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Recent progress in MnBi2nTe3n+1 intrinsic magnetic topological insulators: crystal growth, magnetism and chemical disorder

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National Science Review 2024年第2期11卷 65-80页

作者： Chaowei Hu Tiema Qian ni ni Department of Physics and Astronomy and California Nano Systems Institute University of California-Los Angeles

The search for magnetic topological materials has been at the forefront of condensed matter research for their potential to host exotic states such as axion insulators, magnetic Weyl semimetals, Chern insulators,etc. To date, the MnBi2nTe3n+1family is the only group of materials showcasing van der Waals-layered structures, intrinsic magnetism and non-trivial band topology without trivial bands at the Fermi level. The interplay between magnetism and band topology in this family has led to the proposal of various topological phenomena, including the quantum anomalous Hall effect, quantum spin Hall effect and quantum magnetoelectric effect. Among these, the quantum anomalous Hall effect has been experimentally observed at record-high temperatures, highlighting the unprecedented potential of this family of materials in fundamental science and technological innovation. In this paper, we provide a comprehensive review of the research progress in this intrinsic magnetic topological insulator family, with a focus on single-crystal growth, characterization of chemical disorder, manipulation of magnetism through chemical substitution and external pressure, and important questions that remain to be conclusively answered.

关键词： MnBi2Te4 magnetic topological insulator magnetism tuning antiferromagnetism ferromagnetism pressure chemical doping

Ordered proposition fusion based on consistency and uncertainty measurements

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Science China(Information Sciences) 2017年第8期60卷 117-135页

作者： Dayou LIU yungang ZHU ni ni Jie LIU College of Computer Science and Technology Jilin University Key Laboratory of Symbolic Computation and Knowledge Engineering of Ministry of Education Jilin University Beijing Entry-Exit Inspection and Quarantine Bureau

The fusion of ordered propositions is an important and widespread problem in artificial intelligence,but existing fusion methods have difficulty handling the fusion of ordered propositions. In this paper, we propose a solution based on consistency and uncertainty measurements. The main contributions of this paper are as follows. First, we propose the concept of convexity degree, mean, and center of basic support function to comprehensively describe the basic support function of ordered propositions. Second, we introduce entropy as a measure of uncertainty in the basic support function of ordered propositions. Third, we generalize the indeterminacy of the basic support function and propose a novel method to measure the consistency between two basic support functions. Finally, based on the above researches, we propose a novel algorithm for fusing ordered propositions. Theoretical analysis and experimental results demonstrate that the proposed method outperforms state-of-the-art methods.

关键词： uncertainty processing ordered proposition evidence theory dempster rule of combination information fusion

Hepatitis C:a successful story of cure

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Science Bulletin 2016年第24期61卷 1884-1887页

作者： yi ni Department of Infectious Diseases Molecular VirologyUniversity Hospital Heidelberg 69120 Heidelberg Germany

On September 23, the 2016 Lasker-DeBakey clinical medical research award ceremony was celebrated in New york City. This annual prize has been awarded by the Lasker Foundation for over 71 years, and it is the most prestigious biomedical award in the United States, popu- larly known as ＂America＇s Nobel Prize＂. Indeed, 87 Lasker laureates have received the Nobel Prize, including 41 within the last 30 years （one example is the Chinese pharmaceutical chemist youyou Tu, who won the 2011 Lasker-DeBakey award and four years later received the Nobel Prize）. This year, the honor went to Ralf F. W. Bartenschlager （Heidelberg University, Germany）, Charles M. Rice （Rockefeller University, Ny, USA）, and Michael J. Sofia （Arbutus Biopharma, PA, USA） for the development of cell culture system to study the replication of Hepatitis C virus （HCV） and for the use of this system to develop drugs capable of eliminating Hepatitis C.

关键词：丙型肝炎病毒 Michael 故事治愈诺贝尔奖生物制药开发能力培养系统

Effect of post weld artificial aging and water cooling on microstructure and mechanical properties of friction stir welded 2198-T8 Al-Li joints

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Journal of Materials Science & Technology 2022年第28期123卷 92-112页

作者： y.Tao Z.Zhang P.Xue D.R.ni B.L.Xiao Z.y.Ma Institute of Metal Research Chinese Academy of SciencesShenyang 110016China

Friction stir welding(FSW)under both air cooling and water cooling conditions with welding parameters of 800-1200 rpm rotation rates and 50-200 mm/min welding speeds was carried out on 2198-T8 Al-Li alloys,and post weld artificial aging was performed on the air cooled *** welding defects other than lazy S were observed in the nugget zone(NZ)for all *** air cooling condition,the lowest hardness zone(LHZ)occurred in the heat affected zone(HAZ).FSW resulted in gradual dissolution of original T_(1),θ′andδ′/β′from the base material(BM)to the thermo-mechanically affected zone(TMAZ),and complete dissolution of all precipitates in the NZ withδ′/β′and Guinier-Preston zones precipitating during *** air cooled joints exhibited no noticeable changes in intrinsic tensile strength with a joint strength reaching 81.3%of the BM,but varied elongation with welding parameters,which was closely related to failure in the NZ and fracture along lazy *** weld artificial aging led to the largest hardness recovery in the TMAZ but smaller hardness recovery in the initial LHZ and the *** aging kinetics across the joint was determined by volume fraction of both original precipitate dissolu-tion during welding and coarse particles formed during aging,and by dislocation density inherited from *** weld artificial aging greatly enhanced the joint strength with the ultimate tensile strength reaching 87.3%of the *** compared to air cooling condition,water cooling hardly affected the NZ hardness and did not improve the joint strength,and the reason was discussed in light of precipitates,hardness changes and fracture behavior.

关键词： Friction stir welding Aluminum-lithium alloys Microstructure Mechanical properties

Development of sterically hindered SPOs and enantioselective ni-Al bimetallic catalyzed C-H cyclization of 4-oxoquinazolines with tethered alkenes

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Chinese Chemical Letters 2023年第6期34卷 366-370页

作者： yaqi Zhang Qiang ni Bendu Pan Long Jiang Liqin Qiu School of Chemistry Guangdong Key Lab of Chiral Molecules and Drug DiscoverySun Yat-sen UniversityGuangzhou 510006China Instrumental Analysis and Research Centre Sun Yat-sen UniversityGuangzhou 510275China

The ni-Al bimetallic catalysis of intramolecular enantioselective and regioselective C-H cyclization of4-oxoquinazolines with tethered alkenes has been successfully *** new secondary phosphine oxides(SPOs)with large steric hindrance(SPO6-11)were designed and successfully synthesized from readily available chiral amines or amino *** developed chiral SPOs as ligands or preligands demonstrate much higher efficiency in the asymmetric catalytic reactions than the reported traditional ones.A new class of chiral tricyclic pyrroloquinazolinones were obtained in up to 95%yield and 99%ee.

关键词： ni-Al bimetallic catalysis Secondary phosphine oxides C-H cyclization Asymmetric catalysis 4-Oxoquinazolines

A Characterization of T_(2g+1,2) among Alternating Knots

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Acta Mathematica Sinica,English Series 2021年第12期37卷 1841-1846页

作者： yi ni Department of Mathematics CaltechMC 253-371200 E California BlvdPasadenaCA 91125USA

Let K be a genus g alternating knot with Alexander polynomial Δ_(K)(T)=Σ_(i=-g)^(g)a_(i)T^(i).We show that if |a_(g)|=|a_(g-1)|,then K is the torus knot T_(2g+1,±2).This is a special case of the Fox Trapezoidal ***... 详细信息

关键词： Alternating knots Alexander polynomial strongly quasipositive fibered knots

Signature of helium rain and dilute cores in Jupiter’s interior from empirical equations of state

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Earth and Planetary Physics 2020年第2期4卷 111-119页

作者： DongDong ni State Key Laboratory of Lunar and Planetary Sciences Macao University of Science and Technology Institute for Planets and Exoplanets University of California

Measurements of Jupiter’s gravity field by Juno have been acquired with unprecedented precision, but uncertainties in the planet’s hydrogen–helium equation of state(EOS) and the hydrogen–helium phase separation have meant that differences remain in the interior model predictions. We deduce an empirical EOS from Juno gravity field observations in terms of the hydrostatic equation and then investigate the structure and composition of Jupiter by comparison of the empirical EOS with Jupiter’s adiabats obtained from the physical EOS. The deduced helium mass fraction suggests depletion of helium in the outermost atmosphere and helium concentration in the inner molecular hydrogen region, which is a signature of helium rain in Jupiter’s interior. The deduced envelope metallicity(the heavy-element mass fraction) is as high in the innermost envelope as 11–13 times the solar value. Such a high metallicity provides sharp support to the dilute core model with the heavy elements dissolved in hydrogen and expanded outward. No matter how the core mass is varied, the empirical EOS derived from the two-layer interior model generally suggests higher densities in the innermost envelope than does the best-fit Jupiter’s adiabat;this result is, again, a signature of dilute cores in Jupiter’s interior. Moreover, no matter the core mass,the empirical EOS is found to exhibit an inflexion point in the deep interior, around 10 Mbar, which can be explained as the combined effect of helium concentration in the upper part and dilute cores in the lower part.

关键词： Jupiter,interior abundances,interiors geophysics

Friction Stir Welding of Discontinuously Reinforced Aluminum Matrix Composites:A Review

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Acta Metallurgica Sinica(English Letters) 2014年第5期27卷 816-824页

作者： D.Wang B.L.Xiao D.R.ni Z.y.Ma Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences

Friction stir welding （FSW） is considered a promising welding technique for joining the aluminum matrix composites （AMCs） to avoid the drawbacks of the fusion welding. High joint efficiencies of 60%-100% could be obtained in the FSW joints of AMCs. However, due to the existence of hard reinforcing particles in the AMCs, the wearing of welding tool during FSW is an unavoidable problem. Moreover, the low ductility of the AMCs limits the welding process window. As the hard materials such as Ferro-Titanit alloy, cermet, and WC/Co were applied to produce the welding tools, the wearing of the tools was significantly reduced and the sound joints could be achieved at high welding speed for the AMCs with low reinforcement volume fraction. In this article, current state of understanding and development of welding tool wearing and FSW parameters of AMCs are viewed. Furthermore, the factors affecting the microstructure and mechanical properties of the joints are evaluated in detail.

关键词： Metal matrix composite Friction stir welding Particle, microstructure Wear

Influence of Co Content on Raman and Photoluminescence Spectra of Co Doped ZnO Nanowires

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Journal of Materials Science & Technology 2012年第4期28卷 313-316页

作者： y.Q. Chang P.W. Wang S.L. ni y. Long X.D. Li School of Materials Science anti Engineering University of Science and Technology Beijing Beijing 100083 China Department of Physics National Key Laboratory of Mesoscopic Physics Peking University Beijing 100871 China

Co doped ZnO nanowires with different Co contents have been fabricated by a chemical vapor deposition method. X-ray diffraction results show that all the samples are of single phase and crystallize in wurtzite ZnO structure. The lattice parameter a increases with increasing Co content, while the parameter c has no obvious change with increasing Co. Raman spectra show that the nonpolar E2（High） mode becomes broad and weak with the doping of Co, which indicates that the incorporation of Co causes structural disorder in the crystalline columnar ZnO lattice. The photolurninescence spectra exhibit that the position of the ultraviolet emission shifts to short wavelength and the intensity decreases with increasing Co. The green emission is affected by two contrary factors. It is increased by the introduced defects, but suppressed by the interaction between Co doping and native defects and the later affects it more significantly.

关键词： Co doped ZnO nanowires Raman Photoluminescence Single phase