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排序方式: 共有265条查询结果,搜索用时 15 毫秒
1.
LOUIS KRUH 《Cryptologia》2013,37(1):2-9
Abstract This article presents the original draft of the Zimmermann telegram from 1917 in facsimile. Its various annotations provide interesting insights, such as the idea to promise California to Japan and instructions concerning transmission and encryption. Further documents clarify how the telegram was sent and put various alternatives suggested in the literature to rest. The political background and fallout in Germany are discussed, as well. 相似文献
2.
Taking fully into consideration the fact that one human action can be intuitively considered as a sequence of key poses and atomic motions in a particular order, a human action recognition method using multi-layer codebooks of key poses and atomic motions is proposed in this paper. Inspired by the dynamics models of human joints, normalized relative orientations are computed as features for each limb of human body. In order to extract key poses and atomic motions precisely, feature sequences are segmented into pose feature segments and motion feature segments dynamically, based on the potential differences of feature sequences. Multi-layer codebooks of each human action are constructed with the key poses extracted from pose feature segments and the atomic motions extracted from motion feature segments associated with each two key poses. The multi-layer codebooks represent action patterns of each human action, which can be used to recognize human actions with the proposed pattern-matching method. Three classification methods are employed for action recognition based on the multi-layer codebooks. Two public action datasets, i.e., CAD-60 and MSRC-12 datasets, are used to demonstrate the advantages of the proposed method. The experimental results show that the proposed method can obtain a comparable or better performance compared with the state-of-the-art methods. 相似文献
3.
William Stallings 《Cryptologia》2018,42(2):135-145
This article presents an overview of the concepts of and motivation for the OCB block cipher mode of operation. OCB is well suited for IoT, wireless, and other constrained devices where processing time and energy consumption are design issues. The article describes two versions of the OCB algorithm (OCB1 and OCB3) that have been widely accepted. 相似文献
4.
Scene categorization with category-specific visual-word construction and image representation is proposed in this study. The proposed scene categorization has effective discriminative ability and class extendibility. The reasons are listed as follows. First, since the visual-word construction and image representation are category-specific, the corresponding learning model for classification has substantial discriminating power. Second, since the visual-word construction and image representation are category-specific, image features related to the original classes need not be recreated when new classes are added, which minimizes reconstruction overhead. Experimental results confirm that the accuracy of the proposed method is superior to existing methods with single-type features both in single-scale and in multi-scale versions. 相似文献
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The aim of this study is to generate vector quantisation (VQ) codebooks by integrating principle component analysis (PCA) algorithm, Linde-Buzo-Gray (LBG) algorithm, and evolutionary algorithms (EAs). The EAs include genetic algorithm (GA), particle swarm optimisation (PSO), honey bee mating optimisation (HBMO), and firefly algorithm (FF). The study is to provide performance comparisons between PCA-EA-LBG and PCA-LBG-EA approaches. The PCA-EA-LBG approaches contain PCA-GA-LBG, PCA-PSO-LBG, PCA-HBMO-LBG, and PCA-FF-LBG, while the PCA-LBG-EA approaches contain PCA-LBG, PCA-LBG-GA, PCA-LBG-PSO, PCA-LBG-HBMO, and PCA-LBG-FF. All training vectors of test images are grouped according to PCA. The PCA-EA-LBG used the vectors grouped by PCA as initial individuals, and the best solution gained by the EAs was given for LBG to discover a codebook. The PCA-LBG approach is to use the PCA to select vectors as initial individuals for LBG to find a codebook. The PCA-LBG-EA used the final result of PCA-LBG as an initial individual for EAs to find a codebook. The search schemes in PCA-EA-LBG first used global search and then applied local search skill, while in PCA-LBG-EA first used local search and then employed global search skill. The results verify that the PCA-EA-LBG indeed gain superior results compared to the PCA-LBG-EA, because the PCA-EA-LBG explores a global area to find a solution, and then exploits a better one from the local area of the solution. Furthermore the proposed PCA-EA-LBG approaches in designing VQ codebooks outperform existing approaches shown in the literature. 相似文献
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梁英宏 《计算机工程与应用》2010,46(9):169-172
针对摄像机较远距离拍摄目标的情形,提出一种利用人体行走时的投影周期性特征进行人体目标检测的方法,首先通过运动分割获取每一帧的运动目标,然后通过计算运动目标的投影相似性对目标进行检测。为了简化计算,利用Hausdorff距离对运动目标的投影进行相似性计算,同时为减少存储空间,利用码书作为存储相似性特征的数据结构。 相似文献
9.
针对彩色视频图像提出了一种DCT域内基于矢量量化的高效编码方法。为去掉彩色图像各分量间的相关性,首先将图像由RGB空间转换到YUV空间,然后根据人类视觉特征(HVS)对色度信号U、V进行了亚采样和平均化处理;对亮度信号Y则进行分块DCT变换,并根据HVS特征对变化域内的块矢量进行自适应分类,然后根据矢量的类型分别构造码矢和进行全局码书设计。提出的全局码书设计方案可以根据帧间相关性及码字使用频率,对码书的内容自动进行更新和替换,以适应场景内容的变化。实验结果表明:在保证图像重建质量的前提下,本文提出的方法具有较高的压缩效率,比较适合于视频会议以及水下视频观测等应用场合。 相似文献
10.
针对多用户MIMO-OFDM下行链路由有限反馈导致的性能缺失,提出了一种基于双码本的有限反馈预编码方案。该方案在接收端依据部分子载波信道信息并采用期望用户最大信干比准则,从预置码本中选取主码字及扰动码字反馈给发送端,在发送端根据子载波簇的相关性重构各子载波预编码矩阵,然后利用矩阵线性变换特性对主码字进行线性变换扰动以达到容量最优,从而补偿由于有限反馈导致的性能缺失。仿真结果表明,所提出的方法在保证反馈链路开销与系统误码性能的情况下,有效地改善了系统吞吐量。 相似文献