| 1. |
- Caporaletti, Francesca, 1990-
(författare)
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MYC and MexR interactions with DNA : a Small Angle Scattering perspective
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Protein-DNA complexes govern transcription, that is, the cellular mechanism that converts the information stored in the DNA into proteins. These complexes need to be highly dynamic to respond to external factors that regulate their functions in agreement with what the cells need at that time. Macromolecular X-ray crystallography is very useful for structural studies of large molecular assemblies, but its general application is limited by the difficulties in crystallising highly dynamic and transient complexes. Furthermore, crystal lattices constrain the macromolecular conformation and do not entirely reveal the conformational ensemble adopted by protein-DNA complexes in the solution.Small-Angle X-Ray Scattering (SAXS) and Small-Angle Neutron Scattering (SANS) are two complementary techniques known jointly as Small-angle Scattering (SAS). SAS is a powerful tool for analysing the shape and changes of molecules in solution in their native state. It is beneficial if the variability of conformation or disorder complements high-resolution methods such as NMR or crystallography. With SANS, we can explore non-crystallisable protein-DNA complexes in solution without restrictions of artificially symmetrised DNA and limitations of a protein sequence. Neutrons are well-suited probes for studying protein-DNA complexes for the capability of the neutrons to scatter common atoms in biomolecules differentially and can thereby distinguish between hydrogen and deuterium. Together with varying the solvent deuterium ratio, the contrast variation approach can reveal shapes of distinct components within a macromolecular complex.The goal of this thesis is to explore unchartered territories of regulatory protein-DNA interactions by studying such complexes by SAS, with a specific focus on the flexibility of the complexes. In my study of the MexR-DNA complex, I try to elucidate the molecular mechanism by which the MexR repressor regulates the expression of the MexAB-OPrM efflux pump through DNA binding. This pump is one of the multidrug-resistant tools of the pathogen Pseudomonas Aeruginosa (P. Aer.). It can extrude antibacterial drugs from the bacteria enabling them to survive in hostile environments. In the second project, I strive to explore the MYC:MAX:DNA complex. This heterodimer assembly functions as a central hub in cellular growth control by regulating many biological functions, including proliferation, apoptosis, differentiation and transformation. Overexpression or deregulation of MYC is observed in up to 70% of human aggressive cancer forms, including prostate and breast cancers. By combining SAS with biophysical methods, the work presented in this thesis reveals novel information on the shape and dynamics of biomolecular assemblies critical to health and disease.This thesis comprises five chapters, each dealing with a different aspect of the work in those years. The first chapter introduces the reader to the motivations of this research, and it will give the reader a brief state of the art of the two projects. In the second chapter, I will give you all the theoretical instruments to understand better all the methods used in this thesis, I write first to provide an overview regarding the proteins and their capability to bind other macromolecules. I then will exploit the basics of the small-angle technique, focusing on the neutron contrast variation: the fundamental technique used throughout this thesis and the ab-initio modelling.In the third chapter, Methods, I will discuss the SAS measurements and the requirements for the experiments themselves, the procedure for the data reduction and the data processing and analysis to obtain the structural information.The fourth chapter is a summary of the results of the submitted papers and my contributions:Small-angle X-ray and neutron scattering of MexR and its complex with DNA supports a conformational selection binding modelResolving the DNA interaction of the MexR antibiotic resistance regulatory proteinUpgraded D22 SEC-SANS set-up dedicated to the biology communitySAS studies on the regulation of MYC303:MAX:DNA and MAX:MAX:DNA binding in cancer.
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| 2. |
- Stenlund, Jörgen, 1959-
(författare)
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Visualizing the abyss of time : Students’ interpretation of visualized deep evolutionary time
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The immense time scales involved in Deep evolutionary time (DET) is a threshold concept in biology and interpreting temporal aspects of DET is demanding. DET is communicated through various visualizations that include static two-dimensional representations, low interactivity animations, as well as high interactivity interfaces. Given the importance of DET as fundamental scientific knowledge of potential societal application, there is a need for educational research on students’ interpretation of visually communicated DET. This thesis explores students’ interpretation of different forms of visualized DET along a continuum of interactivity. The research aim is four-fold, and probes how students interpret DET visualizations in terms of temporal aspects, communicated evolutionary concepts, degree of visualization interactivity, and generated affective responses.The work comprises four studies, which as a collective, adopt exploratory and multi-method designs. A total of 505 students participated. Data were collected from questionnaires, task-based questions, and semi-structured interviews. Data analysis was qualitative and quantitative, and incorporated deductive and inductive approaches. In analysing students' interpretation of static two-dimensional DET visualizations, an instrument for measuring knowledge about the visual representation of deep evolutionary time (DET-Vis) was developed. Emergence of a unidimensional construct during validation represents knowledge about the visual communication of DET. Inspection of item performance suggests that interpreting visualized DET requires both procedural and declarative knowledge. Analysis of students’ interpretation of a low interactivity DET animation, communicating hominin evolution revealed five temporal aspects influencing interpretation: events at specific times, relative order, concurrent events, time intervals, and time interval durations. A further shift across the continuum involved analysing students’ interpretation of a high-interactivity DET visualization of a three-dimensional phylogenetic tree. Finger-based zooming was associated with movement within the tree itself, or as movement in time, respectively, and related to identified misinterpretations. Further analysis showed that interpreting DeepTree evoked the epistemic affective responses of awe, curiosity, surprise, and confusion. Affective responses were expressed in relation to five evolutionary conceptual themes, namely biological relationships, evolutionary time, biological diversity, common descent, and biological structure or terminology. The thesis findings have implications for teaching, visualization design and future research. Exposing students to various DET visualizations across the continuum could support DET teaching. Visual communication of temporal aspects should be carefully considered in DET visualization design. Future work on relationships between affect, highly interactive visualizations, and evolution concepts will provide further insight for leveraging learning and teaching of DET.
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| 3. |
- Abedini, Fereshteh, 1989-
(författare)
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2D and 3D Halftoning for Appearance Reproduction
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The appearance of an object is determined by its chromatic and geometric qualities in its surrounding environment using four optical parameters: color, gloss, translucency, and surface texture. Reconstructing the appearance of objects is of great importance in many applications, including creative industries, packaging, fine-art reproduction, medical simulation, and prosthesis-making. Printers are reproduction devices capable of replicating objects’ appearance in 2D and 3D forms. With the introduction of new printing technologies, new inks and materials, and demands for innovative applications, creating accurate reproduction of the desired visual appearance has become challenging. Thus, the appearance reproduction workflow requires improvements and adaptations. Accurate color reproduction is a critical quality measure in reproducing the desired appearance in any printing process. However, printers are devices with a limited number of inks that can either print a dot or leave it blank at a specific position on a substrate; hence, to reproduce different colors, optimal placement of the available inks is needed. Halftoning is a technique that deals with this challenge by generating a spatial distribution of the available inks that creates an illusion of the target color when viewed from a sufficiently large distance. Halftoning is a fundamental part of the color reproduction task in any full-color printing pipeline, and it is an effective technique to increase the potential of printing realistic and complex appearances. Although halftoning has been used in 2D printing for many decades, it still requires improvements in reproducing fine details and structures of images. Moreover, the emergence of new technologies in 3D printing introduces a higher degree of freedom and more parameters to the field of appearance reproduction. Therefore, there is a critical need for extensive studies to revisit existing halftoning algorithms and develop novel approaches to produce high quality prints that match the target appearance faithfully. This thesis aims at developing halftoning algorithms to improve appearance reproduction in 2D and 3D printing. Contributions of this thesis in the 2D domain is a dynamic sharpness-enhancing halftoning approach, which adaptively varies the local sharpness of the halftone image based on different textures in the original image for realistic appearance printing. The results show improvements in halftone quality in terms of sharpness, preserving structural similarity, and decreasing color reproduction error. The main contribution of this thesis in 3D printing is extending a high quality 2D halftoning algorithm to the 3D domain. The proposed method is then integrated with a multi-layer printing approach, where ink is deposited at variable depths to improve the reproduction of tones and fine details. Results demonstrate that the proposed method accurately reproduces tones and details of the target appearance. Another contribution of this thesis is studying the effect of halftoning on the perceived appearance of 3D printed surfaces. According to the results, changing the dot placement based on the elevation variation of the underlying geometry can potentially control the perception of the 3D printed appearance. It implies that the choice of halftone may prove helpful in eliminating unwanted artifacts, enhancing the object’s geometric features, and producing a more accurate 3D appearance. The proposed methods in this thesis have been evaluated using different printing techniques.
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| 4. |
- Abrahamsson, Tobias, 1991-
(författare)
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Synthetic Functionalities for Ion and Electron Conductive Polymers : Applications in Organic Electronics and Biological Interfaces
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the search for understanding and communicating with all biological systems, in humans, animals, plants, and even microorganisms, we find a common language of all communicating via electrons, ions and molecules. Since the discovery of organic electronics, the ability to bridge the gap and communicate be-tween modern technology and biology has emerged. Organic chemistry pro-vides us with tools for understanding and a material platform of polymer electronics for communication. Such insights give us not only the ability to observe fundamental phenomenon but to actively design and construct materials with chemical functionalities towards better interfaces and applications. Organic electronic materials and devices have found their way to be implemented in the field of medicine for diagnostic and therapeutic purposes, but also in water purification and to help tackle the monumental task in creating the next generation of sustainable energy production and storage. Ultimately it’s safe to say that organic electronics are not going to replace our traditional technology based on inorganic materials but rather the two fields can find a way to complement each other for various purposes and applications. Compared to conventional silicon based technology, production of carbon-based organic electronic polymer materials are extremely cheap and devices can even be made flexible and soft with great compatibility towards biology. The main focus of this thesis has been developing and synthesizing new types of organic electronic and ionic conductive polymeric materials. Rational chemical design and modifications of the materials have been utilized to introduce specific functionalities to the materials. The functionalities serving the purpose to facilitate ion and electron conductive charge transport for organic electronics and with biological interface implementation of the polymer materials. Multi-functional ionic conductive hyperbranched polyglycerol polyelectrolytes (dendrolytes) were developed comprising both ionically charged groups and cross-linkable groups. The hyperbranched polyglycerol core structure of the material possesses a hydrophilic solvating platform for both ions and maintenance of solvent molecules, while being a biocompatible structure. Coupled with the peripheral charged ionic functionalities of the polymer, the dendrolyte materials are highly ionic conductive and selective towards cationic and anionic charged atoms and large molecules when implemented as ion-exchange membranes. Homogenous ion-exchange membrane casting has been achieved by the implementation of cross-linkable functionalities in the dendrolytes, utilizing robust click-chemistry for efficient micro and macro fabrication processing of the ion-ex-change membranes for organic electronic devices. The ion-exchange membrane material was implemented in electrophoretic drug delivery devices (organic electronic ion pumps), which are used for delivery of ions and neurotransmitters with spatiotemporal resolution and are able to communicate and be used for therapeutic drug delivery purposes in biological interfaces. The dendrolyte materials were also able to form free-standing membranes, making it possible for implementation in fuel cell and desalination purposes. Trimeric conjugated thiophene pre-polymer structures were also developed in the thesis and synthesized for the purpose of implementation of the material in vivo to form electrically conductive polymer structures, and in such manner to be able to create electrodes and ultimately to connect with the central nervous system. The conjugated pre-polymers being both water soluble and enzymatically polymerizable serve as a platform to realize such a concept. Also, modifying the trimeric structure with cross-linkable functionality created the capability to form better interfaces and stability towards biological environments.
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| 5. |
- Abramian, David, 1992-
(författare)
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Modern multimodal methods in brain MRI
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Magnetic resonance imaging (MRI) is one of the pillars of modern medical imaging, providing a non-invasive means to generate 3D images of the body with high soft-tissue contrast. Furthermore, the possibilities afforded by the design of MRI sequences enable the signal to be sensitized to a multitude of physiological tissue properties, resulting in a wide variety of distinct MRI modalities for clinical and research use. This thesis presents a number of advanced brain MRI applications, which fulfill, to differing extents, two complementary aims. On the one hand, they explore the benefits of a multimodal approach to MRI, combining structural, functional and diffusion MRI, in a variety of contexts. On the other, they emphasize the use of advanced mathematical and computational tools in the analysis of MRI data, such as deep learning, Bayesian statistics, and graph signal processing. Paper I introduces an anatomically-adapted extension to previous work in Bayesian spatial priors for functional MRI data, where anatomical information is introduced from a T1-weighted image to compensate for the low anatomical contrast of functional MRI data. It has been observed that the spatial correlation structure of the BOLD signal in brain white matter follows the orientation of the underlying axonal fibers. Paper II argues about the implications of this fact on the ideal shape of spatial filters for the analysis of white matter functional MRI data. By using axonal orientation information extracted from diffusion MRI, and leveraging the possibilities afforded by graph signal processing, a graph-based description of the white matter structure is introduced, which, in turn, enables the definition of spatial filters whose shape is adapted to the underlying axonal structure, and demonstrates the increased detection power resulting from their use. One of the main clinical applications of functional MRI is functional localization of the eloquent areas of the brain prior to brain surgery. This practice is widespread for various invasive surgeries, but is less common for stereotactic radiosurgery (SRS), a non-invasive surgical procedure wherein tissue is ablated by concentrating several beams of high-energy radiation. Paper III describes an analysis and processing pipeline for functional MRI data that enables its use for functional localization and delineation of organs-at-risk for Elekta GammaKnife SRS procedures. Paper IV presents a deep learning model for super-resolution of diffusion MRI fiber ODFs, which outperforms standard interpolation methods in estimating local axonal fiber orientations in white matter. Finally, Paper V demonstrates that some popular methods for anonymizing facial data in structural MRI volumes can be partially reversed by applying generative deep learning models, highlighting one way in which the enormous power of deep learning models can potentially be put to use for harmful purposes.
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| 6. |
- Achieng, Pauline, 1990-
(författare)
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Reconstruction of solutions of Cauchy problems for elliptic equations in bounded and unbounded domains using iterative regularization methods
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Cauchy problems for elliptic equations arise in applications in science and engineering. These problems often involve finding important information about an elliptical system from indirect or incomplete measurements. Cauchy problems for elliptic equations are known to be disadvantaged in the sense that a small pertubation in the input can result in a large error in the output. Regularization methods are usually required in order to be able to find stable solutions. In this thesis we study the Cauchy problem for elliptic equations in both bounded and unbounded domains using iterative regularization methods. In Paper I and II, we focus on an iterative regularization technique which involves solving a sequence of mixed boundary value well-posed problems for the same elliptic equation. The original version of the alternating iterative technique is based on iterations alternating between Dirichlet-Neumann and Neumann-Dirichlet boundary value problems. This iterative method is known to possibly work for Helmholtz equation. Instead we study a modified version based on alternating between Dirichlet-Robin and Robin-Dirichlet boundary value problems. First, we study the Cauchy problem for general elliptic equations of second order with variable coefficients in a limited domain. Then we extend to the case of unbounded domains for the Cauchy problem for Helmholtz equation. For the Cauchy problem, in the case of general elliptic equations, we show that the iterative method, based on Dirichlet-Robin, is convergent provided that parameters in the Robin condition are chosen appropriately. In the case of an unbounded domain, we derive necessary, and sufficient, conditions for convergence of the Robin-Dirichlet iterations based on an analysis of the spectrum of the Laplacian operator, with boundary conditions of Dirichlet and Robin types.In the numerical tests, we investigate the precise behaviour of the Dirichlet-Robin iterations, for different values of the wave number in the Helmholtz equation, and the results show that the convergence rate depends on the choice of the Robin parameter in the Robin condition. In the case of unbounded domain, the numerical experiments show that an appropriate truncation of the domain and an appropriate choice of Robin parameter in the Robin condition lead to convergence of the Robin-Dirichlet iterations.In the presence of noise, additional regularization techniques have to implemented for the alternating iterative procedure to converge. Therefore, in Paper III and IV we focus on iterative regularization methods for solving the Cauchy problem for the Helmholtz equation in a semi-infinite strip, assuming that the data contains measurement noise. In addition, we also reconstruct a radiation condition at infinity from the given Cauchy data. For the reconstruction of the radiation condition, we solve a well-posed problem for the Helmholtz equation in a semi-infinite strip. The remaining solution is obtained by solving an ill-posed problem. In Paper III, we consider the ordinary Helmholtz equation and use seperation of variables to analyze the problem. We show that the radiation condition is described by a non-linear well-posed problem that provides a stable oscillatory solution to the Cauchy problem. Furthermore, we show that the ill–posed problem can be regularized using the Landweber’s iterative method and the discrepancy principle. Numerical tests shows that the approach works well.Paper IV is an extension of the theory from Paper III to the case of variable coefficients. Theoretical analysis of this Cauchy problem shows that, with suitable bounds on the coefficients, can iterative regularization methods be used to stabilize the ill-posed Cauchy problem.
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| 7. |
- Adam, Rania Elhadi, 1978-
(författare)
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Synthesis and Characterization of Some Nanostructured Materials for Visible Light-driven Photo Processes
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Nanostructured materials for visible light driven photo-processes such as photodegradation of organic pollutants and photoelectrochemical (PEC) water oxidation for hydrogen production are very attractive because of the positive impact on the environment. Metal oxides-based nanostructures are widely used in these photoprocesses due to their unique properties. But single nanostructured metal oxide material might suffer from low efficiency and instability in aqueous solutions under visible light. These facts make it important to have an efficient and reliable nanocomposite for the photo-processes. The combination of different nanomaterials to form a composite configuration can produce a material with new properties. The new properties which are due to the synergetic effect, are a combination of the properties of all the counterparts of the nanocomposite. Zinc oxides (ZnO) have unique optical and electrical properties which grant it to be used in optoelectronics, sensors, solar cells, nanogenerators, and photocatalysis activities. Although ZnO absorbs visible light from the sun due to the deep level band, it mainly absorbs ultraviolet wavelengths which constitute a small portion of the whole solar spectrum range. Also, ZnO has a problem with the high recombination rate of the photogenerated electrons. These problems might reduce its applicability to the photo-process. Therefore, our aim is to develop and investigate different nanocomposites materials based on the ZnO nanostructures for the enhancement of photocatalysis processes using the visible solar light as a green source of energy. Two photo-processes were applied to examine the developed nanocomposites through photocatalysis: (1) the photodegradation of organic dyes, (2) PEC water splitting. In the first photo-process, we used the ZnO nanoparticles (NPs), Magnesium (Mg)-doped ZnO NPs, and plasmonic ZnO/graphene-based nanocomposite for the decomposition of some organic dyes that have been used in industries. For the second photo-process, ZnO photoelectrode composite with different silver-based semiconductors to enhance the performance of the ZnO photoelectrode was used for PEC reaction analysis to perform water splitting. The characterization and photocatalysis experiment results showed remarkable enhancement in the photocatalysis efficiency of the synthesized nanocomposites. The observed improved properties of the ZnO are due to the synergetic effects are caused by the addition of the other nanomaterials. Hence, the present thesis attends to the synthesis and characterization of some nanostructured materials composite with ZnO that are promising candidates for visible light-driven photo-processes.
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| 8. |
- Ahmad, Azeem, 1984-
(författare)
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Contributions to Improving Feedback and Trust in Automated Testing and Continuous Integration and Delivery
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- An integrated release version (also known as a release candidate in software engineering) is produced by merging, building, and testing code on a regular basis as part of the Continuous Integration and Continuous Delivery (CI/CD) practices. Several benefits, including improved software quality and shorter release cycles, have been claimed for CI/CD. On the other hand, recent research has uncovered a plethora of problems and bad practices related to CI/CD adoption, necessitating some optimization. Some of the problems addressed in this work include the ability to respond to practitioners’ questions and obtain quick and trustworthy feedback in CI/CD. To be more specific, our effort concentrated on: 1) identifying the information needs of software practitioners engaged in CI/CD; 2) adopting test optimization approaches to obtain faster feedback that are realistic for use in CI/CD environments without introducing excessive technical requirements; 3) identifying perceived causes and automated root cause analysis of test flakiness, thereby providing developers with guidance on how to resolve test flakiness; and 4) identifying challenges in addressing information needs, providing faster and more trustworthy feedback. The findings of the research reported in this thesis are based on data from three single-case studies and three multiple-case studies. The research uses quantitative and qualitative data collected via interviews, site visits, and workshops. To perform our analyses, we used data from firms producing embedded software as well as open-source repositories. The following are major research and practical contributions. Information Needs: The initial contribution to research is a list of information needs in CI/CD. This list contains 27 frequently asked questions on continuous integration and continuous delivery by software practitioners. The identified information needs have been classified as related to testing, code & commit, confidence, bug, and artifacts. We investigated how companies deal with information needs, what tools they use to deal with them, and who is interested in them. We concluded that there is a discrepancy between the identified needs and the techniques employed to meet them. Since some information needs cannot be met by current tools, manual inspections are required, which adds time to the process. Information about code & commit, confidence level, and testing is the most frequently sought for and most important information. Evaluation of Diversity Based Techniques/Tool: The contribution is to conduct a detailed examination of diversity-based techniques using industry test cases to determine if there is a difference between diversity functions in selecting integrationlevel automated test. Additionally, how diversity-based testing compares to other optimization techniques used in industry in terms of fault detection rates, feature coverage, and execution time. This enables us to observe how coverage changes when we run fewer test cases. We concluded that some of the techniques can eliminate up to 85% of test cases (provided by the case company) while still covering all distinct features/requirements. The techniques are developed and made available as an open-source tool for further research and application. Test Flakiness Detection, Prediction & Automated Root Cause Analysis: We identified 19 factors that professionals perceive affect test flakiness. These perceived factors are divided into four categories: test code, system under test, CI/test infrastructure, and organizational. We concluded that some of the perceived factors of test flakiness in closed-source development are directly related to non-determinism, whereas other perceived factors concern different aspects e.g., lack of good properties of a test case (i.e., small, simple and robust), deviations from the established processes, etc. To see if the developers’ perceptions were in line with what they had labelled as flaky or not, we examined the test artifacts that were readily available. We verified that two of the identified perceived factors (i.e., test case size and simplicity) are indeed indicative of test flakiness. Furthermore, we proposed a light weight technique named trace-back coverage to detect flaky tests. Trace-back coverage was combined with other factors such as test smells indicating test flakiness, flakiness frequency and test case size to investigate the effect on revealing test flakiness. When all factors are taken into consideration, the precision of flaky test detection is increased from 57% (using single factor) to 86% (combination of different factors).
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| 9. |
- Ait Ali, Abderrahman, 1991-
(författare)
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Methods for Capacity Allocation in Deregulated Railway Markets
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Faced with increasing challenges, railways around Europe have recently undergone major reforms aiming to improve the efficiency and competitiveness of the railway sector. New market structures such as vertical separation, deregulation and open access can allow for reduced public expenditures, increased market competition, and more efficient railway systems.However, these structures have introduced new challenges for managing infrastructure and operations. Railway capacity allocation, previously internally performed within monopolistic national companies, are now conferred to an infrastructure manager. The manager is responsible for transparent and efficient allocation of available capacity to the different (often competing) licensed railway undertakings.This thesis aims at developing a number of methods that can help allocate capacity in a deregulated (vertically separated) railway market. It focuses on efficiency in terms of social welfare, and transparency in terms of clarity and fairness. The work is concerned with successive allocation of capacity for publicly controlled and commercial traffic within a segmented railway market.The contributions include cost benefit analysis methods that allow public transport authorities to assess the social welfare of their traffic, and create efficient schedules. The thesis also describes a market-based transparent capacity allocation where infrastructure managers price commercial train paths to solve capacity conflicts with publicly controlled traffic. Additionally, solution methods are developed to help estimate passenger demand, which is a necessary input both for resolving conflicts, and for creating efficient timetables.Future capacity allocation in deregulated markets may include solution methods from this thesis. However, further experimentations are still required to address concerns such as data, legislation and acceptability. Moreover, future works can include prototyping and pilot projects on the proposed solutions, and investigating legal and digitalisation strategies to facilitate the implementation of such solutions.
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| 10. |
- Akram Hassan, Kahin, 1990-
(författare)
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It’s About Time : User-centered Evaluation of Visual Representations for Temporal Data
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The primary goal for collecting and analyzing temporal data differs between individuals and their domain of expertise e.g., forecasting might be the goal in meteorology, anomaly detection might be the goal in finance. While the goal differs, one common denominator is the need for exploratory analysis of the temporal data, as this can aid the search for useful information. However, as temporal data can be challenging to understand and visualize, selecting appropriate visual representations for the domain and data at hand becomes a challenge. Moreover, many visual representations can show a single variable that changes over time, displaying multiple variables in a clear and easily accessible way is much harder, and inference-making and pattern recognition often require visualization of multiple variables. Additionally, as visualization aims to gain insight, it becomes crucial to investigate whether the representations used help users gain this insight. Furthermore, to create effective and efficient visual analysis tools, it is vital to understand the structure of the data, how this data can be represented, and have a clear understanding of the user needs. Developing useful visual representations can be challenging, but through close collaboration and involvement of end-users in the entire process, useful results can be accomplished. This thesis aims to investigate the usability of different visual representations for different types of multivariate temporal data, users, and tasks. Five user studies have been conducted to investigate different representation spaces, layouts, and interaction methods for investigating representations’ ability to facilitate users when analyzing and exploring such temporal datasets. The first study investigated and evaluated the experience of different radial design ideas for finding and comparison tasks when presenting hourly data based on an analog clock metaphor. The second study investigated 2D and 3D parallel coordinates for pattern finding. In the third study, the usability of three linear visual representations for presenting indoor climate data was investigated with domain experts. The fourth study continued on the third study and developed and evaluated a visual analytics tool with different visual representations and interaction techniques with domain experts. Finally, in the fifth study, another visual analytics tool presenting visual representations of temporal data was developed and evaluated with domain experts working and conducting experiments in Antarctica. The research conducted within the scope of this thesis concludes that it is vital to understand the characteristics of the temporal data and user needs for selecting the optimal representations. Without this knowledge, it becomes much harder to choose visual representations to help users gain insight from the data. It is also crucial to evaluate the perception and usability of the chosen visual representations.
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