261 research outputs found
Stability control of nonlinear micromechanical resonators under simultaneous primary and superharmonic resonances
Fast effects of a slow excitation on the main resonance of a nonlinear micromechanical resonator are analytically and experimentally investigated. We show, in particular, how the bifurcation topology of an undesirable unstable behavior is modified when the resonator is simultaneously actuated at its primary and superharmonic resonances. A stabilization mechanism is proposed and demonstrated by increasing the superharmonic excitation
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https://digitalcommons.library.umaine.edu/mmb-vp/2221/thumbnail.jp
Non linear dynamics of Mathieu resonators for resonant gyroscope applications
A complete model describing the non linear dynamics of Mathieu resonators is presented in order to study the stability of resonant MEM gyroscopes
Dynamique non linéaire des résonateurs de Mathieu pour les applications de microgyromètres résonants
Compact and explicit physical model for lateral metal-oxide-semiconductor field-effect transistor with nanoelectromechanical system based resonant gate
We propose a simple analytical model of a metal-oxide-semiconductor
field-effect transistor with a lateral resonant gate based on the coupled
electromechanical equations, which are self-consistently solved in time. All
charge densities according to the mechanical oscillations are evaluated. The
only input parameters are the physical characteristics of the device. No extra
mathematical parameters are used to fit the experimental results. Theoretical
results are in good agreement with the experimental data in static and dynamic
operation. Our model is comprehensive and may be suitable for any
electromechanical device based on the field-effect transduction
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Subsurface Oil-Shale Samples of the Upper Pennsylvanian Cline Shale, Midland Basin, West Texas: Core Sampling for Measured Vitrinite-Reflectance (Ro) Determination
This report summarizes activities carried out by the Bureau of Economic Geology (BEG) during fiscal year (FY) 2015 for the National Coal Resources Data System State Cooperative Program (NCRDS project). In a continuation of the sampling strategy for measured vitrinite-reflectance (Ro) determination initiated 6 years ago (Hentz and others, 2009) and conducted during the following five years (Hentz and others, 2010, 2011, 2012, 2014, 2015), this report provides a collection of oil-shale samples from the Upper Pennsylvanian Cline Shale of the Midland Basin in West Texas (Fig. 1).Bureau of Economic Geolog
Large-Scale Integration of Nanoelectromechanical Systems for Gas Sensing Applications
We have developed arrays of nanomechanical systems (NEMS) by large-scale integration, comprising thousands of individual nanoresonators with densities of up to 6 million NEMS per square centimeter. The individual NEMS devices are electrically coupled using a combined series-parallel configuration that is extremely robust with respect to lithographical defects and mechanical or electrostatic-discharge damage. Given the large number of connected nanoresonators, the arrays are able to handle extremely high input powers (>1 W per array, corresponding to <1 mW per nanoresonator) without excessive heating or deterioration of resonance response. We demonstrate the utility of integrated NEMS arrays as high-performance chemical vapor sensors, detecting a part-per-billion concentration of a chemical warfare simulant within only a 2 s exposure period
Piezoelectric nanoelectromechanical resonators based on aluminum nitride thin films
We demonstrate piezoelectrically actuated, electrically tunable nanomechanical resonators based on multilayers containing a 100-nm-thin aluminum nitride (AlN) layer. Efficient piezoelectric actuation of very high frequency fundamental flexural modes up to ~80 MHz is demonstrated at room temperature. Thermomechanical fluctuations of AlN cantilevers measured by optical interferometry enable calibration of the transduction responsivity and displacement sensitivities of the resonators. Measurements and analyses show that the 100 nm AlN layer employed has an excellent piezoelectric coefficient, d_(31)=2.4 pm/V. Doubly clamped AlN beams exhibit significant frequency tuning behavior with applied dc voltage
From MEMS to NEMS: closed-loop actuation of resonant beams beyond the critical Duffing amplitude
International audienceBecause of its moderate cost in terms of electronics, resonant sensing has become commonplace in the context of MEMS and NEMS devices. It is usual to drive such resonators below the critical open-loop Duffing amplitude, above which the oscillations become unstable. However, when scaling sensors down to NEMS, nonlinearities may occur at very low amplitudes, making oscillations very difficult to detect. This paper describes a very general way to compute the critical amplitude in open-loop operation for beam resonators, before it focuses on closed-loop Duffing-type resonators. The major contribution of this paper is the use of describing function analysis validated by numerical simulations to show that it is possible to obtain stable oscillations with amplitudes much larger than the critical Duffing amplitude. As a practical consequence, the measured currents are significantly increased and the constraints on the sensing electronics can be relaxed
Large amplitude dynamics of micro/nanomechanical resonators actuated with electrostatic pulses
International audienceIn the field of resonant NEMS design, it is a common misconception that large-amplitude motion, and thus large signal-to-noise ratio, can only be achieved at the risk of oscillator instability. In the present paper, we show that very simple closed-loop control schemes can be used to achieve stable largeamplitude motion of a resonant structure, even when jump resonance (caused by electrostatic softening or Duffing hardening) is present in its frequency response. We focus on the case of a resonant accelerometer sensing cell, consisting in a nonlinear clamped-clamped beam with electrostatic actuation and detection, maintained in an oscillation state with pulses of electrostatic force that are delivered whenever the detected signal (the position of the beam) crosses zero. We show that the proposed feedback scheme ensures the stability of the motion of the beam much beyond the critical Duffing amplitude and that, if the parameters of the beam are correctly chosen, one can achieve almost full-gap travel range without incurring electrostatic pull-in. These results are illustrated and validated with transient simulations of the nonlinear closed-loop system
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