Electrode poling of cellular polypropylene films with short high-voltage pulses

Recently, piezoelectric cellular polypropylene (PP) was proposed as a new type of quasi-ferroelectric. The observed hysteresis of the charge density as a function of the electric field could be explained as field-dependent charging inside the gas-filled voids. Interestingly enough, the measurable poling behavior of the macroscopic dipoles formed by charges that are trapped at the internal void surfaces is phenomenologically completely identical to the cooperative poling behavior of microscopic molecular dipoles in ferroelectric polymers. Therefore, it can be assumed that charge separation (or charge redistribution) and subsequent trapping in cellular PP is a rather fast switching process. In order to examine the poling dynamics, we developed an experimental setup for pulsed poling. High-voltage pulses with a duration of 45 μs (FWHM) were applied in direct contact to two-side metallized cellular PP films. The pulsed poling yields piezoelectricity in the cellular PP. We study and discuss the dependence of the resulting piezoelectricity on the poling field. We also characterize the charge separation during application of higher electric poling fields of up to -10 kV in direct contact to the two-side metallized films for longer times.

Avaliação de hábitos de vida e proposta de fluxograma de encaminhamento de escolares com necessidades de cuidado nutricional

Pós-graduação em Enfermagem (mestrado profissional) - FMB

Electrochromic Switching Mechanism of Iron Hexacyanoferrates Molecular Compounds: The Role of Fe2+(CN)(6) Vacancies

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

Differential mixer with NMOS/PMOS stack at switching stage

This paper proposes a novel differential mixer topology. The traditional stage of switching is replaced by a stack of NMOS and PMOS transistors combined. A design is given of a 900 MHz down-conversion mixer using a 0.35 μm CMOS process. Comparison with conventional mixer shows that the topology leads to a better performance in terms of conversion gain and linearity. ©2012 IEEE.

Socialização linguageira, aspectos culturais e uso de code-switching em uma criança bilíngue

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Platform switching: avaliação biomecânica por meio do método de elementos finitos tridimensional

Pós-graduação em Odontologia - FOA

Referência e code-switching: traços de singularidade na linguagem de uma criança bilíngue

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Switching-off in a minimal time a fitzhugh-nagumo system

This paper deals with a system that describes an electrical circuitcomposed by a linear system coupled to a nonlinear one involving a tunneldiode in a flush-and-fill circuit. One of the most comprehensive models for thiskind of circuits was introduced by R. Fitzhugh in 1961, when taking on carebiological tasks. The equation has in its phase plane only two periodic solutions,namely, the unstable singular point S0 and the stable cycle Γ. If the system isat rest on S0, the natural flow of orbits seeks to switch-on the process by going- as time goes by - toward its steady-state, Γ. By using suitable controls it ispossible to reverse such natural tendency going in a minimal time from Γ toS0, switching-off in this way the system. To achieve this goal it is mandatorya minimal enough strength on controls. These facts will be shown by means ofconsiderations on the null control sets in the process.