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Exact Reconstruction From Uniformly Attenuated Helical Cone-Beam Projections in SPECT

Description: In recent years the development of cone-beam reconstruction algorithms has been an active research area in x-ray computed tomography (CT), and significant progress has been made in the advancement of algorithms. Theoretically exact and computationally efficient analytical algorithms can be found in the literature. However, in single photon emission computed tomography (SPECT), published cone-beam reconstruction algorithms are either approximate or involve iterative methods. The SPECT reconstruc… more
Date: December 18, 2008
Creator: Gullberg, Grant T; Huang, Qiu; You, Jiangsheng & Zeng, Gengsheng L.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Neutron streaming through shield ducts using a discrete ordinates/Monte Carlo method

Description: A common problem in shield design is determining the neutron flux that streams through ducts in shields and also that penetrates the shield after having traveled partway down the duct. Obviously the determination of the neutrons that stream down the duct can be computed in a straightforward manner using Monte Carlo techniques. On the other hand those neutrons that must penetrate a significant portion of the shield are more easily handled using discrete ordinates methods. A hybrid discrete ordin… more
Date: August 18, 1993
Creator: Urban, W. T. & Baker, R. S.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

A NEW GHOST-NODE METHOD FOR LINKING DIFFERENT MODELS WITH VARIED GRID REFINEMENT

Description: A flexible, robust method for linking grids of locally refined models that may be constructed using different types of numerical methods is needed to address a variety of hydrologic problems. This work outlines and tests a new ghost-node model-linking method based on the iterative method of Mehl and Hill (2002, 2004). It is applicable to steady-state solutions for ground-water flow. Tests are presented for a homogeneous two-dimensional system that facilitates clear analysis of typical problems.… more
Date: October 18, 2005
Creator: dickinson, J.; James, S.C.; Mehl, S.; Hill, M.C.; Leake, S. & Zyvoloski, G.A.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Ordering schemes for sparse matrices using modern programming paradigms

Description: The Conjugate Gradient (CG) algorithm is perhaps the best-known iterative technique to solve sparse linear systems that are symmetric and positive definite. In previous work, we investigated the effects of various ordering and partitioning strategies on the performance of CG using different programming paradigms and architectures. This paper makes several extensions to our prior research. First, we present a hybrid(MPI+OpenMP) implementation of the CG algorithm on the IBM SP and show that the h… more
Date: November 18, 2000
Creator: Oliker, Leonid; Li, Xiaoye; Husbands, Parry & Biswas, Rupak
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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