Articles written in Sadhana

    • Enhancement of impact toughness on warm forged microalloyed steel- 38MnSiVS6


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      The effect of warm forging in the inter-critical temperature range between 705 and 844°C, in improving the impact toughness of an industrially important micro alloyed steel, 38MnSiVS6 was investigated. The impact properties were enhanced to as high as 148 J after warm forging in the inter critical range, as against19 J in the steel hot rolled from 1200°C and air cooled. In addition, the strength was enhanced by about 100 MPa after warm forging. The microstructure evolution that led to the improved toughness and strength was analyzed. The significantly enhanced toughness with moderate strength enhancement in warm deformation isattributed to the increases in the ferrite content, finer ferrite grain size, finer pearlite colonies and finer interlamellar spacing. The fractography of the impact test samples in hot deformed and air-cooled condition shows poor toughness associated with cleavage facets, while the warm forged steel, showed fine dimple rupture.

    • An efficient flexible hierarchical access control scheme enabling real-life exceptions


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      Most organizations today inherently followed hierarchical access control implemented using a hierarchical key assignment scheme (HKAS). An HKAS enforce reflexive, anti-symmetric, and transitive relations among the nodes (or access classes) in the hierarchy. In real life, the organizations come across rare but practical situations such as anti-symmetric exception, the temporary delegation of access to a user, etc. The traditional HKASs are costly and are not readily implement these exceptions. It motivates to relook at redesigning existing HKASs that efficiently incorporate and revokes the exceptions into the existing hierarchy as and when needed. The current similar work uses asymmetric key cryptosystem to implement the flexible HKAS with exceptions. This work proposes a novel and efficient symmetric key-based flexible HKAS that efficientlyaddresses the flexible hierarchy requirements. To the best of our knowledge, this is the first symmetric key-based flexible HKAS enabling exceptions. The dynamics of the scheme are addressed and compared with the other similar existing schemes. The security of the new HKAS is analyzed formally against a stronger and modern security notion known as key-indistinguishability.

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