Nanocarbon as an eco-friendly and abundant material has strong multi-color fluorescence, which makes it a promising candidate for healthy lighting and display. However, the low fluorescence efficiency and poor stabili...Nanocarbon as an eco-friendly and abundant material has strong multi-color fluorescence, which makes it a promising candidate for healthy lighting and display. However, the low fluorescence efficiency and poor stability of multi-color carbon nanoparticle（CNP） phosphors are main hurdles that hinder their applications. This work demonstrated efficient and stable multi-color CNP phosphors through synergy between inner polar groups and outer silica matrix. The polar groups in polyethylene glycol（PEG） 6,000 are favor of high fluorescence of the CNP phosphors, and the low melting point（64℃） of PEG 6,000 helps to improve the thermal stability of the phosphors, while the silica matrix provides protection to the phosphors. Based on this design,blue, green, yellow and red CNP phosphors with photoluminescence quantum yield of 53.1%, 47.4%, 43.8% and 42.3% have been achieved, all of which are the best values in ever reported multi-color CNP phosphors. Furthermore, the fluorescence of the CNP phosphors keeps almost unchanged at 100℃ and degrades little in one month, indicating their good thermal tolerance and temporal stability. In addition, multicolor devices including white light-emitting devices（LEDs）have been realized by coating the CNP phosphors onto UV chips. The luminous efficiency, correlated color temperature,Commission Internationale de L＇Eclairage and color rendering index of the white LED can reach 12 lm W^-1, 6,107 K,（0.32, 0.33） and 89, respectively, indicating the potential applications of the CNP phosphors in lighting and display.展开更多
The problem of task assignment for multiple cooperating unmanned aerial vehicle(UAV) teams is considered. Multiple UAVs forming several small teams are needed to perform attack tasks on a set of predetermined ground t...The problem of task assignment for multiple cooperating unmanned aerial vehicle(UAV) teams is considered. Multiple UAVs forming several small teams are needed to perform attack tasks on a set of predetermined ground targets. A hierarchical task assignment method is presented to address the problem. It breaks the original problem down to three levels of sub-problems: target clustering, cluster allocation and target assignment. The first two sub-problems are centrally solved by using clustering algorithms and integer linear programming, respectively, and the third sub-problem is solved in a distributed and parallel manner, using a mixed integer linear programming model and an improved ant colony algorithm. The proposed hierarchical method can reduce the computational complexity of the task assignment problem considerably, especially when the number of tasks or the number of UAVs is large. Experimental results show that this method is feasible and more efficient than non-hierarchical methods.展开更多
基金supported by the National Natural Science Foundation of China (21601159, 61604132, 61505033, 11374296, 61404039)the National Science Fund for Distinguished Young Scholars (61425021)
文摘Nanocarbon as an eco-friendly and abundant material has strong multi-color fluorescence, which makes it a promising candidate for healthy lighting and display. However, the low fluorescence efficiency and poor stability of multi-color carbon nanoparticle（CNP） phosphors are main hurdles that hinder their applications. This work demonstrated efficient and stable multi-color CNP phosphors through synergy between inner polar groups and outer silica matrix. The polar groups in polyethylene glycol（PEG） 6,000 are favor of high fluorescence of the CNP phosphors, and the low melting point（64℃） of PEG 6,000 helps to improve the thermal stability of the phosphors, while the silica matrix provides protection to the phosphors. Based on this design,blue, green, yellow and red CNP phosphors with photoluminescence quantum yield of 53.1%, 47.4%, 43.8% and 42.3% have been achieved, all of which are the best values in ever reported multi-color CNP phosphors. Furthermore, the fluorescence of the CNP phosphors keeps almost unchanged at 100℃ and degrades little in one month, indicating their good thermal tolerance and temporal stability. In addition, multicolor devices including white light-emitting devices（LEDs）have been realized by coating the CNP phosphors onto UV chips. The luminous efficiency, correlated color temperature,Commission Internationale de L＇Eclairage and color rendering index of the white LED can reach 12 lm W^-1, 6,107 K,（0.32, 0.33） and 89, respectively, indicating the potential applications of the CNP phosphors in lighting and display.
基金supported by the National Natural Science Foundation of China(7147205871401048)the Fundamental Research Funds for the Central Universities(2012HGZY0009)
文摘The problem of task assignment for multiple cooperating unmanned aerial vehicle(UAV) teams is considered. Multiple UAVs forming several small teams are needed to perform attack tasks on a set of predetermined ground targets. A hierarchical task assignment method is presented to address the problem. It breaks the original problem down to three levels of sub-problems: target clustering, cluster allocation and target assignment. The first two sub-problems are centrally solved by using clustering algorithms and integer linear programming, respectively, and the third sub-problem is solved in a distributed and parallel manner, using a mixed integer linear programming model and an improved ant colony algorithm. The proposed hierarchical method can reduce the computational complexity of the task assignment problem considerably, especially when the number of tasks or the number of UAVs is large. Experimental results show that this method is feasible and more efficient than non-hierarchical methods.
