New devices for unidirectional acoustic cloaking for large objects in infinite frequency bandwidth

2018 ◽  
Vol 32 (24) ◽  
pp. 1850264
Author(s):  
Xiaopeng Wang ◽  
Yu Han ◽  
Lele Wan ◽  
Tianning Chen ◽  
Ailing Song
Keyword(s):  
Plane Waves ◽  
Propagation Direction ◽  
Infinite Length ◽  
Frequency Bandwidth ◽  
Frequency Range ◽  
Incident Plane ◽  
Theoretical Predictions ◽  
New Type ◽  
Pass Through ◽  
Invisibility Cloaks

For years, researchers struggled to realize the acoustic invisibility cloaks with simple for large objects in broadband. In this paper, a new-type unidirectional acoustic cloak is proposed and designed by using eight especial triangles region filled with a certain refractive index inert gas. The acoustic wave can be manipulated to pass through the model but “by-pass” the cloaked region according to the traditional Snell’s law. The incident plane waves will remain without any change. Therefore, the cloaked region cannot be detected. Our designed cloak can realize the infinite length of the invisibility region along the propagation direction and offer good cloaking effect in any frequency range. The simulation results agree well with the theoretical predictions and verify the nondetectability effect of the unidirectional acoustic cloak. Our mechanism may be useful for further actual applications in hiding large objects acoustically.

scholarly journals Model approximation for sound transmission from underwater structures in high-frequency range

2019 ◽  
Vol 283 ◽  
pp. 09007
Author(s):  
Rui Zhang ◽  
Desen Yang ◽  
Shengguo Shi ◽  
Boquan Yang
Keyword(s):  
Incident Wave ◽  
High Frequency ◽  
Cavity Mode ◽  
Plane Waves ◽  
Sound Transmission ◽  
Sound Insulation ◽  
High Frequency Range ◽  
Frequency Range ◽  
Vibration Equation ◽  
Incident Plane

Sound-insulation model provides a straightforward way to describe sound transmission behaviours of the thin-walled structures in engineering applications. The sound transmission characteristics depend on the parameters of incident wave, such as incident wave amplitude and incident angles. However, this model is limited when the sound source is located in an enclosed space (e.g., noise source in underwater cabins), because it is difficult to obtain incident angles especially in the high-frequency range. In this paper, we develop a simply analytical model that can effectively study the sound transmission from an enclosed shell with internal acoustic excitation. In order to extend the application of the sound-insulation model to a submerged shell, the structural vibration equation is firstly simplified to the plate vibration equation. Then, the sound pressure near the inner surface of the shell is decomposed into an expansion of orthogonal cavity eigenmodes, and each cavity mode is replaced by two pairs of incident plane waves. Finally, the acoustic transmission loss can be obtained by substituting the parameters of incident waves into the sound-insulation model. Numerical results show that the sound transmission for the fundamental cavity mode (0, 0, 0) can be explained by the normal incidence in the sound-insulation model, while every other modes corresponds to a group of oblique incident plane waves whose incident angles decrease monotonically with the increase of frequency. In addition, it can be observed that the total reflection phenomenon in the sound-insulation model is consistent with the low radiation efficiency of the high order modes in the shell model.

Designing a New Type of Energy Trap: A Classical Analog of Quantum Landau-Zener Tunneling

2011 ◽  
Author(s):  
Alexander F. Vakakis ◽  
Grigori Sigalov ◽  
Mercedes Mane ◽  
Lawrence A. Bergman ◽  
Leonid I. Manevitch ◽  
...  
Keyword(s):  
Mechanical Systems ◽  
Energy Trap ◽  
Oscillatory Systems ◽  
Weakly Coupled ◽  
Coupled Subsystems ◽  
Asymptotic Equations ◽  
Theoretical Predictions ◽  
New Type ◽  
Zener Tunneling ◽  
Pass Through

We present a novel type of energy trap providing targeted energy transfer (TET) in a system of weakly coupled pendulums. Our approach is based on the analogy, presented in [1, 2], between the behavior of two weakly coupled classical parametric pendulums and nonadiabatic Landau-Zener tunneling (LZT) in a two-state quantum system. The two systems, however dissimilar, turn out to be described by the same asymptotic equations. Well-known properties of LZT allow us to predict the possibility of efficient irreversible transfer of vibration energy from one subsystem to another in mechanical systems. The TET takes place when the eigenfrequency of a subsystem changes in time so that the coupled subsystems pass through internal resonance. The existence of such a phenomenon is not restricted to coupled pendulums but is inherent to a wide class of both linear and nonlinear parametric oscillatory systems. This opens up the possibility of designing new types of energy traps and absorbers for the dynamic protection of various mechanical systems. Experimental data obtained in this work corroborate theoretical predictions.

scholarly journals Localization of Scattering Objects Using Neural Networks

Sensors ◽  
2020 ◽  
Vol 21 (1) ◽  
pp. 11
Author(s):  
Domonkos Haffner ◽  
Ferenc Izsák
Keyword(s):  
Neural Networks ◽  
Plane Waves ◽  
Measurement Data ◽  
Scattered Wave ◽  
Training Data ◽  
Data Set ◽  
Main Compound ◽  
Incident Plane ◽  
The Neural Networks ◽  
Simulation Package

The localization of multiple scattering objects is performed while using scattered waves. An up-to-date approach: neural networks are used to estimate the corresponding locations. In the scattering phenomenon under investigation, we assume known incident plane waves, fully reflecting balls with known diameters and measurement data of the scattered wave on one fixed segment. The training data are constructed while using the simulation package μ-diff in Matlab. The structure of the neural networks, which are widely used for similar purposes, is further developed. A complex locally connected layer is the main compound of the proposed setup. With this and an appropriate preprocessing of the training data set, the number of parameters can be kept at a relatively low level. As a result, using a relatively large training data set, the unknown locations of the objects can be estimated effectively.

scholarly journals Core-Shell Nano-Antenna Configurations for Array Formation with More Stability Having Conventional and Non-Conventional Directivity and Propagation Behavior

Nanomaterials ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 99
Author(s):  
Qaisar Hayat ◽  
Junping Geng ◽  
Xianling Liang ◽  
Ronghong Jin ◽  
Sami Ur Rehman ◽  
...  
Keyword(s):  
Plane Wave ◽  
Propagation Direction ◽  
Core Shell ◽  
Incident Plane Wave ◽  
Polarization Direction ◽  
Shell Nanoparticles ◽  
Incident Plane ◽  
Core Shell Nanoparticles ◽  
Coated Nanoparticle ◽  
2D Array

The enhancement of optical characteristics at optical frequencies deviates with the choice of the arrangement of core-shell nanoparticles and their environment. Likewise, the arrangements of core-shell nanoparticles in the air over a substrate or in liquid solution makes them unstable in the atmosphere. This article suggests designing a configuration of an active spherical coated nanoparticle antenna and its extended array in the presence of a passive dielectric, which is proposed to be extendable to construct larger arrays. The issue of instability in the core-shell nanoantenna array models is solved here by inserting the passive dielectric. In addition to this, the inclusion of a dielectric in the array model reports a different directivity behaviour than the conventional array models. We found at first that the combination model of the active coated nanoparticle and passive sphere at the resonant frequency can excite a stronger field with a rotated polarization direction and a propagation direction different from the incident plane-wave. Furthermore, the extended 2D array also rotates the polarization direction and propagation direction for the vertical incident plane-wave. The radiation beam operates strong multipoles in the 2D array plane at resonant frequency (behaving non-conventionally). Nevertheless, it forms a clear main beam in the incident direction when it deviates from the resonance frequency (behaving conventionally). The proposed array model may have possible applications in nano-amplifiers, nano-sensors and other integrated optics.

Surface and interfacial anti-plane waves in micropolar solids with surface energy

2020 ◽  
pp. 108128652096564
Author(s):  
Mriganka Shekhar Chaki ◽  
Victor A Eremeyev ◽  
Abhishek K Singh
Keyword(s):  
Surface Wave ◽  
Plane Wave ◽  
Numerical Study ◽  
Plane Waves ◽  
Angular Frequency ◽  
Elastic Half Space ◽  
Surface Strain ◽  
Theoretical Frameworks ◽  
Algebraic Form ◽  
New Type

In this work, the propagation behaviour of a surface wave in a micropolar elastic half-space with surface strain and kinetic energies localized at the surface and the propagation behaviour of an interfacial anti-plane wave between two micropolar elastic half-spaces with interfacial strain and kinetic energies localized at the interface have been studied. The Gurtin–Murdoch model has been adopted for surface and interfacial elasticity. Dispersion equations for both models have been obtained in algebraic form for two types of anti-plane wave, i.e. a Love-type wave and a new type of surface wave (due to micropolarity). The angular frequency and phase velocity of anti-plane waves have been analysed through a numerical study within cut-off frequencies. The obtained results may find suitable applications in thin film technology, non-destructive analysis or biomechanics, where the models discussed here may serve as theoretical frameworks for similar types of phenomena.

Optical Vibration and Acceleration Sensor With a Silicon Cantilever

1999 ◽  
Author(s):  
Mitsuteru Kimura ◽  
Katsuhisa Toshima ◽  
Harunobu Satoh
Keyword(s):  
Simple Model ◽  
Optical Fiber ◽  
Resonance Frequency ◽  
Acceleration Sensor ◽  
Frequency Range ◽  
Silicon Cantilever ◽  
All Optical ◽  
New Type ◽  
Good Agreement ◽  
Optical Vibration

Abstract A new type all optical vibration and acceleration sensor using the combination of micromachined Si cantilever and optical fiber is proposed, and its fundamental characteristics are demonstrated. The light emitted from bulb-lens set into the V-groove is reflected at the reflector formed on the Si cantilever and then recoupled into the bulb-lens. Several sensors with different length (0.64–6.0 mm long) of the Si cantilever are fabricated to compare the theoretical resonance frequency fr obtained from the simple model and experimental ones. They had good agreement. From the sensing principle the sensing frequency range of the vibration is suitable below the fr of the Si cantilever of the sensor.

Prelude: A Sense of Place

2016 ◽  
Author(s):  
Connor J. Fitzmaurice ◽  
Brian J. Gareau
Keyword(s):  
Social Relations ◽  
Sense Of Place ◽  
Food System ◽  
Social Connection ◽  
Commodity Chains ◽  
Farming Practice ◽  
Organic Products ◽  
New Type ◽  
Pass Through

The conventionalization of the organic sector has led many to be skeptical about the possibility of organic in and of itself promoting a meaningfully sustainable alternative to the modern agricultural paradigm. However, the bifurcation of the organic market into both mainstream and alternative spheres provides places within the food system where investigating the work involved in creating new economic and social relations of farming practice makes sense. We may very well have come to an era in which most organic products pass through the same types of industrial commodity chains as organic initially set out to challenge. But more and more people desire a new type of economy, one that fosters social connection, meaning, and new relationships of exchange (...

scholarly journals HIS-Based Semiactive Suspension Dual-Frequency-Range Switching Control to Improve Ride Comfort and Antiroll Performance

2019 ◽  
Vol 2019 ◽  
pp. 1-16
Author(s):  
Xiaojian Wu ◽  
Xiang Qiu ◽  
Bing Zhou ◽  
Juhua Huang ◽  
Tingfang Zhang
Keyword(s):  
Ride Comfort ◽  
Control Method ◽  
Excitation Frequency ◽  
Switching Control ◽  
Parameter Sensitivity ◽  
The Body ◽  
Semiactive Control ◽  
Frequency Bandwidth ◽  
Dual Frequency ◽  
Frequency Range

The parameter sensitivity analysis of a hydraulically interconnected suspension (HIS) system shows that the sensitivity of the vibration responses in the bounce and roll modes to the hydraulic parameters are complementary. A novel HIS-based semiactive control method was thereby proposed to improve ride comfort and antiroll performance. In addition, the classic sky-hook max-min damping switched strategy provides significant benefits around the body resonance, but otherwise performs similarly to, or sometimes even worse than, passive suspension. Therefore, a dual-frequency-range switching strategy, which has optimal max-min damping in both frequency ranges, was developed for improving the ride comfort in a wider frequency bandwidth. In this study, a 9-DOF HIS system dynamics model was established, and the hydraulically interconnected subsystem model was validated experimentally. Subsequently, the elastic and damping characteristics of the hydraulically interconnected subsystem, as well as the parameter sensitivity in bounce mode and roll mode, were analyzed. Next, the sensitive parameters were optimized under sinusoidal excitation at various frequencies, and a frequency-range selector used to determine the excitation frequency range and adjust the shock absorber damping was designed. Finally, simulations in the frequency domain and time domain show that the proposed HIS-based semiactive dual-frequency-range switching control suspension improves the ride comfort in a wider frequency bandwidth and enhances the antiroll performance in the transient and steady steering process.

THE ELECTRIC AND MAGNETIC FIELDS IN A STRATIFIED FLAT CONDUCTOR FOR INCIDENT PLANE WAVES

1965 ◽  
Vol 43 (5) ◽  
pp. 898-909 ◽  
Author(s):  
H. W. Dosso
Keyword(s):  
Magnetic Fields ◽  
Plane Waves ◽  
Incident Plane ◽  
Electric And Magnetic Fields

The electric and magnetic fields in the upper layer of a stratified flat conductor in the field of plane waves are studied. Expressions for the amplitude and phase of the components of the electric and magnetic fields are obtained and evaluated for various frequencies, angles of incidence, layer thicknesses, depths, and conductivities. The conductivities σ = 10−11 to 10−16 e.m.u. and the frequencies ƒ = 10−3 to 104 cycles/second considered are of interest in geophysics.

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