Identidade, espaço e tempo: negociações de sentido sobre a "gente de rua"

This research examines the street children s identity construction processes. Recently, the research about this population has focused on the socialization processes that organize their everyday, their situations of interaction, the meanings of their social practices, their street experience. The concept of identitary forms gives coherence to the set of these phenomena, articulating them theoretically, in order to describe their life conditions and details of their trajectories. This research utilized an ethnographic approach with a group of 11 street people, 9 of them boys and girls 16-18 years old, during 3 months. It included participant observation, informal and formal interviews, that resulted in young s narratives of lifestory. These narratives were interpreted according to the principles of positioning analysis and the Labovian Analysis model of oral narratives of personal experience. The observation of interaction among the studied group and other groups has showed that their social practices, supported on many particular bodily technologies, recreate space and time of these interactions semantically, as mediation of meaning negotiations among groups. Such meanings transform again the environment of these interactions, disclosing interpretative systems by means of which the groups apprehend this interaction in a particular way. These street children s bodily technologies imply identitary forms based on scarcity and abandonment, paradoxicalally related to their self-concept. The analysis of narratives revealed diversity and complexity in the meanings assembly for their street experience; it showed that the semantic arrangements reconstruct the temporal experience, creating a moral climate for each lifestory, and determining more or less aperture of identitary forms to change. The study concludes that space and time, builders of interaction regimes, produce identitary forms; that the narratives and the social practices of the studied group are sustained upon a master discourse that opposes the meanings of the home and the life in the streets

Critérios comportamentais utilizados por técnicos na avaliação do desempenho esportivo de futebolista das categorias de base

Currently one of the major concerns in sports is to identify, select, discover and reveal talents in soccer. As principal reasons is perceived the search direct or indirect for resources for players, clubs, media, sports brands and their sponsors. However, high salaries are an exception and not a rule, because the majority of professional players in Brazil receives 1 minimum salary per month. It is also known that on professional clubs, daily, arriving several players to try to be a professional soccer player, however, the majority of clubs - almost all does not present methodological, systematic and analytical aspects to select promising players. The selective processes ("sieves" or "big sieves") developed by technical observers ( olheiros") summarized in the observation of the sportive performance of a big group of players in a period of few minutes given to each player. In this period the target behavior is the ability with the ball. If promising players are identified on that selection, they are referred to the club for a new observation, which will be conducted by the responsible coach of base category in question. It is understood by base categories, the amateur categories (not professional), to serve as a "base" for the formation of the cast of professional clubs. What are sub-13 (under 13 years), sub-15 (under 15 years), sub-17 (under 17 years) and sub-20 (under 20 years). The absence of common criterias and performance indicators of these professionals may hamper the evaluation of promising players, and be a costly activity for the club. This study proposes to identify, characterize and categorize the criterias and methods of behavioral evaluation, used by coaches of base categories of Rio Grande do Norte (RN) to evaluate the sportive performance of young soccer players, with the purpose of to compare the criterias of evaluation of sportive performance of young soccer players, used by coaches with different time of experience in function. The proposal had 2 pilot studies, the first (June and July, 2007) were interviewed 29 coaches, 17 of category sub-13 and 12 of category sub-17. The data were tabulated and organized into spreadsheets in order to describe, and developed a set of descriptors of behavior. And the second (May and June, 2008), with revisions made based on observations, analysis and descriptions found in the first, were interviewed 14 technical of category sub-15. After the results found in pilots, it was possible to outline the study in question, which had 46 coaches base categories of the RN. And from the results show that the characteristic of greatest importance, according to the interviewees was the behavior, the 2nd most important characteristic considered was the motivation, the 3rd was the ability and the 4th was the physical condition and the last was the affiliation. And by analyzing the results to the methods of evaluation of sportive performance used by coaches, it was noted clearly that most uses only the observation to select young soccer players. Therefore, needs a systematization to the selection of soccer players, since there is complexity in the verification of characteristics and aspects involved with purpose to avoid wrong evaluations and selections and the results negligible

Trabalho infantil na agricultura :sentidos produzidos pelas mês e pelos professores

Attempts to explain child labor, for the most part, have been reduced to the economic aspect, looking to establish a causal relationship between work and poverty. Without disregarding this aspect, we intend to approach this phenomenon considering other aspects that could be contributing towards its maintenance. We seek, above all, to articulate it with the concepts of disciplinary power and ideology. The present study, therefore, tries to consider these aspects with the intention of learning the reasons that the mothers and the teachers produce concerning child labor in the cultivation of vegetables. We elected these participants because we considered that child labor has been reinforced by the disciplinary institutions and proponents of ideology, the family and the school, here represented, respectively, by the mothers and the teachers. To affect this study, we created focused groups with the mothers whose children are students and work in the cultivation of vegetables in Gramorezinho (neighborhood situated in the northern part of Natal, RN) and with the teachers of the neighborhood school (Escola Lourdes Goudeiro). The discussion of the participants was handled according to the perspective of discursive practices, attempting to articulate them with the notions of ideology and disciplinary power. In general, we perceived how much ideology and discipline are immersed in the discursive practices of the participants. Whereas, even though in some moments the reference to work as being something that takes time from the child to study and play is apparent, the participants attribute great importance to child labor. Both for the teachers and for the mothers, work is something that can free the children from laziness, from becoming criminals and from using drugs. It too constitutes an important alternative to idleness and to the permanence of the child in the streets

Investigação da capacidade intelectiva de pacientes pediátricos diagnosticados com tumores de fossa posterior

Central Nervous System are the most common pediatric solid tumors. 60% of these tumors arise in posterior fossa, mainly in cerebellum. The first therapeutic approach is surgical resection. Malignant tumors require additional strategies - chemotherapy and radiotherapy. The increasing survival evidences that childhood brain tumors result in academic and social difficulties that compromise the quality of life of the patients. This study investigated the intellectual functioning of children between 7 to 15 years diagnosed with posterior fossa tumors and treated at CEHOPE - Recife / PE. 21 children were eligible - including 13 children with pilocytic astrocytoma (G1) who underwent only surgery resection, and eight children with medulloblastoma (G2) - submitted to surgical resection, chemotherapy and craniospinal radiotherapy. Participants were evaluated by the Wechsler Intelligence Scale for Children - WISC-III. Children of G1 scored better than children of G2. Inferential tools (Mann-Whitney Ü Test) identified significant diferences (p ≤ 0.05) between the Performance IQ (PIQ) and Processing Speed Index (PSI) as a function of treatment modality; Full Scale IQ (FSIQ), PIQ and PSI as a function of parental educational level; PIQ, FSIQ, IVP and Freedom from Distractibility (FDI) as a function of time between diagnosis and evaluation. These results showed the late and progressive impact of radiotherapy on white matter and information processing speed. Furthermore, children whose parents have higher educational level showed better intellectual performance, indicating the influence of xxii socio-cultural variables on cognitive development. The impact of cancer and its treatment on cognitive development and learning should not be underestimated. These results support the need to increase the understanding of such effects in order to propose therapeutic strategies which ensure that, in addition to the cure, the full development of children with this pathology

Investigação do funcionamento cognitivo de pacientes pediátricos diagnosticados com leucemia linfóide aguda - LLA

The present work investigated the cognitive operation of children diagnosed with acute lymphoblastic leukaemia (ALL), accompanied at pediatric oncologic institutions at the city of Natal/RN. Had participated in this study twenty children, of both sexes, between six and twelve years old, with the ALL diagnostic, who were in treatment (n=10) and out of treatment for at least one year (n=10) and were submitted exclusively to chemotherapy as CNS prophylaxis. The utilized protocol of neuropsychological evaluation covered the following cognitive abilities: intellective capability, attentional and memory systems, and executive functions. Data was analyzed through descriptive and inferential measures, with the support of the Mann-Whitney U Test and T-test, considering the influence of the variables sex, age at diagnostic and the past time since the beginning of the treatment over children s performance. The intellective capability evaluation showed low score to the out-of-treatment groups, female and children under five years old to the diagnostic. In concern of attentional systems, groups showed the expected performance. In a relevant way, in the evaluation of executive functions, were found reduced scores within all groups, especially inside the in-treatment group. Memory evaluation pointed to reduced performance in items concerning to learning evolution and spontaneous evocation after interference to the several groups. It can be concluded, reffer to the occurrence of transitory and permanent impact associated to the intrusion of chemotherapic components during the maturational course of the CNS. It s expected that the present investigation and the development of similar studies enable major comprehension about the mode, extension and repercussion of these damages subsidizing the development of strategies which may minimize them and provide better xxiii life quality to this clinical subgroup

Avaliação das habilidades neurocognitivas em crianças e adolescentes sobreviventes da Leucemia Linfoide Aguda - LLA

The present study investigated the impact of the treatment modalities of Acute Lymphoblastic Leukemia on neurocognitive abilities of children and adolescents survivors, aged between 6 and 16 years of age, accompanied in pediatric oncology sectors of public health services in the cities of Campina Grande-PB and Natal-RN. The study included 52 children, 13 of these being children and adolescents diagnosed with leukemia and 39 healthy children matched in relation to the study group considering gender, age, school type and level of maternal education. Later the group of children with leukemia was subdivided into two subgroups depending on treatment modality which were submitted: Group 1A (only chemotherapy) and 1B (chemotherapy and radiotherapy). All participants were subjected to a battery of neuropsychological tests that investigated the following neurocognitive abilities: intellectual ability, memory system, attention, visuospatiality and visuoconstruction, processing speed and executive functions. Data were analyzed using descriptive and inferential measurements with the aid of the U test of Mann-Whitney and T test, considering the influence of the variables: sex, age at diagnosis, time since completion of treatment and level of schooling mothers, on the performance of children. Overall, it is concluded that the illness and the treatment of acute lymphoblastic leukemia significantly favors the emergence of cognitive deficits, particularly in terms of visuospatial skills, and executive skills visoconstrutivas. In turn, the treatment modality of radiotherapy is associated with the presence of more severe deficits, highlighting the significant impact on the speed of information processing. It is hoped that the results presented here will contribute to a better understanding of the nature and extent of neurocognitive effects arising ALL treatment

Análise das dificuldades de aprendizagem numa disciplina de química orgânica do curso de química na modalidade à distância da UFRN

In today`s society the use of so-called information technology and communication (ICT), is promoting a revolution in the forms of teaching and learning through the methods of distance learning courses, especially in higher education. Studies show that students in this way have great difficulties in the learning process, especially when dealing with experimental subjects that require high power of abstraction as chemistry. The goal of this work is to promote improvement in the teaching and learning in the discipline Chemistry of Life offered for the Bachelor`s Degree in Chemistry in distance UFRN. For this we analyzed evidence of the semester 2011.2, in order to identify what are the main difficulties of the students on the assessments. That`s why video lessons related to matters that create the majority of difficulties for students were developed, the final product this work. Being obtained the improvements by video classes in the learning process of the students, from a questionnaire answered by the students in the virtual learning environment, and from their success rate at the end of the course

Interações entre a carboximetilcelulose, carbonato de cálcio e bentonita: repercussões sobre as propriedades dos fluidos de perfuração aquosos

The role of carboxymethylcellulose (CMC) in association to calcium carbonate particles (CaCO3) in most water-based drilling fluids is to reduce the fluid loss to the surrounding formation. Another essential function is to provide rheological properties capable of maintaining in suspension the cuttings during drilling operation. Therefore, it is absolutely essential to correlate the polymer chemical structure (degree of substitution, molecular weight and distribution of substituent) with the physical-chemical properties of CaCO3, in order to obtain the better result at lower cost. Another important aspect refers to the clay hydration inhibitive properties of carboxymethylcellulose (CMC) in drilling fluids systems. The clay swelling promotes an undesirable damage that reduces the formation permeability and causes serious problems during the drilling operation. In this context, this thesis consists of two main parts. The first part refers to understanding of interactions CMC-CaCO3, as well as the corresponding effects on the fluid properties. The second part is related to understanding of mechanisms by which CMC adsorption occurs onto the clay surface, where, certainly, polymer chemical structure, ionic strength, molecular weight and its solvency in the medium are responsible to affect intrinsically the clay layers stabilization. Three samples of carboximetilcellulose with different molecular weight and degree of substitution (CMC A (9 x 104 gmol DS 0.7), CMC B (2.5 x 105 gmol DS 0.7) e CMC C (2.5 x 105 gmol DS 1.2)) and three samples of calcite with different average particle diameter and particle size distribution were used. The increase of CMC degree of substitution contributed to increase of polymer charge density and therefore, reduced its stability in brine, promoting the aggregation with the increase of filtrate volume. On the other hand, the increase of molecular weight promoted an increase of rheological properties with reduction of filtrate volume. Both effects are directly associated to hydrodynamic volume of polymer molecule in the medium. The granulometry of CaCO3 particles influenced not only the rheological properties, due to adsorption of polymers, but also the filtration properties. It was observed that the lower filtrate volume was obtained by using a CaCO3 sample of a low average size particle with wide dispersion in size. With regards to inhibition of clay swelling, the CMC performance was compared to other products often used (sodium chloride (NaCl), potassium chloride (KCl) and quaternary amine-based commercial inhibitor). The low molecular weight CMC (9 x 104 g/mol) showed slightly lower swelling degree compared to the high molecular weight (2.5 x 105 g/mol) along to 180 minutes. In parallel, it can be visualized by Scanning Electron Microscopy (SEM) that the high molecular weight CMC (2.5 x 105 g/mol e DS 0.7) promoted a reduction in pores formation and size of clay compared to low molecular weight CMC (9.0 x 104 g/mol e DS 0.7), after 1000 minutes in aqueous medium. This behavior was attributed to dynamic of interactions between clay and the hydrodynamic volume of CMC along the time, which is result of strong contribution of electrostatic interactions and hydrogen bounds between carboxylate groups and hydroxyls located along the polymer backbone and ionic and polar groups of clay surface. CMC adsorbs on clay surface promoting the skin formation , which is responsible to minimize the migration of water to porous medium. With the increase of degree of substitution, it was observed an increase of pores onto clay, suggesting that the higher charge density on polymer is responsible to decrease its flexibility and adsorption onto clay surface. The joint evaluation of these results indicate that high molecular weight is responsible to better results on control of rheological, filtration and clay swelling properties, however, the contrary effect is observed with the increase of degree of substitution. On its turn, the calcite presents better results of rheological and filtration properties with the decrease of average viii particle diameter and increase of particle size distribution. According to all properties evaluated, it has been obvious the interaction of CMC with the minerals (CaCO3 and clay) in the aqueous medium

Desempenho auditivo ao longo do tempo e satisfação dos usuários de implante coclear com perda auditiva pós-lingual

Most cochlear implant (CI) users, who suffer from post lingual hearing loss, are able to perceive sounds and comprehend speech after the implant. The prediction of maximal benefit over time, with the use of CI, can be useful for counseling patients about their expectations in using the new device. The measurement of satisfaction should be of primary interest in medical intervention, as the results may be used for intervention feedback. The purpose of this study is to analyze auditory performance of CI over time, as well as to evaluate users‟ satisfaction. Therefore two types of study designs were employed: a) retrospective cohort study with the analysis of medical records from 59 subjects about auditory performance before and after surgery. Results were submitted to the Kaplan -Meier estimator of cumulative probability and compared to prognostic factors of auditory performance using the logrank test. b) A sectional study design was conducted to evaluate the satisfaction of 51 subjects. The instrument consists of two specific questionnaires: Satisfaction with Amplification in Daily Life SADL and International Outcome Inventory Cochlear Implant IOI- CI. Results show statistical significant differences (p<0,001) in auditory performance before and after CI. The majority obtained satisfactory results of CI use during the first six months. Logrank tests does not indicate significant correlation between the analyzed covariates and the time in which adequate speech perception occurs. SADL e IOI-CI questionnaires indicate that most of the CI users are satisfied with their devices. The SADL detected a 27, 5% insatisfaction amongst CI users in relation to services and costs involved with the CI. The results of the IOI show 4% of insatisfaction with the use of CI and the social environment. In conclusion CI is capable to rehabilitate social auditory function in a short period of time and CI users demonstrate satisfaction with auditory, social and psychological gain offered through CI device

O estágio não-obrigatório na formação profissional dos(as) assistentes sociais: trabalho precarizado ou processo didático-pedagógico?

Coexisten, en el universo académico, prácticas curriculares obligatorias y no obligatorias que pueden ser remuneradas o no. Delante de la constatación de lagunas en la concepción, gestión y operacionalización de las prácticas no obligatorias remuneradas, escogimos este tema como objeto de nuestra investigación, tratando de analizarlo en el contexto de los cambios sociohistóricos contemporaneos y su influencia en la cualidad de la formación profesional del estudiante de la carrera de Servicio Social. Este estudio tiene como ¨locu¨ de investigación la Facultad de Servicio Social del Estado de Rio Grande del Norte (FASSO/UERN). Este estudio se caracteriza por la adopción de una perspectiva de análisis cualitativa, con la expectativa de develarlo mucho más allá de lo que se muestra en su aparecncia. Para esto, realizamos revisión de literatura, análisis de documentos, observación asistemática y entrevistas con estudiantes y profesionales de las entidades que ofrecen prácticas a los estudiantes. Además se incluyó, en los procedimientos metodológicos, la aplicación de encuestas y conversaciones informales. Constatamos la existencia de lagunas en el desarrolllo de las prácticas no obligatorias remuneradas, ocasionadas por la ausencia de supervisión y por la inclusión de pasantes en sectores y/o actividades desvinculadas de su futura profesión. La investigación nos permitió desvelar situaciones en las que la oferta de plazas ocurre en detrimento de la contratación de empleados, lo que configura un distanciamento de este componente curricular del área de formación profesional, desvirtuando su carácter educacional. Cientes de la coexistencia contradictoria entre situaciones ventajosas y problemáticas en las prácticas no obligatorias remuneradas para el proceso de formación profesional de los asistentes sociales, concluimos que esta modalidad de práctica cuando vinculada a la intervención de la facultad y bajo la supervisión de asistentes sociales, independiente de sus implicaciones en los intereses del mercado, potencializa el desarrollo de competencias y habilidades intrínsecas al proceso de formación profesional; pero si distanciada del área de formación y/o sin el debido acompañamiento didáctico-pedagógico establece poca o ninguna relación con la formación de los asistentes sociales. Pero, incluso distanciadas del ejercicio y de la formación académica en el área de servicio social y/o (llenas de aspectos frágiles) llenas de fallas en el proceso de enseñanza y aprendisaje, estas experiencias ejercen profunda influencia en la formación de los asistentes sociales, pudiendo fragilizar el compromiso con el proyecto ético-político, diseminar el aspecto subalterno de la profesión y hacer confuso y conflictivo el proceso de construcción de la identidad profesional. En este sentido, las inversiones de capital para reducir los gastos con mano de obra, las dificultades vividas por las universidades públicas brasileñas para garantizar la cualidad de la enseñanza delante de la insuficiencia de recursos humanos y materiales y la desvalorización de los componentes no obligatorios del proceso de formación profesional de los asistentes sociales, son factores que obstaculizan el reconocimiento y la materialización del potencial didáctico-pedagógico de las prácticas

Midgard: um middleware baseado em componentes e orientado a recursos para redes de sensores sem fio

On the last years, several middleware platforms for Wireless Sensor Networks (WSN) were proposed. Most of these platforms does not consider issues of how integrate components from generic middleware architectures. Many requirements need to be considered in a middleware design for WSN and the design, in this case, it is possibility to modify the source code of the middleware without changing the external behavior of the middleware. Thus, it is desired that there is a middleware generic architecture that is able to offer an optimal configuration according to the requirements of the application. The adoption of middleware based in component model consists of a promising approach because it allows a better abstraction, low coupling, modularization and management features built-in middleware. Another problem present in current middleware consists of treatment of interoperability with external networks to sensor networks, such as Web. Most current middleware lacks the functionality to access the data provided by the WSN via the World Wide Web in order to treat these data as Web resources, and they can be accessed through protocols already adopted the World Wide Web. Thus, this work presents the Midgard, a component-based middleware specifically designed for WSNs, which adopts the architectural patterns microkernel and REST. The microkernel architectural complements the component model, since microkernel can be understood as a component that encapsulates the core system and it is responsible for initializing the core services only when needed, as well as remove them when are no more needed. Already REST defines a standardized way of communication between different applications based on standards adopted by the Web and enables him to treat WSN data as web resources, allowing them to be accessed through protocol already adopted in the World Wide Web. The main goals of Midgard are: (i) to provide easy Web access to data generated by WSN, exposing such data as Web resources, following the principles of Web of Things paradigm and (ii) to provide WSN application developer with capabilities to instantiate only specific services required by the application, thus generating a customized middleware and saving node resources. The Midgard allows use the WSN as Web resources and still provide a cohesive and weakly coupled software architecture, addressing interoperability and customization. In addition, Midgard provides two services needed for most WSN applications: (i) configuration and (ii) inspection and adaptation services. New services can be implemented by others and easily incorporated into the middleware, because of its flexible and extensible architecture. According to the assessment, the Midgard provides interoperability between the WSN and external networks, such as web, as well as between different applications within a single WSN. In addition, we assessed the memory consumption, the application image size, the size of messages exchanged in the network, and response time, overhead and scalability on Midgard. During the evaluation, the Midgard proved satisfies their goals and shown to be scalable without consuming resources prohibitively

O Turismo como um tema de pesquisa: um diálogo epistemológico a partir das produções dos programas de pós-graduação stricto sensu da Universidade Federal do Rio Grande do Norte, no período de 2007 a 2011

The study consists in an analysis of researches with tourism issues, in Master s and Doctoral level, investigating their epistemological trends, regarding the type of study that is being produced and the methods used. It is characterized as exploratory, documental and bibliographical, having undertaken a cross-sectional study which covers the period from 2007 to 2011. It analyzes the context of academically production in tourism, the nature of these researches, the methodological aspects adopted in these theses and dissertations, the philosophical inclinations and the coherence and contribution of the same. This research uses, the Digital Library of Theses and Dissertations (BDTD) and the secretariats of the Academic Centers of the Federal University of Rio Grande do Norte (UFRN) as means to collect data. It employs the technique of sampling by judgment and undertakes the research in various Academic Centers in UFRN, using the method of content analysis. It shows that, from the 643 studies analyzed, 43 of them have themes related to tourism, which characterized this study sample. This study realizes that PPGA is the largest producer of researches on tourism issues, ahead of PPGTur, which ranks the third position, in this aspect. Also realizes that all surveys analyzed are crosssectional and the theme further investigated, with 21% of the sample, is related to the marketing aspects of tourism, with the theme Directors of Hotels and Restaurants (DHR) . This research demonstrates that all sample surveys make use of interviews, and these are, mostly, structured. Also realizes that most of these studies, with 21% of the sample, employ the method of content analysis. The references in Portuguese are surveyed about five times more than the ones in other languages. It estimates that more than half of the sample is characterized as positivist, associated with aspects of functionalism. A minority of 21% of these researches seeks to identify and recommend solutions to the tourism issues, or even represent part of them. This research concludes that the studies in tourism are mostly unifocal, being driven by issues related to the touristic trade. PPGTur produces a number still unrepresentative of studies. The theses and dissertations of the sample are limited and/or unable to analyze the changes of the phenomenon caused by the time. The studies from the sample present criteria and make use of other methods and techniques to associate with the interviews and content analysis to obtain more solid and reliable data and results. They use a low number of references in languages other than Portuguese. Most of these studies, characterized as positivist-functionalist, investigate the functioning, planning, coordination and expectations in organizations, leaving aside other issues, also relevant for tourism. The number of studies aimed at identifying solutions to the problems of tourism, or that even represents part of them, is not expressive

As múltiplas faces da evasão na educação superior a distância: a experiência do curso de tecnologia em gestão ambiental do IFRN em dois pólos de apoio presencial

This research presents a reflection on the dropout rates in higher education courses available through distance education in a context marked by deep changes in various spheres of society and by the uncontrolled growth of this educational method. For this, the object of analysis is related to the reality of students of Technology in Environmental Management offered by the Instituto Federal de Educação, Ciência e Tecnologia, Rio Grande do Norte (RN), Brazil, through the distance education in presence support poles located in Mossoró (RN) and Martins (RN). In this field research development several strategies of data collection are used, such as participant observation of reality; analysis of documents related to distance education and to the classes in Technology in Environmental Management; questionnaires answered by students who dropped the course. The results of such research enable us to say that the dropout rates in distance higher education is mainly referred to the consequences of a combination of aspects involved in the course development, personal difficulties faced by students during the period they attend the lessons and elements inherent in the context in which the course and students are inserted. Nevertheless there are specific situations in which the student may drop the program due to the influence of a single aspect, whether it is inherent in the development of the course, a personal situation, or even a factor determined by the context in which the course or the student belongs to

Controle adaptativo por modelo de referencia e estrutura variável discreto no tempo

With the technology progess, embedded systems using adaptive techniques are being used frequently. One of these techniques is the Variable Structure Model- Reference Adaptive Control (VS-MRAC). The implementation of this technique in embedded systems, requires consideration of a sampling period which if not taken into consideration, can adversely affect system performance and even takes the system to instability. This work proposes a stability analysis of a discrete-time VS-MRAC accomplished for SISO linear time-invariant plants with relative degree one. The aim is to analyse the in uence of the sampling period in the system performance and the relation of this period with the chattering and system instability

Predição em modelos de tempo de falha acelerado com efeito aleatório para avaliação de riscos de falha em poços petrolíferos

We considered prediction techniques based on models of accelerated failure time with random e ects for correlated survival data. Besides the bayesian approach through empirical Bayes estimator, we also discussed about the use of a classical predictor, the Empirical Best Linear Unbiased Predictor (EBLUP). In order to illustrate the use of these predictors, we considered applications on a real data set coming from the oil industry. More speci - cally, the data set involves the mean time between failure of petroleum-well equipments of the Bacia Potiguar. The goal of this study is to predict the risk/probability of failure in order to help a preventive maintenance program. The results show that both methods are suitable to predict future failures, providing good decisions in relation to employment and economy of resources for preventive maintenance.