| 1. |
- Kristensson, Per Ola, et al.
(författare)
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An Evaluation of Space Time Cube Representation of Spatiotemporal Patterns
- 2009
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Ingår i: IEEE TRANSACTIONS ON VISUALIZATION AND COMPUTER GRAPHICS. - 1077-2626. ; 15:4, s. 696-702
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Tidskriftsartikel (refereegranskat)abstract
- Space time cube representation is an information visualization technique where spatiotemporal data points are mapped into a cube. Information visualization researchers have previously argued that space time cube representation is beneficial in revealing complex spatiotemporal patterns in a data set to users. The argument is based on the fact that both time and spatial information are displayed simultaneously to users, an effect difficult to achieve in other representations. However, to our knowledge the actual usefulness of space time cube representation in conveying complex spatiotemporal patterns to users has not been empirically validated. To fill this gap, we report on a between-subjects experiment comparing novice users error rates and response times when answering a set of questions using either space time cube or a baseline 2D representation. For some simple questions, the error rates were lower when using the baseline representation. For complex questions where the participants needed an overall understanding of the spatiotemporal structure of the data set, the space time cube representation resulted in on average twice as fast response times with no difference in error rates compared to the baseline. These results provide an empirical foundation for the hypothesis that space time cube representation benefits users analyzing complex spatiotemporal patterns.
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| 2. |
- Martensson, Nils, et al.
(författare)
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On the relation between X-ray Photoelectron Spectroscopy and XAFS
- 2013
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Ingår i: 15th International Conference On X-Ray Absorption Fine Structure (XAFS15). - : IOP Publishing.
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Konferensbidrag (refereegranskat)abstract
- XAFS and X-ray Photoelectron Spectroscopy (XPS) are element specific techniques used in a great variety of research fields. The near edge regime of XAFS provides information on the unoccupied electronic states of a system. For the detailed interpretation of the XAFS results, input from XPS is crucial. The combination of the two techniques is also the basis for the so called core-hole clock technique. One of the important aspects of photoelectron spectroscopy is its chemical sensitivity and that one can obtain detailed information about the composition of a sample. We have for a series of carbon based model molecules carefully investigated the relationship between core level photoelectron intensities and stoichiometry. We find strong EXAFS-like modulations of the core ionization cross sections as function of photon energy and that the intensities at high photon energies converge towards values that do not correspond to the stoichiometric ratios. The photoelectron intensities are dependent on the local molecular structure around the ionized atoms. These effects are well described by molecular calculations using multiple scattering theory and by considering the effects due to monopole shake-up and shake-off as well as to intramolecular inelastic scattering processes.
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| 3. |
- Nyholm, Ralf, et al.
(författare)
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N-shell core-level widths for the elements W74 to Bi83
- 1987
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Ingår i: Physical Review B (Condensed Matter). - 0163-1829. ; 36:1, s. 20-24
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Tidskriftsartikel (refereegranskat)abstract
- The Lorentzian lifetime widths of the 4d and 4f levels in the sixth-period elements W74 to Bi83 have been measured using photoelectron spectroscopy. A compilation of 4f-level widths from the literature is also made. The general trend of the 4f-level widths is well reproduced by McGuires calculations, although the absolute widths seem to be underestimated. The 4d5/2-level width shows a remarkable constancy over the whole series of elements and it varies only between 3.6 and 4.0 eV for all the investigated elements. The determined 4d level widths are well reproduced by recent calculations by Ohno and Wendin. Special attention has been paid to lifetime broadenings which are characteristic for the solid phase. Such broadenings are observed for the 4d3/2 level due to N4N5O45 Coster-Kronig processes. In the 4f shell a small Coster-Kronig broadening is also observed in the beginning of the series.
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| 4. |
- Zhang, Teng, 1988-
(författare)
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Synchrotron Radiation Studies of Molecular Building Blocks for Functional Materials
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The research on new materials is a primary driving force for progress in human society. One of the most significant research topic nowadays is the development of new functional materials for technological applications, like perovskite implemented in solar cells, and graphene as a representative for the new 2D materials family. It is then crucial to fully understand the functionality of such materials from a fundamental point of view, as a complementary and useful guide to develop/design new devices of improved performance and energy efficiency.In the thesis, comprehensive characterizations of molecular building blocks used in i) novel energy conversion devices (CoPc, TPA, DPTA and m-MTDATA), and ii) in 2D materials (biphenylene and melamine) have been performed by PhotoElectron Spectroscopy (PES), and Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy carried out at synchrotron radiation facilities, representing effective, powerful light source dedicated to the front-line materials research of great value in both science and industry. PES and NEXAFS spectroscopy, in combination with Density Functional Theory (DFT) calculations have provided a deep understanding of the electronic structure of the investigated systems in relation to their functionality. The investigations always included the combination and comparison between experimental and theoretical results. The studied molecules were characterized as free and adsorbed on surfaces, from the simple building blocks to more complex molecular systems. The characterizations allowed us to identify the electronic structure modifications due to substitutions (Paper III), increasing complexity of the molecules (Paper V), molecule-substrate interactions (Paper I, II, IV, V) and intra-molecular H-bonding interactions (Paper VI).
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