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A divergence-free weak Galerkin method for quasi-Newtonian Stokes flows

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Science China Mathematics 2017年第8期60卷 1515-1528页

作者： zheng xiaobo CHEN Gang XIE XiaoPing School of Mathematics Sichuan University

This paper proposes a weak Galerkin finite element method to solve incompressible quasi-Newtonian Stokes equations. We use piecewise polynomials of degrees k + 1(k 0) and k for the velocity and pressure in the interior of elements, respectively, and piecewise polynomials of degrees k and k + 1 for the boundary parts of the velocity and pressure, respectively. Wellposedness of the discrete scheme is established. The method yields a globally divergence-free velocity approximation. Optimal priori error estimates are derived for the velocity gradient and pressure approximations. Numerical results are provided to confirm the theoretical results.

关键词： quasi-Newtonian Stokes equation weak Galerkin method divergence-free optimal error estimate

Active control of multiscale features in wall-bounded turbulence

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Acta Mechanica Sinica 2020年第1期36卷 12-21页

作者： Xiaotong Cui Nan Jiang xiaobo zheng Zhanqi Tang Department of Mechanics Tianjin UniversityTianjin300354China Tianjin Key Laboratory of Modern Engineering Mechanics Tianjin300354China School of Naval Architecture Ocean&Civil Engineering Shanghai Jiao Tong UniversityShanghai200240China

This study experimentally investigates the impact of a single piezoelectric(PZT)actuator on a turbulent boundary layer from a statistical *** working conditions of the actuator include a range of frequencies and *** streamwise velocity signals in the turbulent boundary layer flow are measured downstream of the actuator using a hot-wire *** mean velocity profiles and other basic parameters are *** results obtained by discrete wavelet decomposition indicate that the PZT vibration primarily influences the near-wall *** turbulent intensities at different scales suggest that the actuator redistributes the near-wall turbulent *** skewness and flatness distributions show that the actuator effectively alters the sweep events and reduces intermittency at smaller ***,under the impact of the PZT actuator,the symmetry of vibration scales’velocity signals is promoted and the structural composition appears in an orderly *** distribution function results indicate that perturbation causes the fluctuations in vibration scales and smaller scales with high intensity and low *** on the flatness factor,the bursting process is also *** vibrations reduce the relative intensities of the burst events,indicating that the streamwise vortices in the buffer layer experience direct interference due to the PZT control.

关键词： Turbulent boundary layer Piezoelectric actuator Drag reduction Discrete wavelet decomposition Bursting process

Emerging low-nuclearity supported metal catalysts with atomic level precision for efficient heterogeneous catalysis

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Nano Research 2022年第9期15卷 7806-7839页

作者： xiaobo zheng Beibei Li Qishun Wang Dingsheng Wang Yadong Li Department of Chemistry Tsinghua UniversityBeijing 100084China

Supported atomically dispersed metal catalysts(ADMCs)have received enormous attention due to their high atom utilization efficiency,mass activity and excellent ***-atom site catalysts(SACs)with monometal-center as the quintessential ADMCs have been extensively studied in the catalysis-related *** SACs,novel atomically dispersed metal catalysts(NADMCs)with flexible active sites featuring two or more catalytically centers including dual-atom and triple-atom catalysts have drawn ever-increasing attention *** to the presence of multiple neighboring active sites,NADMCs could exhibit much higher activity and selectivity compared with SACs,especially in those complicated reactions with multi-step *** review comprehensively outlines the recent exciting advances on the NADMCs with emphasis on the deeper understanding of the synergistic interactions among multiple metal atoms and underlying structure-performance *** starts with the systematical introduction of principal synthetic approaches for NADMCs highlighting the key issues of each fabrication method including the atomically precise control in the design of metal nuclearity,and then the state-of-the-art characterizations for identifying and monitoring the atomic structure of NADMCs are ***,the recent development of NADMCs in energy-related applications is systematically ***,we provide some new insights into the remaining challenges and opportunities for the development of NADMCs.

关键词： dual-atom catalysts atomically precise control synthesis strategy synergistic interactions structure-performance relationships

The leaching of additive-derived flame retardants(FRs) from plastics in avian digestive fluids:The significant risk of highly lipophilic FRs

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Journal of Environmental Sciences 2019年第11期31卷 200-207页

作者： Huiying Guo xiaobo zheng Shuling Ru Xiaojun Luo Bixian Mai State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Protection and Resources Utilization Guangzhou Institute of Geochemistry Chinese Academy of Sciences Guangzhou 510640 China College of Resources and Environment South China Agricultural University Guangzhou 510642 China University of the Chinese Academy of Sciences Beijing 100049 China

The exposure to plastic debris and associated pollutants for wildlife is of urgent concern,but little attention has been paid on the transfer of plastic additives from plastic debris to *** the present study,the leaching of incorporated flame retardants (FRs),including polybrominated diphenyl ethers (PBDEs),alternative brominated FRs (AFRs),and phosphate flame retardants (PFRs),from different sizes of recycled acrylonitrile-butadiene-styrene (ABS) polymer were investigated in avian digestive *** impact of co-ingested sediment on the leaching of additive-derived FRs in digestive fluids was also *** the recycled ABS,BDE 209 (715 μg/g) and 1,2-bis(2,4,6-tribromophenoxy) ethane (BTBPE,1766 μg/g) had the highest concentrations among all target *** leaching proportions of FRs were higher in finer sizes of *** leaching proportions of FRs from recycled ABS increased with elevated logKow of *** the tests with coexisted ABS and sediment,hexato deca-BDEs,BTBPE,and decabromodiphenyl ethane (DBDPE) migrated from ABS to sediment,which resulted in the less bioaccessible fractions of these FRs in gut *** lipophilic chemicals tended to be adsorbed by sediment from *** results suggest the migration of additive-derived FRs from plastics to other indigestible materials in digestive *** findings in this study provide insights into the transfer of additive-derived FRs from plastics to birds,and indicate the significant contribution of FR-incorporated plastics to bioaccumulation of highly lipophilic FRs.

关键词： Recycled plastics Digestive fluids Flame retardants Leaching

Spectral purification improves monitoring accuracy of the comprehensive growth evaluation index for film-mulched winter wheat

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Journal of Integrative Agriculture 2024年第5期23卷 1523-1540页

作者： Zhikai Cheng xiaobo Gu Yadan Du Zhihui Zhou Wenlong Li xiaobo zheng Wenjing Cai Tian Chang Key Laboratory of Agricultural Soil and Water Engineering in Arid and Semiarid AreasMinistry of Education/Northwest A&F University Yangling712100China

In order to further improve the utility of unmanned aerial vehicle(UAV)remote-sensing for quickly and accurately monitoring the growth of winter wheat under film mulching, this study examined the treatments of ridge mulching,ridge–furrow full mulching, and flat cropping full mulching in winter *** on the fuzzy comprehensive evaluation (FCE) method, four agronomic parameters (leaf area index, above-ground biomass, plant height, and leaf chlorophyll content) were used to calculate the comprehensive growth evaluation index (CGEI) of the winter wheat, and 14 visible and near-infrared spectral indices were calculated using spectral purification technology to process the remote-sensing image data of winter wheat obtained by multispectral *** machine learning algorithms, partial least squares, support vector machines, random forests, and artificial neural network networks(ANN), were used to build the winter wheat growth monitoring model under film mulching, and accuracy evaluation and mapping of the spatial and temporal distribution of winter wheat growth status were carried *** results showed that the CGEI of winter wheat under film mulching constructed using the FCE method could objectively and comprehensively evaluate the crop growth *** accuracy of remote-sensing inversion of the CGEI based on the ANN model was higher than for the individual agronomic parameters, with a coefficient of determination of 0.75,a root mean square error of 8.40, and a mean absolute value error of *** purification could eliminate the interference of background effects caused by mulching and soil, effectively improving the accuracy of the remotesensing inversion of winter wheat under film mulching, with the best inversion effect achieved on the ridge–furrow full mulching area after spectral *** results of this study provide a theoretical reference for the use of UAV remote-sensing to monitor the growth status of winter wheat with film mulching.

关键词： mulched winter wheat machine learning fuzzy comprehensive evaluation comprehensive growth evaluation index unmanned aerial vehicle

A Phytophthora sojae gene of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) induced in host infection and its anti-oxidative function in yeast

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Chinese Science Bulletin 2006年第11期51卷 1316-1323页

作者： ZENG Juan WANG Yuanchao SHEN Gu zheng xiaobo Department of Plant Pathology Nanjing Agricultural University Nanjing 210095 China

Glyceraldehyde-3-phosphate dehydro- genase (GAPDH) is a multifunctional protein well defined in eukaryotes, especially in mammalian and Saccharomyces cerevisiae. Using the method of suppression subtractive hybridization (SSH), we identified a Phytophthora sojae cDNA coding GAPDH, which was up-regulated during the early stage of soybean infection. The termed PsGapdh gene pos- sessed three copies in the P. sojae genome. Its amino acid sequence harbored overall conserved domain of GADPH, homologous closest to GapC1 of Achlya bisexualis (oomycete) and adjoined to GapC2s of Odontella sinensis and Phaeodactylum tricornutum (diatom), on the C-Ⅱ branch of subfamily GapC in phylogeny tree of GAPDH. The transcrip- tional level of PsGapdh was up-regulated throughout early infection. Heterogenous expression of PsGapdh in the yeast tdh1-deleted mutant could rescue growth arrest under continuous exposure to H2O2. These results indicated active roles of PsGapdh in patho- gen-host interaction and anti-oxidation.

关键词：甘油醛磷酸盐脱氢酶 GAPDH 病原体-宿主相互作用抗氧化

Cloning of genes encoding nonhost hypersensitive response-inducing elicitors from Phytophthora boehmeriae

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Chinese Science Bulletin 2007年第2期52卷 231-237页

作者： LI Jun ZHANG HaiFeng ZHANG zhengGuang WANG YuanChao zheng xiaobo Department of Plant Pathology Nanjing Agricultural University Nanjing 210095 China Suzhou Plant Protection and Quarantine Station Suzhou 215006 China

We have devised a high-throughput functional cloning method to isolate cDNAs from Phytophthora boehmeriae of which the products elicit a hypersensitive response (HR) in tobacco. The cDNAs were cloned into a binary potato virus X (PVX)-based expression vector and transformed into Agrobacterium tumefeciens (Mog101). 4100 colonies were individually toothpick-inoculated onto leaflets of Nicotiana benthamiana. 12 cDNAs were identified whose expression induced formation of a necrotic lesion around the inoculation site. 7 of these clones have different sequences. One of these clones PBC43 encodes specific elicitin. Clone PBC163 encodes a protein highly homologous to Rab; PBC241 en-codes a prohibitin protein; PBN62 encodes a Heat Shock Protein 60 (HSP60). The other five cDNAs reveal no homology to known protein and are thus considered novel. These observations suggest that this functional screening method is a versatile strategy to identify cDNAs of pathogens that encode elicitors and other HR-inducing proteins.

关键词：基因工程克隆技术敏感机制烟草基因编码

Theory-oriented screening and discovery of advanced energy transformation materials in electrocatalysis

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Advanced Powder Materials

Advanced Powder Materials 2022年第1期1卷 14-26页

作者： Hongyu Jing Peng Zhu xiaobo zheng Zedong Zhang Dingsheng Wang Yadong Li Department of Chemistry Tsinghua UniversityBeijing100084China Institute of Catalysis for Energy and Environment Shenyang Normal UniversityShenyang110034China

Various metal-based electrocatalysts from nanocrystals,to clusters and single-atoms,have been well-discovered towards high-efficient power devices and electrocatalytic *** accelerate energy transformation materials discovery,developing high-throughput DFT calculations and machine-learning techniques is of great *** review comprehensively outlines the latest progress of theory-guided design of advanced energy transformation ***,we focus on the study of single atoms in various power devices,such as fuel cell(oxygen reduction reaction,ORR;acid oxidation reaction;alcohol oxidation reaction),and other reactions for energy-related electrocatalytic conversion of small molecules,such as H_(2)O_(2)evolution reactions(2e−ORR),water splitting(H_(2)evolution reaction/O_(2)evolution reaction,HER/OER),N2 reduction reaction(NRR),and CO_(2)reduction reactions(CO_(2)RR).Firstly,the electronic structure,interaction mechanism,and reaction activation path are discussed to provide an overall blueprint in electrocatalysis and batteries mentioned ***,the experimental synthesis strategies,structural recognition,and electrocatalytic performance for the advanced energy transformation materials are figured ***,some viewpoints into the current issues and future design concept of the advanced energy transformation materials are provided.

关键词： Theory-guided design Reaction mechanism Metal-based catalysts synthesis Power devices Electrocatalytic conversion

Experimental and numerical investigation of the influence of roughness and turbulence on LUT airfoil performance

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Acta Mechanica Sinica 2019年第6期35卷 1178-1190页

作者： Shoutu Li Ye Li Congxin Yang xiaobo zheng Qing Wang Yin Wang Deshun Li Wenrui Hu School of Energy and Power Engineering Lanzhou University of TechnologyLanzhou 730050China Gansu Provincial Technology Centre for Wind Turbines Lanzhou 730050China Key Laboratory of Fluid Machinery and Systems Lanzhou 730050China Lab of Multiple Function Towing Tank School of Naval ArchitectureOcean and Civil EngineeringShanghai Jiao Tong UniversityShanghai 200240China State Key Laboratory of Ocean Engineering School of Naval ArchitectureOcean and Civil EngineeringShanghai Jiao Tong UniversityShanghai 200240China Collaborative Innovation Center for Advanced Ship and Deep-Sea Exploration Shanghai Jiao Tong UniversityShanghai 200240China Key Laboratory of Hydrodynamics(Ministry of Education) Shanghai Jiao Tong UniversityShanghai 200240China Institute of Mechanics Chinese Academy of SciencesBeijing 100080China

Vertical-axis wind turbines(VAWTs)have been widely used in urban environments,which contain dust and experience strong ***,airfoils for VAWTs in urban environments have received considerably less research attention than those for horizontal-axis wind turbines(HAWTs).In this study,the sensitivity of a new VAWT airfoil developed at the Lanzhou University of Technology(LUT)to roughness was investigated via a wind tunnel *** results show that the LUT airfoil is less sensitive to roughness at a roughness height of<0.35 ***,the drag bucket of the LUT airfoil decreases with increasing roughness ***,the loads on the LUT airfoil during dynamic stall were studied at different turbulence intensities using a numerical method at a tip-speed ratio of *** the stall,the turbulence intensity did not considerably affect the normal or tangential force coefficients of the LUT ***,after the stall,the normal force coefficient varied obviously at low turbulence ***,as the turbulence intensity increased,the normal and tangential force coefficients decreased rapidly,particularly in the downwind region of the VAWT.

关键词： Airfoil Dynamic load Roughness Vertical-axis wind turbines(VAWTs) Wind tunnel experiment