背景噪声

Ocean ambient noise is the interference to underwater sound channel, it has great effects on the design and use of all kinds of sonar systems.

海洋环境噪声是水声信道的干扰背景场，任何声纳系统的设计和使用都要受海洋环境噪声的限制。

Ocean ambient noise is the interference to underwater sound channel, it has great effects on the design and use o...

海洋环境噪声是水声信道的干扰背景场，任何声纳系统的设计和使用都要受海洋环境噪声的限制。

Concerning the detection of weak speech signal in stronger noise background, an effective modified model based on Simulink and FDATool is proposed. The model is composed of double bandpass digital filter and traditional adaptive noise canceler.

针对强噪声背景中语音信号提取的难度，提出一种基于Simulink和FDATool的改进型信号提取模型，该模型在传统自适应噪声消除器SIMULINK模型的基础上通过增加双带通数字滤波器实现。

This paper measures the fault vibration signal of the sun-gear in planetary gear box. Bring forward a new arithmetic of time-field average which settle the problem of cycle truncation error affect the result of averaging in substance.

但这些信号又往往被伴随产生的噪声干扰，在噪声较强时，不但信号的时间历程显示不出规律性，而且在频谱图上这些周期分量很可能被淹没在噪声背景中。

By comparing the common edge detection algorithms, the magniloquent Kirsch edge detection algorithm is selected to process the result of background subtraction. The result of edge detection is denoised by mathematical morphology method. Shadow edge restrained arithmetic and detection-line-based background updating method are presented. Shadow edge restrained arithmetic reduces vehicle shadow edge efficaciously. Background updating precision is improved by presented background updating method.

在处理过程中，对常用的背景差方法进行了改进，有效的保留了车辆目标信息；通过对常用的边缘检测方法比较，选用了突出边缘的Kirsch边缘检测方法对背景差后的图像进行了边缘检测；使用形态除噪算法对边缘检测的结果进行了噪声去除；提出了阴影边缘去除算法和基于检测线的背景更新方法，阴影边缘去除算法有效的抑制了车辆阴影边缘，背景更新方法则提高了背景更新的精度。

The results of numerical experiments show that the method has the ability to filter the sample noise from limited number of background error member, to estimate the true background error correlation functions.

试验结果表明：基于球面小波的背景误差协方差模拟方法能够克服由有限背景误差样本引入的取样噪声，有效地估计出真实的背景误差相关函数。

Secondly, 4 methods of azimuth estimation based on vector hydrophone according to forms of nosie and signal are brought forward. The principles of these 4methods are set forth, simulating them by computer. Acoustic intensity averager can effectively suppress isotropic non-coherent interference; DOA based on line-spectra can effectively detect the target radiating line-spectra and estimate its azimuth angle; Bar graph approach can suppress line-spectra coherent interference and distinguish different targets radiating line-spectrum. Weighted bargraph approach can detect target in broadband coherent interference and estimate its azimuth angle.

其次，根据背景干扰和信号样式的不同，提出了单矢量水听器方位估计的4种方法；阐述了这4种方法的原理，并进行了计算机仿真，指出平均声强器方位估计适用于各向同性噪声场背景干扰，讨论了平均声强器的处理增益；目标辐射噪声中有线谱时，线谱方位估计有很好的性能，其中的LOFAR线谱和高频解调得到的DEMON线谱都是目标的特征谱线，可以利用它们进行方位估计，详细讨论了利用特征线谱单个矢量水听器分辨多目标的性能；直方图方位估计能抗强线谱相干干扰；加权直方图方位估计可以抗宽带相干干扰。

This dissertation comprehensibly researches the performance of hybrid DS/FH spread spectrum communication systems, operating in a combined additive white gaussian noise , multiple access interference, and channel fading, particularly operating in hostile interference (partial band interference and multitone jamming). At the same time, the dissertation investigates performance of forward error correction coding and diversity technology against channel noise.

本文以此为背景，较为详细地研究了在信道中出现各种噪声干扰（高斯白噪声、多址干扰和信道衰落），特别是敌方的人为干扰（部分带宽噪声干扰和部分带宽多频干扰）时，混合DS/FH扩频通信系统的性能，以及前向纠错信道编码和分集技术对混合扩频通信系统信道出现噪声干扰时系统性能的改进情况。

Secondly, on the basis of the analysis of the spatial-temporal feature of background and infrared targets in infrared sequence, a method for clutter suppression and noise removement based on the association of spatial self-adaptating Two Dimensional Least Mean Square background predict and temperal Higher-Order Cumulant is presented, and its improved version suitable for strong edge rejection and gaussian noise suppression is proposed.

然后针对红外图像序列中弱小目标和背景的空间和时间特性，提出了一种空域改进的自适应二维LMS背景预测和时域高阶累积量相结合的杂波抑制和滤波降噪的预处理方法，理论和实验结果表明，该方法对于抑制强起伏的红外背景杂波和去除高斯噪声的影响非常有效。

Based on this, aim at the disadvantage on Wigner Distribution and Fractional Fourier Transform that can't restrain noise interference effectively when be used to detect Linear Frequency Modulated signals interfered by heavy noises, we proposed a improved WD. Simulation results show that this method can restrain noise interference effectively and improve the ability of LFM signals detection. On the other hand, in multi-component cases, WD suffers from the cross-terms, which may impair some of the auto-terms. In order to separate original multi-component signals into components and reconstruct them separately, we can use the method of optimal filtering in fractional Fourier domain. But this method also has a problem that if signals have aliasing in the fractional Fourier optimal domain as well, the reconstructed signals will be distorted. In this thesis, a novel method of quasi Fourier transform is proposed in order to solve the problem of multi-component signal reconstruction, and have good results.

在此基础上，针对Wigner分布和分数维傅里叶变换在处理高噪声背景下线性调频信号检测的问题时存在不能有效抑制噪声干扰的缺点，提出了改进Wigner分布的办法，该方法能够抑制噪声，提高信号的检测能力；针对Wigner分布在处理多分量非线性调频信号时存在干扰项的缺点，以及分数域最优滤波方法在处理多分量非线性调频信号分离重构问题时存在的局限性，该局限性表现为在对最优分数域上也有信号分量重叠的情况进行处理时重构信号发生畸变，提出了新颖的类傅里叶变换的方法，该方法对在最优分数域上也有信号分量重叠的情况也能处理，得到的重构信号失真很小。

Since historical times,England ,where the early inhabitants were Celts, has been conquered three times .

从有历史以来，英国，在此地早期居住的是凯尔特人，已经被征服了三次。

Bluetooth OBEX File Transfer Enables the sending and receiving of files on your phone via Bluetooth.

蓝牙OBEX文件移动允许经过蓝牙传送和接受文件。。。。