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Simulation of Fracture Process of Lightweight Aggregate Concrete Based on Digital Image Processing Technology

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Computers, Materials & Continua 2024年第6期79卷 4169-4195页

作者： Safwan Al-sayed Xi wang Yijiang peng Key Laboratory of Urban Security and Disaster Engineering Ministry of EducationBeijing University of TechnologyBeijing100124China

The mechanical properties and failure mechanism of lightweight aggregate concrete(LWAC)is a hot topic in the engineering field,and the relationship between its microstructure and macroscopic mechanical properties is also a frontier research topic in the academic *** this study,the image processing technology is used to establish a micro-structure model of lightweight aggregate *** the information extraction and processing of the section image of actual light aggregate concrete specimens,the mesostructural model of light aggregate concrete with real aggregate characteristics is *** numerical simulation of uniaxial tensile test,uniaxial compression test and three-point bending test of lightweight aggregate concrete are carried out using a new finite element method-the base force element method ***,the image processing technology is used to produce beam specimens,uniaxial compression specimens and uniaxial tensile specimens of light aggregate concrete,which can better simulate the aggregate shape and random distribution of real light aggregate ***,the three-point bending test is numerically ***,the uniaxial compression specimen generated by image processing technology is numerically ***,the uniaxial tensile specimen generated by image processing technology is numerically *** mechanical behavior and damage mode of the specimen during loading were *** results of numerical simulation are compared and analyzed with those of relevant *** feasibility and correctness of the micromodel established in this study for analyzing the micromechanics of lightweight aggregate concrete materials are *** processing technology has a broad application prospect in the field of concrete mesoscopic damage analysis.

关键词： Digital image processing lightweight aggregate concrete mesoscopic model numerical simulation fracture analysis bending beams

Predicting PM_(2.5) Concentration in the Yangtze River Delta Region Using Climate System Monitoring Indices and Machine Learning

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Journal of Meteorological Research 2024年第2期38卷 249-261页

作者： Jinghui MA Shiquan wan Shasha XU Chanjuan wang Danni QIU Shanghai Typhoon Institute Shanghai Meteorological ServiceShanghai 200030 Key Laboratory of Polar Atmosphere-Ocean-Iice System for Weather and Climate Ministry of EducationDepartment of Atmospheric and Oceanic SciencesFudan UniversityShanghai 200438 Shanghai Key Laboratory of Meteorology and Health Shanghai Meteorological ServiceShanghai 200030 Yangzhou Meteorological Office Yangzhou 225001 Department of Physics Yangzhou UniversityYangzhou 225003

Changing meteorological conditions during autumn and winter have considerable impact on air quality in the Yangtze River Delta(YRD)*** climatic factors,such as sea surface temperature and sea ice,together with the atmospheric circulation,directly affect meteorological conditions in the YRD region,thereby modulating the variation in atmospheric PM_(2.5) *** study used the evolutionary modeling machine learning technique to investigate the lag relationship between 144 climate system monitoring indices and autumn/winter PM_(2.5) concentration over 0-12 months in the YRD *** calculating the contribution ratios and lagged correlation coefficients of all indices over the previous 12 months,the top 36 indices were selected for model ***,the nine indices that contributed most to the PM_(2.5) concentration in the YRD region,including the decadal oscillation index of the Atlantic Ocean and the consistent warm ocean temperature index of the entire tropical Indian Ocean,were selected for physical mechanism *** evolutionary model was developed to forecast the average PM_(2.5) concentration in major cities of the YRD in autumn and winter,with a correlation coefficient of *** model testing,the correlation coefficient between the predicted and observed PM_(2.5) concentrations was in the range of 0.73-0.83 and the root-mean-square error was in the range of 9.5-11.6μg m-3,indicating high predictive *** model performed exceptionally well in capturing abnormal changes in PM_(2.5) concentration in the YRD region up to 50 days in advance.

关键词： PM_(2.5)concentration machine learning evolutionary modeling seasonal prediction

Generic load regulation strategy for enhancing energy efficiency of chiller plants

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Building Simulation 2024年第8期17卷 1273-1287页

作者： Hang wan Yuyang Gong Shengwei wang Yongjun Sun Tao Xu Gongsheng Huang Department of Architecture and Civil Engineering City University of Hong KongHong KongChina Department of Building Environment and Energy Engineering Hong Kong Polytechnic UniversityHong KongChina School of Civil Engineering Guangzhou UniversityGuangzhouChina Shenzhen Research Institute of City University of Hong Kong ShenzhenChina

In many chiller plants,high coefficient of performance(COP)is only achieved at a few favorable part load ratios(PLRs),while the COP is low at many other non-favorable *** address this issue,this study proposes a generic load regulation strategy that aims to maintain chiller plants operating at high COP,particularly under non-favorable *** is achieved by incorporating thermal energy storage(TES)units and timely optimizing the charging and discharging power of the integrated TES *** optimal charging and discharging power is determined by solving a dynamic optimization problem,taking into account the performance constraints of the TES units and the chiller *** provide an overview of the energy-saving potential of the proposed strategy,a comprehensive analysis was conducted,considering factors such as building load profiles,COP/PLR curves of chillers,and attributes of the TES *** analysis revealed that the proposed load regulation strategy has the potential to achieve energy savings ranging from 5.7%to 10.8%for chiller plants with poor COPs under unfavorable PLRs,particularly in buildings with significant load variations.

关键词： load regulation thermal energy storage chiller plants building energy efficiency

On the superconvergence of a WG method for the elliptic problem with variable coefficients

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Science China Mathematics 2024年第8期67卷 1899-1910页

作者： Junping wang Xiaoshen wang Xiu Ye Shangyou Zhang peng Zhu Division of Mathematical Sciences National Science FoundationAlexandriaVA 22314USA Department of Mathematics University of Arkansas at Little RockLittle RockAR 72204USA Department of Mathematical Sciences University of DelawareNewarkDE 19716USA College of Data Science Jiaxing UniversityJiaxing 314001China

This article extends a recently developed superconvergence result for weak Galerkin(WG)approximations for modeling partial differential equations from constant coefficients to variable *** superconvergence features a rate that is two orders higher than the optimal-order error estimates in the usual energy and L^(2)*** extension from constant to variable coefficients for the modeling equations is highly *** underlying technical analysis is based on a sequence of projections and *** results confirm the superconvergence theory for second-order elliptic problems with variable coefficients.

关键词： weak Galerkin finite element methods superconvergence second-order elliptic problems stabilizerfree

Divergent contributions of spring and autumn photosynthetic phenology to seasonal carbon uptake of subtropical vegetation in China

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Journal of Geographical Sciences 2024年第7期34卷 1280-1296页

作者： peng Ying LI peng ZHOU Xiaolu LUO Yunpeng ZHANG Cicheng wang Longjun LI Tong peng Changhui School of Geographic Sciences Hunan Normal UniversityChangsha410081China Department for Biogeochemical Integration Max-Planck-Institute for BiogeochemistryJena07745Germany Department of Biology Sciences Institute of Environment SciencesUniversity of Quebec at MontrealC.P.8888Succ.Centre-VilleMontrealH3C 3P8Canada

Phenological changes play a central role in regulating seasonal variation in the ecological processes,exerting significant impacts on hydrologic and nutrient cycles,and ultimately influencing ecosystem functioning such as carbon ***,the potential impact mechanisms of phenological events on seasonal carbon dynamics in subtropical regions are *** knowledge gaps hinder from accurately linking photosynthetic phenology and carbon sequestration *** chlorophyll fluorescence remote sensing and productivity data from 2000 to 2019,we found that an advancement in spring phenology increased spring gross(GPP)and net primary productivity(NPP)in subtropical vegetation of China by 2.1 gC m^(-2)yr^(-1)and 1.4 gC m^(-2)yr^(-1),respectively.A delay in autumn phenology increased the autumnal GPP and NPP by 0.4 gC m^(-2)yr^(-1)and 0.2 gC m^(-2)yr^(-1),***,the contribution of the spring phenology to spring carbon uptake increased significantly during the study period,while this positive contribution showed a nonsignificant trend in *** comparison,the later autumn phenology could significantly contribute to the increase in autumnal carbon uptake;however,this contributing effect was *** analysis indicated that these phenomena have been caused by the increased leaf area and enhanced photosynthesis due to earlier spring and later autumn phenology,*** results demonstrate the diverse impacts of vegetation phenology on the seasonal carbon sequestration ability and it is imperative to consider such asymmetric effects when modeling ecosystem processes parameterized under future climate change.

关键词： subtropics vegetation phenology remote sensing carbon cycle climate change

Two-Dimensional Metallophthalocyanine Nanomaterials for Electrocatalytic Energy Conversion

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Energy & Environmental Materials 2024年第4期7卷 364-385页

作者： Xinqi wang Shaohui Sun Jiahao Yao Hao wan Renzhi Ma Wei Ma School of Chemical Engineering and Zhongyuan Critical Metals Laboratory Zhengzhou University Research Center for Materials Nanoarchitectonics (MANA) National Institute for Materials Science (NIMS)

Crowing energy demand drives the rapid development of clean and reliable energy *** the past years,the exploration of novel materials with considerable efficiency and durability has drawn attention in the area of elec... 详细信息

关键词： conjugated nanostructure electrocatalysis 2D metallophthalocyanines

Effects of physical crust on soil detachment by overland flow in the Loess Plateau region of China

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International Soil and Water Conservation Research 2024年第1期12卷 107-120页

作者： Jiaxin Liu Liding Chen Bing wang Xiaoyu peng School of Ecology and Environmental Science Yunnan UniversityKunming650091China State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau Institute of Soil and Water ConservationNorthwest A&F UniversityYanglingShaanxi712100China University of Chinese Academy of Sciences Beijing100049China

Physical soil crust(PSC),a key component of surface soil structure,exists extensively in loess *** is considered to have a significant effect on soil detachment ***,the long-term effects and the corresponding mechanisms of PSC on soil detachment by overland flow are still not well understood,especially in natural *** investigate temporal variation in soil erosion resistance and the underlying factors during PSC formation,an 8×8-m soil plot was exposed to natural conditions in the Loess Plateau over a 524-day period spanning two rainy seasons and a winter between them.A flume test was conducted to determine soil detachment capacity(Dc)under six designed flow shear stress levels(5.66-22.11 Pa)using crusted(SC)and non-crusted(NSC)soil samples at different PSC development ***,two soil erosion resistance parameters,rill erodibility(K_(r))and critical shear stress(τ_(c)),were *** time,in the SC and NSC treatments,K_(r)decreased from 0.516 to 0.120 s m^(-1)and 0.521 to 0.223 s m^(-1),respectively,whileτ_(c)increased from 0.49 to 4.42 Pa and 0.26-2.46 Pa,*** in soil erosion resistance was rapid in the first one to two months,and then slowed down,with slight fluctuations *** the SC treatment,K_(r)was 42%lower andτ_(c)was 67%greater than those in the NSC *** properties changed greatly for both *** increased from 0 to 7.09 mm in the SC *** increased from 2.91 to 9.04 kPa and 3.01-4.78 kPa in SC and NSC treatments,*** soil erosion resistance parameters could be well predicted by SCT and Coh in the SC treatment(R^(2)≥0.82),while their best predictor was Coh in the NSC treatment(R^(2)≥0.90).The results demonstrate that PSC formation enhances soil erosion resistance in the soil detachment process in the loess region under natural *** study revealed the important role and complexity of PSC in the process of soil erosion,and provided theor

关键词： Physical soil crust formation Soil heterogeneity Rill erodibility Critical shear stress

Effect mechanism of seepage force on the hydraulic fracture propagation

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International Journal of Coal Science & Technology 2024年第3期11卷 223-240页

作者： Haiyang wang Desheng Zhou Yi Zou peng Zheng School of Petroleum Engineering Xi’an Shiyou UniversityXi’an710065China Engineering Research Center of Development and Management for Low to Extra-Low Permeability Oil and Gas Reservoirs in West China Ministry of EducationXi’an Shiyou UniversityXi’an710065ShaanxiChina Xi’an University of Science and Technology Xi’an710054ShaanxiChina

The flow of fluid through the porous matrix of a reservoir rock applies a seepage force to the solid rock *** the seepage force exerted by fluid flow through the porous matrix of a reservoir rock has a notable influence on rock deformation and failure,its effect on hydraulic fracture(HF)propagation remains ***,in this study,we improved a traditional fluid–solid coupling method by incorporating the role of seepage force during the fracturing fluid seepage,using the discrete element ***,we validated the simulation results of the improved method by comparing them with an analytical solution of the seepage force and published experimental ***,we conducted numerical simulations in both homogeneous and heterogeneous sandstone formations to investigate the influence of seepage force on HF *** results indicate that fluid viscosity has a greater impact on the magnitude and extent of seepage force compared to injection rate,and that lower viscosity and injection rate correspond to shorter hydraulic fracture ***,seepage force influences the direction of HF propagation,causing HFs to deflect towards the side of the reservoir with weaker cementation and higher permeability.

关键词： Hydraulic fracturing Seepage force Fracture propagation Discrete element method Reservoir heterogeneity

Pd-catalyzed intermolecular Si–O formation via Si–C activation

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Science China Chemistry 2024年第8期67卷 2661-2669页

作者： Shuang Liu Yu-Shu Chen Yichen Wu peng wang State Key Laboratory of Organometallic Chemistry Shanghai Institute of Organic ChemistryUniversity of Chinese Academy of SciencesShanghai 200032China School of Chemistry and Materials Science Hangzhou Institute for Advanced StudyUniversity of Chinese Academy of SciencesHangzhou 310024China College of Material Chemistry and Chemical Engineering Key Laboratory of Organosilicon Chemistryand Material Technology of Ministry of EducationHangzhou Normal UniversityHangzhou 311121China

The development of efficient Si–O bond formation reaction with 100% atom-economy, excellent functional group tolerance, and broad scope under mild conditions is highly desired due to the prevalence of silanol, silyl ether, and their derivatives in synthetic chemistry and materials science. Here, we have realized the Pd-catalyzed Si–O formation reaction via a Si–C activation approach with 100% atom-economy by employing silacyclobutanes(SCBs) and various hydroxy-containing substrates, including water,alcohols, phenols, and silanols. This protocol features a broad substrate scope, remarkable functional compatibility and mild conditions, providing a series of silanols, silyl ethers in high efficiency. Notably, this protocol could also be used for selective protection of hydroxy functionalities, and for the access of a class of novel polymers containing Si–O main chain. Preliminary mechanistic studies unveiled that this reaction underwent a Pd-catalyzed concerted ring-opening mechanism.

关键词： Si–O formation Si–C activation palladium silacyclobutane silanol silyl ether