Morphology and quantitative analysis of O phase during heat treatment of hot-deformed Ti_2AlNb-based alloy

A 1040°C-hot-deformed Ti_2AlNb-based alloy solution-treated at 950°C and aged at different temperatures was quantitatively investigated. The microstructure, size of the phase, and microhardness of the deformed alloys were measured. The results indicated that the microstructure of the deformed Ti_2AlNb-based alloy specimens comprise coarse O lath, fine O lath, equiaxed O/α_2, and acicular O phase. More O phase was generated in the deformed alloy after heat treatment because the acicular O phase was more likely to nucleate and grow along the deformation-induced crystal defects such as dislocations and subgrain boundaries. After deformation and subsequent heat treatment, the acicular O phase of the resultant alloy became finer compared to that of the undeformed alloy, and the acicular O phase became coarser and longer with the elevated aging temperature, while the width of the O lath exhibited unobvious variations. The hot deformation facilitated the dissolution of the O lath but accelerated the precipitation of the acicular O phase. When the 950°C-solution-treated deformed Ti_2AlNb-based alloy was then aged at 750°C for different periods, the phase content was nearly invariable, O and B2 phases eventually reached equilibrium, and the microstructure became stable and homogeneous.     

上市公司交叉持股对证券市场的影响分析

交叉持股会对上市公司的业绩产生影响,并放大证券市场的波动性,但这种影响的程度主要取决于一国的会计准则。当前,中国证券市场的交叉持股现象并不严重。而且我国大部分公司交叉持股的动机都是为了赚取投资收益,而非为了战略投资或防止收购,因此不会造成证券市场的供应不足及流动性不足。     

非自治Kirchhoff型吊桥方程拉回D-吸引子的存在性

本文运用Faedo-Galerkin逼近方法获得了非自治Kirchhoff型吊桥方程解的存在唯一性,结合拉回D-条件讨论了该方程在空间H■(Ω)×L²(Ω)中的拉回D-吸引子的存在性.     

脉冲电磁场的杀菌实验研究

利用电磁杀菌器对某些细菌进行电磁场杀菌实验,对杀菌效果和脉冲电磁场杀菌参数的选择进行了初步的探讨.     

基于深度学习的输变电设备紫外放电光斑分割方法

随着紫外成像技术的发展,高压电力设备对于紫外成像图谱的量化分析提出了更高的要求。紫外图谱的量化分析需要用到除紫外成像仪所输出“光子数”额外的紫外光斑图像信息,所以需要将紫外放电光斑从可见光的背景中分割出来。然而,传统紫外图谱光斑分割方法仍存在复杂背景及小光斑分离困难、特征选取复杂、分割精准度低等问题。基于上述问题,提出了一种基于深度学习的紫外图谱光斑分割提取的方法。首先,采用紫外成像仪拍摄电力设备放电缺陷紫外图谱;其次,分别构建FCN-32s、FCN-16s、FCN-8s 3种全卷积网络(fully convolutional networks, FCN)子模型架构,并利用随机梯度下降法进行模型训练;最后,实现输变电设备放电缺陷紫外图谱主光斑的自主分割提取。经过对FCN 3种子模型架构的训练、测试和对比分析,结果表明：FCN-16s模型为紫外光斑分割提取的最佳模型,测试准确率可达99.34%。结果表明基于深度学习的紫外图谱光斑分割方法准确高效,为紫外光斑的量化提取及电力设备放电缺陷的紫外诊断提供了参考。     

Shape recovery using high dynamic range images

An effective method for object shape recovery using HDRIs (high dynamic range images) is proposed. The radiance values of each point on the reference sphere and target object are firstly calculated, thus the set of candidate normals of each target point are found by comparing its radiance to that of each reference sphere point. In single-image shape recovery, a smoothness operation is applied to the target normals to obtain a stable and reasonable result; while in photometric stereo, radiance vectors of reference and target objects formed due to illuminations under different light source directions are directly compared to get the most suitable target normals. Finally, the height values can be recovered from the resulting normal field. Because diffuse and specular reflection are handled in an unified framework with radiance, our approach eliminates the limitation presented in most recovery strategies, i.e., only Lambertian model can be used. The experiment results from the real and synthesized images show the performance of our approach.     

Witty蠕虫的传播模型与分析

为了能够深入了解Witty蠕虫传播的具体过程和采取更为有效的防御措施,利用动力学方法提出了一个含有潜伏期且在潜伏期内和感染阶段均具有传染性的模型.根据网络的实际情况,该模型考虑了延时因素,采用了动态感染率.利用该模型得出了蠕虫爆发的阈值.将已有的模型与该模型进行了比较,仿真结果表明:该模型能更好地符合Witty蠕虫的实际传播数据,偏差比已有的模型分别减小了4.4 %和6.2 %.     

Reactive incorporation of Ag into porous TiO_2 coating and its influence on its microstructure,in vitro antibacterial efficacy and cytocompatibility

Ag-doped TiO₂ coatings were successfully fabricated on Ti using plasma electrolytic oxidation(PEO) in the electrolytes containing Ag or Ag₂O nanoparticles(NPs). The results showed that the different Ag sources resulted in significant variations of morphology, composition and chemical state. The thermal decomposition of Ag₂O during PEO process contributed to the formation of Ag NPs, which might reactively incorporate into TiO₂, leading to the presence o...     

非平稳信号处理中的LMS自适应滤波器研究

分析了时域及变换域LMS自适应滤波器的设计,提出了一种基于分数阶Fourier域的LMS自适应滤波算法,并推导了基于离散分数阶Fourier变换的计算方法.     

地黄块根膨大过程中土壤化感物质含量及微生物数量变化研究

以怀地黄为实验材料,对地黄块根膨大速率动态变化及地黄根际土壤中的潜在化感物质阿魏酸、香草酸、香草醛、对羟基苯甲酸含量的动态变化进行了研究分析.结果表明:①块根膨大速率动态变化呈一双峰曲线,第1个高峰出现在栽秧后70～130 d,第2个高峰出现在栽秧后150～190 d.②根际土壤中的阿魏酸、香草酸、香草醛含量变化与块根膨大速率变化动态相似,对羟基苯甲酸表现为先上升后下降;阿魏酸与地黄块根的膨大正相关;地黄块根膨大过程中根际土壤放线菌、真菌数量均明显增加,根际微生物可能将地黄根系分泌物进行生物转化生成了导致地黄连作障碍的酚酸类化感物质.