Numerical and experimental investigation of a vibration system with non-ideal vibration source

An excitation force that is not influenced by the system's states is said to be an ideal energy source. In real situations, a direct and feedback coupling between the excitation source and the system must always exist. This manifestation of the law of conversation of energy is known as Sommerfeld Effect. In the case of obtaining a mathematical model for such system, additional equations are usually necessary to describe the vibration sources and their coupling with the mechanical system. In this work, a cantilever beam and a non-ideal electric DC motor that is fixed to the beam free end is analyzed. The motor has an unbalanced mass that provides excitation to the system proportional to the current applied to the motor. During the motor's coast up operation, as the excitation frequency gets closer to the beam first natural frequency and if the drive power increases further, the DC motor speed remains constant until it suddenly jumps to a much higher value (simultaneously the vibration amplitude jumps to a much lower value) upon exceeding a critical input power. It was found that the Sommerfeld effect depends on some system parameters and the motor operational procedures. These parameters are explored to avoid the resonance capture in Sommerfeld effect. Numerical simulations and experimental tests are used to help insight this dynamic behavior.

Revista Rolling Stone Brasil: em busca do perfil ideal do leitor do site

O presente trabalho tem por objetivo buscar características que ajudem a definir quem é o público leitor do site da Rolling Stone Brasil, levantando a questão da migração de revistas que surgiram antes da internet para o ciberespaço. Para isso, com base em revisão bibliográfica, retornamos na história para resgatar as origens da versão impressa da publicação e das origens do próprio jornalismo de revista. Com base em uma pesquisa sobre o que se chamou de Perfis Digigraficos e com realização de entrevistas com os editores do site e da revista Rolling Stone Brasil, concluímos que este perfil, aqui chamado de ideal, não está relacionado com idade, gênero e gosto musical

A formação continuada de professores: entre o real e o 'ideal'

The objective this study was to highlight the prospects of a group of teachers of Physical Education, highlighting the factors identified as critical to a continuing education "ideal" for a teacher professional development and for the practice pedagogical. Qualitative research, inspired by the method of approaching the history of the present time, in order to register as memory the time when these teachers live. The data source used was oral sources collected by the technique of semistructured interviews and official documents. The data generated were discussed with the production of literature and the highlights are three axes in the reports of teachers: the relationship between theory and practice, the importance of listening to students and the continuity of training activities.

On an energy exchange process and appearance of chaos in a non-ideal portal frame dynamical system

In this paper, we consider non-ideal excitation devices such as DC motors with restrictenergy output capacity. When such motors are attached to structures which needexcitation power levels similar to the source power capacity, jump phenomena and theincrease in power required near resonance characterize the Sommerfeld Effect, actingas a sort of an energy sink. One of the problems often faced by designers of suchstructures is how to drive the system through resonance and avoid this energy sink.Our basic structural model is a simple portal frame driven by a num-ideal powersource-(NIPF). We also investigate the absorption of resonant vibrations (nonlinearand chaotic) by means of a nonlinear sub-structure known as a Nonlinear Energy Sink(NES). An energy exchange process between the NIPF and NES in the passagethrough resonance is investigated, as well the suppression of chaos.

On suppression of chaotic motions of a portal frame structure under non-ideal loading using a magneto-rheological damper

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Análise dinâmica não-linear de um sistema não-ideal, utilizando amortecedor magneto-reológico

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Dinâmica não linear e controle de um sistema vibratório modelado com memória de forma e, excitado por fontes de energia do tipo ideal e não ideal

Pós-graduação em Engenharia Mecânica - FEB

Relação ideal dos aminoácidos essenciais para mantença, crescimento e produção de aves

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