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Multichannel sparse spike deconvolution based on dynamic time warping

Zhao Xiaowei, Wang Shangxu, Yuan Sanyi, Cheng Liang, Cai Youjun

Acta Geophysica

2021

Vol. 69, no. 3

783--793

Seismic sparse spike deconvolution is commonly used to invert for subsurface refectivity series and is usually implemented as an inversion scheme. Conventional sparse spike deconvolution method does not utilize the relationships among adjacent traces resulting in instability and poor lateral continuity of the inverted result. We propose a multichannel sparse spike deconvolution method with a sparsity-promoting constraint and an extra lateral constraint exploiting the spatial relationships among adjacent seismic traces. Firstly, the dynamic time warping (DTW) is performed between any two adjoining seismic traces to obtain the warping path (a series of estimated time shifts of one seismic trace relative to the other). Based on the assumption that if the inverted refectivity series is convolved with the same wavelet used for inversion, the newly constructed adjoining seismic traces shall also be conformable to the relationships exploited among the original seismic traces by DTW. A diference operator is constructed with the estimated time shifts to guarantee the diference operation is performed between corresponding time samples on adjoining seismic traces and the inversion is regularized with this diference operator as the lateral constraint. Synthetic and real data case studies confrm that inverted result obtained by the proposed method is superior to those obtained by single-channel sparse spike deconvolution method and another multichannel deconvolution method based on horizontal frst-order derivative constraint in both signal-to-noise ratio and lateral continuity.

Multi-trace nonstationary sparse inversion with structural constraints

Cheng Liang, Wang Shangxu, Li Shengjun, Ji Yongzhen

Acta Geophysica

2020

Vol. 68, no. 3

675--685

The recorded seismic signals are attenuated and spatially correlated due to their propagation through an elastic earth and the sedimentary rule of strata. This attenuation phenomenon is quantifed by means of the earth quality factor (Q) or the attenuation factor (1∕Q). Nowadays, the related Q-compensation and multi-trace inversion for the seismic data are two challenging problems when used for enhancing the temporal resolution and preserving the spatial continuity. Separately estimating Q and refectivity are difcult and produce the uncertainty or ill-condition problems. To overcome these limitations, we have developed a multi-trace nonstationary sparse inversion with structural constraint. Using prior dipping-angle information and refectivity sparsity property, the proposed method simultaneously estimates equivalent-Q and refectivity with structural constraint. Constructed by the source wavelet and diferent scanned equivalent-Q, a series of time-varying (nonstationary) wavelet matrices are provided for the forward-modeling schemes and the corresponding inversions. When the Q-model is infnitely close to the true attenuation mechanism, the corresponding inverted refectivity is comparatively sparse and quantifed as maximum sparsity or minimum sparse representation. A sparse representation function, such as l0.1-norm, is used for sparsity measurement of the inverted refectivity corresponding to each scanned Q. Through optimizing these sparse representation values, a suitable equivalent-Q, as well as the corresponding inverted refectivity with structural preservation and Q-attenuation, is determined. The synthetic and feld examples both confrmed a substantial improvement on seismic records, especially for Q-estimation, structure preservation and Q-compensation.

Exploring the functions of Al2O3 in the transition of BaAl2SiO8 precipitated from CaO-BaO-Al2O3-B2O3-SiO2 sealing glass for IT-SOFCs

Liu Liangguang, Luo Linghong, Wang Leying, Cheng Liang, Xu Xu, Yu Yongzhi, Qin Ying, Wu Yefan

Materiały Ceramiczne

2019

T. 71, nr 4

368--377

CaO-BaO-Al2O3-B2O3-SiO2 (CBABS) glasses are the promising commercialized sealing materials for intermediate temperature solid oxide fuel cells (IT-SOFCs). Nevertheless, during the high-temperature operation, the behaviour of hexagonal BaAl2Si2O8 phase easily transformed into the monoclinic BaAl2Si2O8 phase would obviously decrease the thermal expansion coefficient of CBABS glasses, and then to form the serious cracks along the interface of bonded materials. Herein, in terms of the viscosity of CBABS glasses at the operating temperature, we studied the effect of Al2O3 on the transformation of BaAl2Si2O8 crystal form. The results showed that the CBABS glass with higher Al2O3 content presented the higher viscosity and crystallization activation energy, which could effectively prevent the excessive silica precipitation to inhibit the transformation of the BaAl2Si2O8 crystal from hexagonal phase to monocline phase. The inhibition effect of BaAl2Si2O8 crystal transformation effectively suppressed the decrease of the expansion coefficient of the glasses during the heat treatment at 973 K for 100 h, and thus to remarkably enhance the thermal stability of CBABS glasses, which would be very beneficial for IT-SOFCs in the future practical applications.

Szkła CaO-BaO-Al2O3-B2O3-SiO2 (CBABS) to obiecujące, komercyjnie dostępne materiały uszczelniające do średniotemperaturowych stałotlenkowych ogniw paliwowych (IT-SOFC). Niemniej jednak podczas działania w wysokiej temperaturze zachowanie heksagonalnej fazy BaAl2Si2O8, łatwo przemieniającej się w jednoskośną fazę BaAl2Si2O8, spowodowałoby oczywiście zmniejszenie współczynnika rozszerzalności cieplnej szkieł CBABS i w efekcie utworzenie poważnych pęknięć na granicy międzyfazowej łączonych materiałów. Tutaj, w kategoriach lepkości szkieł CBABS w temperaturze roboczej, badaliśmy wpływ Al2O3 na przemianę krystalicznej postaci BaAl2Si2O8. Wyniki pokazały, że szkło CBABS o wyższej zawartości Al2O3 wykazywało wyższą lepkość i energię aktywacji krystalizacji, co mogło skutecznie zapobiegać nadmiernemu wytrącaniu krzemionki, hamując przemianę kryształu BaAl2Si2O8 z fazy heksagonalnej do fazy jednoskośnej. Efekt hamowania przemiany kryształów BaAl2Si2O8 skutecznie tłumił spadek współczynnika rozszerzalności szkieł podczas obróbki cieplnej w temperaturze 973 K przez 100 godzin, a tym samym znacznie poprawiał stabilność termiczną szkieł CBABS, co byłoby bardzo korzystne dla IT-SOFC w przyszłych praktycznych zastosowaniach.