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We study the electrothermal actuation of nanomechanical motion using a combination of numerical simulations and analytical solutions. The nanoelectrothermal actuator structure is a u-shaped gold nanoresistor that is patterned on the anchor of a doubly clamped nanomechanical beam or a microcantilever resonator. This design has been used in recent experiments successfully. In our finite-element analysis (FEA) based model, our input is an ac current; we first calculate the temperature oscillations due to Joule heating using Ohm’s law and the heat equation; we then determine the thermally induced bending moment and the displacement profile of the beam by coupling the temperature field to Euler–Bernoulli beam theory with tension. Our model efficiently combines transient and frequency-domain analyses: we compute the temperature field using a transient approach and then impose this temperature field as a harmonic perturbation for determining the mechanical response in the frequency domain. This unique modeling method offers lower computational complexity and improved accuracy and is faster than a fully transient FEA approach. Our dynamical model computes the temperature and displacement fields in the time domain over a broad range of actuation frequencies and amplitudes. We validate the numerical results by directly comparing them with experimentally measured displacement amplitudes of nano-electro-mechanical system beams around their eigenmodes in vacuum. Our model predicts a thermal time constant of 1.9 ns in vacuum for our particular structures, indicating that electrothermal actuation is efficient up to ∼80 MHz. We also investigate the thermal response of the actuator when immersed in a variety of fluids.
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Source Parameter Analysis Using Maximum Amplitudes in the Time Domain
ABSTRACT We measure maximum amplitudes in the time domain on recordings of the 2019 Ridgecrest earthquake sequence to convert ground-motion amplitudes to source spectra. To do this, we modify Richter’s local magnitude relation to measure frequency-dependent empirical amplitude-decay curves and station corrections for a series of narrowband time-domain filters. Peak displacement amplitude in each frequency band is used to construct the displacement spectrum. After correction for attenuation, we determine corner frequency and moment from the resulting source spectra. By this approach, we measure moment magnitudes reliably to as small as ML 1.0. We find stress drop increases with both depth and magnitude and discuss whether this could be an artifact through assumptions about the source, path, and site.
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- Award ID(s):
- 2225216
- PAR ID:
- 10610292
- Publisher / Repository:
- Bulletin of the Seismological Society of America
- Date Published:
- Journal Name:
- Bulletin of the Seismological Society of America
- Volume:
- 115
- Issue:
- 3
- ISSN:
- 0037-1106
- Page Range / eLocation ID:
- 839 to 849
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1785/0120240198
