Academic literature on the topic 'Tree set heterogeneity'
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Journal articles on the topic "Tree set heterogeneity"
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GLEISER, PABLO M., LUCE PRIGNANO, CONRAD J. PÉREZ-VICENTE, and ALBERT DÍAZ-GUILERA. "PACEMAKERS IN A CAYLEY TREE OF KURAMOTO OSCILLATORS." International Journal of Bifurcation and Chaos 22, no. 07 (July 2012): 1250161. http://dx.doi.org/10.1142/s0218127412501611.
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In this work, we study a system of Kuramoto oscillators with identical frequencies in a Cayley tree. Heterogeneity in the frequency distribution is introduced in the root of the tree, allowing for analytical calculations of the phase evolution. In this work, we study a system of Kuramoto oscillators with identical frequencies in a Cayley tree. Heterogeneity in the frequency distribution is introduced in the root of the tree, allowing for analytical calculations of the phase evolution. This simple case can be regarded as a starting point in order to understand how to extract topological features of the connectivity pattern from the dynamic state of the system, and vice versa, for the general situation of a set of phase oscillators located on a tree-like network.
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Keren, Srđan, Miroslav Svoboda, Pavel Janda, and Thomas A. Nagel. "Relationships between Structural Indices and Conventional Stand Attributes in an Old-Growth Forest in Southeast Europe." Forests 11, no. 1 (December 18, 2019): 4. http://dx.doi.org/10.3390/f11010004.
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Structural indices are often proposed as guiding measures for increasing structural heterogeneity. However, few studies have examined the association between such indices and conventional stand attributes. The primary objectives of this study were to evaluate changes in structural heterogeneity and tree species diversity at different plot sizes and to quantify the relationships between conventional stand attributes (mean tree diameter, absolute tree density, basal area, species proportion) and structural indices in a mixed old-growth forest in Southeast Europe. Paired tests were used to identify significant changes in structural heterogeneity with increased plot area, while the relationships between stand attributes and analyzed indices (Gini, diameter differentiation, species mingling, and Shannon’s index) were evaluated with Pearson’s correlations. The index values of Gini, diameter differentiation, and tree species mingling were rather stable with the increase of plot size, whereas tree species diversity increased significantly with the increase of plot area from 200 m2 to 1500 m2. The measures of tree species mingling and tree species diversity were strongly associated with each other, while their association with diameter variability was weak to moderately strong. Tree species mingling index was strongly associated with the changes in tree species proportions. However, conventional stand attributes were generally not strongly correlated with the examined indices. For restoring and maintaining old-growth characteristics, forest managers may use structural indices to increase small-scale structural heterogeneity, tree species mingling, and diversity, but only as an additional set of measures, not as surrogates for conventional stand attributes.
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Karch, Rudolf, Friederike Neumann, Bruno K. Podesser, Martin Neumann, Paul Szawlowski, and Wolfgang Schreiner. "Fractal Properties of Perfusion Heterogeneity in Optimized Arterial Trees." Journal of General Physiology 122, no. 3 (August 11, 2003): 307–22. http://dx.doi.org/10.1085/jgp.200208747.
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Regional blood flows in the heart muscle are remarkably heterogeneous. It is very likely that the most important factor for this heterogeneity is the metabolic need of the tissue rather than flow dispersion by the branching network of the coronary vasculature. To model the contribution of tissue needs to the observed flow heterogeneities we use arterial trees generated on the computer by constrained constructive optimization. This method allows to prescribe terminal flows as independent boundary conditions, rather than obtaining these flows by the dispersive effects of the tree structure. We study two specific cases: equal terminal flows (model 1) and terminal flows set proportional to the volumes of Voronoi polyhedra used as a model for blood supply regions of terminal segments (model 2). Model 1 predicts, depending on the number Nterm of end-points, fractal dimensions D of perfusion heterogeneities in the range 1.20 to 1.40 and positively correlated nearest-neighbor regional flows, in good agreement with experimental data of the normal heart. Although model 2 yields reasonable terminal flows well approximated by a lognormal distribution, it fails to predict D and nearest-neighbor correlation coefficients r1 of regional flows under normal physiologic conditions: model 2 gives D = 1.69 ± 0.02 and r1 = −0.18 ± 0.03 (n = 5), independent of Nterm and consistent with experimental data observed under coronary stenosis and under the reduction of coronary perfusion pressure. In conclusion, flow heterogeneity can be modeled by terminal positions compatible with an existing tree structure without resorting to the flow-dispersive effects of a specific branching tree model to assign terminal flows.
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Chaddad, Ahmad, and Camel Tanougast. "High-Throughput Quantification of Phenotype Heterogeneity Using Statistical Features." Advances in Bioinformatics 2015 (October 20, 2015): 1–7. http://dx.doi.org/10.1155/2015/728164.
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Statistical features are widely used in radiology for tumor heterogeneity assessment using magnetic resonance (MR) imaging technique. In this paper, feature selection based on decision tree is examined to determine the relevant subset of glioblastoma (GBM) phenotypes in the statistical domain. To discriminate between active tumor (vAT) and edema/invasion (vE) phenotype, we selected the significant features using analysis of variance (ANOVA) with p value < 0.01. Then, we implemented the decision tree to define the optimal subset features of phenotype classifier. Naïve Bayes (NB), support vector machine (SVM), and decision tree (DT) classifier were considered to evaluate the performance of the feature based scheme in terms of its capability to discriminate vAT from vE. Whole nine features were statistically significant to classify the vAT from vE with p value < 0.01. Feature selection based on decision tree showed the best performance by the comparative study using full feature set. The feature selected showed that the two features Kurtosis and Skewness achieved a highest range value of 58.33–75.00% accuracy classifier and 73.88–92.50% AUC. This study demonstrated the ability of statistical features to provide a quantitative, individualized measurement of glioblastoma patient and assess the phenotype progression.
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Duduman, Gabriel, Ionuț Barnoaiea, Daniel Avăcăriței, Cătălina-Oana Barbu, Vasile-Cosmin Coșofreț, Iulian-Constantin Dănilă, Mihai-Leonard Duduman, Anca Măciucă, and Marian Drăgoi. "Aboveground Biomass of Living Trees Depends on Topographic Conditions and Tree Diversity in Temperate Montane Forests from the Slătioara-Rarău Area (Romania)." Forests 12, no. 11 (October 31, 2021): 1507. http://dx.doi.org/10.3390/f12111507.
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The study zone includes one of the largest montane old-growth forests in Europe (Slatioara UNESCO site), and understanding the structure and functioning of sill intact forests in Europe is essential for grounding management strategies for secondary forests. For this reason, we set out to analyze the dependencies between aboveground biomass (AgB), tree species and size diversity and terrain morphology, as well as the relationship between biomass and diversity, since neither of these issues have been sufficiently explored. We found that tree species diversity decreases with increased solar radiation and elevation. Tree size heterogeneity reaches its highest mean values at elevations between 1001 and 1100 m, on slopes between 50 and 60 degrees. AgB is differentiated with elevation; the highest mean AgB (293 tonnes per hectare) is recorded at elevations between 801 and 900 m, while it decreases to 79 tonnes per hectare at more than 1500 m a.s.l. It is also influenced by tree species diversity and tree size heterogeneity, with the highest AgB reached in the most complex forest ecosystems in terms of structural diversity. We showed that intact temperate montane forests develop maximum biomass for optimum species diversity and highest size heterogeneity; all three are modulated mainly by elevation.
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LIŠKA, Jiří, and Tomáš HERBEN. "Long-term changes of epiphytic lichen species composition over landscape gradients: an 18 year time series." Lichenologist 40, no. 05 (August 26, 2008): 437–48. http://dx.doi.org/10.1017/s0024282908006610.
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Abstract:The study aimed to determine how the response of the epiphytic lichen vegetation to sulphur air pollution is affected by interaction with other factors (distance from pollution sources, habitat, altitude, initial eutrophication of the tree bark). It was based on a series of four successive recordings taken over a period of 18 years with increasing pollution levels and on the same set of 139 solitary trees. Relationships between habitat variables and lichen community composition are assessed using canonical correspondence analysis. The data set comprised 69 lichen species. Ordination of initial species composition on trees revealed two major gradients: eutrophication and acidity.The species composition significantly changed with time, with a general decrease of the total number of lichen species per tree. In general, species sensitive to air pollution decreased, while tolerant species increased in number. Change over time differed depending on the position of the tree within the landscape (relative to one major source of pollution, the town of Tábor, whereas the distance to the other source, Sezimovo Ústí, was not significant) and on the initial species composition found on the tree. Trees under the effect of eutrophication changed their species composition less, indicating that the effect of eutrophication (mainly increased bark pH) may ameliorate the effects of air pollution; a local effect of eutrophication also seems to play an important role. Distance to pollution sources had only a small impact on the rate of change and perhaps other local conditions (sheltered or humid position, altitude) play a role in this interaction. There was a decrease of the overall heterogeneity of the data set over time. This means that the gradients in species composition attributable to these variables became less important over time. Therefore, one of the effects of air pollution is also a general homogenization of the lichen vegetation of the solitary trees.
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Adams, Richard H., and Todd A. Castoe. "Probabilistic Species Tree Distances: Implementing the Multispecies Coalescent to Compare Species Trees Within the Same Model-Based Framework Used to Estimate Them." Systematic Biology 69, no. 1 (May 14, 2019): 194–207. http://dx.doi.org/10.1093/sysbio/syz031.
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Abstract Despite the ubiquitous use of statistical models for phylogenomic and population genomic inferences, this model-based rigor is rarely applied to post hoc comparison of trees. In a recent study, Garba et al. derived new methods for measuring the distance between two gene trees computed as the difference in their site pattern probability distributions. Unlike traditional metrics that compare trees solely in terms of geometry, these measures consider gene trees and associated parameters as probabilistic models that can be compared using standard information theoretic approaches. Consequently, probabilistic measures of phylogenetic tree distance can be far more informative than simply comparisons of topology and/or branch lengths alone. However, in their current form, these distance measures are not suitable for the comparison of species tree models in the presence of gene tree heterogeneity. Here, we demonstrate an approach for how the theory of Garba et al. (2018), which is based on gene tree distances, can be extended naturally to the comparison of species tree models. Multispecies coalescent (MSC) models parameterize the discrete probability distribution of gene trees conditioned upon a species tree with a particular topology and set of divergence times (in coalescent units), and thus provide a framework for measuring distances between species tree models in terms of their corresponding gene tree topology probabilities. We describe the computation of probabilistic species tree distances in the context of standard MSC models, which assume complete genetic isolation postspeciation, as well as recent theoretical extensions to the MSC in the form of network-based MSC models that relax this assumption and permit hybridization among taxa. We demonstrate these metrics using simulations and empirical species tree estimates and discuss both the benefits and limitations of these approaches. We make our species tree distance approach available as an R package called pSTDistanceR, for open use by the community.
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Hime, Paul M., Alan R. Lemmon, Emily C. Moriarty Lemmon, Elizabeth Prendini, Jeremy M. Brown, Robert C. Thomson, Justin D. Kratovil, et al. "Phylogenomics Reveals Ancient Gene Tree Discordance in the Amphibian Tree of Life." Systematic Biology 70, no. 1 (June 30, 2020): 49–66. http://dx.doi.org/10.1093/sysbio/syaa034.
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Abstract Molecular phylogenies have yielded strong support for many parts of the amphibian Tree of Life, but poor support for the resolution of deeper nodes, including relationships among families and orders. To clarify these relationships, we provide a phylogenomic perspective on amphibian relationships by developing a taxon-specific Anchored Hybrid Enrichment protocol targeting hundreds of conserved exons which are effective across the class. After obtaining data from 220 loci for 286 species (representing 94% of the families and 44% of the genera), we estimate a phylogeny for extant amphibians and identify gene tree–species tree conflict across the deepest branches of the amphibian phylogeny. We perform locus-by-locus genealogical interrogation of alternative topological hypotheses for amphibian monophyly, focusing on interordinal relationships. We find that phylogenetic signal deep in the amphibian phylogeny varies greatly across loci in a manner that is consistent with incomplete lineage sorting in the ancestral lineage of extant amphibians. Our results overwhelmingly support amphibian monophyly and a sister relationship between frogs and salamanders, consistent with the Batrachia hypothesis. Species tree analyses converge on a small set of topological hypotheses for the relationships among extant amphibian families. These results clarify several contentious portions of the amphibian Tree of Life, which in conjunction with a set of vetted fossil calibrations, support a surprisingly younger timescale for crown and ordinal amphibian diversification than previously reported. More broadly, our study provides insight into the sources, magnitudes, and heterogeneity of support across loci in phylogenomic data sets.[AIC; Amphibia; Batrachia; Phylogeny; gene tree–species tree discordance; genomics; information theory.]
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Schierup, Mikkel H., and Jotun Hein. "Consequences of Recombination on Traditional Phylogenetic Analysis." Genetics 156, no. 2 (October 1, 2000): 879–91. http://dx.doi.org/10.1093/genetics/156.2.879.
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Abstract We investigate the shape of a phylogenetic tree reconstructed from sequences evolving under the coalescent with recombination. The motivation is that evolutionary inferences are often made from phylogenetic trees reconstructed from population data even though recombination may well occur (mtDNA or viral sequences) or does occur (nuclear sequences). We investigate the size and direction of biases when a single tree is reconstructed ignoring recombination. Standard software (PHYLIP) was used to construct the best phylogenetic tree from sequences simulated under the coalescent with recombination. With recombination present, the length of terminal branches and the total branch length are larger, and the time to the most recent common ancestor smaller, than for a tree reconstructed from sequences evolving with no recombination. The effects are pronounced even for small levels of recombination that may not be immediately detectable in a data set. The phylogenies when recombination is present superficially resemble phylogenies for sequences from an exponentially growing population. However, exponential growth has a different effect on statistics such as Tajima's D. Furthermore, ignoring recombination leads to a large overestimation of the substitution rate heterogeneity and the loss of the molecular clock. These results are discussed in relation to viral and mtDNA data sets.
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Revell, Liam J., Ken S. Toyama, and D. Luke Mahler. "A simple hierarchical model for heterogeneity in the evolutionary correlation on a phylogenetic tree." PeerJ 10 (August 18, 2022): e13910. http://dx.doi.org/10.7717/peerj.13910.
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Numerous questions in phylogenetic comparative biology revolve around the correlated evolution of two or more phenotypic traits on a phylogeny. In many cases, it may be sufficient to assume a constant value for the evolutionary correlation between characters across all the clades and branches of the tree. Under other circumstances, however, it is desirable or necessary to account for the possibility that the evolutionary correlation differs through time or in different sections of the phylogeny. Here, we present a method designed to fit a hierarchical series of models for heterogeneity in the evolutionary rates and correlation of two quantitative traits on a phylogenetic tree. We apply the method to two datasets: one for different attributes of the buccal morphology in sunfishes (Centrarchidae); and a second for overall body length and relative body depth in rock- and non-rock-dwelling South American iguanian lizards. We also examine the performance of the method for parameter estimation and model selection using a small set of numerical simulations.
Books on the topic "Tree set heterogeneity"
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Garberoglio, Carrie Lou. Secondary Analyses With Large-Scale Data in Deaf Education Research. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780190455651.003.0006.
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This chapter discusses how secondary analyses conducted with large-scale federal data sets offer a way of capturing national samples of the diverse population of deaf students, as well as important features that need to be considered when generalizing findings to practice. The author’s work with federal large-scale data sets has largely focused on an exploration of individual and systemic factors that influence postsecondary outcomes for deaf individuals. Large-scale data sets offer unique opportunities to efficiently test hypotheses and empirically address long-standing assumptions in the field through the use of large sample sizes that bring researchers closer to true representations of the heterogeneity in the Deaf community. Specific examples are shared that highlight some successes and challenges in this approach, and how researchers can best utilize large-scale data sets to conduct secondary analyses in their own work with deaf populations.
Book chapters on the topic "Tree set heterogeneity"
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Davino, Cristina, and Giuseppe Lamberti. "Linear regression pathmox segmentation tree: the case of visitors’ satisfaction to attend a Spanish football match at the stadium." In Proceedings e report, 137–40. Florence: Firenze University Press, 2021. http://dx.doi.org/10.36253/978-88-5518-461-8.26.
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Analysis of a dependency model can be furthered by assessing whether a model and/or the impact of regressors on dependent variables differ if heterogeneity is observed. In other words, it may be interesting to assess differences between a global model estimated for a whole group and models estimated for sub-groups identified on the basis of known categorical variables external to the model, as those variables may identify partitions characterized by dependency structure heterogeneity. This is particularly important in decision-making as policies based on the generic model could yield inaccurate and biased results. In this paper, we propose a procedure, the Pathmox approach that exploits the potential of segmentation trees to identify partitions in an initial set of data characterized by different linear regression patterns. We will apply this new approach to measure the visitors’ satisfaction to attend a Spanish football match at the stadium. Thus, we will analyze the relationship between two significant aspects related to the visitors’ satisfaction: stadium service quality and image of the football team, taking into account five visitors’ background variables as potential sources of heterogeneity: age, gender, if they were tourist (yes or not), if it was the first time at the stadium (yes or not), and level of involvement with the football team. From a decision-making perspective, the paper contributes evidence exemplifying how an apparently representative global model can in fact mask different relationships between variables due to heterogeneous data, underlining the importance of accounting for heterogeneity when defining new policies.
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Gaillard, Jean-Michel, Victor Ronget, Jean-François Lemaître, Christophe Bonenfant, Guillaume Péron, Pol Capdevila, Marlène Gamelon, and Roberto Salguero-Gómez. "Applying comparative methods to different databases: lessons from demographic analyses across mammal species." In Demographic Methods across the Tree of Life, 299–312. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780198838609.003.0018.
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Comparative demographic analyses aim to identify axes of variation in vital rates and the factors that determine the position of species along these axes. These analyses can be performed using different primary data sets, with marked heterogeneity in data quality and structure. Whether the outcome of demographic comparative analyses depends on the database used because theoretical predictions of evolutionary ecology are not that robust and depend on the set of species analysed or because data limitation prevents the identification of the expected patterns has never been investigated. This chapter fills this knowledge gap by performing a comparative demographic analysis across mammalian species from two distinct databases (Comadre and Malddaba) that were built for different purposes. The chapter first estimates some demographic metrics for each database, analyses their allometric relationships, and compares the estimates with theoretical expectations by performing phylogenetic regressions. Using Malddaba led to stronger allometric relationships closer to the expectation than Comadre. Moreover, the contribution of dimensionless demographic metrics to axes of variation in the shape of demographic trajectories was different between databases. The findings in the chapter demonstrate the key role of age dependence in vital rates for shaping demographic tactics across mammalian species and highlight the need for carefully choosing the database and the metrics to use depending on the question asked. Instead of opposing databases, the authors’ analysis nicely illustrates that different databases could be used to address different questions about life history variation.
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Marino, Eva, Stefano Arellano-Pérez, Santiago Martín-Alcón, and José Luis Tomé. "Canopy fuel modelling in Mediterranean forest stands with airborne LiDAR data at regional scale: preliminary results." In Advances in Forest Fire Research 2022, 1416–22. Imprensa da Universidade de Coimbra, 2022. http://dx.doi.org/10.14195/978-989-26-2298-9_215.
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Canopy fuel characterization is highly relevant for wildfire prevention, especially in the context of extreme events involving crown fires. Airborne laser scanning has been proven very useful to retrieve 3D forest structure at large scales, becoming freely available in many countries in the recent years which provide an opportunity to map fuel parameters that are critical for fire behaviour simulation. Previous studies on canopy fuel modelling predict canopy base height (CBH), fuel load (CFL) and bulk density (CBD) mainly in tree species from temperate conifer forest, with specific models still lacking for the main Mediterranean forest stands and especially deciduous species. This work presents preliminary results of models obtained from low density airborne LiDAR data (1.5 p/m2) for canopy fuel characterization of critical structural variables (CBH, CFL and CBD) in the main Mediterranean forest stands existing in Andalusia region, including Pinus sp, Quercus sp and Eucalyptus sp tree species. A set of 750 plots are used to characterize canopy fuels in 15 different forest stands representative of Mediterranean tree species, with a samplig design that consider structural heterogeneity in a wide study area (29000 km2). Different modelling techniques are tested to selected the best formulation and input LiDAR metrics to be included in the final models for each fuel parameter, that are used to generate high resolution maps of canopy fuels at regional scale.
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Boose, Emery R. "Hurricane Impacts in New England and Puerto Rico." In Climate Variability and Ecosystem Response in Long-Term Ecological Research Sites. Oxford University Press, 2003. http://dx.doi.org/10.1093/oso/9780195150599.003.0008.
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Hurricanes have a profound effect on many coastal ecosystems. Direct impacts often include wind damage to trees, scouring and flooding of river channels, and salt-water inundation along shorelines (Simpson and Riehl 1981; Diaz and Pulwarty 1997). In some areas, secondary impacts may include landslides triggered by heavy rains (Scatena and Larson 1991) or catastrophic dry-season fires resulting from heavy fuel loading (Whigham in press). This chapter will focus on the longterm impacts of hurricane wind damage at two LTER sites, the Harvard Forest (HFR) in central New England and the Luquillo Experimental Forest (LUQ) in northeastern Puerto Rico. These two sites, both located in the North Atlantic hurricane basin and occasionally subject to the same storms, provide interesting examples of tropical and temperate hurricane disturbance regimes. Wind damage from a single hurricane is often highly variable (Foster 1988). Damage to individual trees can range from loss of leaves and fine branches, which can significantly alter surface nutrient inputs (Lodge et al. 1991), to bole snapping or uprooting, which can significantly alter coarse woody debris and soil microtopography (Carlton and Bazzaz 1998a and b). At the stand level, damage can range from defoliation to individual tree gaps to extensive blowdowns, creating different pathways for regeneration (Lugo 2000). At landscape and regional levels, complex patterns of damage are created by the interaction of meteorological, topographic, and biological factors (Boose et al. 1994). Adding to this spatial complexity is the fact that successive hurricanes are not necessarily independent in terms of their effects. A single storm lasting several hours may have effects that persist for decades (Foster et al. 1998). And forest susceptibility to wind damage is strongly influenced by composition and structure, which in turn are strongly influenced by previous disturbance history (Foster and Boose 1992). Thus, the impacts of a single hurricane may depend in part on the impacts of earlier storms as well as on other previous disturbances and land use. Hurricanes, like other disturbances, both create and respond to spatial heterogeneity (Turner et al. 2003). To understand the long-term ecological role of hurricanes at a given site, we must consider these three sets of questions: (1) What is the hurricane disturbance regime?
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Paruelo, José María, and Estebán G. Jobbágy. "The Grasslands and Steppes of Patagonia and the Río de la Plata Plains." In The Physical Geography of South America. Oxford University Press, 2007. http://dx.doi.org/10.1093/oso/9780195313413.003.0022.
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The Patagonian steppes and the Río de la Plata grasslands occupy a vast proportion of the plains, plateaus, and hills of southern South America, and are characterized by the almost absolute absence of trees. Prairies and steppes (grass and low shrubs) are the dominant physiognomic types, and forests are restricted to some riparian corridors. Savannas become important only in the ecotones of these regions, whereas meadows may be locally important under particular topographic or edaphic conditions. The Río de la Plata grasslands (RPG), one of the most important grassland regions in the world, extend between 28°S and 38°S latitude, covering about 700,000 km2 of eastern Argentina, Uruguay, and southern Brazil. The boundaries of these grasslands include the Atlantic coastline to the east, dry temperate forests to the south and west, and subtropical humid forests to the north. Woody vegetation within the region is restricted to small areas near water bodies, such as the gallery forests along the large Paraná and Uruguay rivers and their tributary streams. The Patagonian steppes occupy the southern tip of the continent from approximately 40°S, and are framed by the Andes to the west and the Atlantic coast to the east and south and cover more than 800,000 km2 of Chile and Argentina. Toward the west, the region displays a sharp ecotone with the subantarctic forests, whereas to the north it grades into a broad zone of Monte scrublands in central Argentina. The RPG and the Patagonian steppes are separated by a wide strip of woody vegetation, the Monte and Espinal phytogeographic units (see chapter 10; Cabrera and Willkins, 1973). In this chapter, we describe the heterogeneity and main characteristics of the dominant ecosystems of the Patagonian steppes and the RPG, focusing on environmental controls and human-induced changes. Although numerous criteria have been applied to describe the internal heterogeneity of both regions, we emphasize here the structural and functional attributes of vegetation as integrators of climate, physiography, and land use.
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Greenland, David, and Mark Losleben. "Climate." In Structure and Function of an Alpine Ecosystem. Oxford University Press, 2001. http://dx.doi.org/10.1093/oso/9780195117288.003.0007.
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Climate is one of the most important determinants of biotic structure and function in the alpine. High winds and low temperatures are defining elements of this ecosystem, requiring adaptations of the alpine biota. Interaction between topography and snowcover strongly influences spatial heterogeneity of microclimate, which in turn influences and is influenced by the distribution of vegetation. For nearly 50 years investigators have used Niwot Ridge to examine and document the climate and its interaction with the biota of the alpine tundra. This chapter reviews some of the many findings of these ongoing bioclimatic investigations. Climate studies started on Niwot Ridge in October 1952 when Professor John W. Marr and his students set up a transect of climate stations across the Front Range between Boulder and the Continental Divide (Marr 1961). There were originally 16 stations in groups of four representing different slope exposures in what he defined as the Lower and Upper Montane Forest, the Subalpine Forest, and the Alpine Tundra ecosystems of the Front Range. After 1 year, the network was reduced to four stations, called Al, Bl, Cl, and Dl, which all had ridge-top locations and ranged from lower montane (Al) to high alpine (Dl). From time to time, these stations were supplemented by other stations that supported particular studies. This was especially true during the International Biological Programme years in the early 1970s when focus on work on the Saddle research site of the Ridge began. Following the establishment of Niwot Ridge and Green Lakes Valley as a Long-Term Ecological Research (LTER) site in 1980, even more intensive climatological work has been conducted. The construction of the Tundra Laboratory in August 1990 facilitated intensive winter climatological studies. Geographical locations and elevational data on most of the stations has been provided by Greenland (1989) and is also found in the LTER electronic database (http://culter.colorado.edu/). The climate of Niwot Ridge is characterized by large seasonal and annual variability with very windy and cold winters, wet springs, mild summers, and cool, dry autumns.
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Gray, John S., and Michael Elliott. "Diversity." In Ecology of Marine Sediments. Oxford University Press, 2009. http://dx.doi.org/10.1093/oso/9780198569015.003.0008.
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In the previous chapter we covered ways of describing samples of benthos, but specifically did not include diversity. We can talk of primary community variables, such as abundance (A), species richness (S) and biomass (B), and derived variables from these such as true diversity indices, evenness indices, and ratios indicating the relationship between species richness and abundance (A/S, the abundance ratio or the average abundance per species) and between biomass and abundance (B/A, the biomass ratio or the mean biomass per individual). Diversity is not just simply about the number of species found in a sample or area, but also uses data on the abundances of individuals among the species and the way those abundances are distributed among the species within the assemblage. There are many ways of describing diversity. Here we give a summary of the most important ones and reference sources of recent literature on the subject (see also the data analysis summary in Chapter 11). In the following section we consider simple indices (univariate) as measures of diversity; multivariate methods of analysing patterns will be covered in Chapter 7 on the effects of disturbance. The simplest way to measure diversity is the number of species found in a sample, called the species richness (S or SR). Yet diversity is not just about numbers of species; it is also concerned with the distribution of numbers of individuals per species. For example, if one assemblage has 50 individuals of each of 2 species A and B whereas another assemblage has 99 individuals of species A and 1 individual of species B, then both have the same species richness but the first assemblage is the more diverse. Thus a measure of diversity (an index) must take into account not only the number of species, but also the number of individuals per species. To distinguish this from species richness, the combination of individuals per species and number of species is called heterogeneity diversity. In fact there are a large number of diversity indices, and we do not propose to consider them all here (Magurran 2004 gives an excellent and detailed account and others are mentioned in the summary in Chapter 11).
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Luster, Markus, and Michael Lassmann. "Radio-iodine treatment of hyperthyroidism." In Oxford Textbook of Endocrinology and Diabetes, 481–84. Oxford University Press, 2011. http://dx.doi.org/10.1093/med/9780199235292.003.3196.
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Radioactive iodine has been used successfully for almost 70 years since the first treatment took place at the Massachusetts General Hospital in Boston in 1941. However, it was not until after the Second World War that 131I became generally available for clinical applications (1). The radioactive iodine isotope is chemically identical to ‘stable’ iodine (127I) and thus becomes a part of the intrathyroidal metabolism. Its principle of action is based on the emission of β-rays with a range of 0.5–2 mm in the tissue leading to high local radiation absorbed doses while sparing surrounding structures. The additional γ-ray component of 131I allows for scintigraphic imaging of the distribution in the gland and can also be used for pre- and post-therapeutic individual dosimetry (see below). Several therapeutic options are available for the treatment of benign thyroid disorders, namely hyperthyroidism: surgical resection (hemithyroidectomy, near-total, or total thyroidectomy), long-term antithyroid drug medication (ATD), and radio-iodine therapy (RAIT) (2, 3). These different treatment modalities are used in varying frequencies depending on geographical location, e.g. iodine supply, availability and logistics, cultural background, and patient-specific features, e.g. goitre size, presence of local symptoms, age, and hormonal status. The diversity of approaches on an international scale still remains impressive and is reflected by a great heterogeneity throughout Europe and also when compared to the USA where radio-iodine therapy is still being applied more frequently than in most European countries (4–8). Radio-iodine therapy was originally aimed at eliminating hyperthyroidism and thus leaving the patient euthyroid. Up-to-date strategies, however, established postradio-iodine induction of hypothyroidism as the treatment objective and, thus, it is included in the category of ‘cure’. This definition holds especially true for the management of Graves’ disease when long-term hypothyroidism was the rule and stabilization of euthyroidism failed in the majority of cases. In fact, the term ‘ablation’, meaning removal or destruction, has been increasingly used to characterize radio-iodine therapy and administration of larger amounts of radio-iodine have tended to make this a self-fulfilling prophecy. Although many clinicians prefer that the end result of treatment be the more easily managed hypothyroidism, others are still reluctant to give up the therapeutic ideal of euthyroidism as the preferred result of radio-iodine therapy and continue their efforts to solve the enigma of thyroid radiosensitivity.
Conference papers on the topic "Tree set heterogeneity"
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Abu Alsaud, Sara, Klemens Katterbauer, Abdulaziz Alqasim, and Alberto Marsala. "A Decision Tree Framework for Tracking CO2 Fronts in Carbonate Reservoirs from Deep Measurements Data." In International Petroleum Technology Conference. IPTC, 2022. http://dx.doi.org/10.2523/iptc-22394-ms.
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Abstract One of the main challenges in tracking CO2 fronts in carbonate reservoirs is the geological and petrophysical heterogeneity and complexity. This obstacle led to uncertainties in the decision-making and tracking processes. In current practices, empirical petrophysical formulas are utilized to model CO2 fronts in carbonate formations. These formulas has shown tremendous results and advancements in addressing such complexity and they are the stepping-stone to petrophysical modeling. However, the challenge is continuously augmented as the data grow. We present an innovative artificial intelligence framework to estimate CO2 fronts in carbonate reservoirs based on deep measurement data such as electromagnetics surveys and acoustic impedance, together with porosity profiles. The framework processes the deep data and then sets it as training data. Afterward, the framework uses a decision tree model, specifically a regression tree, to estimate the CO2 saturation front map based on the training data. The framework tests four types of regression trees in which each tree has a different minimum leaf size. The framework was tested on synthetic deep measurement data such as electromagnetic surveys, acoustic impedance, and porosity profiles. Expert processing was also included in the processing stage to remove illogical measurements in the training data. The proposed artificial intelligence framework is applied to the training data set. The decision tree framework produces four types of regression trees with different minimum leaf sizes. These different trees are classified as ultra-fine, fine, medium, and coarse. Overall, all regression trees showed a high resemblance to the original CO2 front. However, the tree with the smallest minimum leaf size, which is the ultra-fine tree, has the highest accuracy and certainty. As for the computational time, the coarse tree is considered to be the fastest. This framework represents an innovative approach to track CO2 fronts by combining deep measurement data such as electromagnetic surveys, acoustic impedance, and porosity profiles with an artificial intelligence framework. Also, the framework is aimed to improve inter-well saturation mapping for CO2 sequestration application. The approach is data-driven, and it takes into account the existing data-scarce petrophysical model challenges.
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Hanif, Amer, Elton Frost, Fei Le, Marina Nikitenko, Mikhail Blinov, and Nikolay Velker. "A Fast ANN Trained Solver Enables Real-Time Radial Inversion of Dielectric Dispersion Data & Accurate Estimate of Reserves in Challenging Environments." In SPE Middle East Oil & Gas Show and Conference. SPE, 2021. http://dx.doi.org/10.2118/204904-ms.
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Abstract Dielectric dispersion measurements are increasingly used by petrophysicists to reduce uncertainty in their hydrocarbon saturation analysis, and subsequent reserves estimation, especially when encountered with challenging environments. Some of these challenges are related to variable or unknown formation water salinity and/or a changing rock texture which is a common attribute of carbonate reservoirs found in the Middle East. A new multi-frequency, multi-spacing dielectric logging service, utilizes a sensor array scheme which provides wave attenuation and phase difference measurements at multiple depths of investigation up to 8 inches inside the formation. The improvement in depth of investigation provides a better measurement of true formation properties, however, also provides a higher likelihood of measuring radial heterogeneity due to spatially variable shallow mud-filtrate invasion. Meaningful petrophysical interpretation requires an accurate electromagnetic (EM) inversion, which accommodates this heterogeneity, while converting raw tool measurements to true formation dielectric properties. Forward modeling solvers are typically beset with a slow processing speed precluding use of complex, albeit representative, formation petrophysical models. An artificial neural network (ANN) has been trained to significantly speed up the forward solver, thus leading to implementation and real-time execution of a complex multi-layer radial inversion algorithm. The paper describes, in detail, the development, training and validation of both the ANN network and the inversion algorithm. The presented algorithm and ANN inversion has shown ability to accurately resolve mud filtrate invasion profile as well as the true formation properties of individual layers. Examples are presented which demonstrate that comprehensive, multi-frequency, multi-array, EM data sets are inverted efficiently for dis-similar dielectric properties of both invaded and non-invaded formation layers around the wellbore. The results are further utilized for accurate hydrocarbon quantification otherwise not achieved by conventional resistivity based saturation techniques. This paper presents the development of a new EM inversion algorithm and an artificial neural network (ANN) trained to significantly speed up the solution of this algorithm. This approach leads to a fast turnaround for an accurate petrophysical analysis, reserves estimate and completion decisions.
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Lin, Kangcheng, and Harrison M. Kim. "Investigate the Influence of Online Ratings and Reviews in Purchase Behavior Using Customer Choice Sets." In ASME 2021 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/detc2021-70806.
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Abstract The exponentially growing online reviews have become a great wealth of information into which many researchers have started tapping. Using online reviews as a source of customer feedback, product designers are able to better understand customers’ preferences and improve product design accordingly. However, while predicting future product demand as a function of product attributes and customer heterogeneity has proved to be effective, not many literatures have studied the impact of non-product-related features, such as number of reviews and average ratings, on product demand using a large-scale dataset. As such, this paper proposes a data-driven methodology to investigate the influence of online ratings and reviews in purchase behavior by using discrete choice analysis. In the absence of information about the true customer choice set, we generate an estimated customer choice set based on a probability sampling using customer clustering and product clustering. In order to examine the effect of number of reviews and average rating, we have computed, for all the laptops in the choice set of each customer, the number of reviews and thus average rating at the date of this particular customer’s review. Using laptops for our case study, our experiment has shown that the number of reviews and average ratings are statistically significant, and the inclusion of these features will greatly improve the predictive ability of the model.
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Irick, Kevin, and Nima Fathi. "Evaluation of Pore Geometry Effects on Porous Cell Thermal Behavior." In ASME 2020 Verification and Validation Symposium. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/vvs2020-8835.
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Abstract Heterogeneity in a material’s composition can have significant impacts on the thermal response of the material system at both the fine-scale and macro-scale levels. This is especially true for porous materials, where voids in the bulk material induce thermal resistance across the system and divert heat flow within the material. Within the energy industry, understanding these effects can be critical to designing components and systems that are often subjected to high-temperature environments. The current investigation is dedicated to studying the effect of pore geometry on the effective thermal conductivity, keff, of the whole porous unit cell. To this end, a numerical assessment of non-circular porous material simulated thermal responses was performed. A set of two-dimensional, steady-state models were defined to observe the thermal effects of different pore geometries — including triangular, square, and elliptical — centered in a unit cell porous medium. The finite element method (FEM) was implemented in Fortran — using unstructured triangular meshes — to simulate the thermal response of the systems. The method of manufactured solutions (MMS) was used to perform code verification and shows that the implementation of the numerical methods is approximately second-order accurate. This paper presents a study on the effects of pore size, shape, and rotational orientation on a heterogeneous material’s dimensionless effective thermal conductivity, k*. Comparative thermal responses show the sensitivity of k* with respect to pore shape and the variable sensitivity of response to pore orientation, where pore size is a major driver in the effective thermal response.
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Ponomareva, Daria, Mauricio Corona, Nata Franco, Sajjad Ahmed, and Mohammed AlAwfi. "Integrated Approach to Drill Curve and Vertical Sections Across Multiple Porous Unstable Carbonate Formations with Superior Borehole Quality for Multi-Stage Fracking Completions in Deep Gas Wells." In International Petroleum Technology Conference. IPTC, 2022. http://dx.doi.org/10.2523/iptc-22053-ms.
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Abstract This paper will present the integrated approach taken to ensure high wellbore quality delivered across the reservoir sections while drilling in deep vertical gas wells to successfully run and set multi-stage fracking (MSF) completion or cemented liner. It also covers the integrated approach to drilling the curve section in horizontal wells to ensure well objectives will be met when drilling horizontal holes across the reservoir. The gas field is characterized by a high level of lithological and geological heterogeneity, productions zones in such deep wells (more than 13,000 ft True Vertical Depth (TVD)) with different pore pressure had to be combined in the same section some cases due to well design limitations and production objectives. Applying industry-standard overbalance pressure while drilling is not enough to keep the wellbore stable and create a gauge borehole; therefore, an integrated approach was implemented in the planning and execution stages. As a result, it allowed combining depleted and charged production zones in the same section with a maximum of 4-5 Pounds Per Gallon (PPG) Equivalent Mud Weight (EMW) difference in pore pressure and keep the wellbore stable. This difference in overbalance is still manageable in vertical holes. However, the results can be very challenging in high inclination intervals. Drilling the build-up/landing portion in horizontal wells can be very challenging from the directional work perspective. The landing of this production liner needs to cover most of the caprock as this is the key to avoiding any disturbance on the borehole while drilling the horizontal section below the previous liner shoe across the unstable cap rock. The proper selection of the mud weight requires geomechanics and structural models to anticipate any rock failure. Landing the previous production liner at the planned inclination will help to reduce the directional work amount left in the horizontal section. Any directional work in the horizontal section is limited to 1 deg/100 ft Dog Leg Severity (DLS). Based on the field experience, DLS bigger than 1 deg/100ft will complicate the deployment of the lower completion string, either MSF or Cemented Liner. From the operational point of view, the building angle in the build-up/landing section is limited by the power transmitted from the surface to the downhole tools, rotation, and hydraulic power. Also, the selection of the directional tools is the key for performance; the wrong selection of the directional tool can compromise the directional work due to hydraulic power limitation that can be applied. Last but not least, the high overbalance environment (2000-4000 psi) in the build-up/landing section plus the lithological heterogeneity and interbedded formations represent additional risks that should not be ignored, such as downhole mud losses and stuck pipe incidents. Combined expertise and project experience enabled an integrated approach while planning and executing these challenging wells. The proper geomechanical study, Bottom Hole Assembly configuration, bit selection, fluid bridging strategy, directional work distribution, and selection and control of drilling parameters together allowed achieving main targets in deep gas wells in the Middle East.
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Aslanyan, Artur Mikhailovich, Rushana Rinatovna Farakhova, Danila Nikolayevich Gulyaev, Ramil Anvarovich Mingaraev, and Ruslan Ildarovich Khafizov. "Comparative Analysis of Tracers Against Pressure Pulse Code Interference Testing based on the Numerical Simulations of the Synthetic Oilfields with Complicated Geology." In SPE Russian Petroleum Technology Conference. SPE, 2021. http://dx.doi.org/10.2118/206493-ms.
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Abstract The main objective of the study is to compare the results of the cross-well tracers survey against the pulse code pressure interference testing (PCT) for the complicated geological structures. The study was based on the numerical simulations on the synthetic 3D models with popular geological complications, such as faults, vertical and horizontal reservoir anisotropy and pinch-outs. The study has set a special focus on quantitative analysis of the reservoir properties estimated by tracers and PCT as against the known values. This provides a text-book examples of advantages and disadvantages of both surveillance methods in different geological environment. Pulse code testing is specific implementation of pressure interference testing by creating a series of injection/production rate changes accordingly to a preset schedule to create a "pressure code" and monitoring the pressure response in the offset wells. The use of high-resolution quarts gauges is highly beneficial in case of large cross-well intervals scanning or poor reservoir quality in case of regular inter-well spacing. The tracer survey is based on injecting a liquid with chemical markers and subsequent capturing the markers at surface samples in the offset wells. The modern markers are relatively cheap and can be captured at very low concentrations thus making the cross-well scanning available even for high inter-well spacing. For synthetic models with vertical inhomogeneity the PCT provides a close estimate for compound dynamic reservoir properties (transmissibility and pressure diffusivity). For synthetic models with lateral inhomogeneity the PCT provides an accurate estimation for effective reservoir thickness and permeability. Tracers survey is not able to assess the reservoir thickness. The popular methods to assess reservoir permeability from tracers survey show a substantial deviation from the true reservoir permeability for synthetic models with vertical and lateral heterogeneity. This leads to conclusion that the most reliable application of racers survey is a qualitative assessment of cross-well connectivity and quantitative estimate of permeability in homogenous reservoirs. The first study of quantitative comparison of tracer survey against pressure pulse-code interference survey. Tracer survey and PCT efficiency was compared on 3D numerical models. Presence of synthetic models, describing geological complications, which may be seen very often on real reservoirs, provides a reliable basis for comparison.
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Datir, Harish, Knut Arne Birkedal, Sachin Kriplani, Hege Porten, and Niles Andre Aarseth. "ENHANCING THE RESERVOIR PERFORMANCE BY ACCESSING THE RESERVOIR SWEET SPOTS GUIDED BY FAR-FIELD SONIC IMAGING: AN INTEGRATED CASE STUDY FROM THE NORWEGIAN NORTH SEA." In 2021 SPWLA 62nd Annual Logging Symposium Online. Society of Petrophysicists and Well Log Analysts, 2021. http://dx.doi.org/10.30632/spwla-2021-0057.
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The gas present in the Valhall overburden crest area interferes with the seismic data and obscures the fault detection (minor faults). Spatially resolving fractures and fracture network is essential for subsurface understanding and future well placement in this field, and it is a critical input to the dynamic reservoir model. Additionally, mapping the fracture network in poor permeable reservoir formation beyond the wellbore is crucial to identify completion intervals to maximize productivity/injectivity, and hence field value. The well 2/8-F-18 A was drilled on the crest of the Valhall field as a pilot water injector in Lower Hod formation, where core and data analysis formed the foundation for a future potential 11 well development. The well is placed in the southern section of the Valhall crest, and no major faults or strong amplitude features were mapped out in the overburden via surface seismic before drilling. In this case study, an integrated workflow is proposed and tested within the reservoir formation to identify “sweet” (permeable and fractured) zones beyond the wellbore. This is achieved using borehole acoustic data combined with image and ultrasonic imaging to characterize fracture networks beyond the borehole wall. The sonic imaging workflow identifies reflection events from fractures and faults and provides the true dip, azimuth, and location in 3-dimensions. This data is complemented by nuclear magnetic resonance (NMR), dielectric and spectroscopy data to understand reservoir petrophysics. NMR-derived permeability has also been evaluated for identifying high permeable zone in this formation, which primarily focuses on intergranular permeability of the formation a few inches away from the borehole wall. Reservoir textural heterogeneity and fractures beyond the wellbore wall make this method difficult to estimate or enhance the effective permeability estimate. The baseline assumption for the NMR permeability estimation is also not valid in Hod formation; the Timur and SDR equation needs significant change to match core permeability. Hence, the primary aim is to identify a fracture network that will help support water injection and maximize hydrocarbons production through them. The goal is to establish a workflow from the learnings of this study, performed on the pilot well, validate its findings with the near-field data (core, imaging, and ultrasonic), and optimize it if needed (described in the methodology section). The developed workflow is then intended to be used to optimize the placement of future wells. The results achieved from the integrated workflow identified a key fault and mapped it approximately 23 meters away on each side of the borehole. It also captures acoustic anomalies (high amplitudes), validated based on near-field data, resulting from a fracture network potentially filled with hydrocarbons. The final results show the sub-seismic resolution of the fracture and fault network not visible on surface seismic due to the gas cloud above the reservoir and frequency effect on the surface seismic when compared to borehole sonic data. Evidently enhancing the blurred surface image, which helps enhance the structural and dynamic model of the reservoir.
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Ciabarri, Fabio, Marco Pirrone, and Cristiano Tarchiani. "ANALYTICAL UNCERTAINTY PROPAGATION IN FACIES CLASSIFICATION WITH UNCERTAIN LOG-DATA." In 2021 SPWLA 62nd Annual Logging Symposium Online. Society of Petrophysicists and Well Log Analysts, 2021. http://dx.doi.org/10.30632/spwla-2021-0071.
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Log-facies classification aims to predict a vertical profile of facies at well location with log readings or rock properties calculated in the formation evaluation and/or rock-physics modeling analysis as input. Various classification approaches are described in the literature and new ones continue to appear based on emerging Machine Learning techniques. However, most of the available classification methods assume that the inputs are accurate and their inherent uncertainty, related to measurement errors and interpretation steps, is usually neglected. Accounting for facies uncertainty is not a mere exercise in style, rather it is fundamental for the purpose of understanding the reliability of the classification results, and it also represents a critical information for 3D reservoir modeling and/or seismic characterization processes. This is particularly true in wells characterized by high vertical heterogeneity of rock properties or thinly bedded stratigraphy. Among classification methods, probabilistic classifiers, which relies on the principle of Bayes decision theory, offer an intuitive way to model and propagate measurements/rock properties uncertainty into the classification process. In this work, the Bayesian classifier is enhanced such that the most likely classification of facies is expressed by maximizing the integral product between three probability functions. The latters describe: (1) the a-priori information on facies proportion (2) the likelihood of a set of measurements/rock properties to belong to a certain facies-class and (3) the uncertainty of the inputs to the classifier (log data or rock properties derived from them). Reliability of the classification outcome is therefore improved by accounting for both the global uncertainty, related to facies classes overlap in the classification model, and the depth-dependent uncertainty related to log data. As derived in this work, the most interesting feature of the proposed formulation, although generally valid for any type of probability functions, is that it can be analytically solved by representing the input distributions as a Gaussian mixture model and their related uncertainty as an additive white Gaussian noise. This gives a robust, straightforward and fast approach that can be effortlessly integrated in existing classification workflows. The proposed classifier is tested in various well-log characterization studies on clastic depositional environments where Monte-Carlo realizations of rock properties curves, output of a statistical formation evaluation analysis, are used to infer rock properties distributions. Uncertainty on rock properties, modeled as an additive white Gaussian noise, are then statistically estimated (independently at each depth along the well profile) from the ensemble of Monte-Carlo realizations. At the same time, a classifier, based on a Gaussian mixture model, is parametrically inferred from the pointwise mean of the Monte Carlo realizations given an a-priori reference profile of facies. Classification results, given by the a-posteriori facies proportion and the maximum a-posteriori prediction profiles, are finally computed. The classification outcomes clearly highlight that neglecting uncertainty leads to an erroneous final interpretation, especially at the transition zone between different facies. As mentioned, this become particularly remarkable in complex environments and highly heterogeneous scenarios.
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Gomez Lopez, Claudia, Rosa Lina Cuozzo, and Paula Boldrini. "Impactos de las políticas públicas de hábitat en la construcción del espacio urbano: el caso del Área Metropolitana de Tucumán, Argentina." In International Conference Virtual City and Territory. Roma: Centre de Política de Sòl i Valoracions, 2014. http://dx.doi.org/10.5821/ctv.8026.
Full textAbstract:
En América Latina, la implantación del neoliberalismo como sistema económico ha llevado a un
modelo de desarrollo con elevada heterogeneidad y desigualdad socioeconómica. De la mano
de grandes cambios sociales y demográficos, las áreas urbanas experimentaron un acelerado
desarrollo, crecimiento económico desigual en la distribución del ingreso, el aumento del
desempleo y altos niveles de informalidad urbana.
Enmarcado en esta realidad la producción del espacio urbano, se llevó adelante a través de la
gestión de tres actores sociales: 1.el mercado inmobiliario; 2. el Estado nacional y 3. los
asentamientos informales.
De ellos, el estado cumple un rol fundamental en la construcción de la ciudad encauzando o
restringiendo el desarrollo de ciertos espacios ya sea a través de la acción (implementación de
políticas públicas, normativas, etc.) o de la omisión.
En un contexto en el que persiste la ausencia de planificación, la carencia de un marco que
defina el modo de ocupación del territorio, impone la lógica del mercado inmobiliario como
criterio urbanístico principal, incluso para las actuaciones de promoción pública de vivienda.
Ello impacta de modo negativo en la ciudad en la medida que favorece la especulación en
manos del sector privado, produce segregación residencial y desigualdad en el acceso al suelo
puesto que amplios sectores quedan fuera del mercado formal. Lo cual se tradujo en la
conformación de áreas diferenciadas dentro de la ciudad agudizando la separación entre
sectores sociales.
A partir del 2003, en Argentina en virtud al crecimiento económico que se produce con
posterioridad a la crisis 2001-2002, el Estado Nacional retomó los planes de vivienda a fin de
dar solución al problema habitacional haciendo hincapié en programas de relocalización,
radicación y regularización dominial de villas y asentamientos informales, articulando con
trabajo cooperativo que implicaba la intervención una medida conjunta con el problema de
desocupación.
A las existentes políticas habitaciones de construcción de viviendas ejecutadas por los
Institutos Provinciales de Vivienda (IPV), se sumaron un conjunto de políticas sociales que
articulan programas de diversos órdenes, nacional, municipal, provincial y del IPV. (Argentina
Trabaja, Municipio+Cerca, PROMEVI, PROMEBA, etc) enlazando la problemática habitacional
a la social.
Sin embargo estas medidas no revierten el sentido dominante que poseen las políticas públicas
en materia de vivienda (del Río y Duarte, 2012) puesto que la construcción de viviendas sin sustento normativo ni planificación, o la consolidación y regularización de asentamientos
populares en áreas vulnerables, lejos de mitigar las desigualdades existentes, producen
efectos negativos en la ciudad.
En este contexto, este trabajo analiza las consecuencias de las nuevas políticas habitacionales
en el Área Metropolitana de Tucumán (AmeT), a casi 10 años de implementación de un
conjunto de medidas sociales específicas, en teoría tendientes a la equidistribución del acceso
al suelo urbano. In Latin America, the implementation of neoliberalism as an economic system has led to a
development model with high heterogeneity and socioeconomic inequality.
The adoption of policies of liberalization, deregulation and economic flexibility, along with the
withdrawal of the state of urban management, major changes occurred in the cities.
In the hands of great social and demographic change, urban areas experienced rapid
development, uneven economic growth in the distribution of income, rising unemployment and
high levels of urban informality.
Framed in this reality, the production of urban space, was carried out by the management of
three social actors: 1.The real estate market; 2 and 3 the national state informal settlements.
Of these, the state plays a key role in building the city damming or restricting the development
of certain areas either through action (implementation of public policies, regulations, etc.) or
omission.
Therefore, in a context in which the lack of planning continues, the lack of a framework defining
how land occupation imposes the logic of urban real estate market as the main criterion, even
for actions of public housing development.
This impacts negatively on the city to the extent that speculation favors the private sector,
produce residential segregation and inequality in access to land as large sections remain
outside the formal market. Which results in the formation of distinct areas within the city
exacerbating the gap between social sectors.
In Argentina, under the economic growth that occurs after the 2001-2002 crisis, the Federal
Government returned home plans to solve the housing problem but with a twist to the social, to
meet the needs of the most vulnerable sectors of society.
From being solely residential construction (turnkey system) executed by the Provincial Housing
Institutes (IPV), policies will be passed to a set of social policies that articulate programs of
various orders, domestic, municipal, provincial and IPV. (Argentina Works, Municipality + Close,
PROMEVI, PROMEBA Law Pierri implementation of regularization, etc.) that link to social
housing problems.
However, this has not had the expected results in relation to urban problems.
While the need for regional planning was promoted through the PET National and Provincial
(Regional Strategic Plan), all implemented programs were developed without proper management tools to define the criteria for the consolidation and development from the Federal
Government city and thus ended conspiring against it, as a stage of collective life. The lack of
training of local technicians, the use of these programs clientelitas purposes by local politicians
and rampant corruption, contributed to aggravating the observed trends.
This suggests that the construction of new housing or consolidation or regularization of squatter
settlements in vulnerable areas without legal justification and planning, far from mitigating the
inequalities, negative effects on the city.
Under this hypothesis, this paper analyzes the impact of new housing policies in the
Metropolitan Area of Tucumán (AMET), nearly 10 years of implementing a set of tending to the
equal distribution of access to urban land social measures.
It is concluded that the actions taken by the State produced an increase and consolidate the
processes of fragmentation and emerging socio-spatial segregation of Tucuman AMET.