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  • Public defence: 2017-10-20 10:00 Kollegiesalen, Stockholm
    Soltani, Sofie Safeyeh
    KTH, School of Architecture and the Built Environment (ABE).
    Hydrological Transport in Shallow Catchments:: tracer discharge, travel time and water age2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This focuses on hydrological transport in shallow catchments with topography-driven flow paths. The thesis gives new insight to kinematic pathway models for estimation of tracer discharge at the catchment outlet. A semi-analytical methodology is presented for transient travel time and age distributions referred to as "kinematic pathway approach“(KPA) that accounts for dispersion at two levels of morphological and macro-dispersion. Macro-dispersion and morphological dispersion components are reflected in KPA by assuming an effective Péclet number and topographically driven pathway length distributions, respectively. The kinematic measure of the transport, defined as a characteristic velocity of water flow through the catchment is obtained from the overall water balance in the catchment. To include transformation process in its simplest form of linear decay/degradation a framework is presented that solves one-dimensional reactive transport with numerically simulated travel times as the independent variable. The proposed KPA and coupled transport framework for quantifying tracer discharge at the shallow catchment outlet are applied to two selected catchments in Sweden. KPA is applied to modeling of a 23-year long chloride data series for the Kringlan catchment whereas the implantation of the framework for quantifying natural attenuation is illustrated for the Forsmark catchment. Numerical simulations of Forsmark catchment advective travel times are obtained by means of particle tracking using the fully-integrated flow model MIKE SHE. The KPA is found to provide reasonable estimates of tracer discharge distribution when considering the transport controlled by hillslope processes associated with short topographically driven flow paths to adjacent discharge zones, e.g. rivers and lakes. Simulated natural attenuation for Forsmark is also estimated well provided that the pathway length distribution is skewed toward short pathway lengths. This fact is indicative of the controlling impact of topography on flow path length and travel time distributions in shallow catchments. Our work has shown that the pathway (Lagrangian) methodologies are promising as predictive tools for hydrological transport. 

  • Public defence: 2017-10-20 14:00 Kollegiesalen, Stockholm
    Nemati, Hamed
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    Secure System Virtualization: End-to-End Verification of Memory Isolation2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Over the last years, security-kernels have played a promising role in reshaping the landscape of platform security on embedded devices. Security-kernels, such as separation kernels, enable constructing high-assurance mixed-criticality execution platforms on a small TCB, which enforces isolation between components. The reduced TCB  minimizes the system attack surface and facilitates the use of formal methods to ensure the kernel functional correctness and security.

    In this thesis, we explore various aspects of building a provably secure separation kernel using virtualization technology. We show how the memory management subsystem can be virtualized to enforce isolation of system components. Virtualization is done using direct-paging that enables a guest software to manage its own memory configuration. We demonstrate the soundness of our approach by verifying that the high-level model of the system fulfills the desired security properties. Through refinement, we then propagate these properties (semi-)automatically to the machine-code of the virtualization mechanism.

    Further, we show how a runtime monitor can be securely deployed alongside a Linux guest on a hypervisor to prevent code injection attacks targeting Linux. The monitor takes advantage of the provided separation to protect itself and to retain a complete view of the guest.

    Separating components using a low-level software cannot by itself guarantee the system security. Indeed, current processors architecture involves features that can be utilized to violate the isolation of components. We present a new low-noise attack vector constructed by measuring caches effects which is capable of breaching isolation of components and invalidates the verification of a software that has been verified on a memory coherent model. To restore isolation, we provide several countermeasures and propose a methodology to repair the verification by including data-caches in the statement of the top-level security properties of the system.

  • Public defence: 2017-10-23 10:00 F3, Stockholm
    Walbrühl, Martin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    ICME guided development of cemented carbides with alternative binder systems2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The development of alternative binder systems for tungsten carbide (WC) based cemented carbides has again become of relevance due to possible changes in EU regulations regarding the use of Cobalt (Co). A framework for the ICME (Integrated Computational Materials Engineering) based Materials Design is presented to accelerate the development of alternative binder systems.

    Part one of this work deals with the design of the cemented carbide composite hardness. It has been shown that the intrinsic binder hardness is comparable to a bulk metal alloy and that based on the binder solubilities a solid solution strengthening model developed in this work can be employed. Using a method presented in this work the non-equilibrium, frozen-in binder solubilities can be obtained. Both the design of the binder phase and composite hardness is presented based on a general Materials Design approach.

    Part two deals with a multiscale approach to model the surface gradient formation. The experimentally missing data on liquid binder diffusion has been calculated using AIMD (Ab initio Molecular Dynamics). The diffusion through the liquid cemented carbide binder has to be reduced to an effective diffusion value due to the solid carbides acting as obstacles that increase the diffusion path. The geometrical reduction of the diffusion has been investigated experimentally using the SIMS (secondary ion mass spectroscopy) technique in WC-Nickel-58Nickel diffusion couples. The geometrical contribution of the so-called labyrinth factor has been proven by the combination of the experiments and in conjunction with DICTRA simulations using the precise liquid AIMD diffusivities. Unfortunately, despite the improved kinetic database and the geometrical diffusion reduction, the surface gradient formation cannot be explained satisfactory in complex cemented carbide grades. Additional, but so far unidentified, contributions have to be considered to predict the surface gradient thickness.

  • Public defence: 2017-10-23 13:15 Kollegiesalen, Stockholm
    Westerlund, Per
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Condition measuring and lifetime modelling of disconnectors, circuit breakers and other electrical power transmission equipment2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The supply of electricity is important in modern society, so the outages of the electric grid should be few and short, especially for the transmission grid. A summary of the history of the Swedish electrical system is presented. The objective is to be able to plan the maintenance better by following the condition of the equipment.

    The risk matrix can be used to choose which component to be maintained. The risk matrix is improved by adding a dimension, the uncertainty of the probability. The risk can be reduced along any dimension: better measurements, preventive maintenance or more redundancy. The number of dimensions can be reduced to two by following iso-risk lines calculated for the beta distribution.

    This thesis lists twenty surveys about circuit breakers and disconnectors, with statistics about the failures and the lifetime. It also presents about forty condition-measuring methods for circuit breakers and disconnectors, mostly applicable to the electric contacts and the mechanical parts.

    A method for scheduling thermography based on analysis of variance of the current is tried. Its aim is to reduce the uncertainty of thermography and it is able to explain two thirds of the variation using the time of the day, the day of the week and the week number as explanatory variables. However, the main problem remains as the current is in general too low.

    A system with IR sensors has been installed at the nine contacts of six disconnectors with the purpose of avoiding outages for maintenance if the contacts are in a good condition. The measured temperatures are sent by radio and regressed against the square of the current, the best exponent found. The coefficient of determination $R^2$ is high, greater than 0.9. The higher the regression coefficient is, the more heat is produced at the contact. So this ranks the different contacts.

    Finally a framework for lifetime modelling and condition measuring is presented. Lifetime modelling consists in associating a distribution of time to failure with each subpopulation. Condition measuring means measuring a parameter and estimating its value in the future. If it exceeds a threshold, maintenance should be carried out. The effect of maintenance of the contacts is shown for four disconnectors.

    An extension of the risk matrix with uncertainty, a survey of statistics and condition monitoring methods, a system with IR sensors at contacts, a thermography scheduling method and a framework for lifetime modelling and condition measuring are presented. They can improve the planning of outages for maintenance.

    Finally a framework for lifetime modelling and condition measuring is presented. Lifetime modelling consists in associating a distribution of time to failure with each subpopulation. Condition measuring means measuring a parameter and estimating its value in the future. If it exceeds a threshold, maintenance should be carried out. The effect of maintenance of the contacts is shown for four disconnectors.

    An extension of the risk matrix with uncertainty, a survey of statistics and condition monitoring methods, a system with IR sensors at contacts, a thermography scheduling method and a framework for lifetime modelling and condition measuring are presented. They can improve the planning of outages for maintenance.

  • Public defence: 2017-10-24 13:00 Kollegiesalen, Stockholm
    Babu, Sajeesh
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Reliability Evaluation of Distribution Systems Considering Failure Modes and Network Configuration2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Power distribution networks are recognized as the constituent part of power systems with the highest concentration of failure events. Even though the faults in distribution networks have a local effect when compared to the generation and transmission sides, major contingency escalation events are being more frequently reported from this section. The various aspects regarding the reliability and performance of distribution networks are identified as an important topic. Integration of new technologies, automation and increased penetration of distributed generation is expected to make improving and even sustaining high reliability standards a complex task.

     

    This thesis presents developed approaches to quantify and analyze the complex correlated failure probabilities of different failure modes in distribution networks. A theoretical simulation model that relates to real world data to measure false tripping probabilities is developed and tested. More simplified approaches that utilities can exercise with readily available data in fault registers are also established.  Optimal configurations that could improve system performance and respective investment costs are analyzed and savings in system reliability at the cost of grid investments are modelled. The optimization helps in prioritizing the most critical investments by considering the system impact of reconfigurations focusing on meeting customer demands and respecting transfer capacities of weak links. The value of existing networks and willingness of the grid owner in investing can be integrated into suggestive alterations to assist decision making in planning and maintenance allocation.

     

    The thesis makes both system specific and generalizable observations from detailed data collection from power utilities. The observations and results have potential in aiding future research by giving important understanding of the reliability impacts of network structures and of control and protection equipment.

  • Public defence: 2017-10-26 09:00 Sal Q2, Stockholm
    Wahlström, Marie
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment. Tyréns AB.
    Livable and Sustainable Cities: Explorations of the City Soul and Energy-Efficient Housing based on Swedish Data on Citizens’ Preferences2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Contemporary cities face many challenges, none the least from an urban planning perspective. Global climate change and urbanization is putting pressures on planning for combatting and adapting to, e.g., a warmer climate and an increased need for housing in already dense environments.

    The aim of this thesis is to contribute to a more comprehensive understanding of residents’ opinions and preferences regarding various aspects of city livability and sustainability. Two of the papers discuss energy-efficient housing and two the identity/soul of the city and its neighborhoods. The papers are empirically oriented and rest on relatively large quantitative materials of Swedish data. The database used in the first two articles contains around 77,000 observations of single-family homes. The residential survey used in the two final papers was sent to a random sample of 6,600 residents in four cities, resulting in 2,573 respondents.

    Regression is the primary analytical method and the results indicate a preference for sustainable housing, in terms of a price premium on heat pumps (attributes that both reduce the energy consumption and are easily observed in the house). It is further suggested that the perception of a strong city/neighborhood soul is linked to positive relations to the city and to positive perceptions of its physical characteristics. In particular, feelings of attachment, belonging, and pride as well as perceptions of aesthetics, arts, and symbols, seem to be linked to a strong city/neighborhood soul.

    The presented research contributes to related literature through providing insight to Swedish residents’ preferences and opinions concerning energy-efficient housing and the city/neighborhood soul. It is shown that a citizen perspective based on carefully designed databases and appropriate analytical tools can be used by planners to gain new insights supporting urban livability and sustainability efforts.

  • Public defence: 2017-10-26 09:00 E3, Stockholm
    Granath Hansson, Anna
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Real Estate Planning and Land Law.
    Institutional prerequisites for affordable housing development: A comparative study of Germany and Sweden2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis was written against the background of intense public debate on increasing housing shortages and housing policy reform in Germany and Sweden. Potential reforms to increase housing development volumes, especially in the affordable segment, are analysed using theories of institutional change with focus on urban planning, building law and housing policy. The instruments analysed are divided into measures intended to increase housing supply elasticity and targeted affordable housing measures.

     

    Three measures intended to increase housing supply elasticity that could be transferable to Sweden are identified: 1) Development planning could be reformed through facilitated procedures, the introduction of private initiative in planning and new incentives of planning authorities. 2) The planning and building legislation could be reformed to facilitate building approvals in relation to serial housing construction, which in turn could increase the number of affordable homes being built. 3) City housing policy could promote housing development through more intense use of the policy instruments of organisation, urban planning, municipal land and subsidies, with city organisation and political attention to housing markets being identified as crucial.

     

    However, effectively targeted affordable housing policies are difficult to implement under the current Swedish housing policy regime. In the short term, Swedish housing policy should therefore concentrate on housing supply elasticity-enhancing measures. However, considering the increasing pressure on the affordable housing supply and future expected demographic changes, public discussion of potential future solutions would be valuable. A first step would be to compile housing statistics such that the affordable housing shortage and the opportunities to design effective measures to counter it could be better understood.

  • Public defence: 2017-10-26 10:00 Sal F3, Stockholm
    Lindvall, Mikael
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling. Swerea MEFOS.
    A Study on Vanadium Extraction from Fe-V-P Melts Derived from Primary and Secondary Sources2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Vanadium extraction methods were developed for iron-vanadium-phosphorus (Fe-V-P) melts derived from processing of V-bearing titanomagnetites and steel slags. Studies on phase relationships of V slags were carried out to provide important understanding of the extraction processes. Phase relationship in vanadiferous slag was investigated experimentally at 1573K, 1673K and 1773K, for the compositional range of 0-6mass% Al2O3, 1-5mass% CaO, 10-17mass% SiO2, with MnO and V2O3 fixed at 5.5mass% and 30mass%, balanced with FeO. The slags were found to be solid-liquid mixtures, of liquid, spinel and in some cases free silica. Alumina was identified as the preferred additive to prohibit precipitation of free silica. A method for V extraction to vanadiferous slag was developed based on Fe-V(2mass%)-P(0.1mass%) melts at 1677K using a semi-industrial scale BOF. Oxidation was carried out with an oxygen enriched air jet and iron ore pellets. The complete dissolution of pellets was achieved by deliberately creating good stirring conditions utilising high momentary decarburisation rates. The P distribution to the slag was low when good stirring conditions was obtained. Phase relationship in Al2O3-CaO(25-35mass%)-SiO2-VOx slag was investigated experimentally at an oxygen partial pressure of 9.37•10-11atm and 1873K. The maximum solubility of V-oxide in the slag was 9-10mass% V2O3. Two solid phases were found, a solid solution of Al2O3 in V2O3 (karelianite) and hibonite with fractionation of V into the crystal structure. V extraction experiments to Al2O3-CaO-SiO2 based slags were carried out in 150kg scale by blowing CO2 gas into the metal bath consisting mainly of 1-10mass% V and 1mass% P. At these conditions, oxidation of V was favoured over Fe. Up to 10-13mass% V2O3 could be dissolved in the slag before a viscous slag saturated in V-oxide was observed. The phosphate capacity in the slag was low and as a result this slag could at once be subjected to a final reduction step for production of ferrovanadium with 40-50mass% V.

  • Public defence: 2017-10-26 10:00 L1, Stockholm
    Pardo-Tarifa, Fatima
    KTH, School of Chemical Science and Engineering (CHE).
    Cobalt catalyst supports for Fischer-Tropsch synthesis2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In the Fischer-Tropsch (FT) synthesis, CO and H2 (synthesis gas) are converted into hydrocarbons that can be further upgraded to high-quality fuels and chemicals. Different carbon sources such as natural gas, coal and biomass can be used as feed-stocks for the synthesis gas. In commercial applications, supported cobalt catalysts are commonly used in the FT synthesis, especially when the synthesis gas emanates from natural gas and when the desired final product is diesel. The activity and selectivity of a cobalt catalyst is dependent on several parameters, one of them being the support.

    The present thesis is focused on the design, synthesis and characterization of alumina and silica materials (with and without Ce and Zr promoters) with non-conventional morphology, and evaluation of their feasibility as cobalt supports in the FT synthesis.

    Ce- and Zr-alumina nanoparticles were synthesized by co-precipitation in water-in-oil microemulsion. The obtained product is amorphous alumina with highly dispersed promoters, resulting in strong cobalt-support interactions and low cobalt reducibility. By increasing the calcination temperature of the Ce-promoted support, crystalline CeO2 is obtained which apparently increases the cobalt reducibility and thereby the catalytic activity (per gram catalyst). The small pore size of the materials may induce diffusion limitations on the reactants arrival and/or result in very small cobalt particles, which favour methane over long-chain hydrocarbons. 

    Successful preparations of pore expanded mesoporous silicas with 1D, 2D and 3D pore structures via the atrane route, combined with the addition of swelling agents, have been demonstrated. The advantage of this method is that pore expansion can be achieved at mild conditions and there is no need for a post-synthesis process using an autoclave system. In larger silica support pores, larger cobalt particles will be formed and the weaker the cobalt-support interactions will be. This generally results in a higher cobalt reducibility for larger-pore supports and thereby a higher catalytic activity.

     

  • Public defence: 2017-10-27 09:00 Air and Fire, Science for Life Laboratory, Solna
    Bernhem, Kristoffer
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Quantitative bioimaging in single cell signaling2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Imaging of cellular samples has for several hundred years been a way for scientists to investigate biological systems. With the discovery of immunofluorescence labeling in the 1940’s and later genetic fluorescent protein labeling in the 1980’s the most important part in imaging, contrast and specificity, was drastically improved. Eversince, we have seen a increased use of fluorescence imaging in biological research, and the application and tools are constantly being developed further.

    Specific ion imaging has long been a way to discern signaling events in cell systems. Through use of fluorescent ion reporters, ionic concentrations can be measured inliving cells as result of applied stimuli. Using Ca2+ imaging we have demonstrated that there is a inverse influence by plasma membrane voltage gated calcium channels on angiotensin II type 1 receptor (a protein involved in blood pressure regulation). This has direct implications in treatment of hypertension (high blood pressure),one of the most common serious diseases in the western civilization today with approximately one billion afflicted adults world wide in 2016.

    Extending from this more lower resolution live cell bioimaging I have moved into super resolution imaging. This thesis includes works on the interpretation of super resolution imaging data of the neuronal Na+, K+ - ATPase α3, a receptor responsible for maintaining cell homeostasis during brain activity. The imaging data is correlated with electrophysiological measurements and computer models to point towards possible artefacts in super resolution imaging that needs to be taken into account when interpreting imaging data. Moreover, I proceeded to develop a software for single-molecule localization microscopy analysis aimed for the wider research community and employ this software to identify expression artifacts in transiently transfected cell systems.

    In the concluding work super-resultion imaging was used to map out the early steps of the intrinsic apoptotic signaling cascade in space and time. Using superresoultion imaging, I mapped out in intact cells at which time points and at which locations the various proteins involved in apoptotic regulation are activated and interact.

  • Public defence: 2017-10-27 10:00 Sal F3, Stockholm
    Wang, Huijun
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    A Study on the Reaction between MgO Based Refractories and Slag-Towards the Development of Carbon-free Lining Material2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In present thesis, the fundamental studies on the reaction between MgO based refractories and slag were undertaken for the development of a carbon-free bonding MgO lining material. Alumina was selected as a potential binder material. Due to MgO-Al2O3 chemical reaction, the developed refractory was bonded by MgO·Al2O3 spinel phase. To begin with, an investigation of the dissolution process of dense MgO and MgO·Al2O3 spinel in liquid slag was carried out. To obtain reliable information for dissolution study, a new experimental method was therefore developed. In this method, a cylinder was rotating centrally in a special designed container with a quatrefoil profile. This method also showed a good reliability in revealing the dissolution mechanism by quenching the whole reaction system. The experimental results showed that the dissolution process of MgO and spinel was controlled by both mass transfer and chemical reaction. It was found that the rapid dissolution of spinel was mainly because of its larger driving force. To improve the resistance against slag penetration, two aspects were studied to develop carbon-free MgO refractory. First, colloidal alumina was used and the effect of its addition into MgO matrix was investigated. The use of colloidal alumina was to form bonding products in the grain boundary of MgO. The results showed that the alumina addition greatly improved the resistance of MgO based refractory against slag penetration in comparison with the decarburized MgO-carbon refractory. It was found that the improvement of resistance was mainly related to the spinel-slag reaction products of CaO·Al2O3 and CaO·MgO·Al2O3 solid phases at the grain boundaries. Second, the effect of particle size distribution on the penetration resistance of MgO was investigated. The most profound improvement against the slag penetration was obtained by using a proper particle size distribution. The results highlighted the importance of considering the refractory structure. Experiments were undertaken to investigate the dissolution mechanism of different types of MgO based refractories in liquid slag. It was observed that the dissolution of spinel bonded MgO refractory was much slower than the decarburized MgO-carbon refractory. The primary dissolution in spinel bonded MgO refractory occurred at the slag-penetrated layer, and the removal of this layer by peeling off enhanced the dissolution rate rapidly.

  • Public defence: 2017-10-27 10:00 Sal C, Kista
    Mirsakiyeva, Amina
    KTH, School of Engineering Sciences (SCI), Applied Physics, Material Physics, MF.
    Electronic and optical properties of conducting polymers from quantum mechanical computations2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

        Conductive polymers are also known as "organic metals" due to their semiconducting properties. They are found in a wide range of applications in the field of organic electronics. However, the growing number of experimental works is not widely supported with theoretical calculations. Hence, the field of conductive polymers is experiencing lack of understanding of mechanisms occurring in the polymers. In this PhD thesis, the aim is to increase understanding of conductive polymers by performing theoretical calculations.       

    The polymers poly(3,4-ethylenedioxythiophene) (PEDOT) together with its selenium (PEDOS) and tellurium (PEDOTe) derivatives, poly(p-phenylene) (PPP) and naphthobischalcogenadiazoles (NXz) were studied. Several computational methods were applied for analysis of mentioned structures, including density functional theory (DFT), tight-binding modelling (TB), and Car-Parrinello molecular dynamics (CPMD) calculations. The combination of CPMD and DFT calculations was applied to investigate the PEDOT, PEDOS and PEDOTe. The polymers were studied using four different functionals in order to investigate the full picture of structural changes, electronic and optical properties. Temperature effects were studied using molecular dynamics simulations. Wide statistics for structural and molecular orbitals analysis were collected.        

    The TB method was employed for PPP. The formation and motion of the excitations, polarons and bipolarons, along the polymer backbone was investigated in presence of electric and magnetic fields. The influence of non-magnetic and magnetic impurities was determined.       

    The extended π-conjugated structures of NXz were computed using B3LYP and ωB97XD functionals in combination with the 6-31+G(d) basis set. Here, the structural changes caused by polaron formation were analyzed. The combined analysis of densities of states and absorption spectra was used for understanding of the charge transition.

  • Public defence: 2017-10-27 10:00 Fantum, Stockholm
    Spühler, Jeannette Hiromi
    KTH, School of Computer Science and Communication (CSC), Computational Science and Technology (CST).
    Patient-Specific Finite Element Modeling of the Blood Flow in the Left Ventricle of a Human Heart2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Heart disease is the leading cause of death in the world. Therefore, numerous studies are undertaken to identify indicators which can be applied to discover cardiac dysfunctions at an early age. Among others, the fluid dynamics of the blood flow (hemodymanics) is considered to contain relevant information related to abnormal performance of the heart.This thesis presents a robust framework for numerical simulation of the fluid dynamics of the blood flow in the left ventricle of a human heart and the fluid-structure interaction of the blood and the aortic leaflets.We first describe a patient-specific model for simulating the intraventricular blood flow. The motion of the endocardial wall is extracted from data acquired with medical imaging and we use the incompressible Navier-Stokes equations to model the hemodynamics within the chamber. We set boundary conditions to model the opening and closing of the mitral and aortic valves respectively, and we apply a stabilized Arbitrary Lagrangian-Eulerian (ALE) space-time finite element method to simulate the blood flow. Even though it is difficult to collect in-vivo data for validation, the available data and results from other simulation models indicate that our approach possesses the potential and capability to provide relevant information about the intraventricular blood flow.To further demonstrate the robustness and clinical feasibility of our model, a semi-automatic pathway from 4D cardiac ultrasound imaging to patient-specific simulation of the blood flow in the left ventricle is developed. The outcome is promising and further simulations and analysis of large data sets are planned.In order to enhance our solver by introducing additional features, the fluid solver is extended by embedding different geometrical prototypes of both a native and a mechanical aortic valve in the outflow area of the left ventricle.Both, the contact as well as the fluid-structure interaction, are modeled as a unified continuum problem using conservation laws for mass and momentum. To use this ansatz for simulating the valvular dynamics is unique and has the expedient properties that the whole problem can be described with partial different equations and the same numerical methods for discretization are applicable.All algorithms are implemented in the high performance computing branch of Unicorn, which is part of the open source software framework FEniCS-HPC. The strong advantage of implementing the solvers in an open source software is the accessibility and reproducibility of the results which enhance the prospects of developing a method with clinical relevance.

  • Public defence: 2017-10-27 10:00 Kollegiesalen, Stockholm
    Zhao, Kun
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Mobile Antenna Systems for 4G and 5G Applications with User Body Interaction2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In the thesis, the user body effect on antennas in a mobile terminal is discussed. In order to overcome the degradation of Multiple-Input Multiple-Output (MIMO) performance due to the user body effect, a quad-elements MIMO antenna array which can mitigate the body effect through an adaptive antenna switching method is introduced for 4G mobile terminals. In addition, various bezel MIMO antennas that are robust to the impedance mismatching caused by the user effect have also been presented.

    The study of user body effect is later extended to frequency bands at 15 GHz and 28 GHz for future 5G communication systems. The results reveal that a human body will cause a significant shadowing loss, which will be a critical loss in 5G cellular networks.

    The electromagnetic field (EMF) exposure of a mobile terminal is also studied in this thesis. Below 6 GHz, the simultaneous transmission specific absorption rate (SAR) for MIMO antennas is the primary concern due to its complicated assessment procedures. Above 6 GHz, the free space power density is adopted as the basic parameter of exposure limits globally, and preliminary studies have been presented to address major challenges in EMF exposure assessment for 5G mobile terminals. 

  • Public defence: 2017-10-27 10:00 Q2, Stockholm
    Bigdeli, Sedigheh
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Developing the third generation of Calphad databases: what can ab-initio contribute?2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Developing the third generation of Calphad databases with more physical basis valid within a wider temperature range is the aim of the present work. Atomistic scale (ab-initio) methods, particularly techniques based on DFT theory, are used for modelling dierent phenomena, so as to gauge the capacity for use in Calphad modelling. Several systems are investigated in this work for studying dierent phenomena, such as magnetism and vibration of atoms. In the case of pure elements (unaries), thermodynamic properties of Mn, Al and C are optimized in the whole temperature range by the help of new models. In addition, DFT results and specic characteristics of these elements are also used to develop models for describing magnetic properties and atomic vibrations. With regards to coupling between DFT and Calphad, the EMTO technique is used for determining the magnetic ground state of the metastable hcp phase in Fe and Mn, and the TU-TILD technique is used for modelling solid phases above the melting point. TU-TILD is also used for calculating thermodynamic properties of bcc Mn at nite temperatures. The same phenomena are investigated in higher-order systems, i.e. the binaries Fe-Mn and Mn-C. Thermodynamic properties and phase diagrams of these systems are assessed against experimental data. Moreover, the revised magnetic model is used for modelling magnetic properties in these systems.

    It is shown through this investigation that although the DFT methods are powerful tools for model development and for resolving discrepancies between dierent experimental datasets, they should not be overly-trusted. Caution must be taken when using DFT results, since the approximations and assumptions for computational implementations may cause some errors in the results. Moreover, implementing them into Calphad software as a connected methodology is not currently accessible due to the computational limitations.

    It is concluded that coupling between the DFT and Calphad approaches can currently be achieved by using DFT results as an input in Calphad modelling. This will help to improve them until they can be integrated into the Calphad approach by the progress of computational possibilities.

    One of the advantages of developing the third generation Calphad databases is the possibility of using the 0 K DFT results in Calphad modelling, since the new databases are valid down to 0 K. This has not been possible in the past, and such potential opens a new door to bring more physics into the Calphad approach.

  • Public defence: 2017-10-27 10:00 Senaatszaal, Delft
    Koirala, Binod Prasad
    KTH, School of Electrical Engineering (EES).
    Integrated Community Energy Systems2017Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Energy systems across the globe are going through a radical transformation as a result of technological and institutional changes, depletion of fossil fuel resources, and climate change. Accordingly, local energy initiatives are emerging and increasing number of the business models are focusing on the end-users. This requires the present centralized energy systems to be re-organized. In this context, Integrated community energy systems (ICESs) are emerging as a modern development to re-organize local energy systems allowing simultaneous integration of distributed energy resources (DERs) and engagement of local communities. With the emergence of ICESs new roles and responsibilities as well as interactions and dynamics are expected in the energy system. Although local energy initiatives such as ICESs are rapidly emerging due to community objectives, such as cost and emission reductions as well as resiliency, assessment and evaluation of the value that these systems can provide to both local communities and the whole energy system are still lacking. The value of ICESs is also impacted by the institutional settings internal and external to the system. With this background, this thesis aims to understand the ways in which ICESs can contribute to enhancing the energy transition.

    This thesis utilizes a conceptual framework consisting of institutional and societal levels in order to understand the interaction and dynamics of ICESs implementation.  Current energy trends and the associated technological, socio-economic, environmental and institutional issues are reviewed. The developed ICES model performs optimal planning and operation of ICESs and assesses their performance based on economic and environmental metrics. For the considered community size and local conditions, grid-connected ICESs are already beneficial to the alternative of solely being supplied from the grid, both in terms of total energy costs and CO2 emissions, whereas grid-defected systems, although performing very well in terms of CO2 emissions reduction, are still rather expensive. ICESs ensure self-provision of energy and can provide essential system services to the larger energy system. This thesis has demonstrated the added value of ICESs to the individual households, local communities and the society. A comprehensive institutional design considering techno-economic and institutional perspectives is necessary to ensure effective contribution of ICESs in the energy transition.

    The full text will be freely available from 2017-10-27 12:35
  • Public defence: 2017-11-03 09:00 F3, Stockholm
    Westerborn, Johan
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Mathematical Statistics.
    On particle-based online smoothing and parameter inference in general state-space models2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis consists of 4 papers, presented in Paper A-D, on particle- based online smoothing and parameter inference in general state-space hidden Markov models.

    In Paper A a novel algorithm, the particle-based, rapid incremental smoother (PaRIS), aimed at efficiently performing online approxima- tion of smoothed expectations of additive state functionals in general hidden Markov models, is presented. The algorithm has, under weak assumptions, linear computational complexity and very limited mem- ory requirements. The algorithm is also furnished with a number of convergence results, including a central limit theorem.

    In Paper B the problem of marginal smoothing in general hidden Markov models is tackled. A novel, PaRIS-based algorithm is presented where the marginal smoothing distributions are approximated using a lagged estimator where the lag is set adaptively.

    In Paper C an estimator of the tangent filter is constructed, yield- ing in turn an estimator of the score function. The resulting algorithm is furnished with theoretical results, including a central limit theorem with a uniformly bounded variance. The resulting estimator is applied to online parameter estimation via recursive maximum liklihood.

    Paper D focuses on the problem of online estimation of parameters in general hidden Markov models. The algorithm is based on a for- ward implementation of the classical expectation-maximization algo- rithm. The algorithm uses the PaRIS algorithm to achieve an efficient algorithm. 

  • Public defence: 2017-11-03 13:00 F3, Stockholm
    Karagulyan, Davit
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.).
    Certain results on the Möbius disjointness conjecture2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    We study certain aspects of the Möbius randomness principle and more specifically the Möbius disjointness conjecture of P. Sarnak. In paper A we establish this conjecture for all orientation preserving circle homeomorphisms and continuous interval maps of zero entropy. In paper B we show, that for all subshifts of finite type with positive topological entropy the Möbius disjointness does not hold. In paper C we study a class of three-interval exchange maps arising from a paper of Bourgain and estimate its Hausdorff dimension. In paper D we consider the Chowla and Sarnak conjectures and the Riemann hypothesis for abstract sequences and study their relationship.

  • Public defence: 2017-11-06 10:00 T2, Huddinge
    S. Alvarez, Victor
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Understanding Boundary Conditions for Brain Injury Prediction: Finite Element Analysis of Vulnerable Road Users2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Vulnerable road users (VRUs) are overrepresented in the statistics on severe and deadly injuries in traffic accidents, most commonly involving the head. The finite element (FE) method presents the possibility to model complex interactions between the human body and vehicles in order to better understand the injury mechanisms. While the rapid development of computer capacity has allowed for increasingly detailed FE-models, there is always a benefit of reducing the studied problem. Due to its material properties, the brain is more sensitive to rotational motion than to purely linear, resulting in complex injury causation. When studying brain injuries caused by a direct impact to the head, simulations using an isolated head model significantly increases efficiency compared to using a complete human body model. Also evaluation of head protective systems uses isolated mechanical head representations. It is not, however, established the extent to which the boundary conditions of the head determine the outcome of brain injuries.

    FE models of both the entire human body and the isolated head were used in this thesis to study the effect of the body, as well as active neck muscle tension, on brain injury outcome in VRU accidents. A pediatric neck model was also developed to enable the study of age-specific effects. A vehicle windscreen model was developed to evaluate the necessity of capturing the failure deformation during pedestrian head impacts.

    It was shown that the influence of the neck and body on brain injury prediction is greater in longer duration impacts, such as pedestrian head-to-windscreen impacts with an average difference of 21%. In accidents with shorter duration impacts, such as head-to-ground bicycle accidents, the average influence was between 3-12%. The influence did not consistently increase or limit the severity, and was dependent on the degree of rotation induced by the impact, as well as the mode of deformation induced in the neck. It was also shown that the predicted brain injury severity is dependent on capturing the large deformations of fractured windscreen, with the greatest effect near the windscreen frame. The pediatric neck model showed a large effect of age-dependent anatomical changes on inertial head loading, making it a promising tool to study the age-dependent effects in VRU accidents.

  • Public defence: 2017-11-13 09:00 Kollegiesalen, Stockholm
    Fridlund, Gustav
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Urban and Regional Studies.
    Utan tvivel är en inte klok: En studie om personliga skavningar som resurs för praktisk klokhet inom svensk kommunal planering2017Doctoral thesis, monograph (Other academic)
    Abstract [en]

    How can you as a planner tackle messy realities without losing sight of possible problematic outcomes of what you put in practice? This study explores the value of everyday frictions as a resource for phronetic planning, i.e. the ability to make situated ethical judements of what is ’better’ or ’worse’ in a particular setting. The intent is to offer a situated gaze of frictions from the perspective of a civil servant of the well organised and innovative municipality of Botkyrka in the metropolitan area of Stockholm, Sweden. From this outset, an autoethnographical methodology from a poststructural approach, is used to explore the frictions that the author has experienced as a practicing planner. The study shows that frictions can be used as 'weak signals' to identify possible tricky consequences of the creation and the staging of planning 'simplifications'. Based on this insight a 'seismological' approach to planning is proposed. The argument is that planning practice should on the one hand utilize frictions when they arise and, on the other hand, actively challenge existing 'simplifications'. To achieve this, practical tools are offered to 'evoke', 'narrate' and 'diffract' on frictions and 'trickster-objects' within the constraints of the planner’s role as a municipal civil servant. 

  • Public defence: 2017-11-13 10:15 F3, Stockholm
    Vastesson, Alexander
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Thiol-ene and Thiol-ene-epoxy Based Polymers for Biomedical Microdevices2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Within healthcare there is a market pull for biomedical devices that can rapidly perform laboratory processes, such as diagnostic testing, in a hand-held format. For this reason, biomedical devices must become smaller, more sophisticated, and easier to use for a reasonable cost. However, despite the accelerating academic research on biomedical microdevices, and especially plastic-based microfluidic chips, there is still a gap between the inventions in academia and their benefit to society. To bridge this gap there is a need for new materials which both exhibit similar properties as industrial thermoplastics, and that enable rapid prototyping in academia.

    In this thesis, thiol-ene and thiol-ene-epoxy thermosets are evaluated both in terms of their suitability for rapid prototyping of biomedical microdevices and their potential for industrial manufacturing of “lab-on-chips”.

    The first part of the thesis focuses on material development of thiol-ene and thiol-ene-epoxy thermosets. Chemical and mechanical properties are studied, as well as in vitro biocompatibility with cells.

    The second part of the thesis focuses on microfabrication methods for both thermosets. This includes reaction injection molding, photostructuring, and surface modification. It is demonstrated how thiol-ene and thiol-ene-epoxy both provide advantageous thermo-mechanical properties and versatile surface modifications via “thiol-click chemistry”.

    In the end of the thesis, two applications for both polymer platforms are demonstrated. Firstly, thiol-ene is used for constructing nanoliter well arrays for liquid storage and on-demand electrochemical release. Secondly, thiol-ene-epoxy is used to enhance the biocompatibility of neural probes by tuning their flexibility.

    It is concluded that both thiol-ene and thiol-ene-epoxy thermosets exhibit several properties that are highly suitable for rapid prototyping as well as for scalable manufacturing of biomedical microdevices.

  • Public defence: 2017-11-14 13:00 F3, Stockholm
    Ambrus, Rares
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for Autonomous Systems, CAS. KTH, School of Computer Science and Communication (CSC), Robotics, perception and learning, RPL.
    Unsupervised construction of 4D semantic maps in a long-term autonomy scenario2017Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Robots are operating for longer times and collecting much more data than just a few years ago. In this setting we are interested in exploring ways of modeling the environment, segmenting out areas of interest and keeping track of the segmentations over time, with the purpose of building 4D models (i.e. space and time) of the relevant parts of the environment.

    Our approach relies on repeatedly observing the environment and creating local maps at specific locations. The first question we address is how to choose where to build these local maps. Traditionally, an operator defines a set of waypoints on a pre-built map of the environment which the robot visits autonomously. Instead, we propose a method to automatically extract semantically meaningful regions from a point cloud representation of the environment. The resulting segmentation is purely geometric, and in the context of mobile robots operating in human environments, the semantic label associated with each segment (i.e. kitchen, office) can be of interest for a variety of applications. We therefore also look at how to obtain per-pixel semantic labels given the geometric segmentation, by fusing probabilistic distributions over scene and object types in a Conditional Random Field.

    For most robotic systems, the elements of interest in the environment are the ones which exhibit some dynamic properties (such as people, chairs, cups, etc.), and the ability to detect and segment such elements provides a very useful initial segmentation of the scene. We propose a method to iteratively build a static map from observations of the same scene acquired at different points in time. Dynamic elements are obtained by computing the difference between the static map and new observations. We address the problem of clustering together dynamic elements which correspond to the same physical object, observed at different points in time and in significantly different circumstances. To address some of the inherent limitations in the sensors used, we autonomously plan, navigate around and obtain additional views of the segmented dynamic elements. We look at methods of fusing the additional data and we show that both a combined point cloud model and a fused mesh representation can be used to more robustly recognize the dynamic object in future observations. In the case of the mesh representation, we also show how a Convolutional Neural Network can be trained for recognition by using mesh renderings.

    Finally, we present a number of methods to analyse the data acquired by the mobile robot autonomously and over extended time periods. First, we look at how the dynamic segmentations can be used to derive a probabilistic prior which can be used in the mapping process to further improve and reinforce the segmentation accuracy. We also investigate how to leverage spatial-temporal constraints in order to cluster dynamic elements observed at different points in time and under different circumstances. We show that by making a few simple assumptions we can increase the clustering accuracy even when the object appearance varies significantly between observations. The result of the clustering is a spatial-temporal footprint of the dynamic object, defining an area where the object is likely to be observed spatially as well as a set of time stamps corresponding to when the object was previously observed. Using this data, predictive models can be created and used to infer future times when the object is more likely to be observed. In an object search scenario, this model can be used to decrease the search time when looking for specific objects.

  • Public defence: 2017-11-14 13:00 FB42, Stockholm
    Etcheverry Cabrera, Sebastian
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Advanced all-fiber optofluidic devices2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Significant technological advances of the last years have been possible by developments in Optofluidics, which is a field that deals with the integration of optics and microfluidics into single devices.

    The work described in this thesis is based on five scientific publications related to the use of fiber optic technology to build integrated optofluidic devices. The first three publications are within the field of life-science and point towards in-vivo and point-of-care applications, whereas the last two publications cover the study and the use of plasmonic nanoparticles for electrical modulation of light.

    Aiming at developing useful tools for in-vivo biological applications, the first publication consists of designing and testing a functional optical fiber for real-time monitoring and selective collection of fluorescent microparticles. This probe relies on a microstructured optical fiber with a hole along its cladding, which is used to selectively aspirate individual particles of interest once their fluorescence signal is detected. On the same line of research, the second publication contemplates the fabrication of a fiber probe that traps single microparticles and allows for remote detection of their optical properties. This probe is also based on a microstructured fiber that enables particle trapping by fluidic forces. The third publication addresses the development of an all-fiber miniaturized flow cytometer for point-of-care applications. This system can analyze, with excellent accuracy and sensitivity, up to 2500 cells per second by measuring their fluorescence and scattering signal. A novel microfluidic technique, called Elasto-inertial microfluidics, is employed for aligning the cells into a single-stream to optimize detection and throughput.

    The fourth publication involves the experimental and theoretical study of the electrical-induced alignment of plasmonic gold nanorods in suspension and its applicability to control light transmission. This study is done by using an all-fiber optofluidic device, based on a liquid-core fiber, which facilitates the interaction of light, electric fields, and liquid suspensions. Results show that nanorods can be aligned in microseconds, providing a much better performance than liquid-crystal devices. Finally, the fifth publication consists of an upgrade of the previous device by integrating four electrodes in the cladding of the liquid-core fiber. This improvement enables nanosecond response time and the possibility of digitally switching nanorods between two orthogonal aligned states, overcoming the limitation of slow thermal relaxation.

    The work presented here shows that optofluidics based on optical fibers is a robust and convenient platform, as well as a promising direction for the developing of novel instruments in fields such as life-science, non-linear optics, plasmonic, and sensing.

  • Public defence: 2017-11-17 10:00 Gladan, Stockholm
    Sosa, Mario
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Running-in of gears - surface and efficiency transformation2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    With ever shorter development times and market demands on overall system performance such as efficiency, reliability and low maintenance, accurate predictive tools are necessary and gear drives prove to be no exception. All these characteristics have an impact on a process which has remained a riddle: running-in. Even though no consensus on a definition of this phenomena is readily available, this thesis examines efficiency, surface roughness and simulation through the optics of running-in.

    Geared transmissions are known for their formidable efficiency and their extreme reliability. However, with an ever increasing power density, the ability to accurately predict mesh losses becomes of utmost importance. The accurate quantification of bearing losses as well as efficiency of ground and superfinished gears under dip lubrication are examined with respect to running-in. Results show a considerable influence on the calculation of gear mesh losses originating from which bearing loss model is chosen. Furthermore, when a larger running-in load is used on ground gears, an increase in efficiency can be observed during working operation, while for superfinished no significant changes are found. These efficiency/frictional changes are also shown to occur in the initial cycles of the running-in phase.

    From a surface transformation point of view running-in is shown to be a reduction of asperity tips in case hardened ground gears, while in superfinished gears no changes were seen. These gear surface changes were measured with a novel method with a surface profilometer in-situ before, after running-in and after efficiency testing. Results also show that such changes in ground gear roughness profile occur during the very initial cycles.

    In order to predict running-in, a simulation method was developed. Such method utilizes a 2D surface integral method to simulate contact between rough surfaces, but requires the use of surface hardness and an accurate lower cutoff wavelength. This cutoff wavelength proved to play a pivotal role in determining an accurate contact pressure at the proper level of granularity, hence a well defined real contact area. The predicted and measured run-in surfaces are compared and are found to be in accordance with each other.

  • Public defence: 2017-11-17 13:00 F3, Stockholm
    Vass, Susanna
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Project Communication.
    The Business Value of BIM: Elaborating on Content and Perspective2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The expectations on digitalization and Building Information Modeling (BIM) in the Architectural, Engineering and Construction (AEC) are high. The high expectations are reflected in an increasing interest for the term business value of BIM. However, the practical and theoretical understanding of its content and perspective is characterized by rationalism and positivism commercially promoted by industry. This thesis aims to reflect on, problematize and extend the theoretical understanding of the content and perspective of the business value of BIM. Perceptions about business value of BIM, the associated challenges and costs and the role of the business of BIM in a wider socio-technical context are examined among Swedish and international AEC industry actors and a large Swedish public infrastructure client. To extend the understanding of the content and perspective of the business value of BIM, the rational and process-oriented theories on the business value of IT are combined with the more interpretive and hermeneutic socio-technical systems theory. A social and cognitive dimension is thus added to the understanding of the business value of BIM and business value of IT.  By combining the two research fields and contributing with the socio-technical perspective to the theoretical understanding of business value, this thesis contributes with theory development of the understanding of business value BIM and business value of IT.  For practitioners, the thesis shows the complex, multi-dimensional and challenging aspects of implementing BIM for business value. The journey of perspectives in this thesis from positivism towards increased interpretivism also sheds light on the implications of when different perspectives exert influence on a research field (hegemony) and wishes to provide a contrast and balance to the rational and positivistic perspectives in BIM research. It also wishes to inspire future BIM research to broaden the theoretical perspectives.

  • Public defence: 2017-11-17 15:00 Senaatszaal, Delft
    Eid, Cherrelle
    KTH, School of Electrical Engineering (EES).
    Towards the design of flexibility management in smart grids: A techno-institutional perspective2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The European policy focus on smart grids implies their development as an indispensable part of the future power system. However, the definition of a smart grid is broad and vague, and the actual implementation of a smart grid can differ significantly, depending on the stakeholders involved.This work aims to inform policy makers, the electricity industry and researchers about stakeholder interests and the technical complexities involved by presenting smart grids via a techno-institutional framework. This framework takes account of the technical nature of the electricity transport and supply service as well as the institutional nature of electricity markets, stakeholder perspectives and sector regulation. In addition, this work presents potential revenues resulting from flexibility management in smart grids and proposes a way forward for smart grids and flexibility management in Europe.

  • Public defence: 2017-11-24 12:00 Madrid
    Calvillo Munoz, Christian Francisco
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems. Comillas Pontifical University.
    Energy Management in Smart Cities2017Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Models and simulators have been widely used in urban contexts for many decades. The drawback of most current models is that they are normally designed for specific objectives, so the elements considered are limited and they do not take into account the potential synergies between related systems. The necessity of a framework to model complex smart city systems with a comprehensive smart city model has been remarked by many authors.

    Therefore, this PhD thesis presents: i) a general conceptual framework for the modelling of energy related activities in smart cities, based on determining the spheres of influence and intervention areas within the city, and on identifying agents and potential synergies among systems, and ii) the development of a holistic energy model of a smart city for the assessment of different courses of action, given its geo-location, regulatory and technical constraints, and current energy markets. This involves the creation of an optimization model that permits the optimal planning and operation of energy resources within the city.

    In addition, several analyses were carried out to explore different hypothesis for the smart city energy model, including:

    a)      an assessment of the importance of including network thermal constraints in the planning and operation of DER systems at a low voltage distribution level,

    b)      an analysis of aggregator’s market modelling approaches and the impact on prices due to DER aggregation levels, and

    c)      an analysis of synergies between different systems in a smart city context.

    Some of the main findings are:

    • It is sensible to not consider network thermal constraints in the planning of DER systems. Results showed that the benefit decrement of considering network constraints was approximatively equivalent to the cost of reinforcing the network when necessary after planning without considering network constraints.
    • The level of aggregation affects the planning and overall benefits of DER systems. Also, price-maker approaches could be more appropriate for the planning and operation of energy resources for medium to large aggregation sizes, but could be unnecessary for small sizes, with low expected impact on the market price.
    • Synergies between different energy systems exist in an interconnected smart city context. Results showed that the overall benefits of a joint management of systems were greater than those of the independently managed systems.

    Lastly, the smart city energy model was applied to a case study simulating a real smart city implementation, considering five real districts in the southern area of Madrid, Spain. This analysis allowed to assess the potential benefits of the implementation of a real smart city programme, and showed how the proposed smart city energy model could be used for the planning of pilot projects. To the best of our knowledge, such a smart city energy model and modelling framework had not been developed and applied yet, and no economic results in terms of the potential benefits of such a smart city initiative had been previously reported.