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  • 1.
    Ratynskaia, Svetlana V.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    2023 Nuclear Fusion prize acceptance speech2024In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 64, no 1, article id 010205Article in journal (Other academic)
  • 2.
    Vorburger, Audrey
    et al.
    Physics Institute, University of Bern, Bern, Switzerland; Department of Physics, University of Umeå, Umeå, Sweden.
    Fatemi, Shahab
    Department of Physics, University of Umeå, Umeå, Sweden.
    Carberry Mogan, Shane R.
    Space Sciences Laboratory, University of California, Berkeley, Berkeley, CA, USA.
    Galli, André
    Physics Institute, University of Bern, Bern, Switzerland.
    Liuzzo, Lucas
    Space Sciences Laboratory, University of California, Berkeley, Berkeley, CA, USA.
    Poppe, Andrew R.
    Space Sciences Laboratory, University of California, Berkeley, Berkeley, CA, USA.
    Roth, Lorenz
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Wurz, Peter
    Physics Institute, University of Bern, Bern, Switzerland.
    3D Monte-Carlo simulation of Ganymede's atmosphere2024In: Icarus, ISSN 0019-1035, E-ISSN 1090-2643, Vol. 409, article id 115847Article in journal (Refereed)
    Abstract [en]

    We present new model results for H2O, O2, H2, O, and H in the atmosphere of Ganymede. The results are obtained from a collision-less 3D Monte-Carlo model that includes sublimation, ion and electron sputtering, and ion and electron radiolysis. Because Ganymede has its own magnetic field, its immediate plasma environment is particularly complex. The interaction between Ganymede's and Jupiter's magnetospheres makes it highly variable in both space and time. The recent Juno Ganymede flyby provided us with new data on the electron local environment. Based on the electron measurements recorded by the Jovian Auroral Distributions Experiment (JADE), we implement two electron populations, one for the moon's polar regions and one for the moon's auroral regions. Comparing the atmospheric contribution of these newly defined electron populations to the overall source and loss processes is one of the main goals of this work. Our analysis shows that for H2O, sublimation remains the most important source process even after accounting for the new electron populations, delivering more than three orders of magnitude more H2O molecules to the atmosphere than all other source processes combined. The source fluxes for O2 and H2, on the other hand, are dominated by radiolysis induced by the auroral electrons, assuming that the electron fluxes JADE measured during Juno's transit of Ganymede's magnetopause current layer are representative of auroral electrons. Atomic O and H are mainly added to the atmosphere through the dissociation of O2 and H2, which is primarily induced by auroral electrons. Our understanding of Ganymede's atmosphere today is mainly based on spectroscopic observations. The interpretation of spectroscopic data strongly depends on assumptions taken, though. Our analysis shows that for a holistic understanding of Ganymede's atmosphere, simultaneous observations of the moon's surface, atmosphere, and full plasma environment (thermal and energetic ions and electrons) at different times and locations (both with respect to Ganymede and with respect to Jupiter) are particularly important. Such measurements are planned by ESA's Jupiter ICy moons Explorer (JUICE), in particular by the Particle Environment Package (PEP), which will greatly advance our understanding of Ganymede and its atmosphere and plasma environment.

  • 3.
    Broms, Anna
    et al.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Numerical Analysis, NA.
    Tornberg, Anna-Karin
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Numerical Analysis, NA. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    A barrier method for contact avoiding particles in Stokes flow2024In: Journal of Computational Physics, ISSN 0021-9991, E-ISSN 1090-2716, Vol. 497, p. 112648-112648, article id 112648Article in journal (Refereed)
    Abstract [en]

    Rigid particles in a Stokesian fluid experience an increasingly strong lubrication resistance as particle gaps narrow. Numerically, resolving these lubrication forces comes at an intractably large cost, even for moderate system sizes. Hence, it can typically not be guaranteed that artificial particle collisions and overlaps do not occur in a dynamic simulation, independently of the choice of method to solve the Stokes equations. In this work, the potentially large set of non-overlap constraints, in terms of the Euclidean distance between boundary points on disjoint particles, are efficiently represented via a barrier energy. We solve for the minimum magnitudes of repelling contact forces and torques between any particle pair in contact to correct for overlaps by enforcing a zero barrier energy at the next time level, given a contact-free configuration at a previous instance in time. Robustness for the method is illustrated using a multiblob method to solve the mobility problem in Stokes flow, applied to suspensions of spheres, rods and boomerang shaped particles. Collision free configurations are obtained at all instances in time, and considerably larger time-steps can be taken than without the technique. The effect of the contact forces on the collective order of a set of rods in a background flow that naturally promote particle interactions is also illustrated.

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  • 4.
    Wennman, Maria
    et al.
    OrganoClick AB, Linjalvägen 9, SE-187 66 Täby, Sweden, Linjalvägen 9.
    Pinon, Arthur C.
    Swedish NMR Center, University of Gothenburg, Gothenburg, Sweden.
    Svagan, Anna Justina
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Hellberg, Mårten
    OrganoClick AB, Linjalvägen 9, SE-187 66 Täby, Sweden, Linjalvägen 9.
    Hedenqvist, Mikael S.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    A biobased binder of carboxymethyl cellulose, citric acid, chitosan and wheat gluten for nonwoven and paper2024In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 323, article id 121430Article in journal (Refereed)
    Abstract [en]

    The amount of disposable nonwovens used today for different purposes have an impact on the plastic waste streams which is built up from several single-use products. A particular problem comes from nonwoven products with “hidden” plastic (such as cellulose mixed with synthetic fibers and/or plastic binders) where the consumers cannot see or expect plastic. We have here developed a sustainable binder based on natural components; wheat gluten (WG) and a polyelectrolyte complex (PEC) made from chitosan, carboxymethyl cellulose and citric acid which can be used with cellulosic fibers, creating a fully biobased nonwoven product. The binder formed a stable dispersion that improved the mechanical properties of a model nonwoven. With WG added, both the dry and the wet strength of the impregnated nonwoven increased. In dry-state, PEC increased the tensile index with >30 % (from 22.5 to 30 Nm/g), and with WG, with 60 % (to 36 Nm/g). The corresponding increase in the wet strength was 250 % (from 8 to 28 Nm/g) and 300 % (to 32 Nm/g). The increased strength was explained as an enrichment of covalent bonds (ester and amide bonds) established during curing at 170 °C, confirmed by DNP NMR and infrared spectroscopy.

  • 5.
    Batili, Hazal
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Hamawandi, Bejan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Ergül, Adem Björn
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Szukiewicz, Rafal
    Institute of Experimental Physics, University of Wroclaw, Maxa Borna 9, 50–204 Wroclaw, Poland, Maxa Borna 9.
    Kuchowicz, Maciej
    Institute of Experimental Physics, University of Wroclaw, Maxa Borna 9, 50–204 Wroclaw, Poland, Maxa Borna 9.
    Toprak, Muhammet
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    A comparative study on the surface chemistry and electronic transport properties of Bi2Te3 synthesized through hydrothermal and thermolysis routes2024In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 682, article id 132898Article in journal (Refereed)
    Abstract [en]

    Bismuth telluride-Bi2Te3 is the most promising material for harvesting thermal energy near room temperature. There are numerous works on Bi2Te3 reporting significantly different transport properties, with no clear connection to the synthetic routes used and the resultant surface chemistry of the synthesized materials. It is of utmost importance to characterize the constituent particles’ surface and interfaces to get a better understanding of their influence on the transport properties, that will significantly improve the material design starting from the synthesis step. Electrophoretic deposition (EPD) is a promising technique, enabling the formation of thick films using colloidally stabilized suspensions of pre-made nanoparticles, which can enable the study of the effect of surface chemistry, in connection to the synthetic route, on the material's transport properties. In order to explore the differences in surface chemistry and the resultant transport properties in relation to the synthetic scheme used, here we report on Bi2Te3 synthesised through two wet-chemical routes in water (Hydro-) and oil (Thermo-) as the solvents. XRD analysis showed a high phase purity of the synthesized materials. SEM analysis revealed hexagonal platelet morphology of the synthesized materials, which were then used to fabricate EPD films. Characterization of the EPD films reveal significant differences between the Hydro- and Thermo-Bi2Te3 samples, leading to about 8 times better electrical conductivity values in the Thermo-Bi2Te3. XPS analysis revealed a higher metal oxides content in the Hydro-Bi2Te3 sample, contributing to the formation of a resistive layer, thus lowering the electrical conductivity. Arrhenius plots of electrical conductivity vs inverse temperature was used for the estimation of the activation energy for conduction, revealing a higher activation energy need for the Hydro-Bi2Te3 film, in agreement with the resistive barrier oxide content. Both the samples exhibited negative Seebeck coefficient (S) in the order of 160–170 mV/K. The small difference in S of Hydro- and Themo-Bi2Te3 films was explained by the effective medium theory, revealing that the magnitude of S is linearly correlated with the surface oxide content. Based on the findings, TE materials synthesized through thermolysis route is recommended for further studies using soft treatment/processing of pre-made TE materials. EPD platform presented here is shown to clearly expose the differences in the electronic transport in connection to nanoparticle surface chemistry, proving a promising methodology for the evaluation of morphology, size and surface chemistry dependence of electronic transport for a wide range of materials.

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