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Microstructure characteristics and mechanical properties of NbMoTiVWSix refractory high-entropy alloys

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China Foundry 2022年第6期19卷 495-502页

作者： Qin Xu Qi Wang De-zhi Chen Yi-ang Fu Qing-sheng shi Ya-jun Yin Shu-yan Zhang School of Mechanic and Electrical Engineering Henan University of TechnologyZhengzhou 450001China National Key Laboratory for Precision Hot Processing of Metals Harbin Institute of TechnologyHarbin 150001China State Key Laboratory of Materials Processing and Die&Mould Technology Huazhong University of Science&TechnologyWuhan 430074China Centre of Excellence for Advanced Materials Songshan LakeDongguan 523808GuangdongChina

Refractory high-entropy alloys are considered as potential structural materials for elevated temperature *** obtain refractory high-entropy alloys with high strength,different amounts of Si were added into the NbMoTiVW refractory high-entropy *** effects of Si on the phase constitution,microstructure characteristics and mechanical properties of NbMoTiVWSi_(x) alloys were *** show that when the addition of Si is 0,0.025 and 0.05(molar ratio),the alloys are consisted of primary BCC and secondary BCC in the intergranular *** the addition of Si is increased to 0.075 and 0.1,eutectic structure including silicide phase and secondary BCC phase is *** primary BCC phase shows dendritic morphology,and is refined by adding *** volume fraction of intergranular area is increased from 12.22%to 18.13%when the addition of Si increases from 0 to *** ultimate compressive strength of the NbMoTiVW alloy is improved from 2,242 MPa to 2,532 *** yield strength is also improved by the addition of Si,and the yield strength of NbMoTiVWSi_(0.1) reaches maximum of 2,298 ***,the fracture strain of the alloy is decreased from 15.31%to 12.02%.The fracture mechanism of the alloys is changed from mixed fracture of ductile and quasi-cleavage to cleavage fracture with increasing of *** strengthening of alloys is attributed to the refinement of primary BCC phase,volume fraction increment of secondary BCC phase,and formation of eutectic structure by addition of Si.

关键词： high-entropy alloy second phase microstructure refinement mechanical property strengthening

The Riemannian Manifolds with Boundary and Large Symmetry

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Chinese Annals of Mathematics,Series B 2010年第3期31卷 347-360页

作者： zhi CHEN Yiqian shi Bin XU Department of Mathematics University of Science and Technology of China Hefei 230026 China. Department of Mathematics University of Science and Technology of China Hefei 230026 China.

Seventy years ago, Myers and Steenrod showed that the isometry group of a Riemannian manifold without boundary has a structure of Lie group. In 2007, Bagaev and Zhukova proved the same result for a Riemannian orbifold. In this paper, the authors first show that the isometry group of a Riemannian manifold M with boundary has dimension at most 1/2 dim M（dim M - 1）. Then such Riemannian manifolds with boundary that their isometry groups attain the preceding maximal dimension are completely classified.

关键词： Riemannian manifold with boundary Isometry Rotationally symmetric metric Principal orbit

Manipulation of superconducting qubit with direct digital synthesis

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Chinese Physics B 2019年第9期28卷 78-82页

作者： zhi-Yuan Li Hai-Feng Yu Xin-sheng Tan shi-Ping Zhao Yang Yu National Laboratory of Solid State Microstructures School of PhysicsNanjing UniversityNanjing 210093China Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049China

We investigate the XY control and manipulation of the superconducting qubit state using direct digital synthesis(DDS)for the microwave pulse signal *** decoherence time, gate fidelity, and other qubit properties are measured and carefully characterized, and compared with the results obtained by using the traditional mixing technique for the microwave pulse *** particular, the qubit performance in the state manipulation with respect to the sampling rate of DDS is *** results demonstrate that the present technique provides a simple and effective method for the XY control and manipulation of the superconducting qubit *** applications of the technique for the possible future scalable superconducting quantum computation are discussed.

关键词： superconducting qubit direct digital synthesis arbitrary waveform generator

SOME CONVERGENCE PROBLEM OF ITERATIVE SEQUENCESFOR ACCRETIVE AND PSEUDO-CONTRACTIVETYPE MAPPING IN BANACH SPACES

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Applied Mathematics and Mechanics(English Edition) 2002年第4期23卷 394-408页

作者： ZHANG shi-sheng(张石生) Department of Mathematics Sichuan University Chengdu 610064 P R China

Some necessary and sufficient conditions for convergence of Ishikawa Mann and steepest descent iterative sequence for accretive and pseudo-contractive type mapping in Banach spaces were obtained. The results improve, ... 详细信息

关键词： accretive mapping pseudo-contractive mapping hemi-accretive mapping hemi-pseudo-contractive mapping Ishikawa iterative sequence Mann iterative sequence steepest descent sequence

A Moment Characterization of B-Valued Generalized Functionals of White Noise

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Acta Mathematica Sinica,English Series 2006年第1期22卷 157-168页

作者： Cai shi WANG zhi Yuan HUANG School of Mathematics and Information Science Northwest Normal University Lanzhou 730070 P. R. China Department of Mathematics Huazhong University of Science and Technology Wuhan 430074 P. R. China

Kernel theorems are established for Bananch space-valued multilinear mappings, A moment characterization theorem for Banach space-valued generalized functionals of white noise is proved by using the above kernel theorems. A necessary and sufficient condition in terms of moments is given for sequences of Banach space-valued generalized functionals of white noise to converge strongly. The integration is also discussed of functions valued in the space of Banach space-valued generalized functionals.

关键词： White noise analysis B-valued generalized functionals Moment characterization

Receiver Power Allocation and Transmitter Power Control Analysis for Multiple-Receiver Wireless Power Transfer Systems

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Journal of Electronic Science and Technology 2019年第4期17卷 291-299页

作者： zhi-Hao Guo shi-Er Dong the School of Civil Engineering and Geomatics Southwest Petroleum University

As different power has its own receivers,this paper analyzes and designs a multiple-receiver wireless power transfer(WPT)system *** equivalent circuit model of the system is established to analyze the key parameters including transmitter power,receiver power,transmission efficiency,and each receiver power allocation.A control circuit is proposed to achieve the maximum transmission efficiency and transmitter power control and arbitrary receiver power allocation ratios for different *** the proposed control circuit,receivers with different loads can allocate appropriate power according to its power demand,the transmitter power and system efficiency do not vary with the change of the number of ***,this control circuit is validated using a 130-kHz WPT system with three receivers whose power received is 3:10:12,and the overall system efficiency can reach as high as 55.5%.

关键词： Multiple-receiver receiver power allocation transmitter power control wireless power transfer(WPT).

Electrolytic silicon/graphite composite from SiO_(2)/graphite porous electrode in molten salts as a negative electrode material for lithium-ion batteries

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Rare Metals 2022年第2期41卷 438-447页

作者： Ning Wang Yu-Yang Liu zhi-Xia shi Zhang-Long Yu Hua-Ying Duan sheng Fang Juan-Yu Yang Xing-Ming Wang GRIREM Advanced Materials Co. Ltd.China Automotive Battery Research Institute Co.Ltd.General Research Institute for Nonferrous MetalsBeijing 100088China GRINM Resources and Environment Tech.Co.Ltd. General Research Institute for Nonferrous MetalsBeijing 100088China China Automotive Battery Research Institute Co.Ltd. General Research Institute for Nonferrous MetalsBeijing 100088China

Nano-silicon(nano-Si)and its composites have been regarded as the most promising negative electrode materials for producing the next-generation Li-ion batteries(LIBs),due to their ultrahigh theoretical ***,the commercial applications of nano Si-based negative electrode materials are constrained by the low cycling stability and high *** molten salt electrolysis of SiO_(2)is proven to be suitable to produce nano-Si with the advantages of in-situ microstructure control possibilities,cheap affordability and scale-up process ***,an economical approach for electrolysis,with a SiO_(2)/graphite porous electrode as cathode,is adopted to produce nano-Si/graphite composite negative electrode materials(SGNM)in this *** electrolytic product of the optimized porous electrode is taken as the negative electrode materials for LIBs,and it offers a capacity of 733.2 mAh·g^(-1)and an initial coulombic efficiency of 86.8%in a coin-type ***,the capacity of the SGNM retained 74.1%of the initial discharging capacity after 50 cycles at 0.2C,which is significantly higher than that of the simple mixture of silicon and graphite obtained from the formation of silicon carbide(SiC)between nano-Si and graphite ***,this new approach can be applied to a large-scale production.

关键词： Li-ion battery Negative electrode materials Molten salt electrolysis Nano-silicon

A Filtration of Wick Algebra and Its Application to Quantum SDEs

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Acta Mathematica Sinica,English Series 2004年第6期20卷 999-1008页

作者： Cai shi WANG zhi Yuan HUANG School of Mathematics and Information Science Northwest Normal University Department of Mathematics Huazhong University of Science & Technology

A family of closed subalgebras, indexed by R (the set of real numbers), of the Wick algebra is constructed. Fundamental properties of the family are shown including the increasing property and the right–continuity. The notion of adaptedness to the family is defined for quantum stochastic processes in terms of generalized operators. The existence and uniqueness of solutions adapted to the family is established for quantum stochastic differential equations in terms of generalized operators.

关键词： White noise Wick algebra Filtration

Deactivation Effect Caused by Catalyst-Cocatalyst Pre-contact in Propylene Polymerization with MgCl2-supported Ziegler-Natta Catalyst

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Chinese Journal of Polymer Science 2019年第10期37卷 1023-1030,I0005页

作者： Zhen Zhang Bai-Yu Jiang Biao Zhang zhi-sheng Fu zhi-Qiang Fan Ministry of Education Key Laboratory of Macromolecular Synthesis and Functionalization Department of Polymer Science and Engineering Zhejiang University

Propylene slurry polymerization with a MgCl2-supported Ziegler-Natta catalyst containing internal electron donor was conducted after different durations of pre-contact of the catalyst with triethylaluminum cocatalyst. The number of active centers([C*]/[Ti])was determined by quenching the polymerization with 2-thiophenecarbonyl chloride and measuring sulfur content in the polymer. The pre-contact treatment caused selective deactivation of a part of active centers with low stereoselectivity and much lower activity in the initial stage of polymerization as compared with the polymerization run without the pre-contact stage. The active center concentration and polymerization activity decreased with prolonging of the pre-contact stage. The proportion of stereoselective active centers was increased by prolonging the pre-contact stage, so the isotacticity of produced polypropylene was enhanced. Release of active centers through catalyst particle fragmentation was significantly retarded, and the polymerization rate curve changed from decay type to induction type by the precontact treatment. In the induction period both non-stereoselective and stereoselective active centers were released and activated, resulting in gradual reduction of the polymer’s isotacticity in the first 5-10 min of polymerization. Selective deactivation of non-stereoselective active centers also took place in propylene polymerization using the catalyst without pre-contacting with the cocatalyst. In this case, the polymerization rate decayed with time after a short induction period of 2-5 min. Over reduction of the active center precursors with low stereoselectivity by triethylaluminum was considered as the reason for their deactivation during the pre-contact or the polymerization processes.

关键词： Propylene Polymerization Supported Ziegler-Natta catalyst Cocatalyst Pre-contact