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Controlling the Si/C ratio in SiC matrix based on the modified polymethysilane for C/C-SiC composites with enhanced mechanical properties

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Journal of Advanced Ceramics 2024年第2期13卷 220-236页

作者： Mingdong Liao Xiebo Hu Chenghao Zhong Ping Xu Xiaodong Wang Ze zhang Peng Zhou mingyu zhang Zhean Su Qizhong Huang National Key Laboratory of Science and Technology on High-Strength Structural Materials Central South UniversityChangsha 410083China

Fabricating SiC matrix with controllable Si/C ratio for C/C-SiC composites via precursor infiltration and pyrolysis is difficult to realize due to the absence of suitable precursors.Here,SiC precursors with Si-rich(Si/C=1.23),nearstoichiometric(Si/C=1.01),and C-rich(Si/C=0.88)pyrolyzed ceramics at 1200℃ were successfully synthesized by the novel modification of polymethysilane.The structure and ceramization of synthesized SiC precursors were studied,and C/C-SiC composites with similar Si/C ratio in SiC matrix were also fabricated.The results revealed that the defects and Young’s modulus of SiC matrix and the thermal residual stress on pyrolytic carbon coated carbon fiber were determined by the Si/C ratio.As a result,the Si/C ratio exerted significant effects on the crack deflection behavior and the mechanical properties of the composites.The composites with near-stoichiometric SiC matrix showed excellent mechanical properties because of the effective crack deflection and the moderate Young’s modulus of their SiC matrix.The flexural strength,flexural modulus,and compressive strength were 423±27 MPa,33.41±4.52 GPa,and 393±8 MPa,respectively.Meanwhile,after a heat treatment at 1600℃,the role of carbon fiber toughening was improved and accompanied by a decrease in mechanical properties for all composites,which was attributed to the increased defects in SiC matrix and the damaged interfaces by the thermal residual stress.

关键词： SiC precursor Si/C ratio polymethysilane C/C–SiC composites mechanical properties

Statistical study of magnetic holes in the upstream region of Mercury’s bow shock

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Earth and Planetary Physics 2024年第2期8卷 326-337页

作者： GuoQiang Wang SuDong Xiao mingyu Wu YuanQiang Chen TieLong zhang Institute of Space Science and Applied Technology Harbin Institute of TechnologyShenzhen 518055China Shenzhen Key Laboratory of Numerical Prediction for Space Storm Harbin Institute of TechnologyShenzhen 518055China Mengcheng National Geophysical Observatory University of Science and Technology of ChinaHefei 230026China Chinese Academy of Sciences Center for Excellence in Comparative Planetology Hefei 230026China Space Research Institute Austrian Academy of SciencesGrazAustria

Magnetic holes are magnetic depression structures that exist widely in many plasma environments.The magnetic holes with durations of>1 s in the solar wind at Mercury’s orbit have drawn much attention,but the properties of the magnetic holes with shorter durations are still unclear.Here,we investigate the magnetic holes with durations of 0.1-100 s in the upstream region of Mercury’s bow shock based on observations by the MESSENGER(MErcury Surface,Space ENvironment,GEochemistry,and Ranging)spacecraft.They can be divided into two groups according to the distribution of their duration:small-duration magnetic holes(SDMHs,0.6 s).The duration of each group approximately obeys a log-normal distribution with a median of~0.25 s and 3 s,respectively.Approximately 1.7%(32.6%)of the SDMHs(LDMHs)reduce the magnetic field strength by more than 50%.For both groups,some structures have a linear or quasi-linear polarization,whereas others have an elliptical polarization.The magnetic hole events in both groups tend to have a higher rate of occurrence when the interplanetary magnetic field strength is weaker.Their occurrence rates are also affected by Mercury’s foreshock,which can increase(decrease)the occurrence rate of the SDMHs(LDMHs).This finding suggests that Mercury’s foreshock might be one source of the SDMHs and that the foreshock can destroy some LDMHs.These observations suggest that a new group of magnetic holes with durations of<0.6 s exist in the upstream region of Mercury’s bow shock.

关键词： magnetic hole solar wind Mercury foreshock

High-frequency repetitive transcranial magnetic stimulation promotes neural stem cell proliferation after ischemic stroke

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Neural Regeneration Research 2024年第8期19卷 1772-1780页

作者： Jing Luo Yuan Feng Zhongqiu Hong mingyu Yin Haiqing Zheng Liying zhang Xiquan Hu Department of Rehabilitation Medicine The Third Affiliated HospitalSun Yat-sen UniversityGuangzhouGuangdong ProvinceChina Department of Hepatobiliary Surgery The Third Affiliated HospitalSun Yat-sen UniversityGuangzhouGuangdong ProvinceChina

Prolife ration of neural stem cells is crucial for promoting neuronal regeneration and repairing cerebral infarction damage.Transcranial magnetic stimulation(TMS)has recently emerged as a tool for inducing endogenous neural stem cell regeneration,but its underlying mechanisms remain unclea r In this study,we found that repetitive TMS effectively promotes the proliferation of oxygen-glucose deprived neural stem cells.Additionally,repetitive TMS reduced the volume of cerebral infa rction in a rat model of ischemic stro ke caused by middle cerebral artery occlusion,im p roved rat cognitive function,and promoted the proliferation of neural stem cells in the ischemic penumbra.RNA-sequencing found that repetitive TMS activated the Wnt signaling pathway in the ischemic penumbra of rats with cerebral ischemia.Furthermore,PCR analysis revealed that repetitive TMS promoted AKT phosphorylation,leading to an increase in mRNA levels of cell cycle-related proteins such as Cdk2 and Cdk4.This effect was also associated with activation of the glycogen synthase kinase 3β/β-catenin signaling pathway,which ultimately promotes the prolife ration of neural stem cells.Subsequently,we validated the effect of repetitive TMS on AKT phosphorylation.We found that repetitive TMS promoted Ca2+influx into neural stem cells by activating the P2 calcium channel/calmodulin pathway,thereby promoting AKT phosphorylation and activating the glycogen synthase kinase 3β/β-catenin pathway.These findings indicate that repetitive TMS can promote the proliferation of endogenous neural stem cells through a Ca2+influx-dependent phosphorylated AKT/glycogen synthase kinase 3β/β-catenin signaling pathway.This study has produced pioneering res ults on the intrinsic mechanism of repetitive TMS to promote neural function recove ry after ischemic stro ke.These results provide a stro ng scientific foundation for the clinical application of repetitive TMS.Moreover,repetitive TMS treatment may not only be an efficient and potential approach to support neurogenesis for

关键词： AKT/β-catenin signaling brain stimulation Ca2+influx cell proliferation ischemic stroke middle cerebral artery occlusion neural stem cells neurological rehabilitation repetitive transcranial magnetic stimulation

Spatiotemporal variation of land surface temperature and its driving factors in Xinjiang,China

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Journal of Arid Land 2024年第3期16卷 373-395页

作者： zhang mingyu CAO Yu zhang Zhengyong zhang Xueying LIU Lin CHEN Hongjin GAO Yu YU Fengchen LIU Xinyi College of Sciences Shihezi UniversityShihezi 832000China Key Laboratory of Oasis Town and Mountain-Basin System Ecology Xinjiang Production and Construction CorpsShihezi 832000China Yantai Institute of Coastal Zone Research Chinese Academy of SciencesYantai 264003China

Land surface temperature(LST) directly affects the energy balance of terrestrial surface systems and impacts regional resources, ecosystem evolution, and ecosystem structures. Xinjiang Uygur Autonomous Region is located at the arid Northwest China and is extremely sensitive to climate change. There is an urgent need to understand the distribution patterns of LST in this area and quantitatively measure the nature and intensity of the impacts of the major driving factors from a spatial perspective, as well as elucidate the formation mechanisms. In this study, we used the MOD11C3 LST product developed on the basis of Moderate Resolution Imaging Spectroradiometer(MODIS) to conduct regression analysis and determine the spatiotemporal variation and differentiation pattern of LST in Xinjiang from 2000 to 2020. We analyzed the driving mechanisms of spatial heterogeneity of LST in Xinjiang and the six geomorphic zones(the Altay Mountains, Junggar Basin, Tianshan Mountains, Tarim Basin, Turpan-Hami(Tuha) Basin, and Pakakuna Mountain Group) using geographical detector(Geodetector) and geographically weighted regression(GWR) models. The warming rate of LST in Xinjiang during the study period was 0.24℃/10a, and the spatial distribution pattern of LST had obvious topographic imprints, with 87.20% of the warming zone located in the Gobi desert and areas with frequent human activities, and the cooling zone mainly located in the mountainous areas. The seasonal LST in Xinjiang was at a cooling rate of 0.09℃/10a in autumn, and showed a warming trend in other seasons. Digital elevation model(DEM), latitude, wind speed, precipitation, normalized difference vegetation index(NDVI), and sunshine duration in the single-factor and interactive detections were the key factors driving the LST changes. The direction and intensity of each major driving factor on the spatial variations of LST in the study area were heterogeneous. The negative feedback effect of DEM on the spatial differentiation of LST was the strongest. Lower latitudes, lower

关键词： land surface temperature MOD11C3 climate change geographical detector(Geodetector) geographically weighted regression(GWR) source-sink effect Xinjiang

A systematic review of the inequality of health burdens related to climate change

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Frontiers of Environmental Science & Engineering 2024年第5期18卷 137-153页

作者： Xinke Song Shihui zhang Hai Huang Qun Ding Fang Guo Yaxin zhang Jin Li mingyu Li Wenjia Cai Can Wang State Key Joint Laboratory of Environment Simulation and Pollution Control School of EnvironmentTsinghua UniversityBeijing100084China Department of Earth System Science Tsinghua UniversityBeijing100084China

Climate change significantly impacts human health,exacerbating existing health inequalities and creating new ones.This study addresses the lack of systematic review in this area by analyzing 2440 publications,focusing on four key terms:health,disparities,environmental factors,and climate change.Strict inclusion criteria limited the selection to English-language,peer-reviewed articles related to climate health hazards,ensuring the relevance and rigor of the synthesized studies.This process synthesized 65 relevant studies.Our investigation revealed that recent research,predominantly from developed countries,has broadened its scope beyond temperature-related impacts to encompass diverse climate hazards,including droughts,extreme weather,floods,mental health issues,and the intersecting effects of Coronavirus Disease 2019.Research has highlighted exposure as the most studied element in the causal chain of climate change-related health inequalities,followed by adaptive capability and inherent sensitivity.The most significant vulnerabilities were observed among populations with low socioeconomic status,ethnic minorities,and women.The study further reveals research biases and methodological limitations,such as the paucity of attention to underdeveloped regions,a narrow focus on non-temperature-related hazards,challenges in attributing climate change effects,and a deficit of large-scale empirical studies.The findings call for more innovative research approaches and a holistic integration of physical,socio-political,and economic dimensions to enrich climate-health discourse and inform equitable policy-making.

关键词： Climate change Health impact Human well-being Inequality Vulnerability

Transformation of long-period stacking ordered structures in Mg-Gd-Y-Zn alloys upon synergistic characterization of first-principles calculation and experiment and its effects on mechanical properties

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Journal of Magnesium and Alloys 2024年第5期12卷 1867-1879页

作者： mingyu Li Guangzong zhang Siqi Yin Changfeng Wang Ying Fu Chenyang Gu Renguo Guan School of Materials Science and Engineering Northeastern University Key Laboratory of Near-Net Forming of Light Metals of Liaoning Province Dalian Jiaotong University Engineering Research Center of Continuous Extrusion Ministry of Education Dalian Jiaotong University Songshan Lake Materials Laboratory

Based on experiments and first-principles calculations, the microstructures and mechanical properties of as-cast and solution treated Mg-10Gd-4Y-xZn-0.6Zr(x = 0, 1, 2, wt.%) alloys are investigated. The transformation process of long-period stacking ordered(LPSO) structure during solidification and heat treatment and its effect on the mechanical properties of experimental alloys are discussed. Results reveal that the stacking faults and 18R LPSO phases appear in the as-cast Mg-10Gd-4Y-1Zn-0.6Zr and Mg-10Gd-4Y-2Zn-0.6Zr alloys, respectively.After solution treatment, the stacking faults and 18R LPSO phase transform into 14H LPSO phase. The Enthalpies of formation and reaction energy of 14H and 18R LPSO are calculated based on first-principles. Results show that the alloying ability of 18R is stronger than that of 14H. The reaction energies show that the 14H LPSO phase is more stable than the 18R LPSO. The elastic properties of the 14H and 18R LPSO phases are also evaluated by first-principles calculations, and the results are in good agreement with the experimental results.The precipitation of LPSO phase improves the tensile strength, yield strength and elongation of the alloy. After solution treatment, the Mg-10Gd-4Y-2Zn-0.6Zr alloy has the best mechanical properties, and its ultimate tensile strength and yield strength are 278.7 MPa and 196.4 MPa, respectively. The elongation of Mg-10Gd-4Y-2Zn-0.6Zr reaches 15.1, which is higher than that of Mg-10Gd-4Y0.6Zr alloy. The improving mechanism of elastic modulus by the LPSO phases and the influence on the alloy mechanical properties are also analyzed.

关键词： Mg-Gd-Y-Zn alloys Long-period stacking ordered First-principles calculations Enthalpies Mechanical properties

Zokor activity promotes soil water infiltration in the Mu Us sandy land of northern Shaanxi,China

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Pedosphere 2024年第1期34卷 136-145页

作者： Miao GAN Xuchao ZHU Xueqin YANG Xiaorong WEI Qingyin zhang Tongchuan LI Ming'an SHAO Meixia MI Xi YANG mingyu CHEN State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau Northwest A&F UniversityYangling 712100China College of Natural Resources and Environment Northwest A&F UniversityYangling 712100China State Key Laboratory of Soil and Sustainable Agriculture Institute of Soil ScienceChinese Academy of SciencesNanjing 210008China Henan Institute of Science and Technology Xinxiang 453003China College of Urban and Rural Construction Shanxi Agricultural UniversityJinzhong 030801China

Zokors are common subterranean rodents that inhabit agricultural fields, shrublands, and grasslands in the arid and semi-arid regions of China. Zokor burrowing activities can alter soil structure and affect soil hydrological processes;however, there are few studies regarding their effects on soil preferential flow in the Mu Us sandy land. An evaluation of the effects of zokor disturbance on their habitat and soil water is important for understanding the ecological role of zokors in the soil ecosystem of the Mu Us sandy land. A field dye-tracing experiment was conducted in the Gechougou watershed on the southeastern edge of the Mu Us sandy land to investigate the effect of zokor burrowing activity on soil preferential flow characteristics. Our results showed that the density of zokor tunnels was the highest(0.40–0.46 m m^(-2)) under 30%–50% vegetation coverage and that the tunnels were approximately 3 cm from the surface.Both stained area ratio and stained path number were higher at sites with zokors than without zokors. Stained path widths were 10–80 and > 80 mm at zokor-harboring sites exhibiting homogeneous flow and heterogeneous finger flow, respectively. In the absence of zokors, homogeneous flow and highly interacted macropore flow were predominant. Soil water content below the zokor tunnels was higher than that above the tunnels. Moderate disturbance of soil structure by zokor activity facilitated soil water infiltration. These results enabled a better understanding of the effect of soil fauna on soil structure and hydrological processes and provided recommendations for ecological construction and renovation in arid and semi-arid regions.

关键词： eld dye-tracing experiment preferential flow soil fauna stained area ratio stained path number stained path width subterranean rodent surface tortoise crack

Beyond microbial carbon use efficiency

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National Science Review 2024年第4期11卷 33-35页

作者： Ke-Qing Xiao Chao Liang Zimeng Wang Jingjing Peng Yao Zhao Ming zhang mingyu Zhao Shuiqing Chen Yong-Guan Zhu Caroline L.Peacock State Key Lab of Urban and Regional Ecology Research Center for Eco-Environmental SciencesChinese Academy of Sciences University of Chinese Academy of Sciences Institute of Applied Ecology Chinese Academy of Sciences Department of Environmental Science and Engineering Fudan University College of Resources and Environmental Sciences China Agricultural University State Key Laboratory of Environmental Criteria and Risk Assessment Chinese Research Academy of Environmental Sciences State Key Laboratory of Agricultural Microbiology College of Resources and Environment Huazhong Agricultural University Key Laboratory of Cenozoic Geology and Environment Institute of Geology and Geophysics Chinese Academy of Sciences School of Earth and Environment University of Leeds

Microbial carbon use efficiency (CUE)is defined as the proportion of microbial biomass growth C versus substrate C uptake, and thus provides a useful measure of microbially driven accumulation and loss of soil organic carbon (SOC)[1]. In a recent study published in Nature [2],the authors used a data-driven machinelearning approach to conclude that CUE promotes global SOC storage based on a positive correlation between CUE and SOC content and that, based on sensitivity analysis, CUE is at least four times as important as six other evaluated factors,namely plant C inputs, C input allocation, non-microbial C transfer, substrate decomposability, environmental modifications and vertical transport.

关键词： SOIL-CARBON ORGANIC-MATTER

Improved Unit Commitment with Accurate Dynamic Scenarios Clustering Based on Multi-Parametric Programming and Benders Decomposition

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Energy Engineering 2024年第6期121卷 1557-1576页

作者： zhang Zhi Haiyu Huang Wei Xiong Yijia Zhou mingyu Yan Shaolian Xia Baofeng Jiang Renbin Su Xichen Tian State Grid Corporation of China Beijing100031China Central China Branch State Grid Corporation of ChinaWuhan430077China School of Electric and Electronic Engineering Huazhong University of Science and TechnologyWuhan430074China China Electric Power Research Institute Co. Ltd.Beijing100192China

Stochastic unit commitment is one of the most powerful methods to address uncertainty. However, the existingscenario clustering technique for stochastic unit commitment cannot accurately select representative scenarios,which threatens the robustness of stochastic unit commitment and hinders its application. This paper providesa stochastic unit commitment with dynamic scenario clustering based on multi-parametric programming andBenders decomposition. The stochastic unit commitment is solved via the Benders decomposition, which decouplesthe primal problem into the master problem and two types of subproblems. In the master problem, the committedgenerator is determined, while the feasibility and optimality of generator output are checked in these twosubproblems. Scenarios are dynamically clustered during the subproblem solution process through the multiparametric programming with respect to the solution of the master problem. In other words, multiple scenariosare clustered into several representative scenarios after the subproblem is solved, and the Benders cut obtainedby the representative scenario is generated for the master problem. Different from the conventional stochasticunit commitment, the proposed approach integrates scenario clustering into the Benders decomposition solutionprocess. Such a clustering approach could accurately cluster representative scenarios that have impacts on theunit commitment. The proposed method is tested on a 6-bus system and the modified IEEE 118-bus system.Numerical results illustrate the effectiveness of the proposed method in clustering scenarios. Compared withthe conventional clustering method, the proposed method can accurately select representative scenarios whilemitigating computational burden, thus guaranteeing the robustness of unit commitment.

关键词： Stochastic programming unit commitment scenarios clustering Benders decomposition multi-parametric programming