Ensuring the consistent mechanical performance of three-dimensional(3D)-printed continuous fiber-reinforced composites is a significant challenge in additive manufacturing.The current reliance on manual monitoring exa...Ensuring the consistent mechanical performance of three-dimensional(3D)-printed continuous fiber-reinforced composites is a significant challenge in additive manufacturing.The current reliance on manual monitoring exacerbates this challenge by rendering the process vulnerable to environmental changes and unexpected factors,resulting in defects and inconsistent product quality,particularly in unmanned long-term operations or printing in extreme environments.To address these issues,we developed a process monitoring and closed-loop feedback control strategy for the 3D printing process.Real-time printing image data were captured and analyzed using a well-trained neural network model,and a real-time control module-enabled closed-loop feedback control of the flow rate was developed.The neural network model,which was based on image processing and artificial intelligence,enabled the recognition of flow rate values with an accuracy of 94.70%.The experimental results showed significant improvements in both the surface performance and mechanical properties of printed composites,with three to six times improvement in tensile strength and elastic modulus,demonstrating the effectiveness of the strategy.This study provides a generalized process monitoring and feedback control method for the 3D printing of continuous fiber-reinforced composites,and offers a potential solution for remote online monitoring and closed-loop adjustment in unmanned or extreme space environments.展开更多
A composite anti-disturbance predictive control strategy employing a Multi-dimensional Taylor Network(MTN)is presented for unmanned systems subject to time-delay and multi-source disturbances.First,the multi-source di...A composite anti-disturbance predictive control strategy employing a Multi-dimensional Taylor Network(MTN)is presented for unmanned systems subject to time-delay and multi-source disturbances.First,the multi-source disturbances are addressed according to their specific characteristics as follows:(A)an MTN data-driven model,which is used for uncertainty description,is designed accompanied with the mechanism model to represent the unmanned systems;(B)an adaptive MTN filter is used to remove the influence of the internal disturbance;(C)an MTN disturbance observer is constructed to estimate and compensate for the influence of the external disturbance;(D)the Extended Kalman Filter(EKF)algorithm is utilized as the learning mechanism for MTNs.Second,to address the time-delay effect,a recursiveτstep-ahead MTN predictive model is designed utilizing recursive technology,aiming to mitigate the impact of time-delay,and the EKF algorithm is employed as its learning mechanism.Then,the MTN predictive control law is designed based on the quadratic performance index.By implementing the proposed composite controller to unmanned systems,simultaneous feedforward compensation and feedback suppression to the multi-source disturbances are conducted.Finally,the convergence of the MTN and the stability of the closed-loop system are established utilizing the Lyapunov theorem.Two exemplary applications of unmanned systems involving unmanned vehicle and rigid spacecraft are presented to validate the effectiveness of the proposed approach.展开更多
With the gradual increase in the size and flexibility of composite blades in large wind turbines,problems related toaeroelastic instability and blade vibration are becoming increasingly more important.Given their impa...With the gradual increase in the size and flexibility of composite blades in large wind turbines,problems related toaeroelastic instability and blade vibration are becoming increasingly more important.Given their impact on thelifespan of wind turbines,these subjects have become important topics in turbine blade design.In this article,firstaspects related to the aeroelastic(structural and aerodynamic)modeling of large wind turbine blades are summarized.Then,two main methods for blade vibration control are outlined(passive control and active control),including the case of composite blades.Some improvement schemes are proposed accordingly,with a specialfocus on the industry’s outstanding suppression scheme for stall-induced nonlinear flutter and a new high-frequencymicro-vibration control scheme.Finally,future research directions are indicated based on existingresearch.展开更多
Gypsum was used as substrate,and silica gel was mixed into substrate at a certain mass ratio to prepare humidity-controlling composites;moreover,the moisture absorption and desorption properties of gypsum-based compos...Gypsum was used as substrate,and silica gel was mixed into substrate at a certain mass ratio to prepare humidity-controlling composites;moreover,the moisture absorption and desorption properties of gypsum-based composites were compared with adding different silica gel particle size and proportion.The morphological characteristics,the isothermal equilibrium moisture content curve,moisture absorption and desorption rate,moisture absorption and desorption stability,and humidity-conditioning performance were tested and analyzed.The experimental results show that,compared with pure-gypsum,the surface structure of the gypsum-based composites is relatively loose,the quantity,density and aperture of the pores in the structure increase.The absorption and desorption capacity increase along with the increase of silica gel particle size and silica gel proportion.When 3 mm silica gel particle size is added with a mass ratio of 40%,the maximum equilibrium moisture content of humidity-controlling composites is 0.161 g/g at 98% relative humidity(RH),3.22 times that of pure-gypsum.The moisture absorption and desorption rates are increased,the equilibrium moisture absorption and desorption rates are 2.68 times and 1.61 times that of pure-gypsum at 58.5% RH,respectively.The gypsum-based composites have a good stability,which has better timely response to dynamic humidity changes and can effectively regulate indoor humidity under natural conditions.展开更多
Phase-change material(PCM)is widely used in thermal management due to their unique thermal behavior.However,related research in thermal rectifier is mainly focused on exploring the principles at the fundamental device...Phase-change material(PCM)is widely used in thermal management due to their unique thermal behavior.However,related research in thermal rectifier is mainly focused on exploring the principles at the fundamental device level,which results in a gap to real applications.Here,we propose a controllable thermal rectification design towards building applications through the direct adhesion of composite thermal rectification material(TRM)based on PCM and reduced graphene oxide(rGO)aerogel to ordinary concrete walls(CWs).The design is evaluated in detail by combining experiments and finite element analysis.It is found that,TRM can regulate the temperature difference on both sides of the TRM/CWs system by thermal rectification.The difference in two directions reaches to 13.8 K at the heat flow of 80 W/m^(2).In addition,the larger the change of thermal conductivity before and after phase change of TRM is,the more effective it is for regulating temperature difference in two directions.The stated technology has a wide range of applications for the thermal energy control in buildings with specific temperature requirements.展开更多
Gualou-Xiebai-Banxia Decoction(GXBD)is a traditional Chinese herbal formula including four traditional Chinese medicines:Gualou(Trichosanthis Fructus,TF),Xiebai(Allii Macrostemonis Bulbus,AMB),Banxia(Pinelliae Rhizoma...Gualou-Xiebai-Banxia Decoction(GXBD)is a traditional Chinese herbal formula including four traditional Chinese medicines:Gualou(Trichosanthis Fructus,TF),Xiebai(Allii Macrostemonis Bulbus,AMB),Banxia(Pinelliae Rhizoma,PR)and yellow wine.It is a classical therapy for chest stuffiness and pain syndrome and is widely used in the clinical treatment of coronary heart disease.It also shows significant therapeutic effects on pulmonary heart disease,hyperlipidemia,and arrhythmia.This study conducted a literature review and collected information on GXBD from databases such as PubMed,Web of Science,China National Knowledge Infrastructure,and ScienceDirect.The result indicated that the main active ingredients of GXBD are steroids,flavonoids,terpenoids,alkaloids,amino acids,and organic acids.Trigonelline,macrostemonoside and cucurbitacin B can provide reference for its quality control.GXBD may exert therapeutic effects on coronary heart disease through AMPK,PI3K-AKT,oxLDL,VEGF,and NF-κB signal pathways.This review provides a comprehensive analysis and summary of the chemical composition and in vivo metabolism of three traditional Chinese medicines(TF,AMB,and PR),along with an evaluation of the chemical composition,quality control,pharmacological effects,and clinical application of GXBD.Based on these,areas requiring further research on GXBD have been proposed to provide a reference for its further development and new drug research.展开更多
This paper demonstrated the generation of multi-wavelength bound state noise-like pulse(BNLP)in a dispersion-managed composite-filtered fiber laser consisting of nonlinear polarization rotation(NPR)and loop.In the cas...This paper demonstrated the generation of multi-wavelength bound state noise-like pulse(BNLP)in a dispersion-managed composite-filtered fiber laser consisting of nonlinear polarization rotation(NPR)and loop.In the case of BNLP,the generation is caused by the interaction between two noise-like pulses(NLPs)induced by the comb-filtering effect,and bound state level can be artificially controlled in the researches.Our work provides a new method for generating low-coherence pulses and establishes a research idea for the study of the comb-filtering effects.展开更多
A composite control scheme consisting of modepredictive control （MPC） and disturbance observer （DOB） iproposed to solve the control performance degradationproblem of the turbidity of the treated water in the prese...A composite control scheme consisting of modepredictive control （MPC） and disturbance observer （DOB） iproposed to solve the control performance degradationproblem of the turbidity of the treated water in the presence osignificant changes in raw water quality, water flow rate andinternal model mismatch disturbances. The MPC is employedas a feedback controller for the coagulation process with alarge time delay. The DOB is adopted to estimate the severedisturbances in the turbidity control, such as large changes inraw water quality and water flow rate. The estimated valuesare applied for feed-forward compensation to rejecdisturbances. Finally, the disturbance rejection performancesfor step disturbances and time-varying disturbances in thenominal case and model mismatch case are tested. Thesimulation results illustrate that, compared with the MPCmethod, the proposed method can significantly improve thedisturbance rejection performance in the turbidity control othe treated water, no matter if in the presence of externadisturbances or internal model mismatch disturbances.展开更多
Robots are finding increasing application in aircraft composite structure assembly due to their flexibility and the growing demand of aircraft manufacturers for high production rates.The contact force of the composite...Robots are finding increasing application in aircraft composite structure assembly due to their flexibility and the growing demand of aircraft manufacturers for high production rates.The contact force of the composite frame in a robotic assembly of the aircraft composite fuselage panel can hardly be controlled due to the multi-surface variable contact stiffness caused by compliance and complex shape with multiple mating surfaces.The paper proposes a robotic assembly system for the aircraft composite fuselage frame with a compliant contact force control strategy using the Gaussian process surrogate model.First,a robotic assembly system is introduced,and the global coordinate system transformation model is built.Then,a compliant force control architecture is designed to generate the desired output force.Subsequently,a Gaussian process surrogate model with uncertainties is utilized to model the complicated relationship between the robot’s output force and the normal contact force acting on the mating surface of the composite frame.Furthermore,an optimal contact force control strategy is implemented to improve the contact quality.Finally,an experiment demonstrates that the proposed methodology can ensure that the contact force on each surface is within the limit of the engineering specification and uniformly distributed,improving the quality compared to the traditional assembly process.展开更多
Mg matrix composites(Mg MCs)with enhanced mechanical and functional properties,as well as improved elastic modulus,have aroused rising attention from the aerospace,new energy vehicles,and consumer electronics industri...Mg matrix composites(Mg MCs)with enhanced mechanical and functional properties,as well as improved elastic modulus,have aroused rising attention from the aerospace,new energy vehicles,and consumer electronics industries.The suitability of the fabrication process is crucial for achieving uniform dispersion of various reinforcing materials within the Mg alloy matrix and for forming strong interfacial bonding.This ensures that the produced Mg MCs meet the requirements for fabricating various components with different demands for size and properties.This paper comprehensively reviews the present fabrication methods for MgMCs in four categories:stir casting,external addition methods,in-situ synthesis methods and novel fabrication methods.It comprehensively focuses on the fabrication principles,process characteristics and key parameters optimization of each technology.Through in-depth analysis,their advantages,limitations and applications are evaluated.Meanwhile,the latest research achievements in microstructure control and mechanical performance optimization are explored.Eventually,the development directions of the fabrication methods for MgMCs in the future are also discussed.展开更多
In this paper, the attitude stabilization problem of a rigid spacecraft described by Rodrigues parameters is investigated via a composite control strategy, which combines a feedback control law designed by a finite ti...In this paper, the attitude stabilization problem of a rigid spacecraft described by Rodrigues parameters is investigated via a composite control strategy, which combines a feedback control law designed by a finite time control technique with a feedforward compensator based on a linear disturbance observer （DOB） method. By choosing a suitable coordinate transformation, the spacecraft dynamics can be divided into three second-order subsystems. Each subsystem includes a certain part and an uncertain part. By using the finite time control technique, a continuous finite time controller is designed for the certain part. The uncertain part is considered to be a lumped disturbance, which is estimated by a DOB, and a corresponding feedforward design is then implemented to compensate the disturbance. Simulation results are employed to confirm the effectiveness of the proposed approach.展开更多
Gypsum is a traditional building material. To improve the humidity-controlling properties of gypsum, we prepared a new type of humidity-controlling composite using the sol-gel method. Methods to determine the maximum ...Gypsum is a traditional building material. To improve the humidity-controlling properties of gypsum, we prepared a new type of humidity-controlling composite using the sol-gel method. Methods to determine the maximum equilibrium moisture content and speed of adsorption/desorption were subsequently applied to analyze the performance of the samples. The appearance and structural properties of the samples were characterized by scanning electronic microscopy (SEM). The experimental results show that the humidity-controlling gel with added LiCl exhibits high moisture storage and that the equilibrium maximum moisture content is 5.652 g/g at a 75.29% relative humidity (RH). A mass ratio of LiCl/sol = 0.15 is demonstrated to be appropriate for the preparation of the new humidity-controlling composites. A coarse network with tiny pores is observed on the surface of the new humidity-controlling composites, and this pore network provides sufficient space for moisture adsorption.展开更多
This review summarizes the work carried out in the field of interface study in carbon nanotube reinforced aluminum （CNT/A1） composites. Much research work has been conducted to reveal the evolution of CNT/A1 interfa...This review summarizes the work carried out in the field of interface study in carbon nanotube reinforced aluminum （CNT/A1） composites. Much research work has been conducted to reveal the evolution of CNT/A1 interface in producing the composite with the purpose of achieving uniform distribution of CNTs and tight interfacial bonding. The effect and principles of coating were reviewed along with the illustration of ＂intermetallic interphases＂ design. Different roles of CNT/Al interface in structural and functional application were elucidated, and the future work that needs attention was addressed.展开更多
There is great variation in the lithology and lamination thickness of composite roof in coal-measure strata;thus,the roof is prone to delamination and falling,and it is difficult to control the surrounding rock when d...There is great variation in the lithology and lamination thickness of composite roof in coal-measure strata;thus,the roof is prone to delamination and falling,and it is difficult to control the surrounding rock when developing roadway in such rock strata.In deep mining,the stress environment of surrounding rock is complex,and the mechanical response of the rock mass is different from that of the shallow rock mass.For composite-roof roadway excavated in deep rock mass,the key to safe and efficient production of the mine is ensuring the stability of the roadway.The present paper obtains typical failure characteristics and deformation and failure mechanisms of composite-roof roadway with a buried depth of 650 m at Zhaozhuang Coal Mine(Shanxi Province,China).On the basis of determining a reasonable cross-section shape of the roadway and according to the failure characteristics of the composite roof in different regions,the roof is divided into an unstable layer,metastable layer,and stable layer.The controlled unstable layer and metastable layer are regarded as a small structure while the stable layer is regarded as a large structure.A superimposed coupling support technology of large and small structures with a multi-level prestressed bearing arch formed by strong rebar bolts and highly prestressed cable bolts is put forward.The support technology provides good application results in the field.The study thus provides theoretical support and technical guidance for ground control under similar geological conditions.展开更多
This paper is concerned with fundamental properties of a class of composite systems with fractional degree generalized frequency variables, including controllability, observability and stability. Firstly, some necessa...This paper is concerned with fundamental properties of a class of composite systems with fractional degree generalized frequency variables, including controllability, observability and stability. Firstly, some necessary and sufficient conditions are given to guarantee controllability and observability of such composite systems. Then we prove that the stability problem of such composite systems can be reduced to judging whether a fractional degree polynomial is stable. Finally, the stability analysis result is applied in the supervisory control of fractional-order multi-agent systems, and an example is provided to illustrate the effectiveness of the proposed methods.展开更多
A continuous production process was developed for coating bulk metallic glasses on the metallic wire surface. The effects of processing parameters, including the drawing velocity and coating temperature, on the coatin...A continuous production process was developed for coating bulk metallic glasses on the metallic wire surface. The effects of processing parameters, including the drawing velocity and coating temperature, on the coating thickness were investigated. It is found that the coating thickness increases with the increase in drawing velocity but decreases with the increase in coating temperature. A fluid mechanical model was developed to quantify the coating thickness under various processing conditions. By using this theoretical model, the coating thickness was calculated, and the calculated values are in good agreement with the experimental data.展开更多
Magneto-rheological elastomers （MILEs） are used to construct composite structures for micro-vibration control of equipment under stochastic support-motion excitations. The dynamic behavior of MREs as a smart viscoel...Magneto-rheological elastomers （MILEs） are used to construct composite structures for micro-vibration control of equipment under stochastic support-motion excitations. The dynamic behavior of MREs as a smart viscoelastic material is characterized by a complex modulus dependent on vibration frequency and controllable by external magnetic fields. Frequency-domain solution methods for stochastic micro-vibration response analysis of the MRE-based structural systems are developed to derive the system frequency-response function matrices and the expressions of the velocity response spectrum. With these equations, the root-mean-square （RMS） velocity responses in terms of the one-third octave frequency band spectrum can be calculated. Further, the optimization problem of the complex moduli of the MRE cores is defined by minimizing the velocity response spectra and the RMS velocity responses through altering the applied magnetic fields. Simulation results illustrate the influences of MRE parameters on the RMS velocity responses and the high response reduction capacities of the MRE-based structures. In addition, the developed frequency-domain analysis methods are applicable to sandwich beam structures with arbitrary cores characterized by complex shear moduli under stochastic excitations described by power spectral density functions, and are valid for a wide frequency range.展开更多
The nonlinear dynamic characteristics and optimal control of a giant magnetostrictive film （GMF）-shaped memory alloy （SMA） composite plate subjected to in-plane stochastic excitation are studied. GMF is prepared b...The nonlinear dynamic characteristics and optimal control of a giant magnetostrictive film （GMF）-shaped memory alloy （SMA） composite plate subjected to in-plane stochastic excitation are studied. GMF is prepared based on an SMA plate, and combined into a GMF-SMA composite plate. The Van der Pol item is improved to explain the hysteretic phenomena of GMF and SMA, and the nonlinear dynamics model of a GMF-SMA composite cantilever plate subjected to in-plane stochastic excitation is developed. The stochastic stability of the system is analyzed, and the steady-state probability density function of the dynamic response of the system is obtained. The condition of stochastic Hopf bifurcation is discussed, the reliability function of the system is provided, and then the probability density of the first-passage time is given. Finally, the stochastic optimal control strategy is proposed by the stochastic dynamic programming method. Numerical simulation shows that the stability of the trivial solution varies with bifurcation parameters, and stochastic Hopf bifurcation appears in the process; the system＇s reliability is improved through stochastic optimal control, and the first- passage time is delayed. A GMF-SMA composite plate combines the advantages of GMF and SMA, and can reduce vibration through passive control and active control effectively. The results are helpful for the engineering applications of GMF-SMA composite plates.展开更多
The rendezvous and proximity operations with respect to a tumbling non-cooperative target pose high requirement for the position and attitude control accuracy of servicing spacecraft.However,multiple disturbances incl...The rendezvous and proximity operations with respect to a tumbling non-cooperative target pose high requirement for the position and attitude control accuracy of servicing spacecraft.However,multiple disturbances including parametric uncertainties,flexible vibration,and unknown nonlinear dynamics degrade the control performance significantly.In order to enhance the system anti-disturbance ability,this paper proposes a composite anti-disturbance control law for the spacecraft position and attitude tracking.Firstly,the relative position and attitude dynamic models with multiple disturbances are established,where the refined descriptions of multiple disturbances are accomplished based on their characteristics.Then,by combining a dual Disturbance ObserverBased Control(DOBC)and a sliding mode control,a composite controller with hierarchical architecture is proposed,where the dual DOBC in the feedforward channel is used to reject the flexible vibration,environment disturbance,and complicated nonlinear dynamics,while the parametric uncertainties are attenuated by the sliding mode control in the feedback channel.Stability analysis is carried out for the closed-loop system by unifying the sliding mode dynamics and observer dynamics.Finally,the effectiveness of the proposed controller is verified via numerical simulation and hardware-in-the-loop test.展开更多
Pressure fluctuations during the composite fiber winding process seriously affect the produces compactness strength,fatigue resistance,stress uniformity,and resin content.The accuracy of pressure control systems is af...Pressure fluctuations during the composite fiber winding process seriously affect the produces compactness strength,fatigue resistance,stress uniformity,and resin content.The accuracy of pressure control systems is affected by nonlinear disturbances,such as friction,parameter perturbation,and measurement noise.A robust control algorithm based on linear quadratic optimal control and sliding mode control(LQSMC)is proposed to overcome these problems.The method is based on the system state space expression and linear quadratic optimal control.The state space model of the system is improved by using a Kalman filter and control input for state estimation,and a new sliding surface equation is defined.The ameliorated control algorithm exhibits good performance and can effectively suppress sliding mode control(SMC)chattering.Simulation and experimental results show that LQSMC offers high control precision,much stronger antiinterference,and robustness,which can effectively improve the positioning and tracking accuracy of a pressure control system compared with linear quadratic optimal control(LQC).The winding pressure control precision is improved by 45%to 50%.The results show that the porosity of composite fiber tape winding products decreased thanks to our method.展开更多
基金supported by National Key Research and Development Program of China(Grant No.2023YFB4604100)National Key Research and Development Program of China(Grant No.2022YFB3806104)+4 种基金Key Research and Development Program in Shaanxi Province(Grant No.2021LLRH-08-17)Young Elite Scientists Sponsorship Program by CAST(No.2023QNRC001)K C Wong Education Foundation of ChinaYouth Innovation Team of Shaanxi Universities of ChinaKey Research and Development Program of Shaanxi Province(Grant 2021LLRH-08-3.1).
文摘Ensuring the consistent mechanical performance of three-dimensional(3D)-printed continuous fiber-reinforced composites is a significant challenge in additive manufacturing.The current reliance on manual monitoring exacerbates this challenge by rendering the process vulnerable to environmental changes and unexpected factors,resulting in defects and inconsistent product quality,particularly in unmanned long-term operations or printing in extreme environments.To address these issues,we developed a process monitoring and closed-loop feedback control strategy for the 3D printing process.Real-time printing image data were captured and analyzed using a well-trained neural network model,and a real-time control module-enabled closed-loop feedback control of the flow rate was developed.The neural network model,which was based on image processing and artificial intelligence,enabled the recognition of flow rate values with an accuracy of 94.70%.The experimental results showed significant improvements in both the surface performance and mechanical properties of printed composites,with three to six times improvement in tensile strength and elastic modulus,demonstrating the effectiveness of the strategy.This study provides a generalized process monitoring and feedback control method for the 3D printing of continuous fiber-reinforced composites,and offers a potential solution for remote online monitoring and closed-loop adjustment in unmanned or extreme space environments.
基金co-supported by the National Key R&D Program of China(No.2023YFB4704400)the Zhejiang Provincial Natural Science Foundation of China(No.LQ24F030012)the National Natural Science Foundation of China General Project(No.62373033)。
文摘A composite anti-disturbance predictive control strategy employing a Multi-dimensional Taylor Network(MTN)is presented for unmanned systems subject to time-delay and multi-source disturbances.First,the multi-source disturbances are addressed according to their specific characteristics as follows:(A)an MTN data-driven model,which is used for uncertainty description,is designed accompanied with the mechanism model to represent the unmanned systems;(B)an adaptive MTN filter is used to remove the influence of the internal disturbance;(C)an MTN disturbance observer is constructed to estimate and compensate for the influence of the external disturbance;(D)the Extended Kalman Filter(EKF)algorithm is utilized as the learning mechanism for MTNs.Second,to address the time-delay effect,a recursiveτstep-ahead MTN predictive model is designed utilizing recursive technology,aiming to mitigate the impact of time-delay,and the EKF algorithm is employed as its learning mechanism.Then,the MTN predictive control law is designed based on the quadratic performance index.By implementing the proposed composite controller to unmanned systems,simultaneous feedforward compensation and feedback suppression to the multi-source disturbances are conducted.Finally,the convergence of the MTN and the stability of the closed-loop system are established utilizing the Lyapunov theorem.Two exemplary applications of unmanned systems involving unmanned vehicle and rigid spacecraft are presented to validate the effectiveness of the proposed approach.
基金supported by the Natural Science Foundation of Shandong Provincial of China(Grant Number ZR2022ME093)the Natural Science Foundation of China(Grant Number 51675315).
文摘With the gradual increase in the size and flexibility of composite blades in large wind turbines,problems related toaeroelastic instability and blade vibration are becoming increasingly more important.Given their impact on thelifespan of wind turbines,these subjects have become important topics in turbine blade design.In this article,firstaspects related to the aeroelastic(structural and aerodynamic)modeling of large wind turbine blades are summarized.Then,two main methods for blade vibration control are outlined(passive control and active control),including the case of composite blades.Some improvement schemes are proposed accordingly,with a specialfocus on the industry’s outstanding suppression scheme for stall-induced nonlinear flutter and a new high-frequencymicro-vibration control scheme.Finally,future research directions are indicated based on existingresearch.
基金Funded by the National Natural Science Foundation of China(No.51678254)。
文摘Gypsum was used as substrate,and silica gel was mixed into substrate at a certain mass ratio to prepare humidity-controlling composites;moreover,the moisture absorption and desorption properties of gypsum-based composites were compared with adding different silica gel particle size and proportion.The morphological characteristics,the isothermal equilibrium moisture content curve,moisture absorption and desorption rate,moisture absorption and desorption stability,and humidity-conditioning performance were tested and analyzed.The experimental results show that,compared with pure-gypsum,the surface structure of the gypsum-based composites is relatively loose,the quantity,density and aperture of the pores in the structure increase.The absorption and desorption capacity increase along with the increase of silica gel particle size and silica gel proportion.When 3 mm silica gel particle size is added with a mass ratio of 40%,the maximum equilibrium moisture content of humidity-controlling composites is 0.161 g/g at 98% relative humidity(RH),3.22 times that of pure-gypsum.The moisture absorption and desorption rates are increased,the equilibrium moisture absorption and desorption rates are 2.68 times and 1.61 times that of pure-gypsum at 58.5% RH,respectively.The gypsum-based composites have a good stability,which has better timely response to dynamic humidity changes and can effectively regulate indoor humidity under natural conditions.
基金This work was supported in part by Tsinghua University-Zhuhai Huafa Industrial Share Company Joint Institute for Architecture Optoelectronic Technologies(JIAOT KF202204)in part by STI 2030—Major Projects under Grant 2022ZD0209200+2 种基金in part by National Natural Science Foundation of China under Grant 62374099,Grant 62022047in part by Beijing Natural Science-Xiaomi Innovation Joint Fund under Grant L233009in part by the Tsinghua-Toyota JointResearch Fund,in part by the Daikin-Tsinghua Union Program,in part sponsored by CIE-Tencent Robotics XRhino-Bird Focused Research Program.
文摘Phase-change material(PCM)is widely used in thermal management due to their unique thermal behavior.However,related research in thermal rectifier is mainly focused on exploring the principles at the fundamental device level,which results in a gap to real applications.Here,we propose a controllable thermal rectification design towards building applications through the direct adhesion of composite thermal rectification material(TRM)based on PCM and reduced graphene oxide(rGO)aerogel to ordinary concrete walls(CWs).The design is evaluated in detail by combining experiments and finite element analysis.It is found that,TRM can regulate the temperature difference on both sides of the TRM/CWs system by thermal rectification.The difference in two directions reaches to 13.8 K at the heat flow of 80 W/m^(2).In addition,the larger the change of thermal conductivity before and after phase change of TRM is,the more effective it is for regulating temperature difference in two directions.The stated technology has a wide range of applications for the thermal energy control in buildings with specific temperature requirements.
基金National Natural ScienceFoundation of China (grant number: 81973696).
文摘Gualou-Xiebai-Banxia Decoction(GXBD)is a traditional Chinese herbal formula including four traditional Chinese medicines:Gualou(Trichosanthis Fructus,TF),Xiebai(Allii Macrostemonis Bulbus,AMB),Banxia(Pinelliae Rhizoma,PR)and yellow wine.It is a classical therapy for chest stuffiness and pain syndrome and is widely used in the clinical treatment of coronary heart disease.It also shows significant therapeutic effects on pulmonary heart disease,hyperlipidemia,and arrhythmia.This study conducted a literature review and collected information on GXBD from databases such as PubMed,Web of Science,China National Knowledge Infrastructure,and ScienceDirect.The result indicated that the main active ingredients of GXBD are steroids,flavonoids,terpenoids,alkaloids,amino acids,and organic acids.Trigonelline,macrostemonoside and cucurbitacin B can provide reference for its quality control.GXBD may exert therapeutic effects on coronary heart disease through AMPK,PI3K-AKT,oxLDL,VEGF,and NF-κB signal pathways.This review provides a comprehensive analysis and summary of the chemical composition and in vivo metabolism of three traditional Chinese medicines(TF,AMB,and PR),along with an evaluation of the chemical composition,quality control,pharmacological effects,and clinical application of GXBD.Based on these,areas requiring further research on GXBD have been proposed to provide a reference for its further development and new drug research.
基金supported by the Research Fund of Guangdong-Hong Kong-Macao Joint Laboratory for Intelligent Micro-Nano Optoelectronic Technology(No.2020B1212030010)。
文摘This paper demonstrated the generation of multi-wavelength bound state noise-like pulse(BNLP)in a dispersion-managed composite-filtered fiber laser consisting of nonlinear polarization rotation(NPR)and loop.In the case of BNLP,the generation is caused by the interaction between two noise-like pulses(NLPs)induced by the comb-filtering effect,and bound state level can be artificially controlled in the researches.Our work provides a new method for generating low-coherence pulses and establishes a research idea for the study of the comb-filtering effects.
基金The National Natural Science Foundation of China(No.61504027)the Natural Science Foundation of Jiangsu Province(No.BK20140647)the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘A composite control scheme consisting of modepredictive control （MPC） and disturbance observer （DOB） iproposed to solve the control performance degradationproblem of the turbidity of the treated water in the presence osignificant changes in raw water quality, water flow rate andinternal model mismatch disturbances. The MPC is employedas a feedback controller for the coagulation process with alarge time delay. The DOB is adopted to estimate the severedisturbances in the turbidity control, such as large changes inraw water quality and water flow rate. The estimated valuesare applied for feed-forward compensation to rejecdisturbances. Finally, the disturbance rejection performancesfor step disturbances and time-varying disturbances in thenominal case and model mismatch case are tested. Thesimulation results illustrate that, compared with the MPCmethod, the proposed method can significantly improve thedisturbance rejection performance in the turbidity control othe treated water, no matter if in the presence of externadisturbances or internal model mismatch disturbances.
基金This study was supported by the Aeronautical Manufacturing Technology Institute,COMAC.
文摘Robots are finding increasing application in aircraft composite structure assembly due to their flexibility and the growing demand of aircraft manufacturers for high production rates.The contact force of the composite frame in a robotic assembly of the aircraft composite fuselage panel can hardly be controlled due to the multi-surface variable contact stiffness caused by compliance and complex shape with multiple mating surfaces.The paper proposes a robotic assembly system for the aircraft composite fuselage frame with a compliant contact force control strategy using the Gaussian process surrogate model.First,a robotic assembly system is introduced,and the global coordinate system transformation model is built.Then,a compliant force control architecture is designed to generate the desired output force.Subsequently,a Gaussian process surrogate model with uncertainties is utilized to model the complicated relationship between the robot’s output force and the normal contact force acting on the mating surface of the composite frame.Furthermore,an optimal contact force control strategy is implemented to improve the contact quality.Finally,an experiment demonstrates that the proposed methodology can ensure that the contact force on each surface is within the limit of the engineering specification and uniformly distributed,improving the quality compared to the traditional assembly process.
基金supported by the financial support from the National Natural Science Foundation of China(grant Nos.52471012,52425101 and 52305158)Science Innovation Foundation of Shanghai Academy of Spaceflight Technology(No.USCAST2021–18)Young Elite Scientists Sponsorship Program by China Association for Science and Technology(No.YESS20220350)。
文摘Mg matrix composites(Mg MCs)with enhanced mechanical and functional properties,as well as improved elastic modulus,have aroused rising attention from the aerospace,new energy vehicles,and consumer electronics industries.The suitability of the fabrication process is crucial for achieving uniform dispersion of various reinforcing materials within the Mg alloy matrix and for forming strong interfacial bonding.This ensures that the produced Mg MCs meet the requirements for fabricating various components with different demands for size and properties.This paper comprehensively reviews the present fabrication methods for MgMCs in four categories:stir casting,external addition methods,in-situ synthesis methods and novel fabrication methods.It comprehensively focuses on the fabrication principles,process characteristics and key parameters optimization of each technology.Through in-depth analysis,their advantages,limitations and applications are evaluated.Meanwhile,the latest research achievements in microstructure control and mechanical performance optimization are explored.Eventually,the development directions of the fabrication methods for MgMCs in the future are also discussed.
基金Natural Science Foundation of China(61074013,61203011)Specialized Research Fundfor the Doctoral Program of Higher Education of China(20090092110022)+1 种基金New Century Excellent Talents in University(NCET-10-0328)the Scientific Research Foundation of Graduate School of Southeast University
文摘In this paper, the attitude stabilization problem of a rigid spacecraft described by Rodrigues parameters is investigated via a composite control strategy, which combines a feedback control law designed by a finite time control technique with a feedforward compensator based on a linear disturbance observer （DOB） method. By choosing a suitable coordinate transformation, the spacecraft dynamics can be divided into three second-order subsystems. Each subsystem includes a certain part and an uncertain part. By using the finite time control technique, a continuous finite time controller is designed for the certain part. The uncertain part is considered to be a lumped disturbance, which is estimated by a DOB, and a corresponding feedforward design is then implemented to compensate the disturbance. Simulation results are employed to confirm the effectiveness of the proposed approach.
基金financially supported by the National Natural Science Foundation of China(51172176)
文摘Gypsum is a traditional building material. To improve the humidity-controlling properties of gypsum, we prepared a new type of humidity-controlling composite using the sol-gel method. Methods to determine the maximum equilibrium moisture content and speed of adsorption/desorption were subsequently applied to analyze the performance of the samples. The appearance and structural properties of the samples were characterized by scanning electronic microscopy (SEM). The experimental results show that the humidity-controlling gel with added LiCl exhibits high moisture storage and that the equilibrium maximum moisture content is 5.652 g/g at a 75.29% relative humidity (RH). A mass ratio of LiCl/sol = 0.15 is demonstrated to be appropriate for the preparation of the new humidity-controlling composites. A coarse network with tiny pores is observed on the surface of the new humidity-controlling composites, and this pore network provides sufficient space for moisture adsorption.
基金financially supported by the National Basic Research Program of China (No.2012CB619600)the National Natural Science Foundation of China (Nos.51131004,51071100,and 51001071)+1 种基金the National High Technology Research and Development Program of China (No.2012AA030311)Shanghai Science & Technology Committee (Nos.11JC1405500)
文摘This review summarizes the work carried out in the field of interface study in carbon nanotube reinforced aluminum （CNT/A1） composites. Much research work has been conducted to reveal the evolution of CNT/A1 interface in producing the composite with the purpose of achieving uniform distribution of CNTs and tight interfacial bonding. The effect and principles of coating were reviewed along with the illustration of ＂intermetallic interphases＂ design. Different roles of CNT/Al interface in structural and functional application were elucidated, and the future work that needs attention was addressed.
基金This study was supported by the National Natural Science Foundation of China(No.51804310No.52074301)Fundamental Research Funds for the Central Universities(No.2020XJNY05).
文摘There is great variation in the lithology and lamination thickness of composite roof in coal-measure strata;thus,the roof is prone to delamination and falling,and it is difficult to control the surrounding rock when developing roadway in such rock strata.In deep mining,the stress environment of surrounding rock is complex,and the mechanical response of the rock mass is different from that of the shallow rock mass.For composite-roof roadway excavated in deep rock mass,the key to safe and efficient production of the mine is ensuring the stability of the roadway.The present paper obtains typical failure characteristics and deformation and failure mechanisms of composite-roof roadway with a buried depth of 650 m at Zhaozhuang Coal Mine(Shanxi Province,China).On the basis of determining a reasonable cross-section shape of the roadway and according to the failure characteristics of the composite roof in different regions,the roof is divided into an unstable layer,metastable layer,and stable layer.The controlled unstable layer and metastable layer are regarded as a small structure while the stable layer is regarded as a large structure.A superimposed coupling support technology of large and small structures with a multi-level prestressed bearing arch formed by strong rebar bolts and highly prestressed cable bolts is put forward.The support technology provides good application results in the field.The study thus provides theoretical support and technical guidance for ground control under similar geological conditions.
基金supported by Foundation of Shanxi Scholarship Council(2016-075)Natural Science Foundation of Shanxi Normal University(ZR1601)Fund Program for the Scientific Activities of Selected Returned Overseas Professionals in Shanxi Province(2018-25)
文摘This paper is concerned with fundamental properties of a class of composite systems with fractional degree generalized frequency variables, including controllability, observability and stability. Firstly, some necessary and sufficient conditions are given to guarantee controllability and observability of such composite systems. Then we prove that the stability problem of such composite systems can be reduced to judging whether a fractional degree polynomial is stable. Finally, the stability analysis result is applied in the supervisory control of fractional-order multi-agent systems, and an example is provided to illustrate the effectiveness of the proposed methods.
基金supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China(No.20100006120020)the National Natural Science Foundation of China(Nos.51010001,51071018,and 51001009)+1 种基金the Program of Introducing Talents of Discipline to Universities(the 111 Project,No.B07003)the Program for Changjiang Scholars and Innovative Research Team in Universities of the Ministry of Education of China
文摘A continuous production process was developed for coating bulk metallic glasses on the metallic wire surface. The effects of processing parameters, including the drawing velocity and coating temperature, on the coating thickness were investigated. It is found that the coating thickness increases with the increase in drawing velocity but decreases with the increase in coating temperature. A fluid mechanical model was developed to quantify the coating thickness under various processing conditions. By using this theoretical model, the coating thickness was calculated, and the calculated values are in good agreement with the experimental data.
基金Research Grants Council of the Hong Kong Special Administrative Region,China Under Grant No.PolyU 5252/07EThe Hong Kong Polytechnic University through the Development of Niche Areas Programme Under Grant No.1-BB95Zhejiang Provincial Natural Science Foundation of China Under Grant No.Y607087)
文摘Magneto-rheological elastomers （MILEs） are used to construct composite structures for micro-vibration control of equipment under stochastic support-motion excitations. The dynamic behavior of MREs as a smart viscoelastic material is characterized by a complex modulus dependent on vibration frequency and controllable by external magnetic fields. Frequency-domain solution methods for stochastic micro-vibration response analysis of the MRE-based structural systems are developed to derive the system frequency-response function matrices and the expressions of the velocity response spectrum. With these equations, the root-mean-square （RMS） velocity responses in terms of the one-third octave frequency band spectrum can be calculated. Further, the optimization problem of the complex moduli of the MRE cores is defined by minimizing the velocity response spectra and the RMS velocity responses through altering the applied magnetic fields. Simulation results illustrate the influences of MRE parameters on the RMS velocity responses and the high response reduction capacities of the MRE-based structures. In addition, the developed frequency-domain analysis methods are applicable to sandwich beam structures with arbitrary cores characterized by complex shear moduli under stochastic excitations described by power spectral density functions, and are valid for a wide frequency range.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11272229 and 11302144)the Ph.D.Programs Foundation of the Ministry of Education of China(Grant No.20120032120006)the Tianjin Research Program of Application Foundation and Advanced Technology,China(Grant No.13JCYBJC17900)
文摘The nonlinear dynamic characteristics and optimal control of a giant magnetostrictive film （GMF）-shaped memory alloy （SMA） composite plate subjected to in-plane stochastic excitation are studied. GMF is prepared based on an SMA plate, and combined into a GMF-SMA composite plate. The Van der Pol item is improved to explain the hysteretic phenomena of GMF and SMA, and the nonlinear dynamics model of a GMF-SMA composite cantilever plate subjected to in-plane stochastic excitation is developed. The stochastic stability of the system is analyzed, and the steady-state probability density function of the dynamic response of the system is obtained. The condition of stochastic Hopf bifurcation is discussed, the reliability function of the system is provided, and then the probability density of the first-passage time is given. Finally, the stochastic optimal control strategy is proposed by the stochastic dynamic programming method. Numerical simulation shows that the stability of the trivial solution varies with bifurcation parameters, and stochastic Hopf bifurcation appears in the process; the system＇s reliability is improved through stochastic optimal control, and the first- passage time is delayed. A GMF-SMA composite plate combines the advantages of GMF and SMA, and can reduce vibration through passive control and active control effectively. The results are helpful for the engineering applications of GMF-SMA composite plates.
基金supported by the China National Postdoctoral Program for Innovative Talents(No.BX20200031)the National Natural Science Foundation of China(Nos.62103013,61633003,61973012)the Program for Changjiang Scholars and Innovative Research Team,China(No.IRT 16R03).
文摘The rendezvous and proximity operations with respect to a tumbling non-cooperative target pose high requirement for the position and attitude control accuracy of servicing spacecraft.However,multiple disturbances including parametric uncertainties,flexible vibration,and unknown nonlinear dynamics degrade the control performance significantly.In order to enhance the system anti-disturbance ability,this paper proposes a composite anti-disturbance control law for the spacecraft position and attitude tracking.Firstly,the relative position and attitude dynamic models with multiple disturbances are established,where the refined descriptions of multiple disturbances are accomplished based on their characteristics.Then,by combining a dual Disturbance ObserverBased Control(DOBC)and a sliding mode control,a composite controller with hierarchical architecture is proposed,where the dual DOBC in the feedforward channel is used to reject the flexible vibration,environment disturbance,and complicated nonlinear dynamics,while the parametric uncertainties are attenuated by the sliding mode control in the feedback channel.Stability analysis is carried out for the closed-loop system by unifying the sliding mode dynamics and observer dynamics.Finally,the effectiveness of the proposed controller is verified via numerical simulation and hardware-in-the-loop test.
基金supported by the National Natural Science Foundation of China(No.51505356).
文摘Pressure fluctuations during the composite fiber winding process seriously affect the produces compactness strength,fatigue resistance,stress uniformity,and resin content.The accuracy of pressure control systems is affected by nonlinear disturbances,such as friction,parameter perturbation,and measurement noise.A robust control algorithm based on linear quadratic optimal control and sliding mode control(LQSMC)is proposed to overcome these problems.The method is based on the system state space expression and linear quadratic optimal control.The state space model of the system is improved by using a Kalman filter and control input for state estimation,and a new sliding surface equation is defined.The ameliorated control algorithm exhibits good performance and can effectively suppress sliding mode control(SMC)chattering.Simulation and experimental results show that LQSMC offers high control precision,much stronger antiinterference,and robustness,which can effectively improve the positioning and tracking accuracy of a pressure control system compared with linear quadratic optimal control(LQC).The winding pressure control precision is improved by 45%to 50%.The results show that the porosity of composite fiber tape winding products decreased thanks to our method.
