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Dissertations / Theses on the topic 'Spatial point patterns analysis'

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Published: 4 June 2021
Last updated: 7 February 2022

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1

Wilson, Helen Elizabeth. "Statistical analysis of replicated spatial point patterns." Thesis, Lancaster University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268009.

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The field of pathology provides us with many opportunities for collecting replicated spatial data. Using an ordinary microscope, for example, we can digitise cell positions within windows imposed on pieces of tissue. Suppose now that we have some such replicated spatial data from several groups of individuals, where each point in each window represents a cell position. We seek to determine whether the spatial arrangement of cells differs between the groups. We propose and develop a new method which allows us to answer such questions, and apply it to some spatial neuro-anatomical data. We introduce point process theory, and extend the existing second order methods to deal with replicated spatial data. We conclude the first part of the thesis by defining Sudden Infant Death Syndrome (S.LD.S.) and Intra-Uterine Growth Retardation (LU.G.R.), and stating why these conditions are neuro-anato,mically interesting. We develop and validate a method for comparing groups of spatial data, which is motivated by analysis of variance, and uses a Monte Carlo procedure to attach significance to between-group differences. Having carried out our initial investigative work looking exclusively at the one-way set up, we extend the new methods to cope with two and higher way set ups, and again carry out some validation. We turn our attention to practical issues which arise in the collection of spatial neuroanatomical data. How, for example, should we collect the data to ensure the unbiasedness of any inference we may draw from it? We introduce the field of stereology which facilitates the unbiased sampling of tissue. We note a recent proposal to assess spatial distribution of cells using a stereological approach, and compare it with an existing second order method. We also note the level of structural heterogeneity within the brain, and consider the best way to design a sampling protocol. We conclude with a spatial analysis of cell position data, collected using our specified design, from normal birth-weight non S.LD.S., normal birth-weight S.I.D.S and low birth-weight S.LD.S cases.
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2

Doguwa, S. I. "Statistical analysis of mapped spatial point patterns." Thesis, University of Essex, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383379.

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3

Pereira, Sandra M. C. "Analysis of spatial point patterns using hierarchical clustering algorithms." University of Western Australia. School of Mathematics and Statistics, 2003. http://theses.library.uwa.edu.au/adt-WU2004.0056.

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[Formulae and special characters can only be approximated here. Please see the pdf version of the abstract for an accurate reproduction.] This thesis is a new proposal for analysing spatial point patterns in spatial statistics using the outputs of popular techniques of (classical, non-spatial, multivariate) cluster analysis. The outputs of a chosen hierarchical algorithm, named fusion distances, are applied to investigate important spatial characteristics of a given point pattern. The fusion distances may be regarded as a missing link between the fields of spatial statistics and multivariate cluster analysis. Up to now, these two fields have remained rather separate because of fundamental differences in approach. It is shown that fusion distances are very good at discriminating different types of spatial point patterns. A detailed study on the power of the Monte Carlo test under the null hypothesis of Complete Spatial Randomness (the benchmark of spatial statistics) against chosen alternative models is also conducted. For instance, the test (based on the fusion distance) is very powerful for some arbitrary values of the parameters of the alternative. A new general approach is developed for analysing a given point pattern using several graphical techniques for exploratory data analysis and inference. The new strategy is applied to univariate and multivariate point patterns. A new extension of a popular strategy in spatial statistics, named the analysis of the local configuration, is also developed. This new extension uses the fusion distances, and analyses a localised neighbourhood of a given point of the point pattern. New spatial summary function and statistics, named the fusion distance function H(t), area statistic A, statistic S, and spatial Rg index, are introduced, and proven to be useful tools for identifying relevant features of spatial point patterns. In conclusion, the new methodology using the outputs of hierarchical clustering algorithms can be considered as an essential complement to the existing approaches in spatial statistics literature.
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4

Soale, Abdul-Nasah. "Spatio-Temporal Analysis of Point Patterns." Digital Commons @ East Tennessee State University, 2016. https://dc.etsu.edu/etd/3120.

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In this thesis, the basic tools of spatial statistics and time series analysis are applied to the case study of the earthquakes in a certain geographical region and time frame. Then some of the existing methods for joint analysis of time and space are described and applied. Finally, additional research questions about the spatial-temporal distribution of the earthquakes are posed and explored using statistical plots and models. The focus in the last section is in the relationship between number of events per year and maximum magnitude and its effect on how clustered the spatial distribution is and the relationship between distances in time and space in between consecutive events as well as the distribution of the distances.
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5

González, Monsalve Jonatan A. "Statistical tests for comparisons of spatial and spatio-temporal point patterns." Doctoral thesis, Universitat Jaume I, 2018. http://hdl.handle.net/10803/462034.

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We mainly introduce a new set of tests to compare functional descriptors in point processes context. Firstly, since the study of spatio-temporal point processes has not been widely covered in the literature, a complete review is made. The review is a reference paper of the available techniques and approaches regarding the spatio-temporal context. Secondly, a studentized permutation test is developed in the spatio-temporal case. This test is motivated by locations of tornadoes in the U.S. in a period of 36 years. Some tools have been developed as a non-separable estimator of the first-order intensity, which allows a realistic analysis of the phenomenon through the new test. Finally, a factorial two-way design is considered, where the observations are spatial point patterns in presence of replication. This methodology is motivated by a minerals engineering experiment. We develop statistics to test the influence of the factors and the possible interaction effects.
Desarrollamos un nuevo conjunto de pruebas para comparar descriptores funcionales en el contexto de procesos puntuales. Puesto que el estudio de los procesos puntuales espacio-temporales no ha sido muy exhaustivo en la literatura, hemos hecho un artículo de resumen. Introducimos un test de permutación para grupos de patrones puntuales espacio-temporales motivado por las ubicaciones de ocurrencias de tornados en EE.UU. durante 36 años. Hemos desarrollado algunas técnicas como la estimación de la intensidad de primer-orden sin suponer separabilidad, lo que permite un tratamiento más realista del fenómeno climático en sí mismo a través del nuevo test.Finalmente, hemos desarrollado algunas técnicas para el análisis de la varianza de experimentos de dos factores en presencia de réplicas cuando las observaciones son patrones puntuales espaciales. Esta metodología está motivada por un experimento de ingeniería de minerales. Desarrollamos algunos estadísticos adecuados para probar la influencia de los factores y su posible interacción.
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6

Stanford, Derek C. "Fast automatic unsupervised image segmentation and curve detection in spatial point patterns /." Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/8976.

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7

Eckel, Stefanie. "Statistical analysis of spatial point patterns - applications to economical, biomedical and ecological data." [S.l. : s.n.], 2008. http://nbn-resolving.de/urn:nbn:de:bsz:289-vts-66022.

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8

Umande, Philip Pembe. "Spatial point pattern analysis with application to confocal microscopy data." Thesis, Imperial College London, 2008. http://hdl.handle.net/10044/1/8569.

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9

Wong, Ka Yiu. "Model-free tests for isotropy, equal distribution and random superposition in spatial point pattern analysis." HKBU Institutional Repository, 2015. https://repository.hkbu.edu.hk/etd_oa/202.

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This thesis introduces three new model-free tests for isotropy, equal distribution and random superposition in non-rectangular windows respectively. For isotropy, a bootstrap-type test is proposed. The corresponding test statistic assesses the discrepancy between the uniform distribution and the empirical normalised reduced second-order moment measure of a sector of fixed radius with increasing central angle. The null distribution of the discrepancy is then estimated by stochastic reconstruction, which generates bootstrap-type samples of point patterns that resemble the spatial structure of the given pattern. The new test is applicable for small sample sizes and is shown to have more robust powers to different choices of user-chosen parameter when compared with the asymptotic chi-squared test by Guan et al. (2006) in our simulation. For equal distribution, a model-free asymptotic test is introduced. The proposed test statistic compares the discrepancy between the empirical second-order product densities of the observed point patterns at some pre-chosen lag vectors. Under certain mild moment conditions and a weak dependence assumption, the limiting null distribution of the test statistic is the chi-squared distribution. Simulation results show that the new test is more powerful than the permutation test by Hahn (2012) for comparing point patterns with similar structures but different distributions. The new test for random superposition is a modification of the toroidal shift test by Lotwick and Silverman (1982). The idea is to extrapolate the pattern observed in a non-rectangular window to a larger rectangular region by the stochastic reconstruction so that the toroidal shift test can be applied. Simulation results show that the powers of the test applied to patterns with extrapolated points are remarkably higher than those of the test applied to the largest inscribed rectangular windows, with only slightly increased type I error rates. Real data sets are used to illustrate the advantages of the tests developed in this thesis over the existing tests in the literature.
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10

Catella, Samantha A. "Investigating herbaceous layer plant community patterns: when does abiotic complexity matter?" Case Western Reserve University School of Graduate Studies / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=case1559905264222712.

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11

Ben, Cheikh Bassem. "Morphologie mathématique sur les graphes pour la caractérisation de l’organisation spatiale des structures histologiques dans les images haut-contenu : application au microenvironnement tumoral dans le cancer du sein." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066286/document.

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L'un des problèmes les plus complexes dans l'analyse des images histologiques est l'évaluation de l¿organisation spatiale des structures histologiques dans le tissu. En fait, les sections histologiques peuvent contenir un très grand nombre de cellules de différents types et irrégulièrement réparties dans le tissu, ce qui rend leur contenu spatial indescriptible d'une manière simple. Les méthodes fondées sur la théorie des graphes ont été largement explorées dans cette direction, car elles sont des outils de représentation efficaces ayant la capacité expressive de décrire les caractéristiques spatiales et les relations de voisinage qui sont interprétées visuellement par le pathologiste. On peut distinguer trois familles principales de méthodes des graphes utilisées à cette fin: analyse de structure syntaxique, analyse de réseau et analyse spectrale. Cependant, un autre ensemble distinctif de méthodes basées sur la morphologie mathématique sur les graphes peut être développé et adapté pour ce problème. L'objectif principal de cette thèse est le développement d'un outil capable de fournir une évaluation quantitative des arrangements spatiaux des structures histologiques en utilisant la morphologie mathématique basée sur les graphes
One of the most challenging problems in histological image analysis is the evaluation of the spatial organizations of histological structures in the tissue. In fact, histological sections may contain a very large number of cells of different types and irregularly distributed, which makes their spatial content indescribable in a simple manner. Graph-based methods have been widely explored in this direction, as they are effective representation tools having the expressive ability to describe spatial characteristics and neighborhood relationships that are visually interpreted by the pathologist. We can distinguish three main families of graph-based methods used for this purpose: syntactic structure analysis, network analysis and spectral analysis. However, another distinctive set of methods based on mathematical morphology on graphs can be additionally developed for this issue. The main goal of this dissertation is the development of a framework able to provide quantitative evaluation of the spatial arrangements of histological structures using graph-based mathematical morphology
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12

Zhang, Weimin. "Topics in living cell miultiphoton laser scanning microscopy (MPLSM) image analysis." Texas A&M University, 2006. http://hdl.handle.net/1969.1/4412.

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Multiphoton laser scanning microscopy (MPLSM) is an advanced fluorescence imaging technology which can produce a less noisy microscope image and minimize the damage in living tissue. The MPLSM image in this research is the dehydroergosterol (DHE, a fluorescent sterol which closely mimics those of cholesterol in lipoproteins and membranes) on living cell's plasma membrane area. The objective is to use a statistical image analysis method to describe how cholesterol is distributed on a living cell's membrane. Statistical image analysis methods applied in this research include image segmentation/classification and spatial analysis. In image segmentation analysis, we design a supervised learning method by using smoothing technique with rank statistics. This approach is especially useful in a situation where we have only very limited information of classes we want to segment. We also apply unsupervised leaning methods on the image data. In image data spatial analysis, we explore the spatial correlation of segmented data by a Monte Carlo test. Our research shows that the distributions of DHE exhibit a spatially aggregated pattern. We fit two aggregated point pattern models, an area-interaction process model and a Poisson cluster process model, to the data. For the area interaction process model, we design algorithms for maximum pseudo-likelihood estimator and Monte Carlo maximum likelihood estimator under lattice data setting. For the Poisson Cluster process parameter estimation, the method for implicit statistical model parameter estimate is used. A group of simulation studies shows that the Monte Carlo maximum estimation method produces consistent parameter estimates. The goodness-of-fit tests show that we cannot reject both models. We propose to use the area interaction process model in further research.
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13

Hesselbarth, Maximilian H. K. [Verfasser], Kerstin [Akademischer Betreuer] Wiegand, Holger [Gutachter] Kreft, and Uta [Gutachter] Berger. "Analysing and modelling spatial patterns to infer the influence of environmental heterogeneity using point pattern analysis, individual-based simulation modelling and landscape metrics / Maximilian H. K. Hesselbarth ; Gutachter: Holger Kreft, Uta Berger ; Betreuer: Kerstin Wiegand." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2020. http://d-nb.info/1210264641/34.

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14

Chen, Yan. "Spatial Analysis of Fatal Automobile Crashes in Nashville, TN, 2001-2011." TopSCHOLAR®, 2013. http://digitalcommons.wku.edu/theses/1300.

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With increasing levels of motor vehicle ownership, automobile crashes have become a serious public issue in the U.S. and around the world. Knowing when, where, and how traffic accidents happen is critical in order to ensure road safety and to plan for adequate road infrastructure. There is a rich body of literature pertaining to time-related fatal crashes, most of which focuses on non-spatial factors such as a driver’s visibility at night, drinking and drug use, and road conditions. These studies provide a theoretical basis for understanding the causes of crashes from a non-spatial perspective, and a number of traffic laws and policies consequently have been enacted to minimize the impacts of non-spatial factors. Over the past few years, advances in Geographic Information Systems (GIS) have greatly enhanced our ability to analyze traffic accidents from a spatial perspective. This study aims to fill a void in traffic safety studies by comparing and analyzing the differences in the spatial distribution of fatal crashes based on temporal factors, specifically in three periods: 1) day and night; 2) A.M. rush hours and P.M. rush hours; and 3) weekdays and weekends. With the Nashville Metropolitan Area as the study area, the research utilized a number of spatial point-pattern analysis (SPPA) methods, including planar KDE, planar global auto K function, network global cross K functions, and network local cross K functions. All fatal crashes in the Nashville area were found to be clustered and generally follow the patterns of average daily traffic flow. All time-based subtypes of fatal crashes also were found to be concentrated within the central urban area of Nashville, mostly along major roads, and especially near major road intersections and highway interchanges. No notable spatial differences were detected among the subtypes of fatal crashes when applying network global cross K function. However, with the help of the network local cross K function, some localized spatial differences were identified. Some specific locations of hotspots of nighttime and P.M. rush hour fatal crashes were found not to be at the same locations as those at of daytime and A.M. rush hour fatal crashes, respectively. The approach adopted in this study not only provides a new way to analyze spatial distribution of spatial point events such as fatal crashes, but it also can be applied readily to real-world applications. A good understanding of where these spatial differences are should help various agencies practice effective measures and policies in order to improve road conditions, reduce traffic accidents, and ensure road safety.
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15

Barber, Michael R. "Effects of Hydraulic Dredging and Vessel Operation on Atlantic Sturgeon Behavior in a Large Coastal River." VCU Scholars Compass, 2017. http://scholarscompass.vcu.edu/etd/4792.

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The tidal James River, a focus of VCU's Atlantic Sturgeon program, supports both commercial shipping and hydraulic dredging. These anthropogenic threats present documented but preventable sources of mortality to the endangered species. Using three separate VEMCO Positioning System (VPS) receiver arrays, spatial data of previously-tagged fish were collected. ArcGIS and Programita software were used to analyze fish spatial distributions in the presence and absence of potential threats, using additional data including automatic identification system (AIS) vessel locations, vessel passages compiled using camera footage, and dredge records provided by the US Army Corps of Engineers. The data showed a change in distribution associated with vessels that varied according to river width but not vessel type. Dredging was associated with differences in spatial distribution, but more clearly for adults than sub-adults. The responses of Atlantic Sturgeon provide information necessary to propose potential threat mitigations, including seasonal restrictions for both vessels and dredging.
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Allié, Élodie. "Assemblage des communautés d’arbres à une échelle locale en forêt tropicale : Apport d’une approche intégrative." Thesis, Guyane, 2016. http://www.theses.fr/2016YANE0003/document.

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Les forêts tropicales représentent un ‘hotspot’ de diversité avec un nombre considérable d’espèces qui coexistent jusqu’à une échelle locale fine. Plus particulièrement, 16 000 espèces d’arbres coexistent en Amazonie, 1 800 en Guyane française et entre 120 et plus de 200 espèces d’arbres par hectare. Cependant, le maintien de cette diversité face aux changements globaux actuels et à venir (qu’ils soient anthropiques ou climatiques…) est incertain. Avant de pouvoir prédire l’évolution de la diversité face aux changements globaux, un travail fondamental est nécessaire afin de comprendre les processus d’assemblage des communautés, processus qui maintiennent cette diversité. Ce travail est réalisé depuis de nombreuses années en écologie et reste d’actualité vu l’absence de consensus quant à l’importance relative des processus d’assemblage. Cette thèse s’inscrit dans la continuité de ce travail fondamental en utilisant une approche intégrative innovante, qui aborde de manière multi-échelle trois types de diversité : diversité taxonomique, fonctionnelle et phylogénétique. Nos résultats questionnent sur l'importance du filtrage environnemental quant aux propriétés hydrologiques et chimiques des sols, et sur celle des interactions biotiques dans l’assemblage de la communauté étudiée. Par ailleurs, nos résultats suggèrent que les distributions d’espèces puissent être influencées par la dynamique forestière en lien avec les chutes d’arbres et donc avec la disponibilité en lumière. Enfin, nous avons mis en évidence l’importance de la limitation de dispersion
Tropical forests are a biodiversity hotspot, with the coexistence of numerous species until a fine spatial scale. Particularly, 16.000 tree species coexist in Amazonia, 1.800 in Frenche Guiana and between 120 and more than 200 tree species per hectare. However, there are some uncertainties in maintaining diversity in regard to global changes. Hence before predicting the diversity evolution face of global changes, fundamental studies are needed to understand which assembly processes are involved in the maintenance of diversity. These fundamental studies still relevant given the lack of consensus on the relative importance of assembly processes. This thesis is a continuation of these fundamental studies, using innovative integrative approach, at multi-scale, to address three types of diversity: taxonomic diversity, functional and phylogenetic. Our results challenge the importance of environmental filtering for hydrological and chemical properties of soils, versus the importance of biotic interactions on community assembly. Furthermore, our results suggest that species distributions could be affected by forest dynamics related to falling trees and therefore by light availability. Finally, we have highlighted the importance of dispersal limitation on community assembly
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17

Filho, NarcÃlio de SÃ Pereira. "AnÃlise da dinÃmica espaÃo-temporal (1973 a 2014) das dunas de Jericoacoara, CearÃ, Brasil." Universidade Federal do CearÃ, 2014. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=15910.

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CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior
Dunas costeiras exercem um importante papel na manutenÃÃo do fluxo de sedimentos da zona costeira. O Parque Nacional de Jericoacoara, localizado no estado do CearÃ, regiÃo Nordeste do Brasil, possui uma morfologia pouco frequente, trata-se de um promontÃrio associado com um campo de dunas mÃveis denominadas barcanas, dunas individuais, de grande porte com formato de ferraduras que se deslocam em direÃÃo L â O. Elas realizam o by-pass, o transporte de sedimentos, essencial para a manutenÃÃo da linha de costa. Neste trabalho, foi priorizada a definiÃÃo da evoluÃÃo morfodinÃmica de dunas mÃveis isoladas (dunas Papai Noel, PÃr-do-Sol e Arraia), tendo como referencial teÃrico a anÃlise das paisagens e como procdimento tÃcnico principal a anÃlise espaÃo-temporal do recobrimento de imagens multitemporais dos satÃlites Landsat e Quickbird entre os anos de 1973 a 2014. AtravÃs da comparaÃÃo da distribuiÃÃo espaÃo temporal das morfologias dunares, nesse perÃodo de 41 anos, evidenciaram-se mudanÃas significativas na Ãrea, perÃmetro e deslocamento das dunas. Foi possÃvel constatar a aÃÃo dos fluxos de matÃria e energia vinculados com migraÃÃo continuada direcionada para a faixa de praia (setor de bypassing de sedimentos). A dinÃmica de migraÃÃo das dunas, quando analisadas apÃs as imagens de 2000, evidenciou possibilidades de alteraÃÃes dos aspectos morfolÃgicos influenciados pelo incremento do fluxo turÃstico, quando instituÃdo o PARNA de Jericoacoara. As mudanÃas foram mais significativas, sobretudo, entre os anos de 2001 a 2005, o que pode estar relacionado a uma maior intervenÃÃo humana (fluxo de turistas). A utilizaÃÃo das tÃcnicas de geoprocessamento para o mapeamento da evoluÃÃo morfodinÃmica do campo de dunas do Parque Nacional de Jericoacoara constituiu- se uma ferramenta essencial para a produÃÃo de informaÃÃes que certamente subsidiarÃo a continuidade do planejamento ambiental da referida, que se constitui como uma Unidade de ConservaÃÃo de ProteÃÃo Integral.
Coastal dunes play an important role in the sediment flow of the coastal zone. The unique morphology of the Jericoacoara National Park in the northeastern Brazilian state of Cearà consists of a promontory covered by a mobile dune field consisting of large, horseshoe-shaped dunes known locally as barcanas that migrate from east to west. These dunes are responsible for the by-pass, the transport of sediments essential for the maintenance of the coastline. The present study focused on the morphodynamic evolution of these isolated mobile dunes through the recovery of multitemporal Landsat and Quickbird satellite images from the years between 1975 and 2014. The comparison of the spatio-temporal distribution of the morphology of these dunes over this 41-year period revealed significant shifts in their area, perimeter, and movement. It was possible to confirm that the flow of material and energy were linked to a process of continuous migration in the direction of the beach (sediment bypassing sector). The dynamics of the dune migration in the years following 2000, when the national park was established, indicate possible impacts of the increase in tourism within the area on the morphology of the dunes. The changes were most significant between 2001 and 2005, possibly reflecting a greater influx of tourists and thus more intense anthropogenic impacts. The different geoprocessing techniques applied to the mapping of the morphodynamic evolution of the dune field of the Jericoacoara National Park proved to be an essential tool for the production of information that will guarantee the long-term environmental planning of this integral conservation unit.
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18

Call, Lara J. "Analysis of intraspecific and interspecific interactions between the invasive exotic tree-of-heaven (Ailanthus altissima (Miller) Swingle) and the native black locust (Robinia pseudoacacia L.)." Thesis, Connect to this title online, 2002. http://scholar.lib.vt.edu/theses/available/etd-05162002-132819/.

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19

Bauman, David. "Analyses spatialement explicites des mécanismes de structuration des communautés d'arbres." Doctoral thesis, Universite Libre de Bruxelles, 2018. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/276814.

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La compréhension des processus écologiques qui sous-tendent l’assemblage des communautés végétales et la coexistence des espèces est un objectif central en écologie. Ces processus sont potentiellement nombreux et de natures contrastées. Ainsi, la composition d’une communauté de plantes dépend de processus déterministes liés aux conditions environnementales abiotiques (climat, conditions physiques et chimiques du sol, lumière) et d’interactions biotiques complexes, positives (facilitation, symbioses) comme négatives (compétition, prédation, pathogènes). En outre, les communautés sont influencées par des processus stochastiques (capacité de dispersion limitée, dérive écologique). Si les mécanismes à l’origine de ces processus sont très différents, ils ont néanmoins en commun la génération de motifs (patterns) spatiaux de distribution d’espèces dans les communautés. L’analyse de la structure spatiale des communautés permet ainsi une étude indirecte des processus régissant les communautés. La nature complexe de ces patterns spatiaux a mené au développement de nombreuses méthodes statistiques de détection et de description de patterns. Les méthodes basées sur des vecteurs propres spatiaux sont parmi les plus puissantes et précises pour détecter des patterns complexes et multi-échelles. Ces vecteurs propres, utilisés comme prédicteurs spatiaux, peuvent être combinés à un ensemble de variables environnementales dans un cadre de partition de variation. Celui-ci permet, en théorie, de démêler les effets uniques et l’effet conjoint des variables environnementales et spatiales sur la variation de composition d’une communauté. Il mène ainsi à une quantification de l’action des processus déterministes et des processus stochastiques sur l’assemblage de la communauté. Néanmoins, je montre dans cette thèse qu’un certain flou méthodologique concernant deux étapes déterminantes des analyses basées sur les vecteurs propres spatiaux a mené une proportion élevée d’études à utiliser ces méthodes de manière sous-optimale, voire fortement biaisée. Ceci compromet la fiabilité des patterns spatiaux détectés et des processus écologiques inférés. Une autre limitation de ce cadre d’analyse concerne la fraction de la partition de variation décrivant l’effet environnemental spatialement structurés qu’aucune méthode ne permet de tester.Cette thèse présente des solutions non biaisées, puissantes et précises à ces différentes limitations méthodologiques et permet d’élargir le cadre de l’inférence de processus écologique à partir de patterns spatiaux de communautés. Les différentes étapes d’amélioration de ces méthodes ont également été illustrées dans la thèse au travers de trois cas d’études fournis par deux communautés d’arbres tropicale et tempérée et une communauté de champignons symbiotiques des arbres.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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20

Bui, Manh Hung. "Structure and restoration of natural secondary forests in the Central Highlands, Vietnam." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-216210.

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Introduction and objectives In Vietnam, the forest resources have been declining and degrading severely in recent years. The degradation has decreased the natural forest area, changed the forest structure seriously and reduced timber volume and biodiversity. From 1999 to 2005, the rich forest area has decreased 10.2%, whereas the poor secondary forest has increased dramatically by 20.7%. Forest structure plays an important role in forestry research. Understanding forest structure will unlock an understanding of the history, function and future of a forest ecosystem (Spies, 1998). The forest structure is an excellent basis for restoration measures. Therefore, this research is necessary to contribute to improving forest area and quality, reducing difficulties in forest management. The study also enhances the grasp of forest structure, structure changes after harvesting and fills serious gaps in knowledge. In addition, the research results will contribute to improving and rescuing the poor secondary forest and restoring it, approaching the old-growth forest in Vietnam. Material and methods The study was conducted in Kon Ka Kinh national park. The park is located in the Northeastern region of Gia Lai province, 50 km from Pleiku city center to the Northeast. The park is distributed over seven different communes in three districts: K’Bang, Mang Yang and Đăk Đoa. Data were collected from 10 plots of secondary forests (Type IIb) and 10 plots of primeval forests (Type IV). Stratified random sampling was applied to select plot locations. 1 ha plots were used to investigate gaps. 2000 m2 plots were used to measure overstorey trees such as diameter at breast height, total height, crown width and species names. 500 m2 subplots were used to record tree positions. For regeneration, 25 systematic 4 m2 subplots were established inside 1 ha plots. After data were collected in the field, data analyses were conducted by using R and Excel. Firstly, some stand information, such as density, volume and so on, was calculated, and then descriptive statistics were computed for diameter and height variables. Linear mixed effect models were applied to analyze the difference of diameter and height and to check the effect of random factor between the two forest types. Diameter and height frequency distributions were also generated and compared by using permutational analysis of variance (PERMANOVA). Non-linear regression models were analyzed for diameter and height variables. Similar analyses were implemented for gaps. Regarding spatial point patterns of overstorey trees, replicated point pattern analysis techniques were applied in this research. For biodiversity, some calculations were run such as richness and biodiversity indices, comparison of biodiversity indices by using linear mixed models and biodiversity differences between two forest types tested again by permutational analysis of variance. In terms of regeneration, some analyses were implemented such as: height frequency distribution generation, frequency difference testing, biodiversity indices for the regeneration and spatial distribution checking by using a nonrandomness index. Results and discussion After analyzing the data, some essential findings were obtained as follows: Hypothesis H1 “The overstorey structure of secondary forests is more homogeneous and uniform than old-growth forests” is accepted. In other words, the secondary forest density is about 1.8 times higher than the jungle. However, the volume is only 0.56 times as large. The average diameter and height of the secondary forest is smaller by 5.71 cm and 3.73 m than the old-growth forest, respectively. Linear mixed effect model results indicate that this difference is statistically different and the effect of the random factor (Section) is not important. Type IIb has many small trees and the diameter frequency distribution is quite homogeneous. The old-growth forest has more big trees. For both forest stages, the height frequency distribution is positively skewed. PERMANOVA results illustrate that the frequency distribution is statistically different between the two forest types. Regression functions are also more variant and diverse in the old-growth forest, because all standard deviations of the parameters are greater there. Gap analysis results indicate that the number of gaps in the young forest is slightly higher, while the average gap size is much smaller. The gap frequency distribution is statistically different between the two types. In terms of the spatial point pattern of overlayer trees, the G-test and the pair correlation function results show that trees distribute randomly in the secondary forest. In contrast, the spatial point patterns of trees are more regular and diverse in the old-growth forest. The spatial point pattern difference is not significant, and this is proved by a permutational t-test for pair correlation function (pcf). Envelope function results indicate that the variation of pcf in young forests is much lower than in the primary forests. Hypothesis H2 “The overstorey species biodiversity of the secondary forest is less than in the old-growth forest” is rejected. Results show that the number of species of the secondary forest is much greater than in the old-growth forest, especially richness. The richness of the secondary forest is 1.16 times higher. The Simpson and Shannon indices are slightly smaller in the secondary forest. The average Simpson index for both forest stages is 0.898 and 0.920, respectively. However, the difference is not significant. Species accumulation curves become relatively flatter on the right, meaning a reasonable number of plots have been observed. Estimated number of species from accumulation curves in two forest types are 105 and 95/ha. PERMANOVA results show that number of species and proportion of individuals in each species are significantly different between forest types. Hypothesis H3 “The number regenerating species of the secondary forest is less and they distribute more regularly, compared to the old-growth forest” is rejected. There are both similarities and differences between the two types. The regeneration density of the stage IIb is 22,930 seedlings/ha, greater than the old forest by 9,030 seedlings. The height frequency distribution shows a decreasing trend. Similar to overstorey, the richness of the secondary forest is 141 species, higher than the old-growth forest by 9 species. Biodiversity indices are not statistically different between two types. PERMANOVA results indicate that the number of species and the proportion of individuals for each species are also not significantly different from observed forest types. Nonrandomness index results show that the regeneration distributes regularly. Up to 95% of the plots reflect this distribution trend. Hypothesis H4 “Restoration measures (with and without human intervention) could be implemented in the regenerating forest” is accepted. The investigated results show that the secondary forest still has mother trees, and it has enough seedlings to restore. Therefore, restoration solutions with and without human intervention can be implemented. Firstly, forest protection should be applied. This measure is relevant to national park regulations in Vietnam. Rangers and other related organizations will be responsible for carrying out protection activities. These activities will protect forest resources from illegal logging, grazing and tourist activities. Environmental education and awareness-raising activities for indigenous people is also important. Another measure is additional and enrichment planting. It should focus on exclusive species of the overstorey in Type IIb or exclusive species of the primary forest. Selection of these species will lead to species biodiversity increase in the future. This also meets the purpose of the maximum biodiversity solution. Conclusion Forest resources play a very important role in human life as well as maintaining the sustainability of ecosystems. However, at present, they are under serious threat, particularly in Vietnam. Central Highland, Vietnam, where forest resources are still relatively good, is also threatened by illegal logging, lack of knowledge of people and so on. Therefore, it needs the hands of the people, especially foresters and researchers. Through research, scientists can provide the knowledge and understanding of the forest, including the structure and forest restoration. This study has obtained important findings. The secondary forest is more homogeneous and uniform, while the old-growth forest is very diverse. Biodiversity of the overstorey in the secondary forest is more than the primary. The number of regenerating species in the secondary forest is higher, but other indices are not statistically different between two types. The regeneration distribute regularly on the ground. The secondary forest still has mother trees and sufficient regeneration, so some restoration measures can be applied here. Findings of the study contribute to improve people’s understanding of the structure and the structural changes after harvesting in Kon Ka Kinh national park, Gia Lai. That is a key to have better understandings of the history and values of the forests. These findings and the proposed restoration measures address rescuing degraded forests in Central Highland in particular and Vietnam in general. And further, this is a promising basis for the management and sustainable use of forest resources in the future.
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Moradi, Mohammad Mehdi. "Spatial and spatio-temporal point patterns on linear networks." Doctoral thesis, Universitat Jaume I, 2018. http://hdl.handle.net/10803/664140.

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A thesis submitted in partial fulfillment of the requirements for the degree of Doctor in Information Management, specialization in Geographic Information Systems
The last decade witnessed an extraordinary increase in interest in the analysis of network related data and trajectories. This pervasive interest is partly caused by a strongly expanded availability of such datasets. In the spatial statistics field, there are numerous real examples such as the locations of traffic accidents and geo-coded locations of crimes in the streets of cities that need to restrict the support of the underlying process over such linear networks to set and define a more realistic scenario. Examples of trajectories are the path taken by moving objects such as taxis, human beings, animals, etc. Intensity estimation on a network of lines, such as a road network, seems to be a surprisingly complicated task. Several techniques published in the literature, in geography and computer science, have turned out to be erroneous. We propose several adaptive and non-adaptive intensity estimators, based on kernel smoothing and Voronoi tessellation. Theoretical properties such as bias, variance, asymptotics, bandwidth selection, variance estimation, relative risk estimation, and adaptive smoothing are discussed. Moreover, their statistical performance is studied through simulation studies and is compared with existing methods. Adding the temporal component, we also consider spatio-temporal point patterns with spatial locations restricted to a linear network. We present a nonparametric kernel-based intensity estimator and develop second-order characteristics of spatio-temporal point processes on linear networks such as K-function and pair correlation function to analyse the type of interaction between points. In terms of trajectories, we introduce the R package trajectories that contains different classes and methods to handle, summarise and analyse trajectory data. Simulation and model fitting, intensity estimation, distance analysis, movement smoothing, Chi maps and second-order summary statistics are discussed. Moreover, we analyse different real datasets such as a crime data from Chicago (US), anti-social behaviour in Castell´on (Spain), traffic accidents in Medell´ın (Colombia), traffic accidents in Western Australia, motor vehicle traffic accidents in an area of Houston (US), locations of pine saplings in a Finnish forest, traffic accidents in Eastbourne (UK) and one week taxi movements in Beijing (China).
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22

Liu, Jie. "Exploring Ways of Identifying Outliers in Spatial Point Patterns." Digital Commons @ East Tennessee State University, 2015. https://dc.etsu.edu/etd/2528.

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This work discusses alternative methods to detect outliers in spatial point patterns. Outliers are defined based on location only and also with respect to associated variables. Throughout the thesis we discuss five case studies, three of them come from experiments with spiders and bees, and the other two are data from earthquakes in a certain region. One of the main conclusions is that when detecting outliers from the point of view of location we need to take into consideration both the degree of clustering of the events and the context of the study. When detecting outliers from the point of view of an associated variable, outliers can be identified from a global or local perspective. For global outliers, one of the main questions addressed is whether the outliers tend to be clustered or randomly distributed in the region. All the work was done using the R programming language.
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Packard, Kevin Carew. "Modeling spatial patterns of mixed-species Appalachian forests with Gibbs point processes." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/37385.

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Stochastic point processes and associated methodology provide a means for the statistical analysis and modeling of the spatial point pattern formed from forest tree stem locations. Stochastic Gibbs point processes were explored as models that could simulate short-range clustering arising from reproduction of trees by stump sprouting, and intermediate-range inhibition of trees that may result from competition for light and growing space. This study developed and compared three pairwise interaction processes with parametric models for 2nd-order potentials and three triplets processes with models for 2nd- and 3rd-order potentials applied to a mixed-species hardwood forest in the Southern Appalachian Mountains of western North Carolina. Although the 2nd-order potentials of both the pairwise interaction and triplets processes were allowed to be purely or partially attractive, the proposed Gibbs point process models were demonstrated to be locally stable. The proposed Gibbs point processes were simulated using Markov Chain Monte Carlo (MCMC) methods; in particular, a reversible-jump Metropolis-Hastings algorithm with birth, death, and shift proposals was utilized. Parameters for the models were estimated by a Bayesian inferential procedure that utilizes MCMC methods to draw samples from the Gibbs posterior density. Two Metropolis-Hastings algorithms that do this sampling were compared; one that estimated ratios of intractable normalizing constants of the Gibbs likelihood by importance sampling and another that introduced an auxiliary variable to cancel the normalizing constants with those in the auxiliary variableâ s proposal distribution. Results from this research indicated that attractive pairwise interaction models easily degenerate into excessively clustered patterns, whereas triplets processes with attractive 2nd-order and repulsive 3rd-order interactions are more robust against excessive clustering. Bayesian inference for the proposed triplets models was found to be very computationally expensive. Slow mixing of both algorithms used for the inference combined with the long iteration times limited the practicality of the Bayesian approach. However the results obtained here indicate that triplets processes can be used to draw inference for and simulate patterns of mixed-species Appalachian hardwood forests.
Ph. D.
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Pranchai, Aor. "Spatial patterns and processes in a regenerating mangrove forest." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-171569.

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The global effort to rehabilitate and restore destroyed mangrove forests is unable to keep up with the high mangrove deforestation rates which exceed the average pace of global deforestation by three to five times. Our knowledge of the underlying processes of mangrove forest regeneration is too limited in order to find suitable techniques for the restoration of degraded mangrove areas. The general objective of my dissertation was to improve mangrove restoration by understanding regeneration processes and local plant-plant interaction in a regenerating Avicennia germinans forest. The study was conducted in a high-shore mangrove forest area on the Ajuruteua peninsula, State of Para, Northern Brazil. The dwarf forest consisting of shrub-like trees is recovering from a stand-replacing event caused by a road construction in 1974 which interrupted the tidal inundation of the study area. Consequently, infrequent inundation and high porewater salinity limit tree growth and canopy closure. All trees and seedlings were stem-mapped in six 20 m x 20 m plots which were located along a tree density gradient. Moreover, height, crown extent, basal stem diameter of trees were measured. The area of herbaceous ground vegetation and wood debris were mapped as well. The mapped spatial distribution of trees, seedlings and covariates was studied using point pattern analysis and point process models, such as Gibbs and Thomas point process, in order to infer underlying ecological processes, such as seed dispersal, seedling establishment, tree recruitment and tree interaction. In the first study (chapter 2), I analyzed the influence of abiotic and biotic factors on the seedling establishment and tree recruitment of A. germinans during the recolonization of severely degraded mangrove sites using point process modeling. Most seedlings established adjacent to adult trees especially under their crown cover. Moreover, seedling density was higher within patches of the herbaceous salt-marsh plants Blutaparon portulacoides and Sesuvium portulacastrum than in uncovered areas. The higher density of recruited A. germinans trees in herb patches indicated that ground vegetation did not negatively influence tree development of A. germinans. In addition, tree recruitment occurred in clusters. Coarse wood debris had no apparent effect on either life stage. These results confirm that salt-marsh vegetation acts as the starting point for mangrove recolonization and indicate that the positive interaction among trees accelerates forest regeneration. In the second study (chapter 3), I analyzed how intraspecific interaction among A. germinans trees determines their growth and size under harsh environmental conditions. Interaction among a higher number of neighboring trees was positively related to the development of a focal tree. However, tree height, internode length and basal stem diameter were only positively associated in low-density forest stands (1.2 trees m-2) and not in forest stands of higher tree density (2.7 trees m-2). These results indicated a shift from facilitation, i.e. a positive effect of tree interaction, towards a balance between facilitation and competition. In the third study (chapter 4), I used point process modeling and the individual-based model mesoFON to disentangle the impact of regeneration and interaction processes on the spatial distribution of seedlings and trees. In this infrequently inundated area, propagules of A. germinans are only dispersed at a maximum distance of 3 m from their parent tree. Furthermore, there is no evidence that the following seedling establishment is influenced by trees. I was able to differentiate positive and negative tree interactions simulated by the mangrove model mesoFON regardless of dispersal processes based on static tree size information using the mark-correlation function. The results of this dissertation suggest that mangrove forest regeneration in degraded areas is a result of facilitative and not competitive interactions among mangrove trees, seedling and herbaceous vegetation. This has important implications for the restoration of degraded mangrove forest. Degraded mangrove areas are usually restored by planting a high number of evenly spaced seedlings. However, high costs constrain this approach to small areas. Assisting natural regeneration could be a less costly alternative. Herbaceous vegetation plays a crucial role in forest recolonization by entrapping propagules and possibly ameliorating harsh environmental conditions. So far only competition among mangrove trees has been considered during restoration. However, facilitative tree interactions could be utilized by planting seedling clusters in order to assist natural regeneration instead of planting seedlings evenly-spaced over large areas. This dissertation also showed that point pattern analysis and point process modeling can enable forest ecologists to describe the spatial distribution of trees as well as to infer underlying ecological processes.
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25

Gooding, Susan Catherine. "Second-order analysis of inhomogeneous spatial point processes." Thesis, Lancaster University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414955.

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Kanaan, Mona N. "Cross-spectral analysis for spatial point-lattice processes." Thesis, [n.p.], 2000. http://dart.open.ac.uk/abstracts/page.php?thesisid=94.

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Brunsdon, C. F. M. "Spatial analysis techniques applied to local crime patterns." Thesis, University of Newcastle Upon Tyne, 1989. http://hdl.handle.net/10443/305.

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Despite growing crime rates, and increased computerisation of crime data within the police force, surprisingly little attention has been payed to techniques of analysis that could be applied to this data. This thesis investigates spatial analytical and statistical techniques which may be used for this task, and proposes a Bayesian forecasting technique, allowing the objective pattern detection mechanisms supplied by the quantitative examination of past data to be combined with the subjective knowledge of police officers. This method, along with others, is incorporated into a software package which may be run at a police station (Subdivision). Finally the software package is evaluated by members of the police force.
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Haltigin, Timothy William. "Interpreting polygonal terrain network arrangements on Earth and Mars using spatial point patterns." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=92211.

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Polygonal terrain is one of the most common landforms found throughout the periglacial environments of Earth and Mars. These networks of interconnected trough-like features form through a complex interaction of climatological and rheological processes and often signify the presence of ground ice deposits.
Previous comparisons of morphological similarities amongst sites on both planets have typically relied upon qualitative techniques. In some cases, limited quantitative metrics have been utilized, but there remains no objective, repeatable method by which to compare terrestrial and Martian polygonal terrain.
The overarching goal of this work is to assess the utility of a particular statistical method – Spatial Point Pattern Analysis (SPPA) – for analyzing polygonal network geometries at sites on Earth and Mars. Based around four sets of experimental results, the objectives addressed by this thesis are to:
(i) demonstrate that SPPA is an effective means by which qualitative, observable variations in polygonal morphology can be quantified;
(ii) examine the effects of different input data collection methods on the output of the statistical model;
(iii) establish that the analytical results of SPPA as applied to polygonal terrain are rooted in terrestrial geomorphic theory, and;
(iv) perform a case study in which SPPA is used to reconstruct the landscape history of a particular region of Mars.
Our results show that SPPA successfully differentiates between the geometric patterns observed at various sites, simultaneously providing data pertaining to the cumulative distribution of trough segment lengths and the overall network arrangement. In providing guidelines for future applications of this technique, we demonstrate that SPPA results are the most reliable when using data derived from ground-based terrain surveys or GIS-based analysis of high-resolution (< 0.5m/pixel) satellite or aerial images. Moreover, extensive fieldwork in the Canadian High Arctic illustrates that the observed point pattern of a given site is linked to its substrate composition and relative stage of development. Finally, using the field results as an analogical source to inform the interpretation of Martian geomorphic processes, a landscape evolution model is proposed to explain the development of a poorly-understood landform (scalloped depressions) in the ice-rich terrains of the Martian northern latitudes.
Les formes de terrain polygonales sont parmi les plus communes dans les environnements périglaciaires sur la Terre comme sur Mars. Ces réseaux de dépressions interconnectées sont issus d'interactions complexes entre des processus climatologiques et rhéologiques et indiquent souvent la présence de dépôts de glace souterraine.
Les comparaisons précédentes sur les similarités morphologiques entre des sites à la surface des deux planètes ont souvent été basées sur des techniques qualitatives. Dans certains cas, quelques mesures quantitatives ont été utilisées, mais il n'y avait aucune méthode objective qui permettait de comparer les formes de terrain polygonales terrestres et martiennes.
L'objectif général de cette recherche est d'évaluer l'utilité d'une méthode statistique particulière – l'analyse de patrons spatiaux ponctuels (APSP) – pour analyser la géométrie des réseaux polygonaux sur Terre et sur Mars. À partir de quatre séries de données expérimentales, les objectifs spécifiques de cette thèse sont:
(i) de démontrer que l'APSP est une méthode efficace par laquelle les variations observées de façon qualitative dans la morphologie des polygons peuvent être quantifiées;
(ii) d'examiner les effets de différentes méthodes de cueillette de données à l'entrée sur les résultats du modèle statistique;
(iii) d'établir que les résultats analytiques de l'APSP appliqués à un terrain polygonal ont comme fondement théorique les concepts géomorphologiques terrestres;
(iv) de réaliser une étude de cas qui utilise l'APSP afin de reconstruire l'histoire du paysage dans une région spécifique de Mars.
Nos résultats indiquent que l'APSP permet de différencier avec succès les patrons géométriques observés à différents sites, tout en procurant des données pertinentes sur la distribution cumulative des longueurs de segments de dépression et sur l'agencement général de ces réseaux. En fournissant des directives pour les applications futures de cette technique, nous démontrons que les résultats de l'APSP sont les plus fiables lorsque les données proviennent de relevés de terrain au sol ou d'une analyse par SIG de données satellitaires ou d'imagerie aérienne de fine résolution (≤ 0.5m/pixel). De plus, une vaste campagne de terrain réalisée dans le Haut-Arctique canadien montre que le patron ponctuel observé en un site donné est lié à la composition du substrat ainsi qu'à son stade relatif de développement. Finalement, en utilisant les résultats de terrain comme une source analogue qui nous informe sur l'interprétation des processus géomorphologiques sur Mars, un modèle d'évolution du paysage est développé pour expliquer le développement de formes de terrain peu documentées (depressions festonnées) dans les zones riches en glace des latitudes nord de Mars.
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29

Walsh, Daniel Charles Islip. "Detecting and extracting complex patterns from images and realizations of spatial point processes /." Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/8974.

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30

Lee, Ho Young. "Diagnosing spatial variation patterns in manufacturing processes." Diss., Texas A&M University, 2003. http://hdl.handle.net/1969/122.

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31

Brandenberg, Kristin. "Point of view : How printed patterns evolve through perspective." Thesis, Högskolan i Borås, Akademin för textil, teknik och ekonomi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-12395.

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’Point of view’ is an investigation of changeable surface patterns in the textile design field. The investigation is performed in order to get a deeper understanding of the relationship between changeable surface patterns and three-dimensional contexts to explore alternative methods.  The aim is to design surface patterns in a three dimensional context developed through printing and layering techniques, and to explore how the patterns change depending on the observer’s perspective. Practice based design experiments were carried out to explore materials and printing techniques such as transfer, digital and burn out. The patterns were in turn placed on a cubic frame with inner and outer layers, and studied for their effects on one another.  The project resulted in a series of surface patterns that were applied in a spatial context. The findings propose an alternative method for designing changeable surface patterns in a three-dimensional setting, using layers, transparency and distance as factors.
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Brown, Calum. "Spatial patterns and species coexistence : using spatial statistics to identify underlying ecological processes in plant communities." Thesis, University of St Andrews, 2012. http://hdl.handle.net/10023/3084.

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The use of spatial statistics to investigate ecological processes in plant communities is becoming increasingly widespread. In diverse communities such as tropical rainforests, analysis of spatial structure may help to unravel the various processes that act and interact to maintain high levels of diversity. In particular, a number of contrasting mechanisms have been suggested to explain species coexistence, and these differ greatly in their practical implications for the ecology and conservation of tropical forests. Traditional first-order measures of community structure have proved unable to distinguish these mechanisms in practice, but statistics that describe spatial structure may be able to do so. This is of great interest and relevance as spatially explicit data become available for a range of ecological communities and analysis methods for these data become more accessible. This thesis investigates the potential for inference about underlying ecological processes in plant communities using spatial statistics. Current methodologies for spatial analysis are reviewed and extended, and are used to characterise the spatial signals of the principal theorised mechanisms of coexistence. The sensitivity of a range of spatial statistics to these signals is assessed, and the strength of such signals in natural communities is investigated. The spatial signals of the processes considered here are found to be strong and robust to modelled stochastic variation. Several new and existing spatial statistics are found to be sensitive to these signals, and offer great promise for inference about underlying processes from empirical data. The relative strengths of particular processes are found to vary between natural communities, with any one theory being insufficient to explain observed patterns. This thesis extends both understanding of species coexistence in diverse plant communities and the methodology for assessing underlying process in particular cases. It demonstrates that the potential of spatial statistics in ecology is great and largely unexplored.
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33

Miller, Roy H. III. "Spatial Mapping of Strain Patterns Using GIS." Bowling Green State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1441362674.

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34

Wang, Yamei. "Geospatial Analysis of Spatial Patterns of U.S. Hospital Readmission Rates." ScholarWorks, 2017. https://scholarworks.waldenu.edu/dissertations/4574.

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Unplanned hospital readmission after a recent hospitalization is an indication of poor healthcare quality and a waste of healthcare resources. The Centers for Medicare and Medicaid Services (CMS) initiated the Hospital Readmission Reduction Program (HRRP) to improve healthcare quality and reduce costs; however, studies found the risk adjustment method used in calculating the standardized readmission rate was less accurate without hospital region or community factors. Accordingly, this cross-sectional quantitative study was designed to examine spatial patterns in hospital readmission rates following Andersen's behavioral model of health service utilization. This study was the first geospatial analysis on risk standardized hospital readmissions (RSRR) based on hospital geographic locations. Secondary data from the CMS was used in assessing the global and local geospatial cluster patterns using Global Moran's Index, Anselin local Moran's Index, and graphical analysis tool to identify cluster groups. The study found hospital-wide RSRR was significantly clustered across the country or at the local level. A total of 15 optimal cluster groups were identified with wide variability in cluster size. The hospital-wide and other seven CMS published RSRRs were significantly different among all clusters. The geographically bounded hospital RSRRs provided evidence in support of adding community or regional layer to risk adjustment of RSRR. The specific cluster groups with extremely high or low readmission rates can assist national and local policymakers and hospital administrators to identify specific targets to take actions. This research has social change implications for reducing hospital readmission rates and saving healthcare costs.
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35

Morris, Michelle Anne. "Spatial analysis of dietary cost patterns and implications for health." Thesis, University of Leeds, 2013. http://etheses.whiterose.ac.uk/6894/.

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Background: Chronic diseases such as obesity, cardiovascular disease, diabetes and cancer are a large burden on society, for which diet is the leading modifiable risk factor. ‘Diet’ can encompass a variety of aspects of food consumption. Dietary patterns arguably best reflect food as consumed. The determinants of diet are varied and include cost and availability of foods. The aim of this research is to investigate if dietary patterns and diet cost vary spatially and whether this influences health outcomes, specifically obesity and breast cancer. Methods: Using data from the UKWomen’s Cohort Study, data driven dietary patterns were previously determined. Cost of diet was assigned using a food cost database. Spatial measures for Government Office Region, North South, Urban/ Rural and the Output Area Classification were assigned matched to postcode of the women. Weight status is calculated from self reported height and weight. Time to event analysis investigated association between dietary pattern, diet cost and breast cancer incidence at each spatial scale. Results: There is some spatial variation in dietary patterns both between and within regions. A healthy in more expensive per day than a less healthy one: £6.63 compared to £3.29. The overweight/ obese pay more for their food. Urban and Northern areas have significantly higher BMI than Rural and Southern areas respectively. Those in areas Constrained by Circumstance have highest prevalence of overweight and obesity. There is some spatial variation in breast cancer incidence and variation by dietary pattern. In postmenopausal women, positive association exists between weight status and risk of breast cancer incidence. Methods used for estimating small area dietary patterns and health outcomes may be applicable for use in other developed populations. Conclusion: Understanding determinants of dietary patterns remains important for public health and making healthy diets accessible to all is important. However, while expensive dietary patterns reflect a healthier diet, they do not appear to be the mechanism for which obesity prevalence and breast cancer incidence occur. Geodemographic classifications, combined with other spatial measures could aid more effective targeting of public health nutrition policy.
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36

Khatun, Mahmuda. "Interpolation and extrapolation of point patterns based on variation analysis on measures." Thesis, University of Strathclyde, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.502280.

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Suppose that we observe a point pattern in an observation window W₀ C Rd. In this study we pose ourselves the following two main questions: How can one extend the pattern in a 'reasonable way' to a larger window W ) W₀? Can one predict possible gaps in the observed point pattern where points were 'expected' but somehow failed to realise. We address these questions by assuming that the point pattern is an observed part of a realisation of a non-homogeneous Poisson process in W and estimate its intensity so that to mimic a given distributional characteristic of the pattern, for instance, its sample nearest neighbour distribution. The project aims to develop prediction and extrapolation techniques for random points processes and related techniques of optimisation of functionals depending on a measure. Applications are numerous and important, including restoration of images, detection of impurities in material science, prediction of anomalies in geology, etc.
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Huang, Fang. "Modeling patterns of small scale spatial variation in soil." Link to electronic thesis, 2006. http://www.wpi.edu/Pubs/ETD/Available/etd-011106-155345/.

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Thesis (M.S.)--Worcester Polytechnic Institute.
Keywords: spatial variations; nested random effects models; semivariogram models; kriging methods; multiple logistic regression models; missing; multiple imputation. Includes bibliographical references (p. 35-36).
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Carr, Jake Kenneth. "Retail Choice, Consumer Spaces, and Dynamics in the Spatial Organization of the Goods and Services Sector." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1500310205028892.

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39

Menin, Aline. "eSTIMe : un environnement de visualisation pour l'analyse multi-points de vue des mobilités quotidiennes." Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALS010.

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Le domaine de recherche de la mobilité urbaine vise l'observation et la conception des déplacements humains dans un environnement urbain, dont les informations aident à la prise de décision et à la résolution de problèmes dans le cadre des politiques publiques. De nombreux experts - pas nécessairement spécialistes des transports - doivent traiter des données urbaines plus ou moins standardisées pour en extraire des connaissances synthétiques et facilement exploitables. De ce fait, les agences de transport public mènent couramment des enquêtes de déplacements pour recueillir des informations sur les déplacements quotidiens de la population sur un territoire donné, dont les jeux de données résultant sont larges et complexes en requierant une analyse qui croise les dimensions spatiales, temporelles, thématiques et socio-économiques pour permettre de découvrir les schémas spatio-temporels de la mobilité quotidienne. Dans ce contexte, la visualisation d'informations est une approche appropriée pour soutenir l'analyse des données de mobilité urbaine, puisque les analystes n'ont pas à apprendre des méthodes sophistiquées pour interpréter les visualisations de données qui viennent renforcer leur cognition et permettent la découverte d'aperçus non structurés dans les données.Ainsi, nous proposons un cadre de visualisation pour aider à l'analyse de la mobilité urbaine à travers des indicateurs décrivant des objets d'intérêt complémentaires au sein des données qui permettent d'aborder trois catégories de questions sous-jacentes au phénomène de la mobilité urbaine. Une première question est de savoir comment les habitants d'un territoire se déplacent au quotidien et quels processus d'échanges entre les lieux cela génère, ce qui l'on peut analyser par l'exploration des quantités, des modalités, de la direction et de la variation des flux et des déplacements en fonction des différents aspects socio-économiques des individus et des types d'espaces. Une deuxième question concerne la variation temporelle de la présence de la population sur un territoire, qui permet de comprendre l'utilisation de différents ``sours-espaces'' en tenant compte des caractéristiques socio-économiques des personnes qui s'y rendent et des activités qu'elles y exercent. La troisième question cherche à expliquer le besoin de déplacement des individus à travers l'ordre temporel des déplacements et des activités des individus (aussi nommés ``trajectoires quotidiennes'') dans le contexte spatial du territoire.Nous proposons un cadre visuel à l'aide de la dérivation et l'exploration visuelle d'indicateurs décrivant le territoire, les flux et les déplacements, et les trajectoires quotidiennes, sur de multiples granularités spatio-temporelles et attributs thématiques. Notre interface de visualisation permet de disperser les représentations visuelles sur de multiples tableaux de bords analytiques, permettant aux utilisateurs de personnaliser l'agencement spatial des visualisations et les indicateurs de manière significative en fonction de l'analyse en cours. De plus, nous proposons une interaction basée sur le mouvement, qui repose sur l'inclinaison d'une tablette et qui permet d'explorer la variation temporelle des indicateurs en tirant parti d'une entrée tactile et tangible. La conception de notre approche de visualisation a suivi un processus d'évaluation interactif qui comprend des évaluations successives auprès des utilisateurs visant à affiner un prototype afin d'atteindre la performance et la satisfaction de l'utilisateur
The research field of urban mobility aims at the observation and design of human trips within an urban environment, which information supports decision-making and problem solving within public policies. In this context, there are many experts -- not necessarily transportation specialists -- that need to handle more or less standardized urban data to extract synthetic and easily exploitable knowledge. Hence, public transportation agencies commonly conduct trip-based surveys to collect information about day-to-day travel of the population within a particular territory (i.e. where and when we travel), resulting in large and complex datasets which analysis requires crossing spatial, temporal, thematic and socioeconomic dimensions to enable discoveries of daily urban mobility patterns. This way, information visualization is a suitable approach to support the analysis of urban mobility data, since analysts do not have to learn sophisticated methods to interpret the data visualizations that come to reinforce their cognition and enable the discovery of unstructured insights within the data.Thereby, we propose a visualization framework to assist the analysis of urban mobility through indicators describing complementary objects of interest within the data that allow to address three categories of questions underlying the urban mobility phenomenon. A first question seeks to understand the daily traveling routine of a population and the resulting processes of exchange between places, which can be studied through the exploration of amounts, modalities, direction, and variation of travel flows and trips according to different socioeconomic aspects of individuals and land types. A second questioning concerns the temporal variation of population presence throughout a territory, which allows to understand the use of distinct locations by taking into account the socioeconomic characteristics of the people visiting it and the activities they carry out there. The third question seeks to explain the individuals' need of traveling by studying the temporal ordering of trips and activities of individuals (i.e. daily trajectories) within the spatial context of the territory.Our framework supports the derivation and visual exploration of indicators describing the territory, travel flows and trips, and daily trajectories, over multiple spatio-temporal resolutions and thematic attributes. Our visualization interface allows to disperse visual representations over multiple analytical displays, enabling users to customize the spatial arrangement of visualizations and indicators in meaningful ways according to the ongoing analysis. Furthermore, we propose a movement-based interaction based on the tilting of a tablet that allows to explore the temporal variation of indicators leveraging tactile and tangible input. The conception of our visualization approach followed an interactive evaluation process that consists of successive user-based evaluations aiming to refine a prototype in order to achieve user performance and satisfaction
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40

Ngwa, Gideon Akumah. "The analysis of spatial and spatio-temporal patterns in models for morphogenesis." Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334873.

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41

Narasimhan, Kavin Preethi. "Computational proxemics : simulation-based analysis of the spatial patterns of conversational groups." Thesis, Queen Mary, University of London, 2016. http://qmro.qmul.ac.uk/xmlui/handle/123456789/23843.

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In real-world conversational groups, interactants adjust their body position and orientation relative to one another in order to see and hear clearly. We use an agent-based modelling approach to compare alternative models for simulating the spatial patterns of conversational groups. The models are based on simple rules that control the movement, positioning, and orientation behaviour of individual agents, which in turn leads to the emergence of agent clusters. We identify which model alternative produces agent clusters with characteristics typical of real-world conversational groups. The centroid-based approach, where agents readjust their position and orientation with respect to the group centroid point, is a commonly used method to simulate conversational groups, but has not been empirically validated. This thesis replicates, evaluates, and validates the centroid-based model in a systematic way. Another model, where agents perform positional-orientational readjustments to see as many neighbours as possible within a 180 field of view, called the field-of-view approach is proposed, implemented, evaluated, and validated. Analysis of the spatial patterns of conversational groups has hitherto mostly relied on visual verification. We, novelly, use a combination of qualitative and quantitative methods to analyse the spatial patterns of conversational groups. Evaluations show that the field of- view model and centroid-based model produce agent clusters with significantly different social, spatial, and temporal characteristics. Validation is performed using a dataset which captures the spatial behaviour of 21 participants for the entire duration of a party. This validation shows that the characteristics of agent clusters resulting from the field-of-view model most closely reflects the characteristics of real-world conversational groups. We also show that a local neighbourhood influence works better than an extended neighbourhood influence to simulate conversational groups. The influence of objects in the environment on the spatial patterns of agent clusters are also discussed.
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42

Ho, Lai Ping. "Complete spatial randomness tests, intensity-dependent marking and neighbourhood competition of spatial point processes with applications to ecology." HKBU Institutional Repository, 2006. http://repository.hkbu.edu.hk/etd_ra/770.

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43

Ma, Tingting. "Isotropy test and variance estimation for high order statistics of spatial point process." HKBU Institutional Repository, 2011. https://repository.hkbu.edu.hk/etd_ra/1297.

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44

Zhang, Qian. "Spatial-Temporal Patterns of Urban Growth in Shanghai, China: Monitoring, Analysis, and Simulation." Licentiate thesis, Geoinformatics Division, Department of Urban Planning and Environment, ABE, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11868.

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Supporting huge population, megacities are definitely the hot spots of production, consumption, and waste generation. Without careful investment and planning, megacities will be overwhelmed by burgeoning negative impacts on the environment, natural resources, and human health, as well as a host of social and economic issues. The unprecedented combination of economic and population growth since the Reform and Open Policy has led China into transition from a largely rural society to a predominantly urban one. Chinese cities, without question, have not escaped the danger of the series of problems during the rapid progress of urbanization. Therefore, monitoring the spatial-temporal patterns of urban sprawl and their impact on the environment is of critical importance for urban planning and sustainable development, especially in developing Chinese cities such as Shanghai.

To date, few studies have focused on the urban trajectories of Shanghai over the past 30 years from a remote sensing perspective. Most of the studies were concentrated on the technical issues of image processing and classification. Moreover, research on spatial metrics has focused on analyzing remote sensing classification results rather than on the use of interpreting, assessing, and verifying urban simulation results. Furthermore, many researches merely focused on baseline projection and very few studies took into consideration urban growth scenarios so far. As yet there have been no reported scenario simulations of future Shanghai growth with several land-use categories within urban areas.

The overall objective of this research is to investigate the integration of remote sensing, spatial metrics, and spatial-temporal models in the monitoring, analysis, and simulation of urban growth in Shanghai, China. The specific objectives are to: 1). monitor urban dynamics over time with multi-sensor remote sensing images; 2). quantify spatial-temporal properties of urban growth and representing the urban morphological structures by means of spatial metrics; and 3). simulate the geographic extent, patterns, and detailed catalogs of urban growth under different scenarios using Markov-Cellular Automata (Markov-CA) model to support decision making for a more sustainable Shanghai.

Through this study, the combined approach using remotely sensed data with change detection techniques, spatial metrics, and a scenarios-based simulation model proved to be effective to understand, represent, and predict the spatial-temporal dynamics of urban growth. In detail, the segmented-based hierarchy classification and visual interpretation were effective methods to extract urban and industrial land with high-resolution remotely sensed images. Direct change detection using variables derived from tasseled cap transformation was efficient for monitoring impervious surface sprawl. Spatial metrics is a quick and executable way to assessing the impact of urban sprawl on landscape dynamic. Markov-CA model is a useful tool to simulate the scenarios of future urban developments and therefore provides the policy options for sustainable urban planning.

The research results of urban trajectories and impervious surface sprawl showed that Shanghai experienced high-speed urban sprawl and the rate of urban expansion, however, was not homogeneous spatially and temporally. The general annual urban expansion speed was 34.8 km2 per year; nevertheless, it reached 80.2 km2 per year recent six years from 2001 to 2007, while it touched the bottom speed around 14.3 km2 per year during 1979-1989. The expanded area in the Puxi region was 5.23 times of its original area while that of Pudong region was 19.94 times of its original area during 1979-2007. The research results of landscape analysis demonstrated that greenbelt becomes fractured while infrastructural and commercial area is more and more aggregated in the central Shanghai area, and satellite images such as SPOT Pan, XS and Landsat TM with 10-30 meter resolution are sufficient for the landscape dynamic research in central Shanghai area. The results of scenarios-based simulation indicated that built-up areas in Shanghai will increase significantly in 2025 and Shanghai will experience less urban sprawl and retain a better environment in 2025 under service-oriented center (SOC) than under baseline (NS) or manufacturing-dominant center (MDC) scenario. If favorable policy for MDC scenario is adopted, however, there will be a lot of manufacturing industries gathering in Shanghai and more agricultural lands will be encroached.

The present research focused on the analysis of physical and morphological aspects of urban growth. Urban land-use dynamics are, however, intrinsically linked with socio-economic, political, or demographic drivers. Trying to fill in the missing link between traditional urban geography and urban remote sensing & urban simulation and to improve understanding of the interactions between human and natural aspects in the urban socio-ecosystem is the major focus in the next phase of the Ph.D. research.

Keywords: Urban growth, Spatial-temporal pattern, Remote sensing, Spatial metrics, Scenarios-based simulation, Shanghai

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45

Junge, Justin Andrew. "GIS Spatial Analysis of Arctic Settlement Patterns| A Case Study in Northwest Alaska." Thesis, Portland State University, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10600719.

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Archaeologists have been interested in relationship between environmental variability and cultural change for the last six decades. By understanding how, when, and why humans adapt to environmental change, archaeologists and anthropologists can better understand the development and complexity of human cultures. In northwest Alaska, archaeologists hypothesize that environmental variability was a major factor in both growing coastal population density, with large aggregated villages and large houses, between 1000 and 500 years ago (ya), and subsequent decreasing population density between 500 ya and the contact era. After 500 ya people are thought to have dispersed to smaller settlements with smaller house sizes in coastal areas, and perhaps, upriver. This settlement pattern was identified through research at four site locations over 30 years ago. The changing geographic distribution of sites, associated settlement size, and house size has not been examined in detail. A more careful examination of changing northwest Alaskan settlement patterns is needed before larger questions about socio-economic organization can be addressed. I use Geographic Information Systems (GIS) to evaluate the evidence for a geographic redistribution of Arctic peoples during the Late Holocene.

I constructed a database of settlement location and site attribute information, specifically the number of houses within each settlement and the size (m 2). Data were collected from a dataset of Western Arctic National Parklands (WEAR), the Alaska Heritage Resource Survey (AHRS) database of archaeological sites in Alaska, 409 unpublished site reports and field notes curated by the National Park Service (NPS) and Bureau of Indian Affairs (BIA), and the results of recent fieldwork in northwest Alaska. A total of 486 settlements were identified within the northwest Alaska with 128 settlements having temporal and site attribute data.

I incorporated settlement size data into a GIS database and then carried out global, Moran’s I, local Moran’s I, and local Getis-Ord spatial analyses to test whether settlement redistribution occurred and if key settlement locations shifted after 500 ya. The site attribute data (number of houses and average size of houses) are used to test the additional aspects of the proposed settlement pattern change after 500 ya. A total of 83 settlements with 465 houses are used to test if the average size of settlements and average house size changed after 500 ya.

The results of the spatial analyses indicate no statistically significant patterns in the spatial distribution of settlements. Site attribute analysis shows no statistical difference in the average number of houses per village or the average size of houses before or after 500 ya. The results of this work build our understanding of regional settlement patterns during the late Holocene. By testing settlement pattern change, i.e. settlement distribution, settlement size, and house size, future research into settlement pattern change can begin to evaluate likely causes for the observed changes. My method, specifically the use of GIS as a method for testing settlement pattern change, can be applied to other regions and temporal scales.

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46

Persaud, Steven S. "Contrast Sensitivity to One- and Two-Dimensional Luminance Patterns." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/9910.

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Contrast sensitivities to one- and two-dimensional luminance patterns were compared in a two-alternative forced choice (2AFC) experiment. Space-averaged luminance was also manipulated. Statistical analyses revealed a main effect of stimulus dimension (p < .05) and no effect of space-averaged luminance. The main effect of stimulus dimension was explained in terms of an on-center, off-center receptive field model combined with watershed spatial vision behavior at spatial frequencies below 1 cycle-per-degree (cpd). The non-significant result for space-averaged luminance was explained by the limited range of manipulation of the variable. Two-dimensional luminance patterns were suggested as ideal patterns for reconciling grating-based spatial vision research with spatial vision behavior in an ecological context. Future research directions are suggested.
Master of Science
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47

Patrickson, Shela. "Competition in the Knysna Forest : is GIS suitable for the analysis of spatial patterns?" Thesis, University of Cape Town, 2001. http://hdl.handle.net/11427/25604.

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48

Gillin, Cody Palmer. "Digital terrain analysis to predict soil spatial patterns at the Hubbard Brook Experimental Forest." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/50818.

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Topographic analysis using digital elevation models (DEMs) has become commonplace in soil and hydrologic modeling and analysis and there has been considerable assessment of the effects of grid resolution on topographic metrics using DEMs of 10 m resolution or coarser. However, examining fine-scale (i.e., 1-10 m) soil and hydrological variability of headwater catchments may require higher-resolution data that has only recently become available, and both DEM accuracy and the effects of different high-resolution DEMs on topographic metrics are relatively unknown. This study has two principle research components. First, an error analysis of two high-resolution DEMs derived from light detection and ranging (LiDAR) data covering the same headwater catchment was conducted to assess the applicability of such DEMs for modeling fine-scale environmental phenomena. Second, one LiDAR-derived DEM was selected for computing topographic metrics to predict fine-scale functional soil units termed hydropedological units (HPUs). HPU development is related to topographic and surface/subsurface heterogeneity resulting in distinct hydrologic flowpaths leading to variation of soil morphological expression. Although the two LiDAR datasets differed with respect to data collection methods and nominal post-spacing of ground returns, DEMs interpolated from each LiDAR dataset exhibited similar error. Grid resolution affected DEM-delineated catchment boundaries and the value of computed topographic metrics. The best topographic metrics for predicting HPUs were the topographic wetness index, bedrock-weighted upslope accumulated area, and Euclidean distance from bedrock. Predicting the spatial distribution of HPUs may provide a more comprehensive understanding of hydrological and biogeochemical functionality of headwater systems.
Master of Science
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49

Barton, Mark B. "Spatial and Temporal Patterns of Arctic Nearshore Fish Community and Food Web Structures." FIU Digital Commons, 2018. https://digitalcommons.fiu.edu/etd/3735.

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Climate change and increasing anthropogenic activities are causing rapid changes to environmental and ecological processes in the Arctic Ocean. To better understand these changes, scientists have increased research efforts in these regions, but to date the number of studies on Arctic nearshore habitats are lacking. My dissertation responds to the paucity of information and investigates patterns in Arctic nearshore fish communities and food webs to gain insight to how these ecosystems may shift as these changes continue. I used multivariate statistical analysis to examine patterns in community structure and composition to determine that Arctic nearshore fish communities are largely driven by prey availability, salinity and temperature; and that species that are more abundant in warmer conditions are likely to increase in abundance as climatic conditions in the Arctic continue to warm. I improved the ability to apply stable isotope methods to Arctic food web studies by determining more appropriate model parameters using a laboratory-based isotope study on a common Arctic nearshore fish, and discuss its potential as a biological monitor species. These new parameters are used to confirm that a shift in prey resource dependence occurs across the seasonal shift from ice-covered winter to open-water summer conditions. Changes in basal resource dependence also occur later in the season across a latitudinal gradient where a shift to dependence on allochtonous inputs from nearby rivers increased trophic diversity. Using isotopic niche space theory, it was determined that the Arctic nearshore has a diverse prey base but that niche spaces of Arctic warm-water and cold-water species do overlap, and if numbers of warm-water fish continue to increase it will likely increase competition for resources for potentially less-adaptable, well-established, cold-water forage fish. On the other hand, if pelagic productivity is expected to increase and support larger fish biomasses, then there will be more than enough resources for warm-water and cold-water species to coexist, thus creating a more diverse prey base for piscivores in the Arctic.
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50

Li, Linhua. "A GIS-based Bayesian approach for analyzing spatial-temporal patterns of traffic crashes." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1766.

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