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Sökning: WFRF:(Kumar S) > Högskolan Väst

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1.
  • Jones, Benedict C, et al. (författare)
  • To which world regions does the valence-dominance model of social perception apply?
  • 2021
  • Ingår i: Nature Human Behaviour. - : Springer Science and Business Media LLC. - 2397-3374. ; 5:1, s. 159-169
  • Tidskriftsartikel (refereegranskat)abstract
    • Over the past 10 years, Oosterhof and Todorov's valence-dominance model has emerged as the most prominent account of how people evaluate faces on social dimensions. In this model, two dimensions (valence and dominance) underpin social judgements of faces. Because this model has primarily been developed and tested in Western regions, it is unclear whether these findings apply to other regions. We addressed this question by replicating Oosterhof and Todorov's methodology across 11 world regions, 41 countries and 11,570 participants. When we used Oosterhof and Todorov's original analysis strategy, the valence-dominance model generalized across regions. When we used an alternative methodology to allow for correlated dimensions, we observed much less generalization. Collectively, these results suggest that, while the valence-dominance model generalizes very well across regions when dimensions are forced to be orthogonal, regional differences are revealed when we use different extraction methods and correlate and rotate the dimension reduction solution. PROTOCOL REGISTRATION: The stage 1 protocol for this Registered Report was accepted in principle on 5 November 2018. The protocol, as accepted by the journal, can be found at https://doi.org/10.6084/m9.figshare.7611443.v1 .
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2.
  • Kumar, M., et al. (författare)
  • Development of nano-crystalline cold sprayed Ni-20Cr coatings for high temperature oxidation resistance
  • 2015
  • Ingår i: Surface & Coatings Technology. - 0257-8972 .- 1879-3347. ; 266, s. 122-133
  • Tidskriftsartikel (refereegranskat)abstract
    • In the current investigation a pre-synthesized nano-crystalline Ni-20Cr powder was deposited by cold-spray technique on SA 516 steel. The powder was synthesized by ball milling approach. The nano-crystallinity of the developed coating was established by crystallite size measurements from XRD profile, which was further endorsed by TEM analysis. High-temperature oxidation behavior of uncoated and coated samples was studied under cyclic isothermal conditions at 900 degrees C for 50 cycles in a laboratory tube furnace. The oxidation rates for the bare and coated steel were evaluated in terms of weight gain data. Different characterization techniques, such as X-ray diffraction (XRD), scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), and transmission electron microscopy (TEM) analyses were utilized to characterize the oxide scale. The hardness and oxidation resistance of the steel increased after the application of coating. The reduction in oxidation rate of the base steel was 94%. Moreover, the developed nanostructured coating was observed to reduce weight gain by 64% in comparison with micron-sized Ni-20Cr cold spray coating thus offers a higher oxidation resistance. This may be attributed to relatively denser structure, lower porosity and lower oxide content of the nanostructured coating. (C) 2015 Elsevier B.V. All rights reserved.
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3.
  • Dom, R., et al. (författare)
  • Design and development of ferrite composite film electrode for photoelectrochemical energy application
  • 2014
  • Ingår i: Materials Science Forum. - : Trans Tech Publications Ltd. - 0255-5476 .- 1662-9752. - 9783038350675 ; 781, s. 45-61
  • Tidskriftsartikel (refereegranskat)abstract
    • Development of efficient photoanodes for water splitting under solar light is desirable to surmount the possible fuel crisis in future. Ferrite systems, with their excellent visible light absorption capability, stability, non-toxicity, cost-effectiveness and abundance, are being preferred to titanates, niobates and sulfides. The present work briefly reviews the modified form of ferrites. Additionally, ZnFe2O4 an n-type semiconductor with the low band gap (~1.9eV) has been considered as special case of visible light PEC application. The work further emphasizes on the utilization of solution processed techniques to develop the ferrite photoanodes. The tuning of photoanode properties by virtue of electrode fabrication parameters say deposition parameters viz., precursor concentration, pH, stoichiometry has been reviewed and discussed. © (2014) Trans Tech Publications, Switzerland.
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4.
  • Kaur, N., et al. (författare)
  • Study of mechanical properties and high temperature oxidation behavior of a novel cold-spray Ni-20Cr coating on boiler steels
  • 2015
  • Ingår i: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 328, s. 13-25
  • Tidskriftsartikel (refereegranskat)abstract
    • In the current investigation, high temperature oxidation behavior of a novel cold-spray Ni-20Cr nano-structured coating was studied. The nanocrystalline Ni-20Cr powder was synthesized by the investigators using ball milling, which was deposited on T22 and SA 516 steels by cold spraying. The crystallite size based upon Scherrer's formula for the developed coatings was found to be in nano-range for both the substrates. The accelerated oxidation testing was performed in a laboratory tube furnace at a temperature 900 degrees C under thermal cyclic conditions. Each cycle comprised heating for one hour at 900 degrees C followed by cooling for 20 min in ambient air. The kinetics of oxidation was established using weight change measurements for the bare and the coated steels. The oxidation products were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS) and X-ray mapping techniques. It was found from the results that the coating was successful in reducing the weight gain of SA213-T22 and SA 516-Grade 70 steel by 71% and 94%, respectively. This may be attributed to relatively denser structure, lower porosity and lower oxide content of the coating. Moreover, the developed nano-structured Ni-20Cr powder coating was found to perform better than its counterpart micron-sized Ni-20Cr powder coating, in terms of offering higher oxidation resistance and hardness. (C) 2014 Elsevier B.V. All rights reserved.
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5.
  • Dom, R., et al. (författare)
  • Eco-friendly ferrite nanocomposite photoelectrode for improved solar hydrogen generation
  • 2013
  • Ingår i: RSC Advances. - 2046-2069. ; 3:35, s. 15217-15224
  • Tidskriftsartikel (refereegranskat)abstract
    • For the first time, a ferrite nanocomposite photoelectrode (FNCP) has been fabricated and investigated for photoelectrochemical hydrogen production from water under simulated solar light. The ZnFe2O4:Fe 2O3 nanocomposite photoanode has been fabricated via a single step methodology using a novel approach involving the solution precursor plasma spraying technique. The FNCP is achieved by optimal phase formation during the deposition of the ferrite film (∼10 μm) over a stainless steel substrate. It exhibits an enhanced photoactivity 6 times higher compared to pure ZnFe2O4 (ZFO), under simulated-solar (AM1.5 G) illumination. Its Mott-Schottky characterization reveals an n-type semiconducting behaviour, indicating an order of magnitude higher donor density (Nd ∼ 1017 cm-3) than the pure phase ZnFe2O4 electrode. It also exhibits a low band gap of 1.94 eV demonstrating that it can more efficiently absorb visible light photons than other systems comprising of bare zinc ferrite or iron oxide. The FNCP yielded a solar-to-hydrogen conversion efficiency of 1.25% under simulated solar radiation (AM1.5 G) with a hydrogen evolution rate of 99 μmol h-1. Electrochemical impedance spectroscopy of the FNCP revealed a significantly improved charge transfer characteristic compared to ZnFe2O 4. An enhanced photoactivity for the oxidation of water from the FNCP is attributed to its improved optical absorption and better charge transfer properties induced by the existence of Fe2O3 in ZnFe 2O4. © The Royal Society of Chemistry 2013.
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6.
  • Joshi, S. V., et al. (författare)
  • Influence of Laser Glazing on the Characteristics and Tribological Performance of Plasma and Detonation Sprayed WC-Co Coatings
  • 2001
  • Ingår i: Proceedings of the International Thermal Spray Conference. ; , s. 583-592
  • Konferensbidrag (refereegranskat)abstract
    • This paper deals with a comprehensive evaluation of the laser glazing or re-melting route as a possible means of specifically enhancing the performance of thermal sprayed WC-Co coatings. In the present study, a high-power continuous-wave 9kW CO2 laser was utilized for laser treatment of plasma sprayed as well as detonation sprayed WC-Co coatings. The influence of the two most important laser-related variables, namely laser power and scan speed, on the properties of the laser-treated layers was investigated. Both mere surface densification by melting a thin top layer of the coating as well as melting of the entire portion of the coated layer were targeted during laser treatment. In each case, the laser treated coatings were fully characterized by optical microscopy, scanning electron microscopy, and microhardness measurements. In addition, the influence of laser processing on the elemental distribution, phase constitution and extent of defects in the treated layers was investigated. The tribological performance of the laser-glazed coatings was also evaluated and compared against the performance of their as-sprayed counterparts. The study has revealed significant differences between the response of plasma and detonation sprayed WC-Co layers when subjected to laser treatment. The potential of plasma-sprayed coatings to match the performance of the inherently superior detonation sprayed coatings by adopting laser glazing as a post-processing step has also been assessed.
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9.
  • Kumar, Rajiv, et al. (författare)
  • Effect of chromium and aluminum addition on anisotropic and microstructural characteristics of ball milled nanocrystalline iron
  • 2016
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 671, s. 164-169
  • Tidskriftsartikel (refereegranskat)abstract
    • Prior studies on synthesis of nanocrystalline elements have discussed the effect of ball milling on lattice parameter, crystallite size, and micro-strain. For elemental milled powders, the anisotropic peak broadening does not change with increasing milling time. However, the effect of alloying addition on the anisotropic behavior of ball milled nanocrystalline powders remains an unexplored area. Here we report the effect of chromium and aluminum addition on the anisotropic behavior of iron in nanocrystalline Fe–20Cr–5Al (wt%) alloy powders synthesized by ball milling. The experimental results show that the anisotropic behavior of iron changes towards isotropic with milling. This change was also correlated to the theoretically calculated anisotropic factor from the change in elastic constant of iron due to milling. Addition of alloying elements exhibited a monotonic rise in the lattice parameter with crystallite size, which was attributed to the excess grain boundary interfacial energy and excess free volume at grain boundaries. Transmission electron microscopy image confirmed the crystallite size and nature of dislocation obtained using modified Williamson-Hall method.
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10.
  • Kumar, S., et al. (författare)
  • Microstructure and performance of cold sprayed Al-SiC composite coatings with high fraction of particulates
  • 2017
  • Ingår i: Surface & Coatings Technology. - 0257-8972 .- 1879-3347. ; 318, s. 62-71
  • Tidskriftsartikel (refereegranskat)abstract
    • Deposition of metal matrix composites (MMCs) through thermal spraying has traditionally presented problems associated with heterogeneity, porosity, and low wettability of particulates with matrix. Cold spray is a very rapid deposition process which is suitable for depositing a variety of ductile materials without any thermal degradation. Many researchers have attempted to deposit Al-SiC MMCs with 10–20% SiC using this technique. In the present study, three different powder compositions (FAl-23SiC, FAl-46SiC, FAl-71SiC) obtained by mixing Al and SiC powders were cold sprayed on aluminum substrates. The volume percentage and the average size of the SiC particulates in the cold sprayed coatings were estimated and found to be 23%, 47% and 52% for FAl-23SiC, FAl-46SiC and FAl-71SiC feedstocks, respectively. Effects of percentage and size of the SiC particulate retained in the composite coatings on the mechanical properties and the sliding wear performance were studied at different sliding conditions in the as-sprayed and heat treated conditions. The results were comprehensively analyzed and found to correlate well with the microstructure of the coatings.
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