International Journal of Modern Physics B

In this review paper, we address the important research topic of adsorption on the silicon surface. The deposition of single Si ad-species (adatom and ad-dimer) on the p(2×2) reconstructed Si(100) surface has been simulated by the empirical tight-binding method. Using the clean and defective Si surfaces as the deposition substrates, the deposition energies are mapped out around the clean surface, dimer vacancies, steps and kink structures. The binding sites, saddle points and several possible diffusion paths are obtained from the calculated energy. With further analysis of the deposition and diffusion behaviors, the influences of the surface defects can be found. Then, by adopting the first-principle calculations, the adsorptions of the II-VI group elements on the clean and As-passivated Si(211) substrates have been calculated as the example of adsorption on the high-miller-index Si surface.

We report a noise assisted and optimized resonant transition behavior between two metastable Turing pattern states in a piecewise FitzHu–Nagumo model. The response of the bistable Turing system to a weak periodic signal which modulates the attraction domain of the piecewise function is enhanced with the addition of noise. The quantity that measures the resonant transition between the bistable states and the periodicity of the Turing pattern shows a tent-shape dependence on the intensity of noise, which is the fingerprint of stochastic resonance. As the frequency of the signal is increased to be high enough, the coherent transition disappears.

We report dynamic holographic imaging with organic photorefractive polymer composites, doped with the electro-optic chromophore (2-(p-chlorophenyl)-(3′-nitrobenzo[d])-(4^′′-methoxybenzo[h])-1,3-dioxa-6-aza-2-boracyclonon-6-ene, a push-pull molecule derived from a new class of boronates. The composites are based on the photoconductor poly(9-vinylcarbazole) (PVK) as the polymer matrix, and 9-ethylcarbazole (ECZ) as the plasticizer, with the fullerene C₆₀ as sensitizer. A tilted four-wave mixing geometry was used to record and reconstruct two-dimensional test objects, using a 10 mW He–Ne laser (632.8 nm). The recording response time was less than one second for a light intensity of ≈350 mW/cm² in each writing beam. The erasing time had a similar value. These composites have been used for over one year with no appreciable signs of degradation or crystallization.

The resistance, mass transfer, erosion and arc properties of a new contact material named Ag/LaFe_1-xNi_xO₃ conductive ceramics were investigated. Ag/LaFe_1-xNi_xO₃ performed well under low voltage conditions in contrast with other contact materials such as Ag/CdO and Ag/SnO₂. After 5000 make-and-break operations, life test was made and the surface analysis method together with an arc voltage waveform was used to research the corrosion resisting and mass transfer properties. It was found that the conductive ceramics used in the contact materials could influence the resistance performance and, in turn, influence the mass transfer, erosion and arc characteristics.

We report here the electrical resistivity, ac susceptibility, low field magneto-resistance (LFMR) and structural parameters of the Pr_1-xBa_xMnO₃(x= 0.33–0.80) system. Samples with 33% and 40% Ba-content exhibit two clear transitions in their resistivity-temperature behavior while signatures of higher temperature transition are also seen in the 50% Ba sample. The higher temperature transition (insulator-metal, T_p1), like in other CMR materials, results due to competition between the double exchange and super exchange mechanisms. The lower temperature broad hump (T_p2) in resistivity reflects the strain effect at the grain boundaries due to the ionic radii mismatch between Pr⁺³ and Ba⁺². The low field magneto-resistance (at 0.15T) also corroborates the above results as MR peaks near T_p1 and increases further at lower temperatures, reflecting the contribution from the grain boundaries. Susceptibility measurements show the Curie transition (T_c) to be near T_p1 of the ρ-T data. Results are found to be consistent with the (NdBa) MnO₃ and (LaBa) MnO₃ systems. Resistivity data on the Pr_0.67Sr_0.33MnO₃ system, where the lower temperature transition at T_p2 is not seen due to the smaller ionic size difference of ( Pr⁺³–Sr⁺²) compared to (Pr⁺³–Ba⁺²), also substantiate these results. The observed resistivity upturn at low temperatures is considered in terms of the ensuing localization of carriers due to the varying degree of ionic size mismatch in these systems.

We present several kinds of optical solitary wave solutions for the fourth-order dispersive cubic-quintic nonlinear Schrödinger equation describing the propagation of optical pulses in a medium that exhibits a parabolic nonlinearity law. Among them, apart from some regular fundamental bright solitary wave solutions and dark solitary wave solutions given, there are also two kinds of combined solitary wave solutions, i.e., bright and dark solitary wave and W-shaped solitary wave solutions which describe bright and dark solitary wave properties. It is found that their amplitude may approach nonzero when the time variable approaches infinity. Moreover, when the parameters of the bright and dark solitary wave are selected appropriately, the kink and anti-kink solitary wave solutions, which are first reported in the fourth-order dispersive cubic-quintic nonlinear Schrödinger equation, are discovered.

A series of composite ferrites with chemical formula (1–x)[Mn_0.5Zn_0.5Fe₂O₄]·x[SiO₂](x = 0.0, 0.20, 0.30, 0.40, 0.50) were prepared by the co-precipitation technique. The samples were finally sintered at 1150°C followed by air quenching. The x-ray diffraction analysis confirms the phases precipitated out in the samples. AC magnetic susceptibility of these samples has been measured using the low field mutual inductance technique over the temperature range 298 K to 550 K at a frequency of 250 Hz. The magnetic parameters like Curie constant, C, Curie temperature, T_c, Lande splitting factor, g, effective magnetic moment, P_eff, exchange integral, J/kB, and characteristic temperature, θ(K) were calculated. The reciprocal of susceptibility versus temperature curves of each sample follows the Curie Weiss behaviour above the Curie temperature. Below the Curie temperature, all the samples show the ferrimagnetic behaviour. It was concluded that the magnetic properties were enhanced by the addition of silicon as is evident by the variation of magnetic interactions J, with Si-concentration and followed subsequently by the P_eff, θ(K) and T_c etc.

Starting from a discrete matrix spectral problem, a hierarchy of lattice soliton equations is derived through a discrete zero curvature representation. The Hamiltonian structures are established for the resulting hierarchy. Then the higher-order symmetry constraint for the resulting hierarchy is studied. It is shown that under the higher-order symmetry constraint, each lattice soliton equation in the resulting hierarchy can be factored by an integrable symplectic map and a finite-dimensional Liouville integrable Hamiltonian system.

We report measurements of the copper plasma parameters generated by the fundamental, second and third harmonics of a Nd:YAG laser. The 3d⁹4s5s²D_3/2→3d⁹4 s4p²F_5/2 at 464.25 nm, 4p ²P_3/2→3d⁹4s²D_5/2 at 510.55 nm, 4d ² D_3/2→4p²P_1/2 at 515.32 nm 4d ² D_5/2→4p²P_3/2 at 521.82 nm and 4p ² P_3/2→3d⁹4s²D_3/2 at 570.02 nm transitions have been used to estimate the electron temperature through the Boltzmann plot method. The number density has been estimated from the Stark broadened profiles of the spectral lines. The spatial behaviour of the electron temperature and number density has been examined at different ambient air pressures and with laser irradiance. The temperature and number density are found to be in the range from 14700 to 13600 K and 2.1×10¹⁶ to 1.78×10¹⁶cm^-3 for the 1064 nm laser, from 14200 to 12800 K and 2.2×10¹⁶ to 1.8×10¹⁶cm^-3 for the 532 nm laser and from 14100 to 12500 K and 2.4×10¹⁶ to 1.9×10¹⁶cm^-3 for the 355 nm laser.

In this paper, we consider a continuous map f: X→X, where X is a compact metric space, and discuss the existence of a chaotic set of f specially (as X=[0,1]). We prove that f has a positively topological entropy if and only if it has an uncountably chaotic set in which each point is recurrent and is not weakly periodic.