China University of Petroleum

About: China University of Petroleum is a education organization based out in Beijing, China. It is known for research contribution in the topics: Catalysis & Oil shale. The organization has 39802 authors who have published 39151 publications receiving 483760 citations. The organization is also known as: Zhōngguó Shíyóu Dàxué & China University of Petroleum (Beijing).

Polarity reversal correction for elastic reverse time migration

Abstract: Polarity reversals in PS and SP images of elastic reverse time migration will cause destructive interference in the final stacked results, which may lead to an erroneous interpretation. We derive a polarity reversal correction based on an analysis of the polarity distribution of PS and SP images. The key aspect for a polarity reversal correction is the polarity distribution of the S-wave component. Polarity reversal correction methods can be performed according to the actual patterns of the polarity distribution in gathers. For the 2D isotropic case, a sign factor is introduced to represent the polarity distribution of the S-wave component; this sign factor can be computed using the energy flux density vector. We present a procedure to correct the polarity reversal for elastic reverse time migration in the common-shot domain. First, the sign factor is computed during the wavefield reconstruction for every imaging point. Then, the polarity reversal is corrected by multiplying the PS and SP images with the sign factor at every time step when an elastic imaging condition is applied. We also design a filter algorithm for the sign factor to improve its consistency along an event and thereby to diminish the impact of the inaccuracy of the energy flux density vector and to improve the imaging results. Numerical examples have shown that the polarity reversal correction procedure works and that the sign filter algorithm successfully eliminates the consequences of the inaccuracy of the energy flux density vector. The quality of the migration events is effectively improved.

A fast reduced-rank interpolation method for prestack seismic volumes that depend on four spatial dimensions

Abstract: Rank reduction strategies can be employed to attenuate noise and for prestack seismic data regularization. We present a fast version of Cadzow reduced-rank reconstruction method. Cadzow reconstruction is implemented by embedding 4D spatial data into a level-four block Toeplitz matrix. Rank reduction of this matrix via the Lanczos bidiagonalization algorithm is used to recover missing observations and to attenuate random noise. The computational cost of the Lanczos bidiagonalization is dominated by the cost of multiplying a level-four block Toeplitz matrix by a vector. This is efficiently implemented via the 4D fast Fourier transform. The proposed algorithm significantly decreases the computational cost of rank-reduction methods for multidimensional seismic data denoising and reconstruction. Synthetic and field prestack data examples are used to examine the effectiveness of the proposed method.

Monolithic-structured ternary hydroxides as freestanding bifunctional electrocatalysts for overall water splitting

Abstract: Efficient oxygen and hydrogen evolution electrocatalysts, based on low-cost and earth-abundant elements, are strongly required for sustainable hydrogen production through water splitting. Herein, we fabricated a monolithic-structured electrode by facilely electrodepositing NiCoFe ternary layered double hydroxides (LDHs) onto 3D conductive scaffolds, providing abundant fully exposed active sites for electrochemical reactions. The moderate Co dopant effectively improved the electrical conductivity of the LDH phase and substantially increased its intrinsic activity. When used for oxygen evolution, the as-obtained monolith LDH electrode exhibited superior kinetics with 275 mV overpotential required to achieve 10 mA cm−2 in 0.10 M KOH, as well as a very low activation energy of 21.0 kJ mol−1. Such a freestanding electrode was also able to catalyze hydrogen evolution efficiently in alkaline media, which further enabled a high-efficiency water electrolyzer delivering 10 mA cm−2 at a very low cell voltage of 1.62 V in 1.0 M KOH. This sheds fresh insight into the principle and process of practical water electrolysis through the rational design of precious-metal-free bifunctional electrodes with a monolithic configuration.