Calcium-magnesium-alumino-silicate(CMAS)corrosion is a critical factor which causes the failure of thermal barrier coating(TBC).CMAS attack significantly alters the temperature and stress fields in TBC,resulting in th...Calcium-magnesium-alumino-silicate(CMAS)corrosion is a critical factor which causes the failure of thermal barrier coating(TBC).CMAS attack significantly alters the temperature and stress fields in TBC,resulting in their delamination or spallation.In this work,the evolution process of TBC prepared by suspension plasma spraying(SPS)under CMAS attack is investigated.The CMAS corrosion leads to the formation of the reaction layer and subsequent bending of TBC.Based on the observations,a corrosion model is proposed to describe the generation and evolution of the reaction layer and bending of TBC.Then,numerical simulations are performed to investigate the corrosion process of free-standing TBC and the complete TBC system under CMAS attack.The corrosion model constructs a bridge for connecting two numerical models.The results show that the CMAS corrosion has a significant influence on the stress field,such as the peak stress,whereas it has little influence on the steady-state temperature field.The peak of stress increases with holding time,which increases the risk of the rupture of TBC.The Mises stress increases nonlinearly along the thick direction of the reaction layer.Furthermore,in the traditional failure zone,such as the interface of the top coat and bond coat,the stress obviously changes during CMAS corrosion.展开更多
Avirtual wall thicknessmethod is developed to simulate the temperature field of turbine bladeswith thermal barrier coatings(TBCs),to simplify the modeling process and improve the calculation efficiency.The results sho...Avirtual wall thicknessmethod is developed to simulate the temperature field of turbine bladeswith thermal barrier coatings(TBCs),to simplify the modeling process and improve the calculation efficiency.The results show that the virtualwall thickness method can improve themesh quality by 20%,reduce the number ofmeshes by 76.7%and save the calculation time by 35.5%,compared with the traditional real wall thickness method.The average calculation error of the two methods is between 0.21%and 0.93%.Furthermore,the temperature at the blade leading edge is the highest and the average temperature of the blade pressure surface is higher than that of the suction surface under a certain service condition.The blade surface temperature presents a high temperature at both ends and a low temperature in themiddle height when the temperature of incoming gas is uniformand constant.The thermal insulation effect of TBCs is the worst near the air film hole,and the best at the blade leading edge.According to the calculated temperature field of the substrate-coating system,the highest thermal insulation temperature of the TC layer is 172.01 K,and the thermal insulation proportions of TC,TGO and BC are 93.55%,1.54%and 4.91%,respectively.展开更多
Refurbishment of thermal barrier coating(TBC)has become a valuable technique to prolong the service life of high-temperature components.This study investigates the effect of the refurbishment process(coating removal a...Refurbishment of thermal barrier coating(TBC)has become a valuable technique to prolong the service life of high-temperature components.This study investigates the effect of the refurbishment process(coating removal and recoating)on the microstructure evolution and physical properties of TBC,including oxidation characteristics,element diffusion behavior,and crack failure mechanisms.The results showed that a certain amount of interdiffusion zone(IDZ)with Cr-rich would be retained in DD6 superalloy substrate after coating removal.The microstructure of the refurbished specimens showed equiaxedβ-NiAl phases,while the ordinary specimens have elongated grain shapes with a high aspect ratio.Moreover,mixed oxides in the refurbished TBC specimens were earlier observed during cyclic oxidation,with a greater thickness compared to ordinary TBC,due to the influence of BC layer phase sizes.The growth mechanism of thermally grown oxide(TGO-Al_(2)O_(3)layer)in the refurbished TBC specimens was also different,resulting from the different mechanisms of mixed oxides growth.Furthermore,under cyclic oxidation with water quenching at 1100℃,the cracks in the refurbished specimen tend to occur in the mixed oxides layer,while the cracks in the ordinary specimen occur in the top coat(TC)layer,attributing to the earlier and thicker mixed oxides layer formed in refurbished specimens.展开更多
Solid solution strengthening(SSS)is one of the main contributions to the desired tensile properties of nickel-based superalloys for turbine blades and disks.The value of SSS can be calculated by using Fleischer’s and...Solid solution strengthening(SSS)is one of the main contributions to the desired tensile properties of nickel-based superalloys for turbine blades and disks.The value of SSS can be calculated by using Fleischer’s and Labusch’s theories,while the model parameters are incorporated without fitting to experimental data of complex alloys.In thiswork,four diffusionmultiples consisting of multicomponent alloys and pure Niare prepared and characterized.The composition and microhardness of singleγphase regions in samples are used to quantify the SSS.Then,Fleischer’s and Labusch’s theories are examined based on high-throughput experiments,respectively.The fitted solid solution coefficients are obtained based on Labusch’s theory and experimental data,indicating higher accuracy.Furthermore,six machine learning algorithms are established,providing a more accurate prediction compared with traditional physical models and fitted physical models.The results show that the coupling of highthroughput experiments and machine learning has great potential in the field of performance prediction and alloy design.展开更多
The incidence of pancreatic cancer has been rising worldwide,and its clinical diagnosis and treatment remain a great challenge.To present the update and improvements in the clinical diagnosis and treatment of pancreat...The incidence of pancreatic cancer has been rising worldwide,and its clinical diagnosis and treatment remain a great challenge.To present the update and improvements in the clinical diagnosis and treatment of pancreatic cancer in recent years,Chinese Pancreatic Association,the Chinese Society of Surgery,Chinese Medical Association revised the Guidelines for the Diagnosis and Treatment of Pancreatic Cancer in China(2014)after reviewing evidence-based and problem-oriented literature published during 2015-2021,mainly focusing on highlight issues regarding diagnosis and surgical treatment of pancreatic cancer,conversion strategies for locally advanced pancreatic cancer,treatment of pancreatic cancer with oligo metastasis,adjuvant and neoadjuvant therapy,standardized processing of surgical specimens and evaluation of surgical margin status,systemic treatment for unresectable pancreatic cancer,genetic testing,as well as postoperative follow up of patients with pancreatic cancer.Forty recommendation items were finally proposed based on the above issues,and the quality of evidence and strength of recommendations were graded using the Grades of Recommendation,Assessment,Development,and Evaluation system.This guideline aims to standardize the clinical diagnosis and therapy,especially surgical treatment of pancreatic cancer in China,and further improve the prognosis of patients with pancreatic cancer.展开更多
The purpose of our study was to evaluate the correlation between the β-fibrinogen gene –148C/T and –455G/A polymorphisms and susceptibility to coronary artery disease in the Chinese population using a meta–analyti...The purpose of our study was to evaluate the correlation between the β-fibrinogen gene –148C/T and –455G/A polymorphisms and susceptibility to coronary artery disease in the Chinese population using a meta–analytic approach. Eligible studies about this correlation were identified by searching the PubMed, EMBASE, and CNKI databases. Of the 13 identified, 7 (with 1488 cases and 1234 controls) involved the –148C/T polymorphism and 9 (with 1023 cases and 1081 controls) involved the –455G/A polymorphism. No publication bias was detectable and heterogeneity testing found significant differ-ences between the ORs for both groups of studies. The combined OR for the 7 studies on susceptibility to coronary artery disease in –148T allele carriers compared to the –148C/C wild-type homozygotes was 1.31 (95%CI: 0.94-1.84, P=0.11). The combined OR for the 9 studies on susceptibility to coronary artery disease in –455A allele carriers compared to the –455G/G wild-type homozygotes was 1.75 (95%CI: 1.24-2.46, P=0.001). Our results suggest the absence of an association between the β-fibrinogen gene –148C/T polymorphism and susceptibility to coronary artery disease and the possibility that –455G/A polymorphism (in particular, allele A) increases susceptibility to this disease in the Chinese population.展开更多
基金This study is supported by the National Natural Science Foundation of China(Nos.1171101165 and 11902240).
文摘Calcium-magnesium-alumino-silicate(CMAS)corrosion is a critical factor which causes the failure of thermal barrier coating(TBC).CMAS attack significantly alters the temperature and stress fields in TBC,resulting in their delamination or spallation.In this work,the evolution process of TBC prepared by suspension plasma spraying(SPS)under CMAS attack is investigated.The CMAS corrosion leads to the formation of the reaction layer and subsequent bending of TBC.Based on the observations,a corrosion model is proposed to describe the generation and evolution of the reaction layer and bending of TBC.Then,numerical simulations are performed to investigate the corrosion process of free-standing TBC and the complete TBC system under CMAS attack.The corrosion model constructs a bridge for connecting two numerical models.The results show that the CMAS corrosion has a significant influence on the stress field,such as the peak stress,whereas it has little influence on the steady-state temperature field.The peak of stress increases with holding time,which increases the risk of the rupture of TBC.The Mises stress increases nonlinearly along the thick direction of the reaction layer.Furthermore,in the traditional failure zone,such as the interface of the top coat and bond coat,the stress obviously changes during CMAS corrosion.
基金supported by the National Science and Technology Major Project(J2019-IV-0003-0070)the National Natural Science Foundation of China(Grant No.12102320)+1 种基金the Advanced Aviation Power Innovation Workstation Project(HKCX2019-01-003)China Postdoc-toral Science Foundation(2021M692571).
文摘Avirtual wall thicknessmethod is developed to simulate the temperature field of turbine bladeswith thermal barrier coatings(TBCs),to simplify the modeling process and improve the calculation efficiency.The results show that the virtualwall thickness method can improve themesh quality by 20%,reduce the number ofmeshes by 76.7%and save the calculation time by 35.5%,compared with the traditional real wall thickness method.The average calculation error of the two methods is between 0.21%and 0.93%.Furthermore,the temperature at the blade leading edge is the highest and the average temperature of the blade pressure surface is higher than that of the suction surface under a certain service condition.The blade surface temperature presents a high temperature at both ends and a low temperature in themiddle height when the temperature of incoming gas is uniformand constant.The thermal insulation effect of TBCs is the worst near the air film hole,and the best at the blade leading edge.According to the calculated temperature field of the substrate-coating system,the highest thermal insulation temperature of the TC layer is 172.01 K,and the thermal insulation proportions of TC,TGO and BC are 93.55%,1.54%and 4.91%,respectively.
基金supported by the National Science and Technology Major Project(J2019-IV-0003-0070)National Natural Science Foundation of China(12102320)China Postdoctoral Science Foundation(2021M692571).
文摘Refurbishment of thermal barrier coating(TBC)has become a valuable technique to prolong the service life of high-temperature components.This study investigates the effect of the refurbishment process(coating removal and recoating)on the microstructure evolution and physical properties of TBC,including oxidation characteristics,element diffusion behavior,and crack failure mechanisms.The results showed that a certain amount of interdiffusion zone(IDZ)with Cr-rich would be retained in DD6 superalloy substrate after coating removal.The microstructure of the refurbished specimens showed equiaxedβ-NiAl phases,while the ordinary specimens have elongated grain shapes with a high aspect ratio.Moreover,mixed oxides in the refurbished TBC specimens were earlier observed during cyclic oxidation,with a greater thickness compared to ordinary TBC,due to the influence of BC layer phase sizes.The growth mechanism of thermally grown oxide(TGO-Al_(2)O_(3)layer)in the refurbished TBC specimens was also different,resulting from the different mechanisms of mixed oxides growth.Furthermore,under cyclic oxidation with water quenching at 1100℃,the cracks in the refurbished specimen tend to occur in the mixed oxides layer,while the cracks in the ordinary specimen occur in the top coat(TC)layer,attributing to the earlier and thicker mixed oxides layer formed in refurbished specimens.
基金supported by National Science and Technology Major Project (J2019-IV-0003-0070)the Natural Science Foundation of China (91860105,52074366)+4 种基金China Postdoctoral Science Foundation (2019M662799)Natural Science Foundation of Hunan Province of China (2021JJ40757)the Science and Technology Innovation Program of Hunan Province (2021RC3131)Changsha Municipal Natural Science Foundation (kq2014126)Project Supported by State Key Laboratory of Powder Metallurgy,Central South University,Changsha,China.
文摘Solid solution strengthening(SSS)is one of the main contributions to the desired tensile properties of nickel-based superalloys for turbine blades and disks.The value of SSS can be calculated by using Fleischer’s and Labusch’s theories,while the model parameters are incorporated without fitting to experimental data of complex alloys.In thiswork,four diffusionmultiples consisting of multicomponent alloys and pure Niare prepared and characterized.The composition and microhardness of singleγphase regions in samples are used to quantify the SSS.Then,Fleischer’s and Labusch’s theories are examined based on high-throughput experiments,respectively.The fitted solid solution coefficients are obtained based on Labusch’s theory and experimental data,indicating higher accuracy.Furthermore,six machine learning algorithms are established,providing a more accurate prediction compared with traditional physical models and fitted physical models.The results show that the coupling of highthroughput experiments and machine learning has great potential in the field of performance prediction and alloy design.
文摘The incidence of pancreatic cancer has been rising worldwide,and its clinical diagnosis and treatment remain a great challenge.To present the update and improvements in the clinical diagnosis and treatment of pancreatic cancer in recent years,Chinese Pancreatic Association,the Chinese Society of Surgery,Chinese Medical Association revised the Guidelines for the Diagnosis and Treatment of Pancreatic Cancer in China(2014)after reviewing evidence-based and problem-oriented literature published during 2015-2021,mainly focusing on highlight issues regarding diagnosis and surgical treatment of pancreatic cancer,conversion strategies for locally advanced pancreatic cancer,treatment of pancreatic cancer with oligo metastasis,adjuvant and neoadjuvant therapy,standardized processing of surgical specimens and evaluation of surgical margin status,systemic treatment for unresectable pancreatic cancer,genetic testing,as well as postoperative follow up of patients with pancreatic cancer.Forty recommendation items were finally proposed based on the above issues,and the quality of evidence and strength of recommendations were graded using the Grades of Recommendation,Assessment,Development,and Evaluation system.This guideline aims to standardize the clinical diagnosis and therapy,especially surgical treatment of pancreatic cancer in China,and further improve the prognosis of patients with pancreatic cancer.
基金Supported by Guangdong Science Technology Project Foundation(Grant No.2005B3370321,2006B36007005)Zhuhai Municipal Science Technology Foun-dation(Grant No.PB20051015)
文摘The purpose of our study was to evaluate the correlation between the β-fibrinogen gene –148C/T and –455G/A polymorphisms and susceptibility to coronary artery disease in the Chinese population using a meta–analytic approach. Eligible studies about this correlation were identified by searching the PubMed, EMBASE, and CNKI databases. Of the 13 identified, 7 (with 1488 cases and 1234 controls) involved the –148C/T polymorphism and 9 (with 1023 cases and 1081 controls) involved the –455G/A polymorphism. No publication bias was detectable and heterogeneity testing found significant differ-ences between the ORs for both groups of studies. The combined OR for the 7 studies on susceptibility to coronary artery disease in –148T allele carriers compared to the –148C/C wild-type homozygotes was 1.31 (95%CI: 0.94-1.84, P=0.11). The combined OR for the 9 studies on susceptibility to coronary artery disease in –455A allele carriers compared to the –455G/G wild-type homozygotes was 1.75 (95%CI: 1.24-2.46, P=0.001). Our results suggest the absence of an association between the β-fibrinogen gene –148C/T polymorphism and susceptibility to coronary artery disease and the possibility that –455G/A polymorphism (in particular, allele A) increases susceptibility to this disease in the Chinese population.
