基于声强信号分析和组合神经网络的发动机故障诊断

建立了一个基于声强信号分析和组合神经网络的发动机故障诊断模型。该模型首先运用小波理论分析各类故障下发动机产生的声强信号,获取反映发动机工作状态的频带特征向量,然后将特征向量用于组合神经网络训练,进行故障模式识别。通过对3Y丰田2.0发动机的试验数据分析表明,这种模型可有效提高故障诊断的效率和准确率。

ADP与OBS观测悬沙浓度实验对比研究

光学(OBS)和声学方法(ADP/ADCP)进行现场悬沙浓度观测,是目前悬沙浓度变化研究的重要方法。在长江河口,利用ADP、OBS对水体悬浮泥沙浓度进行大、小潮周期现场定点同步观测:(1)在水平方向上,ADP、OBS观测悬沙浓度具有同步峰值变化,但ADP峰值变化要比OBS平缓;(2)在垂向上,从表层到近底层,悬沙浓度逐渐增加,增加幅度在不同特征时刻、不同水层有较大差异;(3)大、小潮期间,ADP、OBS观测的悬沙浓度与传统方法得到的悬沙浓度的平均相对误差都小于20%;(4)ADP声强信号与OBS浊度、ADP与OBS观测的悬沙浓度,分别具有较好的相关性。主要结论,OBS可观测传感器附近的悬沙浓度,具有较高的精确度;ADP在观测不同水层水动力参数的同时,可同步提取不同水层的悬沙浓度信息,并且对周围水动力环境没有干扰;在特征时刻取悬沙水样率定OBS和ADP,也可用OBS率定ADP,ADP和OBS观测悬沙浓度结果可以相互验证。可见,利用声学与光学仪器进行现场联合观测,可以提高现场悬沙浓度观测的时空分辨率和准确度,同时,也为深入研究悬沙浓度变化的机制、机理,以及悬沙通量计算提供了一个有效而可靠的途径。

Enhancing the quality metric of protein microarray image

The novel method of improving the quality metric of protein microarray image presented in this paper reduces impulse noise by using an adaptive median filter that employs the switching scheme based on local statistics characters; and achieves the impulse detection by using the difference between the standard deviation of the pixels within the filter window and the current pixel of concern. It also uses a top-hat filter to correct the background variation. In order to decrease time consumption, the top-hat filter core is cross structure. The experimental results showed that, for a protein microarray image contaminated by impulse noise and with slow background variation, the new method can significantly increase the signal-to-noise ratio, correct the trends in the background, and enhance the flatness of the background and the consistency of the signal intensity.

Metallurgical behavior and variation of vibro-acoustic signal during preheating assisted friction stir welding between AA6061-T6 and AA7075-T651 alloys

The present work investigated the effects of pin profiles(cylindrical and square),pin eccentricity(0.5 mm and 1 mm)in cylindrical tool and preheating(secondary heating)on metallurgical behavior,variation of vibro-acoustic signal pattern and joint strength during friction stir welding(FSW)between AA6061-T6 and AA7075-T651 alloys.The eccentric tool pins were observed to provide good flowability and intermixing between dissimilar metals,increased the size of stir zone,and the grains in stir zone were sufficiently finer with eccentric tool pin than concentric pin.The magnitude of vibro-acoustic signal increased when shoulder plunging started and drop in signal was noted when the tool shoulder reached its desired depth.The signal magnitude was noted to be higher in welding stage compared to tool plunging stage as the tool took in fresh material during tool movement along the weld path.Preheating the workpiece prior to pin plunging and during welding notably influenced the flow behavior and mixing pattern,and the grains in stir zone were slightly coarser than those in specimen without preheating.Significant reduction in the magnitude of the signal was also observed after preheating.Tensile and flexural strength of joints were also improved slightly when additional heating was employed.

Filter algorithm based on cochlear mechanics and neuron filter mechanism and application on enhancement of audio signals

A filter algorithm based on cochlear mechanics and neuron filter mechanism is proposed from the view point of vibration.It helps to solve the problem that the non-linear amplification is rarely considered in studying the auditory filters.A cochlear mechanical transduction model is built to illustrate the audio signals processing procedure in cochlea,and then the neuron filter mechanism is modeled to indirectly obtain the outputs with the cochlear properties of frequency tuning and non-linear amplification.The mathematic description of the proposed algorithm is derived by the two models.The parameter space,the parameter selection rules and the error correction of the proposed algorithm are discussed.The unit impulse responses in the time domain and the frequency domain are simulated and compared to probe into the characteristics of the proposed algorithm.Then a 24-channel filter bank is built based on the proposed algorithm and applied to the enhancements of the audio signals.The experiments and comparisons verify that,the proposed algorithm can effectively divide the audio signals into different frequencies,significantly enhance the high frequency parts,and provide positive impacts on the performance of speech enhancement in different noise environments,especially for the babble noise and the volvo noise.

A noise cross PSD estimator for dual-microphone speech enhancement based on minimum statistics

Some two-microphone noise reduction techniques that work in the frequency domain exploit coherence function between two noisy signals. They have shown good results when noise signals on two sensors are uncorrelated, but their per-formance decreases with correlated noises. Coherence based methods can be improved when the cross power spectral density (CPSD) of correlated noise signals is available. In this paper, we propose a new method for estimation of the CPSD of the noise, which is based on the minimum tracking technique. Despite the fact that the proposed estimator does not need to implement a voice activity detector (VAD), its performance is comparable to a CPSD estimator that uses an ideal VAD.