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Nonlinear energy harvesting with dual resonant zones based on rotating system

Applied Mathematics and Mechanics(English Edition) 2021年第2期42卷 275-290页

作者： Dan WANG zhifeng hao Fangqi CHEN Yushu CHEN School of Mathematical Sciences University of JinanJinan 250022China College of Aerospace Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China School of Astronautics Harbin Institute of TechnologyHarbin 150001China

An electromagnetic nonlinear energy harvester(NEH)based on a rotating system is proposed,of which the host system rotates at a constant speed and vibrates harmonically in the vertical *** kind of device exhibits several resonant phenomena due to the combinations of the rotating and the vibration frequencies of the host system as well as the cubic nonlinearity of the *** governing equation of motion for the NEH is derived,and the dynamic responses and output power are investigated with the multiple scale method under the 1:1 primary and 2:1 superharmonic resonant *** effects of system parameters including the nondimensional external frequency,the rotating speed,and the nonlinear stiffness on the responses of free vibration for the system are *** results of the primary resonance show that the responses exhibit not only the resonant characteristics but also the nonlinear dynamic characteristics such as the saddle-node(SN)*** coexistence of multiple solutions and the varying trends of responses are verified with the direct numerical ***,the effects of system parameters on the average output power are *** results of the analyses on the two resonant conditions indicate that the large power can be harvested in two resonant frequency *** effect of resonance on the output power is dominant for the 2:1 superharmonic ***,the results also show that introducing the nonlinearity can increase the value of the output power in large frequency bands and induce the occurence of new frequency bands to harvest the large *** efficiency of the harvested power could be improved by the combined effects of the resonance as well as the nonlinearity of the NEH *** parameter conditions could help optimize the power harvesting in design.

关键词： nonlinear energy harvester(NEH) resonance output power multiple scale method rotating system

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Theoretical analysis of the convergence property of a basic pigeon-inspired optimizer in a continuous search space

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Science China(Information Sciences) 2019年第7期62卷 90-98页

作者： Yushan ZHANG Han HUANG Hongyue WU zhifeng hao School of Statistics and Mathematics Guangdong University of Finance and Economics Big Data and Educational Statistics Application Laboratory Guangdong University of Finance and Economics School of Software Engineering South China University of Technology School of Mathematics and Big Data Foshan University

The pigeon-inspired optimization(PIO) algorithm is a newly presented swarm intelligence optimization algorithm inspired by the homing behavior of pigeons. Although PIO has demonstrated effectiveness and superiority in numerous fields, particularly in practical engineering optimization, there have been few results concerning the theoretical foundations of PIO. This paper conducts convergence analysis of basic PIO in a continuous search space in two aspects. First, we analyze the convergence of each pigeon’s expected position using a difference equation and prove that the average position of each pigeon in the swarm will converge to the same value. To further study the stochastic global convergence property of the pigeon swarm, we apply the martingale theory to investigate the basic PIO swarm sequence, and achieve a sufficient condition to guarantee global convergence of the basic PIO. Our theoretical analysis shows that this convergence depends upon the accumulation of the minimum probability with which the pigeon swarm jumps to the global-optimal region at each iteration. The mathematical methods proposed in this study, particularly the martingale technique, also provide a new effective approach for the theoretical analysis of bio-inspired algorithms in continuous optimization.

关键词： pigeon-inspired optimization(PIO) convergence analysis martingale continuous optimization swarm intelligence

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Bifurcation analysis for vibrations of a turbine blade excited by air flows

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Science China(Technological Sciences) 2016年第8期59卷 1217-1231页

作者： WANG Dan CHEN YuShu hao zhifeng CAO QingJie School of Astronautics Harbin Institute of Technology Harbin 150001 China

A reduced three-degree-of-freedom model simulating the fluid-structure interactions （FSI） of the turbine blades and the on- coming air flows is proposed. The equations of motions consist of the coupling of bending and torsion of a blade as well as a van der Pol oscillation which represents the time-varying of the fluid. The 1：1 internal resonance of the system is analyzed with the multiple scale method, and the modulation equations are derived. The two-parameter bifurcation diagrams are computed. The effects of the system parameters, including the detuning parameter and the reduced frequency, on responses of the struc- ture and fluid are investigated. Bifurcation curves are computed and the stability is determined by examining the eigenvalues of the Jacobian matrix. The results indicate that rich dynamic phenomena of the steady-state solutions including the sad- dle-node and Hopf bifurcations can occur under certain parameter conditions. The parameter region where the unstable solu- tions occur should be avoided to keep the safe operation of the blades. The analytical solutions are verified by the direct nu- merical simulations.

关键词： fluid-structure interaction (FSI) internal resonance two-parameter bifurcation diagram saddle-node bifurcation Hopf bifurcation direct numerical simulation

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Exploring serverless computing for stream analytic

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High Technology Letters 2020年第1期26卷 17-24页

作者： Cheng Yingchao hao zhifeng Cai Ruichu School of Computer Science and Technology Guangdong University of TechnologyGuangzhou 510006P.R.China School of Mathematics and Big Data Foshan UniversityFoshan 528000P.R.China Department of Statistics Texas A&M UniversityCollege Station 77840USA

This work proposes ARS(FaaS) serverless framework scheduling and provisioning resources for streaming applications autonomously, which ensures real-time response on unpredictable and fluctuating streaming data. A HPC cloud platform is used as a de facto platform, on which serverless computing for stream analytic is explored. This work enables application developers to build and run steaming applications without worrying about servers, which means that the developers are able to focus on application features instead of scheduling and provisioning resources of the infrastructure. The serverless computing framework, ARS(FaaS), provides function-as-a-service to make the developers write code in discrete event-driven functions. ARS(FaaS) is capable of running and scaling the developer's code automatically, according to the throughput of streaming events. The major contribution of this serverless framework is effective and efficient autonomous resource scheduling for real-time streaming analytic, which enables the developers to build applications faster with autonomous resource scheduling. ARS(FaaS) framework is appropriate for real-time and stream analytic on event-driven data with spiky and variable compute requirements.

关键词： serverless steam processing HPC cloud auto-scaling function-as-a-service(FaaS)

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Kinetics of methanol steam reforming over COPZr-2 catalyst

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Journal of Natural Gas Chemistry 2008年第2期17卷 171-174页

作者： Yongfeng Li Weiming Lin Lin Yu zhifeng hao Rongjian Mai Faculty of Chemical Engineering and Light lndustry Guangdong University of Technology Guangzhou 510006 Guangdong China Sehool of Chemical and Energy Engineering South China University of Technology Guangzhou 510640 Guangdong China

The COPZr-2 catalyst, which was prepared in our prophase research, showed good catalytic performance in methanol steam reforming reaction. In this article, the best one was chosen as an example to study the reaction kinetics of methanol steam reforming over this type of catalyst. First, the effects of methanol conversion to outlet CO2 and methanol conversion to outlet CO on methanol pseudo contact time W/FMeOH were investigated. Then by applying the reaction route that methanol direct reforming （DR） and methanol decomposition （DE） were carried out in parallel, the reaction kinetic model with power function type was established. And the parameters for the model were estimated using a non-linear regression program which computed weighted least squares of the defined objects function. Finally, the kinetic model passed the correlation test and the F-test.

关键词： methanol reforming kinetics COPZr-2

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Detail-preserving smoke simulation using an efficient high-order numerical scheme

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Science China(Information Sciences) 2020年第6期63卷 217-219页

作者： Jian ZHU Zhuo YANG Hanqiu SUN Enhua WU Ruichu CAI zhifeng hao School of Computer Science Guangdong University of Technology Institute of Space and Earth Info.Science the Chinese University of Hong Kong State Key Laboratory of Computer Science Institute of Software Chinese Academy of Sciences Faculty of Science and Technology University of Macau School of Mathematics and Big Data Foshan University

The advection step in Eulerian fluid simulation is prone to numerical dissipation [1], resulting in the loss of fluid details. Among the various attempts to develop accurate advection solvers, high-order advection schemes such as back and forth error compensation and correction (BFECC)[2] and MacCormack [3] are effective solutions. Complementary to high-order advection schemes are

关键词： CIP simulation Detail-preserving smoke simulation using an efficient high-order numerical scheme

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Granger causal representation learning for groups of time series

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Science China(Information Sciences) 2024年第5期67卷 56-68页

作者： Ruichu CAI Yunjin WU Xiaokai HUANG Wei CHEN Tom Z.J.FU zhifeng hao School of Computer Science Guangdong University of Technology Peng Cheng Laboratory College of Science Shantou University

Discovering causality from multivariate time series is an important but challenging *** existing methods focus on estimating the Granger causal structures among multivariate time series,while ignoring the prior knowledge of these time series, e.g., the group of the time series. Focusing on discovering the Granger causal structures among groups of time series, we propose a Granger causal representation learning method to solve this problem. First, we use the multiset canonical correlation analysis method to learn the Granger causal representation of each group of time series. Then, we model the Granger causal relationships among the learned Granger causal representations using a recurrent neural network with temporal information. Finally, we formulate the above two stages into one unified optimization problem, which is efficiently solved using the augmented Lagrangian method. We conduct extensive experiments on synthetic and real-world datasets to validate the correctness and effectiveness of the proposed method.

关键词： Granger causal discovery Granger causal representation learning time series data recurrent neural network multiset canonical correlation analysis

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Search-Based Software Test Data Generation for Path Coverage Based on a Feedback-Directed Mechanism

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Complex System Modeling and Simulation 2023年第1期3卷 12-31页

作者： Stuart Dereck Semujju Han Huang Fangqing Liu Yi Xiang zhifeng hao School of Software Engineering South China University of TechnologyGuangzhou 510006China College of Science Shantou UniversityShantou 515063China

Automatically generating test cases by evolutionary algorithms to satisfy the path coverage criterion has attracted much research attention in software *** the context of generating test cases to cover many target paths,the efficiency of existing methods needs to be further improved when infeasible or difficult paths exist in the program under *** is because a significant amount of the search budget(i.e.,time allocated for the search to run)is consumed when computing fitness evaluations of individuals on infeasible or difficult *** this work,we present a feedback-directed mechanism that temporarily removes groups of paths from the target paths when no improvement is observed for these paths in subsequent *** fulfill this task,our strategy first organizes paths into ***,in each generation,the objective scores of each individual for all paths in each group are summed *** each group,the lowest value of the summed up objective scores among all individuals is assigned as the best aggregated score for a group.A group is removed when no improvement is observed in its best aggregated score over the last two *** experimental results show that the proposed approach can significantly improve path coverage rates for programs under test with infeasible or difficult paths in case of a limited search *** particular,the feedback-directed mechanism reduces wasting the search budget on infeasible paths or on difficult target paths that require many fitness evaluations before getting an improvement.

关键词： automated test case generation software testing path coverage many-objective optimization

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Near-infrared spectroscopy as a promising tool in stroke:Current applications and future perspectives

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Journal of Innovative Optical Health Sciences 2021年第6期4卷 19-41页

作者： Jinyan Sun Richong Pang Sisi Chen Hucheng Chen Yuanrong Xie Dandan Chen Kai Wu Jianbin Liang Kecheng Yan zhifeng hao Department of Biomedical Engineering School of Medicine Foshan UniversityFoshan 528000P.R.China Department of Electronic Information School of Mechatronic Engineering and Automation Foshan University Foshan 528000P.R.China Seventh Affiliated Hospital Sun Yat-Sen UniversityShenzhen 518107P.R.China Department of Biomedical Engineering School of Material Science and Engineering South China University of Technology Guangzhou 510006P.R.China School of Mathematics and Big Data Foshan University Foshan 528000 P.R.China

Stroke is caused by an acute focal disruption of the vasculature in the central nervous ***-related functional deficits are the most devastating consequences for stroke *** signals from stroke patients can reflect the functional statuses of patients and provide insights into the neuronal recovery mechanism for functioning,which could be used as the basis for designing optimal treatment ***-infrared spectroscopy(NIRS)is a low-cost,noninvasive,easily operated neuroimage method and it is compatible with various rehabilitative *** advantages make NIRS an excellent candidate in research for stroke ***,we focused on the brain functions and recovery for stroke patients at stable status,conducted a systematic literature review about NIRS applications in stroke since 2000 and identified a total of 72 references through ScienceDirect and PubMed database *** NIRS studies in stroke include resting-state function and its recovery,motor function and itsrecovery,motor and cognition interference,cognitive function and its recovery,language function and its recovery,emotional function and its recovery and other *** on the results of the quality assessment,we identified some study gaps from the previous research and provided suggestions for some methodological improvement in the *** trend of NIRS gives a boost to its application in stroke,and the potential research directions for NIRS in stroke are pros-pected,including multi-center clinical research,treatment efficacy prediction research and brain-muscle coupling ***,limitations of NIRS are discussed.

关键词： Near-infrared spectroscopy stroke function deficits recovery

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Free Quadratic Bialgebra

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Acta Mathematica Sinica,English Series 1996年第3期12卷 244-248页

作者： hao zhifeng, Department of Applied Mathematics South China University of Technology Guangzhou, 510641 ChinaTong Wenting, Department of Mathematics Nanjing University Nanjing, 210008 China Department of Applied Mathematics South China University of Technology Guangzhou China Department of Mathematics Nanjing University Nanjing China

In this paper, we obtain the following main theorem for a free quadratic bialgebra J: (a) For p≠0, J is a pointed cosemisimple coalgebra. For p=0, J is a hyperalgebra. (b) For p≠0 and q≠0, J has antipode S iff p·q+2=0 and S(x)=x. Forp=0 or q=0, J has antipode and S(x)=-x. (c) All left J*-modules are rational. Also, we give some applications in homological theory and algebraic K-theory.

关键词： Free quadratic bialgebra Antipode Cosemisimple Rational module

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