Focusing with the decomposition of the time reversal operator method in noisy environments

This paper presents a detailed analysis of the effects of noise （reverberation） on the focusing performance of decomposition of the time reversal operator （DORT） in a noise-limited case and in a reverberation-limited case, respectively. Quantitative results obtained from simulations and experiments are presented. The results show the DORT method can be efficiently applied to target detection with enough source level to yield significant backscatter. For a target placed on the bottom, the influence of the reverberation on the focusing performance is slight. However, distinguishing between a target and constant backscattering returning from strong local clutter on the bottom （false alarms） needs further research.     

Response of harmonically and stochastically excited strongly nonlinear oscillators with delayed feedback bang-bang control

We studied the response of harmonically and stochastically excited strongly nonlinear oscillators with delayed feedback bang-bang control using the stochastic averaging method. First, the time-delayed feedback bang-bang control force is expressed approximately in terms of the system state variables without time delay. Then the averaged It6 stochastic differential equations for the system are derived using the stochastic averaging method. Finally, the response of the system is obtained by solving the Fokker-Plank-Kolmogorov （FPK） equation associated with the averaged lt6 equations. A Duffing oscillator with time-delayed feedback bang-bang control under combined harmonic and white noise excitations is taken as an example to illus- trate the proposed method. The analytical results are confirmed by digital simulation. We found that the time delay in feedback bang-bang control will deteriorate the control effectiveness and cause bifurcation of stochastic jump of Duffing oscillator.     

开关电源音频噪声分析及抑制

本文主要分析在开关电源中出现的音频噪声来源,并提出相关措施来抑制。     

降低锅炉进风系统噪声

随着人们健康及环保意识的提高,锅炉房噪声治理工作越来越受到重视,为此,本文对降低锅炉进风系统噪声进行了探讨.主要从存在的问题及分析和改进方法两方面展开了重点论述.     

试论土地测量的面积计算方法

分析高斯投影变形方法在土地测量的面积计算方面的应用,以及几种土地测量的面积计算方法,以实际例子来证明使用这些不同方法所产生的土地测量面积计算的不同结果。     

改进的数学形态学图像去噪算法研究

从二值数学形态学出发着重研究了数学形态学的膨胀、腐蚀、开运算、闭运算,采用了数学形态学算法的腐蚀、膨胀、开启、闭合设计出了一种比较理想的开闭形态学滤波器。实验验证了,本文算法能够有效地去除图像中的高斯噪声,提高了图像的清晰度。     

低频噪声对住宅小区环境影响浅析

通过分析低频噪声的来源、特点以及危害,从噪声源角度分类分析电梯、变压器、高楼中的水泵、中央空调(包括冷却塔)对居住环境的影响,并提出相关的污染防治措施,为环保部门环境管理提供依据。     

一种多元非线性回归模型的发音评测技术

目前,在计算机辅助语言发音评测系统中大部分采用简单的线性回归模型进行机器分与人工评分之间的数据融合,该模型要求机器的评分特征与人的主观评分呈近似的线性关系,而实际呈现非线性。对此,文章引入多元非线性回归模型对分数进行映射融合,使其更符合人的主观评分。同时,在算法优化问题上,用改进步长下的高斯-牛顿算法来求解,大大提高了收敛精度。实验表明,该算法在普通话口语评测中使系统性能得到明显提升。     

电台直播室噪声及其排除探析

录音演播室的噪声,一般是指与录制节目内容无关的声音。由于直播室不同于一般的技术用房,对噪声有严格的要求,噪声应低于40dB。噪声比较不容易解决的问题就在于不能很准确地找出问题存在的根本。在直播室音频系统中,由以调音台为中心的若干子系统组成,包括音频工作站,CD机等。常用电话线路传输音频广播直播信号,还要向远端的发射系统传输信号,这些远距离的连接,必然会产生噪声。     

基于美尔倒谱系数及隐马尔可夫模型的说话人识别系统研究

为了适应强噪声环境下的语音识别,进行了基于美尔倒谱系数特征及隐马尔可夫模型的识别算法研究,主要对提取语音信号的线性预测系数、端点检测、语音特征参数提取、语音算法识别流程等进行了初步研究,并进行了说话人识别系统的仿真验证。