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  • 1.
    Airey, John
    et al.
    Uppsala universitet, Fysikundervisningens didaktik.
    Eriksson, Urban
    Uppsala universitet, Fysikundervisningens didaktik.
    Fredlund, Tobias
    Uppsala universitet, Fysikundervisningens didaktik.
    Linder, Cedric
    Uppsala universitet, Fysikundervisningens didaktik.
    On the Disciplinary Affordances of Semiotic Resources2014Ingår i: IACS-2014 Book of abstracts, 2014, s. 54-55Konferensbidrag (Refereegranskat)
    Abstract [en]

    In the late 70’s Gibson (1979) introduced the concept of affordance. Initially framed around the needs of an organism in its environment, over the years the term has been appropriated and debated at length by a number of researchers in various fields. Most famous, perhaps is the disagreement between Gibson and Norman (1988) about whether affordances are inherent properties of objects or are only present when they are perceived by an organism. More recently, affordance has been drawn on in the educational arena, particularly with respect to multimodality (see Linder (2013) for a recent example). Here, Kress et al. (2001) have claimed that different modes have different specialized affordances. Then, building on this idea, Airey and Linder (2009) suggested that there is a critical constellation of modes that students need to achieve fluency in before they can experience a concept in an appropriate disciplinary manner. Later, Airey (2009) nuanced this claim, shifting the focus from the modes themselves to a critical constellation of semiotic resources, thus acknowledging that different semiotic resources within a mode often have different affordances (e.g. two or more diagrams may form the critical constellation).

    In this theoretical paper the concept of disciplinary affordance (Fredlund et al., 2012) is suggested as a useful analytical tool for use in education. The concept makes a radical break with the views of both Gibson and Norman in that rather than focusing on the discernment of one individual, it refers to the disciplinary community as a whole. Put simply, the disciplinary affordances of a given semiotic resource are determined by those functions that the resource is expected to fulfil by the disciplinary community. Disciplinary affordances have thus been negotiated and developed within the discipline over time. As such, the question of whether these affordances are inherent or discerned becomes moot. Rather, from an educational perspective the issue is whether the meaning that a semiotic resource affords to an individual matches the disciplinary affordance assigned by the community. The power of the term for educational work is that learning can now be framed as coming to discern the disciplinary affordances of semiotic resources.

    In this paper we will briefly discuss the history of the term affordance, define the term disciplinary affordance and illustrate its usefulness in a number of educational settings.

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    bilaga
  • 2.
    An, Siwen
    et al.
    Mittuniversitet.
    Reza, Salim
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektroteknik, matematik och naturvetenskap, Elektronik.
    Norlin, Börje
    Mittuniversitet.
    Fröjdh, Christer
    Mittuniversitet.
    Thungström, Göran
    Mittuniversitet.
    Signal-to-noise ratio optimization in X-ray fluorescence spectrometry for chromium contamination analysis2021Ingår i: Talanta: The International Journal of Pure and Applied Analytical Chemistry, ISSN 0039-9140, E-ISSN 1873-3573, Vol. 230, artikel-id 122236Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In most cases, direct X-ray fluorescence (XRF) analysis of solutions entails technical difficulties due to a high X-ray scattering background resulting in a spectrum with a poor signal-to-noise ratio (SNR). Key factors that determine the sensitivity of the method are the energy resolution of the detector and the amount of scattered radiation in the energy range of interest. Limiting the width of the primary spectrum by the use of secondary targets, or filters, can greatly improve the sensitivity for specific portions of the spectrum. This paper demonstrates a potential method for SNR optimization in direct XRF analysis of chromium (Cr) contamination. The suggested method requires minimal sample preparation and achieves higher sensitivity compared to existing direct XRF analysis. Two states of samples, fly ash and leachate from municipal solid waste incineration, were investigated. The effects of filter material, its absorption edge and filter thickness were analyzed using the combination of Monte Carlo N-Particle (MCNP) code and energy-dispersive XRF spectrometry. The applied filter removes primary photons with energies interfering with fluorescence photons from the element of interest, thus results in lower background scattering in the spectrum. The SNR of Cr peak increases with filter thickness and reaches a saturation value when further increased thickness only increases the measurement time. Measurements and simulations show that a Cu filter with a thickness between 100 μm and 140 μm is optimal for detecting Cr by taking into account both the SNR and the exposure time. With direct XRF analysis for solutions, the limit of quantitation (LOQ) of the achieved system was 0.32 mg/L for Cr, which is well below the allowed standard limitation for landfills in Sweden. This work shows that XRF can gain enough sensitivity for direct monitoring to certify that the Cr content in leachate is below environmental limits.

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    fulltext
  • 3.
    Backenhamn Ohlsson, Margareta
    Högskolan i Gävle, Akademin för teknik och miljö.
    Fysik genom musik: en introduktion av fysikaliska fenomen i förskolans vardag med stöd av ett arbetsmaterial och en lärarhandledning2013Självständigt arbete på grundnivå (yrkesexamen), 210 hpStudentuppsats (Examensarbete)
    Ladda ner fulltext (pdf)
    Examensarbete pdf-fil
  • 4.
    Bennett, J. M.
    et al.
    Physics Division, Michelson Laboratory, Naval Air Warfare Center, China Lake, CA, United States.
    Rönnow, Daniel
    Acreo AB, Kista, Sweden.
    Test of Opticlean strip coating material for removing surface contamination2000Ingår i: Applied Optics, ISSN 0003-6935, E-ISSN 1539-4522, Vol. 39, nr 16, s. 2737-2739Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The strip coating material, Opticlean, which has been reformulated, has been shown to remove 1-5-mu m-diameter particles as well as contamination remaining from previous drag wipe cleaning on a used silicon wafer. In addition, no residue that produced scattering was found on a fresh silicon wafer when Opticlean was applied and then stripped off. The total integrated scattering technique used for the measurements could measure scattering levels of He-Ne laser light as low as a few ppm (parts in 106), corresponding to a surface roughness of <1 Angstrom rms.

  • 5. Beställ onlineKöp publikationen >>
    Björling, Mikael
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Miljöteknik.
    Kemi för de yngre åren2016Ingår i: Ämnesdidaktiska utmaningar inom matematik, naturvetenskap och teknik / [ed] Mikael Björling, Gävle: Gävle University Press , 2016, 1, s. 109-132Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    Abstract [sv]

    Detta är bakgrunden till att små barn är fascinerande av att leka Titt-ut,men som alla föräldrar vet så försvinner den lekens lockelse när barnet blir äldre. Barn utvecklas snabbt i de yngre åren, vilket skapar både möjligheter och begränsningar för hur lärande i naturvetenskap och kemi uppstår i förskolan och grundskolan. Det finns många skäl till att kemirelaterade aktiviteter bör introduceras i de yngre åren och i det här kapitlet diskuteras några av dessa skäl ur ett kemididaktiskt perspektiv. Kapitlet är uppbyggt kring några av de betydande framsteg som gjorts i den utvecklingspsykologiska forskningen under de senaste tjugo åren (Gärdenfors, 2006). Idag vet vi ganska mycket om hur våra hjärnor fungerar och utvecklas. Insprängt i denna beskrivning kommer jag att reflektera kring hur detta skulle kunna påverka valet av innehåll när det gäller naturvetenskapligt lärande för yngre barn. På slutet sammanfattar jag tankarna om innehåll med ett speciellt fokus på kemi.

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    fulltext
  • 6.
    Bondesson, Laban
    et al.
    KTH.
    Hugosson, Håkan Wilhelm
    Calculations of the cavitation volumes and partial molar volumes of drugs in waterManuskript (preprint) (Övrigt vetenskapligt)
  • 7.
    Bustad, Johnny
    Högskolan i Gävle, Institutionen för matematik, natur- och datavetenskap. Natur.
    Computational studies of core level XPS satellites in transition metal systems: Department of Quantum Chemistry, Uppsala University1995Doktorsavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    Upon core ionization of a free molecule or a molecule adsorbed on a metal surface, higher binding energy satellites are observed, so called "shake-up" satellites, which can be viewed as valence excitations simultaneously to the creation of the core hole. In this thesis, theoretical studies of such core level XPS satellites in transition metal systems are presented, as well as cluster calculations of XES spectra, using the quantum mechanical INDO method. The main motivation of these studies is to get a more detailed understanding of the bonding between the adsorbed molecules and the metal and the screening process accompanying the creation of the core hole. This interest is motivated by fundamental questions about the adsorbate-substrate interaction as well as technical applications, such as catalysis.

    It has been found that many aspects of extended adsorbate systems, where CO is coordinated to metal atoms, can be modelled by transition metal carbonyls such as Mo(CO)6, Cr(CO)6 and Ni(CO)4. The bonding between the core ionized CO group and the transition metal, consists of an interaction between, on the one hand, the sigma lone pair of the ligand and, on the other hand, the metal d-orbitals and the CO antibonding pi-star orbital of the CO-group, i.e. a sigma donation from the ligand and pi donation from the metal. It is the changes in this bonding which are responsible for the dominant features of the shake-up spectra in the studied model molecules. The main conclusion of the three abovementioned case studies is that new excitations involving charge transfer from the metal to the ionized ligand occur with significant probability in the metal carbonyls, in addition to the internal excitations present also in free CO.

    In extending the model towards larger systems, calculations of CO/Ni(100), N2//Ni(100), CO/Cu(100) and benzene/Cu(100) were undertaken, where the metal surface was modelled by clusters of 1-12 metal atoms. Many of the features from the metal carbonyls are found also in these systems. The most important added feature is the presence of high-intensity metal-metal excitations, which mainly affect the shape of the main line.

    Ground state cluster calculations were performed to explain the XES spectra of CO adsorbed on Ni(100) and Cu(100) surfaces. It was found that the calculations reproduce the important characteristics of the experimental spectra, and were used as a support for the assignments of the involved states.

  • 8.
    Cardona, M.
    et al.
    Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany.
    Rönnow, Daniel
    Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany.
    Santos, P. V.
    Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany.
    Ellipsometric investigations of piezo-optical effects1998Ingår i: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 313-314, s. 10-17Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An introduction to the stress-induced birefringence of solids, with emphasis on cubic and amorphous materials, is given. Most available experimental data have been obtained in the frequency region below the electronic absorption edge: the corresponding coefficients of the stress-optical tensor are then real. Above the edge (and also in the IR region of the Reststrahlen) they become complex. Ellipsometry is an excellent tool for the investigation of complex stress-optical functions. It also yields the hydrostatic pressure induced changes in the dielectric functions. Data obtained recently for diamond and zincblende-type crystals and their theoretical interpretation are discussed.

  • 9.
    Carreras Bertran, Antoni
    Högskolan i Gävle, Akademin för teknik och miljö.
    Energy System and Economic Analysis of District coolingin the city hall of Gävle2013Självständigt arbete på avancerad nivå (magisterexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Ladda ner fulltext (pdf)
    Energy System and Economic Analysis of District coolingin the city hall of Gävle
  • 10. Chen, R.
    et al.
    Wang, M.
    Wang, S.
    Liang, Hao
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Hu, X.
    Sun, X.
    Zhu, J.
    Ma, L.
    Jiang, M.
    Hu, J.
    Li, J.
    A low cost surface plasmon resonance biosensor using a laser line generator2015Ingår i: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 349, s. 83-88Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Due to the instrument designed by using a common surface plasmon resonance biosensor is extremely expensive, we established a portable and cost-effective surface plasmon resonance biosensing system. It is mainly composed of laser line generator, P-polarizer, customized prism, microfluidic cell, and line Charge Coupled Device (CCD) array. Microprocessor PIC24FJ128GA006 with embedded A/D converter, communication interface circuit and photoelectric signal amplifier circuit are used to obtain the weak signals from the biosensing system. Moreover, the line CCD module is checked and optimized on the number of pixels, pixels dimension, output amplifier and the timing diagram. The micro-flow cell is made of stainless steel with a high thermal conductivity, and the microprocessor based Proportional-Integral-Derivative (PID) temperature-controlled algorithm was designed to keep the constant temperature (25 °C) of the sample solutions. Correspondingly, the data algorithms designed especially to this biosensing system including amplitude-limiting filtering algorithm, data normalization and curve plotting were programmed efficiently. To validate the performance of the biosensor, ethanol solution samples at the concentrations of 5%, 7.5%, 10%, 12.5% and 15% in volumetric fractions were used, respectively. The fitting equation ΔRU=-752987.265+570237.348×RI with the R-Square of 0.97344 was established by delta response units (ΔRUs) to refractive indexes (RI). The maximum relative standard deviation (RSD) of 4.8% was obtained. 

  • 11.
    de Almeida, Katia Julia
    et al.
    KTH.
    Rinkevicius, Zilvinas
    KTH.
    Hugosson, Håkan Wilhelm
    KTH.
    Ferreira, Amary Cesar
    Universidade Federal de Minas Gerais, Brazil.
    Ågren, Hans
    KTH.
    Modeling of EPR parameters of copper(II) aqua complexes2007Ingår i: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 332, nr 2-3, s. 176-187Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper we report density functional theory calculations of the electronic g-tensor and hyperfine coupling constants of the copper dication in sixfold- and fivefold-coordination models of the first aqueous solvation sphere. The obtained results indicate that the electronic g-tensor of these copper complexes in combination with hyperfine coupling constants of copper in principle can be used to elucidate the coordination environment of the hydrated copper dication. In addition to these results, we have designed a methodology for accurate evaluation of electronic g-tensors and hyperfine coupling tensors in copper complexes, and demonstrate the applicability of this approach to copper dication aqua complexes.

  • 12.
    Fredlund, Tobias
    Uppsala universitet, Fysikundervisningens didaktik.
    Exploring physics education using a social semiotic perspective: the critical role of semiotic resources2013Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 13.
    Fredlund, Tobias
    Uppsala universitet, Fysikundervisningens didaktik.
    Exploring Representations in Physics Teaching and Learning2010Konferensbidrag (Refereegranskat)
  • 14.
    Fredlund, Tobias
    Uppsala universitet, Fysikundervisningens didaktik.
    Learning science and the selection of apt signifiers: an example from physics2013Konferensbidrag (Refereegranskat)
  • 15.
    Fredlund, Tobias
    Uppsala universitet, Fysikundervisningens didaktik.
    Multimodality in Students Physics Discussions2010Konferensbidrag (Refereegranskat)
  • 16.
    Fredlund, Tobias
    Uppsala universitet, Fysikundervisningens didaktik.
    Using a Social Semiotic Perspective to Inform the Teaching and Learning of Physics2015Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This thesis examines meaning-making in three different areas of undergraduate physics: the refraction of light; electric circuits; and, electric potential and electric potential energy. In order to do this, a social semiotic perspective was constituted for the thesis to facilitate the analysis of meaning-making in terms of the semiotic resources that are typically used in the teaching and learning of physics. These semiotic resources include, for example, spoken and written language, diagrams, graphs, mathematical equations, gestures, simulations, laboratory equipment and working practices.

    The empirical context of the thesis is introductory undergraduate physics where interactive engagement was part of the educational setting. This setting presents a rich data source, which is made up of video- and audio recordings and field notes for examining how semiotic resources affect physics teaching and learning.

    Theory building is an integral part of the analysis in the thesis, which led to the constitution of a new analytical tool – patterns of disciplinary-relevant aspects. Part of this process then resulted in the development of a new construct, disciplinary affordance, which for a discipline such as physics, refers to the inherent potential of a semiotic resource to provide access to disciplinary knowledge. These two aspects, in turn, led to an exploration of new empirical and theoretical links to the Variation Theory of Learning.

    The implications of this work for the teaching and learning of physics means that new focus is brought to the physics content (object of learning), the semiotic resources that are used to deal with that content, and how the semiotic resources are used to create patterns of variation within and across the disciplinary-relevant aspects. As such, the thesis provides physics teachers with new and powerful ways to analyze the semiotic resources that get used in efforts to optimize the teaching and learning of physics. 

  • 17.
    Fredlund, Tobias
    et al.
    Uppsala universitet, Fysikundervisningens didaktik.
    Airey, John
    Uppsala universitet, Fysikundervisningens didaktik.
    Linder, Cedric
    Uppsala universitet, Fysikundervisningens didaktik.
    Att välja lämpliga semiotiska resurser2013Ingår i: Scientific literacy: teori och praktik / [ed] E. Lundqvist, R. Säljö & L. Östman, Malmö: Gleerups Utbildning AB, 2013, s. 59-70Kapitel i bok, del av antologi (Refereegranskat)
  • 18.
    Fredlund, Tobias
    et al.
    Uppsala universitet, Fysikundervisningens didaktik.
    Airey, John
    Uppsala universitet, Fysikundervisningens didaktik.
    Linder, Cedric
    University of the Western Cape, Cape Town, South Africa.
    Choosing appropriate resources: investigating students’ scientific literacy2012Ingår i: ECER 2012, 2012, artikel-id 18275Konferensbidrag (Refereegranskat)
  • 19.
    Fredlund, Tobias
    et al.
    Uppsala universitet, Fysikundervisningens didaktik.
    Airey, John
    Uppsala universitet, Fysikundervisningens didaktik.
    Linder, Cedric
    Uppsala universitet, Fysikundervisningens didaktik.
    Critical aspects of scientific phenomena -- to the fore, in the background, or not present in scientific representations2012Konferensbidrag (Refereegranskat)
  • 20.
    Fredlund, Tobias
    et al.
    Uppsala universitet, Fysikundervisningens didaktik.
    Airey, John
    Uppsala universitet, Fysikundervisningens didaktik.
    Linder, Cedric
    Uppsala universitet, Fysikundervisningens didaktik.
    Enhancing the possibilities for learning: Variation of disciplinary-relevant aspects in physics representations2015Ingår i: European journal of physics, ISSN 0143-0807, E-ISSN 1361-6404, Vol. 36, nr 5, artikel-id 055001Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this theoretical article we propose three factors that can enhance the possibilities for learning physics from representations, namely: (1) the identification of disciplinary-relevant aspects for a particular disciplinary task, such as solving a physics problem or explaining a phenomenon, (2) the selection of appropriate representations that showcase these disciplinary-relevant aspects, and (3) the creation of variation within the selected representations to help students notice these disciplinary-relevant aspects and the ways in which they are related to each other. An illustration of how these three factors can guide teachers in their efforts to promote physics learning is presented.

  • 21.
    Fredlund, Tobias
    et al.
    Uppsala universitet, Fysikundervisningens didaktik.
    Airey, John
    Uppsala universitet, Fysikundervisningens didaktik.
    Linder, Cedric
    Uppsala universitet, Fysikundervisningens didaktik.
    Exploring the role of physics representations: an illustrative example from students sharing knowledge about refraction2012Ingår i: European journal of physics, ISSN 0143-0807, E-ISSN 1361-6404, Vol. 33, nr 3, s. 657-666Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Research has shown that interactive engagement enhances student learning outcomes. A growing body of research suggests that the representations we use in physics are important in such learning environments. In this paper we draw on a number of sources in the literature to explore the role of representations in interactive engagement in physics. In particular we are interested in the potential for sharing disciplinary knowledge inherent in so-called persistent representations (such as equations, diagrams and graphs), which we use in physics. We use selected extracts from a case study, where a group of senior undergraduate physics students are asked to explain the phenomenon of refraction, to illustrate implications for interactive engagement. In this study the ray diagram that was initially introduced by the students did not appear to sufficiently support their interactive engagement. However, the introduction of a wavefront diagram quickly led their discussion to an agreed conclusion. From our analysis we conclude that in interactive engagement it is important to choose appropriate persistent representations to coordinate the use of other representations such as speech and gestures. Pedagogical implications and future research are proposed.

    Ladda ner fulltext (pdf)
    fulltext
  • 22.
    Fredlund, Tobias
    et al.
    Uppsala universitet, Fysikundervisningens didaktik.
    Linder, Cedric
    Uppsala universitet, Fysikundervisningens didaktik.
    Making physics learning possible: exploring a variation perspective on representations2013Konferensbidrag (Refereegranskat)
  • 23.
    Fredlund, Tobias
    et al.
    Uppsala universitet, Fysikundervisningens didaktik.
    Linder, Cedric
    Uppsala universitet, Fysikundervisningens didaktik.
    Naturvetarnas ‘språk’: användandet av figurer, artefakter, ekvationer och ord i studentdiskussioner om fysikaliska fenomen2010Konferensbidrag (Övrigt vetenskapligt)
    Abstract [sv]

    Klyftan mellan vardagsspråket och språkbruket i en naturvetenskaplig disciplin, som t.ex. fysik, kan upplevas problematisk av den som inte har tillägnat sig det aktuella vetenskapliga språket. Detta blir extra tydligt om vi utökar definitionen av ”språk” till att också innefatta andra semiotiska resurser än talad och skriven text, som t.ex figurer, grafer, ekvationer och andra ”artefakter” såsom laboratorieutrustning. Olika semiotiska resurser kan antas ha olika styrkor, och lämna kompletterande information. Från ett lärandeperspektiv är det viktigt att veta hur den nämnda språkklyftan kan överbryggas, särskilt när nya fenomen ska introduceras i undervisningen. Finns det för ett visst fenomen någon semiotisk resurs (läs språngbräda) som är särskilt viktig för förståelsen av de vetenskapliga förklaringarna?

    Refraktion är ett fysikaliskt fenomen som innebär att exempelvis ljus ändrar riktning, bryts, när det går från ett medium till ett annat, i vilka ljushastigheterna är olika. Denna riktningsändring ger upphov till att en rak pinne som är delvis i luften och delvis nedsänkt i vatten, ser ut att böjas vid vattenytan. Detta fenomen kan beskrivas av en rad olika semiotiska resurser, som olika typer av diagram och ekvationer. I denna undersökning har jag tittat på vilka semiotiska resurser som används när tre fysikstudenter diskuterar hur de skulle förklara upplevelsen att en pinne delvis nedsänkt i vatten ser ut att böjas vid vattenytan för dels en icke fysik-studerande, dels en kurskamrat i en fysikkurs. Diskussionen har videofilmats och transkriberats. Ytterligare material har insamlats från liknande gruppdiskussioner, där deltagarna fått anteckna sina resultat på papper. Data har analyserats efter vilka semiotiska resurser som förekommer, och vilken betydelse de haft för diskussionen.

    Resultatet av undersökningen kommer att presenteras i form av en poster, där bilder på de använda semiotiska resurserna visas. Den pågående analysen antyder att en viss typ av diagram, som utnyttjar ljusets vågnatur, är av särskild vikt för förståelsen av detta fenomen, och en möjlig nyckel till djupare förståelse av fenomenet.

    Ladda ner fulltext (pdf)
    fulltext
  • 24.
    Fredlund, Tobias
    et al.
    Uppsala universitet, Fysikundervisningens didaktik.
    Linder, Cedric
    Uppsala universitet, Fysikundervisningens didaktik.
    Airey, John
    Uppsala universitet, Fysikundervisningens didaktik.
    A case study of the role of representations in enabling and constraining the sharing of physics knowledge in peer discussions2012Konferensbidrag (Refereegranskat)
  • 25.
    Fredlund, Tobias
    et al.
    Uppsala universitet, Fysikundervisningens didaktik.
    Linder, Cedric
    Uppsala universitet, Fysikundervisningens didaktik.
    Airey, John
    Uppsala universitet, Fysikundervisningens didaktik.
    A social semiotic approach to identifying critical aspects2015Ingår i: International Journal for Lesson and Learning Studies, ISSN 2046-8253, E-ISSN 2046-8261, Vol. 4, nr 3, s. 302-316Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Purpose

    This article proposes a social semiotic approach to analysing objects of learning in terms of their critical aspects.

    Design/methodology/approach

    The design for this article focuses on how the semiotic resources – including language, equations, and diagrams – that are commonly used in physics teaching realise the critical aspects of a common physics object of learning. A social semiotic approach to the analysis of a canonical text extract from optics is presented to illustrate how critical aspects can be identified. 

    Findings

    Implications for university teaching and learning of physics stemming from this social semiotic approach are suggested.

    Originality/value

    Hitherto under-explored similarities between the Variation Theory of Learning, which underpins learning studies, and a social semiotic approach to meaning-making are identified. These similarities are used to propose a new, potentially very powerful approach to identifying critical aspects of objects of learning.

    References:

    Airey, J. and Linder, C. (2009), “A disciplinary discourse perspective on university science learning: achieving fluency in a critical constellation of modes”, Journal of Research in Science Teaching, Vol. 46 No. 1, pp. 27-49.

    Bernhard, J. (2010), “Insightful learning in the laboratory: some experiences from 10 years of designing and using conceptual labs”, European Journal of Engineering Education, Vol. 35 No. 3, pp. 271-287.

    Booth, S. (1997), “On phenomenography, learning and teaching”, Higher Education Research & Development, Vol. 16 No. 2, pp. 135-158. 

    Booth, S. and Hultén, M. (2003), “Opening dimensions of variation: an empirical study of learning in a web-based discussion”, Instructional Science, Vol. 31 Nos 1/2, 65-86.

    Chandler, D. (2007), Semiotics: The Basics, Routledge, New York, NY. Clerk-Maxwell, J.C. (1871), “Remarks on the mathematical classification of physical quantities”, Proceedings London Math. Soc., London, pp. 224-233.

    Cope, C. (2000), “Educationally critical aspects of the experience of learning about the concept of an information system”, PhD thesis, La Trobe University, Bundoora.

    Einstein, A. (1936), “Physics and reality”, Journal of the Franklin Institute, Vol. 221 No. 3, pp. 349-382.

    Feynman, R.P., Leighton, R.P. and Sands, M. (1963), The Feynman Lectures on Physics, Vol. I, Perseus Books, Reading, available at: www.feynmanlectures.caltech.edu, (accessed 9 March 2015).

    Fredlund, T., Airey, J. and Linder, C. (2012), “Exploring the role of physics representations: an illustrative example from students sharing knowledge about refraction”, Eur. J. Phys., Vol. 33 No. 3, pp. 657-666.

    Fredlund, T., Airey, J. and Linder, C. (2015), “Enhancing the possibilities for learning: variation of disciplinary-relevant aspects in physics representations”, Eur. J. Phys, Vol. 36, 055001.

    Fredlund, T., Linder, C., Airey, J. and Linder, A. (2014), “Unpacking physics representations: towards an appreciation of disciplinary affordance”, Phys. Rev. ST Phys. Educ. Res., Vol. 10, 020129.

    Gurwitsch, A. (1964), The Field of Consciousness, Vol. 2, Duquesne University Press, Pittsburgh, PA. Halliday, M.A.K. (1978), Language as Social Semiotic, Edward Arnold, London.

    Halliday, M.A.K. (1993), “On the language of physical science”, in Halliday, M.A.K. and Martin, J.R. (Eds), Writing Science: Literacy and Discursive Power, The Falmer Press, London, pp. 59-75.

    Halliday, M.A.K. (1998), “Things and relations: regrammaticising experience as technical knowledge”, in Martin, J.R. and Veel, R. (Eds), Reading Science: Critical and Functional Perspectives on Discourses of Science, Routledge, London, pp. 185-236.

    Halliday, M.A.K. (2004a), “The grammatical construction of scientific knowledge: the framing of the English clause”, in Webster, J.J. (Ed.), Collected Works of M.A.K. Halliday: The Language of Science, Vol. 5, Continuum, London, pp. 102-134.

    Halliday, M.A.K. (2004b), “Language and the reshaping of human experience”, in Webster, J.J. (Ed.), Collected Works of M.A.K. Halliday: The Language of Science, Vol. 5, Continuum, London, pp. 7-23.

    Halliday, M.A.K. and Matthiessen, C.M.I.M. (1999), Construing Experience Through Meaning, Cassell, New York, NY.

    Halliday, M.A.K. and Matthiessen, C.M.I.M. (2004), An Introduction to Functional Grammar, Hodder Education, London.

    Hodge, R. and Kress, G. (1988), Social Semiotics, Cornell University Press, New York, NY.

    Ingerman, Å., Linder, C. and Marshall, D. (2009), “The learners’ experience of variation: following students’ threads of learning physics in computer simulation sessions”, Instructional Science, Vol. 37 No. 3, pp. 273-292.

    Kress, G. (1997), Before Writing: Rethinking the Paths to Literacy, Routledge, London.

    Kress, G. (2010), Multimodality: A Social Semiotic Approach to Contemporary Communication, Routledge, London.

    Kress, G. and Van Leeuwen, T. (2006), Reading Images: The Grammar of Visual Design, Routledge, New York, NY. 

    Kryjevskaia, M., Stetzer, M.R. and Heron, P.R.L. (2012), “Student understanding of wave behavior at a boundary: the relationships among wavelength, propagation speed, and frequency”, Am. J. Phys., Vol. 80 No. 4, pp. 339-347.

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    Lemke, J.L. (1990), Talking Science, Ablex Publishing, Norwood, NJ. Lemke, J.L. (1998), “Multiplying meaning: visual and verbal semiotics in scientific text”, in Martin, J.R. and Veel, R. (Eds), Reading Science: Critical and Functional Perspectives on Discourses of Science, Routledge, London, pp. 87-114.

    Lemke, J.L. (2003), “Mathematics in the middle: measure, picture, gesture, sign and word”, in Anderson M., Saenz-Ludlow A., Zellweger S. and Cifarelli V. (Eds), Educational Perspectives on Mathematics as Semiosis: From Thinking to Interpreting to Knowing, Legas, Ottawa, pp. 215-234.

    Linder, C., Fraser, D. and Pang, M.F. (2006), “Using a variation approach to enhance physics learning in a college classroom”, The Physics Teacher, Vol. 44 No. 9, pp. 589-592.

    Lo, M.L. (2012), Variation Theory and the Improvement of Teaching and Learning, Göteborgs Universitet, Gothenburg.

    Lo, M.L. and Marton, F. (2011), “Towards a science of the art of teaching: using variation theory as a guiding principle of pedagogical design”, International Journal for Lesson and Learning Studies, Vol. 1 No. 1, pp. 7-22.

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    Marton, F. (2006), “Sameness and difference in transfer”, The Journal of the Learning Sciences, Vol. 15 No. 4, pp. 499-535.

    Marton, F. (2015), Necessary Conditions of Learning, Routledge, New York, NY.

    Marton, F. and Booth, S. (1997), Learning and Awareness, Lawrence Erlbaum Associates, Mahwah, NJ.

    Marton, F. and Pang, M.F. (2013), “Meanings are acquired from experiencing differences against a background of sameness, rather than from experiencing sameness against a background of difference: putting a conjecture to the test by embedding it in a pedagogical tool”, Frontline Learning Research, Vol. 1 No. 1, pp. 24-41.

    Marton, F. and Tsui, A.B.M. (2004), Classroom Discourse and the Space of Learning, Lawrence Erlbaum Associates, London.

    Marton, F., Runesson, U. and Tsui, A.B.M. (2004), “The space of learning”, in Marton, F. and Tsui, A.B.M. (Eds), Classroom Discourse and the Space of Learning, Lawrence Erlbaum Associates, London, pp. 3-40.

    New London Group (1996), “A pedagogy of multiliteracies: designing social futures”, Harvard Educational Review, Vol. 66 No. 1, pp. 60-93. Norris, S.P. and Phillips, L.M. (2003), “How literacy in its fundamental sense is central to scientific literacy”, Science Education, Vol. 87 No. 2, pp. 224-240.

    O’Halloran, K.L. (2005), Mathematical Discourse: Language, Symbolism and Visual Images, Continuum, London.

    Pang, M.F. and Marton, F. (2013), “Interaction between the learners’ initial grasp of the object of learning and the learning resource orded”, Instructional Science, Vol. 41 No. 6, pp. 1065-1082.

    Van Leeuwen, T. (2005), Introducing Social Semiotics, Routledge, New York, NY.

    Warrell, D. A. (1994), “Sea snake bites in the Asia-Pacific region”, in Gopalakrishnakone, P. (Ed.), Sea Snake Toxinology, Singapore University Press, Singapore, pp. 1-36. 

    Wignell, P., Martin, J.R. and Eggins, S. (1993), “The discourse of geography: ordering and explaining the experiential world”, in Halliday, M.A.K. and Martin, J.R. (Eds), Writing Science: Literacy and Discursive Power, The Falmer Press, London, pp. 151-183.

    Wood, K. (2013), “A design for teacher education based on a systematic framework of variation to link teaching with learners’ ways of experiencing the object of learning”, International Journal for Lesson and Learning Studies, Vol. 2 No. 1, pp. 56-71.

    Young, H.D. and Freedman, R.A. (2004), University Physics with Modern Physics, Pearson, San Francisco, CA.

  • 26.
    Fredlund, Tobias
    et al.
    Uppsala universitet, Fysikundervisningens didaktik.
    Linder, Cedric
    Uppsala universitet, Fysikundervisningens didaktik.
    Airey, John
    Uppsala universitet, Fysikundervisningens didaktik.
    Learning in terms of the semiotic enactment of patterns of disciplinary-relevant aspects2014Ingår i: IACS-2014 Book of abstracts, 2014, s. 94-94Konferensbidrag (Refereegranskat)
    Abstract [en]

    Student learning typically takes place in a range of situational contexts. In this paper we consider “sets of situations that have certain relevant aspects in common” (Marton, 2006, p. 503) where each aspect involved is qualitatively unique. We argue that in order for students to come to holistically experience the relevant disciplinary knowledge, they need to become familiar with enacting those relevant aspects (i.e. expressing them with semiotic resources, such as spoken and written language, equations and images.).

    We suggest it is possible to construct idealized patterns of the aspects that a discipline deems to be relevant for a given field of knowledge – thus characterizing its typical situations and phenomena. We call such a pattern an “idealized pattern of disciplinary relevant aspects” (IPDRA). Each of the aspects that together constitute an IPDRA can be seen to be manifested in discourse in terms of particular configurations, partly prescribed by the “rules” governing the semiotic resource at hand (such as grammar for language). The discursive configurational patterns (cf. Lemke's, 1990, "thematic patterns"; and Tang et al.'s, 2011, "multimodal thematic patterns") that can be empirically found in student discourse can then be compared with the IPDRA to see whether the required aspects have been enacted.

    The semiotic resources that are used in a scientific discipline are often highly specialized. Any given semiotic resource may therefore be more appropriate for expressing certain (combinations of) situational aspects (what we have called its “disciplinary affordances”, see Fredlund, Airey, & Linder, 2012). We argue it is the disciplinary affordances that determine which semiotic resources that can do which work in terms of representing the knowledge captured by an IPDRA. A pedagogical implication of this is that students need to become fluent in, and learn to choose, those semiotic resources that have the most appropriate disciplinary affordances for enacting a given IPDRA.

    In this paper we demonstrate how different semiotic resources have different disciplinary affordances and thus how changing the semiotic resource can lead to the possibility to enact different aspects of disciplinary knowledge. 

    References

    Fredlund, T., Airey, J., & Linder, C. (2012). Exploring the role of physics representations: an illustrative example from students sharing knowledge about refraction. Eur. J. Phys., 33, 657-666. doi: 10.1088/0143-0807/33/3/657

    Lemke, J. L. (1990). Talking Science. Norwood, New Jersey: Ablex Publishing.

    Marton, F. (2006). Sameness and difference in transfer. The Journal of the Learning Sciences, 15(4), 499-535. 

    Tang, K. S., Tan, S. C., & Yeo, J. (2011). Students' multimodal construction of the work-energy concept. International Journal of Science Education, 33(13), 1775-1804. 

  • 27.
    Fredlund, Tobias
    et al.
    Uppsala universitet, Fysikundervisningens didaktik.
    Linder, Cedric
    Uppsala universitet, Fysikundervisningens didaktik.
    Airey, John
    Uppsala universitet, Fysikundervisningens didaktik.
    Towards addressing transient learning challenges in undergraduate physics: An example from electrostatics2015Ingår i: European journal of physics, ISSN 0143-0807, E-ISSN 1361-6404, Vol. 36, nr 5, artikel-id 055002Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this article we characterize transient learning challenges as learning challenges that arise out of teaching situations rather than conflicts with prior knowledge. We propose that these learning challenges can be identified by paying careful attention to the representations that students produce. Once a transient learning challenge has been identified, teachers can create interventions to address it. By illustration, we argue that an appropriate way to design such interventions is to create variation around the disciplinary-relevant aspects associated with the transient learning challenge.

  • 28.
    Fredlund, Tobias
    et al.
    Uppsala universitet, Fysikundervisningens didaktik.
    Linder, Cedric
    Uppsala universitet, Fysikundervisningens didaktik.
    Airey, John
    Uppsala universitet, Fysikundervisningens didaktik.
    Variation as a method for perceiving the disciplinary affordances of physics representations2014Ingår i: IACS-2014 Book of Abstracts, 2014, s. 32-33Konferensbidrag (Refereegranskat)
    Abstract [en]

    The sharing of knowledge in physics uses representations that the discipline has built a great deal of information into. In many cases, much of this information is not immediately visible because it has been “packed” in ways that can only be accessed by specific disciplinary ways of seeing. For example, consider the de Sitter space represented by a particular hyperboloid.

    This is a powerful representation for physicists working in the field of string theory because, inter alia, it can provide de Sitter space with a multiplicity of coordinate systems (Domert, 2006, p. 30). At the same time such a representation can present challenges to student learning; students would have to learn to “see” what “lies behind” the representation. In this case, for example, how R is related to the concept of a de Sitter horizon.

    While for physicists such a representation might evoke a rich awareness (or perhaps rather help constraining that awareness, cf. Ainsworth, 2006), it conceivably evokes little appropriate disciplinary meaning when first met by students. Northedge (2002) argues that physics teachers may not be aware that what they have learnt to “see” is not directly accessible to learners. That is, while physicists have developed a competency that allows them to immediately see the “disciplinary affordances” of a representation (“the inherent potential of that representation to provide access to disciplinary knowledge”, Fredlund, Airey, & Linder, 2012, p. 658) they fail to recognize that their students may not, or even cannot, see what lies behind that representation.

    Much research has shown that students often learn surprisingly little from traditional teaching resources such as talk-and-chalk followed by problem solving (Redish, 2003). To deal with this challenge several research-informed resources have been developed and empirically shown to enhance students’ learning outcomes. Widely used examples include Tutorials (McDermott & Shaffer, 2002), Active Learning (Van Heuvelen & Etkina, 2006) and Peer Instruction (Crouch & Mazur, 2001). However, these resources have not been accompanied with a theoretical framing that would enable physics teachers to develop their own teaching resources. We believe that such a theoretical framing exists: creating the explicit experience of dimensions of variation (Marton & Booth, 1997). 

    In this presentation we develop this argument and illustrate it using examples of how representations can be varied in ways that facilitate the noticing of educationally critical aspects.

    References

    Ainsworth, S. (2006). DeFT: A conceptual framework for considering learning with multiple representations. Learning and Instruction, 16(3), 183-198.

    Crouch, C. H., & Mazur, E. (2001). Peer Instruction: Ten years of experience and results. Am. J. Phys., 69(9), 970-977.

    Domert, D. (2006). Explorations of university physics in abstract contexts: from de Sitter space to learning space. PhD thesis, Uppsala University, Uppsala.

    Fredlund, T., Airey, J., & Linder, C. (2012). Exploring the role of physics representations: an illustrative example from students sharing knowledge about refraction. Eur. J. Phys., 33, 657- 666.

    Marton, F., & Booth, S. (1997). Learning and Awareness. Mahwah, New Jersey: Lawrence Erlbaum Associates. 

  • 29.
    Fredlund, Tobias
    et al.
    Uppsala universitet, Fysikundervisningens didaktik.
    Linder, Cedric
    Uppsala universitet, Fysikundervisningens didaktik.
    Airey, John
    Uppsala universitet, Fysikundervisningens didaktik.
    Linder, Anne
    Uppsala universitet, Fysikundervisningens didaktik.
    Unpacking physics representations: Towards an appreciation of disciplinary affordance2014Ingår i: Physical Review Special Topics : Physics Education Research, E-ISSN 1554-9178, Vol. 10, nr 2, artikel-id 020129Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This theoretical article problematizes the access to disciplinary knowledge that different physics representations have the possibility to provide; that is, their disciplinary affordances. It is argued that historically such access has become increasingly constrained for students as physics representations have been rationalized over time. Thus, the case is made that such rationalized representations, while powerful for communication from a disciplinary point of view, manifest as learning challenges for students. The proposal is illustrated using a vignette from a student discussion in the physics laboratory about circuit connections for an experimental investigation of the charging and discharging of a capacitor. It is concluded that in order for students to come to appreciate the disciplinary affordances of representations, more attention needs to be paid to their “unpacking.” Building on this conclusion, two questions are proposed that teachers can ask themselves in order to begin to unpack the representations that they use in their teaching. The paper ends by proposing directions for future research in this area.

  • 30.
    Fäldt, Åke
    et al.
    Chalmers University of Technology.
    Fredlund, Tobias
    Högskolan i Gävle, Akademin för utbildning och ekonomi, Avdelningen för utbildningsvetenskap, Utbildningsvetenskap, Didaktik.
    The gyroscopic effect and moment of inertia2023Ingår i: Physics Education, ISSN 0031-9120, E-ISSN 1361-6552, Vol. 58, nr 2, artikel-id 025001Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper describes a lab to help students develop their understanding of rotational motion. The focus is on moment of inertia, which the students investigate by rolling cylinders down a ramp and determine in two different ways for a bicycle wheel. The most important and original part of the lab is the exploration of the gyroscopic effect, where measurements of precession and rotation frequencies are made using the variation of the detected magnetic field, enabling the calculation of the moment of inertia. The lab is received well by the students and can be done with relatively simple equipment easily accessible to them.

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  • 31.
    Granqvist, C. G.
    et al.
    Department of Technology, Uppsala University, Uppsala, Sweden.
    Azens, A.
    Department of Technology, Uppsala University, Uppsala, Sweden.
    Kullman, L.
    Department of Technology, Uppsala University, Uppsala, Sweden.
    Rönnow, Daniel
    Department of Technology, Uppsala University, Uppsala, Sweden.
    Progress in Smart Windows Research: Improved Electrochromic W Oxide Films and Transparent Ti-Ce Oxide Counter Electrodes1996Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 8, nr 1-4, s. 97-106Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We review recent work on sputter deposited W-oxide-based films. Improved electrochemical durability was obtained by electron bombardment during deposition, and enhanced coloration/bleaching dynamics was obtained by fluorination. Spectrally resolved scattering measurements indicated that haze levels ≪ 1 % could be reached. Oblique angle deposition could yield angular selectivity. New results are given for sputtered Ti-Ce oxide films, showing their capacity as counter electrodes in transparent electrochromic devices.

  • 32.
    Granqvist, C.-G.
    et al.
    The Ångström Laboratory, Deptartment of Material Science, Uppsala University, Uppsala, Sweden.
    Azens, A.
    The Ångström Laboratory, Deptartment of Material Science, Uppsala University, Uppsala, Sweden.
    Hjelm, A.
    The Ångström Laboratory, Deptartment of Material Science, Uppsala University, Uppsala, Sweden.
    Kullman, L.
    The Ångström Laboratory, Deptartment of Material Science, Uppsala University, Uppsala, Sweden.
    Niklasson, G. A.
    The Ångström Laboratory, Deptartment of Material Science, Uppsala University, Uppsala, Sweden.
    Rönnow, Daniel
    The Ångström Laboratory, Deptartment of Material Science, Uppsala University, Uppsala, Sweden.
    Strömme, M.
    The Ångström Laboratory, Deptartment of Material Science, Uppsala University, Uppsala, Sweden.
    Veszelei, M.
    The Ångström Laboratory, Deptartment of Material Science, Uppsala University, Uppsala, Sweden.
    Vaivars, G.
    Institute of Solid State Physics, University of Latvia, Riga, Latvia.
    Recent advances in electrochromics for smart windows applications1998Konferensbidrag (Övrigt vetenskapligt)
  • 33.
    Grechnev, G. E
    et al.
    Uppsala universitet; Verkin Institute for Low Temperature Physics, Ukraine.
    Hugosson, Håkan Wilhelm
    Uppsala universitet.
    Ahuja, R
    Uppsala universitet.
    Eriksson, O
    Uppsala universitet.
    Structural Evolution and Hardness of Transition Metal Dioxides at High Pressure2000Ingår i: High Pressure Physics and Technology, Vol. 10, nr 38Artikel i tidskrift (Refereegranskat)
  • 34. Hugosson, Håkan Wilhelm
    A surface coating2000Patent (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

    H.W. Hugosson, “A Surface Coating”, SE0004203-6, WO0240734, US2004076856. This patent was developed from predictions and innovations stemming from my long term theoretical work on transition metal carbides and nitrides, coming to an apex in publication VIII and experimentally verified in publication XV. It is arguably one of the earliest examples of a patented innovation based on the results of electronic structure calculations (2000). 

  • 35. Hugosson, Håkan Wilhelm
    Theoretical Studies of Vacancies and Impurities in Molybdenum2000Ingår i: Frontiers in Interdisciplinary Physics, IAPS Press , 2000Kapitel i bok, del av antologi (Refereegranskat)
  • 36.
    Hugosson, Håkan Wilhelm
    et al.
    Department of Physics, Uppsala University.
    Engqvist, H
    Sandvik Hard Materials AB.
    The connection between the electronic structure and the properties of binderless tungsten carbides2003Ingår i: International journal of refractory metals & hard materials, ISSN 0263-4368, Vol. 21, nr 1-2, s. 55-61Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Using first principles density functional calculations, we here connect the physical properties of binderless tungsten carbides with the theoretical electronic structure as calculated from density functional theory calculations. We show that electronic structure calculations predict and explain various known phenomena in these systems, an example of how such theoretical studies can be a valuable tool in materials science. For example, changes in the energy of formation from 25% substitution with Mo or Ti is used to explain the differences in intermixing between binderless tungsten carbides using TiC or Mo2C as γ binder phase. Substitutions with Ti atoms are also predicted to stabilize tungsten carbide in the NaCl-structure. A study of the charge density redistribution after substitution is also made.

  • 37.
    Hugosson, Håkan Wilhelm
    et al.
    Department of Physics, Uppsala University; Department of Materials Science and Engineering, Royal Institute of Technology.
    Eriksson, O.
    Department of Physics, Uppsala University.
    Jansson, U.
    Ångström Laboratory, Uppsala University.
    Abrikosov, I.A.
    Department of Physics and Measurement Technology, Linköping University.
    Surface segregation of transition metal impurities on the TiC(100) surface2005Ingår i: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 585, nr 1-2, s. 101-107Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The segregation energies of 3d (Sc–Cu), 4d (Y–Ag) and 5d (La–Au) transition metal impurities on the (1 0 0) surface of TiC have been obtained using first-principles electronic structure calculations. The results are in agreement with available experimental data and show that the difference in atomic size between the impurity and host species, as well as the difference in surface energies determines if the impurity will segregate towards the surface or not. The results indicate that the difference in size is the dominant factor for the trends in segregation of transition metal impurities towards the (1 0 0) surface of TiC.

  • 38.
    Hugosson, Håkan Wilhelm
    et al.
    Department of Physics, Uppsala University; Department of Materials Science and Engineering, Royal Institute of Technology.
    Eriksson, O.
    Department of Physics, Uppsala University.
    Jansson, U.
    Department of Materials Chemistry, Uppsala University.
    Ruban, A.V.
    Center for Atomic-Scale Materials Physics and Department of Physics, Technical University of Denmar.
    Souvatzis, P.
    Department of Physics, Uppsala University.
    Abrikosov, I.A.
    Department of Physics, Uppsala University; Department of Physics and Measurements Technology, Linköping University.
    Surface energies and work functions of the transition metal carbides2004Ingår i: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 557, nr 1-3, s. 243-254Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have performed an ab initio study of the surface energies, surface electronic structures and work functions for the (1 0 0) surface of the, existent and hypothetical, cubic 3d (Sc–Cu), 4d (Zr–Ag) and 5d (La–Au) transition metal carbides. The calculated surface energies have been compared to predictions using a so-called bond-cutting model and a model based on the so-called bonding energies. The absolute values and rough trends of the surface energies are fairly well predicted within the simple bond-cutting model, as compared to fully self-consistent calculations, while both trends and absolute values are well reproduced within the bonding energy model. The electronic structure (densities of states) of the transition metal carbides at the surface and in the bulk have been calculated. The trends are discussed in relation to the behavior of the surface energy and the work function across the series.

  • 39.
    Hugosson, Håkan Wilhelm
    et al.
    Department of Physics, Uppsala University.
    Eriksson, Olle
    Ångström Laboratory, Uppsala University.
    Jansson, Ulf
    Department of Physics, Uppsala University.
    Johansson, Börje
    Department of Physics, Uppsala University.
    Phase stabilities and homogeneity ranges in 4d-transition-metal carbides: A theoretical study2001Ingår i: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 63, nr 13, artikel-id 134108Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    First-principles full-potential linear muffin-tin orbital calculations have been used to study the 4d-transition-metal carbides ZrC, NbC, and MoC. The experimental phase diagrams at T=0 of the refractory compounds ZrC, NbC, and MoC have been reproduced with great accuracy from first principles theory. The energy of formation for these compounds has been calculated for several phases and stoichiometries in order to understand the differences in phase stabilities and the changes in homogeneity ranges found between these systems is explained. The results can be regarded as theoretical zero-temperature phase stability diagrams for the three compounds containing not only the experimentally verified but also hypothetical phases and many of the experimental properties and trends are reproduced and explained. A study of the changes and differences in electronic structure and bonding of the studied compounds, phases and stoichiometries is also presented. As a part of this study the hexagonal Me2C (Me being Zr, Nb, or Mo) phases were studied and the theoretical structures, with relaxed interlayer distances and lattice parameters, were obtained. The phase stabilities and electronic structure of the experimentally reported orthorhombic Nb2C and Mo2C phases were also studied.

  • 40.
    Hugosson, Håkan Wilhelm
    et al.
    Uppsala universitet.
    Eriksson, Olle
    Uppsala universitet.
    Nordström, Lars
    Uppsala universitet.
    Jansson, Ulf
    Fast, Lars
    Ångström Laboratory, Uppsala universitet.
    Delin, Anna
    Ångström Laboratory, Uppsala universitet.
    Wills, John M.
    Los Alamos National Laboratory, Los Alamos, New Mexico.
    Johansson, Börje
    Theory of phase stabilities and bonding mechanisms in stoichiometric and substoichiometric molybdenum carbide1999Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 86, nr 7, s. 3758-3767Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    ABSTRACTFirst principles, total energy methods have been applied to predict the relative stabilities of the four experimentally verified MoC phases: the cubic δ(NaCl) phase and the three hexagonal γ(WC), η and γ′(TiAs) phases. The effect of vacancies on the relative stability of these four phases was investigated using a model structure with ordered vacancies within the carbon sublattice. For stoichiometric MoC, the γ phase was found to be the most stable followed by γ′, δ, and η, but for substoichiometric MoC0.75,MoC0.75, the order of relative stability was changed and the substoichiometric δ phase was found to have the lowest energy followed by γ′ and γ. A study of the electronic structure revealed vacancy induced peaks in the density of state and the electron density attached to these peaks was analyzed and found to emanate from unscreened Mo–Mo bonds through the carbon vacancy site. Finally, the oxygen stabilization of the γ′ MoC phase was studied.

  • 41.
    Hugosson, Håkan Wilhelm
    et al.
    Department of Physics, Uppsala University.
    Grechnev, G. E.
    Department of Physics, Uppsala University.
    Ahuja, R.
    Department of Physics, Uppsala University.
    Helmersson, U.
    Department of Physics, Linköping University.
    Sa, L.
    Department of Physics, Uppsala University.
    Eriksson, O.
    Department of Physics, Uppsala University.
    Stabilization of potential superhard RuO2 phases: A theoretical study2002Ingår i: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 66, nr 17, artikel-id 174111Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    First-principles full-potential linear muffin-tin orbital calculations have been used to study RuO2 in the fluorite (CaF2) and rutile structures. An investigation of the effects of metal and nonmetal alloying, oxygen vacancies, and lattice strain on the phase stabilities and electronic structure has been made. From these theoretical results suggestions on how the cubic phase may be stabilized are made. The pressure induced phase transitions between the rutile, CaCl2, Pa3 and fluorite phases and the bulk moduli of several 4d and 5d transition metal dioxides have also been studied.

  • 42.
    Hugosson, Håkan Wilhelm
    et al.
    Department of Materials Science and Engineering, Royal Institute of Technology.
    Högberg, H.
    Sandvik Coromant AB.
    Algren, M.
    Sandvik Coromant AB.
    Rodmar, M.
    Sandvik Coromant AB.
    Selinder, T. I.
    Sandvik Coromant AB.
    Theory of the effects of substitutions on the phase stabilities of Ti1−xAlxN2003Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 93, nr 8, s. 4505-4511Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have performed ab initio studies of the effect of substitutions on the phase stabilities of Ti1−xAl𝑥N,Ti1−xAlxN, x=0−1.x=0−1. The nonmetal substitutions studied include B, C, O, and Si. Metal substitutions studied include Sc, Zr, V, Cr, and Mn. The main objective has been to suggest substitutions that increase the thermal stability of the NaCl structure of Ti1−xAl𝑥NTi1−xAlxN at high Al contents. From these extensive and consistent calculations, some possible avenues for such stabilization present themselves, among which substitution with nonmetal C and Si, and metal V, Cr, and Mn are found to be the most promising.

  • 43.
    Hugosson, Håkan Wilhelm
    et al.
    Department of Physics, Uppsala University.
    Jansson, U.
    Ångström Laboratory, Uppsala University.
    Johansson, B.
    Department of Physics, Uppsala University.
    Eriksson, O.
    Department of Physics, Uppsala University.
    Phase stability diagrams of transition metal carbides, a theoretical study2001Ingår i: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 333, nr 6, s. 444-450Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The experimental phase diagrams at T=0 of the refractory compounds ZrC, NbC and MoC have been reproduced with great accuracy from first principles theory. The energy of formation for these compounds has been calculated for several phases and stoichiometries in order to understand, for example, the differences and changes in homogeneity ranges found in these systems. This determination of relative phase stabilities for a wide range of concentrations is necessary for first principles determination of phase diagrams for these compounds with complex bonding and structural properties as well as technological importance.

  • 44.
    Hugosson, Håkan Wilhelm
    et al.
    Condensed Matter Theory Group, Department of Physics, Uppsala University, Box 530, S-751 21 Uppsala, Sweden..
    Jansson, Ulf
    Department of Materials Chemistry, Ångström Laboratory, Uppsala University, Box 538, S-751 21 Uppsala, Sweden..
    Johansson, Börje
    Condensed Matter Theory Group, Department of Physics, Uppsala University, Box 530, S-751 21 Uppsala, Sweden.;Applied Materials Physics, Department of Materials Science and Engineering, Royal Institute of Technology, S-100 44 Stockholm, Sweden..
    Eriksson, Olle
    Condensed Matter Theory Group, Department of Physics, Uppsala University, Box 530, S-751 21 Uppsala, Sweden..
    Restricting Dislocation Movement in Transition Metal Carbides by Phase Stability Tuning2001Ingår i: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 293, nr 5539, s. 2434-2437Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A mechanism to enhance hardness in multilayer coatings is proposed. Using the technologically important hard transition metal carbides as prototypes, although the principle is transferable also to other systems, we demonstrate, from first-principles calculations, that by suitable alloying the energy difference between several competing structures in the transition metal carbides is small or tunable. This creates multiphase/polytypic compounds with a random or controllable layer stacking sequence, systems in which the propagation of dislocations can be strongly suppressed by a large number of interfaces between structures with different glide systems, accordingly allowing the possibility of a greatly enhanced hardness. With modern thin-film technologies, it should therefore be possible to deposit such materials that will express multilayer characteristics with only minor changes in the chemical constitution of the material, which is in contrast to conventional superlattices.

  • 45. Hugosson, Håkan Wilhelm
    et al.
    Johansson, B
    Eriksson, O
    Theoretical Studies of Sub-Stoichiometric MoC(1-x)1999Ingår i: Proceedings of the International Conference on Solid-Solid Phase Transformations '99, 1999Konferensbidrag (Refereegranskat)
  • 46.
    Hugosson, Håkan Wilhelm
    et al.
    Department of Physics, Uppsala University.
    Korzhavyi, Pavel
    Department of Materials and Engineering, Royal Institute of Technology, Sweden.
    Jansson, Ulf
    Ångström Laboratory, Uppsala University.
    Johansson, Börje
    Department of Physics, Uppsala University; erials and Engineering, Royal Institute of Technology, Sweden.
    Eriksson, Olle
    Department of Physics, Uppsala University.
    Phase stabilities and structural relaxations in substoichiometric TiC1−x2001Ingår i: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 63, nr 16, artikel-id 165116Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    First-principles calculations have been used to study the effect of vacancies and relaxation around the vacancy sites in substoichiometric TiC1−x. The effect of relaxation on phase stabilities, equilibrium volumes, and electronic structure of the substoichiometric phases was studied using a combined approach of pseudopotential plane wave and full-potential linear muffin-tin orbital methods. A relaxation away from the vacancies was found for the titanium atoms, the magnitude of which increased with vacancy concentration and the inclusion of nearest-neighbor carbon atom relaxation. The inclusion of local relaxations was found to correctly predict the off-stoichiometric equilibrium composition of titanium carbide. The anomalous volume behavior of TiC at small vacancy concentration is explained as an effect of the local relaxation of the atoms surrounding the vacancy sites, but we do not find that the lattice parameter of any of the studied stoichiometries is larger than that of ideal stoichiometric TiC.

  • 47.
    Hugosson, Håkan Wilhelm
    et al.
    Laboratory of Computational Chemistry and Biochemistry, Institute of Molecular and BiologicalChemistry, Swiss Federal Institute of Technology EPF Lausanne, Switzerland.
    Laio, Alessandro
    CSCS Science Division, Via Cantonale, 6928 Manno, Switzerland.
    Maurer, Patrick
    Laboratory of Inorganic Chemistry, Swiss Federal Institute of Technology ETH Zürich, Switzerland.
    Rothlisberger, Ursula
    Laboratory of Computational Chemistry and Biochemistry, Institute of Molecular and BiologicalChemistry, Swiss Federal Institute of Technology EPF Lausanne, Switzerland.
    A comparative theoretical study of dipeptide solvation in water2006Ingår i: Journal of Computational Chemistry, ISSN 0192-8651, E-ISSN 1096-987X, Vol. 27, nr 5, s. 672-684Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Molecular dynamics studies have been performed on the zwitterionic form of the dipeptide glycine–alanine in water, with focus on the solvation and electrostatic properties using a range of theoretical methods, from purely classical force fields, through mixed quantum mechanical/molecular mechanical simulations, to fully quantum mechanical Car–Parrinello calculations. The results of these studies show that the solvation pattern is similar for all methods used for most atoms in the dipeptide, but can differ substantially for some groups; namely the carboxy and aminoterminii, and the backbone amid NH group. This might have implications in other theoretical studies of peptides and proteins with charged —NH  and —CO  side chains solvated in water. Hybrid quantum mechanical/molecular mechanical simulations successfully reproduce the solvation patterns from the fully quantum mechanical simulations (PACS numbers: 87.14.Ee, 87.15.Aa, 87.15.He, 71.15.Pd).

  • 48.
    Hugosson, Håkan Wilhelm
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektroteknik, matematik och naturvetenskap, Elektronik.
    Mirsakiyeva, A
    Ab Inition Molecular Dynamics on Conjugated Polymers: Localization of the PolaronManuskript (preprint) (Övrigt vetenskapligt)
  • 49.
    Hugosson, Håkan Wilhelm
    et al.
    Uppsala universitet.
    Nordström, Lars
    Uppsala universitet.
    Jansson, Ulf
    Uppsala universitet.
    Johansson, Börje
    Uppsala universitet.
    Eriksson, Olle
    Uppsala universitet.
    Theoretical studies of substitutional impurities in molybdenum carbide1999Ingår i: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 60, nr 22, s. 15123-15130Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    First-principles full-potential linear muffin-tin orbital calculations have been used to study the effect on the cohesion and electronic structure of cubic δ-MoC when 25% of the carbon is substituted for boron, nitrogen, or oxygen and when 25% of the molybdenum is substituted for niobium, tungsten, or ruthenium. A thorough study of the changes in the electronic structure and the effect of these on the properties of the compounds is made. Special attention is paid to the character (ionic, covalent, or metallic) of the states becoming occupied (or unoccupied) due to the substitution. A study is also made on the properties of the quaternary alloy Mo0.75W0.25C0.75N0.25. This substitution is shown to harden δ-MoC.

  • 50. Hugosson, Håkan Wilhelm
    et al.
    Ågren, H
    Quantum Mechanical / Molecular Mechanical Modeling of Biological Systems2009Ingår i: Multiscale Modeling and Simulation in Science / [ed] B. Engquist, P. Lötstedt, and O. Runborg, Springer , 2009, s. 291-294Kapitel i bok, del av antologi (Refereegranskat)
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