25 research outputs found

    Multimode Decomposition and Wavelet Threshold Denoising of Mold Level Based on Mutual Information Entropy

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    The continuous casting process is a continuous, complex phase transition process. The noise components of the continuous casting process are complex, the model is difficult to establish, and it is difficult to separate the noise and clear signals effectively. Owing to these demerits, a hybrid algorithm combining Variational Mode Decomposition (VMD) and Wavelet Threshold denoising (WTD) is proposed, which involves multiscale resolution and adaptive features. First of all, the original signal is decomposed into several Intrinsic Mode Functions (IMFs) by Empirical Mode Decomposition (EMD), and the model parameter K of the VMD is obtained by analyzing the EMD results. Then, the original signal is decomposed by VMD based on the number of IMFs K, and the Mutual Information Entropy (MIE) between IMFs is calculated to identify the noise dominant component and the information dominant component. Next, the noise dominant component is denoised by WTD. Finally, the denoised noise dominant component and all information dominant components are reconstructed to obtain the denoised signal. In this paper, a comprehensive comparative analysis of EMD, Ensemble Empirical Mode Decomposition (EEMD), Complementary Empirical Mode Decomposition (CEEMD), EMD-WTD, Empirical Wavelet Transform (EWT), WTD, VMD, and VMD-WTD is carried out, and the denoising performance of the various methods is evaluated from four perspectives. The experimental results show that the hybrid algorithm proposed in this paper has a better denoising effect than traditional methods and can effectively separate noise and clear signals. The proposed denoising algorithm is shown to be able to effectively recognize different cast speeds

    Mold-Level Prediction for Continuous Casting Using VMD–SVR

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    In the continuous-casting process, mold-level control is one of the most important factors that ensures the quality of high-efficiency continuous casting slabs. In traditional mold-level prediction control, the mold-level prediction accuracy is low, and the calculation cost is high. In order to improve the prediction accuracy for mold-level prediction, an adaptive hybrid prediction algorithm is proposed. This new algorithm is the combination of empirical mode decomposition (EMD), variational mode decomposition (VMD), and support vector regression (SVR), and it effectively overcomes the impact of noise on the original signal. Firstly, the intrinsic mode functions (IMFs) of the mold-level signal are obtained by the adaptive EMD, and the key parameter of the VMD is obtained by the correlation analysis between the IMFs. VMD is performed based on the key parameter to obtain several IMFs, and the noise IMFs are denoised by wavelet threshold denoising (WTD). Then, SVR is used to predict each denoised component to obtain the predicted IMF. Finally, the predicted mold-level signal is reconstructed by the predicted IMFs. In addition, compared with WTD–SVR and EMD–SVR, VMD–SVR has a competitive advantage against the above three methods in terms of robustness. This new method provides a new idea for mold-level prediction

    Amorphous Ni-P-S@FeOOH/CC catalyst for high oxygen evolution Activity: Preparation, characterization and modeling

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    The oxygen evolution reaction (OER) is the key to prepare electrocatalysts for water splitting. Heteroatom doping is an effective way to improve the catalytic performance of OER by modulating the local electronic environment and stimulating the synergy. However, the complicated manufacturing methods have hindered their practical application. Herein, we demonstrate a method based on FeOOH/CC precursor to realize the preparation of Ni-P-S@FeOOH/CC catalyst through fast electrodeposition method. The overpotential of Ni-P-S@FeOOH/CC catalyst is 210 mV (10 mA cm(-2)), and still has an initial voltage of 97.35 % for 48 h. The surface area analysis shows a higher electrochemically active surface area for the amorphous structure prepared by electrodeposition method. XPS and DFT results show that the co doping of P and S can stimulate the synergistic effect and the minimum energy of adsorption/desorption in OER process is only 0.83 eV. The strategy shows good prospects for preparing efficient OER pre catalysts. (C) 2022 Published by Elsevier Ltd

    Molecular Simulations on Tuning the Interlayer Spacing of Graphene Nanoslits for C4H6/C4H10 Separation

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    There are great challenges in developing efficient membranes to replace the currently energy-intensive cryogenic distillation processes for purifying C4H6 from C4H6/C4H10 mixtures due to their similar physical and chemical properties. Here, we investigated the performance of graphene slits with different interlayer spacings for C4H6/C4H10 separation via molecular simulations. The results demonstrate that the 3.4-angstrom-interlayer-spacing graphene slit only allows the penetration of C4H6 due to the size sieving effect and the permeance of C4H6 is up to 2.09 x 10(6) GPU. When the interlayer spacing increases to 3.6-6.8 angstrom, the graphene slits still exhibit the preferential penetration for C4H6 over C4H10 due to the pi-pi adsorption interaction between graphene sheets and C4H6. Surprisingly, the graphene slits (>10.2 angstrom) exhibit the preferential penetration for C4H10 over C4H6 owing to the diffusivity of C4H10 being much larger than that of C4H6 under confined conditions. In conclusion, by fine-tuning the interlayer spacing of graphene slits, the dominant separation mechanism is switched in the order of size sieving, thermodynamic adsorption, and dynamic diffusion, thereby achieving the controllable regulation of the preferential permeation from C4H6 to C4H10. C4H10 -selective membranes are of great significance for energy saving. The tuning strategy is expected to be applied in different paraffin/olefin separation scenarios such as high-content and low-content olefin feedstocks

    Amorphous Ni-P-S@FeOOH/CC catalyst for high oxygen evolution Activity: Preparation, characterization and modeling

    No full text
    The oxygen evolution reaction (OER) is the key to prepare electrocatalysts for water splitting. Heteroatom doping is an effective way to improve the catalytic performance of OER by modulating the local electronic environment and stimulating the synergy. However, the complicated manufacturing methods have hindered their practical application. Herein, we demonstrate a method based on FeOOH/CC precursor to realize the preparation of Ni-P-S@FeOOH/CC catalyst through fast electrodeposition method. The overpotential of Ni-P-S@FeOOH/CC catalyst is 210 mV (10 mA cm(-2)), and still has an initial voltage of 97.35 % for 48 h. The surface area analysis shows a higher electrochemically active surface area for the amorphous structure prepared by electrodeposition method. XPS and DFT results show that the co doping of P and S can stimulate the synergistic effect and the minimum energy of adsorption/desorption in OER process is only 0.83 eV. The strategy shows good prospects for preparing efficient OER pre catalysts. (C) 2022 Published by Elsevier Ltd

    Research on Hydraulic Conversion Technology of Small Ocean Current Turbines for Low-Flow Current Energy Generation

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    Ocean energy is a kind of renewable energy contained in seawater, which has the characteristics of large total reserves, sustainable use, and its being green and clean. Influenced by rising oil prices and global climate change, an increasing number of countries are attaching great importance to the strategic position of ocean energy in the future energy sector, and are formulating national ocean energy development roadmaps and conducting research and development on ocean energy technologies. Ocean current energy is a widely existing kind of ocean energy with abundant reserves. However, due to the low current velocity in most of the deep sea, low current energy has not been effectively exploited. In this paper, the Blade element momentum (BEM) theory based on Vortex column theory is used to design a special airfoil for low current energy applications, and a prototype turbine with rotor diameter of 4.46 m and tip speed ratio (TSR) of 6 is fabricated. In order to achieve stable electric power output, this paper designs a hydraulic conversion power generation control system with flexible control, and the hydraulic system working pressure designed to 21 MPa. In this paper, we conducted towing experiments on the prototype of an ocean current energy turbine, with hydraulic transmission and a control power generation system applied to the low flow rate, and achieved the target of hydraulic motor speed in the range of 14.7~15.9 r/min and steady-state speed accuracy in the range of ±1%. The research conducted in this paper can provide a research basis for the efficient exploitation of low-flow ocean current energy

    Diversity and Contributions to Nitrogen Cycling and Carbon Fixation of Soil Salinity Shaped Microbial Communities in Tarim Basin

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    Arid and semi-arid regions comprise nearly one-fifth of the earth's terrestrial surface. However, the diversities and functions of their soil microbial communities are not well understood, despite microbial ecological importance in driving biogeochemical cycling. Here, we analyzed the geochemistry and microbial communities of the desert soils from Tarim Basin, northwestern China. Our geochemical data indicated half of these soils are saline. Metagenomic analysis showed that bacterial phylotypes (89.72% on average) dominated the community, with relatively small proportions of Archaea (7.36%) and Eukaryota (2.21%). Proteobacteria, Firmicutes, Actinobacteria, and Euryarchaeota were most abundant based on metagenomic data, whereas genes attributed to Proteobacteria, Actinobacteria, Euryarchaeota, and Thaumarchaeota most actively transcribed. The most abundant phylotypes (Halobacterium, Halomonas, Burkholderia, Lactococcus, Clavibacter, Cellulomonas, Actinomycetospora, Beutenbergia, Pseudomonas, and Marinobacter) in each soil sample, based on metagenomic data, contributed marginally to the population of all microbial communities, whereas the putative halophiles, which contributed the most abundant transcripts, were in the majority of the active microbial population and is consistent with the soil salinity. Sample correlation analyses according to the detected and active genotypes showed significant differences, indicating high diversity of microbial communities among the Tarim soil samples. Regarding ecological functions based on the metatranscriptomic data, transcription of genes involved in various steps of nitrogen cycling, as well as carbon fixation, were observed in the tested soil samples. Metatranscriptomic data also indicated that Thaumarchaeota are crucial for ammonia oxidation and Proteobacteria play the most important role in other steps of nitrogen cycle. The reductive TCA pathway and dicarboxylate-hydroxybutyrate cycle attributed to Proteobacteria and Crenarchaeota, respectively, were highly represented in carbon fixation. Our study reveals that the microbial communities could provide carbon and nitrogen nutrients for higher plants in the sandy saline soils of Tarim Basin
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