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231.
混沌权值变异的Huffman树图像加密算法 总被引:1,自引:0,他引:1
提出一种采用混沌权值变异的Huff man树的图像加密算法.此算法在熵编码过程中,以基本的Huffman树为标准,利用双耦合混沌序列1对DC系数进行树的结构未变异、路径值变异的加密;再利用双耦合混沌序列2对AC系数进行码字序号的加密.论文对算法进行了仿真,并对安全性、计算复杂度、压缩比性能进行了分析.实验结果表明,该算法基本上不影响压缩效率,且计算复杂度低、安全性高和实时性好,可用于网络上的图像服务. 相似文献
232.
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234.
针对二元的互关联后继树模型进行改进,构造三元互关联后继树,并结合Web日志的特点,构造Web事务集的互关联后继树和增量更新模型,设计基于三元互关联后继树的频繁路径挖掘算法,挖掘Web日志中的频繁路径。通过实验证明了基于三元互关联后继树和改进后的模型的出色插入查询性能。 相似文献
235.
Comparing tree-structured data for structural similarity is a recurring theme and one on which much effort has been spent. Most approaches so far are grounded, implicitly or explicitly, in algorithmic information theory, being approximations to an information distance derived from Kolmogorov complexity. In this paper we propose a novel complexity metric, also grounded in information theory, but calculated via Shannon's entropy equations. This is used to formulate a directly and efficiently computable metric for the structural difference between unordered trees. The paper explains the derivation of the metric in terms of information theory, and proves the essential property that it is a distance metric. The property of boundedness means that the metric can be used in contexts such as clustering, where second-order comparisons are required. The distance metric property means that the metric can be used in the context of similarity search and metric spaces in general, allowing trees to be indexed and stored within this domain. We are not aware of any other tree similarity metric with these properties. 相似文献
236.
Rene DriesselLars Mönch 《Computers & Industrial Engineering》2011,61(2):336-345
In this paper, we discuss a scheduling problem for jobs on identical parallel machines. Ready times of the jobs, precedence constraints, and sequence-dependent setup times are considered. We are interested in minimizing the performance measure total weighted tardiness that is important for achieving good on-time delivery performance. Scheduling problems of this type appear as subproblems in decomposition approaches for large scale job shops with automated transport of the jobs as, for example, in semiconductor manufacturing. We suggest several variants of variable neighborhood search (VNS) schemes for this scheduling problem and compare their performance with the performance of a list based scheduling approach based on the Apparent Tardiness Cost with Setups and Ready Times (ATCSR) dispatching rule. Based on extensive computational experiments with randomly generated test instances we are able to show that the VNS approach clearly outperforms heuristics based on the ATCSR dispatching rule in many situations with respect to solution quality. When using the schedule obtained by ATCSR as an initial solution for VNS, then the entire scheme is also fast and can be used as a subproblem solution procedure for complex job shop decomposition approaches. 相似文献
237.
Lélia BlinAuthor Vitae Maria Gradinariu Potop-ButucaruAuthor Vitae Stephane RovedakisAuthor Vitae 《Journal of Parallel and Distributed Computing》2011,71(3):438-449
We propose a self-stabilizing algorithm for constructing a Minimum Degree Spanning Tree (MDST) in undirected networks. Starting from an arbitrary state, our algorithm is guaranteed to converge to a legitimate state describing a spanning tree whose maximum node degree is at most Δ∗+1, where Δ∗ is the minimum possible maximum degree of a spanning tree of the network.To the best of our knowledge, our algorithm is the first self-stabilizing solution for the construction of a minimum degree spanning tree in undirected graphs. The algorithm uses only local communications (nodes interact only with the neighbors at one hop distance). Moreover, the algorithm is designed to work in any asynchronous message passing network with reliable FIFO channels. Additionally, we use a fine grained atomicity model (i.e., the send/receive atomicity). The time complexity of our solution is O(mn2logn) where m is the number of edges and n is the number of nodes. The memory complexity is O(δlogn) in the send-receive atomicity model (δ is the maximal degree of the network). 相似文献
238.
Fuzzy quality function deployment (QFD) has been extensively used for translating customer requirements (CRs) into product design requirements (DRs) in fuzzy environments. Existing approaches, however, for rating technical importance of DRs in fuzzy environments are found problematic, either incorrect or inappropriate. This paper investigates how the technical importance of DRs can be correctly rated in fuzzy environments. A pair of nonlinear programming models and two equivalent pairs of linear programming models are developed, respectively, to rate the technical importance of DRs. The developed models are examined and illustrated with two numerical examples. 相似文献
239.
设计了一种基于龙芯2F的低成本多媒体信息发布系统,并提出了一种基于请求属性的更新调度算法。硬件体系结构以龙芯2F作为服务器CPU,CDMA、WiFi和有线多模更新模块,蓝牙推送模块等构成,软件环境为Linux操作系统。更新调度算法依据应用场景对请求加权予以最优调度,较好地降低了由于等待延迟而产生的系统开销。实验结果表明,系统运行稳定,更新响应实时性高,能够较好地满足用户需求,而且更新调度算法使系统各项指标均好于传统的FCFS算法。 相似文献
240.
MIB浏览器是SNMP开发和网络管理中的常用与必备软件,为了生成可供显示的MIB树,传统的实现方法一般采用在代码中直接写入MIB树内容的方法或通过编码读入MIB文件来生成MIB树,这些方法都存在一定的局限性,也影响了MIB浏览器的适应性。通过使用libsmi与SNMP++可以较为轻松地构建起MIB浏览器,与传统方法相比,该方法实现的MIB浏览器可用性大大提高,且降低了实现的难度。说明并纠正了libsmi与SNMP++在开发中发现的一些缺陷。 相似文献