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Senast inlagda

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Carbon Flows in Life Cycle Assessment of Carbon Capture Assessing Environmental Impacts and Carbon Capture Potential in Industrial Processes
(2023) Carlsson, William; Barclay, Jonathan; Chalmers tekniska högskola / Institutionen för teknikens ekonomi och organisation; Chalmers University of Technology / Department of Technology Management and Economics; Janssen, Mathias; Nyqvist, Evelina
.This thesis presents a detailed analysis of the environmental impacts and carbon capture potential associated with cement production and biomass combustion. Through the use of life cycle assessment and material flow analysis, this study also offers a comprehensive understanding of the carbon capture and purification process within the PYROCO2 system, specifically focusing on a post-combustion amino solventbased approach. Additionally, the research explores opportunities for improving resource efficiency in the cement production process, aiming to the development of sustainable practices in these sectors. The findings of this research provide valuable insights into the potential of carbon capture technologies in mitigating climate change. The life cycle assessment results reveal the environmental impacts associated with cement production and biomass combustion, highlighting the potential of carbon capture methods in reducing emissions. By expanding the knowledge base on carbon capture and utilization technologies, this thesis contributes to the ongoing efforts to address climate change. The research outcomes aim to adopt sustainable practices and further advance carbon capture technologies to address the urgent challenge of climate change, which can contribute towards a more sustainable and carbon-neutral future.
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Digital Audio Interface Jitter
(2024) SINKKONEN, FREDRIK; Chalmers tekniska högskola / Institutionen för data och informationsteknik; Chalmers University of Technology / Department of Computer Science and Engineering; Fjeld, Morten; Fjeld, Morten
Jitter is the short-term deviation of a digital signal from its ideal position in time. Some common issues know to produce jitter in currently used digital audio interface formats were examined and multiple implementations of a Universal Serial Bus (USB) audio interface were designed with the intention of creating a device free from interface jitter. Using the three standardized clock synchronization mechanisms in the USB protocol for isochronous transmissions and a selection of suitable clock sources, USB audio class devices were created for which jitter measurements then were performed. The results were compared with jitter audibility thresholds from three studies containing listening tests. While all implementations were functionally acceptable, their jitter results did differ. For the two isochronous synchronization modes of USB that require a continuously adjustable clock source on the receiving side of the interface the jitter issue consists of two parts. Periodic adjustments of the clock signal are in itself a source of jitter and the way in which an adjustable clock source is constructed is another. The initial core idea was that a USB audio interface using isochronous transfers coupled with the asynchronous clock synchronization mode and a fixed frequency clock source would be able to provide an interface in which no additional jitter on top of the inherent jitter level of the source clock would be added by the transfer of data over the interface. The two fixed frequency clocks that were used did however not perform any better than the results of the best adjustable clock source and when they were attached to the test system their jitter levels increased even further. Analysis of the jitter measurements point in the direction of asynchronous mode being preferable for lowest possible jitter levels but the results are not completely unambiguous and jitter levels below the lowest recorded hearing thresholds were also achieved with one of the other synchronization modes for isochronous USB transfers.
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Torque vectoring using e-axle configuration for 4WD battery electric truck: Utilizing control allocation for motion control and steer by propulsion
(2022) Fahlgren, Emil; Söderberg, Daniel; Chalmers tekniska högskola / Institutionen för mekanik och maritima vetenskaper; Chalmers University of Technology / Department of Mechanics and Maritime Sciences; Jonasson, Mats; Laine, Leo; Janardhanan, Sachin
With the rise of electric drives in vehicle applications, configurations of new powertrain design are emerging. In recent years, this trend has shifted to include heavy vehicles as well. In this thesis, a concept 4x4 battery electric truck with a distributed powertrain is investigated. By using four individual motors on two separate e-axles, different coordination possibilities are available for motion control of the truck. This thesis focuses on using torque vectoring as a principle to allocate the requested global torque. Furthermore, a novel method mentioned to as steer by propulsion (SBP) is proposed, where the steering of the vehicle can be controlled solely by using the electric machines on the front axle. Investigations are conducted to explore the effectiveness of this method on vehicle performance and energy consumption. To distribute the control requests across the available actuators, control allocation (CA) is used. Here, the problem is formulated as a quadratic programming (QP) problem. High level controllers provide the requested global forces as an input to the control allocation, which in turn allocates torques to the separate wheel controllers. Furthermore, different formulations of the control allocator and motion controller are presented and compared. The control system is simulated with a vehicle model provided by Volvo, and the results indicate that steer by propulsion is able to follow a reference path with a lateral offset of a magnitude of an acceptable level. Furthermore, the simulations show that SBP can repeat this behavior at high speeds as well with an oscillatory behavior. Therefore, the method is recommended to use mainly at vehicle speeds below 50 km/h. Finally, simulations show that SBP increases the energy consumption by 2-4 %. Considering that the consumption is on par with using power steering, SBP will be viable for redundancy with some limitations.
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En studie av datahantering och spårbarhet i Volvo Pentas motorfabrik i Vara
(2022) Antblad, Moses; Alkhshman, Ahmad; Chalmers tekniska högskola / Institutionen för elektroteknik; Chalmers University of Technology / Department of Electrical Engineering; Olesen, Veronica
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Leveraging Data Augmentation for Better Named Entity Recognition in Low-Resource Settings
(2024) Björnerud, Philip; Chalmers tekniska högskola / Institutionen för data och informationsteknik; Chalmers University of Technology / Department of Computer Science and Engineering; Bernardy, Jean-Philippe; Dannélls, Dana; Kokkinakis, Dimitrios
This thesis investigates the challenges in the field of Natural Language Processing (NLP), with a focus on Named Entity Recognition (NER), a subtask within NLP that involves classifying entities. Addressing the issue of data scarcity, which is particularly critical in non-English languages like Swedish, this study investigates various data augmentation methods by fine-tuning the transformer-based model, KB-BERT. The datasets are simulated as low-resource settings, drawing inspiration from the study X Dai and H Adel (2020) [1] work, using three sets of training data containing 50, 150, and 500 instances respectively. The thesis also explores whether a newly developed state-of-the-art data augmentation method can outperform other data augmentation methods in enhancing an NLP model, centering on three data augmentation methods: Synonym replacement, Mention replacement, and AugGPT, the last being a state-of-the-art method. The findings of this study highlight that synonym replacement emerged as the most effective data augmentation method across various low-resource settings, achieving the highest F1-score increase in all scenarios. AugGPT achieved the second highest average F1-score, while mention replacement achieved the lowest across the tested settings.