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In this paper, we propose a fast hyperchaotic image encryption scheme based on RSVM and step-by-step scrambling-diffusion. In this scheme, we firstly propose a new algorithm named ring shrinkage with variable modulo (RSVM), which can randomly scramble the elements in a one-dimensional array, which are composed of the row numbers or column numbers of the pixel matrix to be encrypted. Before encryption, we use RSVM algorithm to generate two random one-dimensional arrays of pixel matrix (i.e. row array A s and column array B s ), and each element in the A s / B s represents the row/column number in the pixel matrix. Then the rows/columns of the pixel matrix are scrambled-diffused step-by-step according to the row/column numbers in the A s / B s . The initial control parameters of RSVM algorithm are controlled by SHA-256 of plaintext pixels, and RSVM algorithm controls the step-by-step scrambling-diffusion process of pixel matrix, rows and columns, so the small changes of plaintext pixels will lead to great differences in ciphertext images. In addition, the overall time complexity of the image encryption scheme is only Θ (1. 5 (M + N)) , which can greatly reduce the time cost. Finally, the experimental results and extensive security analysis prove the efficiency and feasibility of this image encryption method. [ABSTRACT FROM AUTHOR]

In this paper, we consider the following critical equation: − Δ u + V (y) u = K (y) u N + 2 N − 2 , u > 0 , u ∈ H 1 (ℝ N) , where (y ′ , y ″) ∈ ℝ 2 × ℝ N − 2 , V (| y ′ | , y ″) and K (| y ′ | , y ″) are two nonnegative and bounded functions. Using a finite-dimensional reduction argument and local Pohozaev type of identities, we show that if N ≥ 5 , K (r , y ″) has a stable critical point (r 0 , y 0 ″) with r 0 > 0 , K (r 0 , y 0 ″) > 0 and B 1 : = V (r 0 , y 0 ″) ∫ ℝ N U 0 , 1 2 d y − Δ K (r 0 , y 0 ″) 2 ∗ N ∫ ℝ N | y | 2 U 0 , 1 2 ∗ d y > 0 , then the above equation has infinitely many positive solutions, where U 0 , 1 is the unique positive solution of − Δ u = u N + 2 N − 2 with u (0) = max y ∈ ℝ N u (y). Combining the results of [S. Peng, C. Wang and S. Wei, Constructing solutions for the prescribed scalar curvature problem via local Pohozaev identities, to appear in J. Differential Equations; S. Peng, C. Wang and S. Yan, Construction of solutions via local Pohozaev identities, J. Funct. Anal.274 (2018) 2606–2633], it implies that the role of stable critical points of K (r , y ″) in constructing bump solutions is more important than that of V (r , y ″) and that V (r 0 , y 0 ″) can influence the sign of Δ K (r 0 , y 0 ″) , i.e. Δ K (r 0 , y 0 ″) can be nonnegative, different from that in [S. Peng, C. Wang and S. Wei, Constructing solutions for the prescribed scalar curvature problem via local Pohozaev identities, to appear in J. Differential Equations]. The concentration points of the solutions locate near the stable critical points of K (r , y ″) , which include the case of a saddle point. [ABSTRACT FROM AUTHOR]

Locally active memristors with multiple coexisting pinched hysteresis loops have attracted the attention of researchers. However, the currently reported multiple coexisting pinched hysteresis loops memristors are obtained by adding additional piecewise-linear terms into the original Chua corsage memristor. This paper proposes a novel locally active memristor by introducing a polynomial characteristic function into the state equation. The novel memristor has three coexisting pinched hysteresis loops, large relative range of active region and simple emulator circuit. The characteristics of the novel memristor such as power-off plot, coexisting pinched hysteresis loops and DC V – I plot are studied. The memristor is used in a Chua chaotic system to investigate the effects of locally active characteristic on the chaotic oscillation system. Furthermore, the memristor emulator and chaotic system are designed and implemented by commercial circuit elements. The hardware experiments are consistent with numerical simulations. [ABSTRACT FROM AUTHOR]

Although multiwing hidden attractor chaotic systems have attracted a lot of interest, the currently reported multiwing hidden attractor chaotic systems are either with no equilibrium point or with an infinite number of equilibrium points. The multiwing hidden attractor chaotic systems with stable equilibrium points have not been reported. This paper reports a four-wing hidden attractor chaotic system, which has only one stable node-focus equilibrium point. The novel system can also generate a hidden attractor with one-wing and hidden attractors with quasi-periodic and periodic coexistence. In addition, a self-excited attractor with one-wing can be generated by adjusting the parameters of the novel system. The hidden attractors of the novel system are verified by the cross-section of attraction basins. And the hidden behavior is investigated by choosing different initial states. Moreover, the coexisting transient four-wing phenomenon of the self-excited one-wing attractor system is studied by the time domain waveforms and attraction basin. The dynamical characteristics of the novel system are studied by Lyapunov exponents spectrum, bifurcation diagram and Poincaré map. Furthermore, the novel hidden attractor system with four-wing and one-wing are implemented by electronic circuits. The hardware experiment results are consistent with the numerical simulations. [ABSTRACT FROM AUTHOR]

Lyapunov exponent (LE), chaotic range and complexity are the key considerations of a discrete chaotic system. A dynamic chaotic system with larger LE and wider parameter space will result in better statistical performance that can be used to generate pseudo random sequences and applied to encryption fields. At the same time, the combination of simple chaotic maps can generate more excellent chaotic behavior. This paper proposes a newly combined chaotic system called Parallel Chaotic System (PCS). Multiple simple chaotic maps are paralleled to construct the novel system. In this system, LE and chaotic range can be improved as much as possible by setting additional parameters. Compared with the existing models made up of same seed maps, PCS is able to get better chaotic behavior by means of a simple structure at the same time. Performance evaluation emphasizes that the chaotic maps generated by PCS are more unpredictable with better complexity. [ABSTRACT FROM AUTHOR]

Based on the study on Jerk chaotic system, a multiscroll hyperchaotic system with hidden attractors is proposed in this paper, which has infinite number of equilibriums. The chaotic system can generate N + M + 2 scroll hyperchaotic hidden attractors. The dynamic characteristics of the multiscroll hyperchaotic system with hidden attractors are analyzed by means of dynamic analysis methods such as Lyapunov exponents and bifurcation diagram. In addition, we have studied the synchronization of the system by applying an adaptive control method. The hardware experiment of the proposed multiscroll hyperchaotic system with hidden attractors is carried out using discrete components. The hardware experimental results are consistent with the numerical simulation results of MATLAB and the theoretical analysis results. [ABSTRACT FROM AUTHOR]

In recent years, scholars studied and proposed some secure color image encryption algorithms. However, the majority of the published algorithms encrypted red, green and blue (called R , G , B for short) components independently. In the paper, we propose a color image encryption scheme based on hyperchaotic system and permutation-diffusion architecture. The encryption algorithm utilizes a block permutation which is realized by mixing R , G , B components to strengthen the dependence of each component. Besides, it can reduce time consumption. Then, the key streams generated by the hyperchaotic system are exploited to diffuse the pixels, the three components affect each other again. And in the diffusion process, we can get two totally different encrypted images even though we change the last pixel because the G component is diffused in reverse order. The experimental results reveal that our algorithm possesses better abilities of resisting statistical attacks and differential attacks, larger key space, closer information entropy to 8, and faster encryption speed compared with other chaos-based color image encryption algorithms. [ABSTRACT FROM AUTHOR]

This paper introduces a novel CMOS second-generation current-controlled current conveyor (CCCII) that has a wide tunable intrinsic resistance ( R x ). The designed structure is achieved by the combination of one ordinary CCCII, one cross-coupled OTA and one active resistor. An inverse relationship between the intrinsic resistance and external bias current is created for the first time in CMOS CCCII design, which results in wide tuning range of R x . Performance of the proposed circuit is discussed by detailed analysis. The CMOS CCCII is simulated in TSMC 0.18 μ m RF CMOS technology. The simulation results confirm that the proposed CMOS CCCII achieves a wide tunable R x (from 197.4 Ω to 27.23 k Ω ) while maintaining favorable performance in bandwidth, transfer gain and linear range. In addition, a new reconfigurable structure, which can function as a universal filter or a quadrature oscillator via controlling an enabled switch, is given as an application example to validate the feasibility of the proposed CMOS CCCII. [ABSTRACT FROM AUTHOR]

Based on the permutation-diffusion architecture, this paper introduces a more sensitive chaotic image encryption scheme using breadth-first search and dynamic diffusion to enhance the security and sensitivity. In the permutation stage, the plain image is traversed by breadth-first search, and then the whole permutation is performed to obtain a shuffled sequence. Similarly, the diffusion key stream is rearranged by breadth-first search. Moreover, a dynamic diffusion method is proposed to encrypt the shuffled sequence in the diffusion stage, which can ensure that encrypting each pixel is related to all other pixels and can enhance the sensitivity of the cryptosystem. In each phase, the hyper-chaotic system in this scheme generates pseudorandom sequences. The simulation results and performance analysis show that the proposed scheme has excellent performances and high security in resisting brute-force attack, statistical attack and differential attack. [ABSTRACT FROM AUTHOR]

By replacing the resistor in a Twin-T network with a generalized flux-controlled memristor, this paper proposes a simple fourth-order memristive Twin-T oscillator. Rich dynamical behaviors can be observed in the dynamical system. The most striking feature is that this system has various periodic orbits and various chaotic attractors generated by adjusting parameter . At the same time, coexisting attractors and antimonotonicity are also detected (especially, two full Feigenbaum remerging trees in series are observed in such autonomous chaotic systems). Their dynamical features are analyzed by phase portraits, Lyapunov exponents, bifurcation diagrams and basin of attraction. Moreover, hardware experiments on a breadboard are carried out. Experimental measurements are in accordance with the simulation results. Finally, a multi-channel random bit generator is designed for encryption applications. Numerical results illustrate the usefulness of the random bit generator. [ABSTRACT FROM AUTHOR]

In this paper, a flux-controlled memristor with linear memductance is proposed. Compared with the memristor with piecewise linear memductance and the memristor with smooth continuous nonlinearity memductance which are widely used in the study of memristive chaotic system, the proposed memristor has simple mathematical model and is easy to implement. Multisim circuit simulation and breadboard experiment are realized, and the memristor can exhibit a pinched hysteresis loop in the voltage-current plane when driven by a periodic voltage. In addition, a new hyper-chaotic system is presented in this paper by adding the proposed memristor into the Lorenz system. The transient chaos and multiple attractors are observed in this memristive system. The dynamical behaviors of the proposed system are analyzed by equilibria, Lyapunov exponents, bifurcation diagram and phase portrait. Finally, an electronic circuit is designed to implement the hyper-chaotic memristive system. [ABSTRACT FROM AUTHOR]

This paper presents a high linearity and low power Low-Noise Amplifier (LNA) for Ultra-Wideband (UWB) receivers based on CHRT 0.18m Complementary Metal-Oxide-Semiconductor (CMOS) technology. In this work, the folded topology is adopted in order to reduce the supply voltage and power consumption. Moreover, a band-pass LC filter is embedded in the folded-cascode circuit to extend bandwidth. The transconductance nonlinearity has a great impact on the whole LNA linearity performance under a low supply voltage. A post-distortion (PD) technique employing an auxiliary transistor is applied in the transconductance stage to improve the linearity. The post-layout simulation results indicate that the proposed LNA achieves a maximum power gain of 12.8dB. The input and output reflection coefficients both are lower than dB over 2.5-11.5GHz. The input third-order intercept point (IIP3) is 5.6dBm at 8GHz and the noise figure (NF) is lower than 4.0dB. The LNA consumes 5.4mW power under a 1V supply voltage. [ABSTRACT FROM AUTHOR]

A memristor is the fourth circuit element, which has wide applications in chaos generation. In this paper, a four-dimensional hyperchaotic jerk system based on a memristor is proposed, where the scroll number of the memristive jerk system is controllable. The new system is constructed by introducing one extra flux-controlled memristor into three-dimensional multiscroll jerk system. We can get different scroll attractors by varying the strength of memristor in this system without changing the circuit structure. Such a method for controlling the scroll number without changing the circuit structure is very important in designing the modern circuits and systems. The new memristive jerk system can exhibit a hyperchaotic attractor, which has more complex dynamic behavior. Furthermore, coexisting attractors are observed in the system. Phase portraits, dissipativity, equilibria, Lyapunov exponents and bifurcation diagrams are analyzed. Finally, the circuit implementation is carried out to verify the new system. [ABSTRACT FROM AUTHOR]

By adding only one smooth flux-controlled memristor into a three-dimensional (3D) pseudo four-wing chaotic system, a new real four-wing hyperchaotic system is constructed in this paper. It is interesting to see that this new memristive chaotic system can generate a four-wing hyperchaotic attractor with a line of equilibria. Moreover, it can generate two-, three- and four-wing chaotic attractors with the variation of a single parameter which denotes the strength of the memristor. At the same time, various coexisting multiple attractors (e.g. three-wing attractors, four-wing attractors and attractors with state transition under the same system parameters) are observed in this system, which means that extreme multistability arises. The complex dynamical behaviors of the proposed system are analyzed by Lyapunov exponents (LEs), phase portraits, Poincaré maps, and time series. An electronic circuit is finally designed to implement the hyperchaotic memristive system. [ABSTRACT FROM AUTHOR]

In this paper, a new memristor is proposed, and then an emulator built from off-the-shelf solid state components imitating the behavior of the proposed memristor is presented. Multisim simulation and breadboard experiment are done on the emulator, exhibiting a pinched hysteresis loop in the voltage-current plane when the emulator is driven by a periodic excitation voltage. In addition, a new simple chaotic circuit is designed by using the proposed memristor and other circuit elements. It is exciting that this circuit with only a linear negative resistor, a capacitor, an inductor and a memristor can generate a chaotic attractor. The dynamical behaviors of the proposed chaotic system are analyzed by Lyapunov exponents, phase portraits and bifurcation diagrams. Finally, an electronic circuit is designed to implement the chaotic system. For the sake of simple circuit topology, the proposed chaotic circuit can be easily manufactured at low cost. [ABSTRACT FROM AUTHOR]

In this paper, a high gain low voltage low power Complementary Metal Oxide Semiconductor (CMOS) Low-noise Amplifier (LNA) using Chartered 0.18m CMOS process for Ultra-wideband (UWB) receiver applications is presented. A novel multiple-feedback network constructed by the shunt feedback resistor with a transformer is adopted to realize desirable bandwidth extension and less chip area occupation in the common-source stage. All the cascaded transistors are configured by current-reuse structure and adjusted by forward body bias technique to further reduce supply voltage and power dissipation. The post-layout simulation results demonstrate that the proposed 3.4-10.1GHz UWB LNA accomplishes a maximum gain of 14.26dB with only 2.33mW power consumption at 0.8V supply voltage, while Noise Figure (NF) is 1.49-3.41dB and the chip area is 0.46mm2 including test pads (core area is 0.23mm2). [ABSTRACT FROM AUTHOR]

In this paper, we propose an image encryption algorithm based on random walk and two hyperchaotic systems. The random walk method is adopted to scramble the position of pixels within a block. Furthermore, the permutation operation between blocks is presented to enhance the scramble effect. Thus, high correlation among pixels of original image is broken by permutation. Moreover, the chosen plaintext attack is used to test the anti-attack ability of the proposed algorithm. By analyzing experimental results and comparing with other image encryption algorithms, we show that the proposed algorithm has better performance and higher security. [ABSTRACT FROM AUTHOR]

The synchronization of chaotic systems plays an extremely imperative and fundamental role in the fields of science and engineering. Notably, various external noise disturbances have a great impact on the synchronization of chaotic systems because chaotic systems are quite sensitive to the change of their initial values. Consequently, the robustness of chaotic system synchronization must be considered in practical applications. From this viewpoint, the present paper proposes a disturbance suppression zeroing neural network (DSZNN) for robust synchronization of chaotic and hyperchaotic systems, and the DSZNN is implemented on Field Programmable Gate Array (FPGA) for further hardware validation. The distinctive features of the proposed DSZNN controller have the ability to suppress disturbance with faster convergent speed and higher accuracy compared with super-exponential zeroing neural network (SEZNN) and conventional zeroing neural network (CZNN). Moreover, theoretical analysis, comparative numerical simulations and hardware validations for the synchronization of a hyperchaotic system are presented to demonstrate the superior performance of the proposed DSZNN. [ABSTRACT FROM AUTHOR]

In this paper, a simple four-wing chaotic attractor is first proposed by replacing the constant parameters of the Chen system with a periodic piecewise function. Then, a new 4D four-wing memristive hyperchaotic system is presented by adding a flux-controlled memristor with linear memductance into the proposed four-wing Chen system. The memristor mathematical structure model is simple and easy to implement. Dynamical analysis and numerical simulation of the memristive hyperchaotic system are carried out. Then, the electronic circuit of the hyperchaotic system is designed and implemented. The results of numerical simulation are in good agreement with the electronic circuit experiment. In addition, shape synchronization control for the 4D four-wing memristive hyperchaotic system is realized, and a communication system is designed by using the shape synchronization method. Finally, secure signal masking application is implemented on Matlab platform. In the developed secure communication scheme, the information signal overlaps with the chaotic masking signal, which improves the security of the system. [ABSTRACT FROM AUTHOR]

In this work, we consider a logistic fishery model and discuss the selective impulsive harvesting of fish above a certain age or size by incorporating a time delay in the impulsive harvesting term. It is proved that there exists an asymptotically stable positive periodic solution $x^*_{l1}(t)$ when the catchability coefficient h is less than some critical value $h^*_{l}$. It is concluded that $h^*_{l}$ and $x^*_{l1}$ are increasing with respect to l. Simulations shows that the delayed harvesting is advantageous to the sustainability of the population. [ABSTRACT FROM AUTHOR]

This work investigates the dynamic behaviors of one-prey multi-predator model with defensive ability of the prey by introducing impulsive biological control strategy. By using the Floquent theorem and the small amplitude perturbation method, it is proved that there exists an asymptotically stable pest-eradication periodic solution when the impulsive period is less than some critical value, and a permanence condition is established via the method of comparison involving multiple Liapunov functions. It is shown that the multi-predator impulsive control strategy is more effective than the classical one and makes the behavior dynamics of the system more complex. [ABSTRACT FROM AUTHOR]