柔性薄壁轴承的内外圈是椭圆,这使得它和普通滚动轴承的振动特性完全不同。这种轴承旋转过程中椭圆长短轴会对轴承造成周期性冲击,这种正常的周期性冲击和轴承元件损伤引起的故障周期性冲击混合在一起,掩盖了故障周期性冲击。分析了这...柔性薄壁轴承的内外圈是椭圆,这使得它和普通滚动轴承的振动特性完全不同。这种轴承旋转过程中椭圆长短轴会对轴承造成周期性冲击,这种正常的周期性冲击和轴承元件损伤引起的故障周期性冲击混合在一起,掩盖了故障周期性冲击。分析了这种正常周期性冲击的频率分布特点,根据奇异值和频率的内在关系,提出利用奇异值分解(Singular Value Decomposition,SVD)来消除这种正常周期性冲击,选择正常周期性冲击的频率成分对应的奇异值进行SVD重构,可以准确地分离出这种正常冲击,从而消除其对故障周期性冲击的干扰。进而采用连续Morlet小波变换对消除了正常周期性冲击的柔性薄壁轴承振动信号进行故障冲击特征提取,选择峭度最大的尺度为故障特征尺度,清晰地提取到了柔性薄壁轴承的故障冲击特征,故障特征提取效果优于没有消除正常冲击时的故障特征提取效果。展开更多
针对机械早期故障引起的冲击特征微弱,易受强背景信号和噪声的干扰而难以提取的问题,提出一种奇异值分解(Singular Value Decomposition,SVD)差分谱与S变换相结合的微弱冲击特征提取方法。将原始信号构造成Hankel矩阵,采用SVD对重构矩...针对机械早期故障引起的冲击特征微弱,易受强背景信号和噪声的干扰而难以提取的问题,提出一种奇异值分解(Singular Value Decomposition,SVD)差分谱与S变换相结合的微弱冲击特征提取方法。将原始信号构造成Hankel矩阵,采用SVD对重构矩阵进行分解;利用奇异值差分谱确定降噪阶次进行降噪;采用S变换对降噪后的信号进行时频分析,提取信号中的微弱冲击特征信息。通过数值仿真和实际轴承故障数据的对比,表明该方法可有效辨别轴承振动信号中故障引起的早期微弱冲击特征,为轴承故障诊断提供先验信息。展开更多
Objective There is a paucity of published works that systematically evaluate gene anomalies or clinical features of patients with renal cysts and diabetes syndrome （RCAD）/maturity onset diabetes of the young type 5 ...Objective There is a paucity of published works that systematically evaluate gene anomalies or clinical features of patients with renal cysts and diabetes syndrome （RCAD）/maturity onset diabetes of the young type 5 （MODY5）. The purpose of this review was to systematically assess the detection rate, genetic and phenotypic implications of heterozygous autosomal dominant TCF2 anomalies. Data sources MEDLINE database was searched to select articles recorded in English from 1997 to 2008. The focus was monoallelic germline TCF2 gene mutations/deletions. Biallelic inactivation, polymorphisms, DNA modification （hypomethylation and hypermethylation）, loci associated with cancer risk, and somatic TCF2 anomalies were all excluded. Study selection After searching the literature, 50 articles were selected. Results The detection rate of TCF2anomalies was 9.7% and varied considerably among MODY （1.4%）, renal structure anomalies （RSA） （21.4%） and RSA with MODY （41.2%） subgroups. Mutations were strikingly located within the DNA binding domain and varied among exons of the DNA binding domain： exons 2 and 4 were the hottest spots, while mutations were sporadically distributed in exon 3. The consistent phenotypes were RSA （89.6%） and diabetes mellitus （DM） （45.0%）. However, the concurrence of RSA and DM was relatively low （27.5%）, which hinders the optimal performance of genetic testing and obtainment of timely diagnosis. Other organ involvements were complementary and necessary for the early identification of patients with TCF2 anomalies. Analysis of phenotypes of TCF2 point mutations showed significant differences in the detection rates of RSA, impaired renal function （IRF） and DM according to mutation type but not mutation location. Conclusion These valuable features of TCF2 anomalies that previously did not receive sufficient attention should not be neglected.展开更多
文摘柔性薄壁轴承的内外圈是椭圆,这使得它和普通滚动轴承的振动特性完全不同。这种轴承旋转过程中椭圆长短轴会对轴承造成周期性冲击,这种正常的周期性冲击和轴承元件损伤引起的故障周期性冲击混合在一起,掩盖了故障周期性冲击。分析了这种正常周期性冲击的频率分布特点,根据奇异值和频率的内在关系,提出利用奇异值分解(Singular Value Decomposition,SVD)来消除这种正常周期性冲击,选择正常周期性冲击的频率成分对应的奇异值进行SVD重构,可以准确地分离出这种正常冲击,从而消除其对故障周期性冲击的干扰。进而采用连续Morlet小波变换对消除了正常周期性冲击的柔性薄壁轴承振动信号进行故障冲击特征提取,选择峭度最大的尺度为故障特征尺度,清晰地提取到了柔性薄壁轴承的故障冲击特征,故障特征提取效果优于没有消除正常冲击时的故障特征提取效果。
文摘针对机械早期故障引起的冲击特征微弱,易受强背景信号和噪声的干扰而难以提取的问题,提出一种奇异值分解(Singular Value Decomposition,SVD)差分谱与S变换相结合的微弱冲击特征提取方法。将原始信号构造成Hankel矩阵,采用SVD对重构矩阵进行分解;利用奇异值差分谱确定降噪阶次进行降噪;采用S变换对降噪后的信号进行时频分析,提取信号中的微弱冲击特征信息。通过数值仿真和实际轴承故障数据的对比,表明该方法可有效辨别轴承振动信号中故障引起的早期微弱冲击特征,为轴承故障诊断提供先验信息。
文摘Objective There is a paucity of published works that systematically evaluate gene anomalies or clinical features of patients with renal cysts and diabetes syndrome （RCAD）/maturity onset diabetes of the young type 5 （MODY5）. The purpose of this review was to systematically assess the detection rate, genetic and phenotypic implications of heterozygous autosomal dominant TCF2 anomalies. Data sources MEDLINE database was searched to select articles recorded in English from 1997 to 2008. The focus was monoallelic germline TCF2 gene mutations/deletions. Biallelic inactivation, polymorphisms, DNA modification （hypomethylation and hypermethylation）, loci associated with cancer risk, and somatic TCF2 anomalies were all excluded. Study selection After searching the literature, 50 articles were selected. Results The detection rate of TCF2anomalies was 9.7% and varied considerably among MODY （1.4%）, renal structure anomalies （RSA） （21.4%） and RSA with MODY （41.2%） subgroups. Mutations were strikingly located within the DNA binding domain and varied among exons of the DNA binding domain： exons 2 and 4 were the hottest spots, while mutations were sporadically distributed in exon 3. The consistent phenotypes were RSA （89.6%） and diabetes mellitus （DM） （45.0%）. However, the concurrence of RSA and DM was relatively low （27.5%）, which hinders the optimal performance of genetic testing and obtainment of timely diagnosis. Other organ involvements were complementary and necessary for the early identification of patients with TCF2 anomalies. Analysis of phenotypes of TCF2 point mutations showed significant differences in the detection rates of RSA, impaired renal function （IRF） and DM according to mutation type but not mutation location. Conclusion These valuable features of TCF2 anomalies that previously did not receive sufficient attention should not be neglected.
