Microstructure and photoluminescence studies of Sb-doped SnO2 zigzag nanobelts

SnO2 zigzag nanobelts were successfully Sb-doped by a simple vapor deposition method. Field emission scanning electron microscope (FESEM), high resolution transmission electron microscope (HRTEM), and X-ray diffraction (XRD) were used to characterize these Sb-doped nanobelts. The Sb doping in SnO2 nanobelts was confirmed by Energy Dispersive X-ray spectrum (EDS) and X-ray photoelectron spectroscopy (XPS). It is found that there is no apparent lattice distance difference between the pure SnO2 and the 0.705 at% Sb doped SnO2 nanobelts. A slight blue-shift in the photoluminescence (PL) spectra was shown with the increase of Sb doping concentration and a reasonable explanation was given.     

Sideband analysis and seismic detection in a large ring laser

Aring laser unlocked by the Earth's Sagnac effect has attained a frequency resolution of 1 part in 3 × 10(21) and a rotational resolution of 300 prad. We discuss both theoretically and experimentally the sideband structure of the Earth rotation-induced spectral line induced in the microhertz-hertz region by frequency modulation associated with extra mechanical motion, such as seismic events. The relative sideband height is an absolute measure of the rotational amplitude of that Fourier component. An initial analysis is given of the ring laser record from the Arthur's Pass-Coleridge seismic event of 18 June 1994.     

Scattering characteristics of a chiral-coated cylindrical reflector embedded in a double-negative metamaterial

The scattering characteristics of a cylindrical reflector coated with a chiral material and embedded in a double-negative metamaterial have been studied using numerical simulation. The effects of double-negative metamaterial background media and chiral admittances of a chiral coating layer upon the co- and cross-polarized echo widths have been investigated. It is shown that a double-negative metamaterial background with relatively larger negative values of the permittivity and the permeability enhances the co-polarized echo width in the forward scattering direction and reduces this echo width in the backward scattering direction as compared to the free space background. It is further shown that by increasing the chiral admittance of a chiral-coated cylindrical reflector embedded in a double-negative metamaterial with fixed background parameters increases the co-polarized echo width in the forward and the backward scattering directions as compared to an achiral-coated cylindrical reflector embedded in the same double-negative metamaterial background.     

Compositional and spin–orbit control on the electronic structure and optical characteristics of ZnHgTe alloys using mBJ–GGA approach

Employing systematic first-principle calculations to the family of tellurium II–VI compounds such as Hg- and Zn-based semiconductors and their related Zn_1?x Hg _x Te ternary alloys, we have simulated the electronic and optical characteristics incorporating the spin–orbit coupling effect. The salient features such as the band gaps and the optical spectra with a satisfactory adequate approach are computed with the so-called modified Becke–Johnson exchange correlation potential as implemented in the full-potential linearized augmented plane-wave scheme. The theoretical finding surmises that a topological insulating state may be caused with 25% of Zn concentration incorporated in HgTe material. Intriguingly, a band gap is conclusively developed near 0.25 eV in Zn_0.25Hg_0.75Te alloy. The relevant components like the band structure, optical response functions such as the real and imaginary parts of dielectric function, spectral dependence of optical conductivity, reflectivity spectrum, refractive index, electron energy loss function, and absorption coefficient are established for the bulk Zn_1?x Hg _x Te ternary alloys, while Zn composition spans in the range 0–1. The overall accordance between our results and other theoretical reports as well as experimental realization is fairly good. We infer that the current work may be beneficial for optical emitters/converters in solar cell devices applications.     

Study of mode I crack dynamic propagation behaviour and rock dynamic fracture toughness by using SCT specimens

To study crack dynamic propagation behaviour and rock dynamic fracture toughness, a single cleavage triangle (SCT) specimen was proposed in this paper. By using these specimens and a drop‐weight test system, impact experiments were conducted, and the crack propagation velocity and the fracture time were measured by using crack propagation gauges. To examine the effectiveness of the SCT specimen and to predict the test results, finite difference numerical models were established by using AUTODYN code, and the simulation results showed that the crack propagation path agrees with the test results, and crack arrest phenomena could happen. Meanwhile, by using these numerical models, the crack dynamic propagation mechanism was investigated. Finite element code ABAQUS was applied in the calculation of crack dynamic stress intensity factors (SIFs) based on specimen dimension and the loading curves measured, and the curves of crack dynamic SIFs versus time were obtained. The fracture toughness (including initiation toughness and propagation toughness) was determined according to the fracture time and crack speeds measured by crack propagation gauges. The results show that the SCT specimen is applicable to the study of crack dynamic propagation behaviour and fracture toughness, and in the process of crack propagation, the propagation toughness decreases with crack propagation velocity, and the crack arrest phenomena could happen. The critical SIF of an arrest crack (or arrest toughness) was higher than the crack propagation toughness but was lower than the initiation toughness.     

单模光纤环轴向磁场问题的理论研究

去偏光纤陀螺的非理想单模光纤,在垂直于光纤环面的轴向磁场作用下,由于Faraday 效应,在其中传播的正反两束光会产生一个与磁场有关的非互易相位差.本文基于单色光对在轴向磁场作用下的单模光纤环进行理论推导、分析,给出仿真结果和实验结果,并提出减小轴向磁场作用下的Faraday非互易相位差的方法.     

AFM氮化硅纳米探针研制

在〈100〉晶向硅片上通过各向异性腐蚀形成作为模板的倒金字塔形尖坑, 用LPCVD和PECVD法淀积一层约 1 μm厚的氮化硅膜, 通过等离子刻蚀形成悬臂梁图形,再把抛光玻璃片静电键合到氮化硅膜上, 最后把衬底硅片腐蚀掉,带有金字塔形针尖的悬臂梁就暴露出来,从而构成可用于原子力显微镜(AFM)描绘纳米图像的氮化硅纳米探针.对针尖的尖度和氮化硅膜悬臂梁的热应力补偿进行了深入研讨, 并报道一种特殊而有效的悬臂梁掩模板图形的新设计.制成的氮化硅纳米探针在原子力显微镜上成功地描绘出了纳米图像, 经检测, 其 Z向偏转检测精度优于10-9量级.     

Facilitating the Rapid Development and Scalable Orchestration of Composite Web Services

The development of new Web services through the composition of existing ones has gained a considerable momentum as a means to realise business-to-business collaborations. Unfortunately, given that services are often developed in an ad hoc fashion using manifold technologies and standards, connecting and coordinating them in order to build composite services is a delicate and time-consuming task. In this paper, we describe the design and implementation of a system in which services are composed using a model-driven approach, and the resulting composite services are orchestrated following a peer-to-peer paradigm. The system provides tools for specifying composite services through statecharts, data conversion rules, and multi-attribute provider selection policies. These specifications are interpreted by software components that interact in a peer-to-peer way to coordinate the execution of the composite service. We report results of an experimental evaluation showing the relative advantages of this peer-to-peer approach with respect to a centralised one.