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  • Public defence: 2017-05-12 10:00 Kollegiesalen, Stockholm
    Barreiro Fidalgo, Alexandre
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Experimental studies of radiation-induced dissolution of UO2: The effect of intrinsic solid phase properties and external factors2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Dissolution of the UO2 matrix is one of the potential routes for radionuclide release in a future deep geological repository for spent nuclear fuel. This doctoral thesis focuses on interfacial reactions of relevance in radiation-induced dissolution of UO2 and is divided in two parts:

    In the first part, we sought to explore the effects of solid phase composition:

    The impact of surface stoichiometry on the reactivity of UO2 towards aqueous radiolytic oxidants was studied. H2O2 reacts substantially faster with stoichiometric UO2 than with hyperstoichiometric UO2. In addition, the release of uranium from stoichiometric UO2 is lower than from hyperstoichiometric UO2. The behavior of stoichiometric powder changes with exposure to H2O2, approaching the behavior of hyperstoichiometric UO2 with the number of consecutive H2O2 additions.

    The impact of Gd-doping on the oxidative dissolution of UO2 in an aqueous system was investigated. A significant decrease in uranium dissolution and higher stability towards H2O2 for (U,Gd)O2 pellets compared to standard UO2 was found.

    In the second part, we sought to look at the effect of external factors:

    The surface reactivity of H2 and O2 was studied to understand the overall oxide surface reactivity of aqueous molecular radiolysis products. The results showed that hydrogen-abstracting radicals and H2O2 are formed in these systems. Identical experiments performed in aqueous systems containing UO2 powder showed that the simultaneous presence of H2 and O2 enhances the oxidative dissolution of UO2 compared to a system not containing H2.

    The effect of groundwater components such as bentonite and sulfide on the oxidative dissolution of UO2 was also explored. The presence of bentonite and sulfide in water could either delay or prevent in part the release of uranium to the environment. The Pd catalyzed H2 effect is more powerful than the sulfide effect. The poisoning of Pd catalyst is not observed under the conditions studied.

  • Public defence: 2017-05-09 13:00 F3, Stockholm
    Tully, Philip
    KTH, School of Computer Science and Communication (CSC), Computational Science and Technology (CST). University of Edinburgh School of Informatics.
    Spike-Based Bayesian-Hebbian Learning in Cortical and Subcortical Microcircuits2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Cortical and subcortical microcircuits are continuously modified throughout life. Despite ongoing changes these networks stubbornly maintain their functions, which persist although destabilizing synaptic and nonsynaptic mechanisms should ostensibly propel them towards runaway excitation or quiescence. What dynamical phenomena exist to act together to balance such learning with information processing? What types of activity patterns

    do they underpin, and how do these patterns relate to our perceptual experiences? What enables learning and memory operations to occur despite such massive and constant neural reorganization? Progress towards answering many of these questions can be pursued through large-scale neuronal simulations. 

     

    In this thesis, a Hebbian learning rule for spiking neurons inspired by statistical inference is introduced. The spike-based version of the Bayesian Confidence Propagation Neural Network (BCPNN) learning rule involves changes in both synaptic strengths and intrinsic neuronal currents. The model is motivated by molecular cascades whose functional outcomes are mapped onto biological mechanisms such as Hebbian and homeostatic plasticity, neuromodulation, and intrinsic excitability. Temporally interacting memory traces enable spike-timing dependence, a stable learning regime that remains competitive, postsynaptic activity regulation, spike-based reinforcement learning and intrinsic graded persistent firing levels. 

     

    The thesis seeks to demonstrate how multiple interacting plasticity mechanisms can coordinate reinforcement, auto- and hetero-associative learning within large-scale, spiking, plastic neuronal networks. Spiking neural networks can represent information in the form of probability distributions, and a biophysical realization of Bayesian computation can help reconcile disparate experimental observations.

  • GW Samuelsson, John
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Stenotic Flows: Direct Numerical Simulation,Stability and Sensitivity to Asymmetric ShapeVariations2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Flow through a sinuous stenosis with varying degrees of shape asymmetry andat Reynolds number ranging from 250 up to 800 is investigated using direct numericalsimulation (DNS), global linear stability analysis and sensitivity analysis.The shape asymmetry consists of an offset of the stenosis throat, quantifiedas the eccentricity parameter, E. At low Reynolds numbers in a symmetricgeometry, the flow is steady and symmetric. Our results show that when Reynoldsnumber is increased, the flow obtains two simultaneous linearly stablesteady states through a subcritical Pitchfork bifurcation: a symmetric stateand an asymmetric state. The critical Reynolds number for transition betweenthe states are found to be very sensitive to asymmetric shape variations, thusbifurcation can also occur with respect to eccentricity for a given Reynoldsnumber. The final state observed in the DNS can be either nearly symmetricor strongly asymmetric, depending on the initial condition. When eccentricityis increased from zero, the symmetric state becomes slightly asymmetric,flow asymmetry varying nearly linearly with eccentricity. When eccentricityis increased further, the nearly symmetric state becomes linearly unstable. Alinear global stability analysis shows that the eigenvalue sensitivity to eccentricityis of the second order, this is also confirmed by preliminary sensitivityanalysis. For higher Reynolds numbers, the asymmetric solution branch displaysregimes of periodic oscillations as well as intermittency. Comparisons aremade to earlier studies and a theory that attempts to explain and unite thedifferent numerical and experimental results within the field is presented.

  • Bronge, Erica
    KTH, School of Computer Science and Communication (CSC).
    Visualization of Feature Dependency Structures: A case study at Scania CV AB2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    As many automotive companies have moved towards a higher degree of variability in the product lines they offer their customers, a necessary need has emerged for so called feature dependency structures that are used to describe product feature dependencies and verify order validity. In this study, the possibility of using a node-link graph representation to visualize such a feature dependency structure and the associated affordances and limitations were investigated by the implementation of a case study at the Swedish automotive company Scania CV AB. Qualitative data gathering methods such as contextual inquiry and semi-structured interviews with employees were used to identify key tasks and issues involved in maintenance and analysis of Scania’s in-house feature dependency structure. These findings were used together with user-supported iterative prototyping to create a few visualization prototypes intended to provide support with performance of some of the identified tasks. User evaluation of the prototypes showed that a node-link graph representation was a viable solution to support users with structure maintenance, exhibiting the following affordances: structure exploration, overview and context. Furthermore, the major limitations of the tested representation were found to be lookup of specific information and access to detail. The findings of this study are expected to be of use for other automotive companies that employ a high degree of feature variability in their product lines through the use of complex feature dependency structures.

  • Rondon, Isaac
    KTH, School of Computer Science and Communication (CSC).
    Eco-visualization for amateur energy work: Supporting energy management in Housing Cooperatives2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Eco-visualization technologies aim to trigger more environmental behaviors by providing feedback about the usage of key resources such as energy. However, the design of these technologies to encourage energy conservation has been mainly focused on individual behaviors in a household level. Addressing a different approach researchers at KTH have designed the housing cooperative app, a web application that provides feedback about the collective energy consumption of housing cooperatives in Stockholm, aiming to reduce the cooperative's collective energy use.

    By using a Research Through Design approach, this thesis explores how data visualization can support amateur energy work through the housing cooperative app. For this, I identified design problems in the data visualization elements of the app, which I aimed to solve by redesigning them; then, I conducted semi structured interviews with amateur energy workers, where they interacted with the application, to generate new insights about how data visualization can be used in an amateur work context.

    Through the interviews it was possible to obtain qualitative answers about the challenges of amateurs energy workers and the way data visualization could be used to address theses challenges and achieve their goals in an efficient way. The interviews was divided in Background, Amateur work, Comprehension and Usefulness of the data, and were supported by a walkthrough in the application presenting to users different scenarios and features in the application.

    Results showed the potential that data visualizations have to support amateur energy workers to overcome their main challenges and to identify the rewards of their work. In this thesis I discuss about this potential, and about design aspects that are important to consider when designing eco-visualization technologies in amateur energy context.

  • Ajami Gale Rashidi, Sam André
    KTH, School of Computer Science and Communication (CSC), Media Technology and Interaction Design, MID.
    Designing for sustainable grocery shopping: A conceptual design to encourage sustainable shopping2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Climate change is one of the biggest issues that the world faces today, and one of the biggest contributors to climate change are groceries. This paper aims at using digital artefacts to create a product or design that will encourage the user to shop more environmentally friendly. To achieve this, I have tried to identify the major hindrances today that grocery shoppers are faced with through the user centered method Contextual Inquiry.  I have then presented the results from the inquiry to students at KTH Royal Institute of Technology during workshops. During these workshops, the students have conceptualized ideas and designs for different solutions. Based on their results, I have created a prototype design that I call the SmartCart. This cart consists of a regular shopping cart with a screen similar to an iPad attached to the handlebars. This screen then delivers easily apprehensible information about different grocery products environmental impact in real time. The design has not been tested in a live environment, but initial testing indicates that a live application could give satisfying results in lowering the sales of grocery products with a high environmental impact, while the design also could simultaneously improve the shopping experience for the customers in the grocery store.

  • Andersson, Ulrika
    KTH, School of Computer Science and Communication (CSC).
    Effect of depth cues on visual search in a web-based environment2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In recent years, 3D graphics has become more available for web development with low-level access to graphics hardware and increased power of web browsers. With core browsing tasks for users being to quickly scan a website and find what they are looking for, can 3D graphics – or depth cues – be used to facilitate these tasks? Therefore, the main focus of this work was to examine user performance on websites in terms of visual attention. Previous research on the use of 3D graphics in web design and other graphical interfaces has yielded mixed results, but some suggest depth cues might be used to segment a visual scene and improve visual attention. In this work, the main question asked was:  How do depth cues affect visual search in a web-based environment? To examine the question, a user study was conducted where participants performed a visual search task on four different web-based prototypes with varying depth cues. The findings suggest depth cues might have a negative effect by increasing reaction time, but certain cues can improve task completion (hit rate) in text-rich web environments. It is further elaborated that it might be useful to look at the problem from a more holistic perspective, also emphasizing other factors such as visual complexity and prototypicality of websites.

  • Patriksson, Andreas
    KTH, School of Computer Science and Communication (CSC).
    Net Neutrality - Do We Care?: A study regarding Swedish consumers' point-of-view upon Net Neutrality2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Net Neutrality implicates that all data being transmitted online is treated equal by Internet Service Providers. In 2016, the public debate regarding Net Neutrality in Sweden started growing as two major Mobile Network Operators were investigated by the Swedish Post and Telecom Authority for violation of European Union Net Neutrality regulations.

    Several studies have been conducted regarding Net Neutrality, most of them written in a legal, financial or technological perspective. This study takes another direction, aimed at understanding the consumer’s point of view regarding Net Neutrality. This study investigates whether or not consumers are aware of the subject and if so, how they value it.

    To measure this, an online survey was constructed, containing a total of 12 questions and statements. 77 people participated in the survey and out of these, 10 people participated in qualitative follow-up interviews. The interviews were semi-structured and individually designed according to each participant’s answers in the survey. This was done in order to gain a deeper understanding of the consumer’s reasoning while answering the survey.

    The results show that consumers lack knowledge regarding Net Neutrality. A major part of the consumers had not heard of the term or did not know the meaning of it, making it hard to determine whether or not the consumers value NN. However, when given a more concrete example of the implications of Internet Traffic Management from ISPs, the participants had a better understanding of what kind of implications NN could have on their Internet usage. They valued the implications of Net Neutrality, even though they did not know the theory of the term itself.

    The study also revealed that consumers have a big confidence in National Regulatory Authorities when it comes to looking after the openness of the Internet. Therefore, it is likely that National Regulatory Authorities must inform and educate consumers in the matter of Net Neutrality for them to value it and see its long-term implications.

  • Lundström, Anton
    KTH, School of Computer Science and Communication (CSC). School of Computer Science and Communication (CSC).
    Developing a Taxonomy for Sustainable ICT: An exploratory study of the feasibility of a taxonomy for sustainable ICT2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Information and Communication Technology (ICT) can have a role to play in transitioning into a sustainable society but it is important to consider that implementation of an ICT-based solution not always lead to sustainability. Kentaro Toyama (2015) has proposed a framework, what he refers to as “Preliminary Thoughts on a Taxonomy of Value for Sustainable Computing”, to be used for classification of sustainable ICT-projects. A working taxonomy for ICT-projects could provide an explicit evaluative framework to be used for evaluating whether a given project might or might not contribute to sustainability goals. The taxonomy includes three dimensions to consider when classifying ICT-projects:

    • Impact - On sustainability
    • Intention - Towards sustainability
    • Effort  - For achieving Impact

    This thesis picks up where Toyama left off with the purpose of exploring if the taxonomy is a feasible approach for addressing ICT and sustainability. This is done by first adding a Secondary Level to the taxonomy with the goal of making the classification process more accurate, but more importantly for the purpose of this thesis, enable a more detailed analysis of the overall feasibility of the taxonomy. Four interviews are conducted with representatives from ICT-projects addressing sustainability. As a result of the interviews four problems are identified that have implications for the feasibility of the taxonomy and that need to be considered in any future and further attempts to operationalize it.

  • Public defence: 2017-05-30 13:00 M108, Stockholm
    Neves, Cláudia
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Structural Health Monitoring of Bridges: Model-free damage detection method using Machine Learning2017Licentiate thesis, monograph (Other academic)
    Abstract [en]

    This is probably the most appropriate time for the development of robust and reliable structural damage detection systems as aging civil engineering structures, such as bridges, are being used past their life expectancy and beyond their original design loads. Often, when a significant damage to the structure is discovered, the deterioration has already progressed far and required repair is substantial. This is both expensive and has negative impact on the environment and traffic during replacement. For the exposed reasons the demand for efficient Structural Health Monitoring techniques is currently extremely high. This licentiate thesis presents a two-stage model-free damage detection approach based on Machine Learning. The method is applied to data gathered in a numerical experiment using a three-dimensional finite element model of a railway bridge. The initial step in this study consists in collecting the structural dynamic response that is simulated during the passage of a train, considering the bridge in both healthy and damaged conditions. The first stage of the proposed algorithm consists in the design and unsupervised training of Artificial Neural Networks that, provided with input composed of measured accelerations in previous instants, are capable of predicting future output acceleration. In the second stage the prediction errors are used to fit a Gaussian Process that enables to perform a statistical analysis of the distribution of errors. Subsequently, the concept of Damage Index is introduced and the probabilities associated with false diagnosis are studied. Following the former steps Receiver Operating Characteristic curves are generated and the threshold of the detection system can be adjusted according to the trade-off between errors. Lastly, using the Bayes’ Theorem, a simplified method for the calculation of the expected cost of the strategy is proposed and exemplified.

  • Tully, Philip
    et al.
    KTH, School of Computer Science and Communication (CSC), Computational Biology, CB. Karolinska Institutet, Sweden; University of Edinburgh, UK.
    Lindén, Henrik
    KTH, School of Computer Science and Communication (CSC), Computational Biology, CB. Karolinska Institutet, Sweden.
    Hennig, Matthias
    Lansner, Anders
    KTH, School of Computer Science and Communication (CSC), Computational Biology, CB. Stockholm University, Stockholm; Karolinska Institutet, Sweden.
    Probabilistic computation underlying sequence learning in a spiking attractor memory network2013In: BMC neuroscience (Online), ISSN 1471-2202, E-ISSN 1471-2202, no 14 (Suppl 1)Article in journal (Refereed)
  • Hällman, Ludvig
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Mathematical Statistics.
    The Rolling Window Method: Precisions of Financial Forecasting2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this thesis we set out to study the prediction accuracy of statistical quantities related to portfolio analysis and risk management implied by a given set of historical data. The considered forecasting procedure rely on rolling-window estimates over varying horizons where the resulting empirical return distributions can be considered the corresponding stationary distributions. By using scenarios generated from a joint interest rate-equity framework the rolling-window method allows to, empirically, study the uncertainty of return statistics as well as risk measures related to market risk. The study shows that, given the chosen models, the method is valid in predicting future statistical quantities related to portfolio return of up to one year. For risk measures, the forecasting uncertainty is found to be too significant and highlights the difficulty in foreseeing extremities of future market movements.

  • Kabir, MD Ahsan
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Techno-economic study of grid connected residential PV system with battery storage - A review of the Local System Operator (LSO) model2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The grid connected solar PV system with battery storage is one of the promising alternativeenergy solutions for electricity consumers. The Local System Operator (LSO) will be a newactor to operate its own energy system by integrating PV and battery system with other technicalsolutions. This thesis investigates the technical and economic viability of a grid connected PVsystem with battery storage in behind-the-meter approach for aggregated residential load toassess the LSO model for the present conditions in Sweden.The system model is developed using the System Advisory Model (SAM) – a simulationsoftware for renewable energy system analysis. The PV system model is designed using solarirradiation profile and fifty multi-dwelling aggregated residential load data from Sweden. Theappropriate design inputs of solar PV module, inverter and system loss are taken from previousstudies. The electricity price is analysed from the comparative study of Nord-pool wholesaleprice, market retail price and distribution grid tariffs. The financial metrics such as discountrate, inflation rate, system cost and currently available PV incentives are considered to make anaccurate model. To help with the assessment, three cases are formed; the first case representsonly the PV system and the other cases include storage - using a lithium-ion or lead-acid battery.This comparative study helps to determine the optimum PV and battery size at two differentlocations in Sweden.The optimum net present value (NPV) and profitability index (PI) is found at the 40 kW PVand 3 kWh battery system at Karlstad, Sweden. The optimum case is considered for furtherinvestigation to evaluate the system life time energy profile, electricity bill saving capabilityand battery performance. The system peak shaving potential is investigated by making twoother scenarios with higher battery capacity. Sensitivity analysis is also performed to assess thesystem’s technical and financial input parameters. The system capacity factor at the site locationis found as an influential parameter to the annual production and profitability. The optimumsize of PV system with a lithium-ion battery investment is found feasible for the LSO realimplementation only considering the current PV incentives and electricity price in Sweden. Thereport concludes with the assessment, the technical and economic feasibility of the studied PVand battery storage system profitability depends on the system site location, residential loadsize, consumer electricity cost and available PV incentives.

  • Kamruzzaman, Hasan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology.
    Pathway to a sustainable building: JM and SKB at Stockholm Royal Seaport: With focus on energy efficiency; technical design of roof, wall, window, basement and adaptability with climate change.2017Independent thesis Basic level (university diploma), 20 credits / 30 HE creditsStudent thesis
  • Abshirini, Ehsan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment.
    Koch, Daniel
    KTH, School of Architecture and the Built Environment (ABE), Architecture, Architectural Design.
    Resilience, space syntax and spatialinterfaces: The case of river cities2017In: A|Z ITU Journal of the Faculty of Architecture, ISSN 1303-7005, Vol. 14, no 1, 25-41 p.Article in journal (Refereed)
    Abstract [en]

    Resilience defined as the capacity of a system to manage impacts, keep its efficiency and continue its development has been scrutinized by researchers from different points of view over the past decades. Due to the prominence of resilience in urban planning, this paper intends to find out how the spatial structure of cities deals with disturbances, and if geographical phenomena such as rivers affect the resilience in cities. Using the space syntax methods syntactically analyze the resilience in cities, we innovatively introduce two measures; similarity and sameness. These measures are in relation with the syntactical properties of cities and compare the degree of resilience between different groups. Similarity measures the degree to which each city retains the relative magnitude of its foreground network after a disturbance and sameness is the degree to which each city retains the same segments as its foreground network after a disturbance. Likewise to network resilience studies, we apply different disturbances on cities and explore the reaction of cities to disturbances in terms of size of the foreground network and which segments are parts thereof. We then compare different groups based on these measurements as a method to analyze sameness and similarity. The results show that the resilience, in the way we define it, is different in different cities depending on in which view and based on which parameters we are discussing the resilience. Additionally morphological phenomena such as rivers have a great impact on the structure of cities and in turn on their resilience.

  • Yi, Xinlei
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Automatic Control.
    Liu, Kun
    Dimarogonas, Dimos V.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Karl H.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Automatic Control.
    Distributed Dynamic Event-Triggered Control for Multi-Agent Systems2017Conference paper (Refereed)
    Abstract [en]

    We propose two distributed dynamic triggering laws to solve the consensus problem for multi-agent systems with event-triggered control. Compared with existing triggering laws, the proposed triggering laws involve internal dynamic variables which play an essential role to guarantee that the triggering time sequence does not exhibit Zeno behavior. Some existing triggering laws are special cases of our dynamic triggering laws. Under the condition that the underlying graph is undirected and connected, it is proven that the proposed dynamic triggering laws together with the event-triggered control make the state of each agent converges exponentially to the average of the agents’ initial states. Numerical simulations illustrate the effectiveness of the theoretical results and show that the dynamic triggering laws lead to reduction of actuation updates and inter-agent communications.

  • Yi, Xinlei
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Automatic Control.
    Yang, Tao
    Wu, Junfeng
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Karl H.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Automatic Control.
    Event-Triggered Control for Multi-Agent Systems with Output Saturation2017Conference paper (Refereed)
    Abstract [en]

    We propose distributed static and dynamic event-triggered control laws to solve the consensus problem for multiagent systems with output saturation. Under the condition that the underlying graph is undirected and connected, we show that consensus is achieved under both event-triggered control laws if and only if the average of the initial states is within the saturation level. Numerical simulations are provided to illustrate the effectiveness of the theoretical results and to show that the control laws lead to reduced need for inter-agent communications.

  • Yi, Xinlei
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Automatic Control.
    Wei, Jieqiang
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Automatic Control.
    Dimarogonas, Dimos V.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Formation Control for Multi-Agent Systems with Connectivity Preservation and Event-Triggered Controllers2017Conference paper (Refereed)
    Abstract [en]

    In this paper, event-triggered controllers and corresponding algorithms are proposed to establish the formation with connectivity preservation for multi-agent systems. Each agent needs to update its control input and to broadcast this control input together with the relative state information to its neighbors at its own triggering times, and to receive information at its neighbors' triggering times. Two types of system dynamics, single integrators and double integrators, are considered. As a result, all agents converge to the formation exponentially with connectivity preservation, and Zeno behavior can be excluded. Numerical simulations show the effectiveness of the theoretical results.

  • Zhou, Yang
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Nonlinear analysis of reinforced concrete slab on partially softening ground: Ickelinjär analys av armerad betongplatta på delvis uppmjuknande grund2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Reinforced concrete slabs are a conventional type of foundation that is widely used in residential, commercial and industrial buildings. Most of the slab foundations are constructed directly on the ground without another structural medium in between and some of the slabs are therefore influenced by ground softening. A slab foundation is designed to transfer vertical loads and bridge imperfections in the ground, but excessive soil distortion may destroy the support conditions of the slab and through this influence the stability of the superstructures.

    The aim of this project is to study how ground softening and its further development influence a typical concrete slab. Furthermore, an approximate analytical method to evaluate the condition of a slab due to ground softening was studied. A practical case has been studied to capture the actual failure behaviours of a reinforced concrete slab, based on a previous project. For the case studied, possible future mining activities close to a high bay warehouse may cause damaging settlement in the underground. The fault that may appear softens the soils underneath the foundation, which may deteriorate and cause collapse of the concrete slab under the warehouse. Two types of failure scenarios were studied; subsoil softening and subsoil collapse.

    The Finite Element Method (FEM) was used to analyse the behaviour of the slab and the development of the failures in the subsoil. A commercial FEM software package, Abaqus, was used as the analytic tool, with a built-in Concrete Damaged Plasticity model (CDP) that for the concrete material model. Both linear and nonlinear material properties have been used in the analyses with same softening effect of the subsoil. A large number of models were analysed to simulate the development of the fault and capture the failure modes of the slab at different stages.

    Excessive tensile cracks and vertical deformations were found in both failure scenarios studied. A possible internal stability problem of the warehouse due to this was also found. The nonlinear behaviour of the concrete slab was captured through the failure scenarios before damage. It is shown that the serviceability of the reinforced concrete slab can be influenced by softening ground, and a more realistic description of the possible failures was here obtained based on the nonlinear model compared to previous elastic analyses.

    Keywords:     Reinforced concrete slab, Nonlinear, Ground softening, Finite Element Method (FEM), Abaqus, Concrete Damaged Plasticity (CDP).

  • Semeniuk, Bradley
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics. Centre for ECO2 Vehicle Design.
    Microstructure based estimation of the dynamic drag impedance of lightweight fibrous materials2017In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 141, no 3, 1360-1370 p.Article in journal (Refereed)
    Abstract [en]

    This paper focusses on the prediction of one of the main mechanisms of acoustic attenuation, the dynamic drag impedance, of a bundle of fibres typical of lightweight fibrous porous materials. The methodology uses geometrical properties derived from microscopy, and is based on the assumption that the interaction between the shear stress fields of neighbouring fibres may be neglected in the predicted drag force of an individual fibre. An analytical procedure is discussed which provides an estimate of the drag forces acting on infinite longitudinal and transversely orientated cylinders oscillating sinusoidally in a viscous incompressible fluid of infinite extent, at rest. The frequency-dependent viscous drag forces are estimated from the shear stresses on the surface of the cylinders, and may be scaled in terms of fibre diameter distributions and orientation angles in order to predict the dynamic drag impedance of a real material. The range of validity for this modelling approach is assessed through finite element solutions of three different fibre arrangements.

  • Public defence: 2017-05-24 10:00 Kollegiesalen, Stockholm
    Liu, Lipeng
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Physics of Electrical Discharge Transitions in Air2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Electrical discharges with a variety of different forms (streamers, glow corona, leaders, etc.) broadly exist in nature and in industrial applications. Under certain conditions, one electrical discharge can be transformed into another form. This thesis is aimed to develop and use numerical simulation models in order to provide a better physical understanding of two of such transitions, namely the glow-to-streamer and the streamer-to-leader transitions in air.

    In the first part, the thesis includes the two-dimensional simulation of the glow-to-streamer transition under a fast changing background electric field. The simulation is performed with a fluid model taking into account electrons. An efficient semi-Lagrangian algorithm is proposed to solve the convection-dominated continuity equations present in the model. The condition required for the glow-to-streamer transition is evaluated and discussed. In order to enable such simulations for configurations with large interelectrode gaps and long simulation times, an efficient simplified model for glow corona discharges and their transition into streamers is also proposed.

    The second part of the thesis is dedicated to investigate the dynamics of the streamer-to-leader transition in long air gaps at atmospheric pressure. The transition is studied with a one-dimensional thermo-hydrodynamic model and a detailed kinetic scheme for N2/O2/H2O mixtures. In order to evaluate the effect of humidity, the kinetic scheme includes the most important reactions with the H2O molecule and its derivatives. The analysis includes the simulation of the corresponding streamer bursts, dark periods and aborted leaders that may occur prior to the inception of a stable leader. The comparison between the proposed model and the widely-used model of Gallimberti is also presented.

  • Public defence: 2017-05-17 13:00 B21, Stockholm
    Sjölander, Andreas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Analyses of shotcrete stress states due to varying lining thickness and irregular rock surfaces2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Shotcrete is sprayed concrete applied pneumatically under high pressure and was invented in the beginning of the 1900's. This new technique decreased the construction time and since steel fibres were introduced in the shotcrete during the 1970's, shotcrete has been the primary support method for tunnels.

    Tunnels excavated with the drill and blast method creates a highly irregular rock surface which results in a shotcrete lining with varying thickness. The structural behaviour as well as the loads acting on the shotcrete lining depends on the interaction between the shotcrete, rock and rock bolts. There are several parameters influencing this interaction, e.g. bond strength, the stiffness of the rock and thickness of the shotcrete. All of these parameters are difficult to predict accurately which makes the structural design of the lining to a complex problem.

    This thesis present the first part of a research project with the long-term goal to improve the understanding of the structural behaviour of the shotcrete lining. To achieve this, numerical modelling have been used to study the build up of stresses and cracking of shotcrete when subjected to restrained loading caused by e.g. temperature differences and drying shrinkage. The response in the lining when subjected to a gravity load from a block has also been studied. The model is capable of describing the non-linear deformation behaviour of both plain and fibre reinforced shotcrete and uses presented in situ variations in thickness to more accurately account for the effects of expected variations in thickness. The thesis discuss and demonstrate the effect of important loads that acts on the shotcrete lining and how the irregular geometry of the rock surface in combination with the varying thickness of the shotcrete affect the development of stresses in the lining. It is also discussed how a full or partial bond failure affect the structural capacity of a shotcrete lining.  

     

  • Yang, Guang
    et al.
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Gross, James
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Al-Zubaidy, Hussein
    Huang, Yongming
    Delay and Backlog Analysis for 60 GHz Wireless Networks2016In: Global Communications Conference (GLOBECOM), 2016 IEEE, IEEE conference proceedings, 2016Conference paper (Refereed)
    Abstract [en]

    To meet the ever-increasing demands on higher throughput and better network delay performance, 60 GHZ networking is proposed as a promising solution for the next generation of wireless communications. To successfully deploy such networks, its important to understand their performance first. However, due to the unique fading characteristic of the 60 GHz channel, the characterization of the corresponding service process, offered by the channel, using the conventional methodologies may not be tractable. In this work, we provide an alternative approach to derive a closed-form expression that characterizes the cumulative service process of the 60 GHz channel in terms of the moment generating function (MGF) of its instantaneous channel capacity. We then use this expression to derive probabilistic upper bounds on the backlog and delay that are experienced by a flow traversing this network, using results from the MGF-based network calculus. The computed bounds are validated using simulation. We provide numerical results for different networking scenarios and for different traffic and channel parameters and we show that the 60 GHz wireless network is capable of satisfying stringent quality-of-Service (QoS) requirements, in terms of network delay and reliability. With this analysis approach at hand, a larger scale 60 GHz network design and optimization is possible.

  • Nikam, Uma
    KTH, School of Information and Communication Technology (ICT).
    Net Neutrality Implications for Internet Actors in Sweden2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A telecom industry is constantly looking for new ways to generate revenues by offering new and innovative services. Segmentation of customers by offering premium services to premium customers is a one way which has immense potential of revenue generation. Also, network and service providers are keen to provide specialized services with high quality and faster speed, with more emphasis on Quality of Experience (QoE), in order to enhance business revenue. The QoE concept offers several benefits to telecom operators as well as end-users, as it constantly monitors customer feedback and modifies services in order to delight customers.

    However, Net Neutrality is a current issue all over world and defined/re-defined in many ways, but many definitions overlooks practical difficulties and market realities. This demands in-depth analysis of Net Neutrality concept from regulatory and business point of view. Current business models for specialized services like Machine to Machine (M2M) communication and video streaming are not adequately designed to tackle regulatory issues such as Net Neutrality. Also the QoE concept needs to be tested on the level of Net Neutrality principles.

    This thesis discusses the business models incorporating QoE concept, along with analysing implications of Net Neutrality principles. The rules and regulations regarding Net Neutrality in Sweden are studied thoroughly in comparison with same principles in other countries like USA, India and countries from EU. The business models of M2M communication and video streaming services are presented and discussed considering effect of Net Neutrality regulations. Implications of Net Neutrality rules on specialize services, customized services, and zero-rating is presented.

    In order to have practical knowledge of telecom market and business strategies, several activities including brainstorming sessions with industrial experts and market surveys are carried out to generate meaningful conclusions. According to EU Net Neutrality rules specialized services, customized services and zero-rating services are allowed in Sweden with incorporating QoE.

  • Sunmark, Henrik
    KTH, School of Information and Communication Technology (ICT).
    Rekommendationssystem för livestreamingtjänster2016Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The usage and demand of recommender systems in digital services has increased in line with their huge range of products, making it more difficult for users to navigate through the content. Recommender systems are used in a wide scope of digital services ranging from E-commerce to music and film streaming. In order to provide users with recommendations on objects, a variety of algorithms, filtering methods and methods of data collections are being used. Applying these in live streaming services puts new demands on such systems since the content is replaced frequently and new objects added regularly. Furthermore, livestreaming services often lack explicit data and metadata, making recommendations less accurate.

    In a case study with Liveguide, recommender systems are evaluated, focusing on whether they are applicable to live streaming services, respecting requirements and demands on such systems. Methods are presented which tests, evaluates and adapts existing solutions to fit in well in context of live streaming. Finally, three models for recommender systems are suggested, based on the methods result. In order to satisfy the identified challenges, hybrid models turned out to be preferable in the context.

  • Annerstål, Viktor
    et al.
    KTH, School of Information and Communication Technology (ICT).
    Ottosson, Peter
    KTH, School of Information and Communication Technology (ICT).
    Modellering och simulering av Multiantennsystem avsett för litet fartyg2016Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Within the military there is great need for reliable communication between vehicles. During the planning and construction of a military RIB, Rigid-hulled Inflatable Boat, it is important to design an efficient antenna system that does not deteriorate out of disorder. It must also be ensured that the antennas transmitted power does not stay in the RIB boat. We have been given assignment to model and simulate a proposed antenna system and assess which tool is best suitable for the task. To analyze the antenna system we will look at the radiated electrical field together with the reflectionand EMC properties. The tool that we choose to use is a software called EMPro produced by Keysight Technologies. In this program we will create 3Dstructures for each individual object, the boat, the three antennas and the seawater. It’s also important to include each objects properties concerning material, so that they correctly reflect the reality. We are covering a broad spectrum with our antennas reaching from 1.6-30MHz, 30-88MHz and 100512MHz. The resulting simulation verifies that electromagnetic field would be powerful enough and that the antennas would not affect each other with the proposed placement. We could also confirm that our antennas reflected an inordinate amount of power but with cause that our models were not an exact replica of the antenna. The software EMPro is a suitable tool for this kind of projects concerning modeling and simulating antenna systems.Within the military there is great need for reliable communication between vehicles. During the planning and construction of a military RIB, Rigid-hulled Inflatable Boat, it is important to design an efficient antenna system that does not deteriorate out of disorder. It must also be ensured that the antennas transmitted power does not stay in the RIB boat. We have been given assignment to model and simulate a proposed antenna system and assess which tool is best suitable for the task. To analyze the antenna system we will look at the radiated electrical field together with the reflectionand EMC properties. The tool that we choose to use is a software called EMPro produced by Keysight Technologies. In this program we will create 3Dstructures for each individual object, the boat, the three antennas and the seawater. It’s also important to include each objects properties concerning material, so that they correctly reflect the reality. We are covering a broad spectrum with our antennas reaching from 1.6-30MHz, 30-88MHz and 100512MHz. The resulting simulation verifies that electromagnetic field would be powerful enough and that the antennas would not affect each other with the proposed placement. We could also confirm that our antennas reflected an inordinate amount of power but with cause that our models were not an exact replica of the antenna. The software EMPro is a suitable tool for this kind of projects concerning modeling and simulating antenna systems.

  • Public defence: 2017-04-28 13:15 E3, Stockholm
    Schickhofer, Lukas
    KTH, School of Engineering Sciences (SCI), Mechanics. Linné Flow Centre.
    Sound Generation and Propagation in the Human Upper Airways2017Licentiate thesis, monograph (Other academic)
    Abstract [en]

    The human upper airways embrace the source of phonation and affect the modulation of the voice, which is of vital importance for communication. Moreover, unwanted sounds may be generated in the upper airways due to elastic, collapsible parts that are susceptible to flow-induced vibration and resonance. The sound resulting from fluid-structure interaction in the upper respiratory tract, commonly known as snoring, can be an important indicator for underlying breathing disorders, such as obstructive sleep apnea (OSA). The scope of this work is the assessment of acoustic sources and the conditions for sound being produced in the upper airways in healthy and diseased state. For the study of the vocal tract under phonation, both low- and high-order numerical methods are applied and the obtained results are compared to experimental data from collaborators. The geometries of the vocal tract are based on magnetic resonance imaging (MRI) data for the different vowel pronunciations under voiced speech of a healthy male subject. Unsteady, direct compressible flow simulations using a finite volume solver are carried out for the computation of the pressure fluctuations and the associated distribution of frequency peaks as a result of the modulation through the static vocal tract. The peaks of the envelope of the far-field Fourier spectrum, which are characterising the spoken tone, are extracted and compared to the Helmholtz eigenfrequencies of the airway volume. The effect of variations of vocal fold closure, fundamental frequency, and vocal tract length on the computed acoustic signal is investigated. Thus, an estimation of the impact of vocal disorders on the ability of vowel production is attempted. A particular advantage of the presented approach is the attainment of time-resolved pressure and velocity fields of the flow, which allows for analysis of the coherent structures at the level of the vocal fold constriction, responsible for sound output during unvoiced speech. Furthermore, fluid-structure interaction simulations are performed for the study of the influence of critical parameters, such as Reynolds number of the flow or elasticity of the structure, on the onset of oscillations for a simplified model. The acoustic sources involved in the generation of the dominant frequencies of tissue vibrations are identified by application of an acoustic analogy. The obtained results of this work contribute to the development of a computational tool that assists physicians in the assessment of the airway function and the effectiveness of treatment plans prior to their application.

  • Otosaka, Inès
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatics.
    A Historic Record of Sea Ice Extents from Scatterometer Data2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Sea ice is a vital component of the cryosphere and does not only influence the polar regions but has a more global influence. Indeed, sea ice plays a major role in the regulation of the global climate system as the sea ice cover reflects the sun radiation back to the atmosphere keeping the polar regions cool. The shrinkage of the sea ice cover entails the warming up of the oceans and as a consequence, a further amplification of the melting of sea ice. Therefore, the polar regions are sensitive to climate change and monitoring the sea ice cover is very important.

    To assess sea ice change in the polar regions, satellite active microwave sensors, scatterometers, are used to observe the evolution of sea ice extent and sea ice types. Thus, this research aims at creating a historic record of daily global Arctic and Antarctic sea ice extents and analysing the change in sea ice types with scatterometer data.

    A Bayesian sea ice detection algorithm, developed for the Advanced scatterometer (ASCAT), is applied and tuned to the configurations of the scatterometers on board the European Remote Sensing satellites, ERS\textendash 1 and ERS\textendash 2. The sea ice geophysical model functions (GMFs) of ERS and ASCAT are studied together to validate the use of ASCAT sea ice GMF extrapolated to the lower incidence angles of ERS. The main adaptations from the initial algorithm aim at compensating for the lower observation densities afforded by ERS with a refined spatial filter and time\textendash variable detection thresholds. To further analyse the backscatter response from sea ice and derive information on the different sea ice types, a new model of sea ice backscattering at C\textendash band is proposed in this study. This model has been derived using ERS and ASCAT backscatter data and describes the variation of sea ice backscatter with incidence angle as a function of sea ice type.

    The improvement of the sea ice detection algorithm for ERS\textendash 1 and ERS\textendash 2, operating between 1992 and 2001, leads to the extension of the existing records of daily global sea ice extents from the Quick scatterometer (QuikSCAT) which operated from 1999 to 2009 and ASCAT operating from 2007 onwards. The sea ice extents from ERS, QuikSCAT and ASCAT show excellent agreement during the overlapping periods, attesting to the consistency and homogeneity of the long\textendash term scatterometer sea ice record. The new climate record is compared against passive microwave derived sea ice extents, revealing consistent differences between spring and summer which are attributed to the lower sensitivity of the passive microwave technique to melting sea ice. The climate record shows that the minimum Arctic summer sea ice extent has been declining, reaching the lowest record of sea ice extent in 2012.

    The new model for sea ice backscatter is used on ERS and ASCAT backscatter data and provides a more precise normalization of sea ice backscatter than was previously available. An application of this model in sea ice change analysis is performed by classifying sea ice types based on their normalized backscatter values. This analysis reveals that the extent of multi\textendash year Arctic sea ice has been declining remarkably over the period covered by scatterometer observations.

  • SANG, YINGZI
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Industrial Ecology.
    Possibility of enhancing algae drying by integrating infrasound.2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    With the aim of designing an infrasound-integrated technology which can enhance the

    algae drying performance, this thesis provided the theoretical possibility of using

    infrasound as an algae dehydration technology. To test the relation between algae drying

    speed and other three parameters namely sound frequency, sound pressure and sample

    mass, four major experimental groups including initial experiments and core

    experiments with fifteen sub-experimental groups are designed. Results of the

    experiments shows expected accordance with the theoretical inferences of infrasound

    being an algae drying technology. Experiment steps and specifications are presented as

    the research methodology. A real system with the drying capacity of 2 ton fresh algae

    per day are designed based on the experimental calculations and results. Several

    revisions including air circulation and infrasound resonance are made when scaling up

    the research from experimental level up to industrial level. Other specifications of the

    real system design follow the experiment results with regard of the research consistency.

    Freeze drying technology is selected for the comparative cost analysis including

    manufacturing costs and energy consumptions. Results shows infrasound-integrated

    technology has a relatively low energy consumption whereas it costs more

    manufacturing costs than freeze drying technology.

    Research assumptions, limitations and recommendations for this research are described

    in this article. From the author’s perspective, this paper can be used as an initiation and

    instruction for larger scale researches in regard of infrasound-integrated algae

    dehydration/drying.

  • Sjölund, Anette
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Beräkning och begränsning av sprickvidd i armerade betongkonstruktioner2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This masters thesis has two aims. The first is to assemble literature regarding the calculation of crackwidths and crack control in reinforced concrete structures. The second aim is to develop a calculationmethodology to design required reinforcement from data produced by the calculation programBRIGADE.There are several reasons why cracks appear in reinforced concrete structures. Except for externalloads, they appear as a result of attack from frost, seawater or chemicals. Also shrinkage or changesin temperature as the concrete hardens can cause cracks in the structure. Crack control in structuresis desirable for a range of reasons including aesthetics, life-span and the ability to provide water orgas proofing. Crack widths can be controlled by providing sufficient reinforcement in a structure andby arranging the reinforcement in the way it has most effect. Additionally, while pouring theconcrete, there are ways to affect the number of cracks in a structure. Treating the concrete in thecorrect way after pouring and also the use of chemicals can reduce cracking.This thesis considers the calculation of crack widths according to British Standard, Eurocode, ACI andBBK 04. Through calculation of crack widths according to these four standards, where one parameterat a time is varied, general conclusions can be drawn. Reducing the reinforcement spacing makes amajor difference to the calculated crack width. Also larger bar diameters give better results, while asmaller cover within the boundaries that the standards permit results in no significant effect.

  • Kasinathan, Gokulnath
    KTH, School of Information and Communication Technology (ICT).
    Data Transformation Trajectories in Embedded Systems2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Mobile phone tracking is the ascertaining of the position or location of a mobile phone when moving from one place to another place. Location Based Services Solutions include Mobile positioning system that can be used for a wide array of consumer-demand services like search, mapping, navigation, road transport traffic management and emergency-call positioning. The Mobile Positioning System (MPS) supports complementary positioning methods for 2G, 3G and 4G/LTE (Long Term Evolution) networks. Mobile phone is popularly known as an UE (User Equipment) in LTE.

    A prototype method of live trajectory estimation for massive UE in LTE network has been proposed in this thesis work. RSRP (Reference Signal Received Power) values and TA(Timing Advance) values are part of LTE events for UE. These specific LTE events can be streamed to a system from eNodeB of LTE in real time by activating measurements on UEs in the network. AoA (Angle of Arrival) and TA values are used to estimate the UE position. AoA calculation is performed using RSRP values. The calculated UE positions are filtered using Particle Filter(PF) to estimate trajectory. To obtain live trajectory estimation for massive UEs, the LTE event streamer is modelled to produce several task units with events data for massive UEs. The task level modelled data structures are scheduled across Arm Cortex A15 based MPcore, with multiple threads.

    Finally, with massive UE live trajectory estimation, IMSI (International mobile subscriber identity) is used to maintain hidden markov requirements of particle filter functionality while maintaining load balance for 4 Arm A15 cores. This is proved by serial and parallel performance engineering. Future work is proposed for Decentralized task level scheduling with hash function for IMSI with extension of cores and Concentric circles method for AoA accuracy.

  • Public defence: 2017-06-13 12:00 Aula Perez Pulgar, Madrid, Spain
    Izadkhast, Seyedmahdi
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Aggregation of Plug-in Electric Vehicles in Power Systems for Primary Frequency Control2017Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The number of plug-in electric vehicles (PEVs) is likely to increase in the near future and these vehicles will probably be connected to the electric grid most of the day time. PEVs are interesting options to provide a wide variety of services such as primary frequency control (PFC), because they are able to quickly control their active power using electronic power converters. However, to evaluate the impact of PEVs on PFC, one should either carry out complex and time consuming simulation involving a large number of PEVs or formulate and develop aggregate models which could efficiently reduce simulation complexity and time while maintaining accuracy.

    This thesis proposes aggregate models of PEVs for PFC. The final aggregate model has been developed gradually through the following steps. First of all, an aggregate model of PEVs for the PFC has been developed where various technical characteristics of PEVs such as operating modes (i.e., idle, disconnected, and charging) and PEV’s state of charge have been formulated and incorporated. Secondly, some technical characteristics of distribution networks have been added to the previous aggregate model of PEVs for the PFC. For this purpose, the power consumed in the network during PFC as well as the maximum allowed current of the lines and transformers have been taken into account. Thirdly, the frequency stability margins of power systems including PEVs have been evaluated and a strategy to design the frequency-droop controller of PEVs for PFC has been described. The controller designed guaranties similar stability margins, in the worst case scenario, to those of the system without PEVs. Finally, a method to evaluate the positive economic impact of PEVs participation in PFC has been proposed.

  • Public defence: 2017-05-12 10:00 E3, Stockholm
    Kucheev, Yury
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.).
    Shooting Stars: The Value of Ranked Analysts' Recommendations2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Financial analysts play a key role in collecting, processing and disseminating information for the stock market. Selecting the best analysts among thousands of analysts is an important task for investors that determines future investment profitability. Extensive research has been dedicated to finding the best analysts of the market based on various criteria for different clienteles. The state of the art approach in this process has developed into so-called Star Rankings with lists of top analysts who have previously outperformed their peers. How useful are such star rankings? Do the recommendations of stars have higher investment value than the recommendations of non-stars (i.e., recommendations of Stars “shoot” more precisely before and after selection)? Or do star rankings simply represent the past performance that will regress to the mean in the future (i.e., in reality, Shooting Stars are not stars and quickly disappear from the sky)?

    The aim of this Ph.D. thesis is to empirically investigate the performance of sell-side analysts’ recommendations by focusing on a group of star analysts. This thesis comprises four papers that address two overarching questions. (1) Do star rankings capture any true skill, and, thus, can investors rely on the rankings? (Papers I and II) (2) How do market conditions impact star analysts? (Papers III and IV)

    Paper I examines the profitability persistence of the investment recommendations from analysts who are listed in the four different star rankings of Institutional Investor magazine, StarMine’s “Top Earnings Estimators”, “Top Stock Pickers” and The Wall Street Journal and shows the predictive power of each evaluation methodology. By investigating the precision of the signals that the various methodologies use in determining who the stars are, the study distinguishes between the star-selection methodologies that capture short-term stock-picking profitability and the methodologies that emphasize the more persistent skills of star analysts. As a result, this study documents that there are star-selection methods that select analysts based on more enduring analyst skills, and, thus, the performance of these methods’ stars persists even after ranking announcements. The results indicate that the choice of analyst ranking is economically important in making investment decisions.

    Paper II investigates the structure of the portfolios that are built on the recommendations of sell-side analysts and confirms that the abnormal returns are explained primarily by analysts’ stock-picking ability and only partially by the effect of over-weight in small-cap stocks. The study examines the number of stocks in the portfolios and the weights that are assigned to market-cap size deciles and GICS sectors and performs an attribution analysis that identifies the sources of overall value-added performance.

    Paper III examines the differences in seasonal patterns in the expected returns on target prices between star and non-star analysts. Although the market returns in the sample period do not possess any of the investigated seasonal effects, the results show that both groups of analysts, stars and non-stars, exhibit seasonal patterns and issue more optimistic target prices during the summer, with non-stars being more optimistic than stars. Interestingly, the results show that analysts are highly optimistic in May, which contradicts the adage “Sell in May and go away” but is consistent with the notion of a trade-generating hypothesis: since analysts face a conflict of interests, they may issue biased recommendations and target prices to generate a trade. A detailed analysis reveals that the optimism cycle is related to the calendar of companies’ earnings announcements rather than the market-specific effects.

    Paper IV discusses how a shift in economic conditions affects the competitiveness of sell-side analysts. The focus is on the changes that were triggered by the financial crisis of 2007-2009 and a post-crisis “uncertainty” period from 2010-2013. The study follows Bagnoli et al. (2008) in using a change in the turnover of rankings as a measure of a transformation in analysts’ competitive advantages. Paper IV extends their research and documents how different ranking systems capture analysts’ ability to handle changes in the economic environment. The results show that market conditions impact analyst groups differently, depending on the group’s competitive advantages.

  • Marcos Conca, Alexandre
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    A Solution to Selecting Cyber-Security Software Tools for an Organization Using Security Controls2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In the last decade, cyber-threats have evolved dramatically, forcing organizations yearafter year to use increasingly sophisticated security measures, security software amongothers. This has led to a huge increase in the number of security tools available in theindustry. The result of the increase is that that companies often do not know in whichsoftware to invest in order to meet their security needs. The purpose of this thesis isto address this problem by developing a solution that helps companies to choose theright security software based on their security needs and that allows to do the selectionprocess in a systematic and reliable way.The solution proposed in the thesis builds on interviews with experts in information security,data collection from the literature and Internet and on a case study. The solutionconsists of rstly an investigate method with which it is possible to categorize any securitytool according to the list of cyber-security controls proposed by CIS Critical SecurityControls (CSC), which were chosen after a comparative study with other publicly availablecontrols because they are actionable, relevant and updated frequently. Secondly,the solution proposes a user-friendly web tool that has been developed to allow the usersto visualize the collected information for comparison. The visualization tool will helpthe users to select the security tools in which the company could be interested to investin. The visualization is done in a simple way and the CSCs that would be covered areshown together with the gaps and the overlaps of the selected tools. In order to verifythe viability of the solution that was developed with real data, the project includes acase study with a representative set of security tools. The case study facilitates thecomprehension of the process undertaken and shows how this method could be appliedin a real case scenario.

  • Adjei-Darko, Priscilla
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatics.
    Remote Sensing and Geographic Information Systems for Flood Risk Mapping and Near Real-time Flooding Extent Assessment in the Greater Accra Metropolitan Area2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Disasters, whether natural or man-made have become an issue of mounting concern all over the world. Natural disasters such as floods, earthquakes, landslides, cyclones, tsunamis and volcanic eruptions are yearly phenomena that have devastating effect on infrastructure and property and in most cases, results in the loss of human life. Floods are amongst the most prevalent natural disasters. The frequency with which floods occur, their magnitude, extent and the cost of damage are escalating all around the globe. Accra, the capital city of Ghana experiences the occurrence of flooding events annually with dire consequences. Past studies demonstrated that remote sensing and geographic information system (GIS) are very useful and effective tools in flood risk assessment and management.  This thesis research seeks to demarcate flood risk areas and create a flood risk map for the Greater Accra Metropolitan Area using remote sensing and Geographic information system. Multi Criteria Analysis (MCA) is used to carry out the flood risk assessment and Sentinel-1A SAR images are used to map flood extend and to ascertain whether the resulting map from the MCA process is a close representation of the flood prone areas in the study area.  The results show that the multi-criteria analysis approach could effectively combine several criteria including elevation, slope, rainfall, drainage, land cover and soil geology to produce a flood risk map. The resulting map indicates that over 50 percent of the study area is likely to experience a high level of flood.  For SAR-based flood extent mapping, the results show that SAR data acquired immediately after the flooding event could better map flooding extent than the SAR data acquired 9 days after.  This highlights the importance of near real-time acquisition of SAR data for mapping flooding extent and damages.  All parts under the study area experience some level of flooding. The urban land cover experiences very high, and high levels of flooding and the MCA process produces a risk map that is a close depiction of flooding in the study area.  Real time flood disaster monitoring, early warning and rapid damage appraisal have greatly improved due to ameliorations in the remote sensing technology and the Geographic Information Systems.

  • Gadhoumi, Shérazade
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatics. Airbus Defence & Space.
    Platforms for Real-time Moving Object Location Stream Processing2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Boarder security is usually based on observing and analyzing the movement of MovingPoint Objects (MPOs): vehicle, boats, pedestrian or aircraft for example. This movementanalysis can directly be made by an operator observing the MPOs in real-time, but theprocess is time-consuming and approximate. This is why the states of each MPO (ID, location,speed, direction) are sensed in real-time using Global Navigation Satellite System(GNSS), Automatic Identification System (AIS) and radar sensing, thus creating a streamof MPO states. This research work proposes and carries out (1) a method for detectingfour different moving point patterns based on this input stream (2) a comparison betweenthree possible implementations of the moving point pattern detectors based on three differentData Stream Management Systems (DSMS). Moving point patterns can be dividedin two groups: (1) individual location patterns are based on the analysis of the successivestates of one MPO, (2) set-based relative motion patterns are based on the analysis ofthe relative motion of groups of MPOs within a set. This research focuses on detectingfour moving point patterns: (1) the geofence pattern consists of one MPO enteringor exiting one of the predefined areas called geofences, (2) the track pattern consists ofone MPO following the same direction for a given number of time steps and satisfying agiven spatial constraint, (3) the flock pattern consists of a group of geographically closeMPOs following the same direction, (4) the leadership pattern consists of a track patternwith the corresponding MPO anticipating the direction of geographically close MPOs atthe last time step. The two first patterns are individual location patterns, while the othersare set-based relative motion patterns. This research work proposes a method for detectinggeofence patterns based on the update of a table storing the last sensed state of eachMPO. The approach used for detecting track, flock and leadership patterns is based on theupdate of a REMO matrix (RElative MOtion matrix) where rows correspond to MPOs,columns to time steps and cells record the direction of movement. For the detection offlock patterns a simple but effective probabilistic grid-based approach is proposed in orderto detect clusters of MPOs within the MPOs following the same direction: (1) the Filteringphase partitions the study area into square-shaped cells -according to the dimensionof the spatial constraint- and selects spatially contiguous grid cells called candidate areasthat potentially contain flock patterns (2) for each candidate area, the Refinement phasegenerates disks of the size of the spatial constraint within the selected area until one diskcontains enough MPOs, so that the corresponding MPOs are considered to build a flockpattern. The pattern detectors are implemented on three DSMSs presenting differentcharacteristics: Esri ArcGIS GeoEvent Extension for Server (GeoEvent Ext.), a workflow-based technology that ingests each MPO state separately, Apache Spark Streaming(Spark), a MapReduce-based technology that processes the input stream in batches in ahighly-parallel processing framework and Apache Flink (Flink), a hybrid technology thatingests the states separately but offers several MapReduce semantics. GeoEvent Ext. onlylends itself for a nature implementation of the geofence detector, while the other DSMSsaccommodate the implementation of all detectors. Therefore, the geofence, track, flockand leadership pattern detectors are implemented on Spark and Flink, and empiricallyevaluated in terms of scalability in time/space based on the variation of parameters characterizingthe patterns and/or the input stream. The results of the empirical evaluationshows that the implementation on Flink uses globally less computer resources than theone on Spark. Moreover, the program based on Flink is less sensitive to the variability ofparameters describing either the input stream or the patterns to be detected.

  • Public defence: 2017-06-12 09:00 F3, Stockholm
    Stiehler, Beate
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.).
    Identification and assessment of luxury brand segments in the emerging markets: Case of South Africa2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Africa has been identified as an upcoming market in which luxury brands should secure future growth opportunities. A review of related academic literature, however, reveals that limited research has been conducted which focuses specifically on the continent’s luxury consumers. This gap in the literature highlights the need to further the body of knowledge on luxury consumer behaviour in this context. However, as the continent comprises a vast number of countries with diverse consumer profiles, it was decided that this study would focus on the assessment of the behaviour of the members of luxury consumer segments in the South African market.

    The specific areas that require research in order to establish an understanding of luxury consumer segments’ behaviour commenced from a review of different trends and developments in the South African market. The core trends, along with calls for further research on luxury brands in the international academic literature were combined to identify numerous avenues for further research. This eclectic approach aimed to not only contribute to an enhanced understanding of the behaviour of luxury consumer segments in the South African market, but to develop and extend the existing body of academic knowledge and literature on luxury brands.

    Four research questions were developed from both the identified avenues from the review of the trends in the market, and the calls for further research in the academic literature. Each of these questions was then addressed by four individual papers.  This thesis makes a number of contributions to the related body of knowledge as it details the behaviour of different luxury brand consumer segments in the South African market, thereby serving as a step towards addressing the gap in the literature on luxury consumers on the African continent. 

  • Zamani, Sam
    KTH, School of Information and Communication Technology (ICT).
    Investigation of using a PRET processor on a low-cost, low- power FPGA2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Mixed-criticality is a current trend in real-time embedded systems, where software tasks are integrated onto fewer hardware platforms. The basic idea is to use one processor to execute multiple tasks with differing requirements of certification, importance or safety. In systems where time is an important key factor the behavior of that system must be predictable at all times, which is hard to achieve when optimizations made to achieve good performance lower predictability at the same time. In 2007 Stephen A. Edwards and Edward A. Lee made a case for the precision-timed (PRET) machine as a solution, arguing that temporal behavior is to be treated equal to functional behavior. One of those PRET machines is FlexPRET, which is the processor we are studying in this thesis.

    This thesis aims to study the generation, synthesis and programming of FlexPRET, a finegrained multithreaded RISC-V based PRET processor developed at UC Berkeley. This is part of a larger-scale project to port FlexPRET to be used as a node processor in a NoC mesh generated by ForSyDe, a programming methodology developed at the Royal Institute of Technology.Previous synthesis of FlexPRET has been done on FPGAs from the Virtex-5 and Spartan-6 families by Xilinx. The FPGA used for this thesis is from the Cyclone IV family by Altera.

    Evaluation of the synthesis results have been performed by running a real-time application on FlexPRET that blinks LEDs on the Altera DE2-115 board.

  • Chen, Qian
    KTH, School of Information and Communication Technology (ICT).
    Data blending in health care: Evaluation of data blending2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This report is aimed at those who are interested in data analysis and data blending. Decision making is crucial for an organization to succeed in today’s market. Data analysis is an important support activity in decision making and is applied in many industries, for example healthcare. For many years data analysts have worked on structured data in small volumes, with traditional methods such as spreadsheet. As new data sources emerged, such as social media, data is generated in higher volume, velocity and variety [1]. The traditional methods data analysts apply are no longer capable of handling this situation.

    Hence scientists and engineers have developed a new technology called data blending. Data blending is the process of merging, sorting, joining and combining all the useful data into a functional dataset [2]. Some of the well-known data blending platforms include Datawatch, Microsoft Power Query for Excel, IBM DataWorks and Alteryx [3].

    Synergus AB is a consulting company engaged in health economics, market access and Health Technology Assessment (HTA) [4]. The company does analysis for their clients. Unfortunately the way they work is not efficient. New tools and methods need to be applied in the company. The company has decided to apply data blending in their daily work. My task in this project was to build datasets for analysis and create workflows for future use with a data blending platform. For my interest, I did a research on data blending to understand how this new technology works.

    During the project I have worked with four data sources. These were Microsoft Excel worksheet, CSV file, MS Access database and JSON file. I built datasets the company needs. I also preceded a case study on data blending process. I focused on the three steps of data handling, namely input, process and output. After the project, I reached a conclusion that data blending offers better performance and functionality. It is easy to learn and use, too.

  • Barbouche, Tarek
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Mathematical Statistics.
    Extreme Value Theory Applied to Securitizations Rating Methodology2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    One of today’s financial trends is securitization. Evaluating Securitization risk requires some strong quantitative skills and a deep understanding of both credit and market risk. For international securitization programs it is mandatory to take into account the exchange-rates-related risks. We will see the di˙erent methods to evaluate extreme variations of the exchange rates using the Extreme Value Theory and Monte Carlo simulations.

  • Belić, Jovana
    et al.
    KTH, School of Computer Science and Communication (CSC), Computational Science and Technology (CST).
    Kumar, Arvind
    KTH, School of Computer Science and Communication (CSC), Computational Science and Technology (CST).
    Hellgren Kotaleski, Jeanette
    KTH, School of Computer Science and Communication (CSC), Computational Science and Technology (CST).
    Interplay between periodic stimulation and GABAergic inhibition in striatal network oscillations2017In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 12, no 4, 1-17 p.Article in journal (Refereed)
    Abstract [en]

    Network oscillations are ubiquitous across many brain regions. In the basal ganglia, oscillations are also present at many levels and a wide range of characteristic frequencies have been reported to occur during both health and disease. The striatum, the main input nucleus of the basal ganglia, receives massive glutamatergic inputs from the cortex and is highly susceptible to external oscillations. However, there is limited knowledge about the exact nature of this routing process and therefore, it is of key importance to understand how time-dependent, external stimuli propagate through the striatal circuitry. Using a network model of the striatum and corticostriatal projections, we try to elucidate the importance of specific GABAergic neurons and their interactions in shaping striatal oscillatory activity. Here, we propose that fast-spiking interneurons can perform an important role in transferring cortical oscillations to the striatum especially to those medium spiny neurons that are not directly driven by the cortical oscillations. We show how the activity levels of different populations, the strengths of different inhibitory synapses, degree of outgoing projections of striatal cells, ongoing activity and synchronicity of inputs can influence network activity. These results suggest that the propagation of oscillatory inputs into the medium spiny neuron population is most efficient, if conveyed via the fast-spiking interneurons. Therefore, pharmaceuticals that target fast-spiking interneurons may provide a novel treatment for regaining the spectral characteristics of striatal activity that correspond to the healthy state.

  • Bruno, Karl
    Philosophy and History, KTH, School of Architecture and the Built Environment (ABE), Philosophy and History of Technology, History of Science, Technology and Environment.
    Silvi-kulturella möten: Sveriges lantbruksuniversitet och högre skoglig utbildning i Etiopien 1986–20092017In: Nordic Journal of Educational History, ISSN 2001-7766, E-ISSN 2001-9076, Vol. 4, no 1, 29-51 p.Article in journal (Refereed)
    Abstract [sv]

    Artikeln behandlar Sveriges lantbruksuniversitets stöd till uppbyggandet av högre skoglig utbildning i Etiopien, som ägde rum mellan 1986 och 2009 inom ramen för det svensk-etiopiska utvecklingssamarbetet. Med utgångspunkt i ett växande utbildningshistoriskt intresse för gränsöverskridande möten analyseras hur svenska skogsexperter utformade utbildningar och undervisade i nya miljöer. Begreppet ”silvi-kultur” introduceras för att beskriva hur de spänningar som växte fram inom ramen för engagemanget både handlade om hur skogsutbildning bör gå till och om divergerande akademiska och sociala kulturer. Artikeln är strukturerad kring tre slags ”silvi-kulturella möten” som beskriver biståndsprojektets utveckling tematiskt och kronologiskt. Dessa möten används för att visa att skogen som en konkret, fysisk plats var av central betydelse för de svenska experterna, och för att visa hur de svenska insatserna formades av en förförståelse utvecklad inom ramen för en svensk silvi-kultur som bara delvis var kompatibel med förhållanden i Etiopien.

  • Masoudi, Meysam
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Zaefarani, Hamid reza
    Mohammadi, Abbas
    Cavdar, Cicek
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Energy and Spectrum Efficient Resource Allocationin Two-Tier Networks: A Multiobjective Approach2017Conference paper (Refereed)
    Abstract [en]

    In this paper we investigate the joint power andchannel allocation problem in two-tier OFDMA femtocell networksusing a multiobjective approach with focus on energyefficiency. Three main objectives are considered in our problemformulations namely, energy efficiency, spectral efficiency, andpower consumption. To solve the muliobjective problems, we haveutilized a non-dominated sorting genetic algorithm (NSGA-II)and an algorithm have been proposed to perform the resourceallocation procedures. In this investigation, to preserve the qualityservice of users, we have applied a minimum data rate thresholdfor all users. Furthermore, we impose an interference thresholdlimit on each subchannel to protect the macrocell user qualityof service. Finally, the simulation results figure out that we canachieve 30% better energy efficiency by trading the throughputby about 20%.

  • Masoudi, Meysam
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Khamidehi, Behzad
    Cavdar, Cicek
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Green Cloud Computing for Multi Cell Networks2017Conference paper (Refereed)
    Abstract [en]

    This paper investigates the power minimizationproblem for the user terminals by application offloading in multicellmulti-user OFDMA mobile cloud computing networks wheresome practical constraints such as backhaul capacity limitation,interference level on each channel and maximum tolerable delayas user’s quality of service is taken into account. Furthermore, themixed integer nonlinear problem is converted into a convex formusing D.C. approximation. Moreover, to solve the optimizationproblem, we have proposed joint power allocation and decisionmaking (J-PAD) algorithm which can make offloading decisionand allocate power at the same time. Simulation results illustratethat by utilizing the J-PAD algorithm, in comparison withbaselines, considerable power saving could be achieved e.g. about30% for delays more than 100 ms.

  • Masoudi, Meysam
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Zaefarani, Hamidreza
    Mohammadi, Abbas
    Cavdar, Cicek
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Energy efficient resource allocation in two-tier OFDMA networks with QoS guarantees2017In: Wireless networks, ISSN 1022-0038, E-ISSN 1572-8196Article in journal (Refereed)
    Abstract [en]

    In this paper, we study joint power and subchannel allocation problem for OFDMA based femtocell networks with focus on uplink direction. We minimize the aggregate power of all Femto user equipments and maximize the total system energy efficiency while satisfying the minimum required rate of all users. An interference limit constraint is considered to protect the QoS of macrocells. The original problem is a mixed-integer non-convex optimization problem which is converted to a convex problem using the time-sharing concept. Three algorithms are proposed to provide a scheme to optimize the goal function while meeting the constraints. The complexity order of all algorithms was investigated and was compared to other alternative solutions. The analytic and simulation results have demonstrated that the proposed algorithms could achieve significant power saving and better energy efficiency compared to existing algorithms. Energy efficient resource allocation in two-tier OFDMA networks with QoS guarantees.

  • Prihodko, Jana
    KTH, School of Information and Communication Technology (ICT).
    Anpassning av Scrum-metod: För förbättrade mjukvaruutvecklingsprojekt2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Software development requires good working methods to be to deliver efficient and effective software. To achieve this, companies require a good working method that they can work with.

    Agile methods are becoming more popular to work with when it comes to software development in today's technology companies. More companies are beginning to work with agile methods for project management instead of the traditional waterfall method. The reason for this is that more and more companies fail to deliver projects on time with the waterfall method, which means more costs for companies. The reason for this is that more and more companies fail to deliver projects on time with the waterfall method, which means more costs for companies. Agile methodologies however help companies to get structure that led to better work, which in turn results in that projects are completed on time.

    This study examined the usage and customization of agile method Scrum in a bank, and if this has led to some improvements in the work of software development projects. The investigation was conducted through interviews with Scrum Master, Agile coaches, product owners and managers who work with the Scrum method.

    The result shows that the agile method Scrum provides more structure and transparency to projects. Adaptations to the product owner role in the company has led to that right assignment are prioritized and teams get a clear backlog to work with. The work with the Scrum method has helped the team to have a clear structure and increased delivery of projects.

  • Public defence: 2017-05-18 13:00 B3, Stockholm
    Bjureland, William
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    On reliability-based design of rock tunnel support2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Tunneling involves large uncertainties. Since 2009, design of rock tunnels in European countries should be performed in accordance with the Eurocodes. The main principle in the Eurocodes is that it must be shown in all design situations that no relevant limit state is exceeded. This can be achieved with a number of different methods, where the most common one is design by calculation. To account for uncertainties in design, the Eurocode states that design by calculation should primarily be performed using limit state design methods, i.e. the partial factor method or reliability-based methods. The basic principle of the former is that it shall be assured that a structure’s resisting capacity is larger than the load acting on the structure, with high enough probability. Even if this might seem straightforward, the practical application of limit state design to rock tunnel support has only been studied to a limited extent.

    The aim of this licentiate thesis is to provide a review of the practical applicability of using reliability-based methods and the partial factor method in design of rock tunnel support. The review and the following discussion are based on findings from the cases studied in the appended papers. The discussion focuses on the challenges of applying fixed partial factors, as suggested by Eurocode, in design of rock tunnel support and some of the practical difficulties the engineer is faced with when applying reliability-based methods to design rock tunnel support.

    The main conclusions are that the partial factor method (as defined in Eurocode) is not suitable to use in design of rock tunnel support, but that reliability-based methods have the potential to account for uncertainties present in design, especially when used within the framework of the observational method. However, gathering of data for statistical quantification of input variables along with clarification of the necessary reliability levels and definition of “failure” are needed.

  • Walldén, Marcus
    et al.
    KTH, School of Information and Communication Technology (ICT).
    Özkan, Aylin
    KTH, School of Information and Communication Technology (ICT).
    A graph database management system for a logistics-related service2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Higher demands on database systems have lead to an increased popularity of certain database system types in some niche areas. One such niche area is graph networks, such as social networks or logistics networks. An analysis made on such networks often focus on complex relational patterns that sometimes can not be solved efficiently by traditional relational databases, which has lead to the infusion of some specialized non-relational database systems. Some of the database systems that have seen a surge in popularity in this area are graph database systems.

    This thesis presents a prototype of a logistics network-related service using a graph database management system called Neo4j, which currently is the most popular graph database management system in use. The logistics network covered by the service is based on existing data from PostNord, Sweden’s biggest provider of logistics solutions, and primarily focuses on customer support and business to business.

    By creating a prototype of the service this thesis strives to indicate some of the positive and negative aspects of a graph database system, as well as give an indication of how a service using a graph database system could be created.

    The results indicate that Neo4j is very intuitive and easy to use, which would make it optimal for prototyping and smaller systems, but due to the used evaluation method more research in this area would need to be carried out in order to confirm these conclusions.

  • Al Sayfi, Anhar
    et al.
    KTH, School of Information and Communication Technology (ICT).
    Kufa, Max
    KTH, School of Information and Communication Technology (ICT).
    Utveckling av webbaserat blixtdetekteringssystem2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In this paper we suggest a lightning detection system capable of warning a local populous of incoming lightning weather using a combination of the AS3935 sensor and the one-board-computer Raspberry Pi, in an attempt to design a product that is cheap, mobile and easy to use.

    The product is composed of a sensor net that registers and reports lightnings on a webserver. The server is reachable as a normal website based on the LAMP method.

    The project reached a stadium which should satisfy a “proof of concept”, however, the product is far from complete, as it lacks the necessary algorithms needed for proper data computation. The current system only uses Raspberry pi, but it is theoretically possible to introduce other hardware to the system, but the current developed product does not support such functionality.

  • An, Junxue
    KTH, School of Chemical Science and Engineering (CHE). KTH.
    Polymers in Aqueous Lubrication2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The main objective of this thesis work was to gain understanding of the layer properties and polymer structures that were able to aid lubrication in aqueous media. To this end, three types of polyelectrolytes: a diblock copolymer, a train-of-brushes and two brush-with-anchor mucins have been utilized. Their lubrication ability in the boundary lubrication regime has been examined by Atomic Force Microscopy with colloidal probe.

    The interfacial behavior of the thermoresponsive diblock copolymer, PIPOZ60-b-PAMPTAM17,on silica was studied in the temperature interval 25-50 ˚C. The main finding is that adsorption hysteresis, due to the presence of trapped states, is important when the adsorbed layers are in contact with a dilute polymer solution. The importance of trapped states was also demonstrated in the measured friction forces, where significantly lower friction forces, at a given temperature, were encountered on cooling than on the preceding heating stage, which was attributed to increased adsorbed amount. On the heating stage the friction force decreased with increasing temperature despite the worsening of the solvent condition, and the opposite trend was observed when using pre-adsorbed layers (constant adsorbed amount) as a consequence of increased segment-segment attraction.

    The second part of the studies was devoted to the interfacial properties of mucins on PMMA. The strong affinity provided by the anchoring group of C-PSLex and C-P55 together with their more extended layer structure contribute to the superior lubrication of PMMA compared to BSM up to pressures of 8-9 MPa. This is a result of minor bridging and lateral motion of molecules along the surface during shearing. We further studied the influence of glycosylation on interfacial properties of mucin by utilizing the highly purified mucins, C-P55 and C-PSLex. Our data suggest that the longer and more branched carbohydrate side chains on C-PSLex provide lower interpenetration and better hydration lubrication at low loads compared to the shorter carbohydrate chains on C-P55. However, the longer carbohydrates appear to counteract disentanglement less efficiently, giving rise to a higher friction force at high loads.