Chaos–hyperchaos transition in a class of models governed by Sommerfeld effect

The present paper points out the scenario of the hyperchaotic attractor formation (an attractor with at least two positive Lyapunov exponents) in a class of models governed by the Sommerfeld effects. The Sommerfeld effect is the result of the conservation law of energy. When a dynamical system is coupled to a power source, it acts like a energy sink for which a part of the source energy is spend to deform the system rather than increasing the drive speed. The Sommerfeld effect involves riddling bifurcation which explains the creation of the hyperchaotic attractor.     

Effect of defects to the band-gaps generation

Effect of defects to the band-gaps generation in sonic composites is investigated in this paper. Acoustic scatterers are composed by piezoceramic hollow spheres of functionally graded materials. Defects are vacancies or foreign interstitial atoms which are supported by the interfaces between the hollow spheres and the matrix. The presence of defects in sonic composites is related to the generation of localized modes in the vicinity of the point defect with a significant evanescent behavior of the waves outside the defect point. As result, the full band-gap is wider than in the case of no defects. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Modeling of non-stationary vibration signals based on the modified Kronecker sequences

The paper establishes a representation model for non-stationary random vibration signals based on the modified Kronecker sequences. The modified Kronecker sequence constructed via generalizing golden ratio is one of the special types of low discrepancy sequences which have better dimensional projections [1]. The actual modeling and simulation of non-stationary random data is more suitable for seismological signals and not for the vehicle vibrations [2, 3]. Under these circumstances, this paper presents a new algorithm for finding the modified Kronecker sequences in order to generate non-stationary vehicle vibration signals which mostly withhold the amplitude-frequency-time distribution of the sample signal. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Projective complex Finsler metrics

In this paper we obtain the conditions under which two complex Finsler metrics are projective, i.e. have the same geodesics as point sets. Two important classes of such metrics are considered: conformal projective and weakly projective complex Finsler spaces. For each of them we study the transformations of the canonical connection. We pay attention to local projectivity in a pure Hermitian or Kähler space.     

Doubly warped product CR -submanifolds in locally conformal K?hler manifolds

In this paper we study doubly warped product CR submanifolds in locally conformal K?hler manifolds, and we found a B.Y. Chen’s type inequality for the second fundamental form of these submanifolds.     

On the dynamics of locally resonant sonic composites

The sound attenuation in a sonic composite is studied using a new method that combines the features of the piezoceramic theory, cnoidal method and genetic algorithms. A sonic composite consists of an array of acoustic scatterers embedded in an epoxy matrix. Acoustic scatterers are piezoceramic hollow spheres made from functionally graded materials – the Reddy and cosine graded hollow spheres. We show that stable attenuation bands may coexist with different patterns of dynamics, including chaos. In order to extend the method towards a tool for analyzing the sound attenuation in sonic composites, the behavior of a real sonic composite is simulated. The results concerning the full band-gaps have been validated by experimental data.     

Heterogeneous catalytic ignition of n-butane/air mixtures on platinum

The heterogeneous catalytic ignition of lean to stoichiometric n-butane/air mixtures were studied at various total pressures between 10 and 100 kPa and at temperatures equal to or larger than the critical ignition temperatures. The induction periods, ignition and extinction temperatures were measured under strict isothermal conditions. The discussion presented in this paper is based on several literature models. The data analysis allowed for the determination of the overall kinetic parameters. The rigorous isothermal conditions indicated that the extinction temperatures are lower than the ignition, a behavior different from the results obtained in stagnation-point flow reactors.      

Monte Carlo simulation of magnetic ordering in the Gd3Fe5O12 Ising ferrite with garnet structure

The simulation of magnetic properties in extended quantum spin networks can be done in good conditions with Ising models within Monte Carlo–Metropolis algorithms, as our systematic studies, employing original computer codes, proved. The present analysis provides interesting insights into the exchange interactions governing the magnetic behavior of the Gd₃Fe₅O₁₂ system, taken as a prototype for ferrites with garnet structure. Effective exchange interaction parameters are estimated by fitting the computed with experimental compensation temperature and temperature dependence of the magnetization.