Indian Institute of Technology Bombay

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    32831 research outputs found

    Sizing of biomass based distributed hybrid power generation systems in India

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    A methodology for optimum sizing of battery integrated biomass gasifier based distributed power generation systems is discussed. Typically, biomass gasifier systems are sized considering peak demand resulting into lower operational efficiency due to part load operation during low demand period. The proposed methodology using design space approach enables designer with multiple combinations of gasifier engine and battery systems for given load profile from which an appropriate combination may be identified considering specific objective or constraints if any. Two gasifier operational strategies are discussed and compared using cost of energy. The methodology is further extended for sizing of hybrid systems incorporating gasifier, solar PV and battery system. The proposed methodology is illustrated using a realistic load profile generated through a structured household survey of an un-electrified hamlet. For given load profile, battery integrated gasifier engine system in intermittent operation mode has the lowest cost of electricity followed by gasifier engine system alone, hybrid system and solar PV battery system. Sensitivity analysis is done to incorporate uncertainty related to variation in key input parameters. The proposed sizing methodology may be helpful in wider replication of gasification systems by providing cost effective sizing of such systems. (C) 2018 Elsevier Ltd. All rights reserved

    A Variability source for nanosheet gaa transistors for sub-7nm nodes

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    Due to the complex process flow of the Gate All Around (GAA) stacked NSFET, new forms of process variability arise which are dominant over the conventional process variability like MGG and LER. Multi-V-{T} options in NSFET are achieved by gate metal thickness modulation, which can cause V-{T}-variability if the process lacks precision. In this paper, we present a new form of process variability called Metal Thickness Variation (MTV) caused by inter-sheet spacing variation, compared to an 'ideal NSFET'. There are currently no models available in TCAD to study the thickness dependent Work-function (WF) V-{T} engineering. Hence, using physics based analytical model, we analyzed the variability in V-{T} due to this new variability source. We obtained the V-{T} distribution caused by MTV and estimated the standard deviation in V-{T}, due to process variations and provided a way to suppress variability. Our results show that MTV emerges as a dominant source of variability and is insensitive for gate length scaling. © 2019 IEEE

    Enhancing the electroluminescence efficiency by controlling the migration of excited states to quenching sites in a truxene-based oligomer

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    Control of unwanted low-energy emission originating due to trap states is crucial for improving the emission efficiency and for maintaining the color purity in blue light-emitting diodes. Here, a truxene-based emitter (T-pyrene) that is a good candidate for the blue emitter is investigated using photophysical studies. Steady-state absorption of the emitter reveals the presence of a charge-transfer state, and the photoluminescence spectrum suggests an occurrence of a strong interchain/exciplex state. Time-resolved photoluminescence (TRPL) and fluence-dependent measurements of the material in the dilute solution show the presence of multiple excitonic processes contributing to the delayed fluorescence. Similar studies on the pristine film suggest that the delayed fluorescence is dominated by the presence of the traps. By blending the oligomer with a higher bandgap polymer matrix, poly(9-vinyl carbazole) (PVK), a type I heterojunction at the T-pyrene:PVK interface is obtained that confines the generated excitons in T-pyrene. With this architecture, device efficiencies with T-pyrene (20 wt. %):PVK show significantly enhanced efficiency than those of the pristine device. We elucidate the relevance of the matrix:T-pyrene system using TRPL and fluence-dependent studies on T-pyrene (20 wt. %):PVK. Time-resolved emission spectra on the T-pyrene (20 wt. %):PVK films do not show red-shifted emission with time delays, which suggests the passivation of the quenching sites due to the dispersion of T-pyrene in PVK to prevent the intermolecular interactions

    Development of a railway junction simulator for evaluation of control strategies and capacity utilization optimization

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    This paper focuses on the development of a Python based tool for analysis and simulation of mixed rail traffic at a railway junction. The tool is helpful for evaluating various open-loop and feedback based strategies for an optimum junction utilization. The tool is implemented in Python using graph theory for finding shortest paths between various source-destination pairs. What signifies a railway junction, as opposed to a railway section is the possibility and the need to allow multiple simultaneous movements within the junction area. The tool applies network (edge and node) based approach for designing the line infrastructure of a railway junction. Source and destination are represented as nodes and every path from a source to a destination through a junction consists of a set of permissible combination of edges and nodes. This tool can be used for simulating scheduled passenger trains through all the allowed paths, and then selecting the best path for traversing through the junction. Further, lower priority trains are scheduled without affecting the edge/node occupancies trains of higher priorities. The best freight paths are identified and a more accurate estimate of the time required for freight trains to pass through the junction is obtained using this tool. In this way, one is able to quantify and then optimize the capacity/utilization of railway junction. In a larger scenario, the tool is useful for identifying bottlenecks in a given infrastructure. As examples, a detailed analysis of Allahabad junction and Kanpur junction of Indian Railways is presented using the tool. © 2019 IEEE

    Synthesis of Spiro- and Fused Heterocycles via (4+4) Annulation of Sulfonylphthalide with o-Hydroxystyrenyl Derivatives

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    An expedient one-pot protocol for the synthesis of functionalized benzofuran containing fused and spiroheterocycles has been accomplished by the modified Hauser Kraus (HK) annulation of sulfonylphthalide with ohydroxychalcones and o-hydroxynitrostyrylisoxazoles. The multicascade process involves Michael addition, Dieckmann cyclization, and a series of cyclizations, eliminations, and rearrangements to deliver the fused and spiro-heterocyclic products. An unusual transformation of fused indenofuran to naphthoquinone, the classical HK adduct, unraveled a novel pathway for the synthesis unsymmetrical naphthoquinones

    The Hessian Discretisation Method for Fourth Order Linear Elliptic Equations

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    In this paper, we propose a unified framework, the Hessian discretisation method (HDM), which is based on four discrete elements (called altogether a Hessian discretisation) and a few intrinsic indicators of accuracy, independent of the considered model. An error estimate is obtained, using only these intrinsic indicators, when the HDM framework is applied to linear fourth order problems. It is shown that HDM encompasses a large number of numerical methods for fourth order elliptic problems: finite element methods (conforming and non-conforming) as well as finite volume methods. We also use the HDM to design a novel method, based on conforming P 1 finite element space and gradient recovery operators. Results of numerical experiments are presented for this novel scheme and for a finite volume scheme. © 2018, Springer Science+Business Media, LLC, part of Springer Nature

    Single image super-resolution for optical satellite scenes using deep deconvolutional network

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    In this paper, we deal with the problem of super-resolution (SR) imaging and propose a deep deconvolutional network based model for the same. In principle, the SR problem considers the construction of the high-resolution (HR) version of a scene given a number of so-called low-level image instances of the respective scene. Moreover, if there is a single low-resolution (LR) image available, the problem becomes even difficult and ill-posed. We deal with such a scenario and show how the popular deconvolutional network can effectively reconstruct the HR image by learning the functional mapping at the patch level. We evaluate the proposed model on a number of optical remote sensing (RS) images obtained from the UC-Merced dataset. Experimental results suggest that the proposed model consistently outperforms the existing deep and shallow models for single image SR for the RS images. © 2019, Springer Nature Switzerland AG

    Skyrmion based spin-torque nano-oscillator

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    Using micromagnetic simulation, we investigate the self-sustained oscillation of magnetic skyrmion in a ferromagnetic circular nanodot, driven by spin-torque which is generated from a reference layer of a circular nanopillar device. We demonstrate, by lowering the value of uniaxial anisotropy constant (K-u), the velocity of the skyrmion can be increased and using this property, gyration frequency of the skyrmion oscillator can be enhanced. Annihilation of the skyrmion at higher current densities, limit the gyration frequency of the oscillator, whereas by modifying the K-u value at the edge of nanodot, we are able to protect the skyrmion from being annihilated at higher current densities which in turn, increases the gyration frequency of the skyrmion based oscillator. By linear fitting the velocity value, obtained from the motion of the skyrmion in a nanostrip, we also predict the gyration frequency of the skyrmion in the nanodot which proves the validity of our idea in an intuitive way. We have also varied the radius of the nanodisk to see its effect on skyrmion

    Fully printed organic solar cells - a review of techniques, challenges and their solutions

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    The emergence of solar cells on flexible and bendable substrates has made the printing process a ubiquitous tool for the fabrication of these devices. The various printing techniques available now such as inkjet, screen and flexography offer cost- effectiveness, user-friendliness and suitability for mass production. While downscaling the fill factor and efficiency of organic solar cells. A multilayered structure, the combination of different printing techniques avails the variety of thickness and resolution required for each layer in the production of an organic solar cell. In this review article, we discuss the suitability of the inkjet and screen printing processes to produce organic solar cells. We also discuss various challenges involved in the fabrication of organic solar cells using these two techniques and the possible solutions for the same. We also provide an analogy that both processes share. Further, we consider future possibilities of combining these printing technologies to produce organic solar cells to improve device performance. (C) 2019 Association of Polish Electrical Engineers (SEP). Published by Elsevier B.V. All rights reserved

    Tunable and Stable White Light Emission in Bi3+-Alloyed Cs2AgInCl6 Double Perovskite Nanocrystals

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    Lead-free double. perovskite nanocrystals (NCs) of Cs2AgIn1-xBixCl6 (x = 0, .0.05,-0.15, 0.3, 0.6, and 1) were synthesized with control over the size distribution. Detailed structural studies were carried out on the resulting double perovskite NCs to confirm the alloying and structural modification. Alloying of Bi leads to change in optical properties, such as the band gap, and enhancement in oscillator strength of first excitonic transition and the white light emission (WLE) properties. The band gap of the double perovskite NCs was estimated; a direct band gap transition value of similar to 3.46 eV is obtained for pure Cs2AgInCl6 NCs. This value of the band gap has reduced with increase of Bi doping, which also leads a band gap transition from direct to indirect band gap. This system exhibits a sub-band gap emission between similar to 570 and 620 nm along with band-edge emission, which is strongly dependent on the alloying concentration. A gamut of emission is observed in the alloyed systems. The Commission International de I'Eclairage (CIE) coordinates of (0.36, 0.35) for the 30% Bi-doped sample, with color rendering index values of similar to 91, and correlated color temperature of 4443 with D-uv of -0.0065 are observed, which are found to be very promising for WLE applications


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