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I. Y. Shen - One of the best experts on this subject based on the ideXlab platform.
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Effects of Corner Frequency on bandwidth and resonance amplitude in designing PZT thin-film actuators
Sensors and Actuators A: Physical, 2006Co-Authors: Cheng Chun Lee, Guozhong Cao, I. Y. ShenAbstract:Abstract In the last decade, lead zirconate titanate oxide (PZT) thin-film actuators have received increasing attention because of their high Frequency bandwidth, large actuation strength, fast response, and small size. The PZT film thickness is usually less than several microns as opposed to hundreds of microns for bulk PZT patches that are commercially available. As a result, PZT thin-film actuators pose unique vibration issues that do not appear in actuators with bulk PZT. Two major issues affecting actuator performance are the Frequency bandwidth and the resonance amplitude. As an electromechanical device, a PZT thin-film actuator's bandwidth and resonance amplitude depend not only on the lowest natural Frequency ωn of the actuator's mechanical structure but also on the Corner Frequency ωc of the actuator's RC-circuit. For PZT thin-film actuators, the small film thickness implies large film capacitance C and small ωc. When the size of the actuator decreases, ωn increases dramatically. As a result, improper design of PZT thin-film actuators could lead to ωc ≪ ωn substantially reducing the actuator bandwidth and the resonance amplitude. This paper is to demonstrate this phenomenon through theoretical analyses and calibrated experiments. In the theoretical analyses, Frequency response functions of a PZT thin-film actuator are obtained to predict 3 dB actuator bandwidth and resonance amplitude for cases when ωc ≪ ωn, ωc ≈ ωn and ωc ≫ ωn. In the experiments, Frequency response functions of a fixed–fixed silicon beam with a 1 μm thick PZT film are measured through use of a laser Doppler vibrometer and a spectrum analyzer. The silicon beam has multiple electrodes with a wide range of resistance R and Corner Frequency ωc. The experimental results confirm that the actuator bandwidth and resonance amplitude are substantially reduced when ωc ≪ ωn.
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Effects of Corner Frequency on Bandwidth and Resonance Amplitude in Designing PZT Thin-Film Actuators: An Experimental Demonstration
Design Engineering Parts A and B, 2005Co-Authors: Cheng Chun Lee, Guozhong Cao, I. Y. ShenAbstract:In the last decade, Lead Zirconate Titanate Oxide (PZT) thin-film actuators have received increasing attention because of their high Frequency bandwidth, large actuation strength, fast response, and small size. The PZT film thickness is usually less than several microns as opposed to hundreds of microns for bulk PZT patches that are commercially available. As a result, PZT thin-film actuators pose unique vibration issues that do not appear in actuators with bulk PZT. Two major issues affecting actuator performance are the Frequency bandwidth and the resonance amplitude. As an electromechanical device, a PZT thin-film actuator’s bandwidth and resonance amplitude depend not only on the lowest natural Frequency ωn of the actuator’s mechanical structure but also on the Corner Frequency ωc of the actuator’s RC-circuit. For PZT thin-film actuators, the small film thickness implies large film capacitance C and small ωc . When the size of the actuator decreases, Frequency ωn increases dramatically. As a result, improper design of PZT thin-film actuators could lead to ωc ≪ ωn substantially reducing the actuator bandwidth and the resonance amplitude. This paper is to demonstrate this phenomenon through calibrated experiments. In the experiments, Frequency response functions of a fixed-fixed silicon beam with a 1-μm thick PZT film are measured through use of a laser Doppler vibrometer and a spectrum analyzer. The silicon beam has multiple electrodes with a wide range of resistance R and Corner Frequency ωc . The experimental results confirm that the actuator bandwidth and resonance amplitude are substantially reduced when ωc ≪ ωn .Copyright © 2005 by ASME
Norman A. Abrahamson - One of the best experts on this subject based on the ideXlab platform.
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A Generalization of the Double-Corner-Frequency Source Spectral Model and Its Use in the SCEC BBP Validation Exercise
Bulletin of the Seismological Society of America, 2014Co-Authors: David M. Boore, Carola Di Alessandro, Norman A. AbrahamsonAbstract:The stochastic method of simulating ground motions requires the speci- fication of the shape and scaling with magnitude of the source spectrum. The spectral models commonly used are either single-Corner-Frequency or double-Corner- Frequency models, but the latter have no flexibility to vary the high-Frequency spectral levels for a specified seismic moment. Two generalized double-Corner-Frequency ω 2 source spectral models are introduced, one in which two spectra are multiplied to- gether and another where they are added. Both models have a low-Frequency depend- ence controlled by the seismic moment and a high-Frequency spectral level controlled by the seismic moment and a stress parameter. Awide range of spectral shapes can be obtained from these generalized spectral models, which makes them suitable for in- versions of data to obtain spectral models that can be used in ground-motion simu- lations in situations in which adequate data are not available for purely empirical determinations of ground motions, such as in stable continental regions. As an exam- ple of the use of the generalized source spectral models, data from up to 40 stations from seven events, plus response spectra at two distances and two magnitudes from recent ground-motion prediction equations, were inverted to obtain the parameters controlling the spectral shapes, as well as a finite-fault factor that is used in point- source, stochastic-method simulations of ground motion. The fits to the data are com- parable to or even better than those from finite-fault simulations, even for sites close to large earthquakes.
Igor A. Beresnev - One of the best experts on this subject based on the ideXlab platform.
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Source Parameters Observable from the Corner Frequency of Earthquake Spectra
Bulletin of the Seismological Society of America, 2002Co-Authors: Igor A. BeresnevAbstract:The Brune (1970) classic theory's suggestion that the source radius be determined from the Corner Frequency of earthquake spectra is based on a number of insufficiently constrained assumptions that make the result virtually a guess. Viewing earthquakes as displacement-discontinuity sources radiating ω -2 spectra indicates that the two other parameters can be accurately resolved from the Corner frequencies, without reliance on any additional assumptions. These parameters are the source duration (rise time) and the maximum slip velocity on the fault; their determination is rooted in the exact formulas of radiation from dislocation sources. These directly observable parameters can serve as important constraints on dynamic theories of friction and faulting. Manuscript received 22 October 2001
Mark D Fisk - One of the best experts on this subject based on the ideXlab platform.
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source spectral modeling of regional p s discriminants at nuclear test sites in china and the former soviet union
Bulletin of the Seismological Society of America, 2006Co-Authors: Mark D FiskAbstract:Theoretical understanding of regional P/S discriminants has been a long- standing research topic with important implications for nuclear explosion monitoring. The observation that discrimination is poor at low frequencies, but becomes significant at higher frequencies, usually at about 3 to 4 Hz, particularly needs understanding. To gain insight, source and attenuation models are used to predict spectra of regional seismic phases ( Pn, Sn , and Lg ) for nuclear explosions and selected earthquakes near the Lop Nor, Semipalatinsk (Balapan and Degelen Mountain), and Novaya Zemlya test sites in China and the former Soviet Union. A modified Brune (1970) model (a la Walter and Taylor, 2002) is used to predict P - and S -source terms for earthquakes. A Mueller/Murphy (1971) model is used for explosions, including a new conjecture that the S waves may be modeled by the same functional form as for P waves, but with Corner Frequency reduced by the ratio of near-source shear and compressional velocities, vs ( S )/ vs ( P ). Results indicate that the Frequency dependence of Pn / Sn and Pn / Lg discrimination performance at all of these hard-rock test sites is primarily due to differences in the Corner frequencies of P and S waves for explosions, qualitatively consistent with observations by Xie and Patton (1999) for Lop Nor. P / S discrimination emerges at the explosion S -wave Corner Frequency and does not improve above the P -wave Corner Frequency. Scaling of the explosion S -wave Corner Frequency with elastic radius as vs ( S )/ Re at all of these test sites suggests that major contributions to S -wave generation from explosions may be occurring at the same distance scale (i.e., the elastic radius) as P waves from explosions. The explicit physical mechanism of this near-source S -wave generation is still being investigated. Implications regarding application of regional P / S discriminants are discussed.
David M. Boore - One of the best experts on this subject based on the ideXlab platform.
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A Generalization of the Double-Corner-Frequency Source Spectral Model and Its Use in the SCEC BBP Validation Exercise
Bulletin of the Seismological Society of America, 2014Co-Authors: David M. Boore, Carola Di Alessandro, Norman A. AbrahamsonAbstract:The stochastic method of simulating ground motions requires the speci- fication of the shape and scaling with magnitude of the source spectrum. The spectral models commonly used are either single-Corner-Frequency or double-Corner- Frequency models, but the latter have no flexibility to vary the high-Frequency spectral levels for a specified seismic moment. Two generalized double-Corner-Frequency ω 2 source spectral models are introduced, one in which two spectra are multiplied to- gether and another where they are added. Both models have a low-Frequency depend- ence controlled by the seismic moment and a high-Frequency spectral level controlled by the seismic moment and a stress parameter. Awide range of spectral shapes can be obtained from these generalized spectral models, which makes them suitable for in- versions of data to obtain spectral models that can be used in ground-motion simu- lations in situations in which adequate data are not available for purely empirical determinations of ground motions, such as in stable continental regions. As an exam- ple of the use of the generalized source spectral models, data from up to 40 stations from seven events, plus response spectra at two distances and two magnitudes from recent ground-motion prediction equations, were inverted to obtain the parameters controlling the spectral shapes, as well as a finite-fault factor that is used in point- source, stochastic-method simulations of ground motion. The fits to the data are com- parable to or even better than those from finite-fault simulations, even for sites close to large earthquakes.
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Generalization of 2-Corner Frequency Source Models Used in SMSIM
2013Co-Authors: David M. BooreAbstract:Many of the source spectra models available in SMSIM have two Corner frequencies, but only one of these models has the option of varying the high-Frequency spectral level, as the other 2Corner models are completely determined by specified relations between the Corner frequencies and magnitude (see Tables 2 and 3 in Boore, 2003, for a concise and convenient summary of the various models). In this note I provide equations for generalizing two-Corner models to allow the high-Frequency source spectral level to be determined by the stress parameter (the basic idea being that the 2-Corner model will have the same high-Frequency source spectral level as a single-Corner source model with the specified ). The first model is already in SMSIM (source model 11); the source spectrum is the multiplication of two function of Frequency. The second model (source model 12) is new to these notes; it is the summation of two functions of Frequency, and as such, it is a generalization of the source spectra used by Atkinson and Boore (1995) and Atkinson and Silva (2000). I first discuss the multiplicative spectrum model, and this is followed by a discussion of the additive spectrum model.