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Global Well-posedness for the Non-viscous MHD Equations with Magnetic Diffusion in Critical Besov Spaces

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Acta Mathematica Sinica,English Series 2022年第9期38卷 1493-1511页

作者： Wei kui YE zhao Yang YIN Institute of Applied Physics and Computational Mathematics P.O.Box 8009Beijing 100088P.R.China Department of Mathematics Sun Yat-sen UniversityGuangzhou 510275P.R.China

In this paper,we mainly investigate the Cauchy problem of the non-viscous MHD equations with magnetic *** first establish the local well-posedness(existence,uniqueness and continuous dependence)with initial data(u_(0),b_(0))in critical Besov spaces B_(p,1)^(d/p+1)×B_(p,1)^(d/p)with 1≤p≤∞,and give a lifespan T of the solution which depends on the norm of the Littlewood–Paley decomposition(profile)of the initial ***,we prove the global existence in critical Besov *** particular,the results of global existence also hold in Sobolev space C([0,∞);H~s(S~2))×(C([0,∞);H^(s-1)(S~2))∩L~2([0,∞);H~s(S~2)))with s>2,when the initial data satisfies∫_(S~2)b_(0)dx=0 and||u_(0)||B_(()∞,1~((S~2)))~1+||b_(0)||B_(()∞,1^(S~2))~0≤ε.It’s worth noting that our results imply some large and low regularity initial data for the global existence.

关键词： The non-viscous MHD equations with magnetic diffusion local well-posedness critical Besov spaces global existence

Decision making module based on stochastic magnetic tunnel junctions

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Science China(Physics,Mechanics & Astronomy) 2025年第1期Mechanics & Astronomy) .卷 202-209页

作者： Yifan Miao Li zhao Yajun Zhang Zhe Yuan Center for Advanced Quantum Studies and Department of Physics Beijing Normal University Institute for Nanoelectric Devices and Quantum Computing Fudan University Interdisciplinary Center for Theoretical Physics and Information Sciences Fudan University

In biological neural systems, noise is ubiquitous but does not affect the correct decisions made in the complex cognitive ***-making in biological neural system is typically achieved by accumulating input information over a period of *** by recent developments in neurosciences, we design a decision-making module based on spintronic devices, utilizing superparamagnetic tunnel junctions as artificial neurons. The feasibility of this decision-making module is verified through circuit simulations. Taking a multi-layer perceptron as an example, the module significantly improves the accuracy of the perceptron in the handwritten digit recognition task. Furthermore, the spintronic decision-making module offers advantages over the conventional pooling methods, such as adaptive decision time, high performance and the absence of analog-to-digital conversion. The decision-making module is flexible to be integrated into artificial neural networks and provides a general yet effective solution to enhance performance against device noise.

关键词： neuromorphic computing spintronics magnetic tunnel junction neural networks

Mechanism of primary Si and Fe-segregation for a hypereutectic 90 wt.%Si-Ti alloy melt in directional solidification via electromagnetism

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Journal of Iron and Steel Research International 2023年第4期30卷 726-735页

作者： kui-song Zhu Li Cao Ying-tao zhao Jun Wang Xiang-kui Cheng College of Vanadium and Titanium Panzhihua UniversityPanzhihua 617000SichuanChina

The electromagnetic directional solidification(DS)phase separation experiments of high silicon 90 wt.%Si–Ti alloy were performed under various pulling-down *** results showed that Si enriched layer,Si+TiSi_(2)-rich layer and Si–Ti–Fe alloy layer appeared successively in axial direction of ingot after electromagnetic DS of 90 wt.%Si–Ti alloy melt at different pulling-down *** of primary Si and segregation mechanism of metal impurities(Fe)during the electromagnetic DS process were controlled by pulling-down speed of ingot and electromagnetic *** pulling-down speed was 5μm/s,minimum thickness of the Si enriched layer was 29.4 mm,and the highest content of primary Si in this layer was 92.46 wt.%;meanwhile,the highest removal rate of Fe as metal impurity was 92.90%.The type of inclusions in the Si enriched layer is determined by Fe content of segregated Si enriched *** the pulling-down speed was 5μm/s,the inclusions in the Si enriched layer were TiSi_(2).Finally,when the pulling-down speed reached greater than 5μm/s,the inclusions in the Si enriched layer evolved into TiSi_(2)+τ_(5).

关键词： High silicon Si-Ti alloy Primary Si Electromagnetic directional solidification Si enriched layer Impurity segregation

Implementation and evaluation of parallel FFT on Engineering and Scientific Computation Accelerator (ESCA) architecture

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Journal of Zhejiang University-Science C(Computers and Electronics) 2011年第12期12卷 976-989页

作者： Dan WU Xue-cheng ZOU kui DAI jin-li RAO Pan CHEN zhao-xia ZHENG Department of Electronic Science ＆： Technology Huazhong University of Science and Technology Wuhan 430074 China

The fast Fourier transform (FFT) is a fundamental kernel of many computation-intensive scientific *** paper deals with an implementation of the FFT on the accelerator system,a heterogeneous multi-core architecture to accelerate computation-intensive parallel computing in scientific and engineering *** Engineering and Scientific Computation Accelerator (ESCA) consists of a control unit and a single instruction multiple data (SIMD) processing element (PE) array,in which PEs communicate with each other via a hierarchical two-level network-on-chip (NoC) with high bandwidth and low *** exploit the architecture features of ESCA to implement a parallel FFT algorithm *** results show that both the proposed parallel FFT algorithm and the ESCA architecture are *** 16-bit fixed-point parallel FFT performance of ESCA is compared with a published work to prove the superiority of the mapping algorithm and the hardware *** floating-point parallel FFT performances of ESCA are evaluated and compared with those of the IBM Cell processor and GPU to demonstrate the computing power of the ESCA system for high performance applications.

关键词： Fast Fourier transform (FFT) Multi-core Parallel computing SIMD

Spectral and self-assembly properties of a series of asymmetrical pyrene derivatives

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Chinese Chemical Letters 2014年第2期25卷 237-242页

作者： Peng-Xia Liang Dong Wang Zong-Cheng Miao zhao-kui jin Huai Yang Zhou Yang School of Materials Science and Engineering University of Science and Technology Beijing

A series of pyrene derivatives with different asymmetrical substituents were successfully synthesized and characterized. The geometrical electronic structures of the asymmetrical pyrene derivatives were performed by density functional theory （DFT） calculations. The results of photophysical spectra and electrochemical analysis indicated that the optical or electric properties of the pyrene derivatives could be tuned by adjust the π-conjugation lengths of the substituents. Furthermore, through a phase exchange self-assembly method, the highly organized morphologies were observed by SEM.

关键词： Asymmetrical Pyrene Self-assembly

Formation of Ultrafine Apatite Fibers by Sol-gel/Electrospinning

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Chemical Research in Chinese Universities 2007年第3期23卷 366-369页

作者： DING Ya-mei YUAN Xiao-yan zhao jin GUO Wan-chun WANG Xiu-kui School of Materials Science and Engineering Tianjin University Tianjin 300072 P. R. China

Ultrafine apatite fibers were prepared by electrospinning of sol-gel precursor/poly（ vinyl pyrrolidone）（PVP） solutions followed by subsequent calcination. The as-electrospun and calcinated fibers were observed under a scanning electron microscope and an optical polarizing microscope. Results show that the morphology and the diameter of as-electrospun fibers strongly depend on the viscosity and the surface tension of sol-gel precursor/PVP solutions. After calcination, the smooth as-electrospun fibers shrink and the fiber diameter decreases because of the removal of the polymer. The chemical evolution upon the transformation of the precursor from a gel to the final apatite fibers was investigated by thermogravimetric-differenfial thermal analysis, X-ray diffraction, and Fourier transform infrared spectroscopy. It is thus suggested that the crystalline structure of the calcined fibers is largely influenced by the calcination temperature. After being calcined at 600 ℃, the apatite fibers with a diameter of about 280 nm containing β-tricalcium phosphate were obtained.

关键词： Apatite Ultrafine fiber Sol-gel Electrospinning

The Radial Structure of Pulsar Radio Emission Regions

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Chinese Journal of Astronomy and Astrophysics 2002年第5期2卷 454-462页

作者： Xin-Ji Wu zhao-kui Huang DepartmentofAstronomy PekingUniversityBeijing100871 TheChineseAcademyofSciences-PekingUniversityJointBeijingAstrophysicsCenter Beijing100871

An important parameter in the study of the radial structure of the pulsar radio emission region is the altitude of the emission, but this cannot be derived directly from the observations. The altitude can be expressed as a function of frequency, γv ∝v-ξ, and the method of K analysis can be used to calculate the power law index ?from observations at different frequencies. We have calculated the value of ?for 18 pulsars observed at two frequencies, 610MHz and 1408MHz and for three pulsars observed at three or more frequencies. The average value of ξ is 0.27, which indicates that the emission altitude increases with decreasing frequency and that the radial structure is compact.

关键词： stars: pulsars

Development of Vertical Buffered Electropolishing for Its Post-Treatment Technology on 1.5GHz Niobium SRF Cavities

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Chinese Physics Letters 2011年第11期28卷 91-94页

作者： jin Song ATWu LU Xiang-Yang RARimmer LIN Lin zhao kui State Key Laboratory of Nuclear Physics and Technology Institute of Heavy Ion PhysicsSchool of PhysicsPeking UniversityBeijing 100871 Thomas Jefferson National Accelerator Facility 12000 Jefferson AvenueNewport NewsVA 23606USA

We report the latest research development of vertical buffered electropolishing on its post-treatment procedure as well as the effects of several major post-treatment techniques for buffered electropolishing(BEP)processed 1.5 GHz niobium(Nb)superconducting radio frequency(SRF)*** the established post-treatment procedure,an accelerating gradient of 28.4MV/m is obtained on a single cell cavity of the cebaf *** is the best result in the history of BEP *** cavity is limited by quench with a high quality factor over 1.2×1010 at the quench *** from optical inspection and temperature-mapping show that the quench should be originated from the pits that were already present on the cavity before this BEP *** of these factors indicate that this procedure will have a great potential to produce better results if cavities without intrinsic performance limiting imperfections are used.

关键词： treatment polishing cavity

Low-cost and fluoride-free synthesis of MFI zeolite nanosheets with enhanced stability for benzene alkylation with ethanol

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Journal of Energy Chemistry 2025年第1期100卷 458-468页

作者： Peng Zhu Cun Liu Yiren Yu Guoshu Gao Yumeng zhao Xiongfu Zhang Guodong Liu Guohui Yang State Key Laboratory of Fine Chemicals School of Chemical Engineering Dalian University of Technology State Key Laboratory of Catalysis Dalian Institute of Chemical Physics Chinese Academy of Sciences

Zeolite nanosheets with a short b-axis thickness are highly desirable in lots of catalytic reactions due to their reduced diffusion resistance. Nevertheless, conventional synthesis methods usually require expensive structure-directing agents(SDAs), pricey raw materials, and eco-unfriendly fluorine-containing additives. Here, we contributed a cost-effective and fluoride-free synthesis method for synthesizing high-quality MFI zeolite nanosheets through a Silicalite-1(Sil-1) seed suspension and urea cooperative strategy, only with inexpensive colloidal silica as the Si source. Our approach was effective for synthesizing both Sil-1 and aluminum-containing ZSM-5 nanosheets. By optimizing key synthesis parameters,including seed aging time, seed quantity, and urea concentration, we achieved precise control over the crystal face aspect ratio and b-axis thickness. We also revealed a non-classical oriented nanosheet growth mechanism, where Sil-1 seeds induced the formation of quasi-ordered precursor particles, and the(010)crystal planes of these particles facilitated urea adsorption, thereby promoting c-axis-oriented *** obtained ZSM-5 nanosheets exhibited exceptional catalytic performance in the benzene alkylation with ethanol, maintaining stability for over 500 h, which is 5 times longer than traditional ZSM-5 catalysts. Furthermore, large-scale production of ZSM-5 nanosheets was successfully carried out in a 3 L highpressure autoclave, yielding samples consistent with those from laboratory-scale synthesis. This work marks a significant step forward in the sustainable and efficient production of MFI nanosheets using inexpensive and environmentally friendly raw materials, offering the broad applicability in catalysis.

关键词： MFI zeolite ZSM-5 Nanosheets Scale-up synthesis Aromatic alkylation