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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

High-performance Monte Carlo Computations for Adhesive Bands Formation

Shah, Karim Ali January 2022 (has links)
We propose a lattice model for three stochastically interacting components that mimicsthe formation of the internal structure of adhesive bands via evaporating one component(the solvent) by thermal gradient. We use high-performance computing resources toinvestigate the formation of rubber-acrylate morphologies. We pay special attentionto the role of varying temperature as well as of the changing the solvent interaction inconnection to the shape of the obtained rubber morphologies.In the lattice model, we start with microscopic spins of three particles in the latticewith short-range interactions between them. This microscopic model is approximatednumerically via a Monte Carlo Metropolis-based algorithm. High-performancecomputing resources and Python-based implementations have been used for thenumerical simulation of the lattice model. The numerical implementation highlights theeffect of the model parameters (volatility of the Solvent, temperature, and interactionbetween the particles) on the structure of the obtained morphologies. We demonstratethat one can utilize a reasonably simple model to explain the impact of parameters onthe creation of morphology in ternary systems when one component evaporates.
2

Morphology formation via a ternary Cahn-Hilliard system during one species evaporation as a moving boundary problem - Finite Element approximation and implementation in FEniCS / Morforlogiformation via ett trekomponents Cahn-Hilliard system under enkomponents avdunstning i en tidsberoende domän - Finita element metoden och implementation i FEniCS

Jävergård, Nicklas January 2020 (has links)
In this thesis we derive a coupled system of Cahn-Hilliard equations posed in a domain with moving boundary using arguments from thermodynamics. The physical setting we have in mind is a ternary solution observed during one species evaporation as a moving boundary problem. The mixture is made of two types of polymers blended in a solvent that is allowed to evaporate at part of the surface of the domain. After formulating the evolution system as a moving-boundary problem with kinetic interface condition, we fix the moving boundary to facilitate a suitable numerical approximation. We project the resulting model equations on a finite element space and then integrate the obtained system in Python using FEniCS. We show numerically the formation of morphologies and track the evolution of the remaining solvent and of the moving boundary position. The conjecture is that such a system would produce phase separation and that the resulting morphologies are mappable to the observations of organic solar cells. Finally, we study the effect of the most relevant parameters on the output of our Cahn-Hilliard system, particularly on the speed of the moving boundary and of the morphology formation. / I denna tes härleder vi ett kopplat system av Cahn-Hilliard ekvationer fomulerad i en tidsberoende domän med hjälp av termodynamiska argument. Den fysiska miljön vi tänker oss är en trekomponents lösning observerad under avdunstning med hänsyn till en tidsberoende domän. Blandningen består av två polymerer utspädda i ett lösningsmedel som tillåts förånga vid en av domänens gränser. Efter att vi formulerat evolutions ekvationerna i en tidsberoende domän med kinetiska gränsvillkor så utförs en transformation till en tidsoberoende domän för att underlätta en lösning med finita elementmetoden. Vi projicerar de resulterande ekvationerna på ett diskret rum skapat m.h.a. finita elementmetoden för att sedan integrera systemet med hjälp av FEniCS platformen skrivet i Python. Vi visar nummeriska lösningar för morfologiformationen och följer evolutionen av lösningsmedlet samt positionen för den rörliga gränsen. Vår förmodan är att ett sådant system kommer producera fas-seperation och den resulterande morfologin kommer vara jämnförbar med det som observeras hos organiska solceller. Slutligen studerar vi hur variationer av dom mest relevanta parametrarna påverkar på vårt Cahn-Hilliard system, i synnerhet positionen som en funktion av tid hos den rörliga gränsen samt morfologiformationen.

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