Quasiparticle correction for electronic transport in molecular wires

In this paper we present calculations of ballistic transport in molecular wires. The calculations are performed using an approximated version of the GW correction in the plasmon-pole framework, which is used to improve the starting Density Functional Theory energy spectrum of the molecule between metallic leads. We show that this correction reduces the error of the correlation part for the electron energy. Finally a model with complex bands is implemented in order to get the damping regime for long polymers.     

基于改进的Levinsion算法对电机转速特性的研究

传统的Levinsion算法忽略了信号自相关序列值代替理论值时的误差，因而降低了算法性能。为了减小该误差的影响，采用改进Levinsion算法、AIC阶数判定准则，将现代谱估计中的AR模型应用于包含广泛频率成分的典型的电机转速振动信号分析，求得AR模型的功率谱。通过AR现代谱与Welch经典谱的实际对比分析，验证了所建AR模型的正确性和对电机转速振动信号分析的适用性，为电机转速振动特性的研究提供了可靠的分析技术。     

基于复杂辐射状配电系统简约模型的可靠性评估算法

建立了一种配电网简约模型，提出了开关节点和负荷区间等概念以及适用于复杂辐射状配电系统的可靠性评估算法。该算法只需考虑开关节点和负荷区间对故障的影响，不需具体到系统各个元件，通过遍历搜索分析故障事件的影响、评估其可靠性。对于分支馈线较多的配电系统，该算法在原理和编程上具有优势，且能计及开关故障、备用电源和计划检修等多种情况。利用C++语言计算RBTS母线6系统 的可靠性指标，验证了该算法的正确性和有效性     

Differential formation of allophane and imogolite: experimental and molecular orbital study

Allophane and imogolite are naturally occurring aluminum silicate soil constituents with nano-ball and nano-tube morphology. Wall of the both materials is composed of Al(OH)₃ sheet with orthosilicic acid attached to it. Synthesis of allophane and imogolite can be controlled by addition of alkali and alkaline-earth metal ions. The main reaction product without or with small amounts addition of the metal ions is imogolite, while allophane forms when the metal ions were much added. The effect of metal ions on facilitating allophane formation and inhibition of imogolite formation were greater in the following order of Na, K < Ca, Mg. These metal ions affect the degree of dissociation of Si–OH group of orthosilicic acid, which may causes differential formation of allophane and imogolite. Structure optimization of the proto-imogolite model, precursor of allophane and imogolite, showed that when the Si–OH was undissociated, the shape of proto-imogolite model was transformed to asymmetrical in molecular configuration. This caused curling of the proto-imogolite model, which lead to formation of imogolite tube. On the other hand, when the Si–OH was dissociated, the shape of the proto-imogolite model was transformed to symmetrical configuration. This model curved to make a hollow sphere with placing the orthosilicic acid inside the sphere (allophane). Both of the experimental and molecular orbital calculation results proved that the dissociation of the Si–OH has an important role during the differential formation of allophane and imogolite.     

Superfluid-Normal Interface of 4He Near a Wall

We observed a profile of nonequilibrium superfluid-normal (SN) interface of ⁴He near a vertical wall. A glass, brass or copper wall was used. The SN interface was produced by cooling liquid ⁴He in a bath from the bottom, where liquid ⁴He was pumped through a flow impedance in order to cool down the liquid. Superfluid (Normal fluid) occupied the lower (upper) part of the bath. The SN interface was visualized by three methods: simple visualization, shadowgraphy and schlieren method. The interface touched a vertical glass wall at almost 90°. A large hollow was observed near a brass wall which had intermediate thermal conductivity. Downward flow was observed on a copper wall due to the very good thermal conductivity of the wall. Various types of interface profile were observed depending on the thermal conductivity of the wall used.      

Growth of β-FeSi2 thin films on β-FeSi2 (110) substrates by molecular beam epitaxy

We have investigated the preparation of β-FeSi₂ substrate and growth condition of β-FeSi₂ thin film on β-FeSi₂ (110) substrate by molecular beam epitaxy. The surface of the substrate was prepared by a wet-etching using HF(50%):HNO₃(60%):H₂O = 1:1:5 solution at 25 °C. It is clear that the optimal etching period to obtain a flat surface was 3 min. The β-FeSi₂ thin film with streak RHEED pattern was obtained at Si/Fe flux ratio of 2.9. Average surface roughness (Ra) of the β-FeSi₂ film was about 0.5 nm in 5 × 5 μm² area.     

Growth and characterization of group-III impurity-doped semiconducting BaSi2 films grown by molecular beam epitaxy

Ga- or In-doped BaSi₂ films were grown on Si(111) by molecular beam epitaxy (MBE). The Ga-doped BaSi₂ showed n-type conductivity. The electron concentration and resistivity of the Ga-doped BaSi₂ depended on the Ga temperature; however, the electron concentration and resistivity could not be controlled properly. In contrast, the In-doped BaSi₂ showed p-type conductivity and its hole concentration was controlled in the range between 10¹⁶ and 10¹⁷ cm^− 3 at RT.     

Virtual crack extension method for calculating the second order derivatives of energy release rates for multiply cracked systems

In this paper, we further generalize the work of Lin and Abel [Lin SC, Abel JF. Variational approach for a new direct-integration form of the virtual crack extension method. Int J Fract 1988;38:217-35.] to the case of higher order derivatives of energy release rates for two-dimensional, multiply cracked systems. The direct integral expressions are presented for the energy release rates and their first and second order derivatives. The salient feature of this numerical method is that the energy release rates and their first and second order derivatives can be computed in a single analysis. It is demonstrated through a set of examples that the proposed method gives expectedly decreasing, but acceptably accurate results for the energy release rates and their first and second order derivatives. The computed errors were approximately 0.5% for the energy release rates, 3-5% for their first order derivatives and 10-20% for their second order derivatives for the mesh densities used in the examples. Potential applications of the present method include a universal size effect model and a probabilistic fracture analysis of cracked structures.     

基于LPC高阶统计量语音活动检测算法的设计与实现

论文提出了一种基于LPC残差信号高阶统计量对加性噪声中的确定性信号及非高斯随机信号进行检测的方法,通过理论分析与实验结果表明,高阶统计量能有效地解决客观存在的非高斯及非线性问题,是现代信号分析与处理研究的重要内容,这种检测方法对加性噪声是否有色或是否为高斯分布并不敏感,而只要求噪声具有对称的概率密度函数。利用这种方法对确定性LPC残差信号进行检测的性能与已知波形时匹配滤波器的检测性能要好。利用这种方法还非常易于实现非高斯随机信号的检测。     

Optical and Structural Properties of CdTe Grown by Molecular Beam Epitaxy at Low Temperature for Resonant-Cavity-Enhanced HgCdTe Detectors

Investigation into resonant-cavity-enhanced (RCE) HgCdTe detectors has revealed a discrepancy in the refractive index of the CdTe layers grown by molecular beam epitaxy (MBE) for the detectors, compared with the reported value for crystalline CdTe. The refractive index of the CdTe grown for RCE detectors was measured using ellipsometry and matches that of CdTe with an inclusion of approximately 10% voids. X-ray measurements confirm that the sample is crystalline and strained to match the lattice spacing of the underlying Hg_(1−x)Cd_(x)Te, while electron diffraction patterns observed during growth indicate that the CdTe layers exhibit some three-dimensional structure. Secondary ion mass spectroscopy results further indicate that there is enhanced interdiffusion at the interface between Hg_(1−x)Cd_(x)Te and CdTe when the Hg_(1−x)Cd_(x)Te is grown on CdTe, suggesting that the defects are nucleated within the CdTe layers.