Backscattered electron SEM imaging of cells and determination of the information depth

Backscattered electron imaging of HT29 colon carcinoma cells in a scanning electron microscope was studied. Thin cell sections were placed on indium‐tin‐oxide‐coated glass slides, which is a promising substrate material for correlative light and electron microscopy. The ultrastructure of HT29 colon carcinoma cells was imaged without poststaining by exploiting the high chemical sensitivity of backscattered electrons. Optimum primary electron energies for backscattered electron imaging were determined which depend on the section thickness. Charging effects in the vicinity of the SiO₂ nanoparticles contained in cell sections could be clarified by placing cell sections on different substrates. Moreover, a method is presented for information depth determination of backscattered electrons which is based on the imaging of subsurface nanoparticles embedded by the cells.     

DESIGN AND PERFORMANCE OF TWO ORTHOGONAL EXTRACTION TIME-OF-FLIGHT SECONDARY ION MASS SPECTROMETERS FOR FOCUSED ION BEAM INSTRUMENTS

The design and performance of two orthogonal extraction time-of-flight mass spectrometers are reported that were adapted to existing focused ion beam microscopes for secondary ion mass spectrometry. The performances of these designs were compared to that of a prototype previously described by our group. The differences include newly designed transfer ion optics and in the use of a larger microscope chamber. The two new prototypes allow a mass resolving power of either 600 Th/Th (compact design) or 3000 Th/Th (high resolution design) while simultaneously achieving a lateral spatial resolution of less than 50 nm. The spectrometers and their performance (effective ion yield, mass resolving power, lateral, and depth resolution) are described and compared. Additionally, example applications are presented with multivariate statistical methods to visualize the data sets. Both time-of-flight mass analyzers use orthogonal extraction which avoids the need to pulse the primary ion beam, and the of use monoisotopic gallium to preserve the mass resolution. The goal of the design was a cost-effective accessory to augment typical focused ion beam-scanning electron microscopy applications as an alternative to the cost of a dedicated secondary ion mass spectrometer. The modified instrument allows excellent non destructive imaging and easy sample access, and benefits from the presence of complementary non destructive analytical and imaging techniques that exploit the presence of an electron microscope.     

斜井施工中针梁模板台车针梁的有限元分析

介绍了隧道混凝土衬砌施工中针梁模板台车的结构和工作原理,应用有限元软件ANSYS对在20°斜井施工中针梁模板台车针梁部分进行结构分析。通过对针梁多次施加不同大小的载荷,找出了针梁的最大允许应力或最大允许变形时的载荷大小,为隧道的准确衬砌和安全施工提供依据。     

SCS-100TU型电子汽车衡秤体结构优化

针对目前汽车衡秤体结构材料利用率低、质量大的问题,将结构优化设计的方法引入到秤体结构设计中。以U型梁和秤台的几何尺寸为设计变量,秤体的最大挠度为约束条件,秤体整体质量为目标函数,利用参数化APDL语言建立了秤体结构的有限元优化模型,对秤体结构进行了优化分析,从而确定了U型梁和秤台的几何尺寸。研究结果表明,在满足秤体刚度和强度设计要求的前提下,秤体结构优化后的质量比原来的降低了6.7%,实现了降低秤体结构质量的目的,提高了材料利用率。     

场桥轨道焊接接头形式对焊接残余应力的影响

针对轨道焊接接头容易产生疲劳裂纹问题,利用Abaqus有限元分析软件分别模拟计算了横角焊、船型焊焊接残余应力,并以此研究了轨道焊接疲劳性。从分析结果可以看出,一道船型焊时,其应力集中最小,而采用横角一道焊时,应力集中最大,易从轨道侧焊趾位置开裂,与现场裂纹位置相吻合。     

圆筒内有接头的细长杆稳定性问题

圆筒内有接头的细长杆受轴压和重力作用下的稳定性问题,均假设接头部分紧贴圆筒壁,由于忽略了钻杆x向重力分量的影响,可能会低估正弦屈曲载荷.基于接头两端点接触的假设,建立了相应的控制微分方程,采用微分求积单元法（DQEM）进行求解.给出了公式和相应的迭代求解算法及具体的算例.结果表明,现有文献中给出的正弦屈曲载荷与忽略了钻杆x向重力分量的影响后得到的结果相同,比计及了钻杆x向重力分量的影响后得到的结果要小.     

一种激光瞄准具瞄准偏差的判读系统

介绍了一种激光瞄准具瞄准偏差判读系统的工作原理、系统组成,利用重心法和圆拟合法二种算法提取光斑中心;重点介绍了软件的实现方法。标定实验结果表明系统对激光光斑中心的判读误差不大于0.1mm。该方法具有较高的工程应用价值。     

变截面悬臂梁的 Pro／Mechanica有限元法设计

由于工程中所使用的承受均布载荷的等截面积悬臂梁并不经济,使用Pro／Mechanica对受均布载荷的变截面矩形悬臂梁进行等强度分析设计,使得矩形截面梁的质量在强度允许范围内达到最小,从而可以避免材料的浪费,有工程的实用价值和现实意义。     

基于改进遗传算法的悬臂起重机悬臂梁优化设计

针对悬臂起重机材料冗余量大、生产成本高的问题,在深入研究优化设计算法的基础上,通过分析悬臂起重机悬臂梁的受力情况,结合悬臂梁多采用工字钢的特点,将离散变量结构优化技术与遗传算法相结合,提出了基于改进遗传算法的悬臂起重机悬臂梁优化设计方法,构建了离散变量结构优化的数学模型和适应度函数,实现了悬臂梁结构的优化设计,验证了该优化设计方法的有效性,降低了生产用钢量,对工程应用具有一定的指导意义。