面向海洋应用的低真空质谱仪操作模式研究

为使质谱仪能够在低真空环境下进行质量分析,扩展其在海洋科学领域的应用,研究了适用于低真空环境的质量分析操作模式。针对圆柱形离子阱质量分析器,在COMSOL Multiphysics中基于Langevin碰撞理论搭建了低真空环境离子运动仿真平台。利用该平台模拟了不同低真空条件下,射频电压频率、射频电压零峰值、离子阱尺寸等参数对质谱仪分辨率和灵敏度的影响。结果表明,增大射频电压频率、减小离子阱尺寸等操作模式可适用于低真空环境质量分析。     

低真空循环水供热对汽轮机运行的影响

低真空循环水供热能够实现能源的梯级利用，具有节能、环保、高效能源利用等优点，有良好的推广应用价值和发展前景。但此项技术的应用会对汽轮机带来一系列问题和安全隐患，影响机组的安全性。文中主要从主机设备安全的角度出发，深入分析应用此技术对汽轮机带来的影响，详列影响因素并提出解决办法，为今后汽轮机低真空改造提供指导性帮助。     

低地板有轨电车集成式真空注油机的设计研究

本文主要根据客户企业需求设计并制造了针对低地板有轨电车抗折弯系统的集成式真空注油机,分别对集成式真空注油机的五个部分(真空除气系统、加压注油系统、电控系统、抗折弯手动加载系统和推车)进行了介绍,经交付客户企业后,集成式真空注油机的各项性能参数均符合预期性能指标。     

小波图像融合改善超声图像横向分辨率的研究

摘要：针对超声图像分辨率较低,尤其是横向分辨率低的特点,采用基于插值和小波图像融合相结合的方法对相控阵超声图像进行了多种方式的对比试验,结果表明：算法采用区域能量大小判定的设计思想对改善超声图像的分辨率是可行的,其中利用小波分解将经过插值放大的待融合图像分解为低频部分和高频部分,然后将低频部分采用平均法,高频部分采用区域能量最大的融合方式对改善超声图像的分辨率取得了较好的效果。     

一种面向低真空环境的质量分析方法仿真研究

在低真空环境进行质谱分析可以大幅降低仪器的成本、体积和功耗,实现质谱仪的便携化。在四极杆质量分析器中,增大压强会导致离子轴向运动能量不足,无法到达检测器。为解决这一问题,提出了一种使用顺向气流作为离子出射动力,适用于低真空环境的质量分析方法,并在COMSOL Multiphysics中搭建仿真模型进行验证。仿真结果表明,利用该方法得到的谱峰强度和谱峰宽度明显优于无气流条件下的分析结果。该研究成果为低真空质谱仪的研发奠定了理论基础,促进质谱仪便携化和传感器化、降低使用门槛、扩展应用领域。     

浅议汽轮机真空低的原因及对策

汽轮机是一种以蒸汽的热能转化为机械能的一种机械设备，在实际生产生活中应用十分广泛，汽轮机在发电、航运等方面有着很重要的作用。但是在汽轮机的实际应用过程中也存在不少问题，其中汽轮机真空低就是影响汽轮机运行的重要因素之一。汽轮机的真空低的原因来自于多方面，只有深入研究汽轮机真空低的原因，并给出解决对策，才能保证其正常运行。下面就汽轮机在实际应用中的问题做分析，探讨解决汽轮机真空低问题的技术措施。     

低真空变压热处理技术的特点及其发展

一、前言 热处理质量取决于热处理工艺,正确完成热处理工艺取决于热处理设备。先进的热处理设备不仅应正确完成热处理工艺,而且应兼有节能和防止污染的特点。 20世纪40～50年代的“老三炉”(老式箱式、井式和盐浴炉的简称),现在仍占领着我国大部分     

汽轮机组低真空改造原理及凝汽器的优化设计

文中说明了未来一些地区机组低真空改造的必要性,通过对大连泰山电厂低真空改造凝汽器优化设计的分析和实际应用,提出了低真空改造对凝汽器的要求和需改造的部件,以及需注意的方面,涵盖了设计到运行方面的要求,为今后电厂的低真空改造提供设计依据和参考。     

提高彩电图像分辨率的研讨

本文简要介绍利用计算机辅助分析程序做为有力工具,研究与分析亮度通道电路,从而提高彩电图像的分辨率。     

软X射线-真空紫外傅里叶变换光谱仪及其光谱分辨率研究

描述在研的软X射线-真空紫外傅立叶变换光谱仪原理样机预期结构和性能,讨论并分析了影响谱仪光谱分辨率及谱线位移的因素,结合大数据量FFT数值算法给出实际仪器参数情况下的典型光谱线模拟曲线。     

Theoretical study of the ultimate resolution of SEM

This work aims to clarify the problem of why the ultimate resolution assessed experimentally from the observation of 0.8 nm separation of Au-Pd fine particles is beyond the theoretical resolution limit of scanning electron microscopy (SEM). The correlation between the spatial distribution of secondary electrons on a sample surface and the resolution estimated by edge-to-edge separation in SEM was studied by a Monte Carlo simulation with secondary electron generation included. The result clearly indicates that the edge-to-edge separation can extend beyond the theoretical ultimate resolution, particularly by image processing for contrast expansion and by improving the signal to noise ratio (S/N).     

Differential contrast imaging of secondary electron signals in cryo-field-emission scanning electron microscopy

Low-temperature scanning electron microscopy (LTSEM) is limited in resolution and image quality by charging of frozen hydrated samples and collection deficiencies of secondary electron signal contrasts. We measured and corrected both effects using differential hysteresis processing (DHP) of LTSEM images, scanned at 15-bit from 5×4 inch Polaroid negatives. Bulk charging produced a major contrast component equal to 44–87% of the intensity range of the image. The strong charging contrast reduced the local high-resolution signal contrasts to an unrecognizable level. Segmentation and imaging of the unaffected surface contrasts produced high-quality images of high contrast from metal-coated samples as well as from uncoated samples. The differential contrast imaging can be used for control of the sequential etching of ice from the non metal-coated sample as well as improved LTSEM imaging of the finally coated sample.     

Low-temperature SEM studies of beam-induced voltage contrast in YBCO thin films

Beam-induced voltage contrast has been demonstrated in a superconducting thin film of YBa₂Cu₃O_7-x (YBCO) grown on MgO. Copper-rich inclusions in the material contribute to spatially varying resistive behaviour but do not account for all the observed details. A new method of scanning in which the beam was moved away from the sample between each data acquisition point was found to increase the resolution by limiting thermalisation, to allow imaging of resistive features as small as 0.5 μm. Direct comparisons of beam-induced contrast and micro-structure at 9000 times magnification were possible using simultaneous image acquisition via a purpose-built image store. Mounting a preamplifier within the scanning electron microscope chamber, to give a variable overall gain of 1000–100,000, was also found to significantly improve the signal-to-noise ratio.     

扫描电镜电子背散射衍射系统的研制

本文介绍了扫描电镜电子背散射衍射接收系统,并将该系统成功地安装在JSM-840扫描电镜上。     

High resolution SE-I SEM study of enamel crystal morphology

Until recently high resolution TEM was the only imaging mode capable of probing the atomic lattice structure of crystals composing tooth enamel. Studies designed to determine the polyhedral shape of normal enamel crystals and initiation of carious lesions in enamel crystals were hampered and limited by interpretation of two-dimensional TEM images from thin section and freeze fracture replica specimens lacking depth of field. The newly developed SE-I signal mode for SEM (SE-I/SE-II ratio) can produce images of enamel crystals approaching beam diameter dimensions (0.7–2.0 nm), rivaling the resolution of the TEM technique and generating topographic contrasts for three dimensional imaging at very high magnification (≈?1,000,000 X). Ultrathin chromium (Cr) films generate enriched high resolution SE-I contrasts of enamel crystal surfaces and when imaged using an immersion lens field emission SEM operated at high voltage (20–30 KeV) produce unsurpassed topographic contrasts. Since the grain size of Cr is below the resolution of any SEM and is ultrathin (≈?1 nm), then SE-I images can provide a more accurate representation of enamel crystal structure than TEM methodologies. Our SE-I SEM observations of normal human enamel crystals reveal fractured spicules which contain angled flat surfaces delineated by a prominent 2 nm wide SE-I edge brightness contrast. Although microscopic observations often show crystals which are hexagonal in cross-section, in both SEM and TEM many other growth habits, including rectangular or irregular crystals (30–40 nm in width) which contain “notches,” are also observed. More detailed morphological studies are therefore required to determine the most likely habit planes and their relevance to the function of the enamel crystals. The granular appearing fine structural contrast imposed onto <100> lattice planes of sectioned enamel in TEM micrographs is also resolved with topographic contrasts in SE-I micrographs. These granules probably represent one or both of the enamel protein classes.     

Collection of secondary electrons in scanning electron microscopes

Collection of the secondary electrons in the scanning electron microscope was simulated and the results have been experimentally verified for two types of the objective lens and three detection systems. The aberration coefficients of both objective lenses as well as maximum axial magnetic fields in the specimen region are presented. Compared are a standard side‐attached secondary electron detector, in which only weak electrostatic and nearly no magnetic field influence the signal trajectories in the specimen vicinity, and the side‐attached (lower) and upper detectors in an immersion system with weak electrostatic but strong magnetic field penetrating towards the specimen. The collection efficiency was calculated for all three detection systems and several working distances. The ability of detectors to attract secondary electron trajectories for various initial azimuthal and polar angles was calculated, too. According to expectations, the lower detector of an immersion system collects no secondary electrons I and II emitted from the specimen and only backscattered electrons and secondary electrons III form the final image. The upper detector of the immersion system exhibits nearly 100% collection efficiency decreasing, however, with the working distance, but the topographical contrast is regrettably suppressed in its image. The collection efficiency of the standard detector is low for short working distances but increases with the same, preserving strong topographical contrast.     

The application of a hot deformation SEM stage, backscattered electron imaging and EBSD to the study of thermomechanical processing

The technique of combining in situ hot‐deformation and high resolution electron backscattered diffraction (EBSD) has been applied to study the mechanisms operating during the thermomechanical processing of metals. A simple hot tensile‐straining stage is installed in a field emission gun scanning electron microscope equipped with an EBSD system and has been used successfully for a number of preliminary investigations. These investigations include substructure formation, dynamic subgrain and grain growth, superplastic deformation in aluminium alloys, and dynamic recrystallization in copper. Despite the surface topography, which inevitably increases during plastic deformation, channelling contrast backscattered electron micrographs have been successfully obtained after strains of up to ～50%. Good quality EBSD maps have been obtained after strains of up to 100%. Most observations and measurements from the in situ experiments are consistent with what is known about the mechanisms occurring in the bulk. The microstructures revealed in the centre of the in situ samples after later repolishing are generally similar to those at the surface.     

Analysis of FIB‐induced damage by electron channelling contrast imaging in the SEM

We have investigated the Ga⁺ ion‐damage effect induced by focused ion beam (FIB) milling in a [001] single crystal of a 316 L stainless steel by the electron channelling contrast imaging (ECCI) technique. The influence of FIB milling on the characteristic electron channelling contrast of surface dislocations was analysed. The ECCI approach provides sound estimation of the damage depth produced by FIB milling. For comparison purposes, we have also studied the same milled surface by a conventional electron backscatter diffraction (EBSD) approach. We observe that the ECCI approach provides further insight into the Ga⁺ ion‐damage phenomenon than the EBSD technique by direct imaging of FIB artefacts in the scanning electron microscope. We envisage that the ECCI technique may be a convenient tool to optimize the FIB milling settings in applications where the surface crystal defect content is relevant.     

Observation of GaAs—AlxGa1 — x as heterostructures and quantum-well-wire structures using backscattered electron image

As a microscale tool for observing GaAs-Al_x Ga_1–xAs heterostructures, backscattered electron (BE) images in the scanning electron microscope (SEM) were compared with conventional secondary electron (SE) images. BE images were found to be more sensitive to compositional differences between GaAs and Al_xGa_1–xAs and less sensitive to surface roughness. BE images have a spatial resolution of 10 nm or better. This method enables the nondestructive observation of ultrafine lateral periodic structures, such as quantum-well-wire (QWW) structures, fabricated by compositional disordering technology using focused Ga ion-beam (Ga-FIB) implantation into GaAs-Al_xGa_1–xAs material.     

Comparative study of dental enamel loss after debonding braces by analytical scanning electron microscopy (SEM)

Clinical procedures when shear forces are applied to brackets suggest adhesion forces between 2.8 and 10.0 MPa as appropriate. In this study dental enamel was evaluated by scanning electron microscopy (SEM) before and after removing the brackets. Thirty bicuspids (previous prophylaxis) with metallic brackets (Roth Inovation 0.022 GAC), Transbond Plus SEP 3M Unitek adhesive and Transbond XT 3M resin were used. The samples were preserved to 37°C during 24 hr and submited to tangential forces with the Instron Universal machine 1.0 mm/min speed load strength resistance debonding. Also the Adhesive Remanent Index (ARI) test was made, evaluating the bracket base and the bicuspid surface. All the bracket SEM images were processed with AutoCAD to determine the enamel detached area. The average value was 6.86 MPa (SD ± 3.2 MPa). ARI value 1= 63.3%, value 2= 20%, value 3= 13.3% and 33% presented value 0. All those samples with dental enamel loss, presented different situations as fractures, ledges, horizontal, and vertical loss in some cases, and some scratch lines. There is no association between the debonding resistance and enamel presence. Less than half of the remanent adhesive on the dental enamel was present in most of the samples when the ARI test was applied. When the resin area increases, the debonding resistance also increases, and when the enamel loss increases, the resin free metallic area of the bracket base decreases in the debonding.