Thang Manh Hoang

A Chaos-Based Secure Direct-Sequence/Spread-Spectrum Communication System

This paper proposes a chaos-based secure direct-sequence/spread-spectrum (DS/SS) communication system which is based on a novel combination of the conventional DS/SS and chaos techniques. In the proposed system, bit duration is varied according to a chaotic behavior but is always equal to a multiple of the fixed chip duration in the communication process. Data bits with variable duration are spectrum-spread by multiplying directly with a pseudonoise (PN) sequence and then modulated onto a sinusoidal carrier by means of binary phase-shift keying (BPSK). To recover exactly the data bits, the receiver needs an identical regeneration of not only the PN sequence but also the chaotic behavior, and hence data security is improved significantly. Structure and operation of the proposed system are analyzed in detail. Theoretical evaluation of bit-error rate (BER) performance in presence of additive white Gaussian noise (AWGN) is provided. Parameter choice for different cases of simulation is also considered. Simulation and theoretical results are shown to verify the reliability and feasibility of the proposed system. Security of the proposed system is also discussed.

Dynamics, Synchronization and SPICE Implementation of a Memristive System with Hidden Hyperchaotic Attractor

The realization of memristor in nanoscale size has received considerate attention recently because memristor can be applied in different potential areas such as spiking neural network, high-speed computing, synapses of biological systems, flexible circuits, nonvolatile memory, artificial intelligence, modeling of complex systems or low power devices and sensing. Interestingly, memristor has been used as a nonlinear element to generate chaos in memristive system. In this chapter, a new memristive system is proposed. The fundamental dynamics properties of such memristive system are discovered through equilibria, Lyapunov exponents, and Kaplan–York dimension. Especially, hidden attractor and hyperchaos can be observed in this new system. Moreover, synchronization for such system is studied and simulation results are presented showing the accuracy of the introduced synchronization scheme. An electronic circuit modelling such hyperchaotic memristive system is also reported to verify its feasibility.

Projective-Lag Synchronization of Coupled Multidelay Feedback Systems

In this study, we investigate the projective-lag synchronization model of coupled multidelay feedback systems. The master synchronizes with the slave under the lag synchronization scheme and there is a scale factor between the amplitudes of state variables. The driving signal is constituted by the sum of multiple nonlinear transformations of a delayed state variable. A sufficient condition for synchronization is considered under the Krasovskii–Lyapunov theory. The effectiveness of the proposed model is demonstrated and verified by examining specific examples using modified Mackey-Glass and Ikeda systems.

Chaos Synchronization of Multi-delay Feedback Systems with Multi-delay Driving Signal

In this paper, we investigate the synchronization scheme of two unidirectionally coupled multi-delay feedback chaotic systems in which the master drives the slave via a multi-delay driving signal. ...

Efficient and reliable camera based multiple-choice test grading system

This paper proposes a new idea for grading multiple-choice test which is based on a camera with reliability and efficiency. The bounds of the answer sheet image captured by the camera is first allocated using Hough transform and then skew-corrected into the proper orientation, followed by the normalization to a given size. Next, the tick mark corresponding to the answer for each question can be recognized by allocation of the mask which wraps the answer area. The experimental results showed that the proposed system has achieved significant improvement in performance in terms of accuracy, reliability, and elapsed time compared with those of the conventional optical mark recognition (OMR) systems. The proposed system also demonstrated that it can also achieve high accuracy of 99.7% while using non-transoptic answer sheet paper with lower cost.

New Encoding Model for Chaos-Based Secure Communication

Previous research has shown that the chaos synchronization of multi-delay feedback systems with multi-delay driving signal has a high potential for application in secure communication due to its complexity in dynamics and in the driving signal. In this paper, a new encoding model for chaos-based secure communication is proposed by using the chaos synchronization of multi-delay feedback systems with multi-delay driving signal. Further, a new scheme of shift keying technique named the synchronization-manifold shift keying is devised and used in the secure communication system. Simulation results validate the new proposed encoding model.

A Three-Dimensional No-Equilibrium Chaotic System: Analysis, Synchronization and Its Fractional Order Form

Recently, a new classification of nonlinear dynamics has been introduced by Leonov and Kuznetsov, in which two kinds of attractors are concentrated, i.e. self-excited and hidden ones. Self-excited attractor has a basin of attraction excited from unstable equilibria. So, from that point of view, most known systems, like Lorenz’s system, Rossler’s system, Chen’s system, or Sprott’s system, belong to chaotic systems with self-excited attractors. In contrast, a few unusual systems such as those with a line equilibrium, with stable equilibria, or without equilibrium, are classified into chaotic systems with hidden attractor. Studying chaotic system with hidden attractors has become an attractive research direction because hidden attractors play an important role in theoretical problems and engineering applications. This chapter presents a three-dimensional autonomous system without any equilibrium point which can generate hidden chaotic attractor. The fundamental dynamics properties of such no-equilibrium system are discovered by using phase portraits, Lyapunov exponents, bifurcation diagram, and Kaplan–Yorke dimension. Chaos synchronization of proposed systems is achieved and confirmed by numerical simulation. In addition, an electronic circuit is implemented to evaluate the theoretical model. Finally, fractional-order form of the system with no equilibrium is also investigated.

Extraction of human facial features based on Haar feature with Adaboost and image recognition techniques

Locating facial feature in face images is an important stage for numerous facial image applications such as face recognition, face expression recognition and face tracking and lip reading. In this paper, we present a robust method for detecting facial feature points in frontal face images. The method adopts face detection algorithm of Viola-Jones face detector. The facial regions are than extracted by applying Haar feature based Adaboost algorithm for detecting eye, nose and mouth regions. Finally, template matching and several image processing techniques are utilized to detect feature points. Experiment on the IMM database, CVL database and our laboratory database is carried out to demonstrate and verify the proposed method.

A Chaotic Pulse-Time Modulation Method for Digital Communication

We present and investigate a method of chaotic pulse-time modulation (PTM) named chaotic pulse-width-position modulation (CPWPM) which is the combination of pulse-position-modulation (PPM) and pulse-width modulation (PWM) with the inclusion of chaos technique for digital communications. CPWPM signal is in the pulse train format, in which binary information is modulated onto chaotically-varied intervals of position and width of pulses, and therefore two bits are encoded on a single pulse. The operation of the method is described and the theoretical evaluation of bit-error rate (BER) performance in the presence of additive white Gaussian noise (AWGN) is provided. In addition, the chaotic behavior with tent map and its effect on average parameters of the system are investigated. Theoretical estimation and numerical simulation of a CPWPM system with specific parameters are carried out in order to verify the performance of the proposed method.

SVM classifier based face detection system using BDIP and BVLC moments

In this paper, a support vector machine (SVM) classifier has been used to detect a face in an authentication application. A face candidate is first allocated from the input frame and then normalized to 200×200 pixels images. The textureness of candidates is then measured by the combination of BDIP and BVLC moments and classified into face and non-face ones by a SVM classifier which is known as efficient classification tool. In SVM learning, a DB of 2500 faces and 2500 non-faces has been created under different light conditions and face expressions. The experiments showed that the effectiveness of the used features for SVM based classification issue in the face-detection system.