Dear Editor,This letter investigates predefined-time optimization problems(OPs) of multi-agent systems(MASs), where the agent of MASs is subject to inequality constraints, and the team objective function accounts for ...Dear Editor,This letter investigates predefined-time optimization problems(OPs) of multi-agent systems(MASs), where the agent of MASs is subject to inequality constraints, and the team objective function accounts for impulse effects. Firstly, to address the inequality constraints,the penalty method is introduced. Then, a novel optimization strategy is developed, which only requires that the team objective function be strongly convex.展开更多
To overcome external environmental disturbances,inertial parameter uncertainties and vibration of flexible modes in the process of attitude tracking,a comprehensively effective predefined-time guaranteed performance c...To overcome external environmental disturbances,inertial parameter uncertainties and vibration of flexible modes in the process of attitude tracking,a comprehensively effective predefined-time guaranteed performance controller based on multi⁃observers for flexible spacecraft is proposed.First,to prevent unwinding phenomenon in attitude description,the rotation matrix is used to represent the spacecraft’s attitude.Second,the flexible modes observer which can guarantee predefined⁃time convergence is designed,for the case where flexible vibrations are unmeasurable in practice.What’s more,the disturbance observer is applied to estimate and compensate the lumped disturbances to improve the robustness of attitude control.A predefined-time controller is proposed to satisfy the prescribed performance and stabilize the attitude tracking system via barrier Lyapunov function.Finally,through comparative numerical simulations,the proposed controller can achieve high-precision convergence compared with the existing finite-time attitude tracking controller.This paper provides certain references for the high-precision predefined-time prescribed performance attitude tracking of flexible spacecraft with multi-disturbance.展开更多
There are always large-scale items in the maintenances schedule of aircraft system, many of which have been fixed to be done in predefined sequences, which leads the workflow to be sys-tematically complex and makes th...There are always large-scale items in the maintenances schedule of aircraft system, many of which have been fixed to be done in predefined sequences, which leads the workflow to be sys-tematically complex and makes this kind of problem quite different from all sorts of existing job-selection modes. On the other hand, the human resources are always limited and men have different working capabilities on different items, which make the allocation operation of human resources be much roomy. However, the final total time span of maintenance is often required to be as short as possible in many practices, in order to suffer only the lowest cost of loss while the system is stopping. A new model for op-timizing the allocation if aircraft maintenance human resources with the constraint of predefined sequence is presented. The ge-netic algorithm is employed to find the optimal solution that holds the shortest total time span of maintenance. To generate the ul-timate maintenance work items and the human resource array, the sequences among all maintenance work items are considered firstly, the work item array is then generated through traversal with the constraint of maintenance sequence matrix, and the human resources are finally allocated according to the work item array with the constraint of the maintenance capability. An example is demonstrated to show that the model and algorithm behave a satisfying performance on finding the optimal solution as expected.展开更多
A non-orthogonal predefined exponential basis set is used to handle half-bounded domains in multi domain spectral method (MDSM). This approach works extremely well for real-valued semi-infinite differential problems. ...A non-orthogonal predefined exponential basis set is used to handle half-bounded domains in multi domain spectral method (MDSM). This approach works extremely well for real-valued semi-infinite differential problems. It spans simultaneously wide range of exponential decay rates with multi scaling and does not suffer from zero crossing. These two conditions are necessary for many physical problems. For comparison, the method is used to solve different problems and compared with analytical and published results. The comparison exhibits the strengths and accuracy of the presented basis set.展开更多
This paper addresses the design of an exponential function-based learning law for artificial neural networks(ANNs)with continuous dynamics.The ANN structure is used to obtain a non-parametric model of systems with unc...This paper addresses the design of an exponential function-based learning law for artificial neural networks(ANNs)with continuous dynamics.The ANN structure is used to obtain a non-parametric model of systems with uncertainties,which are described by a set of nonlinear ordinary differential equations.Two novel adaptive algorithms with predefined exponential convergence rate adjust the weights of the ANN.The first algorithm includes an adaptive gain depending on the identification error which accelerated the convergence of the weights and promotes a faster convergence between the states of the uncertain system and the trajectories of the neural identifier.The second approach uses a time-dependent sigmoidal gain that forces the convergence of the identification error to an invariant set characterized by an ellipsoid.The generalized volume of this ellipsoid depends on the upper bounds of uncertainties,perturbations and modeling errors.The application of the invariant ellipsoid method yields to obtain an algorithm to reduce the volume of the convergence region for the identification error.Both adaptive algorithms are derived from the application of a non-standard exponential dependent function and an associated controlled Lyapunov function.Numerical examples demonstrate the improvements enforced by the algorithms introduced in this study by comparing the convergence settings concerning classical schemes with non-exponential continuous learning methods.The proposed identifiers overcome the results of the classical identifier achieving a faster convergence to an invariant set of smaller dimensions.展开更多
This paper investigates an innovative predefined time output feedback adaptive fuzzy consensus control method for fractional-order nonlinear multi-agent systems(FONMASs).The controlled system includes unmeasurable sta...This paper investigates an innovative predefined time output feedback adaptive fuzzy consensus control method for fractional-order nonlinear multi-agent systems(FONMASs).The controlled system includes unmeasurable states and unknown nonlinear functions.The fuzzy state observer is built to evaluate unmeasurable state variables,unknown nonlinear functions are addressed through fuzzy logic system approximation.Combining with fractional-order dynamic surface control(DSC)and the theory of stability of predefined time,the control method is raised.By employing FODSC techniques,the computational explosion problem can be avoided.The stability of the closed-loop system is analyzed using the Lyapunov function,demonstrating that FONMAS achieves semi-global practical predefined time stability(SGPPTS).Eventually,the validity of the prescribed control strategy is verified by a simulation case.展开更多
This paper discusses the predefined practical finite-time(PPFT)dynamic positioning(DP)control problem for DP vessels subject to internal/external uncertainties.Those heterogeneity uncertainties are handled by a separa...This paper discusses the predefined practical finite-time(PPFT)dynamic positioning(DP)control problem for DP vessels subject to internal/external uncertainties.Those heterogeneity uncertainties are handled by a separate-type treatment approach.The finite-time(FT)DP control is fulfilled by a predefined FT function on the basis of a time-based generator(TBG).Under the dynamic surface control together with the TBG design framework,the convergence time and control accuracy of the DP system can be determined by the designer offline.Meanwhile,the virtual derivation and computational burden problems are dissolved by using a first-order filter and virtual parameter learning technique.To reduce mechanical wear,an event-triggering protocol between the control law and the actuator is built to reduce the operating frequency of the actuator.An event-triggered neuroadaptive PPFT control scheme is presented for DP vessels.The stability of the closed-loop DP control systems is validated via the Lyapunov theorem.Approach efficiency is confirmed by numerical examples.展开更多
This paper focuses on the connectivity-preserving consensus of nonlinear switched multi-agent systems with predefined accuracy.Accordingly,a unified error transformation is adopted to preserve the initial interaction ...This paper focuses on the connectivity-preserving consensus of nonlinear switched multi-agent systems with predefined accuracy.Accordingly,a unified error transformation is adopted to preserve the initial interaction pattern determined by agents’limited communication ranges and initial states.Meanwhile,the so-called congelation of variables method is used to handle the unknown aperiodically time-varying parameters,which are fast-varying in an unknown compact set with only their radii known a priori.In addition,a series of continuously differentiable functions are incorporated into the Lyapunov function to design the controller.Based on Lyapunov stability theory,the proposed control algorithm guarantees that the consensus errors converge with a predefined accuracy,whereas most existing connectivity-preserving results can only ensure uniform ultimate boundedness.Simultaneously,all closed-loop signals remain bounded.Finally,two simulations are provided to validate the effectiveness of the proposed control protocol.展开更多
A nonlinear stiffness actuator(NSA)could achieve high torque/force resolution in low stiffness range and high bandwidth in high stiffness range,both of which are beneficial for physical interaction between a robot and...A nonlinear stiffness actuator(NSA)could achieve high torque/force resolution in low stiffness range and high bandwidth in high stiffness range,both of which are beneficial for physical interaction between a robot and the environment.Currently,most of NSAs are complex and hardly used for engineering.In this paper,oriented to engineering applications,a new simple NSA was proposed,mainly including leaf springs and especially designed cams,which could perform a predefined relationship between torque and deflection.The new NSA has a compact structure,and it is lightweight,both of which are also beneficial for its practical application.An analytical methodology that maps the predefined relationship between torque and deflection to the profile of the cam was developed.The optimal parameters of the structure were given by analyzing the weight of the NSA and the mechanic characteristic of the leaf spring.Though sliding friction force is inevitable because no rollers were used in the cam-based mechanism,the sliding displacement between the cam and the leaf spring is very small,and consumption of sliding friction force is very low.Simulations of different torque‒deflection profiles were carried out to verify the accuracy and applicability of performing predefined torque‒deflection profiles.Three kinds of prototype experiments,including verification experiment of the predefined torque‒deflection profile,torque tracking experiment,and position tracking experiment under different loads,were conducted.The results prove the accuracy of performing the predefined torque‒deflection profile,the tracking performance,and the interactive performance of the new NSA.展开更多
Photogrammetry,reconstructing three-dimensional(3D)models from overlapping two-dimensional(2D)photos,finds application in rock mechanics and rock engineering to extract geometrical details of reconstructed objects,for...Photogrammetry,reconstructing three-dimensional(3D)models from overlapping two-dimensional(2D)photos,finds application in rock mechanics and rock engineering to extract geometrical details of reconstructed objects,for example rock fractures.Fracture properties are important for determining the mechanical stability,permeability,strength,and shear behavior of the rock mass.Photogrammetry can be used to reconstruct detailed 3D models of two separated rock fracture surfaces to characterize fracture roughness and physical aperture,which controls the fluid flow,hydromechanical and shear behavior of the rock mass.This research aimed to determine the optimal number of scale bars required to produce high-precision 3D models of a fracture surface.A workflow has been developed to define the physical aperture of a fracture using photogrammetry.Three blocks of Kuru granite(25 cm×25 cm×10 cm)with an artificially induced fracture,were investigated.For scaling 3D models,321 markers were used as ground control points(GCPs)with predefined distances on each block.When the samples were wellmatched in their original positions,the entire block was photographed.Coordinate data of the GCPs were extracted from the 3D model of the blocks.Each half was surveyed separately and georeferenced by GCPs and merged into the same coordinate system.Two fracture surfaces were extracted from the 3D models and the vertical distance between the two surfaces was digitally calculated as physical aperture.Accuracy assessment of the photogrammetric reconstruction showed a 20-30 mm digital control distance accuracy when compared to known distances defined between markers.To attain this accuracy,the study found that at least 200 scale bars were required.Furthermore,photogrammetry was employed to measure changes in aperture under normal stresses.The results obtained from this approach were found to be in good agreement with those obtained using linear variable displacement transducers(LVDTs),with differences ranging from 1 mm to 8μm.展开更多
According to the principles of simultaneous equilibrium and mass equilibrium, a series of thermodynamic equilibrium equations in Ni（II）-Co（II）-C2O4^2--NH3-NH4^＋-H2O system at ambient temperature were deduced. The...According to the principles of simultaneous equilibrium and mass equilibrium, a series of thermodynamic equilibrium equations in Ni（II）-Co（II）-C2O4^2--NH3-NH4^＋-H2O system at ambient temperature were deduced. The diagrams of logarithm ion concentrations versus pH values at different solution compositions were drawn. The results show that Ni^2＋ and Co^2＋ can completely precipitate at pH less than 5.0 and the predefined Ni/Co ratios can be well kept in the precursor. The precursor morphology is granular aggregation. However, rod aggregation precursor is obtained in the pH range of 5.0-8.0, and fibre-shape precursor is got at pH value higher than 8.0. The Ni/Co ratios in the above two precursors are not reproduced as that in the feed due to the formhtion of multi-coordinated Ni（NH3）n^2＋ and Co（NH3）n^2＋ （n=1-6）. Modification of precipitation medium is favorable for the precursors to keep the predefined Ni/Co ratios of the feed in the pH range of 2.0-8.6. Meanwhile, the precursors with fibrous morphology can be obtained.展开更多
In this paper, we mainly address the position control problem for one-degree of freedom(DOF) link manipulator despite uncertainties and the input saturation via the backstepping technique, active disturbance rejection...In this paper, we mainly address the position control problem for one-degree of freedom(DOF) link manipulator despite uncertainties and the input saturation via the backstepping technique, active disturbance rejection control(ADRC) as well as predefined tracking performance functions. The extended state observer(ESO) is employed to compensate uncertain dynamics and disturbances, and it does not rely on the accurate model of systems. The tracking differentiator(TD) is utilized to substitute the derivative of the virtual control signals, and the explosion of complexity caused by repeated differentiations of nonlinear functions is removed. The auxiliary system is used to deal with the control input limitation, and the tracking accuracy and speed are improved by predefined tracking performance functions.With the help of the input-to-state stability(ISS) and Lyapunov stability theories, it is proven that the tracking error can be gradually converged into arbitrarily small neighborhood of the origin, and the tracking error is adjusted by suitable choice of control parameters. The simulation results are presented for the verification of the theoretical claims.展开更多
Objective To investigate the efficacy and safety of oral semaglutide in Chinese patients with type 2 diabetes mellitus(T2DM)inadequately controlled by diet and exercise only.Methods In the randomized,doubleblind,multi...Objective To investigate the efficacy and safety of oral semaglutide in Chinese patients with type 2 diabetes mellitus(T2DM)inadequately controlled by diet and exercise only.Methods In the randomized,doubleblind,multicenter,multinational PIONEER-1l trial,Chinese patients were prospectively randomly assigned to receive oral semaglutide 3,7,or 14 mg,or placebo.The primary endpoint was the change from baseline in glycated hemoglobin(HbA_(IC))at week 26.This is a predefined subset analysis to assess the efficacy and safety in Chinese patients.Results Totally 390 Chinese T2DM patients were enrolled(mean age 51 years),with a T2DM duration of 1.8 years,HbA_(IC) of 7.9%,and BMI of 26.5 kg/m^(2)at baseline.Overall,changes at week 26 from baseline in HbA_(IC) were-1.1%,-1.6%,-1.6%,and 0.0%,and in bodyweight were-0.7,-1.9,-2.6,and-0.7 kg in oral semaglutide(3,7,or 14 mg)and placebo groups,respectively.Compared to the placebo group,estimated treatment differences(ETDs)in HbAic for the 3,7,and 14 mg groups were-1.2%(95%CI-1.4,-0.9),-1.7%(95%CI-1.9,-1.4),and-1.6%(95%CI-1.9,-1.4)(all P<0.001),respectively,and in weight loss for the 7 mg and 14 mg groups were-1.2 kg(95%CI-2.1,-0.4;P=0.006)and-1.9 kg(95%CI-2.8,-1.0;P<0.001),respectively.The most frequent gastrointestinal adverse events were diarrhea(oral semaglutide:3.1%-12.5%vs placebo:2.0%)and nausea(3.1%-6.3%us 2.0%),mostly mild in severity and transient.Conclusion In Chinese patients with T2DM who had insufficient glycemic control with diet and exercise only,oral semaglutide shows better glycemic control at doses of 3,7,and 14 mg and more weight loss at doses of 7 and 14 mg compared to placebo,with a safety profile consistent.展开更多
基金supported in part by the National Natural Science Foundation of China(62276119)the Natural Science Foundation of Jiangsu Province(BK20241764)the Postgraduate Research & Practice Innovation Program of Jiangsu Province(KYCX22_2860)
文摘Dear Editor,This letter investigates predefined-time optimization problems(OPs) of multi-agent systems(MASs), where the agent of MASs is subject to inequality constraints, and the team objective function accounts for impulse effects. Firstly, to address the inequality constraints,the penalty method is introduced. Then, a novel optimization strategy is developed, which only requires that the team objective function be strongly convex.
基金supported by the National Natural Science Foundation of China(No.12472045)the Shanghai Aerospace Science and Technology Innovation Fund(No.SAST2022-036)。
文摘To overcome external environmental disturbances,inertial parameter uncertainties and vibration of flexible modes in the process of attitude tracking,a comprehensively effective predefined-time guaranteed performance controller based on multi⁃observers for flexible spacecraft is proposed.First,to prevent unwinding phenomenon in attitude description,the rotation matrix is used to represent the spacecraft’s attitude.Second,the flexible modes observer which can guarantee predefined⁃time convergence is designed,for the case where flexible vibrations are unmeasurable in practice.What’s more,the disturbance observer is applied to estimate and compensate the lumped disturbances to improve the robustness of attitude control.A predefined-time controller is proposed to satisfy the prescribed performance and stabilize the attitude tracking system via barrier Lyapunov function.Finally,through comparative numerical simulations,the proposed controller can achieve high-precision convergence compared with the existing finite-time attitude tracking controller.This paper provides certain references for the high-precision predefined-time prescribed performance attitude tracking of flexible spacecraft with multi-disturbance.
文摘There are always large-scale items in the maintenances schedule of aircraft system, many of which have been fixed to be done in predefined sequences, which leads the workflow to be sys-tematically complex and makes this kind of problem quite different from all sorts of existing job-selection modes. On the other hand, the human resources are always limited and men have different working capabilities on different items, which make the allocation operation of human resources be much roomy. However, the final total time span of maintenance is often required to be as short as possible in many practices, in order to suffer only the lowest cost of loss while the system is stopping. A new model for op-timizing the allocation if aircraft maintenance human resources with the constraint of predefined sequence is presented. The ge-netic algorithm is employed to find the optimal solution that holds the shortest total time span of maintenance. To generate the ul-timate maintenance work items and the human resource array, the sequences among all maintenance work items are considered firstly, the work item array is then generated through traversal with the constraint of maintenance sequence matrix, and the human resources are finally allocated according to the work item array with the constraint of the maintenance capability. An example is demonstrated to show that the model and algorithm behave a satisfying performance on finding the optimal solution as expected.
文摘A non-orthogonal predefined exponential basis set is used to handle half-bounded domains in multi domain spectral method (MDSM). This approach works extremely well for real-valued semi-infinite differential problems. It spans simultaneously wide range of exponential decay rates with multi scaling and does not suffer from zero crossing. These two conditions are necessary for many physical problems. For comparison, the method is used to solve different problems and compared with analytical and published results. The comparison exhibits the strengths and accuracy of the presented basis set.
基金supported by the National Polytechnic Institute(SIP-20221151,SIP-20220916)。
文摘This paper addresses the design of an exponential function-based learning law for artificial neural networks(ANNs)with continuous dynamics.The ANN structure is used to obtain a non-parametric model of systems with uncertainties,which are described by a set of nonlinear ordinary differential equations.Two novel adaptive algorithms with predefined exponential convergence rate adjust the weights of the ANN.The first algorithm includes an adaptive gain depending on the identification error which accelerated the convergence of the weights and promotes a faster convergence between the states of the uncertain system and the trajectories of the neural identifier.The second approach uses a time-dependent sigmoidal gain that forces the convergence of the identification error to an invariant set characterized by an ellipsoid.The generalized volume of this ellipsoid depends on the upper bounds of uncertainties,perturbations and modeling errors.The application of the invariant ellipsoid method yields to obtain an algorithm to reduce the volume of the convergence region for the identification error.Both adaptive algorithms are derived from the application of a non-standard exponential dependent function and an associated controlled Lyapunov function.Numerical examples demonstrate the improvements enforced by the algorithms introduced in this study by comparing the convergence settings concerning classical schemes with non-exponential continuous learning methods.The proposed identifiers overcome the results of the classical identifier achieving a faster convergence to an invariant set of smaller dimensions.
基金funded in part by the National Natural Science Foundation of China under Grant Nos.62403226,62176111,and 62333004the Doctoral Research Initiation of Foundation of Liaoning Province,China under Grant No.2021-BS-260+5 种基金the general project of Liaoning Provincial Department of Education under Grant No.LIKZ0627Excellent Young Scientists Fund Program(Overseas)the“Xingliao Talent Plan”for young top talents under Grant No.XLYC22031882024 Fundamental Research Funding of the Educational Department of Liaoning Province under Grant No.LJZZ2224101540062024 Fundamental Research Funding of the Educational Department of Liaoning Province under Grant No.LJZZ2224101540012023 Education Department Basic Research Project(Youth Project)under Grant No.JYTQN2023225。
文摘This paper investigates an innovative predefined time output feedback adaptive fuzzy consensus control method for fractional-order nonlinear multi-agent systems(FONMASs).The controlled system includes unmeasurable states and unknown nonlinear functions.The fuzzy state observer is built to evaluate unmeasurable state variables,unknown nonlinear functions are addressed through fuzzy logic system approximation.Combining with fractional-order dynamic surface control(DSC)and the theory of stability of predefined time,the control method is raised.By employing FODSC techniques,the computational explosion problem can be avoided.The stability of the closed-loop system is analyzed using the Lyapunov function,demonstrating that FONMAS achieves semi-global practical predefined time stability(SGPPTS).Eventually,the validity of the prescribed control strategy is verified by a simulation case.
基金supported in part by the National Natural Science Foundation of China(52022073,62073251 and 52261160383)in part by the Excellent Youth Foundation of Hubei Scientific Committee(2020CFA055)+4 种基金in part by the Natural Science Foundation of Zhejiang Province(LY21E090005)in part by the Innovation Research Team Project of the Hainan Natural Science Foundation(722CXTD518)in part by the Knowledge Innovation Program of Wuhan-Basic Research(2022010801010181)in part by the Science and Technology Project of Zhoushan(2022C41006)in part by the Hubei Key Laboratory of Inland Shipping Technology(NHHY2020004).
文摘This paper discusses the predefined practical finite-time(PPFT)dynamic positioning(DP)control problem for DP vessels subject to internal/external uncertainties.Those heterogeneity uncertainties are handled by a separate-type treatment approach.The finite-time(FT)DP control is fulfilled by a predefined FT function on the basis of a time-based generator(TBG).Under the dynamic surface control together with the TBG design framework,the convergence time and control accuracy of the DP system can be determined by the designer offline.Meanwhile,the virtual derivation and computational burden problems are dissolved by using a first-order filter and virtual parameter learning technique.To reduce mechanical wear,an event-triggering protocol between the control law and the actuator is built to reduce the operating frequency of the actuator.An event-triggered neuroadaptive PPFT control scheme is presented for DP vessels.The stability of the closed-loop DP control systems is validated via the Lyapunov theorem.Approach efficiency is confirmed by numerical examples.
基金supported by the National Natural Science Foundation of China(Grant No.61673014)。
文摘This paper focuses on the connectivity-preserving consensus of nonlinear switched multi-agent systems with predefined accuracy.Accordingly,a unified error transformation is adopted to preserve the initial interaction pattern determined by agents’limited communication ranges and initial states.Meanwhile,the so-called congelation of variables method is used to handle the unknown aperiodically time-varying parameters,which are fast-varying in an unknown compact set with only their radii known a priori.In addition,a series of continuously differentiable functions are incorporated into the Lyapunov function to design the controller.Based on Lyapunov stability theory,the proposed control algorithm guarantees that the consensus errors converge with a predefined accuracy,whereas most existing connectivity-preserving results can only ensure uniform ultimate boundedness.Simultaneously,all closed-loop signals remain bounded.Finally,two simulations are provided to validate the effectiveness of the proposed control protocol.
基金supported by the National Key R&D Program of China (Grant No.2019YFB1312404)the National Natural Science Foundation of China (Grant Nos.51975401 and 51875393).
文摘A nonlinear stiffness actuator(NSA)could achieve high torque/force resolution in low stiffness range and high bandwidth in high stiffness range,both of which are beneficial for physical interaction between a robot and the environment.Currently,most of NSAs are complex and hardly used for engineering.In this paper,oriented to engineering applications,a new simple NSA was proposed,mainly including leaf springs and especially designed cams,which could perform a predefined relationship between torque and deflection.The new NSA has a compact structure,and it is lightweight,both of which are also beneficial for its practical application.An analytical methodology that maps the predefined relationship between torque and deflection to the profile of the cam was developed.The optimal parameters of the structure were given by analyzing the weight of the NSA and the mechanic characteristic of the leaf spring.Though sliding friction force is inevitable because no rollers were used in the cam-based mechanism,the sliding displacement between the cam and the leaf spring is very small,and consumption of sliding friction force is very low.Simulations of different torque‒deflection profiles were carried out to verify the accuracy and applicability of performing predefined torque‒deflection profiles.Three kinds of prototype experiments,including verification experiment of the predefined torque‒deflection profile,torque tracking experiment,and position tracking experiment under different loads,were conducted.The results prove the accuracy of performing the predefined torque‒deflection profile,the tracking performance,and the interactive performance of the new NSA.
基金funding provided by the State Nuclear Waste Management Fund(VYR)and the support of the Ministry of Economic Affairs and Employment of Finland on the Finnish Research Program on Nuclear Waste Management KYT2018 and KYT2022 of the Nuclear Energy Act(990/1987)in the research projects Fluid flow in fractured hard rock mass(RAKKA),funding numbers KYT 1/2021 and KYT 1/2022Additional support was received from the National Nuclear Safety and Waste Management Research Program SAFER2028,funding numbers SAFER 25/2023(MIRKA)and SAFER 42/2023(CORF).
文摘Photogrammetry,reconstructing three-dimensional(3D)models from overlapping two-dimensional(2D)photos,finds application in rock mechanics and rock engineering to extract geometrical details of reconstructed objects,for example rock fractures.Fracture properties are important for determining the mechanical stability,permeability,strength,and shear behavior of the rock mass.Photogrammetry can be used to reconstruct detailed 3D models of two separated rock fracture surfaces to characterize fracture roughness and physical aperture,which controls the fluid flow,hydromechanical and shear behavior of the rock mass.This research aimed to determine the optimal number of scale bars required to produce high-precision 3D models of a fracture surface.A workflow has been developed to define the physical aperture of a fracture using photogrammetry.Three blocks of Kuru granite(25 cm×25 cm×10 cm)with an artificially induced fracture,were investigated.For scaling 3D models,321 markers were used as ground control points(GCPs)with predefined distances on each block.When the samples were wellmatched in their original positions,the entire block was photographed.Coordinate data of the GCPs were extracted from the 3D model of the blocks.Each half was surveyed separately and georeferenced by GCPs and merged into the same coordinate system.Two fracture surfaces were extracted from the 3D models and the vertical distance between the two surfaces was digitally calculated as physical aperture.Accuracy assessment of the photogrammetric reconstruction showed a 20-30 mm digital control distance accuracy when compared to known distances defined between markers.To attain this accuracy,the study found that at least 200 scale bars were required.Furthermore,photogrammetry was employed to measure changes in aperture under normal stresses.The results obtained from this approach were found to be in good agreement with those obtained using linear variable displacement transducers(LVDTs),with differences ranging from 1 mm to 8μm.
基金Project (20090162120080) supported by Research Fund for the Doctoral Program of Higher Education of China Project (20070410989) supported by China Postdoctoral Science Foundation+1 种基金 Project (2010FJ3012) supported by the Program of Science and Technology of Hunan Province, China Project (09JJ4028) supported by Natural Science Foundation of Hunan Province, China
文摘According to the principles of simultaneous equilibrium and mass equilibrium, a series of thermodynamic equilibrium equations in Ni（II）-Co（II）-C2O4^2--NH3-NH4^＋-H2O system at ambient temperature were deduced. The diagrams of logarithm ion concentrations versus pH values at different solution compositions were drawn. The results show that Ni^2＋ and Co^2＋ can completely precipitate at pH less than 5.0 and the predefined Ni/Co ratios can be well kept in the precursor. The precursor morphology is granular aggregation. However, rod aggregation precursor is obtained in the pH range of 5.0-8.0, and fibre-shape precursor is got at pH value higher than 8.0. The Ni/Co ratios in the above two precursors are not reproduced as that in the feed due to the formhtion of multi-coordinated Ni（NH3）n^2＋ and Co（NH3）n^2＋ （n=1-6）. Modification of precipitation medium is favorable for the precursors to keep the predefined Ni/Co ratios of the feed in the pH range of 2.0-8.6. Meanwhile, the precursors with fibrous morphology can be obtained.
基金supported in part by the National Natural Science Foundation of China (61873130,61533010,61503194,61633016)the Natural Science Foundation of Jiangsu Province (BK20140877)+2 种基金the Research and Development Program of Jiangsu (BE2016184)the Jiangsu Government Scholarship for Overseas Studies (2017-037)1311 Talent Project of Nanjing University of Posts and Telecommunications
文摘In this paper, we mainly address the position control problem for one-degree of freedom(DOF) link manipulator despite uncertainties and the input saturation via the backstepping technique, active disturbance rejection control(ADRC) as well as predefined tracking performance functions. The extended state observer(ESO) is employed to compensate uncertain dynamics and disturbances, and it does not rely on the accurate model of systems. The tracking differentiator(TD) is utilized to substitute the derivative of the virtual control signals, and the explosion of complexity caused by repeated differentiations of nonlinear functions is removed. The auxiliary system is used to deal with the control input limitation, and the tracking accuracy and speed are improved by predefined tracking performance functions.With the help of the input-to-state stability(ISS) and Lyapunov stability theories, it is proven that the tracking error can be gradually converged into arbitrarily small neighborhood of the origin, and the tracking error is adjusted by suitable choice of control parameters. The simulation results are presented for the verification of the theoretical claims.
文摘Objective To investigate the efficacy and safety of oral semaglutide in Chinese patients with type 2 diabetes mellitus(T2DM)inadequately controlled by diet and exercise only.Methods In the randomized,doubleblind,multicenter,multinational PIONEER-1l trial,Chinese patients were prospectively randomly assigned to receive oral semaglutide 3,7,or 14 mg,or placebo.The primary endpoint was the change from baseline in glycated hemoglobin(HbA_(IC))at week 26.This is a predefined subset analysis to assess the efficacy and safety in Chinese patients.Results Totally 390 Chinese T2DM patients were enrolled(mean age 51 years),with a T2DM duration of 1.8 years,HbA_(IC) of 7.9%,and BMI of 26.5 kg/m^(2)at baseline.Overall,changes at week 26 from baseline in HbA_(IC) were-1.1%,-1.6%,-1.6%,and 0.0%,and in bodyweight were-0.7,-1.9,-2.6,and-0.7 kg in oral semaglutide(3,7,or 14 mg)and placebo groups,respectively.Compared to the placebo group,estimated treatment differences(ETDs)in HbAic for the 3,7,and 14 mg groups were-1.2%(95%CI-1.4,-0.9),-1.7%(95%CI-1.9,-1.4),and-1.6%(95%CI-1.9,-1.4)(all P<0.001),respectively,and in weight loss for the 7 mg and 14 mg groups were-1.2 kg(95%CI-2.1,-0.4;P=0.006)and-1.9 kg(95%CI-2.8,-1.0;P<0.001),respectively.The most frequent gastrointestinal adverse events were diarrhea(oral semaglutide:3.1%-12.5%vs placebo:2.0%)and nausea(3.1%-6.3%us 2.0%),mostly mild in severity and transient.Conclusion In Chinese patients with T2DM who had insufficient glycemic control with diet and exercise only,oral semaglutide shows better glycemic control at doses of 3,7,and 14 mg and more weight loss at doses of 7 and 14 mg compared to placebo,with a safety profile consistent.
