A robust adaptive hybrid feedback cancellation scheme for hearing aids in the presence of outliers

It has been demonstrated that the Filtered-x Wilcoxon LMS (FxWLMS) based adaptive filter mitigates the effect of the outliers acquired by the microphone signal of hearing aids by minimizing the Wilcoxon norm and hence shows better cancellation performance than the existing Filtered-x LMS (FxLMS) algorithm. The prediction error method based adaptive feedback canceller (PEMAFC) reduces the bias present in the estimate of the feedback path due to the continuous adaptive filtering (CAF). However, the impulse response of the measured feedback path is close to zero for the first many samples due to the delay introduced by ADC converters and then contains few significant values, which results in slow convergence rate when an adaptive filter is used to model the same. To overcome this limitation, we propose a proportionate normalized WLMS (PNWLMS) algorithm based PEMAFC (P-PNWLMS) for feedback cancellation in hearing aid in the presence of outliers. Further, with an objective to improve the convergence rate and performance accuracy simultaneously, this paper proposes a novel convex PNWLMS (CPNWLMS) algorithm which incorporates convex combination of PNWLMS and WLMS algorithms. The weight update equations are derived for PEMAFC trained by PNWLMS (P-PNWLMS) and CPNWLMS (P-CPNWLMS) algorithms respectively. The results of the simulation study show improved performance of the proposed CPNWLMS based adaptive filter over its component filters.     

Nearest-neighbour spacing distributions of the β-Hermite ensemble of random matrices

The evolution with β of the distributions of the spacing ‘s’ between nearest-neighbour levels of unfolded spectra of random matrices from the β-Hermite ensemble (β-HE) is investigated by Monte Carlo simulations. The random matrices from the β-HE are real symmetric and tridiagonal where β, which can take any positive value, is the reciprocal of the temperature in the classical electrostatic interpretation of eigenvalues. The distribution of eigenvalues coincide with those of the three classical Gaussian ensembles for β=1, 2, 4. The use of the β-HE ensemble results in an incomparable speed up and efficiency of numerical simulations of all spectral characteristics of large random matrices. Generalized gamma distributions are shown to be excellent approximations of the nearest-neighbor spacing (NNS) distributions for any β while being still simple. They account both for the level repulsion in ∼s^β when s→0 and for the whole shape of the NNS distributions in the range of ‘s’ which is accessible to experiment or to most numerical simulations. The exact NNS distribution of the GOE (β=1) is in particular significantly better described by a generalized gamma distribution than it is by the Wigner surmise while the best generalized gamma approximation coincides essentially with the Wigner surmise for β>∼2. They describe too the evolution of the level repulsion between that of a Poisson distribution and that of a GOE distribution when β increases from 0 to 1. The distribution of ln (s), related to the electrostatic interaction energy between neighbouring charges, is accordingly well approximated by a generalized Gumbel distribution for any β?0. The distributions of the minimum NN spacing between eigenvalues of matrices from the β-HE, obtained both from as-calculated eigenvalues and from unfolded eigenvalues are Brody distributions which are classically used to characterize the spectral fluctuations of various physical systems.     

干涉型光纤传感器相位生成载波解调方法改进与研究

提出了基于干涉型光纤传感器的相位生成载波解调方法（PGC）的改进方法,通过算法上的改进和增加抗混叠滤波器,有效地改善了解调结果,并大大降低了系统的采样频率,结论对设计干涉型光纤传感器解调系统有重要的参考意义     

响应矩阵分析方法在BEPC储存环上的应用

由于储存环中各种元件误差的存在, 机器的实际运行模式与设计模式有一定的偏差. 目前广泛开展的响应矩阵方法研究, 可以分析出磁铁元件以及束流位置测量元件的误差, 使束流基本参数得到校正. 介绍了用响应矩阵分析方法, 在BEPC储存环上进行的局部轨道校正的实验研究, 以及BEPC储存环束流参数校正的模拟研究.     

镶嵌有纳米硅的氮化硅薄膜键合特性分析

采用螺旋波等离子体化学气相沉积(HWPCVD)技术制备了非化学计量比的氢化氮化硅薄膜,对所沉积样品及氮气环境中920 ℃退火样品的微观结构及键合特性进行了分析。Raman散射结果表明,薄膜中过量硅以非晶纳米粒子形式存在,退火样品呈现纳米晶硅和氮化硅的镶嵌结构。红外吸收和可见光吸收特性比较结果显示,薄膜样品的微观结构依赖于化学计量比以及退火过程,硅含量较低样品因高的键合氢含量而表现出低的纳米硅表面缺陷态密度;退火过程将引起Si—H和N—H键合密度的减少,因晶态纳米颗粒的形成,退火样品表现出更高的结构无序度。     

对《二维六角形晶格伊辛模型的重正化群解》一文的进一步计算

针对《二维六角形晶格伊辛模型的重正化群解》一文中有关〈V〉0的计算进行了修正,给出了新的重正化群的变换、重正化群的线性化变换矩阵以及临界指数.     

对Reissner-Nordstrm-anti-de Sitter黑洞Hawking隧穿辐射的研究

在考虑粒子间的自引力相互作用后,首先采用Parikh-Wilczek的半经典隧穿方法对带电粒子与不带电粒子在Reissner-Nordstrm-anti-de Sitter黑洞视界处的隧穿辐射特征进行了研究.其次,推广复路径方法对该黑洞的辐射谱进行研究.两种方法所得的结果都支持Parikh-Wilczek的观点,即黑洞的隧穿率Bekenstein-Hawking熵变有关,真实的辐射谱不是纯热谱.     

Homography of central points for optical distortion compensation

The paper presents a novel radial lens distortion modelling method for vision systems. It is based on single images of chessboard planar pattern, in which calibration points (corners of chessboard squares) are localised. The points, which are situated near the image centre, where the distortion is negligible, are used to determine undistorted grid of calibration points by the estimation of homographic matrix. The differences in the localisation of undistorted and distorted points are used to find parameters of radial model by the linear least square method. Having the distortion model, the dense compensation is performed with support of bilinear interpolation and a sparse compensation by Newton iterative scheme providing subpixel accuracy.     

一维函数光子晶体的研究

本文提出一种新型函数光子晶体, 其折射率是空间位置函数. 由费马原理, 我们给出光在一维、 二维和三维函数光子晶体中的运动方程, 以及一维函数光子晶体的色散关系、 带隙结构和透射率, 再利用传输矩阵理论研究函数光子晶体周期数、 入射角和介质层的厚度等对透射率和禁带结构的影响, 计算发现通过选择不同的折射率空间分布函数, 可以得到比传统光子晶体更宽或更窄的禁带结构. 这样为我们设计不同带隙结构的光子晶体提供理论依据.