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1.引言
水面舰、潜艇及鱼雷等水声运动目标的瞬态信号波形虽然比较复杂,但其包络有一定的规律或一定的趋势,所以包络分析[1]是水声瞬态信号分析的一种常用方法.本文根据水声瞬态信号包络的统计特性,通过对接收信号的统计处理和相对拟合优度选择,以估计出受噪声污染的瞬态信号的包络.并进行了仿真信号的包络估计,取得了较好的效果. 相似文献
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1.背景介绍
由于海洋声场的复杂性,水声信号往往异常复杂,相应地,水声信号处理也是信号处理领域中一个具有挑战性的研究方向.水声信号处理中,爆炸声是经常遇到的一种信号.这是因为在确定海洋声场特性时,总需要一个宽带的主动信号源,该信号经过传播后的频散结果就携带了关于传播环境的丰富信息. 相似文献
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Measurement Techniques - The article is devoted to the consideration of the features of smoothing of ECG signal against the background of electromyographic distortions of various magnitude. The... 相似文献
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采用超声表面波检测激光熔覆层残余应力时, 表面波检测信号声时差的精确读取非常关键。传统的相关法无法精确地辨别表面超声波的声时差。文中提出基于复数倒频谱的表面超声波声时差辨别算法,采用该算法对计算机模拟信号和实际检测信号做了声时差分析,并与相关法的时间分析结果做了对比。计算机模拟和实验结果均表明,倒频谱分析方法是一种精度高,具有一定抗干扰能力的声时差估计算法。最后结合表面超声波检测信号的特点,从理论上分析了倒频谱分析方法优于相关法的原因。 相似文献
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E. Nazaretski G. Lawes D. M. Lee N. Mulders D. Ponarin J. M. Parpia 《Journal of Low Temperature Physics》2002,126(1-2):685-690
We have constructed a silver alloy cell to investigate low frequency sound propagation in
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He-filled aerogel at various magnetic fields. In this apparatus, two sound modes were observed in the superfluid phase. We observed both the first sound-like mode (fast mode) which is a compression wave also seen in the normal state and the second sound-like mode (slow mode) which is attributed to the out-of-phase oscillation of the superfluid and normal components of
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He clamped to the aerogel matrix. The values of Tc and s can be extracted from the analysis of these two modes. In addition, a Helmholtz resonance provides an in-situ signature of the bulk superfluid transition and allows us to also determine the bulk s. By measuring these quantities over a range of applied magnetic fields we hope to explore the P, T, H phase diagram of
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He in aerogel. 相似文献
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水声材料声性能自由场测量技术研究 总被引:6,自引:0,他引:6
本文提出了一种新的大面积水声无源材料声学性能测量技术,可以在小型消声水池中测量大面积材料的某些声学性能随频率变化规律。材料样品的典型尺寸为1000 m m ×1000 m m 左右,目前的测量频率范围为2 .5 ~20k Hz,测量参数包括反射系数( 回声降低) ,透射系数( 插入损失) 等。对标准样品进行了性能测量,测量结果和平面波理论模型计算值有较好的吻合,表明该技术有很好的发展潜力 相似文献
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M. Elforjani 《Journal of Nondestructive Evaluation》2016,35(4):62
Various direct and indirect sensing methods for machine condition monitoring have been reported in the literature. Among these methods, acoustic emission technique is one of the effective means of monitoring rolling element bearings during industrial processes. Today, many machines use computerized classification in a wide range of applications. Further, recent developments indicate the drive towards integration of diagnosis and prognosis algorithms in future integrated machine health management systems. With this in mind, this paper concentrates on the estimation of the remaining useful life for bearings whilst in operation. To implement this, a linear regression classifier and multilayer artificial neural network model have been proposed to correlate the selected AE features with corresponding bearing wear throughout laboratory experiments. Results showed that the proposed models exhibit good prediction performance. This paper also presents the use of a new representative fault indicator, signal intensity estimator, employed for AE signals originating from natural degradation of slow speed rolling element bearings. It is concluded that the obtained results were promising and selecting this appropriate signal processing technique can significantly affect the defect identification. 相似文献
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Phase differences in the far field of a coherently illuminated object are used to estimate the two-dimensional phase in the measurement plane of an imaging system. A previously derived phase-correlation function is used in a minimum-variance phase-estimation algorithm to map phase-difference measurements optimally to estimates of the phase on a grid of points in the measurement plane. Theoretical and computer-simulation comparisons between the minimum-variance phase estimator and conventional least-squares estimators are made. The minimum-variance phase estimator produces a lower aperture-averaged mean-square phase error for all values of a sampling parameter beta. 相似文献
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先进复合材料的声学特性及其在水声工程中的应用 总被引:4,自引:0,他引:4
通过理论计算及试验,研究了碳纤维增强复合材料(CFRP),芳纶纤维增强复合材料(KFRP)的基本声学性能,分析了其作为水声结构材料在水声工程中应用的可能性及其特点。尤其指出了先进复合材料作为声纳导流罩透声窗材料的现实意义。 相似文献
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The stability of a conducting fluid flow over a rotating disk with a uniform magnetic field applied normal to the disk, is investigated. It is assumed that the magnetic field is unaffected by the motion of the fluid. The mean flow and linear stability equations are solved for a range of magnetic field-strength parameters and the absolute/convective nature of the stability is investigated. It is found that increasing the magnetic field parameter is in general stabilizing. 相似文献
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1.引言 由于水下防卫和民用海洋开发日益增长的需求,水声通信在近几年得到了较快的发展.直到最近,分集接收和自适应处理技术一直是抵抗信道衰落的主要方法,但其效果并不理想[1].组合传感器(矢量水听器)的出现为解决这一问题提供了新的途径,与传统的声压水听器相比,组合传感收器可同时、共点测量声场中的声压和三个正交方向的振速信息,而且组合传感器具有与频率无关的自然指向性.本文提出了一种基于组合传感器的声压和振速联合处理的抗信道多途衰落的方法.仿真结果表明该方法可抑制信道衰落和降低误码率. 相似文献