Analysis of Near-Field Scattering Characteristics Based on High-Frequency Method

2020 ◽  
Author(s):  
Chengjin Liao ◽  
Hao Jiang ◽  
Bo Wu ◽  
Wei Yang
Keyword(s):  
High Frequency ◽  
Near Field ◽  
Frequency Method

An efficient high-frequency method of the EM near-field scattering from an electrically large target

Frequenz ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Conghui Qi ◽  
Yang Yi ◽  
Wei Yang
Keyword(s):  
High Frequency ◽  
Near Field ◽  
Scattering Problem ◽  
Physical Optics ◽  
Field Calculation ◽  
Frequency Method ◽  
Scattering Problems ◽  
Large Target ◽  
Expansion Technique ◽  
Near Zone

Abstract In this paper, an efficient high-frequency method combining physical optics and shooting and bouncing rays is proposed to calculate the electromagnetic near-field scattering from the electrically large target (such as ship) in the near zone. In order to solve the mono-static and bi-static scattering problems, the local expansion technique based on the facets of target is presented to account for the near-field scattering, which has a singularity-free characteristic. And then the near-field contour-integral representation is introduced by refining the formulations in traditional far-field calculation to reduce the computational complexity. Therefore, this method is more straightforward to deal with the near-field scattering problem. Finally, some analyses on the near-field scattering characteristics and Doppler spectra of a surveillance ship in near zone are investigated by using the proposed method.

scholarly journals Measurement of high frequency conductivity of oxide-doped anti-ferromagnetic thin film with a near-field scanning microwave microscope

AIP Advances ◽  
2014 ◽  
Vol 4 (4) ◽  
pp. 047114 ◽  
Author(s):  
Z. Wu ◽  
A. D. Souza ◽  
B. Peng ◽  
W. Q. Sun ◽  
S. Y. Xu ◽  
...  
Keyword(s):  
Thin Film ◽  
High Frequency ◽  
Near Field ◽  
Microwave Microscope ◽  
Near Field Scanning

Investigating Fatigue Strength of Vacuum Carburized 17CrNi6-6 Steel Using a Resonance High Frequency Method

2014 ◽  
Vol 225 ◽  
pp. 45-52 ◽  
Author(s):  
Piotr Kula ◽  
Konrad Dybowski ◽  
Sebastian Lipa ◽  
Robert Pietrasik ◽  
Radomir Atraszkiewicz ◽  
...  
Keyword(s):  
High Pressure ◽  
Fatigue Strength ◽  
High Frequency ◽  
Vacuum Carburizing ◽  
Frequency Method ◽  
Single Degree Of Freedom ◽  
Bending Fatigue ◽  
Single Degree ◽  
Bending Fatigue Strength ◽  
Frequency Changes

The bending fatigue strength of 17CrNi6-6 steel subjected to vacuum carburizing with high pressure gas hardening has been measured using a novel high-frequency technique. The test records the changes in resonance and consists of observing resonance frequency changes in a vibrating system with a single degree of freedom as a result of the forming of a fatigue crack. Moreover, a mechanism of fatigue nucleation and propagation in steel hardened by vacuum carburizing is presented.

scholarly journals A new asymptotic method for the modeling of near-field accelerograms

1984 ◽  
Vol 74 (2) ◽  
pp. 539-557
Author(s):  
P. Bernard ◽  
R. Madariaga
Keyword(s):  
High Frequency ◽  
Near Field ◽  
Dislocation Model ◽  
Rupture Propagation ◽  
Time Step ◽  
Change Of Variables ◽  
High Frequency Waves ◽  
Stopping Phases ◽  
Simple Integration ◽  
Frequency Radiation

Abstract We study high-frequency radiation from a dislocation model of rupture propagation at the earthquake source. We demonstrate that in this case all the radiation emanates from the rupture front and, by a change of variables, that at any instant of time the high-frequency waves reaching an observer come from a line on the fault plane that we call isochrone. An asymptotic approximation to near-source velocity and acceleration is obtained that involves a simple integration along the isochrones for every time step. It is shown that wave front discontinuities (critical or stopping phases) are radiated every time an isochrone becomes tangent to a barrier. This leads to what we call the critical ray approximation which is given in a closed form. The previous results are compared with discrete wavenumber synthetics obtained by Bouchon (1982) for the Gilroy 6 recording of the Coyote Lake earthquake of 1980. The fit between the asymptotic and full numerical method is extremely good. The critical ray approximation permits the identification of different phases in Bouchon's synthetics and the prediction of the behavior of the signal in the vicinity of their arrival time.

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