TEM样品制备中离子束对样品的损伤分析

针对TEM样品制备过程中离子束对样品的损伤所产生的"非晶化"影响进行分析和研究。在总结已有成果的基础上,得到一些新的突破:通过可信、简便的制样方法,可以直接观察到"非晶层";可以量测聚焦离子束制备的可供TEM分析的IC硅衬底样品的极限厚度。通过一系列自主设计的实验,得到如下结果:离子束的能量对"非晶层"厚度的影像非常大;"非晶层"的厚度与切割时离子束的加速电压有关,与离子束电流及入射角度等基本无关。     

一种新颖的基于离子束刻蚀的纳米沟道制备技术

研究了一种新颖的基于MEMS工艺中离子束刻蚀的纳米沟道制备技术,通过研究离子束刻蚀微米级线条时,离子束刻蚀角度与刻蚀的轮廓形状之间的关系,在2μm线条内刻蚀出纳米沟道所需要的掩模图形,并结合KOH的各向异性腐蚀,成功获得了纳米沟道阵列.在两种不同的离子束刻蚀条件下,在2 μm图形内分别制备出单纳米沟道和双纳米沟道,最小宽度可达440 nm.     

显微视觉系统对柱状微零件自动聚焦技术研究

针对显微视觉中的柱状物体图像的清晰度问题,提出了一种实时检测图像特征并跟踪特征区域进行自动聚焦的方法。该聚焦算法包括聚焦评价函数、聚焦搜索算法和聚焦区域选择。该聚焦搜索算法实现了显微视觉系统下快速准确的聚焦,克服了爬山搜索算法的缺点,有效避免搜索结果陷入局部极大值。显微视觉中对聚焦区域的选择尤为重要,以图像特征区域作为聚焦区域,实时检测该特征区域进行聚焦,实现了在景深小于柱状物体半径的情形下对柱状物体边缘的精确聚焦。粗聚焦后电机位置的标准差为205μm,精聚焦后电机位置的标准差为37μm。实验结果表明,该自动聚焦方法能够满足微装配系统对显微视觉的聚焦需求。     

TEM样品制备中离子束对样品的损伤分析

针对TEM样品制备过程中离子束对样品的损伤所产生的"非晶化"影响进行分析和研究.在总结已有成果的基础上,得到一些新的突破:通过可信、简便的制样方法,可以直接观察到"非晶层";可以量测聚焦离子束制备的可供TEM分析的lC硅衬底样品的极限厚度.通过一系列自主设计的实验,得到如下结果:离子束的能量对"非晶层"厚度的影像非常大;"非晶层"的厚度与切割时离子束的加速电压有关,与离子束电流及入射角度等基本无关.     

聚焦爬虫技术研究综述

因特网的迅速发展对万维网信息的查找与发现提出了巨大的挑战。对于大多用户提出的与主题或领域相关的查询需求,传统的通用搜索引擎往往不能提供令人满意的结果网页。为了克服通用搜索引擎的以上不足,提出了面向主题的聚焦爬虫的研究。至今,聚焦爬虫已成为有关万维网的研究热点之一。文中对这一热点研究进行综述,给出聚焦爬虫(Focused Crawler)的基本概念,概述其工作原理;并根据研究的发展现状,对聚焦爬虫的关键技术(抓取目标描述,网页分析算法和网页搜索策略等)作系统介绍和深入分析。在此基础上,提出聚焦爬虫今后的一些研究方向,包括面向数据分析和挖掘的爬虫技术研究,主题的描述与定义,相关资源的发现,W eb数据清洗,以及搜索空间的扩展等。     

毛细管等电聚焦电泳(cIEF)及其理论模拟计算新进展

等电聚焦电泳(IEF)是一种在一个pH梯度内操作的特殊电泳。IEF是表征蛋白质电荷不均一性的强有力工具。在一个pH梯度内,酸碱两性物(例如蛋白质)在电场的作用下会被分离,并最后在pH梯度内pH值与两性物等电点(pI)值相等的地方被聚焦成很窄的区段。IEF的分辨率在所有基于电荷的分离技术中是最高的。薄层凝胶IEF从它在上世纪70年代初被发明的时间起就成为在生物实验室被广泛应用的分析技术。但薄层凝胶IEF的主要问题是不能做定量分析,全靠手工操作及分析速度低。当毛细管IEF(cIEF)在1985年被报道时,科学家们就都立即认为cIEF能够克服IEF所有的问题。虽然cIEF看起来有很多优势,但是20多年后的今天它并没有被生物实验室广泛接受为薄层凝胶IEF的替代技术。究其原因是使用通用毛细电泳仪器的cIEF在操作上有很多困难。这种技术在IEF过程后还需要一个额外的移动过程来把聚在毛细管分离柱内的蛋白质区段推到检测器的检测点。这是由于这些毛细电泳仪器都是使用单点检测器。检测点都是靠近毛细管的一端。这个移动过程破坏IEF的高分辨率,降低重现性并使得分析速度变慢,造成在方法的优化上耗很多时间。全柱检测cIEF是在1992年提出的。该技术结合了凝胶IEF及毛细管分离的全部优点;如定量和自动化。它的分离速度大大提高。本文简单综述cIEF对不同生物实验室样品的应用。这些样品包括单克隆抗体,重组蛋白质,蛋白质复合物及失活病毒。最后,本文简述cIEF理论模拟计算的新进展。     

长焦镜头自动聚焦技术的研究与实现

针对长焦镜头自动聚焦问题,利用图像处理技术及嵌入式平台开发了一套自动聚焦系统.首先确定长焦镜头可调的聚焦范围,并在此范围内以大步进值搜索并到达清晰度最大值处,然后采用小步进值到达清晰点位置.其中清晰度值的实时计算采用硬件IP核的形式在FPGA上实现,并采用SOPC技术实现对各模块的控制.     

纳米三氧化钨制备技术及研究现状

纳米三氧化钨(WO3)作为一种典型的敏感材料已经广泛运用到了工业及民用生活等领域,日益受到研究者们的广泛关注。不同维度的纳米结构可有望得到性能优异的功能材料,通过结构设计及形貌改善可显著提高纳米WO3的气敏性能,本文综述了近年来不同形貌纳米WO3的制备技术及其在气敏传感器方面的研究现状,并指出了在研究过程中存在的问题。     

聚焦《工业控制系统信息安全行动计划(2018-2020年)》

2017年12月27日,工信部正式发布《工业控制系统信息安全行动计划（2018-2020年）》（以下简称行动计划）,这一行动计划的发布,是我国贯彻落实《国务院关于深化制造业与互联网融合发展的指导意见》、《国务院关于深化＂互联网＋先进制造业＂发展工业互联网的指导意见》等文件精神的具体行动,该行动计划的发布,     

面向三维重建的加工基准匹配技术研究

基于加工基准的匹配是制造毛坯动态演变序列三维模型重建过程中的关键点,在前驱三维工序模型投影视图与当前工序图已关联的前提下,通过分析加工基准的类型和特点,结合二维工序图表达形式,提出加工基准的获取方式及基准三元图形这一概念,同时结合这个概念介绍了加工基准匹配算法.最后通过实例验证该算法的可行性和有效性.     

Controlling parameters of focused ion beam (FIB) on high aspect ratio micro holes milling

Focused ion beam (FIB) direct milling is now recognized as a new method of fabrication, due to high flexibility in milling dimensions, the possible geometries and the material selectivity. This paper discusses the fabrication of micro holes using FIB direct milling in terms of high aspect ratio structures, including FIB parameters and the major effects of FIB milling. It is deduced that sputter yield of material gives a major impact to the depth of milling. Optimization parameters coupled control of FIB direct milling will provide a precise means of fabricating of high aspect ratio micro holes whilst resolving the problem of re-deposition and amorphisation which is common in micro milling.     

Study on the method for the reliability test of focused ion beam

We investigate the reliability of the focused ion beam (FIB) system with the designed evaluation patterns. The reliability test patterns are composed of three parts, which are the ion beam quality patterns, the ion beam scanning ability patterns and the stage system patterns. The designed patterns are fabricated with the commercial FIB system, and the common nanometer scale measurement systems, the atomic force microscopy and the scanning electron microscopy are used to evaluate the fabricated patterns. The measurement of the absolute length becomes important in the reliability test, and the measurement systems are calibrated with the standard patterns. The measurement results show the proposed patterns are suitable to measure the characteristics of FIB system and also other machines which can fabricate nanometer scale and high-aspect-ratio patterns.     

Micron-scale polymer-metal cantilever actuators fabricated by focused ion beam

Polymer-metal microcantilever actuators have been fabricated using an innovative approach based on focused ion beam micromachining technology. The fabrication involves depositing a thin metal film onto the surface of the polymer and machining using the ion beam. The microcantilever created is then extracted and transferred to a desirable support using a micromanipulator. This approach demonstrates the potential for maskless and resistless prototyping of cantilevers that can be evaluated for use as MEMS/NEMS actuators. Nanometer-scale displacement of the resulting polystyrene-platinum bimorph microactuator with respect to temperature change is demonstrated via visual monitoring in a scanning electron microscope with a heating stage. The performance of the bimorph cantilever microactuators is verified using both analytical and finite element modeling.     

Deposition property investigation of a focused ion beam for a high-aspect-ratio metal tip

We investigate the deposition properties of a focused ion beam for the fabrication of metal structures. We performed experiments under various beam currents, deposition times, and initial design diameters and analyzed the fabricated diameters and heights with recorded video clips. We observed abnormal deposition phenomena which show the etching effect as well as deposition, and investigated the relationship between the etching and parameters such as beam current and designed diameter. We apply these conditions and finally fabricate a high-aspect-ratio tip without abnormal deposition phenomena.     

Molecular dynamic simulation of orientation-dependent effect on silicon crystalline during sputtering process of focused ion beam

Microsystem Technologies - In this paper, experiments and molecular dynamic simulation are performed to investigate the crystal orientation-dependent effects in a focused ion beam (FIB) sputtering...     

Fast prototyping of high-aspect ratio, high-resolution X-ray masks by gas-assisted focused ion beam

The capacity of chemically-assisted focused ion beam (FIB) etching systems to undertake direct and highly anisotropic erosion of thin and thick gold (or other high atomic number {Z}) coatings on X-ray mask membranes/substrates provides new levels of precision, flexibility, simplification and rapidity in the manufacture of mask absorber patterns, allowing for fast prototyping of high-aspect ratio, high-resolution masks for deep X-ray lithography for the LIGA process. In preliminary demonstrations, an automated FIB system operating at 30 keV with a gallium liquid metal source and an iodine gas injection system was used for direct milling into a few micrometer thick gold of microstructures into the sub-hundred nanometer regime. Three-dimensional micromachining in bulk diamond is also reported to illustrate the capability of the technique.This work was made possible under funding for California Institute of Technology from NASA general contract (# NAS7-1407), the partial funding for CAMD from the DARPA grant HI-MEMS Development and Manufacturing (contract # N66001-98-1-8926). Patrick Deshaye (Norsam) microsculpting work is also gratefully acknowledged.This paper was presented at the Fourth International Workshop on High Aspect Ratio Microstructure Technology HARMST 2001 in June 2001.     

基于贝叶斯分类器的主题爬虫研究*

主题爬虫是实现定题搜索引擎的核心技术。提出了基于贝叶斯分类器实现主题爬虫的方法,介绍了基于贝叶斯分类器的主题爬虫的系统结构以及系统关键部分的实现,包括URL队列、爬行历史、页面下载以及页面分析,并重点介绍了基于贝叶斯分类器的主题相关度算法。爬虫使用改进的TF-IDF算法来提取网页内容的特征,并采用贝叶斯分类器计算其主题相关度。实验结果表明,在搜索大量网络资源的情况下,贝叶斯分类器比PageRank算法更适合用于实现主题爬虫。     

An ion milling pattern transfer technique for fabrication ofthree-dimensional micromechanical structures

We describe a useful method of transferring mask patterns over large distances using ion milling. This technique exploits the anisotropy of a collimated ion beam to etch the projection of a stencil mask pattern into a thin film. This method avoids the difficulties associated with photoresist processing on highly nonplanar substrates, and thus provides an alternative process avenue for the development of three-dimensional microstructures. We demonstrate this technique, in a process including wet anisotropic silicon etching, by fabricating arrays of high aspect ratio barbs which are intended for use in tissue fasteners in biomedical applications     

Research on the directionality of end dynamic compliance dominated by milling robot body structure and milling vibration suppression

The end dynamic characteristics dominated by the milling robot's body structure play a crucial role in vibration control and chatter avoidance in robotic milling. As the excitation source, the milling force may exist in any direction under different process parameters. Consequently, investigating the directional distribution of the end dynamic characteristics becomes essential for studying the direction-dependent dynamic response of a milling robot. In this paper, firstly, the directionality of the end modal vibration is proved based on the body structure mode shape of the milling robot. Subsequently, combined with the multi-body dynamics model of milling robots, the distribution of the end dynamic compliance with the excitation direction in the robot mode is modeled and found to be double-sphere, which is verified experimentally. A convenient method for acquiring the double-sphere dynamic compliance (DSDC) is given and its portability is shown. Then, two application cases of the DSDC in milling vibration suppression are given. In Case 1, based on the DSDC, the milling vibration amplitude is found to be distributed as an eccentric ellipse with a non-orthogonal basis with the feed angle in a robot mode, wherein a feed direction selection method for reducing milling vibration without traversal calculation is given with experimental validation. Case 2 shows that according to the guidance of the DSDC, the tuned mass damper can significantly suppress the milling vibration. It is worth noting that the directionality of the end modal vibration and DSDC constitute fundamental dynamic properties of milling robots, which may provide a new theoretical basis for the research related to the robotic end dynamic characteristics (such as frequency response function identification, mode coupling chatter mechanism and its suppression, etc.), which are well worth exploring.     

Focussed ion beam based fabrication of micro-electro-mechanical resonators

A simple and fast process to fabricate micro-electro-mechanical (MEM) resonators with deep sub-micron transduction gaps in thin SOI is presented. The proposed process is realized on both 350 nm and 1.5 μm thin silicon-on-insulator (SOI) substrates, evaluating the possibilities for MEMS devices on thin SOI for future co-integration with CMOS circuitry on a single chip. Through the combination of conventional UV-lithography and focused ion beam (FIB) milling the process needs only two lithography steps, achieving ∼100 nm gaps, thus ensuring an effective transduction. Different FIB parameters and etching parameters and their effect on the process are reported.