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  • 1.
    Shevtsov, Stepan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för datavetenskap och medieteknik (DM). KU Leuven, Belgium.
    A Control-theoretic Approach to Realize Self-adaptive Software Systems with Guarantees2019Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Engineering modern software systems is a challenging task as these systems are subject to different types of uncertainties. Examples of such uncertainties are disturbances in the environment that are difficult to predict and goals that may change during operation. The idea of self-adaptation is to handle these uncertainties at runtime, when the knowledge becomes available to resolve them. As more software systems with strict requirements are designed to be self-adaptive, the need for adaptation guarantees is becoming a high-priority concern. Providing such guarantees with traditional architecture-based approaches has shown to be challenging, calling for new approaches to engineer self-adaptive systems. To tackle this challenge, this thesis studies control-based software adaptation (CBSA). CBSA applies principles from control theory to design self-adaptive software systems. More specifically, we address the following research problem using CBSA: how to realize self-adaptive software systems that satisfy multiple stakeholder requirements with guarantees in the presence of uncertainties.

    The thesis addresses the research problem in two subsequent stages. The first stage focuses on satisfying multiple stakeholder requirements of different types, and providing adaptation guarantees. This stage starts with a systematic literature review of CBSA, which provides a comprehensive overview of the field, including existing CBSA approaches, applied models and controllers, and analyzed guarantees. From the review, we identify a number of gaps in the existing research and concrete challenges in addressing the research problem. Then, we devise SimCA, a control-theoretic approach to realize self-adaptive software systems that satisfy multiple requirements with guarantees. SimCA combines mathematical models of software system, a control-based adaptation mechanism, and formal analysis of the required guarantees. SimCA is also reusable, meaning that it can be applied to a family of cooperative software systems with strict requirements. The second research stage focuses on handling different types of uncertainty.We first discuss the types of uncertainty and study whether existing CBSA approaches try to deal with these types. We then introduce an enhanced approach called SimCA* that includes components to deal with uncertainty in software parameters, addition or removal of requirements at runtime and software component interactions. In order to obtain evidence about the applicability and reusability of SimCA and SimCA*, we apply informal exploratory case studies with three software systems with strict requirements from different domains.

  • 2.
    Sjökvist, Tinh
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Coated Norway Spruce: Influence of Wood Characteristics on Water Sorption and Coating Durability2019Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Wood used outdoors is often degraded and discoloured by microorganisms as a natural part of its life cycle, particularly when exposed to high levels of moisture for prolonged times. In this case, the application of a coating (i.e. paint) is an option for increasing the service life of the wood.

    Norway spruce (Picea abies (L.) Karst.) is commonly used for outdoor applications in Sweden. Earlier studies have shown that uncoated spruce heartwood is less prone to moisture sorption in outdoor exposure, resulting in lower moisture content (MC) levels, as compared to sapwood. However, studies related to the above mentioned characteristics are rather limited for coated spruce, especially including the influence of outdoor exposure (i.e. weathering).

    The aim of this thesis is, therefore, to increase the knowledge of how heartwood and sapwood of different densities influence on the durability of coated Norway spruce for outdoor use. Different types of coatings with alkyd-, acrylic-, flour- (calcimine paint), or linseed-oil-based resin were included. The objectives were to study the water sorption (including MC variation) behaviour and crack formation of uncoated and coated heartwood and sapwood of different densities.

    Furthermore was an objective to study the microbial growth on the surface of similar samples of coated spruce in outdoor exposure. The used methods included wetting and liquid permeability experiments, accelerated water absorption (with samples floating freely in water), and outdoor field test. The field method lasted between three to five years and involved monitoring of the MC variation, the crack formation and the microbial growth on the samples.

    The results based on wetting measurements using octane as the adsorbed liquid showed no difference in liquid permeability between the spruce heartwood and sapwood samples of comparable densities, and indicated a similar level of pit aspiration (closure). The common flow path between two cells of conifers occurs through the pits. Still, the sapwood samples had in general a clearly higher water sorption rate than heartwood samples. It could be concluded that the increased sorption was presumably caused by a lowered water surface tension, most likely by a contamination effect of the water by surface-active sapwood extractives rather than differences in morphology of heartwood and sapwood.

    However, no clear difference in water absorption and MC levels was seen between coated heartwood and sapwood in the field study or in the accelerated water absorption study. Thus, it is suggested that a coating hinders the surfaceactive extractives to lower the water surface tension, resulting in a similar water absorption behaviour of coated heartwood and sapwood. The influence of density on water sorption of coated spruce was similarly to uncoated spruce, meaning the low-density samples had a higher MC than the high-density samples in the field tests. Furthermore, a one-year weathering of the coated and uncoated samples caused a larger increase in water sorption of high-density heartwood in the accelerated water absorption study.

    The field study on uncoated and calcimine-coated spruce showed a higher number of cracks on the high-density samples than on the low-density samples. Additionally, within each density group, a larger number of cracks were seen on sapwood samples as compared to heartwood samples. High-density samples with an alkyd- or an acrylic coating also showed a higher number of cracks. As expected, the formation of cracks on the samples increased their water sorption significantly. The microbial growth was higher on sapwood than on heartwood samples with a white coloured alkyd coating.

    The main conclusion is that heartwood and sapwood of different densities influence the water sorption and durability of coated Norway spruce. However, the principles in water sorption of uncoated heartwood and sapwood could not be applied to coated samples. Overall, the results point out that low-density heartwood could be the best material combination to improve the durability of coated spruce in outdoor use. The knowledge acquired in this thesis can enable an increased service life of coated spruce in outdoor use. The increase in service life is achieved by a careful selection of the wood material regarding the proportion of heartwood and to the choice of wood density. As a concluding remark, the role of surface-active spruce extractives needs to be explored, and a follow-up investigation in the context of water sorption is suggested for future research.

  • 3.
    Zimmer, Björn
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för datavetenskap och medieteknik (DM).
    Guided Interaction and Collaborative Exploration in Heterogeneous Network Visualizations2019Doktorsavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    The visual exploration of large and complex network structures remains a challenge for many application fields, such as systems biology or social sciences. Often, various domain experts would like to work together to improve the analysis time or the quality of the analysis results. Collaborative visualization tools can facilitate the analysis process in such situations. Moreover, a growing number of real world networks are multivariate and often interconnected with each other. Entities in a network may have relationships with elements of other related data sets, which do not necessarily have to be networks themselves, and these relationships may be defined by attributes that can vary greatly. A challenge is to correctly assign the attributes and relations between different data sets and graphs in order to be able to analyze them visually afterwards. The navigation between the resulting visualizations is also difficult. How can users be guided to other interesting data points relevant to their current view and how can this information be additionally displayed in a graph without losing the overview of the data?

    In this dissertation, we propose our new web-based visualization environment OnGraX, which supports distributed, synchronous and asynchronous collaboration of networks and related multivariate data sets. In addition to standard collaboration features like event tracking or synchronizing, our client/server-based system provides a rich set of visualization and interaction techniques for better navigation and overview of the input network. Changes made by specific analysts or even just visited network elements can be highlighted by heat maps, which enable us to visualize user behavior data without affecting the original graph visualization. We evaluate the usability of the heat map approach against two alternatives in a user experiment.

    Additional features of OnGraX include a comprehensive visual analytics approach that supports researchers to specify and subsequently explore attribute-based relationships across networks, text documents, and derived secondary data. Our approach provides an individual search functionality based on keywords and semantically similar terms over an entire text corpus to find related network nodes. For examining these nodes in the interconnected network views, we introduce a new interaction technique, called Hub2Go, which facilitates the navigation by guiding the user to the information of interest. To showcase these features, we use a large text corpus collected from papers listed in the IEEE VIS publications data set (1990--2015) that consists of 2,752 documents. We analyze relationships between various heterogeneous networks, a Bag-of-Words index, and a word similarity matrix, all derived from the initial corpus and metadata. We also propose a design for the interactive specification of degree-of-interest functions, which can be used to provide and evaluate configurations for guidance based on network attributes and logged user data in heterogeneous networks.

  • 4.
    Gustafsson, Barbro
    et al.
    Linnéuniversitetet, Fakulteten för samhällsvetenskap (FSV), Institutionen för didaktik och lärares praktik (DLP).
    Fonseca, LarsLinnéuniversitetet, Fakulteten för samhällsvetenskap (FSV), Institutionen för pedagogik och lärande (PEL).Gerrevall, PerLinnéuniversitetet, Fakulteten för samhällsvetenskap (FSV), Institutionen för didaktik och lärares praktik (DLP).
    Lämplighetsbedömning inför antagning till lärarutbildningen: Erfarenheter från Linnéuniversitetets försöksverksamhet2019Samlingsverk (redaktörskap) (Övrigt vetenskapligt)
  • 5.
    Ståhlkrantz, Katarina
    Linnéuniversitetet, Fakulteten för samhällsvetenskap (FSV), Institutionen för pedagogik och lärande (PEL).
    Rektors pedagogiska ledarskap: en kritisk policyanalys2019Doktorsavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    The pedagogical leadership is regarded as the most significant of the principal ́s duties. Because there is no clear definition of pedagogical leadership as a concept, it may be difficult for the principal to know how to practice it. Various versions of the concept’s meaning are currently circulating, in turn offering different norms to relate to and act upon. This doctoral thesis takes its point of departure from the policy proposal of a Rektorslyft in the Swedish national budget of 2011, as a solution to the problem that principals were not considered to be good enough pedagogical leaders. The study is designed as a critical policy analysis, with a curriculum theory framework and a critical interpretative perspective. The critical approach is directing focus towards the steering of the school. Further, a poststructuralist perspective adds a discursive approach to the study. The empirical material consists of a selection of official education policy documents, mainly governmental official reports. The aim of the study is to examine and analyse how the pedagogical leader is discursively constructed in official education government documents, what changes and stabilities can be distinguished in these discursive constructions over time and how these can be understood and explained. Bacchi ́s WPR-method and Foucault ́s genealogy is used as a methodological framework for the text analysis. The result shows six discursive breakpoints in the construction of the pedagogical leader from the 1950s to 2010s. These breakpoints have a close relationship to changes in school steering. Principals’ pedagogical leadership can therefore be regarded as a policy to legitimise new steering reforms. The result further indicates that principals from the 1950s to 2010s were given a clearer personal responsibility within the pedagogical leadership. The changes identified through the critical policy analysis can be explained by the context and policy streams. The text analysis also indicated stabilities in the discursive construction of the pedagogical leader. These stabilities can be explained by traditions and school structures. Hopefully, this study has contributed to a better and deepened understanding of principals’ pedagogical leadership, as well as have given the concept an empirical and theoretical basis.

  • 6.
    Kucher, Kostiantyn
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för datavetenskap och medieteknik (DM).
    Sentiment and Stance Visualization of Textual Data for Social Media2019Doktorsavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    Rapid progress in digital technologies has transformed the world in many ways during the past few decades, in particular, with the new means of communication such as social media. Social media platforms typically rely on textual data produced or shared by the users in multiple timestamped posts. Analyses of such data are challenging for traditional manual methods that are unable to scale up to the volume and the variety of the data. While computational methods can partially address these challenges, they have to be used together with the methods developed within information visualization and visual analytics to gain knowledge from the text data by using interactive visual representations.

    One of the most interesting aspects of text data is related to expressions of sentiments and opinions. The corresponding task of sentiment analysis has been studied within computational linguistics, and sentiment visualization techniques exist as well. However, there are gaps in research on the related task of stance analysis, dedicated to subjectivity that is not expressible only in terms of sentiment. Research on stance is an area of interest in linguistics, but support by computational and visual methods has been limited so far. The challenges related to definition, analysis, and visualization of stance in textual data call for an interdisciplinary research effort. The StaViCTA project addressed these challenges with a focus on written text in English. The corresponding results in the area of visualization are reported in this work, based on multiple publications.

    The main goal of this dissertation is to define, categorize, and implement means for visual analysis of sentiment and stance in textual data, in particular, for social media. Our work is based on the theoretical framework and automatic classifier of stance developed by our project collaborators, involving multiple non-exclusive stance categories such as certainty and prediction. We define a design space for sentiment and stance visualization techniques based on literature surveys. We discuss multiple visualization and visual analytics approaches developed by us to facilitate the underlying research on stance analysis, data collection and annotation, and visual analysis of sentiment and stance in real-world text data from several social media sources. The work described in this dissertation was carried out in cooperation with domain experts in linguistics and computational linguistics, and our approaches were validated with case studies, expert user reviews, and critical discussion. The results of this work open up further opportunities for research in text visualization and visual text analytics. The potential application areas are academic research, business intelligence, social media monitoring, and journalism.

  • 7.
    Nordmark, Susanna
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för datavetenskap och medieteknik (DM).
    A Multimodal Seamless Learning Approach Supported by Mobile Digital Storytelling (mDS)2018Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The use of digital tools such as smartphones, tablets and laptops have shown potential to enhance teaching and learning in a wide variety of contexts. 21st century skills such as creativity, problem-solving and innovation as means for supporting learning and knowledge creation, are considered fundamental proficiencies in today's technology- driven society, and they are therefore considered essential to promote, already from the earliest of school years. Hence, there are a number of challenges related to how to design and implement innovative and varied strategies

    for teaching and learning supported by mobile technologies in educational settings. Moreover, it is also crucial to think about how to actively involve teachers into the processes mentioned above, inspiring and inviting them to implement new methods and technologies into their everyday educational practices.

    The work presented in this thesis embodies a series of co-design and design-based research efforts aiming at exploring the interplay between design, information and communication technologies and learning through mobile digital storytelling, guided by the theoretical frameworks of constructivism, multimodality, new media literacies, mobile seamless learning, and technology enhanced learning. Two main research questions have been identified as formulated below, and have served as

    the basis that guided my efforts:

    What design features are necessary to scaffold mobile seamless learning approaches with the support of mobile digital storytelling?

    Considering the role of mobile digital storytelling for educational settings: which design factors and learning requirements could guide and support similar initiatives?

    Over the years of my doctoral studies, a progression of research interventions involving teachers, pupils, and museum staff have been co-designed, developed, tested and validated. These efforts have resulted in a method, a mobile application, and a web service for mobile digital storytelling in educational contexts, named the mobile digital storytelling (mDS) system.

    The mDS system introduces learning technology approaches aiming to support teacher and pupil digital inclusion, mobile seamless learning and multimodal aspects, and serves as a reflective instrument for both collaborative and individual work. The validation of mDS in different educational settings indicates that it can be independent of subject matter, user age, locality and previous knowledge of technology enhanced learning, and is easy to access and manage for teachers as well as pupils. Hence, it proposes several innovative means on multiple levels for meeting the 21st century skills required for supporting contemporary learning and knowledge creation.

  • 8.
    Perez, Miguel
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för matematik (MA).
    A teacher-centred design system to integrate digital technologies in secondary mathematics classrooms2018Doktorsavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    Despite efforts made by teachers and researchers, studies show that digital technologies have not improved conditions for teaching and learning mathematics to the degree expected by stakeholders inside as well as outside the school system.

    In this research, the problem of the integration of digital technologies is addressed through the perspective of design. It sets out to explore the conditions where educational design researchers may succeed in producing valuable and sustainable contributions to teacher change. The design approach developed and used for this purpose is Agile Educational Design (AED). It shares many of the common features of other design methodologies within the field; however, the AED approach is an explicit systems approach to design based on the Singerian philosophy of design. Rather than focus on ready-made products or other resources such as curriculum material, professional development or design principles, the focus is on processes and supporting teachers’ operationalisation of theoretical principles to achieve change. It is argued that all phases of the design process need to be considered from a research perspective. The developmental phases cannot be treated as uncomplicated inputs that only serve as a ‘design base’ for research activities. The Anthropological Theory of the Didactic is used as an overall theoretical framework to describe all aspects of the design process and to analyse the empirical data which consists of three design cycles related to three different ways of interacting with teachers. The design cycles were carried out in various settings, including different schools (secondary level) and with different teachers and different learning objectives. The dynamic geometry software GeoGebra was used in all three cycles.

    The results highlight some of the internal and external constraints that hinder teachers from integrating digital technologies in an effective way to support students learning mathematics. Digital technologies introduce important epistemological changes in the mathematical content that may explain some of the teachers’ difficulties in exploiting the full potential of digital technologies. However, giving teachers the responsibility for orchestrating lessons in accordance with theoretical principles provided by a researcher showed promising results regarding achieving sustainable changes in teachers’ practices. 

  • 9.
    Gunnarsson, Fredrik
    Linnéuniversitetet, Fakulteten för konst och humaniora (FKH), Institutionen för kulturvetenskaper (KV). Kalmar County Museum.
    Archaeological Challenges, Digital Possibilities: Digital Knowledge Development and Communication in Contract Archaeology2018Licentiatavhandling, monografi (Övrigt vetenskapligt)
    Abstract [sv]

    Den här forskningen har studerat digitaliseringen av arkeologin med fokus på svensk uppdragsarkeologi. Målet har varit att öka förståelsen kring hur disciplinen förhåller sig till de förändringar som digitaliseringens innebär och människans roll i dessa processer. Avhandlingen är en studie av digitaliseringens betydelse för de arkeologiska processer som berör kunskapsproduktion och kommunikation. Arbetet problematiserar förståelsen av digitala data inom dessa kontexter men visar också på digitaliseringenspotential och hur arkeologin kan dra nytta av den. Forskningen aktualiserar på nytt det teoretiska angreppssättet reflexivitet i ett digitalt sammanhang och kombinerar detta med kommunikationsteorier i syfte att utmana det arkeologiska arbetsflödet och knyta det närmare dagens samhälle. Resultatet av denna forskning visar på att digital kommunikation baserad på arkeologiskt källmaterial kan vara något mer än förmedling av resultat. Med interaktivt historieberättande finns vägar att skapa emotionella virtuella kopplingar mellan användare och arkeologi som relaterar till nuet och detomgivande samhället. Genom att länka ihop den arkeologiska tolkningsprocessen med kommunikation, skapas möjligheten för kunskapsproduktion att bli kunskapsutveckling.

  • 10.
    Wang, Zhizheng
    Linnéuniversitetet, Ekonomihögskolan (FEH), Institutionen för nationalekonomi och statistik (NS).
    Aspects of Moment Testing when p>n2018Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Avhandlingen undersöker hypotesprövning i höga dimensioner, under förutsättning att det så kallad Kolmogorovvillkoret (Kolmogorov condition) är uppfyllt. Villkoret innerbär att antalet parametrar ökar tillsammans med storleken på stickprovet med en konstant hastighet. Till kategorin multivariat analys räknas de statistiska metoder som analyserar stickprov från flerdimensionella fördelningar, särskilt multivariat normalfördelning. För högdimensionella data fungerar klassiska skattningar av kovariansmatris inte tillfredställande eftersom komplexiteten med att skatta den inversa kovariansmatrisen ökar när dimensionen ökar. I den första uppsatsen utförs en genomgång av Dempsters (non-exact) test där skattning av den inversa kovariansmatrisen inte behövs. Istället används spåret (trace) av en kovariansmatris. I den andra uppsatsen testas antagandet om normalfördelning med hjälp av tredje och fjärde ordningens moment. Tre olika testvariabler har föreslagits där sumuleringar också presenteras för att jämföra hur väl en icke-normalfördelning identifieras av testet.

1234567 1 - 10 av 345
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