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  • 251.
    Bäckström, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Managing and Exploring Large Data Sets Generated by Liquid Separation - Mass Spectrometry2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    A trend in natural science and especially in analytical chemistry is the increasing need for analysis of a large number of complex samples with low analyte concentrations. Biological samples (urine, blood, plasma, cerebral spinal fluid, tissue etc.) are often suitable for analysis with liquid separation mass spectrometry (LS-MS), resulting in two-way data tables (time vs. m/z). Such biological 'fingerprints' taken for all samples in a study correspond to a large amount of data. Detailed characterization requires a high sampling rate in combination with high mass resolution and wide mass range, which presents a challenge in data handling and exploration. This thesis describes methods for managing and exploring large data sets made up of such detailed 'fingerprints' (represented as data matrices).

    The methods were implemented as scripts and functions in Matlab, a wide-spread environment for matrix manipulations. A single-file structure to hold the imported data facilitated both easy access and fast manipulation. Routines for baseline removal and noise reduction were intended to reduce the amount of data without loosing relevant information. A tool for visualizing and exploring single runs was also included. When comparing two or more 'fingerprints' they usually have to be aligned due to unintended shifts in analyte positions in time and m/z. A PCA-like multivariate method proved to be less sensitive to such shifts, and an ANOVA implementation made it easier to find systematic differences within the data sets.

    The above strategies and methods were applied to complex samples such as plasma, protein digests, and urine. The field of application included urine profiling (paracetamole intake; beverage effects), peptide mapping (different digestion protocols) and search for potential biomarkers (appendicitis diagnosis) . The influence of the experimental factors was visualized by PCA score plots as well as clustering diagrams (dendrograms).

    List of papers
    1. Screening for biomarkers in plasma from patients with gangrenous phlegmonous appendicitis using CE and CEC in combination with MS
    Open this publication in new window or tab >>Screening for biomarkers in plasma from patients with gangrenous phlegmonous appendicitis using CE and CEC in combination with MS
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    2007 (English)In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 28, no 9, p. 1435-1443Article in journal (Refereed) Published
    Abstract [en]

    Today a high degree of "false" appendicitis diagnoses are occurring. In this study, a screening experiment of biomarkers of two different kinds of appendicitis, gangrenous and phlegmonous, were conducted with CE and CEC coupled to MS. Plasma samples were obtained from patients pre- and post-surgery. A large amount of data was generated to be able to compare them, and chemometrics tools were utilized to visualize the differences. Indicative patterns were found for both pre- and post-surgery of the two types of inflammation as well as between them. The divergences were traced back to the MS peaks obtained in the CE- and CEC-MS setups as possible biomarkers for the two forms of appendicitis.
    Keywords
    Appendicitis, Biomarker, Fourier transform ion cyclotron resonance-MS, Open tubular CEC, TOF-MS
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:uu:diva-96249 (URN)10.1002/elps.200600606 (DOI)000246557400018 ()17372941 (PubMedID)
    Available from: 2007-09-21 Created: 2007-09-21 Last updated: 2017-12-14Bibliographically approved
    2. Rapid multivariate analysis of LC/GC/CE data (single or multiple channel detection) without prior peak alignment
    Open this publication in new window or tab >>Rapid multivariate analysis of LC/GC/CE data (single or multiple channel detection) without prior peak alignment
    2006 (English)In: Chemometrics and Intelligent Laboratory Systems, ISSN 0169-7439, E-ISSN 1873-3239, Vol. 84, no 1-2, p. 33-39Article in journal (Refereed) Published
    Abstract [en]

    One- or two-dimensional data obtained with LC/GC/CE and single or multiple channel detection (MS, UV/VIS) are often used as 'fingerprints' in order to characterize complex samples. The relation between samples is then explored by multivariate data analysis (PCA, hierarchical clustering), but inevitable more or less random variation in separation conditions obstructs the analysis. Several methods for peak alignment have been developed, with more or less increase of time and efforts for computations. In this work another approach is presented, based on a correlation measure less sensitive for variations in retention/migration time. The merits of the method as a fast initial data exploration tool are demonstrated for a case study of urine profiling with CE/MS.
    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-96250 (URN)10.1016/j.chemolab.2006.04.009 (DOI)000242768200006 ()
    Available from: 2007-09-21 Created: 2007-09-21 Last updated: 2017-12-14Bibliographically approved
    3. Urine profiling using capillary electrophoresis-mass spectrometry and multivariate data analysis
    Open this publication in new window or tab >>Urine profiling using capillary electrophoresis-mass spectrometry and multivariate data analysis
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    2006 In: Urine profiling using capillary electrophoresis-mass spectrometry and multivariate data analysis, ISSN 0021-9673, Vol. 1117, no 1, p. 6-Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-96251 (URN)
    Available from: 2007-09-21 Created: 2007-09-21 Last updated: 2011-03-21
    4. Multivariate comparison between peptide mass fingerprints obtained by liquid chromatography-electrospray ionization-mass spectrometry with different trypsin digestion procedures
    Open this publication in new window or tab >>Multivariate comparison between peptide mass fingerprints obtained by liquid chromatography-electrospray ionization-mass spectrometry with different trypsin digestion procedures
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    2007 (English)In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1171, no 1-2, p. 69-79Article in journal (Refereed) Published
    Abstract [en]

    Peptide mass fingerprints were obtained for three different proteins using three different digestion procedures in triplicates with liquid chromatography coupled to electrospray ionization mass spectrometry. For each protein the results were compared with multivariate data analysis (cluster analysis, kernel principal component analysis) and pair-wise contrast evaluation. Clear systematic differences between the digestion procedures were established for all the proteins. The visual presentation of the pair-wise differences between procedures could to some extent be related to the protein fragments, although the main objective was to identify m/z and retention regions in the original peptide maps that should be subject to further exploration.
    Keywords
    Chemometrics, Cluster analysis, ESI, LC, MS, Multivariate data analysis, PCA, Peptide mapping
    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-96252 (URN)10.1016/j.chroma.2007.09.042 (DOI)000250793400010 ()17927993 (PubMedID)
    Available from: 2007-09-21 Created: 2007-09-21 Last updated: 2017-12-14Bibliographically approved
    5. Comparing CE-MS fingerprints of urine samples, obtained after intake of coffee, tea or water
    Open this publication in new window or tab >>Comparing CE-MS fingerprints of urine samples, obtained after intake of coffee, tea or water
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    Manuscript (Other academic)
    Identifiers
    urn:nbn:se:uu:diva-96253 (URN)
    Available from: 2007-09-21 Created: 2007-09-21 Last updated: 2011-03-21
  • 252.
    Bängtsson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Scientific Computing. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Numerical Analysis.
    Robust Preconditioners Based on the Finite Element Framework2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Robust preconditioners on block-triangular and block-factorized form for three types of linear systems of two-by-two block form are studied in this thesis.

    The first type of linear systems, which are dense, arise from a boundary element type of discretization of crack propagation problems. Numerical experiment show that simple algebraic preconditioning strategies results in iterative schemes that are highly competitive with a direct solution method.

    The second type of algebraic systems, which are sparse, indefinite and nonsymmetric, arise from a finite element (FE) discretization of the partial differential equations (PDE) that describe (visco)elastic glacial isostatic adjustment (GIA). The Schur complement approximation in the block preconditioners is constructed by assembly of local, exactly computed Schur matrices. The quality of the approximation is verified in numerical experiments.

    When the block preconditioners for the indefinite problem are combined with an inner iterative scheme preconditioned by a (nearly) optimal multilevel preconditioner, the resulting preconditioner is (nearly) optimal and robust with respect to problem size, material parameters, number of space dimensions, and coefficient jumps.

    Two approaches to mathematically formulate the PDEs for GIA are compared. In the first approach the equations are formulated in their full complexity, whereas in the second their formulation is confined to the features and restrictions of the employed FE package. Different solution methods for the algebraic problem are used in the two approaches. Analysis and numerical experiments reveal that the first strategy is more accurate and efficient than the latter.

    The block structure in the third type of algebraic systems is due to a fine-coarse splitting of the unknowns. The inverse of the pivot block is approximated by a sparse matrix which is assembled from local, exactly inverted matrices. Numerical experiments and analysis of the approximation show that it is robust with respect to problem size and coefficient jumps.

    List of papers
    1. Algebraic preconditioning versus direct solvers for dense linear systems as arising in crack propagation problems
    Open this publication in new window or tab >>Algebraic preconditioning versus direct solvers for dense linear systems as arising in crack propagation problems
    2005 (English)In: Communications in Numerical Methods in Engineering, ISSN 1069-8299, E-ISSN 1099-0887, Vol. 21, p. 73-81Article in journal (Refereed) Published
    National Category
    Computational Mathematics Computer Sciences
    Identifiers
    urn:nbn:se:uu:diva-73790 (URN)10.1002/cnm.728 (DOI)
    Available from: 2006-05-13 Created: 2006-05-13 Last updated: 2018-01-14Bibliographically approved
    2. Numerical simulations of glacial rebound using preconditioned iterative solution methods
    Open this publication in new window or tab >>Numerical simulations of glacial rebound using preconditioned iterative solution methods
    2005 (English)In: Applications of Mathematics, ISSN 0862-7940, E-ISSN 1572-9109, Vol. 50, p. 183-201Article in journal (Refereed) Published
    National Category
    Computational Mathematics Computer Sciences
    Identifiers
    urn:nbn:se:uu:diva-73787 (URN)10.1007/s10492-005-0013-3 (DOI)
    Available from: 2006-05-13 Created: 2006-05-13 Last updated: 2018-01-14Bibliographically approved
    3. An agglomerate multilevel preconditioner for linear isostasy saddle point problems
    Open this publication in new window or tab >>An agglomerate multilevel preconditioner for linear isostasy saddle point problems
    2006 (English)In: Large-Scale Scientific Computing, Berlin: Springer-Verlag , 2006, p. 113-120Conference paper, Published paper (Refereed)
    Place, publisher, year, edition, pages
    Berlin: Springer-Verlag, 2006
    Series
    Lecture Notes in Computer Science ; 3743
    National Category
    Computational Mathematics Computer Sciences
    Identifiers
    urn:nbn:se:uu:diva-78987 (URN)10.1007/11666806_11 (DOI)000236456400011 ()
    Available from: 2008-07-22 Created: 2008-07-22 Last updated: 2018-01-13Bibliographically approved
    4. Preconditioning of nonsymmetric saddle point systems as arising in modelling of viscoelastic problems
    Open this publication in new window or tab >>Preconditioning of nonsymmetric saddle point systems as arising in modelling of viscoelastic problems
    2008 (English)In: Electronic Transactions on Numerical Analysis, ISSN 1068-9613, E-ISSN 1068-9613, Vol. 29, p. 193-211Article in journal (Refereed) Published
    National Category
    Computational Mathematics Computer Sciences
    Identifiers
    urn:nbn:se:uu:diva-12385 (URN)000207070800013 ()
    Available from: 2007-12-17 Created: 2007-12-17 Last updated: 2018-01-12Bibliographically approved
    5. A comparison between two solution techniques to solve the equations of glacially induced deformation of an elastic Earth
    Open this publication in new window or tab >>A comparison between two solution techniques to solve the equations of glacially induced deformation of an elastic Earth
    2008 (English)In: International Journal for Numerical Methods in Engineering, ISSN 0029-5981, E-ISSN 1097-0207, Vol. 75, p. 479-502Article in journal (Refereed) Published
    National Category
    Computational Mathematics Computer Sciences
    Identifiers
    urn:nbn:se:uu:diva-13603 (URN)10.1002/nme.2268 (DOI)000258113600004 ()
    Available from: 2008-07-14 Created: 2008-07-14 Last updated: 2018-01-12Bibliographically approved
    6. Finite element block-factorized preconditioners
    Open this publication in new window or tab >>Finite element block-factorized preconditioners
    2007 (English)Report (Other academic)
    Series
    Technical report / Department of Information Technology, Uppsala University, ISSN 1404-3203 ; 2007-008
    National Category
    Computational Mathematics
    Identifiers
    urn:nbn:se:uu:diva-10631 (URN)
    Available from: 2007-04-16 Created: 2007-04-16 Last updated: 2011-11-18Bibliographically approved
  • 253.
    Bélanger-Champagne, Camille
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Measurements of Angular Correlations in Minimum Bias Events and Preparatory Studies for Charged Higgs Boson Searches at the Tevatron and the LHC2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Studies of minimum bias events at colliders probe the behavior of QCD in the non-perturbative regime. The phenomenology of events in this regime is described by empirical models that take many parameters, which all need to be tuned to the observed data. Measurements based on angular correlations between the highest transverse momentum charged particle track and the other charged particle tracks in collision events can, because of their robustness against experimental and detector effects, be a component of the tuning inputs for the models. We measure such observables in a variety of pseudorapidity ranges and at many center-of-mass energies at DØ and ATLAS. We observe that such observables are poorly described by current models and tunes that are used to produce simulated event samples, making them valuable information for the tuning process.

    The Matrix Element method is a powerful analysis tool to extract precise measurements from data samples of limited statistics. We have investigated the potential of the Matrix Element method to measure the mass of the charged Higgs in the exclusive decay H±→τ±ν→e±+3ν when produced in top quark decays at the Tevatron, with emphasis on the construction of transfer functions in the τ decay chain. We concluded that the τ decay chain can be successfully parametrized via a transfer function and that the method has the potential to provide an accurate charged Higgs mass measurement in this channel.

    Triggering on τ leptons is a key component for many beyond the Standard Model searches at ATLAS, such as the search for the charged Higgs boson. Events containing Z bosons can be used to measure the efficiency of the ATLAS τ hadronic-decay trigger. We have used a tag-and-probe method on simulated Z boson decays to 2 τ leptons where one decays to a μ while the other decays hadronically. The μ is used as the tag and the τ side is probed. We demonstrated that the efficiency of the τ hadronic-decay trigger can be accurately measured with this method using the first 100 pb-1 of ATLAS data.

    List of papers
    1. Study of φ and η correlations in minimum bias events with the D0 detector at the Fermilab Tevatron collider
    Open this publication in new window or tab >>Study of φ and η correlations in minimum bias events with the D0 detector at the Fermilab Tevatron collider
    2010 (English)Conference paper, Published paper (Other academic)
    Abstract [en]

    We study a new way to describe minimum bias events based on angular distributions in ≈5million minimum bias proton-antiproton collisions collected between April 2002 and February 2006 with the D0 detector at the Fermilab Tevatron Collider. We demonstrate that the distribution of ∆φ in the detector transverse plane between the leading track and all other tracks is a robust observable that can be used for tuning of multiple color interaction models. Pseudorapidity correlations of the ∆φ distributions are also studied.
    Keywords
    QCD, angular correlations, Monte Carlo tunes
    National Category
    Subatomic Physics
    Research subject
    Physics with specialization in Elementary Particle Physics
    Identifiers
    urn:nbn:se:uu:diva-142119 (URN)
    Available from: 2011-01-13 Created: 2011-01-13 Last updated: 2011-03-11Bibliographically approved
    2. Angular correlations between charged particles from proton-proton collisions at √s = 900 GeV and √s = 7 TeV measured with the ATLAS detector
    Open this publication in new window or tab >>Angular correlations between charged particles from proton-proton collisions at √s = 900 GeV and √s = 7 TeV measured with the ATLAS detector
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    2010 (English)Conference paper, Published paper (Other academic)
    Abstract [en]

    This note describes a study of angular correlations between charged primary particles stemming from proton-proton collisions at the Large Hadron Collider. Two observables are defined based on ∆φ, the angle in the transverse plane between the particle with the highest transverse momentum and any other particle in the collision. The shapes of the observables have a very small systematic uncertainty and are different for √s = 900 GeV and 7 TeV. The distributions observed in data are compared to different tunes of the PYTHIA event generator.
    Keywords
    QCD, MC Generators, Tracking, ATLAS, LHC, CERN
    National Category
    Subatomic Physics
    Research subject
    Physics with specialization in Elementary Particle Physics
    Identifiers
    urn:nbn:se:uu:diva-142139 (URN)
    Available from: 2011-01-13 Created: 2011-01-13 Last updated: 2011-03-11Bibliographically approved
    3. Transfer function treatment of leptonic tau decays in the Matrix Element method
    Open this publication in new window or tab >>Transfer function treatment of leptonic tau decays in the Matrix Element method
    2011 (English)In: CHarged2010 / [ed] Arnaud Ferrari, Rikard Enberg, Trieste: Proceedings of Science , 2011, p. 1-7Conference paper, Published paper (Refereed)
    Place, publisher, year, edition, pages
    Trieste: Proceedings of Science, 2011
    Series
    Proceedings of Science, ISSN 1824-8039 ; 006
    National Category
    Subatomic Physics
    Research subject
    Physics with specialization in Elementary Particle Physics
    Identifiers
    urn:nbn:se:uu:diva-142448 (URN)
    Conference
    Prospects for Charged Higgs Discovery at Colliders
    Available from: 2011-01-14 Created: 2011-01-14 Last updated: 2011-03-11Bibliographically approved
    4. The ATLAS tau trigger and planned trigger efficiency studies with early data
    Open this publication in new window or tab >>The ATLAS tau trigger and planned trigger efficiency studies with early data
    Show others...
    2009 (English)In: Proceedings of CHarged2008 / [ed] T. Ekelöf, J. Rathsman, Trieste: Proceedings of Science , 2009, p. 1-7Conference paper, Published paper (Refereed)
    Abstract [en]

    The tau trigger system of the ATLAS detector has been developed to increase the sensitivity ofthe detector to the Higgs boson and searches for physics beyond the Standard Model.  A trigger system split in three levels has been designed for hadronically decaying tau leptons optimized for efficiency and good background rejection.  At the first level the trigger uses only information from the calorimeters while the other two levels include also information from the tracking.  Both energy and shape variables for the hadronic tau jets are used in the trigger algorithms.  The very intense QCD background, however, makes it a challenge to develop an efficient trigger with high purity at low transverse momentum. Thus the tau trigger is best used in combination with other trigger variables such as missing transverse energy or jets.  Before the tau trigger can be used in searches, it has to be commissioned with data and the efficiency and background rejectionof QCD has to be studied in detail.
    Place, publisher, year, edition, pages
    Trieste: Proceedings of Science, 2009
    Series
    Proceedings of Science, ISSN 1824-8039
    Keywords
    ATLAS, LHC, CERN, Trigger, Tau lepton
    National Category
    Subatomic Physics
    Research subject
    Physics with specialization in Elementary Particle Physics
    Identifiers
    urn:nbn:se:uu:diva-142227 (URN)
    Conference
    Prospects for Charged Higgs Discovery at Colliders
    Available from: 2011-01-13 Created: 2011-01-13 Last updated: 2011-03-11Bibliographically approved
  • 254.
    Böhme, Solveig
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Fundamental Insights into the Electrochemistry of Tin Oxide in Lithium-Ion Batteries2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis aims to provide insight into the fundamental electrochemical processes taking place when cycling SnO2 in lithium-ion batteries (LIBs). Special attention was paid to the partial reversibility of the tin oxide conversion reaction and how to enhance its reversibility. Another main effort was to pinpoint which limitations play a role in tin based electrodes besides the well-known volume change effect in order to develop new strategies for their improvement. In this aspect, Li+ mass transport within the electrode particles and the large first cycle charge transfer resistance were studied. Li+ diffusion was proven to be an important issue regarding the electrochemical cycling of SnO2. It was also shown that it is the Li+ transport inside the SnO2 particles which represents the largest limitation. In addition, the overlap between the potential regions of the tin oxide conversion and the alloying reaction was investigated with photoelectron spectroscopy (PES) to better understand if and how the reactions influence each other`s reversibility.

    The fundamental insights described above were subsequently used to develop strategies for the improvement of the performance and the cycle life for SnO2 electrodes in LIBs. For instance, elevated temperature cycling at 60 oC was employed to alleviate the Li+ diffusion limitation effects and, thus, significantly improved capacities could be obtained. Furthermore, an ionic liquid electrolyte was tested as an alternative electrolyte to cycle at higher temperatures than 60 oC which is the thermal stability limit for the conventional LP40 electrolyte. In addition, cycled SnO2 nanoparticles were characterized with transmission electron microscopy (TEM) to determine the effects of long term high temperature cycling. Also, the effect of vinylene carbonate (VC) as an electrolyte additive on the cycling behavior of SnO2 nanoparticles was studied in an effort to improve the capacity retention. In this context, a recently introduced intermittent current interruption (ICI) technique was employed to measure and compare the development of internal cell resistances with and without VC additive.

    List of papers
    1. On the electrochemistry of tin oxide coated tin electrodes in lithium-ion batteries
    Open this publication in new window or tab >>On the electrochemistry of tin oxide coated tin electrodes in lithium-ion batteries
    2015 (English)In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 179, p. 482-494Article in journal (Refereed) Published
    Abstract [en]

    As tin based electrodes are of significant interest in the development of improved lithium-ion batteries it is important to understand the associated electrochemical reactions. In this work it is shown that the electrochemical behavior of SnO2 coated tin electrodes can be described based on the SnO2 and SnO conversion reactions, the lithium tin alloy formation and the oxidation of tin generating SnF2. The CV, XPS and SEM data, obtained for electrodeposited tin crystals on gold substrates, demonstrates that the capacity loss often observed for SnO2 is caused by the reformed SnO2 layer serving as a passivating layer protecting the remaining tin. Capacities corresponding up to about 80 % of the initial SnO2 capacity could, however, be obtained by cycling to 3.5 V vs. Li+/Li. It is also shown that the oxidation of the lithium tin alloy is hindered by the rate of the diffusion of lithium through a layer of tin with increasing thickness and that the irreversible oxidation of tin to SnF2 at potentials larger than 2.8 V vs. Li+/Li is due to the fact that SnF2 is formed below the SnO2 layer. This improved electrochemical understanding of the SnO2/Sn system should be valuable in the development of tin based electrodes for lithium-ion batteries.
    National Category
    Materials Chemistry
    Identifiers
    urn:nbn:se:uu:diva-262075 (URN)10.1016/j.electacta.2015.02.150 (DOI)000362292200059 ()
    Funder
    Swedish Foundation for Strategic Research
    Available from: 2015-09-08 Created: 2015-09-08 Last updated: 2017-12-04Bibliographically approved
    2. Overlapping and Rate Controlling Electrochemical Reactions for Tin(IV) Oxide Electrodes in Lithium-Ion Batteries
    Open this publication in new window or tab >>Overlapping and Rate Controlling Electrochemical Reactions for Tin(IV) Oxide Electrodes in Lithium-Ion Batteries
    (English)In: Article in journal (Other academic) Submitted
    Keywords
    Tin oxide, Lithium-ion batteries, Electrochemistry, Cyclic Voltammetry, Mass transport
    National Category
    Materials Chemistry
    Identifiers
    urn:nbn:se:uu:diva-319389 (URN)
    Funder
    Swedish Foundation for Strategic Research
    Available from: 2017-04-04 Created: 2017-04-04 Last updated: 2017-12-30
    3. Elevated Temperature Lithium-Ion Batteries Containing SnO2 Electrodes and LiTFSI-Pip14TFSI Ionic Liquid Electrolyte
    Open this publication in new window or tab >>Elevated Temperature Lithium-Ion Batteries Containing SnO2 Electrodes and LiTFSI-Pip14TFSI Ionic Liquid Electrolyte
    Show others...
    2017 (English)In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 164, no 4, p. A701-A708Article in journal (Refereed) Published
    Abstract [en]

    The performance of lithium-ion batteries (LIBs) comprising SnO2 electrodes and an ionic liquid (IL) based electrolyte, i.e., 0.5 MLiTFSI in Pip14TFSI, has been studied at room temperature (i.e., 22◦C) and 80◦C. While the high viscosity and low conductivity ofthe electrolyte resulted in high overpotentials and low capacities at room temperature, the SnO2 performance at 80◦C was found to beanalogous to that seen at room temperature using a standard LP40 electrolyte (i.e., 1MLiPF6 dissolved in 1:1 ethylene carbonate anddiethyl carbonate). Significant reduction of the IL was, however, found at 80◦C, which resulted in low coulombic efficiencies duringthe first 20 cycles, most likely due to a growing SEI layer and the formation of soluble IL reduction products. X-ray photoelectronspectroscopy studies of the cycled SnO2 electrodes indicated the presence of an at least 10 nm thick solid electrolyte interphase (SEI)layer composed of inorganic components such as lithium fluoride, sulfates, and nitrides as well as organic species containing C-H,C-F and C-N bonds.
    National Category
    Materials Chemistry
    Identifiers
    urn:nbn:se:uu:diva-316877 (URN)10.1149/2.0861704jes (DOI)000400958600021 ()
    Available from: 2017-03-07 Created: 2017-03-07 Last updated: 2017-06-14Bibliographically approved
    4. Photoelectron Spectroscopic Evidence for Overlapping Redox Reactions for SnO2 Electrodes in Lithium-Ion Batteries
    Open this publication in new window or tab >>Photoelectron Spectroscopic Evidence for Overlapping Redox Reactions for SnO2 Electrodes in Lithium-Ion Batteries
    2017 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 9, p. 4924-4936Article in journal (Refereed) Published
    Abstract [en]

    In-house and synchrotron-based photoelectron spectroscopy (XPSand HAXPES) evidence is presented for an overlap between the conversion andalloying reaction during the cycling of SnO2 electrodes in lithium-ion batteries(LIBs). This overlap resulted in an incomplete initial reduction of the SnO2 as wellas the inability to regenerate the reduced SnO2 on the subsequent oxidative scan.The XPS and HAXPES results clearly show that the SnO2 conversion reactionoverlaps with the formation of the lithium tin alloy and that the conversion reactiongives rise to the formation of a passivating Sn layer on the SnO2 particles. The latterlayer renders the conversion reaction incomplete and enables lithium tin alloy toform on the surface of the particles still containing a core of SnO2. The results alsoshow that the reoxidation of the lithium tin alloy is incomplete when the formationof tin oxide starts. It is proposed that the rates of the electrochemical reactions andhence the capacity of SnO2-based electrodes are limited by the lithium masstransport rate through the formed layers of the reduction and oxidations products.In addition, it is shown that a solid electrolyte interphase (SEI) layer is continuously formed at potentials lower than about 1.2 VLi+/Li during the first scan and that a part of the SEI dissolves on the subsequent oxidative scan. While the SEI was found tocontain both organic and inorganic species, the former were mainly located at the SEI surface while the inorganic species werefound deeper within the SEI. The results also indicate that the SEI dissolution process predominantly involves the organic SEIcomponents.
    National Category
    Physical Chemistry
    Identifiers
    urn:nbn:se:uu:diva-316876 (URN)10.1021/acs.jpcc.7b01529 (DOI)000396295800017 ()
    Funder
    Swedish Foundation for Strategic Research StandUp
    Available from: 2017-03-07 Created: 2017-03-07 Last updated: 2017-04-18Bibliographically approved
    5. The Influence of Al2O3 and Diamond as Additives on the Performance of SnO2 Electrodes in Lithium-Ion Batteries
    Open this publication in new window or tab >>The Influence of Al2O3 and Diamond as Additives on the Performance of SnO2 Electrodes in Lithium-Ion Batteries
    (English)Manuscript (preprint) (Other academic)
    Keywords
    Tin oxide, Lithium-ion batteries, Electrochemistry, Mass transport, SEM
    National Category
    Materials Chemistry
    Identifiers
    urn:nbn:se:uu:diva-319391 (URN)
    Funder
    StandUpSwedish Foundation for Strategic Research
    Available from: 2017-04-04 Created: 2017-04-04 Last updated: 2017-12-30
    6. Effects of Elevated Temperature and Vinylene Carbonate Additive on the Electrochemical Performance of SnO2 Nanoparticles in Lithium-Ion Batteries
    Open this publication in new window or tab >>Effects of Elevated Temperature and Vinylene Carbonate Additive on the Electrochemical Performance of SnO2 Nanoparticles in Lithium-Ion Batteries
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    (English)Manuscript (preprint) (Other academic)
    Keywords
    Tin oxide, Lithium-ion batteries, High temperature cycling, Electrolyte additive, Electrochemistry, Resistance
    National Category
    Materials Chemistry
    Identifiers
    urn:nbn:se:uu:diva-319393 (URN)
    Funder
    Swedish Foundation for Strategic Research
    Available from: 2017-04-04 Created: 2017-04-04 Last updated: 2017-12-30
  • 255.
    Bülow, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    A Generator Perspective on Vertical Axis Wind Turbines2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The wind energy conversion system considered in this thesis is based on a vertical axis wind turbine with a cable wound direct drive PM generator. Diode rectifiers are used to connect several such units to a single DC-bus and a single inverter controls the power flow from the DC-bus to a utility grid. This work considers the described system from a generator perspective i.e. the turbine is primarily seen as a torque and the inverter is seen as a controlled load.

    A 12 kW VAWT prototype with a single turbine has been constructed within the project. The power coefficient of this turbine has been measured when the turbine is operated at various tip speed ratios. This measurement determines both how much energy the turbine can convert in a given wind and at what speed the turbine should be operated in order to maximise the energy capture. The turbine torque variation during the revolution of the turbine has also been studied.

    A PM generator prototype has been constructed in order to study power loss in the stator core at low electrical frequencies. Heat exchange between the stator and the air-gap between the stator and the rotor has been studied. Heat exchange between the stator and the air-gap is increased by turbulence caused by the rotor. The generator was also used in a demonstration of a DC-grid where two diode rectified PM generators supplied power to a single DC load.  An initial study of an inverter suitable for grid connection of the 12 kW PM generator has been performed.

    Several turbine control strategies are evaluated in simulations. The control strategies only require the parameter "turbine speed" to determine the optimal system load.

    List of papers
    1. Offshore underwater substation for wave energy converter arrays
    Open this publication in new window or tab >>Offshore underwater substation for wave energy converter arrays
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    2010 (English)In: IET Renewable Power Generation, ISSN 1752-1416, Vol. 4, no 6, p. 602-612Article in journal (Refereed) Published
    Abstract [en]

    In this study, the design, construction, deployment and operation of an offshore underwater substation is discussed. The seabed placed substation interconnects three linear generator wave energy converters (WECs) at the Swedish Lysekil wave energy research site. The power from the WECs fluctuates because of their direct-driven topology. The generator voltage has varying electrical frequency and amplitude. To reduce the fluctuations, the individual voltages of the WECs are rectified and the power is added on a common DC-bus in the substation. The voltage is inverted, transformed and power is transmitted to an on-shore resistive load. The substation was retrieved on two occasions since the deployment in the spring of 2009. The functionality of the substation is validated by comparing voltage and current wave forms from Simulink with measured results from laboratory experiments. In addition, a sample of results from real offshore operation is illustrated and discussed. With a proportional-integral-derivative (PID)-regulator in the inverter control, the small fluctuations in the DC-bus voltage could be minimised. However, this would reduce the energy storage capability of the DC-link smoothing capacitors.
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-112954 (URN)10.1049/iet-rpg.2009.0180 (DOI)000284511300013 ()
    Available from: 2010-01-22 Created: 2010-01-22 Last updated: 2018-05-31Bibliographically approved
    2. Power coefficient measurement on a 12 kW straight bladed vertical axis wind turbine
    Open this publication in new window or tab >>Power coefficient measurement on a 12 kW straight bladed vertical axis wind turbine
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    2011 (English)In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 36, no 11, p. 3050-3053Article in journal (Refereed) Published
    Abstract [en]

    A 12 kW vertical axis H-rotor type wind turbine has been designed and constructed at Uppsala University. A measurement campaign has been performed to collect data to calculate the power coefficient using the method of bins. The measurement was performed at different constant rotational speeds on the turbine during varying wind speeds to observe the power coefficients dependence on tip speed ratio. The power coefficient peaked at 0.29 for a tip speed ratio equal to 3.3.
    Keywords
    VAWT, H-rotor, Experimental, Measured, Cp
    National Category
    Engineering and Technology
    Research subject
    Engineering Science with specialization in Science of Electricity
    Identifiers
    urn:nbn:se:uu:diva-156579 (URN)10.1016/j.renene.2011.03.031 (DOI)000292441400035 ()
    Available from: 2011-08-07 Created: 2011-08-04 Last updated: 2018-05-30Bibliographically approved
    3. Adapting a VAWT with PM generator to telecom applications
    Open this publication in new window or tab >>Adapting a VAWT with PM generator to telecom applications
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    2010 (English)In: European Wind Energy Conference & Exhibition, Warsaw, Poland, 2010Conference paper, Published paper (Refereed)
    Place, publisher, year, edition, pages
    Warsaw, Poland: , 2010
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-142522 (URN)
    Conference
    European Wind Energy Conference & Exhibition
    Available from: 2011-01-14 Created: 2011-01-14 Last updated: 2018-05-30Bibliographically approved
    4. No-load core loss prediction of PM generator at low electrical frequency
    Open this publication in new window or tab >>No-load core loss prediction of PM generator at low electrical frequency
    2012 (English)In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 43, p. 389-392Article in journal (Refereed) Published
    Abstract [en]

    A method for measurement of frequency dependent electromagnetic core loss of a permanent magnet generator is presented. Core loss of a PM generator is measured at electrical frequencies ranging from 4 to 14 Hz. Core loss in the same interval is simulated using the finite element method and frequency domain loss separation. The specific loss is both extrapolated from specific loss at 50 Hz and measured directly at 4, 8, 12 and 16 Hz. Core loss simulations based on extrapolated specific loss are 38–53% smaller than measured loss. Core loss simulations based on specific loss measured at 4, 8, 12 and 16 Hz are 19–23% smaller than measured loss.
    Keywords
    Core loss Variable speed PM generator Cable wound generator Loss separation
    National Category
    Engineering and Technology
    Research subject
    Engineering Science with specialization in Science of Electricity
    Identifiers
    urn:nbn:se:uu:diva-190099 (URN)10.1016/j.renene.2011.12.002 (DOI)000301311500042 ()
    Available from: 2013-01-07 Created: 2013-01-07 Last updated: 2017-12-06Bibliographically approved