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  • 1.
    A. M. Naiini, Maziar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Horizontal Slot Waveguides for Silicon Photonics Back-End Integration2014Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis presents the development of integrated silicon photonic devices. These devices are compatible with the present and near future CMOS technology. High-khorizontal grating couplers and waveguides are proposed. This work consists of simulations and device design, as well as the layout for the fabrication process, device fabrication, process development, characterization instrument development and electro-optical characterizations.

    The work demonstrates an alternative solution to costly silicon-on-insulator photonics. The proposed solution uses bulk silicon wafers and thin film deposited waveguides. Back-end deposited horizontal slot grating couplers and waveguides are realized by multi-layers of amorphous silicon and high-k materials.

    The achievements of this work include: A theoretical study of fully etched slot grating couplers with Al2O3, HfO2 and AIN, an optical study of the high-k films with spectroscopic ellipsometry, an experimental demonstration of fully etched SiO2 single slot grating couplers and double slot Al2O3 grating couplers, a practical demonstration of horizontal double slot high-k waveguides, partially etched Al2O3 single slot grating couplers, a study of a scheme for integration of the double slot Al2O3  waveguides with selectively grown germanium PIN photodetectors, realization of test chips for the integrated germanium photodetectors, and study of integration with graphene photodetectors through embedding the graphene into a high-k slot layer.

    From an application point of view, these high-k slot waveguides add more functionality to the current silicon photonics. The presented devices can be used for low cost photonics applications. Also alternative optical materials can be used in the context of this photonics platform.

    With the robust design, the grating couplers result in improved yield and a more cost effective solution is realized for integration of the waveguides with the germanium and graphene photodetectors.

     

     

     

     

  • 2. Abasahl, B.
    et al.
    Zand, I.
    Lerma Arce, C.
    Kumar, S.
    Quack, N.
    Jezzini, M. A.
    Hwang, H. Y.
    Gylfason, Kristinn B.
    KTH, Skolan för elektro- och systemteknik (EES), Mikro- och nanosystemteknik.
    Porcel, M. A. G.
    Bogaerts, W.
    Towards Low-Power Reconfigurable Photonic ICs Based on MEMS Technology2018Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    With the progress and industrialization of photonic integrated circuits (PIC) in the past few decades, there is a strong urge towards design and prototyping in a fast, low-cost and reliable manner. In electronics, this demand is met through field programmable gate arrays (FPGA). In the Horizon 2020 MORPHIC (MEMS-based zerO-power Reconfigurable Photonic ICs) project, we are developing a reconfigurable PIC platform to address this demand in the field of photonics and to facilitate the path from idea towards realization for PIC designers and manufacturers.

  • 3.
    ABBASI, MUHAMMAD MOHSIN
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Solving Sudoku by Sparse Signal Processing2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Sudoku is a discrete constraints satisfaction problem which is modeled as an underdetermined linear

    system. This report focuses on applying some new signal processing approaches to solve sudoku and

    comparisons to some of the existing approaches are implemented. As our goal is not meant for

    sudoku only in the long term, we applied approximate solvers using optimization theory methods. A

    Semi Definite Relaxation (SDR) convex optimization approach was developed for solving sudoku. The

    idea of Iterative Adaptive Algorithm for Amplitude and Phase Estimation (IAA-APES) from array

    processing is also being used for sudoku to utilize the sparsity of the sudoku solution as is the case in

    sensing applications. LIKES and SPICE were also tested on sudoku and their results are compared with

    l1-norm minimization, weighted l1-norm, and sinkhorn balancing. SPICE and l1-norm are equivalent

    in terms of accuracy, while SPICE is slower than l1-norm. LIKES and weighted l1-norm are equivalent

    and better than SPICE and l1-norm in accuracy. SDR proved to be best when the sudoku solutions are

    unique; however the computational complexity is worst for SDR. The accuracy for IAA-APES is

    somewhere between SPICE and LIKES and its computation speed is faster than both.

  • 4. Abd Elghany, M. A.
    et al.
    El-Moursy, M. A.
    Korzec, D.
    Ismail, Mohammed
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar. Ohio State University, United States .
    High throughput architecture for OCTAGON network on chip2009Inngår i: 2009 16th IEEE International Conference on Electronics, Circuits and Systems, ICECS 2009, IEEE , 2009, s. 101-104Konferansepaper (Fagfellevurdert)
    Abstract [en]

    High Throughput Octagon architecture to achieve high performance Networks on Chip (NoC) is proposed. The architecture increase. The throughput oy the network by 17% while preservin. The average latency. The area of High Throughput OCTAGON switch is decreased by 18% as compared to OCTAGON switch. The total metal resources required to implement High Throughput OCTAGON design is increased by 8% as compared to the total metal resources required to implement OCTAGON design. The extra power consumption required to achiev. The proposed architecture is 2% oy the total power consumption oy the OCTAGON architecture.

  • 5.
    Abdalmoaty, Mohamed
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Learning Stochastic Nonlinear Dynamical Systems Using Non-stationary Linear Predictors2017Licentiatavhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    The estimation problem of stochastic nonlinear parametric models is recognized to be very challenging due to the intractability of the likelihood function. Recently, several methods have been developed to approximate the maximum likelihood estimator and the optimal mean-square error predictor using Monte Carlo methods. Albeit asymptotically optimal, these methods come with several computational challenges and fundamental limitations.

    The contributions of this thesis can be divided into two main parts. In the first part, approximate solutions to the maximum likelihood problem are explored. Both analytical and numerical approaches, based on the expectation-maximization algorithm and the quasi-Newton algorithm, are considered. While analytic approximations are difficult to analyze, asymptotic guarantees can be established for methods based on Monte Carlo approximations. Yet, Monte Carlo methods come with their own computational difficulties; sampling in high-dimensional spaces requires an efficient proposal distribution to reduce the number of required samples to a reasonable value.

    In the second part, relatively simple prediction error method estimators are proposed. They are based on non-stationary one-step ahead predictors which are linear in the observed outputs, but are nonlinear in the (assumed known) input. These predictors rely only on the first two moments of the model and the computation of the likelihood function is not required. Consequently, the resulting estimators are defined via analytically tractable objective functions in several relevant cases. It is shown that, under mild assumptions, the estimators are consistent and asymptotically normal. In cases where the first two moments are analytically intractable due to the complexity of the model, it is possible to resort to vanilla Monte Carlo approximations. Several numerical examples demonstrate a good performance of the suggested estimators in several cases that are usually considered challenging.

  • 6.
    Abdi Kelishami, Alireza
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    Secure Privacy-Friendly Instant Messaging (IM) for Guidepal2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    It is fascinating, and yet often neglected, that a user’s privacy can be invaded notonly by the absence of security measures and mechanisms, but also by improperor inadequate usage of security services and mechanisms. When designingsecure systems, we must consider what services are needed and what is not.The work in this thesis revolves around privacy-friendly instant messaging (IM)systems. In such a system, an inadequate usage of security measures leads tohaving IM servers being able to intercept or gather users’ private conversations.An improper usage of security measures could bring about non-repudiationwhich is desirable when signing contracts, but unwelcome in IM and privateconversations.We will look into requirements of the desired IM system, study the currentstate-of-the-art solutions, deploy an IM server, and briefly extend an existingmodern privacy-friendly IM protocol and an open source mobile application tomeet our security and privacy requirements. This extended IM application iscalled Guidepal-IM and is available as open source1The thesis work is introduced and carried out at Guidepal, a startup companyin Stockholm. It is therefore supervised partly at Guidepal and partly at KTH.Since Guidepal is also looking into possibilities of integrating an IM featureto its current social media apps, our contribution would also briefly extend tostudying the limitations and recommendations for Guidepal’s social media appto help user privacy preservation.

  • 7.
    Abedin, Ahmad
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektronik, Integrerade komponenter och kretsar.
    Zurauskaite, Laura
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektronik, Integrerade komponenter och kretsar.
    Asadollahi, Ali
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektronik, Integrerade komponenter och kretsar. KTH.
    GOI fabrication for Monolithic 3D integrationInngår i: Artikkel i tidsskrift (Annet vitenskapelig)
  • 8.
    Abeywickrama, K. G. Nilanga B.
    et al.
    Chalmers, Div High Voltage Engn, Dept Mfg & Mat Technol, SE-41296 Gothenburg, Sweden..
    Daszczynski, Tadeusz
    Warsaw Univ Technol, PL-00611 Warsaw, Poland..
    Serdyuk, Yuriy V.
    Chalmers, Div High Voltage Engn, Dept Mfg & Mat Technol, SE-41296 Gothenburg, Sweden.;Natl Acad Sci Ukraine, Inst Electrodynam, Kiev, Ukraine.;ABB High Voltage Technol Ltd, R&D HV Lab, Zurich, Switzerland..
    Gubanski, Stanislaw M.
    KTH.
    Determination of complex permeability of silicon steel for use in high-frequency modeling of power transformers2008Inngår i: IEEE transactions on magnetics, ISSN 0018-9464, E-ISSN 1941-0069, Vol. 44, nr 4, s. 438-444Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Information about frequency dependence of complex permeability of silicon steel is a vital input parameter in calculations of transformer winding inductance used for modeling. high-frequency behavior (100 Hz-1 MHz). We present two ways of determining small signal complex permeability spectra in frequency domain and compare and discuss the results. The first method is based on an optimization procedure, in which inductance of a winding is measured and calculated by analytical formulas and finite-element modeling. The second method makes use of a single sheet tester. We show that the magnitude of effective permeability of the silicon steel laminations remains significant up to about 100 kHz. We also report on the effect of magnetic viscosity on complex permeability.

  • 9.
    Abrahamson, Lars
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Söder, Lennart
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Fast calculation of the dimensioning factors of the railway power supply system2007Inngår i: Computational Methods and Experimental Measurements XIII, WIT Press, 2007, Vol. 46, s. 85-95Konferansepaper (Fagfellevurdert)
    Abstract [en]

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

  • 10.
    Abrahamsson, Lars
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Optimal Railroad Power Supply System Operation and Design: Detailed system studies, and aggregated investment models2012Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

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

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

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

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

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

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

  • 11.
    Abrahamsson, Lars
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Railway Power Supply Models and Methods for Long-term Investment Analysis2008Licentiatavhandling, monografi (Annet vitenskapelig)
    Abstract [en]

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

  • 12.
    Abrahamsson, Lars
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Kjellqvist, Tommy
    Elekt Konsult AB, Kraftelektronik, Sweden.
    Östlund, Stefan
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    High-voltage DC-feeder solution for electric railways2012Inngår i: IET Power Electronics, ISSN 1755-4535, E-ISSN 1755-4543, Vol. 5, nr 9, s. 1776-1784Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 13.
    Abrahamsson, Lars
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Kjellqvist, Tommy
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Östlund, Stefan
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    HVDC Feeder Solution for Electric Railways2012Inngår i: IET Power Electronics, ISSN 1755-4535, E-ISSN 1755-4543Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

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

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

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

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

  • 14.
    Abrahamsson, Lars
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Schütte, Thorsten
    Östlund, Stefan
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Use of converters for feeding of AC railways for all frequencies2012Inngår i: Energy for Sustainable Development, ISSN 0973-0826, Vol. 16, nr 3, s. 368-378Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 15.
    Abrahamsson, Lars
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Söder, Lennart
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    An SOS2-based moving trains,fixed nodes, railway power system simulator2012Inngår i: WIT Transactions on the Built Environment, WIT Press, 2012, s. 813-823Konferansepaper (Fagfellevurdert)
    Abstract [en]

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

  • 16.
    Abrahamsson, Lars
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Söder, Lennart
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Basic modeling for electric traction systems under uncertainty2006Inngår i: PROCEEDINGS OF THE 41ST INTERNATIONAL UNIVERSITIES POWER ENGINEERING CONFERENCE, VOLS 1 AND 2, NEW YORK: IEEE , 2006, s. 252-256Konferansepaper (Fagfellevurdert)
    Abstract [en]

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

  • 17.
    Abrahamsson, Lars
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Söder, Lennart
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Fast calculation of some important dimensioning factors of the railway power supply system2007Konferansepaper (Fagfellevurdert)
    Abstract [en]

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

  • 18.
    Abrahamsson, Lars
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Söder, Lennart
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Fast Estimation of Relations Between Aggregated Train Power System Data and Traffic Performance2011Inngår i: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 60, nr 1, s. 16-29Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 19.
    Abrahamsson, Lars
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Söder, Lennart
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Fast estimation of the relation between aggregated train power system information and the power and energy converted2009Inngår i: Australian Journal of Electrical and Electronic Engineering, ISSN 1448-837X, Vol. 6, nr 3, s. 311-318Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 20.
    Abrahamsson, Lars
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Söder, Lennart
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Fast estimation of the relation between aggregated train power system information and the power and energy converted2008Inngår i: 2008 Australasian Universities Power Engineering Conference, AUPEC 2008, IEEE conference proceedings, 2008, s. 1-6Konferansepaper (Fagfellevurdert)
    Abstract [en]

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

  • 21.
    Abrahamsson, Lars
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Söder, Lennart
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Operation simulation of traction systems2008Inngår i: COMPUTERS IN RAILWAYS XI, 2008, Vol. 103, s. 283-292Konferansepaper (Fagfellevurdert)
    Abstract [en]

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

  • 22.
    Abrahamsson, Lars
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Söder, Lennart
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Railway power supply investment decisions considering the voltage drops: Assuming the future traffic to be known2009Inngår i: 2009 15th International Conference on Intelligent System Applications to Power Systems, ISAP '09, 2009Konferansepaper (Annet vitenskapelig)
    Abstract [en]

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

  • 23.
    Abrahamsson, Lars
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Söder, Lennart
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Traction Power System Capacity Limitations at Various Traffic Levels2011Inngår i: WCRR, World Congress on Railway Research, 2011Konferansepaper (Fagfellevurdert)
    Abstract [en]

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

  • 24.
    Abrahamsson, Lars
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Östlund, Stefan
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Schütte, Thorsten
    Söder, Lennart
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    An electromechanical moving load fixed node position and fixed node number railway power supply systems optimization model2013Inngår i: Transportation Research Part C: Emerging Technologies, ISSN 0968-090X, E-ISSN 1879-2359, Vol. 30, s. 23-40Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 25.
    Abrahamsson, Lars
    et al.
    KTH, Tidigare Institutioner, Elkraftteknik.
    Östlund, Stefan
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Söder, Lennart
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Optimal PowerFlow (OPF) Model with Unified AC-DC Load Flow and Optimal Commitmentfor an AC-catenary Railway Power Supply System (RPSS) fed by aHigh Voltage DC (HVDC) transmission lineManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    In this paper an alternative railway power systems design based on an HVDC feeder is studied. The HVDC feeder is connected to the catenary by converters. Such an HVDC line is also appropriate for DC-fed railways and AC-fed railways working at public frequency.

    A unit commitment optimal power flow model has been developed and is applied on a test system. In this paper, the model is presented in detail. The model, in the form of an MINLP program, uses unified AC-DC power flow to minimize the entire railway power system losses.

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

  • 26.
    Abrahamsson, Lars
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Östlund, Stefan
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Söder, Lennart
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Optimal PowerFlow (OPF) Model with Unified AC-DC Load Flow and Optimal Commitmentfor an AC-catenary Railway Power Supply System (RPSS) fed by aHigh Voltage DC (HVDC) transmission line2012Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper an alternative railway power systems design based on an HVDC feeder is studied. The HVDC feeder is connected to the catenary by converters. Such an HVDC line is also appropriate for DC-fed railways and AC-fed railways working at public frequency. A unit commitment optimal power flow model has been developed and is applied on a test system. In this paper, the model is presented in detail. The model, in the form of an MINLP program, uses unified AC-DC power flow to minimize the entire railway power system losses. Simulations of the proposed solution show clear advantages regarding transmission losses and voltages compared to conventional systems, especially for cases with long distances between feeding points to the catenary, and when there are substantial amounts of regeneration from the trains.

  • 27. Accoto, Nadia
    et al.
    Rydén, Tobias
    Lund University.
    Secchi, Paolo
    Bayesian Hidden Markov Models for Performance-Based Regulation of Continuity of Electricity Supply2010Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 25, nr 3, s. 1236-1249Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A fundamental aspect in the regulation of the continuity of electricity supply is the identification of faults that could be caused by an exceptional event and, therefore, that are outside the utility control and responsibility. Different methods have been proposed during the years: the interpretation of the observed faults as a signal of an underlying system naturally leads to the analysis of the problem by means of a hidden Markov model. Thesemodels, in fact, are widely used for introducing dependence in data and/or for modeling observed phenomena depending on hidden processes. The application of this method shows that the model is able to identify exceptional events; moreover, the study of the estimated model parameters gives rise to reality-linked considerations.

  • 28.
    Ackermann, Thomas
    et al.
    KTH, Tidigare Institutioner.
    Andersson, G.
    Söder, Lennart
    KTH, Tidigare Institutioner.
    Distributed generation: a definition2001Inngår i: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 57, nr 3, s. 195-204Artikkel i tidsskrift (Fagfellevurdert)
  • 29.
    Ackermann, Thomas
    et al.
    KTH, Tidigare Institutioner.
    Andersson, G.
    Söder, Lennart
    KTH, Tidigare Institutioner.
    Overview of government and market driven programs for the promotion of renewable power generation2001Inngår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 22, nr 1-3, s. 197-204Artikkel i tidsskrift (Fagfellevurdert)
  • 30.
    Ackermann, Thomas
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Andersson, Göran
    Söder, Lennart
    KTH, Tidigare Institutioner.
    Electricity market regulations and their impact on distributed generation2000Inngår i: Electric Utility Deregulation and Restructuring and Power Technologies, 2000. Proceedings. DRPT 2000. International Conference on, 2000, s. 608-613Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Distributed generation (DG) has attracted a lot of attention recently and might become more important in future power generation systems. As different definitions are used worldwide, the paper briefly discusses the definition of DG. The future development of DG, however, will, to a not insignificant part, depend on the legal framework. As the legal framework can vary significantly for different competitive electricity markets, this paper briefly identifies and analyses some variations in the regulatory approaches, e.g. for power exchanges, balance services and ancillary services, in different countries. It also illustrates the influence of market regulations on the development of distributed power generation. Based on this analysis, it can be concluded that regulatory aspects might decisively influence the development of distributed power generation

  • 31.
    Ackermann, Thomas
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Centeno-Lopez, Eva
    Söder, Lennart
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Grid Issues for Electricity Production Based on Renewable Energy Sources in Spain, Portugal, Germany, and United Kingdom2008Bok (Annet vitenskapelig)
  • 32.
    Ackermann, Thomas
    et al.
    KTH, Tidigare Institutioner.
    Söder, Lennart
    KTH, Tidigare Institutioner.
    An overview of wind energy-status 20022002Inngår i: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 6, nr 1-2, s. 67-128Artikkel, forskningsoversikt (Fagfellevurdert)
  • 33.
    Ackermann, Thomas
    et al.
    KTH, Tidigare Institutioner.
    Söder, Lennart
    KTH, Tidigare Institutioner.
    Wind energy technology and current status: a review2000Inngår i: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 4, nr 4, s. 315-374Artikkel, forskningsoversikt (Fagfellevurdert)
  • 34.
    Acquaviva,, Alessandro
    et al.
    Chalmers University of Technology, Department of Electrical engineering, Göteborg, Sweden.
    Wallmark, Oskar
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik.
    Grunditz, Emma
    Chalmers University of Technology, Department of Electrical engineering, Göteborg, Sweden.
    Lundmark, Sonja
    Chalmers University of Technology, Department of Electrical engineering, Göteborg, Sweden.
    Thiringer, Torbjörn
    Computationally efficient modeling of electrical machines with cooling jacketInngår i: Artikkel i tidsskrift (Fagfellevurdert)
  • 35. Agustsson, J. S.
    et al.
    Agustsson, B. V.
    Eriksson, A. K.
    Gylfason, Kristinn B.
    KTH, Skolan för elektro- och systemteknik (EES), Mikrosystemteknik (Bytt namn 20121201).
    Olafsson, S.
    Johnsen, K.
    Gudmundsson, J. T.
    Hydrogen uptake in MgO thin films grown by reactive magnetron sputtering2006Konferansepaper (Annet vitenskapelig)
    Abstract
  • 36. Agustsson, J. S.
    et al.
    Arnalds, U. B.
    Ingason, A. S.
    Gylfason, Kristinn B.
    KTH, Skolan för elektro- och systemteknik (EES), Mikrosystemteknik (Bytt namn 20121201).
    Johnsen, K.
    Olafsson, S.
    Gudmundsson, Jon Tomas
    University of Iceland, Iceland.
    Electrical resistivity and morphology of ultra thin Pt films grown by dc magnetron sputtering on SiO(2)2008Inngår i: Journal of Physics Conference Series, IOP Science , 2008, Vol. 100Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Ultra thin platinum films were grown by dc magnetron sputtering on thermally oxidized Si (100) substrates. The electrical resistance of the films was monitored in-situ during growth. The coalescence thickness was determined for various growth temperatures and found to increase from 1.3 nm for films grown at room temperature to 1.8 nm for films grown at 250 degrees C, while a continuous film was formed at a thickness of 3.9 nm at room temperature and 3.5 nm at 250 degrees C. The electrical resistivity increases with increased growth temperature, as well as the morphological grain size, and the surface roughness, measured with a scanning tunneling microscope (STM).

  • 37. Agustsson, Jon S.
    et al.
    Gylfason, Kristinn B.
    KTH, Skolan för elektro- och systemteknik (EES), Mikrosystemteknik (Bytt namn 20121201).
    Olafsson, Sveinn
    Johnsen, Kristinn
    Gudmundsson, Jon T
    Electrical properties of thin MgO films2005Konferansepaper (Annet vitenskapelig)
  • 38.
    Ahmed, Noman
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Ängquist, Lennart
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Norrga, Staffan
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Antonopoulos, Antonios
    ABB Corporate Research Center, Sweden.
    Harnefors, Lennart
    ABB Corporate Research Center, Sweden.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    A computationally efficient continuous model for the modular multilevel converter2014Inngår i: IEEE Journal of Emerging and Selected Topics in Power Electronics, ISSN 2168-6777, Vol. 2, nr 4, s. 1139-1148, artikkel-id 6840290Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Simulation models of the modular multilevel converter (MMC) play a very important role for studying the dynamic performance. Detailed modeling of the MMC in electromagnetic transient simulation programs is cumbersome, as it requires high computational effort and simulation time. Several averaged or continuous models proposed in the literature lack the capability to describe the blocked state. This paper presents a continuous model, which is capable of accurately simulating the blocked state. This feature is very important for accurate simulation of faults. The model is generally applicable, although it is particularly useful in high-voltage dc applications.

  • 39.
    Ahsin, Tafzeel Ur Rehman
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Ben Slimane, Slimane
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Constellation Selection in Network Coded Distributive Antenna System2009Inngår i: GLOBECOM 2009 - 2009 IEEE Global Telecommunications Conference / [ed] Ulema M, IEEE , 2009, s. 342-346Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Relays can improve wireless links by providing an extra path to the direct path which together form a virtual multiple antenna system. Network Coded-Distributive Antenna System (NC-DAS) and Plain-Distributive Antenna System (P-DAS) are examples of realizations of such scenario. Although the asymptotic diversity gain for both the schemes is comparable, the network coded scheme can further take advantage of the redundancy and the extra dimension provided by the relay link. This extra signal dimension can be very useful when multilevel modulation is employed as it gives the possibility for a better spread of the modulation signal points within the augmented signal space. This article presents a simple and effective Constellation Selection (CS) scheme for all the three links within the NC-DAS system. This selection procedure improves the bit error probability in both AWGN and Rayleigh fading channels. Two different detections schemes are considered in the paper. Joint detection where the both users are decoded simultaneously and detection with successive cancelation where the strongest user is detected first followed by cancelation and maximum ratio combining. Analytical expressions for the error probability supported by simulation results are presented. The obtained results show that constellation selection provides good performance gain as compared to the case of same constellation.

  • 40.
    Akay, Altug
    et al.
    KTH, Skolan för teknik och hälsa (STH), Hälso- och systemvetenskap, Systemsäkerhet och organisation.
    Dragomir, A
    Erlandsson, Björn-Erik
    KTH, Skolan för teknik och hälsa (STH), Hälso- och systemvetenskap, Systemsäkerhet och organisation.
    A Novel Data-Mining Approach Leveraging Social Media to Monitor Consumer Opinion of Sitagliptin2015Inngår i: IEEE journal of biomedical and health informatics, ISSN 2168-2194, E-ISSN 2168-2208, Vol. 19, nr 1, s. 389-396Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A novel data mining method was developed to gauge the experience of the drug Sitagliptin (trade name Januvia) by patients with diabetes mellitus type 2. To this goal, we devised a two-step analysis framework. Initial exploratory analysis using self-organizing maps was performed to determine structures based on user opinions among the forum posts. The results were a compilation of user's clusters and their correlated (positive or negative) opinion of the drug. Subsequent modeling using network analysis methods was used to determine influential users among the forum members. These findings can open new avenues of research into rapid data collection, feedback, and analysis that can enable improved outcomes and solutions for public health and important feedback for the manufacturer.

  • 41.
    Akay, Altug
    et al.
    KTH, Skolan för teknik och hälsa (STH), Hälso- och systemvetenskap, Systemsäkerhet och organisation.
    Dragomir, A.
    Erlandsson, Björn-Erik
    KTH, Skolan för teknik och hälsa (STH), Hälso- och systemvetenskap, Systemsäkerhet och organisation.
    A novel data-mining platform leveraging social media to monitor outcomes of Januvia2013Inngår i: Engineering in Medicine and Biology Society (EMBC), 2013 35th Annual International Conference of the IEEE, IEEE conference proceedings, 2013, s. 7484-7487Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A novel data-mining method was developed to gauge the experiences of the diabetes mellitus drug Januvia. Self-organizing maps were used to analyze forum posts numerically to infer user opinion of drug Januvia. Graph theory was used to discover influential users. The result is a word list compilation correlating positive and negative word cluster groups and a web of influential users on Januvia. The implications could open new research avenues into rapid data collection, feedback, and analysis that would enable improved solutions for public health.

  • 42.
    Al Khatib, Iyad
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT. iITC, Sweden .
    Ismail, M.
    WNoC: A microelectronic system architecture suitable for biomedical wireless sensor networks2005Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents a low-cost microelectronic system architecture suitable for single chip CMOS integration. The system architecture consists of a large set of on-chip processing-cores, sensors, and four multi-standard wireless border cores that are interconnected to form an ultra-fast microelectronic network of distributed-computing systems. Our main application areas are: biomedical emergency monitoring systems and healthcare. The hardware platform is based on Network-on-Chip (NoC) design and RF circuitry for wireless connectivity. We focus on the design of this Wireless Network-on-Chip (WNoC). WNoC faces several challenges. A main issue of concern from the application point of view is to have the design support the convergence to a decision within acceptable periods of time, because time is critical in many medical healthcare applications. We define a mechanism to enable many WNoCs to interact together over the wireless media. A key result is a design and protocol for internal and external WNoC communications between the main and backup wireless cores. We run simulations on a biomedical monitoring system for emergency situations, and our results show that the time to converge to a medical warning is in the range of milliseconds, which is acceptable for the related medical scenarios.

  • 43.
    Ala-Laurinaho, J.
    et al.
    Aalto University, Finland.
    Chicherin, Dmitry
    Aalto University, Finland.
    Du, Zhou
    Aalto University, Finland.
    Simovski, C.
    Aalto University, Finland.
    Zvolensky, T.
    Aalto University, Finland.
    Räisänen, Antti V.
    Aalto University, Finland.
    Sterner, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Mikrosystemteknik (Bytt namn 20121201).
    Baghchehsaraei, Zargham
    KTH, Skolan för elektro- och systemteknik (EES), Mikrosystemteknik (Bytt namn 20121201).
    Shah, Umer
    KTH, Skolan för elektro- och systemteknik (EES), Mikrosystemteknik (Bytt namn 20121201).
    Dudorov, Sergey
    KTH, Skolan för elektro- och systemteknik (EES), Mikrosystemteknik (Bytt namn 20121201).
    Oberhammer, Joachim
    KTH, Skolan för elektro- och systemteknik (EES), Mikrosystemteknik (Bytt namn 20121201).
    Boriskin, A. V.
    IETR, France.
    Le Coq, L.
    IETR, France.
    Fourn, Erwan
    IETR, France.
    Muhammad, S. A.
    IETR, France.
    Sauleau, Ronan
    IETR, France.
    Vorobyov, Alexander
    IETR, France.
    Bodereau, F.
    TRW Autocruise, France.
    El Haj Shhade, G.
    TRW Autocruise, France.
    Labia, T.
    TRW Autocruise, France.
    Mallejac, P.
    TRW Autocruise, France.
    Åberg, Jan
    MicroComp Nordic AB, Sweden.
    Gustafsson, M.
    MicroComp Nordic AB, Sweden.
    Schier, T.
    MicroComp Nordic AB, Sweden.
    TUMESA - MEMS tuneable metamaterials for smart wireless applications2012Inngår i: European Microwave Week 2012: "Space for Microwaves", EuMW 2012, Conference Proceedings - 7th European Microwave Integrated Circuits Conference, EuMIC 2012, IEEE , 2012, s. 95-98Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper describes the main results of the EU FP7 project TUMESA - MEMS tuneable metamaterials for smart wireless applications. In this project, we studied several reconfigurable antenna approaches that combine the new technology of MEMS with the new concept of artificial electromagnetic materials and surfaces (metamaterials and metasurfaces) for realisation of millimetre wave phase shifters and beam-steering devices. MEMS technology allows to miniaturise electronic components, reduce their cost in batch production, and effectively compete with semiconductor and ferroelectric based technologies in terms of losses at millimetre wavelengths. Novel tuneable materials and components proposed in this project perform as smart beam steering devices. Fabricated with MEMS technology in batch and on a single chip, proposed tuneable devices allow substituting of larger and more complex sub-system of, e.g., a radar sensor. This substitution provides a dramatic cost reduction on a system level.

  • 44.
    Alameddine, Raged
    et al.
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Data- och elektroteknik.
    Dashtbozorg, Sajad
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Data- och elektroteknik.
    Utredning av för- och nackdelar med TN-S respektive TN-C system2016Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [sv]

    I denna rapport analyseras för- och nackdelar med eldistributionssystem av typ TN-C (fyrledarsystem) respektive TN-S (femledarsystem) system. Det finns olika uppfattningar om vilket system som är lämpligast att bygga ut i distributionsnätet (lågspänningsnätet) och i fastigheternas huvudledning. Med hjälp av litteraturstudier och kontakt med olika elföretag och elbolag har olika ståndpunkter diskuterats och därefter har en sammanställning av resultatet tagits fram. Enligt analysen är TN-C det lämpligaste alternativet att använda i distributionsnätet och TN-S bör användas i fastighetens huvudledning. Detta för att kunna uppnå en god och stabil elmiljö. Detta examensarbete skall underlätta val av teknik och förhoppningsvis öka kunskapen angående ämnet. 

  • 45.
    Alayon Glazunov, Andres
    et al.
    KTH, Skolan för elektro- och systemteknik (EES). Lund University, Sweden.
    Gustafsson, Mats
    Molisch, Andreas F.
    On the Physical Limitations of the Interaction of a Spherical Aperture and a Random Field2011Inngår i: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 59, nr 1, s. 119-128, artikkel-id 5618544Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper derives physical limitations on the interactions of antennas exciting TM or TE modes (but not both) and wireless propagation channels. The derivation is based on the spherical vector wave expansion of the electromagnetic field outside a sphere circumscribing the antennas. The result is an extension of the seminal work of Chu on the classical limitations on maximum antenna gain and radiation Q. Rather than maximizing antenna gain in a single direction we obtain physical limitations on the antenna gain pattern, which is directly translated to more condensed parameters, i.e., the instantaneous effective gain G(i) and the mean effective gain G(e) if instantaneous realizations or correlation statistics of the expansion coefficients of the electromagnetic field are known, spectively. The obtained limitations are on the maximum of G(i)/Q and G(e)/Q, which establish a trade-off between link gain and Q.

  • 46.
    Albertsson, Dagur Ingi
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektronik, Integrerade komponenter och kretsar.
    Zahedinejad, Mohammad
    Department of Physics, University of Gothenburg.
    Åkerman, Johan
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Material- och nanofysik. Department of Physics, University of Gothenburg.
    Rodriguez, Saul
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektronik, Integrerade komponenter och kretsar.
    Rusu, Ana
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektronik, Integrerade komponenter och kretsar.
    Compact Macrospin-Based Model of Three-Terminal Spin-Hall Nano Oscillators2019Inngår i: IEEE transactions on magnetics, ISSN 0018-9464, E-ISSN 1941-0069, Vol. 55, nr 10, artikkel-id 4003808Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Emerging spin-torque nano oscillators (STNOs) and spin-Hall nano oscillators (SHNOs) are potential candidates for microwave applications. Recent advances in three-terminal magnetic tunnel junction (MTJ)-based SHNOs opened the possibility to develop more reliable and well-controlled oscillators, thanks to individual spin Hall-driven precession excitation and read-out paths. To develop hybrid systems by integrating three-terminal SHNOs and CMOS circuits, an electrical model able to capture the analog characteristics of three-terminal SHNOs is needed. This model needs to be compatible with current electric design automation (EDA) tools. This work presents a comprehensive macrospin-based model of three-terminal SHNOs able to describe the dc operating point, frequency modulation, phase noise, and output power. Moreover, the effect of voltage-controlled magnetic anisotropy (VCMA) is included. The model shows good agreement with experimental measurements and could be used in developing hybrid three-terminal SHNO/CMOS systems.

  • 47.
    Al-Breihi, Mohammed
    KTH, Skolan för teknik och hälsa (STH).
    Utveckling av laboration om trefastransformatorn: En studie om transformatorer2014Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Examensarbetet har utforts pa uppdrag av enheten for Data- och

    Elektroteknik pa skolan for Teknik och Halsa, KTH.

    Denna studie om transformatorer omfattar deras funktioner och

    anvandningsomraden, hur de ar uppbyggda, hur karnan och lindningarna

    som ar transformatorns viktigaste delar ar uppbyggda, vilka materiel som

    anvands vid konstruktion av dessa samt vilka typer det finns av dem

    beskrivs i rapporten. Vidare beskrivs flera olika transformatortypers

    funktioner och anvandningsomraden. Eftersom en viktig del av studien

    varit pa vilka satt transformatorer kan utvecklas for okad miljovanlighet

    och livslangd gar rapporten igenom olika vegetabiliska oljor, vilka

    fordelar de har gentemot mineraloljor och vilka egenskaper de har samt

    pa vilket satt de ar skonsammare mot miljon. HVDC-enheter

    transformerar hoga spanningar fran vaxelspanning till likspanning for

    mindre resistiva forluster och darmed lagre energiforluster vilket i sin tur

    leder till en renare miljo.

    Teorigenomgangen av transformatorn ligger till grund for utformningen

    av en laboration for undervisningsbruk, bl.a. i en kurs om elkraftteknik

    som ges i hogskoleingenjorsprogrammet Elektroteknik pa KTH.

  • 48.
    Aldahan, Leith
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem, Hälsoinformatik och logistik.
    Kudoori, Ivan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem, Hälsoinformatik och logistik.
    Utvärdering av roterande borstlösfrekvensomformare tillspårledningar2019Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Spårledningar används inom tunnelbanan för att visa tågets position samt bestämma tågets hastighet genom att bryta spänningsamplituden i signalen vid olika frekvenser. Frekvensen till spårledningen fås från en roterande frekvensomformare. I dagens anläggning används roterande frekvensomformare med borstar. Dessa avger i relärum mycket värme och ger miljöproblem i form av koldamm från borstarna. Det befintliga systemet är gammal och har funnits i drift över 30 år, därför håller reservdelar på att ta slut samt service till systemet svårtillgängligt.

    Detta examensarbete har undersökt möjligheten att uppgradera till nyare system som bygger på en lösning med roterande borstlös frekvensomformare där reservdelarna och service är tillgängliga i minst 25 år.

    Undersökningen jämför olika roterande borstlösa frekvensomformare från olika leverantörer för att hitta en frekvensomformare där kraven från Trafikförvaltningen uppfylls.

    Studien har haft fokus på problemområdet med borstade frekvensomformaren som producerar skadliga ämnen såsom koldamm och värmen i relärum. Diskussioner med tillverkningsföretag av roterande borstlös frekvensomformaren har skett under denna studies gång där möjliga alternativ för vidare utveckling av systemet i relärum analyseras. I projektet har även diskuterat möjligheten att använda det nya systemet av frekvensomformare med borstlösa motor och generator istället för den nuvarande borstade frekvensomformaren som finns i anläggningen. Resultatet har även visat att den roterande borstlösa frekvensomformaren kan omvandla frekvensen till 75 Hz. Det nya systemet uppfyller kraven från Trafikförvaltningen samt att systemet håller i minst 25 år till. Att systemet håller minst i 25 år till var ett stort krav av Trafikförvaltningen som uppfylldes under denna studie.

  • 49.
    Alfrijat, Christopher
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem, Hälsoinformatik och logistik.
    Eriksson, Rasmus
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem, Hälsoinformatik och logistik.
    Analys och utvärdering av LED-belysning i Stockholms tunnelbana2019Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Trafikförvaltningen, som ansvarar för kollektivtrafiken i Stockholm, har startat ett projekt för att byta ut befintliga armaturer i Stockholms tunnelbana mot LED-armaturer. Denna rapport utför förarbetet inför en kommande upphandling.

    Detta arbete utvärderar olika LED-armaturers tekniska specifikationer som är lämpliga för Stockholms tunnelbana där armaturerna ska bytas ut. För denna miljö saknas det i dagsläget standarder som är anpassade för LED-armaturer. Med hjälp av litteraturstudier och mätningar kunde underlag för en kravspecifikation skapas. Mätningar har gjorts på ett urval av LED-armaturer och deras tekniska specifikation har presenterats. Samtliga armaturer klarade EMC-testerna (elektromagnetisk kompabilitet) där inga störningar uppstod vid frekvenserna för Storstockholms Lokaltrafiks (SL) radiokommunikationssystem.

    Arbetet har även hanterat miljö- samt den ekonomiska aspekten av implementeringen av LED-belysning.

  • 50. Al-Hammouri, A.T.
    et al.
    Nordström, Lars
    KTH, Skolan för elektro- och systemteknik (EES), Industriella informations- och styrsystem.
    Chenine, Moustafa
    KTH, Skolan för elektro- och systemteknik (EES), Industriella informations- och styrsystem.
    Vanfretti, Luigi
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Honeth, Nicholas
    KTH, Skolan för elektro- och systemteknik (EES), Industriella informations- och styrsystem.
    Leelaruji, Rujiroj
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Virtualization of synchronized phasor measurement units within real-time simulators for smart grid applications2012Inngår i: Power and Energy Society General Meeting, 2012 IEEE, IEEE , 2012, s. 6344949-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Synchronized phasor measurement units (PMUs) provide GPS-time tagged high-sampling rate positive-sequence voltage and current phasors. When placed in high-voltage substations in power networks, PMUs can provide real-time information that is necessary for the development of Smart Transmission Grid software applications for improving power system monitoring, control and protection. The development of these applications, particularly for use within control centers for on-line purposes, is limited by the availability of and access to real-time PMU data and other information. One attractive approach for application development is the use of real-time simulators to which PMUs can be interfaced as hardware-in-the-loop (HIL) devices to harvest PMU data. However, this approach has technical and economical limitations, which can be tackled by the virtualization of PMU devices. This article describes the development of an entirely software-based synchronized phasor measurement unit for use within real-time simulators that will allow the emulation of a large number of real-life PMUs, which in turn can be used for creating new phasor-based applications.

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