Regularity control of porous anodic alumina and photodegradation activity of highly ordered titania nanostructures

A two-step anodizing process was used to prepare wide-range highly ordered porous anodic alumina membrane （PAA） in the electrolyte of oxalic acid. The effects of anodic voltage, anodizing time, size of aluminium foil and additives on the regularity of PAA membrane were also studied in the process of two-step anodization. The template method was combined with the sol-electrophoresis deposition and sol-gel method respectively to prepare highly ordered titania nanostructures. The diameter and length of the obtained nanostructures were determined by the pore size and depth of the PAA template. Scanning electron microscopy （SEM） and X-ray diffraction （XRD） were, used to characterize the morphology and phase structure of the PAA template and the titania nanostructures. The results show that the anodizing time and the additive of ethanol have a great effect on the regularity of PAA template. This can be explained from the self-organized process and the current density theory. A theoretical model based on the self-organized process was established to discuss the formation mechanism of PAA template from the chemical perspective. The titania nanostructures prepared with this method has a high specific surface area. Furthermore, the photocatalytic activity of titania nanostructures on methyl orange were studied. Compared with ordinary titania membranes, the titania nanostructures synthesized with this method have higher photodegradation activity.     

Influence of intermittently etching on quality of CVD diamond thin films

A new method, called growing-etching repetitional process based on hot filament chemical vapor deposition, was proposed to improve the quality of diamond film. During the deposition carbon source was intermittently closed letting hydrogen etch the surface of the diamond film fi＇om time to time. In order to find whether it is helpful to the films＇ quality, a series of experiments were done. The results show that the new method can enhance the orientation of the chemical vapor deposition diamond films, reduce the graphite phase and increase the film＇s surface resistivity.     

砂轮的自动修整与修锐

砂轮稳定的特性对于数控机床(CNC)和自动磨床是很重要的，一个好的修整／修锐工作可以减小磨削力的变化，使磨削状况更容易控制。可是，同样的砂轮、工件材料和同样的磨削条件却不意味着砂轮每次加工都可以达到同样的表面状态。事实上，磨削过程中砂轮表面的变化是复杂和随机的。这就产生了不需要修整的砂轮被修整了(从而增加了加工时间栅砂轮磨耗)或需要修整时砂轮还继续工作。这可能导致砂轮的烧伤或震颤。通常，在精磨中一般用测试和误差来获得磨削和修整参数的完美结合。本次研究介绍了用不同修整方法修整／修锐不同砂轮的全自动修整系统。本系统由四个主要部件组成，磨床、驱动器和控制部件、软件和测量装置。本系统用新式气动传感器来检测砂轮表面形貌。该传感器用极灵敏的袖珍感应器捕捉感应器中空气冲击砂轮表面时产生的静压变化。这就是所谓的HRPS(高灵敏压力传感器)。传感器探头安置于离砂轮一定距离的位置上。这个距离的预置以确保来自感应器的有效感应。传感器能够检测到砂轮表面的三维尺寸小到0．95μm。本文说明了实际加工和应用中传感器检测韵结果。     

水热法合成和表征有序排列BiFeO3纳米线

以硝酸铋和氯化铁为原料，NaOH为矿化剂，水热条件下制备了有序排列BiFeO3纳米线。利用透射电子显微镜（TEM）、高分辨透射电镜（HRTEM）和X射线衍射仪（XRD）对样品进行了表征。研究了矿化剂浓度和反应温度对产物结构和形貌的影响，结果表明在160-180℃制备了有序排列的BiFe03纳米线，纳米线的直径为50～100nm，长为200-500nm。     

09MnNiDR钢焊接试验

对09MnNiDR钢进行焊接试验，并着重于埋弧焊试验，其接头的力学、弯曲、-70℃冲击性能均满足要求，并对焊缝金属进行了微观分析。     

CO2固化碱性甲阶酚醛树脂粘结剂的研究进展

CO2 固化碱性甲阶酚醛树脂粘结剂是一种新型的造型、制芯材料。自问世以来 ,引起了国内外学者的广泛重视 ,经过十多年的研究 ,已在粘结剂的固化机理、甲阶酚醛树脂的合成与改性、新型固化剂的选择、固化工艺的改进等方面取得了许多新的进展。     

匀速旋转参照系中的类磁引力

针对旋转参照系中假想力等问题,从类磁引力场出发,把惯性系中引力定律的研究结果推广到旋转的非惯性系中,提出了匀速旋转参照系中的三点假设,三点假设在匀速旋转参照系中的应用得到了满意的结果.在匀速旋转系中用真实的类磁引力取代了虚设的惯性力,并把牛顿定律推广到旋转非惯性系中.     

基于卷积神经网络联合多域特征提取的干扰识别算法

干扰识别技术是智能抗干扰通信系统中的关键技术,通过对接收信号中干扰类型的准确判别,可为无线通信系统生成最佳的抗干扰方式提供决策依据。针对无线通信系统中典型压制式干扰的识别问题,本文提出了一种基于卷积神经网络联合多域特征提取（Convolutional Neural Network-based Joint Multi-Domain Feature Extraction,CNN-JMDFE）的干扰识别算法,通过CNN同时对两种预处理增强的数据对象:时频图像与频域序列提取干扰特征,有效利用了两种数据对象的优势,提升了干扰识别性能。仿真结果表明,在对于包含动态和参数随机的干扰识别场景下,CNN-JMDFE算法在干噪比（Jamming-to-Noise Ratio,JNR）≥-2 dB时可准确识别14种类型的干扰,识别性能明显优于基于时频图像或频域序列单一数据对象的基于卷积神经网络自动特征提取（Automatic Feature Extraction-based Convolutional Neural Network,AFE-CNN）算法;与传统的人工特征提取的深度神经网络（Manual Feature Extraction-based Deep Neural Network,MFE-DNN）相比,本文算法显著提升了在低JNR下分类准确率,增强了干扰特征的抗噪性能;对于复合干扰,本文算法同样可取得良好的分类效果,当JNR≥0 dB时可准确分类10种复合干扰。      

一类三次多项式混沌映射的判定及性能分析

该文给出了一般3次多项式映射与分段线性混沌映射拓扑共轭的充分条件,从而间接地给出了一般3次多项式成为混沌系统的充分条件。进一步对拓扑共轭的分段线性映射和多项式映射的均匀性、结构复杂性和随机性进行了分析,结果显示分段线性映射的均匀性优于多项式映射,多项式映射的随机性优于分段线性映射,在结构复杂性方面,二者没有显著差异,但量化方法对二者的结构复杂性影响显著。