一种新的基于极坐标格式的快速后向投影算法

快速分级后向投影算法(Fast Factorized Back-Projection Algorithm, FFBPA)研究了BPA中的冗余计算,通过子孔径划分,在极坐标系下将信号逐级相干积累成像,该方法避免了BPA中每个图像点的重复性全孔径搜索过程,大幅减少了计算量。然而多级插值操作加剧了误差积累,减少分级次数又影响算法效率。为解决这一矛盾,该文结合极坐标格式算法(PFA)提出了一种新的多级迭代快速BP成像算法,并将算法拓展应用到曲线轨道,多模式SAR中。分析表明,该文方法与FFBPA相比更高效。最后通过该文算法与FFBPA的星载0.1 m超高分辨率聚束SAR成像进行仿真实验对比,验证了该方法的优越性。     

结合新型模糊支持向量机和证据理论的多传感器水质数据融合

在多传感器水质数据融合领域,证据理论是有效的数据融合方法之一,但基本概率分配一般不易确定,从而使数据融合能力难以有效发挥。支持向量机是统计学习理论之上的高级分类算法,具有普适性和全局优化等特点,但输出的基本概率分配有待进一步提高。提出了一种基于证据理论和新型模糊支持向量机相结合的数据融合方法,通过建立基于分类超平面距离的模糊隶属度,训练模糊支持向量机提高传统支持向量机的基本概率分配,并结合证据理论进行海河水质数据融合。通过证据理论分别结合支持向量机和模糊综合评价法与上述方法进行对比实验,经精度、平均绝对百分误差、均方根误差等指标验证,精度提高10. 5%,表明所提方法是一种可靠的多传感器的水质融合方法,较其他方法具有更高的融合精度。     

The quantization effects of the CORDIC algorithm

A detailed analysis of the quantization error encountered in the CORDIC (coordinate rotation digital computer) algorithm is presented. Two types of quantization error are examined: an approximation error due to the quantized representation of rotation angles, and a rounding error due to the finite precision representation in both fixed-point and floating-point arithmetic. Tight error bounds for these two types of error are derived. The rounding error due to a scaling (normalization) operation in the CORDIC algorithm is also discussed. An expression for overall quantization error is derived, and several simulation examples are presented     

大规模MU-MIMO系统归一化预编码算法

针对大规模MU-MIMO系统中预编码技术性能不佳的问题,在不完善信道状态信息(CSI)的情况下,对迫零(ZF)和最大比发射(MRT)预编码技术提出了两种归一化算法：向量归一化与矩阵归一化。首先基站通过上行导频序列估计CSI,并在下行链路中用所提的算法对预编码矩阵进行归一化处理,然后将其与发送信号以及信道进行匹配。仿真结果表明,在高信噪比时,ZF预编码使用向量归一化算法实现了更好的系统性能;而在低信噪比时,MRT预编码使用矩阵归一化算法使系统性能得到了良好改善。     

采用非监督得分规整和因子分析的说话人确认

 在文本无关的说话人确认中,规整算法能够有效地调整测试得分的分布.另外,利用前面已经得到的测试语句的得分来调整规整的参数可以取得更好的效果,这种规整叫做非监督得分规整.在本文中,借用开发集得分来建立说话人和冒认者得分的两个先验高斯分布函数,在实际的测试中,利用最大后验概率准则来对规整的模型参数进行调整.在采用因子分析的情况下,在NIST 2006说话人识别测试1conv4w-1conv4w数据库上,能够取得等错误率5.26%.     

抗几何攻击的最低有效位数字水印算法

尽管最低有效位数字水印算法嵌入容量大,但抗几何攻击能力不足.通过分析几何攻击的原理,结合可视密码学和图像归一化技术,提出一种抗几何攻击的最低有效位数字水印算法.首先,利用可视密码学技术将水印隐藏到多幅图片中,同时仅选取一幅图片作为水印.然后对载体图像进行归一化,并以图像的几何中心作为中心提取重要区域.最后,依据重要区域的大小缩放水印,以增强水印与载体间的同步性,并从重要区域像素的低4位中随机选取嵌入位置通过异或运算嵌入水印.实验结果表明,算法具有良好的抗几何攻击能力.     

TD-SCDMA系统Turbo译码的仿真研究

文章介绍了TD-SCDMA系统采用的Turbo码,通过仿真确定了译码的关键参数。使用滑动窗大大降低了对存储空间的要求,归一化操作避免了溢出,不会对译码性能产生大的影响,对外信息乘以因子的操作使得该算法的性能比原来MAX-Log-MAP算法至少提高了0.2dB。     

基于加窗DFT的直扩通信系统窄带干扰抑制研究

针对直扩通信系统中基于门限检测的窄带干扰抑制的关键技术,引入重叠加窗方法,克服了由加窗带来的信号失真。并且提出了一种改进的自适应门限算法——归一化门限干扰检测处理算法。算法是将接收信号的包络经对数放大,归一化处理后得到一种归一化门限,然后将高于门限的谱线幅度抑制到与噪声相近的程度。分析和仿真表明,算法有较强的自适应能力,能有效抑制直扩系统中的窄带干扰。     

利用反向传播算法合理分配缓冲区

该文提出了一种新的缓冲区分配方法,即动态神经共享 (Dynamic Neural Sharing,DNS)方法。这种方法利用反向传播算法合理分配缓冲区资源,从而减少自相似业务的分组丢失率。通过两组仿真实验发现,与完全分割(Complete Partitioning, CP), 完全共享(Complete Sharing, CS), 部分共享(Partial Sharing, PS)这些传统的缓冲区分配方法相比,DNS在减少分组丢失和体现公平性(每个源都占有一定数量的缓冲区资源)之间达到了更好的平衡。     

一种基于3D-CNN的微表情识别算法

微表情是一种持续时间很短暂的面部表情。针对其识别率低的问题,提出了一种基于三维卷积神经网络（3D Convolutionnal Neural Network,3D-CNN）的微表情识别算法。使用Keras作为网络框架,在3D-VGG-Block(3Dimension Visual Geometry Group Block,3D-VGG-Block)的基础上加入批量归一化算法以及丢弃法,提升网络深度与训练速度的同时有效地防止过拟合;针对数据集稀少的问题,采取随机设置起始帧的位置,提前设定每次读取帧序列的长度,循环操作,在将所有数据均遍历的同时,达到数据增广的目的。该算法在CASME II数据集上的识别率最高达68.85%,在识别率上有一定优势。     

Near optimum universal belief propagation based decoding oflow-density parity check codes

In this paper, we propose a belief-propagation (BP)-based decoding algorithm which utilizes normalization to improve the accuracy of the soft values delivered by a previously proposed simplified BP-based algorithm. The normalization factors can be obtained not only by simulation, but also, importantly, theoretically. This new BP-based algorithm is much simpler to implement than BP decoding as it requires only additions of the normalized received values and is universal, i.e., the decoding is independent of the channel characteristics. Some simulation results are given, which show this new decoding approach can achieve an error performance very close to that of BP on the additive white Gaussian noise channel, especially for low-density parity check (LDPC) codes whose check sums have large weights. The principle of normalization can also be used to improve the performance of the max-log-MAP algorithm in turbo decoding, and some coding gain can be achieved if the code length is long enough     

Improved approximate QR-LS algorithms for adaptive filtering

This paper studies a class of O(N) approximate QR-based least squares (A-QR-LS) algorithm recently proposed by Liu in 1995. It is shown that the A-QR-LS algorithm is equivalent to a normalized LMS algorithm with time-varying stepsizes and element-wise normalization of the input signal vector. It reduces to the QR-LMS algorithm proposed by Liu et al. in 1998, when all the normalization constants are chosen as the Euclidean norm of the input signal vector. An improved transform-domain approximate QR-LS (TA-QR-LS) algorithm, where the input signal vector is first approximately decorrelated by some unitary transformations before the normalization, is proposed to improve its convergence for highly correlated signals. The mean weight vectors of the algorithms are shown to converge to the optimal Wiener solution if the weighting factor w of the algorithm is chosen between 0 and 1. New Givens rotations-based algorithms for the A-QR-LS, TA-QR-LS, and the QR-LMS algorithms are proposed to reduce their arithmetic complexities. This reduces the arithmetic complexity by a factor of 2, and allows square root-free versions of the algorithms be developed. The performances of the various algorithms are evaluated through computer simulation of a system identification problem and an acoustic echo canceller.     

New insights into the normalization of the least mean fourth algorithm

The available normalization of the least mean fourth algorithm is investigated. It is shown that that normalization does not protect the algorithm from divergence when the input power of the adaptive filter increases. The reason of this drawback is that the normalization is done by dividing the weight vector update term by the squared norm of the regressor, while the update term is a fourth order polynomial in the regressor. The paper presents a normalized LMF algorithm that is based on dividing the weight vector update term by the fourth power of the norm of the regressor. This normalization protects the algorithm from divergence when the input power increases. An approximate stability step-size bound of the proposed algorithm is derived. The step-size bound depends on the weight initialization, while it does not depend on the input power of the adaptive filter for non-small signal-to-noise ratio. Simulation results support the analytical results of the paper.     

基于模糊故障特征信息的随机集度量信息融合诊断方法

该文给出一种基于模糊故障特征信息随机集度量的信息融合诊断方法。针对信号采集与故障特征提取中的模糊性,首先用模糊隶属度函数分别表示故障档案库中的多种故障样板模式和从不同传感器观测中提取的多类故障特征亦即待检模式,进而基于模糊集的随机集模型,得到样板模式与待检模式的匹配度,即基本概率指派函数(BPA)。然后利用Dempster-Shafer证据组合规则对BPA进行融合,给出诊断结果。该文给出的待检模式是从多个连续观测中提取的,与原有的由单个观测确定待检模式的方式相比,文中提出的特征提取及匹配方法,同时考虑了样板模式和待检模式所具有的模糊性,能够显著降低融合决策中的不确定性,大大提高故障识别的能力。最后通过电机转子故障诊断实例验证方法的有效性。     

基于双波长解调的光纤干涉型传声器研究

提出了一种基于双波长解调的光纤法布里-珀罗(Fabry-Perot,FP)干涉型传声器,采用归一化算法和微分交叉相乘处理(DCM)算法,实现了声信号的准确还原.在归一化算法中,利用椭圆拟合,实现了两路波长光信号的归一化,减小了激光器输出波动对光纤FP干涉型传声器输出特性的影响;在DCM算法中,通过信号处理及滤波,实现了声信号的准确输出,减小了温度等环境因素对光纤FP干涉型传声器输出特性的影响.在实验中,采用对比法,测试了基于双波长解调的光纤FP干涉型传声器的特性,结果显示器件实现了灵敏度为210 mV/Pa、频率响应为100～3 15 0 H z的声信号测量,能够很好地应用于语音识别、噪声测量、空气声探测等领域.     

基于小波变换直方图规定的非均匀性校正算法

为了实现红外探测器的自适应校正,提出了一种基于小波变换的中值直方图规定非均匀性自适应校正方法。新算法利用正交小波变换分解图像,分别统计分解后图像像素的时域直方图,对像素邻域直方图进行排序得到中值,利用中值直方图灰度映射得到校正图像,最后把所有尺度校正后的图像反变换得到最终结果。实际应用证明,与同类自适应非均匀校正算法相比,该算法具有校正精度高、速度快的优点。     

A Bistatic MIMO Radar Angle Estimation Method for Coherent Sources in Impulse Noise Background

In order to solve the angle estimation problem of coherent sources in the impulse noise background, an algorithm based on infinite norm normalization preprocessing and sparse representation (INN-SR) is proposed. First, an infinite norm normalization preprocessing method is used to reduce the impact of the impact noise. Then the sparse decomposition method is used to construct the restoration dictionary to estimate the DOA and DOD. Finally, accurate matching of target DOA and DOD is achieved based on maximum likelihood method. The algorithm does not need to know the number of sources and can also work well for coherent sources.

     

A novel design of a two operand normalization circuit

This paper presents a new design for two operand normalization. The two operand normalization operation involves the normalization of at least one of two operands by left shifting both by the same amount. Our design performs the computation of the shift by making an OR of the bits of both operands in a tree network, encoding the position of the first nonzero bit. The encoded position is obtained most significant bit first, and then there is an overlapping with the shifting operation. The design we propose replaces two leading zero detector circuits and a comparator, that are present in the conventional approach. Our scheme demonstrates to be more area efficient than the conventional one. The circuit we propose is useful in floating point complex multiplication and COordinate Rotation DIgital Computer (CORDIC) processors     

Band partitioning algorithm for surface reconstruction from planarcontours

A heuristic contour triangulation method is proposed for reconstructing a facet model from a set of wire-frame contours. The proposed band partitioning algorithm (BPA) compensates for the disadvantages of optimal and heuristic methods, and produces an improved reconstructed surface. Furthermore, the maximum deviation criterion in span selection prohibits drastic error propagation in the surface definition procedure. Experimental results show that the proposed method is very stable and efficient, making it suitable for a wide range of applications     

Leading-zero anticipatory logic for high-speed floating pointaddition

This paper describes a new leading-zero anticipatory (LZA) logic for high-speed floating-point addition (FADD). This logic carries out the pre-decoding for normalization concurrently with addition for the significand. It also performs the shift operation of normalization in parallel with the rounding operation. The use of simple Boolean algebra allows the proposed logic to be constructed from a simple CMOS circuit. Its area penalty is as small as 30% of the conventional LZA method. The FADD core using the proposed logic was fabricated by 0.5 μm CMOS technology with triple metal interconnections and runs at 164 MHz under the condition of V_DD=3.3 V