共查询到20条相似文献,搜索用时 234 毫秒
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针对深空次表层探测雷达相邻帧道数据相似的特性,提出了一种对相邻帧道差值数据进行分块自适应量化的算法——帧间差分分块自适应量化(Frame Difference Block Adaptive Quantization,FD-BAQ)。该算法首先对数据进行分块,然后进行帧间差分,并对差值数据或原始数据进行Lloyd-Max量化,最后用量化后的数据进行重构。在选择对差值数据或原始数据进行量化时,提出用数据方差作为量化误差的衡量指标,当子块差值数据方差小于原始数据方差时,对差值数据进行量化来替代对原始数据量化,否则直接量化原始数据,从而大幅减小量化误差。将该方法与已有改进型BAQ算法比较,实验结果表明,在相同压缩比条件下,FD-BAQ算法在数据域和图像域均能取得更好的压缩效果。 相似文献
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网络流量建模是网络规划与性能评价的重要基础,传统的业务模型大多基于泊松模型和马尔可夫排队模型,只具有短程相关性,随着网络业务的不断研究发现,实际网络业务流在很长的时间范围内都具有长程相关性,即一种自相似性。本文采用RMD算法和Fourier变换法对网络流量的自相似模型-FBM模型进行了建模及仿真研究,生成了所需的自相似流量序列。然后分别采用R/S法和方差时间图法对其进行自相似参数检测。结果验证了仿真算法所产生的序列存在着自相似性,并同时对RMD算法和Fourier变换法的优缺点进行了分析。 相似文献
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基于DFS的最优路径数据迷乱算法 总被引:1,自引:0,他引:1
提出一种基于深度优先搜索的数据迷乱算法,将数据库中的原始数据通过DFS算法生成邻居关系树,找出生成树中边缘距离最小的路径作为原始数据的替代.对于原始数据中含有相同元素的特殊情况,提出了多种数据迷乱算法并行使用的技术以实现数据项的迷乱.此算法的提出突破了原有数据迷乱技术的简单数据变形,大大增加了攻击者逆向工程的复杂度以达到联机信息保护的目的. 相似文献
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提出了一种处理时间序列中出现数据丢失时的信号谱估计的方法。这时观测所得到的,不再是连续等间隔的时间序列,而是多个数据段,所要进行的即是对这些分段数据的自回归模型的估计。该方法基于标准Burg谱估计算法提出,算法可以建立一个同时适用于各个分段数据的统一的信号模型。在仿真部分的结果显示,与直接使用均值方法进行谱估计相比较,分段Burg算法偏差更小,谱估计更精确。 相似文献
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针对传统频谱占用度自回归移动平均(ARMA)模型由于未考虑序列的条件二阶矩,导致无法准确描述频谱占用状态的非线性时变特性问题,该文提出一种基于指数广义自回归条件异方差(EGARCH)过程的频谱占用状态时间序列建模方法。首先通过对ARMA模型的剩余残差进行条件异方差性检验,表明频谱占用时间序列存在明显的时域波动集聚性;其次基于EGARCH过程构建频谱占用度时间序列模型以及对实测数据的分析,表明该模型相较ARMA模型对频谱占用度的拟合与预测精度更高;最后由EGARCH模型参数存在杠杆效应系数,表明频谱占用状态变化对电磁环境波动的影响具有非对称性。研究结果表明EGARCH模型能够量化反映频谱占用状态的复杂非线性时变过程。 相似文献
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在目前已有的基于数据扰动的隐私保持的分类挖掘方法中,分类算法必须经过改造方可应用于扰动后数据。而且扰动方法不同,使用的分类算法不同,对分类算法进行改造的方法也就不同。这使得该类方法难以在实际中推广应用。本文针对这一问题,提出了一种新的基于数据扰动的隐私保持的分类挖掘方法。通过生成并公开一组与原始数据独立同分布的新数据的方法来实现数据扰动。由于新数据与原始数据独立,因此从新数据得不到关于原始数据的详细信息。由于新数据与原始数据同分布,因此普通的分类挖掘算法可以直接应用于新数据。从而解决了现有方法使用不方便的问题。 相似文献
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Linear Least Squares (LLS) estimation is a low complexity but sub-optimum method for estimating the location of a mobile terminal (MT) from some measured distances. It requires selecting one of the known fixed terminals (FTs) as a reference FT for obtaining a linear set of expressions. In this paper, the choosing of the reference FT is investigated. By analyzing the objective function of LLS algorithm, a new method for selecting the reference FT is proposed, which selects the reference FT based on the minimum residual (denoted as MR-RS) rather than the smallest measured distance and improves the localization accuracy significantly in Line of sight (LOS) environment. In Non-line of sight (NLOS) environment, we combine MR-RS algorithm with two other existing algorithms (residual weighting algorithm and three-stage algorithm) to form new algorithms, which also improve the localization accuracy comparing with the two algorithms. Moreover, the time complexity of the proposed algorithms is analyzed. Simulation results show that the proposed methods are always better than the existing methods for arbitrary geometry position of the MT and the LOS/NLOS conditions. 相似文献
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一种定量检验多维信号非线性的方法 总被引:1,自引:0,他引:1
利用多变量时间序列替代数据生成原理生成了实测多变量时间序列的多组替代时间序列,由广义关联积分计算了实测时间序列和替代时间序列的广义冗余,提出了一种用线性冗余和广义冗余作为显著性检验统计量定量检验多维信号非线性的方法。一个线性自回归模型和Lorenz系统的仿真计算验证了这种方法的有效性。 相似文献
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Searching for the optimum tap-length that best balances the complexity and steady-state performance of an adaptive filter has attracted attention recently. Among existing algorithms that can be found in the literature, two of which, namely the segmented filter (SF) and gradient descent (GD) algorithms, are of particular interest as they can search for the optimum tap-length quickly. In this paper, at first, we carefully compare the SF and GD algorithms and show that the two algorithms are equivalent in performance under some constraints, but each has advantages/disadvantages relative to the other. Then, we propose an improved variable tap-length algorithm using the concept of the pseudo fractional tap-length (FT). Updating the tap-length with instantaneous errors in a style similar to that used in the stochastic gradient [or least mean squares (LMS)] algorithm, the proposed FT algorithm not only retains the advantages from both the SF and the GD algorithms but also has significantly less complexity than existing algorithms. Both performance analysis and numerical simulations are given to verify the new proposed algorithm. 相似文献
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Data broadcast has been suggested as a promising method of information dissemination [2,33]. In such an environment, the information server cannot afford to serve the requests from a large population of users individually. Instead, the server uses a broadcast channel to deliver information to all users. A single transmission of a data item satisfies all pending requests for that item. The response time of a request depends on the broadcast time of the desired data item, which is scheduled by the server according to the overall demands for various data items. Therefore, the response time may vary in a large range. We argue that, in addition to mean response time, the variance of response time should also be taken into account by the broadcast scheduler. In this paper, we address the issue of variance optimization in regard to response time. Building on our previous research on mean response time optimization, we propose an algorithm which can minimize the variance of response time. Furthermore, we evaluate an algorithm that facilitates a tradeoff between the mean and variance of response time. Numerical examples that illustrate the performance of our algorithms are also presented. 相似文献
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针对多雷达数据融合问题,提出了基于时间序列的聚类算法,用于实现航迹相关,即以时间序列为基础把聚类模型转化为基于特征匹配的聚类算法。进一步考虑到多目标密集时,部分来自不同目标的数据可能比来自同一目标的数据更接近,易导致关联错误,为此提出了基于时间序列的模糊聚类算法。对上述两种算法的聚类结果,应用卡尔曼滤波器实现滤波跟踪,在不同的情况下仿真后发现,在跟踪目标较少且相互位置较远的情况下,两种算法均有效,在跟踪目标较多且相互位置靠近的情况下,基于时间序列的模糊聚类算法更有效。 相似文献
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Comparison of predictability of epileptic seizures by a linear and a nonlinear method 总被引:1,自引:0,他引:1
The performance of traditional linear (variance based) methods for the identification and prediction of epileptic seizures are contrasted with "modern" methods from nonlinear time series analysis. We note several flaws of design in demonstrations claiming to establish the efficacy of nonlinear techniques; in particular, we examine published evidence for precursor identification. We perform null hypothesis tests using relevant surrogate data to demonstrate that decreases in the correlation density prior to and during seizure may simply reflect increases in the variance. 相似文献