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Optimal control approach to stability criteria on Hill's equations

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Applied Mathematics(A Journal of Chinese Universities) 2018年第3期33卷 253-273页

作者： ZU jian LI yong School of Mathematics and Statistics & Center for Mathematics and Interdisciplinary Sciences North-east Normal University Key Laboratory of Symbolic Computation and Knowledge Engineering of Ministry of Education Jilin University College of Mathematics Jilin University

This paper gives a tutorial on how to prove Lyapunov type criteria by optimal control methods. Firstly, we consider stability criteria on Hill’s equations with nonnegative potential. By optimal control methods developed in 1990s, we obtain several stability criteria including Lyapunov’s criterion, Neǐgauz and Lidskiǐ’s criterion. Secondly, we present stability criteria on Hill’s equations with sign-changing potential in which Brog’s criterion and Krein’s criterion are included.

关键词： stability criteria optimal control method Hill's equation Lyapunov inequality

Mechanically Robust Polylactide Fibers with super Heat Resistance via Constructing in situ Nanofibrils

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Chinese Journal of Polymer Science 2023年第6期41卷 962-971,I0011页

作者： Jun Lu Li-Xiang Yi yong-Huan Zhao Yang Meng Peng-Xiang Yu Juan-Juan su jian Han College of Materials and Textiles Zhejiang Sci-Tech UniversityHangzhou 310018China The Key Lab of Industrial Textile Material and Manufacturing Technology Zhejiang ProvinceZhejiang Sci-Tech UniversityHangzhou 310018China

All-PLA fibers with excellent comprehensive performance and recycling convenience are realized *** molecular weight poly(D-lactide)(HPDLA)is incorporated into poly(L-lactide)(PLLA)matrix to construct in situ nanofibrils structure by taking advantages of the microphase separation between HPDLA and *** tensile strength of HPDLA/PLLA composite fibers(HDL-8)is enhanced from 2.1 cN/dtex of neat PLLA-8 fibers up to 2.9 cN/*** boiling water shrinkage(BWS)and shrinkage in hot air(HAS)significantly decrease to 7.8%and 2.8%,*** abundance of in situ nanofibrils creates a grille-like structure that is crucial for both heat and hydrolysis *** strikingly,a hybrid shish-kebab structure induced by the in situ nanofibrils serves as a mechanical *** work paves a new way for heat resistance and self-reinforcement modification of PLA materials.

关键词： materials. fibers lactide

A Hybrid Entropy and Blockchain Approach for Network Security Defense in SDN-Based IIoT

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Chinese Journal of Electronics 2023年第3期32卷 531-541页

作者： su jian jianG Mengnan School of Computer Science Nanjing University of Information Science and Technology

In the industrial Internet of things(IIoT), various applications generate a large number of interactions and are vulnerable to various attacks, which are difficult to be monitored in a sophisticated way by traditional network architectures. Therefore, deploying software-defined network(SDN) in IIoT is essential to defend against various attacks. However, SDN has a drawback: there is a security problem of distributed denial-ofservice(DDoS) attacks at the control layer. This paper proposes an effective solution: DDoS detection within the domain using tri-entropy in information theory. The detected attacks are then uploaded to a smart contract in the blockchain, so that the attacks can be quickly cut off even if the same attack occurs in different domains. Experimental validation was conducted under different attack strengths and multiple identical attacks, and the results show that the method has better detection ability under different attack strengths and can quickly block the same attacks.

关键词： Smart contracts Network security Network architecture Denial-of-service attack Entropy Blockchains Software defined networking

CAVITATION CONTROL BY AERATION AND ITS COMPRESSIBLE CHARACTERISTICS

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Journal of Hydrodynamics 2006年第4期18卷 499-504页

作者： DONG Zhi-yong su Pei-lan School of Civil Engineering and Architecture Zhejiang University of Technology Hangzhou 310032 China School of Forestry Shanxi Agricultural University Taigu 030801 China

This paper presents an experimental investigation and a theoretical analysis of cavitation control by aeration and its compressible characteristics at the flow velocity V=20m/s-50m/s. Pressure waveforms with and without aeration in cavitation region were measured. The variation of compression ratio with air concentration was described, and the relation between the least air concentration to prevent cavitation erosion and flow velocity proposed based on our experimental study. The experimental results show that aeration remarkably increases the pressure in cavitation region, and the corresponding pressure wave exhibits a compression wave/shock wave. The pressure increase in cavitation region of high-velocity flow with aeration is due to the fact that the compression waves/shock wave after the flow is aerated. The compression ratio increases with air concentration rising. The relation between flow velocity and least air concentration to prevent cavitation erosion follows a semi-cubical parabola. Also, the speed of sound and Mach number of high-velocity aerated flow were analyzed.

关键词： cavitation control by aeration compression wave/shock wave least air concentration speed of sound compression ratio

Numerical investigation of the interactions between a laser-generated bubble and a particle near a solid wall

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Journal of Hydrodynamics 2021年第2期33卷 311-322页

作者： jian-yong Yin yong-xue Zhang jian-jun Zhu Liang Lü Shi-da Li College of Mechanical and Transportation Engineering China University of Petroleum-BeijingBeijing 102249China Beijing Key Laboratory of Process Fluid Filtration and Separation China University of Petroleum-BeijingBeijing 102249China School of International Education Hainan Medical UniversityHaikou 571199China Department of Thermal Engineering Chengde Petroleum CollegeChengde 067000China

The interactions between the bubbles and the particles near structures are important issues for the applications of the cavitation in the fluid *** study the hidden microscopic mechanisms,a numerical method for simulating the laser-generated bubble between the solid wall and a particle is developed in this paper with considerations of the viscosities and the compressibility of the gas and the liquid phases,as well as the surface tension between *** gas-liquid interface is tracked by the coupling level set and the volume of fluid(CLSVOF)*** numerical results clearly reveal that the particle can influence the cavitation bubble *** potential damage of the nearby structures is numerically quantified in terms of the wall pressure,which helps better understand the synergetic effects of the particle on the *** effects of three dimensionless parameters on the wall pressure are also investigated,especially,on the peak pressure,namely,γ1(defined as L_(1)/R_(max),where L_(1)is the distance from the center of the initial bubble to the solid wall and R_(max)is the maximum bubble radius),γ_(2)(defined as L_(2)/R_(max),where L_(2)is the distance from the lower surface of the spherical particle to the initial bubble center)andθ(defined as Rp/R_(max),where Rp is the spherical particle radius).Further numerical results show that these parameters play a dominant role in determining the peak *** y_(1)sure on the solid wall during the bubble collapse is mainly resulted from the liquid ***γ1>1.00,the peak pressure is caused by the shock *** the increase ofθor decrease ofγ_(2),the peak pressure ***γ_(2)>2.00,the effect of the particle on the bubble behavior can be neglected.

关键词： Cavitation bubble spherical particle coupling level set and the volume of fluid(CLSVOF) solid wall OpenFOAM

Precise 3D shape measurement of three-dimensional digital image correlation for complex surfaces

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Science China(Technological Sciences) 2018年第1期61卷 68-73页

作者： YAN TianHao su yong ZHANG QingChuan CAS Key Laboratory of Mechanical Behavior and Design of Materials Department of Modern Mechanics University of Science and Technology of China

Three dimensional-digital image correlation （3D-DIC） is a widely used optical metrology in the experimental mechanics community because of its reliability, practicality, and flexibility. Although the precision of digital image correlation （DIC） has been thoroughly studied theoretically and numerically, verification experiments have seldom been performed, especially fbr complex surfaces with a small field of view （FOV）. In this work, the shape of a 1-yuan coin was measured using 3D-DIC; the shape was complex due to the presence of many fine details, and the FOV was relatively small because the coin diameter was only 25 mm. During the experiment, a novel strategy for speckle production was developed： white paint was simply sprayed onto the surface. Black paint was not used; instead, taking advantage of the reflective nature of the coin surface, polarized light and a Polaroid filter were introduced, and the polarization direction was carefully adjusted, ensuring that the spray pattern was extremely thin and that high-quality speckle images with significant contrast were captured. The three-dimensional coin shape was also successfully determined for comparison using a stylus profiler. The results demonstrate that 3D-DIC provides high precision in shape measurement even for complex surfaces with small FOV. The precision of 3D-DIC can reach 1/7000 of the field of view, corresponding to about 6 ~tm in this experiment.

关键词： three-dimensional digital image correlation(3D-DIC) measurement precision complex surfaces small field of view polarized light polaroid filter

Improvement of the Bayesian neural network to study the photoneutron yield cross sections

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Nuclear Science and Techniques 2022年第11期33卷 1-9页

作者： yong-Yi Li Fan Zhang Jun su Department of Computing Changzhi UniversityChangzhi 046011China Department of Physics Changzhi UniversityChangzhi 046011China Sino-French Institute of Nuclear Engineering and Technology Sun Yat-sen UniversityZhuhai 519082China

This work is an attempt to improve the Bayesian neural network (BNN) for studying photoneutron yield cross sections as a function of the charge number Z, mass number A, and incident energy ε. The BNN was improved in terms of three aspects:numerical parameters, input layer, and network structure. First, by minimizing the deviations between the predictions and data, the numerical parameters, including the hidden layer number, hidden node number, and activation function, were selected. It was found that the BNN with three hidden layers, 10 hidden nodes, and sigmoid activation function provided the smallest deviations. Second, based on known knowledge,such as the isospin dependence and shape effect, the optimal ground-state properties were selected as input neurons. Third, the Lorentzian function was applied to map the hidden nodes to the output cross sections, and the empirical formula of the Lorentzian parameters was applied to link some of the input nodes to the output cross sections. It was found that the last two aspects improved the predictions and avoided overfitting, especially for the axially deformed nucleus.

关键词： Bayesian neural network Photoneutron cross sections Giant dipole resonance

Direct Laser Writing Facility for Fabrication of submicron Mask

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Chinese Physics Letters 2014年第4期31卷 185-188页

作者： ZHU Feng MA jian-yong Information Optics Laboratory Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Sciences Shanghai 201800

Direct laser writing technique has become a well-established, multi-functional and flexible method for fabricating high quality diffractive optical elements. We propose and build a maskless direct laser writing system with the ability to produce a sub-micron feature size. The high precision lithography is realized by using the astigmatic autofocus method. The minimum feature size of the system, breaking through the diffraction limit with the chromium layer, can achieve 300hm with the 405nm blue laser. A 50 x 50ram2 chromium grating mask with a period of 1 #m and line width of 300 nm is fabricated. This facility will be useful for the fabrication of large-scale submicron diffraction optical elements in the future.

关键词： FABRICATION (Manufacturing) DIFFRACTIVE optical elements CHROMIUM -- Spectra BLUE lasers OPTICAL diffraction ASTIGMATISM (Optics)

Essential Forward Weak KAM Solution for the Convex Hamilton–Jacobi Equation

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Acta Mathematica Sinica,English Series 2022年第5期38卷 797-806页

作者： Xi Feng su jian Lu ZHANG Laboratory of Mathematics and Complex Systems(Ministry of Education) School of Mathematical SciencesBeijing Normal UniversityBeijing 100875P.R.China Hua Loo-Keng Key Laboratory of Mathematics&Mathematics Institute Academy of Mathematics and Systems ScienceChinese Academy of SciencesBeijing 100190P.R.China

For a convex,coercive continuous Hamiltonian on a closed Riemannian manifold M,we construct a unique forward weak KAM solution of H(x,d_(x)u)=c(H)by a vanishing discount approach,where c(H)is the Ma?écritical *** als... 详细信息

关键词： Hamilton-Jacobi equation discounted equation weak KAM solution Aubry-Mather theory viscosity solution