Straightforward recursive relations for computing the locations andamplitudes of extrema of sin x/x function

It is shown that the locations and amplitudes of the extrema of the sinx/x function, when expressed under the form of series expansions, can be calculated very quickly through a straightforward recursion formula. Moreover, very simple accurate algebraic expressions are given for these locations and amplitudes     

Optimal polarizations and application to meteorological targets

Optimal polarizations of targets that yield partially polarized backscatter are considered. Closed-form solutions for the extrema locations for targets that present reflection symmetry are provided. It is also found that for this class of targets the extrema locations define a fork as in the coherent case     

Extrema of sin x/x function

An accurate, closed-form approximation that gives the extrema of the sin x/x function is derived. A simple, rapid recursion formula for exact determination of the extrema is also presented     

Equal intensity and phase contours in focused Gaussian laser beams

The intensity and phase distributions of TEM₀₀ as well as higher-order Gaussian laser beams are illustrated with contour maps. Sufficient mathematical formulation leading to these plots is given. The locations and values of intensity extrema are given for lower-order Hermite- and Laguerre-Gaussian modes     

Parametric sensor array calibration using measured steering vectorsof uncertain locations

We consider the problem of sensor array calibration using a set of unique measured steering vectors of uncertain locations to estimate the unknown deterministic array perturbation parameters in a maximum likelihood framework. The array perturbations are parameterized by the sensor locations, mutual coupling coefficients, and receiver channel mismatch. We introduce a hybrid optimizer based on the amalgamation of gradient-based algorithms and the genetic algorithm. This optimizer is capable of coping with the problem of local extrema attractors, particularly initial estimates with large deviations from their true values. Numerical examples are provided to demonstrate the effectiveness and behavior of the proposed algorithms     

Nonparametric sequential estimation of zeros and extrema of regression functions

Let(X,Y), (X_{l}, Y_{l}), (X_{2}, Y_{2}), cdotsbe independent identically distributed pairs of random variables, and letm(x)=E(Y|X = x)be the regression curve ofYonX. The estimation of zeros and extrema of the regression curve via stochastic approximation methods is considered. Consistency results of some sequential procedures are presented and termination rules are defined providing fixed width confidence intervals for the parameters to be estimated.     

Size determination of a perfectly conducting sphere from the extrema of Mie scattering intensities

It has been found that the size parameteralphaof a perfectly conducting sphere and the angular positions of the extrema of the Mie scattering intensities are related by a simple equation involving one constant characteristic of each extremum. These constants for the first sixteen extrema counted from the forward direction are presented here for0 < alpha leq 90. A simple relation gives the constants for higher order extrema.     

由信号二进小波变换极值重构信号的样条插值算法

本文通过二进小波变换极值或零交叉点可获取信号的多尺度边缘,由此得到信号的绝大部分信息.本文提出了用样条插值重构算法来实现由信号二进小波变换极值点重构原始信号.数值仿真实验显示了该算法的高效性和令人满意的重构效果.与已有的算法相比,该算法原理更简单、更直接,实现更方便,速度更快.     

基于距离、角度、模板的角点检测算法

提出了一种基于距离、角度序列极值和距离模板匹配的角点检测算法。此算法不但与 基于灰度和基于曲率的方法截然不同,而且克服了他们的缺点。首先利用距离、角度序列极值检测得到明显转折部位的角点,然后根据距离模板匹配获得转折平稳部位的角点,最后经过伪角点删除,得到最终结果。仿真实验表明,该算法通过对序列极值判断支撑区域及模板大小的控制,抑制了数字化误差及噪声的影响,可以有效地实现二维图像的角点检测与定位,具有较高的精度,是一种实用、有效的角点探测算法。     

Signals with flattened extrema in balance power analysis of HFHPTA:theory and applications

In this paper a complete and self-contained account of composite periodic signals with two and three harmonics which possess flattened extrema at the zero point, including their application in the balance power analysis of a HF high-power tuned amplifier (HFHPTA), is presented. It is shown that signals obtained in the balance power analysis of HFHPTA and their derivatives can extremely accurately be approximated with the corresponding signals with flattened extrema at the point &thetas;=0. Two theorems presented in the paper give canonical representations of such signals     

An Analytical Expression for Empirical Mode Decomposition Based on B-Spline Interpolation

Although empirical mode decomposition (EMD) lacks a rigorous theoretical basis, it has attracted much attention for analyzing nonstationary signals adaptively. In this paper, the EMD method is investigated from a digital signal processing perspective. Based on an analysis of extrema sampling and B-spline interpolation, we show that the upper and lower envelopes of signals are formed by a succession of three basic operations: decimation of local extrema, interpolation, and filtering by a B-spline filter. We then show that some aliasing noise can be suppressed by the mean of the envelopes, though the extrema sampling is a sub-Nyquist sampling. For uniformly spaced extrema of signals, we derive a general analytical expression of intrinsic mode functions (IMFs) extracted by the EMD method from signals.     

Attribute based salient image extrema detection algorithm

A new salient image extrema detection algorithm applying attribute based morphological analysis is presented. Without the need of image noise filtering, the proposed algorithm can extract effectively salient image extrema by the analysis and valuation of extrema saliency with respect to their morphological attributes. Experimental results show the effectiveness and applicability of our algorithm.     

Statistical properties of local extrema in two-dimensional Gaussianrandom fields

This paper is concerned with the statistical properties of the local extrema and local maxima of two-dimensional (2D) Gaussian random fields (GRFs). A GRF may be represented by a linear filtering operation on a white noise field; the spatial properties of the GRF are then determined by the shape of the filter kernel function. New expressions are derived for the mean spatial density of local extrema and for the distribution of local extrema in a 2-D random field. The work is motivated by the problem of detecting known structures in images using 2D matched filters. The new results enable accurate performance predictions to be made of the reliability of such filters in the presence of noise. Case studies are presented for several well-known 2-D filter kernel functions     

Polarization-mode dispersion measurements based on transmissionspectra through a polarizer

Routine characterization of polarization-mode dispersion (PMD) in single-mode fiber, both at the manufacturing stage and in installed systems, requires an easy-to-implement measurement technique. One method that is particularly simple to implement involves counting the number of extrema (i.e., maxima and minima) per unit wavelength interval in the transmission spectrum measured through a polarizer (analyzer) placed at the output of a test fiber. In this paper, we establish accurate equations relating both the extrema density and mean-level crossing densities in such spectra to the expected value of PMD. These equations are used to measure several fiber samples, and are compared to measured values obtained with a commercially available test set. It is shown that measuring both mean-level crossings and extrema densities provides a simple means for establishing whether a fiber is scaling as √L (long-length regime) or L (short-length regime). Using Monte Carlo simulations, the accuracy of the fixed-analyzer measurements is examined as a function of the width of the wavelength interval over which measurements are made. In addition, the simulations indicate that fixed-analyzer measurements are quite robust with respect to the presence of polarization-dependent loss (PDL) in the span, an important consideration for measurements in amplified systems     

基于折线削波电平的自相关函数法检测基音

基音信息隐含于语音信号的局部极值点处,将语音信号分帧后,通过修正由局部极值点拟合的包络线得到折线削波电平,并将削波后的信号用自相关函数法估计基音。数值实验表明,语音信号经折线削波较中心削波后可保留更多的基音信息,并能有效地减少基音检测的错误。     

Discrete-time wavelet extrema representation: design and consistentreconstruction

The paper studies wavelet transform extrema and zero-crossings representations within the framework of convex representations in ℒ(Z). Wavelet zero-crossings representation of two-dimensional signals is introduced as a convex multiscale edge representation as well. One appealing property of convex representations is that the reconstruction problem can be solved, at least theoretically, using the method of alternating projections onto convex sets. It turns out that in the case of the wavelet extrema and wavelet zero-crossings representations this method yields simple and practical reconstruction algorithms. Nonsubsampled filter banks that implement the wavelet transform for the two representations are also studied in the paper. Relevant classes of nonsubsampled perfect reconstruction FIR filter banks are characterized. This characterization gives a broad class of wavelets for the representations which are derived from those of the filter banks which satisfy a regularity condition     

Optimal design of electrostatic lenses using integral equation field methods

The integral method of solving Laplace's or Poisson's equation results in a formulation for solution which is suitable for directly calculating the change in the domain potentials due to displacing the domain boundaries. Specifically, the order and locations remain the same for the matrix ∂Φ/∂x i.e., the change in potential per boundary change, which is required for the optimum design problem.     

Two-dimensional Fourier spectrum of QRST integral maps in classification of patients prone to ventricular arrhythmia

Two-dimensional Fourier spectra of QRST integral maps, obtained by body surface potential mapping, were analyzed to identify subjects prone to ventricular arrhythmia, when they have not been identified by the extrema count method. The diagnostic performance (84.38 percent) of the peak value of the Fourier spectrum as a classifier for subjects prone to ventricular arrhythmia showed an improvement of 3.65 percent over the use of the extrema count method as a classifier.     

Strain-induced modifications of the band structure ofInxGa1-xP-In0.5Al0.5Pmultiple quantum wells

The effect of strain on the band structure of In_xGa_1-xP-In_0.5Al_0.5P multiple quantum wells (MQW's) has been investigated from high-pressure and low-temperature photoluminescence measurements. The biaxial strain in the wells was varied between +0.6% compressive to -0.85% tensile strain by changing the well composition x from 0.57 to 0.37. Strain increases the valence band offsets in either tensile or compressively strained structures. Whereas relatively insensitive to tensile strain, the valence band offsets showed a strong dependence on the magnitude of the compressive strain. Good agreement is found between the measured valence band offsets and those predicted by the model solid theory, except for the largest compressively strained MQW's, for which the model calculations underestimate the measured valence band offset. Strain and the associated variations in composition also modified the separation among the well states associated with Γ_1c, L_1c , and X_1c. From these results, the bandgaps of each conduction band extrema were calculated in In_xGa_1-xP for 0.37相似文献   

The potential for Laplacian maps to solve the inverse problem ofelectrocardiography

Presents a method to solve the inverse problem of electrocardiography using the Laplacian of the body surface potentials. The method presented is studied first using trade-off curves from a concentric spheres model representing a heart-torso system. Then a more conventional study is undertaken where a limited number of current dipoles are placed within the inner sphere and noise is added to the resulting potentials and Laplacians on the surface of the outer sphere. The results indicate that measurements of the outer surface Laplacian can more accurately reconstruct epicardial potentials than measurements of the outer surface potentials. The reconstructions are more accurate in that extrema are placed very close to their correct positions and multiple extrema and high potential gradients are recovered. Identical conclusions are observed in the presence of noise and even when the Laplacians are subject to greater noise than the potentials