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  • 201.
    Bertilsson, Kent
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Dubaric, Ervin
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Thungström, Göran
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Nilsson, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Petersson, Sture
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Simulation of a low atmospheric-noise modified four-quadrant position sensitive detector2001Inngår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 466, nr 1, s. 183-187Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A modified four-quadrant position sensitive detector (PSD) is developed. This structure is less sensitive to atmospheric turbulence that is a major drawback with the traditional four-quadrant detector. The inter-electrode resistance is as high as for the four-quadrant detector, which is an advantage compared to the lateral effect PSD. The linearity for the modified four-quadrant detector is good in the whole active range of sensing. The structures are limited to small sensing areas with well focused beams and are suitable for use in detectors up to 1 mm in size.

  • 202.
    Bertilsson, Kent
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Harris, C
    Nilsson, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Calculation of lattice heating in SiC RF power devices2004Inngår i: Solid-State Electronics, ISSN 0038-1101, E-ISSN 1879-2405, Vol. 48, nr 12, s. 1721-1725Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Silicon carbide MESFET devices are suitable for high-speed and high-power applications. In this paper we are studying thermal effects in 4H-SiC RF power devices. The simulations are based on a combination of 2D device simulations for the electrical transport, and 3D thermal simulations for the lattice heating. We show that the method gives good accuracy, efficiency, flexibility and capacity dealing with tasks, where a 2D coupled electrical-thermal simulation is not sufficient. We also present an improvement of Roschke and Schwierz mobility model, based on Monte Carlo simulations for the temperature dependencies of the mobility parameters beta and v(sat).

  • 203.
    Bertilsson, Kent
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Harris, C.I.
    Comparison of bipolar and unipolar SiC switching devices for very high power applications2007Inngår i: Silicon Carbide and Related Materials 2006, Trans Tech Publications Inc., 2007, Vol. 556-557, s. 975-978Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Both unipolar and injection SiC devices can be used for high voltage switching applications; it is not determined, however, for which applications one approach is preferred over the other. In this paper, simulation studies are used to compare the suitability of unipolar devices, in this case a JFET (Junction Field Effect Transistor) against an equivalent FCD (Field Controlled Diode) configuration up to very high voltages. The calculations are performed in a finite element approach, with commercial drift-diffusion software. Numerous drift layers have been simulated in a Monte-Carlo approach to ensure that the optimal design of the drift layers for different breakdown is used. In a static case, purely conductive losses in the drift layer in both unipolar and injection configuration are compared. Additionally the total losses are studied and compared in switched applications for different switching frequencies and current levels.

  • 204.
    Bertilsson, Kent
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Nilsson, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Optimization of 2H, 4H and 6H-SiC high-speed vertical MESFETs2002Inngår i: Diamond and related materials, ISSN 0925-9635, E-ISSN 1879-0062, Vol. 11, nr 3-6, s. 1254-1257Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Silicon carbide vertical MESFET devices are well suited for high speed and high power electronic devices. In this work we have optimized the geometry of vertical MESFETs for microwave applications, using iterative two-dimensional simulations. Relevant parasitics are included in the simulations to investigate the performance of realistic devices. The state of the art device has f(T)=7 GHz and we show that vertical MESFETs fabricated with traditional technology are totally limited by parasitics. Two different approaches to reduce the parasitics in the vertical MESFET are proposed where f(T) increases significantly.

  • 205.
    Bertilsson, Kent
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Nilsson, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Optimization of 2H, 4H and 6H-SiC MESFETs for High Frequency Applications2002Inngår i: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 101, s. 75-77Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Silicon carbide MESFET devices are well suited for high speed, high power and high temperature electronics due to high saturation velocity, high critical electrical field, good thermal conductivity and large band-gap. Optimization of a high performance device demands a substantial number of numerical simulations, where several different design parameters have to be investigated thoroughly. In this work, we optimize the geometry of lateral MESFETs for maximal unity current-gain frequency (fT) using iterative 2-dimensional simulations. We also present a comparison of performance for individually optimized devices, realized with lithographic resolutions ranging from 0.2 to 2 μm in different SiC polytypes.

  • 206.
    Bertilsson, Kent
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Nilsson, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    The power of using automatic device optimization, based on iterative device simulation, in design of high-performance devices2004Inngår i: Solid-State Electronics, ISSN 0038-1101, E-ISSN 1879-2405, Vol. 48, nr 10-11, s. 1721-1725Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An automatic optimization tool for semiconductor devices based on iterative device simulations is developed. The tool is used for optimization of different kinds of semiconductor devices using various performance measures. High performance optimization algorithms, both local and global, are used to achieve an efficient design in shortest possible time. In this paper the effects of different optimization algorithms, performance measures, and number of variables in the optimization are studied. Both the computational efficiency and the devices achieved with different performance measures are studied. We give a demonstration of the usefulness of this method in a comparison between different device topologies, which have been optimized for best performance.

  • 207.
    Bertilsson, Kent
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Nilsson, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Hjelm, Mats
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Petersson, Sture
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Käckell, P.
    Persson, C.
    The Effect of Different Transport Models in Simulation of High Frequency 4H-SiC and 6H-SiC Vertical MESFETs2001Inngår i: Solid-State Electronics, ISSN 0038-1101, E-ISSN 1879-2405, Vol. 45, nr 5, s. 645-653Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A full band Monte Carlo (MC) study of the high frequency performance of a 4H-SiC Short channel vertical MESFET is presented. The MC model used is based on data from a full potential band structure calculation using the local density approximation to the density functional theory. The MC results have been compared with simulations using state of the art drift-diffusion and hydrodynamic transport models. Transport parameters such as mobility, saturation velocity and energy relaxation time are extracted from MC simulations

  • 208.
    Bertilsson, Kent
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Nilsson, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Petersson, Sture
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Simulation of anisotropic Breakdown in 4H-SiC Diodes2000Inngår i: IEEE Workshop on Computers in Power Electronics: COMPEL 2000, IEEE , 2000, s. 118-120Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The breakdown characteristics of two-dimensional 4H-SiC diode structures have been studied using an anisotropic drift-diffusion model. The degree of anisotropy was estimated from recent full band Monte Carlo simulations. Identical diode structures have previously been used in the literature to measure the hole impact ionization coefficients of 4H-SiC. The reported measurements from different research groups show large differences in the impact ionization coefficients. Our numerical simulations show that the differences in these measurements can be explained by the difference in device geometry used by the research teams if one considers an anisotropic impact ionization process. This indicates that it is very important to consider anisotropic impact ionization in design and characterization of 4H-SiC power devices.

  • 209.
    Betta, Giovanni
    et al.
    Univ. of Cassino, Italy.
    Capriglione, Domenico
    Univ. of Salerno.
    Corvino, Mariella
    Univ. of Cassino, Italy.
    Lavatelli, Alberto
    Politecnico di Milano.
    Liguori, Consolatina
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion. Univ. of Salerno.
    Sommella, Paolo
    Univ. of Salerno.
    Zappa, Emanuele
    Politecnico di Milano.
    Metrological characterization of 3D biometric face recognition systems in actual operating conditions2017Inngår i: Acta IMEKO, ISSN 2221-870X, Vol. 6, nr 1, s. 33-42Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nowadays, face recognition systems are going to widespread in many fields of application, from automatic user login for financial activities and access to restricted areas, to surveillance for improving security in airports and railway stations, to cite a few.In such scenarios, the architectures based on stereo vision and 3D reconstruction of the face are going to assume a predominant role because they can generally assure a better reliability than solutions based on a single camera (which make use of a single image instead of a couple of images). To realize such systems, different architectures can be considered by varying the positioning of the pair of cameras with respect to the face of the subject to be identified, as well as both kind and resolution of camera considered. These parameters can affect the correct decision rate of the system in classifying the input face, especially in presence of image uncertainty.In this paper, several 3D architectures differing in camera specifications and geometrical positioning of the camera pair (with respect to the input face) are realized and compared. The detection of facial features in the images is made by adopting a popular method based on the Active Appearance Model (AAM) algorithm. 3D position of facial features is then obtained by means of stereo triangulation. The performance of the realized systems has been compared in terms of sensitivity to the quantities of influence and related uncertainty, and of typical indexes for the analysis of classification systems. Main results of such comparison show that the best performance can be reached by reducing the distance between cameras and subject to be identified and by minimizing the horizontal angle between the plane containing the camera pair axis and the face to be identified.

  • 210.
    Bianco, L.
    et al.
    DESY Deutsch Elektronen Synchrotron, Hamburg, Germany.
    Becker, J.
    DESY Deutsch Elektronen Synchrotron, Hamburg, Germany.
    Dinapoli, R. D.
    Fretwurst, E.
    Goettlicher, P.
    DESY Deutsch Elektronen Synchrotron, Hamburg, Germany.
    Graafsma, Heinz
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion. DESY Deutsch Elektronen Synchrotron, Hamburg, Germany.
    Greiffenberg, D.
    Gronewald, M.
    Henrich, B.
    Hirsemann, H.
    DESY Deutsch Elektronen Synchrotron, Hamburg, Germany.
    Jack, S.
    DESY Deutsch Elektronen Synchrotron, Hamburg, Germany.
    Klanner, R.
    Klyuev, A.
    DESY Deutsch Elektronen Synchrotron, Hamburg, Germany.
    Krueger, H.
    Marras, A.
    DESY Deutsch Elektronen Synchrotron, Hamburg, Germany.
    Mozzanica, A.
    Rah, S.
    DESY Deutsch Elektronen Synchrotron, Hamburg, Germany.
    Schmitt, B.
    Shi, X.
    Trunk, U.
    DESY Deutsch Elektronen Synchrotron, Hamburg, Germany.
    Schwandt, J.
    Zhang, J.
    The AGIPD System for the European XFEL2013Inngår i: ADVANCES IN X-RAY FREE-ELECTRON LASERS II: INSTRUMENTATION, 2013, s. Art. no. UNSP 87780V-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The European XFEL will generate extremely brilliant pulses of X-rays organized in pulse trains consisting of 2700 pulses <100 fs long, with >10(12) photons, and with a 220 ns spacing. The pulse trains are running at a 10Hz repetition rate. The detector to be used under these conditions will have to face several challenges: the dynamic range has to cover the detection of single photons and extend up to >10(4) photons/pixel/pulse in the same image, framing rates of 4.5 MHz (220 ns) are required in order to record one image per pulse, and as many images as possible have to be recorded during the pulse trains. Due to the high flux, the detector will have to withstand a dose up to 1GGy integrated over 3 years. To meet these challenges a consortium, consisting of Deutsches Elektronensynchrotron (DESY), Paul-Scherrer-Institut (PSI), University of Hamburg and University of Bonn, is developing the Adaptive Gain Integrating Pixel Detector (AGIPD). It is a hybrid-pixel detector, featuring a charge integrating amplifier with dynamic gain switching to cope with the extended dynamic range, and an analogue on-pixel memory for image storage at the required 4.5 MHz frame rate. The readout chip consists of 64x64 pixels of (200 mu m)(2), 8x2 of these readout chips are bump-bonded to a monolithic silicon sensor to form the basic module with 512 x 128 pixels. 4 of these modules are stacked to form a quadrant of the 1k x 1k detector system. Each quadrant is independently moveable in order to adjust a central hole, needed for the direct beam to pass through. Special designs are employed for both the sensor and the readout chip to withstand the integrated dose for 3 years.

  • 211.
    Birch, J.
    et al.
    Linköping University, Thin Film Physics Division, IFM, Linköping.
    Buffet, J. -C
    Institute Laue Langevin, 71 avenue des Martyrs, Grenoble, France.
    Clergeau, J. -F
    Institute Laue Langevin, 71 avenue des Martyrs, Grenoble, France.
    Van Esch, P.
    Institute Laue Langevin, 71 avenue des Martyrs, Grenoble, France.
    Etxegarai, M.
    European Spallation Source, P.O Box 176, Lund.
    Ferraton, M.
    Institute Laue Langevin, 71 avenue des Martyrs, Grenoble, France.
    Guerard, B.
    Institute Laue Langevin, 71 avenue des Martyrs, Grenoble, France.
    Hall-Wilton, Richard J.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion. European Spallation Source, P.O Box 176, Lund.
    Hultman, L.
    Linköping University, Thin Film Physics Division, IFM, Linköping.
    Höglund, C.
    Linköping University, Thin Film Physics Division, IFM, Linköping; European Spallation Source, P.O Box 176, Lund.
    Khaplanov, A.
    Linköping University, Thin Film Physics Division, IFM, Linköping; European Spallation Source, P.O Box 176, Lund.
    Piscitelli, F.
    Linköping University, Thin Film Physics Division, IFM, Linköping; European Spallation Source, P.O Box 176, Lund.
    Stefanescu, I.
    European Spallation Source, P.O Box 176, Lund.
    Multi-Grid boron-10 detector for time-of-flight spectrometers in neutron scattering science2015Inngår i: 2015 IEEE Nuclear Science Symposium and Medical Imaging Conference, NSS/MIC 2015, Institute of Electrical and Electronics Engineers (IEEE), 2015, artikkel-id 7582004Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The Multi-Grid (MG) detector has been introduced at ILL and developed by a collaboration between ILL, ESS and Linkoping University. This detector design addresses the severely decreased availability of He3, in particular for neutron scattering instruments with large-area detectors, such as time-of-flight neutron spectrometers at ESS and other facilities. The MG detector is based on thin converter films of boron-10 carbide arranged in layers orthogonal to the incoming neutrons. The design of the detector provides position resolution, efficiency competitive with He3 and a strong gamma rejection capability. This paper presents the MG large-area (2.4m2) demonstrator and the progress made in order to meet the needs of production of B4C-coated layers, mechanical parts and assembly on a scale similar to that of the final detectors for ESS. A particular effort was made to produce aluminium detector parts with a low alpha background, successfully reducing the background rate to acceptable levels. Following the IN5 demonstrator, a compact prototype has been designed in order to finalise the electronic readout to be used at the ESS instruments equipped with the MG.

  • 212.
    Birch, J
    et al.
    Thin Film Physics Division, IFM, Linköping University, Linköping, Sweden.
    Buffet, J-C
    Institute Laue Langevin, 71 avenue des Martyrs, Grenoble, France.
    Clergeau, J F
    Institute Laue Langevin, 71 avenue des Martyrs, Grenoble, France.
    Van Esch, P
    Institute Laue Langevin, 71 avenue des Martyrs, Grenoble, France.
    Ferraton, M
    Institute Laue Langevin, 71 avenue des Martyrs, Grenoble, France.
    Guerard, B
    Institute Laue Langevin, 71 avenue des Martyrs, Grenoble, France.
    Hall-Wilton, R
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion. European Spallation Source, P.O Box 176, Lund, Sweden.
    Hultman, L
    Thin Film Physics Division, IFM, Linköping University, Linköping, Sweden.
    Höglund, C
    Thin Film Physics Division, IFM, Linköping University, Linköping, Sweden.
    Jensen, J
    Thin Film Physics Division, IFM, Linköping University, Linköping, Sweden.
    Khaplanov, A
    Institute Laue Langevin, 71 avenue des Martyrs, Grenoble, France.
    Piscitelli, F
    Institute Laue Langevin, 71 avenue des Martyrs, Grenoble, France.
    Investigation of background in large-area neutron detectors due to alpha emission from impurities in aluminium2015Inngår i: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 10, nr 10, artikkel-id P10019Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Thermal neutron detector based on films of 10B4C have been developed as an alternative to 3He detectors. In particular, The Multi-Grid detector concept is considered for future large area detectors for ESS and ILL instruments. An excellent signal-to-background ratio is essential to attain expected scientific results. Aluminium is the most natural material for the mechanical structure of of the Multi-Grid detector and other similar concepts due to its mechanical and neutronic properties. Due to natural concentration of α emitters, however, the background from α particles misidentified as neutrons can be unacceptably high. We present our experience operating a detector prototype affected by this issue. Monte Carlo simulations have been used to confirm the background as α particles. The issues have been addressed in the more recent implementations of the Multi-Grid detector by the use of purified aluminium as well as Ni-plating of standard aluminium. The result is the reduction in background by two orders of magnitude. A new large-area prototype has been built incorporating these modifications.

  • 213.
    Björk, Carl Johan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion.
    PID tuning with Ant Colony Optimization (ACO): A framework for a step response based tuning algorithm2018Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [en]

    The building automation industry lacks an affordable, simple, solution for autonomous PID controller tuning when overhead variables fluctuate. In this project, requested by Jitea AB, a solution was developed, utilising step response process modelling, numerical integration of first order differential equations, and Ant Colony Optimization (ACO). The solution was applied to two control schemes; simulated outlet flow from a virtual water tank, and the physical air pressure in the ventilation system of a preschool in Sweden. An open-loop step response provided the transfer function in each case, which, after some manipulation, could be employed to predict the performance of any given set of PID parameters, based on a weighted cost function. This prediction model was used in ACO to find optimal settings. The program was constructed in both Structured Control Language and Structured Text and documented in an approachable way. The results showed that the program was, in both cases, able to eliminate overshoot and retain the settling time (with a slightly raised rise time) achieved with settings tuned per the current methods of Jitea AB. Noise and oscillations present in the physical system did not appear to have any major negative influence on the tuning process. The program performed above Jitea AB’s expectation, and will be tested in more scenarios, as it showed promise. Autonomous implementation could be of societal benefit through increased efficiency and sustainability in a range of processes. In future studies, focus should be on improving the prediction model, and further optimising the ACO variables.

  • 214.
    Björklund, Johannes
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    PLC-simulering: Virtuell balningslinje i felsökningssyfte2019Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Eftersom Valmet inte har någon metod för att testa styrsystemen för transportörerna de levererar med sina balningslinjer går mycket tid åt till att felsöka på plats. De söker därför en metod som gör det möjligt att simulera styrsystemen för att hitta och lösa fel innan leverans. Tryckt litteratur och artiklar publicerade i vetenskapliga journaler har varit grunden till den studie som utförts under arbetet. Ett tillhandahållet styrsystem innehållande en typ av transportör har studerats för att få förståelse för dess funktion. För att simulera krävs en modell som representerar och uppför sig som systemet i fråga. Om simuleringen ska vara användbar måste modellen vara tillräckligt exakt. En väl fungerande simulering är till väldigt stor fördel då denna kan förhindra förseningar, ge bättre arbetsvillkor, spara pengar och öka säkerheten. Utifrån arbetets mål togs ett koncept fram för simuleringen av styrsystemet. Det framtagna konceptet skriver över värdena av de fysiska ingångarna innan de går in i styrlogiken. Varje transportör simuleras enskilt där de har en funktion som sparar positionen för de virtuella massabalarna på det egna bandet. Simuleringen visualiseras via ett HMI där balarnas förflyttning kan följas. Det framtagna konceptet visade sig fungera bra för att simulera det tillhandahållna styrsystemet. Stora delar kan med säkerhet återanvändas för andra typer av transportörer. Huruvida konceptet faktiskt kan hitta fel i styrsystem är däremot inte fastställt, men högst sannolikt. Slutsatsen som kan dras av det framtagna konceptet är att det har god potential för att simulera verkliga styrsystem om det vidareutvecklas, varigenom uppstartstiden kan förkortas.

     

  • 215.
    Bjørvik, Sindre
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion.
    Using delay line ultrasonic transducer to measure temperature and compensate2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Ultrasonic non-destructive testing are widely used in many branches of the indus-

    try for measurements of materials characteristics.  In some cases there is a need

    for  ultrasonic  transducers  to  measure  at  higher  temperatures,  but  these sensors lack proper sensing quality at elevated temperatures.  With the years it has been developed  several  approaches  to  make  ultrasonic  transducers  able  to  measure  at higher temperatures.

    During this thesis an ultrasonic transducer with a delay line will be used to measure

    thickness of a steel pipe at temperatures up to 300C, the delay line will work as a

    temperature estimator and use the estimated temperature to compensate measure-

    ment errors which is created from higher temperatures.  A measurement system is

    created to make the ultrasonic transducer gather thickness and temperature data,

    this system will then be placed inside ovens for testing.

    At  higher  temperatures  a  problem  with  high  attenuation  of  signal  occurred  due to bad coupling and made it hard to find thickness values,  but the temperature

    estimations showed good results at stable temperatures.

  • 216. Blas, A.
    et al.
    Hancock, S.
    Koscielniak, S.
    Lindroos, M.
    Sjöström, Mårten
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Evaluation of vector signal analyzer for beam transfer function measurements in PS Booster1999Rapport (Annet vitenskapelig)
  • 217. Bocelli, S
    et al.
    Guizzetti, G.
    Marabelli, F.
    Thungström, Göran
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Petersson, Sture
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Experimental identification of the optical phonon of CoSi2 in the infrared1995Inngår i: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 91, nr 1-4, s. 30-33Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A weak but clear optical structure was detected at 329 cm−1 by both reflectance and transmittance measurements in the far infrared on a 430 Å film of CoSi2 grown on Si(100). This is the first observation of the IR vibrational mode of the cubic structure of CoSi2 and the result is in very good agreement with theoretical calculations. In order to characterize the sample, the reflectance was extended up to 5.2 × 104 cm−1 and the refractive index was also directly obtained in a more limited spectral range by spectroscopic ellipsometry. The IR structure was then quantitatively analyzed by means of a fit procedure, obtaining the values of ω0 = 327 cm−1 for the phonon energy, of γ = 10.5 cm−1 for the damping parameter and of 0.006 electronic charges for the screened effective ionic charge.

  • 218.
    Bonafini, Federico
    et al.
    University of Brescia, Italy.
    Depari, Alessandro
    Univeristy of Brescia, Italy.
    Ferrari, Paolo
    University of Brescia, Italy.
    Flammini, Alessandra
    University of Brescia, Italy.
    Pasetti, Marco
    University of Brescia, Italy.
    Rinaldo, Stefano
    University of Brescia, Italy.
    Sisinni, Emiliano
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationssystem och –teknologi. University of Brescia, Italy.
    Gidlund, Mikael
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationssystem och –teknologi.
    Exploiting localization systems for LoRaWAN transmission scheduling in industrial applications2019Inngår i: 2019 15th IEEE International Workshop on Factory Communication Systems (WFCS), IEEE, 2019, artikkel-id 8757999Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The Internet of Things (IoT) paradigm contaminated industrial world, allowing for innovative services. The wireless communications seem to be particularly attracting, especially when complement indoor and outdoor Real Time Location Systems (RTLS) for geo-referencing smart objects (e.g. for asset tracking). In this paper, the LoRaWAN solution is considered for transmitting RTLS data. LoRaWAN is an example of Low Power Wide Area Network: it tradeoffs throughput with coverage and power consumption. However, performance can be greatly improved with limited changes to the standard specifications. In this work, a scheduling layer is suggested above the regular stack for allocating communication resources in a time slot channel hopping medium access strategy. The main innovation is the time synchronization, which is obtained opportunistically from the ranging devices belonging to the RTLSs. The experimental testbed, based on commercially available solutions, demonstrates the affordability and feasibility of the proposed approach. When low-cost GPS (outdoor) and UWB (indoor) ranging devices are considered, synchronization error of few microseconds can be easily obtained. The experimental results show the that time reference pulses disciplined by GPS have a maximum jitter of 180 ns and a standard deviation of 40 ns whereas, if time reference pulses disciplined by UWB are considered, the maximum jitter is 3.3 μs and the standard deviation is 0.7 μs.

  • 219. Bosk, Daniel
    et al.
    Kjellqvist, Martin
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Buchegger, Sonja
    Towards Perfectly Secure and Deniable Communication Using an NFC-Based Key-Exchange Scheme2015Inngår i: SECURE IT SYSTEMS, NORDSEC 2015, 2015, Vol. 9417, s. 72-87Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper we first analyse the possibility for deniability under a strong adversary, who has an Internet-wide transcript of the communication. Secondly, we present a scheme which provides the desirable properties of previous messaging schemes, but with stronger deniability under the new adversary model. Our scheme requires physical meetings for exchanges of large amounts of random key-material via near-field communication and later uses this random data to key a one-time pad for text-messaging. We prove the correctness of the protocol and, finally, we evaluate the practical feasibility of the suggested scheme.

  • 220.
    Bosse, Sebastian
    et al.
    Fraunhofer Institute for Telecommunications – Heinrich Hertz Institute, Berlin, Germany.
    Brunnström, Kjell
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationssystem och –teknologi. Research Intstitutes of Sweden AB.
    Arndt, Sebastian
    Norwegian University of Science and Technology, Trondheim, Norway.
    Martini, Maria G.
    Kingston University, London, UK.
    Ramzan, Naeem
    University of the West of Scotland, Hamilton, UK.
    Engelke, Ulrich
    CSIRO Data61, Kensington, Australia.
    A common framework for the evaluation of psychophysiological visual quality assessment2019Inngår i: Quality and User Experience, ISSN 2366-0139, E-ISSN 2366-0147, Vol. 4, nr 3Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The assessment of perceived quality based on psychophysiological methods recently gained attraction as it potentially overcomes certain flaws of psychophysical approaches. Although studies report promising results, it is not possible to arrive at decisive and comparable conclusions that recommend the use of one or another method for a specific application or research question. The video quality expert group started a project on psychophysiological quality assessment to study these novel approaches and to develop a test plan that enables more systematic research. This test plan comprises of a specifically designed set of quality annotated video sequences, suggestions for psychophysiological methods to be studied in quality assessment, and recommendations for the documentation and publications of test results. The test plan is presented in this article.

  • 221. Brennan, K.F.
    et al.
    Bellotti, E.
    Farahmand, M.
    Nilsson, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Ruden, P.P.
    Zhang, Y.
    Monte Carlo modeling of wurtzite and 4H phase semiconducting materials2001Inngår i: VLSI Design, ISSN 1065-514X, Vol. 13, nr 1-4, s. 117-124Artikkel i tidsskrift (Fagfellevurdert)
  • 222. Brennan, K.F.
    et al.
    Bellotti, E.
    Farahmand, M.
    Nilsson, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Ruden, P.P.
    Zhang, Y.
    Monte Carlo modeling of wurtzite and 4H phase semiconductor materials2001Inngår i: VLSI design (Print), ISSN 1065-514X, E-ISSN 1563-5171, Vol. 13, nr 1-4, s. 117-124Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a discussion of the complexities encountered in particle simulation models for noncubic symmetry materials, focusing on the wurtzite and 4H phases of semiconductors. We have identified three general issues, band structure, scattering mechanisms, and band intersections, which in our opinion, constitute the most important modifications to Monte Carlo simulators for cubic symmetry materials. Owing to the increased number of atoms and size of the unit cell, the band structure is far more complex in wurtzite and 4H polytypes than in zincblende phase semiconductors. This added complexity is reflected by the greater number of bands, smaller Brillouin zone and concomitant increase in the number of band intersections. We have found that the band intersection points greatly influence the transport dynamics. In this paper, we discuss our initial attempts at treating transport near these points

  • 223. Brennan, K.F.
    et al.
    Bellotti, E.
    Farahmand, M.
    Nilsson, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Ruden, P.P.
    Zhang, Y.
    Monte Carlo simulation of noncubic symmetry semiconducting materials and devices2000Inngår i: IEEE Transactions on Electron Devices, ISSN 0018-9383, Vol. 47, nr 10, s. 1882-1890Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, we discuss the complexities that arise in Monte Carlo based modeling of noncubic symmetry semiconductors and their related devices. We have identified three general issues, band structure, scattering mechanisms, and band intersections that require some modification of the Monte Carlo simulator from that for cubic symmetry. Owing to the increased size and number of atoms per unit cell, the band structure is far more complex in noncubic than in zincblende phase semiconductors. This added complexity is reflected by the greater number of bands, smaller Brillouin zone and concomitant increase in the number of band intersections. We present strategies for modeling the effects of band intersections on the carrier dynamics using the Monte Carlo method. It is found that the band intersection points greatly affect the carrier transport, most dramatically in the determination of the impact ionization and breakdown properties of devices and bulk material. Excellent agreement with experimental measurements of the impact ionization coefficients is obtained only when treatment of the band intersections is included within the model.

  • 224.
    Brodén, Jon
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion.
    EAS-tagg med fuktsensor: Design och utvärdering av EAS-alarmteknologi för fuktdetektering2013Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [en]

    Electronic article surveillance (EAS) is widely used in shops and libraries together with an RF-tag attached to the goods or books in order to prevent shoplifting. By implementing the addition of a moisture sensor to the RF-tag, other functions become possible, including the ability to use as an alarm with regards to frozen goods, which have been shipped but which have melted and have, subsequently, refrozen. In- relation to care for the elderly, one time-consuming step involves checking whether there is the necessity for a change of diaper and this can, instead, be based on an RF-tag with an EAS-system alarm. A preliminary investigation was made using the moisture sensors, which involved how the resistance changes when liquid and/or heat is applied. A simulation of the LCCR circuit (RF-tag with the sensor) was conducted in order to determine how the resonance frequency changes for different resistances levels. When the moisture sensors are applied to the RF-tag with the correct resistance no alarm will be triggered, but will be triggered when water is added to the moisture sensor. In order for the tag to be able to induce energy from the transmitter in the EAS-system the resistance must be less than ten ohms in relation to the entire tag. Results show that the implementation of the sensor on the RF-tag is possible and that it works in a satisfactory manner.

  • 225. Brotherton, M.D
    et al.
    Huynh-Thu, Q
    Hands, D
    Brunnström, Kjell
    Subjective Multimedia Quality Assessment.2006Inngår i: IEICE Transactions on Fundamentals of Electronics Communications and Computer Sciences, ISSN 0916-8508, E-ISSN 1745-1337, Vol. E89-A, nr 11, s. 2920-2932Artikkel i tidsskrift (Fagfellevurdert)
  • 226.
    Brundin, Andreas
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion.
    Hydraulisk testbänk: Automatiserad diagnostik av flödesgivare i en hydraulisk testbänk2017Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Hydrauliska testbänkar används för att testa nya och reparerade hydraulventiler och pumpar för att utvärdera deras uthållighet vad gäller tid och tryck. Testbänkar består vanligen av sensorer och mätare som operatören övervakar. Detta arbete behandlar ett diagnostiseringsprogram för en hydraulisk testbänk med avseende på dess flödesmätare. Den testbänk som behandlas är en hydraulisk testbänk med tillhörande hydraul aggregat inklusive sju flödesmätare. Testbänken har även ett tillhörande HMI. HMI:t har en inbyggd PLC och är av modellen Beijer iX T12B-SM. Målet är att designa ett diagnostiseringsprogram som varnar operatören när flödesmätarnas värden inte befinner sig inom den toleransnivå som önskas. Metoden för att konstruera ett diagnostiseringsprogram har fyra faser där den första fasen är att utföra en litteraturstudie gällande de faktorer som kan ha en inverkan på utformningen av diagnostiseringen. Faktorerna innefattar metoder för diagnostisering, utformningen av ett HMI och förväntningar på de flödesmätare som studeras. I den andra fasen utförs mätningar på flödesgivarna som ligger till grund för fas tre. Tredje fasen består i att programmera diagnostiseringsprogrammet. Den fjärde fasen går ut på att programmera visualiseringen av diagnosticeringen. Efter mätningar med flödesgivarna visar det sig att de har den toleransnivå som tillverkaren har utlovat. Vissa problem uppstår i samband med mätningarna då en pump inte fungerar som tänkt samt att en flödesmätare har lägre värden än förväntat. Diagnostiseringsprogrammet tillsammans med HMI:t motsvarar det syftet som finns med arbetet och larmar operatören som förväntat. För framtiden skulle det vara intressant att vidareutveckla diagnostiseringen så att alla aktuella flödesmätare jämför sina värden med varandra och larmar när fel uppstår.

  • 227.
    Brunnstrom, Kjell
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informationssystem och -teknologi. RISE AB Acreo.
    Barkowsky, Marcus
    Deggendorf Institute of Technology (DIT), University of Applied Sciences, Deggendorf.
    Statistical quality of experience analysis: on planning the sample size and statistical significance testing2018Inngår i: Journal of Electronic Imaging (JEI), ISSN 1017-9909, E-ISSN 1560-229X, Vol. 27, nr 5, s. 053013-1-053013-11, artikkel-id 053013Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper analyzes how an experimenter can balance errors in subjective video quality tests betweenthe statistical power of finding an effect if it is there and not claiming that an effect is there if the effect is not there,i.e., balancing Type I and Type II errors. The risk of committing Type I errors increases with the number ofcomparisons that are performed in statistical tests. We will show that when controlling for this and at thesame time keeping the power of the experiment at a reasonably high level, it is unlikely that the number oftest subjects that are normally used and recommended by the International Telecommunication Union (ITU),i.e., 15 is sufficient but the number used by the Video Quality Experts Group (VQEG), i.e., 24 is more likelyto be sufficient. Examples will also be given for the influence of Type I error on the statistical significance ofcomparing objective metrics by correlation. We also present a comparison between parametric and nonparametricstatistics. The comparison targets the question whether we would reach different conclusions on the statisticaldifference between the video quality ratings of different video clips in a subjective test, based on thecomparison between the student T-test and the Mann–Whitney U-test. We found that there was hardly a differencewhen few comparisons are compensated for, i.e., then almost the same conclusions are reached. Whenthe number of comparisons is increased, then larger and larger differences between the two methods arerevealed. In these cases, the parametric T-test gives clearly more significant cases, than the nonparametrictest, which makes it more important to investigate whether the assumptions are met for performing a certaintest.

  • 228.
    Brunnström, K
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    3D user experience and display performance2013Inngår i: Proceedings, 2013Konferansepaper (Fagfellevurdert)
  • 229.
    Brunnström, K
    ACREO AB.
    Percieved QoS and Test suites: keynote2008Inngår i: ETSI Workshop on Effects of transmission Performance on Multimedia QoS, Prague, 2008Konferansepaper (Fagfellevurdert)
  • 230.
    Brunnström, K
    et al.
    Acreo AB, Sweden.
    Hands, D
    BT Innovate, UK.
    Speranza, F
    Communications Research Centre, Canada.
    Webster, A
    NTIA/ITS, United States.
    VQEG Validation and ITU Standardisation of Objective Perceptual Video Quality Metrics2009Inngår i: IEEE signal processing magazine (Print), ISSN 1053-5888, E-ISSN 1558-0792, Vol. 26, nr 3, s. 96-101Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    For industry, the need to access accurate and reliable objective video metrics has become more pressing with the advent of new video applications and services such as mobile broadcasting, Internet video, and Internet Protocol television (IPTV). Industry-class objective quality- measurement models have a wide range of uses, including equipment testing (e.g., codec evaluation), transmission- planning and network-dimensioning tasks, head-end quality assurance, in- service network monitoring, and client-based quality measurement. The Video Quality Experts Group (VQEG) is the primary forum for validation testing of objective perceptual quality models. The work of VQEG has resulted in International Telecommunication Union (ITU) standardization of objective quality models designed for standard- definition television and for multimedia applications. This article reviews VQEG's work, paying particular attention to the group's approach to validation testing.

  • 231.
    Brunnström, K
    et al.
    Acreo, Stockholm, Sweden.
    Nordström, L
    Andrén, B
    Visual experience of quality degradation when viewing computer and notebooks displays from an oblique angle2011Inngår i: Journal of the Society for Information Display, ISSN 1071-0922, E-ISSN 1938-3657, Vol. 19, nr 5, s. 387-397Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study focused on evaluating the user experience of the viewing-angle-dependent quality of computer and notebook displays. The tests were performed in a test lab using a notebook with a prismatic display and a computer monitor with a conventional LCD. The notebook display was tilted and turned during an image-quality test and tilted during an acuity test. On the computer monitor, the turn and tilt was simulated in the image-quality test, for checking the TCO requirements. The results from the image-quality test show that the parameter used in the TCO requirement, luminance ratio, would be a reasonable predictor of image quality. However, the experiment with the notebook display shows that, in general, this is not the case, especially for larger viewing angles where the physical characteristics do not show a gradual variation in luminance. Therefore, the luminance ratio in TCO requirements shall be used with caution. In addition, the results for the notebook display show that the visual acu ity decreased faster with increasing viewing angle than predicted from the luminance decrease alone. This means that it will be harder to resolve small details and will, therefore, have a negative influence on the visual ergonomics.

  • 232.
    Brunnström, K
    et al.
    Acreo AB, Stockholm, Sweden.
    Schenkman, B
    Jacobsen, B
    Object Detection in Cluttered Infrared Images.2003Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 42, nr 2, s. 388-399Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Implementation of the Johnson criteria for infrared images is the probabilities of a discrimination technique. The inputs to the model are the size of the target, the range to it, and the temperature difference against the background. The temperature difference is calculated without taking the background structure into consideration, but it may have a strong influence on the visibility of the target. We investigated whether a perceptually based temperature difference should be used as input. Four different models are discussed: 1. a probability of discrimination model largely based on the Johnson criteria for infrared images, 2. a peak signal-to-noise ratio model, 3. a signal-to-clutter ratio model, and 4. two versions of an image discrimination model based on how human vision analyzes spatial information. The models differ as to how much they try to simulate human perception. To test the models, a psychophysical experiment was carried out with ten test persons, measuring contrast threshold detection in five different infrared backgrounds using a method based on a two-alternative forced-choice methodology. Predictions of thresholds in contrast energy were calculated for the different models and compared to the empirical values. Thresholds depend on the background, and these can be predicted well by the image discrimination models, and better than the other models. Future extensions are discussed.

  • 233.
    Brunnström, K
    et al.
    Acreo AB, Stockholm, Sweden.
    Schenkman, B.N
    Acreo AB, Stockholm, Sweden.
    Comparison of the predictions of a spatio-temporal model with the detection of distortion in small moving images2002Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 41, nr 3, s. 711-722Artikkel i tidsskrift (Fagfellevurdert)
  • 234.
    Brunnström, K
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem. Acreo Swedish ICT AB.
    Wang, K
    Acreo Swedish ICT AB.
    Andrén, B
    Acreo Swedish ICT AB.
    Simulator sickness analysis of 3D video viewing on passive 3DTV2013Inngår i: Stereoscopic Displays and Applications XXIV / [ed] Woods, A. J., Holliman, N. S., and Favalora, G. E., Bellingham, WA, USA: SPIE - International Society for Optical Engineering, 2013, s. 864802-Konferansepaper (Fagfellevurdert)
  • 235.
    Brunnström, Kjell
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informationssystem och -teknologi. RISE ICT/Acreo, Stockholm.
    Allison, R. S.
    York University, Centre for Vision Research, Toronto, Canada.
    Chandler, D. M.
    Dolby Laboratories, United States.
    Colett, H.
    Intel Corp., Santa Clara, CA, United States.
    Corriveau, P.
    Intel Corp., Santa Clara, CA, United States.
    Daly, S.
    Dolby Laboratories, United States.
    Goel, J.
    Qualcomm, Display Video Processing Group, Markham, Canada.
    Knopf, J.
    Intel Corp., Santa Clara, CA, United States.
    Wilcox, L. M.
    York University, Centre for Vision Research, Toronto, Canada.
    Yaacob, Y.
    Shizuoka University, Hamamatsu, Shizuoka, Japan.
    Yang, S. -N
    Pacific University, Forest Grove, OR, United States.
    Zhang, Y.
    Shizuoka University, Hamamatsu, Shizuoka, Japan.
    Industry and business perspectives on the distinctions between visually lossless and lossy video quality: Mobile and large format displays2017Inngår i: IS and T International Symposium on Electronic Imaging Science and Technology, Society for Imaging Science and Technology , 2017, Vol. F130042, s. 118-133Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper will explore the mobile and business perspectives of visually lossless image quality, as well as review recent scientific advances. It is the outcome from the Special Session on Visually Lossless Video Quality for Modern Devices: Research and Industry Perspectives organized at the Human Vision and Electronic Imaging 2017 by IS&T at San Francisco Airport, Burlingame, California, USA, Jan 29 - Feb 2, 2017. It summarizes four presentations and a panel discussion.

  • 236.
    Brunnström, Kjell
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem. NetLab: Visual Media Quality, Acreo Swedish ICT AB, SE-16440 Kista, Sweden.
    Ananth, I. V.
    NetLab: Visual Media Quality, Acreo Swedish ICT AB, SE-16440 Kista, Sweden.
    Hedberg, C.
    NetLab: Visual Media Quality, Acreo Swedish ICT AB, SE-16440 Kista, Sweden.
    Wang, Kun
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem. NetLab: Visual Media Quality, Acreo Swedish ICT AB, SE-16440 Kista, Sweden.
    Andrén, B.
    NetLab: Visual Media Quality, Acreo Swedish ICT AB, SE-16440 Kista, Sweden.
    Barkowsky, M.
    Dept. of Image and Video Communication, IRCCyN, University of Nantes, France .
    Comparison between different rating scales for 3D TV2013Inngår i: SID Symposium Digest of Technical Papers, 2013, Vol. 44, nr 1, s. 509-512Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Stereoscopic 3D viewing experience has been studied quite intensively recently, but still the subjective test methods have not yet been settled. It has become clear that the 3D viewing experience cannot easily be described by just one scale. This paper describes a study where three different rating scales (Quality, Discomfort and Presence) are compared in a subjective test, combined with two viewing distances. The results shows that in a stereoscopic 3D video quality test targeting mainly coding distortions one scale such as video quality could be sufficient. © 2013 Society for Information Display.

  • 237.
    Brunnström, Kjell
    et al.
    RISE Research Institute of Sweden AB.
    Dima, Elijs
    Andersson, Mattias
    Sjöström, Mårten
    quresh, tahir
    HIAB.
    Johanson, Mathias
    Alkit Communications AB.
    Quality of Experience of hand controller latency in a Virtual Reality simulator2019Inngår i: Human Vision and Electronic Imaging 2019 / [ed] Damon Chandler, Mark McCourt and Jeffrey Mulligan, 2019, Springfield, VA, United States, 2019, artikkel-id 3068450Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this study, we investigate a VR simulator of a forestry crane used for loading logs onto a truck, mainly looking at Quality of Experience (QoE) aspects that may be relevant for task completion, but also whether there are any discomfort related symptoms experienced during task execution. A QoE test has been designed to capture both the general subjective experience of using the simulator and to study task performance. Moreover, a specific focus has been to study the effects of latency on the subjective experience, with regards to delays in the crane control interface. A formal subjective study has been performed where we have added controlled delays to the hand controller (joystick) signals. The added delays ranged from 0 ms to 800 ms. We found no significant effects of delays on the task performance on any scales up to 200 ms. A significant negative effect was found for 800 ms added delay. The Symptoms reported in the Simulator Sickness Questionnaire (SSQ) was significantly higher for all the symptom groups, but a majority of the participants reported only slight symptoms. Two out of thirty test persons stopped the test before finishing due to their symptoms.

  • 238.
    Brunnström, Kjell
    et al.
    Kungliga tekniska högskolan.
    Eklund, Jan-Olof
    Kungliga tekniska högskolan.
    Uhlin, Tomas
    Kungliga tekniska högskolan.
    Active fixation for scene exploration1996Inngår i: International Journal of Computer Vision, ISSN 0920-5691, E-ISSN 1573-1405, Vol. 17, nr 2, s. 137-162Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It is well-known that active selection of fixation points in humans is highly context and task dependent. It is therefore likely that successful computational processes for fixation in active vision should be so too. We are considering active fixation in the context of recognition of man-made objects characterized by their shapes. In this situation the qualitative shape and type of observed junctions play an important role. The fixations are driven by a grouping strategy, which forms sets of connected junctions separated from the surrounding at depth discontinuities. We have furthermore developed a methodology for rapid active detection and classification of junctions by selection of fixation points. The approach is based on direct computations from image data and allows integration of stereo and accommodation cues with luminance information. This work form a part of an effort to perform active recognition of generic objects, in the spirit of Malik and Biederman, but on real imagery rather than on line-drawings.

  • 239.
    Brunnström, Kjell
    et al.
    Kungliga tekniska högskolan.
    Eklundh, Jan-Olof
    Kungliga tekniska högskolan.
    Lindeberg, Tony
    Kungliga tekniska högskolan.
    On scale and resolution in active analysis of local image structure1990Inngår i: Image and Vision Computing, ISSN 0262-8856, E-ISSN 1872-8138, Vol. 8, nr 4, s. 289-296Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Focus-of-attention is extremely important in human visual perception. If computer vision systems are to perform tasks in a complex, dynamic world they will have to be able to control processing in a way that is analogous to visual attention in humans. Problems connected to foveation (examination of selected regions of the world at high resolution) are examined. In particular, the problem of finding and classifying junctions from this aspect is considered. It is shown that foveation as simulated by controlled, active zooming in conjunction with scale-space techniques allows for robust detection and classification of junctions.

  • 240.
    Brunnström, Kjell
    et al.
    Acreo.
    Josefsson, Katarina
    Acreo.
    Andrén, Börje
    Acreo.
    The effects of glossy screens on the visual ergonomics of flat panel displays.2008Inngår i: Journal of the Society for Information Display, ISSN 1071-0922, E-ISSN 1938-3657, Vol. 16, nr 10, s. 1041-1049Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The TCO requirements provide well-known and recognized quality labels for displays.For these requirements to remain useful, they must continuously be reviewed and updated when nec-essary. The study described here was performed in response to the market trend of designing flat-paneldisplays and notebooks with glare panels. The purpose of this study was to investigate subjectiveresponses to display screens of different gloss levels for office workers working on different tasks undernormal office-lighting conditions. The study consisted of three parts, one where the users should setan acceptable reflex level, one where the user should rate their disturbance on a category scale, andone where the visual acuity of the users were investigated whether they were affected by glare or not.The results show that increasing gloss and increasing luminance levels had negative effects on theacceptance and the disturbance of reflexes. There were statistically significant differences in theacceptance and the disturbance levels between screens with low gloss and screens with high gloss,which suggests that screens with the highest gloss levels should be avoided. The study did not showan effect on the performance based on acuity testing.

  • 241.
    Brunnström, Kjell
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem. Acreo Swedish ICT AB, Kista, Sweden.
    Tavakoli, S.
    Universidad Politécnica de Madrid, Madrid, Spain.
    Søgaard, J.
    Technical University of Denmark, Kgs Lyngby, Denmark .
    Compensating for Type-I errors in video quality assessment2015Inngår i: 2015 7th International Workshop on Quality of Multimedia Experience, QoMEX 2015, 2015, s. Art. no. 7148080-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper analyzes the impact on compensating for Type-I errors in video quality assessment. A Type-I error is to incorrectly conclude that there is an effect. The risk increases with the number of comparisons that are performed in statistical tests. Type-I errors are an issue often neglected in Quality of Experience and video quality assessment analysis. Examples are given for the analysis of subjective experiments and the evaluation of objective metrics by correlation. © 2015 IEEE.

  • 242.
    Brunnström, Kjell
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem. Dept. of NetLab, Visual Media Quality, Acreo Swedish ICT AB, Sweden .
    Wang, Kun
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för data- och systemvetenskap. Dept. of NetLab, Visual Media Quality, Acreo Swedish ICT AB, Sweden .
    Andrén, B.
    Dept. of NetLab, Visual Media Quality, Acreo Swedish ICT AB, Sweden .
    Simulator Sickness analysis of 3D video viewing on passive 3D TV2013Inngår i: Proceedings of SPIE - The International Society for Optical Engineering, 2013, s. Art. no. 864802-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The MPEG 3DV project is working on the next generation video encoding standard and in this process a call for proposal of encoding algorithms was issued. To evaluate these algorithm a large scale subjective test was performed involving Laboratories all over the world. For the participating Labs it was optional to administer a slightly modified Simulator Sickness Questionnaire (SSQ) from Kennedy et al (1993) before and after the test. Here we report the results from one Lab (Acreo) located in Sweden. The videos were shown on a 46 inch film pattern retarder 3D TV, where the viewers were using polarized passive eye-glasses to view the stereoscopic 3D video content. There were 68 viewers participating in this investigation in ages ranges from 16 to 72, with one third females. The questionnaire was filled in before and after the test, with a viewing time ranging between 30 min to about one and half hour, which is comparable to a feature length movie. The SSQ consists of 16 different symptoms that have been identified as important for indicating simulator sickness. When analyzing the individual symptoms it was found that Fatigue, Eye-strain, Difficulty Focusing and Difficulty Concentrating were significantly worse after than before. SSQ was also analyzed according to the model suggested by Kennedy et al (1993). All in all this investigation shows a statistically significant increase in symptoms after viewing 3D video especially related to visual or Oculomotor system.

  • 243.
    Brunnström, Kjell
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem. Acreo Swedish ICT AB, Kista, Sweden.
    Wang, Kun
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem. Acreo Swedish ICT AB, Kista, Sweden.
    Andrén, Börje
    Acreo Swedish ICT AB, Kista, Sweden.
    Kulyk, Valentin
    Ericsson Research, Sweden.
    Tavakoli, Samira
    Universidad Politécnica de Madrid, Spain.
    Hedberg, Christer
    Acreo Swedish ICT AB, Kista, Sweden.
    Ananth, Indirajith Vijai
    Acreo Swedish ICT AB, Kista, Sweden.
    Hussein, Mahir
    Acreo Swedish ICT AB, Kista, Sweden.
    Folkesson, Mats
    Ericsson Research, Sweden.
    Barkowsky, Marcus
    Acreo Swedish ICT AB, Kista, Sweden.
    3D Video Quality of Experience - Influence of Scale and Crosstalk Invited2014Inngår i: Proceedings of the 8th International Workshop on Video Processing and Quality Metrics for Consumer Electronics VPQM-2014, Scottsdale, AZ, USA, 2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper gives an overview of three recent studies by the authors on the topic of 3D video Quality of Experience (QoE). Two of studies [1,2] investigated different psychological dimension that may be needed for describing 3D video QoE and the third the visibility and annoyance of crosstalk[3]. The results shows that the video quality scale could be sufficient for evaluating S3D video experience for coding and spatial resolution reduction distortions. It was also confirmed that with a more complex mixture of degradations more than one scale should be used to capture the QoE in these cases. The study found a linear relationship between the perceived crosstalk and the amount of crosstalk.

  • 244.
    Brunnström, Kjell
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informationssystem och -teknologi. Acreo Swedish ICT AB.
    Wang, Kun
    Acreo Swedish ICT AB.
    Tavakoli, Samira
    Universidad Politécnica de Madrid, Spain.
    Andrén, Börje
    Acreo Swedish ICT AB.
    Symptoms analysis of 3D TV viewing based on Simulator Sickness Questionnaires2017Inngår i: Quality and User Experience, ISSN 2366-0147, Vol. 2, nr 1Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Stereoscopic 3D TV viewing puts different visual demands on the viewer compared to 2D TV viewing. Previous research has reported on viewers' fatigue and discomfort and other negative effects. This study is to investigate further how severe and what symptoms may arise from somewhat longish 3D TV viewing.

    The MPEG 3DV project is working on the next-generation video encoding standard and in this process, MPEG issued a call for proposal of encoding algorithms. To evaluate these algorithms a large scale subjective test was performed involving Laboratories all over the world[1, 2]. For the participating Labs, it was optional to administer a slightly modified Simulator Sickness Questionnaire (SSQ) before and after the test. One of the SSQ data sets described in this article is coming from this study. The SSQ data from the MPEG test is the largest data set in this study and also contains the longest viewing times. Along with the SSQ data from the MPEG test, we have also collected questionnaire data in three other 3D TV studies. We did two on the same 3D TV (passive film pattern retarder) as in the MPEG test, and one was using a projector system. As comparison SSQ data from a 2D video quality experiment is also presented. 

    This investigation shows a statistically significant increase in symptoms after viewing 3D TV primarily related to the visual or Oculomotor system. Surprisingly, 3D video viewing using projectors did not show this effect.

  • 245.
    Burgos, Peter
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Mittuniversitetets Android-app: Studentportalen som mobilapplikation2012Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Detta projekt går ut på att skapa en stabil och användbar mobilapplikation utvecklad i programspråket Java. Syftet är att underlätta åtkomsten och kommunikationen mellan Studentportalen och studenterna. Slutprodukten är Mittuniversitetets inofficiella applikation, kallad Mittuniversitetets Android-app. som begränsas i första hand till enheter med operativsystemet Android. Genom undersökningar, gjorda via både Mittuniversitetets studentportal i form av en enkät och fysiskt på Mittuniversitetet campus Sundsvall i form av muntliga intervjuer, utreds vilka områden studenterna helst vill ha i applikationen och det är utefter dessa som applikationen utformas. Applikationen betraktas som färdig när studenterna bl.a. kommer åt sina uppgifter och får dessa presenterade på ett stilrent sätt. Tre olika lösningsalternativ ges men jämförelser av för- och nackdelar leder till att endast ”direktanslutning som lösning” genomförs i detta projekt. För att ge läsaren en grund för fortsatt förståelse av rapporten beskrivs vissa delar närmare i rapporten. Rapporten visar även att åtkomsten till Studentportalen effektiviserats till 5 skärmtryck genom Mittuniversitetets applikation från tidigare 24 skärm-tryck genom mobiltelefonens egna webbläsare. Samtliga mål i projektet anses vara uppfyllda och visas som skärmdumpar i rapporten. Avslutningsvis framgår även förslag för vidareutveckling av applikationen.

  • 246.
    Butun, Ismail
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informationssystem och -teknologi.
    Pereira, Nuno
    Polytechnic Institute of Porto, Porto, Portugal .
    Gidlund, Mikael
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informationssystem och -teknologi.
    Analysis of LoRaWAN V1.1 Security2018Inngår i: Proceedings of the 4th ACM MobiHoc Workshop on Experiences with the Design and Implementation of Smart Objects (SMARTOBJECTS '18)., ACM Digital Library, 2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    LoRa and the LoRaWAN specification is a technology for Low Power Wide Area Networks (LPWAN) designed to allow connectivity for connected objects, such as remote sensors. Several previous works revealed various weaknesses regarding the security of LoRaWAN v1.0 (the official 1st draft) and these led to improvements included in LoRaWAN v1.1, released on Oct 11, 2017. In this work, we provide the first look into the security of LoRaWAN v1.1. We present an overview of the protocol and, importantly, present several threats to this new version of the protocol. Besides, we propose our own ramification strategies for the mentioned threats, to be used in developing next version of LoRaWAN. The threats presented were not previously discussed, they are possible even within the security assumptions of the specification and are relevant for practitioners implementing LoRa-based applications as well researchers and the future evolution of the LoRaWAN specification.

  • 247.
    Butun, Ismail
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationssystem och –teknologi.
    Sari, Alparslan
    Department of Computer Engineering, University of Delaware, Newark, Delaware, USA.
    Österberg, Patrik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationssystem och –teknologi.
    Security Implications of Fog Computing on the Internet of Things2019Inngår i: International Conference on Consumer Electronics (ICCE), IEEE, 2019, artikkel-id 8661909Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Recently, the use of IoT devices and sensors has been rapidly increased which also caused data generation (information and logs), bandwidth usage, and related phenomena to be increased. To our best knowledge, a standard definition for the integration of fog computing with IoT is emerging now. This integration will bring many opportunities for the researchers, especially while building cyber-security related solutions. In this study, we surveyed about the integration of fog computing with IoT and its implications. Our goal was to find out and emphasize problems, specifically security related problems that arise with the employment of fog computing by IoT. According to our findings, although this integration seems to be non-trivial and complicated, it has more benefits than the implications. Index Terms—IoT, IIoT, vulnerabilities, trust, end-device, confidentiality, integrity, availability.

  • 248.
    Butun, Ismail
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationssystem och –teknologi.
    Österberg, Patrik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationssystem och –teknologi.
    Detecting Intrusions in Cyber-Physical Systems of Smart Cities: Challenges and Directions2019Inngår i: Secure Cyber-Physical Systems for Smart Cities / [ed] Riaz Ahmed Shaikh, Hershey, USA: IGI Global, 2019, s. 74-102Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    Interfacing the smart cities with cyber-physical systems (CPSs) improves cyber infrastructures while introducing security vulnerabilities that may lead to severe problems such as system failure, privacy violation, and/or issues related to data integrity if security and privacy are not addressed properly. In order for the CPSs of smart cities to be designed with proactive intelligence against such vulnerabilities, anomaly detection approaches need to be employed. This chapter will provide a brief overview of the security vulnerabilities in CPSs of smart cities. Following a thorough discussion on the applicability of conventional anomaly detection schemes in CPSs of smart cities, possible adoption of distributed anomaly detection systems by CPSs of smart cities will be discussed along with a comprehensive survey of the state of the art. The chapter will discuss challenges in tailoring appropriate anomaly detection schemes for CPSs of smart cities and provide insights into future directions for the researchers working in this field.

  • 249.
    Byström, Johan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Automatiserad mätning med Spectrolino2002Rapport (Annet vitenskapelig)
  • 250.
    Bäcklund, Ylva
    et al.
    Uppsala universitet, Institutionen för materialvetenskap.
    Vangbo, Mattias
    Uppsala universitet, Institutionen för materialvetenskap.
    Rangsten, Pelle
    Uppsala universitet, Institutionen för materialvetenskap.
    Hedlund, Christer
    Uppsala universitet, Institutionen för materialvetenskap.
    Wet etching of single crystal quartz1998Inngår i: Workshop of Physical Chemistry of Wet Chemical Etching of Silicon, May 17-19, Holten, The Netherlands, 1998Konferansepaper (Fagfellevurdert)
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