共查询到20条相似文献,搜索用时 46 毫秒
1.
针对北极冰下双声道波导的噪声分布特性研究,采用垂直阵对双声道波导内的噪声场进行了观测,北极冰下噪声物理模型使用混合加性噪声模型描述,统计分布模型使用α稳定分布描述.并将噪声划分为3个频段,按噪声来源分为背景噪声、冲击噪声以及航船噪声3种场景,分析其统计特性,给出了直方图统计、核函数估计与正态分布的比较结果,α稳定分布参数估计结果,峰度与偏度的计算结果以及累积分布函数检验结果。经分析讨论,给出结论:双声道波导中的噪声统计分布可用α稳定分布来描述,但上下表面声道的分布参数具有明显差别,上表面波导背景噪声明显偏离高斯分布而下表面声道的背景噪声接近于高斯分布;上下表面声道中不同频带的噪声分布差异也很明显,其中2~30 Hz差异性最大,30~100 Hz差异性较大,而100~500 Hz差异性相对较小,并且可以认为是对称α稳定分布.此外,上下表面声道中不同频带噪声α稳定特征参数变化也存在差异,上表面波导受冲击噪声影响α值变大,拖尾变薄;而下表面波导受冲击噪声影响α值则会变小,拖尾变重。 相似文献
2.
由于实际海洋环境中存在大量的非高斯噪声,一些基于高斯假设的传统去噪方法在实际海洋环境中性能下降甚至失效。针对非高斯噪声,如α稳定分布噪声、非平稳行船噪声下的脉冲信号的去噪与重构,该文提出一种基于深度学习的方法。去噪模型首先通过学习带噪信号短时傅里叶变换谱与残差谱之间的映射关系以去除环境噪声,之后对去噪信号的时频谱进行逆变换重构脉冲信号。仿真实验结果表明,深度学习模型在非高斯噪声环境下脉冲信号的去噪与重构任务中有着良好的表现,在实测样本上也表现出良好的泛化性,体现了一定的工程应用价值。 相似文献
3.
针对海洋环境噪声的非高斯特性,将α稳定分布模型应用到噪声统计建模中。基于模型特征指数与样本峰度物理意义的相似性,建立了二者的对应关系,并推导得出相互独立的两个随机变量之和的峰度。通过数值仿真,表明了α稳定分布对尖峰态噪声建模的可行性和适应性。以安静环境、气枪干扰、航船干扰3种典型环境下的海上实测数据为样本,借助分位数图判断了样本的非高斯特性,并利用分位数法和特征函数法联合估计了模型的参数,得出了特征指数的统计规律:安静环境下特征指数接近2.0,趋近于正态分布;气枪干扰下特征指数介于1.2~1.7之间,具有尖峰厚尾特性;航船干扰下与航速、干扰源到接收位置距离有关,航船影响越显著,特征指数越小,该现象恰好与干扰噪声的峰度变化在物理意义上一致。模型验证结果表明,α稳定分布对3类样本均表现出良好的建模效果,尤其对具有尖峰特性的气枪干扰噪声,效果远远优于正态分布。 相似文献
4.
为研究冰源噪声的统计特性,扩展了一种用于合成孔径雷达图像信号参数估计的α稳定分布参数估计方法的适用范围,解决了该方法在特征指数α接近2时,偏斜参数β的估计精度严重下降的问题,并将其应用于北极冰源噪声的统计建模中。该方法利用两个特征函数点进行参数估计,第二个特征函数点ω0的取值范围受尺度参数γ值影响。数值仿真表明:当γ∈[0.00006,0.4]时,ω0> 1时的参数估计性能更好;当γ∈(0.4,2]时, 0 <ω0 <0.5时的参数估计性能更好。北极噪声数据的验证结果表明,ω0> 1时的α稳定分布对冰源噪声表现出良好的建模效果。最后给出了不同海冰状态下α值的统计规律。 相似文献
5.
基于n型金属氧化物半导体场效应晶体管(nMOSFET)噪声的数涨落模型,采用高阶统计量双相干系数平方和研究了nMOSFET噪声的非高斯性.通过对nMOSFET实际测试噪声的分析,发现nMOSFET器件噪声存在非高斯性;小尺寸器件噪声的非高斯性强于大尺寸器件;在器件的强反型线性区,其非高斯性随着漏压的增加而增加.文中还通过蒙特卡罗模拟和中心极限定理理论对nMOSFET噪声的非高斯性作了深入的探讨.
关键词:
噪声
非高斯性
n型金属氧化物半导体场效应晶体管
氧化层陷阱 相似文献
6.
7.
针对一般建筑物内空间电场强度时域变化特点,采用时域有限差分方法,数值模拟单极性高斯脉冲、双极性微分高斯脉冲以及窄带调制方波脉冲平面波在建筑物内传播、反射及透射过程;并对比分析不同脉冲参数对空间场强最大值及分布的影响。在一定脉冲宽度的微分高斯脉冲激励下,建筑物空间内最大场强变化范围值较高,为3.0~5.5 dB,其空间场强增强分布区域较大,并随脉宽增加而减小,但脉冲的最小重复频率相对要求最高。相应脉宽的高斯脉冲造成空间最大场强及分布区域范围最小,而脉冲的最小重复频率所需最低。当载频为房间谐振频率的窄带脉冲入射下,空间最大场强变化范围值相对最高,空间场强增强区域总体趋势随脉冲载频频率单调增加。 相似文献
8.
9.
10.
研究了非高斯噪声激励下含周期信号的FHN模型的动力学行为. 通过计算神经元的平均响应时间、观察神经元的共振活化和噪声增强稳定现象,分析了非高斯噪声对神经元动力学行为的影响. 发现通过改变非高斯噪声的相关时间可以有效地改变共振活化和噪声增强稳定现象. 观察到在强相关噪声下不同强度的非高斯噪声抑制了神经元的噪声增强稳定现象而共振活化现象几乎不变,也就是非高斯噪声有效地增强了神经响应的效率. 观察了平均响应时间与非高斯噪声参数q之间的关系,当q为一个有限的小于1的值时,平均响应时间取得最小值. 最后表明在一定条件下,非高斯噪声出现重尺度现象,即非高斯噪声产生的效果可以由高斯白噪声来估计.
关键词:
FHN神经系统
非高斯噪声
平均响应时间
共振活化现象 相似文献
11.
Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide 总被引:1,自引:0,他引:1
Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs. 相似文献
12.
A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output. 相似文献
13.
The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper. 相似文献
14.
S. G. Nedel’ko M. A. Krysyuk A. L. Apanasenko L. N. Lymarenko Z. T. Moroz 《Journal of Applied Spectroscopy》1997,64(1):55-61
Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped
with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly
described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation
(5.5·104 Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum
cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics
of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure
crystals is analyzed (preliminarily).
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997. 相似文献
15.
16.
A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users. 相似文献
17.
A transient suppression method for piezoelectric ceramic transducer is presented. By adding some special pedestal pulses to the original transmitted signal, the transient effects in the output of the transducer can be just precisely transmission by use of a narrowband transducer. canceled, thereby achieving the broadband The experimental results show that the transient responses of the sinusoid pulses and coded signals are suppressed successfully and the acoustic waveforms radiated into the surrounding water are improved significantly. 相似文献
18.
We experimentally demonstrate amplitude squeezed soliton utilizing intensity-dependent self-phase modulation in an asymmetric Sagnac interferometer.The system.whose components are connected via ferrule connector/physical connection(FC/PC)fiber connectors,constitutes all-fiber configuration to generate squeezed soliton.Soliton amplitude reduction measured by homodyne detection is near 4.0 dB below the shot-noise level.Optimal squeezing fields in both simple and compact all-fiber configuration are obtained. 相似文献
19.
The(2 1)-dimensional nonlinear Schr(o)dinger(NLS)equation with spatially inhomogeneous nonlinearities is investigated,which describes propagation of light in(2 1)-dimensional nonlinear optical media with inhomogeneous nonlinearities.New types of optical modes and nonlinear effects in optical media are presented numerically.The results reveal that the regular split of beam can be obtained in (2 1)-dimensional nonlinear optical media with inhomogeneous nonlinearities,by adjusting the guiding parameter.Furthermore,the stability of beam regular split is discussed numerically,and the results reveal that the beam regular split is stable to the finite initial perturbations. 相似文献
20.
In the real-world application of face recognition system, owing to the difficulties of collecting samples or storage space of systems, only one sample image per person is stored in the system, which is so-called one sample per person problem. Moreover, pose and illumination have impact on recognition performance. We propose a novel pose and illumination robust algorithm for face recognition with a single training image per person to solve the above limitations. Experimental results show that the proposed algorithm is an efficient and practical approach for face recognition. 相似文献