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Stability switches and bifurcation analysis in a coupled neural system with multiple delays

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Science China(Technological Sciences) 2016年第6期59卷 920-931页

作者： GE ju Hong xu Jian Department of Mathematics and Information Science Henan University of Economics and Law School of Aerospace Engineering and Applied Mechanics Tongji University

A coupled neural system with multiple delays has been investigated. The number of equilibrium points is analyzed. It implies that the neural system exhibits a unique equilibrium and three ones for the different values of coupling weight by employing the pitchfork bifurcation of the trivial equilibrium point. Further, the local asymptotical stability of the trivial equilibrium point is studied by analyzing the corresponding characteristic equation. Some stability criteria involving multiple delays and coupling weight are obtained. The results show that the neural system exhibits the delay-independent and delay-dependent stability. Increasing delay induces stability switching between resting state and periodic motion in some parameter regions of coupling weight. In addition, the criterion for the global stability of the trivial equilibrium is also derived by constructing a suitable Lyapunov functional. Finally, some numerical simulations are taken to support the theoretical results.

关键词： multiple delays stability switches global stability

The symmetric space,strong isotropy irreducibility and equigeodesic properties

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Science China Mathematics 2024年第1期67卷 129-148页

作者： Ming xu ju Tan School of Mathematical Sciences Capital Normal UniversityBeijing 100048China School of Microelectronics and Data Science Anhui University of TechnologyMa'anshan 243032China

A smooth curve on a homogeneous manifold G/H is called a Riemannian equigeodesic if it is a homogeneous geodesic for any G-invariant Riemannian *** homogeneous manifold G/H is called Riemannian equigeodesic,if for any x∈G/H and any nonzero y∈Tx(G/H),there exists a Riemannian equigeodesic c(t) with c(0)=x and ■(0)=*** two notions can be naturally transferred to the Finsler setting,which provides the definitions for Finsler equigeodesics and Finsler equigeodesic *** prove two classification theorems for Riemannian equigeodesic spaces and Finsler equigeodesic spaces,***,a homogeneous manifold G/H with a connected simply connected quasi compact G and a connected H is Riemannian equigeodesic if and only if it can be decomposed as a product of Euclidean factors and compact strongly isotropy irreducible ***,a homogeneous manifold G/H with a compact semisimple G is Finsler equigeodesic if and only if it can be locally decomposed as a product,in which each factor is Spin(7)/G2,G2/SU (3) or a symmetric space of compact *** results imply that the symmetric space and the strongly isotropy irreducible space of compact type can be interpreted by equigeodesic *** an application,we classify the homogeneous manifold G/H with a compact semisimple G such that all the G-invariant Finsler metrics on G/H are *** suggests a new project in homogeneous Finsler geometry,i.e.,to systematically study the homogeneous manifold G/H on which all the G-invariant Finsler metrics satisfy a certain geometric property.

关键词： equigeodesic equigeodesic space flag manifold orbit type stratification symmetric space strongly isotropy irreducible space

Abnormal nonlinear optical responses on the surface of topological materials

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npj Computational Materials 2022年第1期8卷 1045-1052页

作者： Haowei xu Hua Wang ju Li Department of Nuclear Science and Engineering Massachusetts Institute of TechnologyCambridgeMA02139USA Department of Materials Science and Engineering Massachusetts Institute of TechnologyCambridgeMA02139USA

The nonlinear optical(NLO)responses of topological materials are under active *** previous works studied the surface and bulk NLO responses *** we develop a generic Green’s function framework to investigate the surface and bulk NLO responses *** reveal that the topological surface can behave disparately from the bulk under light ***,the photocurrents on the surface can flow in opposite directions to those in the bulk interior,and the light-induced spin current on the surface can be orders of magnitude stronger than its bulk counterpart on a per-volume *** also study the responses under inhomogeneous field and higher-order NLO effect,which are all distinct on the *** anomalous surface responses suggest that light can be a valuable tool for probing the surface states of topological ***,the surface effects should be prudently considered when investigating the optical properties of topological materials.

关键词： materials. surface. topological

Improved direct P code acquisition technique

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维普期刊数据库

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Journal of Systems Engineering and Electronics 2009年第5期20卷 948-953页

作者： xu Ying Wang ju Wu Siliang Academy of Opto-Electronics Chinese Academy of Science Beijing 100190 P. R. China School of Information Science and Technology Beijing Inst. of Technology Beijing 100081 P. R. China

P code direct acquisition is an important technology in satellite navigation system. As the P code has a long period, it is hard to directly acquire. The traditional average method can process multiple code phases in a time to shorten the acquisition time. But with the increase of average phase error of the input signal and the local code, the correlation signal-to-noise ratio （SNR） loss increases. To reduce the SNR loss, an improved average method is introduced. A new sequence is generated with a summation of phase shifting sequences to decrease correlation peak loss. Simulation results show that compared with direct average method, the improved average method effectively increases correlation SNR.

关键词： P code acquisition direct average algorithm improved average algorithm.

Analysis of SE~τ IR~ω S Epidemic Disease Models with Vertical Transmission in Complex Networks

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Acta Mathematicae Applicatae Sinica 2012年第1期28卷 63-74页

作者： Xia LIU De-ju xu Department of Mathematics Capital Normal UniversityBeijing 100048China

When the role of network topology is taken into consideration, one of the objectives is to understand the possible implications of topological structure on epidemic models. As most real networks can be viewed as complex networks, we propose a new delayed SETIRWS epidemic disease model with vertical transmission in complex networks. By using a delayed ODE system, in a small-world （SW） network we prove that, under the condition R0 ≤ 1, the disease-free equilibrium （DFE） is globally stable. When R0 〉 1, the endemic equilibrium is unique and the disease is uniformly persistent. We further obtain the condition of local stability of endemic equilibrium for R0 〉 1. In a scale-free （SF） network we obtain the condition R1 〉 1 under which the system will be of non-zero stationary prevalence.

关键词： SETIRWS SW network SF network DFE

Visualization and analysis of local and distant population flows on the Qinghai-Tibet Plateau using crowd-sourced data

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Journal of Geographical Sciences 2021年第2期31卷 231-244页

作者： xu jun LIU ju xu Yang PEI Tao State Key Laboratory of Resources and Environmental Information System Institute of Geographic Sciences and Natural Resources ResearchCASBeijing100101China College of Resources and Environment University of Chinese Academy of SciencesBeijing100049China

Human migration between cities is one important aspect of spatial interaction that not only reflects urban attractiveness but also denotes interactions amongst *** therefore implemented a web-based visualization system to analyze and interactively explore local and distant population flow patterns between cities on the Qinghai-Tibet Plateau(QTP).We utilized 2017 Tencent population flow data from which we initially constructed inbound and outbound vectors for cities on the *** then used multidimensional scaling to examine and visualize migration patterns and similarities between *** reveal the presence of six local and three distant human mobility patterns on the QTP as well as average summer monthly migrations more than twice the level of those in the winter.

关键词： population flow visualization Tencent location big data spatiotemporal pattern Qinghai-Tibet Plateau

Durable Ru Nanocrystal with HfO_(2)Modification for Acidic Overall Water Splitting

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Nano-Micro Letters 2024年第9期16卷 462-477页

作者： Xiangkai Kong Jie xu Zhicheng ju Changle Chen School of Materials and Physics China University of Mining and TechnologyXuzhou 221116JiangsuPeople’s Republic of China Anhui Province Key Laboratory of Pollutant Sensitive Materials and Environmental Remediation Huaibei Normal UniversityHuaibei 235000AnhuiPeople’s Republic of China School of Chemistry and Materials Science University of Science and Technology of ChinaHefei 230026AnhuiPeople’s Republic of China School of Chemistry and Chemical Engineering Nanjing UniversityNanjing 210023JiangsuPeople’s Republic of China

Durable and efficient bi-functional catalyst,that is capable of both oxygen evolution reaction and hydrogen evolution reaction under acidic condition,are highly desired for the commercialization of proton exchange membrane water ***,we report a robust L-Ru/HfO_(2)heterostructure constructed via confining crystalline Ru nanodomains by HfO_(2)*** assembled with a proton exchange membrane,the bi-functional L-Ru/HfO_(2)catalyst-based electrolyzer presents a voltage of 1.57 and 1.67 V to reach 100 and 300 mA cm^(-2)current density,prevailing most of previously reported Ru-based materials as well as commercial Pt/C||RuO_(2)*** is revealed that the synergistic effect of HfO_(2)modification and small crystalline domain formation significantly alleviates the over-oxidation of *** importantly,this synergistic effect facilitates a dual-site oxide path during the oxygen evolution procedure via optimization of the binding configurations of oxygenated *** a result,the Ru active sites maintain the metallic state along with reduced energy barrier for the rate-determining step(^(*)O→^(*)OOH).Both of water adsorption and dissociation(Volmer step)are strengthened,while a moderate hydrogen binding is achieved to accelerate the hydrogen desorption procedure(Tafel step).Consequently,the activity and stability of acidic overall water splitting are simultaneously enhanced.

关键词： Ruthenium Hafnium dioxide Oxygen evolution catalysis Anti-oxidation

Distributed dynamic task allocation for unmanned aerial vehicle swarm systems:A networked evolutionary game-theoretic approach

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Chinese Journal of Aeronautics 2024年第6期37卷 182-204页

作者： Zhe ZHANG ju JIANG Haiyan xu Wen-An ZHANG College of Automation Engineering Nanjing University of Aeronautics and AstronauticsNanjing 211106China College of Economics and Management Nanjing University of Aeronautics and AstronauticsNanjing 211106China College of Information Engineering Zhejiang University of TechnologyHangzhou 310023China

Task allocation is a key aspect of Unmanned Aerial Vehicle(UAV)swarm collaborative *** an continuous increase of UAVs’scale and the complexity and uncertainty of tasks,existing methods have poor performance in computing efficiency,robustness,and realtime allocation,and there is a lack of theoretical analysis on the convergence and optimality of the *** paper presents a novel intelligent framework for distributed decision-making based on the evolutionary game theory to address task allocation for a UAV swarm system in uncertain scenarios.A task allocation model is designed with the local utility of an individual and the global utility of the ***,the paper analytically derives a potential function in the networked evolutionary potential game and proves that the optimal solution of the task allocation problem is a pure strategy Nash equilibrium of a finite strategy ***,a PayOff-based Time-Variant Log-linear Learning Algorithm(POTVLLA)is proposed,which includes a novel learning strategy based on payoffs for an individual and a time-dependent Boltzmann *** former aims to reduce the system’s computational burden and enhance the individual’s effectiveness,while the latter can ensure that the POTVLLA converges to the optimal Nash equilibrium with a probability of *** simulation results show that the approach is optimal,robust,scalable,and fast adaptable to environmental changes,even in some realistic situations where some UAVs or tasks are likely to be lost and increased,further validating the effectiveness and superiority of the proposed framework and algorithm.

关键词： Task allocation Unmanned Aerial Vehicles(UAV) Game theory Log-linear learning Distributed optimization algorithm

Photodynamic Therapy of Oligoethylene GlycoI-Dendronized Reduction-Sensitive Porphyrins

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Chinese Journal of Chemistry 2017年第9期35卷 1445-1451页

作者： Mingjie ju jundi Pang Ligong xu School of Sports Science and Engineering East China University of Science and Technology Shanghai 200237 China Kunming Medical University Kunming Yunnan 650500 China

Graphene oxide （GO） and its functionalized derivatives have attracted increasing attention in medical treatment. Herein, a reduction sensitive PEI-GO-SS-TPP was synthesized for photodynamic therapy. More than 80% porphyrin release was observed in the presence of 10 mmol·L^-1 DTT in one day. The confocal laser scanning microscopy confirmed that the cell uptake efficiency of PEI-GO-SS-TPP was remarkably enhanced as compared to free porphyrin which was significantly dependent on incubation time. For photodynamic therapy, GSH-OEt could effectively increase the photodynamic therapy efficiency of PEI-GO-SS-TPE Compared with free porphyrin, the toxicity from PEI-GO-SS-TPP is much higher with a low IC50 （2.1 μg/mL） value. All results indicate that the PEI-GO-SS-TPP PSs are promising for photodynamic therapy.

关键词： graphene oxide photodynamic therapy porphyrindisulfide