Síntese, Caracterização Estrutural e Análise do Potencial Catalítico, para a Preparação de Biodiesel, de Niobatos Não Estequiométricos com Estrutura Tungstênio Bronze

Pós-graduação em Química - IBILCE

Avaliação in vitro da resistência de união de dois sistemas adesivos dentinários à dentina bovina antes e após a termociclagem: teste de cisalhamento e análise estereomicroscópia

Pós-graduação em Odontologia Restauradora - ICT

Análise da efetividade de polimerização, adaptação marginal e interna de restaurações Classe II de resinas compostas de inserção em bloco utilizando diferentes matrizes

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Comparação energética de tijolos comum e sem queima pela análise do ciclo de vida

This work is part of several research related to the plan of design and construction of a sustainable house. The previous researches focused on sustainable materials and it have shown that ceramic material are more interesting to improve the thermal comfort and the reduction of fees and prices of the house, making possible to construct popular home, mainly clay bricks, that have high thermal inertia and low costs, besides the fact that it is easy to find the raw materials in nature and process them. However, a major issue in using clay bricks is that it uses too many energy to be processed during the sintering (burning), a crucial part of the process that assures mechanical resistance. Alternative materials are being proposed by the researchers, as the clay bricks without the sintering mixed with Portland cement, assuring the proper resistance to the brick. Raw materials of cement, however, also need to be thermally processed in rotary kilns, in a process called clinckerization. This research was proposed for comparing the energy used by the two types of bricks and other objectives, in order to determinate which one uses less thermal energy. The intention was to compare the energy used during the sintering of regular clay bricks and the unfired bricks with 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% and 100% of Portland cement. The paper also investigated and compared the use of electrical and thermal energy of all the bricks to identify how important were the thermal stages (sintering or clinkerization) relatively to the total energy spent. At last, a resumed analysis was performed to identify the possible health damages of the many life cycles of the bricks. The conclusion was that unfired bricks with less than 40% of cement use less thermal energy to be processed. In addition, their carbon dioxides emissions were less dangerous to ... (Complete abastract click electronic access below)

Comparação energética de tijolos comum e sem queima pela análise do ciclo de vida

This work is part of several research related to the plan of design and construction of a sustainable house. The previous researches focused on sustainable materials and it have shown that ceramic material are more interesting to improve the thermal comfort and the reduction of fees and prices of the house, making possible to construct popular home, mainly clay bricks, that have high thermal inertia and low costs, besides the fact that it is easy to find the raw materials in nature and process them. However, a major issue in using clay bricks is that it uses too many energy to be processed during the sintering (burning), a crucial part of the process that assures mechanical resistance. Alternative materials are being proposed by the researchers, as the clay bricks without the sintering mixed with Portland cement, assuring the proper resistance to the brick. Raw materials of cement, however, also need to be thermally processed in rotary kilns, in a process called clinckerization. This research was proposed for comparing the energy used by the two types of bricks and other objectives, in order to determinate which one uses less thermal energy. The intention was to compare the energy used during the sintering of regular clay bricks and the unfired bricks with 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% and 100% of Portland cement. The paper also investigated and compared the use of electrical and thermal energy of all the bricks to identify how important were the thermal stages (sintering or clinkerization) relatively to the total energy spent. At last, a resumed analysis was performed to identify the possible health damages of the many life cycles of the bricks. The conclusion was that unfired bricks with less than 40% of cement use less thermal energy to be processed. In addition, their carbon dioxides emissions were less dangerous to ... (Complete abastract click electronic access below)

Análise microscópica de incisões realizadas com três diferentes pontas do laser Erbio YAG

The study analised microscopic wound healing of incision made with Er:YAg laser with three different tips. In six Rattus norvegicus, incision was made with Laser Er-YAG (KeyLaser) using tips 2051, 2055 and 2056. The animals were killed at 7 e 14 and the sites of incision are photographed in this time. The parts containing the incision area were prepared for microscopic analysis, performing sections of 7µm and staining with haematoxylin and eosin. Zone of tissue ablation, zone of thermal necrosis, the presence and character of inflammatory cell infiltrate and wound healing were measured. The 2051 tip produced faster and defined edges of the wound. To create wound 1.30 mm in depth lasers tips required at last five passes within the same line of incision. Microscopic analysis shows no difference with use of three different laser tips

Contêineres metálicos para canteiros de obras: análise experimental de desempenho térmico e melhorias na transferência de calor pela envoltória.

Os contêineres metálicos foram desenvolvidos para a utilização no setor de logística e transporte, mas por sua escala adaptável à das edificações e pela mobilidade e praticidade de instalação, tiveram sua utilização apropriada também pelo setor da construção civil. Essas instalações possuem diversas qualidades ambientalmente amigáveis, mas seu aspecto térmico é extremamente insuficiente: sem isolamento térmico, demandam alta carga térmica de refrigeração e aquecimento, no verão e inverno, respectivamente e, consequentemente, um alto consumo energético. Tal característica foi crucial para que se determinassem como objetivos da presente pesquisa investigar o comportamento térmico dessas construções metálicas, avaliar seus parâmetros de desempenho, conforto e estresse térmicos, por meio de uma ampla coleta de dados experimentais. O experimento com duração de um ano - contou com três tipologias de contêiner em escala real, sendo o primeiro em aço Tipo X sem isolamento térmico, o segundo com um isolamento térmico para o fenômeno da condução e o terceiro com isolamento térmico para o fenômeno da radiação. Os diferentes tipos de tratamentos térmicos proporcionaram melhorias à envoltória dos contêineres, chegando a uma diferença nas temperaturas internas de até 9 °C. Constatou-se a extrema necessidade de adequação do tipo de isolamento térmico dos contêineres ao uso a que tais instalações se destinam escritório ou alojamento, no caso dos canteiros de obras para que as características da envoltória minimizem de fato a demanda ou mesmo atinjam a eliminação da necessidade de condicionamento artificial.

Um sensível espectrômetro de massa de fonte sólida e sua aplicação à análise de K, Rb e Sr

Um espectrômetro de massa de fonte sólida de alta sensibilidade e construído de vidro Pyrex é descrito com detalhe. Um sistema de vácuo convencional, constituído de uma bomba mecânica e uma bomba de difusão de mercúrio de duplo estágio, possibilita obter-se, após cerca de 6 horas de contínuo bombeamento, pressão adequada para início de análise de materiais sólidos pela técnica de ionização térmica. Por esta técnica, quantidades tão pequenas quanto alguns micromicrogramas de potássio ou rubídio podem ser analisadas, enquanto que para estrôncio, quantidades tão pequenas quanto 0,1 μg podem ser dosadas. É apresentada também a precisão média obtida na análise desses elementos, bem como a precisão na medida das razões isotópicas. Finalmente, uma série de resultados obtidos em diferentes tipos de rochas empregando-se tal aparelho, é submetida a estudos estatísticos para melhor aquilatar o comportamento do mesmo.

Análise comparativa dos métodos da ISO 13790 e sua adequabilidade na estimativa das necessidades de energia para aquecimento e arrefecimento e da temperatura do ar interior

Tese de mestrado integrado em Engenharia da Energia e do Ambiente, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2016

Análise da formulação em Monte Carlo dos pacotes de energia multiespectrais aplicada a meios constituídos por vapor d'água

The Monte Carlo method is accurate and is relatively simple to implement for the solution of problems involving complex geometries and anisotropic scattering of radiation as compared with other numerical techniques. In addition, differently of what happens for most of numerical techniques, for which the associated simulations computational time tends to increase exponentially with the complexity of the problems, in the Monte Carlo the increase of the computational time tends to be linear. Nevertheless, the Monte Carlo solution is highly computer time consuming for most of the interest problems. The Multispectral Energy Bundle model allows the reduction of the computational time associated to the Monte Carlo solution. The referred model is here analyzed for applications in media constituted for nonparticipating species and water vapor, which is an important emitting species formed during the combustion of hydrocarbon fuels. Aspects related to computer time optimization are investigated the model solutions are compared with benchmark line-by-line solutions

Análise da eficácia de um refrigerador doméstico com condensador modificado: revestimento com meio poroso dissipativo

The development of home refrigerators generally are compact and economic reasons for using simplified configuration. The thermodynamic coefficient of performance ( COP ) is limited mainly in the condenser design for reasons of size and arrangement ( layout ) of the project ( design ) and climatic characteristics of the region where it will operate. It is noteworthy that this latter limitation is very significant when it comes to a country of continental size like Brazil with diverse climatic conditions. The COP of the cycle depends crucially on the ability of heat dissipated in the condenser. So in hot climates like the northeast, north, and west-central dispel ability is highly attenuated compared to the south and southeast regions with tropical or subtropical climates when compared with other regions. The dissipation in compact capacitors for applications in domestic refrigeration has been the focus of several studies, that due to its impact on reducing costs and power consumption, and better use of the space occupied by the components of refrigeration systems. This space should be kept to a minimum to allow an increase in the useful storage volume of refrigerator without changing the external dimensions of the product. Due to its low cost manufacturing, wire on tube condensers continue to be the most advantageous option for domestic refrigeration. Traditionally, these heat exchangers are designed to operate under natural convection. Not always, the benefits of greater compactness of capacitors for forced outweigh the burden of pumping air through the external heat exchanger. In this work we propose an improvement in convective condenser changing it to a transfer mechanism combined in series with conductive pipes and wire to a moist convective porous medium and the porous medium to the environment. The porous media used in the coating was composed of a gypsum plaster impregnated fiber about a mesh of natural cellulosic molded tubular wire mesh about the original structure of the condenser , and then dried and calcined to greater adherence and increased porosity. The proposed configuration was installed in domestic refrigeration system ( trough ) and tested under the same conditions of the original configuration . Was also evaluated in the dry condition and humidified drip water under natural and forced with an electro - fan ( fan coil ) convection. Assays were performed for the same 134- refrigerant charge e under the same thermal cooling load. The performance was evaluated in various configurations, showing an improvement of about 72 % compared with the original configuration proposed in humidification and natural convection.

Secagem de resíduo de goiaba em secador convectivo de bandejas: modelagem matemática e análise do processo

Actually, Brazil is one of the larger fruit producer worldwide, with most of its production being consumed in nature way or either as juice or pulp. It is important to highlig ht in the fruit productive chain there are a lot lose due mainly to climate reasons, as well as storage, transportation, season, market, etc. It is known that in the pulp and fruit processing industy a yield of 50% (in mass) is usually obtained, with the other part discarded as waste. However, since most this waste has a high nutrient content it can be used to generate added - value products. In this case, drying plays an important role as an alternative process in order to improve these wastes generated by the fruit industry. However, despite the advantage of using this technique in order to improve such wastes, issues as a higher power demand as well as the thermal efficiency limitation should be addressed. Therefore, the control of the main variables in t his drying process is quite important in order to obtain operational conditions to produce a final product with the target specification as well as with a lower power cost. M athematical models can be applied to this process as a tool in order to optimize t he best conditions. The main aim of this work was to evaluate the drying behaviour of a guava industrial pulp waste using a batch system with a convective - tray dryer both experimentally and using mathematical modeling. In the experimental study , the dryin g carried out using a group of trays as well as the power consume were assayed as response to the effects of operational conditions (temperature, drying air flow rate and solid mass). Obtained results allowed observing the most significant variables in the process. On the other hand, the phenomenological mathematical model was validated and allowed to follow the moisture profile as well as the temperature in the solid and gas phases in every tray. Simulation results showed the most favorable procedure to o btain the minimum processing time as well as the lower power demand.

Produção e análise do desempenho óptico e elétrico de filmes finos de SnO2:F para aplicações fotovoltaicas

Conselho Nacional de Desenvolvimento Científico e Tecnológico - CNPq

Análise não-linear do campo de temperaturas desenvolvidas durante a soldagem do tipo TIG contínuo em placas delgadas

This study offers an analytical approach in order to provide a determination of the temperature field developed during the DC TIG welding of a thin plate of aluminum. The non-linear characteristics of the phenomenon, such as the dependence of the thermophysical and mechanical properties with temperature were considered in this study. In addition to the conductive heat exchange process, were taken into account the exchange by natural convection and radiation. A transient analysis is performed in order to obtain the temperature field as a function of time. It is also discussed a three-dimensional modeling of the heat source. The results obtained from the analytical model were be compared with the experimental ones and those available in the literature. The analytical results show a good correlation with the experimental ones available in the literature, thus proving the feasibility and efficiency of the analytical method for the simulation of the heat cycle for this welding process.

Análise tribo-termodinâmica da aplicação de nanopartículas de Al2O3 como aditivo lubrificante em compressor hermético de refrigeração

The thermodynamic performance of a refrigeration system can be improved by reducing the compression work by a particular technique for a specific heat removal rate. This study examines the effect of small concentrations of Al2O3 (50 nm) nanoparticles dispersion in the mineral oil based lubricant on the: viscosity, thermal conductivity, and lubrication characteristics as well as the overall performance (based on the Second Law of Thermodynamics) of the refrigerating system using R134a or R600a as refrigerants. The study looked at the influences of variables: i) refrigerant charge (100, 110, 120 and 130 g), ii) rotational speed of the condenser blower (800 and 1100 RPM) and iii) nanoparticle concentration (0.1 and 0.5 g/l) on the system performance based on the Taguchi method in a matrix of L8 trials with the criterion "small irreversibility is better”. They were carried pulldown and cycling tests according to NBR 12866 and NBR 12869, respectively, to evaluate the operational parameters: on-time ratio, cycles per hour, suction and discharge pressures, oil sump temperature, evaporation and condensation temperatures, energy consumption at the set-point, total energy consumption and compressor power. In order to evaluate the nanolubricant characteristics, accelerated tests were performed in a HFRR bench. In each 60 minutes test with nanolubricants at a certain concentration (0, 0.1 and 0.5 g/l), with three replications, the sphere (diameter 6.00 ± 0.05 mm, Ra 0.05 ± 0.005 um, AISI 52100 steel, E = 210 GPa, HRC 62 ± 4) sliding on a flat plate (cast iron FC200, Ra <0.5 ± 0.005 um) in a reciprocating motion with amplitude of 1 mm, frequency 20 Hz and a normal load of 1,96 N. The friction coefficient signals were recorded by sensors coupled to the HFRR system. There was a trend commented bit in the literature: a nanolubricant viscosity reduction at the low nanoparticles concentrations. It was found the dominant trend in the literature: increased thermal conductivity with increasing nanoparticles mass fraction in the base fluid. Another fact observed is the significant thermal conductivity growth of nanolubricant with increasing temperature. The condenser fan rotational speed is the most influential parameter (46.192%) in the refrigerator performance, followed by R600a charge (38.606%). The Al2O3 nanoparticles concentration in the lubricant plays a minor influence on system performance, with 12.44%. The results of power consumption indicates that the nanoparticles addition in the lubricant (0.1 g/L), together with R600a, the refrigerator consumption is reduced of 22% with respect to R134a and POE lubricant. Only the Al2O3 nanoparticles addition in the lubricant results in a consumption reduction of about 5%.