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1

Resolution-oriented weighted stacking based on global optimization algorithm

Sun Yaoguang, Chen Siyuan, Cao Siyuan

Acta Geophysica

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2023

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Vol. 71, no. 5

2125--2135

EN

Stacking is one crucial seismic data processing technique that gives a composite record made by combining traces from different shot records. The quality of stacking dramatical affects the performance of many seismic data processing tasks. The conventional equal-weight stacking method is the average of all traces in the pre-stack CMP gather, improving the signal-to-noise ratio (SNR) but reducing resolution. Most weighted stacking algorithms aim to enhance image quality by the increased SNR; however, these algorithms do not consider the resolution. Therefore, we proposed a weighted stacking algorithm with resolution enhancement, which is regarded as having maximum bandwidth and dominant frequency. Based on the genetic algorithm (GA), we calculated the stacking weights in common midpoint (CMP), or common-reflection-point (CRP) gathers. Then, we presented a weighted stacking approach to obtain the resolution-enhancement stacked data. The proposed method can obtain the resolution-enhancement stacked data by the single-trace spectrum constraint without wavelet estimation. Applications to synthetic and field seismic datasets demonstrate that compared with the traditional stacking method, the proposed method can improve the stacking resolution better, which is beneficial for subsequent interpretation.

2

Parameter estimation of non-stationary random media driven by partially stacked seismic data

Lin Ying, Zhang Guangzhi, Chen Siyuan, Huang Minmin, Wang Baoli

Acta Geophysica

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2022

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Vol. 70, no 5

2119--2133

EN

The estimation of non-stationary random medium parameters is the key to the application of random medium theory in fine seismic exploration. We propose a method for estimating non-stationary random medium parameters from partially stacked seismic data. To begin with, the relationship between seismic data and random medium p-wave velocity, s-wave velocity, density model in random medium is described, and the principle and method of estimating the parameters of autocorrelation function of random medium are introduced in this paper. Subsequently, the specific steps of applying the power spectrum method for non-stationary random media parameter estimation are also presented. The feasibility and correctness of the method are verified through the estimation test of the two-dimensional theoretical model. Eventually, the estimation test of non-stationary random medium parameters is carried out by field seismic data. The results show that the non-stationary random medium parameters can better describe the elastic parameter information of the subsurface media and provide a reference for the initial model construction of the elastic parameters, reflecting that the method has good application prospects. Compared with previous studies, this method extends the random medium parameter estimation from stationary to non-stationary and from single wave impedance random medium parameter to multi-elastic parameter random medium parameters. It provides a basis for the in-depth application of random media theory in field data. Meanwhile, this estimation method based on the power spectrum method has the advantage of being intuitive and easy to interpret. However, there are also problems in smoothing effect, which needs further improvement and refinement.

3

Simultaneous determination of carbofuran and 3-hydroxycarbofuran in duck liver by an UPLCMS/MS

Chen Siyuan, Yu Yang, Ma Jianshe, Wen Congcong, Wang Xianqin, Zhou Quan

Acta Chromatographica

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2021

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Vol. 33, no. 4

354--360

EN

Carbofuran is a carbamate pesticide, a broad-spectrum, high-efficiency, low-residue, and highly toxic insecticide, acaricide, and nematicide, widely used in agriculture. Carbofuran is most harmful to birds, and birds or insects killed by furan poisoning can be killed by secondary poisoning after being foraged by raptors, small mammals, or reptiles. In this paper, an UPLC-MS/MS method was developed for the determination of carbofuran and its metabolite, 3-hydroxycarbofuran, in duck liver. Liver tissue was first ground into a homogenate and then passed through ethyl acetate liquid-liquid extraction processing samples. Multiple reaction monitoring (MRM) mode was used for quantitative analysis, m/z 222.1 → 165.1 for carbofuran, m/z 238.1 → 180.9 for 3-hydroxycarbofuran and m/z 290.2 → 198.2 for an internal standard. The standard curves of carbofuran and 3-hydroxycarbofuran in duck liver were within a range of 2–2000 ng/g, where the linearity was good, the lower limit of quantification was 2 ng/ g. The intra-day precision of carbofuran and 3-hydroxycarbofuran was <14%, and the inter-day precision was <13%, the accuracy range was between 91.8 and 108.9%, the average extraction efficiency was higher than 75.1% with a matrix effect between 93.4 and 107.7%. The developed method was applied to a situation of suspected duck poisoning at a local farm.

4

UPLC–MS/MS simultaneous determination of methamphetamine, amphetamine, morphine, monoacetylmorphine, ketamine, norketamine, MDMA, and MDA in hair

Chen Siyuan, Ma Jianshe, Wang Xianqin, Geng Peiwu

Acta Chromatographica

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2020

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Vol. 32, no. 2

145--148

EN

Hair is a stable specimen and has a longer detection window (from weeks to months) than blood and urine. Through the analysis of hair, the long-term information of the drug use of the identified person could be explored. Our work is to establish an ultra-performance liquid chromatography–tandem mass spectroscopy (UPLC–MS/MS) method for simultaneous determination of methamphetamine, amphetamine, morphine, monoacetylmorphine, ketamine, norketamine, 3,4-methylenedioxymethamphetamine (MDMA), and 3,4-methylenedioxyamphetamine (MDA) in hair. Methoxyphenamine was used as an internal standard. The chromatographic separation was performed on a UPLC ethylene bridged hybrid (BEH) C18 (2.1 mm × 50 mm, 1.7 μm) column using a mobile phase of acetonitrile–water with 10 mmol/L ammonium acetate solution which containing 0.05% ammonium hydroxide. The multiple reaction monitoring in positive electrospray ionization was used for quantitative determination. The intra-day and inter-day precisions (relative standard deviation [RSD]) were below 15%. The accuracy ranged between 85.5% and 110.4%, the average recovery rate was above 72.9%, and the matrix effect ranged between 92.7% and 109.2%. Standard curves were in the range of 0.05–5.0 ng/mg, and the correlation coefficients were greater than 0.995. The established UPLC–MS/MS method was applied to analyze the hair samples successfully.