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: Computer science & Dielectric. The organization has 16887 authors who have published 38658 publications receiving 714526 citations.

Power allocation in OFDM based NOMA systems: A DC programming approach

Abstract: In this work, we have considered the downlink of an Orthogonal Frequency Division Multiplexing based Non Orthogonal Multiple Access system where transmission to multiple number of users is performed on the same sub-band (time-frequency resource unit) using Superposition Coding (SC) technique. At the receiver side, the SC coded symbols are recovered with Successive Interference Cancellation (SIC). Assuming that complete channel state information is present at the base station, we propose (1) co-channel user set selection, (2) power distribution among the multiplexed users on each sub-band, and (3) power allocation across the sub-bands to maximize the weighted sum rate of the system. Since the problem is a non-convex combinatorial optimization problem, two step heuristic solution is employed. In the first step, for each of the sub-bands, a greedy user selection and iterative sub-optimal power allocation algorithm based on Difference of Convex (DC) programming is presented. In the second step, exploiting the DC structure of the modified problem, power allocation across sub-band is carried out through the same iterative power allocation algorithm. Simulation results are provided to assess and compare the performance of the proposed algorithms.

Rock failure modes under uniaxial compression, Brazilian, and point load tests

Abstract: Rock failure is a serious problem in rock engineering environments Rock failure modes, however, are complex and difficult to quantify or predict A comprehensive study on rock failure modes at laboratory scale is, therefore, potentially important as it helps recognize the adequacy of the support designed on the basis of the nature of an engineering work With due need, this paper analyzes the failure modes of granite, schist, and sandstone under uniaxial compression, Brazilian, and point load tests in relation to corresponding strengths The nature of the principal failure mode changes from axial splitting to shearing along a single plane to multiple fracturing in the case of both granite and sandstone specimens as uniaxial compressive strength (UCS) increases In the case of schist, specimens failed at low UCS show failure along foliations whereas specimens which do not fail along foliations portray high strength The relation between failure modes of all three rocks under uniaxial compression and corresponding UCS values was broadly explained in terms of damage evolution of the rocks Granite and sandstone specimens failed mainly following central or central multiple type of fracturing whereas schist specimens principally failed by layer activation in combination with either central or non-central fractures over the entire range of determined Brazilian tensile strength In the case of granite and sandstone, central multiple failure mode corresponds to high tensile strength Descriptions of different failure modes under point loading were presented It was found that granite and sandstone specimens generally fail through the rock materials in one or more extensional planes containing the line of loading Failure patterns showing triple junctions correspond to high point load strength indices In the case of schist, specimens failed along foliations show a low point load strength index whereas specimens failed through material with a single extensional plane result in high strength

Information communication technology (ICT) infrastructure and economic growth: A causality evinced by cross-country panel data

Abstract: This study examines certain long-run relationships hypothesised to be present among per capita real GDP, information and communication technology (ICT) infrastructure, consumer price index, labour force participation rate, and gross fixed capital formation manifest in G-20 countries recorded for the 2001–2012 period. Using panel cointegration, the study finds that the variables are cointegrated and do not drift apart in the long run. Methodology using vector error correction models (VECM) further confirms that embellishment of ICT infrastructure – an apparent imperative in an economy's information technology (IT) policy formulation – for both fixed broadband and internet users causes a boost in the per capita GDP.

Preparation and Characterization of Nano structured Materials from Fly Ash: A Waste from Thermal Power Stations, by High Energy Ball Milling

Abstract: The Class F fly ash has been subjected to high energy ball milling and has been converted into nanostructured material. The nano structured fly ash has been characterized for its particle size by using particle size analyzer, specific surface area with the help of BET surface area apparatus, structure by X-ray diffraction studies and FTIR, SEM and TEM have been used to study particle aggregation and shape of the particles. On ball milling, the particle size got reduced from 60 μm to 148 nm by 405 times and the surface area increased from 0.249 m2/gm to 25.53 m2/gm i.e. by more than 100%. Measurement of surface free energy as well as work of adhesion found that it increased with increased duration of ball milling. The crystallite was reduced from 36.22 nm to 23.01 nm for quartz and from 33.72 nm to 16.38 nm for mullite during ball milling to 60 h. % crystallinity reduced from 35% to 16% during 60 h of ball milling because of destruction of quartz and hematite crystals and the nano structured fly ash is found to be more amorphous. Surface of the nano structured fly ash has become more active as is evident from the FTIR studies. Morphological studies revealed that the surface of the nano structured fly ash is more uneven and rough and shape is irregular, as compared to fresh fly ash which are mostly spherical in shape.