高分辨率图像抗打印扫描数字水印算法改进研究

目前,从扫描图像中提取出水印比较困难。本文结合数字水印的应用背景和研究现状,提供了一种能够抵抗打印和扫描的数字水印算法,先将高分辨率图像分块并进行下采样,以保证对图像的非几何形变影响较小,然后在相应的块中嵌入导频和水印图样。实验结果显示:本文提出的水印算法对高分辨率图像具有很好的鲁棒性。     

OFDM在LMS信道下的BER性能研究

正交频分复用（OFDM）应用于卫星宽带通信,前提需建立适用的卫星信道模型,目前常用的卫星信道模型主要为窄带模型,因而宽带系统性能分析的基础,首先得建立卫星信道宽带模型。对已有陆地移动卫星（LMS）信道模型进行研究,提出了一种便于仿真实现的四状态宽带信道模型,以此仿真得到OFDM在LMS信道下的BER性能结果。结果表明,宽带状态和窄带状态下BER性能变化较大,在不同环境下的BER性能亦有不同,可将该模型应用于卫星宽带通信的研究分析。     

A novel initial ranging algorithm for OFDMA systems using smart antenna

To improve the capacity of initial ranging （IR） users simultaneously accessing into network and enhance the performance of the IR, a novel IR algorithm is presented for the orthogonal frequency division multiple access systems with the smart antenna. The beamforming weight vectors provided by the antenna array are introduced for the IR users, and the procedures of the multiuser parameter estimation and the interference cancellation are designed. The proposed method can improve the accuracy of the channel estimation of active paths and efficiently reduce the residual multiple access interference. Simulation results show that the proposed method has a much better performance than the available successive multiuser detection and interference cancellation algorithm and accommodates more active ranging users simultaneously accessing into a cell.     

Adaptive detectors in the Krylov subspace

The validity of the application of the Krylov subspace techniques in adaptive filtering and detection is investigated. A new verification of the equivalence of two well-known methods in the Krylov subspace, namely the multistage Wiener filters （MWF） and the auxiliary-vector filtering （AVF）, is given in this paper. The MWF and AVF are incorporated into two well-known detectors, namely, the adaptive matched filter （AMF） and Kelly＇s generalized likelihood ratio test （CLRT） including their diagonally loaded versions, which form new detectors. Compared to the conventional AMF, CLRT, and their diagonally loaded versions as well as the reduced-rank AMF and GLRT, the probabilities of detection （PDs） of the new detectors are improved especially when the sample support is low. More importantly, the new detectors are robust of the rank selection of the clutter subspace compared to the reduced-rank AMF and GLRT. These new detectors all possess asymptotic constant false alarm rate （CFAR） property.     

循环流化床水煤气炉示范工程运行初步总结

初步总结了江苏恒盛化肥有限公司(新沂化肥厂)的循环流化水煤气炉示范工程的运行情况，指出该技术特点是，原料用粉粒煤，气化剂是空气和水蒸汽，不需要建配套的空分装置，操作简单，投资较省。     

牙膏级磷酸氢钙生产工艺的评述

介绍了牙膏级磷酸氢钙的主要生产方法及特点,并就每一种生产工艺的优点及不足作了评价;通过对不同生产条件进行比较,提出了适宜的工艺路线,在分析国内牙膏生产现状的基础上,对牙膏级磷酸氢钙的发展及市场前景进行了展望.     

ICP-AES法测定粉煤灰全组分化学元素的研究

采用偏硼酸锂熔样 ,电感耦合等离子体原子发射光谱 (ICPˉAES)法对粉煤灰实现一次熔样 ,全组分同时分析。对影响光谱测量的各种因素进行了较详细的研究 ,确定了最佳测定条件。该法的检出限为 0 .0 0 9～ 0 .83 1μg·ml-1,回收率为 91.5 4%～ 10 4.45 % ,RSD <3 .2 2 %。方法准确、快速、简便 ,用于粉煤灰中全组分测定 ,结果满意。     

一种基于分簇的传感器网络数据查询方法

基于传感器网络的特性,根据查询与簇头节点的数据关联关系,对簇头节点的通信能量消耗和查询响应时间进行了分析,提出了一个估算模型,给出了节省能量优先和查询响应时间优先的算法.性能分析表明,该方法提高了查询效率,降低了传感器网络的能量消耗.