On non-ideal and non-linear portal frame dynamics analysis using Bogoliubov averaging method

We apply the Bogoliubov Averaging Method to the study of the vibrations of an elastic foundation, forced by a Non-ideal energy source. The considered model consists of a portal plane frame with quadratic nonlinearities, with internal resonance 1:2, supporting a direct current motor with limited power. The non-ideal excitation is in primary resonance in the order of one-half with the second mode frequency. The results of the averaging method, plotted in time evolution curve and phase diagrams are compared to those obtained by numerically integrating of the original differential equations. The presence of the saturation phenomenon is verified by analytical procedures.

On Nonlinear Dynamics and Control of A Particular Portal Frame Foundation Model, Excited by a Non-Ideal Motor

The nonlinear dynamic response and a nonlinear control method of a particular portal frame foundation for an unbalanced rotating machine with limited power (non-ideal motor) are examined. Numerical simulations are performed for a set of control parameters (depending on the voltage of the motor) related to the static and dynamic characteristics of the motor. The interaction of the structure with the excitation source may lead to the occurrence of interesting phenomena during the forward passage through the several resonance states of the systems. A mathematical model having two degrees of freedom simplifies the non-ideal system. The study of controlling steady-state vibrations of the non-ideal system is based on the saturation phenomenon due to internal resonance.

The possible involvement of hyperpolarizing mechanisms in histamine-induced relaxation of the rat portal vein

The present study evaluated the effects of histamine 10 -2 M on longitudinal preparations of rat portal vein. It was observed that histamine 10 -2 M induced relaxation of rat portal vein preparations pre-contracted with phenylephrine 10 -4 M. On the other hand, no pharmacological effects were observed in preparations not pre-contracted. The observed histamine-induced relaxing effect was absent in preparations pre-contracted with KCl (120 mM) or in the presence of depolarizing nutritive solution. However, the histamine-induced relaxation was still present in the endothelium-removed preparations. The histamine-induced relaxation also was not prevented by astemizole (10 -6 M, 10 -5 M and 10 -4 M), cimetidine (10 -5 M, 10 -4 M and 10 -3 M) or thioperamide (10 -6 M, 10 -5 M and 10 -4 M), selective antagonists H 1, H 2 and H 3, respectively. The presence of L-NAME 10 -4 M or L-NAME 10 -4 M plus indomethacin 10 -5 M also did not prevent the histamine-induced relaxation observed in rat portal vein. Thus, the histamine-induced relaxation observed in rat portal vein appears to involve a non-endothelial hyperpolarizing mechanism independent of H 1, H 2 and H 3 receptors.

A teoria de Norbert Elias: uma análise do ser professor

No presente artigo, conforme o entendimento de que modelos te- óricos subsidiam a compreensão de fenômenos investigativos, objetivou-se elucidar os conceitos da teoria sociológica de Norbert Elias, considerando-se que esta é uma excelente fonte de análise para se compreender o universo do ser professor, apesar de o autor não abordar diretamente questões relacionadas ao campo da educação. A partir do conceito de configuração, é possível dizer que a constituição do ser professor resulta das diferentes configurações nas quais ele está imerso, pois, de acordo com Elias, as pessoas (professores, pais, gestores, ministros, alunos etc.) modelam suas ideias a partir de todas as suas experiências e, essencialmente, das experiências vividas no interior do próprio grupo. É observável que as configurações, formadas por grupos interdependentes de pessoas, e não por indivíduos singulares, apresentam-se cada vez mais ampliadas nos contextos escolares, com funções especializadas e específicas (professores, alunos, diretores, coordenadores, supervisores, secretários etc.), em grupos que se tornam cada vez mais funcionalmente dependentes. As cadeias de interdependência estão mais diferenciadas e, consequentemente, mais opacas e dificilmente controláveis por parte de quaisquer grupos ou indiví- duos. Portanto, uma melhor compreensão será possível quando se estudar empiricamente as configurações que estão em jogo na educação brasileira. Daí se justifica a análise das configurações e das teias de interdependência em que os professores estão envolvidos. Enfim, a aplicação dos modelos de competição abordados por Elias possibilita evidenciar as problemáticas sociológicas do ser professor, tornando-as mais evidentes e facilitando o entendimento do jogo para reorganizá-lo em termos de equilíbrio na teia social.

A Prática do Professor que Ensina Matemática e a Colaboração: uma reflexão a partir de processos formativos virtuais

This text presents some reflections about the educational and virtual processes of mathematics teachers drawing on research on the theme. Thus, in this text, considering our experiences with the development of online courses, we discuss issues such as collaboration in virtual environments, which contributes to more effective results in collaborative learning and reduces the potential of isolation of student/teacher that can occur in virtual environments. Through collaborative learning in a virtual community, students/teachers have the opportunity to practice and think in-depth about their learning experiences by sharing new ideas with the group and receiving critical and constructive feedback. Moreover, the virtuality formed by the environment of online courses supports educational spaces for teachers who teach mathematics. Thus, collaboration emerges as an essential element for construction of meanings and for sharing experiences on the practice of teaching.

Educação a distância e formação continuada do professor

Distance Education has had a significant role in further teacher development. The aim of this study was to collect and analyze data related to distance education for the further teacher development related to the inclusion process of people with disability. One hundred and eighty two students from the Distance Training course from Unesp - Bauru / SP participated in the research, constructing and applying a semi-structured questionnaire. The results indicate that scheduling flexibility and attendance of a great number of students in different geographical areas stand out as positive points of this modality, however, for it to be a success, tutors must be adequately prepared to use new tools in the teaching-learning process. It is essential that the students feel they are being assisted in every moment, contributing to the construction of a virtual community and effecting quality development in distance education.

Nonlinear dynamics of a flexible portal frame under support excitation

This paper presents a nonlinear dynamic analysis of a flexible portal frame subjected to support excitation, which is provided by an electro-dynamical shaker. The problem is reduced to a mathematical model of four degrees of freedom and the equations of motion are derived via Lagrangian formulation. The main goal of this study is to investigate the dynamic interactions between a flexible portal frame and a non-ideal support excitation. The numerical analysis shows a complex behavior of the system, which can be observed by phase spaces, Poincaŕ sections and bifurcation diagrams. © 2012 American Institute of Physics.

Comments on the paper by professor Olof Ruin

Comenta sobre las condiciones políticas iniciales que hicieron posible la transformación de la economía y de la sociedad suecas.

Sweden and Latin America: comments on the paper by professor Olof Ruin

Señala las diferencias históricas y estructurales y llama la atención sobre las semejanzas entre el desarrollo sociopolítico de Suecia y el de América Latina.

On elimination of chaotic behavior in a non-ideal portal frame structural system, using both passive and active controls

In this paper, an application is considered of both active and passive controls, to suppression of chaotic behavior of a simple portal frame, under the excitation of an unbalanced DC motor, with limited power supply (non-ideal problem). The adopted active control strategy consists of two controls: the nonlinear (feedforward) in order to keep the controlled system in a desirable orbit, and the feedback control, which may be obtained by considering state-dependent Riccati equation control to bringing the system into the desired orbit using a magneto rheological (MR) damper. To control the electric current applied in control of the MR damper the Bouc-Wen mathematical model was used to the MR damper. The passive control was obtained by means of a nonlinear sub-structure with properties of nonlinear energy sink. Simulations showed the efficiency of both the passive control (energy pumping) and active control strategies in the suppression of the chaotic behavior. © The Author(s) 2012.

Discursos do professor de matemática e suas implicações na compreensão dos alunos

The primary objective of this article is to analyze situations with discursive interactions in math classrooms, which may prompt student's understanding of teacher's speech. To analyze the situations with discursive interactions, this study used elements from Bakhtin's theory of language, mainly its concept of comprehension, and introduces the new concept of intermediate comprehension . The data used in a qualitative approach were collected from class observation through video-recorded lessons. The results showed three situations with discursive interactions that contribute to understanding of the school teacher's speech: 1) speech referring to everyday situations; 2) the teacher's speech math in a less rigorous way 3) teacher comparing different mathematical objects.

A model for analysing data portal performance: The biodiversity case

Currently, many museums, botanic gardens and herbariums keep data of biological collections and using computational tools researchers digitalize and provide access to their data using data portals. The replication of databases in portals can be accomplished through the use of protocols and data schema. However, the implementation of this solution demands a large amount of time, concerning both the transfer of fragments of data and processing data within the portal. With the growth of data digitalization in institutions, this scenario tends to be increasingly exacerbated, making it hard to maintain the records updated on the portals. As an original contribution, this research proposes analysing the data replication process to evaluate the performance of portals. The Inter-American Biodiversity Information Network (IABIN) biodiversity data portal of pollinators was used as a study case, which supports both situations: conventional data replication of records of specimen occurrences and interactions between them. With the results of this research, it is possible to simulate a situation before its implementation, thus predicting the performance of replication operations. Additionally, these results may contribute to future improvements to this process, in order to decrease the time required to make the data available in portals. © Rinton Press.

A non-ideal portal frame energy harvester controlled using a pendulum

A model of energy harvester based on a simple portal frame structure is presented. The system is considered to be non-ideal system (NIS) due to interaction with the energy source, a DC motor with limited power supply and the system structure. The nonlinearities present in the piezoelectric material are considered in the piezoelectric coupling mathematical model. The system is a bi-stable Duffing oscillator presenting a chaotic behavior. Analyzing the average power variation, and bifurcation diagrams, the value of the control variable that optimizes power or average value that stabilizes the chaotic system in the periodic orbit is determined. The control sensitivity is determined to parametric errors in the damping and stiffness parameters of the portal frame. The proposed passive control technique uses a simple pendulum to tuned to the vibration of the structure to improve the energy harvesting. The results show that with the implementation of the control strategy it is possible to eliminate the need for active or semi active control, usually more complex. The control also provides a way to regulate the energy captured to a desired operating frequency. © 2013 EDP Sciences and Springer.

A interação professor-aluno nas atividades de escrita: um estudo em salas de primeiro ano do ensino fundamental

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)