- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
On the numerical investigation of size and surface effects on nonlinear dynamics of a nanoresonator under electrostatic actuation
摘要： This study aims to investigate the influences of nanostructure parameter and surface elasticity parameters on the nonlinear vibration of a nanoelectromechanical system under double-sided electrostatic actuation. For this, the effects of size dependency and surface energy are modeled through applying the consistent couple-stress theory together with the Gurtin–Murdoch elasticity theory. Taking into account the midplane stretching effect for doubly clamped boundary conditions, the nonlinear strain–displacement relationship is considered based on the Euler–Bernoulli beam assumption. Hamilton’s principle is utilized in order to establish the governing differential motion’s equation, and reduced-order model is obtained through implementing Galerkin’s procedure. Bifurcation diagrams are plotted to capture the steady-state response of the system with varying the nondimensional parameter, the ratio of AC to DC voltage amplitude. The influences of the length-scale parameter, surface elasticity modulus and density, and residual surface stress on the system dynamic response have been explored. The results reveal that the pull-in excitation frequency is highly influenced by these parameters, and also the interval length of the bifurcation parameter corresponding to the periodic and chaotic motions is extremely shifted by the amount of couple-stress and residual surface stress parameters.
关键词： Size-dependent NEMS,Chaos,Bifurcation,Surface effects
更新于2025-09-09 09:28:46
-
Encryption of medical image with most significant bit and high capacity in piecewise linear chaos graphics
摘要： Along with the development of cloud computing, data privacy has become the focus of attention. However, the existing methods do not allow large amounts of information to be hidden in reversible ways. In this paper, a MSB prediction-based high-capacity reversible data hiding image encryption algorithm is put forward. Due to the local correlation between the pixels and their adjacent areas in a clear image, the value of adjacent two pixels are very close. For this reason, it seems reasonable to predict pixel values by using previously decrypted images, just as many image encoding and compression methods. However, in some cases, there are some errors. Therefore, the first step of the algorithm includes identifying all prediction errors in the original image and storing the information in a binary map of the error locations. After that, a high-capacity reversible data hiding method (CPHCRDH) is proposed to correct the prediction error. This method first conducts the prediction error correction before encryption, and pre-processes the original image according to the error location map to avoid all prediction errors, and then encrypts the pre-processed image. The clear image can be reconstructed without damage through MSP prediction. Finally, through the simulation experiment on three selected CT image test examples of the eyes, body and brain, it is shown that the proposed method is significantly superior to the selected contrasted algorithm in six indicators such as the horizontal and vertical correlation coefficients.
关键词： Piecewise linear,Digital image,Chaos graphic,Reversible data hiding method,Image encryption
更新于2025-09-09 09:28:46
-
Chaos Synchronization in Visible Light Communications with Variable Delays Induced by Multipath Fading
摘要： Visible Light Communication (VLC) uses light-emitting diodes to provide wireless connectivity in public environments. Transmission security in this emerging channel is not trivial. Chaotic modulation techniques can provide encryption directly in the physical layer based on the random-alike evolution and strong synchronization prospect given by deterministic chaos. In secure chaotic inclusion or embedding methods, continuous-time chaos oscillator models need to be synchronized via a coupling carrier. Here we present a ?rst numerical simulation study for the impact of the variable delays induced by line-of-sight and non-line-of-sight multipath fading in complete chaotic synchronization. More precisely, we analyze a chaotic Colpitts oscillator that is simultaneously transmitting the carrier to several mobile receivers via nine spotlights. Such induced delays depend on both the receiver position and the carrier frequency, in?uencing the complete synchronization required in modulation via chaotic inclusion. Correlation values for several receiver positions and carrier frequencies are presented, examining the progressive emergence of the multipath effect and its impact on chaotic synchronization. We show that, for the chaotic oscillator and coupling applied in the de?ned room settings, complete chaotic synchronization can be achieved and that it is robust up to the tens of MHz region.
关键词： multipath channels,network security,chaotic communication,visible light communication,nonlinear systems,chaos synchronization
更新于2025-09-04 15:30:14
-
Robust nonlinear control of atomic force microscope via immersion and invariance
摘要： This paper reports an immersion and invariance (I&I)–based robust nonlinear controller for atomic force microscope (AFM) applications. The AFM dynamics is prone to chaos, which, in practice, leads to performance degradation and inaccurate measurements. Therefore, we design a nonlinear tracking controller that stabilizes the AFM dynamics around a desired periodic orbit. To this end, in the tracking error state space, we define a target invariant manifold, on which the system dynamics fulfills the control objective. First, considering a nominal case with full state measurement and no modeling uncertainty, we design an I&I controller to render the target manifold exponentially attractive. Next, we consider an uncertain AFM dynamics, in which only the displacement of the probe cantilever is measured. In the framework of the I&I method, we recast the robust output feedback control problem as the immersion of the output feedback closed-loop system into the nominal full state one. For this purpose, we define another target invariant manifold that recovers the performance of the nominal control system. Moreover, to handle large uncertainty/disturbances, we incorporate the method of active disturbance rejection into the I&I output feedback control. Through Lyapunov-based analysis of the closed-loop stability and robustness, we show the semiglobal practical stability and convergence of the tracking error dynamics. Finally, we present a set of detailed, comparative software simulations to assess the effectiveness of the control method.
关键词： output feedback control,chaos,immersion and invariance,disturbance rejection control,atomic force microscope
更新于2025-09-04 15:30:14
-
A parallelizable chaos-based true random number generator based on mobile device cameras for the Android platform
摘要： True random number generators are used in high security applications such as cryptography where non-determinism is required. However, they are slower than their pseudorandom counterparts because they need to extract entropy from physical phenomenon. To overcome this drawback, generators have been designed to extract unpredictability from devices such as computer processing units or microphones. This paper introduces a new generator for the Android mobile platform based on images captured by a built-in camera. Although similar generators exist, they suffer from poor performance and a lack of proper security evaluation. The proposed generator implements a chaos-based postprocessing algorithm that eliminates statistical defects and increases its throughput. These goals are achieved by using the inherent properties of a chaotic system to amplify entropy extracted from the captured images. The proposed generator is evaluated in two phases: first, statistical test suites are executed to identify statistical defects. Next, the generator’s forward and backward security is analysed. Results indicate that the proposed true random number generator is able to generate statistically secure true random number sequences faster than existing mobile-based generators. In addition, the generator is designed to support parallel processing, thus allowing its performance to scale according to the mobile device’s multicore architecture.
关键词： Chaos theory,Digital camera,True random number generator,Mobile device,Android
更新于2025-09-04 15:30:14
-
Wide-band high absorption electromagnetic absorber with Chaos patterned surface
摘要： A resistive metasurface surface featured by Rossler Chaos reaction-diffusion system patterns is proposed and realized in a wideband electromagnetic absorber. The chaos surface consists of units with both random shapes and dimensions. Simulation results show absorption phenomenon and correlation function analysis indicates new wave-absorbing mode can be generated when correlation of the edges of the chaos patterns matches geometrical size of chaos units. Experimental results indicate unconventional bandwidth ratio with reflectivity lower than -10dB, -15dB, -19dB reaches 96.84%, 80.1% and 56.1%, respectively. High absorption nature makes this structure has application potential in modern anechoic chamber or other electromagnetic wave absorbers.
关键词： metasurface,chaos pattern,disordered surface,nonlinear dynamics,absorbing metamaterial
更新于2025-09-04 15:30:14