Indian Institute of Technology Bombay

About: Indian Institute of Technology Bombay is a education organization based out in Mumbai, India. It is known for research contribution in the topics: Population & Thin film. The organization has 16756 authors who have published 33588 publications receiving 570559 citations.

Electrochemical Impedance Spectroscopy of Oxygen Reduction Reaction (ORR) in a Rotating Disk Electrode Configuration: Effect of Ionomer Content and Carbon-Support

Abstract: Oxygen reduction reaction (ORR) in acidic media is investigated at various potentials in a thin-film rotating disk electrode (TF-RDE) configuration using electrochemical impedance spectroscopy (EIS). The ionomer-free and ionomer-containing thin-film catalyst layers are composed of Pt black and carbon-supported Pt catalysts of different metal loadings (5 and 20 wt%). The simplest EI spectrum consisting of an arc or a semi-circle is obtained at high potentials with ionomer-free Pt catalyst layers. The most complex spectrum consisting of a high frequency (HF) arc and two semi-circles is observed in the mixed diffusion-controlled region of the ionomer-containing catalyst layer with high loading of carbon-supported Pt. The nature of the EI spectrum is decided by the constituents of the thin-film catalyst layer and by the operating potential. The evolution of the EI spectra with ionomer and carbon contents is underlined. The effect of rotation rate (rpm) of the electrode on the impedance spectrum is also investigated. A series of equivalent circuits is required to completely describe the EI spectra of ORR. The kinetic parameters and the electrochemical surface area of the catalysts are derived from the impedance spectrum. © The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BY-NC-ND, http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email: oa@electrochem.org. [DOI: 10.1149/2.0141506jes] All rights reserved.

Dye Sensitized Solar Cells: A Review

Abstract: The development of dye sensitized solar cells (DSSCs), which have derived inspiration from photosynthesis, has opened up exciting new possibilities and paradigms for producing solar photovoltaics possibly at lower cost. The dye-sensitized solar cells with moderate power conversion (∼10%) efficiencies can be manufactured under regular lab conditions without needing clean rooms or very specialized facilities. The entire processing need not involve even a single vapour deposition step. The DSSCs can be considered to be electrochemical devices consisting of (a) a photoanode which has a thick film of a wide band gap oxide semiconductor (like TiO2), typically coated on a transparent conductive oxide (TCO) glass substrate, with TiO2 being sensitized with adsorbed dyes that absorb visible light, (b) an electrolyte that establishes the internal electrical continuity between anode and counter electrode and mainly plays the role of regenerating the dye such that the photoexcitation, electron injection and current fl...

Energy dependence and fluctuations of anisotropic flow in Pb-Pb collisions at √sNN = 5.02 and 2.76 TeV

Abstract: Measurements of anisotropic flow coefficients with two- and multi-particle cumulants for inclusive charged particles in Pb-Pb collisions at $ \sqrt{s_{\mathrm{NN}}}=5.02 $ and 2.76 TeV are reported in the pseudorapidity range |η| < 0.8 and transverse momentum 0.2 < p$_{T}$ < 50 GeV/c. The full data sample collected by the ALICE detector in 2015 (2010), corresponding to an integrated luminosity of 12.7 (2.0) μb$^{−1}$ in the centrality range 0-80%, is analysed. Flow coefficients up to the sixth flow harmonic (v$_{6}$) are reported and a detailed comparison among results at the two energies is carried out. The p$_{T}$ dependence of anisotropic flow coefficients and its evolution with respect to centrality and harmonic number n are investigated. An approximate power-law scaling of the form v$_{n}$(p$_{T}$) ∼ p$_{T}^{n}^{/3}$ is observed for all flow harmonics at low p$_{T}$ (0.2 < p$_{T}$ < 3 GeV/c). At the same time, the ratios v$_{n}$/v$_{m}^{n}^{/ }^{m}$ are observed to be essentially independent of p$_{T}$ for most centralities up to about p$_{T}$ = 10 GeV/c. Analysing the differences among higher-order cumulants of elliptic flow (v$_{2}$), which have different sensitivities to flow fluctuations, a measurement of the standardised skewness of the event-by-event v$_{2}$ distribution P(v$_{2}$) is reported and constraints on its higher moments are provided. The Elliptic Power distribution is used to parametrise P(v$_{2}$), extracting its parameters from fits to cumulants. The measurements are compared to different model predictions in order to discriminate among initial-state models and to constrain the temperature dependence of the shear viscosity to entropy-density ratio.

An Improved I a S Relation Incorporating Antecedent Moisture in SCS-CN Methodology

Abstract: Employing a large dataset of 84 small watersheds (area = 0.17 to 71.99 ha) of U.S.A., this paper investigates a number of initial abstraction (Ia)-potential maximum retention (S) relations incorporating antecedent moisture (M) as a function of antecedent precipitation (P5), and finally suggests an improved relation for use in the popular Soil Conservation Service Curve Number (SCS-CN) methodology for determination of direct runoff from given rainfall. The improved performance of the incorporated M = α \(sqrt{P_5S}\) and Ia = λ S2/(S + M) relations, where λ is the initial abstraction coefficient, in the SCS-CN methodology exhibits the dependence of Ia on M, which is close to reality; the larger the M, the lesser will be Ia, and vice versa. Such incorporation obviates sudden jumps in the curve number variation with antecedent moisture condition, an unreasonable and undesirable feature of the existing SCS-CN model.

Visualization of Hyperspectral Images Using Bilateral Filtering

Abstract: This paper presents a new approach for hyperspectral image visualization. A bilateral filtering-based approach is presented for hyperspectral image fusion to generate an appropriate resultant image. The proposed approach retains even the minor details that exist in individual image bands, by exploiting the edge-preserving characteristics of a bilateral filter. It does not introduce visible artifacts in the fused image. A hierarchical fusion scheme has also been proposed for implementation purposes to accommodate a large number of hyperspectral image bands. The proposed scheme provides computational and storage efficiency without affecting the quality and performance of the fusion. It also facilitates the midband visualization of a subset of the hyperspectral image cube. Quantitative performance results are presented to indicate the effectiveness of the proposed method.