Performance of stochastic quantizers employing nonlinear processing

Dithered quantizers are often employed in numerical instrumentation to improve the resolution and accuracy of the analog-to-digital converters used. To this aim, linear post-processing is usually performed on the quantized samples. In the paper, a different processing scheme is described that exhibits a nonlinear behavior. The characteristics of both linear and nonlinear topologies are analyzed, and expressions are given for the quantization error average and variance that make possible the comparison of the two algorithms. It is shown that the nonlinear one provides better performance, so that it can be employed to further improve the estimation capability of a dithered quantizing system. The reported results have been validated by means of meaningful simulations     

栅结构微陀螺大角速度信号输入下分辨率的研究

主要研究了大角速度信号输入对栅结构振动式微陀螺及其检测电路分辨率的影响。在0.01-200°/s的动态范围内,按照设计值,陀螺器件与检测电路组成的系统能够分辨0.01°/s的输入角速度变化。考虑到驱动电压和积分电容与敏感电容的特性差异的影响后,当输入角速度大于10°/s时,整个系统即无法分辨0.01°/s的输入角速度变化。针对这种情况,提出了在传感器件上集成关键元件的方法来解决大角速度信号输入下整个系统分辨率降低的问题。     

Performance of stochastic and deterministic dithered quantizers

In this paper, the authors discuss the use of deterministic and stochastic dither sequences in analog-to-digital conversion including data postprocessing. Properties of both types of dither signals are highlighted, and a performance comparison is carried out by considering residual bias and mean square error. It is concluded that superior performance can be attained by deterministic dither in terms of system resolution and accuracy, at the expense of worse spectral characteristics. Experimental results are provided to support simulations and theoretical analysis     

Scanning near-field optical microscopy signal processing and resolution

To increase the signal-to-noise ratio and to remove the spatially slow varying signals, a lock-in amplifier is often used in scanning probe microscopy. The signal reconstructed from the lock-in data contains the contributions of the evanescent and homogeneous waves that are mixed in the near-field zone (i.e., at a very short distance). The resolution is determined and a method is given to suppress the useless background information. Experimental images of nanoparticles are processed.     

Beam shape effects on grating spectrometer resolution

The collimated optical beam in a grating spectrometer may be circular or elliptical in cross section, so that different parts of the beam illuminate different numbers of grooves on the grating. Here we estimate the consequent loss in spectral resolution relative to that obtained with a beam that illuminates a fixed number of grooves. The effect reduces the intrinsic resolving power of the spectrometer by ~15%, exclusive of other contributions such as finite entrance-slit width.     

信号分辨率增强的机械智能故障诊断方法研究

利用深度学习来增强数据集已成为各个领域的研究热点,即使用有限的数据集生成更多仿真的数据集.不同于目前主流的生成对抗网络算法及其变体算法,基于样本分辨率增强的思想,提出了一种简单有效的算法——高效亚像素全连接神经网络(ESPFCN).ESPFCN的原理为:对原始输入样本进行全连接操作,经过隐层特征映射输出四通道的低分辨率...     

基于小波系数非线性连续函数衰减的脑电信号去噪

环境噪声和工频噪声的干扰对脑电信号(EEG)的进一步处理和分析带来极为不利的影响。针对传统小波系数软阈值消噪方法去噪后产生的波形失真和硬阈值消噪方法去噪后产生的振荡现象,提出了一种新的小波系数非线性连续函数衰减处理算法。通过小波系数的非线性衰减处理,使低值端小波系数连续函数的变化介于硬软阈值函数之间,有效避免了处理后的波形失真和振荡。通过实验数据比较,证明处理后的脑电信号信噪比和均方误差均优于传统的小波去噪处理方法。     

The effect of nonlinear signal transformations on bias errors in elastography

We have reported several artifacts in elastography (1991). These include mechanical artifacts, such as stress concentration, and signal processing artifacts, such as zebras, which are caused by bias errors incurred during the estimation of the peak of correlation functions using a curve-fitting method. We investigate the bias errors and show that bias errors in curve-fitting methods are substantially increased because of nonlinear operations on the echo signals that reduce other errors. We also show that, for typical sampling rates, the bias errors can be ignored in the absence of these nonlinear operations.     

高速数字电路中信号反射的分析及解决方案

随着微电子技术的不断发展，在数字系统设计中系统工作频率不断增加，高速器件的使用越来越广泛。对信号进行完整性分析已经成为高速数字电路设计中的一个必要环节。针对高速数字电路设计存在的信号完整性反射噪声问题，首先从理论上分析了信号反射产生的原因及解决方法。然后以高速数字测试模块为例，利用Mentor GraPhics公司的Hypcdy似软件进行仿真验证，以达到在设计阶段消除反射噪声的目的。     

高速数字电路信号完整性问题分析与解决方案

为确保电路板制作前其信号完整性,缩短产品的开发周期,节约设计成本,利用信号完整性仿真工具,通过采用Cadence的PCBSI软件对其布局前的仿真,重点研究了电路拓扑结构问题,并提出相应的解决措施,具有工程应用实际参考价值。     

基于掩蔽效应和抖动调制的盲水印方案

通过对信号处理领域抖动调制原理的分析,并结合人类视觉系统的掩蔽效应,提出了一个DCT 域盲水印模型。在MATLAB 仿真环境中,针对二值图像水印,实现了水印的预处理、嵌入、提取以及F 范数下水印检测。在水印嵌入过程中,通过自动调节量化步长改善了水印的透明性,水印检测时无需原始宿主图像,实现了盲检测,而且省略了反余弦变换过程,降低了算法复杂度。仿真实验表明,水印算法在JPEG 高强度压缩、剪切、各种噪声叠加以及多重水印等攻击下具有高鲁棒性。算法思想可应用于数字版权保护以及隐秘通讯等领域。     

Mitigating the effects of system resolution on computer simulation of Portland cement hydration

CEMHYD3D is an advanced, three-dimensional computer model for simulating the hydration processes of cement, in which the microstructure of the hydrating cement paste is represented by digitized particles in a cubic domain. However, the system resolution (which is determined by the voxel size) has a prominent influence on the simulation results and, thus, is difficult to choose a priori. In this paper, it is shown that the effects of system resolution on the simulation results are mainly due to the lack of considerations of the diffusion-controlled reactions in the model. A new concept “hydration layer” is proposed for mitigating the effects of system resolution on the model predictions. By performing simulations with different system resolutions, the robustness of the improved model is demonstrated. Comparisons of model predictions with experimental measurements further demonstrate that the use of hydration layer can successfully mitigate the bias brought by the system resolution.     

Salient features of recording of the optical rectification signal from nonlinear optical crystals

Analysis and derived formulas were employed to examine the salient features of the process when the current and voltage due to optical rectification in crystals were used to measure the electric parameters of continuous, pulsed, and pulsed-periodic lasers, with allowance for spatial dispersion. The errors of measurement were evaluated. Meters based on optical rectification show promise for use in laser fusion facilities and for measuring the efficiency of harmonic generation. Translated from Izmeritel'naya Tekhnika, No. 5, pp. 8–14, May, 1997.     

Surface and nonlocal effects on the nonlinear free vibration of non-uniform nanobeams

The surface and nonlocal effects on the nonlinear flexural free vibrations of elastically supported non-uniform cross section nanobeams are studied simultaneously. The formulations are derived based on both Euler–Bernoulli beam theory (EBT) and Timoshenko beam theory (TBT) independently using Hamilton’s principle in conjunction with Eringen’s nonlocal elasticity theory. Green’s strain tensor together with von Kármán assumptions are employed to model the geometrical nonlinearity. The differential quadrature method (DQM) as an efficient and accurate numerical tool in conjunction with a direct iterative method is adopted to obtain the nonlinear vibration frequencies of nanobeams subjected to different boundary conditions. After demonstrating the fast rate of convergence of the method, it is shown that the results are in excellent agreement with the previous studies in the limit cases. The influences of surface free energy, nonlocal parameter, length of non-uniform nanobeams, variation of nanobeam width and elastic medium parameters on the nonlinear free vibrations are investigated.     

Use of nonlinear effects in engineering

The results of investigations into the use of effects produced with hydrodynamic oscillators for solution of certain engineering problems have been presented.     

基于颤振效应的气动比例阀摩擦力补偿研究

针对气动比例阀的摩擦力是造成其死区的主要因素,分析了比例阀摩擦力的产生原因.根据振动对摩擦力的影响,对气动比例阀叠加高频低幅颤振信号进行摩擦力补偿的机理进行了研究,并基于软件VC 和LabVIEW开发出摩擦力颤振补偿器.实验结果表明,通过在控制信号上叠加高频低幅的颤振信号,使阀芯始终处于微小振动状态,可以有效克服比例阀摩擦力,消除爬行现象,缩短滞后时间.该补偿方法具有较高的工程应用价值.