The aim of this study is to estimate the chaos phenomenon in temporomandibular joints (TMJ) sound using fractal dimension (FD),and to examine the diagnostic value of the FD in comparing TMJ sounds produced by 6 asympt...The aim of this study is to estimate the chaos phenomenon in temporomandibular joints (TMJ) sound using fractal dimension (FD),and to examine the diagnostic value of the FD in comparing TMJ sounds produced by 6 asymptomatic and 25 symptomatic TMJ. Multiple mandibular opening and closing cycles recorded were used to calculate the waveform dimension and correlation dimension in the FD. Chaos in the TMJ sounds was estimated by the FD that was saturated with some constant value to an increase of embedding dimension. Results reveal that fractal analysis produces a high degree of reproducibility within,and similarity across subjects,and indicate that both FD values of the asymptomatic TMJ sounds are significantly higher than those of the symptomatic. These findings suggest that chaos is present in TMJ sounds and the difference in the FD is of diagnostic value in evaluation of pathological change in TMJ sound signals.展开更多
电弧-侧壁距离控制是保证窄间隙熔化极活性气体保护焊（Narrow gap metal active gas welding, NG-MAG）侧壁熔合良好的关键。通过对NG-MAG脉冲立焊过程中电弧声的预处理和分析，发现其时域波形呈周期性“振铃”衰减特性，频率与焊接电...电弧-侧壁距离控制是保证窄间隙熔化极活性气体保护焊（Narrow gap metal active gas welding, NG-MAG）侧壁熔合良好的关键。通过对NG-MAG脉冲立焊过程中电弧声的预处理和分析，发现其时域波形呈周期性“振铃”衰减特性，频率与焊接电源脉冲频率相同；电弧声能量的频域分布范围为0.3～12.0 kHz，且能量主要集中在0.3～3.0 kHz和9.0～12.0 kHz两个频带，频谱分布与电弧-侧壁距离高度相关。在此基础上，采用小波变换（Wavelet transform, WT）和联合时频分析（Joint time-frequency analysis, JTFA）实现对电弧声信号的降噪处理和时频分析，结果发现，伴随电弧-侧壁距离的逐渐增大，电弧声能量的低频分布始终存在，呈现“断续-连续-断续”分布特征；而高频分布出现在电弧-侧壁距离2.6 mm以上，呈现“断续-连续”分布特征。利用 NG-MAG 脉冲立焊电弧声的时频分布规律可实现对电弧作用位置的监测预警，为 NG-MAG 焊接过程状态监控提供一种途径。展开更多
基金The Scientific Research Fund of Tianjin Medical UniversityGrant number:98KY21
文摘The aim of this study is to estimate the chaos phenomenon in temporomandibular joints (TMJ) sound using fractal dimension (FD),and to examine the diagnostic value of the FD in comparing TMJ sounds produced by 6 asymptomatic and 25 symptomatic TMJ. Multiple mandibular opening and closing cycles recorded were used to calculate the waveform dimension and correlation dimension in the FD. Chaos in the TMJ sounds was estimated by the FD that was saturated with some constant value to an increase of embedding dimension. Results reveal that fractal analysis produces a high degree of reproducibility within,and similarity across subjects,and indicate that both FD values of the asymptomatic TMJ sounds are significantly higher than those of the symptomatic. These findings suggest that chaos is present in TMJ sounds and the difference in the FD is of diagnostic value in evaluation of pathological change in TMJ sound signals.
文摘电弧-侧壁距离控制是保证窄间隙熔化极活性气体保护焊（Narrow gap metal active gas welding, NG-MAG）侧壁熔合良好的关键。通过对NG-MAG脉冲立焊过程中电弧声的预处理和分析，发现其时域波形呈周期性“振铃”衰减特性，频率与焊接电源脉冲频率相同；电弧声能量的频域分布范围为0.3～12.0 kHz，且能量主要集中在0.3～3.0 kHz和9.0～12.0 kHz两个频带，频谱分布与电弧-侧壁距离高度相关。在此基础上，采用小波变换（Wavelet transform, WT）和联合时频分析（Joint time-frequency analysis, JTFA）实现对电弧声信号的降噪处理和时频分析，结果发现，伴随电弧-侧壁距离的逐渐增大，电弧声能量的低频分布始终存在，呈现“断续-连续-断续”分布特征；而高频分布出现在电弧-侧壁距离2.6 mm以上，呈现“断续-连续”分布特征。利用 NG-MAG 脉冲立焊电弧声的时频分布规律可实现对电弧作用位置的监测预警，为 NG-MAG 焊接过程状态监控提供一种途径。
