Search

Traditionally, regulations employ semi-probabilistic methods with partial safety factors to control design limits. Calibrating these partial safety factors involves estimating the target reliability level and optimizing the partial safety factor values in order to minimize the deviation of the safety index between the considered design scenarios and the target value. This procedure necessitates performing a demanding amount of reliability analyses and is often carried out for simplified design situations. Therefore, high computational costs must be accepted for design problems formulated with complex computational models. This study implements a meta-modeling approach based on active learning in the partial safety calibration procedure, enabling its application to computationally intensive problems. Subsequently, the approach is applied to the running safety of ballasted high-speed railway bridges. This limit state implicitly accounts for the phenomenon of ballast destabilization, the occurrence of which disturbs the load path from the rail level to the bridge structure. The dramatic increase in train operating speeds in recent decades has increased the possibility of this design limit state being violated due to resonance. Despite the evident safety concerns, the adopted safety factors appear to be solely based on engineering judgments rather than calibration through higher-level reliability analysis. Therefore, the proposed calibration method is employed to determine the corresponding partial safety factors for various maximum allowable operating train speeds. The newly calibrated partial safety factors allow for a permissible maximum vertical acceleration of the bridge deck approximately 25% higher than the conventional design approaches. Therefore, incorporating these factors into the design procedure may lead to the construction of lighter bridges., QC 20240115

The operational safety of high-speed trains traversing ballasted bridges is contingent upon the prevention of the ballast destabilization, which can interrupt load transfer from the rail to the bridge. Current design regulations indirectly address this limit-state by specifying a threshold value for the vertical acceleration of the superstructure. This value represents the condition at which the inertial forces induced by train passage exceed the resistive forces. However, this approach is based on limited experimental data and the influence of numerous parameters remains unexplored. As a result, reliability analyses pertaining to running safety are hampered by a lack of knowledge, leading to greater epistemic uncertainties. In this study, the impact of such uncertainties on this dynamic system is investigated using surrogate-based Imprecise Structural Reliability Analysis (ISRA). For this purpose, parametric probability boxes are used to represent lower and upper bounds of the cumulative distribution function for basic random variables with epistemic uncertainties and surrogate models are adaptively trained to reduce computational costs. The obtained results show that neglecting the influence of epistemic uncertainties can lead to permissible operating train speed higher than the speed corresponding to the desired reliability level. In this study, an overestimation of about 13% was observed on average. Furthermore, the rough analyses carried out show that taking epistemic uncertainties into account can lead to a reduction of the system characteristic safety factor by up to 30%. This significant reduction underlines the importance of expanding the available knowledge on the phenomenon of ballast instability., QC 20240108

This paper presents an efficient 2D beam model of a continuous single-trackconcrete slab bridge considering the effect of surrounding soil conditions at the location ofthe retaining walls. A 3D model is used to investigate the backfill soil’s added flexibility fordifferent soil properties. It is shown that for the first bending mode, the additional dynamicstiffness of the backfill soil can be modeled using equivalent vertical and rotational springs.Various experimental tests have been performed on the studied railway bridge, including forcedvibration tests and train passage loadings. Good agreement is found between the 2D model andthe experimental data. It is shown that removing the soil causes both a shift in the structure’snatural frequencies (and their corresponding resonant speed) and a substantial increase inacceleration amplitude. This may give the impression that the bridge is not suitable for highspeedtrain passage. It is also shown that the bridge’s response to train passage is mainlygoverned by the first bending mode., QC 20240402

As far as the authors are aware, the threshold for vertical acceleration of the bridge deck was chosen based on the assumption that the induced dynamic loads would overcome gravity at higher accelerations, resulting in loss of contact between wheels and rail; however, the previous studies do not support this hypothesis. Considering these inconsistencies, a better understanding of the simplified design criteria is essential before conducting further studies suchas the calibration of partial safety factors. Therefore, this study considers a set of representative design scenarios to statistically compare wheel-rail contact loss with other criteria that can bederived from moving load models, such as vertical accelerations and bridge deck deflections. Based on the analyzes performed, deflection seems to be a better criterion than acceleration to control the running safety limit-state; although the results presented do not necessarily show avery strong correlation between these two criteria. Therefore, the k-means clustering approach isused together with 5% lower quantiles of the collected data to propose potential new thresholds. It should be noted that due to the limited number of analyzes, the approach presented in this study can be considered as a possible framework for further updates of the current design method rather than drawing general conclusions., Initially submitted with the title “New Running Safety Design Criteria For Non-ballasted Railway Bridges Based On Statistical And Probabilistic Investigations”QC 20231006

Date: 2nd June 2024 Level: Master Thesis in Product and Process Development, advanced level 30 ECTS Institution: School of Innovation, Design and Engineering at Mälardalens University Authors: Simon Westergren & Andreas Rundh Andersson Title: The Role of Supply Chain Mapping in Complying to ESRS Keywords: Supply chains, Supply chain management, Risk management, Disruptions, Resilience, Visibility, Supply chain mapping, Sustainability, Corporate Sustainability Reporting Directive, European Sustainability Reporting Standards, Sustainable supply chain mapping, Industrial electronics industry. Supervisors: Mikael Johnsson - Mälardalens University, Mikael Steinar & Paulina Wilhelmsson - Case Company Aim: The aim of the study is to explore if and how acompany within the industrial electronics industry could be supported by supply chain mapping in complying with EU's ESRS regulation. Research Question: How can supply chain mapping support an industrial electronics company in complying with EU's ESRS regulation? Methodology: The methodology of this study employs a qualitative research approach, specifically using a case study to explore the implementation of supply chain mapping within an industrial electronics company for EU's ESRS compliance. Adopting an abductive framework, the research intertwines theoretical exploration and empirical data collection. Literature was reviewed from academic journals and industry reports, while empirical data was gathered through comprehensive supply chain mapping, questionnaires, and a series of interviews, including semi-structured and individual discussions. Conclusion: The study concludes that supply chain mapping is a pivotal tool for aiding an industrial electronics company in complying with the EU's ESRS regulation. It was found that comprehensive mapping of the supply chain not only helps in identifying relevant ESRS topics across the value chain but also enhances risk management and visibility. The application of supply

This study utilizes a 3D DEM sleeper-ballast bed model, comprising four sleepers interacting with the actual shape of the ballast, to comprehensively explore the impact of sleeper-ballast interaction and ballast aggregate friction coefficient on the lateral resistance of ballast bed. Based on the DEM numerical simulation, the following conclusion can be drawn: 1) The friction resistance between the sleeper and the ballast is crucial in determining the lateral resistance in railway tracks, with the base ballast contributing to more than 50% of the lateral resistance of the ballast bed on average; 2) The sleeper bottom resistance and sleeper side resistance of lateral force is derived from the sleeper-ballast friction mechanisms, while the friction coefficient between the sleeper end and the shoulder ballast has minimal impact on the sleeper end resistance; 3) The lateral resistance of the ballast bed is more significantly influenced by alterations in the ballast friction coefficient than by changes in the friction coefficient sleeper-ballast interface., QC 20240909

Älvkarlebyhus har länge haft problem med stökiga soprum med hög andel felsorterade sopor. Olika projekt har genomförts för att förbättra situationen: de boende har fått en sopsorteringspåse med fack för de olika fraktionerna, informationskampanjer har genomförts och nya sophus har byggts. Trots detta kvarstod problemen. För att öka sopsorteringsgraden har två olika insatser genomförts och utvärderats i respektive sophus. I det ena sophuset har en övervakningskamera med tillhörande informationsskylt satts upp, i det andra sophuset genomfördes en insats under fyra helger i mars där niondeklassare agerade sophusvärdar. Dessa stod utanför sophuset och informerade om sopsortering. Efter insatserna genomfördes ~22 intervjuer med de boende genom dörrknackningar samt fastighetsskötare och ungdomarna svarade på en enkät. Insatsen med övervakningskamera har enligt fastighetsskötaren ungefär halverat tiden de behöver städa och flytta felsorterade sopor. De intervjuade boende var dessutom samstämmigt positiva till kameran och flertalet uttryckte förhoppningen att kameran skulle få deras grannar att sortera bättre. Insatsen med sophusvärdar gav enligt fastighetsskötaren ingen effekt på nerskräpning eller andel felsorterade sopor och förhållandevis få av de intervjuade boende hade märkt insatsen. En intressant observation från boende och fastighetsskötare var hur boende som var på väg till sophuset vände och gick hem när de såg ungdomarna. En möjlig förklaring till detta är att några av de som sorterar fel vet att de gör något fel och är rädda att bli påkomna av sophusvärdarna som de uppfattar som kontrollanter. Flera boende var positiva till insatsen, även de som inte märkt den, då den uppfattats som ett tecken på att Älvkarlebyhus är angelägna om att komma till rätta med nerskräpning- och sopsorteringsproblemen.

Controversial questions have the potential to awaken strong feelings for students and are common in the civics education. Despite this, research shows that students are not presented with sufficient opportunities to encounter controversial questions. The present study, through semi-structured interviews, examines ten upper secondary school students regarding their experiences with controversial questions. This study aims to contribute knowledge surrounding the experiences of upper secondary school students regarding controversial questions in the civics subject and civics education. The results of this study indicate that topics such as war and gang crime in the civics subject are perceived as controversially loaded based on the students’ classroom situation, as well as the background, opinions, and experiences that the students possess. Furthermore, the results show that some students perceive that they are given certain opportunities to discuss controversial questions, which refutes previous research. At the same time, to a larger extent, the results signify potential limitations regarding students' opportunities to discuss controversial questions in civics education. This is expressed through the students who imply that controversial questions are not presented in certain cases due to the teacher’s approach, the student’s willingness to dare to discuss, but also through the teaching methods that are used. Additionally, multiple students express that their opportunities for sharing opinions regarding controversial questions should be overseen. This is connected to the study’s theoretical framework, the associative agonism by pointing to the necessity of exchanging opinions between students in an open and democratic environment of discourse.

There is a growing intent among engineers, stakeholders, and decision makers to use probabilistic methods for infrastructure assessment or design objectives. However, the corresponding limit state for such problems usually requires the construction of complex computational models, usually using commercial software without parallelization capability. Such a requirement makes performing reliability analysis computationally prohibitive, which is even more challenging for dynamic problems, since a very short time step is required to obtain sufficiently accurate predictions. This concern has led to several methods being proposed to surrogate the limit state function with a generally black box called a meta-model. A variety of them, such as Kriging, Polynomial Chaos Expansion (PCE), Artificial Neural Networks (ANN), and response surfaces (e.g., polynomial, spline, or radial-base functions), have been adopted for this purpose. These meta-models are typically trained on a limited data set collected by computing the true responses of carefully selected input variables. Their applicability for assessing the probability of failure has been studied individually in the literature for both benchmark and practical problems. However, as far as the authors are aware, no comparison has been made between them for dynamic problems. This comparison needs to be made from the point of view of both accuracy and performance (number of calls to the limit state function). In this context, this paper takes a systematic approach to evaluate their performance under identical conditions, i.e., with similar training datasets. For this purpose, the dynamic response of railway bridges with different spans excited by the passage of trains with a wide range of speeds is used as a reference problem., QC 20231004

High-speed railway is expanding drastically in Sweden, necessitating new technology, and improve-ments of existing structures. End-shield bridges are a common and under-tested bridge type inSweden. Their dynamic performance is significantly impacted by their boundary conditions due to thesoil–structure interaction (SSI) and their large masses cantilevering beyond the footings. A specificend-shield bridge was tested under low (5 kN) and high (20kN) amplitude-forced hydraulic excitationfor a wide range of frequencies. Several train passages for typical passenger trains,‘X62’, were meas-ured with the same experimental setup. The results were analysed to isolate the significant modes ofthe system and the natural frequencies. A full 3D numerical model was calibrated and updated inAbaqus, along with a brief sensitivity study to determine the most influential parameters. Finally, theresponse to passing trains and Eurocode design HSLM trains was calculated. The experimental studyshowed that higher loading amplitudes resulted in higher damping and lower natural frequencies. Thenumerical analysis showed that for this bridge type the SSI cannot be neglected and can be success-fully introduced in the model., QC 20240228

This paper studies analytically the steady state response of the generalised coupled modulated pedestrian-beam system. Pedestrians are considered as modulated spring–mass–damper systems with and without a partially attached mass to the structural system. The governing non-dimensional parameters that defined the system's behaviour are found in an analytical framework. An application of the expression is developed, and a parametric analysis is presented considering a reference pedestrian. The frequency shift effect and the dynamic amplification factor, DAFHSI, of the coupled pedestrian-beam system are characterised. The main contribution of this paper is to provide a closed-form solution of the generalised coupled modulated pedestrian-beam system. This solution can consider any distribution of pedestrians and any definition of the pedestrian SDOF properties. A simple and representative example is presented to demonstrate the utility of the found expression in the context of footbridge dynamics., QC 20231006

This study examines what it means to be a Russian LGBTQ emigrant in light of Russia's invasion of Ukraine in 2022. The study follows a phenomenological research approach that differs from the commonly used scientific approach that strives for objective knowledge. Through a qualitative study consisting of 5 participants who identify themselves as Russian LGBTQ emigrants, this research examines findings via affect theory, queer theory, and theories of social and cultural trauma to ask what it means to be a Russian LGBTQ emigrant, how the LGBTQ emigrant is constructed, and how the construct of being a Russian LGBTQ emigrant affects the subject. The study shows how the meaning of being a Russian LGBTQ emigrant is constructed through the effects of affect and how these effects create a collective, social, and cultural trauma that manifests in their everyday lived experiences while shaping their prospects for the future., 2023-09-14

Electromagnetic disturbance can be detrimental to the performance of a radio communication system, and in today’s society where more and more electronic devices are present in our everyday life it is increasingly vital to consider man-made interference. A communication system can take into consideration the noise characteristics and by doing so will excel in such areas, however, this follows that the algorithms utilized in such systems are more computationally complex and are therefore slow. This master thesis aims to explore the possibility of a neural network-based solution that reaches the same accuracy, as existing methods, but more quickly. Numerous different existing model alternatives have been explored and a plethora of different improvement techniques have been outlined. Two models, Hannet and Lannet, have been designed and improved to enable adaptive demodulation both including or excluding decoding at the receiver in an end-to-end communication system. The evaluation results demonstrate that the proposed models are comparable and in some cases even more accurate than current standardized methods. However, the models are unable to fully learn the decoding algorithms present in the experiments. Thus even though demodulation by itself thrives, performing decoding in conjunction with demodulation is out of reach for these models.

Uppsala Kommun is developing a new city district called Sydöstra staden (SÖS) as an innovative and transformative city district. A technical supply system that aligns with the district’s goals is pyrolysis. Pyrolysis is a process where biomass is heated without the supply of oxygen. This leads to carbonization where the energy is converted to biochar and heated gas that can be used for district heating. The biochar, which is considered as a carbon sink, could be the path for the municipality to achieve their climate goals for 2050. The aim of this project is to investigate the viability of providing district heating to SÖS through pyrolysis. Three scenarios based on biomass assets of garden waste, manure, and wooden chips will be evaluated from four perspectives: climate impact, economic feasibility, district heating coverage, and placement considerations. The method is a model constructed in python that simulates how much heat and biochar that can be produced including an income statement and how the price of biochar relates to the return of investment. The biochar price and biomass flow are two parameters that are examined in the sensitivity analysis. The model enables comparisons between the outcomes of the pyrolysis process and the heat energy demands in SÖS, the biochar usage in Uppsala and the municipality’s CO2 emissions. The results show profitable reactor alternatives in all three scenarios even without selling CORCs. However, the profitability is heavily reliant on maximizing the utilization of burned biomass. Furthermore, the first two scenarios had a negligible climate impact while the most profitable reactor in scenario 3 had a large impact on the municipality’s climate goals. Also, the coverage of district heating has been evaluated due to the asset of biomass as well as placement requirements have been stated.

This study focuses on social class in Swedish EFL coursebooks. The aim is to investigate what different social classes are represented and how much space they are given, as well as how they are portrayed in three Swedish EFL coursebooks aimed at English 5 for upper secondary school. The selected coursebooks Viewpoints 1, Blueprint A 3.0, and Pioneer 1 have been analyzed using qualitative content analysis, focusing on texts and images presented in the materials. The analysis emanates from Neo-Marxist theory in order to point to different social class conditions. The results show lower-, middle-, and upper-class representation to various degrees. Mostly the lower class and upper class are visible, while the middle class is underrepresented. The lower class, in most cases, is shown together with the upper class in exploitative circumstances. This is made apparent through the lower class, in most cases, lacking the ability to decide for themselves in relation to their upper-class counterparts. Further, this indicates that the upper class rules the world on behalf of the lower class. Meanwhile, when the middle class is shown, they are mainly depicted through overconsumption, and as victims of upper-class dominance. Despite previous research showing the importance of social class on a global, European and Swedish scale, the coursebooks somewhat disregard its importance in different texts and images.

The fourth industrial revolution also known as Industry 4.0 ushers in new advanced manufacturing technologies that enables companies to improve efficiency and reduce waste. The promising outlook of this era suggests that the implementation degree for Swedish manufacturing SMEs operating in a high-tech context should be high, this is however not empirically observed. The purpose of the paper is to investigate the implementation level of Industry 4.0 technologies in the chosen context, identify barriers that hinder implementation, as well as investigate how the use of the new technologies can be increased. The paper uses a quantitative data approach, using empirical data derived from a survey that was sent out to relevant practitioners acting in the manufacturing industry. Findings indicate that the barriers derived from previous literature match what is experienced by the practitioners surveyed, but that the perceived impact between each barrier is varied depending on if they have implemented Industry 4.0 or not. By combining key themes and findings of the paper, a model is constructed and applied to reduce the perceived impact of the barriers leading to higher implementation levels of new advanced technologies.