In the present study,we concentrate on finding the dual solutions of biomagnetic fluid namely blood flow and heat transfer along with magnetic particles over a two dimensional shrinking cylinder in the presence of a m...In the present study,we concentrate on finding the dual solutions of biomagnetic fluid namely blood flow and heat transfer along with magnetic particles over a two dimensional shrinking cylinder in the presence of a magnetic dipole.To make the results physically realistic,stability analysis is also carried out in this study so that we realized which solution is stable and which is not.The governing partial equations are converted into ordinary differential equations by using similarity transformations and the numerical solution is calculated by applying bvp4c function technique in MATLAB software.The effects of different physical parameters are plotted graphically and discussed according to the outcomes of results.From the present study we observe that ferromagnetic interaction parameter had a great influenced on fluid velocity and temperature distributions.It is also found from the current analysis that the first and second solutions of shrinking cylinder obtained only when we applied particular ranges values of suction parameter.The most important characteristics part of study is to analyze the skin friction coefficient and rate of heat transfer which also covered in this analysis.It reveals that both skin friction coefficient and rate of heat transfer are reduced with rising values of ferromagnetic number.A comparison has also been made to make the solution feasible.展开更多
This research presents an advanced study on the modeling and stability analysis of electro-hydraulic control modules used in intelligent chassis systems.Firstly,a comprehensive nonlinear mathematical model of the elec...This research presents an advanced study on the modeling and stability analysis of electro-hydraulic control modules used in intelligent chassis systems.Firstly,a comprehensive nonlinear mathematical model of the electro-hydraulic power-shift system is developed,incorporating pipeline characteristics through impedance analysis and examining coupling effects between the pilot solenoid valve,main valve,and pipeline.Then,the model’s accuracy is validated through experimental testing,demonstrating high precision and minimal model errors.A comparative analysis between simulation data(both with and without pipeline characteristics)and experimental results reveals that the model considering pipeline parameters aligns more closely with experimental data,highlighting its superior accuracy.The research further explores the influence of key factors on system stability,including damping coefficient,feedback cavity orifice diameter,spring stiffness,pipeline length,and pipeline diameter.Significant findings include the critical impact of damping coefficient,orifice diameter,and pipeline length on stability,while spring stiffness has a minimal effect.These findings provide valuable insights for optimizing electro-hydraulic control modules in intelligent chassis systems,with practical implications for automotive and construction machinery applications.展开更多
In the practical slope engineering,the stability of lower sliding mass(region A)with back tensile cracks of the jointed rock slope attracts more attentions,but the upper rock mass(region B)may also be unstable.Therefo...In the practical slope engineering,the stability of lower sliding mass(region A)with back tensile cracks of the jointed rock slope attracts more attentions,but the upper rock mass(region B)may also be unstable.Therefore,in this study,based on the stepped failure mode of bedding jointed rock slopes,considering the influence of the upper rock mass on the lower stepped sliding mass,the improved failure model for analyzing the interaction force(F_(AB))between two regions is constructed,and the safety factors(F_(S))of two regions and whole region are derived.In addition,this paper proposes a method to determine the existence of F_(AB) using their respective acceleration values(a_(A) and a_(B))when regions A and B are unstable.The influences of key parameters on two regions and the whole region are analyzed.The results show that the variation of the F_(AB) and F_(S) of two regions can be obtained accurately based on the improved failure model.The accuracy of the improved failure model is verified by comparative analysis.The research results can explain the interaction mechanism of two regions and the natural phenomenon of slope failure caused by the development of cracks.展开更多
This article presents a micro-structure tensor enhanced elasto-plastic finite element(FE)method to address strength anisotropy in three-dimensional(3D)soil slope stability analysis.The gravity increase method(GIM)is e...This article presents a micro-structure tensor enhanced elasto-plastic finite element(FE)method to address strength anisotropy in three-dimensional(3D)soil slope stability analysis.The gravity increase method(GIM)is employed to analyze the stability of 3D anisotropic soil slopes.The accuracy of the proposed method is first verified against the data in the literature.We then simulate the 3D soil slope with a straight slope surface and the convex and concave slope surfaces with a 90turning corner to study the 3D effect on slope stability and the failure mechanism under anisotropy conditions.Based on our numerical results,the end effect significantly impacts the failure mechanism and safety factor.Anisotropy degree notably affects the safety factor,with higher degrees leading to deeper landslides.For concave slopes,they can be approximated by straight slopes with suitable boundary conditions to assess their stability.Furthermore,a case study of the Saint-Alban test embankment A in Quebec,Canada,is provided to demonstrate the applicability of the proposed FE model.展开更多
An analysis method based on the fuzzy Lyapunov functions is presented to analyze the stability of the continuous affine fuzzy systems. First, a method is introduced to deal with the consequent part of the fuzzy local ...An analysis method based on the fuzzy Lyapunov functions is presented to analyze the stability of the continuous affine fuzzy systems. First, a method is introduced to deal with the consequent part of the fuzzy local model. Thus, the stability analysis method of the homogeneous fuzzy system can be used for reference. Stability conditions are derived in terms of linear matrix inequalities based on the fuzzy Lyapunov functions and the modified common Lyapunov functions, respectively. The results demonstrate that the stability result based on the fuzzy Lyapunov functions is less conservative than that based on the modified common Lyapunov functions via numerical examples. Compared with the method which does not expand the consequent part, the proposed method is simpler but its feasible region is reduced. Finally, in order to expand the application of the fuzzy Lyapunov functions, the piecewise fuzzy Lyapunov function is proposed, which can be used to analyze the stability for triangular or trapezoidal membership functions and obtain the stability conditions. A numerical example validates the effectiveness of the proposed approach.展开更多
To investigate the effects of initial geometric imperfection and material nonlinearity on the stability analysis of the suspen-dome, the steel roof of Jiangsu Culture Sports Center Gymnasium was utilized as a numerica...To investigate the effects of initial geometric imperfection and material nonlinearity on the stability analysis of the suspen-dome, the steel roof of Jiangsu Culture Sports Center Gymnasium was utilized as a numerical model, and modal analyses were performed. Then, linear buckling analysis,geometric nonlinear stability analysis, geometric nonlinear stability analysis with initial imperfection, and double nonlinear analysis considering material nonlinearity and geometric nonlinearity were discussed in detail to compare the stability performance of the ellipse-like suspen-dome and the single-layer reticulated shell. The results showthat the cable-strut system increases the integrity of the suspen-dome, and moderates the sensibility of the single-layer reticulated shell to initial geometric imperfection. However, it has little influence on integral rigidity, fundamental vibration frequencies, linear ultimate live loads, and geometric nonlinear ultimate live loads without initial imperfection. When considering the material nonlinearity and initial imperfection, a significant reduction occurs in the ultimate stability capacities of these two structures. In this case, the suspen-dome with a lowrise-span ratio is sensitive to the initial imperfection and material nonlinearity. In addition, the distribution pattern of live loads significantly influences the instability modes of the structure, and the uniform live load with full span is not always the most dangerous case.展开更多
The traditional stability analysis method of geogrid reinforced slopes does not consider the effect of lateral swelling,so it is not applicable to reinforced expansive soil slopes.This paper reports a new stability an...The traditional stability analysis method of geogrid reinforced slopes does not consider the effect of lateral swelling,so it is not applicable to reinforced expansive soil slopes.This paper reports a new stability analysis method for geogrid reinforced expansive soil slopes.The additional pullout force of the free zone due to the lateral swelling and the anti-pullout safety factor of each geogrid layer were obtained by ensuring the overall stability of the reinforced slope.The optimum design was carried out to treat an expansive soil cut slope in Hubei Province,China,by changing the spacing and length of geogrid reinforcement.Calculation results show that the additional pullout force caused by lateral swelling has a great influence on the anti-pullout stability of geogrids,and the local stability of the reinforced slope will be overestimated if the swelling effect of soil in the free zone is not considered.展开更多
To investigate the stability of rock mass in high geostress underground powerhouse caverns subjected to excavation,a microseismic(MS)monitoring system was established and the discrete element method(DEM)-based numeric...To investigate the stability of rock mass in high geostress underground powerhouse caverns subjected to excavation,a microseismic(MS)monitoring system was established and the discrete element method(DEM)-based numerical simulation was carried out.The tempo-spatial damage characteristics of rock mass were analyzed.The evolution laws of MS source parameters during the formation of a rock collapse controlled by high geostress and geological structure were investigated.Additionally,a three-dimensional DEM model of the underground powerhouse caverns was built to reveal the deformation characteristics of rock mass.The results indicated that the MS events induced by excavation of high geostress underground powerhouse caverns occurred frequently.The large-stake crown of the main powerhouse was the main damage area.Prior to the rock collapse,the MS event count and accumulated energy release increased rapidly,while the apparent stress sharply increased and then decreased.The amount and proportion of shear and mixed MS events remarkably increased.The maximum displacement was generally located near the spandrel areas.The MS monitoring data and numerical simulation were in good agreement,which can provide significant references for damage evaluation and disaster forecasting in high geostress underground powerhouse caverns.展开更多
Dam construction for hydropower development is a very important subject all around the world, especially in developing countries due to energy crises. Filling of reservoir lakes may trigger or reactivate landslides in...Dam construction for hydropower development is a very important subject all around the world, especially in developing countries due to energy crises. Filling of reservoir lakes may trigger or reactivate landslides in reservoir area. Active landslides in populated districts in the Xiangjiaba Reservoir area have become a striking problem for residents, local government and construction engineers. The key objective of this study is to analyze the role of reservoir filling and fluctuation in the activation/reactivation of the landslide as well as the mechanism of landslide from microstructures of pre-sheared slip surface. A large active landslide with a total volume of 1.25 Mm^3 at the left margin of Jinsha River in Pingshan County of Sichuan Province, Southwest China, was selected as a case study. Field investigation, field monitoring and laboratory tests were carried out to find out the failure mechanism and the stability of the active landslide. The shear strength test and stability analysis confirm that the water level fluctuations have an adverse effect on slope stability. It is obvious from microstructure analysis that the clay minerals contribute to down-slope movement at micro-scale as well as presence of expansive minerals （e.g., montmorillonite） decreases the strength of soil due to water level rise.展开更多
Hybrid-driven underwater glider is a new type of tmmanned underwater vehicle, which combines the advantages of autonomous underwater vehicles and traditional underwater gliders. The autonomous underwater vehicles have...Hybrid-driven underwater glider is a new type of tmmanned underwater vehicle, which combines the advantages of autonomous underwater vehicles and traditional underwater gliders. The autonomous underwater vehicles have good maneuverability and can travel with a high speed, while the traditional underwater gliders are highlighted by low power consumption, long voyage, long endurance and good stealth characteristics. The hybrid-driven underwater gliders can realize variable motion profiles by their own buoyancy-driven and propeller propulsion systems. Stability of the mechanical system determines the performance of the system. In this paper, the Petrel-II hybrid-driven underwater glider developed by Tianjin University is selected as the research object and the stability of hybrid-driven underwater glider unitedly controlled by buoyancy and propeller has been targeted and evidenced. The dimensionless equations of the hybrid-driven underwater glider are obtained when the propeller is working. Then, the steady speed and steady glide path angle under steady-state motion have also been achieved. The steady-state operating conditions can be calculated when the hybrid-driven underwater glider reaches the desired steady-state motion. And the steady- state operating conditions are relatively conservative at the lower bound of the velocity range compared with the range of the velocity derived from the method of the composite Lyapunov function. By calculating the hydrodynamic coefficients of the Petrel-II hybrid-driven underwater glider, the simulation analysis has been conducted. In addition, the results of the field trials conducted in the South China Sea and the Danjiangkou Reservoir of China have been presented to illustrate the validity of the analysis and simulations.and to show the feasibility of the method of the composite Lyapunov function which verifies the stability of the Petrel-II hybrid-driven underwater glider.展开更多
The core task of tracking control is to make the controlled plant track a desired trajectory.The traditional performance index used in previous studies cannot eliminate completely the tracking error as the number of t...The core task of tracking control is to make the controlled plant track a desired trajectory.The traditional performance index used in previous studies cannot eliminate completely the tracking error as the number of time steps increases.In this paper,a new cost function is introduced to develop the value-iteration-based adaptive critic framework to solve the tracking control problem.Unlike the regulator problem,the iterative value function of tracking control problem cannot be regarded as a Lyapunov function.A novel stability analysis method is developed to guarantee that the tracking error converges to zero.The discounted iterative scheme under the new cost function for the special case of linear systems is elaborated.Finally,the tracking performance of the present scheme is demonstrated by numerical results and compared with those of the traditional approaches.展开更多
The Stereo Particle Image Velocimetry(SPIV)technology is applied to measure the wingtip vortices generated by the up-down symmetrical split winglet.Then,the temporal biglobal Linear Stability Analysis(bi-global LSA)is...The Stereo Particle Image Velocimetry(SPIV)technology is applied to measure the wingtip vortices generated by the up-down symmetrical split winglet.Then,the temporal biglobal Linear Stability Analysis(bi-global LSA)is performed on this nearly equal-strength corotating vortex pair,which is composed of an upper vortex(vortex-u)and a down vortex(vortex-d).The results show that the instability eigenvalue spectrum illustrated by(ωr,ω_(i))contains two types of branches:discrete branch and continuous branch.The discrete branch contains the primary branches of vortex-u and vortex-d,the secondary branch of vortex-d and coupled branch,of which all of the eigenvalues are located in the unstable half-plane ofω_(i)>0,indicating that the wingtip vortex pair is temporally unstable.By contrast,the eigenvalues of the continuous branch are concentrated on the half-plane ofω_(i)<0 and the perturbation modes correspond to the freestream perturbation.In the primary branches of vortex-u and vortex-d,Mode P_(u) and Mode Pd are the primary perturbation modes,which exhibit the structures enclosed with azimuthal wavenumber m and radial wavenumber n,respectively.Besides,the results of stability curves for vortex-u and vortex-d demonstrate that the instability growth rates of vortex-u are larger than those of vortex-d,and the perturbation energy of Mode P_(u) is also larger than that of Mode Pd.Moreover,the perturbation energy of Mode P_(u) is up to 0.02650 and accounts for 33.56%percent in the corresponding branch,thereby indicating that the instability development of wingtip vortex is dominated by Mode P_(u).By further investigating the topological structures of Mode P_(u) and Mode Pd with streamwise wavenumbers,the most unstable perturbation mode with a large azimuthal wavenumber of m=5-6 is identified,which imposes on the entire core region of vortex-u.This large azimuthal wavenumber perturbation mode can suggest the potential physical-based flow control strategy by manipulating it.展开更多
The long-term stability of large-span soft rock tunnel is influenced greatly by the creep effect of surrounding rock.The development of a new type of foam concrete which has the property of high compressibility and lo...The long-term stability of large-span soft rock tunnel is influenced greatly by the creep effect of surrounding rock.The development of a new type of foam concrete which has the property of high compressibility and low ductility was introduced.And it was made as filling material of reserved deformation layer between the first lining and the second lining used in large-span soft rock tunnel.The effect of the new type of foam concrete was simulated as filling material of reserved deformation layer using numerical simulation.Through the comparison with the common large-span soft rock tunnel,the vault settlement and surrounding convergence are reduced by about 61% and 45%,respectively,after creep of 100 a.And in the second lining,the plastic zone reduces apparently and the maximum equivalent plastic strain decreases relatively.So,it can be found that the application of the new type of foam concrete as the filling material of reserved deformation layer can relieve the excessive force in second lining induced by rock creep,reduce its deformation and improve the stability of tunnel.展开更多
In order to study the safety factor and instability process of cohesive soil slope, the discrete element method(DEM) was applied. DEM software PFC2 D was used to simulate the triaxial test to study the influence of th...In order to study the safety factor and instability process of cohesive soil slope, the discrete element method(DEM) was applied. DEM software PFC2 D was used to simulate the triaxial test to study the influence of the particle micro parameters on the macroscopic characteristics of cohesive soil and calibrate the micro parameters of DEM model on this basis. Embankment slope stability analysis was carried out by strength reduction and gravity increase method, it is shown that the safety factor obtained by strength reduction method is more conservative, and the arc-shaped feature of the sliding surface under the gravity increase method is more obvious. Throughout the progressive failure process, the failure trends, maximum displacements, and velocity changes obtained by the two methods were consistent. When slope was destroyed, the upper part was cracked, the middle part was sheared, and the lower part was destroyed by extrusion. The conclusions of this paper can be applied to the safety factor calculation of cohesive soil slopes and the analysis of the instability process.展开更多
Terrain texture analysis is an important method of digital terrain analysis in quantitative geomorphological research and in the exploration of the spatial heterogeneity and autocorrelation of terrain features. Howeve...Terrain texture analysis is an important method of digital terrain analysis in quantitative geomorphological research and in the exploration of the spatial heterogeneity and autocorrelation of terrain features. However, a major issue often neglected in previous studies is the calculation unit of the terrain texture, that is, the stability analysis unit. As the test size increases, the derived terrain textures become increasingly similar so that their differences can be ignored. The test size of terrain texture is defined as the stability analysis unit. This study randomly selected 48 areas within the Loess Plateau in northern Shaanxi in China as the study sites and used the gray level co-occurrence matrix to calculate the terrain texture. The stability analysis unit of the terrain texture was then extracted, and its spatial distribution pattern in the Loess Plateau was studiedusing spatial interpolation method. Four terrain texture metrics, i.e., homogeneity, energy, correlation, and contrast, were extracted on the basis of the stability analysis unit, and the spatial variation patterns of these parameters were studied. Results showed that the spatial distribution pattern and the terrain texture metrics reflected a trend of high–low–high from north to south, which correlated with the spatial distribution of the landforms at the Loess Plateau. In addition, the terrain texture measures was significantly correlated with the terrain factors of gully density and slope, and this relationship showed that terrain texture measures based on the stability analysis unit could reflect the basic characteristics of terrain morphology. The stability analysis unit provided a reasonable analytical scale for terrain texture analysis and could be used as a measure of the regional topography to accurately describe basic terrain characteristics.展开更多
The recent research on stability of gas bearing-rotor systems still mostly adopts the same method as in oil-lubricated bearing-rotor systems.The dynamic coefficients of gas bearings in the case that the perturbation f...The recent research on stability of gas bearing-rotor systems still mostly adopts the same method as in oil-lubricated bearing-rotor systems.The dynamic coefficients of gas bearings in the case that the perturbation frequencies are same as the rotating speed are used to carry out the stability analysis of rotor systems.This method does not contact the frequency characteristics of dynamic stiffness and damping coefficients of gas bearings with the dynamical behaviors of rotor systems.Furthermore,the effects of perturbation frequencies on the stability of systems are not taken into account.In this paper,the dynamic stiffness and damping coefficients of tilting-pad gas bearings are calculated by the partial derivative method.On the base of solution of dynamic coefficients,two computational models are produced for stability analysis on rotor systems supported by tilting-pad gas bearings according to whether the degrees of the freedom of pads tilting motions are included in the equations of motion or not.In the condition of considering the frequency effects of dynamic coefficients of tilting-pad gas bearings,the corresponding eigenvalues of the rigid and first five vibration modes of the system with the working speeds of 8-30 kr/min are computed through iteratively solving the equations of motion of rotor-system by using two computational models,respectively.According to the obtained eigenvalues,the stability of rotor system is analyzed.The results indicate that the eigenvalues and the stability of rotor system obtained by these two computational models are well agreement each other.They all can more accurately analyze the stability of rotor systems supported by tilting-pad gas bearings.This research has important meaning for perfecting the stability analysis method of rotor systems supported by gas bearings.展开更多
The large-diameter cylinder structure, which is made of large successive bottomless cylinders placed on foundation bed or partly driven into soil, is a recently developed retaining structure in China. It can be used i...The large-diameter cylinder structure, which is made of large successive bottomless cylinders placed on foundation bed or partly driven into soil, is a recently developed retaining structure in China. It can be used in port, coastal and offshore works. The method for stability analysis of the large-diameter cylinder structure, especially for stability analysis of the embedded large-diameter cylinder structure, is an important issue. In this paper, an idea is presented that is, embedded large-diameter cylinder quays can be divided into two types, i.e. the gravity wall type and the cylinder pile wall type. A method for stability analysis of the large-diameter cylinder quay of the cylinder pile wall type is developed and a method for stability analysis of the large-diameter cylinder quay of the gravity wall type is also proposed. The effect of significant parameters on the stability of the large-diameter cylinder quay of the cylinder pile wall type is investigated through numerical calculation.展开更多
In order to analyze the stability impact of cooperative adaptive cruise control （CACC） platoon, an adaptive control model designed for the lead vehicle in a CACC platoon （LCACC model） in heterogeneous traffic flow...In order to analyze the stability impact of cooperative adaptive cruise control （CACC） platoon, an adaptive control model designed for the lead vehicle in a CACC platoon （LCACC model） in heterogeneous traffic flow with both CACC and manual vehicles is proposed. Considering the communication delay of a CACC platoon, a frequency-domain approach is taken to analyze the stability conditions of the novel lead-vehicle CACC model. Field trajectory data from the next-generation simulation （NGSIM） data is used as the initial condition. To account for car- following behaviors in reality, an intelligent driver model （IDM） is calibrated with the same NGSIM dataset from a previous study to model manual vehicles. The stability conditions of the proposed model are validated by the ring- road stability analysis. The ring-road test results indicate the potential of the LCACC model for improving the traffic flow stability impact of CACC platoons. Sensitivity analysis shows that the CACC fleet size has impact on the parameters of the LCACC model.展开更多
Discontinuous deformation analysis （DDA） provides a powerful numerical tool for the analysis of discontinuous media. This method has been widely applied to the 2D analysis of discontinuous deformation. However, it i...Discontinuous deformation analysis （DDA） provides a powerful numerical tool for the analysis of discontinuous media. This method has been widely applied to the 2D analysis of discontinuous deformation. However, it is hindered from analyzing 3D rock engineering problems mainly due to the lack of reliable 3D contact detection algorithms for polyhedra. Contact detection is a key in 3-D DDA analysis. The limitations and advantages of existing contact detection schemes are discussed in this paper, and a new approach, called the incision body （IB）, is proposed, taking into account the advantages of the existing methods. A computer code 3DIB, which uses the IB scheme as a 3D contact detection algorithm, was programmed with Visual C^＋＋. Static and dynamic stability analysis for three realistic engineering problems has been carried out. Furthermore, the focus is on studying the stability of a gravity dam on jointed rock foundation and dynamic stability of a fractured gravity dam subject to earthquake shaking. The simulation results show that the program 3DIB and incision body scheme are capable of detecting 3D block contacts correctly and hence simulating the open-close and slide process of jointed block masses. In addition, the code 3DIB could provide an effective tool for evaluating the safety of 3D dam structures, which is quite important for engineering problems.展开更多
Currently,industrial robots are considered as an alternative towards traditional machine tools.Especially for the large-scale parts milling,robotic flexibility and low cost make it possess the irreplaceability.However...Currently,industrial robots are considered as an alternative towards traditional machine tools.Especially for the large-scale parts milling,robotic flexibility and low cost make it possess the irreplaceability.However,the milling chatter caused by its weak rigidity hampers robotic application and promotion severely in aviation industry.Rotary ultrasonic milling(RUM)technology with one-dimensional axial vibration has been proven and approved on avoiding robotic chatter.Based on this,the research of project team demonstrates that longitudinal-torsional composite ultrasonic milling(CUM-LT)involving separation characteristic has a greater advantage than RUM in terms of chatter suppression.Thereby,the CUM-LT as a new means is applied to avoid processing vibration of robotic milling system.And its influence mechanism on stability improvement of weak stiffness processing system is clarified.Meanwhile,the approaches to strengthen separation effect are provided innovatively.Moreover,a new analysis method of robotic CUM-LT(RCUM-LT)stability is proposed on the basis of ultrasonic function angles.The simulation and experimental results indicate that compared with robotic RUM(RRUM),stability regions of separated RCUM-LT(SRCUM-LT)and unseparated RCUM-LT(URCUM-LT)are improved by 124.42%and39.20%,respectively.The addition of torsional ultrasonic energy has a wonderful effect on the milling chatter suppression of low stiffness robots.展开更多
文摘In the present study,we concentrate on finding the dual solutions of biomagnetic fluid namely blood flow and heat transfer along with magnetic particles over a two dimensional shrinking cylinder in the presence of a magnetic dipole.To make the results physically realistic,stability analysis is also carried out in this study so that we realized which solution is stable and which is not.The governing partial equations are converted into ordinary differential equations by using similarity transformations and the numerical solution is calculated by applying bvp4c function technique in MATLAB software.The effects of different physical parameters are plotted graphically and discussed according to the outcomes of results.From the present study we observe that ferromagnetic interaction parameter had a great influenced on fluid velocity and temperature distributions.It is also found from the current analysis that the first and second solutions of shrinking cylinder obtained only when we applied particular ranges values of suction parameter.The most important characteristics part of study is to analyze the skin friction coefficient and rate of heat transfer which also covered in this analysis.It reveals that both skin friction coefficient and rate of heat transfer are reduced with rising values of ferromagnetic number.A comparison has also been made to make the solution feasible.
基金Supported by the Basic Product Innovation Plan for Vehicle Power Scientific Research Project(Grant No.JCCPCX201704).
文摘This research presents an advanced study on the modeling and stability analysis of electro-hydraulic control modules used in intelligent chassis systems.Firstly,a comprehensive nonlinear mathematical model of the electro-hydraulic power-shift system is developed,incorporating pipeline characteristics through impedance analysis and examining coupling effects between the pilot solenoid valve,main valve,and pipeline.Then,the model’s accuracy is validated through experimental testing,demonstrating high precision and minimal model errors.A comparative analysis between simulation data(both with and without pipeline characteristics)and experimental results reveals that the model considering pipeline parameters aligns more closely with experimental data,highlighting its superior accuracy.The research further explores the influence of key factors on system stability,including damping coefficient,feedback cavity orifice diameter,spring stiffness,pipeline length,and pipeline diameter.Significant findings include the critical impact of damping coefficient,orifice diameter,and pipeline length on stability,while spring stiffness has a minimal effect.These findings provide valuable insights for optimizing electro-hydraulic control modules in intelligent chassis systems,with practical implications for automotive and construction machinery applications.
基金Projects(52208369,52309138,52108320)supported by the National Natural Science Foundation of ChinaProjects(2023NSFSC0284,2025ZNSFSC0409)supported by the Sichuan Science and Technology Program,ChinaProject(U22468214)supported by the Joint Fund Project for Railway Basic Research by the National Natural Science Foundation of China and China State Railway Group Co.,Ltd.
文摘In the practical slope engineering,the stability of lower sliding mass(region A)with back tensile cracks of the jointed rock slope attracts more attentions,but the upper rock mass(region B)may also be unstable.Therefore,in this study,based on the stepped failure mode of bedding jointed rock slopes,considering the influence of the upper rock mass on the lower stepped sliding mass,the improved failure model for analyzing the interaction force(F_(AB))between two regions is constructed,and the safety factors(F_(S))of two regions and whole region are derived.In addition,this paper proposes a method to determine the existence of F_(AB) using their respective acceleration values(a_(A) and a_(B))when regions A and B are unstable.The influences of key parameters on two regions and the whole region are analyzed.The results show that the variation of the F_(AB) and F_(S) of two regions can be obtained accurately based on the improved failure model.The accuracy of the improved failure model is verified by comparative analysis.The research results can explain the interaction mechanism of two regions and the natural phenomenon of slope failure caused by the development of cracks.
基金supported by the National Natural Science Foundation of China(Grant Nos.51890912,51979025 and 52011530189).
文摘This article presents a micro-structure tensor enhanced elasto-plastic finite element(FE)method to address strength anisotropy in three-dimensional(3D)soil slope stability analysis.The gravity increase method(GIM)is employed to analyze the stability of 3D anisotropic soil slopes.The accuracy of the proposed method is first verified against the data in the literature.We then simulate the 3D soil slope with a straight slope surface and the convex and concave slope surfaces with a 90turning corner to study the 3D effect on slope stability and the failure mechanism under anisotropy conditions.Based on our numerical results,the end effect significantly impacts the failure mechanism and safety factor.Anisotropy degree notably affects the safety factor,with higher degrees leading to deeper landslides.For concave slopes,they can be approximated by straight slopes with suitable boundary conditions to assess their stability.Furthermore,a case study of the Saint-Alban test embankment A in Quebec,Canada,is provided to demonstrate the applicability of the proposed FE model.
基金Specialized Research Fund for the Doctoral Program of Higher Education ( No. 20090092110051)the Key Project of Chinese Ministry of Education ( No. 108060)the National Natural Science Foundation of China ( No. 51076027, 51036002, 51106024)
文摘An analysis method based on the fuzzy Lyapunov functions is presented to analyze the stability of the continuous affine fuzzy systems. First, a method is introduced to deal with the consequent part of the fuzzy local model. Thus, the stability analysis method of the homogeneous fuzzy system can be used for reference. Stability conditions are derived in terms of linear matrix inequalities based on the fuzzy Lyapunov functions and the modified common Lyapunov functions, respectively. The results demonstrate that the stability result based on the fuzzy Lyapunov functions is less conservative than that based on the modified common Lyapunov functions via numerical examples. Compared with the method which does not expand the consequent part, the proposed method is simpler but its feasible region is reduced. Finally, in order to expand the application of the fuzzy Lyapunov functions, the piecewise fuzzy Lyapunov function is proposed, which can be used to analyze the stability for triangular or trapezoidal membership functions and obtain the stability conditions. A numerical example validates the effectiveness of the proposed approach.
基金The National Key Technology R&D Program of China(No.2012BAJ03B06)the National Natural Science Foundation of China(No.51308105)+1 种基金the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)the Fundamental Research Funds for the Southeast University(No.KYLX_0152,SJLX_0084,KYLX_0149)
文摘To investigate the effects of initial geometric imperfection and material nonlinearity on the stability analysis of the suspen-dome, the steel roof of Jiangsu Culture Sports Center Gymnasium was utilized as a numerical model, and modal analyses were performed. Then, linear buckling analysis,geometric nonlinear stability analysis, geometric nonlinear stability analysis with initial imperfection, and double nonlinear analysis considering material nonlinearity and geometric nonlinearity were discussed in detail to compare the stability performance of the ellipse-like suspen-dome and the single-layer reticulated shell. The results showthat the cable-strut system increases the integrity of the suspen-dome, and moderates the sensibility of the single-layer reticulated shell to initial geometric imperfection. However, it has little influence on integral rigidity, fundamental vibration frequencies, linear ultimate live loads, and geometric nonlinear ultimate live loads without initial imperfection. When considering the material nonlinearity and initial imperfection, a significant reduction occurs in the ultimate stability capacities of these two structures. In this case, the suspen-dome with a lowrise-span ratio is sensitive to the initial imperfection and material nonlinearity. In addition, the distribution pattern of live loads significantly influences the instability modes of the structure, and the uniform live load with full span is not always the most dangerous case.
基金Project(51978085)supported by the National Natural Science Foundation of ChinaProject(201808430102)supported by the China Scholarship Council+1 种基金Project(JTG-201507)supported by the Highway Industry Standard Compilation Project of Ministry of Transportation,ChinaProject(kfj180102)supported by the Open Fund of Changsha University of Science&Technology,China。
文摘The traditional stability analysis method of geogrid reinforced slopes does not consider the effect of lateral swelling,so it is not applicable to reinforced expansive soil slopes.This paper reports a new stability analysis method for geogrid reinforced expansive soil slopes.The additional pullout force of the free zone due to the lateral swelling and the anti-pullout safety factor of each geogrid layer were obtained by ensuring the overall stability of the reinforced slope.The optimum design was carried out to treat an expansive soil cut slope in Hubei Province,China,by changing the spacing and length of geogrid reinforcement.Calculation results show that the additional pullout force caused by lateral swelling has a great influence on the anti-pullout stability of geogrids,and the local stability of the reinforced slope will be overestimated if the swelling effect of soil in the free zone is not considered.
基金Project(2017YFC1501100)supported by the National Key R&D Program of ChinaProjects(51809221,51679158)supported by the National Natural Science Foundation of China。
文摘To investigate the stability of rock mass in high geostress underground powerhouse caverns subjected to excavation,a microseismic(MS)monitoring system was established and the discrete element method(DEM)-based numerical simulation was carried out.The tempo-spatial damage characteristics of rock mass were analyzed.The evolution laws of MS source parameters during the formation of a rock collapse controlled by high geostress and geological structure were investigated.Additionally,a three-dimensional DEM model of the underground powerhouse caverns was built to reveal the deformation characteristics of rock mass.The results indicated that the MS events induced by excavation of high geostress underground powerhouse caverns occurred frequently.The large-stake crown of the main powerhouse was the main damage area.Prior to the rock collapse,the MS event count and accumulated energy release increased rapidly,while the apparent stress sharply increased and then decreased.The amount and proportion of shear and mixed MS events remarkably increased.The maximum displacement was generally located near the spandrel areas.The MS monitoring data and numerical simulation were in good agreement,which can provide significant references for damage evaluation and disaster forecasting in high geostress underground powerhouse caverns.
文摘Dam construction for hydropower development is a very important subject all around the world, especially in developing countries due to energy crises. Filling of reservoir lakes may trigger or reactivate landslides in reservoir area. Active landslides in populated districts in the Xiangjiaba Reservoir area have become a striking problem for residents, local government and construction engineers. The key objective of this study is to analyze the role of reservoir filling and fluctuation in the activation/reactivation of the landslide as well as the mechanism of landslide from microstructures of pre-sheared slip surface. A large active landslide with a total volume of 1.25 Mm^3 at the left margin of Jinsha River in Pingshan County of Sichuan Province, Southwest China, was selected as a case study. Field investigation, field monitoring and laboratory tests were carried out to find out the failure mechanism and the stability of the active landslide. The shear strength test and stability analysis confirm that the water level fluctuations have an adverse effect on slope stability. It is obvious from microstructure analysis that the clay minerals contribute to down-slope movement at micro-scale as well as presence of expansive minerals （e.g., montmorillonite） decreases the strength of soil due to water level rise.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51475319 and 51722508)the National Key R&D Plan(Grant No.2016YFC0301100)Aoshan Talents Program of Qingdao National Laboratory for Marine Science and Technology
文摘Hybrid-driven underwater glider is a new type of tmmanned underwater vehicle, which combines the advantages of autonomous underwater vehicles and traditional underwater gliders. The autonomous underwater vehicles have good maneuverability and can travel with a high speed, while the traditional underwater gliders are highlighted by low power consumption, long voyage, long endurance and good stealth characteristics. The hybrid-driven underwater gliders can realize variable motion profiles by their own buoyancy-driven and propeller propulsion systems. Stability of the mechanical system determines the performance of the system. In this paper, the Petrel-II hybrid-driven underwater glider developed by Tianjin University is selected as the research object and the stability of hybrid-driven underwater glider unitedly controlled by buoyancy and propeller has been targeted and evidenced. The dimensionless equations of the hybrid-driven underwater glider are obtained when the propeller is working. Then, the steady speed and steady glide path angle under steady-state motion have also been achieved. The steady-state operating conditions can be calculated when the hybrid-driven underwater glider reaches the desired steady-state motion. And the steady- state operating conditions are relatively conservative at the lower bound of the velocity range compared with the range of the velocity derived from the method of the composite Lyapunov function. By calculating the hydrodynamic coefficients of the Petrel-II hybrid-driven underwater glider, the simulation analysis has been conducted. In addition, the results of the field trials conducted in the South China Sea and the Danjiangkou Reservoir of China have been presented to illustrate the validity of the analysis and simulations.and to show the feasibility of the method of the composite Lyapunov function which verifies the stability of the Petrel-II hybrid-driven underwater glider.
基金This work was supported in part by Beijing Natural Science Foundation(JQ19013)the National Key Research and Development Program of China(2021ZD0112302)the National Natural Science Foundation of China(61773373).
文摘The core task of tracking control is to make the controlled plant track a desired trajectory.The traditional performance index used in previous studies cannot eliminate completely the tracking error as the number of time steps increases.In this paper,a new cost function is introduced to develop the value-iteration-based adaptive critic framework to solve the tracking control problem.Unlike the regulator problem,the iterative value function of tracking control problem cannot be regarded as a Lyapunov function.A novel stability analysis method is developed to guarantee that the tracking error converges to zero.The discounted iterative scheme under the new cost function for the special case of linear systems is elaborated.Finally,the tracking performance of the present scheme is demonstrated by numerical results and compared with those of the traditional approaches.
基金co-supported by the National Basic Research Program of China(No.2014CB744802)Major Research of National Natural Science Foundation of China(No.91952302)China Postdoctoral Science Foundation(No.2018 M642007)。
文摘The Stereo Particle Image Velocimetry(SPIV)technology is applied to measure the wingtip vortices generated by the up-down symmetrical split winglet.Then,the temporal biglobal Linear Stability Analysis(bi-global LSA)is performed on this nearly equal-strength corotating vortex pair,which is composed of an upper vortex(vortex-u)and a down vortex(vortex-d).The results show that the instability eigenvalue spectrum illustrated by(ωr,ω_(i))contains two types of branches:discrete branch and continuous branch.The discrete branch contains the primary branches of vortex-u and vortex-d,the secondary branch of vortex-d and coupled branch,of which all of the eigenvalues are located in the unstable half-plane ofω_(i)>0,indicating that the wingtip vortex pair is temporally unstable.By contrast,the eigenvalues of the continuous branch are concentrated on the half-plane ofω_(i)<0 and the perturbation modes correspond to the freestream perturbation.In the primary branches of vortex-u and vortex-d,Mode P_(u) and Mode Pd are the primary perturbation modes,which exhibit the structures enclosed with azimuthal wavenumber m and radial wavenumber n,respectively.Besides,the results of stability curves for vortex-u and vortex-d demonstrate that the instability growth rates of vortex-u are larger than those of vortex-d,and the perturbation energy of Mode P_(u) is also larger than that of Mode Pd.Moreover,the perturbation energy of Mode P_(u) is up to 0.02650 and accounts for 33.56%percent in the corresponding branch,thereby indicating that the instability development of wingtip vortex is dominated by Mode P_(u).By further investigating the topological structures of Mode P_(u) and Mode Pd with streamwise wavenumbers,the most unstable perturbation mode with a large azimuthal wavenumber of m=5-6 is identified,which imposes on the entire core region of vortex-u.This large azimuthal wavenumber perturbation mode can suggest the potential physical-based flow control strategy by manipulating it.
基金Projects(41072238,51009133)supported by the National Natural Science Foundation of China
文摘The long-term stability of large-span soft rock tunnel is influenced greatly by the creep effect of surrounding rock.The development of a new type of foam concrete which has the property of high compressibility and low ductility was introduced.And it was made as filling material of reserved deformation layer between the first lining and the second lining used in large-span soft rock tunnel.The effect of the new type of foam concrete was simulated as filling material of reserved deformation layer using numerical simulation.Through the comparison with the common large-span soft rock tunnel,the vault settlement and surrounding convergence are reduced by about 61% and 45%,respectively,after creep of 100 a.And in the second lining,the plastic zone reduces apparently and the maximum equivalent plastic strain decreases relatively.So,it can be found that the application of the new type of foam concrete as the filling material of reserved deformation layer can relieve the excessive force in second lining induced by rock creep,reduce its deformation and improve the stability of tunnel.
基金Project(51808116) supported by the National Natural Science Foundation of ChinaProject(BK20180404) supported by the Natural Science Foundation of Jiangsu Province, China+1 种基金Project(KFJ170106) supported by the Changsha University of Science & Technology via Open Fund of National Engineering Laboratory of Highway Maintenance Technology,ChinaProject(242020R40133) supported by Fundamental Research Funds for the Central Universities, China。
文摘In order to study the safety factor and instability process of cohesive soil slope, the discrete element method(DEM) was applied. DEM software PFC2 D was used to simulate the triaxial test to study the influence of the particle micro parameters on the macroscopic characteristics of cohesive soil and calibrate the micro parameters of DEM model on this basis. Embankment slope stability analysis was carried out by strength reduction and gravity increase method, it is shown that the safety factor obtained by strength reduction method is more conservative, and the arc-shaped feature of the sliding surface under the gravity increase method is more obvious. Throughout the progressive failure process, the failure trends, maximum displacements, and velocity changes obtained by the two methods were consistent. When slope was destroyed, the upper part was cracked, the middle part was sheared, and the lower part was destroyed by extrusion. The conclusions of this paper can be applied to the safety factor calculation of cohesive soil slopes and the analysis of the instability process.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41471316, 41571383, 41671389)the Priority Academic Program Development of Jiangsu Higher Education Institutions-PAPD (Grant No. 164320H101)the Key Project of Natural Science Research of Anhui Provincial Department of Education (Grant No. KJ2015A171)
文摘Terrain texture analysis is an important method of digital terrain analysis in quantitative geomorphological research and in the exploration of the spatial heterogeneity and autocorrelation of terrain features. However, a major issue often neglected in previous studies is the calculation unit of the terrain texture, that is, the stability analysis unit. As the test size increases, the derived terrain textures become increasingly similar so that their differences can be ignored. The test size of terrain texture is defined as the stability analysis unit. This study randomly selected 48 areas within the Loess Plateau in northern Shaanxi in China as the study sites and used the gray level co-occurrence matrix to calculate the terrain texture. The stability analysis unit of the terrain texture was then extracted, and its spatial distribution pattern in the Loess Plateau was studiedusing spatial interpolation method. Four terrain texture metrics, i.e., homogeneity, energy, correlation, and contrast, were extracted on the basis of the stability analysis unit, and the spatial variation patterns of these parameters were studied. Results showed that the spatial distribution pattern and the terrain texture metrics reflected a trend of high–low–high from north to south, which correlated with the spatial distribution of the landforms at the Loess Plateau. In addition, the terrain texture measures was significantly correlated with the terrain factors of gully density and slope, and this relationship showed that terrain texture measures based on the stability analysis unit could reflect the basic characteristics of terrain morphology. The stability analysis unit provided a reasonable analytical scale for terrain texture analysis and could be used as a measure of the regional topography to accurately describe basic terrain characteristics.
基金supported by National Natural Science Foundation of China (Grant No. 50635060)National Hi-tech Research and Development Program of China (863 Program,Grant No.2007AA050501)+1 种基金National Key Basic Research Program of China (973 Program,Grant No. 2007CB707705,Grant No. 2007CB707706)Research Funds for the Central Universities of China
文摘The recent research on stability of gas bearing-rotor systems still mostly adopts the same method as in oil-lubricated bearing-rotor systems.The dynamic coefficients of gas bearings in the case that the perturbation frequencies are same as the rotating speed are used to carry out the stability analysis of rotor systems.This method does not contact the frequency characteristics of dynamic stiffness and damping coefficients of gas bearings with the dynamical behaviors of rotor systems.Furthermore,the effects of perturbation frequencies on the stability of systems are not taken into account.In this paper,the dynamic stiffness and damping coefficients of tilting-pad gas bearings are calculated by the partial derivative method.On the base of solution of dynamic coefficients,two computational models are produced for stability analysis on rotor systems supported by tilting-pad gas bearings according to whether the degrees of the freedom of pads tilting motions are included in the equations of motion or not.In the condition of considering the frequency effects of dynamic coefficients of tilting-pad gas bearings,the corresponding eigenvalues of the rigid and first five vibration modes of the system with the working speeds of 8-30 kr/min are computed through iteratively solving the equations of motion of rotor-system by using two computational models,respectively.According to the obtained eigenvalues,the stability of rotor system is analyzed.The results indicate that the eigenvalues and the stability of rotor system obtained by these two computational models are well agreement each other.They all can more accurately analyze the stability of rotor systems supported by tilting-pad gas bearings.This research has important meaning for perfecting the stability analysis method of rotor systems supported by gas bearings.
基金by the National Natural Science Foundation of China(Grant No.59679003)the Natural Science Foundation of Tianjin(Grant No.973606311)
文摘The large-diameter cylinder structure, which is made of large successive bottomless cylinders placed on foundation bed or partly driven into soil, is a recently developed retaining structure in China. It can be used in port, coastal and offshore works. The method for stability analysis of the large-diameter cylinder structure, especially for stability analysis of the embedded large-diameter cylinder structure, is an important issue. In this paper, an idea is presented that is, embedded large-diameter cylinder quays can be divided into two types, i.e. the gravity wall type and the cylinder pile wall type. A method for stability analysis of the large-diameter cylinder quay of the cylinder pile wall type is developed and a method for stability analysis of the large-diameter cylinder quay of the gravity wall type is also proposed. The effect of significant parameters on the stability of the large-diameter cylinder quay of the cylinder pile wall type is investigated through numerical calculation.
基金The National High Technology Research and Development Program of China(863 Program)(No.2011AA110405)
文摘In order to analyze the stability impact of cooperative adaptive cruise control （CACC） platoon, an adaptive control model designed for the lead vehicle in a CACC platoon （LCACC model） in heterogeneous traffic flow with both CACC and manual vehicles is proposed. Considering the communication delay of a CACC platoon, a frequency-domain approach is taken to analyze the stability conditions of the novel lead-vehicle CACC model. Field trajectory data from the next-generation simulation （NGSIM） data is used as the initial condition. To account for car- following behaviors in reality, an intelligent driver model （IDM） is calibrated with the same NGSIM dataset from a previous study to model manual vehicles. The stability conditions of the proposed model are validated by the ring- road stability analysis. The ring-road test results indicate the potential of the LCACC model for improving the traffic flow stability impact of CACC platoons. Sensitivity analysis shows that the CACC fleet size has impact on the parameters of the LCACC model.
基金Key Program of National Natural Science Foundation of China Under Grant No.90510018 and Natural Science Foundation of Liaoning Province of China Under Grant No.20041077.
文摘Discontinuous deformation analysis （DDA） provides a powerful numerical tool for the analysis of discontinuous media. This method has been widely applied to the 2D analysis of discontinuous deformation. However, it is hindered from analyzing 3D rock engineering problems mainly due to the lack of reliable 3D contact detection algorithms for polyhedra. Contact detection is a key in 3-D DDA analysis. The limitations and advantages of existing contact detection schemes are discussed in this paper, and a new approach, called the incision body （IB）, is proposed, taking into account the advantages of the existing methods. A computer code 3DIB, which uses the IB scheme as a 3D contact detection algorithm, was programmed with Visual C^＋＋. Static and dynamic stability analysis for three realistic engineering problems has been carried out. Furthermore, the focus is on studying the stability of a gravity dam on jointed rock foundation and dynamic stability of a fractured gravity dam subject to earthquake shaking. The simulation results show that the program 3DIB and incision body scheme are capable of detecting 3D block contacts correctly and hence simulating the open-close and slide process of jointed block masses. In addition, the code 3DIB could provide an effective tool for evaluating the safety of 3D dam structures, which is quite important for engineering problems.
基金co-supported by the National Natural Science Foundation of China(Nos.91860132,51861145405,52075265)。
文摘Currently,industrial robots are considered as an alternative towards traditional machine tools.Especially for the large-scale parts milling,robotic flexibility and low cost make it possess the irreplaceability.However,the milling chatter caused by its weak rigidity hampers robotic application and promotion severely in aviation industry.Rotary ultrasonic milling(RUM)technology with one-dimensional axial vibration has been proven and approved on avoiding robotic chatter.Based on this,the research of project team demonstrates that longitudinal-torsional composite ultrasonic milling(CUM-LT)involving separation characteristic has a greater advantage than RUM in terms of chatter suppression.Thereby,the CUM-LT as a new means is applied to avoid processing vibration of robotic milling system.And its influence mechanism on stability improvement of weak stiffness processing system is clarified.Meanwhile,the approaches to strengthen separation effect are provided innovatively.Moreover,a new analysis method of robotic CUM-LT(RCUM-LT)stability is proposed on the basis of ultrasonic function angles.The simulation and experimental results indicate that compared with robotic RUM(RRUM),stability regions of separated RCUM-LT(SRCUM-LT)and unseparated RCUM-LT(URCUM-LT)are improved by 124.42%and39.20%,respectively.The addition of torsional ultrasonic energy has a wonderful effect on the milling chatter suppression of low stiffness robots.
