Mecanismos de desgaste, história térmica e ciclo de vida de componentes de um motor de combustão interna de aeromodelo

We developed an assay methodology that considered the temperature variation and the scanning electron microscopy as a method to quantify and characterize respectively the consumption evolution in three 46 LA machines, with internal combustion and two-stroke engines, 7.64 cm3 cylinder capacity, 23.0 millimeters diameter and 18.4 millimeters course, RPM service from 2.000 to 16.000 rpm, 1.2 HP power, and 272 grams weight. The investigated engines components were: (1) head of the engine (Al-Si alloy), (2) piston (Al-Si alloy) and (3) piston pin (AISI 52100 steel). The assays were carried out on a desktop; engines 1 and 2 were assayed with no load, whereas in two assays of engine 3 we added a fan with wind speed that varied from 8.10 m/s to 11.92 m/s, in order to identify and compare the engine dynamic behavior as related to the engines assayed with no load. The temperatures of the engine s surface and surroundings were measured by two type K thermopairs connected to the assay device and registered in a microcomputer with data recording and parameters control and monitoring software, throughout the assays. The consumed surface of the components was analyzed by scanning electron microscopy (SEM) and microanalysis-EDS. The study was complemented with shape deformation and mass measurement assays. The temperature variation was associated with the oxides morphology and the consumption mechanisms were discussed based on the relation between the thermal mechanical effects and the responses of the materials characterization

Mecanismos de desgaste de poliuretano em ensaios de microabrasão

Wear mechanisms and thermal history of two non-conforming sliding surfaces was investigated in laboratory. A micro-abrasion testing setup was used but the traditional rotative sphere method was substituted by a cylindrical surface of revolution which included seven sharp angles varying between 15o to 180o. The micro-abrasion tests lead to the investigation on the polyurethane response at different contact pressures. For these turned counterfaces with and without heat treatment. Normal load and sliding speeds were changed. The sliding distance was fixed at 5 km in each test. The room and contact temperatures were measured during the tests. The polyurethane was characterized using tensile testing, hardness Shore A measurement, Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and Thermomechanical Analyze (TMA). The Vickers micro-hardness of the steel was measured before and after the heat treatment and the metallographic characterization was also carried out. Worn surface of polyurethane was analysed using Scanning Electron Microscope (SEM) and EDS (Electron Diffraction Scanning) microanalyses. Single pass scratch testing in polyurethane using indenters with different contact angles was also carried out. The scar morphology of the wear, the wear mechanism and the thermal response were analyzed in order to correlate the conditions imposed by the pressure-velocity pair to the materials in contact. Eight different wear mechanisms were identified on the polyurethane surface. It was found correlation between the temperature variation and the wear scar morphology.

Desenvolvimento de um destilador solar para tratamento de águas de produção de petróleo com vistas a sua utilização na agricultura e geração de vapor

The production of petroleum is frequently accomplished with great volumes of water, that it is carried of the underground with the oil. It is a challenge of the present century the development of technologies that allow the use of waste water for purposes that consume great amounts of water and don't demand as rigid as the one of the drinking water requirements. The solar distillation has been configuring as an alternative of clean technology for desalination of brine and saline. Besides causing the minimum possible damage to the environment, it takes advantage of an abundant and free energy source: the solar energy. That study aims to develop a Solar Distillator for treatment of the produced water of the oil wells, to obtain an efluent to use in agriculture and vapor generation. The methodology for collection, conservation and analysis of the physical-chemical parameters obeyed the norms in APHA (1995). The sampling was of the composed type. Experiments were accomplished in the solar distillation pilot and simulation in thermostatic bathing. The operation was in batch system and for periods of 4, 6 and 12 h. The developed Distillator is of the type simple effect of two waters. It was still tested two inclination angles for covering; 20º and 45º. The Distillator presented minimum of 2,85 L/m2d revenues and maximum of 7,14 L/m2d. The removals of salts were great than 98%. The removal of TOC in the simulation was great than 90%. In agreement with the data of energy and mass balance, it was verified that the developed solar Distillator presented compatible revenues with those found in literature for similar types. It can be inferred that the obtained distilled water assists to the requirements CONAMA in almost all the points and could be used for irrigation of cultures such as cotton and mamona. As the distilled water has characteristics of fresh water it can be used in the generation of vapor

Análise do modelo troposférico empregado na geração de uma estação de referência virtual utilizando o posicionamento por ponto preciso

In the past few years the interest is accomplishing a high accuracy positioning increasing. One of the methods that has been applied by the scientific community is the network based on positioning. By using multiple reference station data, it is possible to obtain centimetric positioning in a larger coverage area, in addition to gain in reliability, availability and integrity of the service. Besides, using this concept, it is possible to model the atmospheric effects (troposphere refraction and ionosphere effect). Another important question concerning this topic is related to the transmission of the network corrections to the users. There are some possibilities for this fact and an efficient one is the Virtual Reference Station (VRS) concept. In the VRS concept, a reference station is generated near to the rover receiver (user). This provides a short baseline and the user has the possibility of using a single frequency receiver to accomplish the relative positioning. In order to test this kind of positioning method, a software has been developed at São Paulo State University. In this paper, the methodology applied to generate the VRS data is described and the VRS quality is analyzed by using the Precise Point Positioning (PPP) method.

Mecanismos de coesão referencial na produção escrita de alunos concluintes do ensino fundamental

This work aims to identify, describe and analyze the main mechanisms of reference present in the texts produced by students that are finishing their fundamental school. With this in mind, we observe 46 Portuguese classes. The class was in its 9th Fundamental level, in a public school of the Cruzeta, RN. In this period, we collected our corpus that is composed by the papers that students produced. This research has an ethnographic approach and it has as theoretical support some studies about some mechanisms of reference, specifically, the lexical repetition and anaphor. In general, we are based on the studies about cohesive mechanisms from authors as Adam (2008); Beaugrande and Dressler (1981, 1997); Koch (1999, 2004, 2005, 2008), Marcuschi (1983, 1992, 2005, 2006); Bessa Neto (1991) and Neves (2006). In the corpus, we could identify some lexical repetitions (literal, with estrutural variation), as well as, anaphors, mainly pronominal ones. Then, we can notice that most students have showed difficulties in the use of those mechanisms of reference as a strategy of textual progression

Mecanismos de coesão referencial na produção escrita de alunos concluintes do ensino fundamental

This work aims to identify, describe and analyze the main mechanisms of reference present in the texts produced by students that are finishing their fundamental school. With this in mind, we observe 46 Portuguese classes. The class was in its 9th Fundamental level, in a public school of the Cruzeta, RN. In this period, we collected our corpus that is composed by the papers that students produced. This research has an ethnographic approach and it has as theoretical support some studies about some mechanisms of reference, specifically, the lexical repetition and anaphor. In general, we are based on the studies about cohesive mechanisms from authors as Adam (2008); Beaugrande and Dressler (1981, 1997); Koch (1999, 2004, 2005, 2008), Marcuschi (1983, 1992, 2005, 2006); Bessa Neto (1991) and Neves (2006). In the corpus, we could identify some lexical repetitions (literal, with estrutural variation), as well as, anaphors, mainly pronominal ones. Then, we can notice that most students have showed difficulties in the use of those mechanisms of reference as a strategy of textual progression

Ave! Mossoró! : os mecanismos discursivos sobre o episódio da resistência ao bando de Lampião

This thesis has as objective the interdiscursive relations in the process of language construction in use in the poetic and in the journalistic spheres, with the purpose of perceiving how the genre news is constituted in different fields of social activity, as well as to analyze the argumentative processes that structure the written discourses about the resistance episode to the group of Lampião in Mossoró in the year of 1927. The corpus of the research is constituted by the news of the period informed in the printed newspapers: Correio do povo and O Nordeste, both from Mossoró/RN, and the narratives presented in the cordéis de acontecido : Mossoró in the resistance to the group of Lampião; Lampião in Mossoró in 1927, and Mossoró attacking to the group of Lampião, all potiguar poets. The analysis of the texts had as theoretical background the studies of: The texts analysis had as theoretical background The Discourse Analysis; The Argumentation Theory and the studies about Discourse Genres. We focused our discussion in the emphasis given to the news in the discursive perspective of the social-historic memory constructed in the cordéis, from ideological values (political, economical, religious etc.) that pass to be a fundamental element in the constitution of the image of the resistance. Methodologically, this is a documental research, since it makes use essentially of the written document. Regarding to the nature of the data, the research is characterized as a qualitative one. In the analysis, we considered the argumentative techniques adopted in the defense of the thesis, the meaning effects suggested, and the genres mentioned, that revealed to us the manner in which the episode was informed by the newspapers and the cordéis. That way, we affirm, based on the positions assumed by the announcers of the genres analyzed who defended clearly positions in favor of the defense of Mossoró, that the relation between both is captured interdiscursively, since they are asked by the same ideology, and converge to the same discursive formation, defending identical positions, and structuring their discussions with resembling argumentative techniques, reason by which take us to believe that the discourse presented in that social activity demonstrates and develops traces of a manipulation of the subject. In this case, the discursive construction of the text points towards determining standard of repetition, since the linguistic context is characterized in the journalistic field, and in the poetic field assuming, in the first instance, a local expression

Mecanismos de controle do trabalho escolar em propostas de escrita narrativa em livros didáticos de português (1974-2009)

This essay aims at investigating the writing proposals of Portuguese textbooks (LDP Livros Didáticos de Português) for Middle School (EF Ensino Fundamental), from 6th to 9th grade, from the 70s to 2009. It aims to check, though the discourse reported in the Portuguese Textbook, the control directed to the practice of the teacher and the student to do in the teaching situations. Theoretically, we search for contributions that come from the Discourse Analysis of French filiation, so we can analyze the ideological constructions present in the discourse of the ―LDP‖ more specific lly the control directed to the te cher nd student the users of the book, in writing activities. It started from a corpus of 63 textbooks whereof the following steps were performed: a) mapping of the writing proposals contemplated in the ―LDP‖ of high school; b cutting in the selection of propos l ccording to the rese rch go ls intended (writing proposals of narrative texts). After mapping the writing proposals presented in the ―LDP‖ bout the criteri mentioned bove we re d the writing propos ls to ch rt the quantity of proposals of textual writing productions in each textbook (which usually follows a pattern : 12 chapters and, at the end, the writing proposal. Nevertheless, some books present 2 (two) or more writing proposals at the end of each chapter). We did a cutting in the corpus initi lly constituted 63 ―LDP‖ nd we selected 12 writing proposals of narrative texts presented in the ―LDPs‖ to present wh t we intend to n lyze. Then, we separated these proposals into two groups: 1) activities which present ―instruction guide‖ to be followed by the student; 2) writing activities that allow the student write with no need to follow a text pattern, i.e., which encourage authorship. By means of analyses, it was possible to demonstrate that, in the Basic School, generally, the writing practices concentrate, primarily, on copying activities, reproduction, rewriting and, in more advanced levels, in activities that which start from preset models, asking the students to produce text with similar themes, following the suggested structure. It is about ideals that are supposed to be followed and imitated by the students, depriving them to assume their authorship. In order to insert the student in the world of writing it s necess ry to go beyond the model of c nonic l texts pr ctice th t puts the students f r from the possibility to be ― uthors‖. In contr st to this tendency, we face, nowadays, proposals that prioritize the authorship, the creation of a style

Apreciações de alunos de inglês sobre sua produção oral: um estudo com base no sistema de avaliatividade

O vasto número de pesquisas sobre produção oral no ensino de Inglês como Língua Estrangeira (ILE) ao redor do mundo (p. ex. LITTLEWOOD, 1981; BROWN; YULE, 1983; BROWN, 1994; UR, 1996; CARTER; MCCARTHY, 1997; BROWN, 1994; 2004; ELLIS, 2008), assim como estudos sobre aspectos cognitivos e de aquisição da produção oral (SWAIN, 1985; 1995; LEVELT, 1989; SWAIN; LAPKIN, 1995; SKEHAN; FOSTER, 1997; 1999; ROBINSON, 2001; BYGATE, 2001; D‟ELY;WEISSHEIMER, 2004; GUARÁ-TAVARES, 2007; WEISSHEIMER, 2007; BERGSLEITHNER, 2009; dentre outros) têm revelado aspectos para um ensino de ILE mais eficaz e motivador. Com a proposta de contribuir para esse avanço, o presente estudo está inserido no paradigma qualiquantitativo de pesquisa no campo da Linguística Aplicada (LA), primordialmente com base nos estudos de Moita Lopes (1996; 2006), para quem a LA está centrada na resolução de problemas de uso da linguagem, cujo foco está na linguagem de natureza processual. O estudo tem como objetivo verificar as percepções de 34 alunos, de quatro turmas distintas de um curso de ILE, em uma escola privada de línguas, acerca de sua produção oral, ao participarem de atividades orais. O corpus da pesquisa foi gerado pelas respostas dos alunos a questionamentos sobre sua produção oral, em duas fases, no início e no meio do curso, além de uma entrevista semiestruturada realizada com dez dos alunos, ao final do curso, com o intuito de verificar suas percepções sobre sua produção oral. As discussões relacionadas à produção oral em sala de aula de ILE têm respaldo teórico nos trabalhos de Littlewood (1981), Brown e Yule (1983), Almeida Filho (1993), Brown (1994), Ur (1996), Carter e McCarthy (1997), Nunan (1999), Brown (2004) e Ellis (2008), que explicam fenômenos que exercem influência na produção oral, tais como afeto, interação, características de atividades orais, dentre outras variáveis em relação a aspectos cognitivos da produção oral analisadas pelos estudos de Swain (1985; 1995), Levelt (1989), Swain e Lapkin (1995), Skehan e Foster (1997; 1999), Robinson (2001) e Bygate (2001). A análise e discussão dos dados tem como base a Gramática Sistêmico-Funcional proposta por Halliday (1985; 1994) e posteriormente desenvolvida por Halliday e Hasan (1989), Halliday e Mathiessen (2004) e Eggins (2004), dentre outros. O foco desta pesquisa são os mecanismos de Apreciação, um dos domínios avaliativos do subsistema de Atitude, que por sua vez, é parte integrante do Sistema de Avaliatividade, desenvolvido por Martin (2000), Martin e Rose (2003) e Martin e White (2005). Para análise das escolhas linguísticas feitas pelos alunos, utilizamos a ferramenta computacional WordSmith Tools 6.0 (SCOTT, 2010), cuja função Wordlist (lista de palavras) foi utilizada na busca pelos tipos de processos, assim como epítetos, entre outras marcas linguísticas mais recorrentes que caracterizassem suas percepções. Os resultados revelam que nas percepções dos alunos acerca de sua produção oral, ao longo das três fases da geração dos dados para a pesquisa, eles gradativamente deixaram de mencionar aspectos afetivos quanto ao desenvolvimento de sua produção oral e passaram a perceber aspectos mais estruturais de composição da língua

A influência do esqueleto açúcar-fostato no transporte da molécula de DNA

This dissertation analyses the influence of sugar-phosphate structure in the electronic transport in the double stretch DNA molecule, with the sequence of the base pairs modeled by two types of quasi-periodic sequences: Rudin-Shapiro and Fibonacci. For the sequences, the density of state was calculated and it was compared with the density of state of a piece of human DNA Ch22. After, the electronic transmittance was investigated. In both situations, the Hamiltonians are different. On the analysis of density of state, it was employed the Dyson equation. On the transmittance, the time independent Schrödinger equation was used. In both cases, the tight-binding model was applied. The density of states obtained through Rudin-Shapiro sequence reveal to be similar to the density of state for the Ch22. And for transmittance only until the fifth generation of the Fibonacci sequence was acquired. We have considered long range correlations in both transport mechanism

Evolução top-hat hidrodinâmica em campos de velocidades peculiares primordiais

We investigate the cosmology of the vacuum energy decaying into cold dark matter according to thermodynamics description of Alcaniz & Lima. We apply this model to analyze the evolution of primordial density perturbations in the matter that gave rise to the first generation of structures bounded by gravity in the Universe, called Population III Objects. The analysis of the dynamics of those systems will involve the calculation of a differential equation system governing the evolution of perturbations to the case of two coupled fluids (dark matter and baryonic matter), modeled with a Top-Hat profile based in the perturbation of the hydrodynamics equations, an efficient analytical tool to study the properties of dark energy models such as the behavior of the linear growth factor and the linear growth index, physical quantities closely related to the fields of peculiar velocities at any time, for different models of dark energy. The properties and the dynamics of current Universe are analyzed through the exact analytical form of the linear growth factor of density fluctuations, taking into account the influence of several physical cooling mechanisms acting on the density fluctuations of the baryonic component of matter during the evolution of the clouds of matter, studied from the primordial hydrogen recombination. This study is naturally extended to more general models of dark energy with constant equation of state parameter in a flat Universe

Padrões cariotípicos em tetraodontiformes (Osteichthypes) :redução genômica e mecanismos de diversificação

The Tetraodontiformes order is composed for about 400 species of fish, distributed in ten families, with circuntropical distribution. The morphologic diversity of each family reflects in, part, the different levels of specialization. This group represents an ancestry after-Perciformes and constitutes the last branch of the diffusion of the Teleósteos, occupying a position of prominence. The phylogenetics relationships of the Tetraodontiformes exist diverse works examining and, in all, these families are recognized as groups brothers, being Diodontidae next to Tetraodontidae and Balistidae next to Monacanthidae. Although it possesss a representative number of species, the works involving of the families Balistidae and Monacanthidae are few exemplary, especially species of oceanic islands. In this work cytogenetic studies in five species had been analyzed Cantherhines macrocerus, Cantherhines pullus (Monacanthidae), Melichthys niger (Balistidae), Sphoeroides testudíneus (Tetraodontidae) and Chilomycterus antennatus (Diodontidae); through conventional coloration, Ag-NORs and C banding. Ahead of the different karyological trends of evolution presented by the Tetraodontiformes, the present work also searched to verify the relation existence enters the total size of the chromosomes with the amount of DNA in these groups of Tetraodontiformes. For such, they had been correlated the total size of the chromosomes of these species, with values of content of available DNA in literature. The cytogenetics analyses for the species C.macrocerusJ C.pullus (Monacanthidae) and M.niger (Balistidae), had disclosed 40 chromosomes, all acrocentrics. All possess only one pair of NORs and pericentromeric heterochromatin. For S.testudíneus the found dyploid number was equal 2n=46, with NF=78 (16m+18sm+8st+4a), while that for C.antennatus it possesss 2n=50, with NF=76 (4m+22st+24a). Both species possess simple NORs and pericentromeric heterochromatin blocks. In M.niger, the presence of positive marking (heterochromatin and NOR) in the secondary constriction in the second chromosomic pair suggesting the occurrence of a rearrangement, possibly a fusing involving these homologous ones, indicating that these events had been important for the establishment of the karyological history of this group. A maintenance of the chromosomic constancy found in the populations of C.macrocerus (Monacanthidae) and S.testudineus (Tetraodontidae) perhaps if must for the aiding of the gene flow through oceanic chains. These data contrast with the differentiated kinds of chromosomes of C.antennatus between the Northeast coast and Southeastern, suggesting that the ecological standards of each species, added to the conditions of the marine environment, can be responsible for the karyological delineation of each species. The found characteristics for the species C.macrocerus, C.pullus, M.niger, S.testudineus and C.antennatus add it the available data for other species of Tetraodontiformes. From the data gotten in the present study, it can be inferred that the DNA content possesss direct relation with the total length of the chromosomes

Conciliação entre modelos de mecanismos avançados de oxidação eletroquímica

Many pollutants dumped in waterways, such as dyes and pesticides, have become so ubiquitous that they represent a serious threat to human health. The electrochemical oxidation is presented as an alternative clean, efficient and economic degradation of wastewater containing organic compounds and a number of advantages of this technique is to just not make use of chemical reagents, since only electrical energy is consumed during the removal of pollutants organic. However, despite being a promising alternative, still needs some tweaking in order to obtain better efficiency in the elimination of persistent pollutants. Thus, this study sought a relationship between a recently discovered phenomenon that reflects the participation of dissolved oxygen in solution in the electrochemical oxidation process, as an anomaly, present a kinetic model that shows instantaneous current efficiency (ICE) above 100% limited by theory, manifested for some experiments with phenolic compounds with H2SO4 or HClO4 as supporting electrolyte with electrodes under anodic oxidation on boron doped diamond (BDD). Therefore it was necessary to reproduce the data ICE exposes the fault model, and thus the 2-naphthol was used as phenolic compound to be oxidised at concentrations of 9, 12 and 15 mmol L-1, and H2SO4 and HClO4 to 1 mol L-1 as a supporting electrolyte under a current density of 30 mA cm-2 in an electrochemical reactor for continuous flow disk configuration, and equipped with anodes DDB at room temperature (25 oC). Experiments were performed using N2 like as purge gas for eliminate oxygen dissolved in solution so that its influence in the system was studied. After exposure of the anomaly of the ICE model and investigation of its relationship with dissolved O2, the data could be treated, making it possible for confirmation. But not only that, the data obtained from eletranálise and spectroscopic analysis suggest the involvement of other strongly oxidizing species (O3 (ozone) and O radicals and O2 -), since the dissolved O2 can be consumed during the formation of new strong oxidizing species, not considered until now, something that needs to be investigated by more accurate methods that we may know a little more of this system. Currently the performance of the electrocatalytic process is established by a complex interaction between different parameters that can be optimized, so it is necessary to the implementation of theoretical models, which are the conceptual lens with which researchers see

Mecanismos de abertura de sulcos, inoculação e adubação nitrogenada em feijoeiro em sistema plantio direto

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

Estudo da influência do biodiesel de mamona como aditivo antioxidante para o biodiesel de girassol e soja

Biodiesel is a fuel made up by mono-alkyl-esters of long chain fatty acids, derived from vegetable oils or animal fat. This fuel can be used in compression ignition engines for automotive propulsion or energy generation, as a partial or total substitute of fossil diesel fuel. Biodiesel can be processed from different mechanisms. Transesterification is the most common process for obtaining biodiesel, in which an ester compound reacts with an alcohol to form a new ester and a new alcohol. These reactions are normally catalyzed by the addition of an acid or a base. Initially sunflower, castor and soybean oil physicochemical properties are determined according to standard test methods, to evaluate if they had favorable conditions for use as raw material in the transesterification reaction. Sunflower, castor and soybean biodiesel were obtained by the methylic transesterification route in the presence of KOH and presented a yield above 93% m/m. The sunflower/castor and soybean/castor blends were studied with the aim of evaluating the thermal and oxidative stability of the biofuels. The biodiesel and blends were characterized by acid value, iodine value, density, flash point, sulfur content, and content of methanol and esters by gas chromatography (GC). Also studies of thermal and oxidative stability by Thermogravimetry (TG), Differential Scanning Calorimetry High Pressure (P-DSC) and dynamic method exothermic and Rancimat were carried out. Biodiesel sunflower and soybean are presented according to the specifications established by the Resolution ANP no 7/2008. Biodiesel from castor oil, as expected, showed a high density and kinematic viscosity. For the blends studied, the concentration of castor biodiesel to increased the density, kinematic viscosity and flash point. The addition of castor biodiesel as antioxidant in sunflower and soybean biodiesels is promising, for a significant improvement in resistance to autoxidation and therefore on its oxidative stability. The blends showed that compliance with the requirements of the ANP have been included in the range of 20-40%. This form may be used as a partial substitute of fossil diesel