Vignan University

About: Vignan University is a education organization based out in Guntur, Andhra Pradesh, India. It is known for research contribution in the topics: Control theory & CMOS. The organization has 1138 authors who have published 1381 publications receiving 7798 citations.

Role of Friction Stir Processing Parameters on the Microstructure and Hardness of ZE41 Mg Alloy: A Taguchi Approach

Abstract: In the present study, the influence of friction stir processing (FSP) tool rotational speed and tool travel speed on achieving higher hardness in ZE41 Mg alloy was investigated by adopting a Taguchi design model using orthogonal array. The extent of grain refinement, hardness enhancement, and achieving defect-free stir zones in FSP completely depend on process parameters. In the present work, FSP parameters such as tool rotation speed and tool traverse speed were varied. The microscopic and macroscopic observations revealed that tool speeds of 1,400 rpm with 25 and 50 mm/min feeds were found to be optimal to develop fine grain size and wide stir zone, respectively, without defect. These results are in good agreement with the design model and help with choosing optimized parameters with a minimum number of experiments in developing grain-refined ZE41 Mg alloy for emerging lightweight technological applications.

Major and trace metals in suspended and bottom sediments of the Mandovi and Zuari estuaries, western India: distribution, source, and pollution

Abstract: Major elements and trace metals in suspended sediments along transect stations of the Mandovi and Zuari estuaries showed three types of distribution: (a) high concentrations of most metals (Al, Fe, Mn, Cr, Pb, Cu, Ni, Zn, Co, Sc, Mo, and U) in the upper estuary and their decreasing concentrations seaward in every season, (b) lower concentrations of some metals (Mg, Cr, Zr, V, Al, Th) in the upper estuary and bay and their increased concentrations in the lower estuary, and (c) higher concentrations of some metals (Cu, Ni, Zn, Pb, and Cr) in the upper estuary and bay and their decreased concentrations in the lower estuary. Mn was the most significant pollutant in both the estuaries. The Zn, Cr, Fe, and Mo in Mandovi during the monsoon and post-monsoon and, Pb, Ni, and Cr in Zuari during the post- and pre-monsoons were in the range "moderately to heavily polluted." The pollution load index of metals was high at upstream stations, with higher values in Mandovi during monsoon and Zuari during the post- and pre-monsoons. Most trace metals were correlated with Fe and Mn indicating their association primarily with Fe-Mn ore material. The principal component analysis indicated natural and anthropogenic inputs and the latter was predominantly related to ore material in both the estuaries. The distribution factor was high for Al, Mg, Zr, Th, and U in < 2-μm fraction and Cr, Cu, Ni, Zn, Co, V, Sc, and Zr in 2-4-μm size fraction sediments suggesting two sources of sediments. More than 60% concentrations of all trace metals were associated with < 2-μm fraction sediments. The distribution of trace metals along transect was affected by the physico-chemical conditions of the estuary, grain size of sediments, and anthropogenic contribution of metals.

Novel method for the synthesis of lenvatinib using 4-nitrophenyl cyclopropylcarbamate and their pharmaceutical salts

Abstract: 4-Nitrophenyl cyclopropylcarbamate was deployed as a novel synthon for the synthesis of anticancer drug lenvatinib. 4-Nitrophenyl cyclopropylcarbamate was prepared by the reaction of 4-nitrophenyl chloroformate and cyclopropyl amine in acetonitrile at room temperature. Furthermore, lenvatinib was synthesized by reacting 4-(4-amino-3-chlorophenoxy)-7-methoxyquinoline-6-carboxamide with 4-nitrophenyl cyclopropylcarbamate in good yields. Apart from the synthesis of lenvatinib, citrate, phosphate, malate and oxalate salts of lenvatinib were also reported in good yields.