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  • 124151.
    Zukauskas, Andrius
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Grey-Track Resistant Periodically Poled Rb-doped KTiOPO4 For Blue-Light Generation2010In: Optics InfoBase Conference Papers, 2010, p. 5500148-Conference paper (Refereed)
    Abstract [en]

    We present periodic poling of Rb-doped KTiOPO4. The crystal is used to obtain blue radiation at 398 nm with an efficiency of 30% and a peak intensity of 2 MW/cm2 without grey-tracking.

  • 124152.
    Zukauskas, Andrius
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics. Royal Inst Technol, Dept Appl Phys, S-10691 Stockholm, Sweden..
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Grey-Track Resistant Periodically Poled Rb-doped KTiOPO(4) For Blue-Light Generation2010In: 2010 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO) AND QUANTUM ELECTRONICS AND LASER SCIENCE CONFERENCE (QELS), IEEE , 2010Conference paper (Refereed)
    Abstract [en]

    We present periodic poling of Rb-doped KTiOPO(4). The crystal is used to obtain blue radiation at 398 nm with an efficiency of 30% and a peak intensity of 2 MW/cm(2) without grey-tracking.

  • 124153.
    Zukauskas, Andrius
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    High-fidelity periodic domain structures in KTiOAsO4 for the visible spectral range2013In: Optical Materials Express, ISSN 2159-3930, E-ISSN 2159-3930, Vol. 3, no 9, p. 1444-1449Article in journal (Refereed)
    Abstract [en]

    We demonstrate room temperature periodic poling of KTiOAsO4 crystals with a period of 8.49 mu m for second harmonic generation of 1066 nm wavelength. The crystals are tested in a continuous wave SHG setup at 533 nm and show high quality periodic ferroelectric domain structure across the whole 1 mm crystal thickness, exhibiting d(eff) = 10.5 pm/V and normalized conversion efficiency of 1.2%/Wcm.

  • 124154.
    Zukauskas, Andrius
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Periodically poled KTiOAsO4 for second harmonic generation in the green region2013In: 2013 Conference on Lasers and Electro-Optics, CLEO 2013, IEEE Computer Society, 2013, p. 6833702-Conference paper (Refereed)
    Abstract [en]

    We present high-quality room temperature periodic poling of KTiOAsO4 with a period of 8.49 μm. The crystals are evaluated for SHG at 533 nm, and show deff = 10.5 pm/V and ηnorm = 1.19%/Wcm. OCIS codes: 190.4400 (Nonlinear optics, materials); 160.2260 (Ferroelectrics).

  • 124155.
    Zukauskas, Andrius
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Self-assembled ferroelectric nano-domain gratings in bulk RKTP2012In: 2012 Conference on Lasers and Electro-Optics, CLEO 2012, IEEE , 2012, p. 6325938-Conference paper (Refereed)
    Abstract [en]

     We present the fabrication of self-assembled bulk domain gratings of sub-μm periodicity in Rb-doped KTiOPO4 crystals. The structures are used to demonstrate QPM backwards propagating non-collinear second harmonic generation.

  • 124156.
    Zukauskas, Andrius
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Safinas, Maratas
    Ekspla Ltd..
    Michailovas, Andrejus
    Ekspla Ltd..
    High-Performance Periodically Poled Rb-doped KTP For Frequency Conversion In Blue/Green Region2010In: Conference digest, 2010Conference paper (Refereed)
  • 124157.
    Zukauskas, Andrius
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Strömqvist, Gustav
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Fokine, Michael
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Fabrication of submicrometer quasi-phase-matched devices in KTP and RKTP [Invited]2011In: Optical Materials Express, ISSN 2159-3930, Vol. 1, no 7, p. 1319-1325Article in journal (Refereed)
    Abstract [en]

    We review the techniques used for fabrication of bulk submicrometer ferroelectric domain gratings in KTiOPO4 (KTP) and demonstrate that bulk Rb-doped KTiOPO4 (RKTP) is an excellent candidate for implementation of dense domain gratings. Compared to KTP, RKTP presents predominant domain propagation along the polar c-direction, substantially reduced lateral domain broadening, and higher poling yield. As a result we obtain homogeneous sub-μm periodic poling of RKTP with a period of 690 nm in 1 mm thick samples.

  • 124158.
    Zukauskas, Andrius
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Thilmann, Nicky
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    5 mm thick periodically poled Rb-doped KTP for high energy optical parametric frequency conversion2011In: Optical Materials Express, ISSN 2159-3930, Vol. 1, no 2, p. 201-206Article in journal (Refereed)
    Abstract [en]

    A 5 mm thick periodically poled bulk Rb-doped KTiOPO4 (KTP) crystal with a period of 38.86 μm was fabricated by electric field poling. Chemical etching and optical evaluation show a high quality of the periodic ferroelectric domain structure through the whole crystal aperture. The fabricated quasi-phase matching (QPM) device was used in an optical parametric oscillator pumped at 1064 nm with 12 ns pulses at 100 Hz repetition rate to generate 60 mJ parametric radiation with a conversion efficiency of 50%.

  • 124159.
    Zukauskas, Andrius
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Thilmann, Nicky
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    5 mm Thick Periodically Poled Rb:KTiOPO4 for High Power Optical Frequency Conversion2011In: Advanced Solid State Photonics 2011, 2011Conference paper (Refereed)
    Abstract [en]

    A periodically poled bulk Rb-doped KTiOPO 4crystal with 5 mm aperture was fabricated at room temperature. The ferroelectric domain structure is shown to be homogeneous across the whole aperture with a deffof 11 pm/V.

  • 124160.
    Zukauskas, Andrius
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Thilmann, Nicky
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    High Fidelity Large Aperture Periodically Poled Rb:KTiOPO(4) for High Energy Frequency Conversion2011Conference paper (Refereed)
    Abstract [en]

    We demonstrate periodic poling of 5 mm thick Rb-doped KTiOPO(4) crystals at room temperature. The ferroelectric domain grating is shown to be uniform and homogeneous across the whole crystal aperture.

  • 124161.
    Zukauskas, Andrius
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Thilmann, Nicky
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Periodically poled KTiOAsO4 for highly efficient midinfrared optical parametric devices2009In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 95, no 19Article in journal (Refereed)
    Abstract [en]

    We demonstrate high pattern-fidelity periodic poling of KTiOAsO4 at room temperature. The periodically poled crystal shows a d(eff) of 10.1 pm/V and is used in an optical parametric oscillator pumped at 1064 nm to generate parametric radiation at 1538 and 3452 nm with a conversion efficiency of 45%.

  • 124162.
    Zukauskas, Andrius
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Thilmann, Nicky
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Periodically Poled KTiOAsO4 For Mid-Infrared Light Generation2010In: Advanced Solid-State Photonics 2010, 2010Conference paper (Refereed)
    Abstract [en]

    A periodically poled KTiOAsO4crystal was fabricated at room temperature. The poled crystal shows a deffof 10.1 pm/V and gives a parametric conversion efficiency of 45%.

  • 124163.
    Zukauskas, Andrius
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Viotti, Anne-Lise
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Coetzee, Riaan Stuart
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Liljestrand, Charlotte
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Recent advances in sub-mu m PPKTP for non-linear interactions with counter-propagating photons2019In: NONLINEAR FREQUENCY GENERATION AND CONVERSION: MATERIALS AND DEVICES XVIII / [ed] Schunemann, PG Schepler, KL, SPIE-INT SOC OPTICAL ENGINEERING , 2019, article id UNSP 109020GConference paper (Refereed)
    Abstract [en]

    Mirrorless optical parametric oscillators (MOPO) represent a special class of parametric devices based on three-wave nonlinear interaction in which the generated photons counter-propagate. Owing to the phase-matching condition of the counter-propagating waves, MOPOs can sustain oscillation without mirrors and present unique and useful tuning and spectral properties. In this paper, we will review our recent advances in structuring technology to achieve quasi-phase matching periodicities as short as 500 nm in Rb-doped KTiOPO4, which are necessary to compensate for the large phase mismatch. We will also review the performance of MOPOs both in the ps- and ns- pumping regime. In the latter, our crystals reach single-pass conversion efficiencies exceeding 50%, with mJ-level output energies.

  • 124164.
    Zukauskas, Andrius
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Viotti, Anne-Lise
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Liljestrand, Charlotte
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics. KTH, School of Engineering Sciences (SCI), Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics. KTH, School of Engineering Sciences (SCI), Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics. KTH, School of Engineering Sciences (SCI), Physics.
    Cascaded counter-propagating nonlinear interactions inhighly-efficient sub-μm periodically poled crystals2017In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, article id 8037Article in journal (Refereed)
    Abstract [en]

    Mirrorless optical parametric oscillators (MOPOs) are very attractive parametric devices that rely on the nonlinear interaction of counter-propagating photons to inherently establish distributed feedback, without the use of external mirrors or surface coatings. These devices offer unique spectral and coherence properties that will benefit a large variety of applications ranging from spectroscopy to quantum communications. The major obstacle in exploiting their full potential is ascribed to the difficulty in engineering a nonlinear material in which the generation of counter-propagating waves can be phase matched. Here we present a reliable and consistent technique for fabrication of highly-efficient sub-micrometer periodically poled Rb-doped KTiOPO4. We experimentally demonstrate the first cascaded counter-propagating interactions in which the generated forward signal serves as a pump for a secondary MOPO process, reaching pump depletion larger than 60%. The cascaded process exemplifies the high efficiency of our nonlinear photonic structures. Our domain-engineering technique paves the way to realize counter-propagating schemes and devices that have been deemed unfeasible until now.

  • 124165.
    Zuleger, Stefan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Modeling Sheet Forming of CompositeAerospace Component2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The aerospace industry becomes more and more accustomed with automated processing.Current manufacturing techniques are under development for higher automation. Within thiswork the behavior of prepreg material during forming is investigated, conducting simulationson previously performed experiments at SAAB AB. The aim is to implement materialbehavior in the AniForm Virtual Forming Tool simulation. The results of various experimentshave been combined to generate the basic material properties to assemble the materialbehavior and the experiment. With the use of investigated simplifications, the possibilities ofthe AniForm Virtual Forming Tool are used to compare two experiments conducted. Byrelating the simulations of wrinkled and non-wrinkled trials, the analysis of stresses andstrains within the simulation output is conducted. With the outcomes of these simulations,previously taken assumptions on fiber direction behavior are investigated. With the resultsshowing no geometrical wrinkling of the prepreg material itself, indicators for wrinkling areexamined on the output of the results. It can be seen that looking at various parametersexclusively does not necessarily explain the wrinkling of the prepreg material. Multiplefactors need to be taken into account at the same time. The results indicate that alignment ofstress- and strain behavior next to the fiber angle deviations play important parts in futureinvestigations regarding wrinkle development.Die Luftfahrtindustrie wird mehr und mehr mit automatisierten Prozessen vertraut.Fertigungstechnologien werden in Bezug auf einen höheren Automatisierungsgrad entwickelt.Innerhalb dieser Arbeit wird das Verhalten von Prepreg Material während des Formprozessesuntersucht, indem bereits durch die SAAB AB durchgeführte Experimente simuliert werden.Das Ziel ist, das Materialverhalten in die Simulationen mit dem AniForm Virtual FormingTool einzubinden. Die Resultate verschiedener Experimente werden zusammen geführt, umdie Materialeigenschaften für das Prepreg sowie die Simulation zusammen zu stellen. Durchdie Nutzung untersuchter Vereinfachungen werden die Möglichkeiten des AniForm VirtualForming Tools genutzt, um zwei durchgeführte Experimente zu prüfen. Durch dasvergleichen der Simulationsergebnisse von Experimenten mit und ohne Faltenbildung könnendie Resultate im Hinblick auf Spannungen und Dehnungen analysiert werden. Außerdem wirdIImit den Ergebnissen der Simulation das vorausgesagte Verhalten von Faserrichtungenuntersucht. Da die Ergebnisse keine geometrische Faltenbildung des Prepreg Materials selbstzeigen, werden andere Indikatoren für die Faltenbildung untersucht. Es lässt sich erkennen,dass das Betrachten von einzelnen Parametern ohne Verknüpfung mit anderen Resultaten eineeventuelle Faltenbildung im Prepreg Material nicht notwendiger weise erklären kann.Verschiedene Faktoren müssen gleichzeitig betrachtet werden. Die Resultate deuten daraufhin, dass die Ausrichtung von Stress- und Dehnungs-Verhalten sowie die Abweichungen derFaserwinkel eine wichtige Rolle bei zukünftigen Betrachtungen von Faltenbildung spielen.

  • 124166.
    Zuleta, Marcelo
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Electrochemical and ion transport characterisation of a nanoporous carbon derived from SiC2005Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    In this doctoral project, a relatively new form of carbon material, with unique narrow pore size distribution around 7 Å and with uniform structure, has been electrochemically characterised using the single particle microelectrode technique. The carbon has been used as electrode material for supercapacitors. This type of capacitors is used as high power energy buffers in hybrid vehicles and for stationary power backup. The principle for the microelectrode technique consists of connecting a carbon particle with a carbon fibre by means of a micromanipulator. The single particle and carbon fibre together form a microelectrode. Combination of this technique with electroanalytical methods such as cyclic voltammetry and potential step measurements allows for the survey of electrochemical phenomena and for the determination of ion transport parameters inside the nanopores.

    A mathematical model based on Fick’s second law, for diffusion of ions inside the nanopores at non steady state, was used for the determination of effective diffusion coefficients (Deff). The coefficients were calculated from an asymptotic solution of Fick’s equation, applied for a thin layer adjacent to the external surface of the carbon particles and valid for the current response in a short time region. Another asymptotic solution was obtained, using spherical geometry and valid for the current response in a long time region.

    In this doctoral work, the carbon particles have been exposed to potential cycling, which mimics that of large electrodes during operation of a double layer capacitor. The potential-current response, E-I, for the nanoporous carbon, shows a pure capacitive behaviour between –0.5 V and 0.1 V vs. the Hg|HgO reference electrode. The detection of the faradaic processes beyond these potentials was possible by lowering of the voltammometric sweep rate. The electrochemical processes occurring at positive and at negative potential were investigated separately.

    Cyclic voltammometric measurements showed that the chemisorption of hydroxyl groups, occurring between 0.1 and 0.3 V, leads to a mild oxidation of the carbon structure, resulting in surface groups containing an oxygen atom at a specific carbon site (e.g., phenolic or quinine type). These oxygen-containing surface groups caused an increase of the specific capacitance, which remained constant throughout a number of voltammometric cycles. The Deff decreased on the other hand with the number of cycles. The Deff decreases also with the positive potential. The evaluation of Deff indicates adsorption of hydroxyl groups and an increase of the effective tortuosity of the pore system.

    The oxidation of the carbon particles, between 0 and 0.5 V, leads to more extensive oxidation and to surface groups containing two oxygen atoms at a single carbon site, followed by formation of carbonate ions. The oxygen-containing surface groups and carbonate ions formed at these potentials do not contribute to the specific capacitance and drastically retard or obstruct the ion transport inside the nanopores.

    At negative potentials the carbon particles show a dominantly capacitive behaviour. The faradaic processes taking place below –0.5 V vs. Hg|HgO reference electrode are generation and adsorption of hydrogen. These processes do not perturb significantly the electrochemical and ion transport properties of the nanoporous carbon particles. It was found that hydrogen generation occurs at –0.5 V vs. Hg|HgO and that two hydrogen oxidation processes take place at positive potentials. The results indicate that the weakly adsorbed hydrogen undergoes oxidation between 0 and 0.1 V and that the strongly adsorbed hydrogen is oxidised at more positive potentials.

    The single particle technique was adapted for the determination of diffusion coefficients of an organic electrolyte. The different size of the anions and cations caused different transport characteristics at negative and positive potentials. Slow cycling was found important for ion penetration inside the nanopores and for the evaluation of the effective diffusion coefficients.

    The effective diffusion coefficients for the nanoporous carbon using aqueous 6M KOH and 0.1M TEABF4 in acetonitrile were estimated to 1.4 (±0.8).10-9 cm2 s-1 and 1.3 (±0.4) 10-8 cm2 s-1, respectively.

  • 124167.
    Zuleta, Marcelo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Björnbom, Pehr
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Lundblad, Anders
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Characterization of the electrochemical and ion-transport properties of a nanoporous carbon at negative polarization by the single-particle method2006In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 153, no 1, p. A48-A57Article in journal (Refereed)
    Abstract [en]

    In this work, the electrochemical processes occurring in a nanoporous carbon, obtained from silicon carbide and used as negative electrode material for supercapacitors, have been investigated by means of the single-particle microelectrode method. The processes studied deal with hydrogen adsorption, evolution, and oxidation using 6 M KOH as electrolyte. It was found that adsorption of hydrogen started at -0.5 V, hydrogen evolution at -1.4 V vs Hg vertical bar HgO, and that hydrogen oxidation occurs in two steps. The first oxidation process takes place between 0 and 0.1 V, shown by a well-defined current peak on the voltammograms. The second oxidation stage occurs between 0.1 and 0.5 V, indicated by a successive increase in current with the number of cycles. It was also found that after the first oxidation process, subsequent cycling between -0.5 and -1 V leads to a larger accumulation of hydrogen inside the nanopores and to a decrease of the effective diffusion coefficient (D-eff) of potassium ions. Subsequent oxidation, in a second process, leads to a total consumption of hydrogen and to an increase of D-eff.

  • 124168.
    Zuleta, Marcelo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Björnbom, Pehr
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Lundblad, Anders
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Effects of pore surface oxidation on electrochemical and mass-transport properties of nanoporous carbon2005In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 152, no 2, p. A270-A276Article in journal (Refereed)
    Abstract [en]

    A new nanoporous (NP) carbon material with a high surface area and a narrow pore size distribution, around 8 A, has been used to investigate the effects that electrochemical oxidation at positive potentials exerts on the capacitance values and effective diffusion coefficients of ions inside the nanopores. An electroanalytical method, based on the single-particle microelectrode technique with micromanipulator, was applied to calculate the diffusion coefficients of 6 M KOH ions in NP carbon. The results were analyzed for short times using the Cottrell model and for long times using the spherical diffusion model. Using cyclic voltammetry, was found that different stages of oxidation took place between 0 and 0.5 V vs. Hg\HgO. After repeated cycling in the first region of oxidation (0-0.3 V), an activation leading to higher capacitance was observed, but the diffusion coefficients decreased from approximately 2 x 10(-9) to 0.5 x 10(-10) cm(2) s(-1). In the second region of oxidation (0.3-0.5 V), where CO2 and 02 evolution can occur, both the capacitance and the diffusion coefficients decreased more dramatically. The effective diffusion coefficients of ions of an activated carbon particle were dependent on the operation potential; decreasing by an order of magnitude when going from -0.3 to +0.3 V. The results are discussed in terms of chemisorption of small oxygen functional groups (-OH or C=O) and ionic interaction with the pore wall.

  • 124169.
    Zuleta, Marcelo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Björnbom, Pehr
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Lundblad, Anders
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Nurk, G.
    Kasuk, H.
    Lust, E.
    Determination of diffusion coefficients of BF4- inside carbon nanopores using the single particle microelectrode technique2006In: Journal of Electroanalytical Chemistry, ISSN 0022-0728, E-ISSN 1873-2569, Vol. 586, no 2, p. 247-259Article in journal (Refereed)
    Abstract [en]

    The electrochemical and mass transport properties of TEABF(4) in a nanoporous (NP) carbon material, obtained from silicon carbide, was studied using single particles and a microelectrode technique. The carbon particles of size 100-200 mu m were studied by cyclic voltammetry and potential step measurements. The effective diffusion coefficients (D-eff) were calculated starting from the asymptotic solutions of Fick's second law for short and long time regions. The results show that cycling at low sweep rates was needed in order for the electrolyte to penetrate the inner porosity of the particles. The carbon material showed different electrochemical and mass transport properties depending on the applied potential. At negative polarisation, the results suggest that TEA(+) was adsorbed on the pore wall, however, being transported very slowly inside the pores. The average D-eff after cycling at both positive and negative potentials was 1.1(+/- 0.4) x 10(-8) cm(2) s(-1), using the Cottrell relation and 1.5(+/- 0.6) x 10(-8) cm(2) s(-1), using the radial diffusion solution. The average value of D-eff after cycling at negative potentials was 1.7(+/- 0.6) x 10(-8) cm(2) s(-1) using both mathematical solutions.

  • 124170.
    Zuleta, Marcelo
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Bursell, Martin
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Björnbom, Pehr
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Lundblad, Anders
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Determination of the effective diffusion coefficient of nanoporous carbon by means of a single particle microelectrode technique2003In: Journal of Electroanalytical Chemistry, ISSN 0022-0728, E-ISSN 1873-2569, Vol. 549, p. 101-108Article in journal (Refereed)
    Abstract [en]

    A single particle microelectrode technique with a micromanipulator was applied and adapted for characterisation of mass transport properties of ionic species in a high surface area nanoporous carbon, with uniform pore size of 8 Angstrom. The effective diffusivity of 6 M KOH in this material was determined by means of potential step experiments on nanoporous carbon particles of different sizes. The results were analysed for short times (Cottrell model) and for long times (spherical diffusion model). The average effective diffusion coefficient for short and long times was 1.5x10(-9) and 1.2x10(-9) cm(2) s(-1), respectively. The relatively small diffusivity values are discussed in terms of interaction between the ion hydration shell and water molecules adsorbed on the pore wall.

  • 124171.
    Zuleta, Marcelo
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Bursell, Martin
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Lundblad, Anders
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Characterization of ion transport in a nanoporous carbon for double layer capacitors2000In: Proceedings of Advances in Science and technology 29: (Mass and Charge Transport in Inorganic Materials: Fundamentals to devices, part A), 2000, p. 439-446Conference paper (Refereed)
  • 124172.
    Zuleta, Marcelo
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Edvinsson, Tomas
    Yu, Shun
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Ahmadi, Sareh
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Boschloo, Gerrit
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Hagfeldt, Anders
    Light-induced rearrangements of chemisorbed dyes on anatase(101)2012In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 14, no 30, p. 10780-10788Article in journal (Refereed)
    Abstract [en]

    Photoinduced molecular rearrangements are important in daily events essential for life such as visual perception and photo-protection of light harvesting complexes in plants. In this study we demonstrate that similar photoarrangements appear in an analogous technological application where the device performance is controlled by chromophores in sensitized anatase TiO2, one of the main components for light-harvesting in dye-sensitized solar cells (DSC). STM reveals that illumination leads to distortions of organic dyes containing conjugated backbones and of cis-bis(isothiocyanate)-bis-(2,2'-bipyridyl-4,4'-dicarboxylate)ruthenium(II)-bis(tetrabutylammonium), known as N719. The dyes were adsorbed in a closed-packed mode on an anatase(101) single crystal surface and imaged in the dark and under white light illumination in an ultra-high vacuum (UHV). STM images of N719 clearly suggest rearrangements caused by rotation of the dye. Conversely, organic dyes rearrange by photoisomerization depending on the number of double bonds, their position in the molecular structure and on the ligand modifications.

  • 124173.
    Zuleta, Marcelo
    et al.
    KTH, School of Information and Communication Technology (ICT).
    Yu, Shun
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Ahmadi, Sareh
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Boschloo, Gerrit
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Hagfeldt, Anders
    Monitoring N719 Dye Configurations on (1 x n)-Reconstructed Anatase (100) by Means of STM: Reversible Configurational Changes upon Illumination2010In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, no 16, p. 13236-13244Article in journal (Refereed)
    Abstract [en]

    We report experimental results concerning the STM imaging of cis-bis (isothiocyanate)-bis-(2,2'-bipyridyl-4,4'dicarboxylate)ruthenium(II)bis( tetrabutylammonium) dye (known as N719) adsorbed on a single crystal of anatase TiO2(100). The cleaning pretreatment, by sputtering and annealing, of TiO2(100) yields a reproducible (1 x n) surface reconstruction. Previous to dye deposition, TiO2 was covered with one monolayer of 4-tert-butylpyridine (4-TBP) in ultrahigh vacuum (UHV) in order to protect the surface against air contamination. N719 was subsequently deposited by dipping the crystal into the dye solution. 4-TBP was removed partially in the solution and totally by heating the sample to around 285-300 degrees C in UHV. The images of the deposited 4-TBP on TiO2(100) revealed a complete surface coverage showing three modes of adsorption on TiO2. The relatively uncomplicated desorption of 4-TBP enables the accommodation and chemisorption of most N719 molecules directly onto the TiO2 surface. The STM imaging of N719 was affected, in a reversible way, by illumination, because the quality of the image changed after a few hours in the dark or under illumination conditions. The results presented herein are discussed in terms of changes in molecular configurations and in open circuit potentials.

  • 124174. Zulkafli, Zed
    et al.
    Perez, Katya
    Vitolo, Claudia
    Buytaert, Wouter
    Karpouzoglou, Timothy
    Public Administration and Policy Group, Wageningen University, Netherlands.
    Dewulf, Art
    De Bièvre, Bert
    Clark, Julian
    Hannah, David M.
    Shaheed, Simrita
    User-driven design of decision support systems for polycentric environmental resources management2017In: Environmental Modelling & Software, ISSN 1364-8152, E-ISSN 1873-6726, Vol. 88, p. 58-73Article in journal (Refereed)
    Abstract [en]

    Open and decentralized technologies such as the Internet provide increasing opportunities to create knowledge and deliver computer-based decision support for multiple types of users across scales. However, environmental decision support systems/tools (henceforth EDSS) are often strongly science-driven and assuming single types of decision makers, and hence poorly suited for more decentralized and polycentric decision making contexts. In such contexts, EDSS need to be tailored to meet diverse user requirements to ensure that it provides useful (relevant), usable (intuitive), and exchangeable (institutionally unobstructed) information for decision support for different types of actors. To address these issues, we present a participatory framework for designing EDSS that emphasizes a more complete understanding of the decision making structures and iterative design of the user interface. We illustrate the application of the framework through a case study within the context of water-stressed upstream/downstream communities in Lima, Peru.

  • 124175.
    Zulu, Andrew Wisdom
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Thick Composite Properties and Testing Methods2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In most application to date reinforced carbon fiber composites have been used in relatively smaller thickness, less than 10mm thick and essentially for carrying in-plane loads. As a result, design and testing procedures were developed which reflected the need to understand the in-plane response of the material. recently, engineers and designers have begun to use reinforced carbon fiber composites in thicker sections, where an understanding of the through-thickness response is of para-mount importance in designing reliable structures, particularly where the through-thickness strength has a controlling influence on the overall structural strength of the component. In this thesis tests will be done on carbon fiber non-crimp fabric (NCF) which will be loaded in compression and shear and elastic moduli and strength will be evaluated. In characterizing the through-thickness mechanical properties of a composite, the objective is to produce a state of stress in the test specimen which is uniform and will repeatedly measure the true properties with accuracy. In this study, specimens were machined from two blocks of thick (~20 mm) laminates of glass/epoxy and NCF carbon fiber infused with vinylester and tested in compression, and shear.

  • 124176.
    Zumalacarregui, Miguel
    et al.
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.
    Bellini, Emilio
    Sawicki, Ignacy
    Lesgourgues, Julien
    Ferreira, Pedro G.
    hi_class: Horndeski in the Cosmic Linear Anisotropy Solving System2017In: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, E-ISSN 1475-7516, no 8, article id 019Article in journal (Refereed)
    Abstract [en]

    We present the public version of hi cl a ss (www . hiclass-code . net), an extension of the Boltzmann code CLASS to a broad ensemble of modifications to general relativity. In particular, hi cl a ss can calculate predictions for models based on Horndeski's theory, which is the most general scalar-tensor theory described by second-order equations of motion and encompasses any perfect-fluid dark energy, quintessence, Brans-Dicke, f( R) and covariant Galileon models. hi-class has been thoroughly tested and can be readily used to understand the impact of alternative theories of gravity on linear structure formation as well as for cosmological parameter extraction.

  • 124177.
    Zumalacarregui, Miguel
    et al.
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA. Berkeley Center for Cosmological Physics, LBNL, University of California at Berkeley, Berkeley, CA 94720, United States; Institut de Physique Théorique, Université Paris Saclay CEA, CNRS, Gif-sur-Yvette, 91191, France.
    Seljak, U.
    Limits on Stellar-Mass Compact Objects as Dark Matter from Gravitational Lensing of Type Ia Supernovae2018In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 121, no 14, article id 141101Article in journal (Refereed)
    Abstract [en]

    The nature of dark matter (DM) remains unknown despite very precise knowledge of its abundance in the Universe. An alternative to new elementary particles postulates DM as made of macroscopic compact halo objects (MACHO) such as black holes formed in the very early Universe. Stellar-mass primordial black holes (PBHs) are subject to less robust constraints than other mass ranges and might be connected to gravitational-wave signals detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO). New methods are therefore necessary to constrain the viability of compact objects as a DM candidate. Here we report bounds on the abundance of compact objects from gravitational lensing of type Ia supernovae (SNe). Current SNe data sets constrain compact objects to represent less than 35.2% (Joint Lightcurve Analysis) and 37.2% (Union 2.1) of the total matter content in the Universe, at 95% confidence level. The results are valid for masses larger than ∼0.01 M (solar masses), limited by the size SNe relative to the lens Einstein radius. We demonstrate the mass range of the constraints by computing magnification probabilities for realistic SNe sizes and different values of the PBH mass. Our bounds are sensitive to the total abundance of compact objects with M0.01 M and complementary to other observational tests. These results are robust against cosmological parameters, outlier rejection, correlated noise, and selection bias. PBHs and other MACHOs are therefore ruled out as the dominant form of DM for objects associated to LIGO gravitational wave detections. These bounds constrain early-Universe models that predict stellar-mass PBH production and strengthen the case for lighter forms of DM, including new elementary particles.

  • 124178.
    Zuna, Lea
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatics.
    Understanding and Improving the Utilization of Web and Mobile GIS Solutions for Outdoor Environment Management2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Trees, plants, water,playgrounds, green areas and benches are just a few out of many components thatforms a pleasant outdoor environment. Not only are management and maintenancenecessary to keep the environment clean and nice for everybodys well-being, butalso documentation and records of geographic data representing the outdoorenvironment. Management and maintenance requires plans and cost calculationwhere the geographic data is used as a basis. The data needs to therefor bereliably and continuously controlled and updated, especially due to thecomponents of an outdoor environment constant change and move. An effective wayto store, visualize and manage data related to geographic locations is to useGeographic Information System (GIS) solutions.This thesis is applying a user-centered design approach to derive a prototypethat encourages use of web and mobile GIS solutions in the field duringcontrols and maintenance and thereby resulting in more efficient data updateprocedures and maintenance operations. A case study is performed involving thetwo housing companies Svenska Bostäder and Stockholmshem where management andmaintenance of geographic data representing the outdoor housing environment isinvolved in their work and is today managed by primitive methods. Theuser-centered design approach Focus Rapid Contextual Design is applied toderive user requirements in terms of functionality and user interface forfurther use to develop and integrate a prototype within the housing companiesexisting GIS solutions. The overall objective is to investigate, document andevaluate how an user-centered design approach can be applied to introduce webGIS solutions that will improve the workflow between office and field, this byreducing the number of steps performed during a field control by replacingprimitive tools such as paper and PDF maps used today with the suggested GISsolutions. The potential long term impact of this study is to encourage thelayman users that are working in field to use these new solutions instead ofprimitive methods, this by adapting functionalities and user interface in theweb and mobile GIS solutions according to the layman users needs and levels byapplying the user-centered design approach.The Focus Rapid Contextual Design method shows to be successful in terms ofgathering and managing user data in a structured way. Due to tight timeschedule and project resource limitations, an iterative prototype process whereuser feedback is used to redesign the prototype for further improvement was notperformed. Only one prototype evaluation was performed and did not take placein context of use. This lead to weak user feedback meaning that the prototypemost likely could have been further adapted to the users needs if an iterativeprocess that took place in context of use was performed. It would most likelyfacilitate the faster adaptation for the web GIS solutions in the housingcompanies daily work. Encouraging layman users to change from manual to digitalsystems is seen as one if the major challenges during this thesis. Even thougha user centered design approach contributes to reach the potential long termimpact of this study which is to encourage layman user to use the suggestedsolutions, most likely organizational changes and policies are needed toaccomplish process changes and make field workers change their working manners.A small case study like the one performed in this thesis could possibly havebeen performed excluding the Working Models and Storyboarding in the Focus RapidContextual Design method without affecting the final result, this to gain moretime for the iterative prototype process as well as time for involving moreusers. Doing so could improve the work in this study to better reach the statedgoals.

  • 124179.
    Zuniga-Arias, Guillermo
    et al.
    Wageningen University.
    Meijer, Sebastiaan
    Wageningen University.
    Hofstede, Gert Jan
    Wageningen University.
    Ruben, Ruerd
    Wageningen University.
    Bargaining power and revenue distribution in the Costa Rican mango supply chain: a gaming simulation approach with local producers2007In: Journal on Chain and Network Science, ISSN 1569-1829, E-ISSN 1875-0931, Vol. 7, no 2, p. 143-160Article in journal (Refereed)
    Abstract [en]

    By the time a European consumer eats a Costa Rican mango, the product has been traded in several transactions between producers, traders, retailers and consumers. This paper investigates the position of Costa Rican smallholders in the mango supply chain in terms of bargaining power and revenue distribution. It examines data derived using a specially developed research tool: the Mango Chain Game (MCG), a gaming simulation that mimics the negotiation conditions in the Costa Rican mango supply chain. The MCG defines roles for all agents in the chain and records transaction attributes. Five sessions with the MCG were played with different groups of mango producers, resulting in a data set of 82 transactions and 43 bargaining power positions. Bargaining power was assessed at a 10-point Likert scale. Revenue distribution was measured in terms of value added. The results show that self-perceived bargaining power was dependent on negotiation skills, wealth and good partnership of the negotiators, but independent of market imperfections. Revenue distribution was related to the bargaining power of the trading partner, risk perception and the duration of the contract. Conclusions include that using a gaming simulation as data source can help identify less tangible issues in supply chain research, which is a new field of application for gaming simulations. Agency cooperation, skills and being able to bear risks play a role for improving the efficiency of the mango supply chain in Costa Rica as seen from a producers' perspective. The gaming results indicate that initiatives for improving the bargaining power of producers are more promising if they focus on improving skills and relations in trade rather than on solving market imperfections.

  • 124180.
    Zuniga-Arias, Guillermo
    et al.
    Wageningen University.
    Meijer, Sebastiaan
    Wageningen University.
    Ruben, Ruerd
    Wageningen University.
    Hofstede, Gert Jan
    Wageningen University.
    Bargaining power in mango supply chains: An experimental gaming approach2006In: International Agri-Food Chains and Networks: Management and Organization / [ed] J. Bijman, S.W.F. Omta,,, J.H.M. Wijnands & E.M.F. Wubben, Wageningen: Wageningen Academic Publishers, 2006, p. 231-255Conference paper (Refereed)
    Abstract [en]

    Transactions between producers, traders, retailers and consumers in the mango supply chain are characterised by contractual arrangements concerning outlet choice, price, volume, quality and frequency. We used a gaming simulation approach to identify the intrinsic agency characteristics that typically result in specific contracts and assess the underlying differences in perceived bargaining power and that are conducive for reaching these arrangements. A stylised mango chain game is developed that permits the appraisal of different sets of delivery transactions. Agency roles are defined for all participants in the mango supply chain. Attributes of all transactions are recorded, also permitting contract breach, hold-up and repeated contracts. Bargaining power is assessed at a 10-point Likert scale and revenue distribution is measured in terms of money. The game has been played five times with different groups of mango producers, resulting in a data set of 82 transactions and 43 bargaining power positions. The game design closely mimics the negotiation conditions in the Costa Rican mango supply chain. The game results confirm the important role of trust and information exchange for reaching mutually acceptable contracts. Bargaining power is strongly related to the negotiation skills, wealth and partnerships of the negotiator. Revenue distribution is related to the bargaining power of the trade partner, risk and the length of the contract. Transparency and agency cooperation thus play important roles for improving the efficiency of mango supply chains in Costa Rica.

  • 124181.
    Zunino, Guido
    KTH, Superseded Departments, Numerical Analysis and Computer Science, NADA.
    Simultaneous localization and mapping for navigation in realistic environments2002Licentiate thesis, monograph (Other scientific)
  • 124182.
    Zuo, Haisu
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.).
    How could the innovation policy be implemented effectively?: A comparative analysis of institution between Sweden and China2011Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
  • 124183.
    Zuo, Minyu
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Enhanced phosphorus removal from wastewater using virgin and modified slags: performance, speciation and mechanisms2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Argon oxygen decarburization slag (AOD) was tested in batch and column experiments to investigate its phosphorus (P) removal performance. The effects of factors such as AOD dose, initial P concentration of the feeding solution, and aging on the P removal ability of the slags were analyzed. In a column experiment, electric arc furnace slag (EAF), blast furnace slag (BFS) and AOD were combined in five different ways to determine optimal conditions for P removal. In another column experiment, the three types of slag were modified with polyethylene glycol (PEG) and NaOH to adjust their dissolution properties and the effect on P removal performance was examined. In the batch experiments, AOD exhibited very promising P removal ability. It removed 94.8% of P from 6.5 mg P L-1 synthetic solution in 4 hours with a dose of 5 g L-1. Maximum P removal capacity of 27.5 mg P g-1 was achieved. In the dual-filter column experiment, the column packed with only EAF had the best P removal performance (consistently above 93%). Amorphous calcium phosphate (ACP) was identified as the main P species in the five slag samples collected from the outlet chambers. The contributions from crystalline calcium phosphate (Ca-P) and P adsorbed on iron/aluminum (hydr)oxides were greater in samples from the inlet chambers. The P speciation results revealed that P was predominantly removed by the slags through formation of ACP. The second column experiment showed that modification with PEG and NaOH solution only enhanced short-term P removal by the slags. However, exhaustion of the modified slags occurred much earlier, indicating that the modification process had shortened the lifespan of the slags. Untreated AOD showed better P removal than untreated EAF until pore volume 244, probably due to faster dissolution rate of gamma dicalcium silicate (dominating in AOD according to the XRD results) than of beta dicalcium silicate (dominating in EAF).

  • 124184.
    Zuo, Minyu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Renman, Gunno
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Effect of aging on phosphorus removal of metallurgical slag and heat reactivation of aged slag2016Conference paper (Other academic)
  • 124185.
    Zuo, Minyu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Renman, Gunno
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering. Swedish University of Agricultural Sciences, Sweden.
    Klysubun, Wantana
    Dual slag filters for enhanced phosphorus removal from domestic waste water: performance and mechanisms2018In: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 25, no 8, p. 7391-7400Article in journal (Refereed)
    Abstract [en]

    The phosphorus (P) removal of five combinations of dual filters consisting of blast furnace slag (BFS), argon oxygen decarburisation slag (AOD) and electric arc furnace slag (EAF) was evaluated in column experiments with domestic waste water. The columns were fed with waste water for 24 days. The column with only EAF had the best P removal performance (above 93% throughout the experiment). The speciation of the bound P was evaluated by P K-edge X-ray absorption near-edge structure (XANES) spectroscopy. In all five columns, the main P species of the slag packed in the outlet chamber was amorphous calcium phosphate (ACP). In samples from the inlet chambers, the contributions from crystalline Ca phosphates, P adsorbed on gibbsite and P adsorbed on ferrihydrite were usually much greater, suggesting a shift of P removal mechanism as the waste water travelled from the inlet to the outlet. The results provide strong evidence that P was predominantly removed by the slags through the formation of ACP. However, as the pH decreased with time due to the progressively lower dissolution of alkaline silicate minerals from the slag, the ACP was rendered unstable and hence redissolved, changing the P speciation. It is suggested that this process strongly affected the lifespan of the slag filters. Of the slags examined, EAF slag had the best P removal characteristics and BFS the worst, which probably reflected different dissolution rates of alkaline silicates in the slags.

  • 124186.
    Zuo, Minyu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Renman, Gunno
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering. Swedish University of Agricultural Sciences, Uppsala.
    Klysubun, Wantana
    Dual slag filters for enhanced phosphorus removal from domestic wastewater: performance and mechanismsIn: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499Article in journal (Refereed)
  • 124187.
    Zuo, Minyu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Renman, Gunno
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering. Swedish University of Agricultural Sciences, Uppsala.
    Klysubun, Wantana
    Synchrontron Light Research Institute.
    Phosphorus removal performance and lifespan prediction through mineralogical composition: A comparative study of AOD and EAF slagsManuscript (preprint) (Other academic)
  • 124188.
    Zuo, Minyu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Renman, Gunno
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Klysubun, Wantana
    Phosphorus removal performance and lifespan prediction through minerology analysis: A comparative study of AOD and EAF slagsManuscript (preprint) (Other academic)
  • 124189.
    Zuo, Minyu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Renman, Gunno
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. Swedish University of Agricultural Sciences, Sweden.
    Renman, Agnieszka
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Phosphorus removal performance and speciation in virgin and modified argon oxygen decarburisation slag designed for wastewater treatment2015In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 87, p. 271-281Article in journal (Refereed)
    Abstract [en]

    Argon oxygen decarburisation (ADD) slag may be used for phosphorus (P) removal, as its high pH and weatherable calcium (Ca) minerals provide sufficient Ca2+ and OH- for calcium phosphate (Ca-PO4) precipitation. This study examined the P removal performance of AOD slag for use as wastewater treatment material. Batch experiments were carried out using both synthetic P solution and real wastewater, followed by chemical modelling and X-ray absorption near edge structure (XANES) spectroscopy. The influences of initial P concentration, slag dose and modification by polyethylene glycol (PEG), an effective agent for generation of porous materials, were investigated to determine the optimal conditions for P removal by AOD slag. It was found that virgin AOD slag removed 94.8% of P from a synthetic P solution in 4 h and 97.8% in 10 h. This high P removal was accompanied by a rapid increase in pH from 7.0 to 10.74. The maximum P removal capacity (PRC) from synthetic P solution ranged from 1.3 to 27.5 mg P g(-1). The optimal AOD dose for P removal from wastewater, determined in 8-h batch experiments, was 25 g L-1. PEG modification increased the reaction rate and resulted in higher final pH, increasing PRC by 47.9%. Combined Visual MINTEQ and XANES analysis for detailed examination of P removal mechanisms revealed that the main P removal mechanism was precipitation of calcium phosphate. According to the XANES analysis, the main Ca-PO4 precipitate formed on virgin AOD slag under low initial P concentration and high pH was apatite, while brushite was the dominant product at high initial P concentration and low pH.

  • 124190.
    Zurauskaite, Laura
    KTH, School of Information and Communication Technology (ICT).
    Fabrication and electrical characterization of Ge/GeOx/Al2O3/HfO2 MOS capacitors2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Continuous scaling of complementary metal oxide semiconductor (CMOS) devices has led to constant increase in device performance. However, as scaling becomes more difficult with every technological node, alternative channel materials that could replace silicon (Si) are being investigated [1]. Germanium (Ge) is an attractive material because of its four times higher hole mobility and twice higher electron mobility compared to silicon [2]. Nevertheless, Ge suffers from surface passivation issues that need further investigation.

    A modification of oxidation through a barrier layer method proposed by Takagi group[3] has been employed for the fabrication of MOS capacitors. Ozone oxidation has been performed in-situ in atomic layer deposition (ALD) chamber using Al2O3 layer as a barrier. Combinations of barrier thickness and ozone generator power have been investigated together with the influence of the oxidation time. Electrical characterization has revealed that the Ge/oxide interface is improved while employing high ozone generator power oxidation through a thin (~0.47 nm) barrier as well as prolonged oxidation times up to 15 min. Interface state density has been suppressed to lowto mid 1012 cm-2eV-1.

  • 124191.
    Zurauskaite, Laura
    et al.
    KTH, School of Information and Communication Technology (ICT), Electronics, Integrated devices and circuits.
    Hellström, Per-Erik
    KTH, School of Information and Communication Technology (ICT), Electronics.
    Östling, Mikael
    KTH, School of Information and Communication Technology (ICT), Electronics, Integrated devices and circuits.
    The impact of atomic layer depositions on high quality Ge/GeO2 interfaces fabricated by rapid thermal annealing in O-2 ambient2017In: 2017 IEEE Electron Devices Technology and Manufacturing Conference, EDTM 2017 - Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 164-166, article id 7947553Conference paper (Refereed)
    Abstract [en]

    This work demonstrates high quality Ge/GeO2 interfaces fabricated by O-2 RTA that are degraded by a good quality SiO2 layer deposited by ALD. However, neither O-3 and H2O precursors commonly used during subsequent high-k ALDs nor Si precursor AP-LTO-330 do not degrade the interface. Thus Dit increase after SiO2 deposition is likely due to intermixing. Therefore, the effect of subsequent ALDs on the interface quality has to be considered while designing Ge-based gate stacks.

  • 124192.
    Zurauskaite, Laura
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electronics.
    Jones, L.
    Dhanak, V. R.
    Mitrovic, I. Z.
    Hellström, Per-Erik
    KTH, School of Electrical Engineering and Computer Science (EECS), Electronics.
    Östling, Mikael
    KTH, School of Electrical Engineering and Computer Science (EECS), Electronics.
    Investigation of Tm2Oj as a gate dielectric for Ge MOS devices2018In: ECS Transactions, Electrochemical Society, 2018, Vol. 86, no 7, p. 67-73Conference paper (Refereed)
    Abstract [en]

    In this work atomic layer deposited TnOj has been investigated as a high-k dielectric for Ge-based gate stacks. It is shown that when Tm203 is deposited on high-quality Ge/Ge02 gates, the interface state density of the gate stack is degraded. A series of post-deposition anneals are studied in order to improve the interface state density of Ge/GeO/TmjOs gates, and it is demonstrated that a rapid thermal anneal in O2 ambient can effectively reduce the interface state density to below 5-10" cmeV1 without increasing the equivalent oxide thickness. Fixed charge density in Ge/GeOx/Tm20j gates has also been investigated, and it is shown that while O2 post-deposition anneal improves the interface state density, the fixed charge density is degraded.

  • 124193. Zurauskiene, N.
    et al.
    Asmontas, S.S.
    Dargys, A.
    Kundrotas, J.
    Janssen, G.
    Goovaerts, E.
    Marcinkevicius, Saulius
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Koenraad, P.M.
    Wolter, J.H.
    Leon, R.
    Semiconductor nanostructures for infrared applications2004In: Functional Nanomaterials For Optoelectronics And Other Applications / [ed] Lojkowski, W; Blizzard, JR, Trans Tech Publications Inc., 2004, Vol. 99-100, p. 99-108Conference paper (Refereed)
    Abstract [en]

    The results of time-resolved photo luminescence (TRPL) and optically detected microwave resonance (ODMR) spectroscopy investigations of semiconductor quantum dots and quantum wells are presented. The ODMR spectra of InAs/GaAs QDs were detected via modulation of the total intensity of the QDs emission induced by 95 GHz microwave excitation and the exciton fine structure was studied. Very long life times (up to 10 ns) of photoexcited carriers were observed in this system using TRPL at low temperatures and excitation intensities promising higher responsitivity of such QDs for infrared photodetector development. The effects of proton and alpha particles irradiation on carrier dynamics were investigated on different InGaAs/GaAs, InAlAs/AlGaAs and GaAs/AlGaAs QD and QW systems. The results showed that carrier lifetimes in QDs are much less affected by proton irradiation than that in QWs. A strong influence of irradiation on PL intensity was observed in multiple QWs after high-energy alpha particles irradiation.

  • 124194. Zurauskiene, N.
    et al.
    Marcinkevicius, Saulius
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Janssen, G.
    Goovaerts, E.
    Notzel, R.
    Koenraad, P. M.
    Wolter, J. H.
    Optically detected microwave resonance and carrier dynamics in InAs/GaAs quantum dots2005In: Acta Physica Polonica. A, ISSN 0587-4246, E-ISSN 1898-794X, Vol. 107, no 2, p. 435-439Article in journal (Refereed)
    Abstract [en]

    The properties of small-sized high density InAs/GaAs quantum dots (emitting at 1.25 eV) are studied by means of optically detected microwave resonance spectroscopy and time resolved photoluminescence techniques. The results are discussed in terms of trapping and thermal escape of the carriers as well as their relaxation and recombination in quantum dots. The data are compared with those recently obtained on shallowly formed InAs quantum dot structures.

  • 124195.
    Zurita Ares, Benigno
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Park, Pan Gun
    KTH, School of Electrical Engineering (EES).
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Speranzon, Alberto
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Karl Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    On power control for wireless sensor networks: System model, middleware component and experimental evaluation2015In: 2007 European Control Conference, ECC 2007, 2015, p. 4293-4300Conference paper (Refereed)
    Abstract [en]

    In this paper, we investigate strategies for radio power control for wireless sensor networks that guarantee a desired packet error probability. Efcient power control algorithms are of major concern for these networks, not only because the power consumption can be signicantly decreased but also because the interference can be reduced, allowing for higher throughput. An analytical model of the Received Signal Strength Indicator (RSSI), which is link quality metric, is proposed. The model relates the RSSI to the Signal to Interference plus Noise Ratio (SINR), and thus provides a connection between the powers and the packet error probability. Two power control mechanisms are studied: a Multiplicative-Increase Additive-Decrease (MIAD) power control described by a Markov chain, and a power control based on the average packet error rate. A component-based software implementation using the Contiki operating system is provided for both the power control mechanisms. Experimental results are reported for a test-bed with Telos motes.

  • 124196.
    Zuxing, Li
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Assessment of Privacy in Distributed Detection Problems2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    As a promising technology, wireless sensor networks have a wide range of applications. However, the development of wireless sensor networks is stillin face of multiple challenges. Among these challenges, the privacy issue is acritical parameter involved in providing secure and reliable services and attracts much attention from researchers and engineers. In the last decade, alarge number of privacy solutions for wireless sensor networks have been proposed. However, most of them are taken as additional secure functionality blocks rather than being integrated in the original sensor network designs.

    In this thesis project, we will focus on the privacy assessment of a parallel distributed detection network, which represents a simplied physical-layer of wireless sensor networks. The security threat is assumed to come from a passive eavesdropper. Four privacy leakage criteria are proposed to evaluate the privacy issue of the distributed detection network in dierent scenarios. As references, the privacy leakages are evaluated by dierent criteria when the distributed detection system is optimized in the perspectives of Bayesian detection theory and information theory without considering the presence of the eavesdropper. Then, we propose the corresponding privacy-concerned distributed detection systems. Comparisons to the optimal detection systems are performed and they reveal the trade-off between privacy leakage suppression and detection performance degradation.

  • 124197. Zvolensky, T.
    et al.
    Chicherin, Dmitry
    Department of Radio Science and Engineering, SMARAD Centre of Excellence, Aalto University.
    Räisäinen, Antti
    Department of Radio Science and Engineering, SMARAD Centre of Excellence, Aalto University.
    Simovski, C.
    Sterner, Mikael
    KTH, School of Electrical Engineering (EES), Microsystem Technology.
    Oberhammer, Joachim
    KTH, School of Electrical Engineering (EES), Microsystem Technology.
    Hakojarvi, H.
    Leaky-wave antenna at 77 GHz2011In: Proceedings of the 41st European Microwave Conference, 2011, p. 1039-1042Conference paper (Refereed)
    Abstract [en]

    Microelectromechanical (MEMS) technology is being used for many purposes in reconfigurable devices due to its advantages compared to other technologies, e.g., varactors. In this paper MEMS are suggested to be used for the development of leaky-wave antenna for 77 GHz. Antenna comprises a right-left handed transmission line, where a microstrip is used as the right handed transmission line. The left handed loading comprises series reconfigurable MEMS capacitors and shunt narrow strip inductors. Analytical design, simulation and measurement of a planar leaky-wave antenna structure are carried out and compared.

  • 124198. Zwieg, Thomas
    et al.
    Cucarella, Victor
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Kauffeld, Michael
    Novel biomimetically based ice-nucleating coatings2007In: International Journal of Materials Research - Zeitschrift für Metallkunde, ISSN 1862-5282, E-ISSN 2195-8556, Vol. 98, no 7, p. 597-602Article in journal (Refereed)
    Abstract [en]

    Ice nucleation and ice repellence are properties which appear to be contradictory. Both are of great importance: The former for ice generation in the food and cooling industry and the latter for avoiding the adhesion of ice to structures. By mimicking a peculiar survival mechanism of some cold-adapted organisms a new type of coating system, able to both nucleate and repel the ice was developed. A heterogeneous surface containing locally isolated nucleation points in a low surface energy matrix were synthesised by a sol-gel process. The ice nucleating and ice releasing performance of the new ice nucleating coatings (INC) has been tested in a specially designed crystallisation chamber in comparison to commercial low surface energy coating systems. A mixture of demineralised water and a water freezing point depressant was used in the experiments. Compared to the commercial coatings, the INC surfaces showed a much higher ice nucleation rate but also a distinctly better ice releasing ability. Obviously the novel concept of local embedded nucleation points improves the ice repellent properties of surfaces.

  • 124199. Zwiller, V.
    et al.
    Björk, Gunnar
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Improved light extraction from emitters in high refractive index materials using solid immersion lenses2002In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 92, no 2, p. 660-665Article in journal (Refereed)
    Abstract [en]

    Solid immersion lenses (SILs) are optically transparent, truncated spheres, brought in contact with a sample to be imaged. The combination of a conventional optical microscope and a SIL results in a highly effective numerical aperture of the imaging system that can improve the resolution. In addition, when imaging high refractive index samples, such as semiconductors, the light collection efficiency can be increased drastically. We investigate the collection efficiency as a function of the SILs geometry and refractive index, using an analytical expression for the light dispersion through an arbitrarily truncated sphere. The theoretical results are compared to experimental measurements obtained on single quantum dots and are found to be in good agreement.

  • 124200. Zwiller, V.
    et al.
    Chitica, N.
    Persson, J.
    Pistol, M. -E
    Seifert, W.
    Samuelson, L.
    Hammar, M.
    Streubel, K.
    Goobar, E.
    Björk, G.
    Studies of self-assembled InP quantum dots in planar microcavities2000In: Materials Science and Engineering B: Solid-State Materials for Advanced Technology, Vol. 69, no Lausanne, Switzerland, p. 314-317Article in journal (Refereed)
    Abstract [en]

    Self-assembled InP quantum dots have been grown in planar microcavities. The dots were embedded in a Ga0.52In0.48P spacer grown on top of a high reflectance epitaxial Al0.29Ga0.71As/AlAs distributed Bragg reflector (DBR) to obtain a 33λ/4 cavity. The Fabry-Perot microcavity is formed between the AlGaAs/AlAs DBR and a dielectric SiNx/SiO2 DBR deposited on top of the GaInP spacer. The quantum dot emission is centered at 1.62 eV at 7 K. The microcavity resonance is centered at 1.65 eV, with a linewidth of 2 meV. Micro-photoluminescence (PL) studies using different objectives with different numerical apertures enable the collection of transversal modes.

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