This paper investigates the parametric excitation of a micro-pipe conveying fluid suspended between two symmetric electrodes. Electrostatically actuated micro-pipes may become unstable when the exciting voltage is greater than the pull-in value. It is demonstrated that the parametric excitation of a micro-pipe by periodic (ac) voltages may have a stabilizing effect and permit an increase of the...

Electrostatic micro-electro-mechanical system (MEMS) is a special branch with a wide range of applications in sensing and actuating devices in MEMS. This paper provides a survey and analysis of the electrostatic force of importance in MEMS, its physical model, scaling effect, stability, nonlinearity and reliability in detail. It is necessary to understand the effects of electrostatic forces in ...

In the present work the pull-in voltage of a micro cracked cantilever beam subjected to nonlinear electrostatic pressure was studied. Two mathematical models were employed for modeling the problem: a lumped mass model and a classical beam model. The effect of crack in the lumped mass model is the reduction of the effective stiffness of the beam and in the beam model; the crack is modeled as a m...

We present a unique experimental configuration that allows us to determine the interfacial forces on nearly parallel plates made from the thinnest possible mechanical structures, single and few layer graphene membranes. Our approach consists of using a pressure difference across a graphene membrane to bring the membrane to within ~10-20 nm above a circular post covered with SiOx or Au until a c...

An accurate frequency of the Helmholtz–Duffing oscillator is obtained by a sophisticated modification He’s formulation. The pull-down instability existing in symmetric breaking phenomenon newly discovered dynamic motion for oscillators with even nonlinearities. A criterion predicting asymmetrical amplitude and built measuring change. good matching performance between analytic results numerical ...

This article analyses the push and pull factors that bring visitors to the Iranian national parks. The study used a structured questionnaire to collect data on these factors and the socio-demographic profile of the visitors. Survey conducted in Boujagh National Park, an area of 3177 hectares located in the north of the Iran, produced 400 questionnaires. The factor analysis identified four push ...

This paper presents results about fabrication and operation of electrostatic actuators in liquids with various permittivities. In the static mode, we provide experimental and theoretical demonstration that the pull-in effect can be shifted beyond one third of the initial gap and even be eliminated when electrostatic actuators are operated in liquids. This should benefit to applications in micro...

introduction professional sports injuries are usually all dealt with at one single operation to return the player to the sport after appropriate rehabilitation. we questioned the assumption that rotator cuff tears must be repaired concurrently with instability syndromes, and aimed to allow a professional rugby league player to achieve career goals by not correcting all pathology at one surgery....