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Euler-type schemes for weakly coupled forward-backward stochastic differential equations and optimal convergence analysis

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Frontiers of Mathematics in China 2015年第2期10卷 415-434页

作者： Wei zhang weidong ZHAO School of Mathematics Finance Institute Shandong University Jinan 250100 China

We introduce a new Euler-type scheme and its iterative algorithm for solving weakly coupled forward-backward stochastic differential equations （FBSDEs）. Although the schemes share some common features with the ones proposed by C. Bender and J. zhang [Ann. Appl. Probab., 2008, 18： 143-177], less computational work is needed for our method. For both our schemes and the ones proposed by Bender and zhang, we rigorously obtain first-order error estimates, which improve the half-order error estimates of Bender and zhang. Moreover, numerical tests are given to demonstrate the first-order accuracy of the schemes.

关键词： Weakly coupled forward-backward stochastic differential equations (FBSDEs) Euler-type scheme time discretization first-order error estimate

Adsorption equilibrium and the effect of honeycomb heat exchanging device on charge/discharge characteristic of methane on MIL-101(Cr)and activated carbon

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Chinese Journal of Chemical Engineering 2020年第7期28卷 1964-1972页

作者： Guobin Zhao Qingrong Zheng Xuan zhang weidong zhang Provincial Key Laboratory of Naval Architecture&Ocean Engineering Institute of Marine EngineeringJimei UniversityXiamen 361021China

Experiments were conducted for developing suitable ANG adsorbents for vehicular ***-101 and activated carbon samples were respectively prepared by hydrothermal and chemical activation *** samples were undergone structure analysis on adsorption data of nitrogen at 77.15 K,and adsorption data of methane were then volumetrically measured within temperature-pressure range 293.15 K-313.15 K and 0-8 MPa.A conformable vessel in volume 2.5 L was employed for charge/discharge tests under the flow rate 10-30 L·min^-*** shows that limit isostreic heat of methane adsorption is respectively about 25.15 k J·mol^-1 and22.94 k J·mol^-1 on the activated carbon and the MIL-101,and isosteric heat within the experimental condition is 14-19.5 k J·mol^-1;employing a smaller charge/discharge flow rate can weaken the temperature fluctuation of the adsorbent bed and increase the charge/discharge amount;employing honeycomb heat exchanging device enhance the thermal conductivity of the adsorbent bed by consuming a negligible part of volume of the *** suggests that a smaller flow rate for charge/discharge should be employed,and MOFs together with the honeycomb heat exchanging device are promising for practical applications.

关键词： Natural gas MOFs Activated carbon Adsorption

Observer-based asynchronous self-triggered control for a dynamic positioning ship with the hysteresis input

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Science China(Information Sciences) 2022年第11期65卷 232-245页

作者： Guoqing zhang Mingqi YAO Qihe SHAN weidong zhang Navigation College Dalian Maritime University Department of Automation Shanghai Jiao Tong University

This paper focuses on the asynchronous self-triggered control scheme for a dynamic positioning ship considering the hysteresis input. A novel self-triggered mechanism is designed to relax the limitation of the continuous monitoring required for the triggered condition, and the next triggered instant depends on the information at the current instant. In particular, multiple controller-thruster channels are asynchronously self-triggered; i.e., the self-triggered mechanism for each thruster is independent and noninteracting. A neural network observer is constructed to estimate the unavailable velocities for the control design. Meanwhile,unknown backlash-like hysteresis inputs are considered in this scheme through the fusion of the adaptive backstepping recursive design technique. Furthermore, the explosion of complexity existing in conventional backstepping design is avoided on the basis of the dynamic surface technique. Through the Lyapunov theory,considerable effort is made to guarantee semi-global uniform ultimate bounded stability. Finally, numerical simulations are provided to validate the feasibility of the proposed scheme.

关键词： dynamic positioning ship self-triggered control neural networks hysteresis input robust control

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Robust neural output-feedback stabilization for stochastic nonlinear process with time-varying delay and unknown dead zone

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Science China(Information Sciences) 2017年第12期60卷 20-32页

作者： Guoqing zhang Yingjie DENG weidong zhang Zhijian SUN Department of Automation Shanghai Jiao Tong University Navigation College Dalian Maritime University

This article investigates the output-feedback control of a class of stochastic nonlinear system with time-varying delay and unknown dead zone. A robust neural stabilizing algorithm is proposed by using the circle criterion, the NNs approximation and the MLP(minimum learning parameter) technique. In the scheme, the nonlinear observer is first designed to estimate the unmeasurable states and the assumption "linear growth" of the nonlinear function is released. Furthermore, the uncertainty of the whole system(including the perturbation of time-varying delay) is lumped and compensated by employing one RBF NNs(radial basis function neural networks). Though, only two weight-norm related parameters are required to be updated online for the merit of the MLP technique. And the gain-inversion related adaptive law is targetly designed to mitigate the adverse effect of unknown dead zone. Comparing with the previous work, the proposed algorithm obtains the advantage:a concise form and easy to implementation due to its less computational burden. The theoretical analysis and comparison example demonstrate the substantial effectiveness of the proposed scheme.

关键词： stochastic system robust neural control time delay dead zone output-feedback

INDIRECT ACCELERATED ADAPTIVE FUZZY CONTROLLER

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Chinese Journal of Mechanical Engineering 2008年第1期21卷 91-93页

作者： ZHU Liye FANG Yuan zhang weidong Baosteel Research Institute Shanghai 201900 China Department of Automation Shanghai Jiaotong University Shanghai 200240 China

According to a type of normal nonlinear system, an indirect adaptive fuzzy （IAF） controller has been applied to those systems where no accurate mathematical models of the systems under control are available. To satisfy with system performance, an indirect accelerated adaptive fuzzy （IAAF） controller is proposed, and its general form is presented. The general form IAAF controller ensures necessary control criteria and system＇s global stability using Lyapunov Theorem. It has been proved that the close-loop system error converges to a small neighborhood of equilibrium point. The optimal IAAF controller is derived to guarantee the process＇s shortest settling time. Simulation results indicate the IAAF controller make the system more stable, accurate, and fast.

关键词： Indirect adaptive fuzzy controller Accelerated controller Stability System error Settling time

Asynchronous control for 2-D Markov jump cyber-physical systems against aperiodic denial-of-service attacks

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Science China(Information Sciences) 2023年第7期66卷 195-209页

作者： Peng CHENG Di WU Shuping HE weidong zhang Department of Automation Shanghai Jiao Tong University School of Electrical Engineering and Automation Anhui University

This work focuses on the asynchronous controller design for two-dimensional Markov jump cyberphysical systems against denial-of-service attacks. Firstly, due to the openness of the network, it is vulnerable to cyber-attacks, resulting in the control input signal may not being sent to the designated location. Meanwhile, considering the influence of transmission delays and unavoidable packet dropout, a hidden Markov model can help to deal with the unavoidable asynchronous phenomenon between the plant mode and the controller mode. Then, by introducing the concepts of time instants and global states into two-dimensional systems, an asynchronous control scheme for two-dimensional Markov jump cyber-physical systems is successfully formulated. Subsequently, recurring to the multi-Lyapunov function method and iterative technology,sufficient conditions are achieved to make sure that the dynamic hidden two-dimensional Markov jump cyberphysical systems are asymptotically mean-square stable. To conclude, an application example related to the metal rolling process is provided to illustrate the feasibility and effectiveness of the presented asynchronous control scheme under aperiodic denial-of-service attacks.

关键词： asynchronous two-dimensional Markov jump cyber-physical systems denial-of-service attacks hidden Markov model

Effects of gaps on regeneration of woody plants: a meta-analysis

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Journal of Forestry Research 2014年第3期25卷 501-510页

作者： Jiaojun Zhu Deliang Lu weidong zhang State Key Laboratory of Forest and Soil Ecology Qingyuan Experimental Station of Forest Ecology Institute of Applied Ecology Chinese Academy of Sciences University of Chinese Academy of Sciences

Forest gaps, openings in the canopy caused by death of one or more trees, have a profound effect on forest regeneration and drive the forest growth cycle. It is therefore necessary to understand the effects of forest gaps on regeneration for modern forest management. In order to provide a quantitative assessment of the effects of forest gaps on regen-eration of woody plants, we conducted this review of gap effects on woody plant regeneration on the basis of 527 observations from 42 indi-vidual papers, and reported the results of these data in a meta-analysis. Overall, densities of regenerated woody plants were significantly greater （359%） in forest gaps than on the closed-canopy forest floor. The regen-eration density in gaps of plantation forests was significantly greater （P＆lt;0.05） than that of natural forest because the regeneration in gaps of plan-tation forests was improved by both gap effects and experimental meas-ures. Similarly, in comparison to natural gaps, regeneration was better enhanced in artificial gaps. Regeneration density exhibited a significantly positive correlation with gap size, but a negative correlation with gap age because the gap size decreased with increasing gap age. Shade tolerance of woody plants affected regeneration density in gaps and understory. Average regeneration density of shade-tolerant species exhibited a sig-nificantly positive response to gaps but densities remained lower in total than those of intermediate and shade-intolerant species. Gap effects on regeneration decreased in response to increasing temperature and pre-cipitation because of the limiting effects of lower temperature and moisture on woody plant regeneration. In summary, forest gaps enhance woody plant regeneration, and the effects of gaps varied by forest type, gap characteristics, environmental factors and plant traits. The results of this meta-analysis are useful for better understanding the effects and roles of gaps on forest regeneration and forest manage

关键词： forest gap regeneration disturbance gap size gap age,shade tolerance

The catalytic effect of both oxygen-bearing functional group and ash in carbonaceous catalyst on CH_(4)-CO_(2) reforming

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Frontiers of Chemical Science and Engineering 2010年第2期4卷 147-152页

作者： weidong zhang Yongfa zhang Key Laboratory of Coal Science and Technology of Shanxi Province and Ministry of Education Taiyuan University of TechnologyTaiyuan 030024China

A kind of new catalyst-carbonaceous catalyst-for CH_(4)-CO_(2) reformation has been developed in our *** effect of both oxygen-bearing functional group such as phenolic hydroxyl,carbonyl,carboxyl,and lactonic,and ash such as Fe_(2)O_(3),Na_(2)CO_(3),and K_(2)CO_(3) in the carbonaceous catalyst on the CH_(4)-CO_(2) reforming has been investigated with a fixed-bed *** has been found that the carbonaceous catalyst is an efficient catalyst on CO_(2)-CH_(4) *** the decrease of oxygen-bearing functional group,the catalytic activity of carbonaceous catalyst decreases *** oxygen-bearing functional groups play a significant role in the carbonaceous-catalyzed CO_(2)-CH_(4) reforming;the ash components in carbonaceous catalyst also have an important influence on the CO_(2)-CH_(4) ***_(2)O_(3),Na_(2)CO_(3),and K_(2)CO_(3) in the ash can catalyze the CO_(2)-CH_(4) reforming reaction;CaO has little effect on CO_(2)-CH_(4) reforming *** can catalyze the gasification between carbonaceous catalyst and CO_(2);Al_(2)O_(3) and MgO inhibit the CO_(2)-CH_(4) reforming.

关键词： carbonaceous catalyst CH_(4)-CO_(2)eforming oxygen-bearing functional group ash

Safety-Critical Trajectory Tracking for Mobile Robots With Guaranteed Performance

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IEEE/CAA Journal of Automatica Sinica 2024年第9期11卷 2033-2035页

作者： Wentao Wu Di Wu Yibo zhang Shukang Chen weidong zhang Department of Automation Shanghai Jiao Tong UniversityShanghai 200240China Department of Information and Communication Engineering Hainan UniversityHaikou 570288China

Dear Editor,This letter considers a collision-free trajectory tracking problem for performance-guaranteed mobile robots(MRs)subject to *** propose a safety-critical performance-guaranteed trajectory tracking method based on control barrier functions(CBFs).First,an auxiliary system is established to generate the non-negative signals for inflexible bounds such that the performance constraints are not violated when avoiding obstacles.

关键词： constraints bounds collision