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  • 1. Abramov, V.
    et al.
    Paal, E.Tallinn University of Technology.Silvestrov, Sergei D.Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.Stolin, A.Chalmers University of Techology.
    Proceedings of the 3rd Baltic-Nordic Workshop “Algebra, Geometry, and Mathematical Physics”2008Conference proceedings (editor) (Refereed)
  • 2.
    af Klinteberg, Ludvig
    et al.
    KTH, Sweden.
    Sorgentone, Chiara
    KTH, Sweden.
    Tornberg, Anna-Karin
    KTH, Sweden.
    Quadrature error estimates for layer potentials evaluated near curved surfaces in three dimensions2022In: Computers and Mathematics with Applications, ISSN 0898-1221, E-ISSN 1873-7668, Vol. 111, p. 1-19Article in journal (Refereed)
    Abstract [en]

    The quadrature error associated with a regular quadrature rule for evaluation of a layer potential increases rapidly when the evaluation point approaches the surface and the integral becomes nearly singular. Error estimates are needed to determine when the accuracy is insufficient and a more costly special quadrature method should be utilized.& nbsp;The final result of this paper are such quadrature error estimates for the composite Gauss-Legendre rule and the global trapezoidal rule, when applied to evaluate layer potentials defined over smooth curved surfaces in R-3. The estimates have no unknown coefficients and can be efficiently evaluated given the discretization of the surface, invoking a local one-dimensional root-finding procedure. They are derived starting with integrals over curves, using complex analysis involving contour integrals, residue calculus and branch cuts. By complexifying the parameter plane, the theory can be used to derive estimates also for curves in R3. These results are then used in the derivation of the estimates for integrals over surfaces. In this procedure, we also obtain error estimates for layer potentials evaluated over curves in R2. Such estimates combined with a local root-finding procedure for their evaluation were earlier derived for the composite Gauss-Legendre rule for layer potentials written in complex form [4]. This is here extended to provide quadrature error estimates for both complex and real formulations of layer potentials, both for the Gauss-Legendre and the trapezoidal rule.& nbsp;Numerical examples are given to illustrate the performance of the quadrature error estimates. The estimates for integration over curves are in many cases remarkably precise, and the estimates for curved surfaces in R-3 are also sufficiently precise, with sufficiently low computational cost, to be practically useful.

  • 3.
    Arnlind, Joakim
    et al.
    Max Planck Institute for Gravitational Physics (AEI), Am Mühlenberg 1, D-14476 Golm, Germany.
    Makhlouf, Abdenacer
    Université de Haute Alsace, Lab. de Mathématiques Informatique et Applications, 4, rue des Frères Lumière, F-68093 Mulhouse, France.
    Silvestrov, Sergei
    Mälardalen University, School of Education, Culture and Communication.
    Construction of n-Lie algebras and n-ary Hom-Nambu-Lie algebras2011In: Journal of Mathematical Physics, ISSN 0022-2488, E-ISSN 1089-7658, Vol. 52, no 12, p. 123502-Article in journal (Refereed)
    Abstract [en]

    As n-ary operations, generalizing Lie and Poisson algebras, arise in many different physical contexts, it is interesting to study general ways of constructing explicit realizations of such multilinear structures. Generically, they describe the dynamics of a physical system, and there is a need of understanding their quantization. Hom-Nambu-Lie algebras provide a framework that might be an appropriate setting in which n-Lie algebras (n-ary Nambu-Lie algebras) can be deformed, and their quantization studied. We present a procedure to construct (n + 1)-ary Hom-Nambu-Lie algebras from n-ary Hom-Nambu-Lie algebras equipped with a generalized trace function. It turns out that the implications of the compatibility conditions, that are necessary for this construction, can be understood in terms of the kernel of the trace function and the range of the twisting maps. Furthermore, we investigate the possibility of defining (n + k)-Lie algebras from n-Lie algebras and a k-form satisfying certain conditions. (C) 2011 American Institute of Physics. [doi:10.1063/1.3653197]

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  • 4.
    Ataguema, H.
    et al.
    Universit́e de Haute Alsace, France .
    Makhlouf, A.
    Universit́e de Haute Alsace, France .
    Silvestrov, S. D.
    Lund University.
    Generalization of n-ary Nambu algebras and beyond2009In: Journal of Mathematical Physics, ISSN 0022-2488, E-ISSN 1089-7658, Vol. 50, no 8, p. Article number 083501-Article in journal (Refereed)
    Abstract [en]

    The aim of this paper is to introduce n-ary Hom-algebra structures generalizing the n-ary algebras of Lie type including n-ary Nambu algebras, n-ary Nambu-Lie algebras and n-ary Lie algebras, and n-ary algebras of associative type including n-ary totally associative and n-ary partially associative algebras. We provide examples of the new structures and present some properties and construction theorems. We describe the general method allowing one to obtain an n-ary Hom-algebra structure starting from an n-ary algebra and an n-ary algebra endomorphism. Several examples are derived using this process. Also we initiate investigation of classification problems for algebraic structures introduced in the article and describe all ternary three-dimensional Hom-Nambu-Lie structures with diagonal homomorphism.

  • 5.
    Baev, A.
    et al.
    Royal Institute of Technology, Sweden.
    Gel'mukhanov, F.
    Royal Institute of Technology, Sweden.
    Rubio-Pons, O.
    Mälardalen University, Department of Mathematics and Physics.
    Cronstrand, P.
    Royal Institute of Technology, Sweden.
    Ågren, H.
    Royal Institute of Technology, Sweden.
    Upconverted lasing based on many-photon absorption: An all dynamic description2004In: Journal of the Optical Society of America B, ISSN 0740-3224, Vol. 21, no 2, p. 384-396Article in journal (Refereed)
    Abstract [en]

    A theory is developed for the propagation through a nonlinear medium of strong pump and amplifiedspontaneous-emission pulses. The theory is based on a solution of the density matrix equations that aims at providing an adequate treatment of the nonlinear polarization of the material without addressing the Taylor expansion over the powers of intensity. The theory has been applied for modeling of three-photon absorption induced upconverted stimulated emission of organic molecules in solvents. Numerical results are presented for the organic chromophore 4-[N-(2-hydroxyethyl)-N-(methyl)amino phenyl]-4'-(6-hydroxyhexyl sulfonyl) stilbene dissolved in dimethyl sulfoxide. The results are in good agreement with available experimental results. 

  • 6.
    Bodnar, Olha
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics. Physikalisch-Technische Bundesanstalt, Berlin, Germany.
    Analysis of Key Comparisons with Two Reference Standards: Extended Random Effects Meta-Analysis2018In: Advanced Mathematical and Computational Tools in Metrology and Testing XI / [ed] Alistair B Forbes; Nien-Fan Zhang; Anna Chunovkina; Sascha Eichstädt, Singapore: World Scientific, 2018, p. 1-8Chapter in book (Refereed)
    Abstract [en]

    We propose a statistical method for analyzing key comparisons with two transfer standards measured in two petals. The new approach is based on an extension of the established random effects model. A full Bayesian analysis based on the reference prior is developed and analytic expressions for the results are derived. One benefit of the suggested approach is that it provides a comprehensive assessment of the laboratory biases in terms of their posterior distributions. Another advantage is that it can easily be applied in practice. The approach is illustrated for the CCM.M-K7 key comparison data.

  • 7.
    Bodnar, Olha
    et al.
    Physikalisch-Technische Bundesanstalt, Germany.
    Elster, Clemens
    Physikalisch-Technische Bundesanstalt, Germany.
    Wübbeler, Gerd
    Physikalisch-Technische Bundesanstalt, Germany.
    Robust Bayesian Linear Regression with Application to an Analysis of the CODATA Values for the Planck Constant2017In: Metrologia, ISSN 0026-1394, E-ISSN 1681-7575, Vol. 55, no 1, p. 20-28Article in journal (Refereed)
    Abstract [en]

    Weighted least-squares estimation is commonly applied in metrology to fit models to measurements that are accompanied with quoted uncertainties. The weights are chosen in dependence on the quoted uncertainties. However, when data and model are inconsistent in view of the quoted uncertainties, this procedure does not yield adequate results.

    When it can be assumed that all uncertainties ought to be rescaled by a common factor, weighted least-squares estimation may still be used, provided that a simple correction of the uncertainty obtained for the estimated model is applied. We show that these uncertainties and credible intervals are robust, as they do not rely on the assumption of a Gaussian distribution of the data. Hence, common software for weighted least-squares estimation may still safely be employed in such a case, followed by a simple modification of the uncertainties obtained by that software. We also provide means of checking the assumptions of such an approach.

    The Bayesian regression procedure is applied to analyze the CODATA values for the Planck constant published over the past decades in terms of three different models: a constant model, a straight line model and a spline model. Our results indicate that the CODATA values may not have yet stabilized

  • 8.
    Bodnar, Olha
    et al.
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Possolo, Antonio
    National Institute of Standards and Technology, USA.
    Approximate Bayesian Evaluations of Measurement Uncertainty2018Conference paper (Other academic)
  • 9.
    Bodnar, Olha
    et al.
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Possolo, Antonio
    National Institute of Standards and Technology, USA.
    Approximate Bayesian evaluations of measurement uncertainty2018In: Metrologia, ISSN 0026-1394, E-ISSN 1681-7575, Vol. 55, p. 147-157Article in journal (Refereed)
    Abstract [en]

    The Guide to the Expression of Uncertainty in Measurement (GUM) includes formulas that produce an estimate of a scalar output quantity that is a function of several input quantities, and an approximate evaluation of the associated standard uncertainty.

    This contribution presents approximate, Bayesian counterparts of those formulas for the case where the output quantity is a parameter of the joint probability distribution of the input quantities, also taking into account any information about the value of the output quantity available prior to measurement expressed in the form of a probability distribution on the set of possible values for the measurand.

    The approximate Bayesian estimates and uncertainty evaluations that we present have a long history and illustrious pedigree, and provide sufficiently accurate approximations in many applications, yet are very easy to implement in practice. Differently from exact Bayesian estimates, which involve either (analytical or numerical) integrations, or Markov Chain Monte Carlo sampling, the approximations that we describe involve only numerical optimization and simple algebra. Therefore, they make Bayesian methods widely accessible to metrologists.

    We illustrate the application of the proposed techniques in several instances of measurement: isotopic ratio of silver in a commercial silver nitrate; odds of cryptosporidiosis in AIDS patients; height of a manometer column; mass fraction of chromium in a reference material; and potential-difference in a Zener voltage standard.

  • 10.
    Castleton, Christopher
    et al.
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics. Uppsala universitet, Sweden.
    Höglund, Andreas
    Uppsala universitet, Sweden.
    Mirbt, Susanne
    Uppsala universitet, Sweden.
    Managing the supercell approximation for charged defects in semiconductors: Finite-size scaling, charge correction factors, the band-gap problem, and the ab initio dielectric constant2006In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 73, no 035215Article in journal (Refereed)
    Abstract [en]

    The errors arising in ab initio density functional theory studies of semiconductor point defects using the supercell approximation are analyzed. It is demonstrated that (a) the leading finite size errors are inverse linear and inverse cubic in the supercell size and (b) finite size scaling over a series of supercells gives reliable isolated charged defect formation energies to around +-0.05 eV. The scaled results are used to test three correction methods. The Makov-Payne method is insufficient, but combined with the scaling parameters yields an ab initio dielectric constant of 11.6+-4.1 for InP. Gamma point corrections for defect level dispersion are completely incorrect, even for shallow levels, but realigning the total potential in real-space between defect and bulk cells actually corrects the electrostatic defect-defect interaction errors as well. Isolated defect energies to +-0.1 eV are then obtained using a 64 atom supercell, though this does not improve for larger cells. Finally, finite size scaling of known dopant levels shows how to treat the band gap problem: in < or = 200 atom supercells with no corrections, continuing to consider levels into the theoretical conductin band (extended gap) comes closest to experiment. However, for larger cells or when supercell approximation errors are removed, a scissors scheme stretching the theoretical band gap onto the experimental one is in fact correct.

  • 11.
    Castleton, Christopher
    et al.
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics. Linköpings universitet, Tekniska högskolan, Sweden.
    Kullgren, J.
    Department of Materials Chemistry, Uppsala University, Box 538, SE-75121, Sweden.
    Hermansson, K.
    Department of Materials Chemistry, Uppsala University, Box 538, SE-75121, Sweden.
    Tuning LDA+U for electron localization and structure at oxygen vacancies in ceria2007In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 127, no 24Article in journal (Refereed)
    Abstract [en]

    We examine the real space structure and the electronic structure (particularly Ce4f electron localization) of oxygen vacancies in Ce O2 (ceria) as a function of U in density functional theory studies with the rotationally invariant forms of the LDA+U and GGA+U functionals. The four nearest neighbor Ce ions always relax outwards, with those not carrying localized Ce4f charge moving furthest. Several quantification schemes show that the charge starts to become localized at U˜3 eV and that the degree of localization reaches a maximum at ~6 eV for LDA+U or at ~5.5 eV for GGA+U. For higher U it decreases rapidly as charge is transferred onto second neighbor O ions and beyond. The localization is never into atomic corelike states, at maximum localization about 80-90% of the Ce4f charge is located on the two nearest neighboring Ce ions. However, if we look at the total atomic charge we find that the two ions only make a net gain of (0.2-0.4) e each, so localization is actually very incomplete, with localization of Ce4f electrons coming at the expense of moving other electrons off the Ce ions. We have also revisited some properties of defect-free ceria and find that with LDA+U the crystal structure is actually best described with U=3-4 eV, while the experimental band structure is obtained with U=7-8 eV. (For GGA+U the lattice parameters worsen for U>0 eV, but the band structure is similar to LDA+U.) The best overall choice is U˜6 eV with LDA+U and ˜5.5 eV for GGA+U, since the localization is most important, but a consistent choice for both Ce O2 and Ce2 O3, with and without vacancies, is hard to find. 

  • 12.
    Castleton, Christopher
    et al.
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics. Nottingham Trent University, UK.
    Lee, A.
    Nottingham Trent University, UK.
    Kullgren, J.
    Uppsala University, Sweden.
    Benchmarking Density Functional Theory Functionals for Polarons in Oxides: Properties of CeO22019In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 123, no 9, p. 5164-5175Article in journal (Refereed)
    Abstract [en]

    We examine methods for studying polarons in metal oxides with density functional theory (DFT), using the example of cerium dioxide and the functionals, local density approximation + U (LDA+U), generalized gradient approximation + U (GGA+U) in the Perdew-Burke-Ernzerhof parametrization (PBE+U), as well as the hybrid functionals B3LYP, Heyd?Scuseria?Ernzerhof (HSE)03, HSE06, and PBE0. We contrast the four polaron energies commonly reported in different parts of the literature: formation energy, localization/relaxation energy, density-of-states level, and polaron-hopping activation barrier. Qualitatively, all these functionals predict "small" (Holstein) polarons on the scale of a single lattice site, although LDA+U and GGA+U are more effective than the hybrids at localizing the Ce 4f electrons. The improvements over pure LDA/GGA appear because of changes in the filled Ce 4f states when using LDA/GGA+U but due to changes in the empty Ce 4f states when using the hybrids. DFT is shown to have sufficient correlation to predict both adiabatic and (approximate) diabatic hopping barriers. Overall, LDA+U = 6 eV provides the best description in comparison to the experiment, followed by GGA+U = 5 eV. The hybrids are worse, tending to overestimate the gap and significantly underestimate the polaron-hopping barriers.

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  • 13.
    Ekström, Mikael
    et al.
    Mälardalen University, School of Innovation, Design and Engineering. Uppsala University, Sweden.
    Hartmann, Ola
    Uppsala University, Sweden.
    Karlsson, Erik
    Uppsala University, Sweden.
    Lidström, Erik
    Uppsala University, Sweden.
    Granberg, Per
    Uppsala University, Sweden.
    Nygren, M
    Mälardalen University, School of Innovation, Design and Engineering. Stockholm University, Sweden.
    Antiferromagnetism in Zn-doped La2CuO4 as observed by muon spin resonance spectroscopy2001In: Physical Review B - Condensed Matter and Materials Physics, ISSN 0163-1829, Vol. 64, no 18, p. 1845221-1845226, article id 184522Article in journal (Refereed)
    Abstract [en]

    The local fields seen by positive muons implanted in Zn-doped La2CuO4 show a distribution with a main peak attributed to muon sites far from the Zn ions and a satellite structure corresponding to muons residing closer to the Zn. The temperature dependence indicates a strong loss of magnetic order for Cu moments near the Zn atoms. The data can be understood in terms of a model where a Zn ion not only introduces a vacancy in the magnetic Cu lattice but also creates a RKKY-type disturbance. The electron spin polarization around the Zn ions induces a change of the magnetic moments on surrounding Cu ions. The AF lattice is found to be strongly perturbed within a radius of 10 Angstrom around each Zn ion. Possible consequences for the superconductivity of the corresponding Sr-doped materials are discussed.

  • 14.
    Ghobadi, Nader
    et al.
    Malayer Univ, Fac Sci, Dept Phys, Malayer, Iran..
    Arman, Ali
    Sharif Univ Branch, Vacuum Technol Res Grp, ACECR, Tehran, Iran..
    Sadeghi, Mohammad
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Luna, Carlos
    Univ Autonoma Nuevo Leon UANL, Fac Ciencias Fis Matemat FCFM, Av Univ S-N, San Nicolas De Los Garza 66455, Nuevo Leon, Mexico..
    Mirzaei, Saeed
    Brno Univ Technol, CEITEC BUT, Purkynova 123, Brno 61200, Czech Republic.;Fraunhofer Inst Mat & Beam Technol, Winterbergstr 28, DE-01277 Dresden, Germany..
    Zelati, Amir
    Birjand Univ Technol, Dept Basic Sci, Birjand, Iran..
    Shakoury, Reza
    Imam Khomeini Int Univ, Fac Sci, Dept Phys, Qazvin, Iran..
    Optical transitions and photocatalytic activity of NiSe films prepared by the chemical solution deposition method2022In: The European Physical Journal Plus, E-ISSN 2190-5444, Vol. 137, no 6, article id 661Article in journal (Refereed)
    Abstract [en]

    In this work, nanostructured NiSe thin films were prepared by the chemical solution deposition method at different pH fixing the deposition time. The surface morphology, structural and semiconductor properties of such films were investigated utilizing different methodologies. It was found that slight changes in pH can influence the optical bandgap and structure of NiSe films. The results of Tauc's plot and the derivation of the ineffective thickness method were compared to estimate the optical bandgap energy and the transition index. Additionally, the Urbach energy was also assessed. The potential of the NiSe nanostructured samples as photocatalysts was evaluated by analyzing the decomposition of azoic Congo red dye under visible light radiation.

  • 15.
    Gkoutzamanis, V. G.
    et al.
    Aristotle University of Thessaloniki, Thessaloniki, Greece.
    Tsentis, S. E.
    Aristotle University of Thessaloniki, Thessaloniki, Greece.
    Mylonas, O. S. V.
    Aristotle University of Thessaloniki, Thessaloniki, Greece.
    Kalfas, A. I.
    Aristotle University of Thessaloniki, Thessaloniki, Greece.
    Kyprianidis, Konstantinos
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Tsirikoglou, P.
    Limmat Scientific, Zurich, Switzerland.
    Sielemann, M.
    Modelon Deutschland GmbH, Munich, Germany.
    Thermal Management System Considerations for a Hybrid-Electric Commuter Aircraft2022In: Journal of thermophysics and heat transfer, ISSN 0887-8722, E-ISSN 1533-6808, Vol. 36, no 3, p. 650-666Article in journal (Refereed)
    Abstract [en]

    When it comes to novel aircraft concepts, thermal management system (TMS) design is a ubiquitous task, even at the conceptual design phase. This is owing to its impact on the total weight of the aircraft, cooling drag, and overall performance. The commuter air transportation has recently regained attention and is seen as a solution to employ partial or full electrification in the upcoming decades due to its low power requirement and potential benefit of faster “door-to-door” traveling. This work examines the TMS characteristics to cool a battery-powered aft-fan engine. A literature review is initially performed on other research associated with TMS design. The development and weight evaluation of the baseline TMS for this type of propulsive technology are then presented, including the characterization of system redundancy effects on the overall TMS weight. Results show that the TMS design is a function of the selected propulsive configuration and energy management throughout the mission. Primarily, this relates to the cooling method selected, the heat exchangers as the major mass contributors of the TMS, the positioning of components used for the propulsive configuration, and the imposed certification constraints. Finally, the selected TMS design is calculated to have a combined specific cooling of 0.79 kW∕kg. 

  • 16.
    Gul, E.
    et al.
    University of Perugia, Department of Engineering, Perugia, Italy.
    Campana, Pietro Elia
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Chandrasekaran, A.
    Chemical Engineering Department, Indian Institute of Technology, Assam, Guwahati, India.
    Subbiah, S.
    Chemical Engineering Department, Indian Institute of Technology, Assam, Guwahati, India.
    Yang, H.
    State Key Laboratory of Coal Combustion, Huazhong University of Science and Technolog, Wuhan, Chin.
    Yang, Q.
    Department of New Energy Science and Engineering, School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan, China.
    Yan, Jinyue
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Li, Hailong
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Desideri, U.
    Department of Energy, Systems, Territory and Constructions Engineering, University of Pisa, Pisa, 56122, Italy.
    Barelli, L.
    University of Perugia, Department of Engineering, Perugia, Italy.
    Bidini, G.
    University of Perugia, Department of Engineering, Perugia, Italy.
    Fantozzi, F.
    University of Perugia, Department of Engineering, Perugia, Italy.
    Uddin, I.
    CAS Key Laboratory of Science and Technology on Applied catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China.
    Hayat, A.
    College of Chemistry, Fuzhou University, Fuzhou, China.
    Alrawashdeh, K. A.
    Mechanical Engineering Department, Al-Huson University College, Al-Balqa’ Applied University, Irbid, Jordan.
    Bartocci, P.
    University of Perugia, Department of Engineering, Perugia, Italy.
    Perspectives and state of the art in producing solar fuels and chemicals from CO22021In: Advanced Technology for the Conversion of Waste into Fuels and Chemicals: Volume 2: Chemical Processes, Elsevier , 2021, p. 181-219Chapter in book (Other academic)
    Abstract [en]

    Solar Fuels and chemicals from CO2 can be produced through two main reactions: one is CO2 photoreduction, using different catalysts and different reducing agents; the other is CO2 fixation, which is usually performed through natural photosynthesis. The research nowadays is directed on the production of fuels and chemicals with one or two atoms of carbon, for example CH4, CO, HCOOH, HCHO, CH3OH, C2H5OH, etc. The chapter aims at comparing natural photosynthesis processes and reactions with artificial photosynthesis. After taking into consideration the natural photosynthetic process, the chapter focuses on heterogeneous and homogeneous photocatalysis. Heterogeneous catalysis can be performed with semiconductors and powder catalysts. Special attention is given to TiO2 as a promising photocatalyst. Homogeneous photocatalysts are usually represented by molecular catalysts, which are dissolved in water or another solvent. Usually, homogeneous photocatalysis is performed in complex systems which are composed by: a light harvesting unit (LHU) (i.e. the photosensitizer); one catalytic site for the oxidation process, where the electrons are supplied by a sacrificial donor; one reduction site, where the electrons are transmitted to CO2. Finally, even more complex systems are represented by those based on photoelectrocatalysis. These have the main advantage to separate the oxidation and reduction reactions at the two different electrodes of the system. In principle photoelectrochemical cells can be a way to mimic artificially the working principle of natural photosynthesis.

  • 17.
    Habibi, Maryam
    et al.
    Plasma Physics Research Center, Science and Research Branch Islamic Azad University, Tehran, Iran.
    Sadeghi, Mohammad
    Arman, Ali
    ACECR, Vacuum Technology Research Group Sharif University Branch, Tehran, Iran.
    Sobola, Dinara
    Faculty of Electrical Engineering and Communication, Department of Physics Brno University of Technology Brno Czech Republic;Department of Inorganic Chemistry and Chemical Ecology Dagestan State University, Makhachkala, Russia.
    Luna, Carlos
    Facultad de Ciencias Físico Matemáticas (FCFM) Universidad Autónoma de Nuevo León (UANL), San Nicolás de los Garza, Mexico.
    Mirzaei, Saeed
    CEITEC BUT Brno University of Technology, Brno, Czech Republic.
    Zelati, Amir
    Department of Basic Sciences Birjand University of Technology, Birjand, Iran.
    Fonseca Filho, Henrique Duarte
    Laboratory of Synthesis of Nanomaterials and Nanoscopy, Physics Department Federal University of Amazonas‐UFAM, Manaus, Brazil.
    Ţălu, Ştefan
    The Directorate of Research, Development and Innovation Management (DMCDI) Technical University of Cluj‐Napoca, Cluj‐Napoca, Romania.
    Corrosion resistance and surface microstructure of Mg 3 N 2 / SS thin films by plasma focus instrument2022In: Microscopy research and technique (Print), ISSN 1059-910X, E-ISSN 1097-0029, Vol. 85, no 8, p. 2880-2893Article in journal (Refereed)
    Abstract [en]

    Utilizing a plasma focus (PF) instrument, magnesium nitride (Mg3 N2 ) thin films were synthesized on stainless steel substrates. Twenty five optimum focus shots at 8 cm distance from the anode tip were used to deposit the films at different angular positions regarded to the anode axis. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray diffraction (XRD) analyses were performed to assess the surface morphology and structural characteristics of Mg3 N2 films. Based on AFM images, these films were studied to understand the effect of angular position variation on their surfaces through morphological and fractal parameters. By increasing the angle, we verify that the grain size decreased from 130(0) nm to 75(5) nm and also the mean quadratic surface roughness of the films reduced in its average values from (28.97 ± 3.24) nm to (23.10 ± 1.34) nm. Power spectrum density analysis indicated that films become more self-affine at larger angles. Furthermore, the corrosion behavior of the films was investigated through a potentiodynamic polarization test in H2 SO4 solution. It was found that the ion energy and flux, varying with the angular positions from the anode tip, directly affected the nanostructured roughness and surface morphology of the samples. The electrochemical studies of films show that the uncoated sample presented the lowest corrosion resistance. The highest corrosion resistance was obtained for the sample deposited with 25 optimum shots and at 0° angular position reaching a reduction in the corrosion current density of almost 800 times compared to the pure stainless steel-304 substrate. 

  • 18.
    Hansson, Björn A. M.
    et al.
    Roy. Inst. of Technology/Albanova, Sweden.
    Hemberg, Oskar
    Roy. Inst. of Technology/Albanova, Sweden.
    Hertz, Hans M.
    Roy. Inst. of Technology/Albanova, Sweden.
    Berglund, Magnus
    Roy. Inst. of Technology/Albanova, Sweden.
    Choi, Hee-June
    Roy. Inst. of Technology/Albanova, Sweden.
    Jacobsson, Björn
    Roy. Inst. of Technology/Albanova, Sweden.
    Janin, Emmanuelle
    Roy. Inst. of Technology/Albanova, Sweden.
    Mosesson, Sofia
    Roy. Inst. of Technology/Albanova, Sweden.
    Rymell, Lars
    Roy. Inst. of Technology/Albanova, Sweden.
    Thoresen, Jalmar
    Roy. Inst. of Technology/Albanova, Sweden.
    Wilner, Martin
    Roy. Inst. of Technology/Albanova, Sweden.
    Characterisation of a liquid-xenon jet laser-plasma extreme-ultraviolet source2004In: Review of Scientific Instruments, ISSN 0034-6748, Vol. 75, no 6, p. 2122-2129Article in journal (Refereed)
    Abstract [en]

    A liquid-xenon-jet laser-plasma source for extreme-ultraviolet (EUV) and soft-x-ray generation has been characterized. Being a source candidate for EUV lithography (EUVL), we especially focus on parameters important for the integration of the source in EUVL systems. The deep-ultraviolet (DUV) out-of-band radiation (=120–400 nm) was quantified, to within a factor of two, using a flying-circus tool together with a transmission-grating spectrograph resulting in a total DUV conversion efficiency (CE) of ~0.33%/2sr. The size and the shape of the xenon plasma was investigated using an in-band-only EUV microscope, based on a spherical Mo/Si multilayer mirror and a charge-coupled device detector. Scalability of the source size from 20–270 µm full width at half maximum was shown. The maximum repetition-rate sustainable by the liquid-xenon-jet target was simulated by a double-pulse experiment indicating feasibility of >17 kHz operation. The xenon-ion energy distribution from the plasma was determined in a time-of-flight experiment with a Faraday-cup detector showing the presence of multi-kilo-electron-volt ions. Sputtering of silicon witness plates exposed to the plasma was observed, while a xenon background of >1 mbar was shown to eliminate the sputtering. It is concluded that the source has potential to meet the requirements of future EUVL systems.

  • 19. Höglund, A
    et al.
    Castleton, Christopher W.M
    KTH, Materialfysik, Sweden.
    Mirbt, S
    Relative concentration and structure of native defects in GaP2005In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 72, no 19, p. 195213-Article in journal (Refereed)
    Abstract [en]

    The native defects in the compound semiconductor GaP have been studied using a pseudopotential density functional theory method in order to determine their relative concentrations and the most stable charge states. The electronic and atomic structures are presented and the defect concentrations are estimated using calculated formation energies. Relaxation effects are taken into account fully and produce negative-U charge transfer levels for V-P and P-Ga. The concentration of V-Ga is in good agreement with the results of positron annihilation experiments. The charge transfer levels presented compare qualitatively well with experiments where available. The effect of stoichiometry on the defect concentrations is also described and is shown to be considerable. The lowest formation energies are found for P-Ga(+2) in p-type and V-Ga(-3) in n-type GaP under P-rich conditions, and for Ga-P(-2) in n-type GaP under Ga-rich conditions. Finally, the finite size errors arising from the use of supercells with periodic boundary conditions are examined.

  • 20.
    Höglund, Andreas
    et al.
    Uppsala universitet, Sweden.
    Castleton, Christopher
    Uppsala universitet, Sweden.
    Göthelid, Mats
    Johansson, Börje
    Uppsala universitet, Sweden.
    Mirbt, Susanne
    Uppsala universitet, Sweden.
    Point defects on the (110) surfaces of InP, InAs, and InSb: A comparison with bulk2006In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 74, no 7, p. 075332-Article in journal (Refereed)
    Abstract [en]

    The basic properties of point defects, such as local geometries, positions of charge-transfer levels, and formation energies, have been calculated using density-functional theory, both in the bulk and on the (110) surface of InP, InAs, and InSb. Based on these results we discuss the electronic properties of bulk and surface defects, defect segregation, and compensation. In comparing the relative stability of the surface and bulk defects, it is found that the native defects generally have higher formation energies in the bulk. From this it can be concluded that at equilibrium there is a considerably larger fraction of defects at the surface and under nonequilibrium conditions defects are expected to segregate to the surface, given sufficient time. In most cases the charge state of a defect changes upon segregation, altering the charge-carrier concentrations. The photothresholds are also calculated for the three semiconductors and are found to be in good agreement with experimental data.

  • 21.
    Jääskeläinen, Markku
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Gravitationally self-bound quantum states in unstable potentials2018In: Physical Review A: covering atomic, molecular, and optical physics and quantum information, ISSN 2469-9926, E-ISSN 2469-9934, Vol. 97, no 4, article id 042116Article in journal (Refereed)
    Abstract [en]

    Quantum mechanics at present cannot be unified with the theory of gravity at the deepest level, and to guide research towards the solution of this fundamental problem, we need to look for ways to observe or refute predictions originating from attempts to combine quantum theory with gravity. The influence of the gravitational field created by the material density given by the wave function itself gives rise to nontrivial phenomena. In this study I consider the wave function for the center-of-mass coordinate of a spherical mass distribution under the influence of the self-interaction of Newtonian gravity. I solve numerically for the ground state in the presence of an unstable potential and find that the energy of the free-space bound state can be lowered despite the nontrapping character of the potential. The center-of-mass ground state becomes increasingly localized for the used unstable potentials, although only in a limited parameter regime. The feebleness of the energy shift makes the observation of these effects demanding and requires further developments in the cooling of material particles. In addition, the influence of gravitational perturbations that are present in typical laboratory settings necessitates the use of extremely quiet and controlled environments such as those provided by recently proposed space-borne experiments.

  • 22.
    Jääskeläinen, Markku
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Spatial and temporal bounds on quantum effects for micro-organisms2020In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 95, no 7, article id 075001Article in journal (Refereed)
    Abstract [en]

    Progress in the experimental nano-sciences and laser cooling has led to the manipulation of material objects with sizes and temperatures such that quantum effects start to appear. This range of sizes coincides with that of the smallest bacteria as well as of the largest viruses, and is often considered to be the boundary between living and nonliving entities. Experiments are rapidly progressing towards putting micro-organisms into quantum superposition states in a controlled manner, resulting in nontrivial quantum effects that we normally do not attribute to living systems. In order to set limits for the occurrence of such effects, I model micro-organisms quantum mechanically and investigate how relevant physical properties are modified from their classical bulk values in the presence of classical self-gravity. The results show that a transition between quantum-like and classical behavior exists right at sizes corresponding to the broad boundary between the smallest bacteria and the largest giant viruses.

  • 23.
    Jääskeläinen, Markku
    Högskolan Dalarna, Sweden.
    The wave function as matter density: ontological assumptions and experimental consequences2015In: Foundations of physics, ISSN 0015-9018, E-ISSN 1572-9516, Vol. 45, no 6, p. 591-610Article in journal (Refereed)
    Abstract [en]

    The wavefunction is the central mathematical entity of quantum mechanics, but it still lacks a universally accepted interpretation. Much effort is spent on attempts to probe its fundamental nature. Here I investigate the consequences of a matter ontology applied to spherical masses of constant bulk density. The governing equation for the center-of-mass wavefunction is derived and solved numerically. The ground state wavefunctions and resulting matter densities are investigated. A lowering of the density from its bulk value is found for low masses due to increased spatial spreading. A discussion of the possibility to experimentally observe these effects is given and the possible consequences for choosing an ontological interpretation for quantum mechanics are commented upon.

  • 24.
    Jääskeläinen, Markku
    et al.
    Högskolan Dalarna, Sweden.
    Lagerkvist, Andreas
    Högskolan Dalarna, Matematik/tillämpad matematik.
    Why do they not answer and do they really learn?: A case study in analysing student response flows in introductory physics using an audience response system2017In: European journal of physics, ISSN 0143-0807, E-ISSN 1361-6404, Vol. 38, no 4, article id 045705Article in journal (Refereed)
    Abstract [en]

    In this paper we investigate teaching with a classroom response system in introductory physics with emphasis on two issues. First, we discuss retention between question rounds and the reasons why students avoid answering the question a second time. A question with declining response rate was followed by a question addressing the student reasons for not answering. We find that there appear to be several reasons for the observed decline, and that the students need to be reminded. We argue that small drops are unimportant as the process appears to work despite the drops. Second, we discuss the dynamics of learning in a concept-sequence in electromagnetism, where a majority of the students, despite poor statistics in a first round, manage to answer a followup question correctly. In addition, we analyse the response times for both situations to connect with research on student reasoning on situations with misconception-like answers. From the combination of the answer flows and response time behaviours we find it plausible that conceptual learning occurred during the discussion phase.

  • 25.
    Karlsson, Patrik G.
    et al.
    Uppsala University.
    Göthelid, Emmanuelle
    Mälardalen University, School of Sustainable Development of Society and Technology. Mälardalen University, Department of Biology and Chemical Engineering.
    Richter, Jan H.
    Uppsala University.
    Sandell, Anders
    Uppsala University.
    Initial stages of ZrO2 chemical vapour deposition on Si(100)-(2x1) from zirconium tetra-tert-butoxide.2008In: Surface Science, Vol. 602, no 10, p. 1803-1809Article in journal (Refereed)
    Abstract [en]

    The initial stages of chemical vapor deposition of ZrO2 from zirconium tetra-tert-butoxide (ZTB) on Si(100)-(2x1) have been studied by Scanning Tunneling Microscopy (STM) and synchrotron radiation excited Photoelectron Spectroscopy (PES). The STM images and core level (PES) spectra indicate that the predominant surface modifications induced by ZTB are due to silicon carbonization and formation of zirconium dioxide. The carbonization reaction leads to formation of subsurface carbon and two types of reconstructions are discussed: dimer vacancies and dimer vacancies in conjunction with a rotated surface Si-dimer. Indications for the formation of small amounts of zirconium silicide are also found. No evidence for silicon oxidation can be observed with PES, in contrast to the interface properties previously found after larger exposures to ZTB.

  • 26.
    Krause, Marta
    et al.
    Mälardalen University, School of Business, Society and Engineering.
    Larsson, Amanda
    Mälardalen University, School of Business, Society and Engineering.
    En resa bland planeterna med Lova, Melker och Pixi.: Ett undervisningsmaterial inom astronomi för årskurs ett till tre.2013Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    During our practical teacher training we became aware of children’s alternative conceptions in astronomy.  We turned our faces towards science education literature and found evidence that children’s conceptions is not corresponding to scientific explanations. We also realized that there is a lack of Swedish teaching aids in astronomy for younger children (school year 1-3), therefore we have chosen to develop a teaching tool in astronomy.

    The teaching material is meant to be accessible and easy to use for teachers, as well as the teaching material shall meet one of the key requirements of Lgr 11 for grades 1-3 in science: "The earth, sun and moon movements relative to each other. Phases of the moon". (own translation)

    To find out what a good teaching aid is and get tips to our own, we made a survey at our part­ner schools. We also performed a compilation of nonfiction, fiction, educational materials and Internet sites. The material was then analyzed with the help of a qualitative method which then formed the basis of the development of the teaching aid. Our main results from the survey are that the educators are seeking teaching aids which includes practical exercises linked to Lgr 11and photocopiable documents. From the inventory of literature, we have come to the conclusion that there is no Swedish teaching aid in Astronomy for the younger children in primary school and that such teaching materials that the teachers in the questionnaire are asking fore can’t be found in today’s market.

     

    The teaching material consists of a teacher's guide and a workbook for students. The teach­er's guide is divided by the headlines: story, discussion topics, facts and instructions for ac­tivities with photocopiable documents. Students’ workbook is divided into headings: facts, instructions for activities and a glossary. These teaching materials are based on the methods: storyline, story and reading aloud. For students to be able to make meaning of Space the teaching aid contains tool as experiments and discussion questions. The teaching material is primarily aimed at teachers and students in primary school, grades 1 to 3, but the teaching material is also intended to accommodate children in preschool.

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    Examensarbete
  • 27. Kullgren, Jolla
    et al.
    Hermansson, Kersti
    KTH, Teoretisk kemi och biologi.
    Castleton, Christopher
    Nottingham Trent Univ, Sch Sci & Technol, Nottingham NG11 8NS, England.
    Many competing ceria (110) oxygen vacancy structures: From small to large supercells2012In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 137, no 4, p. 044705-Article in journal (Refereed)
    Abstract [en]

    We present periodic "DFT+U" studies of single oxygen vacancies on the CeO2(110) surface using a number of different supercells, finding a range of different local minimum structures for the vacancy and its two accompanying Ce(III) ions. We find three different geometrical structures in combination with a variety of different Ce(III) localization patterns, several of which have not been studied before. The desired trapping of electrons was achieved in a two-stage optimization procedure. We find that the surface oxygen nearest to the vacancy either moves within the plane towards the vacancy, or rises out of the surface into either a symmetric or an unsymmetric bridge structure. Results are shown in seven slab geometry supercells, p(2 x 1), p(2 x 2), p(2 x 3), p(3 x 2), p(2 x 4), p(4 x 2), and p(3 x 3), and indicate that the choice of supercell can affect the results qualitatively and quantitatively. An unsymmetric bridge structure with one nearest and one next-nearest neighbour Ce(III) ion (a combination of localizations not previously found) is the ground state in all (but one) of the supercells studied here, and the relative stability of other structures depends strongly on supercell size. Within any one supercell the formation energies of the different vacancy structures differ by up to 0.5 eV, but the same structure can vary by up to similar to 1 eV between supercells. Furthermore, finite size scaling suggests that the remaining errors (compared to still larger supercells) can also be similar to 1 eV for some vacancy structures.

  • 28.
    Li, H.
    et al.
    Royal Institute of Technology, Sweden.
    Ji, X.
    Royal Institute of Technology, Sweden.
    Yan, Jinyue
    Mälardalen University, School of Sustainable Development of Society and Technology. Royal Institute of Technology, Sweden.
    A new modification on RK EOS for gaseous CO2 and gaseous mixtures of CO2 and H2O2006In: International Journal of Energy Research, ISSN 0363-907X, E-ISSN 1099-114X, Vol. 30, no 3, p. 135-148Article in journal (Refereed)
    Abstract [en]

    To develop an equation of state with simple structure and reasonable accuracy for engineering application, Redlich-Kwong equation of state was modified for gaseous CO2 and CO2-H2O mixtures. In the new modification, parameter a of gaseous CO2 was regressed as a function of temperature and pressure from recent reliable experimental data in the range: 220-750 K and 0.1-400 MPa. Moreover, a new mixing rule was proposed for gaseous CO2-H2O mixtures. To verify the accuracy of the new modification, densities were calculated and compared with experimental data. The average error is 1.68% for gaseous CO2 and 0.93% for gaseous mixtures of CO2 and H2O. Other thermodynamic properties, such as enthalpy and heat capacities of CO2 and excess enthalpy of gaseous CO2-H2O mixtures, were also calculated; results fit experimental data well, except for the critical region.

  • 29. Lu, Zhansheng
    et al.
    Yang, Zongxian
    He, Bingling
    Castleton, Christopher
    Nottingham Trent Univ, Sch Sci & Technol, Nottingham NG11 8NS, England; Uppsala Univ, Angstrom Lab, SE-75121 Uppsala, Sweden.
    Hermansson, Kersti
    KTH, Teoretisk kemi och biologi.
    Cu-doped ceria: Oxygen vacancy formation made easy2011In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 510, no 1-3, p. 60-66Article in journal (Refereed)
    Abstract [en]

    DFT + U calculations of Cu-doped bulk ceria are presented. The first oxygen vacancy in Cu-doped ceria forms almost spontaneously and the second vacancy is also easily created. Whether zero, one or two oxygen vacancies, the Cu dopant is in the form Cu(+ II), and prefers to be 4-coordinated in a close to planar structure. Charge compensation, structural relaxation and available Cu-O states all play roles in lowering the O vacancy formation energies, but to different degrees when the first and second oxygen vacancies are formed. The Cu-doped ceria(1 1 1) surface system behaves in a similar fashion.

  • 30.
    Malyarenko, Anatoliy
    et al.
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Ostoja-Starzewski, M.
    University of Illinois at Urbana-Champaign, Urbana, IL, United States.
    Amiri-Hezaveh, A.
    University of Illinois at Urbana-Champaign, Urbana, IL, United States.
    The Continuum Theory of Piezoelectricity and Piezomagnetism2020In: SpringerBriefs in Applied Sciences and Technology, Springer Science and Business Media Deutschland GmbH , 2020, p. 1-24Chapter in book (Refereed)
    Abstract [en]

    Following the motivation of this work, this chapter introduces the basic concepts of continuum mechanics and electromagnetism. Attention is then focused on linear piezoelectricity, elaborating two ways of writing the governing equations: the displacement approach and the stress approach. This leads to variational principles. The final section provides a basis for generalising piezoelectricity—and, by mathematical analogy, piezomagnetism—to random media whose description necessitates tensor-valued random fields.

  • 31.
    Malyarenko, Anatoliy
    et al.
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Ostoja-Starzewski, Martin
    University of Illinois at Urbana-Champaign, USA.
    Fractal planetary rings: energy inequalities and random field model2017In: International Journal of Modern Physics B, ISSN 0217-9792, Vol. 31, no 30, article id 1750236Article in journal (Refereed)
    Abstract [en]

    This study is motivated by a recent observation, based on photographs from the Cassini mission, that Saturn’s rings have a fractal structure in radial direction. Accordingly, two questions are considered: (1) What Newtonian mechanics argument in support of such a fractal structure of planetary rings is possible? (2) What kinematics model of such fractal rings can be formulated? Both challenges are based on taking planetary rings’ spatial structure as being statistically stationary in time and statistically isotropic in space, but statistically nonstationary in space. An answer to the first challenge is given through an energy analysis of circular rings having a self-generated, noninteger-dimensional mass distribution [V. E. Tarasov, Int. J. Mod Phys. B 19, 4103 (2005)]. The second issue is approached by taking the random field of angular velocity vector of a rotating particle of the ring as a random section of a special vector bundle. Using the theory of group representations, we prove that such a field is completely determined by a sequence of continuous positive-definite matrix-valued functions defined on the Cartesian square F^2 of the radial cross-section F, where F is a fat fractal.

  • 32.
    Malyarenko, Anatoliy
    et al.
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Ostoja-Starzewski, Martin
    University of Illinois at Urbana-Champaign.
    Tensor Random Fields in Continuum Mechanics2020In: Encyclopedia of Continuum Mechanics / [ed] Altenbach, Holm and Öchsner, Andreas, Berlin, Heidelberg: Springer Berlin/Heidelberg, 2020, p. 2433-2441Chapter in book (Refereed)
  • 33.
    Malyarenko, Anatoliy
    et al.
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Ostoja-Starzewski, Martin
    University of Illinois at Urbana-Champaign, USA.
    Tensor-Valued Random Fields in Continuum Physics2016In: Materials with internal structure: Multiscale and Multifield Modeling and Simulation / [ed] P. Trovalusci, Berlin/Heidelberg: Springer Science+Business Media B.V., 2016, p. 75-88Chapter in book (Refereed)
    Abstract [en]

    This article reports progress on homogeneous isotropic tensor random fields (TRFs) for continuum mechanics. The basic thrust is on determinin most general representations of the correlation functions as well as their spectral expansions. Once this is accomplished, the second step is finding the restrictionsdictated by a particular physical application. Thus, in the case of fields of material properties (like conductivity and stiffness), the restriction resides in the positive-definiteness, whereby a connection to experiments and/or computational micromechanics can be established. On the other hand, in the case of fields of dependent properties (e.g., stress, strain and displacement), restrictions are due to the respective field equations.

  • 34.
    Manjunath, A.
    et al.
    Government PU College Shahapur, Yadgiri, Karnataka, India.
    Mahalesh, D.
    Gulbarga University, Gulbarga, Karnataka, India.
    Biradar, B.
    B. V. Bhoomaraddi Degree College, Bidar, Karnataka, India.
    Kerur, B. R.
    Gulbarga University, Gulbarga, Karnataka, India.
    Pushpanjali, Gurubasappa Metri
    Mälardalen University. Sangameshwar College, Solapur, Maharashtra, India.
    Study of Rayleigh to Compton Scattering Ratio and Effective Atomic Number as a Function of Photon Energy and Scattering Angle2019In: Macromolecular Symposia, ISSN 1022-1360, E-ISSN 1521-3900, Vol. 387, no 1, article id 1900017Article in journal (Refereed)
    Abstract [en]

    For photon energies below 1 MeV the predominant phenomenon involved is photoelectric absorption, coherent scattering (Rayleigh), and incoherent scattering (Compton). Biological samples with small thickness attenuate the transmitted beam very little and the application of transmission technique is not possible, when atomic number variations are more significant. Indeed, the Rayleigh to Compton scattering ratio enables the material to be characterized only by its atomic number, independent of the material density or of the attenuation inside the tested object. Hence, evaluation of the parameter “effective atomic number” is still necessary to characterize the measurement sensibility and to establish a correlation with the estimated Rayleigh to Compton scattering ratio.

  • 35.
    Monsefi, Farid
    et al.
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Otterskog, Magnus
    Mälardalen University, School of Innovation, Design and Engineering. Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Silvestrov, Sergei
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Direct and Inverse Computational Methods for Electromagnetic Scattering in Biological Diagnostics2013Report (Other academic)
    Abstract [en]

    Scattering theory has had a major roll in twentieth century mathematical physics. Mathematical modeling and algorithms of direct,- and inverse electromagnetic scattering formulation due to biological tissues are investigated. The algorithms are used for a model based illustration technique within the microwave range. A number of methods is given to solve the inverse electromagnetic scattering problem in which the nonlinear and ill-posed nature of the problem are acknowledged.

  • 36.
    Niedderer, Hans
    et al.
    Mälardalen University, School of Education, Culture and Communication. Mälardalen University, Department of Mathematics and Physics.
    Budde, Marion
    Givry, Damien
    Psillos, Dimitris
    Tiberghien, Andree
    Learning process studies2007In: Contributions from Science Education Research / [ed] R. Pinto, Springer, The Netherlands , 2007, p. 159-171Chapter in book (Other (popular science, discussion, etc.))
    Abstract [en]

    Learning processes will be analysed as “evolution of student’s ideas” or as “conceptual change” on a timescale of several hours. The idea is to follow a single student’s constructions “during” the whole process of learning in more detail, including analyses of learning effects. The paper in part two discusses theoretical and methodological issues of such learning process studies. Here, the focus is on the unit of analysis (expressed ideas or conceptions) and on the relation between teaching and learning. In part three, a more recent study about the evolution of students’ ideas about gases is presented, describing learning by using three categories: A student expresses a new idea, a student increases the domain of validity of an idea, or a student establishes a link between several ideas and develops a network. In part four, another more recent study about analysing learning effects of the learning environment on single students learning is presented. Here, different types of resonances are used as categories, e.g. congruent or disgruent resonance, spontaneous or retarded resonance. Both studies come to grounded hypotheses how to improve teaching. In part five, more general issues about learning process studies are discussed.

  • 37. Nilson, Katharina
    et al.
    Palmgren, Pål
    Åhlund, John
    Schiessling, Joachim
    Göthelid, Emmanuelle
    Mälardalen University, School of Sustainable Development of Society and Technology. Mälardalen University, Department of Biology and Chemical Engineering.
    Mårtensson, Nils
    Puglia, Carla
    Göthelid, Mats
    STM and XPS characterization of zinc phthalocyanine on InSb(0 0 1)2008In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 602, no 2, p. 452-459Article in journal (Other (popular science, discussion, etc.))
    Abstract [en]

    Zinc phthalocyanine (ZnPc) adsorbed on the InSb(0 0 1)-c(8 × 2) surface has been studied by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). Coverages from sub-monolayer to monolayer (ML) have been investigated. The molecules form ordered structures on the reconstructed rows of the surface with the molecular plane parallel to the surface. A change in the electronic structure between the sub-ML and higher coverages has been observed. Moreover, in order to study the influence of annealing on the electronic and geometric structures, the samples have been heated to elevated temperatures (about 640 K). In addition, multi-layer ZnPc films have been characterized by XPS measurements.

  • 38.
    Ostoja-Starzewski, Martin
    et al.
    University of Illinois in Urbana-Champaigne, USA.
    Malyarenko, Anatoliy
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Continuum Mechanics beyond the Second Law of Thermodynamics2014In: Proceedings of the Royal Society. Mathematical, Physical and Engineering Sciences, ISSN 1364-5021, E-ISSN 1471-2946, Vol. 1470, no 2171, p. 1-17, article id 20140531Article in journal (Refereed)
    Abstract [en]

    The results established in contemporary statistical physics indicating that, on very small space and time scales, the entropy production rate may be negative, motivate a generalization of continuum mechanics. On account of the fluctuation theorem, it is recognized that the evolution of entropy at a material point is stochastically (not deterministically) conditioned by the past history, with an increasing trend of average entropy production. Hence, the axiom of Clausius-Duhem inequality is replaced by a submartingale model, which, by the Doob decomposition theorem, allows classification of thermomechanical processes into four types depending on whether they are conservative or not and/or conventional continuum mechanical or not. Stochastic generalizations of thermomechanics are given in the vein of either thermodynamic orthogonality or primitive thermodynamics, with explicit models formulated for Newtonian fluids with, respectively, parabolic or hyperbolic heat conduction. Several random field models of the martingale component, possibly including spatial fractal and Hurst effects, are proposed. The violations of the second law are relevant in those situations in continuum mechanics where very small spatial and temporal scales are involved. As an example, we study an acceleration wavefront of nanoscale thickness which randomly encounters regions in the medium characterized by a negative viscosity coefficient.

  • 39.
    Pettersson, Linda
    et al.
    Mälardalen University, School of Education, Culture and Communication.
    Edstein, Rebecca
    Mälardalen University, School of Education, Culture and Communication.
    Krafter och rörelser i lekparken, utomhusmiljön och klassrummet i årskurs 1-3: En studie med en kvalitativ metod om lärares undervisningsmetoder2021Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Syftet med studien är att undersöka vilka undervisningsmetoder som lärare tillämpar i undervisningen om krafter och rörelser. Datainsamlingsmetoden som ligger till grund för studien är en digital enkät som består av öppna frågor och har besvarats av tio personer. Insamlat datamaterial har bearbetats utifrån en tematisk analysmetod och diskuterats utifrån tidigare forskning och teoretisk utgångspunkt. Denna studie utgår ifrån ett sociokulturellt perspektiv. Undervisningsmiljöer såsom lekparken, utomhusmiljön och klassrummet är tre miljöer som kan tillämpas som resurs för undervisningen om krafter och rörelser. Miljöerna tillämpas på ett varierat sätt utifrån olika lärare som deltagit i studien. Lekaprken anses som en lärorik miljö för undervisningen medan skogen som utomhusmiljö anses lärorik men tillämpas mer sällan. Slutsatsen är att lärare tillämpar lekaprken och klassrummet som undervisningsmiljö men att den påverkas av lärarens kompetens och tolkning av läroplanen om hur ofta och mycket metoden används. Lärarna i studien anser dock att varierande arbetssätt ökar elevens lärande och konkretiseringen av de abstrakta fysikaliska begreppen. 

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  • 40.
    Prytz, Kjell
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    A laborative model of geomagnetism as an example of creative learning2015In: Physics Education, ISSN 0031-9120, E-ISSN 1361-6552, Vol. 50, no 6, p. 699-705Article in journal (Refereed)
    Abstract [en]

    Creative learning is discussed with respect to a specific physics topic. A teaching example, based on an apparatus that demonstrates the standard dynamo model of geomagnetism, is presented. It features many of the basic physics concepts within the syllabus of electromagnetism at high-school and university.

    To stimulate conceptual learning and to invite student explorations, the apparatus is designed to exhibit simplicity and transparency. Due to the connection to natural phenomena and to engineering applications it promotes a holistic view of physics. The apparatus is therefore useful for practising creative learning.

  • 41.
    Prytz, Kjell
    Högskolan i Gävle, Ämnesavdelningen för naturvetenskap.
    Analysis of the QCD Evolution in the Pomeron and a Search for Gluon Recombination2002Report (Other academic)
  • 42.
    Prytz, Kjell
    Högskolan i Gävle, Ämnesavdelningen för naturvetenskap.
    Analysis of the QCD evolution in the pomeron and a search for gluon recombination2002In: Journal of Physics G: Nuclear and Particle Physics, ISSN 0954-3899, E-ISSN 1361-6471, Vol. 29, no 2, p. 285-291Article in journal (Refereed)
    Abstract [en]

    The pomeron structure function is-extracted from the HI data and is subject to a leading-order QCD analysis. We compare the results obtained from the DGLAP equations with and without corrected for gluon recombination. Both cases give good fits to data but different results for the gluon distribution.

  • 43.
    Prytz, Kjell
    Högskolan i Gävle, Avdelningen för elektronik, matematik och naturvetenskap.
    Electrodynamics: the field-free approach: Electrostatics, magnetism, induction, relativity and field theory2015 (ed. 1)Book (Refereed)
    Abstract [en]

    This book is intended as an undergraduate textbook in electrodynamics at basic or advanced level. The objective is to attain a general understanding of the electrodynamic theory and its basic experiments and phenomena in order to form a foundation for further studies in the engineering sciences as well as in modern quantum physics.

    The outline of the book is obtained from the following principles:

    •         Base the theory on the concept of force and mutual interaction

    •         Connect the theory to experiments and observations accessible to the student

    •         Treat the electric, magnetic and inductive phenomena cohesively with respect to force, energy, dipoles and material

    •         Present electrodynamics using the same principles as in the preceding mechanics course

    •         Aim at explaining that theory of relativity is based on the magnetic effect

    •         Introduce field theory after the basic phenomena have been explored in terms of force

    Although electrodynamics is described in this book from its 1st principles, prior knowledge of about one semester of university studies in mathematics and physics is required, including vector algebra, integral and differential calculus as well as a course in mechanics, treating Newton’s laws and the energy principle.

    The target groups are physics and engineering students, as well as professionals in the field, such as high school teachers and employees in the telecom industry. Chemistry and computer science students may also benefit from the book.

  • 44.
    Prytz, Kjell
    Högskolan i Gävle, Ämnesavdelningen för naturvetenskap.
    Electrolocation of the Weak Electric Fish2004Report (Other academic)
  • 45.
    Prytz, Kjell
    Högskolan i Gävle, Avdelningen för elektronik, matematik och naturvetenskap.
    Elektrodynamik i nytt ljus: elektrostatik, magnetism, induktion och relativitetsteori2013 (ed. 1)Book (Refereed)
    Abstract [sv]

    Det är kanske inte helt enkelt att ge en allmänt accepterad definition av ämnet fysik. Både uppslagsböcker och fysiker ger skiftande svar på frågan. Min egen uppfattning är att fysik handlar om och utgår ifrån begreppet kra  vilket tillsammans med begreppet energi bildar dess kärna. Särskilt vill jag framhålla den definition som anges av Bonniers svenska ordbok: Fysik är "vetenskapen om naturkrafterna och energin i dess olika former". Min strävan är att låta denna definition löpa som en röd tråd i undervisningen och i denna bok.

    Innehåll

    Vi lägger därför största vikt på kraftbegreppet och dess konsekvens: växelverkningen. I första kapitlet (kapitel 2) fokuserar vi på de olika slag av kraftverkan som förekommer mellan elektriska laddningar vilka direkt kan relateras till deras rörelse, dvs. laddningar i vila, i likformig rörelse och i acceleration. Dessa krafter benämns elektrisk, magnetisk respektive induktiv. Vi behandlar alltså dessa växelverkningar sammanhållet och formulerar de kraftformler som beskriver observationer och mätningar.

    De följande kapitlen är mer eller mindre raka tillämpningar av kraftformlerna. Begreppet energi, som införs i kapitel 3, utgår ifrån och är en direkt konsekvens av kraft via begreppet arbete. Vi visar hur denna princip tillämpas för både elektrisk och magnetisk energi. Kapitel 4 behandlar makroskopiska system vars egenskaper erhålls via en summering av ömsesidiga växelverkningar mellan infinitesimala element. I tillämpningar är systemen ofta homogena och beräkningarna kan då förenklas med hjälp av de geometriska kvantiteterna kapacitans och induktans. I kapitel 5 och 6 diskuteras ledaren och elektriska kretsar vilket utgör den experimentella miljö ur vilken elektrodynamiken har utvecklats och tekniska tillämpningar har sitt ursprung. Vi behandlar först den mikroskopiska beskrivningen av elektrisk ledning, resistansens ursprung och dess relation till värmeutveckling. Vidare diskuteras resonanskretsen och de övriga två kretskomponenterna: kapacitans och induktans.

    I kapitel 7 introduceras den elektriska och magnetiska dipolen, väsentliga begrepp eftersom naturen vanligen är konstruerad eller kan åtminstone approximeras till att bestå av dylika objekt. Centralt är då uttrycken för elektrisk och magnetisk dipol-dipolväxelverkan. Dessa är fundamentala för naturens dynamik. I kapitel 8 studerar vi hur olika elektriskt och magnetiskt neutrala material responderar på elektrisk och magnetisk påverkan och utgår då ifrån att materialet är uppbyggt av dipoler. Den matematiskt strikta behandlingen av dipol-, eller generellt multipol-, växelverkan presenteras i tillhörande appendix A och B.

    I kapitel 9 visar vi konceptuellt hur den magnetiska och induktiva dynamiken följer som rörelsekonsekvenser av den elektriska under antagandet att växelverkningar tar tid, de förmedlas med ljusets fart. Alternativt kan man utifrån kännedom om elektrisk och magnetisk kraft härleda ljusets fart. Vi kommer i ett specialfall kunna härleda såväl den magnetiska kraften som Faraday- Henrys induktionslag. Vidare visas hur elektrodynamiken är relaterad till relativitetsteorin. Faktum är att magnetism är den rörelsekonsekvens på vilken den speciella relativitetsteorin baseras. Eftersom vi utgår ifrån begreppet kraft är materialet unikt för denna bok.

    I kapitel 9 introduceras också Lorentz-tranformationer i form av en handledning för att självständigt kunna utveckla denna den formella basen för speciell relativitetsteori. Förkunskaper till kapitel 9 är endast kapitel 1-3 varför dessa fyra kapitel kan utgöra en kortkurs inom basal elektrodynamik och dess relation till relativitetsteori. I kapitel 10, slutligen, introduceras fältteorin för elektrodynamiken vilket leder oss till Maxwells ekvationer, grunden för den elektrobaserade ingenjörsvetenskapen. Fälten är förvisso redan definierade genom kraftformlerna, men uttrycks i Maxwells ekvationer som sin divergens och rotation. Vi motiverar detta genom att visa att fältens randvillkor är på så sätt givna.

    Ett viktigt särdrag hos denna bok är sålunda att fältteorin introduceras det att de fysiska fenomen som utgör elektrodynamiken beskrivits, tolkats och behandlats i termer av de grundläggande krafterna.

  • 46.
    Prytz, Kjell
    Högskolan i Gävle, Ämnesavdelningen för naturvetenskap.
    Evidence for Gluon Recombination in Deep Inelastic Scattering2001Report (Other academic)
  • 47.
    Prytz, Kjell
    Högskolan i Gävle, Ämnesavdelningen för naturvetenskap.
    Gravitationen, Elektromagnetismen, Kvantmekaniken och Ljuset2001Report (Other academic)
  • 48.
    Prytz, Kjell
    Högskolan i Gävle, Ämnesavdelningen för naturvetenskap.
    Gravitationen, Elektromagnetismen, Kvantmekaniken och Ljuset2001Report (Other academic)
  • 49.
    Prytz, Kjell
    Högskolan i Gävle, Ämnesavdelningen för naturvetenskap.
    Gravitationen, elektromagnetismen, kvantmekaniken och ljuset2001In: Elementa : tidskrift för matematik, fysik och kemi, ISSN 0013-5933, Vol. 84, no 3, p. 103-114Article in journal (Other academic)
  • 50.
    Prytz, Kjell
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Introducing Magnetism - an Alternative2020In: Physics Education, ISSN 0031-9120, E-ISSN 1361-6552, Vol. 55, no 6, article id 065004Article in journal (Refereed)
    Abstract [en]

    An alternative way of introducing magnetism at all levels of education isproposed. It is stressed that magnetism can be introduced through theinteraction between current-carrying conductors giving the students, at thesame time, the possibility to measure the magnetic permeability μo. Focusingon currents instead of permanent magnets provides a pathway to explore thefull dynamics between the basic constituents, i.e. the elementary charges. Italso connects better to some modern applications of magnetism such as thedefinition of mass, which utilizes a current balance and the link betweenmagnetism and special relativity

12 1 - 50 of 73
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