Publikationer från Uppsala Universitet
Not a member yet
127603 research outputs found
Sort by
Improving Register Automata Learning by Leveraging Testing Methods for Finite State Machines
No full textActive automata learning is a technique for modeling the runtime behaviour of software and hardware components. Finite state machines have long been used to model control flow. Register automata can also describe data flow but active automata learning with register automata does not scale well. This project aims to optimise register automata learning by leveraging testing algorithms for finite state machines. A hypothesised register automaton is abstracted to a finite state machine to generate counterexamples. These are translated for the register automaton to make the structure of the system emerge. After the learning converges, a standard method is used to further refine the register automaton model. Performance of the new algorithm is evaluated against the current best available option. Results show that the new oracle finds a sufficient number of locations to be of theoretical interest in register automata testing, but in practice the number of resets and inputs are uncertain, mainly due to restrictions of the method used in the refinement phase
Bridging The Gap In Humanitarian Access : A Comparative Analysis of Swiss Diplomacy and Local Initiatives in Darfur
No full textHumanitarian access remains one of the most critical challenges in contemporary conflict settings, particularly in fragmented environments like Darfur. This thesis examines how Switzerland’s humanitarian diplomacy and localised initiatives, specifically Emergency Response Rooms (ERRs), shaped access between 2022 and 2024, with a focus on the post-2023 escalation of conflict. Switzerland employs a top-down approach based on neutrality, diplomatic negotiation, and funding, while ERRs represent grassroots, community-led coordination mechanisms. Drawing on policy documents, humanitarian reports, and semi-structured interviews, the study compares the strengths and limitations of both models. It finds that Switzerland’s strategies are effective at the macro level but often lack flexibility in volatile contexts, while ERRs secure access through local trust and embeddedness but face sustainability and recognition challenges. Using legitimacy theory, the thesis argues that neither approach alone overcomes the barriers to humanitarian access. It proposes instead a hybrid model that combines diplomatic leverage with local legitimacy, offering more adaptive and resilient strategies. The study contributes to debates on humanitarian access by bridging formal and informal paradigms and providing practical recommendations for international actors and donors
Utveckling av linesource-högtalare med integrerad hängkonstruktion : En studie om att minimera uppkomst av oönskade vibrationer
No full textOne challenge that can arise in loudspeaker systems is the occurrence of unwanted vibrations. Standing waves and resonant frequencies can produce interfering sounds that disrupt the soundstage and impair the user experience. Prevas AB therefore wanted to investigate different design solutions and develop a functional prototype for a lincesource speaker together with an integrated rigging system. During the study a functional prototype was developed where several technical and physical requirements were considered. An exploratory and iterative measurement process of the speaker drivers' frequency response was carried out using a microphone. The measurements showed peaks and troughs in the frequency response, indicating the emergence of resonances and standing waves within the speaker. By testing design solutions with damping materials and structural reinforcements, their impact on vibrations in the speaker could be evaluated. The reinforcements consisted of extra internal braces and glued baffles, which were intended to brace the cabinet and reduce oscillations. Finally, the impact of the integrated rigging system was evaluated. The implemented design solutions resulted in more even sound reproduction. The rigging system contributed to a marginally higher sound pressure level across the entire frequency range, indicating a stiffening effect on the speaker. The results have created a basis for further development and production of new prototypes, as well as opportunities for continued research in the subject area. The purpose of the study was fulfilled by answering the research questions and by developing a functional prototype where several of the established requirements were met
Configurations of weight, voice and distance and headquarters positive attention : Weight matters most
No full textWeight, voice, and distance are proposed in the literature as determinants of positive attention from MNC headquarters for subsidiaries. Few studies have, however, investigated how combinations of these three causal conditions may jointly impact positive attention. Based on the existing literature, we hypothesize how different combinations result in subsidiaries' gaining headquarters attention. We test our hypotheses using qualitative comparative analysis (QCA) leading to the surprising result that any combination of conditions including subsidiary weight leads to attention as outcome, including weight alone. We further substantiate this result through regression analysis using survey data. Together, our empirical studies show that weight alone is related to headquarters' positive attention, while voice and distance do not play a decisive role in influencing headquarters' positive attention for subsidiaries abroad. These findings challenge existing research claiming voice as a means to gain headquarters' attention, especially for distant or peripheral subsidiaries
A prospective study on prognostic value of ventilatory efficiency in asymptomatic patients with severe primary mitral regurgitation.
No full textOBJECTIVES: Patients with severe primary mitral regurgitation (PMR) remain asymptomatic at first. In the long term, however, severe PMR leads to cardiac decompensation. Exercise testing in asymptomatic PMR is recommended in selected patients by guidelines. Cardiopulmonary exercise testing (CPET), which additionally measures ventilation (VE), oxygen consumption (VO2) and carbon dioxide production (VCO2), has been scarcely studied in PMR. We hypothesized that CPET might have prognostic value in asymptomatic PMR and therefore studied if CPET, including assessment of ventilation efficiency, has prognostic value for asymptomatic patients with severe PMR. METHODS: Asymptomatic patients with severe PMR were prospectively recruited between 2013 and 2018. Exclusion criteria were coronary artery disease, chronic kidney disease, diabetes mellitus, concomitant valve disease, symptomatic lung disease or class 1 recommendation for valvular surgery. Echocardiography and serial CPET were conducted at one university hospital in Sweden. Primary outcome was mitral valve intervention. RESULTS: Forty-eight patients were recruited to the study. Median follow-up period was 4.4 (2.1-6.9) years, during which 28 (58%) patients underwent mitral valve surgery. Ventilation efficiency, the relationship of VE to VCO2 during CPET, predicted surgical treatment of the mitral valve. Increased VE/VCO2 ratio at the anaerobic threshold had the highest predictive value, remaining an independent predictor after adjusting for impaired VO2 at peak exercise (HR 4.42 (1.52-12.92), p = 0.007) and echocardiographic thresholds for left ventricular and atrial remodelling, as defined by current guideline-based recommendation for intervention (HR 3.72 (1.41-9.82), p = 0.008). CONCLUSION: Impaired ventilatory efficiency, but not peak VO2, predicted surgical treatment of the mitral valve in asymptomatic patients with severe PMR. Ventilatory efficiency, a CPET index less dependent on peak exercise performance, may be a new useful tool in risk stratification
Water, people and climate-change exposure in the Western Pacific : Anticipating the arrival of a 'perfect storm'
No full textAs climate change accelerates, there is a growing need to ensure that sustainable adaptive solutions are effective and equitable, especially in the Global South where many countries depend on external funding to attain water security. Perceptions of vulnerability and need among Pacific Island Countries are not always based on a region-wide evidence base. This study examines ten Western Pacific Island countries (Federated States of Micronesia [FSM], Fiji, Kiribati, Marshall Islands, Nauru, New Caledonia [French dependency], Palau, Solomon Islands, Tuvalu, Vanuatu) that include both high-island groups and low-island (atoll) groups. This study evaluates the equitability of the distribution of external funding for attaining water security. Needs are evaluated in terms of (a) population densities and growth compared with water and land availability and (b) the uneven distribution of water-focused livelihood stressors across this region, specifically those linked to climate variability, sea-level rise, tropical cyclones, and geophysical phenomena. Measures of comparative exposure of people in these countries show that those living along high-island coasts, especially in Fiji, Solomon Islands and Vanuatu, are considerably more exposed than their counterparts elsewhere, especially in atoll nations which have received greater amounts of per capita climate funding for water security. Results show that there is a 'perfect storm' brewing in the high-island nations of the Southwest Pacific resulting from their comparatively high exposure to livelihood stressors. This could be addressed by reassessing the distribution of external climate funding within the Western Pacific region. Key findings are the importance of aligning need with assistance and the foundational role of water in livelihood sustainability, both having implications for the hundreds of coastal communities forced to relocate, mostly locally on the same island, in the next few decades. The imperative of addressing such deficiencies in an era of accelerating climate change and declining levels of global support is clear
Return Dynamics of Leveraged Certificates Under Heston’s Stochastic Volatility Model
No full textThis thesis examines the return dynamics of leveraged exchange-traded notes (LETNs), focusing on value erosion caused by volatility decay. Using a calibrated Heston stochastic volatility model, we simulate LETN performance under realistic market conditions for different fixed investment horizons to investigate what returns look like under a naive buyand-hold strategy for different leverage ratios and market conditions. The results show that realized variance significantly reduces returns over time, especially at higher leverage levels, highlighting the risks and magnitude of value erosion in LETNs. The model is calibrated to European vanilla options using the Fourier-Cosine expansion method, and returns for certificates are generated by an Almost Exact Simulation of the Heston model.
Practical Identifiability in a Viscoelastic Respiratory Model for Mechanical Ventilation
No full textMechanical ventilation is a life support system for patients with acute respiratory distress syndrome (ARDS). As part of strategies to protect the lung during ventilation, plateau pressure can be determined via an end-inspiratory pause; however, there is no agreed-upon pause duration in medical protocols. Mechanical ventilation can be modelled using the Viscoelastic model (VEM) for respiration. The identification of static compliance is of clinical interest, as it can be used to estimate plateau pressure. Practical identifiability analysis quantifies the confidence with which model parameters can be estimated from finite, noisy data. This paper evaluates the robustness of plateau pressure estimates in clinical data by analysing practical identifiability of the VEM identified in data with varying durations of end expiratory pauses. Profile likelihood and Hamiltonian Monte Carlo (HMC) simulations were used to determine estimation robustness. The methods were applied to mechanical ventilation data from a previous ARDS study. Profile likelihood and HMC showed strong agreement in both parameter estimates and identifiability results with similar confidence distributions. Both methods demonstrated a loss of parameter robustness that would preclude clinical utility when the end expiratory pause was reduced. By quantifying the confidence in parameter estimation and finding trade-offs in parameters that may be previously unknown when parameters are estimated, the methods give insight into the certainty of the estimate and parameter behaviours, even when the model fits the data well
On phase-field modeling of brittle crack growth under compression
No full textFracture in brittle and rock-like materials presents significant modeling challenges due to the combined effects of tensile, compressive, and shear mechanisms, particularly under dynamic and mixed-mode loading conditions. This thesis develops an enhanced phase-field modeling framework that introduces a hydrostatic-spectral-deviatoric strain energy decomposition. The model incorporates pressure sensitivity through a Mohr-type failure criterion and distinguishes between mode I and mode II fracture via separate critical energy release rates. This method enables a clear distinction between crack-driving and non-crack-driving compressive strains, which is essential for accurately reproducing realistic crack paths in rock-like materials subjected to compressive stress states. The model is implemented in a finite element code and validated against benchmark problems, published experiments, and newly conducted quasi-static and dynamic tests on gypsum plaster specimens. The simulations reproduce key fracture phenomena, including multiple crack modes, loading curves, and crack tip velocity evolution, with an acceptable level of agreement across a wide range of strain rates. Comparisons with conventional spectral and hydrostatic-deviatoric decompositions demonstrate the improved predictive capability of the proposed approach. Overall, this work offers a robust and experimentally validated framework for simulating fracture in brittle, rock-like materials under realistic loading conditions
Reviewing the EU policy nexus of energy efficiency and social policy
No full textThis paper aims to analyse how the European Union (EU) energy policy has merged social policy concepts with energy efficiency policy. Energy efficiency has increasingly become understood through social policy concepts such as energy poverty, energy inequality, and lack of cohesion. Previous research has shown how the social aspects of energy efficiency have been highlighted by the European Commission when talking about the multiple benefits of energy efficiency increasing efforts, such as renovating buildings. Using a mixed-method approach with material from the European Commission, the Council of the European Union and the European Parliament we review energy policy from a social policy perspective. Our analysis is done in two steps: (i) identifying which of the EU institutions acted as an agenda-setter introducing the social aspects of energy efficiency, and (ii) describing and analysing the framing process of merging social concepts with energy policy. We do this through qualitative and quantitative analysis of EU policy documents. A range of key words are utilized to explore the links between social policy and energy policy as part of the quantitative part of the analysis. We conclude that social aspects are first connected to the energy policy field by the European Parliament. The established connection is then reinforced by the Commission by the inclusion of social policy aspects, mainly in the policy on the transition to energy efficiency and zero-carbon buildings, where concepts such as energy poverty become central