Qtech-413 粘弹阻尼材料在盾构隧道中减振性能研究

根据盾构隧道的结构特点,用Qtech-413 粘弹阻尼材料对盾构管片标准块进行约束阻尼处理,通过单点锤击振动实验,得到处理前后结构的时域波形、固有频率、复合损耗因子等振动特性。实验结果显示:经过约束阻尼处理后,盾构管片振动加速度幅值降低了26.7%,振动时长降低了50%;各阶固有频率均有所降低,且随着频率的增加,降幅逐渐增加;各阶复合损耗因子均有所升高,高频增幅比低频增幅更大;振动总级值降低了10 dB 左右。因此,Qtech-413 粘弹阻尼材料应用于盾构隧道能降低振动加速度幅值、振动时间、固有频率和振动总级值,增加复合损耗因子,对高阶固有频率和复合损耗因子影响较大,低阶影响较小

Constant current etching of gold tips suitable for tip-enhanced Raman spectroscopy

<div class="aip-paragraph">We introduce a setup and method to produce gold tips that are suitable for tip-enhanced Raman spectroscopy by using a single step constant current electrochemical etch. The etching process is fully automated with only three preset parameters: the etching current, the reference voltage and the immersed length of gold wires. By optimizing these parameters, reproducible high quality tips with smooth surface and a radius curvature of about 20 nm can be formed. Tips prepared with this method were examined by tip-enhanced Raman spectroscopy experiments on the samples of single-wall carbon nanotube, <em class="emphitalic">p</em>-aminothiophenol, and graphene. In the Raman mapping of single-wall carbon nanotubes, the spatial resolution is about 15 nm.</div

Graphene in ohmic contact for both n-GaN and p-GaN

The wrinkles of single layer graphene contacted with either n-GaN or p-GaN were found both forming ohmic contacts investigated by conductive atomic force microscopy. The local I-V results show that some of the graphene wrinkles act as high-conductive channels and exhibiting ohmic behaviors compared with the flat regions with Schottky characteristics. We have studied the effects of the graphene wrinkles using density-functional-theory calculations. It is found that the standing and folded wrinkles with zigzag or armchair directions have a tendency to decrease or increase the local work function, respectively, pushing the local Fermi level towards n- or p-type GaN and thus improving the transport properties. These results can benefit recent topical researches and applications for graphene as electrode material integrated in various semiconductor devices. (C) 2014 AIP Publishing LLC

Growth mechanism of large-size anthracene single crystals grown by a solution technique

<font face="times new roman,times" size="2">Large-size and high-quality anthracene single crystals have been grown by a solution technique. The size of crystals reaches 2.2 cm and the crystals with rhombic plane have been obtained for the first time. FTIR and Raman analysis indicate that the crystals did not incorporate the solvent at the detection level. XRD analysis indicates that the anthracene single crystals have good quality. The morphology of surface and transect of anthracene single crystals was observed by optical microscope, atomic force microscope (AFM), and scanning electron microscope (SEM). Anthracene monolayers and the array of large straight steps were observed on the surface of anthracene single crystals. Layer-like structure was also observed in the interior of single crystals. All results indicate that the growth mechanism of anthracene single crystals is a two-dimensional nucleation-elementary steps-large straight steps-layer-by-layer periods growth.</font