Time domain surface impedance concept for low frequency electromagnetic problems—Part II: Application to transient skin and proximity effect problems in cylindrical conductors

2005 ◽  
Vol 152 (5) ◽  
pp. 207-216 ◽  
Author(s):  
S. Barmada ◽  
L. Di Rienzo ◽  
S. Yuferev ◽  
N. Ida
Keyword(s):  
Time Domain ◽  
Proximity Effect ◽  
Surface Impedance ◽  
Low Frequency ◽  
Electromagnetic Problems ◽  
Cylindrical Conductors

Methods to isolate retrograde and prograde Rayleigh-wave signals

2019 ◽  
Vol 219 (2) ◽  
pp. 975-994 ◽  
Author(s):  
Gabriel Gribler ◽  
T Dylan Mikesell
Keyword(s):  
Rayleigh Wave ◽  
Time Domain ◽  
Fundamental Mode ◽  
Poisson Ratio ◽  
Low Frequency ◽  
Wave Dispersion ◽  
Low Frequencies ◽  
Retrograde Motion ◽  
Mode Identification ◽  
Time Frequency

SUMMARY Estimating shear wave velocity with depth from Rayleigh-wave dispersion data is limited by the accuracy of fundamental and higher mode identification and characterization. In many cases, the fundamental mode signal propagates exclusively in retrograde motion, while higher modes propagate in prograde motion. It has previously been shown that differences in particle motion can be identified with multicomponent recordings and used to separate prograde from retrograde signals. Here we explore the domain of existence of prograde motion of the fundamental mode, arising from a combination of two conditions: (1) a shallow, high-impedance contrast and (2) a high Poisson ratio material. We present solutions to isolate fundamental and higher mode signals using multicomponent recordings. Previously, a time-domain polarity mute was used with limited success due to the overlap in the time domain of fundamental and higher mode signals at low frequencies. We present several new approaches to overcome this low-frequency obstacle, all of which utilize the different particle motions of retrograde and prograde signals. First, the Hilbert transform is used to phase shift one component by 90° prior to summation or subtraction of the other component. This enhances either retrograde or prograde motion and can increase the mode amplitude. Secondly, we present a new time–frequency domain polarity mute to separate retrograde and prograde signals. We demonstrate these methods with synthetic and field data to highlight the improvements to dispersion images and the resulting dispersion curve extraction.

scholarly journals Low-frequency optical phonon modes and carrier mobility in the halide perovskite CH3NH3PbBr3 using terahertz time-domain spectroscopy

2017 ◽  
Vol 111 (20) ◽  
pp. 201903 ◽  
Author(s):  
Daming Zhao ◽  
Jonathan M. Skelton ◽  
Hongwei Hu ◽  
Chan La-o-vorakiat ◽  
Jian-Xin Zhu ◽  
...  
Keyword(s):  
Time Domain ◽  
Optical Phonon ◽  
Carrier Mobility ◽  
Low Frequency ◽  
Terahertz Time Domain Spectroscopy ◽  
Phonon Modes ◽  
Time Domain Spectroscopy ◽  
Halide Perovskite

Temperature dependence of the low-frequency surface impedance of metals near the extreme anomalous limit

1978 ◽  
Vol 17 (4) ◽  
pp. 1721-1737 ◽  
Author(s):  
A. Manz ◽  
J. Black ◽  
Kh. Pashaev ◽  
D. L. Mills
Keyword(s):  
Temperature Dependence ◽  
Surface Impedance ◽  
Low Frequency

Prediction of Surge Motion Response of Floating Structure Using Kalman Smoother Adaptive Filters Based Time-Domain Volterra Model

2014 ◽  
Vol 660 ◽  
pp. 799-803
Author(s):  
Edwar Yazid ◽  
M.S. Liew ◽  
Setyamartana Parman ◽  
V.J. Kurian ◽  
C.Y. Ng
Keyword(s):  
Time Series ◽  
Transfer Function ◽  
Time Domain ◽  
Adaptive Filters ◽  
Low Frequency ◽  
Volterra Model ◽  
Floating Structure ◽  
Frequency Responses ◽  
Kalman Smoother ◽  
System Output

This work presents an approachto predict the low frequency and wave frequency responses (LFR and WFR) of afloating structure using Kalman smoother adaptive filters based time domain Volterramodel. This method utilized time series of a measured wave height as systeminput and surge motion as system output and used to generate the linear andnonlinear transfer function (TFs). Based on those TFs, predictions of surgemotion in terms of LFR and WFR were carried out in certain frequency ranges ofwave heights. The applicability of the proposed method is then applied in ascaled 1:100 model of a semisubmersible prototype.

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