Blind estimation of OFDM carrier frequency offset via oversampling

Blind deterministic estimation of the orthogonal frequency division multiplexing (OFDM) frequency offset via oversampling is proposed in this paper. This method utilizes the intrinsic phase shift of neighboring sample points incurred by the frequency offset that is common among all subcarriers. The proposed method is data efficient - it requires only a single OFDM symbol to achieve reliable estimation, hence making it more suitable to systems with stringent delay requirement and mobility-induced channel variation. The proposed scheme is devised to perfectly retrieve frequency offset in the absence of noise. Quite remarkably, we show that in the presence of channel noise, this intuitive scheme is indeed the maximum likelihood estimate of the carrier frequency offset. The possible presence of virtual carriers are also accommodated in the system model, and some interesting observations are obtained. The Cramer-Rao lower bound is derived for the oversampling-based signal model, and we show through numerical simulation that the proposed algorithm is efficient. Practical issues such as identifiability, the front-end filter bandwidth, and the possible presence of correlated noises are also carefully addressed.     

用CMOS工艺实现非接触IC卡天线的集成化设计

论述了用CMOS工艺实现非接触式IC卡天线的集成化需要考虑的各个方面,建立了集成天线的模型,给出了合理的设计方案,并通过实验验证了模型和设计方案.实验结果表明,采用片上天线完全可以提供非接触式IC卡工作所需要的能量.在频率为2 2 .5 MHz、感应强度为6×10 - 4 T的磁场中,面积为2 m m×2 mm的集成天线可以为10 kΩ的负载提供1.2 2 5 m W的能量.     

Mining predecessor–successor rules from DAG data

Data mining extracts implicit, previously unknown, and potentially useful information from databases. Many approaches have been proposed to extract information, and one of the most important ones is finding association rules. Although a large amount of research has been devoted to this subject, none of it finds association rules from directed acyclic graph (DAG) data. Without such a mining method, the hidden knowledge, if any, cannot be discovered from the databases storing DAG data such as family genealogy profiles, product structures, XML documents, task precedence relations, and course structures. In this article, we define a new kind of association rule in DAG databases called the predecessor–successor rule, where a node x is a predecessor of another node y if we can find a path in DAG where x appears before y. The predecessor–successor rules enable us to observe how the characteristics of the predecessors influence the successors. An approach containing four stages is proposed to discover the predecessor–successor rules. © 2006 Wiley Periodicals, Inc. Int J Int Syst 21: 621–637, 2006.     

高粘度指数润滑油生产工艺探讨

详细介绍了中国石油抚顺石化分公司石油一厂新区以沈阳、大庆混合原油的减二、减三线馏分油为原料,采用甲苯、甲乙酮脱蜡、糠醛精制、白土补充精制工艺生产HVI润滑油基础油的生产经验。并结合理论分析,提出了完善此类工艺的一系列建议。生产HVI200基础油,要求蒸馏减二线润滑油馏分粘度不大于4.75 mm2/s,脱蜡油粘度不大于56 mm2/s。为保证HVI200基础油粘度指数合格,要降低减二线馏分中多环环烷烃含量。     

提高深井硬地层钻井速度技术难点及对策

乌龙1井地层为南方海相沉积,地层古老、岩石硬度大、研磨性强、可钻性差、地层倾角大(最大为80°)井斜难以控制、蹩跳钻严重,制约了该地区深井钻井速度。文章介绍了解决提高钻井速度这一瓶颈问题,从深井优快钻井及其配套技术、硬地层钻进的钻头优选、优化钻井参数、引用新技术、新工艺、新工具等方面进行了探索,钻井速度有了大幅度地提高,对类似井具有一定的借鉴作用。     

基于形态学top-hat算子的多传感器图像融合

本文根据形态学top-hat算子能够提取图像中极大值与极小值区域的特点,将其应用于多传感器图像融合的两个重要领域——多聚焦图像融合和高分辨、多光谱图像融合.实验中将本文方法与Laplacian塔型变换、子波变换、主分量分析等方法进行了比较,结果表明本文所提的基于top-hat算子的融合方法具有优越的性能,拓广了top-hat算子的应用范围.     

大型往复式压缩机的配管设计

大型往复式压缩机功率大、占地面积大,管道振动问题也更为突出。笔者结合实践经验,对大型往复式压缩机的配管设计进行探讨,说明了平面布置与管道防振设计的密切关系,并介绍了管道防振设计的方法和步骤,以及相对简单的复杂管系气柱固有频率的转移矩阵计算方法。     

区域分割法辅助计算复杂图像面积

介绍计算具有复杂边缘轮廓的图像面积的区域分割法。采用鼠标多边形作图法近似圈定待处理的图像区域。本文由格林定理出发得到有限连续边界与其包围区域面积之间的函数关系,并且应用这一函数关系得出多边形与其包围区域面积的数学关系,近似得到图像区域面积。文中以烟幕图像为例对上述结论进行了验证。文章最后给出了在VC++环境下实现多边形分割的部分源代码。     

Data-efficient blind OFDM channel estimation using receiver diversity

We investigate non data-aided channel estimation for cyclically prefixed orthogonal frequency division multiplexing (OFDM) systems. By exploiting channel diversity using only two receive antennas, a blind deterministic algorithm is proposed. Identifiability conditions are derived that guarantee the perfect channel retrieval in the absence of noise. In the presence of noise, the proposed method has the desired property of being data efficient-only a single OFDM block is needed to achieve good estimation performance for a wide range of SNR values. The algorithm is also robust to input symbols as it does not have any restriction on the input symbols with regard to their constellation or their statistical properties. In addition, this diversity-based algorithm is computationally efficient, and its performance compares favorably to most existing blind algorithms.     

不同表面预处理对有机电致发光显示器性能的影响

从生产角度研究了基板表面的预处理工艺对OLED性能的影响,分别用UVOzone、氧Plasma以及两者相结合的方式对基板进行表面处理,并按照生产工艺制作器件,从接触角、方阻以及光电特性等测试结果对各种表面处理的样品进行比较。结果表明以上处理都改善了器件性能,不同程度提高了器件的清洁度、亮度和发光效率,其中UVOzone和氧Plasma结合的方式处理效果最为显著,器件在10V时亮度达到79920cd/m2,比其他两种处理方式亮度提高约25%。