Fast Digital Convolutions using Bit-Shifts

An exact, one-to-one transform is presented that not only allows digital circular convolutions, but is free from multiplications and quantisation errors for transform lengths of arbitrary powers of two. The transform is analogous to the Discrete Fourier Transform, with the canonical harmonics replaced by a set of cyclic integers computed using only bit-shifts and additions modulo a prime number. The prime number may be selected to occupy contemporary word sizes or to be very large for cryptographic or data hiding applications. The transform is an extension of the Rader Transforms via Carmichael's Theorem. These properties allow for exact convolutions that are impervious to numerical overflow and to utilise Fast Fourier Transform algorithms.Comment: 4 pages, 2 figures, submitted to IEEE Signal Processing Letter

IIT-Hyderabad professor Chandra Shekhar Sharma bags award

Professor Chandra Shekhar Sharma from the department of chemical engineering, Indian Institute of Technology, Hyderabad (IIT-H), has won the prestigious Young Scientist Platinum Jubilee Award, instituted by the National Academy of Sciences, India. He has been selected for his work on electrospun nanofibers and nanostructured carbon materials which can be used in environmental protection and healthcare. Professor Chandra Shekhar and his team recently introduced female sanitary napkins, using electrospun nanofibers (biodegradable polymer). Most sanitary napkins use non-biodegradable superabsorbent polymers (SAP) to increase their commercial value. However, they cause health hazards and also environmental problems. The product will soon hit the market after field trials. Furthermore, the team has also received a grant from the department of science and technology under the nano mission programme. The team has also developed an inexpensive way of creating electrodes. The award, started in 2005, is given to scientists in the field of physical, chemical and biological sciences

Photoresist Derived Carbon Films as High Capacity Anodes for Lithium Ion Battery

An epoxy-based negative photoresist (SU-8) was spin-coated on stainless steel (SS) wafers followed by two-step pyrolysis in inert atmosphere to yield dense carbon films to be used as anodes for lithium (Li) ion batteries. The selection of SS wafer substrates was in accordance with commercial Li ion battery architecture. Cyclic voltammograms confirm the passive layer formation by electrolyte decomposition in the initial cycle. Galvanostatic charge/discharge experiments in the range 0.01-3 V performed at a C-rate=0.1 C confirms the reversible intercalation of Li ions and shows higher gravimetric reversible capacity for these photoresist-derived carbon films on SS wafer substrates than graphite (400 mAh/g vs. 372 mAh/g for graphite). This high reversible capacity may be attributed to high disorder in photoresist derived-carbon as characterized by X-ray diffraction and Raman spectroscopy

IIT Hyderabad develops sanitary napkins that absorb better

Chandra Shekhar Sharma from the Department of Chemical Engineering, IIT Hyderabad and his team turned to nanotechnology to produce cellulose-based nanofibre for use as an absorbent core in sanitary napkins. They chose cellulose acetate biopolymer and subjected it to electrospinning to synthesise fibre of nanoscale size

Planar Hall effect in the Weyl semimetal GdPtBi

Observation of Weyl and Dirac Fermions in condensed matter systems is one of the most important discoveries. Among the very few available tools to characterize Weyl semimetals through electrical transport, negative magnetoresistance is most commonly used. Considering shortcomings of this method, new tools to characterize chiral anomaly in Weyl semimetals are desirable. We employ planar Hall effect as an effective technique in half Heusler Weyl semimetal GdPtBi to study chiral anomaly. This compound exhibits a large value of 1.5 mohm cm planar Hall resistivity at 2 K and in 9 T. Our analysis reveals that the observed amplitude is dominated by Berry curvature and chiral anomaly contributions. Through the angle dependent transport studies we establish that GdPtBi with relatively small orbital magnetoresistance is an ideal candidate to observe large planar Hall effect .Comment: Updated text