Examensarbeten för masterexamen
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- PostRegeneration of Foam Electrodes Used for for the Removal of Mercury from Aqueous Solutions(2024) Gustafsson, Pontus; Chalmers tekniska högskola / Institutionen för fysik; Chalmers University of Technology / Department of Physics; Wickman, Björn; Roth, VeraMercury is a heavy metal of great environmental concern. It possesses great environmental mobility and is highly toxic for both humans and wildlife. An electrochemical mercury decontamination technique that uses Pt-Hg alloy formation to collect mercury from aqueous sources has been developed and shows great promise and many advantages over existing techniques. The goal of this thesis is to study the regenerative capacity of platinum-coated foam electrodes used in this technique over decontamination cycles. Regeneration in this case refers to the re-release of mercury in the form of Hg-ions via the oxidation of Pt-Hg alloy. Using a three-electrode set-up in batch experiments, mercury was removed from 0.5 M sulphuric acid with a mercury concentration of 1000 ppb using a platinum-coated stainless steel foam. Mercury was also removed from contaminated concentrated sulphuric acid from a zinc smelter using a platinum-coated RVC foam. Unfortunately, complete regeneration was not achieved in any experiment, typically releasing less than half of the collected mercury. This partial regeneration is likely due to suboptimal experimental conditions. Despite this, the stability of the foams was demonstrated over multiple formations/regenerations. The problems identified also highlight possible ways forward for future research on the studied mercury decontamination technique. Decontamination with the RVC foam in concentrated sulphuric acid managed to reach mercury levels below the industry standard for high purity, something that has not been presented in previously published research.
- PostSD Map Localization: A Deep Learning Approach(2024) Abdul Rahuman, Sheik Meeran Rasheed; Jathavedan, Sameer; Chalmers tekniska högskola / Institutionen för fysik; Chalmers University of Technology / Department of Physics; Granath, Mats; Granath, MatsAccurate localization is critical for the safe and efficient operation of autonomous vehicles, enabling precise navigation and real-time decision-making. This thesis focuses on improving Standard Definition (SD) map based localization, by leveraging deep learning techniques. The research addresses key questions, including how to optimally encode SD map data and sensor data, particularly the Global Navigation Satellite System and Inertial Navigation System sensor, for deep learning, and train models to perform accurate map matching and vehicle localization along the correct road segment. The thesis develops a deep learning-based localization framework for autonomous vehicles, focusing on SD map data. It introduces three main components: a Polyline Encoder using either Graph Neural Networks (GNN) or Transformers, a Map Matching Network based on cross-attention, and a Point Prediction Network consisting of a simple Multi-Layer Perceptron. The model encodes ego trajectories and map links, matches the map data with the vehicle’s trajectory, and predicts precise location. Our results show that the GNN consistently outperforms the Transformer on both map matching and point prediction. The model’s performance varies based on the training and testing data used, with the last point of the trajectory often being sufficient for accurate localization. The study also compares the deep learning model with classical algorithms and finds that the GNN-based localization model significantly improves localization accuracy. Overall, our thesis demonstrates that leveraging deep learning techniques, particularly GNN-based architecture for encoding, along with cross-attention based architecture for map matching, has the potential to significantly enhance SD map localization for autonomous vehicles.
- PostExperimental study of hydrogen trapping by carbides in low alloyed steels using Atom Probe Tomography(2024) Moritz, Ludwig; Chalmers tekniska högskola / Institutionen för fysik; Chalmers University of Technology / Department of Physics; Thuvander, Mattias; Jakob, SeverinHydrogen embrittlement (HE) of high-strength low-alloy (HSLA) steels is a big problem. Several options are known to prevent/delay the embrittlement of the steels. One option is to trap the hydrogen at or inside the carbides. This could be interpreted as an energetic interaction, as the nano-sized carbides contribute to the mechanical strength of the material. This work investigates three different low alloyed steels, named in the thesis Steel-1, Ti-steel and V-steel. For the electrochemical D loading process, a 0.1M NaOH in D2O is used. The specimens are transferred at room temperature (RT) to the atom probe (AP). Crystallographic calibration was carried out for all measurements. For Steel-1 in the quenched state, no trapping can be seen. For the annealed specimens, the trapping capability can be argued. The Ti- and V-steel show D trapping. Besides the standard measurement, a room temperature degassing experiment was carried out for the Ti- and V-steel to get a qualitative insight into the strength of the traps.
- PostDevelopment of proximal tubule-on-a-chip assays for predicting kidney toxicity(2024) Johansson, Emma; Chalmers tekniska högskola / Institutionen för fysik; Chalmers University of Technology / Department of Physics; Adiels, Caroline
- PostFermi Surfaces of Holographic Metals(2024) ISMAILOV, ELI; Chalmers tekniska högskola / Institutionen för fysik; Chalmers University of Technology / Department of Physics; Gran, Ulf; Nilsson, EricOne of the most challenging endeavours in theoretical condensed matter physics is solving models of strongly correlated metals. In these systems, the standard techniques from Fermi liquid theory have limited applicability, necessitating new descriptions. One particularly promising approach is known as holographic duality, which conjectures a relation between the seemingly unapproachable physics of strongly coupled quantum field theories and classical gravitational theories in one higher dimension. While successful in many regards, the usual holographic approach for metals fails to incorporate a satisfactory description of a Fermi surface, an indisputably important ingredient for any theory describing a metal. Specifically, any theory of a metal ought to have a Fermi surface that satisfies Luttinger’s theorem. In this thesis, we introduce a holographic model that exhibits the necessary behaviour of metal. Diverging from the typical holographic treatment where all scales are described, we instead assume the dual theory to be an infrared effective field theory. We explore the behaviour of the theory across various temperatures by numerically solving the differential equations of motion for the gravity theory. Motivated by the numerical predictions, we suggest a UV cutoff scale for the theory. We discuss some potential limitations and plausible modifications of the model.