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Fixed-interval smoothing of an aeroelastic airfoil model with cubic or free-play nonlinearity in incompressible flow

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Acta Mechanica Sinica 2021年第7期37卷 1168-1182,I0003页

作者： Qi liu Yong Xu yongge li Jurgen Kurths Xiaochuan liu School of Mathematics and Statistics Northwestern Polytechnical UniversityXi’an 710072China MIIT Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical UniversityXi’an 710072China Potsdam Institute for Climate Impact Research Potsdam 14473Germany Lobachevsky University of Nizhny Novgorod Nizhnij NovgorodRussia AVIC Aircraft Strength Research Institute Xi’an 710065China

Fixed-interval smoothing,as one of the most important types of state estimation,has been concerned in many practical problems especially in the analysis of flight test ***,the existing sequential filters and smoothers usually cannot deal with nonlinear or high-dimensional systems well.A state-of-the-art technique is employed in this study to explore the fixed-interval smoothing problem of a conceptual two-dimensional airfoil model in incompressible flow from noisy measurement ***,the governing equations of the airfoil model are assumed to be known or only partially known.A single objective optimization problem is constructed with the classical Runge–Kutta scheme,and then estimations of the system states,the measurement noise and even the unknown parameters are obtained simultaneously through minimizing the objective *** and feasibility of the method are examined under several simulated measurement data corrupted by different measurement *** the obtained results indicate that the introduced algorithm is applicable for the airfoil model with cubic or free-play structural nonlinearity and leads to accurate state and parameter ***,it is highly robust to Gaussian white and even more complex heavy-tailed measurement *** should be emphasized that the employed algorithm is still effective to high-dimensional nonlinear aeroelastic systems.

关键词： Airfoil model Incompressible flow State estimation Parameter estimation

Slowing down critical transitions via Gaussian white noise and periodic force

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Science China(Technological Sciences) 2019年第12期62卷 2144-2152页

作者： MA JinZhong XU Yong XU Wei li yongge KURTHS Jirge Department of Applied Mathematics Northwestern Polytechnical UniversityXi'an 710072China MIIT Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical UniversiyXi'an 710072China Center for Mathematical Sciences&School of Mathematics and Statistics Huazhong University of Science and TechmologyWuhan 430074China Potsdam Institute for Climate Impact Research Potsdam 14412Germany Department of Physics Humboldt UniversityBerlin 12489Germany

Stochastic perturbations and periodic excitations are generally regarded as sources to induce critical transitions in complex systems. However, we find that they are also able to slow down an imminent critical transition. To illustrate this phenomenon, a periodically driven bistable eutrophication model with Gaussian white noise is introduced as a prototype class of real *** residence probability(RP) is presented to measure the possibility that the given system stays in the oligotrophic state versus Gaussian white noise and periodic force. Variations in the mean first passage time(MFPT) and the mean velocity(MV) of the first right-crossing process are also calculated respectively. We show that the frequency of the periodic force can increase the MFPT while reduce the MV under different control parameters. Nevertheless, the noise intensity or the amplitude may result in an increase of the RP only in the case of control parameters approaching the critical values. Furthermore, for an impending critical transition, an increase of the RP appears with the interaction between the amplitude and noise intensity or the combination of the noise intensity and frequency, while the interaction of the frequency and amplitude leads to an extension of the MFPT or a decrease of the MV. As a result, an increase of the RP and MFPT, and a decrease of the MVobtained from our results claim that it is possible to slow down an imminent critical transition via Gaussian white noise and periodic force.

关键词： critical transition slowing down bistable eutrophication model Gaussian white noise periodic force residence probability mean first passage time mean velocity

Probabilistic description of extreme oscillations and reliability analysis in rolling motion under stochastic excitation

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Science China(Technological Sciences) 2023年第9期66卷 2586-2596页

作者： ZHAO Dan li yongge XU Yong liU Qi KURTHS Jürgen School of Mathematics and Statistics Northwestern Polytechnical UniversityXi’an 710072China MOE Key Laboratory for Complexity Science in Aerospace Northwestern Polytechnical UniversityXi’an 710072China Potsdam Institute for Climate Impact Research Potsdam 14412Germany Department of Physics Humboldt University BerlinBerlin 12489Germany

Large-amplitude rolling motions, also regarded as extreme oscillations, are a great threat to marine navigation, which may lead to capsizing in ship motion. Therefore, it is important to quantify extreme oscillations, assess reliability of ship systems, and establish a suitable indicator to characterize extreme oscillations in ship systems. In this work, extreme events are investigated in a ship model considering a complex ocean environment, described by a single-degree-of-freedom nonlinear system with stochastic harmonic excitation and colored Gaussian noise. The stationary probability density function(PDF) of the system is derived through a probabilistic decomposition-synthesis method. Based on this, we infer the classical damage rate of the system. Furthermore, a new indicator, independent of the PDF, is proposed to quantify the damage related only to the fourth-order moment of the system and the threshold for extreme events. It is more universal and easier to determine as compared with the classical damage rate. A large damping ratio, a large noise intensity, or a short correlation time can reduce the damage rate and the value of the *** findings provide new insights and theoretical guidance to avoid extreme oscillations and assess the reliability of practical ship movements.

关键词： rolling motion colored noise extreme oscillations reliability probabilistic decomposition-synthesis method

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Global dynamics and noise-induced transitions for a two-dimensional panel system in subsonic flow

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Acta Mechanica Sinica 2024年第8期40卷 253-264页

作者： Xiaole Yue Huikang Zhang yongge li Yong Xu School of Mathematics and Statistics Northwestern Polytechnical UniversityXi’an710129China MOE Key Laboratory for Complexity Science in Aerospace Northwestern Polytechnical UniversityXi’an710129China

A two-dimensional panel in subsonic flow with stochastic excitation is studied by assuming that the aerodynamic pressure contains random pressure *** on the global properties,the sensitivities of system parameters and noise intensities are ***,the parameter region with multiple coexisting attractors under different dynamic pressures is *** is found that the coexistence of multiple attractors extensively appears and the basin structure may be *** the periodic time history diagrams are calculated by simulating the random pressure fluctuation as Poisson white *** results show that under typical bistable conditions,the noise sensitivity of the subsonic panel system is related to the basin structures and the disposition of the coexisting attractors to the *** transition between two attractors diffuses along the unstable manifold and tends to the position where the basin boundary curvature is relatively *** findings underscore the importance of global analysis in assessing the noise load carrying capacity,which provides some valuable insights into the safety design of subsonic panel systems.

关键词： Global analysis Transition Subsonic panel Multistability

Quantifying the parameter dependent basin of the unsafe regime of asymmetric Lévy-noise-induced critical transitions

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Applied Mathematics and Mechanics(English Edition) 2021年第1期42卷 65-84页

作者： Jinzhong MA Yong XU yongge li Ruilan TIAN Shao juan MA J.KURTHS School of Mathematical Sciences Shanxi UniversityTaiyuan 030000China Department of Applied Mathematics Northwestern Polytechnical UniversityXi’an 710072China MIIT Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical UniversityXi’an 710072China Department of Engineering Mechanics Shijiazhuang Tiedao UniversityShijiazhuang 050043China School of Mathematics&Information Science North Minzu UniversityYinchuan 750021China Potsdam Institute for Climate Impact Research Potsdam 14412Germany Department of Physics Humboldt University at BerlinBerlin 12489Germany

In real systems,the unpredictable jump changes of the random environment can induce the critical transitions(CTs)between two non-adjacent states,which are more *** an asymmetric Lévy-noise-induced tri-stable model with desirable,sub-desirable,and undesirable states as a prototype class of real systems,a prediction of the noise-induced CTs from the desirable state directly to the undesirable one is carried *** first calculate the region that the current state of the given model is absorbed into the undesirable state based on the escape probability,which is named as the absorbed ***,a new concept of the parameter dependent basin of the unsafe regime(PDBUR)under the asymmetric Lévy noise is *** is an efficient tool for approximately quantifying the ranges of the parameters,where the noise-induced CTs from the desirable state directly to the undesirable one may *** importantly,it may provide theoretical guidance for us to adopt some measures to avert a noise-induced catastrophic CT.

关键词： tri-stable model asymmetric Lévy noise critical transition(CT) escape probability absorbed region parameter dependent basin of unsafe regime(PDBUR)

Chemical characteristics of precipitation and the indicative significance for sand dust events in the northern and southern slopes of Wushaoling Mountain, northwestern China

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Journal of Arid Land 2017年第6期9卷 911-923页

作者： li Zongjie liU Fei SONG Yong SONG lingling TIAN Qing JIA Bing li yongge MA Jinzhu Key Laboratory of Western China's Environmental Systems (Ministry of Education) College of Earth and Environmental Sciences Lanzhou University Lanzhou 730000 China CSIRO Land and Water Private Bag 10 Clayton South VIC 3169 Australia College of Forestry Gansu Agricultural University Lanzhou 730070 China Key Laboratory of Ecohydrology of Inland River Basin Gansu/Hydrology and Water Resources Engineering Research Center Northwest Institute of Eco-Environment and Resources Chinese Academy of Sciences Lanzhou 730000 China

Precipitation chemistry analysis is essential to evaluate the atmospheric environmental quality and identify the sources of atmospheric pollutants. In this study, we collected a total of 480 precipitation samples at 6 sampling sites in the northern and southern slopes of Wushaoling Mountain from May 2013 to July 2014 to analyze the chemical characteristics of precipitation and to identify the main sources of ions in precipitation. Furthermore, we also explored the indicative significance for sand dust events in the northern and southern slopes of Wushaoling Mountain based on the precipitation chemistry *** the sampling period（from May 2013 to July 2014）, the p H values, EC（electrical conductivity）values and concentrations of cations（Ca^（2＋）, Mg^（2＋）, Na~＋, K~＋ and NH_4~＋） and anions（SO_4^（2–）, NO_3~–, Cl~–, NO_2~– and F~–） in precipitation were different in the northern and southern slopes at daily and seasonal time scales, with most of the values being higher in the northern slope than in the southern slope. The chemical type of precipitation in the southern and northern slopes was the same, i.e.,SO_4^（2–）-Ca^（2＋）-NO_3~–-Na~＋. The concentrations of ions in precipitation were mainly controlled by terrigenous material and anthropogenic activities（with an exception of Cl~–）. The concentration of Cl~– in precipitation was mainly controlled by the sea salt fraction. The concentrations of Na＋ and Cl~– showed an increasing trend after the occurrence of sand dust events both in the northern and southern slopes. In addition, after the occurrence of sand dust events, the concentrations of K~＋, Mg^（2＋）, SO_4^（2–）, NO_3~– and Ca^（2＋） showed an increasing trend in the southern slope and a decreasing trend in the northern slope. It is our hope that the results may be helpful to further understand the atmospheric pollution caused by sand dust events in the Wushaoling Mountain and can also provide a scientific basis for the effective prevention of atmospheric pollution

关键词： precipitation chemistry source assessment sand dust event Wushaoling Mountain

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 *** 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 *** example,the stochastic resonance has been utilized effectively in mechanical fault diagnosis and weak signal ***,many methods have been developed to get the stochastic responses,including stochastic averaging method.

关键词： method. stochastic dynamics

Effect of sub-cloud evaporation on the δ^18O of precipitation in Qilian Mountains and Hexi Corridor, China

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Research in Cold and Arid Regions 2016年第5期8卷 378-387页

作者： ZongXing li Qi Feng YaMin Wang JianGuo li XiaoYan Guo yongge li Key Laboratory of Ecohydrology of Inland River Basins/Gansu Hydrology and Water Resources Engineering Research Center Northwest Institute of Eco-Environment and Resources Chinese Academy of Sciences Lanzhou Gansu 730000 China Changsha Normal University Changsha Hunan 410100 China

The sub-cloud evaporation effect refers to the evaporation process for raindrops that fall from the cloud base to the ground, which is usually accompanied by depleted light isotopes and enriched heavy isotopes in the precipitation. Based on 461 event-based precipitation samples collected from 12 weather stations in the Qilian Mountains and the Hexi Corridor from May to August of 2013, our results indicated that sub-cloud evaporation has a great influence on the δ^18O of precipitation, especially in small-amount precipitation events. In May, June, July, and August the δ18O composition was enriched by 35%, 26%, 39%, and 41%, respectively, from the cloud base to the ground. This influence clearly strengthened with temperature rise, from the Qilian Mountains to the Hexi Corridor. When falling raindrops are evaporated by 1.0% in the Qilian Mountains and the Hexi Corridor, the composition of δ18O would be enriched by 1.2% and 2.6%, respectively. Temperature dominated the sub-cloud evaporation in the Qilian Mountains, whereas relative humidity controlled it in the Hexi Corridor. These results provide new proofs of the evolutional process of stable isotopes in precipitation in arid regions.

关键词： sub-cloud evaporation precipitation stable isotope Qilian Mountains

Response of fractional Duffing oscillator with viscoelastic term under random excitation

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Response of fractional Duffing oscillator with viscoelastic ...