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The disappearance and reappearance of chaos by adjusting the internal parameters of dynamics in Lorenz system are studied. We observe monotonous and periodic time-dependent changes of Rayleigh number. There exists relaxation time for the disappearance of chaos, when we use the snapshot attractors to observe the change of the system attractors. We show that the rate of disappearance and reappearance of chaos is positively correlated with the control parameters. To reflect the relaxation phenomenon of chaotic disappearance and the sensitivity of trajectory, the concept of finite-time Lyapunov exponent is used. Then the statistical characteristics of the system can be presented by standard deviation. The chaotic disappearance and reappearance are manifested in the decrease and increase of the standard deviation. The standard deviation decreases continuously during chaotic disappearance, but increases discontinuously during chaotic reappearance. A distinctive scenario is that no matter which parameter changes, when we use the same rate of change in the process of chaotic disappearance and reappearance, their paths are different. [ABSTRACT FROM AUTHOR]

The various levels (5%, 10% and 15%) of Cu-doped TiO2 thin films were grown on the n -type silicon (Si) wafer by spin coating technique to obtain Al/(Cu:TiO 2) / n -Si (MOS) capacitors. Both the real and imaginary components of complex dielectric ( ε ∗ = ε ′ − j ε ′ ′) , complex electric modulus ( M ∗ = M ′ + j M ′ ′) , loss tangent (tan δ) and alternating electrical conductivity ( σ ac ) of the obtained Al/(Cu:TiO 2) ∕ n -Si (MOS) capacitors were studied by taking into account the effects of Cu-doping levels into TiO2 viaimpedance spectroscopy method (ISM) in the wide range voltage (± 5 V) and frequency (10 kHz–1 MHz). All the obtained dielectric parameters were obtained as strongly dependent on frequency, voltage and Cu doping level. The observed anomalous peak in the forward bias region both in the real and imaginary components of ε ∗ , tan  δ , complex electric modulus ( M ∗) and σ ac were attributed to the Cu:TiO2 interlay er, series resistance ( R s) , surface states ( N ss ) , interfacial/surface and dipole polarizations. The higher values of ε ′ at low and intermediate frequencies implied that N ss have enough time to follow external ac signal, and also dipoles respond to the applied field to reorient themselves. Consequently, the fabricated Al/(Cu:TiO 2) ∕ n -Si can be successfully used as MOS capacitor or MOS-field-effect transistor (MOSFET) in the industrial applications in near future. [ABSTRACT FROM AUTHOR]

This paper provides information on a self-consistent model of an anomalously slow relaxation of nonwetting liquid-nanoporous medium systems with a random size distribution of pores, which introduces changes in interaction between local liquid cluster configurations in the process of liquid outflow from the porous medium. A self-consistent equation was deduced, the solution of which determines a functional connection of porous medium filling degree or time . It is shown that the anomalously slow relaxation is presented as a process of decay of interacting local metastable configurations, initialized by thermal fluctuations. As time increments, relaxation acceleration takes place with subsequent avalanche fluid outflow from the porous medium, which is connected with interaction decrease between local configurations. The dependence of the fraction of volume of liquid remaining in a porous medium changes by the power law . It is shown that for a system of water-L23 at the initial stage in the time range of , an index assumes a constant value , while at the following stage the acceleration of relaxation and the increase of parameter are observed. [ABSTRACT FROM AUTHOR]

The trapping process and saturation effect of trapped magnetic flux of bulk high-temperature superconductors by static field-cooling magnetization (FCM) are reported in the paper. With a cryogenic Bell Hall sensor attached on the center of the bulk surface, the synchronous magnetic signals were recorded during the whole magnetization process. It enables us to know the flux trapping behavior since the removal of the excitation field, as well as the subsequent flux relaxation phenomenon and the flux dissipation in the quench process of the bulk sample. With the help of flux mapping techniques, the relationship between the trapped flux and the applied field was further investigated; the saturation effect of trapped flux was discussed by comparing the peak trapped field and total magnetic flux of the bulk sample. These studies are useful to understand the basic flux trapping properties of bulk superconductors. [ABSTRACT FROM AUTHOR]

The dynamic mechanism of liquid-glass transition for Mg7Zn3 alloy is studied by the molecular dynamics simulations. The temperature dependences of dynamic properties during the liquid-glass transition are investigated. Two relaxation processes are clearly observed near the glass transition temperature. The diffusivity deviates from the Arrhenius law after the melting temperature Tm and satisfies the power law before the dynamic singularity temperature Tc owing to the cage effect. The solid- and liquid-like atoms are defined according to the vibration characteristic of atoms. It is found that the solid-like atoms have higher local packing density, lower mobility and potential energy than the liquid-like ones. Based on the evolutions of solid- and liquid-like atoms, the atomic mechanism of dynamic liquid-glass transition is systematically elucidated, which is consistent with the potential energy landscape. [ABSTRACT FROM AUTHOR]

The U(1) gauge theory on a space with Lie type noncommutativity is constructed. The construction is based on the group of translations in Fourier space, which in contrast to space itself is commutative. In analogy with lattice gauge theory, the object playing the role of flux of field strength per plaquette, as well as the action, is constructed. It is observed that the theory, in comparison with ordinary U(1) gauge theory, has an extra gauge field component. This phenomena is reminiscent of similar ones in formulation of (N) gauge theory in space with canonical noncommutativity, and also appearance of gauge field component in discrete direction of Connes' construction of the Standard Model. [ABSTRACT FROM AUTHOR]

The concept of information asymmetry in complex networks is introduced on the basis of information asymmetry in economics and symmetry breaking. Information flowing between two nodes on a link is bidirectional, whose size is closely related to traffic dynamics on the network. Based on asymmetric information theory, we proposed information flow between network nodes is asymmetrical. We designed two methods to calculate the amount of information flow based on two mechanisms of complex network. Unequal flow of two opposite directions on the same link proved information asymmetry exists in the complex network. A complex network evolution model based on symmetry breaking is established, which is a truthful example for complex network mimicking nature. The evolution mechanism of symmetry breaking can best explain the phenomenon of the weak link and long tail theory in complex network. [ABSTRACT FROM AUTHOR]

We consider the dynamics of two pendulum clocks (with pendulums of the same length but different masses) suspended on the same beam. We give evidence that besides the complete and phase synchronizations, the considered system can exhibit long period synchronization and chaotic behavior. We argue that the observed phenomena are robust. [ABSTRACT FROM AUTHOR]

Geometric and electronic properties and vacancy formation energies for two kinds of oxygen-vacancy Cu2O (111) surfaces have been investigated by first-principles calculations. Results show that the relaxation happens mainly on the top three trilayers of surfaces. Two vacancies trap electrons of -0.11e and -0.27e, respectively. The effects of oxygen vacancies on the electronic structures are found rather localized. The electronic structures suggest that the oxygen vacancies enhance the electron donating ability of the surfaces to some extent. The energies of 1.75 and 1.43 eV for the formation of oxygen vacancies are rather low, which indicates the partially reduced surfaces are stable and easy to produce. [ABSTRACT FROM AUTHOR]

Transparent films of PMMA (poly methyl methacrylate), PVAc (polyvinyl acetate) and their blends, have been prepared by using a solution-casting technique. The dielectric properties and the electrical conductivity are reported. The frequency and temperature dependence of the dielectric constant, ε′ and tan δ, have been investigated for the studied samples in the frequency range from 1 kHz to 5 MHz and over a range of temperature from 303-413 K. In addition, AC conductivity values were calculated from the dielectric data and the conduction mechanism is discussed. The frequency-dependent conductivity behavior at different temperatures provides a qualitative description of the conduction mechanism. Also, differential scanning calorimetry (DSC) scans have been measured for the studied samples. [ABSTRACT FROM AUTHOR]

The renormalized dynamics described by the equations of nonlinear fluctuating hydrodynamics (NFH) treated at one loop order gives rise to the basic model of the mode coupling theory (MCT). We investigate here by analyzing the density correlation function, a crucial prediction of ideal MCT, namely the validity of the multi step relaxation scenario. The equilibrium density correlation function is calculated here from the direct solutions of NFH equations for a hard sphere system. We make first detailed investigation for the robustness of the correlation functions obtained from the numerical solutions by varying the size of the grid. For an optimum choice of grid size we analyze the decay of the density correlation function to identify the multi-step relaxation process. Weak signatures of two step power law relaxation is seen with exponents which do not match predictions from the one loop MCT. For the final relaxation stretched exponential (KWW) behavior is seen and the relaxation time grows with increase of density. But apparent power law divergences indicate a critical packing fraction much higher than the corresponding MCT predictions for a hard sphere fluid. [ABSTRACT FROM AUTHOR]

We explore how some ideas that have been used before for optimal design problems with two materials through a variational approach, can be extended to cover three or more materials. In particular, we focus on two paradigmatic situations where we consider a linear-in-the-gradient cost functional, and a typical quadratic situation. In both cases, we are able to formulate, quite explicitly, a full relaxation of the problem through which optimal microstructures for the original non-convex problem can be understood. [ABSTRACT FROM AUTHOR]

In our recent work [Gusev and Lurie, Int. J. Mod. Phys. B 26 (2012) 125003], we have presented the theory of spacetime elasticity. The theory advocates its own law of heat conduction in solids, involving both wave and relaxation (diffusion) modes of heat propagation. Here we use that heat conduction law -- together with the classical Fourier's and Maxwell-Cattaneo laws -- to analyze the temperature dynamics occurring in Fermi-Pasta-Ulam (FPU-&bgr;) chains. We focus on the acoustic limit and use a combination of the Langevin and molecular dynamics to study the corresponding temperature decay func-tions. We have found that all the three laws suit well for describing the high-temperature, exponential-form temperature decay functions. However, at low temperatures the wave dynamics becomes prevailing and it is only the spacetime-elasticity heat conduction law that provides the appropriate functional forms. At all the temperatures and wave-lengths studied, the observed temperature dynamics is anomalous, and we discuss both theoretical and practical implications of such anomalous behavior [ABSTRACT FROM AUTHOR]

We make the study of the relationship between symmetrical coupling of coupling qubits and non-Markovian relaxation characteristics by utilizing concurrence. The results show that the relaxation characteristics of quantum system strongly depend on the coupling way between qubits and environment and the decoherence-free subspace may form under certain conditions. We find that when the system is initially at state or the mixed state generated by this state, we can make the quantum system always at the entangled state without entanglement sudden death (ESD) phenomenon by regulating the coupling between qubits and environment at complete anti-symmetric state. In contrast, when the system is initially at state or the mixed state generated by this state, then we must regulate the coupling way between qubits and environment at complete symmetric state to make the quantum system maintain at the entanglement state. [ABSTRACT FROM AUTHOR]

The structures of 5,5′-bis(naphth-2-yl)- 2,2′-bithiophene (NaT2), 5,5″-bis(naphth-2-yl)-2,2′:5′,2′-terthiophene (NaT3), 5,5‴-bis(naphth-2-yl)-2,2′:5′,2″:5″,2‴-tetrathiophene (NaT4), 5,5″″-bis(naphth-2-yl)-2,2′:5′,2″:5″,2‴:5‴,2″″-quinquethiophene (NaT5) and 5,5′″″-bis(naphth-2-yl)-2,2′:5′,2″:5″,2‴:5‴,2″″:5″″,2′″″-sexithiophene (NaT6) have been optimized at PBE1PBE/6-31G* level of theory. By increasing the chain length (thiophene units) energy gap decreases. The hole reorganization energy also decreases from NaT2-NaT6. We have observed that mobility of NaT5 and NaT6 can be enhanced by minimizing the polarization and relaxation. The end-capped naphthyl groups have been rotated from 0°-60° in the case study of NaT2, it was found that hole reorganization energy increases with the increment in angle. Furthermore the charge transport properties of 5,5′-bis(thionaphth-2-yl)-2,2′-bithiophene (TNT2), 5,5″-bis(thionaphth-2-yl)-2,2′:5′,2″-terthiophene (TNT3), and 5,5‴-bis(thionaphth-2-yl)-2,2′:5′,2″:5″,2‴-quaterthiophene (TNT4) have been investigated at the same level of theory. It has been studied that cis isomers have higher hole reorganization energies as compared to trans ones thus these isomers would diminish the mobility. [ABSTRACT FROM AUTHOR]

We propose kinetic models to describe dust particles in a rarefied atmosphere in order to model the beginning of a Loss of Vacuum Accident (LOVA) in the framework of safety studies in the International Thermonuclear Experimental Reactor (ITER). After having studied characteristic time and length scales at the beginning of a LOVA in ITER and underlined that these characteristic scales justify a kinetic approach, we firstly propose a kinetic model by supposing that the collisions between dust particles and gas molecules are inelastic and are given by a diffuse reflexion mechanism on the surface of dust particles. This collision mechanism allows us to take into account the macroscopic character of dust particles compared to gas molecules. This leads to establish new Boltzmann type kinetic operators that are non-classical. Then, by noting that the mass of a dust particle is huge compared to the mass of a gas molecule, we perform an asymptotic expansion to one of the dust-molecule kinetic operators with respect to the ratio of mass between a gas molecule and a dust particle. This allows us to obtain a dust-molecule kinetic operator of Vlasov type whose any numerical discretization is less expensive than any numerical discretization of the original Boltzmann type operator. At last, we perform numerical simulations with Monte-Carlo and Particle-In-Cell (PIC) methods which validate and justify the derivation of the Vlasov operator. Moreover, examples of 3D numerical simulations of a LOVA in ITER using these kinetic models are presented. [ABSTRACT FROM AUTHOR]

The motivation for this work was a simple experiment [P. M. C. de Oliveira, S. Moss de Oliveira, F. A. Pereira and J. C. Sartorelli, preprint (2010), arXiv:1005.4086], where a little polystyrene ball is released falling in air. The interesting observation is a speed breaking. After an initial nearly linear time-dependence, the ball speed reaches a maximum value. After this, the speed finally decreases until its final, limit value. The provided explanation is related to the so-called von Kármán street of vortices successively formed behind the falling ball. After completely formed, the whole street extends for some hundred diameters. However, before a certain transient time needed to reach this steady-state, the street is shorter and the drag force is relatively reduced. Thus, at the beginning of the fall, a small and light ball may reach a speed superior to the sustainable steady-state value. Besides the real experiment, the numerical simulation of a related theoretical problem is also performed. A cylinder (instead of a 3D ball, thus reducing the effective dimension to 2) is positioned at rest inside a wind tunnel initially switched off. Suddenly, at t = 0 it is switched on with a constant and uniform wind velocity $\vec{V}$ far from the cylinder and perpendicular to it. This is the first boundary condition. The second is the cylinder surface, where the wind velocity is null. In between these two boundaries, the velocity field is determined by solving the Navier-Stokes equation, as a function of time. For that, the initial condition is taken as the known Stokes laminar limit V → 0, since initially the tunnel is switched off. The numerical method adopted in this task is the object of the current text. [ABSTRACT FROM AUTHOR]

We study the Cole-Cole diagram for the case of a paraelectric particle for which the relaxation time is the same for every mode and the resonance frequency changes and there is an infinite number of such modes. We will calculate the Cole-Cole diagram for temperature a = 10 and damping g = 1 in a and g units (see below) from exact expression for the dynamic susceptibility. We have found that there is a smooth Cole-Cole diagram the curve of which starts from small frequencies 0.001 from the point near Y = 1.5 and X = 0 on the diagram down to the peak (in imaginary part) values of X near 1.6 and Y near 0.5 increasing frequency. Increasing further frequency to 20, the real and imaginary parts tend to zero value. Thus there exists a single maximum of the imaginary part of the susceptibility (for 1000 modes and for 5000 modes), and a single maximum and minimum for the real part of the susceptibility. [ABSTRACT FROM AUTHOR]

We investigate the possibility of appearance of new phenomena derived from the influence of noise on quantum systems. As a starting point we study the entanglement evolution of two coupled qubits in interaction with an external environment and in the presence of an external magnetic field with a stochastic component. The results show the expected degradation of entanglement due to the noise. The new effect is that for particular initial states the time of disentanglement depends in a non-monotonous way on the strength of the noise. We find that it is shortest for an intermediate strength value of the noise. This we call "stochastic anti-resonance." Our new result indicates that there are noise values which are particularly harmful and should be avoided. This could lead to a better understanding of noisy perturbations and their role for optimal designing of quantum devices. [ABSTRACT FROM AUTHOR]

In this paper, for the first time in our knowledge, the influence of nonuniform and continuous doping in semiconductor on amplification of spin polarization current especially in n-type GaAs semiconductor have been studied. Numerical calculations based on a selfconsistent solution of the continuity equation, the Poisson equation and rate-equation are used to explain the amplification of spin polarization density. The influences of the diffusion coefficient (Dn) and relaxation time (τsf) on the spin polarization density are also studied. The amplifying effect of nonuniform doping on spin polarization density is important because it might have many applications in spintronic devices. [ABSTRACT FROM AUTHOR]

The subcharacteristic condition for hyperbolic relaxation systems states that wave velocities of an equilibrium system cannot exceed the corresponding wave velocities of its relaxation system. This condition is central to the stability of hyperbolic relaxation systems, and is expected to hold for most such models describing natural phenomena. In this paper, we study a hierarchy of two-phase flow models. We consider relaxation with respect to volume transfer, heat transfer and mass transfer. We formally verify that our relaxation processes are consistent with the first and second laws of thermodynamics, and present analytical expressions for the wave velocities for each model in the hierarchy. Through an appropriate choice of variables, we prove directly by sums-of-squares that for all relaxation processes considered, the subcharacteristic condition holds for any thermodynamically stable equation of state. [ABSTRACT FROM AUTHOR]

In this paper, we use molecular dynamics (MD) simulations and a modified analytic embedded-atom method to investigate the edge dislocation movement without imposed strain at 0 K. The obtained results indicate that the straight lines of the partial dislocations always preserve their original shapes and are parallel to each other during the simulation process. According to the energy of each atom, the positions of both partial dislocation cores are determined. Then the velocities in the period of the relaxation process are investigated in detail. The MD simulations reveal that the MD relaxation time dependence of the edge dislocation mobility is divided into two parts. First, during the initial period ranging from 0 to 6 ps, the relative velocity of the dislocation movement lineally increases with the incremental relaxation time. Second, in the latter period from 6 ps to the end of the simulated process the velocity decreases exponentially as the MD simulation time evolves. [ABSTRACT FROM AUTHOR]

We report the temperature dependent coercivity behavior and the improvement of room temperature soft magnetic properties in interacting amorphous Fe-Mn-Zr-B powder nanoparticles prepared by mechanical alloying of elemental powders. With increasing Mn concentration from 5 to 20 at.% in Fe-Zr-B alloys, the coercivity (HC) reduces drastically from 170 to 25 Oe. Temperature dependent HC behavior shows exponential variation of HC with temperature. Interparticle interactions dominate the low temperature behavior and surface effect on the nanoparticles is more pronounced at low temperatures. Magnetic relaxation behavior shows slow relaxation in the interacting amorphous nanoparticles and the relaxation process is observed to be thermally activated in the present studies. [ABSTRACT FROM AUTHOR]

We report ultrafast response of femtosecond photoexcited carriers in single layer reduced graphene oxide flakes suspended in water as well as few layer thick film deposited on indium tin oxide coated glass plate using pump-probe differential transmission spectroscopy at 790 nm. The carrier relaxation dynamics has three components: ~200 fs, 1 to 2 ps, and ~25 ps, all of them independent of pump fluence. It is seen that the second component (1 to 2 ps) assigned to the lifetime of hot optical phonons is larger for graphene in suspensions whereas other two time constants are the same for both the suspension and the film. The value of third order nonlinear susceptibility estimated from the pump-probe experiments is compared with that obtained from the open aperture23 Z-scan results for the suspension. [ABSTRACT FROM AUTHOR]

The broad visible photoluminescence (PL) observed in ZnO nanocrystals (NCs) is widely attributed to multiple low lying surface-defects. We have performed steady state and time-resolved PL measurements on size-selected ZnO NCs in the strong confinement regimes. Our results show that radiative relaxation rates and coupling between excitons and surface defect states vary dramatically for sizes between 2 nm and 3 nm. Energy dependent PL lifetimes reveal that relaxation dynamics of these defect states in the blue- and red-edge of the emission are very different from each other. [ABSTRACT FROM AUTHOR]

The aggregation behavior of superparamagnetic iron oxide nanoparticles in an aqueous medium has been studied using SQUID magnetometry and XRD analysis. Iron oxide nanoparticles were synthesized by the coprecipitation method using iron salt and sodium hydroxide as precursors. The reactions were initially carried out at high temperature with different concentrations of iron salt. The synthesized nanoparticles were then collected for subsequent bio-functionalization. Structural characterizations were done using XRD and TEM measurements and show that the particles are magnetite (cubic spinel structure) with an average size of 9.5 nm. Magnetic measurements done using SQUID predict a magnetic particle size of 7.75 nm, which suggests a "magnetically dead layer" is present on the surface. [ABSTRACT FROM AUTHOR]

The Euler-Maxwell system regarded as a hydrodynamic model for plasma physics describes the dynamics of 'compressible electrons' in a constant, charged, non-moving ion background. A global smooth flow with small amplitude is constructed here in three space dimensions when the electron velocity relaxation is taken into account. The speed of the electron flow tending to a uniform equilibrium, and the pointwise behavior of solutions to the linearized homogeneous system in the frequency space are investigated in detail. [ABSTRACT FROM AUTHOR]

In this paper, we review recent developments in the emerging field of electron quantum optics, stressing analogies and differences with the usual case of photon quantum optics. Electron quantum optics aims at preparing, manipulating and measuring coherent single electron excitations propagating in ballistic conductors such as the edge channels of a 2DEG in the integer quantum Hall regime. Because of the Fermi statistics and the presence of strong interactions, electron quantum optics exhibits new features compared to the usual case of photon quantum optics. In particular, it provides a natural playground to understand decoherence and relaxation effects in quantum transport. [ABSTRACT FROM AUTHOR]

Solution-based chemical method was used to prepare the compound LiCoVO4. Compound formation was checked by X-ray diffraction (XRD) study and it revealed a cubic unit cell structure with lattice parameter: a = 8.2840 (3) Å. Complex impedance result shows bulk contribution to electrical properties up to 225°C, grain boundary effects for all T ≥ 250°C, and evidence of temperature-dependent electrical relaxation phenomena in the material. The values of activation energy were determined from the Arrhenius plot of DC conductivity versus 103/T and were equal to ~0.09 eV at 50-200°C and ~0.48 eV at 200-350°C. Complex modulus study indicates non-Debye type (polydispersive) conductivity relaxation in the compound. [ABSTRACT FROM AUTHOR]

The lattice thermal conductivity of InSb and CdS has been analyzed on the basis of the most acquiescent Callaway model in the temperature range 2-300.779 K and 2.296-283.565 K. To reinvigorate the effects of phonon anharmonicities, more rigorous expressions for the phonon-phonon interactions, resonance, impurity and interference scattering relaxation times have been introduced to theoretically justify the experimentally observed results. A fairly good agreement between theory and experiments has been presented. [ABSTRACT FROM AUTHOR]

This paper develops the optimal time-step ratio and the critical damping for nonlinear structural analysis, when using dynamic relaxation method (DRM). The convergence rate of the DRM depends on the value of the time step and the critical damping factor. In the present study, the effect of the time-step ratio is separated from the time-step value. Additionally, the effect of the eigenvalue on the error function is investigated. Using the eigenvalue definition, the critical damping is updated in each dynamic relaxation (DR) step to decrease the required computations. Moreover, the optimal time-step ratio is calculated. It is also shown that the value of the constant time step has no effect on the rate of convergence. The proposed procedure provides a simple and accelerated DRM, which can be used in the linear and nonlinear analyses of structures. The efficiency of the new method was verified by its application to a wide range of typical structures. The results show that the suggested scheme accelerates the convergence rate of the DR process. [ABSTRACT FROM AUTHOR]

We establish pointwise bounds for the Green function and consequent linearized stability for multidimensional planar relaxation shocks of general relaxation systems whose equilibrium model is scalar, under the necessary assumption of spectral stability. Moreover, we obtain nonlinear L2 asymptotic behavior/sharp decay rate of perturbed weak shocks of general simultaneously-symmetrizable relaxation systems, under small L1 ∩ H[d/2]+3 perturbations with first moment in the normal direction to the front. [ABSTRACT FROM AUTHOR]

The electrochemical formation and reduction of O-layers on gold (111) films in 1 m sulfuric acid under different potentiodynamic routines are investigated utilizing in situ scanning tunneling microscopy. The surface dynamics is interpreted considering the anodic and cathodic reaction pathways recently proposed complemented with concurrent relaxation phenomena occurring after gold (111) lattice mild disruption (one gold atom deep) and moderate disruption (several atoms deep). The dynamics of both oxidized and reduced gold topographies depends on the potentiodynamic routine utilized to form OH/O surface species. The topography resulting from a mild oxidative disruption is dominated by quasi-2D holes and hillocks of the order of 5 nm, involving about 500–600 gold atoms each, and their coalescence. A cooperative turnover process at the O-layer, in which the anion ad-layer and interfacial water play a key role, determines the oxidized surface topography. The reduction of these O-layers results in gold clusters, their features depending on the applied potential routine. A moderate oxidative disruption produces a surface topography of hillocks and holes several gold atoms high and deep, respectively. The subsequent reduction leads to a spinodal gold pattern. Concurrent coalescence appears to be the result of an Ostwald ripening that involves the surface diffusion of both gold atoms and clusters. These processes produce an increase in surface roughness and an incipient gold faceting. The dynamics of different topographies can be qualitatively explained employing the arguments from colloidal science theory. For 1.1 V ≤ E ≅ Epzc weak electrostatic repulsions favor gold atom/cluster coalescence, whereas for E < Epzc the attenuated electrostatic repulsions among gold surfaces stabilize small clusters over the substrate producing string-like patterns. [ABSTRACT FROM AUTHOR]

A relationship between the temperature and the dielectric strength of a Maxwell–Wagner (MW) type relaxation was deduced based on the conventional two-layer model for inhomogeneous systems and under the usual assumptions that the conductivity of each layer obeys the thermally activated law and the dielectric constant of each layer is relatively temperature independent. The relation shows that the relaxation peak height in the imaginary part of the complex permittivity for a MW-type relaxation increases with decreasing temperature and saturates at low enough temperature. This behavior was well-proved by both numeral and experimental results and therefore could be regarded as a fingerprint of a MW-type relaxation in most practical cases. [ABSTRACT FROM AUTHOR]

The evolution of the current-voltage characteristic in K0.3MoO3 was observed intuitively with the presence of current cycling. No variation of the ohmic conductivity was distinguished, while the threshold field for the charge density waves depinning exhibited distinct enhancement with the current cycling. These results were attributed to the electric field-assisted metastable states' relaxation of the charge density waves. [ABSTRACT FROM AUTHOR]

The evolution of the current-voltage characteristic in K0.3MoO3 was observed intuitively with the presence of current cycling. No variation of the ohmic conductivity was distinguished, while the threshold field for the charge density waves depinning exhibited distinct enhancement with the current cycling. These results were attributed to the electric field-assisted metastable states' relaxation of the charge density waves. [ABSTRACT FROM AUTHOR]

Exciton recombination in asymmetric CdMgTe/CdTe/CdMgTe/CdTe/CdMnTe double quantum wells (ADQW) with different barrier widths is studied in magnetic field up to 10 T. As grown structures were subjected to temperature annealing to introduce Mn and Mg atoms from the barriers into the CdTe quantum wells (QW). At low fields exciton transition in QW with magnetic impurity (Mn) is higher in energy than that in QW with nonmagnetic impurity (Mg), and interwell exciton relaxation is fast independently on the spin state. In contrast, at high fields, when the energy order reverses, an unexpectedly low relaxation rate of σ- polarized excitons from nonmagnetic QW to the ground σ+ polarized state in magnetic QW has been observed. Effect strongly correlates with hh–lh splitting value Δhh–lh and discussed in terms of valence band mixing. Such a slowing down of relaxation allows separation of oppositely polarized excitons in different QWs. [ABSTRACT FROM AUTHOR]

Based on the property of a passive system, the essential conditions under which a hyperchaotic Lorenz system could be equivalent to a passive system via smooth state feedback are derived, making the minimum phase hyperchaotic Lorenz system globally asymptotically stabilized at zero and at any desired equilibrium points. The results of simulation on Matlab and the circuit experiment on EWB confirm the effectiveness of the proposed hyperchaos control method. [ABSTRACT FROM AUTHOR]

The complex perovskite oxide barium iron antimonate, BaFe1/2Sb1/2O3 (BFS) is synthesized by a solid-state reaction technique for the first time. The X-ray diffraction of the sample at room temperature shows a monoclinic phase. The field dependences of dielectric response and the loss tangent of the sample are measured in a frequency range from 50 Hz to 1 MHz and in a temperature range from 143 to 463 K. An analysis of the loss factor with frequency is performed by the scaling behavior of the dielectric loss spectra. The frequency dependence of the loss peaks are found to obey the Arrhenius law with an activation energy ≃0.81 eV. The scaling behavior of the dielectric loss spectra suggests that the distribution of relaxation times is temperature-independent. The frequency-dependent electrical data are also analyzed in the framework of conductivity and electric modulus formalisms. The scaling behavior of the imaginary electric modulus shows the temperature-independent nature of the distribution of relaxation times. All these formalisms resulted in the qualitative similarities in the relaxation time. The relationship between relaxation parameters and electrical conduction indicates the hopping motion of electrons from Fe(II) to Fe(III) ions in BFS. [ABSTRACT FROM AUTHOR]

The complex perovskite oxide barium iron antimonate, BaFe1/2Sb1/2O3 (BFS) is synthesized by a solid-state reaction technique for the first time. The X-ray diffraction of the sample at room temperature shows a monoclinic phase. The field dependences of dielectric response and the loss tangent of the sample are measured in a frequency range from 50 Hz to 1 MHz and in a temperature range from 143 to 463 K. An analysis of the loss factor with frequency is performed by the scaling behavior of the dielectric loss spectra. The frequency dependence of the loss peaks are found to obey the Arrhenius law with an activation energy ≃0.81 eV. The scaling behavior of the dielectric loss spectra suggests that the distribution of relaxation times is temperature-independent. The frequency-dependent electrical data are also analyzed in the framework of conductivity and electric modulus formalisms. The scaling behavior of the imaginary electric modulus shows the temperature-independent nature of the distribution of relaxation times. All these formalisms resulted in the qualitative similarities in the relaxation time. The relationship between relaxation parameters and electrical conduction indicates the hopping motion of electrons from Fe(II) to Fe(III) ions in BFS. [ABSTRACT FROM AUTHOR]

In this paper we study the steady-state quantum hydrodynamic model for semiconductors. The existence of solutions on the bipolar QHD model is obtained in the case of sufficiently small relaxation time. Uniqueness results are showed both in the thermal equilibrium states and the scaled Planck constant being large enough. The relaxation time and dispersive limit are performed on the bipolar and unipolar equations, respectively. In a sense, we have made a complete answer to the original unsolved problems of the steady-state QHD model. [ABSTRACT FROM AUTHOR]

A model for the displacement of self-driven organisms is studied by means of extensive computer simulations. Local interactions influenced by noisy communications among organisms, leads to the onset of collective motion at low noise levels. When the noise is increased the system undergoes first-order transitions into disordered states of motion. We have also studied the relaxation process between these states. By fitting the time dependence of the order parameter when the system is annealed from a state below coexistence to another above it, we conclude that the relaxation can be well described by means of a stretched exponential. In this way the characteristic relaxation times are obtained. [ABSTRACT FROM AUTHOR]

Finite element method is used to simulate the high-speed melt spinning process, based on the equation system proposed by Doufas et al. Calculation predicts a neck-like deformation, as well as the related profiles of velocity, diameter, temperature, chain orientation, and crystallinity in the fiber spinning process. Considering combined effects on the process such as flow-induced crystallization, viscoelasticity, filament cooling, air drag, inertia, surface tension and gravity, the simulated material flow behaviors are consistent with those observed for semi-crystalline polymers under various spinning conditions. The structure change of polymer coils in the necking region described by the evolution of conformation tensor is also investigated. Based on the relaxation mechanism of macromolecules in flow field different types of morphology change of polymer chains before and in the neck are proposed, giving a complete prospect of structure evolution and crystallization of semi-crystalline polymer in the high speed fiber spinning process. [ABSTRACT FROM AUTHOR]

Based on the premise that the addition of glass beads (GB) could hardly influence the linear viscoelasticity in low frequency (ω) region for homogeneous polymer systems, the dynamic rheological behaviors of unfilled and filled poly(methyl methyacrylate) (PMMA)/poly(styrene-co-acrylonitrile) (SAN) blends were studied in order to explore the effect of GB on the phase-separation of binary polymer matrix. Results show that GB has an induced effect on the phase-separation, which embodies that the phase-separation temperature (Ts) of PMMA/SAN blend filled with GB is lower than that of the unfilled system. The higher content of GB, the higher is the "secondary plateau" of ω in the terminal region of storage modulus (G′) versus ω plot. The "secondary plateau" appearing in the terminal region is attributed to the phase-separation of PMMA/SAN blends and it becomes more flat for filled polymer blends under the same conditions. However, it is suggested that this kind of "induced effect" is related to the GB content; the higher content of GB particles might enhance the interaction between the particles and polymer matrix. Moreover, it is found that the addition of GB also has an influence more or less on the morphology and domain size of polymer matrix. It is believed that the plot of dynamic viscosity (η′) versus the loss viscosity (η") is sensitive to examine the effect induced by GB on the phase-separation of binary polymer matrix. [ABSTRACT FROM AUTHOR]