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Multi-scale Analysis (multi-scale + analysis)
Selected AbstractsMulti-Scale Analysis of IN-718 Microstructure Evolution During Linear Friction WeldingADVANCED ENGINEERING MATERIALS, Issue 6 2008C. Mary The present investigation focuses on Linear Friction Welding of a widely used Ni-based superalloy: IN-718. Blocks of commercial IN-718 alloy were linear friction welded under optimized processing conditions and the evolution of the weld joint microstructure was investigated using optical and scanning electron microscopy. In particular, visual examinations and macroscopic observations of microstructure evolution in the transverse cuts through the weld revealed a specific shape and a dual nature for the flash. [source] Multi-scale analysis of soil erosion dynamics in Kwazulu-Natal, South AfricaLAND DEGRADATION AND DEVELOPMENT, Issue 3 2005M. P. W. Sonneveld Abstract For a case study area in the Okhombe catchment in the province of KwaZulu-Natal, South Africa, a multi-scale analysis of soil erosion dynamics was performed. At sub-catchment level, the dynamics of erosional features were investigated by means of aerial photographs. At site level, the changes in soil physical and chemical properties were investigated by means of a fence-line contrast study. Attention was paid to both surface and subsurface erosion phenomena. The number of erosional features in the study area in 2000 was not substantially different from the number of features in 1945. At sub-catchment level, an increase in the number of gullies was observed from 1975 to 2000 but this followed a substantial inactivation of most erosional features from 1962 to 1975. Increases in erosional activity in 1962 compared to 1945 were mainly related to abandoned cultivated fields. At site level, a significant decrease in soil C/N ratio was observed within the fenced site within three years. For the same site, total carbon, saturated hydraulic conductivity and bulk density were not significantly different for the topsoil inside the fenced area compared with outside. Subsurface erosion phenomena mainly occur in the communal grazing areas and are mostly related to transitions between permeable and less permeable layers. The complex relationships between soil erosion, land use change and climate might further be understood by involving local people in the development, monitoring and evaluation of alternative types of land use, which is also likely to facilitate future steps in controlled grazing management. Copyright © 2005 John Wiley & Sons, Ltd. [source] Multi-scale analysis of the 25,27 July 2006 convective period over Niamey: Comparison between Doppler radar observations and simulationsTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue S1 2010Christelle Barthe Abstract The present study investigates the multi-scale processes associated with a sequence of convective events that occurred over Niamey during the period 25,26 July 2006. This period corresponds to the active stage of the first intense monsoon surge over Sahel for 2006. During this two-day period, two successive sequences of mesoscale convective systems (MCSs) were located ahead of and in phase with the trough of an African Easterly Wave (AEW). They were followed by suppressed or isolated convection behind the trough and in the vicinity of the ridge. The large AMMA-SOP dataset, in particular the UHF radar and the MIT Doppler radar in Niamey, are used in combination with a low-resolution (5 km) cloud-resolving model to understand the convection organization and its interaction with the environment. Several initial and boundary conditions have been tested, but only the simulation starting with the ECMWF AMMA reanalysis succeeds in reproducing the observed features; this emphasizes the importance of the initial state. From the simulated MCSs, the along-line component of the apparent source of momentum due to the convection is found to be up to 1 m s,1h,1. It seems that MCSs globally reduce the monsoon flow and generate southerlies at mid levels which can reinforce the rotation of the wind at the passage of the trough. During the afternoon of 26 July, the local convection over Niamey resulted from some favourable factors (humidity, CAPE, CIN) that triggered convection, while inhibiting factors (mid-level dry layer, weaker low-level wind shear pointing to the north, anticyclonic curvature of the streamlines at 700 hPa) prevented it organizing itself and propagating. In particular, the low-level wind shear seems of critical importance. Copyright © 2010 Royal Meteorological Society [source] Broad-scale environmental response and niche conservatism in lacustrine diatom communitiesGLOBAL ECOLOGY, Issue 5 2010Joseph R. Bennett ABSTRACT Aim, (1) To resolve theoretical debates regarding the role of environment versus dispersal limitation, the conservatism of niches across distances and the prevalence of environmental specialists in diatom communities. (2) To provide guidance on the use of diatom communities and other microbial analogues to analyse ecological response to environmental change. Location, Eight hundred and ninety-one lakes in five regional datasets from north-western Europe and four regional datasets from north-eastern North America. Methods, Lacustrine diatom communities were analysed at three scales: inter-continental, intra-continental and regional. Nested partial redundancy analyses (RDAs) were used to determine spatial versus environmental components of community variation. Weighted-averaging (WA) regression and calibration, as well as logistic and quadratic regressions, were used to detect niche conservatism and the prevalence of environmental specialists. Results, Community patterns indicate that dispersal limitation acts predominantly at the inter-continental scale, while at the regional (less than c. 1,000,000 km2) scale, a single environmental variable (pH) explains more than five times the community variation as spatial (dispersal-related) variables. In addition, pH niche components appear to be conserved at the inter-continental scale, and environmental specialization does not impose relative rarity, as specialists apparently readily disperse to suitable environments. Main conclusions, Analysis at multiple scales is clearly important in determining the influences of community variation. For diatom communities, dispersal limitation acts most strongly at the broadest scales, giving way to environment at the scales considered by most analyses. The availability of a wide variety of propagules with consistent niches across regions indicates that diatom communities reflect the succession of taxa according to local environmental conditions, rather than disequilibrium with the environment or adaptation of local populations. While multi-scale analyses must be undertaken for other groups to resolve debates over community drivers and determine appropriate scales for prediction, for diatoms (and probably other microbial communities), responses to environmental change can be inferred using analogue datasets from large geographic areas. [source] Multi-scale system reliability analysis of lifeline networks under earthquake hazardsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 3 2010Junho Song Abstract Recent earthquake events evidenced that damage of structural components in a lifeline network may cause prolonged disruption of lifeline services, which eventually results in significant socio-economic losses in the affected area. Despite recent advances in network reliability analysis, the complexity of the problem and various uncertainties still make it a challenging task to evaluate the post-hazard performance and connectivity of lifeline networks efficiently and accurately. In order to overcome such challenges and take advantage of merits of multi-scale analysis, this paper develops a multi-scale system reliability analysis method by integrating a network decomposition approach with the matrix-based system reliability (MSR) method. In addition to facilitating system reliability analysis of large-size networks, the multi-scale approach enables optimizing the level of computational effort on subsystems; identifying the relative importance of components and subsystems at multiple scales; and providing a collaborative risk management framework. The MSR method is uniformly applied for system reliability analyses at both the lower-scale (for link failure) and the higher-scale (for system connectivity) to obtain the probability of general system events, various conditional probabilities, component importance measures, statistical correlation between subsystem failures and parameter sensitivities. The proposed multi-scale analysis method is demonstrated by its application to a gas distribution network in Shelby County of Tennessee. A parametric study is performed to determine the number of segments during the lower-scale MSR analysis of each pipeline based on the strength of the spatial correlation of seismic intensity. It is shown that the spatial correlation should be considered at both scales for accurate reliability evaluation. The proposed multi-scale analysis approach provides an effective framework of risk assessment and decision support for lifeline networks under earthquake hazards. Copyright © 2009 John Wiley & Sons, Ltd. [source] Macro,micro analysis method for wave propagation in stochastic mediaEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 4 2006T. Ichimura Abstract This paper presents a new analysis method, called macro,micro analysis method (MMAM) for numerical simulation of wave propagation in stochastic media, which could be used to predict distribution of earthquake strong motion with high accuracy and spatial resolution. This MMAM takes advantage of the bounding medium theory (BMT) and the singular perturbation expansion (SPE). BMT can resolve uncertainty of soil and crust structures by obtaining optimistic and pessimistic estimates of expected strong motion distribution. SPE leads to efficient multi-scale analysis for reducing a huge amount of computation. The MMAM solution is given as the sum of waves of low resolution covering a whole city and waves of high resolution for each city portion. This paper presents BMT and SPE along with the formulation of MMAM for wave propagation in three-dimensional elastic media. Application examples are presented to verify the validity of the MMAM and demonstrate potential usefulness of this approach. In a companion paper (Earthquake Engng. Struct. Dyn., this issue) application examples of earthquake strong motion prediction are also presented. Copyright © 2005 John Wiley & Sons, Ltd. [source] Distribution, abundance, and individual strategies: a multi-scale analysis of dasyurid marsupials in arid central AustraliaECOGRAPHY, Issue 3 2006Adele S. Haythornthwaite We investigated the effects of different environmental factors on the distribution and abundance of 6 species of dasyurid marsupials using a multiple-scale analysis. Data collected in the spinifex dunefields of the Simpson Desert, Australia, were analysed at 3 spatial scales spanning more than 5 orders of magnitude: "metasite" (covering an area of 1000,2000 km2), site (2,12 km2) and grid (0.01 km2). Temporal variability was also investigated, using data collected in March, April, and May in 4 consecutive years from 1997 to 2000. Both abiotic and biotic factors influenced the capture rates of different species at different times and spatial scales. At the coarsest spatial scale, Dasycercus cristicauda (mulgara) was consistently limited in its distribution by the intensity of rainfall, probably as an indirect result of increased grazing pressure from pastoral activity and a higher density of feral predators in high rainfall areas. However, at the finest spatial scale, this partly carnivorous species was scarce in areas of dense spinifex, perhaps because such habitats yield lowest returns during foraging, and was more common in areas where small invertebrate prey were abundant. Factors affecting the distribution of the most abundant dasyurid species in the study area, Sminthopsis youngsoni (lesser hairy-footed dunnart), could not be identified at any scale; we conclude that this reflects the opportunistic foraging strategies and flexible habitat requirements of this insectivorous species. Both Ningaui ridei (wongai ningaui) and Sminthopsis hirtipes (hairy-footed dunnart) were less abundant throughout the study region. For N. ridei, a spinifex specialist, predictors of occurrence could be identified only at the finest scale of analysis; at the grid level, a close positive association was detected in 2 of the 4 study years between capture rate and spinifex cover. For S. hirtipes, all 3 levels of spatial analysis revealed a negative association between capture rate and both rainfall and spinifex density. For the rarely-caught S. crassicaudata (fat-tailed dunnart) and Planigale tenuirostris (narrow-nosed planigale), no clear results were obtained at any spatial scale, and we interpret this to indicate that the study region represents sub-optimal habitat for these species. Given that different factors affected the distribution and abundance of dasyurids at different spatial scales over time, we conclude that a multiple-scale approach to population and community analysis is vital to accurately identify which environmental processes shape population and community dynamics. Understanding the interplay between regional and local processes will be crucial for management of existing species populations and for prediction of their distributions and abundances in future. [source] A second-order homogenization procedure for multi-scale analysis based on micropolar kinematicsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 12 2007Ragnar Larsson Abstract The paper presents a higher order homogenization scheme based on non-linear micropolar kinematics representing the macroscopic variation within a representative volume element (RVE) of the material. On the microstructural level the micro,macro kinematical coupling is introduced as a second-order Taylor series expansion of the macro displacement field, and the microstructural displacement variation is gathered in a fluctuation term. This approach relates strongly to second gradient continuum formulations, presented by, e.g. Kouznetsova et al. (Int. J. Numer. Meth. Engng 2002; 54:1235,1260), thus establishing a link between second gradient and micropolar theories. The major difference of the present approach as compared to second gradient formulations is that an additional constraint is placed on the higher order deformation gradient in terms of the micropolar stretch. The driving vehicle for the derivation of the homogenized macroscopic stress measures is the Hill,Mandel condition, postulating the equivalence of microscopic and macroscopic (homogenized) virtual work. Thereby, the resulting homogenization procedure yields not only a stress tensor, conjugated to the micropolar stretch tensor, but also the couple stress tensor, conjugated to the micropolar curvature tensor. The paper is concluded by a couple of numerical examples demonstrating the size effects imposed by the homogenization of stresses based on the micropolar kinematics. Copyright © 2006 John Wiley & Sons, Ltd. [source] Wavelet Galerkin method in multi-scale homogenization of heterogeneous mediaINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 3 2006Shafigh Mehraeen Abstract The hierarchical properties of scaling functions and wavelets can be utilized as effective means for multi-scale homogenization of heterogeneous materials under Galerkin framework. It is shown in this work, however, when the scaling functions are used as the shape functions in the multi-scale wavelet Galerkin approximation, the linear dependency in the scaling functions renders improper zero energy modes in the discrete differential operator (stiffness matrix) if integration by parts is invoked in the Galerkin weak form. An effort is made to obtain the analytical expression of the improper zero energy modes in the wavelet Galerkin differential operator, and the improper nullity of the discrete differential operator is then removed by an eigenvalue shifting approach. A unique property of multi-scale wavelet Galerkin approximation is that the discrete differential operator at any scale can be effectively obtained. This property is particularly useful in problems where the multi-scale solution cannot be obtained simply by a wavelet projection of the finest scale solution without utilizing the multi-scale discrete differential operator, for example, the multi-scale analysis of an eigenvalue problem with oscillating coefficients. Copyright © 2005 John Wiley & Sons, Ltd. [source] Multi-scale analysis of soil erosion dynamics in Kwazulu-Natal, South AfricaLAND DEGRADATION AND DEVELOPMENT, Issue 3 2005M. P. W. Sonneveld Abstract For a case study area in the Okhombe catchment in the province of KwaZulu-Natal, South Africa, a multi-scale analysis of soil erosion dynamics was performed. At sub-catchment level, the dynamics of erosional features were investigated by means of aerial photographs. At site level, the changes in soil physical and chemical properties were investigated by means of a fence-line contrast study. Attention was paid to both surface and subsurface erosion phenomena. The number of erosional features in the study area in 2000 was not substantially different from the number of features in 1945. At sub-catchment level, an increase in the number of gullies was observed from 1975 to 2000 but this followed a substantial inactivation of most erosional features from 1962 to 1975. Increases in erosional activity in 1962 compared to 1945 were mainly related to abandoned cultivated fields. At site level, a significant decrease in soil C/N ratio was observed within the fenced site within three years. For the same site, total carbon, saturated hydraulic conductivity and bulk density were not significantly different for the topsoil inside the fenced area compared with outside. Subsurface erosion phenomena mainly occur in the communal grazing areas and are mostly related to transitions between permeable and less permeable layers. The complex relationships between soil erosion, land use change and climate might further be understood by involving local people in the development, monitoring and evaluation of alternative types of land use, which is also likely to facilitate future steps in controlled grazing management. Copyright © 2005 John Wiley & Sons, Ltd. [source] Reinforcement of a thin plate by a thin layerMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 3 2008Leila Rahmani Abstract We study the bending of a thin plate, stiffened with a thin elastic layer, of thickness ,. We describe the complete construction of an asymptotic expansion with respect to , of the solution of the Kirchhoff,Love model and give optimal estimates for the remainder. We identify approximate boundary conditions, which take into account the effect of the stiffener at various orders. Thanks to the tools of multi-scale analysis, we give optimal estimates for the error between the approximate problems and the original one. We deal with a layer of constant stiffness, as well as with a stiffness in ,,1. Copyright © 2007 John Wiley & Sons, Ltd. [source] The extensive episode of derecho-producing convective systems in the United States during May and June 1998: A multi-scale analysis and reviewMETEOROLOGICAL APPLICATIONS, Issue 3 2007Walker S. Ashley Abstract A multi-scale analysis is presented on widespread and long-lived convectively generated windstorms, known as derechos. Analyses of the derecho-producing environments during 15 May,30 June 1998 indicate that this exceptional episode of derechos and derecho groupings (or series) was supported by ingredients (i.e. moisture, instability, and wind shear) that were supplied by the large-scale setting. In particular, the semi-stagnant subtropical ridge and associated capping inversion across the southern tier of the U.S. were important in supplying amplified moisture and instability to derecho-genesis regions through an underrunning process. Regions of preferred derecho formation appeared to correspond to shifts in the overall strength and position of the ridge, illustrating the importance of the ridge in focusing successive organized convection. Initiating mechanisms varied widely and were not restricted to warm-air advection regimes along quasi-stationary boundaries that forecasters often associate with warm-season derecho environments. In several cases, derecho-producing convective systems were generated by tropospheric features not consistent with common conceptual models of derecho environments such as closed lows and strong vorticity maxima. Further, three distinct series types were identified and classified based on their initiating mechanisms. Copyright © 2007 Royal Meteorological Society [source] Examination of intermediate species in GaN metal-organic vapor-phase epitaxy by selective-area growthPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7-8 2010Masakazu Sugiyama Abstract The major reactive intermediate species of GaN has been deduced and its surface reaction rate constant has been obtained through the analysis of multi-scale growth-rate profiles both in the reactor-scale and in the micrometer-scale that were obtained by selective-area growth. Usually, it is difficult to explore surface reaction kinetics, especially for metal-organic vapour phase epitaxy (MOVPE), because of mass-transfer-limited kinetics. This multi-scale analysis, however, has clarified that a single precursor, a gas-phase reaction product between (CH3)3Ga and NH3, leads to the growth of GaN with a surface reaction probability of approximately 0.4 at 1400 K which is a typical growth temperature of GaN. Contribution of higher-order polymers was not significant in growth rate, but they seemed to be a cause of degraded surface morphology. A lumped reaction model of GaN MOVPE was proposed that led to reasonable agreement between a simulated growth-rate profile in the reactor-scale and a corresponding measured profile, which would lead to improved design of reactors and growth conditions. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Multi-scale sampling and statistical linear estimators to assess land use status and changeAPPLIED VEGETATION SCIENCE, Issue 2 2009D. Rocchini Abstract Question: Multi-temporal analysis of remotely sensed imagery has proven to be a powerful tool for assessment and monitoring of landscape diversity. Here the feasibility of assessing land-use diversity and land-use change was tested at multiple scales and over time by means of statistical linear estimators based on a probabilistic sampling design. Location: The study area (the district of Asciano, Tuscany, Italy) is characterized by erosional forms typical of Pliocene claystone (i.e. calanchi and biancane) that have been subject to the phenomenon of biancane reworking over the past 50 years, mainly owing to the expansion of intensive agriculture. Methods: Cells at two different scales (50 m × 50 m and 10 m × 10 m) were classified by two operators according to a multilevel legend, using 1954 and 2000 aerial photographs. Inter-operator agreement and accuracy were tested by Cohen's K coefficient. Total land cover estimation for each class was carried out using a multistage estimator, while the variance was estimated by means of the Wolter estimator. Field-based information on plant species composition was recorded in order to test for a relationship between land use and plant community composition by anova and indicator species analysis. Results: Agreement between photointerpreters and accuracy were significantly higher than those expected by chance, proving that the approach proposed is reproducible, as long as proper quality assurance methods are used. Our data show that, at the two scales considered (50 m × 50 m and 10 m × 10 m), crops have increased against woodlands and semi-natural areas, the latter showing the highest and significantly different mean species richness. Meanwhile, an increase in the coverage of trees and shrubs was found within the semi-natural areas, probably as a result of secondary succession occurring on typical landscape elements such as biancane. Conclusions: Inferential statistics made it possible to acquire quantitative information on the abundance of land cover classes, allowing formal multi-temporal and multi-scale analysis. Sampling design-based statistical linear estimators were found to be a powerful tool for assessing landscape trends considering both time expenditure and other costs. They make it possible to maintain the same scale of analysis over time series data and to detect both coarse- and fine-grained changes in spatial patterns. [source] | ||||||||||||||||