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  • Public defence: 2017-01-20 10:00 Ka-Sal C (Sal Sven-Olof Öhrvik), Kista
    Salemi, Arash
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Salemi, Arash
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Silicon Carbide Technology for High- and Ultra-High-Voltage Bipolar Junction Transistors and PiN Diodes2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Silicon carbide (SiC) is an attractive material for high-voltage and high-temperature electronic applications owing to the wide bandgap, high critical electric field, and high thermal conductivity. High- and ultra-high-voltage silicon carbide bipolar devices, such as bipolar junction transistors (BJTs) and PiN diodes, have the advantage of a low ON-resistance due to conductivity modulation compared to unipolar devices. However, in order to be fully competitive with unipolar devices, it is important to further improve the off-state and on-state characteristics, such as breakdown voltage, leakage current, common-emitter current gain, switching, current density, and ON-resistance.

    In order to achieve a high breakdown voltage with a low leakage current, an efficient and easy to fabricate junction edge protection or termination is needed. Among different proposed junction edge protections, a mesa design integrated with junction termination extensions (JTEs) is a powerful approach. In this work, implantation-free 4H-SiC BJTs in two classes of voltage, i.e., 6 kV-class and 15 kV-class with an efficient and optimized implantation-free junction termination (O-JTE) and multiple-shallow-trench junction termination extension (ST-JTE) are designed, fabricated and characterized. These terminations result in high termination efficiency of 92% and 93%, respectively.

    The 6 kV-class BJTs shows a maximum current gain of β = 44. A comprehensive study on the geometrical design is done in order to improve the on-state performances. For the first time, new cell geometries (square and hexagon) are presented for the SiC BJTs. The results show a significant improvement of the on-state characteristics because of a better utilization of the base area. At a given current gain, new cell geometries show a 42% higher current density and 21% lower ON-resistance. The results of this study, including an optimized fabrication process, are utilized in the 15 kV-class BJTs where a record high current gain of β = 139 is achieved.

    Ultra-high-voltage PiN diodes in two classes of voltage, i.e., 10+ kV using on-axis 4H-SiC and 15 kV-class off-axis 4H-SiC, are presented. O-JTE is utilized for 15 kV-class PiN diodes, while three steps ion-implantation are used to form the JTE in 10+ kV PiN diodes. Carbon implantation followed by high-temperature annealing is also performed for the 10+ kV PiN diodes in order to enhance the lifetime. Both type diodes depict conductivity modulation in the drift layer. No bipolar degradation is observed in 10+ kV PiN diodes.

  • Public defence: 2017-01-20 13:00 F3, Stockholm
    Oertel, Catharine
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH.
    Oertel, Catharine
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH.
    Modelling Engagement in Multi-Party Conversations: Data-Driven Approaches to Understanding Human-Human Communication Patterns for Use in Human-Robot Interactions2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The aim of this thesis is to study human-human interaction in order to provide virtual agents and robots with the capability to engage into multi-party-conversations in a human-like-manner. The focus lies with the modelling of conversational dynamics and the appropriate realization of multi-modal feedback behaviour. For such an undertaking, it is important to understand how human-human communication unfolds in varying contexts and constellations over time. To this end, multi-modal human-human corpora are designed as well as annotation schemes to capture conversational dynamics are developed. Multi-modal analysis is carried out and models are built. Emphasis is put on not modelling speaker behaviour in general and on modelling listener behaviour in particular.

    In this thesis, a bridge is built between multi-modal modelling of conversational dynamics on the one hand multi-modal generation of listener behaviour in virtual agents and robots on the other hand. In order to build this bridge, a unit-selection multi-modal synthesis is carried out as well as a statistical speech synthesis of feedback. The effect of a variation in prosody of feedback token on the perception of third-party observers is evaluated. Finally, the effect of a controlled variation of eye-gaze is evaluated, as is the perception of user feedback in human-robot interaction.​

  • Public defence: 2017-01-20 13:00 FA32, Stockholm
    Riber Marklund, Anders
    KTH, School of Engineering Sciences (SCI), Physics, Reactor Technology.
    Riber Marklund, Anders
    KTH, School of Engineering Sciences (SCI), Physics, Reactor Technology.
    Passive acoustic leak detection in energy conversion systems of sodium fast reactors2016Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Reaching the goals of Generation IV nuclear power is challenging. However, no less than six reactor concepts have been identified as capable of fulfilling the demands. Among these, the Sodium Fast Reactor (SFR), probably represents the most mature technology as about 20 SFR plants have been operated to this day.

     

    One design-specific issue of the SFR is the risk of leak and sodium-water reaction inside a steam generator. Standard monitoring is based on hydrogen detection, resulting in high sensitivity but slow response. The alternative of acoustic leak detection methods has been studied since the 1970s since they are able to respond much faster. Demonstrating low false alarm rate while detecting the fairly weak and possibly unknown acoustic signals of leaks has however proven to be difficult.

     

    Today, the CEA performs R&D, notably within the scope of the ASTRID project, with the aim of eliminating the sodium-water reaction risk. This is achieved by a Brayton cycle, using a nitrogen turbine and compact sodium-nitrogen heat exchangers. In case of a leak in this system, the low solubility of nitrogen in sodium and the high pressure in the tertiary circuit would increase the secondary pressure, locally deteriorate performance and possibly result in harmful hydrodynamic effects. Together with the risks of a potential gas leak over to the reactor, this motivates the use of leak detection also for this design.

     

    This thesis concerns passive acoustic leak detection, primarily for a SFR sodium-nitrogen heat exchanger, arguing that this method is suitable based on experiments, numerical simulations and studies on algorithms. The word “passive” here refers to a system that does not send out any signals, but rather records the noise of the plant and detects leaks as changes in this signal. The thesis covers experiments on normal operation and leak-simulating setups as well as machine-learning based detection methods intended to be of interest also for change detection in general.

  • Public defence: 2017-01-20 14:00 D2, Stockholm
    Mikša, Mladen
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    Mikša, Mladen
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    On Complexity Measures in Polynomial Calculus2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Proof complexity is the study of different resources that a proof needs in different proof systems for propositional logic. This line of inquiry relates to the fundamental questions in theoretical computer science, as lower bounds on proof size for an arbitrary proof system would separate P from NP.

    We study two simple proof systems: resolution and polynomial calculus. In resolution we reason using clauses, while in polynomial calculus we use polynomials. We study three measures of complexity of proofs: size, space, and width/degree. Size is the number of clauses or monomials that appear in a resolution or polynomial calculus proof, respectively. Space is the maximum number of clauses/monomials we need to keep at each time step of the proof. Width/degree is the size of the largest clause/monomial in a proof.

    Width is a lower bound for space in resolution. The original proof of this claim used finite model theory. In this thesis we give a different, more direct proof of the space-width relation. We can ask whether a similar relation holds between space and degree in polynomial calculus. We make some progress on this front by showing that when a formula F requires resolution width w then the XORified version of F requires polynomial calculus space Ω(w). We also show that space lower bounds do not imply degree lower bounds in polynomial calculus.

    Width/degree and size are also related, as strong lower bounds for width/degree imply strong lower bounds for size. Currently, proving width lower bounds has a well-developed machinery behind it. However, the degree measure is much less well-understood. We provide a unified framework for almost all previous degree lower bounds. We also prove some new degree and size lower bounds. In addition, we explore the relation between theory and practice by running experiments on some current state-of-the-art SAT solvers.

  • Public defence: 2017-01-27 09:00 A124, Stockholm
    Karlsson, Sandra
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Urban and Regional Studies.
    Karlsson, Sandra
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Urban and Regional Studies.
    Områdesbaserad politik – möjligheter till strukturell förändring: Lokalt utvecklingsarbete i marginaliserade bostadsområden i Malmö2016Doctoral thesis, monograph (Other academic)
    Abstract [en]

    In 1995 the Swedish government launched the first area-based initiative Special initiatives in immigrant-dense neighbourhoods as a response to the current debate concerning the failings of the integration policy. The area-based policy and projects undertake the mission to reverse the trend in marginalized neighbourhoods in Sweden’s major cities from 1995 to 2014. The empirical material is from the projects Area-programs for a socially sustainable Malmö (2010-2015) and Lindängen towards the future (2012-2014), Malmö municipality. Adopting a social constructionist approach the study’s aim is to examine the projects’ assumptions concerning what – and who – should be changed and how.  Based on the policy´s claim to achieve structural change the study also examines if, and if so what, possibilities the projects have to create opportunities for structural change.

     

    The study shows that the area-based projects cannot create opportunities for structural change but rather work to reduce the social consequences of structural deficiencies that are made visible through the reproduction of marginalised neighbourhoods. In the projects the social problem is constructed as consisting of four interrelated factors: long-term unemployment, foreign background, segregation and lack of social responsibility. The strategy is to mobilise public, private and civil sector actors so that they – despite society’s exclusion of people of foreign background in situations of long-term unemployment – take their social responsibility and make available resources to individual residents in order to prepare them for becoming active citizens. As they are not able to reduce poverty, promote inclusive political and economic processes or legitimate relationships between those in power and representatives of civil society with demands for changing conditions, their ability to create opportunities for structural change is found to be  limited.

  • Public defence: 2017-01-27 10:00 V2, Stockholm
    Onifade, Ibrahim
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Onifade, Ibrahim
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Development of Energy-based Damage and Plasticity Models for Asphalt Concrete Mixtures2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Characterizing the full range of damage and plastic behaviour of asphalt mixtures under varying strain-rates and stress states is a complex and challenging task. One reason for this  is partly due to the strain rate and temperature dependent nature of the material as well as the variation in the properties of the constituent materials that make up the composite asphalt mixture. Existing stress-based models for asphalt concrete materials are developed based on mechanics principles, but these models are, however, limited in their application for actual pavement analysis and design since rate dependency parameters are needed in the constitutive model to account for the influence of the strain rate on the stress-based yield and evolution criteria. Till date, we are yet to arrive at simple and comprehensive constitutive models that can be used to model the behaviour of asphalt mixture over a wide range of strain-rate which is experienced in the actual pavement sections. The aim of this thesis is to develop an increased understanding of the strength and deformation mechanism of asphalt mixtures through multi-scale modeling and to develop simple and comprehensive continuum models to characterize the non-linear behaviour of the material under varying stress-states and conditions. An analysis framework is developed for the evaluation of the influence of asphalt mixture morphology on its mechanical properties and response using X-Ray CT and digital image processing techniques. The procedure developed in the analysis framework is then used to investigate the existence of an invariant critical energy threshold for meso-crack initiation which serves as the basis for the development of a theory for the development of energy-based damage and plastic deformation models for asphalt mixtures. A new energy-based viscoelastic damage model is developed and proposed based on continuum damage mechanics (CDM) and the thermodynamics of irreversible processes. A second order damage variable tensor is introduced to account for the distributed damage in the material in the different principal damage directions. In this way, the material response in tension and compression can be decoupled and the effects of both tension- and compression stress states on the material behaviour can be accounted for adequately. Based on the finding from the energy-based damage model, an equivalent micro-crack stress approach is developed and proposed for the damage and fracture characterization of asphalt mixtures. The effective micro-crack stress approach takes account of the material stiffness and a critical energy threshold for micro-crack initiation in the characterization of damage and fracture properties of the mixture. The effective micro-crack stress approach is developed based on fundamental mechanics principles and it reduces to the Griffith's energy balance criterion when purely elastic materials are considered without the need for the consideration of the surface energy and a crack size in the determination of the fracture stress. A new Continuum Plasticity Mechanics (CPM) model is developed within the framework of thermodynamics to describe the plastic behaviour of asphalt concrete material with energy-based criteria derived for the initiation and evolution of plastic deformation. An internal state variable termed the "plasticity variable" is introduced to described the distributed dislocation movement in the microstructure. The CPM model unifies aspects of existing elasto-plastic and visco-plastic theories in one theory and shows particular strength in the modeling of rate-dependent plastic behaviour of materials without the need for the consideration of rate dependency parameters in the constitutive relationships. The CPM model is further extended to consider the reduction in the stiffness properties with incremental loading and to develop a unified energy-based damage and plasticity model. The models are implemented in a Finite Element (FE) analysis program for the validation of the models. The result shows that the energy-based damage and plastic deformation models are capable of predicting the behaviour of asphalt concrete mixtures under varying stress-states and strain-rate conditions. The work in this thesis provides the basis for the development of more fundamental understanding of the asphalt concrete material response and the application of sound and solid mechanics principles in the analysis and design of pavement structures.

  • Public defence: 2017-01-27 10:00 F3, Stockholm
    Lindh, Erik L
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Lindh, Erik L
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Cellulose-water interaction: a spectroscopic study2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The human society of today has a significantly negative impact on the environment and needs to change its way of living towards a more sustainable path if to continue to live on a healthy planet. One path is believed to be an increased usage of naturally degradable and renewable raw materials and, therefore, attention has been focused on the highly abundant biopolymer cellulose. However, a large drawback with cellulose-based materials is the significant change of their mechanical properties when in contact with water. Despite more than a century of research, the extensively investigated interaction between water and cellulose still possesses many unsettled questions, and if the answer to those were known, cellulose-based materials could be more efficiently utilized.

    It is well understood that one interaction between cellulose and water is through hydrogen bonds, established between water and the hydroxyl groups of the cellulose. Due to the very similar properties of the hydroxyl groups in water and the hydroxyl groups of the cellulose, the specific interaction-induced effect on the hydroxyl groups at a cellulose surface is difficult to investigate.  Therefore, a method based on 2H MAS NMR spectroscopy has been developed and validated in this work. Due to the verified ability of the methodology to provide site-selective information regarding the molecular dynamics of the cellulose deuteroxyl groups (i.e. deuterium-exchanged hydroxyl groups), it was shown by investigating 1H-2H exchanged cellulose samples that only two of the three accessible hydroxyl groups (on the surface of cellulose fibrils) exchange with water. This finding was also verified by FT-IR spectroscopy, and together with MD simulations we could establish that it is O(2)H and O(6)H hydroxyl groups (of the constituting glucose units) that exchange with water. From the MD simulations additional conclusion could be drawn regarding the molecular interactions required for hydrogen exchange; an exchanging hydroxyl group needs to donate its hydrogen in a hydrogen bond to water.

    Exchange kinetics of thin cellulose films were investigated by monitoring two different exchange processes with FT-IR spectroscopy. Specific information about the two exchanging hydroxyl/deuteroxyl groups was then extracted by deconvoluting the changing intensities of the recorded IR spectra. It was recognized that the exchange of the hydroxyl groups were well described by a two-region model, which was assessed to correspond to two fibrillary surfaces differentiated by their respective positions in the fibril aggregate. From the detailed deconvolution it was also possible to estimate the fraction of these two surfaces, which indicated that the average aggregate of cotton cellulose is built up by three to four fibrils.                      

    2H MAS NMR spectroscopy was used to examine different states of water in cellulose samples, hydrated at different relative humidities of heavy water. The results showed that there exist two states of water adsorbed onto the cellulose, differentiated by distinct different mobilities. These two states of water are well separated and had negligible exchange on the time scale of the experiments. It was suggested that they are located at the internal and external surfaces of the fibril aggregates.

    By letting cellulose nanofibrils undergo an epoxidation reaction with a mono epoxide some indicative results regarding how to protect the cellulose material from the negative impact of water were presented. The protecting effect of the epoxidation were examined by mechanically testing and NMR spectroscopy. It was proposed that by changing the dominant interaction between the fibril aggregates from hydrophilic hydrogen bonds to hydrophobic π-interactions the sensitivity to moisture was much reduced. The results also indicated that the relative reduction in moisture sensitivity was largest for the samples with highest moisture content.

  • Public defence: 2017-01-27 10:00 Q2, Stockholm
    Lopez Nina, Luis Gagarin
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology. UMSA-Universidad Mayor de San Andrés, Bolivia.
    Lopez Nina, Luis Gagarin
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology. UMSA-Universidad Mayor de San Andrés, Bolivia.
    Catalytic conversion of syngas to ethanol and higher alcohols over Rh and Cu based catalysts2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The thermochemical process converts almost any kind of biomass to a desired final product, i.e. gaseous or liquid transportation fuels and chemicals. The transportation fuels obtained in this way are renewable biofuels, which are alternatives to fossil fuels. During the last few years, thermochemical plants for the production of bioethanol have been launched and another is under construction. A total of about 290 million liters of ethanol are expected to be processed per year, mostly using municipal solid waste. Considerable efforts have been made in order to find a more selective catalyst for the conversion of biomass-derived syngas to ethanol.

    The thesis is the summary of five publications. The first two publications (Papers I and II) review the state of the art of ethanol and higher alcohols production from biomass, as well as the current status of synthetic fuels production by other processes such as the Fischer-Tropsch synthesis. Paper III analyses the catalytic performance of a mesoporous Rh/MCM-41 (MCM-41 is a hexagonal mesoporous silica) in the synthesis of ethanol which is compared to a typical Rh/SiO2 catalyst. Exhaustive catalytic testing including the addition of water vapor and modifying the hydrogen partial pressure in the syngas feed-stream which, in addition to the catalyst characterization (XRD, BET, XPS, chemisorption, TEM and TPR) before and after the catalytic testing, have allowed concluding that some water vapor can be concentrated in the pores of the Rh/MCM-41 catalyst. The concentration of water-vapor promotes the occurrence of the water gas shift reaction, which in turn induces some secondary reactions that change the product distribution, as compared to results obtained from the typical Rh/SiO2 catalyst. These results have been verified in a wide range of syngas conversion levels (1-68 %) and for different catalyst activation procedures (catalyst reduction at 200 °C, 500 °C and no-reduction) as shown in Paper IV. Finally, similar insights about the use of mesoporous catalyst have been found over a Cu/MCM-41 catalyst, shown in Paper V. Also in Paper V, the effect of metal promoters (Fe and K) has been studied; a noticeable increase of ethanol reaction rate was found over Cu-Fe-K/MCM-41 catalyst as compared to Cu/MCM-41. 

    The full text will be freely available from 2017-02-03 17:05
  • Public defence: 2017-01-27 10:00 D2, Stockholm
    Rynell, Anders
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Rynell, Anders
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    An experimental and numerical study of an automotive cooling module2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Heavy vehicles are major emitters of noise. Especially at idle or low vehicle speeds a large portion of the noise emanates from the fan that forces the flow through the cooling module. The aim of this work is to investigate and reveal aerodynamic and acoustic installation effects linked to the cooling package. This introduces a multidisciplinary approach involving examination of the flow field, sound generation and sound propagation. The work includes two main parts: an experimental and a numerical part. The cooling module used throughout this work, named reduced cooling module, primarily includes a radiator, a shroud, a fan and a hydraulic engine to simplify the aeroacoustics analysis.

    The experimental part comprises measurements of the sound emanated from the cooling package. A new approach to the spectral decomposition method is developed yielding the fan sound power or spectrum to be formulated as a product of a source part and a system part scaling with the Strouhal number and the Helmholtz number. Also, a separate determination of the transmission loss of the radiator is performed. The impact of the radiator on the transmitted noise was found to be negligible.

    The numerical part incorporates comparisons from two aeroacoustics studies; a configuration where the fan is forced to operate at a fixed operation point and measured flow and turbulence statistics are available and the reduced cooling module. A hybrid turbulence modeling technique, IDDES, is adopted for the flow simulations. The sound propagation is calculated by the Ffowcs-Williams and Hawkings acoustic analogy when assuming a free-field sound propagation and by a finite element solver in the frequency domain to capture the installation effects. The simulated SPL conforms to the measured SPL and the blade response to the turbulent inflow and to the tip resolution, respectively, produce noise which spectral shape distribution is modified in accordance with earlier experimental findings published. Furthermore, the influence of an upstream radiator in close contact with the fan on the flow and sound fields is investigated. Here, the simulated aeroacoustic characteristics were found to change similarly to the acoustic measurements with and without radiator.

  • Public defence: 2017-01-27 10:00 Kollegiesalen, Stockholm
    Kosmack Vaara, Elsa
    KTH, School of Computer Science and Communication (CSC), Media Technology and Interaction Design, MID. SICS, Swedish ICT.
    Kosmack Vaara, Elsa
    KTH, School of Computer Science and Communication (CSC), Media Technology and Interaction Design, MID. SICS, Swedish ICT.
    Exploring the Aesthetics of Felt Time2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    By building a felt time repertoire, designers can sensitively feed a sense of time into their design work. And this in turn can help them produce an interaction gestalt that is richer, more sensual. My research on this suggests that this is not entirely easy, however. One has to develop a ‘feel’ for time. My research exploration began when I worked on designing a biofeedback data system, Affective Health, struggling with the tension and division between clocktime and the users’ unceasingly changing, ‘felt’ experiences. By turning to artistic practice, of music and culinary arts, I hoped to find keys to this question. Through connecting interaction-design research to these practices, I could start unfolding possibilities of temporal aesthetics in interaction design. I point to a space where designers can expand their understanding of felt time and playfully explore the sense of time that interactive systems and physical materials can deliver. Through the aspects below I point to the importance of being sensitive to felt forms and expressions of time to approach the temporal gestalt in interaction.

     

    • Through my research I have strived to move outside clocktime and re-imagine the sense of time that interactive systems deliver.

    • One part of this space is felt rhythms and how they shape temporal experiences.

    • In common to those rhythms are the rest and pause moments that form their vitality.

    • One way of working with rhythm is to see how felt shapes and rhythms of time resonate through the temporal gestalt in interaction.

    • Aesthetic sensitivity, felt timers, can help us to orient ourselves in time.

    • By approaching time as plastic: time as a form and shape that we can hold on to, squeeze and weave together, we can start finding tools for remoulding the sense of time in systems, artefacts and services.

    • Finally, I have worked with aesthetic transformations that can encourage people to start experiencing temporality from new perspectives and with a different approach.

  • Public defence: 2017-01-31 10:00 FA32, Stockholm
    Pegonen, Reijo
    KTH, School of Engineering Sciences (SCI), Physics, Reactor Technology.
    Pegonen, Reijo
    KTH, School of Engineering Sciences (SCI), Physics, Reactor Technology.
    Development of an Improved Thermal-Hydraulic Modeling of the Jules Horowitz Reactor2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The newest European high performance material testing reactor, the Jules Horowitz Reactor, is under construction at CEA Cadarache research center in France. The reactor will support existing and future nuclear reactor technologies, with the first criticality expected at the end of this decade.

    The current/reference CEA methodology for simulating the thermalhydraulic behavior of the reactor gives reliable results. The CATHARE2 code simulates the full reactor circuit with a simplified approach for the core. The results of this model are used as boundary conditions in a three-dimensional FLICA4 core simulation. However this procedure needs further improvement and simplification to shorten the computational requirements and give more accurate core level data. The reactor’s high performance (e.g. high neutron fluxes, high power densities) and its design (e.g. narrow flow channels in the core) render the reactor modeling challenging compared to more conventional designs. It is possible via thermal-hydraulic or solely hydraulic Computational Fluid Dynamics (CFD) simulations to achieve a better insight of the flow and thermal aspects of the reactor’s performance. This approach is utilized to assess the initial modeling assumptions and to detect if more accurate modeling is necessary. There were no CFD thermal-hydraulic publications available on the JHR prior to the current PhD thesis project.

    The improvement process is split into five steps. In the first step, the state-of-the-art CEA methodology for thermal-hydraulic modeling of the reactor using the system code CATHARE2 and the core analysis code FLICA4 is described. In the second and third steps, a CFD thermal-hydraulic simulations of the reactor’s hot fuel element are undertaken with the code STAR-CCM+. Moreover, a conjugate heat transfer analysis is performed for the hot channel. The knowledge of the flow and temperature fields between different channels is important for performing safety analyses and for accurate modeling. In the fourth step, the flow field of the full reactor vessel is investigated by conducting CFD hydraulic simulations in order to identify the mass flow split between the 36 fuel elements and to describe the flow field in the upper and lower plenums. As a side study a thermal-hydraulic calculation, similar to those performed in previous steps is undertaken utilizing the outcome of the hydraulic calculation as an input. The final step culminates by producing an improved, more realistic, purely CATHARE2 based, JHR model, incorporating all the new knowledge acquired from the previous steps.

    The primary outcome of this four year PhD research project is the improved, more realistic, CATHARE2 model of the JHR with two approaches for the hot fuel element. Furthermore, the project has led to improved thermal-hydraulic knowledge of the complex reactor (including the hot fuel element), with the most prominent findings presented.

  • Public defence: 2017-02-02 10:00 F3, Stockholm
    Skoglund, Sara
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Skoglund, Sara
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Surface reactivity of metal nanoparticles: - importance of surface active agents and biomolecules from a transformation, mobility and toxicity perspective2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Metallic nanoparticles possess unique properties due to their size and are widely used in e.g. consumer products. From this follows a need to identify and assess potential risks of human and environmental exposure. Their size facilitates uptake in organisms and disruption of various biological processes. Together with a high reactivity, mainly due to their large surface area in solution, they are both commonly used in different applications and of a potential safety concern. Risk assessment requires hence in-depth knowledge on the particle characteristics and their behavior in solution but also how these properties change with time and exposure conditions and whether these characteristics can be linked to toxicity following nanoparticle exposure. This thesis addresses these aspects with a main focus on metal nanoparticles and elaborates on the importance of characterization, how such measurements can be done, and on interactions with surfactants and biomolecules and toxic effects.Silver nanoparticles are, due to their antibacterial properties, often used in sportswear to prevent sweat odor. During laundry they may be dispersed and interact with surfactants of the washing powder, influencing their properties and stability in solution. These aspects are addressed in Papers I, III and V on silver nanoparticles of different size and surface coatings. The stability was shown to depend on the surface charge and the concentration of the surfactant. The stability and extent of silver release were reduced upon sequential exposure, indicating the importance of the particle history on their bioaccessibility, mobility and potential toxicity. A mechanism was proposed for how silver nanoparticles are stabilized in surfactant solutions.Toxic effects of silver nanoparticles of different size and coatings on cultivated lung cells, Paper II, and effects of copper-containing nanoparticles on different blood cells, Paper IV, were studied in vitro. The smallest particles were most cytotoxic and the “Trojan horse” mechanism played an important role, meaning that the nanoparticles facilitate cellular uptake followed by ion-release.Difficulties in the determination and interpretation of the zeta potential, related to the surface charge, of metal nanoparticles in complex solutions are elucidated in Paper VI. Guidelines are provided on how to accurately assess this property.

    The full text will be freely available from 2018-01-11 12:22
  • Public defence: 2017-02-02 10:00 KTH - room B2, Stockholm
    Samuelsson, Peter
    KTH.
    Samuelsson, Peter
    KTH.
    Management of technology in the process industries:  Matching market and machine2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The process industries span multiple industrial sectors and constitute a substantial part of the entire manufacturing industry. Since companies belonging to this family of industries are often very asset intensive, their ability to respond to changes is often limited in the short term.

    The adaptation of the capabilities of existing processes, and conversely finding products and market segments to match the production system capabilities, are an important part of product- and market development activities in the process industry. The importance to companies in the process industry of having a well-articulated manufacturing strategy congruent with the business strategy is second to none. However, to facilitate manufacturing strategy developments, it is essential to start with an improved characterization and understanding of the material transformation system.

    To that end an extensive set of variables was developed and related measures and scales were defined. The resulting configuration model, focusing on company generic process capabilities in the process industries, is to be regarded as a conceptual taxonomy and as a proposition available for further testing. The usability of the model was subsequently assessed using “mini-cases” in the forestry industry, where the respondents confirmed that the company’s overall strategy could benefit from this kind of platform as a possible avenue to follow.

    The model was deployed as an instrument in the profiling of company material transformation systems to facilitate the further development of companies' functional and business strategies. The use of company-generic production capabilities was studied in three case companies representing the mineral, food and steel industries. The model was found by the respondents to be usable as a knowledge platform to develop production strategies. In the final analysis of the research results, a new concept emerged called “production capability configuration":

    A process-industrial company’s alignment of its generic production capabilities in the areas of raw materials, process technology and products to improve the consistency among the variable elements that define operations and improve the congruence between operations and its environment.

    From the perspective of value creation and capture, firms must be able to manufacture products in a competitive cost structure within the framework of a proper business model. By using the configuration model, the relationship between manufacturing and innovation activities has been studied in the previously mentioned three case studies.

    In many cases the gap in capability appears as a limitation in the production system, requiring development efforts and sometimes investments to overcome. This is illustrated with two examples from the steel industry, where development efforts of the production system capabilities are initiated to better match the market demands. One example is the increase the volume- and product flexibility of an existing stainless steel melt shop, resulting in a proposed oblong Argon Oxygen Decarburisation (AOD) converter configuration that was subsequently verified using water modelling. The second example is from a carbon steel mill, where the target was to increase the raw material- and volume flexibility of another melt shop, by modifying the capabilities of the Electric Arc Furnace (EAF). Enabling EAF technologies are further described and evaluated using operational data and engineering type of estimates. 

  • Public defence: 2017-02-03 13:00 sal C (Sal Sven-Olof Öhrvik), Electrum, Kungl Tekniska Högskolan,, Stockholm
    Martinez Ballesteros, Luis Guillermo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab). KTH, Superseded Departments, Wireless at KTH.
    Martinez Ballesteros, Luis Guillermo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab). KTH, Superseded Departments, Wireless at KTH.
    On the Incorporation of Quality of Experience (QoE) in Mobile Networks: A technical, regulatory and business analysis2017Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Mobile operators face a scenario characterised by new challenges such as growing data consumption, a slowdown in subscriber growth and reduced revenues due to the success of OTT providers. To remain competitive, mobile operators must offer affordable services and think on strategies to retain current customers.

    Quality of Experience (QoE) is a well-established methodology for measuring and understanding the overall level of customer satisfaction with a service and has been presented as a way to improve telecommunication services. Even though QoE can be used to solve problems such as customer loyalty and optimisation of network resources in mobile networks, there is a great lack of knowledge on how mobile operators can take advantage of QoE and its potential benefits.

    This thesis explores the incorporation of QoE in mobile networks to improve their service offering from a technical, regulatory and business perspective.The technical level focuses on the definition of the mechanism to integrate QoE in the operation of mobile networks. The second part of this study has been focused on the regulatory framework on Net Neutrality. Finally,the third part of this thesis focuses on the identification of potential business scenarios and models based on the incorporation of QoE in mobile networks. An important conclusion is that due to the nature of the challenges faced by the mobile industry, a QoE analysis cannot be limited to a technical discussion. A technical solution can be the first step to the first step to overcoming industry challenges. However, it is important that a technical decision comes along with an informed analysis of the regulatory conditions and the business implications of the proposed solution. On the other hand, mobile operators require new methods that integrate technical, market and business considerations to improve their service offer. A method analysed in this dissertation is a Customer Experience Management (CEM) platform. Given the technical, regulatory and business factors covered in this thesis, a CEM platform can be used by mobile operators to make a better use of QoE in their business operation.

  • Public defence: 2017-02-03 13:00 Kollegiesalen, Stockholm
    Bülow, William
    Philosophy and History, KTH, School of Architecture and the Built Environment (ABE), Philosophy and History of Technology, Philosophy.
    Bülow, William
    Philosophy and History, KTH, School of Architecture and the Built Environment (ABE), Philosophy and History of Technology, Philosophy.
    Unfit to live among others: Essays on the ethics of imprisonment2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis provides an ethical analysis of imprisonment as a mode of punishment. Consisting in an introduction and four papers the thesis addresses several important questions concerning imprisonment from a number of different perspectives and theoretical starting points. One overall conclusion of this thesis is that imprisonment, as a mode of punishment, deserves more attention from moral and legal philosophers. It is also concluded that a more complete ethical assessment of prison conditions and prison management requires a broader focus. It must include an explicit discussion of both how imprisonment directly affects prison inmates and its negative side-effects on third parties. Another conclusion is that ethical discussions on prison conditions should not be too easily reduced to a question about how harsh or lenient is should be.

    Paper 1 argues that prisoners have a right to privacy. It is argued that respect for inmates’ privacy is related to respect for them as moral agents. Consequently, respect for inmates’ privacy is called for by different established philosophical theories about the justification of legal punishment. Practical implications of this argument are discussed and it is argued that invasion of privacy should be minimized to the greatest extent possible, without compromising other important values or the rights to safety and security. It is also proposed that respect for privacy should be part of the objective of creating and upholding a secure environment.

    Paper 2 discusses whether the collateral harm of imprisonment to the children and other close family members of prison inmates may give rise to special moral obligations towards them. Several collateral harms, including decreased psychological wellbeing, financial costs, loss of economic opportunities, and intrusion and control over their private lives, are identified. Two perspectives in moral philosophy, consequentialism and deontology, are then applied in order to assess whether these harms are permissible. It is argued that from either perspective it is hard to defend the claim that allowing for these harms are morally permissible. Consequently, imprisonment should be used only as a last resort. Where it is deemed necessary, it gives rise to special moral obligations. Using the notion of residual obligation, these obligations are then categorized and clarified.

    Paper 3 focuses on an argument that has figured in the philosophical debate on felon disenfranchisement. This argument states that as a matter of democratic self-determination, a legitimate democratic collective has the collective right to decide whether to disenfranchise felons as a way of defining their political identity. Yet, such a collective’s right to self-determination is limited, since the choice to disenfranchise anyone must be connected to normative considerations of political significance. This paper defends this argument against three charges that has been raised to it. In doing so it also explores under what circumstances felon disenfranchisement can be permissible.

    Paper 4 explores the question of whether prison inmates suffering from ADHD should be administered psychopharmacological intervention (methylphenidate) for their condition. The theoretical starting point for the discussion is the communicative theory of punishment, which understands criminal punishment   as a form of secular penance. Viewed through the lens of the communicative theory it is argued that the provision of pharmacological treatment to offenders with ADHD need not necessarily be conceived of as an alternative to punishment, but as an aid to achieving the penological ends of secular penance. Thus, in this view offenders diagnosed with ADHD should have the option to undergo pharmacological treatment.

  • Public defence: 2017-02-10 09:00 Air and Fire at Science for Life Laboratory, Solna
    Vickovic, Sanja
    KTH, School of Biotechnology (BIO), Gene Technology.
    Vickovic, Sanja
    KTH, School of Biotechnology (BIO), Gene Technology.
    Transcriptome-wide analysis in cells and tissues2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    High-throughput sequencing has greatly influenced the amount of data produced and biological questions asked and answered. Sequencing approaches have also enabled rapid development of related technological fields such as single-cell and spatially resolved expression profiling. The introductory parts of this thesis give an overview of the basic molecular and technological apparatus needed to analyse the transcriptome in cells and tissues. This is succeeded by a summary of present investigations that report recent advancements in RNA profiling.

    RNA integrity needs to be preserved for accurate gene expression analysis. A method providing a low-cost alternative for RNA preservation was reported. Namely, a low concentration of buffered formaldehyde was used for fixation of human cell lines and peripheral blood cells (Paper I). The results from bulk RNA sequencing confirmed gene expression was not negatively impacted with the preservation procedure (r2>0.88) and that long-term storage of such samples was possible (r2=0.95). However, it is important to note that a small population of cells overexpressing a limited amount of genes can skew bulk gene expression analyses making them sufficient only in carefully designed studies. Therefore, gene expression should be investigated at the single cell resolution when possible. A method for high-throughput single cell expression profiling termed microarrayed single-cell sequencing was developed (Paper II). The method incorporated fluorescence-activated cell sorting, sample deposition and profiling of thousands of barcoded single cells in one reaction. After sample attachment to a barcoded array, a high-resolution image was taken which linked the position of each array barcode sequence to each individual deposited cell. The cDNA synthesis efficiency was estimated at 17.3% while detecting 27,427 transcripts per cell on average. Additionally, spatially resolved analysis is important in cell differentiation, organ development and pathological changes. Current methods are limited in terms of throughput, cost and time. For that reason, the spatial transcriptomics method was developed (Paper III). Here, the barcoded microarray was used to obtain spatially resolved expression profiles from tissue sections using the same imaging principle. The mouse olfactory bulb was profiled on a whole-transcriptome scale and the results showed that the expression correlated well (r2=0.94-0.97) as compared to bulk RNA sequencing. The method was 6.9% efficient, reported signal diffusion at ~2 μm and accurately deconvoluted layer-specific transcripts in an unbiased manner. Lastly, the spatial transcriptomics concept was applied to profile human breast tumours in three dimensions (Paper IV). Unbiased clustering revealed previously un-annotated regions and classified them as parts of the immune system, providing a detailed view into complex interactions and crosstalk in the whole tissue volume. Spatial tumour classification divulged that certain parts of the tumour clearly classified as other subtypes as compared to bulk analysis providing useful data for current practice diagnostics.

    The last part of the thesis discusses a look towards the future, how the presented methods could be used, improved upon or combined in translational research.

  • Public defence: 2017-02-10 10:00 F3, Stockholm
    Valenzuela Pacheco, Patricio E.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Valenzuela Pacheco, Patricio E.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    On risk-coherent input design and Bayesian methods for nonlinear system identification2016Doctoral thesis, monograph (Other academic)
    Abstract [en]

    System identification deals with the estimation of mathematical models from experimental data. As mathematical models are built for specific purposes, ensuring that the estimated model represents the system with sufficient accuracy is a relevant aspect in system identification. Factors affecting the accuracy of the estimated model include the experimental data, the manner in which the estimation method accounts for prior knowledge about the system, and the uncertainties arising when designing the experiment and initializing the search of the estimation method.

    As the accuracy of the estimated model depends on factors that can be affected by the user, it is of importance to guarantee that the user decisions are optimal. Hence, it is of interest to explore how to optimally perform an experiment in the system, how to account for prior knowledge about the system and how to deal with uncertainties that can potentially degrade the model accuracy.

    This thesis is divided into three topics. The first contribution concerns an input design framework for the identification of nonlinear dynamical models. The method designs an input as a realization of a stationary Markov process. As the true system description is uncertain, the resulting optimization problem takes the uncertainty on the true value of the parameters into account. The stationary distribution of the Markov process is designed over a prescribed set of marginal cumulative distribution functions associated with stationary processes. By restricting the input alphabet to be a finite set, the parametrization of the feasible set can be done using graph theoretical tools. Based on the graph theoretical framework, the problem formulation turns out to be convex in the decision variables. The method is then illustrated by an application to model estimation of systems with quantized measurements.

    The second contribution of this thesis is on Bayesian techniques for input design and estimation of dynamical models. In regards of input design, we explore the application of Bayesian optimization methods to input design for identification of nonlinear dynamical models. By imposing a Gaussian process prior over the scalar cost function of the Fisher information matrix, the method iteratively computes the predictive posterior distribution based on samples of the feasible set. To drive the exploration of this set, a user defined acquisition function computes at every iteration the sample for updating the predictive posterior distribution. In this sense, the method tries to explore the feasible space only on those regions where an improvement in the cost function is expected. Regarding the estimation of dynamical models, this thesis discusses a Bayesian framework to account for prior information about the model parameters when estimating linear time-invariant dynamical models. Specifically, we discuss how to encode information about the model complexity by a prior distribution over the Hankel singular values of the model. Given the prior distribution and the likelihood function, the posterior distribution is approximated by the use of a Metropolis-Hastings sampler. Finally, the existence of the posterior distribution and the correctness of the Metropolis-Hastings sampler is analyzed and established.

    As the last contribution of this thesis, we study the problem of uncertainty in system identification, with special focus in input design. By adopting a risk theoretical perspective, we show how the uncertainty can be handled in the problems arising in input design. In particular, we introduce the notion of coherent measure of risk and its use in the input design formulation to account for the uncertainty on the true system description. The discussion also introduces the conditional value at risk, which is a risk coherent measure accounting for the mean behavior of the cost function on the undesired cases. The use of risk coherent measures is also employed in application oriented input design, where the input is designed to achieve a prescribed performance in the intended model application.

  • Public defence: 2017-02-10 14:00 Sal F3, Stockholm
    Linvill, Eric
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.). KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Linvill, Eric
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.). KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    3-D Forming of Paper Materials2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Paper materials have a long history of use as a packaging material, although traditional paper-based packaging is limited in its shape, complexity, and design. In order to better understand the deformation and failure mechanisms during 3-D forming, two experimental studies of paper materials have been conducted. Furthermore, constitutive modeling combined with explicit finite element modeling have been validated against numerous experimental setups and utilized to develop further understanding of 3-D forming processes.

    Two experimental studies were necessary to further investigate and model the 3-D formability of paper materials. The combined effect of moisture and temperature on the uniaxial mechanical properties of paper was investigated, providing new insights into how moisture and temperature affect both the elastic and plastic properties of paper materials. Furthermore, the in-plane, biaxial yield and failure surfaces were experimentally investigated in both stress and strain space, which gave an operating window for 3-D forming processes as well as input parameters for the constitutive models.

    The constitutive modeling of paper materials and explicit finite element modeling were directed towards two 3-D forming processes: deep drawing and hydroforming. The constitutive models were calibrated and validated against simple (typically uniaxial) mechanical tests, and the explicit finite element models (which utilize the developed constitutive models) were validated against 3-D forming experiments. Hand-made papers with fibers partially oxidized to dialcohol cellulose, which has greater extensibility than typical paper materials, was furthermore characterized, modeled, and 3-D formed as a demonstration of the potential of modified paper fiber products for 3-D forming applications.

    The full text will be freely available from 2017-01-21 09:00
  • Public defence: 2017-02-17 10:00 Kollegiesalen
    Anderson, Mattias
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Anderson, Mattias
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Amine Transaminases in Multi-Step One-Pot Reactions2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Amine transaminases are enzymes that catalyze the mild and selective formation of primary amines, which are useful building blocks for biologically active compounds and natural products. In order to make the production of these kinds of compounds more efficient from both a practical and an environmental point of view, amine transaminases were incorporated into multi-step one-pot reactions. With this kind of methodology there is no need for isolation of intermediates, and thus unnecessary work-up steps can be omitted and formation of waste is prevented. Amine transaminases were successfully combined with other enzymes for multi-step synthesis of valuable products: With ketoreductases all four diastereomers of a 1,3-amino alcohol could be obtained, and the use of a lipase allowed for the synthesis of natural products in the form of capsaicinoids. Amine transaminases were also successfully combined with metal catalysts based on palladium or copper. This methodology allowed for the amination of alcohols and the synthesis of chiral amines such as the pharmaceutical compound Rivastigmine. These examples show that the use of amine transaminases in multi-step one-pot reactions is possible, and hopefully this concept can be further developed and applied to make industrial processes more sustainable and efficient in the future.

  • Public defence: 2017-02-17 13:00 Q2, Stockholm
    Yajnanarayana, Vijaya Parampalli
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Yajnanarayana, Vijaya Parampalli
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Ultra Wideband: Communication and Localization2017Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The first part of this thesis develops methods for UWB communication. To meet the stringent regulatory body constraints, the physical layer signaling technique of the UWB transceiver should be optimally designed. We propose two signaling schemes which are variants of pulse position modulation (PPM) signaling for impulse radio (IR) UWB communication. We also discuss the detectors for the signaling schemes and evaluate the performance of these detectors.  IR-UWB can be used for precise range measurements as it provides a very high time resolution. This enables accurate time of arrival (TOA) estimations from which precise range values can be derived. We propose methods which use range information to arrive at optimal schedules for an all-to-all broadcast problem. Results indicate that throughput can be increased on average by three to ten times for typical network configurations compared to the traditional methods. Next, we discuss hypothesis testing in the context of UWB transceivers. We show that, when multiple detector outputs from a hardware platform are available, fusing the results from them can yield better performance in hypothesis testing than relying on a single detector output. In the second part of this thesis, the emphasis is placed on localization and joint estimation of location and communication parameters. Here, we focus on estimating the TOA of the signal. The wide bandwidth of the UWB signal requires high speed analog to digital converts (ADC) which makes the cost of the digital transceivers prohibitively high. To address this problem, we take two different strategies. In the first approach, we propose a multichannel receiver with each channel having a low-cost energy detector operating at a sub-Nyquist rate. In the second approach, we consider a compressive sampling based technique. Here, we propose a new acquisition front end, using which the sampling rate of the ADC can be significantly reduced. We extended the idea of compressive sampling based TOA estimation towards joint estimation of TOA and PPM symbols. Here, two signaling methods along with the algorithms are proposed based on the dynamicity of the target. They provide similar performance to the ML based estimation, however with a significant savings in the ADC resources.

  • Public defence: 2017-02-17 13:00 F3, Stockholm
    Schaufelberger, Fredrik
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Schaufelberger, Fredrik
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Catalysis in Dynamic Systems: Control within Molecular Reaction Networks2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Life as we know it is based on complex networks of biochemical reactions that constantly interact within large dynamic systems. The field of systems chemistry uses chemical models to study how reaction networks – and thereby life – function on a molecular level. This thesis focuses on different aspects of catalysis in dynamic systems of interconnected reversible reactions. Using the reversible imine bond as the primary tool, such dynamic systems have both been used for catalyst screening and to achieve emergent systemic behavior.

    First, constitutional dynamic chemistry was used to discover catalysts within large mixtures. A method based on dynamic deconvolution was used to identify a bifunctional organocatalyst for the Morita-Baylis-Hillman (MBH) reaction from a mixture of 16 candidates. A second method involved amplification of an organometallic intermediate from a dynamic system and was used to discover directing group/metal combinations for C-H functionalization of aldehydes.

    Subsequently, the consequences of integrating the catalyst itself into a dynamic system were investigated. Here, dynamic covalent catalysts formed reaction networks with programmable systemic properties. Using the MBH reaction and dynamic imine exchange, catalysts capable of self-resolution, feedback regulation and error-correction were constructed.

    Finally, selective catalyst systems for activation of new reversible covalent behavior for imines were developed. H-bond catalysis was used to facilitate imine exchange under mild conditions, and transamination was introduced as a dynamic covalent linkage that could change the directionality of the imine bond.

    The research in this thesis should both be applicable for catalyst discovery within synthetic organic chemistry, for understanding connectivity in chemical and biological systems as well as for studies of the origin of life on earth and the evolution of simple molecules into advanced systems with emergent functionality.

    The full text will be freely available from 2017-01-27 08:00
  • Public defence: 2017-02-24 10:15 99133, Gävle
    Amin, Shoaib
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Amin, Shoaib
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Characterization and Linearization of Multi-band Multi-channel RF Power Amplifiers2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The World today is deeply transformed by the advancement in wireless technology. The envision of a smart society where interactions between physical and virtual dimensions of life are intertwined and where human interaction is mediated by machines, e.g., smart phones, demands increasingly more data traffic. This continual increase in data traffic requires re-designing of the wireless technologies for increased system capacity and flexibility. In this thesis, aspects related to behavioral modeling, characterization, and linearization of multi-channel/band power amplifiers (PAs) are discussed.

    When building a model of any system, it is advantageous to take into account the knowledge of the physics of the system and include into the model. This approach could help to improve the model performance. In this context, three novel behavioral models and DPD schemes for nonlinear MIMO transmitters are proposed.

    To model and compensate distortions in GaN based RF PAs in presence of long-term memory effects, novel models for SISO and concurrent dual-band PAs are proposed. These models are based on a fixed pole expansion technique and have infinite impulse response. They show substantial performance improvement. A behavioral model based on the physical knowledge of the concurrent dual-band PA is derived, and its performance is investigated both for behavioral modeling and compensation of nonlinear distortions.

    Two-tone characterization is a fingerprint method for the characterization of memory effects in dynamic nonlinear systems. In this context, two novel techniques are proposed. The first technique is a dual two-tone characterization technique to characterize the memory effects of self- and cross-modulation products in concurrent dual-band transmitter. The second technique is for the characterization and analysis of self- and cross-Volterra kernels of nonlinear 3x3 MIMO systems using three-tone signals.