For statically indeterminate structure, the internal force will be changed with the translation of the supports, because the internal force is related to the absolute value of the stiffness EI. When the tension is dif...For statically indeterminate structure, the internal force will be changed with the translation of the supports, because the internal force is related to the absolute value of the stiffness EI. When the tension is different with the compression modulus, EI is the function of internal force and is not constant any more that is different from classic mechanics. In the other words, it is a nonlinear problem to calculate the internal force. The expression for neutral axis of the statically indeterminate structure was derived in the paper. The iterative program for nonlinear internal force was compiled. One case study was presented to illustrate the difference between the results using the different modulus theory and the single modulus theory as in classical mechanics. Finally, some reasonable suggestions were made for the different modulus structures.展开更多
Aiming to mitigate the aerodynamic lift force imbalance between pantograph strips,which exacerbates wear and affects the current collection performance of the pantograph-catenary system,a study has been conducted to s...Aiming to mitigate the aerodynamic lift force imbalance between pantograph strips,which exacerbates wear and affects the current collection performance of the pantograph-catenary system,a study has been conducted to support the beam deflector optimization using a combination of experimental measurements and computational fluid dynamics(CFD)simulations.The results demonstrate that the size,position,and installation orientation of the wind deflectors significantly influence the amount of force compensation.They also indicate that the front strip deflectors should be installed downwards and the rear strip deflectors upwards,thereby forming a“π”shape.Moreover,the lift force compensation provided by the wind deflectors increases with the size of the deflector.Alternative wind compensation strategies,such as control circuits,are also discussed,putting emphasis on the pros and cons of various pantograph types and wind compensation approaches.展开更多
Kilns are the key equipment in the metallurgy,architectural and chemistry industry. It is the statically indeterminate system with over load, large torque and multi-support. The kiln move axis warp resulting in that t...Kilns are the key equipment in the metallurgy,architectural and chemistry industry. It is the statically indeterminate system with over load, large torque and multi-support. The kiln move axis warp resulting in that the load distribution is asymmetry, cause many mechanical failure and safe accidents and the interruption of the produce, which bring a great losses. Treating the distribution of the kiln load and the complexity of the stiffness change, the all-purpose model and matrix, used to solve the variable-stiffness beam upon complex load, are established in this paper. The resultant force of kiln in vertical and horizontal direction is calculated. Accordingly, the liner formulas for calculating the supporting force of the support wheels are obtained, and the wheel supporting force also can be easily obtained based on each shell warp. This will provide theory conference for safety management and rational maintenance.展开更多
The application of steel strut force servo systems in deep excavation engineering is not widespread,and there is a notable scarcity of in-situ measured datasets.This presents a significant research gap in the field.Ad...The application of steel strut force servo systems in deep excavation engineering is not widespread,and there is a notable scarcity of in-situ measured datasets.This presents a significant research gap in the field.Addressing this,our study introduces a valuable dataset and application scenarios,serving as a reference point for future research.The main objective of this study is to use machine learning(ML)methods for accurately predicting strut forces in steel supporting structures,a crucial aspect for the safety and stability of deep excavation projects.We employed five different ML methods:radial basis function neural network(RBFNN),back propagation neural network(BPNN),K-Nearest Neighbor(KNN),support vector machine(SVM),and random forest(RF),utilizing a dataset of 2208 measured points.These points included one output parameter(strut forces)and seven input parameters(vertical position of strut,plane position of strut,time,temperature,unit weight,cohesion,and internal frictional angle).The effectiveness of these methods was assessed using root mean square error(RMSE),correlation coefficient(R),and mean absolute error(MAE).Our findings indicate that the BPNN method outperforms others,with RMSE,R,and MAE values of 72.1 kN,0.9931,and 57.4 kN,respectively,on the testing dataset.This study underscores the potential of ML methods in precisely predicting strut forces in deep excavation engineering,contributing to enhanced safety measures and project planning.展开更多
The current research on gear system dynamics mainly utilizes linear spring damping model to calculate the contact force between gears. However, this linear model cannot correctly describe the energy transfer process o...The current research on gear system dynamics mainly utilizes linear spring damping model to calculate the contact force between gears. However, this linear model cannot correctly describe the energy transfer process of collision that often occurs in gear system. Focus on the contact-impact events, this paper proposes an improved gear contact force model for dynamic analysis in helical gear transmission system. In this model, a new factor associated with hysteresis damping is developed for contact-impact state, whereas the traditional linear damping factor is utilized for normal meshing state. For determining the selection strategy of these two damping factors, the fundamental contact mechanics of contact-impact event a ected by supporting forces are analyzed. During this analysis, an e ect factor is proposed for evaluating the influence of supporting forces on collision. Meanwhile, a new restitution of coe cient is deduced for calculating hysteresis damping factor, which suitable for both separation and non-separation states at the end of collision. In addition, the time-varying meshing sti ness(TVMS) is obtained based on the potential energy approach and the slice theory. Finally, a dynamic analysis of a helical gear system is carried out to better understand the contact force model proposed in this paper. The analysis results show that the contribution of supporting forces to the dynamic response of contact-impact event within gear pair is important. The supporting forces and dissipative energy are the main reasons for gear system to enter a steady contact state from repeated contact-impact state. This research proposes an improved contact force model which distinguishes meshing and collision states in gear system.展开更多
A general method was developed for promoting peptide assembly and protein polymerization to form nanoscale patterns on various surfaces with an atomic force microscope(AFM) operated in a liquid. By scanning solid surf...A general method was developed for promoting peptide assembly and protein polymerization to form nanoscale patterns on various surfaces with an atomic force microscope(AFM) operated in a liquid. By scanning solid surfaces with an AFM tip, we showed that peptide monomers assemble at a higher rate in the tip-scanned area compared to other regions. The promotion is attributed to the mechanical force applied by the scanning tip. This kind of mechanical-force-promoted assembly was also observed with different peptides on various substrates. The force promoting peptide assembly provides a simple and practical solution for preparing and building peptide and protein architectures for future nanodevices.展开更多
文摘For statically indeterminate structure, the internal force will be changed with the translation of the supports, because the internal force is related to the absolute value of the stiffness EI. When the tension is different with the compression modulus, EI is the function of internal force and is not constant any more that is different from classic mechanics. In the other words, it is a nonlinear problem to calculate the internal force. The expression for neutral axis of the statically indeterminate structure was derived in the paper. The iterative program for nonlinear internal force was compiled. One case study was presented to illustrate the difference between the results using the different modulus theory and the single modulus theory as in classical mechanics. Finally, some reasonable suggestions were made for the different modulus structures.
文摘Aiming to mitigate the aerodynamic lift force imbalance between pantograph strips,which exacerbates wear and affects the current collection performance of the pantograph-catenary system,a study has been conducted to support the beam deflector optimization using a combination of experimental measurements and computational fluid dynamics(CFD)simulations.The results demonstrate that the size,position,and installation orientation of the wind deflectors significantly influence the amount of force compensation.They also indicate that the front strip deflectors should be installed downwards and the rear strip deflectors upwards,thereby forming a“π”shape.Moreover,the lift force compensation provided by the wind deflectors increases with the size of the deflector.Alternative wind compensation strategies,such as control circuits,are also discussed,putting emphasis on the pros and cons of various pantograph types and wind compensation approaches.
基金Supported by the Key Project of Hunan Provincial Natural Science Foundation ( Grant No.05JJ20012)Supported by Project of Hunan Provincial Research Scheme(Grant No.05CK3034)
文摘Kilns are the key equipment in the metallurgy,architectural and chemistry industry. It is the statically indeterminate system with over load, large torque and multi-support. The kiln move axis warp resulting in that the load distribution is asymmetry, cause many mechanical failure and safe accidents and the interruption of the produce, which bring a great losses. Treating the distribution of the kiln load and the complexity of the stiffness change, the all-purpose model and matrix, used to solve the variable-stiffness beam upon complex load, are established in this paper. The resultant force of kiln in vertical and horizontal direction is calculated. Accordingly, the liner formulas for calculating the supporting force of the support wheels are obtained, and the wheel supporting force also can be easily obtained based on each shell warp. This will provide theory conference for safety management and rational maintenance.
基金supported by the National Natural Science Foundation of China(Grant No.51778575).
文摘The application of steel strut force servo systems in deep excavation engineering is not widespread,and there is a notable scarcity of in-situ measured datasets.This presents a significant research gap in the field.Addressing this,our study introduces a valuable dataset and application scenarios,serving as a reference point for future research.The main objective of this study is to use machine learning(ML)methods for accurately predicting strut forces in steel supporting structures,a crucial aspect for the safety and stability of deep excavation projects.We employed five different ML methods:radial basis function neural network(RBFNN),back propagation neural network(BPNN),K-Nearest Neighbor(KNN),support vector machine(SVM),and random forest(RF),utilizing a dataset of 2208 measured points.These points included one output parameter(strut forces)and seven input parameters(vertical position of strut,plane position of strut,time,temperature,unit weight,cohesion,and internal frictional angle).The effectiveness of these methods was assessed using root mean square error(RMSE),correlation coefficient(R),and mean absolute error(MAE).Our findings indicate that the BPNN method outperforms others,with RMSE,R,and MAE values of 72.1 kN,0.9931,and 57.4 kN,respectively,on the testing dataset.This study underscores the potential of ML methods in precisely predicting strut forces in deep excavation engineering,contributing to enhanced safety measures and project planning.
基金Supported by National Natural Science Foundation of China(Grant No.51475263)
文摘The current research on gear system dynamics mainly utilizes linear spring damping model to calculate the contact force between gears. However, this linear model cannot correctly describe the energy transfer process of collision that often occurs in gear system. Focus on the contact-impact events, this paper proposes an improved gear contact force model for dynamic analysis in helical gear transmission system. In this model, a new factor associated with hysteresis damping is developed for contact-impact state, whereas the traditional linear damping factor is utilized for normal meshing state. For determining the selection strategy of these two damping factors, the fundamental contact mechanics of contact-impact event a ected by supporting forces are analyzed. During this analysis, an e ect factor is proposed for evaluating the influence of supporting forces on collision. Meanwhile, a new restitution of coe cient is deduced for calculating hysteresis damping factor, which suitable for both separation and non-separation states at the end of collision. In addition, the time-varying meshing sti ness(TVMS) is obtained based on the potential energy approach and the slice theory. Finally, a dynamic analysis of a helical gear system is carried out to better understand the contact force model proposed in this paper. The analysis results show that the contribution of supporting forces to the dynamic response of contact-impact event within gear pair is important. The supporting forces and dissipative energy are the main reasons for gear system to enter a steady contact state from repeated contact-impact state. This research proposes an improved contact force model which distinguishes meshing and collision states in gear system.
基金supported by the National Natural Science Foundation of China(No.11674344)the National Basic Research Program of China(973 program,No.2013CB932801)the Key Research Program of Frontier Sciences,Chinese Academy of Sciences(No.QYZDJ-SSW-SLH019-2)
文摘A general method was developed for promoting peptide assembly and protein polymerization to form nanoscale patterns on various surfaces with an atomic force microscope(AFM) operated in a liquid. By scanning solid surfaces with an AFM tip, we showed that peptide monomers assemble at a higher rate in the tip-scanned area compared to other regions. The promotion is attributed to the mechanical force applied by the scanning tip. This kind of mechanical-force-promoted assembly was also observed with different peptides on various substrates. The force promoting peptide assembly provides a simple and practical solution for preparing and building peptide and protein architectures for future nanodevices.
