Natural soil generally exhibits significant transverse isotropy(TI)due to weathering and sedimentation,meaning that horizontal moduli differ from their vertical counterpart.The TI mechanical model is more appropriate ...Natural soil generally exhibits significant transverse isotropy(TI)due to weathering and sedimentation,meaning that horizontal moduli differ from their vertical counterpart.The TI mechanical model is more appropriate for actual situations.Although soil exhibits material nonlinearity under earthquake excitation,existing research on the TI medium is limited to soil linearity and neglects the nonlinear response of TI sites.A 2D equivalent linear model for a layered TI half-space subjected to seismic waves is derived in the transformed wave number domain using the exact dynamic stiffness matrix of the TI medium.This study introduces a method for determining the effective shear strain of TI sites under oblique wave incidence,and further describes a systematic study on the effects of TI parameters and soil nonlinearity on site responses.Numerical results indicate that seismic responses of the TI medium significantly differ from those of isotropic sites and that the responses are highly dependent on TI parameters,particularly in nonlinear cases,while also being sensitive to incident angle and excitation intensity.Moreover,the differences in peak acceleration and waveform for various TI materials may also be amplified due to the strong nonlinearity.The study provides valuable insights for improving the accuracy of seismic response analysis in engineering applications.展开更多
A rotating packed bed is a typical chemical process enhancement equipment that can strengthen micromixing and mass transfer.During the operation of the rotating packed bed,the nonreactants and products irregularly adh...A rotating packed bed is a typical chemical process enhancement equipment that can strengthen micromixing and mass transfer.During the operation of the rotating packed bed,the nonreactants and products irregularly adhere to the wire mesh packing in the rotor,thus resulting in an imbalance in the vibration of the rotor,which may cause serious damage to the bearing and material leakage.This study proposes a model prediction for estimating the bearing residual life of a rotating packed bed based on rotor imbalance response analysis.This method is used to determine the influence of the mass on the imbalance in the vibration of the rotor on bearing damage.The major influence on rotor vibration was found to be exerted by the imbalanced mass and its distribution radius,as revealed by the results of orthogonal experiments.Through implementing finite element analysis,the imbalance response curve for the rotating packed bed rotor was obtained,and a correlation among rotor imbalance mass,distribution radius of imbalance mass,and bearing residue life was established via data fitting.The predicted value of the bearing life can be used as the reference basis for an early safety warning of a rotating packed bed to effectively avoid accidents.展开更多
This paper introduces an orthogonal expansion method for general stochastic processes. In the method, a normalized orthogonal function of time variable t is first introduced to carry out the decomposition of a stochas...This paper introduces an orthogonal expansion method for general stochastic processes. In the method, a normalized orthogonal function of time variable t is first introduced to carry out the decomposition of a stochastic process and then a correlated matrix decomposition technique, which transforms a correlated random vector into a vector of standard uncorrelated random variables, is used to complete a double orthogonal decomposition of the stochastic processes. Considering the relationship between the Hartley transform and Fourier transform of a real-valued function, it is suggested that the first orthogonal expansion in the above process is carried out using the Hartley basis function instead of the trigonometric basis function in practical applications. The seismic ground motion is investigated using the above method. In order to capture the main probabilistic characteristics of the seismic ground motion, it is proposed to directly carry out the orthogonal expansion of the seismic displacements. The case study shows that the proposed method is feasible to represent the seismic ground motion with only a few random variables. In the second part of the paper, the probability density evolution method （PDEM） is employed to study the stochastic response of nonlinear structures subjected to earthquake excitations. In the PDEM, a completely uncoupled one-dimensional partial differential equation, the generalized density evolution equation, plays a central role in governing the stochastic seismic responses of the nonlinear structure. The solution to this equation will yield the instantaneous probability density function of the responses. Computational algorithms to solve the probability density evolution equation are described. An example, which deals with a nonlinear frame structure subjected to stochastic ground motions, is illustrated to validate the above approach.展开更多
Discrete models such as the lumped parameter model and the finite element model are widely used in the solution of soil amplification of earthquakes. However, neither of the models will accurately estimate the natural...Discrete models such as the lumped parameter model and the finite element model are widely used in the solution of soil amplification of earthquakes. However, neither of the models will accurately estimate the natural frequencies of soil deposit, nor simulate a damping of frequency independence. This research develops a new discrete model for onedimensional viscoelastic response analysis of layered soil deposit based on the mode equivalence method. The new discrete model is a one-dimensional equivalent multi-degree-of-freedom（MDOF） system characterized by a series of concentrated masses, springs and dashpots with a special configuration. The dynamic response of the equivalent MDOF system is analytically derived and the physical parameters are formulated in terms of modal properties. The equivalent MDOF system is verified through a comparison of amplification functions with the available theoretical solutions. The appropriate number of degrees of freedom（DOFs） in the equivalent MDOF system is estimated. A comparative study of the equivalent MDOF system with the existing discrete models is performed. It is shown that the proposed equivalent MDOF system can exactly present the natural frequencies and the hysteretic damping of soil deposits and provide more accurate results with fewer DOFs.展开更多
Rate capability,peak power,and energy density are of vital importance for the capacitive energy storage(CES)of electrochemical energy devices.The frequency response analysis(FRA)is regarded as an efficient tool in stu...Rate capability,peak power,and energy density are of vital importance for the capacitive energy storage(CES)of electrochemical energy devices.The frequency response analysis(FRA)is regarded as an efficient tool in studying the CES.In the present work,a bi-scale impedance transmission line model(TLM)is firstly developed for a single pore to a porous electrode.Not only the TLM of the single pore is reparameterized but also the particle packing compactness is defined in the bi-scale.Subsequently,the CES properties are identified by FRA,focused on rate capability vs.characteristic frequency,peak power vs.equivalent series resistance,and energy density vs.low frequency limiting capacitance for a single pore to a porous electrode.Based on these relationships,the CES properties are numerically simulated and theoretically predicted for a single pore to a porous electrode in terms of intra-particle pore length,intra-particle pore diameter,inter-particle pore diameter,electrolyte conductivity,interfacial capacitance&exponent factor,electrode thickness,electrode apparent surface area,and particle packing compactness.Finally,the experimental diagnosis of four supercapacitors(SCs)with different electrode thicknesses is conducted for validating the bi-scale TLM and gaining an insight into the CES properties for a porous electrode to a single pore.The calculating results suggest,to some extent,the inter-particle pore plays a more critical role than the intra-particle pore in the CES properties such as the rate capability and the peak power density for a single pore to a porous electrode.Hence,in order to design a better porous electrode,more attention should be given to the inter-particle pore.展开更多
Vibration induced by shield construction can lead to liquefaction of saturated sand.Based on FLAC3D software,a numerical model of tunnel excavation is established and sinusoidal velocity loads with different frequenci...Vibration induced by shield construction can lead to liquefaction of saturated sand.Based on FLAC3D software,a numerical model of tunnel excavation is established and sinusoidal velocity loads with different frequencies are applied to the excavation face.The pattern of the excess pore pressure ratio with frequency,as well as the dynamic response of soil mass under different frequency loads before excavation,is analyzed.When the velocity sinusoidal wave acts on the excavation surface of the shield tunnel with a single sand layer,soil liquefaction occurs.However,the ranges and locations of soil liquefaction are different at different frequencies,which proves that the vibration frequency influences the liquefaction location of the stratum.For sand-clay composite strata with liquefiable layers,the influence of frequency on the liquefaction range is different from that of a single stratum.In the frequency range of 5-30 Hz,the liquefaction area and surface subsidence decrease with an increase in vibration frequency.The research results in this study can be used as a reference in engineering practice for tunneling liquefiable strata with a shield tunneling machine.展开更多
To evaluate the coupling pounding-friction effect between bridge girders and retainers and its influence on bridge seismic response, a reinforced concrete （RC） continuous bridge is selected as the research object. T...To evaluate the coupling pounding-friction effect between bridge girders and retainers and its influence on bridge seismic response, a reinforced concrete （RC） continuous bridge is selected as the research object. Three bridge finite element （FE） models were built using OpenSees, in which the longitudinal and transverse pounding elements, as well as the transverse failure element of bearings were introduced. Based on this, tire seismic response analysis considering the coupling pounding-friction effect was conducted for the continuous bridge subjected to bi-directional ground motions. Furthermore, the influential parameters were analyzed. The analysis results indicate that the coupling pounding-friction effect can alter the internal force distribution of the bridge structure and generate additional torsional force to bridge columns. The friction coefficient and longitudinal pounding gap size are two important factors. The appropriate friction coefficient and longitudinal pounding gap size can significantly reduce seismic response of girders, and effectively transfer part of the girder inertia force from the fixed columns to the sliding columns, which can reduce the seismic demands of the fixed columns and improve the seismic performance of continuous bridge structures.展开更多
Making an analysis for vibration modal and frequency response of the lathe spindle,respectively by using finite element method based on ANSYS and experiment of CA6140 type lathe in machining,and the calculation result...Making an analysis for vibration modal and frequency response of the lathe spindle,respectively by using finite element method based on ANSYS and experiment of CA6140 type lathe in machining,and the calculation results are compared and analyzed,which verified the accuracy of ANSYS method. Numerical simulation and experimental results show that: Spindle in the first order and fifth order are prone to resonance,but did not reach resonance,the low order natural frequency have more effect than the high order natural frequency of the spindle vibration; by the experiments can conclude that the maximum vibration of the main shaft in the working state is mainly concentrated in the vicinity of its two ends,therefore,the improved bearing is an important way to reduce the vibration of the main shaft and ensure the machining accuracy,and the research results can provide a theoretical reference for the structural optimization design of the lathe.展开更多
As to motorized spindle system, this paper builds a simplified 3D model of spindle and bearing, performs structure modal analysis, reveals its dynamic characteristics under the free model; furthermore, modifies bearin...As to motorized spindle system, this paper builds a simplified 3D model of spindle and bearing, performs structure modal analysis, reveals its dynamic characteristics under the free model; furthermore, modifies bearing radial stiffness and number of model and studies the change of modal parameters. On this basis, through the harmonic response analysis of the finite element model, dy- namic response characteristic caused by imbalance of monitored spindle system and law of vibration response to different amount of unbalance is analyzed.展开更多
This paper constructs a new two-dimensional arbitrary polygonal stress hybrid dynamic(APSHD)element for structural dynamic response analysis.Firstly,the energy function is established based on Hamilton's principle...This paper constructs a new two-dimensional arbitrary polygonal stress hybrid dynamic(APSHD)element for structural dynamic response analysis.Firstly,the energy function is established based on Hamilton's principle.Then,the finite element time-space discrete format is constructed using the generalized variational principle and the direct integration method.Finally,an explicit polynomial form of the combined stress solution is give,and its derivation process is shown in detail.After completing the theoretical construction,the numerical calculation program of the APSHD element is written in Fortran,and samples are verified.Models show that the APSHD element performs well in accuracy and convergence.Furthermore,it is insensitive to mesh distortion and has low dependence on selecting time steps.展开更多
This article deals with the dynamic response analysis and active vibration control of the smart functionally graded material(FGM)composite core plate with FG piezoelectric material(FGPM)surface actuators and sensors.C...This article deals with the dynamic response analysis and active vibration control of the smart functionally graded material(FGM)composite core plate with FG piezoelectric material(FGPM)surface actuators and sensors.Considering a power law distribution,the mechanical and electrical material characteristics of the FGM and FGPM layers change continually along the thickness plane.The finite element method(FEM)and the first-order shear deformation theory(FSDT)are utilized in the modeling process for the FGM and FGPM layers.In the dynamic analysis,the dynamic response of the sandwich structure under the impact of sinusoidally distributed step load and the corresponding sensor voltage is obtained.To ensure that the simulations are accurate,the findings are compared with previously published research.To analyze the control efficiency of FGPM sensors and actuators on the FGM host structure,the linear quadratic regulator(LQR)controller is utilized.The sandwich structure is considered a multiple-input multiple-output system(MIMO),so sensors and actuators are placed at different locations on the plate surface.The modal strain energy method is utilized to find the appropriate location of the FGPM layers.According to the results of the analysis,it has been determined that piezoelectric material coefficients as well as mechanical properties are extremely important for obtaining optimum control performance from FGPM sensors and actuators.In addition,it is emphasized that active vibration control of FGM plates can be performed effectively with the proper selection of sensors and actuators and their accurate distribution on the plate.These results are expected to contribute to micro-electromechanical system(MEMS)sensor and actuator applications,soft robotics applications,and vibration protection and vibration damping applications of nanostructures.展开更多
This paper proposes a hybrid algorithm based on the physics-informed kernel function neural networks(PIKFNNs)and the direct probability integral method(DPIM)for calculating the probability density function of stochast...This paper proposes a hybrid algorithm based on the physics-informed kernel function neural networks(PIKFNNs)and the direct probability integral method(DPIM)for calculating the probability density function of stochastic responses for structures in the deep marine environment.The underwater acoustic information is predicted utilizing the PIKFNNs,which integrate prior physical information.Subsequently,a novel uncertainty quantification analysis method,the DPIM,is introduced to establish a stochastic response analysis model of underwater acoustic propagation.The effects of random load,variable sound speed,fluctuating ocean density,and random material properties of shell on the underwater stochastic sound pressure are numerically analyzed,providing a probabilistic insight for assessing the mechanical behavior of structures in the deep marine environment.展开更多
The seismic safety of offshore wind turbines is an important issue that needs to be solved urgently.Based on a unified computing framework,this paper develops a set of seawater-seabed-wind turbine zoning coupling anal...The seismic safety of offshore wind turbines is an important issue that needs to be solved urgently.Based on a unified computing framework,this paper develops a set of seawater-seabed-wind turbine zoning coupling analysis methods.A 5 MW wind turbine and a site analysis model are established,and a seismic wave is selected to analyze the changes in the seismic response of offshore monopile wind turbines under the change of seawater depth,seabed wave velocity and seismic wave incidence angle.The analysis results show that when the seawater increases to a certain depth,the seismic response of the wind turbine increases.The shear wave velocity of the seabed affects the bending moment and displacement at the bottom of the tower.When the angle of incidence increases,the vertical displacement and the acceleration of the top of the tower increase in varying degrees.展开更多
Long-term responses of floating structures pose a great concern in their design phase. Existing approaches for addressing long-term extreme responses are extremely cumbersome for adoption. This work aims to develop an...Long-term responses of floating structures pose a great concern in their design phase. Existing approaches for addressing long-term extreme responses are extremely cumbersome for adoption. This work aims to develop an approach for the long-term extreme-response analysis of floating structures. A modified gradient-based retrieval algorithm in conjunction with the inverse first-order reliability method(IFORM) is proposed to enable the use of convolution models in long-term extreme analysis of structures with an analytical formula of response amplitude operator(RAO). The proposed algorithm ensures convergence stability and iteration accuracy and exhibits a higher computational efficiency than the traditional backtracking method. However, when the RAO of general offshore structures cannot be analytically expressed, the convolutional integration method fails to function properly. A numerical discretization approach is further proposed for offshore structures in the case when the analytical expression of the RAO is not feasible. Through iterative discretization of environmental contours(ECs) and RAOs, a detailed procedure is proposed to calculate the long-term response extremes of offshore structures. The validity and accuracy of the proposed approach are tested using a floating offshore wind turbine as a numerical example. The long-term extreme heave responses of various return periods are calculated via the IFORM in conjunction with a numerical discretization approach. The environmental data corresponding to N-year structural responses are located inside the ECs, which indicates that the selection of design points directly along the ECs yields conservative design results.展开更多
Double-shaft-driven needle punching machine is a specialized equipment designed for processing C/C crucible preforms.Its main needle punching module is operated by two sets of reciprocating crank-slider mechanisms.The...Double-shaft-driven needle punching machine is a specialized equipment designed for processing C/C crucible preforms.Its main needle punching module is operated by two sets of reciprocating crank-slider mechanisms.The intense vibration during needle punching not only generates huge noise,but also substantially reduces the quality of the preform.It is imperative to perform a dynamic analysis and optimization of the entire needle punching machine.In this paper,the three-dimensional(3D)model of the entire double-shaft-driven needle punching machine for C/C crucible preforms is established.Based on the modal analysis theory,the modal characteristics of the needle punching machine under various operating conditions are analyzed and its natural frequencies and vibration modes are determined.The harmonic response analysis is then employed to obtain the amplitude of the needle plate at different frequencies,and the structural weak points of the needle punching machine are identified and improved.The feasibility of the optimized scheme is subsequently reevaluated and verified.The results indicate that the first six natural frequencies of the machine increase,and the maximum amplitude of the needle plate decreases by 70.3%.The enhanced dynamic characteristics of the machine significantly improve its performance,enabling more efficient needle punching of C/C crucible preforms.展开更多
Actuator dynamics introduce a synchronization disparity between commanded displacements transmitted to the actuator and the actual displacements generated by the actuator,thereby affecting its precision and potentiall...Actuator dynamics introduce a synchronization disparity between commanded displacements transmitted to the actuator and the actual displacements generated by the actuator,thereby affecting its precision and potentially leading to instability in real-time hybrid simulation(RTHS).This study aims to elucidate the relationship between calculated and measured displacements by analyzing their magnitude and phase in the frequency domain via transformations.The physical implications of these relationships are explored in the context of frequency domain evaluation indices(FEI),the transfer function of actuator dynamics,and delay compensation.Formulations for achieving perfect compensation of actuator dynamics are developed,and an enhanced compensation approach,termed improved windowed frequency domain evaluation index-based compensation(IWFEI),is introduced.The efficacy of IWFEI is assessed using a RTHS benchmark model,with perturbed simulations conducted to validate its robustness.Uncertainties inherent in actuator dynamics are represented as random variables in these simulations.Comparative analysis of the mean values and variances of evaluation criteria demonstrates that IWFEI enables more accurate and robust compensation.Furthermore,strong correlations observed among criteria in the time and frequency domains underscore the effectiveness of the proposed frequency domain-based compensation method in mitigating amplitude errors and phase delays in RTHS.展开更多
Structures modelled with flexible-base assumptions,incorporating soil effects,generally exhibit longer natural periods and higher damping compared to fixed-base models that exclude soil-structure interaction(SSI).Howe...Structures modelled with flexible-base assumptions,incorporating soil effects,generally exhibit longer natural periods and higher damping compared to fixed-base models that exclude soil-structure interaction(SSI).However,the beneficial or detrimental nature of SSI remains contentious in current earthquake damage analyses and research findings.This study introduces a numerical modelling technique,validated by experimental shaking table tests,to examine the effects of SSI on high-rise buildings.The study considers various substructure parameters,including foundation types,soil types,and bedrock depths.Both advantageous and adverse impacts of SSI are identified and analysed.Numerical simulations reveal that increased subsoil stiffness significantly amplifies the base shear of structures compared to bedrock depth effects.Additionally,increased foundation rocking results in higher inter-storey drifts and reduced base shear.Overall,SSI tends to amplify inter-storey drifts,indicating detrimental effects.Specifically,the study found that the inclusion of SSI increased maximum inter-storey drifts by up to 38%,particularly in softer soils,while reducing base shear by up to 44%in structures with classical compensated foundations on D_(e)and E_(e)soil types.In contrast,piled foundation systems experienced an increase in base shear of up to 27%under the same conditions.Conversely,SSI has beneficial impacts on base shear for structures with classical compensated foundations on soil types of D_(e)and E_(e),as it reduces the base shear.For structures with piled foundations and those with classical compensated foundations on C_(e)soil,SSI effects are detrimental.C_(e),D_(e),and E_(e)soils correspond to geotechnical classifications per AS1170,representing stiff,medium,and soft soils respectively.The study also presents minimum base shear ratios considering SSI reduction effects for various foundation types.展开更多
We calculate the multicomponent responses of surface-hole transient electromagnetic method. The methods and models are unsuitable as geoelectric models of conductive surrounding rocks because they are based on regular...We calculate the multicomponent responses of surface-hole transient electromagnetic method. The methods and models are unsuitable as geoelectric models of conductive surrounding rocks because they are based on regular local targets. We also propose a calculation and analysis scheme based on numerical simulations of the subsurface transient electromagnetic fields. In the modeling of the electromagnetic fields, the forward modeling simulations are performed by using the finite-difference time-domain method and the discrete image method, which combines the Gaver–Stehfest inverse Laplace transform with the Prony method to solve the initial electromagnetic fields. The precision in the iterative computations is ensured by using the transmission boundary conditions. For the response analysis, we customize geoelectric models consisting of near-borehole targets and conductive wall rocks and implement forward modeling simulations. The observed electric fields are converted into induced electromotive force responses using multicomponent observation devices. By comparing the transient electric fields and multicomponent responses under different conditions, we suggest that the multicomponent-induced electromotive force responses are related to the horizontal and vertical gradient variations of the transient electric field at different times. The characteristics of the response are determined by the varying the subsurface transient electromagnetic fields, i.e., diffusion, attenuation and distortion, under different conditions as well as the electromagnetic fields at the observation positions. The calculation and analysis scheme of the response consider the surrounding rocks and the anomalous field of the local targets. It therefore can account for the geological data better than conventional transient field response analysis of local targets.展开更多
Background:Polygonati cyrtonema Hua(PC)has many pharmacological effects such as immune regulation,hypoglycemic and lipid-lowering,anti-oxidation and anti-tumor.Oligosaccharide is one of the main active components of P...Background:Polygonati cyrtonema Hua(PC)has many pharmacological effects such as immune regulation,hypoglycemic and lipid-lowering,anti-oxidation and anti-tumor.Oligosaccharide is one of the main active components of PC.At present,the research on Polygonatum cyrtonema oligosaccharides(PCOS)is not deep,and there is a lack of systematic research on the optimization of extraction process of pcos and the change of pcos and Polygonatum cyrtonema polysaccharide content before and after wine steaming.Methods:The optimum extraction process of oligosaccharides from PC was optimized,and the content of oligosaccharides before and after wine steaming of PC was investigated.The single factor experiment was carried out with the ratio of liquid to material,extraction temperature and extraction time as the investigation factors.The extraction process of PCOS was optimized by Box Behnken design-response surface methodology,and the changes of total oligosaccharides and total polysaccharides before and after wine steaming were studied.Results:The optimal extraction process for the PCOS was 32:1 mL/g,85℃,and 1.5 h.The total PCOS decreased slightly after steaming,but the percentage of the total sugar increased.Conclusion:The extraction process of PCOS optimized by response surface method is reasonable and feasible.The changes of total oligosaccharides and total polysaccharides during the steaming process of PC can reveal the processing mechanism of PC to a certain extent,and provide scientific basis and technical support for better in-depth excavation and development and utilization of PCOS.展开更多
Due to the energy crisis and the environmental issues like pollution and global warming, the exploration for renewable and clean energies becomes crucial. The offshore floating wind turbines（OFWTs） draw a great deal...Due to the energy crisis and the environmental issues like pollution and global warming, the exploration for renewable and clean energies becomes crucial. The offshore floating wind turbines（OFWTs） draw a great deal of attention recently as a means to exploit the steadier and stronger wind resources available in deep water seas. This paper studies the hydrodynamic characteristics of a spar-type wind turbine known as the OC3-Hywind concept and the dynamic responses of the turbine. Response characteristics of motions and mooring loads of the system under different sea states are evaluated and the effects of the loads induced by the wind and the wave on the system are discussed. The calculations are carried out with the numerical simulation code FAST in the time domain and the frequency analysis is made by using the FFT method. The results and the conclusions from this paper might help better understand the behavior characteristics of the floating wind turbine system under actual ocean environments and provide valuable data in design and engineering practice.展开更多
基金National Natural Science Foundation of China under Grant No.U2139208。
文摘Natural soil generally exhibits significant transverse isotropy(TI)due to weathering and sedimentation,meaning that horizontal moduli differ from their vertical counterpart.The TI mechanical model is more appropriate for actual situations.Although soil exhibits material nonlinearity under earthquake excitation,existing research on the TI medium is limited to soil linearity and neglects the nonlinear response of TI sites.A 2D equivalent linear model for a layered TI half-space subjected to seismic waves is derived in the transformed wave number domain using the exact dynamic stiffness matrix of the TI medium.This study introduces a method for determining the effective shear strain of TI sites under oblique wave incidence,and further describes a systematic study on the effects of TI parameters and soil nonlinearity on site responses.Numerical results indicate that seismic responses of the TI medium significantly differ from those of isotropic sites and that the responses are highly dependent on TI parameters,particularly in nonlinear cases,while also being sensitive to incident angle and excitation intensity.Moreover,the differences in peak acceleration and waveform for various TI materials may also be amplified due to the strong nonlinearity.The study provides valuable insights for improving the accuracy of seismic response analysis in engineering applications.
基金the High-Performance Computing Platform of Beijing University of Chemical Technology(BUCT)for supporting this papersupported by the Fundamental Research Funds for the Central Universities(JD2319)+2 种基金the CNOOC Technical Cooperation Project(ZX2022ZCTYF7612)the National Natural Science Foundation of China(51775029,52004014)the Chinese Universities Scientific Fund(XK2020-04)。
文摘A rotating packed bed is a typical chemical process enhancement equipment that can strengthen micromixing and mass transfer.During the operation of the rotating packed bed,the nonreactants and products irregularly adhere to the wire mesh packing in the rotor,thus resulting in an imbalance in the vibration of the rotor,which may cause serious damage to the bearing and material leakage.This study proposes a model prediction for estimating the bearing residual life of a rotating packed bed based on rotor imbalance response analysis.This method is used to determine the influence of the mass on the imbalance in the vibration of the rotor on bearing damage.The major influence on rotor vibration was found to be exerted by the imbalanced mass and its distribution radius,as revealed by the results of orthogonal experiments.Through implementing finite element analysis,the imbalance response curve for the rotating packed bed rotor was obtained,and a correlation among rotor imbalance mass,distribution radius of imbalance mass,and bearing residue life was established via data fitting.The predicted value of the bearing life can be used as the reference basis for an early safety warning of a rotating packed bed to effectively avoid accidents.
基金National Natural Science Foundation of China for Innovative Research Groups Under Grant No.50321803 & 50621062National Natural Science Foundation of China Under Grant No.50808113 & 10872148
文摘This paper introduces an orthogonal expansion method for general stochastic processes. In the method, a normalized orthogonal function of time variable t is first introduced to carry out the decomposition of a stochastic process and then a correlated matrix decomposition technique, which transforms a correlated random vector into a vector of standard uncorrelated random variables, is used to complete a double orthogonal decomposition of the stochastic processes. Considering the relationship between the Hartley transform and Fourier transform of a real-valued function, it is suggested that the first orthogonal expansion in the above process is carried out using the Hartley basis function instead of the trigonometric basis function in practical applications. The seismic ground motion is investigated using the above method. In order to capture the main probabilistic characteristics of the seismic ground motion, it is proposed to directly carry out the orthogonal expansion of the seismic displacements. The case study shows that the proposed method is feasible to represent the seismic ground motion with only a few random variables. In the second part of the paper, the probability density evolution method （PDEM） is employed to study the stochastic response of nonlinear structures subjected to earthquake excitations. In the PDEM, a completely uncoupled one-dimensional partial differential equation, the generalized density evolution equation, plays a central role in governing the stochastic seismic responses of the nonlinear structure. The solution to this equation will yield the instantaneous probability density function of the responses. Computational algorithms to solve the probability density evolution equation are described. An example, which deals with a nonlinear frame structure subjected to stochastic ground motions, is illustrated to validate the above approach.
基金National Natural Science Foundation of China(51208296&51478343)Shanghai Committee of Science and Technology(13231200503)+2 种基金Fundamental Research Funds for the Central Universities(2013KJ095&101201438)Shanghai Educational Development Foundation(13CG17)National Key Technology R&D Program(2012BAK24B04)
文摘Discrete models such as the lumped parameter model and the finite element model are widely used in the solution of soil amplification of earthquakes. However, neither of the models will accurately estimate the natural frequencies of soil deposit, nor simulate a damping of frequency independence. This research develops a new discrete model for onedimensional viscoelastic response analysis of layered soil deposit based on the mode equivalence method. The new discrete model is a one-dimensional equivalent multi-degree-of-freedom（MDOF） system characterized by a series of concentrated masses, springs and dashpots with a special configuration. The dynamic response of the equivalent MDOF system is analytically derived and the physical parameters are formulated in terms of modal properties. The equivalent MDOF system is verified through a comparison of amplification functions with the available theoretical solutions. The appropriate number of degrees of freedom（DOFs） in the equivalent MDOF system is estimated. A comparative study of the equivalent MDOF system with the existing discrete models is performed. It is shown that the proposed equivalent MDOF system can exactly present the natural frequencies and the hysteretic damping of soil deposits and provide more accurate results with fewer DOFs.
基金financial support from the National Science Foundation of China(22078190)the National Key R&D Plan of China(2020YFB1505802)。
文摘Rate capability,peak power,and energy density are of vital importance for the capacitive energy storage(CES)of electrochemical energy devices.The frequency response analysis(FRA)is regarded as an efficient tool in studying the CES.In the present work,a bi-scale impedance transmission line model(TLM)is firstly developed for a single pore to a porous electrode.Not only the TLM of the single pore is reparameterized but also the particle packing compactness is defined in the bi-scale.Subsequently,the CES properties are identified by FRA,focused on rate capability vs.characteristic frequency,peak power vs.equivalent series resistance,and energy density vs.low frequency limiting capacitance for a single pore to a porous electrode.Based on these relationships,the CES properties are numerically simulated and theoretically predicted for a single pore to a porous electrode in terms of intra-particle pore length,intra-particle pore diameter,inter-particle pore diameter,electrolyte conductivity,interfacial capacitance&exponent factor,electrode thickness,electrode apparent surface area,and particle packing compactness.Finally,the experimental diagnosis of four supercapacitors(SCs)with different electrode thicknesses is conducted for validating the bi-scale TLM and gaining an insight into the CES properties for a porous electrode to a single pore.The calculating results suggest,to some extent,the inter-particle pore plays a more critical role than the intra-particle pore in the CES properties such as the rate capability and the peak power density for a single pore to a porous electrode.Hence,in order to design a better porous electrode,more attention should be given to the inter-particle pore.
基金Research Grants for Returned Students of China under Grant No.2020-038the National Natural Science Foundation of China under Grant No.51408392。
文摘Vibration induced by shield construction can lead to liquefaction of saturated sand.Based on FLAC3D software,a numerical model of tunnel excavation is established and sinusoidal velocity loads with different frequencies are applied to the excavation face.The pattern of the excess pore pressure ratio with frequency,as well as the dynamic response of soil mass under different frequency loads before excavation,is analyzed.When the velocity sinusoidal wave acts on the excavation surface of the shield tunnel with a single sand layer,soil liquefaction occurs.However,the ranges and locations of soil liquefaction are different at different frequencies,which proves that the vibration frequency influences the liquefaction location of the stratum.For sand-clay composite strata with liquefiable layers,the influence of frequency on the liquefaction range is different from that of a single stratum.In the frequency range of 5-30 Hz,the liquefaction area and surface subsidence decrease with an increase in vibration frequency.The research results in this study can be used as a reference in engineering practice for tunneling liquefiable strata with a shield tunneling machine.
基金The National Natural Science Foundation of China(No.51678141)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX17_0128)the Fundamental Research Funds for the Central Universities
文摘To evaluate the coupling pounding-friction effect between bridge girders and retainers and its influence on bridge seismic response, a reinforced concrete （RC） continuous bridge is selected as the research object. Three bridge finite element （FE） models were built using OpenSees, in which the longitudinal and transverse pounding elements, as well as the transverse failure element of bearings were introduced. Based on this, tire seismic response analysis considering the coupling pounding-friction effect was conducted for the continuous bridge subjected to bi-directional ground motions. Furthermore, the influential parameters were analyzed. The analysis results indicate that the coupling pounding-friction effect can alter the internal force distribution of the bridge structure and generate additional torsional force to bridge columns. The friction coefficient and longitudinal pounding gap size are two important factors. The appropriate friction coefficient and longitudinal pounding gap size can significantly reduce seismic response of girders, and effectively transfer part of the girder inertia force from the fixed columns to the sliding columns, which can reduce the seismic demands of the fixed columns and improve the seismic performance of continuous bridge structures.
基金financially supported by Independent Innovation Research Fund of Wuhan University of Technology(No.2014-ND-B1-09)
文摘Making an analysis for vibration modal and frequency response of the lathe spindle,respectively by using finite element method based on ANSYS and experiment of CA6140 type lathe in machining,and the calculation results are compared and analyzed,which verified the accuracy of ANSYS method. Numerical simulation and experimental results show that: Spindle in the first order and fifth order are prone to resonance,but did not reach resonance,the low order natural frequency have more effect than the high order natural frequency of the spindle vibration; by the experiments can conclude that the maximum vibration of the main shaft in the working state is mainly concentrated in the vicinity of its two ends,therefore,the improved bearing is an important way to reduce the vibration of the main shaft and ensure the machining accuracy,and the research results can provide a theoretical reference for the structural optimization design of the lathe.
基金Special Topic of the Ministry of Education about Humanities and Social Sciences(12JDGC007)National Science and Technology Support Project(2011BAF09B01)Key State Science and Technology Projects(2009ZX04010-021)
文摘As to motorized spindle system, this paper builds a simplified 3D model of spindle and bearing, performs structure modal analysis, reveals its dynamic characteristics under the free model; furthermore, modifies bearing radial stiffness and number of model and studies the change of modal parameters. On this basis, through the harmonic response analysis of the finite element model, dy- namic response characteristic caused by imbalance of monitored spindle system and law of vibration response to different amount of unbalance is analyzed.
基金funded by the National Natural Science Foundation of China(Grant No.12072135).
文摘This paper constructs a new two-dimensional arbitrary polygonal stress hybrid dynamic(APSHD)element for structural dynamic response analysis.Firstly,the energy function is established based on Hamilton's principle.Then,the finite element time-space discrete format is constructed using the generalized variational principle and the direct integration method.Finally,an explicit polynomial form of the combined stress solution is give,and its derivation process is shown in detail.After completing the theoretical construction,the numerical calculation program of the APSHD element is written in Fortran,and samples are verified.Models show that the APSHD element performs well in accuracy and convergence.Furthermore,it is insensitive to mesh distortion and has low dependence on selecting time steps.
文摘This article deals with the dynamic response analysis and active vibration control of the smart functionally graded material(FGM)composite core plate with FG piezoelectric material(FGPM)surface actuators and sensors.Considering a power law distribution,the mechanical and electrical material characteristics of the FGM and FGPM layers change continually along the thickness plane.The finite element method(FEM)and the first-order shear deformation theory(FSDT)are utilized in the modeling process for the FGM and FGPM layers.In the dynamic analysis,the dynamic response of the sandwich structure under the impact of sinusoidally distributed step load and the corresponding sensor voltage is obtained.To ensure that the simulations are accurate,the findings are compared with previously published research.To analyze the control efficiency of FGPM sensors and actuators on the FGM host structure,the linear quadratic regulator(LQR)controller is utilized.The sandwich structure is considered a multiple-input multiple-output system(MIMO),so sensors and actuators are placed at different locations on the plate surface.The modal strain energy method is utilized to find the appropriate location of the FGPM layers.According to the results of the analysis,it has been determined that piezoelectric material coefficients as well as mechanical properties are extremely important for obtaining optimum control performance from FGPM sensors and actuators.In addition,it is emphasized that active vibration control of FGM plates can be performed effectively with the proper selection of sensors and actuators and their accurate distribution on the plate.These results are expected to contribute to micro-electromechanical system(MEMS)sensor and actuator applications,soft robotics applications,and vibration protection and vibration damping applications of nanostructures.
基金the National Natural Science Foundation of China,Grant Number:12372196,12302258,52325803,U22A20229,12402238State Key Laboratory of Ocean Engineering(Shanghai Jiao Tong University),Grant Number:GKZD010089+2 种基金the Six Talent Peaks Project in Jiangsu Province of China,Grant Number:2019-KTHY-009Jiangsu Funding Program for Excellent Postdoctoral Talent,Grant Number:2023ZB506Postdoctoral Fellowship Program of CPSF,Grant Number:GZC20230667。
文摘This paper proposes a hybrid algorithm based on the physics-informed kernel function neural networks(PIKFNNs)and the direct probability integral method(DPIM)for calculating the probability density function of stochastic responses for structures in the deep marine environment.The underwater acoustic information is predicted utilizing the PIKFNNs,which integrate prior physical information.Subsequently,a novel uncertainty quantification analysis method,the DPIM,is introduced to establish a stochastic response analysis model of underwater acoustic propagation.The effects of random load,variable sound speed,fluctuating ocean density,and random material properties of shell on the underwater stochastic sound pressure are numerically analyzed,providing a probabilistic insight for assessing the mechanical behavior of structures in the deep marine environment.
基金supported in part by the National Natural Science Foundation of China(Nos.51978337,U2039209).
文摘The seismic safety of offshore wind turbines is an important issue that needs to be solved urgently.Based on a unified computing framework,this paper develops a set of seawater-seabed-wind turbine zoning coupling analysis methods.A 5 MW wind turbine and a site analysis model are established,and a seismic wave is selected to analyze the changes in the seismic response of offshore monopile wind turbines under the change of seawater depth,seabed wave velocity and seismic wave incidence angle.The analysis results show that when the seawater increases to a certain depth,the seismic response of the wind turbine increases.The shear wave velocity of the seabed affects the bending moment and displacement at the bottom of the tower.When the angle of incidence increases,the vertical displacement and the acceleration of the top of the tower increase in varying degrees.
基金Supported by the National Natural Science Foundation of China (Grant Nos.52088102 and 51879287)National Key Research and Development Program of China (Grant No.2022YFB2602301)。
文摘Long-term responses of floating structures pose a great concern in their design phase. Existing approaches for addressing long-term extreme responses are extremely cumbersome for adoption. This work aims to develop an approach for the long-term extreme-response analysis of floating structures. A modified gradient-based retrieval algorithm in conjunction with the inverse first-order reliability method(IFORM) is proposed to enable the use of convolution models in long-term extreme analysis of structures with an analytical formula of response amplitude operator(RAO). The proposed algorithm ensures convergence stability and iteration accuracy and exhibits a higher computational efficiency than the traditional backtracking method. However, when the RAO of general offshore structures cannot be analytically expressed, the convolutional integration method fails to function properly. A numerical discretization approach is further proposed for offshore structures in the case when the analytical expression of the RAO is not feasible. Through iterative discretization of environmental contours(ECs) and RAOs, a detailed procedure is proposed to calculate the long-term response extremes of offshore structures. The validity and accuracy of the proposed approach are tested using a floating offshore wind turbine as a numerical example. The long-term extreme heave responses of various return periods are calculated via the IFORM in conjunction with a numerical discretization approach. The environmental data corresponding to N-year structural responses are located inside the ECs, which indicates that the selection of design points directly along the ECs yields conservative design results.
基金Open Project of Shanghai Key Laboratory of Lightweight Composite,China(No.2232021A4-04)。
文摘Double-shaft-driven needle punching machine is a specialized equipment designed for processing C/C crucible preforms.Its main needle punching module is operated by two sets of reciprocating crank-slider mechanisms.The intense vibration during needle punching not only generates huge noise,but also substantially reduces the quality of the preform.It is imperative to perform a dynamic analysis and optimization of the entire needle punching machine.In this paper,the three-dimensional(3D)model of the entire double-shaft-driven needle punching machine for C/C crucible preforms is established.Based on the modal analysis theory,the modal characteristics of the needle punching machine under various operating conditions are analyzed and its natural frequencies and vibration modes are determined.The harmonic response analysis is then employed to obtain the amplitude of the needle plate at different frequencies,and the structural weak points of the needle punching machine are identified and improved.The feasibility of the optimized scheme is subsequently reevaluated and verified.The results indicate that the first six natural frequencies of the machine increase,and the maximum amplitude of the needle plate decreases by 70.3%.The enhanced dynamic characteristics of the machine significantly improve its performance,enabling more efficient needle punching of C/C crucible preforms.
基金Ministry of Science and Technology of China under Grant No.2023YFC3804300National Science Foundation of China under Grant No.52178114。
文摘Actuator dynamics introduce a synchronization disparity between commanded displacements transmitted to the actuator and the actual displacements generated by the actuator,thereby affecting its precision and potentially leading to instability in real-time hybrid simulation(RTHS).This study aims to elucidate the relationship between calculated and measured displacements by analyzing their magnitude and phase in the frequency domain via transformations.The physical implications of these relationships are explored in the context of frequency domain evaluation indices(FEI),the transfer function of actuator dynamics,and delay compensation.Formulations for achieving perfect compensation of actuator dynamics are developed,and an enhanced compensation approach,termed improved windowed frequency domain evaluation index-based compensation(IWFEI),is introduced.The efficacy of IWFEI is assessed using a RTHS benchmark model,with perturbed simulations conducted to validate its robustness.Uncertainties inherent in actuator dynamics are represented as random variables in these simulations.Comparative analysis of the mean values and variances of evaluation criteria demonstrates that IWFEI enables more accurate and robust compensation.Furthermore,strong correlations observed among criteria in the time and frequency domains underscore the effectiveness of the proposed frequency domain-based compensation method in mitigating amplitude errors and phase delays in RTHS.
文摘Structures modelled with flexible-base assumptions,incorporating soil effects,generally exhibit longer natural periods and higher damping compared to fixed-base models that exclude soil-structure interaction(SSI).However,the beneficial or detrimental nature of SSI remains contentious in current earthquake damage analyses and research findings.This study introduces a numerical modelling technique,validated by experimental shaking table tests,to examine the effects of SSI on high-rise buildings.The study considers various substructure parameters,including foundation types,soil types,and bedrock depths.Both advantageous and adverse impacts of SSI are identified and analysed.Numerical simulations reveal that increased subsoil stiffness significantly amplifies the base shear of structures compared to bedrock depth effects.Additionally,increased foundation rocking results in higher inter-storey drifts and reduced base shear.Overall,SSI tends to amplify inter-storey drifts,indicating detrimental effects.Specifically,the study found that the inclusion of SSI increased maximum inter-storey drifts by up to 38%,particularly in softer soils,while reducing base shear by up to 44%in structures with classical compensated foundations on D_(e)and E_(e)soil types.In contrast,piled foundation systems experienced an increase in base shear of up to 27%under the same conditions.Conversely,SSI has beneficial impacts on base shear for structures with classical compensated foundations on soil types of D_(e)and E_(e),as it reduces the base shear.For structures with piled foundations and those with classical compensated foundations on C_(e)soil,SSI effects are detrimental.C_(e),D_(e),and E_(e)soils correspond to geotechnical classifications per AS1170,representing stiff,medium,and soft soils respectively.The study also presents minimum base shear ratios considering SSI reduction effects for various foundation types.
基金supported by the Young Scientists Fund of the National Natural Science Foundation of China(No.41304082)the China Postdoctoral Science Foundation(No.2016M590731)+2 种基金the Young Scientists Fund of the Natural Science Foundation of Hebei Province(No.D2014403011)the Program for Young Excellent Talents of Higher Education Institutions of Hebei Province(No.BJ2016046)the Geological survey project of China Geological Survey(No.1212011121197)
文摘We calculate the multicomponent responses of surface-hole transient electromagnetic method. The methods and models are unsuitable as geoelectric models of conductive surrounding rocks because they are based on regular local targets. We also propose a calculation and analysis scheme based on numerical simulations of the subsurface transient electromagnetic fields. In the modeling of the electromagnetic fields, the forward modeling simulations are performed by using the finite-difference time-domain method and the discrete image method, which combines the Gaver–Stehfest inverse Laplace transform with the Prony method to solve the initial electromagnetic fields. The precision in the iterative computations is ensured by using the transmission boundary conditions. For the response analysis, we customize geoelectric models consisting of near-borehole targets and conductive wall rocks and implement forward modeling simulations. The observed electric fields are converted into induced electromotive force responses using multicomponent observation devices. By comparing the transient electric fields and multicomponent responses under different conditions, we suggest that the multicomponent-induced electromotive force responses are related to the horizontal and vertical gradient variations of the transient electric field at different times. The characteristics of the response are determined by the varying the subsurface transient electromagnetic fields, i.e., diffusion, attenuation and distortion, under different conditions as well as the electromagnetic fields at the observation positions. The calculation and analysis scheme of the response consider the surrounding rocks and the anomalous field of the local targets. It therefore can account for the geological data better than conventional transient field response analysis of local targets.
基金sponsored by National Key Research and Development Program of China(Grant No.2023YFC3504200)High Level Key Discipline Construction of Traditional Chinese Medicine Program(Grant No.zyyzdxk-2023272).
文摘Background:Polygonati cyrtonema Hua(PC)has many pharmacological effects such as immune regulation,hypoglycemic and lipid-lowering,anti-oxidation and anti-tumor.Oligosaccharide is one of the main active components of PC.At present,the research on Polygonatum cyrtonema oligosaccharides(PCOS)is not deep,and there is a lack of systematic research on the optimization of extraction process of pcos and the change of pcos and Polygonatum cyrtonema polysaccharide content before and after wine steaming.Methods:The optimum extraction process of oligosaccharides from PC was optimized,and the content of oligosaccharides before and after wine steaming of PC was investigated.The single factor experiment was carried out with the ratio of liquid to material,extraction temperature and extraction time as the investigation factors.The extraction process of PCOS was optimized by Box Behnken design-response surface methodology,and the changes of total oligosaccharides and total polysaccharides before and after wine steaming were studied.Results:The optimal extraction process for the PCOS was 32:1 mL/g,85℃,and 1.5 h.The total PCOS decreased slightly after steaming,but the percentage of the total sugar increased.Conclusion:The extraction process of PCOS optimized by response surface method is reasonable and feasible.The changes of total oligosaccharides and total polysaccharides during the steaming process of PC can reveal the processing mechanism of PC to a certain extent,and provide scientific basis and technical support for better in-depth excavation and development and utilization of PCOS.
基金Project supported by the State Key Laboratory of Ocean Engineering,Shanghai Jiao Tong University(Grant No.GKZD010023)
文摘Due to the energy crisis and the environmental issues like pollution and global warming, the exploration for renewable and clean energies becomes crucial. The offshore floating wind turbines（OFWTs） draw a great deal of attention recently as a means to exploit the steadier and stronger wind resources available in deep water seas. This paper studies the hydrodynamic characteristics of a spar-type wind turbine known as the OC3-Hywind concept and the dynamic responses of the turbine. Response characteristics of motions and mooring loads of the system under different sea states are evaluated and the effects of the loads induced by the wind and the wave on the system are discussed. The calculations are carried out with the numerical simulation code FAST in the time domain and the frequency analysis is made by using the FFT method. The results and the conclusions from this paper might help better understand the behavior characteristics of the floating wind turbine system under actual ocean environments and provide valuable data in design and engineering practice.
