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Grundvattenmodellering i BadelundaåsenLorentzon, Martin January 2005 (has links)
<p>Over an extended period of time there have been plans to establish a shared facility in Lennheden to extract groundwater from the Badelunda esker to provide drinking water for the cities of Borlänge and Falun. The city of Falun is dissatisfied with the quality of its drinking water and the city of Borlänge is concerned about the risk of contamination of its existing groundwater supply at its current location. To provide a basis for a decision on this issue, the company Midvatten AB has been commissioned to perform hydrogeological investigations in the area of Lennheden.</p><p>The purpose of this thesis is to design a functional groundwater model of the area between Lennheden, place of planned extraction, and Övre Tjärna, place of existing extraction, to get a better understanding of the groundwater situation in the area. A groundwater model enables simulations of different scenarios in risk assessment and contaminant transport. The aim of the thesis is that the model can be used as an aid in Midvatten’s investigations in Lennheden and that it also can be used in future projects in the area.</p><p>The model has been made in Processing Modflow 5.3 and encompasses an area of 19,5 × 11 km along the Badelunda esker and the river Dalälven between Djurmo and Frostbrunnsdalen. The model has 6 layers and a cell resolution of 50 × 50 meters and 50 × 100 meters. The physical parameters of the model are comprised from different hydrological and geological investigations in the area.</p><p>The Badelunda esker and the river Dalälven totally dominate the groundwater situation in the area. A large part of the work in the thesis has been focused on the calibration of the horizontal hydraulic conductivity in the esker and the vertical hydraulic conductivity in the riverbed of Dalälven. The calibration of the model implies a vertical hydraulic conductivity of 0,01 – 0,1 md-1 in the riverbed of Dalälven, depending on the riverbed thickness.</p><p>Between Bäsna and Övre Tjärna, simulated and observed groundwater levels correspond well. The transport time of the water in the esker, simulated in PMPATH, also corresponds well with estimated transport times. The model can be used for simpler studies of contaminant transport.</p><p>Simulation of the pumping test in Lennheden gives a good correspondence eastward in the esker from Lennheden to Övre Tjärna. Westward in the esker, from Lennheden to Bäsna, the draw down is sharper than observed. Possible reasons for the sharper draw down is an underestimation of the bulk of the esker and that the vertical hydraulic conductivity of the riverbed is set too low between Lennheden and Bäsna.</p><p>In order to improve the model, the most important step should be to thoroughly investigate the river Dalälven with regards to vertical hydraulic conductivity in the riverbed and riverbed thickness.</p> / <p>Under en längre tid har det funnits planer på att upprätta en ny, gemensam vattentäkt för Borlänge och Falu kommun i Badelundaåsen i Lennheden nordväst om Borlänge stad. Falu kommun är missnöjd med vattenkvaliteten i sin ytvattentäkt och Borlänge är oroad över riskerna med att ha sin nuvarande vattentäkt i Badelundaåsen lokaliserad i nära anslutning till riksväg 70 och järnvägen. Beslut i frågan ska tas under 2006 och Midvatten AB har fått i uppdrag att genomföra geohydrologiska undersökningar i och runt Lennheden som underlag till beslutet.</p><p>Syftet med det här examensarbetet är att skapa en fungerande grundvattenmodell för området mellan Lennheden, plats för planerat vattenuttag, och Övre Tjärna, plats för befintligt vattenuttag, för att få en större förståelse för grundvattenmagasinet. En grundvattenmodell möjliggör simulering av olika scenarion så som föroreningstransport i grundvattnet och bestämning av skyddsområden. Målet är att modellen ska kunna användas som ett komplement i Midvattens undersökningar och även användas i framtida projekt i området.</p><p>Modellen är gjord i Processing Modflow 5.3 och omfattar ett 19,5 × 11 km stort område längs Badelundaåsen och Dalälven mellan Djurmo och Frostbrunnsdalen. Modellen består av 6 lager där cellernas upplösning är 50 × 50 meter och 50 × 100 meter. De fysiska parametrar som modellen är uppbyggd av är sammanställda från olika hydrologiska och geologiska undersökningar som har utförts i området de senaste 30 åren.</p><p>Badelundaåsen och Dalälven är de två komponenter som totalt dominerar grundvattensituationen i området. En stor del av arbetet har fokuserats på kalibreringen av den horisontella hydrauliska konduktiviteten i åsen och den vertikala hydrauliska konduktiviteten i Dalälvens botten. I modellen är den vertikala hydrauliska konduktiviteten i Dalälvens botten kalibrerad till intervallet 0,01 – 0,1 md-1 beroende på bottnens mäktighet.</p><p>På sträckan mellan Bäsna och Övre Tjärna så fungerar modellen bra. Simulerade och observerade grundvattennivåer stämmer väl överens. Även vattnets transporttider i åsen, simulerade i PMPATH, stämmer väl överens med uppskattade transporttider. Modellen kan användas för enklare studier av ämnestransport.</p><p>Vid simulering av provpumpningen i Lennheden så är överensstämmelsen god österut i åsen, från Lennheden till Övre Tjärna. Västerut i åsen, från Lennheden till Bäsna, är avsänkningen av grundvattennivån för kraftig. Möjliga orsaker till den för kraftiga avsänkningen är att åsens utbredning är underskattad och att Dalälvens botten har en för lågt ansatt vertikal hydraulisk konduktivitet längs sträckan Lennheden – Bäsna.</p><p>Den klart viktigaste åtgärden för att förbättra modellen skulle vara att grundligt undersöka Dalälven, särskilt längs sträckan Djurmo – Båtsta, med avseende på dess bottens vertikala hydrauliska konduktivitet och mäktighet.</p>
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Performance Analysis of Dispersed Spectrum Cognitive Radio SystemsMohammad, Muneer 2009 December 1900 (has links)
Dispersed spectrum cognitive radio systems represent a promising approach to exploit the utilization of spectral resources to full extent. Therefore, the performance analysis of such systems is conducted in this research. The Average symbol error probability of dispersed spectrum cognitive radio systems is derived for two cases: where each channel realization experiences independent and dependent Nakagami-m fading, respectively. In addition, the derivation is extended to include the effects of modulation type and order by considering M-PSK and M-QAM modulation schemes. We then study the impacts of topology on the effective transport capacity performance of ad hoc dispersed spectrum cognitive radio systems where the nodes assume 3- dimensional (3D) configurations. We derive the effective transport capacity considering a cubic grid distribution. In addition, numerical results are presented to demonstrate the effects of topology on the effective transport capacity of ad hoc dispersed cognitive radio systems.
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The Sediment Transport and Capacity in the Channelized Portion of Hocking River, Athens, OhioBennett, Rebecca A. 20 July 2012 (has links)
No description available.
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Areal Modeling of Erosion for Environmental Nonpoint Applications (AMEENA)Al-Smadi, Mohammad Ahmed 24 April 2008 (has links)
Erosion and sediment delivery from upland areas to waterbodies is a major problem impacting water quality in the United States and elsewhere. Measures to reduce these impacts are either targeted at reducing erosion on-site or at reducing delivery of sediment to waterbodies. AMEENA (Areal Modeling of Erosion for Environmental Nonpoint Applications) is a spatially distributed model that estimates erosion and deposition on a watershed scale by predicting erosion and transport over the landscape surface. Erosion is predicted based on the Revised Universal Soil Loss Equation (RUSLE), and sediment transport capacity is estimated as a function of upslope flow volume, local gradient, and land use. Gross erosion is routed to edge-of-stream with a routing algorithm that iteratively compares available sediment with transport capacity on a cell by cell basis from ridge cells to stream cells. The model is implemented completely within a raster GIS to facilitate use of the model as a tool to readily evaluate impact of land use practices on sediment delivery to streams.
AMEENA was validated using field data of net erosion and sediment deposition from three field studies. AMEENA predicted the spatial distribution of net erosion and deposition better than WaTEM/SEDEM which is a distributed parameter erosion model based on a similar modeling approach. AMEENA's suitability to simulate the impact of management practices such as filter strips and critical area planting was evaluated on plot (profile) scale and catchment scale simulations. Results of plot scale simulations were intuitive and the model proved more reasonable for these scenarios than did RUSLE2 and WEPP. The catchment scale study highlighted features of AMEENA that are not available in RUSLE2 and WEPP in terms of identifying erosion “hot spots” and the ability to utilize the explicit sediment flow path identification in locating best placement of off-site sediment control measures. Since AMEENA does not account for in-stream erosion processes, it is not suitable for simulating areas dominated by channel or gully erosion. / Ph. D.
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Grundvattenmodellering i BadelundaåsenLorentzon, Martin January 2005 (has links)
Over an extended period of time there have been plans to establish a shared facility in Lennheden to extract groundwater from the Badelunda esker to provide drinking water for the cities of Borlänge and Falun. The city of Falun is dissatisfied with the quality of its drinking water and the city of Borlänge is concerned about the risk of contamination of its existing groundwater supply at its current location. To provide a basis for a decision on this issue, the company Midvatten AB has been commissioned to perform hydrogeological investigations in the area of Lennheden. The purpose of this thesis is to design a functional groundwater model of the area between Lennheden, place of planned extraction, and Övre Tjärna, place of existing extraction, to get a better understanding of the groundwater situation in the area. A groundwater model enables simulations of different scenarios in risk assessment and contaminant transport. The aim of the thesis is that the model can be used as an aid in Midvatten’s investigations in Lennheden and that it also can be used in future projects in the area. The model has been made in Processing Modflow 5.3 and encompasses an area of 19,5 × 11 km along the Badelunda esker and the river Dalälven between Djurmo and Frostbrunnsdalen. The model has 6 layers and a cell resolution of 50 × 50 meters and 50 × 100 meters. The physical parameters of the model are comprised from different hydrological and geological investigations in the area. The Badelunda esker and the river Dalälven totally dominate the groundwater situation in the area. A large part of the work in the thesis has been focused on the calibration of the horizontal hydraulic conductivity in the esker and the vertical hydraulic conductivity in the riverbed of Dalälven. The calibration of the model implies a vertical hydraulic conductivity of 0,01 – 0,1 md-1 in the riverbed of Dalälven, depending on the riverbed thickness. Between Bäsna and Övre Tjärna, simulated and observed groundwater levels correspond well. The transport time of the water in the esker, simulated in PMPATH, also corresponds well with estimated transport times. The model can be used for simpler studies of contaminant transport. Simulation of the pumping test in Lennheden gives a good correspondence eastward in the esker from Lennheden to Övre Tjärna. Westward in the esker, from Lennheden to Bäsna, the draw down is sharper than observed. Possible reasons for the sharper draw down is an underestimation of the bulk of the esker and that the vertical hydraulic conductivity of the riverbed is set too low between Lennheden and Bäsna. In order to improve the model, the most important step should be to thoroughly investigate the river Dalälven with regards to vertical hydraulic conductivity in the riverbed and riverbed thickness. / Under en längre tid har det funnits planer på att upprätta en ny, gemensam vattentäkt för Borlänge och Falu kommun i Badelundaåsen i Lennheden nordväst om Borlänge stad. Falu kommun är missnöjd med vattenkvaliteten i sin ytvattentäkt och Borlänge är oroad över riskerna med att ha sin nuvarande vattentäkt i Badelundaåsen lokaliserad i nära anslutning till riksväg 70 och järnvägen. Beslut i frågan ska tas under 2006 och Midvatten AB har fått i uppdrag att genomföra geohydrologiska undersökningar i och runt Lennheden som underlag till beslutet. Syftet med det här examensarbetet är att skapa en fungerande grundvattenmodell för området mellan Lennheden, plats för planerat vattenuttag, och Övre Tjärna, plats för befintligt vattenuttag, för att få en större förståelse för grundvattenmagasinet. En grundvattenmodell möjliggör simulering av olika scenarion så som föroreningstransport i grundvattnet och bestämning av skyddsområden. Målet är att modellen ska kunna användas som ett komplement i Midvattens undersökningar och även användas i framtida projekt i området. Modellen är gjord i Processing Modflow 5.3 och omfattar ett 19,5 × 11 km stort område längs Badelundaåsen och Dalälven mellan Djurmo och Frostbrunnsdalen. Modellen består av 6 lager där cellernas upplösning är 50 × 50 meter och 50 × 100 meter. De fysiska parametrar som modellen är uppbyggd av är sammanställda från olika hydrologiska och geologiska undersökningar som har utförts i området de senaste 30 åren. Badelundaåsen och Dalälven är de två komponenter som totalt dominerar grundvattensituationen i området. En stor del av arbetet har fokuserats på kalibreringen av den horisontella hydrauliska konduktiviteten i åsen och den vertikala hydrauliska konduktiviteten i Dalälvens botten. I modellen är den vertikala hydrauliska konduktiviteten i Dalälvens botten kalibrerad till intervallet 0,01 – 0,1 md-1 beroende på bottnens mäktighet. På sträckan mellan Bäsna och Övre Tjärna så fungerar modellen bra. Simulerade och observerade grundvattennivåer stämmer väl överens. Även vattnets transporttider i åsen, simulerade i PMPATH, stämmer väl överens med uppskattade transporttider. Modellen kan användas för enklare studier av ämnestransport. Vid simulering av provpumpningen i Lennheden så är överensstämmelsen god österut i åsen, från Lennheden till Övre Tjärna. Västerut i åsen, från Lennheden till Bäsna, är avsänkningen av grundvattennivån för kraftig. Möjliga orsaker till den för kraftiga avsänkningen är att åsens utbredning är underskattad och att Dalälvens botten har en för lågt ansatt vertikal hydraulisk konduktivitet längs sträckan Lennheden – Bäsna. Den klart viktigaste åtgärden för att förbättra modellen skulle vara att grundligt undersöka Dalälven, särskilt längs sträckan Djurmo – Båtsta, med avseende på dess bottens vertikala hydrauliska konduktivitet och mäktighet.
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A multi-agent based system to promote collaboration among Namibian transport stakeholders in order to reduce empty runsFransman, Logan 03 July 2015 (has links)
The main aim of transport stakeholders has always been to transport freight efficiently, as this efficiency contributes to the growth and success of their business. A country like Namibia is no different as the efficiency of transport lies in the effective utilisation of carrier capacity in any direction. Due to the various types of freight, transport operators rarely have the capacity to cover all freight movement requests. This research put the empty runs experienced by most of the Namibian transporters at 33%. Empty runs could however be reduced through collaboration and sharing of capacity among transport stakeholders.
Multi-agent systems (MAS) are various individual computer agents that are configured independently to interact with other agents to achieve one goal. These systems have been explored as an approach to achieve collaboration among transporter stakeholders. Taking into consideration the characteristics and requirements of MAS, this research was able to conduct a feasibility of its implementation within Namibia. Concluding with an evaluation of available Multi-agent based systems that could achieve collaboration and reduce empty runs in the Namibian transport environment. / Information Science / M.Tech. (Information Technology)
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Modelagem do escoamento, da produção de sedimentos e da transferência de fósforo em bacia rural no sul do Brasil / Modeling of water, sediment and phosphorus loads in an agricultural watershed in southern BrazilBonumá, Nadia Bernardi 01 March 2011 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Areas under intensive tobacco crop cultivation have been impacting the water
balance and increasing soil erosion in Southern Brazil. Application of large amounts
of mineral fertilizers, higher than the tobacco requirement, contributes to excessive
phosphorus loads in soil and water bodies. The assessment of potential
environmental impacts due to changes in land use and management practices is
necessary to achieve the sustainable management of natural resources such as soil
and water. In this study the hydrological processes, the sediment yield and the
phosphorus transfer in the Arroio Lino watershed were evaluated by using the Soil
and Water Assessment Tool (SWAT) model. The small watershed (4.18 km2
) is
located in Southern Brazil and its main land use is tobacco crop under conventional
tillage. Measured streamflow and sediment yield at the watershed outlet were used
for model streamflow sensitivity analysis, calibration and validation. Phosphorus
loads at four sub-watersheds (A1, A2, B, C) and at the watershed outlet were used
for model sensitivity analysis and calibration. A Latin Hypercube (LH) and One-factor-
At-a-Time (OAT) sensitivity analysis was performed on input variables. Model
calibration was performed with the Shuffled Complex Evolution Algorithm-Uncertainty
Analysis (SCE-UA). Time series plots and standard statistical measures were used to
verify model predictions. Adaptations of the model parameters for the reality of the
region in which the watershed is located were made during the calibration and
validation of the model. The predicted monthly streamflow matched the observed
values, with a Nash Sutcliffe coefficient (NSE) of 0.87 for calibration and 0.76 for
validation. In an attempt to account for sediment transport and deposition processes
across the landscape, the SWAT model was modified to simulate landscape
sediment transport capacity. The new deposition routine performed better during
calibration (NSE of 0.70) than SWAT standard version (NSE of -0.14) in the studied
watershed. The modified model provided reasonable simulations of sediment
transport across the landscape positions. The results suggest that the integration of
the sediment deposition routine in SWAT increases model predictions accuracy in
steeper areas, while at the same time significantly improves the ability to predict
spatial distribution of sediment deposition areas. The predicted P loads are in the
order of magnitude of the measured ones, however, the model failed to predict the P
loads in three sub-watersheds (A1, A2 and B). Although occupying only 29% of the
total land cover, cropland is the primary source of nutrients in the watershed (80%).
After calibration of streamflow, sediment yield and phosphorus loads, the simulation
of distinct management scenarios was done for the Arroio Lino watershed. Three
scenarios of management practices: conventional tillage (CT), minimum tillage (MT)
and no-tillage cultivation (NT) with reduction of 50% of fertilizer rate application were
tested over a period of 30 years. No-tillage practices did not significantly affect water
yield, but greatly affected sediment yield due to reduction of soil erosion. The soluble
phosphorus losses decreased mainly when the fertilizer doses decreased. The
simulation results suggest that conventional tillage practices should be replaced by
less intensive tillage practices in order to minimize environmental impacts caused by
a single land use. / Áreas com culturas de tabaco cultivadas intensivamente, no sul do Brasil, vêm
afetando a qualidade da água e aumentando a erosão do solo nesta região. A
aplicação de grandes quantidades de fertilizantes minerais, maiores do que a
exigência da cultura, contribui para a excessiva carga de fósforo nos solos e corpos
d'água. A avaliação dos impactos potenciais das mudanças no uso e manejo do solo
é fundamental para propiciar uma gestão sustentável dos recursos naturais como
solo e água. Neste estudo foram avaliados os processos hidrológicos, a produção de
sedimentos e a transferência de fósforo na bacia hidrográfica do Arroio Lino, por
meio do modelo Soil and Water Assessment Tool (SWAT). A pequena bacia (4,18
km2
) localiza-se no sul do Brasil e seu principal uso da terra é a cultura de fumo sob
plantio convencional. As vazões e a produção de sedimentos medidos no exutório
da bacia foram utilizadas para análise de sensibilidade, calibração e validação dos
parâmetros do modelo. Cargas de fósforo em quatro sub-bacias (A1, A2, B, C) e no
exutório foram utilizados para a análise de sensibilidade e calibração do modelo. A
análise de sensibilidade foi feita com o uso de um algoritmo que combina as técnicas
de Hipercubo Latino (LH) e One-factor-At-a-Time (OAT). A calibração foi realizada
com o algoritmo Shuffled Complex Evolution (SCE-UA). Análises gráficas e medidas
estatísticas foram utilizadas para verificar as previsões do modelo. Adaptações nos
parâmetros do modelo foram feitas durante as etapas de calibração e validação,
tendo em vista a realidade da região em que a bacia está localizada. Na simulação
de vazões mensais obtiveram-se valores do índice de eficiência de Nash e Sutcliffe
(NSE) de 0,87 na calibração e 0,76 na validação. Com o intuito de representar
melhor os processos de deposição de sedimentos nas encostas, o modelo SWAT foi
modificado com a incorporação de um termo de capacidade de transporte de
sedimentos na paisagem. Com a nova rotina de sedimentos obteve-se um melhor
desempenho durante a calibração (NSE de 0,70) em relação ao modelo SWAT
original (NSE de -0,14). As simulações com o modelo modificado foram satisfatórias
para o transporte de sedimentos em diferentes posições da paisagem. Os resultados
sugerem que a integração da rotina de deposição de sedimentos no SWAT aumenta
a precisão do modelo de previsões em áreas mais íngremes e, ao mesmo tempo,
melhora significativamente a capacidade de prever a distribuição espacial das áreas
de deposição de sedimentos. As previsões de cargas de fósforo foram na ordem de
grandeza das cargas medidas; no entanto, o modelo não conseguiu prever
satisfatoriamente as cargas de fósforo em três sub-bacias (A1, A2 e B). Apesar das
lavouras ocuparem apenas 29% da área total da bacia, de acordo com a simulação
elas são a principal fonte de nutrientes na bacia hidrográfica (80%). Após a
calibração da vazão, da produção de sedimentos e de fósforo, foi realizada a
simulação de cenários de manejo do solo na bacia hidrográfica do Arroio Lino. Três
cenários de práticas de manejo: preparo convencional (PC), cultivo mínimo (CM) e
plantio direto de cultivo (NT) com redução de 50% da taxa de aplicação de
fertilizantes foram testados durante um período de 30 anos. A prática de plantio
direto não afetou significativamente o escoamento, no entanto afetou fortemente a
produção de sedimentos devido à redução da erosão do solo. Houve redução das
perdas de fósforo principalmente devido à redução das doses de fertilizantes. Os
resultados indicam que as práticas de preparo convencional do solo deveriam ser
substituídas por práticas de cultivo mínimo ou direto, a fim de minimizar os impactos
ambientais causados por um determinado uso do solo.
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Analise de desempenho de redes de sensores sem fio / Analysis of wireless sensor networks perfomanceMignaco, Andre Gustavo 22 December 2005 (has links)
Orientador: Paulo Cardieri / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e Computação / Made available in DSpace on 2018-08-06T17:02:09Z (GMT). No. of bitstreams: 1
Mignaco_AndreGustavo_M.pdf: 1003880 bytes, checksum: e71bd78fe77a5cd7d4f324c8bc14791b (MD5)
Previous issue date: 2005 / Resumo: As redes de sensores sem fio têm merecido atenção especial nos últimos anos graças às suas características intrínsecas que as tornam atrativas em diversas aplicações, como em atividades industriais, de monitoramento de meio ambientes e segurança, entre outros. As mesmas características que tornam atrativas as redes de sensores sem fio fazem a análise do seu desempenho dificultoso. Diversos conceitos de medida da capacidade de redes ad hoc em geral têm sido propostos, incluindo a capacidade de transporte e a eficiência de informação. Nesta dissertação é introduzida uma variação do conceito de eficiência de informação, denominada eficiência de informação agregada, que leva em conta a habilidade da rede em reutilizar o canal de comunicação espacialmente. É apresentada uma análise da eficiência de informação agregada de uma rede de sensores sem fio em diversos cenários, utilizando-se diferentes modelagens da rede sem fio. Os resultados mostram que o meio em que a rede é empregada tem grande importância no seu desempenho, podendo ser decisivo na escolha do esquema de modulação a ser empregado. Também foi observado que transmitir em curtas distâncias é mais vantajoso que transmitir em longas distâncias na maioria dos casos / Abstract: Wireless sensor networks have deserved special attention in the last years due to their intrinsic characteristics that become them attractive in various applications, such as in the industrial activities, in the environment monitoring and security, among others. The same characteristics that become the wireless sensor networks attractive make hard the analysis of their performance. Many concepts of measure of capacities of ad hoc networks have been proposed, including the transport capacity and the information efficiency. In this dissertation is introduced a variation of the concept of information efficiency, called aggregated information efficiency, that takes into account the ability of the network in reusing spatially the communication channel. It is presented an analysis of the aggregated information efficiency of a wireless ad hoc network in many scenarios, where are used different models of the wireless network. The results show that the environment where the network is employed has a big importance in its performance, and it can be decisive in the choice of the modulation scheme to be used. Also was observed that to transmit in short distances is better than do it in longer ones in the majority of the cases / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica
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Reconstructing environmental forcings on aeolian dune fields : results from modern, ancient, and numerically-simulated dunesEastwood, Erin Nancy. 08 September 2014 (has links)
This dissertation combines studies of aeolian bedforms and aeolian dune-field patterns to create a comprehensive set of tools that can be used in tandem (or separately) to extract information about climate change and landscape evolution, and to identify the controls on formation for specific modern dune fields or ancient aeolian sequences. The spatial distribution of surface processes, erosion/deposition rates, and lee face sorting on aeolian dunes are each a function of the incident angle. This correlation between stratification style and incidence angle can be used to develop a “toolbox” of methods based on measurements of key suites of parameters found in ancient aeolian deposits. Information obtained from the rock record can be used as input data for different kinds of numerical models. Regional-scale paleowind conditions can be used to validate paleoclimate and global circulation models. Understanding the natural variability in the Earth’s climate throughout its history can help predict future climate change. Reconstructed wind regimes and bedform morphologies can be used in numerical models of aeolian dune-field pattern evolution to simulate patterns analogous to those reconstructed from ancient aeolian systems. Much of the diversity of aeolian dune-field patterns seen in the real world is a function of the sediment supply and transport capacity, which in turn determine the sediment availability of the system. Knowledge of the sediment supply, availability, and transport capacity of aeolian systems can be used to predict the amount of sand in the system and where it might have migrated. This information can be extremely useful for development and production of oil and gas accumulations, where a discovery has been made but the spatial extent of the aeolian reservoir is unknown. / text
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Analyse spatio-temporelle de la morphologie du chenal du Rhône du Léman à la Méditerranée / Spatio-temporal analysis of the Rhone channel morphology from Geneva Lake to the Mediterranean SeaParrot, Elsa 17 December 2015 (has links)
Cette thèse étudie l’organisation longitudinale du lit du Rhône français et son évolution depuis plus d’un siècle afin d’améliorer la gestion des sédiments du fleuve. Elle décrit d’abord la complexité géographique, géologique, et hydrologique des 512 km du système fluvial. Les extractions, l’endiguement, la chenalisation et les aménagements hydroélectriques ont simplifié le tracé latéral du chenal, incisé et pavé le fond du lit et appauvri les habitats aquatiques et riverains. La thèse caractérise ensuite plus précisément les dynamiques de fond. Elle repose sur des données bathymétriques de 1897-2010 et sur des données granulométriques issues de plus de 300 prélèvements réalisés dans le cadre de ces travaux sur l’ensemble du linéaire. Un protocole d’échantillonnage homogène a été spécialement élaboré. Les variations altimétriques du lit (zones de stockage-érosion et faciès morphologiques) et sa composition granulométrique (zones pavées ou comblées par des fines) ont été caractérisées afin d’évaluer la mobilité potentielle de la charge de fond, les apports des affluents et l’impact des ouvrages sur les conditions de transport. Il ressort 1) que l’incision du lit est principalement due à la chenalisation, 2) que les aménagements hydroélectriques ont compartimenté le continuum en provoquant le stockage de sédiments fins dans certaines retenues et en favorisant le pavage dans les vieux Rhône à l’aval de Lyon et 3) qu’une dynamique résiduelle subsiste lors de crues majeures avec une remobilisation modérée de la charge de fond. Les données des secteurs les plus pavés ont été intégrées dans un modèle hydraulique 1D permettant de quantifier la capacité de transport et le débit solide et confirmant les résultats précédents. Ces travaux permettent de formuler des recommandations de gestion durable et de restauration écologique du fleuve telles que l’ouverture des vannes de fond en crue, la modification des consignes aux barrages ou la réinjection de graviers. / This thesis studies the French Rhone riverbed longitudinal organisation and its evolution over a century, with a view to improve the management strategy for the sediments. It first describes the geographic, geologic and hydrologic peculiarities of the 512-km long fluvial system. Gravel mining, dikes construction, channelization and dams construction have simplified the lateral pattern of the channel, incised and paved the riverbed and impoverished the aquatic and riparian habitats. The thesis then more precisely characterizes the riverbed dynamics. It relies on bathymetric data collected since 1897 and on grainsize data collected specifically for this study from over 300 samples on the whole 512-km river length. An homogeneous sampling protocol was elaborated on purpose. The vertical bed evolution and grainsize distribution were analysed to assess the riverbed potential mobility, tributaries’ sediment recharge and infrastructures’ impact on sediment transport. It thus appears that 1) riverbed incision is mainly due to channelization, 2) hydroelectric dams partitioned the continuum with the accumulation of fine sediments in some backwaters and the pavement of bypassed reaches downstream of Lyon and 3) a residual dynamic persists during major floods, with moderate gravels transport. The data of paved reaches were used in a 1D hydraulic model to quantify transport capacity and bedload discharge, confirming the aforementioned results. This study helps formulate such recommendations for sustainable river management and ecological restoration as opening slush gates during floods, changing dams management instructions or reinjecting gravel.
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