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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.
261

Weighted Least Squares Kinetic Upwind Method Using Eigendirections (WLSKUM-ED)

Arora, Konark 11 1900 (has links)
Least Squares Kinetic Upwind Method (LSKUM), a grid free method based on kinetic schemes has been gaining popularity over the conventional CFD methods for computation of inviscid and viscous compressible flows past complex configurations. The main reason for the growth of popularity of this method is its ability to work on any point distribution. The grid free methods do not require the grid for flow simulation, which is an essential requirement for all other conventional CFD methods. However, they do require point distribution or a cloud of points. Point generation is relatively simple and less time consuming to generate as compared to grid generation. There are various methods for point generation like an advancing front method, a quadtree based point generation method, a structured grid generator, an unstructured grid generator or a combination of above, etc. One of the easiest ways of point generation around complex geometries is to overlap the simple point distributions generated around individual constituent parts of the complex geometry. The least squares grid free method has been successfully used to solve a large number of flow problems over the years. However, it has been observed that some problems are still encountered while using this method on point distributions around complex configurations. Close analysis of the problems have revealed that bad connectivity of the nodes is the cause and this leads to bad connectivity related code divergence. The least squares (LS) grid free method called LSKUM involves discretization of the spatial derivatives using the least squares approach. The formulae for the spatial derivatives are obtained by minimizing the sum of the squares of the error, leading to a system of linear algebraic equations whose solution gives us the formulae for the spatial derivatives. The least squares matrix A for 1-D and 2-D cases respectively is given by (Refer PDF File for equation) The 1-D LS formula for the spatial derivatives is always well behaved in the sense that ∑∆xi2 can never become zero. In case of 2-D problems can arise. It is observed that the elements of the Ls matrix A are functions of the coordinate differentials of the nodes in the connectivity. The bad connectivity of a node thus can have an adverse effect on the nature of the LS matrices. There are various types of bad connectivities for a node like insufficient number of nodes in the connectivity, highly anisotropic distribution of nodes in the connectivity stencil, the nodes falling nearly on a line (or a plane in 3-D), etc. In case of multidimensions, the case of all nodes in a line will make the matrix A singular thereby making its inversion impossible. Also, an anisotropic distribution of nodes in the connectivity can make the matrix A highly illconditioned thus leading to either loss in accuracy or code divergence. To overcome this problem, the approach followed so far is to modify the connectivity by including more neighbours in the connectivity of the node. In this thesis, we have followed a different approach of using weights to alter the nature of the LS matrix A. (Refer PDF File for equation) The weighted LS formulae for the spatial derivatives in 1-D and 2-D respectively are are all positive. So we ask a question : Can we reduce the multidimensional LS formula for the derivatives to the 1-D type formula and make use of the advantages of 1-D type formula in multidimensions? Taking a closer look at the LS matrices, we observe that these are real and symmetric matrices with real eigenvalues and a real and distinct set of eigenvectors. The eigenvectors of these matrices are orthogonal. Along the eigendirections, the corresponding LS formulae reduce to the 1-D type formulae. But a problem now arises in combining the eigendirections along with upwinding. Upwinding, which in LS is done by stencil splitting, is essential to provide stability to the numerical scheme. It involves choosing a direction for enforcing upwinding. The stencil is split along the chosen direction. But it is not necessary that the chosen direction is along one of the eigendirections of the split stencil. Thus in general we will not be able to use the 1-D type formulae along the chosen direction. This difficulty has been overcome by the use of weights leading to WLSKUM-ED (Weighted Least Squares Kinetic Upwind Method using Eigendirections). In WLSKUM-ED weights are suitably chosen so that a chosen direction becomes an eigendirection of A(w). As a result, the multi-dimensional LS formulae reduce to 1-D type formulae along the eigendirections. All the advantages of the 1-D LS formuale can thus be made use of even in multi-dimensions. A very simple and novel way to calculate the positive weights, utilizing the coordinate differentials of the neighbouring nodes in the connectivity in 2-D and 3-D, has been developed for the purpose. This method is based on the fact that the summations of the coordinate differentials are of different signs (+ or -) in different quadrants or octants of the split stencil. It is shown that choice of suitable weights is equivalent to a suitable decomposition of vector space. The weights chosen either fully diagonalize the least squares matrix ie. decomposing the 3D vector space R3 as R3 = e1 + e2 + e3, where e1, e2and e3are the eigenvectors of A (w) or the weights make the chosen direction the eigendirection ie. decomposing the 3D vector space R3 as R3 = e1 + ( 2-D vector space R2). The positive weights not only prevent the denominator of the 1-D type LS formulae from going to zero, but also preserve the LED property of the least squares method. The WLSKUM-ED has been successfully applied to a large number of 2-D and 3-D test cases in various flow regimes for a variety of point distributions ranging from a simple cloud generated from a structured grid generator (shock reflection problem in 2-D and the supersonic flow past hemisphere in 3-D) to the multiple chimera clouds generated from multiple overlapping meshes (BI-NACA test case in 2-D and FAME cloud for M165 configuration in 3-D) thus demonstrating the robustness of the WLSKUM-ED solver. It must be noted that the second order acccurate computations using this method have been performed without the use of the limiters in all the flow regimes. No spurious oscillations and wiggles in the captured shocks have been observed, indicating the preservation of the LED property of the method even for 2ndorder accurate computations. The convergence acceleration of the WLSKUM-ED code has been achieved by the use of LUSGS method. The use of 1-D type formulae has simplified the application of LUSGS method in the grid-free framework. The advantage of the LUSGS method is that the evaluation and storage of the jacobian matrices can be eliminated by approximating the split flux jacobians in the implicit operator itself. Numerical results reveal the attainment of a speed up of four by using the LUSGS method as compared to the explicit time marching method. The 2-D WLSKUM-ED code has also been used to perform the internal flow computations. The internal flows are the flows which are confined within the boundaries. The inflow and the outflow boundaries have a significant effect on these flows. The accurate treatment of these boundary conditions is essential particularly if the flow condition at the outflow boundary is subsonic or transonic. The Kinetic Periodic Boundary Condition (KPBC) which has been developed to enable the single-passage (SP) flow computations to be performed in place of the multi-passage (MP) flow computations, utilizes the moment method strategy. The state update formula for the points at the periodic boundaries is identical to the state update formula for the interior points and can be easily extended to second order accuracy like the interior points. Numerical results have shown the successful reproduction of the MP flow computation results using the SP flow computations by the use of KPBC. The inflow and the outflow boundary conditions at the respective boundaries have been enforced by the use of Kinetic Outer Boundary Condition (KOBC). These boundary conditions have been validated by performing the flow computations for the 3rdtest case of the 4thstandard blade configuration of the turbine blade. The numerical results show a good comparison with the experimental results.
262

Optimal Control Of Numerical Dissipation In Modified KFVS (m-KFVS) Using Discrete Adjoint Method

Anil, N 05 1900 (has links)
The kinetic schemes, also known as Boltzmann schemes are based on the moment-method-strategy, where an upwind scheme is first developed at the Boltzmann level and after taking suitable moments we arrive at an upwind scheme for the governing Euler or Navier-Stokes equations. The Kinetic Flux Vector Splitting (KFVS)scheme, which belongs to the family of kinetic schemes is being extensively used to compute inviscid as well as viscous flows around many complex configurations of practical interest over the past two decades. To resolve many flow features accurately, like suction peak, minimising the loss in stagnation pressure, shocks, slipstreams, triple points, vortex sheets, shock-shock interaction, mixing layers, flow separation in viscous flows require an accurate and low dissipative numerical scheme. The first order KFVS method even though is very robust suffers from the problem of having much more numerical diffusion than required, resulting in very badly smearing of the above features. However, numerical dissipation can be reduced considerably by using higher order kinetic schemes. But they require more points in the stencil and hence consume more computational time and memory. The second order schemes require flux or slope limiters in the neighbourhood of discontinuities to avoid spurious and physically meaningless wiggles or oscillations in pressure, temperature or density. The limiters generally restrict the residue fall in second order schemes while in first order schemes residue falls up to machine zero. Further, pressure and density contours or streamlines are much smoother for first order accurate schemes than second order accurate schemes. A question naturally arises about the possibility of constructing first order upwind schemes which retain almost all advantages mentioned above while at the same time crisply capture the flow features. In the present work, an attempt has been made to address the above issues by developing yet another kinetic scheme, known as the low dissipative modified KFVS (m-KFVS) method based on modified CIR (MCIR) splitting with molecular velocity dependent dissipation control function. Different choices for the dissipation control function are presented. A detailed mathematical analysis and the underlying physical arguments behind these choices are presented. The expressions for the m-KFVS fluxes are derived. For one of the choices, the expressions for the split fluxes are similar to the usual first order KFVS method. The mathematical properties of 1D m-KFVS fluxes and the eigenvalues of the corresponding flux Jacobians are studied numerically. The analysis of numerical dissipation is carried out both at Boltzmann and Euler levels. The expression for stability criterion is derived. In order to be consistent with the interior scheme, modified solid wall and outer boundary conditions are derived by extending the MCIR idea to boundaries. The cell-centred finite volume method based on m-KFVS is applied to several standard test cases for 1D, 2D and 3D inviscid flows. In the case of subsonic flows, the m-KFVS method produces much less numerical entropy compared to first order KFVS method and the results are comparable to second order accurate q-KFVS method. In transonic and supersonic flows, m-KFVS generates much less numerical dissipation compared to first order KFVS and even less compared to q-KFVS method. Further, the m-KFVS method captures the discontinuities more sharply with contours being smooth and near second order accuracy has been achieved in smooth regions, by still using first order stencil. Therefore, the numerical dissipation generated by m-KFVS is considerably reduced by suitably choosing the dissipation control variables. The Euler code based on m-KFVS method almost takes the same amount of computational time as that of KFVS method. Although, the formal accuracy is of order one, the m-KFVS method resolves the flow features much more accurately compared to first order KFVS method but the numerical dissipation generated by m-KFVS method may not be minimal. Hence, the dissipation control vector is in general not optimal. If we can find the optimal dissipation control vector then we will be able to achieve the minimal dissipation. In the present work, the above objective is attained by posing the minimisation of numerical dissipation in m-KFVS method as an optimal control problem. Here, the control variables are the dissipation control vector. The discrete form of the cost function, which is to be minimised is considered as the sum of the squares of change in entropy at all cells in the computational domain. The number of control variables is equal to the total number of cells or finite volumes in the computational domain, as each cell has only one dissipation control variable. In the present work, the minimum value of cost function is obtained by using gradient based optimisation method. The sensitivity gradients of the cost function with respect to the control variables are obtained using discrete adjoint approach. The discrete adjoint equations for the optimisation problem of minimising the numerical dissipation in m-KFVS method applied to 2D and 3D Euler equations are derived. The method of steepest descent is used to update the control variables. The automatic differentiation tool Tapenade has been used to ease the development of adjoint codes. The m-KFVS code combined with discrete adjoint code is applied to several standard test cases for inviscid flows. The test cases considered are, low Mach number flows past NACA 0012 airfoil and two element Williams airfoil, transonic and supersonic flows past NACA 0012 airfoil and finally, transonic flow past Onera M6 wing. Numerical results have shown that the m-KFVS-adjoint method produces even less numerical dissipation compared to m-KFVS method and hence results in more accurate solution. The m-KFVS-adjoint code takes more computational time compared to m-KFVS code. The present work demonstrates that it is possible to achieve near second order accuracy by formally first order accurate m-KFVS scheme while retaining advantages of first order accurate methods.
263

Concentrations et flux d'azote dans les sédiments hypoxiques de l'Estuaire Maritime du St-Laurent.

Kowarzyk, Jacqueline 12 1900 (has links)
Les sédiments sont des sites importants d’élimination d’azote (N) puisqu’ils possèdent des gradients d’oxydoréduction leur conférant les conditions idéales pour les réactions microbiennes de transformation de N. L’eutrophisation des régions côtières peut altérer ces gradients, par des changements dans la concentration d’oxygène (O2) de l’eau interstitielle, et modifier l’importance relative des processus transformant le N. Afin de mieux comprendre comment l’O2 pourrait influencer les transformations de N, nous avons mesuré les flux diffusifs de diazote (N2), nitrate (NO3-), oxygène et ammonium (NH4+) dans les sédiments de l’Estuaire Maritime du St-Laurent (EMSL), et nous avons estimé les taux de dénitrification. L’importance du couple nitrification-dénitrification en fonction d’un gradient de concentrations d’O2 dans la zone d’hypoxie de l’EMSL fut aussi évaluée. La concentration des gaz dissous fut mesurée en utilisant une nouvelle approche développée dans cette étude. Les flux diffusifs de N2, O2, NO3- et NH4+ variaient de 5.5 à 8.8, de -37.1 à -84.8, de -4.0 à -5.8 et de 0.6 à 0.8 μmol N m-2 h-1 respectivement. Les concentrations de N2 et NO3- dans l’eau porale et les flux de NO3- et de N2 des sédiments, suggèrent que la diffusion de NO3- provenant de l’eau à la surface des sédiments ne peut pas expliquer par elle-même la production de N2 observée. En utilisant une approche stoichiométrique, les taux de nitrification potentielle estimés comptent pour 0.01 à 52% du flux total de NO3 nécessaire pour aboutir aux flux de N2 observés et diminuent avec l’augmentation de l’hypoxie. / Sediments display strong redox gradients and represent important sites of various microbially mediated nitrogen (N) transformation pathways resulting in the loss of fixed N. Increased eutrophication of coastal systems will likely impact the overall function of these sediments via changes in the oxygen (O2) concentration in the overlying water, thus influencing the redox gradient and the relative importance of different N processes. To have a better understanding of how O2 could influence N transformations, we measured dinitrogen (N2), nitrate (NO3-), oxygen and ammonium (NH4+) diffusive fluxes in the sediments of the Lower St. Lawrence Estuary (LSLE) and estimated denitrification rates. The importance of the nitrification-denitrification couple as a function of a gradient of hypoxic O2 concentrations was also evaluated. Dissolved gas concentrations were measured using a new approach developed in this study. N2, O2, NO3- and NH4+ diffusive fluxes varied respectively from 5.5 to 8.8, from -37.1 to -84.8, from -4 to -5.8 and from 0.6 to 0.8 μmol N m-2 h-1 among the five stations sampled. N2 and NO3- concentrations in sediment pore water and measured fluxes of NO3- in and N2 out of the sediments suggested that NO3- diffusion from the overlying water alone could not support N2 production. Using a stoichiometric approach, estimated potential nitrification rates varied among sites, from 0.01 to 52% of the total NO3 supply rate. The relative importance of nitrification decreased with increasing hypoxia.
264

Effects of Hypoxia and Exercise on In Vivo Lactate Kinetics and Expression of Monocarboxylate Transporters in Rainbow Trout

Omlin, Teye D. 21 February 2014 (has links)
The current understanding of lactate metabolism in fish is based almost entirely on interpretation of concentration measurements that cannot be used to infer changes in flux. Moreover, the transporters regulating these fluxes have never been characterized in rainbow trout. My goals were: (1) to quantify lactate fluxes in rainbow trout under normoxic resting conditions, during acute hypoxia, and exercise by continuous infusion of [U-14C] lactate; (2) to determine lactate uptake capacity of trout tissues by infusing exogenous lactate in fish rest and during graded exercise, and (3) to clone monocarboxylate transporters (MCTs) and determine the effects of exhausting exercise on their expression. Such information could prove important to understand the mechanisms underlying the classic “lactate retention” seen in trout white muscle after intense exercise. In normoxic resting fish, the rates of appearance (Ra) and disappearance (Rd) of lactate were always matched (~18 to 13 µmol kg-1 min-1), thereby maintaining a low baseline blood lactate concentration (~0.8 mM). In hypoxic fish, Ra lactate increased from baseline to 36.5 µmol kg-1 min-1, and was accompanied by an unexpected 52% increase in Rd reaching 30.3 µmol kg-1 min-1, accounting for a rise in blood lactate to 8.9 mM. In exercising fish, lactate flux was stimulated > 2.4 body lengths per second (BL s-1). As the fish reached critical swimming speed (Ucrit), Ra lactate was more stimulated (+67% to 40.4 μmol kg-1 min-1) than Rd (+41% to 34.7 μmol kg-1 min-1), causing an increase in blood lactate to 5.1mM. Fish infused with exogenous lactate stimulated Rd lactate by 300% (14 to 56 μmol kg-1 min-1) during graded exercise, whereas the Rd in resting fish increased by only 90% (21 to 40 µmol kg-1 min-1). Four MCT isoforms were partially cloned and characterized in rainbow trout: MCT1b was the most abundant in heart, and red muscle, but poorly expressed in gill and brain where MCT1a and MCT2 were prevalent. MCT4 was more expressed in the heart. Transcript levels of MCT2 (+260%; brain), MCT1a (+90%; heart) and MCT1b (+50%; heart) were stimulated by exhausting exercise. This study shows that: (i) the increase in Rd lactate plays a strategic role in reducing the lactate load imposed on the circulation. Without this response, blood lactate accumulation would double; (ii) a high capacity for lactate disposal in rainbow trout tissues is elicited by the increased blood-to-tissue lactate gradient when extra lactate is administered; and (iii) rainbow trout may be unable to release large lactate loads rapidly from white muscle after exhausting exercise (lactate retention) because they poorly express MCT4 in white muscle and fail to upregulate its expression during exercise.
265

Silicon cycling in the Baltic Sea : Trends and budget of dissolved silica / Kisels kretslopp i Östersjön : Trender och budget av löst kisel

Papush, Liana January 2011 (has links)
The dissolved silicon (DSi) has a crucial role for growth of a large group of primary producers – diatoms and, hence, impact on functioning of the aquatic food web. This thesis contributes to an increased understanding of the modifications of the DSi cycling in the Baltic Sea. The results provide new information about spatial and temporal changes in DSi concentrations and nutrient ratios for the period 1970-2001 as well as during the 20th century. For the period 1970-2001, the declining DSi trends were found at the majority of monitoring stations all over the Baltic Sea. This decrease is assumed to be mainly due to the ongoing eutrophication. It is supported by the increasing trends of inorganic nitrogen and phosphorus. The trends have implications for the nutrient ratios, DSi:DIN and DSi:DIP, which are important indicators of the state of an ecosystem. The long-term retrospective DSi budget has shown that the DSi concentrations before major hydrological alterations and eutrophication were about twice the present ones. This decrease is related to both eutrophication and anthropogenic perturbations in the catchment. The occurrence of DSi concentrations close to the potentially limiting levels has been also analysed. While DSi concentrations are still high in the northern regions of the Baltic, other areas may be at risk of developing Si limitation if the decrease in DSi concentrations persists. The results depict the Baltic Sea journey from being water body with DSi levels sufficient to support diatom production to one that may experience Si limitation and its adverse ecological consequences. / Löst kisel (DSi) har en viktig roll för tillväxten av en stor grupp av primärproducenter – kiselalger, och därmed även påverkar hela den akvatiska näringskedjan. Denna avhandling bidrar till en ökad förståelse av förändringarna i DSi kretsloppet i Östersjön. Resultaten tillhandahåller ny information om rumsliga och tidsmässiga förändringar i DSi koncentrationer såväl för perioden 1970-2001 som för hela 1900-talet. För perioden 1970-2001 återfanns minskade DSi koncentrationer på mätstationer över hela Östersjön. Minskningen antas främst bero på den pågående övergödningen. Detta antagande stöds av stigande halter av oorganiskt kväve och fosfor. Sammantaget har dessa trender en inverkan på ekosystemets tillstånd och näringsämnenas kvoter, DSi: DIN och DSi: DIP. Ur ett längre tidsperspektiv kan man se att innan övergödningen och de stora hydrologiska ombildningar i Östersjöområdet var DSi koncentrationerna ungefär dubbelt så höga som idag. Dagens förekomst av DSi koncentrationer som ligger nära de potentiellt begränsande nivåerna har också analyserats. DSi koncentrationerna är fortfarande höga i norra delar av Östersjön, men är i andra områden i riskzonen för att utveckla Si begränsning om minskningen av DSi koncentrationer fortsätter. Resultaten skildrar Östersjöns resa från att vara ett havsområde med DSi halter som är tillräckliga för att understödja kiselalgernas produktion till ett sådant som kan uppleva Si begränsning och dess negativa ekologiska konsekvenser.
266

Formation and Maintenance of the Southern Bay of Bengal Cold Pool

Das, Umasankar January 2015 (has links) (PDF)
Around Sri Lanka and to the south of India sea surface temperatures (SST) are cooler compared to the surrounding region during summer monsoon. This region where SSTs are relatively cooler is known as the cold pool. Owing to its possible impact on monsoon variability, some studies have been carried out to understand the evolution of cold pool SST during this period. These studies suggest, coastal upwelling along southern coast of Sri Lanka and eastward advection of cooler water contributes to the decrease in SST during summer monsoon. However, the processes leading to the formation of cold pool, still, remain unknown. In this study, we have investigated the mechanism responsible for the formation and maintenance of southern Bay of Bengal (BOB) cold pool using high resolution satellite data, model simulations and in-situ observations for the year 2009. Our study reveals formation of cold pool is dominated by atmospheric processes, whereas oceanic processes dominate its maintenance. Cooling of SSTs during premonsoon and onset phase acts as a prerequisites for the formation of cold pool, which are linked to the reduction in Net Heat flux (NHFX) during theses periods. The changes in NHFX during premonsoon and onset phase are dominated by reduction in Short-wave (SW) radiation associated with strong convective activity over cold pool. Convective activity over the cold pool are associated with the northward movement of Maximum Cloud Zone (MCZ) that forms over Equatorial Indian Ocean (EIO) during these periods. SST within the cold pool after the steady increase during February-April months, cools first during premonsoon rain event and then during monsoon onset. Analysis of high resolution satellite data for the period 2003-2009 suggest that, these sequence of events occurs with minor amount of inter-annual variability. Lead-lag correlation also made it clear that SST response in 5 days to the corresponding variation in atmospheric processes. SST within the cold pool shows several intraseasonal cooling events during the summer mon-soon. Considering that rainfall above the cold pool is very low during the summer monsoon, these cooling events occurring within the summer should be necessary for maintaining the cold pool. The seasonal evolution of SST shows that it continues to decrease till the end of the summer monsoon. In-situ data collected during CTCZ field program in 2009, at two time series locations (TSL) and model simulations were used to determine the processes responsible for such cooling events. To estimate the contribution from advection to the observed SST tendency at fixed location, a measurement stratergy called ‘opertaion advection’ was used in this study. This stratergy involves measurement of oceanographic parameters along four edges from TSL directod along North, South, East and West for estimation of horizontal temperature gradients. Our results from SST cooling events captured by CTD at two fixed locations suggests that horizontal advection and entrainment dominate the SST evolution. Model temperature equation evaluated near the TSLs are convinient with the observations and suggest that atmospheric forcing is not responsible for intraseasonal cooling events.
267

Mesoscale Turbulence on the Ocean Surface from Satellite Altimetry

Khatri, Hemant January 2015 (has links) (PDF)
The dynamics captured in the ocean surface current data provided by satellite altimetry has been a subject of debate since the past decade. In particular, the contribution of surface and interior dynamics to altimetry remains unclear. One avenue to settling this issue is to compare the turbulence (for example, the nature of spectra and interscale fluxes) captured by altimetry to theories of two-dimensional, surface and interior quasigeostrophic turbulence. In this thesis, we focus on mesoscales (i.e., scales of the order of few hundred kms) that are well resolved by altimetry data. Aspects of two dimensional, three dimensional, geotropic and surface quasigeostrophic turbulence are revisited and compared with the observations. Specifically, we compute kinetic energy (KE) spectra and fluxes in five geographical regions (all over the globe) using 21 years of 0.25◦resolution daily data as provided by the AVISO project. We report a strong forward cascade of KE at small scales (accompanied by a spectral scaling of the form k−3) and a robust inverse cascade at larger scales. Further, we show that the small diver-gent part in horizontal velocity data drives the strong forward flux of KE. Indeed, on considering only the non-divergent part of the flow, in accord with incompressible two-dimensional turbulence, the inverse cascade is unaffected, but the forward transfer becomes very weak and the spectral slopes over this range of scales tend to a relatively steeper k−3.5scaling. We note that our results do not agree with interior first bar clinic mode quasigeostrophic (incorrect strength of forward flux) or surface-quasigeostrophic (incorrect spectral slopes) turbulence. Rather, the results are compatible with rotating shallow water and rotating stratified Boussinesq models in which condition of geostrophic balance is dominant but the divergence of horizontal velocity field is not exactly zero. Having seen the “mean” picture of fluxes and spectra from altimetry, in the second part of the thesis we investigate the variability of these entities. In particular, we employ Empirical Or-thogonal Function (EOF) analysis and focus on the variability in the spectral flux. Remarkably, over the entire globe, irrespective of the region under consideration, we see that the first two EOFs explain a large part of the variability in flux anomalies. The geometry of these modes is distinct, the first represents a single signed transfer across scales (i.e. large to small or small to large depending on the sign of the associated principal component), while the second is a mixed mode in that it exhibits a forward/inverse transfer at large/small scales.
268

Concentrations et flux d'azote dans les sédiments hypoxiques de l'Estuaire Maritime du St-Laurent

Kowarzyk, Jacqueline 12 1900 (has links)
No description available.
269

Por cima do mar eu vim, por cima do mar eu vou voltar : políticas angoleiras em performance na circulação Brasil-França

Gravina, Heloisa Corrêa January 2010 (has links)
Ce travail est une expérimentation ethnographique du monde de la capoeira Angola transnational basée sur le choix méthodologique de suivre les flux de personnes, de pratiques, d'idées et d'images dans le transit Brésil-France. Je conçois ce monde comme un paysage (dans le sens proposé par Appadurai), approprié et agencé de manière dynamique à partir de chaque contexte spécifique. Le paradigme de la performance en anthropologie fournit le cadre théorique pour l'ensemble de la recherche. En dynamisant sa caractéristique de collaboration entre disciplines, j'explore spécialement le potentiel des savoirs, techniques et procédés anthropologiques en inter-locution avec ceux de la danse. Dans ce dialogue, je m'inscris dans la tradition de l'anthropologie de la performance (et de la danse contemporaine) pour mettre en question la place du corps dans la production de savoir. Dans ce sens, je considère mon investissement dans l'apprentissage de la capoeira Angola comme partie intégrante de la méthode ethnographique, poursuivant une ethnographie à partir du corps. Le terme « expérimentation », dans ce cas; se réfère tant au caractère expérimental du projet qu'à la dimension de l'expérience comme instance réflexive. J'organise le texte à la façon d'un parcours narratif passant par différents points de vue qui configurent cet univers plus vaste – le paysage – de la capoeira Angola: un voyage initiatique à Salvador de Bahia, avec l'accueil du Grupo Nzinga de Capoeira Angola; le processus quotidien d'apprentissage de la pratique – entraînements, rondes, rencontres – au sein de l'Escola de Capoeira Angola Áfricanamente, à Porto Alegre, et les dynamiques de la circulation internationale, vécues à partir du groupe Filhos de Angola, à Marseille (France). Au long de ce parcours, je mobilise les notions-clefs de corporéité (Csordas), corpsconscience (Gil) et performance (Turner) pour comprendre les dynamiques de l'expérience corporelle en tant que constitution du sujet dans le monde et du monde dans le sujet. J'articule le vécu spécifique du corps dans l'espace circonscrit de la ronde de capoeira avec les différents contextes sociaux et politiques en interaction avec cette pratique dans le monde contemporain. Au travers des circulations qu'elle promeut, la capoeira inscrit de nouveaux espaces – imaginaires et concrets – de France, Brésil et Afrique dans l'expérience corporelle des pratiquants. Je conçois la capoeira Angola comme une pratique diasporique noire, dans les termes proposés par Paul Gilroy. J'observe l'engagement des pratiquants dans la lutte antiraciste au travers de la capoeira. A partir des spécificités de la pratique elle-même – le transit, la circularité, la réversibilité – j'explore également son potentiel politique, en tant que piste pour désessentialiser des catégories (corps-esprit, blancs-noirs, esthétique-politique) et inscrire des espaces disruptifs (Bhabha) capables de faire émerger des narratives divergentes au sein d'une modernité occidentale hégémonique. / Este trabalho é uma experimentação etnográfica do mundo da capoeira Angola transnacional baseada na escolha metodológica de seguir os fluxos de pessoas, práticas, ideias e imagens na circulação Brasil-França. Compreendo esse mundo como uma paisagem (no sentido proposto por Appadurai), apropriada e agenciada dinamicamente a partir de cada contexto. O paradigma da performance na antropologia é o enquadramento teórico para a pesquisa como um todo. Dinamizando sua própria característica de colaboração entre disciplinas, exploro especialmente o potencial dos saberes, técnicas e procedimentos antropológicos em interlocução com os da dança. Pretendo, neste diálogo, seguir a tradição da antropologia da performance (e da dança contemporânea) enquanto ferramenta para problematizar o lugar do corpo na produção de conhecimento. Nesse sentido, incluí meu investimento no aprendizado da capoeira Angola como parte do método etnográfico, buscando uma etnografia desde o corpo. “Experimentação”, nesse caso, refere-se tanto ao caráter experimental do projeto quanto à dimensão da experiência enquanto instância reflexiva. Organizo o texto como um percurso narrativo por diferentes pontos de vista que configuram esse mapa mais amplo – a paisagem – da capoeira Angola: uma viagem iniciática a Salvador, experimentada sob a acolhida do Grupo Nzinga de Capoeira Angola; o processo diário de aprendizado da prática – treinos, rodas, convivência – na Áfricanamente Escola de Capoeira Angola, em Porto Alegre, e as dinâmicas da circulação internacional, vividas a partir do grupo Filhos de Angola, em Marseille (França). Ao longo do percurso, mobilizo as noções-chave de corporeidade (Csordas), corpoconsciência (Gil) e performance (Turner) para compreender as dinâmicas da experiência corporal enquanto constituição do sujeito no mundo e do mundo no sujeito. Articulo a vivência específica do corpo no espaço circunscrito da roda de capoeira com os diferentes contextos sociais e políticos em interação com esta prática hoje. Através das circulações que promove, a capoeira inscreve novos espaços – imaginários e concretos – de França, Brasil e África na experiência corporal dos praticantes. Compreendo a capoeira Angola como uma prática diaspórica negra, nos termos colocados por Paul Gilroy. Observo o engajamento dos praticantes na luta antirracista através da capoeira. A partir das especifidades da própria prática – o trânsito, a circularidade, a reversibilidade – exploro também seu potencial político como via para desessencializar categorias (corpo-mente, brancos-negros, estético-político) e inscrever espaços disruptivos (Bhabha) capazes de propiciar a emergência de narrativas divergentes no seio de uma modernidade ocidental hegemônica. / This thesis stands as a form of ethnographically experience transnational Capoeira Angola. The methodology that serves as a basis for this work includes following the fluxes of people, practices, ideas and images along the France-Brazil circuit. I understand this realm of capoeira as a landscape as in Appadurai´s work; that is, dynamically held and managed from specific contexts. The research as a whole is framed within the performance paradigm in anthropology. As I bring diverse disciplines together in an effort to enhance the very spirit of the performance theory – its collaboration among disciplines – I explore the anthropological knowledge, techniques and procedures as they engage in a dialogue with the realm of dancing. I, therefore, follow the traditions of both anthropology of performance and contemporary dance as a means of problematizing the lieu of the body in the production knowledge. Therefore, I included my own learning of Capoeira Angola as a part of the ethnographic method, in a search for an ethnography from the body. Thus, the term experience refers both to the experimental character of this project and to its reflexive dimension as well. The text is organized in such a way that it moves through the diverse viewpoints that configure the broader map of the landscape of capoeira: an initial encounter with the realm of capoeira aided by the Grupo Nzinga de Capoeira Angola, in the city of Salvador, was followed by daily training sections and experience sharing with Africanamente Escola de Capoeira Angola, in the city of Porto Alegre. The process ended with the experiencing of the international circuit dynamics in a Marseille-based group named Filhos de Angola. Along the process, I resorted to the notions of embodiment (Csordas), corporal awareness (Gil) and performance (Turner), in order to comprehend the dynamics of corporal experience as a composition of an in-the-world-subject and of the world that dwells within this subject. I articulate the specific experience of the body, as it is circumscribed to the capoeira circle, with the diverse social and political contexts that presently interact with the practice of capoeira. In the face of the international circulation that the practice of capoeira encourages, the practice of capoeira installs imaginary and concrete spaces of Africa, France and Brazil on the subjects´corporal experiences. I understand capoeira as a black and diasporic practice, as in Paul Gilroy´s works. I point to the subjects´ engagement in the struggle against racism through the practice of capoeira. On the bases of the specificities of the capoeira practice – transit, circularity and reversibility – I also explore its political potentiality as a means of dismantling certain long essentialized categories (body-mind, black-white, aesthetic-politic) and install disruptive spaces (Bhabha) that can enable the arousal of diverse narratives in the core of an hegemonic western modernity.
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Análise espaço-temporal da vegetação do manguezal no rio Ceará, Ceará, Brasil / Space-time analysis of vegetation of mangrove river Ceará, Ceará, Brazil

Reis Neto, Armando Soares dos January 2013 (has links)
REIS NETO, Armando Soares dos. Análise espaço-temporal da vegetação do manguezal no rio Ceará, Ceará, Brasil. 2013. 103 f. : Dissertação (mestrado) - Universidade Federal do Ceará, Centro de Ciências, Pró-Reitoria de Pesquisa e Pós-Graduação, Programa de Pós-Graduação em Desenvolvimento e Meio Ambiente, Fortaleza-CE, 2013. / Submitted by demia Maia (demiamlm@gmail.com) on 2016-04-19T12:30:58Z No. of bitstreams: 1 2013_dis_asreisneto.pdf: 6243965 bytes, checksum: dc9a4abc37fe6bbff408f3851b886953 (MD5) / Approved for entry into archive by demia Maia (demiamlm@gmail.com) on 2016-04-19T12:43:25Z (GMT) No. of bitstreams: 1 2013_dis_asreisneto.pdf: 6243965 bytes, checksum: dc9a4abc37fe6bbff408f3851b886953 (MD5) / Made available in DSpace on 2016-04-19T12:43:25Z (GMT). No. of bitstreams: 1 2013_dis_asreisneto.pdf: 6243965 bytes, checksum: dc9a4abc37fe6bbff408f3851b886953 (MD5) Previous issue date: 2013 / Mangrove ecosystem occurs in Brazil in estuaries, shore lagoons and marine channels inside land, from the extreme North of the country, to well beyond the Tropic of Capricorn, near Laguna, Brazilians’ south coast. In the Ceará state (02°46 S), Brazil´s northeast region, the climate is semi-arid, with seasonal rains and high reception of solar radiation. In the last few decades the human occupations intensify in Ceara river estuarine complex, and modify the landscape in results of their actions, interfering in the natural development of the mangrove ecosystem. This case study reports a description and an analyses of the temporal-spatial development of the mangrove area in the Ceará river (Fortaleza – CE), focusing on new colonization areas in abandoned saltworks. It was produced thematic maps estimating the mangrove areas and the saltwork areas in the years of: 1968, 1997, and 2009 using remote sensing techniques. In 2009 the mangrove area was 1006.6 ha, 65% more than in 1968, the growth rate was 133.25 ha/10years between 1997 and 2009. In abandoned saltworks areas it was evidenced 395 ha of new colonized mangroves areas. A fitosociologic study was accomplished to demonstrate the detailed description of the mangrove forest structure. The mangrove forest near the main channel of the Ceará river is described as fringe, an advance development forest, with dominance of Rhizophora mangle and Avicennia spp., medium height of 10 meters, medium DHB 14,06 cm and density of 1333.33 trunk/ha. Down to the terrestrial environment it´s evidenced basin mangrove forests, in new mangrove´s colonization areas. The pioneer specie was Laguncularia racemosa associated with other associated species Portulaca oleracea (beldroega) and Batis marítima (brejo do mangue). Although the quantitative increment in mangrove forest areas the environment quality was considered low, due the evidenced of the variety of environmental impacts. To highlight the environment services it was necessary a systemic analysis approach of the flows of energy and matter. The relation between the human activities and the environment fluxes related shows the interference of the environment impacts in the environment services, for example, the shore fluxes (sediment deficit) fluvial-marine flux (estuary salinization and water contamination) and the gravitational fluxes (abandoned saltwork, soil impermeabilization and dense urban occupation in dune areas). Consideration about the state resolution COEMA n° 02/2002 were made to discuss the recent flexibilization of Brazilian environmental legislation, in order to provide legal tools to appropriations of mangrove areas to industry exploration, the case of shrimp farms legalization. A new posture in mangrove conservation programs in the Ceará river would represent higher costs of opportunities in a sustainability receipt of human development in estuary regions and shore areas in the Ceará state, in Brazil and in the whole world. The Ceará river recuperation will only be possible after the mitigation of the main environmental impacts. It is recommended to install priority conservation zones, natural regeneration monitoring zones and environment rehabilitation zones, in order to enhance the mangrove management plan. / Os manguezais estão distribuídos do extremo norte do Brasil até Laguna, região costeira sul do país, ocorrendo em estuários, lagoas litorâneas e canais de maré. No estado do Ceará (02°46 S), nordeste brasileiro, o clima semi-árido apresenta características que condicionam o crescimento dos bosques de mangue como a sazonalidade das chuvas e a alta incidência de radiação solar. As características climáticas favoreceram a escolha pela região para implementação da industria salineira no século passado, como no caso do complexo estuarino do rio Ceará, localizado na divisa costeira entre os municípios de Fortaleza e Caucaia. O presente estudo descreve e analisa a evolução espaço-temporal do manguezal do rio Ceará (Fortaleza-CE), com foco na colonização da vegetação típica de mangue em áreas de salinas abandonadas. O estudo da paisagem foi realizado através de técnicas de sensoriamento remoto, uso de fotografias áreas e imagens de satélites, além de visitas de campo, sendo produzidos e analisados mapas temáticos dos anos de 1968, 1997 e 2009, estimando-se as áreas de manguezais e de salinas para cada ano. Para o ano de 2009, foram estimados 1006,6 ha de manguezais, 165% a mais do que em 1968, apresentando sua maior taxa de crescimento por década entre 1997 e 2009, de 133,25ha/10anos. No período estudado de 41 anos uma área de 395 ha de salinas abandonadas foi colonizada naturalmente por bosques de mangue. Uma descrição mais detalhada da estrutura desses bosques foi realizada através do estudo fitossociológico na salina Margarida. Na região mais próxima à margem do rio foi encontrado um bosque em um estágio de desenvolvimento avançado, com dominância de Rhizophora mangle e presença de Avicennia spp., altura média do bosque 10m, DAP médio 14,06 cm e densidade de 1333,33trocos/ha. Em direção ao continente, evidenciou-se um bosque em processo de colonização inicial na salina, sendo a espécie pioneira Laguncularia racemosa associada à outras espécies vegetais, Portulaca oleracea (beldroega) e a Batis marítima (brejo do mangue). Apesar do crescimento quantitativo dos bosques de mangue foram evidenciados diversos impactos ambientais, que acumulados, ocasionaram desequilíbrio ambiental e perda qualitativa nos benefícios proporcionados pelo manguezal do rio Ceará. Para evidenciar os bens e serviços do ecossistema foi realizada uma análise sistêmica dos fluxos de matéria e energia que compõe o complexo estuarino do rio Ceará. A relação dos fluxos com as atividades humanas estabelecidas no ambiente evidenciaram principalmente uma interferência dos impactos ambientais nos serviços ambientais relacionados com os fluxos litorâneos (construção de espigões e déficit de sedimentos na costa), fluxos fluvio-marinhos (salinização do estuário e contaminação das águas) e os fluxos de sedimentos e gravitacionais (abandono das salinas, impermeabilização do solo e ocupação intensa nas áreas de dunas). A partir das evidências da recuperação do manguezal em áreas de salinas abandonadas no rio Ceará, põe-se em discussão as definições da resolução estadual 02/2002 do COEMA, ao legitimar a conversão de áreas de salinas e apicum para o estabelecimento da carcinicultura, em detrimento de recuperar e conservar os serviços ambientais já disponíveis no ecossistema manguezal. Uma nova postura de conservação do manguezal do rio Ceará representaria custos de oportunidade maiores em uma receita sustentável do desenvolvimento humano nas regiões estuarinas e áreas litorâneas do estado no Ceará, no Brasil e no mundo. A recuperação do manguezal do rio Ceará só será possível após a mitigação dos principais impactos ambientais. Para a gestão do manguezal do rio Ceará propõe-se um sistema de manejo baseado em zonas de recuperação de áreas degradadas, zonas de monitoramento da regeneração natural dos bosques de mangue e zonas de máxima conservação.

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