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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
211

Spatio-Temporal Analysis of Point Patterns

Soale, Abdul-Nasah 01 August 2016 (has links)
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.
212

Ecologie évolutive des limites de niche : cas de l’adaptation à la salinité de l'artémie / Evolutionary ecology of niche limits : the adaptation to salinity of Artemia

Nougué, Odrade 19 June 2015 (has links)
Le concept de niche a été défini par Hutchinson comme un espace multidimensionnel de variables environnementales où l'espèce survie. Au cours de ce travail, je me suis intéressée à différentes limites conceptuelles et opérationnelles du concept de niche. En m'appuyant sur le cas de l'adaptation à la salinité chez le genre Artemia – branchiopode extrêmophile – nous nous sommes intéressés : (i) aux mécanismes à l'origine du maintien du polymorphisme génétique d'une large population clonale, qui m'a permis de m'interroger sur l'échelle utile à l'application du concept de niche ; (ii) à l'impact de la flore bactérienne sur l'adaptation de l'artémie aux faibles salinités, qui m'a permis d'évaluer plus globalement l'impact que les interactions biotiques peuvent avoir dans le contexte multidimensionnel de la niche ; (iii) aux effets de la plasticité et de la qualité d'habitat sur l'adaptation de l'artémie aux fortes salinités, qui pose des questions opérationnelles sur l'évaluation de l'influence de ces facteurs sur la niche. Le travail détaillé dans ce manuscrit s'appuie sur des méthodologies variées et a apporté des éléments de réponses aux problématiques posées. Tout d'abord, nous avons pu montrer que la diversité génétique d'une large population clonale était structurée par des déterminants environnementaux tels que la salinité ou la température. Ce travail a aussi montré que dans le cas d'une population asexuée, le concept de niche pouvait s'appliquer à un groupe d'individu génétiquement proche et pouvant (selon le mode de reproduction) appartenir à une lignée commune. Ensuite, nous avons montré que la niche de la flore intestinale de l'artémie facilite la digestion des algues, mais contraint leur tolérance aux faibles salinités. Il faut alors envisager que les interactions biotiques peuvent avoir différents effets (parfois même contradictoires) sur les différents axes de la niche de l'espèce focale. Enfin, nous avons apporté des solutions méthodologiques pour évaluer séparément l'impact de la plasticité et de la qualité d'habitat sur l'adaptation des artémies aux fortes salinités. Au final, nous avons apporté des solutions conceptuelles et/ou opérationnelles permettant de solidifier le concept de niche qui est une notion clé en écologie évolutive. / Hutchinson defined the niche concept as the multidimensional space of environmental variables where the specie survives. During this work, I focused on several conceptual and operational limits of this concept. Basing our work on the adaptation to salinity of the genus Artemia – an extremophile branchipod – we studied: (i) mechanisms involved in the polymorphism maintenance in a large clonal population, which asked the question of the scaling in the use of the niche concept; (ii) impact of the gut microbiota on the adaptation to low salinities, which asked the question on the impact of biotic interactions on the niche; (iii) the effects of habitat quality and phenotypic plasticity on the tolerance to high salinities, which asked operational questions on the evaluation of theses factors and there impact on the niche. The work detailed in this manuscript is based on a large variety of methodologies and helped providing elements of answers to solve the problematic. First, we showed that the important diversity found in the large clonal population was structured by environmental variables such as salinity and temperature. Therefore, in the case of a large asexual population, the niche concept can apply to a group of genetically close individual that might share (depending on the reproduction mode) common ancestry. Then, we showed that the niche of the gut microbiota, associated with Artemia for algae digestion, constrained their host tolerance to low salinities. Thus, biotic interactions may have different effects (even conflicting sometimes) on the different axes of their host niche. Finally, we provided some methodological solutions to evaluate separately the impact of plasticity and habitat quality on the adaptation of Artemia to high salinities. In the end, we provided conceptual and/or operational solutions that strengthen the evolutionary ecology key concept of the niche.
213

空間模式與追求圖案:維珍妮亞‧吳爾芙《燈塔行》中時空互動關係 / Spatial Form and Search Patterns: The Spatio-temporal Interdependence in Virginia Woolf's <u>To the Lighthouse</u>

李秋虹, Li, Ch'iu Hung Unknown Date (has links)
維珍妮亞‧吳爾芙《燈塔行》揉合小說與繪畫,在作者創新的手法、精湛的技巧背後藏有模仿人物情緒、情感最纖細的體味。《燈塔行》不論筆觸、內容或意境在在表現出吳爾芙追尋主題、濃厚的繪畫知性與感性傾向,對吳爾芙而言,生命與藝術的追求便是唯善至美的永久追求。本論文第一章試就作品“空間模式”的技巧運用檢視其分裂斷折的文字敘述,框化的造形藝術,視覺官能的虛擬情境。第二章說明“空間模式”中不可或缺的時間因素,進而將時空互動關係演至“空”這觀念,說明吳爾芙的生命觀與追尋的價值。在作者形象語言中,追尋具有圖案或圖畫,不管是藍姆西先生的線條邏列、藍姆西太太的靜態平面、或第三章中討論的莉莉‧柏斯蔻的畫作,都可以感受到這些人物對世間萬事萬物的企圖和努力。 / This study examines Virginia Woolf's innovative form and style in <u>To the Lighthouse</u> designed to imitate the confusion of thoughts, emotions, and views of life and to reveal man's search for life's meaning and his struggle to give shape to his experiences. Chapter One of this thesis investigates the spatial form of the text, particularly the disrupted narrative, the use of frames and the focus on virtual reality. In this chapter, I try to show that the spatial writing in fact produces simultaneity and that simultaneity often makes the thoughts and emotions arise all at once. Chapter Two discusses the notion of the spatio-temporal interdependence with demonstrations of the Ramsays' search patterns, the line and the surface, the facing and the fusing. This chapter explains the idea of man's searching for order through time and the empty space as exemplified by the novel's middle part, "Time Passes." In using the similar plastic language of colors and shapes, Mr and Mrs. Ramsay suggest their common destiny, a quest for order and unity that is extended to the final chapter. Chapter Three follows and develops the search motif in Lily Briscoe's painting process, a process that combines visual actualities and memories.
214

Plant-seed predator interactions – ecological and evolutionary aspects

Östergård, Hannah January 2008 (has links)
<p>Plant-animal interactions are affected by both abundance and distribution of interacting species and the community context in which they occur. However, the relative importance of these factors is poorly known. I examined the effects of predator host range, environmental factors, host plant populations, plant traits and fruit abortion on the intensity of pre-dispersal seed predation in 46 host populations of the perennial herb <i>Lathyrus vernus</i>. I recorded damage by beetle pre-dispersal seed predators, mainly <i>Apion opeticum </i>and <i>Bruchus atomarius</i> with different host ranges on <i>L. vernus</i> as well as on two additional host plants. Local seed predator population size was mainly influenced by plant population size, current seed production and beetle population size in the previous year, but was not strongly affected by connectivity. The monophagous seed predator was less abundant and had lower densities than the oligophagous. Both predator species had a strong ability to track fluctuations in seed production; intensity of predation increased with relative increases in seed production. Oligophagous predation on<i> L. vernus i</i>ncreased with the abundance of alternative hosts, but presence of<i> L. vernus</i> did not affect predation on alternative hosts. Abundances and trait preferences differed among three co-occurring seed predators, but were also associated with the abundance of the other species. Overall, seed predation influenced selection on flower number. I found clear indications of seed predator offence but no obvious plant defence. The pattern of fruit abortion was associated with reduced plant fitness since the seed predator had an advanced ability to locate fruits with high probability of retention. Taken together, different factors influencing abundance of the seed predator species, different preferences, and context dependent trait selection are likely to result in complex spatio-temporal variation in overall seed losses and trait selection in the common host plant.</p>
215

ANTHROPISATION ET DYNAMIQUE SPATIO-TEMPORELLE DE PAYSAGES FORESTIERS EN REPUBLIQUE DEMOCRATIQUE DU CONGO

Bamba, Issouf 13 October 2010 (has links)
A l’image du bassin du Congo, la République Démocratique du Congo (République Démocratique du Congo) fait face à une réduction de la qualité et de la superficie de son couvert forestier. La présente étude avait pour objectif d’étudier l’effet de l’anthropisation, à travers la présence et les activités humaines sur la dynamique des paysages forestiers en République Démocratique du Congo. L’écologie du paysage, en tant que science pluridisciplinaire offre une très bonne approche à travers les indices et une méthodologie alliant la structure et la composition du paysage pour mettre en évidence les causes et les conséquences des processus écologiques. Ces approches sont basées sur le fait que en analysant la structure du paysage, des déductions utiles au sujet des processus écologiques fondamentaux peuvent être faites et vice versa. Les résultats ont montré, en quantifiant la dynamique spatio-temporelle de l’occupation du sol et par l’analyse et la caractérisation de la structure spatiale, que l’anthropisation est le moteur de la dynamique dans ces milieux forestiers. L’impact humain se traduit par une déstabilisation ou un dysfonctionnement des écosystèmes forestiers entraînant la dégradation, la fragmentation et la déforestation. Ainsi il a été montré que la proximité des villes est fortement corrélée à la dégradation et la perte d’habitats forestiers. Cela est fonction de l’importance socio-économique de ces villes car plus la ville est importante, plus elle attire la population ; que la densité de la population influence la fragmentation et l’incursion dans la forêt se fait en suivant les pistes et les routes mises en place généralement par les sociétés d’exploitation forestière. Le tout amplifié par la situation socio-économique difficile des populations et le manque de politiques de gestion appropriées de la part des gestionnaires publiques. Cette dynamique régressive du paysage forestier en République Démocratique du Congo aura une incidence négative sur les cycles climatiques globaux vu que le bassin du Congo est le plus grand bloc forestier après le bloc de l’Amazonie. La présente étude est donc un argument supplémentaire qui milite en faveur de la nécessité de prendre en compte les caractéristiques des populations locales dans les programmes de gestion de la forêt du bassin du Congo pour un meilleur équilibre écologique de la planète. / Like Congo basin, Democratic Republic of Congo’s forest covers are facing their reduction in quality and size. This study aimed to investigate the effect of human impact on forest landscape dynamics in DR Congo, through the human presence and its activities. Landscape ecology as a multidisciplinary science offers a very good approach through the index and a methodology combining the structure and the composition of the landscape to highlight the causes and the consequences of ecological processes. These approaches are based on the fact that by analyzing the structure of landscape, useful deductions about the underlying ecological processes can be made and vice versa. By quantifying the spatio-temporal dynamics of land use and by analysis and characterization of spatial structure, our results showed that anthropization is the driver of the dynamics in these forest environments. Human impact results in a destabilization or a dysfunction of the forest ecosystems involving degradation, fragmentation and deforestation. Thus it was shown that proximity to cities is strongly correlated to the degradation and loss of forest habitats. This depends on the socioeconomic importance of these cities because more the city is important, more it attracts people. Population density influences the fragmentation and the incursion into the forest is done by following the tracks and roads generally implemented by the logging companies. All amplified by socio-economic problems of population and lack of appropriate management policies on the part of public managers.This regressive dynamic forest landscape in République Démocratique du Congo will have a negative impact on global climate cycles because the Congo Basin is the largest forest block after Amazonia block. This study is another argument which advocates the need to take into account the characteristics of local population in forest management programs in the Congo Basin for a better ecological balance of planet.
216

Plant-seed predator interactions – ecological and evolutionary aspects

Östergård, Hannah January 2008 (has links)
Plant-animal interactions are affected by both abundance and distribution of interacting species and the community context in which they occur. However, the relative importance of these factors is poorly known. I examined the effects of predator host range, environmental factors, host plant populations, plant traits and fruit abortion on the intensity of pre-dispersal seed predation in 46 host populations of the perennial herb Lathyrus vernus. I recorded damage by beetle pre-dispersal seed predators, mainly Apion opeticum and Bruchus atomarius with different host ranges on L. vernus as well as on two additional host plants. Local seed predator population size was mainly influenced by plant population size, current seed production and beetle population size in the previous year, but was not strongly affected by connectivity. The monophagous seed predator was less abundant and had lower densities than the oligophagous. Both predator species had a strong ability to track fluctuations in seed production; intensity of predation increased with relative increases in seed production. Oligophagous predation on L. vernus increased with the abundance of alternative hosts, but presence of L. vernus did not affect predation on alternative hosts. Abundances and trait preferences differed among three co-occurring seed predators, but were also associated with the abundance of the other species. Overall, seed predation influenced selection on flower number. I found clear indications of seed predator offence but no obvious plant defence. The pattern of fruit abortion was associated with reduced plant fitness since the seed predator had an advanced ability to locate fruits with high probability of retention. Taken together, different factors influencing abundance of the seed predator species, different preferences, and context dependent trait selection are likely to result in complex spatio-temporal variation in overall seed losses and trait selection in the common host plant.
217

Atmospheric Tomography Using Satellite Radio Signals

Flores Jiménez, Alejandro 04 February 2000 (has links)
Los sistemas de posicionamiento global GNSS (GPS y GLONASS) se han convertido en una herramienta básica para obtener medidas geodésicas de la Tierra y en una fuente de datos para el estudio atmosférico. Proporcionan cobertura global y permanente y por la precisión, exactitud y densidad de datos, las señales radio transmitidas pueden ser usadas para la representación espacio-temporal de la atmósfera.La tecnología de los receptores GPS ha evolucionado con una sorprendente rapidez, resultando en instrumentos con suficiente calidad de medida para ser utilizados en estudios geodésicos, comparables a los resultados de técnicas como la interferometría de muy larga base (VLBI), y estudios atmosféricos cuyos resultados pueden ser usados en meteorología.En la tesis Tomografía Atmosférica utilizando Señales Radio de Satélites nos hemos centrado en el uso del sistema GPS por disponer mayor cantidad y calidad de referencias y herramientas para el procesado de los datos. No obstante, se ha demostrado la posibilidad de extender el concepto a cualquier sistema de transmisión radio desde satélite como sondeador atmosférico. La estructura de la tesis se ha dividido en dos áreas: el procesado de datos GPS para extraer información referente a los parámetros atmosféricos de interés, y la aplicación de técnicas tomográficas para la resolución de problemas inversos. En particular, la tomografía se ha aplicado a la ionosfera y la atmósfera neutra. En ambos casos, los resultados tienen un innegable impacto socio-económico: a) la monitorización del estado ionosférico es fundamental por las perturbaciones que la ionosfera provoca en las transmisiones radio que la atraviesan, y b) la estimación del contenido de vapor de agua de la troposfera es de utilidad en la predicción meteorológica y climática.La tomografía ionosférica se empezó a desarrollar usando únicamente datos de la red global IGS. A continuación se mejoró la resolución vertical mediante la utilización de datos de ocultaciones del experimento GPS/MET. La mejora de la resolución se ve limitada a la región en la que estos datos existen. Finalmente, se utilizaron datos de altimetría del satélite TOPEX/POSEIDON para mejorar los mapas y para demostrar la posibilidad de calibración instrumental de los altímetros radar usando técnicas tomográficas.La aplicación a la troposfera se obtuvo tras la mejora y refinamiento tanto del procesado de datos GPS como del proceso de inversión tomográfica. Los primeros resultados se obtuvieron mediante los datos experimentales de la red permanente en Kilauea, Hawaii, por la configuración particular de los receptores. Estos resultados demostraban la capacidad de obtener representaciones espacio-temporales de la troposfera mediante datos GPS. El análisis de los datos de la campaña REGINA, realizada en el Onsala Space Observatory, nos permitió la descripción de un fenómeno meteorológico complejo mediante la tomografía troposférica usando datos GPS y su verificación por comparación directa con medidas realizadas por radiosondeo.En conclusión, se ha demostrado la posibilidad de aplicar tomografía a la atmósfera utilizando señales radio de satélites y, en particular, la constelación GPS. / The Global Navigation Satellite Systems (GPS and GLONASS) have become a basic tool to obtain geodetic measurements of the Earth and a source of data for the atmospheric analysis. Since these systems provide a global, dense and permanent coverage with precise and accurate data, the radio signals they transmit can be used for the spatio-temporal representation of the atmosphere.GPS receivers technology has evolved at a surprising pace: nowadays they have sufficient measurement quality as to be used in geodetic studies, together with other techniques such as the Very Long Base Interferometry (VLBI), and in atmospheric studies whose results can be input into meteorological analysis.In the thesis "Atmospheric Tomography Using Satellite Radio Signals" we have focused on the use of GPS system due to the better quality and quantity of references and tools for the data processing. This notwithstanding, we have proven the possibility to broaden the concept to include any other radio signal transmitting satellite system as an atmospheric sounder. The thesis has been divided into two main areas: GPS data processing to extract the information related to the atmospheric parameters under study, and the implementation of tomographic techniques to the solution of the inverse problem. In particular, tomography has been applied to the ionosphere and to the neutral atmosphere. In both cases, results have a socio-economic impact: a) monitoring the ionosphere is essential for radio transmissions across it because of the perturbations it may produce on the signal, and b) estimating water vapour content in the troposphere is highly useful for meteorological and climate forecastFor the ionospheric tomography we initally only used the data from the global IGS network. Vertical resolution was afterwards improved using the occultation data of the GPS/MET experiment. The improvement, however, was limited to the region where these data existed. Finally, we used altimeter data from the TOPEX/POSEIDON satellite to improve the maps and to prove the radar altimeter calibration capability of the tomographic technique.The application to the troposphere was possible after the improvement and refinement of both the GPS data processing and the tomographic inversion. The first results were obtained using the experimental data from the permanent network in Kilauea, Hawaii. The particular geometry of the receivers in this local network made it highly suited for these initial results, which proved the possibility of obtaining spatio-temporal representations of the troposphere using GPS data. The data analysis of the REGINA campaign, which took place at the Onsala Space Observatory, provided the description of a complex meteorological phenomenon using only GPS data tropospheric tomography. We verified the results with a direct comparison with radiosonde data.Concluding, we have demonstrated the capabilities of atmospheric tomography using satellite radio signals, with particular emphasis on the GPS signals.
218

Fuzzy Association Rule Mining From Spatio-temporal Data: An Analysis Of Meteorological Data In Turkey

Unal Calargun, Seda 01 January 2008 (has links) (PDF)
Data mining is the extraction of interesting non-trivial, implicit, previously unknown and potentially useful information or patterns from data in large databases. Association rule mining is a data mining method that seeks to discover associations among transactions encoded within a database. Data mining on spatio-temporal data takes into consideration the dynamics of spatially extended systems for which large amounts of spatial data exist, given that all real world spatial data exists in some temporal context. We need fuzzy sets in mining association rules from spatio-temporal databases since fuzzy sets handle the numerical data better by softening the sharp boundaries of data which models the uncertainty embedded in the meaning of data. In this thesis, fuzzy association rule mining is performed on spatio-temporal data using data cubes and Apriori algorithm. A methodology is developed for fuzzy spatio-temporal data cube construction. Besides the performance criteria interpretability, precision, utility, novelty, direct-to-the-point and visualization are defined to be the metrics for the comparison of association rule mining techniques. Fuzzy association rule mining using spatio-temporal data cubes and Apriori algorithm performed within the scope of this thesis are compared using these metrics. Real meteorological data (precipitation and temperature) for Turkey recorded between 1970 and 2007 are analyzed using data cube and Apriori algorithm in order to generate the fuzzy association rules.
219

A Case Study In Weather Pattern Searching Using A Spatial Data Warehouse Model

Koylu, Caglar 01 June 2008 (has links) (PDF)
Data warehousing and Online Analytical Processing (OLAP) technology has been used to access, visualize and analyze multidimensional, aggregated, and summarized data. Large part of data contains spatial components. Thus, these spatial components convey valuable information and must be included in exploration and analysis phases of a spatial decision support system (SDSS). On the other hand, Geographic Information Systems (GISs) provide a wide range of tools to analyze spatial phenomena and therefore must be included in the analysis phases of a decision support system (DSS). In this regard, this study aims to search for answers to the problem how to design a spatially enabled data warehouse architecture in order to support spatio-temporal data analysis and exploration of multidimensional data. Consequently, in this study, the concepts of OLAP and GISs are synthesized in an integrated fashion to maximize the benefits generated from the strengths of both systems by building a spatial data warehouse model. In this context, a multidimensional spatio-temporal data model is proposed as a result of this synthesis. This model addresses the integration problem of spatial, non-spatial and temporal data and facilitates spatial data exploration and analysis. The model is evaluated by implementing a case study in weather pattern searching.
220

An Ontology-driven Video Annotation And Retrieval System

Demirdizen, Goncagul 01 October 2010 (has links) (PDF)
In this thesis, a system, called Ontology-Driven Video Annotation and Retrieval System (OntoVARS) is developed in order to provide a video management system which is used for ontology-driven semantic content annotation and querying. The proposed system is based on MPEG-7 ontology which provides interoperability and common communication platform with other MPEG-7 ontology compatible systems. The Rhizomik MPEG-7 ontology is used as the core ontology and domain specific ontologies are integrated to the core ontology in order to provide ontology-based video content annotation and querying capabilities to the user. The proposed system supports content-based annotation and spatio-temporal data modeling in video databases by using the domain ontology concepts. Moreover, the system enables ontology-driven query formulation and processing according to the domain ontology instances and concepts. In the developed system, ontology-driven concept querying, spatio-temporal querying, region-based and time-based querying capabilities are performed as simple querying types. Besides these simple query types, compound queries are also generated by combining simple queries with &quot / (&quot / , &quot / )&quot / , &quot / AND&quot / and &quot / OR&quot / operators. For all these query types, the system supports both general and video specific query processing. By this means, the user is able to pose queries on all videos in the video databases as well as the details of a specific video of interest.

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