Modern Physics Letters B

This paper reviews experimental and modeling efforts aimed at the determination of the shear viscosity of strongly-coupled Yukawa liquids. After briefly reviewing prior work on three-dimensional (3D) systems, recent experimental and computer simulation studies of two-dimensional (2D) settings are presented in detail. In the experiments two counterpropagating laser beams were used to perturb a dusty plasma monolayer and monitoring of the velocity field reconstructed from particle trajectories allowed the determination of the shear viscosity with the aid of an analytical model. Subsequent computer simulations based on the molecular dynamics approach resulted in velocity profiles which are in very good agreement with the experimental ones. Further simulation studies of idealized 2D Yukawa liquids (in which gas friction is neglected) gave results for the shear viscosity over a wide range of system parameters and demonstrated the existence of the shear thinning effect (non-Newtonian behavior) of the liquid at high shear rates.

We have investigated the influences of the heating rate and film thickness on the growth of GdBa₂Cu₃O_y (GBCO) thin films prepared by the BaF₂ex-situ process without water vapor. Critical current density (J_c) and surface morphology of the GBCO films were improved by increasing the heating rate during growth from 30 to 50°C/min. The GBCO films prepared by the heating rate of 50°C/min had the maximum J_c of 2.1 MA/cm². The J_c value of the GBCO films was about 2 MA/cm² up to 200 nm, and decreased to 0.92 MA/cm² at 400 nm.

In this paper, we study the elementary excitations and energy spectrum proposed by L. D. Landau in liquid helium II. On the basis of the energy spectrum for the phonons and rotons, we put forward a uniform expression of energy spectrum in liquid helium II, which is limited in a specific temperature range. By using the wave function for low energy excited states proposed by R. P. Feynman or the modified one proposed by Feynman and Cohen, it can be found that the estimated energy spectrum is quite different from the experimental data, especially for the region with large wave numbers. By proposing an improved form for the wave function, we re-analyze the energy spectrum in liquid helium II, and our results show a better agreement with the experimental data.

The near-stoichiometric In:Fe:LiNbO₃ crystals (In:Fe:SLN) were grown by the TSSG technology for the first time. The infrared spectra and the photo-scattering resistance ability were measured. The threshold concentration of In³⁺ decreased to 2 mol% from 3 mol% of the congruent In:Fe:LiNbO₃(In:Fe:CLN) crystal. The mechanism of OH^- absorption peak shift was studied with the infrared spectra. The diffraction efficiency, writing time and erasure time were studied by using the two-wave coupling method, and the photorefractive sensitivity and dynamic range were calculated. The comprehensive indexes of the photorefractive properties of In:Fe:SLN crystals were superior to those of Fe:LN and In:Fe:CLN crystals. The In:Fe:SLN crystal was used as the storage material and the relative recognition of photorefractive volume holographic images was first realized with the material and good results were obtained.

In this paper, we studied four-electron systems confined in one-, two-, and four-layer quantum dots, by the exact diagonalization method. A vertical magnetic field to the confinement plane is considered. The ground-state electronic structures and the spin and angular momentum transitions for different magnetic fields are investigated. Series of magic numbers of angular momentum which minimize the ground-state electron–electron interaction energy have been discovered. These are connected to the exchange and rotational symmetries of the systems.

In this work, the simultaneous effect of mechanical tension (σ) and electrical strength (E) on electrical lifetime (τ_E) for pure low density polyethylene (LDPE)/polypropylene (PP) and composites with different commercial diamond-additive/glass fiber additive percentages is experimentally studied. The role of this effect on degradation mechanisms is investigated. logτ_E,σ-f(E) and E_σ-f(σ) graphs are drawn, new equations are proposed and determined parameters at constant temperature for pure LDPE and PP, and for optimum composites (LDPE/0.5% diamond, PP/0.5% glass fiber) are listed. The results indicate that the degradation speed decreases more for composites than for pure LDPE and PP. The electrical durability for composites after the simultaneous effect of σ decreases 18–20%, while for pure LDPE and PP, it decreases 50–55%.

Active powder of Cu-substituted Mn-Zn ferrite was synthesized by soft chemical approach called co-precipitation method. The initial permeability, density, grain size, Curie temperature and dc resistivity were studied. X-ray diffraction (XRD) method confirmed the sample to be a single-phase spinel and of nano-structure (~ 65 nm). Further, scanning electron micrograph (SEM) also confirmed nano-phase and the uniformity of the particles. The initial permeability values did not exhibit much variation with temperature, except near Curie temperature where it falls sharply. The initial permeability was found to increase with the increase in sintering temperature. This is attributed to the increase in the grain size.

The present work is aimed at studying the effect of phosphorus addition on physical and electrical properties of tantalum powder. Tantalum anodes were compacted from tantalum powder, which were doped with different concentrations of phosphorus in the form of phosphoric acid. Anodes were sintered at 1550°C for 30 min. Properties such as density, microstructure, CV (capacitance times voltage constant) and DC leakage were studied. Significant improvement in electrical properties was observed, results of which are presented here.