Hardware implementation of pseudo-random number generators based on chaotic maps

We show the usefulness of bifurcation diagrams to implement a pseudo-random number generator (PRNG) based on chaotic maps. We provide details on the selection of the best parameter values to obtain high entropy and positive Lyapunov exponent from the bifurcation diagram of four chaotic maps, namely: Bernoulli shift map, tent, zigzag, and Borujeni maps. The binary sequences obtained from these maps are analyzed to implement a PRNG both in software and in hardware. The software implementation is realized using 32 and 64 bits microprocessor architectures, and with floating point and fixed point computer arithmetic. The hardware implementation is done by using a field-programmable gate array (FPGA) architecture. We developed a serial communication interface between the PRNG on the FPGA and a personal computer to obtain the generated sequences. We validate the randomness of the generated binary sequences with the NIST test suite 800-22-a both in floating point and fixed point arithmetic. At the end, we show that those chaotic maps are suitable to implement a PRNG but according to the hardware resources, the one based on the Bernoulli shift map is better. In addition, another advantage is that the required initial value for the sequences can be within the whole interval \([-1,1]\), including its bounds.     

Utilizing true periodic orbits in chaos-based cryptography

Nonlinear Dynamics - Digital realizations of chaos-based cryptosystems suffer from lack of a reliable method for implementation. The common choice for implementation is to use fixed or...     

Two-level chaos-based video cryptosystem on H.263 codec

Chaos-based video encryption algorithms are designed based on selective encryption method. Different from many prevailing MPEG-based video encryption designs, this paper lays out a scheme for a two-level H.263-based video cryptosystem, which skillfully combines the traditional selective encryption algorithm with permutation and subsequent masking operation of the coded H.263-based stream. Lastly, the implementation of the proposed cryptosystem on a local area network (LAN) strongly illustrates the efficiency and feasibility of the two-level chaos-based cryptosystem for practical use in many respects, including processing speed, compression ratio, quality of reconstructed image and security level.     

Unsteadiness in non-transferred dc arc plasma generators

Non-transferred dc arc plasma generators are widely used in materials processing. They are generally considered steadily-operating devises. However, unsteady phenomena do exist in them, and may cause non-ideal effects in processes which require high controllability and reproducibility. These unsteady phenomena can cause parameter fluctuations in the arc and the plasma jet, some of which have been studied in recent years. Several types and mechanisms of these phenomena have been identified. This paper reviews the research progress in this specific area, hoping to present a more complete picture of this subject.     

Boundary layer development in supersonic MHD generators

A numerical model of the turbulent boundary layers in the gas dynamic channel of a supersonic MHD generator is constructed. This model describes the development and structure of the layers in the nozzle, on the electrode and insulating walls of the duct, in the two-dimensional approximation. The characteristics of the boundary layers in various generator operating regimes are investigated numerically. The integral boundary layer thicknesses characterizing the nonuniformity of the gas dynamic and electrodynamic quantities are calculated. The limits of applicability of the integral calculation method are determined for typical MHD generator operating conditions.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 35–41, May–June, 1990.The authors wish to thank A. B. Vatazhin, V. A. Bityurin, and V. A. Zhelnin for discussing the formulation of the problem, A. A. Yakushev for participating in the discussion of the results, and Yu. V. Rakseeva and L. V. Yashina for preparing the article.     

Chaotic behavior of logistic map in superior orbit and an improved chaos-based traffic control model

With a vital role of discrete chaos, standard logistic map has found a celebrated place in the dynamics of chaos theory and in various applications of science, such as a discrete traffic flow model, image encryption in cryptography, secure communication, and weather forecasting. Traditionally, this discrete chaos is controlled by one parameter \(\lambda \) using Picard orbit, a one-step feedback procedure. This article presents a one-step forward, applying Mann orbit (superior orbit) the chaotic properties such as period-doubling, period-3 window, and Lyapunov exponent of the standard logistic map is investigated. The results are illustrated analytically and experimentally followed by concluding remarks and a few counter examples. Due to the extra degree of freedom in parameter \(\lambda \), the map provides improved chaotic properties that increases the performance of dynamical phenomena. Moreover, this study describes an improved chaos-based discrete traffic control model. Surprisingly, added new parameter \(\alpha \) in Mann orbit works as control variable that increases the stability performance of the traffic model.     

高g值加速度发生器中的波形整形技术

以Hopkinson压杆实验装置作为火工品抗过载实验中的高g值加速度发生器,通过数值模拟分析了子弹（形状）、波形整形器（材料、直径、厚度）对加载脉冲的影响规律,并获得了所需的加速度脉冲,实现了有效控制和改善火工品冲击实验中的加载环境。研究结果可为检验火工品在冲击环境下或经冲击后性能可靠度的实验设计、测试等提供依据。     

An experiment with arithmetic precision in linear algebra computations

Several techniques for experimental determination of floating point precision in practical computations are examined, and applied to linear algebra algorithms. These techniques are simple enough to be directly applicable to existing production codes, requiring a very limited amount of software on many machines, and yet they yield interesting information on the numerical precision of a computation. Our choice of linear algebra algorithms includes a direct solver (namely the MA32 program from the Harwell Library) and several variants of preconditioned conjugate gradients (the methods DIAG, INV, MINV and POL of Reference 1). The results may be of interest as method selection criteria, and thus complement Mflop performance data available from several sources.     

Mathematical simulation of hydrodynamic generators of oscillations

Unsteady turbulent swirled water flow in a channel in the presence of cavitation is calculated. It is shown that in the near-axial channel zone a fluctuating vapor region, or cavity, arises and variations in the cavity shape and dimensions lead to the onset of undamped pressure fluctuations. The amplitude-frequency characteristics of the oscillations are obtained in different channel cross-sections. The amplitude maximum position in the channel expansion zone is in agreement with the available experimental data. The dynamics of toroidal vortices formed in the hydrodynamic generator channel and in the expansion zone at its exit are established.     

Control of pressure distribution in shock generators with elliptic cross-sections

Theoretical investigation of a liquid shock generating device with an elliptically shaped chamber is presented. A device of such kind has been previously fabricated and tested experimentally. Experimental observations confirmed the results of earlier theoretical analysis of the problem, showing that shock waves produced by an electric discharge at one of the foci of the elliptic chamber will converge at the second focus after the reflection off the cavity wall. In the present paper a previous two-dimensional model is extended to account for the height variation in the chamber. Expression for the pressure distribution behind the converging wave front is obtained and a relation between the shape of the upper bounding surface of the chamber and pressure distribution behind the converging wave front is investigated. It is shown that a desired pressure distribution may be obtained by an appropriate choice of the upper surface of the chamber.This article was processed using Springer-Verlag T_EX Shock Waves macro package 1.0 and the AMS fonts, developed by the American Mathematical Society.     

Heat flux-flow coupling effects in the stability of vapour generators

A study has been carried out to investigate the dynamics of two-phase flow in vapour generators, with special reference to the effect of flux-flow couplings on density wave instability. A distributed parameter time-varying theoretical analysis of the conservation equations, together with the constitutive laws of two-phase flow, has been derived. The analysis takes into account the dynamics of the heater wall, revealing the predominant role of the heat flux-flow couplings on the stability of the system. A digital computer program has been written and developed to implement the theoretical analysis. Results from the analysis are used for comparison with the available data and the effect of the flux-flow couplings on instability is demonstrated and discussed. These results are also used to explain the dynamic behaviour of a specially constructed “Arcton-113”¹ closed loop comprising a helical, electrically heated, once-through vapour generator in a parallel channel arrangement with high thermal capacitance. Kopplungseffekte zwischen Wärmefluß und Strömung bei der Stabilität von Dampferzeugern     

Chaos in three-dimensional hybrid systems and design of chaos generators

The existence of horseshoes is proved in a class of 3-dim piecewise linear systems, in which a homoclinic orbit connecting the origin to itself is explicitly given. Based on these results, a mathematically rigorous methodology for design of chaos generators is proposed. Implementation of such chaos generators by circuit is easy and the chaotic attractor is robust under small perturbations.     

Stability of shells of revolution with curvilinear generators in axial compression

Summary Curvilinearity of the generators forces the structure to behave in a qualitatively different way under the action of axial forces. Firstly, up to loss of stability the individual generators of the system are in a state of longitudinal-transverse bending. Secondly for a shell with negative Gaussian curvature there may be a sharp drop in the critical axial compressive loads even in structures that deviate only slightly from the cylindrical.All this means that shells of revolution with curvilinear generators in axial compression cannot be designed for stability using the formulas derived for cylindrical systems.Prikladnaya Mekhanika, Vol. 2, No. 1, pp. 59–68, 1966     

Design and development of planar reconfigurable motion generators

This article presents the concept of a new class of mechanical devices for multi-phase motion generation tasks. Reconfigurable Motion Generators are a new class of mechanical devices that are designed for a specific part family and their associated motion generation tasks. The research endeavors to realize a novel concept for Reconfigurable Motion Generators (RMGs) for multi-phase planar motion generation. Reconfigurable Motion Generators are capable of configuration changes according to variations in the motion generation requirements. Thus, Reconfigurable Motion Generators bridge the gap between the relative high flexibility and high cost of totally flexible devices (e.g., industrial robots) and the low flexibility and low cost of fully dedicated devices (e.g., cams and linkages). This paper introduces the concept of Reconfigurable Motion Generators that may be deployed in various automated manufacturing environments involving multi-phase motion generation tasks. The development, manufacturing, and testing of a prototype and the control system for a planar Reconfigurable Motion Generator based on a five-bar mechanism are discussed.     

A novel fast chaos-based algorithm for generating random permutations with high shift factor suitable for image scrambling

The good qualities of permutations with a high shift factor in terms of speech scrambling have been proven in the last 20 years. Nevertheless, the absence of a fast algorithm for generating them has limited their use in cryptographic applications. In this paper, we propose a new fast chaos-based method for generating random permutations with a high shift factor, and we compare it with some similar schemes, classical or chaos-based. The permutations generated by the proposed method have very few fixed points, too, making them theoretically suitable for image scrambling or for use as a diffusion stage in an image cryptosystem. We prove this fact using some standard indicators as MSE, UACI, NPCR, PCC, etc. and by comparisons to the results obtained for other algorithms of this type. All the results obtained are very good, including a speed of pixels permutation of 14 MB/s, allowing us to say that the proposed algorithm is a fast and efficient one, which can be used even in real-time scrambling.