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91.
A lossless digital watermarking scheme,which was zero- perturbation on the content and graphics for the digital image maps,is proposed.During the simulation,the scheme has been utilized to model the copyright protection program as a commerce application.Compared to the traditional digital watermarking schemes,our scheme operates in redundancy areas of maps and is scalable to topology changes.Experimental results show that,with respect to the geometric attacks and image transformed,the performance of our scheme is better than the classical algorithms based space or frequency domain with much lower complexity.. 相似文献
92.
93.
TGSOM:一种用于数据聚类的动态自组织映射神经网络 总被引:17,自引:1,他引:17
针对传统Kohonen自组织特征映射(SOFM)神经网络模型结构需预先指定的限制,提出一种新的树形动态自组织映射(TGSOM)神经网络,当用于数据挖掘时该网络以其生成速度快可视性好具有显著优越性。该文详尽描述了该网络模型的生成算法,研究了算法中扩展因子的作用。扩展因子与训练样本数据的维数无关,其作用是控制网络的生长,扩展因子可以反映数据聚类的精度,即扩展因子值的大小与聚类精度的高低成正比。在聚类的不同阶段使用大小不等的扩展因子还可以实现层次聚类。 相似文献
94.
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96.
It is shown that the elements of a large class of discrete-time periodically varying
nonlinear input-output maps can be uniformly approximated arbitrarily well, over infinite
time intervals, using a certain structure that can be implemented in many ways using,
for example, radial basis functions, polynomial functions, piecewise linear functions, sigmoids,
or combinations of these functions. For the special case in which these functions
are taken to be certain polynomial functions, the input-output map of our structure is a
generalized finite discrete-time Volterra series. Results are given for the case in which
inputs and outputs are defined on the integers. The case in which inputs and outputs are
defined on the nonnegative integers is also addressed. 相似文献
97.
《Journal of Location Based Services》2013,7(2):138-166
With the prevalence of mobile computing systems and location based services, large amounts of spatio-temporal data are nowadays being collected, representing the mobility of people performing various activities. However, despite the increasing interest in the exploration of these data, there are still open challenges in various application contexts, e.g. related to visualisation and human–computer interaction. In order to support the extraction of useful and relevant information from the spatio-temporal and the thematic properties associated with human trajectories, it is crucial to develop and study adequate interactive visualisation techniques. In addition to the properties of the visualisations themselves, it is important to take into consideration the types of information present within the data and, more importantly, the types of tasks that a user might need to consider in order to achieve a given goal. The understanding of these factors may, in turn, simplify the development and the assessment of a given interactive visualisation. In this paper, we present and analyse the most relevant concepts associated to these topics. In particular, our analysis addresses the main properties associated with (human) trajectory data, the main types of visualisation tasks/objectives that the users may require in order to analyse that data and the high-level classes of techniques for visualising trajectory data. In addition, this paper also presents an overview on a user study, conducted in function of this analysis, to compare two classes of visualisation techniques, namely static maps and space-time cubes, regarding their adequacy in helping users completing basic visualisation tasks. 相似文献
98.
E.O. Olakanmi 《Journal of Materials Processing Technology》2013,213(8):1387-1405
Selective laser sintering/melting (SLS/SLM) processing difficulties of aluminium powders had been attributed to issues associated with laser–materials interaction only while neglecting the role of powder properties. This study provides a wholistic understanding of factors that influence the development of SLS/SLM processing window, densification, and microstructure of pure Al, Al–Mg, and Al–Si powders, fabricated in single and multiple layer parts by exploring the roles of processing and material parameters. It was demonstrated that similarities existing in the SLS/SLM processing maps of the powders could be attributed to similarities in their packing densities with the alloying addition of magnesium and silicon having no predominant effect on their processing maps’ boundaries. Rather, alloying addition has significant effect on the nature of the evolved surface morphology of SLS/SLM processed aluminium powders in their processing windows. In addition, the flow and solidification behaviour of the melt pool of the powders during single layer scan was strongly influenced by the particle morphology and oxygen content of the powders as well as applied energy density. The energy density in the range of 12–16 J/mm2 was found to be the threshold below which SLS was predominant and above which SLM occurred for the investigated powders. Moreover, successful oxide disruption phenomena which is necessary for inter-particulate coalescence in multi-layered SLS/SLM processed aluminium powders are found to be mainly controlled by the amount of oxide in the as-received powder, the degree of the uniformity of the distribution of the surface oxide film covering the aluminium particles, the nature of thermal mismatch existing between the oxide film and the parent aluminium particle which was dependent on the phase present in the oxide film. Al–12 wt% Si powder is hereby affirmed as a suitable candidate material for SLS/SLM process due to its low thermal expansion and uniform distribution of its surface oxide films as well as the mullite phase in its oxide film. 相似文献
99.
Daobin Wang Jie Zhang Guanjun Gao Xiaofei Cheng Sai Chen Yongli Zhao Wanyi Gu 《Optical Fiber Technology》2011,17(4):305-309
The real-time scheduling and routing in dynamic transparent optical networks requires fast and accurate evaluation of transmission penalty caused by nonlinear kerr effects with different dispersion maps. However, the conventional method using nonlinear phase shift can only be applied to assess the nonlinear penalty with optimized dispersion maps. In this paper, we introduce pulse broadening factor into the approach and propose a novel method to accurately evaluate nonlinear penalty and numerically investigate the feasibility of our novel method in 40-Gb/s Return-to-Zero Differential Quadrature Phase-Shift Keying (RZ-DQPSK) systems. Simulation results show that our approach can achieve good evaluation performance even with non-optimized dispersion maps. 相似文献
100.
Jose S. Cánovas 《Dynamical Systems: An International Journal》2009,24(4):473-483
The topological entropy of a continuous transitive map f : ? → ? is studied. We find lower bounds for the topological entropy of f and prove that transitive real maps can have finite entropy. 相似文献