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针对传统的m序列、Gold序列可用作扩频码的数量有限这一问题,提出了用混沌序列代替传统的m序列、Gold序列的方法。针对单个低维混沌映射产生的混沌序列存在抗攻击能力差、密钥空间小、保密性不理想等缺点,依据优选结果将单个低维的改进型Logistic序列与Chebyshev序列组合产生了一种新的混合序列。仿真结果表明,新的混合混沌序列平衡性高、类随机、相关性好,且该混合混沌序列和m序列、Gold序列的抗AWGN干扰和抗单频干扰的能力相近。 相似文献
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Writing correct English sentences can be challenging. Furthermore, writing correct formulaic sequences can be especially difficult because accepted combinations do not follow clear rules governing which words appear together in a sequence. One solution is to provide examples of correct usage accompanied by statistical feedback from web‐based applications for learners to emulate. The goal of the study was to investigate whether such a dedicated web‐based program that provides instant examples of correct word combinations and detailed results of who used these examples, where and when, can improve students' writing. Data were collected from 74 ESL (English as a Second Language) undergraduate students divided into control and experimental groups, who performed formulaic sequence tests, wrote passages in English, followed by interviews with members of the experimental group. The results show that students who used the software outperformed those who did not, on the tests and the overall grades for their writing. Implementing formulaic sequence check programs in writing classes to help students decide which words can appear together, under which circumstances, and in which context is recommended. 相似文献
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In this paper the nodes of the hexagonal grid are used as points. There are three types of neighbours on this grid, therefore neighbourhood sequences contain values 1, 2, 3. The grid is coordinatized by three coordinates in a symmetric way. Digital circles are classified based on digital distances using neighbourhood sequences. They can be triangle, hexagon, enneagon and dodecagon. Their corners and side-lengths are computed, such as their perimeters and areas. The radius of a digital disk is usually not well-defined, i.e., the same disk can have various radii according to the neighbourhood sequence used. Therefore the non-compactness ratio is used to measure the quality of approximation of the Euclidean circles. The best approximating neighbourhood sequence is presented. It is shown that the approximation can be improved using two neighbourhood sequences in parallel. Comparisons to other approximations are also shown. 相似文献
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Dong Han Kim 《Theoretical computer science》2011,412(29):3413-3417
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基于新的超混沌系统的图像加密方案 总被引:7,自引:0,他引:7
提出了一个新的超混沌系统,分析了新系统的混沌吸引子相图、平衡点及其性质、工yapunov指数等非线性动力学特性,并用该超混沌系统对图像进行加密研究。给出了一种新的基于四维超混沌系统的图像加密算法。实验结果及安全性分析表明,该算法具有较强的抵御穷举攻击、统计攻击、已知明文攻击能力,因而具有较高的安全性。 相似文献
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In this paper we propose a connectionist model for variable binding. The model is topology dependent on the graph it builds based on the predicates available. The irregular connections between perceptron-like assemblies facilitate forward and backward chaining. The model treats the symbolic data as a sequence and represents the training set as a partially connected network using basic set and graph theory to form the internal representation. Inference is achieved by opportunistic reasoning via the bidirectional connections. Consequently, such activity stabilizes to a multigraph. This multigraph is composed of isomorphic subgraphs which all represent solutions to the query made. Such a model has a number of advantages over other methods in that irrelevant connections are avoided by superimposing positionally dependent sub-structures that are identical, variable binding can be encoded and multiple solutions can be extracted simultaneously. The model also has the ability to adapt its existing architecture when presented with new clauses and therefore add new relationships/rules to the model explicitly; this is done by some partial retraining of the network due to the superimposition properties. 相似文献
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为了准确及时获取船舶在船闸中的运动信息,提出了一种基于概率速度场的实时检测船闸中船舶的方法。该方法首先分析了船舶在船闸中运行的各种环境因素;其次为了消除和减弱阴影和光斑的影响,从监测图象灰度直方图中派生出一个高斯概率分布模型,进而获取图象的概率场;最后定义了一个基于光流计算的可实时检测船舶的概率速度场。该方法已成功地测试了大量通过三峡临时船闸和葛洲坝船闸的船舶序列图象。 相似文献