对一种混沌图像密码的选择明文攻击   总被引：2，自引：0，他引：2  

刘婷  闵乐泉 《武汉大学学报(信息科学版)》2010,(5)

对基于广义猫映射和加法模运算的混沌密码进行了安全性分析,指出了该密码设计上的几处瑕疵。在选择明文攻击下,该密码系统在1轮加密时不够安全,仅选择3幅明文图像就可破译。讨论了该密码在多轮加密时待解决的问题以及可能采取的改进措施。  相似文献   

Chaos and chaotic control in a relative rotation nonlinear dynamical system under parametric excitation     

时培明  韩东颖  刘彬 《海洋学报(英文版)》2010,29(9)

This paper studies the chaotic behaviours of a relative rotation nonlinear dynamical system under parametric excitation and its control. The dynamical equation of relative rotation nonlinear dynamical system under parametric excitation is deduced by using the dissipation Lagrange equation. The criterion of existence of chaos under parametric excitation is given by using the Melnikov theory. The chaotic behaviours are detected by numerical simulations including bifurcation diagrams, Poincaré map and maximal Lyapunov exponent. Furthermore, it implements chaotic control using non-feedback method. It obtains the parameter condition of chaotic control by the Melnikov theory. Numerical simulation results show the consistence with the theoretical analysis. The chaotic motions can be controlled to period-motions by adding an excitation term.  相似文献   

横向磁场中大挠度金属薄板的混沌振动     

薛春霞  张善元  树学锋 《海洋学报》2010,32(9):6599-6605

利用Karman关于板的大挠度理论,考虑涡电流在板中引起的Lorentz力,导出了在横向磁场和横向载荷共同作用下薄板的非线性运动方程.借助Bubnov-Galerkin法将非线性偏微分方程转化为含三次非线性项的常微分方程.在定性分析的基础上,利用次谐轨道的Melnikov函数给出了发生Smale马蹄型混沌运动的阈值条件,进而数值计算了系统的分岔图、相应的相图、Poincaré映射和时程曲线,给出了混沌运动的数字特征.分析结果表明:磁感应强度和外载荷都会影响系统的振动特性.  相似文献   

简易混沌振荡器的混沌特性及其反馈控制电路的设计     

史正平 《海洋学报》2010,32(9):5940-5948

研究了一个新的简易混沌振荡电路系统的稳定性和混沌特性,从理论上推导了该混沌振荡电路系统的稳定和混沌的条件,并对该系统进行了精确反馈线性化控制.最后,通过电路仿真实验和硬件实验验证了理论分析的准确性.  相似文献   

Editorial 2020 Part II: Data from nowhere?     

Stuart N. Lane 《地球表面变化过程与地形》2020,45(1):5-10

  相似文献   

Young Age for the Veritas Asteroid Family Confirmed?     

Knežević  Z.  Pavlović  R. 《Earth, Moon, and Planets》2000,88(3):155-166

We present a comprehensive analysis of the dynamics of Veritas family members located in a chaotic strip centeredat 3.174 AU. A total of 600 chaotic members of the family and their clones were integrated for 100 Myr, and the variation of the distance with respect to the barycenter of the family have been computed forall of them. A simple classification of the prevailing behaviors hasbeen introduced to help identify typical dynamical patterns and states that could affect an estimate of the upper bound to the age of the family. We pointed out the importance of the temporary captures in thequasi-stable states, which occur often enough to affect the statistical analysis of the exits. The results are compatible with the young age (<100 Myr) for the family of Veritas, but we cannot say precisely how young it really is. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

CHARACTERISTICS OF TECTONIC MIXTITE ZONE IN THE LANCANG RIVER,WESTERN YUNNAN     

Liu Dengzhong  Wang Guozhi  Tao Xiaofeng  Zhui Lidong  Li Youguo  Xu XinhuangWT  ”BX 《地学前缘》2000,(Z1)

CHARACTERISTICS OF TECTONIC MIXTITE ZONE IN THE LANCANG RIVER,WESTERN YUNNAN  相似文献   

Ricker子波视主频的变化对混沌振子检测效果的影响   总被引：2，自引：2，他引：0       下载免费PDF全文

袁野  罗正玮  李月 《地球物理学进展》2006,21(1):70-73

针对地震勘探资料中存在加性强随机噪声干扰,已经提出用混沌振子系统处理的方法技术.为完善该方法,需要研究诸如地震勘探同相轴完整程度、组成同相轴的地震子波变化等对系统检测效果的影响.本文以Ricker子波模拟地震子波,研究Ricker子波视主频变化的相应检测效果.研究结果：随着Ricker子波视主频的升高,检测SNR逐渐变差,在高频部分SNR的变化明显比低频部分缓慢;在通常地震勘探频率范围内,混沌振子系统检测SNR有可能部分补偿由于地震波传播引起的幅度降低;为检测由畸变子波构成的同相轴提供一定的可能.  相似文献   

多点锚泊系统吸引子和吸引域的计算     

欧阳茹荃  朱继懋 《海洋工程》1999,17(3)

针对单自由度多点锚泊系统的纵荡运动模型,研究系统在浪和流作用下的多吸引子和吸引域。以布锚参数,来流和波浪尺度为变参数,运用数值积分和胞映射分析相结合的方法,求得系统的多种形式的振动解,与前人采用完全数值积分方法相比,结果一致。认为在实际中只需研究解的定范围渐近稳定性。文中采用胞映射法,计算了多种振动解的定范围吸引域,以及混沌吸引子的吸引域。并由此分析了吸引子的渐近稳定特性和对初值的敏感性  相似文献   

The origin of chaotic behaviour in the Miranda-Umbriel 3 : 1 resonances     

Jacques Henrard  Massae Sato 《Celestial Mechanics and Dynamical Astronomy》1989,47(4):391-417

We have investigated the pericentric resonances through which Miranda and Umbriel are believed to have passed when, due to tidal evolution, their orbital mean motions reached a 3 : 1 commensurability. Our investigation is based upon a perturbative treatment. The predictions of this theory are in good agreement with the results of numerical integrations concerning both the extend of the chaotic layers generated by the separatrices of the primary resonances and the location of the secondary resonances. The effect of tidal evolution is discussed on the bases of the adiatatic invariant theory and its extension to separatrix crossing. We recover qualitatively the mean features of the numerical experiments of Tittermore and Wisdom (1988–1989), Dermott et al (1988) and Malhotra and Dermott (1989).  相似文献