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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Krigföringsförmåga : Svensk doktrin och dess stöd i internationella teorier / Warfare capability : Swedish doctrine and its support in international theories

Haendler, Rebecka January 2012 (has links)
Att mäta och värdera motståndarens och sin egen krigföringsförmåga är angeläget i alla typer av militära konflikter. Svensk doktrin presenterar pelarmodellen som ett verktyg för detta. Med tanke på att den svenska försvarsmakten genomgått stora förändringar sedan pelarmodellen först introducerades i de svenska doktrinerna är det möjligt att den inte fyller sin funktion i de typer av militära konflikter som Sverige nu deltar i. I denna uppsats genomförs en teoriprövande studie av modellen i syfte att undersöka om den fortfarande är tillämpbar i sin befintliga form. Modellen prövas mot teorier av David Galula och John Warden vilka beskriver två typer av militära operationer som den svenska försvarsmakten deltar eller nyligen har deltagit i. Undersökningen visar att de faktorer som ingår i pelarmodellen också förekommer i Galulas och Wardens teorier samt att pelarmodellen fortfarande är tillämpbar i sin befintliga form. Dock kan modellen tolkas på en mängd olika sätt och betydelsen av dess ingående faktorer skiljer sig för olika typer av konflikter. För att öka användbarheten krävs kompletterande förklaringar kring modellen och begreppet krigföringsförmåga samt ett förtydligande av hur de fysiska, konceptuella och moraliska faktorerna är beroende av varandra. / To measure and evaluate the opponent’s and your own warfare capability is essential in all types of military conflicts. Swedish doctrine presents the column model as a tool for this. Given that the Swedish armed forces have undergone major changes since the column model was first introduced in the Swedish doctrines, it is possible that it doesn’t fulfill its role in the types of military conflicts that Sweden is now participating in. In this paper it is carried out a theory testing study of the model in order to study if it is still applicable in its existing form. The model is tested toward the theories of David Galula and John Warden which describes two types of military operations that the Swedish armed forces are or have recently participated in.The study shows that the factors included in the column model also are present in Galula’s and Warden's theories and that the column model still applies in its existing form. However, the model can be interpreted in a variety of ways and the importance of its constituent elements are different for different types of conflicts. To enhance the usability additional explanations about the model and the concept of warfare capability is needed as well as a clarification of how the physical, conceptual and moral factors are interdependent.
2

Développement d'un modèle hydrologique de colonne représentant l'interaction nappe - végétation - atmosphère et applications à l'échelle du bassin versant / Development of a soil column model for simulating the water table - vegetation - atmosphere interaction and applications to the catchment scale

Maquin, Mathilde 30 September 2016 (has links)
Dans le cadre de la modélisation climatique, la représentation du cycle de l'eau des surfaces continentales est primordiale. Actuellement, les "modèles de surface continentale" représentent l'évolution des flux d'eau verticaux dans des colonnes de sol de quelques mètres de profondeur et leur interaction avec l'atmosphère. En revanche, l'interaction avec les nappes de faible profondeur n'est pas prise en compte alors que leur présence influence fortement les flux d'évapotranspiration à l'échelle locale, et, en conséquence, le climat à l'échelle régionale. Une difficulté est que les zones où cette interaction apparaît relèvent d'une échelle inférieure à celle du maillage des modèles de surface continentale. L'objectif de cette thèse est de proposer un modèle qui permette de prendre en compte l'impact des nappes de faible profondeur sur les flux d'évapotranspiration pour les modélisations climatiques à l'échelle globale. La contrainte principale associée relève des temps de calculs, qui doivent être réduits pour permettre la réalisation de simulations sur de grandes échelles de temps et d'espace. Dans ce cadre, un nouveau modèle de colonne de sol est proposé. Une fonction de drainage imposée en bas de colonne permet de reproduire l'évolution temporelle du toit de la nappe, en interaction avec les processus d'infiltration et d'évapotranspiration. Le modèle est testé et validé sur des cas tests académiques simples dans un premier temps, puis sur le cas d'un bassin versant réel dans un second temps (bassin versant du Strengbach, en France). Enfin, une méthodologie basée sur ce modèle de colonne et permettant d'estimer les flux d'évapotranspiration en tenant compte de leur variabilité dans l'espace est introduite. Elle est appliquée à un bassin versant dont la superficie est proche de celle d'une maille classique des modèles de surface continentale (bassin versant du Little Washita, aux États-Unis). / The representation of the water cycle on land surfaces is essential for climate modeling. Nowadays, the "Land Surface Models" (LSMs) represent soil columns of a few meters deep and they simulate the temporal evolution of the vertical water flows and the interaction with the atmosphere. However, the interaction with a near-surface water table is not taken into account although it strongly influences the evapotranspiration fluxes at the local scale, and therefore the climate at the regional scale. This interaction, which occurs at a smaller scale than the grid scale of the LSMs, is difficult to model. The objective of this PhD is to propose a model that incorporates the impact of a near-surface water table on evapotranspiration fluxes for global climate models. The computation time of the model must be small enough to enable simulations at large spatial and temporal scales. In this context, a new soil column model is proposed with a drainage function that is imposed at the bottom of the column. This function aims at reproducing the temporal evolution of the water table level in interaction with both the infiltration and the evapotranspiration fluxes. The model is tested and validated on numerical experiments and on a real catchment (Strengbach, France). A methodology based on this column model is introduced to estimate the evapotranspiration fluxes taking into account their subgrid variability. This methodology is applied to a catchment whose area is similar to the one of a classic grid cell of LSMs (Little Washita, USA).
3

Processes important for forecasting of clouds over snow

Hagman, Martin January 2020 (has links)
The Swedish Armed Forces setup of the Weather Research and Forecasting Model (WRF) has problems to forecast low clouds in stably stratified conditions when the ground is covered by snow. The aim of this thesis is to understand what causes this deficit. Simulations during January and February 2018 are here compared with observations from Sodankylä in northern Finland. It is revealed that neither type of planetary boundary layer parameterization chosen nor vertical or horizontal interpolation are responsible for the deficiency. Instead, our experiments show that, to first order, poor initialization of Stratocumulus (Sc) clouds from the host model, Atmospheric Model High Resolution (HRES), of the Integrated Forecast System (IFS) is the missing link. In situations when Sc clouds are missing in the IFS analysis, although they exist in reality, we use information from vertical soundings from Sodankylä. In the initialization process we used the fact that liquid potential temperature is constant in a well-mixed cloud. Initializing cloud water and cloud ice from IFS HRES and from soundings with different methods improves the model performance and the formation of very low artificial clouds at the first model level is prohibited.
4

IMPLEMENTAÇÃO DE UM MODELO DE COLUNA SIMPLES PARA A CAMADA LIMITE ESTÁVEL UTILIZANDO DIFERENTES FORMULAÇÕES DE TURBULÊNCIA / IMPLEMENTATION OF A SINGLE COLUMN MODEL FOR THE STABLE BOUNDARY LAYER USING DIFFERENT TURBULENCE FORMULATIONS

Schmengler, Moacir 01 October 2012 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In this work a single column model is implemented, aiming primarily to simulate the Stable Boundary Layer (SBL). The model is composed of prognostic equations for the potential temperature, specific humidity and the wind components. A prognostic equation for the turbulent kinetic energy (TKE) is also used. The turbulent fluxes are approximated from diffusion coefficients that are directly proportional to TKE and to the turbulent mixing length, with a adjustable proportionality factor. To estimate the turbulent mixing lengths, four different parametrizations from the literature are considered. First, a stable case in the Arctic is simulated, then the model is adjusted to reproduce previously published Large Eddy Simulations (LES) results for the same case. After the calibration, the model is validated through a comparison with observed nocturnal data, from tethered balloon soundings performed at a deforested area in the Amazon region, in the months of July and October 2001 and November 2003. The temporal evolution of potential temperature and specific humidity vertical profiles are simulated and compared to the observations from 13 different nights. The performance of the different formulations is evaluated through a statistic analysis for all nights. Potential temperature profiles were better represented by the model than specific humidity ones. In spite being able to reproduce different stability conditions, the model represented the most stable nights better. Finally, the model was coupled to a surface energy budget scheme and for these simulations the initial conditions from the night of 28 July 2001 were used. The scheme was used to evaluate how the simulated atmospheric variables depend on the wind intensity at the top of the vertical domain for the different formulations and with or without the energy budget scheme being added. / Neste trabalho é implementado um Modelo de Coluna Simples, com o intuito de simular a Camada Limite Estável (CLE). O modelo é composto por equações prognósticas para a temperatura potencial, umidade específica e para as componentes horizontais do vento, além de uma equação prognóstica para a energia cinética turbulenta (ECT). Os fluxos turbulentos são aproximados por coeficientes de difusão que são diretamente proporcionais à ECT e ao comprimento de mistura turbulenta, de forma que o coeficiente de proporcionalidade é um fator ajustável. Para estimar os comprimentos de mistura turbulentos são utilizadas quatro diferentes parametrizações encontradas na literatura. Primeiramente, é simulado um caso estável no Ártico, sendo o modelo ajustado de forma a produzir resultados próximos aos da Simulação dos Grandes Turbilhões (LES), obtidos por outros autores para o mesmo caso. Realizados os ajustes, o modelo é validado através da comparação com dados noturnos, obtidos por sondagens de balão cativo realizadas em um sítio experimental localizado numa área desmatada da região Amazônica, nos meses de julho e outubro de 2001 e de novembro de 2003. São simulados os perfis verticais de temperatura potencial e de umidade específica e comparados com as observações de 13 diferentes noites. A avaliação do desempenho das diferentes formulações utilizadas é feita através de uma análise estatística, utilizando dados de todas as noites. Observou-se, que os perfis verticais de temperatura potencial foram melhor representados do que os de umidade específica. Embora o modelo tenha sido capaz de reproduzir as diferentes condições de estabilidade, as noites mais estáveis foram melhor simuladas. Finalmente, é acrescentado um esquema que resolve o balanço de energia em superfície ao modelo, sendo utilizadas para este fim as condições iniciais da noite de 28 de julho de 2001. Este esquema foi utilizado para avaliar como as variáveis atmosféricas simuladas dependem da intensidade do vento no topo do domínio vertical, para as diferentes formulações analisadas e com ou sem a utilização do balanço de superfície.
5

X-ray analysis of praseodymia

Weisemöller, Thomas 11 November 2009 (has links)
In this thesis, it was shown that thin films of hexagonal praseodymium sesquioxide on Si(111) can be transformed to B-oriented twin free films of cubic praseodymium dioxide with oxygen vacancies by post deposition annealing in 1 atm. oxygen at temperatures from 300°C up to 700°C for 30 minutes. Films annealed at 100°C and 200°C are still purely hexagonal praseodymium sesquioxide after the annealing process. In the transformed films, two stoichiometric phases coexist laterally. The lateral lattice constant of both species is almost identical to the one of the originally deposited hexagonal praseodymium sesquioxide. Therefore, we assume that the lateral lattice constant is pinned throughout the oxidation process.The species are hence strained and show different vertical lattice constants, depending on the amount of oxygen vacancies. In some samples, those vacancies were partly ordered vertically, leading to a unit cell twice as large as expected for stoichiometric praseodymium dioxide.During the annealing process, an amorphous interfacial layer between substrate and oxide was detected. While the existence of this layer was known before, it was possible for the first time to quantify the thickness of the praseodymium rich part of this interface for epitaxially grown films. It was shown that this layer starts to grow significantly only during post deposition annealing at 500°C or more.These and other results for thin films were connected to previously published data for bulk praseodymia. The multi column model mentioned above for laterally coexisting praseodymia species in thin films was backed up by powder data. As a matter of fact, it was shown that this coexistence of several praseodymia species can be expected to be the rule rather than the exception.Strong evidence was found that results interpreted previously as stoichiometric cubic praseodymium sesquioxide contain more oxygen than originally thought...
6

Probabilistic Characterization of Bond Behavior at Rebar-concrete Interface in Corroded RC Structures: Experiment, Modeling, and Implementation

Soraghi, Ahmad January 2021 (has links)
No description available.
7

Untersuchungen zur Neuverteilung der Rücklaufflüssigkeit in Packungskolonnen

Bartlok, Guido 01 July 2002 (has links)
Bei der Rektifikation werden heute zunehmend Füllkörperkolonnen mit geordneten Packungen eingesetzt. Die Maldistribution, ein bislang ungelöstes Problem in Füllkörperkolonnen, wirkt sich negativ auf die Stoffaustauschleistung aus. Zur Verringerung der Maldistribution wird zwischen den Packungssektionen mehrfach die Rücklaufflüssigkeit gesammelt und erneut gleichmäßig über den Kolonnenquerschnitt verteilt. Diese Neuverteilung realisieren Zwischenverteiler, die somit einen Großteil der Kolonnenhöhe beanspruchen und damit die Investitions- und Betriebskosten erheblich erhöhen. Hauptursache für die Bauhöhe der Zwischenverteiler ist der Wunsch nach einem vollständigen Konzentrationsausgleich vor der Neuverteilung. Um die Kolonnenhöhe zu verringern und dennoch die gleiche Trennleistung zu erreichen, mangelt es den Anlagenbauern bislang an einer praktikablen Lösung. Entgegen der bisherigen Lehrbuchmeinung wird in dieser Arbeit die Bedeutung des vollständigen Konzentrationsausgleich grundsätzlich in Frage gestellt. Es erfolgen deshalb theoretische und experimentelle Untersuchungen für ein besseres Verständnis der Neuverteilung der Rücklaufflüssigkeit und deren Auswirkung auf die Trennleistung. Durch Modifizierung des klassischen Zwei-Kolonnen-Modells gelingt es, den Einfluss der Maldistribution, der Dampfquervermischung und der hydraulisch gleichmäßigen Flüssigkeitsneuverteilung mit und ohne vollständigen Konzentrationsausgleich numerisch zu simulieren. Die Überprüfung der Simulationsmodelle erfolgt an einer Pilotkolonne mit einem inneren Durchmesser von 1 m. Die Kolonne ist mit Sulzer MellapakPlus 752.Y ausgerüstet und als Testgemisch dient trans-/cis-Dekalin. Im Ergebnis zeigt sich, dass vor allem der hydraulische Ausgleich erforderlich ist und es praktisch keinen Unterschied zwischen vollständigen und unvollständigen Konzentrationsausgleich bei sonst gleichen Betriebsbedingungen gibt. Überlegungen für deutlich flachere Verteilerkonstruktionen werden vorgestellt.

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