Frolov, Nikita S.Khorev, Vladimir S.Grubov, Vadim V.Badarin, Artem A....
10页
查看更多>>摘要：We study experimentally and numerically the dynamics of a balance platform during a short-term training. The results of experiments with sixteen untrained subjects and a developed empirical biomechanical model exhibit the coexistence of three attractors under adaptive control of multistability. During the experiments, we measure the balance bar angle, angular velocity, and angular acceleration. Simultaneously, superficial electromyography (EMG) is recorded on the flexors and extensors of the ankle and knee joints. Phase-space analysis of the platform movement shows that the time the platform spends near the unstable equilibrium correlates with the average muscle activity. We also observe that the balance platform dynamics differs when the subject starts balancing with his/her dominant or non-dominant leg. In addition, we find that subjects with better symmetry between the strength of dominant and non-dominant legs demonstrate higher training efficiency. Therefore, the balance control efficiency can be enhanced by training muscles of the non-dominant leg. The results of numerical simulations are in good agreement with experiments. (C) 2022 The Authors. Published by Elsevier Ltd.
查看更多>>摘要：The neuron models have been widely applied to neuromorphic computing systems and chaotic circuits. How-ever, discrete neuron models and their application in image encryption have not gotten a lot of attention yet. This paper first presents a novel neuron model with significant chaotic characteristics, by coupling a memristor into the proposed neuron, a memristive neuron model is further obtained. Relevant control parameter-relied dy-namical evolution is demonstrated using several numerical methods. The explorations manifest that memristor can boost chaos complexity of the discrete neuron, resulting in hyperchaos, infinite coexisting hidden attractors and attractor growing. Particularly, the NIST test verifies the generated hyperchaotic sequences exhibit high com-plexity, which makes them applicable to many applications based on chaos. Additionally, digital experiments based on developed hardware platform are designed to implement the memristive neuron model and get the hyperchaos. We also propose a new encryption scheme to apply the memristive neuron to the application of image encryption. The evaluation results show that the conceived algorithm appears excellent security charac-teristics and can effectively protect the information security of images. (c) 2021 Elsevier Ltd. All rights reserved.
查看更多>>摘要：In the latest image chaotic encryption research, more and more encryption schemes associate the key generation mechanism with the plaintext in order to resist the chosen plaintext attack. However, large amounts of the additional data related to the plaintext need to be sent to the receiver when the sender encrypts a large number of images, which leads to the problems of large transmission cost, high key storage space requirement and complicated key management. In order to solve such problems, this paper proposes a novel plaintext-related chaotic image encryption scheme with no additional plaintext information. The relationship between the plaintext and the secret keys is established by selecting some key pixels in the original image randomly and securely by Henon map. The encryption process is divided into two parts. The first part is to encrypt the selected key pixel while keeping their secret positions unchanged. The second part is to encrypt the remainder pixels based on hyperchaotic Lorenz system and DNA encoding using the generated keys. The proposed encryption mechanism can not only achieve the equivalent effect of one-time pad to resist the chosen plaintext attack, but also avoid transmitting additional information associated with the plaintext in the communication channel, which greatly saves the transmission cost and the required key storage space, and simplify the key management. The encryption scheme in this paper has also passed various security analyses to ensure the security of the ciphertext image. (c) 2022 Elsevier Ltd.
查看更多>>摘要：We extend the definition of n-dimensional difference equations to complex order. We investigate the stability of linear systems defined by an n-dimensional matrix and derive the conditions for the stability of zero solution of linear systems. For the one-dimensional case, we find that the stability region, if any is enclosed by a boundary curve and we obtain a parametric equation for the same. Furthermore, we find that there is no stable region if this parametric curve is self-intersecting. Even for the real eigenvalues, the solutions can be complex and dynamics in one-dimension is richer than the case for real order. These results can be extended to n-dimensions. For nonlinear systems, we observe that the stability of the linearized system determines the stability of the equilibrium point.
查看更多>>摘要：Finite-time stability of stochastic fractional-order delay differential equations is researched here. Firstly, we derive the equivalent form of the considered system by using the Laplace transformation and its inverse. Subsequently, by defining the maximum weighted norm in Banach space and using the principle of contraction mapping, we prove that the solution of researched system is unique. What's more, by virtue of HenryGronwall delay inequality and interval translation, we derive the criterion of finite-time stability for the system with and without impulses, respectively. Finally, as a verification, examples are provided to expound the correctness of the deduced results.
查看更多>>摘要：Space-fractional parity-time symmetry, featuring the fractional Laplacian operator rather than the standard op-erator, continues to be a challenge. This report analytically and numerically assesses the dynamics of wave packets in a space-fractional parity-time symmetric lattice by invoking Kerr nonlinearity. By adjusting the Levy index, the basic properties of Floquet-Bloch modes in parity-time symmetric optical lattices are examined. It is demonstrated that the width of the first three Floquet-Bloch modes increases as the Levy index decreases and that the corresponding band structure becomes symmetrically linear. These features result in peculiar properties during propagation, including splitting or diffraction-free propagation, preferential propagation, unidirectional propagation, and phase dislocations. In the two-dimensional fractional case, when the band structure is cone-like, it causes conical diffraction, and non-diffracting propagation occurs when the Floquet-Bloch mode of the upper band is excited by the input beam. Kerr nonlinearity modulates the energy in a certain nonlinear region toward the middle and suppresses the formation of conical diffraction.(c) 2022 Elsevier Ltd. All rights reserved.
查看更多>>摘要：Community group buying is the preferred shopping method for many consumers during the COVID-19 epidemic in China. This new Internet pre-sale mode has a lead-lag effect and non-linear characteristics. Therefore, studying the prediction of community group buying has practical significance. In this paper, the lead-lag term of vector autoregressive model is coupled with the nonlinear term in the GM (1, 1, t(alpha)) model. Then, lead-lag factor tau and nonlinear factor t(mu) are added in the grey modelling process, and a novel hybrid grey forecasting model of lead-lag and nonlinearity (GAPM) is established by means of optimising the background value. Firstly, the least squares method and derivation method are used to obtain the model parameter values and time response expressions, and the stability of GAPM is studied on the basis of condition number theory of matrices. Secondly, the grey evolutionary algorithm is introduced to obtain the optimal solution of the background value and nonlinear factor, and the weighted geometric average weakening buffer operator is used to preprocess the original data. Finally, the new model is used to fit and predict the daily sales of Orange Optimization Company in Wuhan, China for two consecutive months of community group buying. Results show that the model has good stability and high prediction accuracy. Compared with the other five common grey models that do not consider the lead-lag influence of the system, GAPM has better predictive ability. Therefore, the introduction of the new model constructed by using the lead-lag factor is reasonable and effective in the case of community group buying with lead-lag effect. (C)& nbsp;2022 Elsevier Ltd. All rights reserved.
Hammouch, ZakiaRasul, Rando R. Q.Ouakka, AbdellahElazzouzi, Abdelhai...
11页
查看更多>>摘要：The aim of this paper is to construct and analyze a mathematical model for the response of T-cytotoxic lymphocytes to the Ebola virus using the Herz-tuckwill model with nonlinear Conformable order differential equations which derive from real biological data, then study the global stability of the equilibria using an appropriate Lyapunov function and the LaSalle invariance principle. Furthermore, we demonstrate the impact of the non integer order of the model compared with the integral order. Finally consider a numerical simulation that justifies the biological hypotheses and the theory results. The numerical results provided that, the non-integer order has a great impact on the treatments of Ebola virus in this model.(c) 2022 Elsevier Ltd. All rights reserved.
查看更多>>摘要：Indirect reciprocity facilitates cooperation in social dilemmas by assessing the behaviors of agents through social norms. In this paper, we introduce two new types of second-order social norms with keeping rule and reversing rule, respectively. Besides, this paper also considers two different reputation scenarios, namely, public and private reputation scenarios. To verify the impact of social norms with keeping or reversing rules on cooperation, we develop an evolutionary theoretical model. Through numerical multi-agent simulations, we find that social norms with keeping or reversing are conducive to cooperation. Specifically, for the low benefit-cost ratio, the keeping rule can encourage cooperation, while for the high benefit-cost ratio, the reversing rule can promote cooperation. In addition, simulation results also suggest that the influences of the two reputation scenarios on the evolution of cooperation are different. The public reputation scenario provides a more favorable environment for cooperation than the private reputation scenario. Moreover, we observe that the increase of system noise level, whether action error or mutation rate, will have negative impacts on the emergence of cooperation.(c) 2022 Published by Elsevier Ltd.
NSTL
Elsevier