Influences on amplitude estimation using three-parameter sine fitting algorithm in the velocity mode of the Planck-Balance

The Planck-Balance is a table-top version of a Kibble balance. In contrast to many other Kibble balances, the coil is moved sinusoidally and an ac rather than a dc signal is generated in the velocity mode. The three-parameter sine fitting algorithm is applied to estimate the amplitudes of the induced voltage and the coil motion, which are used to determine the force factor Bl of the voice coil of the electromagnetic force compensation balance. However, the three-parameter sine fitting algorithm is not robust against some perturbations, e.g. additive Gaussian white noise, quantization error, harmonic distortion, frequency error and time jitter. These effects have influences on the accuracy of the amplitude estimation. Based on numerical simulations and correlation analyses, the effects of these perturbations are determined. By optimizing measurement and data processing approach, the bias and standard deviation of the estimated amplitude can be effectively reduced, and thus the accuracy of the force factor Bl in the velocity mode can be improved.

Multiplicative Noise Removal Based on Unbiased Box-Cox Transformation

Multiplicative noise removal is a challenging problem in image restoration. In this paper, by applying Box-Cox transformation, we convert the multiplicative noise removal problem into the additive noise removal problem and the block matching three dimensional (BM3D) method is applied to get the final recovered image. Indeed, BM3D is an effective method to remove additive Gaussian white noise in images. A maximum likelihood method is designed to determine the parameter in the Box-Cox transformation. We also present the unbiased inverse transform for the Box-Cox transformation which is important. Both theoretical analysis and experimental results illustrate clearly that the proposed method can remove multiplicative noise very well especially when multiplicative noise is heavy. The proposed method is superior to the existing methods for multiplicative noise removal in the literature.

Accurate 2-D AOA Estimation and Ambiguity Resolution for a Single Source under Fixed Uniform Circular Arrays

This paper presents an analytic algorithm for accurate two-dimensional (2-D) angle of arrival (AOA) estimation of a single source under fixed uniform circular arrays (UCAs). Algebraic and explicit formulations for 2-D AOA estimation are first developed in the Fourier domain. It is shown that three is the minimum number of antennas for 2-D AOA estimation based on phase measurement. Then a signal model for phase extraction is established with equivalent phase noises through observations of signal samples corrupted by additive Gaussian white noise. Under fixed UCAs, 2-D AOA estimation of a single source would suffer from phase ambiguity, and hence, ambiguity resolution is also addressed in the Fourier domain by integer search. Numerical examples are provided to verify the effectiveness and appealing performance of the proposed 2-D AOA estimation algorithm.

A novel diversiform stochastic resonance of a domain wall and its performance at different states

The response of an underdamped stochastic resonance (SR) with a new pining potential model of domain wall (DW) in ferromagnetic strips driven by additive Gaussian white noise to an additive weak harmonic forcing is investigated. We address that the new nonlinear system can be converted between bi-stable and mono-stable freely by tuning the system parameters. Analytical expressions of signal-to-noise ratio (SNR) of the bi-stable stage is obtained based on the linear response theory. In addition, another type of SR, which occurs when the system is mono-stable, is also reported with the intrinsic frequency derived analytically. The SR in mono-stable stage confirms to the typical physical resonance better with frequency-selection characteristic. Numerical simulation of both stages is carried out with outputs conforming to the theoretical derivation. Owing to the diversity of potential model, the new system possesses considerable merits for engineering applications.

Effect of external noise on the hysteresis characteristics of a thermoacoustic system

We present the effect of noise on the hysteresis characteristics of a prototypical thermoacoustic system, a horizontal Rijke tube. As we increase the noise intensity, we find that the width of the hysteresis zone decreases. However, we find that the rate of decrease in hysteresis width is constant for all the mass flow rates considered in the present study. We also show that the subcritical transition observed in the absence of noise is no longer discernible once the intensity of noise is above a threshold value and the transition appears to be continuous. We compare our experimental observations with the results obtained from a numerical model perturbed with additive Gaussian white noise and we find a qualitative agreement between the experimental and the numerical results.

2-D DOA Joint Estimation Method Based on Polarization Array

A new joint method is presented to estimate the 2-D DOA and polarization parameters of far-field sources based on four order cumulant. The method adopts L array, and every sensor consists of orthogonal dipole-pairs with the same coordinate axis direction, which measure the x-axis and y-axis electric-field components of the far-field signals. The method constructs four four-order cumulant matrixes by receiving polarized array data and does not require any spectral peak search and parameter pairing, can be applied to additive Gaussian white noise or color noise environment. The performance of the proposed method is verified by computer simulations.