Analysis of the 3D distribution of stacked self-assembled quantum dots by electron tomography

The 3D distribution of self-assembled stacked quantum dots (QDs) is a key parameter to obtain the highest performance in a variety of optoelectronic devices. In this work, we have measured this distribution in 3D using a combined procedure of needle-shaped specimen preparation and electron tomography. We show that conventional 2D measurements of the distribution of QDs are not reliable, and only 3D analysis allows an accurate correlation between the growth design and the structural characteristics.     

Kuznetsov–Ma waves train generation in a left-handed material

We analyze the behavior of an electromagnetic wave which propagates in a left-handed material. Second-order dispersion and cubic–quintic nonlinearities are considered. This behavior of an electromagnetic wave is modeled by a nonlinear Schrödinger equation which is solved by collective coordinates theory in order to characterize the light pulse intensity profile. More so, a specific frequency range has been outlined where electromagnetic wave behavior will be investigated. The perfect combination of second-order dispersion and cubic nonlinearity leads to a robust soliton. When the quintic nonlinearity comes into play, it provokes strong and long internal perturbations which lead to Benjamin–Feir instability. This phenomenon, also called modulational instability, induces appearance of a Kuznetsov–Ma waves train. We numerically verify the validity of Kuznetsov–Ma theory by presenting physical conditions which lead to Kuznetsov–Ma waves train generation. Thereafter, some properties of such waves train are also verified.     

Bandgap measurement of thin dielectric films using monochromated STEM-EELS

High-resolution electron energy-loss spectroscopy (HR-EELS), achieved by attaching electron monochromators to transmission electron microscopes (TEM), has proved to be a powerful tool for measuring bandgaps. However, the method itself is still uncertain, due to Cerenkov loss and surface effects that can potentially influence the quality of EELS data. In the present study, we achieved an energy resolution of about 0.13 eV at 0.1 s, with a spatial resolution of a few nanometers, using a monochromated STEM-EELS technique. We also assessed various methods of bandgap measurement for a-SiNx and SiO₂ thin dielectric films. It was found that the linear fit method was more reliable than the onset reading method in avoiding the effects of Cerenkov loss and specimen thickness. The bandgap of the SiO₂ was estimated to be 8.95 eV, and those of a-SiNx with N/Si ratios of 1.46, 1.20 and 0.92 were measured as 5.3, 4.1 and 2.9 eV, respectively. These bandgap-measurement results using monochromated STEM-EELS were compared with those using Auger electron spectroscopy (AES)-reflective EELS (REELS).     

高效选择性激光烧结系统的研究

选择性激光烧结(Selective Laser Sintering,SLS)是快速成形技术的一种,其成形效率是需要考虑的重要指标之一。为了提高成形效率,我们从机械和工艺两方面着手研究和改进,并在华中科技大学研制的HRPS-III型SLS快速成形系统中应用,取得了良好的效果。     

肉苁蓉在保健食品中的应用

肉苁蓉具有多种保健功能,已批准的含有肉苁蓉为原料的保健食品共47种,其保健功能主要为缓解体力疲劳、延缓衰老、增强免疫力、通便等,以肉苁蓉为原料开发保健食品具有广阔的前景。本文总结了肉苁蓉作为原料在保健食品中的使用情况,介绍了肉苁蓉的化学成分与药理作用、安全性评价的相关内容,汇总了已批准的以肉苁蓉为原料的保健食品情况,分析了肉苁蓉在保健食品中的应用情况,以期为肉苁蓉作为保健食品原料开发利用提供参考。     

大牛地气田马五5亚段碳酸盐岩气水层识别方法

大牛地气田碳酸盐岩缝洞型储层的非均质性、泥浆的侵入、矿化度的高低、井径扩径等因素,造成对碳酸盐岩流体性质的识别成为世界性难题,对此,根据现有资料统计和分析,采用7种气、水层识别方法,确定了马五5亚段储层、气层、气水同层、水层的识别标准。     

鄂尔多斯盆地高桥地区奥陶系马家沟组马五1+2亚段储层特征

综合利用岩心薄片、铸体薄片、扫描电镜、压汞测定等资料,对鄂尔多斯盆地高桥地区奥陶系马家沟组马五1+2亚段的储层特征进行了研究。结果表明:高桥地区马五1+2亚段储集岩的类型主要为溶蚀孔洞状白云岩、泥晶—粉晶白云岩,其次是颗粒(砂屑)白云岩和角砾状白云岩;储集岩的孔隙类型主要为溶蚀孔、晶间孔、晶间溶孔,其次为膏模孔和裂隙;储集岩的物性较差,平均孔隙度为3.26%,平均渗透率为1.2mD,且孔隙度与渗透率呈正相关性,总体为非均质性较强的低孔、低渗透储层。通过对该区储层特征的研究,可为下一步的勘探开发提供地质依据。     

Mapping of valence energy losses via energy-filtered annular dark-field scanning transmission electron microscopy

The advent of electron monochromators has opened new perspectives on electron energy-loss spectroscopy at low energy losses, including phenomena such as surface plasmon resonances or electron transitions from the valence to the conduction band. In this paper, we report first results making use of the combination of an energy filter and a post-filter annular dark-field detector. This instrumental design allows us to obtain energy-filtered (i.e. inelastic) annular dark-field images in scanning transmission electron microscopy of the 2-dimensional semiconductor band-gap distribution of a GaN/Al₄₅Ga₅₅N structure and of surface plasmon resonances of silver nanoprisms. In comparison to other approaches, the technique is less prone to inelastic delocalization and relativistic artefacts. The mixed contribution of elastic and inelastic contrast is discussed.     

浅谈马军巷街坊的规划设计

文章通过对旧城区马军巷街坊的改建规划设计，结合周围地形条件，区位特点，文化传统诸因素，     

水胶炸药排放污水中硝酸钠快速测定法

采用ＰＮａ玻璃电极测定了水胶炸药生产排放污水中的Ｎａ＾＋含量，此法保持了直接电位测定法中干扰因素少的优点，分析速度快且结果准确。