1,725,975 research outputs found
sj-docx-2-pie-10.1177_09544089221112069 - Supplemental material for Numerical analysis of non-isothermal warm deep drawing of an Al-Mg alloy using different yield criteria and experimental validation
No full textSupplemental material, sj-docx-2-pie-10.1177_09544089221112069 for Numerical analysis of non-isothermal warm deep drawing of an Al-Mg alloy using different yield criteria and experimental validation by Ved Prakash and D Ravi Kumar in Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering</p
sj-docx-1-pie-10.1177_09544089221112069 - Supplemental material for Numerical analysis of non-isothermal warm deep drawing of an Al-Mg alloy using different yield criteria and experimental validation
No full textSupplemental material, sj-docx-1-pie-10.1177_09544089221112069 for Numerical analysis of non-isothermal warm deep drawing of an Al-Mg alloy using different yield criteria and experimental validation by Ved Prakash and D Ravi Kumar in Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering</p
Light-matter interactions with Flying Doughnuts
No full textThe field of toroidal electrodynamics has gained attention following the detection of toroidal dipole excitations in metamaterials in 2010. Distinct from electric and magnetic dipoles, a toroidal dipole is a localised electromagnetic excitation that corresponds to currents flowing on the surface of a torus. The electromagnetic radiation from toroidal dipole excitations can destructively interfere with the radiation from other modes of excitation, providing a new mechanism of induced transparency and scattering suppression. Toroidal electrodynamics expands with the observation of toroidal light pulses, also known as Flying Doughnuts (FD), which propagate in free space at the speed of light. FDs are solutions to Maxwell’s equations introduced by Hellwarth and Nouchi in 1996, which possess toroidal topology and exist only as short bursts of electromagnetic energy. However, it is little known about how these toroidal pulses interact with matter. This thesis reports on the interaction of toroidal light pulses with matter, focusing on toroidal excitations and non-radiating modes.I have numerically demonstrated supertoroidal anapoles, which are non-radiating charge current configurations that involve supertoroidal currents. Supertoroidal currents are fractal current configurations where each iteration replaces the previous one with a toroidal current loop, accompanied by a toroidal solenoidal current forming the smallest loop. Unlike conventional anapoles formed by the destructive interference of electric and toroidal dipoles, supertoroidal anapoles consist of the interference of a toroidal dipole, the first-order mean square radius of the toroidal dipole, and an electric dipole. I also observed (numerically) the higher-order anapoles formed from quadrupoles and octupoles of electric and toroidal type. I show numerically that under illumination with an FD pulse, scattering from a dielectric torus is substantially suppressed by supertoroidal anapoles by more than 72%. Further, I studied supertoroidal anapoles’dependence on the torus’s geometric parameters. I discovered that a dielectric torus with the largest major radius R and the smallest minor radius r is the best strategy to support supertoroidal anapoles, where R ≫ r and R+r < λ. Moreover, I show that, in contrast to plane wave illumination, FD illumination suppresses scattering by an order of magnitude due to supertoroidal anapoles.I demonstrated that by carefully tuning the geometric parameters of a dielectric disc, it is possible to engineer anapole modes (scattering suppression) over a broad bandwidth of 315nm within the wavelength range from 665nm to 980nm with the maximum suppression at 780nm, when transverse magnetic (TM) FD is an illuminating source and a disc-shaped particle is the scatterer. Further, I show that the disc radius defines the anapole excitation wavelength, and the disc height defines the bandwidth of the anapole; the taller the disc (h < λ), the broader the anapole. Additionally, I show the electric and toroidal dipoles and the anapole mode in the transient regime. I also demonstrate that even though the duration of the incident pulse is ≈ 4 fs, the excitations take up to 15 fs to dissipate their energy through electromagnetic radiation. Further, I investigated the effect of material loss on scattering suppression and observed broadly similar behaviour to lossless material, supporting broad and strong anapole modes. Moreover, unlike plane wave illumination, I report that FD illumination suppresses scattering by an order of magnitude due to the conventional anapole modes.I also investigated the interaction of FD with films and curved interfaces. I demonstrated that the reflection of transverse electric (TE) FD on dielectric film and plasmonic films is 20% and 15% stronger, respectively, compared to TM FD illumination. Moreover, the multipole expansion of displacement current within a high-index dispersive film reveals that the scattering is mediated by the combination of electric and toroidal dipoles (however, their contributions cannot be distinguished with the exact multipole expressions). Investigating FD interactions with curved interfaces shows that the radial spectra distribution of FD does not change upon reflection from the curved interface, which ensures that FD survives after interacting with a curved interface. The findings of FD interactions with curved interfaces are crucial for the experimental realisation of FD-matter interaction, as such experiments involve curved optical components such as parabolic mirrors for the tight focusing of FD.The findings outlined in this thesis contribute to the expanding field of toroidal electrodynamics, firmly establishing its potential for diverse applications, including sensing and spectroscopy using toroidal light sources, anapole nanolasers, anapole-assisted absorption engineering applications, and beyond
sj-docx-1-pie-10.1177_09544089231156068 - Supplemental material for Investigation of fused deposition modeling parameters on mechanical properties and characterization of ABS/carbon fiber composites
No full textSupplemental material, sj-docx-1-pie-10.1177_09544089231156068 for Investigation of fused deposition modeling parameters on mechanical properties and characterization of ABS/carbon fiber composites by Krishnan Ravi Kumar, Nisha Soms and Murugesan Kumar in Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering</p
Stochastic models for tabbed browsing
No full textWe present a model of tabbed browsing that represents a hybrid between a Markov process capturing the graph of hyperlinks, and a branching process capturing the birth and death of tabs. We present a mathematical criterion to characterize whether the process has a steady state independent of initial conditions, and we show how to characterize the limiting behavior in both cases. We perform a series of experiments to compare our tabbed browsing model with pagerank, and show that tabbed browsing is able to explain 15-25% of the deviation between actual measured browsing behavior and the behavior predicted by the simple pagerank model. We find this to be a surprising result, as the tabbed browsing model does not make use of any notion of site popularity, but simply captures deviations in user likelihood to open and close tabs from a particular node in the graph. © 2010 International World Wide Web Conference Committee (IW3C2)
High thermally stable NTDA-SO3H based sulfonated polymer metal composite based on Nafion/MWCNT and Nafion/TEOS nanocomposite
No full textMax-cover in map-reduce
No full textThe NP-hard Max-k-cover problem requires selecting k sets from a collection so as to maximize the size of the union. This classic problem occurs commonly in many settings in web search and advertising. For moderately-sized instances, a greedy algorithm gives an approximation of (1-1/e). However, the greedy algorithm requires updating scores of arbitrary elements after each step, and hence becomes intractable for large datasets. We give the first max cover algorithm designed for today's large-scale commodity clusters. Our algorithm has provably almost the same approximation as greedy, but runs much faster. Furthermore, it can be easily expressed in the MapReduce programming paradigm, and requires only polylogarithmically many passes over the data. Our experiments on five large problem instances show that our algorithm is practical and can achieve good speedups compared to the sequential greedy algorithm. © 2010 International World Wide Web Conference Committee (IW3C2)
Reliability testing and heat transfer enhancement of organic phase change materials / Ravi Kumar Sharma
Full text linkThe design and development of a thermal energy storage device require discrete selection of the appropriate phase change material (PCM) and a suitable container to contain them. This study focuses on the selection of PCMs for solar thermal energy storage devices and the improvement in their thermophysical properties. In addition, a new shape of the PCM container is also investigated using computational fluid dynamics.
The accelerated thermal cycle test is an essential requirement to ensure the thermal and chemical stability of selected PCMs to be used in practical applications. Solar energy being an unlimited natural energy source is used in a large number of applications such as solar water/air heating, cooking, drying and other domestic and commercial applications. On the other hand, this energy also has limitations as this is available only in the daytime. Storage of this abundantly available solar energy can be effectively used in the night hours or when there are no sunny days. Four organic PCMs-paraffin wax, palmitic acid, myristic acid, and polyethylene glycol (PEG) 6000, all in the melting temperature range of 50-70 ˚C, have been considered in this study and the changes in their thermal and chemical properties have been measured using the differential scanning calorimetry and the Fourier transform infrared techniques. The results of this research work revealed that the changes in the melting temperature of paraffin wax, palmitic acid, myristic acid, and PEG 6000 were in the range of +0.72 ˚C to +3.27 ˚C, -0.29 ˚C to +1.76 ˚C, -2 ˚C to +1.2 ˚C, and 3.77 to 3.94 ˚C respectively. The variation in the latent heat of fusion was found in the range of -9.8 to 14%, 3.28 to 18%, 0.9 to 10%, and 13 to 25 % for paraffin wax, palmitic acid, myristic acid, and PEG 6000 respectively.
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The low thermal conductivity of organic PCMs is a well-known drawback which limits their use in many domestic and industrial applications. A composite of palmitic acid and nano titanium dioxide (TiO2) was prepared and its phase change behavior was investigated. TiO2 nanoparticles of 0.5%, 1.0%, 3.0%, and 5.0% were dispersed into palmitic acid and the thermophysical properties of these nano composites were measured. The composite PCMs were characterized by FESEM, XRD, and FT-IR. The thermal properties, thermal stability and thermal reliability were ensured by DSC, TGA, and thermal cycle testing. FESEM images show the uniform dispersion of nanoparticles in the palmitic acid and FT-IR spectrum indicate that the composite PCM possesses good chemical stability and interaction between PCM and nanoparticles. The results of a thermal conductivity test show that the dispersion of the 5% nanoparticles enhances the thermal conductivity of palmitic acid by 80%.
Finally, a novel trapezoidal cavity is proposed for containing the PCM and a detailed parametric study was carried out using two nano enhanced PCMs, paraffin-Cu and water-Cu based on the computational study. The effect of side wall inclination angle, cold wall temperature, nanofluid’s initial temperature, cavity inclination, Grashof number on the total solidification time of nanofluid was simulated. The total solidification time for different wt% of Cu nanoparticles was also investigated in the trapezoidal cavity. The enthalpy–porosity technique is used to trace the solid–liquid interface. The inclination angle can be used efficiently to control the solidification time. In addition, the average Nusselt number along the hot wall for different angles, nanoparticles volume fractions, and Grashof number are presented graphically. The proposed predictions are very helpful in developing an improved latent heat thermal energy storage for the solar heat collector and for casting and mold design
The complexity of LSH feasibility
No full textIn this paper we study the complexity of the following feasibility problem: given an n × n similarity matrix S as input, is there a locality sensitive hash (LSH) for S? We show that the LSH feasibility problem is NP-hard even in the following strong promise version: either S admits an LSH or S is at l1-distance at least n2 - ε{lunate} from every similarity that admits an LSH. We complement this hardness result by providing an over(O, ̃) (3n) algorithm for the LSH feasibility problem, which improves upon the naïve nΘ (n) time algorithm; we prove that this running time is tight, modulo constants, under the Exponential Time Hypothesis. © 2014 Elsevier B.V. All rights reserved
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