首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   4篇
  免费   30篇
物理学   34篇
  2014年   3篇
  2012年   1篇
  2011年   1篇
  2010年   3篇
  2009年   1篇
  2008年   2篇
  2007年   5篇
  2006年   2篇
  2005年   4篇
  2004年   1篇
  2003年   1篇
  2001年   5篇
  2000年   5篇
排序方式: 共有34条查询结果,搜索用时 16 毫秒
1.
李恒建  张家树  陈怀新 《光子学报》2014,38(11):3009-3015
提出了一种基于分层树型结构正交匹配追踪算法的快速图像去噪方法.通过选择高斯函数和墨西哥草帽小波母函数构建混合冗余字典,采用分层树状结构表示字典,结合构正交匹配追踪算法,实现图像稀疏表示,提高了图像表示的稀疏性,降低了算法的复杂度.依据噪音能量阈值,通过多次迭代达到图像去噪的目的.实验结果表明,在相同的噪音水平下,该迭代去噪算法取得了较高的较好的PSNR,获得更好的视觉效果.  相似文献   
2.
廖东  王小敏  张家树  张文芳 《物理学报》2012,61(23):103-112
结合并行Hash函数和多混沌的设计思想,提出了一种基于空间伸缩结构的参数可控的混沌Hash函数构造方法.该方法结合空间结构的伸缩特性,使用动态密钥控制消息在空间的"膨胀-收缩-置乱"方式,有效地提高了系统的混乱和扩散特性,同时使用空间并行结构在提高Hash函数安全性的同时也提高了系统的执行效率.研究结果表明:新算法的并行计算速度快,且产生的Hash序列满足均匀分布,具有更为理想的混淆与扩散特性.  相似文献   
3.
An adaptive nonlinear feedback-control method is proposed to control continuous-time chaotic dynamical systems, where the adaptive nonlinear controller acts on only one-dimensional error signal between the desired state and the observed chaotic state of a system. The reduced parameter adaptive quadratic predictor used in adaptive feedback cancellation of the nonlinear terms can control the system to any desired state. Computer simulation results on the Lorenz system are shown to demonstrate the effectiveness of this feedback-control method.  相似文献   
4.
李恒超  张家树 《中国物理快报》2005,22(11):2776-2779
Based on phase space delay-coordinate reconstruction of a chaotic dynamics system, we propose a local prediction of chaotic time series using a support vector machine (SVM) to overcome the shortcomings of traditional local prediction methods. The simulation results show that the performance of this proposed predictor for making onestep and multi-step prediction is superior to that of the traditional local linear prediction method and global SVM method. In addition, it is significant that its prediction performance is insensitive to the selection of embedding dimension and the number of nearest neighbours, so the satisfying results can be achieved even if we do not know the optimal embedding dimension and how to select the number of nearest neighbours.  相似文献   
5.
王小敏  张家树  张文芳 《物理学报》2005,54(12):5566-5573
在对多个满足Kelber条件的滤波器组成的复合系统进行初步分析的基础上,提出了一个基于复合非线性数字滤波器的带密钥的Hash算法.算法首先构建能产生高维混沌序列的复合滤波器系统,然后在明文作用的复合序列控制下随机选择滤波器子系统,并以复合系统的初态作为密钥,以粗粒化的量化迭代轨迹作为明文的Hash值.讨论了复合系统实现Hash函数的不可逆性、防伪造性、初值敏感性等特点.研究结果表明:基于复合非线性数字滤波器的Hash算法简单快速,比基于单一混沌映射的Hash算法有着更高的安全性,同时滤波器结构中没有复杂的浮点运算,比一般复合混沌系统更易于软硬件实现. 关键词: Hash 函数 混沌 非线性自回归数字滤波器  相似文献   
6.
混沌时间序列的Volterra自适应预测   总被引:41,自引:0,他引:41       下载免费PDF全文
张家树  肖先赐 《物理学报》2000,20(1):403-408
  相似文献   
7.
张家树  肖先赐 《中国物理》2000,9(6):408-413
A fast evolutionary programming (FEP) is proposed to train multi-layer perceptrons (MLP) for noisy chaotic time series modeling and predictions. This FEP, which uses a Cauchy mutation operator that results in a significantly faster convergence to the optimal solution, can help MLP to escape from local minima. A comparison against back-propagation-trained networks was performed. Numerical experimental results show that the FEP can help MLP better capturing dynamics from noisy chaotic time series than the back-propagation algorithm and produce a more consistently modeling and prediction.  相似文献   
8.
9.
张祖涛  张家树 《中国物理 B》2010,19(10):104601-104601
The unscented Kalman filter is a developed well-known method for nonlinear motion estimation and tracking. However, the standard unscented Kalman filter has the inherent drawbacks, such as numerical instability and much more time spent on calculation in practical applications. In this paper, we present a novel sampling strong tracking nonlinear unscented Kalman filter, aiming to overcome the difficulty in nonlinear eye tracking. In the above proposed filter, the simplified unscented transform sampling strategy with n+2 sigma points leads to the computational efficiency, and suboptimal fading factor of strong tracking filtering is introduced to improve robustness and accuracy of eye tracking. Compared with the related unscented Kalman filter for eye tracking, the proposed filter has potential advantages in robustness, convergence speed, and tracking accuracy. The final experimental results show the validity of our method for eye tracking under realistic conditions.  相似文献   
10.
李恒建  张家树 《中国物理 B》2010,19(5):50508-050508
In this study an adaptive arithmetic coder is embedded in the Baptista-type chaotic cryptosystem for implementing secure data compression.To build the multiple lookup tables of secure data compression,the phase space of chaos map with a uniform distribution in the search mode is divided non-uniformly according to the dynamic probability estimation of plaintext symbols.As a result,more probable symbols are selected according to the local statistical characters of plaintext and the required number of iterations is small since the more probable symbols have a higher chance to be visited by the chaotic search trajectory.By exploiting non-uniformity in the probabilities under which a number of iteration to be coded takes on its possible values,the compression capability is achieved by adaptive arithmetic code.Therefore,the system offers both compression and security.Compared with original arithmetic coding,simulation results on Calgary Corpus files show that the proposed scheme suffers from a reduction in compression performance less than 12% and is not susceptible to previously carried out attacks on arithmetic coding algorithms.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号