Von Neumann Entropy of an Electron in One-Dimensional Determined Potentials

By using the measure of von Neumann entropy, we numerically investigate quantum entanglement of an electron moving in the one-dimensional Harper model and in the one-dimensional slowly varying potential model. The delocalized and localized eigenstates can be distinguished by von Neumann entropy of the individual eigenstates.There are drastic decreases in von Neumann entropy of the individual eigenstates at mobility edges. In the curve of the spectrum averaged von Neumann entropy as a function of potential parameter λ, a sharp transition exists at the metal-insulator transition point λc = 2. It is found that the von Neumann entropy is a good quantity to reflect localization and metal-insulator transition.     

强$J$-Semiclean环

We in this note introduce a new concept, so called strongly J-semiclean ring, that is a generalization of strongly J-clean rings. We first observe the basic properties of strongly J-semiclean rings, constructing typical examples. We next investigate conditions on a local ring R that imply that the upper triangular matrix ring T_n(R) is a strongly J-semiclean ring. Also,the criteria on strong J-semicleanness of 2 × 2 matrices in terms of a quadratic equation are given. As a consequence, several known results relating to strongly J-clean rings are extended to a more general setting.     

扩压器几何参数对离心风机噪声的影响

本文试验研究了扩压器几何参数对一高速离心风机的噪声的影响。扩压器的几何参数包括叶片数、叶轮与扩压器的径向间隙和倾斜前缘倾角以及它们的耦合作用对风机噪声的影响。试验结果表明:(1)风机A声级噪声随扩压器叶片数增加而下降,但气动性能也随之下降;(2)扩压器前缘半径从R_3/R_2=1.03增加到1.07,在设计点风机A声级噪声降了约3 dB(A),继续增大至1.09则基本不变;(3)适当倾斜扩压器前缘可有效降低风机噪声,在设计点30°倾角扩压器相应的风机A声级噪声下降了约3.6 dB(A);(4)倾斜扩压器前缘与增大径向间隙的降噪效果不能叠加。     

Study on the pre-chopper in CSNS LEBT

Physical designing of the pre-chopper in CSNS LEBT is carried out, which includes the deflecting voltage, the length and the width of the deflecting plates, and the gap between the deflecting plates. The most outstanding feature of the design is that both the gap and the width vary with the beam envelope size. So both the requried deflecting voltage and the loaded capacitance are lowered. In order to avoid destruction of the space charge neutralization by the pre-chopper in the whole LEBT, an electron-trapping electrode is arranged to confine the electrostatic field of the pre-chopper to the local area. To examine the reliability of the pre-chopping design in CSNS LEBT, a similar pre-chopping design in ADS RFQ LEBT is set up and an experiment on the pre-chopper is prepared. 3-dimensional simulations are carried out to determine the loaded capacitance and the applied voltage of the electron-trapping electrode.     

一种基于决策矩阵的DST-AHP多属性决策方法

针对层次分析法决策时存在两两判断、一致性检验次数过多和判断矩阵残缺性等问题,本文提出了一种基于决策矩阵的DST-AHP多属性决策方法。该方法结合决策矩阵的特征值,构建DST-AHP方法层次结构模型和判断矩阵,并根据判断矩阵定义不同属性下各焦元的基本概率分配函数;然后利用Dempster合成法则对基本概率分配函数值进行合成,依据合成后值对方案进行排序。最后对AHP和DST-AHP两种方法进行比较分析,说明该方法的有效性。     

Spin-Dependent Electron Properties of a Triple-Terminal Quantum Dot Structure

Electron transport properties of a triple-terminal Aharonov-Bohm interferometer are theoretically studied. By applying a Rashba spin-orbit coupling to a quantum dot locally, we find that remarkable spin polarization comes about in the electron transport process with tuning the structure parameters, i.e., the magnetic flux or quantum dot levels. When the quantum dot levels are aligned with the Fermi level, there only appear spin polarization in this structure by the presence of an appropriate magnetic flux. However, in absence of magnetic flux spin polarization and spin separation can be simultaneously realized with the adjustment of quantum dot levels, namely, an incident electron from one terminal can select a specific terminal to depart from the quantum dots according to its spin state.     

Linear Analysis of Folded Double-Ridged Waveguide Slow-Wave Structure for Millimeter Wave Traveling Wave Tube

A novel slow-wave structure （SWS）, the folded double-ridged waveguide structure, is presented and its linear gain properties are investigated. The perturbed dispersion equation is derived and the small signal growth rate is caleulated for dimensions of the ridge-loaded region and the parameters of the electron beam. The novel structure has potential applications in the production of high power and broad band radiation. For a cold beam, the linear theory predicts a gain of 1.1-1.27dB/period and a 3-dB small-signal gain bandwidth of 30% in W-band. A comparison between the folded double-ridged waveguide SWS and folded waveguide SWS （FWSWS） shows that with the same physical parameters, the novel SWS has an advantage over the FWSWS on the bandwidth and electron efficiency.     

氮胁迫下水稻的激光诱导荧光光谱特性

为了指导水稻的田间施肥,解决因过量施肥造成资源的大量浪费以及环境污染,特别是水体富营养化等问题,搭建了基于紫外激光诱导荧光技术的荧光光谱探测系统,以研究水稻叶片的氮水平与荧光强度的相关性。文中先用植物营养测定仪(TYS-3N)测定水稻叶片氮含量和叶绿素含量（样本为水稻分蘖期的倒二叶,采集于中国江汉平原地区）,再用搭建的测量系统采集了不同氮水平的荧光光谱。获得了不同氮水平下水稻叶片的荧光光谱数据库,分析了荧光光谱参数F₇₄₀/F₆₈₅（为峰值740,685 nm处的荧光强度比）与氮水平的相关性,发现氮含量的变化对水稻叶片荧光光谱特性影响明显。通过该实验验证了荧光参数的峰值比F₇₄₀/F₆₈₅与氮含量呈明显的线性正相关,相关系数（r）为0.871 8,均方根误差（RMSE）为0.076 82。实验表明采用激光诱导荧光光谱探测技术具有快速无损等优点,且有一定潜力用于定量测量植被营养元素的含量,为采用荧光技术对农作物施氮管理提供了支持。     

水泥生料品质激光在线检测设备研制

水泥质量的优劣直接影响到建筑工程的安全,使用品质合格的水泥材料是保证工程结构质量的必要前提,因此快速检测水泥生料成份对于及时指导调整原料配比和保障水泥产品品质具有重要意义。传统的生料检测需要经过取样、制样、化验等环节,检测结果严重滞后于生产。我们通过产学研协同攻关,研制了一套基于激光诱导击穿光谱(laser-induced breakdown spectroscopy, LIBS)技术的水泥生料品质在线检测设备,该设备由LIBS光学检测系统和气动取送样系统两部分组成,实现了对水泥生产线上水泥生料品质的实时连续测量,避免了传统的取制样环节,从而大大缩短了化验时间,所测水泥生料成分的实时数据能够及时指导调整水泥原料的配比,保证水泥质量的合格。我们利用该LIBS水泥品质在线检测设备对水泥生产线上生料中的主成分Al₂O₃,CaO,Fe₂O₃,MgO和SiO₂进行了定量分析,利用全谱归一化和支持向量机(support vector machine,SVM)对水泥生料建立定标模型,对水泥生料中Al₂O₃,CaO,Fe₂O₃,MgO和SiO₂测量的最大误差分别是0.34%,0.35%,0.07%,0.14%和0.55%。现场实验结果表明,本水泥生料品质激光在线检测设备的测量结果与传统化验法的结果相吻合,测量精度与X射线荧光光谱法(XRF)相接近,从而证实了LIBS可以作为水泥在线检测的一种有前景的方法。     

梯形管内壁等离子体离子注入鞘层扩展MATLAB-PIC数值模拟

基于MATLAB利用Particle-in-cell模型,对梯形管内壁等离子体离子注入过程,进行了二维数值模拟.计算结果表明在中心电极附近出现了"阳极鞘层",该鞘层内部不存在离子,而且在鞘层边缘离子密度最高.在上下管壁上的离子注入剂量呈现"m"形分布.通过对注入过程中等离子体密度分布和不同时间段管壁不同位置离子注入剂量的跟踪,发现"阳极鞘层"扩展行为是导致"m"形分布的原因.由于梯形管形状的不对称性,"阳极鞘层"的边缘向梯形长底方向扩展较快.在注入初始时刻离子注入的能量很低,随着时间延长离子能量逐渐升高,这是由离子初始位置决定的.可见梯形管自身形状决定了鞘层形状和最终的离子注入能量和剂量分布.