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  • Fahlgren, Anton
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Mathematics (Div.).
    Combining Acoustic Echo Cancellation and Voice Activity Detection in Social Robotics2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis is partly a theoretical introduction to some basic concepts of signal processing such as the Fourier transform, linear time invariant systems and spectral analysis of random signals, both in the continuous and discrete setting. A second part is devoted to theory and applications of echo cancellation and voice activity detection in so called social robotics. Existing methods are presented along with new specialized methods and both are later evaluated.

  • Björk, Folke
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology.
    Olofsson, Bo
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Sederholm, Bror
    Trägårdh, Jan
    RISE Cement- och betonginstitutet.
    Dränering av fukt i betong genom elektrokemisk metodik (elektroosmos) 2018Report (Other academic)
    Abstract [sv]

    Syftet med detta projekt är att studera funktionen av elektroosmos som åtgärd mot fukt-problem i byggnader i Sverige samt att utifrån detta ge rekommendationer kring om och i så fall när det är lämpligt/olämpligt att använda metodiken under de varierande fuktighets-förhållanden som vanligtvis råder i Sverige.

    I projektet har vi gjort en litteraturstudie, en modellering av fysikaliska processer, studie-besök i byggnader med installationer för elektroosmos och mätningar av fukt i en källarvägg där en installation för elektroosmos blivit gjord.

    Vi ser metoden elektroosmos som en möjlighet för att hantera fuktproblem i grunder. Det behövs dock en del av utveckling både kring tekniken för metoden och kring vad som ska kunna förväntas av den.

    Det behövs bättre möjligheter att kunna förutsäga att metoden kommer att fungera i ett visst fall. Att inte kunna förutsäga detta bör vara ett bekymmer för dem som marknadsför metoden.

    Elektroosmos kräver höga fuktnivåer för att fungera. Torkning ned till under kritiska fuktnivåer kräver komplettering med andra torkmetoder. Det krävs en tydlighet kring hur detta ska lösas.

    Det behövs en bättre förståelse kring hur elektroderna ska placeras för bästa funktion.

    Fuktvandring i jorden kan ha stor betydelse för processen i praktiken. Det är idé att undersöka om detta kan användas för att utveckla metoden.

    Det behövs klara regler kring hur elinstallationen ska utformas på ett säkert sätt.

    Eftersom jontransporten i betongen är av ganska liten omfattning så tror vi inte att elektroosmos kommer att påverka, eller skada, betongens egenskaper på lång sikt.

  • Cao, Phuong
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering.
    Oechtering, Tobias J.
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering.
    Optimal Transmit Strategies for Gaussian MISO Wiretap Channels2018In: IEEE Transactions on Information Forensics and Security, ISSN 1556-6013, E-ISSN 1556-6021Article in journal (Other academic)
    Abstract [en]

    This paper studies the optimal tradeoff between secrecy and non-secrecy rates of the MISO wiretap channels for different power constraint settings:sum power constraint only, per-antenna power constraints only and joint sum and per-antenna power constraints. The problem is motivated by the fact thatchannel capacity and secrecy capacity are generally achieved by different transmit strategies. First, a necessary and sufficient condition to ensure a positive secrecy capacity is shown. The optimal tradeoff between secrecy rate and transmission rate is characterized by a weighted rate sum maximization problem. Since this problem is not necessarily convex, equivalent problem formulations are introduced to derive the optimal transmit strategies. Under sum power constraint only, a closed-form solution is provided. Under per-antenna power constraints, necessary conditions to find the optimal power allocation are provided. Sufficient conditions are provided for the special case of two transmit antennas. For the special case of parallel channels, the optimal transmit strategies can deduced from an equivalent point-to-point channel problem. Lastly, the theoretical results are illustrated by numerical simulations.

  • Wendel, Erik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Evaluation of potential for metal/polymer/metal sandwich material as outer panels for trucks2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Reducing the weight of the truck vehicle conveys more cargo to be carried by thetrailer. This has a significant impact on the efficiency of the transport lowering both the total cost of cargo moved and the total carbon dioxide emitted. Half of the body in-white weight of a truck is comprised out of panels made out of thin mild forming steel which cannot be made thinner to reduce weight due to the lowered stiffness it would entail. Sandwich materials have a high stiffness to weight ratio and would for the same panel thickness as regular forming steel have a comparable bending stiffness but lowered weight. This master thesis is intended to be a preliminary study for Scania CV AB on sandwich materials and its potential use as lightweight panels in their trucks. With the intention of investigating whether a commercial sandwich material is capable of filling the role as outer panels of a truck, comparative tests regarding significant matters such as forming and painting was made on identically manufactured demonstrators comparing a sandwich material and a regular forming steel material. The tests identified weaknesses in the current manufacturing process for parts of a sandwich material. Such limitations are problems with painting and joining due to isolated cover sheets, forming problems revealing sink marks likely due to different spring back of the material and hemming flaws due to inadequately optimized hemming technique and anisotropy. Now that more knowledge of sandwich materials has been gained, counter measures for these findings can be made in order to take another step towards lowering the weight of the truck and a more efficient way of transporting goods.

  • Public defence: 2019-05-03 10:00 Sal F3, Stockholm
    Tomé Torquemada, Silvia
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Studies of some thermodynamic aspects related to the production of silicon and ferrosilicon2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis presents a fundamental study on some thermodynamic aspects regarding the silicon and ferrosilicon production. The purity requirements for silicon and ferrosilicon alloys are stringent. In order to achieve a successful and efficient refining of the silicon and ferrosilicon produced by carbothermic reduction, it is of great importance to know the phase relations in the system and to have reliable thermodynamic, kinetic and other physical data for the elements involved.

    The first part of the thesis includes a study of different phase relationships of the SrO-SiO2 and SiO2-SrO-Al2O3 systems. Experiments were performed to determine the phase relationships at temperatures between 1300 °C and 1625 °C in the binary system and at 1450 °C, 1500 °C and 1600 °C in the ternary system. The present result would be valuable when determining the compositions of the refining slags. A fully liquid slag would ensure favorable kinetic conditions in the refining process.

    The activities of some metallic elements in the silicon melt were determined in the second part of the thesis. The activities of Sr, Al, Zr and Ca in silicon were experimentally determined at temperatures that varied between 1450 °C and 1600 °C. These activities would provide useful information regarding the process temperature and the design of refining slags.

    The third part of the thesis covers the study of the activities in a ferrosilicon alloy. The activity coefficients for Al and Ca in FeSi50 were experimentally determined by equilibrating SiO2-Al2O3-CaO slags with ferrosilicon at 1550 °C. The activities obtained would be very useful information for the optimization of the refining process.

  • Söder, Lennart
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    EG2220 Power Generation, Environment and Markets: Compendium for future system design2017Report (Other academic)
    Abstract [en]

    Design of future power systems includes several tasks including power plant type, power plant location,transmission design, market design etc. In this compendium we will study only the design of the amountsand types of power plants and some issues which are of high relevance and importance. This means,e.g., that we will not discuss transmission expansion planning here. There are then many dierentalternatives both concerning the dierent types of units with dierent costs etc, but also many dierentways of dening what a "good" future power system is. Here we will analyze the impact from dierenttypes of assumptions on the resulting future power system.

  • Wegener, Moritz
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. Polytechnic University of Catalonia - UPC.
    Isalgué, Antonio
    Malmquist, Anders
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Martin, Andrew R.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    3E-Analysis of a Bio-Solar CCHP System for theAndaman Islands, India—A Case Study2019In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 12, no 6Article in journal (Refereed)
    Abstract [en]

    Energy services are especially expensive on remote islands due to longer and more unstable fuel supply chains. In this paper, different renewable energy systems utilizing locally available biomass and solar energy are proposed as alternatives for a hotel resort on Neil Island, India. Based on local demand data, commercial information, and scientific literature, four cases are modelled with the simulation software HOMER and their economic, energetic, as well as ecological (3E) performances are compared. The robustness of each case configuration is tested with a sensitivity analysis. The results show that a biomass-based, solar-assisted combined cooling, heating, and power (CCHP) system offers an economic saving potential of more than 500,000 USD over twenty years and could decrease CO2 emissions by 365 t per year. When not applying CCHP measures, system performance is significantly worsened. A solar and battery-assisted diesel generator system shows similar economic outcomes as the CCHP system but worse ecological performance. Implementing the biomass-based CCHP system could improve the ecological footprint of the island, substantially decrease expenditure for the hotel owner, and generate a new source of income for surrounding farmers through biomass selling.

  • Public defence: 2019-05-17 15:50 E2, Stockholm
    Khosrowjerdi, Hojat
    KTH, School of Electrical Engineering and Computer Science (EECS), Theoretical Computer Science, TCS.
    Learning-based Testing for Automotive Embedded Systems: A requirements modeling and Fault injection study2019Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis concerns applications of learning-based testing (LBT) in the automotive domain. In this domain, LBT is an attractive testing solution, since it offers a highly automated technology to conduct safety critical requirements testing based on machine learning. Furthermore, as a black-box testing technique, LBT can manage the complexity of modern automotive software applications such as advanced driver assistance systems. Within the automotive domain, three relevant software testing questions for LBT are studied namely: effectiveness of requirements modeling, learning efficiency and error discovery capabilities.

    Besides traditional requirements testing, this thesis also considers fault injection testing starting from the perspective of automotive safety standards, such as ISO26262. For fault injection testing, a new methodology is developed based on the integration of LBT technologies with virtualized hardware emulation to implement both test case generation and fault injection. This represents a novel application of machine learning to fault injection testing. Our approach is flexible, non-intrusive and highly automated. It can therefore provide a complement to traditional fault injection methodologies such as hardware-based fault injection.

  • Lundgren, Berndt
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Building and Real Estate Economics.
    Schultzberg, Mårten
    Department of Statistics, Uppsala University, Sweden.
    Application of the economic theory of self-control to model energy conservation behavioral change in householdsManuscript (preprint) (Other academic)
    Abstract [en]

    Smart meters and in-house displays hold a promise of energy conservation for those who invest in such technology. Research has shown that households only have a limited interest in such technology and information is thus often neglected, with rather limited energy savings. Surprisingly few empirical investigations have a theoretical foundation that may explain what is going on from a behavioral perspective. In this study the economic theory of self-control is used to model energy-efficient behavior in middle-income households in Sweden. Our results show that different levels of energy-efficient behavior do not really have any impact on the actual consumption levels of electricity. Instead, different beliefs exist of being energy-efficient, but the households do not act accordingly. Our results suggest that the payment time period should be changed to stimulate the monitoring of bills and to introduce a gaming strategy to change incentives for energy conservation.

  • Hincks, Rebecca
    KTH, School of Education and Communication in Engineering Science (ECE), Learning, Language and communication.
    Recently hired tenure-track faculty and Swedish: An unsolicited report for KTH leadership2018Report (Other academic)
    Abstract [en]

    The new KTH development plan acknowledges that many KTH environments are no longer bilingual, and that efforts must be made to strengthen the position of Swedish. Unfortunately, it appears that many KTH leaders underestimate the time and resources necessary for most adults to learn a second language to the high proficiency level necessary for teaching or for academic leadership.

    An examination of job advertisements found that it is at present a common practice across northern Europe to specify that applicants to faculty positions be prepared to learn the local language well enough to use it for teaching within two years. The language expectations placed on newly hired KTH faculty hired to tenure-track positions were investigated to find out what extent this is true at KTH. Of 49 non-Swedish speakers who answered a survey, eight were met with the teaching-within-two-year expectation when hired, and 14 are meeting the expectation at present. The Swedish learning is to take place mostly in one’s free time, and little progress toward adequate proficiency is being made among the faculty. These findings are discussed in light of what is known about the time it takes for adults to learn a second language to a high level of professional proficiency.

    If departments seriously expect transnational faculty to teach in Swedish within two years, they should allow the individual the equivalent of six months of full-time study of the language. A more reasonable timeframe for learning high-proficiency Swedish would be five or six years. Language-learning plans should be written for all new hires to tenure-track positions, and followed up at regular intervals.

  • Sremac, Stefan
    et al.
    Wang, Fei
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Wolkowicz, Henrik
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.).
    Pettersson, Lars
    Noisy Euclidean Distance Matrix Completion with a Single Missing Node2019In: Journal of Global Optimization, ISSN 0925-5001, E-ISSN 1573-2916Article in journal (Refereed)
  • Atterlönn, Anton
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Hedberg, Benjamin
    KTH, School of Electrical Engineering and Computer Science (EECS).
    GUI Performance Metrics Framework: Monitoring performance of web clients to improve user experience2019Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    When using graphical user interfaces (GUIs), the main problems that frustrates users are long response times and delays. These problems create a bad impression of the GUI, as well as of the company that created it.When providing a GUI to users it is important to provide intuition, ease of use and simplicity while still delivering good performance. However, some factors that play a major role regarding the performance aspect is outside the developers’ hands, namely the client’s internet connection and hardware. Since every client has a different combination of internet connection and hardware, it can be a hassle to satisfy everyone while still providing an intuitive and responsive GUI.The aim of this study is to find a way to monitor performance of a web GUI, where performance comprises response times and render times, and in doing so, enable the improvement of response times and render times by collecting data that can be analyzed.A framework that monitors the performance of a web GUI was developed as a proof of concept. The framework collects relevant data regarding performance of the web GUI and stores the data in a database. The stored data can then be manually analyzed by developers to find weak points in the system regarding performance. This is achieved without interfering with the GUI or impacting the user experience negatively.

  • Stål, Sandra
    KTH, School of Electrical Engineering and Computer Science (EECS).
    En studie i kommunikationsprotokoll inom valutahandel2019Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    A communication protocol is a specification of how a communication between two or more parties works. It can specify what type of connection the parties share, what data can be sent, how the data should be formatted, and more. To improve the communication between SEBs internal systems, this essay investigates alternative protocols and their pros and cons to the existing communication protocol. Interviews with those working in the systems and protocol documentation are compiled to find differences between the protocols and to weigh the alternatives to each other. The protocol used today is slow and difficult to maintain according to the interview results. The protocol which, according to the essay, has the greatest benefits, is ProtoBuf. With binary, clear messages, ProtoBuf can solve many of the problems that exist in the existing solution.

  • Kayahan, Hüseyin
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Treatment Framework: Traffic Steering via Source-Routing in SDN for Service Function Chaining2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The middlebox architecture is long known for its inharmonious presence within the Internet architecture. Network functions realized in middleboxes are inclined to interpose end to end connections, modifying the datagram header or spawning new connections on behalf, which renders policy enforcement challenging. Moreover, their tight coupling with metadata makes its distributed persistence difficult, which hampers the flexible utilization and scalable provisioning of the middlebox infrastructure resources under varying loads. Existing attempts at mitigating these problems include middlebox placement, packet tagging and metadata migration; each solving only a part of the problem.Investing in the extensible nature of IPv6, the Treatment Framework (TRF) exploits source routing with the flavor of a discretionarily classifiable address space. Datagrams traverse the treatment domain with an extension header pushed and popped at the domain’s edges, for which forwarding takes place based on the information encoded within. The forwarding mechanics that leverage SDN consists of one match and three OpenFlow actions implementation, whereby TRF obviates the need for an underlying transport. Customizable address space allows providers to tailor routing aggregation to their middlebox farms topology, reducing the number of flow rules in the core to preinstallable sizes.Middleboxes in a treatment domain match traffic to the respective local policy based on the information encoded in the extension header. Extension headers are native to IPv6 and defined by standards, hence the middlebox modification problem is addressed without requiring alteration nor visibility into proprietary code. The framework resolves the policy enforcement problem altogether and allows asymmetric service chaining. While eliminating the flow setup time in the core, the framework’s footprint at ingress that push the extension header can get heavy with respect to flow churn rate.

  • Liang, Zijie
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Evaluation and Optimization of ETSI DCC Reactive Approaches for Platooning2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    IEEE802.11p is considered as de facto standard for road communication. However, channel congestion is still the main challenge of IEEE802.11p based vehicular networks. Target to solve this issue, European Telecommunication Standards Institute (ETSI) has standardized a set of Decentralized Congestion Control (DCC) mechanisms in which mainly provide reactive and adaptive methods to mitigate communication channel congestion issue. Many efforts have been carried out over these years in order to solve this problem. Most of the results show that the DCC framework is capable of Channel Load (CL) control to some extend. Platooning system is one of these topics which needs to achieve reliable CL control, especially when there are large amount of vehicles communicating on the road. It is a pity that there are few papers of investigating on DCC framework for Platooning channel congestion control. For this purpose, we focus on investigating DCC reactive control approaches, aiming to provide comprehensive insights of how DCC framework transmission parameters, i.e. message generation rate, transmission power and datarate, will impact on the stability of Platooning system. Besides, for each instance of transmission parameter, we target to optimize the parameter, and propose more stable control algorithms by running repetitive simulations. According to our results, the method of adjusting transmission power has the best benefits.

  • Sunneland, Johanna
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Naval Systems.
    Gutiérrez Dufourq, María Sofía
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Naval Systems.
    An alternative future for shipping – the way there: Risks and benefits of energy efficiency measures and alternative fuels for CO2 reduction in2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Shipping is the world’s largest mode of transportation, considering mass moved a distance: it is the most e˙effective way to carry large volumes far. In order for the shipping industry to keep its position and develop even further, efforts are made to increase efficiency and reduce the environmental footprint from the industry. More efficient ships, reduced fuel consumption, use of alternative fuels and exhaust gas treatment are some of the choices to reduce shipping’s environmental footprint and achieve the sustainability goal established by EU and enforced by the International Maritime Organization.Throughout the thesis, en evaluation of 18 energy efficiency measures and 4 alternative fuels is performed. Energy efficiency measures reduce a ship’s fuel consumption and alternative fuels substitutes fossil fuels with higher content of environmentally harmful content. The measures and fuels, covered in the study, are evaluated for nine representative container ship´s. Data from year 2016 are used for the nine container ships. The current procedure followed for new investments is analyzed for all measures and fuels for each ship, focused on the financial study of each measure and fuel. The results are then included in a risk and benefit analysis that introduces external aspects, not included in the traditional financial evaluation, that include: those that influence the ship and the ship’s environment and those affected by the ship’s operations.The main goal is to evaluate the possibilities to reduce emissions by considering these aspects and involve more stakeholders in the investment of measures and fuels for shipping to keep its position as the most efficient mode of transportation.

  • Sriram, Ajay
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Joint Functional Splitting and Content Placement for Green Hybrid CRAN2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A hybrid cloud radio access network (H-CRAN) architecture has been proposed to alleviate the midhaul capacity limitation in C-RAN. In this architecture, functional splitting is utilized to distribute the processing functions between a central cloud and edge clouds. The flexibility of selecting specific split point enables the H-CRAN designer to reduce midhaul bandwidth, or reduce latency, or save energy, or distribute the computation task depending on equipment availability. Meanwhile, techniques for caching are proposed to reduce the content delivery latency and the required bandwidth. However, caching imposes new constraints on the functional splitting. In this study, considering H-CRAN, a constraint programming problem is formulated to minimize the overall power consumption by selecting the optimal functional split point and content placement, taking into account the content access delay constraint. We also investigate the trade-off between the overall power consumption and occupied midhaul bandwidth in the network. Our results demonstrate that functional splitting together with enabling caching at edge clouds reduces not only content access delays but also fronthaul bandwidth consumption but at the expense of higher power consumption.

  • Han, Lei
    et al.
    School of Material Science and Engineering, Tianjin University, Tianjin 300072.
    Song, Shizhe
    School of Material Science and Engineering, Tianjin University, Tianjin 300072 ; State Key Laboratory for Corrosion and Protection, Shenyang 110016.
    Zhang, Fan
    School of Material Science and Engineering, Tianjin University, Tianjin 300072.
    A VIRTUAL INSTRUMENT FOR CORROSION RATE MEASUREMENT BY ELECTROCHEMICAL FREQUENCY MODULATION TECHNIQUE2008In: Journal of Chinese Society for Corrosion and Protection, ISSN 1005-4537, Vol. 28, no 2Article in journal (Refereed)
    Abstract [en]

    An EFM system for corrosion rate test based on electrochemical frequency modulation technique has been established by means of virtual instrument, which consists of a potentiostat, a laptop equipped with a DAQ card and applications developed in LabVIEW. Experiments has been performed in laboratory to determine anodic and cathodic Tafel slopes as well as corrosion current densities for the systems 304 stainless steel/HCl and Q235 steel in H2SO4 and NaCl.It was shown that the EFM system could be used successfully for corrosion rate mea?鄄surement under various corrosion conditions.

  • JImenez Lopez, Carlos
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.
    Performance analysis and validation of high-temperature cooling panels in passive geothermal system2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    High Temperature Cooling, HTC, is a thermal conditioning strategy, which aims to reducemixing and transfer heat losses. Cooling capacity strongly depends on heat transfer coefficientsand offers a great response and several advantages in terms of efficiency and sustainability.Among the advantages, there is evidence that HTC offers an increment of energy efficiency ofHVAC systems, provision of healthier and more comfortable indoor climate and provide widepotentials for the applications of renewable. This principle leads to a higher energy efficiency ofwater-based radiant cooling systems.This paper intends to focus on the research of the thermal capacity and performance of a newalternative. This is where Cooling Radiant Ceiling Panels, CRCP, becomes a major innovationwithin the sector and begin to take on certain relevance. The cooling capacity curve of thisparticular CRCP panels has been only measured in an idealized room environment according toDIN EN 14240. Thus, further studies of this key parameter through climate chamber testingand Computational Fluid Dynamics simulations, CFD, are necessary. CFD particularly focuseson fluids in motion, their behavior and their influences in complex processes such as heat transfer.The fluid motion can be described through fundamental mathematical equations and it isbecoming widely used within the building sector.Two different cases are going to be investigated. The first case will determine the mostoptimal peripheral gap to enhance cooling performance through Natural Convection, NC. Thisstudy states the existence of a peripheral gap around the panels has proven to be inefficientin terms of enhancing natural convection in the climate chamber. The second case is aboutcalculating the cooling capacity as a function of the internal heat loads. The cooling capacity ofthe CRCP panels followed an expected behavior. The R-squared factor of the linear regressionwas found to be 0.986, hence, it does not affect the performance of the CRCP panels dependingon the inclusion of the IHLs.This thesis provides the necessary information for the implementation of CRCP panels anddifferent possible operating environments, including considerations, limitations and recommendationsfor future implementation of this strategy.

  • Presutto, Matteo
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Squeezing and Accelerating Neural Networks on Resource Constrained Hardware for Real Time Inference2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    As the internet user base increases over the years, so do the logistic difficulties of handling higher and higher volumes of data. This large amount of information is now being exploited by Artificial Intelligence algorithms to deliver value to our society on a global scale. Among all the algorithms employed, the widespread adoption of Neural Networks in industrial settings is promoting the automation of tasks previously unsolvable by computers. As of today, efficiency limits the applicability of such technology on Big Data and efforts are being put to develop new acceleration solutions.In this project, we analyzes the computational capabilities of a multicore Digital Signal Processor called the EMCA (Ericsson Many-Core Architecture) when it comes to executing Neural Networks. The EMCA is a proprietary chip used for real-time processing of data in the pipeline of a Radio Base Station.We developed an inference engine to run Neural Networks on the EMCA. The software of such engine has been produced using a proprietary operating system called Flake OS, which runs on the EMCA. On top of the inference engine, we wrote a neural network squeezing pipeline based on quantization. On MNIST, the quantization algorithm can reduce the size of the networks by 4x folds with sub 1% accuracy degradation. The inference engine has been optimized to exploit the quantization utility and can run quantized neural networks. Tests have been done to understand the direct implications of using such algorithm. We show that the quantization is indeed beneficial for inference on DSPs.Finally, the EMCA has demonstrated state of the art computational capabilities for neural network inferencing.

  • Dushi, Denis
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Using Deep Learning to Answer Visual Questions from Blind People2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A natural application of artificial intelligence is to help blind people overcome their daily visual challenges through AI-based assistive technologies. In this regard, one of the most promising tasks is Visual Question Answering (VQA): the model is presented with an image and a question about this image. It must then predict the correct answer. Recently has been introduced the VizWiz dataset, a collection of images and questions originating from blind people. Being the first VQA dataset deriving from a natural setting, VizWiz presents many limitations and peculiarities. More specifically, the characteristics observed are the high uncertainty of the answers, the conversational aspect of questions, the relatively small size of the datasets and ultimately, the imbalance between answerable and unanswerable classes. These characteristics could be observed, individually or jointly, in other VQA datasets, resulting in a burden when solving the VQA task. Particularly suitable to address these aspects of the data are data science pre-processing techniques. Therefore, to provide a solid contribution to the VQA task, we answered the research question “Can data science pre-processing techniques improve the VQA task?” by proposing and studying the effects of four different pre-processing techniques. To address the high uncertainty of answers we employed a pre-processing step in which it is computed the uncertainty of each answer and used this measure to weight the soft scores of our model during training. The adoption of an “uncertainty-aware” training procedure boosted the predictive accuracy of our model of 10% providing a new state-of-the-art when evaluated on the test split of the VizWiz dataset. In order to overcome the limited amount of data, we designed and tested a new pre-processing procedure able to augment the training set and almost double its data points by computing the cosine similarity between answers representation. We addressed also the conversational aspect of questions collected from real world verbal conversations by proposing an alternative question pre-processing pipeline in which conversational terms are removed. This led in a further improvement: from a predictive accuracy of 0.516 with the standard question processing pipeline, we were able to achieve 0.527 predictive accuracy when employing the new pre-processing pipeline. Ultimately, we addressed the imbalance between answerable and unanswerable classes when predicting the answerability of a visual question. We tested two standard pre-processing techniques to adjust the dataset class distribution: oversampling and undersampling. Oversampling provided an albeit small improvement in both average precision and F1 score.

  • Henriksson, David
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Sundberg, Eliaz
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Evaluation of the NESizer2 method as a means of wrapping embedded legacy systems2019Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Legacy computer systems are systems where several of the main hardware and software components date back several decades. Modernizing these systems is often considered a large monetary and temporal investment with high risk, and to keep maintaining them usually becomes more and more difficult over time, which is why these legacy systems are still being used to this day in many industry sectors. A solution is therefore to try and integrate the legacy system components into modern systems, and there are several ways of achieving this. This bachelor thesis project work aims to analyze one approach known as “wrapping”. More specifically it analyzes NESizer2 Method, a method which utilizes relatively simple hardware and software interfaces to control the Ricoh RP2A03 processor found in the Nintendo Entertainment System, using an Atmega328 microprocessor. During the design and development phases of the project work a literature study was conducted, and experimental research method was utilized. The testing and experimental phases of the project work was focused on examining how identified key variables behaved when modifying certain parameters in the system. While we were able to produce some valid data, the results proved to be somewhat inconclusive, as certain operations such as memory operations did not work, leading to the conclusion that our circuit contained a faulty component.

  • Raheem, Muhammad
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Mitigation of inter-domain Policy Violations at Internet eXchange Points2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Economic incentives and the need to efficiently deliver Internet have led to the growth of Internet eXchange Points (IXPs), i.e., the interconnection networks through which a multitude of possibly competing network entities connect to each other with the goal of exchanging traffic. At IXPs, the exchange of traffic between two or more member networks is dictated by the Border gateway Protocol (BGP), i.e., the inter-domain routing protocol used by network operators to exchange reachability information about IP prefix destinations. There is a common “honest-closed-world” assumption at IXPs that two IXP members exchange data traffic only if they have exchanged the corresponding reachability information via BGP. This state of affairs severely hinders security as any IXP member can send traffic to another member without having received a route from that member. Filtering traffic according to BGP routes would solve the problem. However, IXP members can install filters but the number of filtering rules required at a large IXP can easily exceed the capacity of the network devices. In addition, an IXP cannot filter this type of traffic as the exchanged BGP routes between two members are not visible to the IXP itself. In this thesis, we evaluated the design space between reactive and proactive approaches for guaranteeing consistency between the BGP control-plane and the data-plane. In a reactive approach, an IXP member operator monitors, collects, and analyzes the incoming traffic to detect if any illegitimate traffic exists whereas, in a proactive approach, an operator configures its network devices to filter any illegitimate traffic without the need to perform any monitoring. We focused on proactive approaches because of the increased security of the IXP network and its inherent simplified network management. We designed and implemented a solution to this problem by leveraging the emerging Software Defined Networking (SDN) paradigm, which enables the programmability of the forwarding tables by separating the controland dataplanes. Our approach only installs rules in the data-plane that allow legitimate traffic to be forwarded, dropping anything else. As hardware switches have high performance but low memory space, we decided to make also use of software switches. A “heavy-hitter” module detects the forwarding rules carrying most of the traffic and installs them into the hardware switch. The remaining forwarding rules are installed into the software switches.We evaluated the prototype in an emulated testbed using the Mininet virtualnetwork environment. We analyzed the security of our system with the help of static verification tests, which confirmed compliance with security policies. The results reveal that with even just 10% of the rules installed in the hardware switch, the hardware switch directly filter 95% of the traffic volume with nonuniform Internet-like traffic distribution workloads. We also evaluated the latency and throughput overheads of the system, though the results are limited by the accuracy of the emulated environment. The scalability experiments show that, with 10K forwarding rules, the system takes around 40 seconds to install and update the data plane. This is due to inherent slowness of emulated environment and limitations of the POX controller, which is coded in Python.

  • Drahorad, Nicolò
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Quantification of tribological effects in expansion fasteners2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Post-installed anchors for civil construction are elements that ensure the integrity of building structures even under the most severe static, seismic and shock loadings. Despite the high popularity of this technology in construction sites all over the world, the current state of knowledge is limited and there is still a great potential for significant improvements.

    Specifically, expansion anchors’ mechanism relies purely on friction, therefore being able to manipulate and optimize their tribological behavior is key to meet strict safety regulations and develop outperforming and outlasting design solutions.

    This research project, conducted at Hilti Corporation in Schaan (Liechtenstein), presents an investigation of several antifriction coating solutions. Laboratory-scale tests have been performed to quantify the different coefficient of friction while, with full-scale standardized tests (anchor set in concrete), it has been possible to evaluate the overall mechanical performances of the specimens. Afterwards, the obtained data have been analyzed with numerical software and the samples have been further investigated with optical microscopy.

    The outcome of this thesis work is crucial for the development of the next generation of expansion fasteners and gives additional insights for a deeper understanding in the tribology of functional coatings.

  • Devaux, Caroline Alexandra
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Wool Production, Systematic review of Life Cycle Assessment studies2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Wool is often being marketed as sustainable. However, when looking at LCA studies, results can be significantly different from one study to another and wool sometimes shows higher impacts than other fabrics. Based on a comprehensive literature review, this thesis aims at understanding the key environmental impacts of wool production and assessing the influence of main methodological choices on wool LCA results. In particular, the choice of the scope, allocation method and further considerations on water consumption and land use indicators have a great significance on the results of the studies. In order to provide with a fair representation of wool environmental impacts, the whole life-cycle should be taken into account, and methodological choices, such as the scope definition and allocation methods are to be clearly stated. The current tools that are the most widely used in the textile industry to rank fibres according to their sustainability performance are not suitable for wool due to unresolved methodological issues. Indeed, the impact categories that are taken into account in those tools are disadvantageous for wool compared to other alternative fibres, especially regarding water consumption and land use. This thesis also explores the construction of a single score based on the eco-costs of environmental impacts as a more suitable option to build a representative tool.

  • Östling, Per-Anders
    Utveckling och bevarande av excellenta miljöer på KTH2018Report (Other academic)
  • Aden Hassan, Abdullahi
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Karlsson Källqvist, Rasmus
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Evaluating LoRa Physical as a Radio Link Technology for use in a Remote-Controlled Electric Switch System for a Network Bridge Radio-Node2019Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This report explores the design of a system for remotely switching electronics on and off within a range of at least 15 km, to be used with battery driven radio nodes for outdoor Wi-Fi network bridging. The application of the network bridges are connecting to remote networks, should Internet infrastructure fail during an emergency.The problem statement for the report was “What is a suitable radio link technology for use in a remote controlled electrical switch system and how should it best be put to use?” To answer the question, delimitation was done to exploring Low Power Wide Area Network (LPWAN) link technologies, due to their prior use within power constrained devices.Long Range-radio, abbreviated LoRa, is a LPWAN radio modulation technique and was determined to be a good candidate as a suitable link technology for the remote electrical switch system. The range of LoRa is achieved by drastically lowering the data rate of the transmission, and is suitable for battery-powered or energy harvesting devices such as those found in the field of Internet of Things.A LoRa-based transmitter and receiver pair was implemented, and measured to have a packet delivery ratio of over 95% at a distance of 2 km, measured between two bridges. Data at further distances could not be accurately determined, because of the LoRa transceiver giving faulty readings.No conclusion could be made about the suitability for using a LoRa based system to solve the problem, partially due to an improper method for testing the radio performance was used, and partially due to an inconclusive measurement result.

  • Djekanovic, Nikolina
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Design of Resonant Filters for AC Current Magnification: Heating of Li-ion Batteries by Using AC Currents2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Using alternating current in order to heat batteries at sub-zero temperatures is a method,which is investigated in-depth by an increasing number of study groups. The thesis considersthe resonance phenomenon with the intention to use alternating current amplificationand battery’s impedance in order to induce power dissipation inside the battery, and in thisway increase its temperature. A battery cell is thereby modelled as an impedance transferfunction, estimated from electrochemical impedance spectroscopy measurements, whichare taken for a LiNi 13Mn13Co13O2 cell. Note that at 1 kHz and room temperature (20 ◦C),the ohmic resistance of the selected cell amounts to only 0.76m. Five resonant circuitsare investigated and one of them is selected for further investigation, and as a basis for afilter design. The chosen resonant circuit lead to an LCL filter with current magnification.The experimental setup used for conducting practical experiments, offers the possibilityof operating the voltage source converter both as a Full-bridge and as a Half-bridge, withand without current control. For each possible configuration, an LCL filter and a currentcontroller are designed, taking into account the corresponding limitations in frequency,current and controller voltage. The filter design is based on a multiobjective optimizationmethod used to determine filter components that yield the highest gain value for everyconfiguration. The method minimizes two objective functions in order to find an optimalsolution. The first objective is the reversed absolute value of the gain, whereas thesecond one is the absolute impedance of the circuit, consisting of the filter and batterycells. The gain is thereby defined as the ratio between the induced cell current and thecurrent entering the circuit. The obtained results of the proposed method are experimentallyvalidated. Depending on how the filters were physically designed and taking intoaccount the corresponding voltage source converter configuration, gains of 16 were experimentallyachieved. Finally, the three investigated configurations are compared againstthe reference case (Half-bridge voltage source converter with current control and a singleinductor) regarding their power efficiencies. The power measurements showed that despitehigh obtained gains, the overall filter power losses remained approximately in thesame range, compared to the power losses of the reference case. This is due to the factthat stray resistances of the designed LCL filters easily reached values of around 40m,which hindered an efficient power transfer with the chosen voltage source converter andthe used battery cells. This further indicates the importance of building filters with lowstray resistances and in this thesis, it represents a primary source of improvement.

  • Kastensson Fan, Daniel
    KTH, School of Electrical Engineering and Computer Science (EECS).
    A Blockchain-Based Solution to High-Volume Web Scraping With Smart Contracts on Ethereum2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Since it is dicult to protect servers from high-volume scraping, a new wayto reduce excessive requests is needed. Using rougher methods such as ratelimit or IP control mechanisms are not sucient. In this report we propose anew solution to counter high-volume web scraping with blockchain technology.We create a cryptographic algorithm and use it on a mobile device tocommunicate with an Ethereum network with the purpose to control serveraccess. Our studies seem to indicate that blockchain technology on mobiledevices has potential to limit the way information is accessed. Furthermore,blockchains have potential to act as an additional security layer rather thansimply a network solution. To determine the practical eectiveness of thissolution, more studies are needed.

  • Poggi, Daniele
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Physical modeling of optical modulators for optical link analysis: Optical link analysis in silicon photonics technologies2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    According to the 2018 Ethernet Roadmap projections, the requirements for high speed links keep increasing every year, always keeping an eye on the energy per bit consumption of the communication system. The Ethernet requirements are estimated to reach 1Tbps by 2022-2025. Optical links are one of the most concrete solutions to satisfy bandwidth requirements at low energy consumption. An optical link is a communication system that consists of a single end-to-end optical circuit. In contrast with vertical-cavity surface-emitting laser (VCSEL) technology, which is based on a direct laser modulation, silicon photonics technology (SPT) is based on indirect modulation. In order to perform the modulation, electro-optical modulators are needed in the optical link system for electrically modulating the optical power.This master thesis, developed at imec, will present the modeling of two different technologies of optical modulators: Silicon Ring Modulator and the Franz-Keldysh ElectroAbsorption Modulator. The work was initiated, since there were no available models of these devices in the actual framework for link analysis. First a preliminary study of the physical principles of the two devices was performed, in order to build the Matlab models. Then, these models were fitted with measurements, in order to adjust them to real-life behavior. After having obtained two working models of the two modulators, an alreadyexisting framework was used, to compare the energy consumption per bit in the optical link. However, the results obtained with the simulation didn’t highlight a technology to be preferred to the other.

  • Xu, Yang
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Analysis of on-grid and off-grid cost for rural electrification in developing countries2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Electricity is a fundamental energy carrier for modern life and for economic prosperity. All kinds of equipment use electricity as their power source, including domestic and industrial applications. There is a trend to adopting more electricity-based equipment in all areas. The modern power infrastructures can sufficiently supply most cities and developed areas. However, certain rural areas are still unable to get access to electric power due to the inconvenient locations or less developed economy. This makes the living conditions in such areas extremely inconvenient and further hinders the economic development in those areas.Electrification for rural areas has been a critical task for some developing countries. To accomplish this task, the options are limited to build a stand-alone power system or construct a power transmission line for the chosen location. A stand-alone power system has commonly been based on fossil fuel, such as a diesel generator, with low capital cost compared to a long connection, but with significant running cost of fuel. Recent improvements of renewable sources and storage, and more efficient loads, have made renewable sources much more competitive than before for a stand-alone electricity supply. The choice between different renewable energies depends on the local natural resources. It is a more flexible way to providing the electricity and a more efficient and environmental-friendly way since the energy loss caused by transmission is eliminated. On the other hand, the grid connection option involves building a transmission line to connect the rural area to the national grid, which is a more traditional approach to provide power. The cost of this method depends on the relative distance between the rural area and the nation grid.The choice between the above two mentioned electrification options is the first step when considering providing power to the rural area. This thesis focuses on the electrification for rural areas and comparing the above two methods, finding out the break-even point. It is of current interest as the technology for both options is changing, and the break-even is also changing.In this thesis, a mathematical model for on-grid electrification is proposed and simulated on MATLAB. The off-grid option is simulated by HOMER. The results show how the LCOE of on-grid and off-grid electrification as well as the off-grid configuration are affected by different parameters like the distance to grid, load demand level, PV cost, WT cost, storage cost, the diesel price and so on. By comparing the results, the break-even point of two options is also presented.

  • Borsub, Jatesada
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Hardened Registration Process for Participatory Sensing2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Participatory sensing systems need to gather information from a largenumber of participants. However, the openness of the system is a doubleedgedsword: by allowing practically any user to join, the system can beabused by an attacker who introduces a large number of virtual devices.This work proposes a hardened registration process for participatory sensingto raise the bar: registrations are screened through a number of defensivemeasures, towards rejecting spurious registrations that do not correspondto actual devices. This deprives an adversary from a relatively easytake-over and, at the same time, allows a flexible and open registrationprocess. The defensive measures are incorporated in the participatorysensing application.

  • Canat, Mert
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Enterprise Architecture Success Factors2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Enterprise architecture aligns organizations business processes, information systems andtechnical layers. Its role has become more challenging than ever before with the modern dayrapidly changing environment and technological advances. Considering these aspects, this thesistries to evaluate the success factors that affect enterprise architecture management.The thesis is done at Volvo Cars, in collaboration with Ferrologic. Twelve success factorssignificant for Volvo Cars’ enterprise architecture management are defined after a series of semistructuredinterviews with architects working at the company. This is followed by a surveyevaluating the factors sent to architects throughout Sweden. In the end, the factors are dividedinto four groups according to their impact level. The survey reveals that the businessunderstanding of the technical side, requirement definitions & handling requirement changes,high-level management involvement, and cross-functionality are perceived to be most impactfulsuccess factors for the industry professionals, in no particular order.

  • Hylamia, Abdullah
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Towards Battery-free Radio Tomographic Imaging: Battery-free Boundary Crossing Detection2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Radio tomographic imaging (RTI) is a novel device-free localization technique which utilizes the changes in radio signals caused by obstruction to enable various sensing applications. However, the deployment of these applications is hindered by the energy-expensive radio sensing techniques employed in these systems. In this thesis, we tackle this issue by introducing a novel way to realize a battery-free RTI sensor. We go through the design process and produce and evaluate a working prototype that operates on minuscule amounts of energy. Our design reduces power consumption by orders of magnitude compared to traditional RTI sensors by eliminating the energy-expensive components used in current RTI systems, enabling battery-free operation of RTI sensors. We demonstrate the efficiency and accuracy of our system in a boundary crossing scenario. We Discuss its limitations and tackle some of the security threats correlated with the deployment of such a system.

  • Andre do Nascimento, Allan
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Robust Model Predictive Control for Marine Vessels2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This master thesis studies the implementation of a Robust MPC controllerin marine vessels on different tasks. A tube based MPC is designed based onsystem linearization around the target point guaranteeing local input to statestability of the respective linearized version of the original nonlinear system.The method is then applied to three different tasks: Dynamic positioningon which recursive feasibility of the nominal MPC is also guaranteed, Speed-Heading control and trajectory tracking with the Line of sight algorithm.Numerical simulation is then provided to show technique’s effectiveness.

    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Modelling towards a lean product development process: A case study at Scania customized truck development2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The increasing demands on producing products in an effective and resource efficient manner has put more focus on modelling internal processes within organizations. Models of internal processes show what work is to be done and how to do the work in order to get to the desired result. Modelling internal processes is also a way to capture knowledge that by many is seen as the most meaningful resource and valuable asset in today’s organizations. 

    This thesis project has created a model of the project process for customized truck development (s-order) at Scania. The purpose has been to create a model that facilitates the everyday work of the project managers and can be used to improve the process. The goal of this report is to add to the theoretic field of process modelling by focusing on how to use a process model. A qualitative case study was conducted in parallel to a literature study. The result is a model in two layers providing different levels of detail. The model can be used for project planning, project execution, project control and project development the most important part being to create a standardized way of working which is the basis for a lean product development. The process of modelling can in itself generate important insights into a process, the report therefore ends with a discussion on suggestions for improvement of the s-order projects towards becoming a more lean product development process.

  • Xu, Shuqi
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Learning Model Predictive Control for Autonomous Racing: Improvements and Model Variation in Model Based Controller2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this work, an improved Learning Model Predictive Control (LMPC)architecture for autonomous racing is presented. The controller is referencefree and is able to improve lap time by learning from history data of previouslaps. A terminal cost and a sampled safe set are learned from history data toguarantee recursive feasibility and non-decreasing performance at each lap.Improvements have been proposed to implement LMPC on autonomousracing in a more efficient and reliable way. Improvements have been doneon three aspects. Firstly, system identification has been improved to be runin a more efficient way by collecting feature data in subspace, so that thesize of feature data set is reduced and time needed to run sorting algorithmcan be reduced. Secondly, different strategies have been proposed toimprove model accuracy, such as least mean square with/without lifting andGaussian process regression. Thirdly, for reducing algorithm complexity,methods combining different model construction strategies were proposed.Also, running controller in a multi-rate way has also been proposed toreduced algorithm complexity when increment of controller frequency isnecessary. Besides, the performance of different system identificationstrategies have been compared, which include strategy from newton’s law,strategy from classical system identification and strategy from machinelearning. Factors that can possibly influence converged result of LMPCwere also investigated, such as prediction horizon, controller frequency.Experiment results on a 1:10 scaled RC car illustrates the effectiveness ofproposed improvements and the difference of different system identificationstrategies.

  • Fiusco, Francesco
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Improvement of a Space Surveillance and Tracking Analysis tool2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis deals with the improvement of SPOOK (SPace Objects Observation and Kalmanltering), an orbit calculation tool developed by Airbus Defence and Space GmbH. The workdescribed in this thesis aims at improving the architecture and analysis capabilities of thesoftware on dierent levels: Design and build a framework that can use SPOOK as a calculation engine and use itscapabilities to build a complete SST system for man-made objects orbiting the Earth,providing commercial services (e.g. collision avoidance, visualization, re-entry analysis,etc.), catalog maintenance and simulations. A complete Python API was designed andimplemented, which makes now SPOOK a complete cataloguing system for man-madespace objects that can provide services to the end user; Estimate covariance information from TLE data published by the US Space Command(available e.g. on Space-track.org); Devise and validate metrics that can assess the quality of an orbit determination processautomatically, to ensure as small human interaction as possible; Preliminarily implement a fast Lambert problem solver.In addition to this, a variety of miscellaneous activities were performed.

  • Ganesan, Sudakshin
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Real Time Reachability Analysis for Marine Vessels2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Safety verification of continuous dynamical systems require the computationof the reachable set. The reachable set comprises those states the systemcan reach at a specific point in time. The present work aims to compute thisreachable set for the marine vessel, in the presence of uncertainties in thedynamic modeling of the system and in the presence of external disturbancesin the form of wind, waves and currents. The reachable set can then be usedto check if the vessel collides with an obstacle. The dynamic model used isthat of a nonlinear maneuvering model for the marine vessel. The dynamicson the azipod actuators are also considered.Several methods are considered to solve the reachability problem for themarine vessel. The first method considered is that of the Hamilton JacobiReachability analysis, where a dynamic game between the control input andthe disturbance input is played. This results in a dynamic programmingproblem known as the Hamilton Jacobi Bellman Isaacs (HJBI) equation. Itis solved using the Level-Set method, but it suffers from the curse of dimensionality.The other method considered is the use of set-theoretic approach,where an over-approximation of the reachable set is computed, in the contextof safety verification. But on the downside, large sets of admissible controlyields highly over-approximated reachable sets, which cannot be usedIn order to overcome the disadvantages posed by the first two methods,emphasizing on the real-time computation, a third method is developed, wherea supervised classification algorithm is used to compute the reachable setboundary. The dataset required for the classification algorithm is computedby solving a 2 Point Boundary Value Optimal Control Problem for the marinevessel. The features for classification algorithm can be extended, so as toinclude the uncertainties and disturbances in the system. The computationtime is greatly reduced and the accuracy of the method is comparable to theexact reachable set computation.

  • Tsumak, Dmitri
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Securing BGP using blockchain technology2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The Border Gateway Protocol (BGP) is an important routing protocol used to exchangerouting information among autonomous systems on the Internet. The BGP version 4 doesnot include specific protection mechanisms against attacks or deliberate errors that couldcause disruptions of routing behavior. There were several securing solutions developedto mitigate security issues of BGP. In this thesis, current secure solutions are reviewedand evaluated against a list of security and deployment requirements. Furthermore, a newBGP securing solution is proposed which uses blockchain technology and smart contractsto exchange information required for messages validation among peers. This allows todecouple security-related data from the protocol itself and fix the problems introduced inother BGP solutions.

  • Mattsson, Filip
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Centralized Model Predictive Control of a Vehicle Platoon2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A centralized model predictive controller for longitudinal control of a vehicleplatoon is designed based on previous work on a distributed platooningcontroller. The vehicles in the platoon track a varying speed referenceand a constant timegap to the preceding vehicle. The designed controller isimplemented and compared to the distributed controller in simulation experimentsand in a simple practical setup. The experiments show that thecontroller works but does in general not outperform the distributed controller.

  • Jarnehammar, Filip
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Asset management of electrical transportation systems using alternative charging technologies: case study Stockholm Arlanda Airport2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In order to tackle the increasing problem of emitting greenhouse gases, electricityhas been seen as one way forward. The ability to provide energy from renewablesources is something that has to be made universal in the very near future. One ofthe larger parts of the problem is the transportation industry. Big ships, trucks andairplanes travel many times around the world each day and in order to give the environmenta chance to stop deteriorating goals and frameworks have been set in placefrom different organizations and countries. One road forward is by way of electrification.An electrified transportation system can satisfy the need for heavy and fasttransportation and doing so while not spewing out emissions. A difficult section ofthe transportation industry to electrify is the aviation. Airplanes can not afford theextra weight of the enormous battery packs required to make a transatlantic flight.We must however begin somewhere. This thesis considers an electrification of theground vehicles that service the airplane while on the ground. This project is part ofa group containing five interlinked parts concerning (1) electrification of airplane, (2)LCC of electrified ground vehicle fleet, (3) how the aging of lithium ion batteries isaffected by charging strategies, (4) LCC of a lithium ion battery with regards to theaging and (5) what an electrified ground vehicle fleet means in terms of grid connectionrequirements. These five different objectives are applied on the same caseof Stockholm Arlanda Airport. The conclusions regarding the grid connection arethat an electrification of the ground vehicle fleet itself might not require an upgradeto the existing grid connection. This however depends on the charging strategyadopted and the degree to which the aviation transportation system in its entirety iselectrified.

  • Jiang, Ge
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Preparation and Characteristics of Bi0.5Na0.5TiO3 based Lead-Free thin films by Pulsed Laser Deposition2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Lead-based piezoelectric materials, such as PbZrxTi1-xO3 (PZT), have attracted considerable attention and have been widely used in actuators, sensors and transducers due to their excellent electric properties. However, considering the toxicity of lead and its oxides, environmentally friendly lead-free piezoelectric materials are attracting more attention as potential replacements for PZT. Among them, Bi0.5Na0.5TiO3 (BNT)-based materials exhibit good electrical properties and electromechanical coupling response. In this work, the 0.97Bi0.5Na0.5TiO3-0.03BiAlO3 (BNTBA) thin films (~120 nm thickness) were successfully prepared using the pulsed laser deposition (PLD) method on Pt/TiO2/SiO2/Si substrates. The effects of substrate temperature, oxygen pressure, laser repetition rate, and post-annealing treatment were investigated. X-ray diffraction (XRD) and scanning electron microscope (SEM) are used to study the structure of the films and the ferroelectric and dielectric properties are measured. The results show that it is necessary to introduce excess sodium and bismuth to compensate for their evaporation in further thermal treatment. The values of remnant polarization increase from 8.7 μC/cm2 to 12.3 μC/cm2 with the introduction BiAlO3. The dielectric constant increases from 600-550 to 710-600 and the dielectric loss increases from 4.2% to 6.7% at higher frequency when the oxygen pressure increases from 20 Pa to 30 Pa.

  • Åkerberg, Viktor
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Effects on lifetime of lithium ion batteries using different charging strategies: case study Stockholm Arlanda Airport2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Electric vehicles are necessary in the shift away from combustion engine vehicles inorder to reduce the transport sectors greenhouse gas emissions. Unlike vehicles withcombustion engines, electric vehicles need to be charged, a process that takes variableduration of time depending on the power of the charger, the battery size and thecharging pattern. This report focuses on lithium ion batteries in an electric vehicle.Lithium-ion batteries are the most common batteries in electric vehicles due to theirhigh specific energy and energy density. The first chapter explains the composition ofa lithium ion battery from a single battery cell up to an entire battery system, and aliterature review was made in order to further understand failure causes of lithum ionbatteries. The second chapter analyses how the lifetime of a battery is affected by threedifferent charging strategies and the ambient temperature. The analysis was done ona case study of ground support vehicles on Stockholm Arlanda Airport, Sweden. Theconclusions drawn from the analysis are that the battery should be charged with stateof charge limits close to 50 %, a low charging power and a temperature close to 20°C in order to maximize lifetime. Since charging with low power takes a significantlylonger time compared to higher power charging options, future work should focus onweighing the efficiency of the ground support vehicles with the need for a long batterylifetime.

  • Prasad, Rohit
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Characterization, Clock Tree Synthesis and Power Grid Dimensioning in SiLago Framework2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A hardware design methodology or platform is complete if it has the capabilities to successfully implement clock tree, predict the power consumption for cases like best and worst Parasitic Interconnect Corners (RC Corners), supply power to every standard cell, etc.This thesis has tried to solve the three unsolved engineering problems in SiLago design. First, power characterization of the flat design which was designed using the SiLago methodology. Second, designing a hierarchical clock tree and harden it inside the SiLago logic. Third, dimensioning hierarchical power grids. Out of these, clock tree illustrates some interesting characteristics as it is programmable and predictable.The tools used for digital designing are Cadence Innovus, Synopsys Design Vision, and Mentor Graphics Questasim. These are very sophisticated tools and widely accepted in industries as well as in academia.The work done in this thesis has enabled SiLago platform one step forward toward its fruition.

  • Gómez, Francisco José
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Abstract [en]

    There are different reasons for combining different modeling languages and simulation

    languages: Exchange of more detailed information about power network components, their

    parameters and, most importantly, mathematical equations describing their behavior and

    the exchange of a mathematical description, using equation-based languages (e.g.:

    Modelica), allows models to be detached from the mathematical solver. This leads to the

    development of new APIs within software tools, which can handle standardized modeling

    language used for model implementation. Furthermore, the mathematical description of

    models and the integration of new simulation standards, such as the FMI, could help

    avoiding ambiguities on how power system models are implemented, by providing

    additional means for the exchange of the complete description of models or parts of a

    model between software tools.

    The aim of this thesis is to provide a new approach for the development of power

    systems modeling and simulation software tools. The thesis is focused on proposing new

    methods, based on available information and simulation standards for the exchange,

    modeling, and simulation of power systems dynamic models; and to show a proof of

    concept of the feasibility of the proposed methods. To this aims, the Common Information

    Model (CIM) for the modeling and exchange of power system information is studied.

    Furthermore, the equation-based language Modelica is described and proposed with the

    aim of complementing the use of the CIM for the modeling and simulation of those

    dynamics models.

    The application of these standards lead to a different view on the modeling and

    simulation of power dynamic network models. The conventional view is that of black box

    modeling. The implementation of network model components is strongly connected to the

    simulation software tool used for steady-state and dynamics calculations. Thus, a modeler

    or test engineer only has access to the parameters of a model and relies on the software

    capabilities to calculate the states and the behavior of that model. This thesis proposes a

    different view per the application of the white box modeling and simulation concept: full

    detail and transparency on the development of a mathematical description of power system

    components and discrete events. Moreover, the combination of information standards with

    equation-based standards to produce network models allows full access and manipulation

    of the complete model details. Finally, transparency regarding the implementation of

    software tools can support either information-based, equations-based languages or

    simulation standards, which are suitable for simulation of dynamic network models.

  • Höglund, Emma
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Urban and Regional Studies.
    Äldrevänlig stadsplanering i Stockholms stad2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Cities are facing a major demographic change where the proportion of older people isexpected to increase. This has drawn attention to the need to make cities more age-friendly,and thus promote health, independence and the active lives of the elderly. In 2010, theWorld Health Organization (WHO) created a global network for age-friendly cities andcommunities with the aim of spreading knowledge and information about how to betteradapt cities for older people. Stockholm is one of many cities that have now joined thenetwork and thus committed to making the city more age-friendly. The aim of this thesis hastherefore been to investigate how Stockholm can plan to become an age-friendly city basedon the WHO guidelines and the age-friendly planning processes in other cities.First, a literature study of articles concerning other cities’ age-friendly work was made.Based on this literature study, a theoretical framework was developed around the themesthat emerged as particular important regarding age-friendly planning. The theories werecollaborative planning, institutional capacity and integrated planning. Furthermore, studiesof documents dealing with the future development of Stockholm City were conducted toexamine the elderly perspective in these. Finally, interviews with municipal officials andpoliticians were made to get a deeper understanding of how the cities age-friendly planninglooks today.The study’s results indicate that Stockholm has good opportunities to plan for an agefriendlycity, while there are still several obstacles to overcome. The city’s strengths are thedesire to become more age-friendly, which is evidenced by political support and a givenbudget, as well as the recognition of the importance of including the urban planning office.However, some of the obstacles that remain are the lack of cross-sectorial collaboration(between the urban planning office and the elderly administration office), that the elderlyadministration office comes in too late in urban planning processes, and that the needs ofthe elderly have long been adopted through the accessibility perspective only. The studyends with a number of solutions to help overcome these obstacles.