Investigation of polarization back-scattering characteristics of metal cube in sub-THz frequency range by the quasi-optical waveguide modeling method

2014 ◽  
Author(s):  
Sergey Mizrakhy ◽  
Pavel Nesterov
Keyword(s):  
Optical Waveguide ◽  
Modeling Method ◽  
Frequency Range ◽  
Back Scattering

Intrinsic and Scattering Attenuations in the Crust of the Racha Region, Georgia

2019 ◽  
Vol 14 (02) ◽  
pp. 2050006
Author(s):  
Ia Shengelia ◽  
Nato Jorjiashvili ◽  
Tea Godoladze ◽  
Zurab Javakhishvili ◽  
Nino Tumanova
Keyword(s):  
Time Window ◽  
Frequency Range ◽  
Quality Factors ◽  
Lapse Time ◽  
Intrinsic Attenuation ◽  
Total Attenuation ◽  
Relative Contribution ◽  
Normalization Methods ◽  
Coda Normalization ◽  
Back Scattering

Three hundred and thirty-five local earthquakes were processed and the attenuation properties of the crust in the Racha region were investigated using the records of seven seismic stations. We have estimated the quality factors of coda waves ([Formula: see text]) and the direct [Formula: see text] waves ([Formula: see text]) by the single back scattering model and the coda normalization methods, respectively. The Wennerberg’s method has been used to estimate relative contribution of intrinsic ([Formula: see text]) and scattering ([Formula: see text]) attenuations in the total attenuation. We have found that [Formula: see text] and [Formula: see text] parameters are frequency-dependent in the frequency range of 1.5–24[Formula: see text]Hz. [Formula: see text] values increase both with respect to lapse time window from 20[Formula: see text]s to 60[Formula: see text]s and frequency. [Formula: see text] and [Formula: see text] parameters are nearly similar for all frequency bands, but are smaller than [Formula: see text]. The obtained results show that the intrinsic attenuation has more significant effect than scattering attenuation in the total attenuation. The increase of [Formula: see text] with lapse time shows that the lithosphere becomes more homogeneous with depth.

Optical waveguide switch through magnetic reflectance wall

2016 ◽  
Vol 30 (19) ◽  
pp. 1650119
Author(s):  
Yuntuan Fang ◽  
Zhiyao Ni ◽  
Lixia Yang
Keyword(s):  
Magnetic Field ◽  
Optical Waveguide ◽  
Mode Analysis ◽  
Photonic Crystal Waveguide ◽  
Frequency Range ◽  
Yttrium Iron ◽  
Iron Garnet ◽  
Rod Array ◽  
Two Sides ◽  
The Magnetic Field

We propose a new design to achieve optical waveguide switch. We construct a photonic crystal waveguide with one yttrium iron garnet (YIG) rod array on the two sides of the waveguide. Through the mode analysis, we find in special frequency range a few YIG rods under magnetic field can form the magnetic reflectance wall that blocks the light flow. Removing the magnetic field will delete the reflection wall and let the blocked light to be switched on.

A Research for Broadband Modeling Method of Electro-Absorption Modulator

2011 ◽  
Vol 130-134 ◽  
pp. 3242-3246
Author(s):  
Jian Wu ◽  
Qian Zhao
Keyword(s):  
Equivalent Circuit ◽  
Relative Error ◽  
Measurement Data ◽  
Equivalent Circuit Model ◽  
Modeling Method ◽  
Maximum Relative Error ◽  
Frequency Range ◽  
Circuit Partitioning ◽  
Impedance Model ◽  
Simulation Results

This paper improves the broadband equivalent circuit model (ECM) modeling method of Electro-absorption Modulator. According to the principle of Circuit Partitioning Simplified, the series form of the original increased frequency impedance model is transformed into the parallel form. The result shows that the new method eliminates the process of the impedance type verification, will not introduce new nodes, and reduces the computation. After testing, the maximum relative error of this model to fit measurement data is only 0.693%. This method’s simulation results are consistent with the test data of ECM better in 0-8GHz frequency range.

scholarly journals Experimental realization of a reconfigurable electroacoustic topological insulator

2020 ◽  
Vol 117 (28) ◽  
pp. 16138-16142 ◽  
Author(s):  
Amir Darabi ◽  
Manuel Collet ◽  
Michael J. Leamy
Keyword(s):  
Topological Insulator ◽  
Elastic Waves ◽  
Domain Walls ◽  
Frequency Range ◽  
Finite Frequency ◽  
Experimental Realization ◽  
Interface Waves ◽  
Back Scattering ◽  
Sharp Edges ◽  
Valley Hall Effect

A substantial challenge in guiding elastic waves is the presence of reflection and scattering at sharp edges, defects, and disorder. Recently, mechanical topological insulators have sought to overcome this challenge by supporting back-scattering resistant wave transmission. In this paper, we propose and experimentally demonstrate a reconfigurable electroacoustic topological insulator exhibiting an analog to the quantum valley Hall effect (QVHE). Using programmable switches, this phononic structure allows for rapid reconfiguration of domain walls and thus the ability to control back-scattering resistant wave propagation along dynamic interfaces for phonons lying in static and finite-frequency regimes. Accordingly, a graphene-like polyactic acid (PLA) layer serves as the host medium, equipped with periodically arranged and bonded piezoelectric (PZT) patches, resulting in two Dirac cones at theKpoints. The PZT patches are then connected to negative capacitance external circuits to break inversion symmetry and create nontrivial topologically protected bandgaps. As such, topologically protected interface waves are demonstrated numerically and validated experimentally for different predefined trajectories over a broad frequency range.

Density-based discrimination of protein and RNA in the ribosome

1992 ◽  
Vol 50 (1) ◽  
pp. 464-465
Author(s):  
Joachim Frank
Keyword(s):  
Transfer Function ◽  
Spatial Frequency ◽  
Three Dimensional ◽  
Wiener Filter ◽  
Dark Field Image ◽  
Dark Field ◽  
Frequency Range ◽  
Bright Field ◽  
Contrast Transfer Function ◽  
Pass Filter

Cryo-electron microscopy combined with single-particle reconstruction techniques has allowed us to form a three-dimensional image of the Escherichia coli ribosome.In the interior, we observe strong density variations which may be attributed to the difference in scattering density between ribosomal RNA (rRNA) and protein. This identification can only be tentative, and lacks quantitation at this stage, because of the nature of image formation by bright field phase contrast. Apart from limiting the resolution, the contrast transfer function acts as a high-pass filter which produces edge enhancement effects that can explain at least part of the observed variations. As a step toward a more quantitative analysis, it is necessary to correct the transfer function in the low-spatial-frequency range. Unfortunately, it is in that range where Fourier components unrelated to elastic bright-field imaging are found, and a Wiener-filter type restoration would lead to incorrect results. Depending upon the thickness of the ice layer, a varying contribution to the Fourier components in the low-spatial-frequency range originates from an “inelastic dark field” image. The only prospect to obtain quantitatively interpretable images (i.e., which would allow discrimination between rRNA and protein by application of a density threshold set to the average RNA scattering density may therefore lie in the use of energy-filtering microscopes.

Evaluation of Special Hearing Aids for Deaf Children

1971 ◽  
Vol 36 (4) ◽  
pp. 527-537 ◽  
Author(s):  
Norman P. Erber
Keyword(s):  
Hearing Aids ◽  
High Frequency ◽  
Hearing Aid ◽  
Low Frequency ◽  
Acoustic Stimulation ◽  
Deaf Children ◽  
Frequency Range ◽  
Frequency Limit ◽  
Unpublished Studies ◽  
Published Research

Two types of special hearing aid have been developed recently to improve the reception of speech by profoundly deaf children. In a different way, each special system provides greater low-frequency acoustic stimulation to deaf ears than does a conventional hearing aid. One of the devices extends the low-frequency limit of amplification; the other shifts high-frequency energy to a lower frequency range. In general, previous evaluations of these special hearing aids have obtained inconsistent or inconclusive results. This paper reviews most of the published research on the use of special hearing aids by deaf children, summarizes several unpublished studies, and suggests a set of guidelines for future evaluations of special and conventional amplification systems.

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