1234 1 - 50 of 183
rss atomLink to result list
Permanent link
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
  • Public defence: 2017-06-13 11:15 F3, Stockholm
    Bamzar, Roya
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Urban and Regional Studies.
    Ensuring elderly mobility: environmental and safety issues2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The aim of this thesis is to provide a better understanding of the issues of safe mobility ‎for the elderly population in Sweden. ‎This is achieved first by assessing the geography and patterns of ‎elderly falls at the county level and then by conducting a detailed survey with residents in senior ‎housing to investigate the relationship between indoor and/or outdoor environmental ‎characteristics and elderly safety. Safety is regarded as a multidimensional concept that ‎involves risk of falls, crime victimization and elderly people’s perception of their ‎overall safety. Using a case study approach, the study also assesses the types of outdoor places where most crimes ‎against the elderly take place and the types of places most feared by them. The study ‎adapts a set of qualitative and quantitative methods ‎to capture the nature of the phenomena; trends, patterns and frameworks that support ‎the analysis and implications of the results for both research and practice. The findings show ‎that elderly falls in Sweden vary geographically and exhibit gender, age, environmental, and socio-‎economic differences. The mobility of the older population is influenced by their ‎perceived safety in indoor and outdoor environments. Certain features of apartment layout and furniture arrangement are identified as potential causes of falls. Older adults’ ‎perception of safety exhibits a distance-decay effect from their senior housing building. Distance decay indicates that safety is deemed highest closest to their homes and decreases as the distance increases. There are indications that older adults take longer routes and increase their mobility because they are fearful at certain spots in their neighbourhood. The thesis ‎concludes with a discussion of the results and implications for both research and policy making at the local and ‎county levels. ‎

  • Public defence: 2017-06-08 10:00 M3, Stockholm
    Mentis, Dimitris
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy Systems Analysis.
    Spatially explicit electrification modelling insights: Applications, benefits, limitations and an open tool for geospatial electrification modelling2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Developing countries confront the challenge of generating more electricity to meet demands in a sustainable manner. According to the World Bank’s 2015 Global Tracking Framework, roughly 15% of world population (or 1.1 billion people) lack access to electricity, and many more rely on poor quality electricity supplies. In September 2015, the United Nations General Assembly adopted Agenda 2030 comprised of a set of 17 Sustainable Development Goals (SDGs) and defined by 169 targets. “Ensuring access to affordable, reliable, sustainable and modern energy for all by 2030” is the seventh goal (SDG7). While energy access refers to more than electricity, it is the central focus of this work.

    Models addressing electrification and access typically need large volumes of reliable energy-related data and information, which in most developing countries have been limited or not available. This paucity of information has decelerated energy planning in the developing World. That situation has fundamentally changed with increasing availability and application of Geographic Information Systems (GIS). GIS layers can provide location specific energy-related information that has not been previously accessible. The focus of this thesis lies on integrating a simple electricity supply model into GIS. In so doing a novel open source spatial electrification tool is developed. It estimates power capacity needs and associated investment (and other) costs for achieving universal access to electricity in developing countries.

    The dissertation includes a cover essay and six appended papers presenting quantitative methods on coupling selected aspects of GIS and energy systems. It strives to answer three key research questions. 

    The first research question is: What is the spatially explicit renewable energy potential that can be technically and economically exploited? This information is currently either missing or scattered in developing countries. The provision of low cost, locally available energy can provide a significant opportunity to empower a better standard of living. The first paper presents a GIS based approach to assess the onshore technical wind energy potential on the African continent by applying socioeconomic and geographic restrictions regarding the localization of wind farms and state of the art wind data analysis. The second paper builds on this knowledge and moves one step further by assessing the economic potential and providing cost indicators to assess the viability of wind power (this time in India). The third paper maps the economic wind power potential in Africa based on the methodologies developed in the two preceding papers. Not only wind power but most energy resources have a spatial nature and their availability is linked to geography. Evaluating these other energy sources (solar, hydro etc.) are included and analysed in Papers IV-VI.

    The second research question is: what is the least-cost set of technologies needed to meet different levels of electricity use accounting for different geographies? Increasing access to electricity effectively requires, inter alia, strategies and programmes that address and account for the geographical, infrastructural and socioeconomic characteristics of a country or region. Paper IV introduces a GIS based methodology to inform electrification planning. It builds on the previous work by taking into account the techno-economic wind, and other resource mapping. This methodology is applied in Nigeria in order to determine the least cost technology mix considering the country’s infrastructure and resource availability on a spatial basis. Paper V utilizes this method and in so doing demonstrates the importance of geospatial calculations in energy access planning. It highlights differences in investment estimates between alternate scenarios with regards to energy demand and technology deployment. Paper VI enhances this methodology and applies it to every square kilometre of Sub-Saharan Africa. The method is subsequently implemented in an Open Source Spatial Electrification Tool (OnSSET) to facilitate education, repeatability and further research.

    Finally, the third question is: Are there gains to be had by linking geographically explicit analysis with typical (non-spatially explicit) long term energy systems models? The work shows that not only do long-term systems models influence geospatially optimal technology deployment. But vice versa, their output influences long term systems models’ investment profile.  That is because the geospatial disaggregation allows for a better determination of grid versus off-grid connections, and in turn power demand on the national grid. This thesis demonstrates that energy system models should take into consideration the geographic dimension of energy-related parameters, as these play a fundamental role in determining the optimal energy system of a region.

  • Public defence: 2017-06-15 09:00 Kollegiesalen, Stockholm
    Sadik, Diane-Perle
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    On Reliability of SiC Power Devices in Power Electronics2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Silicon Carbide (SiC) is a wide-bandgap (WBG) semiconductor materialwhich has several advantages such as higher maximum electric field, lowerON-state resistance, higher switching speeds, and higher maximum allowablejunction operation temperature compared to Silicon (Si). In the 1.2 kV - 1.7kV voltage range, power devices in SiC are foreseen to replace Si Insulatedgatebipolar transistors (IGBTs) for applications targeting high efficiency,high operation temperatures and/or volume reductions. In particular, theSiC Metal-oxide semiconductor field-effect transistor (MOSFET) – which isvoltage controlled and normally-OFF – is the device of choice due to the easeof its implementation in designs using Si IGBTs.In this work the reliability of SiC devices, in particular that of the SiCMOSFET, has been investigated. First, the possibility of paralleling two discreteSiC MOSFETs is investigated and validated through static and dynamictests. Parallel-connection was found to be unproblematic. Secondly, drifts ofthe threshold voltage and forward voltage of the body diode of the SiC MOSFETare investigated through long-term tests. Also these reliability aspectswere found to be unproblematic. Thirdly, the impact of the package on thechip reliability is discussed through a modeling of the parasitic inductancesof a standard module and the impact of those inductances on the gate oxide.The model shows imbalances in stray inductances and parasitic elementsthat are problematic for high-speed switching. A long-term test on the impactof humidity on junction terminations of SiC MOSFETs dies and SiCSchottky dies encapsulated in the same standard package reveals early degradationfor some modules situated outdoors. Then, the short-circuit behaviorof three different types (bipolar junction transistor, junction field-effect transistor,and MOSFET) of 1.2 kV SiC switching devices is investigated throughexperiments and simulations. The necessity to turn OFF the device quicklyduring a fault is supported with a detailed electro-thermal analysis for eachdevice. Design guidelines towards a rugged and fast short-circuit protectionare derived. For each device, a short-circuit protection driver was designed,built and validated experimentally. The possibility of designing diode-lessconverters with SiC MOSFETs is investigated with focus on surge currenttests through the body diode. The discovered fault mechanism is the triggeringof the npn parasitic bipolar transistor. Finally, a life-cycle cost analysis(LCCA) has been performed revealing that the introduction of SiC MOSFETsin already existing IGBT designs is economically interesting. In fact,the initial investment is saved later on due to a higher efficiency. Moreover,the reliability is improved, which is beneficial from a risk-management pointof-view. The total investment over 20 years is approximately 30 % lower fora converter with SiC MOSFETs although the initial converter cost is 30 %higher.

  • Nordstrand, Lina
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Environmental Strategies Research (fms).
    Health and wellbeing in Swedish office buildings: A study on WELL Building Standard, Swedish legislation and Miljöbyggnad2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Environmental certification systems has, apart from improving the environment, contributed to buildings with a better indoor air quality. The realization of this has led to the next focustrend in the built environment, building for occupant health and wellbeing. It is recognized that if buildings are designed with the occupant health and wellbeing at center, it increases employee productivity and reduce absenteeism, which in turn yields economic benefits for a business.

    This thesis project is set out to investigate how building for occupant health and wellbeing, wellbeing and productivity can be done in Swedish office buildings. The project is partly based on the relatively new WELL Building Standard, a tool for certifying, measuring and monitoring the functions of a building in terms of health and wellbeing. The largest  part of the project is the analysis,method used for investigate the subject is a case study, where WELL Building Standard is compared to Swedish legislation and building practice as well as the Swedish environmental certification system Miljöbyggnad. A literature study is also included in order to see how the health situation looks like in Sweden, and what aspects are the most important to highlight in the scope of this thesis.

    The thesis project is a pilot study of the health and wellbeing, wellbeing and productivity in Swedish offices and it shows that Swedish legislation includes a large number of issues set forth in WELL Building Standard. In some cases, Swedish legislation goes quite a bit further than WELL and in some cases Swedish projects can gather inspiration from WELL in order to build even healthier. Miljöbyggnad also fulfills some of the subjects presented in WELL.

    As WELL Building Standard is a very extensive system, not all parts of it could be included in the analysis of this project. There are a lot of further research that needs to be conducted before drawing too general conclusions on how Swedish projects perform on the aspects of health and wellbeing. Generally, WELL is a usefulgreat system to use if a project intends to be as healthy as can be, even though the project does not use it to be certified. The system provides the building owners with arguments they can use to communicate how the building may benefit health and wellbeing to the tenants, as WELL puts the human at center rather than the building.

  • Kuokkanen, Senja Karoliina
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Environmental Strategies Research (fms).
    Assessing future scenarios and absolute sustainability targets with environmentally extended input-output analysis2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this master’s thesis project, future scenarios for year 2050 were constructed for Denmark, Finland and Sweden using an environmentally extended input-output analysis (EEIOA). Scenarios were constructed based on national sustainability targets. A case-specific five stage modeling approach was developed. Approach consists of changes in input-output tables for Electricity grid, Fossil primary energy, Industry sectors, Transport and Allocation of fossil fuel replacements. To represent business-as-usual development, EEIO tables for 2009 were used as reference and baseline scenarios. Constructed scenario models resulted in substantial CO2 emission reductions compared to baseline scenario. In scenario results for Denmark, emissions reduced 98.17 %, in Finland 81.41 % and in Sweden 77.90 %.

    Furthermore, based on Planetary Boundary framework, greenhouse gas emission carrying capacities were estimated in sectoral level for 2050. Carrying capacities for year 2050 for Denmark, Finland and Sweden were 9909.99 kton CO2-eq, 9049.42 kton CO2-eq and 18691.96 kton CO2-eq, respectively. Compared to radically reduced emissions in scenario results, Denmark and Sweden reached emission levels below estimated national carrying capacities. For Finland, carrying capacity level was exceeded by 2437.77 ktons.

    EEIOA was found to be an efficient tool for constructing and analyzing explorative long-term scenarios. In addition, it is possible to integrate absolute sustainability thresholds to EEIOA. Scenario results indicate that implementation of the existing national sustainability targets would lead to radical emission reductions in Denmark, Finland and Sweden by 2050 compared to business-as-usual development. Based on the scenario results, transport and industry sectors were identified as the emission hotspot sectors in 2050.

    EEIOA is a noteworthy method for decision-support for assessing sustainability strategies. With EEIOA, it is possible to allocate and study national sustainability targets on a sectoral level, and that way potentially substantially increase the effectiveness and implementation of defined sustainability targets. However, further research on modeling dynamics, data quality and underlined uncertainties are needed before studied approaches can develop into decision-support tools.

  • Public defence: 2017-06-09 14:00 Kollegiesalen, Stockholm
    Najari Moghadam, Nima
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    On Multiantenna Cellular Communications: From Theory to Practice2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Today, wireless communications are an essential part of our everyday life. Both the number of users and their demands for wireless data have increasedtremendously during the last decade. Multiantenna communicationsis a promising solution to meet this ever-growing traffic demands. However, impairments that exist in most practical communication networks may substantially limit the performance of a multiantenna system. The characterizationof such a performance loss and how to minimize that are still largelyopen problems. The present thesis addresses this important research gap. Inparticular, we focus on three major impairments of a multiantenna cellularnetwork: impairment in the channel state information (CSI), interference andimpairment in the transceiver hardware components.To fully realize the benefits of multiantenna communications, the users need to acquire a certain level of information about their propagation environment; that is, their corresponding CSI. In practice, the CSI is not known bythe users and should be acquired by allocating part of the network resourcesfor pilot transmission. This problem is mainly important in the systems with a large number of antennas, as in general the required network resources for CSI acquisition scales with the number of transmitting antennas. Theproblem of CSI acquisition in a single-cell multiuser multiple-input multipleoutput(MIMO) system is addressed in this thesis. A linear spatial precodingand combining scheme for pilot transmission is proposed. This scheme requiresless number of network resources for channel estimation compared tothe conventional schemes. The gains of the proposed scheme are characterized by finding an upper-bound and a lower-bound on the channel estimation error.Moreover, as an ultimate performance metric, an achievable sum-rate ofthe network is formulated and analyzed numerically.Due to the broadcast nature of the wireless channels, the performanceof the users in a network is intertwined; the desired signal of one user mayinterfere other users. Hence, the interference is another major impairment inwireless communication systems. In this thesis, the practical challenges of aninterference management technique, namely MIMO interference alignment isinvestigated by implementation on a multiuser MIMO testbed. Then, in thecontext of interference alignment, the problem of optimal power allocation forpilot and data transmission is studied and verified by the measurements.The impairment in the hardware components of the transceivers, that is, any deviation of the components from their ideal behavior, degrades the performance of a communication system. In particular, the impact of nonlineartransmitter power amplifiers (PA)s is investigated in this thesis. First, consideringa memoryless third-order polynomial model for the PAs, a model forthe transmitted nonlinear distortion signal from a multiantenna transmitter isproposed and validated by measurements. This model implies that the spatialdirection of the transmitted distortion is dependent on the spatial directionof the desired signal. Then, this model is extended for a general arbitrary order polynomial model. Exploiting the developed distortion model, the energyefficiency of a multiantenna system operating at millimeter wave frequenciesis studied.

  • Public defence: 2017-06-15 10:00 Sal V1, Stockholm
    Kholoma, Ezekiel
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. KTH Royal Institute of Technology.
    Fortification of soil-based wastewater treatment systems with versatile ubiquitous reactive media for enhanced removal of phosphorus and other pollutants2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Concerns about potential risks posed by discharge from small-scale wastewater treatment (SWT) systems to receiving water bodies have prompted robust enforcement of national discharge quality standards in rural areas of most developed countries. Consequently, communities in such places are in need of effective technologies with which to achieve compliance. Currently, reactive filter (RF) media are increasingly preferred over advanced alternatives, due mainly to their simplicity, affordability and proven potential. However, many of the field-tested filters are commercial products which are costly and scarce but also only capable of removing few contaminants they are engineered to target hence often requiring to be coupled with other treatment units to achieve full treatment. In the preliminary findings of this study, biochar (BC) was identified and thus suggested basing on existing literature, as a versatile ubiquitous low-cost material for treating wastewater. Its effectiveness in fortifying sand (Sa) and gas concrete (GC)-based SWT facilities was later demonstrated in long-term experiments using laboratory packed bed reactors and field constructed filter beds. The efficacy of SaBC and GCBC systems in reducing turbidity (>95%), DOC (60%; p<0.05) and PO43- (40-90%; p<0.05) was significantly higher than for their reference counterparts. Further, sorbed P was more leachable from Sa (11.2 mgkg-1) and SaBC (20.5 mgkg-1) filters but more extractable and hence plant-available in GC (65-91 mgkg-1). Therefore, the study concluded that fortification of soil-based systems with biochar filters may be a promising solution in enhancing performances of soil-based wastewater treatment systems, while P-rich RF media can act as a nutrient source for plants if recycled to agriculture.

  • Public defence: 2017-06-14 09:00 F3, Stockholm
    Okwir, Simon
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.), Industrial Management.
    Collaborative Measures: Challenges in Airport Operations2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Over the last 20 years, internal use of Performance Management(PM) within organizations has become much more complex in terms measurement techniques and approaches as well as their deployment within different organizational structures. In contrast to the traditional use of PM as an intra-organizational system, the emergence of networked operations, has extended organizational boundaries of Performance Management System (PMS) to new operational settings where actors often deal with a challenge of Collaborative Measures. Consequently, there is a significant lack of feedback and feedforward reporting mechanisms. This raises an important question for Performance Measurement & Management (PMM) literature. How do actors manage operations through inter- organizational performance measures? Hence, the purpose of this thesis is to investigate the management of collaborative measures in a quest to attain better operational performance for inter- organizational PM.

    The thesis builds on four studies investigating a collaborative PMS for capacity enhancements in airport operations. Due to their operational complexity and highly networked subsystems, airport operations provided a fitting empirical scene for studying PM that transcends organizational boundaries. Within the context of this thesis, airports are viewed as a System of System (SoS), and inter- organizational PM is investigated with the dimensions Organizational Complexity, Continuous Improvement and Social system. The studies use a multimethod approach, including longitudinal action research, multiple-case study, Systematic Literature Review (SLR), Classification and Regression Tree method (CART) and Artificial Neural Network (ANN) Method.

    The findings show that that (1) inter- organizational performance is affected by intrinsic Performance Measurement Complexity (PMC) which aggregates as interactive complexity with many actors. (2) The challenge of feedback and feedforward mechanisms as a dual control for collaborative performance is analysed with four cybernetic functions: sensor, commander, actuator and process. (3) The concept of Reflective Performance Measurement System (RPMS) is introduced with general conditions to facilitate collaborative decision-making within such platforms.

  • Hamisi, Rajabu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering. SEED-KTH.
    Renman, Gunno
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. SEED -KTH.
    Brokking Balfors, Berit
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. SEED-KTH.
    Thunvik, Roger
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. SEED-KTH.
    A new modeling approach for phosphorus mobility and retention processes in the Oxundaån catchment, SwedenManuscript (preprint) (Other academic)
    Abstract [en]

    Eutrophication is the most significant threat to water quality in the entire Baltic Sea region. Its causes are nutrient over-enrichment from diffuse and point sources. Thematic strategies for sustainable mitigation of phosphorus loss from sewage drainage systems and runoffs from arable land require a holistic approach to identify the critical polluting sources and implement relevant policy for adaptive water quality management. The use of constructed wetlands constitutes one such strategy that can mitigate phosphorus loss. However, insufficient understanding about phosphorus mobility and retention in catchments significantly hinders efforts to identify suitable sites for constructed wetlands and implement alternative, adaptive and effective management actions. This study aims to evaluate the long-term phosphorus mobility and retention in the Oxudaån catchment in Sweden, and thereby propose suitable sites to localize constructed wetlands. The Soil and Water Assessment watershed model was applied to map and quantify the phosphorus loading from diffuse and point sources under the scenarios of land use management practices. Simulation results have demonstrated the positive correlation between the phosphorus concentration with the surface runoffs and negative correlation with the pH. Overall, Oxundaån catchment indicates a decreasing trend of phosphorus loading in the Verkaån and Oxundaån riverine of around 2.1 % and 1.3 % per year, respectively. The present study suggests the suitable sites for localizing constructed wetlands in the south-west and north-east of Oxundaån lake based on the factor of low slope topography and soil permeability. The simulation results from the SWAT model offer evidence that can guide the localization and choice of management interventions to achieve a sustainable mitigation of phosphorus loss. This study concludes that, while single management actions can help solve the problem of eutrophication, a more effective and sustainable mitigation of eutrophication will require the integration of multiple adaptive land use management approaches.

  • Public defence: 2017-06-09 10:15 D3, Stockholm
    Shokri-Ghadikolaei, Hossein
    KTH, School of Electrical Engineering (EES), Network and Systems engineering. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Millimeter-wave Networking: Fundamental Limits, Scalable Algorithms, and Design Insights2017Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The current demands for extremely high data rate wireless services and the spectrum scarcity at the sub-6 GHz bands are forcefully motivating the use of the millimeter-wave (mmWave) frequencies. The main characteristics of mmWave communications are severe attenuation, sparse-scattering environment, huge bandwidth, vulnerability to obstacles and antenna misalignment, massive beamforming, and possible noise-limited operation. These characteristics constitute a major difference with respect to legacy communication technologies, primarily designed for the sub-6 GHz bands, and are posing major theoretical design challenges that have not been sufficiently addressed so far. Motivated by these challenges, this doctoral thesis considers mmWave communications and investigates medium access control (MAC) layer design principles and performance analysis. Specifically, we focus on fundamental performance metrics, including coverage, fairness, robustness, throughput, and delay, which we address by three main research threads of increasing complexity.

    The first thread of the thesis analyzes the interference behavior in mmWave networks.We first propose a new index for assessing the accuracy of any interference model under any network scenario, which helps us develop a simple interference model of adequate accuracy. We then derive closed-form expressions for the throughput of mmWave ad hoc networks. The new analysis reveals that mmWave networks may exhibit a non-negligible transitional behavior from a noise-limited to an interference-limited behavior, depending on the system parameters such as density of transmitters, transmission power, and operating beamwidth. The second thread of this thesis builds on the previous one and addresses resource allocation in mmWave networks. For the short-term resource allocation, we establish a mathematical framework to investigate the impact of beam training (alignment) overhead on the network throughput. For the long-term resource allocation, we formulate a series of optimization problems that address relaying capability, frequent handovers, small multiuser interference, and load balancing. The third thread of this thesis extends the second one toward spectrum sharing in mmWave networks and characterizes the gains of beamforming and coordination in spectrum sharing via several optimization problems. We analyze these problems in the asymptotic regimes when the number of antennas becomes large and conclude that spectrum sharing with light on-demand coordination is feasible, especially at higher mmWave frequencies (for example, 73 GHz).

    The original analysis proposed in this thesis gives novel insights into many MAC layer issues such as resource allocation, interference management, random access, mobility management, and synchronization in future mmWave networks. The thesis also highlights that the design of mmWave networks poses open problems at the intersection of optimization and learning theories. Given the recent interest in the standardization of mmWave cellular networks and the highly sub-optimal nature of the existing standards for mmWave short-range networks, the results of this thesis may have the potential to substantially steer future standardizations.

  • Dabert, Geoffrey
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Application of Machine Learning techniques to Optimization algorithms2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Optimization problems have been immuned to any attempt of combination with machine learning until a decade ago but it is now an active research field. This thesis has studied the potential implementation of a machine learning heuristic to improve the resolution of the optimization scheduling problems based on a Constraint Programming solver. Some scheduling problems, known as N P -hard problems, suffer from large computational cost (large number of jobs to schedule) and consequent human effort (well-suited heuristics need to be derived). Moreover industrial scheduling problems obviously evolves over time but a lot of features and the basic structure remain the same. Hence they have potential in the implementation a supervised-learning-based heuristic.

    First part of the study was to model a given benchmark of instances and im- plement some famous heuristics (as earliest due date, combined with the largest duration) in order to solve the benchmark.  Based on the none-optimality of returned solutions, primaries instances were choosen to implement our method. The second part represents the procedure which has been set up to design a supervised-learning-based heuristic. An instance generator was first  built to map the potential industrial evolutions of the instances. It returned secondaries instances representing the learning database. Then a CP-well-suited node ex- traction scheme was set up to collect relevant information from the resolution of the search tree. It will  collect data from nodes of the search tree given a proper criteria. These nodes are next projected onto a constant-dimensional space which described the system, the underlying subtree and the impact of the affectations. Upon these features and designed target values statistical mod- els are implemented. A linear and a gradient  boosting regressions have been implemented, calibrated and tuned upon the data. Last was to integrate the supervised-learning model into an heuristic framework. This has been done via a soft propagation module to try  the instantiation of all the children of the considered node and apply the given module upon them. The selection decision rule was based upon a reconstructed score. Third part was to test the procedure implemented. New secondaries instances were generated and supervised- learning-based heuristic tested against the earliest due date one.

    The procedure was tested upon two different instances. The integrated heuristic returned positive results for both instances. For the first one (10 jobs to schedule) a gain in the first solution found (resp. the number of backtracks) of 18% (resp. 13% were realized. For the second instance (90 jobs to schedule) a gain in the first solution found of at least 16%. The results come to validate the procedure implemented and the methodology used.

  • Blomdahl, Kajsa-My
    KTH, School of Chemical Science and Engineering (CHE).
    Numerical Calculations of Efimov States in Ultracold Atomic Systems2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In systems of ultracold atoms, the quantum Emov eect can appear

    where identical bosons form an innite tower of bound trimer states in the

    resonant limit, at the bound dimer dissociation threshold. The most characteristic

    feature of this eect is that their energy spectrum obey a geometric

    scaling law, which is universal in the sense that it emerges irrespective of the

    nature of the two-body forces. Using a model potential, constructed to resemble

    the two-body interaction between alkali atoms, which was ne-tuned

    to control the scattering length, energy eigenvalues for the two- and threebody

    problem were calculated numerically. The results where tted to the

    analytic theory and the appearance of the rst Emov state was positioned

    at a scattering length of -9.23 rvdW , which is in good agreement with the

    universal value -9.2 rvdW.

  • Public defence: 2017-06-12 13:00 V1, STOCKHOLM
    Hamisi, Rajabu
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Modelling phosphorus dynamics in constructed wetlands upgraded with reactive filter media2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Phosphorus mobility and sorption mechanisms underlying the removal efficiency of different adsorbent media were evaluated using the SWAT model and 3Dreactive transport model. The aims of the thesis were to: i) improve understanding of phosphorus mobility in the Oxundaån catchment; ii) identify suitable sites for constructing wetlands; iii) develop the numerical reactive transport model in order to identify key parameters which affects sorption efficiencies of the reactive adsorbent media; iv) predict the media's sorption efficiencies; and v) evaluate the viable reactive adsorbent media for mitigating eutrophication in the Baltic Sea. To predict phosphorus removal efficiencies of the adsorbent media and visualize the sorption process within the constructed wetlands, a three-dimensional model was developed within the COMSOL Multiphysics®. The reactive transport model was developed by coupling four physics interfaces to simulate the processes of water flow dynamics, transport of diluted phosphorus species, reaction kinetics and heat transfer in the porous media. The SWAT modelling results showed that arable land with the less background phosphorus retention, lower soil permeability and lower land slope could provide suitable sites for constructing wetlands. The simulated phosphorus sorption efficiency of the reactive filter media was ranked: 88 % (113 g P kg-1) for Polonite®, 85 % (81gP kg-1) for Filtralite P®, 62 % (61 gPkg-1) for Blast furnace slag, 57 % (44gP kg-1) for Wollastonite. In comparison to other media, Polonite® was observed to be a suitable reactive adsorbent media for wetland applications under different hydraulic loading rates and pH change, whose P-removal efficiency last for six years. Moreover, the modelling results showed less significant effects of particle size on the phosphorus removal efficiency as compared to solution pH and Ca mineral content. Precipitation was identified to be the dominant mechanisms for phosphorus removal in these media with the positive correlation to pH increase (R2 = 0.94, p-value = 0.002) and Calcium content (R2 = 0.73, p-value = 0.004). The good agreements between the simulated outputs and experimental data accurately captured the processes of phosphorus mobility and removal. The results suggest that the reactive transport models are valuable tools for providing insight into sorption processes in subsurface systems and improving design criteria for constructed wetlands. More experimental data are needed to calibrate the sensitivity of local parameters in order to better assess the performance of subsurface flow constructed wetlands.

  • Public defence: 2017-06-14 10:00 B2, Stockholm
    Yin, Jiaqing
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Formation of Bainite in Steels2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    A systematic survey of morphology of bainite and proeutectoid ferrite was carried out in order to validate some old thoughts of bainite transformation mechanism. It is confirmed that there is no morphological evidence supporting a sharp change neither between Widmanstätten ferrite and the ferritic component of upper bainite, nor between upper and lower bainite. Both Widmanstätten ferrite and upper bainite start with precipitation of ferrite plates at a grain boundary while lower bainite starts with intragranular nucleation. In case of grain boundary nucleation, a group of parallel plates with same crystallographic orientation to the parent austenite grain forms. This process is followed by a second stage of decomposition of the austenitic interspace, which remained in between the primary ferrite plates. At high temperature, the austenitic interspace would either retain as thin slabs or transform into pearlite through a nodule originated from a grain boundary. At lower temperature, cementite precipitation starts to be possible and initiates simultaneous growth of ferrite. Generally, there are two modes of such eutectoid reactions operating in the second stage, i.e. a degenerate and a cooperative mode, which would lead to typical upper and lower bainite, respectively, in definition of carbides morphology. Both upper and lower bainite according to this definition are observed in a wide temperature range. A sharp temperature between the upper and lower bainite structures thus exists only when the definition is based on their nucleation sites, i.e. grain boundary nucleation for upper bainite and intragranular nucleation for lower bainite. Supposing that the first stage is a diffusionless process it should have a high growth rate to prevent carbon diffusion. This is not supported by lengthening rate obtained in current study as well as data from literature for Fe-C alloys. Finally, it is shown that the “subunits” play no role in the lengthening process of bainite.

  • Public defence: 2017-06-15 10:00 M311, Stockholm
    Daemi, Bita
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Enhanced image analysis, a tool for precision metrology in the micro and macro world2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The need for high speed and cost efficient inspection in manufacturing lineshas led to a vast usage of camera-based vision systems. The performance ofthese systems is sufficient to determine shape and size, but hardly to an accuracylevel comparable with traditional metrology tools. To achieve highprecision shape/position/defect measurements, the camera techniques haveto be combined with high performance image metrology techniques whichare developed and adapted to the manufactured components. The focus ofthis thesis is the application of enhanced image analysis as a tool for highprecision metrology. Dedicated algorithms have been developed, tested andevaluated in three practical cases ranging from micro manufacturing at submicronprecision to meter sized aerospace components with precision requirementsin the 10 μm range.The latter measurement challenge was solved by low cost standard consumerproducts, i.e. digital cameras in a stereo configuration and structured lightfrom a gobo-projector. Combined with high-precision image analysis and anew approach in camera calibration and 3D reconstruction for precise 3Dshape measurement of meter sized surfaces, the achievement was fulfilledand verified by two conventional measurement systems; a high precisioncoordinate measurement machine and a laser scanner.The sub-micron challenge was the implementation of image metrology forverification of micro manufacturing installations within a joint Europeaninfrastructure network, EUMINAfab. The results were an unpleasant surprisefor some of the participating laboratories, but became a big step forwardto improve the dimensional accuracy of the investigated laser micromachining, micro milling and micro-printing systems, since the accuracy ofthese techniques are very difficult to assess.The third high precision metrology challenge was the measurement of longrange,low-amplitude topographic structures on specular (shiny) aerodynamicsurfaces. In this case Fringe Reflection Technique (FRT) was appliedand image analysis algorithms were used to evaluate the fringe deformationas a measure of the surface slopes to obtain high resolution data. The resultwas compared with an interferometric analysis showing height deviation inthe range of tens of micrometers over a lateral extension of several cm.

  • Public defence: 2017-06-12 13:15 Sal D3, Stockholm
    Chen, Rongzhen
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    First-Principles Study on Electronic and Optical Properties of Copper-Based Chalcogenide Photovoltaic Materials2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    To accelerate environmentally friendly thin film photovoltaic (PV) technologies, copper-based chalcogenides are attractive as absorber materials. Chalcopyrite copper indium gallium selenide (CIGS ≡ CuIn1–xGaxSe2) is today a commercially important PV material, and it is also in many aspects a very interesting material from a scientific point of view. Copper zinc tin sulfide selenide (CZTSSe ≡ Cu2ZnSn(S1–xSex)4) is considered as an emerging alternative thin film absorber material. Ternary Cu2SnS3 (CTS) is a potential absorber material, thus its related alloys Cu2Sn1–xGexS3 (CTGS) and Cu2Sn1–xSixS3 (CTSS) are attractive due to the tunable band gap energies. CuSb(Se1–xTex)2 and CuBi(S1–xSex)2 can be potential as ultra-thin (≤ 100 nm) film absorber materials in the future. In the thesis, analyses of these Cu-based chalcogenides are based on first-principles calculations performed by means of the projector augmented wave method and the full-potential linearized augmented plane wave formalisms within the density functional theory as implemented in the VASP and WIEN2k program packages, respectively.

    The electronic and optical properties of CIGS (x = 0, 0.5, and 1) are studied, where the lowest conduction band (CB) and the three uppermost valence bands (VBs) are parameterized and analyzed in detail. The parameterization demonstrates that the corresponding energy dispersions of the topmost VBs are strongly anisotropic and non-parabolic even very close to the Γ-point. Moreover, the density-of-states and constant energy surfaces are calculated utilizing the parameterization, and the Fermi energy level and the carrier concentration are modeled for p-type CIGS. We conclude that the parameterization is more accurate than the commonly used parabolic approximation. The calculated dielectric function of CuIn0.5Ga0.5Se2 is also compared with measured dielectric function of CuIn0.7Ga0.3Se2 collaborating with experimentalists. We found that the overall shapes of the calculated and measured dielectric function spectra are in good agreement. The transitions in the Brillouin zone edge from the topmost and the second topmost VBs to the lowest CB are responsible for the main absorption peaks. However, also the energetically lower VBs contribute significantly to the high absorption coefficient.

    CTS and its related alloys are explored and investigated. For a perfectly crystalline CTS, reported experimental double absorption onset in dielectric function is for the first time confirmed by our calculations. We also found that the band gap energies of CTGS and CTSS vary almost linearly with composition over the entire range of x. Moreover, those alloys have comparable absorption coefficients with CZTSSe. Cu2XSnS4 (X = Be, Mg, Ca, Mn, Fe, Ni, and Zn) are also studied, revealing rather similar crystalline, electronic, and optical properties. Despite difficulties to avoid high concentration of anti-site pairs disordering in all compounds, the concentration is reduced in Cu2BeSnS4 partly due to larger relaxation effects. CuSb(Se1–xTex)2 and CuBi(S1–xSex)2 are suggested as alternative ultra-thin film absorber materials. Their maximum efficiencies considering the Auger effect are ~25% even when the thicknesses of the materials are between 50 and 300 nm.

  • Public defence: 2017-06-07 10:15 E2, Stockholm
    Kleusberg, Elektra
    KTH, School of Engineering Sciences (SCI), Mechanics, Stability, Transition and Control.
    Wind turbine simulations using spectral elements2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Understanding the flow around wind turbines is a highly relevant research question due to the increased interest in harvesting energy from renewable sources. This thesis approaches the topic by means of numerical simulations using the actuator line method and the incompressible Navier–Stokes equations in the spectral element code Nek5000. The aim is to gain enhanced understanding of the wind turbine wake structure and wind turbine wake interaction. A verification study of the method and implementation is performed against the finite volume solver EllipSys3D using two types of turbines, an idealized constant circulation turbine and the Tjæreborg turbine. It is shown that Nek5000 requires significantly lower resolution to accurately compute the wake development, however, at the cost of a smaller time step.The constant circulation turbine is investigated further with the goal of establishing guidelines for the use of the actuator line method in spectral element codes, where the mesh is inherently non-equidistant and currently used guidelines of force distribution based on Gaussian kernels are difficult to apply. It is shown that Nek5000 requires a larger kernel width in the fixed frame of reference to remove numerical instabilities. Further, the impact of different Gaussian widths on the wake development is investigated in the rotating frame of reference, showing that the convection velocity and the breakdown of the spiral tip and root vortices are dependent on the Gaussian width. In the second part, the flow around single and multiple wind-turbine setups at different operating conditions is investigated and compared with experimental results. The focus is placed on comparing the power and thrust coefficients and the wake development based on the time-averaged streamwise velocity and turbulent stresses. Further the influence of the tower model is investigated both upstream and downstream of the turbine. The results show that the wake is captured accurately in most cases. The loading exhibits a significant dependence on the Reynolds number at which the airfoil data is extracted. When the helical tip vortices are stable the turbulent stresses at the tip vortices are underestimated in the numerical simulations. This is due to the finite resolution and the projection of the actuator line forces in the numerical domain using a prescribed Gaussian width, which leads to lower induced velocities in the helical vortices.

  • Public defence: 2017-06-15 09:30 Air-Fire, Science for Life Laboratories, Solna
    Unnersjö-Jess, David
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cellular Biophysics.
    High-resolution imaging of kidney tissue samples2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The kidney is one of the most important and complex organs in the human body, filtering hundreds of litres of blood daily. Kidney disease is one of the fastest growing causes of death in the modern world, and this motivates extensive research for better understanding the function of the kidney in health and disease. Some of the most important cellular structures for blood filtration in the kidney are of very small dimensions (on the sub-200 nm scale), and thus electron microscopy has been the only method of choice to visualize these minute structures. In one study, we show for the first time that by combining optical clearing with STED microscopy, protein localizations in the slit diaphragm of the kidney, a structure around 75 nanometers in width, can now be resolved using light microscopy. In a second study, a novel sample preparation method, expansion microscopy, is utilized to physically expand kidney tissue samples. Expansion improves the effective resolution by a factor of 5, making it possible to resolve podocyte foot processes and the slit diaphragm using confocal microscopy. We also show that by combining expansion microscopy and STED microscopy, the effective resolution can be improved further. In a third study, influences on the development of the kidney were studied. There is substantial knowledge regarding what genes (growth factors, receptors etc.) are important for the normal morphogenesis of the kidney. Less is known regarding the physiology behind how paracrine factors are secreted and delivered in the developing kidney. By depleting calcium transients in explanted rat kidneys, we show that calcium is important for the branching morphogenesis of the ureteric tree. Further, the study shows that the calcium-dependent initiator of exocytosis, synaptotagmin, is expressed in the metanephric mesenchyme of the developing kidney, indicating that it could have a role in the secretion of paracrine growth factors, such as GDNF, to drive the branching.

  • Public defence: 2017-06-13 09:00 Sal M235, Stockholm
    Woldemariam, Daniel Minilu
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    District Heating-driven Membrane Distillation for Water Purification in Industrial Applications2017Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Domestic and industrial water demands are growing globally due to population growth and rapid economic development, placing increasing strains on water resources. Wastewater effluents generated from these and other activities impact the environment and are thus subject to tightening regulation. The focus of research and development in water treatment processes aims at both pollutant removal efficiency and cost of purification.

    Membrane distillation (MD) is a developing thermally driven technology capable of achieving extremely high environmental performance utilizing renewable energy sources to a high degree. District heating networks, and in particular those driven by biomass, represent an ideal heat supply for MD systems.

    This thesis presents a technoeconomic assessment of district heating driven MD for water purification in selected industrial applications. The study covers analysis of MD separation performance and the related costs from different district heating integration scenarios. The analyses are based on three types of semi-commercial MD modules, with experiments conducted at laboratory and pilot scales. The case studies include pharmaceutical residue removal from effluents of municipal wastewater treatment plant, wastewater purification in pharmaceutical industry, and ethanol concentration in bioethanol production plant. Full-scale simulation studies were carried out for the identified case studies based on the experimental data obtained from MD module along with process information gathered from the industries. Results from the pharmaceutical residue removal pilot trials showed very good to excellent separation efficiency for 37 compounds at feed concentrations ranging from ng/L to mg/L. From alcohol-water feeds, ethanol concentrations were increased from 5% to nearly 90%. Simulation studies revealed that district heating integration of MD systems is feasible. Costs per unit volume of purified water are higher than competing technologies, however the configurations enable enhanced environmental performance that would be difficult to achieve otherwise.

  • Hamisi, Rajabu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering. SEED - KTH.
    Renman, Gunno
    SEED- KTH.
    Thunvik, Roger
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Brokking Balfors, Berit
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering. SEED-KTH.
    Welin, A.
    Larm., T.
    Modelling phosphorus recovery by reactive adsorbent in a vertical subsurface flow constructed wetlandManuscript (preprint) (Other academic)
    Abstract [en]

    Phosphorusremoval efficiencies by four low - costs reactive adsorbent media wereevaluated in the long - time period using the three - dimensional model of thevertical subsurface flow constructed wetlands in the COMSOL Multiphysics®software. Evaluations were made for Polonite, Filtralite P, Sorbulite andWollastonite adsorbent media with the aims of predicting their long - termsorption capacity and describing the phenomena of sorption mechanisms whenapplied in the vertical subsurface flow constructed wetlands for wastewaterpurification. The 3D model of the vertical flow constructed wetlands weredimensioned to Swedish EPA guidelines for small scale wastewater treatment, andcalibrated at saturated media using the breakthrough data derived from thecolumn experiments of similar adsorbent media application, and the localsensitivity analysis were performed for water quality and hydraulic loadingparameters. It was observed that the breakthrough curves developed by model weresignificantly correlated to the experimental data. The overall findings showedthat Polonite® could be the potential reactive adsorbent for phosphorus removalin the VF-CWs application, and its removal efficiency was discovered to lastfor 5 years. The large variation of media sorption capacities discovered to beaffected more by factor of pH and hydraulic loading rates than the particlesize. High degree of prediction accuracy which is demonstrated by this modelsuggest that the proposed model is a useful tool for predicting pollutantsremoval in various reactive porous media

  • Daemi, Bita
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Mattsson, Lars
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Performance evaluation of a micro screen printing installation2017Report (Other academic)
    Abstract [en]

    Micro- and nano-manufacturing is an expanding industry and many different manufacturing techniques are used, from advanced focused ion beam treatment to reasonably simple printing technologies. Common to all of them are the needs to verify the manufactured geometries and dimensions. This report presents the results of the second round of benchmarking activities within the EUMINAfab European Research Infrastructure, in order to establish more knowledge about the capabilities of a screen printing installation. To obtain a better understanding of the accuracy of the screen printing installation, a precise verification test is needed to measure the absolute performance of the machine. Predicted performance and capability information is based on specifications given for the machine installation by the machine deliverer. But, in practice the absolute performances of the installation is often off from the specification. When forming the EUMINAfab infrastructure consortium it was decided that independent high precision verification tests should be made on different installations to help the micro-manufacturers to get the real capability information of their equipment and be able to improve performance to a higher EUMINAfab level. In this study a comprehensive verification test was designed and carried out by using an ultra-precision metrology method in order to establish more knowledge about the capabilities of the screen printing equipment. The measurement results show the machine’s X,Y position accuracy, pseudo-repeatability and reproducibility. It is not as good as predicted.

  • Daemi, Bita
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Mattsson, Lars
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Analysis of camera image repeatability using manual and automatic lenses2017Report (Other academic)
    Abstract [en]

    Autofocus lenses are conveniently used for applications such as video metrology. In this study we investigate the stability of capturing images and show that for precision metrology applications the autofocus lenses are not as accurate as manual lenses. The investigation was done by analyzing series of seven repeated images captured from a highly accurate reference artifact using two different lenses; autofocus and manual, mounted on a same camera system.

  • Public defence: 2017-06-09 10:15 Munin, Stockholm
    Blanco, Blas
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Railway track dynamic modelling2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The railway vehicles are an increasing mean of transportation due to, its reduced impact on environment and high level of comfort provided. These reasons have contributed to settle a positive perception of railway traffic into the European society. In this upward context, the railway industrial sector tackles some important challenges; maintaining low operational costs and controlling the nuisance by-products of trains operation, the most important being railway noise. Track dynamic plays a main role for both issues, since a significant part of the operational costs are associated with the track maintenance tasks and, the noise generated by the track can be dominant in many operational situations. This explains why prediction tools are highly valued by railway companies. The work presented in this licentiate thesis proposes methodologies for accurate and efficient modelling of railway track dynamics. Two core axes have led the development of this task, on one hand, the rail modelling and, on the other hand, the characterisation of the finite length nature of track supports. Firstly, concerning the rail modelling technique, it has evolved under two major premises. On one hand, regarding the frequency domain, it should describe high frequency behaviour of the rail. In order to accomplish with this first premise, a model based on Timoshenko beam theory is used, which can accurately account for the vertical rail behaviour up to 2500 Hz. On the other hand, with respect to the time domain, the response should be smooth and free of discontinuities. This last condition is fulfilled by implementation of the Timoshenko local deformation. Secondly, a model of support that considers its finite length nature is sought. For this purpose, a Timoshenko element over elastic foundation is formulated. Thus, the common model of support, which is based on a concentrated connection, is substituted by a distributed model of support. In this way, several enhancements are achieved; the temporal contact force response is smoothed and a more realistic shape is obtained, the amplitude of the displacement due to the parametric excitation is reduced and the magnitude associated to the ‘pin-pin’ frequency is not overestimated.

  • Sundberg, Elisabet
    KTH, School of Chemical Science and Engineering (CHE).
    Granskning av avancerade pyrolysprocesser med lignocellulosa som råvara – tekniska lösningar och marknadsförutsättningar2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The population growth as well as a rapid technical and economic development globally affects the energy consumption. This requires a secure, stable and sustainable supply of energy. Today fossil fuels dominate globally and this results in environmental problems. Fossil fuels are also a finite, unsustainable resource. Thus, there is a need to replace fossil fuels with sustainable alternative sources of energy. This is also central for environmental goals both in Sweden and in the European Union. There are expectations that processes for the conversion of lignocellulosic biomass to solid, liquid and gaseous fuels can contribute to a transition from fossil to renewable fuels. In this thesis, carried out in collaboration between KTH and IVL Swedish Environmental Research Institute, one of the conversion processes is investigated in detail – pyrolysis. Pyrolysis is a thermal process that converts lignocellulose under anaerobic conditions at temperatures between about 300-650°C. Three phases can be obtained as products. A volatile which can be condensed into pyrolysis oil, a solid which may be termed biochar or charcoal depending on the end use, and a gas phase. The yield and the quality of the products is dependent upon the type of raw material, the type of reactor and the process conditions. An examination of the status of different pyrolysis processes on or on the way to the market has been made. The current degree of commercialization and what the future may look like for both the technology and the products have been assessed through literature studies, internet searches, and interviews with selected companies and individuals with expertise in pyrolysis.


    This report reveals that continuous pyrolysis is not yet a fully commercial process, but that it has the opportunity to reach commercialization during the right conditions. It is difficult to say when it occurs, due to various external factors, continued technical development, increased knowledge of the pyrolysis process and results of the current demonstrations. In this report, several critical factors for the commercialization of pyrolysis in Sweden have been identified, e.g. increased stability for policy instruments and that will limit the risk for investments (uncertainty and short-term decisions frightens investors) and the establishment of a value chain for the products, i.e. a stable market. Prices on fossil fuels and biomass feedstock are also important factors. Processes for the production of biochar is in the early stages of commercialization, and seem to have reached further in their development than processes for pyrolysis oil. The only fully commercial application of pyrolysis today is the production of charcoal that commonly is performed in traditional batch-wise processes. There are many possible uses for the products in which they have the potential to reduce carbon emissions and contribute to a more sustainable future. Standardization and certification of products is important, and demonstration of the use. Stabilization and further upgrading of pyrolysis oil is another important factor for commercialization. It seems like processes for catalytic upgrading are not yet sufficiently technically or financially developed to be able to provide a competitive product. Research and development in this area are ongoing. Integration of the process with incumbent industrial processes seems to be able to offer increased energy efficiency and reduced production costs.

  • Bergström, Louise
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology.
    Uttorkning av betongbjälklag: En utmaning och en möjlighet2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Betong har länge varit det mest använda byggnadsmaterialet. Dess goda beständighet, formbarhet och hållfasthet har gjort att den till ett av våra viktigaste byggnadsmaterial. Uttorkningen av betongbjälklagen är en del av ett projekts kritiska linje eftersom det inte är möjligt att applicera golvbeläggningen innan detta moment är utfört.

    JM inledde 2016 ett pilotprojekt där man istället för utfackningsväggar prövade att använda prefabricerade betongytterväggar, vilket förkortar produktionsledtiden och gör att huset blir tätare. I samband med detta väcktes frågan om hur de prefabricerade betongväggarna påverkade uttorkningen av betongen.

    Detta examensarbete syftar till att undersöka hur JM arbetar med uttorkningen av betongbjälklag och att utreda vad JM kan göra för att undvika att betonguttorkning blir ett problem för byggarbetsplatserna.

    För att ta reda på hur JM arbetar med uttorkning av betongbjälklag intervjuades platschefer och arbetsledare. Intervjuerna visade att platsledningen upplever att betonguttorkningen utgör ett problem i vartannat till vart tredje projekt och att det skulle behöva fokuseras betydligt mer på den. De visade även att de som arbetar med betongen har god kunskap om uttorkning av betong och eventuella åtgärdsmetoder om torkningen går för långsamt. Hur betonguttorkningen hanteras beror dock till stor del på platsledningens erfarenhet.

    När ett projekt påbörjas görs en fuktdimensionering av BetongIndustri som visar vilken betongkvalitet som krävs för att betongen ska hinna torka till den önskade relativa fuktigheten under utsatt tid. Den visar även om det finns en risk att det uppstår problem någonstans. Det finns dock flera moment som kan leda till att det senare uppstår problem, t.ex. simuleras inte nederbörd på ett verklighetstroget sätt i beräkningsprogrammet, det är problematiskt att olika definitioner används och frånvaro av tydliga riktlinjer kring ventilation ökar risken för att det missas eller startas för sent.

    En mätning utfördes även av den relativa fuktigheten i ett torkande bjälklag på projektet Berghus 3 i Liljeholmen i Stockholm. Mätningarna visade att betongen i princip inte torkar alls innan huset är tätt och värmen slagits på. Mätningarna visade även att torkklimatet i byggnaden endast under en kort period befinner sig inom det intervall som uttorkningen beräknats för.

    Det finns åtgärder för att motverka problem med torkningen uppstår. Genom att undvika nederbörd och stående vatten på bjälklagen får betongen bättre förutsättningar och kan torka snabbare. För att säkerställa att omgivningen uppfyller det som krävs för att betongen ska torka ut behöver torkklimatet kontrolleras och det behövs även en beredskap för hur torkinsatser ska ske vid för långsam torkning.

  • Public defence: 2017-05-29 10:15 F3, Stockholm
    Sack, Stefan
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Experimental and Numerical Multi-port Eduction for Duct Acoustics2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Sound generation and propagation in circular ducts for frequencies beyond the cut-on frequencies of several higher order acoustic modes is investigated. To achieve this, experimental and numerical set-ups are designed and used to research aeroacoustic interactions between in-duct components and to conceive noise mitigation strategies.

    Describing in-duct sound for frequencies with a moderate number of propagating modes is important, for example, for improving the noise emission from mid-size ventilation systems. Challenges that are largely unacknowledged in the literature involve efficient test rig design, quantification of limits in the methods, numerical modelling, and development of effective noise mitigation strategies for higher order modes.

    In this thesis, in-duct sound is mapped on a set of propagating pressure eigenmodes to describe aeroacoustic components as multi-ports with sound scattering (passive properties) and a source strength (active properties). The presented analysis includes genetic algorithms and Monte Carlo Methods for test rig enhancement and evaluation, multi-port network predictions to identify model limitations, and scale resolving (IDDES) and Linearized Navier Stokes computations for numerical multi-port eduction and the silencer design.

    It is first shown that test rig optimization improves the quality of multi-port data significantly. Subsequently, measurements on orifice plates are used to test the network prediction model. The model works with high accuracy for two components that are sufficiently separated. For small separations, strong coupling effects are observed for the source strength but not for the scattering of sound. The measurements are used for numerical validation, which gives reliable results for coupled and uncoupled systems. The total acoustic power of tandem orifices is predicted with less than 2 dB deviation and the passive properties for most frequencies with less than 5 % difference from the measurement. The numerical (FEM) models are also used to design a completely integrated silencer for spinning modes that is based on micro-perforated plates and gives broadband attenuation of 3-6 dB per duct diameter silencer length.

    The multi-port method is a powerful tool when describing aerodynamically decoupled in-duct components in the low- to mid-frequency range. Due to a robust passive network prediction, multi-port methods are particular interesting for the design of silencer stages. Furthermore, the demonstrated applicability to numerical data opens novel application areas.

  • Public defence: 2017-06-08 10:00 Brinellsalen M311, Stockholm
    A Asif, Farazee M
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Machine and Process Technology.
    Circular Manufacturing Systems: A development framework with analysis methods and tools for implementation2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The society today lives on the philosophy of ‘take-make-use-dispose.’ In the long run, this is not sustainable as the natural resources and the waste carrying capacity of the earth are limited. Therefore, it is essential to reduce dependency on the natural resources by decoupling the growth from the consumption. In this venture, both the society and the manufacturing industry have a vital role to play. The society needs to shift towards Circular Economy that rests upon the philosophy of ‘take-make-use-reuse’ and the manufacturing industry has to be a major stakeholder in this shift. Despite being proven to be both economically and environmentally beneficial, successful examples of circular systems are few today. This is primarily due to two reasons; firstly, there is a lack of systemic and systematic approach to guide industries and secondly, there is a lack of analysis methods and tools that are capable of assessing different aspects of circular manufacturing systems. Taking on to these challenges, the objective of this research is to bring forward a framework with methods and decision support tools that are essential to implement circular manufacturing systems. The initial conceptual framework with the systemic approach is developed based on extensive review and analysis of research, which is further adapted for industrial implementation. Systematic analysis methods, decision support and implementation tools are developed to facilitate this adaptation. This development has been supported by four cases from diverse manufacturing sectors. Behind each decision support tool, there are analysis methods built upon mainly system dynamics principles. These tools are based on simulation platforms called Stella and Anylogic. Among other things, these tools are capable of assessing the performance of closed-loop supply chains, consequences of resource scarcity, potential gains from resource conservation and overall economic and environmental performance of circular manufacturing systems.

  • Public defence: 2017-06-09 10:00 Hörsal E2, Stockholm
    Magnusson, Jesper
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Studies on Current Commutation in Hybrid DC-breakers2017Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Compared to conventional AC-circuit breakers, a DC-breaker has to act fast and force the current down to zero. Many different DC-breaker topologies are available, and this thesis is focused on the hybrid DC-breaker comprising a mechanical switch and high power semiconductors.

    The main part of this thesis is focused on the current commutations in the hybrid DC-breaker. The two current commutations: from the mechanical switch to the semiconductor branch, and from the semiconductor to the metal oxide varistor, have completely different characteristics. When the mechanical switch opens, the metallic contacts separate and an electric arc is formed. As the voltage across the arc is higher than the voltage across the semiconductors, the current is pushed over to the semiconductor branch. The undesired stray inductance in the loop limits the current derivative and slows down the commutation. As the contacts keep separating, the arc voltage increases and eventually all current is conducted by the semiconductor and the arc ceases.

    For a hybrid DC-breaker, the worst case is a solid ground fault, as the fast rising current results in high current levels and makes the commutation from the mechanical switch to the semiconductor both difficult and slow. However, the fast rise of the current can be used to enhance the commutation by using coupled inductors in the two parallel branches. When the fault current rises in the semiconductor branch, the mutual coupling of the inductors causes the current in the mechanical switch to decrease and helps the commutation. The result is that the commutation time decreases with decreasing fault impedance, and makes the solid ground fault easier to handle.

    The commutation from the semiconductor to the metal oxide varistor is controlled by the turn-off of the semiconductor. When the semiconductor is turned off, it pulls the current down to zero with a rather constant current derivative regardless of the surrounding circuit and the system current is taken over by the metal oxide varistor. Hence, any inductance in the commutation loop will result in an over-voltage proportional to this inductance on top of the varistor voltage. By connecting a smaller metal oxide varistor, as a snubber, close to the semiconductor, the over-voltage can be controlled and the commutation from the snubber to the metal oxide varistor will be driven by the voltage difference between the two varistors.

    It is shown that for a 12 kV DC-system, a possible design of the mechanical switch in the hybrid DC-breaker comprises two contact gaps in series and opens with a velocity of 11 m/s. It has been experimentally verified that when starting the commutation at 4 kA, the commutation takes less than 700 us and is over before the switch has opened 1 mm.

    The thesis also contains proposed designs for an 80 kV DC-breaker that can be used as a modular solution for higher system voltages. For this higher voltage, the design will be a choice of the combination between the number of contact gaps in series and the opening velocity of the mechanical switch.

  • Public defence: 2017-06-09 10:00 M311, Stockholm
    Ratanathavorn, Wallop
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology.
    Dissimilar joining of aluminium to ultra-high strength steels by friction stir welding2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Multi-material structures are increasingly used in vehicle bodies to reduce weight of cars. The use of these lightweight structures is driven by requirements to improve fuel economy and reduce CO2 emissions. The automotive industry has replaced conventional steel components by lighter metals such as aluminium alloy. This is done together with cutting weight of structures using more advanced strength steels. However, sound joining is still difficult to achieve due to differences in chemical and thermal properties.


    This research aims to develop a new innovative welding technique for joining aluminium alloy to ultra-high strength steels. The technique is based on friction stir welding process while the non-consumable tool is made of an ordinary tool steel. Welding was done by penetrating the rotating tool from the aluminium side without penetrating into the steel surface. One grade of Al-Mg aluminium alloy was welded to ultra-high strength steels under lap joint configuration. Different types of steel surface coatings including uncoated, hot-dipped galvanised and electrogalvanised coating have been studied in order to investigate the influence of zinc on the joint properties. The correlation among welding parameters, microstructures, intermetallic formation and mechanical properties are demonstrated in this thesis.  Results have shown that friction stir welding can deliver fully strong joints between aluminium alloy and ultra-high strength steels. Two intermetallic phases, Al5Fe2 and Al13Fe4, were formed at the interface of Al to Fe regardless of surface coating conditions. The presence of zinc can improve joint strength especially at low heat input welding due to an increased atomic bonding at Al-Fe interface. The formation of intermetallic phases as well as their characteristics has been demonstrated in this thesis. The proposed welding mechanisms are given based on metallography investigations and related literature.

  • Public defence: 2017-06-15 13:00 Kollegiesalen, Stockholm
    Liljeblad, Elisabet
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Structures and processes in the Mercury magnetosphere2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The mechanisms involved in the transfer of mass and energy from the solar wind to any planetary magnetosphere is considered an important topic in space physics. With the use of the Mercury spacecraft MESSENGER's data, it has been possible to study these processes in an environment different, yet similar, to Earth's. These data have resulted in new knowledge advancing not only the extraterrestrial space plasma research, but also the general space physics field.


    This thesis aims to investigate mechanisms for the transfer of mass and energy into Mercury’s magnetosphere, and magnetospheric regions affected by, and processes directly driven by, these. The work includes the Kelvin-Helmholtz instability (KHI) at the magnetopause, which is one of the main drivers for mass and energy transfer on Earth, the low-latitude boundary layer (LLBL), which is in direct connection to the magnetopause and proposed to be affected by the KHI, magnetospheric ultra-low frequency (ULF) waves driven by the KHI, and isolated magnetic field structures in the magnetosheath as possible analogues to the Earth magnetosheath plasmoids and jets.


    Kelvin-Helmholtz waves (KHW) and the LLBL are identified and characterized. The KHWs are observed almost exclusively on the duskside magnetopause, something that has not been observed on Earth. In contrast, the LLBL shows an opposite asymmetry. Results suggest that the KHI and LLBL are connected, possibly by the LLBL creating the asymmetry observed for the KHWs.


    Isolated changes of the total magnetic field strength in the magnetosheath are identified. The similar properties of the solar wind and magnetosheath negative magnetic field structures suggest that they are analogues to diamagnetic plasmoids found on Earth. No clear analogues to paramagnetic plasmoids are found.  


    Distinct magnetospheric ULF wave signatures are detected frequently in close connection to KHWs. Results from the polarization analysis on the dayside ULF waves indicate that the majority of these are most probably driven by the KHI. In general, likely KHI driven ULF waves are observed frequently in the Hermean magnetosphere. 

    Although similar in many aspects, Mercury and Earth show fundamental differences in processes and structures, making Mercury a highly interesting planet to study to increase our knowledge of Earth-like planets.

  • Public defence: 2017-06-09 13:00 M3, Stockholm
    Taliotis, Constantinos
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy Systems Analysis.
    Large scale renewable energy deployment - Insights offered by long-term energy models from selected case studies2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The United Nations’ Sustainable Development Goal 7 (SDG7) of Agenda 2030 calls for an increase in the use of renewable energy sources, among other targets. The percentage of fossil fuel-fired thermal generation for electricity is increasingly being reduced as renewable energy technologies (RET) advance in cost-competitiveness, and as greenhouse gas and industrial air pollutant emission limits become more stringent. In certain cases, renewable energy contributes to energy security by improving a nation’s trade balance, since local resources are harnessed and imports are reduced. RET investments are becoming more frequent gaining a sizeable share in the electric power mix of numerous countries.

    However, RET is affected by existing fossil fuel-fired electricity generation, especially in countries that have domestic reserves. While coal may be dirty, others such as natural gas provide multiple benefits, presenting a challenge to renewables. Additionally, RET endowment varies for each geographical location. This often does not correspond to the location of major electricity demand centers.  Therefore, large scale RET adoption and integration becomes logistically more cumbersome, as it necessitates existence of a developed grid network.

    Utilizing a series of analyses in two different settings – Africa and Cyprus – this thesis draws insights on RET growth policy and the level of technology representation in long term energy models. In order to capture specific challenges of RET integration, enhancements in traditional long-term energy system models are called for and carried out.

     The case of Africa is used to assess adoption of RET under various trade scenarios. It is home to some of the world’s greatest RET resource potential and the single largest potential RET project, Grand Inga.  While, the island of Cyprus has goals of introducing large percentages of RET into its electric power mix. Each have important idiosyncrasies which are reflected in the analysis. On the one hand, natural gas competes with RET in Cyprus and forms a key transition fuel away from oil. On the other hand, lack of cross-border interconnectors limit RET project development across Africa.

  • Eriksson, Marcus
    KTH, School of Chemical Science and Engineering (CHE).
    Accelerated degradation of bipolar plates in the PEMFC2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The aging of bipolar plates in the polymer electrolyte membrane fuel cell was evaluated using different accelerated degradation tests. From previous studies, it is well known that the startups and shutdowns of a polymer electrolyte membrane fuel cell is the primary cause of fuel cell component degradation. Therefore, the aim of these tests was to simulate the number of startups/shutdowns that normally occur during the lifetime of a polymer electrolyte membrane fuel cell, e.g. for automobile applications. The tests were carried out in situ in order to be as realistic and close to operational conditions in real applications as possible. Mechanical stress and degradation normally occurring during polymer electrolyte membrane fuel cell operation was thereby included. The accelerated degradation tests were designed for maximum fuel cell stress, including use of the no purge and the air purge strategy, short cycle duration as well as an increased number of startups/shutdowns. Since the no purge strategy avoids prevention of local H

    2/O2 fronts, this strategy was implemented first. Other strategies e g the air purge strategy, where air is used to purge the anode, where also implemented. Parameters influencing the tests were varied and the cathode gas was changed between O2 and air depending on the test. Electrochemical methodology was implemented for the detection of corrosion in the tests and for analysis/ studies of the test results. These techniques include cell voltage/current readings, polarization curves, electrochemical impedance spectroscopy, contact resistance and current density decrease at constant cell voltage. In addition, scanning electron microscope was used to visualize the actual corrosion of the bipolar plates. It was found that implementation of the air purge strategy resulted in localized corrosion, i.e. oxide film formation, on the surface of the bipolar plates increasing both the corrosion resistance and the interfacial contact resistance.

  • Dahlbom Norgren, Nils
    KTH, School of Computer Science and Communication (CSC).
    Relation Classification Between the Extracted Entities of Swedish Verdicts2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This master thesis investigated how well a multiclass support vector machine approach is at classifying a fixed number of interpersonal relations between extracted entities of people from Swedish verdicts. With the help of manually tagged extracted pairs of people entities called relations, a multiclass support vector machine was used to train and test the performance of the classification. Different features and parameters were tested to optimize the method, and for the final experiment, a micro precision and recall of 91.75% were found. For macro precision and recall, the result was 73.29% and 69.29% respectively. This resulted in an macro F score of 71.23% and micro F score of 91.75%. The results showed that the method worked for a few of the relation classes, but more balanced data would have been needed to answer the research question to a full extent.

  • Berger, Victor
    KTH, School of Computer Science and Communication (CSC).
    Anomaly detection in user behavior of websites using Hierarchical Temporal Memories: Using Machine Learning to detect unusual behavior from users of a web service to quickly detect possible security hazards.2017Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
    Abstract [en]

    This Master's Thesis focuses on the recent Cortical Learn-ing Algorithm (CLA), designed for temporal anomaly detection. It is here applied to the problem of anomaly detec-tion in user behavior of web services, which is getting moreand more important in a network security context.

    CLA is here compared to more traditional state-of-the-art algorithms of anomaly detection: Hidden Markov Models (HMMs) and t-stide (an N-gram-based anomaly detector), which are among the few algorithms compatible withthe online processing constraint of this problem.

    It is observed that on the synthetic dataset used forthis comparison, CLA performs signicantly better thanthe other two algorithms in terms of precision of the detection. The two other algorithms don't seem to be able tohandle this task at all. It appears that this anomaly de-tection problem (outlier detection in short sequences overa large alphabet) is considerably different from what hasbeen extensively studied up to now.

  • Public defence: 2017-06-15 14:00 M311, Stockholm
    Li, Yujiang
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Computer Systems for Design and Manufacturing.
    Architecting model driven system integration in production engineering2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    System integration is a key enabler to maximize information value in an engineering context. The valuable information is normally represented by information models which play a decisive role in the implementation of system integration. The information models are designed to efficiently and effectively capture, process and communicate information among different functional and business units. However, use of the information models in implementing system integration is challenged by insufficient support from current settings of modeling architectures. This situation calls for new strategies to ease the use of information models.

    To address this challenge, this study presents a new twofold solution: Model driven system integration. It includes 1) a modeling architecture to guide the development of information models and 2) an integrated implementation process to guide the use of information models. Thus, this work improves practical applicability of an information model in its entire modeling lifecycle.

    The results contribute not only to the performance of modeling practices but also to improved understanding of information modeling in system integration. Implementation contexts and implementation models are introduced to develop an implementation-oriented modeling architecture. Further, the potential of information models as a knowledge base to sup-port implementation practices is identified.

    To concretely discuss behaviors and structures of information models, this study adopts ISO 10303 and the related standards as major references of existing information models.

    Case studies on model driven system integration validate this research in scenarios concerning kinematic modeling, kinematic error modeling, cutting tools classification and product catalogue modeling. Model driven system integration exhibits high efficiency in implementation, enhanced interoperability and increased value of information models.

  • Public defence: 2017-06-15 10:00 Q2, Stockholm
    Bleiker, Simon J.
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Heterogeneous 3D Integration and Packaging Technologies for Nano-Electromechanical Systems2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Three-dimensional (3D) integration of micro- and nano-electromechanical systems (MEMS/NEMS) with integrated circuits (ICs) is an emerging technology that offers great advantages over conventional state-of-the-art microelectronics. MEMS and NEMS are most commonly employed as sensor and actuator components that enable a vast array of functionalities typically not attainable by conventional ICs. 3D integration of NEMS and ICs also contributes to more compact device footprints, improves device performance, and lowers the power consumption. Therefore, 3D integration of NEMS and ICs has been proposed as a promising solution to the end of Moore’s law, i.e. the slowing advancement of complementary metal-oxide-semiconductor (CMOS) technology.In this Ph.D. thesis, I propose a comprehensive fabrication methodology for heterogeneous 3D integration of NEM devices directly on top of CMOS circuits. In heterogeneous integration, the NEMS and CMOS components are fully or partially fabricated on separate substrates and subsequently merged into one. This enables process flexibility for the NEMS components while maintaining full compatibility with standard CMOS fabrication. The first part of this thesis presents an adhesive wafer bonding method using ultra-thin intermediate bonding layers which is utilized for merging the NEMS components with the CMOS substrate. In the second part, a novel NEM switch concept is introduced and the performance of CMOS-integrated NEM switch circuits for logic and computation applications is discussed. The third part examines two different packaging approaches for integrated MEMS and NEMS devices with either hermetic vacuum cavities or low-cost glass lids for optical applications. Finally, a novel fabrication approach for through silicon vias (TSVs) by magnetic assembly is presented, which is used to establish an electrical connection from the packaged devices to the outside world.

  • Public defence: 2017-06-15 09:15 FA32, Stockholm
    Liljestrand, Charlotte
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Advanced nano- and microdomain engineering of Rb-doped KTiOPO4 for nonlinear optical applications2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Fine-pitch ferroelectric domain gratings are extensively used for generation of light in the visible and near-infrared spectral regions through quasi-phase matched (QPM) frequency conversion. Sub-μm QPM devices enables demonstration of nonlinear optics with counterpropagating waves, a field of nonlinear optics which remains sparsely explored due to the difficulty of fabricatinghigh quality gratings.

    In recent years, bulk Rb-doped KTiOPO4 (RKTP) has emerged as a highly promising nonlinear materials for fabrication of fine-pitch QPM devices through periodic electric-field poling. RKTP possesses large optical nonlinearity and high resistance to optical damage, while demonstrating improved material homogeneity and lower ionic conductivity than its isomorphs, which are important features for poling. Although fine-pitch QPM gratings, as well as large aperture QPM devices, have been demonstrated, fabrication of sub-μm high quality QPM devices remains a challenge.

    The primary aim of this research was to develop a reliable method to fabricate high-quality sub-μm periodically poled RKTP crystals (PPRKTP) and exploit them in novel optical applications. For this purpose, a novel poling method was developed. It was based on periodic modulation of the coercive field through ion exchange, where K+ ions are exchanged with Rb+ in the crystal, to modulate the coercive field and the ionic conductivity. This enables periodic poling of higher quality and with shorter period than ever before.

    High quality PPRKTP with a period of 755 nm were fabricated and used to demonstrate the first cascaded mirrorless optical parametric oscillator (MOPO), as well as the first MOPO pumped by a Q-switched laser. PPRKTP samples for blue light generation were fabricated, and second harmonic generation (SHG) was investigated with a high power 946 nm fiber laser. Up to 2 W of blue power was demonstrated for bulk samples, where the output power was limited by absorption of the SHG, leading to thermal dephasing of the devices. Laser-written waveguides were fabricated in PPRKTP for the first time, and a record high SHG power of 76 mW was obtained.

    Finally, the high-temperature stability of ferroelectric domain gratings was investigated. This is of utmost importance when a PPRKTP crystal is used as a seed for crystal growth. It was found that for charged domains walls, the domain-wall motion was highly anisotropic with rapid movement in y-direction while only small movements were observed in the x-direction of the crystal.

  • Tingström, Emil
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Mathematical Statistics.
    Optimal Investment with Corporate Tax Payments2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This Master's thesis examines the problem of optimal investment when corporate taxes have to be paid on capital gains. Tax payments share a lot of similarities with payoff from a call option where the underlying is the firm's capital. How to optimally deal with this tax-option is a non-trivial problem that is complicated by the feedback between the value of the tax-option and the strategy the firm uses to handle it.

    For the case with only one tax payment it is possible to derive an explicit expression for the optimal strategy using a martingale method. The tax payment introduces some interesting properties to the optimal wealth process, such as a non-zero probability of ending up exactly at the tax basis at the terminal date.  

    The optimal strategy is then generalized to the problem with multiple tax payments using the martingale framework. A numerical method of calculating the optimal strategy based on trinomial trees is also presented and implemented. This is then used to verify the theoretical results and to calculate the optimal strategy with an increasing number of tax payments. 

    For the case with only one tax payment at a terminal date numerical results show that the increase in utility is small and a close to optimal strategy can be derived by ignoring tax. With multiple tax payments however, the increase in utility from using the tax-optimal strategy is significant.

  • Heckscher, Hans
    KTH, School of Biotechnology (BIO).
    Monoklonala antrikroppar - en översiktsstudie2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • Lindman, Jonas
    KTH, School of Chemical Science and Engineering (CHE).
    Synthesis of functional polylactide: Monomer synthesis scale-up and poly(ethylene glycol) functionalization2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This master’s degree project optimized the synthesis route to a functional lactide by increasing the total yield from 25 to 33 % and reducing the number of unit operations from 17 to 10. This was done by optimizing an existing synthetic pathway to better fit larger scale manufacturing. The monomer was also successfully copolymerized with ʟ-lactide and functionalized by attaching poly(ethylene glycol) units of varying chain lengths to the polylactide chain, which gives some antifouling properties to the copolymer. The resulting material, a functionalized polylactide, is an interesting material suitable for the use in medical implats, largely thanks to its versatility and ability to be tailored for a specific purpose.

    et al.
    KTH, School of Chemical Science and Engineering (CHE).
    KTH, School of Chemical Science and Engineering (CHE).
    KTH, School of Chemical Science and Engineering (CHE).
    KTH, School of Chemical Science and Engineering (CHE).
    Utformning av bränslecellssystem för fordon2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    I detta kandidatexamensarbete var målet att optimera ett bränslecellssystem med avseende på ett antal olika parametrar. Bränslecellssystemet var tänkt att användas i fordonet Sleipner V som är konstruerad i samarbete med andra KTH studenter. En annan bränslecell av företaget Horizon användes för att driva fordonet Sleipner i tävlingen Shell-Eco Marathon eftersom den ursprungliga bränslecellen var i dåligt skick. Sleipner utrustat med bränslecellen från Horizon klarade av att köra två varv i Shell-Eco Marathon.

    I denna rapport tas det upp grundläggande teori om bränsleceller, försökuppställning för experimenten och resultat med tillhörande analys. För att åstadkomma målet med detta arbete så skulle olika parametrar undersökas, men detta kunde inte utföras. På grund av diverse problem med bränslecellen så ändrades fokus till att reparera bränslecellen, vid undersökningen av problemen har vissa resultat uppnåtts.

    Vid körning uppstod spänningsfall och det kan ha berott på masstransportbegränsningar. För att åtgärda dessa problem utfördes en torknings- respektive fuktningsprocess som hade olika påverkan på de individuella cellerna. Efter torkningsprocessen fungerade 18 av 22 celler medan 19 celler fungerade efter fuktningsprocessen.  De icke fungerade cellerna som gav låg spänning kan ha varit för blöta eller för torra.

  • Lambertsson, Christoffer
    KTH, School of Computer Science and Communication (CSC).
    Expectations of Privacy in Voice Interaction – A Look at Voice Controlled Bank Transactions2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    There is a strong mainstream interest in the tech world for voice interaction, in parts thanks to the technological advancements in the field and the use of big data which in some cases make speech recognition on par with humans. The aim of this paper is to explore the relationship between voice interaction and privacy. Two prototypes on voice interaction of bank services were created, they had differences in feedback, correctness and need of physical interaction. Twelve participants were instructed to perform tasks like checking balance and transferring money with the prototypes. Then they were asked about their relation to privacy in the context of their previous experiences with voice interaction and the two prototypes they used. The results show that what was perceived as private and the need for privacy varied a lot between the participants. In the end a respectful and empowering design to voice interaction is proposed in which the user could customize how the application provides feedback by adding contextual sensitivity e.g. using GPS to know if you are home, or a camera to know if you are looking at the device.

  • Public defence: 2017-06-13 09:00 F3, Stockholm
    Güler, Püren
    KTH, School of Computer Science and Communication (CSC), Robotics, perception and learning, RPL.
    Learning Object Properties From Manipulation for Manipulation2017Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The world contains objects with various properties - rigid, granular, liquid, elastic or plastic. As humans, while interacting with the objects, we plan our manipulation by considering their properties. For instance, while holding a rigid object such as a brick, we adapt our grasp based on its centre of mass not to drop it. On the other hand while manipulating a deformable object, we may consider additional properties to the centre of mass such elasticity, brittleness etc. for grasp stability. Therefore, knowing object properties is an integral part of skilled manipulation of objects. 

    For manipulating objects skillfully, robots should be able to predict the object properties as humans do. To predict the properties, interactions with objects are essential. These interactions give rise distinct sensory signals that contains information about the object properties. The signals coming from a single sensory modality may give ambiguous information or noisy measurements. Hence, by integrating multi-sensory modalities (vision, touch, audio or proprioceptive), a manipulated object can be observed from different aspects and this can decrease the uncertainty in the observed properties. By analyzing the perceived sensory signals, a robot reasons about the object properties and adjusts its manipulation based on this information. During this adjustment, the robot can make use of a simulation model to predict the object behavior to plan the next action. For instance, if an object is assumed to be rigid before interaction and exhibit deformable behavior after interaction, an internal simulation model can be used to predict the load force exerted on the object, so that appropriate manipulation can be planned in the next action. Thus, learning about object properties can be defined as an active procedure. The robot explores the object properties actively and purposefully by interacting with the object, and adjusting its manipulation based on the sensory information and predicted object behavior through an internal simulation model.

    This thesis investigates the necessary mechanisms that we mentioned above to learn object properties: (i) multi-sensory information, (ii) simulation and (iii) active exploration. In particular, we investigate these three mechanisms that represent different and complementary ways of extracting a certain object property, the deformability of objects. Firstly, we investigate the feasibility of using visual and/or tactile data to classify the content of a container based on the deformation observed when a robotic hand squeezes and deforms the container. According to our result, both visual and tactile sensory data individually give high accuracy rates while classifying the content type based on the deformation. Next, we investigate the usage of a simulation model to estimate the object deformability that is revealed through a manipulation. The proposed method identify accurately the deformability of the test objects in synthetic and real-world data. Finally, we investigate the integration of the deformation simulation in a robotic active perception framework to extract the heterogenous deformability properties of an environment through physical interactions. In the experiments that we apply on real-world objects, we illustrate that the active perception framework can map the heterogeneous deformability properties of a surface.

  • Public defence: 2017-06-09 10:15 sal E3, Stockholm
    Kabral, Raimo
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Turbocharger Aeroacoustics and Optimal Damping of Sound2017Doctoral thesis, comprehensive summary (Other academic)
  • Eldh, Ida
    KTH, School of Computer Science and Communication (CSC).
    Navigation and informational architecture in smart electrical testing and diagnostic devices2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This degree project begins with a general introduction of the topic embedded systems in electrical testing and diagnostic devices in industries within the field of human-computer interaction. Then it continues with a deeper view of the problem area and the specific products which are in focus of this project. The company which the study is carried out in, produces and develops many types of test equipment (in a more generalized term called smart electrical testing and diagnostic devices) to the electrical supply industry. The importance of a usable user-interface is greater today than several years ago as the competition between companies include not only technical performance but also usability [4]. Therefore it is highly important to design a user-interface and navigation structure to combine a company’s all products and create a sense of recognition within them. A high level of recognition is in this case, a userinterface and a navigation structure that are recognizable and understandable when the end-user interacts with different products. The information architecture and user-interface design is not very often prioritized in a company as the budget is often much greater for technology than it is for information architecture. Prior the information architecture was more about technology but today it is about system information and content [8]. In this study, three methods are used to make an attempt to collect data to answer and discuss the research question “Is it possible to design a homogenous navigation structure in electrical testing and diagnostic devices for different end-user types?”  This study shows that it is very difficult to get a straight forward answer to how a sustainable and homogeneous information architecture and navigation structure for smart electrical testing and diagnostic devices should be designed. Although, the results could give a substantial input and information towards a common userinterface platform and act as guidelines for the development of products.

  • Linder, Åsa
    KTH, School of Computer Science and Communication (CSC).
    Key Factors for Feeling Present During a Music Experience in Virtual Reality Using 360° Video2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This is a study on what factors are important for a user to feel present when watching a 360° video of a musical experience. This is of interest because experiences in VR are still under exploration. Some artists are trying to live stream their concerts in VR showing that music in VR is something that is of interest. The video used in this study was recorded in Adolf Fredriks Kyrka, a church in Stockholm. I used a GoPro Omni Rig that records 360 degrees simultaneously to shoot the video in the church. The video was then shown in a user study with 23 participants divided into two groups, one VR-group that watched the video with an Oculus Rift and one control group that watched the video on a regular computer screen. The participants got to answer questions regarding their experience both before and after having watched the video. The result shows that there are few differences in the experience between the two groups. For example the VR-group felt more present in the virtual world than the control group. The thing that most participants commented on was the image quality of the video. It was not high enough according to some and it was also a bit blurry. Even though the image quality was a bit poor, the VR-group did not feel that it was too distracting for them to feel present. Overall the participants felt that it was a good and fun experience to watch. The most important factor for the feeling of presence is the level of immersion in the system. A fully immersive system will most likely give a higher feeling of presence than a non-immersive system. Two other factors that are important are the image quality and the audio. These three factors combined with interesting content will most likely lead to an experience where the user feels present in the virtual world and forgets the real world for a while.

  • Public defence: 2017-06-09 10:00 Kollegiesalen, Stockholm
    Peñaloza, Diego
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. RISE - Research Institutes of Sweden.
    The role of biobased building materials in the climate impacts of construction: Effects of increased use of biobased materials in the Swedish building sector2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    A significant share of the global climate change impacts can be attributed to the construction sector. One mitigation strategy is increasing the use of biobased materials. Life cycle assessment (LCA) has been used to demonstrate the benefits of this, but forest complexities create uncertainty due to omission of key aspects. This aim of this thesis is to enhance understanding of the effects of increasing use of biobased materials in climate change mitigation of construction works with a life cycle perspective. Non-traditional LCA methodology aspects were identified and the climate impact effects of increasing the use of biobased materials while accounting for these was studied. The method applied was dynamic LCA combined with forest carbon data under multi-approach scenarios. Diverse case studies (a building, a small road bridge and the Swedish building stock) were used. Most scenarios result in impact reductions from increasing the use of biobased materials in construction. The inclusion of non-traditional aspects affected the results, but not this outcome. Results show that the climate mitigation potential is maximized by simultaneously implementing other strategies (such as increased use of low-impact concrete). Biobased building materials should not be generalised as climate neutral because it depends on case-sensitive factors. Some of these factors depend on the modelling of the forest system (timing of tree growth, spatial level approach, forest land use baseline) or LCA modelling parameters (choice of the time horizon, end-of-life assumptions, service life). To decrease uncertainty, it is recommended to use at least one metric that allows assessment of emissions based on their timing and to use long-term time horizons. Practitioners should clearly state if and how non-traditional aspects are handled, and study several methodological settings. Technological changes should be accounted for when studying long-term climate impacts of building stocks.

  • Public defence: 2017-06-02 10:00 M402, Borås
    Ferreira, Javier
    KTH, School of Technology and Health (STH), Medical Engineering. Högskolan i Borås.
    Modular textile-enabled bioimpedance system for personalized health monitoring applications2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    A growing number of factors, including costs, technological advancements, ageing populations, and medical errors, are leading industrialized countries to invest in research on alternative solutions to improve their health-care systems and increase patients’ quality of life. Personal health systems (PHS) examplify the use of information and communication technologies that enable a paradigm shift from the traditional hospital-centered healthcare delivery model toward a preventive and person-centered approach. PHS offer the means to monitor a patient’s health using wearable, portable or implantable systems that offer ubiquitous, unobtrusive biodata

    acquisition, allowing remote monitoring of treatment and access to the patient’s status. Electrical bioimpedance (EBI) technology is non-invasive, quick and relatively affordable technique that can be used for assessing and monitoring different health conditions, e.g., body composition assessments for nutrition. When combined with state-of-the-art advances in sensors and textiles, EBI technologies are fostering the implementation of wearable bioimpedance monitors that use functional garments for personalized healthcare applications. This research work is

    focused on the development of wearable EBI-based monitoring systems for ubiquitous health monitoring applications. The monitoring systems are built upon portable monitoring instrumentation and custom-made textile electrode garments.

    Portable EBI-based monitors have been developed using the latest material technology and advances in system-on-chip technology. For instance, a portable EBI spectrometer has been validated against a commercial spectrometer for total body composition assessment using functional textile electrode garments. The development of wearable EBI-based monitoring units using functional garments and dry textile electrodes for body composition assessment and respiratory monitoring has been shown to be a feasible approach. The availability of these measurement systems indicates progress toward the real implementation of personalized healthcare systems.

  • Söder, Carl-Johan
    KTH, School of Engineering Sciences (SCI). Wallenius Marine AB.
    Controlling the Roll Responses of Volume Carriers2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Modern volume carriers such as container vessels, cruise ships and Pure Car and Truck Carriers (PCTC’s) have become more vulnerable to critical roll responses as built in margins have been traded against increased transport efficiency. The research presented in this doctoral thesis aims at enhancing the predictability and control of these critical roll responses. The thesis presents a holistic framework for predicting and assessing the roll damping, which is a crucial parameter for predicting roll motions, based on a unique combination of full scale trials, model tests, semi-empirical methods and computational fluid dynamics. The framework is intended to be used from the early design stage and gradually improved until delivery of the ship and finally to provide input for decision support in the operation. The thesis also includes a demonstration of a new application for rudder control to be used for mitigation of parametric roll. This is performed by simulating real incidents that have occurred with PCTC’s in service. Simulations with rudder roll control show promising results and reveal that the approach could be very efficient for mitigation of parametric roll. Finally, an approach for monitoring of roll induced stresses, so-called racking stresses in PCTC’s, is presented. The approach involves measurement of the ship motions and scaling of pre-calculated structural responses from global finite element analysis. Based on full scale motion and stress measurements from a PCTC in-service the approach is evaluated and demonstrated to be an efficient alternative to conventional methods.

  • Kontothanasis, Epameinondas
    KTH, School of Information and Communication Technology (ICT).
    Dynamic Optical Resource Allocation in Transport Networks Based on Mobile Traffic Patterns2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Mobile traffic increases rapidly. Based on Ericsson’s forecast [1], mobile traffic is expected to grow at a compound annual growth rate on percentage of 45% as the number of smartphone subscriptions and the consumption per subscriber increase. The monthly data traffic volume is expected to grow 6 times between 2015 and 2021. As demand increases, new technologies are investigated and deployed to cover the user requirements. Intense effort is given by researchers for the arrival of fifth generation (5G) network. High performance and increased capacity requirements drive research to heterogeneous networks. With the term “heterogeneous network”, a network that consists of different technologies and architectures is described. A heterogeneous wireless network involves the combination of macro and micro cells to improve coverage and capacity. All the traffic generated from the mobile network should be transferred from the antenna, through an access network, to the main office and from there to the backbone network. Optical networks are considered as the ideal solution for this purpose and research drives technology towards the usage of optical networks in the Fixed Mobile Convergence (FMC) architectures. The FMC architectures are proposed architectures [2] that focus to converge the fixed, mobile access and aggregation networks into a single transport network.

    In this study, we analyze the FMC architecture. We particularly analyze the Fronthaul architecture in combination with transport technologies such as Next Generation – Passive Optical Network 2 (NG-PON2) and Wavelength Routed Wavelength Division Multiplexing PON (WR-WDM-PON). We also take under consideration traffic patterns of mobile networks generated in various urban areas in the city of Stockholm, based in different use of land. Based on the traffic pattern, the number of small cells needed per area is calculated.

    In this thesis project, the traffic patterns from the mobile network and the transport network architectures are studied. The purpose of this thesis is to create an algorithm and study different sharing scenarios of the underlying transport infrastructure. The results of this algorithm will reveal if sharing and reusing resources in the transport infrastructure is beneficial in terms of saving resources.