大体积混凝土施工缝布设形式的探讨和建议

道路、桥梁结构（扶臂式现浇挡墙、桥台和闭合框架）中混凝土施工缝的形式,多为结构缝、装饰缝,近几年出现了温度缝。从缝的布设效果看,温度缝未达到彻底解决混凝土竖向裂缝的目的,其原因有多方面。本文通过近年来的工程实践总结的经验,论述了混凝土施工缝的布设问题,提出了以预留缝取代温度缝,解决混凝土竖向裂缝问题的观点,与同行进行交流和探讨。     

Photocatalytic performance of ZnGa2O4 for degradation of methylene blue and its improvement by doping with Cd

ZnGa₂O₄ powder catalysts, synthesized by a sol–gel process, exhibit high photocatalytic activity for methylene blue (MB) degradation. The pH value at the point of zero charge (pH_pzc) was determined to be 5.9 by a titrations method and MB conversion increased with the increase of the pH value. The valence and conduction band positions were determined at 3.35 V and − 1.45 V (Normal Hydrogen Electrode, NHE), respectively, indicating high photocatalytic ability. Improved photocatalytic efficiency was achieved by substituting cadmium for zinc in the ZnGa₂O₄. The improvement can be attributed to high UV absorption efficiency and high separation of photogenerated electron-hole pairs.     

Preparation and luminescent characteristics of Sr3RE2(BO3)4:Dy (RE = Y, La, Gd) phosphors for white LED

Dysprosium-activated Sr₃RE₂(BO₃)₄ (RE = Y, La, Gd) phosphors were synthesized by a high temperature solid-state reaction method. The phase uniformity of the phosphors was characterized by X-ray powder diffraction (XRD) and the luminescence characteristics were investigated. The excitation spectra at 575 nm emission show strong spectral bands in the region of 300-500 nm. The emission spectra of the phosphors with 365 nm excitation show three bands centered at 484 nm, 575 nm and 680 nm, which originate from the transitions of ⁴F_9/2 → ⁶H_15/2, ⁴F_9/2 → ⁶H_13/2 and ⁴F_9/2 → ⁶H_11/2 of Dy³⁺, respectively. The effect of Dy³⁺ concentration on the emission intensity of the phosphors was investigated. The fluorescence decay curves for ⁴F_9/2 → ⁶H_13/2 excited at 365 nm and monitored at λ_em of 575 nm were measured. The decay times decreased slowly with increasing Dy³⁺ doping concentration due to a trap capturing to resonance fluorescence transfer of the activated ions and due to the exchange interactions between activated ion pairs. In order to determine the type of interaction between activated ions, the concentration dependence curves (lg(I/x) versus lg x) of Sr₃RE₂(BO₃)₄:Dy³⁺ (RE = Y, La, Gd) were plotted. The concentration quenching mechanism of the ⁴F_9/2 → ⁶H_13/2 (575 nm) transition of Dy³⁺ is the d-d interaction. All results indicate these phosphors are promising white-color luminescent materials.     

The production of nitrogen-doped graphene from mixed amine plus ethanol flames

A simple process is described for directly synthesizing pure graphene and N-doped graphene sheets from ethanol flame and amine plus ethanol flames respectively. The microstructures and nitrogen contents of the graphenes were characterized using scanning and transmission electron spectroscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. The results reveal that: (1) The graphene sheets from flame exhibit good transparency and a large size up to 400 μm² with few layers and folded edges; (2) The nitrogen-doped graphene sheets have a dominant ‘pyridine-type’ structure with CN bonds (one N atom bonded to two C atoms); (3) Compared with other methods, the graphene sheets from flame have more surface defects due to the environmental conditions and introduction of nitrogen atoms, which makes it a promising material for supercapacitors and catalyst supports.     

WCDMA终端互操作性测试

WCDMA终端一致性测试的广泛应用,满足了终端最基本的需求。为达到运营商和厂商对终端提出的更高级别的要求,互操作性测试（IOT）变得尤为重要并且日渐成熟,弥补了一致性测试的不足。IOT测试运用开发系统提供的一系列工具及其中层应用接口,模拟现网环境,可实现灵活的测试过程。