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Security analysis of image encryption based on two-dimensional chaotic maps and improved algorithm
Feng HUANG, Yong FENG
Front Elect Electr Eng Chin. 2009, 4 (1): 5-9.
https://doi.org/10.1007/s11460-009-0016-z
The article proposes a new algorithm to improve the security of image encryption based on two-dimensional chaotic maps. Chaotic maps are often used in encrypting images. However, the encryption has periodicity, no diffusion, and at the same time, the real keys space of encryption are fewer than the theoretical keys space, which consequently results in potential security problems. Thus, this article puts forward several ways to solve the problems including adding diffusion mechanism, changing the design of keys and developing a composite encryption system. It designs an algorithm for the version B of the discretized baker map, which is one of the most prevalent chaotic maps, based on which a new image encryption is proposed to avoid the above problems. The simulation results show that the new encryption algorithm is valid and the result can be applied to other two-dimensional chaotic maps, such as the cat map.
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Compression algorithm for electrocardiograms based on sparse decomposition
Chunguang WANG, Jinjiang LIU, Jixiang SUN
Front Elect Electr Eng Chin. 2009, 4 (1): 10-14.
https://doi.org/10.1007/s11460-009-0009-y
Sparse decomposition is a new theory in signal processing, with the advantage in that the base (dictionary) used in this theory is over-complete, and can reflect the nature of a signal. Thus, the sparse decomposition of signal can obtain sparse representation, which is very important in data compression. The algorithm of compression based on sparse decomposition is investigated. By training on and learning electrocardiogram (ECG) data in the MIT-BIH Arrhythmia Database, we constructed an over-complete dictionary of ECGs. Since the atoms in this dictionary are in accord with the character of ECGs, it is possible that an extensive ECG datum is reconstructed by a few nonzero coefficients and atoms. The proposed compression algorithm can adjust compression ratio according to practical request, and the distortion is low (when the compression ratio is 20∶1, the standard error is 5.11%). The experiments prove the feasibility of the proposed compression algorithm.
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Text clustering based on fusion of ant colony and genetic algorithms
Yun ZHANG, Boqin FENG, Shouqiang MA, Lianmeng LIU
Front Elect Electr Eng Chin. 2009, 4 (1): 15-19.
https://doi.org/10.1007/s11460-009-0019-9
Focusing on the problem that the ant colony algorithm gets into stagnation easily and cannot fully search in solution space, a text clustering approach based on the fusion of the ant colony and genetic algorithms is proposed. The four parameters that influence the performance of the ant colony algorithm are encoded as chromosomes, thereby the fitness function, selection, crossover and mutation operator are designed to find the combination of optimal parameters through a number of iteration, and then it is applied to text clustering. The simulation results show that compared with the classical k-means clustering and the basic ant colony clustering algorithm, the proposed algorithm has better performance and the value of F-Measure is enhanced by 5.69%, 48.60% and 69.60%, respectively, in 3 test data sets. Therefore, it is more suitable for processing a larger dataset.
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Luminescence and recombine centre in ZnO/Si films
Cihui LIU, Ran YAO, Jianfeng SU, Zeyu MA, Zhuxi FU
Front Elect Electr Eng Chin. 2009, 4 (1): 93-97.
https://doi.org/10.1007/s11460-008-0081-8
The D0h luminescence of ZnO films deposited on p-type Si substrates is produced by metal-organic chemical vapor deposition (MOCVD). After annealing in the air at 700°C for an hour, the photoluminescence (PL) spectra, the I-V characteristics and the deep level transient spectroscopy (DLTS) of the samples are measured. All the samples have a rectification characteristic. DLTS signals show two deep levels of E1 and E2. The Gaussian fit curves of the PL spectra at room temperature show three luminescence lines b, c and d, of which b is attributed to the exciton emission. The donor level E1 measured by DLTS and the location state donor ionization energy Ed of the closely neighboring emission lines c and d are correlated. E1 is judged as neutral donor bound to hole emission (D0h). Moreover, the intensity of the PL spectra decreases while the relative density of E2 increases, showing that E2 has the property of a non-radiative center.
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Development and test in grid of 630 kVA three-phase high temperature superconducting transformer
Yinshun WANG, Xiang ZHAO, Junjie HAN, Huidong LI, Yin GUAN, Qing BAO, Xi XU, Shaotao DAI, Naihao SONG, Fengyuan ZHANG, Liangzhen LIN, Liye XIAO
Front Elect Electr Eng Chin. 2009, 4 (1): 104-113.
https://doi.org/10.1007/s11460-009-0010-5
A 630-kVA 10.5 kV/0.4 kV three-phase high temperature superconducting (HTS) power transformer was successfully developed and tested in a live grid. The windings were wound by hermetic stainless steel-reinforced multi-filamentary Bi2223/Ag tapes. The structures of primary windings are solenoid with insulation and cooling path among layers, and those of secondary windings consist of double-pancakes connected in parallel. Toroidal cryostat is made from electrical insulating glass fiber reinforced plastics (GFRP) materials with room temperature bore for commercial amorphous alloy core with five limbs. Windings are laid in the toroidal cryostat so that the amorphous core operates at room temperature. An insulation technology of double-half wrapping up the Bi2223/Ag tape with Kapton film is used by a winding machine developed by the authors. Fundamental characteristics of the transformer are obtained by standard short-circuit and no-load tests, and it is shown that the transformer meets operating requirements in a live grid.
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21 articles
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