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黄河下游河相关系与平滩流量特征关系的随机演化模拟

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Journal of Geographical Sciences 2020年第5期30卷 843-864页

作者：宋晓龙钟德钰王光谦 State Key Laboratory of Hydro-science and Engineering Tsinghua UniversityBeijing 100084China State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin UniversityTianjin 300072China

Extreme weather is an important noise factor in affecting dynamic access to river morphology information.The response characteristics of river channel on climate disturbances draw us to develop a method to investigate the dynamic evolution of bankfull channel geometries(including the hydraulic geometry variables and bankfull discharges)with stochastic differential equations in this study.Three different forms of random inputs,including single Gaussian white noise and compound Gaussian/Fractional white noise plus Poisson noise,are explored respectively on the basis of the classical deterministic models.The model parameters are consistently estimated by applying a composite nonparametric maximum likelihood estimation(MLE)method.Results of the model application in the Lower Yellow River reveal the potential responses of bankfull channel geometries to climate disturbances in a probabilistic way,and,the calculated average trends mainly run to synchronize with the measured values.Comparisons among the three models confirm the advantage of Fractional jump-diffusion model,and through further discussion,stream power based on such a model is concluded as a better systematic measure of river dynamics.The proposed method helps to offer an effective tool for analyzing fluvial relationships and improves the ability of crisis management of river system under varying environment conditions.

关键词： stochastic differential equation bankfull channel geometry river system extreme weather Lower Yellow River

Useful life prediction using a stochastic hybrid automata model for an ACS multi-gyro subsystem

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Journal of Systems Engineering and Electronics 2019年第1期30卷 154-166页

作者： CHENG Yuehua JIANG Liang JIANG Bin LU Ningyun College of Astronautics Engineering Nanjing University of Aeronautics and Astronautics College of Automation Engineering Nanjing University of Aeronautics and Astronautics

A useful life prediction method based on the integration of the stochastic hybrid automata(SHA) model and the frame of the dynamic fault tree(DFT) is proposed. The SHA model can incorporate the orbit environment, work modes, system configuration, dynamic probabilities and degeneration of components,as well as spacecraft dynamics and kinematics. By introducing the frame of DFT, the system is classified into several layers, and the problem of state combination explosion is artfully overcome.An improved dynamic reliability model(DRM) based on the Nelson hypothesis is investigated to improve the defect of cumulative failure probability(CFP), which is used to address the failure probability of components in the SHA model. The simulation using the Monte-Carlo method is finally conducted on two satellites, which are deployed with the same multi-gyro subsystem but run on different orbits. The results show that the predicted useful life of the attitude control system(ACS) with consideration of abrupt failure,degradation, and running environment is quite different between the two satellites.

关键词： useful life prediction stochastic hybrid automata (SHA) multi-gyro subsystem dynamic fault tree (DFT) dynamic reliability.

Technical efficiency of hybrid maize growers: A stochastic frontier model approach

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Journal of Integrative Agriculture 2019年第10期18卷 2408-2421页

作者： Imad Ali HUO Xue-xi Imran Khan Hashmat Ali Khan Baz Sufyan Ullah Khan College of Economics and Management Northwest A&F UniversityYangling 712100P.R.China School of Economics Dongbei University of Finance and EconomicsDalian 116025P.R.China School of Economics and Management China University of GeosciencesWuhan 430074P.R. China

This study investigated the effect of credit constraints and credit unconstraints on the technical efficiency of hybrid maize growers in the Khyber Pakhtunkhwa Province(KPK) of Pakistan. The primary data were collected by a direct elicitation method from 510 maize growers of KPK Province. stochastic frontier model techniques were used for technical efficiency analyses. The results revealed that the mean technical efficiency difference between the two groups was 10.2%. The results of technical inefficiency effect modeling demonstrated that education of the household head, family size, number of married family members, off-farm income, farming experience, tractor drill, water irrigation through a lined course, certified seed, extension services, household saving variables, and a credit size variable had positive effects on technical efficiency for both credit constrained farmers(CCFs) and credit unconstrained farmers(UCCFs). In addition, age of household head and fragmented land values had negative effects on technical efficiency for both groups. However, the interest rate had positive and negative impacts on the technical efficiency of CCFs and UCCFs, respectively. Our results have significant implications for policies related to land use, interest rate, and banking sector expansion in the rural areas of Pakistan.

关键词： stochastic frontier analysis maize growers technical efficiency credit rationing and credit markets in Pakistan

Stationary response of stochastic viscoelastic system with the right unilateral nonzero offset barrier impacts

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Chinese Physics B 2019年第1期28卷 195-204页

作者：王德莉徐伟谷旭东 Department of Applied Mathematics Northwestern Polytechnical UniversityXi’an 710072China Department of Engineering Mechanics Northwestern Polytechnical UniversityXi’an 710072China

The stationary response of viscoelastic dynamical system with the right unilateral nonzero offset barrier impacts subjected to stochastic excitations is investigated. First, the viscoelastic force is approximately treated as equivalent terms associated with effects. Then, the free vibro-impact(VI) system is absorbed to describe the periodic motion without impacts and quasi-periodic motion with impacts based upon the level of system energy. The stochastic averaging of energy envelope(SAEE) is adopted to seek the stationary probability density functions(PDFs). The detailed theoretical results for Van der Pol viscoelastic VI system with the right unilateral nonzero offset barrier are solved to demonstrate the important effects of the viscoelastic damping and nonzero rigid barrier impacts condition. Monte Carlo(MC) simulation is also performed to verify the reliability of the suggested approach. The stochastic P-bifurcation caused by certain system parameters is further explored. The variation of elastic modulus from negative to zero and then to positive witnesses the evolution process of stochastic P-bifurcation. From the vicinity of the common value to a wider range, the relaxation time induces the stochastic P-bifurcation in the two interval schemes.

关键词： viscoelastic system right unilateral nonzero offset barrier impacts stochastic averaging of energy envelope(SAEE) stochastic P-bifurcation

stochastic Stabilization for Nonhomogeneous Markovian Jump Discrete-Time Singular Systems

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Journal of Donghua University(English Edition) 2018年第6期35卷 486-490页

作者：陈利雄崔文霞刘昱昊 School of Mathematics Physics and Statistics Shanghai University of Engineering Science

stochastic stability analysis and control synthesis problems are studied for a class of nonhomogeneous Markovian jump discretetime singular systems( MJDSS). The time-varying character is considered to be the model in a polytopic sense. Based on the parameter dependent stochastic Lyapunov functional and the matrix analysis techniques, sufficient criteria are derived to ensure regularity, causality and stochastic stability of the closed-loop singular system in terms of linear matrix inequalities. Finally,one example is provided to illustrate the effectiveness of our results.

关键词： stochastic stability nonhomogeneous Lyapunov function singular system Markovian switching

General decay asymptotic stability of neutral stochastic differential delayed equations with Markov switching

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Frontiers of Mathematics in China 2019年第4期14卷 793-818页

作者： Guangqiang LAN Fang XIA College of Mathematics and Physics Beijing University of Chemical Technology Beijing 100029 China

The p-th moment and almos t sure st ability with general decay rate of the exact solutions of neutral stochastic differential delayed equations with Markov switching are investigated under given conditions. Two exampl... 详细信息

关键词： Neutral stochastic differential delayed equations with Markov switching (NSDDEswMS) global solution general decay rate, p-th moment stability almost sure st ability

Path independence of additive functionals for stochastic differential equations under G-framework

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Frontiers of Mathematics in China 2019年第1期14卷 135-148页

作者： Panpan REN Fen-Fen YANG Departmen t of Mat hematics Swansea University Swansea SAI 8EN UK Center for Applied Mathematics Tianjin University Tianjin 300072 China

The path independence of additive functionals for stochastic differential equations (SDEs) driven by the G-Brownian motion is characterized by the nonlinear partial differential equations. The main result generalizes ... 详细信息

关键词： stochastic differential equation (SDE) partial differential equation (PDE) additive functional G-SDEs G-Brownian motion nonlinear PDE

Advance on stochastic dynamics/nonlinear and stochastic dynamics

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Theoretical & Applied Mechanics Letters 2023年第4期13卷 249-250页

作者： Yong Xu Yongge Li Stefano Lenci Northwestern Polytechnical University School of Mathematics and Statistics at the Northwestern Polytechnical University Polytechnic University of Marche Technical Committee Multibody System and Nonlinear Dynamics of ASME Italian Association for Theoretical and Applied Mechanics(AIMeTA)

Nonlinear and stochastic dynamics is essential and practical in almost all branches of natural science and engineering.It has been a central subject to understand various complex dynamics,such as random vibration,stochastic transition,synchronization,et al.,in the areas of mechanical and aerospace engineering,physics and chemistry.For example,the stochastic resonance has been utilized effectively in mechanical fault diagnosis and weak signal detection.Naturally,many methods have been developed to get the stochastic responses,including stochastic averaging method.

关键词： method. stochastic dynamics

stochastic resonance whole body vibration reduces musculoskeletal pain:A randomized controlled trial

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World Journal of Orthopedics 2011年第12期2卷 116-120页

作者： Achim Elfering Jan Thomann Volker Schade Lorenz Radlinger Department of Psychology University of Bern3000 BernSwitzerland Centre for Human Resource Management and Organizational Engineering 3000 BernSwitzerland Bern University of Applied Sciences Health3000 BernSwitzerland

AIM:To examined the effects of stochastic resonance whole-body vibration training on musculoskeletal pain in young healthy individuals.METHODS:Participants were 43 undergraduate students of a Swiss University.The study was designed as a randomized controlled trial(RCT)with randomized group allocation.The RCT consisted of two groups each given 12 training sessions during four weeks with either 5 Hz-Training frequency(training condition)or 1.5 Hz Training frequency(control condition).Outcome was current musculoskeletal pain assessed in the evening on each day during the four week training period.RESULTS:Multilevel regression analysis showed musculoskeletal pain was significantly decreased in the training condition whereas there was no change in the control condition(B=-0.023,SE=0.010,P=0.021).Decrease in current musculoskeletal pain over four weeks was linear.CONCLUSION:stochastic resonance whole-body vibration reduced musculoskeletal pain in young healthy individuals.stochastic resonance vibration and not any other exercise component within training caused pain reduction.

关键词： Randomized controlled trial Musculoskeletal pain Training study stochastic vibration