Uma técnica de linearização por realimentação para compensação de agarramento em válvulas de controle pneumáticas

In control loops valve stiction is a very common problem. Generally, it is one of main causes of poor performance of industrial systems. Its most commonly observed effect is oscillation in the process variables. To circumvent the undesirable effects, friction compensators have been proposed in order to reduce the variability in the output. This work analyzes the friction compensation in pneumatic control valves by using feedback linearization technique. The valve model includes both dead zone and jump. Simulations show that the use of this more complete model results in controllers with superior performance. The method is also compared through simulations with the method known as Constant Reinforcement (CR), widely used in this problem.

Estimação e compensação de não linearidades inerentes aos atuadores dos processos industriais

The oscillations presents in control loops can cause damages in petrochemical industry. Canceling, or even preventing such oscillations, would save up to large amount of dollars. Studies have identified that one of the causes of these oscillations are the nonlinearities present on industrial process actuators. This study has the objective to develop a methodology for removal of the harmful effects of nonlinearities. Will be proposed an parameter estimation method to Hammerstein model, whose nonlinearity is represented by dead-zone or backlash. The estimated parameters will be used to construct inverse models of compensation. A simulated level system was used as a test platform. The valve that controls inflow has a nonlinearity. Results and describing function analysis show an improvement on system response

Controle por modos deslizantes com compensação difusa aplicado a sistemas com descontinuidade

The development of non-linear controllers gained space in the theoretical ambit and of practical applications on the moment that the arising of digital computers enabled the implementation of these methodologies. In comparison with the linear controllers more utilized, the non -linear controllers present the advantage of not requiring the linearity of the system to determine the parameters of control, which permits a more efficient control especially when the system presents a high level of non-linearity. Another additional advantage is the reduction of costs, since to obtain the efficient control through linear controllers it is necessary the utilization of sensors and more refined actuators than when it is utilized a non-linear controller. Among the non-linear theories of control, the method of control by gliding ways is detached for being a method that presents more robustness, before uncertainties. It is already confirmed that the adoption of compensation on the region of residual error permits to improve better the performance of these controllers. So, in this work it is described the development of a non-linear controller that looks for an association of strategy of control by gliding ways, with the fuzzy compensation technique. Through the implementation of some strategies of fuzzy compensation, it was searched the one which provided the biggest efficiency before a system with high level of nonlinearities and uncertainties. The electrohydraulic actuator was utilized as an example of research, and the results appoint to two configurations of compensation that permit a bigger reduction of the residual error

Estabilização de órbitas periódicas instáveis utilizando controle por modos deslizantes com compensação adaptativa

The chaotic behavior has been widely observed in nature, from physical and chemical phenomena to biological systems, present in many engineering applications and found in both simple mechanical oscillators and advanced communication systems. With regard to mechanical systems, the effects of nonlinearities on the dynamic behavior of the system are often of undesirable character, which has motivated the development of compensation strategies. However, it has been recently found that there are situations in which the richness of nonlinear dynamics becomes attractive. Due to their parametric sensitivity, chaotic systems can suffer considerable changes by small variations on the value of their parameters, which is extremely favorable when we want to give greater flexibility to the controlled system. Hence, we analyze in this work the parametric sensitivity of Duffing oscillator, in particular its unstable periodic orbits and Poincar´e section due to changes in nominal value of the parameter that multiplies the cubic term. Since the amount of energy needed to stabilize Unstable Periodic Orbits is minimum, we analyze the control action needed to control and stabilize such orbits which belong to different versions of the Duffing oscillator. For that we will use a smoothed sliding mode controller with an adaptive compensation term based on Fourier series.

Um olhar crítico sobre a individualização da curva de compensação em prótese total

Objetivo: Buscar na literatura evidências científicas que suportem os benefícios da individualização da curva de compensação em prótese total, pela técnica do desgaste de Paterson, em relação à curva de compensação não individualizada. Metodologia: Realizou-se, em Dezembro de 2009, uma revisão sistemática da literatura nas bases de dados MEDLINE, LILACS e BBO com os termos “prótese total” e “oclusão”. Para abranger uma maior quantidade de dados, realizou-se uma busca manual através das referências dos artigos inicialmente selecionados. Resultados: Obteve-se 1273 referências na base dados MEDLINE, 64 na LILACS e 103 na BBO, num total de 1440 referências. Dessas, apenas 24 tratavam do assunto “curva de compensação”, as quais somaram-se mais 13 artigos selecionados manualmente. Conclusão: A partir dos resultados obtidos, conclui-se que não existem dados suficientes que comprovem clinicamente os benefícios da individualização da curva de compensação em relação às próteses totais com curva de compensação não individualizada. Ensaios clínicos controlados e randomizados são necessários para que se possa determinar qual o procedimento mais adequado.

Um olhar crítico sobre a individualização da curva de compensação em prótese total

Objetivo: Buscar na literatura evidências científicas que suportem os benefícios da individualização da curva de compensação em prótese total, pela técnica do desgaste de Paterson, em relação à curva de compensação não individualizada. Metodologia: Realizou-se, em Dezembro de 2009, uma revisão sistemática da literatura nas bases de dados MEDLINE, LILACS e BBO com os termos “prótese total” e “oclusão”. Para abranger uma maior quantidade de dados, realizou-se uma busca manual através das referências dos artigos inicialmente selecionados. Resultados: Obteve-se 1273 referências na base dados MEDLINE, 64 na LILACS e 103 na BBO, num total de 1440 referências. Dessas, apenas 24 tratavam do assunto “curva de compensação”, as quais somaram-se mais 13 artigos selecionados manualmente. Conclusão: A partir dos resultados obtidos, conclui-se que não existem dados suficientes que comprovem clinicamente os benefícios da individualização da curva de compensação em relação às próteses totais com curva de compensação não individualizada. Ensaios clínicos controlados e randomizados são necessários para que se possa determinar qual o procedimento mais adequado.

Controle ativo de vibração em estruturas inteligentes utilizando um controlador por modos deslizantes com compensação difusa

Smart structures and systems have the main purpose to mimic living organisms, which are essentially characterized by an autoregulatory behavior. Therefore, this kind of structure has adaptive characteristics with stimulus-response mechanisms. The term adaptive structure has been used to identify structural systems that are capable of changing their geometry or physical properties with the purpose of performing a specific task. In this work, a sliding mode controller with fuzzy inference is applied for active vibration control in an SMA two-bar truss. In order to obtain a simpler controller, a polynomial model is used in the control law, while a more sophisticated version, which presents close agreement with experimental data, is applied to describe the SMA behavior of the structural elements. This system has a rich dynamic response and can easily reach a chaotic behavior even at moderate loads and frequencies. Therefore, this approach has the advantage of not only obtaining a simpler control law, but also allows its robustness be evidenced. Numerical simulations are carried out in order to demonstrate the control system performance.

Controle ativo de vibração em estruturas inteligentes utilizando um controlador por modos deslizantes com compensação difusa

Smart structures and systems have the main purpose to mimic living organisms, which are essentially characterized by an autoregulatory behavior. Therefore, this kind of structure has adaptive characteristics with stimulus-response mechanisms. The term adaptive structure has been used to identify structural systems that are capable of changing their geometry or physical properties with the purpose of performing a specific task. In this work, a sliding mode controller with fuzzy inference is applied for active vibration control in an SMA two-bar truss. In order to obtain a simpler controller, a polynomial model is used in the control law, while a more sophisticated version, which presents close agreement with experimental data, is applied to describe the SMA behavior of the structural elements. This system has a rich dynamic response and can easily reach a chaotic behavior even at moderate loads and frequencies. Therefore, this approach has the advantage of not only obtaining a simpler control law, but also allows its robustness be evidenced. Numerical simulations are carried out in order to demonstrate the control system performance.

Estimação e compensação de não linearidades inerentes aos atuadores dos processos industriais

The oscillations presents in control loops can cause damages in petrochemical industry. Canceling, or even preventing such oscillations, would save up to large amount of dollars. Studies have identified that one of the causes of these oscillations are the nonlinearities present on industrial process actuators. This study has the objective to develop a methodology for removal of the harmful effects of nonlinearities. Will be proposed an parameter estimation method to Hammerstein model, whose nonlinearity is represented by dead-zone or backlash. The estimated parameters will be used to construct inverse models of compensation. A simulated level system was used as a test platform. The valve that controls inflow has a nonlinearity. Results and describing function analysis show an improvement on system response

Cooperação e competição entre políticas no Brasil: os cursos da governabilidade no presidencialismo da catalização

Public policies have been studied in the various fields of humanities and social sciences, from different theoretical and technical aspects. However, there is still a lack of studies that incorporate the dimension that encompasses the political action and its interference in such actions, also recognizing the importance of the institutional setting of the Brazilian presidential model in implementing these policies. This fragmented and multiparty system has led to power heterogeneous sets of political parties. Thus, the ministerial offices, more than assisting the President´s government project, manage particularized agendas, which are party biased and have the influence of interest groups in hegemonic themes addressed by government agencies. When these agendas operate in sectoral and specialized policies, the friction level is apparently low. However, when this occurs in intersectoral actions, such as in regional development, there is evidence of strong signs of competition among government agencies, which in theory, should operate in an integrated manner. Although this is not a specific feature of Luiz Inacio Lula da Silva´s government- the period to be studied- there was similar behavior in Fernando Henrique Cardoso´s presidency, one realizes that the expansion of coalition on behalf of governance is increasingly interfering in the outcome of intersectoral public policies, due to these multiple arguments in action. In order to understand these processes, this study focused on the Sustainable and Integrated Development Programme for Differentiated Meso-Regions (PROMESO), part of the National Policy for Regional Development (NPRD). The program provides interface with various government agencies and their public policies in a clear intersectoral design. The research sought to identify and analyze the relationships between government agencies and their programs with interest groups, whether political parties or other segments of civil society, highlighting the logic of favoritism, which poses in second place the integration of actions in the intersectoral policies. Therefore, besides the theoretical debate that incorporates several categories of political science, public administration, public policy, geography and economics, the study focused on secondary sources, using different government agencies databases in order to raise information. It was observed that the interference of partisan politics has been disastrous for some public policies. Thus, the research confirms that cooperative character is fragile within government agencies, often limited to official documents, and that there is indeed, a striking feature of competition, especially when it comes to transversalized policies

Qualidade de vida no trabalho: o caso de enfermeiros dos Hospitais Públicos Walfredo Gurgel e Santa Catarina

The theoretical foundation of this study addresses the construct Quality of Worklife involving pro-active reading organizations in face to social developments of the working class, which is a challenge to the people s management. In this sense, as a contribution to the studies of quality of worklife (QOWL), this study addresses the quality of lifework of nurses at Walfredo Gurgel and Santa Catarina public hospitals. The goal is to make a diagnosis about the quality of lifework of these employees taking as a basis dimensions and performance indicators shown in the model by Fernandes (1996). The research is characterized by field, in a descriptive way. This survey comprised 75 nurses, with 49 by Walfredo Gurgel hospital and 26 by Santa Catarina one. The data collection was carried out through structured questionnaire. The questions were processed in the software Statistic 6.0, with factor analysis and multiple regressions, after the systematization of data. As a result, the most nurses in hospitals are dissatisfied with the quality of lifework, with the highest incidence in Santa Catarina hospital. The variable occupational health assessment was more negative in the hospital Santa Catarina one, whereas in Walfredo Gurgel, was family assistance. The variable guarantee of employment was more positive assessment in two hospitals without, though, implying in high importance on QOWL of nurses. The factor structure and decision showed greater sensitivity to explain the QOWL of nurses, joining 17 variables from 40 of the model. The factor working conditions, joining 6 variables, showed the second highest sensitivity. The compensation factor, gathering 5 variables, showed the third highest sensitivity while image and health factors showed minor importance

Otimização e análise mecânica de pastas geopoliméricas para uso em poços sujeitos à injeção cíclica de vapor

Oil wells subjected to cyclic steam injection present important challenges for the development of well cementing systems, mainly due to tensile stresses caused by thermal gradients during its useful life. Cement sheath failures in wells using conventional high compressive strength systems lead to the use of cement systems that are more flexible and/or ductile, with emphasis on Portland cement systems with latex addition. Recent research efforts have presented geopolymeric systems as alternatives. These cementing systems are based on alkaline activation of amorphous aluminosilicates such as metakaolin or fly ash and display advantageous properties such as high compressive strength, fast setting and thermal stability. Basic geopolymeric formulations can be found in the literature, which meet basic oil industry specifications such as rheology, compressive strength and thickening time. In this work, new geopolymeric formulations were developed, based on metakaolin, potassium silicate, potassium hydroxide, silica fume and mineral fiber, using the state of the art in chemical composition, mixture modeling and additivation to optimize the most relevant properties for oil well cementing. Starting from molar ratios considered ideal in the literature (SiO2/Al2O3 = 3.8 e K2O/Al2O3 = 1.0), a study of dry mixtures was performed,based on the compressive packing model, resulting in an optimal volume of 6% for the added solid material. This material (silica fume and mineral fiber) works both as an additional silica source (in the case of silica fume) and as mechanical reinforcement, especially in the case of mineral fiber, which incremented the tensile strength. The first triaxial mechanical study of this class of materials was performed. For comparison, a mechanical study of conventional latex-based cementing systems was also carried out. Regardless of differences in the failure mode (brittle for geopolymers, ductile for latex-based systems), the superior uniaxial compressive strength (37 MPa for the geopolymeric slurry P5 versus 18 MPa for the conventional slurry P2), similar triaxial behavior (friction angle 21° for P5 and P2) and lower stifness (in the elastic region 5.1 GPa for P5 versus 6.8 GPa for P2) of the geopolymeric systems allowed them to withstand a similar amount of mechanical energy (155 kJ/m3 for P5 versus 208 kJ/m3 for P2), noting that geopolymers work in the elastic regime, without the microcracking present in the case of latex-based systems. Therefore, the geopolymers studied on this work must be designed for application in the elastic region to avoid brittle failure. Finally, the tensile strength of geopolymers is originally poor (1.3 MPa for the geopolymeric slurry P3) due to its brittle structure. However, after additivation with mineral fiber, the tensile strength became equivalent to that of latex-based systems (2.3 MPa for P5 and 2.1 MPa for P2). The technical viability of conventional and proposed formulations was evaluated for the whole well life, including stresses due to cyclic steam injection. This analysis was performed using finite element-based simulation software. It was verified that conventional slurries are viable up to 204ºF (400ºC) and geopolymeric slurries are viable above 500ºF (260ºC)

Propriedades tribomecânicas de superfícies de titânio carbonitretadas por plasma

Interstitial compounds of titanium have been mainly studied due to the large range of properties acquired when C, N, O and H atoms are added. In this work, surfaces of TiCxNy were produced by thermochemical treatments assisted by plasma with different proportions of Ar + N2 + CH4 gas mixture. The Ar gas flow was fixed in 4 sccm, varying only N2 and CH4 gas flows. During the thermochemical treatment, the plasma was monitored by Optical Emission Spectroscopy (OES) for the investigation of the influence of active species. After treatments, C and N concentration profile, crystalline and amorphous phases were analyzed by Nuclear Reaction (NRA). Besides tribomechanical properties of the Ti surface were studied through the nanohardness measurements and friction coefficient determination. The worn areas were evaluated by profilometry and Scanning Electronic Microscope (SEM) in order to verify the wear mechanism present in each material. It has been seen which the properties like nanohardness and friction coefficient have strong relation with luminous intensity of species of the plasma, suggesting a using of this characteristic as a parameter of process

Dança Folclórica: um estudo das qualidades físicas básicas em universitários de diferentes níveis técnicos

Health and life quality can be preserved and improved by the regular practice of physical activity. Sedentarism is an undesirable condition and represents risk for the health. This study has as objective to analyze the caloric cost and the basic physical qualities in college students of different technical levels. The research was descriptive and applied to 35 students, volunteers, from 19 to 34 years old, from both sexes, participants of the Dance Body of State University of Piauí, in the city of Teresina, in the activities of folkloric dance and walking. The caloric cost was evaluated with the accelerometer Caltrac 100/100 Plan, the basic physical qualities through the sitting and reaching test (flexibility); the vertical impulsion test, crouch (inferior members strength); the abdominal test (located muscular resistance); and the Burpee test (motor coordination). The participants were separated in two groups according to their time of practice: group 1 (beginners), group 2 (advanced). The parametric tests t by Student and correlation by Pearson were used, observing a significance p<0,05 in the sense of comparing the observed results, which showed that there are no significant differences between the two groups of students, according to the time of practice, in which concerns the caloric cost. The results of Strength, Resistance and Co-ordination test did not differ so much between the two groups. On the other hand, in the variable flexibility significant differences were observed (sig.p = 0,0022 << 0,05) between the observed groups, being Group 1 (31,5 ± 6,3) meaningfully less than Group 2 (38,1 ± 4,9), which constitutes a difference of about 21%. Such results present relations of caloric cost compensation between the studied groups, the motivation to the beginners group and flexibility to tne advanced group, justifying the lack of significant distinctions. In this sense the folkloric dance, as a physical activity, appears to be efficient, for significant co-relations are still noticed between the caloric cost levels of the dance with the walking, besides not presenting expressive differences between them.

O PROEJA ensino médio no ifrn, campus Caicó: causas da desistência e motivos da permanência

This dissertation deals about the theme of National Integration Program of the Professional Education to the Basic Education in the form of Youth and Adults Education - PROEJA, which was developed at the Federal Institute of Education Science and Technology of Rio Grande do Norte - IFRN - Campus Caicó. It aims to analyze the causes of the abandonment and the reasons for the permanence of students within the mentioned program. To substantiate this research, we used methodologically, some procedures such as bibliographical research, documentary analysis, semi-structured interviews and focus group. To analyze the data, we discussed the contradiction that involves duality and educational compensation based in the struggles and achievements of rights at the core of public policies for high schools, for vocational education and the education of youth and adults in the 2000s. We analyze the integrated high school under PROEJA, having as reference the conception of the total human formation; the inseparability of the primary education system and vocational education and the integration of knowledge and expertise as a whole, discussing the specificities of the modality EJA, discussing the causes of abandonment and the reasons for the permanence of the students of education for youth and adults (EJA) in the primary education system. As for the results, we found that although the PROEJA be a program that aims to provide a complete human formation to contribute to the full citizenship of their graduate members, what is announced in the document that guides its creation has not been materialized in Caicó Campus. The curriculum of the course was not designed for the students of EJA, nor teachers have had an adequate training to work with these specific individuals, and its specificities of being workers with differentiated learning times have not been considered. In addition, the courses are predominantly of instrumentalist characteristics. This indicates that the material and institutional conditions to achieve the promised total and complete training have not being fully materialized at the researched school. Associated with the difficulties concerning the intra-school and extra-school conditions, personal and socioeconomic conditions which are related to the obligation to work that implies in limitations to balance work, school and family, they influenced in the interruption of the school trajectory of these subjects. Through research, we confirmed that the motives of students who remain have to do also with intraescolares conditions the quality of education (qualification of technical staff and teachers) involved in the educational process, as well as socioeconomic and personal issues represented by the support of colleagues and family.Then it is concluded that the causes of abandonment and the reasons of the permanence are of institutional, socioeconomic and personal origins. Finally, it is observed that capitalist society demands as much as possible high levels of educated workers, and at the same time makes difficult the access to that education for much of the population, and it is not randomly. The objects of that exclusion are the popular worker classes and their children