超声波激励时长对煤体孔裂隙结构及渗透特性的影响

为探究超声波激励作用下不同激励时长对煤体损伤的特性,利用超声波激励试验系统、核磁共振成像系统、体视显微镜、煤岩芯渗透率自动测试系统等,分析不同超声波激励时长下煤体孔隙结构、表面裂隙及渗透特性的变化特征。结果表明:随着超声波激励时长不断增加,煤体微小孔、中孔、大孔的T 2谱峰面积变化率和总孔隙率变化率、表面裂隙面积变化率、渗透率变化率均呈线性增大关系;超声波激励煤体30~150 min,微小孔、中孔、大孔的T 2谱峰面积变化率分别由14.60%、52.50%、24.90%增大至61.30%、145.50%、235.70%;总孔隙率变化率、表面裂隙面积变化率、渗透率变化率分别由5.04%、47.27%、41.67%增大至24.93%、127.91%、208.33%。在不同超声波时长激励下,煤体渗透率变化率与总孔隙率变化率、表面裂隙面积变化率均符合线性增大关系;随着超声波激励时长增加,煤体孔隙、裂隙改造效果提升,渗透率得以提高。

基于超声波辅助的阳树脂复苏工艺优化试验研究

为优化超声波清洗-复苏药剂复苏受铁离子污染的阳离子交换树脂处理工艺,采用单因素试验和正交试验方法,考察了阳树脂在不同复苏试剂、超声波功率、超声波时长等因素影响下的复苏效果。试验结果表明:在超声波功率为60 W,超声波时长为90 min,采用亚硫酸钠复苏时,可将树脂的交换容量恢复至92.6%。复苏药剂的种类对树脂复苏效果的影响最大,其次是超声波功率、超声波时长。超声波功率过高会造成树脂颗粒破碎,从而导致树脂的交换容量不可逆降低。

Joint spectrogram segmentation and ridge-extraction method for separating multimodal guided waves in long bones

Ultrasonic guided waves (GWs) can be used to evaluate long bones effectively because of the ability to provide the information of the whole bone. In this study, a joint spectrogram segmentation and ridge-extraction (JSSRE) method was proposed to separate multiple modes in long bones. First, the Gabor time-frequency transform was applied to obtain the spectrogram of multimodal signals. Then, a multi-class image segmentation algorithm was used to find the corresponding region of each mode in the spectrogram, including an improved watershed transform and a region growing procedure. Finally, the ridges were extracted and the time domain signals representing individual modes were reconstructed from these ridges in each region. The validations of this method were discussed by simulated multimodal signals with different signal-to-noise ratios (SNR). The correlation coefficients between the original signals without noise and the reconstructed signals were calculated to analyze the results quantitatively. The results showed that the extracted ridges were in good agreement with generated theoretical dispersion curves, and the reconstructed signals were highly related to the original signals, even under the SNR=3 dB situation.