双δ掺杂In0.65Ga0.35As/In0.52Al0.48As赝型高迁移率晶体管材料子带电子特性研究

研究了基于InP基的In0.65Ga0.35As/In0.52Al0.48As赝型高迁移率晶体管材料中纵向磁电阻的Shubnikov-deHaas(SdH)振荡效应和霍耳效应,通过对纵向磁电阻SdH振荡的快速傅里叶变换分析,获得了各子带电子的浓度,并因此求得了各子带能级相对于费米能级的位置.联立求解Schrdinger方程和Poisson方程,自洽计算了样品的导带形状、载流子浓度分布以及各子带能级和费米能级位置.理论计算和实验结果很好符合.实验和理论计算均表明,势垒层的掺杂电子几乎全部转移到了量子阱中,转移率在95%以上.     

“Positive” and “negative” electric-pulse-induced reversible resistance switching effect in Pr<Subscript>0.7</Subscript>Ca<Subscript>0.3</Subscript>MnO<Subscript>3</Subscript> films

“Negative” electric-pulse-induced reversible resistance (EPIR) switching phenomenon was found in In/PCMO/Pt sandwich, in which the high resistance can be written with positive voltage pulses, and the low resistance can be reset using negative voltage pulses (the positive voltage direction is defined as going from the top electrode to the bottom electrode). This is just the opposite from the “positive” EPIR effect in Ag/PCMO/Pt sandwich, in which the high resistance can be written only with negative voltage pulses, and the low resistance can be reset using positive voltage pulses. The I–V hysteresis curves of In/PCMO/Pt and Ag/PCMO/Pt sandwiches also show opposite directions, i.e., counterclockwise and clockwise under a negative voltage region for indium and Ag electrode systems, respectively. C–V characteristics show that the barrier does not exist in Ag/PCMO/Pt sandwich, while In/PCMO/Pt sandwich exhibits an obvious Schottky-like barrier. We suggest that in the negative EPIR behavior in In/PCMO/Pt structure, the resistance states are mainly controlled changing the Schottky-like barrier at the interface with the weak effect of carrier trapping process, while the positive EPIR behavior in Ag/PCMO/Pt sandwich mainly depends on the carrier trapping process at the interface. PACS 72.80.-r; 73.40.-C; 75.70.-i     

X射线CCD标定及模拟

 在北京同步辐射光源4B7B实验站上,采用透射光栅配X射线电荷耦合元件(CCD)的方法对单色光进行了检验,在优化高次谐波抑制方法后,开展了X射线CCD的灵敏度标定实验研究;在标定数据处理过程中,提出了等效曝光时间的概念,修正了快门开合造成的曝光时间误差。标定实验获得了100~1 500 eV能区CCD的灵敏度,补充了300~600 eV能区CCD灵敏度标定数据,验证了简化模型的正确性。     

A full-duplex radio-over-fiber link with 12-tupling mm-wave generation and wavelength reuse for upstream signal

A full-duplex radio-over-fiber (RoF) link with a novel scheme to generate 60 GHz mm-waves from a 5 GHz RF signal source is investigated. In the RoF downlink, the required frequency of the RF oscillator is reduced greatly. Since the optical carrier is not modulated by downstream data, part of it is reused to carry upstream data and the upstream data is transmitted to the central station using optical single-sideband modulation. In this way, a single wavelength is used for both downstream and upstream transmissions. Based on this scheme, a full-duplex RoF link is built and its transmission performance is analyzed. Theoretical analysis and numerical simulation show that the downstream signal cannot only eliminate code form distortion caused by time shift of the code edges, but also reduce the influence of the fading effect as the 60 GHz DSB optical mm-wave signal is transmitted along the fiber, and the upstream signal is immune to both fading effect and time shift of the code edges.     

The global responses characteristics of a rotor/stator rubbing system with dry friction effects

Rotor/stator rubbing systems may undertake a number of quite different responses. Recent experiments on rotor/stator rubbing have revealed that two or three different responses may coexist. In this paper the global response characteristics of a general rotor/stator rubbing system, which takes into account the dominant factors in the process of rotor/stator rubbing, especially, the dry friction effect that is mostly neglected in the previous works and is the main factor for the self-excited dry friction backward whirl, are studied. The different solutions of the piecewise nonlinear system are derived and their stability are analyzed to get the existence boundaries of the different responses. An overall picture of the global response characteristics of this model is then obtained by drawing the existence boundaries in a same parameter space. The present results provide good understanding on the coexistence of different rubbing responses observed in tests. Moreover, deeper insight into the types of coexistence of different rubbing responses and their relationship with the system parameters is gained.     

用方差定义的激光束横向尺寸的测量

用方差定义的激光束横向尺寸,有着普适、简单和便于利用光学元件并行运算功能的特点.本文提出一种借助改变柱形容器内吸收液浓度来直接测量各种波长激光束横向尺寸的理论和方法.     

非线性光纤方向耦合器孤子动力特性分析

利用变分方法,导出了双曲正割型光孤子在非线性光纤耦合器中传输时满足的动力学方程组,分析了该方程组的平衡点性态,讨论了光孤子的开关特性.指出参数|β|<2π.是能实现完全的开关操作的必要条件.     

Scanning moiré and phase shifting with time delay and integration imaging

Scanning moiré is generated by undersampling of a phase-modulated grating pattern. In projection profilometry the scanning moiré pattern represents equal height and depth contours on a test object. By use of time delay and integration (TDI) imaging, it is possible to generate an on-line scanning moiré pattern from the complete periphery of a rotating cylindrical object. For automated phase and profile unwrapping from scanning moiré fringes, phase-shifting interferometry techniques are most desirable. However, lack of spatial information in the undersampled scanning moiré fringes introduces serious errors in phase unwrapping. We report a method that uses oversupply of data to balance the effect of undersampling. This oversupply is achieved with a TDI feature that permits programmable image magnification in the scanning direction.     

Development of Central Collective Flow in 100MeV/u Au+Au Central Collisions

Using QMD model the time evolution of Au+Au system at 100MeV/u is studied.For very central collisions the conditions for freeze-out and how the different physical quantities approaching equlibrium are investigated.The calculated results show that for 100MeV/u Au+Au at b=0fm,the maximum density can reach 1.6ρ₀ and after that the system expands to a low density region.A position correlated central flow is developed during the expansion stage.By studying the two pamicle reladve momentum spectrum it is able to separate central flow from random thenmal motion.The dependence of this central flow on E.O.S.is also discussed.     

两等同双能级原子与q模腔场任意N∑光子共振相互作用辐射谱研究

本文建立了“q模腔场-两原子”系统的任意N^∑光子相互作用模型,利用这一模型研究了两个偶极一偶极力关联的等同双能级原子与q模腔场任意N^∑光子.共振相互作用的辐射谱.对q模腔场分别处于不同数态:即q模腔场均为真空场、q模腔场均为强场、1模为真空场(q-1)模为强场、q₀模为真空场(qq₀)模为强场、以及(q-1)模为真空场1模为强场时辐射谱的结构持征及物理特性进行了详细分析,揭示出“q模腔场-两原子”系统任意N^∑光子共振相互作用辐射谱的一般特征.现有文献报道,仅仅是本文的普遍性结果在各种不同情况下的特例.