Dynamics of vibrating systems with tuned liquid column dampers and limited power supply

Tuned liquid column dampers are U-tubes filled with some liquid, acting as an active vibration damper in structures of engineering interest like buildings and bridges. We study the effect of a tuned liquid column damper in a vibrating system consisting of a cart which vibrates under driving by a source with limited power supply (non-ideal excitation). The effect of a liquid damper is studied in some dynamical regimes characterized by coexistence of both periodic and chaotic motion. (c) 2005 Elsevier Ltd. All rights reserved.

A simple feedback control for a chaotic oscillator with limited power supply

We proposed a simple feedback control method to suppress chaotic behavior in oscillators with limited power supply. The small-amplitude controlling signal is applied directly to the power supply system, so as to alter the characteristic curve of the driving motor. Numerical results are presented showing the method efficiency for a wide range of control parameters. Moreover, we have found that, for some parameters, this kind of control may introduce coexisting periodic attractors with complex basins of attraction and, therefore, serious problems with predictability of the final state the system will asymptote to. (c) 2006 Elsevier Ltd. All rights reserved.

Impact dampers for controlling chaos in systems with limited power supply

We investigate numerically the dynamical behavior of a non-ideal mechanical system consisting of a vibrating cart containing a particle which can oscillate back and forth colliding with walls carved in the cart. This system represents an impact damper for controlling high-amplitude vibrations and chaotic motion. The motion of the cart is induced by an in-board non-ideal motor driving an unbalanced rotor. We study the phase space of the cart and the bouncing particle, in particular the intertwined smooth and fractal basin boundary structure. The control of the chaotic motion of the cart due to the particle impacts is also investigated. Our numerical results suggests that impact dampers of small masses are effective to suppress chaos, but they also increase the final-state sensitivity of the system in its phase space. (C) 2004 Elsevier Ltd. All rights reserved.

On saturation control of a non-ideal vibrating portal frame foundation type shear-building

In this paper, we examine the nonlinear control method based on the saturation phenomenon and of systems coupled with quadratic nonlinear ties applied to a shear-building portal plane frame foundation that supports an unbalanced direct cut-rent with limited power supply (non-ideal system). We analyze the equations of motion by using the method of averaging and numerical simulation. The interaction of the non-ideal structure with the saturation controller may lead to the occurrence of interesting phenomena during the forward passage through the several resonance states of the systems. Special attention is focused on passage through resonance when the non-ideal excitation frequency is near the portal frame natural frequency and when the non-ideal system frequency is approximately twice the controller frequency (two-to-one internal resonance).

Chaos control of a nonlinear oscillator with shape memory alloy using an optimal linear control: Part II: Nonideal energy source

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Snakes from coastal islands of State of São Paulo, Southeastern Brazil

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

Aplicação de enxofre em cobertura no feijoeiro em sistema de plantio direto

Em lavouras de feijão, principalmente em cultivos com alta tecnologia, não tem sido dada a devida atenção ao fornecimento adequado de enxofre (S), utilizando doses subestimadas ou não aplicando o elemento via adubação, o que pode estar sendo um fator limitante ao incremento de produtividade. O objetivo deste trabalho foi avaliar a influência da aplicação de S em cobertura na nutrição, nos componentes da produção e na produtividade de grãos do feijoeiro, em sistema de plantio direto (SPD). O delineamento experimental utilizado foi o de blocos ao acaso, com cinco repetições. Os tratamentos foram constituídos por cinco doses de S (0, 20, 40, 60 e 80 kg ha-1) aplicados em cobertura no estádio V4, tendo como fonte o sulfato de amônio. Aplicação de S em cobertura aumentou o teor do elemento nas folhas, a produção de matéria seca da parte aérea, o número vagens por planta e a produtividade de grãos do feijoeiro em SPD. em lavouras com alto nível tecnológico, a produtividade de grãos de feijão pode estar sendo limitado pela utilização de doses insuficientes de enxofre.

LIMITED MULTIPLE-MATING IN MALES AND SINGLE-MATING IN FEMALES OF THE ANT SPECIES, PARATRECHINA-FLAVIPES (FR SMITH) (HYMENOPTERA, FORMICIDAE)

This study determined how many times alates of Paratrechina flavipes (Hymenoptera: Formicidae) can copulate in the field and laboratory. In the field, females preferred to mate once and the mating number of males is unknown. In the laboratory, females mated singly but males could inseminate two or three females. The duration of succeeding copulations was greater than the first copulation. Multiple mating males died sooner than single mating ones. The results suggest that male death is promoted by sperm consumption.

Gaze pursuit and arm control of adolescent males diagnosed with attention deficit hyperactivity disorder (ADHD) and normal controls: evidence of a dissociation in processing visual information of short and long duration

Three-dimensional kinematic analysis of line of gaze, arm and ball was used to describe the visual and motor behaviour of male adolescents diagnosed with attention deficit hyperactivity disorder (ADHD). The ADHD participants were tested when both on (ADHD-On) and off (ADHD-Off) their medication and compared to age-matched normal controls in a modified table tennis task that required tracking the ball and hitting to cued right and left targets. Long-duration information was provided by a pre-cue, in which the target was illuminated approximately 2 s before the serve, and short-duration information by an early-cue illuminated about 350 ms after the serve, leaving -500 ms to select the target and perform the action. The ADHD groups differed significantly from the control group in both the pre-cue and early-cue conditions in being less accurate, in having a later onset and duration of pursuit tracking, and a higher frequency of gaze on and off the ball. The use of medication significantly reduced the gaze frequency of the ADHD participants, but surprisingly this did not lead to an increase in pursuit tracking, suggesting a barrier was reached beyond which ball flight information could not be processed. The control and ADHD groups did not differ in arm movement onset, duration and velocity in the short-duration early-cue condition; in the long-duration pre-cue condition, however, the ADHD group's movement time onset and arm velocity differed significantly from controls. The results show that the ADHD groups were able to process short-duration information without experiencing adverse effects on their motor behaviour; however, long-duration information contributed to irregular movement control.