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瞬变电磁场探测中低阻屏蔽层影响的时-频分析  [PDF]
石显新,闫述,傅君眉,陈明生
煤田地质与勘探 , 2009,
Abstract: 瞬变电磁法在低阻覆盖层地区施工时会受到低阻层的屏蔽影响。虽然观测数据如感应电动势有较大的数值,但实际上探测深度却大大减小了。当有上覆低阻层存在时,要探测同样的深度,需要较长的观测时间。采用平滑伪Wigner-Ville分布和Gabor展开,分别将典型的二层地电模型(D、G型)与三层地电模型(H、A、K、Q型)的感应电动势衰减曲线映射成为时间-频率平面上的二维信号,通过对时-频能量谱的分析及模型之间的对比研究表明,瞬变电磁场能量在低阻层中聚集和损耗,尤其是对于描述我国华北型煤田的A型地电模型(地表为低阻层),瞬变电磁场的能量在由地面向下扩散的过程中,能量通过基底以上各低阻层的聚集和损耗,到达最有观测意义的底层界面(奥灰与煤系的界面)时,已经消耗殆尽。因此,当在A型模型地层地区进行瞬变电磁勘探时,应充分考虑低阻屏蔽层的影响,在施工设计时应选择较长的观测时窗以保证探测深度,并采用大功率仪器来提高信噪比。
小地震与人工爆破记录的时频分析
Time-frequency Analysis of Records of Small Earthquakes and Explosions
 [PDF]

崔鑫,许力生,许忠淮,李铂,王峰
- , 2016, DOI: 10.3969/j.issn.1000-0844.2016.01.0071
Abstract: 基于Matlab软件,编制了对近震记录进行时-频分析试验研究的程序,搜集2006—2008年间首都圈地区震级介于ML2.4~2.7的5次天然地震和5次人工爆破的27个台站的宽频带记录,根据震中距离的相似性挑选5组天然地震和人工爆破地震,分析其时频特征。对于所有的数据都给出其三分向的时频图、原始波形图和频谱图,以及水平向和三分向的叠加图。分析结果表明,天然地震和人工爆破的记录具有明显不同的时频特征,天然地震的时频呈现出"多峰"特征,而人工爆破的时频分布则相对"少峰";天然地震的时频峰值分布在较宽的频率范围内,人工爆破的峰值则分布在频率较低的相对狭窄的范围内。通过以上实践,发现时频分析在分析不同时间点的频谱信息以及整个数据的时频分布特点时比傅里叶变换具有优势。
In this study, we developed a program to analyze the time-frequency spectrum of seismology events using MATLAB software. Among all the time-frequency analysis tools, we selected short-time Fourier transform (STFT) owing to its computational simplicity, adequate time and frequency resolution, and absence of undesirable cross terms. One disadvantage of STFT is the tradeoff between window length and time and frequency resolution. In order to determine the optimal window length, we wrote the code according to the sample rate of data records. We collected 82 broadband records, including data of 27 stations, of 5 natural earthquakes and 5 explosion events that occurred in the capital area between 2006 and 2008 having a magnitude in the range of 2.4 to 2.7. For the sake of convenience, we selected five pairs of events, each pair with one natural earthquake and one explosion event at similar epicenter distance, and analyzed the time-frequency spectrum. We plotted the time-frequency spectrum for each record with its original waveform and Fourier spectrum including the three components and their combination. Different time-frequency patterns exist for natural earthquakes and explosion events. In the first place, more peaks can be seen in the natural earthquake time-frequency spectrum, while the explosion events spectrum has fewer peaks. In the second place, the peaks of natural earthquakes are located in a broad frequency band, whereas the peaks of explosion time-frequency spectrum are concentrated in a narrow area. We analyzed all the data, not restricted to the five pairs of events, and the time-frequency spectrum pattern was found to be consistent. However, this pattern may be applicable only in the capital area because the explosion techniques are fairly complicated. The operator can use completely different explosion plans, and different local seismological wave propagation models produce diverse wave fields. When compared with Fourier analysis, the time-frequency spectrum, which is the time domain expansion of Fourier Spectrum, provides more information.
地铁引发环境振动的时频能量评价方法
Time-Frequency Energy Evaluation Method of the Vibration Induced by Underground Subway
 [PDF]

张斌, 宗刚, 李广振, 任晓崧
Hans Journal of Civil Engineering (HJCE) , 2014, DOI: 10.12677/HJCE.2014.36022
Abstract:
振动测试与评价是现代城市轨交建设环评工作不可或缺的工作内容之一,如何合理有效的对振动进行评价是近年来的研究热点。基于振动信号时频分析,提出了地铁引发场地振动响应的时频能量评价方法。优选Margenau-Hill-Spectrogram时频分布作为基本时频分布类型,对地铁实测信号的时频特性进行了统计分析,而后对地铁振动信号进行了局部化时频能量和累积时频能量的深入分析,并与传统评价方进行了对比。研究结果表明,地铁引发的场地振动信号具备显著的局部化时频特性,其局部化时频能量和累积时频能量均具有较好的统计稳定性,时频能量评价指标可较好涵盖传统评价指标表征特点的同时,对信号能量的描述更为准确和全面,时频能量评价方法适用于地铁引发场地振动的环境评价。
Evaluation of environmental vibration is essential to environmental dynamic testing and analysis. How to reasonably evaluate the vibration is a widely concerned issue. This paper proposed the time-frequency energy analysis method. Firstly, the Margenau-Hill-Spectrogram time-frequency distribution was selected as the optimal analysis distribution and statistical analysis of the time- frequency characteristics of the measured vibration signals was given. Secondly, further analysis of the local time-frequency energy and accumulated time-frequency energy was done. By comparing with traditional evaluation methods, the results show that the vibration induced by underground subway has remarkable local time-frequency characteristics, and that both the local and accumulated time-frequency energy has statistics stability. The time-frequency energy evaluation can be used to replace the traditional evaluation method and to describe the energy accurately and comprehensively. Time-frequency energy evaluation is suitable for the vibration induced by underground subway.
瞬变电磁法资料的联合时—频分析初探  [PDF]
陈明生,李正斌
煤田地质与勘探 , 1999,
Abstract: 依据联合时-频分析原理,研究了几个地电模型瞬态响应信号的时-频分布特征,说明瞬变场信号的时频分布强度在随深度减弱的总趋势下,受电阻率影响有明显变化电阻率低分布强度大;电阻率高分布强度小。据此建立起瞬变场信号的联合时-频分布与地电结构的关系,可以更好地解释瞬变场资料。
Experimental Study of Frequency Effect on Rocks
岩石时频效应的实验研究

WAN Xin-lin,DU Yun,XUE Yan-wei,XI Dao-ying,
宛新林
,杜赟,薛彦伟,席道瑛

实验力学 , 2009,
Abstract: 对饱和泵油南京砂岩和饱水大理岩在MTS上进行了单轴压缩实验和正弦波加载实验,求得两种饱和岩石的单轴抗压强度和屈服强度,并获得随正弦波频率的提高,饱和泵油南京砂岩的杨氏模量、纵横波速度增大,具有较明显的频散效应.饱和岩石中的微细观缺陷在正弦波加载中引起滞后,导致瞬时杨氏模量与应力成不对称"X"形,获得随正弦波频率增高,"X"交点在模量轴上的位置增高,杨氏模量增大,模量的频散增强.本文揭示了岩石的非线性时频响应的一些物理机理,对于岩石介质中的非线性波动研究以及地震、工程等理论研究和应用都具有重要意义.
有耗分层媒质上瞬变电磁测深的联合时-频解释  [PDF]
闫述
煤田地质与勘探 , 2004,
Abstract: 时-频分析是信号分析中非常有力的工具,近年来在处理非稳态信号方面获得了很大的成功。本文将联合时-频分析(JTFA)用于处理地球物理勘探中具有扩散性质的瞬变电磁场信号。首先用数字滤波和逆拉氏算法模拟了分层大地表面上中心回线装置的瞬变响应,然后用Gabor展开研究它们的时-频谱,结果将地层序列成功地区分开来,为瞬变电磁法勘探提供了新的解释手段。
基于CSLBP的轴承信号时频特征提取方法
Time-Frequency Feature Extraction Method Based on CSLBP for Bearing Signals
 [PDF]

张云强,张培林,吴定海,李兵
- , 2016, DOI: 10.16450/j.cnki.issn.1004-6801.2016.01.004
Abstract: 针对滚动球轴承振动加速度信号特征提取问题,提出一种基于中心对称局部二值模式(center symmetric local binary pattern,简称CSLBP)的时频特征提取方法。首先,利用广义S变换对滚动球轴承振动加速度信号进行处理,通过采用时频聚集性度量准则自适应地确定广义S变换的调整参数,从而获取时频分辨性较好的二维时频图;然后,计算二维时频图的CSLBP,提取CSLBP纹理谱描述滚动球轴承振动加速度信号的时频特征。对滚动球轴承正常、外圈故障、内圈故障和滚动体故障4种不同状态的振动加速度信号进行了研究。结果表明,CSLBP纹理谱能有效地表达滚动球轴承振动加速度信号的时频特征,与局部二值模式(local binary pattern,简称LBP)和统一模式LBP纹理谱相比,CSLBP纹理谱具有特征维数低和区分性能好的优点。
A time-frequency feature extraction method based on center-symmetric local binary pattern (CSLBP) is proposed for vibration acceleration signals of rolling bearings. First, the generalized S transform is employed to process vibration acceleration signals of rolling bearings. Two-dimensional time-frequency images with good resolution performance of the bearing signals are obtained by utilizing the time-frequency aggregation measurement criterion to adaptively set the adjustment parameter of the generalized S transform. Then, the CSLBP of the images is calculated. Texture spectra of CSLBP are extracted and utilized to describe time-frequency characteristics of the vibration acceleration signals of rolling bearings. Vibration acceleration signals from four different rolling bearing states are studied. The experimental results indicate that the texture spectrum of CSLBP can effectively express the time-frequency characteristics of the vibration acceleration signals of rolling bearings. It has low dimensional feature and satisfactory separability compared with the texture spectra of local binary pattern (LBP) and uniform pattern LBP.
水下爆炸船体结构壁压信号时频特征分析
Analysis of time-frequency characteristics of wall pressure signals of hull structure subjected to underwater explosion
 [PDF]

谢耀国,郭君,李新飞,崔洪斌,姚熊亮
- , 2015, DOI: 10.7511/dllgxb201505007
Abstract: 为了研究水下爆炸条件下船体结构壁压信号时频特征,基于某船体结构模型水下爆炸实验壁压数据,利用小波变换良好的时频局部化性质,对壁压信号进行时频特征分析,得到壁压信号在不同频带上的压力时程曲线和能量分布.结果表明,利用小波变换可以方便地获得壁压信号强度、频率和持续时间等时频细节信息.能量统计表明,壁压信号频带分布很广,超过80%的能量主要集中在20 kHz以下,5 kHz以下频带能量最大.
With a view to obtaining the time-frequency characteristics of wall pressure signals of hull structure subjected to underwater explosion, based on the experimental wall pressure data of a hull structure model subjected to underwater explosion, the time-frequency characteristics of the wall pressure signals were studied by means of wavelet transform characterized with good time-frequency localization. By using these wall pressure signals, the pressure-time curves and the energy distributions in different frequency bands were obtained. The experimental results show that it is easy to get the time-frequency information details of the wall pressure signals by the wavelet transform, such as intensity, frequency and duration, etc.. Energy statistics show that frequency bands of the wall pressure signals have a wide distribution, more than 80% of the energy of the wall pressure signals is mainly concentrated in the area of less than 20 kHz and the highest level of energy is below the frequency of 5 kHz.
基于SPWVD时频图纹理特征的滚动轴承故障诊断
Rolling Bearing Faults Diagnostics Based on SPWVD Time-Frequency Distribution Image Texture Feature
 [PDF]

王亚萍,许迪,葛江华,孙永国,隋秀凛
- , 2017, DOI: 10.16450/j.cnki.issn.1004-6801.2017.01.018
Abstract: 针对如何提高滚动轴承故障诊断准确率的问题,提出一种基于平滑伪维格纳-威利分布(smooth and pseudo Wigner Ville distribution, 简称SPWVD)时频图纹理特征的故障诊断方法,对滚动轴承不同故障类型及故障程度进行识别。首先,采用SPWVD时频分析方法处理轴承故障振动信号,并获取时频图,从中提取选择表征能力优秀的特征参量作为故障特征;其次,将故障特征作为输入,结合支持向量机(support vectors machine,简称 SVM)建立滚动轴承故障诊断模型;最后,采用轴承故障数据,比较SPWVD时频图纹理特征、维格纳 威利分布(Wigner-Ville distribution, 简称WVD)时频图纹理特征和小波尺度谱图纹理特征3种故障特征的模式识别能力及准确率。分析结果表明,SPWVD时频图纹理故障特征分类效果最佳,敏感性最强,具有较高的故障诊断精度。
In order to improve the accuracy of fault diagnosis for rolling bearings, this paper proposes an intelligent fault diagnosis method based on smooth and pseudo Wigner-Ville distribution (SPWVD) time-frequency distribution image texture features. First, we used the SPWVD time-frequency analysis method to process the bearing fault vibration signal. We acquired the time-frequency distribution image, then extracted the texture features from the images for the formation of the rolling bearing fault feature vectors based on certain sensitive texture features. Then, we introduced the fault feature vectors as the input to achieve fault diagnosis of rolling bearings based on the support vector machine (SVM). Finally, we extracted three kinds of feature vectors from the bearing fault data using the SPWVD time-frequency analysis method, Wigner-Ville distribution time-frequency analysis method, and wavelet scale spectrum method, respectively. We acquired the fault diagnosis accuracy of these feature vectors experimentally. The comparison results showed that the performance of the SPWVD time frequency texture fault feature outperformed the two other kinds of feature vectors with the best classification accuracy and sensitivity.
适用于广播信道的时频调制音频隐藏算法
Audio information hiding algorithm based on Time-Frequency modulation method applied in broadcast channel
 [PDF]

李丹,高勇
- , 2017,
Abstract: 广播信道中包含大量音频信息,给音频信息隐藏应用提供了广阔空间,但在广播信道上缺乏行之有效的音频隐藏算法。针对上述问题提出了一种时频调制音频信息隐藏算法,时频调制技术具有较强的抗信道干扰特性,在广播信道上具有很强的适用性。该算法在音频载体中嵌入一定幅度的时频调制信息序列,用时频调制信息序列在不同时隙和频点的排列组合来表示秘密信息,通过控制时频调制信息序列的幅度将秘密信息隐藏到载体音频中,不被人耳所察觉。实验结果表明,该算法可应用在不同的FM调频广播信道上,并可保持96%以上的信息恢复率。
A lot of audio information is contained in Broadcast channel, which provides a broad space for information hiding application, but effective audio hiding algorithm rarely shows up. In view of the above problems, a kind of Time-Frequency modulated audio information hiding algorithm is put forward. Time-Frequency modulation technology possesses strong interference-robusted characteristics, which results in its strong applicability in the broadcast channel. In the algorithm, certain range of Time-Frequency modulation information sequence is embedded in the audio carrier, secret information is represented by the permutation and combination of different time slots and frequency points of the Time-Frequency modulation information sequence. By controlling the amplitude of the Time-Frequency modulation information sequence, the secret information is hidden into the audio carrier, which is not detected by the human ear. The experimental results show that the proposed algorithm can be applied to different FM broadcast channels, and can maintain the information recovery rate of over 96%
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