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Block Method (block + method)
Selected AbstractsNitrogen fixation and denitrification in a floodplain forest near Manaus, BrazilHYDROLOGICAL PROCESSES, Issue 7 2003Heidi Kreibich Abstract The Amazon floodplain (várzea) is seasonally affected by water level fluctuations of the Solimőes/Amazon River. The drastic environmental changes that occur also include microbiological processes, such as nitrogen (N2) fixation and denitrification. Both processes were measured in the soil by the acetylene reduction assay and the acetylene block method in a várzea forest on Ilha de Marchantaria, Central Amazonia, Brazil. In the surface soil horizon (0,5 cm), N2 fixation was highest during the exposed period (0·04,0·26 nmolN h,1 g,1 dry weight (dw)). In contrast, denitrification varied from 0 to 1·40 nmolN h,1 g,1 dw, with high rates during the submerged and the transition periods. No significant difference between locations with legume trees, with non-legume trees and without trees could be observed. N2 fixation rates of incubations (litter down to 450 cm depth) for samples collected during the exposed period ranged from 0 to 0·11 nmolN h,1 g,1 dw, with highest rates in the surface soil horizon (0,5 cm). Denitrification ranged from 0 to 0·05 nmolN h,1 g,1 dw, with the highest rate at 250,300 cm depth, which was just below the water table. The maximum N2 fixation rate (0·89 nmolN h,1 g,1dw) and denitrification rate (0·09 nmolN h,1 g,1 dw) occurred in the litter layer. On average, at least three times as much N is lost from the surface soil horizon via denitrification than is gained by N2 fixation annually, but the rates are strongly influenced by the flood pulse. Copyright © 2003 John Wiley & Sons, Ltd. [source] On solving the cracked-beam problem by block methodINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 11 2008A. A. Dosiyev Abstract An extremely accurate solution is obtained for the cracked-beam problem by one-block version of the block method (BM). The obtained numerical results demonstrate the exponential convergence of the BM with respect to the number of quadrature nodes. A simple and high accurate formula to compute the stress intensity factor is given. The comparisons with other high accurate results in the literature have been carried out. Copyright © 2007 John Wiley & Sons, Ltd. [source] On parallel solution of linear elasticity problems.NUMERICAL LINEAR ALGEBRA WITH APPLICATIONS, Issue 3 2002Part II: Methods, some computer experiments Abstract This is the second part of a trilogy on parallel solution of the linear elasticity problem. We consider the plain case of the problem with isotropic material, including discontinuous coefficients, and with homogeneous Dirichlet boundary condition. The discretized problem is solved by the preconditioned conjugate gradient (pcg) method. In the first part of the trilogy block- diagonal preconditioners based on the separate displacement component part of the elasticity equations were analysed. The preconditioning systems were solved by the pcg-method, i.e. inner iterations were performed. As preconditioner, we used modified incomplete factorization MIC(0), where possibly the element matrices were modified in order to give M -matrices, i.e. in order to guarantee the existence of the MIC(0) factorization. In the present paper, the second part, full block incomplete factorization preconditioners are presented and analysed. In order to avoid inner/outer iterations we also study a variant of the block-diagonal method and of the full block method, where the matrices of the inner systems are just replaced by their MIC(0)-factors. A comparison is made between the various methods with respect to rate of convergence and work per unknown. The fastest methods are implemented by message passing utilizing the MPI system. In the third part of the trilogy, we will focus on the use of higher-order finite elements. Copyright © 2002 John Wiley & Sons, Ltd. [source] Application of 3-D Geoscience Modeling Technology for the Estimation of Solid Mineral ReservesACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 3 2009Mao PAN Abstract: Applying new approaches, methods, and technologies for the estimation of reserves can effectively improve the efficiency and accuracy of assessments of solid mineral resources. After analyzing the development of 3-D geoscience modeling technology (3-D GMT), this paper discusses the application of 3-D GMT for the estimation of solid mineral reserves, emphatically introducing its workflow and two key technologies, 3-D orebody surface modeling, and property modeling. Moreover, the paper analyzes the limitations of traditional methods, such as the section method and geological block method, and points out the advantages of 3-D GMT: building more accurate 3-D orebody models, expressing the internal inhomogeneous attributes of an orebody, reducing the potential for errors in the estimation of reserves, and implementing dynamic estimations of reserves. [source] | ||||||||||