钢轨表面缺陷检测的图像预处理改进算法

由于线阵相机拍摄的图像光照不均、对比度低,使得钢轨表面离散缺陷检测成为机器视觉检测的难点,为此提出局部非线性对比度增强法和改进最大熵阈值分割法对钢轨图像进行预处理.该算法将局部区域内相对较低的灰度级映射到更低的范围,相对较高的灰度级映射到更高的范围,实现对比度拉伸;通过分析图像的目标熵、背景熵、灰度概率分布曲线,使用图像目标熵最大、目标概率较小的改进最大熵阈值分割法对图像进行分割,得到包含噪声相对较少的图像.实验结果表明,文中提出的非线性对比度图像增强算法简单、快速、有效,而且增强效果与光照无关;与原始的最大熵、目标最大熵、OSTU阈值分割法相比,改进的最大熵分割阈值较小,分割后的图像包含的噪声少;改进的预处理算法对测试图像的漏检率和误检率分别是6.2%和7.3%.     

基于缺陷比例限制的背景差分钢轨表面缺陷检测方法

针对钢轨表面图像具有的光照不均匀、可识别特征有限、对比度低、反射特性易变等特性,提出基于缺陷比例限制的背景差分钢轨表面缺陷检测方法。该方法主要包括轨面图像预处理、背景建模与差分、缺陷比例限制滤波、缺陷比例限制最大熵阈值分割和连通区域标记5个步骤。首先结合轨面图像列灰度均值和列灰度中值进行快速背景建模,将预处理后的图像与背景图像进行差分操作;其次利用轨面图像缺陷占比较低的特征对差分图进行缺陷比例上限的阈值截断,以增强差分图的对比度;随后利用此特征改进最大熵阈值分割,采用自适应加权因子对目标熵进行全局可变加权,并选择出一个合适的阈值使熵值最大化,使得在保留真实缺陷的同时减弱诸如阴影、锈迹等噪声的干扰;最后利用连通区域标记法对阈值分割后的二值图像中的缺陷区域进行统计,并把缺陷面积低于钢轨损伤标准的区域判定为噪声并进行去除,以实现钢轨表面缺陷检测。仿真实验结果表明,新方法可以对钢轨表面缺陷进行很好的检测,其检测结果的召回率、精确率和加权调和平均值分别达到94.19%、88.34%和92.96%,平均错误分类误差值为0.006 4,具有一定的实用价值。     

基于缺陷比例限制的背景差分钢轨表面缺陷检测方法

针对钢轨表面图像具有的光照不均匀、可识别特征有限、对比度低、反射特性易变等特性，提出基于缺陷比例限制的背景差分钢轨表面缺陷检测方法。该方法主要包括轨面图像预处理、背景建模与差分、缺陷比例限制滤波、缺陷比例限制最大熵阈值分割和连通区域标记5个步骤。首先结合轨面图像列灰度均值和列灰度中值进行快速背景建模，将预处理后的图像与背景图像进行差分操作；其次利用轨面图像缺陷占比较低的特征对差分图进行缺陷比例上限的阈值截断，以增强差分图的对比度；随后利用此特征改进最大熵阈值分割，采用自适应加权因子对目标熵进行全局可变加权，并选择出一个合适的阈值使熵值最大化，使得在保留真实缺陷的同时减弱诸如阴影、锈迹等噪声的干扰；最后利用连通区域标记法对阈值分割后的二值图像中的缺陷区域进行统计，并把缺陷面积低于钢轨损伤标准的区域判定为噪声并进行去除，以实现钢轨表面缺陷检测。仿真实验结果表明，新方法可以对钢轨表面缺陷进行很好的检测，其检测结果的召回率、精确率和加权调和平均值分别达到94.19%、88.34%和92.96%，平均错误分类误差值为0.006 4，具有一定的实用价值。     

一种改进的图像模糊增强算法

针对传统模糊增强算法的缺陷,提出了一种改进的算法。该算法中隶属函数和模糊增强算子均采用连续分段函数,利用OTSU法将图像分为高灰度和低灰度两个区域,对高灰度区域像素进行灰度增强运算,对低灰度区域像素则进行灰度衰减运算。仿真结果表明,该算法具有较强的模糊边缘和细小边缘分辨能力,是一种实用、高效的图像对比度增强算法。     

基于双模态深度学习的钢轨表面缺陷检测方法

针对目前钢轨顶面擦伤检测系统缺少第三维关键深度信息，检测结果易受干扰误报率高的问题，提出了一种基于双模态结构光传感器的钢轨表面缺陷检测方法。通过构建轨道表面缺陷的多模态深度学习检测网络，可以检测双模态钢轨图像中的擦伤缺陷。提出的深度网络分别融合了双模态图像的多尺度特征，并进行多尺度钢轨顶面擦伤检测。实验结果表明，该方法在显著降低检测误报的同时能够保持较高的检出率。与当前缺陷检测中常见的深度学习检测模型对比，平均精度均值（mAP）有大幅提升，性能优于以往的检测算法，在钢轨顶面擦伤检测任务中的应用前景良好。     

基于背景差分与最大熵的轨面缺陷分割

为了提高钢轨表面缺陷检测的效率和准确率,提出了一种基于背景差分与最大熵的轨面缺陷检测算法.首先建立钢轨图像背景模型并将原图像与背景图进行差分操作,以此来避免光照变化和反射不均的影响,更准确地突出缺陷区域;然后将改进的遗传算法与最大熵值法相结合来寻找最佳分割阈值并对差分图进行二值化,通过结合改进遗传算法加快了最大熵值法的运算速度;最后对二值图进行滤波操作,完成钢轨表面缺陷的分割.仿真结果表明该方法能够更加快速准确地分割出缺陷,精确率、召回率和正确率分别达88.6%、93.4%和90.6%.     

基于图像增强与分水岭分割的隧道低对比度裂缝提取方法

在实际的隧道裂缝检测中,存在细小、对比度低且有污渍点干扰的隧道裂缝,利用常规方法很容易漏检裂缝。为了解决此问题,提出一种基于图像增强与分水岭分割的裂缝提取算法,该算法有效利用背景信息补偿了污渍点,均衡了图像背景对比度。结合高低帽变换方法对图像进行增强,然后根据分水岭算法获取分水岭分割线;比较分割线所在位置的灰度值与其周边灰度值,并通过灰度值差异判断裂缝边缘,从而提取裂缝。实验结果表明,所提算法能够准确、有效地检测出完整的隧道裂缝,且对噪声具有鲁棒性。     

基于粗糙集的微小缺陷图像对比度增强算法

设计了一种微小缺陷图像对比度增强算法。采用粗糙集理论将图像划分为不同类别,同一类别中像素间为不可分辨关系。并依据图像灰度值和噪声属性进一步将图像划分为子图,在子图中得到图像的明暗区域。对图像不同区域进行直方图均衡变换和直方图指数变换处理,处理后即可增强图像的对比度。仿真实验表明,处理后可突出显示图像中的微小细节,图像不同区域之间的划分效果更加明显,可以有效提升图像的对比度和视觉效果。     

基于白Top—Hat变换的医学图像局部对比度增强算法

提出了一种简单、高效的医学图像局部对比度增强算法.该算法的主要特点是在对医学图像进行多尺度形态学top-hat变换增强对比度时,仅采用白top-hat变换和用增加亮对比度区域的灰度值方法来代替黑top-hat变换,从而避免了常用形态学增强方法中丢失原始医学图像灰度信息的弊端.通过使用CT,MR医学图像与已有的局部对比度增强典型算法进行实验比较,结果表明,本文算法在增强图像局部对比度和减少计算时间均具有优势.     

基于显著性和深度卷积神经网络的输送带表面故障定位

提出了一种基于显著性和深度卷积神经网络的输送带表面故障定位方法。该方法在输送带上、下表面的边缘烙上数字,利用图像处理技术检测输送带图像中的数字来间接定位输送带表面故障。首先,将采集的输送带图像进行高斯滤波、灰度线性变换等预处理,以提高图像质量、增强背景与目标的对比度;然后根据谱残差理论对预处理后的图像进行视觉显著性处理,获取包含数字区域的视觉显著图;最后,运用卷积神经网络对显著图进行分类,以区分出数字区域和非数字区域。实验结果表明,该方法可以很好地检测输送带图像上的数字,进而实现对输送带表面故障的定位。     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。     

How do children do mathematics with LOGO?

Abstract  This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development.     

Editorial: Special issue on recent advances in hybrid control theory and applications

正The demands of a rapidly advancing technology for faster and more accurate controllers have always had a strong influence on the progress of automatic control theory.In recent years control problems have been arising with increasing frequency in widely different areas,which cannot be addressed using conventional control techniques.The principal reason for this is the fact that a highly competitive economy is forcing systems to operate in regimes where     

Information for Authors

正Aim The Journals of Zhejiang University-SCIENCE(A/B/C)areedited by the international board of distinguished Chinese andforeign scientists,and are aimed to present the latest devel-opments and achievements in scientific research in China andoverseas to the world’s scientific circles,especially to stimulateand promote academic exchange between Chinese and for-eign scientists everywhere.     

Enhancing a leaf radiative transfer model to estimate concentrations and in vivo specific absorption coefficients of total carotenoids and chlorophylls a and b from single-needle reflectance and transmittance

The relative concentrations of different pigments within a leaf have significant physiological and spectral consequences. Photosynthesis, light use efficiency, mass and energy exchange, and stress response are dependent on relationships among an ensemble of pigments. This ensemble also determines the visible characteristics of a leaf, which can be measured remotely and used to quantify leaf biochemistry and structure. But current remote sensing approaches are limited in their ability to resolve individual pigments. This paper focuses on the incorporation of three pigments—chlorophyll a, chlorophyll b, and total carotenoids—into the LIBERTY leaf radiative transfer model to better understand relationships between leaf biochemical, biophysical, and spectral properties.Pinus ponderosa and Pinus jeffreyi needles were collected from three sites in the California Sierra Nevada. Hemispheric single-leaf visible reflectance and transmittance and concentrations of chlorophylls a and b and total carotenoids of fresh needles were measured. These data were input to the enhanced LIBERTY model to estimate optical and biochemical properties of pine needles. The enhanced model successfully estimated reflectance (RMSE = 0.0255, BIAS = 0.00477, RMS%E = 16.7%), had variable success estimating transmittance (RMSE = 0.0442, BIAS = 0.0294, RMS%E = 181%), and generated very good estimates of carotenoid concentrations (RMSE = 2.48 µg/cm², BIAS = 0.143 µg/cm², RMS%E = 20.4%), good estimates of chlorophyll a concentrations (RMSE = 10.7 µg/cm², BIAS = − 0.992 µg/cm², RMS%E = 21.1%), and fair estimates of chlorophyll b concentrations (RMSE = 7.49 µg/cm², BIAS = − 2.12 µg/cm², RMS%E = 43.7%). Overall root mean squared errors of reflectance, transmittance, and pigment concentration estimates were lower for the three-pigment model than for the single-pigment model. The algorithm to estimate three in vivo specific absorption coefficients is robust, although estimated values are distorted by inconsistencies in model biophysics. The capacity to invert the model from single-leaf reflectance and transmittance was added to the model so it could be coupled with vegetation canopy models to estimate canopy biochemistry from remotely sensed data.     

Mr. Twinn’s bombes

This article discusses the history and design of the special versions of the bombe key-finding machines used by Britain’s Government Code & Cypher School (GC&CS) during World War II to attack the Enigma traffic of the Abwehr (the German military intelligence service). These special bombes were based on the design of their more numerous counterparts used against the traffic of the German armed services, but differed from them in important ways that highlight the adaptability of the British bombe design, and the power and flexibility of the diagonal board. Also discussed are the changes in the Abwehr indicating system that drove the development of these machines, the ingenious ways in which they were used, and some related developments involving the bombes used by the U.S. Navy’s cryptanalytic unit (OP-20-G).