Controle inteligente de sistemas eletroidráulicos utilizando redes neurais artificiais

This work describes the development of a nonlinear control strategy for an electro-hydraulic actuated system. The system to be controlled is represented by a third order ordinary differential equation subject to a dead-zone input. The control strategy is based on a nonlinear control scheme, combined with an artificial intelligence algorithm, namely, the method of feedback linearization and an artificial neural network. It is shown that, when such a hard nonlinearity and modeling inaccuracies are considered, the nonlinear technique alone is not enough to ensure a good performance of the controller. Therefore, a compensation strategy based on artificial neural networks, which have been notoriously used in systems that require the simulation of the process of human inference, is used. The multilayer perceptron network and the radial basis functions network as well are adopted and mathematically implemented within the control law. On this basis, the compensation ability considering both networks is compared. Furthermore, the application of new intelligent control strategies for nonlinear and uncertain mechanical systems are proposed, showing that the combination of a nonlinear control methodology and artificial neural networks improves the overall control system performance. Numerical results are presented to demonstrate the efficacy of the proposed control system

Estudo das propriedades físico-químicas do biodiesel e suas influências na deterioração dos elastômeros aplicados no sistema de injeção dos motores diesel

The biodiesel use has become important due to its renewable character and to reduce environmental impacts during the fuel burning. Theses benefit will be valid if the fuel shows good performance, chemistry stability and compatibility with engines. Biodiesel is a good fuel to diesel engines due to its lubricity. Then, the aimed of this study was to verify the physicalchemistry properties of biodiesel and their correlations with possible elastomers damage after biodiesel be used as fuel in an injection system. The methodology was divided in three steps: biodiesels synthesis by transesterification of three vegetable oil (soybean, palm and sunflower) and their physical-chemistry characterization (viscosity, oxidative stability, flash point, acidity, humidity and density); pressurized test of compatibility between elastomers (NBR and VITON) and biodiesel, and the last one, analyze of biodiesels lubricity by tribological test ball-plan( HFRR). Also, the effect of mixture of biodiesel and diesel in different concentrations was evaluated. The results showed that VITON showed better compatibility with all biodiesel blends in relation to NBR, however when VITON had contact with sunflower biodiesel and its blends the swelling degree suffer higher influences due to biodiesel humidity. For others biodiesels and theirs blends, this elastomer kept its mechanical properties constant. The better tribological performance was observed for blends with high biodiesel concentration, lower friction coefficient was obtained when palm biodiesel was used. The main mechanisms observed during the HFRR tests were abrasive and oxidative wear

Caracterização do óleo de carnaúba para uso como biolubrificante

Lubricant is responsible for reducing the wear on the friction protect the metal against oxidation, corrosion and dissipates excess heat, making it essential for the balance of a mechanical system, consequently prolonging the useful life of such a system. The origin of lubricating oils is usually mineral being extracted from the petroleum. But the search for a new source of production of lubricants and fuels it is necessary to meet future demands and reduce the possible environmental damage. For this reason, looking alternative means to produce certain products derived from petroleum, such as biodiesel, for example. Returning to the realm of lubricants, also one realizes this need for new raw materials for their production. Vegetable oil is a renewable resource and biodegradable, and its use entails advantages in environmental, social and economic. The development of this project aims to characterize the carnauba oil as a lubricant plant, or biolubricant. To analyze the oil carnauba tests as checking density, flash point, fire point, viscosity, viscosity, acid number, pH, copper corrosion, thermal conductivity and thermal resistivity were developed. In addition, for conducting the wear on the friction and the gradient of the system temperature, the analysis equipment is designed for wear on the friction. Based on these results, it is observed that the oil carnauba show good correlation to its application as biolubricant

Estudo tribológico de biolubrificantes com adição de nanopartículas de óxidos (zinco e cobre)

Currently, vegetable oils have been studied for bio-lubricants base that fits the new environmental standards. Since, in a world full of finite natural resources, mineral oils bring consequences to the environment due to its low biodegradability and toxicity, also it is important to consider that synthetic oils have a high cost The aim of this work is to obtain a biolubricant additived with oxide nanoparticles (ZnO and CuO) for better resistance to friction and wear, which is not toxic to the environment and have better adherence under boundary lubrication. The methodology consisted in the synthesis of bio-lubricants (soybean and sunflower base) by epoxidation reaction. Then, some physical-chemical analysis in bio-lubricants are made to characterize theses lubricants, such as, density, acidity, iodine value, viscosity, viscosity index. Later, the lubricants were additive with nanoparticles. The tribological performance was evaluated by the equipment HFRR (High Frequency Reciprocating Rig) consisting of a wear test ball-plan type. The characterization of wear analysis was performed by SEM / EDS. The results show that bio-lubricants may be synthesized by reaction of epoxidation with good conversion. Tribological point of view, the epoxidized oils are more effective than lubricant additived with the oxide nanoparticles, they had lower coefficients of friction and better rate of film formation in the study. However, because they are environmentally friendly, bio-lubricants gain the relevant importance in tribological field

Avaliação da molhabilidade de soluções de tensoativos em aço inoxidável

With the increasing industrialization of the planet caused by globalization, it has become increasingly common to search for highly resistant and durable materials for many diverse branches of activities. Thus, production and demand for materials that meet these requirements have constantly increased with time. In view of this, stainless steel is presented as one of the materials which are suitable applications, due to many features that are interesting for several segments of the industry. Concerns of oil companies over heavy oil reservoirs have grown steadily for the last decades. Rheological properties of these oils impair their transport in conventional flow systems. This problem has created the need to develop technologies to improve flow and transport, reducing operation costs so as to enable oil production in the reservoir. Therefore, surfactant-based chemical systems are proposed to optimize transport conditions, effected by reduction of interfacial tensions, thereby enhancing the flow of oil in ducts and reducing load losses by friction. In order to examine such interactions, a study on the wettability of metallic surfaces has been undertaken, represented by measuring of contact angle of surfactant solutions onto flat plates of 304 stainless steel. Aqueous solutions of KCl, surfactants and mixtures of surfactants, with linear and aromatic hydrocarbon chain and ethoxylation degrees ranging between 20 to 100, have been tested. The wettability was assessed by means of a DSA 100 krüss goniometer. The influence of roughness on the wettability was also investigated by machining and polished the stainless steel plates with sandpapers of references ranging between 100 of 1200. The results showed that sanding and polishing plates result in decrease of wettability. As for the solutions, they have provided better wettability of the stainless steel than the KCl solutions tested. It was also been concluded that surfactant mixtures is an option to be considered, since they promote interactions that generate satisfactory contact angles for a good wettability on the stainless steel plate. Another conclusion refers to the influence of the ethoxylation degree of the nonionic surfactant molecules on wettability. It has been observed that contact angles decrease with decreasing ethoxylation degrees. This leads us to conclude that molecules with higher ethoxylation degree, being more hydrophobic, decrease the interaction of water with the ducts, thereby reducing friction and improving the flow

Viabilidade técnica de uma rota não convencional para a produção de leite de cabra em pó em cooperativas do Rio Grande do Norte

Nowadays, Brazil has both the greatest goat herd and the greatest goat milk production of South America. The state of Rio Grande do Norte, located in northeast of Brazil, has an average year production of three thousand cubic meters of goat milk in natura. Part of this milk production is homemade and it comes from small farms, which unite in rural cooperatives created to encourage the production and implementation of industrial processes for preservation and processing of milk. Results presented by literature and obtained from preliminary essays in this thesis show that non conventional dryer of spouted bed with inert particles is able to produce powder milk from in natura milk (cattle or goat), with the same quality of spray dryer, however, operating at low cost. The method of drying in spouted bed consists of injecting milk emulsion on the bed of inert particles gushed by hot air. This emulsion covers the particles with a thin film, which dries and is reduced to powder during the circulation of inerts inside the bed. The powder is dragged by exhaustion air and separated in the cyclone. The friction among particles resulted from the particles circulation, encourages high taxes of shear in the thin film of emulsion, breaking the cohesive forces and making this process possible. Studying the drying process and the powder goat milk production in one unit of spouted bed with inert particles, seeing the development of a low cost technological route for powder milk production is the aim of this thesis. The powder milk produced by this route must attend the local demand of food industries which need an intermediate product to be used as a food ingredient (ice-cream, milk candy). In order to reach this aim, this thesis approaches the aspects related to physical, thermodynamics and physic-chemicals characteristics of goat milk, whose complete data are still inexistent in the literature. The properties of materials are of great importance to the project of any process which involves the operations of transportation of movement, heat and mass quantity, such as the dryers which operate in fluid dynamically active regime, like the spouted bed. It was obtained new data related to the goat milk properties in function of concentration of solids and temperature. It is also important to mention the study developed about the kinetic of solids retention in the bed of inert particles during the drying of goat milk. It was found more adequate processes conditions to the proposed technological route to be implemented in small and micro-industries, with simplifications in the system of milk injection as well as in the form of operation of the dryer. Important data were obtained for a posterior stage of this research which involves the v modeling, simulation, control and optimization of the process. The results obtained in this thesis, in relation to process performance as well as to the quality of produced powder milk validate the proposal of using the spouted bed dryer in the production of powder goat milk

Síntese e caracterização de materiais nanoporosos para pirólise catalítica de óleos pesados

The present work reports the study of nanoporous structures, aiming at their use in research directed to the current demand of the petroleum industry to value heavy oil. Initially, two ways were chosen for the synthesis of porous structures from the molecular sieves of type Si-MCM-41. In the first way, the structure MCM-41 is precursory for heteroatom substitutes of silicon, generating catalyst of the type Al-MCM-41 from two different methods of incorporation of the metal. This variation of the incorporation method of Aluminum in the structure of Si-MCM-41 was carried out through the conventional procedure, where the aluminum source was incorporated to the gel of synthesis, and the procedure post-synthesis, where the Aluminum source was incorporated in catalyst after the synthesis of Si-MCM-41. In the second way, the MCM-41 acts as a support for growth of nanocrystals of zeolite embedded in their mesoporous, resulting in hybrid MCM-41/ZSM-5 catalyst. A comparative analysis was carried through characterizations by XRD, FTIR, measures of acidity through n-butylamine adsorption for TGA, SEM-XRF and N2 adsorption. Also crystalline aluminosilicate with zeolitic structure MFI of type ZSM-5 was synthesized without using organic templates. Methodologies to the preparation of these materials are related by literature using conventionally reactants that supply oxides of necessary silicon and aluminum, as well as a template agent, and in some cases co-template. The search for new routes of preparation for the ZSM-5 aimed at, above all, the optimization of the same as for the time and the temperature of synthesis, and mainly the elimination of the use of organic templates, that are material of high cost and generally very toxic. The current study is based on the use of the H2O and Na+ cations playing the role of structural template and charge compensation in the structure. Characterizations by XRD, FTIR, SEM-XRF and N2 adsorption were also conducted for this material in order to compare the samples of ZSM-5 synthesized in the absence of template and those used industrially and synthesized using structuring

Síntese de catalisadores nanoporosos na ausência total e parcial de direcionadores orgânicos para pirólise catalítica de óleos pesados e intermediários

The processing of heavy oil produced in Brazil is an emergency action and a strategic plan to obtain self-sufficiency and economic surpluses. Seen in these terms, it is indispensable to invest in research to obtain new catalysts for obtaining light fraction of hydrocarbons from heavy fractions of petroleum. This dissertation for the degree of Doctor of Philosophy reports the materials preparation that combine the high catalytic activity of zeolites with the greater accessibility of the mesoporosity, more particularly the HZSM-5/MCM-41 hybrid, done by synthesis processes with less environmental impact than conventional ones. Innovative methodologies were developed for the synthesis of micro-mesoporous hybrid material by dual templating mechanism and from crystalline zeolitic aluminosilicate in the absence of organic template. The synthesis of hybrid with pore bimodal distribution took place from one-single organic directing agent aimed to eliminate the use of organic templates, acids of any kind or organic solvents like templating agent of crystalline zeolitic aluminosilicate together with temperature-programmed microwave-assisted, making the experimental procedures of preparation most practical and easy, with good reproducibility and low cost. The study about crystalline zeolitic aluminosilicate in the absence of organic template, especially MFI type, is based on use of H2O and Na+ cation playing a structural directing role in place of an organic template. Advanced characterization techniques such as X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Highresolution Transmission Electron Microscopy (HRTEM), Adsorption of N2 and CO2, kinetic studies by Thermogravimetric Analysis (TGA) and Pyrolysis coupled to Gas Chromatography/Mass Spectrometry (Pyrolysis-GC/MS) were employed in order to evaluate the synthesized materials. Achieve the proposed objectives, has made available a set of new methodologies for the synthesis of zeolite and hybrid micro-mesoporous material, these suitable for catalytic pyrolysis of heavy oils aimed at producing light fraction

Estudo de alterações na cavidade oral em pacientes com doença do refluxo gastroesofágico

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Contribuições para a detecção e identificação de faltas em inversores Multiníveis

This work presents contributions in the detection and identication of faults in multilevel inverters through the study of the converters behavior under these operation conditions. Basically, the approached fault consists of an open-circuit in any switch of a three-level clamped diode inverter. The converter operation is characterized in the pre and post-fault states. A wave form behavior analysis of the pole voltage, phase current and dc-bus current is also done, which highlights characteristics that allow the detection of failure and, even, under favorable conditions, the identication of the faulty device. A compensation strategy of the approached fault (open-switch) is also investigated with the purpose of maintaining the driving system operational when a failure occurs. The proposed topology uses SCRs in parallel with the internal switches of the inverter, which allows, in some occasions, the full utilization of the dc-bus

Aspectos clínicos, ultra-sonográficos e venográficos da tromboflebite jugular experimental em equinos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Rheological and thermophysical properties of blackberry juice

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Respostas fisiológicas ao déficit hídrico em duas cultivares enxertadas de seringueira (RRIM 600 e GT 1) crescidas em campo

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Comparison of the dehydration kinetics of solid state compounds of 2-methoxybenzylidenepyruvate with some divalent metal ions

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

The hydraulic management of the Barra Bonita reservoir (SP, Brazil) as a factor influencing the temporal succession of its fish community

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)