共查询到19条相似文献，搜索用时 250 毫秒
1.
提出了一种钟控密钥流生成器模型,该模型由三个线性移位寄存器组成,且相互控制。并对该生成器的周期和线性复杂度进行了分析,得出了序列的周期和线性复杂度与各线性移位寄存器级数之间的关系,以及序列得到最大周期及线性复杂度时线性移位寄存器级数所满足的条件。 相似文献
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从代数角度讨论了加法型组合生成器输出序列的密码学特性,得到了其输出序列具有较长的周期、较高的线性复杂度、尖锐的自相关特性和弱的互相关特性,并具有相关免疫性等结果． 相似文献
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本文利用相空间重构技术和混沌理论讨论了开都河日径流的混沌性质。通过日径流时间序列的功率谱分析,从定性角度讨论了日径流时间序列的混沌特征。进一步根据互信息量法得到相空间重构的延时,再根据Cao方法得到相空间重构的嵌入维数。利用Matlab软件计算得到相空间重构的延时和最佳嵌入维数分别为τ=6,m=14。这样将一维的开都河日径流时间序列重构成14维的相空间。通过最小数据量法计算出开都河日径流时间序列最大Lyapunov指数。利用最大Lyapunov指数对开都河日径流时间序列进行定量混沌分析。最后通过二阶Volterra自适应一步模型进行模拟。结果表明：开都河日径流时间序列的功率谱是连续的,功率谱呈现随频率增高而以指数方式递减趋势,区别于具有离散尖峰谱特征的周期时间序列和具有连续的、频率和振幅不相关谱特征的随机时间序列。这从定性角度表明开都河日径流时间序列具有混沌特征。通过计算得到开都河日径流时间序列的最大Lyapunov指数0〈λmax=0.0097〈1,从定量角度表明开都河日径流时间序列具有较弱的混沌特征。利用二阶Volterra自适应一步模型模拟得到相关系数和相对均方根误差分别0.9376和0.2390。这说明利用Volterra自适应模型模拟效果较好。 相似文献
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相空间重构参数选择方法的研究 总被引：2，自引：0，他引：2
基于目前相空间重构中常用的参数选择方法,提出了一种新的相空间重构的联合算法,联合算法以时间窗口法和互信息法为基础,在综合考虑嵌入窗宽的基础上,可同时确定嵌入延迟和嵌入维数.仿真实验表明,用该算法计算Lorenz混沌时间序列关联维相对误差由传统算法的0.83%降低到0.44%,有效地提高了计算相空间重构中不变量的精度. 相似文献
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针对医学序列图像的特点,概述了两种压缩的方法[1-3],并在此基础上提出了一种基于最大互信息配准法的压缩方法,更有效的减少序列图像之间的相关冗余.该方法充分利用了帧间相关性,具有很好的压缩性能,可以有效满足现代医学图像的压缩要求. 相似文献
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信息安全是信息时代的首要任务。一些科技生产企业往往碰到需将涉密信息带到用户现场进行离线浏览的问题,确保数据安全显得至关重要。离线浏览需要依靠技术手段对数据进行信息安全处理,椭圆典线密码机制（ECC）属于非对称的公钥密码机制,基于椭圆曲线离散对数计算问题的数学困难,是目前优秀的加密算法,具有单比特强度高,密钥短的优点,简述了椭圆曲线密码机制的基本原理与加解密过程,伪随机序列是一种对称密码,由序列生成器逐比特生成,具有良好的随机性。本文结合椭圆曲线密码机制与伪随机序列机制二者的技术优势与特点,对离线的涉密信息浏览进行强化加密,描述了离线浏览系统的总体结构与功能,并在windows平台下实现。 相似文献
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扩频码的设计及性能分析是直扩无线搜救系统设计的关键技术。从直扩无线搜救系统的实际应用出发,以工程中常用的扩频码m序列和Walsh序列为例,将m序列与Walsh序列级联并经改进得到一种新的具有正交性的m-Walsh复合序列,它具有良好自相关性和优秀互相关性,将其应用于直扩无线搜救系统中,更有利于码的同步和增强系统的抗干扰能力。 相似文献
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BP神经网络在我国粮食产量预测中的应用 总被引：14，自引：0，他引：14
本文基于BP神经网络模型，进行了2001－2010年我国粮食产量的预测。通过对比传统的“平均增长率一阶滞后模型”拟合及预测1992－2000年粮食产量与实际产量的误差值大小，可明显看出BP神经网络对于处理单输入单输出的时间序列预测问题是一种更具优越性的方法，它具有很强的学习与泛化（推广）能力，具有很好的应用价值。 相似文献
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《Journal of The Franklin Institute》1987,324(1):27-42
A new algorithm to reconstruct a one-dimensional sequence from its Fourier transform magnitude and 1-bit phase information is presented. Since the minimum-phase and maximum-phase sequences are uniquely specified by the magnitude alone, the algorithm reconstructs these sequences from magnitude only but it requires additional sign information in the case of mixed-phase signals. A minimum or maximum-phase sequence is recursively obtained using the cepstrum of the given magnitude function. In the case of mixed-phase sequences the sequence calculated from the magnitude is the minimum-phase equivalent of the original sequence. This together with the 1-bit phase information permits us to obtain by interpolation an approximation of the original phase and therefore reconstruct the sequence. To reduce the computational effort, we propose a test to distinguish between the minimum (maximum) and mixed-phase sequences using the sign information. With this additional information, the procedure becomes very efficient. We compare the reconstruction of signals using our algorithm with that obtained by well known iterative methods. 相似文献
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This paper studies mathematical properties of h-index sequences as developed by Liang [Liang, L. (2006). h-Index sequence and h-index matrix: Constructions and applications. Scientometrics,69(1), 153–159]. For practical reasons, Liming studies such sequences where the time goes backwards while it is more logical to use the time going forward (real career periods). Both type of h-index sequences are studied here and their interrelations are revealed. We show cases where these sequences are convex, linear and concave. We also show that, when one of the sequences is convex then the other one is concave, showing that the reverse-time sequence, in general, cannot be used to derive similar properties of the (difficult to obtain) forward time sequence. We show that both sequences are the same if and only if the author produces the same number of papers per year. If the author produces an increasing number of papers per year, then Liang’s h-sequences are above the “normal” ones. All these results are also valid for g- and R-sequences. The results are confirmed by the h-, g- and R-sequences (forward and reverse time) of the author. 相似文献
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模糊金库(fuzzy vault)算法作为目前较流行的一种指纹密钥技术,得到了人们越来越多的关注.本文基于原有模糊金库算法,提出了一种新的模糊金库算法,该算法中:首先,上锁时利用一组随机数建立一线性函数,函数的长度不再与密钥信息的长度有关;其次,引入伪随机序列发牛器,以指纹特征值作为生成元,产生随机数组用于构建模糊金库... 相似文献
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根据鸡白细胞介素18（IL-18）cDNA基因序列设计了1对特异性引物，应用RT-PCR技术，从脂多糖（lipopolysaccharide，LPS）刺激的我国地方品种萧山鸡原代鸡脾细胞中扩增并克隆鸡IL-18全长基因（Genbank accession，AY628648）。扩增片段全长591bp，共编码197个氨基酸的前体蛋白，其中含有表达完整功能蛋白所必需的起始密码子和终止密码子。该序列与国外报道的鸡IL-18全长基因核苷酸序列及推导的氨基酸序列的同源性为98．99％。只在引导序列中出现两个氨基酸残基的缺失，分子进化分析表明萧山鸡IL-18基因与火鸡以及家鸭基因形成一个独立的分支。将萧山鸡IL-18成熟蛋白序列插入pGEX-4T-2载体并在Ecoli中得到表达，获得45kD的GST-IL-18融合蛋白。经纯化后用于制备多克隆抗体。本研究对萧山鸡白细胞介素18的全长基因进行了克隆及表达，并对其分子进化进行了分析。为深入研究其功能奠定了基础。 相似文献
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借鉴社会网络理论中的濡染模型,将网络节点行为变量引入知识生产函数,对模型进行扩展,基于扩展后的模型考察我国电子信息领域和生物医药领域区域间技术交易网络、吸收能力与区域创新产出的关系。研究表明：（1）区域间知识溢出模式具有明显的技术领域特征,在电子信息领域,不同区域节点是通过模仿结构相似的竞争者的行为获取外部知识;在生物医药领域,不同区域节点是在互惠网络中获取新知识。（2）知识吸收能力对区域间技术交易网络与区域创新产出的关系具有调节作用。吸收能力高的区域和吸收能力低的区域,都可以通过嵌入区域间技术交易网络,实现区域创新能力提升。 相似文献
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The identification of linear, discrete time, scalar output systems which are driven exclusively by white, zero mean, inaccessible noise sequences is discussed. Two principal results are presented. First, two methods (least squares and an autocorrelation technique) for identifying the system characteristic equation coefficients are compared. The least squares approach is shown to be biased except for special cases. In general, the bias cannot be removed. If the state transition matrix is of the phase variable form, bias removal requires a knowledge of the measurement noise variance and all but one of the state driving noise variances. The autocorrelation technique is not biased asymptotically and does not require a knowledge of the noise variances.Secondly, it is shown that the m2 elements of the state transition matrix cannot be identified uniquely from the scalar output sequence autocorrelation coefficients if the system order is higher than one. The implication of this uncertainty in the state transition matrix on optimal filtering of the output sequence is briefly discussed. 相似文献
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Novel closed-form expressions for the probability density function and the average output signal-to-noise ratio at the output of a selection combiner in Weibull fading are derived. Using these expressions, the spectral efficiency of a direct sequence code division multiple access system is analytically obtained and performance evaluation results are presented. 相似文献
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《Journal of The Franklin Institute》2021,358(16):8419-8442
In this study, the distributed output consensus control issue is investigated for a class of linear cluster multi-agent systems (CMASs) under the control strategy of the reset observer. We consider a communication network consisting of several clusters, each of which is directed and contains a leader. The interactions among agents include continuous-discrete hybrid communication. Specifically, an instantaneous connectivity only exists between the clusters at discrete moments, called the reset time sequence. At the reset time, an instantaneous fixed directed network is formed such that only the leaders will consider the available information of neighboring leaders to reset their own states. During non-reset intervals, only the intra-clusters are connected while the inter-clusters are equivalent to a disconnected network topology. Considering that in practice, the state information may be partially unavailable, only the relative output information is utilized to estimate the unavailable state and thus control protocols are developed with the help of the reset full-order and reduced-order observers, respectively. The stability of the closed-loop CMAS at both the reset time and non-reset intervals is studied based on Lyapunov analysis. The consensus value depends only on the initial conditions and the network topology involved, and not on the reset time sequence. Finally, numerical simulations are provided to illustrate the theoretical results. 相似文献
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固定引文窗口的h类指数序列——以中、印、日物理学为例 总被引：1，自引：0，他引：1
h类指数是集发文与引文为一体的文献计量指标。h类指数序列可用于展示研究对象绩效的动态演化。已发表的h类指数序列研究采用的是全引文窗口,不同发文年的h类指数因引文窗口不同而不可比较。本文介绍了基于固定引文窗口构建h类指数序列的方法。固定引文窗口保证了不同发文年h类指数的可比性。利用SCI数据库1978-2009年期间中国、印度、日本发表的物理学论文的数据,分别构建了三个国家基于5年引文窗口的h指数序列、g指数序列、a指数序列以及r指数序列,并对三国物理学发展做了比较研究。 相似文献