In this paper, a summary of our work in the area of tunable microwave circuits based on thin film ferroelectrics is presented. First, a technique is introduced to improve the linearity of thin film ferroelectric tunable capacitors. Measurements show an improvement in the 3rd order intermodulation point at the input (IIP3) of 16 dB. Next, the design and fabrication of an impedance tuner employin...

The use of intelligent nanocomposites in sensing and actuation applications has become quite common over the past decade. In this article, electro-thermo-mechanical nonlinear dynamic buckling of an orthotropic piezoelectric nanocomposite (PNC) cylindrical shell conveying viscous fluid is investigated. The composite cylindrical shell is made from Polyvinylidene Fluoride (PVDF) and reinforced by ...

A unified boundary element method ~BEM! is developed in this paper to model both the exterior acoustic field and the elastic shell-like structure in a coupled analysis. The conventional boundary integral equation ~BIE! for three-dimensional ~3D! elastodynamics is applied to thin shell-like structures which can have arbitrary shapes and small thicknesses. The nearly singular integrals existing i...

The stability of lightweight space structures composed longitudinal thin-shell elements connected transversely by thin rods is investigated, extending recent work on the cylindrical and spherical shells. role localization in buckling these investigated early transitions into post-buckling regime are unveiled using a probe that locally displaces structure. Multiple locations studied force versus...

We present an idealised model of gravitational collapse, describing a collapsing rotating cylindrical shell of null dust in flat space, with the metric of a spinning cosmic string as the exterior. We find that the shell bounces before closed timelike curves can be formed. Our results also suggest slightly different definitions for the mass and angular momentum of the string. Introduction A stat...

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Nanocomposites provide new properties and exploit unique synergism between materials. Polyvinylidene fluoride (PVDF) is an ideal piezoelectric matrix applicable in nanocomposites in a broad range of industries from oil and gas to electronics and automotive. And boron nitride nanotubes (BNNTs) show high mechanical, electrical and chemical properties. In this paper, the critical torsional load of...

Previous research of the authors pointed out that side-resonators can be applied to reduce fan noise. However, the noise reduction capabilities of most resonator geometries, e.g. tube resonators, cylindrical resonators (cylindrical air layers) and circular resonators (disc shaped air layers), are relatively narrow banded. This is disadvantageous in case resonators are used in combination with a...