透明红外硫系薄膜非均匀性检测及影响因素

薄膜非均匀性的无损检测对于制备大面积高质量的红外透明薄膜尤为重要。针对红外薄膜光学均匀性难以获取的困难,提出了一种同时获得单层透明红外薄膜厚度和折射率均匀性的无损检测方法。实验上,通过磁控溅射法在二氧化硅衬底上制备了厚度约1.4μm红外透明Ge-Sb-Se硫系薄膜,然后在该薄膜上标定出36个80μm×80μm区域,利用显微傅里叶红外光谱仪测得该36个区域的透射谱,通过分段滤波的方法滤除背景噪声,运用改进的Swanepoel方法计算得到了薄膜每一个区域的厚度和折射率,进而精确获得该薄膜的厚度和折射率均匀性,结果表明精度优于0.5%。     

5G光模块技术及方案对比

论述了5G光模块的技术和产业化发展现状,分析了4种波分复用技术应用于5G前传网络的优缺点,给出了后续5G光模块发展的策略建议.     

新一代多模型迭代算法在70 kVp成人副鼻窦CT扫描中的应用

探讨成人在70 kVp副鼻窦CT检查中降低有效辐射剂量的同时,获取最佳图像质量的新一代多模型迭代算法(Adaptive Statistical Iterative Reconstruction-V,Asir-V)的权重。本研究对20例成人患者进行副鼻窦Revolution CT检查,采用70 kVp、230 mA条件下进行螺旋CT扫描,扫描完成后对每例患者的原始数据采用不同权重(0,20%,40%,60%,80%,100%)的后置新一代多模型迭代算法(Adaptive Statistical Iterative Reconstruction-V,Asir-V)重建的方法,共获得120幅图像,并对每例6组图像进行客观评价及主观评分。客观评价包括噪声(standard deviations, SD)和对比噪声比(contrast noise ratio,CNR),主观评价由2名评价医生对图像质量评分并对两者的主观一致性进行评价。每例患者扫描完成后,记录其剂量长度乘积(dose-length product,DLP)和CT容积剂量指数(CT dose index volume,CTDI_vol),并计算其平均有效辐射剂量(effective dose,ED)。客观评价结果表明不同权重的Asir-V图像噪声随着Asir-V权重的提升而降低,CNR值随着Asir-V权重的提升而升高,且有效辐射剂量ED较常规头颈部CT检查的平均辐射剂量明显减少;主观评价结果表明不同权重的Asir-V图像评分不同,在Asir-V 60% 时评分最高,且2名医生主观评价一致性好。结合主客观评价结果,认为在70 kVp、230 mA成人副鼻窦Revolution CT检查中,Asir-V 60％的图像既可满足临床诊断的需要,也可明显降低有效辐射剂量。     

数字化羊绒测色法及其在长度测量中的应用

针对光电法测试纤维长度等性质时,存在纤维的透光及反光信号与颜色高度相关的问题,采用数字化方法表征羊绒的颜色类别并精准地测量羊绒的长度。将彩色光电耦合器作为测色传感器,搭建了更适合纤维材料的测色装置;通过颜色模型在3种色空间的转换,得到3类颜色的羊绒在三维色空间的分布;基于系列实验,创建了有色羊绒的光学参数即无穷厚时的表观反射率表观反射率与测色装置计算的亮度指标之间的换算模型,并用实验证明采用测得的表观反射率可计算得到准确的须丛线密度曲线,从而可用光电法精准测量有色羊绒的长度。结果表明,该测色方法的测样面积大,代表性好,成本低,同时可用于其他纤维和纺织品的颜色测量。     

Damage evolution around white etching layer during uniaxial loading

Rolling contact fatigue cracks and thermally induced defects are common problems in the railway industry especially as demands for increasing loads, speeds, and safety continue to rise. Often, the two types of defects are found together in the field, however, whether one causes the other to occur is not completely agreed upon. The effect of thermal damage, in the form of a martensite spot on pearlitic steel test bars, on the fatigue life in uniaxial low cycle fatigue experiments was investigated by the authors. However, the focus of the current work was to characterize the damage evolution from the low cycle fatigue (LCF) tests and correlate the crack initiation and propagation with the initial thermal damage. Residual stress measurements, digital image correlation, and X‐ray tomography were used to characterize the effects of the thermal damage before, during, and after fatigue testing, respectively. It was found that the thermal damage causes strain accumulation and crack initiation at the interface between the two materials. The strain evolution was visualized using digital image correlation (DIC), clearly showing the strain concentrations at the top and bottom of the white etching layers (WEL), where the residual stresses are also most tensile. X‐ray tomography confirmed the planar crack growth from the martensite spot.     

Shape from focus based on 3D structure tensor using optical microscopy

Shape from focus (SFF) is a widely used passive optical method for 3D shape reconstruction. In SFF, a focus measure, which is used to estimate the relative focus level, plays a critical role in depth estimation. In this article, we present a new focus measure for accurate 3D shape estimation in optical microscopy based on the analysis of 3D structure tensor. First, the 3D tensors are computed from the input image sequence for each pixel. Then, each tensor is decomposed into point, curve, and surface tensors by decomposing tensors into eigenvalues and eigenvectors. Finally, the surfaceness is used to measure the quality of sharpness. The proposed focus measure provides accurate focus values and better resistance against noise. The proposed measure is evaluated by conducting experiments using image sequences of simulated and microscopic real objects. The comparative analysis demonstrates the effectiveness of the proposed focus measure in recovering 3D shape.     

Crack initiation and propagation in braided SiC/SiC composite tubes: Effect of braiding angle

Crack initiation and propagation in three braided SiC/SiC composite tubes with different braiding angles are investigated by in situ tensile tests with synchrotron micro-computed tomography. Crack networks are precisely detected after an image subtraction procedure based on Digital Volume Correlation. FFT based simulations are performed on the full-resolution 3D images to assess elastic stress/strain fields. Quantitative measurements of the crack geometries are performed using a novel method based on grey levels. The results show that braiding angle has no obvious effect on the location of crack onsets (initiation always occurs at tow interfaces), whereas it significantly affects the paths of crack propagation. This work provides an explicit demonstration of the crack propagation scenarios with respect to the mesoscopic fibre architectures.     

Polytetrafluoroethylene-intercalated MXene membranes with good photothermal performance for enhanced laser ignition

Photothermal effect has been widely used in many areas such as cancer therapy, photothermal energy harvesting, and laser ignition. However, exploring reliable and efficient free-standing energy converter for enhancing the photothermal performance is still a challenge. Herein, free-standing membrane based on two-dimensional MXene (Ti₃C₂) nanosheets and polytetrafluoroethylene (PTFE) was fabricated and characterized by X-ray diffraction, scanning electron microscopy and differential scanning calorimetry, which demonstrated a drastic temperature rise by laser irradiation and was further used as energy converter for enhancing the photothermal performance of laser ignition. Furthermore, the initiating power of the laser initiator can be largely reduced by adding a thin layer of MXene/PTFE membrane above the B/KNO₃ cylinder. This work can give great promise for MXene-based membranes as the laser energy converter for reducing the initiating energy and promote the development of laser initiators with low initiating energy.     

用于低损耗特种玻璃熔炼的高纯致密锆英石的研制

以纯度大于99.9%(质量分数)的高纯ZrO₂和SiO₂为原料,少量TiO₂为添加剂,采用高温固相法合成高纯锆英石(ZrSiO₄)粉料。研究温度和反应时间对高纯锆英石合成效率的影响,发现粒度小于50 μm的原料粉末经1 500 ℃反应48 h后,ZrSiO₄相的含量可以达到95.77%(质量分数)。将合成的高纯锆英石粉料球磨并冷等静压成型后,在1 550 ℃高温烧结成高纯致密锆英石砖。高纯致密锆英石中杂质Fe的含量仅为29 μg/g,Cu的含量小于1 μg/g,是普通商用致密锆英石的1/10;对磷酸盐玻璃静态光吸收损耗的影响仅为普通致密锆英石材料的1/3。将这种高纯致密锆英石材料用于激光玻璃窑炉,有助于降低玻璃对1 053 nm激光的损耗,提升激光玻璃的激光性能。