The objective and constraint functions related to structural optimization designs are classified into economic and performance indexes in this paper.The influences of their different roles in model construction of str...The objective and constraint functions related to structural optimization designs are classified into economic and performance indexes in this paper.The influences of their different roles in model construction of structural topology optimization are also discussed.Furthermore,two structural topology optimization models,optimizing a performance index under the limitation of an economic index,represented by the minimum compliance with a volume constraint（MCVC）model,and optimizing an economic index under the limitation of a performance index,represented by the minimum weight with a displacement constraint（MWDC）model,are presented.Based on a comparison of numerical example results,the conclusions can be summarized as follows：（1）under the same external loading and displacement performance conditions,the results of the MWDC model are almost equal to those of the MCVC model;（2）the MWDC model overcomes the difficulties and shortcomings of the MCVC model;this makes the MWDC model more feasible in model construction;（3）constructing a model of minimizing an economic index under the limitations of performance indexes is better at meeting the needs of practical engineering problems and completely satisfies safety and economic requirements in mechanical engineering,which have remained unchanged since the early days of mechanical engineering.展开更多
In recent decades,control performance monitoring(CPM)has experienced remarkable progress in research and industrial applications.While CPM research has been investigated using various benchmarks,the historical data be...In recent decades,control performance monitoring(CPM)has experienced remarkable progress in research and industrial applications.While CPM research has been investigated using various benchmarks,the historical data benchmark(HIS)has garnered the most attention due to its practicality and effectiveness.However,existing CPM reviews usually focus on the theoretical benchmark,and there is a lack of an in-depth review that thoroughly explores HIS-based methods.In this article,a comprehensive overview of HIS-based CPM is provided.First,we provide a novel static-dynamic perspective on data-level manifestations of control performance underlying typical controller capacities including regulation and servo:static and dynamic properties.The static property portrays time-independent variability in system output,and the dynamic property describes temporal behavior driven by closed-loop feedback.Accordingly,existing HIS-based CPM approaches and their intrinsic motivations are classified and analyzed from these two perspectives.Specifically,two mainstream solutions for CPM methods are summarized,including static analysis and dynamic analysis,which match data-driven techniques with actual controlling behavior.Furthermore,this paper also points out various opportunities and challenges faced in CPM for modern industry and provides promising directions in the context of artificial intelligence for inspiring future research.展开更多
This study involved numerical simulations of a double tube heat exchanger using the ANSYS FLUENT programversion 22.The study aims to examine methods for minimizing pressure loss and consequently enhancing the thermal ...This study involved numerical simulations of a double tube heat exchanger using the ANSYS FLUENT programversion 22.The study aims to examine methods for minimizing pressure loss and consequently enhancing the thermal performance index(TPI)of a heat exchanger fitted with wavy edge tape that is a heat recovery system(the hot air in simulation instead of t heat from the exhaust gases of the brick factory furnaces and return it to warm the heavy fuel oil by substituting the electrical heater with a heat exchanger to recuperate waste heat from the flue gases,so elevating the temperature of Heavy fuel oil(HFO)to inject from the roof nozzles of combustion chamber of the furnace furthermore reducing cost(by finding the optimal design of wavy edge tape))and energy consumption.Air was selected as the hot gas in the inner pipe instead of furnace exhaust gases due to their similar thermal characteristics.A numerical analysis was conducted to create a novel wavy edge tape with varying widths(50%Di,75%Di,and 95%Di),lengths(1000,1200,1400)mm,amplitudes(5,10,15)mm,and periods of wavy length(5,10,15)mm.The flow rate of the outer pipe fluid(oil)ranges from(0.06 to 0.1)kg/s,while the velocity of the hot fluid(air)varies from(1 to 27)m/s,Re_(air)(6957 to 187,837).The entrance temperature of the hot fluid can be either(200,225,and 250)℃.The study finds that wavy edge tape tubes are more effective than smooth tubes in terms of oil outlet temperature;results revealed that an increase in the oil mass flow rate leads to a decrease in the oil outlet temperature and an increase in the heat transfer rate,at the air temperature 250℃.Additionally,the results indicate that increasing the width,length,and amplitude also leads to an increase in the oil outlet temperature of(94-94.12)℃,the pressure drop of(568.3)Pa,and the Nusselt number(65.7-66.5)respectively on the oil side.Finally,the heat exchanger’s best thermal performance index was found by investigating temperature contour at amplitude(A=5),period(p=15),width(w=75%Di),and length(L=1200 mm).The values for these parameters are,in order(1.02,1.025,1.02,and 1.0077).展开更多
Objective Assessment of right ventricular function in patients with atrial septal defect(ASD)is difficult.The Doppler myocardial performance index(MPI)may provide a method of assessing function in these patients.The p...Objective Assessment of right ventricular function in patients with atrial septal defect(ASD)is difficult.The Doppler myocardial performance index(MPI)may provide a method of assessing function in these patients.The purposes of this study were to evaluate the right ventricular function and its changes in patients with ASD after transcatheter closure of ASD.Methods MPI,defined as the sum of isovolumic relaxation time and isovolumic contraction time derived by ejection time,was measured from tricuspid inflow and right ventricular outflow;Doppler velocity profiles recorded during routine echocardiography.Twenty nine patients(13 men,16 women;mean age 25.28±12.69,range 6 to 57 years)were diagnosed to secundum ASD[the stretched diameters of ASD were from 9 To 36(24.91±7.98)mm],and had a successfully placed Amplatzer septal occluder(ASO)(the sizes of ASO were from 11 to 40 mm);there were 81 sex-matched,age-matched healthy people(control group 41men,40 women;mean age 29.02±14.22,range 4 to 45 years).MPI was measured again on 3 days and 1 month after closure of ASD.Change in the study group was assessed and compared to the control subjects with structurally normal hearts.A complete 2-dimensional and Doppler echocardiographic examination was performed in all study groups.Results 1)The isovolumic relaxation and isovolumic contraction times[respectively(77.59±14.39)ms vs(60.93±12.94)ms,P<0.0001;(28.28±10.88)ms vs(23.64±9.01)ms,P=0.027]were prolonged,and ejection time[(260.65±21.86)ms vs(271.85±21.92)ms,P=0.033]was shortened in patients with ASD compared with that in control subjects,resulting in a marked increase in the MPI(0.40±0.07 vs 0.31±0.05,P<0.0001)from normal values;2)by Pearson's correlations,the MPI had no correlation with heart rate and blood pressure in control subjects and patients with ASD,but it correlated positively with age in patients with ASD;3)by Pearson's correlations,the MPI correlated positively with the diameter of ASD and pulmonary artery pressure;4)after transcatheter closure of ASD,the MPI decreased markedly.Conclusions 1)MPI is a conceptually new,simple,and reproducible Doppler index in patients with ASD;2)MPI is free from the effect of age,heart rate and blood pressure;(3)MPI appears to be relatively dependent on changes in the diameter of ASD and pulmonary artery pressure;4)the right ventricular function was improved after transcatheter closure of ASD.展开更多
Forests produce several types of benefits to both forest landowners and society.The social benefit of private forestry is equal to private benefit plus positive externalities minus negative externalities.This study de...Forests produce several types of benefits to both forest landowners and society.The social benefit of private forestry is equal to private benefit plus positive externalities minus negative externalities.This study developed alternative metrics for the evaluation of the social benefit of forest management.Forest management was assessed in terms of five criteria:economic,socio-cultural,environmental and ecological performance and the resilience of the forest ecosystem.Each criterion was described with three numerical indicators.Alternative performance indices were calculated from the indicator values using methods developed for multi-criteria decision making.It was concluded that indices based on the multiplicative Cobb-Douglas utility function might be the most recommendable when forestry should produce a balanced combination of different ecosystem services.When the indices were used to compare alternative silvicultural systems in terms of their social performance,continuous cover management was ranked better than even-aged management.The performance of even-aged management improved when it aimed at increasing the share of mixed stands and broadleaf species.Maximizing net present value(NPV) with a 1 % discount rate led to better social performance than maximizing NPV with a 4% discount rate.展开更多
The deformation performance index limits of high reinforced concrete （RC） shear wall components based on Chinese codes were discussed by the nonlinear finite element method. Two typical RC shear wall specimens in th...The deformation performance index limits of high reinforced concrete （RC） shear wall components based on Chinese codes were discussed by the nonlinear finite element method. Two typical RC shear wall specimens in the previous work were first used to verify the correctness of the nonlinear finite element method. Then, the nonlinear finite element method was applied to study the deformability of a set of high RC shear wall components designed according to current Chinese codes and with shear span ratio λ≥2.0. Parametric studies were made on the influence of shear span ratio, axial compression ratio, ratio of flexural capacity to shear capacity and main flexural reinforcement ratio of confined botmdary members. Finally, the deformation performance index and its limits of high RC shear wall components under severe earthquakes were proposed by the finite element model results, which offers a reference in determining the performance status of RC shear wall components designed based on Chinese codes.展开更多
The H∞ proportional-integral-differential(PID) feedback for arbitrary-order delayed multi-agent system is investigated to improve the system performance. The closed-loop multi-input multi-output(MIMO) control framewo...The H∞ proportional-integral-differential(PID) feedback for arbitrary-order delayed multi-agent system is investigated to improve the system performance. The closed-loop multi-input multi-output(MIMO) control framework with the distributed PID controller is firstly described for the multi-agent system in a unified way. Then, by using the matrix theory, the prescribed H∞performance criterion of the multi-agent system is shown to be equivalent to several independent H∞ performance constraints of the single-input single-output(SISO) subsystem with respect to the eigenvalues of the Laplacian matrix. Subsequently, for each subsystem,the set of the PID controllers satisfying the required H∞ performance constraint is analytically characterized based on the extended Hermite-Biehler theorem. Finally, the three-dimensional set of the decentralized H∞ PID control parameters is derived by finding the intersection of the H∞ PID regions for all the decomposed subsystems. The simulation results reveal the effectiveness of the proposed method.展开更多
A newly designed approach of simultaneous stabilization is given for linear discrete time-delay systems. The problem of stabilization for a collection of systems is discussed initially. Adequate condition are obtained...A newly designed approach of simultaneous stabilization is given for linear discrete time-delay systems. The problem of stabilization for a collection of systems is discussed initially. Adequate condition are obtained in terms of linear matrix inequalities （LMIs） which are independent of time delays such that the resultant collection of discrete time-delay systems are stable with an upper bound of the quadratic performance index. Subsequently, controllers are designed such that the resultant closed-loop discrete time-delay systems are simultaneously stabilized with the upper bound of the quadratic performance index. Finally,a numerical example is given to illustrate the design method.展开更多
The Code for Seismic Design of Buildings(GB50011-2010)in 2016 and the method of seismic performance-based design for high-rise buildings in the Guide for Performance-based Design of High-Rise Buildings(TBI2017)are com...The Code for Seismic Design of Buildings(GB50011-2010)in 2016 and the method of seismic performance-based design for high-rise buildings in the Guide for Performance-based Design of High-Rise Buildings(TBI2017)are compared.In view of the characteristics and limitations of the seismic performance index set by the Sino-US seismic code,a“three-index”performance index system and evaluation process considering the displacement angle of the structural interlayer,the plastic damage degree of components and the plastic strain of material is put forward;combining the example of time-history analysis of a out-of-code high-rise building under the rare earthquakes is verified.The results show that the method of seismic performance evaluation by using deformation control index in Sino-US seismic code is relatively simple;however,both are lacking in the setting of specific components and the whole structure level respectively.The"three-index"system can comprehensively and quantitatively evaluate the seismic performance of out-of-code high-rise buildings.展开更多
Hamiltonian function is firstly constituted for solving optimal control. When character of controlled object is known,Hamiltonian function is determined by performance index. In this paper,by constituting Hamiltonian ...Hamiltonian function is firstly constituted for solving optimal control. When character of controlled object is known,Hamiltonian function is determined by performance index. In this paper,by constituting Hamiltonian function and solving optimal control of a sort of performance index,we can understand optimal control theory and apply optimal control method better.展开更多
This paper studies the evaluation method of the performances of corporation that was set up by the Financial Ministry in 1999, and then analyzes the advantages and the problems of the method. Finally, this paper studi...This paper studies the evaluation method of the performances of corporation that was set up by the Financial Ministry in 1999, and then analyzes the advantages and the problems of the method. Finally, this paper studies the theoretical method of the evaluation of the performances of corporation.展开更多
Knowledge has become the most important strategic resource of firms, and the competition among firms is more based on knowledge than before. To deal with this challenge, some firms are trying to develop knowledge stra...Knowledge has become the most important strategic resource of firms, and the competition among firms is more based on knowledge than before. To deal with this challenge, some firms are trying to develop knowledge strategies to direct their knowledge management activities, but current strategic performance measurement systems can＇t evaluate the performance of knowledge strategies appropriately. This article develops a performance measurement system for knowledge strategies based on Balanced Scorecard, and simulates the system with an improved Data Envelopment Analysis （DEA） model.展开更多
Reconfigurable parallel mechanisms were first discovered in response to the growing demand for flexible and adaptive systems in various fields.Unlike traditional mechanisms,which are designed for specific tasks and ha...Reconfigurable parallel mechanisms were first discovered in response to the growing demand for flexible and adaptive systems in various fields.Unlike traditional mechanisms,which are designed for specific tasks and have fixed topology and mobility characteristics,a reconfigurable parallel mechanism can be adapted to different situations by changing its structure,motion,and function.This adaptability enables a single mechanism to perform a wide range of tasks,reducing the need for multiple dedicated systems.This paper presents a comprehensive review of reconfigurable parallel mechanisms.The characteristics of their designs,analyses of their properties,and challenges they face are reported.The beginning of this paper features an introduction of reconfigurable parallel mechanisms and their classification into different types.Methods for synthesizing reconfigurable parallel mechanisms are discussed.A performance evaluation index related to reconfigurability,workspace,singularity,stiffness,and dynamics,among other indices,is presented.This review covers the challenges faced in the creation of systematic design theories,unified performance analyses,evaluation index systems,and in the implementation of reconfigurable parallel mechanisms,such as the development of efficient control strategies and integration with other technologies.The paper concludes with a discussion of future research directions for reconfigurable parallel mechanisms.展开更多
The objective of this research is to determine the effect earthquakes have on the performance of transportation network systems.To do this,bridge fragility curves,expressed as a function of peak ground acceleration(PG...The objective of this research is to determine the effect earthquakes have on the performance of transportation network systems.To do this,bridge fragility curves,expressed as a function of peak ground acceleration(PGA)and peak ground velocity(PGV),were developed.Network damage was evaluated under the 1994 Northridge earthquake and scenario earthquakes.A probabilistic model was developed to determine the effect of repair of bridge damage on the improvement of the network performance as days passed after the event.As an example,the system performance degradation measured in terms of an index,'Drivers Delay,'is calculated for the Los Angeles area transportation system,and losses due to Drivers Delay with and without retrofit were estimated.展开更多
During path planning, it is necessary to satisfy the requirements of multiple objectives. Multi-objective synthesis is based on the need of flight mission and subjectivity inclination of decision-maker. The decision-m...During path planning, it is necessary to satisfy the requirements of multiple objectives. Multi-objective synthesis is based on the need of flight mission and subjectivity inclination of decision-maker. The decision-maker, however, has illegibility for under- standing the requirements of multiple objectives and the subjectivity inclination. It is important to develop a reasonable cost performance index for describing the illegibility of the decision-maker in multi-objective path planning. Based on Voronoi dia- gram method for the path planning, this paper studies the synthesis method of the multi-objective cost performance index. Ac- cording to the application of the cost performance index to the path planning based on Voronoi diagram method, this paper ana- lyzes the cost performance index which has been referred to at present. The analysis shows the insufficiency of the cost per- formance index at present, i.e., it is difficult to synthesize sub-objective flmctions because of the great disparity of the sub-objective fimctions. Thus, a new approach is developed to optimize the cost performance index with the multi-objective fuzzy optimization strategy, and an improved performance index is established, which could coordinate the weight conflict of the sub-objective functions. Finally, the experimental result shows the effectiveness of the proposed approach.展开更多
Multi-target tracking(MTT) is a research hotspot of wireless sensor networks at present.A self-organized dynamic cluster task allocation scheme is used to implement collaborative task allocation for MTT in WSN and a s...Multi-target tracking(MTT) is a research hotspot of wireless sensor networks at present.A self-organized dynamic cluster task allocation scheme is used to implement collaborative task allocation for MTT in WSN and a special cluster member(CM) node selection method is put forward in the scheme.An energy efficiency model was proposed under consideration of both energy consumption and remaining energy balance in the network.A tracking accuracy model based on area-sum principle was also presented through analyzing the localization accuracy of triangulation.Then,the two models mentioned above were combined to establish dynamic cluster member selection model for MTT where a comprehensive performance index function was designed to guide the CM node selection.This selection was fulfilled using genetic algorithm.Simulation results show that this method keeps both energy efficiency and tracking quality in optimal state,and also indicate the validity of genetic algorithm in implementing CM node selection.展开更多
Optimal design theory for linear tuned mass dampers （TMD） has been thoroughly investigated, but is still under development for nonlinear TMDs. In this paper, optimization procedures in the time domain are proposed f...Optimal design theory for linear tuned mass dampers （TMD） has been thoroughly investigated, but is still under development for nonlinear TMDs. In this paper, optimization procedures in the time domain are proposed for design of a TMD with nonlinear viscous damping. A dynamic analysis of a structure implemented with a nonlinear TMD is conducted first. Optimum design parameters for the nonlinear TMD are searched using an optimization method to minimize the performance index. The feasibility of the proposed optimization method is illustrated numerically by using the Taipei 101 structure implemented with TMD. The sensitivity analysis shows that the performance index is less sensitive to the damping coefficient than to the frequency ratio. Time history analysis is conducted using the Taipei 101 structure implemented with different TMDs under wind excitation. For both linear and nonlinear TMDs, the comfort requirements for building occupants are satisfied as long as the TMD is properly designed. It was found that as the damping exponent increases, the relative displacement of the TMD decreases but the damping force increases.展开更多
Energy optimization is one of the key problems for ship roll reduction systems in the last decade. According to the nonlinear characteristics of ship motion, the four degrees of freedom nonlinear model of Fin/Rudder r...Energy optimization is one of the key problems for ship roll reduction systems in the last decade. According to the nonlinear characteristics of ship motion, the four degrees of freedom nonlinear model of Fin/Rudder roll stabilization can be established. This paper analyzes energy consumption caused by overcoming the resistance and the yaw, which is added to the fin/rudder roll stabilization system as new performance index. In order to achieve the purpose of the roll reduction, ship course keeping and energy optimization, the self-tuning PID controller based on the multi-objective genetic algorithm （MOGA） method is used to optimize performance index. In addition, random weight coefficient is adopted to build a multi-objective genetic algorithm optimization model. The objective function is improved so that the objective function can be normalized to a constant level. Simulation results showed that the control method based on MOGA, compared with the traditional control method, not only improves the efficiency of roll stabilization and yaw control precision, but also optimizes the energy of the system. The proposed methodology can get a better performance at different sea states.展开更多
Due to low viscosity of seawater,it is difficult to form a seawater-lubricated film.It is easy to cause the overload and burning phenomenon of seawater-lubrication sliding bearing,and then the operation stability and ...Due to low viscosity of seawater,it is difficult to form a seawater-lubricated film.It is easy to cause the overload and burning phenomenon of seawater-lubrication sliding bearing,and then the operation stability and service life can be shortened seriously.Therefore,the paper introduces an electromagnetic suspension theory into the seawater lubricated sliding bearing.Then a novel magnetic-liquid double suspension bearing can be formed,which can enhance bearing capacity and stiffness greatly.Firstly,the structural characteristics,support-adjustment mechanism of magnetic-liquid double suspension bearing is analyzed.Secondly,based on force balance equation,electromagnetic equation and flow equation,the transfer functions of single DOF bearing system of magnetic-liquid double suspension bearing under constant-flow supply model are deduced.Then bearing capacity,static stiffness and total power loss are selected as static performance indexes.The influence rule of operaton and structural parameters on the static performance of single DOF bearing system will be analyzed.The results show that bearing capacity decreases with the increase of liquid film thickness and width of edge seals,bias current and coil turns decrease.Static stiffness decreases with the increase of liquid film thickness,edge seals width,bias current and coil turns.Total power loss decreases with the increase of liquid film thickness,edge seals width,bias current and coil turns decrease.And static performance indexes can not be affected by liquid viscosity.The proposed research provides some theoretical and experimental basis for the parameter design of magnetic-liquid double suspension bearing.展开更多
基金supported by the National Natural Science Foundation of China(Grant 11172013)
文摘The objective and constraint functions related to structural optimization designs are classified into economic and performance indexes in this paper.The influences of their different roles in model construction of structural topology optimization are also discussed.Furthermore,two structural topology optimization models,optimizing a performance index under the limitation of an economic index,represented by the minimum compliance with a volume constraint（MCVC）model,and optimizing an economic index under the limitation of a performance index,represented by the minimum weight with a displacement constraint（MWDC）model,are presented.Based on a comparison of numerical example results,the conclusions can be summarized as follows：（1）under the same external loading and displacement performance conditions,the results of the MWDC model are almost equal to those of the MCVC model;（2）the MWDC model overcomes the difficulties and shortcomings of the MCVC model;this makes the MWDC model more feasible in model construction;（3）constructing a model of minimizing an economic index under the limitations of performance indexes is better at meeting the needs of practical engineering problems and completely satisfies safety and economic requirements in mechanical engineering,which have remained unchanged since the early days of mechanical engineering.
基金supported in part by the National Natural Science Foundation of China(62125306)Zhejiang Key Research and Development Project(2024C01163)the State Key Laboratory of Industrial Control Technology,China(ICT2024A06)
文摘In recent decades,control performance monitoring(CPM)has experienced remarkable progress in research and industrial applications.While CPM research has been investigated using various benchmarks,the historical data benchmark(HIS)has garnered the most attention due to its practicality and effectiveness.However,existing CPM reviews usually focus on the theoretical benchmark,and there is a lack of an in-depth review that thoroughly explores HIS-based methods.In this article,a comprehensive overview of HIS-based CPM is provided.First,we provide a novel static-dynamic perspective on data-level manifestations of control performance underlying typical controller capacities including regulation and servo:static and dynamic properties.The static property portrays time-independent variability in system output,and the dynamic property describes temporal behavior driven by closed-loop feedback.Accordingly,existing HIS-based CPM approaches and their intrinsic motivations are classified and analyzed from these two perspectives.Specifically,two mainstream solutions for CPM methods are summarized,including static analysis and dynamic analysis,which match data-driven techniques with actual controlling behavior.Furthermore,this paper also points out various opportunities and challenges faced in CPM for modern industry and provides promising directions in the context of artificial intelligence for inspiring future research.
文摘This study involved numerical simulations of a double tube heat exchanger using the ANSYS FLUENT programversion 22.The study aims to examine methods for minimizing pressure loss and consequently enhancing the thermal performance index(TPI)of a heat exchanger fitted with wavy edge tape that is a heat recovery system(the hot air in simulation instead of t heat from the exhaust gases of the brick factory furnaces and return it to warm the heavy fuel oil by substituting the electrical heater with a heat exchanger to recuperate waste heat from the flue gases,so elevating the temperature of Heavy fuel oil(HFO)to inject from the roof nozzles of combustion chamber of the furnace furthermore reducing cost(by finding the optimal design of wavy edge tape))and energy consumption.Air was selected as the hot gas in the inner pipe instead of furnace exhaust gases due to their similar thermal characteristics.A numerical analysis was conducted to create a novel wavy edge tape with varying widths(50%Di,75%Di,and 95%Di),lengths(1000,1200,1400)mm,amplitudes(5,10,15)mm,and periods of wavy length(5,10,15)mm.The flow rate of the outer pipe fluid(oil)ranges from(0.06 to 0.1)kg/s,while the velocity of the hot fluid(air)varies from(1 to 27)m/s,Re_(air)(6957 to 187,837).The entrance temperature of the hot fluid can be either(200,225,and 250)℃.The study finds that wavy edge tape tubes are more effective than smooth tubes in terms of oil outlet temperature;results revealed that an increase in the oil mass flow rate leads to a decrease in the oil outlet temperature and an increase in the heat transfer rate,at the air temperature 250℃.Additionally,the results indicate that increasing the width,length,and amplitude also leads to an increase in the oil outlet temperature of(94-94.12)℃,the pressure drop of(568.3)Pa,and the Nusselt number(65.7-66.5)respectively on the oil side.Finally,the heat exchanger’s best thermal performance index was found by investigating temperature contour at amplitude(A=5),period(p=15),width(w=75%Di),and length(L=1200 mm).The values for these parameters are,in order(1.02,1.025,1.02,and 1.0077).
文摘Objective Assessment of right ventricular function in patients with atrial septal defect(ASD)is difficult.The Doppler myocardial performance index(MPI)may provide a method of assessing function in these patients.The purposes of this study were to evaluate the right ventricular function and its changes in patients with ASD after transcatheter closure of ASD.Methods MPI,defined as the sum of isovolumic relaxation time and isovolumic contraction time derived by ejection time,was measured from tricuspid inflow and right ventricular outflow;Doppler velocity profiles recorded during routine echocardiography.Twenty nine patients(13 men,16 women;mean age 25.28±12.69,range 6 to 57 years)were diagnosed to secundum ASD[the stretched diameters of ASD were from 9 To 36(24.91±7.98)mm],and had a successfully placed Amplatzer septal occluder(ASO)(the sizes of ASO were from 11 to 40 mm);there were 81 sex-matched,age-matched healthy people(control group 41men,40 women;mean age 29.02±14.22,range 4 to 45 years).MPI was measured again on 3 days and 1 month after closure of ASD.Change in the study group was assessed and compared to the control subjects with structurally normal hearts.A complete 2-dimensional and Doppler echocardiographic examination was performed in all study groups.Results 1)The isovolumic relaxation and isovolumic contraction times[respectively(77.59±14.39)ms vs(60.93±12.94)ms,P<0.0001;(28.28±10.88)ms vs(23.64±9.01)ms,P=0.027]were prolonged,and ejection time[(260.65±21.86)ms vs(271.85±21.92)ms,P=0.033]was shortened in patients with ASD compared with that in control subjects,resulting in a marked increase in the MPI(0.40±0.07 vs 0.31±0.05,P<0.0001)from normal values;2)by Pearson's correlations,the MPI had no correlation with heart rate and blood pressure in control subjects and patients with ASD,but it correlated positively with age in patients with ASD;3)by Pearson's correlations,the MPI correlated positively with the diameter of ASD and pulmonary artery pressure;4)after transcatheter closure of ASD,the MPI decreased markedly.Conclusions 1)MPI is a conceptually new,simple,and reproducible Doppler index in patients with ASD;2)MPI is free from the effect of age,heart rate and blood pressure;(3)MPI appears to be relatively dependent on changes in the diameter of ASD and pulmonary artery pressure;4)the right ventricular function was improved after transcatheter closure of ASD.
文摘Forests produce several types of benefits to both forest landowners and society.The social benefit of private forestry is equal to private benefit plus positive externalities minus negative externalities.This study developed alternative metrics for the evaluation of the social benefit of forest management.Forest management was assessed in terms of five criteria:economic,socio-cultural,environmental and ecological performance and the resilience of the forest ecosystem.Each criterion was described with three numerical indicators.Alternative performance indices were calculated from the indicator values using methods developed for multi-criteria decision making.It was concluded that indices based on the multiplicative Cobb-Douglas utility function might be the most recommendable when forestry should produce a balanced combination of different ecosystem services.When the indices were used to compare alternative silvicultural systems in terms of their social performance,continuous cover management was ranked better than even-aged management.The performance of even-aged management improved when it aimed at increasing the share of mixed stands and broadleaf species.Maximizing net present value(NPV) with a 1 % discount rate led to better social performance than maximizing NPV with a 4% discount rate.
基金Project(2009ZA04) supported by the Independent Research Foundation of State Key Laboratory of Subtropical Architecture Science,China
文摘The deformation performance index limits of high reinforced concrete （RC） shear wall components based on Chinese codes were discussed by the nonlinear finite element method. Two typical RC shear wall specimens in the previous work were first used to verify the correctness of the nonlinear finite element method. Then, the nonlinear finite element method was applied to study the deformability of a set of high RC shear wall components designed according to current Chinese codes and with shear span ratio λ≥2.0. Parametric studies were made on the influence of shear span ratio, axial compression ratio, ratio of flexural capacity to shear capacity and main flexural reinforcement ratio of confined botmdary members. Finally, the deformation performance index and its limits of high RC shear wall components under severe earthquakes were proposed by the finite element model results, which offers a reference in determining the performance status of RC shear wall components designed based on Chinese codes.
基金supported by National Natural Science Foundationof China(Nos.61273116 and 61074039)National Natural ScienceFund for Distinguished Young Scholar of China(No.61026016)Natural Science Foundation of Zhejiang Province(No.Y1111012)
文摘The H∞ proportional-integral-differential(PID) feedback for arbitrary-order delayed multi-agent system is investigated to improve the system performance. The closed-loop multi-input multi-output(MIMO) control framework with the distributed PID controller is firstly described for the multi-agent system in a unified way. Then, by using the matrix theory, the prescribed H∞performance criterion of the multi-agent system is shown to be equivalent to several independent H∞ performance constraints of the single-input single-output(SISO) subsystem with respect to the eigenvalues of the Laplacian matrix. Subsequently, for each subsystem,the set of the PID controllers satisfying the required H∞ performance constraint is analytically characterized based on the extended Hermite-Biehler theorem. Finally, the three-dimensional set of the decentralized H∞ PID control parameters is derived by finding the intersection of the H∞ PID regions for all the decomposed subsystems. The simulation results reveal the effectiveness of the proposed method.
基金This project was Supported by the National Natural Science Foundation of China (50335020,60574011) PostdoctoralFund (2005038553) Science Research Important Foundation in Hubei Provincial Department of Education(2002z04001).
文摘A newly designed approach of simultaneous stabilization is given for linear discrete time-delay systems. The problem of stabilization for a collection of systems is discussed initially. Adequate condition are obtained in terms of linear matrix inequalities （LMIs） which are independent of time delays such that the resultant collection of discrete time-delay systems are stable with an upper bound of the quadratic performance index. Subsequently, controllers are designed such that the resultant closed-loop discrete time-delay systems are simultaneously stabilized with the upper bound of the quadratic performance index. Finally,a numerical example is given to illustrate the design method.
文摘The Code for Seismic Design of Buildings(GB50011-2010)in 2016 and the method of seismic performance-based design for high-rise buildings in the Guide for Performance-based Design of High-Rise Buildings(TBI2017)are compared.In view of the characteristics and limitations of the seismic performance index set by the Sino-US seismic code,a“three-index”performance index system and evaluation process considering the displacement angle of the structural interlayer,the plastic damage degree of components and the plastic strain of material is put forward;combining the example of time-history analysis of a out-of-code high-rise building under the rare earthquakes is verified.The results show that the method of seismic performance evaluation by using deformation control index in Sino-US seismic code is relatively simple;however,both are lacking in the setting of specific components and the whole structure level respectively.The"three-index"system can comprehensively and quantitatively evaluate the seismic performance of out-of-code high-rise buildings.
文摘Hamiltonian function is firstly constituted for solving optimal control. When character of controlled object is known,Hamiltonian function is determined by performance index. In this paper,by constituting Hamiltonian function and solving optimal control of a sort of performance index,we can understand optimal control theory and apply optimal control method better.
文摘This paper studies the evaluation method of the performances of corporation that was set up by the Financial Ministry in 1999, and then analyzes the advantages and the problems of the method. Finally, this paper studies the theoretical method of the evaluation of the performances of corporation.
文摘Knowledge has become the most important strategic resource of firms, and the competition among firms is more based on knowledge than before. To deal with this challenge, some firms are trying to develop knowledge strategies to direct their knowledge management activities, but current strategic performance measurement systems can＇t evaluate the performance of knowledge strategies appropriately. This article develops a performance measurement system for knowledge strategies based on Balanced Scorecard, and simulates the system with an improved Data Envelopment Analysis （DEA） model.
基金the financial support from the Research Institute for Artificial Intelligence of Things(RIAIoT)the Research Institute for Advanced Manufacturing(RIAM)+1 种基金the Research Institute for Intelligent Wearable Systems(RI-IWEAR)the Research Centre of Textiles for Future Fashion(RCTFF)at the Hong Kong Polytechnic University。
文摘Reconfigurable parallel mechanisms were first discovered in response to the growing demand for flexible and adaptive systems in various fields.Unlike traditional mechanisms,which are designed for specific tasks and have fixed topology and mobility characteristics,a reconfigurable parallel mechanism can be adapted to different situations by changing its structure,motion,and function.This adaptability enables a single mechanism to perform a wide range of tasks,reducing the need for multiple dedicated systems.This paper presents a comprehensive review of reconfigurable parallel mechanisms.The characteristics of their designs,analyses of their properties,and challenges they face are reported.The beginning of this paper features an introduction of reconfigurable parallel mechanisms and their classification into different types.Methods for synthesizing reconfigurable parallel mechanisms are discussed.A performance evaluation index related to reconfigurability,workspace,singularity,stiffness,and dynamics,among other indices,is presented.This review covers the challenges faced in the creation of systematic design theories,unified performance analyses,evaluation index systems,and in the implementation of reconfigurable parallel mechanisms,such as the development of efficient control strategies and integration with other technologies.The paper concludes with a discussion of future research directions for reconfigurable parallel mechanisms.
基金The Federal Highway Administration(FHWA)under Contract No.DTFH61-98-C-00094the California Department of Transportation(CALTRANS)
文摘The objective of this research is to determine the effect earthquakes have on the performance of transportation network systems.To do this,bridge fragility curves,expressed as a function of peak ground acceleration(PGA)and peak ground velocity(PGV),were developed.Network damage was evaluated under the 1994 Northridge earthquake and scenario earthquakes.A probabilistic model was developed to determine the effect of repair of bridge damage on the improvement of the network performance as days passed after the event.As an example,the system performance degradation measured in terms of an index,'Drivers Delay,'is calculated for the Los Angeles area transportation system,and losses due to Drivers Delay with and without retrofit were estimated.
文摘During path planning, it is necessary to satisfy the requirements of multiple objectives. Multi-objective synthesis is based on the need of flight mission and subjectivity inclination of decision-maker. The decision-maker, however, has illegibility for under- standing the requirements of multiple objectives and the subjectivity inclination. It is important to develop a reasonable cost performance index for describing the illegibility of the decision-maker in multi-objective path planning. Based on Voronoi dia- gram method for the path planning, this paper studies the synthesis method of the multi-objective cost performance index. Ac- cording to the application of the cost performance index to the path planning based on Voronoi diagram method, this paper ana- lyzes the cost performance index which has been referred to at present. The analysis shows the insufficiency of the cost per- formance index at present, i.e., it is difficult to synthesize sub-objective flmctions because of the great disparity of the sub-objective fimctions. Thus, a new approach is developed to optimize the cost performance index with the multi-objective fuzzy optimization strategy, and an improved performance index is established, which could coordinate the weight conflict of the sub-objective functions. Finally, the experimental result shows the effectiveness of the proposed approach.
基金Projects(90820302,60805027)supported by the National Natural Science Foundation of ChinaProject(200805330005)supported by the Research Fund for the Doctoral Program of Higher Education,ChinaProject(2009FJ4030)supported by Academician Foundation of Hunan Province,China
文摘Multi-target tracking(MTT) is a research hotspot of wireless sensor networks at present.A self-organized dynamic cluster task allocation scheme is used to implement collaborative task allocation for MTT in WSN and a special cluster member(CM) node selection method is put forward in the scheme.An energy efficiency model was proposed under consideration of both energy consumption and remaining energy balance in the network.A tracking accuracy model based on area-sum principle was also presented through analyzing the localization accuracy of triangulation.Then,the two models mentioned above were combined to establish dynamic cluster member selection model for MTT where a comprehensive performance index function was designed to guide the CM node selection.This selection was fulfilled using genetic algorithm.Simulation results show that this method keeps both energy efficiency and tracking quality in optimal state,and also indicate the validity of genetic algorithm in implementing CM node selection.
文摘Optimal design theory for linear tuned mass dampers （TMD） has been thoroughly investigated, but is still under development for nonlinear TMDs. In this paper, optimization procedures in the time domain are proposed for design of a TMD with nonlinear viscous damping. A dynamic analysis of a structure implemented with a nonlinear TMD is conducted first. Optimum design parameters for the nonlinear TMD are searched using an optimization method to minimize the performance index. The feasibility of the proposed optimization method is illustrated numerically by using the Taipei 101 structure implemented with TMD. The sensitivity analysis shows that the performance index is less sensitive to the damping coefficient than to the frequency ratio. Time history analysis is conducted using the Taipei 101 structure implemented with different TMDs under wind excitation. For both linear and nonlinear TMDs, the comfort requirements for building occupants are satisfied as long as the TMD is properly designed. It was found that as the damping exponent increases, the relative displacement of the TMD decreases but the damping force increases.
基金Foundation item： Supported by the National Natural Science Foundation of China （Grant No. 61174047） and the Fundamental Research Funds for the Central Universities （HEUCF041406）.
文摘Energy optimization is one of the key problems for ship roll reduction systems in the last decade. According to the nonlinear characteristics of ship motion, the four degrees of freedom nonlinear model of Fin/Rudder roll stabilization can be established. This paper analyzes energy consumption caused by overcoming the resistance and the yaw, which is added to the fin/rudder roll stabilization system as new performance index. In order to achieve the purpose of the roll reduction, ship course keeping and energy optimization, the self-tuning PID controller based on the multi-objective genetic algorithm （MOGA） method is used to optimize performance index. In addition, random weight coefficient is adopted to build a multi-objective genetic algorithm optimization model. The objective function is improved so that the objective function can be normalized to a constant level. Simulation results showed that the control method based on MOGA, compared with the traditional control method, not only improves the efficiency of roll stabilization and yaw control precision, but also optimizes the energy of the system. The proposed methodology can get a better performance at different sea states.
基金Support by the National Natural Science Foundation of China(No.51705445)the Open Project Funding of Hebei Provincial Key Laboratory of Heavy Machinery Fluid Power Transmission and Controlthe Open Project Funding of Jiangsu Provincial Key Laboratory of Advanced Manufacture and Process for Marine Mechanical Equipment
文摘Due to low viscosity of seawater,it is difficult to form a seawater-lubricated film.It is easy to cause the overload and burning phenomenon of seawater-lubrication sliding bearing,and then the operation stability and service life can be shortened seriously.Therefore,the paper introduces an electromagnetic suspension theory into the seawater lubricated sliding bearing.Then a novel magnetic-liquid double suspension bearing can be formed,which can enhance bearing capacity and stiffness greatly.Firstly,the structural characteristics,support-adjustment mechanism of magnetic-liquid double suspension bearing is analyzed.Secondly,based on force balance equation,electromagnetic equation and flow equation,the transfer functions of single DOF bearing system of magnetic-liquid double suspension bearing under constant-flow supply model are deduced.Then bearing capacity,static stiffness and total power loss are selected as static performance indexes.The influence rule of operaton and structural parameters on the static performance of single DOF bearing system will be analyzed.The results show that bearing capacity decreases with the increase of liquid film thickness and width of edge seals,bias current and coil turns decrease.Static stiffness decreases with the increase of liquid film thickness,edge seals width,bias current and coil turns.Total power loss decreases with the increase of liquid film thickness,edge seals width,bias current and coil turns decrease.And static performance indexes can not be affected by liquid viscosity.The proposed research provides some theoretical and experimental basis for the parameter design of magnetic-liquid double suspension bearing.
