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Journal of Materials Science & Technology 2022年第34期129卷 96-107页

作者： h.R.zhang h.z.niu M.C.zang Y.h.zhang S.Liu D.L.zhang School of Materials Science and Engineering Northeastern UniversityShenyang 110819China State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110819China

An extra-low interstitial near alpha alloy Ti-3Al-2zr-2Mo(wt%) was fabricated by hydrogenation and thermomechanical consolidation(TMC) of the coarse and spherical pre-alloyed powder with particle sizes of 60 to 270 μm. The coarse powder is a byproduct of pre-alloyed powder produced for selective laser and electron beam additive manufacturing. The TMC process involves powder compaction, fast sintering,in-situ dehydrogenation and an immediate hot extrusion to form a fully dense and fine-grained martensitic microstructure. Further dehydrogenation in vaccum at 700 °C converted the martensitic microstructure into an interwoven α/β microstructure which exhibited an improved yield strength, apparent necking and premature cracking at grain boundary α(α_(GB)) ribbons. A further annealing of 880 ℃/1 h/AC led to the formation of a fine-grained α/β_(t)composite structure, which achieved an enhance ultimate tensile strength of 835 MPa and excellent tensile ductility of 16.0%. Analysis of the deformation behavior of the alloy in different states revealed that the α/β_(t)composite structures brought about an enhanced strain hardening capability by heterogeneous deformation effect of hard β_(t)and soft α-laths, which inhibited the formation of microcracks and consequently improved the coordinated deformation.

关键词： Nearα-Ti alloy Coarse pre-alloyed powder hydrogenation Tensile properties Deformation behaviour

Rational design of AgGaS/znS/znS quantum dots with a near-unity photoluminescence quantum yield via double shelling scheme

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Journal of Materials Science & Technology 2024年第2期169卷 235-242页

作者： h.X.Lu h.Liu z.z.Fu Y.Y.Chen h.Q.Dai z.hu W.L.zhang R.Q.Guo Institute for Electric Light Sources School of Information Science and TechnologyFudan UniversityShanghai 200433China Institute of Future Lighting Academy for Engineering and TechnologyFudan UniversityShanghai 200433China Yiwu Research Institute of Fudan University YiwuZhejiang 322000China zhongshan-Fudan Joint Innovation Center Zhongshan 528437China

In this study,a two-step method was used to synthesize highly luminescent AgGaS/znS/znS quantum dots(QDs).In the first step,an inner znS shell was formed via a one-pot method,which resulted in a smaller lattice mismatch between the AgGaS core and the outer znS shell,thereby facilitating the formation of a thick outer *** the two-step shelling process,the synthesized AgGaS/znS/znS QDs showed an excellent photoluminescence quantum yield(PLQY)of 96.4%with a peak wavelength of 508 nm,repre-senting the highest PLQY reported thus far for AgGaS ***,the effect of halogen ions in zn precursors on the shelling process was *** was proposed that the capacity of halogen ions to coordinate with the QDs influenced the balance between zn cation diffusion and znS shelling ***,the znS shelling reaction was dominant when znCl_(2)was employed,while zn cation diffusion was the dominant process under the I^(−)-rich *** work provides insights into the interfacial restructuring during the znS shelling and offers a clear map for the tailored synthesis of core/shell QDs.

关键词： AgGaS Quantum dots Photoluminescence Core/shell Alloyed core/shell interface

Design and Verification of Parallel hip Exoskeleton Considering Output Torque Anisotropy

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Journal of Bionic Engineering 2024年第3期21卷 1305-1320页

作者： Jilong Xu Yunzhan niu Fucai Liu Engineering Research Center of the Ministry of Education for Intelligent Control System and Intelligent Equipment Yanshan UniversityQinhuangdao066004China Key Laboratory of Industrial Computer Control Engineering of heibei Province Yanshan UniversityQinhuangdao066004China College of Mechanical Engineering Yanshan UniversityQinhuangdao066004China

In rehabilitation training,it is crucial to consider the compatibility between exoskeletons and human legs in ***,most exoskeletons today adopt an anthropomorphic serial structure,which results in rotational centers that are not precisely aligned with the center of the hip *** address this issue,we introduce a novel exoskeleton called the Parallel hip Exoskeleton(Ph-Exo)in this ***-Exo is meticulously designed based on the anisotropic law of output *** the friction of the drive components,a dynamic model of the human-machine complex is *** analysis demonstrates that Ph-Exo not only exhibits outstanding torque performance but also achieves high controllability in both flexion/extension and adduction/abduction ***,a robust controller is designed to address model uncertainty,friction,and external *** experiments indicate that under the control of the robust controller,each motor achieves excellent tracking performance.

关键词： hip exoskeleton Parallel mechanism Misalignment Anisotropy Output torque

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 University of Michigan-Shanghai Jiao Tong University 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 constraints 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

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 Particle-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 properties. 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

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 varying 3D microenvironments.

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

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 version 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 partially 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

Precipitation of multi-type nano-quasicrystals in a Mg-zn-Y alloy

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Journal of Magnesium and Alloys 2024年第3期12卷 997-1008页

作者： W.z.Wang X.z.zhou L.F.zhang h.Q.Ye z.Q.Yang Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of ScienceShenyang 110016China Ji hua Laboratory Foshan 528251China Foshan University Foshan 528231China

Mg-6zn-1Y(at.%)ribbons with strengthening precipitates of multi-type nanoquasicrystals were prepared by melt-spinning followed by aging *** evolution of the rapidly solidified ribbons during isothermal aging was comprehensively studied using various electron microscopy *** new kinds of decagonal quasicrystals were formed in aged ribbons,in addition to precipitation of nanometer icosahedral ***-resolution observations reveal that both decagonal quasicrystals can be modeled by quasiperiodic tiling with decagonal clusters of 2.5 nm in diameter,but overlap of neighboring clusters in both decagonal quasicrystals is different from the Gummelt model observed in other quasicrystals.A shell composed of complex Laves Mg-zn domains was formed surrounding each decagonal quasicrystal precipitate upon prolonged *** addition,all kinds of nanoprecipitates exhibit excellent structure and size stability at 573 *** findings may have implications for not only fundamental studies about quasicrystals,but also microstructural manipulation of high-performance Mg alloys.

关键词： Quasicrystal Mg alloys Rapid solidification Scanning-transmission electron microscopy.

Event-triggered sliding mode control of linear repetitive processes and its application in metal rolling process

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Science China(Information Sciences) 2024年第3期67卷 167-181页

作者： Xinyu LV Yugang niu James LAM Key Laboratory of Smart Manufacturing in Energy Chemical Process (East China University of Science and Technology) Ministry of Education Department of Mechanical Engineering The University of Hong Kong

This paper investigates the design problem of a sliding mode controller for linear repetitive processes(LRPs) with a finite pass length on each pass. Under limited communication resources, an eventtriggered mechanism is implemented from the sensors to the controller, whose triggered sequence is consistent with the evolution direction of LRPs. To periodically orchestrate communication between the controller and actuator, a round-robin scheduling mechanism is established based on the pass length. A sliding function involving the state and pass profile is constructed, and the sliding mode controller is designed using triggered states and pass profile signals. Feasible controller gains are attained to ensure the stability of the resultant closed-loop system. Finally, the proposed strategy is implemented for a multi-roll metal rolling process.

关键词： event-triggered mechanism linear repetitive processes metal rolling process round-robin scheduling sliding mode control

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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