liu.seSearch for publications in DiVA
1 - 4 of 4
rss atomLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
  • Presentation: 2018-12-14 10:15 ACAS, A-huset, Linköping
    Wärner, Hugo
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    High-Temperature Fatigue Behaviour of Austenitic Stainless Steel: Influence of Ageing on Thermomechanical Fatigue and Creep-Fatigue Interaction2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The global energy consumption is increasing and together with global warming from greenhouse gas emission, create the need for more environmental friendly energy production processes. Higher efficiency of biomass power plants can be achieved by increasing temperature and pressure in the boiler section and this would increase the generation of electricity along with the reduction in emission of greenhouse gases e.g. CO2. The power generation must also be flexible to be able to follow the demands of the energy market, this results in a need for cyclic operating conditions with alternating output and multiple start-ups and shut-downs.

    Because of the demands of flexibility, higher temperature and higher pressure in the boiler section of future biomass power plants, the demands on improved mechanical properties of the materials of these components are also increased. Properties like creep strength, thermomechanical fatigue resistance and high temperature corrosion resistance are critical for materials used in the next generation biomass power plants. Austenitic stainless steels are known to possess such good high temperature properties and are relatively cheap compared to the nickel-base alloys, which are already operating at high temperature cyclic conditions in other applications. The behaviour of austenitic stainless steels during these widened operating conditions are not yet fully understood.

    The aim of this licentiate thesis is to increase the knowledge of the mechanical behaviour at high temperature cyclic conditions for austenitic stainless steels. This is done by the use of thermomechanical fatigue- and creepfatigue testing at elevated temperatures. For safety reasons, the effect of prolonged service degradation is investigated by pre-ageing before mechanical testing. Microscopy is used to investigate the microstructural development and resulting damage behaviour of the austenitic stainless steels after testing. The results show that creep-fatigue interaction damage, creep damage and oxidation assisted cracking are present at high temperature cyclic conditions. In addition, simulated service degradation resulted in a detrimental embrittling effect due to the deterioration by the microstructural evolution.

    List of papers
    1. Creep-Fatigue Interaction in Heat Resistant Austenitic Alloys
    Open this publication in new window or tab >>Creep-Fatigue Interaction in Heat Resistant Austenitic Alloys
    2018 (English)In: MATEC Web of Conferences 165 , 05001 (2018) / [ed] EDP Sciences, EDP Sciences, 2018, Vol. 165Conference paper, Published paper (Refereed)
    Place, publisher, year, edition, pages
    EDP Sciences, 2018
    National Category
    Materials Engineering
    Identifiers
    urn:nbn:se:liu:diva-148182 (URN)10.1051/matecconf/2018165505001 (DOI)
    Conference
    Fatigue 2018 , 12th International Fatigue Congress, 27 May-1 June 2018, Poitiers, France
    Available from: 2018-06-01 Created: 2018-06-01 Last updated: 2018-11-27
  • Presentation: 2018-12-18 10:15 Ada Lovelace, B-huset, Linköping
    Albrektsson, Jörgen
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Optimisation of Off-Road Transport Missions2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Mines, construction sites, road construction and quarries are examples of applications where construction equipment are used. In a production chain consisting of several construction machines working together, the work needs to be optimised and coordinated to achieve an environmental friendly, energy efficient and productive production. Recent rapid development within positioning services, telematics and human machine interfaces (HMI) opens up for control of individual machines and optimisation of transport missions where several construction machines co-operate.

    The production chain on a work site can be split up in different sub-tasks of which some can be transport missions. Taking off in a transport mission where one wheel loader ("loader" hereinafter) and two articulated haulers ("haulers" hereinafter) co-operate to transport material at a set production rate [ton/h], a method for fuel optimal control is developed. On the mission level, optimal cycle times for individual sub-tasks such as wheel loader loading, hauler transport and hauler return, are established through the usage of Pareto fronts.

    The haulers Pareto fronts are built through the development of a Dynamic Programming (DP) algorithm that trades fuel consumption versus cycle time for a road stretch by means of a time penalty constant. Through varying the time penalty constant n number of times, discrete fuel consumption - cycle time values can be achieved, forming the Pareto front. At a later stage, the same DP algorithm is used to generate fuel optimal vehicle speed and gear trajectories that are used as control signals for the haulers. Input to the DP algorithm is the distance to be travelled, road inclination, rolling resistance coefficient and a max speed limit to avoid unrealistic optimisation results.

    Thus, a method to describe the road and detect the road related data is needed to enable the optimisation. A map module is built utilising an extended Kalman Filter, Rauch-Tung-Striebel smoother and sensor fusion to merge data and estimate parameters not observable by sensors. The map module uses a model of the vehicle, sensor signals from a GPS or GNSS sensor and machine sensors to establish a map of the road.

    The wheel loader Pareto front is based on data developed in previous research combined with Volvo in-house data. The developed optimisation algorithms are implemented on a PC and in an interactive computer tablet based system. A human machine interface is created for the tablet, guiding the operators to follow the optimal control signals, which is speed for the haulers and cycle time for the loader. To evaluate the performance of the system it is tested in real working conditions.

    The contributions develop algorithms, set up a demo mission control system and carry out experiments. Altogether rendering in a platform that can be used as a base for a future design of an off-road transport mission control system.

    List of papers
    1. Road estimation and fuel optimal control of an off-road vehicle
    Open this publication in new window or tab >>Road estimation and fuel optimal control of an off-road vehicle
    2017 (English)In: Proceedings of the 3rd International Conference on Vehicle Technology and Intelligent Transport Systems, SciTePress, 2017, p. 58-67Conference paper, Published paper (Refereed)
    Place, publisher, year, edition, pages
    SciTePress, 2017
    National Category
    Control Engineering
    Identifiers
    urn:nbn:se:liu:diva-142731 (URN)10.5220/0006247200580067 (DOI)978-989-758-242-4 (ISBN)
    Conference
    3rd International Conference on Vehicle Technology and Intelligent Transport Systems, VEHITS 2017, April 22-24, 2017, in Porto, Portugal
    Available from: 2018-04-03 Created: 2018-04-03 Last updated: 2018-11-22
    2. Fuel Optimal Control of an Articulated Hauler Utilising a Human Machine Interface
    Open this publication in new window or tab >>Fuel Optimal Control of an Articulated Hauler Utilising a Human Machine Interface
    2019 (English)In: Smart Cities, Green Technologies, and Intelligent Transport Systems / [ed] Donnellan, Brian; Klein, Cornel; Helfert, Markus; Gusikhin, Oleg; Pascoal, António, Springer International Publishing , 2019, p. 190-208Conference paper, Published paper (Refereed)
    Abstract [en]

    Utilising optimal control presents an opportunity to increase the fuel efficiency in an off-road transport mission conducted by an articulated hauler. A human machine interface (HMI) instructing the hauler operator to follow the fuel optimal vehicle speed trajectory has been developed and tested in real working conditions. The HMI implementation includes a Dynamic Programming based method to calculate the optimal vehicle speed and gear shift trajectories. Input to the optimisation algorithm is road related data such as distance, road inclination and rolling resistance. The road related data is estimated in a map module utilising an Extended Kalman Filter (EKF), a Rauch-Tung-Striebel smoother and a data fusion algorithm. Two test modes were compared: (1) The hauler operator tried to follow the optimal vehicle speed trajectory as presented in the HMI and (2) the operator was given a constant target speed to follow. The objective of the second test mode is to achieve an approximately equal cycle time as for the optimally controlled transport mission, hence, with similar productivity. A small fuel efficiency improvement was found when the human machine interface was used.

    Place, publisher, year, edition, pages
    Springer International Publishing, 2019
    Series
    Communications in Computer and Information Science book series (CCIS), ISSN 1865-0929, E-ISSN 1865-0937 ; 921
    Keywords
    Off-road, Construction equipment, Human machine interface, Optimal control, Dynamic programming, Kalman filters
    National Category
    Vehicle Engineering
    Identifiers
    urn:nbn:se:liu:diva-153311 (URN)10.1007/978-3-030-02907-4_10 (DOI)978-3-030-02906-7 (ISBN)978-3-030-02907-4 (ISBN)
    Conference
    6th International Conference, SMARTGREENS 2017 and Third International Conference, VEHITS 2017, Porto, Portugal, April 22–24, 2017
    Available from: 2018-12-12 Created: 2018-12-12 Last updated: 2018-12-12
    3. Fuel optimal control of an off-road transport mission
    Open this publication in new window or tab >>Fuel optimal control of an off-road transport mission
    2018 (English)In: 2018 IEEE International Conference on Industrial Technology (ICIT), 2018, p. 175-180Conference paper, Published paper (Refereed)
    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-151856 (URN)10.1109/ICIT.2018.8352172 (DOI)978-1-5090-5949-2 (ISBN)
    Conference
    2018 IEEE International Conference on Industrial Technology (ICIT), 19-22 Feb.,Lyon, France
    Available from: 2018-10-06 Created: 2018-10-06 Last updated: 2018-11-22
  • Presentation: 2018-12-19 10:15 Alan Turing, E-huset, Linköping
    Falkenjack, Johan
    Linköping University, Department of Computer and Information Science, Human-Centered systems. Linköping University, Faculty of Science & Engineering.
    Towards a Model of General Text Complexity for Swedish2018Licentiate thesis, monograph (Other academic)
    Abstract [en]

    In an increasingly networked world, where the amount of written information is growing at a rate never before seen, the ability to read and absorb written information is of utmost importance for anything but a superficial understanding of life's complexities. That is an example of a sentence which is not very easy to read. It can be said to have a relatively high degree of text complexity. Nevertheless, the sentence is also true. It is important to be able to read and understand written materials. While not everyone might have a job where they have to read a lot, access to written material is necessary in order to participate in modern society. Most information, from news reporting, to medical information, to governmental information, come primarily in a written form.

    But what makes the sentence at the start of this abstract so complex? We can probably all agree that the length is part of it. But then what? Researches in the field of readability and text complexity analysis have been studying this question for almost 100 years. That research has over time come to include many computational and data driven methods within the field of computational linguistics.

    This thesis cover some of my contributions to this field of research, though with a main focus on Swedish rather than English text. It aims to explore two primary questions (1) Which linguistic features are most important when assessing text complexity in Swedish? and (2) How can we deal with the problem of data sparsity with regards to complexity annotated texts in Swedish?

    The first issue is tackled by exploring the task of identifying easy-to-read ("lättläst") text using classification with Support Vector Machines. A large set of linguistic features is evaluated with regards to predictive performance and is shown to separate easy-to-read texts from regular texts with a very high accuracy. Meanwhile, using a genetic algorithm for variable selection, we find that almost the same accuracy can be reached with only 8 features. This implies that this classification problem is not very hard and that results might not generalize to comparing less easy-to-read texts.

    This, in turn, brings us to the second question. Except for easy-to-read labeled texts, the data with text complexity annotations is very sparse. It consist of multiple small corpora using different scales to label documents. To deal with this problem, we propose a novel statistical model. The model belongs to the larger family of Probit models and is implemented in a Bayesian fashion and estimated using a Gibbs sampler based on extending a well established Gibbs sampler for the Ordered Probit model. This model is evaluated using both simulated and real world readability data with very promising results.

  • Presentation: 2019-02-15 13:15 K2, Kåkenhus, Norrköping
    Ågren, Axel
    Linköping University, Department of Social and Welfare Studies, Division Ageing and Social Change. Linköping University, Faculty of Arts and Sciences.
    Loneliness among older people in the Swedish media: Constructions, discourses and the designation of responsibility2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Feelings of belonging or not belonging to other people are commonly seen as an essential and universal part of human existence. How loneliness is talked about and understood is, however, found to differ depending on historical, cultural and societal contexts. Today, there are intense discussions on loneliness among older people in the Swedish news-press. Constructions within mass media and - in this licentiate thesis - news-press are found to have a significant influence on how older people evaluate their own life and how older people are treated by the surrounding society. Research with this focus is, however, scarce despite the large amount of studies on loneliness and despite research on constructions of older people within mass media being a frequently addressed issue for ageing research. The aim of this thesis is to explore how loneliness among older people is constructed and how the responsibility for reducing loneliness is designated within the Swedish news-press.

    In Paper 1 the empirical material consisted of 94 news-press articles from the years 2013-2014. The prime finding was that loneliness was not the main focus in the articles from the Swedish news-press. The concept was used more to motivate the need for political change, enhancing the importance of volunteer work and described as a risk factor within research reports. The material analysed in Paper 2 consisted of 40 news-press articles from October 2016. The responsibility for reducing loneliness among older people was found to be designated between welfare state institutions on different levels. Institutions and political parties both defend the planned or performed measures to reduce loneliness, but also admit to not doing enough in this regard. Older people were found to be constructed as recipients of activities for reducing loneliness, and the “we” in “society” were those who should perform activities in order to reduce loneliness among older people.

    The main overall finding of the thesis is that loneliness was not the main focus in the articles from Swedish news-press. Instead, loneliness was used as a motive for political change and to enhance the value of volunteer work. Furthermore, loneliness among older people is understood as a problem that needs to be solved. The contexts and logics of the mass media were found to have an influence on how loneliness among older people was constructed, as the issue was mainly addressed in local debate articles with ambitions of achieving change.

    List of papers
    1. What are we talking about?: Constructions of loneliness among older people in the Swedish news-press
    Open this publication in new window or tab >>What are we talking about?: Constructions of loneliness among older people in the Swedish news-press
    2017 (English)In: Journal of Aging Studies, ISSN 0890-4065, E-ISSN 1879-193X, Vol. 41, p. 18-27Article in journal (Refereed) Published
    Abstract [en]

    Loneliness among older people is an issue that engages the general public and various professions and organizations in contemporary Swedish society. One public arena where this engagement is particularly evident is within the Swedish news-press, where articles on loneliness among older people are frequently published. Loneliness is commonly perceived as significantly related to ageing and older people. In addition, the mass media is considered to have a crucial influence in shaping general perceptions of older people. The aim of this study is to examine how loneliness among older people is constructed in the Swedish news-press and whether there is a prevailing “loneliness discourse” within this context. The empirical material consists of 94 articles from the Swedish news-press from the years 2013–2014. Two dominating discourses was found. Loneliness — within the discourse of eldercare, politics and the welfare society, is primarily written about in news articles and debate articles by a variety of authors, such as politicians and representatives from organizations. Within this discourse, loneliness is utilized as a concept to motivate the need for political change and the allocations of resources and to amplify deficiencies within eldercare, politics and the welfare society. The second discourse, Loneliness — within the discourse of volunteer work, is addressed in reportage articles written by journalists. In this discourse focus was on depicting volunteers and enhancing the importance of volunteer work. Here, loneliness serves as a motive for performing volunteer work. In addition, the discourse of Research reports on older people's health was found, although less significant compared to the two major discourses. Within this discourse ageing is presented as a risk, where loneliness is one of these risk factors. Despite some minor differences, loneliness, within all three discourses, is given the meaning of being a problem that needs to be solved. A central finding in this study is that focus in the articles, from Swedish news-press, is not mainly on loneliness but rather on eldercare, politics and the welfare state, volunteer work and health among older people. Loneliness is, consequently, used as a concept to motivate the need for political change and the allocation of resources for older people, to enhance the values of volunteer work and to emphasize the risks associated with ageing.

    Place, publisher, year, edition, pages
    Elsevier, 2017
    Keywords
    Loneliness, Older people, Mass media, Discourse theory
    National Category
    Social Sciences Interdisciplinary
    Identifiers
    urn:nbn:se:liu:diva-136131 (URN)10.1016/j.jaging.2017.03.002 (DOI)000404490400003 ()28610751 (PubMedID)
    Note

    Fundingagencies: Norrkepingsfonden [KS 2013/0721]

    Available from: 2017-03-28 Created: 2017-03-28 Last updated: 2018-12-13Bibliographically approved
    2. Reducing loneliness among older people – who is responsible?
    Open this publication in new window or tab >>Reducing loneliness among older people – who is responsible?
    (English)In: Ageing & Society, ISSN 0144-686X, E-ISSN 1469-1779Article in journal (Refereed) Epub ahead of print
    Abstract [en]

    In the Swedish news-press, loneliness among older people is presented as a severe problem that needs to be solved. The issue of who is responsible for reducing loneliness and how this responsibility is designated is, however, rarely discussed. In this study, we have analysed how responsibility is designated and constructed in articles from the Swedish news-press. Focus has been on identifying responsibility in discourses proceeding from the concept of subject positions. This concept has enabled analysis on how responsibility is negotiated and who is positioned as a responsible actor with the ability to perform actions that reduce loneliness. Three dominating discourses were found. In the discourse of responsibility within politics and the welfare state, the responsibility is both self-taken and designated to other institutions held responsible for not initiating sufficient measures to reduce loneliness. In the discourse of responsibility within societal and evolutionary perspectives on loneliness, developments beyond the individual's control are considered to contribute to loneliness. At the same time ‘we’ in ‘society’ are considered capable of reducing loneliness, thereby constructing individuals as responsible actors. Within the discourses of responsibility within senior organisations, both senior organisations and people who participate in activities are constructed as responsible actors. In conclusion, the responsibility for reducing loneliness is, apart from the discourse on senior organisations, designated to those working with older people.

    Place, publisher, year, edition, pages
    Cambridge: Cambridge University Press
    Keywords
    loneliness, responsibility, news-press, subject positions, discourses
    National Category
    Social Sciences Interdisciplinary
    Identifiers
    urn:nbn:se:liu:diva-153334 (URN)10.1017/S0144686X18001162 (DOI)
    Available from: 2018-12-13 Created: 2018-12-13 Last updated: 2018-12-13