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  • 1.
    Nilsson, Daniel
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Bioenergy from Swedish forests: A Study of extraction methods, quality and effects for forest owners2020Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The forest constitutes a very important element of renewable natural resources and makes a significant contribution to the Swedish bioeconomy. Biofuels are Sweden’s largest source of energy; of all the energy we use, 32% comes from biofuels, and of this approximately 85% comes from the forest and the forestry sector. In spite of this, logging residues constitute only a small component, compared to for example byproducts from sawmills and pulpindustry, and there is considered to be great potential for increasing their use.

    In 2019 the Swedish Forestry Agency issued new recommendations for logging residue harvest and ash recycling. This was a further development of the 2008 recommendations, which formed the foundation for how forest fuel producers work today, and were based on several decades of research into, for example, the impact on forest productivity and technological development of machinery. This practice of logging residue harvest aims to yield a dry and defoliated fuel where the needles are left at the clear felled area.

    However, if we are to increase the use of green renewable energy from forestry, it is very important to understand how different procurement systems affect the handling and storability of fuels from a quality perspective. It is also of great importance to understand, from the forest owners’ perspective, how removal of additional products from forestry influences nutritional balance and long-term productivity. If harvesting of logging residues does not affect long-term productivity, it is up to small-scale private forest owners to decide if removal of logging residues will be performed on their land. This thesis addresses some of these issues regarding removal of logging residues from the point of tree harvest up to the point of delivery to the energy conversion industry when the fuel chips are measured.

    Regarding different methods of handling of logging residues, the traditional method – dry-stacking – was compared with the, fresh-stacking method. The logging residues investigated came from stands that mainly consisted of Norway spruce (Picea abies (L.) Karst). The loads investigated in Paper 3 also came from logging of spruce-dominated forests. Both methods aim to dry the logging residues to an acceptable moisture content for delivery to the energyconversion industry. For the later part in the supply chain, moisture content measurements of logging residues were compared during a winter and summer season.

    The results of the studies indicate that the two methods do not create results that differ from what is allowed by the Swedish Forestry Agency and that they are quite similar with respect to dry mass- and nutrient removal from the clearfelled area. The results also show that similar yields and distributions of material are obtained from the logging residues with different stacking methods; in addition, the final felling itself, combined with the work performed by the forwarder operator, has a greater impact on the result than the method chosen for residue stacking of the logging residues. For the individual clear-felled area and the individual forest owner the increased removal associated with freshstacked logging residue has no major impact, however from a national perspective this small increase in removed logging residues may yield a supplement of between 0.5 – 1 TWh of green energy annually.

    Regardless of treatment, the studies indicated that the delivered fuel chips will have similar characteristics. The moisture content measurement techniques currently in use are sufficiently accurate and reliable. However, if the forest owner is unlucky and an error in measurement occurs or comminution and delivery happens during an especially wet period they may suffer a significant financial loss; indeed, it is generally not under the individual forest owners’ control when the logging residues are comminuted and delivered.

    Fulltekst (pdf)
    Licentiate Thesis (Comprehensive Summary)
    Download (jpg)
    Front Page
  • 2.
    Skandylas, Charilaos
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för datavetenskap och medieteknik (DM).
    Design and Analysis of Self-protection: Adaptive Security for Software-Intensive Systems2020Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Today’s software landscape features a high degree of complexity, frequent changes in requirements and stakeholder goals, and uncertainty. Uncertainty and high complexity imply a threat landscape where cybersecurity attacks are a common occurrence, while their consequences are often severe. Self-adaptive systems have been proposed to mitigate the complexity and frequent degree of change by adapting at run-time to deal with situations not known at design time. They, however, are not immune to attacks, as they themselves suffer from high degrees of complexity and uncertainty. Therefore, systems that can dynamically defend themselves from adversaries are required. Such systems are called self-protecting systems and aim to identify, analyse and mitigate threats autonomously. This thesis contributes two approaches towards the goal of providing systems with self-protection capabilities.

    The first approach aims to enhance the security of architecture-based selfadaptive systems and equip them with (proactive) self-protection capabilities that reduce the exposed attack surface. We target systems where information about the system components and its adaptation decisions is available, and control over its adaptation is also possible. We formally model the security of the system and provide two methods to analyze its security that help us rank adaptations in terms of their security level: a method based on quantitative risk assessment and a method based on probabilistic verification. The results indicate an improvement to the system security when either of our solutions is employed. However, only the second method can provide self-protecting capabilities. We have identified a direct relationship between security and performance overhead, i.e., higher security guarantees impose analogously higher performance overhead.

    The second approach targets open decentralized systems where we have limited information about and control over the system entities. Therefore, we attempt to employ decentralized information flow control mechanisms to enforce security by controlling interactions among the system elements. We extend a classical decentralized information flow control model by incorporating trust and adding adaptation capabilities that allow the system to identify security threats and self-organize to maximize the average trust between the system entities. We arrange entities of the system in trust hierarchies that enforce security policies among their elements and can mitigate security issues raised by the openness and uncertainty in the context and environment, without the need for a trusted central controller. The experiment results show that a reasonable level of trust can be achieved and at the same time confidentiality and integrity can be enforced with a low impact on the throughput and latency of messages exchanged in the system.

    Fulltekst (pdf)
    Licentiate Thesis (Comprehensive Summary)
    Download (jpg)
    Front Page
  • 3.
    Hönel, Sebastian
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för datavetenskap och medieteknik (DM).
    Efficient Automatic Change Detection in Software Maintenance and Evolutionary Processes2020Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Software maintenance is such an integral part of its evolutionary process that it consumes much of the total resources available. Some estimate the costs of maintenance to be up to 100 times the amount of developing a software. A software not maintained builds up technical debt, and not paying off that debt timely will eventually outweigh the value of the software, if no countermeasures are undertaken. A software must adapt to changes in its environment, or to new and changed requirements. It must further receive corrections for emerging faults and vulnerabilities. Constant maintenance can prepare a software for the accommodation of future changes.

    While there may be plenty of rationale for future changes, the reasons behind historical changes may not be accessible longer. Understanding change in software evolution provides valuable insights into, e.g., the quality of a project, or aspects of the underlying development process. These are worth exploiting, for, e.g., fault prediction, managing the composition of the development team, or for effort estimation models. The size of software is a metric often used in such models, yet it is not well-defined. In this thesis, we seek to establish a robust, versatile and computationally cheap metric, that quantifies the size of changes made during maintenance. We operationalize this new metric and exploit it for automated and efficient commit classification.

    Our results show that the density of a commit, that is, the ratio between its net- and gross-size, is a metric that can replace other, more expensive metrics in existing classification models. Models using this metric represent the current state of the art in automatic commit classification. The density provides a more fine-grained and detailed insight into the types of maintenance activities in a software project.

    Additional properties of commits, such as their relation or intermediate sojourn-times, have not been previously exploited for improved classification of changes. We reason about the potential of these, and suggest and implement dependent mixture- and Bayesian models that exploit joint conditional densities, models that each have their own trade-offs with regard to computational cost and complexity, and prediction accuracy. Such models can outperform well-established classifiers, such as Gradient Boosting Machines.

    All of our empirical evaluation comprise large datasets, software and experiments, all of which we have published alongside the results as open-access. We have reused, extended and created datasets, and released software packages for change detection and Bayesian models used for all of the studies conducted.

    Fulltekst (pdf)
    Licentiate Thesis (Comprehensive Summary)
  • 4.
    Gunnarsson, Ingemar
    Linnéuniversitetet, Fakulteten för konst och humaniora (FKH), Institutionen för kulturvetenskaper (KV).
    En skandinavisk järnvägskontraktörs karriär i Indien 1860–1867: ackumulering av socialt och kulturellt kapital som framgångsstrategi i en kolonial kontext2020Licentiatavhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    This study is about Joseph Samuel Frithiof Stephens (1841–1934) and how he as a Scandinavian contractor acquired an economic fortune in the colonial India. The fortune was used for the acquisition of the mill property Huseby Bruk in Småland and also contributed to the Stephens family's strategy of advancing in the then Danish bourgeois class establishment. The study aims to present an individual actor's opportunities to achieve financial success through access to non-financial capital forms. Social capital in the form of important social relations and cultural capital in the form of information, skills, etc., can be used for transformation into economic capital. The identification and analysis of the personal networks that occurred in Joseph's career determines the importance of family networks and professional networks for access to the various alternative forms of capital. Joseph's career in British India in the 1850s and 60s was surrounded by the colonial power context linked to global capitalist progression and characterized by civilization ambitions, technological transfer and dominance. The aftermath of the Revolt 1857–1858 opened the playing field for wealth-seeking risk-takers from Europe. The power structures previously maintained by the East India Company were gradually replaced by the British central power apparatus. The new power relations established a new administration and altered social institutions in the emerging crown colony. The Indian railways became a significant element in the colonial intervention and consisted of trunk lines that crossed the subcontinent. The used source material in the form of private letters, diaries, business correspondence and more, constitutes the research basis for the studies, and are included in the India-related material stored in the Huseby Archives at Linnaeus University in Växjö, Sweden. The results of the study show that network contacts and access to alternative forms of capital became crucial success factors for Joseph Stephen's career and wealth accumulation. The networks were linked to both the private and traditional spheres as well as to the professional and rational spheres and sometimes seemed cross-border. The study has further demonstrated the structures, colonial thought patterns and hierarchies that the individual actor was actively related to, and that affected the often-strained everyday life of the contractor.

    Fulltekst (pdf)
    Licentiate Thesis (Fulltext)
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    Front Page
  • 5.
    Dutra Leivas, Ivonne
    Linnéuniversitetet, Fakulteten för konst och humaniora (FKH), Institutionen för kulturvetenskaper (KV).
    Stadsarkeologi, Förmedling och Skolan: Bortom historieämnets horisont2020Licentiatavhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    The title of this licentiate thesis is: Urban contract archaeology, public outreach and schools. Beyond the horizons of history teaching.  

    The aim of my licentiate thesis is to investigate how educational programs for schools are implemented within the framework of contract archaeology. I study the underlying incentives that motivate public outreach within contract archaeology, who carries out the outreach and what impact educational programs have on schools. My research project also aims to explore how public outreach within contract archaeology can be organized to meet schools´ demand for knowledge and activities. With an interdisciplinary approach, taken from archaeology and educational sciences, the goal is to instigate a dialogue between the scientific community and contract archaeology, as well as between contract archaeology and schools.

    As a primary goal, midway into in my doctoral degree, I have chosen in this licentiate thesis to study the practices of public outreach on urban excavation sites in Sweden, specifically studying outreach practices towards schools.

    The research queries in the licentiate thesis are:

     

    1. What are the purposes and objectives with public outreach in contract archaeology?
    2. What are the preconditions for working with public outreach in contract archaeology?
    3. How are the practices of public outreach aimed at schools conducted at urban excavation sites?
    4. How do educational programs within contract archaeology address the needs and goals of school education?

     

    Based on these queries, I also discuss how contract archaeology in the future can make possible broader collaborations with schools. This serves as an introduction to how archaeo-didactics can evolve bringing together contract archaeology's goals and potential in an educational situation, with the needs and goals of school education.

    Fulltekst (pdf)
    Licentiate Thesis (Fulltext)
    Download (jpg)
    Front Page
  • 6.
    Miao, Dingquan
    Linnéuniversitetet, Ekonomihögskolan (FEH), Institutionen för nationalekonomi och statistik (NS).
    Two Essays in Public Economics2020Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis consists of two self-contained essays.

     Essay I. 

    I compute how optimal income tax schedules optimally should be differentiated between immigrants and natives. I use a calibrated optimal tax model with heterogeneous labor supply elasticities across and within groups and employ Utilitarian and Rawlsian social welfare functions. As compared to an optimal tax system that treats both groups the same, the optimal differentiated tax system increases marginal tax rates for the majority of natives, with a decrease in the marginal tax rates of immigrants. However, there is not much redistribution between the groups.

     

    Essay II. (with Håkan Selin and Martin Söderström)

    Sweden introduced a phase-out of the earned income tax credit in 2016. As a consequence, taxpayers belonging to the top 5 percent of the earnings distribution, already facing high taxes, experienced a 7% reduction in their net-of-tax shares. While exploiting rich full-population administrative data up to 2017, we evaluate earnings responses to the reform. When graphically and econometrically comparing earnings growth at different segments of the distribution, we estimate a significant relative earnings reduction in the treatment group immediately appearing in 2016, and growing in 2017. The implied earnings elasticity is fairly low and around 0.1. We interpret the essential features of the response using a simulation model, in which people have noisy perceptions of the piece-wise linear tax code. To simulate the empirically observed response, we need to add more noise to perceptions than what is motivated by earnings uncertainty alone.

     

    Fulltekst (pdf)
    Licentiate Thesis (Fulltext)
    Download (jpg)
    Front Page
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