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The spectrum and stability of travelling pulses in a coupled FitzHugh-Nagumo equation

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Science China Mathematics 2024年第5期67卷 975-1010页

作者： qi qiao Xiang Zhang School of Mathematical Sciences Shanghai Jiao Tong UniversityShanghai 200240China Key Laboratory of Scientific and Engineering Computing(Ministry of Education) and Shanghai Frontier Science Center of Modern Analysis(CMA-Shanghai)Shanghai Jiao Tong UniversityShanghai 200240China

For a coupled slow-fast FitzHugh-Nagumo(FHN)equation derived from a reaction-diffusionmechanics(RDM)model,Holzer et al.(2013)studied the existence and stability of the travelling pulse,which consists of two fast orbit arcs and two slow ones,where one fast segment passes the unique fold point with algebraic decreasing and two slow ones follow normally hyperbolic critical curve *** and Zhang(2021)obtained the existence of the travelling pulse,whose two fast orbit arcs both exponentially decrease,and one of the slow orbit arcs could be normally hyperbolic or not at the ***,we characterize both the nonlinear and spectral stability of this travelling pulse.

关键词： coupled FitzHugh-Nagumo equation singular perturbation travelling pulse spectrum nonlinear stability spectral stability

Physical layer security for massive access in cellular Internet of Things

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Science China(Information Sciences) 2020年第2期63卷 104-115页

作者： qiao qi Xiaoming CHEN Caijun ZHONG Zhaoyang ZHANG College of Information Science and Electronic Engineering Zhejiang University

The upcoming fifth generation(5G) cellular network is required to provide seamless access for a massive number of Internet of Things(IoT) devices over the limited radio spectrum. In the context of massive spectrum sharing among heterogeneous Io T devices, wireless security becomes a critical issue owing to the broadcast nature of wireless channels. According to the characteristics of the cellular IoT network,physical layer security(PHY-security) is a feasible and effective way of realizing secure massive access. This article reviews the security issues in the cellular IoT network with an emphasis on revealing the corresponding challenges and opportunities for the design of secure massive access. Furthermore, we provide a survey on PHY-security techniques to improve the secrecy performance. Especially, we propose a secure massive access framework for the cellular Io T network by exploiting the inherent co-channel interferences. Finally, we discuss several potential research directions to further enhance the security of massive IoT.

关键词： 5G and beyond PHY-security massive access cellular IoT

Toward an Ecological Civilization:China’s Progress as Documented by the Second National General Survey of Pollution Sources

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Engineering 2021年第9期7卷 1336-1341页

作者： Minghui Xie Huabo Duan Peng Kang qi qiao Lu Bai State Key Laboratory of Environmental Criteria and Risk Assessment Chinese Research Academy of Environmental SciencesBeijing 100012China Key Laboratory of Coastal Urban Resilient Infrastructures(Shenzhen University) Ministry of EducationUnderground Polis AcademyCollege of Civil and Transportation EngineeringShenzhen UniversityShenzhen 518060China

The relationship between environmental quality and economic growth has been a hot topic for *** years of rapid industrialization and urbanization,China’s environmental challenges are approaching a turning *** the principles of ecological civilization construction,China is on its way to maintaining high-quality and green economic *** 10 June 2020,the Chinese Government reported the key findings of the Second National General Survey of Pollution Sources(fiscal year 2017),which provides strong quantitative evidence of progress toward ecological *** terms of our comparison between the two National General Surveys in 2007 and 2017,it was found that environmental pollution,measured in terms of many wastewater and air emission pollutant discharges,is decreasing despite the steady growth in economic activities—and at a noticeably fast *** national and local governments can adopt some of China’s ecological civilization practices,within their own individual contexts.

关键词： Ecological civilization National General Survey of Pollution Sources Green development Sustainable development

Advance in Research of Ecology and Landscape Reconstruction of the River Floodplain In China

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湿地科学 2008年第1期6卷 80-86页

作者： qiao Lifang qi Anguo ZHANG Yichuan College of Landscape Architecture Henan Institute of Science and Technology Xinxiang 453003 Henan P. R. China

The research of ecology and landscape reestablishment of river floodplain is considered favorable to its conservation and *** similarity and difference among river floodplain,wetland,riverside and shore have been reviewed,as well as the progress in the research of floodplain ecology reestablishment in quantitative evaluation,vegetation restoration,the influence on animal habitat and the application of eco-engineering;and of the landscape reestablishment in resource development and utilization,landscape feature and changes,landscape function,structure and *** potentially important fields are expected to be the change of landscape pattern in different scales,the reasonable protection and utilization in the floodplain tourism,the simulating and monitoring of landscape dynamics,the planning and designing methods of floodplain landscape and the management of floodplain ecosystems.

关键词：生态再造景观改造中国洪水

STABILITY OF SWITCHED POLYNOMIAL SYSTEMS

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Journal of Systems Science & Complexity 2008年第3期21卷 362-377页

作者： Zhiqiang LI Yupeng qiao Hongsheng qi Daizhan CHENG Institute of Systems Science Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing 100190 China

This paper investigates the stability of （switched） polynomial systems. Using semi-tensor product of matrices, the paper develops two tools for testing the stability of a （switched） polynomial system. One is to convert a product of multi-variable polynomials into a canonical form, and the other is an easily verifiable sufficient condition to justify whether a multi-variable polynomial is positive definite. Using these two tools, the authors construct a polynomial function as a candidate Lyapunov function and via testing its derivative the authors provide some sufficient conditions for the global stability of polynomial systems.

关键词： Global asymptotical stability semi-tensor product switched polynomial systems

A two-step solvothermal procedure to improve crystallinity of covalent organic frameworks and achieve scale-up preparation

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Chinese Chemical Letters 2022年第5期33卷 2464-2468页

作者： Xiang-Hao Han Jia-qi Chu Wen-Zhuang Wang qiao-Yan qi Xin Zhao Key Laboratory of Synthetic and Self-Assembly Chemistry for Organic Functional Molecules Center for Excellence in Molecular SynthesisShanghai Institute of Organic ChemistryUniversity of Chinese Academy of SciencesChinese Academy of SciencesShanghai 200032China Shanghai Normal University Shanghai 200234China

Covalent organic frameworks(COFs),as a novel class of functional polymers,exhibit versatile applica-tions due to their crystalline porous structures and conjugated ***,synthesis of COFs with high crystallinity still faces great challenges,especially for scale-up *** we report a two-step solvothermal process to improve crystallinity of *** first step focuses on polycondensa-tion of monomers with no need for optimizing crystallization *** the second step,appropriate solvothermal conditions are used to facilitate crystallization of the COFs through defects correction and structural ***,this strategy could also be applicable to scale-up synthesis of high qual-ity COFs,which lays a foundation for their practical applications.

关键词： Covalent organic frameworks Synthesis Solvothermal condensation High crystallinity Scale-up preparation

Designed Synthesis of a Two-Dimensional Covalent Organic Framework with Three-Level Hierarchical Porosity

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Chinese Journal of Chemistry 2020年第12期38卷 1676-1680页

作者： Xiang-Hao Han qiao-Yan qi Zhi-Bei Zhou Xin Zhao Key Laboratory of Synthetic and Self-Assembly Chemistry for Organic Functional Molecules Center for Excellence in Molecular SynthesisShanghai Institute of Organic ChemistryUniversity of Chinese Academy of SciencesChinese Academy of Sciences345 Lingling RoodShanghai 200032China

of main observation and conclusion Covalent organic frameworks(COFs)with hierarchical porosity have drawn considerable attention very recently due to their advantages over the COFs with uniform porosity in some ***,the design strategies for the construction of this type of COFs,namely heteropore COFs,are quite *** herein report a facile approach to constructing a two-dimensional COF which possesses three different kinds of *** structure is confirmed by powder X-ray diffraction and nitrogen sorption *** successful construction of the triple-pore COF represents a new method to access COFs with high hierarchical porosity.

关键词： porosity valent constructing

Machine learning for molecular thermodynamics

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Chinese Journal of Chemical Engineering 2021年第3期34卷 227-239页

作者： Jiaqi Ding Nan Xu Manh Tien Nguyen qi qiao Yao Shi Yi He qing Shao College of Chemical and Biological Engineering Zhejiang UniversityHangzhou 310027China Chemical and Materials Engineering Department University of KentuckyLexingtonKY 40506USA Key Laboratory of Biomass Chemical Engineering of Ministry of Education Zhejiang UniversityHangzhou 310027China Department of Chemical Engineering University of WashingtonSeattleWA 98195USA

Thermodynamic properties of complex systems play an essential role in developing chemical engineering *** remains a challenge to predict the thermodynamic properties of complex systems in a wide range and describe the behavior of ions and molecules in complex *** learning emerges as a powerful tool to resolve this issue because it can describe complex relationships beyond the capacity of traditional mathematical *** minireview will summarize some fundamental concepts of machine learning methods and their applications in three aspects of the molecular thermodynamics using several *** first aspect is to apply machine learning methods to predict the thermodynamic properties of a broad spectrum of systems based on known *** second aspect is to integer machine learning and molecular simulations to accelerate the discovery of *** third aspect is to develop machine learning force field that can eliminate the barrier between quantum mechanics and all-atom molecular dynamics *** applications in these three aspects illustrate the potential of machine learning in molecular thermodynamics of chemical *** will also discuss the perspective of the broad applications of machine learning in chemical engineering.

关键词： Machine learning Thermodynamic properties Molecular engineering Molecular simulation Force field

Deep-learning architecture for PM_(2.5) concentration prediction: A review

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Environmental Science and Ecotechnology 2024年第5期21卷 17-33页

作者： Shiyun Zhou Wei Wang Long Zhu qi qiao Yulin Kang Institute of Environmental Information Chinese Research Academy of Environmental SciencesBeijing 100012China School of Optics and Photonics Beijing Institute of TechnologyBeijing 100081China College of Water Sciences Beijing Normal UniversityBeijing 100875China

Accurately predicting the concentration of fine particulate matter(PM_(2.5))is crucial for evaluating air pollution levels and public *** advancements have seen a significant rise in using deep learning(DL)models for forecasting PM_(2.5) ***,there is a lack of unified and standardized frameworks for assessing the performance of DL-based PM_(2.5) prediction *** we extensively reviewed those DL-based hybrid models for forecasting PM_(2.5) levels according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses(PRISMA)*** examined the similarities and differences among various DL models in predicting PM_(2.5) by comparing their complexity and *** categorized PM_(2.5) DL methodologies into seven types based on performance and application conditions,including four types of DL-based models and three types of hybrid learning *** research indicates that established deep learning architectures are commonly used and respected for their ***,many of these models often fall short in terms of innovation and ***,models hybrid with traditional approaches,like deterministic and statistical models,exhibit high interpretability but compromise on accuracy and ***,hybrid DL models,representing the pinnacle of innovation among the studied models,encounter issues with *** introduce a novel three-dimensional evaluation framework,i.e.,Dataset-MethodExperiment Standard(DMES)to unify and standardize the evaluation for PM_(2.5) predictions using DL *** review provides a framework for future evaluations of DL-based models,which could inspire researchers to standardize DL model usage in PM_(2.5) prediction and improve the quality of related studies.

关键词： PM_(2.5) concentration prediction Deep-learning based model Bibliometrics analysis Evaluation framework