• K Kumar

      Articles written in Sadhana

    • Parameter estimation using compensatory neural networks

      M Sinha P K Kalra K Kumar

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      Proposed here is a new neuron model, a basis for Compensatory Neural Network Architecture (CNNA), which not only reduces the total number of interconnections among neurons but also reduces the total computing time for training. The suggested model has properties of the basic neuron model as well as the higher neuron model (multiplicative aggregation function). It can adapt to standard neuron and higher order neuron, as well as a combination of the two. This approach is found to estimate the orbit with accuracy significantly better than Kalman Filter (KF) and Feedforward Multilayer Neural Network (FMNN) (also simply referred to as Artificial Neural Network, ANN) with lambda-gamma learning. The typical simulation runs also bring out the superiority of the proposed scheme over Kalman filter from the standpoint of computation time and the amount of data needed for the desired degree of estimated accuracy for the specific problem of orbit determination.

    • Influence of processing and reinforcement on microstructure and impact behaviour of magnesium alloy AM100

      S Jayalakshmi S Seshan S V Kailas K Kumar S Srivatsan

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      Reinforcing magnesium alloys with a discontinuously dispersed ceramic phase has engineered a new family of materials that are marketed under the trade name “metal-matrix composites”. Continuous research efforts in the processing of these materials have provided the necessary impetus for their emergence and use in structural, automotive and even aerospace-related components. In this paper we report the results of a study aimed at understanding the role of short-fibre reinforcements (discontinuously dispersed through the metal-matrix of magnesium alloy AM 100) on impact deformation and fracture behaviour. In particular, the role of volume fraction of the reinforcing phase on impact energy and fracture behaviour is presented and discussed. An increase in short-fibre reinforcement content in the magnesium alloy metal-matrix is observed to have a detrimental influence on impact energy when compared to the unreinforced counterpart. Micro cracking in the metal-matrix coupled with failure of the reinforcing fibres, both independently dispersed and in clusters, dominates the fracture sequence at the microscopic level. The final fracture behaviour of the composite material is discussed in the light of the concurrent and mutually interactive influences of nature of loading, local stress state, intrinsic microstructural effects and deformation characteristics of the composite constituents.

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