Erratum to Extended-Time Multitaper Frequency Domain Cross-Correlation Receiver-Function Estimation

2008 ◽  
Vol 98 (3) ◽  
pp. 1608-1608
Author(s):  
G. Helffrich
Keyword(s):  
Frequency Domain ◽  
Cross Correlation ◽  
Receiver Function ◽  
Extended Time ◽  
Function Estimation ◽  
Correlation Receiver

scholarly journals Acoustic imaging with conventional frequency domain beamforming and generalized cross correlation: a comparison study

2021 ◽  
Vol 177 ◽  
pp. 107914
Author(s):  
Thomas Padois ◽  
Jeoffrey Fischer ◽  
Con Doolan ◽  
Olivier Doutres
Keyword(s):  
Frequency Domain ◽  
Cross Correlation ◽  
Acoustic Imaging ◽  
Comparison Study

scholarly journals A Novel Gesture Recognition System Based on CSI Extracted from a Smartphone with Nexmon Firmware

Sensors ◽  
2020 ◽  
Vol 21 (1) ◽  
pp. 222
Author(s):  
Tao Li ◽  
Chenqi Shi ◽  
Peihao Li ◽  
Pengpeng Chen
Keyword(s):  
Frequency Domain ◽  
Gesture Recognition ◽  
Channel State Information ◽  
Cross Correlation ◽  
Recognition Accuracy ◽  
Correlation Method ◽  
Bottom Layer ◽  
Recognition System ◽  
Channel State ◽  
State Information

In this paper, we propose a novel gesture recognition system based on a smartphone. Due to the limitation of Channel State Information (CSI) extraction equipment, existing WiFi-based gesture recognition is limited to the microcomputer terminal equipped with Intel 5300 or Atheros 9580 network cards. Therefore, accurate gesture recognition can only be performed in an area relatively fixed to the transceiver link. The new gesture recognition system proposed by us breaks this limitation. First, we use nexmon firmware to obtain 256 CSI subcarriers from the bottom layer of the smartphone in IEEE 802.11ac mode on 80 MHz bandwidth to realize the gesture recognition system’s mobility. Second, we adopt the cross-correlation method to integrate the extracted CSI features in the time and frequency domain to reduce the influence of changes in the smartphone location. Third, we use a new improved DTW algorithm to classify and recognize gestures. We implemented vast experiments to verify the system’s recognition accuracy at different distances in different directions and environments. The results show that the system can effectively improve the recognition accuracy.

scholarly journals Parsimonious truncated Newton method for time-domain full waveform inversion based on Fourier-domain full-scattered-field approximation

Geophysics ◽  
2021 ◽  
pp. 1-147
Author(s):  
Peng Yong ◽  
Romain Brossier ◽  
Ludovic Métivier
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Cross Correlation ◽  
Waveform Inversion ◽  
Field Approximation ◽  
Second Order ◽  
Vector Product ◽  
First Order ◽  
Full Waveform ◽  
Truncated Newton

In order to exploit Hessian information in Full Waveform Inversion (FWI), the matrix-free truncated Newton method can be used. In such a method, Hessian-vector product computation is one of the major concerns due to the huge memory requirements and demanding computational cost. Using the adjoint-state method, the Hessian-vector product can be estimated by zero-lag cross-correlation of the first-order/second-order incident wavefields and the second-order/first-order adjoint wavefields. Different from the implementation in frequency-domain FWI, Hessian-vector product construction in the time domain becomes much more challenging as it is not affordable to store the entire time-dependent wavefields. The widely used wavefield recomputation strategy leads to computationally intensive tasks. We present an efficient alternative approach to computing the Hessian-vector product for time-domain FWI. In our method, discrete Fourier transform is applied to extract frequency-domain components of involved wavefields, which are used to compute wavefield cross-correlation in the frequency domain. This makes it possible to avoid reconstructing the first-order and second-order incident wavefields. In addition, a full-scattered-field approximation is proposed to efficiently simplify the second-order incident and adjoint wavefields computation, which enables us to refrain from repeatedly solving the first-order incident and adjoint equations for the second-order incident and adjoint wavefields (re)computation. With the proposed method, the computational time can be reduced by 70% and 80% in viscous media for Gauss-Newton and full-Newton Hessian-vector product construction, respectively. The effectiveness of our method is also verified in the frame of a 2D multi-parameter inversion, in which the proposed method almost reaches the same iterative convergence of the conventional time-domain implementation.

Experimental On-Line Frequency Domain Identification and Adaptive Control of a Flexible Slewing Beam

1996 ◽  
Vol 118 (1) ◽  
pp. 58-65 ◽  
Author(s):  
R. I. Milford ◽  
S. F. Asokanthan
Keyword(s):  
Frequency Domain ◽  
Real Time ◽  
Parametric Estimation ◽  
Identification Algorithm ◽  
Function Estimation ◽  
Persistent Excitation ◽  
Domain Identification ◽  
Frequency Domain Identification ◽  
On Line ◽  
And Control

This paper presents experimental results for the real-time adaptive identification and control of a flexible, slewing beam. A frequency domain identification algorithm incorporating non-parametric transfer function estimation and least squares parametric estimation is used to reconstruct an accurate parametric model of the system, capable of accurately tracking changing plant dynamics in real time. This model is subsequently used to produce an LQG compensator which actively damps beam vibration caused by rapid slewing manoeuvres with large payload changes. Non-persistent excitation is addressed in the context of identification during nominal motion. It is shown that after a short duration learning period, the proposed identification scheme will yield a model which is sufficiently accurate for controller synthesis.

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