Modern Physics Letters B

Recent experimental works of mono-disperse particles flowing in two-dimensional hoppers and silos under gravity are reviewed. Three steady flow states, namely, dilute flow, dense flow and jammed flow, have been observed. The transitions between these steady flow states can be triggered as the particle inflow rate or the exit size is changed. It is found that the transition between the dilute flow and the dense flow states is hysteristic while that between the dense flow and the jammed states is stochastic. Although all these transitions are initiated near the exit, experimental data for the flow rate at the dilute-to-dense transition depends on the system size (width) of the silo, showing the global nature of the dilute-to-dense transition. On the other hand, the statistics (number of particles flowing through the hopper or silo before jamming) measured in dense-to-jammed transition implies a Markovian jamming process. Using the probability of arch formation at the exit, the exit size dependence of the jamming probability can be analyzed by treating the arch as the trajectory of a random walker.

The investigation on the oxidation behavior of Si_1-xGe_x alloys (x=0.05, 0.15 and 0.25) is carried out. It is found for the first time that on the oxide film a germanium nano-cap with a thickness of 1.8~2.8 nm and a few Ge nanoparticles with diameters ranging from 5.5 nm to 10 nm are formed by rapid oxidation of Si_1-xGe_x substrate. A new scanning method on the decline cross-section of the multiple layer sample is adapted to measure the layer thickness and the composition. Some new peaks in photoluminescence (PL) spectra are discovered, which could be related to the nano-cap and the nanoparticles of germanium. A suitable model and several new calculating formulas with the unrestricted Hartree–Fock–Roothaan (UHFR) method and quantum confinement analysis are proposed to interpret the PL spectra and the nano-structure mechanism in the oxide.

Polycrystalline aluminium nitride (AlN) films were deposited on silicon substrates by pulsed laser deposition (PLD) at a substrate temperature in the range room temperature (RT)-800°C. Films grown on Si(111) substrates feature (002) and (110) preferred orientations at substrate temperatures below 400°C and above 600°C, respectively. Films morphology is good enough for surface acoustic wave (SAW) devices. The mechanism for formation and transformation of different preferred orientations in AlN films is discussed.

The effect of niobium doping on the structure and electrical properties with the following compositions Pb(Zr_0.52Ti_0.48)_1-5X/4Nb_XO₃ with 0<x<0.025 was investigated. The materials were prepared by the usual ceramic technique using high purity raw materials. Disc-shaped samples of each compositions were sintered at 1250°C for 3 hours. The sample structure was determined by X-ray diffractometry. The average grain size, the maximum dielectric permittivity and the remnant polarization first increases up to x = 0.005 concentration of Nb⁵⁺ and then decreases with higher concentration of niobium, while the coercive field does not show any variation. The transition temperature decreases with the increase in niobium concentration.

We investigate the possible angular momentum, l, dependence of the ground state energy of normal liquid ³He. The method of lowest order constrained variational (LOCV) which includes the three-body cluster energy and normalization constraint (LOCVE) is used with angular momentum dependent two-body correlation functions. A functional minimization is performed with respect to each l-channel correlation function. It is shown that this dependence increases the binding energy of liquid ³He by 8% with respect to calculations without angular momentum dependent correlation functions. The l=0 state has completely different behavior with respect to other l-channels. It is also found that the main contribution from potential energy comes from the l=1 state (p-waves) and the effect of l≥11 is less than about 0.1%. The effective interactions and two-body correlations in different channels are being discussed. Finally we conclude that this l-dependence can be verified experimentally by looking into the magnetization properties of liquid helium 3 and interatomic potentials.

We investigate the mutual information and entanglement of stationary states of two locally driven qubits under the influence of collective dephasing. It is shown that both the mutual information and the entanglement of two qubits in the stationary state exhibit damped oscillation with the scaled action time γT of the local external driving field. It means that we can control both the entanglement and total correlation of the stationary state of two qubits by adjusting the action time of the driving field. We also consider the influence of collective dephasing on the entanglement of two qutrits and obtain the sufficient condition that the stationary state is entangled.