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Does palynological diversity reflect floristic diversity?A case study from Northeast China

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Science China Earth Sciences 2023年第9期66卷 2097-2108页

作者： Yifan cui Feng QIN Yan zhao Qiaoyu cui Rongwei GENG Quan LI Key Laboratory of Land Surface Pattern and Simulation Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China Cluster of Excellence ROOTS Institute of Pre-and Protohistoric ArchaeologyKiel UniversityKiel 24118Germany

Fossil pollen data can provide important information of past vegetation diversity,on the basis of established relationship between modern palynological and floristic ***,current studies on modern pollen assemblages in China have not examined this relationship ***,we report a case study from Northeast China,aiming to investigate the representation of modern palynological diversity to regional floristic diversity.A total of 87 sets of modern pollen and vegetation data from various vegetation types were applied to assess modern palynological diversity and floristic diversity in Northeast China,and the relationship between palynological and floristic diversity was studied using spatial pattern comparison and correlation ***,to reduce representation bias related to pollen production and dispersal,we calibrated pollen data using the Regional Estimates of Vegetation Abundance from Large Sites(REVEALS)model with Pollen Productivity Estimates(PPEs)and Fall Speeds of Pollen(FSP).The results show that the spatial variations of palynological and floristic richness among vegetation types are similar,and have a good positive correlation(r=0.41,p0.05).The calibration on pollen data using REVEALS model minimized the differences in spatial patterns between palynological and floristic diversity,and improved the correlations between them(richness,r=0.50,p<0.01;evenness,r=0.33,p<0.01).Our study indicates that palynological richness in Northeast China could reflect regional floristic richness in general,and the calibration with REVEALS model is recommended for reconstructing past floristic diversity from pollen data.

关键词： Northeast China Modern palynological diversity Floristic diversity Richness and evenness Community dissimilarity index REVEALS model

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Microstructure evolution and mechanical properties of brazing joint for ultra-thin-walled Inconel 718 considering grain size effect and brazing temperature

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Chinese Journal of Aeronautics 2024年第2期37卷 541-556页

作者： Rui zhao Yueshuai SONG Hui KANG Min wan School of Mechanical Engineering and Automation Beihang UniversityBeijing 100191China Jiangxi Research Institute of Beihang University Jiangxi 330000China

The systematic investigation of the mechanical properties and microstructure evolution process of ultra-thin-walled Inconel 718 capillary brazing joints is of great significance because of the exceptionally high demands on its *** achieve this objective,this study investigates the impact of three distinct brazing temperatures and five typical grain sizes on the brazed joints’mechanical properties and microstructure evolution *** evolution analysis was conducted based on Electron Back Scatter Diffraction(EBSD),Scanning Electron Microscopy(SEM),X-Ray Diffraction(XRD),High-Resolution Transmission Electron Microscopy(HRTEM),and Focused Ion Beam(FIB).Besides,the mechanical properties and fracture behavior were studied based on the uniaxial tension tests and in-situ tension *** findings reveal that the brazing joint’s strength is higher for the fine-grain capillary than the coarse-grain one,primarily due to the formation of a dense branch structure composed of G-phase in the brazing *** effects of grain size,such as pinning and splitting,are amplified at higher brazing ***,micro-cracks initiate around brittle intermetallic compounds and propagate through the eutectic zone,leading to a cleavage fracture *** fracture stress of fine-grain specimens is higher than that of coarse-grain due to the complex micro-crack ***,this study contributes significantly to the literature by highlighting the crucial impact of grain size on the brazing properties of ultra-thin-walled Inconel 718 structures.

关键词： EYWORDS Ultra-thin-walled structure Brazing Inconel 718 Grain size effect Brazing temperature

Numerical simulations of multi-layer-liquid sloshing by multiphase MPS method

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Journal of Hydrodynamics 2021年第5期33卷 938-949页

作者： Xiao Wen Wei-wen zhao De-cheng wan Computational Marine Hydrodynamics Lab(CMHL) School of Naval ArchitectureOcean and Civil EngineeringShanghai Jiao Tong UniversityShanghai 200240China

In this paper,a multiphase moving particle semi-implicit(MPS)method is developed by introduction of various multiphase models into the original MPS method for single-phase flows,and is then applied to the numerical simulations of two-layer-liquid and three-layer-liquid sloshing in a 2-D rectangular tank under different external *** validate the accuracy of the present multiphase MPS method,the qualitative and quantitative results,including wave profiles,interface elevations and impact pressures,are compared with experimental data and other numerical results,which show a good *** particular,the evolutions of free surface and phase interfaces are compared and an obvious discrepancy is found,indicating that the phase interfaces may suffer from complex deformations while the free surface keeps relatively ***,the different modes of phase interface are observed under different excitation ***,the violent sloshing of a three-layer-liquid system is simulated and the phenomenon of internal wave breaking is well captured,which mainly benefitted from the Lagrangian basis of MPS method and its advantage in multiphase flows with complex ***,the three-layer-liquid sloshing with a vertical baffle are simulated to investigate the suppressing effect of baffle on multi-layer-liquid sloshing.

关键词： Moving particle semi-implicit(MPS) multiphase flows multi-layer-liquid liquid sloshing

Non-Fourier heat conduction analysis of a 2-D plate with inner cracks at arbitrary direction angles

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Chinese Journal of Aeronautics 2022年第3期35卷 537-549页

作者： Zhuoxin WEN Chi HOU Meiying zhao Xiaopeng wan School of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China

This paper investigates the problem of a 2-D plate containing internal cracks at arbitrary angles to the heating surface under thermal *** finite difference method is applied to solve the temperature distribution and a difference scheme of the oblique crack is *** the first time,a non-Fourier heat transfer analysis method of a 2-D plate with inner cracks at arbitrary direction angles is ***,for a strip with an inner crack paralleling to the surface,numerical results are compared with the analytical solutions by rotating the boundary,and perfect agreement is *** experiments are further presented to investigate the influence of crack orientation angle and multi-crack distribution on non-Fourier heat conduction.

关键词： Difference scheme Finite difference method Multi-crack Non-Fourier heat conduction Temperature distribution

One-pot synthesis of Fe/Cu-SSZ-13 catalyst and its highly efficient performance for the selective catalytic reduction of nitrogen oxide with ammonia

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Journal of Environmental Sciences 2021年第2期33卷 306-316页

作者： Jie wan Jiawei Chen Ru zhao Renxian Zhou Energy Research Institute Nanjing Institute of TechnologyNanjing 211167China Institute of Catalysis Zhejiang UniversityHangzhou 310028China

Series of Fe/Cu-SSZ-13 catalysts with different Fe loading content were synthesized by simple one-pot *** obtained catalysts were subjected to selective catalytic reduction(SCR)of NO x with NH 3 and were characterized by various *** results show that Fe 0.63/Cu 1.50-SSZ-13 catalyst with proper Fe content exhibits excellent catalytic activity with widest operation temperature window from 160 to 580℃,excellent hydrothermal stability as well as good resistance to sulfur poisoning when compared with Cu-SSZ-13,signifying its great potential for practical *** characterizations reveal that the synthesized Fe/Cu-SSZ-13 catalysts present typical chabazite(CHA)structure with good crystallinity,while isolated Cu^2+and monomeric Fe 3+are revealed as the predominant copper and iron *** low temperatures,isolated Cu^2+species act as primary active sites for SCR reaction,while monomeric Fe^3+species provide sufficient active sites for sustain the SCR activity at high ***,Fe over doping would lead to the damage of zeolite structure,destruction of isolated Cu^2+site,as well as the formation of highly oxidizing Fe2O3,thus causing deterioration of catalytic performances.

关键词： NH3-SCR Fe/Cu-SSZ-13 One-pot synthesis Active species

A Hydraulic Performance Comparison of Centrifugal Pump Operating in Pump and Turbine Modes

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Journal of Thermal Science 2020年第6期29卷 1594-1605页

作者： DAI cui DONG Liang LIN Haibo zhao Fei School of Energy and Power Engineering Jiangsu UniversityZhenjiang 212013China Sichuan Provincial Key Lab of Process Equipment and Control Sichuan University of Science&EngineeringZigong 643000China Research Center of Fluid Machinery Engineering and Technology Jiangsu UniversityZhenjiang 212013China School of Mechanical Research Center of Technology Wuxi Institute of TechnologyWuxi 214121China

The modifications of impeller may show diverse impact on centrifugal pump operating in pump and turbine *** clarify this problem,the hydraulic performance of a low specific speed centrifugal pump operating in both modes was firstly obtained by CFD method and verified by ***,based on the single-factor design method,a series of calculations have been conducted to identify the effects of impeller geometry parameters on the hydraulic performance in different *** variations of head,shaft power and hydraulic efficiency curves with different impeller parameters were *** is found that compared with turbine,the pump shows a more obvious variation of *** outlet angle has positive impact both on the head consumed by pump or generated by *** change of turbine shaft power is apparently smaller than that of pump for different impeller geometry *** the outlet width somewhat changes the turbine shaft *** hydraulic efficiency in both modes shows different variation under different impeller geometric parameters,while the hydraulic efficiency of both modes is reduced with the outlet angle ***,the response amount of hydraulic efficiency caused by certain change of impeller parameters was estimated by sensitivity analysis *** is found that only the appropriate blade number and outlet width can improve the hydraulic performance both in pump and turbine ***,the hydraulic loss,skin friction loss and theoretical analysis were performed to explore the reason of hydraulic performance variation due to different impeller *** change of slip factor,impeller inlet area,impeller outlet area or hydraulic loss results in the change of hydraulic performance in both *** results can be useful for hydraulic performance improvement for both pump and turbine modes through impeller geometry modification.

关键词： Computational Fluid Dynamics centrifugal pump impeller modification pump mode turbine mode

Liquid phase in-situ synthesis of LiF coated boron powder composite and performance study

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Defence Technology（防务技术） 2020年第3期16卷 635-641页

作者： Yang Xu Qing-zhong cui Cheng-wen zhao State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China Shanxi Jiangyang Chemical Factory Shanxi 030000China

Among practical metal additives,boron(B) has a high volumetric heating value,making it a promising choice as a fuel *** B can theoretically yield a large amount of energy upon complete combustion,its combustion is retarded by the initial presence of B oxide,which coats the surfaces of B *** improve the ignition and combustion properties of B powder,LiOH and NH4F were used as precursors to synthesize uniformly LiF-coated B composites(LiF-B) in *** LiF-B mixture was also prepared for comparison using a physical method.X-ray diffraction(XRD),Fourier-transform infrared(FTIR),scanning electron microscope(SEM),and energy-dispersive X-ray spectroscopy(EDS) were used to characterize the morphologies and compositions of the *** thermal and combustion properties of the samples were characterized by thermal gravity-differential thermal gravity(TG-DTG),differential scanning calo rimetry(DSC) and closed bomb *** XRD,FTIR,SEM and EDS results demonstrated the successful preparation of the coated LiF-B *** TG-DTG and closed bomb experiment results indicated that the addition of LiF decreased the ignition temperature of B powder,and increasing its reaction *** results show that when LiF-B was added,the released heat of underwater explosive increased by 6727.2,7280.4 and 3109.6 J/g at heating rates of 5,10,and 15℃/min,***,LiF-B decreased the activation energy of secondary combustion reaction of explosive system as calculated through Kissinger’s method by 28.9%,which indicated an excellent catalytic effect for the thermal decomposition of underwater *** results reveal that LiF can improve the combustion efficiency of B powder,thereby increasing the total energy of *** mechanical sensitivity increased slightly after adding LiF-B to the underwater *** mpared to the underwater explosive with added B,the mechanical sensitivity of the explosive with added LiF-B was significantly

关键词： Boron LiF Coating Thermal decomposition properties Energy efficiency

Space charge characteristics of silicone elastomer for device packaging under positive square wave voltage

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High Voltage 2023年第2期8卷 401-411页

作者： Jinqiang Zhang Xuebao Li Zhibin zhao Xiang cui State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power UniversityBeijingChina

With the rapid development of power electronic devices towards high voltage and power,the insulation challenges faced by devices have attracted widespread *** elastomer is widely used in device packaging as one insulating material,and the study of its insulating properties is helpful to the reliable operation of *** this end we obtained the space charge characteristics of silicone elastomer under positive square wave voltage by using the pulse-electroacoustic(PEA)*** based on the existing research and IEC standards,the selection criteria of the resistance and capacitance parameters of a PEA system for space charge measurement under square wave voltage are *** this experimental system,the space charge distribution under the positive square wave voltage with different waveform parameters is obtained,and the influences of the waveform parameters on the space charge accumulation are *** amounts of charges under the action of square wave voltage with different waveform parameters are calculated,and the influences of waveform parameters on the amounts of charges are *** addition,the reasons for the difference in the accumulation of positive and negative charges are explained through Schottky injection model,the synthesis reaction and the infrared spectrum of the silicone elastomer.

关键词： charge wave characteristics

Stress response to nanoplastics with different charges in Brassica napus *** seed germination and seedling growth stages

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Frontiers of Environmental Science & Engineering 2023年第4期17卷 41-52页

作者： Tao Li Xiufeng Cao Rui zhao zhaojie cui School of Environmental Science and Engineering Shandong UniversityQingdao 266237China School of Municipal&Environmental Engineering Shandong Jianzhu UniversityJinan 250101China

Nanoplastic pollution has become a significant problem in farmland systems ***,research on the effects of nanoplastics(NPs)with different charges on field crops is still *** our study,NPs with different charges,including unmodified polystyrene nanoplastics(PS),positively charged polystyrene nanoplastics(PS-NH_(2)),and negatively charged polystyrene nanoplastics(PSSO3H),were investigated for their impacts on seed germination and seedling growth of *** results showed that seed water uptake(after 12 h),seed germination,seed vigour,and relative root elongation were all significantly reduced under exposure to NPs(200 mg/L).Similarly,remarkable decreases in plant biomass(root weight,shoot weight),growth(root length,plant height),photosynthesis ability(chlorophyll a,chlorophyll b,carotenoids),essential nutrient uptake(Fe,Mn,Zn,Cu),and plant quality(soluble protein,soluble sugar,crude fibre content)of rape seedlings were also observed after exposure to *** the three kinds of NPs,PS-NH_(2)showed stronger ***,superoxide dismutase,peroxidase,and catalase activities of rape seedlings were changed,and the content of malondialdehyde was significantly increased under exposure to ***,positively charged PS-NH_(2)showed stronger effects on the phenotype,physiology,biochemistry,nutrient uptake,and plant quality of ***,a comprehensive toxicity evaluation revealed that PS-NH_(2)had the strongest toxicity to *** present study provides important implications for the interaction and risk assessment of NPs and crops in soil-plant systems.

关键词： Nanoplastics Rape(Brassica napus L.) Physiology and biochemistry Nutrient absorption Plant quality Toxicity