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| 1 | Analysis of 1/2 sub-harmonic resonance in a maneuvering rotor system显示文摘This paper focuses on the 1/2 sub-harmonic resonance of an aircraft’s rotor system under hovering flight that can be modeled as a maneuver load G in the equations of motion.The effect on the rotor system is analyzed by using theoretical methods.It is shown that the sub-harmonic resonance may occur due to maneuvering flight conditions.The larger the eccentricity E and the maneuver load G,the greater the sub-harmonic resonance.The effects of nonlinear stiffness,damping of the system,maneuver load,and eccentricity on the sub-harmonic resonance region in parameter planes are also investigated.Bifurcation diagrams of the analytical solutions are in good agreement with that of the numerical simulation solutions.These results will contribute to the understanding of the nonlinear dynamic behaviors of maneuvering rotor systems. | HOU Lei CHEN YuShu | 2014 | Science China(Technological Sciences)2014，57，1： | 10 |
| 2 | Influencing factors of the dynamic hysteresis in varying compliance vibrations of a ball bearing显示文摘We focus on the hysteretic characteristics of the varying compliance(VC) principal resonance in a ball bearing. The branches of the periodic VC response are traced by the harmonic balance method and the alternating frequency/time domain technique(HB-AFT) embedding Arc-length continuation, and the stability of these solutions is investigated by using Floquet theory. We find that the resonant response displays a swallow-tail structure due to the coupling nonlinearities between the Hertzian contact and the bearing clearance, which differs from the soft hysteresis of the non-loss Hertzian contact resonances. Furthermore, we find that period-1 VC branch cannot completely characterize the response of the system for a large bearing clearance, because multiple instability regions may occur from the cyclic fold, the secondary Hopf bifurcations, supercritical and subcritical period doubling bifurcations, in which case co-existences of period-1, period-2, and even quasi-periodic VC motions emerge in the hysteretic resonant range. | ZHANG ZhiYong CHEN YuShu LI ZhongGang | 2015 | Science China(Technological Sciences)2015，58，5： | 10 |
| 3 | Bifurcation analysis on full annular rub of a nonlinear rotor system显示文摘In this paper, analytical and numerical studies are carried out on the full annular rub motions of a nonlinear Jeffcott rotor. Transition sets of the synchronous full annular rub are given with the help of averaging method and constraint bifurcation theory to discuss the effects of system parameters on jump phenomena. Routh-Hurwitz criteria are employed to analyze the stability of synchronous full annular rub solution and determine the boundaries of static and Hopf bifurcations. Finally, the response and onset condition of reverse dry whip are investigated numerically, and at the same time, the influences of rotor parameters and rotation speed on the characteristics of the rotor response are investigated. | ZHANG HuaBiao CHEN YuShu | 2011 | Science China(Technological Sciences)2011，54，8： | 9 |
| 4 | Super-harmonic responses analysis for a cracked rotor system considering inertial excitation显示文摘In this paper, an investigation on the nonlinear vibration, especially on the super-harmonic resonances, in a cracked rotor system is carried out to provide a novel idea for the detection of crack faults in rotor systems. The motion equations of the system are formulated with the consideration of the additional excitation from an inertial environment as well as the forced excitation of the rotor unbalance. By using the harmonic balance method, the analytical solutions of the equations with four orders of harmonic exponents are obtained to analyze the nonlinear response of the system. Then through numerical calculations, the vibration responses affected by system parameters including the inertial excitation, the forced excitation, the crack and damping factors are investigated in detail. The results show that the occurrence of the super-harmonic resonances of the rotor system is due to the interaction between crack breathing and the inertial excitation. Correspondingly, the super-harmonic responses are significantly affected by the inertial excitation and the crack stiffness(or depth). The rotor unbalance, however, does not make apparent effects on the super-harmonic responses. Consequently, the super-harmonic resonances peaks can be viewed as an identification signal of the crack fault due to the application of the inertial excitation. By utilizing the inertial excitation, the super-harmonic response signals in rotor systems with early crack faults can be amplified and detected more easily. | HOU Lei CHEN YuShu | 2015 | Science China(Technological Sciences)2015，58，11： | 9 |
| 5 | Singular analysis of bifurcation systems with two parameters显示文摘有二个参数的动态系统的分叉性质在这份报纸被调查。设置的转变的定义被建议,并且开发的途径被用来与非线性的反馈控制器调查非线性的强迫的未击中的系统的动态特征。整个参量的飞机被转变集合划分成几个坚持的区域,然后在不同坚持的区域的分叉图被获得。关键词二个参数 - 分叉 - 单个分析工程被中国(10632040 ) 的国家自然科学基础支持。 | Zhaohong Qin Yushu Chen | 2010 | Acta Mechanica Sinica2010，26，3： | 8 |
| 6 | Bifurcation analysis for vibrations of a turbine blade excited by air flows显示文摘模仿汽轮机片和即将来临的空气流动的液体结构相互作用(FSI ) 的一个减少的 three-degree-of-freedom 模型被建议。运动的方程由联合弯曲和片以及代表的货车 der Pol 摆动的扭转组成液体变化时间。1:1 系统的内部回声与多重规模方法被分析,并且调整方程被导出。二参数的分叉图被计算。包括 detuning 参数和减少的频率,系统参数的效果在结构和液体的回答上被调查。分叉曲线被计算,稳定性被检验 Jacobian 矩阵的特征值决定。结果显示包括僵绳的不变的解决方案的富有的动态现象 -- 节点和 Hopf 分叉能发生在某些参数条件下面。不稳定的答案发生的参数区域应该被避免保留片的安全操作。分析答案被直接数字的模拟验证。 | WANG Dan CHEN YuShu HAO ZhiFeng CAO QingJie | 2016 | Science China(Technological Sciences)2016，59，8： | 7 |
| 7 | Variability of soil organic carbon reservation capability between coastal salt marsh and riverside freshwater wetland in Chongming Dongtan and its microbial mechanism显示文摘Two representative zones in Chongming Dongtan which faced the Yangtze River and East China Sea respectively were selected to study the variability of soil organic carbon (SOC) reservation capability between coastal wetland and riverside wetland in the Chongming Dongtan wetland as well as its mechanism by analyzing soil characteristics and plant biomass.The results showed the SOC content of riverside wetland was only 48.61% (P=0.000 < 0.05) that of coastal wetland.As the organic matter inputs from plant litter of the coastal wetland and riverside wetland were approximately the same,the higher soil microbial respiration (SMR) of riverside wetland led to its lower SOC reservation capability.In the riverside wetland,the high soil microbial biomass,higher proportion of β-Proteobacteria,which have strong carbon metabolism activity and the existence of some specific aerobic heterotrophic bacteria such as Bacilli and uncultured Lactococcus,were the important reasons for the higher SMR compared to the coastal wetland.There were additional differences in soil physical and chemical characteristics between the coastal wetland and riverside wetlands.Path analysis of predominant bacteria and microbial biomass showed that soil salinity influenced β-Proteobacteria and microbial biomass most negatively among these physical and chemical factors.Therefore the low salinity of the riverside area was suitable for the growth of microorganisms,especially β-Proteobacteria and some specific bacteria,which led to the high SMR and low SOC reservation capability when compared to the coastal area. | Yu Hu Yanli Li Lei Wang Yushu Tang Jinhai Chen Xiaohua Fu Yiquan Le Jihua Wu | 2012 | Journal of Environmental Sciences2012，24，6： | 7 |
| 8 | Periodic response analysis of a misaligned rotor system by harmonic balance method with alternating frequency/time domain technique显示文摘A dynamic model is established for an offset-disc rotor system with a mechanical gear coupling, which takes into consideration the nonlinear restoring force of rotor support and the effect of coupling misalignment. Periodic solutions are obtained through harmonic balance method with alternating frequency/time domain(HB-AFT) technique, and then compared with the results of numerical simulation. Good agreement confirms the feasibility of HB-AFT scheme. Moreover, the Floquet theory is adopted to analyze motion stability of the system when rotor runs at different speed intervals. A simple strategy to determine the monodromy matrix is introduced and two ways towards unstability are found for periodic solutions: the period doubling bifurcation and the secondary Hopf bifurcation. The results obtained will contribute to the global response analysis and dynamic optimal design of rotor systems. | LI HongLiang CHEN YuShu HOU Lei ZHANG ZhiYong | 2016 | Science China(Technological Sciences)2016，59，11： | 6 |
| 9 | Bifurcation and chaos of the bladed overhang rotor system with squeeze film dampers显示文摘To study the nonlinear dynamic behavior of the bladed overhang rotor system with squeeze film damper (SFD), a blade-overhang rotor-SFD model is formulated using the lumped mass method and the Lagrange approach. The cavitated short bearing model is employed to describe the nonlinear oil force of the SFD. To reduce the scale of the nonlinear coupling system, a set of orthogonal transformations is employed to decouple the one nodal diameter equations of blades, which are coupled with the dy- namical equations of the rotor, with other equations of blades. In this way, the original system with 16+4n (n≥3) degrees of freedom (DoF) is reduced to a system with 24 DoF only. Then the parametric excitation terms in the blade-overhang rotor-SFD model are simplified in terms of periodic transforma- tions. The coupling equations are numerically solved and the solutions are used to analyze the dy- namic behavior of the system in terms of the bifurcation diagram, whirl orbit, Poincaré map and spec- trum plot. A variety of motion types are found such as multi-periodic, quasi-periodic, and chaotic mo- tions. Moreover, the typical nonlinear dynamic evolutions including the periodic-doubling bifurcation and reverse bifurcation are noted. It is noticed that there exist apparent differences in the dynamic behavior between the blade-overhang rotor-SFD models without and with considering the effect of blades. | CAO DengQing WANG LiGang CHEN YuShu HUANG WenHu | 2009 | Science China(Technological Sciences)2009，52，3： | 5 |
| 10 | A novel smooth and discontinuous oscillator with strong irrational nonlinearities显示文摘In this paper,we propose a novel nonlinear oscillator with strong irrational nonlinearities having smooth and discontinuous characteristics depending on the values of a smoothness parameter.The oscillator is similar to the SD oscillator,originally introduced in Phys Rev E 69(2006).The equilibrium stability and the complex bifurcations of the unperturbed system are investigated.The bifurcation sets of the equilibria in parameter space are constructed to demonstrate transitions in the multiple well dynamics for both smooth and discontinuous regimes.The Melnikov method is employed to obtain the analytical criteria of chaotic thresholds for the singular closed orbits of homoclinic,homo-heteroclinic,cuspidal heteroclinic and tangent homoclinic orbits of the perturbed system. | HAN YanWei CAO QingJie CHEN YuShu WIERCIGROCH Marian | 2012 | Science China(Physics,Mechanics & Astronomy)2012，55，10： | 4 |
| 11 | Evaluation of the Biodiversity Conservation Function in Liaohe Delta Wetland,Northeastern China显示文摘The scientific evaluation of the wetland biodiversity conservation function is the basis of balanced wetland protection and development. Our research sought to provide references for the protection of wetland ecological environments as well as the related planning and management policies. The study established a fitting model for evaluating the biodiversity conservation function in the Liaohe Delta, northeastern China. The new model, the Wetland Biodiversity Conservation Indicator(WBCI), was with four input factors, including the vegetation coverage(VC), habitat suitability index(HI), land use and land cover(LULC) index(LI), and threat factor index(TI) of the LULC type. The values assigned to HI and TI were based on Integrated Valuation of Ecosystem Services and Tradeoffs(In VEST)habitat quality models. The weights of all the factors in WBCI were valued with the Principal Component Analysis(PCA). We evaluated the wetland biodiversity conservation function of Panjin, Liaohe Delta, China, by using the WBCI model based on Gaofen-1(GF-1) satellite data in 2018, and the result was verified with In VEST and other models. It showed that the output map was similar to that of In VEST, with the higher-quality habitat including the wetland, tidal flat, water body, and forest, as well as the lower-quality land use types including the paddy field, crop field, construction land, and land used by traffic. The wetland biodiversity conservation function was better in areas less affected by human disturbance, with very abundant species and good-quality habitat. It was poor in areas impacted by more frequent human activities such as the land cultivation, housing, and traffic, which led to the landscape fragmentation. The WBCI model provided a more accurate reflection of the bird distribution than the In VEST model. The WBCI model was able to reflect the difference in quality of each habitat grade, in contrast to the net primary productivity(NPP) method and species distribution models(SDMs). The new model was, therefore, simpler and suitable in reflecting the quality of wetland biodiversity function in the Liaohe Delta. | Wenying YU Ruipeng JI Xiuzhen HAN Long CHEN Rui FENG Jinwen WU Yushu ZHANG | 2020 | Journal of Meteorological Research2020，34，4： | 4 |
| 12 | Singular analysis of two-dimensional bifurcation system显示文摘Bifurcation properties of two-dimensional bifurcation system are studied in this paper.Universal unfolding and transition sets of the bifurcation equations are obtained.The whole parametric plane is divided into several different persistent regions according to the type of motion,and the different qualitative bifurcation diagrams in different persistent regions are given.The bifurcation properties of the two-dimensional bifurcation system are compared with its reduced one-dimensional system.It is found that the system which is reduced to one dimension has lost many bifurcation properties. | CHEN YuShu& QIN ZhaoHong School of Astronautics,Harbin Institute of Technology,Harbin 150001,China | 2010 | Science China(Technological Sciences)2010，53，3： | 3 |
| 13 | Bifurcation and dynamic response analysis of rotating blade excited by upstream vortices显示文摘A reduced model is proposed and analyzed for the simulation of vortexinduced vibrations(VIVs) for turbine blades. A rotating blade is modelled as a uniform cantilever beam, while a van der Pol oscillator is used to represent the time-varying characteristics of the vortex shedding, which interacts with the equations of motion for the blade to simulate the fluid-structure interaction. The action for the structural motion on the fluid is considered as a linear inertia coupling. The nonlinear characteristics for the dynamic responses are investigated with the multiple scale method, and the modulation equations are derived. The transition set consisting of the bifurcation set and the hysteresis set is constructed by the singularity theory and the effects of the system parameters,such as the van der Pol damping. The coupling parameter on the equilibrium solutions is analyzed. The frequency-response curves are obtained, and the stabilities are determined by the Routh-Hurwitz criterion. The phenomena including the saddle-node and Hopf bifurcations are found to occur under certain parameter values. A direct numerical method is used to analyze the dynamic characteristics for the original system and verify the validity of the multiple scale method. The results indicate that the new coupled model is useful in explaining the rich dynamic response characteristics such as possible bifurcation phenomena in the VIVs. | Dan WANG Yushu CHEN M.WIERCIGROCH Qingjie CAO | 2016 | Applied Mathematics and Mechanics(English Edition)2016，37，9： | 3 |
| 14 | Bifurcation analysis of aero-engine's rotor system under constant maneuver load显示文摘When an aircraft is hovering or doing a dive-hike flight at a fixed speed, a constant additional inertial force will be induced to the rotor system of the aero-engine,which can be called a constant maneuver load.Take hovering as an example.A Jeffcott rotor system with a biased rotor and several nonlinear elastic supports is modeled, and the vibration characteristics of the rotor system under a constant maneuver load are analytically studied.By using the multiple-scale method, the differential equations of the system are solved, and the bifurcation equations are obtained.Then, the bifurcations of the system are analyzed by using the singularity theory for the two variables.In the E G-plane, where E refers to the eccentricity of the rotor and G represents the constant maneuver load, two hysteresis point sets and one double limit point set are obtained.The bifurcation diagrams are also plotted.It is indicated that the resonance regions of the two variables will shift to the right when the aircraft is maneuvering.Furthermore, the movement along the horizontal direction is faster than that along the vertical direction.Thus, the different overlapping modes of the two resonance regions will bring about different bifurcation modes due to the nonlinear coupling effects.This result lays a theoretical foundation for controlling the stability of the aero-engine's rotor system under a maneuver load. | Lei HOU Yushu CHEN | 2015 | Applied Mathematics and Mechanics(English Edition)2015，36，11： | 2 |
| 15 | Convective Bursts Episode of the Rapidly Intensified Typhoon Mujigae(2015)显示文摘Convective burst(CB) characteristics at distinct stages of a rapidly intensified Typhoon Mujigae(2015), are investigated based on a 72-h simulation. The spatial features show that almost all CB elements develop in the eyewall. The number of CBs in the inner-core region within a 100 km radius—which account for a large proportion of the total CBs, with a sharp increase about 6 h before the onset of rapid intensification(RI)—provides some indication of the RI of the typhoon. The CBs during pre-RI and RI are examined from dynamic and thermodynamic viewpoints. The combination of lower-level convergent inflow and upper-level divergent outflow pushes a relay-race-like transmission of convective activity, favorable for the development of deep convection. A double warm-core structure is induced by the centripetal outflow sinking and warming associated with CBs, which directly accelerates RI by a sudden decrease in hydrostatic pressure. By utilizing the convection activity degree(CAD) index derived from the local total energy anomaly, a correlation formula between CBs and CAD is deduced.Furthermore, an intense CAD(ICAD) signal threshold(with a value equal to 100) to predict CBs is obtained. It is verified that this ICAD threshold is effective for estimating the occurrence of a CB episode and predicting RI of a typhoon. Therefore,this threshold may be a valuable tool for identifying CB episodes and forecasting rapidly intensified typhoons. | Shuai YANG Xiba TANG Shuixin ZHONG Bin CHEN Yushu ZHOU Shouting GAO Chengxin WANG | 2019 | Advances in Atmospheric Sciences2019，36，5： | 2 |
| 16 | Super-harmonic resonance characteristic of a rigid-rotor ball bearing system caused by a single local defect in outer raceway显示文摘The studies on dynamics of a fault bearing system are prevalent in recent years, however, we are studying a completely different frequency range than the one where the bearing faults are best seen. Considering a local defect on outer raceway,a two-degree-of-freedom analytical model of a rigid-rotor ball bearing system is established. Three pulse force models are introduced to simulate the local defect. The frequency domain method—harmonic balance method with alternating frequency/time domain technique (HB-AFT) is used to calculate the response in a large frequency range. By comparing the performance at different frequencies, the fault systems with different defect models and parameters reveal the super-harmonic resonances,and the reasons for this phenomenon are uncovered as well. Finally, the theoretical calculation is verified qualitatively by the experimental results, through comparing the frequency spectrums of the defective bearing rotor system to the fault-free one.Therefore, the super-harmonic resonances can be regarded as a dynamic feature. Besides, the obvious super-harmonic resonances indicate the magnification of the harmonics of the 'characteristic defect frequency' for outer race in the corresponding speed regions, which may be helpful for the diagnosis of a rotor ball bearing system with a local defect. | YANG Rui JIN YuLin HOU Lei CHEN YuShu | 2018 | Science China(Technological Sciences)2018，61，8： | 2 |
| 17 | STUDY ON THE PREDICTION METHOD OF LOW-DIMENSION TIME SERIES THAT ARISE FROM THE INTRINSIC NONLINEAR DYNAMICS显示文摘The prediction methods and its applications of the nonlinear dynamic systems determined from chaotic time series of low-dimension are discussed mainly. Based on the work of the foreign researchers, the chaotic time series in the phase space adopting one kind of nonlinear chaotic model were reconstructed. At first, the model parameters were estimated by using the improved least square method. Then as the precision was satisfied,the optimization method was used to estimate these parameters. At the end by using the obtained chaotic model, the future data of the chaotic time series in the phase space was predicted. Some representative experimental examples were analyzed to testify the models and the algorithms developed in this paper. The results show that if the algorithms developed here are adopted, the parameters of the corresponding chaotic model will be easily calculated well and true. Predictions of chaotic series in phase space make the traditional methods change from outer iteration to interpolations. And if the optimal model rank is chosen, the prediction precision will increase notably. Long term superior predictability of nonlinear chaotic models is proved to be irrational and unreasonable. | MA Junhai(马军海) CHEN Yushu(陈予恕) | 2001 | Applied Mathematics and Mechanics(English Edition)2001，22，5： | 2 |
| 18 | Nonlinear resonance characteristics of a dual-rotor system with a local defect on the inner ring of the inter-shaft bearing显示文摘In this paper,the nonlinear resonance characteristics of a dual-rotor system are investigated with the consideration of a local defect on the inter-shaft bearing of the system.A simplified model of the dual-rotor system is proposed by considering that there is a local defect on the inner ring of inter-shaft bearing.The local defect is modelled as an inverted isosceles trapezoidal groove,which can make great influence on the inter-shaft bearing force due to the change of radial clearance of the inter-shaft bearing.The motion equations of the dual-rotor system are formulated by using the Lagrange equation.The Runge-Kutta method is employed to solve the motion equation.The amplitude-frequency response curve of the dual-rotor system is obtained,the abnormal resonance characteristics are analyzed.In addition,the influence of defect parameters,rotors and support parameters and inter-shaft bearing parameters on the amplitude-frequency characteristics of the system are discussed.The results show that there are two main resonance peaks and four abnormal resonance peaks on the amplitude-frequency response curve of the dual-rotor with a local defect on the inner ring of the inter-shaft bearing.Through analyzing the vibration response of the abnormal resonance peaks,it is found that the first two abnormal resonances are caused by the combined resonance,which are related to the inner ring fault and the rotational speed of high or low pressure rotors,and the last two resonances are caused by the induced resonance of the inner ring fault.At the same time,when the parameters of defect,rotors and support and inter-shaft bearing change,the resonance of the system also shows the corresponding change law. | Haiming YI Lei HOU Peng GAO Yushu CHEN | 2021 | Chinese Journal of Aeronautics2021，34，12： | 2 |
| 19 | Thermally rearranged covalent organic framework with flame-retardancy as a high safety Li-ion solid electrolyte显示文摘Solid polymer electrolytes have demonstrated high promise to solve the safety problems caused by conventional liquid electrolytes in lithium ion batteries.However,the inherent flammability of most polymer electrolyte materials remains unresolved,hence hindering their further industrial application.Addressing this challenge,we designed and constructed a thermal-responsive imide-linked covalent organic framework(COF)bearing ortho-positioned hydroxy groups as precursors,which can conduct a thermal rearrangement to transform into a highly crystalline and robust benzoxazole-linked COF upon heating.Benefiting from the release of carbon dioxide through thermal rearrangement reaction,this COF platform exhibited excellent flame retardant properties.By contrast,classic COFs(e.g.,boronate ester,imine,olefin,imide linked)were all flammable.Moreover,incorpo-rating polyethylene glycol and Li salt into the COF channels can produce solid polymer electrolytes with outstanding flame retardancy,high ionic conductivity(6.42×10^(-4) S cm^(-1))and a high lithium-ion transference number of 0.95.This thermal rearrangement strategy not only opens a new route for the fabrication of ultrastable COFs,but also provides promising perspectives to designing flame-retardant materials for energy-related applications. | Zhifang Wang Yushu Zhang Penghui Zhang Dong Yan Jinjin Liu Yao Chen Qi Liu Peng Cheng Michael JZaworotko Zhenjie Zhang | 2022 | eScience2022，2，3： | 2 |
| 20 | Bifurcation and chaos of an airfoil with cubic nonlinearity in incompressible flow显示文摘Using a combination of analytical and numerical methods, the paper studies bifurcations and chaotic motions of a two-dimensional airfoil with cubic nonlinearity in incompressible flow. One type of critical points (characterized by a negative eigenvalue, a simple zero eigenvalue and a pair of purely imaginary eigenvalues) for the bifurcation response equations is considered. With the aid of the normal form theory, the explicit expressions of the critical bifurcation lines leading to incipient and secondary bifurcations are obtained. The stability of the bifurcation solutions is also investigated. By using the undetermined coefficient method, the homoclinic orbit is found, and the uniform convergence of the homoclinic orbit series expansion is proved. It analytically demonstrates that there exists a homoclinic orbit joining the initial equilibrium point to itself, therefore Smale horseshoe chaos occurs for this system via Si'lnikov criterion. The system evolves into chaotic motion through period-doubling bifurcation, and is periodic again as the dimensionless airflow speed increases. Numerical simulations are also given, which confirm the analytical results. | CHEN FangQi ZHOU LiangQiang CHEN YuShu | 2011 | Science China(Technological Sciences)2011，54，8： | 2 |
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