Representation of a Monotone Curve by a Contour with Regular Change in Curvature

The problem of modelling a smooth contour with a regular change in curvature representing a monotone curve with specified accuracy is solved in this article. The contour was formed within the area of the possible location of a convex curve, which can interpolate a point series. The assumption that if a sequence of points can be interpolated by a monotone curve, then the reference curve on which these points have been assigned is monotone, provides the opportunity to implement the proposed approach to estimate the interpolation error of a point series of arbitrary configuration. The proposed methods for forming a convex regular contour by arcs of ellipses and B-spline ensure the interpolation of any point series in parts that can be interpolated by a monotone curve. At the same time, the deflection of the contour from the boundaries of the area of the possible location of the monotone curve can be controlled. The possibilities of the developed methods are tested while solving problems of the interpolation of a point series belonging to monotone curves. The problems are solved in the CAD system of SolidWorks with the use of software application created based on the methods developed in the research work.     

Speech synthesis by linear interpolation of spectral parameters between dyad boundaries.

A recent study [Olive and Spickenagel, J. Acoust. Soc. Am. 59, 993-996 (1976)] has shown that area parameters derived from linear prediction analysis can be linearly interpolated between dyad boundaries with very little distortion in the resultant synthesized speech. The success of area parameter interpolation raises a question: can other acoustic parameters, such as the power spectrum of the speech waveform, be similarly interpolated? The spectrum is of special interest because speech can be synthesized in real time from spectral parameters on a programmable digital filter. To study this question a speech analysis-synthesis system using spectral parameters (samples of power spectra at different frequencies) was simulated. These parameters were determined from the speech signal at every dyad boundary, and interpolated for intermediate values. Dyad boundaries (representing the limits of transition regions between phonemes) were determined manually. Informal listening tests comparing synthetic speech with and without linear interpolation showed slight degradation in the interpolated speech. This degradation is significantly reduced by using an additional point within the dyad boundaries for interpolation.     

一种新的截断线及标志点处缺失相位插补方法

在基于相位信息的三维面形测量中,为了得到正确的相位展开而引入的截断线和为了便于三维拼接而附加在物体表面的标志点都会造成其覆盖区域的相位缺失,需要进行人为地插补修复。一种新的缺失相位插补方法——八方向梯度估算法,通过计算待插补点周围八方向梯度和其八邻域内的相位平均值,可估算出缺失的相位。与其它常用缺失相位插补方法相比,该方法运算速度快、插补效果好,运算过程无需人为参与,便于计算机自动实现,尤其适合于插补倾斜相位面上的较大标志点,有助于提高相位重建质量和在此基础上的三维面形重建质量。     

Three-dimensional myocardial strain analysis based on short- and long-axis magnetic resonance tagged images using a 1D displacement field

A robust algorithm to estimate three-dimensional strain in the left-ventricular heart wall, based on magnetic resonance (MR) grid-tagging in two sets of orthogonal image planes, is presented. Starting-point of this study was to minimize global interpolation and smoothing. Only the longitudinal displacement was interpolated between long-axis images. Homogeneous strain analysis was performed using small tetrahedrons. The method was tested using a stack of short-axis images and three long-axis images in six healthy volunteers. In addition, the method was subjected to an analytical test case, in which the effect of noise in tag point position on the observed strains was explored for normally distributed noise (0.5 mm RMS). In volunteers, the error in the longitudinal displacement due to interpolation between the long-axis image planes was -0.10 +/- 0. 48 mm (mean +/- SD). The resulting error in the longitudinal strain epsilon(l) was -0.003 +/- 0.02. The analytical test case was used to quantify the effects of three sources of errors on the observed strain. The SD of the difference between homogeneous strain and true strain was 0.06 for epsilon(r.) The error due to the 3-D reconstruction was 0.004 for epsilon(r.) The error in epsilon(r) resulting from simulated noise in the tag point position was 0.10. Equivalent results were obtained for all other strain parameters; thus, the error resulting from noise in the tag point position dominates the error introduced by approximations in the method. Because the proposed method uses a minimum of global interpolation and smoothing, it offers the prospect to detect small regions of aberrant contraction.     

GENSPECT: a line-by-line code with selectable interpolation error tolerance

Current line-by-line radiative transfer codes accelerate calculations by interpolating the line function where it varies slowly. This can increase calculation performance by a factor of 10 or more but causes a reduction in calculation accuracy. We present a new line-by-line algorithm that computes absorption coefficients to a specified percentage-error tolerance in a near minimal number of calculations. The algorithm employs a novel binary division of a calculation's spectral interval, coupled with a pre-computed lookup table that predicts where it is appropriate to reduce the resolution of a particular line without exceeding the required error tolerance. Line contributions are computed piecewise across a cascaded series of grids which are then interpolated and summed to derive the absorption coefficient. The algorithm is coded in MATLAB as part of a toolbox of radiative transfer functions for the analysis of planetary atmospheres and laboratory experiments.     

A novel area measurement scheme based on a multi-resolution dynamic contour

A novel scheme for an object's surface area measurement is proposed, which is suitable for area computation of an object with smooth and irregular edges. A multi-resolution dynamic contour is applied and this scheme consists of four steps. Firstly, a photoelectric image collimation system is applied to obtain a target image of a detected object. An image pyramid for the target image is constructed by wavelet decomposition and reconstruction. Secondly, in the image pyramid, a multi-resolution dynamic contour converges to the target's contour edge from coarse to fine scale, via feature search and an iteration algorithm. Thirdly, for the convergent dynamic contour, two formulas for the area and centroid computation of a closed B-spline curve are applied to compute the image target's area and centroid exactly. Finally, a novel centroid self-calibration technology is applied, which measures the pixel's size equivalence with the computed centroid and a dual-frequency laser to measure the true object's surface area exactly. Experiments indicate that this scheme's single-measurement error decreases to ±0.2%, when the number of control points is 20. Compared to conventional measurement approaches, this scheme is robust for a target image with noises or complicated edges.     

基于曲线拟合的亚像素边缘定位方法的研究

图像的边缘定位是图像测量的关键之一,随着测量精度要求的提高,已由早期的像素级边缘定位发展到了现在的亚像素级边缘定位。根据地球在地球敏感器CCD阵面中的成像特性,提出了一种基于曲线拟合的亚像素边缘定位方法以获取地球“灼热圆盘”的边缘。该方法利用曲线拟合获得的拟合斜率以及灰度值来提取图像的边缘。仿真结果表明,采用曲线拟合亚像素边缘定位法可使图像的边缘定位精度达到百分之几个像素,具有较高的精度。     

Voigt-function evaluation using a two-dimensional interpolation scheme

A method of evaluating the Voigt function for the shape of spectral lines is described. The method relies on interpolation from a two-dimensional table using simply-transformed coordinates. High-level mathematical functions are avoided wherever possible, and no series summations are made. The relative error on a 400 by 100 table is less than 3 × 10^?3 over the region where the interpolation method is faster than other expansions. Computing speed is comparable to that of built-in scientific functions.     

光栅投影三维测量系统标定技术研究

相机与投影仪的标定是影响光栅投影三维测量系统精度的因素之一，且标定所得参数的精度直接影响系统的测量精度。分析标志点边缘成像时的退化模型，提出了基于高斯曲线拟合与边缘局部区域效应相结合的亚像素边缘检测方法，获取高精度边缘，提高标志点检测精度；使用基于透视变换图像矫正的标志点快速排序匹配方法，进行相机快速高精度标定。分析投影仪标定时的相位误差，提出了一种基于径向基的线性插值方式，提高标志点圆心相位获取精度。实验验证，使用上述亚像素边缘检测方式，标志点的边缘残差为0.0871，对比基于高斯曲线的拟合方式，精度提高了41%，相机标定重投影误差均值为0.0524像素；使用上述相位插值方式，投影仪标定重投影误差均值为0.1203像素，对比使用双线性插值方式，标定精度提高23.9%。     

机械加工塑料齿廓偏差影像法测量及抽样特性

应用影像法,对机械加工的渐开线塑料齿轮齿廓偏差进行测量。由于塑料齿轮在机械加工中受机械应力和热应力影响较大,而导致齿廓应变较大,为精确反映塑料齿轮的齿廓偏差,并判定塑料齿轮齿廓公差的精度等级,对测量中出现的回转偏心误差、回转分度误差、瞄准示值误差和重复性测量误差进行了不确定度的A类和B类综合评定。并通过统计控制方法中的极差控制图进行分析,得到相同的评定结果。利用对塑料齿轮单齿齿廓偏差的检验,结合随机抽样检验的原理,对塑料齿轮齿廓精度等级进行了判定。最终得出机械加工塑料齿轮,齿形误差较大,超出国标中规定的齿轮精度等级的范围,适合实验室模型展示而不适合用作工业齿轮的结论。     

基于TFT-LCD的动态星模拟器星点位置修正方法

介绍了基于TFT-LCD的动态星模拟器的工作原理及星点位置误差的计算方法。利用经纬仪对动态星模拟器显示的网格星点进行测量,计算了各星点的位置误差及修正系数。对网格上星点的修正系数进行分区处理,并利用Matlab软件对各分区的修正系数进行曲线拟合,得到修正系数关于星点位置（方位或俯仰）坐标的方程。结果表明,修正后星点的位置误差均小于35″,满足动态星模拟器的设计要求。     

基于NURBS曲线直接插补算法的嵌入式数控系统设计与实现

提出了一种结合486SX级别的X86微处理器和可编程逻辑器件CPLD两级控制的嵌入式数控系统设计方案,阐述了该系统的硬件接口电路设计;提出了基于改进S形加减速的NURBS曲线直接插补算法,在满足最大弦高误差、最大法向加速度以及最大进给速度要求的情况下,对插补曲线的加速段和减速段进行速度规划。最后采用基于该插补算法的嵌入式数控系统,在半圆形毛坯上进行了五角星NURBS曲线的实际加工,验证了所设计嵌入式数控系统的可行性和有效性,具有一定的工程应用价值。     

On contour crossings in contour-advective simulations – part 1 – algorithm for detection and quantification

This is the first of two papers devoted to the analysis of contour crossing errors that occur in contour-advective simulations of fluid motion. Here an algorithm is presented for quantifying the error due to contour crossings. The first step is to determine the relative proximity of all possible pairs of contours. A digital representation of each contour is produced to aid in the corresponding calculation. Simple analysis of functions is then used to find any crossings between contours deemed close to each other by the digital representation method. Next, the area in error of a pair of crossing contours is calculated by identifying the polygon or polygons that approximately bound the erroneous region. Finally, some preliminary results of analysis of contour crossings that occur in contour-advective semi-lagrangian (CASL) simulations of single layer quasigeostrophic turbulence are presented. It is shown that the error due to contour crossings is small in the simulations considered here.     

核燃料棒反光表面条纹自适应中心提取方法

针对水下检测中激光条纹中心难以准确提取的问题,提出了一种适用于水下核燃料棒反光表面的条纹自适应中心提取方法。根据检测环境中存在水体散射及物体表面高反光的特点,去除水下噪点、反光噪点,实现激光条纹分割提取;充分利用BP神经网络曲线拟合及由光条几何信息生成的自适应卷积模板,实现反光区域的轮廓与灰度分布修正,使光条截面灰度分布符合高斯分布;经灰度重心法在光条截面方向实现激光条纹中心的亚像素精度定位与提取。实验结果表明:该方法有效地解决了被测物体反光表面光条中心线不连续、噪点多的问题,点云三维重建误差在0.2 mm以内,保证了条纹中心提取的精度与稳定性,满足核燃料棒水下检测工程要求。     

Taming the Chaos in Neural Network Time Series Predictions

Machine learning methods, such as Long Short-Term Memory (LSTM) neural networks can predict real-life time series data. Here, we present a new approach to predict time series data combining interpolation techniques, randomly parameterized LSTM neural networks and measures of signal complexity, which we will refer to as complexity measures throughout this research. First, we interpolate the time series data under study. Next, we predict the time series data using an ensemble of randomly parameterized LSTM neural networks. Finally, we filter the ensemble prediction based on the original data complexity to improve the predictability, i.e., we keep only predictions with a complexity close to that of the training data. We test the proposed approach on five different univariate time series data. We use linear and fractal interpolation to increase the amount of data. We tested five different complexity measures for the ensemble filters for time series data, i.e., the Hurst exponent, Shannon’s entropy, Fisher’s information, SVD entropy, and the spectrum of Lyapunov exponents. Our results show that the interpolated predictions consistently outperformed the non-interpolated ones. The best ensemble predictions always beat a baseline prediction based on a neural network with only a single hidden LSTM, gated recurrent unit (GRU) or simple recurrent neural network (RNN) layer. The complexity filters can reduce the error of a random ensemble prediction by a factor of 10. Further, because we use randomly parameterized neural networks, no hyperparameter tuning is required. We prove this method useful for real-time time series prediction because the optimization of hyperparameters, which is usually very costly and time-intensive, can be circumvented with the presented approach.     

新型光谱曲线特征参数与水稻叶绿素含量间的关系研究

利用高光谱信息检测作物叶绿素含量信息是田间作物长势诊断的重要研究内容。利用水稻光谱和叶绿素含量田间实测数据,从作物叶绿素含量不同,光谱曲线峰谷波形有高矮胖瘦形态变化的观点出发,提出光谱曲线峰谷波形中特征边的上升、下降速率以及组成峰谷波形两边的夹角等新型特征量,利用归一化光谱信息,分析了这些变量与水稻叶绿素含量间的相关关系。研究结果显示:(1)可见光波段范围520～740nm之间的归一化光谱反射率与叶绿素含量间呈良好的负相关关系;(2)绿峰反射光谱曲线特征边的变化速率及绿峰两边的夹角等变量与水稻叶绿素含量具有较好的相关性,表明利用这些新型变量开展叶绿素含量高光谱无损监测成为可能,这将为利用高光谱信息开展作物长势与营养诊断提供新的思路和方法。     

工业CT切片图像直接生成快速原型层片数据

为了将工业CT与快速原型直接集成,提出了一种由工业CT切片图像直接生成快速原型层片数据的方法。首先对工业CT切片图像进行边缘提取、去噪、细化、连接和轮廓跟踪,获取样件的内外结构轮廓点数据;然后在相邻断层间建立轮廓匹配点对,线性插值层间轮廓数据,以满足快速原型加工对层片厚度的要求,并用三次B样条曲线对所有轮廓进行拟合;最后经过轮廓数据点采样和内外轮廓判断后,生成通用层接口文件输入快速原型系统。试验验证了该方法的有效性与正确性。     

飞马Ⅱ号润滑油中燃油污染红外光谱检测研究

针对航空发动机润滑油燃油污染造成非计划停机、飞行故障等一系列问题,需要对在用润滑油进行必要的监测,从而确定润滑油换油的最佳时机.采用美国PerkinElmer公司的Spectrum Two红外光谱仪及Spectrum Quant软件,结合美国材料与试验协会标准(ASTM-E2412-10)关于合成酯类润滑油的监测说明,...     

Study on the method of automatic measurement of flexible material processing path based on computer vision and wavelet

Straightness, roundness, and primitive angle error of contour are important indicators of evaluating path precision during flexible material path processing. As processing path is composed of small arc or small line segment primitives, also the deformation of the flexible material during the processing path, making the captured image of processing path not clear, the edge of processing image over local uneven gray, the pixels of boundaries between the processing path image edge and background organizations not obvious. In order to extract the flexible material path contour effectively, mosaic method for flexible material processing path image is studied, next fast positioning strategy is introduced, and then we puts forward the search algorithm which taking processing path corner search as the cut-in-point, designing slope angle curve of starting and terminal point of each primitive and conducting slope angle curve for multiple scales wavelet transform by regarding DB(4) as wavelet operator based on wavelet edge modulus maxima extract principle. By judging whether one point of the curve appears at wavelet transform extremum, it can be determined whether the point is a corner one. In order to accelerate wavelet transform computing speed, FPGA IP core is 8-tap transpose is used to design the decomposition and reconfigurable of DB(4). The total time consumed by IP core wavelet decomposition increased only 2.802% compared to the PC computation time; path angle relative error is 8%, and the average measurement time is 198.22 ms.     

Plate impulse response spatial interpolation with sub-Nyquist sampling

Impulse responses of vibrating plates are classically measured on a fine spatial grid satisfying the Shannon-Nyquist spatial sampling criterion, and interpolated between measurement points. For homogeneous and isotropic plates, this study proposed a more efficient sampling and interpolation process, inspired by the recent paradigm of compressed sensing. Remarkably, this method can accommodate any star-convex shape and unspecified boundary conditions. Here, impulse responses are first decomposed as sums of damped sinusoids, using the Simultaneous Orthogonal Matching Pursuit algorithm. Finally, modes are interpolated using a plane wave decomposition. As a beneficial side effect, these algorithms can also be used to obtain the dispersion curve of the plate with a limited number of measurements. Experimental results are given for three different plates of different shapes and boundary conditions, and compared to classical Shannon interpolation.