基才高维局部特征和LSH索引的图像检索技术

基于内容的图像检索（CBIR）技术使从海量图像资源中快速高效地提取有价值的信息得以实现,采用局部特征来表示图像并在此基础上进行图像相似性检索是当前的热门研究课题。文中将图像高维局部不变特征提取算法和LSH索引算法应用到基于内容的图像检索系统中,实验结果表明了该方法的有效性。     

Nanoporous Surface High-Entropy Alloys as Highly Efficient Multisite Electrocatalysts for Nonacidic Hydrogen Evolution Reaction

Electrocatalytic hydrogen evolution in alkaline and neutral media offers the possibility of adopting platinum-free electrocatalysts for large-scale electrochemical production of pure hydrogen fuel, but most state-of-the-art electrocatalytic materials based on nonprecious transition metals operate at high overpotentials. Here, a monolithic nanoporous multielemental CuAlNiMoFe electrode with electroactive high-entropy CuNiMoFe surface is reported to hold great promise as cost-effective electrocatalyst for hydrogen evolution reaction (HER) in alkaline and neutral media. By virtue of a surface high-entropy alloy composed of dissimilar Cu, Ni, Mo, and Fe metals offering bifunctional electrocatalytic sites with enhanced kinetics for water dissociation and adsorption/desorption of reactive hydrogen intermediates, and hierarchical nanoporous Cu scaffold facilitating electron transfer/mass transport, the nanoporous CuAlNiMoFe electrode exhibits superior nonacidic HER electrocatalysis. It only takes overpotentials as low as ≈240 and ≈183 mV to reach current densities of ≈1840 and ≈100 mA cm⁻² in 1 m  KOH and pH 7 buffer electrolytes, respectively; ≈46- and ≈14-fold higher than those of ternary CuAlNi electrode with bimetallic Cu–Ni surface alloy. The outstanding electrocatalytic properties make nonprecious multielemental alloys attractive candidates as high-performance nonacidic HER electrocatalytic electrodes in water electrolysis.     

基于提升小波的图像水印算法

文中提出了一种基于能量特性分块的小波域图像水印算法，采用JPEG2000静态图像压缩标准的变换核——Daubechies9／7双正交小波进行小波变换，利用其三段低频小波系数之间的能量关系，将随机置乱的水印嵌入到图像中，并自适应调整嵌入强度因子。实验证明，该算法具有良好的不可见性和鲁棒性。     

大尺寸气孔微结构光纤在光纤光栅中的应用

将微结构光纤分为光子晶体光纤和大尺寸气孔微结构光纤两种。详细介绍了大尺寸气孔微结构光纤。其包层的气孔硅结构（或者聚合物硅结构）影响了包层模式的空间分布以及包层模式的有效折射率，使其表现出与传统光纤不同的光学特性。基于这种微结构光纤的光纤光栅对外部折射率的变化显示了很好的稳定性。偏振特性（对长周期光纤光栅）可以大大加强。基于聚合物硅包层的长周期光纤光栅显示了优良的温度调谐性能。     

激光处理共晶型硼化物显微组织与相变过程分析

本文采用固体渗硼+激光表面处理的复合热处理工艺,使表层得到共晶型硼化物以期降低渗硼层脆性,提高其耐磨性。利用三维热传导偏微分方程验证了工艺参数的合理性。借助扫描电镜和光镜对试样表层、显微组织进行观察,着重分析了渗硼层在激光作用下的行为和相变过程。     

夹竹桃对钉螺肝损伤的超微结构观察

钉螺经夹竹桃叶水浸液处理后，用扫描电镜和透射电镜分别观察了其肝表面及肝细胞结构的变化。处理后的肝表肿胀，明显的沟纹消失，其上的孔隙破损；24h后肝细胞核肿胀，核仁消失，核质稀疏，内质网断裂，线粒体增多，且随处理时间的延长（48h），损伤加重，内质网几乎全部囊泡化，细胞核开始破裂，线粒体也破裂。文中也讨论了钉螺可能致死的原因，为探明夹竹桃对钉螺的损伤程度和灭螺机制提供了亚显微结构依据。     

Kerr介质中"耦合双原子-单模光场"模型的反聚束效应

利用全量子理论,研究了在Kerr介质中,耦合二能级双原子与单模光场相互作用过程的反聚束效应,着重讨论了Kerr介质对场的二阶相干度的影响,并揭示了初始场强及原子间耦合系数的变化与场的二阶相干度的关系。     

Nitrogen vacancy scattering in GaN grown by metal–organic vapor phase epitaxy

Electron mobility limited by nitrogen vacancy scattering was taken into account to evaluate the quality of n-type GaN grown by metal–organic vapor phase epitaxy. Two assumptions were made for this potential for the nitrogen vacancy (1) it acts in a short range, and (2) does not diverge at the vacancy core. According to the above assumptions, a general expression to describe the scattering potential U(r)=−U₀exp[−(r/β)ⁿ], (n=1,2,…,∞) was constructed, where β is the potential well width. The mobilities for n=1,2, and ∞ were calculated based on this equation, corresponding to the simple exponential, Gaussian and square well scattering potentials, respectively. In the limiting case of kβ1 (where k is the wave vector), all of the mobilities calculated for n=1,2, and ∞ showed a same result but different prefactor. Such difference was discussed in terms of the potential tail and was found that all of the calculated mobilities have T^−1/2 temperature and β⁻⁶ well width dependences. A mobility taking account of a spatially complicate scattering potential was studied and the same temperature dependence was also found. A best fit between the calculated results and experimental data was obtained by taking account of the nitrogen vacancy scattering.     

单频网分布式外辐射源雷达技术

外辐射源雷达的研究和应用正朝着由单收发对向多收发对体制发展。作为该型雷达的一种重要机会照射源,新一代数字广播电视广泛采用单频(或同频)网覆盖方式,其内在决定了基于此的外辐射源雷达是分布式和网络化的。鉴于照射源单频网配置下外辐射源雷达不同寻常的工作和处理方式,该文归纳提出了单频网分布式外辐射源雷达的概念,阐述了该型雷达的主要特性以及所面临的核心问题,并就部分关键技术讨论了若干可供尝试的解决方案,结合原理实验结果展示了该型雷达的可行性,最后提出了集外辐射源雷达探测网的四网融合的概念并展望了其应用前景。      

One Method for Fast Gate Oxide TDDB Lifetime Prediction

提出了一种快速推算栅极氧化膜TDDB寿命的新方法.该方法可以用于对工艺的实时监控.通常情况下,为了得到栅极氧化膜在器件使用温度下的TDDB寿命,必须得到三个在一定温度下的不同电压下的TDDB寿命.然后使用一定模型(E模型或者1/E模型)和这个三个寿命推算出氧化膜在器件使用温度下的寿命.比较常用的是E模型.但是为了保证使用E模型推得的寿命的准确性,必须尽量使用较低电压下的寿命来推算想要的寿命.显然,为了获得低电压下的TDDB寿命,必须花费相当长的测试时间(甚至1个月).这对于工艺的实时监控来说,是不能接受的.文中提出一种新的推算栅氧化膜TDDB寿命的方法.运用该方法,可以快速、准确获得栅氧化膜的TDDB寿命,而花费的测试时间不到普通方法的1/1000000.在该方法中,巧妙地同时利用了1/E模型和E模型.