Cold-flow experiments on planar Expansion Deflection(ED)nozzle flows are conducted under a simulated startup-shutdown process of rocket motors.The purpose is to investigate the flow and performance characteristics in ...Cold-flow experiments on planar Expansion Deflection(ED)nozzle flows are conducted under a simulated startup-shutdown process of rocket motors.The purpose is to investigate the flow and performance characteristics in ED nozzles,capture the behavior of shock flapping,and explore asymmetric flow dynamics utilizing a symmetric nozzle.A total pressure condition,characterized by rapid rise followed by a slow fall,is employed to simulate the continuous startup and shutdown processes.The schlieren imaging technique and high-frequency pressure transducers are employed to obtain the flow information.The experimental results indicate that the flow characteristics differ between the startup and shutdown processes with a hysteresis observed in the nozzle wake mode transition.During the startup process,the shock waves are pushed outward of the nozzle,while during the shutdown process,the flow propagates inward dominated by Mach stems.Counterintuitive results are demonstrated,namely,the mode transition is not the cause of the sudden thrust decrease,and the moment of maximum thrust does not coincide with the moment of maximum total pressure.During the operation of the nozzle,two stages of shock wave flapping occur,accompanied by significant wall pressure oscillations.These oscillation frequencies are demonstrated to be related to the inherent acoustic frequencies of the test chamber.An improved pressure ratio method is proposed to predict the position of the shock oscillation separation point.The prediction results revealed the shock behavior during the flapping process.展开更多
This paper presents a deep learning architecture combined with exploratory data analysis to estimate maximum wall deflection in deep excavations.Six major geotechnical parameters were studied.Statistical methods,such ...This paper presents a deep learning architecture combined with exploratory data analysis to estimate maximum wall deflection in deep excavations.Six major geotechnical parameters were studied.Statistical methods,such as pair plots and Pearson correlation,highlighted excavation depth(correlation coefficient=0.82)as the most significant factor.For method prediction,five deep learning models(CNN,LSTM,BiLSTM,CNN-LSTM,and CNN-BiLSTM)were built.The CNN-BiLSTM model excelled in training performance(R^(2)=0.98,RMSE=0.02),while BiLSTM reached superior testing results(R^(2)=0.85,RMSE=0.06),suggesting greater generalization ability.Based on the feature importance analysis from model weights,excavation depth,stiffness ratio,and bracing spacing were ranked as the highest contributors.This point verified a lack of prediction bias on residual plots and high model agreement with measured values on Taylor diagrams(correlation coefficient 0.92).The effectiveness of integrated techniques was reliably assured for predicting wall deformation.This approach facilitates more accurate and efficient geotechnical design and provides engineers with improved tools for risk evaluation and decision-making in deep excavation projects.展开更多
The challenge of solving nonlinear problems in multi-connected domains with high accuracy has garnered significant interest.In this paper,we propose a unified wavelet solution method for accurately solving nonlinear b...The challenge of solving nonlinear problems in multi-connected domains with high accuracy has garnered significant interest.In this paper,we propose a unified wavelet solution method for accurately solving nonlinear boundary value problems on a two-dimensional(2D)arbitrary multi-connected domain.We apply this method to solve large deflection bending problems of complex plates with holes.Our solution method simplifies the treatment of the 2D multi-connected domain by utilizing a natural discretization approach that divides it into a series of one-dimensional(1D)intervals.This approach establishes a fundamental relationship between the highest-order derivative in the governing equation of the problem and the remaining lower-order derivatives.By combining a wavelet high accuracy integral approximation format on 1D intervals,where the convergence order remains constant regardless of the number of integration folds,with the collocation method,we obtain a system of algebraic equations that only includes discrete point values of the highest order derivative.In this process,the boundary conditions are automatically replaced using integration constants,eliminating the need for additional processing.Error estimation and numerical results demonstrate that the accuracy of this method is unaffected by the degree of nonlinearity of the equations.When solving the bending problem of multi-perforated complex-shaped plates under consideration,it is evident that directly using higher-order derivatives as unknown functions significantly improves the accuracy of stress calculation,even when the stress exhibits large gradient variations.Moreover,compared to the finite element method,the wavelet method requires significantly fewer nodes to achieve the same level of accuracy.Ultimately,the method achieves a sixth-order accuracy and resembles the treatment of one-dimensional problems during the solution process,effectively avoiding the need for the complex 2D meshing process typically required by conventional methods when solving problems with multi-connected domains.展开更多
In weak field limits,we compute the deflection angle of a gravitational decoupling extended black hole(BH)solution.We obtained the Gaussian optical curvature by examining the null geodesic equations with the help of G...In weak field limits,we compute the deflection angle of a gravitational decoupling extended black hole(BH)solution.We obtained the Gaussian optical curvature by examining the null geodesic equations with the help of Gauss-Bonnet theorem(GBT).We also looked into the deflection angle of light by a black hole in weak field limits with the use of the Gibbons-Werner method.We verify the graphical behavior of the black hole after determining the deflection angle of light.Additionally,in the presence of the plasma medium,we also determine the deflection angle of the light and examine its graphical behavior.Furthermore,we compute the Einstein ring via gravitational decoupling extended black hole solution.We also compute the quasi-periodic oscillations and discuss their graphical behavior.展开更多
An embedded cylinder is a large-diameter cylinder embedded in a soil foundation. The state of failure of such an embedded cylindrical structure shows large deflection instead of slide and overturn of the traditional g...An embedded cylinder is a large-diameter cylinder embedded in a soil foundation. The state of failure of such an embedded cylindrical structure shows large deflection instead of slide and overturn of the traditional gravity type of structure placed on a rubble base or foundation base. The critical value of deflection of the embedded cylindrical structure, which is the maximum allowable deflection for stability calculation of the cylinder, is a vital control value. Through investigation on deflection and soil pressures on an embedded cylinder by model experiments, the variations of the angle of rotation θ of a cylinder with effective anti-overturning ratio η and moment MH of thrust are discussed. On the basis of experimental study, the critical value of deflection of the cylindrical structure is proposed in the paper. Meanwhile, the formulas for calculating deflection of cylinders are derived.展开更多
Based on the equivalence principle of deflection and stress, the concentrated vehicle load which acts on the center of continuously reinforced concrete pavement （CRCP） is translated into the equivalent half-wave sin...Based on the equivalence principle of deflection and stress, the concentrated vehicle load which acts on the center of continuously reinforced concrete pavement （CRCP） is translated into the equivalent half-wave sine load by the Fourier transform. On the basis of this transform and the small deflection theory of elastic thin plates, the deflection and stress formulae of CRCP under the concentrated vehicle load with a hollow foundation are put forward. The sensitivity of parameters is analyzed. The results show that maximum deflection is directly proportional to the concentrated vehicle load and the slab width, and inversely proportional to the lateral bending stiffness and slab thickness. The effects of slab width and thickness are significant with regard to maximum deflection. Maximum stress is directly proportional to the concentrated vehicle load and the slab width as well as inversely proportional to slab thickness. The effect of slab thickness is significant with regard to maximum stress. According to the calculation results, the most effective measure to reduce maximum deflection and stress is to increase slab thickness.展开更多
To control the deflection of the gas plasma jet, a new analytical method is proposed based on the Magnetohydrodynamic(MHD) technique. Based on the typical MHD power generation model, the applied voltage is applied to ...To control the deflection of the gas plasma jet, a new analytical method is proposed based on the Magnetohydrodynamic(MHD) technique. Based on the typical MHD power generation model, the applied voltage is applied to the staggered electrodes, that is, a pair of electrodes on the same side wall are connected to generate an axial current in the channel. Under the action of the magnetic field perpendicular to the direction of the flow, the plasma is subjected to electromagnetic forces perpendicular to these two directions, and the jet is deflected. The computational model including the Navier-Stokes equations coupled with electromagnetic source terms, the electric potential equation and Ohm’s law is solved. The deflection of the gas jet under the action of an electromagnetic field is observed, and the maximum deflection angle is about 14.8°. The influences of the electric field, magnetic field, and conductivity on the jet deflection are studied. Results show that although the influences of these three factors on the deflection are similar, and the effect of increasing the electric field strength is slightly greater, priority should be given to increasing the magnetic field strength from the perspective of reducing energy consumption. The Stuart number is introduced to assess the ability of electromagnetic force to control jet deflection. When the electromagnetic parameters are constant, this solution provides better control of low-density and low-speed fluid flows. The calculation results show that using the staggered electrode method configuration is feasible in terms of controlling the deflection of a plasma jet deflection.展开更多
The deflection of the vertical reflects the mass distribution and density anomaly of celestial bodies. Lunar deflections of the vertical include directional information of the Moon’s gravity field. SGM90d, recovered ...The deflection of the vertical reflects the mass distribution and density anomaly of celestial bodies. Lunar deflections of the vertical include directional information of the Moon’s gravity field. SGM90d, recovered from SELENE mission, revealed the lunar far side gravity field for the first time in history owes to 4-way Doppler data. Lunar deflections of the vertical and their meridional and prime vertical components are calculated from SGM90d, and then their global distributions are also given in the paper. The gradients of lunar deflections of the vertical are defined and computed as well. The correlations between the lunar deflections of the vertical and the lunar terrain have been fully discussed. Many different characteristics of lunar deflections of vertical have been found between the near side and the far side of the Moon, which may be caused from the lithospheric compensation and the uplifting of mantle.展开更多
Deflection is the most direct indicator that reflects the bearing capacity of the bridge and the overall stiffness. There are many ways to measure the deflection of Bridges, and the inclination angle method is the mos...Deflection is the most direct indicator that reflects the bearing capacity of the bridge and the overall stiffness. There are many ways to measure the deflection of Bridges, and the inclination angle method is the most commonly used indirect method, but the existing theory of inclination angle method is relatively complicated. Based on the facts of the bridge small inclination, this article proposes the method of obtaining the bridge deflection by the inclination of the secant line constructed from the adjacent measurement points. Firstly, according to the bending deformation curve of general simply supported beam, the deflection calculation formula of each measuring point is derived based on the assumption of small deformation and the inclination Angle of measuring point. Secondly, a large commercial finite element software ANSYS 10.0 is used to carry out numerical simulation on the simply-supported beam under concentrated load in mid-span, and the deflection results of the numerical simulation are compared and verified with the theoretical results of the proposed method. Finally, the measured deflection results of the simply-supported beam model under mid-span load are compared with the theoretical results of the proposed method. The verification results show that if the actual model is consistent with the theoretical model, the proposed method has good accuracy.展开更多
This paper adopts the NGI-ADP soil model to carry out finite element analysis,based on which the effects of soft clay anisotropy on the diaphragm wall deflections in the braced excavation were evaluated.More than one ...This paper adopts the NGI-ADP soil model to carry out finite element analysis,based on which the effects of soft clay anisotropy on the diaphragm wall deflections in the braced excavation were evaluated.More than one thousand finite element cases were numerically analyzed,followed by extensive parametric studies.Surrogate models were developed via ensemble learning methods(ELMs),including the e Xtreme Gradient Boosting(XGBoost),and Random Forest Regression(RFR)to predict the maximum lateral wall deformation(δhmax).Then the results of ELMs were compared with conventional soft computing methods such as Decision Tree Regression(DTR),Multilayer Perceptron Regression(MLPR),and Multivariate Adaptive Regression Splines(MARS).This study presents a cutting-edge application of ensemble learning in geotechnical engineering and a reasonable methodology that allows engineers to determine the wall deflection in a fast,alternative way.展开更多
Electro-hydraulic servo-valves are widely used components in the mechanical industry,aerospace and aerodynamic devices which precisely control the airplane or missile wings.Due to the small size and complex structure ...Electro-hydraulic servo-valves are widely used components in the mechanical industry,aerospace and aerodynamic devices which precisely control the airplane or missile wings.Due to the small size and complex structure in the pilot stage of deflection flapper servo-valves,accurate mathematical models for the flow and pressure characteristics have always been very difficult to be built.In this paper,mathematical models for the pilot stage of deflection flapper servo-valve are investigated to overcome some gaps between the theoretical formulation and overall performance of the valve by considering different flow states.Here,a mathematical model of the velocity distribution at the flapper groove exit is established by using Schlichting velocity equations for incompressible laminar fluid flow.Moreover,when the flow becomes turbulent,a mathematical model of pressure characteristics in the receiving ports is built on the basis of the assumption of the collision between the liquid and the jet as the impact of the jet on a moving block of fluid particles.To verify the analytical models for both laminar and turbulent flows,the pressure characteristics of the deflection flapper pilot stage are calculated and tested by using numerical simulation and experiment.Experimental verification of the theory is also presented.The computed numerical and analytical results show a good agreement with experimental data.展开更多
Distributed X-ray sources comprise a single vacuum chamber containing multiple X-ray sources that are triggered and emit X-rays at a specific time and location. This process facilitates an application for innovative s...Distributed X-ray sources comprise a single vacuum chamber containing multiple X-ray sources that are triggered and emit X-rays at a specific time and location. This process facilitates an application for innovative system concepts in X-ray and computer tomography. This paper proposes a novel electron beam focusing, shaping,and deflection electron gun for distributed X-ray sources.The electron gun uses a dispenser cathode as an electron emitter, a mesh grid to control emission current, and two electrostatic lenses for beam shaping, focusing, and deflection. Novel focusing and deflecting electrodes were designed to increase the number of focal spots in the distributed source. Two identical half-rectangle opening electrodes are controlled by adjusting the potential of the two electrodes to control the electron beam trajectory, and then, multifocal spots are obtained on the anode target. The electron gun can increase the spatial density of the distributed X-ray sources, thereby improving the image quality. The beam experimental results show that the focal spot sizes of the deflected(deflected amplitude 10.5 mm)and non-deflected electron beams at full width at half maximum are 0.80 mm 90.50 mm and 0.55 mm 90.40 mm, respectively(anode voltage 160 kV; beam current 30 mA). The imaging experimental results demonstrate the excellent spatial resolution and time resolution of an imaging system built with the sources, which has an excellent imaging effect on a field-programmable gate array chip and a rotating metal disk.展开更多
This study presents an electromechanical engineering model for the analysis of the large deflection curves of ionic polymer-metal composite(IPMC)cantilever actuators under direct current(DC)voltages.In this paper,the ...This study presents an electromechanical engineering model for the analysis of the large deflection curves of ionic polymer-metal composite(IPMC)cantilever actuators under direct current(DC)voltages.In this paper,the longitudinal normal strain performance of the material was investigated using digital image correlation on a micro-scale.The deflection of the actuator is analytically obtained with the application of an elliptic integration method based on the relationship between strain gradient and excitation voltage,and the minimum excitation voltage is derived based on the assumption that the actuators have small deformations.The validity of the electromechanical model is then justified with the experimental results obtained from Pt-and Ag-IPMC actuators at various excitation voltages.The findings of this study confirm that the introduced electromechanical model can accurately describe the large nonlinear deflection behavior of IPMC actuators.展开更多
In practical application, it is very important to master the influence of structure parameters on the mid-span deflection quantificationally. For large-span and heavy-duty gantry cranes, the influence of the rigid leg...In practical application, it is very important to master the influence of structure parameters on the mid-span deflection quantificationally. For large-span and heavy-duty gantry cranes, the influence of the rigid leg and the soft leg on mid-span deflection has not been considered in the past. In the paper, the mathematical model is established for universal large-span and heavy-duty gantry cranes. The analytical solution for the mid-span deflection of gantry-frame structure girder is derived and obtained based on the variation principle by considering the coupling effect of the bending moments of girder and legs, the axial force and the secondary bending moments. The relation between the load and the deflection on the mid-span of the gantry-frame structure girder is known. Then, the experimental model is designed according to dimensional analysis method. And experiments were performed on the WEW-600 B type testing machine. Hackling experimental data, the regular of the load and deflection on the girder mid-span is obtained, namely, the deformation of the gantry-frame structure resists the external load to do work. The validity of the nonlinear analytical solution of the girder deflection is verified. Experimental results show that the analytical solution of the gantry-frame structure deflection has much higher calculation accuracy than previous calculation method. This work provides a theoretical basis for the design and inspection of gantry-frame structures.展开更多
Deep excavation during the construction of underground systems can cause movement on the ground,especially in soft clay layers.At high levels,excessive ground movements can lead to severe damage to adjacent structures...Deep excavation during the construction of underground systems can cause movement on the ground,especially in soft clay layers.At high levels,excessive ground movements can lead to severe damage to adjacent structures.In this study,finite element analyses(FEM)and the hardening small strain(HSS)model were performed to investigate the deflection of the diaphragm wall in the soft clay layer induced by braced excavations.Different geometric and mechanical properties of the wall were investigated to study the deflection behavior of the wall in soft clays.Accordingly,1090 hypothetical cases were surveyed and simulated based on the HSS model and FEM to evaluate the wall deflection behavior.The results were then used to develop an intelligent model for predicting wall deflection using the functional linked neural network(FLNN)with different functional expansions and activation functions.Although the FLNN is a novel approach to predict wall deflection;however,in order to improve the accuracy of the FLNN model in predicting wall deflection,three swarm-based optimization algorithms,such as artificial bee colony(ABC),Harris’s hawk’s optimization(HHO),and hunger games search(HGS),were hybridized to the FLNN model to generate three novel intelligent models,namely ABC-FLNN,HHO-FLNN,HGS-FLNN.The results of the hybrid models were then compared with the basic FLNN and MLP models.They revealed that FLNN is a good solution for predicting wall deflection,and the application of different functional expansions and activation functions has a significant effect on the outcome predictions of the wall deflection.It is remarkably interesting that the performance of the FLNN model was better than the MLP model with a mean absolute error(MAE)of 19.971,root-mean-squared error(RMSE)of 24.574,and determination coefficient(R^(2))of 0.878.Meanwhile,the performance of the MLP model only obtained an MAE of 20.321,RMSE of 27.091,and R^(2)of 0.851.Furthermore,the results also indicated that the proposed hybrid models,i.e.,ABC-FLNN,HHO-FLNN,HGS-FLNN,yielded more superior performances than those of the FLNN and MLP models in terms of the prediction of deflection behavior of diaphragm walls with an MAE in the range of 11.877 to 12.239,RMSE in the range of 15.821 to 16.045,and R^(2)in the range of 0.949 to 0.951.They can be used as an alternative tool to simulate diaphragm wall deflections under different conditions with a high degree of accuracy.展开更多
A perforation model is developed to predict the attitude deflection in the oblique perforation of concrete targets by a rigid projectile,in which the inertial moment of the projectile is introduced,together with takin...A perforation model is developed to predict the attitude deflection in the oblique perforation of concrete targets by a rigid projectile,in which the inertial moment of the projectile is introduced,together with taking the attitude deflection during the shear plugging sub-stage into account,and the shape of the plug formed on the rear surface of target is also re-investigated.Moreover,a new classification of concrete targets is proposed based on the target thickness,with which the attitude deflections in different kinds of concrete targets are analyzed.It is found that the numerical results by using the new perforation model are in good agreement with the previous experimental data and simulated results.Furthermore,the variations of the attitude deflection with the initial conditions(the initial attitude angle and the initial impact velocity) are investigated.展开更多
In flatness measuring system, the flatness measuring signal can be affected by the deflection of flatness measuring roll. The stress on flatness measuring roll was analyzed and a deflection model for the flatness meas...In flatness measuring system, the flatness measuring signal can be affected by the deflection of flatness measuring roll. The stress on flatness measuring roll was analyzed and a deflection model for the flatness measuring roll was obtained by using the influence function method. The model was developed on the basis of the deformation of flatness measuring roll in roiling process and compensation curve was obtained. The results indicated that the set curve of flatness is in good agreement with the online measured curve of flatness, and good strip flatness can be obtained.展开更多
Since its first introduction to the industry the control systems of electron beam machines have gone through an enormous evolution.With the availability of fast amplifier components and digital beam controllers the ad...Since its first introduction to the industry the control systems of electron beam machines have gone through an enormous evolution.With the availability of fast amplifier components and digital beam controllers the advantages of the electron beam have further increased making it a truly software controlled thermal processing tool.Modern beam controllers enable multi-beam and multi-focus technologies,where the beam is split in up to 60 individual beams.These technologies can reduce the processing time by parallel processing or improve the quality by optimized thermal expansion of the part.Multi-process technologies,where several processes are performed in one run (e.g.welding and cosmetic treatment) further extend the application range of the electron beam process.Fast beam deflection in conjunction with electron-optical monitoring is the fundamental component for advanced seam tracking systems.They allow automating the EB application in order to optimize the process costs and improve the quality of the re-sults in a reproducible manner.Basis for a high quality of the EB process is the condition of the tool,the electron beam itself.By in-troducing the beam parameter product to the electron beam,reliable information about the quality of the beam can be derived.Im-plemented into automatic beam alignment systems repeatable results with high quality are achieved.展开更多
Based on the three-phase model, the propagation behavior of a matrix crack in an intelligent coating system is investigated by an energy criterion. The effect of the elastic mismatch parameters and the thickness of th...Based on the three-phase model, the propagation behavior of a matrix crack in an intelligent coating system is investigated by an energy criterion. The effect of the elastic mismatch parameters and the thickness of the interface layer on the ratio of the energy release rate for infinitesimal deflected and penetrated crack is evaluated with the finite element method. The results show that the ratio of the energy release rates strongly depends on the elastic mismatch al between the substrate and the driving layer. It also strongly depends on the elastic mismatch a2 between the driving layer and the sensing layer for a thinner driving layer when a primary crack reaches an interface between the substrate and the driving layer. Moreover, with the increase in the thickness of the driving layer, the dependence on a2 gradually decreases. The experimental observation on aluminum alloys monitored with intelligent coating shows that the established model can better explain the behavior of matrix crack penetration and can be used in optimization design of intelligent coating.展开更多
For decades,nacre has inspired researchers because of its sophisticated hierarchical structure and remarkable mechanical properties,especially its extreme fracture toughness compared with that of its predominant const...For decades,nacre has inspired researchers because of its sophisticated hierarchical structure and remarkable mechanical properties,especially its extreme fracture toughness compared with that of its predominant constituent,CaCO_(3),in the form of aragonite.Crack deflection has been extensively reported and regarded as the principal toughening mechanism for nacre.In this paper,our attention is focused on crack evolution in nacre under a quasi-static state.We use the notched three-point bending test of dehydrated nacre in situ in a scanning electron microscope(SEM)to monitor the evolution of damage mechanisms ahead of the crack tip.The observations show that the crack deflection actually occurs by constrained microcracking.On the basis of our findings,a crack propagation model is proposed,which will contribute to uncovering the underlying mechanisms of nacre’s fracture toughness and its damage evolution.These investigations would be of great value to the design and synthesis of novel biomimetic materials.展开更多
基金supported by the National Natural Science Foundation of China(No.12002102)。
文摘Cold-flow experiments on planar Expansion Deflection(ED)nozzle flows are conducted under a simulated startup-shutdown process of rocket motors.The purpose is to investigate the flow and performance characteristics in ED nozzles,capture the behavior of shock flapping,and explore asymmetric flow dynamics utilizing a symmetric nozzle.A total pressure condition,characterized by rapid rise followed by a slow fall,is employed to simulate the continuous startup and shutdown processes.The schlieren imaging technique and high-frequency pressure transducers are employed to obtain the flow information.The experimental results indicate that the flow characteristics differ between the startup and shutdown processes with a hysteresis observed in the nozzle wake mode transition.During the startup process,the shock waves are pushed outward of the nozzle,while during the shutdown process,the flow propagates inward dominated by Mach stems.Counterintuitive results are demonstrated,namely,the mode transition is not the cause of the sudden thrust decrease,and the moment of maximum thrust does not coincide with the moment of maximum total pressure.During the operation of the nozzle,two stages of shock wave flapping occur,accompanied by significant wall pressure oscillations.These oscillation frequencies are demonstrated to be related to the inherent acoustic frequencies of the test chamber.An improved pressure ratio method is proposed to predict the position of the shock oscillation separation point.The prediction results revealed the shock behavior during the flapping process.
文摘This paper presents a deep learning architecture combined with exploratory data analysis to estimate maximum wall deflection in deep excavations.Six major geotechnical parameters were studied.Statistical methods,such as pair plots and Pearson correlation,highlighted excavation depth(correlation coefficient=0.82)as the most significant factor.For method prediction,five deep learning models(CNN,LSTM,BiLSTM,CNN-LSTM,and CNN-BiLSTM)were built.The CNN-BiLSTM model excelled in training performance(R^(2)=0.98,RMSE=0.02),while BiLSTM reached superior testing results(R^(2)=0.85,RMSE=0.06),suggesting greater generalization ability.Based on the feature importance analysis from model weights,excavation depth,stiffness ratio,and bracing spacing were ranked as the highest contributors.This point verified a lack of prediction bias on residual plots and high model agreement with measured values on Taylor diagrams(correlation coefficient 0.92).The effectiveness of integrated techniques was reliably assured for predicting wall deformation.This approach facilitates more accurate and efficient geotechnical design and provides engineers with improved tools for risk evaluation and decision-making in deep excavation projects.
基金supported by the National Natural Science Foundation of China(Grant No.11925204).
文摘The challenge of solving nonlinear problems in multi-connected domains with high accuracy has garnered significant interest.In this paper,we propose a unified wavelet solution method for accurately solving nonlinear boundary value problems on a two-dimensional(2D)arbitrary multi-connected domain.We apply this method to solve large deflection bending problems of complex plates with holes.Our solution method simplifies the treatment of the 2D multi-connected domain by utilizing a natural discretization approach that divides it into a series of one-dimensional(1D)intervals.This approach establishes a fundamental relationship between the highest-order derivative in the governing equation of the problem and the remaining lower-order derivatives.By combining a wavelet high accuracy integral approximation format on 1D intervals,where the convergence order remains constant regardless of the number of integration folds,with the collocation method,we obtain a system of algebraic equations that only includes discrete point values of the highest order derivative.In this process,the boundary conditions are automatically replaced using integration constants,eliminating the need for additional processing.Error estimation and numerical results demonstrate that the accuracy of this method is unaffected by the degree of nonlinearity of the equations.When solving the bending problem of multi-perforated complex-shaped plates under consideration,it is evident that directly using higher-order derivatives as unknown functions significantly improves the accuracy of stress calculation,even when the stress exhibits large gradient variations.Moreover,compared to the finite element method,the wavelet method requires significantly fewer nodes to achieve the same level of accuracy.Ultimately,the method achieves a sixth-order accuracy and resembles the treatment of one-dimensional problems during the solution process,effectively avoiding the need for the complex 2D meshing process typically required by conventional methods when solving problems with multi-connected domains.
基金funded by the National Natural Science Foundation of China under Grant No.11975145。
文摘In weak field limits,we compute the deflection angle of a gravitational decoupling extended black hole(BH)solution.We obtained the Gaussian optical curvature by examining the null geodesic equations with the help of Gauss-Bonnet theorem(GBT).We also looked into the deflection angle of light by a black hole in weak field limits with the use of the Gibbons-Werner method.We verify the graphical behavior of the black hole after determining the deflection angle of light.Additionally,in the presence of the plasma medium,we also determine the deflection angle of the light and examine its graphical behavior.Furthermore,we compute the Einstein ring via gravitational decoupling extended black hole solution.We also compute the quasi-periodic oscillations and discuss their graphical behavior.
文摘An embedded cylinder is a large-diameter cylinder embedded in a soil foundation. The state of failure of such an embedded cylindrical structure shows large deflection instead of slide and overturn of the traditional gravity type of structure placed on a rubble base or foundation base. The critical value of deflection of the embedded cylindrical structure, which is the maximum allowable deflection for stability calculation of the cylinder, is a vital control value. Through investigation on deflection and soil pressures on an embedded cylinder by model experiments, the variations of the angle of rotation θ of a cylinder with effective anti-overturning ratio η and moment MH of thrust are discussed. On the basis of experimental study, the critical value of deflection of the cylindrical structure is proposed in the paper. Meanwhile, the formulas for calculating deflection of cylinders are derived.
基金The Science Foundation of Ministry of Transport of the People's Republic of China(No.200731822301-7)
文摘Based on the equivalence principle of deflection and stress, the concentrated vehicle load which acts on the center of continuously reinforced concrete pavement （CRCP） is translated into the equivalent half-wave sine load by the Fourier transform. On the basis of this transform and the small deflection theory of elastic thin plates, the deflection and stress formulae of CRCP under the concentrated vehicle load with a hollow foundation are put forward. The sensitivity of parameters is analyzed. The results show that maximum deflection is directly proportional to the concentrated vehicle load and the slab width, and inversely proportional to the lateral bending stiffness and slab thickness. The effects of slab width and thickness are significant with regard to maximum deflection. Maximum stress is directly proportional to the concentrated vehicle load and the slab width as well as inversely proportional to slab thickness. The effect of slab thickness is significant with regard to maximum stress. According to the calculation results, the most effective measure to reduce maximum deflection and stress is to increase slab thickness.
文摘To control the deflection of the gas plasma jet, a new analytical method is proposed based on the Magnetohydrodynamic(MHD) technique. Based on the typical MHD power generation model, the applied voltage is applied to the staggered electrodes, that is, a pair of electrodes on the same side wall are connected to generate an axial current in the channel. Under the action of the magnetic field perpendicular to the direction of the flow, the plasma is subjected to electromagnetic forces perpendicular to these two directions, and the jet is deflected. The computational model including the Navier-Stokes equations coupled with electromagnetic source terms, the electric potential equation and Ohm’s law is solved. The deflection of the gas jet under the action of an electromagnetic field is observed, and the maximum deflection angle is about 14.8°. The influences of the electric field, magnetic field, and conductivity on the jet deflection are studied. Results show that although the influences of these three factors on the deflection are similar, and the effect of increasing the electric field strength is slightly greater, priority should be given to increasing the magnetic field strength from the perspective of reducing energy consumption. The Stuart number is introduced to assess the ability of electromagnetic force to control jet deflection. When the electromagnetic parameters are constant, this solution provides better control of low-density and low-speed fluid flows. The calculation results show that using the staggered electrode method configuration is feasible in terms of controlling the deflection of a plasma jet deflection.
文摘The deflection of the vertical reflects the mass distribution and density anomaly of celestial bodies. Lunar deflections of the vertical include directional information of the Moon’s gravity field. SGM90d, recovered from SELENE mission, revealed the lunar far side gravity field for the first time in history owes to 4-way Doppler data. Lunar deflections of the vertical and their meridional and prime vertical components are calculated from SGM90d, and then their global distributions are also given in the paper. The gradients of lunar deflections of the vertical are defined and computed as well. The correlations between the lunar deflections of the vertical and the lunar terrain have been fully discussed. Many different characteristics of lunar deflections of vertical have been found between the near side and the far side of the Moon, which may be caused from the lithospheric compensation and the uplifting of mantle.
文摘Deflection is the most direct indicator that reflects the bearing capacity of the bridge and the overall stiffness. There are many ways to measure the deflection of Bridges, and the inclination angle method is the most commonly used indirect method, but the existing theory of inclination angle method is relatively complicated. Based on the facts of the bridge small inclination, this article proposes the method of obtaining the bridge deflection by the inclination of the secant line constructed from the adjacent measurement points. Firstly, according to the bending deformation curve of general simply supported beam, the deflection calculation formula of each measuring point is derived based on the assumption of small deformation and the inclination Angle of measuring point. Secondly, a large commercial finite element software ANSYS 10.0 is used to carry out numerical simulation on the simply-supported beam under concentrated load in mid-span, and the deflection results of the numerical simulation are compared and verified with the theoretical results of the proposed method. Finally, the measured deflection results of the simply-supported beam model under mid-span load are compared with the theoretical results of the proposed method. The verification results show that if the actual model is consistent with the theoretical model, the proposed method has good accuracy.
基金supported by the High-end Foreign Expert Introduction program(No.G20190022002)Chongqing Construction Science and Technology Plan Project(2019-0045)+1 种基金the Science and Technology Research Program of Chongqing Municipal Education Commission(Grant No.KJZD-K201900102)The financial support is gratefully acknowledged。
文摘This paper adopts the NGI-ADP soil model to carry out finite element analysis,based on which the effects of soft clay anisotropy on the diaphragm wall deflections in the braced excavation were evaluated.More than one thousand finite element cases were numerically analyzed,followed by extensive parametric studies.Surrogate models were developed via ensemble learning methods(ELMs),including the e Xtreme Gradient Boosting(XGBoost),and Random Forest Regression(RFR)to predict the maximum lateral wall deformation(δhmax).Then the results of ELMs were compared with conventional soft computing methods such as Decision Tree Regression(DTR),Multilayer Perceptron Regression(MLPR),and Multivariate Adaptive Regression Splines(MARS).This study presents a cutting-edge application of ensemble learning in geotechnical engineering and a reasonable methodology that allows engineers to determine the wall deflection in a fast,alternative way.
基金The National Natural Science Foundation of China(No.51675119)。
文摘Electro-hydraulic servo-valves are widely used components in the mechanical industry,aerospace and aerodynamic devices which precisely control the airplane or missile wings.Due to the small size and complex structure in the pilot stage of deflection flapper servo-valves,accurate mathematical models for the flow and pressure characteristics have always been very difficult to be built.In this paper,mathematical models for the pilot stage of deflection flapper servo-valve are investigated to overcome some gaps between the theoretical formulation and overall performance of the valve by considering different flow states.Here,a mathematical model of the velocity distribution at the flapper groove exit is established by using Schlichting velocity equations for incompressible laminar fluid flow.Moreover,when the flow becomes turbulent,a mathematical model of pressure characteristics in the receiving ports is built on the basis of the assumption of the collision between the liquid and the jet as the impact of the jet on a moving block of fluid particles.To verify the analytical models for both laminar and turbulent flows,the pressure characteristics of the deflection flapper pilot stage are calculated and tested by using numerical simulation and experiment.Experimental verification of the theory is also presented.The computed numerical and analytical results show a good agreement with experimental data.
文摘Distributed X-ray sources comprise a single vacuum chamber containing multiple X-ray sources that are triggered and emit X-rays at a specific time and location. This process facilitates an application for innovative system concepts in X-ray and computer tomography. This paper proposes a novel electron beam focusing, shaping,and deflection electron gun for distributed X-ray sources.The electron gun uses a dispenser cathode as an electron emitter, a mesh grid to control emission current, and two electrostatic lenses for beam shaping, focusing, and deflection. Novel focusing and deflecting electrodes were designed to increase the number of focal spots in the distributed source. Two identical half-rectangle opening electrodes are controlled by adjusting the potential of the two electrodes to control the electron beam trajectory, and then, multifocal spots are obtained on the anode target. The electron gun can increase the spatial density of the distributed X-ray sources, thereby improving the image quality. The beam experimental results show that the focal spot sizes of the deflected(deflected amplitude 10.5 mm)and non-deflected electron beams at full width at half maximum are 0.80 mm 90.50 mm and 0.55 mm 90.40 mm, respectively(anode voltage 160 kV; beam current 30 mA). The imaging experimental results demonstrate the excellent spatial resolution and time resolution of an imaging system built with the sources, which has an excellent imaging effect on a field-programmable gate array chip and a rotating metal disk.
基金This work was supported by the National Natural Science Foundation of China(Grants 11372132 and 11502109).
文摘This study presents an electromechanical engineering model for the analysis of the large deflection curves of ionic polymer-metal composite(IPMC)cantilever actuators under direct current(DC)voltages.In this paper,the longitudinal normal strain performance of the material was investigated using digital image correlation on a micro-scale.The deflection of the actuator is analytically obtained with the application of an elliptic integration method based on the relationship between strain gradient and excitation voltage,and the minimum excitation voltage is derived based on the assumption that the actuators have small deformations.The validity of the electromechanical model is then justified with the experimental results obtained from Pt-and Ag-IPMC actuators at various excitation voltages.The findings of this study confirm that the introduced electromechanical model can accurately describe the large nonlinear deflection behavior of IPMC actuators.
基金Project(51175442)supported by the National Natural Science Foundation of ChinaProject(QD2012A09)supported by Teachers’College Research Project,ChinaProject(14ZA0263)supported by Research Project of Sichuan Provincial Department of Education,China
文摘In practical application, it is very important to master the influence of structure parameters on the mid-span deflection quantificationally. For large-span and heavy-duty gantry cranes, the influence of the rigid leg and the soft leg on mid-span deflection has not been considered in the past. In the paper, the mathematical model is established for universal large-span and heavy-duty gantry cranes. The analytical solution for the mid-span deflection of gantry-frame structure girder is derived and obtained based on the variation principle by considering the coupling effect of the bending moments of girder and legs, the axial force and the secondary bending moments. The relation between the load and the deflection on the mid-span of the gantry-frame structure girder is known. Then, the experimental model is designed according to dimensional analysis method. And experiments were performed on the WEW-600 B type testing machine. Hackling experimental data, the regular of the load and deflection on the girder mid-span is obtained, namely, the deformation of the gantry-frame structure resists the external load to do work. The validity of the nonlinear analytical solution of the girder deflection is verified. Experimental results show that the analytical solution of the gantry-frame structure deflection has much higher calculation accuracy than previous calculation method. This work provides a theoretical basis for the design and inspection of gantry-frame structures.
基金financially supported by the Natural Science Foundation of Hunan Province(2021JJ30679)。
文摘Deep excavation during the construction of underground systems can cause movement on the ground,especially in soft clay layers.At high levels,excessive ground movements can lead to severe damage to adjacent structures.In this study,finite element analyses(FEM)and the hardening small strain(HSS)model were performed to investigate the deflection of the diaphragm wall in the soft clay layer induced by braced excavations.Different geometric and mechanical properties of the wall were investigated to study the deflection behavior of the wall in soft clays.Accordingly,1090 hypothetical cases were surveyed and simulated based on the HSS model and FEM to evaluate the wall deflection behavior.The results were then used to develop an intelligent model for predicting wall deflection using the functional linked neural network(FLNN)with different functional expansions and activation functions.Although the FLNN is a novel approach to predict wall deflection;however,in order to improve the accuracy of the FLNN model in predicting wall deflection,three swarm-based optimization algorithms,such as artificial bee colony(ABC),Harris’s hawk’s optimization(HHO),and hunger games search(HGS),were hybridized to the FLNN model to generate three novel intelligent models,namely ABC-FLNN,HHO-FLNN,HGS-FLNN.The results of the hybrid models were then compared with the basic FLNN and MLP models.They revealed that FLNN is a good solution for predicting wall deflection,and the application of different functional expansions and activation functions has a significant effect on the outcome predictions of the wall deflection.It is remarkably interesting that the performance of the FLNN model was better than the MLP model with a mean absolute error(MAE)of 19.971,root-mean-squared error(RMSE)of 24.574,and determination coefficient(R^(2))of 0.878.Meanwhile,the performance of the MLP model only obtained an MAE of 20.321,RMSE of 27.091,and R^(2)of 0.851.Furthermore,the results also indicated that the proposed hybrid models,i.e.,ABC-FLNN,HHO-FLNN,HGS-FLNN,yielded more superior performances than those of the FLNN and MLP models in terms of the prediction of deflection behavior of diaphragm walls with an MAE in the range of 11.877 to 12.239,RMSE in the range of 15.821 to 16.045,and R^(2)in the range of 0.949 to 0.951.They can be used as an alternative tool to simulate diaphragm wall deflections under different conditions with a high degree of accuracy.
基金This work was supported by the National Natural Science Foundation of China[grant numbers 11521062].
文摘A perforation model is developed to predict the attitude deflection in the oblique perforation of concrete targets by a rigid projectile,in which the inertial moment of the projectile is introduced,together with taking the attitude deflection during the shear plugging sub-stage into account,and the shape of the plug formed on the rear surface of target is also re-investigated.Moreover,a new classification of concrete targets is proposed based on the target thickness,with which the attitude deflections in different kinds of concrete targets are analyzed.It is found that the numerical results by using the new perforation model are in good agreement with the previous experimental data and simulated results.Furthermore,the variations of the attitude deflection with the initial conditions(the initial attitude angle and the initial impact velocity) are investigated.
基金Item Sponsored by National Natural Science Foundation of China(50534020)
文摘In flatness measuring system, the flatness measuring signal can be affected by the deflection of flatness measuring roll. The stress on flatness measuring roll was analyzed and a deflection model for the flatness measuring roll was obtained by using the influence function method. The model was developed on the basis of the deformation of flatness measuring roll in roiling process and compensation curve was obtained. The results indicated that the set curve of flatness is in good agreement with the online measured curve of flatness, and good strip flatness can be obtained.
文摘Since its first introduction to the industry the control systems of electron beam machines have gone through an enormous evolution.With the availability of fast amplifier components and digital beam controllers the advantages of the electron beam have further increased making it a truly software controlled thermal processing tool.Modern beam controllers enable multi-beam and multi-focus technologies,where the beam is split in up to 60 individual beams.These technologies can reduce the processing time by parallel processing or improve the quality by optimized thermal expansion of the part.Multi-process technologies,where several processes are performed in one run (e.g.welding and cosmetic treatment) further extend the application range of the electron beam process.Fast beam deflection in conjunction with electron-optical monitoring is the fundamental component for advanced seam tracking systems.They allow automating the EB application in order to optimize the process costs and improve the quality of the re-sults in a reproducible manner.Basis for a high quality of the EB process is the condition of the tool,the electron beam itself.By in-troducing the beam parameter product to the electron beam,reliable information about the quality of the beam can be derived.Im-plemented into automatic beam alignment systems repeatable results with high quality are achieved.
基金Project supported by the National Natural Science Foundation of China(No.51175404)
文摘Based on the three-phase model, the propagation behavior of a matrix crack in an intelligent coating system is investigated by an energy criterion. The effect of the elastic mismatch parameters and the thickness of the interface layer on the ratio of the energy release rate for infinitesimal deflected and penetrated crack is evaluated with the finite element method. The results show that the ratio of the energy release rates strongly depends on the elastic mismatch al between the substrate and the driving layer. It also strongly depends on the elastic mismatch a2 between the driving layer and the sensing layer for a thinner driving layer when a primary crack reaches an interface between the substrate and the driving layer. Moreover, with the increase in the thickness of the driving layer, the dependence on a2 gradually decreases. The experimental observation on aluminum alloys monitored with intelligent coating shows that the established model can better explain the behavior of matrix crack penetration and can be used in optimization design of intelligent coating.
基金supported by the National Natural Science Foundation of China(Grants 91216108,11432014,11672301,11372318,and 11502273)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant XDB22040501)
文摘For decades,nacre has inspired researchers because of its sophisticated hierarchical structure and remarkable mechanical properties,especially its extreme fracture toughness compared with that of its predominant constituent,CaCO_(3),in the form of aragonite.Crack deflection has been extensively reported and regarded as the principal toughening mechanism for nacre.In this paper,our attention is focused on crack evolution in nacre under a quasi-static state.We use the notched three-point bending test of dehydrated nacre in situ in a scanning electron microscope(SEM)to monitor the evolution of damage mechanisms ahead of the crack tip.The observations show that the crack deflection actually occurs by constrained microcracking.On the basis of our findings,a crack propagation model is proposed,which will contribute to uncovering the underlying mechanisms of nacre’s fracture toughness and its damage evolution.These investigations would be of great value to the design and synthesis of novel biomimetic materials.
