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 requireme...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.展开更多
Philip’s two-term infiltration equation has been widely used to infer soil saturated hydraulic conductivity(Ks),the accuracy of which is usually influenced by the size of infiltration rings and soil conditions.Previo...Philip’s two-term infiltration equation has been widely used to infer soil saturated hydraulic conductivity(Ks),the accuracy of which is usually influenced by the size of infiltration rings and soil conditions.Previous studies have primarily focused on exploring the ring-size dependence of Ks estimations under specific soil conditions(e.g.,soil isotropy and/or uniform initial water content).This study aimed to provide a comprehensive analysis by systematically considering eight heterogeneous and anisotropic soils with nonuniform initial water contents.Specifically,we examined the validity of Philip’s infiltration equation as well as the recently proposed two forms(i.e.,infiltration and time forms)of Parlange’s infiltration equation both theoretically and in practical applications of double-ring infiltration.Then the time form of Parlange’s equation was applied to infer Ks using double-ring infiltrometer measurements with different combinations of six inner ring diameters(10,20,40,80,120,and 200 cm)and three buffer index(defined as the ratio of the difference between inner and outer ring diameters to the outer ring diameter)values(0.20,0.33,and 0.50).For each infiltrometer set,20 stochastic Ks fields were randomly generated by adopting five standard deviation values(0.1,0.3,0.5,0.7,and 0.9).Furthermore,we investigated the effects of five horizontal correlation lengths(30,60,150,300,and 600 cm)on Ks estimations.The results demonstrated that Parlange’s equation,compared to Philip’s equation,was more universal in describing the cumulative infiltration relationship for the test soils.The combination of inner ring diameter and buffer index of 40 cm and 0.2,respectively,which satisfied most of the practical requirements for determining Ks in the Soil Water Infiltration Global(SWIG)database was optimal.When the horizontal correlation length exceeded a threshold(i.e.,150 cm in our study),the inner ring diameter was required to increase to 80 cm.Our findings contribute to accurate Ks estimations of different soils using double-ring infiltrometers.展开更多
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...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.展开更多
Carbon nanotubes(CNTs)hold immense promise for a wide array of applications due to their exceptional physical and chemical properties.Understanding and controlling their structural characteristics,particu-larly the di...Carbon nanotubes(CNTs)hold immense promise for a wide array of applications due to their exceptional physical and chemical properties.Understanding and controlling their structural characteristics,particu-larly the diameter and number of walls,is crucial for harnessing their full potential.We investigated the relationship between these parameters for both commercially available and lab-scale CNTs,spanning a wide range of outer diameters(1-13 nm)and numbers of walls(1-13).Our findings revealed a com-monality among the structural diversity,rather than a random distribution,as evidenced by a piecewise linear relationship between the outer diameter and number of walls,with an inflection point occurring at approximately 4 nm in diameter.This observation is unexpected,as the CNTs were synthesized using different approaches and growth conditions;yet,as a group,they exhibit a“structural scaling”.Addi-tionally,we made an intriguing observation:despite increases in outer diameter and number of walls,the inner diameters remained relatively constant(4-5 nm)for thicker CNTs with more than three walls.These results suggest that structural properties can be estimated based on diameter,which not only ad-vances our fundamental understanding of CNT synthesis but also provides practical insights for tailoring CNT properties for various applications.展开更多
基金the financial support provided by the National Natural Science Foundation of China (No. 51475237)the National High-Tech Research and Development Program of China (No. 2013AA040101)+1 种基金the Program for New Century Excellent Talents in University (No. NCET-12-0627) of Chinathe Funding of Jiangsu Innovation Program for Graduate Education (No. KYLX_0232) of China
文摘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.
基金supported by the National Natural Science Foundation of China(Nos.42107066 and 42007004)the Natural Science Foundation of Jiangsu Province,China(No.BK20201105)。
文摘Philip’s two-term infiltration equation has been widely used to infer soil saturated hydraulic conductivity(Ks),the accuracy of which is usually influenced by the size of infiltration rings and soil conditions.Previous studies have primarily focused on exploring the ring-size dependence of Ks estimations under specific soil conditions(e.g.,soil isotropy and/or uniform initial water content).This study aimed to provide a comprehensive analysis by systematically considering eight heterogeneous and anisotropic soils with nonuniform initial water contents.Specifically,we examined the validity of Philip’s infiltration equation as well as the recently proposed two forms(i.e.,infiltration and time forms)of Parlange’s infiltration equation both theoretically and in practical applications of double-ring infiltration.Then the time form of Parlange’s equation was applied to infer Ks using double-ring infiltrometer measurements with different combinations of six inner ring diameters(10,20,40,80,120,and 200 cm)and three buffer index(defined as the ratio of the difference between inner and outer ring diameters to the outer ring diameter)values(0.20,0.33,and 0.50).For each infiltrometer set,20 stochastic Ks fields were randomly generated by adopting five standard deviation values(0.1,0.3,0.5,0.7,and 0.9).Furthermore,we investigated the effects of five horizontal correlation lengths(30,60,150,300,and 600 cm)on Ks estimations.The results demonstrated that Parlange’s equation,compared to Philip’s equation,was more universal in describing the cumulative infiltration relationship for the test soils.The combination of inner ring diameter and buffer index of 40 cm and 0.2,respectively,which satisfied most of the practical requirements for determining Ks in the Soil Water Infiltration Global(SWIG)database was optimal.When the horizontal correlation length exceeded a threshold(i.e.,150 cm in our study),the inner ring diameter was required to increase to 80 cm.Our findings contribute to accurate Ks estimations of different soils using double-ring infiltrometers.
基金National natural science foundation of China(No.81970313)Key research and development plan of Anhui province(No.180h08020246)。
文摘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.
文摘Carbon nanotubes(CNTs)hold immense promise for a wide array of applications due to their exceptional physical and chemical properties.Understanding and controlling their structural characteristics,particu-larly the diameter and number of walls,is crucial for harnessing their full potential.We investigated the relationship between these parameters for both commercially available and lab-scale CNTs,spanning a wide range of outer diameters(1-13 nm)and numbers of walls(1-13).Our findings revealed a com-monality among the structural diversity,rather than a random distribution,as evidenced by a piecewise linear relationship between the outer diameter and number of walls,with an inflection point occurring at approximately 4 nm in diameter.This observation is unexpected,as the CNTs were synthesized using different approaches and growth conditions;yet,as a group,they exhibit a“structural scaling”.Addi-tionally,we made an intriguing observation:despite increases in outer diameter and number of walls,the inner diameters remained relatively constant(4-5 nm)for thicker CNTs with more than three walls.These results suggest that structural properties can be estimated based on diameter,which not only ad-vances our fundamental understanding of CNT synthesis but also provides practical insights for tailoring CNT properties for various applications.
