lnu.sePublications
Change search
Refine search result
1234567 151 - 200 of 649
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 151.
    Bengtsson, Therese
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    "Det är ljudmolkyler som flyger": Elevers föreställningar om fenomenet ljud 2019Independent thesis Advanced level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Studien är en kvalitativ studie som syftar till att kartlägga elevers föreställningar om ljudets spridning, utifrån vetenskapliga föreställningar och vardagsföreställning. Studien kartlägger även elevernas föreställningar om vad som påverkar ljudets hastighet. Den insamlade empirin bygger på elevintervjuer. Intervjuerna genomfördes med totalt 16 elever från årskurs 4 och 6, detta för att kunna jämföra elevernas föreställningar mellan årskurserna.

     

    Studien visar att elever anser att ljud är ett abstrakt ämne som de har svårt att förklara. Resultatet visar att elever i årskurs 4 och 6 har flertalet vardagsföreställningar om ljud. Vardagsföreställningarna i studien kan tolkas utifrån att eleverna använder sina erfarenheter och försöker skapa individuella förklaringar på abstrakta fenomen. En av de vanligaste vardagsföreställningarna som går att identifiera i denna studie är att ljud ses som en egen enhet. I intervjuerna visade det sig även att eleverna har föreställningar om ljudets hastighet som inte kan ses grundas på vetenskapliga föreställningar. Inga stora skillnader kunde identifieras mellan föreställningarna hos eleverna i årskurs 4 och 6, förutom användningen av fysikaliska begrepp.

    Download full text (pdf)
    "Det är ljudmolkyler som flyger"
  • 152.
    Bergkvist, Jonas
    et al.
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Gustafsson, Fredrik
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Avbrottsfri Kraft med användning av ultrakondensatorer2014Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The supply of uninterruptible power can be applied to many areas where

    continuous operation is highly prioritized.

    The application of uninterruptible power for motor operation is facilitated

    using a frequency converter. Direct current operated frequency converters can

    be applied directly to the power reserve which removes the need for additional

    power-converting.

    Batteries have long constituted the power reserve but advancements in

    the development of ultracapacitors have created a viable substitution. Ultra-capacitors have high energy storing capabilities and can be applied to high

    power applications.

    Maxwell is a leading manufacturing company of ultracapacitors and pro-vide different modules with built-in solutions for voltage balancing. Uneven

    voltages between series-connected capacitors is a phenomenon caused by vary-ing capacitance. A configuration containing Maxwell’s 56V module is created

    and constitutes the power reserve in the simulations.

    The discharge simulation shows a significant current that could damage

    the system. A current limiting transistor is introduced in the circuit to provide

    a safer course of discharge. The result of the simulations confirms that the

    application of ultracapacitors in uninterruptible power for motor operation is

    viable.

    Download full text (pdf)
    avbrottsfri_kraft.pdf
  • 153.
    Berglund, Johan
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    After Fukushima: Safety culture and fostering critical thinking2020In: Safety Science, ISSN 0925-7535, E-ISSN 1879-1042, Vol. 124, p. 1-6, article id 104613Article in journal (Refereed)
    Abstract [en]

    This paper discusses the background and aftermath of the Fukushima Daiichi accident, exploring safety culture in relation to three essential elements: (I) knowledge, (II) leadership (power), and (III) critical thinking. In my discussion, I establish links between safety culture and these key issues, advocating a long-term outlook on safety and risk management. These findings are based on case study analyses, involving evaluations of accident reports, dialogue seminars, and interviews with representatives of the nuclear community in Japan and Sweden. For the most part, the argument I will pursue is not concerned with what Japan could or should have done differently but the trials and hazards of our society. How, then, can we give the Japanese experience a broader significance? In safety-critical activities, we consider best practice the reliable response although its formulas may have to be modified to particular conditions and circumstances. In other words, there are tacit dimensions of knowledge related to professional activities that are vital to their overall quality. However, the impact of commercial pressures, formalization and the desire to measure, monitor, and control the culture and behavior of workers may force professionals to deprioritize their judgments. Also, disempowerment of knowledge tends to upset the proactive and critical thinking of operatives and employees. If we interpret this as a process of complacency or degeneration, we should consider possible counterweights.

  • 154.
    Berglund, Johan
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Why safety cultures degenerate: and how to revive them2016Book (Refereed)
    Abstract [en]

    From Chernobyl to Fukushima, have we come full circle, where formalisation has replaced ambiguity and a decadent style of management, to the point where it is becoming counter-productive? Safety culture is a contested concept and a complex phenomenon, which has been much debated in recent years. In some high-risk activities, like the operating of nuclear power plants, transparency, traceability and standardisation have become synonymous with issues of quality. Meanwhile, the experience-based knowledge that forms the basis of manuals and instructions is liable to decline. In the long-term, arguably, it is the cultural changes and its adverse impacts on co-operation, skill and ability of judgement that will pose the greater risks to the safety of nuclear plants and other high-risk facilities. Johan Berglund examines the background leading up to the Fukushima Daiichi accident in 2011 and highlights the function of practical proficiency in the quality and safety of high-risk activities. The accumulation of skill represents a more indirect and long-term approach to quality, oriented not towards short-term gains but (towards) delayed gratification. Risk management and quality professionals and academics will be interested in the links between skill, quality and safety-critical work as well as those interested in a unique insight into Japanese culture and working life as well as fresh perspectives on safety culture.

  • 155.
    Blakaj, Valon
    et al.
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Gashi, Gent
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Implementation of a 3D terrain-dependent Wave Propagation Model in WRAP2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The radio wave propagation prediction is one of the key elements for designing an efficient radio network system. WRAP International has developed a software for spectrum management and radio network planning.This software includes some wave propagation models which are used to predict path loss. Current propagation models in WRAP perform the calculation in a vertical 2D plane, the plane between the transmitter and the receiver. The goal of this thesis is to investigate and implement a 3D wave propagation model, in a way that reflections and diffractions from the sides are taken into account.The implemented 3D wave propagation model should be both fast and accurate. A full 3D model which uses high resolution geographical data may be accurate, but it is inefficient in terms of memory usage and computational time. Based on the fact that in urban areas the strongest path between the receiver and the transmitter exists with no joint between vertical and horizontal diffractions [10], the radio wave propagation can be divided into two parts, the vertical and horizontal part. Calculations along the horizontal and vertical parts are performed independently, and after that, the results are combined. This approach leads to less computational complexity, faster calculation time, less memory usage, and still maintaining a good accuracy.The proposed model is implemented in C++ and speeded up using parallel programming techniques. Using the provided Stockholm high resolution geographical data, simulations are performed and results are compared with real measurements and other wave propagation models. In addition to the path loss calculation, the proposed model can also be used to estimate the channel power delay profile and the delay spread.

    Download full text (pdf)
    fulltext
  • 156.
    Bolarinwa, Sherifdeen O.
    et al.
    King Abdulaziz Univ, Saudi Arabia.
    Sattar, Shahid
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering. Linnaeus University, Linnaeus Knowledge Environments, Advanced Materials.
    AlShaikhi, Abdullah A.
    King Abdulaziz Univ, Saudi Arabia.
    Superior gas sensing properties of beta-In2Se3: A first-principles investigation2022In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 201, article id 110880Article in journal (Refereed)
    Abstract [en]

    Using first-principles calculations, we report structural and electronic properties of CO, NO2 and NO molecular adsorption on beta-In2Se3 in comparison to a previous study on a-phase. Analysis and comparison of adsorption energies and extent of charge transfer indicates beta-In2Se3 to be selective in detecting gas molecules. We found NO molecules acting as charge donor whereas CO and NO2 molecules as charge acceptors, respectively, experiencing physisorption in all cases. Owing to enhanced adsorption, faster desorption and improved selectivity of the gas molecules discussed in detail, we conclude beta-In2Se3 to be a superior gas sensing material ideal for chemoresistive-type gas sensing applications.

    Download full text (pdf)
    fulltext
  • 157.
    Bollström, Nadja
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    A gamma-ray study of a highly variable blazar: The Fermi-LAT analysis and the modeling of the FSRQ PKS 1510–0892021Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The subject of this thesis is the analysis and modeling of the active galactic nucleus PKS 1510-089. The aim is to present a thorough background of active galactic nuclei combined with the analysis and modeling of a specific active galactic nucleus. The results will then be  linked to previous research and theories about active galactic nuclei. The data used in the analysis were retrieved from the Fermi Gamma-ray Space Telescope. A light curve analysis that extended over 12 years provided knowledge about variability and presented four interesting flaring periods. The four periods underwent a spectral analysis, and the results showed that a log parabolic curvature could best describe all four periods. The last step before the modeling was to create spectral energy distributions for all four periods to retrieve spectral points from wavelengths other than those available from Fermi. Unfortunately, there were only sufficient data for one period. That period was later used in the modeling and resulted in a well-fitted external Compton model, which was compared, with relatively good results, with previous research.

    Download full text (pdf)
    fulltext
  • 158.
    Bonardi, A.
    et al.
    Radboud University Nijmegen, Netherlands.
    Buanes, T.
    University of Bergen, Norway.
    Chadwick, P.
    Durham University, UK.
    Dazzi, F.
    Max Planck Institute, Germany.
    Förster, A.
    Max Planck Institute, Germany.
    Hörandel, J. R.
    Radboud University Nijmegen, Netherlands.
    Punch, Michael
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Wagner, R. M.
    Stockholm University.
    CTA Consortium,
    Central acceptance testing for camera technologies for the cherenkov telescope array2015In: Proceedings of Science, 2015Conference paper (Refereed)
    Abstract [en]

    The Cherenkov Telescope Array (CTA) is an international initiative to build the next generation ground based very-high energy gamma-ray observatory. It will consist of telescopes of three different sizes, employing several different technologies for the cameras that detect the Cherenkov light from the observed air showers. In order to ensure the compliance of each camera technology with CTA requirements, CTA will perform central acceptance testing of each camera technology. To assist with this, the Camera Test Facilities (CTF) work package is developing a detailed test program covering the most important performance, stability, and durability requirements, including setting up the necessary equipment. Performance testing will include a wide range of tests like signal amplitude, time resolution, dead-time determination, trigger efficiency, performance testing under temperature and humidity variations and several others. These tests can be performed on fully-integrated cameras using a portable setup at the camera construction sites. In addition, two different setups for performance tests on camera sub-units are being built, which can provide early feedback for camera development. Stability and durability tests will include the long-term functionality of movable parts, water tightness of the camera housing, temperature and humidity cycling, resistance to vibrations during transport or due to possible earthquakes, UV-resistance of materials and several others. Some durability tests will need to be contracted out because they will need dedicated equipment not currently available within CTA. The planned test procedures and the current status of the test facilities will be presented.

  • 159.
    Bonardi, A.
    et al.
    Radboud University, Netherlands.
    Buitink, S.
    Vrije Universiteit Brussel, Belgium.
    Corstanje, A.
    Radboud University, Netherlands.
    Falcke, H.
    Radboud University, Netherlands;NIKHEF, Netherlands;Netherlands Institute of Radio Astronomy (ASTRON), Netherlands.
    Hare, B. M.
    University Groningen, Netherlands.
    Hörandel, J. R.
    Radboud University, Netherlands;NIKHEF, Netherlands.
    Mitra, P.
    Vrije Universiteit Brussel, Belgium.
    Mulrey, K.
    Vrije Universiteit Brussel, Belgium.
    Nelles, A.
    Radboud University, Netherlands;University of California, USA.
    Rachen, J. P.
    Radboud University, Netherlands.
    Rossetto, L.
    Radboud University, Netherlands.
    Schellart, P.
    Radboud University, Netherlands;Princeton University, USA.
    Scholten, O.
    University Groningen, Netherlands;Vrije Universiteit Brussel, Belgium.
    Ter Veen, S.
    Radboud University, Netherlands;Netherlands Institute of Radio Astronomy (ASTRON), Netherlands.
    Thoudam, Satyendra
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering. Radboud University, Netherlands.
    Trinh, T. N. G.
    University Groningen, Netherlands.
    Winchen, T.
    Vrije Universiteit Brussel, Belgium.
    Study of the LOFAR radio self-trigger and single-station acquisition mode2018In: 35th International Cosmic Ray Conference, ICRC 2017, 10-20 July 2017, Sissa Medialab Srl , 2018, article id 402Conference paper (Refereed)
    Abstract [en]

    The LOw Frequency ARay (LOFAR) observatory is a multipurpose radio antenna array aimed to detect radio signals in the frequency range 10-240 MHz. Radio antennas are clustered into over 50 stations, and are spread along Central and Northern Europe. The LOFAR core, where the density of stations is highest, is instrumented with the LOfar Radboud air shower Array (LORA), covering an area of about 300 m diameter centered at the LOFAR core position. Since 2011 the LOFAR core has been used for detecting radio-signals associated to cosmic-ray air showers in the energy range 1016 - 1018 eV. Data acquisition is triggered by the LORA scintillator array, which provides energy, arrival direction, and core position estimates of the detected air shower too. Thus only the core of the LOFAR array is currently used for cosmic-ray detection. In order to extend the energy range of the detected cosmic rays, it is necessary to expand the effective collecting area to the whole LOFAR array. On this purpose, a detailed study about the LOFAR potentialities of working in self-trigger mode, i.e. with the cosmic-ray data acquisition trigger provided by the radio-antenna only, is presented here. A new method based on the intensity and the frequency spectrum for determining the air shower position to be implemented on LOFAR remote stations is presented too. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives 4.0 International License (CC BY-NC-ND 4.0).

  • 160.
    Bonardi, Antonio
    et al.
    Radboud Univ Nijmegen, Netherlands.
    Buitink, Stijn
    Vrije Univ Brussel, Belgium.
    Corstanje, Arthur
    Radboud Univ Nijmegen, Netherlands.
    Falcke, Heino
    Radboud Univ Nijmegen, Netherlands;NIKHEF, Netherlands;Netherlands Inst Radio Astron ASTRON, Netherlands.
    Hare, Brian M.
    Univ Groningen, Netherlands.
    Horande, Jorg R.
    Radboud Univ Nijmegen, Netherlands;NIKHEF, Netherlands.
    Mitra, Pragati
    Vrije Univ Brussel, Belgium.
    Mulrey, Katie
    Vrije Univ Brussel, Belgium.
    Nelles, Anna
    DESY, Germany;Humboldt Univ, Germany.
    Rachen, Jorg P.
    Radboud Univ Nijmegen, Netherlands.
    Rossetto, Laura
    Radboud Univ Nijmegen, Netherlands.
    Schellart, Pim
    Princeton Univ, USA.
    Scholten, Olaf
    Univ Groningen, Netherlands;Vrije Univ Brussel, Belgium.
    Thoudam, Satyendra
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Trinh, Gia T. N.
    Univ Groningen, Netherlands.
    Veen, Sanderter
    Netherlands Inst Radio Astron ASTRON, Netherlands.
    Winchen, Tobias
    Vrije Univ Brussel, Belgium.
    Towards real-time cosmic-ray identification with the LOw Frequency ARay2019In: 8th International Conference on Acoustic and Radio EeV Neutrino Detection Activities (ARENA 2018) / [ed] Riccobene, G Biagi, S Capone, A Distefano, C Piattelli, P, EDP Sciences , 2019, p. 1-3, article id 04005Conference paper (Refereed)
    Abstract [en]

    The radio signals emitted by Extensive Air Showers have been successfully used for the last decade by LOFAR to reconstruct the properties of the primary cosmic rays. Since an effective real-time recognition system for the very short radio pulses is lacking, cosmic-ray acquisition is currently triggered by an external array of particle detector, called LORA, limiting the LOFAR collecting area to the area covered by LORA. A new algorithm for the real-time cosmic-ray detection has been developed for the LOFAR Low Band Antenna, which are sensitive between 10 and 90 MHz, and is here presented together with the latest results.

  • 161.
    Borwankar, Chinmay
    et al.
    Bhabha Atom Res Ctr, India.
    Bhatt, Nilay
    Bhabha Atom Res Ctr, India.
    Bhattacharyya, Subir
    Bhabha Atom Res Ctr, India.
    Rannot, R. C.
    Bhabha Atom Res Ctr, India.
    Tickoo, A. K.
    Bhabha Atom Res Ctr, India.
    Koul, R.
    Bhabha Atom Res Ctr, India.
    Thoudam, Satyendra
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Simulation studies of MACE-I: Trigger rates and energy thresholds2016In: Astroparticle physics, ISSN 0927-6505, E-ISSN 1873-2852, Vol. 84, p. 97-106Article in journal (Refereed)
    Abstract [en]

    The MACE (Major Atmospheric Cherenkov Experiment) is an upcoming Very High Energy (VHE) gamma-ray telescope, based on imaging atmospheric Cherenkov technique, being installed at Hanle, a high altitude astronomical site in Ladakh, India. Here we present Monte Carlo simulation studies of trigger rates and threshold energies of MACE in the zenith angle range of 0 degrees-60 degrees for on-axis gamma-ray coming from point source and various cosmic ray species. We have simulated the telescope's response to gamma-rays, proton, electron and alpha initiated atmospheric Extensive Air Showers (EAS) in the broad energy range of 5 GeV to 20 TeV. For gamma-rays we consider power law and log parabolic spectra while other particles are simulated with their respective cosmic ray spectrum. Trigger rates and threshold energies are estimated for the trigger configuration of 4 Close Cluster Nearest Neighbour(CCNN) pixels as implemented in MACE hardware, in combination with single channel discriminator threshold ranging from 6-10 photo electrons (pe). We find that MACE can achieve the gamma-ray trigger energy threshold of similar to 17 GeV (4 CCNN, 9 pe) at 0 degrees zenith angle for power law spectrum. The total trigger rate at 0 degrees zenith is expected to be similar to 650 Hz, with protons contributing similar to 80% to it. For the zenith range of 0 degrees-40 degrees we find that the telescope can achieve gamma-gray trigger threshold energies of similar to 22 GeV at 20 degrees zenith angle and similar to 40 GeV at 40 degrees zenith angle. Integral rates are also almost constant for this zenith angle range. At zenith angle of 60 degrees, trigger energy threshold increases to similar to 173 GeV and total integral rate falls down to similar to 305 Hz. (C) 2016 Elsevier B.V. All rights reserved.

  • 162.
    Boström, Johan
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Hur kan man undervisa om energi i grundskolan för att skapa demokratiska medborgare?: En studie av elevers uppfattningar av energi och energisystemet2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Jag har gjort en kvalitativ undersökning av elevers uppfattningar av energi, energisystemet och sin

    egen och människans roll i detta system. Fokus har varit på karaktären av elevernas beskrivningar; vardagliga, samhälleliga eller naturvetenskapliga, och om dessa har något samband med elevernas uppfattning av sin egen roll i samhällets strävan mot en hållbara utveckling. Undersökningen bygger på en fenomenografisk analys av intervjuer genomförda med sex elever i årskurs 9. Resultatet av undersökningen visar att eleverna till stor del använder en vardaglig förklaringsmodell för att förklara begreppet energi. Några använder sig delvis av en naturvetenskaplig förklaringsmodell. Dessa elever har dessutom en större förståelse av energisystemet, både genom att de kan spåra energins väg i systemet men också genom en större komponentkännedom av systemets delar. Dessa elever lägger också fram argument om varför det är viktigt att spara energi, resterande elever anser endast att det är viktigt. Slutsatser man kan dra av detta är att det är svårt att,som elev, verkligen få en fullständig bild av hur människans energianvändning påverkar en själv, samhället och miljön. Förståelse av både energibegreppet och det system detta ingår i är kunskaper eleverna behöver för att, både nu och i framtiden, göra väl avvägda val. 

    Download full text (pdf)
    fulltext
  • 163.
    Boström, Johan
    et al.
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Hulten, Magnus
    Linköping University, Sweden.
    Gyberg, Per
    Linköping University, Sweden.
    Rethinking construction in preschool: discerning didactic strategies in Swedish preschool activities2022In: International journal of technology and design education, ISSN 0957-7572, E-ISSN 1573-1804, Vol. 32, p. 2039-2061Article in journal (Refereed)
    Abstract [en]

    Even though construction tasks have a long history as an activity in the Swedish preschool, technology as a content matter (e.g., construction) is relatively new. Hence, preschool teachers are generally unsure of the content of technology and how to handle it from a teaching perspective. Thus, there is need for deeper understanding of how construction tasks in preschool can be enacted and what kind of premises are offered to the children. To investigate this, we took our stance in activity theory and the concepts of mediating artifacts, rules and division of labour. This helped us discern what type of instructional practices that were enacted by preschool teachers when working with construction tasks. Activity theory in combination with thematic analysis helped us distinguish four general didactic actions that the teachers used to bring about the construction task-to engage, to guide, to coordinate, to show. These four strategies were then formulated into specific technology didactic actions through the perspectives of technology as product, process and concepts.

    Download full text (pdf)
    fulltext
  • 164.
    Boström, Johan
    et al.
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Hulten, Magnus
    Linköping University, Sweden.
    Gyberg, Per
    Linköping University, Sweden.
    Who counts?: Legitimate solutions in construction activities in preschool2023In: International journal of technology and design education, ISSN 0957-7572, E-ISSN 1573-1804, Vol. 33, p. 1309-1344Article in journal (Refereed)
    Abstract [en]

    As has been pointed out in previous research, teacher-led learning plays an important role in developing preschool children's technological skills and technological self-esteem. What is missing in research are more detailed analysis of how the children's and teachers' actions and interactions shape the learning process. In order to study this within the field of construction, an action research project was conducted, where construction activities were developed, implemented and revised in an iterative procedure. Data from the second cycle were analyzed for this article using graphic transcriptions and multimodal analysis, with a focus on action, interaction and experience from a pragmatist perspective. Our findings show that children who quickly and decisively engage with the material, the teachers and their peers in suggesting which material to use and/or how the material can be used, end up in a central role in the design process. These children (or their actions) often get legitimized by the teachers. Thus, in order to give children access to equal opportunities in the construction activities, it is important for teachers to understand how the children's construction-focused actions become constitutive and what their role in that process is.

    Download full text (pdf)
    fulltext
  • 165.
    Bozkurt, M.
    et al.
    Photonics and Semiconductor Nanophysics, Department of Applied Physics, Eindhoven University of Technology, P. O. Box 513, NL-5600 MB Eindhoven, The Netherlands.
    Mahani, Mohammad Reza
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Studer, P.
    London Center for NanoTechnology, 17-19 Gordon Street, WC1H 0AH, London, U.K..
    Tang, J.-M.
    5Department of Physics, University of New Hampshire, Durham, New Hampshire 03824-3520, USA.
    Schofield, S.
    London Center for NanoTechnology, 17-19 Gordon Street, WC1H 0AH, London, U.K..
    Curson, N.
    London Center for NanoTechnology, 17-19 Gordon Street, WC1H 0AH, London, U.K..
    Flatt’e, M.E.
    Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242-1479,U.S.A..
    Silov, A.Yu.
    Photonics and Semiconductor Nanophysics, Department of Applied Physics, Eindhoven University of Technology, P. O. Box 513, NL-5600 MB Eindhoven, The Netherlands.
    Hirjibehedin, C. F.
    Department of Chemistry, UCL, London, WC1H 0AJ, United Kingdom.
    Canali, Carlo M.
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Koenraad, P.M.
    Photonics and Semiconductor Nanophysics, Department of Applied Physics, Eindhoven University of Technology, P. O. Box 513, NL-5600 MB Eindhoven, The Netherlands.
    Magnetic anisotropy of single Mn acceptors in GaAs in an external magnetic field2013In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 88, p. Article ID: 205203-Article in journal (Refereed)
    Abstract [en]

    We investigate the effect of an external magnetic field on the physical properties of the acceptor hole statesassociated with single Mn acceptors placed near the (110) surface of GaAs. Cross-sectional scanning tunnelingmicroscopy images of the acceptor local density of states (LDOS) show that the strongly anisotropic hole wavefunction is not significantly affected by a magnetic field up to 6 T. These experimental results are supported bytheoretical calculations based on a tight-binding model of Mn acceptors in GaAs. For Mn acceptors on the (110)surface and the subsurfaces immediately underneath, we find that an applied magnetic field modifies significantlythe magnetic anisotropy landscape. However, the acceptor hole wave function is strongly localized around theMn and the LDOS is quite independent of the direction of the Mn magnetic moment. On the other hand, for Mnacceptors placed on deeper layers below the surface, the acceptor hole wave function is more delocalized andthe corresponding LDOS is much more sensitive on the direction of the Mn magnetic moment. However, themagnetic anisotropy energy for these magnetic impurities is large (up to 15 meV), and a magnetic field of 10 Tcan hardly change the landscape and rotate the direction of the Mn magnetic moment away from its easy axis.We predict that substantially larger magnetic fields are required to observe a significant field dependence of thetunneling current for impurities located several layers below the GaAs surface.

  • 166.
    Brink, Jonas
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Att upptäcka och förändra elevers vardagsföreställningar om Newtons lagar: Fysiklärares erfarenheter gällande elevers föreställningar kring Newtons lagar samt fysiklärares arbetssätt att hantera elevers svårigheter att förstå Newtons lagar.2023Independent thesis Advanced level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    I denna undersökning diskuteras vanliga vardagsföreställningar som elever har kring Newtons lagar men undersökningen tar också sikte på hur lärare märker och upptäcker elevers eventuella vardagsföreställningar samt lärares eventuella strategier för att motverka dessa.

    Undersökningen genomfördes genom kvalitativa intervjuer med 7 lärare på 3 gymnasieskolor varav en lärare hade med sig en lärarstudent. I undersökningen kommer det fram att lärare är väl medvetna om elevers vardagsföreställningar och att dessa går att identifiera i den presenterade litteraturöversikten. Lärarna har ett flertal olika sätt att märka elevers vardagsföreställningar kring Newtons lagar men den mest förekommande i den här undersökningen var i samband med att elever räknade uppgifter. Dessutom diskuterade eleverna sina tankar och på så sätt kunde eventuella vardagsföreställningar komma fram i ljuset.

    När det kommer till lärares strategier att motverka elevers vardagsföreställningar och rentav ersätta dessa med en konceptuell förståelse av Newtons lagar så varierade dessa. Flera lärare var överens om att laborationer och demonstrationer var ett bra verktyg för att nå en konceptuell förståelse men framförallt var ett sunt och gott klassrumsklimat av stor vikt för att lärande skall kunna ske.

    Download full text (pdf)
    Självständigt arbete
  • 167.
    Buitink, S.
    et al.
    Vrije Universiteit Brussel, Belgium.
    Bonardi, A.
    Radboud University, Netherlands.
    Corstanje, A.
    Radboud University, Netherlands.
    Falcke, H.
    Radboud University, Netherlands;NIKHEF, Netherlands;Netherlands Institute of Radio Astronomy (ASTRON), Netherlands.
    Hare, B. M.
    University Groningen, Netherlands.
    Hörandel, J. R.
    Vrije Universiteit Brussel, Belgium;NIKHEF, Netherlands.
    Mitra, P.
    Vrije Universiteit Brussel, Belgium.
    Mulrey, K.
    Vrije Universiteit Brussel, Belgium.
    Nelles, A.
    Radboud University, Netherlands;University of California, USA.
    Rachen, J. P.
    Radboud University, Netherlands.
    Rossetto, L.
    Radboud University, Netherlands.
    Schellart, P.
    Radboud University, Netherlands;Princeton University, USA.
    Scholten, O.
    University Groningen, Netherlands;Vrije Universiteit Brussel, Belgium.
    Ter Veen, S.
    Radboud University, Netherlands;Netherlands Institute of Radio Astronomy (ASTRON), Netherlands.
    Thoudam, Satyendra
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering. Radboud University, Netherlands.
    Trinh, T. N. G.
    University Groningen, Netherlands.
    Winchen, T.
    Vrije Universiteit Brussel, Belgium.
    Cosmic ray mass composition with LOFAR2018In: 35th International Cosmic Ray Conference — ICRC2017. 10–20 July, 2017. Bexco, Busan, Korea, Sissa Medialab Srl , 2018, article id 499Conference paper (Refereed)
    Abstract [en]

    The LOFAR radio telescope measures the radio emission from extensive air showers with unprecedented precision. In the dense core individual air showers are detected by hundreds of dipole antennas. By fitting the complex radiation pattern to Monte Carlo radio simulation codes we obtain measurements of the atmospheric depth of the shower maximum X max with a precision of < 20 g/cm 2 . This quantity is sensitive to the mass composition of cosmic rays. We discuss the first mass composition results of LOFAR and the improvements that are currently being made to enhance the accuracy of future analysis. Firstly, a more realistic treatment of the atmosphere will decrease the systematic uncertainties due to the atmosphere. Secondly, a series of upgrades to the LOFAR system will lead to increased effective area, duty cycle, and the possibility to extend the composition analysis down to the energy of 10 16.5 eV. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives 4.0 International License (CC BY-NC-ND 4.0).

  • 168.
    Bylund, Tomas
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Seeking the faint extremes: Detection and characterisation of extragalactic soft-spectrum gamma-ray sources and exploring methods to enhance their detection with machine learning in the 50 GeV-50 TeV energy range2022Doctoral thesis, monograph (Other academic)
    Abstract [en]

    This thesis deals with an observational study of Blazars, strong gamma-ray sources with Very High Energies (VHE) located far outside our Galaxy. Blazars are a class of galaxies that contain a supermassive black hole that is actively consuming large quantities of matter, a process that results in the liberation of tremendous amounts of energy that then powers the emission of huge bulks of charged particles that get accelerated almost to the speed of light.

    The details of the extreme processes involved are still very uncertain, and more observational studies are still required to discriminate between the various theories. Because it takes a lot of energy to create VHE gamma-rays, they are tightly coupled to the most energy-rich places in Blazars.

    This means that observations of gamma rays directly probe the central engine responsible for the enormous amounts of radiation we detect.

    Direct studies have been carried out with the H.E.S.S. observatory, an Imaging Atmospheric Cherenkov Telescope which uses our atmosphere as an integral part of its detector and is able to detect gamma-ray photons with energies from over 50 GeV up to tens of TeV.

    Using H.E.S.S., seven new sources of gamma-rays in the VHE regime were carefully studied in this thesis, significantly expanding the collection of known sources of TeV photons.

    Computer studies were also performed exploring the possibility of using deep learning to improve the sensitivity of ALTO, a newly-proposed observatory belonging to an emerging class of gamma-ray instruments, the particle detector arrays.

    Download full text (pdf)
    fulltext
    Download (jpg)
    presentationsbild
  • 169.
    Bylund, Tomas
    et al.
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Kukec Mezek, Gasper
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Senniappan, Mohanraj
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Becherini, Yvonne
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Punch, Michael
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering. Univ Paris, France.
    Thoudam, Satyendra
    Khalifa University, United Arab Emirates.
    Ernenwein, Jean-Pierre
    Aix Marseille Univ, France.
    Studies of Gamma-Ray Shower Reconstruction UsingDeep Learning2021In: Proceedings of Science: 37th International Cosmic Ray Conference (ICRC 2021), July 12th – 23rd, 2021 Online – Berlin, German, 2021, article id 758Conference paper (Refereed)
    Abstract [en]

    The ALTO project aims to build a particle detector array for very high energy gamma ray observations optimized for soft spectrum sources. The accurate reconstruction of gamma ray events, in particular their energies, using a surface array is an especially challenging problem at the low energies ALTO aims to optimize for. In this contribution, we leverage Convolutional Neural Networks (CNNs) to improve reconstruction performance at lower energies ( smaller 1 TeV ) as compared to the SEMLA analysis procedure, which is a more traditional method using mainly manually derived features.rnWe present performance figures using different network architectures and training settings, both in terms of accuracy and training time, as well as the impact of various data augmentation techniques.

  • 170.
    Cao, Letian
    et al.
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Guan, Yuankai
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Use of digital filters based on Labview and Matlab2015Independent thesis Basic level (degree of Bachelor), 180 HE creditsStudent thesis
    Download full text (pdf)
    fulltext
  • 171.
    Cao, Letian
    et al.
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering. Linnaeus University.
    Wang, Yazhou
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering. Linnaeus University.
    Fingerprint image enhancement and minutiae extraction algorithm2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This work aims to study the procedures of fingerprint identification system and to present some efficient algorithms for pre-processing and minutiae extraction. Most pre-processing steps consist of normalization, segmentation and orientation estimation, and background which focus on decreasing the variance of fingerprints, separating fore and background areas and tracking the direction of ridge lines, respectively. Minutiae extractionis typically divided into two approaches: binarization based method and directgray scale extraction. However, we put emphasis on binarization based method in thisresearch since it is more commonly used method in research papers. The results of simulationbased on a set of fingerprints downloaded from FVC 2006 database showed thatalgorithms we used are accurate and reliable.

    Download full text (pdf)
    fulltext
  • 172.
    Capone, Luigino
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Machine learning and statistical methods in search of cosmic neutrino sources2022Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Download full text (pdf)
    fulltext
  • 173.
    Carlzon, Madeleine
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Fysiklaborationer i fokus: En kvalitativ studie av fysiklaborationer ur ett lärarperspektiv2019Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Denna studie undersöker vilka syften lärare har med sin laborativa undervisning i fysik på gymnasiet samt om det finns några faktorer som kan vara till hjälp för att skapa eller utvärdera laborationer utifrån de syften som lärarna har. Fyra gymnasielärare intervjuades och de fick utvärdera sex utvalda laborationer. De faktorer som undersöktes och kvantifieras som parametrar var huruvida laborationen är kvalitativ/kvantitativ, induktiv/deduktiv, praktisk/teoretisk, laborationens frihetsgrad, vardagsrelevans, hanterbarhet, begriplighet, tidseffektivitet, omfattning samt hur laborationen påverkar elevernas motivation. 

    Resultatet indikerar att lärare har flera olika syften med sin laborativa undervisning i fysik på gymnasiet. Bland dessa syften nämns att eleverna ska lära sig naturvetenskapliga arbetsmetoder, få bättre begreppsförståelse och att verifiera teori. Det visade sig finnas samband mellan tidigare nämnda faktorer såsom att en kvantitativ laboration tenderar att också vara deduktiv och att en kvalitativ laboration tvärtom oftare är induktiv. I analysen av resultatet ges exempel på fall både när lärare är överens och inte överens om såväl laborationers syften som faktorer och i sina argument.

    Download full text (pdf)
    Fysiklaborationer i fokus
  • 174.
    Cerruti, M.
    et al.
    Univ Paris Diderot, France.
    Bottcher, M.
    North West Univ, South Africa.
    Chakraborty, N.
    Max Planck Inst Kernphys, Germany.
    Davids, I. D.
    North West Univ, South Africa ; Univ Namibia, Namibia.
    Fuessling, M.
    DESY, Germany.
    Jankowsky, F.
    Heidelberg Univ, Germany.
    Lenain, J. P.
    Univ Paris Diderot, France.
    Meyer, M.
    Stockholm University.
    Prokoph, Heike
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Wagner, S.
    Heidelberg Univ, Germany.
    Zaborov, D.
    Ecole Polytech, France.
    Zacharias, M.
    Heidelberg Univ, Germany.
    Target of Opportunity Observations of Blazars with HESS2017In: HIGH ENERGY GAMMA-RAY ASTRONOMY / [ed] Aharonian, FA Hofmann, W Rieger, FM, American Institute of Physics (AIP), 2017, article id UNSP 050029Conference paper (Refereed)
    Abstract [en]

    The very high energy (VHE, E > 100 GeV) sky is dominated by blazars, radio-loud active galactic nuclei whose relativistic jet is closely aligned with the line of sight. Blazars are characterized by rapid variability at all wavelengths and thus an important part of the H.E.S.S. blazar program is devoted to target of opportunity (ToO) observations. H.E.S.S. triggers blazar ToOs on the basis of publicly available blazar observations at longer wavelengths (optical, X-rays, and gamma-rays), from private optical observations with the ATOM telescope, and from private communications by gamma-ray partners in the context of MoUs. In 2015, about 70 hours of H.E.S.S. data were taken in the form of blazar ToOs, which represents 15% of all extragalactic observations. In this contribution, we present the H.E.S.S. blazar ToO status, and we focus on two major results from the 2015 season: the detection of VHE emission from 3C 279 during the June 2015 flare, and the discovery of PKS 0736+017 as a new VHE quasar.

  • 175.
    Chahrur, Amer
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Vad ligger bakom läromedelsval?: En kvalitativ intervjustudie om högstadielärares val av läromedel i fysikämnet2023Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Download full text (pdf)
    fulltext
  • 176.
    Chen, Boyang
    et al.
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Xu, Mingyi
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Design of a Quay Crane Training Simulator2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Download full text (pdf)
    fulltext
  • 177.
    Chibueze, J. O.
    et al.
    North West Univ, South Africa;Univ Nigeria, Nigeria.
    Caleb, M.
    Univ Manchester, UK;Univ Sydney, Australia.
    Spitler, L.
    Max Planck Inst Radioastron, Germany.
    Ashkar, H.
    Univ Paris Saclay, France;Ecole Polytech, France.
    Schussler, F.
    Univ Paris Saclay, France.
    Stappers, B. W.
    Univ Sydney, Australia.
    Venter, C.
    North West Univ, South Africa.
    Heywood, I
    Rhodes Univ, South Africa;South African Radio Astron Observ, South Africa;Univ Oxford, UK.
    Richards, A. M. S.
    Univ Manchester, UK.
    Williams, D. R. A.
    Univ Manchester, UK.
    Kramer, M.
    Univ Manchester, UK;Max Planck Inst Radioastron, Germany.
    Beswick, R.
    Univ Manchester, UK.
    Bezuidenhout, M. C.
    Univ Manchester, UK.
    Breton, R. P.
    Univ Manchester, UK.
    Driessen, L. N.
    CSIRO, Australia.
    Jankowski, F.
    Univ Manchester, UK.
    Keane, E. F.
    Natl Univ Ireland Galway, Ireland.
    Malenta, M.
    Univ Manchester, UK.
    Mickaliger, M.
    Univ Manchester, UK.
    Morello, V
    Univ Manchester, UK.
    Qiu, H.
    Jodrell Bank Observ, UK.
    Rajwade, K.
    Univ Manchester, UK.
    Sanidas, S.
    Univ Manchester, UK.
    Surnis, M.
    Univ Manchester, UK.
    Scragg, T. W.
    Univ Manchester, UK.
    Walker, C. R. H.
    Max Planck Inst Radioastron, Germany.
    Wrigley, N.
    Univ Manchester, UK.
    Aharonian, F.
    Dublin Inst Adv Studies, Ireland.;Max Planck Inst Kernphys, Germany;RAU, Armenia.
    Benkhali, F. Ait
    Heidelberg Univ, Germany.
    Anguener, E. O.
    Aix Marseille Univ, France.
    Backes, M.
    North West Univ, South Africa;Univ Namibia, Namibia.
    Baghmanyan, V
    Inst Fizyki Jadrowej PAN, Poland.
    Martins, V. Barbosa
    DESY, Germany.
    Batzofin, R.
    Univ Witwatersrand, South Africa.
    Becherini, Yvonne
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering. Univ Paris, France.
    Berge, D.
    DESY, Germany.
    Bottcher, M.
    North West Univ, South Africa.
    Boisson, C.
    Univ Paris, France..
    Bolmont, J.
    Sorbonne Univ, France.
    de Lavergne, M. de Bony
    Univ Savoie Mt Blanc, France.
    Breuhaus, M.
    Max Planck Inst Kernphys, Germany.
    Brose, R.
    Dublin Inst Adv Studies, Ireland.
    Brun, F.
    Univ Paris Saclay, France.
    Bulik, T.
    Univ Warsaw, Poland.
    Cangemi, F.
    Sorbonne Univ, France.
    Caroff, S.
    Sorbonne Univ, France.
    Casanova, S.
    Inst Fizyki Jadrowej PAN, Poland.
    Catalano, J.
    Friedrich Alexander Univ Erlangen Nurnberg, Germany.
    Cerruti, M.
    Univ Paris, France.
    Chand, T.
    North West Univ, South Africa.
    Chen, A.
    Univ Witwatersrand, South Africa.
    Chibueze, O. U.
    North West Univ, South Africa.
    Cotter, G.
    Univ Oxford, UK.
    Cristofari, P.
    Univ Paris, France.
    Mbarubucyeye, J. Damascene
    DESY, Germany.
    Devin, J.
    Univ Bordeaux, France.
    Djannati-Atai, A.
    Univ Paris, France.
    Dmytriiev, A.
    North West Univ, South Africa.
    Egberts, K.
    Univ Potsdam, Germany.
    Ernenwein, J-P
    Aix Marseille Univ, France.
    Fiasson, A.
    Univ Savoie Mt Blanc, France.
    de Clairfontaine, G. Fichet
    Univ Paris, France.
    Fontaine, G.
    Ecole Polytech, France.
    Funk, S.
    Friedrich Alexander Univ Erlangen Nurnberg, Germany.
    Gabici, S.
    Univ Paris, France.
    Ghafourizadeh, S.
    Heidelberg Univ, Germany.
    Giavitto, G.
    DESY, Germany.
    Glawion, D.
    Friedrich Alexander Univ Erlangen Nurnberg, Germany.
    Grondin, M-H
    Univ Bordeaux, France.
    Horbe, M.
    Univ Oxford, UK.
    Hoischen, C.
    Univ Potsdam, Germany.
    Holch, T. L.
    DESY, Germany.
    Huang, Zhiqiu
    Max Planck Inst Kernphys, Germany.
    Jamrozy, M.
    Uniwersytet Jagiellonski, Poland.
    Jankowsky, F.
    Heidelberg Univ, Germany.
    Joshi, V
    Friedrich Alexander Univ Erlangen Nurnberg, Germany.
    Jung-Richardt, I
    Friedrich Alexander Univ Erlangen Nurnberg, Germany.
    Kasai, E.
    Univ Namibia, Namibia.
    Katarzynski, K.
    Nicolaus Copernicus Univ, Poland.
    Katz, U.
    Friedrich Alexander Univ Erlangen Nurnberg, Germany.
    Khelifi, B.
    Univ Paris, France.
    Kluzniak, W.
    Polish Acad Sci, Poland.
    Komin, Nu
    Univ Witwatersrand, South Africa.
    Kosack, K.
    Univ Paris Saclay, France..
    Kostunin, D.
    DESY, Germany.
    Lemiere, A.
    Univ Paris, France.
    Lenain, J-P
    Sorbonne Univ, France.
    Leuschner, F.
    Univ Tubingen, Germany.
    Lohse, T.
    Humboldt Univ, Germany.
    Luashvili, A.
    Univ Paris, France.
    Lypova, I
    Heidelberg Univ, Germany.
    Mackey, J.
    Dublin Inst Adv Studies, Ireland.
    Malyshev, D.
    Univ Tubingen, Germany.
    Marandon, V
    Max Planck Inst Kernphys, Germany.
    Marchegiani, P.
    Univ Witwatersrand, South Africa.
    Marcowith, A.
    Univ Montpellier, France.
    Marti-Devesa, G.
    Leopold Franzens Univ Innsbruck, Austria.
    Marx, R.
    Heidelberg Univ, Germany.
    Mitchell, A.
    Max Planck Inst Kernphys, Germany;Friedrich Alexander Univ Erlangen Nurnberg, Germany.
    Moderski, R.
    Polish Acad Sci, Poland.
    Mohrmann, L.
    Max Planck Inst Kernphys, Germany.
    Moulin, E.
    Univ Paris Saclay, France.
    Muller, J.
    Ecole Polytech, France.
    Nakashima, K.
    Friedrich Alexander Univ Erlangen Nurnberg, Germany.
    de Naurois, M.
    Ecole Polytech, France.
    Nayerhoda, A.
    Inst Fizyki Jadrowej PAN, Poland.
    Niemiec, J.
    Inst Fizyki Jadrowej PAN, Poland.
    Noel, A. Priyana
    Uniwersytet Jagiellonski, Poland.
    O'Brien, P.
    Univ Leicester, UK.
    Ohm, S.
    DESY, Germany.
    Olivera-Nieto, L.
    Max Planck Inst Kernphys, Germany.
    Wilhelmi, E. de Ona
    DESY, Germany..
    Ostrowski, M.
    Uniwersytet Jagiellonski, Poland.
    Panny, S.
    Leopold Franzens Univ Innsbruck, Austria.
    Parsons, R. D.
    Humboldt Univ, Germany.
    Pita, S.
    Univ Paris, France.
    Poireau, V
    Univ Savoie Mt Blanc, France.
    Prokhorov, D. A.
    Univ Amsterdam, Netherlands.
    Prokoph, H.
    DESY, Germany.
    Puehlhofer, G.
    Univ Tubingen, Germany.
    Quirrenbach, A.
    Heidelberg Univ, Germany.
    Reichherzer, P.
    Univ Paris Saclay, France.
    Reimer, A.
    Leopold Franzens Univ Innsbruck, Austria.
    Reimer, O.
    Leopold Franzens Univ Innsbruck, Austria.
    Rowell, G.
    Univ Adelaide, Australia.
    Rudak, B.
    Polish Acad Sci, Poland.
    Ruiz-Velasco, E.
    Max Planck Inst Kernphys, Germany.
    Sahakian, V
    Yerevan Phys Inst, Armenia.
    Sailer, S.
    Max Planck Inst Kernphys, Germany.
    Salzmann, H.
    Univ Tubingen, Germany.
    Sanchez, D. A.
    Univ Savoie Mt Blanc, France.
    Santangelo, A.
    Univ Tubingen, Germany.
    Sasaki, M.
    Friedrich Alexander Univ Erlangen Nurnberg, Germany.
    Schutte, H. M.
    North West Univ, South Africa.
    Schwanke, U.
    Humboldt Univ, Germany.
    Shapopi, J. N. S.
    Univ Namibia, Namibia.
    Specovius, A.
    Friedrich Alexander Univ Erlangen Nurnberg, Germany.
    Spencer, S.
    Univ Oxford, UK.
    Steenkamp, R.
    Univ Namibia, Namibia.
    Steinmassl, S.
    Max Planck Inst Kernphys, Germany.
    Takahashi, T.
    Univ Tokyo, Japan.
    Tanaka, T.
    Konan Univ, Japan.
    Thorpe-Morgan, C.
    Univ Tubingen, Germany.
    Tsuji, N.
    RIKEN, Japan.
    van Eldik, C.
    Friedrich Alexander Univ Erlangen Nurnberg, Germany.
    Veh, J.
    Friedrich Alexander Univ Erlangen Nurnberg, Germany.
    Vink, J.
    Univ Amsterdam, Netherlands.
    Wagner, S. J.
    Heidelberg Univ, Germany.
    Wierzcholska, A.
    Inst Fizyki Jadrowej PAN, Poland.
    Wong, Yu Wun
    Friedrich Alexander Univ Erlangen Nurnberg, Germany.
    Yusafzai, A.
    Friedrich Alexander Univ Erlangen Nurnberg, Germany.
    Zacharias, M.
    North West Univ, South Africa;Univ Paris, France.
    Zargaryan, D.
    Dublin Inst Adv Studies, Ireland;RAU, Armenia.
    Zdziarski, A. A.
    Polish Acad Sci, Poland.
    Zech, A.
    Univ Paris, France.
    Zhu, S. J.
    DESY, Germany.
    Zouari, S.
    Univ Paris, France.
    Zywucka, N.
    North West Univ, South Africa.
    A MeerKAT, e-MERLIN, HESS, and Swift search for persistent and transient emission associated with three localized FRBs2022In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 515, no 1, p. 1365-1379Article in journal (Refereed)
    Abstract [en]

    We report on a search for persistent radio emission from the one-off fast radio burst (11(B) 20190714A, as well as from two repeating FRBs, 20190711A and 20171019A, using the MeerKAT radio telescope. For FRB 20171019A, we also conducted simultaneous observations with the High-Energy Stereoscopic System (H.E.S.S.) in very high-energy gamma rays and searched for signals in the ultraviolet, optical, and X-ray bands. For this FRB, we obtain a UV flux upper limit of 1.39 x 10(-16) erg cm(-2) s(-1) angstrom(-1), X-ray limit of similar to 6.6 x 10(-14) erg cm(-2) s(-1) and a limit on the very high energy gamma-ray flux Phi(E > 120 GeV) < 1.7 x 10(-12) erg cm(-2) S-1. We obtain a radio upper limit of similar to 15 mu Jy beam(-1) for persistent emission at the locations of both FRBs 20190711A and 20171019A with MeerKAT. However, we detected an almost unresolved (ratio of integrated flux to peak flux is similar to 1.7 beam) radio emission, where the synthesized beam size was similar to 8 arcsec size with a peak brightness of similar to 53 mu Jy beam(-1) at MeerKAT and similar to 86 mu Jy beam(-1) at e-MERLIN, possibly associated with FRB 20190714A at z = 0.2365. This represents the first detection of persistent continuum radio emission potentially associated with a (as-yet) non- repeating FRB. If the association is confirmed, one of the strongest remaining distinction between repeaters and non-repeaters would no longer be applicable. A parallel search for repeat bursts from these FRBs revealed no new detections down to a fluence of 0.08 Jy ms for a 1 ms duration burst.

  • 178.
    Christiansen, Adrian
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Simulering av tidskontinuerliga inkrementella sigma-delta A/D-omvandlare: Med hjälp av MATLAB/Simulink2022Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Detta arbete inleds med en översiktlig teoretiskt bakgrund om analog till digital-omvandlare(A/D-omvandlare). Vartefter arbetet beskriver två kända metoder för att transformera återkopplingsloopar konstruerade i den tidsdiskreta z-domänen till den tidskontinuerliga Laplace-domänen. En simulering genomfördes för att visa hur en av dessa metoder gav en förväntadbrusformning.

    Mätning av brus med diskret Fouriertransform beskrivs och en modell av en inkrementellsigma-delta A/D-omvandlare simuleras för att visa hur en enkel räknare kan användas i deci-meringen.

    Download full text (pdf)
    fulltext
  • 179.
    Cinar, Gökhan
    et al.
    Eskisehir Osmangazi University, Turkey.
    Aksimsek, Sinan
    Istanbul KÄultÄur University, Turkey.
    Nilsson, Börje
    Linnaeus University, Faculty of Technology, Department of Mathematics.
    Nordebo, Sven
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Cinar, Özge
    Eskisehir Osmangazi University, Turkey.
    Wiener-Hopf analysis of TM wave reflection by a step discontinuity on the junction of two coaxial waveguides with perfectly conducting and impedance walls2015In: Progress In Electromagnetics Research Symposium Abstracts, Prague, Czech Republic, July 6-9, 2015, Electromagnetics Academy , 2015, p. 1062-Conference paper (Other academic)
    Download full text (pdf)
    fulltext
  • 180.
    Citrohn, Björn
    et al.
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Stolpe, Karin
    Linköping University, Sweden.
    Svensson, Maria
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering. University of Gothenburg, Sweden.
    The use of models and modelling in design projects in three different technology classrooms2023In: International journal of technology and design education, ISSN 0957-7572, E-ISSN 1573-1804, Vol. 33, p. 63-90Article in journal (Refereed)
    Abstract [en]

    In this study, we aim to investigate activities using models in a design project in three technology classrooms. Activities that use models are important for students' development of knowledge and skills connected to the design process. Nevertheless, few empirical studies have thus far examined how models and modelling are used in a classroom environment when students and teachers are involved in a design project. In order to meet our aim, we video-recorded eight lessons from three different technology classrooms (students aged 13-15), where the students were involved in different problem-solving activities using models and modelling. The three projects had different specifications, and the students' degrees of freedom thereby varied. The video recordings were analysed using a qualitative content analysis. The analysis resulted in seven activities being identified where the teachers and students talked about models and modelling in order to solve the problem. The results also revealed three different dimensions of models: material, structure and function. These dimensions are present in almost all activities that use models. In a project with a high degree of freedom, all three dimensions of models are present. On the contrary, in a project with a lower freedom, only one of the dimensions is present, resulting in a lower degree of complexity for the students. The study emphasizes that the presumptions and openness of a design project in technology education can provide different possibilities for students learning in relation to models and modelling.

    Download full text (pdf)
    fulltext
  • 181.
    Citrohn, Björn
    et al.
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Svensson, Maria
    University of Gothenburg, Sweden.
    Technology teacher's perceptions of model functions in technology education2022In: International journal of technology and design education, ISSN 0957-7572, E-ISSN 1573-1804, Vol. 32, p. 805-823Article in journal (Refereed)
    Abstract [en]

    In this study we investigate how 11 Swedish technology teachers perceive model functions in technology education. The main reason for investigating model functions in technology is an identified lack of knowledge about, and research studies into, a conscious use of models when teaching technology, even though models are part of technology education in many countries. In order to answer the research question of how technology teachers perceive model functions in technology education, we have used directed content analysis where Nia and de Vries (J Technol Des Educ 27:627-653, 2017) model functions constituted a framework. The teachers connect model functions to two teaching contexts:Design processandExplain and facilitate understanding of technological solutions.Model functions are understood as parts of the design process which relate to technology/engineering knowledge, a prescriptive way of understanding models. Models are also used to explain and clarify specific technological situations or functions when teaching technology closely related to a scientific, descriptive way of using models. Five of Nia and de Vries model functions are identified in this empirical study. This strengthens the importance of addressing model functions in technological education.

    Download full text (pdf)
    fulltext
  • 182.
    Citrohn, Björn
    et al.
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Svensson, Maria
    University of Gothenburg, Sweden.
    Technology Teachers’ Perceptions of Models in Technology Education2021In: PATT38 Rauma, Finland 2021, Technology in our Hands. Creative Pedagogy and Ambitious Teacher Education, Olso: Universitetsbiblioteket OsloMet , 2021, Vol. 28, p. 425-431Conference paper (Refereed)
    Abstract [en]

    In this study we investigate how 11 Swedish technology teachers perceive the use of models in technology education. Models are part of technology education in many countries even though there are few studies investigating teachers’ understanding of models as part of the subject and how models are used in education. The use of models and modelling in technology is connected to problem solving and builds on both practical and theoretical knowledge. Models could be understood as both cognitive and physical, used for describing complex artefacts and solutions as well as working with developing solutions.

    Our study involves empirical interviews with technology teachers, teaching technology and science in grade 7-9 (pupils 13-15 years old). By using a content analysis, we explore how teachers perceive the use of models in technology education. The analysis resulted in two themes and five different categories used to understand how teachers perceive models. When comparing with the dual nature of models (Nia & De Vries, 2017) the Swedish technology teachers mainly relate the use of models to an intentional nature. This indicates that there are model functions that the technology teachers do not perceive at all or only perceive to a limited extent which could have a negative effect on the possibilities for pupils to understand and learn about complex technological relationships and phenomena, as well as for pupils' ability to solve problems.

  • 183. Collaboration, H. E. S. S.
    et al.
    Abramowski, A.
    Aharonian, F.
    Benkhali, F. Ait
    Akhperjanian, A. G.
    Anguener, E.
    Anton, G.
    Balenderan, S.
    Balzer, A.
    Barnacka, A.
    Becherini, Yvonne
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Tjus, J. Becker
    Bernloehr, K.
    Birsin, E.
    Bissaldi, E.
    Biteau, J.
    Boettcher, M.
    Boisson, C.
    Bolmont, J.
    Bordas, P.
    Brucker, J.
    Brun, F.
    Brun, P.
    Bulik, T.
    Carrigan, S.
    Casanova, S.
    Cerruti, M.
    Chadwick, P. M.
    Chalme-Calvet, R.
    Chaves, R. C. G.
    Cheesebrough, A.
    Chretien, M.
    Colafrancesco, S.
    Cologna, G.
    Conrad, J.
    Couturier, C.
    Cui, Y.
    Dalton, M.
    Daniel, M. K.
    Davids, I. D.
    Degrange, B.
    Deil, C.
    de Wilt, P.
    Dickinson, H. J.
    Djannati-Atai, A.
    Domainko, W.
    Drury, L. O 'C.
    Dubus, G.
    Dutson, K.
    Dyks, J.
    Dyrda, M.
    Edwards, T.
    Egberts, K.
    Eger, P.
    Espigat, P.
    Farnier, C.
    Fegan, S.
    Feinstein, F.
    Fernandes, M. V.
    Fernandez, D.
    Fiasson, A.
    Fontaine, G.
    Foerster, A.
    Fuessling, M.
    Gajdus, M.
    Gallant, Y. A.
    Garrigoux, T.
    Giavitto, G.
    Giebels, B.
    Glicenstein, J. F.
    Grondin, M. -H
    Grudzinska, M.
    Haeffner, S.
    Hahn, J.
    Harris, J.
    Heinzelmann, G.
    Henri, G.
    Hermann, G.
    Hervet, O.
    Hillert, A.
    Hinton, J. A.
    Hofmann, W.
    Hofverberg, P.
    Holler, M.
    Horns, D.
    Jacholkowska, A.
    Jahn, C.
    Jamrozy, M.
    Janiak, M.
    Jankowsky, F.
    Jung, I.
    Kastendieck, M. A.
    Katarzynski, K.
    Katz, U.
    Kaufmann, S.
    Khelifi, B.
    Kieffer, M.
    Klepser, S.
    Klochkov, D.
    Kluzniak, W.
    Kneiske, T.
    Kolitzus, D.
    Komin, Nu.
    Kosack, K.
    Krakau, S.
    Krayzel, F.
    Krueger, P. P.
    Laffon, H.
    Lamanna, G.
    Lefaucheur, J.
    Lemiere, A.
    Lemoine-Goumard, M.
    Lenain, J. -P
    Lennarz, D.
    Lohse, T.
    Lopatin, A.
    Lu, C. -C
    Marandon, V.
    Marcowith, A.
    Marx, R.
    Maurin, G.
    Maxted, N.
    Mayer, M.
    McComb, T. J. L.
    Mehault, J.
    Meintjes, P. J.
    Menzler, U.
    Meyer, M.
    Moderski, R.
    Mohamed, M.
    Moulin, E.
    Murach, T.
    Naumann, C. L.
    de Naurois, M.
    Niemiec, J.
    Nolan, S. J.
    Oakes, L.
    Ohm, S.
    Wilhelmi, E. de Ona
    Opitz, B.
    Ostrowski, M.
    Oya, I.
    Panter, M.
    Parsons, R. D.
    Arribas, M. Paz
    Pekeur, N. W.
    Pelletier, G.
    Perez, J.
    Petrucci, P. -O
    Peyaud, B.
    Pita, S.
    Poon, H.
    Puehlhofer, G.
    Punch, Michael
    Univ Paris Diderot, APC, AstroParticule & Cosmology, CNRS,IN2P3,CEA,Irfu, Observ Paris,Sorbonne Paris C, 10 Rue Alice Domon & Leonie Duquet, F-75205 Paris 13, France.
    Quirrenbach, A.
    Raab, S.
    Raue, M.
    Reimer, A.
    Reimer, O.
    Renaud, M.
    de los Reyes, R.
    Rieger, F.
    Rob, L.
    Romoli, C.
    Rosier-Lees, S.
    Rowell, G.
    Rudak, B.
    Rulten, C. B.
    Sahakian, V.
    Sanchez, D. A.
    Santangelo, A.
    Schlickeiser, R.
    Schuessler, F.
    Schulz, A.
    Schwanke, U.
    Schwarzburg, S.
    Schwemmer, S.
    Sol, H.
    Spengler, G.
    Spies, F.
    Stawarz, L.
    Steenkamp, R.
    Stegmann, C.
    Stinzing, F.
    Stycz, K.
    Sushch, I.
    Szostek, A.
    Tavernet, J. -P
    Tavernier, T.
    Taylor, A. M.
    Terrier, R.
    Tluczykont, M.
    Trichard, C.
    Valerius, K.
    van Eldik, C.
    van Soelen, B.
    Vasileiadis, G.
    Venter, C.
    Viana, A.
    Vincent, P.
    Voelk, H. J.
    Volpe, F.
    Vorster, M.
    Vuillaume, T.
    Wagner, S. J.
    Wagner, P.
    Ward, M.
    Weidinger, M.
    Weitzel, Q.
    White, R.
    Wierzcholska, A.
    Willmann, P.
    Woernlein, A.
    Wouters, D.
    Zabalza, V.
    Zacharias, M.
    Zajczyk, A.
    Zdziarski, A. A.
    Zech, A.
    Zechlin, H. -S
    HESS observations of the Crab during its March 2013 GeV gamma-ray flare2014In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 562, p. Article ID: UNSP L4-Article in journal (Refereed)
    Abstract [en]

    Context. On March 4, 2013 the Fermi-EAT and AGILE reported a flare from the direction of the Crab nebula in which the high-energy (HE; E > 100 MeV) flux was six times above its quiescent level. Simultaneous observations in other energy bands give us hints about the emission processes during the flare episode and the physics of pulsar wind nebulae in general. Aims. We search for variability in the emission of the Crab nebula at very-high energies (VHF,; E > 100 GeV), using contemporaneous data taken with the H.E.S.S. array of Cherenkov telescopes. Methods. Observational data taken with the H.E.S.S. instrument on five consecutive days during the flare were analysed for the flux and spectral shape of the emission from the Crab nebula. Night-wise light curves are presented with energy thresholds of 1 TeV and 5 TeV. Results. The observations conducted with H.E.S.S. on March 6 to March 10, 2013 show no significant changes in the flux. They limit the variation in the integral flux above 1 TeV to less than 63% and the integral flux above 5 TeV to less than 78% at a 95% confidence level.

  • 184.
    Corstanje, A.
    et al.
    Radboud University Nijmegen, Netherlands.
    Bonardi, A.
    Radboud University Nijmegen, Netherlands.
    Buitink, S.
    Radboud University Nijmegen, Netherlands ; Vrije Universiteit Brussel, Belgium.
    Falcke, H.
    Radboud University Nijmegen, Netherlands ; ASTRON Netherlands Institute for Radio Astronomy, Netherlands ; Nikhef, Sci Pk Amsterdam, NL-1098 XG Amsterdam, Netherlands.;Max Planck Inst Radioastron, Hugel 69, D-53121 Bonn, Germany..
    Horandel, J. R.
    Radboud University Nijmegen, Netherlands ;Nikhef, Sci Pk Amsterdam, NL-1098 XG Amsterdam, Netherlands..
    Mitra, R.
    Vrije Univ Brussel, Inst Astrophys, Pleinlaan 2, B-1050 Brussels, Belgium..
    Mulrey, K.
    Vrije Univ Brussel, Inst Astrophys, Pleinlaan 2, B-1050 Brussels, Belgium..
    Nelles, A.
    Radboud University Nijmegen, Netherlands ;Nikhef, Sci Pk Amsterdam, NL-1098 XG Amsterdam, Netherlands.;Univ Calif Irvine, Dept Phys & Astron, Irvine, CA 92697 USA..
    Rachen, J. P.
    Radboud University Nijmegen, Netherlands.
    Rossetto, L.
    Radboud University Nijmegen, Netherlands.
    Schellart, P.
    Radboud University Nijmegen, Netherlands ;Princeton Univ, Dept Astrophys Sci, Princeton, NJ 08544 USA..
    Scholten, O.
    Vrije Univ Brussel, Interuniv Inst High Energy, Pleinlaan 2, B-1050 Brussels, Belgium.;Univ Groningen, POB 72, NL-9700 AB Groningen, Netherlands..
    ter Veen, S.
    Radboud University Nijmegen, Netherlands.
    Thoudam, Satyendra
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering. Radboud University Nijmegen, Netherlands.
    Trinh, G.
    Univ Groningen, POB 72, NL-9700 AB Groningen, Netherlands..
    Winchen, T.
    Vrije Univ Brussel, Inst Astrophys, Pleinlaan 2, B-1050 Brussels, Belgium..
    The effect of the atmospheric refractive index on the radio signal of extensive air showers2017In: Astroparticle physics, ISSN 0927-6505, E-ISSN 1873-2852, Vol. 89, p. 23-29Article in journal (Refereed)
    Abstract [en]

    For the interpretation of measurements of radio emission from extensive air showers, an important systematic uncertainty arises from natural variations of the atmospheric refractive index n. At a given altitude, the refractivity N = 10(6) (n - 1) can have relative variations on the order of 10% depending on temperature, humidity, and air pressure. Typical corrections to be applied to N are about 4%. Using CoREAS simulations of radio emission from air showers, we have evaluated the effect of varying N on measurements of the depth of shower maximum X-max. For an observation band of 30-80 MHz, a difference of 4% in refractivity gives rise to a systematic error in the inferred X-max between 3.5 and 11 g/cm(2), for proton showers with zenith angles ranging from 15 to 50 degrees. At higher frequencies, from 120 to 250 MHz, the offset ranges from 10 to 22 g/cm(2). These offsets were found to be proportional to the geometric distance to X-max. We have compared the results to a simple model based on the Cherenkov angle. For the 120-250 MHz band, the model is in qualitative agreement with the simulations. In typical circumstances, we find a slight decrease in X-max compared to the default refractivity treatment in CoREAS. While this is within commonly treated systematic uncertainties, accounting for it explicitly improves the accuracy of X-max measurements. (C) 2017 Elsevier B.V. All rights reserved.

  • 185.
    Corstanje, A.
    et al.
    Radboud University, Netherlands.
    Mitra, P.
    Vrije Universiteit, Belgium.
    Bonardi, A.
    Radboud University, Netherlands.
    Buitink, S.
    Vrije Universiteit, Belgium.
    Falcke, H.
    Radboud University, Netherlands;NIKHEF, Netherlands;Netherlands Institute of Radio Astronomy (ASTRON), Netherlands.
    Hare, B. M.
    University Groningen, Netherlands.
    Hörandel, J. R.
    Radboud University, Netherlands;NIKHEF, Netherlands.
    Mulrey, K.
    Vrije Universiteit, Belgium.
    Nelles, A.
    Radboud University, Netherlands;University of California, USA.
    Rachen, J. P.
    Radboud University, Netherlands.
    Rossetto, L.
    Radboud University, Netherlands.
    Schellart, P.
    Radboud University, Netherlands;Princeton University, USA.
    Scholten, O.
    University Groningen, Netherlands.
    Ter Veen, S.
    Radboud University, Netherlands;Netherlands Institute of Radio Astronomy (ASTRON), Netherlands.
    Thoudam, Satyendra
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering. Radboud University, Netherlands.
    Trinh, T. N. G.
    University Groningen, Netherlands.
    Winchen, T.
    Vrije Universiteit, Belgium.
    The effect of the atmospheric refractive index on the radio signal of extensive air showers using Global Data Assimilation System (GDAS)2018In: 35th International Cosmic Ray Conference, ICRC 2017, 10-20 July 2017, Bexco, Busan, Korea, Sissa Medialab Srl , 2018Conference paper (Refereed)
    Abstract [en]

    One of the major systematic uncertainties in the measurement of Xmax from radio emission of EAS arises from variations of the refractive index in the atmosphere. The refractive index n varies with temperature, humidity and pressure, and the variations can be on the order of 10% for (n-1) at a given altitude. The effect of a varying refractive index on Xmax measurements is evaluated using CoREAS: a microscopic simulation of the radio emission from the individual particles in the cascade simulated with CORSIKA. We discuss the resulting offsets in Xmax for different frequency regimes, and compare them to a simple physical model. Under typical circumstances, the offsets in Xmax range from 4-11 g/cm2 for the 30-80 MHz frequency band. Therefore, for precise measurements it is required to include atmospheric data at the time and place of observation of the air shower into the simulations. The aim is to implement this in the next version of CoREAS/CORSIKA using the Global Data Assimilation System (GDAS), a global atmospheric model based on meteorological measurements and numerical weather predictions. This can then be used to re-evaluate the air shower measurements of the LOFAR radio telescope. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives 4.0 International License (CC BY-NC-ND 4.0).

  • 186.
    Costanza, Gabriele
    et al.
    Lund University.
    Ioannidis, Andreas
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Remarks on the mathematical solution of the hollow cavity eigenvalue problem2013In: Progress in Electromagnetics Research Symposium, Electromagnetics Acad. , 2013, p. 79-83Conference paper (Refereed)
    Abstract [en]

    We discuss the eigenvalue problem for a perfectly conducting hollow cavity under a strict functional analytic point of view. We make use of a variant of the classical spectral theorem for compact selfadjoint operators and we pay extra attention on the null space of the Maxwell operator. We also discuss the corresponding inhomogeneous problem, where currents are present, even when they may depend on the fields.

  • 187.
    Dahlskog, Robert
    et al.
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Arnell, Martin
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    En ljusbåges energi och konsekvenser: Att öka säkerheten och belysa konsekvenserna vid en ljusbåge på Mörrums Bruk2019Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Syftet med den här rapporten är att uppmärksamma elriskerna med ljusbågar som i många fall glömts bort, vilka risker man utsätter sig för när man oskyddad rör sig i närheten av transformatorer och ställverk. Rapporten ger också en överblick av vad som behöver förbättras på Södra Cell Mörrum för att öka elsäkerheten och undvika elskador. Ett mål är även att med hjälp av beräkningar kunna välja rätt skyddskläder och ha möjlighet att avgöra när en anläggning ska göras spänningslös vid elunderhållsarbete. Ett beräkningsblad har skapats i Excel för att enklare räkna ut energierna på olika transformatorer.

    Download full text (pdf)
    fulltext
  • 188.
    Dahlström, Peter
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Att ha en blick och en fallenhet för det.: En studie av yrkeskunnande inom lastbilsföraryrket.2014Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The purpose of the study was to get an insight into what it is that hides behind the statement to have an eye for something and an aptitude for something. In this study i have been in contact with two male truck drivers who have a long experience from truck driving.In the study they told me what knowledge they see as needed to be seen as a competent and skilled truck driver. The knowledge that the truck drivers brings out is to have an eye and an aptitude for the profession. The study showed that truck drivers had a hard time putting into words what they mean by having an eye and an aptitude for the profession.

     

    The results of the study showed that when it comes to having an eye and an aptitude for the profession that stems from Aristotle's concept of knowledge, techne seen as skill knowledge and phronesis seen as familiarity or intimate knowledge.Within skill knowledge fit to have an aptitude for something, you have the ability to perform an action. This ability develops with practice and experience, and it is not possible to predict how long an individual's ability can develop. Within familiarity knowledge fit to have an eye for something, you can see patterns or behaviors that can be interpreted.

     

    But, you can´t have a look for something you have not experienced before. The knowledge is based upon what you have accumulated over time. The knowledge interacts with each other to different degrees depending on personal characteristics, and the specific situation they face.

    Download full text (pdf)
    Att ha en blick och en fallenhet för det
  • 189.
    Dalarsson, Mariana
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    General theory of wave propagation through graded interfaces between positive- and negative-refractive-index media2017In: Physical Review A: covering atomic, molecular, and optical physics and quantum information, ISSN 2469-9926, E-ISSN 2469-9934, Vol. 96, no 4, article id 043848Article in journal (Refereed)
    Abstract [en]

    The introduction of metamaterials and transformation optics has brought the possibilities for manipulating electromagnetic waves to an unprecedented level, suggesting applications like super-resolution imaging, cloaking, subwavelength focusing, and field localization. The refractive index of metamaterial structures in transformation optics typically has to be spatially graded. This paper presents a full analytical method for description of the field propagation through composites with gradient refractive index. The remarkable property of this approach is that it gives explicit general expressions for the field intensity and transmission and reflection coefficients, without reference to any boundary conditions. This opens a possibility for a novel fundamental theory of a number of important electromagnetic phenomena. The method enables calculation of wave propagation parameters within structures with arbitrary losses, arbitrary spectral dispersions, and arbitrary slopes of permittivity and permeability gradients, from mild to abrupt.

  • 190.
    Dalarsson, Mariana
    et al.
    KTH Royal instute of technology, Sweden.
    Ivanenko, Yevhen
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering. Blekinge institute of technology, Sweden.
    Nordebo, Sven
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Wave propagation in waveguides with graded plasmonic obstacles2021In: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 38, no 1, p. 104-113Article in journal (Refereed)
    Abstract [en]

    In this paper, wave propagation in a hollow waveguide with a graded dielectric layer is studied. Analytic formulas are derived for the electric field components as well as general analytical results for the reflection and transmission coefficients for propagating waves. These results are all valid for waveguides of arbitrary cross sections, and the derived reflection and transmission coefficients are in exact asymptotic agreement with those obtained for a wry thin homogeneous dielectric layer using cascading and mode-matching techniques. Furthermore, the power transmission, reflection, and absorption coefficients, as functions of frequency and layer width, are studied, showing the expected behavior of these parameters. The method proposed in this paper gives directly applicable results that do not require cascading and mode matching, while at the same time having the ability to model smooth transitions that are more realistic in several applications.

  • 191.
    Dalarsson, Mariana
    et al.
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Jaksic, Zoran
    Univ Belgrade, Serbia.
    Phase Integral Approach to Wave Propagation in Continuously Graded Models of Flat Lenses2017In: 2017 13th International Conference on Advanced Technologies, Systems and Services in Telecommunications (TELSIKS) / [ed] BD Milovanovic, NS Doncov, ZZ Stankovic, TZ Dimitrijevic, Piscataway, NJ: IEEE, 2017, p. 38-41Conference paper (Refereed)
    Abstract [en]

    We propose a method to determine approximate phase-integral analytical solutions for electric and magnetic fields in flat lenses with the refractive index varying in the radial direction. In our model the gradient of refractive index is approximated by a large number of concentric annuli with step-increasing index. Here the central part contributes to a bulk of the phase transformation, while the external layers act as a graded antireflective structure, matching the impedance of the lens to that of the free space. Such lenses can be modeled as compact composites with continuous permittivity and (if needed) permeability functions which asymptotically approach unity at the boundaries of the composite cylinder. We illustrate the phase-integral approach by obtaining the approximate analytic solutions for the electric and magnetic fields for a special class of composite designs with radially graded parameters.

  • 192.
    Dalarsson, Mariana
    et al.
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Mittra, Raj
    Penn State Univ, USA.
    Exact analytical solutions of continuously graded models of flat lenses based on transformation optics2017In: Facta Universitatis Series: Electronics and Energetics, ISSN 0353-3670, E-ISSN 2217-5997, Vol. 30, no 4, p. 639-646Article in journal (Refereed)
    Abstract [en]

    We present a study of exact analytic solutions for electric and magnetic fields in continuously graded flat lenses designed utilizing transformation optics. The lenses typically consist of a number of layers of graded index dielectrics in both the radial and longitudinal directions, where the central layer in the longitudinal direction primarily contributes to a bulk of the phase transformation, while other layers act as matching layers and reduce the reflections at the interfaces of the middle layer. Such lenses can be modeled as compact composites with continuous permittivity (and if needed) permeability functions which asymptotically approach unity at the boundaries of the composite cylinder. We illustrate the proposed procedures by obtaining the exact analytic solutions for the electric and magnetic fields for one simple special class of composite designs with radially graded parameters. To this purpose we utilize the equivalence between the Helmholtz equation of our graded flat lens and the quantummechanical radial Schrodinger equation with Coulomb potential, furnishing the results in the form of Kummer confluent hypergeometric functions. Our approach allows for a better physical insight into the operation of our transformation optics-based graded lenses and opens a path toward novel designs and approaches.

  • 193.
    Dalarsson, Mariana
    et al.
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Nordebo, Sven
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    TE-wave propagation in a graded waveguide structure2018In: 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials), IEEE, 2018, p. 93-95Conference paper (Refereed)
    Abstract [en]

    We investigate TE-wave propagation in a hollow waveguide with a graded dielectric barrier, using an equivalent model of the waveguide filled with a stratified medium. General formulae for the electric field components of the TE-waves, applicable to hollow waveguides with arbitrary cross sectional shapes, are presented. As an illustration, we obtain the exact analytical results for the electric field components in a rectangular waveguide, as well as the exact analytical results for reflection and transmission coefficients which are valid for waveguides of arbitrary cross sectional shapes.

  • 194.
    Dalarsson, Mariana
    et al.
    Lund University, Sweden.
    Nordebo, Sven
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    TE-wave propagation in graded waveguide structures2020In: OSA Continuum, E-ISSN 2578-7519, Vol. 3, no 1, p. 67-76Article in journal (Refereed)
    Abstract [en]

    We investigate TE-wave propagation in a hollow waveguide with a graded dielectric layer, described using a hyperbolic tangent function. General formulae for the electric field components of the TE-waves, applicable to hollow waveguides with arbitrary cross sectional shapes, are presented. We illustrate the exact analytical results for the electric field components in the special case of a rectangular waveguide. Furthermore, we derive exact analytical results for the reflection and transmission coefficients valid for waveguides of arbitrary cross sectional shapes. Finally, we show that the obtained reflection and transmission coefficients are in exact asymptotic agreement with those obtained for a very thin homogeneous dielectric layer using mode-matching and cascading. The proposed method gives analytical results that are directly applicable without the need of mode-matching, and it has the ability to model realistic, smooth transitions. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

  • 195.
    Dalarsson, Mariana
    et al.
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Nordebo, Sven
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    The absorption of electromagnetic (EM) waves by a spherical dilute suspension of nanoparticles2017Report (Other academic)
    Download full text (pdf)
    fulltext
  • 196.
    Dalarsson, Mariana
    et al.
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Nordebo, Sven
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    TM-wave propagation in a graded waveguide structure2019In: 2019 URSI International Symposium on Electromagnetic Theory (EMTS), IEEE , 2019, p. 1-4Conference paper (Refereed)
    Abstract [en]

    We investigate TM-wave propagation in a hollow waveguide with a graded dielectric layer, described using a hyperbolic tangent function. General formulae for the electric field components of the TM-waves, applicable to hollow waveguides with arbitrary cross sectional shapes, are presented. We derive the analytical results for the reflection and transmission coefficients valid for waveguides of arbitrary cross sectional shapes. Thereby, we show that the obtained reflection and transmission coefficients are in exact asymptotic agreement with those obtained for a very thin homogeneous dielectric layer using mode-matching and cascading. The proposed method is tractable since it gives analytical results that are directly applicable without the need of mode-matching, and it has the ability to model realistic, smooth transitions.

  • 197.
    Dalarsson, Mariana
    et al.
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Nordebo, Sven
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Sjöberg, Daniel
    Lund University, Sweden.
    Optimal plasmonic resonances for small arbitrarily shaped particles in lossy media2017In: 32nd URSI GASS, Montreal, 19–26 August 2017, URSI , 2017, p. 2667-2667Conference paper (Refereed)
  • 198.
    Dalarsson, Mariana
    et al.
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Nordebo, Sven
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Sjöberg, Daniel
    Lund University.
    Bayford, Richard
    Middlesex Univ, UK.
    Absorption and optimal plasmonic resonances for small ellipsoidal particles in lossy media2017In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 50, no 34, article id 345401Article in journal (Refereed)
    Abstract [en]

    A new simplified formula is derived for the absorption cross section of small dielectric ellipsoidal particles embedded in lossy media. The new expression leads directly to a closed form solution for the optimal conjugate match with respect to the surrounding medium, i.e. the optimal permittivity of the ellipsoidal particle that maximizes the absorption at any given frequency. This defines the optimal plasmonic resonance for the ellipsoid. The optimal conjugate match represents a metamaterial in the sense that the corresponding optimal permittivity function may have negative real part (inductive properties), and can not in general be implemented as a passive material over a given bandwidth. A necessary and sufficient condition is derived for the feasibility of tuning the Drude model to the optimal conjugate match at a single frequency, and it is found that all the prolate spheroids and some of the (not too flat) oblate spheroids can be tuned into optimal plasmonic resonance at any desired center frequency. Numerical examples are given to illustrate the analysis. Except for the general understanding of plasmonic resonances in lossy media, it is also anticipated that the new results can be useful for feasibility studies with e.g. the radiotherapeutic hyperthermia based methods to treat cancer based on electrophoretic heating in gold nanoparticle suspensions using microwave radiation.

  • 199.
    Dautbegovic, Dino
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Convex Optimization Methods for System Identification2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The extensive use of a least-squares problem formulation in many fields is partly motivated by the existence of an analytic solution formula which makes the theory comprehensible and readily applicable, but also easily embedded in computer-aided design or analysis tools. While the mathematics behind convex optimization has been studied for about a century, several recent researches have stimulated a new interest in the topic. Convex optimization, being a special class of mathematical optimization problems, can be considered as generalization of both least-squares and linear programming. As in the case of a linear programming problem there is in general no simple analytical formula that can be used to find the solution of a convex optimization problem. There exists however efficient methods or software implementations for solving a large class of convex problems. The challenge and the state of the art in using convex optimization comes from the difficulty in recognizing and formulating the problem. The main goal of this thesis is to investigate the potential advantages and benefits of convex optimization techniques in the field of system identification. The primary work focuses on parametric discrete-time system identification models in which we assume or choose a specific model structure and try to estimate the model parameters for best fit using experimental input-output (IO) data. By developing a working knowledge of convex optimization and treating the system identification problem as a convex optimization problem will allow us to reduce the uncertainties in the parameter estimation. This is achieved by reecting prior knowledge about the system in terms of constraint functions in the least-squares formulation.

    Download full text (pdf)
    fulltext
  • 200.
    de Gelidi, S.
    et al.
    Middlesex Univ, UK.
    Seifnaraghi, N.
    Middlesex Univ, UK.
    Bardill, A.
    Middlesex Univ, UK.
    Tizzard, A.
    Middlesex Univ, UK.
    Wu, Y.
    UCL, UK.
    Sorantin, E.
    Med Univ Graz, Austria.
    Nordebo, Sven
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Demosthenous, A.
    UCL, UK.
    Bayford, R.
    Middlesex Univ, UK.
    Torso shape detection to improve lung monitoring2018In: Physiological Measurement, ISSN 0967-3334, E-ISSN 1361-6579, Vol. 39, no 7, article id 074001Article in journal (Refereed)
    Abstract [en]

    Objective: Newborns with lung immaturity often require continuous monitoring and treatment of their lung ventilation in intensive care units, especially if born preterm. Recent studies indicate that electrical impedance tomography (EIT) is feasible in newborn infants and children, and can quantitatively identify changes in regional lung aeration and ventilation following alterations to respiratory conditions. Information on the patient-specific shape of the torso and its role in minimizing the artefacts in the reconstructed images can improve the accuracy of the clinical parameters obtained from EIT. Currently, only idealized models or those segmented from CT scans are usually adopted. Approach: This study presents and compares two methodologies that can detect the patient-specific torso shape by means of wearable devices based on (1) previously reported bend sensor technology, and (2) a novel approach based on the use of accelerometers. Main results: The reconstruction of different phantoms, taking into account anatomical asymmetries and different sizes, are produced for comparison. Significance: As a result, the accelerometers are more versatile than bend sensors, which cannot be used on bigger cross-sections. The computational study estimates the optimal number of accelerometers required in order to generate an image reconstruction comparable to the use of a CT scan as the forward model. Furthermore, since the patient position is crucial to monitoring lung ventilation, the orientation of the phantoms is automatically detected by the accelerometer-based method.

1234567 151 - 200 of 649
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf