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A hybrid contact approach for modeling soil-structure interaction using the material point method

Journal of Rock Mechanics and Geotechnical Engineering 2024年第5期16卷 1864-1882页

作者： Qinyang Sang Yonglin Xiong Rongyue Zheng Xiaohua Bao Guanlin Ye Feng Zhang Key Laboratory of impact and Safety Engineering Ministry of EducationSchool of Mechanical Engineering and MechanicsNingbo UniversityNingbo315211China Institute of Geotechnical Engineering Ningbo UniversityNingbo315211China College of Civil and Transportation Engineering Shenzhen UniversityShenzhen518060China Department of Civil Engineering Shanghai Jiao Tong UniversityShanghai200240China Department of Civil Engineering Nagoya Institute of TechnologyShowa-kuGokiso-choNagoya466-8555Japan

The grid-based multi-velocity field technique has become increasingly popular for simulating the Material Point Method(MPM)in contact ***,this traditional technique has some shortcomings,such as(1)early contact and contact penetration can occur when the contact conditions are unsuitable,and(2)the method is not available for contact problems involving rigid-nonrigid materials,which can cause numerical *** study presents a new hybrid contact approach for the MPM to address these limitations to simulate the soil and structure *** approach combines the advantages of point-point and point-segment contacts to implement contact detection,satisfying the impenetrability condition and smoothing the corner contact *** proposed approach is first validated through a disk test on an inclined ***,several typical cases,such as granular collapse,bearing capacity,and deformation of a flexible retaining wall,are simulated to demonstrate the robustness of the proposed approach compared with FEM or analytical ***,the proposed method is used to simulate the impact of sand flow on a deformable *** results show that the proposed contact approach can well describe the phenomenon of soil-structure interaction problems.

关键词： Material point method Soil-structure interaction Numerical simulation Contact algorithm

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Post deformation analysis of the ballistic impacted magnesium alloys,a short-review

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Journal of Magnesium and Alloys 2021年第5期9卷 1518-1535页

作者： Abdul Malik Yangwei Wang Cheng Huanwu Faisal Nazeer Muhammad Abubaker Khan School of Material Science and Engineering Beijing Institute of TechnologyBeijing 100081China National Key Laboratory of Science and Technology on Materials under Shock and impact Beijing 100081China

From the mechanistic point of view,magnesium alloys are lightweight materials and are receiving increasing attention in the past several years in various *** Zhen from Harbin Institute of Technology,China and the United State military are showing keen interest in the development of magnesium alloys as ballistic resistant ***,their use is still limited owing to low ductility,low formability,and average mechanical *** magnesium alloys components must withstand the shockwave under hypervelocity ballistic *** ballistic testing can produce gradient variations of the strain and stress-energy away from the crater,and useful for the development of these alloys in the military and aerospace ***,the present review article shed light on the post deformation analysis of the Mg alloys subjected to the different projectiles under ballistic impact,and the underlying mechanisms were *** the end,some important issues regarding the ballistic impact and further studies in this field were proposed.

关键词： Ballistic behavior Mg alloys Deformed zones Texture Hardness

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Risk factors for long COVID in children and adolescents:a systematic review and meta-analysis

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World Journal of Pediatrics 2024年第2期20卷 133-142页

作者： Daniel G.Rayner Elaine Wang Cloris Su Om D.Patel Stephanie Aleluya Alessandra Giglia Evelyn Zhu Maha Siddique Department of Health Research Methods Evidenceand ImpactFaculty of Health SciencesMcMaster University1280 Main St WHamiltonONL8S 4K1Canada Faculty of Health Sciences McMaster University1280 Main St WHamiltonON L8S 4K1Canada Faculty of Science McMaster University1280 Main St WHamiltonONL8S 4K1Canada

Background The long-term sequelae of COVID-19 in children and adolescents remain poorly understood and *** systematic review and meta-analysis sought to summarize the risk factors for long COVID in the pediatric *** We searched six databases from January 2020 to May 2023 for observational studies reporting on risk factors for long COVID or persistent symptoms those were present 12 or more weeks post-infection using multivariable regression *** registries,reference lists of included studies,and preprint servers were hand-searched for relevant ***-effects meta-analyses were conducted to pool odds ratios for each risk *** study risk of bias was rated using QUIPS,and the GRADE framework was used to assess the certainty of evidence for each unique *** Sixteen observational studies(N=46,262)were included,and 19 risk factors were amenable to *** moderate certainty in the evidence,age(per 2-year increase),allergic rhinitis,obesity,previous respiratory diseases,hospitalization,severe acute COVID-19,and symptomatic acute COVID-19 are probably associated with an increased risk of long *** sex,asthma,comorbidity,and heart diseases may be associated with an increased risk of long COVID,and Asian and Black races may be associated with a decreased risk of long *** did not observe any credible subgroup effects for any risk *** The current body of literature presents several compelling risk factors for the development of long COVID in the pediatric *** research is necessary to elucidate the pathophysiology of long COVID.

关键词： COVID-19 Long COVID Post-acute COVID-19 syndrome Pediatrics Risk factors

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Fixed-effect and random-effects models in meta-analysis

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Chinese Medical Journal 2024年第1期137卷 1-4页

作者： Chunjuan Zhai Gordon Guyatt Department of Cardiology Shandong Provincial Hospital Affiliated to Shandong First Medical UniversityJinanShandong 250021China Department of Health Research Methods Evidence and ImpactMcMaster UniversityHamilton L8S 4L8OntarioCanada

A systematic review synthesizes evidence addressing a structured clinical question using systematic and explicit methods to search,identify,screen,critically appraise,and extract and analyze data from relevant studies.[1]A meta-analysis,on the other hand,is a statistical method that combines the quantitative results of available primary studies addressing the same question to generate a pooled summary estimate and confidence interval(CI).[2]Meta-analyses can increase statistical power,enhance precision,and answer questions that single trials are underpowered to *** there are systematic reviews where meta-analyses are not appropriate,when they are well-conducted and reported,systematic reviews combined with meta-analyses provide valuable information for clinicians,researchers,and policymakers.

关键词： Fixed analysis effect

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Character of Convective Systems Producing Short-Term Heavy Precipitation in Central China Revealed by Kilometer and Minute Interval Observations

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Journal of Meteorological Research 2024年第3期38卷 530-541页

作者： Zitong CHEN Yunying LI Zhiwei ZHANG Jing SUN Chengzhi YE Anyuan XIONG College of Meteorology and Oceanography National University of Defense TechnologyChangsha410073China High impact Weather Key Laboratory of China Meteorological Administration Changsha410073China Unit No.92192 of Chinese People’s Liberation Army Ningbo315000China Hubei Key Research Laboratory for Heavy Rain Monitoring and Warning Institute of Heavy RainChina Meteorological AdministrationWuhan430223China Institute of Meteorological Sciences of Hunan Province Hunan Meteorological BureauChangsha410118China National Meteorological Information Centre China Meteorological AdministrationBeijing100081China

Accurate forecasting of heavy precipitation in central China is still a challenge,within which a key issue is our still incomplete understanding of the convective systems(CSs)responsible for such *** this study,through use of an iterative rain-cell tracking algorithm,the macroscale characteristics(scale,intensity,duration,etc.)of the CSs that produced 595 short-term heavy precipitation events in Hunan Province,central China,are quantitatively analyzed,based on radar reflectivity,echo top,and rainfall observations at 1-km and 6-min intervals in April-September of *** results show that CSs present significant seasonal and diurnal *** CSs usually cover a larger echo area with stronger convective cores and thus generate more precipitation than summer CSs,though summer CSs develop more vigorously and *** initiated at 1400-1600 local time are characterized by the strongest convection and a smaller spatiotemporal scale,causing violent and transient showers with typical areal precipitation of 0.5-1 mm km^(−2),but less total *** analyses of the relationships among the scale,intensity,duration,and total precipitation of CSs reveal that the convective intensity is linearly correlated to the spatiotemporal scale of CSs,with the duration increasing on average by 0.0372 h dBZ^(−1);the echo area is significantly correlated to the total precipitation,and the duration and rainfall amount are connected with the area expansion rate(AER)of CSs:when the AER exceeds 50%,CSs expand rapidly with increasing total precipitation,but the duration is *** findings provide a helpful reference for the forecasting of short-term heavy precipitation induced by CSs in central China.

关键词： convective system radar reflectivity factor total precipitation iterative rain-cell tracking

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Tuning microstructures of TC4 ELI to improve explosion resistance

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Defence Technology（防务技术） 2024年第3期33卷 78-99页

作者： Changle Zhang Yangwei Wang Lin Wang Zixuan Ning Guoju Li Dongping Chen Zhi-Wei Yan Yuchen Song Xucai Wang School of Materials Science and Engineering Beijing Institute of TechnologyBeijing 100081China National Key Laboratory of Science and Technology on Materials under Shock and impact Beijing 100081China State Key Laboratory of Explosive Science and Technology Beijing Institute of TechnologyBeijing 100081China Aerospace Information Research Institute Chinese Academy of SciencesBeijing 100094China School of Aeronautical Engineering Zhengzhou University of AeronauticsHenan ProvinceZhengzhou 450046China Shanxi Jiangyang Chemical Co. Ltd.Shanxi ProvinceTaiyuan 030041China Shandong Institute of Non-metallic Materials Shandong ProvinceJinan 250031China

A reasonable heat treatment process for TC4 ELI titanium alloy is crucial to tune microstructures to improve its explosion ***,there is limited investigation on tuning microstructures of TC4 ELI to improve explosion ***,the current challenge is quantifying microstructural changes'effects on explosion resistance and incorporating microstructural changes into finite element *** work aims to tune microstructures to improve explosion resistance and elucidate their anti-explosion mechanism,and find a suitable method to incorporate microstructural changes into finite element *** this work,we systematically study the deformation and failure characteristics of TC4 ELI plates with varying microstructures using an air explosion test and LS-DYNA finite element *** Johnson-Cook(JC)constitutive parameters are used to quantify the effects of microstructural changes on explosion resistance and incorporate microstructural changes into finite element *** of the heat treatment,one plate has equiaxed microstructure and the other has bimodal *** convex of the plate after the explosion has a quadratic relationship with the charge mass,and the simulation results demonstrate high reliability,with the error less than 17.5%.Therefore,it is feasible to obtain corresponding JC constitutive parameters based on the differences in microstructures and mechanical properties and characterize the effects of microstructural changes on explosion *** bimodal target exhibits excellent deformation *** response of bimodal microstructure to the shock wave may be more intense under explosive *** well-coordinated structure of the bimodal target enhances its resistance to deformation.

关键词： Microstructure Finite element modelling Parameter optimization Failure characteristics Explosion resistance

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Survivability assessment of spacecraft impacted by orbit debris

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Defence Technology（防务技术） 2021年第3期17卷 961-970页

作者： Di-qi Hu Bao-jun Pang Run-qiang Chi Zhang-chi Song Hao Wu Hypervelocity impact Research Center Harbin Institute of Technology150080HarbinChina Beijing Institute of Aerospace Automatic Control 100854BeijingChina Changchun Institute of Optics Fine Mechanics and PhysicsChinese Academy of Sciences130033ChangchunChina

To help optimize the spacecraft design and reduce the risk of spacecraft mission failure, a new approach to assess the survivability of spacecraft in orbit is presented here, including the following three steps: 1)Sensitivity Analysis of spacecraft. A new sensitivity analysis method, a ray method based on virtual outer wall, is presented here. Using rays to simulate the debris cloud can effectively address the component shadowing issues. 2) Component Vulnerability analysis of spacecraft. A function "Component functional reduction degree-Component physical damage degree" is provided here to clearly describe the component functional reduction. 3) System-level Survivability Assessment of spacecraft. A new method based on expert knowledge reasoning, instead of traditional artificial failure tree method, is presented here to greatly improve the efficiency and accuracy of calculation.

关键词： Survivability Hypervelocity impact Orbit debris Ray method

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Atomistic Investigation of Shock-Induced Amorphization within Micro-shear Bands in Hexagonal Close-Packed Titanium

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Acta Metallurgica Sinica(English Letters) 2024年第9期37卷 1590-1600页

作者： Z.C.Meng K.G.Wang T.Ali D.Li C.G.Bai D.S.Xu S.J.Li A.H.Feng G.J.Cao J.H.Yao Q.B.Fan H.Wang R.Yang Institute of Metal Research Chinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China Interdisciplinary Centre for Additive Manufacturing(ICAM) School of Materials and ChemistryUniversity of Shanghai for Science and TechnologyShanghai 200093China School of Materials Science and Engineering Tongji UniversityShanghai 201804China Key Laboratory for Light-Weight Materials Nanjing Tech UniversityNanjing 210009China National Key Laboratory of Science and Technology on Materials Under Shock and impact School of Materials Science and EngineeringBeijing Institute of TechnologyBeijing 100081China Beijing Institute of Technology Chongqing Innovation Center Chongqing 401135China

The mechanical response of a single crystal titanium sample against(0001)α surface impact was investigated using molecular dynamics ***,non-uniform plastic deformation was observed in the *** high strain rates,amorphization occurred near the edge of the contact region where severe shear strain induced a large number of stacking faults(SFs)and *** contrast,the central part of the contact region underwent less deformation with significantly fewer ***,instead of amorphization by consuming SFs and dislocations,there was a gradual increase in the density of dislocations and SFs during the process of *** local amorphous regions eventually grew into shear bands.

关键词： Shock compression Amorphization Shear band Titanium Molecular dynamics

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Linkage Between European and East Asian Heatwaves on Synoptic Scales

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Journal of Tropical Meteorology 2024年第2期30卷 97-105页

作者：蔡奋颖刘彩红杨崧邓开强 KURTHS Jürgen School of Atmospheric Sciences Sun Yat-sen Universityand Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)ZhuhaiGuangdong 519082 China Department of Complexity Science Potsdam Institute for Climate Impact Research(PIK)Member of the Leibniz AssociationPotsdam 14473 Germany Department of Water and Climate Risk Institute for Environmental StudiesVrije Universiteit AmsterdamAmsterdam 1087HV Netherlands Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies Sun Yat-sen UniversityZhuhaiGuangdong 519082 China Department of Physics Humboldt-Universität zu BerlinBerlin 12489 Germany

Concurrent extreme weather events in geographically distant areas potentially cause high-end risks for *** using network analysis,the present study managed to identify significant nearly-simultaneous occurrences of heatwaves between the grid cells in East Asia and Eastern Europe,even though they are geographically far away from each *** further composite analysis,this study revealed that hot events first occurred in Eastern Europe,typically with a time lag of3-4 days before the East Asian heatwave *** eastward propagating atmospheric wave train,known as the circumglobal teleconnection(CGT)pattern,bridged the sequent occurrences of extreme events in these two remote *** blockings,amplified by surface warming over Eastern Europe,not only enhanced local heat extremes but also excited a CGT-like pattern characterized by alternative anomalies of high and low *** downstream anticyclones in the middle and upper troposphere reduced local cloud cover and increased downward solar radiation,thereby facilitating the formation of heatwaves over East *** half of East Asian heatwave events were preceded by Eastern European heatwave events in the 10-day time range before East Asian heatwave *** investigation of heatwave teleconnection in the two distant regions exhibits strong potential to improve the prediction accuracy of East Asian heatwaves.

关键词： concurrent heatwaves Eastern Europe East Asia circum-global teleconnection pattern

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A study on the application of diffuse axonal multi-axis general evaluation for braininjury assessment in small overlap barrier crash test

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Chinese Journal of Traumatology 2024年第4期27卷 200-210页

作者： Zhi Fu Yi Chang Tao Xiong Wen-Kai Gao Kui Li Yu Liu China Automotive Engineering Research Institute Co. Ltd.Chongqing401122China Chongqing University of Technology Chongqing400054China Chongqing Key Laboratory of Vehicle Crash/Bio-impact and Traffic Safety Chongqing400042China College of Medical Informatics Chongqing Medical UniversityChongqing400016China

Purpose:Head injury criterion(HIC)companied by a rotation-based metric was widely believed to behelpful for head injury prediction in road traffic ***,the Euro-New Car AssessmentProgram utilized a newly developed metric called diffuse axonal multi-axis general evaluation(DAMAGE)to explain test device for human occupant restraint(THOR)head injury,which demonstratedexcellent ability in capturing concussions and diffuse axonal ***,there is still a lack ofcomprehensive understanding regarding the effectiveness of using DAMAGE for Hybrid III 50thpercentile male dummy(H50th)head injury *** objective of this study is to determinewhether the DAMAGE could capture the risk of H50th brain injury during small overlap barrier ***:To achieve this objective,a total of 24 vehicle crash loading curves were collected as input datafor the multi-body *** commercially available mathematical dynamic models,namelyH50th and THOR,were utilized to investigate the differences in head injury ***,adecision method known as simple additive weighting was employed to establish a comprehensive braininjury metric by incorporating the weighted HIC and either DAMAGE or brain injury ***,35 sets of vehicle crash test data were used to analyze these brain injury ***:The rotational displacement of the THOR head is significantly greater than that of the *** maximum linear and rotational head accelerations experienced by H50th and THOR modelswere(544.6±341.7)m/s^(2),(2468.2±1309.4)rad/s^(2) and(715.2±332.8)m/s^(2),(3778.7±1660.6)rad/s^(2),*** the same loading condition during small overlap barrier(SOB)tests,THOR exhibits ahigher risk of head injury compared to the H50th *** was observed that the overall head injuryresponse during the small overlap left test condition is greater than that during the small overlap ***,an equation was formulated to establis

关键词： Diffuse axonal multi-axis general evaluation Head injury criterion Head injury assessment Small overlap barrier Biomechanical response

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