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Exponentially Convergent Multiscale Finite Element Method

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Communications on Applied Mathematics and Computation 2024年第2期6卷 862-878页

作者： yifan chen Thomas y.Hou yixuan Wang Applied and Computational Mathematics CaltechPasadena 91106USA

We provide a concise review of the exponentially convergent multiscale finite element method(ExpMsFEM)for efficient model reduction of PDEs in heterogeneous media without scale separation and in high-frequency wave *** ExpMsFEM is built on the non-overlapped domain decomposition in the classical MsFEM while enriching the approximation space systematically to achieve a nearly exponential convergence rate regarding the number of basis *** most generalizations of the MsFEM in the literature,the ExpMsFEM does not rely on any partition of unity *** general,it is necessary to use function representations dependent on the right-hand side to break the algebraic Kolmogorov n-width barrier to achieve exponential ***,there are online and offline parts in the function representation provided by the *** online part depends on the right-hand side locally and can be computed in parallel *** offline part contains basis functions that are used in the Galerkin method to assemble the stiffness matrix;they are all independent of the right-hand side,so the stiffness matrix can be used repeatedly in multi-query scenarios.

关键词： Multiscale method Exponential convergence Helmholtz's equation Domain decomposition Nonlinear model reduction

Five-year long-term outcomes of laparoscopic surgery for colon cancer

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World Journal of Gastroenterology 2010年第39期16卷 4992-4997页

作者： Bai HL chen B Zhou y Wu XT. Department of Gastrointestinal Surgery West China Hospital Sichuan University 37 Guo Xue Rd Chengdu 610041 Sichuan Province China. wxt1@***

AIM:To perform a meta-analysis to answer whether long-term recurrence rates after laparoscopic-assisted surgery are comparable to those reported after open ***:A comprehensive literature search of the MEDLINE database,EMBASE database,and the Cochrane Central Register of Controlled Trials for the years 1991-2010 was *** randomized clinical trials(RCTs)were eligible if they included patients with colon cancer treated by laparoscopic surgery vs open surgery and followed for more than five ***:Three studies involving 2147 patients reported long-term outcomes based on five-year data and were included in the *** overall mortality was similar in the two groups(24.9%,268/1075 in the laparoscopic group and 26.4%,283/1072 in open group).No significant differences between laparoscopic and open surgery were found in overall mortality during the follow-up period of these studies[OR(fixed) 0.92,95%confidence intervals(95%CI):0.76-1.12,P=0.41].No significant difference in the development of overall recurrence was found in colon cancer patients,when comparing laparoscopic and open surgery [2147 pts,19.3%vs 20.0%;OR(fixed)0.96,95% CI:0.78-1.19,P=0.71].CONCLUSION:This meta-analysis suggests that laparoscopic surgery was as efficacious and safe as open surgery for colon cancer,based on the five-year data of these included RCTs.

关键词： Colon cancer Laparoscopic surgery Open surgery Randomized clinical trials Meta-analysis

Behaviors of recycled aggregate concrete-filled steel tubular columns under eccentric loadings

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Frontiers of Structural and Civil Engineering 2019年第3期13卷 628-639页

作者： Vivian W.y.TAM Jianzhuang XIAO Sheng LIU Zixuan chen Department of Structural Engineering Tongji UniversityShanghai 200092China University of Western Sydney School of ComputingEngineering and Mathematics and Institute for Infrastructure EngineeringLocked Bag 1797PenrithNSW 2751Australia

The paper investigates the behaviors of recycled aggregate concrete-filled steel tubular(RACFST)columns under eccentric loadings with the incorporation of expansive agents.A total of 16 RACFST columns were tested in this *** main parameters varied in this study are recycled coarse aggregate replacement percentages(0%,30%,50%,70%,and 100%),expansive agent dosages(0%,8%,and 15%)and an eccentric distance of compressive load from the center of the column(0 and 40 mm).Experimental results showed that the ultimate stresses of RACFST columns decreased with increasing recycled coarse aggregate replacement percentages but appropriate expansive agent dosages can reduce the decrement;the incorporation of expansive agent decreased the ultimate stresses of RACFST columns but an appropriate dosage can increase the deformation *** recycled coarse aggregate replacement percentages have limited influence on the ultimate stresses of the RACFST columns and has more effect than that of the normal aggregate concretesteel tubular columns.

关键词： concrete filled steel tubes recycled aggregate concrete columns expansive agent eccentric load

Multifunctional Nacre-Like Nanocomposite Papers for Electromagnetic Interference Shielding via Heterocyclic Aramid/MXene Template-Assisted In-Situ Polypyrrole Assembly

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NANO-MICRO LETTERS 2025年第1期17卷 1-18页

作者： Xiong, Jinhua Zhao, Xu Liu, Zonglin chen, He yan, Qian Lian, Huanxin chen, yunxiang Peng, Qingyu He, Xiaodong Harbin Inst Technol Ctr Composite Mat & Struct Natl Key Lab Sci & Technol Adv Composites Special Harbin 150080 Peoples R China

The large-scale, high-strength, super-tough, and multifunctional nacre-like heterocyclic aramid (HA)/MXene@polypyrrole (PPy) (HMP) nanocomposite papers were fabricated using the in-situ assembly of PPy onto the HA/MXene hydrogel *** "brick-and-mortar" layered structure and abundant hydrogen-bonding interactions among MXene, PPy, and HA respond cooperatively to external stress and effectively increase the mechanical properties of HMP nanocomposite *** templating effect from HA/MXene was utilized to guide the assembly of conducting polymers, leading to high electrical conductivity and outstanding electromagnetic interference shielding performance. Robust, ultra-flexible, and multifunctional MXene-based electromagnetic interference (EMI) shielding nanocomposite films exhibit enormous potential for applications in artificial intelligence, wireless telecommunication, and portable/wearable electronic equipment. In this work, a nacre-inspired multifunctional heterocyclic aramid (HA)/MXene@polypyrrole (PPy) (HMP) nanocomposite paper with large-scale, high strength, super toughness, and excellent tolerance to complex conditions is fabricated through the strategy of HA/MXene hydrogel template-assisted in-situ assembly of PPy. Benefiting from the "brick-and-mortar" layered structure and the strong hydrogen-bonding interactions among MXene, HA, and PPy, the paper exhibits remarkable mechanical performances, including high tensile strength (309.7 MPa), outstanding toughness (57.6 MJ m-3), exceptional foldability, and structural stability against ultrasonication. By using the template effect of HA/MXene to guide the assembly of conductive polymers, the synthesized paper obtains excellent electronic conductivity. More importantly, the highly continuous conductive path enables the nanocomposite paper to achieve a splendid EMI shielding effectiveness (EMI SE) of 54.1 dB at an ultra-thin thickness (25.4 mu m) and a high specific EMI SE of 17,204.7 dB cm2 g-1. In addit

关键词： MXene Remarkable mechanical properties Heterocyclic aramid Electromagnetic interference shielding Polypyrrole Multifunctionality

IMPROVEMENT OF BUBBLE MODEL FOR CAVITATING FLOW SIMULATIONS

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Journal of Hydrodynamics 2009年第1期21卷 41-46页

作者： TAMURA y. MATSUMOTO y. Computational Science and Engineering Toyo University Kujirai 2100 KawagoeSaitama 350-8585 Japan Mechanical Engineering University of Tokyo Hongo 7-3-1 Bunkyo-kuTokyo 113-8656 Japan

In the present research, a bubble dynamics based model for cavitating flow simulations is extended to higher void fraction region for wider range of applications. The present bubble model is based on the so-called Rayleigh-Plesset equation that calculates a temporal bubble radius with the surrounding liquid pressure and is considered to be valid in an area below a certain void fraction. The solution algorithm is modified so that the Rayleigh-Plesset equation is no more solved once the bubble radius （or void fraction） reaches at a certain value till the liquid pressure recovers above the vapor pressure in order to overcome this problem. This procedure is expected to stabilize the numerical calculation. The results of simple two-dimensional flow field are presented compared with the existing bubble model.

关键词： cavitation model Computational Fluid Dynamics (CFD) cavitation flow Rayleigh-Plesset equation

Mesospheric tide comparisons at low latitudes observed by two collocated meteor radars

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Earth and Planetary Physics 2025年第1期9卷 54-68页

作者： Jian Li Wen yi XiangHui Xue Jie Zeng HaiLun ye Jianyuan Wang JinSong chen Na Li TingDi chen Chinese Academy of Sciences(CAS)Key Laboratory of Geospace Environment Department of Geophysics and Planetary SciencesUniversity of Science and Technology of ChinaHefei 230026China CAS Center for Excellence in Comparative Planetology Anhui Mengcheng Geophysics National Observation and Research StationUniversity of Science and Technology of ChinaHefei 230026China Hefei National Laboratory University of Science and Technology of ChinaHefei 230026China Collaborative Innovation Center of Astronautical Science and Technology Harbin 150001China National Key Laboratory of Electromagnetic Environment China Research Institute of Radiowave PropagationQingdao 266107China yunnan Kunming Electromagnetic Environment National Observation and Research Station Qujing Kunming 655000China

Accurate knowledge of mesospheric winds and waves is essential for studying the dynamics and climate in the mesosphere and lower thermosphere(MLT)*** this study,we conduct a comparative analysis of the mesosphere tidal results obtained from two adjacent meteor radars at low latitudes in Kunming,China,from November 2013 to December *** two radars operate at different frequencies of 37.5 MHz and 53.1 MHz,***,overall good agreement is observed between the two radars in terms of horizontal winds and tide *** results show that the dominant tidal waves of the zonal and meridional winds are diurnal and semidiurnal ***,we conduct an exhaustive statistical analysis to compare the tidal amplitudes and vertical wavelengths recorded by the dual radar systems,which reveals a high degree of alignment in tidal *** investigation includes variances and covariances of tidal amplitudes,which demonstrate remarkable consistency across measurements from both *** finding highlights clear uniformity in the mesospheric tidal patterns observed at low latitudes by the two neighboring meteor *** of the comparative analysis specifically underscore the significant correlation in vertical wavelength measurements,validating the robustness of radar observations for tidal research.

关键词： mesosphere and lower thermosphere region meteor radar mesospheric winds tides

Creep Behavior and Microstructure Evolution of Sand–Cast Mg–4y–2.3Nd–1Gd–0.6Zr Alloy Crept at 523–573 K

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Journal of Materials Science & Technology 2017年第1期33卷 79-89页

作者： y.H.Kang H.yan R.S.chen The Group of Magnesium Alloys and Their Applications Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China University of the Chinese Academy of Sciences Beijing 100049China

High temperature tensile-creep behavior of Mg-4y-2.3Nd-IGd-O.6Zr （wt%, WE43（T6）） alloy at 523- 573 K was investigated. The creep stress exponent is equal to 4.6, suggesting the underlying dislocation creep mechanism. The activation energy is （199 _＋ 23） kJ/mol, which is higher than that for self- diffusion in Mg and is believed to be associated with precipitates coarsening or cross slip. The creep mechanism is further suggested to be dislocation climb at 523 K, while a cross slip at 573 K is possible. The metastable 13＇ and ~]1 phases in the WE43（T6） alloy were relatively thermal stable at 523 K and could be effective to hinder the dislocation climb, which contributed to its excellent creep resistance. However, at 573 K it readily transforms into equilibrium/3e phase and coarsens within two hours, thereby causing a decrease of creep resistance. In addition, precipitate free zones approximately normal to applied stress direction （directional PFZs） developed during the creep deformation, especially at 573 K. Those zones became preferential sites to nucleate, extend and connect microcracks and cavities, which lead to the intergranular creep fracture. Improving the thermal stability of precipitates or introducing thermally stable fine plate-shaped precipitates on the basal planes of Mg matrix could enhance the high temperature creep resistance.

关键词： WE43 alloy Creep PFZs Precipitate Fracture

New methods to find solutions and analyze stability of equilibrium of nonholonomic mechanical systems

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Acta Mechanica Sinica 2018年第6期34卷 1136-1144页

作者： J.chen y.X.Guo F.X.Mei School of Aerospace Engineering Beijing Institute of TechnologyBeijing 100081China School of Physics Liaoning UniversityShenyang 110000China

A large proportion of constrained mechanical systems result in nonlinear ordinary differential equations,for which it is quite difficult to find analytical *** initial motions method proposed by Whittaker is effective to deal with such problems for various constrained mechanical systems,including the nonholonomic systems discussed in the first part of this paper,where in addition to differential equations of motion,nonholonomic constraints *** final equations of motion for these systems are obtained in the form of corresponding power ***,an alternative,direct method to determine the initial values of higher-order derivatives(q)0,(q)0,…is proposed,being different from that of *** second part of this work analyzes the stability of equilibrium of less complex,nonholonomic mechanical systems represented by gradient *** discuss the stability of equilibrium of such systems based on the properties of the gradient *** advantage of this novel method is its avoidance of the difficulty of directly establishing Lyapunov functions aimed at such unsteady nonlinear ***,these theoretical considerations are illustrated through four examples.

关键词： Nonholonomic system Initial motions Gradient system Lyapunov function Stability

Microstructure and Strain Hardening of a Friction Stir Welded High-Strength Al–Zn–Mg Alloy

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Acta Metallurgica Sinica(English Letters) 2014年第4期27卷 723-729页

作者： A.H.Feng D.L.chen Z.y.Ma W.y.Ma R.J.Song School of Materials Science and Engineering Tongji University State Key Laboratory of Advanced Welding Production Technology School of Materials Science and EngineeringHarbin Institute of Technology Department of Mechanical and Industrial Engineering Ryerson UniversityTorontoON M5B 2K3Canada Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences

Microstructural evolution and strain hardening behavior of a friction stir welded（FSWed） high-strength7075Al-T651 alloy were *** nugget zone was observed to consist of fine and equiaxed recrystallized grains with a low dislocation density and free of original precipitates,but containing uniformly distributed *** strength,joint efficiency,and ductility of the FSWed joints increased with increasing welding speed.A joint efficiency of ＊91% was achieved at a welding speed of 400 mm/min and rotational rate of 800 r/min,while the ductility remained basically the same as that of the base *** was no obvious strain rate sensitivity observed in both base metal and welded *** both the base metal and FSWed joints exhibited stage III and IV hardening characteristics,the hardening capacity,strain hardening exponent,and strain hardening rate all increased after friction stir welding.

关键词： Aluminum alloy Friction stir welding Mechanical properties Strain hardening