顺磁性La2/3Sr1/3MnO3层对Bi0.8Ba0.2FeO3薄膜多铁性能的影响

界面效应在提升异质结构材料的多铁性能方面有着重要的作用. 本文采用脉冲激光沉积技术在SrTiO₃(STO)基片上制备了Bi_0.8Ba_0.2FeO₃(BBFO)/La_2/3Sr_1/3MnO₃(LSMO)异质结. X-射线衍射图谱表明异质结呈现单相外延生长, 利用高分辨透射电镜进一步证实了BBFO为四方相结构. X-射线光电子能谱证实异质结中只存在Fe³⁺ 离子, 没有产生价态的变化, 揭示了异质结铁电和铁磁性的增强与BBFO/LSMO的界面有关. 同时, 测试了磁电阻(MR)和磁介电(MD), 当磁场强度为0.8 T, 温度为70 K时, MR约为-42.2%, MD约为21.2%. 并且发现在180 K时出现磁相的转变. 实验结果揭示出异质界面效应在提升材料的多铁性和磁电耦合效应方面具有超常的优点, 是加快多铁材料实际应用的有效途径.     

含有周期球腔的黏弹性覆盖层消声性能分析

利用散射矩阵法分析了单个球状空腔在黏弹性橡胶中的Mie散射特性以及振动模式.以此为基础，利用多重散射法分析了不同背衬条件下，含有单层周期球状空腔的橡胶覆盖层(厚度为8mm)的消声性能.结果表明，单个球腔的径向共振对覆盖层的低频消声性能有重要贡献，覆盖薄层在共振区具有良好的消声性能.最后，设计了双层消声覆盖层(厚度为20mm)，有效拓展了消声带宽. 关键词： Mie散射 多重散射法 消声材料 声子晶体     

等离子体天线色散关系和辐射场数值计算

研究了电磁波沿轴向对称柱形等离子体天线传播的特性、色散关系及辐射方向图、增益等天线参数.通过对腔体材料介电系数、内外半径、等离子体密度、碰撞频率等参数的分析，结果表明要减小波沿等离子体天线传播的衰减，应当增加等离子体密度，减小碰撞频率，增加等离子体半径，减小腔体厚度，采用介电系数较小的材料.计算了在不同参数条件下，等离子体天线的辐射方向图、增益的变化，这些结果对于等离子体天线的设计很有参考价值. 关键词： 等离子体天线 色散关系 增益 辐射方向图     

奇相干光源的测量设备无关量子密钥分配研究

刻画了奇相干光源的光子数分布特征,研究了奇相干光源下诱骗态测量设备无关量子密钥分配系统的密钥生成率与安全传输距离的关系,推导了奇相干光源下的计数率下界和误码率上界.仿真结果表明,奇相干光源光子数分布中多光子脉冲的比例低于弱相干光,可以有效提高诱骗态测量设备无关密钥分配系统的最大安全通信距离,为实用的量子密钥分配实验提供了重要的理论参数.     

Kalman滤波辅助的室内伪卫星相对定位算法

在室内伪卫星独立定位系统中, 伪卫星以及接收机的钟差会给定位精度带来非常大的误差. 针对这一问题, 提出了一种适用于室内环境的相对定位算法. 使用Kalman定位算法粗略计算接收机位置, 获得粗略基线, 建立室内相对定位模型, 得到载波相位双差和伪距双差. 载波相位双差通过互补Kalman滤波器来平滑伪距双差, 进一步得到精确基线, 获得接收机精确位置, 并将其代替Kalman定位算法的校正结果, 对接收机进行下一状态预测. 实验结果表明, 该算法具有较高的定位精度, 定位误差在20 cm以内. 关键词： 伪卫星 相对定位 双基线 Kalman滤波     

Theoretical study of stereodynamics for the N+H2/D2/T2 reactions

The effects of isotopic variants on stereodynamic properties for the title reactions have been investigated using a quasi-classical trajectory method based on the first excited state NH2（I^2A＇） potential energy surface [Li Y Q and Varandas A J C 2010 J. Phys. Chem. A 114 9644]. The forward–backward symmetry scattering of the differential cross section can be observed, which demonstrates that all these reactions follow the insertion mechanism. Three angle distribution functions P（θr）, P（φr）, and P（θr, φr） with different collision energies and target molecules H2/D2/T2 are calculated. It is shown that the product rotational angular momentum is not only aligned, but also oriented along the direction perpendicular to the scattering plane. The title reaction is mainly governed by the ＂in-plane＂ mechanism through the calculated distribution function P（θr, φr）. The observable influences on the rotational polarization of the product by the isotopic substitution of H/D/T can be demonstrated.     

A computational investigation of topological insulator Bi2Se3 film

Topological insulators have a bulk band gap like an ordinary insulator and conducting states on their edge or surface which are formed by spin–orbit coupling and protected by time-reversal symmetry. We report theoretical analyses of the electronic properties of three-dimensional topological insulator Bi₂Se₃ film on different energies. We choose five different energies (–123, –75, 0, 180, 350 meV) around the Dirac cone (–113 meV). When energy is close to the Dirac cone, the properties of wave function match the topological insulator’s hallmark perfectly. When energy is far way from the Dirac cone, the hallmark of topological insulator is broken and the helical states disappear. The electronic properties of helical states are dug out from the calculation results. The spin-momentum locking of the helical states are confirmed. A 3-fold symmetry of the helical states in Brillouin zone is also revealed. The penetration depth of the helical states is two quintuple layers which can be identified from layer projection. The charge contribution on each quintuple layer depends on the energy, and has completely different behavior along K and M direction in Brillouin zone. From orbital projection, we can find that the maximum charge contribution of the helical states is p_z orbit and the charge contribution on p_yand p_x orbits have 2-fold symmetry.     

Contact position and width effect of graphene electrode on the electronic transport properties of dehydrobenzoannulenne molecule under bias

By applying nonequilibrium Green?s function formalism in combination with density functional theory, we have investigated the electronic transport properties of dehydrobenzoannulenne molecule attached to different positions of the zigzag graphene nanoribbons (ZGNRs) electrode. The different contact positions are found to drastically turn the transport properties of these systems. The negative differential resistance (NDR) effect can be found when the ZGNRs electrodes are mirror symmetry under the xz midplane, and the mechanism of NDR has been explained. Moreover, parity limitation tunneling effect can be found in a certain symmetry two-probe system and it can completely destroy electron tunneling process. The present findings might be useful for the application of ZGNRs-based molecular devices.     

一种云环境下的发动机健康管理系统及其应用

针对航空公司对大量飞机发动机进行健康管理的需求,通过建立发动机健康管理云端数据中心,建立了一种云环境下的民航发动机健康管理系统,该系统对于验证发动机故障诊断方法的有效性具有突出优势,并且对于实现多种方法协同进行发动机故障诊断具有重要价值;提出了一种基于灰色关联分析的灰色故障识别方法,通过在云端平台使用灰色故障识别方法实现JT9D-7R4发动机的典型气路性能故障诊断为例,表明云环境下的发动机健康管理系统可以有效地进行航空发动机故障诊断。