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RISS 인기검색어
- 검색키워드
- 저자 : Harlen, Oliver G. (검색결과 5 건)
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Hwang, Wook Ryol,Harlen, Oliver G.,Walkley, Mark A. 한국유변학회 2013 Korea-Australia rheology journal Vol.25 No.1
In this work, we present a new efficient iterative solution technique for large sparse matrix systems that are necessary in the mixed finite-element formulation for flow simulations of porous media with complex 3D architectures in a representative volume element. Augmented Stokes flow problems with the periodic boundary condition and the immersed solid body as constraints have been investigated, which form a class of highly constrained saddle point problems mathematically. By solving the generalized eigenvalue problem based on block reduction of the discrete systems, we investigate structures of the solution space and its subspaces and propose the exact form of the block preconditioner. The exact Schur complement using the fundamental solution has been proposed to implement the block-preconditioning problem with constraints. Additionally, the algebraic multigrid method and the diagonally scaled conjugate gradient method are applied to the preconditioning sub-block system and a Krylov subspace method (MINRES) is employed as an outer solver. We report the performance of the present solver through example problems in 2D and 3D, in comparison with the approximate Schur complement method. We show that the number of iterations to reach the convergence is independent of the problem size, which implies that the performance of the present iterative solver is close to O(N).
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황욱렬,Oliver G. Harlen,Mark A. Walkley 한국유변학회 2013 Korea-Australia rheology journal Vol.25 No.1
In this work, we present a new efficient iterative solution technique for large sparse matrix systems that are necessary in the mixed finite-element formulation for flow simulations of porous media with complex 3D architectures in a representative volume element. Augmented Stokes flow problems with the periodic boundary condition and the immersed solid body as constraints have been investigated, which form a class of highly constrained saddle point problems mathematically. By solving the generalized eigenvalue problem based on block reduction of the discrete systems, we investigate structures of the solution space and its subspaces and propose the exact form of the block preconditioner. The exact Schur complement using the fundamental solution has been proposed to implement the block-preconditioning problem with constraints. Additionally, the algebraic multigrid method and the diagonally scaled conjugate gradient method are applied to the preconditioning sub-block system and a Krylov subspace method (MINRES) is employed as an outer solver. We report the performance of the present solver through example problems in 2D and 3D, in comparison with the approximate Schur complement method. We show that the number of iterations to reach the convergence is independent of the problem size, which implies that the performance of the present iterative solver is close to O(N).
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Adila A. Azahar,Oliver G. Harlen,Mark A. Walkley 한국유변학회 2019 Korea-Australia rheology journal Vol.31 No.4
The flow of a bi-disperse polymer melt through a hyperbolic contraction is simulated using the recently proposed Rolie-Double-Poly constitutive model (Boudara et al., 2019). This simplified tube model takes account of the nonlinear coupling between the dynamics of the long and short-chains in a bi-disperse blend, in particular it reproduces the enhancement of the stretch relaxation time that arises from the coupling between constraint release and chain retraction. Flow calculations are performed by implementing both the Rolie-Double-Poly and multimode Rolie-Poly models in OpenFOAM® using the RheolTool library. While both models predict very similar flow patterns, the enhanced stretch relaxation of the Rolie-Double-Poly models results in an increase in the molecular stretch of the long chain component in the pure extensional flow along the centre-line of the contraction, but a decrease in the stretch in shear-flow near the channel walls.
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Chintha Pradeepika,Sarkar Dipayan,Pecota Kenneth,Dogramaci Munevver,Hatterman-Valenti Harlene,Shetty Kalidas 한국원예학회 2023 Horticulture, Environment, and Biotechnology Vol.64 No.5
Sweet potato is a rich source of antioxidant phytohemicals, like β-carotene, vitamin C, anthocyanins, xanthophylls, and phenolics, which are relevant for providing dietary protections against chronic oxidative stress-associated diseases, like type 2 diabetes. However, the health protective phytochemical profi les and associated antioxidant and anti-diabetic properties of sweet potatoes vary widely between diff erent fl esh color and among cultivars. Therefore, the aim of this study was to screen aqueous and ethanol (12%) extracts of seven sweet potato cultivars with diff erent fl esh colors (white–yellow, orange, and purple) for their phenolic phytochemical-linked functional qualities. Total soluble phenolic (TSP) content, phenolic profi le, protein content, total antioxidant activity, anti-hyperglycemic function relevant α-amylase, α-glucosidase, and antihypertensive function related angiotensin-I-converting enzyme (ACE) inhibitory activities of sweet potato cultivars were determined using rapid in vitro assay models. The purple fl esh cv. NIC-413 had signifi cantly higher phenolic content (2.8 mg GAE 100 g −1 FW) and associated high antioxidant activity. Catechin, gallic, and dihydroxybenzoic acids were found in all cultivars, while chlorogenic acid was present only in purple-fl esh cultivar. Anti-hyperglycemic property relevant α-amylase (74–84%), and α-glucosidase (21–60%) enzyme inhibitory activities were present in all sweet potato cultivars. Additionally, anti-hypertensive property relevant ACE (10–88%) enzyme inhibitory activity were present across all sweet potato cultivars. The results of this in vitro screening study suggested that sweet potato cultivars like NIC-413, Murasaki, Evangeline, and Covington are good dietary source of phenolic antioxidants and can be relevant for anti-hyperglycemic and anti-hypertensive benefi ts to target type 2 diabetes associated health risks.
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