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Träfflista för sökning "WFRF:(Kumar S) ;lar1:(kau)"

Sökning: WFRF:(Kumar S) > Karlstads universitet

  • Resultat 1-10 av 13
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1.
  • Rabiee, Navid, et al. (författare)
  • Green Biomaterials : fundamental principles
  • 2023
  • Ingår i: Green Biomaterials. - : Taylor & Francis. - 2993-4168. ; 1:1, s. 1-4
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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2.
  • Bhowmik, Avit Kumar, et al. (författare)
  • From Climate Endgame to Climate Long Game
  • 2022
  • Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 119:45
  • Tidskriftsartikel (refereegranskat)
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3.
  • Bogers, J., et al. (författare)
  • A multiscale domain decomposition approach for chemical vapor deposition
  • 2013
  • Ingår i: Journal of Computational and Applied Mathematics. - Amsterdam, Netherlands : Elsevier. - 0377-0427 .- 1879-1778. ; 246, s. 65-73
  • Tidskriftsartikel (refereegranskat)abstract
    • We consider the process of chemical vapor deposition on a trenched Si substrate. To understand the process (including e.g. the layer conformality) at the trench scale (microscale), we need solutions at both the trench and reactor scales (macroscale). Due to the huge difference in size of these scales, straightforward numerical computations are very challenging. To overcome this difficulty, we consider a multiscale approach by introducing an intermediate scale (the mesoscale). We start with a time-continuous model describing the transport processes and then perform time discretization. At each time step, using the ideas of domain decomposition inspired from Lions (1988) [4], we provide iterative coupling conditions for these three different scales. Using a weak formulation for the time-discrete equations, we prove the convergence of this iterative scheme at each time step. The approach also provides an alternative proof for the existence of the solutions for the time-discrete formulation. (C) 2012 Elsevier B.V. All rights reserved.
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4.
  • Endo Kokubun, M. A., et al. (författare)
  • A pore-scale study of transport of inertial particles by water in porous media
  • 2019
  • Ingår i: Chemical Engineering Science. - : Elsevier. - 0009-2509 .- 1873-4405. ; 207, s. 397-409
  • Tidskriftsartikel (refereegranskat)abstract
    • We study the transport of inertial particles in water flow in porous media. Our interest lies in understanding the accumulation of particles including the possibility of clogging. We propose that accumulation can be a result of hydrodynamic effects: the tortuous paths of the porous medium generate regions of dominating strain, which favour the accumulation of particles. Numerical simulations show that essentially two accumulation regimes are identified: for low and for high flow velocities. When particles accumulate at the entrance of a pore throat (high-velocity region), a clog is formed. This significantly modifies the flow, as the partial blockage of the pore causes a local redistribution of pressure, which diverts the upstream water flow into neighbouring pores. Moreover, we show that accumulation in high velocity regions occurs in heterogeneous media, but not in homogeneous media, where we refer to homogeneity with respect to the distribution of the pore throat diameters.
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5.
  • Kumar, Kundan, et al. (författare)
  • Convergence analysis for a conformal discretization of a model for precipitation and dissolution in porous media
  • 2014
  • Ingår i: Numerische Mathematik. - Heidelberg, Germany : Springer. - 0029-599X .- 0945-3245. ; 127:4, s. 715-749
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper we discuss the numerical analysis of an upscaled (core scale) model describing the transport, precipitation and dissolution of solutes in a porous medium. The particularity lies in the modeling of the reaction term, especially the dissolution term, which has a multivalued character. We consider the weak formulation for the upscaled equation and provide rigorous stability and convergence results for both the semi-discrete (time discretization) and the fully discrete schemes. In doing so, compactness arguments are employed.
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7.
  • Kumar, Kundan, et al. (författare)
  • Effective dispersion equations for reactive flows involving free boundaries at the microscale
  • 2011
  • Ingår i: Multiscale Modeling & simulation. - : Society for Industrial and Applied Mathematics. - 1540-3459 .- 1540-3467. ; 9:1, s. 29-58
  • Tidskriftsartikel (refereegranskat)abstract
    • We consider a pore-scale model for reactive flow in a thin two-dimensional strip, where the convective transport dominates the diffusion. Reactions take place at the lateral boundaries of the strip (the walls), where the reaction product can deposit in a layer with a nonnegligible thickness compared to the width of the strip. This leads to a free boundary problem, in which the moving interface between the fluid and the deposited (solid) layer is explicitly taken into account. Using asymptotic expansion methods, we derive an upscaled, one-dimensional model by averaging in the transversal direction. The result is consistent with (Taylor dispersion) models obtained previously for a constant geometry. Finally, numerical computations are presented to compare the outcome of the effective (upscaled) model with the transversally averaged, two-dimensional solution.
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9.
  • Kumar, Kundan, et al. (författare)
  • Rigorous upscaling of rough boundaries for reactive flows
  • 2014
  • Ingår i: Zeitschrift für angewandte Mathematik und Mechanik. - : John Wiley & Sons. - 0044-2267 .- 1521-4001. ; 94:7-8, s. 623-644
  • Tidskriftsartikel (refereegranskat)abstract
    • We consider a mathematical model for reactive flow in a channel having a rough (periodically oscillating) boundary with both period and amplitude ε. The ions are being transported by the convection and diffusion processes. These ions can react at the rough boundaries and get attached to form the crystal (precipitation) and become immobile. The reverse process of dissolution is also possible. The model involves non‐linear and multi‐valued rates and is posed in a fixed geometry with rough boundaries. We provide a rigorous justification for the upscaling process in which we define an upscaled problem defined in a simpler domain with flat boundaries. To this aim, we use periodic unfolding techniques combined with translation estimates. Numerical experiments confirm the theoretical predictions and illustrate a practical application of this upscaling process.
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10.
  • Kumar Singh, Suneet, et al. (författare)
  • Hybrid P4 Programmable Pipelines for 5G gNodeB and User Plane Functions
  • 2022
  • Ingår i: IEEE Transactions on Mobile Computing. - : IEEE. - 1536-1233 .- 1558-0660. ; , s. 1-18
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper focuses on hybrid pipeline designs for User Plane Function and next-generation NodeB leveraging target-specific features and an insightful discussion of P4 and target challenges and limitations. The entire or disaggregated UPF runs on P4 targets and allocates packet processing data paths in P4 hardware or DPDK/x86 software based on flow characteristics (e.g., heavy hitters) and QoS requirements (e.g., low-latency slices). For the hybrid gNodeB, most packet processing is executed in commodity Tofino hardware, while unsupported functions such as Automatic Repeat Request and cryptography are performed in DPDK/x86. We show that our hybrid UPF improves the scalability by 18× and reduces latency up to 50%. The results also suggest that careful traffic allocation to pipeline targets is required to optimize each target's strength and avoid processing delays. Finally, we demonstrate a QoS-oriented application of the hybrid UPF and present gNodeB buffer service benchmarks. 
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  • Resultat 1-10 av 13

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