Laser tracers are a three-dimensional coordinate measurement system that are widely used in industrial measurement.We propose a geometric error identification method based on multi-station synchronization laser tracer...Laser tracers are a three-dimensional coordinate measurement system that are widely used in industrial measurement.We propose a geometric error identification method based on multi-station synchronization laser tracers to enable the rapid and high-precision measurement of geometric errors for gantry-type computer numerical control(CNC)machine tools.This method also improves on the existing measurement efficiency issues in the single-base station measurement method and multi-base station time-sharing measurement method.We consider a three-axis gantry-type CNC machine tool,and the geometric error mathematical model is derived and established based on the combination of screw theory and a topological analysis of the machine kinematic chain.The four-station laser tracers position and measurement points are realized based on the multi-point positioning principle.A self-calibration algorithm is proposed for the coordinate calibration process of a laser tracer using the Levenberg-Marquardt nonlinear least squares method,and the geometric error is solved using Taylor’s first-order linearization iteration.The experimental results show that the geometric error calculated based on this modeling method is comparable to the results from the Etalon laser tracer.For a volume of 800 mm×1000 mm×350 mm,the maximum differences of the linear,angular,and spatial position errors were 2.0μm,2.7μrad,and 12.0μm,respectively,which verifies the accuracy of the proposed algorithm.This research proposes a modeling method for the precise measurement of errors in machine tools,and the applied nature of this study also makes it relevant both to researchers and those in the industrial sector.展开更多
In order to meet the polishing requirement of faucets and other products,a novel multi-station rotary polishing robot is designed,which is a PPPR + RR type of degree of freedom( DOF) distribution structure,and is simi...In order to meet the polishing requirement of faucets and other products,a novel multi-station rotary polishing robot is designed,which is a PPPR + RR type of degree of freedom( DOF) distribution structure,and is similar to dual-arm robot. Forward and inverse kinematic analysis is carried out by robot modeling. In order to make this robot structure more compact,first of all,X,Y and Z three moving degrees of freedom( DOF) limit stroke polishing need is calculated by using an artificial fish swarm algorithm,which analyzes dexterous workspace of this robot. Then,on the basis of the above analysis,the three DOF stroke is optimized. Simulation and polishing experimental results verify that this polishing robot with optimized stroke parameters can meet the polishing needs of faucets and other bathroom pieces.展开更多
To analyze the physical structure of assembly process and assure product quality, the quality stability of multi-station assembly process was investigated. First, the assembly process was modeled as a one-dimensional ...To analyze the physical structure of assembly process and assure product quality, the quality stability of multi-station assembly process was investigated. First, the assembly process was modeled as a one-dimensional discrete variant system by state space equation based on variation stream. Then, the criterion to judge whether the process is stable or not and the index, stability degree, to show the level of stability were proposed by analyzing the bounded-input bounded-output (BIBO) stability of system. Finally, a simulated example of a sheet metal assembly process with three stations, was provided to verify the effectiveness of the proposed method.展开更多
Based on features of dimension variation propagation in multi-station assembly processes,a new quality evaluation model of assembly processes is established. Firstly,the error source of multi-station assembly system i...Based on features of dimension variation propagation in multi-station assembly processes,a new quality evaluation model of assembly processes is established. Firstly,the error source of multi-station assembly system is analyzed,the relationship of dimension variation propagation in multi-station assembly processes is studied and the state equation for variation propagation is constructed too. Then,the feature parameters which influence variation propagation and accumulation in multi-station assembly processes are found to evaluate quality characteristic of the assembly system. Through the derivation of equation on dimension variation propagation,station coefficient matrices which are combined and conversed to determine the max eigenvalue are educed. The max eigenvalue is multiplied by the weight coefficient to establish the quality evaluation model in multi-station assembly processes. Furthermore,assembly variation indexes are proposed to judge of the assembly technology process. Finally,through the practical example,the application of the model and assembly variation indexes are presented.展开更多
Tribological tests play an important role on the evaluation of long-term bio-tribological performances of prosthetic materials for commercial fabrication.Those tests focus on the motion simulation of a real joint in v...Tribological tests play an important role on the evaluation of long-term bio-tribological performances of prosthetic materials for commercial fabrication.Those tests focus on the motion simulation of a real joint in vitro with only normal loads and constant velocities,which are far from the real friction behavior of human joints characterized with variable loads and multiple directions.In order to accurately obtain the bio-tribological performances of artificial joint materials,a tribological tester with a miniature four-station tribological system is proposed with four distinctive features.Firstly,comparability and repeatability of a test are ensured by four equal stations of the tester.Secondly,cross-linked scratch between tribo-pairs of human joints can be simulated by using a gear-rack meshing mechanism to produce composite motions.With this mechanism,the friction tracks can be designed by varying reciprocating and rotating speeds.Thirdly,variable loading system is realized by using a ball-screw mechanism driven by a stepper motor,by which loads under different gaits during walking are simulated.Fourthly,dynamic friction force and normal load can be measured simultaneously.The verifications of the performances of the developed tester show that the variable frictional tracks can produce different wear debris compared with one-directional tracks,and the accuracy of loading and friction force is within ？5%.Thus the high consistency among different stations can be obtained.Practically,the proposed tester system could provide more comprehensive and accurate bio-tribological evaluations for prosthetic materials.展开更多
Nowadays, the Multi-Shuttle and Multi-Station Transportation System (MMTS)<span><span><span style="font-family:;" "=""> is one of the most interesting research topics in many...Nowadays, the Multi-Shuttle and Multi-Station Transportation System (MMTS)<span><span><span style="font-family:;" "=""> is one of the most interesting research topics in many fields of industries. It is an effective solution to reduce unexpected accidents that occur during transportation as well as increase productivity in manufacturing. The aim of this paper is to introduce the controller design for the MMTS which is built in our BK-Recme BioMech Lab at Ho Chi Minh City University of Technology (VNU-HCM), Viet Nam. Based on the design of this system, the control algorithms will be conducted to check the operation of the whole system. To evaluate the feasibility and effectiveness of this model, we design a series of random instances for different quantities of nodes as well as the different quantities of shuttles. Our system includes 4 stations and 6 shuttles which are assembled in the serial chain system. However, the number of stations and number of shuttles can be expanded to any desired ones which are based on the requirement of the industries. In this paper, we mainly focus on the controller design of this system to make it operate in an effective way that the goods will be transported and delivered to the target station as fast as possible. In order to solve the large</span></span></span><span><span><span style="font-family:;" "="">-</span></span></span><span><span><span style="font-family:;" "="">scale instances and realistic transport prob<span>lems, we propose three algorithms for three progresses as shuttles calling</span>, path reading and shuttles communicating. The shuttles calling is to decide which <span>shuttle should be called to the star</span></span></span></span><span><span><span style="font-family:;" "="">t</span></span></span><span><span><span style="font-family:;" "="">-node. Path reading to determine the shortest</span></span></span><span><span><span style="font-family:;" "=""> <span>way to go from start-node to end-node. Finally, shuttles communicating,</span> which allow one shuttle to interact with the next shuttles so we have a loop of orders (shuttle 1 to shuttle 2;shuttle 2 to shuttle 3;etc</span></span></span><span><span><span style="font-family:;" "="">.</span></span></span><span><span><span style="font-family:;" "="">;shuttle n-1 to shuttle n). This proposes solution can help us to solve the huge numbers of shuttles <span>and stations in the system. The specific result of this study is applying</span> Dijkstra’s algorithm to propose an algorithm that allows handling a transportation system without caring about the number of shuttles as well as the number of stations for the closed-loop path. Several test problems are carried out in order to check the feasibility and the effectiveness of our purposed control algorithm.</span></span></span>展开更多
Laser marking refers to the process of etching patterns (including graphics and characters) by using laser beam emitted by laser emitting device to make the components to be processed undergo chemical and physical cha...Laser marking refers to the process of etching patterns (including graphics and characters) by using laser beam emitted by laser emitting device to make the components to be processed undergo chemical and physical changes through light energy. With the continuous development of laser marking technology, marking technology has been applied more and more widely in manufacturing industry. However, the traditional single-machine laser marking production mode cant meet the characteristics of small batch and multi-category order production, and frequent switching affects the marking quality and efficiency. This paper mainly expounds the working principle of laser marking equipment and the influence of process parameters, and on this basis, studies the technical scheme and mechanism operation mode of multi-station laser marking. Explain the advantages of technological innovation and transformation in the production and application of enterprises, and improve the utilization rate of equipment by optimizing technology and reforming tooling and equipment.展开更多
Current large-scale access to distributed power and rapid growth of electric vehicles are seriously affecting power quality and reliability of distribution networks.The above issues can be resolved by using a multi-st...Current large-scale access to distributed power and rapid growth of electric vehicles are seriously affecting power quality and reliability of distribution networks.The above issues can be resolved by using a multi-station integrated system(MSIS)composed of an energy storage system,distributed generation(DG)system and transformer substation.This paper proposes a new topology and coordinated control strategy for MSIS.The top control layer receives dispatching commands from the power grid superior to realize top layer control.The soft normally open point(SNOP)receives instructions from the top control layer to realize high-degree-of-integration mode of generation-network-load-storage.Remaining converters and energy storage devices receive instructions to realize access and integration of distributed power stations,such as energy storage systems,electric-vehicle charging systems,and photovoltaic(PV)power systems.Eight working schemes of the autonomous operation of the system are analyzed.The small-signal model of the MSIS is derived.Feasibility of the proposed topological structure and control strategy for achieving a hierarchical power supply of MSIS can be verified by real-time digital simulation results.展开更多
A multi-station integration system(MSIS)integrat-ing other multi-type stations provides a new way to realize an intensive development of resources and promote low-carbon en-ergy and its high-efficiency utilization.To ...A multi-station integration system(MSIS)integrat-ing other multi-type stations provides a new way to realize an intensive development of resources and promote low-carbon en-ergy and its high-efficiency utilization.To this end,a novel multi-station integration planning method and coordinated operation strategy model for the MSIS are established in a new business model.In this study,a new business model of the MSIS,with substations as the carrier,integrating distributed photovoltaic,energy storage,electric vehicle charging,data center,and 5G base stations is proposed.From the social environment,natural conditions,and complementary characteristics,a comprehensive index system is established to analyze expansion capability of substations and multi-station combination scheme.Scenario reduction is performed by extracting feature vectors and build-ing a comprehensive evaluation function to select the optimal combination scheme under a specific scenario.Moreover,for the combination scheme in a specific scenario,the optimal ca-pacity configuration and coordinated operation strategy chance-constrained programming model of the MSIS are established under different operating conditions.Finally,simulations are performed on a practical MSIS located in Wuxi,China,and simulation results demonstrate the rationality and effectiveness of the planning method and coordinated operation strategy model for the MSIS.展开更多
Stochastic resonance can utilize the energy of noise to enhance weak frequency characteristic.This paper proposes an adaptive multi-stable stochastic resonance method assisted by the neural network(NN)and physics supe...Stochastic resonance can utilize the energy of noise to enhance weak frequency characteristic.This paper proposes an adaptive multi-stable stochastic resonance method assisted by the neural network(NN)and physics supervision(directly numerical simulation of the physical system).Different from traditional adaptive algorithm,the evaluation of the objective function(i.e.,fitness function)in iteration process of adaptive algorithm is through a trained neural network instead of the numerical simulation.It will bring a dramatically reduction in computation time.Considering predictive bias from the neural network,a secondary correction procedure is introduced to the reevaluate the top performers and then resort them in iteration process through physics supervision.Though it may increase the computing cost,the accuracy will be enhanced.Two examples are given to illustrate the proposed method.For a classical multi-stable stochastic resonance system,the results show that the proposed method not only amplifies weak signals effectively but also significantly reduces computing time.For the detection of weak signal from outer ring in bearings,by introducing a variable scale coefficient,the proposed method can also give a satisfactory result,and the characteristic frequency of the fault signal can be extracted correctly.展开更多
Importance measures can be used to identify the vulnerable components in an aviation system at the early design stage.However,due to lack of knowledge or less available information on the component or system,the epist...Importance measures can be used to identify the vulnerable components in an aviation system at the early design stage.However,due to lack of knowledge or less available information on the component or system,the epistemic uncertainties may be one of the challenging issues in importance evaluation.In addition,the properties of the aircraft system,which are the fundamentals of the component importance measure,including the hierarchy,dependency,randomness,and uncertainty,should be taken into consideration.To solve these problems,this paper proposes the component Uncertainty Integrated Importance Measure(component UIIM)which considers multiple epistemic uncertainties in the complex multi-state systems.The degradation process for the components is described by a Markov model,and the system reliability model is developed using the Markov hierarchal evidential network.The concept of integrated importance measure is then extended into component UIIM to evaluate the component criticality rather than the component state change criticality,from the perspective of system performance.A case study on displacement compensation hydraulic system is presented to show the effectiveness of the proposed uncertainty importance measure.The results show that the component UIIM can be an effective method for evaluating the component criticality from system performance perspective at the system early design.展开更多
Background:Patients with type 2 diabetes are at high risk for developing multiple chronic complications.However,there is a lack of studies of the cumulative number of diabetic complications in China.Methods:A retrospe...Background:Patients with type 2 diabetes are at high risk for developing multiple chronic complications.However,there is a lack of studies of the cumulative number of diabetic complications in China.Methods:A retrospective cohort study was performed from 2009 to 2021.Type 2 diabetes patients who were first diagnosed after the age of 35 years between January 1,2009,and December 31,2017,were included.Five states were defined according to the number of chronic complications:no(S0),one(S1),two(S2),three(S3),and four or more complications(S4).A multi-state Markov model was constructed to estimate transition probability,transition intensity,mean sojourn time,and the possible factors for each state.Results:The study included 32653 type 2 diabetes patients(mean age,59.59 years;15929(48.8%)male),and mean follow-up time of 7.75 years.In all,4375 transitions were observed.The 12-year transition probability of from state S0 to S1 was the lowest at 16.4%,while that from S2 to S3 was the highest,at 45.6%.Higher fasting blood glucose,lower high-density lipoprotein cholesterol,higher total cholesterol,and an unhealthy diet were associated with higher risk of progression from S0 to S1.Being female,less than 60 years old,weekly physical activity,and vegetarian diet decreased this risk.Being female and less than 60 years old reduced the likelihood of transition from S1 to S2,whereas lower high-density lipoprotein cholesterol increased this likelihood.Conclusions:Following the occurrence of two complications in type 2 diabetes patients,the risk for accumulating a third complication within a short time is significantly increased.It is important to take advantage of the stable window period when patients have fewer than two complications,strengthen the monitoring of blood glucose and blood lipids,and encourage patients to maintain good living habits to prevent further deterioration.展开更多
基金Supported by Natural Science Foundation of Shaanxi Province of China(Grant No.2021JM010)Suzhou Municipal Natural Science Foundation of China(Grant Nos.SYG202018,SYG202134).
文摘Laser tracers are a three-dimensional coordinate measurement system that are widely used in industrial measurement.We propose a geometric error identification method based on multi-station synchronization laser tracers to enable the rapid and high-precision measurement of geometric errors for gantry-type computer numerical control(CNC)machine tools.This method also improves on the existing measurement efficiency issues in the single-base station measurement method and multi-base station time-sharing measurement method.We consider a three-axis gantry-type CNC machine tool,and the geometric error mathematical model is derived and established based on the combination of screw theory and a topological analysis of the machine kinematic chain.The four-station laser tracers position and measurement points are realized based on the multi-point positioning principle.A self-calibration algorithm is proposed for the coordinate calibration process of a laser tracer using the Levenberg-Marquardt nonlinear least squares method,and the geometric error is solved using Taylor’s first-order linearization iteration.The experimental results show that the geometric error calculated based on this modeling method is comparable to the results from the Etalon laser tracer.For a volume of 800 mm×1000 mm×350 mm,the maximum differences of the linear,angular,and spatial position errors were 2.0μm,2.7μrad,and 12.0μm,respectively,which verifies the accuracy of the proposed algorithm.This research proposes a modeling method for the precise measurement of errors in machine tools,and the applied nature of this study also makes it relevant both to researchers and those in the industrial sector.
基金Supported by the Key Research and Development Project of Yangzhou--Industry Preview and Key Projects(No.YZ2015011)
文摘In order to meet the polishing requirement of faucets and other products,a novel multi-station rotary polishing robot is designed,which is a PPPR + RR type of degree of freedom( DOF) distribution structure,and is similar to dual-arm robot. Forward and inverse kinematic analysis is carried out by robot modeling. In order to make this robot structure more compact,first of all,X,Y and Z three moving degrees of freedom( DOF) limit stroke polishing need is calculated by using an artificial fish swarm algorithm,which analyzes dexterous workspace of this robot. Then,on the basis of the above analysis,the three DOF stroke is optimized. Simulation and polishing experimental results verify that this polishing robot with optimized stroke parameters can meet the polishing needs of faucets and other bathroom pieces.
基金Supported bythe National High-Tech Research and Development Plan (National"863"Plan) (No2006AA04Z115)Tianjin Science andTechnology Key Project (No05YFGDGX08700)
文摘To analyze the physical structure of assembly process and assure product quality, the quality stability of multi-station assembly process was investigated. First, the assembly process was modeled as a one-dimensional discrete variant system by state space equation based on variation stream. Then, the criterion to judge whether the process is stable or not and the index, stability degree, to show the level of stability were proposed by analyzing the bounded-input bounded-output (BIBO) stability of system. Finally, a simulated example of a sheet metal assembly process with three stations, was provided to verify the effectiveness of the proposed method.
基金supported by the National Natural Science Foundation of China ( Grant No.50575072)Scientific Research Fund of Hunan Provincial Education Department(Grant No.07C281)
文摘Based on features of dimension variation propagation in multi-station assembly processes,a new quality evaluation model of assembly processes is established. Firstly,the error source of multi-station assembly system is analyzed,the relationship of dimension variation propagation in multi-station assembly processes is studied and the state equation for variation propagation is constructed too. Then,the feature parameters which influence variation propagation and accumulation in multi-station assembly processes are found to evaluate quality characteristic of the assembly system. Through the derivation of equation on dimension variation propagation,station coefficient matrices which are combined and conversed to determine the max eigenvalue are educed. The max eigenvalue is multiplied by the weight coefficient to establish the quality evaluation model in multi-station assembly processes. Furthermore,assembly variation indexes are proposed to judge of the assembly technology process. Finally,through the practical example,the application of the model and assembly variation indexes are presented.
基金Supported by Funding of State Key Laboratory of Mechanical Transmissions,Chongqing University,China(Grant No.SKLMT-KFKT-201504)National Natural Science Foundation of China(Grant No.51275381)Science and Technology Planning Project of Shaanxi Province,China(Grant No.2012GY2-37)
文摘Tribological tests play an important role on the evaluation of long-term bio-tribological performances of prosthetic materials for commercial fabrication.Those tests focus on the motion simulation of a real joint in vitro with only normal loads and constant velocities,which are far from the real friction behavior of human joints characterized with variable loads and multiple directions.In order to accurately obtain the bio-tribological performances of artificial joint materials,a tribological tester with a miniature four-station tribological system is proposed with four distinctive features.Firstly,comparability and repeatability of a test are ensured by four equal stations of the tester.Secondly,cross-linked scratch between tribo-pairs of human joints can be simulated by using a gear-rack meshing mechanism to produce composite motions.With this mechanism,the friction tracks can be designed by varying reciprocating and rotating speeds.Thirdly,variable loading system is realized by using a ball-screw mechanism driven by a stepper motor,by which loads under different gaits during walking are simulated.Fourthly,dynamic friction force and normal load can be measured simultaneously.The verifications of the performances of the developed tester show that the variable frictional tracks can produce different wear debris compared with one-directional tracks,and the accuracy of loading and friction force is within ？5%.Thus the high consistency among different stations can be obtained.Practically,the proposed tester system could provide more comprehensive and accurate bio-tribological evaluations for prosthetic materials.
文摘Nowadays, the Multi-Shuttle and Multi-Station Transportation System (MMTS)<span><span><span style="font-family:;" "=""> is one of the most interesting research topics in many fields of industries. It is an effective solution to reduce unexpected accidents that occur during transportation as well as increase productivity in manufacturing. The aim of this paper is to introduce the controller design for the MMTS which is built in our BK-Recme BioMech Lab at Ho Chi Minh City University of Technology (VNU-HCM), Viet Nam. Based on the design of this system, the control algorithms will be conducted to check the operation of the whole system. To evaluate the feasibility and effectiveness of this model, we design a series of random instances for different quantities of nodes as well as the different quantities of shuttles. Our system includes 4 stations and 6 shuttles which are assembled in the serial chain system. However, the number of stations and number of shuttles can be expanded to any desired ones which are based on the requirement of the industries. In this paper, we mainly focus on the controller design of this system to make it operate in an effective way that the goods will be transported and delivered to the target station as fast as possible. In order to solve the large</span></span></span><span><span><span style="font-family:;" "="">-</span></span></span><span><span><span style="font-family:;" "="">scale instances and realistic transport prob<span>lems, we propose three algorithms for three progresses as shuttles calling</span>, path reading and shuttles communicating. The shuttles calling is to decide which <span>shuttle should be called to the star</span></span></span></span><span><span><span style="font-family:;" "="">t</span></span></span><span><span><span style="font-family:;" "="">-node. Path reading to determine the shortest</span></span></span><span><span><span style="font-family:;" "=""> <span>way to go from start-node to end-node. Finally, shuttles communicating,</span> which allow one shuttle to interact with the next shuttles so we have a loop of orders (shuttle 1 to shuttle 2;shuttle 2 to shuttle 3;etc</span></span></span><span><span><span style="font-family:;" "="">.</span></span></span><span><span><span style="font-family:;" "="">;shuttle n-1 to shuttle n). This proposes solution can help us to solve the huge numbers of shuttles <span>and stations in the system. The specific result of this study is applying</span> Dijkstra’s algorithm to propose an algorithm that allows handling a transportation system without caring about the number of shuttles as well as the number of stations for the closed-loop path. Several test problems are carried out in order to check the feasibility and the effectiveness of our purposed control algorithm.</span></span></span>
文摘Laser marking refers to the process of etching patterns (including graphics and characters) by using laser beam emitted by laser emitting device to make the components to be processed undergo chemical and physical changes through light energy. With the continuous development of laser marking technology, marking technology has been applied more and more widely in manufacturing industry. However, the traditional single-machine laser marking production mode cant meet the characteristics of small batch and multi-category order production, and frequent switching affects the marking quality and efficiency. This paper mainly expounds the working principle of laser marking equipment and the influence of process parameters, and on this basis, studies the technical scheme and mechanism operation mode of multi-station laser marking. Explain the advantages of technological innovation and transformation in the production and application of enterprises, and improve the utilization rate of equipment by optimizing technology and reforming tooling and equipment.
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences(XDA21050304).
文摘Current large-scale access to distributed power and rapid growth of electric vehicles are seriously affecting power quality and reliability of distribution networks.The above issues can be resolved by using a multi-station integrated system(MSIS)composed of an energy storage system,distributed generation(DG)system and transformer substation.This paper proposes a new topology and coordinated control strategy for MSIS.The top control layer receives dispatching commands from the power grid superior to realize top layer control.The soft normally open point(SNOP)receives instructions from the top control layer to realize high-degree-of-integration mode of generation-network-load-storage.Remaining converters and energy storage devices receive instructions to realize access and integration of distributed power stations,such as energy storage systems,electric-vehicle charging systems,and photovoltaic(PV)power systems.Eight working schemes of the autonomous operation of the system are analyzed.The small-signal model of the MSIS is derived.Feasibility of the proposed topological structure and control strategy for achieving a hierarchical power supply of MSIS can be verified by real-time digital simulation results.
基金the Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(KYCX22_0606)。
文摘A multi-station integration system(MSIS)integrat-ing other multi-type stations provides a new way to realize an intensive development of resources and promote low-carbon en-ergy and its high-efficiency utilization.To this end,a novel multi-station integration planning method and coordinated operation strategy model for the MSIS are established in a new business model.In this study,a new business model of the MSIS,with substations as the carrier,integrating distributed photovoltaic,energy storage,electric vehicle charging,data center,and 5G base stations is proposed.From the social environment,natural conditions,and complementary characteristics,a comprehensive index system is established to analyze expansion capability of substations and multi-station combination scheme.Scenario reduction is performed by extracting feature vectors and build-ing a comprehensive evaluation function to select the optimal combination scheme under a specific scenario.Moreover,for the combination scheme in a specific scenario,the optimal ca-pacity configuration and coordinated operation strategy chance-constrained programming model of the MSIS are established under different operating conditions.Finally,simulations are performed on a practical MSIS located in Wuxi,China,and simulation results demonstrate the rationality and effectiveness of the planning method and coordinated operation strategy model for the MSIS.
文摘Stochastic resonance can utilize the energy of noise to enhance weak frequency characteristic.This paper proposes an adaptive multi-stable stochastic resonance method assisted by the neural network(NN)and physics supervision(directly numerical simulation of the physical system).Different from traditional adaptive algorithm,the evaluation of the objective function(i.e.,fitness function)in iteration process of adaptive algorithm is through a trained neural network instead of the numerical simulation.It will bring a dramatically reduction in computation time.Considering predictive bias from the neural network,a secondary correction procedure is introduced to the reevaluate the top performers and then resort them in iteration process through physics supervision.Though it may increase the computing cost,the accuracy will be enhanced.Two examples are given to illustrate the proposed method.For a classical multi-stable stochastic resonance system,the results show that the proposed method not only amplifies weak signals effectively but also significantly reduces computing time.For the detection of weak signal from outer ring in bearings,by introducing a variable scale coefficient,the proposed method can also give a satisfactory result,and the characteristic frequency of the fault signal can be extracted correctly.
基金the National Natural Science Foundation of China(Nos.52375036,U2233212,52272409,62303030)Beijing Municipal Natural Science Foundation-Fengtai Rail Transit Frontier Research Joint Foundation,China(No.L221008)+1 种基金the fellowship of China Postdoctoral Science Foundation(No.2022M710305)the program of China Scholarship Council(Nos.202106020106,202306020133).
文摘Importance measures can be used to identify the vulnerable components in an aviation system at the early design stage.However,due to lack of knowledge or less available information on the component or system,the epistemic uncertainties may be one of the challenging issues in importance evaluation.In addition,the properties of the aircraft system,which are the fundamentals of the component importance measure,including the hierarchy,dependency,randomness,and uncertainty,should be taken into consideration.To solve these problems,this paper proposes the component Uncertainty Integrated Importance Measure(component UIIM)which considers multiple epistemic uncertainties in the complex multi-state systems.The degradation process for the components is described by a Markov model,and the system reliability model is developed using the Markov hierarchal evidential network.The concept of integrated importance measure is then extended into component UIIM to evaluate the component criticality rather than the component state change criticality,from the perspective of system performance.A case study on displacement compensation hydraulic system is presented to show the effectiveness of the proposed uncertainty importance measure.The results show that the component UIIM can be an effective method for evaluating the component criticality from system performance perspective at the system early design.
基金supported by the National Natural Science Foundation of China(grant No.72074011)the Real World Study Project of Hainan Boao Lecheng Pilot Zone(Real World Study Base of NMPA)(HNLC2022RWS012)+1 种基金the fundamental research funds for central public welfare research institutes(2023CZ-11)National Natural Science Foundation of China(No.82003536).
文摘Background:Patients with type 2 diabetes are at high risk for developing multiple chronic complications.However,there is a lack of studies of the cumulative number of diabetic complications in China.Methods:A retrospective cohort study was performed from 2009 to 2021.Type 2 diabetes patients who were first diagnosed after the age of 35 years between January 1,2009,and December 31,2017,were included.Five states were defined according to the number of chronic complications:no(S0),one(S1),two(S2),three(S3),and four or more complications(S4).A multi-state Markov model was constructed to estimate transition probability,transition intensity,mean sojourn time,and the possible factors for each state.Results:The study included 32653 type 2 diabetes patients(mean age,59.59 years;15929(48.8%)male),and mean follow-up time of 7.75 years.In all,4375 transitions were observed.The 12-year transition probability of from state S0 to S1 was the lowest at 16.4%,while that from S2 to S3 was the highest,at 45.6%.Higher fasting blood glucose,lower high-density lipoprotein cholesterol,higher total cholesterol,and an unhealthy diet were associated with higher risk of progression from S0 to S1.Being female,less than 60 years old,weekly physical activity,and vegetarian diet decreased this risk.Being female and less than 60 years old reduced the likelihood of transition from S1 to S2,whereas lower high-density lipoprotein cholesterol increased this likelihood.Conclusions:Following the occurrence of two complications in type 2 diabetes patients,the risk for accumulating a third complication within a short time is significantly increased.It is important to take advantage of the stable window period when patients have fewer than two complications,strengthen the monitoring of blood glucose and blood lipids,and encourage patients to maintain good living habits to prevent further deterioration.
