研究彩色多普勒超声检测下肢动脉闭塞患者的临床意义，下肢动脉闭塞病变的超声检测特征、与踝臂指数检测（ankle arm index， ABI）结果的一致性。方法前瞻性分析2010年1月～2012年12月间就诊的30例下肢动脉闭塞患者的彩色多普勒超声检...研究彩色多普勒超声检测下肢动脉闭塞患者的临床意义，下肢动脉闭塞病变的超声检测特征、与踝臂指数检测（ankle arm index， ABI）结果的一致性。方法前瞻性分析2010年1月～2012年12月间就诊的30例下肢动脉闭塞患者的彩色多普勒超声检测结果，测量内中膜厚度，并且分析病变特点、及超声检测与ABI检测结果的比较观察。同期正常健康体检者作为对照组。结果彩色多普勒超声可提示动脉内中膜增厚，局部斑块形态多样，血流改变，与ABI异常一致性高。与健康对照组相比，下肢动脉硬化组动脉中层厚度（media thickness） MT〉1.0mm的患者明显增多，差异有统计学意义（P〈0.05）。结论彩色多普勒超声无创检测下肢动脉闭塞症，可显示病变特征，早期发现MT增高的患者，与ABI的检测结果一致性高，具有重要的临床意义。展开更多
The purpose of this work is the study of a mathematical model to discretize cracks at continuous mechanical systems, applying all the available properties at computational algorithm using the methodology of state obse...The purpose of this work is the study of a mathematical model to discretize cracks at continuous mechanical systems, applying all the available properties at computational algorithm using the methodology of state observers to detect, localize and evaluate the crack conditions, seeking the model limitations through an experiment developed at the mechanical department of UNESP, llha Solteira, S^o Paulo-Brazil. Three different notch sizes were placed, one by one, at the top surface of a cantilever beam （to be considered as a crack at the mechanical system） and harmonic forces were applied at the tip of the beam with three different frequencies, for each notch size, to obtain experimental data to run the diagnosis algorithm. From the results it was possible to infer that the observation system performance increases with the raising of the crack size, which can be explained by the model, that gets more accurate with bigger crack sizes, however, when the propagation of the crack is considered at the model, the diagnosis of the crack presence tends to be more difficult. It was also possible to conclude that the developed algorithm works properly for systems which excitation frequencies are higher than 20 Hz and different from the natural frequencies of the system, due to influence of dynamic response of the crack at the model.展开更多
文摘The purpose of this work is the study of a mathematical model to discretize cracks at continuous mechanical systems, applying all the available properties at computational algorithm using the methodology of state observers to detect, localize and evaluate the crack conditions, seeking the model limitations through an experiment developed at the mechanical department of UNESP, llha Solteira, S^o Paulo-Brazil. Three different notch sizes were placed, one by one, at the top surface of a cantilever beam （to be considered as a crack at the mechanical system） and harmonic forces were applied at the tip of the beam with three different frequencies, for each notch size, to obtain experimental data to run the diagnosis algorithm. From the results it was possible to infer that the observation system performance increases with the raising of the crack size, which can be explained by the model, that gets more accurate with bigger crack sizes, however, when the propagation of the crack is considered at the model, the diagnosis of the crack presence tends to be more difficult. It was also possible to conclude that the developed algorithm works properly for systems which excitation frequencies are higher than 20 Hz and different from the natural frequencies of the system, due to influence of dynamic response of the crack at the model.
