Double-clamped bistable buckled beams demonstrate great versatility in various fields such as robotics,energy harvesting,and microelectromechanical system(MEMS).However,their design often requires time-consuming and e...Double-clamped bistable buckled beams demonstrate great versatility in various fields such as robotics,energy harvesting,and microelectromechanical system(MEMS).However,their design often requires time-consuming and expensive computations.In this work,we present a method to easily and rapidly design bistable buckled beams subjected to a transverse point force.Based on the Euler–Bernoulli beam theory,we establish a theoretical model of bistable buckled beams to characterize their snapthrough properties.This model is verified against the results from a finite element analysis(FEA)model,with maximum discrepancy less than 7%.By analyzing and simplifying our theoretical model,we derive explicit analytical expressions for critical behavioral values on the force-displacement curve of the beam.These behavioral values include critical force,critical displacement,and travel,which are generally sufficient for characterizing the snapthrough properties of a bistable buckled beam.Based on these analytical formulas,we investigate the influence of a bistable buckled beam's key design parameters,including its actuation position and precompression,on its critical behavioral values,with our results validated by FEA simulations.Our analytical method enables fast and computationally inexpensive design of bistable buckled beams and can guide the design of complicated systems that incorporate bistable mechanisms.展开更多
The situation of an off-center casing under non-uniform ground stress can occur in the process of drilling a salt-gypsum formation,and the related casing stress calculation has not yet been solved analytically. In add...The situation of an off-center casing under non-uniform ground stress can occur in the process of drilling a salt-gypsum formation,and the related casing stress calculation has not yet been solved analytically. In addition,the experimental equipment in many cases cannot meet the actual conditions and the experimental cost is very high. These comprehensive factors cause the existing casing design to not meet the actual conditions and cause casing deformation,affecting the drilling operation in Tarim oil field. The finite element method is the only effective method to solve this problem at present,but the re-modelling process is time-consuming because of the changes in the parameters,such as the cement properties,casing centrality,and the casing size. In this article,an artificial intelligence method based on support vector machine(SVM) to predict the maximum stress of an offcenter casing under non-uniform ground stress has been proposed. After a program based on a radial basis function(RBF)-support vector regression(SVR)(ε-SVR) model was established and validated,we constructed a data sample with a capacity of 120 by using the finite element method,which could meet the demand of the nine-factor ε-SVR model to predict the maximum stress of the casing. The results showed that the artificial intelligence prediction method proposed in this manuscript had satisfactory prediction accuracy and could be effectively used to predict the maximum stress of an off-center casing under complex downhole conditions.展开更多
After analyzing the multivariate Cpm method （Chan et al. 1991）, this paper presents a spatial multivariate process capability index （PCI） method, which can solve a multivariate off-centered case and may provide re...After analyzing the multivariate Cpm method （Chan et al. 1991）, this paper presents a spatial multivariate process capability index （PCI） method, which can solve a multivariate off-centered case and may provide references for assuring and improving process quality level while achieving an overall evaluation of process quality. Examples for calculating multivariate PCI are given and the experimental results show that the systematic method presented is effective and actual.展开更多
A theoretical study has been undertaken to determine the flow characteristics associated with a three-dimensional laminar impinging jet issuing from a square pipe nozzle. Interesting flow structures around the jet are...A theoretical study has been undertaken to determine the flow characteristics associated with a three-dimensional laminar impinging jet issuing from a square pipe nozzle. Interesting flow structures around the jet are detected. The numerical result reveals the existence of four streamwise velocity off-center peaks near the impingement plate, which is different from the rectangular jet impingement. The mechanism of the formation of the off-center velocity peaks and the parameters affecting the flow-field characteristics are discussed by comparison of the computed results with different nozzle-to-plate spacings and Reynolds numbers.展开更多
We investigate the effect of Zn doping on the dielectricity and ferroelectricity of a series of polycrystalline Sr0.9-xZnxBa0.1TiO3（0.0% ≤ x ≤ 5.0%） ceramics. It is surprisingly observed that the Zn doping will pr...We investigate the effect of Zn doping on the dielectricity and ferroelectricity of a series of polycrystalline Sr0.9-xZnxBa0.1TiO3（0.0% ≤ x ≤ 5.0%） ceramics. It is surprisingly observed that the Zn doping will produce the multifold polar states, i.e., the Zn-doped ceramic will convert a reduced polar state into an enhanced polar state, and eventually into a stabilized polar state with increasing the doping level x. It is revealed that in the background of quantum fluctuations, the competition between the Zn-doping-induced lattice contraction and the Ba-doping-induced lattice expansion is responsible for both the reduced polar state and the enhanced polar state coming into being. Also, the addition of the antiferrodistortive effect, which is the antipolar interaction originating from the opposite tilted-Ti O6 octahedra rotation, represents the core physics behind the stabilized polar state.展开更多
基金financial support from the National Science Foundation of the United State (Grants 1752575 and 1644579)
文摘Double-clamped bistable buckled beams demonstrate great versatility in various fields such as robotics,energy harvesting,and microelectromechanical system(MEMS).However,their design often requires time-consuming and expensive computations.In this work,we present a method to easily and rapidly design bistable buckled beams subjected to a transverse point force.Based on the Euler–Bernoulli beam theory,we establish a theoretical model of bistable buckled beams to characterize their snapthrough properties.This model is verified against the results from a finite element analysis(FEA)model,with maximum discrepancy less than 7%.By analyzing and simplifying our theoretical model,we derive explicit analytical expressions for critical behavioral values on the force-displacement curve of the beam.These behavioral values include critical force,critical displacement,and travel,which are generally sufficient for characterizing the snapthrough properties of a bistable buckled beam.Based on these analytical formulas,we investigate the influence of a bistable buckled beam's key design parameters,including its actuation position and precompression,on its critical behavioral values,with our results validated by FEA simulations.Our analytical method enables fast and computationally inexpensive design of bistable buckled beams and can guide the design of complicated systems that incorporate bistable mechanisms.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.U1663205,51704191 and 51804194)the Shanghai Leading Academic Discipline Project(Grant No.S30106)+1 种基金the Shanghai Municipal Education Commission(Peak Discipline Construction Program)the Shanghai Sailing Program(Grant No.17YF1428000)。
文摘The situation of an off-center casing under non-uniform ground stress can occur in the process of drilling a salt-gypsum formation,and the related casing stress calculation has not yet been solved analytically. In addition,the experimental equipment in many cases cannot meet the actual conditions and the experimental cost is very high. These comprehensive factors cause the existing casing design to not meet the actual conditions and cause casing deformation,affecting the drilling operation in Tarim oil field. The finite element method is the only effective method to solve this problem at present,but the re-modelling process is time-consuming because of the changes in the parameters,such as the cement properties,casing centrality,and the casing size. In this article,an artificial intelligence method based on support vector machine(SVM) to predict the maximum stress of an offcenter casing under non-uniform ground stress has been proposed. After a program based on a radial basis function(RBF)-support vector regression(SVR)(ε-SVR) model was established and validated,we constructed a data sample with a capacity of 120 by using the finite element method,which could meet the demand of the nine-factor ε-SVR model to predict the maximum stress of the casing. The results showed that the artificial intelligence prediction method proposed in this manuscript had satisfactory prediction accuracy and could be effectively used to predict the maximum stress of an off-center casing under complex downhole conditions.
基金Project supported by the Natural Science Foundation of Shaanxi Province(No.2012JQ8048)the Basic Research Foundation of North-western Polytechnical University(No.JC20110232)
文摘After analyzing the multivariate Cpm method （Chan et al. 1991）, this paper presents a spatial multivariate process capability index （PCI） method, which can solve a multivariate off-centered case and may provide references for assuring and improving process quality level while achieving an overall evaluation of process quality. Examples for calculating multivariate PCI are given and the experimental results show that the systematic method presented is effective and actual.
文摘A theoretical study has been undertaken to determine the flow characteristics associated with a three-dimensional laminar impinging jet issuing from a square pipe nozzle. Interesting flow structures around the jet are detected. The numerical result reveals the existence of four streamwise velocity off-center peaks near the impingement plate, which is different from the rectangular jet impingement. The mechanism of the formation of the off-center velocity peaks and the parameters affecting the flow-field characteristics are discussed by comparison of the computed results with different nozzle-to-plate spacings and Reynolds numbers.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.1130415851431006+5 种基金51102277and 11104118)the Scientific Research Foundation of Nanjing University of Posts and TelecommunicationsChina(Grant No.NY213020)the Qing Lan Project of Jiangsu ProvinceChina
文摘We investigate the effect of Zn doping on the dielectricity and ferroelectricity of a series of polycrystalline Sr0.9-xZnxBa0.1TiO3（0.0% ≤ x ≤ 5.0%） ceramics. It is surprisingly observed that the Zn doping will produce the multifold polar states, i.e., the Zn-doped ceramic will convert a reduced polar state into an enhanced polar state, and eventually into a stabilized polar state with increasing the doping level x. It is revealed that in the background of quantum fluctuations, the competition between the Zn-doping-induced lattice contraction and the Ba-doping-induced lattice expansion is responsible for both the reduced polar state and the enhanced polar state coming into being. Also, the addition of the antiferrodistortive effect, which is the antipolar interaction originating from the opposite tilted-Ti O6 octahedra rotation, represents the core physics behind the stabilized polar state.
