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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.
51

Etude numérique de la dynamique sous écoulement de gouttes et vésicules avec viscosités de surface / Numerical study of the dynamics of droplets and vesicles with surface viscosities under flow

Degonville, Maximilien 21 December 2018 (has links)
De nombreux systèmes fluides dans les domaines de la biologie ou encore de la cosmétique sont limités par une interface dont les propriétés mécaniques régissent la stabilité. En particulier, les objets tels que des gouttes, vésicules ou polymersomes se déforment dans un écoulement simple et mènent à une grande richesse de dynamiques spatio-temporelles contrôlées par la nature des matériaux qui composent l'interface. Les travaux présentés concernent l'étude numérique de la déformation de ces objets dans un écoulement de Stokes, en particulier dans des situations où les viscosités de l'interface jouent un rôle important. Un code de calcul couplant intégrales de frontières et éléments finis a été utilisé afin de décrire la physique interfaciale et étudier leur comportement une fois plongés dans un écoulement. Ces travaux ont permis d'étudier l'influence des viscosités interfaciales sur la dynamique d'une goutte dans un écoulement extensionnel plan, leur influence sur sa dynamique de déformation et sur les conditions de rupture de celle-ci. Les études réalisées sur une vésicule fortement dégonflée et plongée dans un écoulement cisaillé ont caractérisé la bifurcation entre les deux familles de forme existantes dans ces conditions. Ces formes ayant une influence sur la dynamique de la vésicule dans l'écoulement, celle-ci a été étudiée dans le cadre d'un écoulement infini puis proche d'une paroi parallèle à l'écoulement. Enfin, de premiers résultats sur la dynamique d'un polymersome dans un écoulement cisaillé permettent de construire un diagramme de phase illustrant les différents comportement de cet objet en fonction de la viscosité de la membrane et du taux de cisaillement / There are many fluid systems in the biology, food industry, pharmacology or cosmestics fields that are bound by an interface which mechanical properties rule the system stability. Objects like droplets, vesicles or polymersomes change their shape in a simple flow which lead to a wealth of space and time dynamics. These properties are controlled by the nature of the interface material. The aim of this work is the numerical study of the deformation of droplets, vesicles and polymersomes in a Stokes flow, especially when the interfacial viscosities play an important role. A numerical computation code coupling boundary integrals and finite elements was used to describe the interfacial physics of these objects and study their behaviour when immerged in a flow. Multiple resolution strategies where developped to this end in order to optimize the numerical computation in the cas of an interface with viscosities.Using this work, the influence of interfacial viscosities on the dynamics of a droplet in an extensional flow is studied : in particular, their influence on the stretching dynamics of a droplet and its break up conditions was characterized. The study of a vesicle, droplet bounded by a lipid bilayer, strongly deflated and immerged in a shear flow detailed the bifurcation between two shape types existing for this system. These shapes have an influence on the vesicle dynamics under flow, which is studied for an unbounded flow and a near-wall flow. Finally, we show first results about the dynamics of a polymersome in a shear flow. We used them to build a phase diagram for the behaviour of this object depending on the membrane viscosity and the shear rate
52

Analysis of Flow Structures in Wake Flows for Train Aerodynamics

Muld, Tomas W. January 2010 (has links)
Train transportation is a vital part of the transportation system of today anddue to its safe and environmental friendly concept it will be even more impor-tant in the future. The speeds of trains have increased continuously and withhigher speeds the aerodynamic effects become even more important. One aero-dynamic effect that is of vital importance for passengers’ and track workers’safety is slipstream, i.e. the flow that is dragged by the train. Earlier ex-perimental studies have found that for high-speed passenger trains the largestslipstream velocities occur in the wake. Therefore the work in this thesis isdevoted to wake flows. First a test case, a surface-mounted cube, is simulatedto test the analysis methodology that is later applied to a train geometry, theAerodynamic Train Model (ATM). Results on both geometries are comparedwith other studies, which are either numerical or experimental. The comparisonfor the cube between simulated results and other studies is satisfactory, whiledue to a trip wire in the experiment the results for the ATM do not match.The computed flow fields are used to compute the POD and Koopman modes.For the cube this is done in two regions of the flow, one to compare with a priorpublished study Manhart & Wengle (1993) and another covering more of theflow and especially the wake of the cube. For the ATM, a region containing theimportant flow structures is identified in the wake, by looking at instantaneousand fluctuating velocities. To ensure converged POD modes two methods toinvestigate the convergence are proposed, tested and applied. Analysis of themodes enables the identification of the important flow structures. The flowtopologies of the two geometries are very different and the flow structures arealso different, but the same methodology can be applied in both cases. For thesurface-mounted cube, three groups of flow structures are found. First groupis the mean flow and then two kinds of perturbations around the mean flow.The first perturbation is at the edge of the wake, relating to the shear layerbetween the free stream and the disturbed flow. The second perturbation isinside the wake and is the convection of vortices. These groups would then betypical of the separation bubble that exists in the wake of the cube. For theATM the main flow topology consists of two counter rotating vortices. Thiscan be seen in the decomposed modes, which, except for the mean flow, almostonly contain flow structures relating to these vortices. / QC 20100518 / Gröna Tåget
53

Integration of Digital tools in Product Realization Process

Salaam, Abdul, Mehmood, Sultan January 2021 (has links)
The market has been evolving lately, with the introduction of more and more digital tools that industries are making use to improve their overall operations within the Production process. The integration of digital tools within the Product realization process has major advantages in improving production performance. Many large industries make use of digital tools to digitize their products making them smart products. Implementing these digital tools can be beneficial for reshaping the organization which can lead to better customer satisfaction and improve business strategy. This project explores different digital tools that can be integrated with the product realization process and how these tools contribute to the different production development phases. This thesis presents a detailed study of the digital tools Simulation, Visualization, Emulation, and Digital twins which can be integrated with the product development process. A pre-study is conducted to gather knowledge regarding the application of these tools and further discover how these tools can support the Product realization process and is used to describe which tool works best at which stage of the product realization process, which can be used to improve the efficiency and accuracy of the production process. Implementing these digital tools within the production facility can be associated to smart factory paradigm of the Fourth industrial revolution Industry4.0.This research aims to contribute to the use of digital tools in the production processes and aids in bridging the gap between traditional and modern manufacturing methods. The outcome of this study is to clarify how the above-mentioned digital tools are linked to the product realization process to support an efficient and digitalized production development, also mentioning the strengths and weaknesses of these tools. The resulting analysis has provided a framework developed to support an efficient digitalized production development and preparation process for assembly tasks utilizing human and robot collaboration. This research paper can be used as a guide for companies that want to explore how implementing digital tools in their product realization process and how it may improve their productivity.
54

Shared Autonomous Vehicles Implementation for a Disrupted Public Transport Network

Jaber, Sara, Mahdavi, Hassan, Bhouri, Neila 23 June 2023 (has links)
The paper proposes the management of bus disruption (e.g. fleet failure) and maintain a resilient transportation system through a synergy between shared autonomous vehicles and the existing public transport system based on the organizational structure and demand characteristics. The methodology is applied to the region of Rennes (France) and its surroundings.
55

Optimization Of A Virtual Power Plant In The German Electricity Market

Le Louarn, Theobald January 2017 (has links)
Distributed energy sources are becoming more and more important in the German electricitynetwork. One solution to manage this growing number of distributed assets liesin the Virtual Power Plant concept. A Virtual Power Plant aggregates decentralizedgenerators and loads to behave like a large power plant. Based on new technologies, ituses advanced communication technologies to provide different services (generation ofenergy, steering of power systems, balancing services ...). This thesis proposes a mixedintegerstochastic model of a Virtual Power Plant. The participation to different productsis being studied: selling power on day-ahead basis on the spot market, providingflexibility to the secondary and tertiary reserve market. The particularity of this modelis to consider the revenue generated by the stochastic activation of the reserve market.An operational tool named AlocaBid is implemented in Python, based on the developedmathematical model. The performance of the model is being evaluated using four studycases, representing typical market situations. The results demonstrate the advantage ofthe proposed model over state-of-the-art method for bids’ allocation. / Distribuerade energik¨allor blir allt viktigare i det tyska eln¨atverket. En l¨osning f¨or atthantera det v¨axande antalet distribuerade tillg°angar ¨ar Virtual Power Plant-konceptet.Ett virtuellt kraftverk styr decentraliserade generatorer och laster f¨or att efterlikna ettnormalt kraftverk. Baserat p°a ny teknik anv¨ander det avancerad kommunikationsteknikf¨or att tillhandah°alla olika tj¨anster (generering av energi, styrning av kraftsystem, balanseringstj¨anster ...). Denna avhandling f¨oresl°ar en stokastisk blanda heltalsmodell avett virtuellt kraftverk. Deltagandet i olika produkter studeras: F¨ors¨aljning av maktp°a daglig basis p°a spotmarknaden, vilket ger flexibilitet till den sekund¨ara och terti¨arareservmarknaden. Det speciella med denna modell ¨ar att den tar h¨ansyn till de int¨aktersom genereras av den stokastiska aktiveringen av reservmarknaden. Ett operationsverktygmed namnet AlocaBid implementeras i Python, baserat p°a den utvecklade matematiskamodellen. Modellens prestanda utv¨arderas med fyra studiefall, som representerartypiska marknadssituationer. Resultaten visar f¨ordelen med den f¨oreslagna modelleframf¨or den senaste tekniken f¨or budgivningens f¨ordelning.
56

Water Contamination Detection With Artificial Neural Networks

Gelin, Martin, Fridsén Skogsberg, Rikard January 2020 (has links)
Drinking water is one of our most important re- sources, so the ability to reliably monitor harmful contaminations in our water distribution network is vital. In order to minimize false alarms for water monitoring, while keeping a high sensitivity, a machine learning approach was evaluated in this project. Measurement data captured with a new kind of sensor, an electronic tongue, was provided by Linköping university. The solution was an artificial neural network, in the structure of an Autoencoder, which could learn the dynamic behaviour of natural deviations and with a false alarm rate of approximately one false alarm per week. This was done by evaluating the data and assembling an input structure to account for daily cyclic phenomena, which then was used to train the neural network. The solution could detect anomalies as small as 1.5% by comparing the input with the reconstructed vector, and raise an alarm. In conclusion, an Autoencoder is a viable method for detecting anomalies in water quality. / Drickvatten är en av våra mest värdefulla tillgångar, det är därför mycket viktigt att det finns sätt att pålitligt övervaka om dricksvattennätet blivit förorenat. För att kunna minimera antalet falsklarm och samtidigt ha hög känslighet mot dessa föroreningar undersöktes och implementerades en lösning med maskininlärningsalgoritmer. Mätdata tillhandahölls av Linköpings universitet och kom från en ny sensor kallad elektronisk tunga. Lösningen var ett artificiellt neuralt nätverk i form av en Autoencoder, som kunde lära sig det dynamiska beteende som ofarliga avvikelser utgjorde. Detta gav en lösning som i medel gav ett falsklarm per sju dagar. Detta gjordes genom att utvärdera rådata och konstruera en struktur på indata som tar hänsyn till dygnsbunda naturliga fenomen. Denna struktur användes sedan för att träna det neurala nätverket. Lösningen kunde upptäcka fel ner till 1.5% genom att jämföra indata med den rekonstruerade vektorn, och på så sätt ge ett alarm. / Kandidatexjobb i elektroteknik 2020, KTH, Stockholm
57

Numerical Simulation of CO2 Injection in Peridotite for Geological Storage / Numerisk simulering av CO2-injektion i peridotit för geologisk lagring

Matsumoto, Mirai January 2024 (has links)
The problem of global warming is becoming more and more serious, and carbon dioxide is one of the main causes of climate problems. Therefore, in order to re-duce CO2 emissions, the use of mineralization to store CO2 has become one of the potential methods. In addition, due to the high mineralization rate of peridotite, it will become the research object of this study. This study uses COMSOL Multiphysics to simulate the changing characteristics of carbon dioxide after injection into peridotite. Sensitivity analysis is performed by changing the porosity of the rock and the rate of CO2 injection to further understand the impact on CO2. The results show that at a lower injection rate, the pressure distribution is relatively uniform, the CO2 concentration range is also small, and the saturation increases slowly. On the other hand, when the porosity decreases, the pressure will increase significantly, the diffusion range of CO2 will be relatively expanded, and the saturation will increase. In addition, no matter which factor, it will tend to decrease with the increase of distance and time, and eventually stabilize. Therefore, in order to avoid the possibility of formation rupture and potential leakage of CO2, it is necessary to combine these influencing factors to seek a stable and effective CO2 storage solution. / Problemet med den globala uppvärmningen blir mer och mer allvarligt och kol-dioxid är en av huvudorsakerna till klimatproblemen. Därför, för att minska CO2 utsläppen, har användningen av mineralisering för att lagra CO2 blivit en av de möjliga metoderna. Dessutom, på grund av den höga mineraliseringshastigheten för peridotit, kommer det att bli forskningsobjektet för denna studie. Denna studie använder COMSOL Multiphysics för att simulera de förändrade egenskaperna hos koldioxid efter injektion i peridotit. Känslighetsanalys utförs genom att ändra bergartens porositet och hastigheten för CO2 injektion för att ytterligare förstå påverkan på CO2. Resultaten visar att vid en lägre injektionshastighet är tryckfördelningen relativt jämn, koncentrationsområdet CO2 är också litet och mättnaden ökar långsamt. Å andra sidan, när porositeten minskar, kommer trycket att öka av-sevärt, diffusionsområdet för CO2 kommer att vara relativt expanderat, och mättnaden kommer att öka. Dessutom, oavsett vilken faktor, kommer den att tendera att minska med ökningen av avstånd och tid, och så småningom stabiliseras. Därför, för att undvika risken för formationsbrott och potentiellt läckage av CO2, är det nödvändigt att kombinera dessa påverkande faktorer för att söka en stabil och effektiv CO2 förvaringslösning.
58

Historieundervisning på två sidor av Östersjön : En komparativ studie av ämnesplaner för historieämnet i Finland och Sverige mellan åren 1985–2020 / History on two sides of the Baltic Sea : A comparative study of course plans in the subject of history in Finland and Sweden 1985-2020

Persson, Pontus January 2024 (has links)
This study aims to determine the similarities and differences between the Finnish and Swedish course plans for the history subject, focusing particularly on the content contained in the course plans and the amount of national history included in them as well as the changes over time. The essay is based on the comparative research method with a theoretical basis in Ulf P. Lundgren's theories about the curriculum and how it is influenced by the society in which it is written. Three different course plans were used from each country, spanning the period between 1985-2020. The main conclusion of this study was that while there are many similarities between the two countries' course plans, they differ in the amount of guiding they yield for the teachers. The Finnish course plans also include more obligatory parts about Finnish history, in contrast to the Swedish which barely touches the subject. Finally, the most distinct change over time is the shift towards a more source-critical point of view when it comes to the importance of the history subject.
59

Jag lydde bara order : Byråkratins strukturella konsekvenser för tillämpningen av ett Individ- och helhetsperspektiv / I just obeyed order

Friborg, Alexandra, Hultgren, Renée January 2008 (has links)
<p><p>In this paper, we have studied the consequences of the bureaucratic or-ganizational structure for the individual- and holistic perspective pre-scribed in the Swedish legislation for social work. We have asked what consequences bureaucratic organizational structure in Max Weber’s terms can have for the individual and how it can affect the street level bureaucrats’ work performance. This is a theoretical study using and comparing earlier theoretical and empirical studies. Several organizational aspect of bureaucracy, listed and discussed in this study, makes it more difficult to implement the prescribed individual- and holistic perspective. At the same time it is demonstrated that the very same organizational features gives the street level bureaucrats the tools to an administrative fast and effective process. Bureaucracy can also create loyalty-bonds, demonstrated in this study, which render possible a structure where one closes the eyes to eventual moral dilemmas that may have negative consequences for the client.</p></p>
60

Ris, skäver och skärva : Folklig kategorisering av några barnsjukdomar ur ett kognitivt semantiskt perspektiv

Westum, Asbjörg January 1999 (has links)
In Swedish dialects we find the terms ris,skäver and skärva referring to illnesses in children. The words are also parts of various compounds which refer to variants of the illnesses. The terms are linguistic expressions denoting two folk categories of illnesses, RIS and SKÄVER/SKÄRVA. These categories are investigated from a cognitive semantic perspective. The cognitive perspective argues that we organize our understanding of reality by using Idealized Cognitive Models (ICM) based on our physical, mental and emotional experiences of the world. The aim is twofold: to demonstrate the bases on which an experienced illness is placed in a certain category, and to show how a folk conception of illness is reflected in the word formation strategies. The word formation strategies emanate from notions of characteristic symptoms, and from notions of causes of illnesses. Both categories, RIS and SKÄVER/SKÄRVA, are based on a number of ICM's. The category RIS is a radial structure, which means that the category is held together although its members have no structural criteria in common. The category SKÄVER/SKÄRVA is a concentrating structure, meaning that all members share all structural criteria. There is a strong connection between word formation strategies and the structures of the categories. Terms related to symptoms refer to members of a category which are part of a radial structure, while terms related to causes refer to members of a category which are part of a concentrating structure. This can be explained by two of the basic assumptions of cognitive semantics: semantic content is structred and symbolized overtly on the surface form of a language and categories are conventional, based on cultural assumptions about the world. / digitalisering@umu

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