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Topological states in quasicrystals

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Frontiers of physics 2022年第1期17卷 123-142页

作者： jiahao fan Huaqing Huang School of Physics Peking UniversityBeijing100871China Center for High Energy Physics Peking UniversityBeijing100871China Collaborative Innovation Center of Quantum Matter Beijing100871China

With the rapid development of topological states in crystals, the study of topological states has been extended to quasicrystals in recent years. In this review, we summarize the recent progress of topological states in quasicrystals, particularly focusing on one-dimensional (1D) and 2D systems. We first give a brief introduction to quasicrystalline structures. Then, we discuss topological phases in 1D quasicrystals where the topological nature is attributed to the synthetic dimensions associated with the quasiperiodic order of quasicrystals. We further present the generalization of various types of crystalline topological states to 2D quasicrystals, where real-space expressions of corresponding topological invariants are introduced due to the lack of translational symmetry in quasicrystals. Finally, since quasicrystals possess forbidden symmetries in crystals such as five-fold and eight-fold rotation, we provide an overview of unique quasicrystalline symmetry-protected topological states without crystalline counterpart.

关键词： topological states quasicrystals quantum Hall effect topological insulator topological superconductor

New proof of continuity of Lyapunov exponents for a class of smooth Schrödinger cocycles with weak Liouville frequencies

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Frontiers of Mathematics in China 2020年第3期15卷 467-489页

作者： Linlin FU jiahao XU fan WU Department of Mathematics Sun Yat-sen UniversityGuangzhou 510275China Chern Institute of Mathematics and LPMC Nankai UniversityTianjin 300017China Department of Mathematics Nanjing UniversityNanjing 210093China

We reconsider the continuity of the Lyapunov exponents for a class of smooth Schrödinger cocycles with a C2 cos-type potential and a weak Liouville *** propose a new method to prove that the Lyapunov exponent is conti... 详细信息

关键词： Schrodinger cocycle Lyapunov exponent(LE) weak Liouville frequency C2 cos-type potential large deviation theorem(LDT)

Aerodynamic design of tractor propeller for high-performance distributed electric propulsion aircraft

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Chinese Journal of Aeronautics 2021年第10期34卷 20-35页

作者： Kelei WANG Zhou ZHOU Zhongyun fan jiahao GUO School of Aeronautics Northwestern Poly technical UniversityXi'an 710072China

Aiming to maximize the aerodynamic performance of the Distributed Electric Propulsion(DEP)aircraft,a hybrid design framework which focuses on the aerodynamic performance of the propeller/wing integration has been developed and validated ***-fidelity modelling for propeller aerodynamics has been used to achieve computational efficiency with reasonable *** optimizing the aerodynamic loading distributions on the tractor propeller disk,the induced slipstream is redistributed into a form that is beneficial for the wing downstream,based on which the propeller blade geometry is generated through a rapid inversed design *** compared with the Minimum Induced Loss(MIL)propeller at a specified thrust level,significant improvements of both the lift-to-drag ratio of the wing and the propeller/wing integrated aerodynamic efficiency is achieved,which shows great promise to deliver aerodynamic benefits for the wing within the propeller slipstream without any additional devices.

关键词： Aerodynamic loading distributions Aerodynamic performance Distributed electric propulsion Hybrid design framework Propeller/wing integration Variable-fidelity propeller modelling and aerodynamic analyses methods

Two-dimensional Stiefel-Whitney insulators in liganded Xenes

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npj Computational Materials 2022年第1期8卷 9-14页

作者： Mingxiang Pan Dexin Li jiahao fan Huaqing Huang School of Physics Peking University100871BeijingChina Collaborative Innovation Center of Quantum Matter 100871BeijingChina Center for High Energy Physics Peking University100871BeijingChina

Two-dimensional(2D)Stiefel-Whitney insulator(SWI),which is characterized by the second Stiefel-Whitney class,is a class of topological phases with zero Berry *** an intriguing topological state,it has been well studied in theory but seldom realized in realistic *** we propose that a large class of liganded Xenes,i.e.,hydrogenated and halogenated 2D group-IV honeycomb lattices,are 2D *** nontrivial topology of liganded Xenes is identified by the bulk topological invariant and the existence of protected corner ***,the large and tunable bandgap(up to 3.5 eV)of liganded Xenes will facilitate the experimental characterization of the 2D SWI *** findings not only provide abundant realistic material candidates that are experimentally feasible but also draw more fundamental research interest towards the topological physics associated with Stiefel-Whitney class in the absence of Berry curvature.

关键词： materials. topological Stiefel

Strategies for enhancing peroxymonosulfate activation by heterogenous metal-based catalysis:A review

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Chinese Journal of Chemical Engineering 2022年第10期50卷 12-28页

作者： jiahao Wei fan Li Lina Zhou Dandan Han Junbo Gong State Key Laboratory of Chemical Engineering School of Chemical Engineering and TechnologyTianjin UniversityTianjin 300072China The Co-Innovation Center of Chemistry and Chemical Engineering of Tianjin Tianjin 300072China

Sulfate radical-advanced oxidation processes(SR-AOPs)are promising technologies for organic pollutants *** metal-based catalysis has been widely studied and applied to activate peroxymonosulfate(PMS)for producing sulfate *** highly efficient catalysts is crucial for future extensive ***,the catalytic activity is mainly determined by mass and electron *** paper aims to overview the recent enhancement strategies for developing heterogeneous metalbased catalysts as effective PMS *** main strategies,including surface engineering,structural engineering,electronic modulation,external energy assistance,and membrane filtration enhancement,are *** potential mechanisms for improving catalytic activity are also ***,the challenges and future research prospects of heterogenous metal-based catalysis in SR-AOPs are *** work is hoped to guide the rational design of highly efficient heterogenous catalysts in SR-AOPs.

关键词： Peroxymonosulfate Heterogeneous catalyst Sulfate radical-advancedoxidation processes(SR-AOPs) Water treatment Enhancement strategies

Multi-path based secure communication in wireless mesh networks

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Journal of Systems Engineering and Electronics 2007年第4期18卷 818-824页

作者： Ding Xuyang fan Mingyu Lu Xiaojun Zhu Dayong Wang jiahao School of Computer Science and Engineering Univ. of Electronic Science and Technology of China Chengdu 610054 P. R. China

Communication security is a critical aspect of QoS provisioning in wireless mesh network （WMN）. Because of the inherent characteristics of WMN, conventional security mechanisms cannot be applied. In order to guarantee the communication security, a novel communication security mechanism is proposed. The mechanism uses a communication encryption scheme to encrypt data packets and employs a risk avoidance scheme to avoid the malicious nodes during communications. Simulation results indicate that the mechanism is able to provide secure communication effectively and reduce the damage of attacks through multiple paths.

关键词： wireless mesh network secure communication key exchange risk avoidance

Clustered trajectories anonymity in wireless sensor networks

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High Technology Letters 2015年第2期21卷 140-146页

作者： Seble Hailu Dady Wang jiahao Qin Zhiguang Yang fan School of Computer Science & Engineering University of Electronic Science and Technology of China

This paper proposes a clustered trajectories anonymity scheme （CTA） that enhances the kano nymity scheme to provide the intended level of source location privacy in mobile event monitoring when a global attacker is assumed. CTA applies isomorphic property of rotation to create traces of the fake sources distributions which are similar to those of the real sources. Thus anonymity of each trajectory and that of the clustered is achieved. In addition, location kdiversity is achieved by dis tributing fake sources around the base station. To reduce the time delay, tree rooted at the base sta tion is constructed to overlap part of the beacon interval of the nodes in the hierarchy. Both the ana lytical analysis and the simulation results prove that proved energy overhead and time delay. our scheme provides perfect anonymity with improved energy overhead and time delay.

关键词： clustered trajectories anonymity scheme (CTA) source location privacy k-anonymity global attackers wireless sensor networks (WSNs)

Recent progress of two-dimensional nanosheet membranes and composite membranes for separation applications

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Frontiers of Chemical Science and Engineering 2021年第4期15卷 793-819,F0004页

作者： Wei Wang Yanying Wei Jiang fan jiahao Cai Zong Lu Li Ding Haihui Wang School of Chemistry&Chemical Engineering South China University of TechnologyGuangzhou 510640China

Two-dimensional(2D)materials have emerged as a class of promising materials to prepare high-performance 2D membranes for various separation *** precise control of the interlayer nano-channel/sub-nanochannel between nanosheets or the pore size of nanosheets within 2D membranes enables 2D membranes to achieve promising molecular sieving *** date,many 2D membranes with high permeability and high selectivity have been reported,exhibiting high separation *** review presents the development,progress,and recent breakthrough of different types of 2D membranes,including membranes based on porous and non-porous 2D nanosheets for various *** mechanism of 2D membranes and their fabrication methods are also *** but not the least,challenges and future directions of 2D membranes for wide utilization are discussed in brief.

关键词： membrane separation 2D membranes,2D materials nanosheet

Cerium refinement of grains and primary carbides during solidification of Cr_(4)Mo_(4)V bearing steel

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Journal of Rare Earths 2024年第4期42卷 783-792页

作者： Weifeng Liu Jianqiang Wang Mingyue Sun Bin Xu jiahao Yao Qunbo fan Dianzhong Li Chongqing Innovation Center Beijing Institute of TechnologyChongqing401135China Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang110016China

The effect of cerium(Ce)on the solidification microstructure of Cr_(4)Mo_(4)V bearing steel was investigated via a combined experimental and theoretical *** a trace amount(0.056 wt%)of Ce addition,the coarse columnar grains in as-cast microstructure transform into equiaxed ones,and the average diameter is reduced from 56 to 27μ*** network-like and bulky primary MC and M2C carbides at the interdendritic regions become disconnected and refined,and their volume percentage decreases from4.15 vol%to 2.1 vol%.Ce-inclusions acting as heterogeneous nucleation agents of prior-austenite grains and Ce atoms segregating at grain boundaries,both contribute to the refinement of *** calculations reveal that primary carbides are precipitated afterγ-austenite forms near the end of the solidification *** modification of primary carbides in size and amount is mainly attributed to the isolated remaining melt separated by refinedγ-austenite grains in which the nucleation of carbides is promoted,while the growth is restrained owing to the less segregation of alloying elements.

关键词： Cr_(4)Mo_(4)V bearing steel Rare Earths Grains Primary carbides Refinement