefit both areas, opening a great opportunity to move towards sustainable development and to minimize environmental impacts. Therefore, the aim of this study was to evaluate the use of BR as an alternative source of Al2O3 and Fe2O3 in Portland cements clinker. Four formulations were developed: one without BR, which was used as a reference composition (C1),and three others containing 3wt%(C2)7 wt%(C3) and13 wt% (C4) of BR. As the main phases-C3S, C2S, C3A e C4AF- were detected in the produced clinker, it was clear that BR addition did not affect the mineralogical composition. Nevertheless, BR contents equal or greater than7wt% resulted in the formation of C3A doped with Na, which has an orthorhombic structure. Based on the quantitative X ray diffraction results and on the phase s morphology it was found that although the presence of residue has altered the chemical composition of the clinker, the mechanical behavior of the material was not affected. The mortars prepared with these clinkers reached satisfactory compressive strength and C4 materials had values of 39MPa. The results demonstrated that the presence of the BR did not affect negatively the quality of the produced material which indicates an interesting potential application for the BR.
Contribuições para a otimização da programação da produção de bebidas a base de frutas
(Universidade Federal de São Carlos, 2013-03-19) Pagliarussi, Marina Sanches; Morabito Neto, Reinaldo; https://lattes.cnpq.br/6595717122698262
Beverage factories have been trying to improve production planning and control to increase competitive advantages and market shares. In order to achieve such goals, the industries attempted to improve the process of meeting demands, manufacture larger product variety in less time, use less resources and considering the factory´s operating limit. This work considers a production planning problem which lies in the factories which manufactures non-alcoholic beverages fruit. The research problem is the lotscheduling of drinks, characterized by: finite planning horizon, multi-period, multimachine, capacity constraints, setup time and cost, special machine constraints (the machines must be cleaned after certain production time). An optimization approach based on mathematical modeling is proposed, considering different scenarios and using optimization softwares. The proposed models are variations of mixed-integer programming models well-known in the literature, such as the GLSPPL (General Lot Sizing and Scheduling Problem for Parallel Production Lines) and CLSP (Capacitated lot sizing problem). However, instead of considering parallel machines, different arrangements of machines are considered to obtain better representation of the production processes. In order to validate the models, we proposed an approach involving a case study in a beverage factory in the state of São Paulo. The solutions obtained by the models were compared with those used in practice. The results show that the proposed approach has good potential for practical use.
Abordagem ativa da acústica no ensino médio com a confecção de artefatos musicais pelos alunos
(Universidade Federal de São Carlos, 2013-03-19) Pereira, Rodrigo Machado; Leodoro, Marcos Pires; https://lattes.cnpq.br/2929842229198829; https://lattes.cnpq.br/1138096178145802
This paper aims to present, as experience report, an active approach to teaching about the content of Acoustics by contextualized knowledge of music, from the design and construction of sound artifacts with low cost materials for high school students. The activities were conducted in a public school of the state of São Paulo in the city of Mogi Guaçu. The acoustic content were worked both quantitatively and qualitatively. Qualitative analysis was applied to the study of the properties of sound musical artifacts produced by students taking into account the aspects of production, propagation and amplification of sound. The quantitative phase of didactic activity was conducted using the software "Soundcard Scope V1.4" which allowed the harmonic analysis of the sound produced by these devices and captured by the sound card of a computer. The active approach we present has its theoretical foundations in education and social constructivist approach is inspired by Kuhn's epistemology. Process is guided by social contextualization of knowledge and consideration, the teacher, the students' spontaneous conceptions, as well as the cooperative work between them. The mediation of the teacher tried to always be located within the Zone of Proximal Development (ZPD) of the students and thus contributing to the formalization of scientific concepts worked. We have also added strategies such as the use of Information and Communication Technologies (ICT) and the approach of the relations between Science, Culture and Society. The material production of students through the sound artifacts that confected, and the monitoring of the production process of these signs indicate that the work has motivated students for learning physics, and also contributed to make it meaningful to them, some concepts of acoustics.
Desenvolvimento da microscopia de força química usando modelagem molecular
(Universidade Federal de São Carlos, 2013-03-19) Amarante, Adriano Moraes; Leite, Fabio de Lima; https://lattes.cnpq.br/5490031389817518; https://lattes.cnpq.br/5625045786963147; Campos, Sérgio Dias; http://lattes.cnpq.br/5443100596356812; Cruz, Térsio Guilherme de Souza; http://lattes.cnpq.br/0705292304279277
In this work was developed a prototype of a new nanobiosensor with molecular specificity through a study of theoretical models of Chemical Force Microscope. For the sensing were used molecular modeling techniques as well as experimental models of the functionalized Atomic Force Microscope tip with the Acetil co-A Carboxylase (ACC) attached. Specific and non-specific inhibitors were used to evaluate substrate-enzyme interactions. The nanobiosensor investigates specific enzymatic inhibition characteristics of the ACC enzyme through the herbicide Diclofop by reversing this process applying a force in a determined direction. The force is theoretically calculated by using molecular dynamic techniques associated to the adhesion force experimentally obtained. Theoretical and experimental questions involving nanobiosensors of AFM tips still obscure until now, such as, the number of functional enzymes attached on the AFM tip, the number of the active sites available to interact after immobilization process, the consequences of the enzyme immobilization as well as the substrate and theoretical adhesion between AFM tip and substrate were analyzed here.