Small and high-density GeSiC dots stacked on buried Ge hut-clusters in Si

Self-assembled GeSiC dots stacked on a Ge hut-cluster layer buried in Si have been investigated. The critical thickness for formation of GeSiC dots is reduced owing to the strain fields from the buried hut-clusters. By utilizing the stacked structure, the dot size is decreased and the uniformity is improved. The highest density of the GeSiC dots with stacked structures is 7.4×10¹⁰ cm⁻², which is six times larger than that of single GeSiC dots. The formation of the self-assembled GeSiC dots is strongly influenced by being stacked with buried Ge dots as well as C incorporation.     

Ergodic isospectral theory of the Lax pairs of Euler equations with harmonic analysis flavor

Isospectral theory of the Lax pairs of both 3D and 2D Euler equations of inviscid fluids is developed. Eigenfunctions are represented through an ergodic integral. The Koopman group and mean ergodic theorem are utilized. Further harmonic analysis results on the ergodic integral are introduced. The ergodic integral is a limit of the oscillatory integral of the first kind.

     

Dynamical significance in alkali metasilicate glasses

In this work, we elucidate the effect of the less mobile ions on the dynamics of the more mobile ions by molecular dynamics simulations of lithium ions motion in lithium metasilicate glass by freezing some randomly chosen lithium ions (5%, 10% and 25%) at their initial locations at 700 K. A remarkable slowing down of the dynamics of the majority mobile Li ions was observed both in the self-part of the density–density correlation function, F_s(k,t), and in the diffusion coefficients. On the other hand, there is no significant change in the structure. These results show many similarities to the mixed alkali effect (MAE) with mixing of the small content of foreign alkali (10% and 25% of K₂O), where large reduction of the dynamics was also observed in both experiments and MD simulations. This immobilization of faster ions causes the large MAE as already discussed in relation to the mechanism of the cooperative ion jump motions. Although of lesser importance, the ion dynamics are influenced by the matrix of oxygen atoms, because the jump motions of Li ions are assisted by the localized motions of oxygen atoms.     

Assessment of two‐equation turbulence modelling for high Reynolds number hydrofoil flows

This paper presents an evaluation of the capability of turbulence models available in the commercial CFD code FLUENT 6.0 for their application to hydrofoil turbulent boundary layer separation flow at high Reynolds numbers. Four widely applied two‐equation RANS turbulence models were assessed through comparison with experimental data at Reynolds numbers of 8.284×106 and 1.657×107. They were the standard k–εmodel, the realizable k–εmodel, the standard k–ωmodel and the shear‐stress‐transport (SST) k–ωmodel. It has found that the realizable k–εturbulence model used with enhanced wall functions and near‐wall modelling techniques, consistently provides superior performance in predicting the flow characteristics around the hydrofoil. Copyright © 2004 John Wiley & Sons, Ltd.     

Experimental investigation and theoretical modeling of liquid entrainment in a horizontal tee with a vertical-up branch

This article describes a comprehensive literature review of liquid entrainment in horizontal pipes with vertical-up branches. Deficiencies in the available data and correlations were identified. The Air–water Test Loop for Advanced Thermal–hydraulic Studies (ATLATS) was constructed and entrainment onset and steady-state data were collected for a wide range of flow conditions. Using new insights gained from experimental testing, the authors developed a model for predicting the onset of entrainment and steady-state entrainment rate. Previously published correlations, along with the new model, are compared against all available data. The new model shows very good agreement with the onset data, but is not very good at predicting branch quality at high liquid flow rates.     

Fast Si magic-angle-spinning NMR acquisitions by RAPT-CP Al → Si polarization transfer

Using enhancement of the ²⁷Al central-transition magnetization by applying RAPT prior to ²⁷Al → ²⁹Si cross-polarization, we demonstrate fast acquisition of ²⁹Si one-dimensional MAS and two-dimensional ²⁷Al–²⁹Si HETCOR spectra on a new sialon phase Ba₂Al₃Si₉N₁₃O₅.     

Decay kinetics of the green emission in tungstates and molybdates

Luminescence characteristics of a number of undoped and variously doped PbWO₄ crystals were studied at 0.4–400 K by the time-resolved spectroscopy and compared with those of ZnWO₄,CdWO₄ and PbMoO₄ crystals. Two types of green emission centres are detected in PbWO₄ crystals. The centres of the first type are responsible for the low-temperature 2.3–2.4 eV emission observed under excitation around 3.90–3.95 eV. The structure and parameters of their relaxed excited states were determined. It was concluded that the origin of defects responsible for the green emission of the first type could vary for different crystals. The centres of the second type with the emission around 2.5 eV appear in crystals containing oxygen vacancies after the thermal destruction of Pb⁺-WO₃ centres at T>180 K. Decomposition of the exciton and various defect-related states was also studied, and activation energies of this process were calculated.     

Rare earth photoionization study by the resonant microwave cavity technique

Photoconductivity spectra of rare earth-doped insulating materials are measured using the resonant microwave cavity method. This technique is based on the detection of the cavity Q-factor changes induced by irradiation of the sample (inserted in the cavity) by a pulsed tunable laser. Results obtained with Lu₂(SiO₄)O:Ce³⁺ and BaF₂:Eu²⁺ are presented and discussed. Photoionization thresholds at 400 nm (3.1 eV) and 310 nm (4.0 eV) are measured for Lu₂(SiO₄)O:Ce³⁺ and BaF₂:Eu²⁺, respectively.     

Status of heavy element research using a gas-filled recoil separator at RIKEN

A gas-filled type of recoil separator for heavy element research was installed at an experimental hall of RIKEN Linear Accelerator facility to realize getting higher intensity of primary beam and long beam time. Performance of the separator was studied using target recoils and various nuclear reactions. The results show the high performance of the separator for heave element research. As an application of the GARIS, production and identification of an isotope of the 110th element ²⁷¹[110] have been performed using the ²⁰⁸Pb(⁶⁴Ni,1n)²⁷¹[110] reaction. Three decay chains coincide well both in decay times and energies with the ones reported by the group of SHIP experiment at GSI, Germany. Our results provide a confirmation of the synthesis of an isotope ²⁷¹[110] of element 110.