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Lagrangian-based investigation of multiphase flows by finite-timeLyapunov exponents

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Acta Mechanica Sinica 2012年第3期28卷 612-624页

作者： Jia-ning Tang Chien-Chou Tseng ning-FeiWang School of Aerospace Engineering Beijing Institute of Technology100081 Beijing China Department of Mechanical and Electro-Mechanical Engineering National Taiwan Sun Yat-Sen UniversityKaohsiung Taiwan China Department of Aerospace Engineering University of Michigan Ann ArborM148109 USA

Multiphase flows are ubiquitous in our daily life and engineering applications. It is important to investigate the flow structures to predict their dynamical behaviors ef- fectively. Lagrangian coherent structures （LCS） defined by the ridges of the finite-time Lyapunov exponent （FTLE） is utilized in this study to elucidate the multiphase interactions in gaseous jets injected into water and time-dependent turbu- lent cavitation under the framework of Navier-Stokes flow computations. For the gaseous jets injected into water, the highlighted phenomena of the jet transportation can be observed by the LCS method, including expansion, bulge, necking/breaking, and back-attack. Besides, the observation of the LCS reveals that the back-attack phenomenon arises from the fact that the injected gas has difficulties to move toward downstream re- gion after the necking/breaking. For the turbulent cavitating flow, the ridge of the FTLE field can form a LCS to capture the front and boundary of the re-entraint jet when the ad- verse pressure gradient is strong enough. It represents a bar- rier between particles trapped inside the circulation region and those moving downstream. The results indicate that the FFLE field has the potential to identify the structures of mul- tiphase flows, and the LCS can capture the interface/barrier or the vortex/circulation region.

关键词： Finite-time Lyapunov exponents Lagrangiancoherent structures Multiphase flow Gaseous jets injectedinto water Cavitation

Flow structures of gaseous jets injected into water for underwater propulsion

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Acta Mechanica Sinica 2011年第4期27卷 461-472页

作者： Jia-ning Tang ning-Fei Wang Wei Shyy School of Aerospace Engineering Beijing Institute of Technology 100081 Beijing China Department of Aerospace Engineering University of Michigan Ann Arbor MI 48109 USA

Gaseous jets injected into water are typically found in underwater propulsion, and the flow is essentially unsteady and turbulent. Additionally, the high water-to-gas density ratio can result in complicated flow structures; hence measuring the flow structures numerically and experimentally remains a challenge. To investigate the performance of the underwater propulsion, this paper uses detailed NavierStokes flow computations to elucidate the gas-water interactions under the framework of the volume of fluid （VOF） model. Furthermore, these computations take the fluid compressibility, viscosity, and energy transfer into consideration. This paper compares the numerical results and experimental data, showing that phenomena including expansion, bulge, necking/breaking, and back-attack are highlighted in the jet process. The resulting analysis indicates that the pressure difference on the rear and front surfaces of the propul- sion system can generate an additional thrust. The strong and oscillatory thrust of the underwater propulsion system is caused by the intermittent pulses of the back pressure and the nozzle exit pressure. As a result, the total thrust in underwater propulsion is not only determined by the nozzle geometry but also by the flow structures and associated pressure distri- butions.

关键词： Gaseous jets - Underwater propulsion Highdensity ratio Gas-water interactions

The effects of hydrogen on the helium behavior in palladium

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Nuclear Science and Techniques 2016年第5期27卷 114-119页

作者： Chang-ning Peng Electrical Engineering College Longdong University

As one candidate of tritium storage materials,palladium subjects to the damage from helium atoms introduced by the(3-decay of tritium *** mechanical properties of palladium will be greatly degraded deriving from the accumulation of helium atoms.A set of interatomic potentials has been fitted based on ab initio calculation according to the Morse *** dynamic methods are utilized to investigate the existence of H atoms on the release of helium atoms from palladium with the present fitted *** is found that hydrogen atoms play significant roles in the diffusion and release of helium *** presence of hydrogen atoms tends to obstacle the diffusion and release of helium atoms in palladium.

关键词：氦原子氢原子行为钯分子动力学存储材料机械性能莫尔斯

Resilient Event-Triggered Control of Connected Automated Vehicles Under Cyber Attacks

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IEEE/CAA Journal of Automatica Sinica 2023年第12期10卷 2300-2302页

作者： ning Zhao Xudong Zhao ning Xu Liang Zhang the College of Control Science and Engineering Bohai UniversityJinzhou 121013China the Institute of Ocean Research Bohai UniversityJinzhou 121013China the Faculty of Electronic Information and Electrical Engineering Dalian University of TechnologyDalian 116024China the College of Information Science and Technology Bohai UniversityJinzhou 121013China

Dear Editor,This letter contributes to designing a resilient event-triggered controller for connected automated vehicles under cyber attacks,including denial-of-service(DoS)and deception *** characterize the effect of... 详细信息

关键词： DoS service automated

Bipartite quasi-synchronization of multiple neural networks with generalized cooperative-competitive topology

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Science China(Technological Sciences) 2023年第6期66卷 1855-1866页

作者： LI ning CAO JinDe School of Mathematics and Information Science Henan University of Economics and LawZhengzhou 450046China School of Mathematics Southeast UniversityNanjing 210096China Yonsei Frontier Lab Yonsei UniversitySeoul 03722Korea

This study examines the bipartite quasi-synchronization(B-Q synchronization)issue of coupled networks with general cooperative-competitive topology and the event-triggered communications between nodes to curb the communication *** the existing literature concerning bipartite synchronization,the network topology is required to be structurally balanced,which necessitates that competitive interactions exist only between two distinct *** this study,we aim to lengthen the network’s topology to a more general signed network in which antagonistic interactions can exist in the same or different *** to signed graph theory and the markovian stochastic event-triggering mechanism,the dynamical model of multiple neural networks(MNNs)with structurally unbalanced and markovian event-triggered communication is *** utilizing the stochastic Lyapunov stability analysis,some adequate criteria for B-Q synchronization of MNNs with the structurally unbalanced graph are obtained;also,a bound for the B-Q synchronization error is *** a special case,the bipartite synchronization criteria for MNNs with the structurally balanced graph are also ***,two simulations are performed to verify the theoretical result.

关键词： B-Q synchronization structurally unbalanced event-triggered communication Markovian switching topology

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Approximating Special Social Influence Maximization Problems

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Tsinghua Science and Technology 2020年第6期25卷 703-711页

作者： Jie Wu ning Wang the Department of Computer and Information Sciences Temple University.PhiladelphiaPA 19122USA the Department of Computer Science Rowan UniversityGlassboroNJ 08028USA

Social Influence Maximization Problems(SIMPs)deal with selecting k seeds in a given Online Social Network(OSN)to maximize the number of eventually-influenced *** is done by using these seeds based on a given set of influence probabilities among neighbors in the *** the SIMP has been proved to be NP-hard,it has both submodular(with a natural diminishing-return)and monotone(with an increasing influenced users through propagation)that make the problem suitable for approximation ***,several special SIMPs cannot be modeled as submodular or monotone *** this paper,we look at several conditions under which non-submodular or non-monotone functions can be handled or *** is a profit-maximization SIMP where seed selection cost is included in the overall utility function,breaking the monotone *** other is a crowd-influence SIMP where crowd influence exists in addition to individual influence,breaking the submodular *** then review several new techniques and notions,including double-greedy algorithms and the supermodular degree,that can be used to address special *** main results show that for a specific SIMP model,special network structures of OSNs can help reduce its time complexity of the SIMP.

关键词： influence maximization online social networks submodular function

Topological quantum states of matter in iron-based superconductors:from concept to material realization

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National Science Review 2019年第2期6卷 213-226页

作者： ning Hao Jiangping Hu Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions High Magnetic Field Laboratory of Chinese Academy of Sciences Beijing National Laboratory for Condensed Matter Physics and Institute of Physics Chinese Academy of Sciences CAS Center of Excellence in Topological Quantum Computation and Kavli Institute of Theoretical Sciences University of Chinese Academy of Sciences Collaborative Innovation Center of Quantum Matter

We review recent progress in the exploration of topological quantum states of matter in iron-based superconductors. In particular, we focus on the non-trivial topology existing in the band structures and superconducting states of iron’s 3d orbitals. The basic concepts, models, materials and experimental results are reviewed. The natural integration between topology and high-temperature superconductivity in iron-based superconductors provides great opportunities to study topological superconductivity and Majorana modes at high temperature.

关键词： iron-based superconductor topological insulator topological superconductor spin–orbit coupling

Hybrid Navigation Method for Multiple Robots Facing Dynamic Obstacles

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Tsinghua Science and Technology 2022年第6期27卷 894-901页

作者： Kaidong Zhao Li ning Shenzhen Institutes of Advanced Technology Chinese Academy of SciencesShenzhen 518055China University of Chinese Academy of Sciences Beijing 100049China

With the continuous development of robotics and artificial intelligence,robots are being increasingly used in various *** traditional navigation algorithms,such as Dijkstra and A*,many dynamic scenarios in life are difficult to cope *** solve the navigation problem of complex dynamic scenes,we present an improved reinforcement-learning-based algorithm for local path planning that allows it to perform well even when more dynamic obstacles are *** method applies the gmapping algorithm as the upper layer input and uses reinforcement learning methods as the *** algorithm enhances the robots’ability to actively avoid obstacles while retaining the adaptability of traditional methods.

关键词： simultaneous localization and mapping(SLAM) reinforcement learning multirobots dynamic obstacles robot operating system(ROS) navigation

Effect of Axial Deformation on Elastic Properties of Irregular Honeycomb Structure

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Chinese Journal of Mechanical Engineering 2021年第4期34卷 276-287页

作者： ning Wang Qingtian Deng School of Science Chang’an UniversityXi’an 710064China

Irregular honeycomb structures occur abundantly in nature and in man-made products,and are an active area of *** this paper,according to the optimization of regular honeycomb structures,two types of irregular honeycomb structures with both positive and negative Poisson’s ratios are *** elastic properties of irregular honeycombs with varying structure angles were investigated through a combination of material mechanics and structural mechanics methods,in which the axial deformation of the rods was *** numerical results show that axial deformation has a significant influence on the elastic properties of irregular honeycomb *** elastic properties of the structure can be considered by the enclosed area of the unit structure,the shape of the unit structure,and the elastic properties of the original *** elastic properties considering the axial deformation of rods studied in this study can provide a reference for other scholars.

关键词： Axial deformation Elastic modulus Positive Poisson’s ratio Negative Poisson’s ratio Irregular honeycombs