Effect of tube-electrode inner diameter on electrochemical discharge machining of nickel-based superalloy

Nickel-based superalloys are widely employed in modern aircraft engines because of their excellent material characteristics, particularly in the fabrication of film cooling holes. However, the high machining requirement of a large number of film cooling holes can be extremely challenging. The hybrid machining technique of tube electrode high-speed electrochemical discharge drilling (TEHECDD) has been considered as a promising method for the production of film cooling holes. Compared with any single machining process, this hybrid technique requires the removal of more complex machining by-products, including debris produced in the electrical discharge machining process and hydroxide and bubbles generated in the electrochemical machining process. These by-products significantly affect the machining efficiency and surface quality of the machined products. In this study, tube electrodes in different inner diameters are designed and fabricated, and the effects of inner diameter on the machining efficiency and surface quality of TEHECDD are investigated. The results show that larger inner diameters could effectively improve the flushing condition and facilitate the removal of machining by-products. Therefore, higher material removal efficiency, surface quality, and electrode wear rate could be achieved by increasing the inner diameter of the tube electrode. (C) 2015 The Authors. Production and hosting by Elsevier Ltd. on behalf of Chinese Society of Aeronautics and Astronautics.

Detection of ST-2 and TGF-β2 levels in patients with atrial fibrillation and their correlation with atrial fibrillation remodeling

Objective:To observe the changes of serum soluble ST-2(suppressive tumorigenicity-2,sST2)and serum transforming growth factor-β2(TGF-β2)levels in patients with atrial fibrillation,and analyze the two with known left atrium The correlation of left atrial diameter(LAD),to explore its relationship with the development of atrial fibrillation.Methods:126 patients with atrial fibrillation(AF)who were treated in the Department of Cardiology of the First Affiliated Hospital of Bengbu Medical College from December 2019 to July 2020 were selected,including 69 males and 57 females,aged 62-74 years,average(64.38±5.31)years old,patients with atrial fibrillation were divided into three groups according to the relevant guidelines,namely,paroxysmal AF group(Paroxysmal AF group)45 cases,persistent atrial fibrillation AF group(Persistent AF group)42 cases,permanent 39 cases in the Permanent AF group.64 healthy sinus rhythms(SR)were selected as the healthy control group during the same period of physical examination,including 34 males and 30 females,aged 60-75 years,average(65.25±4.37)years,using enzyme-linked adsorption Immunoassay(ELISA)was used to determine the levels of ST-2 and TGF-β2 in the serum,and to analyze the correlation with the measured LAD.Results:Compared with the control group,the ST-2 level in the experimental group was significantly higher,and the serum ST-2 level:permanent atrial fibrillation group>persistent atrial fibrillation group>paroxysmal atrial fibrillation group.Compared with the control group,the TGF-β2 level in the experimental group was significantly higher,and the serum TGF-β2 level:permanent atrial fibrillation group>persistent atrial fibrillation group>paroxysmal atrial fibrillation group.The correlation analysis between ST-2,TGF-β2 and LAD was carried out.Correlation analysis showed that the concentration of ST-2 was significantly positively correlated with the size of LAD in all experimental groups(γ=0.784,P<0.001).Correlation analysis showed that there was a significant positive correlation between TGF-β2 and LAD in all experimental groups(γ=0.815,P<0.001).Correlation analysis showed that there was a significant positive correlation between ST-2 and TGF-β2 concentrations in all experimental groups(γ=0.777,P<0.001).Conclusion:ST-2 and TGF-β2 are closely related in the development of atrial fibrillation,and can be used as new indicators to predict the prognosis of atrial fibrillation and provide new ideas and references for the diagnosis and treatment of atrial fibrillation.ST-2 and TGF-β2 are correlated with the development of atrial fibrillation.High levels of ST-2 and TGF-β2 may indicate poor prognosis and treatment effects in patients with atrial fibrillation.