基于改进YOLOv4的扫描电镜磨粒图像智能识别

磨损颗粒分析是设备磨损故障诊断和预测的有效手段,为了提高磨粒检测的自动化和智能化程度,提出1种基于改进YOLOv4的目标检测算法,并应用于航空发动机扫描电镜磨粒图像识别.首先,新算法采用VoVNetv2-39替换YOLOv4原主干网络CSPDarknet53,并引入BiFPN特征金字塔结构与新主干相连,同时调整模型中所有3×3标准卷积为深度可分离卷积,以加强多层次特征融合,构造轻量级网络;其次,利用迁移学习解决扫描电镜磨粒图像数量较少的问题,并通过冻结训练加速模型训练过程;最后,应用实际发动机扫描电镜磨粒图像验证,结果表明：新算法相较于原YOLOv4网络,在保证精度的前提下,网络参数量大幅降低,识别速度提升51.1%,满足实际扫描电镜磨粒图像快速、简洁和高精度的检测需求,具备潜在的工程应用价值.     

Growth mechanism of octahedron-like BaMoO4 microcrystals processed in microwave-hydrothermal: Experimental observations and computational modeling

Octahedron-like BaMoO4 microcrystals were synthesized by the co-precipitation method at room temperature and processed in microwave-hydrothermal at 413 K for different times （from 30 min to 5 h）. These microcrystals were analyzed by X-ray diffraction （XRD）, field-emission gun scanning electron microscopy （FEG-SEM） and transmission electron microscopy （TEM）. XRD patterns showed that this material presents a tetragonal structure without the presence of deleterious phases. FEG-SEM and TEM micrographs revealed that the BaMoO4 microcrystals present an octahedron-like morphology with agglomerate nature and polydisperse particle size distribution. These micrographs also indicated that the microcrystals grow along the [0 01 ] direction. The observed crystallographic planes in these structures were modeled computationally and a crystal growth model was proposed in order to explain the morphological changes as a function of processing time.     

耕耘不息 求索不止——记吴自勤教授对电子显微学的贡献

在中国电子显微学领域,吴自勤教授是一位勤奋工作、求实进取、成绩卓著而深受同行敬重的学者.在他临近八十华诞之际,我们撰写这篇贺文,希望能弘扬他为电子显微学和中国电镜事业的发展所做出的贡献.     

冷场扫描电镜结合X-射线光电子能谱解析表面活性剂对含聚油泥稳定结构的影响

为解决胜利油田孤岛聚合物产生的高稳定性含聚油泥难以处理的问题,采用冷场扫描电镜(SEM)结合X-射线光电子能谱(XPS),对含聚油泥体系的结构及不同类型表面活性剂对油泥的作用进行分析.结果表明,聚丙烯酰胺(HPAM)和聚合氯化铝(PAC)作用产生的Al-O键和N+-Cl键会形成空间网状沉淀物质,而此种空间网状沉淀物质正...     

红外窗口复合材料的制备与表征

利用无机、有机复合的方法获得了性能优良的红外窗口复合材料。扫描电镜观察发现无机粒子在有机基质中分布均匀。透过率测试结果表明,复合材料透过率的截止波长是由无机粒子和有机基质材料的光透过性能共同决定的．并且透过率随材料厚度增加而降低。     

矿物掺合料作为砂浆细集料的水化产物与光谱性能研究

粉煤灰、锂渣和钢渣作为工业废渣,等质量替代水泥时其利用率往往较低,为了大量地使用这些工业废渣。采用X射线单晶衍射仪、同步热分析仪、傅里叶红外光谱仪和电镜扫描分析方法,研究了锂渣、粉煤灰和钢渣替代细集料后砂浆的水化产物、光谱特性、微观形貌,并探讨了砂浆抗折/抗压强度随替代率(0%,30%,50%,70%和100%)增长的变化规律。研究结果表明：四种浆体的水化产物主要为CSH凝胶、Ca(OH)₂、少量的AFt和未水化的颗粒(Al₂O₃,SiO₂),其中水泥-锂渣浆体、水泥-粉煤灰浆体、水泥-钢渣浆体中的未水化颗粒还含有一定的Li₂O·Al₂O₃·SiO₂,Ca_1.56SiO_3.5·xH₂O和RO phas。四种浆体以3 467,3 438,2 923,2 348,1 638,1 429,1 111,1 000,768,696和462 cm-1为特征峰,但其峰强有所不同,其活性也不同,参与二次水化反应的程度也不同,因此,水泥-钢渣浆体中Ca(OH)₂的含量明显高于水泥-粉煤灰浆体和水泥-锂渣浆体的现象;但不管是矿物掺合料替代水泥还是细集料,都在浆体中发挥着火山灰活性和填充作用。含三种100%矿物掺合料砂浆的抗折强度和抗压强度均高于纯水泥砂浆,分别(锂渣、粉煤灰和钢渣)约高37.77%/51.88%,14.71%/11.70%,91.95%/34.88%,但其达到峰值的掺量不同。因此,采用矿物掺合料替代细集料是可行的,能大幅度提高工业废渣在混凝土行业中的使用,且能达到节能减排的效果。     

铀矿坑水样中铀电沉积层的表征

描述了硫酸铵溶液中铀矿坑水样品中铀的电沉积层特性。 电沉积液为10 ml 0.8 M的硫酸铵溶液, 电流密度0.6 A/cm2, pH值为2.5, 电镀1 h。 电沉积经化学分离后的水样品和电沉积的纯硝酸铀酰样品进行了比较, 并对二者分别做了红外(IR)光谱、 扫描电镜(SEM)、 元素分析以及α能谱测量。 IR谱上铀酰离子的反对称伸缩振动峰在887 cm-1附近, 使电沉积在不锈钢片上的铀主要以铀酰离子水合物的形式存在, 有一部分NH+4以NH3的形式替代水合物中的水, 使电沉积层中铀的化合物形式为UO2(OH)2·xNH3·yH2O或者UO2(OH)2-x·(ONH4)x·yH2O, 铀酰离子通过链的形式形成聚合结构。 SEM照片显示电沉积层均匀, 没堆积成团现象出现。 α谱表明电沉积层中铀的同位素主要是238U和234U, 相应的α能量峰4198和4773 keV很显著, 没其它峰的干扰。 Characteristics of electrodeposited uranium films of uranium ore water sample in ammonium sulphate was investigated in this work. The optimized electrodeposited conditions were as follows: electrolyte was ammonium sulphate of 0.8 M, and current density at the cathode was 0.6 A/cm2, electrolyte pH value was 2.5, the time of plating on the electrodeposition was 1 h. In this situation, the uniform, thin and adheresive films were produced by electrodeposition method. Two samples were made, one electrodeposition of pure uranyl nitrate, and another electrodeposition of uranium ore water sample after chemical separation. Characteristics of electrodeposited uranium films of uranium ore water sample after chemical separation was studied, making comparisons with electrodeposited films of uranyl nitrate. The analysis of film characteristics was done through infrared (IR) spectrum, scanning electron microscopy(SEM), element analysis and α spectrum measurment. According to Fourier transform infrared spectra, the asymmetric stretching vibration band of uranyl group is around 887 cm-1. In addition, according to IR spectrum, we know that uranium exists mainly as the form of hydrated polymeric compound in the film. Electrodeposited uranium films also included many NH+4. Polymeric structures of variable composition were present in the electrodeposited samples, with the unit monomeric formula UO2(OH)2·xNH3·yH2O or UO2(OH)2-x·(ONH4)x·yH2O. Scanning electron microscopy shows that the two samples have similar surface characteristics and no cluster is observed. The samples were also measured by spectrometer equipped with Passivated Implanted Planar Silicon(PIPS) detector. From the α spectrum, we know that isotopes of uranium in the film are 238U and 234U. 235U is not found in the α spectrum. It also shows that the chemical separation process can isolate uranium from other interfering elements effectively, the result of chemical separation is very satisfactory and electrodeposited process is rather efficient. Source electrodeposited in ammonium sulphate through optimized conditions satisfies the need of high resolution α spectrum.     

莫桑鼻给非鲫卵子发生的扫描电镜观察

用冰冻断裂术制样,通过扫描电镜首次观察了莫桑鼻给非鲫的卵子发生过程。结果表明卵母细胞内卵黄积累迅速,卵黄球最先在细胞核周围出现,然后逐渐充满细胞内,卵膜由卵母细胞产生。     

超声疲劳试验方法及其应用

超声疲劳是一种加速的疲劳试验方法,它的测试频率(20kHz)远远超过了常规疲劳测试频率(小于200Hz)．超声疲劳试验研究表明50^#车轴钢和40Cr钢直到10^10个应力循环后仍会发生疲劳断裂,并不存在常规疲劳试验曲线所示的“疲劳极限”,因此用10^7周次的疲劳试验数据进行疲劳强度设计并不安全．50^#车轴钢和40Cr钢超声疲劳性能优于常规疲劳性能．扫描电镜分析表明,超长寿命阶段50^#车轴钢裂纹萌生于次表面夹杂．介绍了超声疲劳试验系统、工作原理及超声疲劳试样的设计．