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Near-zero effective impedance with finite phase velocity for sensing and actuation enhancement by resonator pairing.

ABSTRACT: In spite of the extensive studies of zero-index metamaterials, the realization of zero impedance with finite phase velocity has not been explored. Here, we show that this extreme case, realized by elaborately-tuned paired resonators, can effectively enhance sensing and actuation. To explain the formation mechanism of the near-zero effective impedance with finite phase velocity by paired resonators at a target frequency, a theory using an equivalent model based on mechanical longitudinal waves is developed. If the frequency of the extreme property is further tuned at a Fabry-Pérot resonance frequency, highly efficient enhancement is possible. Experiments using a piezoceramic transducer (PZT) installed on the plate region bounded by two resonators confirm that the proposed extreme property mechanism highly enhances the sensing and actuation outputs of the transducer.

SUBMITTER: Kim K

PROVIDER: S-EPMC6288096 | biostudies-literature | 2018 Dec

REPOSITORIES: biostudies-literature

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Near-zero effective impedance with finite phase velocity for sensing and actuation enhancement by resonator pairing.

Kim Kiyean K Park Chung Il CI Lee Hyuk H Kim Yoon Young YY

Nature communications 20181210 1

In spite of the extensive studies of zero-index metamaterials, the realization of zero impedance with finite phase velocity has not been explored. Here, we show that this extreme case, realized by elaborately-tuned paired resonators, can effectively enhance sensing and actuation. To explain the formation mechanism of the near-zero effective impedance with finite phase velocity by paired resonators at a target frequency, a theory using an equivalent model based on mechanical longitudinal waves is ...[more]

PMID: 30531944

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Project description:In functional magnetic resonance imaging (fMRI), temporal onsets of BOLD events contain crucial information on activity-inducing signals and make a significant impact in the analysis of functional connectivity (FC). In literature, the estimation of the onsets of the BOLD events from the acquired blood oxygen level-dependent (BOLD) signal using fMRI is mostly performed by choosing locations with a high value of the BOLD signal. This approach may give false onset points because it can incorporate redundant onsets which could be due to non-neuronal activity or can exclude true low-valued BOLD signals. In this study, we present a novel approach to estimating the temporal onsets of the BOLD events using a zero frequency resonator (ZFR) without necessitating information regarding the experimental paradigm (EP). The proposed approach exploits the impulse-like characteristic of activity-inducing signal to estimate the temporal onset points of BOLD events using ZFR which has been widely studied in the area of speech signal processing to estimate the glottal closure instances. The idea behind the approach is that an ideal neuronal impulse has, in principle, equal energy at all frequencies, including around the zero frequency, and will preserve the information of the temporal onsets of the BOLD events at its output. The ZFR-based approach estimates two important features, namely: 1) task-induced temporal onsets of the BOLD events in the fMRI time course and 2) high SNR (HSNR) regions around the estimated BOLD events. Both the estimated features are used to obtain the FC. Results are demonstrated using both the synthetic and experimental (event-related finger tapping and block design working memory) data. We show that a small number of plausible time points, estimated by ZFR, can convey sufficient information indicating the associated activation pattern. The method also illustrates its significance over the conventional correlation and threshold-based conditional rate analysis to estimate FC. The study demonstrates that ZFR-estimated BOLD events and HSNR regions can produce sufficient functionality of the brain in the task paradigm.

Dataset Information

Near-zero effective impedance with finite phase velocity for sensing and actuation enhancement by resonator pairing.

Publications

Near-zero effective impedance with finite phase velocity for sensing and actuation enhancement by resonator pairing.

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