The purpose of this thesis is to effectively model the time history of the temperature distribution during the selective laser sintering process and use this information to investigate the resulting relative density. The temperature is a critical parameter of the process because it directly effects the overall quality of the part. First, an efficient, affordable, and reliable simulation was developed within the finite element software, Abaqus. Next, the results from the simulations were compared to the experimental results performed by Wang et al. (2016). The FEA model consisted of a 3 layer simulation. Multiple simulations at various laser recipes were conducted using W-Ni-Fe as the powder material. The P/v (laser power/scanning speed) was plotted against the resulting total time above the melting temperature for various simulation. It was concluded that a linear relationship exists between the P/v parameters used in the laser recipe and the resulting time above the melting temperature. The average R2 values for the W-Ni-Fe simulations for layer 1, 2, 3 were 0.962, 0.950, and 0.939, respectively. Additionally, the experimental results from the Wang et al. (2016) study confirmed that a linear relationship is present. Thus, it can be concluded that the P/v parameters used within the laser recipe has a direct relation to the resulting relative density of the SLS part.

No description available.

No description available.

No description available.

This thesis investigates the mechanically controlled break junctions, with a particular emphasis on elucidating the behaviour of molecular currents at room temperature. The core of this experimental investigation involves a detailed analysis of conductance, examining how it varies over time and with changes in the gap between electrodes. Additionally, this study thoroughly evaluates transmission properties, coupling effects, and current characteristics. A pivotal aspect of the research was the meticulous current measurement, followed by carefully selecting optimal data sets. This process set the stage for an in-depth analysis of resonant tunnelling phenomena observed through a single channel. Notably, these experiments were conducted under open atmospheric conditions at room temperature. A significant finding from this study is the recognition that our current model requires refinement. This adjustment is necessary to more accurately encapsulate a broader spectrum of molecular transport mechanisms. Furthermore, this work significantly advances our comprehension of quantum effects in single-molecule junctions, particularly concerning similar molecules to Corannulene extending to some organometallics. One of the essential disclosures is the identification of deviations in the transport model, primarily attributable to electron-electron interactions. This insight is crucial as it paves the way for developing a more comprehensive and precise model, enhancing our understanding of molecular-scale electronic transport.:List of Figures xi List of Tables xiii Acronyms xiii Terminology xv Symbols xvi Abstract xvii 1 Introduction 1 1.1 Motivation and Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Molecular Electronics Background . . . . . . . . . . . . . . . . . . . . . . . . 2 1.3 RelatedWork, the State of Art . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.4 Structure of the work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2 Methods and Implementations 7 2.1 Mechanically Controlled Break Junctions Principle . . . . . . . . . . . . . . 8 2.1.1 Setups forMCBJ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.1.2 Measurement Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2.1.3 Electrical Diagramof theMeasurement . . . . . . . . . . . . . . . . . 15 2.1.4 Criteria to Select the Data . . . . . . . . . . . . . . . . . . . . . . . . 15 2.2 Experiment Realisation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 3 Molecules and Transport 20 3.1 Molecules in the Scope of this Thesis . . . . . . . . . . . . . . . . . . . . . . 20 3.1.1 Fixation of pi-Conjugated Molecules on Gold Surfaces via Thiol Bond 20 i 3.2 Ballistic Transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 3.2.1 Tunnelling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 3.3 Single Level Model (SLM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 3.3.1 Chemical Nature of theMolecular Channels . . . . . . . . . . . . . . 24 3.4 TransportMechanisms inMolecules attached toMCBJ . . . . . . . . . . . . 25 4 Results and Discussions 28 4.1 Discussions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 4.1.1 Opening Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 4.1.2 HistogramfromtheMeasurements . . . . . . . . . . . . . . . . . . . 30 4.2 Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 4.2.1 Current in Toluene . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 4.2.2 Current in Corannulene . . . . . . . . . . . . . . . . . . . . . . . . . 44 4.2.3 Current in Fe+3 Salen . . . . . . . . . . . . . . . . . . . . . . . . . . 49 4.2.4 Current Measurement after Consecutive Opening - Case Study: Fe+3 Salen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 4.2.5 Single LevelModel - Case Study: Corannulene . . . . . . . . . . . . . 53 4.2.6 Lorentzian Distribution and Fitting in Salen organometallics and Corannulene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 4.2.7 Single Level Model - Study of the case: Fe+3 Salen . . . . . . . . . . 66 4.3 Transmission and Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 4.3.1 Transmission and Coupling - Case Study: Fe+3 Salen . . . . . . . . . 70 4.4 Conclusive Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 4.4.1 Hypothesis of Scattering . . . . . . . . . . . . . . . . . . . . . . . . . 76 5 Conclusion and Further Work 78 5.1 The CurrentMeasurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 5.2 Further Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 A Current with Mean Normalization i A.1 Categories ofMeasurements . . . . . . . . . . . . . . . . . . . . . . . . . . . ii A.1.1 Measurements without hysteresis or very small . . . . . . . . . . . . . ii A.1.2 Measurements with hysteresis . . . . . . . . . . . . . . . . . . . . . . vi A.2 Measurements without Fitting . . . . . . . . . . . . . . . . . . . . . . . . . . xii B Our best fits where the SLM fails xi

Large Language Models (LLMs) have the potential to enhance learning among students. These tools can be used in chatbot systems allowing students to ask questions about course material, in particular when plugged with the so-called Retrieval Augmented Systems (RAGs). RAGs allow LLMs to access external knowledge, which improves tailored responses when used in a chatbot system. This thesis studies different RAGs through an experimentation approach where each RAG is constructed using different sets of parameters and tools, including small and large language models. We conclude by suggesting which of the RAGs best adapts to high school courses in Physics and undergraduate courses in Mathematics, such that the retrieval systems together with the LLMs are able to return the most relevant answers from provided course material. We conclude with two RAG-powered LLM with different configurations performing over 64% accuracy in physics and 66% in mathematics.

The main problem encountered in this thesis is the lack of research and knowledge of selective laser melted-printing with Uddeholm Dievar®. This absence of information could cause issues regarding quality and properties of the alloy as well as uncertainty regarding an appropriate heat treatment cycle. This thesis mainly focuses on observing the changes that occur in the microstructure when Uddeholm Dievar® is manufactured through the additive manufacturing (AM) method known as selective laser melting (SLM). The SLM- method consists of a high-power laser that melts together thin layers of powder, one layer at a time, until a three-dimensional product is created according to selected drawings. The methodology on which this thesis is based on is the execution of a theoretical study, scientific experiments and thermodynamic calculations. Analysis of the microstructure is performed using a scanning electron microscope with techniques such as Energy-dispersive X-ray spectroscopy (EDS) and Electron backscatter diffraction (EBSD). The purpose of the methods are to map the constituent elements of the alloy and observe the orientation of the crystallographic phases in the atomic lattice respectively. The results show that the powder, both before and after printing, mainly consists of martensite with a low amount of residual austenite. The amount of primary carbides is relatively low and has been classified as MC (V-rich) and/or M6C (Mo- rich) type. The remaining residual austenite could be explained by the segregation of constituent alloying elements, where the carbon content is a dominant factor to why the MS -temperature lowers significantly causing the presence of retained austenite even though SLM has a cooling rate that varies between 103 and 108 [K/s]. / Det huvudsakliga problemet som denna avhandling behandlar är bristen på forskning och kunskap inom selective laser melting (SLM) 3D-printing med Uddeholm Dievar®. Avsaknaden kan leda till sämre kvalité och produktegenskaper hos legeringen. Det kan även leda till ovisshet gällande val av lämplig värmebehandling. Arbetet fokuserar på att dokumentera utformningen av stålets mikrostruktur när Uddeholm Dievar® tillverkas med den additiva tillverkningsmetoden SLM. Tillverkningsprocessen består av en högeffektslaser som detaljerat smälter samman tunna lager pulver, ett lager i taget, tills att en tredimensionell produkt skapats utefter valda ritningar. Använda metoder är; utförandet av en teoretisk studie, vetenskapliga experiment och thermodynamiska beräkningar. Analys av mikrostrukturen genomförs med hjälp av svepelektronmikroskåp där teknikerna Energy-dispersive X-ray spectroscopy (EDS) och Electron backscatter diffraction (EBSD) används. Syftet med EDS är att kartlägga de ingående elementen i legeringen, syftet med EBSD är att se orientering av de kristallografiska faserna i atomgittret. Resultaten visar på att legeringen, både före och efter printing, till största del består av martensit med en låg mängd restaustenit. Mängden primärkarbider är relativt låg och har klassifiserats som typen MC (V-rik) och/eller M6C (Mo- rik). Den kvarstående restausteniten kan möjligen förklaras av segringen av ingående legeringsämnen där kolhalten är en dominerande faktor som sänker MS-temperaturen. Detta gör att restaustenit förekommer trots den höga kylhastigheten som varierar mellan 103 och 108 [K/s] i SLM.

Cette étude acoustico-perceptive concerne les limites de la perception et de la production des voyelles orales du français [i, e, ɛ, a, u, o, ɔ, y, ø, œ], en isolation et en contextes consonantiques divers, chez dix tchécophones, futures enseignantes de Français Langue Étrangère (FLE). Les résultats montrent que (1) La maîtrise phonétique des voyelles dépend de leurs graphies et de l’entourage consonantique. (2) Les voyelles fermées [i, y, u] et le [a] sont globalement maîtrisées avec authenticité. (3) Les capacités de perception des contrastes entre les voyelles moyennes e/ɛ, ø/œ et o/ɔ ainsi que leur production sont limitées. Ces résultats ne sont que partiellement en accord avec les prédictions établies à partir du Speech Learning Model (SLM) de Flege (1995), basé sur la notion de similarité phonétique qui existe entre la langue maternelle (LM) et la langue étrangère (LE). / This acoustic-perceptual study concerns the limits of perception and production of French oral vowels [i, e, ɛ, a, u, o, ɔ, y, ø, œ], in isolation and in different consonantal contexts, in ten pre-service Czech teachers of French as a Foreign Language (FFL). The results show that (1) Phonetic proficiency in vowels depends on their spellings and consonantal context. (2) Vowels [i, y, u] and [a] are generally mastered with authenticity. (3) The ability to hear contrasts between the vowels e/ɛ, ø/œ and o/ɔ and pronounce them is limited. These results are only partially consistent with the predictions established in the Speech Learning Model (SLM) by Flege (1995), based on the notion of phonetic similarity between the mother tongue (MT) and the foreign language (FL).

Cette étude acoustico-perceptive concerne les limites de la perception et de la production des voyelles orales du français [i, e, ɛ, a, u, o, ɔ, y, ø, œ], en isolation et en contextes consonantiques divers, chez dix tchécophones, futures enseignantes de Français Langue Étrangère (FLE). Les résultats montrent que (1) La maîtrise phonétique des voyelles dépend de leurs graphies et de l’entourage consonantique. (2) Les voyelles fermées [i, y, u] et le [a] sont globalement maîtrisées avec authenticité. (3) Les capacités de perception des contrastes entre les voyelles moyennes e/ɛ, ø/œ et o/ɔ ainsi que leur production sont limitées. Ces résultats ne sont que partiellement en accord avec les prédictions établies à partir du Speech Learning Model (SLM) de Flege (1995), basé sur la notion de similarité phonétique qui existe entre la langue maternelle (LM) et la langue étrangère (LE). / This acoustic-perceptual study concerns the limits of perception and production of French oral vowels [i, e, ɛ, a, u, o, ɔ, y, ø, œ], in isolation and in different consonantal contexts, in ten pre-service Czech teachers of French as a Foreign Language (FFL). The results show that (1) Phonetic proficiency in vowels depends on their spellings and consonantal context. (2) Vowels [i, y, u] and [a] are generally mastered with authenticity. (3) The ability to hear contrasts between the vowels e/ɛ, ø/œ and o/ɔ and pronounce them is limited. These results are only partially consistent with the predictions established in the Speech Learning Model (SLM) by Flege (1995), based on the notion of phonetic similarity between the mother tongue (MT) and the foreign language (FL).

Additive Fertigungsverfahren stellen in den letzten Jahren einen Megatrend dar, da sich mit diesen Verfahren endkonturnahe Werkstücke mit hohem Materialausnutzungsgrad herstellen lassen. Die auch als 3D-Druck bekannt gewordenen additiven Fertigungsverfahren sind jedoch nicht auf die Prototypenfertigung aus Kunststoffen begrenzt. Beim selektiven Laserschmelzen werden metallische Werkstoffe im Pulverbettverfahren mittels Laserstrahl aufgeschmolzen und somit schichtweise aufgebaut. Das Verfahren findet bereits in der Luft- und Raumfahrt, der Medizintechnik, aber auch in der Automobilindustrie und im Maschinenbau Anwendung für Prototypen, Einzelanfertigungen oder Kleinstserien. Des Weiteren ermöglicht es auch die Herstellung von Werkstücken mit besonders hoher Komplexität, die mit spanenden Verfahren nicht herstellbar sind, und bietet dadurch neue Gestaltungsmöglichkeiten bei der Konstruktion. Innerhalb des Vortrags werden nach der Vorstellung des Verfahrens verschiedene Methoden zur numerischen Simulation des selektiven Laserschmelzens von Edelstahl (1.4404) am Beispiel der kommerziellen Software Simufact Additive erläutert. Dazu werden der mechanische und thermo-mechanische Lösungsansatz betrachtet sowie die Methode zur Kalibrierung der Simulationen erläutert. Die Erläuterung eines voll transienten thermo-mechanischen Ansatzes erfolgt unter Verwendung der Software MSC Marc. Des Weiteren wird der Einfluss der Orientierung des Werkstücks im Herstellungsprozess auf resultierende Spannungen, Verzug sowie mechanische Eigenschaften analysiert und mit experimentellen Untersuchungen untersetzt.