This study investigates the aerodynamic performance of the NACA 633-421 airfoil and the effectiveness and feasibility of intermittent disturbance flow control methods on laminar separation bubbles(LSBs).It is found th...This study investigates the aerodynamic performance of the NACA 633-421 airfoil and the effectiveness and feasibility of intermittent disturbance flow control methods on laminar separation bubbles(LSBs).It is found that the average velocity and influence range of the synthetic jet actuator increase with the increasing of driving frequency and driving amplitude.LSB occurs at Re=1.0×10^(5),and ruptures atα=6°.But with intermittent disturbance control,the stall angle of attack(AoA)increases while significantly reducing drag.Research shows that although certain disturbance cannot fully recover from LSB stall,decreasing driving amplitude partially restores wing aerodynamic performance,more effectively than increasing driving amplitude.展开更多
O438 97021010一种用于图象压缩的神经网络结构的研究=Re- search on a neural network structure for imagecompression[刊,中]/江芳泽,李昕(上海大学自动化学院.上海(200072))//电子技术应用.-1995,(7).-8-10讨论了用于图象压缩的神...O438 97021010一种用于图象压缩的神经网络结构的研究=Re- search on a neural network structure for imagecompression[刊,中]/江芳泽,李昕(上海大学自动化学院.上海(200072))//电子技术应用.-1995,(7).-8-10讨论了用于图象压缩的神经网络结构,提出了一种与离散余弦变换相结合的基本边缘特征的神经网络结构,以期获得更好的图象压缩效果。图6参7(方舟)展开更多
Amplitude quantization is one of the main sources of spurious noise frequencies in Direct Digital Frequency Synthesizers (DDFSs), which affect their application to many wireless telecommu- nication systems. In this pa...Amplitude quantization is one of the main sources of spurious noise frequencies in Direct Digital Frequency Synthesizers (DDFSs), which affect their application to many wireless telecommu- nication systems. In this paper, two different kinds of spurious signals due to amplitude quantization in DDFSs are exactly formulated in the time domain and detailedly compared in the frequency do- main, and the effects of the DDFS parameter variations on the spurious performance are thoroughly studied. Then the spectral properties and power levels of the amplitude-quantization spurs in the absence of phase-accumulator truncation are emphatically analyzed by waveform estimation and computer simulation, and several important conclusions are derived which can provide theoretical support for parameter choice and spurious performance evaluation in the application of DDFSs.展开更多
文摘This study investigates the aerodynamic performance of the NACA 633-421 airfoil and the effectiveness and feasibility of intermittent disturbance flow control methods on laminar separation bubbles(LSBs).It is found that the average velocity and influence range of the synthetic jet actuator increase with the increasing of driving frequency and driving amplitude.LSB occurs at Re=1.0×10^(5),and ruptures atα=6°.But with intermittent disturbance control,the stall angle of attack(AoA)increases while significantly reducing drag.Research shows that although certain disturbance cannot fully recover from LSB stall,decreasing driving amplitude partially restores wing aerodynamic performance,more effectively than increasing driving amplitude.
文摘O438 97021010一种用于图象压缩的神经网络结构的研究=Re- search on a neural network structure for imagecompression[刊,中]/江芳泽,李昕(上海大学自动化学院.上海(200072))//电子技术应用.-1995,(7).-8-10讨论了用于图象压缩的神经网络结构,提出了一种与离散余弦变换相结合的基本边缘特征的神经网络结构,以期获得更好的图象压缩效果。图6参7(方舟)
基金Supported by National High-Technology Research and Development Plan of China (Grant No.2006AA01Z452)
文摘Amplitude quantization is one of the main sources of spurious noise frequencies in Direct Digital Frequency Synthesizers (DDFSs), which affect their application to many wireless telecommu- nication systems. In this paper, two different kinds of spurious signals due to amplitude quantization in DDFSs are exactly formulated in the time domain and detailedly compared in the frequency do- main, and the effects of the DDFS parameter variations on the spurious performance are thoroughly studied. Then the spectral properties and power levels of the amplitude-quantization spurs in the absence of phase-accumulator truncation are emphatically analyzed by waveform estimation and computer simulation, and several important conclusions are derived which can provide theoretical support for parameter choice and spurious performance evaluation in the application of DDFSs.
