| 1. |
- Andreasson, Jakob, 1975, et al.
(författare)
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Electron-phonon interactions in perovskites containing Fe and Cr studied by Raman scattering using oxygen-isotope and cation substitution
- 2008
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X .- 2469-9950 .- 2469-9969. ; 78:23, s. 235103-
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Tidskriftsartikel (refereegranskat)abstract
- We use temperature-dependent inelastic light scattering to study the origin of the strong multiphonon scattering of a local oxygen breathing mode present in the mixed B-site orthorhombic (space group Pnma) perovskite LaFe0.5Cr0.5O3 but absent in isostructural LaFeO3 and LaCrO3. It is seen that the multiphonon scattering is critically sensitive to the presence of both Fe and Cr ions on the B site. These results support our interpretation that the multiphonon scattering is activated by local electron-phonon interactions according to the Franck-Condon picture following an Fe-Cr charge transfer. Further, O-18 substitution is performed on the x=0, 0.04, and 0.5 compounds and clearly shows that all modes appearing above the first-order phonon-scattering region in these compounds originate from higher-order oxygen stretching vibrations. In particular this is the case for the strong second-order scattering dominating the scattering response in LaFeO3. Accordingly we propose that these modes are generated by infrared-active longitudinal optical (IR LO) two-phonon and combination scattering activated by Frohlich interaction. For x=0.02 and 0.04 the characteristic IR LO two-phonon and Franck-Condon multiphonon-scattering profiles mix. We also study the influence of isovalent cation substitution and Sr doping in AFe(0.5)Cr(0.5)O(3) (A=La, Nd, and Gd) and La1-ySryFe0.5Cr0.5O3-delta (y=0, 0.16, and 0.5) on the strong electron-phonon coupling present in LaFe0.5Cr0.5O3. The Franck-Condon effect in LaFe0.5Cr0.5O3, is not significantly affected by isovalent A-site substitution, despite the increasing orthorhombic distortion associated with decreasing A-site ionic radii. On the contrary, aliovalent Sr doping causes a rapid decrease in the Franck-Condon scattering. This shows that the strong electron-phonon coupling in these compounds is highly sensitive to local lattice and electronic decoherence but insensitive to global lattice distortions. Finally, a preliminary assignment of the A(g) and B-2g phonon modes in AFe(0.5)Cr(0.5)O(3) (A=La, Nd, and Gd) is made based on the present observations and published results for LaCrO3 and AMnO(3). The modes associated with oxygen octahedral tilt and bending vibrations are heavily influenced by the magnitude of the orthorhombic distortion.
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| 2. |
- Abel, I, et al.
(författare)
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Overview of the JET results with the ITER-like wall
- 2013
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 53:10, s. 104002-
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Tidskriftsartikel (refereegranskat)abstract
- Following the completion in May 2011 of the shutdown for the installation of the beryllium wall and the tungsten divertor, the first set of JET campaigns have addressed the investigation of the retention properties and the development of operational scenarios with the new plasma-facing materials. The large reduction in the carbon content (more than a factor ten) led to a much lower Z(eff) (1.2-1.4) during L- and H-mode plasmas, and radiation during the burn-through phase of the plasma initiation with the consequence that breakdown failures are almost absent. Gas balance experiments have shown that the fuel retention rate with the new wall is substantially reduced with respect to the C wall. The re-establishment of the baseline H-mode and hybrid scenarios compatible with the new wall has required an optimization of the control of metallic impurity sources and heat loads. Stable type-I ELMy H-mode regimes with H-98,H-y2 close to 1 and beta(N) similar to 1.6 have been achieved using gas injection. ELM frequency is a key factor for the control of the metallic impurity accumulation. Pedestal temperatures tend to be lower with the new wall, leading to reduced confinement, but nitrogen seeding restores high pedestal temperatures and confinement. Compared with the carbon wall, major disruptions with the new wall show a lower radiated power and a slower current quench. The higher heat loads on Be wall plasma-facing components due to lower radiation made the routine use of massive gas injection for disruption mitigation essential.
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| 3. |
- Eriksson, Annika, 1975, et al.
(författare)
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Effects of A-site substitution on the structure and magnetic properties of Bi(0.15)Sr(0.85-y)Ae(y)Co(1-x)Fe(x)O(3-delta) perovskites
- 2009
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Ingår i: Solid State Sciences. - : Elsevier BV. - 1293-2558. ; 11:11, s. 1945-1954
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Tidskriftsartikel (refereegranskat)abstract
- The effects of partial substitution of Sr2+ by Ca2+ and Ba2+ on the A-site of oxygen-deficient perovskites, Bi(0.15)Sr(0.85-y)Ae(y)Co(1-x)FeO(3-delta), where y = 0.28 for Ae = Ba and y = 0.17 for Ae = Ca, and 0.0 = 0.25. The samples were studied with PXRD, NPD, TGA, electron microscopy and magnetic susceptibility measurements. All as-prepared samples exhibited long range G-type antiferromagnetic ordering. The effect of oxygen annealing was dramatic for the Bi0.15Sr0.68Ca0.17Co1-xFexO3-delta series, with a disappearance of magnetic order for x >= 0.25 linked to increasing spin-glass properties. The oxygen content of the Bi0.15Sr0.57Ba0.28Co1-xFexO3-delta as-prepared materials was generally higher than their Ca substituted counterparts, and the long range antiferromagnetic order was more resistant to oxygen annealing. (C) 2009 Elsevier Masson SAS. All rights reserved.
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| 4. |
- Eriksson, Annika, 1975, et al.
(författare)
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High temperature phase transition of the magnetoelectric double perovskite Sr2NiMoO6 by neutron diffraction
- 2006
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Ingår i: Materials Research Bulletin. - 0025-5408. ; 41, s. 144-157
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Tidskriftsartikel (refereegranskat)abstract
- The magnetic ferroelectric double perovskite Sr2NiMoO6 has been characterised using neutron powder diffraction (NPD) data and magnetic susceptibility measurements. High temperature NPD data indicate that the material undergoes a continuous structural phase transition from tetragonal (I4/m) to cubic (Fm(3) over barm) at approximately 550 K. The transition is linked to the level of rotation of the NiO6 and MoO6 octahedra, which form perfectly segregated sub-lattices in the material. The reduction in symmetry at 550 K is linked to the onset of a spontaneous dipole in the material allowing the structural perturbation to be described as an improper ferroelectric phase transition. The appearance of low angle reflections in the 20 K dataset indicates the presence of an antiferromagnetic ordered around state. The magnetic moment was refined to 1.88(8) mu(B) confirming that the magnetism originates from the Ni2+ (S = 1) ions. (C) 2005 Elsevier Ltd. All rights reserved.
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| 5. |
- Eriksson, Annika, 1975, et al.
(författare)
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Influence of iron addition on the oxygen-deficient Sr0.85Bi0.15Co1-xFexO3-d (0.0
- 2008
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Ingår i: Journal of Solid state chemistry. - 0022-4596 .- 1095-726X. ; 181, s. 2031-2040
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Tidskriftsartikel (refereegranskat)abstract
- A series of oxygen-deficient Sr0.85Bi0.15Co1-xFexO3-d (0.00.8. Evidence of weak superstructures, reflecting local oxygen ordering, is also obtained from electron diffraction. For all oxygen-annealed phases the average structure reverts to cubic Pm-3m. The as-prepared samples show G-type antiferromagnetic order at room temperature. The oxygen annealed x = 0.10, 0.25 and 1.0 samples display low-temperature spin-glass transitions.
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| 6. |
- Eriksson, Annika, 1975, et al.
(författare)
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Phase stability study of Bi0.15Sr0.85-xAexCoO3-δ (x = 0 and Ae = Ba0.28; Ca0.17) perovskites by in-situ neutron diffraction
- 2010
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Ingår i: Materials Research Bulletin. - : Elsevier BV. - 0025-5408. ; 45:12, s. 1875-1882
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Tidskriftsartikel (refereegranskat)abstract
- The oxygen deficient perovskites, Bi0.15Sr0.85-xAexCoO3-δ, x = 0 and Aex = Ba0.28, Ca0.17, were studied with in-situ neutron powder diffraction and combined TGA/DSC in order to investigate their behaviour at elevated temperatures in oxidising conditions. The phase stability of the I4/mmm supercell structure adopted by Bi0.15Sr0.85CoO3-δ is shown to be dependent on temperature and the oxygen content of the phase, with three structural events, at T 250, 590 and 880 °C, detected. The first transition occurs as the perovskite supercell vanishes due to oxygen absorption; the second transition is also associated with oxidation and involves the decomposition of the perovskite phase via an exothermic process to yield a dominant hexagonal phase. Finally, at T 900 °C the perovskite phase re-forms. For the Ba and Ca containing materials the decomposition to the hexagonal phase occurs at T 600 °C and 650 °C respectively. The presence of Ca at the A-site is found to stabilise the I4/mmm supercell structure in the range RT - 650 °C. The antiferromagnetic to paramagnetic transitions occur at TN 250 °C, TN 175 °C and TN 145 °C for the samples with Aex = Ba0.28, x = 0 and Aex = Ca0.17, respectively.
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| 7. |
- Eriksson, Jenny, 1975-, et al.
(författare)
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Intressent- och behovsanalys för resvaneundersökningar : resultat från intervjuer och enkätundersökning
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- I Sverige genomförs en nationell resvaneundersökning med viss regelbundenhet med Trafikanalys som ansvarig myndighet. Undersökningen har problem med bortfall, täckning, kostnader och uppgiftslämnarbörda. Ett projekt pågår som syftar till att utveckla nya metoder för att samla in data om personers mobilitet. Projektet är indelat i fem arbetspaket, varav detta arbete är ett. Syftet är att utföra en intressent- och behovsanalys avseende framtida resvaneundersökningar. I detta ingår att identifiera syften och frågeställningar som resvaneundersökningar ska kunna hantera och besvara.Det genomfördes 20 telefonintervjuer och utskick av webbenkät till 142 personer (svar från 81 personer, svarsfrekvens 57 procent). Intressenterna delades in i tre olika grupper: offentlig sektor, forskningsorganisation och övriga aktörer. Tillsammans med egna erfarenheter har en analys gjorts av vad som efterfrågas från den nationella resvaneundersökningen. Frågeställningar som centrala för användare av resvaneundersökningar är val av färdsätt, resans ärende samt mått på hur resvanorna förändras över tid och hur olika grupper reser. För detta behövs både uppgifter om individen och resorna. Utöver detta önskar man bra data på kommunal nivå eller lägre. Dock kan Trafikanalys i nuläget inte erbjuda den möjligheten, men här finns det möjlighet för kommuner, regioner och andra aktörer att välja ett extraurval från den befintliga nationella resvaneundersökningen.
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| 8. |
- Eriksson, Jenny, 1975-, et al.
(författare)
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New ways of collecting individual travel information : Evaluation of data collection and recruitment methods
- 2018
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The overall purpose of the project is to conduct a demonstration study that shows how two data collection methods that have been developed to collect travel survey data perform in the field, and how they perform compared with traditional TS (i.e., postal questionnaires and/or telephone interviews). The project is also intended to provide a better understanding of the ways in which different recruitment methods of respondents can be used so that future TS can be more cost effective.The two collection methods tested consist of a mobile app and an online questionnaire with a map to assist the respondents to identify travel destinations. Three recruitment methods were used, i.e., recruitment via random sampling, a web panel, and crowdsourcing. The portion of the random sample that received an online questionnaire was divided into two groups. Half the group was given no incentive, while the other half received a gift card worth SEK 100 after answering the questioner. Those who were recruited via a web panel and were to use the mobile app were rewarded in the form of a gift card worth SEK 100 if, at minimum, they made corrections to trips made on one day registered in the mobile app. A nonresponse analysis was performed of the random sample for both the online questionnaire and the mobile app. Cost estimates for each collection method and recruitment method were also performed, as were uncertainty estimates.Overall, the study shows that the mobile app registered significantly more trips per respondent than did the online questionnaire, while the distances travelled were comparable. There are several possible interpretations of this. One is that people who responded to the online questionnaire either forget about and/or combined short trips (particularly trips made for the purposes of leisure or shopping, and using the travel modes walking and car). One presumable explanation for this is that it is easier to confirm/correct the trips that the mobile app suggests than it is to recall and enter all trips in an online questionnaire. Another possible interpretation is that people responding to different data collection methods have different travel patterns. Yet another explanation is connected to technique issues regarding the different data collection methods.
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| 9. |
- Eriksson, Jenny, 1975-, et al.
(författare)
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Nya sätt att samla in individuell resvaneinformation : Utvärdering av insamlings- och rekryteringsmetoder
- 2018
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Inom samverkansprogrammet Nästa generations resor och transporter, som Trafikanalys är huvudansvarig för, har man identifierat ett behov av att finna och utveckla nya lösningar för resvaneundersökningar (RVU:er). Bakgrunden till detta är bland annat sjunkande svarsfrekvenser med dagens metoder, vilket skulle kunna ge problem med representativiteten. Det anses som mycket angeläget att utveckla nya metoder för datainsamling för framtidens RVU:er, både på kort och lång sikt.Det övergripande syftet med projektet är att göra en demonstrationsstudie som visar hur två datainsamlingsmetoder som har utvecklats för att samla in resevaneundersökningsdata presterar i fält, samt hur de presterar jämfört med ”traditionell” RVU (postal enkät och/eller telefonintervjuer). Projektet syftar också till att få bättre förståelse för hur olika rekryteringsmetoder kan användas för att framtida RVU:er ska kunna bli mer kostnadseffektiva. De två insamlingsmetoder som testats är webbenkät med karta och mobilapp. Tre rekryteringsmetoder har använts och dessa är rekrytering via slumpmässigt urval, webbpanel och crowdsourcing.
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| 10. |
- Malmgren, Christine, et al.
(författare)
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Nanocrystallinity in RuO2 coatings-Influence of precursor and preparation temperature
- 2010
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 518:14, s. 3615-3618
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Tidskriftsartikel (refereegranskat)abstract
- The effects of precursor and calcination temperature on the nano morphology of ruthenium dioxide on titanium, prepared from thermal decomposition of aqueous salt solutions were investigated. Transmission electron microscopy. X-ray diffraction, gas porosimetry and cyclic voltammetry showed that lower calcination temperature yielded smaller crystallites. The crystallites were between 6 and 22 nm in diameter. When using ruthenium nitrosyl nitrate the firing temperature had a large impact on the grain size, but for chloride there was only a minor effect in the temperature range 350-550 degrees C.
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