Design and optimization of left-handed materials with specific frequency bands

Abstract Vibration attenuation is an important factor while designing rotating machinery since frequency lying in the range corresponding to natural modes of structures can result in resonance and ultimately failure. Damping dissipates energy in the system, which reduces the vibration level. The mitigation of vibrations can be achieved by designing the base frame with periodic air holes. The periodicity in air holes result in vibration attenuation by providing a stop band. A finite element-based approach is developed to predict the modal and frequency response. The analysis is carried out with different shapes of periodic cavities in order to study the effectiveness of periodic stop bands in attenuating vibrations. The amount of mass removed due to the periodic cavities is kept constant. It is seen that better attenuation is obtained in case of periodic cavities compared to a uniform base frame. Among the different geometries tested, rectangular cavities showed better results than circular and square cavities. As a result, it is seen that waves propagate along periodic cells only within specific frequency bands called the “Pass bands”, while these waves are completely blocked within other frequency bands called the “Stopbands”. The air cavities filter structural vibrations in certain frequency bands resulting in effective attenuation.

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Effects of spectral gaps on the contribution of specific frequency bands to the loudness of broadband sounds

The Journal of the Acoustical Society of America ◽

10.1121/1.4970367 ◽

2016 ◽

Vol 140 (4) ◽

pp. 3268-3268

Author(s):

Walt Jesteadt ◽

Marcin Wróblewski ◽

Katie Thrailkill

Keyword(s):

Spectral Gaps ◽

Frequency Bands ◽

Specific Frequency

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Passive Periodic Engine Mount

Volume 5: 13th Design for Manufacturability and the Lifecycle Conference; 5th Symposium on International Design and Design Education; 10th International Conference on Advanced Vehicle and Tire Technologies ◽

10.1115/detc2008-49523 ◽

2008 ◽

Author(s):

Ling Zheng ◽

Woojin Jung ◽

Zheng Gu ◽

A. Baz

Keyword(s):

Spectral Width ◽

Shear Mode ◽

Effective Width ◽

Frequency Bands ◽

Automotive Engine ◽

New Class ◽

Mechanical Filter ◽

Transfer Matrix Approach ◽

Specific Frequency ◽

Engine Mount

The transmission of automotive engine vibrations to the chassis is isolated using a new class of mounts which rely in their operation on optimally designed and periodically distributed viscoelastic inserts. The proposed mount acts as mechanical filter for impeding the propagation of vibration within specific frequency bands called the ‘Stop Bands’. The spectral width of these bands is enhanced by making the viscoelastic inserts operate in a shear mode rather than compression mode. The theory governing the operation of this class of periodic mounts is presented using the theory of finite elements combined with the transfer matrix approach. The predictions of the performance of the mount are validated against the predictions of the commercial finite element code ANSYS and against experimental results obtained from prototypes of plain and periodic mounts. The obtained results demonstrate the feasibility of the shear mode periodic mount as an effectiveness means for blocking the transmission of vibration over a broad frequency band. Extending the effective width of the operating frequency bands of this class of mount through active control means is the ultimate goal of this study.

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Comparison of Two Methods of Solving Electromagnetic Parameters of Metamaterials with the Unit Cell of Symmetrically Arranged SRRs

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.531-532.351 ◽

2012 ◽

Vol 531-532 ◽

pp. 351-357

Author(s):

Wang Zhou Zhang ◽

Zhu Ying Li ◽

Ye Liu

Keyword(s):

Effective Permittivity ◽

Split Ring Resonator ◽

Index Of Refraction ◽

Electromagnetic Parameters ◽

Structured Materials ◽

Left Handed ◽

S Parameter ◽

Circular Structure ◽

Retrieval Result ◽

Specific Frequency

Based on the principle that metamaterials-composite structured materials, in which permittivity(ε)and permeability(μ)are both negative in some frequencice, can be structured with periodically arranged SRRs and thin metallic wires which have negative effective permeability and negative effective permittivity respectively, the circular structure of SRRs was modified and a new split-ring resonator with symmetric structure was proposed. A detailed description of the design and simulation procedure was given simultaneously. According to the pattern of symmetric SRRs, ε and μ were calculated in analytic formula. Furthermore, metamaterials with symmetric SRRs was simulated with the software ANSOFT, and electromagnetic parameters were retried from S parameter. From analytic result and the retrieval result of electromagnetic parameters, left-handed behavior was obvious in a specific frequency range and the permittivity, the permeability and the index of refraction are all negative.

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Information Decomposition in the Frequency Domain: a New Framework to Study Cardiovascular and Cardiorespiratory Oscillations

10.1101/2020.10.14.338939 ◽

2020 ◽

Author(s):

Luca Faes ◽

Riccardo Pernice ◽

Gorana Mijatovic ◽

Yuri Antonacci ◽

Jana Cernanova Krohova ◽

...

Keyword(s):

Time Series ◽

Spectral Measures ◽

Short Term ◽

Information Theoretic ◽

Frequency Bands ◽

Information Measures ◽

Head Up Tilt ◽

Specific Frequency ◽

Domain Information ◽

New Framework

SummaryWhile cross-spectral and information-theoretic approaches are widely used for the multivariate analysis of physiological time series, their combined utilization is far less developed in the literature. This study introduces a framework for the spectral decomposition of multivariate information measures, which provides frequency-specific quantifications of the information shared between a target and two source time series and of its expansion into amounts related to how the sources contribute to the target dynamics with unique, redundant and synergistic information. The framework is illustrated in simulations of linearly interacting stochastic processes, showing how it allows to retrieve amounts of information shared by the processes within specific frequency bands which are otherwise not detectable by time-domain information measures, as well as coupling features which are not detectable by spectral measures. Then, it is applied to the time series of heart period, systolic and diastolic arterial pressure and respiration variability measured in healthy subjects monitored in the resting supine position and during head-up tilt. We show that the spectral measures of unique, redundant and synergistic information shared by these variability series, integrated within specific frequency bands of physiological interest, reflect the mechanisms of short term regulation of cardiovascular and cardiorespiratory oscillations and their alterations induced by the postural stress.

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Quantification of EEG Brain Activity in the Self-Paced Regime

U Porto Journal of Engineering ◽

10.24840/2183-6493_004.001_0001 ◽

2018 ◽

Vol 4 (1) ◽

pp. 1-8

Author(s):

Joana Silva ◽

A. Martins Da Silva ◽

Luís Coelho

Keyword(s):

Brain Activity ◽

Rhythmic Activity ◽

The Self ◽

Automatic Quantification ◽

Frequency Bands ◽

Cerebral Activity ◽

Cognitive Information ◽

Specific Frequency ◽

Electroencephalogram Eeg ◽

The Brain

The processing of motor, sensory and cognitive information by the brain can result in changes of the electroencephalogram (EEG) by Event Related Desynchronization (ERD) or Event Related Synchronization (ERS). The first one concerns a decrease in the amplitude of a rhythmic activity while the second corresponds to its increase. The analysis of these two phenomena in specific frequency bands - alpha (8-13 Hz) and beta (14-30 Hz) - allows the understanding of the cerebral activity. This study focuses on the quantification of cerebral activity by determining the ERD and ERS on the referred band, induced by self-paced movements, by using EEGLAB and MATLAB tools. This was achieved by the creation of a new and automatic quantification algorithm. The results indicate that a greater desynchronization of the signal is accompanied by a decrease in the amplitude of the same. As a conclusion, the cerebral activity varies in terms of synchronization and desynchronization among certain frequency bands in several zones, according to the tasks performed.

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Multilayered CRLH Metamaterials Using Magnetic Dipole-Like Resonant Dielectric Particles and Cut-Off TE Modes in Metallic Structures

Additional Conferences (Device Packaging HiTEC HiTEN & CICMT) ◽

10.4071/cicmt-wa11 ◽

2013 ◽

Vol 2013 (CICMT) ◽

pp. 000076-000084

Author(s):

Tetsuya Ueda ◽

Yoshiaki Sato ◽

Yuichi Kado ◽

Tatsuo Itoh

Keyword(s):

Uniaxial Anisotropy ◽

Multilayered Structure ◽

The Other ◽

Metallic Structures ◽

Dielectric Particles ◽

Left Handed ◽

Dielectric Layers ◽

Metallic Mesh ◽

Specific Frequency ◽

Plane Direction

Composite right/left handed (CRLH) metamaterial structures designed based on one-dielectric-resonator (DR) scheme in an epsilon-negative host medium are discussed. The scheme is a combination of dielectric and metals, but can avoid several problems often met in the other schemes composed of all dielectric metamaterials. The structure under consideration is composed of stacked layers including TE-cut-off metallic mesh plates with holes and dielectric layers with 2-D array of DRs. A volumetric multilayered 2-D CRLH structure that is impedance-matched to free space can be designed by optimally adjusting electromagnetic couplings between neighboring dielectric layers through metallic mesh holes. In addition, the multilayered structure is promising for easy fabrication of the 3-D isotropic CRLH metamaterials, compared to the other structures reported previously. It can support balanced CRLH propagation not only in the in-plane direction, but also in the direction normal to the layers. The structure has strong uniaxial anisotropy and polarization dependence, but the dispersion diagram can have almost isotropic characteristics in a specific frequency region by appropriately designing the configuration parameters.

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