The effects of quadrature sampling imbalances on a phase difference analysis technique

Accurate location and depth determination of underground pipes, especially the attribute recognition, are of great importance yet remake a challenging issue in municipal environments. Single-trace phase difference analysis remains a bottleneck due to its inherent and strong randomness in object identification. This paper developed a multi-trace phase difference analysis framework for ground-penetrating radar (GPR) data based on K-means cluster analysis technique and the theory of region of interest (ROI), which could serve as a new criterion for successful pipe attribute recognition. After improving signal-to-noise ratio of GPR data by using the preprocessing techniques, the connected components algorithms (CCA) based on image segmentation and morphological operation is performed to delineate the ROI. The K-means cluster analysis technique is further employed to efficiently extract the multi-trace phase statistical features for comprehensively evaluating the attributes of ROI. We verify this proposed framework by simulated GPR signals, laboratory data and field datasets. Results demonstrate that the proposed method can not only facilitate the attribute recognition of pipes, but also reduce the interpretation ambiguity of the pipe material even in the field site environment. Specifically, if the phase difference of pipe turns out to be even multiples of π, the target can be automatically identified as metallic-category pipes, whereas odd multiples of π, point to non-metallic-category pipes with a lower permittivity than that of the background. This criterion presents promising applicability in subsurface pipeline identification and attributes recognition, especially in constructing a more appropriate initial model of GPR full waveform inversion for survey in pipes.

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Polarization Phase Difference Analysis for Selection of Persistent Scatterers in SAR Interferometry

IEEE Geoscience and Remote Sensing Letters ◽

10.1109/lgrs.2010.2072904 ◽

2011 ◽

Vol 8 (2) ◽

pp. 331-335 ◽

Cited By ~ 14

Author(s):

Sergey Samsonov ◽

Kristy Tiampo

Keyword(s):

Phase Difference ◽

Sar Interferometry ◽

Difference Analysis ◽

Persistent Scatterers ◽

Polarization Phase ◽

Selection Of

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Instantaneous phase difference analysis between thoracic and abdominal movement signals based on complementary ensemble empirical mode decomposition

BioMedical Engineering OnLine ◽

10.1186/s12938-016-0233-7 ◽

2016 ◽

Vol 15 (1) ◽

Cited By ~ 1

Author(s):

Ya-Chen Chen ◽

Tzu-Chien Hsiao

Keyword(s):

Empirical Mode Decomposition ◽

Phase Difference ◽

Ensemble Empirical Mode Decomposition ◽

Difference Analysis ◽

Instantaneous Phase ◽

Mode Decomposition ◽

Thoracic And Abdominal ◽

Abdominal Movement

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A persistent quiet-Sun small-scale tornado

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038951 ◽

2020 ◽

Vol 643 ◽

pp. A166

Author(s):

K. Tziotziou ◽

G. Tsiropoula ◽

I. Kontogiannis

Keyword(s):

Time Series ◽

Phase Difference ◽

Vortex Flow ◽

Wave Mode ◽

Doppler Velocity ◽

Small Scale ◽

Time Interval ◽

Difference Analysis ◽

Quiet Sun ◽

Wave Modes

Context. Vortex flows can foster a variety of wave modes. A recent oscillatory analysis of a persistent 1.7 h vortex flow with a significant substructure has suggested the existence of various types of waves within it. Aims. We investigate the nature and characteristics of waves within this quiet-Sun vortex flow, over the course of an uninterrupted 48-min observing time interval, in order to better understand its physics and dynamics. Methods. We used a cross-wavelet spectral analysis between pairs of Hα and Ca II 8542 Å intensity time series at different wavelengths and, hence, atmospheric heights, acquired with the CRisp Imaging SpectroPolarimeter at the Swedish Solar Telescope, as well as the derived Hα Doppler velocity and full width at half maximum time series. We constructed halftone frequency-phase difference plots and investigated the existence and propagation characteristics of different wave modes. Results. Our analysis suggests the existence of Alfvénic type waves within the vortex flow that propagate upwards with phase speeds of ∼20–30 km s−1. The dominant wave mode seems to be the fast kink wave mode, however, our analysis also suggests the existence of localised Alfvénic torsional waves, which are related to the dynamics of individual chromospheric swirls that characterise the substructure of the vortex flow. The Hα V–I phase difference analysis seems to imply the existence of a standing wave pattern that is possibly arising from the interference of upwards propagating kink waves with downwards propagating ones that are reflected at the transition region or the corona. Moreover, the results provide further evidence that the central chromospheric swirl drives the dynamics of the vortex flow. Conclusions. This is the first exhaustive phase difference analysis within a vortex flow that explores the nature and dynamics of different wave modes within it. The question, however, of whether, and how, the dissipation of the derived wave modes occurs remains open, and given that such structures are ubiquitous on the solar surface, it’s also important to investigate whether they might ultimately play a significant role in the energy budget of the upper layers of the solar atmosphere.

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