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Fundamentals and progress of the manifold method based on independent covers

Science China(Technological Sciences) 2024年第4期67卷 966-991页

作者： SU HaiDong LIN ShaoZhong XIE ZhiQiang GONG YaQi QI YongFeng Material and engineering Structure Department Yangtze River Scientific Research InstituteWuhan 430010China research center of water engineering Safety and Disaster Prevention of Ministry of water resources Wuhan 430010China

Aiming to solve mesh generation,computational stability,accuracy control,and other problems encountered with existing numerical methods,such as the finite element method and the finite volume method,a new numerical computational method for continuum mechanics,namely the manifold method based on independent covers(MMIC),is proposed based on the concept of mathematical manifolds,to form partitioned series solutions of partial differential equations.As partitions,the cover meshes have the characteristics of arbitrary shape,arbitrary connection,and arbitrary refinement.They are expected to fundamentally solve the mesh generation problem and can also simulate the precise geometric boundaries of the CAD model and strictly impose boundary conditions.In the selection of series solutions,local analytical solutions(such as series solutions at crack tips and series solutions in infinite domains)or proper forms of complete series can be used to reflect the local or global characteristics of the physical field to accelerate convergence.Various applications are presented.A new method of beam,plate,and shell analysis is proposed.The deformation characteristics of beams,plates,and shells are simulated with polynomial series of suitable forms,and the analysis of curved beams and shells with accurate geometric representation is realized.For the static elastic analysis of two-dimensional structures,a mesh splitting algorithm is proposed,and h-p version adaptive analysis is carried out with error estimation.Thus,automatic computation integrated with CAD is attempted.Adaptive analysis is also attempted for the solution of differential equations of fluids.For the one-dimensional convection-diffusion equation and Burgers equation,calculation results with high precision are obtained in strong convection and shock wave simulations,avoiding nonphysical oscillations.And solving the two-dimensional incompressible Navier-Stokes equation is also attempted.The series solution formula is used to obtain the physical quantity of interest of the m

关键词： series solutions mesh generation adaptive analysis fixed meshes numerical manifold method

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Synthesis of chitosan-based grafting magnetic flocculants for flocculation of kaolin suspensions

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Journal of Environmental Sciences 2024年第5期139卷 193-205页

作者： Chuang Liu Xiaoyu Wang Sicong Du Wenyan Liang Beijing Key Lab for Source Control Technology of water Pollution/engineering research center for water Pollution Source Control&Eco-remediation/College of Environmental Science and engineering Beijing Forestry UniversityBeijing 100083China

A series of novel chitosan-based magnetic flocculants FS@CTS-P(AM-DMC)was prepared by molecular structure control.The characterization results showed that FS@CTS-P(AM-DMC)had a uniform size of about 21.46 nm,featuring a typical core-shell structure,and the average coating layer thickness of CTS-P(AM-DMC)was about 5.03 nm.FS@CTS-P(AM-DMC)exhibited excellent flocculation performance for kaolin suspension,achieved 92.54% turbidity removal efficiency under dosage of 150 mg/L,pH 7.0,even at high turbidity(2000 NTU)with a removal efficiency of 96.96%.The flocculation mechanism was revealed to be dominated by charge neutralization under acidic and neutral conditions,while adsorption and bridging effects play an important role in alkaline environments.The properties of magnetic aggregates during flocculation,breakage,and regeneration were studied at different pH levels and dosages.In the process of magnetophoretic,magnetic particles collide and adsorb with kaolin particles continuously due to magnetic and electrostatic attraction,transform into magnetic chain clusters,and then further form three-dimensional network magnetic aggregates that can capture free kaolin particles and other chain clusters.Particle image velocimetry confirmed the formation of eddy current of magnetic flocs and experienced three stages:acceleration,stabilization,and deceleration.

关键词： Magnetic flocculation Chitosan Fe_(3)O_(4) Graft copolymerization PIV

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Comparative Assessment of Impacts of Future Climate Change on Runoff in Upper Daqinghe Basin,China

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Chinese Geographical Science 2024年第3期34卷 564-578页

作者： INGABIRE Romaine CHANG Yuru LIU Xia CAO Bo UMUGWANEZA Adeline SHEN Yanjun Key Laboratory of agricultural water resources Hebei-Key Laboratory of Water Saving AgricultureCenter for Agricultural Re-sources ResearchInstitute of Genetics and Developmental BiologyChinese Academy of SciencesShijiazhuang 050022China Uni-versity of Chinese Academy of Sciences Beijing 100049China State Key Laboratory of Desert and Oasis Ecology Xinjiang Insti-tute of Ecology and GeographyChinese Academy of SciencesUrumqi 830011China

Assessing runoff changes is of great importance especially its responses to the projected future climate change on local scale basins because such analyses are generally done on global and regional scales which may lead to generalized conclusions rather than specific ones.Climate change affected the runoff variation in the past in the upper Daqinghe Basin,however,the climate was mainly considered uncertain and still needs further studies,especially its future impacts on runoff for better water resources management and planning.Integrated with a set of climate simulations,a daily conceptual hydrological model(MIKE11-NAM)was applied to assess the impact of climate change on runoff conditions in the Daomaguan,Fuping and Zijingguan basins in the upper Daqinghe Basin.Historical hydrological data(2008–2017)were used to evaluate the applicability of the MIKE11-NAM model.After bias correction,future projected climate change and its impacts on runoff(2025–2054)were analysed and compared to the baseline period(1985–2014)under three shared social economic pathways(SSP1-2.6,SSP2-4.5,and SSP5-8.5)scenarios from Coupled Model Intercomparison Project Phase 6(CMIP6)simulations.The MIKE-11 NAM model was applicable in all three Basins,with both R^(2)and Nash-Sutcliffe Efficiency coefficients greater than 0.6 at daily scale for both calibration(2009–2011)and validation(2012–2017)periods,respectively.Although uncertainties remain,temperature and precipitation are projected to increase compared to the baseline where higher increases in precipitation and temperature are projected to occur under SSP2-4.5 and SSP5-8.5 scenarios,respectively in all the basins.Precipitation changes will range between 12%–19%whereas temperature change will be 2.0℃–2.5℃ under the SSP2-4.5 and SSP5-8.5 scenarios,respectively.In addition,higher warming is projected to occur in colder months than in warmer months.Overall,the runoff of these three basins is projected to respond to projected climate changes differently because runoff is projected to only increas

关键词： runoff climate change MIKE11-NAM model Coupled Model Intercomparison Project Phase 6(CMIP6) upper Daqinghe Basin,China

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research progresses of nanomaterials as lubricant additives

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Friction 2024年第7期12卷 1347-1391页

作者： Zhengquan JIANG Yankun SUN Bokang LIU Laigui YU Yuping TONG Mingming YAN Zhongzheng YANG Yongxing HAO Linjian SHANGGUAN Shengmao ZHANG Weihua LI School of Materials Science and engineering North China University of Water Resources and Electric PowerZhengzhou 450045China Institute of Special Friction and Lubricating Materials North China University of Water Resources and Electric PowerZhengzhou 450045China Nanomaterials engineering research center Henan UniversityKaifeng 475001China School of Mechanical engineering North China University of Water Resources and Electric PowerZhengzhou 450045China

Friction and wear are unavoidable in mechanical movement.The use of lubricants with nano-additives can effectively reduce friction and wear,which is of great significance to saving energy and protecting the environment.At present,great progress has been made in the scientific research and industrial application of nano-additives for lubricants.This paper mainly introduces the types of nano-additives for lubricants(such as carbon nanomaterials,nano-metals,nano-oxides,sulfides,complexes,polymers,etc.),the tribological properties of lubricants with different components of nano-additives,and the lubrication mechanisms of the nano-additives(including tribofilm formation,rolling ball bearing effect,repairing effect,polishing effect,and synergistic effect).It also deals with the dispersion of nano-additives in lubricants and the influences of their particle size and microstructure on the tribological properties of lubricants.This review outlines the performance requirements of nano-additives in different lubrication states,discusses the use of nano-additives in challenging working conditions,and identifies various industrial oil nano-additives with reference to the appropriate options in diverse working environments.Furthermore,the existing problems of nano-additives and their application prospects are summarized.This review,hopefully,would help to shed light on the design and synthesis of novel high-performance nano-additives and promote their application in engineering.

关键词： nanomaterials lubricant additive lubrication mechanism research progress

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Regulation effects of water and nitrogen on yield,water,and nitrogen use efficiency of wolfberry

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Journal of Arid Land 2024年第1期16卷 29-45页

作者： GAO Yalin QI Guangping MA Yanlin YIN Minhua WANG Jinghai WANG Chen TIAN Rongrong XIAO Feng LU Qiang WANG Jianjun College of water Conservancy and Hydropower engineering Gansu Agricultural UniversityLanzhou 730070China Jingtaichuan Electric Power Irrigation water Resource Utilization center in Gansu Province Baiyin 730900China

Wolfberry(Lycium barbarum L.)is important for health care and ecological protection.However,it faces problems of low productivity and resource utilization during planting.Exploring reasonable models for water and nitrogen management is important for solving these problems.Based on field trials in 2021 and 2022,this study analyzed the effects of controlling soil water and nitrogen application levels on wolfberry height,stem diameter,crown width,yield,and water(WUE)and nitrogen use efficiency(NUE).The upper and lower limits of soil water were controlled by the percentage of soil water content to field water capacity(θ_(f)),and four water levels,i.e.,adequate irrigation(W0,75%-85%θ_(f)),mild water deficit(W1,65%-75%θ_(f)),moderate water deficit(W2,55%-65%θ_(f)),and severe water deficit(W3,45%-55%θ_(f))were used,and three nitrogen application levels,i.e.,no nitrogen(N0,0 kg/hm^(2)),low nitrogen(N1,150 kg/hm^(2)),medium nitrogen(N2,300 kg/hm^(2)),and high nitrogen(N3,450 kg/hm^(2))were implied.The results showed that irrigation and nitrogen application significantly affected plant height,stem diameter,and crown width of wolfberry at different growth stages(Pwater treatment.Dry weight per hundred grains and dry weight percentage increased with increasing nitrogen application under W0 treatment.However,under other water treatments,the values first increased and then decreased with increasing nitrogen application.Yield and its component of wolfberry first increased and then decreased as water deficit increased under the same nitrogen treatment.Irrigation water use efficiency(IWUE,8.46 kg/(hm^(2)·mm)),WUE(6.83 kg/(hm^(2)·mm)),partial factor productivity of nitrogen(PFPN,2.56 kg/kg),and NUE(14.29 kg/kg)reached their highest values in W2N2,W1N2,W1N2,and W1N1 treatments.Results of principal component analysis(PCA)showe

关键词： water deficit growth characteristics yield water and nitrogen use efficiency principal component analysis

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Mixed D-vine copula-based conditional quantile model for stochastic monthly streamflow simulation

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water Science and engineering 2024年第1期17卷 13-20页

作者： Wen-zhuo Wang Zeng-chuan Dong Tian-yan Zhang Li Ren Lian-qing Xue Teng Wu College of water resources and Hydrology Hohai UniversityNanjing 210098China Yellow River research center Hohai UniversityNanjing 210098China

Copula functions have been widely used in stochastic simulation and prediction of streamflow.However,existing models are usually limited to single two-dimensional or three-dimensional copulas with the same bivariate block for all months.To address this limitation,this study developed a mixed D-vine copula-based conditional quantile model that can capture temporal correlations.This model can generate streamflow by selecting different historical streamflow variables as the conditions for different months and by exploiting the conditional quantile functions of streamflows in different months with mixed D-vine copulas.The up-to-down sequential method,which couples the maximum weight approach with the Akaike information criteria and the maximum likelihood approach,was used to determine the structures of multivariate Dvine copulas.The developed model was used in a case study to synthesize the monthly streamflow at the Tangnaihai hydrological station,the inflow control station of the Longyangxia Reservoir in the Yellow River Basin.The results showed that the developed model outperformed the commonly used bivariate copula model in terms of the performance in simulating the seasonality and interannual variability of streamflow.This model provides useful information for water-related natural hazard risk assessment and integrated water resources management and utilization.

关键词： Stochastic monthly streamflow simulation Mixed D-vine copula Conditional quantile model Up-to-down sequential method Tangnaihai hydrological station

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Experimental study of erosion wear on hydrofoils with emphasis on wear morphology

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排灌机械工程学报 2024年

作者： ZHONG Qinqin QIAN Zhongdong State key laboratory of water resources engineering and Management Hydropower Research Center for Himalaya RegionWuhan University

Erosion wear is a major challenge for hydraulic machinery operating in sediment-laden rivers.The results shows four main wear morphologies on the hydrofoil which includes pits,smooth grooves,sharp grooves,and scratches.Additionally,we could also observe iridescent rings and ripple patterns.On the leading edge of the hydrofoil,we can mainly observe pits and smooth grooves.We as well discover all four wear morphologies and iridescent rings in the middle.on the trailing edge,we see pits,sharp grooves,and ripple patterns.The dominant wear mechanisms and sub-mechanisms on the hydrofoil are surface fatigue(indenting),abrasion(microploughing,micro-cutting,and sliding),and tribochemical reactions(heating).

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利用纳米气泡控制农业废水灌溉系统复合污垢的机制

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engineering 2024年第4期35卷 214-225页

作者： Yang Xiao Bo Zhou Siyuan Tan Lei Li Tahir Muhammad Buchun Si Changjian Ma Sunny C.Jiang Yunkai Li College of water resources and Civil engineering China Agricultural UniversityBeijing 100083China engineering research center for agricultural water-saving and water resources(Ministry of Education of the People’s Republic of China) China Agricultural UniversityBeijing 100083China School of Environment and Civil engineering Dongguan University of TechnologyDongguan 523808China State Key Laboratory of Nutrient Use and Management Institute of Agricultural Resources and EnvironmentShandong Academy of Agricultural SciencesJinan 250100China Department of Civil and Environmental engineering University of California-IrvineIrvineCA 92617USA

The increasing demand for wastewater treatment has become a notable trend for addressing global water scarcity.However,fouling is a significant challenge for wastewater distribution engineering systems.This study provides an approach using nanobubbles(NBs)to control fouling.The antifouling capacities of three types of NBs,six oxygen concentrations,and two application procedures(prevention and removal)are investigated.The results show that NBs effectively mitigate composite fouling—including biofouling,inorganic scaling,and particulate fouling—in comparison with the non-NBs group.More specifically,hydroxyl radicals generated by the self-collapse of NBs oxidize organics and kill microorganisms in wastewater.The negatively charged surfaces of the NBs transform the crystalline form of CaCO_(3)from calcite to looser aragonite,which reduces the likelihood of ion precipitation.Furthermore,the NBs gas-liquid interfaces act as gas"bridges"between colloidal particles,enhancing the removal of particles from wastewater.Lastly,although the NBs inhibit the growth of fouling,they do not significantly remove the already adhered fouling in non-NBs treated groups.This study anticipates that the application of NBs will address the significant fouling issue for various wastewater distribution engineering systems in order to meet the global challenge of sustainable water supplies.

关键词： Biofouling Scaling Colloidal fouling Wastewater Antifouling mechanism

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Effect of carbonation on the properties of granite-bearing oxysulfate oxide cement

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Chongqing Daxue Xuebao/Journal of Chongqing University 2024年第6期47卷 35-42页

作者： Jin K. Zhang X. Bi W. Wang D. Han J. School of Civil & water Conservancy engineering Ningxia University Yinchuan 750021 China College of Materials and Metallurgy University of Science and Technology Liaoning Anshan 114051 China water resources engineering research center in Modern Agriculture in Arid Regions Ningxia University Yinchuan 750021 China Ningxia center for research on Earthquake Protection and Disaster Mitigation in Civil engineering Ningxia University Yinchuan 750021 China engineering Technology research center of water-saving and water Resource Regulation Ningxia University Yinchuan 750021 China School of Civil engineering North Minzu University Yinchuan 750030 China

The properties of magnesium oxysulfate (MOS) cement with different granite powder (GP) contents with CO2 curing were studied. The hydration products and microstructure of MOS cement were analyzed using X-ray diffraction (XRD), simultaneous comprehensive thermal analyzer (TG-DSC), scanning electron microscope (SEM) and mercury porosimeter (MIP). The results shows that the strength retention coefficient of MOS cement containing 40% GP reached 1.12 with standard curing for 28 days followed by 28 days of CO2 curing; when MOS cement was CO2-cured for 28 days and then immersed in water for 120 days, the strength retention coefficient reached 0.94, which was 123.8% higher than that of blank samples. MgCO3·zH2O crystals were generated after MOS cement underwent CO2 curing, which had a positive effect on the mechanical properties and water resistance by reducing matrix expansion caused by MgO hydrating to Mg(OH)2. GP increased the matrix density, reduced the CO2 capture rate, and decreased CO2 erosion of MOS cement by optimizing the pore structure. The presence of GP and magnesium carbonate phases improved the compressive strength of MOS cement after carbonation and immersion. © 2024 Chongqing University. All rights reserved.

关键词： carbonation magnesium carbonate magnesium oxysulfate cement water resistance

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Synergistic effect of adsorption and photocatalytic degradation of oilfield-produced water by electrospun photocatalytic fibers of Polystyrene/Nanorod-Graphitic carbon nitride

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Journal of Environmental Sciences 2024年第7期141卷 287-303页

作者： Parisa Azmoon Mehrdad Farhadian Alireza Pendashteh Amir H.Navarchian Department of Chemical engineering Faculty of EngineeringUniversity of IsfahanIsfahanIran Department of Chemical engineering Faculty of EngineeringUniversity of GuilanRashtIran Department of water and Environmental engineering Caspian Sea Basin Research CenterUniversity of GuilanRashtIran

Graphitic carbon nitride with nanorod structure(Nr-GCN)was synthesized using melamine as a precursor without any other reagents by hydrothermal pretreatment method.XRD,FTIR,SEM,N_(2)adsorption-desorption from BET,UV-Vis DRS spectroscopy,and photoluminescence were used to characterize the prepared samples.Also,the photoelectrochemical behavior of nanoparticles was studied by photocurrent transient response and cyclic voltammetry analysis.Polystyrene(PS)fibrous mat was fabricated by electrospinning technique and used as a support for the stabilization of the nanoparticles.The performance of the synthesized nanoparticles and photocatalytic fibers(PS/Nr-GCN)was evaluated in oilfield-produced water treatment under visible light irradiation.During this process,oil contaminants were adsorbed by hydrophobic polystyrene fibers and simultaneously degraded by Nr-GCN.The removal efficiency of chemical oxygen demand(COD)has been obtained 96.6%and 98.4%by Nr-GCN and PS/Nr-GCN,respectively,at the optimum conditions of pH4,photocatalyst dosage 0.5 g/L,COD initial concentration 550 mg/L,and illumination time 150 min.The gas chromatography-mass spectroscopy analysis results showed 99.3%removal of total petroleum hydrocarbons using photocatalytic fibers of PS/Nr-GCN.The results demonstrated that the GCN has outstanding features like controllable morphology,visible-light-driven,and showing high potential in oily wastewater remediation.Moreover,the synergistic effect of adsorption and photocatalytic degradation is an effective technique in oilfield-produced water treatment.

关键词： Graphitic carbon nitride(GCN) Nanorod structure Polystyrene fibrous mat Photocatalytic fibers Oilfield-produced water(OPW)

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