Modern Physics Letters B

We present a detailed study of the ferromagnetism in nano-Ni-doped SnO₂ and ZnO. It is shown that the ferromagnetic behavior is not an intrinsic property of the systems but rather associated with the presence of nNi particles in both matrices. The ferromagnetic transition of all Ni-doped samples is at 631(2) K, the same as the T_C value for bulk Ni and nano-Ni powder. The saturation moments of the nano-Ni-doped samples scale with the Ni concentration and are much lower than that of pure Ni. This is due to the large surface area of nano-Ni particles which are partially oxidized due to nano-NiO. ¹¹⁹Sn Mössbauer spectroscopy studies on Sn_0.96Ni_0.04O₂ do not show any transferred hyperfine field on the Sn nuclei, confirming that the magnetic properties stem from a different phase.

The q-deformed Bose–Einstein distribution is used to study the Bose–Einstein condensation (BEC) of a q-deformed Bose gas in random box. It is shown that the BEC transition temperature is lowered due to random boundary conditions. The effects of q-deformation on the properties of the system are also discussed. We find some properties of a q-deformed Bose gas, which are different from those of an ordinary Bose gas. Similar results are also shown for q-bosons confined in a harmonic oscillator potential well.

The dynamics of the coexisting ultracold atomic and molecular condensates in the presence of Feshbach resonance, atom–atom, molecule–molecule and atom–molecule interactions is described in terms of coupled Gross–Pitaevskii equation. We show that the appearence of oscillation or the existence of Josephson-like currents in the condensates is the natural consequence of the Gross–Pitaevskii equation under a suitable approximation regarding the nature of the condensate wave function.

Ordered large-scale alumina nanowire arrays on the surface of porous anodic alumina membranes (AAMs) have been synthesized by chemical etching. The analysis shows that amorphous alumina nanowires directly formed from AAMs have uniform size and shape. The mean length and mean diameter of alumina nanowires are about 6 μm and 24 nm, respectively. It is observed that chemical etching parameters affect the synthesis of alumina nanowires and preferable experimental conditions for the synthesis of alumina nanowire arrays. The intensity of photoluminescence excited from alumina nanowire is affected by post-annealing temperatures. The mechanisms for the synthesis and PL emission of alumina nanowires are discussed.

Using the finite element method, we have calculated the transmission spectra of Lamb wave modes which propagate in one-dimensional three-component Fibonacci quasiperiodic composite plates made of three different materials, and analyzed the influence of filling fraction, the ratio of the thickness of the plates to the lattice period and especially the number of generations on the band gaps of Lamb wave modes. The band gap splitting depends on the number of generations which is different from those of one-dimensional two-component Fibonacci composite plates. Engineering band gaps can be obtained by turning different parameters and the number of generations.

The microstructure and magnetic properties of Mg–Cu–Zn ferrites prepared by using solid-state reaction method have been investigated. X-ray diffraction (XRD), a scanning electron microscope (SEM), impedance analyzer and a vibrating sample magnetometer (VSM) were utilized in order to study the effect of copper substitution and its impact on the crystal structure, grain size, microstructure and magnetic properties of the Mg–Cu–Zn ferrite. The formation of cubic spinel phase was identified using XRD technique. The microstructures of the samples show that the grain growth is greatly enhanced by the addition of CuO which is attributed to the liquid phase during sintering. The average grain size (D_m) increases significantly with increasing Cu content. The initial permeability (μ') of the samples increases appreciably with increasing Cu content which is attributed to the increase of grain size and density of the samples. The resonance frequency (f_r) of the samples shifts toward the lower frequency as the Cu content increases. The sharp fall of μ' in μ'-T curves is observed for all the samples which indicate the homogeneity of the samples. The saturation magnetization (M_s) of the Mg–Cu–Zn ferrites increases slightly with increasing Cu concentration.

By considering a new four-by-four matrix eigenvalue problem, a hierarchy of Lax integrable evolution equations with four potentials is derived. The Hamiltonian structures of the resulting hierarchy are established by means of the generalized trace identity. The Liouville integrability for the hierarchy of the resulting Hamiltonian equations is presented.

The secondary amide unit is a subject of particular interest, because of its occurrence in peptides and proteins. Molecular interaction between N-benzylformamide (NBF) with 1-alcohols (1-propanol, 1-butanol, 1-pentanol) has been studied in carbon tetrachloride by using X-band microwave bench at 936 GHz. Dielectric constant (ε') and dielectric loss (ε″) of alcohol and NBF and their binary mixture for different mole fractions of NBF have been determined. Dielectric relaxation time (τ) of the binary system is obtained by both Higasi's method and the Gopalakrishna single-frequency concentration variational method. The results show that the most likely interaction between alcohols and NBF is 1:1 complex for binary mixture through the free hydroxyl group of the alcohol and the carbonyl group of NBF. The alkyl chain-length of both alcohol and amide plays an important role in the determination of the strength of hydrogen bond (O–H: C=O) formed. The variation of relaxation time of NBF+1-alcohol mixtures in CCl₄ indicates a weak solute-solvent type of molecular association. The result shows that as the relaxation time of the proton acceptor increases, the donating ability of the solute environment increase.

In this paper, the field parameters for the magnetic field of a Helmholtz coil is defined, as predicted by the theory of magnetic multipolar fields. In accordance with Biot–Savart law, eleven series of field parameters for the Helmholtz coil are calculated and the effect of each parameter thoroughly analyzed. This is then shown to provide a theoretical basis for obtaining a uniform magnetic field.

In this letter, we propose a new synchronization method, called a delayed feedback fuzzy synchronization (DFFHS) method, for time-delayed chaotic systems with external disturbance. Based on Lyapunov–Krasovskii theory, T–S fuzzy model, and delayed feedback control scheme, the DFFHS controller is presented to not only guarantee aymptotical synchronization but also reduce the effect of external disturbance to an norm constraint. The proposed controller can be obtained by solving the linear matrix inequality (LMI) problem. A numerical example for time-delayed Lorenz system is presented to demonstrate the validity of the proposed DFFHS method.

The nonlinear dynamics of a vibration-controlled magnetic system are studied via a three-mode discretization of the governing partial differential equations. The analysis focuses specifically on the effects of modal coupling through the nonlinear terms of the system equation. A bifurcation analysis of the system is performed using sophisticated nonlinear theories, including the center manifold theory and the normal form theorem. The results show that when the first mode and the higher modes are excited simultaneously by the control forces, the three-mode approximation method predicts the existence of a triple zero degeneracy accompanied by complicated bifurcation phenomena. Comparing the dynamics structure predicted by the three-mode approximation model with that obtained from a single-mode approach, it is found that if the higher modes are excited by the control forces, the effects of modal coupling should be taken into consideration since a complicated dynamics structure may exist as a result.

A liquid fuel high velocity oxy-fuel (HVOF) thermal spray process has been used to deposit TiO₂ photocatalytic coatings utilizing a commercially available anatase/rutile nano-powder as the feedstock. The coatings were characterized in terms of the phases present, its crystallite size and coating morphology by means of X-ray diffraction analysis, scanning electron microscopy and transmission electron microscopy, respectively. The results indicate that the sprayed TiO₂ coatings were composed of both TiO₂ phases, namely anatase and rutile with different phase content and crystallite size. A high anatase content of 80% by volume was achieved at 0.00015 fuel to oxygen ratio with nanostructure coating by grain size smaller than feedstock powder.

It is found that fuel to oxygen ratio strongly influenced on temperature and velocity of particles in stream jet consequently on phase transformation of anatase to rutile and their crystallite size and by optimizing the ratio which can promote structural transformation and grain coarsening in coating.