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  • 201. Abermann, S.
    et al.
    Sjoblom, G.
    Efavi, J.
    Lemme, Max C.
    AMO GmbH, AMICA, Aachen, Germany.
    Olsson, J.
    Bertagnolli, E.
    Comparative study on the impact of TiN and Mo metal gates on MOCVD-grown HfO2 and ZrO2 high-kappa dielectrics for CMOS technology2007In: Physics of Semiconductors, Pts A and B, 2007, p. 293-294Conference paper (Refereed)
    Abstract [en]

    We compare metal oxide semiconductor capacitors, investigating Titanium-Nitride and Molybdenum as gate materials, as well as metal organic chemical vapor deposited ZrO2 and HfO2 as high-kappa dielectrics, respectively. The impact of different annealing steps on the electrical characteristics of the various gate stacks is a further issue. The positive effect of post metallization annealing in forming gas atmosphere as well as observed mid-gap pinning of TiN and Mo metal gates is presented.

  • 202.
    Abeywardana, Asela M.A.J.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Solar-Biomass hybrid system for process heat supply in medium scale hotels in Sri Lanka2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This study aimed at evaluating and demonstrating the feasibility of using Concentrated Solar Thermal technology combined with biomass energy technology as a hybrid renewable energy system to supply the process heat requirements in small scale industries in Sri Lanka. Particularly, the focus was to apply the concept to the expanding hotel industry, for covering the thermal energy demand of a medium scale hotel.

    Solar modules utilize the rooftop area of the building to a valuable application. Linear Fresnel type of solar concentrator is selected considering the requirement of the application and the simplicity of fabrication and installation compared to other technologies. Subsequently, a wood-fired boiler is deployed as the steam generator as well as the balancing power source to recover the effects due to the seasonal variations in solar energy. Bioenergy, so far being the largest primary energy supply in the country, has a good potential for further growth in industrial applications like small hotels. 

    When a hotel with about 200-guests capacity and annual average occupancy of 65% is considered, the total annual CO2 saving is accounted as 207 tons compared with an entirely fossil fuel (diesel) fired boiler system. The annual operational cost saving is around $ 40,000 and the simple payback period is within 3-4 years. The proposed hybrid system can generate additional 26 employment opportunities in the proximity of the site location area.  

    This solar-biomass hybrid concept mitigates the weaknesses associated with these renewable technologies when employed separately. The system has been designed in such a way that the total heat demand of hot water and process steam supply is managed by renewable energy alone. It is thus a self-sustainable, non-conventional, renewable energy system. This concept can be stretched to other critical medium temperature applications like for example absorption refrigeration. The system is applicable to many other industries in the country where space requirement is available, solar irradiance is rich and a solid biomass supply is assured.

  • 203. Abeyweera, Ruchira
    et al.
    Senanayake, Nihal S.
    Senaratne, Chamindie
    Jayasuriya, Jeevan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. EIT InnoEnergy, Sweden.
    Fransson, Torsten H.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. EIT InnoEnergy, Sweden.
    Capacity Building Through a Web Based Master Degree Programme in Sustainable Energy Engineering2017In: PROCEEDINGS OF 2017 IEEE GLOBAL ENGINEERING EDUCATION CONFERENCE (EDUCON2017), IEEE, 2017, p. 800-805Conference paper (Refereed)
    Abstract [en]

    Open Distance Learning is gaining popularity as a successful alternative for on-campus higher education especially with the emergence of web based platforms which enable the online delivery of courses worldwide. This emerging educational pedagogy can successfully be employed as means of capacity building of the people living in the less fortunate parts of the world where higher education especially at master level are scarce. This paper presents a two-year collaborative master study programme in sustainable energy engineering offered in synchronous with an on-campus study programme conducted by the KTH Royal Institute of Technology of Sweden, to students of Sri Lanka, which was facilitated by the Open University of Sri Lanka. The paper describes the need of such a programme, the format of course delivery and assessment thereof, plus the benefits gained. This programme has produced 72 post graduates in Sri Lanka alone and more than 200 distant postgraduates worldwide in the field of sustainable energy engineering during last 10 years period. In terms of capacity building in the energy sector in Sri Lanka this is considered a great achievement. The experience gained by the local staff in the role of local facilitators who engaged in some of the academic related activities such as evaluation of students' presentation and co-supervision of thesis projects have been greatly appreciated as being additional benefits to the staff in terms of their own academic development and capacity building. Finally, conclusions are made on how remote programmes of study could successfully be delivered to places where such know-how is scarce by adapting appropriate technologies in training personnel at postgraduate level to meet the needs of the industry.

  • 204. Abeywickrama, Sandu
    et al.
    Furdek, Marija
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Monti, Paolo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Wong, Elaine
    Protecting core networks with dual-homing: A study on enhanced network availability, resource efficiency, and energy-savings2016In: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 381, p. 327-335Article in journal (Refereed)
    Abstract [en]

    Core network survivability affects the reliability performance of telecommunication networks and remains one of the most important network design considerations. This paper critically examines the benefits arising from utilizing dual-homing in the optical access networks to provide resource-efficient protection against link and node failures in the optical core segment. Four novel, heuristic-based RWA algorithms that provide dedicated path protection in networks with dual-homing are proposed and studied. These algorithms protect against different failure scenarios (i.e. single link or node failures) and are implemented with different optimization objectives (i.e., minimization of wavelength usage and path length). Results obtained through simulations and comparison with baseline architectures indicate that exploiting dual-homed architecture in the access segment can bring significant improvements in terms of core network resource usage, connection availability, and power consumption.

  • 205.
    Abhijeet, Kumar
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630).
    Governing water pollution effectively: A comparative study of legal frameworks & their implementation in India & Sweden.2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Case studies from India have shown that the legal regime governing water pollution control in India has miserably failed. Sectoral approach to water management is quite evident. On the other hand Sweden has shown a remarkable change with regard to environment management. The poor management of a resource makes the resource further poor. Thus effective management of the resources becomes crucial. Good governance has been vital in conservation of a resource. But the issue is what constitutes good governance with respect to water? Law has always played a steering role in governance aspect. But despite having pollution control laws the effective governance of water pollution has not been attainable in India. Are the pollution control laws fundamentally wrong or some other factors prevail which is beyond the reach of law to control the pollution problem. The thesis which is a comparative study of legal framework and their implementation in India and Sweden attempts to explore how control of water pollution has been effectively governed in Sweden and what needs to been done in India.

  • 206.
    Abid, Fahim
    et al.
    KTH.
    Ghorbani, Hossein
    Pourrahimi, Amir Masoud
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Edin, Hans Ezz
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Differences in morphology and polarization properties of heat-treated XLPE and LDPE insulation2016In: 2016 IEEE CONFERENCE ON ELECTRICAL INSULATION AND DIELECTRIC PHENOMENA (IEEE CEIDP), IEEE conference proceedings, 2016, p. 113-116Conference paper (Refereed)
    Abstract [en]

    Cross-linked polyethylene (XLPE) is the most commonly used insulating material for extruded high voltage cable applications. Degassing is a heat-treatment process that is performed to remove methane from XLPE insulation which is formed during the crosslinking reactions as a by-product. Apart from removing methane, heat-treatment influences the electrical properties through changing the morphology due to annealing and also removal of polar crosslinking by-products. Scanning electron microscopy (SEM) is generally used to observe the changes in crystalline structure of the polymer. Frequency domain spectroscopy (FDS) is widely used to study polarization properties of dielectric materials. In this study these two methods are used for a comparative analysis of XLPE and LDPE subjected to different heat-treatment time, with or without a diffusion barrier. Electrical measurements are performed at room temperature. From the SEM imaging conducted after permanganate acid etching, formation of spherulites due to heat-treatment is not obvious in neither LDPE nor in XLPE. However, distinctions between LDPE and XLPE in SEM micrographs are evident. From studies with dielectric polarization spectroscopy, it is found that the LDPE samples are less sensitive to heat-treatment in comparison to the XLPE samples while dissipation factor of XLPE samples are influenced by the choice of pressing film used during sample preparation.

  • 207.
    Abid, Muhammad
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.).
    Global Supply Chain Design: Exploring configurational and coordination factors2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis addresses the topic of global supply chain design. One major challenge concerns how to manage the tension between separation and integration pertaining to the localization of business activities. In this regard Ferdows (2008) worked to create two new production network models (rooted production network and footloose production network). Earlier studies have highlighted the choices that are involved in the network of facilities but lack in providing a comprehensive picture in terms of both configurational and coordination factors that govern the design of global supply chain. There is a need for a conceptual model where factors affecting the design process of a global supply chain can be applied. Two main research questions have been addressed in this study. First, exploring and identifying the factors affecting global supply chain design. Second, investigating the factors that influence the position on the spectrum of rooted and footloose supply chain design.      

    A literature review analysis and multi-case studies have been performed for this study in order to explore the factors. The companies were selected in order to reflect upon the two types of network, i.e., rooted and footloose. The primary data were selected through interviews with the managers.

    This study highlighted that there are many factors that affect configurational and coordination decision areas within a global supply chain. This study categorized the factors and the configurational/coordination decision areas with two main competitive priorities, i.e., cost and differentiation in the form of a “conceptual model.” The study also highlighted the factors in a matrix, which showed their position on the spectrum of rooted and footloose network configurations. For instance, the coordination factors that drive towards a footloose network include: high orchestration capabilities, need access to new technology and knowledge, proximity to suppliers, etc. The configurational factors that drive towards a rooted network include: economic stability, proximity to market, concerns for sustainability issues, high transportation cost, need for high proximity between key functions, need for intellectual property rights protection, etc.

  • 208.
    Abid, Muhammad
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.). Högskolan i Gävle, Sweden.
    Relationship between competitive priorities and global supply chain design: A conceptual frameworkManuscript (preprint) (Other academic)
  • 209.
    Abid, Muhammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.). Högskolan i Gävle, Sweden.
    Bengtsson, Lars
    Dabhilkar, Mandar
    Factors affecting shifts in global supply chain networks: A configurational approach2013In: Proceedings of the 20th International Annual EurOMA conference, Dublin, Ireland, 9-12 June 2013, 2013, 2013Conference paper (Refereed)
    Abstract [en]

    In certain situations, global companies strive to take advantage of short-term changes in economic and exchange rates on the never-ending journey of competitiveness. This paper seeks to extend Ferdows’s (2008) production network models by adding the factors affecting shifts between rooted and footloose network configurations. Two companies were selected in order to illustrate the models and reveal other possible factors. The identified factors are differentiated in terms of configuration and coordination and merged in a matrix. The trends and implications on global supply chains are also discussed.

  • 210.
    Abid, Muhammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.). Högskolan i Gävle, Sweden.
    Bengtsson, Lars
    Hellberg, Roland
    Dabhilkar, Mandar
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.).
    Factors affecting global supply chain design2012Conference paper (Refereed)
    Abstract [en]

    Due to the limited existing knowledge pertaining to the factors which govern localization of operations and capabilities in a global supply chain, the purpose of the paper is to find out which factors and how they jointly affect the design of global supply chains. The relevant literature is reviewed and a concept matrix is developed. Five companies were selected in order to illustrate the issues of global supply chain design. Among them, three companies are considered to have efficient supply chain and less complex products, while the two others are considered to have responsive supply chain and more complex products. The issues discussed with the selected companies cover global sourcing, challenges, technological advancement and issues related to management control. The study identifies about fifty factors that affect global supply chain design, and specifically how theses relate to design decisions on location of factories and production, supplier selection and development, distribution of products and organisation of interfaces along the supply chain. The discrepancies between theory and practice as well as the implications for further research are discussed.

  • 211.
    Abolafya, Natan
    KTH, School of Information and Communication Technology (ICT).
    Secure Documents Sharing System for Cloud Environments2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    With the current trend of cloud services available in every market area in IT business, it is somewhat surprising that security services are not migrated to the cloud widely. Security as a Service (SECaaS) model is hardly popular at the moment even though the infrastructure of the cloud, or web, can support most of the functionalities of conventional distributed security services.

    Another uncommon phenomenon in the cloud is sharing secure files with multi-tenant support. This kind of service would be best available integrated with a SECaaS platform that may offer more similar application services. This thesis proposes, studies, designs, develops and evaluates a Secure Documents Sharing System for Cloud Environment with the possibility of integrating to a SECaaS platform.

  • 212.
    Abou Jaoudeh, Elie
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Developement of Optimization Method/A Tool for RE applications in Intermittent Grids with focus on Lebanon2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Renewable energy applications require sound design and optimization of life cycle costs because they need upfront investments and as long as possible operating lifetimes are expected. Using modern tools for optimizing designs of grid-tied and autonomous plants allows investors to deploy these technologies while keeping risks within acceptable limits.

    Nevertheless in Lebanon, the grid is intermittent and the most adapted solutions are dual-mode plants that can operate autonomously and with grid-tie. There are no existent simulation models particularly adapted to optimize these applications for such a situation. The objective of this research is to suggest and test a model adapted from commercially available software that can simulate the particular conditions of Lebanon. The studied solution has a PV generator associated with a PV charge controller, lead acid battery, a dual mode inverter, and transfer switchgear and protections. The research successfully met the objective of finding a setup in HOMER 2.68beta for simulating and optimizing a PV-Battery AC plant for an intermittent grid with scheduled blackouts.

    The setup and adaptation in HOMER is made to replicate an existing reference PV-Battery plant at a public school. The measured data from this public school is used to validate the results obtained from the adapted HOMER simulation. The grid is supplied for an average of 12 hours per day at the reference site with a tariff of USD 0.1/kWh.

    After the validation process, a sensitivity analysis is performed to simulate this plant under

    1. Different grid supply hours, 12 and 18 hours of supply daily
    2. Different grid electricity prices, USD 0.1 and 0.1375 /kWh
    3. Simulation of PV plants to meet other load profiles typical of community and municipality building centers

    All the simulations cross matched 20 different PV generator sizes to 7 different battery sizes for 5 different total setups.

    The levelized cost of electricity, COE, is the main parameter used to find the optimum setups, whereas options that shortened the battery life to less than 12 years or couldn’t meet at least 90% of the required yearly load were filtered out. The COE is calculated manually since several corrections related to grid and net-metering limitations are not obtained directly from HOMER.

    The simulated results can serve as a good indicator on how the systems would perform for typical public institutions in Lebanon, given the current conditions, and knowing that the range of this study is limited to small scale institutions with consumption levels less than 30 kWh/day. Storage capacity should also be limited to 100 kWh/day of useful storage, since batteries are not the best option to use for storage capacities higher than the mentioned limit.

    The setup has a great potential for advancement and acts as a first step for Lebanon to have a specialized tool for simulating the performance of PV-battery AC plants optimized for the conditions existing in the country. Future steps could be made to improve and diversify the software to include:

    • irradiation data that come from actual data logging data from other PV sites which are installed around the whole country, almost a 100
    • financial analysis for offsetting private generation with fossil fueled gensets, which is the main backup for electricity blackouts
    • wind turbine simulations, several installations are provisioned to be completed by the end of 2012, and it would be possible to carry out a similar validation process for small wind turbines
    • pollution and other environmental costs
    • value of lost load, “VOLL”, to compare different options in parallel with COE.

  • 213.
    Aboudi, U
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Altaie, K
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Solvärme i krypgrunder2009Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
  • 214.
    Aboudi, Ula
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Altaie, Kenan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Solvärme för krypgrunder2008Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
  • 215. Abouelhoda, Mohamed
    et al.
    Issa, Shady
    Center for Informatics Sciences, Nile University, Giza, Egypt.
    Ghanem, Moustafa
    Tavaxy: integrating Taverna and Galaxy workflows with cloud computing support.2012In: BMC Bioinformatics, ISSN 1471-2105, E-ISSN 1471-2105, Vol. 13Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Over the past decade the workflow system paradigm has evolved as an efficient and user-friendly approach for developing complex bioinformatics applications. Two popular workflow systems that have gained acceptance by the bioinformatics community are Taverna and Galaxy. Each system has a large user-base and supports an ever-growing repository of application workflows. However, workflows developed for one system cannot be imported and executed easily on the other. The lack of interoperability is due to differences in the models of computation, workflow languages, and architectures of both systems. This lack of interoperability limits sharing of workflows between the user communities and leads to duplication of development efforts.

    RESULTS: In this paper, we present Tavaxy, a stand-alone system for creating and executing workflows based on using an extensible set of re-usable workflow patterns. Tavaxy offers a set of new features that simplify and enhance the development of sequence analysis applications: It allows the integration of existing Taverna and Galaxy workflows in a single environment, and supports the use of cloud computing capabilities. The integration of existing Taverna and Galaxy workflows is supported seamlessly at both run-time and design-time levels, based on the concepts of hierarchical workflows and workflow patterns. The use of cloud computing in Tavaxy is flexible, where the users can either instantiate the whole system on the cloud, or delegate the execution of certain sub-workflows to the cloud infrastructure.

    CONCLUSIONS: Tavaxy reduces the workflow development cycle by introducing the use of workflow patterns to simplify workflow creation. It enables the re-use and integration of existing (sub-) workflows from Taverna and Galaxy, and allows the creation of hybrid workflows. Its additional features exploit recent advances in high performance cloud computing to cope with the increasing data size and complexity of analysis.The system can be accessed either through a cloud-enabled web-interface or downloaded and installed to run within the user's local environment. All resources related to Tavaxy are available at http://www.tavaxy.org.

  • 216.
    Aboufazeli, N.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Production Systems.
    Semere, D.T.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Production Systems.
    Ease of Reconfigurability Index: For Evaluation of the Reconfigurable Machine Tools2012Conference paper (Refereed)
    Abstract [en]

    One of the latest developments in manufacturing systems is reconfigurable manufacturing systems in which reconfigurable machine tools are the heart of such systems. The aim of application of this type of machine tool is having rapid cost-effective responsiveness to changes in new product variants or volume in manufacturing companies because of different interests, needs and desires of customers in global competitive market. The important tools to implement this kind of systems are systematic methodologies and enablers like open architecture controllers, Interface standard and comprehensive and integrated software to make the couple of limited optimized configurations of the machine tool. To choose the best configuration among proposed configuration by the software we need some evaluation methods based on smart chosen criteria to choose the best modular machine tool structure. One of the important points to choose the best configuration is ease of reconfigurability. The aim of this paper is to introduce a flexible and practical index for different products in reconfigurable manufacturing systems. This Index is defined based on two important factors: number of the changeable modules and the complexity of the interfaces including mechanical, informational and power (hydraulic, pneumatic or electrical).Generally the more number of the modules and the more complex interfaces means the more difficult to reconfigure the machine tool structure.

  • 217.
    Aboufazeli, Nasser
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Reconfigurable Machine Tools Design Methodologies and Measuring Reconfigurability for Design Evaluation2012Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 218.
    Aboutalebi, Ghareman
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Optimering av fackverksstolpar med konisk eller parallell form2005Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 219.
    Abouzari, Sara
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Solid solution strengthening effect on creep strength of austenitic stainless steel2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Sanicro 25 is a newly developed austenitic stainless steel, designed for the next generation of Ultrasupercritical coal-fired boilers in electrical power plants. This material is applicable in reheater and superheater tubes, where the material temperature is up to 700

    °C. One of the main strengthening mechanisms in high temperature materials is solid solution strengthening. A combination of this mechanism and precipitation hardening, promotes creep strength of heat resistance materials. The aim of this work was to characterize the effects of solid solution strengthening on creep strength of Sanicro 25.Previous works has been done for effects of phosphorous in copper and also for influence of laves phase on the creep properties of CrMo alloys. The results of these two works are used and the model is adapted to austenitic stainless steel. First a Zero starting state was defined which was Alloy 316H and then the calculation was made for Sanicro 25. Thermodynamic calculations were made using DICTRA and Thermo-Calc. Elastic misfit parameter was determined using ab initio calculations. The results from the simulation in this work indicate that solutes with larger size misfit compare to the parent atoms have better solid solution strengthening effect. A decrease in the creep strength by increasing temperature has been observed which could be attributed to growth of laves phase.

  • 220. Abou-Zleikha, Mohamed
    et al.
    Székely, Eva
    University College Dublin, Ireland.
    Cahill, Peter
    Carson-Berndsen, Julie
    Multi-level exemplar-based duration generation for expressive speech synthesis2012In: Proceedings of Speech Prosody, 2012, Vol. 2012Conference paper (Refereed)
    Abstract [en]

    The generation of duration of speech units from linguistic in- formation, as one component of a prosody model, is consid- ered to be a requirement for natural sounding speech synthesis. This paper investigates the use of a multi-level exemplar-based model for duration generation for the purposes of expressive speech synthesis. The multi-level exemplar-based model has been proposed in the literature as a cognitive model for the pro- duction of duration. The implementation of this model for dura- tion generation for speech synthesis is not straightforward and requires a set of modifications to the model and that the linguis- tically related units and the context of the target units should be taken into consideration. The work presented in this paper implements this model and presents a solution to these issues through the use of prosodic-syntactic correlated data, full con- text information of the input example and corpus exemplars. 

  • 221.
    Abraham, Adonai
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Göranson, Max
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Att tänka utanför arket: En kartläggning över samarbeten som lett till produktinnovationer inom svensk pappers- och massaindustri 2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    During the last decade has the market for printing paper begun to decline. The introduction of the smart phones and tablets quickly became a disturbing factor for the printing paper companies. This has forced the product development in the Swedish pulp and paper companies, to a greater extent, to look at more radical innovations. This requires the exploration of new applications and possibilities for the forest resource, an approach that requires expertise beyond what the companies possess internally.

    This study aims to investigate various forms of collaboration within the Swedish pulp and paper industry to identify factors that have been and are successful for product innovations. The aim has also been to investigate whether there is a change in the character of collaborations in the last 25 years. The participating companies in the study were

    SCA, Södra Cell, Holmen/MoDo, Stora Enso, BillerudKorsnäs, and Rottneros, plus some of their collaboration companies.

    The results show that the forms of collaboration in which the Swedish forest industry cooperate have changed considerably. The industry has begun to seek more cooperation with other industries, while collaboration with competitors has decreased. It seems to have become more important to regulate collaborative agreements, primarily how the intangible resources, like patents, are distributed among the participants in collaborations.

    Another conclusion is that there is a link between collaboration and the success of a firm’s product innovation. Companies are dependent on external knowledge for the success of radical innovations and a broad knowledge base is preferable to best be able to generate product innovations. External knowledge could, for example, help companies increase their understanding of other or new markets and may thus be a way to find new uses for the valuable raw material forest offers.

    Key words: radical innovation, collaboration, Swedish pulp and paper industry

  • 222.
    Abraham, Benjamin
    et al.
    KTH, School of Chemical Science and Engineering (CHE).
    Hultgren, Marcus
    KTH, School of Chemical Science and Engineering (CHE).
    Ibert, Tommie
    KTH, School of Chemical Science and Engineering (CHE).
    Möller, Johan
    KTH, School of Chemical Science and Engineering (CHE).
    Termovåtstyrka i oblekt papper2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The wet strength unbleached paper displays after heat treatment is examined in this thesis in which the authors examine the underlying mechanisms of this phenomena by experiments on differently treated paper. Two wet strength mechanism theories are examined; Lignin working as a resin versus carbonyl bonds being the main driving force behind the wet strength after thermal treatment. The authors find that using oxygen bleaching does not increase the wet strength as it would if carbonyl bonds were the main wet strength drivers, the results thus point towards the resin theory but further corroboration is needed before inference can be drawn.

  • 223.
    Abraham, Jonatan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Industrial Ecology.
    Strand, Anna
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Industrial Ecology.
    Reseavdrag: En analys av ett arbetsmarknadspolitiskt styrmedel ur ett hållbarhetsperspektiv2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The ability to make tax deductions on travel expenses have been present in Sweden since the late 1920s. The main purpose of the state subsidy has been to improve the mobility in the label market. However, in recent years there has been a heated debate as to if the subsidy is truly socio-economically sustainable or not. The favoritism of car users has also made the matter a question of ecological sustainability.

    The aim of this essay is to analyse and provide general knowledge of the swedish system of deductible travel expenses. The text is divided into four major parts:

    • A litterature review presenting the history of the subsidy, previous research, and the current political debate.
    • A questionnaire survey where the general public’s opinion of tax-deductible travel expenses is examined. 
    • A discussion of possible adjustments of the different parameters of the system, where the most optimal ammendment is chosen
    • An analysis of 3 different scenarios; keeping the current system, using the ammended system obtained in the calibration, and removing the system.

    From the results we could conclude that an ammended system would be noticeably more socio-economically viable and ecologically sustainable, compared with the current system. However, a complete removal of the system would be the most optimal. In addition, the questionnaire surveys results shows that the public is mostly positive to travel deductions. However, it was apparent that the views of many could shift completely, when presenting facts.

  • 224.
    Abrahamson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Fast calculation of the dimensioning factors of the railway power supply system2007In: Computational Methods and Experimental Measurements XIII, WIT Press, 2007, Vol. 46, p. 85-95Conference paper (Refereed)
    Abstract [en]

    Because of environmental and economical reasons, in Sweden and the rest of Europe, both personal and goods transports on railway are increasing. Therefore great railway infrastructure investments are expected to come. An important part of this infrastructure is the railway power supply system. Exactly how much, when and where the traffic will increase is not known for sure. This means investment planning for an uncertain future. The more uncertain parameters, such as traffic density and weight of trains, and the further future considered, the greater the inevitable amount of cases that have to be considered. When doing simulations concerning a tremendous amount of cases, each part of the simulation model has to be computationally fast - in real life this means approximations. The two most important issues to estimate given a certain power system configuration, when planning for an electric traction system, are the energy consumption of the and and the train delays that a too weak system would cause. In this paper, some modeling suggestions of the energy consumption and the maximal train velocities are presented. Two linear, and one nonlinear model are presented and compared. The comparisons regard both computer speed and representability. The independent variables of these models are a selection of parameters describing the power system, i.e.: power system technology used on each section, and traffic intensity.

  • 225.
    Abrahamsson, Anna-Carin
    KTH, School of Technology and Health (STH).
    Den fysiska arbetsmiljön i förskolan: utveckling, användning och granskning av en riskbedömningsmodell2016Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The occupational environment in preschool is becoming increasingly important. Occupational injury statistics show an increased incidence of illness among employees in education, health and care. Before action can be taken to improve the working environment, a careful assessment must be made and an action plan created. To include all possible components requires a comprehensive approach. Mapping of the physical work in Hudiksvall Municipality at all preschools provides a means by which to get an overall picture of risk areas within the preschool staff work environment.

    The aim of this work is to describe how the risk assessment model was developed and used with the ambition that it can be used in other municipalities. The model has been tested in Hudiksvall, on two occasions, in 2005 and 2010. The findings from the survey in 2010 are reported here and a comparison with 2005 is made.

    The risk assessment model is based on a survey with open questions for preschool staff combined with observation and assessment of ergonomics and safety engineer of 11 risk areas within the physical environment of the pre-school.

    The results of the survey give a clear picture of current health risks and can be used as a basis for the development of pre-school activities as well as improved maintenance of the municipal buildings. The results have also been communicated to the individual pre-schools to demonstrate their particular areas of risk.

    The combination of survey and professional assessment of several risk areas has been shown to enable a quick identification of possible causes of illness among pre-school staff. To report both positive and negative environmental factors has been an advantage. The clear method of reporting has facilitated decision-making on what if any actions to take. There is a continuing need to develop this and other instruments for the work environment survey of schools, health and social care.

  • 226.
    Abrahamsson, Cajsa
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Miljöpåverkan, hälsopåverkan och LCC för direktdrivna kontra växellådsdrivna vindkraftverk med avseende på deras innehåll av jordartsmetaller2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Vindkraftverk med olika magnetiseringsmetoder (elektromagneter eller permanentmagneter) och maskindriftstyper (direktdrift eller växellådsdrift) undersöks i denna rapport, gällande användningen av jordartsmetaller i dessa. I första delen av rapporten studeras miljö- och hälsopåverkan från jordartsmetallindustrin i den kinesiska provinsen Baotou. Detta då Baotou står för en stor del av försörjningen av jordartsmetaller till vindkraftverksindustrin. I den andra delen av rapporten undersöks skillnaderna i livscykelkostnader mellan vindkraftverk med olika generator- och maskindriftsystem. Rapporten innehåller informationssökningar om olika aspekter som berör dessa teman såsom exempelvis olika typer av vindkraftverksgeneratorer på marknaden, miljöpåverkan från olika ämnen i jordartsmineraler, återvinning av jordartsmetaller och processen från jordartsmineral till permanent-magnet. Informationen är främst inhämtad från vindkraftverkstillverkare, tekniska rapporter och artiklar.

    I miljö- och hälsoanalysen blev slutsatsen att den negativa påverkan från jordartsmetallindustrin i Kina var för omfattande för att användningen av jordartsmetaller skulle rättfärdigas ur ett etiskt och miljömässigt perspektiv. Gruvdriften och bearbetningen av jordartsmetaller har lett till stora utsläpp av skadliga ämnen, såsom exempelvis tungmetaller och radioaktivt avfall, i provinsen Baotou. Dessa har gett allvarliga negativa konsekvenser för djur, människor och växtlighet.

    Livscykelkostnaderna för vindkraftverk med olika generatorsystem beräknades med hjälp av LCC-metoden. Slutsatsen blev att det i dagsläget inte skiljde så mycket kostnadsmässigt i valet av maskindrifttyp eller magnetiseringsmetod. Enligt beräkningar ledde användningen av permanent-magneter inte till några ekonomiska fördelar. Istället var det kostnadsförhandlingar och osäkerhet i indata som gav de största kostnadsskillnaderna. Drift och underhållskostnaderna stod för de definitivt största utgifterna och investeringskostnaderna till generatorsystemen för de näststörsta utgifterna.

  • 227.
    Abrahamsson, Cajsa
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Carlberg, Marcus
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Studie i att ersätta kärnkraftsreaktor med biobränslealternativ2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This report contains a study of replacing nuclear power with biofuel. The nuclear plant, OKG north of Oskarshamn in Sweden has been chosen and an extensive literature study about the nuclear plant has been implemented. The main aspect of this report is the availability of biofuels and whether it would be economically sustainable. Sweden’s most common biofuels are examined with regard to scope of use and potential. In the economic analysis the investments and variable costs are investigated. To conclude the work the carbon emissions due to transports of biofuel are examined.The literature study on biofuels were discussed and resulted in that the project was defined towards woodchips. Due to several aspects the project focused on replacing OKG's oldest reactor O1. Furthermore the project focused on just electricity production and combustion with CFB-boilers. Due to the Economic analysis the plant will not be profitable in the current situation. The plant profitability was examined by the net present value method. With 2011s prices, a discount rate of 6 % and an initial investment of 5.78 billion SEK the economic analysis yielded a net present value of -3.53 billion SEK. A higher price of electricity or an alternate income, for example by district heating, would be required to make the plant profitable. It would require a price of electricity of 0.55 SEK/kWh to make the plant profitable. The carbon emission due to transports of biofuel for the new plant was estimated to 6 gram/kWh and this emission was higher than that for the reactor O1.

  • 228.
    Abrahamsson, Erik
    KTH, School of Biotechnology (BIO).
    Changing or improving the enantioselectivity of ω-transaminase towards (R)-amines, utilizing a semi-rational design approach2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis gives a brief insight on how protein engineering is made with ω-Transaminases - enzymes that are used to create chiral amines which are included in many pharmaceuticals, fine chemicals and agrochemicals - in order to find ω-Transaminase variants that have potential for scale up in industrial processes.

    Several ways to produce (S)-amines with ω-Transaminases exist today as most characterized ω-Transaminases are (S)-selective. The (R)-selective ω-Transaminases are in the other hand rare and in 2003, only 1 (R)-selective ω-Transaminases was known. In 2012, the group of Svedendahl Humble et al. to change the enantioselectivity for the substrate 2-aminotetralin from E = 3.9 (S) to E = 63 (R) by introducing two poiny mutations (F88A/A231F) in the active site of Chromobacterium violaceum ω-Transaminase.

    By using the same variant (F88A/A231F) as a starting template, two new residues in the active site were targeted for site directed mutagenesis that hopefully would give variatns with increased E-caalue for (R)-2-aminotetralin or with changed enantiopreference, frpm (S) to (R), for other stubstrates.

    This report covers most of the steps, starting from the rational design of the active site and ends up with screening and kinetics of the possible hits using one template substrate, 1-aminotetralin.

  • 229.
    Abrahamsson, Erik
    et al.
    KTH, School of Engineering Sciences (SCI).
    Svensson, Anton
    Design och konstruktion av experimentrigg: För planande skrov i lugnt vatten2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Den här rapporten är ett kandidatsexamensarbete vid Kungliga Tekniska Högskolan,KTH, för institutionen för Marina System. Arbetet utfördes på campus i Stockholm och experiment utfördes på GIH-Badet. Kandidatsexamensarbetet genomfördes mellan Jan 2016-Juni2016.Författarna skulle vilja ge ett stort tack till handledaren Mikael Razola för bra vägledning och stöd genom hela projektet där han hela tiden sett till attprojektet rört sig framåt och i rätt riktning. Hans feedback och snabba svar närfrågor uppstått samt hans input vid möten uppskattades enormt. Karl Garme tackas också för att han delade med sig av sin erfarenhet av projektplaneringoch också såg till att projektet rörde sig framåt med sitt övergripande ansvar för kandidatsexamensarbetet. Alla medstudenter som deltagit under kursens gång vill även tackas för feedback och diskussioner under seminarierna.Ett stort tack vill också ges till Björn Magnusson som hjälpte till med CNCfräsning av modellen och Monica Norrby för hennes tid med tips och tricks i labbet vid tillverkning av modellen.

  • 230.
    Abrahamsson, Felix
    KTH, School of Engineering Sciences (SCI).
    Microscopic Models for Trac Dynamics2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    As the volume of vehicular trac has been increasing ever since its

    advent in the early 20th century, trac dynamics has become a popu-

    lar topic of study amongst physicists and mathematicians. This paper

    aims to explain di erent ways of modeling and simulating trac and

    trac dynamics. In general, modeling of trac can be divided into

    two types of models, microscopic and macroscopic. In this paper, pri-

    mary focus is on microscopic models. Examples are shown on how

    to implement simulations of so called car-following models as well as

    models based on cellular automata. Certain problems and scenarios

    regarding trac are studied as well. These include how to eciently

    distribute a roadblock, how to set the green/red time periods of a traf-

    c light in order to achieve a high trac ow or a low vehicle density,

    and how trac ow can be maximized with respect to density or other

    parameters. Results show that simulations using cellular automata

    models generally compute faster than simulations using car-following

    models. However, the results obtained from cellular automata models

    tend to be more dicult to interpret and apply to real-world sce-

    narios. A high level of stochasticity in the cellular automata models

    was also found to be necessary for the models to give applicable re-

    sults. Car-following models, on the other hand, were found to have

    the advantage of being more deterministic.

  • 231.
    Abrahamsson, Felix
    KTH, School of Engineering Sciences (SCI).
    Microscopic Models for Trac Dynamics2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    As the volume of vehicular trac has been increasing ever since its

    advent in the early 20th century, trac dynamics has become a popu-

    lar topic of study amongst physicists and mathematicians. This paper

    aims to explain di erent ways of modeling and simulating trac and

    trac dynamics. In general, modeling of trac can be divided into

    two types of models, microscopic and macroscopic. In this paper, pri-

    mary focus is on microscopic models. Examples are shown on how

    to implement simulations of so called car-following models as well as

    models based on cellular automata. Certain problems and scenarios

    regarding trac are studied as well. These include how to eciently

    distribute a roadblock, how to set the green/red time periods of a traf-

    c light in order to achieve a high trac ow or a low vehicle density,

    and how trac ow can be maximized with respect to density or other

    parameters. Results show that simulations using cellular automata

    models generally compute faster than simulations using car-following

    models. However, the results obtained from cellular automata models

    tend to be more dicult to interpret and apply to real-world sce-

    narios. A high level of stochasticity in the cellular automata models

    was also found to be necessary for the models to give applicable re-

    sults. Car-following models, on the other hand, were found to have

    the advantage of being more deterministic.

  • 232.
    Abrahamsson, Johan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Danmo, Johan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    The Stabilizing Spoon: Self-stabilizing utensil to help people withimpaired motor skills2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The technology for assisting people who are functionallychallenged has improved over the recent decades. With today’stechnology, people with Parkinson’s disease can, witha device on their wrist, be able to draw pictures. Humanlimbs lost due to accidents can be replaced with bionic limbsand with help from smartphones, blind people can by audiobe informed what kind of object that appear in frontof them. These are a few examples where technology haseased everyday life for people with impaired functionality.The purpose of this thesis is to analyze how an Arduino microcontrollercan be utilized to help people with impairedmotor skills during their eating process. A prototype of astabilizing spoon was constructed to work under real circumstancesand intended to be a complement for peoplewho are in need of assistance during their eating process.To make this possible, a sensor with gyroscopes combinedwith accelerometers was used to identify which directionthe device’s handle was being tilted, as well as how fastits position was changed. Two servo motors were placedorthogonally to each other to establish a system of two degreesof freedom. With this setup, the spoon was intendedto maintain its spoon bowl in a horizontal position. Experimentalresults of the spoon showed promising performancewith some limitations.

  • 233.
    Abrahamsson, Johanna
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Urban and Regional Studies.
    Vild natur: Värden, attityder och associationer2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Modern humans are considered to have lost connection to nature and actions to reduce the separation between man and nature has been demanded. Green areas are often valued from a broad perspective and few studies have investigated the specific nature of the wild habitat. There also seem to be definitive problems and conflicts regarding the concept of "wild nature". The purpose of this report is to identify the specific values of wild nature ​​and to investigate what the concept really can include. Another purpose is to investigate attitudes and associations to wild nature and how wild nature is being worked on in planning.

    A literature study has been used as the primary method. The literature study has been supplemented with a minor case study including a documentary study, interviews and questionnaires.

    The conclusion is that wild nature offers values ​​of ecological, educational and experiential character. The ecological value is that wild nature allows biodiversity. The educational value includes aspects that help strengthen the connection to nature, which may lead to changed environmental behavior. Wild nature also has values ​​that concerns for example the experience of spiritual and reflective emotions, contributing to stress reduction and increased well-being. Moreover, wild nature is associated with large areas unaffected by humans. The same approaches are in the planning process, and the experience of wild nature is often evaluated from an ecological perspective. This means that the potential of green spaces that does not fit into the traditional image is not taken advantage of. Wild nature can also be defined based on the experience qualities related to wildness. A development towards such an approach could mean that the specific nature of the wild nature is taken advantage of. This could contribute to the increased well-being of the residents, but in the long term, a more sustainable society.

  • 234.
    Abrahamsson, Lars
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Optimal Railroad Power Supply System Operation and Design: Detailed system studies, and aggregated investment models2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Railway power supply systems (RPSSs) differ mainly from public power systems from that the loads are moving. These moving loads are motoring trains. Trains can also be regenerating when braking and are then power sources. These loads consume comparatively much power, causing substantial voltage drops, not rarely so big that the loads are reduced. By practical reasons most RPSSs are single-phase AC or DC. Three-phase public grid power is either converted into single-phase for feeding the railway or the RPSS is compartmentalized into separate sections fed individually from alternating phase-pairs of the public grid. The latter is done in order not to overload any public grid phase unnecessarily much.

    This thesis summarizes various ways of optimally operating or designing the railway power supply system. The thesis focuses on converter-fed railways for the reasons that they are more controllable, and also has a higher potential for the future. This is also motivated in a literature-reviewing based paper arguing for the converter usage potential. Moreover, converters of some kind have to be used when the RPSS uses DC or different AC frequency than the public grid.

    The optimal operation part of this thesis is mainly about the optimal power flow controls and unit commitments of railway converter stations in HVDC-fed RPSSs. The models are easily generalized to different feeding, and they cope with regenerative braking. This part considers MINLP (mixed integer nonlinear programming) problems, and the main part of the problem is non-convex nonlinear. The concept is presented in one paper. The subject of how to model the problem formulations have been treated fully in one paper.

    The thesis also includes a conference article and a manuscript for an idea including the entire electric train driving strategy in an optimization problem considering power system and mechanical couplings over time. The latter concept is a generalized TPSS (Train Power Systems Simulator), aiming for more detailed studies, whereas TPSS is mainly for dimensioning studies. The above optimal power flow models may be implemented in the entire electric train driving strategy model.

    The optimal design part of this thesis includes two aggregation models for describing reduction in train traffic performance. The first one presented in a journal, and the second one, adapted more useful with different simulation results was presented at a conference. It also includes an early model for optimal railway power converter placements.

    The conclusions to be made are that the potential for energy savings by better operation of the railway power system is great. Another conclusion is that investment planning models for railway power systems have a high development potential. RPSS planning models are computationally more attractive, when aggregating power system and train traffic details.

  • 235.
    Abrahamsson, Lars
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Railway Power Supply Models and Methods for Long-term Investment Analysis2008Licentiate thesis, monograph (Other scientific)
    Abstract [en]

    The aim of the project is to suggest an investment planning programwhere the welfare of the society is to be maximized. In order to beable to decide on a wise investment plan, one needs to know theconsequences of different choices of power system configurations.Therefore the impacts of different future traffic demands are ofinterest for a railway power system owner.Since investments are supposed to last a long time, their futureusage has to be considered. Moreover, the lead times of investmentscan be of considerable duration lengths. Because of the uncertaintyof the future, deterministic case studies might not be suitable andthen a large number of outcomes are to be studied, probable outcomesas well as outcomes with a high level of impact.In order to be able to make a valid long-term investment analysis ofthe railway power supply system, one needs to use proper railwaypower supply models and methods. The aim of this thesis is topresent a stable modeling and methodological basis for the cominginvestment planning phase of this PhD research project. The focus isset on studying the consequences of a railway power supply systemwhich is too weak.The thesis contains an overview of models of some electrical andmechanical relations important for electric traction systems. Someof these models are further developed, and some are modified forimproved computational properties. A flexible electric tractionsystem simulator based on the above mentioned models has beendeveloped and the applied methods and resulting abilities arepresented.The main scientific contribution of this thesis is that a fast andapproximative neural network model, which calculates some importantaggregated results of the interaction between the railway powersystem and the train traffic, has been developed. This approximativemodel was developed in order to reduce computation times. Reductionof computation times is very important when a huge number ofoutcomes are studied. A complete simulation of a train power systemin operation takes a long time, often not less than about a tenth ofthe simulated traffic time. The neural network is trained with someselected aggregated results extracted from a wide set of railwayoperation simulation cases. The choices of network inputs andoutputs are motivated in the thesis. The performance of thesimulator as well as the approximator are visualized in casestudies.

  • 236.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Kjellqvist, Tommy
    Elekt Konsult AB, Kraftelektronik, Sweden.
    Östlund, Stefan
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    High-voltage DC-feeder solution for electric railways2012In: IET Power Electronics, ISSN 1755-4535, E-ISSN 1755-4543, Vol. 5, no 9, p. 1776-1784Article in journal (Refereed)
    Abstract [en]

    For AC railway power supply systems with a different frequency than the public grid, high-voltage AC transmission lines are common, connected to the catenary by transformers. This study suggests an alternative design based on an high-voltage DC (HVDC)-feeder, which is connected to the catenary by converters. Such an HVDC line would also be appropriate for DC-fed railways and AC-fed railways working at a public-grid frequency. The converter stations between the public grid and the HVDCfeeder can be sparsely distributed, not denser than on 100 km distances, whereas the converters connecting the HVDC-feeder to the catenary are distributed denser. Their ratings can be lower than present-day substation transformers or converters, since the power flows can be fully controlled. Despite a relatively low-power rating, the proposed converters can be highly efficient because of the use of medium frequency technology. The proposed feeding system results in lower material usage, lower losses and higher controllability compared with the present solutions. Simulations of the proposed solution show clear advantages regarding transmission losses and voltages compared with conventional systems, especially for cases with weak feeding, and when there are substantial amounts of regeneration from the trains.

  • 237.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Kjellqvist, Tommy
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Östlund, Stefan
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    HVDC Feeder Solution for Electric Railways2012In: IET Power Electronics, ISSN 1755-4535, E-ISSN 1755-4543Article in journal (Refereed)
    Abstract [en]

    The railway power supply systems in many sparsely populated countries are relatively weak. Weak railway power supply systems causes problems with power quality, voltage drops, and high transmission losses.

    For AC railway power supply systems with a different frequency than the public grid, high-voltage AC (HVAC) transmission lines are common, connected to the catenary by transformers.

    In this paper an alternative design based on an HVDC feeder is suggested. The HVDC feeder is connected to the catenary by converters. Such an HVDC line would also be appropriate for DC-fed railways and AC-fed railways working at public frequency. The converter stations between the public grid and the HVDC feeder can be sparsely distributed, in the range of 100 km or more, whereas the converters connecting the HVDC feeder to the catenary are distributed with a much closer spacing. Their ratings can be lower than substation transformers or electro-mechanical converters, since the power flow can be fully controlled.

    Despite a relatively low power rating, the proposed converters can be highly efficient due to the use of medium frequency technology. The HVDC-based feeding system results in lower material usage, lower losses and higher controllability compared to present solutions.

    Simulations of the proposed solution show clear advantages regarding transmission losses and voltages compared to conventional systems, especially for cases with long distances between feeding points to the catenary, and when there are substantial amounts of regeneration from the trains.

  • 238.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Schütte, Thorsten
    Östlund, Stefan
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Use of converters for feeding of AC railways for all frequencies2012In: Energy for Sustainable Development, ISSN 0973-0826, Vol. 16, no 3, p. 368-378Article in journal (Refereed)
    Abstract [en]

    Railways are the most energy-efficient land-based mode of transport, and electrification is the most energy-efficient way to power the trains. There are many existing solutions to supply the trains with electricity. Regardless of which particular technology is chosen, it is beneficial to interconnect the public power grids to grids supplying power to the railways. This paper shows that the most efficient, flexible, and gentle-for-the-public-grid way of doing that is through power electronic-based power converters. Converters offer great benefits regardless of whether the overhead contact lines are of DC-type or AC type, and regardless of the AC grid frequency. This paper presents neither new theory nor new experimental results. Based on already available information, this paper presents logical arguments leading to this conclusion from collected facts. Over time what used to be advanced and high-cost equipment earlier can nowadays be purchased at reasonable cost. It is obvious that for most electrically-fed railways, the use of modern power converters is attractive. Where the individual trains are high consumers of energy, the railway gradients are substantial, and the public grids feeding the railway are weak, the use of converters would be technically desirable, if not necessary for electrification.It is expected that more high-speed railways will be built, and more existing railways will be electrified in the foreseeable future. This paper could provide some insights to infrastructure owners and decision makers in railway administrations about value additions that converter-fed electric railways would provide.

  • 239.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Skogberg, Ronny
    Östlund, Stefan
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Lagos, Mario
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Identifying electrically infeasible traffic scenarios on the iron ore line: Applied on the present-day system, converter station outages, and optimal locomotive reactive power strategies2015In: PROCEEDINGS OF THE ASME JOINT RAIL CONFERENCE, 2015, AMER SOC MECHANICAL ENGINEERS , 2015Conference paper (Refereed)
    Abstract [en]

    This paper presents the main findings of a Master's Thesis project carried out in cooperation between Transrail and Royal Institute of Technology (KTH). The main objective was to create a plugin for checking the electric power system feasibility of a train traffic plan with an associated driving strategy created by TRAINS a Transrail software product. Secondary aims with the project was to study power system feasibilities during converter station outages, and to which extent optimal operation of the locomotive converters' reactive power assure power system feasibilities. In the developed optimal reactive power strategies, the main priority was to fulfill the desired traffic plans, whereas the secondary priority was to minimize railway power system power consumption. The case studies are applied on representative traffic scenarios and power system models representing the northern part of the Iron Ore line in Northern Sweden. The focus of the study is set on the IORE locomotives and the iron ore trains they haul. The optimized locomotive reactive power regards IORE, so also the investigated power system feasibilities of the traffic plans.

  • 240.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    An SOS2-based moving trains,fixed nodes, railway power system simulator2012In: WIT Transactions on the Built Environment, WIT Press, 2012, p. 813-823Conference paper (Refereed)
    Abstract [en]

    This paper presents and proposes an optimization model for railway power supply system simulations. It includes detailed power systems modeling train movements in discretized time considering running resistance and other mechanical constraints, and the voltage-drop-induced reduction of possible train tractive forces. The model has a xed number of stationary power system nodes. The proposed model uses SOS2 (special ordered sets of type 2) variables to distribute the train loads to the two most adjacent power system nodes available. The impact of the number of power system nodes along the contact line and the discretized time step length impacts on model accuracy and computation times are investigated. The program is implemented in GAMS (General Algebraic Modeling System). Experiences from various solver choices are also presented. The train traveling times are minimized in the example. Other studies could, e.g. consider energy consumption minimization. The numerical example is representative for a Swedish non-centralized, rotary-converter fed railway power supply system. The proposed concept is however generalizable and could be applied for all kinds of moving load power system studies.

  • 241.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Basic modeling for electric traction systems under uncertainty2006In: PROCEEDINGS OF THE 41ST INTERNATIONAL UNIVERSITIES POWER ENGINEERING CONFERENCE, VOLS 1 AND 2, NEW YORK: IEEE , 2006, p. 252-256Conference paper (Refereed)
    Abstract [en]

    The objective of this paper is initially to present a basic modeling of the railway traction system. This model includes the basic technologies used today. The voltage dependencies of the maximal possible power consumption as well as the maximal velocity of the common Re-locomotives are included. The latter is very crucial for the studies of time table sensitivity, which is of our immediate interest. Moreover, a method is presented, that estimates the expected train delay time for a given feeding technology. The reference timetable assumes the same train and surrounding conditions, but no voltage drops. In the numerical example where the developed model is applied to a realistic test system, a set of possible amounts of railway traffic are treated as uncertainties. Mainly, the contributions of this paper are three: compiling and connecting already accepted models, the development of a method for numerical calculations using this model compilation, and an example to apply this model on.

  • 242.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Fast calculation of some important dimensioning factors of the railway power supply system2007Conference paper (Refereed)
    Abstract [en]

    Because of environmental and economical reasons, in Sweden and the rest of Europe, both personal and goods transports on railway are increasing. Therefore great railway infrastructure investments are expected to come. An important part of this infrastructure is the railway power supply system. Exactly how much, when and where the traffic will increase is not known for sure. This means investment planning for an uncertain future. The more uncertain parameters, such as traffic density and weight of trains, and the further future considered, the greater the inevitable amount of cases that have to be considered. When doing simulations concerning a tremendous amount of cases, each part of the simulation model has to be computationally fast – in real life this means approximations. The two most important issues to estimate given a certain power system configuration, when planning for an electric traction system, are the energy consumption of the grid and the train delays that a too weak system would cause. In this paper, some modeling suggestions of the energy consumption and the maximal train velocities are presented. Two linear models, and one nonlinear model are presented and compared. The comparisons regard both computer speed and representability. The independent variables of these models are a selection of parameters describing the power system, i.e.: power system technology used on each section, and traffic intensity.

  • 243.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    Fast estimation of aggregated results of many load flow solutions in electric traction systems2008In: COMPUTERS IN RAILWAYS XI, WIT Press, 2008, Vol. 103, p. 411-423Conference paper (Other academic)
    Abstract [en]

    Transports on rail are increasing and major railway infrastructure investments are expected. An important part of this infrastructure is the railway power supply system. The future railway power demands are naturally not known for certain. This means investment planning for an uncertain future. The more remote the uncertain future, the greater the amount of scenarios that have to be considered. Large numbers of scenarios make time demanding (some tens of minutes, each) simulations less attractive and simplifications more so. The aim of this paper is to present a fast approximator that uses aggregated traction system information as inputs and outputs. This facilitates studies of many future railway power system loading scenarios, combined with different power system configurations, for investment planning analysis. Since the electrical and mechanical relations governing an electric traction system are quite intricate, an approximator based on neural networks (NN), is applied. This paper presents a design suggestion for a NN estimating power system caused limits on active and reactive power load, i.e., limits on the levels of train traffic.

  • 244.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Fast Estimation of Relations Between Aggregated Train Power System Data and Traffic Performance2011In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 60, no 1, p. 16-29Article in journal (Refereed)
    Abstract [en]

    Transports via rail are increasing, and major railway infrastructure investments are expected. An important part of this infrastructure is the railway power supply system (RPSS). Future railway power demands are not known. The more distant the uncertain future, the greater the number of scenarios that have to be considered. Large numbers of scenarios make time-demanding (some minutes, each) full simulations of electric railway power systems less attractive and simplifications more so. The aim, and main contribution, of this paper is to propose a fast approximator that uses aggregated traction system information as inputs and outputs. This approximator can be used as an investment planning constraint in the optimization. It considers that there is a limit on the intensity of the train traffic, depending on the strength of the power system. This approximator approach has not previously been encountered in the literature. In the numerical example of this paper, the approximator inputs are the power system configuration; the distance between a connection from contact line to the public grid, to another connection, or to the end of the contact line; the average values and the standard deviations of the inclinations of the railway; the average number of trains; and their average velocity for that distance. The output is the maximal attainable average velocity of an added train for the described railway power system section. The approximator facilitates studies of many future railway power system loading scenarios, combined with different power system configurations, for investment planning analysis. The approximator is based on neural networks. An additional value of the approximator is that it provides an understanding of the relations between power system configuration and train traffic performance.

  • 245.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Fast estimation of the relation between aggregated train power system information and the power and energy converted2009In: Australian Journal of Electrical and Electronic Engineering, ISSN 1448-837X, Vol. 6, no 3, p. 311-318Article in journal (Refereed)
    Abstract [en]

    Transports on rail are increasing and major investments in the railway infrastructure, including the railway power supply system (RPSS), are expected. The future railway power demands are naturally not known for certain. The more remote the uncertain future, the greater the number of scenarios that have to be considered. Large numbers of scenarios make time-demanding simulations unattractive. The aim of this paper is to present a fast approximator that uses aggregated RPSS information. Since the electrical and mechanical relations governing an RPSS are quite intricate, an approximator based on neural networks (NN) is applied. This paper presents a design suggestion for an NN estimating the power and energy flows through each converter station, given RPSS data and levels of train traffic. Even if the future usage of the NN is investment planning, the modelling of such an approximator has a value in itself concerning the understanding of the relations between RPSS and train traffic.

  • 246.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Fast estimation of the relation between aggregated train power system information and the power and energy converted2008In: 2008 Australasian Universities Power Engineering Conference, AUPEC 2008, IEEE conference proceedings, 2008, p. 1-6Conference paper (Refereed)
    Abstract [en]

    Transports on rail are increasing and major investments in the railway infrastructure, including the Railway Power Supply System (RPSS), are expected. The future railway power demands are naturally not known for certain. The more remote the uncertain future, the greater the number of scenarios that have to be considered. Large numbers of scenarios make time demanding simulations unattractive. The aim of this paper is to present a fast approximator that uses aggregated RPSS information. Since the electrical and mechanical relations governing an RPSS are quite intricate, an approximator based on Neural Networks (NN), is applied. This paper presents a design suggestion for an NN estimating the power and energy flows through each converter station, given RPSS data and levels of train traffic. Even if the future usage of the NN is investment planning, the modeling of such an approximator has a value in itself concerning the understanding of the relations between RPSS and train traffic.

  • 247.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Operation simulation of traction systems2008In: COMPUTERS IN RAILWAYS XI, 2008, Vol. 103, p. 283-292Conference paper (Refereed)
    Abstract [en]

    The objective of this paper is initially to present a basic modeling of the railway traction system. This model includes the basic technologies used today. The voltage dependencies of the maximal possible power consumption as well as the maximal velocity of the common Rc-locomotives are included. The latter is very crucial for the studies of time table sensitivity, which is of our immediate interest. Moreover, a method is presented that estimates the expected train delay time for a given feeding technology. The reference timetable assumes the same train and surrounding conditions, but no voltage drops. In the numerical example where the developed model is applied to a realistic test system, a set of possible amounts of railway traffic are treated as uncertainties. Mainly, the contributions of this paper are three: compiling and connecting already accepted models, the development of a method for numerical calculations using this model compilation, and an example to apply this model on.

  • 248.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Railway power supply investment decisions considering the voltage drops: Assuming the future traffic to be known2009In: 2009 15th International Conference on Intelligent System Applications to Power Systems, ISAP '09, 2009Conference paper (Other academic)
    Abstract [en]

    Transports on rail are increasing and major railway infrastructure investments are expected. An important part of this infrastructure is the railway power supply system. The future railway power demands are naturally not known for certain. The more distant the uncertain future is, the greater the number of scenarios that have to be considered. Large numbers of scenarios make time demanding simulations unattractive. Therefore a fast approximator that uses aggregated railway power supply system information has been developed. In particular the approximator studies the impacts of voltage drops on the traffic flow. The weaker the power system and the heavier the traffic, the greater the voltage drops. And the greater the voltage drops, the more limited the maximal attainable tractive force on the locomotives. That approximator is in this paper used as a constraint in the embryo of a railway power supply system investment planning program, where investment decisions are assumed to be realized immediately, and there is no preexisting power supply system to consider. The traffic forecasts are in this first approach assumed to be perfect. This stepwise creation of the planning program makes evaluating it easier. The basic investment planning model presented here constitutes the foundation for further improvements.

  • 249.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Traction Power System Capacity Limitations at Various Traffic Levels2011In: WCRR, World Congress on Railway Research, 2011Conference paper (Refereed)
    Abstract [en]

    The aim, and main contribution, of this paper is to propose a fine-tuned fast approximator, based on neural networks, that uses aggregated traction system information as inputs and outputs. This approximator can be used as an investment planning constraint in the optimization. It considers that there is a limit on the intensity of the train traffic, depending on the strength of the power system. In the numerical examples of this paper, the approximator inputs are the power system configuration, the distance between a connection from contact line to the public grid to another connection, and the average number of trains for that distance. The output is the maximal attainable average velocity of trains of a specific kind for the by the inputs described railway power system section. An alternative output – the traveling time is also presented. The main emphasis of this paper is on the example section, since the contribution of this paper is mainly to show on the improved simplicity and reality compliance. The applicative contribution is twofold, an improved TPSA as a planning/decision making program constraint, whereas it also can be used as a scientifically developed rule of thumb for a planner active in the field. The aim is not primarily to show that the idea works, or to motivate the principal idea, since that is done earlier. The approximator facilitates studies of many railway power system loading scenarios, combined with different power system configurations, for investment planning analysis. The approximator is based on neural networks. An additional value of the approximator is that it provides an understanding of the relations between power system configuration and train traffic performance.

  • 250.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Östlund, Stefan
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Optimizing the power flows in a railway power supply system FED by rotary converters2015In: PROCEEDINGS OF THE ASME JOINT RAIL CONFERENCE, 2015, AMER SOC MECHANICAL ENGINEERS , 2015Conference paper (Refereed)
    Abstract [en]

    This study focuses on optimizing the operation of rotary railway-feeding converters. Since a large share of rotary converters can be expected to be in operation for decades to come in the railway power supply systems (RPSSs), it is important to make their operation as efficient as possible. The existing rotary converters may have unused capabilities particularly in load sharing, but also to some extent in reactive power compensation. Load-sharing improvement can be done in two steps; (1) coarsely by unit commitment within a converter station, (2) fine-tuned by controlling the terminal voltage of the converter station on the railway-side. The proposed optimization models minimize RPSS losses, including losses in the converters. The models are implemented and solved in the GAMS environment. The case studies are applied on Sweden-inspired RPSS designs and configurations, and the train load situations are varied. Ideas and experiences regarding improved computational efficiency for solving the problems are discussed.

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