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On the security of a chaotic encryption scheme: problems with computerized chaos in finite computing precision 总被引:1,自引:0,他引:1
Zhou et al. have proposed a chaotic encryption scheme, which is based on a kind of computerized piecewise linear chaotic map (PWLCM) realized in finite computing precision. In this paper, we point out that Zhou's encryption scheme is not secure enough from strict cryptographic viewpoint. The reason lies in the dynamical degradation of the computerized piecewise linear chaotic map employed by Zhou et al. The dynamical degradation of the computerized chaos induces many weak keys to cause large information leaking of the plaintext. In addition, we also discuss three simple countermeasures to enhance the security of Zhou's cryptosystem, but none of them can essentially enhance the security. 相似文献
23.
R. Trujillo J. Mou P. E. Phelan D. S. Chau 《The International Journal of Advanced Manufacturing Technology》2004,23(3-4):176-182
Abstact This paper presents an investigation of the use of electrostrictive silicone polymers as actuators for mesoscale devices. The generated strains of both flat and rolled actuators, based on Dow Corning Sylgard 182 and 184, with sputtered gold electrodes, are presented as functions of the applied electric field. Variables examined in this study include silicone film thickness, gold electrode thickness, cycling of the applied electric field, and actuator configuration (flat or rolled). In general, thinner silicone films and gold electrodes yielded greater strains, at a constant applied field. The actuator performance tended to deteriorate with repeated application of the electric field, and the gold electrodes cracked after being subjected to a large percentage strain.Nomenclature
A
Cross sectional area, mm2
-
a
1
, a
2
electrostrictive constants, m2/V2
-
D
diameter, mm
-
E
electric field, V/m
-
o
permittivity of free space, F/m
-
dielectric constant for silicones, F/m
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F
force, N
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J
work, J
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l
length, m
-
S
ij
strain tensor, dimensionless
-
S
ijkl
tensor of elastic compliance coefficients, m
-
t
thickness, m
-
T
kl
stress tensor, Pa
-
u
i
displacement vector, mm
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V
volume, mm3
-
Poisson ratio, dimensionless
-
w
width, m
-
Y
Youngs modulus, Pa 相似文献
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为了提高永磁直驱型风电机组的并网性能,分析永磁直驱型风电机组的基本结构,讨论应用于永磁直驱型风电机组的各种低电压穿越技术,变桨距控制,增加功率开关器件的额定容量,网侧加装辅助变流器,STATCOM运行模式控制,不同位置加装撬棒Crowbar耗能元件,加装超级电容器,储能电池或超级电容器与储能电池组合,连接点出现事故性不对称故障时,改进网侧变流器的控制策略,配合撬棒Crowbar保护电路控制机组的功率平衡,实现不对称故障穿越。文中分析的各种故障穿越技术为后续永磁直驱型风电机组并网能力的提高有一定的理论指导。 相似文献
25.
以预设不同尺度裂缝的水泥砂浆块体和无裂缝水泥砂浆块体等三组试件为试验研究对象,基于交流阻抗谱测试技术,采用变化频率的正弦波脉冲作为激励信号,测试各试件电压信号峰峰值和相位差,计算相应的阻抗幅模量和进行相关数据分析。结果表明,同类试件的阻抗谱具有很好的相似性和一致性,阻抗谱可作为表征水泥砂浆材料性能的本征参数;有无预设裂缝水泥砂浆试件的阻抗幅模量差异明显,基于阻抗谱检测水泥砂浆内部裂缝可行;阻抗特性与裂缝几何尺度之间存在量化关系;水泥砂浆试件呈现电容性。 相似文献
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Rutile Nanorod/Anatase Nanowire Junction Array as Both Sensor and Power Supplier for High‐Performance,Self‐Powered,Wireless UV Photodetector 下载免费PDF全文
Xin Yu Zhenhuan Zhao Jian Zhang Weibo Guo Jichuan Qiu Deshuai Li Zhou Li Xiaoning Mou Linlin Li Aixue Li Hong Liu 《Small (Weinheim an der Bergstrasse, Germany)》2016,12(20):2759-2767
Self‐powered UV photodetectors based on TiO2 nanotree arrays have captured much attention in recent years because of their many advantages. In this work, rutile/anatase TiO2 (R/A‐TiO2) heterostructured nanotree arrays are fabricated by assembling anatase nanowires as branches on rutile nanorods. External quantum efficiencies as high as 90% are reached at 325 nm. These high quantum efficiencies are related to the higher amount of light harvesting due to the larger surface area, the better separation ability of the photogenerated carriers by the rutile/anatase heterostructure, and the faster electron transport, related to the 1D nanostructure and lattice connection at the interface of the two kinds of TiO2. Furthermore, a self‐powered wireless UV photodetector is shown with excellent wireless detection performance. Such devices will enable significant advances for next‐generation photodetection and photosensing applications. 相似文献
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