Due to the popularity of the systems with input redundancy,this paper focuses on the problems with input redundancy,where we concern about the effects of adding new input redundancy into the controllable systems.Time ...Due to the popularity of the systems with input redundancy,this paper focuses on the problems with input redundancy,where we concern about the effects of adding new input redundancy into the controllable systems.Time optimal control problems are discussed,where such effects are evaluated by the optimal time.Based on the assumption of the existence and uniqueness of the optimal control,the paper proves that increasing the number of input redundancy will result in a strict reduction of the optimal time from the same initial state if there exists non-idle channel among the redundant input channels.Moreover,if the problem is normal,then all of the redundant input channels are used to shorten the optimal time.On the other hand,without the assumption of normality,the optimal time will also be smaller for the redundant system as comparing to the original system if at least one of these redundant input channels is completely controllable.Finally,two numerical examples are deployed to demonstrate the main results of this paper.展开更多
Severe resource shortage and waste of resource in agricultural production make it necessary to assess efficiency to increase productivity with high efficiency and ensure sustainable agricultural development. This pape...Severe resource shortage and waste of resource in agricultural production make it necessary to assess efficiency to increase productivity with high efficiency and ensure sustainable agricultural development. This paper adopted an input-oriented data envelopment analysis(DEA) method with the assumption of variable returns to scale to evaluate agricultural production efficiency of 100 major irrigation districts in Northwest China in 2010.Major findings of this paper were as follows: firstly, the average value of total technical efficiency, pure technical efficiency and scale efficiency of those irrigation districts in Northwest China were 0.770, 0.825 and 0.931,respectively; secondly, 30% of irrigation districts were technically efficient, while 42% and 32% of them showed pure technical and scale efficiency respectively. Among inefficient decision-making units, total technical efficiency score varied from 0.313 to 0.966, showing significant geographical differences, but geographical differences of pure technical efficiency was more consistent with that of total technical efficiency; thirdly, input redundancy was evident. Inputs of agricultural population, irrigation area,green water, blue water, consumption of fertilizer and agricultural machinery could be reduced by 34.88%,40.19%, 43.85%, 47.10%, 41.53% and 42.21% respectively without reducing agricultural outputs. Furthermore,irrigation area, green water and blue water had relatively high slack movement though Northwest China which is short of water resources. Based on these results, this paper drew the following conclusions: First, there is huge potential for Northwest China to improve its agricultural production efficiency, and agro-technology not input scale had greater influence on improvement. Second, farmers needed proper guidance in order to reduce agricultural inputs and it is time to centralize agricultural management for overall agricultural inputs regulation and control.展开更多
This paper discusses the harmonic problems in control systems from two aspects:Oneis the harmonic control among different subsystems,and the other is the harmonic control amongmultiple inputs.Some intrinsic problems i...This paper discusses the harmonic problems in control systems from two aspects:Oneis the harmonic control among different subsystems,and the other is the harmonic control amongmultiple inputs.Some intrinsic problems in such systems are discussed.It is pointed out that somesubsystems must be unstable to stabilize the whole interconnected system by an example.Especiallyfor discrete-time multi-input systems,a necessary and sufficient condition is presented for the strictdecrease of the quadratic optimal performance index with the control input extensions.This showsan essential difference between single-input and multi-input control systems.Finally,some futureresearch directions are discussed in harmonic control of interconnected systems,allocation of multi-control inputs,fault-tolerant control,and fault-diagnosis.展开更多
基金Supportecl by National Natural Science Foundation-of-China(60874011,90916003)
文摘Due to the popularity of the systems with input redundancy,this paper focuses on the problems with input redundancy,where we concern about the effects of adding new input redundancy into the controllable systems.Time optimal control problems are discussed,where such effects are evaluated by the optimal time.Based on the assumption of the existence and uniqueness of the optimal control,the paper proves that increasing the number of input redundancy will result in a strict reduction of the optimal time from the same initial state if there exists non-idle channel among the redundant input channels.Moreover,if the problem is normal,then all of the redundant input channels are used to shorten the optimal time.On the other hand,without the assumption of normality,the optimal time will also be smaller for the redundant system as comparing to the original system if at least one of these redundant input channels is completely controllable.Finally,two numerical examples are deployed to demonstrate the main results of this paper.
基金supported by the National Key Research and Development Program (2016YFC0400201, 2016YFC0400 205)the ‘111’ Project from the Ministry of Education of China and the State Administration of Foreign Experts Affairs of China (B12007)the Science and Technology Planning Project of Yangling Demonstration Zone (2015NY-16)
文摘Severe resource shortage and waste of resource in agricultural production make it necessary to assess efficiency to increase productivity with high efficiency and ensure sustainable agricultural development. This paper adopted an input-oriented data envelopment analysis(DEA) method with the assumption of variable returns to scale to evaluate agricultural production efficiency of 100 major irrigation districts in Northwest China in 2010.Major findings of this paper were as follows: firstly, the average value of total technical efficiency, pure technical efficiency and scale efficiency of those irrigation districts in Northwest China were 0.770, 0.825 and 0.931,respectively; secondly, 30% of irrigation districts were technically efficient, while 42% and 32% of them showed pure technical and scale efficiency respectively. Among inefficient decision-making units, total technical efficiency score varied from 0.313 to 0.966, showing significant geographical differences, but geographical differences of pure technical efficiency was more consistent with that of total technical efficiency; thirdly, input redundancy was evident. Inputs of agricultural population, irrigation area,green water, blue water, consumption of fertilizer and agricultural machinery could be reduced by 34.88%,40.19%, 43.85%, 47.10%, 41.53% and 42.21% respectively without reducing agricultural outputs. Furthermore,irrigation area, green water and blue water had relatively high slack movement though Northwest China which is short of water resources. Based on these results, this paper drew the following conclusions: First, there is huge potential for Northwest China to improve its agricultural production efficiency, and agro-technology not input scale had greater influence on improvement. Second, farmers needed proper guidance in order to reduce agricultural inputs and it is time to centralize agricultural management for overall agricultural inputs regulation and control.
基金supported by National Natural Science Foundation of China under Grant Nos. 90916003 and 60674093the Key Projects of Educational Ministry under Grant No. 107110
文摘This paper discusses the harmonic problems in control systems from two aspects:Oneis the harmonic control among different subsystems,and the other is the harmonic control amongmultiple inputs.Some intrinsic problems in such systems are discussed.It is pointed out that somesubsystems must be unstable to stabilize the whole interconnected system by an example.Especiallyfor discrete-time multi-input systems,a necessary and sufficient condition is presented for the strictdecrease of the quadratic optimal performance index with the control input extensions.This showsan essential difference between single-input and multi-input control systems.Finally,some futureresearch directions are discussed in harmonic control of interconnected systems,allocation of multi-control inputs,fault-tolerant control,and fault-diagnosis.
