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Refractory high-entropy alloys:A focused review of preparation methods and properties

Journal of Materials Science & Technology 2023年第11期142卷 196-215页

作者： Wei Xiong Amy X.y.guo Shuai Zhan chain-Tsuan Liu Shan cecilia cao Materials Genome Institute Shanghai UniversityShanghai 200444China Hong Kong Institute of Advanced Study City University of Hong KongKowloonHong KongChina

In recent years,high-entropy alloys(HEAs)have become prominent metallic materials due to their unique design strategies and excellent mechanical *** HEAs-inherent high-entropy,lattice-distortion,sluggish-diffusion,and cocktail effects make HEAs maintain high strength,oxidation resistance,corrosion resistance,wear resistance,and other excellent comprehensive properties,showing stronger competitiveness relative to traditional *** high-entropy alloys(RHEAs)are considered as a new kind of high-temperature materials with great application prospects due to their excellent mechanical properties and have the potential to replace nickel-based superalloy as the next generation of high-temperature *** reviewed the research status and preparation methods of RHEAs in recent years,including the metallurgical smelting,powder metallurgy,magnetron sputtering,and additive manufacturing *** microstructure and phase-transformation process of RHEAs were *** mechan-ical properties and main strengthening and toughening mechanisms of RHEAs,such as solid-solution strengthening,precipitation strengthening,and the transformation-induced plasticity(TRIP),were discussed,and the deformation mechanism of RHEAs was *** properties of RHEAs,including high strength,oxidation resistance,corrosion and wear resistance were *** will meet the huge market demand in the engineering materials field,but there are still many challenges,such as the tradeoff between high strength and high ductility,structural design,and performance optimization of RHEAs with brittle Bcc *** believe that this combination of knowledge may shape the future of RHEAs and break through the mutually exclusive conundrum of high strength and high toughness for RHEAs.

关键词： Refractory high-entropy alloy Preparation technology Phase transformation Mechanical properties Strengthening and toughening mechanisms Deformation mechanisms

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One kind motion of controllable constrained Birkhoffian system:the absence of constraints

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Acta Mechanica Sinica 2020年第3期36卷 735-741页

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

This paper is devoted to discuss the motion of controllable constrained Birkhoffian system along with its absence of *** first step is to establish the autonomous and non-autonomous differential equations of motion of the system,based on Pfaff-Birkhoff ***,the existence of constraint multipliers are exhaustively ***,the definition of one kind motion of the system,called free motion,is given,which is described and analyzed by the absence of constraints that are determined by constraint *** 2 illustrates that one system can realize its free motion by selecting proper control *** particular,theorem 2 provides that one system can naturally realize free motion when we consider the integral of the unconstrained Birkhoffian system as the constraints of constrained Birkhoffian ***,the results obtained are illustrated by several examples.

关键词： constrained Birkhoffian system Kinematic control Absence of constraint Free motion

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State-of-the-art survey on digital twin implementations

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Advances in Manufacturing 2022年第1期10卷 1-23页

作者： y.K.Liu S.K.Ong A.y.c.Nee Department of Mechanical Engineering National University of Singapore9 Engineering Drive 1Singapore 117575Singapore

Digital twin(DT)has garnered attention in both industry and *** advances in big data and internet of things(IoTs)technologies,the infrastructure for DT implementation is becoming more readily *** an emerging technology,there are both potential and *** is a promising methodology to leverage the modern data explosion to aid engineers,managers,healthcare experts and politicians in managing production lines,patient health and smart cities by providing a comprehensive and high fidelity monitoring,prognostics and diagnostics *** research and surveys into the topic are published regularly,as interest in this technology is high although there is a lack of standardization to the definition of a *** to the large amount of information present in a DT system and the dual cyber and physical nature of a DT,augmented reality(AR)is a suitable technology for data visualization and interaction with *** paper seeks to classify different types of DT implementations that have been reported,highlights some researches that have used AR as data visualization tool in DT,and examines the more recent approaches to solve outstanding challenges in DT and the integration of DT and AR.

关键词： Industry 4.0 Internet of thing(IoT) cyberphysical systems Digital twin(DT) Augmented reality(AR)

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Electrodeposition mechanism of Ni-Mo-P alloy in the solution of ammoniac citrate

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chinese Journal of chemistry 1997年第3期15卷 193-200页

作者： Zeng, y yao, SW cao, XQ Huang, HX Zhong, Zy guo, HT TIANJIN UNIV DEPT APPL CHEMTIANJIN 300072PEOPLES R CHINA

The induced codeposition mechanism of Mo, P and Ni from the solution of ammoniac citrate was studied by means of steady-state polarization, Ac impedance and X-ray Photoelectron Spectroscopy (XPS). The result of electrochemical measurements proved that [Nicit(NH3)(2)](-) is the electro-active species of nickel, though nickel ions exist mainly as [Nicit(NH3)(3)](-) in ammoniac citrate. XPS experiments proved the existence of tetravalent molybdenum corresponding to MoO2 on the surface of some deposits. The intermediate product, MoO2, was probably reduced to Mo in the alloy deposit by atomic hydrogen adsorbed on the induced metal nickel. The reduction of H2PO2- occurs through two distinctive steps with PH3 as an, intermediate, which subsequently reacts with atomic hydrogen to form P in the alloy deposit. The electrodeposition mechanism was proposed in this paper.

关键词： Ni-Mo-P alloy electrodeposition mechanism

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Influence of the velocity barrier on the massive Dirac electron transport in a monolayer MoS2 quantum structure

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Frontiers of physics 2020年第3期15卷 113-121页

作者： X.-J.Hao R.-y.yuan J.-J.Jin y.guo center for Theoretical Physics Department of PhysicsCapital Normal UniversityBeijing100048China Department of Physics and State Key Laboratory of Low-Dimensional Quantum Physics Tsinghua UniversityBeijing100084China collaborative Innovation center of Quantum Matter BeijingChina

Using the transfer matrix method,spin-and valley-dependent electron transport properties modulated by the velocity barrier were studied in the normal/ferromagnetic/normal monolayer MoS2 quantum *** on Snell’s Law in optics,we define the velocity barrier asξ=v2/v1 by changing the Fermi velocity of the intermediate ferromagnetic region to obtain a deflection condition during the electron transport process in the *** results show that both the magnitude and the direction of spin-and valley-dependent electron polarization can be regulated by the velocity barrier.−100%polarization of spin-and valley-dependent electron can be achieved forξ>1,while 100%polarization can be obtained forξct spin and valley transport always occur at a large incident *** addition,the spin-and valley-dependent electron transport considerably depends on the length kFL and the gate voltage U(x)of the intermediate ferromagnetic *** findings provide an effective method for designing novel spin and valley electronic devices.

关键词： velocity barrier monolayer MoS2 spin valley polarization

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Development of dipole magnet power supply for BEPc-II energy upgrading project

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Radiation Detection Technology and Methods 2019年第2期3卷 32-36页

作者： X.L.guo B.chen c.Han y.Gao University of chinese Academy of Sciences Beijing 100049China Institute of High Energy Physics Chinese Academy of SciencesBeijing 100049China Dongguan Neutron Science center Dongguan 523803China

Purpose In order to make BEPc-II to run at a higher energy,the Institute of High Energy Physics undertook an upgrading *** of the important factors limiting the energy boost is the power and performance of the dipole magnet power supplies;therefore,these four magnet power supplies are developed for the BEPc-II *** The power supplies adopt topologies of thyristor rectifiers to realize a high-power *** the control unit of each power supply,a digital current closed loop is adopted,and the key components in the feedback loop are thermostatically *** order to improve the performances of the power supplies,analog voltage regulators are added to the inner control *** These four power supplies have been tested and have already been officially used in BEPc-II,and their powers have reached the requirements of the *** test results of the current stability are described and shown in this paper,which testifies that the stabilities meet the design *** A digital control is applied to each ScR rectifier *** performances of the power supplies are improved by the combination of digital current control loops and the analog voltage control loops,which makes the performances of the dipole magnet power supplies meet the requirements of the upgrading project.

关键词： ScR rectifier Dipole magnet power supply Stability BEPc-II

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IMPROVEMENT OF DISPERSION ABILITy OF NANOMETER PARTIcLES By MEANS OF PLASMA POLyMERIZATION

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Acta Metallurgica Sinica(English Letters) 2002年第1期15卷 73-76页

作者： G.Q. Zhang X.G. guo y.M. Liu y.J. Ge Beijing Institute of Printing Beijing 102600 China

In order to find a new way to improve the dispersion ability of nanometer material, an investigation on preparation of thin film with low surface energy on the surface of nanometer material by means of plasma polymerization has been done. Some physical behaviors and chemical constitution of prepared film as well as the influence of polymerized film on nanometer material were tested. All the experimental results showed that this is a possible way to improve the dispersion ability of nanometer materials.

关键词： plasma polymerization nanometer material

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A new design of dual-constituent triangular lattice metamaterial with unbounded thermal expansion

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Acta Mechanica Sinica 2019年第3期35卷 507-517页

作者： y.c.Zhang y.J.Liang S.T.Liu y.D.Su State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of TechnologyDalian 116024China New Functional Structural Design and Verification Key Laboratory of Aeronautical Technology Shenyang 110035China

Triangular lattice metamaterials composed of bi-layer curved rib elements (called the Lehman-Lakes lattice) possess unbounded thermal expansion, high stiffness and impossibility of thermal buckling, which are highly desirable in many engineering structural applications subjected to large fluctuations in temperature. However, the requirement of such lattice metamaterial is that it must be a hinged joint in order to achieve the bending deformation upon heating freely, which directly leads to poor manufacturability, especially in small dimensions. In this study, a new design of dual-constituent triangular lattice metamaterial (DTLM) with good manufacturability is proposed to achieve the identical unbounded thermal expansion. In this lattice, a special bi-layer curved rib element where layer one is partially covered by layer two is presented, where the hinge joints are not necessary because the flexural rigidity in the single-layer part is much smaller than that in the bi-layer part, and the desirable thermal bending deformation can be achieved. A sample fabricated by additive manufacturing is given in order to show the good manufacturability;simultaneously, the multifunctional performance of the tailored DTLM with zero, large positive or negative coefficient of thermal expansion (cTE) can remain excellent, as well as the Lehman-Lakes lattice. Examples illustrate that the DTLM with zero cTE has about 34.2% improvement in stiffness and meanwhile has 17% reduction in weight compared with the Lehman-Lakes lattice. The stiffness of the DTLM has a moderate reduction when achieving the same large positive or negative cTE. In addition, the thermomechanical properties of the DTLM are given by the closed-form analytical solution and their effectiveness is verified by the detailed numerical simulation.

关键词： Metamaterial Zero thermal expansion Lattice material Multifunctional design Additive manufacturing

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Studies on Diastereoselective Intramolecular meta-cycloaddition ofArene to Olefin (Part I)

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chinese chemical Letters 1998年第4期9卷 131-134页

作者： Shen, XM guo, Xc Sun, LD Zhang, c Beijing Normal Univ Dept Chem Beijing 100875 Peoples R China

The photoinduced intramolecular meta-cycloaddition of bichromophores 1a-1d gave diastereoselectively two types of adducts, 2a-2d and 3a-3d. respectively. The observed stereochemistry of cycloaddition was rationalized ... 详细信息

关键词： arene olefin meta-cycloaddition diastereoselectivity

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Ruin Probabilities in cox Risk Models with Two Dependent classes of Business

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Acta Mathematica Sinica,English Series 2007年第7期23卷 1281-1288页

作者： Jun yi guo Kam c.yUEN Ming ZHOU School of Mathematical Sciences and LPMc Nankai University Department of Statistics and Actuarial Science The University of Hong Kong

In this paper we consider risk processes with two classes of business in which the two claim-number processes are dependent cox processes. We first assume that the two claim-number processes have a two-dimensional Markovian intensity. Under this assumption, we not only study the sum of the two individual risk processes but also investigate the two-dimensional risk process formed by considering the two individual processes separately. For each of the two risk processes we derive an expression for the ruin probability, and then construct an upper bound for the ruin probability. We next assume that the intensity of the two claim-number processes follows a Markov chain. In this case, we examine the ruin probability of the sum of the two individual risk processes. Specifically, a differential system for the ruin probability is derived and numerical results are obtained for exponential claim sizes.

关键词： cox risk model ruin probability Markov process infinitesimal generator

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