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  • 51.
    Händel, Peter
    et al.
    Department of Information Science and Engineering, KTH Royal Institute of Technology, Stockholm, Sweden.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Electronics.
    Modeling Mixer and Power Amplifier Impairments2019In: IEEE Microwave and Wireless Components Letters, ISSN 1531-1309, E-ISSN 1558-1764, Vol. 29, no 7, p. 441-443, article id 8733818Article in journal (Refereed)
    Abstract [en]

    Combating the effects of mixer and power amplifier (PA) imperfections on transmitter performance is crucial for the design of wireless systems. PA compression and in-phase/quadrature imbalance are analyzed for a single-input-single-output transmitter model. The influence of the imperfection on the normalized mean squared error (NMSE) of the transmitter is studied using an analytical framework that relies on the classic Bussgang theory. The study concludes with a closed-form expression for the NMSE that provides insights into the behavior of the transmitter. © 2019 IEEE.

  • 52.
    Ivanchenko, Igor
    et al.
    O.Ya. Usikov Institute for Radiophysics and Electronics of the National Academy of Sciences of Ukraine, Ukraine.
    Khruslov, Maksym
    O.Ya. Usikov Institute for Radiophysics and Electronics of the National Academy of Sciences of Ukraine, Ukraine.
    Popenko, Nina
    O.Ya. Usikov Institute for Radiophysics and Electronics of the National Academy of Sciences of Ukraine, Ukraine.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Electronics.
    Combined L–S-bands antenna module2019In: IET Microwaves, Antennas & Propagation, ISSN 1751-8725, E-ISSN 1751-8733, Vol. 13, no 5, p. 541-545Article in journal (Refereed)
    Abstract [en]

    A combined L-S-band antenna module consists of four rectangular patch antennas, two of which operate at the frequencies of the first harmonics (L-band), and two others at the frequencies of the second harmonics (S-band). The module is intended for use in super heterodyne signal reception circuits, for example in studying the various non-linear phenomena. The results of this study are presented in terms of improving the performance of each antenna and minimising their mutual influence. The resonance frequencies of the L-band antenna differ by 50MHz. All the antennas radiate close to the zenith and their beamwidths in two principal planes are virtually the same. At the resonance frequencies, the reflection coefficient is S-11<-30dB for the transmitting antenna, and S-11<-20dB for the receiving antenna. The minimum allowable distance between the antennas is determined, at which their mutual influence can be neglected (S-12<-50dB).

  • 53.
    Ivarsson, Lena Norback
    et al.
    Sodertorn Univ, Sch Nat Sci Technol & Environm Studies, Huddinge, Sweden..
    Andren, Thomas
    Sodertorn Univ, Sch Nat Sci Technol & Environm Studies, Huddinge, Sweden..
    Moros, Matthias
    Leibniz Inst Baltic Sea Res Warnemunde, Rostock, Germany..
    Andersen, Thorbjorn Joest
    Univ Copenhagen, Dept Geosci & Nat Resource Management, Copenhagen, Denmark..
    Lönn, Mikael
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Biology. Södertörn Univ.
    Andren, Elinor
    Sodertorn Univ, Sch Nat Sci Technol & Environm Studies, Huddinge, Sweden..
    Baltic Sea Coastal Eutrophication in a Thousand Year Perspective2019In: Frontiers in Environmental Science, ISSN 2296-665X, Vol. 7, article id 88Article in journal (Refereed)
    Abstract [en]

    Sediment cores from three sites along the east-coast of Sweden, north-western Baltic Proper, have been studied with respect to lithologies, geochemistry, and diatom assemblages to trace and date early human impact with emphasis on nutrient discharge. The three sites Braviken, Himmerfjarden, and Adfjarden, have been impacted to various degree during the last millennia by multiple stressors like excessive nutrient discharge and hazardous substances, leading to coastal hypoxia, eutrophication, and pollution. These stressors are mainly caused by drivers in the drainage area as increased human population, changed land use, and point sources as industries and a sewage treatment plant. Even though their detailed history differs, the results show similar general patterns for all three sites. We find no evidence in our data from the coastal zone supporting the hypothesis that the extensive areal distribution of hypoxia in the open Baltic Sea during the Medieval Climate Anomaly was caused by human impact. Timing of the onset of man-made eutrophication, as identified from delta N-15 and changes in diatom composition, differs between the three sites, reflecting the site specific geography and local environmental histories of these areas. The onset of eutrophication dates to similar to 1800 CE in Braviken and Himmerfjarden areas, and to similar to 1900 CE in the less urban area of Adfjarden. We conclude that the recorded environmental changes during the last centuries are unique in a thousand year perspective.

  • 54.
    Jerez-Hanckes, C.
    et al.
    Universidad Adolfo Ibáñez Diagonal Las Torres, Peñalolén, Santiago, 2700, Chile.
    Pettersson, Irina
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Mathematics.
    Rybalko, V.
    B. Verkin Institute for Low Temperature Physics and Engineering of NASU, 47 Nauky Ave., Kharkiv, 61103, Ukraine.
    Derivation of cable equation by multiscale analysis for a model of myelinated axons2020In: Discrete and continuous dynamical systems. Series B, ISSN 1531-3492, E-ISSN 1553-524X, Vol. 25, no 3, p. 815-839Article in journal (Refereed)
    Abstract [en]

    We derive a one-dimensional cable model for the electric potential propagation along an axon. Since the typical thickness of an axon is much smaller than its length, and the myelin sheath is distributed periodically along the neuron, we simplify the problem geometry to a thin cylinder with alternating myelinated and unmyelinated parts. Both the microstructure period and the cylinder thickness are assumed to be of order ε, a small positive parameter. Assuming a nonzero conductivity of the myelin sheath, we find a critical scaling with respect to ε which leads to the appearance of an additional potential in the homogenized nonlinear cable equation. This potential contains information about the geometry of the myelin sheath in the original three-dimensional model. 

  • 55.
    Johansson, Anders
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Mathematics.
    Öberg, Anders
    Uppsala University.
    Pollicott, Mark
    University of Warwick, Coventry, UK.
    Phase transitions in long-range Ising models and an optimal condition for factors of g-measures2019In: Ergodic Theory and Dynamical Systems, ISSN 0143-3857, E-ISSN 1469-4417, Vol. 39, no 5, p. 1317-1330Article in journal (Refereed)
    Abstract [en]

    We weaken the assumption of summable variations in a paper by Verbitskiy [On factors of g-measures. Indag. Math. (N.S.) 22 (2011), 315-329] to a weaker condition, Berbee's condition, in order for a one-block factor (a single-site renormalization) of the full shift space on finitely many symbols to have a g-measure with a continuous g-function. But we also prove by means of a counterexample that this condition is (within constants) optimal. The counterexample is based on the second of our main results, where we prove that there is a critical inverse temperature in a one-sided long-range Ising model which is at most eight times the critical inverse temperature for the (two-sided) Ising model with long-range interactions.

  • 56.
    Johansson, Gustav
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Electronics.
    Grunden till en simulering av batterier och batterisystem2019Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
  • 57.
    Johansson, Sophie
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science.
    Läromedelsbokens tillämpning i NO-undervisningen för årskurs 1–3: – en läromedelsanalys samt webbenkät kopplad till läroplanens centrala innehåll för de naturorienterande ämnena i grundskolans tidigare år2019Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    I denna undersökning så har en läromedelsanalys samt en enkätundersökning genomförts i syfte om att studera hur väl anknutna läromedelsböcker för de naturorienterande ämnena (NO) är till den svenska läroplanen Lgr11. Två läromedelsböcker har analyserats för att undersöka hur läroplanens centrala innehåll avseende naturorienterande ämnen behandlas och om det finns någonting som har uteslutits. NO-undervisningen ska behandla ämnena fysik, kemi och biologi. Det finns däremot inga nationella riktlinjer om hur undervisningstiden i de naturorienterande ämnena för årskurs 1–3 ska fördelas på dessa tre ämnena. Analys av hur läroplanens centrala innehåll i NO behandlas i läromedelsböcker visar att de olika rubrikerna från det centrala innehållet prioriteras olika högt. De punkter som handlar om djur och natur behandlas i mycket större grad än de övriga punkterna. Ämnet biologi får större plats i NO-undervisningen för årskurs 1–3 jämfört med ämnena kemi och fysik. De tillfrågade lärarna anser att läromedelsböcker ofta har tydliga kopplingar till läroplanen, speciellt det centrala innehållet, och att de flesta lärare ser stora fördelar i att använda sig av en läromedelsbok i sin NO-undervisning tillsammans med kompletterande material i form av filmer, experiment och liknande. 

  • 58.
    Kaltenböck, Viktor
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Electronics.
    Measurement system for low frequency and low amplitude AC voltage of given frequency2019Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This work is about digital signal processing methods to be used to determine information of low frequency low amplitude signals of known frequency. Different adaptive filter concepts such as Wiener filter, NLMS filter and lock-in are implemented and compared to each other. The comparison carried out for different input signal amplitude and noise variance with the objective to find the best algorithm for noise cancelling. The comparison is done using a signal of interest combined with white noise as input to the filter element. The aim of the comparison is to find the most appropriate filter for further signal analyzis. The key topics for the evaluation are the efficiency of noise cancelling and ease of implementation in a data processing unit.

  • 59.
    Karlsson, Camilla
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science.
    Digitala verktyg och spelifiering i matematikundervisning inriktning grundskolan f-32019Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    På grund av digitaliseringskravet i läroplanen för årskurs f-3 och spelifieringens utveckling avinteraktiva program så har arbetet fokuserat på hur och i vilket syfte digitala verktyg användsinom matematikundervisningen i grundskolan f-3 samt om lärares kunskap om spelifieringkan påverka elevers resultat när de arbetar med interaktiva program inom matematiken.Undersökningar gjordes via en enkät och intervjuer med fyra verksamma lärare med olikabakgrund. Resultatet visade att digitala verktyg används ofta i matematikundervisningen ochatt den största anledningen till det var i motivationssyfte samt att det går att individualiserauppgifter. Begreppet spelifiering hade lärarna inte full kunskap om, men de var överens omatt det är viktigt för lärare att lära sig mer om begreppet för att kunna maximera sinmatematikundervisning. Den viktigaste slutsatsen blev att spelifiering är något som läraremåste komplettera sin kunskap om för att matematikundervisningen ska bli bättre samt merindividualiserad.

  • 60.
    Kellner, Eva
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Biology.
    Attorps, Iris
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Mathematics.
    The school–university intersection as a professional learning arena: evaluation of a two-year action research project2019In: Teacher Development, ISSN 1366-4530, E-ISSN 1747-5120Article in journal (Refereed)
  • 61.
    Khulbe, Manisha
    et al.
    Ambedkar Institute of Advanced Communication Technologies and Research (AIACTR), Delhi, India.
    Tripathy, Malay Ranjan
    Amity School of Engineerng and Technology, Amity University, Noida, India.
    Parthasarathy, Harish
    Netaji Subhash Institute of Technology (NSIT), N. Delhi, India.
    Shestopalov, Yury
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Mathematics.
    Lagovsky, Boris
    Russian Technological University, MIREA, Moscow, Russia.
    Inverse Scattering and Imaging Using Second Order Optical Nonlinearities2019In: 2019 6th International Conference on Signal Processing and Integrated Networks, SPIN 2019, IEEE, 2019, p. 1086-1089Conference paper (Refereed)
    Abstract [en]

    In this paper a mathematical technique is developed to find the parameters of a medium in terms of its scattered electromagnetic fields. Optical nonlinearity plays an important role in finding the scattering parameters of a medium. Using perturbation theory and nonlinear inverse scattering techniques with first order, second order and third order optical nonlinearity we find scattered electromagnetic fields. Using error minimization techniques parameters are estimated in term of permittivity and permeability up to second order. © 2019 IEEE.

  • 62.
    Kimsis, Karlis
    et al.
    Riga Technical University.
    Semenjako, Janis
    Riga Technical University.
    Shestopalov, Yury
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Mathematics.
    Mechanically tunable coupled resonator waveguide bandpass filter2019In: 2019 IEEE Microwave Theory and Techniques in Wireless Communications (MTTW), 2019, Vol. 1, p. 52-56Conference paper (Refereed)
    Abstract [en]

    This paper proposes a novel mechanically tunable waveguide filter design, based on a coupled resonator topology. The resonator geometry consists of a rectangular waveguide cavity and a dielectric cylinder. Unlike conventional cylindrical resonators which are made out of a single part, here the cylinders are cut in half. By changing the distance between these two parts, the resonating frequency of the resonator can be changed, which allows for a tunable filter design. A filter using the proposed geometry has a large tuning bandwidth as well as relatively constant passband frequencies. The performance of the proposed filter is demonstrated by evaluating the filter using 3D simulation software CST Studio Suite.

  • 63.
    Krishnan, Rakesh
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Electronics. Robotics, Perception and Learning, School of Computer Science and Communication, KTH - Royal Institute of Technology, Stockholm, Sweden; BioMEx Center, Royal Institute of Technology (KTH), Stockholm, Sweden.
    Björsell, Niclas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Electronics.
    Gutierrez-Farewik, Elena
    KTH Engineering Sciences, Mechanics, Royal Institute of Technology (KTH), Stockholm, Sweden; BioMEx Center, Royal Institute of Technology (KTH), Stockholm, Sweden .
    Smith, Christian
    Robotics, Perception and Learning, School of Computer Science and Communication, KTH - Royal Institute of Technology, Stockholm, Sweden; BioMEx Center, Royal Institute of Technology (KTH), Stockholm, Sweden.
    A survey of human shoulder functional kinematic representations2019In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 57, no 2, p. 339-367Article, review/survey (Refereed)
    Abstract [en]

    In this survey, we review the field of human shoulder functional kinematic representations. The central question of this review is to evaluate whether the current approaches in shoulder kinematics can meet the high-reliability computational challenge. This challenge is posed by applications such as robot-assisted rehabilitation. Currently, the role of kinematic representations in such applications has been mostly overlooked. Therefore, we have systematically searched and summarised the existing literature on shoulder kinematics. The shoulder is an important functional joint, and its large range of motion (ROM) poses several mathematical and practical challenges. Frequently, in kinematic analysis, the role of the shoulder articulation is approximated to a ball-and-socket joint. Following the high-reliability computational challenge, our review challenges this inappropriate use of reductionism. Therefore, we propose that this challenge could be met by kinematic representations, that are redundant, that use an active interpretation and that emphasise on functional understanding.

  • 64.
    Krishnan, Rakesh
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Electronics.
    Cruciani, Silvia
    KTH, Stockholm, Sweden.
    Gutierrez-Farewik, Elena M
    KTH, Stockholm, Sweden.
    Björsell, Niclas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Electronics.
    Smith, Christian
    KTH, Stockholm, Sweden.
    Reliably Segmenting Motion Reversals of a Rigid-IMU Cluster Using Screw-Based Invariants2019In: 2018 IEEE-RAS 18TH INTERNATIONAL CONFERENCE ON HUMANOID ROBOTS (HUMANOIDS), 2019, p. 88-95, article id 8624969Conference paper (Refereed)
    Abstract [en]

    Human-robot interaction (HRI) is moving towards the human-robot synchronization challenge. In robots like exoskeletons, this challenge translates to the reliable motion segmentation problem using wearable devices. Therefore, our paper explores the possibility of segmenting the motion reversals of a rigid-IMU cluster using screw-based invariants. Moreover, we evaluate the reliability of this framework with regard to the sensor placement, speed and type of motion. Overall, our results show that the screw-based invariants can reliably segment the motion reversals of a rigid-IMU cluster.

  • 65.
    Käck, Caroline
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science.
    Programmeringskompetens ur ett genusperspektiv - bland elever och lärare2019Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 66.
    Lagovsky, B. A.
    et al.
    Russian Technological University (MIREA), Moscow, Russia.
    Samokhin, A. B.
    Russian Technological University (MIREA), Moscow, Russia.
    Shestopalov, Yury V.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Mathematics.
    Regression Methods of Obtaining Angular Superresolution2019In: 2019 URSI Asia-Pacific Radio Science Conference (AP-RASC), New Dehli: IEEE, 2019, article id 8738539Conference paper (Refereed)
    Abstract [en]

    New methods of signal processing based on nonlinear regression methods are presented. They allow us to restore images of individual objects of group targets with superresolution at signal-to-noise ratios that are significantly lower than those provided by the known methods.

  • 67.
    Larsson, Marina
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science.
    Teknikintresse i grundskolans lägre åldrar: Påverkansfaktorer för elevers intresse och motivation inom teknikämnet i grundskolans tidigare år2019Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Denna studie syftar till att undersöka vilka elever som gynnas respektive missgynnas av teknikundervisningen i skolans tidigare år, vad det är som påverkar motivation och intresse för teknik under dessa år samt vilken sorts undervisning eleverna möter i klassrummet idag. Studien syftar också till att undersöka huruvida det finns någon könsskillnad gällande teknikintresse hos de yngre eleverna.

    Grounded Theory användes som analysmetod för studien, som utmynnade i en teoretisk modell.

    Resultatet av studien visar att majoriteten av eleverna i förskoleklass ännu inte fått en bild av teknikbegreppet. Den undervisning eleverna mött i teknik har antingen varit integrerad i övrig undervisning eller ytterst begränsad. Elevernas upplevelser har inte alltid kopplats samman med begreppen. Lärarna upplever en otrygghet med att undervisa i teknik.

    Någon könsskillnad menade varken elever eller lärare att det skulle finnas gällande teknikintresset, men studien visar att de drömyrken samt fritidsintressen eleverna redovisat tenderar att vara könsstereotypa.

  • 68.
    Lie, Amber
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science.
    Vad har lärare för förutsättningar att undervisa i programmering?2019Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 69.
    Liljemark, Mathilda
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science.
    Bärande begrepp i biologi: En analys av läroplanen i biologi, skolans läroböcker och lärares läromedel i biologi2019Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Studiens syfte var att lyfta fram centrala begrepp i biologi utifrån det centrala innehållet i Lgr11 och se hur läromedel och lärares kursläromedel behandlar dessa begrepp. Begreppen som förekom delades upp tematiskt och ett av de teman som förekom var hållbar utveckling. Temat bestod av sex stycken begrepp och genom dessa begrepp och studiens litteraturanalys behandlades relationen mellan Lgr 11, läromedel och lärares kursläromedel. Fem läromedel för elever och 4 kursläromedel för lärare behandlas i studien.  Resultatet visar att elevers läromedel och lärares kursläromedel behandlar temat hållbar utvecklings begrepp med stor variation. Genom detta påvisar resultatet att relationen mellan Lgr11, läromedel och kursläromedel är varierande. Sammantaget visar det rent procentuellt att begreppen förekom endast i hälften av litteraturen. Med detta resultats stora variation leder det till vetskap om att det inte är självklart att begrepp, som enligt Lgr11, ska vara styrande förekommer i den utsträckning man kan förvänta sig i lärares kursläromedel och elevers läromedel. Läromedels och kursläromedlens gemensamma strategi ska vara att främst fokusera på de centrala begrepp som förekommer i Lgr11.

  • 70.
    Linde, Johanna
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science.
    Matematik utanför matteboken: -en idébank med praktiska övningar i matematik, utifrån LGR11 och Favorit matematik 1B2019Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 71.
    Ludvigsson, Fanny
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science.
    1-3 lärares uppfattningar om utomhuspedagogik utifrån läroplanens centrala innehåll2019Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 72. Maes, Dirk
    et al.
    Verovnik, Rudi
    Wiemers, Martin
    Brosens, Dimitri
    Beshkov, Stoyan
    Bonelli, Simona
    Buszko, Jaroslaw
    Cantú-Salazar, Lisette
    Cassar, Louis-Francis
    Collins, Sue
    Dincă, Vlad
    Djuric, Milan
    Dušej, Goran
    Elven, Hallvard
    Franeta, Filip
    Garcia-Pereira, Patricia
    Geryak, Yurii
    Goffart, Philippe
    Gór, Ádám
    Hiermann, Ulrich
    Höttinger, Helmut
    Huemer, Peter
    Jakšić, Predrag
    John, Eddie
    Kalivoda, Henrik
    Kati, Vassiliki
    Kirkland, Paul
    Komac, Benjamin
    Kőrösi, Ádám
    Kulak, Anatolij
    Kuussaari, Mikko
    L’Hoste, Lionel
    Lelo, Suvad
    Mestdagh, Xavier
    Micevski, Nikola
    Mihoci, Iva
    Mihut, Sergiu
    Monasterio-León, Yeray
    Morgun, Dmitry V.
    Munguira, Miguel L.
    Murray, Tomás
    Nielsen, Per Stadel
    Ólafsson, Erling
    Õunap, Erki
    Pamperis, Lazaros N.
    Pavlíčko, Alois
    Pettersson, Lars B.
    Popov, Serhiy
    Popović, Miloš
    Pöyry, Juha
    Prentice, Mike
    Reyserhove, Lien
    Ryrholm, Nils
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Biology.
    Šašić, Martina
    Savenkov, Nikolay
    Settele, Josef
    Sielezniew, Marcin
    Sinev, Sergey
    Stefanescu, Constanti
    Švitra, Giedrius
    Tammaru, Toomas
    Tiitsaar, Anu
    Tzirkalli, Elli
    Tzortzakaki, Olga
    van Swaay, Chris A. M.
    Viborg, Arne Lykke
    Wynhoff, Irma
    Zografou, Konstantina
    Warren, Martin S.
    Integrating national Red Lists for prioritising conservation actions for European butterflies2019In: Journal of Insect Conservation, ISSN 1366-638X, E-ISSN 1572-9753, Vol. 23, no 2, p. 301-330Article in journal (Refereed)
    Abstract [en]

    Red Lists are very valuable tools in nature conservation at global, continental and (sub-) national scales. In an attempt to prioritise conservation actions for European butterflies, we compiled a database with species lists and Red Lists of all European countries, including the Macaronesian archipelagos (Azores, Madeira and Canary Islands). In total, we compiled national species lists for 42 countries and national Red Lists for 34 of these. The most species-rich countries in Europe are Italy, Russia and France with more than 250 species each. Endemic species are mainly found on the Macaronesian archipelagos and on the Mediterranean islands. By attributing numerical values proportionate to the threat statuses in the different national Red List categories, we calculated a mean Red List value for every country (cRLV) and a weighted Red List value for every species (wsRLV) using the square root of the country’s area as a weighting factor. Countries with the highest cRLV were industrialised (NW) European countries such as the Netherlands, Belgium, the Czech Republic and Denmark, whereas large Mediterranean countries such as Spain and Italy had the lowest cRLV. Species for which a Red List assessment was available in at least two European countries and with a relatively high wsRLV (≥ 50) are Colias myrmidone, Pseudochazara orestes, Tomares nogelii, Colias chrysotheme and Coenonympha oedippus. We compared these wsRLVs with the species statuses on the European Red List to identify possible mismatches. We discuss how this complementary method can help to prioritise butterfly conservation on the continental and/or the (sub-)national scale.

  • 73.
    Mattsson, Per
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Electronics.
    Zachariah, Dave
    Department of Information Technology, Uppsala University, Uppsala, Sweden.
    Björsell, Niclas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Electronics.
    Flexible Models for Smart Maintenance2019In: Proceedings 2019 IEEE International Conference on Industrial Technology (ICIT), IEEE, 2019, p. 1772-1777Conference paper (Refereed)
    Abstract [en]

    Smart maintenance strategies are becoming increasingly important in the industry, and can contribute to environmentally and economically sustainable production. In this paper a recently developed latent variable framework for nonlinear-system identification is considered for use in smart maintenance. A model is first identified using data from a system operating under normal conditions. Then the identified model is used to detect when the system begins to deviate from normal behavior. Furthermore, for systems that operate on separate batches (units), we develop a new method that identifies individual models for each batch. This can be used both to detect anomalous batches and changes in the system behavior. Finally, the two methods are evaluated on two different industrial case studies. In the first, the purpose is to detect fouling in a heat exchanger. In the second, the goal is to detect when the tool in a wood moulder machine should be changed.

  • 74.
    Mellåker, Noel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science. Uppsala kommun.
    Biologiundervisning: Ett examensarbete om lärares syn på teoretisk och praktisk biologiundervisning.2019Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 75. Mendoza Montoya, Javier
    et al.
    Chilo, José
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Electronics.
    RealTime Wireless Monitoring System of CO2 and CH4 in Juliaca-Perú2019Conference paper (Refereed)
    Abstract [en]

    This paper presents a measurement system to greenhouse gases (GHG) monitoring. GHGs are formed by the emission of Carbon Dioxide (CO 2 ) and Methane (CH 4 ) from vehicles and near located landfills in Juliaca city in Perú. A wireless system is developed using MOS sensors (MQ2, MQ4, TGS2611 and MQ-135), Arduino-nano, XBee wireless communications modules and the interface to the computer is written in Python. The system was tested in real field measurements and the results show gas concentration difference in different points of the city. We could observe that the CO 2 content in places with a large number of vehicles is high and places with organic waste, like fresch product market, the CH 4 content is also high.

  • 76.
    Mixter, Susanna
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational Health Science and Psychology, Occupational Health Science. University of Gävle, Centre for Musculoskeletal Research.
    Mathiassen, Svend Erik
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational Health Science and Psychology, Occupational Health Science. University of Gävle, Centre for Musculoskeletal Research.
    Lindfors, Petra
    Department of Psychology, Stockholm University, Stockholm, Sweden.
    Dimberg, Kenth
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Biology.
    Jahncke, Helena
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational Health Science and Psychology, Occupational Health Science. University of Gävle, Centre for Musculoskeletal Research.
    Lyskov, Eugene
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational Health Science and Psychology, Occupational Health Science. University of Gävle, Centre for Musculoskeletal Research.
    Hallman, David
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational Health Science and Psychology, Occupational Health Science. University of Gävle, Centre for Musculoskeletal Research.
    Stress-related responses to alternations between repetitive physical work and cognitive tasks of different difficulties2019In: Applied Ergonomics, ISSN 0003-6870, E-ISSN 1872-9126Article in journal (Refereed)
    Abstract [en]

    This experimental study aimed to determine the extent to which a repetitive physical task alternatingwith a cognitive task (CT) influences stress responses and whether the CT difficulty is important. Fifteen women performed three sessions of 10 consecutive work bouts, each including a seven-minutere petitive physical task and a three-minute CT at either of three difficulty levels. Stress-related responses were assessed using heart rate variability, blood pressure, salivary alpha-amylase, salivary cortisol, perceived stress and cognitive performance.The alternating work did not result in any marked increase in perceived stress or changes in stressresponses. CT difficulty did not influence stress responses (all p>0.05), apart from alpha-amylase which was higher during the easiest CT (F= 5.34, p= 0.02). Thus, introducing cognitive work bouts into repetitive physical work did not result in increased levels of stress, suggesting this approach to be viable in job rotation.

  • 77.
    Nakonechnyi, Oleksandr
    et al.
    National Taras Shevchenko University, Kiev, Ukraine .
    Podlipenko, Yuri
    National Taras Shevchenko University, Kiev, Ukraine .
    Shestopalov, Yury
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Mathematics.
    The Minimax Estimation Method for a Class of Inverse Helmholtz Transmission Problems2019In: Minimax Theory and its Applications, ISSN 2199-1413, Vol. 4, no 2, p. 305-328Article in journal (Refereed)
    Abstract [en]

    We present complete mathematical statements and perform detailed investigations of the minimax estimation problems of unknown data for the Helmholtz transmission problems from indirect noisy observations of their solutions. We construct optimal, in certain sense, estimates, which are called minimax mean-square estimates, of the values of linear functionals from unknown data. It is established that when unknown data and correlation functions of errors in observations belong to special sets, the minimax mean square estimates are expressed via solutions to certain transmission problems for systems of Helmholtz equations. We prove that these systems are uniquely solvable. Several possible generalizations of the techniques and results are proposed including applications to the problems with incomplete data and pointwise observations. 

  • 78.
    Nardi, Elena
    et al.
    School of Education and Lifelong Learning, University of East Anglia, Norwich, UK.
    Ryve, Andreas
    School of Education, Culture and Communication, Mälardalen University, Västerås, Sweden.
    Stadler, Erika
    Department of Mathematics and Science Education, Stockholm University, Stockholm, Sweden.
    Viirman, Olov
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Mathematics. Department of Mathematics, Karlstad University, Karlstad, Sweden.
    Commognitive analyses of the learning and teaching of mathematics at university level: The case of discursive shifts in the study of Calculus2014In: Research in Mathematics Education, ISSN 1479-4802, E-ISSN 1754-0178, Vol. 16, no 2, p. 182-198Article in journal (Refereed)
    Abstract [en]

    In this paper we outline the main tenets of the commognitive approach and we exemplify its application in studies that investigate the learning and teaching of mathematics at university level. Following an overview of such applications, we focus on three studies that explore fundamental discursive shifts often occurring in the early stages of studying Calculus. These shifts concern the lecturers' and students' communicative practices, routines of constructing mathematical objects and ways of resolving commognitive conflicts. We then propose that commognitive constructs such as subjectification can be deployed towards 'scaling-up' the hitherto fine-grained focus of commognitive analyses. Finally, we conclude with observing how the commognitive approach relates to constructs from other sociocultural approaches to research in university mathematics education, such as "legitimate peripheral participation" from the theory of Communities of Practice and "didactic contract" from the Theory of Didactic Situations. 

  • 79.
    Nyman, Rebecka
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science. 8604301708.
    Fotosyntesen: Att undervisa det abstrakta för elever i åk. 4-62019Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Syftet med studien var att undersöka lärares upplevelser gällande undervisningen av fotosyntesen i grundskolans årskurs 4-6 med fokus på svårigheter och progression. I undersökningen deltog åtta lärare som undervisar i NO och materialet samlades in via semistrukturerade intervjuer. Lärarna lyfter fram tre typer av svårigheter: elevens svårigheter som till exempel att förstå gasbegreppet, lärarens svårigheter som att visualisera det abstrakta och svårigheter vilka gäller hinder i undervisningen som tidsbrist, ekonomiska begränsningar eller elevgruppen i sig. Undersökningen visar att lärare ofta använder sig av multimodala undervisningssätt, där fler än ett sinne stimuleras, de varierar mellan olika tekniker för att nå så många elever som möjligt. Lärarna anser att en varierande undervisning med olika tekniker som repeterar men sakta bygger på kunskaperna hos eleven även är det som ger det bästa resultatet för elevens förståelse (progression).  Att ge eleven vederläggande texter är en teknik som enligt tidigare forskning visat sig vara effektiv men var inte en teknik som lyftes av någon lärare i undersökningen. Resultaten indikerar att lärare behöver en tydligare plan för vad som ska läras ut när och till viss del hur, vilket inte bara skulle kunna underlätta progressionen utan även förebygga några av de svårigheter som finns med undervisningen om fotosyntesen.

  • 80.
    Nyxén, Emmy
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Biology.
    Collecting rainwater, a comparison between Zambia and Sweden: Can farmers learn from each other?2016Independent thesis Advanced level (degree of Master (Two Years)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This thesis investigates if rainwater collection methods in Zambia are efficient compared to methods used in Sweden. Since the climate changes will affect the rainwater distribution in Sweden, with heavy rainfall, storms and droughts, the comparison is necessary to provide methods for future collection and usage of rainwater in Sweden. The investigation includes the collection of rainwater and two methods for the supply of water onto the ground and the plants. The results show that a correctly built dam will create a good supply of water and thus makes a positive impact for the farm. A proper dam can be the key success factor for water supply all year around. One of the key elements for the dam is the collection of rainwater. The results show that in Zambia it is crucial to obtain a solid capacity of water. The results have shown that the techniques used in Zambia can make a positive impact for methods in Sweden for the collection of rainwater.

  • 81.
    Panigrahi, Smruti Ranjan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Electronics.
    Björsell, Niclas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Electronics.
    Bengtsson, Mats
    KTH Royal Institute of Technology, Stockholm, Sweden .
    Data Fusion in the Air With Non-Identical Wireless Sensors2019In: IEEE Transactions on Signal and Information Processing over Networks, ISSN 2373-776X, Vol. 5, no 4, p. 646-656Article in journal (Refereed)
    Abstract [en]

    In this paper, a multi-hypothesis distributed detection technique with non-identical local detectors is investigated. Here, for a global event, some of the sensors/detectors can observe the whole set of hypotheses, whereas the remaining sensors can either see only some aspects of the global event or infer more than one hypothesis as a single hypothesis. Another possible option is that different sensors provide complementary information. The local decisions are sent over a multiple access radio channel so that the data fusion is formed in the air before reaching the decision fusion center (DFC). An optimal energy fusion rule is formulated by considering the radio channel effects and the reliability of the sensors together, and a closed-form solution is derived. A receive beamforming algorithm, based on a modification of Lozano's algorithm, is proposed to equalize the channel gains from different sensors. Sensors with limited detection capabilities are found to boost the overall system performance when they are used along with fully capable sensors. The additional transmit power used by these sensors is compensated by the designed fusion rule and the antenna array gain. Additionally, the DFC, equipped with a large antenna array, can reduce the overall transmit energy consumption without sacrificing the detection performance.

  • 82.
    Panigrahi, Smruti Ranjan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Electronics. School of Electrical Engineering and Computer Science, KTH Royal Institute of Technology, Sweden.
    Björsell, Niclas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Electronics.
    Bengtsson, Mats
    School of Electrical Engineering and Computer Science, KTH Royal Institute of Technology, Sweden.
    Distributed detection with non-identical wireless sensors for industrial applications2019In: Proceedings of the IEEE International Conference on Industrial Technology, IEEE, 2019, p. 1403-1408Conference paper (Refereed)
    Abstract [en]

    There has been very little exploration when it comes to design distributed detection techniques and data fusion rules with non-identical sensors. This concept can be utilized in many possible applications within industrial automation, surveillance and safety. Here, for a global event, some of the sensors/detectors in the network can observe the full set of the hypotheses, whereas the remaining sensors infer more than one hypotheses as a single hypothesis. The local decisions are sent to the decision fusion center (DFC) over a multiple access wireless channel. In this paper, a fusion rule based on minimization of variance of the local mis-detection is proposed. The presence of sensors with limited detection capabilities is found to have a positive impact on the overall system performance, both in terms of probability of detection and transmit power consumption. Additionally, when the DFC is equipped with a large antenna array, the overall transmit power consumption can be reduced without sacrificing the detection performance. 

  • 83. Postigo-Málaga, Mauricio
    et al.
    Porras Figueroa, Luis
    Chilo, José
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Electronics.
    Low Cost Outdoors WSN Parking System for Metropolitan Areas Based on RSS2019In: 2019 10th IEEE International Conference on Intelligent Data Acquisition and Advanced Computing Systems: Technology and Applications (IDAACS), IEEE, 2019, Vol. 1Conference paper (Refereed)
    Abstract [en]

    Finding a free parking space in the metropolitan areas during rush hour is time consuming and it leads to traffic congestions and air pollution. Wireless Sensor Network (WSN) can be used to obtain information related to the parking condition requiring very little installation and maintenance costs. In this work, we present the design and implementation of an outdoor parking system based on Wireless Sensor Networks (WSNs), received signal strength (RSS) and pattern recognition algorithms to effectively find free parking spaces. Simulation and experiment results show good performance in the verification of the parking system. XBee-PRO 900HP-S3B modules with high performance and low power consumption were used. These modules support the IEEE-802.15.4 protocol for communication in the 900 MHz band and can be configured in different network topologies. The received signal strength (RSS) was measured to form fingerprints for the parking spaces availability (busy or vacant). Kalman filters were implemented to improve RSS which varies due to the effects of short-term fading. The parking spaces availability was evaluated with different classification algorithms in the WEKA environment with results up to 85%.

  • 84.
    Rahmani, Rizan
    et al.
    Mittuniversitetet.
    Carrasco, David
    SLU; University of Montpellier.
    Svensson, Glenn P.
    Lunds universitet.
    Roweck, Hartmut
    Christian Albrecht University, Kiel, Germany.
    Ryrholm, Nils
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Biology.
    Larsson, Mattias C.
    SLU.
    Hedenström, Erik
    Mittuniversitetet.
    Identification and synthesis of putative pheromone components of the threatened salt marsh bagworm moth, Whittleia retiella (Lepidoptera: Psychidae): Psychidae)2020In: Journal of Chemical Ecology, ISSN 0098-0331, E-ISSN 1573-1561Article in journal (Refereed)
    Abstract [en]

    Whittleia retiella (Newman, 1847) is a threatened salt marsh species of the bagworm moth family Psychidae. For its preservation it is necessary to develop efficient tools to survey its distribution and habitat requirements in order to use appropriate conservation methods. Such tools may be pheromone-based monitoring systems, which have documented efficacy in establishing the occurrence of cryptic insect species in nature. By using gas chromatography combined with electroantennographic detection (GC-EAD), we found two compounds in female W. retiella headspace samples and whole-body extracts that elicited electrophysiological activity in male antennae. Gas chromatograpy coupled with mass spectrometry (GC-MS) operating in electron impact (EI) mode and comparison of the analytical data with those of synthetic reference compounds showed the chemical structures of these putative pheromone components to be (1S)-1-methylpropyl (5Z)-dec-5-enoate and 1-methylethyl (5Z)-dec-5-enoate. Field assays using baits loaded with synthetic compounds revealed that conspecific males were attracted to (1S)-1-methylpropyl (5Z)-dec-5-enoate alone or in combination with 1-methylethyl (5Z)-dec-5-enoate, whereas 1-methylethyl (5Z)-dec-5-enoate neither attracted nor repelled males in the field assays when tested alone. This study shows the potential of using (1S)-1-methylpropyl (5Z)-dec-5-enoate for monitoring W. retiella to gather more detailed information about the geographic distribution and habitat needs of this rare moth.

  • 85.
    Ryrholm, Nils
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Biology.
    Larsson, Mattias C.
    Molander, Mikael A.
    Eriksson, Björn
    Hotade insekter medlockande dofter2019In: Yrfän, ISSN 2002-1151, no 2, p. 15-17Article in journal (Other (popular science, discussion, etc.))
  • 86.
    Rönnander, Jonas
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Chemistry.
    Ljunggren, Joel
    Department of Chemical Engineering, Mid Sweden University, Sundsvall, Sweden.
    Hedenström, Erik
    Department of Chemical Engineering, Mid Sweden University, Sundsvall, Sweden.
    Wright, Sandra A. I.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Biology.
    Biotransformation of vanillin into vanillyl alcohol by a novel strain of Cystobasidium laryngis isolated from decaying wood2018In: AMB Express, ISSN 2191-0855, E-ISSN 2191-0855, Vol. 8, no 1, article id 137Article in journal (Refereed)
    Abstract [en]

    Vanillin is an aromatic aldehyde found as a component of lignocellulosic material, and in the cured pods of orchidaceae plants. Like other phenolic substances, vanillin has antimicrobial activity and can be extracted from lignin either by a thermo-chemical process or through microbial degradation. Vanillin, can serve as a model monomer in biodegradation studies of lignin. In the present study, a yeast isolated from decaying wood on the Faroe Islands, was identified as Cystobasidium laryngis strain FMYD002, based on internal transcribed spacer sequence analysis. It demonstrated the ability to convert vanillin to vanillyl alcohol, as detected by ultra-high performance liquid chromatography–quadrupole-time-of-flight. Structural analysis of vanillyl alcohol was carried out by using gas chromatography–mass spectrometry and 1H NMR spectroscopy, and further verified by synthesis. The reduction of vanillin to vanillyl alcohol has been documented for only a few species of fungi. However, to our knowledge, this biotransformation has not yet been reported for basidiomycetous yeast species, nor for any representative of the subphylum Pucciniomycotina. The biotransformation capability of the present strain might prove useful in the industrial utilisation of lignocellulosic residues.

  • 87.
    Rönnow, Daniel
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Electronics.
    Händel, Peter
    Signal Processing, Royal Institute of Technology, Stockholm, Sweden.
    Nonlinear distortion noise and linear attenuation in MIMO systems - theory and application to multiband transmitters2019In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 67, no 20, p. 5203-5212, article id 8805179Article in journal (Refereed)
    Abstract [en]

    Nonlinear static multiple-input multiple-output (MIMO) systems are analyzed. The matrix formulation of Bussgang's theorem for complex Gaussian signals is rederived and put in the context of the multivariate cumulant series expansion. The attenuation matrix is a function of the input signals' covariance and the covariance of the input and output signals. The covariance of the distortion noise is in addition a function of the output signal's covariance. The effect of the observation bandwidth is discussed. Models of concurrent multiband transmitters are analyzed. For a transmitter with dual non-contiguous bands expressions for the normalized mean square error (NMSE) vs input signal power are derived for uncorrelated, partially correlated, and correlated input signals. A transmitter with arbitrary number of non-contiguous bands is analysed for correlated and uncorrelated signals. In an example, the NMSE is higher when the input signals are correlated than when they are uncorrelated for the same input signal power and it increases with the number of frequency bands. A concurrent dual band amplifier with contiguous bands is analyzed; in this case the NMSE depends on the bandwidth of the aggregated signal.

  • 88.
    Sahlin, Matilda
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science.
    Så du menar att du har tagit tior, istället för femmor?: - En studie om laborativ matematikundervisning ur ett lärarperspektiv2019Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    I dagens skola har det givits större plats till den laborativa matematikundervisningen för att minska den teoretiska tysta räkningen. Det här kommer studien att fördjupa sig igenom frågeställningarna:

     

    ·      Vilka laborativa material använder lärare i grundskolans yngre åldrar i matematikundervisningen inom addition och subtraktion i Gävleområdet?

    ·      Vilka upplevelser har lärare i Gävleområdet av det laborativa arbetssättet i matematikundervisningen? Och vad deras upplevelser beror på?

    ·      På vilket sätt kan en lektion med ett laborativt material inom området addition och subtraktion, skapa a-didaktiska-situationer?

     

    Två metoder kommer att användas för att samla in data för studien: två enkäter och en observation genom ett teoretiskt ramverk. Enkäterna visar vilka laborativa material som lärare använder i Gävleområdet, samt deras upplevelser kring materialet. Observationen är en fallstudie där eleverna får arbeta med laborativt material och resultatet visar att det laborativa materialet ökar elevernas kommunikation kring innehållet. Resultatet från undersökningarna stärks även av tidigare forskning som tyder på att laborativ undervisning har en positiv effekt på elevers kunskapsutveckling.

  • 89.
    Sarika, n/a
    et al.
    Department of Electronics and Communication Engineering, ASET, Amity University, Noida, Uttar Pradesh, India.
    Kumar, R.
    Department of Electronics and Communication Engineering, ASET, Amity University, Noida, Uttar Pradesh, India.
    Tripathy, Malay Tripathy
    Department of Electronics and Communication Engineering, ASET, Amity University, Noida, Uttar Pradesh, India.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Electronics.
    An approach to improve gain and bandwidth in bowtie antenna using frequency selective surface2019In: Smart Innovations in Communication and Computational Sciences: Proceedings of ICSICCS 2017, Volume 1 / [ed] Bijaya Ketan Panigrahi, Munesh C. Trivedi, Krishn K. Mishra, Shailesh Tiwari, Pradeep Kumar Singh, Springer, 2019, p. 219-227Conference paper (Refereed)
    Abstract [en]

    A novel approach of improving gain and bandwidth of bowtie antenna using Frequency Selective Surface (FSS) is presented. A 42 × 66 mm2 bowtie antenna is used. The 5 mm × 5 mm FSS unit cell consists of metallic square loop and grid wires on FR4 substrate with permittivity of 4.4 and loss tangent = 0.02. The effect of FSS layer on bowtie antenna is investigated in terms of parameters like gain and bandwidth. Simulation results show that gain and bandwidth of the bowtie antenna gets increased by a factor of two when the FSS layer is kept on it. Further, the effect of change of height of the substrate on gain and bandwidth is also studied. The proposed structure shows applications in X-band and Ku-band range. High-Frequency Structural Simulator (HFSS) software is used for the simulation. © Springer Nature Singapore Pte Ltd. 2019.

  • 90.
    Shakhverdiev, A. K.
    et al.
    Sergo Ordzhonikidze Russian State Geological Prospecting University, Moscow.
    Shestopalov, Yury
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Mathematics.
    Mandrik, I. E.
    Lukoil.
    Arefiev, S. V.
    Lukoil.
    Alternative concept of monitoring and optimization water flooding of oil reservoirs in the conditions of instability of the displacement front2019In: Neftânoe hozâjstvo, ISSN 0028-2448, Vol. 2019, no 12, p. 118-123Article in journal (Refereed)
    Abstract [en]

    It has always been an urgent issue for the oil and gas industry to improve oil, gas, and condensate recovery at liquid and gaseous hydrocarbon fields developed with the use of artificial formation pressure maintenance techniques that involve injection of water or water combined with other displacement agents. Therefore, due to the aforesaid issues, permanent attention should still be paid to the practical problem of optimizing the non-stationary hydrodynamic pressure applied to a reservoir by regulating the operating conditions of the production and injection wells, development process optimization in general, and water flooding in particular. The theory of Buckley and Leverett, does not take into account the loss of stability of the displacement front, which provokes a stepwise change and the triple value of water saturation. Traditionally a mathematically simplified approach was proposed-a repeatedly differentiable approximation to eliminate the “jump” in water saturation. Such a simplified solution led to negative consequences well-known from the water flooding practice, recognized by experts as “viscous instability of the displacement front” and “fractal geometry of displacement front”. The core of the issue is an attempt to predict the beginning of the stability loss of the front of oil displacement by water and to prevent its negative consequences on the water flooding process under difficult conditions of interaction of hydro-thermodynamics, capillary, molecular, inertial, and gravitational forces. In this study, catastrophe theory methods applied for the analysis of nonlinear polynomial dynamical systems are used as a novel approach. Namely, a mathematical growth model is developed and an inverse problem is formulated so that the initial coefficients of the system of differential equations for a two-phase flow can be deter mined using this model. A unified control parameter has been selected, which enables one to propose and validate a discriminant criterion for oil and water growth models for monitoring and optimizing. 

  • 91.
    Shestopalov, Yury
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Mathematics.
    A General Approach to the Analysis of Complex Waves2019In: 2019 URSI International Symposium on Electromagnetic Theory (EMTS), 2019, p. 1-2Conference paper (Refereed)
    Abstract [en]

    We propose a technique for the search and calculation of complex waves in open and shielded circularly symmetric metal-dielectric waveguides with piecewise homogeneous filling by proving the existence and determination of the location of roots of the corresponding dispersion equations in the complex domain. The approach develops the method employing generalized cylindrical polynomials applied earlier to the rigorous analysis and determination of real waves.

  • 92.
    Shestopalov, Yury
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Mathematics.
    Justification of mathematical imaging technique for the permittivity determination of layered dielectrics in a waveguide2019In: 2019 International Conference on Electromagnetics in Advanced Applications (ICEAA), 2019, p. 0143-0146Conference paper (Refereed)
    Abstract [en]

    An introduction to mathematical imaging technique for solving inverse scattering problems is given. Applications are considered to inverse waveguide problems of recontructing permittivity of layered dielectric inclusions. The solution is justified of the inverse microwave imaging by establishing one-to-one correspondence between the sought quantities and the measured noisy data.

  • 93.
    Shestopalov, Yury
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Mathematics.
    On a Method of Solution to Dispersion Equations in Electromagnetics2019In: 2019 URSI Asia-Pacific Radio Science Conference (AP-RASC), New Dehli, 2019, article id 8738297Conference paper (Refereed)
    Abstract [en]

    A possible general approach to the analysis of dispersion equations (DEs) of electromagnetics is presented. The method takes into account the known explicit forms of DEs describing eigenoscillations and normal waves in layered structures and is based on the development of the notion of generalized cylindrical polynomials. The approach enables one to complete rigorous proofs of existence and determine domains of localization of the DE roots and validate iterative numerical solution techniques.

  • 94.
    Shestopalov, Yury
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Mathematics.
    Trigonometric and cylindrical polynomials and their applications in electromagnetics2019In: Applicable Analysis, ISSN 0003-6811, E-ISSN 1563-504XArticle in journal (Refereed)
    Abstract [en]

    Development of the theory of trigonometric polynomials (TPs) is considered that involves generalization of the notion of TP and extension of the methods and results to cylindrical polynomials (CPs). On the basis of the proposed augmentation of TPs and CPs, a general approach is presented to the analysis of guided waves and resonances in electromagnetics and beyond. The method employs the known explicit forms of dispersion equations (DEs) describing eigenoscillations and normal waves in layered structures and is based on the development of the theory of generalized TPs and CPs performed in the study. The approach enables one to complete rigorous proofs of existence and determine domains of localization of the TP and CP zeros and the DE roots and validate iterative numerical solution techniques.

  • 95.
    Shestopalov, Yury
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Mathematics.
    Aboltins, A
    Litvinenko, A
    Mathematical methods for inverse waveguide problems2019In: 2019 IEEE Microwave Theory and Techniques in Wireless Communications  (MTTW). Proceedings, 2019Conference paper (Refereed)
    Abstract [en]

    An introduction is given to mathematical methods for inverse waveguide  problems. Applications are considered to the solution of the inverse  waveguide problems of reconstructing permittivity of layered dielectric  inclusions. It is shown that the existence and uniqueness can be justified by  establishing one-to-one correspondence between the sought quantities and the  measured noisy data.

  • 96.
    Shestopalov, Yury
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Mathematics.
    Kuzmina, Ekaterina
    Moscow Technological University MIREA, Moscow, Russia.
    On Recent Findings in the Theory of Complex Waves in Open Metal-Dielectric Waveguides2018In: 2018 2ND URSI Atlantic Radio Science Meeting (AT-RASC), IEEE, 2018Conference paper (Refereed)
    Abstract [en]

    Theory of complex waves (see e.g. [1] and references therein) accumulated a big volume of results. However, its biggest drawback remains which brakes significantly the development of the theory: absence of rigorous proofs of the existence of complex waves. In this respect, studies of complex waves in open metal-dielectric waveguides has been essentially enhanced when two new families of symmetric (angle-independent) complex waves have been identified [2, 3] in a dielectric rod (DR) and Goubau line (GL) with homogeneous dielectric cover: surface complex waves occurring as perturbations of real surface waves caused by the presence of lossy dielectric, and pure complex waves which have no counterpart in the set of real waves. Existence of the latter family of complex waves has been shown using a special technique and the proof [3] of the existence of an infinite set of complex roots of the dispersion equation (DE) describing waves in DR and GL.

    In this work, a development of the analytical and numerical methods [2, 3] are considered for the analysis of the electromagnetic wave propagation in metal-dielectric waveguides with multi-layered dielectric filling. The first step constitutes extension of the results obtained for symmetric complex waves in DR and GLto the case of non-symmetric (angle-dependent) waves, and the second step, to multi-layered dielectric covers. Both steps are accomplished using specific forms of DEs obtained in [3]by construction analytical continuation of the functions involved in DEs to multi-sheet Riemann surfaces of the spectral parameter and applying appropriate generalization the techniques [4]forfinding complex roots of the DEs.

    Calculation ofnon-symmetric complex waves employs numerical solution of the DEs with the help of parameter differentiation in the complex domain using multi-parameter setting and analysis of implicit functions of several complex variables [5] and reduction [2, 3] to numerical solution of auxiliary Cauchy problems.

    1. A. S. Raevskiiand S. B. Raevskii, Complex Waves, Radiotekhnika, Moscow, 2010.

    2. E. Kuzmina and Y. Shestopalov, “Waves in a lossyGoubau line,”10th European Conf. on Antennas and Propagation (EuCAP), Davos, Switzerland, 2016, doi: 10.1109/EuCAP.2016.7481368.

    3. E. Kuzmina and Y. Shestopalov, “Complex waves in a dielectric rod and Goubau line,” 19th Int. Conf. on Electromagneticsin Advanced Applications (ICEAA), Verona, Italy, 2017, pp. 963-966, doi: 10.1109/ICEAA.2017.8065417.

    4. Y. Shestopalov, “Resonant states in waveguide transmission problems,”PIER B,64: pp.119-143, 2015, doi: 10.2528/PIERB15083001.

    5.Y. Shestopalov,“On unique solvability of multi-parameter waveguide inverse problems, ”19th Int. Conf. on Electromagnetics in Advanced Applications (ICEAA), Verona, Italy, 2017, pp. 372-376, doi: 10.1109/ICEAA.2017.8065253.

  • 97.
    Shestopalov, Yury
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Mathematics.
    Shakhverdiev, Azizaga
    Russian State Geological Prospecting University, Moscow, 117997 Russia.
    Qualitative Analysis of Quadratic Polynomial Dynamical Systems Associated with the Modeling and Monitoring of Oil Fields2019In: Lobachevskii Journal of Mathematics, ISSN 1995-0802, E-ISSN 1818-9962, Vol. 40, no 10, p. 1695-1710Article in journal (Refereed)
    Abstract [en]

    The behavior and properties of solutions of two-dimensional quadratic polynomial dynamical system on the phase plane of variables and time are considered. A complete qualitative theory is constructed which includes the analysis of all singular points and the features of solutions depending on all parameters of the problem. A main result is that, with the discriminant criteria created on the basis of the growth model constructed in the present study, it is possible to formulate practical recommendations for regulating and monitoring the process of waterflooding and the development of an oil field.

  • 98.
    Shestopalov, Yury
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Mathematics.
    Shakhverdiev, Azizaga
    S. Ordzhonikidze Russian State Geological Prospecting University, Moscow, Russia.
    Mandrik, I.E.
    LUKOIL, PJSC, Moscow, Russia.
    Arefiev, S.V.
    LUKOIL, Western Siberia, Kogalym, Russia.
    Alternative conception of the monitoring and optimization of water flooding of oil reservoirs  under instability of displacement front2019In: Oil industry (Neftyanoye khozyaystvo), ISSN 0028-2448, no 12, p. 118-123Article in journal (Refereed)
    Abstract [en]

    The theory of Buckley and Leverett does not take into account the loss of stability of the displacement front whch provokes a stepwise change and the triple value of water saturation. Traditionally a mathematically simplified approach was proposed: a differentiable approximation to eliminate the ' jump' in water saturation. Such a simplified solution led to negative consequences well-know from the water flooding practice, recognized by experts as 'viscous instability of the displacement front' and 'fractal geometry of the displacement front'.The core of the issue is to attempt to predict the beginning of the stability loss of the front of oil displacement by water and to prevent its negative effect on the water flooding process under difficult conditions of interaction of hydro-thermodynamic, capillary, molecular, inertial, and gravitational forces. In this study, catastrophe theory methods applied for the analysis of nonlinear polynomial dynamical systems are used as a novel approach. namely, a mathematical growth model is developed and an inverse problem is formulated so that the initial coefficients of the system of differential equations for a two-phase flow can be determined using this model. A unified control parameter has been selected which enables one to propose and validate a discriminant criterion for  oil and water growth models for monitoring and optimization.

  • 99.
    Shestopalov, Yury
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Mathematics.
    Smolkin, Eugene
    Smirnov, Yury
    Department of Mathematics and Supercomputing, Penza State University, Krasnaya Str. 40, Penza, 440026, Russia.
    On the existence of the nonlinear leaky TE-polarized waves in a metal–dielectric cylindrical waveguide2019In: Wave motion, ISSN 0165-2125, E-ISSN 1878-433X, Vol. 91, article id 102378Article in journal (Refereed)
    Abstract [en]

    We consider propagation of leaky waves in the Goubau line (a perfectly conducting cylinder covered by a concentric dielectric layer) filled with nonlinear inhomogeneous medium. The problem is reduced to the analysis of a nonlinear integral equation with a kernel in the form of the Green’s function of an auxiliary boundary value problem on an interval. The existence of propagating nonlinear leaky waves for the chosen nonlinearity (Kerr law) is proved using the method of contraction. Conditions under which a finite number of waves can propagate are obtained and the intervals of localization of the corresponding propagation constants are determined. For the numerical solution, a method based on solving an auxiliary Cauchy problem (a version of the shooting method) is proposed. In numerical experiments, two types of nonlinearities are considered and compared: Kerr nonlinearity and nonlinearity with saturation. New propagation regimes are discovered.

  • 100.
    Shestopalov, Yury
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Mathematics.
    Smolkin, Eugene
    Department of Mathematics and Supercomputing, Penza State University, Penza, Russia.
    Snegur, Maxim
    Department of Mathematics and Supercomputing, Penza State University, Penza, Russi.
    New Propagation Regimes of TE Waves in a Waveguide filled with a Nonlinear Dielectric Metamaterial2019In: 2019 URSI Asia-Pacific Radio Science Conference (AP-RASC), New Dehli: IEEE, 2019, article id 8738241Conference paper (Refereed)
    Abstract [en]

    We consider propagation of surface TE waves in a circular metal-dielectric waveguide filled with nonlinear (Kerr nonlinearity) metamaterial medium. Analysis is reduced to solving a nonlinear transmission eigenvalue problem for an ordinary differential equation; eigenvalues of the problem correspond to propagation constants of the waveguide. For the numerical solution, a method is proposed based on solving an auxiliary Cauchy problem (a version of the shooting method). As a result of comprehensive numerical modeling, new propagation regimes are discovered.

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