High strength-to-weight ratio of non-ferrous alloys, such as aluminium, magnesium and titanium alloys, are considered to be possible replacement of widely accepted steels in transportation and automobile sectors. Amon...High strength-to-weight ratio of non-ferrous alloys, such as aluminium, magnesium and titanium alloys, are considered to be possible replacement of widely accepted steels in transportation and automobile sectors. Among these alloys, magnesium is self explosive and titanium is costlier, and aluminium is most likely to replace steels. Application of aluminium or its alloys is also thought of as an appropriate replacement in defence field, especially to enhance the easiness in mobility of combat vehicles while maintaining the same standard as that of conventional armour grade steels. Hence most of the investigations have been confined to aluminium or its alloys as base material and open an era of developing the newer composite materials to address the major limitation, i.e. tribological properties. The surface composites can be fabricated by incorporating the ceramic carbides like silicon carbide, carbides of transition metals and oxides of aluminium using surface modification techniques, such as high energy laser melt treatment, high energy electron beam irradiation and thermal spray process which are based on fusion route. These techniques yield the fusion related problems, such as interfacial reaction, pin holes, shrinkage cavities or voids and other casting related defects, and pave the way to need of an efficient technique which must be based on solid state. Recently developed friction stir processing technique was used in the present investigation for surface modification of AA7075 aluminum alloy, which is an alternative to steels. In the present investigation, 160 μm sized boron carbide powder was procured and was reduced to 60 μm and 30 μm using high energy ball mill. Subsequently these powders were used to fabricate the surface composites using friction stir processing.Ballistic performance testing as per the military standard(JIS.0108.01) was carried out. In the present work, an analytical method of predicting the ballistic behavior of surface composites was developed. This method was based on energy balance, i.e., the initial energy of impact is same as that of energy absorbed by multi layers. An attempt also has been made to validate the analytical results with the experimental findings. Variation between the analytical and experimental results may be accounted due to the assumptions considering such as isotropic behavior of target and shearing area of contact as cylindrical instead of conical interface As the analytical model yields the ballistic performance in the closer proximity of experimentally obtained, it can be considered to be an approximation to evaluate the ballistic performance of targets.展开更多
Although boron has been a chemical element of interest since the ancient times,only a few boron-containing compounds(BCCs)had been used for medicinal purposes before the 21^(st) century.Among these,only boric acid has...Although boron has been a chemical element of interest since the ancient times,only a few boron-containing compounds(BCCs)had been used for medicinal purposes before the 21^(st) century.Among these,only boric acid has been explored in multiple therapeutic applications.Hence,it is common to extrapolate from boric acid to all BCCs,supposing a similar biological effect.However,boric acid is just one of dozens of BCCs in nature and thousands available from chemical synthesis.Nowadays,there is a boom in research on new BCCs as potential tools in the prevention,diagnosis and therapy of human disease.We herein discuss the new role of BCCs in drug development,with emphasis on the compounds for which a mechanism of action has been proposed or demonstrated.Because of data gathered in recent years,BCCs have expanded beyond the well-known fields of antimicrobial and antineoplastic agents,now being explored for their possible use as enzyme inhibitors,regulators of protein expression and modulators of the immune response,as well as in biomaterials.We suggest that translational medicine can accelerate the medicinal applications of BCCs,which is especially important for the human diseases that are generating a high global burden.展开更多
基金Financial assistance from Armament research board,New Delhi,India
文摘High strength-to-weight ratio of non-ferrous alloys, such as aluminium, magnesium and titanium alloys, are considered to be possible replacement of widely accepted steels in transportation and automobile sectors. Among these alloys, magnesium is self explosive and titanium is costlier, and aluminium is most likely to replace steels. Application of aluminium or its alloys is also thought of as an appropriate replacement in defence field, especially to enhance the easiness in mobility of combat vehicles while maintaining the same standard as that of conventional armour grade steels. Hence most of the investigations have been confined to aluminium or its alloys as base material and open an era of developing the newer composite materials to address the major limitation, i.e. tribological properties. The surface composites can be fabricated by incorporating the ceramic carbides like silicon carbide, carbides of transition metals and oxides of aluminium using surface modification techniques, such as high energy laser melt treatment, high energy electron beam irradiation and thermal spray process which are based on fusion route. These techniques yield the fusion related problems, such as interfacial reaction, pin holes, shrinkage cavities or voids and other casting related defects, and pave the way to need of an efficient technique which must be based on solid state. Recently developed friction stir processing technique was used in the present investigation for surface modification of AA7075 aluminum alloy, which is an alternative to steels. In the present investigation, 160 μm sized boron carbide powder was procured and was reduced to 60 μm and 30 μm using high energy ball mill. Subsequently these powders were used to fabricate the surface composites using friction stir processing.Ballistic performance testing as per the military standard(JIS.0108.01) was carried out. In the present work, an analytical method of predicting the ballistic behavior of surface composites was developed. This method was based on energy balance, i.e., the initial energy of impact is same as that of energy absorbed by multi layers. An attempt also has been made to validate the analytical results with the experimental findings. Variation between the analytical and experimental results may be accounted due to the assumptions considering such as isotropic behavior of target and shearing area of contact as cylindrical instead of conical interface As the analytical model yields the ballistic performance in the closer proximity of experimentally obtained, it can be considered to be an approximation to evaluate the ballistic performance of targets.
基金Supported by Consejo Nacional de Ciencia y Tecnología de México,No.CB235785
文摘Although boron has been a chemical element of interest since the ancient times,only a few boron-containing compounds(BCCs)had been used for medicinal purposes before the 21^(st) century.Among these,only boric acid has been explored in multiple therapeutic applications.Hence,it is common to extrapolate from boric acid to all BCCs,supposing a similar biological effect.However,boric acid is just one of dozens of BCCs in nature and thousands available from chemical synthesis.Nowadays,there is a boom in research on new BCCs as potential tools in the prevention,diagnosis and therapy of human disease.We herein discuss the new role of BCCs in drug development,with emphasis on the compounds for which a mechanism of action has been proposed or demonstrated.Because of data gathered in recent years,BCCs have expanded beyond the well-known fields of antimicrobial and antineoplastic agents,now being explored for their possible use as enzyme inhibitors,regulators of protein expression and modulators of the immune response,as well as in biomaterials.We suggest that translational medicine can accelerate the medicinal applications of BCCs,which is especially important for the human diseases that are generating a high global burden.
