A force modulation study on crystallization process in ferroelectric vinylidene fluoride and trifluoroethylene copolymer films

This paper introduces the Force Modulation technique to the study of crystallization process in ferroelectric vinylidene fluoride and trifluoroethylene copolymer films. Using this technique we have successfully visualized ferroelectric crystalline domains and observed that these ferroelectric domains grow out from amorphous phase, unite into strip-like structures, and finally congregate into a union. Force Modulation can weaken the influence of topography on imaging of ferroelectric domains, and reveal more details, which are difficult to be observed in topographical image.     

一种移频MODEM芯片AM7911的扩展

扼要介绍移频MODEM芯片AMK7911，论述将其中心频率从普通话路频段移入载波复用的上音频带宽内的设计思想和计算方法。     

EDA介质快慢横波时差和振幅-方位曲线的实验分析

在含垂直定向裂隙的各向异性（EDA）介质中，地震快、慢横波传播的时差及振幅随裂隙（缝）方位变化曲线能反映裂缝的密度、走向和介质的性质，这对多波地震资料的处理、解释有着重要意义。但受观测条件限制以及噪声的影响，在横波分裂记录上，同相轴往往会出现扭曲、倾斜和不规则抖动等现象，给快、慢横波时差的求取和振幅-方位曲线的绘制带来误差。设计了EDA介质物理模型，并利用岩石超声波测量系统获得了快、慢横波记录；分析记录可知，在相同传播方向的分裂横波具有走时和传播速度不随裂缝方位变化的恒定性特征；以此为基础，提出了利用平均法和瞬时振幅法来计算快、慢横波的走时时差和绘制振幅-方位曲线，以提高精度。利用物理模型实验得到的2个正交横波（S1波与S2波）的快、慢横波记录，分别用平均法和瞬时振幅法计算了快、慢横波走时的平均值、时差和均方差，并绘制了相应的振幅一方位曲线。结果表明，采用上述2种方法，消除了同相轴扭曲、倾斜和不规则抖动等对计算结果的影响，时差的计算是可靠的，振幅一方位曲线的绘制是合理的。     

非AWGN环境下调制类型自动识别

在非AWGN环境下，针对CW，AM，FM，OOK，PSK，QPSK，16QAM，FSK，MSK，SSB十种混合调制信号，对调制类型特征提取方法和自动识别算法进行了分析、综合、设计和计算机仿真。提出了梯层电平分析方法、频率瞬时信号分析、剔除载波的归一化能量分析、平方后信号的频谱分析、四次方后的信号频谱分析等方法。当SNR=10dB时，计算机仿真结果是正确识别率不低于95％，自动识别的平均处理时间为不超过10s。     

新型智能加速度传感器的设计

详细介绍了一种智能加速度传感器的具体实现方案.试验证明,该传感器性能稳定,具有测量精度高、价格较低、便携性好、灵活可靠的特点,克服了传统加速度传感器测量精度低,元器件精度要求较高,测试系统复杂昂贵,应用范围具有局限性的缺陷.它大大提高了加速度测量的自动化水平,具有重要的应用价值.     

波长为515nm的氩离子激光器的频率稳定

用声光晶体对氩离子激光作频率调制,获得了碘分子的差拍饱和吸收信号。将得到的斜率极陡的—阶微商形式的饱和吸收信号作为鉴频曲线把氩离子频率激光稳定到~(127)I_2分子的p(13)43—0的a_3超精细分量上。通过与一稳定到相同精细分量的稳频氩离子激光拍频,给出激光频率稳定性优于±6.5×10~(-12),重复性优于±3.4×10~(-11)。     

相干OFDM系统中导引符号功率优化

在瑞利衰落信道下，本文研究了导引符号功率对相干OFDM系统性能的影响，计算了由于不精确信道估计引起的系统性能损失，优化分析了导引符号与数据符号功率比，并给出完整的最优功率分配数学表达式。理论分析和仿真结果给出了各种参数对最优功率比的影响，同时理论结果为系统设计提供了依据。     

数字电视技术的内涵及发展趋势

以有线电视为重点介绍了电视信号的数字化概念、优点及数字电视发展的趋势     

A Review of Wavelets for Digital Wireless Communication

Wavelets have been favorably applied in almost all aspects of digital wireless communication systems including data compression, source and channel coding, signal denoising, channel modeling and design of transceivers. The main property of wavelets in these applications is in their flexibility and ability to characterize signals accurately. In this paper recent trends and developments in the use of wavelets in wireless communications are reviewed. Major applications of wavelets in wireless channel modeling, interference mitigation, denoising, OFDM modulation, multiple access, Ultra Wideband communications, cognitive radio and wireless networks are surveyed. The confluence of information and communication technologies and the possibility of ubiquitous connectivity have posed a challenge to developing technologies and architectures capable of handling large volumes of data under severe resource constraints such as power and bandwidth. Wavelets are uniquely qualified to address this challenge. The flexibility and adaptation provided by wavelets have made wavelet technology a strong candidate for future wireless communication. Madan Kumar Lakshmanan was born in Chennai, India, in 1979. He received the B.E. (with distinction) in electrical engineering from the University of Madras, Chennai, India, in 2000. He joined the Indian Software firm, Polaris Software Labs Ltd., in 2000 where he wrote software for Telecommunication applications. At Polaris, he was awarded the “On The Spot Of Excellence Award” for his efforts. In 2003, he moved to the Indian Institute of Technology-Madras, to develop and establish a wireless communications network for rural connectivity. In 2004, he was awarded the Royal Dutch/Shell Chevning scholarship to pursue a Master degree in Telecommunications at the Delft University of Technology (TUDelft). At TUDelft he is affiliated to the International Research Center for Telecommunications-Transmission and Radar (IRCTR) where he is undertaking research in the field of wavelets applications in Wireless Communications. Homayoun Nikookar received his Ph.D. in Electrical Engineering from Delft University of Technology (TUDelft), The Netherlands, in 1995. From 1995 to 1998 he was a postdoc researcher at the International Research Center for Telecommunications-Transmission and Radar, TUDelft, where since 1999 he has been an Assistant Professor. Dr. Nikookar has done research on different areas of wireless communications, including wireless channel modeling, UWB, MIMO, multicarrier transmission, Wavelet-based OFDM and CDMA. He is a senior member of the IEEE.     

模块化蓝光光存储性能静态测试系统

蓝光光存储是信息存储领域发展的一个重要方向。测试系统是研究蓝光光存储材料的必备条件，为建立蓝光光存储研究平台，设计和搭建了一套模块化蓝光光存储性能静态测试系统。激光工作波长为406．7nm。系统采用调制解调技术降低系统噪声，提高测量粘度：采用光点移动模式降低对样品尺寸的要求；采用纳米平台提高记录点的反复定位性能。实验结果证明测试系统性能良好，可以满足蓝光光存储性能静态测试要求。