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Local Analysis (local + analysis)
Selected AbstractsThe stability of stars of triangular equilibrium plate elementsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 7 2009E. A. W. Maunder Abstract Equilibrium models for finite element analyses are becoming increasingly important in complementary roles to those from conventional conforming models, but when formulating equilibrium models questions of stability, or admissibility of loads, are of major concern. This paper addresses these questions in the context of flat plates modelled with triangular hybrid elements involving membrane and/or flexural actions. Patches of elements that share a common vertex are considered, and such patches are termed stars. Stars may be used in global analyses as assemblies of elements forming macro-elements, or in local analyses. The conditions for stability, or the existence and number of spurious kinematic modes, are determined in a general algebraic procedure for any degree of the interpolation polynomials and for any geometric configuration. The procedure involves the determination of the rank of a compatibility matrix by its transformation to row echelon form. Examples are presented to illustrate some of the characteristics of spurious kinematic modes when they exist in stars with open or closed links. Copyright © 2008 John Wiley & Sons, Ltd. [source] DNA barcoding Central Asian butterflies: increasing geographical dimension does not significantly reduce the success of species identificationMOLECULAR ECOLOGY RESOURCES, Issue 5 2009VLADIMIR A LUKHTANOV Abstract DNA barcoding employs short, standardized gene regions (5' segment of mitochondrial cytochrome oxidase subunit I for animals) as an internal tag to enable species identification. Prior studies have indicated that it performs this task well, because interspecific variation at cytochrome oxidase subunit I is typically much greater than intraspecific variation. However, most previous studies have focused on local faunas only, and critics have suggested two reasons why barcoding should be less effective in species identification when the geographical coverage is expanded. They suggested that many recently diverged taxa will be excluded from local analyses because they are allopatric. Second, intraspecific variation may be seriously underestimated by local studies, because geographical variation in the barcode region is not considered. In this paper, we analyse how adding a geographical dimension affects barcode resolution, examining 353 butterfly species from Central Asia. Despite predictions, we found that geographically separated and recently diverged allopatric species did not show, on average, less sequence differentiation than recently diverged sympatric taxa. Although expanded geographical coverage did substantially increase intraspecific variation reducing the barcoding gap between species, this did not decrease species identification using neighbour-joining clustering. The inclusion of additional populations increased the number of paraphyletic entities, but did not impede species-level identification, because paraphyletic species were separated from their monophyletic relatives by substantial sequence divergence. Thus, this study demonstrates that DNA barcoding remains an effective identification tool even when taxa are sampled from a large geographical area. [source] A political ecology of violence and territory in West KalimantanASIA PACIFIC VIEWPOINT, Issue 1 2008Nancy Lee Peluso Abstract: This paper uses a political ecology perspective to examine relationships between violence and territory in West Kalimantan, focusing on the violent incidents of 1996,1997 and 1967,1968. Besides a regional account, the paper examines some of the ways residents of one village were drawn into and chose to participate in violence. The author concludes that while regional analyses can identify broad patterns, local analyses enable a greater understanding of both variation and the processes by which ethnic categories are constructed through violence. [source] Regional and local influence of grazing activity on the diversity of a semi-arid dung beetle communityDIVERSITY AND DISTRIBUTIONS, Issue 1 2006Jorge M. Lobo ABSTRACT This study analyses the effect of resource availability (i.e. sheep dung) on dung beetle communities in an arid region of Central Spain, both at regional and at local scales. A total of 18 sites within 600 km2 were sampled for the regional analysis and 16 sites within the 30 km2 of an Iberian municipality were sampled for the local analysis. Spatial and environmental characteristics of sampling sites were also compiled at both scales, including measures of grazing activity (livestock density at regional scale, and two counts of rabbit and sheep dung at local scale). At a regional scale, any environmental or spatial variable can help to explain the variation in abundance. However, species richness was related to summer precipitation and composition was related to elevation. At local scale, abundance is not significantly related to any of the environmental variables, but species richness was related to the local amount of sheep dung (27% of variance). The amount of dung in a 2-km buffer around the site accounts for 27,32% of variance in abundance and 60,65% of variance in species richness. The presence of the flock with the highest sheep density explains 53% of abundance variability and 73% of species richness variance. A cluster analysis of localities identified two main groups, one characterized by a lower abundance and species richness that can be considered a nested subsample of the species-rich group. The mean and maximum amount of sheep dung in the sites separated by less than 2 km are the only significant explanatory variables able to discriminate both groups. These results suggest that grazing intensity (and the associated increase in the amount of trophic resources) is a key factor in determining local variation in the diversity and composition of dung beetle assemblages. However, dung beetle assemblages are not spatially independent at the analysed resolution, and the amount of dung in the surroundings seems to be more important for locally collected species than the dung effectively found in the site. Although differences in the availability and quantity of trophic resources among nearby sites could be affecting the population dynamics and dispersion of dung beetles within a locality, sites with larger populations, and greater species numbers would not be able to exercise enough influence as to bring about a complete local faunistic homogenization. [source] Numerical local analysis of relevant internal variables for constitutive modelling of granular materialsINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 11 2010Yuhanis Yunus Abstract DEM simulations on spherical materials have been performed to study the behaviour of model granular materials not only under monotonous stress path such as triaxial compression or extension, but also under two-way cycling loading paths. Three reference states have been considered to characterize the behaviour of the granular material: the characteristic state, transitory state between volumetric contraction and dilation, the state of maximum resistance and the critical state. These states are regarded with respect to void ratio and anisotropy of fabric which are the two internal variables retained for the description of the internal state of the material. The characteristic state and the state at maximum resistance are clearly dependent on both levels of density and anisotropy at the beginning of a loading path. Bilinear models involving the two internal variables were designed for the characteristic state, the maximum dilatancy and the extent of the dilatancy domain for axisymetric loadings. They show that in each case the effect of density and anisotropy are different in compression and extension. The influence of anisotropy and density seems to be of the same order of magnitude. Copyright © 2009 John Wiley & Sons, Ltd. [source] Comparison of global and local sensitivity techniques for rate constants determined using complex reaction mechanismsINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 12 2001James J. Scire Jr. Many rate constant measurements, including some "direct" measurements, involve fitting a complex reaction mechanism to experimental data. Two techniques for estimating the error in such measurements were compared. In the first technique, local first-order elementary sensitivities were used to rapidly estimate the sensitivity of the fitted rate constants to the remaining mechanism parameters. Our group and others have used this technique for error estimation and experimental design. However, the nonlinearity and strong coupling found in reaction mechanisms make verification against globally valid results desirable. Here, the local results were compared with analogous importance-sampled Monte Carlo calculations in which the parameter values were distributed according to their uncertainties. Two of our published rate measurements were examined. The local uncertainty estimates were compared with Monte Carlo confidence intervals. The local sensitivity coefficients were compared with coefficients from first and second-degree polynomial regressions over the whole parameter space. The first-order uncertainty estimates were found to be sufficiently accurate for experimental design, but were subject to error in the presence of higher order sensitivities. In addition, global uncertainty estimates were found to narrow when the quality of the fit was used to weight the randomly distributed points. For final results, the global technique was found to provide efficient, accurate values without the assumptions inherent in the local analysis. The rigorous error estimates derived in this way were used to address literature criticism of one of the studies discussed here. Given its efficiency and the variety of problems it can detect, the global technique could also be used to check local results during the experimental design phase. The global routine, coded using SENKIN, can easily be extended to different types of data, and therefore can serve as a valuable tool for assessing error in rate constants determined using complex mechanisms. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 784,802, 2001 [source] Toroidal magnetic fields in type II superconducting neutron starsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2008T. Akgün ABSTRACT We determine constraints on the form of axisymmetric toroidal magnetic fields dictated by hydrostatic balance in a type II superconducting neutron star with a barotropic equation of state. Using Lagrangian perturbation theory, we find the quadrupolar distortions due to such fields for various models of neutron stars with type II superconducting and normal regions. We find that the star becomes prolate and can be sufficiently distorted to display precession with a period of the order of years. We also study the stability of such fields using an energy principle, which allows us to extend the stability criteria established by R. J. Tayler for normal conductors to more general media with magnetic free energy that depends on density and magnetic induction, such as type II superconductors. We also derive the growth rate and instability conditions for a specific instability of type II superconductors, first discussed by P. Muzikar, C. J. Pethick and P. H. Roberts, using a local analysis based on perturbations around a uniform background. [source] A multilevel method for discontinuous Galerkin approximation of three-dimensional anisotropic elliptic problemsNUMERICAL LINEAR ALGEBRA WITH APPLICATIONS, Issue 5 2008J. K. Kraus Abstract We construct optimal order multilevel preconditioners for interior-penalty discontinuous Galerkin (DG) finite element discretizations of three-dimensional (3D) anisotropic elliptic boundary-value problems. In this paper, we extend the analysis of our approach, introduced earlier for 2D problems (SIAM J. Sci. Comput., accepted), to cover 3D problems. A specific assembling process is proposed, which allows us to characterize the hierarchical splitting locally. This is also the key for a local analysis of the angle between the resulting subspaces. Applying the corresponding two-level basis transformation recursively, a sequence of algebraic problems is generated. These discrete problems can be associated with coarse versions of DG approximations (of the solution to the original variational problem) on a hierarchy of geometrically nested meshes. A new bound for the constant , in the strengthened Cauchy,Bunyakowski,Schwarz inequality is derived. The presented numerical results support the theoretical analysis and demonstrate the potential of this approach. Copyright © 2007 John Wiley & Sons, Ltd. [source] Investigation of InN layers grown by MOCVD using analytical and high resolution TEM: The structure, band gap, role of the buffer layersPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2006P. Ruterana Abstract In this work we investigate the microstructure of InN layers grown by MOCVD on different buffer layers using TEM (InN, GaN). The large mismatch between the various lattices (InN, sapphire or GaN) leads to particular interface structures. Our local analysis allows to show that at atomic scale, the material has the InN lattice parameters and that no metallic In precipitates are present, meaning that the PL emission below 0.8 eV is a genuine property of the InN semiconductor. It is also shown that the N polar layers, which exhibit a 2D growth, have poorer PL emission than In polar layers. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||||||||