N-Doped carbon dots decorated ceria hollow spheres for enhanced activity of RhB degradation by visible light

The fabrication of low-cost and environmentally friendly photocatalysts with superior photodegradation efficiency remains one of the most pressing challenges in present research. Herein, we elaborately designed and synthesized a promising N-doped carbon quantum dots/CeO₂ hollow microsphere (NCQDs/h-CeO₂) photocatalyst with superior photoresponse property and photoactivity in visible light. The removal efficiencies of rhodamine B (RhB) under visible light illumination for NCQDs/h-CeO₂ exhibits a 30.3% enhancement compared with pure h-CeO₂. The results of EIS and PL imply that the excellent performance may be attributed to the strong synergistic effect between NCQDs and h-CeO_2, thus effectively promoting charge transfer and restraining the recombination of photogenerated holes and electrons. Accordingly, a synergistic photocatalysis mechanism was proposed to explain the photocatalytic reaction process. Besides, the NCQDs/h-CeO₂ exhibits better cycle stability than common CQDs/h-CeO₂ after a four-cycle photocatalytic test. Therefore, the NCQDs/h-CeO₂ may represent a promising strategy for the current water pollution issues.     

Noise processing of flaw reconstruction by wavelet transform in ultrasonic guided SH waves

The ultrasonic guided wave technique is a potential and useful tool for nondestructive testing. The scattered or reflected wave from a flaw can give its qualitative or even quantitative information such as location, size and severity. However, in experiments and in situ tests, the noises always exist together with signals. In this paper, we propose a wavelet-transform based noise processing approach for reflected wave signals to the quantitative reconstruction of surface flaws on a plate using guided SH waves. We suggest two different denoising methods based on wavelet transform (WT) in time and wavenumber domains respectively. Numerical results show that wavenumber-domain WT operation gives a better denoising effect than direct time-domain WT denoising. Using the former, one can successfully perform the inverse reconstruction of flaw by reflected signals with signal noise ratio as high as ?5 dB. This research can act as a theoretical reference for practical applications of ultrasonic guided SH waves in quantitative nondestructive evaluation.     

被动差分光学吸收光谱法监测污染源排放总量研究

研究了一种测量污染源污染气体(如SO2、NO2)排放总量的光学遥测方法,即采用被动差分光学吸收光谱(DOAS)系统在移动平台(如汽车)上对污染源排放烟羽进行扫描测量,利用被动差分光学吸收光谱处理方法对系统采集的天顶太阳散射光谱进行处理获取柱密度,在结合测量时段的气象(风场)信息后获得污染气体的排放通量,最终得到排放总量。着重描述了获得烟羽垂直柱密度的差分光学吸收光谱方法以及污染气体排放通量的计算方法,并利用车载被动差分光学吸收光谱系统对某一热电厂SO2排放进行了外场测量,实验结果与在线设备的对比表明:这种基于被动差分光学吸收光谱光学遥测方法能够用于污染源排放总量的快速测量。     

Shape and composition control of Bi19S27(Br3–x,Ix) alloyed nanowires: the role of metal ions

We present the first colloidal synthesis of highly uniform single-crystalline Bi₁₉S₂₇Br₃ nanowires (NWs) with a mean diameter of ∼9 nm and tunable lengths in the range of 0.15–2 μm in the presence of foreign metal ions (Al³⁺). The Al³⁺ ions not only control the growth of NWs, but also achieve species transformation, i.e., from Bi₂S₃ to Bi₁₉S₂₇Br₃, and are not present in the resulting NWs. This colloidal chemistry approach can be expanded to prepare a family of single-crystalline Bi₁₉S₂₇(Br_3–x,I_x) alloyed NWs with controlled compositions (0 ≤ x ≤ 3). Interestingly, these alloyed NWs show an unusual composition-independent band gap of ∼0.82 eV, and theoretical calculations indicate that this phenomenon comes from the very minor contributions of the halogens to the valence band maximum and conduction band minimum. The photodetectors made of Bi₁₉S₂₇(Br_3–x,I_x) alloyed NWs show a pronounced photoresponse with high stability and reproducibility, which makes the NWs potentially useful candidates in optoelectronic devices.     

Polymer and Membrane Design for Low Temperature Catalytic Reactions

Catalytically active asymmetric membranes have been developed with high loadings of palladium nanoparticles located solely in the membrane's ultrathin skin layer. The manufacturing of these membranes requires polymers with functional groups, which can form insoluble complexes with palladium ions. Three polymers have been synthesized for this purpose and a complexation/nonsolvent induced phase separation followed by a palladium reduction step is carried out to prepare such membranes. Parameters to optimize the skin layer thickness and porosity, the palladium loading in this layer, and the palladium nanoparticles size are determined. The catalytic activity of the membranes is verified with the reduction of a nitro‐compound and with a liquid phase Suzuki–Miyaura coupling reaction. Very low reaction times are observed.

     

钛硅分子筛中铝杂质对其性能的影响

 以四丙基溴化铵为模板剂,以硅溶胶为硅源,采用水热合成法制备了不同铝杂质含量的钛硅分子筛,并系统考察了铝杂质对钛硅分子筛性能的影响．结果表明,原料中的铝杂质可促进钛硅分子筛晶化,但同时也引入了酸性中心;在丙烯环氧化反应中,铝杂质形成的酸性中心会催化环氧丙烷与溶剂的副反应;加入少量碱性添加物可抑制铝杂质的酸催化作用,提高环氧丙烷的选择性,但过量碱性添加物会使钛硅分子筛失活．     

狭缝摄影胶片图象运动参量测量和处理

狭缝摄影胶片图象运动参量测量和处理采用了胶片扫描仪对狭缝摄影胶片图象进行数字化,利用软件进行图象处理.文章介绍了对胶片扫描仪进行检验和标定方法;对由于狭缝摄影机的胶片速度和目标的实际影象速度不一致产生的畸变进行了分析和修正,实现了数据的精确测量和处理.     

超导变压器的性能检测方法研究

目前一些超导电力装置已进入试验运行阶段,为适应不久的将来超导电力技术应用的商品化,对一些有代表性的超导电力装置的试验、检测方法及其主要设备进行研究是十分必要的。文中从超导变压器的电磁特性出发,探讨了超导变压器的试验、检测项目;重点介绍了其超导电磁特性试验,并阐述了超导变压器的试验方法及其主要设备。     

熔体法制备无机钙钛矿半导体核辐射探测晶体与器件的研究进展

钙钛矿材料在太阳能电池和光电探测等领域的快速发展,带动了其在核辐射探测领域的应用研究。钙钛矿晶体结构拥有多样化的结构容忍性,如何设计组分并挖掘材料的相关特性具有很大的科学挑战。其次,针对新型钙钛矿材料特性,需要根据应用场景来优化半导体器件设计,才能最大限度地发挥其辐射探测性能。鉴于此,本文从熔体法晶体生长及半导体器件设计等角度,探讨了不同维度钙钛矿结构的材料特性及辐射探测器件性能,以期为该材料在核辐射探测领域的发展提供参考。     

An analytical approach to reconstruction of axisymmetric defects in pipelines using T(0, 1) guided waves

Torsional guided waves have been widely utilized to inspect the surface corrosion in pipelines due to their simple displacement behaviors and the ability of longrange transmission. Especially, the torsional mode T(0, 1), which is the first order of torsional guided waves, plays the irreplaceable position and role, mainly because of its non-dispersion characteristic property. However, one of the most pressing challenges faced in modern quality inspection is to detect the surface defects in pipeli...