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An Asynchronous Variational integrator for Contact Problems involving Elastoplastic Solids

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Acta Mechanica Solida Sinica 2024年第2期37卷 305-315页

作者： Zongwu niu Zixiao Wang Yongxing Shen Univer.ity of Michigan-Shanghai Jiao Tong Univer.ity Joint institute Shanghai Jiao Tong UniversityShanghai200240China School of Agriculture and Biology Shanghai Jiao Tong UniversityShanghai200240China Department of Biostatistics Johns Hopkins Bloomberg School of Public HealthBaltimoreMaryland21205USA

Simulations of contact problems involving at least one plastic solid may be costly due to their strong nonlinearity and requirements of *** this work,we develop an explicit asynchronous variational integrator(AVi)for.inelastic non-frictional contact problems involving a plastic *** AVi assigns each element in the mesh an independent time step and updates the solution at the elements and nodes *** asynchrony makes the AVi highly efficient in solving such bi-material *** advantage of the AVi,the constitutive update is locally performed in one element at a time,and contact constr.ints are also enforced on only one *** time step of the contact element is subdivided into multiple segments,and the fields are updated *** a contact event,only one element involving a few degrees of freedom is considered,leading to high *** proposed formulation is first verified with a pure elastodynamics benchmark and further applied to a contact problem involving an elastoplastic solid with non-associative volumetric *** numerical results indicate that the AVi exhibits excellent energy behaviors and has high computational efficiency.

关键词： Asynchronous variational integrator Plasticity Contact Computational efficiency Finite element method

Vascularization ability of glioma stem cells in different three-dimensional microenvironments

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regenerative Biomaterials 2024年第1期3卷 34-43页

作者： Xuanzhi Wang Tao Xu Chaoshi niu Department of Neurosurgery The First Affliated Hospital of USTCDivision of Life Sciences and MedicineUniversity of Science and Technology of ChinaHefeiAnhui230036China Department of Neurosurgery Sichuan Provincial People's HospitalUniversity of Electronic Science and Technology of ChinaChengdu 610072People's Republic of China Center for Bio-intelligent Manufacturing and Living Matter Bioprinting Research Institute of Tsinghua University in ShenzhenTsinghua UniversityShenzhen 518057People's Republicof China

Glioblastoma(GBM)is among the most common and aggressive adult central nervous system *** prominent charac-teristic of GBM is the presence of abnormal microvessels.A significant correlation between angiogenesis and prognosis has been *** reconstructing this neovascula-rization and tumor microenvironment through personalized in vitro disease models presents a significant ***,it is crucial to develop new anti-angiogenic therapies for *** this study,3D bioprinted glioma stem cell(GSC)-laden hydrogel scaffolds,hybrid Gsc hydrogels and ceil-free hydrogel scaffolds were manufactured to investigate the vas-cularization ability of GsCs in var.ing 3D microenvironments.

关键词： 3D bioprinting xenograft tumors GSC-laden hydrogel scaffold glioblastoma angiogenesis

An integrative mathematical model of microwave ion thruster for mHz-frequency thrust noise analysis

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Chinese Journal of Aeronautics 2024年第4期37卷 121-136页

作者： Xiang niu Hui LiU Daren YU Plasma Propulsion Laboratory Harbin Institute of TechnologyHarbin 150001China

Many high-precision space missions need thrusters to produce thrust with low noise to compensate for disturbances and ensure satellite platform stability. Microwave ion thruster.is characterized with a wide thrust range and potential for these missions. A cost-effective and accurate mathematical model is crucial for mHz-frequency thrust noise analysis and feedback controller design. The Par.icle-in-Cell(PiC) and global models are two common simulation tools. The PiC model is characterized with high accuracy but huge computation cost, which is difficult to analyze long-time performance characteristics. Now, the global model is only used for the discharge chamber with low accuracy and cannot reflect ion extraction proper.ies. in this paper, an integrative mathematical model is built for a 1-cm microwave ion thruster and can reflect ion beamlet divergence and impingement on the Accelerator Grid(AG). Simulation results show good agreement with experiments at 0.06 sccm. However, the model demonstrates worse consistency with experiments when the flux increases to 0.1 sccm, which may be because the influence of neutral gas on the Electron Cyclotron resonance(ECr) is not considered in the model. A long-time(1000 s) simulation is conducted with this model under 35 μN. it takes 3 hrs, and the thrust noise reaches 1 μN/Hz^(0.5) at 1 mHz.

关键词： Electric propulsion Microwave ion thruster integrative model Sheath property ion beamlet divergence Thrust noise Plasma

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Jackson-type inequalities on high-dimensional spheres

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Science China Mathematics 2024年第11期67卷 2571-2586页

作者： Yeli niu Feng Dai Department of Mathematics Shanghai Normal University Department of Mathematical and Statistical Sciences University of Alberta

We study Jackson's inequality on high-dimensional spheres with respect to the modulus of smoothness defined via the rotation *** obtain a ver.ion of Jackson's inequality with a dimensionfree constant,extending Newman and Shapiro's well-known results in 1964 from the case of r = 1 and p = ∞ to more general *** results par.ially overcome the curse of *** also establish similar results on the equivalence of the K-functional and modulus of smoothness.

关键词： modulus of smoothness $K$-functional Jackson's inequality high-dimensional approximation

Bilayer solid-electrolyte interphase structure enables a 440 Wh kg^(-1) lithium metal pouch cell to achieve 130 cycles

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Science China Chemistry 2024年第3期67卷 751-752页

作者： Xiong Liu Chaojiang niu School of Materials Science and Engineering Zhengzhou UniversityZhengzhou 450001China

Lithium(Li) metal has been considered one of the most promising anodes due to its high theoretical capacity, lightweight and low electrochemical potential. The cell-level energy density of rechargeable lithium metal batteries(LMBs) is expected to surpass 500 Wh kg^(-1) after replacing the graphite anode in lithium-ion batteries [1].

关键词： lithium electrolyte layer

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Modeling tuberous sclerosis complex with human induced pluripotent stem cells

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World Journal of Pediatrics 2024年第3期20卷 208-218页

作者： Weibo niu Benjamin Siciliano Zhexing Wen Department of Psychiatry and Behavioral Sciences Emory University School of MedicineWhitehead Research Building 447615 Michael StreetAtlantaGA 30322USA The Graduate Program in Molecular and Systems Pharmacology Laney Graduate SchoolEmory UniversityAtlanta.GA 30322.USA Department of Cell Biology Emory University School of MedicineWhitehead Research Building 447615 Michael StreetAtlantaGA30322USA Department of Neurology Emory University School of MedicineWhitehead Research Building 447.615 Michael StreetAtlantaGA 30322USA

Background Tuberous sclerosis complex(TSC)is an autosomal dominant genetic disorder with a birth incidence of i:6000 in the United States that is characterized by the growth of non-cancerous tumors in multiple organ systems including the br.in,kidneys,lungs,and ***,TSCis also associated with signicant neurological manifestations including epilepsy TSC-associated neuropsychiatric disorders,intellectual disabilities,and autism spectrum *** in the TSCi or TSC2 genes are well-established causes of TSC,which lead to TSC1/TSC2 deficiency in organs and hyper-activation of the mammalian target of rapamycin signaling *** models have been widely used to study the effect of TSCl/2 genes on the development and function of the *** considerable progress in understanding the molecular mechanisms underlying TSC in animal models,a human-specific model is urgently needed to investigate the effects of TSCl/2 mutations that are unique to human *** sources Literature reviews and research ar.icles were published in PubMed-indexed *** Human-induced pluripotent stem cells(iPSCs),which capture risk alleles that are identical to their donors and have the capacity to differentiate into virtually any cell type in the human body,pave the way for the empirical study of previously inaccessible biological systems such as the developing human *** in this review,we present an over.iew of the recent progress in modeling TSC with human iPSC models,the existing limitations,and potential directions for future research.

关键词： induced pluripotent stem cells Three-dimensional cultures Tuberous sclerosis complex Two-dimensional cultures

The Exchange Attack and the Mixture Differential Attack revisited: From the Perspective of Automatic Evaluation

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Chinese Journal of Electronics 2024年第1期33卷 19-29页

作者： Kexin QiAO Zhiyu ZHANG Zhongfeng niu Liehuang ZHU School of Cyberspace Science and Technology Beijing Institute of Technology State Key Laboratory of Cryptology institute of information Engineering Chinese Academy of Sciences School of Cryptography University of Chinese Academy of Sciences

recent results show that the differential proper.ies within quadruples boom as a new inspiration in cryptanalysis of Advanced Encryption Standard(AES)-like constructions. These methods include the exchange attack proposed in Asiacrypt’19, the mixture differential attack proposed in To SC’18, etc., where the essential proper.ies are obtained by manually scrutinizing the structures of the AES-like constructions. This paper presents a novel framework and an automatic tool based on mixed integer linear programming to search for mixture differential distinguishers for general constructions. This framework considers what equality patterns among quadruples can make a distinguisher and traces how the patterns propagate through cipher components with accurate probability *** this tool, a 5-round AES distinguishing attack with lower complexity and more 6-round distinguishing attacks in the chosen plaintext scenarios are deduced. We prove that no exchange-type or mixture differential distinguisher exists for 7 and above rounds AES if the details of the Sbox and Mix Columns matrix are not taken into account.

关键词： Ciphers Estimation Encryption Mixed integer linear programming Complexity theory Standards

Precise phase adjustment and antibacterial property of copper sulfide par.icles in confined mesoporous silica nanoreactor

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Par.icuology 2024年第2期85卷 113-121页

作者： Shiyu Xu Jinyong Wu Zhongzhen ren Dechao niu Low Dimensional Materials Chemistry Laboratory Key Laboratory for Ultrafine Materials of Ministry of EducationFrontier Science Center of the Materials Biology and Dynamic ChemistryShanghai Engineering Research Center of Hierarchical NanomaterialsSchool of Materials Science and EngineeringEast China University of Science and TechnologyShanghai200237China

Bacteria-caused wound infection greatly threatens human health,thus developing an efficient and safe antibacterial agent without drug resistance is still a great ***,a confined vulcanization strategy is proposed to construct copper sulfides-loaded dual-mesoporous silica nanospheres(Cux-Sy@DMSNs)with various crystal phases for reactive oxygen species(rOS)-mediated and photothermal antibacterial *** the pore confinement of DMSNs,the crystal phases of copper sulfides including CuS,Cu_(9)S_(5)and Cui.96S can be easily controlled by changing the vulcanization *** relationships between the crystal phases and photothermal proper.ies as well as peroxidase-like activity of copper sulfides were systematically *** show that the obtained CuS@DMSNs exhibited higher photothermal ability with remarkable photothermal conver.ion efficiency of 36.86%in the second near.infrared region(Nir.ii)and better peroxidase-like activity,compared to those of Cu_(9)S_(5)@DMSNs and Cu_(1.96)S@*** a result,the in vitro experiments showed the good antibacterial effect against both gram-negative *** and gram-positive *** under 1064 nm laser.irradiation and the presence of H_(2)O_(2).Besides,the CCK-8 assay indicated that CuS@p-DMSNs have minimal cytotoxicity against normal human umbilical vein endothelial cells at the ranged ***,the resultant CuS@p-DMSNs could act as a promising antibacterial agent for deep wound bacterial infection treatment.

关键词： Copper sulfides Mesoporous silica Photothermal reactive oxygen species Antibacterial agent

An active high-static-low-dynamic-stiffness vibration isolator with adjustable buckling beams:theory and experiment

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Applied Mathematics and Mechanics(English Edition) 2024年第3期45卷 425-440页

作者： Kefan XU Muqing niu Yewei ZHANG Liqun CHEN School of Science Harbin Institute of TechnologyShenzhen 518055Guangdong ProvinceChina College of Aerospace Engineering Shenyang Aerospace UniversityShenyang 110136China Shanghai Key Laboratory of Mechanics in Energy Engineering Shanghai Frontier Science Center of MechanoinformaticsShanghai Institute of Applied Mathematics and MechanicsSchool of Mechanics and Engineering ScienceShanghai UniversityShanghai 200444China Shanghai institute of Aircraft Mechanics and Control Shanghai 200092China

High-static-low-dynamic-stiffness(HSLDS)vibration isolators with buckling beams have been widely used to isolate external *** active adjustable device composed of propor.ion integration(Pi)active controllers and piezoelectric actuators is proposed for.improving the negative stiffness stroke of buckling beams.A nonlinear output frequency response function is used to analyze the effect of the vibration *** prototype of the active HSLDS device is built,and the verification experiment is *** results show that compared with the traditional HSLDS vibration isolator,the active HSLDS device can broaden the isolation frequency bandwidth,and effectively reduce the resonant amplitude by adjusting the active control *** maximum vibration reduction rate of the active HSLDS vibration isolator can attain 89.9%,and the resonant frequency can be reduced from 31.08 Hz to 13.28 ***,this paper devotes to providing a new design scheme for enhanced HSLDS vibration isolators.

关键词： active control high-static-low-dynamic-stiffness(HSLDS) vibration isola-tor dynamic analysis

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