Far-field frequency domain electromagnetic time reversal subwavelength imaging of scatterers assisted with grating plate

2016 ◽  
Author(s):  
Zhi-Shuang Gong ◽  
Bing-Zhong Wang ◽  
Xiao-Hua Wang ◽  
Qiang Gao
Keyword(s):  
Frequency Domain ◽  
Time Reversal ◽  
Far Field ◽  
Subwavelength Imaging ◽  
Field Frequency

scholarly journals Far-field time reversal subwavelength imaging of sources based on grating structure

2017 ◽  
Vol 66 (4) ◽  
pp. 044101
Author(s):  
Gong Zhi-Shuang ◽  
Wang Bing-Zhong ◽  
Wang Ren ◽  
Zang Rui ◽  
Wang Xiao-Hua
Keyword(s):  
Time Reversal ◽  
Far Field ◽  
Subwavelength Imaging ◽  
Grating Structure

Time-Domain Nonlinear SSI Analysis of Foundation Sliding Using Frequency-Dependent Foundation Impedance Derived From SASSI

2008 ◽  
Author(s):  
Mansour Tabatabaie ◽  
Thomas Ballard
Keyword(s):  
Frequency Domain ◽  
Linear Systems ◽  
Time Domain ◽  
Soil Structure ◽  
Wave Radiation ◽  
Far Field ◽  
Frequency Dependent ◽  
Nonlinear Springs ◽  
Mat Foundation ◽  
The Time Domain

Dynamic soil-structure interaction (SSI) analysis of nuclear power plants is often performed in frequency domain using programs such as SASSI [1]. This enables the analyst to properly a) address the effects of wave radiation in an unbounded soil media, b) incorporate strain-compatible soil shear modulus and damping properties and c) specify input motion in the free field using the de-convolution method and/or spatially variable ground motions. For structures that exhibit nonlinearities such as potential base sliding and/or uplift, the frequency-domain procedure is not applicable as it is limited to linear systems. For such problems, it is necessary to solve the problem in the time domain using the direct integration method in programs such as ADINA [2]. The authors recently introduced a sub-structuring technique called distributed parameter foundation impedance (DPFI) model that allows the structure to be partitioned from the total SSI system and analyzed in the time domain while the foundation soil is modeled using the frequency-domain procedure [3]. This procedure has been validated for linear systems. In this paper we have expanded the DPFI model to incorporate nonlinearities at the soil/structure interface by introducing nonlinear shear and normal springs arranged in series between the DPFI and structure model. This combination of the linear far-field impedance (DPFI) plus nonlinear near-field soil springs allows the foundation sliding and/or uplift behavior be analyzed in time domain while maintaining the frequency-dependent stiffness and radiation damping nature of the far-field foundation impedance. To check the accuracy of this procedure, a typical NPP foundation mat supported at the surface of a layered soil system and subjected to harmonic forced vibration was first analyzed in the frequency domain using SASSI to calculate the target linear response and derive a linear, far-field DPFI model. The target linear solution was then used to validate two linear time-domain ADINA models: Model 1 consisting of the mat foundation+DPFI derived from the linear SASSI model and Model 2 consisting of the total SSI system (mat foundation plus a soil block). After linear alignment, the nonlinear springs were added to both ADINA models and re-analyzed in time domain. Model 2 provided the target nonlinear solution while Model 1 provided the results using the DPFI+nonlinear springs. By increasing the amplitude of the vibration load, different levels of foundation sliding were simulated. Good agreement between the results of two models in terms of the displacement response of the mat and cyclic force-displacement behavior of the springs validates the accuracy of the procedure presented herein.

A Hybrid Synthetic Aperture and Time-Reversal MUSIC Algorithm for Subwavelength Radar Imaging

2021 ◽  
Author(s):  
Nathaniel Tamminga ◽  
Brianna Christensen ◽  
Sarah Petry ◽  
Enson Chang
Keyword(s):  
Synthetic Aperture Radar ◽  
Millimeter Wave ◽  
Time Reversal ◽  
Radar Imaging ◽  
Synthetic Aperture ◽  
Music Algorithm ◽  
Subwavelength Imaging ◽  
Chipless Rfid ◽  
Imaging Approach ◽  
Printing Cost

A promising chipless RFID approach uses millimeter-wave synthetic aperture radar (SAR) to image metal ink-printed ID tags from a meter or more away. Due to printing cost, it is desirable to minimize the size and spacing of metal patches within a tag, preferably into the subwavelength regime. Although circular SAR (CSAR) has a sharply peaked point response in 2D, its side lobes of closely-spaced targets interfere strongly with each other to distort the image. An alternative 2D subwavelength imaging approach with minimal side lobes is Time-Reversal MUSIC (TR-MUSIC). Traditional TR-MUSIC, however, requires a large number of transmitters and receivers. We propose a hybrid synthetic aperture TR-MUSIC algorithm (SATR-MUSIC) that combines the benefits of both approaches. Using relatively few transceivers, SATR-MUSIC is able to resolve objects separated by approximately  in 2D with minimal background artifacts. It does so by averaging TR-MUSIC’s imaging kernel incoherently over the synthetic aperture.

Subwavelength Focussing in Metamaterials Using Far Field Time Reversal

2013 ◽  
pp. 141-168 ◽  
Author(s):  
Mathias Fink ◽  
Fabrice Lemoult ◽  
Julien de Rosny ◽  
Arnaud Tourin ◽  
Geoffroy Lerosey
Keyword(s):  
Time Reversal ◽  
Far Field

Robust far-field subwavelength imaging of scatterers by an acoustic superlens

2019 ◽  
Vol 146 (6) ◽  
pp. 4131-4143
Author(s):  
Yongkang Dong ◽  
Gaokun Yu ◽  
Ning Wang
Keyword(s):  
Far Field ◽  
Subwavelength Imaging

Three-Dimensional Lightning Positioning in Low-Frequency Band Using Time Reversal in Frequency Domain

2020 ◽  
Vol 62 (3) ◽  
pp. 774-784 ◽  
Author(s):  
Bo Liu ◽  
Li-Hua Shi ◽  
Shi Qiu ◽  
Heng-Yi Liu ◽  
Zheng Sun ◽  
...  
Keyword(s):  
Frequency Domain ◽  
Frequency Band ◽  
Time Reversal ◽  
Three Dimensional ◽  
Low Frequency
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