Ti and its alloys have been broadly adopted across various industries owing to their outstanding proper-ties,such as high strength-to-weight ratio,excellent fatigue performance,exceptional corrosion resistance and so ...Ti and its alloys have been broadly adopted across various industries owing to their outstanding proper-ties,such as high strength-to-weight ratio,excellent fatigue performance,exceptional corrosion resistance and so on.Additive manufacturing(AM)is a complement to,rather than a replacement for,traditional manufacturing processes.It enhances flexibility in fabricating complex components and resolves machin-ing challenges,resulting in reduced lead times for custom designs.However,owing to distinctions among various AM technologies,Ti alloys fabricated by different AM methods usually present differences in mi-crostructure and defects,which can significantly influence the mechanical performance of built parts.Therefore,having an in-depth knowledge of the scientific aspects of fabrication and material properties is crucial to achieving high-performance Ti alloys through different AM methods.This article reviews the mechanical properties of Ti alloys fabricated by two mainstream powder-type AM techniques:powder bed fusion(PBF)and directed energy deposition(DED).The review examines several key aspects,en-compassing phase formation,grain size and morphology,and defects,and provides an in-depth analysis of their influence on the mechanical behaviors of Ti alloys.This review can aid researchers and engi-neers in selecting appropriate PBF or DED methods and optimizing their process parameters to fabricate high-performance Ti alloys for a wide range of industrial applications.展开更多
Boldenone is a protein-assimilating androgen steroid that can promote protein synthesis,support nitrogen storage,and enhance renal erythropoietin release.The industrial production of boldenone mainly relies on chemica...Boldenone is a protein-assimilating androgen steroid that can promote protein synthesis,support nitrogen storage,and enhance renal erythropoietin release.The industrial production of boldenone mainly relies on chemical synthesis,which has various problems,such as a complex conversion process,excessive byproducts,and serious environmental pollution.There-fore,it is of great significance to explore a new biosynthetic route.Recently,the enzymatic synthesis of steroid compounds has been performed more frequently than in the past.In this work,boldenone was produced from androstenedione(AD)in two steps by a dual-enzyme cascade of 17β-hydroxysteroid dehydrogenase(17β-HSD)and 3-sterone-Δ^(1)-dehydrogenase(KstD).The conversion efficiency of three isoenzymes of 17β-HSD from Mycobacterium sp.LY-1 for substrate AD was first analyzed.After that,the 17β-HSD2 with high selectivity and specificity for AD was screened and co-expressed with KstD3 in Escherichia coli BL21 to construct a dual-enzyme catalytic system.The results showed that the synthesis of boldenone from AD could be achieved by constructing the dual-enzyme expression system of 17β-HSD and KstD,as we determined that the concentration of boldenone reached 24.3 mg/L.To further improve the synthesis efficiency of boldenone,the expression conditions of the dual-enzyme system were optimized,and the concentration of boldenone reached 31.9 mg/L.The explora-tion of this route will provide a foundation for the efficient enzymatic synthesis of boldenone.展开更多
To obtain a better understanding of the effect of vehicle fires on rigid pavement,a nondestructive test method utilizing an ordinary digital camera to capture images of mortar at five elevated temperatures was underta...To obtain a better understanding of the effect of vehicle fires on rigid pavement,a nondestructive test method utilizing an ordinary digital camera to capture images of mortar at five elevated temperatures was undertaken.These images were then analyzed by“image color-intensity analyzer”software.In image analysis,the RGB color model was the basic system used to represent the color information of images.HSI is a derived-color model that is transformed from an RGB model by formulae.In order to understand more about surface color changes and temperatures after a vehicle fire,various transformation formulae used in different research areas were applied in this study.They were then evaluated to obtain the optimum HSI model for further studies of fire-damaged mortar through the use of image analysis.展开更多
基金the financial support provided by the industrial grant(No.G1006320).
文摘Ti and its alloys have been broadly adopted across various industries owing to their outstanding proper-ties,such as high strength-to-weight ratio,excellent fatigue performance,exceptional corrosion resistance and so on.Additive manufacturing(AM)is a complement to,rather than a replacement for,traditional manufacturing processes.It enhances flexibility in fabricating complex components and resolves machin-ing challenges,resulting in reduced lead times for custom designs.However,owing to distinctions among various AM technologies,Ti alloys fabricated by different AM methods usually present differences in mi-crostructure and defects,which can significantly influence the mechanical performance of built parts.Therefore,having an in-depth knowledge of the scientific aspects of fabrication and material properties is crucial to achieving high-performance Ti alloys through different AM methods.This article reviews the mechanical properties of Ti alloys fabricated by two mainstream powder-type AM techniques:powder bed fusion(PBF)and directed energy deposition(DED).The review examines several key aspects,en-compassing phase formation,grain size and morphology,and defects,and provides an in-depth analysis of their influence on the mechanical behaviors of Ti alloys.This review can aid researchers and engi-neers in selecting appropriate PBF or DED methods and optimizing their process parameters to fabricate high-performance Ti alloys for a wide range of industrial applications.
基金supported by National Key Research and Development Program of China(No.2019YFA0905300)the National Natural Science Foundation of China(No.22078126)+1 种基金Qing Lan Project in Jiangsu ProvinceFundamental Research Funds for Central Universities of China(No.JUSRP221025).
文摘Boldenone is a protein-assimilating androgen steroid that can promote protein synthesis,support nitrogen storage,and enhance renal erythropoietin release.The industrial production of boldenone mainly relies on chemical synthesis,which has various problems,such as a complex conversion process,excessive byproducts,and serious environmental pollution.There-fore,it is of great significance to explore a new biosynthetic route.Recently,the enzymatic synthesis of steroid compounds has been performed more frequently than in the past.In this work,boldenone was produced from androstenedione(AD)in two steps by a dual-enzyme cascade of 17β-hydroxysteroid dehydrogenase(17β-HSD)and 3-sterone-Δ^(1)-dehydrogenase(KstD).The conversion efficiency of three isoenzymes of 17β-HSD from Mycobacterium sp.LY-1 for substrate AD was first analyzed.After that,the 17β-HSD2 with high selectivity and specificity for AD was screened and co-expressed with KstD3 in Escherichia coli BL21 to construct a dual-enzyme catalytic system.The results showed that the synthesis of boldenone from AD could be achieved by constructing the dual-enzyme expression system of 17β-HSD and KstD,as we determined that the concentration of boldenone reached 24.3 mg/L.To further improve the synthesis efficiency of boldenone,the expression conditions of the dual-enzyme system were optimized,and the concentration of boldenone reached 31.9 mg/L.The explora-tion of this route will provide a foundation for the efficient enzymatic synthesis of boldenone.
基金supported by the National Science Council of Republic of China(Grant No.NSC-90-2211-E-214-004).
文摘To obtain a better understanding of the effect of vehicle fires on rigid pavement,a nondestructive test method utilizing an ordinary digital camera to capture images of mortar at five elevated temperatures was undertaken.These images were then analyzed by“image color-intensity analyzer”software.In image analysis,the RGB color model was the basic system used to represent the color information of images.HSI is a derived-color model that is transformed from an RGB model by formulae.In order to understand more about surface color changes and temperatures after a vehicle fire,various transformation formulae used in different research areas were applied in this study.They were then evaluated to obtain the optimum HSI model for further studies of fire-damaged mortar through the use of image analysis.
