基于高频雷达多普勒谱预测风向的一种新方法

通过高频雷达一阶多普勒谱与海上风向的关系, 提出了一种基于神经网络和多波束采样法相结合预测海面风向的新方法. 在神经网络不同输入、输出参数情况下对扩展因子为奇数时的仿真数据进行了风向预测, 并在扩展因子为偶数时结合多波束采样法进行风向预测, 消除了风向的模糊性. 通过预测数据和仿真数据对比, 发现两者符合较好. 从神经网络和多波束采样法相结合的预测结果中可以看出, 风向的误差大约为4°—6°, 风向扩展因子的平均误差为0.26, 为预测海面风场的研究提供一种新的思路和方法.     

应用于ICF实验的软X射线平面镜反射率

在北京同步辐射装置上,通过对应用于惯性约束聚变（ICF）实验的平面镜反射率的进一步研究,提高了辐射温度的测量精度。进行了对软X射线平面镜反射率的测量、反射镜的清洗、反射率的模拟计算,证明影响反射率变化的主要因素是平面镜的安装角度和沾污。实验结果表明:平面镜的沾污主要来源于ICF实验中的油沾污,采用射频辉光放电清洗非常有效。     

PbS quantum dot fiber amplifier based on a tapered SMF fiber

A PbS quantum dot coated (QD-coated) tapered fiber amplifier with a broad bandwidth is theoretically demonstrated. The QD layer is coated on the surface of a tapered fiber and is excited by the evanescent wave of a pump. An optical gain of 10.5 dB, with a 160-nm broad bandwidth of at 1530-nm center wavelength, is achieved. The gain efficiency is over 4 dB/cm. This QD-tapered fiber amplifier has a concentration control of the QDs, a lower insertion loss, and shows good suppression of amplified spontaneous emission (ASE), while its structure is also quite simple. Therefore, the proposed fiber amplifier has great potential in fiber-optic communication systems.     

Quantum information splitting of an arbitrary three-qubit state via the cavity input–output process

We propose a realizable quantum information splitting (QIS) scheme for an arbitrary three-qubit state via the cavity input–output process. In our scheme, a four-qubit cluster state and a three-qubit Greenberger–Horne–Zeilinge (GHZ) state are used as quantum channel. The sender and controller only need to perform Bell-state measurements and a single-qubit measurement, respectively. The receiver can reconstruct the arbitrary three-qubit state by classical communication and local operations. Compared with the scheme in Nie et al. [Optics Communications 284 (2011) 1457], the quantum resources and classical information in our scheme are decreased by 5 qubits and 1 bit, respectively. Moreover, we replace the W-state category measurement in the former with Bell-state measurements and a single-qubit measurement, which is more simple and feasible in experiment.     

Unique geometric and electronic structure of CO adsorbed on Ge(100): A DFT study

CO adsorption on the Ge(100) surface has been investigated using a slab model with density functional theory implemented in SIESTA. CO was found to be exclusively adsorbed on the asymmetric dimer with C attaching on the lower Ge dimer atom. The adsorption process is barrierless. The calculated adsorption energy and vibration frequencies are comparable to previous experimental results. The crystal orbital Hamilton analysis showed that the bonding between Ge and CO is mainly attributable to the Ge 4p_z orbital overlapping with C 2 s, or with CO molecular orbitals 3σ and 4σ. The repulsive energy between adsorbed CO molecules is less than 1 kcal/mol. The diffusion barrier of CO on the Ge(100) surface is about 14 kcal/mol.     

Observation of D+(s)K- and evidence for D+(s)pi- final states in neutral B decays

We report the first observation of a B meson decay that is not accessible by a direct spectator process. The channel B(0)-->D(+)(s)K- is found in a sample of 85 x 10(6) BB; events, collected with the Belle detector at KEKB, with a branching fraction B(B(0)-->D(+)(s)K-)=(4.6(+1.2)(-1.1)+/-1.3) x 10(-5). We also obtain evidence for the B0-->D(+)(s)pi(-) decay with branching fraction B(B0-->D(+)(s)pi(-))=(2.4(+1.0)(-0.8)+/-0.7) x 10(-5). This value may be used to extract a model-dependent value of |V(ub)|.     

A new method of detecting interferogram in differential phase-contrast imaging system based on special structured x-ray scintillator screen

An x-ray scintillator screen with a special structure,functioning as detector and analyser grating,was proposed for collecting the interferogram of differential phase contrast imaging without absorption grating and difficulty of fabrication by a state of the art technique.On the basis of phase grating diffraction,a detecting model of the scintillator screen was built for analysing the phase and absorption information of objects.According to the analysis,a new method of phase retrievals based on two-images and the optimal structure of screen were presented.     

使用AlN/GaN超晶格势垒层生长高Al组分AlGaN/GaN HEMT结构

在蓝宝石衬底上生长了以AlN/GaN超晶格准AlGaN合金作为势垒的HEMT结构材料,并与传统AlGaN合金势垒样品进行了对比.在高Al组分(≥40%)情况下,超晶格势垒样品的表面形貌明显改进,电学性能特别是2DEG面电子浓度也有所改进.对超晶格势垒生长参数进行了初步优化,使得HEMT结构薄层电阻进一步降低,最后获得了251 Ω/□的薄层电阻. 关键词： AlGaN/GaN 结构 AlN/GaN超晶格 二维电子气 高电子迁移率晶体管     

核物质状态方程中动量相关作用可能的探针

研究了动量相关作用对于中子-质子比动能谱rb(Ek)的效应,发现rb(Ek)灵敏的依赖于动量相关作用而弱的依赖于介质中核子-核子碰撞截面和对称势.因此rb(Ek)是提取重离子碰撞中动量相关作用信息的可能探针.同时,对于丰中子弹核和相同质量稳定弹核在相同入射道条件下,丰中子碰撞系统明显加强了动量相关作用对rb(Ek)的效应.故两个碰撞系统rb(Ek)结果的比较为在重离子碰撞中提取动量相关作用的知识提供了另一个重要的判据。