Evidence for two energy levels associated with EL2 trap in GaAs

By photocapacitance technique, applied to n-type LEC-grown GaAs, two energy levels:E _v +0.45 eV andE _c –0.75 eV are identified, for the first time, as being associated with the EL2 trap. As follows from the analysis of photo-EPR results on highly resistive GaAs crystals, the same energy levels can be attributed to the arsenic antisite defect, As_GA. In view of these findings, it is argued that the occupied EL2 level corresponds to the neutral charge state of As_Ga defect.     

A transient process observation method based on the non-homogeneous Poisson process model

The current-mode-counting method is a new approach to observing transient processes,especially in transient nuclear fusion,based on the non-homogeneous Poisson process(NHPP)model.In this paper,a new measurement process model of the pulsed radiation field produced by transient nuclear fusion is built based on the NHPP.A simulated measurement is performed using the model,and the current signal from the detector is obtained by simulation based on Poisson process thinning.The neutron time spectrum is reconstructed and is in good agreement with the theoretical value,with its maximum error of a characteristic parameter less than 2.3%.Verification experiments were carried out on a CPNG-6 device at the China Institute of Atomic Energy,with a detection system with a nanosecond response time.The experimental charge amplitude spectra are in good agreement with those obtained by the traditional counting mode,and the characteristic parameters of the time spectrum are in good agreement with the theoretical values.This shows that the current-mode-counting method is effective for the observation of transient nuclear fusion processes.     

New scaling law based on the hydrodynamical model of particle production

It is shown that Landau's hydrodynamical model of particle production accounts for many features of pion production in proton-proton collisions observed in recent experiments. A new energy-dependent scaling is proposed, in terms of which the distribution of secondaries at various energies falls on a universal curve having no adjustable parameters.     

Music separation method based on repeating structural model and sound source separation

In order to solve the problem of separation between singing and accompaniment in the musical signals,a music separation method based on repeating structural mod...     

A note on the pressure dependence of the EL2 level in Gallium Arsenide

Various experiments involving the application of hydrostatic pressure and uniaxial stress to the EL2 level in Gallium Arsenide are compared with a 4 × 4 Impurity Superlattice Model. This is used to study the pressure dependence of the unoccupied level and verifies that it does indeed follow the conduction band edge as observed in photocapacitance. It also supports the view that the seperation from the conduction band with pressure of EL2 observed in transient capacitance is due in large part to the pressure dependence of the Franck-Condon shift. It is noted that as compared with Ga_1?xAl_xAs in the appropriate range of x, the variation of the level with pressure is approximately correct and that it would seem that the frequently-made analogy between alloying and pressure dependence is justified here.     

New structural picture of the Ge2Sb2Te5 phase-change alloy

Using electron microscopy and diffraction techniques, as well as first-principles calculations, we demonstrate that as much as 35% of the total Ge atoms in the cubic phase of Ge2Sb2Te5 locate in tetrahedral environments. The Ge-vacancy interactions play a crucial stabilizing role, leading to Ge-vacancy pairs and the sharing of vacancies that clusters tetrahedral Ge into domains. The Ge2Sb2Te5 structure with coexisting octahedral and tetrahedral Ge produces optical and structural properties in good agreement with experimental data and explains the property contrast as well as the rapid transformation in this phase-change alloy.     

A deterministic model of impact noise transmission through structural connections based on modal analysis

Vibration transmission through structural connections is modelled in a deterministic way by means of modal analysis. This model is used first to study the effect of elastic joints across the floor in the transmission of impact noise. They are an effective means of reducing impact noise propagation, and can almost eliminate it for small values of the joint stiffness. The method is also used to study the acoustic relevance of studs in lightweight floor transmission. Different ways of modelling the studs are presented and compared. For the examples developed, the best option is to use springs for modelling the studs rather than more complex models involving springs and beams. Also the different behaviour of point and line connections is verified, as well as the influence of the position of the studs.     

An implementation of structural change detection procedure based on experimental and numerical model correlation

A correlation of the experimental and the numerical model is implemented in order to detect structural change. The implementation of the method involves two steps: in the first the respective location is detected, and in the second the structural change is quantified. The method can detect changes in mass, stiffness or both. The numerical simulations demonstrate that the method is accurate and reliable. The method is implemented analytically and experimentally in parallel with laboratory test-cases. Improvements of the procedure are suggested and implemented in order to study the applicability to real-world cases. This study shows that model update significantly contributes to the successful structural change detection. The influence of the model reduction and model update on the detection accuracy is studied.     

Can we explain the coexistence of ferromagnetism and superconductivity based on two parameters model?

A possible explanation about the coexistence of ferromagnetism (FM) and superconductivity (SC) based on a two parameters mean field model in a two-dimensional system is discussed. The key feature of this model is that there are two independent parameters which are responsible for ferromagnetism and superconductivity, respectively. We point out that the coexisting FM and s-wave pairing SC state is energetically not favorable among all possible state. We generalize the two parameter model to include the coexistence of FM with p-wave SC. We find that the phase diagram is not consistent with what experimentally discovered in UGe₂.     

金属/有机界面势垒对单层有机电致发光器件发光效率的影响

基于高场下电荷的注入过程及激子的解离和复合过程,建立了单层有机发光器件电致发光(EL)效率的理论模型。计算表明：(1)当金属／有机界面势垒高度大于0．3eV时,器件的EL效率很低,降低金属／有机界面势垒可以显著提高器件的EL效率;(2)在较低偏压下,注入过程对器件的电致发光效率起主要作用,但在高偏压下复合过程起支配作用。这一模型可以阐明注入和复合过程对有机发光器件EL效率的影响,对选择发光材料、优化器件结构和提高器件EL效率具有指导意义。