量子点环嵌入Aharonov-Bohm干涉器中电子的退耦合态及反共振现象

采用Anderson模型哈密顿量和非平衡态格林函数方法对量子点环以不同构型嵌入A-B干涉器中电子输运的退耦合态及反共振现象进行了理论研究. 结果表明,量子点环A-B干涉器的结构对称性以及穿过A-B干涉器的磁通量是诱发退耦合现象的两种物理机理. 耦合量子点结构的对称性越高,体系在相干电子输运过程中表现出来的退耦合及反共振现象越明显. 而且在具有高度对称性的耦合量子点结构中,通过磁场调节体系的结构参数可以分别使第奇数或第偶数分子本征态从电极上退耦合,从而使电子输运电导表现出奇偶对等振荡现象. 这为设计纳米电子开关器件提供了一个新的物理模型. 关键词： 量子点环 A-B干涉器 退耦合 反共振     

利用电光相位调制和交叉相位调制制作时间透镜的实验及仿真分析

对时间成像理论进行简要研究. 利用电光相位调制器进行光脉冲压缩实验,并分别对基于电光相位调制和交叉相位调制的时间透镜组成的时间成像系统进行了仿真和讨论. 实验结果表明,基于电光相位调制的时间透镜组成的时间成像系统可以有效压缩光脉冲,但是该系统受到了孔径限制,压缩系数较小,分辨率较低. 进一步的仿真分析结果表明,基于交叉相位调制的时间透镜组成的时间成像系统不受孔径限制,能够获得更大的压缩系数和更高的分辨率,但是该系统的实现难度较大. 关键词： 光脉冲压缩 时间透镜 电光相位调制 交叉相位调制     

Determinants of the structured and structureless green emissions of ZnO

Green emission can be identified as either a structured or a structureless emission. In the downward surface band bending region, the influence of defects on the continuous change in the 0-0 electronic transition was found to be a dominating factor that differentiates the characteristics of green emission. Such a change in the 0-0 electronic transition gives rise to the structureless green emission at higher energy, while the 0-0 electronic transition in the bulk of ZnO plays an important role resulting in structured green emission with lower energy.     

Application of a broadband blue laser diode to trace NO2 detection using off-beam quartz-enhanced photoacoustic spectroscopy

We applied for the first time, to our knowledge, broadband off-beam quartz-enhanced photoacoustic spectroscopy (BB-OB-QEPAS) to trace NO2 detection using a broadband blue laser diode centered at 450?nm. A detection limit of 18?ppbv (parts in 10(9) by volume) for NO2 in N2 at atmospheric pressure was achieved with an average laser power of 7?mW at a 1?s integration time, which corresponds to a 1?σ normalized noise equivalent absorption coefficient of 4.1×10(-9) cm(-1)?W=Hz(1=2). An Allan variance analysis was performed to investigate the long-term stability of the BB-OB-QEPAS-based NO2 sensor.     

Phase singularity of surface plasmon polaritons generated by optical vortices

We demonstrate an experimental result that shows the phase singularity of surface plasmon waves generated by the direct transform of optical vortices at normal incidence focused on a structureless metal surface. The near-field two-dimensional intensity distribution near the focal plane is experimentally examined by using near-field scanning optical microscopy and shows a good agreement with the finite-difference time-domain simulation result. The experimental realization demonstrates a potential of the proposed excitation scheme to be reconfigured locally with advantages over structures milled into optically thick metallic films for plasmonics applications involving plasmonic vortices.     

Self-consistent treatment of spin and magnetization dynamic effect in spin transfer switching

The effect of itinerant spin moment (m) dynamic in spin transfer switching has been ignored in most previous theoretical studies of the magnetization (M) dynamics. Thus in this paper, we proposed a more refined micromagnetic model of spin transfer switching that takes into account in a self-consistent manner of the coupled m and M dynamics. The numerical results obtained from this model further shed insight on the switching profiles of m and M, both of which show particular sensitivity to parameters such as the anisotropy field, the spin torque field, and the initial deviation between m and M.     

A model for simulation of crowd behaviour in the evacuation from a smoke-filled compartment

The modelling of crowd evacuation from a building has been studied over the past decades. In this study, a numerical model based on cellular automaton is proposed to simulate the human behaviour termed “flow with the stream” in emergency evacuation from a large smoke-filled compartment. In the model, the smoke effect in the context of visibility is considered since visibility range can affect the human behaviour significantly. To simulate the reality that the smoke concentration in a fire compartment is not constant, the proposed model is developed to deal with the scenario in which the visibility range varies in the course of time. An empirical formula is incorporated into the proposed model to estimate the visibility range. The results of numerical tests show that the proposed model can also be used to investigate the effect of the number of guiders through case study.     

自然的改进型节点电压方程

通过对节点导纳矩阵的进一步分析,得出节点电压方程一种新的形式,用节点电压方程能够直观地从电路图直接绘制出信号流图而不需列写KCL,KVL和器件方程.类似的,通过圈阻抗矩阵的分析,也得到了新形式的圈电流方程.     

Rectifying and photovoltage characteristics of Bi<Subscript>2</Subscript>Sr<Subscript>2</Subscript>Co<Subscript>2</Subscript>O<Subscript>y</Subscript>/Nb-doped SrTiO<Subscript>3</Subscript> heterojunction

A heterojunction was fabricated by growing a layer of Bi₂Sr₂Co₂O _y thin film on the 0.7 wt% Nb-doped SrTiO₃ substrate. Such heterojunction showed good rectifying characteristics over a wide temperature range, and its transport mechanism under the forward bias can be attributed to a space charge limited conduction mechanism via defects near the interface of the heterojunction. Photovoltaic properties of the heterojunction were studied by using both continuous-wave and pulsed irradiations and the results can be well explained by the photovoltaic effect of a p–n junction.     

A Note on Large Rainbow Matchings in Edge-coloured Graphs

A rainbow subgraph in an edge-coloured graph is a subgraph such that its edges have distinct colours. The minimum colour degree of a graph is the smallest number of distinct colours on the edges incident with a vertex over all vertices. Kostochka, Pfender, and Yancey showed that every edge-coloured graph on n vertices with minimum colour degree at least k contains a rainbow matching of size at least k, provided ${n\geq \frac{17}{4}k^2}$ . In this paper, we show that n ≥ 4k ? 4 is sufficient for k ≥ 4.