Dalarna University's logo and link to the university's website

du.sePublications
Change search
Refine search result
1234567 1 - 50 of 1382
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • chicago-author-date
  • chicago-note-bibliography
  • 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.
  • 1. Aarnio, A
    et al.
    Johansson, Sverker
    Högskolan för lärande och kommunikation, Högskolan i Jönköping, HLK, Ämnesforskning.
    Measurement of the mass and width of the Zo particle from multihadron final states produced in e+e--annihilations1989In: Physics Letters, no 231, p. p 539-Article in journal (Other academic)
  • 2. Aarnio, A
    et al.
    Johansson, Sverker
    Högskolan för lärande och kommunikation, Högskolan i Jönköping, HLK, Ämnesforskning.
    Study of the hadronic decays of the Zo boson1990In: Physics Letters, no 240, p. p 271-Article in journal (Other academic)
  • 3. Aarnio, A
    et al.
    Johansson, Sverker
    Högskolan för lärande och kommunikation, Högskolan i Jönköping, HLK, Ämnesforskning.
    Study of the leptonic decays of the Zo boson1990In: Physics Letters, no 241, p. p 425-Article in journal (Other academic)
  • 4. Abdollahi, S.
    et al.
    Acero, F.
    Ackermann, M.
    Ajello, M.
    Atwood, W. B.
    Axelsson, M.
    Baldini, L.
    Ballet, J.
    Larsson, Stefan
    Dalarna University, School of Education, Health and Social Studies, Natural Science. KTH Royal Inst Technol / AlbaNova, Oskar Klein Ctr Cosmoparticle Phys.
    Zaharijas, G.
    Fermi Large Area Telescope Fourth Source Catalog2020In: Astrophysical Journal Supplement Series, ISSN 0067-0049, E-ISSN 1538-4365, Vol. 247, no 1, article id 33Article in journal (Refereed)
    Abstract [en]

    We present the fourth Fermi Large Area Telescope catalog (4FGL) of gamma-ray sources. Based on the first eight years of science data from the Fermi Gamma-ray Space Telescope mission in the energy range from 50 MeV to 1 TeV, it is the deepest yet in this energy range. Relative to the 3FGL catalog, the 4FGL catalog has twice as much exposure as well as a number of analysis improvements, including an updated model for the Galactic diffuse gamma-ray emission, and two sets of light curves (one-year and two-month intervals). The 4FGL catalog includes 5064 sources above 4 sigma significance, for which we provide localization and spectral properties. Seventy-five sources are modeled explicitly as spatially extended, and overall, 358 sources are considered as identified based on angular extent, periodicity, or correlated variability observed at other wavelengths. For 1336 sources, we have not found plausible counterparts at other wavelengths. More than 3130 of the identified or associated sources are active galaxies of the blazar class, and 239 are pulsars.

  • 5. Abdollahi, S.
    et al.
    Acero, F.
    Ackermann, M.
    Baldini, L.
    Ballet, J.
    Barbiellini, G.
    Bastieri, D.
    Bellazzini, R.
    Larsson, Stefan
    Dalarna University, School of Teacher Education, Natural Science. Department of Physics, KTH Royal Institute of Technology, AlbaNova, Stockholm; The Oskar Klein Centre for Cosmoparticle Physics, AlbaNova, Stockholm.
    Zaharijas, G.
    Search for New Cosmic-Ray Acceleration Sites within the 4FGL Catalog Galactic Plane Sources2022In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 933, no 2, article id 204Article in journal (Refereed)
    Abstract [en]

    Cosmic rays are mostly composed of protons accelerated to relativistic speeds. When those protons encounter interstellar material, they produce neutral pions, which in turn decay into gamma-rays. This offers a compelling way to identify the acceleration sites of protons. A characteristic hadronic spectrum, with a low-energy break around 200 MeV, was detected in the gamma-ray spectra of four supernova remnants (SNRs), IC 443, W44, W49B, and W51C, with the Fermi Large Area Telescope. This detection provided direct evidence that cosmic-ray protons are (re-)accelerated in SNRs. Here, we present a comprehensive search for low-energy spectral breaks among 311 4FGL catalog sources located within 5° from the Galactic plane. Using 8 yr of data from the Fermi Large Area Telescope between 50 MeV and 1 GeV, we find and present the spectral characteristics of 56 sources with a spectral break confirmed by a thorough study of systematic uncertainty. Our population of sources includes 13 SNRs for which the proton-proton interaction is enhanced by the dense target material; the high-mass gamma-ray binary LS I+61 303; the colliding wind binary η Carinae; and the Cygnus star-forming region. This analysis better constrains the origin of the gamma-ray emission and enlarges our view to potential new cosmic-ray acceleration sites. © 2022. The Author(s). Published by the American Astronomical Society.

    Download full text (pdf)
    fulltext
  • 6. Abdollahi, S.
    et al.
    Acero, F.
    Baldini, L.
    Ballet, J.
    Bastieri, D.
    Bellazzini, R.
    Berenji, B.
    Berretta, A.
    Larsson, Stefan
    Dalarna University, School of Teacher Education, Natural Science.
    Zaharijas, G.
    Incremental Fermi Large Area Telescope Fourth Source Catalog2022In: Astrophysical Journal Supplement Series, ISSN 0067-0049, E-ISSN 1538-4365, Vol. 260, no 2, article id 53Article in journal (Refereed)
    Abstract [en]

    We present an incremental version (4FGL-DR3, for Data Release 3) of the fourth Fermi Large Area Telescope (LAT) catalog of 3-ray sources. Based on the first 12 years of science data in the energy range from 50 MeV to 1 TeV, it contains 6658 sources. The analysis improves on that used for the 4FGL catalog over eight years of data: more sources are fit with curved spectra, we introduce a more robust spectral parameterization for pulsars, and we extend the spectral points to 1 TeV. The spectral parameters, spectral energy distributions, and associations are updated for all sources. Light curves are rebuilt for all sources with 1 yr intervals (not 2 month intervals). Among the 5064 original 4FGL sources, 16 were deleted, 112 are formally below the detection threshold over 12 yr (but are kept in the list), while 74 are newly associated, 10 have an improved association, and seven associations were withdrawn. Pulsars are split explicitly between young and millisecond pulsars. Pulsars and binaries newly detected in LAT sources, as well as more than 100 newly classified blazars, are reported. We add three extended sources and 1607 new point sources, mostly just above the detection threshold, among which eight are considered identified, and 699 have a plausible counterpart at other wavelengths. We discuss the degree-scale residuals to the global sky model and clusters of soft unassociated point sources close to the Galactic plane, which are possibly related to limitations of the interstellar emission model and missing extended sources. © 2022. The Author(s). Published by the American Astronomical Society.

    Download full text (pdf)
    fulltext
  • 7.
    Abdulkarim, Rekan
    et al.
    Dalarna University, School of Technology and Business Studies, Information Systems.
    Lopez Fredriksson, Christoffer
    Dalarna University, School of Technology and Business Studies, Information Systems.
    Nyckelfaktorer som påverkar framgång av e-röstningssystem – en fallstudie av fyra europeiska länder2020Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This study examines the current situation regarding e-voting in four selected European countries as well as whether Sweden can implement e-voting and achieve success. With the help of a literature study, the study defines the advantages and disadvantages of e-voting and the traditional voting procedure and through a case study, the current situation is identified by the selected European countries and an interview is conducted to gain an insight into the Swedish voting procedure and where Sweden stands when it comes to e-voting. By analyzing the interview and doing a comparative analysis of the key factors that affected the failure or success of e-voting in the selected countries with the key factors identified in Sweden, the result will be clear whether an implementation in Sweden can be successful or not.

    Download full text (pdf)
    fulltext
  • 8. Acosta-Vargas, P.
    et al.
    Salvador-Acosta, B.
    Gonzalez, M.
    Pérez-Medina, J. -L
    Acosta-Vargas, G.
    Jimenes-Vargas, K.
    Rybarczyk, Yves
    Dalarna University, School of Technology and Business Studies, Microdata Analysis.
    Web Accessibility Analysis of a Tele-Rehabilitation Platform: The Physiotherapist Perspective2020In: Advances in Human Factors and Systems Interaction: Proceedings of the AHFE 2020 Virtual Conference on Human Factors and Systems Interaction, July 16-20, 2020, USA / [ed] Isabel L. Nunes, 2020, p. 215-221Conference paper (Refereed)
  • 9. Acosta-Vargas, P.
    et al.
    Salvador-Acosta, B.
    Zalakeviciute, R.
    Alexandrino, K.
    Pérez-Medina, J. -L
    Rybarczyk, Yves
    Dalarna University, School of Technology and Business Studies, Microdata Analysis.
    Gonzalez, M.
    Accessibility Assessment of Mobile Meteorological Applications for Users with Low Vision2020In: Advances in Human Factors and Systems Interaction: Proceedings of the AHFE 2020 Virtual Conference on Human Factors and Systems Interaction, July 16-20, 2020, USA / [ed] Isabel L. Nunes, 2020, p. 199-205Conference paper (Refereed)
  • 10. Adami, C.
    et al.
    Hintze, Arend
    Michigan State University, East Lansing, United States.
    Erratum: Evolutionary instability of zero-determinant strategies demonstrates that winning is not everything (Nature Communications (2013) 4:2193 DOI: 10.1038/ncomms3193)2014In: Nature Communications, E-ISSN 2041-1723, Vol. 5, article id 3764Article in journal (Refereed)
  • 11. Adami, C.
    et al.
    Hintze, Arend
    Michigan State University, East Lansing, United States.
    Evolutionary instability of zero-determinant strategies demonstrates that winning is not everything2013In: Nature Communications, E-ISSN 2041-1723, Vol. 4, article id 2193Article in journal (Refereed)
    Abstract [en]

    Zero-determinant strategies are a new class of probabilistic and conditional strategies that are able to unilaterally set the expected payoff of an opponent in iterated plays of the Prisoner's Dilemma irrespective of the opponent's strategy (coercive strategies), or else to set the ratio between the player's and their opponent's expected payoff (extortionate strategies). Here we show that zero-determinant strategies are at most weakly dominant, are not evolutionarily stable, and will instead evolve into less coercive strategies. We show that zero-determinant strategies with an informational advantage over other players that allows them to recognize each other can be evolutionarily stable (and able to exploit other players). However, such an advantage is bound to be short-lived as opposing strategies evolve to counteract the recognition. © 2013 Macmillan Publishers Limited. All rights reserved.

    Download full text (pdf)
    fulltext
  • 12. Adami, C.
    et al.
    Hintze, Arend
    Michigan State University, East Lansing, United States.
    Thermodynamics of evolutionary games2018In: Physical review. E, ISSN 2470-0045, E-ISSN 2470-0053, Vol. 97, no 6, article id 062136Article in journal (Refereed)
    Abstract [en]

    How cooperation can evolve between players is an unsolved problem of biology. Here we use Hamiltonian dynamics of models of the Ising type to describe populations of cooperating and defecting players to show that the equilibrium fraction of cooperators is given by the expectation value of a thermal observable akin to a magnetization. We apply the formalism to the public goods game with three players and show that a phase transition between cooperation and defection occurs that is equivalent to a transition in one-dimensional Ising crystals with long-range interactions. We then investigate the effect of punishment on cooperation and find that punishment plays the role of a magnetic field that leads to an "alignment" between players, thus encouraging cooperation. We suggest that a thermal Hamiltonian picture of the evolution of cooperation can generate other insights about the dynamics of evolving groups by mining the rich literature of critical dynamics in low-dimensional spin systems. © 2018 American Physical Society.

  • 13. Adami, C.
    et al.
    Qian, J.
    Rupp, M.
    Hintze, Arend
    Keck Graduate Institute of Applied Life Sciences, Claremont, United States; Michigan State University, East Lansing, United States.
    Information content of colored motifs in complex networks2011In: Artificial Life, ISSN 1064-5462, E-ISSN 1530-9185, Vol. 17, no 4, p. 375-390Article in journal (Refereed)
    Abstract [en]

    We study complex networks in which the nodes are tagged with different colors depending on their function (colored graphs), using information theory applied to the distribution of motifs in such networks. We find that colored motifs can be viewed as the building blocks of the networks (much more than the uncolored structural motifs can be) and that the relative frequency with which these motifs appear in the network can be used to define its information content. This information is defined in such a way that a network with random coloration (but keeping the relative number of nodes with different colors the same) has zero color information content. Thus, colored motif information captures the exceptionality of coloring in the motifs that is maintained via selection. We study the motif information content of the C. elegans brain as well as the evolution of colored motif information in networks that reflect the interaction between instructions in genomes of digital life organisms. While we find that colored motif information appears to capture essential functionality in the C. elegans brain (where the color assignment of nodes is straightforward), it is not obvious whether the colored motif information content always increases during evolution, as would be expected from a measure that captures network complexity. For a single choice of color assignment of instructions in the digital life form Avida, we find rather that colored motif information content increases or decreases during evolution, depending on how the genomes are organized, and therefore could be an interesting tool to dissect genomic rearrangements. © 2011 Massachusetts Institute of Technology.

  • 14. Adami, C.
    et al.
    Schossau, J.
    Hintze, Arend
    Michigan State University, East Lansing, United States.
    Evolution and stability of altruist strategies in microbial games2012In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, ISSN 1539-3755, E-ISSN 1550-2376, Vol. 85, no 1, article id 011914Article in journal (Refereed)
    Abstract [en]

    When microbes compete for limited resources, they often engage in chemical warfare using bacterial toxins. This competition can be understood in terms of evolutionary game theory (EGT). We study the predictions of EGT for the bacterial "suicide bomber" game in terms of the phase portraits of population dynamics, for parameter combinations that cover all interesting games for two-players, and seven of the 38 possible phase portraits of the three-player game. We compare these predictions to simulations of these competitions in finite well-mixed populations, but also allowing for probabilistic rather than pure strategies, as well as Darwinian adaptation over tens of thousands of generations. We find that Darwinian evolution of probabilistic strategies stabilizes games of the rock-paper-scissors type that emerge for parameters describing realistic bacterial populations, and point to ways in which the population fixed point can be selected by changing those parameters. © 2012 American Physical Society.

  • 15. Adami, C.
    et al.
    Schossau, J.
    Hintze, Arend
    Michigan State University, East Lansing, United States.
    Evolutionary game theory using agent-based methods2016In: Physics of Life Reviews, ISSN 1571-0645, E-ISSN 1873-1457, Vol. 19, p. 1-26Article in journal (Refereed)
    Abstract [en]

    Evolutionary game theory is a successful mathematical framework geared towards understanding the selective pressures that affect the evolution of the strategies of agents engaged in interactions with potential conflicts. While a mathematical treatment of the costs and benefits of decisions can predict the optimal strategy in simple settings, more realistic settings such as finite populations, non-vanishing mutations rates, stochastic decisions, communication between agents, and spatial interactions, require agent-based methods where each agent is modeled as an individual, carries its own genes that determine its decisions, and where the evolutionary outcome can only be ascertained by evolving the population of agents forward in time. While highlighting standard mathematical results, we compare those to agent-based methods that can go beyond the limitations of equations and simulate the complexity of heterogeneous populations and an ever-changing set of interactors. We conclude that agent-based methods can predict evolutionary outcomes where purely mathematical treatments cannot tread (for example in the weak selection–strong mutation limit), but that mathematics is crucial to validate the computational simulations. © 2016 Elsevier B.V.

    Download full text (pdf)
    fulltext
  • 16. Adami, C.
    et al.
    Schossau, J.
    Hintze, Arend
    Michigan State University, East Lansing, United States.
    The reasonable effectiveness of agent-based simulations in evolutionary game theory: Reply to comments on “Evolutionary game theory using agent-based methods”2016In: Physics of Life Reviews, ISSN 1571-0645, E-ISSN 1873-1457, Vol. 19, p. 38-42Article in journal (Refereed)
  • 17.
    Adolfsson, Alexander
    et al.
    Dalarna University, School of Information and Engineering.
    Ovesson, Christoffer
    Dalarna University, School of Information and Engineering.
    Utvärdering av sökmotorer i en svensk kontext2023Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The focus of this study was to evaluate different search engines on Swedish text. Information retrieval is widely used by both people and organizations, and it is important to be able to efficiently retrieve needed information at the right time. The study determined that relevance and speed are the most important factors in search engines. The evaluation measures the precision and recall which are relevance measurements, and speed of two search engines, Elastic search and MarkLogic. The evaluation has determined that there is no significant difference in the relevance of the retrieved results between the engines. The evaluation has also determined that there is a statistically significant difference in speed between the engines, with Elastic search outperforming MarkLogic. Both search engines performed very well in terms of successful searches, meaning to return a relevant document in the first 20 results. Both engines succeeded in fulfilling the information need 96% of the time.

    Download full text (pdf)
    fulltext
  • 18.
    Ager, B.
    et al.
    Dalarna University, School of Technology and Business Studies, Wood Technology.
    Bergqvist, M.
    Ahlström-Söderling, R.
    Fallstudier av lokal utveckling och nätverk i träförädling: Taxonomi för vardagsbruk och lite teori1999Report (Other academic)
  • 19.
    Ager, Bengt
    Dalarna University, School of Technology and Business Studies, Wood Technology.
    Möjligheter att utveckla skogsbruket och den lokala träindustrin i Dalaregionen.: Programskrivning för LEADER II DALARNA - ett EU-program för regional utveckling.1997Report (Other academic)
    Download full text (pdf)
    FULLTEXT01
    Download full text (pdf)
    FULLTEXT02
  • 20.
    Ager, Bengt
    Dalarna University, School of Technology and Business Studies, Wood Technology.
    Utveckling av småskaliga system för träförädling: FoU-projekt för Mål 6-området1997Report (Other academic)
  • 21.
    Ager, Bengt
    Dalarna University, School of Technology and Business Studies, Wood Technology.
    Utveckling av småskaliga system för träförädling: Slutrapport för Mål6-projekt 1997-20002000Report (Other academic)
  • 22.
    Ager, Bengt
    et al.
    Dalarna University, School of Technology and Business Studies, Wood Technology.
    Bergqvist, Mathias
    Bengtsson, Patrik
    Studier av lokal utveckling och samverkan i träbranschen: Forskarforum 98. Lokal och regional utveckling. Östersund 17-18 nov 19981998Report (Other academic)
  • 23.
    Ager, Bengt
    et al.
    Dalarna University, School of Technology and Business Studies, Wood Technology.
    Bergqvist, Mathias
    Bengtsson, Patrik
    Ahlström-Söderling, Ragnar
    Fröding, Anders
    Johansson, Lars
    Samverkan i träförädling: Dokumentation och preliminär analys av ett 30-tal samverkansfall1998Report (Other academic)
  • 24.
    Aghanavesi, Somayeh
    Dalarna University, School of Technology and Business Studies, Microdata Analysis.
    Sensor-based knowledge- and data-driven methods: A case of Parkinson’s disease motor symptoms quantification2020Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The overall aim of this thesis was to develop and evaluate new knowledge- and data-driven methods for supporting treatment and providing information for better assessment of Parkinson’s disease (PD).

    PD is complex and progressive. There is a large amount of inter- and intravariability in motor symptoms of patients with PD (PwPD). The current evaluation of motor symptoms that are done at clinics by using clinical rating scales is limited and provides only part of the health status of PwPD. An accurate and clinically approved assessment of PD is required using frequent evaluation of symptoms.

    To investigate the problem areas, the thesis adopted the microdata analysis approach including the stages of data collection, data processing, data analysis, and data interpretation. Sensor systems including smartphone and tri-axial motion sensors were used to collect data from advanced PwPD experimenting with repeated tests during a day. The experiments were rated by clinical experts. The data from sensors and the clinical evaluations were processed and used in subsequent analysis.

    The first three papers in this thesis report the results from the investigation, verification, and development of knowledge- and data-driven methods for quantifying the dexterity in PD. The smartphone-based data collected from spiral drawing and alternate tapping tests were used for the analysis. The results from the development of a smartphone-based data-driven method can be used for measuring treatment-related changes in PwPD. Results from investigation and verification of an approximate entropy-based method showed good responsiveness and test-retest reliability indicating that this method is useful in measuring upper limb temporal irregularity.

    The next two papers, report the results from the investigation and development of motion sensor-based knowledge- and data-driven methods for quantification of the motor states in PD. The motion data were collected from experiments such as leg agility, walking, and rapid alternating movements of hands. High convergence validity resulted from using motion sensors during leg agility tests. The results of the fusion of sensor data gathered during multiple motor tests were promising and led to valid, reliable and responsive objective measures of PD motor symptoms.

    Results in the last paper investigating the feasibility of using the Dynamic Time-Warping method for assessment of PD motor states showed it is feasible to use this method for extracting features to be used in automatic scoring of PD motor states.

    The findings from the knowledge- and data-driven methodology in this thesis can be used in the development of systems for follow up of the effects of treatment and individualized treatments in PD.

    Download full text (pdf)
    fulltext
    Download (jpg)
    presentationsbild
  • 25.
    Aghanavesi, Somayeh
    Dalarna University, School of Technology and Business Studies, Microdata Analysis.
    Smartphone-based Parkinson’s disease symptom assessment2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis consists of four research papers presenting a microdata analysis approach to assess and evaluate the Parkinson’s disease (PD) motor symptoms using smartphone-based systems. PD is a progressive neurological disorder that is characterized by motor symptoms. It is a complex disease that requires continuous monitoring and multidimensional symptom analysis. Both patients’ perception regarding common symptom and their motor function need to be related to the repeated and time-stamped assessment; with this, the full extent of patient’s condition could be revealed. The smartphone enables and facilitates the remote, long-term and repeated assessment of PD symptoms. Two types of collected data from smartphone were used, one during a three year, and another during one-day clinical study. The data were collected from series of tests consisting of tapping and spiral motor tests. During the second time scale data collection, along smartphone-based measurements patients were video recorded while performing standardized motor tasks according to Unified Parkinson’s disease rating scales (UPDRS).

    At first, the objective of this thesis was to elaborate the state of the art, sensor systems, and measures that were used to detect, assess and quantify the four cardinal and dyskinetic motor symptoms. This was done through a review study. The review showed that smartphones as the new generation of sensing devices are preferred since they are considered as part of patients’ daily accessories, they are available and they include high-resolution activity data. Smartphones can capture important measures such as forces, acceleration and radial displacements that are useful for assessing PD motor symptoms.

    Through the obtained insights from the review study, the second objective of this thesis was to investigate whether a combination of tapping and spiral drawing tests could be useful to quantify dexterity in PD. More specifically, the aim was to develop data-driven methods to quantify and characterize dexterity in PD. The results from this study showed that tapping and spiral drawing tests that were collected by smartphone can detect movements reasonably well related to under- and over-medication.

    The thesis continued by developing an Approximate Entropy (ApEn)-based method, which aimed to measure the amount of temporal irregularity during spiral drawing tests. One of the disabilities associated with PD is the impaired ability to accurately time movements. The increase in timing variability among patients when compared to healthy subjects, suggests that the Basal Ganglia (BG) has a role in interval timing. ApEn method was used to measure temporal irregularity score (TIS) which could significantly differentiate the healthy subjects and patients at different stages of the disease. This method was compared to two other methods which were used to measure the overall drawing impairment and shakiness. TIS had better reliability and responsiveness compared to the other methods. However, in contrast to other methods, the mean scores of the ApEn-based method improved significantly during a 3-year clinical study, indicating a possible impact of pathological BG oscillations in temporal control during spiral drawing tasks. In addition, due to the data collection scheme, the study was limited to have no gold standard for validating the TIS. However, the study continued to further investigate the findings using another screen resolution, new dataset, new patient groups, and for shorter term measurements. The new dataset included the clinical assessments of patients while they performed tests according to UPDRS. The results of this study confirmed the findings in the previous study. Further investigation when assessing the correlation of TIS to clinical ratings showed the amount of temporal irregularity present in the spiral drawing cannot be detected during clinical assessment since TIS is an upper limb high frequency-based measure. 

    Download full text (pdf)
    Smartphone-based Parkinson’s disease symptom assessment
  • 26.
    Aghanavesi, Somayeh
    et al.
    Dalarna University, School of Technology and Business Studies, Microdata Analysis.
    Memedi, Mevludin
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Dougherty, Mark
    Dalarna University, School of Technology and Business Studies, Microdata Analysis.
    Nyholm, Dag
    Westin, Jerker
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Verification of a method for measuring Parkinson’s disease related temporal irregularity in spiral drawings2017In: Sensors, E-ISSN 1424-8220, Vol. 17, no 10, article id 2341Article in journal (Refereed)
    Abstract [en]

    Parkinson's disease (PD) is a progressive movement disorder caused by the death of dopamine-producing cells in the midbrain. There is a need for frequent symptom assessment, since the treatment needs to be individualized as the disease progresses. The aim of this paper was to verify and further investigate the clinimetric properties of an entropy-based method for measuring PD-related upper limb temporal irregularities during spiral drawing tasks. More specifically, properties of a temporal irregularity score (TIS) for patients at different stages of PD, and medication time points were investigated. Nineteen PD patients and 22 healthy controls performed repeated spiral drawing tasks on a smartphone. Patients performed the tests before a single levodopa dose and at specific time intervals after the dose was given. Three movement disorder specialists rated videos of the patients based on the unified PD rating scale (UPDRS) and the Dyskinesia scale. Differences in mean TIS between the groups of patients and healthy subjects were assessed. Test-retest reliability of the TIS was measured. The ability of TIS to detect changes from baseline (before medication) to later time points was investigated. Correlations between TIS and clinical rating scores were assessed. The mean TIS was significantly different between healthy subjects and patients in advanced groups (p-value = 0.02). Test-retest reliability of TIS was good with Intra-class Correlation Coefficient of 0.81. When assessing changes in relation to treatment, TIS contained some information to capture changes from Off to On and wearing off effects. However, the correlations between TIS and clinical scores (UPDRS and Dyskinesia) were weak. TIS was able to differentiate spiral drawings drawn by patients in an advanced stage from those drawn by healthy subjects, and TIS had good test-retest reliability. TIS was somewhat responsive to single-dose levodopa treatment. Since TIS is an upper limb high-frequency-based measure, it cannot be detected during clinical assessment.

    Download full text (pdf)
    fulltext
  • 27.
    Ahlberg, Grete
    Dalarna University, School of Culture and Society.
    Personliga amatörfilmer, ett professionellt bildberättande inom reklamfilm?: Analys av personliga amatörfilmer i fyra reklamfilmer2021Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Personliga amatörfilmer och hemmafilmer används allt mer av bland annatvarumärkesjättar i sin marknadsföring. Estetiken i amatörfilmerna går totalt emot detekniska aspekterna i professionell film där bland annat kvaliteten är mycket lägre iamatörfilm. Denna studie syftar till att undersöka dels vad amatörfilmerna har förkommunikativa egenskaper utifrån valda reklamfilmer men också egenskaper imarknadsföringssyfte i stort. Trots att amatörfilmer och hemmafilmer har en estetiksom inte ses som professionell inom bildproduktion, finns det ett innehåll i dessasekvenser som ännu inte har framhävts i övertygande reklamfilm/informationsfilm.Studiens resultat visar exempelvis att bland annat den låga kvaliteten ochperspektivet från den som filmar, visar en djupare och mer verklig inblick i filmenskaraktärer. Amatörfilmerna ger med andra ord en personlig synvinkel påsammanhanget, vilket är ett användbart verktyg för avsändaren att kommunicera påsamma nivå som mottagaren.

    Download full text (pdf)
    fulltext
  • 28.
    Ahlin, Erik
    Dalarna University, School of Humanities and Media Studies, Moving Image Production.
    Redigeringsprogrammens påverkan på bilden: En jämförelse mellan Avid Media Composer och Adobe Premiere Pro2014Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Uppsatsen söker att svara på frågeställningen: Uppstår det skillnad i bildkvaliteten på material som komprimerats med redigeringsprogrammet Avid Media Composer till H.264, i jämförelse med material som har komprimerats till H.264 med Adobe Premiere Pro. Baserat på resultat från tidigare jämförelser och personlig erfarenhet är förförståelsen att det kommer finnas en märkbar skillnad men ingen av programmen kommer att överskugga den andra.Metoden som använts är att en undersökning i form av enkät har fyllts i av mediastudenter baserad på deras upplevelser av sex stycken bildexempel från varje redigeringsprogram utifrån fem faktorer som rör bildkvalitet: Kontrast, skärpa, brus, färg och rörelseåtergivning. Djupgående intervjuer har sedan utförts med fem av informanterna. Resultatet på undersökningen visar överlag små skillnader mellan Avid Media Composer och Adobe Premiere Pro. Informanterna upplevde i majoritet att materialet från Avid hade högre bildkvalitet.

  • 29.
    Ahmed, Omar
    et al.
    Dalarna University, School of Information and Engineering.
    Kelli, Philip
    Dalarna University, School of Information and Engineering.
    Analysing recommended content provided by YouTube and users preferences: A Case Study at Dalarna University in Sweden2022Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The application YouTube released in 2005 is today known as the most prominent platform on the world wide web for sharing, creating, and discovering video content(s). By utilizing technology trends such as Machine learning, YouTube can take advantage of algorithms such as deep neural networks to entice the users with a massive amount of personalized recommended content(s)t to watch based on the user's data.

    The algorithm in the YouTube recommendation system collects the users' personalized data such as location, watch history and search history to recommend video content. The YouTube recommendation system gives personalized recommended content(s) to a YouTube user with the collected data. The user may deem the recommended content as ethically wrong. Therefore, bring up meaningful discussions such as a YouTube consumer's sentiment towards those contents they deem unethical.

    This research study examines what ethical challenges exist in the YouTube recommendation system and how those challenges affect the YouTube consumers trust in the recommendation system.

    • The research questions that were examined in this study are: What kind of ethical challenges does the YouTube recommendation system have?

    • What kind of impact do those ethical challenges have on the user’s trust in the YouTube recommendation system?

    The respondents consisted of students at Dalarna University. This research was conducted with semistructured interviews and a questionnaire that consisted of 11 questionnaires.

    By examining the results from the literature reviews, interviews, and questionnaire, the gathered results show that challenges such as inappropriate, misinformed content and privacy exist with the YouTube recommendation system. Numerous of our respondents felt like they did not trust the YouTube recommendation system with their personalized data, primarily because of receiving video content that is not relevant, which has made some of the respondent question what YouTube does with the influx of the individual data.

    Based on the result it can be concluded that there are many concerns related to ethical issues in the YouTube recommendation system. In essence, the respondents highlighted the significance of privacy when using a platform such as YouTube. The respondents desired more transparency with their data.

    Download full text (pdf)
    fulltext
  • 30.
    Ahmed, Salim Saif Saeed
    Dalarna University, School of Technology and Business Studies, Microdata Analysis.
    Identify the driving behaviour in a parking lot in terms of distance.2018Independent thesis Advanced level (degree of Master (Two Years)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Parking a vehicle can often lead to frustration, air pollution and congestion due to limited availability of parking spaces. With increasing population density this problem can certainly increase unless addressed. Parking lots occupy large areas of scarce land resource therefore it is necessary to identify the driving behaviour in a parking lot to improve it further. This Paper tries study the driving behaviour in the parking lot and for this endeavours it conducted direct observation in three parking lots and used GPS data that was collected prior to this study by the University of Dalarna.

    To evaluate the driving behaviour in the parking lot direct observation was conducted to obtain overall indices of the parking lot vehicles movement. The parking route taken by the driver was compared with the optimal path to identify the driving behaviour in parking lot in terms of distance. The collected data was evaluated, filtered and analysed to identify the route, the distance and the time the vehicle takes to find a parking space.

    The outcome of the study shows that driving behaviour in the parking lots varies significantly among the parking user where most of the observed vehicles took unnecessary long time to complete their parking. The study shows that 56% of the 430 observed vehicles demonstrated inefficient driving behaviour as they took long driving path rather the than the optimal path. The study trace this behaviour to two factors, first, the absent of parking guidance in the parking lots and the second is the selectivity of the drivers when choosing the parking space.

    The study also shows that the ability of GPS data to identify the driving behaviour in the parking lots varies based on the time interval and the type of the device that is being used. The small the time interval the more accurate the GPS data in detecting the driving behaviour in the parking lots.

    Download full text (pdf)
    fulltext
  • 31. Ajello, M.
    et al.
    Angioni, R.
    Axelsson, M.
    Ballet, J.
    Barbiellini, G.
    Bastieri, D.
    Becerra Gonzalez, J.
    Bellazzini, R.
    Larsson, Stefan
    Dalarna University, School of Education, Health and Social Studies, Natural Science. KTH Royal Inst Technology / AlbaNova, Oskar Klein Ctr Cosmoparticle Phys.
    Yassine, M.
    The Fourth Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope2020In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 892, no 2, article id 105Article in journal (Refereed)
    Abstract [en]

    The fourth catalog of active galactic nuclei (AGNs) detected by the Fermi Gamma-ray Space Telescope Large Area Telescope (4LAC) between 2008 August 4 and 2016 August 2 contains . It includes 85% more sources than the previous 3LAC catalog based on 4 yr of data. AGNs represent at least 79% of the high-latitude sources in the fourth Fermi-Large Area Telescope Source Catalog (4FGL), which covers the energy range from 50 MeV to 1 TeV. In addition, gamma-ray AGNs are found at low Galactic latitudes. Most of the 4LAC AGNs are blazars (98%), while the remainder are other types of AGNs. The blazar population consists of 24% Flat Spectrum Radio Quasars (FSRQs), 38% BL Lac-type objects, and 38% blazar candidates of unknown types (BCUs). On average, FSRQs display softer spectra and stronger variability in the gamma-ray band than BL Lacs do, confirming previous findings. All AGNs detected by ground-based atmospheric Cerenkov telescopes are also found in the 4LAC.

  • 32.
    Ajello, M.
    et al.
    Clemson Univ, Kinard Lab Phys, Dept Phys & Astron, Clemson, SC 29634 USA..
    Arimoto, M.
    Kanazawa Univ, Inst Sci & Engn, Fac Math & Phys, Kanazawa, Ishikawa 9201192, Japan..
    Asano, K.
    Univ Tokyo, Inst Cosm Ray Res, 5-1-5 Kashiwanoha, Kashiwa, Chiba 2778582, Japan..
    Axelsson, M.
    Stockholm Univ, AlbaNova, Dept Phys, SE-10691 Stockholm, Sweden.;KTH Royal Inst Technol, Dept Phys, AlbaNova, SE-10691 Stockholm, Sweden..
    Baldini, L.
    Univ Pisa, I-56127 Pisa, Italy.;Ist Nazl Fis Nucl, Sez Pisa, I-56127 Pisa, Italy..
    Barbiellini, G.
    Ist Nazl Fis Nucl, Sez Trieste, I-34127 Trieste, Italy.;Univ Trieste, Dipartimento Fis, I-34127 Trieste, Italy..
    Bastieri, D.
    Ist Nazl Fis Nucl, Sez Padova, I-35131 Padua, Italy.;Univ Padua, Dipartimento Fis & Astron G Galilei, I-35131 Padua, Italy..
    Bellazzini, R.
    Ist Nazl Fis Nucl, Sez Pisa, I-56127 Pisa, Italy..
    Larsson, Stefan
    Dalarna University, School of Education, Health and Social Studies, Natural Science. KTH / The Oskar Klein Centre for Cosmoparticle Physics.
    Tajima, H.
    Stanford Univ, WW Hansen Expt Phys Lab, Kavli Inst Particle Astrophys & Cosmol, Dept Phys, Stanford, CA 94305 USA.;Stanford Univ, SLAC Natl Accelerator Lab, Stanford, CA 94305 USA.;Nagoya Univ, Solar Terr Environm Lab, Nagoya, Aichi 4648601, Japan..
    Bright Gamma-Ray Flares Observed in GRB 131108A2019In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 886, no 2, article id L33Article in journal (Refereed)
    Abstract [en]

    GRB 131108A is a bright long gamma-ray burst (GRB) detected by the Large Area Telescope and the Gamma-ray Burst Monitor on board the Fermi Gamma-ray Space Telescope. Dedicated temporal and spectral analyses reveal three ?-ray flares dominating above 100 MeV, which are not directly related to the prompt emission in the Gamma-ray Burst Monitor band (10 keV?10 MeV). The high-energy light curve of GRB 131108A (100 MeV?10 GeV) shows an unusual evolution: a steep decay, followed by three flares with an underlying emission, and then a long-lasting decay phase. The detailed analysis of the ?-ray flares finds that the three flares are 6?20 times brighter than the underlying emission and are similar to each other. The fluence of each flare, (1.6?2.0)10(?6) erg cm(?2), is comparable to that of emission during the steep decay phase, 1.710(?6) erg cm(?2). The total fluence from three ?-ray flares is 5.310(?6) erg cm(?2). The three ?-ray flares show properties similar to the usual X-ray flares that are sharp flux increases, occurring in ?50% of afterglows, in some cases well after the prompt emission. Also, the temporal and spectral indices during the early steep decay phase and the decaying phase of each flare show the consistency with a relation of the curvature effect (<CDATA<i=2 + <CDATA<i), which is the first observational evidence of the high-latitude emission in the GeV energy band.

  • 33. Ajello, M.
    et al.
    Arimoto, M.
    Axelsson, M.
    Baldini, L.
    Barbiellini, G.
    Bastieri, D.
    Bellazzini, R.
    Berretta, A.
    Larsson, Stefan
    Dalarna University, School of Education, Health and Social Studies, Natural Science. KTH / The Oskar Klein Centre for Cosmoparticle Physics, AlbaNova.
    De Pasquale, M.
    Fermi and Swift Observations of GRB 190114C: Tracing the Evolution of High-energy Emission from Prompt to Afterglow2020In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 890, no 1, article id 9Article in journal (Refereed)
    Abstract [en]

    We report on the observations of gamma-ray burst (GRB) 190114C by the Fermi Gamma-ray Space Telescope and the Neil Gehrels Swift Observatory. The prompt gamma-ray emission was detected by the Fermi GRB Monitor (GBM), the Fermi Large Area Telescope (LAT), and the Swift Burst Alert Telescope (BAT) and the long-lived afterglow emission was subsequently observed by the GBM, LAT, Swift X-ray Telescope (XRT), and Swift UV Optical Telescope. The early-time observations reveal multiple emission components that evolve independently, with a delayed power-law component that exhibits significant spectral attenuation above 40 MeV in the first few seconds of the burst. This power-law component transitions to a harder spectrum that is consistent with the afterglow emission observed by the XRT at later times. This afterglow component is clearly identifiable in the GBM and BAT light curves as a slowly fading emission component on which the rest of the prompt emission is superimposed. As a result, we are able to observe the transition from internal-shock- to external-shock-dominated emission. We find that the temporal and spectral evolution of the broadband afterglow emission can be well modeled as synchrotron emission from a forward shock propagating into a wind-like circumstellar environment. We estimate the initial bulk Lorentz factor using the observed high-energy spectral cutoff. Considering the onset of the afterglow component, we constrain the deceleration radius at which this forward shock begins to radiate in order to estimate the maximum synchrotron energy as a function of time. We find that even in the LAT energy range, there exist high-energy photons that are in tension with the theoretical maximum energy that can be achieved through synchrotron emission from a shock. These violations of the maximum synchrotron energy are further compounded by the detection of very high-energy (VHE) emission above 300 GeV by MAGIC concurrent with our observations. We conclude that the observations of VHE photons from GRB 190114C necessitates either an additional emission mechanism at very high energies that is hidden in the synchrotron component in the LAT energy range, an acceleration mechanism that imparts energy to the particles at a rate that is faster than the electron synchrotron energy-loss rate, or revisions of the fundamental assumptions used in estimating the maximum photon energy attainable through the synchrotron process. © 2020. The American Astronomical Society..

    Download full text (pdf)
    fulltext
  • 34. Ajello, M
    et al.
    Atwood, W B
    Axelsson, M
    Bagagli, R
    Bagni, M
    Baldini, L
    Bastieri, D
    Bellardi, F
    Larsson, Stefan
    Dalarna University, School of Teacher Education, Natural Science.
    Zaharijas, G.
    Fermi Large Area Telescope Performance after 10 Years of Operation2021In: Astrophysical Journal Supplement Series, ISSN 0067-0049, E-ISSN 1538-4365, Vol. 256, no 1, article id 12Article in journal (Refereed)
    Abstract [en]

    The Large Area Telescope (LAT), the primary instrument for the Fermi Gamma-ray Space Telescope (Fermi) mission, is an imaging, wide field-of-view, high-energy gamma-ray telescope, covering the energy range from 30 MeV to more than 300 GeV. We describe the performance of the instrument at the 10 yr milestone. LAT performance remains well within the specifications defined during the planning phase, validating the design choices and supporting the compelling case to extend the duration of the Fermi mission. The details provided here will be useful when designing the next generation of high-energy gamma-ray observatories.

  • 35. Ajello, M.
    et al.
    Atwood, W. B.
    Axelsson, M.
    Baldini, L.
    Barbiellini, G.
    Baring, M. G.
    Bastieri, D.
    Bellazzini, R.
    Larsson, Stefan
    Dalarna University, School of Teacher Education, Natural Science. KTH Royal Inst Technol / Oskar Klein Ctr Cosmoparticle Phys.
    Zaharijas, G.
    High-energy emission from a magnetar giant flare in the Sculptor galaxy2021In: Nature Astronomy, E-ISSN 2397-3366, Vol. 5, no 4, p. 385-391Article in journal (Refereed)
    Abstract [en]

    Magnetars are the most highly magnetized neutron stars in the cosmos (with magnetic field 10(13)-10(15) G). Giant flares from magnetars are rare, short-duration (about 0.1 s) bursts of hard X-rays and soft gamma rays(1,2). Owing to the limited sensitivity and energy coverage of previous telescopes, no magnetar giant flare has been detected at gigaelectronvolt (GeV) energies. Here, we report the discovery of GeV emission from a magnetar giant flare on 15 April 2020 (refs. (3,4) and A. J. Castro-Tirado et al., manuscript in preparation). The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope detected GeV gamma rays from 19 s until 284 s after the initial detection of a signal in the megaelectronvolt (MeV) band. Our analysis shows that these gamma rays are spatially associated with the nearby (3.5 megaparsecs) Sculptor galaxy and are unlikely to originate from a cosmological gamma-ray burst. Thus, we infer that the gamma rays originated with the magnetar giant flare in Sculptor. We suggest that the GeV signal is generated by an ultra-relativistic outflow that first radiates the prompt MeV-band photons, and then deposits its energy far from the stellar magnetosphere. After a propagation delay, the outflow interacts with environmental gas and produces shock waves that accelerate electrons to very high energies; these electrons then emit GeV gamma rays as optically thin synchrotron radiation. This observation implies that a relativistic outflow is associated with the magnetar giant flare, and suggests the possibility that magnetars can power some short gamma-ray bursts.

  • 36. Ajello, M.
    et al.
    Atwood, W. B.
    Baldini, L.
    Ballet, J.
    Barbiellini, G.
    Bastieri, D.
    Bellazzini, R.
    Berretta, A.
    Larsson, Stefan
    Dalarna University, School of Teacher Education, Natural Science.
    Zaharijas, G.
    A gamma-ray pulsar timing array constrains the nanohertz gravitational wave background2022In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 376, no 6592, p. 521-523Article in journal (Refereed)
  • 37.
    Ajello, M.
    et al.
    Clemson Univ, Dept Phys & Astron, Kinard Lab Phys, Clemson, SC 29634 USA..
    Baldini, L.
    Univ Pisa, I-56127 Pisa, Italy.;Ist Nazl Fis Nucl, Sez Pisa, I-56127 Pisa, Italy..
    Ballet, J.
    Univ Paris, Univ Paris Saclay, CNRS, AIM,CEA, F-91191 Gif Sur Yvette, France..
    Barbiellini, G.
    Ist Nazl Fis Nucl, Sez Trieste, I-34127 Trieste, Italy.;Univ Trieste, Dipartimento Fis, I-34127 Trieste, Italy..
    Bastieri, D.
    Ist Nazl Fis Nucl, Sez Padova, I-35131 Padua, Italy.;Univ Padua, Dipartimento Fis & Astron G Galilei, I-35131 Padua, Italy..
    Bellazzini, R.
    Ist Nazl Fis Nucl, Sez Pisa, I-56127 Pisa, Italy..
    Berretta, A.
    Univ Perugia, Dipartimento Fis, I-06123 Perugia, Italy..
    Bissaldi, E.
    Univ & Politecn Bari, Dipartimento Fis M Merlin, Via Amendola 173, I-70126 Bari, Italy.;Ist Nazl Fis Nucl, Sez Bari, I-70126 Bari, Italy..
    Larsson, Stefan
    Dalarna University, School of Teacher Education, Natural Science. KTH Royal Inst Technol; AlbaNova, Oskar Klein Ctr Cosmoparticle Phys.
    Zrake, J.
    Clemson Univ, Dept Phys & Astron, Kinard Lab Phys, Clemson, SC 29634 USA..
    Gamma Rays from Fast Black-hole Winds2021In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 921, no 2, article id 144Article in journal (Refereed)
    Abstract [en]

    Massive black holes at the centers of galaxies can launch powerful wide-angle winds that, if sustained over time, can unbind the gas from the stellar bulges of galaxies. These winds may be responsible for the observed scaling relation between the masses of the central black holes and the velocity dispersion of stars in galactic bulges. Propagating through the galaxy, the wind should interact with the interstellar medium creating a strong shock, similar to those observed in supernovae explosions, which is able to accelerate charged particles to high energies. In this work we use data from the Fermi Large Area Telescope to search for the gamma-ray emission from galaxies with an ultrafast outflow (UFO): a fast (v similar to 0.1 c), highly ionized outflow, detected in absorption at hard X-rays in several nearby active galactic nuclei (AGN). Adopting a sensitive stacking analysis we are able to detect the average gamma-ray emission from these galaxies and exclude that it is due to processes other than UFOs. Moreover, our analysis shows that the gamma-ray luminosity scales with the AGN bolometric luminosity and that these outflows transfer similar to 0.04% of their mechanical power to gamma-rays. Interpreting the observed gamma-ray emission as produced by cosmic rays (CRs) accelerated at the shock front, we find that the gamma-ray emission may attest to the onset of the wind-host interaction and that these outflows can energize charged particles up to the transition region between galactic and extragalactic CRs.

  • 38. Ajello, M.
    et al.
    Baldini, L.
    Bastieri, D.
    Bellazzini, R.
    Berretta, A.
    Bissaldi, E.
    Blandford, R. D.
    Bonino, R.
    Larsson, Stefan
    Dalarna University, School of Teacher Education, Natural Science. KTH Royal Institute of Technology, AlbaNova, Stockholm; The Oskar Klein Centre for Cosmoparticle Physics, AlbaNova, Stockholm.
    Zaharijas, G.
    First fermi-LAT solar flare catalog2021In: Astrophysical Journal Supplement Series, ISSN 0067-0049, E-ISSN 1538-4365, Vol. 252, no 2, article id abd32eArticle in journal (Refereed)
  • 39.
    Al Zoghbi, Amal
    Dalarna University, School of Education, Health and Social Studies, Educational Work.
    Problemlösning i matematik: En litteraturstudie om svårigheter i problemlösning i matematik för elever i grundskolans tidiga åldrar2016Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Elevers problemlösningsförmåga uppmärksammas i PISA undersökningar som visar att svenska elever

    inte uppnår goda resultat inom området. Problemlösning är en viktig färdighet som elever behöver i

    och utanför skolan. Problemlösning har förekommit sedan flera decennier tillbaka i skolans kursplan i

    matematik.

    Syftet med den här studien är att få kunskap om svårigheter elever kan ha när de arbetar med

    problemlösning i matematik i grundskolans tidiga skolår och, om så möjligt, vilka orsaker som kan

    påverka dessa svårigheter. Resultaten visar att språkfärdigheter som läsförmåga, förståelseförmåga,

    läsflyt samt det matematiska tänkandet påverkar elevers förmåga att förstå och lösa matematiska

    problem. Likaså är färdigheter i matematiska ord och begrepp samt matematisk text- och talförståelse

    väsentliga. Språk- och problemlösningsfärdigheter främjas av färdigheterna i tänkandet som har sin

    grund i språket. Resultaten visar även att kognitiva faktorer och föräldrars utbildningsnivå är orsaker

    som kan ha en inverkan på elevers förmågor i förståelsen och lösningen av problemlösningsuppgifter.

    Slutsatserna som dras i den här studien är att språkfärdigheter och kognitiva faktorer är de mest

    dominerande i de svårigheter elever kan ha i arbetet med problemlösning. Förståelsen av det

    matematiska problemet utgör den viktigaste delen i problemlösningsprocessen som beskrivs av

    matematikern George Polya och består av en fyra stegs process. Ytterligare en slutsats som dras i

    studien är lärarens roll och undervisningens upplägg som utgör en viktig del i elevers förståelse av

    matematiska problem samt förmågan att lösa dem. Metoden som har använts till den här studien är en

    systematisk litteraturstudie där sökningar på svenska och engelska efter vetenskaplig forskning har

    genomförts i olika databaser.

  • 40.
    Alam, Moudud
    Dalarna University, School of Technology and Business Studies, Statistics.
    An efficient algorithm for the pseudo likelihood estimation of the generalized linear mixed models (GLMM) with correlated random effects2009Report (Other academic)
    Abstract [en]

    This paper presents a two-step pseudo likelihood estimation technique for generalized linear mixed models with correlated random effects. The proposed estimation technique does not require reparametarisation of the model. Multivariate Taylor's approximation has been used to approximate the intractable integrals in the likelihood function of the GLMM. Based on the analytical expression for the estimator of the covariance matrix of the random effects, a condition has been presented as to when such a covariance matrix can be estimated through the estimates of the random effects. An application of the model with a binary response variable has been presented using a real data set on credit defaults from two Swedish banks. Due to the use of two-step estimation technique, proposed algorithm outperforms the conventional pseudo likelihood algorithms in terms of computational time.

  • 41.
    Alam, Moudud
    Dalarna University, School of Technology and Business Studies, Statistics.
    Feasible computation of the generalized linear mixed models with application to credit risk modelling2010Doctoral thesis, monograph (Other academic)
    Abstract [en]

    This thesis deals with developing and testing feasible computational procedures to facilitate the estimation of and carry out the prediction with the generalized linear mixed model (GLMM) with a scope of applying them to large data sets. The work of this thesis is motivated from an issue arising in credit risk modelling. We have access to a huge data set, consisting of about one million observations, on credit history obtained from two major Swedish banks. The principal research interest involved with the data analysis is to model the probability of credit defaults by incorporating the systematic dependencies among the default events. In order to model the dependent credit defaults we adopt the framework of GLMM which is a popular approach to model correlated binary data. However, existing computational procedures for GLMM did not offer us the flexibility to incorporate the desired correlation structure of defaults events. For the feasible estimation of the GLMM we propose two estimation techniques being the fixed effects (FE) approach and the two-step pseudo likelihood approach (2PL). The preciseness of the estimation techniques and their computational advantages are studied by Monte-Carlo simulations and by applying them to the credit risk modelling. Regarding the prediction issue, we show how to apply the likelihood principle to carry out prediction with GLMM. We also provide an R add-in package to facilitate the predictive inference for GLMM.

  • 42.
    Alam, Moudud
    Dalarna University, School of Technology and Business Studies, Statistics.
    Feasible estimation of generalized linear mixed models (GLMM) with weak dependency between groups2010Manuscript (preprint) (Other academic)
    Abstract [en]

    This paper presents a two-step pseudo likelihood estimation technique for generalized linear mixed models with the random effects being correlated between groups. The core idea is to deal with the intractable integrals in the likelihood function by multivariate Taylor's approximation. The accuracy of the estimation technique is assessed in a Monte-Carlo study. An application of it with a binary response variable is presented using a real data set on credit defaults from two Swedish banks. Thanks to the use of two-step estimation technique, the proposed algorithm outperforms conventional pseudo likelihood algorithms in terms of computational time.

    Download full text (pdf)
    fulltext
  • 43.
    Alam, Moudud
    Dalarna University, School of Technology and Business Studies, Statistics.
    Industry shocks and empirical evidences on defaults comovement2009Report (Other academic)
    Abstract [en]

    It is commonly agreed that the credit defaults are correlated. However, the mechanism of such dependence is not yet fully understood. This paper contributes to the current understanding about the defaults comovement in the following way. Assuming that the industries provides the basis of defaults comovement it provides empirical evidence as to how such comovements can be modeled using correlated industry shocks. Generalized linear mixed model (GLMM) with correlated random effects is used to model the defaults comovement. Empirical evidences are drawn through analyzing individual borrower level credit history data obtained from two major Swedish banks between the period 1994-2000. The results show that the defaults are correlated both within and between industries but not over time (quarters). A discussion has also been presented as to how a GLMM for defaults correlation can be explained.

  • 44.
    Alam, Moudud
    Dalarna University, School of Technology and Business Studies, Statistics.
    Likelihood prediction for generalized linear mixed models under covariate uncertainty2014In: Communications in Statistics - Theory and Methods, ISSN 0361-0926, E-ISSN 1532-415X, Vol. 43, no 2, p. 219-234Article in journal (Refereed)
    Abstract [en]

    This paper presents the techniques of likelihood prediction for the generalized linear mixed models. Methods of likelihood prediction is explained through a series of examples; from a classical one to more complicated ones. The examples show, in simple cases, that the likelihood prediction (LP) coincides with already known best frequentist practice such as the best linear unbiased predictor. The paper outlines a way to deal with the covariate uncertainty while producing predictive inference. Using a Poisson error-in-variable generalized linear model, it has been shown that in complicated cases LP produces better results than already know methods.

    Download full text (pdf)
    fulltext
  • 45.
    Alam, Moudud
    et al.
    Dalarna University, School of Technology and Business Studies, Statistics.
    Carling, Kenneth
    Dalarna University, School of Technology and Business Studies, Statistics.
    Computionally feasible estimation of the covariance structure in generalized linear mixed models2008In: Journal of Statistical Computation and Simulation, ISSN 0094-9655, E-ISSN 1563-5163, Vol. 78, no 12, p. 1229-1239Article in journal (Refereed)
    Abstract [en]

    In this paper, we discuss how a regression model, with a non-continuous response variable, which allows for dependency between observations, should be estimated when observations are clustered and measurements on the subjects are repeated. The cluster sizes are assumed to be large. We find that the conventional estimation technique suggested by the literature on generalized linear mixed models (GLMM) is slow and sometimes fails due to non-convergence and lack of memory on standard PCs. We suggest to estimate the random effects as fixed effects by generalized linear model and to derive the covariance matrix from these estimates. A simulation study shows that our proposal is feasible in terms of mean-square error and computation time. We recommend that our proposal be implemented in the software of GLMM techniques so that the estimation procedure can switch between the conventional technique and our proposal, depending on the size of the clusters.

  • 46.
    Alam, Moudud
    et al.
    Dalarna University, School of Technology and Business Studies, Statistics.
    Carling, Kenneth
    Dalarna University, School of Technology and Business Studies, Statistics.
    Chen, Rui
    Liang, Yuli
    How to determine the progression of young skiers?2008In: CHANCE: New Directions for Statistics and Computing, ISSN 0933-2480, Vol. 21, no 4, p. 13-19Article in journal (Refereed)
  • 47.
    Alam, Moudud
    et al.
    Dalarna University, School of Technology and Business Studies, Statistics.
    Carling, Kenneth
    Dalarna University, School of Technology and Business Studies, Statistics.
    Linde, Olof
    Sweco Eurofutures.
    Nääs, Ola
    Dalarna University, School of Technology and Business Studies, Statistics.
    Sandén, Peter
    Sweco Eurofutures.
    Wing, Stefan
    Sweco Eurofutures.
    Utvärdering av det arbetsmarknadspolitiska projektet "Volvo Cars och dess underleverantörer"2012Report (Other academic)
    Abstract [sv]

    Denna rapport är en utvärdering av det arbetsmarknadspolitiska projektet "Volvo Cars och dess underleverantörer", som har genomförts av Arbetsförmedlingen i samarbete med Skolverket och Svenska ESF-rådet. Den 5 juni 2009 ansökte Sveriges regering om medel hos den Europeiska globaliseringsfonen (EGF)2 för att kunna erbjuda åtgärder för personer som blivit uppsagda från Volvo Cars AB och dess underleverantörer. Syftet med projektet var att kunna erbjuda de som blivit uppsagda kompetensutveckling, nya yrkeskunskaper och möjlighet att etablera egna företag.

    På operativ nivå drevs projektet i samverkan mellan Arbetsförmedlingen och den kom-munala yrkesvuxenutbildningen ("Yrkesvux"). Yrkesvux i Göteborgs kommun fick i upp-drag av Skolverket att samordna den del av verksamheten som berörde kommunal yr-kesvuxenutbildning. Projektet startade 1 januari 2010 och avslutades 31 maj 2011. Enligt kommissionens beslut fick medel även användas retroaktivt för insatser som hade givits till de uppsagda i form av olika arbetsmarknadsutbildningar, det s.k. snabbspåret, under 2009 innan projektet hade startat.

    Av nästan 5 000 individer i målgruppen som registrerade sig vid Arbetsförmedlingen del-tog knappt en fjärdedel i projektets insatser (exkl. vägledning). Av dessa gick 55 procent i aktiviteter enbart genom Arbetsförmedlingen, 37 procent enbart genom Yrkesvux och åtta procent genom både Arbetsförmedlingen och Yrkesvux. De vanligaste förekommande utbildningsinriktningarna var industri och bygg, fordonsindustri, transport och magasine-ring, omvårdnad och handel.

    Download full text (pdf)
    fulltext
  • 48.
    Alam, Moudud
    et al.
    Dalarna University, School of Technology and Business Studies, Statistics.
    Hao, Chengcheng
    Carling, Kenneth
    Dalarna University, School of Technology and Business Studies, Statistics.
    Review of the literature on credit risk modeling: development of the past 10 years2010In: Banks and Bank Systems, ISSN 1816-7403, Vol. 5, no 3, p. 43-60Article in journal (Refereed)
    Abstract [en]

    This paper traces the developments of credit risk modeling in the past 10 years. Our work can be divided into two parts: selecting articles and summarizing results. On the one hand, by constructing an ordered logit model on historical Journal of Economic Literature (JEL) codes of articles about credit risk modeling, we sort out articles which are the most related to our topic. The result indicates that the JEL codes have become the standard to classify researches in credit risk modeling. On the other hand, comparing with the classical review Altman and Saunders(1998), we observe some important changes of research methods of credit risk. The main finding is that current focuses on credit risk modeling have moved from static individual-level models to dynamic portfolio models.

    Download full text (pdf)
    fulltext
  • 49.
    Alam, Moudud
    et al.
    Dalarna University, School of Technology and Business Studies, Statistics.
    Maengseok, Noh
    Department of Statistics, Pukyong National University, South Korea.
    Lee, Youngjo
    Department of Statistics, Seoul National University, South Korea.
    Likelihood estimate of treatment effects under selection bias2013In: Statistics and its Interface, ISSN 1938-7989, E-ISSN 1938-7997, Vol. 6, no 3, p. 349-359Article in journal (Refereed)
    Abstract [en]

    We consider methods for estimating the causal effects of treatment in the situation where the individuals in the treatment and the control group are self selected, i.e., the selection mechanism is not randomized. In this case, a simple comparison of treated and control outcomes will not generally yield valid estimates of casual effect. The propensity score method is frequently used for the evaluation of treatment effect. However, this method is based on some strong assumptions, which are not directly testable. In this paper, we present an alternative modelling approach to draw causal inferences by using a shared random-effect model and the computational algorithm to draw likelihood based inference with such a model. With small numerical studies and a real data analysis, we show that our approach gives not only more efficient estimates but also is less sensitive to model misspecifications, which we consider, than existing methods.

  • 50.
    Alam, Moudud
    et al.
    Dalarna University, School of Technology and Business Studies, Statistics.
    Noh, Maengseok
    Department of Statistics, Pukyong National Univeristy.
    Lee, Youngjo
    Department of Statistics, Seoul National Univeristy.
    Likelihood estimate of treatment effects under selection bias2012Report (Other academic)
    Abstract [en]

    We consider methods for estimating causal effects of treatment in the situation where the individuals in the treatment and the control group are self selected, i.e., the selection mechanism is not randomized. In this case, simple comparison of treated and control outcomes will not generally yield valid estimates of casual effects. The propensity score method is frequently used for the evaluation of treatment effect. However, this method is based onsome strong assumptions, which are not directly testable. In this paper, we present an alternative modeling approachto draw causal inference by using share random-effect model and the computational algorithm to draw likelihood based inference with such a model. With small numerical studies and a real data analysis, we show that our approach gives not only more efficient estimates but it is also less sensitive to model misspecifications, which we consider, than the existing methods.

    Download full text (pdf)
    fulltext
1234567 1 - 50 of 1382
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • chicago-author-date
  • chicago-note-bibliography
  • 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