201 |
Desenvolvimento e validação de metodologia para determinação de metais em amostras de água por espectrometria de emissão óptica com plasma de argônio (ICP-OES) / Development and validation of methodology for determination of metals in water samples by optical emission with argon plasma spectrometry (ICP-OES)FAUSTINO, MAINARA G. 08 April 2016 (has links)
Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2016-04-08T12:48:16Z
No. of bitstreams: 0 / Made available in DSpace on 2016-04-08T12:48:16Z (GMT). No. of bitstreams: 0 / Para atender a legislação ambiental do Conselho Nacional do Meio Ambiente (CONAMA), a Resolução CONAMA 357/2005, é necessário desenvolver metodologias que se aplicam na medição analítica de forma correta e para um controle de qualidade é necessário a aplicação da validação de metodologia. Para atender as exigências legais, o presente trabalho desenvolveu uma metodologia para a identificação de 12 elementos metálicos, tais como: Al, Ba, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na e Ni em águas, avaliando 14 pontos, sendo eles GU000-01 (23°46\'49.6\"S-46°47\'22\"0W), GU000-02 (23°45\'29.5\"S-46°46\'18.7\"W), GU000-03 (23°44\'52.2\"S-46°46\'13.6\"W), GU106-04 (23°44\'44.6\"S-46°45\'25.8\"W), GU000-05 (23°44\'57.5\"S-46°45\'24.2\"W), GU107-06 (23°45\'01.2\"S-46°43\'61.5\"W), GU108-07 (23°43\'64.7\"S-46°43\'42.3\"W), GU000-08 (23°42\'96.9\"S-46°43\'61.2\"W), GU109-09 (23°43\'04.6\"S-46°43\'34.0\"W), GU105-10 (23°42\'89.9\"S-46°44\'68.7\"W), GU108-11 (23°42\'53.4\"S-46°43\'44.9\"W), GU103-12 (23°41\'88.5\"S-46°44\'67.3\"W), GU102-13 (23°41\'58.0\"S-46°43\'57.3\"W), GU000-14 (23°40\'78.2\"S-46°43\'55.0\"W), distribuídos pela Represa Guarapiranga, situada no Estado de São Paulo, aplicando a metodologia validade, realizada com base no guia do Instituto Nacional de Metrologia, Qualidade e Tecnologia (INMETRO), Orientação sobre Validação de Métodos Analíticos - DOQ-CGCE-008. Foram avaliados os parâmetros: seletividade, faixa de trabalho/linearidade, limites de detecção e quantificação, tendência/recuperação, precisão, robustez e incerteza de medição. Foi utilizado a técnica de espectrometria de Emissão Óptica com Plasma de Argônio (ICP-OES). O teste de seletividade comprovou que a matriz não interfere nas curvas analíticas elaborada; a faixa de trabalho apresentou um comportamento linear, para as amostras com e sem a matriz de interesse, com um coeficiente de correlação (r), entre 0,9965 a 1,0; os limites de detecção e quantificação do método atendem aos valores máximos permitidos pela Resolução CONAMA 357/2005; com os testes de repetitividade e de recuperação o método demonstrou ser preciso e exato, além de robusto. Posteriormente foi estimado uma incerteza de medição do método. A incerteza expandida estimada variou entre 3 e 18% da concentração encontrada. A validação da metodologia permitiu a sua aplicação para a avaliação da distribuição dos 12 elementos, nas águas da represa Guarapiranga. Foram observados valores altos para Ca, Na e K, em todos os pontos de coletas analisados, evidenciando que são os elementos que fazem parte da característica geológica da área. Os elementos Fe e Al obtiveram valores acima da legislação nos pontos da Represa (G000-01, G000-02 e G000-03). Com os testes dos parâmetros para a validação, com os cálculos estatísticos aplicados, foi possível desenvolver e aplicar uma metodologia adequada para o uso pretendido. / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
|
202 |
Determinação de metais em óleos lubrificantes utilizando a técnica de espectrometria de emissão óptica com plasma induzido por laser / Determination of metals in lubricating oils by laser induced breakdown spectroscopyALVES, LUANA F.N. 22 June 2016 (has links)
Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2016-06-22T11:09:13Z
No. of bitstreams: 0 / Made available in DSpace on 2016-06-22T11:09:13Z (GMT). No. of bitstreams: 0 / Neste trabalho foi desenvolvido uma metodologia para a determinação de metais (Cr, Cu, Fe, Mg, Mo, Pb), em óleos lubrificantes e estes quantificados pela técnica de espectrometria de emissão optica com plasma induzido por laser (LIBS). As amostras de óleo usadas foram coletadas em oficina de troca de óleo, variando-se a quilometragem, ano, marca do carro e a marca do óleo, com o preenchimento de formulários contendo as informações necessárias à pesquisa. A preparação de amostras foi realizada com o depósito ds mesmas em substrato de papel e sequente otimização dos parâmetros instrumentais. Para a calibração, foi utilizado o padrão de óleo S-21 multielementar da Conostan (SCP Science, Champlain, NY). Para a avaliação da exatidão do método desenvolvido foi utilizado o padrão de óleos lubrificantes (SRM 1084a) obtidos junto ao Instituto Nacional de Padrões e Tecnologia (NIST, Gaithersburg, MD). O método proposto apresentou as seguintes vantagens quando comparado com métodos de análise tradicionais (espectrometria de absorção atômica ou espectrometria de emissão optica acoplado ao plasma indutivo com diluição da amostra): mais rápida, sem desgaste do equipamento (em função da não introdução de solvente), geração de resíduo praticamente nula e menor consumo de reagentes. O método desenvolvido foi aplicado em amostras reais e o tratamento de dados realizado por análise estatística (equação de Stuarges, teste não paramétrico de Kruskalwallis). / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
|
203 |
Polimorfismo líquido e efeito hidrofóbico através de modelos simplificados / Liquid polymorphism and hydrophobic effect through simplified modelsNara Cristina Guisoni 13 December 2002 (has links)
Desenvolvemos dois modelos estatísticos para água, nos quais diferentes aspectos de sua estrutura são considerados. O modelo geométrico permite diferentes números de coordenação. Em uma aproximação de campo médio mostramos que sob pressão o modelo apresenta linha de coexistência entre fases de baixa e alta densidade, e ponto crítico. A entropia das ligações de hidrogênio tem papel fundamental na definição da inclinação da linha de coexistência. O comportamento do modelo pode estar realcionado como segundo ponto crítico da água super resfriada e com transições líquido-líquido em geral.O modelo da água quadrada é uma versão térmica do modelo do gelo, no qual considera-se a direcionalidade das ligações de hidrogênio. O modelo foi estudado na rede de Bethe e através de simulações de Monte Carlo em três situações diferentes: para a água pura e na presença de solutos polares e apolares. A água quadrada pura não apresenta transição de fase. No modelo para solvente com solutos apolares, medidas de frequência relativa de ligações e do tempo de correlação mostram que o modelo apresenta estruturação da camada de hidratação. Medidas de correlação temporal no modelo de Ising mostram comportamento oposto. Em um estudo preliminar para uma solução com solutos que realizam ligações de hidrogênio não conseguimos encontrar diagramas de coexistência com círculo fechado, para o conjunto de parâmetros utilizados, possivelmente devido à ausência de buracos. / We have developed two statistical models for water in which different features of water structure are considered. In the geometrical model different coordination numbers are present and the model allows for translational disorder. A mean-field treatment shows that under pressure the model exhibits phases of different densities and a coexistence line ending in a critical point. Entropy of the hydrogen network plays an essential role in defining the slope of the coexistence line. The model behavior might be related with the second critical point in supercooled water and to liquid-liquid transitions in general. The square water model is a thermal version of the ice model, and takes into account the directionality of the hydrogen bonds. The model was studied on a Bethe lattice and through Monte Carlo simulations, for three different situations: as pure water and in the presence of polar and apolar solutes. Pure square water does not present a phase transition. In the presence of apolar solutes, first shell square water presents ordering, as shown from comparison of relative frequency of bonds, as well as from study of time correlations. The latter was shown to present opposite behavior in case of an Ising system. In a preliminary study for a solution of hydrogen bonding solutes we were unable to find a closed loop for the sets of parameters chosen. Vacancies might need to be included.
|
204 |
Tests d'hypothèses pour les processus de Poisson dans les cas non réguliers / Hypotheses testing problems for inhomogeneous Poisson processesYang, Lin 22 January 2014 (has links)
Ce travail est consacré aux problèmes de testd’hypothèses pour les processus de Poisson nonhomogènes.L’objectif principal de ce travail est l’étude decomportement des différents tests dans le cas desmodèles statistiques singuliers. L’évolution de lasingularité de la fonction d'intensité est comme suit :régulière (l'information de Fisher finie), continue maisnon différentiable (singularité de type “cusp”),discontinue (singularité de type saut) et discontinueavec un saut de taille variable. Dans tous les cas ondécrit analytiquement les tests. Dans le cas d’un saut detaille variable, on présente également les propriétésasymptotiques des estimateurs.En particulier, on décrit les statistiques de tests, le choixdes seuils et le comportement des fonctions depuissance sous les alternatives locales. Le problèmeinitial est toujours le test d’une hypothèse simple contreune alternative unilatérale. La méthode principale est lathéorie de la convergence faible dans l’espace desfonctions discontinues. Cette théorie est appliquée àl’étude des processus de rapport de vraisemblancenormalisé dans les modèles singuliers considérés. Laconvergence faible du rapport de vraisemblance sousl’hypothèse et sous les alternatives vers les processuslimites correspondants nous permet de résoudre lesproblèmes mentionnés précédemment.Les résultats asymptotiques sont illustrés par dessimulations numériques contenant la construction destests, le choix des seuils et les fonctions de puissancessous les alternatives locales. / This work is devoted to the hypotheses testing problems for inhomogeneous Poisson processes.The main object of the work is the study of the behaviour of different tests in the case of singular statistical models. The “evolution of singularity” of the intensity function is the following: regular (finite Fisherinformation), continuous but not differentiable (“cusp”type singularity), discontinuous (jump type singularity)and discontinuous with variable jump size. In all thecases we describe analytically the tests. In the case ofvariable jump size we present as well the asymptoticproperties of the estimators.In particular we describe the test statistics, the choice ofthresholds and the form of the power functions for thelocal alternatives. The initial problem is always the testof a simple hypothesis against a one-sided alternative.The main tool is the weak convergence theory in thespace of discontinuous functions. This theory is appliedto the study of the normalized likelihood ratio processesin the considered singular models. The weakconvergence of the likelihood ratio processes underhypothesis and under alternatives to the correspondinglimit processes allows us to solve the mentioned aboveproblems.The asymptotic results are illustrated by numericalsimulations which contain the construction of the tests,the choice of the thresholds, and the power functions forlocal alternatives.
|
205 |
Sistemas aquosos bifásicos de polietilenoglicol e sais inorgânicos : modelo estatístico / Aqueous two-phase systems of polyethylene glycol and inorganic salts : statistical modelsBraga, Filipe Leôncio, 1985- 26 August 2018 (has links)
Orientador: Mário Noboru Tamashiro / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-26T19:25:53Z (GMT). No. of bitstreams: 1
Braga_FilipeLeoncio_D.pdf: 3256250 bytes, checksum: 73d43bfd44605cb6f23213feb8aeedf9 (MD5)
Previous issue date: 2015 / Resumo: Modelos termo-estatísticos que tentam reproduzir o comportamento de soluções aquosas de polímeros foram amplamente estudados ao longo dos anos. Entretanto, o número de trabalhos relacionados a sistemas aquosos contendo polímeros e sais adicionados ainda é bem restrito. Na tese desenvolvida, abordamos através de uma modelagem de Flory-Huggins a formação de sistemas aquosos bifásicos contendo cadeias poliméricas longas de polietileno-glicol em misturas contendo sais inorgânicos monovalentes. Dentro da modelagem, a competição entre a formação de ligações de hidrogênio por parte das moléculas de água e os monômeros da cadeia polimérica, além das interações íon-dipolo entre água e os íons dos sais dissociados, desempenham papel fundamental na formação das configurações de equilíbrio. Através de ajustes numéricos de dados experimentais, para cada tipo de sal introduzido na mistura, com previsões do modelo para as menores temperaturas para a formação das duas fases, as chamadas Cloud Point Temperatures (CPT), encontramos um conjunto de quatro parâmetros de interação que possibilitam a reprodução adequada do comportamento contínuo das CPT's em função das concentrações dos solutos / Abstract: Thermal-statistical models that try to reproduce the behavior of aqueous polymer solutions have been extensively studied over the years. However, the number of articles related to aqueous systems containing polymers and added salts is still very restricted. Across the developed thesis, we work with a Flory-Huggins theory to model the formation of aqueous two-phase systems containing long-polymer chains of polyethylene-glycol in mixtures containing monovalent inorganic salts. Within the model, the competition between the hydrogen-bond formation between water molecules and the monomers of the polymer chain, in addition to the ion-dipole interactions between water and the dissociated salt ions play a key role in shaping equilibrium configurations. Through numerical fits of experimental data for each type of salt introduced into the mixture with model predictions for the lowest temperatures for the formation of two phases, so-called Cloud Point Temperature (CPT), we find a set of four parameters of interaction that enable proper representation of the continuous behavior of CPT's as a function of the solutes concentration / Doutorado / Física / Doutor em Ciências
|
206 |
Analyse du risque de mildiou de la vigne dans le Bordelais à partir de données régionales et d’informations locales collectées en cours de saison / Grape downy mildew risk analysis in Bordeaux vineyards based on regional survey data and local expert knowledge analysisChen, Mathilde 12 December 2019 (has links)
L’utilisation de pesticides permet de réduire les pertes de récolte mais génère des impacts environnementaux négatifs. Il est important de fournir des informations précises sur les risques épidémiques concernant les bioagresseurs afin de raisonner l’utilisation des pesticides, en particulier dans le cas du mildiou de la vigne, responsable en moyenne de 43% des traitements utilisés dans le Bordelais. Cette thèse évalue l’intérêt de la date d’apparition des symptômes de mildiou de la vigne pour raisonner l’usage des fongicides dans la lutte contre cette maladie.En nous basant sur des observations régionales et de l’expertise locale, nous montrons que dans le Bordelais, les premiers traitements sont réalisés en moyenne quatre semaines avant l’apparition des premiers symptômes. Nous montrons que reporter la date du premier traitement anti-mildiou à la date d’apparition de la maladie permet d’économiser en moyenne 56% des traitements, par rapport aux pratiques actuelles de cette région. Nos résultats montrent que combiner cette stratégie avec le port d’équipements de protection réduit l’exposition des opérateurs de plus de 70%.En utilisant des méthodes de machine learning, nous montrons que la précocité et la gravité des épidémies de mildiou sont fortement liées. Les prévisions de nos modèles peuvent être utilisées pour déclencher les traitements contre la maladie dans les cas de risques élevés, entraînant une réduction de plus de 50% des traitements anti-mildiou par rapport aux pratiques actuelles.Nos résultats et les méthodes employées sont discutés et mis en perspective avec d’autres moyens de réduction de l’usage des pesticides en viticulture. / Abstract: Pesticides reduce yield losses but have negative environmental consequences. It is important to provide precise information on the epidemic risks concerning harmful organisms in order to reason the use of pesticides, in particular in the case of grape downy mildew, which is responsible on average for 43% of pesticides used in Bordeaux vineyards.The objective of this work is to estimate the benefits of using downy mildew onset date to avoid unjustified sprays in the control of this disease. Based on regional observations and local expertise, we show that in Bordeaux, the first treatments are applied on average four weeks before the first symptoms appear.We show that postponing the date of the first downy mildew spray to disease onset reduces fungicide use by an average of 56% compared to current practices in this region. For operators, our results show that combining this strategy with the use of personal protective equipment reduces exposure by more than 70%.By using machine learning methods, we also show that the precocity and severity of downy mildew epidemics are strongly linked. Our predictions can be used to trigger disease treatments only in high-risk cases, resulting in a reduction of more than 50% in mildew treatments compared to current practices. Our results and the used methods are discussed and compared with other methods for reducing the use of pesticides in viticulture.
|
207 |
Time-lapse monitoring of sidewall mass-wasting events in a Northeast Tennessee gullyMcConnell, Nicholas, Luffman, Ingrid, Nandi, Arpita 05 April 2018 (has links)
In the southern Appalachians, the dominant soil order, Ultisols, is highly susceptible to erosion. If left unmanaged these soils can develop into gully systems resulting in land degradation. This study examines gully development through sidewall mass-wasting events at a high temporal resolution using 30 minute time-lapse photography. Prior research at this site found significant mass wasting events occurring between weekly monitoring periods. By shortening the interval of observation to 30-minutes, a more accurate understanding of the frequency and intensity of these mass-wasting events, and their relation to meteorological factors, can be determined. Photographs of a gully (approximately 1.5 m deep by 3 m wide at the top) were captured every 30 minutes from 11/29/17 - 2/18/2018 with a WingScape outdoor time-lapse camera mounted on a plastic stake 3.16 m from the gully facing northwest and upstream into the gully channel. A total of n=1648 images were coded using presence/absence indices for six observed geomorphic processes: creep on NE facing sidewall, creep on SW facing sidewall, slump on NE facing sidewall, slump on SW facing sidewall, channel aggradation, and channel development. Precipitation and temperature data were collected every 5 minutes using a Davis Vantage Pro 2 weather station located 240 m from the gully, and were aggregated to various time intervals. Precipitation received in previous 0.5, 1, 1.5, 2, 3, 6, 12, 24, 36, 48, and 72 hours were calculated for each image. Two binary temperature variables were generated with values of “1” if temperature dropped below 0 °C (32 °F) during the prior 30 minutes or 24 hours, respectively, and “0” otherwise. Logistic regression models (forward conditional method) for the six geomorphic index variables were generated using the precipitation and temperature data. For creep on the NE facing sidewall, the significant independent variables are 3 hour and 72 hour prior rain, and freeze conditions in the previous 0.5 and 24 hours. On the SW facing sidewall, rain and temperature variables were also important for creep; rain in the previous 12 and 24 hours, and freeze conditions within the previous 24 hours were retained in the model. For slumping on both the NE and SW facing sidewall, recent and prolonged rain were important. Specifically, 1, 6, 12, and 24 hour rainfall were retained in both models, with the addition of 3 hour rainfall in the NE facing sidewall slump model. No temperature variables were retained. For channel aggradation (deposition of material in the channel), rain in the prior 12 and 72 hours, and freezing in the prior 24 hours were important, suggesting that freeze-thaw processes loosen the soil, and subsequent rain events carry material into the channel. When rain stops, the material is then deposited in the channel. Interestingly, no viable model could be developed for channel development (erosion) using these parameters. These results will be useful to quantify meteorological controls on gully erosion at short temporal scales.
|
208 |
Real-Time Dengue Forecasting In Thailand: A Comparison Of Penalized Regression Approaches Using Internet Search DataKusiak, Caroline 25 October 2018 (has links)
Dengue fever affects over 390 million people annually worldwide and is of particu- lar concern in Southeast Asia where it is one of the leading causes of hospitalization. Modeling trends in dengue occurrence can provide valuable information to Public Health officials, however many challenges arise depending on the data available. In Thailand, reporting of dengue cases is often delayed by more than 6 weeks, and a small fraction of cases may not be reported until over 11 months after they occurred. This study shows that incorporating data on Google Search trends can improve dis- ease predictions in settings with severely underreported data. We compare penalized regression approaches to seasonal baseline models and illustrate that incorporation of search data can improve prediction error. This builds on previous research show- ing that search data and recent surveillance data together can be used to create accurate forecasts for diseases such as influenza and dengue fever. This work shows that even in settings where timely surveillance data is not available, using search data in real-time can produce more accurate short-term forecasts than a seasonal baseline prediction. However, forecast accuracy degrades the further into the future the forecasts go. The relative accuracy of these forecasts compared to a seasonal average forecast varies depending on location. Overall, these data and models can improve short-term public health situational awareness and should be incorporated into larger real-time forecasting efforts.
|
209 |
Analyse et description de la morphologie foliaire : application à la classification et l'identification d'espèces de plantes / Analysis and description of leaf morphology : application to the classification and identification of plant speciesMzoughi, Olfa 14 May 2016 (has links)
De nos jours, l’identification automatique des espèces de plantes par l’analyse d’images, devient incontournable pour faire perdurer, standardiser voire approfondir les connaissances relatives à la communauté végétale. Cette thèse aborde le problème d’identification automatique des espèces de plantes en utilisant les images de feuilles. Elle s’attaque à deux principaux challenges: Le premier challenge est le grand nombre et la large variabilité de la morphologie foliaire des espèces et le deuxième challenge est la variabilité intra-espèces qui se manifeste localement au niveau de régions particulières des feuilles. Pour pallier à ces deux problèmes, un retour à la botanique et notamment aux concepts botaniques foliaires a été établi pour définir une structuration automatique des feuilles à deux niveaux: Le premier niveau concerne un schéma de catégorisation selon les deux concepts botaniques “arrangement” et “lobation”. Le deuxième niveau consiste à définir les parties sémantiques qui composent la feuille. L’approche de la thèse s’articule autour de deux principaux volets: Dans le premier volet, nous nous intéressons à mettre en place cette structuration guidée par la sémantique botanique en définissant des propriétés géométriques simples corrélées avec les définitions et les observations botaniques. Dans le deuxième volet, nous étudions la faisabilité et la pertinence d’intégrer cette structuration dans la chaîne d’identification. Particulièrement, nous établissons des recherches ciblées dans les catégories et nous définissons des modèles de parties à significations botaniques. Nous établissons notre évaluation sur les deux bases d’images de Scans de feuilles ImageCLEF 2011 et ImageCLEF 2012. Nous comparons notre approche par rapport à un schéma d’identification de référence, appliqué sur la totalité de la base et en utilisant l’image entière, et par rapport à plusieurs méthodes référencées dans la littérature. / Nowadays, automatic identification of plant species, by image analysis, has become crucial to maintain, standardize or deepen knowledge about the plant community. This thesis focus on the problem of automatic identification of plant species using leaf images. It addresses two main challenges: The first challenge is the large number and the high variability in foliar morphology across species. The second challenge is the intra-species variability which occurs locally at particular regions of leaves. To overcome these two problems, a return to botany and especially to leaf botanical concepts is established in order to define an automatic structuring of leaves at two levels: The first level concerns a categorisation scheme according to the botanical concepts “arrangement” and “lobation". The second level consists in decomposing leaves into semantic parts. The approach of the thesis is based on two key parts: In the first part, we focus on establishing this botanical-based structuring process by defining simple geometric properties correlated with botanical definitions and observations. In the second part, we investigate the feasibility and opportunities to integrate this structuring process in the identification scheme. Particularly, we make targeted researches in categories and we define specific part-based models.Experiments are conducted using the ImageCLEF 2011 and 2012 Scan images leaf databases. We compare our approach with respect to the reference identification scheme, applied on the whole databaseand using the entire images, and with respect to several methods referenced in the literature.
|
210 |
Condition assessment of concrete dams in cold climate / Tillståndsbedömning av betongdammar i kallt klimatHellgren, Rikard January 2019 (has links)
Dams in many countries are approaching their expected service life. Proper assessment of the aging dams structural health increase the knowledge of the current safety, and allow for better planning of renovation and rebuilding investments. The behavior of concrete dams is, to a great extent, governed by the ambient variation in temperature and water level. In cold regions, the ice sheet formed in the reservoir may subject a pressure load on the dams. Theoretically, this load has a significant impact on the structural behavior of dams. Despite this, the maximum magnitude, as well as the seasonal variation of the ice load, constitute the most considerable uncertainty in the safety assessment of dams. This thesis presents research that examines how to model the expected behavior of dams in cold climate. The underlying problem is to predict the response of dams due to variation in the external conditions. Since the ice load is such a vital part of the external conditions in cold climate, the understanding and modeling of ice loads have been given extra attention. Models suitable to predict the long-term behavior of dams can be divided between theoretical, data-based, and hybrid. Prediction accuracy is essential to set alert thresholds, and in that regard, the data-based models are generally superior. The major contribution of this thesis is the design and installation of a prototype ice load panel with direct measurement of the ice pressure acting on a dam. The panel is attached on the upstream face of the dam and is large enough so that the whole thickness of the ice sheet is in contact with the panel. The predicted ice load from the best available model that includes loads from both thermal events and water level changes did not correspond to the measured ice loads. As there are no validated models or measurement methods for ice load on the dam, continued research is necessary, both through further measurements to increase knowledge and development of models. / I många länder närmar sig vattenkraftsdammarna deras förväntade tekniska livslängd. Korrekt utvärdering av dammens strukturella status ökar kunskapen om det nuvarande säkerhetsläget och möjliggör för bättre planering av renoveringar och ombyggnadsinvesteringar. Betongdammarnas beteende styrs till stor del av variationen i omgivande temperaturer och vattennivå. I kalla regioner kan is som bildas i magasinet utsätta dammen för en tryckande last. Teoretiskt har denna belastning en betydande inverkan på dammarsstrukturella beteende. Trots detta är den maximala storleken såväl som säsongsvariationen för islasten en av de mest betydande osäkerheterna vidsäkerhetsbedömningen av dammar. Denna uppsats presenterar forskning som undersöker hur förväntat beteendehos dammar i kallt klimat kan modelleras. Den underliggande frågeställningen är att förutsäga en damms respons orsakad av variation i de yttre förhållandena. Extra fokus har lagts på förståelsen och modelleringen av islasten då den är en viktig del av de yttre förhållandena för dammar i kalla klimat. Modeller som är lämpliga för att förutsäga dammars beteende kan delas upp i teoretiska, databaserad, och hybridmodeller. Förutsägbarhetsnoggrannhet är avgörande för att ställa in varningsnivåer, och i det avseendet är de databaserade modellerna i allmänhet överlägsna. Det huvudsakliga bidraget från detta projekt är utvecklandet och installationen av en prototyp av en islast panel, fäst på en damms uppströmssida. Panelen mäter istrycket direkt mot dammen och är tillräckligt stor så att helaisens tjocklek förblir i kontakt med panelen. Panelen bidrar till ökad kunskap om säsongsvariationen i istryck och mekanismen för islaster orsakad av variation i vattennivån. Den predikterade islaten från den bästa tillgängliga islastmodellen som inkluderar termiska islaster och islaster från vattennivåförändringar överensstämmer inte med de uppmätta islastpanelen som uppmätts med panelen. Då det saknas validerade modeller eller mätmetoder för islast är det viktigt med fortsatt forskning, dels genom ytterligare mätningar för att öka kunskapen men även fortsatt modellutveckling. / <p>QC 20190926</p>
|
Page generated in 0.1904 seconds