This study,which is about pre-listening activities in language comprehension,seeks to obtain a better understanding of Chinese EFL students’listening comprehension in relation to radio news broadcasts.It investigates...This study,which is about pre-listening activities in language comprehension,seeks to obtain a better understanding of Chinese EFL students’listening comprehension in relation to radio news broadcasts.It investigates listeners’evaluation of the effects of pre-listening activities involving three listening texts with three kinds of different pre-listening activities.The findings yielded that the pre-listening activities had some impact on influencing the listeners’listening comprehension and it differed for effective and less-effective listeners.展开更多
We report a high power Ku band internally matched power amplifier （IMPA） with high power added efficiency （PAE） using 0.3 μm A1GaN/GaN high electron mobility transistors （HEMTs） on 6H-SiC substrate. The intemal...We report a high power Ku band internally matched power amplifier （IMPA） with high power added efficiency （PAE） using 0.3 μm A1GaN/GaN high electron mobility transistors （HEMTs） on 6H-SiC substrate. The intemal matching circuit is designed to achieve high power output for the developed devices with a gate width of 4 mm. To improve the bandwidth of the amplifier, a T type pre-matching network is used at the input and output circuits, respectively. After optimization by a three-dimensional electromagnetic （3D-EM） simulator, the amplifier demonstrates a maximum output power of 42.5 dBm （17.8 W）, PAE of 30% to 36.4% and linear gain of 7 to 9.3 dB over 13.8-14.3 GHz under a 10% duty cycle pulse condition when operated at Vas = 30 V and Vgs = -4 V. At such a power level and PAE, the amplifier exhibits a power density of 4.45 W/mm.展开更多
文摘This study,which is about pre-listening activities in language comprehension,seeks to obtain a better understanding of Chinese EFL students’listening comprehension in relation to radio news broadcasts.It investigates listeners’evaluation of the effects of pre-listening activities involving three listening texts with three kinds of different pre-listening activities.The findings yielded that the pre-listening activities had some impact on influencing the listeners’listening comprehension and it differed for effective and less-effective listeners.
基金Project supported by the National Basic Research Program of China(No.2010CB327503)the National Natural Science Foundation of China(No.60890191)
文摘We report a high power Ku band internally matched power amplifier （IMPA） with high power added efficiency （PAE） using 0.3 μm A1GaN/GaN high electron mobility transistors （HEMTs） on 6H-SiC substrate. The intemal matching circuit is designed to achieve high power output for the developed devices with a gate width of 4 mm. To improve the bandwidth of the amplifier, a T type pre-matching network is used at the input and output circuits, respectively. After optimization by a three-dimensional electromagnetic （3D-EM） simulator, the amplifier demonstrates a maximum output power of 42.5 dBm （17.8 W）, PAE of 30% to 36.4% and linear gain of 7 to 9.3 dB over 13.8-14.3 GHz under a 10% duty cycle pulse condition when operated at Vas = 30 V and Vgs = -4 V. At such a power level and PAE, the amplifier exhibits a power density of 4.45 W/mm.
