Thermoelectric generators and their applications: Progress,challenges, and future prospects

Our community currently deals with issues such as rising electricity costs, pollution, and global warming. Scientists work to improve energy harvesting-based power generators in order to reduce their impacts. The Seebeck effect has been used to illustrate the capacity of thermoelectric generators(TEGs) to directly convert thermal energy to electrical energy. They are also ecologically beneficial since they do not include chemical products, function quietly because they lack mechanical structures...     

Fundamentals of synchronization in chaotic systems,concepts, and applications

The field of chaotic synchronization has grown considerably since its advent in 1990. Several subdisciplines and "cottage industries" have emerged that have taken on bona fide lives of their own. Our purpose in this paper is to collect results from these various areas in a review article format with a tutorial emphasis. Fundamentals of chaotic synchronization are reviewed first with emphases on the geometry of synchronization and stability criteria. Several widely used coupling configurations are examined and, when available, experimental demonstrations of their success (generally with chaotic circuit systems) are described. Particular focus is given to the recent notion of synchronous substitution-a method to synchronize chaotic systems using a larger class of scalar chaotic coupling signals than previously thought possible. Connections between this technique and well-known control theory results are also outlined. Extensions of the technique are presented that allow so-called hyperchaotic systems (systems with more than one positive Lyapunov exponent) to be synchronized. Several proposals for "secure" communication schemes have been advanced; major ones are reviewed and their strengths and weaknesses are touched upon. Arrays of coupled chaotic systems have received a great deal of attention lately and have spawned a host of interesting and, in some cases, counterintuitive phenomena including bursting above synchronization thresholds, destabilizing transitions as coupling increases (short-wavelength bifurcations), and riddled basins. In addition, a general mathematical framework for analyzing the stability of arrays with arbitrary coupling configurations is outlined. Finally, the topic of generalized synchronization is discussed, along with data analysis techniques that can be used to decide whether two systems satisfy the mathematical requirements of generalized synchronization. (c) 1997 American Institute of Physics.     

Stabilizing near-nonhyperbolic chaotic systems with applications

Based on the invariance principle of differential equations a simple, systematic, and rigorous feedback scheme with the variable feedback strength is proposed to stabilize nonlinearly finite-dimensional chaotic systems without any prior analytical knowledge of the systems. Especially the method may be used to control near-nonhyperbolic chaotic systems, which, although arising naturally from models in astrophysics to those for neurobiology, all Ott-Grebogi-York type methods will fail to stabilize. The technique is successfully used for the famous Hindmarsh-Rose neuron model, the FitzHugh-Rinzel neuron model, and the R?ssler hyperchaos system, respectively.     

Generalized projective synchronization of fractional order chaotic systems

In this paper, based on the idea of a nonlinear observer, a new method is proposed and applied to “generalized projective synchronization” for a class of fractional order chaotic systems via a transmitted signal. This synchronization approach is theoretically and numerically studied. By using the stability theory of linear fractional order systems, suitable conditions for achieving synchronization are given. Numerical simulations coincide with the theoretical analysis.     

改进的保群算法及其在混沌系统中的应用

混沌系统的跟踪控制是近年来非线性控制领域研究的热点之一. 本文提出了一种基于快速下降控制方法的保群算法, 此方法使受控混沌系统能够快速稳定到相空间的一个不动点; 另外提出一种基于滑模控制方法的保群算法, 此方法使受控混沌系统能够快速跟踪一个确定的运动轨迹. 应用这两种新方法分别对两个经典的混沌系统(Lorenz系统和Duffing系统)进行了相应的数值实验, 实验结果表明这两种方法都具用较高的精度和稳定性.     

Can two chaotic systems give rise to order?

The recently discovered Parrondo's paradox claims that two losing games can result, under random or periodic alternation of their dynamics, in a winning game: “losing + losing = winning”. In this paper we follow Parrondo's philosophy of combining different dynamics and we apply it to the case of one-dimensional quadratic maps. We prove that the periodic mixing of two chaotic dynamics originates an ordered dynamics in certain cases. This provides an explicit example (theoretically and numerically tested) of a different Parrondian paradoxical phenomenon: “chaos + chaos = order”.     

基于反馈和多最小二乘支持向量机的分数阶混沌系统控制

根据分数阶线性系统的稳定理论,将混沌系统分成稳定的线性部分和相应的非线性部分.设计主动控制器,对非线性部分进行补偿,从而将分数阶混沌系统控制到平衡点.为了提高主动控制器的补偿能力,提出基于反馈的多最小二乘支持向量机(M-LS-SVM)拟合模型.通过减聚类方法将输入空间划分为一些小的局部空间,在每个局部空间中用LS-SVM建立子模型.为解决子模型相互之间的严重相关问题,提高模型的精度和鲁棒性,各个子模型的预测输出通过主元递归(PCR)方法连接.仿真实验表明该方法有助于提高补偿精度和系统响应指标. 关键词： 分数阶 混沌系统 多最小二乘支持向量机 反馈     

Adaptive lag synchronization and parameter identification of fractional order chaotic systems

This paper proposes a simple scheme for the lag synchronization and the parameter identification of fractional order chaotic systems based on the new stability theory. The lag synchronization is achieved and the unknown parameters are identified by using the adaptive lag laws. Moreover, the scheme is analytical and is simple to implement in practice. The well-known fractional order chaotic Lü system is used to illustrate the validity of this theoretic method.     

Impulsive control of chaotic systems and its applications in synchronization

In this paper,some novel sufficient conditions for asymptotic stability of impulsive control systems are presented by comparison systems.The results are used to obtain the conditions under which the chaotic systems can be asymptotically controlled to the origin via impulsive control.Compared with some existing results,our results are more relaxed in the sense that the Lyapunov function is required to be nonincreasing only along a subsequence of switchings.Moreover,a larger upper bound of impulsive intervals for stabilization and synchronization is obtained.     

一类分数阶混沌系统的研究

推广了一类分数阶混沌系统并证明了这类分数阶混沌系统的拓扑等价性,指出分数阶系统产生混沌吸引子的必要条件是系统平衡点的稳定性不变.通过数值模拟表明,此分数阶系统与整数阶系统一样仍然产生一对互不相交的2-涡卷混沌吸引子. 关键词： 分数阶 混沌 稳定性     

Catalytic applications of amorphous alloys: Expectations, achievements, and disappointments

This review intends to summarize the major achievements in the application of amorphous alloys as precursors of catalyst materials. This non-traditional catalyst preparation method may provide supported catalysts with novel chemical and structural properties. Selected examples for both glassy alloy precursors and those fabricated by mechanochemistry include CO oxidation over binary and ternary alloys, dehydrogenation over Cu-M (M = Ti, Zr or Hf), one-step synthesis of methyl isobutyl ketone, and selective hydrogenation of unsaturated carbonyl compounds. Ni alloys for methanation developed for the project to solve global warming by recycling carbon dioxide are also discussed.     

Channeling radiation: Past achievements and future prospects

Abstract

When a relativistic charged particle passes through a single crystal very nearly along a major crystalline plane or axis so that it is channeled in that direction, it undergoes periodic motion in the plane transverse to this direction and hence it can radiate. Quantum mechanically, this channeling radiation corresponds to a radiative transition between two eigenstates of the transverse crystalline potential; when the transition occurs between two bound states, a sharp spectral line is emitted. When there are only two bound states (for incident electrons), or when the interplaner potential is nearly harmonic (as for incident positrons), the emitted radiation is nearly monochromatic. Since the discovery of channeling radiation at the LLNL Electron-Positron Linear Accelerator, many of its properties have been delineated, both there and elsewhere. For example, channeling radiation is very intense, forward-directed, easily tunable, and for the planar case, linearly polarized. Channeling radiation has been used as a probe both of the interplanar potentials and other properties of perfect crystals and of the effects of impurities and defects in imperfect crystals. Finally, channeling radiation has great potential use as a photon source for numerous other applications in several fields of science and technology.

This paper is intended to keynote the first International Conference on Coherent Radiation Processes in Strong Fields by recalling some history of the discovery and exploitation to date of channeling radiation. Studies of channeling radiation, in addition to elucidating the physics of the process itself, its application to the determination of properties of perfect and imperfect crystals, and its potential application to a large variety of fields by its use as an intense, monochromatic, forward-directed, tunable, and polarized photon source, have spawned an entire industry of studies of other coherent radiation processes, all consisting of photon production from beams of relativistic charged particles traversing periodic structures, which constitute the principal subject matter of this Conference. This paper will be limited to the discussion of channeling radiation and some of its applications. It will be in the nature of an illustrative exposition, showing many of the features of channeling radiation and its applications in a qualitative way. Several detailed studies of channeling radiation will be presented later in the Conference.     

Hybrid projective synchronization of chaotic fractional order systems with different dimensions

The hybrid projective synchronization of different dimensional fractional order chaotic systems is investigated in this paper. It is shown that the slave system can be synchronized with the projection of the master system generated through state transformation. Based on the stability theorem of linear fractional order systems, a suitable controller for achieving the synchronization is given. The hybrid projective synchronization between the fractional order chaotic system and hyperchaotic system is successfully achieved in both reduced order and increased order. The corresponding numerical results verify the effectiveness of the proposed method.     

Investigation of Q-S synchronization in coupled chaotic incommensurate fractional order systems

Chaos and synchronization in fractional order systems have received increasing attention in recent years. In this paper, the problem of Q-S synchronization for different dimensional incommensurate fractional order chaotic systems is investigated. Based on Laplace transform and stability theory of linear integer order differential systems, some synchronization schemes are designed to achieve Q-S synchronization between n-D and m-D incommensurate fractional order chaotic systems. Test problems and numerical simulations are used to show the effectiveness of the proposed approach.     

Synchronization of incommensurate non-identical fractional order chaotic systems using active control

Chaos synchronization in fractional order chaotic systems is receiving increasing attention due to its applications in secure communications. In this article we use an active control technique to synchronize incommensurate non-identical fractional order chaotic dynamical systems. The relation between system order and the synchronization time is discussed. It is observed that the synchronization can be achieved faster by increasing the system order. Further we provide an application of the proposed theory in secure communication.     

Fractional kinetic equations: solutions and applications

Fractional generalization of the diffusion equation includes fractional derivatives with respect to time and coordinate. It had been introduced to describe anomalous kinetics of simple dynamical systems with chaotic motion. We consider a symmetrized fractional diffusion equation with a source and find different asymptotic solutions applying a method which is similar to the method of separation of variables. The method has a clear physical interpretation presenting the solution in a form of decomposition of the process of fractal Brownian motion and Levy-type process. Fractional generalization of the Kolmogorov-Feller equation is introduced and its solutions are analyzed. (c) 1997 American Institute of Physics.     

Synchronization between fractional-order chaotic systems and integer orders chaotic systems (fractional-order chaotic systems)

Based on the idea of tracking control and stability theory of fractional-order systems, a controller is designed to synchronize the fractional-order chaotic system with chaotic systems of integer orders, and synchronize the different fractional-order chaotic systems. The proposed synchronization approach in this paper shows that the synchronization between fractional-order chaotic systems and chaotic systems of integer orders can be achieved, and the synchronization between different fractional-order chaotic systems can also be realized. Numerical experiments show that the present method works very well.     

Reduced-order anti-synchronization of the projections of the fractional order hyperchaotic and chaotic systems

The article aims to study the reduced-order anti-synchronization between projections of fractional order hyperchaotic and chaotic systems using active control method. The technique is successfully applied for the pair of systems viz., fractional order hyperchaotic Lorenz system and fractional order chaotic Genesio-Tesi system. The sufficient conditions for achieving anti-synchronization between these two systems are derived via the Laplace transformation theory. The fractional derivative is described in Caputo sense. Applying the fractional calculus theory and computer simulation technique, it is found that hyperchaos and chaos exists in the fractional order Lorenz system and fractional order Genesio-Tesi system with order less than 4 and 3 respectively. The lowest fractional orders of hyperchaotic Lorenz system and chaotic Genesio-Tesi system are 3.92 and 2.79 respectively. Numerical simulation results which are carried out using Adams-Bashforth-Moulton method, shows that the method is reliable and effective for reduced order anti-synchronization.     

Control of fractional chaotic and hyperchaotic systems based on a fractional order controller

We present a new fractional-order controller based on the Lyapunov stability theory and propose a control method which can control fractional chaotic and hyperchaotic systems whether systems are commensurate or incommensurate.The proposed control method is universal, simple, and theoretically rigorous. Numerical simulations are given for several fractional chaotic and hyperchaotic systems to verify the effectiveness and the universality of the proposed control method.     

Sliding observer for synchronization of fractional order chaotic systems with mismatched parameter

In this paper, we propose an observer-based fractional order chaotic synchronization scheme. Our method concerns fractional order chaotic systems in Brunovsky canonical form. Using sliding mode theory, we achieve synchronization of fractional order response with fractional order drive system using a classical Lyapunov function, and also by fractional order differentiation and integration, i.e. differintegration formulas, state synchronization proved to be established in a finite time. To demonstrate the efficiency of the proposed scheme, fractional order version of a well-known chaotic system; Arnodo-Coullet system is considered as illustrative examples.