基于统计特征和显著度的光谱信号提取算法

各类光谱信号都会受到噪声和基线畸变的影响,在提取光谱信号过程中若不考虑基线畸变和噪声的影响,将会严重影响信号提取的精度和准确性,所以需要在信号提取前消除噪声和基线畸变的影响。大多数信号提取算法的步骤是先提取整体基线,再提取信号,这样难以保证基线的提取精度。为了降低信号提取过程中背景噪声、基线畸变等不利因素的影响,根据信号的存在总是会导致该区域的统计特征不同于背景的特点,提出了一种基于显著度和统计特征的光谱信号检测与提取算法（SSD算法）。首先,在待测数据的不同尺度空间中计算出信号在各尺度下的显著度,将检测出的显著信号点作为候选信号点;其次,利用信号特征去除候选信号点中的伪信号点;最后,对候选信号点所在区域采用二次多项式进行基线拟合以剔除伪信号区域并实现最终的信号提取。为验证SSD算法的综合性能,首先,通过仿真的方法对高斯信号和矩形信号在不同基线类型、不同信噪比下进行实验;然后将该算法与AirPLS算法、Wavelet算法以及DoG算法对两种信号在不同信噪比,不同基线类型下的提取结果进行比较。仿真实验结果表明：与其他算法相比,SSD算法信号提取结果基本不受信号类型和基线畸变类型的影响,且当信噪比大于40时基本不受信噪比的影响;在不同基线畸变类型下,SSD算法对两种信号提取结果的准确度、稳定性、离散度均较好,其他算法则只适用于某种基线畸变类型。从总体提取结果上看,SSD算法提取结果的绝对误差的均值仅为AirPLS算法的8.71%、Wavelet算法的3.52%、DoG算法的2.01%;绝对误差的均方根也仅为AirPLS算法的13.08%、Wavelet算法的5.45%、DoG算法的3.11%。因此,所提出的SSD算法在提取信号时具有良好的综合性能,能够在不同的信噪比及基线畸变情况下准确的提取出信号。     

基于卷积神经网络的光谱预处理方法

光谱的预处理在光谱分析中占有非常重要的地位。针对现有光谱去噪算法对弱峰保存能力差、基线校正算法对光谱能量过扣除、光谱特征峰定位不准确以及各种预处理算法串行处理造成的误差累计等问题,设计了一个端到端的卷积神经网络。该网络由两个模块组成：基线校正和去噪模块和特征峰定位模块。这两个模块相互连接又独立输出。理想条件下,可以依据光谱的线型函数和特征峰的位置拟合出无噪声无基线的光谱,所以在基线校正和光谱去噪模块中连接特征峰定位模块的输出可以有效的提高去噪和基线校正的精度;而高质量的光谱有助于更加精确的估计光谱峰的位置,因此这两个模块相互连接可以有效提高重建光谱的质量。光谱基线校正和去噪模块是一个前馈网络,该模块由多个卷积层、激活函数和批归一化层构成,每一层均连接了特征峰定位模块的输出。特征峰定位模块是一个多尺度特征融合网络,该模块使用不同尺寸的卷积核将光谱分为不同的尺度,融合大小不同尺度的特征估计光谱特征峰的具体位置。在网络训练时,使用不同温度、湿度和不同预热时间的光谱仪获得光谱作为输入样本,使用中国计量院的标准仪器获得光谱数据作为输出样本。在实验中,首先对合成的光谱分别添加不同信噪比的噪声和不同峰值的高斯基线,分别评价该网络在噪声抑制、基线校正、光谱特征峰校正的能力;然后将添加噪声和基线后的玉米的近红外光谱作为样本,用最先进的算法对它们进行预处理,然后用偏最小二乘法估计玉米中的水和油的浓度。估计的浓度与用标准仪器测量的真实浓度进行比较,以证明所提出的CNN的优势。实验证明,所设计的网络在单任务和多任务处理中均能取得良好的结果。而且经过该网络处理的光谱在定量分析中可以得到更准确的结果,具有较强的实用价值。     

基于匹配追踪的拉曼光谱信号重构算法

拉曼光谱技术是一种高灵敏度、无损伤、振动分子光谱技术,在医药、生物、分析化学等诸多领域有着重要的作用。然而,由于拉曼散射强度低,实际测得的拉曼信号容易被噪声所污染。特别是在较短的曝光时间,收集到的拉曼光谱的信噪比很低。因此,提出了一种基于匹配追踪算法的信号重构方法,用于提取低信噪比的拉曼信号。该方法首先通过阈值循环迭代的方法在平均谱上找出特征峰的位置、估计峰的区间。根据峰的位置区间等信息,用高斯密度函数生成字典。在噪声谱上,根据特征峰位置和区间,将其区分为有信号区间和无信号区间,在有信号区间上利用匹配追踪算法重构被噪声所掩盖的拉曼信号。该算法不仅能够很好的逼近掩盖在噪声中的拉曼信号,且在重构信号的过程中也会对基线进行扣除,无须作基线校正处理。在仿真和实验中对该算法与常规算法进行了比较,结果证明,该算法在低信噪比条件下能够较好的恢复拉曼信号。该算法不同于传统光谱去噪算法,能同时对拉曼光谱进行了基线扣除以及噪声的处理,且能取得较为理想的结果,不需要使用不同的算法对基线和噪声分别处理。其次,在算法上我们创造性地将匹配追踪算法用于拉曼光谱信号的稀疏逼近求解。     

基于凸优化的激光诱导击穿光谱基线校正方法

在激光诱导击穿光谱定量分析中,基线是LIBS光谱信号的重要组成部分,由于受到实验参数设置及实验环境变化等影响,导致等离子体的发射谱线呈现不同程度的基线漂移现象,因此基线校正是光谱分析的重要环节。现有算法如多项式拟合通常需要设定关键参数,不具备自适应性。由于激光诱导产生的等离子体光谱信号的特征峰具有明显的独立性和稀疏性,以及基线具有低通特性,因此在凸优化约束框架下,提出了非参数化基线校正模型。同时,利用高效率的迭代算法来保证结果的收敛性。首先对23个高合金钢样本的光谱信号进行基线校正,然后以合金钢样本中的铬(Cr)元素为分析对象,并选取11条分析线进行定量分析。分别采用PLS和SVM定量模型进行训练和预测,并且与传统方法相比较,证明了所提出方法可以提高定量分析精度。     

基于能量色散X射线荧光光谱的鱼粉产地溯源方法研究

鱼粉是一种在养殖业中占有重要地位的高蛋白饲料原料.我国对鱼粉的市场需求很大,但不同产地的鱼粉存在品质差异的问题.为保证鱼粉品质安全,建立鱼粉产地溯源系统具有非常重要的意义.能量色散X射线荧光光谱根据元素辐射X射线荧光光子能量不同,能够检测样品矿物质元素种类和含量.鱼粉所含矿物质元素种类和含量会因鱼粉产地不同而存在差异,...     

一种光电容积脉搏信号的峰值点自动识别方法

光电容积脉搏信号的峰值点自动识别直接关系到无创血氧饱和度测量与脉搏波峰-峰间期提取的准确率。提出一种小波联合识别方法：基于小波多分辨率分析原理校正影响脉搏波峰值点幅值的基线干扰,再利用二次样条小波模极大算法自动识别峰值点。将该方法应用到自行研制的光电容积脉搏波测量系统中,对采集的信号进行了校正与峰值点识别,通过在信号中增加随机噪声以评价方法的稳定性与可靠性,然后利用10组实测数据,对比本方法与传统差分阈值法的峰值点识别准确率,进一步评价方法的有效性。结果表明：本方法在较好地消除了基线干扰的基础上,在染噪的信号中仍然会较精确地检测出脉搏波主波峰,具有较好的抗干扰能力,有利于提高血氧饱和度检测及峰-峰间期提取的准确性,从而有助于后期人体呼吸功能评价与心率变异性分析。     

小波变换的EDXRF光谱金属组分特征峰位置识别

主要研究X射线荧光光谱金属组分特征谱位置的确定。依据不同金属组分的特征谱特性,分析了特征谱的选取规律,在奇异值分析理论和模极大值理论的基础上,分析了基于特征谱小波分解系数的模极大值提取方法,在不同分解尺度下的特点及其传播特性,提出了基于模极大值传播的区间特征峰筛选方法,并对实际测量光谱进行了实验分析。结果表明：利用bior4.4小波作为基函数对实验测量的全能谱数据进行4层小波变换,利用模极大值传播特性,可以消除全能谱上叠加的部分噪声对光谱分析造成的阶跃影响;为提高特征峰的位置识别概率,对小波变换中小于给定阈值的分解系数进行压缩,将实验获取的X射线荧光全能谱第4层小波分解系数直接进行特征峰识别,得到的677个峰值位置,压缩到186个;在此基础上,再采用模极大值传播的区间特征峰筛选方法,筛选区间初始值设置为600 eV,经识别得到的特征峰峰值位置仅为27个,识别准确率得到有效提高。     

A Practical Method for the Analysis of Overlapped Peaks in Energy Dispersive X-Ray Spectra

ABSTRACT

In this study a practical method for the spectral analysis of some overlapped characteristic X-ray peaks is presented. The overlapped characteristic K, and K, peaks and the artificially overlapped two K, peaks (peak doublet) of arsenic obtained by the radioisotope-excited, energy dispersive X-ray fluorescence (EDXRF) technique, are resolved. A total of 34 overlapped peak systems were investigated: the proposed method provided 18 reliable results, whereas the first and the second methods gave 15 and 1, respectively. The intensity ratios of K_β/K_α, obtained by the novel method are also in good agreement with the theoretical relativistic Hartree-Slater values.     

能量色散X荧光分析中元素间效应的蒙特卡罗模拟

针对能量色散X荧光分析(EDXRF)技术中元素间效应实验研究的难点问题,采用蒙特卡罗方法对基于Si（PIN）探测器的EDXRF系统建立模拟模型,并对模拟微束软X射线注量谱建立了高斯展宽算法。对Fe-Ni样品进行模拟计算,表明经该算法展宽后的注量谱与实测K系特征X射线谱吻合度较高,并得到了各元素特征X射线归一计数与元素含量关系曲线,结果表明该方法可自行校正EDXRF中元素间效应,获得准确的元素K系特征X射线谱理论强度。     

对称旋转不变相干分布式非圆信号二维波达方向估计

在相干分布式非圆信号二维波达方向估计中,利用信号非圆特性可提升估计精度,但现有的低复杂度算法利用泰勒级数近似建立的旋转不变关系会引入额外误差.针对该问题,考虑中心对称的三维立体线阵,提出了一种基于对称旋转不变关系的二维波达方向估计算法.算法首先利用信号非圆特性建立了扩展阵列模型;然后证明了对于任意的中心对称阵列,相干分布源的确定性角信号分布函数矢量具有对称特性,利用此特性在三维立体线阵的三个子阵中分别建立了扩展广义方向矢量的对称旋转不变关系;基于此,通过无须搜索的多项式求根方式分别得到中心方位角和俯仰角估计;最后利用整个阵列广义方向矢量的对称旋转不变关系构造代价函数实现了参数匹配.理论分析和仿真实验表明,相比于现有的低复杂度算法,所提算法避免了泰勒级数近似引入的额外误差,以较小的复杂度代价获得了性能的较大提升.同时,所提算法能够实现三维空间全方位的角度估计.     

Digital image correlation using iterative least squares and pointwise least squares for displacement field and strain field measurements

Digital image correlation (DIC) method using iterative least squares algorithm (ILS) for displacement field measurement and pointwise least squares algorithm (PLS) for strain field measurement is proposed in this paper. A more general and practical intensity change model is employed with consideration of the linear intensity change of the deformed image, followed by an iterative least squares algorithm for calculating displacement field with sub-pixel accuracy. The concept of correlation function is not used in the ILS method, even though we prove that the algorithm is actually equivalent to the optimization of the sum of squared difference correlation function using improved Newton–Raphson method. Besides, different from the conventional strain estimation approaches based on smoothing the displacement fields first and followed by differentiation of the smoothed displacement fields, a simple yet effective PLS algorithm is proposed for extracting strain fields from the computed displacement fields. The effectiveness and accuracy of the proposed techniques is verified through numerical simulation experiments. A practical application of the algorithms to residual plastic deformation field measurement of GH4169 alloy subjected to tensile fatigue is also presented.     

前后向子分段相位差频率估计法

为提高直接频率估计法的精度并推导出估计误差方差的闭合表达式,本文提出基于前后向子分段相位差的直接频率估计法. 该方法对样本的前向和后向两个子段做快速傅里叶变换,再提取这两个子段变换后的峰值谱相位差而获得频率估计. 本文证明了该估计器具有无偏性,并推导出其频率估计方差的闭合理论表达式. 仿真实验验证了该闭合表达式的正确性,故本文方法具有更高的测频精度和广泛的应用前景. 关键词： 频率估计 前后向子段 相位差 克拉美罗限     

X射线管激发X荧光光谱连续本底扣除方法研究

X射线管是目前X射线荧光光谱分析中最常采用的激发源,它所产生的原级谱成为了X荧光光谱中本底成分的主要来源,在对这种光谱进行进一步的分析处理之前需要对其本底进行扣除,对本底估计的准确性直接影响后续处理步骤的效果。对射线管激发X荧光光谱的成分进行了分析,针对其本底特点构造了一种本底强度的估计方法,并根据实测谱线构建了理论测试谱线以便对光谱处理算法的效果进行评价。该方法利用测得X射线荧光光谱中不包含特征峰的谱段对X射线管原级谱造成的本底成分进行估计,使用只包含连续本底的谱段对整个测量谱段进行插值,从而避免了谱线特征峰重叠或对半高宽估计不当时所产生的影响。利用构建的测试光谱对SNIP法、傅里叶变换法和本文的本底估计方法的使用效果进行了比较,使用该方法估计的本底与理论本底更加接近。结果表明使用的方法对X射线管激发的X荧光光谱的本底估计准确,可以采用这种方法对连续本底进行扣除,在对实际测得的X射线荧光光谱的本底扣除中取得了较好的应用效果。     

Robust infrared target tracking using discriminative and generative approaches

The process of designing an efficient tracker for thermal infrared imagery is one of the most challenging tasks in computer vision. Although a lot of advancement has been achieved in RGB videos over the decades, textureless and colorless properties of objects in thermal imagery pose hard constraints in the design of an efficient tracker. Tracking of an object using a single feature or a technique often fails to achieve greater accuracy. Here, we propose an effective method to track an object in infrared imagery based on a combination of discriminative and generative approaches. The discriminative technique makes use of two complementary methods such as kernelized correlation filter with spatial feature and AdaBoost classifier with pixel intesity features to operate in parallel. After obtaining optimized locations through discriminative approaches, the generative technique is applied to determine the best target location using a linear search method. Unlike the baseline algorithms, the proposed method estimates the scale of the target by Lucas-Kanade homography estimation. To evaluate the proposed method, extensive experiments are conducted on 17 challenging infrared image sequences obtained from LTIR dataset and a significant improvement of mean distance precision and mean overlap precision is accomplished as compared with the existing trackers. Further, a quantitative and qualitative assessment of the proposed approach with the state-of-the-art trackers is illustrated to clearly demonstrate an overall increase in performance.     

冷原子荧光光谱中数字基线估计方法的研究

水体中汞的存在形态有单质汞、无机汞和有机汞三种。其中,甲基汞是主要的有机汞形态,毒性远高于单质汞和无机汞。测量水体中的甲基汞的方法有很多,冷原子荧光光谱法是测量水体中甲基汞的推荐方法。冷原子荧光光谱法是原子发射光谱法和原子吸收光谱法综合发展而来的元素分析方法。经过多年的发展与完善,是元素分析最常用的分析技术之一,具有灵敏度高、检出限低等特点,被广泛应用于环境科学、生命科学、地质等领域。由于检测仪器的背景噪声和色谱柱分离效果的影响,冷原子荧光光谱出现基线漂移和信号拖尾等干扰因素,严重影响冷原子荧光光谱数据的峰面积计算和痕量甲基汞的定量分析。其中,基线漂移是最主要干扰因素。目前,改进模拟器件参数和数字基线估计是解决基线漂移的的两种重要手段。在改进模拟器件参数方面,有激发光源使用空心阴极汞灯、闭环控制的热阴极低压汞灯等,但存在实验设备复杂、成本高昂等缺陷;在数字基线估计方面,有最小二乘法、差值拟合法等,但存在基线估计不稳,含量计算不准等缺点。基于此,提出了一种基于小波变换的数字基线估计方法。首先,分析甲基汞的冷原子荧光光谱微观信号和基线漂移现象,建立冷原子荧光光谱信号和基线漂移数理模型;其次,根据冷原子荧光光谱信号模型的特点,以小波变换为研究基础,研究合适的母小波模型,将母小波模型与基线漂移模型进行卷积,卷积结果恒为零,理论上证明了基线漂移现象经过小波变换后会被消除;再次,以100 pg标样甲基汞为例,实验验证了小波变换能够有效地消除基线漂移的干扰和信号拖尾的影响;最后,在仪器相对标准差（RSD）为1.29%~3.40%的条件下,对0,10,20,50,100,500以及1 000 pg的标样甲基汞溶液进行5次重复实验,分别建立小波变换前后峰面积平均值校准曲线,校准曲线的相关系数（R2）由小波变换前的0.994提高到小波变换后的0.997。实验结果表明,该方法能够有效地消除测量仪器基线漂移和信号拖尾的影响,提升了系统测量准确性。     

基于优化迭代算法的细胞荧光光谱解析

使用光谱测量方法进行细胞多色荧光分析时, 发射光谱会产生部分光谱重叠, 为定性和定量分析造成了一定的困难。为此, 提出基于优化迭代算法的细胞荧光光谱解析算法, 建立重叠峰模型并确定单峰顶点; 根据每次构造峰面积的大小, 重新确定构造峰的构造方式, 最终得到模拟峰的顶点及面积信息。利用该算法对高斯函数叠加形成的重叠峰进行解析, 并与常规方法进行对比, 结果表明优化迭代算法解析误差稳定在0.15%以内; 加入随机噪声后, 解析误差可稳定在0.85%以内, 均优于另外两种算法。此外, 计算了该算法下的迭代效率, 结果表明该算法较常规方法提高了32.2%。     

Review of energy-dispersive X-ray fluorescence on food elements detection

Energy-dispersive X-ray fluorescence (EDXRF) is a physical rapid detection method to analyze the types of elements through the energy characteristics of fluorescent X-ray particles. When applied to the detection of food element content, it not only needs simple sample pretreatment but also the element measurement time generally does not exceed 10 min to have the accuracy of μg/g, which can greatly reduce the time and cost of detection. Due to the limitations of the EDXRF instrument and measurement mechanism, it has low sensitivity to light elements in food, and the detection sensitivity varies with elements in food element analysis. For example, the detection sensitivity of Ca, Mg, Fe, Zn, Cu and other elements concerned by people is not high when the content is low, and the measurement accuracy is extremely dependent on the detector resolution. However, with the improvement of detector performance and algorithm optimization of EDXRF, the detection limit of this technology can reach 0.1 μg/g, the detection of trace elements has also been improved, which has made a new breakthrough in the field of food element detection. Therefore, this paper reviews that in recent 20 years, in order to overcome the various difficulties of EDXRF in food detection, the hardware optimization of EDXRF (For example, the development of an analyzer without sample preparation can greatly reduce the time required for the detection of food elements, and a series of instruments combined with EDXRF and cluster capillary technology can greatly improve the excitation efficiency of lighter elements in food. The spectrometer with a high-resolution detector can improve the detection accuracy of target elements with low content in food) and in order to solve the problem of spectrum resolution in food detection, (For example, the wavelet transform method which has good performance in spectrum smoothing, identifying weak peaks and maintaining peak shape is applied to EDXRF spectrum resolution, which can better solve the problem that the X-ray characteristic peaks of elements with a low atomic number in food are submerged) the reform and innovation of spectrum resolution methods are introduced. This paper summarizes and analyzes the representative application examples of EDXRF in food safety detection, discusses the advantages and disadvantages of EDXRF compared with other rapid detection or food detection methods in different situations, concludes its application conditions, and discusses the application prospect of EDXRF technology in the field of food detection.     

A Hybrid Preaching Optimization Algorithm Based on Kapur Entropy for Multilevel Thresholding Color Image Segmentation

Multilevel thresholding segmentation of color images plays an important role in many fields. The pivotal procedure of this technique is determining the specific threshold of the images. In this paper, a hybrid preaching optimization algorithm (HPOA) for color image segmentation is proposed. Firstly, the evolutionary state strategy is adopted to evaluate the evolutionary factors in each iteration. With the introduction of the evolutionary state, the proposed algorithm has more balanced exploration-exploitation compared with the original POA. Secondly, in order to prevent premature convergence, a randomly occurring time-delay is introduced into HPOA in a distributed manner. The expression of the time-delay is inspired by particle swarm optimization and reflects the history of previous personal optimum and global optimum. To better verify the effectiveness of the proposed method, eight well-known benchmark functions are employed to evaluate HPOA. In the interim, seven state-of-the-art algorithms are utilized to compare with HPOA in the terms of accuracy, convergence, and statistical analysis. On this basis, an excellent multilevel thresholding image segmentation method is proposed in this paper. Finally, to further illustrate the potential, experiments are respectively conducted on three different groups of Berkeley images. The quality of a segmented image is evaluated by an array of metrics including feature similarity index (FSIM), peak signal-to-noise ratio (PSNR), structural similarity index (SSIM), and Kapur entropy values. The experimental results reveal that the proposed method significantly outperforms other algorithms and has remarkable and promising performance for multilevel thresholding color image segmentation.     

改进X荧光光谱仪快速检测土壤中重金属

针对传统能量色散X荧光仪(energy dispersive X-ray fluorescence,EDXRF)分析土壤中微量重金属测量精确度低的问题,提出了一种X荧光仪改进方法。为了减少反射X射线的影响,入射X射线垂直照射样品,探测器平行放置与样品一侧且垂直于X射线。样品与探测器之间由准直器连接。对国家标样测量结果表明,仪器对Mo,Zn,Cu,Pb,Zr,Nb的检出限为0.4,6.68,1.97,6.84,1.60,7.59 mg·kg-1。各元素对数偏差在0～0.05之间。元素含量在三倍检出限以上RSD%(GBW)小于7,元素含量在三倍检出限内RSD%(GBW)小于15。为了验证改进后X荧光仪测量效果,在大兴安岭地区采集土壤样品与传统荧光仪进行比较分析。改进X荧光仪提高了土壤中微量重金属测量精度,满足野外地质普查要求。     

利用波导不变量进行运动单线阵的无源测距测速

为克服单线阵难以无源测距、测速的缺点,提出了利用目标辐射低频声场干涉结构和波导不变量的运动单线阵无源测距、测速方法。定义了运动目标的距离距变率比（目标距离与距离变化率的比值）,并利用与目标辐射声场的时间-频率干涉结构和波导不变量相关的变量来表征距离距变率比。根据此定义,通过对目标辐射声场的时间-频率干涉结构图进行Radon变换等处理,实现对距离距变率比的估计。利用所估计的距离距变率比,结合平台速度、目标方位角和目标航向角实现对目标距离和速度的同时估计。仿真实验验证了所提方法在测距、测速时的正确性和有效性。结果表明:所提方法在目标航向角较大时有较高的距离、速度估计精度;同时,目标方位估计误差越小,所提方法的距离、速度估计精度越高。