微型零件中圆孔的高精度定位方法

根据微型零件中圆孔的成像特点,为了实现其高精度定位,提出了基于双三次样条插值的圆孔定位方法.首先使用Canny算子得到被测圆孔图像的单像素边缘,然后在此基础上利用双三次样条函数在边缘法线方向上对图像进行插值,对插值的结果进行差分,从而得到边缘的亚像素位置,再通过椭圆最小二乘拟合计算出亚像素精度的圆心坐标,精度优于0.025个像素.实验结果证明,此方法可以有效的提高圆孔的定位精度.     

基于人脸识别技术的智能门禁系统设计

设计了基于人脸识别技术的智能门禁系统。该人脸图像识别系统通过系统各种链接功能的设置,将人脸图像的特征提取、分类识别及识别结果的输出等仿真试验过程进行直观的操作。仿真试验数据表明,该系统在人脸图像识别准确率和减少计算时间方面具有实用价值,基于MATLAB的人脸图像识别系统能够方便用户进行识别测试操作。     

New methods for chicken embryo manipulations

The capacity to image a growing embryo while simultaneously studying the developmental function of specific molecules provides invaluable information on embryogenesis. However, until recently, this approach was accomplished with difficulty both because of the advanced technology needed and because an easy method of minimizing damage to the embryo was unavailable. Here, we present a novel way of adapting the well‐known EC culture of whole chick embryos to time‐lapse imaging and to functional molecular studies using blocking agents. The novelty of our method stems from the ability to apply blocking agents ex ovo as well as in ovo. We were able to study the function of a set of molecules by culturing developing embryos ex ovo in tissue culture media containing these molecules or by injecting them underneath the live embryo in ovo. The in ovo preparation is particularly valuable, because it extends the period of time during which the developmental function of the molecule can be studied and it provides an easy, reproducible method for screening a batch of molecules. These new techniques will prove very helpful in visualizing and understanding the role of specific molecules during embryonic morphogenesis, including blood vessel formation. Microsc. Res. Tech., 2009. © 2009 Wiley‐Liss, Inc.     

Design and dynamics of a 3-DOF flexure-based parallel mechanism for micro/nano manipulation

This paper presents the mechanical design and dynamics of a 3-DOF (degree of freedom) flexure-based parallel mechanism. Flexure hinges are used as the revolute joints to provide smooth and high accurate motion with nanometer level resolution. Three piezoelectric actuators are utilized to drive active links of the flexure-based mechanism. The inverse dynamics of the proposed mechanism is established by simplifying flexure hinges into ideal revolute joints with constant torsional stiffnesses. Finite element analysis is used to validate the performance of the proposed 3-DOF flexure-based parallel mechanism. The interaction between the actuators and the flexure-based mechanism is extensively investigated based on the established model. Experiments are carried out to verify the dynamic performance of the 3-DOF flexure-based mechanism.     

Towards mechanical characterization of biomolecules by MNEMS tools

Single‐molecule micromanipulations have provided information that has been awaited for a long time. However, these experiments relying on optical tweezers (OT) or magnetic tweezers (MT) have a low throughput since the molecular preparation is done one at a time. In order to move towards systematic biological or medical analysis, micro‐nano‐electromechanical systems (MNEMS) are the appropriate devices, as they integrate accurate molecular level engineering tools and can be cheaply produced with highly parallel fabrication processes. This paper investigates the ability of MNEMS tweezers to perform molecular manipulations. The mechanical forces relevant in biological interactions are first reviewed and compared to the performances of biophysical instruments. MNEMS tweezers are then presented. The tweezers integrate opposing sharp tips to capture the molecules, an actuator to stretch them and a displacement sensor to measure in real time the produced molecular extension. DNA molecular bundles are readily assembled and manipulated. The sensor provides a 0.3‐nm stretching resolution, equivalent to the interbase pair distance in double‐stranded DNA. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

对一起母线保护动作造成的发电机停机事故的分析

记述了某电厂一台300 MW发电机组运行中母线保护动作造成的发电机停机事故.分析了事故起因,确定是误操作和误整定两个因素共同作用导致.进一步阐明了事故中继电保护的动作情况及原理,并对发变组保护功能是否受到影响,为什么母线保护先于发变组保护动作以及厂用电切换方式三个问题进行了说明.提出了纠正继电保护定值设置的具体方案,明...     

The Horace Brown Medal Lecture: Forty Years of Brewing Research

Horace Brown spent fifty years conducting brewing research in Burton‐on‐Trent, Dublin and London. His contributions were remarkable and his focus was to solve practical brewing problems by employing and developing fundamental scientific principles. He studied all aspects of the brewing process including raw materials, wort preparation, fermentation, yeast and beer stability. As a number of previous presenters of the Horace Brown Lecture have discussed Brown's achievements in detail, the focus of this paper is a review of the brewing research that has been conducted by the author and his colleagues during the past forty years. Similar to Horace Brown, fundamental research has been employed to solve brewing problems. Research studies that are discussed in this review paper include reasons for premature flocculation of ale strains resulting in wort underattenuation including mechanisms of co‐flocculation and pure strain flocculation, storage procedures for yeast cultures prior to propagation, studies on the genetic manipulation of brewer's yeast strains with an emphasis on the FLO1 gene, spheroplast fusion and the respiratory deficient (petite) mutation, the uptake and metabolism of wort sugars and amino acids, the influence of wort density on fermentation characteristics and beer flavour and stability, and finally, the contribution that high gravity brewing has on brewing capacity, fermentation efficiency and beer quality and stability.     

水分调控对烟叶钾及钙、镁含量的影响

在褐土和棕壤上进行了盆栽试验,研究土壤含水率与烟叶钾以及钙、镁含量之间的关系。结果表明:在两种土壤上种植的烟株生长中期适度干旱、后期充分灌水均可以提高烟叶的钾、钙含量,提高褐土上种植的烟叶镁含量。两种土壤含水率低的处理烟叶钙、镁含量较高,其原因可能与土壤溶液中阳离子之间的交换以及对根吸收位点的竞争有关。烟叶中钾的含量与钙、镁的含量之间总体负相关,钙和镁之间呈正相关。回归分析表明,移栽后30~60d、61~90d的土壤含水率(W1、W2)、烟叶钙和镁含量这4个因子对两种土壤上种植的烟叶钾含量的影响程度不同,在褐土上Mg>Ca>W2,棕壤土上Ca>W1。     

视觉深度伪造检测技术综述

随着生成式深度学习算法的发展,深度伪造技术发展并应用于各个领域。深度伪造技术的滥用使人们逐渐意识到其带来的威胁,伪造检测技术随之而生。本文基于视觉深度伪造技术研究进行综述。1)简要介绍了视觉深度伪造技术的发展历程及技术原理,包括生成对抗网络在深度伪造制品中的应用;2)对现有的视觉深度伪造数据集进行汇总并归类;3)对目前的视觉深度伪造检测技术进行了分类,将现有的检测方法归纳为基于具体伪影的、基于数据驱动的、基于信息不一致和其他类型视觉深度伪造检测等4种分类。其中,基于伪影的检测方法着重于寻找伪造制品与真实图像之间的像素级差异,通过机器学习识别深度伪造制品中的人工伪影痕迹,基于信息不一致的方法则着重于寻找伪造制品与真实图像或视频之间的信息级差异,这两种方法都具有识别效率高、训练便捷等优点;基于数据驱动的方法通过大量的数据集和机器学习训练,直接使用神经网络本身对深度伪造制品进行训练,并通过改善网络架构增进模型以提高训练效率,因为其模型的多变和高精确率成为目前深度伪造检测的热门方向。同时,本文分析了4种方法的具体优缺点,并进一步给出了未来视觉深度伪造检测研究的重点和难点。