A principal component analysis-cerebellar model articulation controller （PCA-CMAC） model is proposed for machine performance degradation assessment.PCA is used to feature selection,which eliminates the redundant inf...A principal component analysis-cerebellar model articulation controller （PCA-CMAC） model is proposed for machine performance degradation assessment.PCA is used to feature selection,which eliminates the redundant information among the features from the sensor signals and reduces the dimension of the input to CMAC.CMAC is used to assess degradation states quantitatively based on its local generalization ability.The implementation of the model is presented and the model is applied in a drilling machine to assess the states of the cutting tool. The results show that the model can assess the wear states quantitatively based on the normal state of the cutting tool.The influence of the quantization parameter g and the generalization parameter r in the CMAC model on the assessment results is analyzed.If g is larger,the generalization ability is better,but the difference of degradation states is not obvious.If r is smaller,the different states are distinct,but memory requirements for storing the weights are larger.The principle for selecting two parameters is that the memory storing the weights should be small while the degradation states should be easily distinguished.展开更多
A quite severe degradation was found in all seven types of grasslands in the study area involving 12counties of the northwestern Qinghai Province. The slightly, moderately and severely degraded grasslandsoccupied 49.7...A quite severe degradation was found in all seven types of grasslands in the study area involving 12counties of the northwestern Qinghai Province. The slightly, moderately and severely degraded grasslandsoccupied 49.7%, 32.0% and 18.3% of the area respectively. The major factors resulting in the degradationwere overgrazing, the damages from mice and grasshopper and blown sands, and improper use of grasslands.The measures to deal with these problems should be: 1) to make livestock development in accordancewith grassland carrying capacity for animals; 2) to build more artificial grasslands with a stable and highergraas yield; 3) to put more widely the rotation grazing system into practice; 4) to clear up the poisonousgrass species; and 5) to adopt more effective measures to deal with the damages to grasslands by mice andgrasshoppers.展开更多
The reasons for the Yangtze River flood calamity in 1998 are briefly introduced. The authors believe that using a 'soil reservoir' concept is an important means to help control flooding of the Yangtze River.A ...The reasons for the Yangtze River flood calamity in 1998 are briefly introduced. The authors believe that using a 'soil reservoir' concept is an important means to help control flooding of the Yangtze River.A 'soil reservoir' has a large potential storage capacity and its water can be rapidly 'discharged' into the underground water in a timely fashion. The eroded, infertile soils of the Yangtze River Watershed are currently an obstacle to efficient operation of the 'soil reservoir'. The storage capacity of this 'soil reservoir'has been severely hampered due to intensive soil erosion and the formation of soil crusts. Therefore, possible measures to control floods in the Yangtze River Watershed include: rehabilitating the vegetation to preserve soil and water on the eroded infertile soils, enhancing infiltration of the different soil types, and utilizing the large 'soil reservoir' of the upper reaches of the Yangtze River.展开更多
As molecular weight controls the biological activities of polysaccharides, screening the optimal molecular weight of polysaccharides is important in drug research and application. In this study, hydrogen peroxide was ...As molecular weight controls the biological activities of polysaccharides, screening the optimal molecular weight of polysaccharides is important in drug research and application. In this study, hydrogen peroxide was employed as oxidant, and temperature, reaction time, and concentration of polysaccharides and hydrogen peroxide were examined for their effects on the preparation of polysaccharides in different molecular weights from Ulva pertusa. Our experiment suggested that the optimal degradation concentrations for polysac-charides and hydrogen peroxide were 2.5% (w/v) and 8.0% (v/v), respectively. The range of degradation measured by relative viscosity was mainly controlled by temperature and time. Results revealed that 35℃ was the optimal temperature for obtaining low-degradation samples, and 50℃ was the most favorable temperature to accelerate the reaction to yield highly-degraded samples. Four samples in different molecular weights A, B, C and D were finally prepared. The controllability was evaluated by the relative standard deviation (RSD) of relative viscosity, and the peak molecular weights and the polydispersity indexes (Mw/Mn) of molecular weights were measured by high performance gel permeation chromatography (HPGPC).展开更多
This paper is devoted to a study of the null controllability problems for one-dimensional linear degenerate wave equations through a boundary controller. First, the well-posedness of linear degenerate wave equations i...This paper is devoted to a study of the null controllability problems for one-dimensional linear degenerate wave equations through a boundary controller. First, the well-posedness of linear degenerate wave equations is discussed. Then the null controllability of some degenerate wave equations is established, when a control acts on the non-degenerate boundary. Different from the known controllability results in the case that a control acts on the degenerate boundary, any initial value in state space is controllable in this case. Also, an explicit expression for the controllability time is given. Furthermore, a counterexample on the controllability is given for some other degenerate wave equations.展开更多
Impulse observability and impulse controllability of regular degenerate evolution systems are discussed by using functional analysis and operator theory in Banach space. Necessary and sufficient conditions for the imp...Impulse observability and impulse controllability of regular degenerate evolution systems are discussed by using functional analysis and operator theory in Banach space. Necessary and sufficient conditions for the impulse observability and impulse controllability of the system are obtained. This research is theoretically important for studying the design of the degenerate evolution system.展开更多
Software Defined Networking （SDN） is an emerging networking paradigm that assumes a logically centralized control plane separated from the data plane. Despite all its advantages, separating the control and data plan...Software Defined Networking （SDN） is an emerging networking paradigm that assumes a logically centralized control plane separated from the data plane. Despite all its advantages, separating the control and data planes introduces new challenges regarding resilient communications between the two. That is, disconnec- tions between switches and their controllers could result in substantial packet loss and performance degradation. This paper addresses this challenge by studying the issue of control traffic protection in SDNs with arbitrary numbers of controllers. Specifically, we propose a control traffic protection scheme that combines both local rerouting and constrained reverse path forwarding protections, through which switches can locally react to fail- ures and redirect the control traffic using standby backup forwarding options. Our goal is then to find a set of primary routes for control traffic, called protected control network, where as many switches as possible can benefit from the proposed protection scheme. We formulate the protected control network problem, prove its NP-hardness, and develop an algorithm that reconciles proteetability and performance （e.g., switch-to-control latency）. Through extensive simulations based on real topologies, we show that our approach significantly im- proves protectability of control traffic. The results should help further the process of deploying SDN in real-world networks.展开更多
In this paper,we discuss the optimal control of growth rate for a class of population systems governed by nonlinear degenerate parabolic equations.Given an ap-propriate cost functional,we prove the existence of the op...In this paper,we discuss the optimal control of growth rate for a class of population systems governed by nonlinear degenerate parabolic equations.Given an ap-propriate cost functional,we prove the existence of the optimal growth rate and give some necessary conditions for optimal growth rate.展开更多
基金The National Natural Science Foundation of China(No.60443007,50390063).
文摘A principal component analysis-cerebellar model articulation controller （PCA-CMAC） model is proposed for machine performance degradation assessment.PCA is used to feature selection,which eliminates the redundant information among the features from the sensor signals and reduces the dimension of the input to CMAC.CMAC is used to assess degradation states quantitatively based on its local generalization ability.The implementation of the model is presented and the model is applied in a drilling machine to assess the states of the cutting tool. The results show that the model can assess the wear states quantitatively based on the normal state of the cutting tool.The influence of the quantization parameter g and the generalization parameter r in the CMAC model on the assessment results is analyzed.If g is larger,the generalization ability is better,but the difference of degradation states is not obvious.If r is smaller,the different states are distinct,but memory requirements for storing the weights are larger.The principle for selecting two parameters is that the memory storing the weights should be small while the degradation states should be easily distinguished.
文摘A quite severe degradation was found in all seven types of grasslands in the study area involving 12counties of the northwestern Qinghai Province. The slightly, moderately and severely degraded grasslandsoccupied 49.7%, 32.0% and 18.3% of the area respectively. The major factors resulting in the degradationwere overgrazing, the damages from mice and grasshopper and blown sands, and improper use of grasslands.The measures to deal with these problems should be: 1) to make livestock development in accordancewith grassland carrying capacity for animals; 2) to build more artificial grasslands with a stable and highergraas yield; 3) to put more widely the rotation grazing system into practice; 4) to clear up the poisonousgrass species; and 5) to adopt more effective measures to deal with the damages to grasslands by mice andgrasshoppers.
基金Project supported by the National Key Basic Research Support Foundation (NKBRSF) of China (No. G1999011810) the National Natural Science Foundation of China (No. 49971039).
文摘The reasons for the Yangtze River flood calamity in 1998 are briefly introduced. The authors believe that using a 'soil reservoir' concept is an important means to help control flooding of the Yangtze River.A 'soil reservoir' has a large potential storage capacity and its water can be rapidly 'discharged' into the underground water in a timely fashion. The eroded, infertile soils of the Yangtze River Watershed are currently an obstacle to efficient operation of the 'soil reservoir'. The storage capacity of this 'soil reservoir'has been severely hampered due to intensive soil erosion and the formation of soil crusts. Therefore, possible measures to control floods in the Yangtze River Watershed include: rehabilitating the vegetation to preserve soil and water on the eroded infertile soils, enhancing infiltration of the different soil types, and utilizing the large 'soil reservoir' of the upper reaches of the Yangtze River.
基金This work was supported by the Scientific and Technical Bureau of Shandong Province.
文摘As molecular weight controls the biological activities of polysaccharides, screening the optimal molecular weight of polysaccharides is important in drug research and application. In this study, hydrogen peroxide was employed as oxidant, and temperature, reaction time, and concentration of polysaccharides and hydrogen peroxide were examined for their effects on the preparation of polysaccharides in different molecular weights from Ulva pertusa. Our experiment suggested that the optimal degradation concentrations for polysac-charides and hydrogen peroxide were 2.5% (w/v) and 8.0% (v/v), respectively. The range of degradation measured by relative viscosity was mainly controlled by temperature and time. Results revealed that 35℃ was the optimal temperature for obtaining low-degradation samples, and 50℃ was the most favorable temperature to accelerate the reaction to yield highly-degraded samples. Four samples in different molecular weights A, B, C and D were finally prepared. The controllability was evaluated by the relative standard deviation (RSD) of relative viscosity, and the peak molecular weights and the polydispersity indexes (Mw/Mn) of molecular weights were measured by high performance gel permeation chromatography (HPGPC).
基金supported by the National Natural Science Foundation of China under Grant Nos.11371084,11471070 and 11171060the Fundamental Research Funds for the Central Universities under Grant Nos.14ZZ2222 and 2412015BJ011+1 种基金the National Basic Research Program of China(973 Program)under Grant No.2011CB808002the Fok Ying Tong Education Foundation under Grant No.141001
文摘This paper is devoted to a study of the null controllability problems for one-dimensional linear degenerate wave equations through a boundary controller. First, the well-posedness of linear degenerate wave equations is discussed. Then the null controllability of some degenerate wave equations is established, when a control acts on the non-degenerate boundary. Different from the known controllability results in the case that a control acts on the degenerate boundary, any initial value in state space is controllable in this case. Also, an explicit expression for the controllability time is given. Furthermore, a counterexample on the controllability is given for some other degenerate wave equations.
基金supported by the National Natural Science Foundation of China under Grant No.61174081
文摘Impulse observability and impulse controllability of regular degenerate evolution systems are discussed by using functional analysis and operator theory in Banach space. Necessary and sufficient conditions for the impulse observability and impulse controllability of the system are obtained. This research is theoretically important for studying the design of the degenerate evolution system.
基金supported in part by National High-tech R&D Program of China(863 Program)(Grant Nos.2013AA0133012015AA016101)
文摘Software Defined Networking （SDN） is an emerging networking paradigm that assumes a logically centralized control plane separated from the data plane. Despite all its advantages, separating the control and data planes introduces new challenges regarding resilient communications between the two. That is, disconnec- tions between switches and their controllers could result in substantial packet loss and performance degradation. This paper addresses this challenge by studying the issue of control traffic protection in SDNs with arbitrary numbers of controllers. Specifically, we propose a control traffic protection scheme that combines both local rerouting and constrained reverse path forwarding protections, through which switches can locally react to fail- ures and redirect the control traffic using standby backup forwarding options. Our goal is then to find a set of primary routes for control traffic, called protected control network, where as many switches as possible can benefit from the proposed protection scheme. We formulate the protected control network problem, prove its NP-hardness, and develop an algorithm that reconciles proteetability and performance （e.g., switch-to-control latency）. Through extensive simulations based on real topologies, we show that our approach significantly im- proves protectability of control traffic. The results should help further the process of deploying SDN in real-world networks.
基金This research is supported by the National Natural Science Foundation of China.
文摘In this paper,we discuss the optimal control of growth rate for a class of population systems governed by nonlinear degenerate parabolic equations.Given an ap-propriate cost functional,we prove the existence of the optimal growth rate and give some necessary conditions for optimal growth rate.
