Articles written in Pramana – Journal of Physics
Volume 96 All articles Published: 15 September 2022 Article ID 0175 Research Article
Josephson junction snap oscillator with megastability: Microcontroller implementation and its applications to secure medical images
BALAMURALI RAMAKRISHNAN NESTOR TSAFACK ALEX STEPHANE KEMNANG TSAFACK ZERIC TABEKOUENG NJITACKE SIFEU TAKOUGANG KINGNI
Megastability and coexisting attractors between periodic and self-excited chaotic attractors in the Josephson junction snap oscillator (JJSO) are reported in this paper. Two different cases are considered for this study. In one case, the JJSO is driven by a direct current (DC) whereas in the other case, it is driven by an alternative current (AC). The JJSO is implemented using a microcontroller to verify the numerical simulation results. The numerical simulations and microcontroller results have a qualitatively good agreement. Finally, an encryption scheme based on the modified Julia set, deoxyribonucleic acid (DNA) principle, and the sequences of the chaotic JJSO in this work are used to build a secure key to secure medical images. The plain colour image is decomposed into a blue component. The generated secure key is applied to one component to obtain the corresponding sparse components. Confusion keys are obtained from the chaotic JJSO to scramble each sparse component. Besides, the chaotic sequence is used to compress the confused sparse matrices corresponding to the blue components. Lastly, the component is quantified and a diffusion step is then applied to improve the randomness and consequently the information entropy.
Volume 97 All articles Published: 28 February 2023 Article ID 0046 Research Article
Control, synchronisation and antisynchronisation of chaos in two non-identical Josephson junction models via sliding mode control and its FPGA implementation
BALAMURALI RAMAKRISHNAN VICTOR KAMDOUM TAMBA JULES METSEBO DIANORRÉ TOKOUE NGATCHA KARTHIKEYAN RAJAGOPAL
The control, synchronisation and antisynchronisation of chaos in Josephson junction (JJ) and linear piecewise JJ models via sliding mode control method are investigated in this paper. Thanks to the Routh–Hurwitz stability criterion, the slidingmode controllers are designed to control chaos in JJ models and achieve synchronisation schemes between two non-identical JJ models. Numerical simulations are shown to clarify and confirm the chaos control and synchronisation schemes. Finally, field programmable gate array (FPGA) implementation is designed to reproduce the above-mentioned results and its correctness is confirmed using the FPGA analysis.
Volume 97, 2023
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