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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.
1

Spatial distribution, input and dispersion of plastic pellets in coastal zones / Distribuição espacial, aporte e dispersão de grânulos de plástico em zonas costeiras

Danilo Balthazar Silva 25 August 2016 (has links)
The production and the usage of plastic material increases since the decade of 1950. Nowadays, the elevated production rate, the misusing and the waste turned plastic material in an urgent environmental and economic problem. One of the major environmental problems related to this issue is the contamination of marine environments by microplastics. These constitute plastic particles of size between 1 and 5 mm. Microplastics might occur by breaking of larger plastic pieces or as a manufactured product. The plastic pellets are among this second class, these are small plastic spherules (≥ 5 mm) used in the plastics industry as raw material for the production of manufactured products. It is hypothesized that plastic pellets reach the marine environment due to losses in port terminals or accidental and intentional releases by commercial ships. The present study evaluated the contamination of the coastal zone by microplastics in different spatial and temporal scales. This evaluation approached the dispersion of microplastics in coastal zones, and used the spatial distribution, the stranding and the accumulation of plastic pellets in sandy beaches as a proxy to disclose the behavior of the variation of microplastics in coastal zones. The results of the present paper reveal that microplastics vary both in small and large temporal and spatial scales. Therefore, the present paper brings new insights to the knowledge on microplastics pollution in coastal zones, which might give a new baseline to methodological approaches adopted in management and monitoring programs. / A produção e o consumo de plásticos vêm aumentando desde a década de 1950. Nos dias de hoje, a taxa elevada de produção, o mal-uso e o desperdício tornaram os plásticos em um problema ambiental e econômico urgente. Um dos principais problemas relacionados à esta questão é a poluição dos ambientes marinhos por microplásticos. Estes constituem partículas de plástico de tamanho que varia entre 1 e 5 mm. Microplásticos podem ocorrer em decorrência da quebra de pedaços de plásticos grandes ou podem ocorrer como um produto fabricado. Os grânulos de plástico estão nesta segunda categoria, estes são pequenas esférulas de plástico (≥ 5 mm) utilizadas como matéria prima para a produção de utensílios variados pela indústria dos plásticos. A hipótese é de que os grânulos de plástico cheguem ao ambiente marinho a partir de perdas em terminais portuários ou após liberações acidentais ou intencionais por embarcações comerciais. O presente estudo avaliou a contaminação da zona costeira por grânulos de plástico em diferentes escalas espaciais e temporais. Esta avaliação abordou a dispersão de microplásticos em regiões costeiras e utilizou a distribuição espacial o aporte e o acúmulo de grânulos de plástico como um modelo para desvendar o comportamento da variação de microplásticos em zonas costeiras. O presente estudo revelou que os microplásticos varia em escalas espaciais e temporais grandes e pequenas. Os resultados apresentados aqui podem conferir embasamento e questões metodológicas para serem adotadas em estratégias de monitoramento e gestão.
2

Spatial distribution, input and dispersion of plastic pellets in coastal zones / Distribuição espacial, aporte e dispersão de grânulos de plástico em zonas costeiras

Silva, Danilo Balthazar 25 August 2016 (has links)
The production and the usage of plastic material increases since the decade of 1950. Nowadays, the elevated production rate, the misusing and the waste turned plastic material in an urgent environmental and economic problem. One of the major environmental problems related to this issue is the contamination of marine environments by microplastics. These constitute plastic particles of size between 1 and 5 mm. Microplastics might occur by breaking of larger plastic pieces or as a manufactured product. The plastic pellets are among this second class, these are small plastic spherules (≥ 5 mm) used in the plastics industry as raw material for the production of manufactured products. It is hypothesized that plastic pellets reach the marine environment due to losses in port terminals or accidental and intentional releases by commercial ships. The present study evaluated the contamination of the coastal zone by microplastics in different spatial and temporal scales. This evaluation approached the dispersion of microplastics in coastal zones, and used the spatial distribution, the stranding and the accumulation of plastic pellets in sandy beaches as a proxy to disclose the behavior of the variation of microplastics in coastal zones. The results of the present paper reveal that microplastics vary both in small and large temporal and spatial scales. Therefore, the present paper brings new insights to the knowledge on microplastics pollution in coastal zones, which might give a new baseline to methodological approaches adopted in management and monitoring programs. / A produção e o consumo de plásticos vêm aumentando desde a década de 1950. Nos dias de hoje, a taxa elevada de produção, o mal-uso e o desperdício tornaram os plásticos em um problema ambiental e econômico urgente. Um dos principais problemas relacionados à esta questão é a poluição dos ambientes marinhos por microplásticos. Estes constituem partículas de plástico de tamanho que varia entre 1 e 5 mm. Microplásticos podem ocorrer em decorrência da quebra de pedaços de plásticos grandes ou podem ocorrer como um produto fabricado. Os grânulos de plástico estão nesta segunda categoria, estes são pequenas esférulas de plástico (≥ 5 mm) utilizadas como matéria prima para a produção de utensílios variados pela indústria dos plásticos. A hipótese é de que os grânulos de plástico cheguem ao ambiente marinho a partir de perdas em terminais portuários ou após liberações acidentais ou intencionais por embarcações comerciais. O presente estudo avaliou a contaminação da zona costeira por grânulos de plástico em diferentes escalas espaciais e temporais. Esta avaliação abordou a dispersão de microplásticos em regiões costeiras e utilizou a distribuição espacial o aporte e o acúmulo de grânulos de plástico como um modelo para desvendar o comportamento da variação de microplásticos em zonas costeiras. O presente estudo revelou que os microplásticos varia em escalas espaciais e temporais grandes e pequenas. Os resultados apresentados aqui podem conferir embasamento e questões metodológicas para serem adotadas em estratégias de monitoramento e gestão.
3

Detecting Group Turns of Speaker Groups in Meeting Room Conversations Using Audio-Video Change Scale-Space

Krishnan, Ravikiran 30 June 2010 (has links)
Automatic analysis of conversations is important for extracting high-level descriptions of meetings. In this work, as an alternative to linguistic approaches, we develop a novel, purely bottom-up representation, constructed from both audio and video signals that help us char- acterize and build a rich description of the content at multiple temporal scales. Nonverbal communication plays an important role in describing information about the communication and the nature of the conversation. We consider simple audio and video features to extract these changes in conversation. In order to detect these changes, we consider the evolution of the detected change, using the Bayesian Information Criterion (BIC) at multiple temporal scales to build an audio-visual change scale-space. Peaks detected in this representation yields group turn based conversational changes at dierent temporal scales. We use the NIST Meeting Room corpus to test our approach. Four clips of eight minutes are extracted from this corpus at random, and the other ten are extracted after 90 seconds of the start of the entire video in the corpus. A single microphone and a single camera are used from the dataset. The group turns detected in this test gave an overall detection result, when compared with dierent thresholds with xed group turn scale range, of 82%, and a best result of 91% for a single video. Conversation overlaps, changes and their inferred models oer an intermediate-level de- scription of meeting videos that are useful in summarization and indexing of meetings. Since the proposed solutions are computationally e cient, require no training and use little domain knowledge, they can be easily added as a feature to other multimedia analysis techniques.
4

Prostorové a časové škály v dynamice atmosféry / Spatial and temporal scales of atmospheric dynamics

Jajcay, Nikola January 2018 (has links)
DOCTORAL THESIS Nikola Jajcay Spatial and temporal scales of atmospheric dynamics Abstract Earth climate, in general, varies on many temporal and spatial scales. In particular, climate observables exhibit recurring patterns and quasi- oscillatory phenomena with different periods. Although these oscillations might be weak in amplitude, they might have a non-negligible influence on variability on shorter time-scales due to cross-scale interactions, recently observed by Paluš[1]. This thesis supplies an introductory material for inferring the cross-scale information transfer from observational data, where the time series of interest are obtained using wavelet transform, and possible information transfer is studied using the tools from information theory. Finally, cross- scale interactions are studied in two climate phenomena: air temperature variability in Europe, in which we study phase-amplitude coupling from a slower oscillatory mode with an 8-year period on faster variability and its effects, and El Niño/ Southern Oscillation where we observe a causal chain of phase-phase and phase-amplitude couplings among distinct oscillatory modes. [1] M. Paluš. Multiscale atmospheric dynamics: cross-frequency phase-amplitude coupling in the air temperature. Physical Review Letters, 112(7):078702, 2014.
5

"Ecologia de manguezais: desenvolvimento espaço-temporal no sistema costeiro Cananéia-Iguape, São Paulo, Brasil" / Mangrove Ecology: spatial and temporal development at Cananéia-Iguape Coastal System, São Paulo, Brazil

Lignon, Marília Cunha 16 December 2005 (has links)
Manguezais desenvolvem-se de formas distintas, em função dos cenários ambiental e geomorfológico. O desenvolvimento espaço-temporal de bosques de mangue, no Sistema Costeiro Cananéia-Iguape, foi estudado no contexto da ecologia da paisagem. Manguezais foram analisados nos níveis hierárquicos Stand (unidade de paisagem) e Site (bosque ou parcela). No nível Stand, o tratamento de fotografias aéreas com uso de Sistema de Informação Geográfica (SIG), indicou variação espacial distinta, em duas áreas de estudo do Mar de Cananéia, no mesmo intervalo temporal, 16 anos (1981 – 1997). No nível Site, bosques de mangue adjacentes ao Mar de Cananéia e à Baía do Trapandé foram monitorados durante 2 anos (2002 – 2004), em parcelas fixas, fornecendo informações sobre o desenvolvimento destes. Bancos de sedimento emersos são, primeiramente, colonizados pela gramínea Spartina alterniflora, espécie pioneira e determinante no estabelecimento de propágulos. Os bosques de mangue, estudados no Mar de Cananéia, nas fases inicial e jovem são dominados por Laguncularia racemosa, em áreas em progradação, como proposto na literatura. Na área de estudo da Baía do Trapandé, a espécie dominante é Rhizophora mangle. Bosques maduros são dominados pelas espécies R. mangle ou Avicennia schauerianna, em função das características das áreas de estudo. Padrões de sucessão dos bosques de mangue estudados seguem modelo proposto na literatura. / Mangrove forests get developed in distinct patterns, depending on geomorphological and environmental scenarios. Its spatial and temporal development was studied in a landscape ecology context, at the Cananéia-Iguape Coastal System. Stand and Site hierarchical levels had been used to analyze mangrove forests. At Stand level, aerial photography processing along with Geographical Information System (GIS) showed distinct spatial variations during the same 16 years period (1981-1997) in the two case areas: Mar de Cananéia and Baia de Trapandé. At Site level, mangrove forests surrounding Mar de Cananéia and Baia de Trapandé had been monitored during 2 years (2002-2004) using fixed plots, providing information on its development. Gramineous Spartina alterniflora, pioneer species and determinative for propagule establishment, colonize at first emerged sandbanks. Studied mangrove forests surrounding Mar de Cananéia are, during initial and youth phases, dominated by Laguncularia racemosa, in deposition areas, as suggested in bibliography. At Baia de Trapandé surround, the dominant species was Rhizophora mangle. Mature forests are dominated by R. mangle or Avicennia schauerianna, depending on area’s characteristics. Studied mangrove forests follow model of succession seen in bibliography.
6

"Ecologia de manguezais: desenvolvimento espaço-temporal no sistema costeiro Cananéia-Iguape, São Paulo, Brasil" / Mangrove Ecology: spatial and temporal development at Cananéia-Iguape Coastal System, São Paulo, Brazil

Marília Cunha Lignon 16 December 2005 (has links)
Manguezais desenvolvem-se de formas distintas, em função dos cenários ambiental e geomorfológico. O desenvolvimento espaço-temporal de bosques de mangue, no Sistema Costeiro Cananéia-Iguape, foi estudado no contexto da ecologia da paisagem. Manguezais foram analisados nos níveis hierárquicos Stand (unidade de paisagem) e Site (bosque ou parcela). No nível Stand, o tratamento de fotografias aéreas com uso de Sistema de Informação Geográfica (SIG), indicou variação espacial distinta, em duas áreas de estudo do Mar de Cananéia, no mesmo intervalo temporal, 16 anos (1981 – 1997). No nível Site, bosques de mangue adjacentes ao Mar de Cananéia e à Baía do Trapandé foram monitorados durante 2 anos (2002 – 2004), em parcelas fixas, fornecendo informações sobre o desenvolvimento destes. Bancos de sedimento emersos são, primeiramente, colonizados pela gramínea Spartina alterniflora, espécie pioneira e determinante no estabelecimento de propágulos. Os bosques de mangue, estudados no Mar de Cananéia, nas fases inicial e jovem são dominados por Laguncularia racemosa, em áreas em progradação, como proposto na literatura. Na área de estudo da Baía do Trapandé, a espécie dominante é Rhizophora mangle. Bosques maduros são dominados pelas espécies R. mangle ou Avicennia schauerianna, em função das características das áreas de estudo. Padrões de sucessão dos bosques de mangue estudados seguem modelo proposto na literatura. / Mangrove forests get developed in distinct patterns, depending on geomorphological and environmental scenarios. Its spatial and temporal development was studied in a landscape ecology context, at the Cananéia-Iguape Coastal System. Stand and Site hierarchical levels had been used to analyze mangrove forests. At Stand level, aerial photography processing along with Geographical Information System (GIS) showed distinct spatial variations during the same 16 years period (1981-1997) in the two case areas: Mar de Cananéia and Baia de Trapandé. At Site level, mangrove forests surrounding Mar de Cananéia and Baia de Trapandé had been monitored during 2 years (2002-2004) using fixed plots, providing information on its development. Gramineous Spartina alterniflora, pioneer species and determinative for propagule establishment, colonize at first emerged sandbanks. Studied mangrove forests surrounding Mar de Cananéia are, during initial and youth phases, dominated by Laguncularia racemosa, in deposition areas, as suggested in bibliography. At Baia de Trapandé surround, the dominant species was Rhizophora mangle. Mature forests are dominated by R. mangle or Avicennia schauerianna, depending on area’s characteristics. Studied mangrove forests follow model of succession seen in bibliography.
7

Prediction of Mosquito Abundance in Temperate Regions, Using Ecological, Hydrological and Remote Sensing Models

Jian, Yun January 2014 (has links)
<p>New and old mosquito-borne diseases have emerged and re-emerged in temperate regions over the recent past, but an understanding of mosquito population dynamics, a fundamental step toward disease control, remains elusive. In particular, we are still lacking reliable predictive models of mosquito abundance in temperate areas due to the subtle links between the fluctuation of mosquito population and highly heterogeneous environmental drivers. Hence, this doctoral dissertation presents an interdisciplinary approach towards an improved understanding and prediction of the fluctuations in mosquito abundance in temperate regions. In the first part of this dissertation a hierarchical Gompertz-based model is used to assess the relative importance of endogenous (density dependence) and exogenous (environmental forcings) controls and their interactions in regulating the dynamics of a West Nile Virus vector (Culex pipiens) in the Po River delta in Italy. The results clearly detect the effects of density-dependence in the observed population dynamics for the mosquito species analyzed and highlight the controls exerted by environmental forcings and habitat conditions. Subsequently, the characteristic scales of temporal variability in mosquito populations, and the representativeness of observations at different sampling resolutions, are investigated using a 10 year daily mosquito sample from Brunswick County, North Carolina. The species present in the sample (among which Aedes vexans and Culiseta melanura are addressed in greater detail, as vectors of East Equine Encephalitis and West Nile Virus) are investigated using a combination of time series analysis, individual based simulations, and density-dependent modeling approaches. Significant population fluctuations with characteristic periodicity between 2 days and several years are found in response to different regulation mechanisms. In particular, the observed fast fluctuations are importantly determined by a varying mosquito activity, rather than by reproduction/mortality processes, driven by rapid changes in meteorological conditions. Finally, in the third part of this study, a state space reconstruction (SSR) approach is used to understand how the predictability of mosquito abundance varies with aggregation time scale and with the prediction horizon, and how much can the prediction of mosquito abundance be improved by using daily observations compared to the commonly used once-per-week samples. The results show that the predictability of mosquito abundance decreases as the time scale of the models increases from one week to one month, while the predictability of per capita growth rate increases together with the modeling scale. It is also shown that the prediction of mosquito per capita growth rate can be improved using daily abundance observations. Furthermore, many mosquito models compare the observed and predicted abundance as a measure of model performance. However, my results suggest that short term forecasts of mosquito abundance may appear to have a significant capability due to the positive autocorrelation between abundance in subsequent time steps, even when the model's ability to predict the abundance change is low. Model capability should thus be evaluated comparing observed and modelled per capita rates of change.</p> / Dissertation
8

Modelling evaporation with local, regional and global BROOK90 frameworks: importance of parameterization and forcing

Vorobevskii, Ivan, Luong, Thi Thanh, Kronenberg, Rico, Grünwald, Thomas, Bernhofer, Christian 19 April 2024 (has links)
Evaporation plays an important role in the water balance on a different spatial scale. However, its direct and indirect measurements are globally scarce and accurate estimations are a challenging task. Thus the correct process approximation in modelling of the terrestrial evaporation plays a crucial part. A physically based 1D lumped soil–plant–atmosphere model (BROOK90) is applied to study the role of parameter selection and meteorological input for modelled evaporation on the point scale. Then, with the integration of the model into global, regional and local frameworks, we made cross-combinations out of their parameterization and forcing schemes to show and analyse their roles in the estimations of the evaporation. Five sites with different land uses (grassland, cropland, deciduous broadleaf forest, two evergreen needleleaf forests) located in Saxony, Germany, were selected for the study. All tested combinations showed a good agreement with FLUXNET measurements (Kling–Gupta efficiency, KGE, values 0.35–0.80 for a daily scale). For most of the sites, the best results were found for the calibrated model with in situ meteorological input data, while the worst was observed for the global setup. The setups' performance in the vegetation period was much higher than for the winter period. Among the tested setups, the model parameterization showed higher spread in performance than meteorological forcings for fields and evergreen forests sites, while the opposite was noticed in deciduous forests. Analysis of the of evaporation components revealed that transpiration dominates (up to 65 %–75 %) in the vegetation period, while interception (in forests) and soil/snow evaporation (in fields) prevail in the winter months. Finally, it was found that different parameter sets impact model performance and redistribution of evaporation components throughout the whole year, while the influence of meteorological forcing was evident only in summer months.
9

Suivi des peuplements ichtyologiques en milieu estuarien par approche acoustique : application à l’estuaire de la Gironde / Monitoring fish population in estuarine ecosystem with acoustic surveys : the Gironde estuary case

Samedy, Valérie 28 June 2013 (has links)
Depuis de nombreuses années, les évaluations de la faune circulante au sein de l’estuaire de la Gironde s’appuient sur plusieurs dispositifs de suivis ichtyologiques, chroniques de pêches scientifiques et professionnelles. Cependant, ces approches conventionnelles nécessitent souvent un échantillonnage conséquent, restent ponctuelles dans le temps, spatialement limitées et destructrices. Tester la mise en œuvre d’un suivi acoustique prend ainsi toute son sens et son intérêt. Plus largement appliqué en milieux marin et lacustre, cette approche reste encore rarement utilisée en estuaires. En raison de l’extrême variabilité intrinsèque de ce type d’écosystème, la mise en œuvre de cet outil est un réel défi. En s’appuyant sur la connaissance préalablement acquise, une réflexion méthodologique approfondie a été menée pour définir des stratégies d’échantillonnage acoustiques afin d’optimiser la récolte de ce type de données. Plusieurs stratégies acoustiques ont d’abord été testées en tenant compte de la complexité et de la taille importante de l’écosystème étudié. La pertinence de ces données recueillies a ensuite été confrontée aux données des pêches scientifiques. Enfin, l’hydroacoustique a été mis à profit pour répondre à des questions sur la dynamique ichtyologique à des échelles spatiales et temporelles plus fines notamment pour étudier les influences tidales et nycthémérales. Ce travail démontre qu’il est possible de mettre en place un suivi acoustique des peuplements ichtyologiques pour un estuaire comme la Gironde. Comme outil complémentaire aux approches traditionnelles, l’hydroacoustique ouvre un large champ de possibilités pour appréhender la biocénose piscicole pour les milieux estuariens. / For many years, assessments of fish densities within the Gironde estuary have been based on a number of different fish monitoring techniques, as well as professional and scientific surveys. However, these approaches are often destructive. They require substantial sampling, and are limited from the points of view of both time and space. With this in mind, the benefits of non-invasive acoustic monitoring are clear. While such methods are often used in lakes and other marine environments, they have yet to be widely applied to shallow-water areas, in particular estuaries. Applying an acoustic approach to this kind of intrinsically changeable environment represents a real challenge. In this research project, an in-depth methodological study was carried out to determine the optimum way of applying acoustic sampling. Several acoustic monitoring strategies were then tested, keeping in mind the size and complexity of the ecosystem under investigation. The results of these tests were then checked for relevance against data from scientific fisheries. Finally, hydroacoustics was used to examine fish dynamics at finer spatial and temporal scales, notably in the study of diurnal and tidal influences. The results of this study show that it is possible to use acoustic monitoring to complement traditional methods of estimating fish populations in estuarine areas, and that the use of such a combination opens up a broad range of new possibilities.
10

Changing valuations of cultural ecosystem services along an urban-periurban gradient in Berlin / Qualitative and quantitative assessment

Riechers, Maraja 14 July 2015 (has links)
No description available.

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