A Cognitive radio communication link is possible to be interrupted easily when its physical channel suffers severe fading. Relay technology is an effective way to mitigate the fading effect of wireless channels in a n...A Cognitive radio communication link is possible to be interrupted easily when its physical channel suffers severe fading. Relay technology is an effective way to mitigate the fading effect of wireless channels in a network. Based on the highest achievable rate of the relay channels, this paper considers a cognitive radio relay network where the secondary transmitter communicates with the receiver through the best relay node under the peak power constraint of a primary receiver. Intuitively, the secondary transmission can benefit from an intermediate relay node chosen from N possible nodes. To quantify this benefit, outage probability of cognitive radio relay networks is derived and also the closed-form expressions for outage capacity and ergodic capacity of cognitive radio relay networks are obtained in Rayleigh fading channels. Numerical simulation results are provided to show that the outage capacity and ergodic capacity benefit tremendously by properly increasing the number of relaying nodes.展开更多
A series of carbonaceous mesophase spherule/activated carbon composites were prepared as anode materials for super lithium ion capacitors using carbonaceous mesophase spherules as the core materials and pitch as the a...A series of carbonaceous mesophase spherule/activated carbon composites were prepared as anode materials for super lithium ion capacitors using carbonaceous mesophase spherules as the core materials and pitch as the active carbon shell precursor.The structures of the composites were examined by scanning electron microscopy and X-ray diffractometry.The electrochemical performance was investigated in electric double layer capacitor and half-cell.The results show that,the composite exhibits good performance in both capacitor and battery with a high reversible capacity of 306.6 mA·h/g(0.2C) in the half-cell,along with a capacitance of 25.8 F/g in the capacitor when an optimum ratio of carbonaceous mesophase spherules to active carbon is adopted.The composite also shows a favorable rate performance and good cycle ability.A working model of this anode in super lithium ion capacitors was established.展开更多
文摘A Cognitive radio communication link is possible to be interrupted easily when its physical channel suffers severe fading. Relay technology is an effective way to mitigate the fading effect of wireless channels in a network. Based on the highest achievable rate of the relay channels, this paper considers a cognitive radio relay network where the secondary transmitter communicates with the receiver through the best relay node under the peak power constraint of a primary receiver. Intuitively, the secondary transmission can benefit from an intermediate relay node chosen from N possible nodes. To quantify this benefit, outage probability of cognitive radio relay networks is derived and also the closed-form expressions for outage capacity and ergodic capacity of cognitive radio relay networks are obtained in Rayleigh fading channels. Numerical simulation results are provided to show that the outage capacity and ergodic capacity benefit tremendously by properly increasing the number of relaying nodes.
基金Project(2007BAE12B00) supported by the National Key Technology R&D Program of ChinaProject(50974136) supported by the National Natural Science Foundation of China
文摘A series of carbonaceous mesophase spherule/activated carbon composites were prepared as anode materials for super lithium ion capacitors using carbonaceous mesophase spherules as the core materials and pitch as the active carbon shell precursor.The structures of the composites were examined by scanning electron microscopy and X-ray diffractometry.The electrochemical performance was investigated in electric double layer capacitor and half-cell.The results show that,the composite exhibits good performance in both capacitor and battery with a high reversible capacity of 306.6 mA·h/g(0.2C) in the half-cell,along with a capacitance of 25.8 F/g in the capacitor when an optimum ratio of carbonaceous mesophase spherules to active carbon is adopted.The composite also shows a favorable rate performance and good cycle ability.A working model of this anode in super lithium ion capacitors was established.
