Indian Institute of Technology Kharagpur

About: Indian Institute of Technology Kharagpur is a education organization based out in Kharagpur, India. It is known for research contribution in the topics: Natural rubber & Dielectric. The organization has 16887 authors who have published 38658 publications receiving 714526 citations.

Sub-zero treatments of AISI D2 steel: Part I. Microstructure and hardness

Abstract: Microstructure, hardness and wear behavior of AISI D2 steel subjected to varied sub-zero treatments have been examined with reference to conventional heat treatment. Part I of this work presents the variations of microstructure and hardness, whereas part II deals with the wear behavior. The sub-zero treatments studied are cold treatment, shallow cryogenic treatment and deep cryogenic treatment. The developed microstructures have been characterized by XRD, optical microscopy and SEM examinations coupled with EDX and image analyses. Macrohardness and microhardness of the specimens have been evaluated by Vickers indentation technique. The obtained results infer that (i) retained austenite content is reduced by cold treatment, but is almost completely eliminated by both shallow and deep cryogenic treatments, (ii) the sub-zero treatments modify the precipitation behavior of secondary carbides; lower the temperature of sub-zero treatment higher is the degree of modification, (iii) the deep cryogenic treatment refines the secondary carbides, increases their amount and population density, and leads to more uniform distribution, and (iv) bulk hardness increases marginally but apparent hardness of the matrix improves considerably by deep cryogenic treatment.

A Natural Silk Fibroin Protein-Based Transparent Bio-Memristor

Abstract: The recent discovery of nanoelectronics memristor devices has opened up a new wave of enthusiasm and optimism in revolutionizing electronic circuit design, marking the beginning of new era for the advancement of neuromorphic, high-density logic and memory applications. Here a highly non-linear dynamic response of a bio-memristor is demonstrated using natural silk cocoon fibroin protein of silkworm, Bombyx mori. A film that is transparent across most of the visible spectrum is obtained with the electronic-grade silk fibroin aqueous solution of ca. 2% (wt/v). Bipolar memristive switching is demonstrated; the switching mechanism is confirmed to be the filamentary switching as observed by probing local conduction behavior at nanoscale using scanning tunneling microscopy. The memristive transition is elucidated by a physical model based on the carrier trapping or detrapping in silk fibroin films and this appears to be due to oxidation and reduction procedures, as evidenced from cyclic voltammetry measurements. Hence, silk fibroin protein could be used as a biomaterial for bio-memristor devices for applications in advanced bio-inspired very large scale integration circuit design as well as in biologically inspired synapse links for energy-efficient neuromorphic computing.

The cosmic microwave background radiation fluctuations from H i perturbations prior to reionization

Abstract: Loeb and Zaldarriaga have recently proposed that observations of the cosmic microwave background radiation (CMBR) brightness temperature fluctuations produced by H I inhomogeneities prior to reionization hold the promise of probing the primordial power spectrum to a hitherto unprecedented level of accuracy. This requires a precise quantification of the relation between density perturbations and brightness temperature fluctuations. Brightness temperature fluctuations arise from two sources: (1) fluctuations in the spin temperature, and (2) fluctuations in the H I optical depth, both of which are caused by density perturbations. For the spin temperature, we investigate in detail its evolution in the presence of H I fluctuations. For the optical depth, we find that it is affected by density perturbations both directly and through peculiar velocities which move the absorption features around in frequency. The latter effect, which has not been included in earlier studies, is similar to the redshift space distortion seen in galaxy surveys and this can cause changes of 50 per cent or more in the brightness temperature