A Comprehensive Evaluation Method of Sensor Selection for PHM Based on Grey Clustering.

Sensor selection plays an essential and fundamental role in prognostics and health management technology, and it is closely related to fault diagnosis, life prediction, and health assessment. The existing methods of sensor selection do not have an evaluation standard, which leads to different selection results. It is not helpful for the selection and layout of sensors. This paper proposes a comprehensive evaluation method of sensor selection for prognostics and health management (PHM) based on grey clustering. The described approach divides sensors into three grey classes, and defines and quantifies three grey indexes based on a dependency matrix. After a brief introduction to the whitening weight function, we propose a combination weight considering the objective data and subjective tendency to improve the effectiveness of the selection result. Finally, the clustering result of sensors is obtained by analyzing the clustering coefficient, which is calculated based on the grey clustering theory. The proposed approach is illustrated by an electronic control system, in which the effectiveness of different methods of sensor selection is compared. The result shows that the technique can give a convincing analysis result by evaluating the selection results of different methods, and is also very helpful for adjusting sensors to provide a more precise result. This approach can be utilized in sensor selection and evaluation for prognostics and health management.

[Effects of total C-21 steroidal glucosides from Cynanchum auriculatum on oxidative stress pathway in mice with liver injury].

The study aimed to investigate the mechanism of hepatoprotective effect of C-21 steroidal glucosides from Cynanchum auriculatum( Baishouwu) on oxidative stress in mice with liver injury. Mice were randomly divided into normal group,model group,positive control group,Baishouwu high group and Baishouwu low group. The liver injury model was induced by intraperitoneal injection of CCl4 peanut oil solution. All mice were sacrificed to collect blood and liver specimens. The activities of serum levels of ALT and AST were detected. The content of MDA and the activity of SOD in liver homogenate were examined by colorimetry method. Tissues were stained with hematoxylin-eosin for histological examination. The hepatic protein expressions of NF-κB p65,p-IκBα,i NOS and COX-2 were detected by Western blot. The mRNA expressions of TNF-α and IL-6 were determined by RT-PCR. It was found that treatment with C-21 steroidal glucosides from Baishouwu successfully attenuated liver injury induced by CCl4,as shown by decreased levels of serum biochemical indicators( AST,ALT)( P<0. 01). Administration of total C-21 steroidal glucosides enhanced the activity of SOD( P<0. 01) and decreased the content of MDA( P<0. 01) in liver homogenate. Microscopic features suggested that treatment with C-21 steroidal glucosides from Baishouwu was effective in inhibiting CCl4-induced hepatocyte edema and degeneration. Further studies showed that NF-κB p65 overexpression induced by CCl4 was decreased by C-21 steroidal glucosides,leading to the markedly down-regulated protein expression levels of p-IκBα,i NOS and COX-2,as well as the depression of TNF-α and IL-6 mRNA expressions. In conclusion,total C-21 steroidal glucosides from Baishouwu exhibited potent effect on oxidative stress pathway in mice with liver injury induced by CCl4,with enhanced activity of SOD,decreased content of MDA,and down-regulated levels of NF-κB p65,p-IκBα,i NOS and COX-2.