In this paper .fatigue strength of T-type tubularjoints subjected to in-planebending or out-of-plane bending load is investigated By, considering material constantsand initial crack sizes as random variables and appl...In this paper .fatigue strength of T-type tubularjoints subjected to in-planebending or out-of-plane bending load is investigated By, considering material constantsand initial crack sizes as random variables and applying Monte Carlo simulation method, we have giyen a statistical analvsis on fatigue life. Simultaneously, linearregression analyses of computed resuldts are performed and compared with that of theknown experimental data.展开更多
Diamond-like carbon （DLC） thin film is one of the most widely used optical thin films. The fraction of chemical bondings has a great influence on the properties of the DLC film. In this work, DLC thin films are prep...Diamond-like carbon （DLC） thin film is one of the most widely used optical thin films. The fraction of chemical bondings has a great influence on the properties of the DLC film. In this work, DLC thin films are prepared by ion-beam sputtering deposition in Ar and CH4 mixtures with graphite as the target. The influences of the ion-beam voltage on the surface morphology, chemical structure, mechanical and infrared optical properties of the DLC films are investigated by atomic force microscopy （AFM）, Raman spectroscopy, nanoindentation, and Fourier transform infrared （FTIR） spec- troscopy, respectively. The results show that the surface of the film is uniform and smooth. The film contains sp2 and sp3 hybridized carbon bondings. The film prepared by lower ion beam voltage has a higher sp3 bonding content. It is found that the hardness of DLC films increases with reducing ion-beam voltage, which can be attributed to an increase in the fraction of sp3 carbon bondings in the DLC film. The optical constants can be obtained by the whole infrared optical spectrum fitting with the transmittance spectrum. The refractive index increases with the decrease of the ion-beam voltage, while the extinction coefficient decreases.展开更多
Background The probability of prosthesis-patient mismatch(PPM)is high in aortic valve replacement surgery for small aortic valve annulus,which increases the postoperative prosthetic valve transvalvular pressure gradie...Background The probability of prosthesis-patient mismatch(PPM)is high in aortic valve replacement surgery for small aortic valve annulus,which increases the postoperative prosthetic valve transvalvular pressure gradient.Concurrent aortic annuloplasty is a commonly applied surgical procedure,but there is currently no uniform standard or guideline on the type of prosthetic valve that should be used during surgery.Therefore,this study aimed to analyze whether there was any difference in the short-term prognosis between the choice of mechanical valves and bioprosthetic valves during aortic valve replacement surgery with concomitant aortic annuloplasty by the Nicks procedure.Methods A retrospective analysis was conducted based on the clinical data from 55 patients undergoing aortic valve replacement surgery with concomitant annuloplasty by the Nicks procedure at the Cardiac Surgery Department of Guangdong Provincial People’s Hospital from November 2021 to December 2023.In this study,all patients received aortic annuloplasty by the Nicks procedure.Among these patients,30 were in the mechanical valve group,while the other 25 were in the bioprosthetic valve group.Data including left ventricular end-diastolic/endsystolic diameters,left ventricular ejection fraction,interventricular septal thickness,left ventricular posterior wall thickness,transvalvular pressure gradient,left ventricular fractional shortening,and left ventricular mass index were collected 1 week preoperatively and 1 week and 3 months postoperatively.Information on gender,age,body surface area,types of perioperative complications,operation time,complication rates,and outcomes was also collected.Results Among the 55 patients enrolled in this study,4 died.The main causes of death included postoperative low cardiac output syndrome,severe pulmonary infection,and multi-organ dysfunction.Meanwhile,there was a statistically significant difference in left ventricular end-diastolic diameter between the mechanical valve group and the biological valve group 1 week after surgery.However,differences in other indicators such as aortic crossclamp duration,cardiopulmonary bypass duration,postoperative ventilator support duration,postoperative intensive care unit(ICU)stay,total postoperative hospital stay,and echocardiography results 1 week and 3 months postoperatively were not significant between the two groups.Conclusions For patients undergoing aortic annuloplasty by the Nicks procedure in the aortic valve replacement surgery,the postoperative recovery time is not significantly different between the bioprosthetic and mechanical valve groups.Additionally,there is no notable difference in the improvement of left ventricular function or the reduction of PPM incidence between the two types of valves.[S Chin J Cardiol 2024;25(1):29-37].展开更多
The characteristics of weld shape,microstructure,mechanical properties and defects of 5A90 Al-Li alloy joint by laser welding (LBW) and laser welding with filler wire (LWFW) were studied and analyzed.The results indic...The characteristics of weld shape,microstructure,mechanical properties and defects of 5A90 Al-Li alloy joint by laser welding (LBW) and laser welding with filler wire (LWFW) were studied and analyzed.The results indicated that the microstructure of joint by LWFW was fine-grained layer and the equiaxed grain in most of seams,which were similar to the joint by LBW.Compared with the joint by LBW,the microstructure of joint by LWFW tended to fine,and the range of the columnar crystals zone was prone to decrease.The Microhardness of the joint by LWFW (92.57HV0.2) was lower than that by LBW (95.65HV0.2),but the uniformity was better.The ultimate tensile strength of the joint by LWFW was lower than that by LBW slightly,which reached to 73.03% and 79.22% of the base metal respectively.However,the elongation of the LWFW joint was higher than that of the LBW joint significantly,which reached to 38.65% and 20.38% of the base metal respectively.The microstructure and mechanical properties of 5A90 Al-Li alloy by LWFW were better than that by LBW.The defects of joint were mainly forming defects which were caused by improper parameters and porosity inside the joint,which was caused by uncleaned surface and incomplete penetration.展开更多
文摘In this paper .fatigue strength of T-type tubularjoints subjected to in-planebending or out-of-plane bending load is investigated By, considering material constantsand initial crack sizes as random variables and applying Monte Carlo simulation method, we have giyen a statistical analvsis on fatigue life. Simultaneously, linearregression analyses of computed resuldts are performed and compared with that of theknown experimental data.
基金Project supported by the National Natural Science Foundation of China(Grant No.61235011)the Science Foundation of the Science and Technology Commission of Tianjin Municipality,China(Grant Nos.13JCYBJC17300 and 12JCQNIC01200)
文摘Diamond-like carbon （DLC） thin film is one of the most widely used optical thin films. The fraction of chemical bondings has a great influence on the properties of the DLC film. In this work, DLC thin films are prepared by ion-beam sputtering deposition in Ar and CH4 mixtures with graphite as the target. The influences of the ion-beam voltage on the surface morphology, chemical structure, mechanical and infrared optical properties of the DLC films are investigated by atomic force microscopy （AFM）, Raman spectroscopy, nanoindentation, and Fourier transform infrared （FTIR） spec- troscopy, respectively. The results show that the surface of the film is uniform and smooth. The film contains sp2 and sp3 hybridized carbon bondings. The film prepared by lower ion beam voltage has a higher sp3 bonding content. It is found that the hardness of DLC films increases with reducing ion-beam voltage, which can be attributed to an increase in the fraction of sp3 carbon bondings in the DLC film. The optical constants can be obtained by the whole infrared optical spectrum fitting with the transmittance spectrum. The refractive index increases with the decrease of the ion-beam voltage, while the extinction coefficient decreases.
文摘Background The probability of prosthesis-patient mismatch(PPM)is high in aortic valve replacement surgery for small aortic valve annulus,which increases the postoperative prosthetic valve transvalvular pressure gradient.Concurrent aortic annuloplasty is a commonly applied surgical procedure,but there is currently no uniform standard or guideline on the type of prosthetic valve that should be used during surgery.Therefore,this study aimed to analyze whether there was any difference in the short-term prognosis between the choice of mechanical valves and bioprosthetic valves during aortic valve replacement surgery with concomitant aortic annuloplasty by the Nicks procedure.Methods A retrospective analysis was conducted based on the clinical data from 55 patients undergoing aortic valve replacement surgery with concomitant annuloplasty by the Nicks procedure at the Cardiac Surgery Department of Guangdong Provincial People’s Hospital from November 2021 to December 2023.In this study,all patients received aortic annuloplasty by the Nicks procedure.Among these patients,30 were in the mechanical valve group,while the other 25 were in the bioprosthetic valve group.Data including left ventricular end-diastolic/endsystolic diameters,left ventricular ejection fraction,interventricular septal thickness,left ventricular posterior wall thickness,transvalvular pressure gradient,left ventricular fractional shortening,and left ventricular mass index were collected 1 week preoperatively and 1 week and 3 months postoperatively.Information on gender,age,body surface area,types of perioperative complications,operation time,complication rates,and outcomes was also collected.Results Among the 55 patients enrolled in this study,4 died.The main causes of death included postoperative low cardiac output syndrome,severe pulmonary infection,and multi-organ dysfunction.Meanwhile,there was a statistically significant difference in left ventricular end-diastolic diameter between the mechanical valve group and the biological valve group 1 week after surgery.However,differences in other indicators such as aortic crossclamp duration,cardiopulmonary bypass duration,postoperative ventilator support duration,postoperative intensive care unit(ICU)stay,total postoperative hospital stay,and echocardiography results 1 week and 3 months postoperatively were not significant between the two groups.Conclusions For patients undergoing aortic annuloplasty by the Nicks procedure in the aortic valve replacement surgery,the postoperative recovery time is not significantly different between the bioprosthetic and mechanical valve groups.Additionally,there is no notable difference in the improvement of left ventricular function or the reduction of PPM incidence between the two types of valves.[S Chin J Cardiol 2024;25(1):29-37].
文摘The characteristics of weld shape,microstructure,mechanical properties and defects of 5A90 Al-Li alloy joint by laser welding (LBW) and laser welding with filler wire (LWFW) were studied and analyzed.The results indicated that the microstructure of joint by LWFW was fine-grained layer and the equiaxed grain in most of seams,which were similar to the joint by LBW.Compared with the joint by LBW,the microstructure of joint by LWFW tended to fine,and the range of the columnar crystals zone was prone to decrease.The Microhardness of the joint by LWFW (92.57HV0.2) was lower than that by LBW (95.65HV0.2),but the uniformity was better.The ultimate tensile strength of the joint by LWFW was lower than that by LBW slightly,which reached to 73.03% and 79.22% of the base metal respectively.However,the elongation of the LWFW joint was higher than that of the LBW joint significantly,which reached to 38.65% and 20.38% of the base metal respectively.The microstructure and mechanical properties of 5A90 Al-Li alloy by LWFW were better than that by LBW.The defects of joint were mainly forming defects which were caused by improper parameters and porosity inside the joint,which was caused by uncleaned surface and incomplete penetration.
