Correction of distorted X-ray absorption spectra collected with capillary sample cell

In certain exceptional cases,capillary samples must be used to measure X-ray absorption spectra(XAS).However,the inho-mogeneous thickness of capillary samples causes XAS distortion.This study discusses the distortion and correction of the XAS curve caused by the inhomogeneous thickness of capillary samples.The relationship between the distorted XAS curveμ′d_(eq)(measured values)and the real absorption coefficientμ_(s)d_(eq)(true values)of the sample was established.The distortion was slight and negligible when the vertical size(2h)of the X-ray beam spot was smaller than 60%of the capillary tube’s inner diameter(2R_(in)).When h/R_(in)>1,X-ray leakage is inevitable and should be avoided during measurement.Partial X-ray leakage caused by an X-ray beam spot size larger than the inner diameter of the capillary tube leads to serious compressed distortion of the XAS curve.When h/R_(in)<1,the distorted XAS data were well corrected.Possible errors and their influence on the corrected XAS are also discussed.Simulations and corrections for distortions verify the feasibility and effectiveness of the corrected method.

Low/distortion on Exterior Surface of Auto Body and Its Correction Method

Surface low/distortion is one of the most challenging surface deflections that have a great effect on the exterior appearance of automobiles.Most studies on surface distortion/deflection have focused on evaluation and visualization techniques,the research work on correction or prevention of surface low/distortion is limited,and there is no perfect surface low/distortion corrective method that can satisfy the needs of the engineering.A B-spline based geometry morphing algorithm is proposed and then a new program based on UG-NX platform is developed to modify the die face in the surface low/distortion areas.To verify this developed system,the experimental dies that can replicate the surface low/distortion phenomenon successfully is put to use.Five geometric variables are introduced to describe the basic geometry of typical depression features of automotive outer panels.The experimental dies are then designed to reflect various combinations of these geometric parameters.The stamping experiments are conducted on cold rolled grade 5（CR5） sheet steel and various static measurements,such as oil-stoning,laser scanner,etc,are performed to measure and record the surface low/distortions.Three approaches including good bearing,holds in blank and die face morphing that aim to correct low/distortions are tried out and surface low/distortions are observed in the specimen with reverse draw depth of 10 mm.The measurement results show that die morphing is a practical and effective method to correct the surface low/distortion.The correction method proposed can be used to minimize the occurrence of surface low/distortion in die manufacturing,which has certain reference significance to the correction of surface low/distortion.

Straight line feature based image distortion correction

An image distortion correction method is proposed, which uses the straight line features. Many parallel lines of different direction from different images were extracted, and then were used to optimize the distortion parameters by nonlinear least square. The thought of step by step was added when the optimization method working. 3D world coordination is not need to know, and the method is easy to implement. The experiment result shows its high accuracy.

Correction Optimization of Lens Radial Distortion with Bending Measurement Function

In this paper, a distortion correction method with reduced complexity is proposed. With the singleparameter division model, the initial approximation of distortion parameters and the distortion center can be calibrated. Based on the distance from the image center to the fitting lines of the extracted curves, a bending measurement function with a weighted factor is proposed to optimize the initial value. Simulation and experiments verify the proposed method.

Stick-slip nonuniform rotation distortion correction in distal scanning optical coherence tomography catheters

We present a robust and fiducial-marker-free algorithm that can identify and correct stick-slip distortion caused by nonuniform rotation(or beam scanning)in distally scanned catheters for endoscopic optical coherence tomography(OCT)images.This algorithm employs spatial fre-quency analysis to select and remove distortions.We demonstrate the feasibility of this algorithm on images acquired from ex vivo rat colon with a distally scanned DC motor-based endoscope.The proposed algorithm can be applied to general endoscopic OCT images for correcting non-uniform rotation distortion.

AN EXPANSION AND CORRECTION ALGORITHM FOR PHOTOELECTRIC IMAGE WITH GEOMETRIC DISTORTION^1

A creepy photoelectric endoscopy system with good performance is studied, and anexpansion and correction algorithm for a compressed photoelectric image with serious geometricdistortion is presented. The algorithm can not only correct the geometric distortion, but alsorestore the gray-level distribution by means of ternary convolution algorithm. The details andthe outline in the image are very clear. It is proved to be of high performance in practice.

A corrected method of distorted printed circuit board image

This paper proposes a corrected method of distorted image based on adaptive control. First, the adaptive control relationship of pixel point positions between distorted image and its corrected image is given by using polynomial fitting, thus control point pairs between the distorted image and its corrected image are found. Secondly, the value of both image distortion centre and polynomial coefficient is obtained with least square method, thus the relationship of each control point pairs is deduced. In the course of distortion image processing, the gray value of the corrected image is changed into integer with bilinear interpolation. Finally, the experiments are performed to correct two distorted printed circuit board images. The results are perfect and the mean square errors of residual error are tiny.

Depth distortion correction for consumer-grade depth cameras in crop reconstruction

Modern consumer-grade RGB-D cameras provide intensive depth estimation and high frame rates.They have been widely used in agriculture.However,depth anamorphose occurswhen using the RGB-D camera.In order to address this issue,this paper proposes a novel approach to correct the distorted depth images that fit the relationship between the true distances and the depth values from depth images.This study considers the structured light camera ASUS Xtion PRO LIVE as example to develop a system for obtaining a series of depth images at different distances from the target plane.A comparison analysis is conducted between the images before and after correction to evaluate the performance of the distortion correction.The point cloud image of corrected maize leaves is well coincident with the original plant.This approach improves the accuracy of depth measurement and optimizes the subsequent use of the depth camera in crop reconstruction and phenotyping studies.

New DCM Operated Single Phase Bridgeless Cuk Derived Converters for Power Factor Correction

This paper presents a power factor corrected (PFC) new bridgeless (BL) Cuk Topologies for low power applications. A BL configuration of Cuk converter is proposed which eliminates the usage of diode bridge rectifier at the front end of the PFC converter, thus reducing the switching and conduction losses coupled with it. This new BL Cuk converter has two semiconductors switches. The current flow during each switching cycle interval of the converter reduces the conduction losses compared to the conventional Cuk PFC converter. It also reduces the input current ripple and Electromagnetic Interference (EMI). The inrush current during the starting period is limited and the input, output currents of the converter are continuous with minimum current ripple. Hence it is preferred mostly compared to other PFC circuits. The proposed topology works in the Discontinuous Conduction Mode (DCM) with simple control circuitry to achieve almost a unity power factor with less distortion in the input AC current. The switching of the power switches is done under zero current. The proposed PFC topologies are theoretically investigated and performance comparisons are made with the conventional rectifiers. The proposed PFC converter is simulated in MATLAB/SIMULINK with Fuzzy Logic Controller (FLC) and results are demonstrated to evaluate the effectiveness of the controller.

工程降水对钻孔应变的干扰特征及干扰机制研究

抽水干扰在钻孔应变观测中常见且影响显著,为了能真实捕捉到地震前兆信息,须对其干扰机制进行研究.随着城市化进程,基坑工程及其伴随的工程降水逐步增多,工程降水对钻孔应变的干扰比普通单井抽水干扰更为严重.工程降水对钻孔应变观测有何干扰特征、干扰机制如何、干扰数据能否修复等问题对地震异常的探测具有重要意义.本文基于莱阳体应变受到附近御龙湾项目工程降水干扰的观测案例,研究了工程降水的干扰特征,修复了干扰畸变,通过数值模拟确定了干扰机制.结果表明:(1)工程降水在干扰体应变趋势变化的基础上叠加了方向明确、量级稳定的固体潮畸变,可以通过一阶差分逆运算进行修复.修复固体潮畸变并扣除背景速率后,工程降水干扰量级达-15.65×10^(-9)/d;(2)通过建立基于集中载荷模型的网格算法,模拟出工程降水在体应变异常初期和后期分别产生6.61×10^(9) N和1.73×10^(10) N的集中力载荷,干扰量级明显大于常见的单井抽水干扰,压性干扰集中于体应变仪与抽水井连线的垂直方向;(3)通过固体潮畸变特征及力学机制分析确定了工程降水造成固体潮畸变的干扰机制为"抽水引起压性趋势下降—抽水暂停引起张性台阶上升—抽水引起压性趋势下降"周期行为,固体潮畸变时间间隔(频次)和钻孔水位之间呈显著同步特征,线性系数为0.737.

液晶空间光调制器及其在自适应光学中的应用

液晶空间光调制器(LC-SLM)通过对液晶折射率的调制来实现对光程的控制,在自适应光学中起着重要的作用。文章梳理了国内外LC-SLM的发展现状,对LC-SLM的工作原理和相位标定原理进行了详细介绍,针对LC-SLM在自适应光学中的应用,对国内外LC-SLM关键技术研究状况进行了讨论,分析总结了西安理工大学在该领域的实验研究。最后展望了LC-SLM的应用前景。

山地地震勘探中的静校正对成像质量的影响及改进策略

在山地地震勘探中,地震数据常常被校正到固定基准面上进行偏移成像,从而造成成像失真。本文从数学上直接推导公式,证明了静校正后从基准面进行偏移会造成倾角误差;通过山地起伏地表正演模型,说明了静校正后从基准面偏移会扭曲波场,导致严重的偏移成像失真。此外,应用四川南部山区的实际案例,分别从基准面偏移及从起伏地表偏移,叠前时间偏移和深度偏移结果均表明,在复杂的山地地形中,剧烈的高差变化会导致固定基准面偏移成像失真,应用起伏地表偏移能改进山地地震勘探资料的成像质量。本文的研究结果对理论研究和实际地震数据处理具有重要意义。

基于AMASPGD算法的FSOC系统波前畸变校正及性能分析

为了抑制相干自由空间光通信系统中大气湍流引起光信号波前失真的不利影响,提出了一种基于聚合动量(AM)和自适应矩边界(AdaMod)优化器的增强型随机并行梯度下降(SPGD)算法。仿真结果表明,该优化算法可以显著提高收敛速度和鲁棒性,并有效降低波前畸变的峰谷值和均方根,从而更有效地抑制大气湍流对相干自由空间光通信(FSOC)系统混频效率和误码率的负面影响。

一种大视场红外相机的畸变校正方法

本文针对大视场红外相机的畸变校正过程复杂的问题,提出了一种新的畸变校正方法。首先,选择单参数除法模型(division model,DM)作为相机畸变模型,使用改进的加速特征稳健算法(speed-up robust features,SURF)自动获取两幅有相同场景的畸变红外图像的特征点对,然后利用九点非迭代算法和核密度估计方法获取图像的畸变参数,最后根据求得的畸变参数使用基于边缘保持的灰度插值方法对图像进行畸变校正。在整个过程中,不需要预先知道相机的参数和场景信息,通过输入两幅具有相同场景的图像,完成畸变校正,为大视场红外相机的畸变校正提供了一种新的解决方法。实验结果表明,使用该方法对大视场红外相机进行畸变校正具有可行性和鲁棒性。

用于高精度准直测量的鱼眼相机标定方法

为了扩展准直测量的应用领域,提高测量范围是最为有效的手段之一,因此用于准直测量的鱼眼相机应运而生。针对准直测量用鱼眼相机标定精度不高的问题,提出了一种基于插值形式的径向粗标定及基于栅格形式的补偿精标定的两步式准直测量用鱼眼相机标定方法。该方法使用插值而并非构建成像模型,能够有效避免模型不准确及参数设置不合理而引入的系统误差,并且可以在一定程度上抑制镜片加工的非对称性及光学系统装调所带来的偏差。区别于图像评价的峰值信噪比(PSNR)以及结构相似性(SSIM)等性能指标,该方法选择的平均重投影误差(MRE)这一指标能够更有效地衡量准直测量使用条件下相机标定结果的优劣。仿真对比实验结果表明该方法在4种虚拟鱼眼相机模型上的标定效果皆优于传统标定方法,与传统的方法相比,标定的不确定度最大能够改善82.63%。样机标定实验结果表明,该方法能够有效标定真实的准直测量用鱼眼相机,在搭建的真实样机上应用该标定方法后,样机的入射矢量解算的不确定度能够提升至角秒级。

基于SSA-CatBoost 的颜色校正模型仿真

针对图像采集设备在采集过程中出现的颜色失真以及传统方法存在校正效果不佳的问题,提出了一种结合SSA算法的CatBoost颜色校正模型。首先,建立三个CatBoost模型,并使用SSA算法分别搜索三个模型的最佳参数;然后将所得到的最优参数赋值给三个CatBoost模型,并分别对三通道的测量值与真实值进行拟合;最后,与传统多项式回归方法进行对比,校验此模型校正效果。模型仿真结果表明,上述模型可将色差值ΔE控制在3以内,证实了SSA-CatBoost模型具有更好的颜色校正。

面向开环扫描系统的超声图像畸变校正方法

超声显微成像技术广泛应用于工业无损检测领域。相较于闭环、半闭环扫描系统硬件复杂、成本高,开环扫描系统结构简单、成本低,但由于无反馈机制会导致步进电机的非线性运动引起图像像素错位畸变。因此,消除非线性运动带来的错位畸变是采用开环扫描系统实现高质量超声成像的关键。该文提出集最大值投影法、最大类间方差法和中心坐标校正法于一体的MIP-Otsu-C3M方法,对开环扫描系统获得的硬币回波数据采用最大值投影法获取初始灰度图像,采用最大类间方差法获取感兴趣区域的B扫描图像边缘像素位置,并采用中心坐标校正法成功消除像素错位,解决了超声C扫描图像畸变问题。对消除错位畸变的回波数据进行飞行时间法和傅里叶变换法图像重建,直接获得了非畸变的三维图像和透视图像。该新颖算法也验证了最大值投影法可拓展至图像畸变校正应用。

一种船舶历史活动热力图实时生成策略

在船舶信息大数据系统中,针对在客户端向服务器请求大批量历史数据并实时绘制热力图时,会出现耗时较长、热力图效果失真以及地图软件漫游时跟随性差或卡顿等问题,提出一种改进的船舶历史活动热力图实时生成策略。该策略在基于像素聚类思想的热力图生成方法基础上,采用基于非线性变换的图像增强算法和像素补点方法,对传统方法绘制的热力图所存在的显示失真问题进行校正和优化,并在此基础上,提出动态加载与绘制策略和多线程实时成图策略,来生成船舶历史活动的热力图。试验表明,所提出策略在热力图绘制的效率、成图效果以及地图软件的交互体验上都得到了提升。

负反馈和状态空间重构的UPWM失真问题校正方法

针对数字D类音频功率放大器中的均匀采样脉冲宽度调制(Uniform-Sampling Pulse Width Modulation,UPWM)失真,提出了一种负反馈和状态空间重构的全数字UPWM失真问题校正方法。该方法利用数字Σ-Δ(Sigma-Delta)调制器的高开环增益特性,通过构造包含数字Σ-Δ调制器和UPWM发生器的闭环负反馈环路,使得环路的输入与输出近似呈线性关系,从而校正UPWM产生的失真。在构造闭环时,通过对数字Σ-Δ调制器的状态空间表达式进行重构,并添加插零值模块和抽取模块使该环路在保持稳定性的同时,拥有与原数字Σ-Δ调制器相同的噪声整形效果。实验结果表明,该方法相比其他的UPWM失真校正方法,不仅能降低谐波失真,还能大幅降低数字UPWM调制器输出信号的本底噪声,从而可使数字UPWM调制器在频率6 kHz和幅度为满量程的-5 dB的正弦数字信号输入情况下,输出信噪失真比达到95.26 dB,同时所提方法可全数字电路实现、硬件实现简单且易于移植。

基于单三相兼容PFC的过零点畸变抑制策略

单三相兼容功率因数校正(PFC)变换器应用广泛,具有效率高、稳定性好、兼容单相和三相电源等优点。但该拓扑在单相运行时,网侧输入电流在采用传统控制策略下的过零点畸变严重,影响着单三相兼容PFC变换器的稳态运行性能。此处首先分析了所采用的单三相兼容PFC变换器的拓扑结构,指出了变换器单相运行时电流过零点畸变的产生机理。这里采用延时补偿和采样电压幅值补偿策略,解决控制延时带来的过零点畸变问题。在此基础上,通过对过零点处高频开关管和工频开关管采取分时开关策略,解决过零点处开关逻辑混乱导致的过零点畸变问题。为验证理论分析的正确性,搭建了一台1 kW单三相兼容PFC变换器实验平台,测试结果表明,所提出的策略能够抑制电流的过零点畸变,提高单三相兼容PFC变换器的稳定性。